ALBERT

Description: Commercial, industrial, and military aerospace designs are increasingly deploying MEMS micro inertial measurement unit (MIMU) for motion control, automation, and positioning applications, such as the unmanned aerial vehicle (UAV), robot, and smart phone. On the one hand, MIMU has the merit of low cost, small size, low-power consumption, and high shock resistance, but on the other hand, low-cost MIMU is affected by systematic error caused by the instability of the drift, scaling factors, and axes misalignment, which may lead to large errors in the position and attitude’s determination from time to time. That means calibration before use is an effective way to improve the practical precision of MIMU. However, many customers have no precise turntable to calibrate the MIMU before they use it. To address these problems, this paper presents an easy self-calibration method to implement calibration of the MIMU on a common table only with an inclined surface, no precise turntable is needed. The calibration method is based on the following principles. First, the module of the output vector of the orthogonal configured three-axis accelerometers is equal to unit gravity. Second, when IMU rotates to a known gesture with a stable axis, the angles can be calculated through integration. Third, when the accelerometers’ parameters are calculated, it can act as a level datum. Furthermore, the accelerometers on the inclined surface are used to determine the rotating heading datum. Finally, after a series static positions test and rotating test, the parameters can be extracted and estimated. To demonstrate the success and the convenience of the proposed method, comparison experiments with the precision turntable have been made on an ADI’s MIMU. The calibration results show that the accuracy and precision of this method is quite equivalent with the turntable-based calibration, and the scale factors error with an order of magnitude always equal or less than $10^{-5}$ . The observed static and dynamic yaw maximum angular error in a certain period is <0.8°, the pitch maximum angular error is <0.5°, and the roll maximum angular error is <0.3°.

Description: Low-energy technologies in the Internet of Things (IoTs) era are still unable to provide the reliability needed by the industrial world, particularly in terms of the wireless operation that pervasive deployments demand. While the industrial wireless performance has achieved an acceptable degree in communications, it is no easy task to determine an efficient energy-dimensioning of the device in order to meet the application requirements. This is especially true in the face of the uncertainty inherent in energy harvesting. Thus, it is of utmost importance to model and dimension the energy consumption of the IoT applications at the pre-deployment or pre-production stages, especially when considering critical factors, such as reduced cost, life-time, and available energy. This paper presents a comprehensive model for the power consumption of wireless sensor nodes. The model takes a system-level perspective to account for all energy expenditures: communications, acquisition and processing. Furthermore, it is based only on parameters that can empirically be quantified once the platform (i.e., technology) and the application (i.e., operating conditions) are defined. This results in a new framework for studying and analyzing the energy life-cycles in applications, and it is suitable for determining in advance the specific weight of application parameters, as well as for understanding the tolerance margins and tradeoffs in the system.

Description: With the development of Internet of Things (IoT), a large amount of machine-to-machine (M2M) devices produce the data from a huge number of M2M communications. A massive access congestion control scheme in M2M communication is important in a wireless M2M network, where a wireless M2M network is constituted by a large number of wireless M2M devices. In this paper, we developed a spiderweb-based massive access management protocol for M2M wireless networks. The wireless M2M network topology considered, in this paper, is a spiderweb-based topology, which belongs to a regular topology. The spiderweb-based topology is split into a number of sub-spiderweb, while each sub-spiderweb can be seen as a small reservoir. The main function of the small reservoir is to temporarily store the massive access if the congestion problem is occurred due to the massive assess has been suddenly happened from the M2M devices. When the congestion problem is alleviated gradually, the temporarily-stored massive assess can be digested from these small reservoirs. The contribution of the proposed scheme is to reduce the packet loss rate and prolong the wireless M2M network lifetime. In addition, a dynamically adjustment of the different sub-spiderweb size is developed based on the amount of different data traffics. Simulation result finally illustrates that the proposed mechanism significantly reduces the packet loss rate and keeps the maximum network lifetime.

Description: The paper presents the methodology including the deployment of a structure comprising of C-clamp magnetic stripes and a self-calibration scheme using a four-coil design to resolve the issues of the interference and misplacement problems existing in the flexible nonintrusive current sensor tag for the current detection of household two-wire power lines. Experimental results show that the stripe structure can effectively screen out the magnetic flux originating from the nearby power line for the reduction of sensing error caused by the electromagnetic field interference and the calibration scheme containing the correction of horizontal misplacement and the analysis of power cable thickness via the four-coil design can provide the information of sensor location for accurate current sensing. Less than 4% of sensing error indicates that the proposed methodology can indeed facilitate the flexible current sensor tag for practical use.

Description: Rapidly emerging batteryless sensors are creating tremendous opportunities for truly wearable sensors for activity recognition. However, data streams from such sensors are characterized by sparsity and noise, which make activity recognition a challenging task. In this paper, we study the feasibility of passive computational RFID sensors for ambulatory monitoring. In particular, we focus on recognizing transfers out of beds or chairs and walking. Ideally, all these activities need to be monitored by movement sensor alarm systems to alert caregivers to provide supervision during the ambulation of older people in hospitals and nursing homes to prevent a fall. Our novel approach to partition continuous sensor data on natural activity boundaries and to identify transfers out of beds or chairs and walking as transitions between sequences of movements overcomes issues posed by the sparsity and the noise. We demonstrate through in-depth experiments the high performance (F-score > 93%) and the responsiveness of our approach.

Description: This paper proposes an approach to design multiple-input multiple-output radar waveforms that are orthogonal on both the transmitter and receiver. The proposed method jointly utilizes the direct sequence spread spectrum coding and orthogonal frequency division multiplexing (OFDM) chirp signaling techniques. We name it spread spectrum-coded OFDM chirp waveform diversity design. The performance of the designed waveforms is analyzed by examining the ambiguity function and correlation function. The influences of the spread spectrum code choice and the OFDM chirp parameters are also investigated. It is verified that the proposed design scheme can ensure these waveforms stay orthogonal on the receiver and have large time-bandwidth product which is beneficial to separate closely spaced targets.

Description: Studies have presented that the driver vigilance level has serious implication in the causation of road accidents. This paper focuses on integrating both the vehicle-based control behavior and physiological state to predict the driver vigilance index which is evaluated by using a smartwatch. The vehicle control behavior can be observed from the steering wheel movement. Our study utilized the smartwatch motion sensors to study the steering wheel behavior. Meanwhile, physiological state of driver reflects the driver capability of safety alert driving which is estimated by photoplethysmogram (PPG) and respiration signals in this paper. The PPG sensor is integrated in a sport wristband with a Bluetooth low energy module, transmitted the PPG signals to smartwatch in real time. The steering angle is derived by the reading from smartwatch built-in accelerometer and gyroscope sensors. On the other hand, the respiration is derived using the PPG peak baseline method. In order to utterly investigate the sleepiness-induced factors, the time, spectral, and phase space domain features are calculated. Considering the smartwatch processing capability, mutual-information technique is applied to designate the ten most descriptive features. Then, the extracted descriptive features are serve as parameters to a classifier to determine the driver aptitude status. The features are analyzed for their correlation with the subjective Koralinska sleepiness scale and through recorded video observations. The experimental results reveal that our system is capable of estimating driver hypervigilance at average of 96.5% accuracy rate by evaluating on both driving behavior and driver physiological state, provided a novel and low-cost implementation.

Description: A cavitating two-phase flow of water in a pipe with area shrinkage was experimentally investigated, acquiring at high sampling rate pressure signals and images of the cavitating flow field. The time series of the pressure fluctuations was analyzed in terms of power spectral density and related to the cavitation regimes. Furthermore, the fluctuations of the pressure measurements were also decomposed using the wavelet transform to analyze the frequency distribution of the signals energy with respect to the flow behavior. The energy content at each frequency band of the acquire signals is well related to cavitation flow-field behavior. Moreover, the artificial neural network and the least squares support vector machine (LS-SVM) were implemented to identify the cavitation regime, using, as inputs, the power spectral density distributions of the pressure fluctuations, and some features of the decomposed signals, as the wavelet energy for each decomposition level and wavelet entropy. Results indicate the most accurate model to be used in the cavitation regime identification, underlining the enhanced capability of LS-SVM trained with the input data set based on the wavelet decomposition features.

Description: In this paper, we present a novel silicon-on-insulator (SOI) complementary metal–oxide–semiconductor (CMOS) microelectromechanical-system thermal wall shear stress sensor based on a tungsten hot-wire and a single thermopile. Devices were fabricated using a commercial 1- $mu text{m}$ SOI-CMOS process followed by a deep reactive ion etching back-etch step to release a silicon dioxide membrane, which mechanically supports and thermally isolates heating and sensing elements. The sensors show an electrothermal transduction efficiency of $50~mu text{W}$ /°C, and a very small zero flow offset. Calibration for wall shear stress measurement in air in the range of 0–0.48 Pa was performed using a suction type, 2-D flow wind tunnel. The sensors were found to be extremely sensitive, up to 4 V/Pa for low wall shear stress values. Furthermore, we demonstrate the superior signal-to-noise ratio (up to five times higher) of a single thermopile readout configuration compared with a double thermopile readout configuration (embedded for comparison purposes within the same device). Finally, we verify that the output of the sensor is proportional to the cube root of the wall shear stress and we propose an accurate semiempirical formula for its modeling.

Description: We propose an optical fiber hydrostatic pressure sensor based on micro-cavities generated by the fiber fuse effect. The presented sensor is manufactured through the recycling of optical fiber destroyed by the fiber fuse effect, being, therefore, a cost-effective solution, when compared with other similar micro-cavity-based solutions. The developed sensor was characterized for pressures up to 20 kPa, showing a linear sensitivity coefficient of $0.47pm 0.03~{rm nm}cdot {rm kPa}^{-1}$ , for pressure values below 8 kPa. Furthermore, we propose a new theoretical model to describe the behavior of the microcavities embedded in optical fibers. This allows us to solve the discrepancies, already identified by other authors, between the experimental results and the ones attained with the flat mirrors Fabry-Perot model. By this way, we were able to describe the sensor response, within the full dynamic range.

Description: The monitoring and control of crops in precision agriculture sometimes requires a high collection frequency of information (e.g., temperature, humidity, and salinity) due to the variability in crops. Data acquisition and transmission are generally achieved thanks to wireless sensor networks. However, sensor nodes have limited resources. Thus, it is necessary to adapt the increase in sampling frequency for different crops, under application constraints (reliability, packet delay, and lifetime duration). In this paper, we propose to properly tune IEEE 802.15.4 MAC parameters ( macMinBE and macMaxCSMABackoffs ) and the sampling frequency of deployed sensor nodes. An analytical model of network performance is derived and used to perform the tuning of these tradeoff parameters. Simulation analysis shows that our scheme provides an efficient increase of sampling frequency of sensor nodes while satisfying application requirements.

Description: Sensors based on the magnetoelectric (ME) effect have the potential to be genuine alternatives for measuring bio-magnetic signals. Unfortunately, the sensor structure usually inhibits the problem that several non-magnetic types of noise couple mechanically into the sensor: in this contribution, we will focus on undesired acoustic coupling. Therefore, an adaptive cancellation approach based on a computationally efficient gradient estimation algorithm with a pseudo-optimally control scheme is proposed. The approach is using a microphone as a noise reference sensor and is implemented in real time. An evaluation in terms of measurements is performed inside a magnetically shielded chamber. For a particular scenario, which is characterized by double excitation, an algorithm with binary control-scheme improves the signal-to-noise ratio (SNR) only by around 4dB. If the proposed control scheme is used instead, an improvement of the SNR of around 13dB is achieved.

