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Sensors, Volume 15, Issue 12 (December 2015)

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Open AccessArticle
WiFi-Based Real-Time Calibration-Free Passive Human Motion Detection
Sensors 2015, 15(12), 32213-32229; https://doi.org/10.3390/s151229896
Received: 26 October 2015 / Revised: 11 December 2015 / Accepted: 14 December 2015 / Published: 21 December 2015
Cited by 21 | Viewed by 2939 | PDF Full-text (1850 KB) | HTML Full-text | XML Full-text
Abstract
With the rapid development of WLAN technology, wireless device-free passive human detection becomes a newly-developing technique and holds more potential to worldwide and ubiquitous smart applications. Recently, indoor fine-grained device-free passive human motion detection based on the PHY layer information is rapidly developed. [...] Read more.
With the rapid development of WLAN technology, wireless device-free passive human detection becomes a newly-developing technique and holds more potential to worldwide and ubiquitous smart applications. Recently, indoor fine-grained device-free passive human motion detection based on the PHY layer information is rapidly developed. Previous wireless device-free passive human detection systems either rely on deploying specialized systems with dense transmitter-receiver links or elaborate off-line training process, which blocks rapid deployment and weakens system robustness. In the paper, we explore to research a novel fine-grained real-time calibration-free device-free passive human motion via physical layer information, which is independent of indoor scenarios and needs no prior-calibration and normal profile. We investigate sensitivities of amplitude and phase to human motion, and discover that phase feature is more sensitive to human motion, especially to slow human motion. Aiming at lightweight and robust device-free passive human motion detection, we develop two novel and practical schemes: short-term averaged variance ratio (SVR) and long-term averaged variance ratio (LVR). We realize system design with commercial WiFi devices and evaluate it in typical multipath-rich indoor scenarios. As demonstrated in the experiments, our approach can achieve a high detection rate and low false positive rate. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle
Far-Infrared Based Pedestrian Detection for Driver-Assistance Systems Based on Candidate Filters, Gradient-Based Feature and Multi-Frame Approval Matching
Sensors 2015, 15(12), 32188-32212; https://doi.org/10.3390/s151229874
Received: 13 October 2015 / Revised: 23 November 2015 / Accepted: 9 December 2015 / Published: 21 December 2015
Cited by 9 | Viewed by 2868 | PDF Full-text (8698 KB) | HTML Full-text | XML Full-text
Abstract
Far-infrared pedestrian detection approaches for advanced driver-assistance systems based on high-dimensional features fail to simultaneously achieve robust and real-time detection. We propose a robust and real-time pedestrian detection system characterized by novel candidate filters, novel pedestrian features and multi-frame approval matching in a [...] Read more.
Far-infrared pedestrian detection approaches for advanced driver-assistance systems based on high-dimensional features fail to simultaneously achieve robust and real-time detection. We propose a robust and real-time pedestrian detection system characterized by novel candidate filters, novel pedestrian features and multi-frame approval matching in a coarse-to-fine fashion. Firstly, we design two filters based on the pedestrians’ head and the road to select the candidates after applying a pedestrian segmentation algorithm to reduce false alarms. Secondly, we propose a novel feature encapsulating both the relationship of oriented gradient distribution and the code of oriented gradient to deal with the enormous variance in pedestrians’ size and appearance. Thirdly, we introduce a multi-frame approval matching approach utilizing the spatiotemporal continuity of pedestrians to increase the detection rate. Large-scale experiments indicate that the system works in real time and the accuracy has improved about 9% compared with approaches based on high-dimensional features only. Full article
(This article belongs to the Special Issue Sensors in New Road Vehicles)
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Open AccessArticle
Design, Implementation and Evaluation of an Indoor Navigation System for Visually Impaired People
Sensors 2015, 15(12), 32168-32187; https://doi.org/10.3390/s151229912
Received: 1 October 2015 / Revised: 16 December 2015 / Accepted: 17 December 2015 / Published: 21 December 2015
Cited by 24 | Viewed by 3519 | PDF Full-text (4257 KB) | HTML Full-text | XML Full-text
Abstract
Indoor navigation is a challenging task for visually impaired people. Although there are guidance systems available for such purposes, they have some drawbacks that hamper their direct application in real-life situations. These systems are either too complex, inaccurate, or require very special conditions [...] Read more.
Indoor navigation is a challenging task for visually impaired people. Although there are guidance systems available for such purposes, they have some drawbacks that hamper their direct application in real-life situations. These systems are either too complex, inaccurate, or require very special conditions (i.e., rare in everyday life) to operate. In this regard, Ultra-Wideband (UWB) technology has been shown to be effective for indoor positioning, providing a high level of accuracy and low installation complexity. This paper presents SUGAR, an indoor navigation system for visually impaired people which uses UWB for positioning, a spatial database of the environment for pathfinding through the application of the A* algorithm, and a guidance module. The interaction with the user takes place using acoustic signals and voice commands played through headphones. The suitability of the system for indoor navigation has been verified by means of a functional and usable prototype through a field test with a blind person. In addition, other tests have been conducted in order to show the accuracy of different relevant parts of the system. Full article
(This article belongs to the Special Issue Sensors for Indoor Mapping and Navigation)
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Open AccessArticle
A TSR Visual Servoing System Based on a Novel Dynamic Template Matching Method
Sensors 2015, 15(12), 32152-32167; https://doi.org/10.3390/s151229884
Received: 28 October 2015 / Revised: 7 December 2015 / Accepted: 10 December 2015 / Published: 21 December 2015
Cited by 13 | Viewed by 2313 | PDF Full-text (5381 KB) | HTML Full-text | XML Full-text
Abstract
The so-called Tethered Space Robot (TSR) is a novel active space debris removal system. To solve its problem of non-cooperative target recognition during short-distance rendezvous events, this paper presents a framework for a real-time visual servoing system using non-calibrated monocular-CMOS (Complementary Metal Oxide [...] Read more.
