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Sensors, Volume 13, Issue 10 (October 2013), Pages 12744-14247

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Open AccessArticle Tip-Enhanced Raman Imaging and Nano Spectroscopy of Etched Silicon Nanowires
Sensors 2013, 13(10), 12744-12759; doi:10.3390/s131012744
Received: 2 August 2013 / Accepted: 12 September 2013 / Published: 25 September 2013
Cited by 6 | PDF Full-text (485 KB) | HTML Full-text | XML Full-text
Abstract
Tip-enhanced Raman spectroscopy (TERS) is used to investigate the influence of strains in isolated and overlapping silicon nanowires prepared by chemical etching of a (100) silicon wafer. An atomic force microscopy tip made of nanocrystalline diamond coated with a thin layer of [...] Read more.
Tip-enhanced Raman spectroscopy (TERS) is used to investigate the influence of strains in isolated and overlapping silicon nanowires prepared by chemical etching of a (100) silicon wafer. An atomic force microscopy tip made of nanocrystalline diamond coated with a thin layer of silver is used in conjunction with an excitation wavelength of 532 nm in order to probe the first order optical phonon mode of the [100] silicon nanowires. The frequency shift and the broadening of the silicon first order phonon are analyzed and compared to the topographical measurements for distinct configuration of nanowires that are disposed in straight, bent or overlapping configuration over a microscope coverslip. The TERS spatial resolution is close to the topography provided by the nanocrystalline diamond tip and subtle spectral changes are observed for different nanowire configurations. Full article
(This article belongs to the Special Issue Spectral Imaging at the Microscale and Beyond)
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Open AccessArticle Micro Ethanol Sensors with a Heater Fabricated Using the Commercial 0.18 μm CMOS Process
Sensors 2013, 13(10), 12760-12770; doi:10.3390/s131012760
Received: 6 August 2013 / Revised: 11 September 2013 / Accepted: 17 September 2013 / Published: 25 September 2013
Cited by 4 | PDF Full-text (981 KB) | HTML Full-text | XML Full-text
Abstract
The study investigates the fabrication and characterization of an ethanol microsensor equipped with a heater. The ethanol sensor is manufactured using the commercial 0.18 µm complementary metal oxide semiconductor (CMOS) process. The sensor consists of a sensitive film, a heater and interdigitated [...] Read more.
The study investigates the fabrication and characterization of an ethanol microsensor equipped with a heater. The ethanol sensor is manufactured using the commercial 0.18 µm complementary metal oxide semiconductor (CMOS) process. The sensor consists of a sensitive film, a heater and interdigitated electrodes. The sensitive film is zinc oxide prepared by the sol-gel method, and it is coated on the interdigitated electrodes. The heater is located under the interdigitated electrodes, and it is used to supply a working temperature to the sensitive film. The sensor needs a post-processing step to remove the sacrificial oxide layer, and to coat zinc oxide on the interdigitated electrodes. When the sensitive film senses ethanol gas, the resistance of the sensor generates a change. An inverting amplifier circuit is utilized to convert the resistance variation of the sensor into the output voltage. Experiments show that the sensitivity of the ethanol sensor is 0.35 mV/ppm. Full article
(This article belongs to the Special Issue Gas Sensors - 2013)
Open AccessArticle Satellite Angular Velocity Estimation Based on Star Images and Optical Flow Techniques
Sensors 2013, 13(10), 12771-12793; doi:10.3390/s131012771
Received: 20 July 2013 / Revised: 13 September 2013 / Accepted: 17 September 2013 / Published: 25 September 2013
Cited by 4 | PDF Full-text (571 KB) | HTML Full-text | XML Full-text
Abstract
An optical flow-based technique is proposed to estimate spacecraft angular velocity based on sequences of star-field images. It does not require star identification and can be thus used to also deliver angular rate information when attitude determination is not possible, as during [...] Read more.
An optical flow-based technique is proposed to estimate spacecraft angular velocity based on sequences of star-field images. It does not require star identification and can be thus used to also deliver angular rate information when attitude determination is not possible, as during platform de tumbling or slewing. Region-based optical flow calculation is carried out on successive star images preprocessed to remove background. Sensor calibration parameters, Poisson equation, and a least-squares method are then used to estimate the angular velocity vector components in the sensor rotating frame. A theoretical error budget is developed to estimate the expected angular rate accuracy as a function of camera parameters and star distribution in the field of view. The effectiveness of the proposed technique is tested by using star field scenes generated by a hardware-in-the-loop testing facility and acquired by a commercial-off-the shelf camera sensor. Simulated cases comprise rotations at different rates. Experimental results are presented which are consistent with theoretical estimates. In particular, very accurate angular velocity estimates are generated at lower slew rates, while in all cases the achievable accuracy in the estimation of the angular velocity component along boresight is about one order of magnitude worse than the other two components. Full article
(This article belongs to the Special Issue Optomechatronics) Print Edition available
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Open AccessArticle A Gold Nanoparticles Enhanced Surface Plasmon Resonance Immunosensor for Highly Sensitive Detection of Ischemia-Modified Albumin
Sensors 2013, 13(10), 12794-12803; doi:10.3390/s131012794
Received: 18 July 2013 / Revised: 12 September 2013 / Accepted: 17 September 2013 / Published: 25 September 2013
Cited by 8 | PDF Full-text (649 KB) | HTML Full-text | XML Full-text
Abstract
In this study a novel sensitive nanogold particle sensor enhancement based on mixed self-assembled monolayers was explored and used to construct a Surface Plasmon Resonance (SPR) immunosensor to detect Ischemia Modified Albumin (IMA). Compared with a direct binding SPR assay at a [...] Read more.
In this study a novel sensitive nanogold particle sensor enhancement based on mixed self-assembled monolayers was explored and used to construct a Surface Plasmon Resonance (SPR) immunosensor to detect Ischemia Modified Albumin (IMA). Compared with a direct binding SPR assay at a limit of detection (LOD) of 100 ng/L, gold nanoparticles (AuNPs) of 10 nm dramatically improved the LOD of IMA to 10 ng/L. Meanwhile, no interfering substance that may lead to false positive results was identified. These results suggested that the SPR biosensor presented superior properties, and provided a simple label-free strategy to increase assay sensitivity for further acute coronary syndrome (ACS) diagnosis. Full article
Open AccessArticle 3D Multi-Spectrum Sensor System with Face Recognition
Sensors 2013, 13(10), 12804-12829; doi:10.3390/s131012804
Received: 20 August 2013 / Revised: 16 September 2013 / Accepted: 17 September 2013 / Published: 25 September 2013
PDF Full-text (4472 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a novel three-dimensional (3D) multi-spectrum sensor system, which combines a 3D depth sensor and multiple optical sensors for different wavelengths. Various image sensors, such as visible, infrared (IR) and 3D sensors, have been introduced into the commercial market. Since [...] Read more.
This paper presents a novel three-dimensional (3D) multi-spectrum sensor system, which combines a 3D depth sensor and multiple optical sensors for different wavelengths. Various image sensors, such as visible, infrared (IR) and 3D sensors, have been introduced into the commercial market. Since each sensor has its own advantages under various environmental conditions, the performance of an application depends highly on selecting the correct sensor or combination of sensors. In this paper, a sensor system, which we will refer to as a 3D multi-spectrum sensor system, which comprises three types of sensors, visible, thermal-IR and time-of-flight (ToF), is proposed. Since the proposed system integrates information from each sensor into one calibrated framework, the optimal sensor combination for an application can be easily selected, taking into account all combinations of sensors information. To demonstrate the effectiveness of the proposed system, a face recognition system with light and pose variation is designed. With the proposed sensor system, the optimal sensor combination, which provides new effectively fused features for a face recognition system, is obtained. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Best Basis Selection Method Using Learning Weights for Face Recognition
Sensors 2013, 13(10), 12830-12851; doi:10.3390/s131012830
Received: 24 July 2013 / Revised: 26 August 2013 / Accepted: 16 September 2013 / Published: 25 September 2013
PDF Full-text (682 KB) | HTML Full-text | XML Full-text
Abstract
In the face recognition field, principal component analysis is essential to the reduction of the image dimension. In spite of frequent use of this analysis, it is commonly believed that the basis faces with large eigenvalues are chosen as the best subset [...] Read more.
In the face recognition field, principal component analysis is essential to the reduction of the image dimension. In spite of frequent use of this analysis, it is commonly believed that the basis faces with large eigenvalues are chosen as the best subset in the nearest neighbor classifiers. We propose an alternative that can predict the classification error during the training steps and find the useful basis faces for the similarity metrics of the classical pattern algorithms. In addition, we also show the need for the eye-aligned dataset to have the pure face. The experiments using face images verify that our method reduces the negative effect on the misaligned face images and decreases the weights of the useful basis faces in order to improve the classification accuracy. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Cooperation among Wirelessly Connected Static and Mobile Sensor Nodes for Surveillance Applications
Sensors 2013, 13(10), 12903-12928; doi:10.3390/s131012903
Received: 9 August 2013 / Revised: 17 September 2013 / Accepted: 18 September 2013 / Published: 25 September 2013
Cited by 7 | PDF Full-text (1072 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a bio-inspired networking strategy to support the cooperation between static sensors on the ground and mobile sensors in the air to perform surveillance missions in large areas. The goal of the proposal is to provide low overhead in the [...] Read more.
This paper presents a bio-inspired networking strategy to support the cooperation between static sensors on the ground and mobile sensors in the air to perform surveillance missions in large areas. The goal of the proposal is to provide low overhead in the communication among sensor nodes, while allocating the mobile sensors to perform sensing activities requested by the static ones. Simulations have shown that the strategy is efficient in maintaining low overhead and achieving the desired coordination. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Automatic Detection and Recognition of Pig Wasting Diseases Using Sound Data in Audio Surveillance Systems
Sensors 2013, 13(10), 12929-12942; doi:10.3390/s131012929
Received: 13 June 2013 / Revised: 16 September 2013 / Accepted: 22 September 2013 / Published: 25 September 2013
Cited by 5 | PDF Full-text (681 KB) | HTML Full-text | XML Full-text
Abstract
Automatic detection of pig wasting diseases is an important issue in the management of group-housed pigs. Further, respiratory diseases are one of the main causes of mortality among pigs and loss of productivity in intensive pig farming. In this study, we propose [...] Read more.
Automatic detection of pig wasting diseases is an important issue in the management of group-housed pigs. Further, respiratory diseases are one of the main causes of mortality among pigs and loss of productivity in intensive pig farming. In this study, we propose an efficient data mining solution for the detection and recognition of pig wasting diseases using sound data in audio surveillance systems. In this method, we extract the Mel Frequency Cepstrum Coefficients (MFCC) from sound data with an automatic pig sound acquisition process, and use a hierarchical two-level structure: the Support Vector Data Description (SVDD) and the Sparse Representation Classifier (SRC) as an early anomaly detector and a respiratory disease classifier, respectively. Our experimental results show that this new method can be used to detect pig wasting diseases both economically (even a cheap microphone can be used) and accurately (94% detection and 91% classification accuracy), either as a standalone solution or to complement known methods to obtain a more accurate solution. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Degradation of Bacterial Quorum Sensing Signaling Molecules by the Microscopic Yeast Trichosporon loubieri Isolated from Tropical Wetland Waters
Sensors 2013, 13(10), 12943-12957; doi:10.3390/s131012943
Received: 15 August 2013 / Revised: 8 September 2013 / Accepted: 12 September 2013 / Published: 25 September 2013
Cited by 9 | PDF Full-text (718 KB) | HTML Full-text | XML Full-text
Abstract
Proteobacteria produce N-acylhomoserine lactones as signaling molecules, which will bind to their cognate receptor and activate quorum sensing-mediated phenotypes in a population-dependent manner. Although quorum sensing signaling molecules can be degraded by bacteria or fungi, there is no reported work on [...] Read more.
Proteobacteria produce N-acylhomoserine lactones as signaling molecules, which will bind to their cognate receptor and activate quorum sensing-mediated phenotypes in a population-dependent manner. Although quorum sensing signaling molecules can be degraded by bacteria or fungi, there is no reported work on the degradation of such molecules by basidiomycetous yeast. By using a minimal growth medium containing N-3-oxohexanoylhomoserine lactone as the sole source of carbon, a wetland water sample from Malaysia was enriched for microbial strains that can degrade N-acylhomoserine lactones, and consequently, a basidiomycetous yeast strain WW1C was isolated. Morphological phenotype and molecular analyses confirmed that WW1C was a strain of Trichosporon loubieri. We showed that WW1C degraded AHLs with N-acyl side chains ranging from 4 to 10 carbons in length, with or without oxo group substitutions at the C3 position. Re-lactonisation bioassays revealed that WW1C degraded AHLs via a lactonase activity. To the best of our knowledge, this is the first report of degradation of N-acyl-homoserine lactones and utilization of N-3-oxohexanoylhomoserine as carbon and nitrogen source for growth by basidiomycetous yeast from tropical wetland water; and the degradation of bacterial quorum sensing molecules by an eukaryotic yeast. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Electrical Resistivity-Based Study of Self-Sensing Properties for Shape Memory Alloy-Actuated Artificial Muscle
Sensors 2013, 13(10), 12958-12974; doi:10.3390/s131012958
Received: 11 July 2013 / Revised: 8 September 2013 / Accepted: 12 September 2013 / Published: 26 September 2013
Cited by 4 | PDF Full-text (909 KB) | HTML Full-text | XML Full-text
Abstract
Shape memory alloy (SMA) has great potential to develop light and compact artificial muscle (AM) due to its muscle-like high power-to-weight ratio, flexibility and silent operation properties. In this paper, SMA self-sensing properties are explored and modeled in depth to imitate the [...] Read more.
Shape memory alloy (SMA) has great potential to develop light and compact artificial muscle (AM) due to its muscle-like high power-to-weight ratio, flexibility and silent operation properties. In this paper, SMA self-sensing properties are explored and modeled in depth to imitate the integrated muscle-like functions of actuating and self-sensing for SMA-AM based on the investigation of SMA electrical resistivity (ER). Firstly, an ER transformation kinetics model is proposed based on the simulation of SMA differential scanning calorimetry (DSC) curves. Then a series of thermal-electrical-mechanical experiments are carried out to verify the validity of the ER model, whereby the SMA-AM self-sensing function is well established under different stress conditions. Finally the self-sensing capability is further demonstrated by its application to a novel SMA-AM-actuated active ankle-foot orthosis (AAFO). Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Low Density Microarray Method for the Identification of Human Papillomavirus Type 18 Variants
Sensors 2013, 13(10), 12975-12993; doi:10.3390/s131012975
Received: 9 July 2013 / Revised: 8 August 2013 / Accepted: 30 August 2013 / Published: 26 September 2013
Cited by 3 | PDF Full-text (439 KB) | HTML Full-text | XML Full-text
Abstract
We describe a novel microarray based-method for the screening of oncogenic human papillomavirus 18 (HPV-18) molecular variants. Due to the fact that sequencing methodology may underestimate samples containing more than one variant we designed a specific and sensitive stacking DNA hybridization assay. [...] Read more.