Description: Target detection is an important issue in the unattended ground sensors. In this paper, inspired by the idea of subspace-based direction of arrival estimation algorithms, a new target detection algorithm called subspace-based target detection (SBTD) is proposed to detect moving targets. The SBTD employs the SNR of the acoustic signals to decide whether moving targets are exiting or not. Although the SBTD has good detection performance, its cost maybe a little high for unattended sensors with low-cost hardware and long-term monitoring. To relieve the cost, we propose the hierarchical detection scheme and develop a two-stage detection method based on the SBTD for target detection in the wild, in which the first stage detection algorithm is chosen from current detection algorithms, while the second stage detection algorithm employs the SBTD. Experiments are conducted to verify the proposed detection method through acoustic signals gathered by the micro-electro-mechanical systems (MEMS) microphone array in the wild. Results show that the detector constructed by our two-stage detection method cannot only estimate the SNR of the acoustic signals but also can reduce the false alarm rate significantly with the detection rate almost unchanged in comparison with the detector chosen by its first-stage detection algorithm. The results indicate that a better detection performance is achieved in terms of the receiver operator characteristic curves.

Description: Internet of Things (IoTs) is a technology to connect machines, objects, and people with electronic devices. Many researchers have focused their works on architecture design from different perspectives. The deployment of IoT applications contains a variety of things that are attached with end-point devices, such as sensors, actuators, and radio frequency identification tags to perform sensing, controlling, and/or identifying things. The GS1 EPCglobal Architecture and IEEE 1451 standards are adopted as the cornerstone of our IoT architecture framework. In this paper, we focus on how to resolve the heterogeneity and dynamic characteristics of this variety of things. A uniform expression mechanism based on electronic product coding (EPC) scheme is introduced. The practical facilities are presented and examples of how to generate EPC scheme for transducers are illustrated. By integrating the IEEE 1451 compatible transducers, based on transducer electronic data sheet, to the identify layer of the extended GS1 EPCglobal Architecture, we can process more versatile data of different things in IoT applications. The uniform EPC scheme of heterogeneous things in the identify layer will make a consistent expression of things and compatible with the upper layer. This mechanism plays a fundamental role to support transducer capability in GS1 EPCglobal Architecture.

Description: Hierarchical routing in wireless sensor networks (WSNs) is a very important topic that has been attracting the research community in the last decade. Typical hierarchical routing is called clustering routing, in which the network is divided into multiple clusters. Recently, some types of atypical hierarchical routing arise, including chain-based, tree-based, grid-based routing, and area-based routing. There are several survey papers that present and compare the hierarchical routing protocols from various perspectives, but a survey on atypical hierarchical routing is still missing. This paper makes a first attempt to provide a comprehensive review on atypical hierarchical routing. We offer a classification of atypical hierarchical routing of WSNs, and give detailed analysis of different logical topologies. The most representative atypical hierarchical routing protocols are described, discussed, and qualitatively compared. In particular, the advantages and disadvantages of different atypical hierarchical routing protocols are analyzed with respect to their significant performances and application scenarios. Finally, we put forward some open issues concerning the design of hierarchical WSNs. This survey aims to provide useful guidance for system designers on how to evaluate and select appropriate logical topologies and hierarchical routing protocols for specific applications.

Description: A novel fiber-optic relative humidity (RH) sensor with thermal compensation based on a fiber Bragg grating (FBG) is presented. Changes in the RH are transduced to the FBG properties by an ORMOCER coating. The cross sensitivity to temperature is compensated by inscribing the Bragg grating in a highly birefringent fiber and using the individual Bragg peaks of each polarization direction for separation (discrimination) of temperature and humidity influences.

Description: This paper focuses on the nondestructive dielectric measurement for thin dielectric material using open-ended coaxial probe. The probe calibration procedure requires only a measurement of a half-space air and three open standard kits. The measured reflection coefficient for thin sample, which is backed by metal plate, is taken with a vector network analyzer up to 7 GHz and the reflection coefficient is converted to relative dielectric constant and tangent loss via closed form capacitance model and simple calibration process.

Description: We present a physical model to study the dark current and noise characteristics of quantum-dot infrared photodetectors (QDIPs). This model considers both carrier’s thermoexcitaion and carrier’s field-assisted tunneling, which are the main origin of dark current and noise in QDIPs. We use this model to analyze the effect of different structural parameters, such as QDs lateral size and density of QD, and environmental parameters, such as bias voltage and operating temperature on the dark current and the noise of QDIP. The theoretical results obtained from our model are in excellent agreement with reported experimental data. Therefore, the validity of the model is proven for these reasons. This model can be extended to other quantum structure detectors to evaluate the noise and dark current characteristics.

Description: Wireless sensor networks (WSNs) are a key part of the Internet of Things vision which aims at bridging together the physical and the digital worlds in several application domains. In the building automation field, WSNs are widely adopted for energy optimization, safety and security purposes, and could greatly benefit from existing information already available in preexisting building information models (BIMs). Such BIMs are normally developed during the building design phase and reused continuously during the construction and operation phases of the building life-cycle. In current deployments, however, due to lack of interoperability such information (e.g., walls geometry, materials, and so on) must often be recollected and reinputed by WSN commissioning specialists. Open development and planning tools and methodologies can play a key role in fostering interoperability and convergence of BIM and WSN systems. This paper aims at demonstrating how increased interoperability between WSN development-support tools and BIM systems could provide advantages to developers, integrators, domain specialist, and BIM users. The methodology is validated by applying a newly proposed tool exploiting BIM interoperability to support the planning of the topology of a WSN based on ultrawideband technologies. The proposed approach is evaluated through a small-scale experimentation held in a historical building in Torino (Italy).

Description: We propose to exploit filter stopband for high sensitivity radio frequency (RF) interferometer operation by utilizing reflection scattering parameters. Combined with passband filter operation, the modified RF interferometer effectively expands its frequency coverage. A simple model is described to analyze and predict interferometer performance. A high-pass filter and a low-pass filter are designed and built to demonstrate the interferometer operation as well as to verify the model over a frequency of 1–4 GHz. Lossy materials are shown to significantly degrade filter sensitivity enhancement effects due to reduced group delay and lower RF fields. Further work is needed to address the issue.

Description: In this paper, we present a radar sensor system for real-time blast furnace burden surface imaging inside a fully operative blast furnace, called BLASTDAR, the blast furnace radar. The designed frequency-modulated continuous-wave (FMCW) radar sensor array operates in the frequency band around 77 GHz and consists of several nonuniformly spaced receive and transmit antennas, making it a multiple-input multiple-output radar system with large aperture. Mechanical steering is replaced by digital array processing techniques. Off-the-shelf automotive-qualified multichannel monolithic microwave integrated circuits are used. By means of this configuration, a virtual antenna array with 256 elements was developed that guarantees the desired angular resolution of better than 3°, and a range resolution of about 15 cm. Based on the single-channel FMCW signal model, this paper will derive a multichannel signal model in combination with a digital beamforming approach and further advanced signal processing algorithms. The implementation of a simulation tool covering the whole design process is shown. Based on these simulation results, a system configuration is chosen and the obtained setup is defined and presented. A description of the manufactured cost-efficient radio frequency and baseband boards together with the housing design shows the practical implementation of the sensor. For the system calibration, two different methods are listed and compared regarding their performance. Verification measurements confirm the predicted performance of the developed sensor. Several measurements inside a fully operational blast furnace demonstrate the proper long-term functionality of the system, to the best of our knowledge, for the first time worldwide. It is in continuous operation since about two years in blast furnace #5 of voestalpine Stahl GmbH, Linz.

Description: Indoor lighting systems with wireless sensor-equipped luminaires are considered as an infrastructure for offering location-based illumination control. Wireless occupancy and light sensors transmit sensing information to a lighting controller, which then adapts artificial illumination from luminaires to user occupancy and daylight changes. Such wireless sensor transmissions can be used to collect received signal strength indicator (RSSI) values at a user device. We propose to use the RSSI measurements at the user device, in combination with accelerometer sensor data, to determine user location zone when a user seeks personalized light control. Based on its location zone, the user is granted control of associated luminaires. The performance of the proposed system and positioning method is evaluated in a large indoor lighting open-plan office model.

Description: In this paper, a Pd–TiO 2 nanofiber structure with photoactivation capability for H 2 gas sensing is made using the electrospinning procedure. The solution which was stacked into the syringe for electrospinning Pd–TiO 2 nanofibers consisted of titanium tetraisopropoxide, acetic acid, ethanol, polyvinyl pyrrolidone, and different amounts of Pd solution. The X-ray diffraction, field emission scanning microscopy, transmission electron microscopy, and spectrophotometry techniques were employed to analyze the crystalline structure and surface morphology of the nanofibers. Moreover, Fe 2 O 3 and HNO 3 were also used as additional additives and the effect of additives in the absorption spectrum shift towards the visible light spectrum was investigated. About 95-nm red shift toward visible light from 370 to 465 nm for TiO 2 /Pd/N/Fe 2 O 3 was observed in comparison with the pure TiO 2 nanofibers. By using additives and visible light irradiation, the operating temperature lowered from 290 °C to 130 °C and the response increased from 11 to 368. At an operating temperature of 150 °C, the response time also reduced from 25 to 0.9 s and recovery times reduced from 40 to 2 s. The response dropped only by $sim 30$ %, 12%, and 5% after nine months for the TiO 2 , TiO 2 /Pd, and TiO 2 /Pd/N/Fe 2 O 3 samples, respectively.

Description: Over the years, several QRS complex detection algorithms have been proposed with different features, but the remaining problem is their implementation in low-cost portable platforms for real-time applications, where hardware resources are limited, still providing the accuracy level required for medical applications. The proposed algorithm copes at the same time with both requirements: 1) accuracy and 2) low resource consumption. In this paper, a real-time QRS complex detector is proposed. This algorithm is based on a differentiation at the pre-processing stage combined with a dynamic threshold to detect R peaks. The thresholding stage is based on a finite-state machine, which modifies the threshold value according to the evolution of the signal and the previously detected peak. It has been evaluated on several databases, including the standard ones, thus resulting sensitivities and positive predictivities better than 99.3%. In order to analyze the computational complexity of the algorithm, it has been compared with the well-known Pan and Tompkins’ algorithm. As a result, the proposed detector achieves a reduction in processing time of almost 50% by using only the 25% of hardware resources (memory, adders, and multipliers).

Description: 1-D oxide nanostructures-based metal-insulator–metal structures represent potential gas sensor devices, owing to their vertical electron transport feature. In this paper, we demonstrate that for achieving optimum gas sensing by a TiO 2 nanotube (NT) array in vertical mode, tuning of NTs (1-D) surface area as well as carrier transport path length by tailoring the NT length can be a valuable approach. For anodization times of 1, 4, 8, 12, and 16 h, the corresponding NT length was found to be 280–320, 506–514, 1730–1790, 2000–2200, and 2380–2420 nm, respectively, with almost no variation in tube diameters or separations. The carrier concentrations of the NTs were found to be decreasing with increasing tube length. The vertical device structure, employing NT arrays of different lengths as the sensing layer, was investigated in the temperature range of 50 °C–250 °C for sensing acetone, as a test gas/vapor, in the concentration range of 10–1000 ppm. The response magnitude of the sensor was increased with increased NT length, possibly owing to the availability of larger amounts of gas interaction sites due to higher surface area at increased length. The response time and recovery time of the developed sensor also increased with increasing tube length and became excessively sluggish after the critical tube length exceeded 2250 nm owing to slower adsorption/desorption and diffusion kinetics.