The so-called Tethered Space Robot (TSR) is a novel active space debris removal system. To solve its problem of non-cooperative target recognition during short-distance rendezvous events, this paper presents a framework for a real-time visual servoing system using non-calibrated monocular-CMOS (Complementary Metal Oxide Semiconductor). When a small template is used for matching with a large scene, it always leads to mismatches, so a novel template matching algorithm to solve the problem is presented. Firstly, the novel matching algorithm uses a hollow annulus structure according to a FAST (Features from Accelerated Segment) algorithm and makes the method be rotation-invariant. Furthermore, the accumulative deviation can be decreased by the hollow structure. The matching function is composed of grey and gradient differences between template and object image, which help it reduce the effects of illumination and noises. Then, a dynamic template update strategy is designed to avoid tracking failures brought about by wrong matching or occlusion. Finally, the system synthesizes the least square integrated predictor, realizing tracking online in complex circumstances. The results of ground experiments show that the proposed algorithm can decrease the need for sophisticated computation and improves matching accuracy. Full article
(This article belongs to the Special Issue Sensors for Robots)
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Open AccessArticle
Fatigue Crack Length Sizing Using a Novel Flexible Eddy Current Sensor Array
Sensors 2015, 15(12), 32138-32151; https://doi.org/10.3390/s151229911
Received: 22 October 2015 / Revised: 6 December 2015 / Accepted: 16 December 2015 / Published: 21 December 2015
Cited by 17 | Viewed by 2908 | PDF Full-text (8234 KB) | HTML Full-text | XML Full-text
Abstract
The eddy current probe, which is flexible, array typed, highly sensitive and capable of quantitative inspection is one practical requirement in nondestructive testing and also a research hotspot. A novel flexible planar eddy current sensor array for the inspection of microcrack presentation in [...] Read more.
The eddy current probe, which is flexible, array typed, highly sensitive and capable of quantitative inspection is one practical requirement in nondestructive testing and also a research hotspot. A novel flexible planar eddy current sensor array for the inspection of microcrack presentation in critical parts of airplanes is developed in this paper. Both exciting and sensing coils are etched on polyimide films using a flexible printed circuit board technique, thus conforming the sensor to complex geometric structures. In order to serve the needs of condition-based maintenance (CBM), the proposed sensor array is comprised of 64 elements. Its spatial resolution is only 0.8 mm, and it is not only sensitive to shallow microcracks, but also capable of sizing the length of fatigue cracks. The details and advantages of our sensor design are introduced. The working principal and the crack responses are analyzed by finite element simulation, with which a crack length sizing algorithm is proposed. Experiments based on standard specimens are implemented to verify the validity of our simulation and the efficiency of the crack length sizing algorithm. Experimental results show that the sensor array is sensitive to microcracks, and is capable of crack length sizing with an accuracy within ±0.2 mm. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle
Focusing Bistatic FMCW SAR Signal by Range Migration Algorithm Based on Fresnel Approximation
Sensors 2015, 15(12), 32123-32137; https://doi.org/10.3390/s151229910
Received: 21 September 2015 / Revised: 15 December 2015 / Accepted: 17 December 2015 / Published: 21 December 2015
Cited by 4 | Viewed by 2212 | PDF Full-text (2732 KB) | HTML Full-text | XML Full-text
Abstract
Frequency modulated continuous wave (FMCW) technique has recently been employed by synthetic aperture radar (SAR) to decrease the radar cost and volume. However, the operation range is limited by the direct energy leakage from the transmitting channel to receiving channel due to the [...] Read more.
Frequency modulated continuous wave (FMCW) technique has recently been employed by synthetic aperture radar (SAR) to decrease the radar cost and volume. However, the operation range is limited by the direct energy leakage from the transmitting channel to receiving channel due to the operation principle of FMCW technique. Bistatic configuration is an efficient way to increase the isolation between the transmitter and receiver, which could significantly increase the radar standoff range. A bistatic FMCW SAR spectrum model is proposed by using the Fresnel approximation in this paper. This model is similar to that of a monostatic FMCW SAR spectrum, which allows the existing imaging algorithms to be used on bistatic image processing. Based on the new model and the characteristics of FMCW signal, a modified range migration algorithm (RMA) for FMCW SAR is proposed to focus the image, which requires less memory and computational load than the traditional RMA. Point-target simulation is used to verify the proposed spectral model and real data processing verified the effectiveness of the proposed RMA. Full article
(This article belongs to the Section Remote Sensors, Control, and Telemetry)
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Open AccessConcept Paper
Cloud-Based Automated Design and Additive Manufacturing: A Usage Data-Enabled Paradigm Shift
Sensors 2015, 15(12), 32079-32122; https://doi.org/10.3390/s151229905
Received: 4 November 2015 / Revised: 9 December 2015 / Accepted: 16 December 2015 / Published: 19 December 2015
Cited by 27 | Viewed by 5795 | PDF Full-text (5851 KB) | HTML Full-text | XML Full-text
Abstract
Integration of sensors into various kinds of products and machines provides access to in-depth usage information as basis for product optimization. Presently, this large potential for more user-friendly and efficient products is not being realized because (a) sensor integration and thus usage information [...] Read more.
Integration of sensors into various kinds of products and machines provides access to in-depth usage information as basis for product optimization. Presently, this large potential for more user-friendly and efficient products is not being realized because (a) sensor integration and thus usage information is not available on a large scale and (b) product optimization requires considerable efforts in terms of manpower and adaptation of production equipment. However, with the advent of cloud-based services and highly flexible additive manufacturing techniques, these obstacles are currently crumbling away at rapid pace. The present study explores the state of the art in gathering and evaluating product usage and life cycle data, additive manufacturing and sensor integration, automated design and cloud-based services in manufacturing. By joining and extrapolating development trends in these areas, it delimits the foundations of a manufacturing concept that will allow continuous and economically viable product optimization on a general, user group or individual user level. This projection is checked against three different application scenarios, each of which stresses different aspects of the underlying holistic concept. The following discussion identifies critical issues and research needs by adopting the relevant stakeholder perspectives. Full article
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Open AccessArticle
Robust Road Condition Detection System Using In-Vehicle Standard Sensors
Sensors 2015, 15(12), 32056-32078; https://doi.org/10.3390/s151229908
Received: 29 September 2015 / Revised: 30 November 2015 / Accepted: 11 December 2015 / Published: 19 December 2015
Cited by 11 | Viewed by 6678 | PDF Full-text (3356 KB) | HTML Full-text | XML Full-text
Abstract
The appearance of active safety systems, such as Anti-lock Braking System, Traction Control System, Stability Control System, etc., represents a major evolution in road safety. In the automotive sector, the term vehicle active safety systems refers to those whose goal is to [...] Read more.