We describe a novel microarray based-method for the screening of oncogenic human papillomavirus 18 (HPV-18) molecular variants. Due to the fact that sequencing methodology may underestimate samples containing more than one variant we designed a specific and sensitive stacking DNA hybridization assay. This technology can be used to discriminate between three possible phylogenetic branches of HPV-18. Probes were attached covalently on glass slides and hybridized with single-stranded DNA targets. Prior to hybridization with the probes, the target strands were pre-annealed with the three auxiliary contiguous oligonucleotides flanking the target sequences. Screening HPV-18 positive cell lines and cervical samples were used to evaluate the performance of this HPV DNA microarray. Our results demonstrate that the HPV-18’s variants hybridized specifically to probes, with no detection of unspecific signals. Specific probes successfully reveal detectable point mutations in these variants. The present DNA oligoarray system can be used as a reliable, sensitive and specific method for HPV-18 variant screening. Furthermore, this simple assay allows the use of inexpensive equipment, making it accessible in resource-poor settings. Full article
(This article belongs to the Special Issue Microarray Sensors)
Open AccessCommunication Highly Selective Fluorescent Sensing of Proteins Based on a Fluorescent Molecularly Imprinted Nanosensor
Sensors 2013, 13(10), 12994-13004; doi:10.3390/s131012994
Received: 24 July 2013 / Revised: 5 August 2013 / Accepted: 16 August 2013 / Published: 26 September 2013
Cited by 4 | PDF Full-text (1509 KB) | HTML Full-text | XML Full-text
Abstract
A fluorescent molecularly imprinted nanosensor was obtained by grafting imprinted polymer onto the surface of multi-wall carbon nanotubes and post-imprinting treatment with fluorescein isothiocyanate (FITC). The fluorescence of lysozyme-imprinted polymer (Lys-MIP) was quenched more strongly by Lys than that of nonimprinted polymer [...] Read more.
A fluorescent molecularly imprinted nanosensor was obtained by grafting imprinted polymer onto the surface of multi-wall carbon nanotubes and post-imprinting treatment with fluorescein isothiocyanate (FITC). The fluorescence of lysozyme-imprinted polymer (Lys-MIP) was quenched more strongly by Lys than that of nonimprinted polymer (NIP), which indicated that the Lys-MIP could recognize Lys. The resulted imprinted material has the ability to selectively sense a target protein, and an imprinting factor of 3.34 was achieved. The Lys-MIP also showed selective detection for Lys among other proteins such as cytochrome C (Cyt C), hemoglobin (HB) and bovine serum albumin (BSA) due to the imprinted sites in the Lys-MIP. This approach combines the high selectivity of surface molecular imprinting technology and fluorescence, and converts binding events into detectable signals by monitoring fluorescence spectra. Therefore, it will have further applications for Lys sensing. Full article
(This article belongs to the Special Issue Biomimetic Receptors and Sensors)
Open AccessArticle Simple and Rapid Determination of Ferulic Acid Levels in Food and Cosmetic Samples Using Paper-Based Platforms
Sensors 2013, 13(10), 13039-13053; doi:10.3390/s131013039
Received: 8 August 2013 / Revised: 2 September 2013 / Accepted: 16 September 2013 / Published: 26 September 2013
Cited by 6 | PDF Full-text (328 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Ferulic acid is an important phenolic antioxidant found in or added to diet supplements, beverages, and cosmetic creams. Two designs of paper-based platforms for the fast, simple and inexpensive evaluation of ferulic acid contents in food and pharmaceutical cosmetics were evaluated. The [...] Read more.
Ferulic acid is an important phenolic antioxidant found in or added to diet supplements, beverages, and cosmetic creams. Two designs of paper-based platforms for the fast, simple and inexpensive evaluation of ferulic acid contents in food and pharmaceutical cosmetics were evaluated. The first, a paper-based electrochemical device, was developed for ferulic acid detection in uncomplicated matrix samples and was created by the photolithographic method. The second, a paper-based colorimetric device was preceded by thin layer chromatography (TLC) for the separation and detection of ferulic acid in complex samples using a silica plate stationary phase and an 85:15:1 (v/v/v) chloroform: methanol: formic acid mobile phase. After separation, ferulic acid containing section of the TLC plate was attached onto the patterned paper containing the colorimetric reagent and eluted with ethanol. The resulting color change was photographed and quantitatively converted to intensity. Under the optimal conditions, the limit of detection of ferulic acid was found to be 1 ppm and 7 ppm (S/N = 3) for first and second designs, respectively, with good agreement with the standard HPLC-UV detection method. Therefore, these methods can be used for the simple, rapid, inexpensive and sensitive quantification of ferulic acid in a variety of samples. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessCommunication Autonomic Nervous System Responses Can Reveal Visual Fatigue Induced by 3D Displays
Sensors 2013, 13(10), 13054-13062; doi:10.3390/s131013054
Received: 14 August 2013 / Revised: 17 September 2013 / Accepted: 17 September 2013 / Published: 26 September 2013
Cited by 9 | PDF Full-text (367 KB) | HTML Full-text | XML Full-text
Abstract
Previous research has indicated that viewing 3D displays may induce greater visual fatigue than viewing 2D displays. Whether viewing 3D displays can evoke measureable emotional responses, however, is uncertain. In the present study, we examined autonomic nervous system responses in subjects viewing [...] Read more.
Previous research has indicated that viewing 3D displays may induce greater visual fatigue than viewing 2D displays. Whether viewing 3D displays can evoke measureable emotional responses, however, is uncertain. In the present study, we examined autonomic nervous system responses in subjects viewing 2D or 3D displays. Autonomic responses were quantified in each subject by heart rate, galvanic skin response, and skin temperature. Viewers of both 2D and 3D displays showed strong positive correlations with heart rate, which indicated little differences between groups. In contrast, galvanic skin response and skin temperature showed weak positive correlations with average difference between viewing 2D and 3D. We suggest that galvanic skin response and skin temperature can be used to measure and compare autonomic nervous responses in subjects viewing 2D and 3D displays. Full article
(This article belongs to the collection Sensors for Globalized Healthy Living and Wellbeing)
Open AccessArticle Fast and Sensitive Detection of Pb2+ in Foods Using Disposable Screen-Printed Electrode Modified by Reduced Graphene Oxide
Sensors 2013, 13(10), 13063-13075; doi:10.3390/s131013063
Received: 10 August 2013 / Revised: 16 September 2013 / Accepted: 16 September 2013 / Published: 26 September 2013
Cited by 16 | PDF Full-text (617 KB) | HTML Full-text | XML Full-text
Abstract
In this study, reduced graphene oxide (rGO) was electrochemically deposited on the surface of screen-printed carbon electrodes (SPCE) to prepare a disposable sensor for fast detection of Pb2+ in foods. The SEM images showed that the rGO was homogeneously deposited onto [...] Read more.
In this study, reduced graphene oxide (rGO) was electrochemically deposited on the surface of screen-printed carbon electrodes (SPCE) to prepare a disposable sensor for fast detection of Pb2+ in foods. The SEM images showed that the rGO was homogeneously deposited onto the electrode surface with a wrinkled nanostructure, which provided 2D bridges for electron transport and a larger active area for Pb2+ adsorption. Results showed that rGO modification enhanced the activity of the electrode surface, and significantly improved the electrochemical properties of SPCE. The rGO modified SPCE (rGO-SPCE) was applied to detect Pb2+ in standard aqueous solution, showing a sharp stripping peak and a relatively constant peak potential in square wave anodic stripping voltammetry (SWASV). The linear range for Pb2+ detection was 5~200 ppb (R2 = 0.9923) with a low detection limit of 1 ppb (S/N = 3). The interference of Cd2+ and Cu2+ at low concentrations was effectively avoided. Finally, the rGO-SPCE was used for determination of lead in real tap water, juice, preserved eggs and tea samples. Compared with results from graphite furnace atomic absorption spectroscopy (GFAAS), the results based on rGO-SPCE were both accurate and reliable, suggesting that the disposable sensor has great potential in application for fast, sensitive and low-cost detection of Pb2+ in foods. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle A Temperature Sensor Based on a Polymer Optical Fiber Macro-Bend
Sensors 2013, 13(10), 13076-13089; doi:10.3390/s131013076
Received: 7 July 2013 / Revised: 16 September 2013 / Accepted: 18 September 2013 / Published: 26 September 2013
Cited by 11 | PDF Full-text (433 KB) | HTML Full-text | XML Full-text
Abstract
The design and development of a plastic optical fiber (POF) macrobend temperature sensor is presented. The sensor has a linear response versus temperature at a fixed bend radius, with a sensitivity of . The sensor system used a dummy fiber-optic sensor for [...] Read more.
The design and development of a plastic optical fiber (POF) macrobend temperature sensor is presented. The sensor has a linear response versus temperature at a fixed bend radius, with a sensitivity of . The sensor system used a dummy fiber-optic sensor for reference purposes having a resolution below 0.3 °C. A comprehensive experimental analysis was carried out to provide insight into the effect of different surrounding media on practical macro-bend POF sensor implementation. Experimental results are successfully compared with bend loss calculations. Full article
(This article belongs to the Special Issue Photonic Sensors for Industrial, Environmental and Health Monitoring)
Open AccessArticle Active Angular Alignment of Gauge Blocks in Double-Ended Interferometers
Sensors 2013, 13(10), 13090-13098; doi:10.3390/s131013090
Received: 14 August 2013 / Revised: 12 September 2013 / Accepted: 23 September 2013 / Published: 27 September 2013
PDF Full-text (473 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a method implemented in a system for automatic contactless calibration of gauge blocks designed at ISI ASCR. The system combines low-coherence interferometry and laser interferometry, where the first identifies the gauge block sides position and the second one measures [...] Read more.
This paper presents a method implemented in a system for automatic contactless calibration of gauge blocks designed at ISI ASCR. The system combines low-coherence interferometry and laser interferometry, where the first identifies the gauge block sides position and the second one measures the gauge block length itself. A crucial part of the system is the algorithm for gauge block alignment to the measuring beam which is able to compensate the gauge block lateral and longitudinal tilt up to 0.141 mrad. The algorithm is also important for the gauge block position monitoring during its length measurement. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Exploratory Data Analysis of Acceleration Signals to Select Light-Weight and Accurate Features for Real-Time Activity Recognition on Smartphones
Sensors 2013, 13(10), 13099-13122; doi:10.3390/s131013099
Received: 26 June 2013 / Revised: 10 September 2013 / Accepted: 18 September 2013 / Published: 27 September 2013
Cited by 13 | PDF Full-text (1180 KB) | HTML Full-text | XML Full-text
Abstract
Smartphone-based activity recognition (SP-AR) recognizes users’ activities using the embedded accelerometer sensor. Only a small number of previous works can be classified as online systems, i.e., the whole process (pre-processing, feature extraction, and classification) is performed on the device. Most of these [...] Read more.
Smartphone-based activity recognition (SP-AR) recognizes users’ activities using the embedded accelerometer sensor. Only a small number of previous works can be classified as online systems, i.e., the whole process (pre-processing, feature extraction, and classification) is performed on the device. Most of these online systems use either a high sampling rate (SR) or long data-window (DW) to achieve high accuracy, resulting in short battery life or delayed system response, respectively. This paper introduces a real-time/online SP-AR system that solves this problem. Exploratory data analysis was performed on acceleration signals of 6 activities, collected from 30 subjects, to show that these signals are generated by an autoregressive (AR) process, and an accurate AR-model in this case can be built using a low SR (20 Hz) and a small DW (3 s). The high within class variance resulting from placing the phone at different positions was reduced using kernel discriminant analysis to achieve position-independent recognition. Neural networks were used as classifiers. Unlike previous works, true subject-independent evaluation was performed, where 10 new subjects evaluated the system at their homes for 1 week. The results show that our features outperformed three commonly used features by 40% in terms of accuracy for the given SR and DW. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Programmable Gain Amplifiers with DC Suppression and Low Output Offset for Bioelectric Sensors
Sensors 2013, 13(10), 13123-13142; doi:10.3390/s131013123
Received: 4 July 2013 / Revised: 17 September 2013 / Accepted: 22 September 2013 / Published: 27 September 2013
Cited by 4 | PDF Full-text (1209 KB) | HTML Full-text | XML Full-text
Abstract
DC-offset and DC-suppression are key parameters in bioelectric amplifiers. However, specific DC analyses are not often explained. Several factors influence the DC-budget: the programmable gain, the programmable cut-off frequencies for high pass filtering and, the low cut-off values and the capacitor blocking [...] Read more.
DC-offset and DC-suppression are key parameters in bioelectric amplifiers. However, specific DC analyses are not often explained. Several factors influence the DC-budget: the programmable gain, the programmable cut-off frequencies for high pass filtering and, the low cut-off values and the capacitor blocking issues involved. A new intermediate stage is proposed to address the DC problem entirely. Two implementations were tested. The stage is composed of a programmable gain amplifier (PGA) with DC-rejection and low output offset. Cut-off frequencies are selectable and values from 0.016 to 31.83 Hz were tested, and the capacitor deblocking is embedded in the design. Hence, this PGA delivers most of the required gain with constant low output offset, notwithstanding the gain or cut-off frequency selected. Full article
(This article belongs to the Special Issue Biomedical Sensors and Systems)
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Open AccessArticle Taking Advantage of Selective Change Driven Processing for 3D Scanning
Sensors 2013, 13(10), 13143-13162; doi:10.3390/s131013143
Received: 1 August 2013 / Revised: 10 September 2013 / Accepted: 22 September 2013 / Published: 27 September 2013
Cited by 2 | PDF Full-text (8390 KB) | HTML Full-text | XML Full-text
Abstract
This article deals with the application of the principles of SCD (Selective Change Driven) vision to 3D laser scanning. Two experimental sets have been implemented: one with a classical CMOS (Complementary Metal-Oxide Semiconductor) sensor, and the other one with a recently developed [...] Read more.
This article deals with the application of the principles of SCD (Selective Change Driven) vision to 3D laser scanning. Two experimental sets have been implemented: one with a classical CMOS (Complementary Metal-Oxide Semiconductor) sensor, and the other one with a recently developed CMOS SCD sensor for comparative purposes, both using the technique known as Active Triangulation. An SCD sensor only delivers the pixels that have changed most, ordered by the magnitude of their change since their last readout. The 3D scanning method is based on the systematic search through the entire image to detect pixels that exceed a certain threshold, showing the SCD approach to be ideal for this application. Several experiments for both capturing strategies have been performed to try to find the limitations in high speed acquisition/processing. The classical approach is limited by the sequential array acquisition, as predicted by the Nyquist - Shannon sampling theorem, and this has been experimentally demonstrated in the case of a rotating helix. These limitations are overcome by the SCD 3D scanning prototype achieving a significantly higher performance. The aim of this article is to compare both capturing strategies in terms of performance in the time and frequency domains, so they share all the static characteristics including resolution, 3D scanning method, etc., thus yielding the same 3D reconstruction in static scenes. Full article
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Open AccessArticle Identification and Quantification of Explosives in Nanolitre Solution Volumes by Raman Spectroscopy in Suspended Core Optical Fibers
Sensors 2013, 13(10), 13163-13177; doi:10.3390/s131013163
Received: 8 August 2013 / Revised: 18 September 2013 / Accepted: 24 September 2013 / Published: 30 September 2013
Cited by 9 | PDF Full-text (1193 KB) | HTML Full-text | XML Full-text
Abstract
A novel approach for identifying explosive species is reported, using Raman spectroscopy in suspended core optical fibers. Numerical simulations are presented that predict the strength of the observed signal as a function of fiber geometry, with the calculated trends verified experimentally and [...] Read more.
A novel approach for identifying explosive species is reported, using Raman spectroscopy in suspended core optical fibers. Numerical simulations are presented that predict the strength of the observed signal as a function of fiber geometry, with the calculated trends verified experimentally and used to optimize the sensors. This technique is used to identify hydrogen peroxide in water solutions at volumes less than 60 nL and to quantify microgram amounts of material using the solvent’s Raman signature as an internal calibration standard. The same system, without further modifications, is also used to detect 1,4-dinitrobenzene, a model molecule for nitrobenzene-based explosives such as 2,4,6-trinitrotoluene (TNT). Full article
(This article belongs to the Special Issue Photodetectors)
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Open AccessArticle A Micro-Force Sensor with Slotted-Quad-Beam Structure for Measuring the Friction in MEMS Bearings
Sensors 2013, 13(10), 13178-13191; doi:10.3390/s131013178
Received: 2 August 2013 / Revised: 5 September 2013 / Accepted: 11 September 2013 / Published: 30 September 2013
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Abstract
Presented here is a slotted-quad-beam structure sensor for the measurement of friction in micro bearings. Stress concentration slots are incorporated into a conventional quad-beam structure to improve the sensitivity of force measurements. The performance comparison between the quad-beam structure sensor and the [...] Read more.