Description: One of the key studies in the cognitive radio networks is maximizing some important metrics such as transmission/energy efficiencies or throughput with respect to network parameters such as sensing and transmission time. There is always a tradeoff between sensing time and transmission time. While longer sensing times results in higher detection accuracy, it loses transmission opportunities and hence decreases transmission efficiency. Many works have been done to find the best transmission and sensing time to maximize the efficiencies such as transmission and energy, but the interference and hence the probability of collision was not defined and formulated correctly. In this paper, we consider the trilateral tradeoff between sensing, transmission, and contention times. To do this, the interference between primary user (PU) and secondary user (SU) is formulated. We consider interference due to both imperfect sensing and PU-return. Furthermore, the interference among SUs has been also formulated. These metrics are used in defining transmission efficiency and probability of collision as a constraint.

Description: In this paper, a 2-D air holes in silicon slab photonic crystal-based structure with line defect has been designed and simulated for detection of high glucose concentration in urine from 0–15 to 10 gm/dl in the wavelength range of 1530–1565 nm. High glucose concentration in urine is referred as glycosuria. The proposed sensor structure is modeled and simulated in time domain by using Massachusetts Institute of Technology (MIT) electromagnetic equation propagation simulation tool. Finite-difference time-domain method has been used for the analysis. Band structure has been computed and eigen frequencies have been extracted for each k-point for the designed sensor structure by using (MIT photonic bands) simulation tool. The changes in the normalized output power levels, quality ( $Q$ )-factor, and resonant frequency have been observed for different concentrations of glucose present in urine. The calculated value of $Q$ -factor obtained is $Q=23,575$ . This paper has been done for normal urine and glycosuric urine. It is clear from the simulated graphs of transmission spectrum and band structure that for minute changes in the refractive index, the transmitted output power level range varies from 0.2298 to −0.091 dB and the resonant frequency range varies from 0.229259–0.22914 (in units of c/a) and hence it acts as a sensor for detection for glycosuria. Our designed sensor has achieved sensitivity of 638 nm /RIU.

Description: This paper reports a simple fluorescence-based tapered fiber optic probe for fluoride ion having a detection range of $2.08 times 10^{mathrm { {-6}}}$ – $2.005 times 10^{mathrm { {-4}}}$ M. The performance of the tapered probe is evaluated with respect to the probes that consist of combinations of bare uncladded multimode optical fibers. The effect of fluorescence quenching of a natural dye curcumin in the presence of fluoride ion is used in the implementation of the probes. The probe effectively uses multiple mechanisms for the excitation and collection of fluorescence from the medium enabling higher sensitivity compared with conventional spectrophotometry especially at very low concentrations of fluoride.

Description: In this paper, the arrayed flexible pH sensor and glucose biosensor modified by magnetic beads and graphene were proposed. The ruthenium dioxide (RuO 2 ) sensing films were deposited by radio frequency sputtering system and the screen-printed technique was used to construct the silver conducting wires and insulation layer of the RuO 2 electrodes. In order to enhance performance of the pH sensor and glucose biosensor, the microfluidic device had been utilized and developed. In the measurement processes, the different pH and glucose solutions were investigated in various flow rates. According to the experimental results, the average sensitivity of the pH sensor was enhanced from 52.280 to 57.981 mV/pH and the average sensitivity of the RuO 2 /graphene/magnetic bead-GO x -Nafion glucose biosensor was enhanced from 10.628 to 13.541 mV/mM. With regard to the wireless sensing measurements, the wireless sensing system which complied the ZigBee standard was employed to transmit the signals of the pH or glucose measurements in this investigation, and the system consisted of the Xbee device, Arduino Mega 2560, readout circuit, pH or glucose biosensor and computer. According to the experimental results, the average sensitivity and linearity of the pH sensor were 51.063 mV/pH and 0.988, respectively, and the average sensitivity and linearity of the RuO 2 /graphene/magnetic bead-GO x -Nafion glucose biosensor were 11.005 mV/mM and 0.995, respectively.

Description: This paper considers the throughput maximization of a secondary user (SU) in a realistic cognitive radio (CR) network where the battery suffers from constant energy leakage. We investigate two different CR scenarios where the primary user (PU) switches between idle and active states in a time-slotted manner. In the first scenario, the SU knows the exact state of the PU at the beginning of each time slot, whereas in the second scenario, the SU attempts to detect state of the PU by spectrum sensing. For both scenarios, we determine the maximum throughput of the SU with consideration of battery leakage of the SU and interference constraint of the PU. The optimal solutions of transmitting power and sensing duration are achieved by using golden section search method and a simplified brute-force search method. Finally, the theoretical analysis is verified through the Monte Carlo simulations.

Description: A rotameter is a variable-area-type flow rate measuring instrument in which the position of a metallic float in a transparent conical tube is taken as a flow rate indicator. It has the disadvantage that it is a local indicating type instrument and special type of transducer is used for its remote indication. In this paper, a noncontact flow rate measurement technique using Hall probe sensor and rotameter is designed, developed, and tested. In this design, a float carrying a thin circular permanent magnet is used, and a Hall probe sensor placed outside the rotameter tube has been used to sense the variation of magnetic field of the magnet with the variation of float position. A signal conditioner unit has been used to convert the Hall probe sensor output into 1–5 V dc signal. This dc signal output of the signal conditioner has been sent to a PC-based flow indicator through optoisolator and analog input channel of a data acquisition system (DAS) card. The PC-based flow indicator has been designed using the Lab Tech Note Book Pro software and the PC-based supervisory control and DAS. A theoretical equation has been derived to explain the operation of the system. The performance of the system has been tested experimentally, and the experimental results are reported in this paper. A very good repeatability and linearity of results has been observed.

Description: Traditional wet or gel impedimetric electrodes for neuro-physiological signal (e.g., electroencephalography and electrocardiography) monitoring are usable for a short duration, as the performance of electrodes deteriorates rapidly when exposed to the environment. Dry impedimetric electrode is a promising alternative tool for long duration monitoring, however suffers from high interfacing impedance. This paper describes a novel dry interfacing electrode utilizing patterned vertical carbon nanotube (pvCNT) for impedimetric sensing. The electrodes were fabricated on circular stainless steel foil substrates (thickness = 2 mil) that are laser cut to circular discs (Ø = 10 mm). Pattern on the substrate was developed with a custom shadow mask while sputter coating the substrate with Al 2 O 3 and iron. Electrically conductive multiwalled CNTs were then grown vertically in pillar formation ( $100~mu text{m}^{}$ each side of square footprint) with various interpillar spacing (50, 100, and $200~mu text{m}$ for various masks). The heights of the CNT pillars were between 1 and 1.5 mm. The impedances of the electrodes were 1.92, 3.11, and $8.15~Omega $ for 50-, 100-, and 200- $mu text{m}$ spacing, respectively. A comparative in vitro study with commercial wet and gel electrodes showed pvCNT electrode has lower interfacial impedance, comparable signal capture quality, and ability to be used for stimulation. Long duration study showed minimal impedance degradation for pvCNT electrodes over a week. The results demonstrate pvCNT is a promising dry electrode for impedimetric sensing and stimulation of neurophysiological signals over - prolonged duration.

Description: In the case of an unavoidable frontal collision between a vehicle and a pedestrian, the activation of a protection system can reduce the severity of injuries caused by the collision. However, to fulfill this objective, it is necessary to determine when the shock will occur. To overcome this problem, we place inside the front bumper a metallic sheet that emits an electric field. This field is oriented toward the front of the vehicle by means of various guard screens. The intrusion into the emitted electric field induces a capacitive coupling with the sensor. Which will enable the electronic device to detect the presence of the pedestrian at a distance of 1 m. To avoid slow drifts in time, the change in capacity is measured every millisecond. The last hundred acquisitions are considered as a history. This history is compared with the signature of a pedestrian who was established in the laboratory. When the pedestrian is about a thirty centimeters of the vehicle and the shock is inevitable, the protection systems are activated. When the vehicle is at very low speed, this device can be used as parking assistance.

Description: In this paper, power allocation in distributed multiple-input multiple-output radar is investigated for range-only target tracking such that the determinant of Bayesian Fisher information matrix (B-FIM) is maximized. First, the B-FIM is derived for a signal model that incorporates the propagation path loss, the target reflectivity, the transmitted power, and the target prior density. Then, we model the problem as a cooperative game and exploit the solution concept of the Shapley value to distribute a given power budget among all transmitting radars for target tracking. In numerical examples, it is shown that uniform power allocation is not in general optimal. We illustrate the effects of the radar network geometry configuration, target prior density and number of antenna upon the power allocation results, and further demonstrate the superior performance of the proposed optimal power allocation scheme via Monte Carlo simulations.

Description: A fiber Bragg grating (FBG) accelerometer based on a push–pull elastic cylinder structure is demonstrated. First, the model based on the uniform cylinder structure is analyzed and the optimized accelerometer parameters are given. Then, by designing a radius-varying cylinder structure, the FBG strain becomes larger than the cylinder strain, which leads to enhanced sensitivity amplification for a small accelerometer size and relatively high resonant frequency. Meanwhile, the influence of the transverse force on the accelerometer is theoretically analyzed. These results indicate that the transverse-induced FBG deformation is very big so that a strict transverse constrain is needed. The formula of the strain magnification is derived and the design rules of the strain magnification are given. After structure optimization according to the rules, the FBG strain increases to 1.5 times, the sensitivity increases to 1.82 times, whereas the resonant frequency reduces to 0.9 times compared with the parameters of accelerometer based on uniform cylinder structure. Finally, the accelerometer size reduces to $Phi {20~{rm mm}times 34~{rm mm}}$ , the sensitivity increases to 623 pm/g, and the resonant frequency reduces to 449 Hz.

Description: The proliferation of radio frequency (RF) communication technology in biomedical signal transmission is frequently flustered by electromagnetic interference. Even though the flexibility and mobility of RF-based communication have much attraction, the radiation brings damage to hospital equipments and even harm to humans. In this letter, we propose a novel scheme for transmission of electroencephalography (EEG) biomedical signal using a visible light communication (VLC) link. The data transmission is performed in line of sight (LOS) condition using ON–OFF keying nonreturn-to-zero modulation by utilizing all three components, red, green, and blue, of RGB LED. Experiments are carried out for transmitting EEG signals using the VLC link. The transmitter consists of RGB LEDs, and at the receiver side, three photodiodes with red, green, and blue color filters are installed. The experimental results show excellent reliability and accuracy of the proposed scheme.