The appearance of active safety systems, such as Anti-lock Braking System, Traction Control System, Stability Control System, etc., represents a major evolution in road safety. In the automotive sector, the term vehicle active safety systems refers to those whose goal is to help avoid a crash or to reduce the risk of having an accident. These systems safeguard us, being in continuous evolution and incorporating new capabilities continuously. In order for these systems and vehicles to work adequately, they need to know some fundamental information: the road condition on which the vehicle is circulating. This early road detection is intended to allow vehicle control systems to act faster and more suitably, thus obtaining a substantial advantage. In this work, we try to detect the road condition the vehicle is being driven on, using the standard sensors installed in commercial vehicles. Vehicle models were programmed in on-board systems to perform real-time estimations of the forces of contact between the wheel and road and the speed of the vehicle. Subsequently, a fuzzy logic block is used to obtain an index representing the road condition. Finally, an artificial neural network was used to provide the optimal slip for each surface. Simulations and experiments verified the proposed method. Full article
(This article belongs to the Special Issue Sensors in New Road Vehicles)
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Open AccessArticle
Surface Acoustic Waves (SAW)-Based Biosensing for Quantification of Cell Growth in 2D and 3D Cultures
Sensors 2015, 15(12), 32045-32055; https://doi.org/10.3390/s151229909
Received: 11 September 2015 / Revised: 8 December 2015 / Accepted: 11 December 2015 / Published: 19 December 2015
Cited by 14 | Viewed by 4617 | PDF Full-text (4225 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Detection and quantification of cell viability and growth in two-dimensional (2D) and three-dimensional (3D) cell cultures commonly involve harvesting of cells and therefore requires a parallel set-up of several replicates for time-lapse or dose–response studies. Thus, developing a non-invasive and touch-free detection of [...] Read more.
Detection and quantification of cell viability and growth in two-dimensional (2D) and three-dimensional (3D) cell cultures commonly involve harvesting of cells and therefore requires a parallel set-up of several replicates for time-lapse or dose–response studies. Thus, developing a non-invasive and touch-free detection of cell growth in longitudinal studies of 3D tumor spheroid cultures or of stem cell regeneration remains a major unmet need. Since surface acoustic waves (SAWs) permit mass loading-based biosensing and have been touted due to their many advantages including low cost, small size and ease of assembly, we examined the potential of SAW-biosensing to detect and quantify cell growth. Herein, we demonstrate that a shear horizontal-surface acoustic waves (SH-SAW) device comprising two pairs of resonators consisting of interdigital transducers and reflecting fingers can be used to quantify mass loading by the cells in suspension as well as within a 3D cell culture platform. A 3D COMSOL model was built to simulate the mass loading response of increasing concentrations of cells in suspension in the polydimethylsiloxane (PDMS) well in order to predict the characteristics and optimize the design of the SH-SAW biosensor. The simulated relative frequency shift from the two oscillatory circuit systems (one of which functions as control) were found to be concordant to experimental data generated with RAW264.7 macrophage and A549 cancer cells. In addition, results showed that SAW measurements per se did not affect viability of cells. Further, SH-SAW biosensing was applied to A549 cells cultured on a 3D electrospun nanofiber scaffold that generate tumor spheroids (tumoroids) and the results showed the device's ability to detect changes in tumor spheroid growth over the course of eight days. Taken together, these results demonstrate the use of SH-SAW device for detection and quantification of cell growth changes over time in 2D suspension cultures and in 3D cell culture models, which may have potential applications in both longitudinal 3D cell cultures in cancer biology and in regenerative medicine. Full article
(This article belongs to the Special Issue Micro/Nano Fluidic Devices and Bio-MEMS)
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Open AccessArticle
A Simulation Environment for Benchmarking Sensor Fusion-Based Pose Estimators
Sensors 2015, 15(12), 32031-32044; https://doi.org/10.3390/s151229903
Received: 17 November 2015 / Revised: 14 December 2015 / Accepted: 17 December 2015 / Published: 19 December 2015
Cited by 4 | Viewed by 2666 | PDF Full-text (2510 KB) | HTML Full-text | XML Full-text
Abstract
In-depth analysis and performance evaluation of sensor fusion-based estimators may be critical when performed using real-world sensor data. For this reason, simulation is widely recognized as one of the most powerful tools for algorithm benchmarking. In this paper, we present a simulation framework [...] Read more.
In-depth analysis and performance evaluation of sensor fusion-based estimators may be critical when performed using real-world sensor data. For this reason, simulation is widely recognized as one of the most powerful tools for algorithm benchmarking. In this paper, we present a simulation framework suitable for assessing the performance of sensor fusion-based pose estimators. The systems used for implementing the framework were magnetic/inertial measurement units (MIMUs) and a camera, although the addition of further sensing modalities is straightforward. Typical nuisance factors were also included for each sensor. The proposed simulation environment was validated using real-life sensor data employed for motion tracking. The higher mismatch between real and simulated sensors was about 5% of the measured quantity (for the camera simulation), whereas a lower correlation was found for an axis of the gyroscope (0.90). In addition, a real benchmarking example of an extended Kalman filter for pose estimation from MIMU and camera data is presented. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle
Technological Advancement in Tower-Based Canopy Reflectance Monitoring: The AMSPEC-III System
Sensors 2015, 15(12), 32020-32030; https://doi.org/10.3390/s151229906
Received: 11 November 2015 / Revised: 8 December 2015 / Accepted: 17 December 2015 / Published: 19 December 2015
Cited by 7 | Viewed by 2871 | PDF Full-text (3548 KB) | HTML Full-text | XML Full-text
Abstract
Understanding plant photosynthesis, or Gross Primary Production (GPP), is a crucial aspect of quantifying the terrestrial carbon cycle. Remote sensing approaches, in particular multi-angular spectroscopy, have proven successful for studying relationships between canopy-reflectance and plant-physiology processes, thus providing a mechanism to scale up. [...] Read more.