Presented here is a slotted-quad-beam structure sensor for the measurement of friction in micro bearings. Stress concentration slots are incorporated into a conventional quad-beam structure to improve the sensitivity of force measurements. The performance comparison between the quad-beam structure sensor and the slotted-quad-beam structure sensor are performed by theoretical modeling and finite element (FE) analysis. A hollow stainless steel probe is attached to the mesa of the sensor chip by a tailor-made organic glass fixture. Concerning the overload protection of the fragile beams, a glass wafer is bonded onto the bottom of sensor chip to limit the displacement of the mesa. The calibration of the packaged device is experimentally performed by a tri-dimensional positioning stage, a precision piezoelectric ceramic and an electronic analytical balance, which indicates its favorable sensitivity and overload protection. To verify the potential of the proposed sensor being applied in micro friction measurement, a measurement platform is established. The output of the sensor reflects the friction of bearing resulting from dry friction and solid lubrication. The results accord with the theoretical modeling and demonstrate that the sensor has the potential application in measuring the micro friction force under stable stage in MEMS machines. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering 2013)
Open AccessArticle N-acyl Homoserine Lactone-Producing Pseudomonas putida Strain T2-2 from Human Tongue Surface
Sensors 2013, 13(10), 13192-13203; doi:10.3390/s131013192
Received: 16 August 2013 / Revised: 28 August 2013 / Accepted: 22 September 2013 / Published: 30 September 2013
Cited by 4 | PDF Full-text (317 KB) | HTML Full-text | XML Full-text
Abstract
Bacterial cell-to-cell communication (quorum sensing) refers to the regulation of bacterial gene expression in response to changes in microbial population density. Quorum sensing bacteria produce, release and respond to chemical signal molecules called autoinducers. Bacteria use two types of autoinducers, namely autoinducer-1 [...] Read more.
Bacterial cell-to-cell communication (quorum sensing) refers to the regulation of bacterial gene expression in response to changes in microbial population density. Quorum sensing bacteria produce, release and respond to chemical signal molecules called autoinducers. Bacteria use two types of autoinducers, namely autoinducer-1 (AI-1) and autoinducer-2 (AI-2) where the former are N-acylhomoserine lactones and the latter is a product of the luxS gene. Most of the reported literatures show that the majority of oral bacteria use AI-2 for quorum sensing but rarely the AI-1 system. Here we report the isolation of Pseudomonas putida strain T2-2 from the oral cavity. Using high resolution mass spectrometry, it is shown that this isolate produced N-octanoylhomoserine lactone (C8-HSL) and N-dodecanoylhomoserine lactone (C12-HSL) molecules. This is the first report of the finding of quorum sensing of P. putida strain T2-2 isolated from the human tongue surface and their quorum sensing molecules were identified. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle A Wireless Laser Displacement Sensor Node for Structural Health Monitoring
Sensors 2013, 13(10), 13204-13216; doi:10.3390/s131013204
Received: 5 August 2013 / Revised: 24 September 2013 / Accepted: 24 September 2013 / Published: 30 September 2013
Cited by 5 | PDF Full-text (403 KB) | HTML Full-text | XML Full-text
Abstract
This study describes a wireless laser displacement sensor node that measures displacement as a representative damage index for structural health monitoring (SHM). The proposed measurement system consists of a laser displacement sensor (LDS) and a customized wireless sensor node. Wireless communication is [...] Read more.
This study describes a wireless laser displacement sensor node that measures displacement as a representative damage index for structural health monitoring (SHM). The proposed measurement system consists of a laser displacement sensor (LDS) and a customized wireless sensor node. Wireless communication is enabled by a sensor node that consists of a sensor module, a code division multiple access (CDMA) communication module, a processor, and a power module. An LDS with a long measurement distance is chosen to increase field applicability. For a wireless sensor node driven by a battery, we use a power control module with a low-power processor, which facilitates switching between the sleep and active modes, thus maximizing the power consumption efficiency during non-measurement and non-transfer periods. The CDMA mode is also used to overcome the limitation of communication distance, which is a challenge for wireless sensor networks and wireless communication. To evaluate the reliability and field applicability of the proposed wireless displacement measurement system, the system is tested onsite to obtain the required vertical displacement measurements during the construction of mega-trusses and an edge truss, which are the primary structural members in a large-scale irregular building currently under construction. The measurement values confirm the validity of the proposed wireless displacement measurement system and its potential for use in safety evaluations of structural elements. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Short Chain N-acyl Homoserine Lactone Production by Soil Isolate Burkholderia sp. Strain A9
Sensors 2013, 13(10), 13217-13227; doi:10.3390/s131013217
Received: 6 August 2013 / Revised: 9 September 2013 / Accepted: 22 September 2013 / Published: 30 September 2013
Cited by 24 | PDF Full-text (401 KB) | HTML Full-text | XML Full-text
Abstract
In the bacteria kingdom, quorum sensing (QS) is a cell-to-cell communication that relies on the production of and response to specific signaling molecules. In proteobacteria, N-acylhomoserine lactones (AHLs) are the well-studied signaling molecules. The present study aimed to characterize the production [...] Read more.
In the bacteria kingdom, quorum sensing (QS) is a cell-to-cell communication that relies on the production of and response to specific signaling molecules. In proteobacteria, N-acylhomoserine lactones (AHLs) are the well-studied signaling molecules. The present study aimed to characterize the production of AHL of a bacterial strain A9 isolated from a Malaysian tropical soil. Strain A9 was identified as Burkholderia sp. using matrix-assisted laser desorption ionization-time-of-flight mass spectrometry and 16S rDNA nucleotide sequence analysis. AHL production by A9 was detected with two biosensors, namely Chromobacterium violaceum CV026 and Escherichia coli [pSB401]. Thin layer chromatography results showed N–hexanoylhomoserine lactone (C6-HSL) and N–octanoylhomoserine lactone (C8-HSL) production. Unequivocal identification of C6-HSL and C8-HSL was achieved by high resolution triple quadrupole liquid chromatography-mass spectrometry analysis. We have demonstrated that Burkholderia sp. strain A9 produces AHLs that are known to be produced by other Burkholderia spp. with CepI/CepR homologs. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Design and Implementation of a MAC Protocol for Timely and Reliable Delivery of Command and Data in Dynamic Wireless Sensor Networks
Sensors 2013, 13(10), 13228-13257; doi:10.3390/s131013228
Received: 17 June 2013 / Revised: 24 September 2013 / Accepted: 27 September 2013 / Published: 30 September 2013
Cited by 8 | PDF Full-text (957 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes and implements a new TDMA-based MAC protocol for providing timely and reliable delivery of data and command for monitoring and control networks. In this kind of network, sensor nodes are required to sense data from the monitoring environment periodically [...] Read more.
This paper proposes and implements a new TDMA-based MAC protocol for providing timely and reliable delivery of data and command for monitoring and control networks. In this kind of network, sensor nodes are required to sense data from the monitoring environment periodically and then send the data to a sink. The sink determines whether the environment is safe or not by analyzing the acquired data. Sometimes, a command or control message is sent from the sink to a particular node or a group of nodes to execute the services or request further interested data. The proposed MAC protocol enables bidirectional communication, controls active and sleep modes of a sensor node to conserve energy, and addresses the problem of load unbalancing between the nodes near a sink and the other nodes. It can improve reliability of communication significantly while extending network lifetime. These claims are supported by the experimental results. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle A New Corrosion Sensor to Determine the Start and Development of Embedded Rebar Corrosion Process at Coastal Concrete
Sensors 2013, 13(10), 13258-13275; doi:10.3390/s131013258
Received: 27 August 2013 / Revised: 17 September 2013 / Accepted: 17 September 2013 / Published: 30 September 2013
Cited by 1 | PDF Full-text (668 KB) | HTML Full-text | XML Full-text
Abstract
The corrosion of reinforcements induced by chloride has resulted to be one of the most frequent causes of their premature damage. Most corrosion sensors were designed to monitor corrosion state in concrete, such as Anode-Ladder-System and Corrowatch System, which are widely used [...] Read more.
The corrosion of reinforcements induced by chloride has resulted to be one of the most frequent causes of their premature damage. Most corrosion sensors were designed to monitor corrosion state in concrete, such as Anode-Ladder-System and Corrowatch System, which are widely used to monitor chloride ingress in marine concrete. However, the monitoring principle of these corrosion sensors is based on the macro-cell test method, so erroneous information may be obtained, especially from concrete under drying or saturated conditions due to concrete resistance taking control in macro-cell corrosion. In this paper, a fast weak polarization method to test corrosion state of reinforcements based on electrochemical polarization dynamics was proposed. Furthermore, a new corrosion sensor for monitoring the corrosion state of concrete cover was developed based on the proposed test method. The sensor was tested in cement mortar, with dry-wet cycle tests to accelerate the chloride ingress rate. The results show that the corrosion sensor can effectively monitor chloride penetration into concrete with little influence of the relative humidity in the concrete. With a reasonable corrosion sensor electrode arrangement, it seems the Ohm-drop effect measured by EIS can be ignored, which makes the tested electrochemical parameters more accurate. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Quantification of Mesenchymal Stem Cell Growth Rates through Secretory and Excretory Biomolecules in Conditioned Media via Fresnel Reflection
Sensors 2013, 13(10), 13276-13288; doi:10.3390/s131013276
Received: 15 June 2013 / Revised: 13 September 2013 / Accepted: 19 September 2013 / Published: 30 September 2013
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Abstract
An efficient and low cost optical method for directly measuring the concentration of homogenous biological solutes is proposed and demonstrated. The proposed system operates by Fresnel reflection, with a flat-cleaved single-mode fiber serving as the sensor probe. A laser provides a 12.9 [...] Read more.
An efficient and low cost optical method for directly measuring the concentration of homogenous biological solutes is proposed and demonstrated. The proposed system operates by Fresnel reflection, with a flat-cleaved single-mode fiber serving as the sensor probe. A laser provides a 12.9 dBm sensor signal at 1,550 nm, while a computer-controlled optical power meter measures the power of the signal returned by the probe. Three different mesenchymal stem cell (MSC) lines were obtained, sub-cultured and trypsinized daily over 9 days. Counts were measured using a haemocytometer and the conditioned media (CM) was collected daily and stored at −80 °C. MSCs release excretory biomolecules proportional to their growth rate into the CM, which changes the refractive index of the latter. The sensor is capable of detecting changes in the number of stem cells via correlation to the change in the refractive index of the CM, with the measured power loss decreasing approximately 0.4 dB in the CM sample per average 1,000 cells in the MSC subculture. The proposed system is highly cost-effective, simple to deploy, operate, and maintain, is non-destructive, and allows reliable real-time measurement of various stem cell proliferation parameters. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Hyperspectral Reflectance Imaging Technique for Visualization of Moisture Distribution in Cooked Chicken Breast
Sensors 2013, 13(10), 13289-13300; doi:10.3390/s131013289
Received: 25 June 2013 / Revised: 22 September 2013 / Accepted: 26 September 2013 / Published: 30 September 2013
Cited by 16 | PDF Full-text (781 KB) | HTML Full-text | XML Full-text
Abstract
Spectroscopy has proven to be an efficient tool for measuring the properties of meat. In this article, hyperspectral imaging (HSI) techniques are used to determine the moisture content in cooked chicken breast over the VIS/NIR (400–1,000 nm) spectral range. Moisture measurements were [...] Read more.
Spectroscopy has proven to be an efficient tool for measuring the properties of meat. In this article, hyperspectral imaging (HSI) techniques are used to determine the moisture content in cooked chicken breast over the VIS/NIR (400–1,000 nm) spectral range. Moisture measurements were performed using an oven drying method. A partial least squares regression (PLSR) model was developed to extract a relationship between the HSI spectra and the moisture content. In the full wavelength range, the PLSR model possessed a maximum  of 0.90 and an SEP of 0.74%. For the NIR range, the PLSR model yielded an  of 0.94 and an SEP of 0.71%. The majority of the absorption peaks occurred around 760 and 970 nm, representing the water content in the samples. Finally, PLSR images were constructed to visualize the dehydration and water distribution within different sample regions. The high correlation coefficient and low prediction error from the PLSR analysis validates that HSI is an effective tool for visualizing the chemical properties of meat. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Application of a Coaxial-Like Sensor for Impedance Spectroscopy Measurements of Selected Low-Conductivity Liquids
Sensors 2013, 13(10), 13301-13317; doi:10.3390/s131013301
Received: 9 August 2013 / Accepted: 16 September 2013 / Published: 30 September 2013
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Abstract
The paper presents a coaxial-like sensor operating in the 20 Hz–2 MHz frequency range used to determine the electrical properties of selected liquids of low electrical conductivity. Examined materials included low-concentrated aqueous solutions of potassium chloride, sodium chloride and trisodium citrate, which [...] Read more.
The paper presents a coaxial-like sensor operating in the 20 Hz–2 MHz frequency range used to determine the electrical properties of selected liquids of low electrical conductivity. Examined materials included low-concentrated aqueous solutions of potassium chloride, sodium chloride and trisodium citrate, which are common food additives. Impedance spectra of the measurement cell filled with particular liquids were obtained and analyzed using the electrical equivalent circuit approach. The values of physical quantities and parameters describing the equivalent circuit components, including a constant phase element, were calculated for each sample. The applied sensor was also calibrated for electrical conductivity measurements up to 8 mS/m. The constant phase element parameters differed among the studied solutions and concentrations. This may provide a basis for a detection method of small amounts of compounds, such as food additives in low-concentrated aqueous solutions. To demonstrate the potential of the presented method, samples of purchased mineral water and a flavored drink containing various additives were tested. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle A Visual Servoing-Based Method for ProCam Systems Calibration
Sensors 2013, 13(10), 13318-13333; doi:10.3390/s131013318
Received: 3 July 2013 / Revised: 27 August 2013 / Accepted: 23 September 2013 / Published: 1 October 2013
Cited by 3 | PDF Full-text (12146 KB) | HTML Full-text | XML Full-text
Abstract
Projector-camera systems are currently used in a wide field of applications, such as 3D reconstruction and augmented reality, and can provide accurate measurements, depending on the configuration and calibration. Frequently, the calibration task is divided into two steps: camera calibration followed by [...] Read more.
Projector-camera systems are currently used in a wide field of applications, such as 3D reconstruction and augmented reality, and can provide accurate measurements, depending on the configuration and calibration. Frequently, the calibration task is divided into two steps: camera calibration followed by projector calibration. The latter still poses certain problems that are not easy to solve, such as the difficulty in obtaining a set of 2D–3D points to compute the projection matrix between the projector and the world. Existing methods are either not sufficiently accurate or not flexible. We propose an easy and automatic method to calibrate such systems that consists in projecting a calibration pattern and superimposing it automatically on a known printed pattern. The projected pattern is provided by a virtual camera observing a virtual pattern in an OpenGL model. The projector displays what the virtual camera visualizes. Thus, the projected pattern can be controlled and superimposed on the printed one with the aid of visual servoing. Our experimental results compare favorably with those of other methods considering both usability and accuracy. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Lower Limb Wearable Capacitive Sensing and Its Applications to Recognizing Human Gaits
Sensors 2013, 13(10), 13334-13355; doi:10.3390/s131013334
Received: 31 July 2013 / Revised: 10 September 2013 / Accepted: 25 September 2013 / Published: 1 October 2013
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Abstract
In this paper, we present an approach to sense human body capacitance and apply it to recognize lower limb locomotion modes. The proposed wearable sensing system includes sensing bands, a signal processing circuit and a gait event detection module. Experiments on long-term [...] Read more.