Description: In this paper, we propose a monocular multiframe high dynamic range (HDR) monocular vision system to improve the imaging quality of traditional CMOS/charge-coupled device (CCD)-based vision system for advanced driver assistance systems (ADASs). Conventional CMOS/CCD image sensors are confined to limited dynamic range that it impairs the imaging quality under undesirable environments for ADAS (e.g., strong contrast of bright and darkness, strong sunlight, headlights at night, and so on). Contrary to current HDR video solutions relying on expensive specially designed sensors, we implement a multiframe HDR algorithm to enable one common CMOS/CCD sensor capturing HDR video. Key parts of the realized HDR vision system are: 1) circular exposure control; 2) latent image calculation; and 3) exposure fusion. We have successfully realized a prototype of monocular HDR vision system and mounted it on our SetCar platform. The effectiveness of this technique is demonstrated by our experimental results, while its bottleneck is the processing time. By exploring the capability of the proposed method in the future, a low-cost HDR vision system can be achieved for ADAS.

Description: In this paper, a fiber-optic surface plasmon resonance (SPR) biosensor is presented, in which a sheet of graphene acting as a sensing layer is coated around the gold film. A theoretical study of the proposed fiber-optic biosensor has been carried out by applying four-layer modal, which shows that by incorporating a graphene sensing layer, the sensitivity of the proposed SPR fiber biosensor can be greatly enhanced than the conventional gold film SPR fiber sensors. The relationship between resonance wavelengths and sensitivity of the proposed graphene sensing layer-based SPR fiber biosensor with the number of sensing layer has also been studied.

Description: We report the development of cantilever-based cold cathode ionization pressure sensor that works on the principle of dielectric breakdown of gaseous medium. The high electric field ( $E_{m}=1$ MV/m) developed at the corners of the microtip produced dielectric breakdown of the medium, sufficient to produce ionization current at a relatively low bias voltage $V_{b} 〈10$ V. With increase in pressure, the availability of molecules in the vicinity of the micro-tip increased which when ionized by the application of $V_{b}$ , produced enhanced ionization current through the device. The devices with cantilever lengths $L=50$ , 150, 250, 350, and $450~mu text{m}$ were designed with interelectrode spacing ( ${d}_{textrm {int}} )$ of 1250 nm, which was further reduced by the application of suitable $V_{b}$ to enhance the sensor performance. The device with $L=450~mu text{m}$ provides the widest dynamic range of $10^{mathrm {mathbf {-4}}}-10^{mathrm {mathbf {2}}}$ mbar and the highest sensitivity of 2.44 $mu text{A}$ /mbar with power consumption of $1.32times 10^{-1}~mu text{W}$ at 10 V, which is $10^{4}$ - times lower than previously reported device. The device offers a service life of 60 cycles assuming a tolerance of 10% in device performance.

Description: A simple noncontact displacement microfiber sensor using adiabatic U-shaped tapered fiber is proposed and demonstrated. The microfiber is fabricated using a systematic fiber flame brushing technique, where the fiber waist diameter is proportional to the duration of the heating cycles. The sensor is capable of measuring a wide displacement distance up to 12 mm. A sensitivity of 0.2 dB/mm is recorded at a minimum tapered diameter of 8 $mu text{m}$ . In comparison with the previous works of using Fresnel reflection method, the results of our proposed method show significant improvement in sensing range, which is indicated by distinct inclination of the loss slope. The microfiber probe shows a promise for a sensitive sensing at low development cost.

Description: In this paper, wireless sensing in the presence of complex electromagnetic media created by combinations of reinforcing bars and concrete is investigated. The wireless displacement sensing system, primarily designed for use in structural health monitoring (SHM), is composed of a comb-like nested split-ring resonator (NSRR) probe and a transceiver antenna. Although each complex medium scenario is predicted to have a detrimental effect on sensing in principle, it is demonstrated that the proposed sensor geometry is able to operate fairly well in all scenarios except one. In these scenarios that mimic real-life SHM, it is shown that this sensor exhibits a high displacement resolution of 1 $mu text{m}$ , a good sensitivity of 7 MHz/mm in average, and a high dynamic range extending over 20 mm. For the most disruptive scenario of placing concrete immediately behind NSRR, a solution based on employing a separator behind the probe is proposed to overcome the handicaps introduced by the medium. In order to obtain a one-to-one mapping from the measured frequency shift to the displacement, a numerical fit is proposed and used. The effects of several complex medium scenarios on this fit are discussed. These results indicate that the proposed sensing scheme works well in real-life SHM applications.

Description: Due to electromagnetic silence, passive tracking systems for emitter targets usually produce track segments (i.e., tracklets) rather than an entire trajectory of the target. Therefore, a multistage method for emitter target tracking is proposed in this paper. In the stage of tracklet generation, the Gaussian mixture-probability hypothesis density tracker with adaptive estimation of target birth intensity is applied to generate reliable tracklets of the emitter targets. After that, in the stage of tracklet association, the multipoint motion information and emitter signal information are integrated to compute the similarities between the tracklets. The affinity propagation algorithm, which does not impose the constraint of one-to-one correspondence, is then used to cluster the tracklets. In the stage of association refining, the clustering result is adjusted to refine the final trajectories according to the spatial-temporal constraint of the tracklets. The simulation results show that the proposed method is robust and performs well.

Description: Entomologists need to observe and monitor insects in their natural habitats for various reasons. One of the most common techniques in use today is to attach low-cost harmonic sensor or transponder to insects and to track them using an associated harmonic radar. Existing harmonic transponders based on monopoles, loop-dipoles, and Minkowski loops have been successfully attached to small low-flying insects. However, they offer significant constraints from a mounting perspective, weight and size considerations, aerodynamic drag, and the elevation of the insect center of gravity. This paper addresses these issues by presenting novel design methodologies for millimeter wave harmonic sensors and radar. The sensors address the challenges of ease of design and fabrication, robustness, conversion efficiency, miniaturization, antenna entangling, and attachment problems that are generally encountered with other transponders.

Description: This paper presents an ultra-low power DC–DC converter to be embedded into body sensor nodes. The proposed DC–DC converter is used to step-up the voltage at the output of a micro-thermoelectric generator up to a usable supply voltage between 0.42 and 1.05 V. Measurements have been conducted on ten available samples. The resulting mean value of the minimum input voltage is 96 mV. At the minimum input voltage, the power consumption is only 0.23 $mu text{W}$ . The operating temperature ranges from −40 °C to 100 °C.

Description: Various jamming techniques have been developed to prevent interferometric synthetic aperture radar from effective detection and observation. In this paper, a thorough analysis of the jamming effects on correlation and interferometric phase is provided. To derive the jamming result, a general signal model for the interference is first presented and the corresponding imaging results are produced through the range-Doppler algorithm. Then, the impacts of the interference on correlation are analyzed. The non-center located jammer decreases the correlation seriously due to the low correlation of the interference. However, the center located jammer clearly increases the correlation when the input jamming-to-signal ratio is large enough. Finally, the jammed interferometric phases for different jammer positions are discussed. It shows that the non-center located jammer results in large phase errors, while for the center located jammer, the interferometric phase approaches a constant. The effects of interference are demonstrated by simulated data based on the TerraSAR system.

Description: This paper demonstrates the measurement of respiration waveform during sleep with a noncontact radar sensor. Instead of measuring only the respiration rate, the methods that allow monitoring the absolute respiration displacement were studied. Absolute respiration displacement can in theory be measured with a quadrature microwave Doppler radar sensor and using the nonlinear demodulation as the channel combining method. However, in this paper, relative respiration displacement measures were used as a reference. This is the first time that longer data sets have been analyzed successfully with the nonlinear demodulation method. This paper consists of whole-night recordings of three patients in an uncontrolled environment. The reference respiration data were obtained from a full polysomnography recorded simultaneously. The feasibility of the nonlinear demodulation in a real-life setting has been unclear. However, this paper shows that it is successful most of the time. The coverage of successfully demodulated radar data was $sim 58$ %–78%. The use of the nonlinear demodulation is not possible in the following cases: 1) if the chest wall displacement is too small compared with the wavelength of the radar; 2) if the radar data do not form an arc-like shape in the $IQ$ -plot; or 3) if there are large movement artifacts present in the data. Both in academic literature and in commercial radar devices, the data are processed based on the presumption that it forms either an arc or a line in the $IQ$ -plot. Our measurements show that the presumption is not always valid.

Description: This paper presents a demodulation algorithm based on the synchronous integrator circuit for the MEMS tuning fork gyroscope utilizing the digital processing technology. The synchronous integral demodulator (SID) is adopted to demodulate the drive-detection signal and sense-axis output signal separately. Combining with automatic gain control and phase-locked loop technology, the closed-loop control of drive mode has been implemented, and high precision output of the gyroscope has been achieved. The simulation results have verified the effectiveness of the synchronous integrator circuit, which is in good agreement with the theoretical analysis. Compared with other demodulation algorithms, the SID has the advantages of the lower noise level, a better ability to attenuate the harmonics, and the best hardware efficiency. The frequency characteristic of the synchronous integrator is also analyzed, which is vital to the bandwidth of gyroscope. The print circuit board based on field-programmable gate array digital circuit is manufactured and the corresponding experiment is carried out. The experimental results show that the SID algorithm of digital control system for the gyroscope developed in our laboratory has achieved a good performance. The bias instability of tested gyroscope is measured to be 0.2°/h with the angle random walk of 0.14°/ $surd text{h}$ and the nonlinearity of the scale factor is <60 ppm with the measurement range of ±100°/s.

Description: We report the observed bifurcation in extraordinary electroconductance (EEC) sensor response to direct reverse bias based on measurement lead location as well as a dramatic enhancement in responsivity achieved via a modification of the shunt geometry. A maximum percent change in the four-point resistance of 130856% was achieved under a direct reverse bias of −1 V using an enhanced shunt design, a 325 fold increase over the conventional EEC square shunt design. This result was accompanied by an observed bifurcation in sensor response, driven by a rotation of the four-point measurement leads.

Description: This paper introduces joint neighbor discovery (ND) and coarse time-of-arrival (ToA) estimation in wireless sensor networks (WSNs) via orthogonal frequency-division multiple access. In the proposed technique, each sensor node exploits at least one orthogonal sub-carrier as its allocated signature, to respond the ND and ToA estimation requests transmitted by target nodes. The target node utilizes the orthogonality across sub-carriers to detect the transmitted signatures and their corresponding delays. This technique is energy efficient as it avoids multiple transmissions and receptions inherent in traditional ND protocols and ToA estimation techniques in WSN. Moreover, in this technique, network initiation process does not require channel information or time synchronization across sensor nodes. The performance of the proposed method is studied by evaluating the probabilities of false alarm and miss detection of the ND. In addition, ToA estimation error is calculated theoretically and via simulations. Moreover, the impact of available bandwidth on the performance and energy efficiency of ND and ToA estimation are investigated. Simulation results confirm the energy efficiency and the feasibility of the proposed method even at low signal-to-noise ratio regimes and in multi-path and frequency selective channels.

Description: This paper presents a new method for sensing and the quantification of the number of solid microparticles using surface acoustic wave (SAW) devices. In contrast to the standard mass loaded delay line approach, microcavities with varying geometrical shapes and sizes are formed between SAW interdigitated transducer pairs. The system operation relies on the resonance condition occurring inside the microcavity through the coupling of Rayleigh waves to the sample, and the output phase angle is used for obtaining measurement results. It is shown through measurements that it is possible to interact with polystyrene solid microbeads trapped inside the microcavity and extract information about the size of the sample. Furthermore, the number of microbeads placed in a single file along the microcavity width can be quantified using this platform. Experimental results are compared and verified with finite-element method simulations. In essence, this novel approach resulted in a platform capable of analyzing sample volumes less than 10 pL in a non-invasive manner. For size differentiation, experimental phase shifts of 0.14° ± 0.05°, 0.81° ± 0.26°, and 3.54° ± 0.49° were obtained in rectangular microcavities for 10, 15, and 20 $mu text{m}$ microbeads, respectively. On the other hand, a distribution of phase shifts as 0.51° ± 0.19°, 0.98° ±0.12°, and 1.34° ± 0.15° are obtained for counting one, two, or three microbeads, respectively. The proposed system was designed, simulated, fabricated, and tested successfully.

