http://www.mdpi.com/journal/sensors Latest open access articles published in Sensors at http://www.mdpi.com/journal/sensors http://www.mdpi.com/1424-8220/13/6/7774 A novel and integrated membrane sensing platform for DNA detection is developed based on an anodic aluminum oxide (AAO) membrane. Platinum electrodes (~50–100 nm thick) are coated directly on both sides of the alumina membrane to eliminate the solution resistance outside the nanopores. The electrochemical impedance technique is employed to monitor the impedance changes within the nanopores upon DNA binding. Pore resistance (Rp) linearly increases in response towards the increasing concentration of the target DNA in the range of 1 × 10−12 to 1 × 10−6 M. Moreover, the biosensor selectively differentiates the complementary sequence from single base mismatched (MM-1) strands and non-complementary strands. This study reveals a simple, selective and sensitive method to fabricate a label-free DNA biosensor. Sensors 2013-06-17 13 6 Article 10.3390/s130607774 7774 7785 1424-8220 2013-06-17 doi: 10.3390/s130607774 Jiajia Deng Chee-Seng Toh http://www.mdpi.com/1424-8220/13/6/7756 We have already proposed a method for detecting vehicle positions and their movements (henceforth referred to as “our previous method”) using thermal images taken with an infrared thermal camera. Our experiments have shown that our previous method detects vehicles robustly under four different environmental conditions which involve poor visibility conditions in snow and thick fog. Our previous method uses the windshield and its surroundings as the target of the Viola-Jones detector. Some experiments in winter show that the vehicle detection accuracy decreases because the temperatures of many windshields approximate those of the exterior of the windshields. In this paper, we propose a new vehicle detection method (henceforth referred to as “our new method”). Our new method detects vehicles based on tires’ thermal energy reflection. We have done experiments using three series of thermal images for which the vehicle detection accuracies of our previous method are low. Our new method detects 1,417 vehicles (92.8%) out of 1,527 vehicles, and the number of false detection is 52 in total. Therefore, by combining our two methods, high vehicle detection accuracies are maintained under various environmental conditions. Finally, we apply the traffic information obtained by our two methods to traffic flow automatic monitoring, and show the effectiveness of our proposal. Sensors 2013-06-17 13 6 Article 10.3390/s130607756 7756 7773 1424-8220 2013-06-17 doi: 10.3390/s130607756 Yoichiro Iwasaki Masato Misumi Toshiyuki Nakamiya http://www.mdpi.com/1424-8220/13/6/7735 Human motion monitoring and analysis can be an essential part of a wide spectrum of applications, including physical rehabilitation among other potential areas of interest. Creating non-invasive systems for monitoring patients while performing rehabilitation exercises, to provide them with an objective feedback, is one of the current challenges. In this paper we present a wearable multi-sensor system for human motion monitoring, which has been developed for use in rehabilitation. It is composed of a number of small modules that embed high-precision accelerometers and wireless communications to transmit the information related to the body motion to an acquisition device. The results of a set of experiments we made to assess its performance in real-world setups demonstrate its usefulness in human motion acquisition and tracking, as required, for example, in activity recognition, physical/athletic performance evaluation and rehabilitation. Sensors 2013-06-17 13 6 Article 10.3390/s130607735 7735 7755 1424-8220 2013-06-17 doi: 10.3390/s130607735 Lara González-Villanueva Stefano Cagnoni Luca Ascari http://www.mdpi.com/1424-8220/13/6/7714 Facial expressions are widely used in the behavioral interpretation of emotions, cognitive science, and social interactions. In this paper, we present a novel method for fully automatic facial expression recognition in facial image sequences. As the facial expression evolves over time facial landmarks are automatically tracked in consecutive video frames, using displacements based on elastic bunch graph matching displacement estimation. Feature vectors from individual landmarks, as well as pairs of landmarks tracking results are extracted, and normalized, with respect to the first frame in the sequence. The prototypical expression sequence for each class of facial expression is formed, by taking the median of the landmark tracking results from the training facial expression sequences. Multi-class AdaBoost with dynamic time warping similarity distance between the feature vector of input facial expression and prototypical facial expression, is used as a weak classifier to select the subset of discriminative feature vectors. Finally, two methods for facial expression recognition are presented, either by using multi-class AdaBoost with dynamic time warping, or by using support vector machine on the boosted feature vectors. The results on the Cohn-Kanade (CK+) facial expression database show a recognition accuracy of 95.17% and 97.35% using multi-class AdaBoost and support vector machines, respectively. Sensors 2013-06-14 13 6 Article 10.3390/s130607714 7714 7734 1424-8220 2013-06-14 doi: 10.3390/s130607714 Deepak Ghimire Joonwhoan Lee http://www.mdpi.com/1424-8220/13/6/7680 Recent advances in biosensor design and sensing efficacy need to be amalgamated with research in responsive drug delivery systems for building superior health or illness regimes and ensuring good patient compliance. A variety of illnesses require continuous monitoring in order to have efficient illness intervention. Physicochemical changes in the body can signify the occurrence of an illness before it manifests. Even with the usage of sensors that allow diagnosis and prognosis of the illness, medical intervention still has its downfalls. Late detection of illness can reduce the efficacy of therapeutics. Furthermore, the conventional modes of treatment can cause side-effects such as tissue damage (chemotherapy and rhabdomyolysis) and induce other forms of illness (hepatotoxicity). The use of drug delivery systems enables the lowering of side-effects with subsequent improvement in patient compliance. Chronic illnesses require continuous monitoring and medical intervention for efficient treatment to be achieved. Therefore, designing a responsive system that will reciprocate to the physicochemical changes may offer superior therapeutic activity. In this respect, integration of biosensors and drug delivery is a proficient approach and requires designing an implantable system that has a closed loop system. This offers regulation of the changes by means of releasing a therapeutic agent whenever illness biomarkers prevail. Proper selection of biomarkers is vital as this is key for diagnosis and a stimulation factor for responsive drug delivery. By detecting an illness before it manifests by means of biomarkers levels, therapeutic dosing would relate to the severity of such changes. In this review various biosensors and drug delivery systems are discussed in order to assess the challenges and future perspectives of integrating biosensors and drug delivery systems for detection and management of chronic illness. Sensors 2013-06-14 13 6 Review 10.3390/s130607680 7680 7713 1424-8220 2013-06-14 doi: 10.3390/s130607680 Mpho Ngoepe Yahya Choonara Charu Tyagi Lomas Tomar Lisa du Toit Pradeep Kumar Valence Ndesendo Viness Pillay http://www.mdpi.com/1424-8220/13/6/7668 A fast and non-destructive voltammetric method to detect cocaine in confiscated samples based on carbon paste electrode modified with methoxy-substituted N,N'-ethylene-bis(salcylideneiminato)uranyl(VI)complexes, [UO2(X-MeOSalen)(H2O)]·H2O, where X corresponds to the positions 3, 4 or 5 of the methoxy group on the aromatic ring, is described. The electrochemical behavior of the modified electrode and the electrochemical detection of cocaine were investigated using cyclic voltammetry. Using 0.1 mol·L−1 KCl as supporting-electrolyte, a concentration-dependent, well-defined peak current for cocaine at 0.62 V, with an amperometric sensitivity of 6.25 × 104 μA·mol·L−1 for cocaine concentrations ranging between 1.0 × 10−7 and 1.3 × 10−6 mol·L−1 was obtained. Chemical interference studies using lidocaine and procaine were performed. The position of the methoxy group affects the results, with the 3-methoxy derivative being the most sensitive. Sensors 2013-06-14 13 6 Article 10.3390/s130607668 7668 7679 1424-8220 2013-06-14 doi: 10.3390/s130607668 Laura de Oliveira Ana dos Santos Poles Marco Balbino Matheus Teles de Menezes José de Andrade Edward Dockal Heloísa Tristão Marcelo de Oliveira http://www.mdpi.com/1424-8220/13/6/7652 A new wireless sensor network (WSN), called CrossVit, and based on MEMSIC products, has been tested for two growing seasons in two vineyards in Italy. The aims are to evaluate the monitoring performances of the new WSN directly in the vineyard and collect air temperature, air humidity and solar radiation data to support vineyard management practices. The WSN consists of various levels: the Master/Gateway level coordinates the WSN and performs data aggregation; the Farm/Server level takes care of storing data on a server, data processing and graphic rendering; Nodes level is based on a network of peripheral nodes consisting of a MDA300 sensor board and Iris module and equipped with thermistors for air temperature, photodiodes for global and diffuse solar radiation, and an HTM2500LF sensor for relative humidity. The communication levels are: WSN links between gateways and sensor nodes by ZigBee, and long-range GSM/GPRS links between gateways and the server farm level. The system was able to monitor the agrometeorological parameters in the vineyard: solar radiation, air temperature and air humidity, detecting the differences between the canopy treatments applied. The performance of CrossVit, in terms of monitoring and reliability of the system, have been evaluated considering: its handiness, cost-effective, non-invasive dimensions and low power consumption. Sensors 2013-06-13 13 6 Article 10.3390/s130607652 7652 7667 1424-8220 2013-06-13 doi: 10.3390/s130607652 Alessandro Matese Francesco Vaccari Diego Tomasi Salvatore Di Gennaro Jacopo Primicerio Francesco Sabatini Silvia Guidoni http://www.mdpi.com/1424-8220/13/6/7633 Progress in sensor technique and electronics has led to a decrease in the costs of electronic and sensor components. In modern dairy farms, having udders in good condition, a lower frequency of udder disease and an extended service life of dairy cows will help ensure competitiveness. The objective of this study was to develop a teat-end vacuum control system with individual quarter actor reaction. Based on a review of the literature, this system is assumed to protect the teat tissue. It reduces the mean teat-end vacuum in the maximum vacuum phase (b) to a level of 20 kPa at a flow rate of 0.25 L/min per quarter. At flow rates higher than 1.50 L/min per quarter, the teat-end vacuum can be controlled to a level of 30 kPa, because in this case it is desirable to have a higher vacuum for the transportation of the milk to the receiver. With this system it is possible for the first time to supply the teat end with low vacuum at low flow rates and with higher vacuum at increasing flow rates in a continuous process with a three second reaction-rate on individual quarter level. This system is completely automated. Sensors 2013-06-13 13 6 Article 10.3390/s130607633 7633 7651 1424-8220 2013-06-13 doi: 10.3390/s130607633 Ulrich Ströbel Sandra Rose-Meierhöfer Hülya Öz Reiner Brunsch http://www.mdpi.com/1424-8220/13/6/7618 This paper introduces a novel contactless sensing principle conceived for measuring the rotation angle of a shaft. The sensor is based on a smart combination of low-cost components that can be effectively integrated in a mechanical assembly of a rotary joint. The working principle is based on the relative rotation of a small diametrically magnetized cylindrical or annular magnet and at least one Hall effect sensor. One of the main strengths of the new sensing principle is to be adaptable to any assigned dimensions and encumbrances without typical design limitations given by the use of standard components. A numerical model is developed for predicting the sensor output characteristic on the base of the concept of magnetic charge. Such a model is validated against results from laboratory experiments. The parameters that define the geometry and layout of the sensor are optimized in order to maximize linearity over an assigned angular range of measurement. Two examples of mechatronic systems that employ the new sensing principle are presented in order to show the possibility of obtaining with the new principle a compact/integrated sensor-design. Sensors 2013-06-13 13 6 Article 10.3390/s130607618 7618 7632 1424-8220 2013-06-13 doi: 10.3390/s130607618 Marco Fontana Fabio Salsedo Massimo Bergamasco http://www.mdpi.com/1424-8220/13/6/7599 Non-rigid multi-modal image registration plays an important role in medical image processing and analysis. Existing image registration methods based on similarity metrics such as mutual information (MI) and sum of squared differences (SSD) cannot achieve either high registration accuracy or high registration efficiency. To address this problem, we propose a novel two phase non-rigid multi-modal image registration method by combining Weber local descriptor (WLD) based similarity metrics with the normalized mutual information (NMI) using the diffeomorphic free-form deformation (FFD) model. The first phase aims at recovering the large deformation component using the WLD based non-local SSD (wldNSSD) or weighted structural similarity (wldWSSIM). Based on the output of the former phase, the second phase is focused on getting accurate transformation parameters related to the small deformation using the NMI. Extensive experiments on T1, T2 and PD weighted MR images demonstrate that the proposed wldNSSD-NMI or wldWSSIM-NMI method outperforms the registration methods based on the NMI, the conditional mutual information (CMI), the SSD on entropy images (ESSD) and the ESSD-NMI in terms of registration accuracy and computation efficiency. Sensors 2013-06-13 13 6 Article 10.3390/s130607599 7599 7617 1424-8220 2013-06-13 doi: 10.3390/s130607599 Feng Yang Mingyue Ding Xuming Zhang Yi Wu Jiani Hu http://www.mdpi.com/1424-8220/13/6/7570 This article presents design issues of high-sensitive laser absorption spectroscopy systems for nitrogen oxides (NOx) detection. Examples of our systems and their investigation results are also described. The constructed systems use one of the most sensitive methods, cavity enhanced absorption spectroscopy (CEAS). They operate at different wavelength ranges using a blue—violet laser diode (410 nm) as well as quantum cascade lasers (5.27 µm and 4.53 µm). Each of them is configured as a one or two channel measurement device using, e.g., time division multiplexing and averaging. During the testing procedure, the main performance features such as detection limits and measurements uncertainties have been determined. The obtained results are 1 ppb NO2, 75 ppb NO and 45 ppb N2O. For all systems, the uncertainty of concentration measurements does not exceed a value of 13%. Some experiments with explosives are also discussed. A setup equipped with a concentrator of explosives vapours was used. The detection method is based either on the reaction of the sensors to the nitrogen oxides directly emitted by the explosives or on the reaction to the nitrogen oxides produced during thermal decomposition of explosive vapours. For TNT, PETN, RDX and HMX a detection limit better than 1 ng has been achieved. Sensors 2013-06-10 13 6 Review 10.3390/s130607570 7570 7598 1424-8220 2013-06-10 doi: 10.3390/s130607570 Jacek Wojtas Janusz Mikolajczyk Zbigniew Bielecki http://www.mdpi.com/1424-8220/13/6/7546 The demand for Wireless Body Sensor Networks (WBSNs) is rapidly increasing due to the revolution in wearable systems demonstrated by the penetration of on-the-body sensors in hospitals, sports medicine and general health-care practices. In WBSN, the body acts as a communication channel for the propagation of electromagnetic (EM) waves, where losses are mainly due to absorption of power in the tissue. This paper shows the effects of the dielectric properties of biological tissues in the signal strength and, for the first time, relates these effects with the human body composition. After a careful analysis of results, this work proposes a reactive algorithm for power transmission to alleviate the effect of body movement and body type. This policy achieves up to 40.8% energy savings in a realistic scenario with no performance overhead. Sensors 2013-06-10 13 6 Article 10.3390/s130607546 7546 7569 1424-8220 2013-06-10 doi: 10.3390/s130607546 Mónica Vallejo Joaquín Recas Pablo del Valle José Ayala http://www.mdpi.com/1424-8220/13/6/7522 Neuro-evolutive development from birth until the age of six years is a decisive factor in a child’s quality of life. Early detection of development disorders in early childhood can facilitate necessary diagnosis and/or treatment. Primary-care