In this paper, we present an approach to sense human body capacitance and apply it to recognize lower limb locomotion modes. The proposed wearable sensing system includes sensing bands, a signal processing circuit and a gait event detection module. Experiments on long-term working stability, adaptability to disturbance and locomotion mode recognition are carried out to validate the effectiveness of the proposed approach. Twelve able-bodied subjects are recruited, and eleven normal gait modes are investigated. With an event-dependent linear discriminant analysis classifier and feature selection procedure, four time-domain features are used for pattern recognition and satisfactory recognition accuracies (97:3% ± 0:5%, 97:0% ± 0:4%, 95:6% ± 0:9% and 97:0% ± 0:4% for four phases of one gait cycle respectively) are obtained. The accuracies are comparable with that from electromyography-based systems and inertial-based systems. The results validate the effectiveness of the proposed lower limb capacitive sensing approach in recognizing human normal gaits. Full article
(This article belongs to the Special Issue Wearable Gait Sensors)
Open AccessArticle Digital Sequences and a Time Reversal-Based Impact Region Imaging and Localization Method
Sensors 2013, 13(10), 13356-13381; doi:10.3390/s131013356
Received: 21 August 2013 / Revised: 24 September 2013 / Accepted: 24 September 2013 / Published: 1 October 2013
Cited by 4 | PDF Full-text (518 KB) | HTML Full-text | XML Full-text
Abstract
To reduce time and cost of damage inspection, on-line impact monitoring of aircraft composite structures is needed. A digital monitor based on an array of piezoelectric transducers (PZTs) is developed to record the impact region of impacts on-line. It is small in [...] Read more.
To reduce time and cost of damage inspection, on-line impact monitoring of aircraft composite structures is needed. A digital monitor based on an array of piezoelectric transducers (PZTs) is developed to record the impact region of impacts on-line. It is small in size, lightweight and has low power consumption, but there are two problems with the impact alarm region localization method of the digital monitor at the current stage. The first one is that the accuracy rate of the impact alarm region localization is low, especially on complex composite structures. The second problem is that the area of impact alarm region is large when a large scale structure is monitored and the number of PZTs is limited which increases the time and cost of damage inspections. To solve the two problems, an impact alarm region imaging and localization method based on digital sequences and time reversal is proposed. In this method, the frequency band of impact response signals is estimated based on the digital sequences first. Then, characteristic signals of impact response signals are constructed by sinusoidal modulation signals. Finally, the phase synthesis time reversal impact imaging method is adopted to obtain the impact region image. Depending on the image, an error ellipse is generated to give out the final impact alarm region. A validation experiment is implemented on a complex composite wing box of a real aircraft. The validation results show that the accuracy rate of impact alarm region localization is approximately 100%. The area of impact alarm region can be reduced and the number of PZTs needed to cover the same impact monitoring region is reduced by more than a half. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Adaptive Multi-Node Multiple Input and Multiple Output (MIMO) Transmission for Mobile Wireless Multimedia Sensor Networks
Sensors 2013, 13(10), 13382-13401; doi:10.3390/s131013382
Received: 2 September 2013 / Revised: 25 September 2013 / Accepted: 26 September 2013 / Published: 2 October 2013
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Abstract
Mobile wireless multimedia sensor networks (WMSNs), which consist of mobile sink or sensor nodes and use rich sensing information, require much faster and more reliable wireless links than static wireless sensor networks (WSNs). This paper proposes an adaptive multi-node (MN) multiple input [...] Read more.
Mobile wireless multimedia sensor networks (WMSNs), which consist of mobile sink or sensor nodes and use rich sensing information, require much faster and more reliable wireless links than static wireless sensor networks (WSNs). This paper proposes an adaptive multi-node (MN) multiple input and multiple output (MIMO) transmission to improve the transmission reliability and capacity of mobile sink nodes when they experience spatial correlation. Unlike conventional single-node (SN) MIMO transmission, the proposed scheme considers the use of transmission antennas from more than two sensor nodes. To find an optimal antenna set and a MIMO transmission scheme, a MN MIMO channel model is introduced first, followed by derivation of closed-form ergodic capacity expressions with different MIMO transmission schemes, such as space-time transmit diversity coding and spatial multiplexing. The capacity varies according to the antenna correlation and the path gain from multiple sensor nodes. Based on these statistical results, we propose an adaptive MIMO mode and antenna set switching algorithm that maximizes the ergodic capacity of mobile sink nodes. The ergodic capacity of the proposed scheme is compared with conventional SN MIMO schemes, where the gain increases as the antenna correlation and path gain ratio increase. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle GeoCENS: A Geospatial Cyberinfrastructure for the World-Wide Sensor Web
Sensors 2013, 13(10), 13402-13424; doi:10.3390/s131013402
Received: 8 August 2013 / Revised: 29 August 2013 / Accepted: 26 September 2013 / Published: 2 October 2013
Cited by 9 | PDF Full-text (1435 KB) | HTML Full-text | XML Full-text
Abstract
The world-wide sensor web has become a very useful technique for monitoring the physical world at spatial and temporal scales that were previously impossible. Yet we believe that the full potential of sensor web has thus far not been revealed. In order [...] Read more.
The world-wide sensor web has become a very useful technique for monitoring the physical world at spatial and temporal scales that were previously impossible. Yet we believe that the full potential of sensor web has thus far not been revealed. In order to harvest the world-wide sensor web’s full potential, a geospatial cyberinfrastructure is needed to store, process, and deliver large amount of sensor data collected worldwide. In this paper, we first define the issue of the sensor web long tail followed by our view of the world-wide sensor web architecture. Then, we introduce the Geospatial Cyberinfrastructure for Environmental Sensing (GeoCENS) architecture and explain each of its components. Finally, with demonstration of three real-world powered-by-GeoCENS sensor web applications, we believe that the GeoCENS architecture can successfully address the sensor web long tail issue and consequently realize the world-wide sensor web vision. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Development of a Multiplex Sandwich Aptamer Microarray for the Detection of VEGF165 and Thrombin
Sensors 2013, 13(10), 13425-13438; doi:10.3390/s131013425
Received: 30 August 2013 / Revised: 20 September 2013 / Accepted: 29 September 2013 / Published: 3 October 2013
Cited by 11 | PDF Full-text (517 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this work we have developed a multiplex microarray system capable of detecting VEGF165 and thrombin. We recently described a Sandwich Aptamer Microarray (SAM) for thrombin detection feasible for use in multiplex microarrays; here we describe a new aptasensor for VEGF [...] Read more.
In this work we have developed a multiplex microarray system capable of detecting VEGF165 and thrombin. We recently described a Sandwich Aptamer Microarray (SAM) for thrombin detection feasible for use in multiplex microarrays; here we describe a new aptasensor for VEGF165 detection employing Vap7 and VEa5, two DNA aptamers recognizing different sites of the protein. The aptamers were modified to be adapted to the solid phase platform of SAM and their capability to simultaneously recognize VEGF165 by forming a ternary complex was analyzed in solution. Having so defined the best tandem arrangement of modified aptamers, we set up the aptasensor for VEGF165, and finally analyzed the multiplex system with the two aptasensors for the simultaneous detection of VEGF165 and thrombin. The results indicate that each sandwich is specific, even when the two proteins are mixed. The system performance is consistent with the behavior evidenced by the biochemical analysis, which proves to be valuable to drive the evaluation and refinement of aptamers prior to or along the development of a detection platform. Since thrombin upregulates VEGF expression, the simultaneous recognition of these two proteins could be useful in the analysis of biomarkers in pathologies characterized by neo-angiogenesis. Full article
(This article belongs to the Special Issue Aptasensors)
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Open AccessArticle Remote Gaze Tracking System on a Large Display
Sensors 2013, 13(10), 13439-13463; doi:10.3390/s131013439
Received: 1 July 2013 / Revised: 13 September 2013 / Accepted: 29 September 2013 / Published: 7 October 2013
Cited by 7 | PDF Full-text (1420 KB) | HTML Full-text | XML Full-text
Abstract
We propose a new remote gaze tracking system as an intelligent TV interface. Our research is novel in the following three ways: first, because a user can sit at various positions in front of a large display, the capture volume of the [...] Read more.
We propose a new remote gaze tracking system as an intelligent TV interface. Our research is novel in the following three ways: first, because a user can sit at various positions in front of a large display, the capture volume of the gaze tracking system should be greater, so the proposed system includes two cameras which can be moved simultaneously by panning and tilting mechanisms, a wide view camera (WVC) for detecting eye position and an auto-focusing narrow view camera (NVC) for capturing enlarged eye images. Second, in order to remove the complicated calibration between the WVC and NVC and to enhance the capture speed of the NVC, these two cameras are combined in a parallel structure. Third, the auto-focusing of the NVC is achieved on the basis of both the user’s facial width in the WVC image and a focus score calculated on the eye image of the NVC. Experimental results showed that the proposed system can be operated with a gaze tracking accuracy of ±0.737°~±0.775° and a speed of 5~10 frames/s. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Robust Kalman Filtering Cooperated Elman Neural Network Learning for Vision-Sensing-Based Robotic Manipulation with Global Stability
Sensors 2013, 13(10), 13464-13486; doi:10.3390/s131013464
Received: 10 August 2013 / Revised: 2 September 2013 / Accepted: 2 September 2013 / Published: 8 October 2013
Cited by 2 | PDF Full-text (1719 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a global-state-space visual servoing scheme is proposed for uncalibrated model-independent robotic manipulation. The scheme is based on robust Kalman filtering (KF), in conjunction with Elman neural network (ENN) learning techniques. The global map relationship between the vision space and [...] Read more.
In this paper, a global-state-space visual servoing scheme is proposed for uncalibrated model-independent robotic manipulation. The scheme is based on robust Kalman filtering (KF), in conjunction with Elman neural network (ENN) learning techniques. The global map relationship between the vision space and the robotic workspace is learned using an ENN. This learned mapping is shown to be an approximate estimate of the Jacobian in global space. In the testing phase, the desired Jacobian is arrived at using a robust KF to improve the ENN learning result so as to achieve robotic precise convergence of the desired pose. Meanwhile, the ENN weights are updated (re-trained) using a new input-output data pair vector (obtained from the KF cycle) to ensure robot global stability manipulation. Thus, our method, without requiring either camera or model parameters, avoids the corrupted performances caused by camera calibration and modeling errors. To demonstrate the proposed scheme’s performance, various simulation and experimental results have been presented using a six-degree-of-freedom robotic manipulator with eye-in-hand configurations. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Force Sensitive Handles and Capacitive Touch Sensor for Driving a Flexible Haptic-Based Immersive System
Sensors 2013, 13(10), 13487-13508; doi:10.3390/s131013487
Received: 8 July 2013 / Revised: 20 September 2013 / Accepted: 24 September 2013 / Published: 9 October 2013
Cited by 4 | PDF Full-text (17302 KB) | HTML Full-text | XML Full-text
Abstract
In this article, we present an approach that uses both two force sensitive handles (FSH) and a flexible capacitive touch sensor (FCTS) to drive a haptic-based immersive system. The immersive system has been developed as part of a multimodal interface for product [...] Read more.
In this article, we present an approach that uses both two force sensitive handles (FSH) and a flexible capacitive touch sensor (FCTS) to drive a haptic-based immersive system. The immersive system has been developed as part of a multimodal interface for product design. The haptic interface consists of a strip that can be used by product designers to evaluate the quality of a 3D virtual shape by using touch, vision and hearing and, also, to interactively change the shape of the virtual object. Specifically, the user interacts with the FSH to move the virtual object and to appropriately position the haptic interface for retrieving the six degrees of freedom required for both manipulation and modification modalities. The FCTS allows the system to track the movement and position of the user’s fingers on the strip, which is used for rendering visual and sound feedback. Two evaluation experiments are described, which involve both the evaluation and the modification of a 3D shape. Results show that the use of the haptic strip for the evaluation of aesthetic shapes is effective and supports product designers in the appreciation of the aesthetic qualities of the shape. Full article
(This article belongs to the Special Issue Tactile Sensors and Sensing Systems)
Open AccessArticle Harmful Gas Recognition Exploiting a CTL Sensor Array
Sensors 2013, 13(10), 13509-13520; doi:10.3390/s131013509
Received: 23 July 2013 / Revised: 4 September 2013 / Accepted: 18 September 2013 / Published: 9 October 2013
Cited by 5 | PDF Full-text (537 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a novel cataluminescence (CTL)-based sensor array consisting of nine types of catalytic materials is developed for the recognition of several harmful gases, namely carbon monoxide, acetone, chloroform and toluene. First, the experimental setup is constructed by using sensing nanomaterials, [...] Read more.
In this paper, a novel cataluminescence (CTL)-based sensor array consisting of nine types of catalytic materials is developed for the recognition of several harmful gases, namely carbon monoxide, acetone, chloroform and toluene. First, the experimental setup is constructed by using sensing nanomaterials, a heating plate, a pneumatic pump, a gas flow meter, a digital temperature device, a camera and a BPCL Ultra Weak Chemiluminescence Analyzer. Then, unique CTL patterns for the four types of harmful gas are obtained from the sensor array. The harmful gases are successful recognized by the PCA method. The optimal conditions are also investigated. Finally, experimental results show high sensitivity, long-term stability and good linearity of the sensor array, which combined with simplicity, make our system a promising application in this field. Full article
(This article belongs to the Special Issue Gas Sensors - 2013)
Open AccessArticle Improving Electronic Sensor Reliability by Robust Outlier Screening
Sensors 2013, 13(10), 13521-13542; doi:10.3390/s131013521
Received: 16 August 2013 / Revised: 24 September 2013 / Accepted: 25 September 2013 / Published: 9 October 2013
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Abstract
Electronic sensors are widely used in different application areas, and in some of them, such as automotive or medical equipment, they must perform with an extremely low defect rate. Increasing reliability is paramount. Outlier detection algorithms are a key component in screening [...] Read more.
Electronic sensors are widely used in different application areas, and in some of them, such as automotive or medical equipment, they must perform with an extremely low defect rate. Increasing reliability is paramount. Outlier detection algorithms are a key component in screening latent defects and decreasing the number of customer quality incidents (CQIs). This paper focuses on new spatial algorithms (Good Die in a Bad Cluster with Statistical Bins (GDBC SB) and Bad Bin in a Bad Cluster (BBBC)) and an advanced outlier screening method, called Robust Dynamic Part Averaging Testing (RDPAT), as well as two practical improvements, which significantly enhance existing algorithms. Those methods have been used in production in Freescale® Semiconductor probe factories around the world for several years. Moreover, a study was conducted with production data of 289,080 dice with 26 CQIs to determine and compare the efficiency and effectiveness of all these algorithms in identifying CQIs. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering 2013)
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Open AccessArticle A Spherically-Shaped PZT Thin Film Ultrasonic Transducer with an Acoustic Impedance Gradient Matching Layer Based on a Micromachined Periodically Structured Flexible Substrate
Sensors 2013, 13(10), 13543-13559; doi:10.3390/s131013543
Received: 6 August 2013 / Revised: 16 September 2013 / Accepted: 8 October 2013 / Published: 9 October 2013
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Abstract
This paper presents the microfabrication of an acoustic impedance gradient matching layer on a spherically-shaped piezoelectric ultrasonic transducer. The acoustic matching layer can be designed to achieve higher acoustic energy transmission and operating bandwidth. Also included in this paper are a theoretical [...] Read more.
