ALBERT

Description: A novel design and assembly technology is developed for a three-dimensional (3-D) flexible thermal flow sensor based on convective heat transfer to reduce detection error caused by position variation of a sensor inside the flow of narrow and curved geometries, such as coronary artery. The 3-D sensor has three independent sensing elements equally distributed around the catheter tube. This arrangement introduces three independent information channels, and cross-comparisons are used to provide accurate flow measurement. The resistance of the sensing elements is measured at ${sim}{1}-1.2~{rm k}Omega$ with the temperature coefficient of resistance at $0.086%/^{circ}{rm C}$ . Using a constant-current circuit, the three sensing elements are heated to ${sim}10^{circ}{rm C}$ above ambient temperature. Flow testing is implemented in a pipe channel at two positions: on the wall and along the center line. Experimental results from these two positions are discussed and computational fluid dynamic simulation based on Newtonian fluid properties is implemented, showing comparable results within an acceptable range of experimental to simulation errors. Therefore, we demonstrate the capability of 3-D thermal flow sensor for detecting the position of the catheter in the flow channel, thereby providing an accurate flow measurement.

Description: We discuss the fabrication and performance of an all-polymer, flexural plate wave gravimetric sensor using flexible, piezoelectric Polyvinylidene fluoride as the substrate and an inkjet-printed interdigital transducer (IDT) employing conductive poly(3, 4-ethylenedioxythiophene) poly(styrenesulfonate) to excite Lamb waves within the film. Lamb waves are measured both electronically, using a second IDT, and mapped directly using a scanning laser Doppler vibrometer. Pulsed wave excitation is utilized to isolate the weak acoustic signal from the electromagnetic crosstalk, enabling the measurement of relative changes in the resonant frequency, $Delta f/f_{0}$ , in response to added mass, $Delta m$ , to the sensing area. A gravimetric mass sensitivity equivalent to $Delta f/(f_{0}Delta m)=-153~{rm cm}^{2}/{rm g}$ is measured by mass loading the sensor with printed polymer layers. It is found that the low stiffness of the substrate contributes significantly to the response of the sensor, yielding a measured overall sensitivity of $Delta f/(f_{0}Delta m)=-83~{rm cm}^{2}/{rm g}$ .

Description: In this paper, we propose a novel technological approach for the implementation of large-area flexible artificial skin based on arrays of piezoelectric polymer transducers. Polyvinylidene fluoride (PVDF) transducers are chosen for the high electromechanical transduction frequency bandwidth (up to 1 kHz). A low-cost and scalable technique for extracting PVDF signals is used to directly provide the piezoelectric film with patterned electrodes. If the skin is meant to cover large areas of a robot body, specific requirements have to be fulfilled from the point of view of the overall system and of the technology. Experimental tests on the prototype skin modules demonstrate the feasibility of the proposed approach and reveal the potentiality to build large area flexible skin.

Description: This paper presents ultra-thin silicon chips (flex–chips) on flexible foils, realized through post-processing steps such as wafer thinning, dicing, and transferring the thinned chips to flexible polyimide foils. The cost effective chemical etching is adopted for wafer thinning and the transfer printing approach, to transfer quasi 1-D structures such as micro/nanoscale wires and ribbons, that is adapted for transferring large ultra-thin flex–chips (widths 4.5–15 mm, lengths 8–36 mm, and thickness ${approx}{rm 15}~mu{rm m}$ ). The post-processing capability is demonstrated with passive structures such as metal interconnects realized on the flex–chips before carrying out the chip thinning step. The resistance values of metal interconnects do not show any appreciable change because of bending of chips for the tested range viz., radius of curvature 9 mm and above. Further, the bending mechanics of silicon membranes on foil is investigated to evaluate the bending limits before a mechanical fracture/failure occurs. The distinct advantages of this paper are: attaining bendability through post-processing of chips, cost effective fabrication process, and easy transfer of chips to the flexible substrates without using conventional and sophisticated equipment such as pick and place set up.

Description: A sensor was made of a polymer composite composed of electrically-conductive carbon nanotubes embedded in elastic polyurethane. The composite was prepared using a polyurethane filter membrane, enmeshing it, and melding together with carbon nanotubes. Testing has shown that the composite can be elongated as much as 400% during which the electrical resistance is increased 270 times. The composite is also sensitive to compression and to organic solvent vapors. These properties indicate the composite could have applications as a highly-deformable strain and chemical vapors sensing element and also as flexible electromagnetic shielding or protection against lightning. As an example of the use of the composite as a strain sensor, the pressure variation between a shoe and floor during walking and knee flexion during cycling has been monitored.

Description: This paper presents a novel concept for stretchable conductors. Metal coated polymer spheres were densely packed in biocompatible silicone tubes. The resistivity of the conductors were in the approximate range of $1times 10^{-4}~Omega{rm m}$ at 0% strain and 50% strain could be applied before degrading their electrical performance. Initial results showed good reproducibility and no drift in resistance values up to 1000 cycles with 0%–25% strain. This make the conductors well suited for digital low speed data transmission. The initial application is intended for integration of electronics in clothing; the conductors have been tested with success transmitting data from a commercial digital combined humidity and temperature sensor.

Description: Recently, there are innovative mechanoluminescent (ML) particles made available, each of which repeatedly emits light in response to small applied stresses even in elastic region. When dispersedly coated onto a structure, each particle acts as a sensitive mechanical sensor, while the two-dimensional emission pattern of the whole assembly reflects the dynamical stress distribution inside the structure and the mechanical information around the crack and defect. To use the remarkable advantage of the ML sensor in flexibility, electricity/lead-free, low-cost, and so forth, and to answer social needs for historical-log of stress/damage accumulation on social infra-structure, we investigate historical-log recording system for crack opening and fatigue crack growth, and finally succeed to record it with responding position and intensity reflecting the trace of propagating crack tip and stress intensity factor around the tip. Furthermore, crack mouse opening displacement accompanied by general traffic of bridge in use is successfully detected.