Description: This paper describes printed resonant structures on a flexible substrate for humidity detection. The devices consist of a screen-printed spiral inductor working as radio frequency identification (RFID) antenna and two different inkjet-printed planar capacitive structures forming LC resonators. The sensitive material is directly the chosen substrate: a polyimide whose electrical permittivity is dependent on the moisture content. Therefore, no extra sensitive layer is required to functionalize these structures. In particular, two different approaches can be followed to use it. On one hand, the resonant structure can be used as a threshold tag including an RFID chip. The tags will be detected or not by an RFID reader depending on the humidity. On the other hand, these structures can be directly used as quantitative humidity sensors where the moisture content is associated with the resonant frequency of the structure.

Description: A novel signal-processing algorithm based on phase tracking in frequency domain of optical fiber Fabry-Perot interferometric spectrum is described. The concept was demonstrated with three fiber Fabry-Perot interferometers for relative humidity measurement. Experimental results show that the proposed method can yield optical path difference measurement with high resolution, especially in the lower range of absolute humidity under 2000 ppm.

Description: Digital false-target image synthesizer (DIS) has been proposed as a deceptive jamming method for countering inverse synthetic aperture radar (ISAR) with an RF imaging false-target capability. However, to efficiently generate jamming signal in real time, a specific-designed generator is unavoidable for the implementation of this algorithm, where parallel and pipeline processing are both included because jamming signal is generated according to each range bin. This paper proposes an improved two-stage DIS method (T-DIS). The implementation of the T-DIS can be effectively simplified by separating the modulation process of a repeat jammer into two stages: 1) the offline stage and 2) the real-time stage. The modulation signal can be easily extracted from the modulation-matrix buffered in the offline stage. Only an element-by-element matrix multiplication between the modulation signal and the intercepted ISAR signal is needed in the real-time stage. In contrast to the conventional DIS method, the proposed algorithm exhibits simplicity and flexibility significantly, which reduces the computation time and hardware constraints. Experimental results of scattering model of the Yak-42 plane and real data illuminate the validity of the proposed method.

Description: This paper presents an information processing framework for distributed sensor networks. The framework is capable of directly processing temporally and spatially distributed multimodality sensor data to extract information buried in the noise clutter. Moreover, we introduce distributed algorithms to implement spatio-temporal filtering applications in grid sensor networks within the context of the framework. The proposed framework is based on the belief notions in Dempster–Shafer (DS) evidence theory and evidence filtering method. Further analysis is done by exploiting a fire propagation scenario when high noise is present in the sensed data. We compare intuitively appealing results against DS fusion method to grant further credence to the proposed framework.

Description: In this paper, we demonstrate a novel robust miniature three-axis vibrational energy-harvester using a mechanical-piezoelectric configuration. Using the configuration, the harvester employs Newton’s law of inertia and the piezoelectric effect to convert either the $x$ -axis or $y$ -axis in-plane and $z$ -axis out-of-plane ambient vibrations into piezoelectric voltage-responses. Under the $x$ -axis vibration (sine-wave, 75 Hz, 3.5 g), our modeled, finite-element analyzed/simulated, and experimental root mean square voltage-response with power-outputs of the harvester (stimulated in resonant with the optimum load) is 525.36 mV with 0.477 $mu text{W}$ , 516.51 mV with 0.461 $mu text{W}$ , and 548 mV with 0.519 $mu text{W}$ , respectively. Under the $z$ -axis vibration (sine-wave, 95 Hz, 3.8 g), the modeled, finite-element analyzed/simulated, and experimental root mean square voltage-response with power-output of the harvester (stimulated in resonant with the optimum load) is 157.35 mV with 0.066 $mu text{W}$ , 170.25 mV with 0.0772 $mu text{W}$ , and 168 mV with 0.075 $mu text{W}$ , respectively. These show that not only both of our modeling and finite-element analysis/si- ulation can successfully predict the experimental results, but also our harvester is capable of harnessing three-axial ambient vibrations. Moreover, through the piezoelectric lead–zirconate–titanate-connected-in-series approach, the voltage and power outputs are increased. According to these achievements, we believe that our harvester would be an important design reference in industry for future development of microfabrication-based (MEMS-based) three-axial piezoelectric energy harvesters and accelerometers.

Description: A good port management system must be able to perform safe, predictable, and efficient execution of transport processes. In order to improve the quality of the port management, a robust navigation system is required, which enables to provide the positions of vessels 24/7 on either open or impeded environment. This paper describes a robust georeferencing system that could satisfy centimeter-level accuracy requirements in port environments. The design is based on the loosely coupled integration of global navigation satellite system (GNSS) technology, a terrestrial radio frequency ranging system known as Locata, and an inertial navigation system (INS). GNSS observations are processed using the precise point positioning (PPP) approach instead of the conventional differential approach. To satisfy both accuracy and reliability requirements, three integration algorithms—centralized Kalman filtering (CKF), federated Kalman filtering (FKF), and global optimal filtering (GOF)—are investigated and implemented into a triple-integrated PPP-GNSS/Locata/INS system. A preliminary performance assessment, which is based on the analysis of real data, concludes that all the three integration algorithms are able to provide centimeter-level positioning solutions. The results show that the FKF and CKF algorithms have similar performance, whereas the GOF solution has higher accuracy. Moreover, the outlier simulation is conducted and the result verifies the outlier fault-tolerant capability of the GOF-based PPP-GNSS/Locata/INS integrated system.

Description: Dexterous continuum manipulators (DCMs) can largely increase the reachable region and steerability for minimally and less invasive surgery. Many such procedures require the DCM to be capable of producing large deflections. The real-time control of the DCM shape requires sensors that accurately detect and report large deflections. We propose a novel, large deflection, shape sensor to track the shape of a 35 mm DCM designed for a less invasive treatment of osteolysis. Two shape sensors, each with three fiber Bragg grating sensing nodes is embedded within the DCM, and the sensors’ distal ends fixed to the DCM. The DCM centerline is computed using the centerlines of each sensor curve. An experimental platform was built and different groups of experiments were carried out, including free bending and three cases of bending with obstacles. For each experiment, the DCM drive cable was pulled with a precise linear slide stage, the DCM centerline was calculated, and a 2D camera image was captured for verification. The reconstructed shape created with the shape sensors is compared with the ground truth generated by executing a 2D–3D registration between the camera image and 3D DCM model. Results show that the distal tip tracking accuracy is 0.40 ± 0.30 mm for the free bending and 0.61 ± 0.15 mm, 0.93 ± 0.05 mm and 0.23 ± 0.10 mm for three cases of bending with obstacles. The data suggest FBG arrays can accurately characterize the shape of large-deflection DCMs.

Description: We report an evaluation of an epitaxially grown uncooled InAs photodiode for the use in radiation thermometry. Radiation thermometry measurements was taken using the photodiode covered blackbody temperatures of 50 °C–300 °C. By determining the photocurrent and signal-to-noise ratio, the temperature error of the measurements was deduced. It was found that an uncooled InAs photodiode, with the peak and cutoff wavelengths of 3.35 and 3.55 $mu text{m}$ , respectively, measured a temperature of 50 °C, with an error of 0.17 °C. Many plastics have $C$ – $H$ molecular bond absorptions at 3.43 $mu text{m}$ and hence radiate thermally at this wavelength. Our results suggest that InAs photodiodes are well suited to measure the temperature of plastics above 50 °C. When tested with a narrow bandpass filter at 3.43 $mu text{m}$ and blackbody temperatures from 50 °C–300 °C, the InAs photodiode was also found to produce a higher output photocurrent, compared with a commercial PbSe detectors.

Description: State-of-the-art calibration very often constructs models motivated by a real-world device. Recently, artificial neural networks (ANNs) have been proposed as a more universal, accurate, and practical black-box approach. For a galvanometric triangulation device based on two mirrors, we embrace this proposal and set it into context with other supervised data-driven approaches: 1) ridge regression; 2) support vector regression; and 3) Gaussian processes. We show that they outperform available model-based approaches and yield similar performance compared with a memorizing lookup table calibration. The results demonstrate that an off-the-shelf usage of ANNs may run into generalization problems. Restricting the space of functions using kernel-based learning has proven to be advantageous. Finally, all approaches and distinct properties are discussed in a broader context, since each application entails differently relevant requirements for its calibration. This also holds for any calibration other than the considered triangulation device.

Description: This paper describes the design and the implementation of a new structure for an ac current sensor based on a magnetoelectric laminated composite slice. Two layers of longitudinally magnetized magnetostrictive material Terfenol-D (Tb 0.3 Dy 0.7 Fe 1.92 ) and one layer of transversely polarized piezoelectric material Pb(Zr,Ti)O 3 (PZT) were epoxy-bonded and the wire conducting the current coiled along the slice and the output voltage obtained across the two surfaces of the PZT. Compared with the reported ring-type or close-magnetic-circuit-type magnetostrictive current sensor topologies, there was no requirement for any interruption of the power supply to enable the installation and the maintenance of the sensor, which was very convenient and practical. The dimensions of the slice sensor were 30 mm $times $ 8 mm $times $ 2.8 mm. An averaging method was used to perform the theoretical analysis and the simulation is carried out using the COMSOL multiphysics software. The analysis, simulation, and experimental results were compared thoroughly. The current sensitivity was 1.03 mV/mA over input currents ranging from 15 mA to 2.1 A. A stable output voltage over a frequency range from 20 Hz to 5 kHz was attained by the slice. Further research on the influence of the dc bias magnetic field and the number of turns of the current coil on the output characteristics of the sensor has been carried out. This current sensor has great potential for further research and applications.

Description: We present in this paper an acoustic indoor location system that allows a simultaneous localization of sources with different location precisions. This is achieved by the use of the time reversal technique and the code-division multiple-access operation. The system was evaluated in terms of accuracy, precision, and location delay. Simulations and experiments were carried out while varying the number of sources and that of the precision levels. The effect of the signal-to-noise ratio on system performance was also studied. Results showed that our location system can achieve accuracy of 1.5 cm with 83% precision. Finally, we aimed to reduce the audibility of the location signal. An equalization filter based on the absolute threshold of hearing was applied to the emitted signal and a matched filter was introduced at the receiver. Results showed an improvement in location precision when compared with the location system without the equalization filter. A reduction in signal audibility was noted.

Description: An approach to multiple gas sensing on decorated porous silicon (PS) substrates is presented. The simple microelectromechanical systems/nanoelectromechanical systems platform that we have developed facilitates the modeling of the interaction of nanostructured metal oxide islands with the analytes of interest, which are exemplified by NO and NH 3 . These conductometric sensors operate at room temperature and atmospheric pressure and, as they are forgiving, do not require film-based technology or lithography for their construction. We show that diffusion dominates the conductometric response. The direct response and the derivatives of this response are considered. The first derivative allows a quick evaluation of sensor response and the derivative is linear with concentration. The spectral simulations have been refined to include adsorption/desorption effects of the analyte gas and assess subsequent non-linear interface sensitivities. By including the physics of adsorption/desorption, the simulated sensor response is now a non-linear function of concentration. We model the absorption/diffusion through the use of the Langmuir absorption isotherm and find substantial agreement with experiment for the mixed analyte interactions of NH 3 and NO combinations on several metal oxide decorated PS interfaces.