This paper presents the microfabrication of an acoustic impedance gradient matching layer on a spherically-shaped piezoelectric ultrasonic transducer. The acoustic matching layer can be designed to achieve higher acoustic energy transmission and operating bandwidth. Also included in this paper are a theoretical analysis of the device design and a micromachining technique to produce the novel transducer. Based on a design of a lead titanium zirconium (PZT) micropillar array, the constructed gradient acoustic matching layer has much better acoustic transmission efficiency within a 20–50 MHz operation range compared to a matching layer with a conventional quarter-wavelength thickness Parylene deposition. To construct the transducer, periodic microcavities are built on a flexible copper sheet, and then the sheet forms a designed curvature with a ball shaping. After PZT slurry deposition, the constructed PZT micropillar array is released onto a curved thin PZT layer. Following Parylene conformal coating on the processed PZT micropillars, the PZT micropillars and the surrounding Parylene comprise a matching layer with gradient acoustic impedance. By using the proposed technique, the fabricated transducer achieves a center frequency of 26 MHz and a −6 dB bandwidth of approximately 65%. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering 2013)
Open AccessArticle Thermal Tracking in Mobile Robots for Leak Inspection Activities
Sensors 2013, 13(10), 13560-13574; doi:10.3390/s131013560
Received: 31 July 2013 / Revised: 23 September 2013 / Accepted: 27 September 2013 / Published: 9 October 2013
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Abstract
Maintenance tasks are crucial for all kind of industries, especially in extensive industrial plants, like solar thermal power plants. The incorporation of robots is a key issue for automating inspection activities, as it will allow a constant and regular control over the [...] Read more.
Maintenance tasks are crucial for all kind of industries, especially in extensive industrial plants, like solar thermal power plants. The incorporation of robots is a key issue for automating inspection activities, as it will allow a constant and regular control over the whole plant. This paper presents an autonomous robotic system to perform pipeline inspection for early detection and prevention of leakages in thermal power plants, based on the work developed within the MAINBOT (http://www.mainbot.eu) European project. Based on the information provided by a thermographic camera, the system is able to detect leakages in the collectors and pipelines. Beside the leakage detection algorithms, the system includes a particle filter-based tracking algorithm to keep the target in the field of view of the camera and to avoid the irregularities of the terrain while the robot patrols the plant. The information provided by the particle filter is further used to command a robot arm, which handles the camera and ensures that the target is always within the image. The obtained results show the suitability of the proposed approach, adding a tracking algorithm to improve the performance of the leakage detection system. Full article
(This article belongs to the Special Issue Sensors for Fluid Leak Detection) Print Edition available
Open AccessArticle Silicon Carbide-Based Hydrogen Gas Sensors for High-Temperature Applications
Sensors 2013, 13(10), 13575-13583; doi:10.3390/s131013575
Received: 1 August 2013 / Revised: 10 September 2013 / Accepted: 30 September 2013 / Published: 9 October 2013
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Abstract
We investigated SiC-based hydrogen gas sensors with metal-insulator-semiconductor (MIS) structure for high temperature process monitoring and leak detection applications in fields such as the automotive, chemical and petroleum industries. In this work, a thin tantalum oxide (Ta2O5) layer [...] Read more.
We investigated SiC-based hydrogen gas sensors with metal-insulator-semiconductor (MIS) structure for high temperature process monitoring and leak detection applications in fields such as the automotive, chemical and petroleum industries. In this work, a thin tantalum oxide (Ta2O5) layer was exploited with the purpose of sensitivity improvement, because tantalum oxide has good stability at high temperature with high permeability for hydrogen gas. Silicon carbide (SiC) was used as a substrate for high-temperature applications. We fabricated Pd/Ta2O5/SiC-based hydrogen gas sensors, and the dependence of their I-V characteristics and capacitance response properties on hydrogen concentrations were analyzed in the temperature range from room temperature to 500 °C. According to the results, our sensor shows promising performance for hydrogen gas detection at high temperatures. Full article
(This article belongs to the Special Issue Gas Sensors - 2013)
Open AccessArticle Design and Development of a Low-Cost Optical Current Sensor
Sensors 2013, 13(10), 13584-13595; doi:10.3390/s131013584
Received: 23 July 2013 / Revised: 22 September 2013 / Accepted: 30 September 2013 / Published: 10 October 2013
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Abstract
In this paper we demonstrate the design of a low-cost optical current sensor. The sensor principle is the Faraday rotation of a light beam through a magneto-optical material, SF2, when a magnetic field is present. The prototype has a high sensitivity and [...] Read more.
In this paper we demonstrate the design of a low-cost optical current sensor. The sensor principle is the Faraday rotation of a light beam through a magneto-optical material, SF2, when a magnetic field is present. The prototype has a high sensitivity and a high linearity for currents ranging from 0 up to 800 A. The error of the optical fibre sensor is smaller than 1% for electric currents over 175 A. Full article
Open AccessArticle A Thermoelectric Generator Using Porous Si Thermal Isolation
Sensors 2013, 13(10), 13596-13608; doi:10.3390/s131013596
Received: 2 August 2013 / Revised: 30 August 2013 / Accepted: 25 September 2013 / Published: 10 October 2013
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Abstract
In this paper we report on a thermoelectric generator (TEG) using thermal isolation provided by a thick porous Si layer locally formed on the Si wafer and thermocouples composed of p-doped polycrystalline Si/Al. The “hot” contacts of the thermocouples lie on the [...] Read more.
In this paper we report on a thermoelectric generator (TEG) using thermal isolation provided by a thick porous Si layer locally formed on the Si wafer and thermocouples composed of p-doped polycrystalline Si/Al. The “hot” contacts of the thermocouples lie on the porous Si layer, while the “cold” contacts lie on bulk crystalline Si. A housing was also designed and fabricated in order to transfer any external temperature change on the “hot” contacts of the thermocouples, the “cold” contacts being isolated from the “hot” contacts by a thick resist layer. The fabrication of the sensing element (Si die) is fully compatible with batch Si processing. The output power of the thermoelectric generator depends on the porous Si isolation layer thickness, porosity, structure and morphology. For a mesoporous Si layer of 60% porosity and a macroscopic temperature differential of 10 K, an output power of 0.39 μW/cm2 was measured for a 50 μm thick porous Si layer. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle On Using Maximum a Posteriori Probability Based on a Bayesian Model for Oscillometric Blood Pressure Estimation
Sensors 2013, 13(10), 13609-13623; doi:10.3390/s131013609
Received: 15 July 2013 / Revised: 2 September 2013 / Accepted: 24 September 2013 / Published: 10 October 2013
Cited by 4 | PDF Full-text (476 KB) | HTML Full-text | XML Full-text
Abstract
The maximum amplitude algorithm (MAA) is generally utilized in the estimation of the pressure values, and it uses heuristically obtained ratios of systolic and diastolic oscillometric amplitude to the mean arterial pressure (known as systolic and diastolic ratios) in order to estimate [...] Read more.
The maximum amplitude algorithm (MAA) is generally utilized in the estimation of the pressure values, and it uses heuristically obtained ratios of systolic and diastolic oscillometric amplitude to the mean arterial pressure (known as systolic and diastolic ratios) in order to estimate the systolic and diastolic pressures. This paper proposes a Bayesian model to estimate the systolic and diastolic ratios. These ratios are an improvement over the single fixed systolic and diastolic ratios used in the algorithms that are available in the literature. The proposed method shows lower mean difference (MD) with standard deviation (SD) compared to the MAA for both SBP and DBP consistently in all the five measurements. Full article
(This article belongs to the collection Sensors for Globalized Healthy Living and Wellbeing)
Open AccessArticle Eyeglasses Lens Contour Extraction from Facial Images Using an Efficient Shape Description
Sensors 2013, 13(10), 13638-13658; doi:10.3390/s131013638
Received: 24 July 2013 / Revised: 12 September 2013 / Accepted: 8 October 2013 / Published: 10 October 2013
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Abstract
This paper presents a system that automatically extracts the position of the eyeglasses and the accurate shape and size of the frame lenses in facial images. The novelty brought by this paper consists in three key contributions. The first one is an [...] Read more.
This paper presents a system that automatically extracts the position of the eyeglasses and the accurate shape and size of the frame lenses in facial images. The novelty brought by this paper consists in three key contributions. The first one is an original model for representing the shape of the eyeglasses lens, using Fourier descriptors. The second one is a method for generating the search space starting from a finite, relatively small number of representative lens shapes based on Fourier morphing. Finally, we propose an accurate lens contour extraction algorithm using a multi-stage Monte Carlo sampling technique. Multiple experiments demonstrate the effectiveness of our approach. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Video Sensor-Based Complex Scene Analysis with Granger Causality
Sensors 2013, 13(10), 13685-13707; doi:10.3390/s131013685
Received: 10 June 2013 / Revised: 10 September 2013 / Accepted: 13 September 2013 / Published: 11 October 2013
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Abstract
In this report, we propose a novel framework to explore the activity interactions and temporal dependencies between activities in complex video surveillance scenes. Under our framework, a low-level codebook is generated by an adaptive quantization with respect to the activeness criterion. The [...] Read more.
In this report, we propose a novel framework to explore the activity interactions and temporal dependencies between activities in complex video surveillance scenes. Under our framework, a low-level codebook is generated by an adaptive quantization with respect to the activeness criterion. The Hierarchical Dirichlet Processes (HDP) model is then applied to automatically cluster low-level features into atomic activities. Afterwards, the dynamic behaviors of the activities are represented as a multivariate point-process. The pair-wise relationships between activities are explicitly captured by the non-parametric Granger causality analysis, from which the activity interactions and temporal dependencies are discovered. Then, each video clip is labeled by one of the activity interactions. The results of the real-world traffic datasets show that the proposed method can achieve a high quality classification performance. Compared with traditional K-means clustering, a maximum improvement of 19.19% is achieved by using the proposed causal grouping method. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Silicon Nanomembrane Detector for Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) of Large Proteins
Sensors 2013, 13(10), 13708-13716; doi:10.3390/s131013708
Received: 8 August 2013 / Revised: 22 September 2013 / Accepted: 8 October 2013 / Published: 11 October 2013
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Abstract
We describe a MALDI-TOF ion detector based on freestanding silicon nanomembrane technology. The detector is tested in a commercial MALDI-TOF mass spectrometer with equimolar mixtures of proteins. The operating principle of the nanomembrane detector is based on phonon-assisted field emission from these [...] Read more.
We describe a MALDI-TOF ion detector based on freestanding silicon nanomembrane technology. The detector is tested in a commercial MALDI-TOF mass spectrometer with equimolar mixtures of proteins. The operating principle of the nanomembrane detector is based on phonon-assisted field emission from these silicon nanomembranes, in which impinging ion packets excite electrons in the nanomembrane to higher energy states. Thereby the electrons can overcome the vacuum barrier and escape from the surface of the nanomembrane via field emission. Ion detection is demonstrated of apomyoglobin (16,952 Da), aldolase (39,212 Da), bovine serum albumin (66,430 Da), and their equimolar mixtures. In addition to the three intact ions, a large number of fragment ions are also revealed by the silicon nanomembrane detector, which are not observable with conventional detectors. Full article
(This article belongs to the Special Issue Nanomechanical Sensors)
Open AccessArticle Tissue Discrimination by Uncorrected Autofluorescence Spectra: A Proof-of-Principle Study for Tissue-Specific Laser Surgery
Sensors 2013, 13(10), 13717-13731; doi:10.3390/s131013717
Received: 15 July 2013 / Accepted: 27 September 2013 / Published: 11 October 2013
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Abstract
Laser surgery provides a number of advantages over conventional surgery. However, it implies large risks for sensitive tissue structures due to its characteristic non-tissue-specific ablation. The present study investigates the discrimination of nine different ex vivo tissue types by using uncorrected (raw) [...] Read more.
Laser surgery provides a number of advantages over conventional surgery. However, it implies large risks for sensitive tissue structures due to its characteristic non-tissue-specific ablation. The present study investigates the discrimination of nine different ex vivo tissue types by using uncorrected (raw) autofluorescence spectra for the development of a remote feedback control system for tissue-selective laser surgery. Autofluorescence spectra (excitation wavelength 377 ± 50 nm) were measured from nine different ex vivo tissue types, obtained from 15 domestic pig cadavers. For data analysis, a wavelength range between 450 nm and 650 nm was investigated. Principal Component Analysis (PCA) and Quadratic Discriminant Analysis (QDA) were used to discriminate the tissue types. ROC analysis showed that PCA, followed by QDA, could differentiate all investigated tissue types with AUC results between 1.00 and 0.97. Sensitivity reached values between 93% and 100% and specificity values between 94% and 100%. This ex vivo study shows a high differentiation potential for physiological tissue types when performing autofluorescence spectroscopy followed by PCA and QDA. The uncorrected autofluorescence spectra are suitable for reliable tissue discrimination and have a high potential to meet the challenges necessary for an optical feedback system for tissue-specific laser surgery. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Sensing Lanthanide Metal Content in Biological Tissues with Magnetic Resonance Spectroscopy
Sensors 2013, 13(10), 13732-13743; doi:10.3390/s131013732
Received: 22 August 2013 / Revised: 22 September 2013 / Accepted: 27 September 2013 / Published: 11 October 2013
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Abstract
The development and validation of MRI contrast agents consisting of a lanthanide chelate often requires a determination of the concentration of the agent in ex vivo tissue. We have developed a protocol that uses 70% nitric acid to completely digest tissue samples [...] Read more.
The development and validation of MRI contrast agents consisting of a lanthanide chelate often requires a determination of the concentration of the agent in ex vivo tissue. We have developed a protocol that uses 70% nitric acid to completely digest tissue samples that contain Gd(III), Dy(III), Tm(III), Eu(III), or Yb(III) ions, or the MRI contrast agent gadodiamide. NMR spectroscopy of coaxial tubes containing a digested sample and a separate control solution of nitric acid was used to rapidly and easily measure the bulk magnetic susceptibility (BMS) shift caused by each lanthanide ion and gadodiamide. Each BMS shift was shown to be linearly correlated with the concentration of each lanthanide ion and gadodiamide in the 70% nitric acid solution and in digested rat kidney and liver tissues. These concentration measurements had outstanding precision, and also had good accuracy for concentrations ³10 mM for Tm(III) Eu(III), and Yb(III), and ³3 mM for Gd(III), gadodiamide, and Dy(III). Improved sample handling methods are needed to improve measurement accuracy for samples with lower concentrations. Full article
(This article belongs to the Special Issue Magnetic Resonance Sensors) Print Edition available
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Open AccessArticle A Buoy for Continuous Monitoring of Suspended Sediment Dynamics
Sensors 2013, 13(10), 13779-13801; doi:10.3390/s131013779
Received: 29 July 2013 / Revised: 5 September 2013 / Accepted: 25 September 2013 / Published: 14 October 2013
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Abstract
Knowledge of Suspended Sediments Dynamics (SSD) across spatial scales is relevant for several fields of hydrology, such as eco-hydrological processes, the operation of hydrotechnical facilities and research on varved lake sediments as geoarchives. Understanding the connectivity of sediment flux between source areas [...] Read more.
Knowledge of Suspended Sediments Dynamics (SSD) across spatial scales is relevant for several fields of hydrology, such as eco-hydrological processes, the operation of hydrotechnical facilities and research on varved lake sediments as geoarchives. Understanding the connectivity of sediment flux between source areas in a catchment and sink areas in lakes or reservoirs is of primary importance to these fields. Lacustrine sediments may serve as a valuable expansion of instrumental hydrological records for flood frequencies and magnitudes, but depositional processes and detrital layer formation in lakes are not yet fully understood. This study presents a novel buoy system designed to continuously measure suspended sediment concentration and relevant boundary conditions at a high spatial and temporal resolution in surface water bodies. The buoy sensors continuously record turbidity as an indirect measure of suspended sediment concentrations, water temperature and electrical conductivity at up to nine different water depths. Acoustic Doppler current meters and profilers measure current velocities along a vertical profile from the water surface to the lake bottom. Meteorological sensors capture the atmospheric boundary conditions as main drivers of lake dynamics. It is the high spatial resolution of multi-point turbidity measurements, the dual-sensor velocity measurements and the temporally synchronous recording of all sensors along the water column that sets the system apart from existing buoy systems. Buoy data collected during a 4-month field campaign in Lake Mondsee demonstrate the potential and effectiveness of the system in monitoring suspended sediment dynamics. Observations were related to stratification and mixing processes in the lake and increased turbidity close to a catchment outlet during flood events. The rugged buoy design assures continuous operation in terms of stability, energy management and sensor logging throughout the study period. We conclude that the buoy is a suitable tool for continuous monitoring of suspended sediment concentrations and general dynamics in fresh water bodies. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle A Coded Structured Light System Based on Primary Color Stripe Projection and Monochrome Imaging
Sensors 2013, 13(10), 13802-13819; doi:10.3390/s131013802
Received: 1 August 2013 / Revised: 13 September 2013 / Accepted: 8 October 2013 / Published: 14 October 2013
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Abstract
Coded Structured Light techniques represent one of the most attractive research areas within the field of optical metrology. The coding procedures are typically based on projecting either a single pattern or a temporal sequence of patterns to provide 3D surface data. In [...] Read more.