pediatricians play a key role in its detection as they can undertake the preventive and therapeutic actions requested to promote a child’s optimal development. However, the lack of time and little specific knowledge at primary-care avoid to applying continuous early-detection anomalies procedures. This research paper focuses on the deployment and evaluation of a smart system that enhances the screening of language disorders in primary care. Pediatricians get support to proceed with early referral of language disorders. The proposed model provides them with a decision-support tool for referral actions to trigger essential diagnostic and/or therapeutic actions for a comprehensive individual development. The research was conducted by starting from a sample of 60 cases of children with language disorders. Validation was carried out through two complementary steps: first, by including a team of seven experts from the fields of neonatology, pediatrics, neurology and language therapy, and, second, through the evaluation of 21 more previously diagnosed cases. The results obtained show that therapist positively accepted the system proposal in 18 cases (86%) and suggested system redesign for single referral to a speech therapist in three remaining cases. Sensors 2013-06-10 13 6 Article 10.3390/s130607522 7522 7545 1424-8220 2013-06-10 doi: 10.3390/s130607522 María Martín-Ruiz Miguel Angel Valero Duboy Iván Pau de la Cruz http://www.mdpi.com/1424-8220/13/6/7505 This paper presents an analysis of a golf swing to detect improper motion in the early phase of the swing. Led by the desire to achieve a consistent shot outcome, a particular golfer would (in multiple trials) prefer to perform completely identical golf swings. In reality, some deviations from the desired motion are always present due to the comprehensive nature of the swing motion. Swing motion deviations that are not detrimental to performance are acceptable. This analysis is conducted using a golfer’s leading arm kinematic data, which are obtained from a golfer wearing a motion sensor that is comprised of gyroscopes and accelerometers. Applying the principal component analysis (PCA) to the reference observations of properly performed swings, the PCA components of acceptable swing motion deviations are established. Using these components, the motion deviations in the observations of other swings are examined. Any unacceptable deviations that are detected indicate an improper swing motion. Arbitrarily long observations of an individual player’s swing sequences can be included in the analysis. The results obtained for the considered example show an improper swing motion in early phase of the swing, i.e., the first part of the backswing. An early detection method for improper swing motions that is conducted on an individual basis provides assistance for performance improvement. Sensors 2013-06-10 13 6 Article 10.3390/s130607505 7505 7521 1424-8220 2013-06-10 doi: 10.3390/s130607505 Sara Stančin Sašo Tomažič http://www.mdpi.com/1424-8220/13/6/7492 A simple two-step method was employed for preparing nano-sized gold nanoparticles-graphene composite to construct a GNPs-GR-SDS modified electrode. Hemoglobin (Hb) was successfully immobilized on the surface of a basal plane graphite (BPG) electrode through a simple dropping technique. Direct electrochemistry and electrocatalysis of the hemoglobin-modified electrode was investigated. The as-prepared composites showed an obvious promotion of the direct electro-transfer between hemoglobin and the electrode. A couple of well-defined and quasi-reversible Hb CV peaks can be observed in a phosphate buffer solution (pH 7.0). The separation of anodic and cathodic peak potentials is 81 mV, indicating a fast electron transfer reaction. The experimental results also clarified that the immobilized Hb retained its biological activity for the catalysis toward NO. The biosensor showed high sensitivity and fast response upon the addition of NO, under the conditions of pH 7.0, potential ‒0.82 V. The time to reach the stable-state current was less than 3 s, and the linear response range of NO was 0.72–7.92 μM, with a correlation coefficient of 0.9991. Sensors 2013-06-07 13 6 Article 10.3390/s130607492 7492 7504 1424-8220 2013-06-07 doi: 10.3390/s130607492 Miao-Qing Xu Jian-Feng Wu Guang-Chao Zhao http://www.mdpi.com/1424-8220/13/6/7472 An essential application of wireless sensor networks is to successfully respond to user queries. Query packet losses occur in the query dissemination due to wireless communication problems such as interference, multipath fading, packet collisions, etc. The losses of query messages at sensor nodes result in the failure of sensor nodes reporting the requested data. Hence, the reliable and successful dissemination of query messages to sensor nodes is a non-trivial problem. The target of this paper is to enable highly successful query delivery to sensor nodes by localized and energy-efficient discovery, and recovery of query losses. We adopt local and collective cooperation among sensor nodes to increase the success rate of distributed discoveries and recoveries. To enable the scalability in the operations of discoveries and recoveries, we employ a distributed name resolution mechanism at each sensor node to allow sensor nodes to self-detect the correlated queries and query losses, and then efficiently locally respond to the query losses. We prove that the collective discovery of query losses has a high impact on the success of query dissemination and reveal that scalability can be achieved by using the proposed approach. We further study the novel features of the cooperation and competition in the collective recovery at PHY and MAC layers, and show that the appropriate number of detectors can achieve optimal successful recovery rate. We evaluate the proposed approach with both mathematical analyses and computer simulations. The proposed approach enables a high rate of successful delivery of query messages and it results in short route lengths to recover from query losses. The proposed approach is scalable and operates in a fully distributed manner. Sensors 2013-06-07 13 6 Article 10.3390/s130607472 7472 7491 1424-8220 2013-06-07 doi: 10.3390/s130607472 Rui Teng Kenji Leibnitz Ryu Miura http://www.mdpi.com/1424-8220/13/6/7454 Network simulators are useful for researching protocol performance, appraising new hardware capabilities and evaluating real application scenarios. However, these tasks can only be achieved when using accurate models and real parameters that enable the extraction of trustworthy results and conclusions. This paper presents an underwater wireless sensor network ecosystem for the ns-3 simulator. This ecosystem is composed of a new energy-harvesting model and a low-cost, low-power underwater wake-up modem model that, alongside existing models, enables the performance of accurate simulations by providing real weather and marine conditions from the location where the real application is to be deployed. Sensors 2013-06-07 13 6 Article 10.3390/s130607454 7454 7471 1424-8220 2013-06-07 doi: 10.3390/s130607454 Salvador Climent Juan Capella Sara Blanc Angel Perles Juan Serrano http://www.mdpi.com/1424-8220/13/6/7443 Surface plasmon resonance (SPR) sensor is widely used for its high precision and real-time analysis. Fiber-optic SPR sensor is easy for miniaturization, so it is commonly used in the development of portable detection equipment. It can also be used for remote, real-time, and online detection. In this study, a wavelength modulation fiber-optic SPR sensor is designed, and theoretical analysis of optical propagation in the optical fiber is also done. Compared with existing methods, both the transmission of a skew ray and the influence of the chromatic dispersion are discussed. The resonance wavelength is calculated at two different cases, in which the chromatic dispersion in the fiber core is considered. According to the simulation results, a novel multi-channel fiber-optic SPR sensor is likewise designed to avoid defaults aroused by the complicated computation of the skew ray as well as the chromatic dispersion. Avoiding the impact of skew ray can do much to improve the precision of this kind of sensor. Sensors 2013-06-07 13 6 Article 10.3390/s130607443 7443 7453 1424-8220 2013-06-07 doi: 10.3390/s130607443 Linlin Liu Jun Yang Zhong Yang Xiaoping Wan Ning Hu Xiaolin Zheng http://www.mdpi.com/1424-8220/13/6/7414 This paper presents an intelligent surveillance platform based on the usage of large numbers of inexpensive sensors designed and developed inside the European Eureka Celtic project HuSIMS. With the aim of maximizing the number of deployable units while keeping monetary and resource/bandwidth costs at a minimum, the surveillance platform is based on the usage of inexpensive visual sensors which apply efficient motion detection and tracking algorithms to transform the video signal in a set of motion parameters. In order to automate the analysis of the myriad of data streams generated by the visual sensors, the platform’s control center includes an alarm detection engine which comprises three components applying three different Artificial Intelligence strategies in parallel. These strategies are generic, domain-independent approaches which are able to operate in several domains (traffic surveillance, vandalism prevention, perimeter security, etc.). The architecture is completed with a versatile communication network which facilitates data collection from the visual sensors and alarm and video stream distribution towards the emergency teams. The resulting surveillance system is extremely suitable for its deployment in metropolitan areas, smart cities, and large facilities, mainly because cheap visual sensors and autonomous alarm detection facilitate dense sensor network deployments for wide and detailed coverage. Sensors 2013-06-07 13 6 Article 10.3390/s130607414 7414 7442 1424-8220 2013-06-07 doi: 10.3390/s130607414 Jorge Fernández Lorena Calavia Carlos Baladrón Javier Aguiar Belén Carro Antonio Sánchez-Esguevillas Jesus Alonso-López Zeev Smilansky http://www.mdpi.com/1424-8220/13/6/7399 Asthma is a chronic disease that is commonly suffered by children. Asthmatic children have a lower quality of life than other children. Physicians and pediatricians recommend that parents record the frequency of attacks and their symptoms to help manage their children’s asthma. However, the lack of a convenient device for monitoring the asthmatic condition leads to the difficulties in managing it, especially when it is suffered by young children. This work develops a wheeze detection system for use at home. A small and soft stethoscope was used to collect the respiratory sound. The wheeze detection algorithm was the Adaptive Respiratory Spectrum Correlation Coefficient (RSACC) algorithm, which has the advantages of high sensitivity/specificity and a low computational requirement. Fifty-nine sound files from eight young children (one to seven years old) were collected in the emergency room and analyzed. The results revealed that the system provided 88% sensitivity and 94% specificity in wheeze detection. In conclusion, this small soft stethoscope can be easily used on young children. A noisy environment does not affect the effectiveness of the system in detecting wheeze. Hence, the system can be used at home by parents who wish to evaluate and manage the asthmatic condition of their children. Sensors 2013-06-06 13 6 Article 10.3390/s130607399 7399 7413 1424-8220 2013-06-06 doi: 10.3390/s130607399 Chun Yu Tzu-Hsiu Tsai Shi-Ing Huang Chii-Wann Lin http://www.mdpi.com/1424-8220/13/6/7385 When it comes to measuring blade-tip clearance or blade-tip timing in turbines, reflective intensity-modulated optical fiber sensors overcome several traditional limitations of capacitive, inductive or discharging probe sensors. This paper presents the signals and results corresponding to the third stage of a multistage turbine rig, obtained from a transonic wind-tunnel test. The probe is based on a trifurcated bundle of optical fibers that is mounted on the turbine casing. To eliminate the influence of light source intensity variations and blade surface reflectivity, the sensing principle is based on the quotient of the voltages obtained from the two receiving bundle legs. A discrepancy lower than 3% with respect to a commercial sensor was observed in tip clearance measurements. Regarding tip timing measurements, the travel wave spectrum was obtained, which provides the average vibration amplitude for all blades at a particular nodal diameter. With this approach, both blade-tip timing and tip clearance measurements can be carried out simultaneously. The results obtained on the test turbine rig demonstrate the suitability and reliability of the type of sensor used, and suggest the possibility of performing these measurements in real turbines under real working conditions. Sensors 2013-06-05 13 6 Article 10.3390/s130607385 7385 7398 1424-8220 2013-06-05 doi: 10.3390/s130607385 Iker García Josu Beloki Joseba Zubia Gotzon Aldabaldetreku María Illarramendi Felipe Jiménez http://www.mdpi.com/1424-8220/13/6/7345 This paper comprehensively reviews the emerging topic of optoacoustic imaging from the image reconstruction and quantification perspective. Optoacoustic imaging combines highly attractive features, including rich contrast and high versatility in sensing diverse biological targets, excellent spatial resolution not compromised by light scattering, and relatively low cost of implementation. Yet, living objects present a complex target for optoacoustic imaging due to the presence of a highly heterogeneous tissue background in the form of strong spatial variations of scattering and absorption. Extracting quantified information on the actual distribution of tissue chromophores and other biomarkers constitutes therefore a challenging problem. Image quantification is further compromised by some frequently-used approximated inversion formulae. In this review, the currently available optoacoustic image reconstruction and quantification approaches are assessed, including back-projection and model-based inversion algorithms, sparse signal representation, wavelet-based approaches, methods for reduction of acoustic artifacts as well as multi-spectral methods for visualization of tissue bio-markers. Applicability of the different methodologies is further analyzed in the context of real-life performance in small animal and clinical in-vivo imaging scenarios. Sensors 2013-06-04 13 6 Review 10.3390/s130607345 7345 7384 1424-8220 2013-06-04 doi: 10.3390/s130607345 Christian Lutzweiler Daniel Razansky http://www.mdpi.com/1424-8220/13/6/7323 Many applications of metal oxide gas sensors can benefit from reliable algorithms to detect significant changes in the sensor response. Significant changes indicate a change in the emission modality of a distant gas source and occur due to a sudden change of concentration or exposure to a different compound. As a consequence of turbulent gas transport and the relatively slow response and recovery times of metal oxide sensors, their response in open sampling configuration exhibits strong fluctuations that interfere with the changes of interest. In this paper we introduce TREFEX, a novel change point detection algorithm, especially designed for metal oxide gas sensors in an open sampling system. TREFEX models the response of MOX sensors as a piecewise exponential signal and considers the junctions between consecutive exponentials as change points. We formulate non-linear trend filtering and change point detection as a parameter-free convex optimization problem for single sensors and sensor arrays. We evaluate the performance of the TREFEX algorithm experimentally for different metal oxide sensors and several gas emission profiles. A comparison with the previously proposed GLR method shows a clearly superior performance of the TREFEX algorithm both in detection performance and in estimating the change time. Sensors 2013-06-04 13 6 Article 10.3390/s130607323 7323 7344 1424-8220 2013-06-04 doi: 10.3390/s130607323 Sepideh Pashami Achim Lilienthal Erik Schaffernicht Marco Trincavelli http://www.mdpi.com/1424-8220/13/6/7308 When a body sensor network (BSN) that is linked to the backbone via a wireless network interface moves from one coverage zone to another, a handover is required to maintain network connectivity. This paper presents an optimized handover scheme with movement trend awareness for BSNs. The proposed scheme predicts the future position of a BSN user using the movement trend extracted from the historical position, and adjusts the handover decision accordingly. Handover initiation time is optimized when the unnecessary handover rate is estimated to meet the requirement and the outage probability is minimized. The proposed handover scheme is simulated in a BSN deployment area in a hospital environment in UK. Simulation results show that the proposed scheme reduces the outage probability by 22% as compared with the existing hysteresis-based handover scheme under the constraint of acceptable handover rate. Sensors 2013-06-03 13 6 Article 10.3390/s130607308 7308 7322 1424-8220 2013-06-03 doi: 10.3390/s130607308 Wen Sun Zhiqiang Zhang Lianying Ji Wai-Choong Wong http://www.mdpi.com/1424-8220/13/6/7296 The present paper aims to