Description: This special issue focuses on the sensors and sensing systems having features like flexibility, bendability, conformability, stretchability, and presence over large areas and 3D surfaces. Like conventional sensors, flexible sensors are also used to measure parameters and agents like pH, temperature, humidity, force, gasses, velocity, flow etc. In addition, they possess the ability to bend. This requires special front-end processing techniques compatible with the flexible materials that these sensors are made of. In response to the call for papers for this special issue, 114 manuscripts were received. Of those, 39 were found not to fit to the scope of the special issue and were separated to be handled by the permanent editors of the Journal. The peer review process resulted in 29 innovative manuscripts to be published here submitted from over 45 institutions, with a few trailing manuscripts to be published at a later issue due to time constraints. Of the work presented here, nine papers describe sensors for health and medical applications. Five papers detail sensors for the general fields of environmental and structural health monitoring. Four are on robotic applications. Although majority of the manuscripts focus on a single sensing function such as fluidic flow, force, pH, temperature or presence of a specific gas, four papers present multifunctional flexible sensors.

Description: Thin, highly compliant sensing skins could provide valuable information for a host of grasping and locomotion tasks with minimal impact on the host system. We describe the design, fabrication, and characterization of a novel soft multi-axis force sensor made of highly deformable materials. The sensor is capable of measuring normal and in-plane shear forces. This soft sensor is composed of an elastomer (modulus: 69 kPa) with embedded microchannels filled with a conductive liquid. Depending on the magnitude and the direction of an applied force, all or part of the microchannels will be compressed, changing their electrical resistance. The two designs presented in this paper differ in their flexibility and channel configurations. The channel dimensions are approximately 200 $,times,$ 200 $mu{rm m}$ and 300 $,times,$ 700 $mu{rm m}$ for the two prototypes, respectively. The overall size of each sensor is 50 $,times,$ 60 $,times,$ 7 mm. The first prototype demonstrated force sensitivities along the two principal in-plane axes of 37.0 and ${-}{rm 28.6}~{rm mV/N}$ . The second prototype demonstrated the capability to detecting and differentiating normal and in-plane forces. In addition, this paper presents the results of a parameter study for different design configurations.

Description: We have developed a fabric sensor knitted of tension-sensitive electro-conductive yarns. Each yarn has an elastic core, around which is wound two other separate, tension-sensitive electro-conductive threads, making this sensor inherently flexible and stretchable and allowing it to conform to any complicated surface on a robot, acting as a robotic skin. The pile-shaped surface of the sensor enhances its ability to detect tangential traction, while also enabling it to sense a normal load. Our aim is to use this sensor in applications involving relative sliding between its surface and a touched object, such as contact recognition, slip detection, and surface identification through a sliding motion. We carefully analyzed the static and dynamic characteristics of this sensor while varying the load and stretching force to fully understand its response and determine its degree of flexibility and stretchability. We found that a discrete wavelet transformation may be used to indicate stick/slip states while the sensor is sliding over surfaces. This method was then used to detect slippage events acting on the sensor's surface, and to decode textures in a classification test using an artificial neural network. Because of its flexibility and sensitivity, this sensor can be used widely as a robotic skin in humanoid robots.

Description: Carbon nanotubes (CNTs) are demonstrated as one of the most interesting materials for gas sensing. The possibility to obtain CNT thin-films via solution-processing techniques has paved the way for low-cost applications of such sensors. In this paper, we demonstrate that high performance gas sensors based on CNT thin-films can be obtained by direct spray deposition onto flexible substrates. The results obtained for ${rm NH}_{3}$ sensing using CNT films deposited on polyimide show exceptionally high as well as immediate response to the test gas, with performance comparable with that obtained on oxidized silicon substrates. In addition, a good repeatability of the sensor response to defined gas concentrations is demonstrated. This represents a major step toward low-cost large-scale production of this class of devices.

Description: This investigation aims to study energy conversion and actuation properties of the modified near-field electrospinning piezoelectric polyvinylidene fluoride (PVDF) fibers. Conceptually, the mixed PVDF solution was electrospun, and highly aligned fibers were collected using a rotating glass tube collector. In order to grow $beta$ -form extended-chain crystallites in PVDF fibers, during electrospining process, a polymer solution experiences two forces. For the purpose of producing a stable jet of polymer solution, under a high electric field $(1.6times 10^{7}~{rm V}/{rm m})$ , polymer jet was elongated and accelerated due to a greater Coulombic force. The other one is a strong extensional force when a glass tube collector (rotating speed: 700–2100 r.p.m) was used to collect PVDF fibers. After carbon nanotubes (CNTs) were added to the orderly aligned PVDF fibers (diameter: 0.2–1.6 $mu{rm m}$ ), CNTs may interact with PVDF, resulting in obvious $beta$ -phase enhancement. Software of FEA with model solution was employed to assist us in estimating the two significant piezoelectric actuation deformations. In actuation experiment, the suspended PVDF fiber presented a large deflection under high electric field. The bending results in a mechanical strain (0.05%–0.1%) distributed along the PVDF fibers, and the induced maximum voltage and current output of the harvesters were 43.6 ${rm mV}_{{rm p}hbox{-}{rm p}}$ and 240 ${rm nI}_{{rm p}hbox{-}{rm p}}$ at 15-Hz impact frequency, respectively.