Description: A simple colorimetric method for the determination of vaporous aliphatic amines has been developed. Importantly, the recognition of vaporous aliphatic amines could be observed by naked eyes owing to color change of the synthesized azobenzothiazole-polyene dye from orange to dark blue in the solution. The results revealed that primary amines can form 1:2 and secondary amines 1:1 complexes with the dye, respectively. The sensing of this chemosensor is capable over a dynamic linear ranges between $10^{mathrm {-2}}$ – $10^{mathrm {-6}}text{M}$ for primary aliphatic amines and $10^{mathrm {-2}}$ – $10^{mathrm {mathbf {-4}}}text{M}$ for secondary aliphatic amines. The response of the dye to tertiary amines or aromatic amines was not strong enough to make a strong color change. Validation of the assay method revealed excellent performance characteristics, including high repeatability and highly recognizable color change.

Description: In recent years, the development of information and communication technologies has notably improved the water management processes, but the technologies for water quality control still leave much scope for improvement. Specially, in situ and inline water monitoring has an increasing interest in order to take decisions at real time. The main drawbacks of the current portable meters are their high cost and their high power consumption. In this paper, it is proposed a portable compact meter for measuring simultaneously oxidation–reduction potential, conductivity, temperature, and amperometric parameters like chlorine. This system includes microsensors fabricated with microelectronic technologies, and a commercial temperature sensor, all them allowing a very low power consumption. Validation of the system has been carried out using standard solutions and comparing the results with commercial sensors. The response characteristics of sensors, in terms of sensitivity and repeatability, showed good agreement with those obtained with standard equipment using the same microelectrodes.

Description: We deal with the problem of estimating the true measured scalar quantity from the output signal of a sensor that is afflicted with hysteresis and noise. We use a probabilistic, nonparametric sensor model based on heteroscedastic Gaussian processes (GPs), which is trained using a data set of sensor output and ground truth pairs. The inference problem is formulated as state estimation in a dynamical system. We exploit the low dimensionality of the latent state space of the sensor to perform exact probabilistic inference of the measured quantity from a time series of the sensor’s output. Compared with the state-of-the-art assumed density filtering algorithm for GPs, which analytically approximates the posterior by a normal distribution during inference, our method reduces the prediction error by 33% on a data set obtained from a novel flexible tactile sensor based on carbon-black filled elastomers. The proposed model can be applied, but is not limited, to any sensor for which the Preisach model of hysteresis holds. The use of probabilistic modeling and inference not only provides a most likely estimate of the measured quantity but also the corresponding confidence interval.

Description: In this paper, a joint detection and tracking processing (JDTP) algorithm is proposed for target tracking in clutter using a multiple radar system. In this paper, the data association events are formed with a reasonable assumption that each radar can at most receive one measurement originated from a target. Moreover, we explore the idea of feeding the information from the tracker to the detector. In this scenario, the tracker can guide the detectors of multiple radars where to look for a target while keeping the constant false alarm rate property. From a practical point of view, the detection threshold is depressed near where a target is expected to be and elevated where it is unexpected. Simulation results demonstrate the efficiency of the proposed JDTP algorithm, in terms of the detection and the tracking performance, when compared with the existing works.

Description: An omni-directional (OD) magnetostriction-based electromagnetic acoustic transducer (EMAT) is suitable for use in the guided wave (GW) tomography of steel plate defects. Because the GW is characterized by multiple modes and frequency dispersion, the waveforms detected by the traditional magnetostriction-based OD GW EMATs are complex, which substantially reduces the accuracy of projection data extraction and then decreases the quality of GW tomography and the accuracy of defect quantification. This paper proposes a new magnetostriction-based OD EMAT to generate shear-horizontal (SH) GWs of a special mode to reduce the interference of multiple modes and the frequency dispersion of GWs. The new EMAT consists of a contra-flexure coil and a pre-magnetized thin circular nickel foil. The theoretical background and working principle of this EMAT are presented. The results of pitch–catch experiments on a healthy steel plate demonstrate that the new EMATs can transmit and receive purer single SH1-mode GWs and have improved the accuracy of projection data extraction, compared with the traditional EMATs. The performance of SH1 wave tomography of the traditional and new EMAT arrays are compared via experiments implemented on a 3-mm-thick steel plate with an artificial corrosion defect. The experimental results indicate that higher tomographic reconstruction quality, clearer normalized slowness curves with less noise and higher accuracy of tomographic defect quantification can be achieved by the new EMAT array, which has improved the projection data extraction accuracy, compared with the traditional EMAT array.

Description: A system for wireless power transfer and data communication of implantable bio-monitoring systems is presented. The proposed solution uses a servo-controlled power transmitter moved under the animal moving space. An $x$ - $y$ movable magnetic coil transmits the required power with a level able to keep constant the received energy by the bio-sensor system. The power is transferred via the optimized remote powering link at 13.56 MHz. The received ac signal is converted to dc voltage with a passive full-wave integrated rectifier and the voltage regulator supplies 1.8 V for the implantable sensor system. The sensor control and readout circuit measures the current on the bio-sensors and transmit the data to the transmitter. The sensor data are transmitted to an external reader by a low-power OOK transmitter and received by a custom designed receiver at 869 MHz. The results are shown in a tablet computer in real time continuously. The long-term characterization of the implantable system is verified by a fully bio-compatible packaged implant with 30 days measurement. A complete prototype is also presented to prove the overall system performance with the experimental in vitro measurement.

Description: Built upon a distributed-deflection sensor, an experimental technique is presented in this paper that allows for measuring the synchronized heterogeneous indentation behavior of viscoelastic materials upon macroscopic compression. The core of the distributed-deflection sensor is a whole polymer microstructure embedded with a resistive transducer array underneath. A cylinder probe is utilized to exert macroscopic compression on a material sample placed on the distributed-deflection sensor, and the synchronized heterogeneous indentation behavior of the sample is then translated to distributed deflections of the microstructure and is recorded as distributed resistances by the transducer array. In a measurement, the input signal is the indentation depth of the probe, the output signals are the macroscopic compression load and the distributed resistance changes of the sensor. From the measured distributed load-deflection relations of a sample along its length at multiple indentation depths with the same 5s hold time and 5s recovery time, the instant and the 5s relaxed indentation modulus of a sample are extracted, revealing non-negligible effect of the neighboring regions on the indentation behavior at a location in a sample.

Description: With the recent introduction of the new Kinect II, the second generation of the well-known Microsoft Kinect sensors, the connection between RGB-D sensors, reverse engineering, and computer vision applications is reinforced. This new sensor is based on a time-of-flight technology, which differs from the previous generation of RGB-D sensors, including other devices, such as the Asus Xtion Pro and PrimeSense Carmine, which was based on structured light. Although characterized by better technical specifications, this does not neccessarily translate to the improvements in its application tasks. This paper aims at comparing quantitatively the Kinect II with respect to the first generation of RGB-D sensors in terms of two specific application scenarios: 1) 3-D reconstruction and 2) object recognition. To this end, we propose a novel data set with ground truth obtained with a metrological laser scanner, which allows a twofold analysis: 1) a performance comparison in terms of reconstruction accuracy and 2) a comparison in terms of object recognition and 3-D pose estimation. The obtained results confirm that the new version of the Kinect sensor demonstrate higher precision and less noise under controlled conditions. Furthermore, we provide a quantitative estimation of how much such factors turn out into an improvement in terms of object recognition rate and 3-D pose estimation.

Description: Acoustic transmission, inherent to aquatic environments and used in underwater sensor networks (UWSNs), presents its own challenges in terms of energy consumption, long propagation delay, and available bandwidth. These UWSN challenges make it difficult to directly adapt ideas which have already been proven reliable in open-air networks. End-to-end latency is one of the key elements for delay-sensitive UWSN applications. In this paper, we apply the idea of opportunistic-based routing (OR) for maximizing goodput while meeting end-to-end latency requirements for delay-sensitive UWSN applications. In doing so, we introduce a new metric called $mathit {EEL}vert_{mathit {success}}$ ( $F_{i}$ ), which is the expected end-to-end latency from node $i$ to the destination when at least one forwarder of $F_{i}$ successfully receives a packet; we then formulate this UWSN OR routing problem as a nonlinear optimization model. To effectively solve this problem, we propose a two-step heuristic algorithm, which is composed of per-node forwarding set determination and packet forwarding prioritization. The results of a performance study show that our scheme outperforms other existing works in terms of network goodput and energy costs.

Description: A streak-mode optical sensor in standard 0.35- $mu text{m}$ SiGe BiCMOS technology is presented. The circuit consists of a column of 64 photodetectors coupled to a linear array of transimpedance amplifiers and a 128-deep analog sampling and storage unit. The sweep speed of the sensor is continuously adjustable from 125 ps/pixel to 1 ns/pixel through a closed-loop delay generator. The sensor reaches a total sampling rate of 512 GS/s and a vertical dynamic range of 59 dB. The measured temporal resolution is 465 ps at $lambda =400$ nm. At $lambda =800$ nm, this figure is degraded down to 600 ps due to the increased penetration depth of the incident radiation. In a post-processing phase, the frequency response of the system was equalized, allowing the sensor to exhibit sub-500-ps temporal resolution over the entire visible spectrum. The reported streak-mode optical imager is thus suitable for the recording of nanosecond-order transients over a large range of wavelengths and can be used in applications, such as fluorescence metrology, time-resolved spectroscopy, and optical tomography.

Description: Monitoring of structural health plays a crucial role in condition-based maintenance and degradation prediction of infrastructures. In this paper, we developed a novel interdigitated capacitive (IDC) strain sensor which could be integrated in a wireless monitoring system for structural health monitoring (SHM) applications. The IDC sensors were fabricated by laser-micromachining a 127- $mu text{m}$ -thick brass sheet followed by encapsulation in deformable thermoset polymers. The wireless monitoring system was implemented using a commercial wireless module (eZ430-RF2500 from Texas Instruments) which could provide multi-modality monitoring simultaneously. A graphical user interface was developed to display and store data as well as perform real-time analysis remotely. The wireless communication distance was up to 35 m inside buildings. The sensitivity of the sensor was characterized in both stretching and bending aspects, yielding a limit of detection with respect to strain of 0.025%. The gauge factor was found in the range of 6–9 which is much higher than those of commercially available strain gauges. The bending detection is reliable up to 20°. Hysteresis and temperature dependence were also investigated, revealing predictable responses. Finally, the entire system was demonstrated with both single and multiple sensors for a real-time SHM case.

Description: A resistive type displacement transducer that employs a floating (contactless) wiper and a relaxation oscillator-based signal conditioning circuit is presented here. The proposed transducer provides an output that is linear to the displacement of the floating wiper. Since, only a couple of dc reference voltages influence the output of the proposed transducer, a good degree of linearity and accuracy is easily obtained just by employing a couple of precision dc voltages. The simulation studies and the test results on a prototype unit presented here establishes the efficacy of the proffered method. The detailed analysis of the proposed transducer, given in here, identifies the pitfalls to be avoided while designing the sensor and the signal conditioning circuitry.