miniaturize a graphite-epoxy and synthetic zeolite-modified graphite-epoxy composite macroelectrode as a quasi-microelectrode aiming in vitro and also, envisaging in vivo simultaneous electrochemical detection of dopamine (DA) and ascorbic acid (AA) neurotransmitters, or DA detection in the presence of AA. The electrochemical behavior and the response of the designed materials to the presence of dopamine and ascorbic acid without any protective membranes were studied by cyclic voltammetry and constant-potential amperometry techniques. The catalytic effect towards dopamine detection was proved for the synthetic zeolite-modified graphite-epoxy composite quasi-microelectrode, allowing increasing the sensitivity and selectivity for this analyte detection, besides a possible electrostatic attraction between dopamine cation and the negative surface of the synthetic zeolite and electrostatic repulsion with ascorbic acid anion. Also, the synthetic zeolite-modified graphite-epoxy composite quasi-microelectrode gave the best electroanalytical parameters for dopamine detection using constant-potential amperometry, the most useful technique for practical applications. Sensors 2013-06-03 13 6 Article 10.3390/s130607296 7296 7307 1424-8220 2013-06-03 doi: 10.3390/s130607296 Elida Ilinoiu Florica Manea Pier Serra Rodica Pode http://www.mdpi.com/1424-8220/13/6/7279 In diabetes research, non-invasive continuous glucose monitoring (NI-CGM) devices represent a new and appealing frontier. In the last years, some multi-sensor devices for NI-CGM have been proposed, which exploit several sensors measuring phenomena of different nature, not only for measuring glucose related signals, but also signals reflecting some possible perturbing processes (temperature, blood perfusion). Estimation of glucose levels is then obtained combining these signals through a mathematical model which requires an initial calibration step exploiting one reference blood glucose (RBG) sample. Even if promising results have been obtained, especially in hospitalized volunteers, at present the temporal accuracy of NI-CGM sensors may suffer because of environmental and physiological interferences. The aim of this work is to develop a general methodology, based on Monte Carlo (MC) simulation, to assess the robustness of the calibration step used by NI-CGM devices against these disturbances. The proposed methodology is illustrated considering two examples: the first concerns the possible detrimental influence of sweat events, while the second deals with calibration scheduling. For implementing both examples, 45 datasets collected by the Solianis Multisensor system are considered. In the first example, the MC methodology suggests that no further calibration adjustments are needed after the occurrence of sweat events, because the “Multisensor+model” system is able to deal with the disturbance. The second case study shows how to identify the best time interval to update the model’s calibration for improving the accuracy of the estimated glucose. The methodology proposed in this work is of general applicability and can be helpful in making those incremental steps in NI-CGM devices development needed to further improve their performance. Sensors 2013-06-03 13 6 Article 10.3390/s130607279 7279 7295 1424-8220 2013-06-03 doi: 10.3390/s130607279 Mattia Zanon Giovanni Sparacino Andrea Facchinetti Mark Talary Martin Mueller Andreas Caduff Claudio Cobelli http://www.mdpi.com/1424-8220/13/6/7250 The use of wireless sensor networks (WSN) in tracking applications is growing at a fast pace. In these applications, the sensor nodes discover, monitor and track an event or target object. A significant number of proposals relating the use of WSNs for target tracking have been published to date. However, they either focus on the tracking algorithm or on the communication protocol, and none of them address the problem integrally. In this paper, a comprehensive proposal for target detection and tracking is discussed. We introduce a tracking algorithm to detect and estimate a target location. Moreover, we introduce a low-overhead routing protocol to be used along with our tracking algorithm. The proposed algorithm has low computational complexity and has been designed considering the use of a mobile sink while generating minimal delay and packet loss. We also discuss the results of the evaluation of the proposed algorithms. Sensors 2013-06-03 13 6 Article 10.3390/s130607250 7250 7278 1424-8220 2013-06-03 doi: 10.3390/s130607250 Carlos Calafate Carlos Lino Arnoldo Diaz-Ramirez Juan-Carlos Cano Pietro Manzoni http://www.mdpi.com/1424-8220/13/6/7224 Terrestrial laser scanners are sophisticated instruments that operate much like high-speed total stations. It has previously been shown that unmodelled systematic errors can exist in modern terrestrial laser scanners that deteriorate their geometric measurement precision and accuracy. Typically, signalised targets are used in point-based self-calibrations to identify and model the systematic errors. Although this method has proven its effectiveness, a large quantity of signalised targets is required and is therefore labour-intensive and limits its practicality. In recent years, feature-based self-calibration of aerial, mobile terrestrial, and static terrestrial laser scanning systems has been demonstrated. In this paper, the commonalities and differences between point-based and plane-based self-calibration (in terms of model identification and parameter correlation) are explored. The results of this research indicate that much of the knowledge from point-based self-calibration can be directly transferred to plane-based calibration and that the two calibration approaches are nearly equivalent. New network configurations, such as the inclusion of tilted scans, were also studied and prove to be an effective means for strengthening the self-calibration solution, and improved recoverability of the horizontal collimation axis error for hybrid scanners, which has always posed a challenge in the past. Sensors 2013-05-31 13 6 Article 10.3390/s130607224 7224 7249 1424-8220 2013-05-31 doi: 10.3390/s130607224 Jacky Chow Derek Lichti Craig Glennie Preston Hartzell http://www.mdpi.com/1424-8220/13/6/7212 Information obtained from multiple sensory modalities, such as vision and touch, is integrated to yield a holistic percept. As a haptic approach usually involves cross-modal sensory experiences, it is necessary to develop an apparatus that can characterize how a biological system integrates visual-tactile sensory information as well as how a robotic device infers object information emanating from both vision and touch. In the present study, we develop a novel visual-tactile cross-modal integration stimulator that consists of an LED panel to present visual stimuli and a tactile stimulator with three degrees of freedom that can present tactile motion stimuli with arbitrary motion direction, speed, and indentation depth in the skin. The apparatus can present cross-modal stimuli in which the spatial locations of visual and tactile stimulations are perfectly aligned. We presented visual-tactile stimuli in which the visual and tactile directions were either congruent or incongruent, and human observers reported the perceived visual direction of motion. Results showed that perceived direction of visual motion can be biased by the direction of tactile motion when visual signals are weakened. The results also showed that the visual-tactile motion integration follows the rule of temporal congruency of multi-modal inputs, a fundamental property known for cross-modal integration. Sensors 2013-05-31 13 6 Article 10.3390/s130607212 7212 7223 1424-8220 2013-05-31 doi: 10.3390/s130607212 Yu-Cheng Pei Ting-Yu Chang Tsung-Chi Lee Sudipta Saha Hsin-Yi Lai Manuel Gomez-Ramirez Shih-Wei Chou Alice Wong http://www.mdpi.com/1424-8220/13/6/7184 Various models using radiometric approach have been proposed to solve the problem of estimating the distance between a camera and an infrared emitter diode (IRED). They depend directly on the radiant intensity of the emitter, set by the IRED bias current. As is known, this current presents a drift with temperature, which will be transferred to the distance estimation method. This paper proposes an alternative approach to remove temperature drift in the distance estimation method by eliminating the dependence on radiant intensity. The main aim was to use the relative accumulated energy together with other defined models, such as the zeroth-frequency component of the FFT of the IRED image and the standard deviation of pixel gray level intensities in the region of interest containing the IRED image. By using the abovementioned models, an expression free of IRED radiant intensity was obtained. Furthermore, the final model permitted simultaneous estimation of the distance between the IRED and the camera and the IRED orientation angle. The alternative presented in this paper gave a 3% maximum relative error over a range of distances up to 3 m. Sensors 2013-05-31 13 6 Article 10.3390/s130607184 7184 7211 1424-8220 2013-05-31 doi: 10.3390/s130607184 Angel Cano-García José Galilea Pedro Fernández Arturo Infante Yamilet Pompa-Chacón Carlos Vázquez http://www.mdpi.com/1424-8220/13/6/7170 In many biological and environmental applications spatially resolved sensing of molecular oxygen is desirable. A powerful tool for distributed measurements is optical time domain reflectometry (OTDR) which is often used in the field of telecommunications. We combine this technique with a novel optical oxygen sensor dye, triangular-[4] phenylene (TP), immobilized in a polymer matrix. The TP luminescence decay time is 86 ns. The short decay time of the sensor dye is suitable to achieve a spatial resolution of some meters. In this paper we present the development and characterization of a reflectometer in the UV range of the electromagnetic spectrum as well as optical oxygen sensing with different fiber arrangements. Sensors 2013-05-31 13 6 Article 10.3390/s130607170 7170 7183 1424-8220 2013-05-31 doi: 10.3390/s130607170 Susanne Eich Elmar Schmälzlin Hans-Gerd Löhmannsröben http://www.mdpi.com/1424-8220/13/6/7156 Quartz Tuning Fork (QTF)-based Scanning Probe Microscopy (SPM) is an important field of research. A suitable model for the QTF is important to obtain quantitative measurements with these devices. Analytical models have the limitation of being based on the double cantilever configuration. In this paper, we present an electromechanical finite element model of the QTF electrically excited with two free prongs. The model goes beyond the state-of-the-art of numerical simulations currently found in the literature for this QTF configuration. We present the first numerical analysis of both the electrical and mechanical behavior of QTF devices. Experimental measurements obtained with 10 units of the same model of QTF validate the finite element model with a good agreement. Sensors 2013-05-30 13 6 Article 10.3390/s130607156 7156 7169 1424-8220 2013-05-30 doi: 10.3390/s130607156 Roger Oria Jorge Otero Laura González Luis Botaya Manuel Carmona Manel Puig-Vidal http://www.mdpi.com/1424-8220/13/6/7140 Mechanical loads cause severe damage to perishable agricultural products. In order to quantify the mechanical impact during harvest and postharvest processes, several electronic fruits have been developed. The objective of the work described here was to compare on a laboratory scale different types of impact acceleration recording electronic fruits: Mikras implanted in a real potato tuber as well as in a dummy tuber, IRD, Smart Spud and TuberLog. The acquisition of mechanical impacts was performed using a drop simulator with optional steel or PVC as impact material as well as a processing line simulator. Our results show that drops from 10 cm height on PVC caused similar peak accelerations of Mikras implanted in a real potato or a dummy, IRD and TuberLog. When dropped onto steel however, IRD, TuberLog and Mikras implanted in a dummy recorded higher peak values than Mikras in real potatoes. Impact on the flat side of a tuber led to higher peak values than impact on the apical region. This could be caused by different elastic compliance of synthetic materials as well as material thickness. Running through the processing line simulator TuberLog recorded the most impact; Smart Spud recorded a low number of impacts compared to the other electronic fruits. In all experiments the least sensitive measurements were recorded using Smart Spud. Sensors 2013-05-30 13 6 Article 10.3390/s130607140 7140 7155 1424-8220 2013-05-30 doi: 10.3390/s130607140 Ulrike Praeger Jelena Surdilovic Ingo Truppel Bernd Herold Martin Geyer http://www.mdpi.com/1424-8220/13/6/7121 A variety of gyroscopes have been extensively studied due to their capability of precision detection of rotation rates and extensive applications in navigation, guidance and motion control. In this work, a new Hybrid Gyroscope (HG) which combines the traditional Dynamically Tuned Gyroscope (DTG) with silicon micromachined technology is investigated. The HG not only has the potentiality of achieving the same high precision as the traditional DTG, but also features a small size and low cost. The theoretical mechanism of the HG with a capacitance transducer and an electrostatic torquer is derived and the influence of the installation errors from the capacitance plate and the disc rotor module is investigated. A new tuning mechanism based on negative stiffness rather than the traditional dynamic tuning is proposed. The experimental results prove that the negative stiffness tuning is practicable and a tuning voltage of as high as 63 V is demonstrated. Due to the decreased installation error, the non-linearity of the scale factor is reduced significantly from 11.78% to 0.64%, as well as the asymmetry from 93.3% to 1.56% in the open loop condition. The rebalancing close-loop control is simulated and achieved experimentally, which proves that the fundamental principle of the HG is feasible. Sensors 2013-05-30 13 6 Article 10.3390/s130607121 7121 7139 1424-8220 2013-05-30 doi: 10.3390/s130607121 Bo Yang Yumei Guan Shourong Wang Qi Zou Xian Chu Haiyan Xue http://www.mdpi.com/1424-8220/13/6/7104 Many analyses of acoustic signals processing have been proposed for different applications over the last few years. When considering a bar-based structure, if the material through which the sound waves propagate is considered to be acoustically homogeneous and the sound speed is well known, then it is possible to determine the position and time of impact by a simple observation of the arrival times of the signals of all the transducers that are strategically disposed on the structure. This paper presents a generalized method for impact detection and location on a flat plate, together with a calibration procedure with which to obtain the sound speed from only one set of measurements. This propagation speed is not well known as a result of either imprecise material properties or the overlapping of longitudinal and transversal waves with different propagation velocities. The use of only three piezoelectric sensors allows the position and time of impact on the flat plate to be obtained when the sound speed is well known, while the use of additional sensors permits a larger detection area to be covered, helps to estimate the sound speed and/or avoids the wrong timing of difference measurements. Experimental results are presented using a robot with a specially designed knocking tool that produces impacts on a metallic flat plate. Sensors 2013-05-30 13 6 Article 10.3390/s130607104 7104 7120 1424-8220 2013-05-30 doi: 10.3390/s130607104 José Somolinos Amable López Rafael Morales Carlos Morón http://www.mdpi.com/1424-8220/13/6/7079 This paper describes development of a novel mid-infrared light emitting diode (LED) and photodiode (PD) light source/detector combination and use within a non-dispersive infrared (NDIR) carbon dioxide gas sensor. The LED/PD based NDIR sensor provides fast stabilisation time (time required to turn on the sensor from cold, warm up, take and report a measurement, and power down again ≈1 second), longevity (>15 years), low power consumption and low cost. Described performance is compatible with “fit and forget” wireless deployed sensors in applications such as indoor air quality monitoring/control & energy conservation in buildings, transport systems, horticultural greenhouses and portable deployment for safety, industrial and medical applications. Fast stabilisation time, low intrinsic power consumption and cycled operation offer typical energy consumption per measurement of mJ’s, providing extended operation using battery and/or energy harvesting strategies (measurement interval of ≈ 2 minutes provides >10 years operation from one AA battery). Specific performance data is provided in relation to measurement accuracy and noise, temperature performance, cross sensitivity, measurement range (two pathlength variants are described covering ambient through to 100% gas concentration), comparison with NDIR utilizing thermal source/pyroelectric light source/detector combination and compatibility with energy harvesting. Semiconductor based LED/PD processing together with injection moulded reflective optics and simple assembly provide a route to low cost high volume