Understanding plant photosynthesis, or Gross Primary Production (GPP), is a crucial aspect of quantifying the terrestrial carbon cycle. Remote sensing approaches, in particular multi-angular spectroscopy, have proven successful for studying relationships between canopy-reflectance and plant-physiology processes, thus providing a mechanism to scale up. However, many different instrumentation designs exist and few cross-comparisons have been undertaken. This paper discusses the design evolution of the Automated Multiangular SPectro-radiometer for Estimation of Canopy reflectance (AMSPEC) series of instruments. Specifically, we assess the performance of the PP-Systems Unispec-DC and Ocean Optics JAZ-COMBO spectro-radiometers installed on an updated, tower-based AMSPEC-III system. We demonstrate the interoperability of these spectro-radiometers, and the results obtained suggest that JAZ-COMBO can successfully be used to substitute more expensive measurement units for detecting and investigating photosynthesis and canopy spectra. We demonstrate close correlations between JAZ-COMBO and Unispec-DC measured canopy radiance (0.75 ≤ R2 ≤ 0.85) and solar irradiance (0.95 ≤ R2 ≤ 0.96) over a three month time span. We also demonstrate close agreement between the bi-directional distribution functions obtained from each instrument. We conclude that cost effective alternatives may allow a network of AMSPEC-III systems to simultaneously monitor various vegetation types in different ecosystems. This will allow to scale and improve our understanding of the interactions between vegetation physiology and spectral characteristics, calibrate broad-scale observations to stand-level measurements, and ultimately lead to improved understanding of changing vegetation spectral features from satellite. Full article
(This article belongs to the Special Issue Sensors for Agriculture)
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Open AccessArticle
One Small Step for a Man: Estimation of Gender, Age and Height from Recordings of One Step by a Single Inertial Sensor
Sensors 2015, 15(12), 31999-32019; https://doi.org/10.3390/s151229907
Received: 2 October 2015 / Revised: 9 December 2015 / Accepted: 11 December 2015 / Published: 19 December 2015
Cited by 17 | Viewed by 3004 | PDF Full-text (992 KB) | HTML Full-text | XML Full-text
Abstract
A number of previous works have shown that information about a subject is encoded in sparse kinematic information, such as the one revealed by so-called point light walkers. With the work at hand, we extend these results to classifications of soft biometrics from [...] Read more.
A number of previous works have shown that information about a subject is encoded in sparse kinematic information, such as the one revealed by so-called point light walkers. With the work at hand, we extend these results to classifications of soft biometrics from inertial sensor recordings at a single body location from a single step. We recorded accelerations and angular velocities of 26 subjects using integrated measurement units (IMUs) attached at four locations (chest, lower back, right wrist and left ankle) when performing standardized gait tasks. The collected data were segmented into individual walking steps. We trained random forest classifiers in order to estimate soft biometrics (gender, age and height). We applied two different validation methods to the process, 10-fold cross-validation and subject-wise cross-validation. For all three classification tasks, we achieve high accuracy values for all four sensor locations. From these results, we can conclude that the data of a single walking step (6D: accelerations and angular velocities) allow for a robust estimation of the gender, height and age of a person. Full article
(This article belongs to the collection Sensors for Globalized Healthy Living and Wellbeing)
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Open AccessArticle
Synthesis and Sensing Applications of Fluorescent 3-Cinnamoyl Coumarins
Sensors 2015, 15(12), 31987-31998; https://doi.org/10.3390/s151229902
Received: 26 September 2015 / Revised: 5 December 2015 / Accepted: 10 December 2015 / Published: 19 December 2015
Cited by 6 | Viewed by 2789 | PDF Full-text (2332 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We have synthesized two novel fluorescent 3-(4-diethylaminocinnamoyl) coumarins that exhibit fluorescence quenching upon exposure to a nerve agent simulant, diethylchlorophosphate (DCP), providing a basis for rapid and sensitive DCP chemosensing. Furthermore, these coumarin derivatives display two-photon fluorescence upon illumination with near-infrared laser pulses [...] Read more.
We have synthesized two novel fluorescent 3-(4-diethylaminocinnamoyl) coumarins that exhibit fluorescence quenching upon exposure to a nerve agent simulant, diethylchlorophosphate (DCP), providing a basis for rapid and sensitive DCP chemosensing. Furthermore, these coumarin derivatives display two-photon fluorescence upon illumination with near-infrared laser pulses and their two-photon (TP) absorption cross-section was evaluated. The potential for TP bio-imaging of these compounds was investigated by their cellular uptake in HeLa cells by TP confocal microscopy. Full article
(This article belongs to the Special Issue The Use of New and/or Improved Materials for Sensing Applications)
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Open AccessArticle
Pharmacokinetics of Chiral Dendrimer-Triamine-Coordinated Gd-MRI Contrast Agents Evaluated by in Vivo MRI and Estimated by in Vitro QCM
Sensors 2015, 15(12), 31973-31986; https://doi.org/10.3390/s151229900
Received: 2 November 2015 / Revised: 8 December 2015 / Accepted: 11 December 2015 / Published: 18 December 2015
Cited by 3 | Viewed by 2516 | PDF Full-text (2857 KB) | HTML Full-text | XML Full-text
Abstract
Recently, we developed novel chiral dendrimer-triamine-coordinated Gd-MRI contrast agents (Gd-MRI CAs), which showed longitudinal relaxivity (r1) values about four times higher than that of clinically used Gd-DTPA (Magnevist®, Bayer). In our continuing study of pharmacokinetic differences derived from [...] Read more.
Recently, we developed novel chiral dendrimer-triamine-coordinated Gd-MRI contrast agents (Gd-MRI CAs), which showed longitudinal relaxivity (r1) values about four times higher than that of clinically used Gd-DTPA (Magnevist®, Bayer). In our continuing study of pharmacokinetic differences derived from both the chirality and generation of Gd-MRI CAs, we found that the ability of chiral dendrimer Gd-MRI CAs to circulate within the body can be directly evaluated by in vitro MRI (7 T). In this study, the association constants (Ka) of chiral dendrimer Gd-MRI CAs to bovine serum albumin (BSA), measured and calculated with a quartz crystal microbalance (QCM) in vitro, were found to be an extremely easy means for evaluating the body-circulation ability of chiral dendrimer Gd-MRI CAs. The Ka values of S-isomeric dendrimer Gd-MRI CAs were generally greater than those of R-isomeric dendrimer Gd-MRI CAs, which is consistent with the results of our previous MRI study in vivo. Full article
(This article belongs to the Section Biosensors)
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Open AccessCommunication
Development and Preliminary Evaluation of a Spray Deposition Sensing System for Improving Pesticide Application
Sensors 2015, 15(12), 31965-31972; https://doi.org/10.3390/s151229898
Received: 24 September 2015 / Revised: 2 December 2015 / Accepted: 14 December 2015 / Published: 17 December 2015
Cited by 7 | Viewed by 1883 | PDF Full-text (1827 KB) | HTML Full-text | XML Full-text
Abstract
An electronic, resistance-based sensor array and data acquisition system was developed to measure spray deposition from hydraulic nozzles. The sensor surface consisted of several parallel tin plated copper traces of varying widths with varying gap widths. The system contained an embedded microprocessor to [...] Read more.