Description: As the measurement of wide-band (multi-megahertz) electric fields is often of practical interest in industrial and commercial environments, in this paper, a methodology of design and implementation of a wide-band electric field sensing scheme, using optical delays as information carriers is described. The scheme is based on a lithium niobate $({rm LiNbO}_{3})$ birefringent optical waveguide that performs simultaneously as an optical retarder and as a dielectric (electrode-less) sensor. In this scheme, the ${rm LiNbO}_{3}$ sensor introduces an optical delay and simultaneously senses an on-air electric field and imprints it around an optical delay. At the receiver, the sensed electric field is detected when the sensor and demodulator are optically matched, i.e., when both introduce identical optical delays. An important aspect, when sensing electric fields using ${rm LiNbO}_{3}$ dielectric sensors, is that the optically sensed field is weaker than the external field by a factor given by the ratio of the permittivity of the surrounding dielectric media over the ${rm LiNbO}_{3}$ permittivity (boundary condition for normal electric fields). When the surrounding media is air, the optically sensed electric field is 35 times weaker than the external field, as described in this paper. Another practical issue is that a birefringent optical waveguide is highly sensitive to optical polarization variations. Such a sensitivity implies that the output dc component of the received light changes with time (dc-drift). The dc-drift performance of the proposed electric field sensing scheme is measured and reported in this paper. The dc-drift can be minimized using polarization-insensitive ${rm LiNbO}_{3}$ unbalanced Mach–Zehnder interferometers.

Description: Recently, printed electronics have received growing attention as a method to produce low-cost large-area electronics on flexible substrates. This technology relies on printing techniques to deposit electrically functional materials onto flexible substrates to fabricate circuits with various electronic components such as resistors, capacitors, and transistors. In this paper, we apply the printed electronics technology to the development of strain sensors for measuring dynamic strain of a structure. To print sensors, we develop an aerosol printing system capable of atomizing a material solution into microscopic particles and depositing the particles on a target surface. Using this system, a water-based conductive polymer, PEDOT:PSS solution is deposited on a plastic beam. Then, piezoresistive sensing capabilities of the printed strain sensor are studied for low frequency cyclic loadings. Finally, the performance of the printed sensor is compared with a conventional thin-foil strain gauge for measuring dynamic strain of a beam under free vibration. The results show that this type of printed strain sensor can be used to accurately measure structural vibrations.

Description: Ensuring the synchronization of backscattered Raman light and improving the sampling rate are of great importance to improve the spatial resolution of a distributed Raman temperature measurement system. To keep the synchronization of the Anti-Stokes and Stokes light and improve the sampling rate, four effective methods are proposed in this paper. First, the asynchrony caused by the difference in the hardware is eliminated by attaching a fiber to the pigtail of APD, which detects the earlier arriving signal. Next, the data acquisition card chooses different sampling rates for the Anti-Stokes and Stokes light according to the velocity of propagation. Then, a new algorithm is adopted to decrease the difference in the fiber position between the Anti-Stokes and Stokes signals. Finally, the optical switch with different length of pigtails is applied to improve the sampling rate without upgrading the hardware of data acquisition card. By theoretical analysis and experimental simulation, the proposed measures in this paper can improve the spatial resolution effectively.

Description: The accuracy of leak localization of conventional sensing cable systems is related to the current stability of constant current source. To improve the performance of sensing cable systems, a novel integrated method is proposed for distributed liquid leak detection and localization, which includes an online self-test and parametric self-calibration, adaptive threshold leak detection and alarm generation, accurate leak localization based on share voltage compensation, and rough estimation of leak contaminant size. With the proposed method and algorithms, an improved flexible sensing cable system employing a standard programmable controller is developed; it performs real time and reliable leakage incident monitoring. The leak detection sensitivity, leak localization accuracy, and effectiveness of the developed system for extendable sensing cable are demonstrated by means of experimental results and simulations.

Description: State-of-the-art GMR sensors are becoming increasingly popular for a variety of applications, due to of the progress in the area of magnetic field sensor technologies in the recent years. Especially in the area of nondestructive testing, the number of applications based on magnetic field sensors is steadily increasing. Until now, a major concern of these applications has been to improve the sensors sensitivity to be able to measure even minimal magnetic field variations. However, an equally important characteristic, the sensors spatial resolution, is often neglected in discussions. In this paper, the spatial resolution of two different GMR sensors is analyzed. The sensors are modeled as linear spaceinvariant systems. With the analytical solution for the magnetic field above a current carrying conductor and a corresponding measurement, the attainable spatial resolution is determined comparing two different deconvolution methods, an inverse and a Wiener filter. Finally, the determined sensor characteristics are used to improve the measurement accuracy significantly.

Description: In this paper, an arrayed glucose biosensor is integrated to the poly-dimethylsiloxane microchannel as the microfluidic device for measuring the characteristics of the arrayed glucose biosensor at dynamical conditions. The radio frequency sputtering system and screen printed technology are used to fabricate the arrayed glucose biosensor. Furthermore, the computer numerical control technique is used to fabricate the microchannel mold. The polypyrrole differential reference electrode has good stable characteristics and provides a stable potential for the arrayed pH sensor. At static conditions, the average sensitivity and linearity of the arrayed pH sensor are 57.85 mV/pH and 0.977, respectively. And at dynamical conditions with 20 mL/min flow rate, the average sensitivity and linearity of the arrayed pH sensor are 66.73 mV/pH and 0.993, respectively. The arrayed pH sensor is dropped glucose sensing membranes as an arrayed glucose biosensor. The arrayed glucose biosensor is measured in different glucose concentrations at static conditions, and the average sensitivity and linearity of the arrayed glucose biosensor are 11.84 ${rm mV}(100~{rm mg}/{rm dl})^{-1}$ and 0.995, respectively. At dynamical conditions with 25 mL/min flow rate, the average sensitivity and linearity of the arrayed glucose biosensor are 30.41 ${rm mV}(100~{rm mg}/{rm dl})^{-1}$ and 0.975, respectively.