Coded Structured Light techniques represent one of the most attractive research areas within the field of optical metrology. The coding procedures are typically based on projecting either a single pattern or a temporal sequence of patterns to provide 3D surface data. In this context, multi-slit or stripe colored patterns may be used with the aim of reducing the number of projected images. However, color imaging sensors require the use of calibration procedures to address crosstalk effects between different channels and to reduce the chromatic aberrations. In this paper, a Coded Structured Light system has been developed by integrating a color stripe projector and a monochrome camera. A discrete coding method, which combines spatial and temporal information, is generated by sequentially projecting and acquiring a small set of fringe patterns. The method allows the concurrent measurement of geometrical and chromatic data by exploiting the benefits of using a monochrome camera. The proposed methodology has been validated by measuring nominal primitive geometries and free-form shapes. The experimental results have been compared with those obtained by using a time-multiplexing gray code strategy. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Potential of Visible and Near Infrared Spectroscopy and Pattern Recognition for Rapid Quantification of Notoginseng Powder with Adulterants
Sensors 2013, 13(10), 13820-13834; doi:10.3390/s131013820
Received: 22 August 2013 / Revised: 13 September 2013 / Accepted: 24 September 2013 / Published: 14 October 2013
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Abstract
Notoginseng is a classical traditional Chinese medical herb, which is of high economic and medical value. Notoginseng powder (NP) could be easily adulterated with Sophora flavescens powder (SFP) or corn flour (CF), because of their similar tastes and appearances and much lower [...] Read more.
Notoginseng is a classical traditional Chinese medical herb, which is of high economic and medical value. Notoginseng powder (NP) could be easily adulterated with Sophora flavescens powder (SFP) or corn flour (CF), because of their similar tastes and appearances and much lower cost for these adulterants. The objective of this study is to quantify the NP content in adulterated NP by using a rapid and non-destructive visible and near infrared (Vis-NIR) spectroscopy method. Three wavelength ranges of visible spectra, short-wave near infrared spectra (SNIR) and long-wave near infrared spectra (LNIR) were separately used to establish the model based on two calibration methods of partial least square regression (PLSR) and least-squares support vector machines (LS-SVM), respectively. Competitive adaptive reweighted sampling (CARS) was conducted to identify the most important wavelengths/variables that had the greatest influence on the adulterant quantification throughout the whole wavelength range. The CARS-PLSR models based on LNIR were determined as the best models for the quantification of NP adulterated with SFP, CF, and their mixtures, in which the rP values were 0.940, 0.939, and 0.867 for the three models respectively. The research demonstrated the potential of the Vis-NIR spectroscopy technique for the rapid and non-destructive quantification of NP containing adulterants. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle G3 Assisted Rational Design of Chemical Sensor Array Using Carbonitrile Neutral Receptors
Sensors 2013, 13(10), 13835-13860; doi:10.3390/s131013835
Received: 20 March 2013 / Revised: 30 July 2013 / Accepted: 16 August 2013 / Published: 14 October 2013
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Abstract
Combined computational and experimental strategies for the systematic design of chemical sensor arrays using carbonitrile neutral receptors are presented. Binding energies of acetonitrile, n-pentylcarbonitrile and malononitrile with Ca(II), Mg(II), Be(II) and H+ have been investigated with the B3LYP, G3, CBS-QB3, [...] Read more.
Combined computational and experimental strategies for the systematic design of chemical sensor arrays using carbonitrile neutral receptors are presented. Binding energies of acetonitrile, n-pentylcarbonitrile and malononitrile with Ca(II), Mg(II), Be(II) and H+ have been investigated with the B3LYP, G3, CBS-QB3, G4 and MQZVP methods, showing a general trend H+ > Be(II) > Mg(II) > Ca(II). Hydrogen bonding, donor-acceptor and cation-lone pair electron simple models were employed in evaluating the performance of computational methods. Mg(II) is bound to acetonitrile in water by 12.5 kcal/mol, and in the gas phase the receptor is more strongly bound by 33.3 kcal/mol to Mg(II) compared to Ca(II). Interaction of bound cations with carbonitrile reduces the energies of the MOs involved in the proposed σ-p conjugated network. The planar malononitrile-Be(II) complex possibly involves a π-network with a cationic methylene carbon. Fabricated potentiometric chemical sensors show distinct signal patterns that can be exploited in sensor array applications. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Development of a Real Time Sparse Non-Negative Matrix Factorization Module for Cochlear Implants by Using xPC Target
Sensors 2013, 13(10), 13861-13878; doi:10.3390/s131013861
Received: 19 July 2013 / Revised: 9 September 2013 / Accepted: 26 September 2013 / Published: 14 October 2013
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Abstract
Cochlear implants (CIs) require efficient speech processing to maximize information transmission to the brain, especially in noise. A novel CI processing strategy was proposed in our previous studies, in which sparsity-constrained non-negative matrix factorization (NMF) was applied to the envelope matrix in [...] Read more.
Cochlear implants (CIs) require efficient speech processing to maximize information transmission to the brain, especially in noise. A novel CI processing strategy was proposed in our previous studies, in which sparsity-constrained non-negative matrix factorization (NMF) was applied to the envelope matrix in order to improve the CI performance in noisy environments. It showed that the algorithm needs to be adaptive, rather than fixed, in order to adjust to acoustical conditions and individual characteristics. Here, we explore the benefit of a system that allows the user to adjust the signal processing in real time according to their individual listening needs and their individual hearing capabilities. In this system, which is based on MATLABR , SIMULINKR and the xPC TargetTM environment, the input/outupt (I/O) boards are interfaced between the SIMULINK blocks and the CI stimulation system, such that the output can be controlled successfully in the manner of a hardware-in-the-loop (HIL) simulation, hence offering a convenient way to implement a real time signal processing module that does not require any low level language. The sparsity constrained parameter of the algorithm was adapted online subjectively during an experiment with normal-hearing subjects and noise vocoded speech simulation. Results show that subjects chose different parameter values according to their own intelligibility preferences, indicating that adaptive real time algorithms are beneficial to fully explore subjective preferences. We conclude that the adaptive real time systems are beneficial for the experimental design, and such systems allow one to conduct psychophysical experiments with high ecological validity. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in the UK 2013)
Open AccessArticle A Fast Smoothing Algorithm for Post-Processing of Surface Reflectance Spectra Retrieved from Airborne Imaging Spectrometer Data
Sensors 2013, 13(10), 13879-13891; doi:10.3390/s131013879
Received: 20 August 2013 / Revised: 26 September 2013 / Accepted: 29 September 2013 / Published: 14 October 2013
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Abstract
Surface reflectance spectra retrieved from remotely sensed hyperspectral imaging data using radiative transfer models often contain residual atmospheric absorption and scattering effects. The reflectance spectra may also contain minor artifacts due to errors in radiometric and spectral calibrations. We have developed a [...] Read more.
Surface reflectance spectra retrieved from remotely sensed hyperspectral imaging data using radiative transfer models often contain residual atmospheric absorption and scattering effects. The reflectance spectra may also contain minor artifacts due to errors in radiometric and spectral calibrations. We have developed a fast smoothing technique for post-processing of retrieved surface reflectance spectra. In the present spectral smoothing technique, model-derived reflectance spectra are first fit using moving filters derived with a cubic spline smoothing algorithm. A common gain curve, which contains minor artifacts in the model-derived reflectance spectra, is then derived. This gain curve is finally applied to all of the reflectance spectra in a scene to obtain the spectrally smoothed surface reflectance spectra. Results from analysis of hyperspectral imaging data collected with the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data are given. Comparisons between the smoothed spectra and those derived with the empirical line method are also presented. Full article
(This article belongs to the Special Issue Spectral Imaging at the Microscale and Beyond)
Open AccessArticle Multi-Channel Hyperspectral Fluorescence Detection Excited by Coupled Plasmon-Waveguide Resonance
Sensors 2013, 13(10), 13892-13902; doi:10.3390/s131013892
Received: 5 August 2013 / Revised: 6 October 2013 / Accepted: 8 October 2013 / Published: 14 October 2013
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Abstract
We propose in this paper a biosensor scheme based on coupled plasmon-waveguide resonance (CPWR) excited fluorescence spectroscopy. A symmetrical structure that offers higher surface electric field strengths, longer surface propagation lengths and depths is developed to support guided waveguide modes for the [...] Read more.
We propose in this paper a biosensor scheme based on coupled plasmon-waveguide resonance (CPWR) excited fluorescence spectroscopy. A symmetrical structure that offers higher surface electric field strengths, longer surface propagation lengths and depths is developed to support guided waveguide modes for the efficient excitation of fluorescence. The optimal parameters for the sensor films are theoretically and experimentally investigated, leading to a detection limit of 0.1 nM (for a Cy5 solution). Multiplex analysis possible with the fluorescence detection is further advanced by employing the hyperspectral fluorescence technique to record the full spectra for every pixel on the sample plane. We demonstrate experimentally that highly overlapping fluorescence (Cy5 and Dylight680) can be distinguished and ratios of different emission sources can be determined accurately. This biosensor shows great potential for multiplex detections of fluorescence analytes. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Omnidirectional Structured Light in a Flexible Configuration
Sensors 2013, 13(10), 13903-13916; doi:10.3390/s131013903
Received: 14 August 2013 / Revised: 20 September 2013 / Accepted: 23 September 2013 / Published: 14 October 2013
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Abstract
Structured light is a perception method that allows us to obtain 3D information from images of the scene by projecting synthetic features with a light emitter. Traditionally, this method considers a rigid configuration, where the position and orientation of the light emitter [...] Read more.
Structured light is a perception method that allows us to obtain 3D information from images of the scene by projecting synthetic features with a light emitter. Traditionally, this method considers a rigid configuration, where the position and orientation of the light emitter with respect to the camera are known and calibrated beforehand. In this paper we propose a new omnidirectional structured light system in flexible configuration, which overcomes the rigidness of the traditional structured light systems. We propose the use of an omnidirectional camera combined with a conic pattern light emitter. Since the light emitter is visible in the omnidirectional image, the computation of its location is possible. With this information and the projected conic in the omnidirectional image, we are able to compute the conic reconstruction, i.e., the 3D information of the conic in the space. This reconstruction considers the recovery of the depth and orientation of the scene surface where the conic pattern is projected. One application of our proposed structured light system in flexible configuration consists of a wearable omnicamera with a low-cost laser in hand for visual impaired personal assistance. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle An InN/InGaN Quantum Dot Electrochemical Biosensor for Clinical Diagnosis
Sensors 2013, 13(10), 13917-13927; doi:10.3390/s131013917
Received: 18 July 2013 / Revised: 11 September 2013 / Accepted: 4 October 2013 / Published: 15 October 2013
Cited by 4 | PDF Full-text (493 KB) | HTML Full-text | XML Full-text
Abstract
Low-dimensional InN/InGaN quantum dots (QDs) are demonstrated for realizing highly sensitive and efficient potentiometric biosensors owing to their unique electronic properties. The InN QDs are biochemically functionalized. The fabricated biosensor exhibits high sensitivity of 97 mV/decade with fast output response within two [...] Read more.
Low-dimensional InN/InGaN quantum dots (QDs) are demonstrated for realizing highly sensitive and efficient potentiometric biosensors owing to their unique electronic properties. The InN QDs are biochemically functionalized. The fabricated biosensor exhibits high sensitivity of 97 mV/decade with fast output response within two seconds for the detection of cholesterol in the logarithmic concentration range of 1 × 10−6 M to 1 × 10−3 M. The selectivity and reusability of the biosensor are excellent and it shows negligible response to common interferents such as uric acid and ascorbic acid. We also compare the biosensing properties of the InN QDs with those of an InN thin film having the same surface properties, i.e., high density of surface donor states, but different morphology and electronic properties. The sensitivity of the InN QDs-based biosensor is twice that of the InN thin film-based biosensor, the EMF is three times larger, and the response time is five times shorter. A bare InGaN layer does not produce a stable response. Hence, the superior biosensing properties of the InN QDs are governed by their unique surface properties together with the zero-dimensional electronic properties. Altogether, the InN QDs-based biosensor reveals great potential for clinical diagnosis applications. Full article
Open AccessArticle Biodiversity Assessment Using Hierarchical Agglomerative Clustering and Spectral Unmixing over Hyperspectral Images
Sensors 2013, 13(10), 13949-13959; doi:10.3390/s131013949
Received: 7 August 2013 / Revised: 29 September 2013 / Accepted: 30 September 2013 / Published: 15 October 2013
Cited by 2 | PDF Full-text (216 KB) | HTML Full-text | XML Full-text
Abstract
Hyperspectral images represent an important source of information to assess ecosystem biodiversity. In particular, plant species richness is a primary indicator of biodiversity. This paper uses spectral variance to predict vegetation richness, known as Spectral Variation Hypothesis. Hierarchical agglomerative clustering is our [...] Read more.
Hyperspectral images represent an important source of information to assess ecosystem biodiversity. In particular, plant species richness is a primary indicator of biodiversity. This paper uses spectral variance to predict vegetation richness, known as Spectral Variation Hypothesis. Hierarchical agglomerative clustering is our primary tool to retrieve clusters whose Shannon entropy should reflect species richness on a given zone. However, in a high spectral mixing scenario, an additional unmixing step, just before entropy computation, is required; cluster centroids are enough for the unmixing process. Entropies computed using the proposed method correlate well with the ones calculated directly from synthetic and field data. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Real-Time Label-Free Surface Plasmon Resonance Biosensing with Gold Nanohole Arrays Fabricated by Nanoimprint Lithography
Sensors 2013, 13(10), 13960-13968; doi:10.3390/s131013960
Received: 16 September 2013 / Revised: 10 October 2013 / Accepted: 11 October 2013 / Published: 16 October 2013
Cited by 6 | PDF Full-text (486 KB) | HTML Full-text | XML Full-text
Abstract
In this work we present a surface plasmon resonance sensor based on enhanced optical transmission through sub-wavelength nanohole arrays. This technique is extremely sensitive to changes in the refractive index of the surrounding medium which result in a modulation of the transmitted [...] Read more.
In this work we present a surface plasmon resonance sensor based on enhanced optical transmission through sub-wavelength nanohole arrays. This technique is extremely sensitive to changes in the refractive index of the surrounding medium which result in a modulation of the transmitted light. The periodic gold nanohole array sensors were fabricated by high-throughput thermal nanoimprint lithography. Square periodic arrays with sub-wavelength hole diameters were obtained and characterized. Using solutions with known refractive index, the array sensitivities were obtained. Finally, protein absorption was monitored in real-time demonstrating the label-free biosensing capabilities of the fabricated devices. Full article
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Open AccessArticle Identification of Volatiles Produced by Cladosporium cladosporioides CL-1, a Fungal Biocontrol Agent That Promotes Plant Growth
Sensors 2013, 13(10), 13969-13977; doi:10.3390/s131013969
Received: 1 August 2013 / Revised: 12 October 2013 / Accepted: 15 October 2013 / Published: 16 October 2013
Cited by 9 | PDF Full-text (314 KB) | HTML Full-text | XML Full-text
Abstract
Certain microbial Volatile Organic Compounds (VOCs) have been reported to enhance the growth and development of plants. The biocontrol fungi, Cladosporium cladosporioides CL-1 significantly improved the growth of tobacco seedlings in vitro when they were co-cultivated without physical contact. SPME Quadrupole GC/MS/MS [...] Read more.