manufacturing. Sensors 2013-05-29 13 6 Article 10.3390/s130607079 7079 7103 1424-8220 2013-05-29 doi: 10.3390/s130607079 Desmond Gibson Calum MacGregor http://www.mdpi.com/1424-8220/13/6/7065 The use of Vehicular Ad-Hoc Networks (VANETs) is growing nowadays and it includes both roadside-to-vehicle communication (RVC) and inter-vehicle communication (IVC). The purpose of VANETs is to exchange useful information between vehicles and the roadside infrastructures for making an intelligent use of them. There are several possible applications for this technology like: emergency warning system for vehicles, cooperative adaptive cruise control or collision avoidance, among others. The objective of this work is to develop a VANET prototype system for urban environments using IEEE 802.15.4 compliant devices. Simulation-based values of the estimated signal strength and radio link quality values are obtained and compared with measurements in outdoor conditions to validate an implemented VANET system. The results confirm the possibility of implementing low cost vehicular communication networks operating at moderate vehicular speeds. Sensors 2013-05-29 13 6 Article 10.3390/s130607065 7065 7078 1424-8220 2013-05-29 doi: 10.3390/s130607065 Juan Nazabal Francisco Falcone Carlos Fernández-Valdivielso Ignacio Matías http://www.mdpi.com/1424-8220/13/6/7053 A polymer-ceramic pressure-sensitive paint (PC-PSP) is a fast responding and sprayable PSP which has been applied for capturing global unsteady flows. The luminophore application process is studied to enhance the characterization of the PC-PSP. A dipping deposition method is used to apply a luminophore on a polymer-ceramic coating. The method selects a solvent by its polarity index. The characterization includes the signal level, pressure sensitivity, temperature dependency, and response time. It is found that the luminophore application process affects the steady-state characterizations, such as the signal level, pressure sensitivity, and temperature dependency. A range of change for each characterization, which is based on the minimum quantity, is a factor of 4.7, 9, and 3.8, respectively. A response time on the order of ten microseconds is shown. The application process is not a dominant factor for changing the response time, which is within the uncertainty of the thickness variation. Comparisons of the effects on the luminophore application process and the polymer content are made to discuss the PC-PSP characterization results. Sensors 2013-05-29 13 6 Article 10.3390/s130607053 7053 7064 1424-8220 2013-05-29 doi: 10.3390/s130607053 Hirotaka Sakaue Tatsunori Hayashi Hitoshi Ishikawa http://www.mdpi.com/1424-8220/13/6/7033 Multi-Input Multi-Output (MIMO) techniques can be used to increase the data rate for a given bit error rate (BER) and transmission power. Due to the small form factor, energy and processing constraints of wireless sensor nodes, a cooperative Virtual MIMO as opposed to True MIMO system architecture is considered more feasible for wireless sensor network (WSN) applications. Virtual MIMO with Vertical-Bell Labs Layered Space-Time (V-BLAST) multiplexing architecture has been recently established to enhance WSN performance. In this paper, we further investigate the impact of different modulation techniques, and analyze for the first time, the performance of a cooperative Virtual MIMO system based on V-BLAST architecture with multi-carrier modulation techniques. Through analytical models and simulations using real hardware and environment settings, both communication and processing energy consumptions, BER, spectral efficiency, and total time delay of multiple cooperative nodes each with single antenna are evaluated. The results show that cooperative Virtual-MIMO with Binary Phase Shift Keying-Wavelet based Orthogonal Frequency Division Multiplexing (BPSK-WOFDM) modulation is a promising solution for future high data-rate and energy-efficient WSNs. Sensors 2013-05-28 13 6 Article 10.3390/s130607033 7033 7052 1424-8220 2013-05-28 doi: 10.3390/s130607033 Zimran Rafique Boon-Chong Seet Adnan Al-Anbuky http://www.mdpi.com/1424-8220/13/6/7021 We present and analyze a method to improve the morphology and mechanical properties of gold thin films for use in optical sensors or other settings where good adhesion of gold to a substrate is of importance and where controlled topography/roughness is key. To improve the adhesion of thermally evaporated gold thin films, we introduce a gold deposition step on SU-8 photoresist prior to UV exposure but after the pre-bake step of SU-8 processing. Shrinkage and distribution of residual stresses, which occur during cross-linking of the SU-8 polymer layer in the post-exposure baking step, are responsible for the higher adhesion of the top gold film to the post-deposition cured SU-8 sublayer. The SU-8 underlayer can also be used to tune the resulting gold film morphology. Our promoter-free protocol is easily integrated with existing sensor microfabrication processes. Sensors 2013-05-28 13 6 Article 10.3390/s130607021 7021 7032 1424-8220 2013-05-28 doi: 10.3390/s130607021 Behrang Moazzez Stacey O'Brien Erika Merschrod S. http://www.mdpi.com/1424-8220/13/6/7004 Healthcare environments, as many other real world environments, present many changing and unpredictable situations. In order to use a social robot in such an environment, the robot has to be prepared to deal with all the changing situations. This paper presents a robot self-configuration approach to overcome suitably the commented problems. The approach is based on the integration of a semantic framework, where a reasoner can take decisions about the configuration of robot services and resources. An ontology has been designed to model the robot and the relevant context information. Besides rules are used to encode human knowledge and serve as policies for the reasoner. The approach has been successfully implemented in a mobile robot, which showed to be more capable of solving situations not pre-designed. Sensors 2013-05-28 13 6 Article 10.3390/s130607004 7004 7020 1424-8220 2013-05-28 doi: 10.3390/s130607004 Gorka Azkune Pablo Orduña Xabier Laiseca Eduardo Castillejo Diego López-de-Ipiña Miguel Loitxate Jon Azpiazu http://www.mdpi.com/1424-8220/13/6/6981 Neuroimaging has improved our understanding of the evolution of stroke at discreet time points helping to identify irreversibly damaged and potentially reversible ischemic brain. Neuroimaging has also contributed considerably to the basic premise of acute stroke therapy which is to salvage some portion of the ischemic region from evolving into infarction, and by doing so, maintaining brain function and improving outcome. The term neurovascular unit (NVU) broadens the concept of the ischemic penumbra by linking the microcirculation with neuronal-glial interactions during ischemia reperfusion. Strategies that attempt to preserve the individual components (endothelium, glia and neurons) of the NVU are unlikely to be helpful if blood flow is not fully restored to the microcirculation. Magnetic resonance imaging (MRI) is the foremost imaging technology able to bridge both basic science and the clinic via non-invasive real time high-resolution anatomical delineation of disease manifestations at the molecular and ionic level. Current MRI based technologies have focused on the mismatch between perfusion-weighted imaging (PWI) and diffusion weighted imaging (DWI) signals to estimate the tissue that could be saved if reperfusion was achieved. Future directions of MRI may focus on the discordance of recanalization and reperfusion, providing complimentary pathophysiological information to current compartmental paradigms of infarct core (DWI) and penumbra (PWI) with imaging information related to cerebral blood flow, BBB permeability, inflammation, and oedema formation in the early acute phase. In this review we outline advances in our understanding of stroke pathophysiology with imaging, transcending animal stroke models to human stroke, and describing the potential translation of MRI to image important interactions relevant to acute stroke at the interface of the neurovascular unit. Sensors 2013-05-27 13 6 Review 10.3390/s130606981 6981 7003 1424-8220 2013-05-27 doi: 10.3390/s130606981 Philip Barber http://www.mdpi.com/1424-8220/13/6/6957 X-ray Computed Tomography (CT) is one of the most commonly utilized anatomical imaging modalities for both research and clinical purposes. CT combines high-resolution, three-dimensional data with relatively fast acquisition to provide a solid platform for non-invasive human or specimen imaging. The primary limitation of CT is its inability to distinguish many soft tissues based on native contrast. While bone has high contrast within a CT image due to its material density from calcium phosphate, soft tissue is less dense and many are homogenous in density. This presents a challenge in distinguishing one type of soft tissue from another. A couple exceptions include the lungs as well as fat, both of which have unique densities owing to the presence of air or bulk hydrocarbons, respectively. In order to facilitate X-ray CT imaging of other structures, a range of contrast agents have been developed to selectively identify and visualize the anatomical properties of individual tissues. Most agents incorporate atoms like iodine, gold, or barium because of their ability to absorb X-rays, and thus impart contrast to a given organ system. Here we review the strategies available to visualize lung, fat, brain, kidney, liver, spleen, vasculature, gastrointestinal tract, and liver tissues of living mice using either innate contrast, or commercial injectable or ingestible agents with selective perfusion. Further, we demonstrate how each of these approaches will facilitate the non-invasive, longitudinal, in vivo imaging of pre-clinical disease models at each anatomical site. Sensors 2013-05-27 13 6 Review 10.3390/s130606957 6957 6980 1424-8220 2013-05-27 doi: 10.3390/s130606957 Connor Wathen Nathan Foje Tony Avermaete Bernadette Miramontes Sarah Chapaman Todd Sasser Raghuraman Kannan Steven Gerstler W. Leevy http://www.mdpi.com/1424-8220/13/6/6946 A quartz crystal microbalance (QCM) biosensor with nanogram sensitivity has been constructed through a reasonable designing and biological processing of the piezoelectric quartz crystals. Due to its highly sensitivity, real time detection and low cost, the proposed QCM biosensor has a promising potential in blood coagulation research. In the current study, the QCM biosensor was used to determine the activated partial thromboplastin time (APTT) for 120 anticoagulated plasma specimens. A good linear relationship was found in a double-logarithmic plot of APTT versus fibrinogen concentration in the range of 1.58–6.30 g/L. For factor VIII, the detection range by the QCM biosensor is 0.0185–0.111 mg/L. The QCM biosensor results were compared with those obtained by commercial optical coagulometry and a good agreement (correlation coefficient is 0.949 for fibrinogen, and 0.948 for factor VIII) was reached. Furthermore, the QCM determination can be completed within 10 min. Our study suggested that the proposed QCM biosensor could provide for more convenient and time saving operations, which may be useful in clinical situations for rapid monitoring of anticoagulant therapy using small volume (20 μL) plasma specimens. Sensors 2013-05-24 13 6 Article 10.3390/s130606946 6946 6956 1424-8220 2013-05-24 doi: 10.3390/s130606946 Chunyan Yao Ling Qu Weiling Fu http://www.mdpi.com/1424-8220/13/6/6936 A flow biosensor for the detection of toxicity in water using the ammonia-oxidizing bacterium (AOB) Nitrosomonas europaea as a bioreceptor and a polymeric membrane ammonium-selective electrode as a transducer is described. The system is based on the inhibition effects of toxicants on the activity of AOB, which can be evaluated by measuring the ammonium consumption rates with the ammonium-selective membrane electrode. The AOB cells are immobilized on polyethersulfone membranes packed in a holder, while the membrane electrode is placed downstream in the flow cell. Two specific inhibitors of the ammonia oxidation‒allylthiourea and thioacetamide‒have been tested. The IC50 values defined as the concentration of an inhibitor causing a 50% reduction in the ammonia oxidation activity have been measured as 0.17 μM and 0.46 μM for allylthiourea and thioacetamide, respectively. The proposed sensor offers advantages of simplicity, speed and high sensitivity for measuring toxicity in water. Sensors 2013-05-24 13 6 Article 10.3390/s130606936 6936 6945 1424-8220 2013-05-24 doi: 10.3390/s130606936 Qianyu Zhang Jiawang Ding Lijuan Kou Wei Qin http://www.mdpi.com/1424-8220/13/6/6910 Langasite surface acoustic wave devices can be used to implement harsh-environment wireless sensing of gas concentration and temperature. This paper reviews prior work on the development of langasite surface acoustic wave devices, followed by a report of recent progress toward the implementation of oxygen gas sensors. Resistive metal oxide films can be used as the oxygen sensing film, although development of an adherent barrier layer will be necessary with the sensing layers studied here to prevent interaction with the langasite substrate. Experimental results are presented for the performance of a langasite surface acoustic wave oxygen sensor with tin oxide sensing layer, and these experimental results are correlated with direct measurements of the sensing layer resistivity. Sensors 2013-05-24 13 6 Article 10.3390/s130606910 6910 6935 1424-8220 2013-05-24 doi: 10.3390/s130606910 David Greve Tao-Lun Chin Peng Zheng Paul Ohodnicki John Baltrus Irving Oppenheim http://www.mdpi.com/1424-8220/13/6/6900 In this study, we explored magnetic nanoparticles translocating through a nanopore in the presence of an inhomogeneous magnetic field. By detecting the ionic current blockade signals with a silicon nitride nanopore, we found that the translocation velocity that is driven by magnetic and hydrodynamic forces on a single magnetic nanoparticle can be accurately determined and is linearly proportional to the magnetization of the magnetic nanoparticle. Thus, we obtained the magneto-susceptibility of an individual nanoparticle and the average susceptibility over one hundred particles within a few minutes. Sensors 2013-05-24 13 6 Article 10.3390/s130606900 6900 6909 1424-8220 2013-05-24 doi: 10.3390/s130606900 SangYoon Park Jaekwan Lim Y. Pak Seunghyun Moon Yoon-Kyu Song http://www.mdpi.com/1424-8220/13/6/6882 Despite technical advances, respiratory motion remains a major impediment in a substantial amount of patients undergoing coronary magnetic resonance angiography (CMRA). Traditionally, respiratory motion compensation has been performed with a one-dimensional respiratory navigator positioned on the right hemi-diaphragm, using a motion model to estimate and correct for the bulk respiratory motion of the heart. Recent technical advancements has allowed for direct respiratory motion estimation of the heart, with improved motion compensation performance. Some of these new methods, particularly using image-based navigators or respiratory binning, allow for more advanced motion correction which enables CMRA data acquisition throughout most or all of the respiratory cycle, thereby significantly reducing scan time. This review describes the three components typically involved in most motion compensation strategies for CMRA, including respiratory motion estimation, gating and correction, and how these processes can be utilized to perform advanced respiratory motion compensation. Sensors 2013-05-24 13 6 Review 10.3390/s130606882 6882 6899 1424-8220 2013-05-24 doi: 10.3390/s130606882 Markus Henningsson Rene Botnar http://www.mdpi.com/1424-8220/13/5/6865 In this paper, a panel of single-stranded DNA aptamers with high affinity and specificity against Salmonella Paratyphi A was selected from an enriched oligonucleotide pool by a whole-cell-Systematic Evolution of Ligands by Exponential Enrichment (SELEX) procedure, during which four other Salmonella serovars were used as counter-selection targets. It was determined through a fluorescence assay that the selected aptamers had high binding ability and specificity to this pathogen. The dissociation constant of these aptamers were up to nanomolar range, and aptamer Apt22 with the lowest Kd (47 ± 3 nM) was used in cell imaging experiments. To detect this bacteria with high specificity and cost-efficiently, a novel useful detection method was also constructed based on the noncovalent self-assembly of single-walled carbon nanotubes (SWNTs) and DNAzyme-labeled aptamer detection probes. The amounts of target bacteria could be quantified by exploiting chemoluminescence intensity changes at 420 nm and the detection limit of the method was 103 cfu/mL. This study demonstrated the applicability of Salmonella specific aptamers and their potential for use in the detection of Salmonella in food, clinical and environmental samples. Sensors 2013-05-22 13 5 Article 10.3390/s130506865 6865 6881 1424-8220 2013-05-22 doi: 10.3390/s130506865 Ming Yang Zhihui Peng Yi Ning Yongzhe Chen Qin Zhou Le Deng http://www.mdpi.com/1424-8220/13/5/6832 In this paper, a human electrocardiogram (ECG) identification system based on ensemble empirical mode decomposition (EEMD) is designed. A