Description: It is known that the rate of acetone in human breath changes in diabetics. The organs in the human body produce different gases. During cleaning of the blood, which is transmitted to the lungs and into the blood gases, the breath passes through the alveoli. Human breath acetone concentration is very low (0.1–10 ppm). This paper aims to determine human blood glucose and HbA1c levels from exhaled breath as a non-invasive method with the help of an electronic nose system based on quartz crystal microbalance (QCM) sensors. The amount of acetone vapor, which is the marker of blood glucose, is 0.1–10 ppm in human expiration. Data of the QCM sensor used in the electronic nose are compared against glucose and HbA1c parameters in blood by using a radial basis function neural network (RBFNN). When breath data are implemented to the RBFNN, the average accuracy rate is 83.03% and 74.76% for HbA1c parameter predictions and glucose parameter predictions, respectively.

Description: The fundamental sensitivity characterization of a novel whisking sensor for applications in nondestructive evaluation is presented. The whisking sensors, originally developed for proximity detection applications in autonomous robotics are evaluated for measurements of surface roughness and surface form change. These surface parameters are the representatives of the typical changes associated with corrosion and surface breaking defects in real structures. The authors demonstrate that the whisking sensor can be used to accurately quantify surface roughness in the range 14–53 $mu{rm m}$ with excellent correlation $({>}{0.97})$ to a standard reference. Furthermore, it is shown that that the sensor can detect 14 mm diameter flat bottomed holes with depths ranging from 0.4 to 1.0 mm. In contrast to conventional ultrasonic and eddy current techniques, the sensor is insensitive to surface liftoff, producing an error of only 1.2% for liftoffs of several mm. This liftoff insensitivity is a highly desirable characteristic for real-world deployment of the sensors, and the authors describe how the sensor can be incorporated into autonomous inspection robots.

Description: For time-harmonic motions, we generalize a 2-D scalar differential equation derived previously by Tiersten for slowly-varying thickness-shear vibrations of AT-cut quartz resonators. The purpose of the generalization is to include the effects of surface acoustic impedance from, e.g., mass layers or fluids for sensor applications. In addition to the variation of fields along the plate thickness, which is considered in the usual 1-D acoustic wave sensor models, the equation obtained also describes in-plane variations of the fields, and therefore can be used to study the vibrations of finite plate sensors with edge effects. The equation is compared with the theory of piezoelectricity in the special cases of acoustic waves and pure thickness vibrations in unbounded plates. An example of a finite rectangular plate is also given.

Description: At present, several solutions are available for monitoring patient health using body sensors. In hospitals, healthcare wireless sensor networks (HWSNs) offer support to access these sensors to allow for continuous patient monitoring. To improve the quality-of-life of the hospitalized patients, it is important to let them walk around the monitored area. This ability brings several challenges to HWSNs with mobility support. Because of the crucial importance of the sensed parameters, the HWSNs must be in continuous communication with the body sensors. The connection between body sensors and a HWSN is performed through an access point. Indoor communications are limited in terms of signal propagation and, therefore, several access points to cover large areas are deployed. To maintain the sensors' accessibility, these should frequently change their point of attachment by performing a mechanism known as a handover. Handover mechanisms are able to support the intra-mobility of sensors in networks within the same domain. This paper surveys the most recent intra-mobility solutions with special focus on handover approaches that can be used in HWSNs. An in depth review of the related literature is performed in order to present the state of the art on this paper, to discuss the available solutions, and to point out open issues for further research.

Description: A temperature-independent reflective refractometer configuration based on a core-diameter-mismatch is proposed and experimentally demonstrated. The configuration consists of a short section of thin-core fiber (TCF) with a multimode fiber (MMF) tip inscribed with a fiber Bragg grating (FBG). The TCF excites cladding modes into the downstream MMF via the mismatch-core splicing interface, and the parts of the core and cladding modes are reflected back to the lead-in fiber core by the MFBG. The recoupling efficiency of the core and cladding modes is highly dependent on the surrounding refractive index (SRI) of the TCF and MMF. Experimental results show that some recoupled modes show a high sensitivity to SRI. Power-referenced and temperature-independent SRI measurement with improved sensitivity for resolutions with SRI values near 1.33 is achieved through the wavelengths of selective mode monitoring.

Description: Exercise training is a crucial component of pulmonary rehabilitation for patients with chronic obstructive pulmonary disease. With fuzzy logic control and wireless sensor networking, we develop an approach with calibration, rehabilitation, artifact/safety monitoring, and endpoint decision (CRASE) to perform adaptive subject exercise training and monitoring. This paper investigates an exercise training model with overload principle and safety concern. To show the correctness and effectiveness of the proposed protocol, the system performance is examined through case studies, simulation analysis, and prototype implementation. In addition, the performance difference in training-sensitivity zone (%) between the conventional incremental shuttle walking test and the proposed CRASE is presented and discussed. The experimental results show that the proposed CRASE scheme has better capability to adjust the exercise training level and is promising to efficiently put exercise training into practice for home-based rehabilitation.