Description: Directional sensors are gaining importance due to applications, including surveillance, detection, and tracking. Such sensors have a limited field of view and a discrete set of directions they can be pointed to. The directional sensor control problem (DSCP) consists in assigning a direction of view to each sensor. The location of the targets is known with uncertainty given by a joint a priori Gaussian distribution, while the sensor locations are known exactly. In this paper, we study the exact and heuristic approaches for the DSCP with the goal of maximizing information gain on the location of a given set of immobile target objects. In particular, we propose an exact mixed integer convex programming (MICP) formulation to be solved by a black-box MICP solver and several metaheuristic approaches based on local search. A computational evaluation shows the very good performance of both methods.

Description: This paper presents a flexible and low-power Read-Out Circuit (ROC) with tunable sensitivity, designed to interface a wide range of commercial resistive pressure sensors for robotic applications. The ROC provides contact detection, monitoring small capacitance variations at low pressure (<100 mbar), and encodes pressure measurement on 8 bit, evaluating resistive variations. Two all-digital circuits implement the conversion of the input resistance and capacitance-to-frequency, exploiting an on-chip ring oscillator as timing reference. A 130 nm RFCMOS prototype (with an active area of $428times 159~mu text{m}^{2}$ ) has a power consumption of 27.2 $mu text{W}$ , for $V_{mathrm {DD}}~1$ V. Using digital control inputs, the ROC allows a wide range tuning of measurement sensitivity (6.7–46.4 mbar/LSB) and adjustable acquisition time (226.6–461.7 $mu text{s}$ and 648–890 $mu text{s}$ , for contact detection and pressure evaluation, respectively). The read-out time of $sim 1$ ms is compatible with human response after touch.

Description: A multisensor data fusion approach via acoustics, infrared camera, and marine radar is proposed and described in the application of avian monitoring. The ultimate scope of avian monitoring is to preserve the population of birds and bats, especially those listed in the endangered list, by observing their activity and behavior over the migration period. With the significant attention toward the construction of off-shore/on-shore wind farms in recent decades, the wind turbines are more threatening the avian life with increasing the risk of birds/bats collision with turbine blades. In order to address this problem, this paper proposes a fuzzy Bayesian-based multisensory data fusion approach to provide the activity information regarding the targets in the application of avian monitoring. The developed technique is used to process the Spring and Fall 2011 migration period.

Description: A tunable gas sensor based on an asymmetric external cavity semiconductor lasers oscillating on two spectral lines is presented and investigated experimentally and theoretically. In order to minimize the cost and size of the gas sensor, relative intensity noise (RIN) as a detection methodology is used to measure the intensity levels and intensity differences of two lines. The influence of the spectral separation of the two lines on the RIN has been investigated and explained in the framework of the interplay of the linewidth enhancement factor and two different cavity lengths of the two lines. Each line is related to a different cavity length, which we denote as an asymmetric laser. It has been found that for larger line spacing, the sensor reveals a higher sensitivity to intensity variations of the lines than for smaller line spacing. The experiments show the largest change of RIN at an intensity difference between the two lines of −5 and +5 dB. Very interesting is the experimental result that each line can be tuned in a stable single line condition. For a line intensity ratio between −40 and −15 dB as well as around +20 dB, two ranges of constant RIN have been found, which are different in the averaged RIN by $approx 6$ up to 10 dB depending on the line separation. The difference of $approx 6$ up to 10 dB can be quantitatively explained by the asymmetric cavity design and linewidth enhancement factor.

Description: A new method of signal analysis from a polarimetric optical fiber sensor is presented. The proposed method is based on the Hilbert transform and utilizes only one light detector to calculate a strain-induced phase shift, thereby overall sensor cost and complexity is minimized. The demodulation algorithm is optimized for the dynamic strain measurement used in composite materials monitoring. The method is implemented to measure the dynamic strain in a reflective sensor configuration. Vibration and mechanical impact measurements as well as Fourier analysis prove the reliability of the proposed method.

Description: Maximization of network lifetime through the efficient utilization of energy is one of the main objectives in wireless sensor network (WSN) design. Although energy balancing throughout the network for relaying the data traffic generated by sensor nodes toward a static base station prolongs network lifetime, some of the nodes are required to dissipate their energies suboptimally, i.e., farther nodes transmit some of their data to extended distances so that nodes closer to the base station are not overburdened. Base station mobility is proposed as a remedy for countering the suboptimal energy dissipation trends in WSNs. As the base station relocates, the burden of relaying the data coming from all nodes can be shared by a larger set of nodes, and hence, suboptimal energy dissipation can be mitigated. In order to take advantage of base station mobility for prolonging WSN lifetime, determining the optimal mobility patterns is of utmost importance. In this paper, we built a mixed integer programming framework to characterize the impact of various mobility patterns on WSN lifetime. Our results reveal that optimal Gaussian and spiral mobility patterns give the highest network lifetime values throughout the parameter space we explored.

Description: In this paper, a novel selective, sensitive, and reversible copper (II) ion optical sensor was prepared based on the impregnation of N, $text{N}{}^{prime }$ -bis (2-hydroxynaphthaldehyde)-1, and 3-phenylenediimine (HNPD) into plasticized polyvinyl chloride (PVC) film. The optimal values of pH and response time at which the maximum performance of prepared optical sensor is achieved were found to be 6 and 2 min, respectively. After the optimization of pH and response time, small central composite design (CCD) and desirability function were applied to evaluate the effects of variables including amount of dibuthylphthalate, anion excluder (sodium tetraphenylborate), PVC, and HNPD content on the sensor as figures of merit. The possible interactions between the variables were also investigated using the CCD. Low detection limit and good selectivity in presence of other ions such as Fe 3+ , Ag 2+ , Cr 3+ , Zn 2+ , Hg 2+ , and SO 4 2− make it feasible to accurately and repeatedly monitor Cu 2+ ions content in real samples with complicated matrices. The optode was successfully regenerated by its exposure in 0.1 mol/L of ethylenediaminetetraacetic acid solution while its response was reversible with the relative standard deviation lower than 1.5%. This optode was stable and stored for at least 17 days without observing any change in its sensitivity.

Description: Applications of millimeter waves (MMWs), especially MMW imaging, are required in medicine, homeland security, communication, and space technology. The lack of a fast and inexpensive room temperature detector makes it difficult to realize those applications. Recently we found that the commercially available miniature neon lamps, known as glow discharge detectors (GDD), can be used as room temperature, sensitive, and inexpensive MMW detectors. Furthermore, they have shown a fast response time of about one microsecond. The disadvantages of using the GDD are high power consumption and for relatively large bias current, aging of the electrode coating due to electrode bombardment by heavy ions inside the plasma. Those disadvantages can be overcome by electronically switching on the detector bias current during detection period only, leaving the detector OFF most of the time. In this paper, the influence of the detector aging on the responsivity is investigated experimentally, and an electronic circuit for fast ON/OFF switching operation is demonstrated.

Description: A novel method is proposed for capturing deviation in gait using a wearable accelerometer. Previous research has outlined the importance of gait analysis to assess frailty and fall risk in elderly patients. Several solutions, based on wearable sensors, have been proposed to assist geriatricians in mobility assessment tests, such as the Timed Up-and-Go test. However, these methods can only be applied to supervised scenarios and do not allow continuous and unobtrusive monitoring of gait. The method we propose is designed to achieve continuous monitoring of gait in a completely unsupervised fashion, requiring the use of a single waist-mounted accelerometer. The user’s gait patterns are automatically learned using specific acceleration-based features, while anomaly detection is used to capture subtle changes in the way the user walks. All the required processing can be executed in real time on the wearable device. The method was evaluated with 30 volunteers, who simulated a knee flexion impairment. On average, our method obtained $sim 84$ % accuracy in the recognition of abnormal gait segments lasting $sim 5$ s. Prompt detection of gait anomalies could enable early intervention and prevent falls.

Description: The detection limit of thin film giant magneto-impedance (GMI) magnetic sensors has been investigated by measuring their magnetic noise. The GMI sensing elements are multilayers based on Fe 20 Ni 80 Permalloy (Py), deposited by sputtering and patterned by photolithography in the form of 2-mm long and 50- to 130- $mu text{m}$ wide stripes. The multilayered samples had the following structure: [Py(170 nm)/Ti(6 nm)] 3 /Cu(250 nm)/[Ti(6 nm)/Py(170 nm)] 3 . As electronic conditioning circuits, different configurations of oscillators and detectors were tested in order to determine their influence on the total output voltage sensor noise. The latter was measured using a dynamic signal analyzer and the equivalent magnetic noise of the sensor was determined through the measured Fourier transfer function of the device at the operating point. Filtering and impedance matching strategies were implemented to minimize the equivalent magnetic sensor noise. Presently, a white noise level of 120 pT/ $surd $ Hz at 2 kHz is obtained.

Description: The optimization of fluorinated bisphenol-containing polymer (BSP3)-coated surface acoustic wave (SAW) chemical sensor was performed for sensing organophosphorous compounds with trace concentration in this contribution. First, the response mechanism was characterized using the classical perturbational approach. Optimal sensitive film thickness and operation frequency are determined theoretically to achieve a relative linear characteristic response and a high gas sensitivity. Next, to improve of the corrosion resistance and frequency response characteristics of the sensor chip, Al/Au electrodes are used to form the resonator acted as the feedback element for oscillator. In addition, the substantial improvement is obtained in frequency stability of the resonator–oscillator referring to phase modulation approach. The measured short-term frequency stability of the oscillator at the operation frequency of 300 MHz is up to 2 Hz/s. The theoretical predictions are confirmed by the measured responses from the BSP3-coated SAW sensor for dimethylmethylphosphonate (DMMP) detection. Excellent threshold detection limit less than 0.004 mg/ $text{m}^{3}$ and good sensitivity ( $sim 3.09$ kHz/mg/ $text{m}^{3})$ were achieved from the developed BSP3-coated SAW chemical sensor in the DMMP detection.

Description: This paper presents a new method for thermal imaging of hydroelectric generators stators. The method is based on distributed temperature optical fiber sensing using Raman scattering. The thermal image is generated by combining the information of temperature and the spatial position of the sensor with the 3-D model of the structure. Regarding the use of conventional sensors, such as resistance temperature detector or PT100, the main advantage is the possibility to identify temperature variations over the entire stator surface. The results were obtained over a 22-h test with a 200-MW hydroelectric generator. The produced thermal images showed a great potential for monitoring the temperature distribution in the stator according to the generator load. The new method can contribute for identification of fault in the structure insulation, which when early identified can reduce damage caused by short circuit in the stator windings.

Description: Multiple-input multiple-output radar systems can offer improved performance over traditional single-input multiple-output systems, such as in radar imaging. Performance greatly depends on the recovery method used. For sparse targets, compressed sensing (CS) is used as it is well-suited as a target recovery method. Performance of CS is dependent on the sensing matrix, which includes the transmit sequence and antenna configuration. In this paper, we propose adaptively varying the transmit spacing in order to seek an optimal sensing matrix. Numerical results show the proposed method has potential to significantly improve image recovery under a variety of system conditions while using the same number of antennas.