An electronic, resistance-based sensor array and data acquisition system was developed to measure spray deposition from hydraulic nozzles. The sensor surface consisted of several parallel tin plated copper traces of varying widths with varying gap widths. The system contained an embedded microprocessor to monitor output voltage corresponding to spray deposition every second. In addition, a wireless module was used to transmit the voltage values to a remote laptop. Tests were conducted in two stages to evaluate the performance of the sensor array in an attempt to quantify the spray deposition. Initial tests utilized manual droplet placement on the sensor surface to determine the effects of temperature and droplet size on voltage output. Secondary testing utilized a spray chamber to pass nozzles at different speeds above the sensor surface to determine if output varied based on different application rates or spray droplet classification. Results from this preliminary analysis indicated that manual droplets of 5 and 10 μL resulted in significantly different values from the sensors while temperature did not consistently affect output. Spray chamber test results indicated that different application rates and droplet sizes could be determined using the sensor array. Full article
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Open AccessArticle
Flexibility Support for Homecare Applications Based on Models and Multi-Agent Technology
Sensors 2015, 15(12), 31939-31964; https://doi.org/10.3390/s151229899
Received: 10 November 2015 / Revised: 11 December 2015 / Accepted: 13 December 2015 / Published: 17 December 2015
Cited by 9 | Viewed by 2276 | PDF Full-text (5814 KB) | HTML Full-text | XML Full-text
Abstract
In developed countries, public health systems are under pressure due to the increasing percentage of population over 65. In this context, homecare based on ambient intelligence technology seems to be a suitable solution to allow elderly people to continue to enjoy the comforts [...] Read more.
In developed countries, public health systems are under pressure due to the increasing percentage of population over 65. In this context, homecare based on ambient intelligence technology seems to be a suitable solution to allow elderly people to continue to enjoy the comforts of home and help optimize medical resources. Thus, current technological developments make it possible to build complex homecare applications that demand, among others, flexibility mechanisms for being able to evolve as context does (adaptability), as well as avoiding service disruptions in the case of node failure (availability). The solution proposed in this paper copes with these flexibility requirements through the whole life-cycle of the target applications: from design phase to runtime. The proposed domain modeling approach allows medical staff to design customized applications, taking into account the adaptability needs. It also guides software developers during system implementation. The application execution is managed by a multi-agent based middleware, making it possible to meet adaptation requirements, assuring at the same time the availability of the system even for stateful applications. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle
Formation of High-Purity Indium Oxide Nanoparticles and Their Application to Sensitive Detection of Ammonia
Sensors 2015, 15(12), 31930-31938; https://doi.org/10.3390/s151229895
Received: 22 October 2015 / Revised: 7 December 2015 / Accepted: 11 December 2015 / Published: 17 December 2015
Cited by 5 | Viewed by 2251 | PDF Full-text (3984 KB) | HTML Full-text | XML Full-text
Abstract
High-purity In2O3 nanoparticles were recovered from scrap indium tin oxide substrates in a stepwise process involving acidic leaching, liquid-liquid extraction with a phosphine oxide extractant, and combustion of the organic phase. The morphological and structural parameters of the recovered nanoparticles [...] Read more.
High-purity In2O3 nanoparticles were recovered from scrap indium tin oxide substrates in a stepwise process involving acidic leaching, liquid-liquid extraction with a phosphine oxide extractant, and combustion of the organic phase. The morphological and structural parameters of the recovered nanoparticles were investigated to support the formation of the desired products. These In2O3 nanoparticles were used for sensitive sensing of ammonia gas using a four-probe electrode device. The proposed sensor offered very quick response time (around 10 s) and highly sensitive detection of ammonia (at a detection limit of 1 ppm). Full article
(This article belongs to the Special Issue The Use of New and/or Improved Materials for Sensing Applications)
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Open AccessArticle
An Analog Circuit Approximation of the Discrete Wavelet Transform for Ultra Low Power Signal Processing in Wearable Sensor Nodes
Sensors 2015, 15(12), 31914-31929; https://doi.org/10.3390/s151229897
Received: 11 November 2015 / Revised: 12 December 2015 / Accepted: 14 December 2015 / Published: 17 December 2015
Cited by 2 | Viewed by 2891 | PDF Full-text (1158 KB) | HTML Full-text | XML Full-text
Abstract
Ultra low power signal processing is an essential part of all sensor nodes, and particularly so in emerging wearable sensors for biomedical applications. Analog signal processing has an important role in these low power, low voltage, low frequency applications, and there is a [...] Read more.
Ultra low power signal processing is an essential part of all sensor nodes, and particularly so in emerging wearable sensors for biomedical applications. Analog signal processing has an important role in these low power, low voltage, low frequency applications, and there is a key drive to decrease the power consumption of existing analog domain signal processing and to map more signal processing approaches into the analog domain. This paper presents an analog domain signal processing circuit which approximates the output of the Discrete Wavelet Transform (DWT) for use in ultra low power wearable sensors. Analog filters are used for the DWT filters and it is demonstrated how these generate analog domain DWT-like information that embeds information from Butterworth and Daubechies maximally flat mother wavelet responses. The Analog DWT is realised in hardware via g m C circuits, designed to operate from a 1.3 V coin cell battery, and provide DWT-like signal processing using under 115 nW of power when implemented in a 0.18 μm CMOS process. Practical examples demonstrate the effective use of the new Analog DWT on ECG (electrocardiogram) and EEG (electroencephalogram) signals recorded from humans. Full article
(This article belongs to the Section State-of-the-Art Sensors Technologies)
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Open AccessArticle
A Dual Sensor for pH and Hydrogen Peroxide Using Polymer-Coated Optical Fibre Tips
Sensors 2015, 15(12), 31904-31913; https://doi.org/10.3390/s151229893
Received: 28 October 2015 / Revised: 7 December 2015 / Accepted: 11 December 2015 / Published: 17 December 2015
Cited by 20 | Viewed by 3252 | PDF Full-text (780 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This paper demonstrates the first single optical fibre tip probe for concurrent detection of both hydrogen peroxide (H2O2) concentration and pH of a solution. The sensor is constructed by embedding two fluorophores: carboxyperoxyfluor-1 (CPF1) and seminaphtharhodafluor-2 (SNARF2) within a [...] Read more.