Description: In this paper, we develop a method of detecting 1,3,5-trinitroperhydro-1,3,5-triazine [research department explosive (RDX)]. RDX is one of the main components of plastic explosives. Initially, we prepare an anti-RDX monoclonal antibody that specifically binds to RDX. The antibody is prepared from hybridoma cells that are prepared by the iliac lymph node method. The dissociation constant of the antibody against RDX is estimated to be 9.6 nM from the results of indirect competitive enzyme-linked immunosorbent assay. We fabricate a sensor chip on which RDX analogues are immobilized through a self-assembled monolayer with oligo(ethylene glycol) chains. High reliability and low false recognition rate are particularly required for sensors used for detecting explosives. Therefore, the nonspecific adsorption of the fabricated sensor chip is evaluated to confirm whether the sensor chip inhibits this nonspecific adsorption. The response characteristics of the prepared antibody against RDX are examined by indirect competitive assay. Under an incubation time of 0 min in the indirect competitive assay, a detection limit of 40 ppt is realized at a sample injection duration of 6 min.

Description: Mosquito traps offer researchers and health officials a reasonable estimate of mosquito abundances to assess the spatial and temporal occurrences of mosquito-transmitted pathogens. Existing traps, however, have issued efficient design to detect mosquito and energy consumption of the device. We designed a novel mosquito collection device that sensitively detects the presence of a mosquito via a fiber-optic sensor. In this prototype, a pushing capture mechanism selectively powers and efficiently captures live mosquitoes without destroying identifying morphological features of the specimens. Because the trap sensor selectively powers the capture mechanism, it allows for greatly reduced power consumption when compared with existing continuously operated devices. With appropriate programming, the fans ON and OFF based on the triggering of a fiber-optic sensor detected and counted each mosquito that entered the trap. This trapping platform can be used with a variety of power sources including renewable sources (e.g., solar, wind, or hydroelectric power) in remote settings. The experimental results show a high success ratio 93%–100% for detection of live mosquitoes.

Description: This paper proposes the application of the modified Cramér-Rao bound (MCRB) in a sensor network to perform a prior analysis of the operation in the localization task. This analysis allows knowledge of the behavior of the system without a complete deployment. It also provides essential information to select properly fundamental parameters. To do so, a complete formulation of the modified information matrix and MCRB is developed for the most common measurement models, such as received signal strength, time of arrival, and angle of arrival. In addition, this formulation is extended for heterogeneous models that combine different measurement models. Simulation results demonstrate the utility of the proposed analysis and point out the similarity between MCRB and Cramér-Rao bound.

Description: The cost for increasing the accuracy of cooperative spectrum sensing in cognitive radio requires a long time for collecting sensing data. Sequential fusion, in which the sensing data reports are sequentially collected, combined, and tested with two thresholds for deciding to wait for the next data report or concluding the presence or absence of the primary signal, is considered to reduce the collecting time. A further reduction in the average sequential report number (ASN) can be achieved by arranging the reports in descending order of data quality where the better sensing data is reported earlier. In this paper, the ASN and the error probability of the ordered sequential fusion are analytically calculated based on the direct method. The results are then adopted to design an optimal method for obtaining the optimal sequential thresholds and truncated point. The optimal truncated point enables one to minimize the ASN by discarding the sensing data with low quality, while the optimal sequential thresholds ensure the maintaining of the sensing performance of sequential fusion be the same level to that of the conventional parallel fusion.

Description: A fiber sensor for simultaneous measurement of refractive index (RI) and temperature in solutions based on multimode interference is presented. The intensity and the wavelength of the interference minimum will vary with the RI and the temperature of the solution, respectively. The sensitivity of the RI and the temperature are 94.58 dB/RI and 0.0085 ${rm nm}/^{circ}{rm C}$ , respectively. Its ease of fabrication and low-cost offer the attractive applications in chemical and biological sensing.

Description: This paper describes a portable passive millimeter-wave sensor designed for remote detection of both metallic and non-metallic objects hidden on a human body under cloth. The sensor is based on a directly detection and analyses of the energy emitted by a human body. The algorithm of detection estimates unimodality features of traces recorded in the process of a manual scan. The sensor demonstrates a detection probability in the laboratory environment close to 100% at a distance of up to 3 m for the tested samples of explosives and metal objects hidden under cloth.

Description: A long period fiber grating (LPFG) coated with a combination of cobalt chloride and gelatin is proposed and demonstrated for the monitoring of relative humidity (RH) levels. The thin overlay of the combination and its spectral properties with respect to different ambient humidity levels are observed. Field emission scanning electron microscope and atomic force microscope have provided detailed evidence of attachment of the amalgamation on LPFG surface using adapted coating methodology. The results show a significant shift in the resonance wavelength of the coated LPFG when the RH is varied from 35% to 90%, with a sensitivity of 0.18 nm/% RH and accuracy of 98.55%.

Description: Determining an object location in a specific region is an important task in many machine vision applications. Different parameters affect the accuracy of the localization process. The quantization process in charge-coupled device of a camera is one of the sources of error that causes estimation rather than identifying the exact position of the observed object. A cluster of points, in the field of view of a camera are mapped into a pixel. These points form an uncertainty region. In this paper, we present a geometrical model to analyze the volume of this uncertainty region as a criterion for object localization error. The proposed approach models the field of view of each pixel as an oblique cone. The uncertainty region is formed via the intersection of two cones, each emanating from one of the two cameras. Because of the complexity in modeling of two oblique cones' intersection, we propose three methods to simplify the problem. In the first two methods, only four lines are used. Each line goes through the camera's lens, modeled as a pinhole, and then passes one of the four vertices of a square that is fitted around the circular pixel. The first proposed method projects all points of these four lines into an image plane. In the second method, the line-cone intersection is used instead of intersection of two cones. Therefore, by applying line-cone intersection, the boundary points of the intersection of the two cones are determined. In the third approach, the extremum points of the intersection of two cones are determined by the Lagrangain method. The validity of our methods is verified through extensive simulations. In addition, we analyze effects of parameters, such as the baseline length, focal length, and pixel size, on the amount of the estimation error.