Certain microbial Volatile Organic Compounds (VOCs) have been reported to enhance the growth and development of plants. The biocontrol fungi, Cladosporium cladosporioides CL-1 significantly improved the growth of tobacco seedlings in vitro when they were co-cultivated without physical contact. SPME Quadrupole GC/MS/MS revealed that CL-1 emited the volatiles α-pinene, (−)-trans-caryophyllene, tetrahydro-2,2,5,5-tetramethylfuran, dehydroaromadendrene, and (+)-sativene. Potential roles of these volatiles in plant growth and development are discussed. Even though there were several fungal VOCs reported in the past that could influence plant growth, their exact mechanisms of action are not fully known. Fungal VOC-mediated plant growth promotion requires in-depth study in order for this technology to be used in large scale for crops, especially those grown under greenhouse conditions. Full article
Open AccessArticle Accelerometer-Based Event Detector for Low-Power Applications
Sensors 2013, 13(10), 13978-13997; doi:10.3390/s131013978
Received: 23 July 2013 / Revised: 2 October 2013 / Accepted: 8 October 2013 / Published: 16 October 2013
Cited by 1 | PDF Full-text (1419 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, an adaptive, autocovariance-based event detection algorithm is proposed, which can be used with micro-electro-mechanical systems (MEMS) accelerometer sensors to build inexpensive and power efficient event detectors. The algorithm works well with low signal-to-noise ratio input signals, and its computational [...] Read more.
In this paper, an adaptive, autocovariance-based event detection algorithm is proposed, which can be used with micro-electro-mechanical systems (MEMS) accelerometer sensors to build inexpensive and power efficient event detectors. The algorithm works well with low signal-to-noise ratio input signals, and its computational complexity is very low, allowing its utilization on inexpensive low-end embedded sensor devices. The proposed algorithm decreases its energy consumption by lowering its duty cycle, as much as the event to be detected allows it. The performance of the algorithm is tested and compared to the conventional filter-based approach. The comparison was performed in an application where illegal entering of vehicles into restricted areas was detected. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering 2013)
Open AccessArticle Dynamic Task Allocation in Multi-Hop Multimedia Wireless Sensor Networks with Low Mobility
Sensors 2013, 13(10), 13998-14028; doi:10.3390/s131013998
Received: 19 August 2013 / Revised: 4 October 2013 / Accepted: 9 October 2013 / Published: 16 October 2013
Cited by 3 | PDF Full-text (763 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a task allocation-oriented framework to enable efficient in-network processing and cost-effective multi-hop resource sharing for dynamic multi-hop multimedia wireless sensor networks with low node mobility, e.g., pedestrian speeds. The proposed system incorporates a fast task reallocation algorithm to quickly [...] Read more.
This paper presents a task allocation-oriented framework to enable efficient in-network processing and cost-effective multi-hop resource sharing for dynamic multi-hop multimedia wireless sensor networks with low node mobility, e.g., pedestrian speeds. The proposed system incorporates a fast task reallocation algorithm to quickly recover from possible network service disruptions, such as node or link failures. An evolutional self-learning mechanism based on a genetic algorithm continuously adapts the system parameters in order to meet the desired application delay requirements, while also achieving a sufficiently long network lifetime. Since the algorithm runtime incurs considerable time delay while updating task assignments, we introduce an adaptive window size to limit the delay periods and ensure an up-to-date solution based on node mobility patterns and device processing capabilities. To the best of our knowledge, this is the first study that yields multi-objective task allocation in a mobile multi-hop wireless environment under dynamic conditions. Simulations are performed in various settings, and the results show considerable performance improvement in extending network lifetime compared to heuristic mechanisms. Furthermore, the proposed framework provides noticeable reduction in the frequency of missing application deadlines. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle Simultaneous Determination of Dopamine, Serotonin and Ascorbic Acid at a Glassy Carbon Electrode Modified with Carbon-Spheres
Sensors 2013, 13(10), 14029-14040; doi:10.3390/s131014029
Received: 7 September 2013 / Revised: 6 October 2013 / Accepted: 12 October 2013 / Published: 16 October 2013
Cited by 6 | PDF Full-text (727 KB) | HTML Full-text | XML Full-text
Abstract
A novel glassy carbon electrode (GCE) modified with carbon-spheres has been fabricated through a simple casting procedure. The modified GCE displays high selectivity and excellent electrochemical catalytic activities towards dopamine (DA), serotonin (5-HT), and ascorbic acid (AA). In the co-existence system, the [...] Read more.
A novel glassy carbon electrode (GCE) modified with carbon-spheres has been fabricated through a simple casting procedure. The modified GCE displays high selectivity and excellent electrochemical catalytic activities towards dopamine (DA), serotonin (5-HT), and ascorbic acid (AA). In the co-existence system, the peak separations between AA and DA, DA and 5-HT, and AA and 5-HT are large up to 230, 180, and 410 mV, respectively. Differential pulse voltammetry (DPV) has been employed to simultaneously detect DA, 5-HT, and AA, and the linear calibration curves for DA, 5-HT, and AA are obtained in the range of 20.0–150.0 μM, 40.0–750.0 μM and 300.0–2,000.0 μM with detection limits (S/N = 3) of 2.0 μM, 0.7 μM and 0.6 μM, respectively. The proposed electrode has been applied to detect DA, 5-HT, and AA in real samples using standard addition method with satisfactory results. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Acoustic Emission Source Location Using a Distributed Feedback Fiber Laser Rosette
Sensors 2013, 13(10), 14041-14054; doi:10.3390/s131014041
Received: 16 August 2013 / Revised: 22 September 2013 / Accepted: 11 October 2013 / Published: 17 October 2013
Cited by 2 | PDF Full-text (1285 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes an approach for acoustic emission (AE) source localization in a large marble stone using distributed feedback (DFB) fiber lasers. The aim of this study is to detect damage in structures such as those found in civil applications. The directional [...] Read more.
This paper proposes an approach for acoustic emission (AE) source localization in a large marble stone using distributed feedback (DFB) fiber lasers. The aim of this study is to detect damage in structures such as those found in civil applications. The directional sensitivity of DFB fiber laser is investigated by calculating location coefficient using a method of digital signal analysis. In this, autocorrelation is used to extract the location coefficient from the periodic AE signal and wavelet packet energy is calculated to get the location coefficient of a burst AE source. Normalization is processed to eliminate the influence of distance and intensity of AE source. Then a new location algorithm based on the location coefficient is presented and tested to determine the location of AE source using a Delta (Δ) DFB fiber laser rosette configuration. The advantage of the proposed algorithm over the traditional methods based on fiber Bragg Grating (FBG) include the capability of: having higher strain resolution for AE detection and taking into account two different types of AE source for location. Full article
(This article belongs to the Section Physical Sensors)
Open AccessCommunication Highly Sensitive Refractive Index Sensor Based on Adiabatically Tapered Microfiber Long Period Gratings
Sensors 2013, 13(10), 14055-14063; doi:10.3390/s131014055
Received: 23 July 2013 / Accepted: 9 October 2013 / Published: 17 October 2013
Cited by 9 | PDF Full-text (409 KB) | HTML Full-text | XML Full-text
Abstract
We demonstrate a refractive index sensor based on a long period grating (LPG) inscribed in a special photosensitive microfiber with double-clad profile. The fiber is tapered gradually enough to ensure the adiabaticity of the fiber taper. In other words, the resulting insertion [...] Read more.
We demonstrate a refractive index sensor based on a long period grating (LPG) inscribed in a special photosensitive microfiber with double-clad profile. The fiber is tapered gradually enough to ensure the adiabaticity of the fiber taper. In other words, the resulting insertion loss is sufficiently small. The boron and germanium co-doped inner cladding makes it suitable for inscribing gratings into its tapered form. The manner of wavelength shift for refractive indices (RIs) differs from conventional LPG, and the refractive index detection limit is 1.67 × 10−5. Full article
(This article belongs to the Special Issue Photonic Sensors for Industrial, Environmental and Health Monitoring)
Open AccessArticle An Electronic Tongue Designed to Detect Ammonium Nitrate in Aqueous Solutions
Sensors 2013, 13(10), 14064-14078; doi:10.3390/s131014064
Received: 20 August 2013 / Revised: 2 October 2013 / Accepted: 15 October 2013 / Published: 18 October 2013
Cited by 4 | PDF Full-text (544 KB) | HTML Full-text | XML Full-text
Abstract
An electronic tongue has been developed to monitor the presence of ammonium nitrate in water. It is based on pulse voltammetry and consists of an array of eight working electrodes (Au; Pt; Rh; Ir; Cu; Co; Ag and Ni) encapsulated in a [...] Read more.
An electronic tongue has been developed to monitor the presence of ammonium nitrate in water. It is based on pulse voltammetry and consists of an array of eight working electrodes (Au; Pt; Rh; Ir; Cu; Co; Ag and Ni) encapsulated in a stainless steel cylinder. In a first step the electrochemical response of the different electrodes was studied in the presence of ammonium nitrate in water in order to further design the wave form used in the voltammetric tongue. The response of the electronic tongue was then tested in the presence of a set of 15 common inorganic salts; i.e.; NH4NO3; MgSO4; NH4Cl; NaCl; Na2CO3; (NH4)2SO4; MgCl2; Na3PO4; K2SO4; K2CO3; CaCl2; NaH2PO4; KCl; NaNO3; K2HPO4. A PCA plot showed a fairly good discrimination between ammonium nitrate and the remaining salts studied. In addition Fuzzy Art map analyses determined that the best classification was obtained using the Pt; Co; Cu and Ni electrodes. Moreover; PLS regression allowed the creation of a model to correlate the voltammetric response of the electrodes with concentrations of ammonium nitrate in the presence of potential interferents such as ammonium chloride and sodium nitrate. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle A Wearable Inertial Measurement Unit for Long-Term Monitoring in the Dependency Care Area
Sensors 2013, 13(10), 14079-14104; doi:10.3390/s131014079
Received: 12 July 2013 / Revised: 27 September 2013 / Accepted: 29 September 2013 / Published: 18 October 2013
Cited by 12 | PDF Full-text (464 KB) | HTML Full-text | XML Full-text
Abstract
Human movement analysis is a field of wide interest since it enables the assessment of a large variety of variables related to quality of life. Human movement can be accurately evaluated through Inertial Measurement Units (IMU), which are wearable and comfortable devices [...] Read more.
Human movement analysis is a field of wide interest since it enables the assessment of a large variety of variables related to quality of life. Human movement can be accurately evaluated through Inertial Measurement Units (IMU), which are wearable and comfortable devices with long battery life. The IMU’s movement signals might be, on the one hand, stored in a digital support, in which an analysis is performed a posteriori. On the other hand, the signal analysis might take place in the same IMU at the same time as the signal acquisition through online classifiers. The new sensor system presented in this paper is designed for both collecting movement signals and analyzing them in real-time. This system is a flexible platform useful for collecting data via a triaxial accelerometer, a gyroscope and a magnetometer, with the possibility to incorporate other information sources in real-time. A µSD card can store all inertial data and a Bluetooth module is able to send information to other external devices and receive data from other sources. The system presented is being used in the real-time detection and analysis of Parkinson’s disease symptoms, in gait analysis, and in a fall detection system. Full article
(This article belongs to the collection Sensors for Globalized Healthy Living and Wellbeing)
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Open AccessArticle Pandoraea sp. RB-44, A Novel Quorum Sensing Soil Bacterium
Sensors 2013, 13(10), 14121-14132; doi:10.3390/s131014121
Received: 26 August 2013 / Revised: 20 September 2013 / Accepted: 30 September 2013 / Published: 18 October 2013
Cited by 15 | PDF Full-text (214 KB) | HTML Full-text | XML Full-text
Abstract
Proteobacteria are known to communicate via signaling molecules and this process is known as quorum sensing. The most commonly studied quorum sensing molecules are N-acylhomoserine lactones (AHLs) that consists of a homoserine lactone moiety and an N-acyl side chain with [...] Read more.
Proteobacteria are known to communicate via signaling molecules and this process is known as quorum sensing. The most commonly studied quorum sensing molecules are N-acylhomoserine lactones (AHLs) that consists of a homoserine lactone moiety and an N-acyl side chain with various chain lengths and degrees of saturation at the C-3 position. We have isolated a bacterium, RB-44, from a site which was formally a landfill dumping ground. Using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry analysis, this isolate was identified as a Pandoraea sp.which was then screened for AHL production using biosensors which indicated its quorum sensing properties. To identify the AHL profile of Pandoraea sp. RB-44, we used high resolution tandem mass spectrometry confirming that this isolate produced N-octanoylhomoserine lactone (C8-HSL). To the best of our knowledge, this is the first report that showed quorum sensing activity exhibited by Pandoraea sp. Our data add Pandoraea sp. to the growing number of bacteria that possess QS systems. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Multi Sensor Fusion Framework for Indoor-Outdoor Localization of Limited Resource Mobile Robots
Sensors 2013, 13(10), 14133-14160; doi:10.3390/s131014133
Received: 26 August 2013 / Revised: 9 October 2013 / Accepted: 10 October 2013 / Published: 21 October 2013
Cited by 9 | PDF Full-text (11829 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a sensor fusion framework that improves the localization of mobile robots with limited computational resources. It employs an event based Kalman Filter to combine the measurements of a global sensor and an inertial measurement unit (IMU) on an event [...] Read more.
This paper presents a sensor fusion framework that improves the localization of mobile robots with limited computational resources. It employs an event based Kalman Filter to combine the measurements of a global sensor and an inertial measurement unit (IMU) on an event based schedule, using fewer resources (execution time and bandwidth) but with similar performance when compared to the traditional methods. The event is defined to reflect the necessity of the global information, when the estimation error covariance exceeds a predefined limit. The proposed experimental platforms are based on the LEGO Mindstorm NXT, and consist of a differential wheel mobile robot navigating indoors with a zenithal camera as global sensor, and an Ackermann steering mobile robot navigating outdoors with a SBG Systems GPS accessed through an IGEP board that also serves as datalogger. The IMU in both robots is built using the NXT motor encoders along with one gyroscope, one compass and two accelerometers from Hitecnic, placed according to a particle based dynamic model of the robots. The tests performed reflect the correct performance and low execution time of the proposed framework. The robustness and stability is observed during a long walk test in both indoors and outdoors environments. Full article
Open AccessArticle Development of Anodic Titania Nanotubes for Application in High Sensitivity Amperometric Glucose and Uric Acid Biosensors
Sensors 2013, 13(10), 14161-14174; doi:10.3390/s131014161
Received: 24 August 2013 / Revised: 29 September 2013 / Accepted: 9 October 2013 / Published: 21 October 2013
Cited by 3 | PDF Full-text (614 KB) | HTML Full-text | XML Full-text
Abstract
The purpose of this study was to develop novel nanoscale biosensors using titania nanotubes (TNTs) made by anodization. Titania nanotubes were produced on pure titanium sheets by anodization at room temperature. In this research, the electrolyte composition ethylene glycol 250 mL/NH4 [...] Read more.