This paper demonstrates the first single optical fibre tip probe for concurrent detection of both hydrogen peroxide (H2O2) concentration and pH of a solution. The sensor is constructed by embedding two fluorophores: carboxyperoxyfluor-1 (CPF1) and seminaphtharhodafluor-2 (SNARF2) within a polymer matrix located on the tip of the optical fibre. The functionalised fibre probe reproducibly measures pH, and is able to accurately detect H2O2 over a biologically relevant concentration range. This sensor offers potential for non-invasive detection of pH and H2O2 in biological environments using a single optical fibre. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle
Study on the Sensing Coating of the Optical Fibre CO2 Sensor
Sensors 2015, 15(12), 31888-31903; https://doi.org/10.3390/s151229890
Received: 31 August 2015 / Revised: 10 December 2015 / Accepted: 11 December 2015 / Published: 17 December 2015
Cited by 8 | Viewed by 2791 | PDF Full-text (2304 KB) | HTML Full-text | XML Full-text
Abstract
Optical fibre carbon dioxide (CO2) sensors are reported in this article. The principle of operation of the sensors relies on the absorption of light transmitted through the fibre by a silica gel coating containing active dyes, including methyl red, thymol blue [...] Read more.
Optical fibre carbon dioxide (CO2) sensors are reported in this article. The principle of operation of the sensors relies on the absorption of light transmitted through the fibre by a silica gel coating containing active dyes, including methyl red, thymol blue and phenol red. Stability of the sensor has been investigated for the first time for an absorption based CO2 optical fiber sensor. Influence of the silica gel coating thickness on the sensitivity and response time has also been studied. The impact of temperature and humidity on the sensor performance has been examined too. Response times of reported sensors are very short and reach 2–3 s, whereas the sensitivity of the sensor ranges from 3 to 10 for different coating thicknesses. Reported parameters make the sensor suitable for indoor and industrial use. Full article
(This article belongs to the Special Issue Gas Sensors—Designs and Applications)
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Open AccessArticle
Quantitative Evaluation of Stereo Visual Odometry for Autonomous Vessel Localisation in Inland Waterway Sensing Applications
Sensors 2015, 15(12), 31869-31887; https://doi.org/10.3390/s151229892
Received: 5 November 2015 / Revised: 8 December 2015 / Accepted: 9 December 2015 / Published: 17 December 2015
Cited by 5 | Viewed by 3163 | PDF Full-text (5216 KB) | HTML Full-text | XML Full-text
Abstract
Autonomous survey vessels can increase the efficiency and availability of wide-area river environment surveying as a tool for environment protection and conservation. A key challenge is the accurate localisation of the vessel, where bank-side vegetation or urban settlement preclude the conventional use of [...] Read more.
Autonomous survey vessels can increase the efficiency and availability of wide-area river environment surveying as a tool for environment protection and conservation. A key challenge is the accurate localisation of the vessel, where bank-side vegetation or urban settlement preclude the conventional use of line-of-sight global navigation satellite systems (GNSS). In this paper, we evaluate unaided visual odometry, via an on-board stereo camera rig attached to the survey vessel, as a novel, low-cost localisation strategy. Feature-based and appearance-based visual odometry algorithms are implemented on a six degrees of freedom platform operating under guided motion, but stochastic variation in yaw, pitch and roll. Evaluation is based on a 663 m-long trajectory (>15,000 image frames) and statistical error analysis against ground truth position from a target tracking tachymeter integrating electronic distance and angular measurements. The position error of the feature-based technique (mean of ±0.067 m) is three times smaller than that of the appearance-based algorithm. From multi-variable statistical regression, we are able to attribute this error to the depth of tracked features from the camera in the scene and variations in platform yaw. Our findings inform effective strategies to enhance stereo visual localisation for the specific application of river monitoring. Full article
(This article belongs to the Special Issue Robotic Sensory Systems for Environment Protection and Conservation)
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Open AccessArticle
Localization of Mixed Completely and Partially Polarized Signals with Crossed-Dipole Sensor Arrays
Sensors 2015, 15(12), 31859-31868; https://doi.org/10.3390/s151229894
Received: 12 October 2015 / Revised: 9 December 2015 / Accepted: 14 December 2015 / Published: 17 December 2015
Cited by 7 | Viewed by 1964 | PDF Full-text (320 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we investigate the problem of source localization and classification under the coexistence of both completely polarized (CP) and partially polarized (PP) electromagnetic (EM) signals, using a crossed-dipole sensor array. We propose a MUltiple SIgnal Classification (MUSIC)-based solution, which does not [...] Read more.
In this paper, we investigate the problem of source localization and classification under the coexistence of both completely polarized (CP) and partially polarized (PP) electromagnetic (EM) signals, using a crossed-dipole sensor array. We propose a MUltiple SIgnal Classification (MUSIC)-based solution, which does not require multidimensional searches. Moreover, the proposed method need no estimation of the degree of polarization of signals. The efficacy of the proposed method is examined by comparing with existing methods. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle
A Security Assessment Mechanism for Software-Defined Networking-Based Mobile Networks
Sensors 2015, 15(12), 31843-31858; https://doi.org/10.3390/s151229887
Received: 9 November 2015 / Revised: 4 December 2015 / Accepted: 8 December 2015 / Published: 17 December 2015
Cited by 11 | Viewed by 3032 | PDF Full-text (2901 KB) | HTML Full-text | XML Full-text
Abstract
Software-Defined Networking-based Mobile Networks (SDN-MNs) are considered the future of 5G mobile network architecture. With the evolving cyber-attack threat, security assessments need to be performed in the network management. Due to the distinctive features of SDN-MNs, such as their dynamic nature and complexity, [...] Read more.