Description: Cognitive sensor network (CSN) is a promising paradigm to address the spectrum scarcity problem in traditional wireless sensor networks. Reliable spectrum sensing is essential to enable the normal operation of a CSN. Existing researches showed that by exploiting spatial diversity, cooperative sensing can greatly improve the detection performance over non-cooperative sensing in opportunity-homogeneous environment. At a given time, cognitive sensors at different locations, however, may experience heterogeneous spectrum opportunities making the cooperation among cognitive sensors intractable. In this paper, we show the limitations and drawbacks of merely using temporal-domain detection performance metrics and introduce novel spatio-temporal detection performance metrics to guide the design of joint spatio-temporal spectrum sensing. An efficient one-bit hard decision based three-phase (i.e., a global cooperation phase, a local cooperation phase, and a joint decision phase) spatio-temporal sensing algorithm is proposed and numerical results demonstrates the effectiveness of the proposed algorithm.

Description: A new frequency to voltage closed-loop integrated sensor circuit suitable for the read-out module of a monolithically integrated SAW sensor on Si is proposed. This closed-loop system consists of a voltage controlled oscillator, a peak detecting comparator, a finite state machine, and the monolithically integrated SAW sensor device. The output of the system is forced to oscillate within a narrow voltage range that correlates with the SAW pass-band response. The period of oscillation is of the order of the SAW phase delay. The output voltage range varies with changes in SAW center frequency, thus tracking mass sensing events in real time. The analysis and simulation of the system are presented for two SAW devices operating at 374 and 140 MHz, respectively. Experimental results for a test chip fabricated with AMIC5N 0.5 $mu{rm m}$ process are presented for comparison with simulation data of the 140 MHz design. Because of this frequency to voltage conversion, this approach is uniquely suitable for full monolithic integration of autonomous sensor systems and tags.

Description: This paper introduces the structure and working principles of the digital dissolved oxygen (DO) analytical sensor of ppb-level. The new-style tri-electrode electrochemical sensor composed of working electrode (WE), auxiliary electrode (AE), and reference electrode (RE) is reported in this paper because of the limit reaction area of the WE, the long reaction time, and the little reaction cavity of the existing sensors. We prepare a nano-porous gold electrode with high specific surface area to increase the area ratio of the AE and the WE. It makes the new-style tri-electrode electrochemical sensor steadier, more reliable and stronger in anti-interference. This paper also introduces the design of the work system, which is composed of hardware circuit, signal sampling and processing circuit, and temperature compensation circuit. Compared with the DO analyzer made in the Swiss Orbisphere Company (tri-electrode structure), the precision of self-made DO analyzer reach to ppb-level and the full scale error is less than ${pm}{3%}$ . In conclusion, the new-style tri-electrode electrochemical sensor can be widely used to measure DO in boiler feed water in thermal power plants.

Description: Semi-packed columns containing an array of micropillars embedded within an open rectangular column structure are a new class of micro gas chromatography $(mu{rm GC})$ columns introduced to provide higher separation efficiency and higher sample capacity. Three different semi-packed column configurations are evaluated with respect to pillar spacing along the flow direction and number of pillars across channel. The efficiencies of semi-packed columns, in terms of height-equivalent-to-a-theoretical-plate (HETP), are compared with two microfabricated open-rectangular columns. According to simulation results, arranging the pillars in a symmetrical configuration with spacing equal to the post dimension can suppress multi-path flows. Experimental results confirm the simulation prediction as the design with 2 $mu{rm m}$ post spacing (SP1) demonstrates the highest performance among other designs. SP1 is found to have HETP of 0.010 cm (15 000 plates/m) at an optimal velocity of 18 cm/s. An open channel design with comparable channel width yields an HETP of 0.025 cm (6000 plates/m) at an optimal velocity of 45 cm/s. The pressure drop in semi-packed columns is experimentally measured to be ${sim}{rm 9}~{rm kPa}$ which falls within the practical range of microfabricated pumps.

Description: This paper presents a wireless energy transfer and a wireless data communication link for neural signal monitoring—more specifically, fast ripple detection for epilepsy patients. Wireless data are transferred on the same channel as the wireless energy transfer link by shifting resonance frequency of the implanted part. The remote powering link consists of a four-coil resonant inductive link structure and a power management unit on the implant side. Modulated information on the implant is demodulated using an envelope detector type amplitude shift keying demodulator in the external unit. Power transfer efficiency in air without data communication is measured as 36% for 10 mW output power at 8.4 MHz excitation frequency, while the external and the implanted coils are separated by 10 mm. Under the same experimental conditions, 1 Mbit/s data communication is achieved while maintaining a power transfer efficiency of 33%. Moreover, in-vitro tests employing mock cerebrospinal fluid are performed and 1 Mbit/s data communication is performed with an efficiency of 33% while all other parameters are preserved. Finally, hermetical sealing capability of the packaging that is composed of epoxy and Parylene-C is successfully tested for one month to evaluate the implant's short-term performance.