robust preprocessing method comprising noise elimination, heartbeat normalization and quality measurement is proposed to eliminate the effects of noise and heart rate variability. The system is independent of the heart rate. The ECG signal is decomposed into a number of intrinsic mode functions (IMFs) and Welch spectral analysis is used to extract the significant heartbeat signal features. Principal component analysis is used reduce the dimensionality of the feature space, and the K-nearest neighbors (K-NN) method is applied as the classifier tool. The proposed human ECG identification system was tested on standard MIT-BIH ECG databases: the ST change database, the long-term ST database, and the PTB database. The system achieved an identification accuracy of 95% for 90 subjects, demonstrating the effectiveness of the proposed method in terms of accuracy and robustness. Sensors 2013-05-22 13 5 Article 10.3390/s130506832 6832 6864 1424-8220 2013-05-22 doi: 10.3390/s130506832 Zhidong Zhao Lei Yang Diandian Chen Yi Luo http://www.mdpi.com/1424-8220/13/5/6811 It is easy to measure energy consumption with a power meter. However, energy savings cannot be directly computed by the powers measured using existing power meter technologies, since the power consumption only reflects parts of the real energy flows. The International Performance Measurement and Verification Protocol (IPMVP) was proposed by the Efficiency Valuation Organization (EVO) to quantify energy savings using four different methodologies of A, B, C and D. Although energy savings can be estimated following the IPMVP, there are limitations on its practical implementation. Moreover, the data processing methods of the four IPMVP alternatives use multiple sensors (thermometer, hygrometer, Occupant information) and power meter readings to simulate all facilities, in order to determine an energy usage benchmark and the energy savings. This study proposes a simple sensor platform to measure energy savings. Using usually the Electronic Product Code (EPC) global standard, an architecture framework for an information system is constructed that integrates sensors data, power meter readings and occupancy conditions. The proposed sensor platform is used to monitor a building with a newly built vertical garden system (VGS). A VGS shields solar radiation and saves on energy that would be expended on air-conditioning. With this platform, the amount of energy saved in the whole facility is measured and reported in real-time. The data are compared with those obtained from detailed measurement and verification (M&V) processes. The discrepancy is less than 1.565%. Using measurements from the proposed sensor platform, the energy savings for the entire facility are quantified, with a resolution of ±1.2%. The VGS gives an 8.483% daily electricity saving for the building. Thus, the results show that the simple sensor platform proposed by this study is more widely applicable than the four complicated IPMVP alternatives and the VGS is an effective tool in reducing the carbon footprint of a building. Sensors 2013-05-22 13 5 Article 10.3390/s130506811 6811 6831 1424-8220 2013-05-22 doi: 10.3390/s130506811 Yen-Chieh Tseng Da-Sheng Lee Cheng-Fang Lin Ching-Yuan Chang http://www.mdpi.com/1424-8220/13/5/6793 The objective of the current research was not only to provide a fast and automatic positioning platform for single cells, but also improved biomolecular manipulation techniques. In this study, an automatic platform for cell positioning using electroosmotic flow and image processing technology was designed. The platform was developed using a PCI image acquisition interface card for capturing images from a microscope and then transferring them to a computer using human-machine interface software. This software was designed by the Laboratory Virtual Instrument Engineering Workbench, a graphical language for finding cell positions and viewing the driving trace, and the fuzzy logic method for controlling the voltage or time of an electric field. After experiments on real human leukemic cells (U-937), the success of the cell positioning rate achieved by controlling the voltage factor reaches 100% within 5 s. A greater precision is obtained when controlling the time factor, whereby the success rate reaches 100% within 28 s. Advantages in both high speed and high precision are attained if these two voltage and time control methods are combined. The control speed with the combined method is about 5.18 times greater than that achieved by the time method, and the control precision with the combined method is more than five times greater than that achieved by the voltage method. Sensors 2013-05-21 13 5 Article 10.3390/s130506793 6793 6810 1424-8220 2013-05-21 doi: 10.3390/s130506793 Chyung Ay Chao-Wang Young Jhong-Yin Chen http://www.mdpi.com/1424-8220/13/5/6775 A single-chip sensor system-on-a-chip (SoC) that implements radio for 2.4 GHz, complete digital baseband physical layer (PHY), 10-bit sigma-delta analog-to-digital converter and dedicated sensor calibration hardware for industrial sensing systems has been proposed and integrated in a 0.18-μm CMOS technology. The transceiver’s building block includes a low-noise amplifier, mixer, channel filter, receiver signal-strength indicator, frequency synthesizer, voltage-controlled oscillator, and power amplifier. In addition, the digital building block consists of offset quadrature phase-shift keying (OQPSK) modulation, demodulation, carrier frequency offset compensation, auto-gain control, digital MAC function, sensor calibration hardware and embedded 8-bit microcontroller. The digital MAC function supports cyclic redundancy check (CRC), inter-symbol timing check, MAC frame control, and automatic retransmission. The embedded sensor signal processing block consists of calibration coefficient calculator, sensing data calibration mapper and sigma-delta analog-to-digital converter with digital decimation filter. The sensitivity of the overall receiver and the error vector magnitude (EVM) of the overall transmitter are −99 dBm and 18.14%, respectively. The proposed calibration scheme has a reduction of errors by about 45.4% compared with the improved progressive polynomial calibration (PPC) method and the maximum current consumption of the SoC is 16 mA. Sensors 2013-05-21 13 5 Article 10.3390/s130506775 6775 6792 1424-8220 2013-05-21 doi: 10.3390/s130506775 Dong-Sun Kim Sung-Joon Jang Tae-Ho Hwang http://www.mdpi.com/1424-8220/13/5/6759 Bio-composite coatings consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) and tyrosinase (Ty) were successfully electrodeposited on conventional size gold (Au) disk electrodes and microelectrode arrays using sinusoidal voltages. Electrochemical polymerization of the corresponding monomer was carried out in the presence of various Ty amounts in aqueous buffered solutions. The bio-composite coatings prepared using sinusoidal voltages and potentiostatic electrodeposition methods were compared in terms of morphology, electrochemical properties, and biocatalytic activity towards various analytes. The amperometric biosensors were tested in dopamine (DA) and catechol (CT) electroanalysis in aqueous buffered solutions. The analytical performance of the developed biosensors was investigated in terms of linear response range, detection limit, sensitivity, and repeatability. A semi-quantitative multi-analyte procedure for simultaneous determination of DA and CT was developed. The amperometric biosensor prepared using sinusoidal voltages showed much better analytical performance. The Au disk biosensor obtained by 50 mV alternating voltage amplitude displayed a linear response for DA concentrations ranging from 10 to 300 μM, with a detection limit of 4.18 μM. Sensors 2013-05-21 13 5 Article 10.3390/s130506759 6759 6774 1424-8220 2013-05-21 doi: 10.3390/s130506759 Stelian Lupu Cecilia Lete Paul Balaure Dan Caval Constantin Mihailciuc Boris Lakard Jean-Yves Hihn Francisco Campo http://www.mdpi.com/1424-8220/13/5/6746 High-rise buildings subjected to lateral loads such as wind and earthquake loads must be checked not to exceed the limits on the maximum lateral displacement or the maximum inter-story drift ratios. In this paper, a sensing model for deformed shapes of a building structure in motion is presented. The deformed shape sensing model based on a 2D scanner consists of five modules: (1) module for acquiring coordinate information of a point in a building; (2) module for coordinate transformation and data arrangement for generation of time history of the point; (3) module for smoothing by adjacent averaging technique; (4) module for generation of the displacement history for each story and deformed shape of a building, and (5) module for evaluation of the serviceability of a building. The feasibility of the sensing model based on a 2D laser scanner is tested through free vibration tests of a three-story steel frame structure with a relatively high slenderness ratio of 5.0. Free vibration responses measured from both laser displacement sensors and a 2D laser scanner are compared. In the experimentation, the deformed shapes were obtained from three different methods: the model based on the 2D laser scanner, the direct measurement based on laser displacement sensors, and the numerical method using acceleration data and the displacements from GPS. As a result, it is confirmed that the deformed shape measurement model based on a 2D laser scanner can be a promising alternative for high-rise buildings where installation of laser displacement sensors is impossible. Sensors 2013-05-21 13 5 Article 10.3390/s130506746 6746 6758 1424-8220 2013-05-21 doi: 10.3390/s130506746 Se Choi Bub Kim Hong Lee Yousok Kim Hyo Park http://www.mdpi.com/1424-8220/13/5/6730 The work presented here is part of a larger study to identify novel technologies and biomarkers for early Alzheimer disease (AD) detection and it focuses on evaluating the suitability of a new approach for early AD diagnosis by non-invasive methods. The purpose is to examine in a pilot study the potential of applying intelligent algorithms to speech features obtained from suspected patients in order to contribute to the improvement of diagnosis of AD and its degree of severity. In this sense, Artificial Neural Networks (ANN) have been used for the automatic classification of the two classes (AD and control subjects). Two human issues have been analyzed for feature selection: Spontaneous Speech and Emotional Response. Not only linear features but also non-linear ones, such as Fractal Dimension, have been explored. The approach is non invasive, low cost and without any side effects. Obtained experimental results were very satisfactory and promising for early diagnosis and classification of AD patients. Sensors 2013-05-21 13 5 Article 10.3390/s130506730 6730 6745 1424-8220 2013-05-21 doi: 10.3390/s130506730 Karmele López-de-Ipiña Jesus-Bernardino Alonso Carlos Travieso Jordi Solé-Casals Harkaitz Egiraun Marcos Faundez-Zanuy Aitzol Ezeiza Nora Barroso Miriam Ecay-Torres Pablo Martinez-Lage Unai Lizardui http://www.mdpi.com/1424-8220/13/5/6713 In this paper, we present a new reset tree-based scheme to protect cryptographic hardware against optical fault injection attacks. As one of the most powerful invasive attacks on cryptographic hardware, optical fault attacks cause semiconductors to misbehave by injecting high-energy light into a decapped integrated circuit. The contaminated result from the affected chip is then used to reveal secret information, such as a key, from the cryptographic hardware. Since the advent of such attacks, various countermeasures have been proposed. Although most of these countermeasures are strong, there is still the possibility of attack. In this paper, we present a novel optical fault detection scheme that utilizes the buffers on a circuit’s reset signal tree as a fault detection sensor. To evaluate our proposal, we model radiation-induced currents into circuit components and perform a SPICE simulation. The proposed scheme is expected to be used as a supplemental security tool. Sensors 2013-05-21 13 5 Article 10.3390/s130506713 6713 6729 1424-8220 2013-05-21 doi: 10.3390/s130506713 Dong-Geon Lee Dooho Choi Jungtaek Seo Howon Kim http://www.mdpi.com/1424-8220/13/5/6687 Sensors utilize a large number of heterogeneous technologies for a varied set of application environments. The sheer number of devices involved requires that this Internet be the Future Internet, with a core network based on IPv6 and a higher scalability in order to be able to address all the devices, sensors and things located around us. This capability to connect through IPv6 devices, sensors and things is what is defining the so-called Internet of Things (IoT). IPv6 provides addressing space to reach this ubiquitous set of sensors, but legacy technologies, such as X10, European Installation Bus (EIB), Controller Area Network (CAN) and radio frequency ID (RFID) from the industrial, home automation and logistic application areas, do not support the IPv6 protocol. For that reason, a technique must be devised to map the sensor and identification technologies to IPv6, thus allowing homogeneous access via IPv6 features in the context of the IoT. This paper proposes a mapping between the native addressing of each technology and an IPv6 address following a set of rules that are discussed and proposed in this work. Specifically, the paper presents a technology-dependent IPv6 addressing proxy, which maps each device to the different subnetworks built under the IPv6 prefix addresses provided by the internet service provider for each home, building or user. The IPv6 addressing proxy offers a common addressing environment based on IPv6 for all the devices, regardless of the device technology. Thereby, this offers a scalable and homogeneous solution to interact with devices that do not support IPv6 addressing. The IPv6 addressing proxy has been implemented in a multi-protocol Sensors 2013, 13 6688 card and evaluated successfully its performance, scalability and interoperability through a protocol built over IPv6. Sensors 2013-05-17 13 5 Article 10.3390/s130506687 6687 6712 1424-8220 2013-05-17 doi: 10.3390/s130506687 Antonio Jara Pedro Moreno-Sanchez Antonio Skarmeta Socrates Varakliotis Peter Kirstein http://www.mdpi.com/1424-8220/13/5/6669 Strain distributions are crucial criteria of cross-beams six-axis force/torque sensors. The conventional method for calculating the criteria is to utilize Finite Element Analysis (FEA) to get numerical solutions. This paper aims to obtain analytical solutions of strains under the effect of external force/torque in each dimension. Genetic mechanical models for cross-beams six-axis force/torque sensors are proposed, in which deformable cross elastic beams and compliant beams are modeled as quasi-static Timoshenko beam. A detailed description of model assumptions, model idealizations, application scope and model establishment is presented. The results are validated by both numerical FEA simulations and calibration experiments, and test results are found to be compatible with each other for a wide range of geometric properties. The proposed analytical solutions are demonstrated to be an accurate estimation algorithm with higher efficiency. Sensors 2013-05-17 13 5 Article 10.3390/s130506669 6669 6686 1424-8220 2013-05-17 doi: 10.3390/s130506669 Junqing Ma Aiguo Song http://www.mdpi.com/1424-8220/13/5/6651 Traversal time and hop count analysis (TTHCA) is a recent wormhole detection algorithm for mobile ad hoc networks (MANET) which provides enhanced detection performance against all wormhole attack variants and network types. TTHCA involves each node measuring the processing time of routing packets during the route discovery process and then delivering the measurements to the source node. In a participation mode (PM) wormhole where malicious nodes appear in the routing tables as legitimate nodes, the time measurements can potentially be altered so preventing TTHCA from successfully detecting the wormhole. This paper analyses the prevailing conditions for time tampering attacks to succeed for PM wormholes, before introducing an extension to the TTHCA detection algorithm called ∆T Vector which is designed to identify time tampering, while preserving low false positive rates. Simulation results confirm that the ∆T Vector extension is able to effectively detect time tampering attacks, thereby providing an important security enhancement to the TTHCA algorithm. Sensors 2013-05-17 13 5 Article 10.3390/s130506651 6651 6668 1424-8220 2013-05-17 doi: 10.3390/s130506651 Jonny Karlsson Laurence Dooley Göran Pulkkis http://www.mdpi.com/1424-8220/13/5/6636 The current trend of the civil aviation technology is to modernize the legacy air traffic control (ATC) system that is mainly supported by many ground based navigation aids to be the new air traffic management (ATM) system that is enabled by global positioning system (GPS) technology. Due to the low receiving power of GPS signal, it is a major concern to aviation authorities that the operation of the ATM system might experience service interruption when the GPS signal is jammed by either intentional or unintentional radio-frequency interference. To maintain the normal operation of the ATM system during the period of GPS outage, the use of the current