Software-Defined Networking-based Mobile Networks (SDN-MNs) are considered the future of 5G mobile network architecture. With the evolving cyber-attack threat, security assessments need to be performed in the network management. Due to the distinctive features of SDN-MNs, such as their dynamic nature and complexity, traditional network security assessment methodologies cannot be applied directly to SDN-MNs, and a novel security assessment methodology is needed. In this paper, an effective security assessment mechanism based on attack graphs and an Analytic Hierarchy Process (AHP) is proposed for SDN-MNs. Firstly, this paper discusses the security assessment problem of SDN-MNs and proposes a methodology using attack graphs and AHP. Secondly, to address the diversity and complexity of SDN-MNs, a novel attack graph definition and attack graph generation algorithm are proposed. In order to quantify security levels, the Node Minimal Effort (NME) is defined to quantify attack cost and derive system security levels based on NME. Thirdly, to calculate the NME of an attack graph that takes the dynamic factors of SDN-MN into consideration, we use AHP integrated with the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) as the methodology. Finally, we offer a case study to validate the proposed methodology. The case study and evaluation show the advantages of the proposed security assessment mechanism. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle
PCF Based Sensor with High Sensitivity, High Birefringence and Low Confinement Losses for Liquid Analyte Sensing Applications
Sensors 2015, 15(12), 31833-31842; https://doi.org/10.3390/s151229891
Received: 7 November 2015 / Revised: 1 December 2015 / Accepted: 13 December 2015 / Published: 16 December 2015
Cited by 46 | Viewed by 2561 | PDF Full-text (1738 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we report a design of high sensitivity Photonic Crystal Fiber (PCF) sensor with high birefringence and low confinement losses for liquid analyte sensing applications. The proposed PCF structures are designed with supplementary elliptical air holes in the core region vertically-shaped [...] Read more.
In this paper, we report a design of high sensitivity Photonic Crystal Fiber (PCF) sensor with high birefringence and low confinement losses for liquid analyte sensing applications. The proposed PCF structures are designed with supplementary elliptical air holes in the core region vertically-shaped V-PCF and horizontally-shaped H-PCF. The full vectorial Finite Element Method (FEM) simulations performed to examine the sensitivity, the confinement losses, the effective refractive index and the modal birefringence features of the proposed elliptical air hole PCF structures. We show that the proposed PCF structures exhibit high relative sensitivity, high birefringence and low confinement losses simultaneously for various analytes. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle
Co-Design Method and Wafer-Level Packaging Technique of Thin-Film Flexible Antenna and Silicon CMOS Rectifier Chips for Wireless-Powered Neural Interface Systems
Sensors 2015, 15(12), 31821-31832; https://doi.org/10.3390/s151229885
Received: 9 October 2015 / Revised: 5 December 2015 / Accepted: 14 December 2015 / Published: 16 December 2015
Cited by 6 | Viewed by 4275 | PDF Full-text (6510 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a co-design method and a wafer-level packaging technique of a flexible antenna and a CMOS rectifier chip for use in a small-sized implantable system on the brain surface are proposed. The proposed co-design method optimizes the system architecture, and can [...] Read more.
In this paper, a co-design method and a wafer-level packaging technique of a flexible antenna and a CMOS rectifier chip for use in a small-sized implantable system on the brain surface are proposed. The proposed co-design method optimizes the system architecture, and can help avoid the use of external matching components, resulting in the realization of a small-size system. In addition, the technique employed to assemble a silicon large-scale integration (LSI) chip on the very thin parylene film (5 μm) enables the integration of the rectifier circuits and the flexible antenna (rectenna). In the demonstration of wireless power transmission (WPT), the fabricated flexible rectenna achieved a maximum efficiency of 0.497% with a distance of 3 cm between antennas. In addition, WPT with radio waves allows a misalignment of 185% against antenna size, implying that the misalignment has a less effect on the WPT characteristics compared with electromagnetic induction. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle
Mechanism of Electrochemical Delamination of Two-Dimensional Materials from Their Native Substrates by Bubbling
Sensors 2015, 15(12), 31811-31820; https://doi.org/10.3390/s151229888
Received: 3 November 2015 / Revised: 8 December 2015 / Accepted: 14 December 2015 / Published: 16 December 2015
Cited by 3 | Viewed by 2741 | PDF Full-text (2596 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A capacitor-based circuit model is proposed to explain the electrochemical delamination of two-dimensional materials from their native substrates where produced gas bubbles squeeze into the interface. The delamination is actually the electric breakdown of the capacitor formed between the solution and substrate. To [...] Read more.
A capacitor-based circuit model is proposed to explain the electrochemical delamination of two-dimensional materials from their native substrates where produced gas bubbles squeeze into the interface. The delamination is actually the electric breakdown of the capacitor formed between the solution and substrate. To facilitate the procedure, the backside of the ubstrate has to be shielded so that the capacitor breakdown voltage can be reached. The screening effect can be induced either by nonreactive ions around the electrode or, more effectively, by an undetachable insulator. This mechanism serves as a guideline for the surface science and applications involving the bubbling delamination. Full article
(This article belongs to the Special Issue Graphene and 2D Material Bionanosensors: Chemistry Matters)
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Open AccessArticle
Sensing Traffic Density Combining V2V and V2I Wireless Communications
Sensors 2015, 15(12), 31794-31810; https://doi.org/10.3390/s151229889
Received: 27 August 2015 / Revised: 5 November 2015 / Accepted: 10 December 2015 / Published: 16 December 2015
Cited by 13 | Viewed by 3506 | PDF Full-text (1429 KB) | HTML Full-text | XML Full-text
Abstract
Wireless technologies are making the development of new applications and services in vehicular environments possible since they enable mobile communication between vehicles (V2V), as well as communication between vehicles and infrastructure nodes (V2I). Usually, V2V communications are dedicated to the transmission of small [...] Read more.