Description: The intensity measurement of facial muscle activity can be used in several applications such as human–computer interaction and behavioral science. A new method for the intensity measurement is presented. It is based on a contactless, capacitive measurement of the movements that the facial activity produces. The muscles responsible for raising the eyebrows, lowering the eyebrows, raising the mouth corners, and pulling down the mouth corners are measured simultaneously with the capacitive method and electromyography (EMG) during controlled experiments. Each muscle is activated by 10 participants at three different intensity levels (low, medium, and high), 10 repetitions at each level. The capacitive intensity values are in good agreement with the ones registered with the EMG: average mean absolute errors are between 7% and 12% of the observed intensity range. However, compared with the EMG, the capacitive intensity values are noticed to have offsets that may be partly caused by the measurement itself and partly by the EMG reference. As a result, the measurement may require a calibration for more intensity values than just the maximum. In the capacitive method, it is also required to distinguish between the muscle activations originating from the same facial regions to determine which activation is taking place. This is done with an almost perfect performance by using hierarchical clustering to cluster the intensity values.

Description: Odor approximation is a technique of creating a scent similar to a target scent by blending multiple odor components. This technique expands the range of odors that can be presented even if the number of odor components is limited. This is a key technology for both odor reproduction using an odor recorder and an olfactory display. As a set of odor components that can cover a wide range of smells is not yet revealed, we study a selection of odor components using an essential-oil and food-flavor mass-spectrum database. Basis vectors are extracted by the nonnegative matrix factorization (NMF) method, and then the nonnegative least-squares method is used to determine the recipe. To increase the approximation accuracy, two methods are proposed. One method is to increase the contributions of the samples with less frequent occurrence. The other method is to set appropriate initial values of the basis vectors in the NMF method using clustering analysis. The accuracy of the odor approximation is increased using these methods.

Description: Continuous monitoring of respiratory rate is crucial in forecasting health crises and other major physiological instabilities. Current respiratory monitoring methods limit the mobility of the patient or require constant battery replacement. Wireless, wearable technology can collect continuous physiological data without immobilizing or inconveniencing patients, and human energy harvesting can be used to power these wearable sensors. In this paper, we explore this zero-net energy biosensor concept through simultaneous sensing and harvesting of respiratory effort. An off-the-shelf dc brushed motor is modified into a chest belt, and tested on a mechanical chest simulator as well as on 20 human subjects, using a spirometer as a reference. The electromagnetic biosensor is used to successfully harvest 7–70 $mu{rm W}$ from human subjects. On the mechanical chest, respiratory rate is detected with a mean absolute error of 0.00027 breaths/min with a standard deviation of 0.00019 breaths/min. For human subjects, respiratory rate is detected with a mean difference of 0.36 breaths/min with a standard deviation of 2.83 breaths/min (sitting), 0.23 breaths/min with a standard deviation of 2.64 breaths/min (standing), and 0.48 breaths/min with a standard deviation of 3.06 breaths/min (walking).

Description: This paper presents analysis of the noise spectra of closed-loop mode-matched vibratory gyros. Closed-form expressions for the noise-equivalent angular rate spectrum as well as the integrated angular rate (angle) variance are derived to explore the effects of modal frequency mismatch, closed-loop bandwidth, and the spectra of noise sources appearing at the sensor's input and output. It is shown that noise sources located at the output of the sensor's electromechanical transfer function create angle white noise in the closed-loop sensor. The angle white noise dominates the integrated rate behavior until it crosses the angle random walk asymptote at integration times exceeding the sensor's open-loop time constant. Even though the closed-loop sensor asymptotically recovers the angle random walk figure associated with the mode-matched open-loop sensor, the results can be used to quantify the larger integrated rate variance that is produced as a consequence of extending the sensor's bandwidth through feedback. A parameter, called the effective bandwidth, is introduced to capture the relative importance of the input noise versus output noise in determining the noise-equivalent rate spectrum. It is shown that the rate noise spectrum is robust to frequency mismatch as long as it does not exceed the effective bandwidth parameter. Empirical data obtained with a high performance MEMS vibratory gyro shows excellent agreement with the model predictions for a variety of sensor configurations including frequency-matched, frequency-mismatched, modified bandwidth, and manipulated input noise intensity cases.

Description: A localized surface plasmon resonance (LSPR) sensor based on self-assembled Au nanoparticle (AuNP) multilayers is developed for the detection of volatile terpenes that are considered to be biomarker gases during the growth process of plants. The sensor is fabricated by an alternate deposition of a bifunctional dithiol cross-linker and AuNPs. UV-vis spectra, atomic force microscopy images, and scanning electron microscope images of AuNP multilayers are investigated to analyze their LSPR spectra and refractive index sensitivity to terpene vapors. The results show that the optical properties of NP multilayers are jointly decided by the molecular length and chemical nature of dithiol linkers. The electric field coupling of AuNPs occurred in inter- and intra-layers determined by the refractive index sensitivity (RIS) of the sensor. The normalized RIS of the AuNP multilayer is about three times higher than that of the monolayer. The responses of AuNP multilayer sensors to changes in terpene vapor concentration are rapid, reversible, and reproducible.

Description: Underwater Acoustic Sensor Networks (UASNs) have recently been attracted significant attention from both academia and industry for resources exploration and for scientific data gathering in underwater environments. The important characteristic of a UASN is that most underwater acoustic sensor nodes have a certain beam width and a three dimension direction, which is ignored by the existing underwater routing protocols. This characteristic will reduce the network connectivity and cause a large number of asymmetric links, so it will lead to sharp decline of the existing protocol performance. We develop a routing protocol to tackle this problem in UASNs. A link detection mechanism is employed to get link state information (symmetrical link or asymmetric link), and an adaptive routing feedback method is adopted to make full use of the underwater asymmetric link and save energy. We propose a time-based priority forwarding mechanism and utilize downstream node table to prevent flooding, and a credit-based routing table update mechanism is adopted to avoid energy consumption caused by frequent update of routing table. The proposed protocol is compared with a representative routing protocol for UASNs. The simulation results verify the effectiveness and feasibility of the proposed protocol.