radar system is proposed in this paper. However, the tracking performance of the current radar system could not meet the required performance of the ATM system, and an enhanced tracking algorithm, the interacting multiple model and probabilistic data association filter (IMMPDAF), is therefore developed to support the navigation and surveillance services of the ATM system. The conventional radar tracking algorithm, the nearest neighbor Kalman filter (NNKF), is used as the baseline to evaluate the proposed radar tracking algorithm, and the real flight data is used to validate the IMMPDAF algorithm. As shown in the results, the proposed IMMPDAF algorithm could enhance the tracking performance of the current aviation radar system and meets the required performance of the new ATM system. Thus, the current radar system with the IMMPDAF algorithm could be used as an alternative system to continue aviation navigation and surveillance services of the ATM system during GPS outage periods. Sensors 2013-05-17 13 5 Article 10.3390/s130506636 6636 6650 1424-8220 2013-05-17 doi: 10.3390/s130506636 Shau-Shiun Jan Yu-Chun Kao http://www.mdpi.com/1424-8220/13/5/6605 Biosignal analysis is one of the most important topics that researchers have tried to develop during the last century to understand numerous human diseases. Electroencephalograms (EEGs) are one of the techniques which provides an electrical representation of biosignals that reflect changes in the activity of the human brain. Monitoring the levels of anesthesia is a very important subject, which has been proposed to avoid both patient awareness caused by inadequate dosage of anesthetic drugs and excessive use of anesthesia during surgery. This article reviews the bases of these techniques and their development within the last decades and provides a synopsis of the relevant methodologies and algorithms that are used to analyze EEG signals. In addition, it aims to present some of the physiological background of the EEG signal, developments in EEG signal processing, and the effective methods used to remove various types of noise. This review will hopefully increase efforts to develop methods that use EEG signals for determining and classifying the depth of anesthesia with a high data rate to produce a flexible and reliable detection device. Sensors 2013-05-17 13 5 Review 10.3390/s130506605 6605 6635 1424-8220 2013-05-17 doi: 10.3390/s130506605 Mahmoud Al-Kadi Mamun Reaz Mohd Ali http://www.mdpi.com/1424-8220/13/5/6578 In this paper we present a new optical, flexible pressure sensor that can be applied as smart skin to a robot or to consumer electronic devices. We describe a mechano-optical transduction principle that can allow the encoding of information related to an externally applied mechanical stimulus, e.g., contact, pressure and shape of contact. The physical embodiment that we present in this work is an electronic skin consisting of eight infrared emitters and eight photo-detectors coupled together and embedded in a planar PDMS waveguide of 5.5 cm diameter. When a contact occurs on the sensing area, the optical signals reaching the peripheral detectors experience a loss because of the Frustrated Total Internal Reflection and deformation of the material. The light signal is converted to electrical signal through an electronic system and a reconstruction algorithm running on a computer reconstructs the pressure map. Pilot experiments are performed to validate the tactile sensing principle by applying external pressures up to 160 kPa. Moreover, the capabilities of the electronic skin to detect contact pressure at multiple subsequent positions, as well as its function on curved surfaces, are validated. A weight sensitivity of 0.193 gr−1 was recorded, thus making the electronic skin suitable to detect pressures in the order of few grams. Sensors 2013-05-17 13 5 Article 10.3390/s130506578 6578 6604 1424-8220 2013-05-17 doi: 10.3390/s130506578 Alessandro Levi Matteo Piovanelli Silvano Furlan Barbara Mazzolai Lucia Beccai http://www.mdpi.com/1424-8220/13/5/6552 As an innovative as well as an interdisciplinary research project, this study performed an analysis of brain signals so as to establish BrainIC as an auxiliary tool for physician diagnosis. Cognition behavior sciences, embedded technology, system on chips (SOC) design and physiological signal processing are integrated in this work. Moreover, a chip is built for real-time electroencephalography (EEG) processing purposes and a Brain Electrical Activity Mapping (BEAM) system, and a knowledge database is constructed to diagnose psychosis and body challenges in learning various behaviors and signals antithesis by a fuzzy inference engine. This work is completed with a medical support system developed for the mentally disabled or the elderly abled. Sensors 2013-05-16 13 5 Article 10.3390/s130506552 6552 6577 1424-8220 2013-05-16 doi: 10.3390/s130506552 Wen-Tsai Sung Jui-Ho Chen Kung-Wei Chang http://www.mdpi.com/1424-8220/13/5/6542 This study integrated a fiber loop manufactured by using commercial fiber (SMF-28, Corning) and a fiber Bragg grating (FBG) to form a fiber optic sensor that could simultaneously measure displacement and temperature. The fiber loop was placed in a thermoelectric cooling module with FBG affixed to the module, and, consequently, the center wavelength displacement of FBG was limited by only the effects of temperature change. Displacement and temperature were determined by measuring changes in the transmission of optical power and shifts in Bragg wavelength. This study provides a simple and economical method to measure displacement and temperature simultaneously. Sensors 2013-05-16 13 5 Article 10.3390/s130506542 6542 6551 1424-8220 2013-05-16 doi: 10.3390/s130506542 Yao-Tang Chang Chih-Ta Yen Yue-Shiun Wu Hsu-Chih Cheng http://www.mdpi.com/1424-8220/13/5/6524 With the recent technological advances, it is possible to monitor vital signs using Bluetooth-enabled biometric mobile devices such as smartphones, tablets or electric wristbands. In this manuscript, we present a system to estimate the risk of cardiovascular diseases in Ambient Assisted Living environments. Cardiovascular disease risk is obtained from the monitoring of the blood pressure by means of mobile devices in combination with other clinical factors, and applying reasoning techniques based on the Systematic Coronary Risk Evaluation Project charts. We have developed an end-to-end software application for patients and physicians and a rule-based reasoning engine. We have also proposed a conceptual module to integrate recommendations to patients in their daily activities based on information proactively inferred through reasoning techniques and context-awareness. To evaluate the platform, we carried out usability experiments and performance benchmarks. Sensors 2013-05-16 13 5 Article 10.3390/s130506524 6524 6541 1424-8220 2013-05-16 doi: 10.3390/s130506524 Ramón Hervás Jesús Fontecha David Ausín Federico Castanedo José Bravo Diego López-de-Ipiña http://www.mdpi.com/1424-8220/13/5/6492 This paper presents an intelligent streetlight management system based on LED lamps, designed to facilitate its deployment in existing facilities. The proposed approach, which is based on wireless communication technologies, will minimize the cost of investment of traditional wired systems, which always need civil engineering for burying of cable underground and consequently are more expensive than if the connection of the different nodes is made over the air. The deployed solution will be aware of their surrounding’s environmental conditions, a fact that will be approached for the system intelligence in order to learn, and later, apply dynamic rules. The knowledge of real time illumination needs, in terms of instant use of the street in which it is installed, will also feed our system, with the objective of providing tangible solutions to reduce energy consumption according to the contextual needs, an exact calculation of energy consumption and reliable mechanisms for preventive maintenance of facilities. Sensors 2013-05-16 13 5 Article 10.3390/s130506492 6492 6523 1424-8220 2013-05-16 doi: 10.3390/s130506492 Pilar Elejoste Ignacio Angulo Asier Perallos Aitor Chertudi Ignacio Zuazola Asier Moreno Leire Azpilicueta José Astrain Francisco Falcone Jesús Villadangos http://www.mdpi.com/1424-8220/13/5/6477 The evaluation of patients in the emergency room department (ER) through more accurate imaging methods such as computed tomography (CT) has revolutionized their assistance in the early 80s. However, despite technical improvements seen during the last decade, surgical planning in the ER has not followed the development of image acquisition methods. The authors present their experience with DICOM image processing as a navigation method in the ER. The authors present 18 patients treated in the Emergency Department of the Hospital das Clínicas of the University of Sao Paulo. All patients were submitted to volumetric CT. We present patients with epidural hematomas, acute/subacute subdural hematomas and contusional hematomas. Using a specific program to analyze images in DICOM format (OsiriX®), the authors performed the appropriate surgical planning. The use of 3D surgical planning made it possible to perform procedures more accurately and less invasively, enabling better postoperative outcomes. All sorts of neurosurgical emergency pathologies can be treated appropriately with no waste of time. The three-dimensional processing of images in the preoperative evaluation is easy and possible even within the emergency care. It should be used as a tool to reduce the surgical trauma and it may dispense methods of navigation in many cases. Sensors 2013-05-16 13 5 Article 10.3390/s130506477 6477 6491 1424-8220 2013-05-16 doi: 10.3390/s130506477 Mauricio Mandel Robson Amorim Wellingson Paiva Marcelo Prudente Manoel Teixeira Almir Andrade http://www.mdpi.com/1424-8220/13/5/6448 The extensive usage of wireless sensor networks (WSNs) has led to the development of many power- and energy-efficient routing protocols. Cooperative routing in WSNs can improve performance in these types of networks. In this paper we discuss the existing proposals and we propose a routing algorithm for wireless sensor networks called Power Efficient Location-based Cooperative Routing with Transmission Power-upper-limit (PELCR-TP). The algorithm is based on the principle of minimum link power and aims to take advantage of nodes cooperation to make the link work well in WSNs with a low transmission power. In the proposed scheme, with a determined transmission power upper limit, nodes find the most appropriate next nodes and single-relay nodes with the proposed algorithm. Moreover, this proposal subtly avoids non-working nodes, because we add a Bad nodes Avoidance Strategy (BAS). Simulation results show that the proposed algorithm with BAS can significantly improve the performance in reducing the overall link power, enhancing the transmission success rate and decreasing the retransmission rate. Sensors 2013-05-15 13 5 Article 10.3390/s130506448 6448 6476 1424-8220 2013-05-15 doi: 10.3390/s130506448 Juanfei Shi Anna Calveras Ye Cheng Kai Liu http://www.mdpi.com/1424-8220/13/5/6423 Biosensors are devices that are capable of detecting specific biological analytes and converting their presence or concentration into some electrical, thermal, optical or other signal that can be easily analysed. The first biosensor was designed by Clark and Lyons in 1962 as a means of measuring glucose. Since then, much progress has been made and the applications of biosensors are today potentially boundless. This review is limited to their clinical applications, particularly in the field of oncohematology. Biosensors have recently been developed in order to improve the diagnosis and treatment of patients affected by hematological malignancies, such as the biosensor for assessing the in vitro pre-treatment efficacy of cytarabine in acute myeloid leukemia, and the fluorescence resonance energy transfer-based biosensor for assessing the efficacy of imatinib in chronic myeloid leukemia. The review also considers the challenges and future perspectives of biosensors in clinical practice. Sensors 2013-05-14 13 5 Review 10.3390/s130506423 6423 6447 1424-8220 2013-05-14 doi: 10.3390/s130506423 Nicola Fracchiolla Silvia Artuso Agostino Cortelezzi http://www.mdpi.com/1424-8220/13/5/6405 Airborne Light Detection and Ranging (LIDAR) has become a mainstream technology for terrain data acquisition and mapping. High sampling density of LIDAR enables the acquisition of high details of the terrain, but on the other hand, it results in a vast amount of gathered data, which requires huge storage space as well as substantial processing effort. The data are usually stored in the LAS format which has become the de facto standard for LIDAR data storage and exchange. In the paper, a hardware accelerated compression of LIDAR data is presented. The compression and decompression of LIDAR data is performed by a dedicated FPGA-based circuit and interfaced to the computer via a PCI-E general bus. The hardware compressor consists of three modules: LIDAR data predictor, variable length coder, and arithmetic coder. Hardware compression is considerably faster than software compression, while it also alleviates the processor load. Sensors 2013-05-14 13 5 Article 10.3390/s130506405 6405 6422 1424-8220 2013-05-14 doi: 10.3390/s130506405 Anton Biasizzo Franc Novak http://www.mdpi.com/1424-8220/13/5/6394 Whole cell biosensors always face the challenge of low stability of biological components and short storage life. This paper reports the effects of poly(2-hydroxyethyl methacrylate) (pHEMA) immobilization on a whole cell fluorescence biosensor for the detection of heavy metals (Cu, Pb, Cd), and pesticides (dichlorophenoxyacetic acid (2,4-D), and chlorpyrifos). The biosensor was produced by entrapping the cyanobacterium Anabaena torulosa on a cellulose membrane, followed by applying a layer of pHEMA, and attaching it to a well. The well was then fixed to an optical probe which was connected to a fluorescence spectrophotometer and an electronic reader. The optimization of the biosensor using several factors such as amount of HEMA and drying temperature were undertaken. The detection limits of biosensor without pHEMA for Cu, Cd, Pb, 2,4-D and chlorpyrifos were 1.195, 0.027, 0.0100, 0.025 and 0.025 µg/L respectively. The presence of pHEMA increased the limits of detection to 1.410, 0.250, 0.500, 0.235 and 0.117 µg/L respectively. pHEMA is known to enhance the reproducibility of the biosensor with average relative standard deviation (RSD) of ±1.76% for all the pollutants tested, 48% better than the biosensor without pHEMA (RSD = ±3.73%). In storability test with Cu 5 µg/L, the biosensor with pHEMA performed 11.5% better than the test without pHEMA on day-10 and 5.2% better on day-25. pHEMA is therefore a good candidate to be used in whole cell biosensors as it increases reproducibility and enhances biosensor storability. Sensors 2013-05-14 13 5 Article 10.3390/s130506394 6394 6404 1424-8220 2013-05-14 doi: 10.3390/s130506394 Ling Shing Wong Yook Heng Lee Salmijah Surif http://www.mdpi.com/1424-8220/13/5/6380 The Leap Motion Controller is a new device for hand gesture controlled user interfaces with declared sub-millimeter accuracy. However, up to this point its capabilities in real environments have not been analyzed. Therefore, this paper presents a first study of a Leap Motion Controller. The main focus of attention is on the evaluation of the accuracy and repeatability. For an appropriate evaluation, a novel experimental setup was developed making use of an industrial robot with a reference pen allowing a position accuracy of 0.2 mm. Thereby, a deviation between a desired 3D position and the average measured positions below 0.2mmhas been obtained for static setups and of 1.2mmfor dynamic setups. Using the conclusion of this analysis can improve the development of applications for the Leap Motion controller in the field of Human-Computer Interaction. Sensors 2013-05-14 13 5 Article 10.3390/s130506380 6380 6393 1424-8220 2013-05-14 doi: 10.3390/s130506380 Frank Weichert Daniel Bachmann Bartholomäus Rudak Denis Fisseler http://www.mdpi.com/1424-8220/13/5/6365 This paper presents an improved monitoring system for the failure detection of engraving tool steel inserts during the injection molding cycle. This system uses acoustic emission PZT sensors mounted through acoustic waveguides on the engraving insert. We were thus able to clearly distinguish the defect through measured AE signals. Two engraving tool steel inserts were tested during the production of standard test specimens, each under the same processing conditions. By closely comparing the captured AE signals on both engraving inserts during the filling and packing stages, we were able to detect the presence of macro-cracks on one engraving insert. Gabor wavelet analysis was used for closer examination of the captured AE signals’ peak amplitudes during the filling and packing stages. The obtained results revealed that such a system could be used successfully as an improved tool for monitoring the integrity of an injection molding process. Sensors 2013-05-14 13 5 Article 10.3390/s130506365 6365 6379 1424-8220 2013-05-14 doi: 10.3390/s130506365 