The purpose of this study was to develop novel nanoscale biosensors using titania nanotubes (TNTs) made by anodization. Titania nanotubes were produced on pure titanium sheets by anodization at room temperature. In this research, the electrolyte composition ethylene glycol 250 mL/NH4F 1.5 g/DI water 20 mL was found to produce the best titania nanotubes array films for application in amperometric biosensors. The amperometric results exhibit an excellent linearity for uric acid (UA) concentrations in the range between 2 and 14 mg/dL, with 23.3 (µA·cm−2)·(mg/dL)−1 UA sensitivity, and a correlation coefficient of 0.993. The glucose biosensor presented a good linear relationship in the lower glucose concentration range between 50 and 125 mg/dL, and the corresponding sensitivity was approximately 249.6 (µA·cm−2)·(100 mg/dL)−1 glucose, with a correlation coefficient of 0.973. Full article
(This article belongs to the Special Issue Nanotube and Nanowire Sensors)
Open AccessArticle Remote Driven and Read MEMS Sensors for Harsh Environments
Sensors 2013, 13(10), 14175-14188; doi:10.3390/s131014175
Received: 4 September 2013 / Revised: 29 September 2013 / Accepted: 29 September 2013 / Published: 21 October 2013
Cited by 2 | PDF Full-text (415 KB) | HTML Full-text | XML Full-text
Abstract
The utilization of high accuracy sensors in harsh environments has been limited by the temperature constraints of the control electronics that must be co-located with the sensor. Several methods of remote interrogation for resonant sensors are presented in this paper which would [...] Read more.
The utilization of high accuracy sensors in harsh environments has been limited by the temperature constraints of the control electronics that must be co-located with the sensor. Several methods of remote interrogation for resonant sensors are presented in this paper which would allow these sensors to be extended to harsh environments. This work in particular demonstrates for the first time the ability to acoustically drive a silicon comb drive resonator into resonance and electromagnetically couple to the resonator to read its frequency. The performance of this system was studied as a function of standoff distance demonstrating the ability to excite and read the device from 22 cm when limited to drive powers of 30 mW. A feedback architecture was implemented that allowed the resonator to be driven into resonance from broadband noise and a standoff distance of 15 cm was demonstrated. It is emphasized that no junction-based electronic device was required to be co-located with the resonator, opening the door for the use of silicon-based, high accuracy MEMS devices in high temperature wireless applications. Full article
(This article belongs to the Special Issue Sensors for Harsh-Environment Applications)
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Open AccessArticle Quorum Sensing Activity of Enterobacter asburiae Isolated from Lettuce Leaves
Sensors 2013, 13(10), 14189-14199; doi:10.3390/s131014189
Received: 19 August 2013 / Revised: 26 September 2013 / Accepted: 30 September 2013 / Published: 22 October 2013
Cited by 19 | PDF Full-text (323 KB) | HTML Full-text | XML Full-text
Abstract
Bacterial communication or quorum sensing (QS) is achieved via sensing of QS signaling molecules consisting of oligopeptides in Gram-positive bacteria and N-acyl homoserine lactones (AHL) in most Gram-negative bacteria. In this study, Enterobacteriaceae isolates from Batavia lettuce were screened for AHL production. [...] Read more.
Bacterial communication or quorum sensing (QS) is achieved via sensing of QS signaling molecules consisting of oligopeptides in Gram-positive bacteria and N-acyl homoserine lactones (AHL) in most Gram-negative bacteria. In this study, Enterobacteriaceae isolates from Batavia lettuce were screened for AHL production. Enterobacter asburiae, identified by matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) was found to produce short chain AHLs. High resolution triple quadrupole liquid chromatography mass spectrometry (LC/MS) analysis of the E. asburiae spent supernatant confirmed the production of N-butanoyl homoserine lactone (C4-HSL) and N–hexanoyl homoserine lactone (C6-HSL). To the best of our knowledge, this is the first report of AHL production by E. asburiae. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle A Highly Sensitive Fiber Optic Sensor Based on Two-Core Fiber for Refractive Index Measurement
Sensors 2013, 13(10), 14200-14213; doi:10.3390/s131014200
Received: 18 July 2013 / Revised: 12 September 2013 / Accepted: 13 September 2013 / Published: 22 October 2013
Cited by 6 | PDF Full-text (1344 KB) | HTML Full-text | XML Full-text
Abstract
A simple and compact fiber optic sensor based on a two-core fiber is demonstrated for high-performance measurements of refractive indices (RI) of liquids. In order to demonstrate the suitability of the proposed sensor to perform high-sensitivity sensing in a variety of applications, [...] Read more.
A simple and compact fiber optic sensor based on a two-core fiber is demonstrated for high-performance measurements of refractive indices (RI) of liquids. In order to demonstrate the suitability of the proposed sensor to perform high-sensitivity sensing in a variety of applications, the sensor has been used to measure the RI of binary liquid mixtures. Such measurements can accurately determine the salinity of salt water solutions, and detect the water content of adulterated alcoholic beverages. The largest sensitivity of the RI sensor that has been experimentally demonstrated is 3,119 nm per Refractive Index Units (RIU) for the RI range from 1.3160 to 1.3943. On the other hand, our results suggest that the sensitivity can be enhanced up to 3485.67 nm/RIU approximately for the same RI range. Full article
(This article belongs to the Special Issue Photonic Sensors for Industrial, Environmental and Health Monitoring)
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Review

Jump to: Research

Open AccessReview Real-Time Human Ambulation, Activity, and Physiological Monitoring: Taxonomy of Issues, Techniques, Applications, Challenges and Limitations
Sensors 2013, 13(10), 12852-12902; doi:10.3390/s131012852
Received: 19 July 2013 / Revised: 2 September 2013 / Accepted: 10 September 2013 / Published: 25 September 2013
Cited by 11 | PDF Full-text (962 KB) | HTML Full-text | XML Full-text
Abstract
Automated methods of real-time, unobtrusive, human ambulation, activity, and wellness monitoring and data analysis using various algorithmic techniques have been subjects of intense research. The general aim is to devise effective means of addressing the demands of assisted living, rehabilitation, and clinical [...] Read more.
Automated methods of real-time, unobtrusive, human ambulation, activity, and wellness monitoring and data analysis using various algorithmic techniques have been subjects of intense research. The general aim is to devise effective means of addressing the demands of assisted living, rehabilitation, and clinical observation and assessment through sensor-based monitoring. The research studies have resulted in a large amount of literature. This paper presents a holistic articulation of the research studies and offers comprehensive insights along four main axes: distribution of existing studies; monitoring device framework and sensor types; data collection, processing and analysis; and applications, limitations and challenges. The aim is to present a systematic and most complete study of literature in the area in order to identify research gaps and prioritize future research directions. Full article
(This article belongs to the collection Sensors for Globalized Healthy Living and Wellbeing)
Open AccessReview Assessing Routing Strategies for Cognitive Radio Sensor Networks
Sensors 2013, 13(10), 13005-13038; doi:10.3390/s131013005
Received: 5 July 2013 / Revised: 5 September 2013 / Accepted: 5 September 2013 / Published: 26 September 2013
Cited by 7 | PDF Full-text (495 KB) | HTML Full-text | XML Full-text
Abstract
Interest in the cognitive radio sensor network (CRSN) paradigm has gradually grown among researchers. This concept seeks to fuse the benefits of dynamic spectrum access into the sensor network, making it a potential player in the next generation (NextGen) network, which is [...] Read more.
Interest in the cognitive radio sensor network (CRSN) paradigm has gradually grown among researchers. This concept seeks to fuse the benefits of dynamic spectrum access into the sensor network, making it a potential player in the next generation (NextGen) network, which is characterized by ubiquity. Notwithstanding its massive potential, little research activity has been dedicated to the network layer. By contrast, we find recent research trends focusing on the physical layer, the link layer and the transport layers. The fact that the cross-layer approach is imperative, due to the resource-constrained nature of CRSNs, can make the design of unique solutions non-trivial in this respect. This paper seeks to explore possible design opportunities with wireless sensor networks (WSNs), cognitive radio ad-hoc networks (CRAHNs) and cross-layer considerations for implementing viable CRSN routing solutions. Additionally, a detailed performance evaluation of WSN routing strategies in a cognitive radio environment is performed to expose research gaps. With this work, we intend to lay a foundation for developing CRSN routing solutions and to establish a basis for future work in this area. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessReview Aptamers as Theranostic Agents: Modifications, Serum Stability and Functionalisation
Sensors 2013, 13(10), 13624-13637; doi:10.3390/s131013624
Received: 7 August 2013 / Revised: 24 September 2013 / Accepted: 27 September 2013 / Published: 10 October 2013
Cited by 24 | PDF Full-text (449 KB) | HTML Full-text | XML Full-text
Abstract
Aptamers, and the selection process known as Systematic Evolution of Ligands by Exponential Enrichment (SELEX) used to generate them, were first described more than twenty years ago. Since then, there have been numerous modifications to the selection procedures. This review discusses the [...] Read more.
Aptamers, and the selection process known as Systematic Evolution of Ligands by Exponential Enrichment (SELEX) used to generate them, were first described more than twenty years ago. Since then, there have been numerous modifications to the selection procedures. This review discusses the use of modified bases as a means of enhancing serum stability and producing effective therapeutic tools, as well as functionalising these nucleic acids to be used as potential diagnostic agents. Full article
(This article belongs to the Special Issue Aptasensors)
Open AccessReview Microelectrode Arrays with Overlapped Diffusion Layers as Electroanalytical Detectors: Theory and Basic Applications
Sensors 2013, 13(10), 13659-13684; doi:10.3390/s131013659
Received: 23 July 2013 / Revised: 14 August 2013 / Accepted: 28 August 2013 / Published: 11 October 2013
Cited by 10 | PDF Full-text (903 KB) | HTML Full-text | XML Full-text
Abstract
This contribution contains a survey of basic literature dealing with arrays of microelectrodes with overlapping diffusion layers as prospective tools in contemporary electrochemistry. Photolithographic thin layer technology allows the fabrication of sensors of micrometric dimensions separated with a very small gap. This [...] Read more.
This contribution contains a survey of basic literature dealing with arrays of microelectrodes with overlapping diffusion layers as prospective tools in contemporary electrochemistry. Photolithographic thin layer technology allows the fabrication of sensors of micrometric dimensions separated with a very small gap. This fact allows the diffusion layers of single microelectrodes to overlap as members of the array. Various basic types of microelectrode arrays with interacting diffusion layers are described and their analytical abilities are accented. Theoretical approaches to diffusion layer overlapping and the consequences of close constitution effects such as collection efficiency and redox cycling are discussed. Examples of basis applications in electroanalytical chemistry such as amperometric detectors in HPLC and substitutional stripping voltammetry are also given. Full article
(This article belongs to the Special Issue Ultramicroelectrode Electrochemistry - Theory and Applications)
Open AccessReview Development of an Amorphous Selenium-Based Photodetector Driven by a Diamond Cold Cathode
Sensors 2013, 13(10), 13744-13778; doi:10.3390/s131013744
Received: 19 August 2013 / Revised: 12 September 2013 / Accepted: 23 September 2013 / Published: 11 October 2013
Cited by 4 | PDF Full-text (1896 KB) | HTML Full-text | XML Full-text
Abstract
Amorphous-selenium (a-Se) based photodetectors are promising candidates for imaging devices, due to their high spatial resolution and response speed, as well as extremely high sensitivity enhanced by an internal carrier multiplication. In addition, a-Se is reported to show sensitivity against wide variety [...] Read more.
Amorphous-selenium (a-Se) based photodetectors are promising candidates for imaging devices, due to their high spatial resolution and response speed, as well as extremely high sensitivity enhanced by an internal carrier multiplication. In addition, a-Se is reported to show sensitivity against wide variety of wavelengths, including visible, UV and X-ray, where a-Se based flat-panel X-ray detector was proposed. In order to develop an ultra high-sensitivity photodetector with a wide detectable wavelength range, a photodetector was fabricated using a-Se photoconductor and a nitrogen-doped diamond cold cathode. In the study, a prototype photodetector has been developed, and its response to visible and ultraviolet light are characterized. Full article
(This article belongs to the Special Issue Photodetectors)
Open AccessReview Recent Advances in Optical Biosensors for Environmental Monitoring and Early Warning
Sensors 2013, 13(10), 13928-13948; doi:10.3390/s131013928
Received: 11 July 2013 / Revised: 20 September 2013 / Accepted: 5 October 2013 / Published: 15 October 2013
Cited by 28 | PDF Full-text (315 KB) | HTML Full-text | XML Full-text
Abstract
The growing number of pollutants requires the development of innovative analytical devices that are precise, sensitive, specific, rapid, and easy-to-use to meet the increasing demand for legislative actions on environmental pollution control and early warning. Optical biosensors, as a powerful alternative to [...] Read more.
The growing number of pollutants requires the development of innovative analytical devices that are precise, sensitive, specific, rapid, and easy-to-use to meet the increasing demand for legislative actions on environmental pollution control and early warning. Optical biosensors, as a powerful alternative to conventional analytical techniques, enable the highly sensitive, real-time, and high-frequency monitoring of pollutants without extensive sample preparation. This article reviews important advances in functional biorecognition materials (e.g., enzymes, aptamers, DNAzymes, antibodies and whole cells) that facilitate the increasing application of optical biosensors. This work further examines the significant improvements in optical biosensor instrumentation and their environmental applications. Innovative developments of optical biosensors for environmental pollution control and early warning are also discussed. Full article
(This article belongs to the Section Biosensors)
Open AccessReview Optical Fiber-Based MR-Compatible Sensors for Medical Applications: An Overview
Sensors 2013, 13(10), 14105-14120; doi:10.3390/s131014105
Received: 30 July 2013 / Revised: 6 September 2013 / Accepted: 9 October 2013 / Published: 18 October 2013
Cited by 36 | PDF Full-text (414 KB) | HTML Full-text | XML Full-text
Abstract
During last decades, Magnetic Resonance (MR)—compatible sensors based on different techniques have been developed due to growing demand for application in medicine. There are several technological solutions to design MR-compatible sensors, among them, the one based on optical fibers presents several attractive [...] Read more.
During last decades, Magnetic Resonance (MR)—compatible sensors based on different techniques have been developed due to growing demand for application in medicine. There are several technological solutions to design MR-compatible sensors, among them, the one based on optical fibers presents several attractive features. The high elasticity and small size allow designing miniaturized fiber optic sensors (FOS) with metrological characteristics (e.g., accuracy, sensitivity, zero drift, and frequency response) adequate for most common medical applications; the immunity from electromagnetic interference and the absence of electrical connection to the patient make FOS suitable to be used in high electromagnetic field and intrinsically safer than conventional technologies. These two features further heightened the potential role of FOS in medicine making them especially attractive for application in MRI. This paper provides an overview of MR-compatible FOS, focusing on the sensors employed for measuring physical parameters in medicine (i.e., temperature, force, torque, strain, and position). The working principles of the most promising FOS are reviewed in terms of their relevant advantages and disadvantages, together with their applications in medicine. Full article
(This article belongs to the Special Issue Magnetic Resonance Sensors) Print Edition available
Open AccessReview Towards a Chemiresistive Sensor-Integrated Electronic Nose: A Review
Sensors 2013, 13(10), 14214-14247; doi:10.3390/s131014214
Received: 7 August 2013 / Revised: 28 September 2013 / Accepted: 9 October 2013 / Published: 22 October 2013
Cited by 30 | PDF Full-text (3007 KB) | HTML Full-text | XML Full-text
Abstract
Electronic noses have potential applications in daily life, but are restricted by their bulky size and high price. This review focuses on the use of chemiresistive gas sensors, metal-oxide semiconductor gas sensors and conductive polymer gas sensors in an electronic nose for [...] Read more.
Electronic noses have potential applications in daily life, but are restricted by their bulky size and high price. This review focuses on the use of chemiresistive gas sensors, metal-oxide semiconductor gas sensors and conductive polymer gas sensors in an electronic nose for system integration to reduce size and cost. The review covers the system design considerations and the complementary metal-oxide-semiconductor integrated technology for a chemiresistive gas sensor electronic nose, including the integrated sensor array, its readout interface, and pattern recognition hardware. In addition, the state-of-the-art technology integrated in the electronic nose is also presented, such as the sensing front-end chip, electronic nose signal processing chip, and the electronic nose system-on-chip. Full article

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