Description: The potential abilities of distributed multiple-radar architectures in the electronic counter–countermeasure are analyzed based on the difference between target echoes and deception jamming in spatial scattering properties. The deception signals received by different receivers are fully correlated, while the correlation of target echoes varies gradually with the interval of view angles. According to this difference, the thought of signal fusion is first adopted and a corresponding algorithm is proposed to discriminate the deception jamming from radar targets in the Neyman–Pearson sense. In this algorithm, active false targets are identified by correlation tests between arbitrary two targets’ complex envelopes in different receivers. To evaluate its discrimination performance, the theoretical expression for the rejection probability of false targets is derived. Simulations verify the feasibility of the new algorithm and its performance improvement over the existing data fusion-based methods. The merit of the method lies in that it can discriminate deception signals generated by arbitrary modulation and can be used in series with data fusion-based methods to improve discrimination performance further.

Description: A non-contact capacitance type liquid-level transducer for a conducting liquid consists of a short circuited non-inductive coil wound on a uniform cylinder made of insulating material, such as glass, PVC, nylon, and teflon. The cylinder is connected with a storage tank through a metallic connector and the capacitance between upper short circuited end of the coil and metallic connector varies linearly with liquid level measured from datum level. The capacitance at datum level depends on atmospheric condition and the fringe effect of other conductors. So, the transducers require frequent recalibration depending on atmospheric and environmental conditions. In the present paper, this non-contact capacitive sensor has been further modified in order to minimize this defect of non-contact capacitive sensor. Furthermore, all the conventional capacitance type-level sensors are associated with a perpendicular plate capacitance between liquid and electrode, which varies with the length of the electrode. In this paper, the effect of this perpendicular capacitor on liquid level measured has been studied and its effect is minimized. The proposed modified transducer has been designed and developed and its theory of operation has been derived. The performance of the developed transducer has been experimentally studied and the experimental results are reported in the paper. A good linear performance characteristic of the transducer with very minimum parasitic capacitance effect has been observed.

Description: Coherent radars have multiple applications; among them, they can obtain multiple pulses and improve the radar detection ability with the help of coherent integration technique. However, the coherent integration performance can be greatly influenced by the range migration (RM), and Doppler frequency migration (DFM) effects for the highly maneuvering targets. In this paper, a fast non-searching method based on adjacent correlation function (ACF) and Lv’s transform (LT), is proposed to realize the coherent integration for a maneuvering target. In particular, it first employs the ACF to correct the RM and reduce the order of DFM. Then, the coherent integration is obtained via LT. The advantage of the presented method is that it can achieve the coherent integration without any searching procedure, and thus the computational cost is reduced significantly. Finally, the simulations are provided to demonstrate the effectiveness.

Description: A new selective and sensitive Lanthanum (La) ions optical sensor based on immobilization of $N$ -(2-aminoethyl)-salicylaldimine (AESI) on a triacetylcellulose membrane was prepared. The prepared optode exhibited a linear range of 30–150 part per billion (ppb) of the La (III) ion concentration with a detection limit of 14.38 ppb. The response time of the newly designed optode was derived within 30–60 s, depending on the La (III) ion concentration, however is independent to the pH of the solution in the range of 3–5. The proposed optode indicated a low detection limit, fast response time, and also remarkable selectivity regarding to the number of transition metals ions (i.e. Ce 3+ , Cu 2+ , Cd 2+ , Cr 3+ , Zn 2+ , Hg 2+ , and Fe 2+ ). The optode was successfully regenerated with a thiourea solution, and its response which might be reversible and reproducible showed the relative standard deviation of less than 1.48%. This optode was applied for determining the La (III) ions in water samples.

Description: Magnetic sensors have previously been used for position measurement only at very small distances between the magnet and the sensor. While they could potentially also be used at larger distances by exploiting nonlinear magnetic field functions, a serious challenge comes from magnetic disturbances. The presence of foreign ferromagnetic objects, variations in the Earth’s magnetic field with location, and electromagnetic disturbances can cause such position estimation systems to have significant errors. This paper enables robust large-distance position estimation using redundant sensors and real-time disturbance estimation. Adaptive estimation algorithms that auto-calibrate magnetic parameters and compensate for disturbances are developed. Experimental results with a pneumatic cylinder demonstrate that sub-millimeter accuracies in position measurement can be obtained with such a system in spite of disturbances from external ferromagnetic objects. The developed sensing principle has a large number of applications, including position estimation in pneumatic cylinders, hydraulic actuators, spool valves, and many other machinery.

Description: This letter proposes a novel method of noninvasive detection of voids in fiber reinforced plastics (FRPs). An ideal nondestructive evaluation method for the detection of subsurface defects that utilizes the capabilities of a magnetoinductive planar microstrip sensor is examined through a finite-integration-based model in this letter. A combination of magneto inductive waveguide as (MIW) and a patch radiator is used as the sensing element. The magnetoinductive waveguide increases the sensitivity of the patch to the presence of voids in the FRP.

Description: In this paper, a polarization navigation sensor is designed based on the polarization sensitivity mechanisms of insects. A new calibration model by taking full advantage of both reference angle of polarization and constant degree of polarization is presented to determine calibration parameters. Unlike existing calibration algorithms, the proposed algorithm makes the calibration problem well-posed. The results of simulations and experiments show that the proposed algorithm is more stable than the compared methods for the calibration applications of polarization navigation sensors.

Description: Multihop underwater acoustic sensor networks (UASNs) suffer from low throughput caused by low channel utilization and unreasonable bandwidth allocation. The existing media access control (MAC) protocols for UASNs mainly aim to improve channel utilization but neglect to optimize bandwidth, so that they cannot achieve high throughput in miltihop networks. We propose the idea of joint bandwidth optimization and MAC in this paper. We first present a system model to optimize bandwidth for miltihop UASNs. Both the complicated interference relations between links and the different transmission demands of nodes are modeled. Thus, it can accurately reflect the characteristics of miltihop UASNs. By analyzing a 1-D linear miltihop network, we find and formulate a maximum hop number which is determined by nodes’ traffic load and channel capacity. The other finding is that an optimal scheduling needs to allocate the bandwidth based on traffic load, and the nodes with more traffic load should be allocated more bandwidth. This finding inspire us to develop a distributed traffic-based scheduling MAC protocol. This protocol can optimize bandwidth allocation by letting the older packet to be transmitted preferentially. To improve channel utilization, multiple packets are allowed to be transmitted in each data transmission round. Simulation results have confirmed that our protocol can achieve excellent performance owing to its core idea of joint bandwidth optimization and MAC.

Description: Ultrasonic guided waves (UGW) can be used to inspect and monitor a structure from a single test location. Piezoelectric transducers are commonly dry-coupled with force to the surface of the waveguide in order to excite UGWs. These UGWs propagating within the waveguide will interact and reflect from known features, thus possible damage could be detected. In this paper, the interaction of UGWs with piezoelectric transducers is reported and investigated. A Finite Element Analysis (FEA) approach has been used to conduct a parametric study in order to quantify the effect of the waveguide diameter on the guided wave response. Laboratory experiments are carried out to measure the effect of the force on the dry-coupled piezoelectric transducers and the corresponding guided wave response, including reflections and mode conversions. A test rig is used to apply and measure the force on the piezoelectric transducers. For verification, a 3D Laser Doppler Vibrometry (3D-LDV) scan is performed on the waveguide in order to quantitatively identify the modes of interest. The conclusions reached this paper, particularly with respect to the quantification of the wave mode properties, lead to useful recommendations which may contribute to field inspection scenarios.

Description: The application of solid-state nanopore technology for biosensing is a rapidly developing area of research with high commercial potential. Different synthetic materials, including silicon nitride, alumina, and polymers, are employed to fabricate single and multiple pores and offer a good platform for selective biomolecule detection. Two solid-state pore arrays, one with integrated silicon microfluidic system, were considered and an immobilization strategy suitable for detecting a single-stranded DNA (ssDNA) sequence was investigated. For the silicon nitride pores, a modification method based on the use of 3-aminopropyltriethoxysilane for silanization and 1,4-phenylene diisothiocyanate for amine crosslinking was applied to immobilize 100-nM ssDNA (amine C6) and a 100-nM limit of detection for complementary to probe ssDNA (Cy5) was estimated. The polycarbonate pores (the second type of the pore arrays) underwent surface modification based on an oxidation reduction reaction using sodium periodate and sodium borohydride and was used to immobilize 10-nM ssDNA and an estimated 100-nM limit of detection was also achieved. Linear sweep voltammetry was used to characterize the pores and a current potential profile was obtained after both immobilization of probe ssDNA and hybridization of complementary to probe ssDNA on the modified pore array surface. A decrease in current amplitude was measured after surface modification of both pore arrays, and this was attributed to the appearance of an additional layer on the pore surface reducing the pore opening and hindering the current flow. The hybridization event was also supported by contact angle measurements, where an increase in hydrophilicity was recorded at the different surface modification steps that were applied to produce the biofunctionalized nanopore. In addition, fluorescence was observed on the surfaces after hybridization, through incorporation of a CY5 fluorescent tag attached on the 5’ end of the complemen- ary to probe DNA. These results show the potential to use both silicon nitride and polycarbonate nanopores in DNA detection applications.

Description: In this paper, we are proposing a simple energy efficient on-chip temperature to frequency converter circuit. The proposed arrangement senses the temperature in terms of the proportional to absolute temperature (PTAT) current. The temperature equivalent PTAT current is then converted into frequency using the source coupled multivibrator circuit. The proposed circuit has been designed and fabricated in a standard 180-nm CMOS technology and occupies silicon area of $approx 0.058$ mm $^{2}$ . The measurements were performed on ten prototypes. The proposed architecture is capable of working in the temperature range of −40 °C to +85 °C with the supply voltage of 0.9 V ± 10%. The smart temperature sensor achieves a maximum temperature inaccuracy <±1 °C after applying single point calibration. The average power consumption is $approx 600$ nW at +85 °C for 0.9 V supply voltage.

Description: Recording shear stresses is becoming relevant in an increasing number of applications, e.g., in rehabilitation sciences, where detecting foot-sole interaction is very important. This paper describes a portable and complete system to record multiaxial shear stresses. The sensing operation itself is based on the changing coupling of light between a vertical-cavity surface-emitting laser (VCSEL) and a segmented photodiode. Applying shear stress causes lateral displacement of both optoelectronic components leading to variation in the photocurrent. By combining signals from different photodiode segments, multiaxial shear stresses can be detected. A standalone system was designed to drive the VCSEL and to readout the signals from the different photodiode segments in order to measure shear stress as well as to evaluate the sensing system performance. Furthermore, the sensor signals can be efficiently monitored and visualized on a tablet or PC in real-time using dedicated software. The design presented in this article is optimized to measure shear forces with a magnitude up to 2 N and arbitrary direction. Yet, by changing the transducer material this range can be tuned for a specific application.

Description: Microsoft Kinect sensor has been widely used in many applications since the launch of its first version. Recently, Microsoft released a new version of Kinect sensor with improved hardware. However, the accuracy assessment of the sensor remains to be answered. In this paper, we measure the depth accuracy of the newly released Kinect v2 depth sensor, and obtain a cone model to illustrate its accuracy distribution. We then evaluate the variance of the captured depth values by depth entropy. In addition, we propose a trilateration method to improve the depth accuracy with multiple Kinects simultaneously. The experimental results are provided to ascertain the proposed model and method.