Rajko Svečko Dragan Kusić Tomaž Kek Andrej Sarjaš Aleš Hančič Janez Grum http://www.mdpi.com/1424-8220/13/5/6355 In this work an Intrinsic Fabry-Perot Interferometer (IFPI) based on an air-microcavity is presented. Here the air microcavity, with silica walls, is formed at a segment of a hollow core photonic crystal fiber (HCPCF), which is fusion spliced with a single mode fiber (SMF). Moreover, the spectral response of the IFPI is experimentally characterized and some results are provided. Finally, the viability to use the IFPI to implement a simple, compact size, and low cost refractive index sensor is briefly analyzed. Sensors 2013-05-14 13 5 Article 10.3390/s130506355 6355 6364 1424-8220 2013-05-14 doi: 10.3390/s130506355 Daniel Jáuregui-Vázquez Julián Estudillo-Ayala Roberto Rojas-Laguna Everardo Vargas-Rodríguez Juan Sierra-Hernández Juan Hernández-García Ruth Mata-Chávez http://www.mdpi.com/1424-8220/13/5/6334 Because of the global economic turmoil, nowadays a lot of companies are adopting a “deal of the day” business model, some of them with great success. Generally, they try to attract and retain customers through discount coupons and gift cards, using, generally, traditional distribution media. This paper describes a framework, which integrates intelligent environments by using NFC, oriented to the full management of this kind of businesses. The system is responsible for diffusion, distribution, sourcing, validation, redemption and managing of vouchers, loyalty cards and all kind of mobile coupons using NFC, as well as QR codes. WingBonus can be fully adapted to the requirements of marketing campaigns, voucher providers, shop or retailer infrastructures and mobile devices and purchasing habits. Security of the voucher is granted by the system by synchronizing procedures using secure encriptation algorithms. The WingBonus website and mobile applications can be adapted to any requirement of the system actors. Sensors 2013-05-14 13 5 Article 10.3390/s130506334 6334 6354 1424-8220 2013-05-14 doi: 10.3390/s130506334 Francisco Borrego-Jaraba Pilar Garrido Gonzalo García Irene Ruiz Miguel Gómez-Nieto http://www.mdpi.com/1424-8220/13/5/6319 We present a reproducible fast prototyping procedure based on micro-drilling to produce homogeneous tubular ultramicroelectrode arrays made from poly(3,4-ethylenedioxythiophene) (PEDOT), a conductive polymer. Arrays of Ø 100 µm tubular electrodes each having a height of 0.37 ± 0.06 µm were reproducibly fabricated. The electrode dimensions were analyzed by SEM after deposition of silver dendrites to visualize the electroactive electrode area. The electrochemical applicability of the electrodes was demonstrated by voltammetric and amperometric detection of ferri-/ferrocyanide. Recorded signals were in agreement with results from finite element modelling of the system. The tubular PEDOT ultramicroelectrode arrays were modified by prussian blue to enable the detection of hydrogen peroxide. A linear sensor response was demonstrated for hydrogen peroxide concentrations from 0.1 mM to 1 mM. Sensors 2013-05-14 13 5 Article 10.3390/s130506319 6319 6333 1424-8220 2013-05-14 doi: 10.3390/s130506319 Jan Kafka Steen Skaarup Oliver Geschke Niels Larsen http://www.mdpi.com/1424-8220/13/5/6295 Reliable source to sink communication is the most important factor for an efficient routing protocol especially in domains of military, healthcare and disaster recovery applications. We present weighted energy aware multipath reliable routing (WEAMR), a novel energy aware multipath routing protocol which utilizes hotline-assisted routing to meet such requirements for mission critical applications. The protocol reduces the number of average hops from source to destination and provides unmatched reliability as compared to well known reactive ad hoc protocols i.e., AODV and AOMDV. Our protocol makes efficient use of network paths based on weighted cost calculation and intelligently selects the best possible paths for data transmissions. The path cost calculation considers end to end number of hops, latency and minimum energy node value in the path. In case of path failure path recalculation is done efficiently with minimum latency and control packets overhead. Our evaluation shows that our proposal provides better end-to-end delivery with less routing overhead and higher packet delivery success ratio compared to AODV and AOMDV. The use of multipath also increases overall life time of WSN network using optimum energy available paths between sender and receiver in WDNs. Sensors 2013-05-13 13 5 Article 10.3390/s130506295 6295 6318 1424-8220 2013-05-13 doi: 10.3390/s130506295 Ali Tufail Arslan Qamar Adil Khan Waleed Baig Ki-Hyung Kim http://www.mdpi.com/1424-8220/13/5/6272 Electroencephalogram (EEG)-based brain-computer interfaces (BCIs) have been used in various applications, including human–computer interfaces, diagnosis of brain diseases, and measurement of cognitive status. However, EEG signals can be contaminated with noise caused by user’s head movements. Therefore, we propose a new method that combines an EEG acquisition device and a frontal viewing camera to isolate and exclude the sections of EEG data containing these noises. This method is novel in the following three ways. First, we compare the accuracies of detecting head movements based on the features of EEG signals in the frequency and time domains and on the motion features of images captured by the frontal viewing camera. Second, the features of EEG signals in the frequency domain and the motion features captured by the frontal viewing camera are selected as optimal ones. The dimension reduction of the features and feature selection are performed using linear discriminant analysis. Third, the combined features are used as inputs to support vector machine (SVM), which improves the accuracy in detecting head movements. The experimental results show that the proposed method can detect head movements with an average error rate of approximately 3.22%, which is smaller than that of other methods. Sensors 2013-05-13 13 5 Article 10.3390/s130506272 6272 6294 1424-8220 2013-05-13 doi: 10.3390/s130506272 Jae Bang Jong-Suk Choi Kang Park http://www.mdpi.com/1424-8220/13/5/6254 Harrowing is often used to reduce weed competition, generally using a constant intensity across a whole field. The efficacy of weed harrowing in wheat and barley can be optimized, if site-specific conditions of soil, weed infestation and crop growth stage are taken into account. This study aimed to develop and test an algorithm to automatically adjust the harrowing intensity by varying the tine angle and number of passes. The field variability of crop leaf cover, weed density and soil density was acquired with geo-referenced sensors to investigate the harrowing selectivity and crop recovery. Crop leaf cover and weed density were assessed using bispectral cameras through differential images analysis. The draught force of the soil opposite to the direction of travel was measured with electronic load cell sensor connected to a rigid tine mounted in front of the harrow. Optimal harrowing intensity levels were derived in previously implemented experiments, based on the weed control efficacy and yield gain. The assessments of crop leaf cover, weed density and soil density were combined via rules with the aforementioned optimal intensities, in a linguistic fuzzy inference system (LFIS). The system was evaluated in two field experiments that compared constant intensities with variable intensities inferred by the system. A higher weed density reduction could be achieved when the harrowing intensity was not kept constant along the cultivated plot. Varying the intensity tended to reduce the crop leaf cover, though slightly improving crop yield. A real-time intensity adjustment with this system is achievable, if the cameras are attached in the front and at the rear or sides of the harrow. Sensors 2013-05-13 13 5 Article 10.3390/s130506254 6254 6271 1424-8220 2013-05-13 doi: 10.3390/s130506254 Victor Rueda-Ayala Martin Weis Martina Keller Dionisio Andújar Roland Gerhards http://www.mdpi.com/1424-8220/13/5/6229 There is an increasing number of Ambient Intelligence (AmI) systems that are time-sensitive and resource-aware. From healthcare to building and even home/office automation, it is now common to find systems combining interactive and sensing multimedia traffic with relatively simple sensors and actuators (door locks, presence detectors, RFIDs, HVAC, information panels, etc.). Many of these are today known as Cyber-Physical Systems (CPS). Quite frequently, these systems must be capable of (1) prioritizing different traffic flows (process data, alarms, non-critical data, etc.), (2) synchronizing actions in several distributed devices and, to certain degree, (3) easing resource management (e.g., detecting faulty nodes, managing battery levels, handling overloads, etc.). This work presents FTT-MA, a high-level middleware architecture aimed at easing the design, deployment and operation of such AmI systems. FTT-MA ensures that both functional and non-functional aspects of the applications are met even during reconfiguration stages. The paper also proposes a methodology, together with a design tool, to create this kind of systems. Finally, a sample case study is presented that illustrates the use of the middleware and the methodology proposed in the paper. Sensors 2013-05-13 13 5 Article 10.3390/s130506229 6229 6253 1424-8220 2013-05-13 doi: 10.3390/s130506229 Adrián Noguero Isidro Calvo Federico Pérez Luis Almeida http://www.mdpi.com/1424-8220/13/5/6217 Quorum sensing is a system of stimuli and responses in relation to bacterial cell population density that regulates gene expression, including virulence determinants. Consequently, quorum sensing has been an attractive target for the development of novel anti-infective measures that do not rely on the use of antibiotics. Anti-quorum sensing has been a promising strategy to combat bacterial infections as it is unlikely to develop multidrug resistant pathogens since it does not impose any selection pressure. A number of anti-quorum sensing approaches have been documented and plant-based natural products have been extensively studied in this context. Plant matter is one of the major sources of chemicals in use today in various industries, ranging from the pharmaceutical, cosmetic, and food biotechnology to the textile industries. Just like animals and humans, plants are constantly exposed to bacterial infections, it is therefore logical to expect that plants have developed sophisticated of chemical mechanisms to combat pathogens. In this review, we have surveyed the various types of plant-based natural products that exhibit anti-quorum sensing properties and their anti-quorum sensing mechanisms. Sensors 2013-05-13 13 5 Review 10.3390/s130506217 6217 6228 1424-8220 2013-05-13 doi: 10.3390/s130506217 Chong-Lek Koh Choon-Kook Sam Wai-Fong Yin Li Tan Thiba Krishnan Yee Chong Kok-Gan Chan http://www.mdpi.com/1424-8220/13/5/6204 A glassy carbon electrode (GCE) coated with a graphene/polymer film was fabricated for rapid determination of phenols in aqueous solutions. The electrochemical behavior of different phenols at the graphene/polymer-coated GCE was also investigated. In PBS buffer solution with a pH of 6.5, hydroquinone exhibits a well-defined reduction peak at the modified GCE. Based on this, an electrochemical method for the direct determination of phenols is proposed. Investigating different parameters revealed the optimized detection conditions for the electrode are a scan rate of 50 mV/s, dosage of graphene-polyaniline of 8 μL, dosage of tyrosinase of 3 μL, and pH of 6.5. Under the optimal conditions, the reduction peak current varies linearly with the concentration of phenols, with a linear regression equation of I (10−6A) = −4.887 × 10−4C (mol/L)−5.331 × 10−6 with a correlation coefficient of 0.9963 and limit of detection (S/N = 3) of 2.00 × 10−4 mol/L. The electrochemical sensor is also used to detect phenols in actual samples, where it shows great promise for rapid, simple and quantitative detection of phenols. Sensors 2013-05-13 13 5 Article 10.3390/s130506204 6204 6216 1424-8220 2013-05-13 doi: 10.3390/s130506204 Kun Chen Zai-Li Zhang Yong-Mei Liang Wei Liu http://www.mdpi.com/1424-8220/13/5/6183 Accurate acoustic channel models are critical for the study of underwater acoustic networks. Existing models include physics-based models and empirical approximation models. The former enjoy good accuracy, but incur heavy computational load, rendering them impractical in large networks. On the other hand, the latter are computationally inexpensive but inaccurate since they do not account for the complex effects of boundary reflection losses, the multi-path phenomenon and ray bending in the stratified ocean medium. In this paper, we propose a Stratified Acoustic Model (SAM) based on frequency-independent geometrical ray tracing, accounting for each ray’s phase shift during the propagation. It is a feasible channel model for large scale underwater acoustic network simulation, allowing us to predict the transmission loss with much lower computational complexity than the traditional physics-based models. The accuracy of the model is validated via comparisons with the experimental measurements in two different oceans. Satisfactory agreements with the measurements and with other computationally intensive classical physics-based models are demonstrated. Sensors 2013-05-13 13 5 Article 10.3390/s130506183 6183 6203 1424-8220 2013-05-13 doi: 10.3390/s130506183 Ping Wang Lin Zhang Victor Li http://www.mdpi.com/1424-8220/13/5/6171 Hierarchical flower-like ZnO nanorods, net-like ZnO nanofibers and ZnO nanobulks have been successfully synthesized via a surfactant assisted hydrothemal method. The synthesized products were characterized by X-ray powder diffraction and field emission scanning electron microscopy, respectively. A possible growth mechanism of the various hierarchical ZnO nanostructures is discussed in detail. Gas sensors based on the as-prepared ZnO nanostructures were fabricated by screen-printing on a flat ceramic substrate. Furthermore, their gas sensing characteristics towards methane were systematically investigated. Methane is an important characteristic hydrocarbon contaminant found dissolved in power transformer oil as a result of faults. We find that the hierarchical flower-like ZnO nanorods and net-like ZnO nanofibers samples show higher gas response and lower operating temperature with rapid response-recovery time compared to those of sensors based on ZnO nanobulks. These results present a feasible way of exploring high performance sensing materials for on-site detection of characteristic fault gases dissolved in transformer oil. Sensors 2013-05-10 13 5 Article 10.3390/s130506171 6171 6182 1424-8220 2013-05-10 doi: 10.3390/s130506171 Qu Zhou Weigen Chen Lingna Xu Shudi Peng http://www.mdpi.com/1424-8220/13/5/6141 This paper presents the results of using a commercial pulsimeter as an electrocardiogram (ECG) for wireless detection of cardiac alterations and stress levels for home control. For these purposes, signal processing techniques (Continuous Wavelet Transform (CWT) and J48) have been used, respectively. The designed algorithm analyses the ECG signal and is able to detect the heart rate (99.42%), arrhythmia (93.48%) and extrasystoles (99.29%). The detection of stress level is complemented with Skin Conductance Response (SCR), whose success is 94.02%. The heart rate variability does not show added value to the stress detection in this case. With this pulsimeter, it is possible to prevent and detect anomalies for a non-intrusive way associated to a telemedicine system. It is also possible to use it during physical activity due to the fact the CWT minimizes the motion artifacts. Sensors 2013-05-10 13 5 Article 10.3390/s130506141 6141 6170 1424-8220 2013-05-10 doi: 10.3390/s130506141 María Villarejo Begoña Zapirain Amaia Zorrilla http://www.mdpi.com/1424-8220/13/5/6109 Wearable computing is a form of ubiquitous computing that offers flexible and useful tools for users. Specifically, glove-based systems have been used in the last 30 years in a variety of applications, but mostly focusing on sensing people’s attributes, such as finger bending and heart rate. In contrast, we propose in this work a novel flexible and reconfigurable instrumentation platform in the form of a glove, which can be used to analyze and measure attributes of fruits by just pointing or touching them with the proposed glove. An architecture for such a platform is designed and its application for intuitive fruit grading is also presented, including experimental results for several fruits. Sensors 2013-05-10 13 5 Article 10.3390/s130506109 6109 6140 1424-8220 2013-05-10 doi: 10.3390/s130506109 Rafael Aroca Rafael Gomes Rummennigue Dantas Adonai Calbo Luiz Gonçalves http://www.mdpi.com/1424-8220/13/5/6089 Detection of ultrasmall masses such as proteins and pathogens has been made possible as a result of advancements in nanotechnology. Development of label-free and highly sensitive biosensors has enabled the transduction of molecular recognition into detectable physical quantities. Microcantilever (MC)-based systems have played a widespread role in developing such biosensors. One of