Wireless technologies are making the development of new applications and services in vehicular environments possible since they enable mobile communication between vehicles (V2V), as well as communication between vehicles and infrastructure nodes (V2I). Usually, V2V communications are dedicated to the transmission of small messages mainly focused on improving traffic safety. Instead, V2I communications allow users to access the Internet and benefit from higher level applications. The combination of both V2V and V2I, known as V2X communications, can increase the benefits even further, thereby making intelligent transportation systems (ITS) a reality. In this paper, we introduce V2X-d, a novel architecture specially designed to estimate traffic density on the road. In particular, V2X-d exploits the combination of V2V and V2I communications. Our approach is based on the information gathered by sensors (i.e., vehicles and road side units (RSUs)) and the characteristics of the roadmap topology to accurately make an estimation of the instant vehicle density. The combination of both mechanisms improves the accuracy and coverage area of the data gathered, while increasing the robustness and fault tolerance of the overall approach, e.g., using the information offered by V2V communications to provide additional density information in areas where RSUs are scarce or malfunctioning. By using our collaborative sensing scheme, future ITS solutions will be able to establish adequate dissemination protocols or to apply more efficient traffic congestion reduction policies, since they will be aware of the instantaneous density of vehicles. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle
GSA-Tuning IPD Control of a Field-Sensed Magnetic Suspension System
Sensors 2015, 15(12), 31781-31793; https://doi.org/10.3390/s151229879
Received: 24 August 2015 / Revised: 7 December 2015 / Accepted: 11 December 2015 / Published: 16 December 2015
Cited by 3 | Viewed by 3003 | PDF Full-text (4221 KB) | HTML Full-text | XML Full-text
Abstract
The purpose of this paper is to propose a GSA-tuning IPD control technique for magnetic suspension systems. An educational demonstration on a magnetic-field sensed magnetic suspension system is examined for effectiveness. For the magnetic-field sensed magnetic suspension system (FSMSS), the current transducer is [...] Read more.
The purpose of this paper is to propose a GSA-tuning IPD control technique for magnetic suspension systems. An educational demonstration on a magnetic-field sensed magnetic suspension system is examined for effectiveness. For the magnetic-field sensed magnetic suspension system (FSMSS), the current transducer is employed for measuring the electromagnetic coil current, and a Hall effect device is used for detecting the position of the suspended object. To achieve optimal performance, the gravitational search algorithm (GSA) is adopted for tuning the integral-proportional-derivative (IPD) controller. The IPD control includes the specified PD controller and an integrator. The specified PD control is employed for stabilizing the inherently unstable FSMSS, whereas the integral control is utilized for eliminating the steady-state error. The GSA can tune the IPD control parameters to enable optimal FSMSS performance. We achieved excellent results from the simulations and hands-on experiments for the proposed control strategies and structures. Full article
(This article belongs to the Special Issue Magnetic Sensor Device-Part 1)
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Open AccessArticle
Smart Capture Modules for Direct Sensor-to-FPGA Interfaces
Sensors 2015, 15(12), 31762-31780; https://doi.org/10.3390/s151229878
Received: 10 October 2015 / Revised: 25 November 2015 / Accepted: 11 December 2015 / Published: 16 December 2015
Cited by 10 | Viewed by 2286 | PDF Full-text (5151 KB) | HTML Full-text | XML Full-text
Abstract
Direct sensor–digital device interfaces measure time dependent variables of simple circuits to implement analog-to-digital conversion. Field Programmable Gate Arrays (FPGAs) are devices whose hardware can be reconfigured to work in parallel. They usually do not have analog-to-digital converters, but have many general purpose [...] Read more.
Direct sensor–digital device interfaces measure time dependent variables of simple circuits to implement analog-to-digital conversion. Field Programmable Gate Arrays (FPGAs) are devices whose hardware can be reconfigured to work in parallel. They usually do not have analog-to-digital converters, but have many general purpose I/O pins. Therefore, direct sensor-FPGA connection is a good choice in complex systems with many sensors because several capture modules can be implemented to perform parallel analog data acquisition. The possibility to work in parallel and with high frequency clock signals improves the bandwidth compared to sequential devices such as conventional microcontrollers. The price to pay is usually the resolution of measurements. This paper proposes capture modules implemented in an FPGA which are able to perform smart acquisition that filter noise and achieve high precision. A calibration technique is also proposed to improve accuracy. Resolutions of 12 effective number of bits are obtained for the reading of resistors in the range of an example piezoresistive tactile sensor. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle
An RFID Based Smart Feeder for Hummingbirds
Sensors 2015, 15(12), 31751-31761; https://doi.org/10.3390/s151229886
Received: 12 November 2015 / Revised: 8 December 2015 / Accepted: 9 December 2015 / Published: 16 December 2015
Cited by 3 | Viewed by 2459 | PDF Full-text (32983 KB) | HTML Full-text | XML Full-text
Abstract
We present an interdisciplinary effort to record feeding behaviors and control the diet of a hummingbird species (Phaethornis longirostris, the long-billed hermit or LBH) by developing a Radio Frequency Identification (RFID) based smart feeder. The system contains an RFID reader, a [...] Read more.
We present an interdisciplinary effort to record feeding behaviors and control the diet of a hummingbird species (Phaethornis longirostris, the long-billed hermit or LBH) by developing a Radio Frequency Identification (RFID) based smart feeder. The system contains an RFID reader, a microcontroller, and a servo-controlled hummingbird feeder opener; the system is presented as a tool for studying the cognitive ability of the LBH species. When equipped with glass capsule RFID tags (which are mounted on the hummingbird), the smart feeder can provide specific diets for predetermined sets of hummingbirds at the discretion of biologists. This is done by reading the unique RFID tag on the hummingbirds and comparing the ID number with the pre-programmed ID numbers stored in the smart feeder. The smart feeder records the time and ID of each hummingbird visit. The system data is stored in a readily available SD card and is powered by two 9 V batteries. The detection range of the system is approximately 9–11 cm. Using this system, biologists can assign the wild hummingbirds to different experimental groups and monitor their diets to determine if they develop a preference to any of the available nectars. During field testing, the smart feeder system has demonstrated consistent detection (when compared to detections observed by video-recordings) of RFID tags on hummingbirds and provides pre-designed nectars varying water and sugar concentrations to target individuals. The smart feeder can be applied to other biological and environmental studies in the future. Full article
(This article belongs to the Section Physical Sensors)
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