the most important drawbacks of all of the available biosensors is that they all come at a very high cost. Moreover, there are certain limitations in the measurement equipments attached to the biosensors which are mostly optical measurement systems. A unique self-sensing detection technique is proposed in this paper in order to address most of the limitations of the current measurement systems. A self-sensing bridge is used to excite piezoelectric MC-based sensor functioning in dynamic mode, which simultaneously measures the system’s response through the self-induced voltage generated in the piezoelectric material. As a result, the need for bulky, expensive read-out equipment is eliminated. A comprehensive mathematical model is presented for the proposed self-sensing detection platform using distributed-parameters system modeling. An adaptation strategy is then implemented in the second part in order to compensate for the time-variation of piezoelectric properties which dynamically improves the behavior of the system. Finally, results are reported from an extensive experimental investigation carried out to prove the capability of the proposed platform. Experimental results verified the proposed mathematical modeling presented in the first part of the study with accuracy of 97.48%. Implementing the adaptation strategy increased the accuracy to 99.82%. These results proved the measurement capability of the proposed self-sensing strategy. It enables development of a cost-effective, sensitive and miniaturized mass sensing platform. Sensors 2013-05-10 13 5 Article 10.3390/s130506089 6089 6108 1424-8220 2013-05-10 doi: 10.3390/s130506089 Samira Faegh Nader Jalili Srinivas Sridhar http://www.mdpi.com/1424-8220/13/5/6054 Movement ecology is a field which places movement as a basis for understanding animal behavior. To realize this concept, ecologists rely on data collection technologies providing spatio-temporal data in order to analyze movement. Recently, wireless sensor networks have offered new opportunities for data collection from remote places through multi-hop communication and collaborative capability of the nodes. Several technologies can be used in such networks for sensing purposes and for collecting spatio-temporal data from animals. In this paper, we investigate and review technological solutions which can be used for collecting data for wildlife monitoring. Our aim is to provide an overview of different sensing technologies used for wildlife monitoring and to review their capabilities in terms of data they provide for modeling movement behavior of animals. Sensors 2013-05-10 13 5 Review 10.3390/s130506054 6054 6088 1424-8220 2013-05-10 doi: 10.3390/s130506054 Mitra Baratchi Nirvana Meratnia Paul Havinga Andrew Skidmore Bert Toxopeus http://www.mdpi.com/1424-8220/13/5/6032 Information and services personalization is essential for an optimal user experience. Systems have to be able to acquire data about the user’s context, process them in order to identify the user’s situation and finally, adapt the functionality of the system to that situation, but the development of context-aware systems is complex. Data coming from distributed and heterogeneous sources have to be acquired, processed and managed. Several programming frameworks have been proposed in order to simplify the development of context-aware systems. These frameworks offer high-level application programming interfaces for programmers that complicate the involvement of domain experts in the development life-cycle. The participation of users that do not have programming skills but are experts in the application domain can speed up and improve the development process of these kinds of systems. Apart from that, there is a lack of methodologies to guide the development process. This article presents as main contributions, the implementation and evaluation of a web platform and a methodology to collaboratively develop context-aware systems by programmers and domain experts. Sensors 2013-05-10 13 5 Article 10.3390/s130506032 6032 6053 1424-8220 2013-05-10 doi: 10.3390/s130506032 David Martín Diego López-de-Ipiña Aurkene Alzua-Sorzabal Carlos Lamsfus Emilio Torres-Manzanera http://www.mdpi.com/1424-8220/13/5/6014 We have developed a prototype cortical neural sensing microsystem for brain implantable neuroengineering applications. Its key feature is that both the transmission of broadband, multichannel neural data and power required for the embedded microelectronics are provided by optical fiber access. The fiber-optic system is aimed at enabling neural recording from rodents and primates by converting cortical signals to a digital stream of infrared light pulses. In the full microsystem whose performance is summarized in this paper, an analog-to-digital converter and a low power digital controller IC have been integrated with a low threshold, semiconductor laser to extract the digitized neural signals optically from the implantable unit. The microsystem also acquires electrical power and synchronization clocks via optical fibers from an external laser by using a highly efficient photovoltaic cell on board. The implantable unit employs a flexible polymer substrate to integrate analog and digital microelectronics and on-chip optoelectronic components, while adapting to the anatomical and physiological constraints of the environment. A low power analog CMOS chip, which includes preamplifier and multiplexing circuitry, is directly flip-chip bonded to the microelectrode array to form the cortical neurosensor device. Sensors 2013-05-10 13 5 Article 10.3390/s130506014 6014 6031 1424-8220 2013-05-10 doi: 10.3390/s130506014 Sunmee Park David Borton Mingyu Kang Arto Nurmikko Yoon-Kyu Song http://www.mdpi.com/1424-8220/13/5/5996 This work presents the design, construction and characterization of air-coupled piezoelectric transducers using 1–3 connectivity piezocomposite disks with a stack of matching layers being the outer one an active quarter wavelength layer made of polypropylene foam ferroelectret film. This kind of material has shown a stable piezoelectric response together with a very low acoustic impedance (<0.1 MRayl). These features make them a suitable candidate for the dual use or function proposed here: impedance matching layer and active material for air-coupled transduction. The transducer centre frequency is determined by the l/4 resonance of the polypropylene foam ferroelectret film (0.35 MHz), then, the rest of the transducer components (piezocomposite disk and passive intermediate matching layers) are all tuned to this frequency. The transducer has been tested in several working modes including pulse-echo and pitch-catch as well as wide and narrow band excitation. The performance of the proposed novel transducer is compared with that of a conventional air-coupled transducers operating in a similar frequency range. Sensors 2013-05-10 13 5 Article 10.3390/s130505996 5996 6013 1424-8220 2013-05-10 doi: 10.3390/s130505996 Tomás Gómez Alvarez-Arenas http://www.mdpi.com/1424-8220/13/5/5958 Finding a complete mesh-based solution for low-rate wireless personal area networks (LR-WPANs) is still an open issue. To cope with this concern, different competing approaches have emerged in the Wireless Mesh Sensor Networks (WMSNs) field in the last few years. They are usually supported by the IEEE 802.15.4 standard, the most commonly adopted LR-WPAN recommendation for point-to-point topologies. In this work, we review the most relevant and up-to-date WMSN solutions that extend the IEEE 802.15.4 standard to multi-hop mesh networks. To conduct this review, we start by identifying the most significant WMSN requirements (i.e., interoperability, robustness, scalability, mobility or energy-efficiency) that reveal the benefits and shortcomings of each proposal. Then, we re-examine thoroughly the group of proposals following different design guidelines which are usually considered by end-users and developers. Among all of the approaches reviewed, we highlight the IEEE 802.15.5 standard, a recent recommendation that, in its LR-WPAN version, fully satisfies the greatest number of WMSN requirements. As a result, IEEE 802.15.5 can be an appropriate solution for a wide-range of applications, unlike the majority of the remaining solutions reviewed, which are usually designed to solve particular problems, for instance in the home, building and industrial sectors. In this sense, a description of IEEE 802.15.5 is also included, paying special attention to its efficient energy-saving mechanisms. Finally, possible improvements of this recommendation are pointed out in order to offer hints for future research. Sensors 2013-05-10 13 5 Review 10.3390/s130505958 5958 5995 1424-8220 2013-05-10 doi: 10.3390/s130505958 David Rodenas-Herraiz Antonio-Javier Garcia-Sanchez Felipe Garcia-Sanchez Joan Garcia-Haro http://www.mdpi.com/1424-8220/13/5/5945 One objective of precision agriculture is to provide accurate information about soil and crop properties to optimize the management of agricultural inputs to meet site-specific needs. This paper describes the development of a sensor equipped with RTK-GPS technology that continuously and efficiently measures soil cutting resistance at various depths while traversing the field. Laboratory and preliminary field tests verified the accuracy of this prototype soil strength sensor. The data obtained using a hand-operated soil cone penetrometer was used to evaluate this field soil compaction depth profile sensor. To date, this sensor has only been tested in one field under one gravimetric water content condition. This field test revealed that the relationships between the soil strength profile sensor (SSPS) cutting force and soil cone index values are assumed to be quadratic for the various depths considered: 0–10, 10–20 and 20–30 cm (r2 = 0.58, 0.45 and 0.54, respectively). Soil resistance contour maps illustrated its practical value. The developed sensor provides accurate, timely and affordable information on soil properties to optimize resources and improve agricultural economy. Sensors 2013-05-10 13 5 Article 10.3390/s130505945 5945 5957 1424-8220 2013-05-10 doi: 10.3390/s130505945 Juan Agüera Jacob Carballido Jesús Gil Chris Gliever Manuel Perez-Ruiz http://www.mdpi.com/1424-8220/13/5/5937 Temperature is of major importance in most branches of science and technology as well as in everyday life, and with the miniaturization of electronic devices and the increasing ability to make research into small-scale systems, a specific need for very small thermostats and thermometers has been created. Here we describe how DNA molecules can be used as nanoscale sensors to meet these requirements. We illustrate how the hybridization kinetics between bases in DNA molecules combined with conformational changes of the DNA backbone can be exploited in the construction of simple but versatile temperature switches and thermometers, which can be built into electronic systems. DNA based sensors are at the same time applicable as ion detectors to monitor the chemical environment of a specific system. Sensors 2013-05-10 13 5 Article 10.3390/s130505937 5937 5944 1424-8220 2013-05-10 doi: 10.3390/s130505937 Anette Jonstrup Jacob Fredsøe Anni Andersen http://www.mdpi.com/1424-8220/13/5/5923 This paper presents an innovative access control system, based on human detection and path analysis, to reduce false automatic door system actions while increasing the added values for security applications. The proposed system can first identify a person from the scene, and track his trajectory to predict his intention for accessing the entrance, and finally activate the door accordingly. The experimental results show that the proposed system has the advantages of high precision, safety, reliability, and can be responsive to demands, while preserving the benefits of being low cost and high added value. Sensors 2013-05-10 13 5 Article 10.3390/s130505923 5923 5936 1424-8220 2013-05-10 doi: 10.3390/s130505923 Jie-Ci Yang Chin-Lun Lai Hsin-Teng Sheu Jiann-Jone Chen http://www.mdpi.com/1424-8220/13/5/5897 This paper will discuss a SAW passive, wireless multi-sensor system under development by our group for the past several years. The device focus is on orthogonal frequency coded (OFC) SAW sensors, which use both frequency diversity and pulse position reflectors to encode the device ID and will be briefly contrasted to other embodiments. A synchronous correlator transceiver is used for the hardware and post processing and correlation techniques of the received signal to extract the sensor information will be presented. Critical device and system parameters addressed include encoding, operational range, SAW device parameters, post-processing, and antenna-SAW device integration. A fully developed 915 MHz OFC SAW multi-sensor system is used to show experimental results. The system is based on a software radio approach that provides great flexibility for future enhancements and diverse sensor applications. Several different sensor types using the OFC SAW platform are shown. Sensors 2013-05-10 13 5 Article 10.3390/s130505897 5897 5922 1424-8220 2013-05-10 doi: 10.3390/s130505897 Donald Malocha Mark Gallagher Brian Fisher James Humphries Daniel Gallagher Nikolai Kozlovski http://www.mdpi.com/1424-8220/13/5/5881 Surface waves are commonly used for vibration-based nondestructive testing for infrastructure. Spectral Analysis of Surface Waves (SASW) has been used to detect subsurface properties for geologic inspections. Recently, efforts were made to scale down these subsurface detection approaches to see how they perform on small-scale structures such as concrete slabs and pavements. Additional efforts have been made to replace the traditional surface-mounted transducers with non-contact acoustic transducers. Though some success has been achieved, most of these new approaches are inefficient because they require point-to-point measurements or off-line signal analysis. This article introduces a Mobile Acoustic Subsurface Sensing system as MASS, which is an improved surface wave based implementation for measuring the subsurface profile of roadways. The compact MASS system is a 3-wheeled cart outfitted with an electromagnetic impact source, distance register, non-contact acoustic sensors and data acquisition/ processing equipment. The key advantage of the MASS system is the capability to collect measurements continuously at walking speed in an automatic way. The fast scan and real-time analysis advantages are based upon the non-contact acoustic sensing and fast air-coupled surface wave analysis program. This integration of hardware and software makes the MASS system an efficient mobile prototype for the field test. Sensors 2013-05-08 13 5 Article 10.3390/s130505881 5881 5896 1424-8220 2013-05-08 doi: 10.3390/s130505881 Yifeng Lu Yi Zhang Yinghong Cao J. McDaniel Ming Wang http://www.mdpi.com/1424-8220/13/5/5870 In this work a radio-frequency self-referencing WDM intensity-based fiber-optic sensor operating in reflective configuration and using virtual instrumentation is presented. The use of virtual delay lines at the reception stage, along with novel flexible self-referencing techniques, and using a single frequency, avoids all-optical or electrical-based delay lines approaches. This solution preserves the self-referencing and performance characteristics of the proposed WDM-based optical sensing topology, and leads to a more compact solution with higher flexibility for the multiple interrogation of remote sensing points in a sensor network. Results are presented for a displacement sensor demonstrating the concept feasibility. Sensors 2013-05-07 13 5 Article 10.3390/s130505870 5870 5880 1424-8220 2013-05-07 doi: 10.3390/s130505870 David Montero Carmen Vázquez http://www.mdpi.com/1424-8220/13/5/5857 This paper reports our work on developing a surface tension actuated micro-robotic platform supported by three bubbles (liquid environment) or droplets (gaseous environment). The actuation principle relies on the force developed by surface tension below a millimeter, which benefits from scaling laws, and is used to actuate this new type of compliant robot. By separately controlling the pressure inside each bubble, three degrees of freedom can be actuated. We investigated three sensing solutions to measure the platform attitude in real-time (z-position of each droplet, leading to the knowledge of the z position and Θx and Θy tilts of the platform). The comparison between optical, resistive, and capacitive measurement principles is hereafter reported. The optical technique uses SFH-9201 components. The resistive technique involves measuring the electrical resistance of a path flowing through two droplets and the platform. This innovative technique for sensing table position combines three pairs of resistances, from which the resistance in each drop can be deduced, thus determining the platform position. The third solution is a more usual high frequency (~200 MHz) capacitive measurement. The resistive method has been proven reliable and is simple to implement. This work opens perspectives toward an interesting sensing solution for micro-robotic platforms. Sensors 2013-05-07 13 5 Article 10.3390/s130505857 5857 5869 1424-8220 2013-05-07 doi: 10.3390/s130505857 Renaud Casier Cyrille Lenders Marion Lhernould Michaël Gauthier Pierre Lambert