Description: An energy-harvester-powered wireless sensor node is a complicated system with many design parameters. To investigate the various trade-offs among these parameters, it is desirable to explore the multi-dimensional design space quickly. Because of the large number of parameters and costly simulation CPU times, it is, however, often difficult or even impossible to explore the design space via simulation. This paper presents a response surface model (RSM) based technique for fast design space exploration of a complete wireless sensor node powered by a tunable energy harvester. As a proof of concept, a software toolkit is developed that implements the proposed design flow and incorporates either real data or parametrized models of the vibration source, the energy harvester, tuning controller, and wireless sensor node. Several test scenarios are considered, which illustrate how the proposed approach permits the designer to adjust a wide range of system parameters and evaluate the effect almost instantly but still with high accuracy. In the developed toolkit, the estimated CPU time of one RSM estimation is 25 $mu{rm s}$ and the average RSM estimation error is less than 16.5%.

Description: The dual-channel self-mixing vibration measurement system in a linear cavity fiber laser with high sensitivity, flexibility, and potential remote sensing is proposed and studied in this paper. In addition, the output power with optical feedback is theoretically deduced and simulated on the basis of the three-cavity model. Experimental results show that the different movements of each channel can be detected from the dual-channel linear cavity fiber laser self-mixing interference system on the basis of the filter technology and that are in good agreement with the theoretical analysis. In addition, this paper introduces a new way to measure two-dimensional vibration.

Description: This paper proposes a new method for re-calibration of multi-axis force/torque sensors. The method makes several improvements to traditional methods. It can be used without dismantling the sensor from its application and requires a smaller number of standard loads for calibration. It is also cheaper and faster method in comparison with traditional calibration methods. The method was developed in response to re-calibration issues with the force sensor used in the welding/machining robot of the international thermonuclear experimental reactor (ITER) vacuum vessel (VV) and the approach aimed to avoid dismantling and on-site assembly of components of the ITER robot. A major complication with the ITER robot is difficult to access the robot when it operates inside the VV; especially after the first plasma, which will make the vessel radioactive. The proposed technique is based on the design of experiment methodology. It has been successfully applied to different force/torque sensors and this paper presents experimental results for the use of the calibration method with the force sensor that would be used on the ITER robot.

Description: Polyvinylidene flouride (PVDF) sensors are shown to exhibit very high stress sensitivity and high speed operation, with nanosecond response times. These characteristics allow PVDF sensors to measure in-plane stress waves in a structure. The voltage output of these sensors can be related to the average stress acting on the sensor. This paper presents an analysis on the effects of stress averaging for both in-plane sinusoidal stress waves and in-plane impact-induced stresses. Analytical models are developed that show the relationship between measured PVDF output voltage and sensor parameters, structure material, and input stress conditions. Parametric studies are conducted, which show that the error introduced by stress averaging is minimal for most typical cases; however, the effects of stress averaging become more significant as the sensor length increases, density of the structure's material increases, and magnitude of the input stress increases. For sinusoidal stress inputs, the error increases as the sensor length approaches the wavelength of the stress in the structure.

Description: Relay selection is a technique that can considerably increase the performance of cooperative communications. In this paper, we propose a new relay selection algorithm using fuzzy logic aiming at both network lifetime and end-to-end throughput. The new algorithm operates in a distributed way, running independently at each node, not requiring a central entity for complex coordination. The method considers the channel state of the relay-destination link and the residual energy of its battery. It is shown that the proposed scheme can transmit a larger amount of information during the network lifetime with respect to both the opportunistic (which focuses on throughput) and random (which focuses on lifetime) selection algorithms, increasing the network utility.

Description: This paper describes the design, fabrication, and performance of a thin film humidity sensor fabricated in standard CMOS process, hence it may be combined with an integrated circuit. The sensor is based on a capacitance between interdigitated electrodes in the top metal layer and water adsorption in the polyimide layer. The design is optimized by analytical and then finite element models which show that, within the constraint of the CMOS structure, the sensitivity can be no greater than one third of the sensitivity of the polyimide alone. Experimental sensors were fabricated in-house before an improved design was fabricated in a commercial foundry. The different behavior of these sensors, despite their similar designs, leads to an investigation into the effects of fabrication process on the sensor linearity. Characterizing the polyimide film by contact angle, AFM and FTIR revealed that the difference in linearity of the response between the two sensors resulted from different etching techniques employed to pattern the film.

Description: This paper describes a high-performance interface electronics system design for a high-density flexible biomechanical ground reaction sensor array (GRSA). The prototype system can be incorporated into a personal boot heel to measure real-time ground force, shear strain, and sole deformation associated with a human bipedal locomotion, thus providing zero-velocity correction to an inertial measurement unit placed in a close proximity. This approach can greatly reduce inertial error accumulation and improve positioning accuracy. The sensing electronics consist of a front-end multiplexer that can sequentially connect individual sensing nodes from a 13 $,times,$ 13 GRSA to a capacitance-to-voltage converter followed by a 12-bit algorithmic ADC with a sampling rate of 66.7 k-samples/s. The entire sensor array can be scanned within 10 ms. The GRSA employs capacitive sensing scheme and is fabricated using PDMS deformable dielectric layer. The integrated sensing electronics are fabricated in XFAB 0.35 $mu{rm m}$ CMOS process and dissipate 3 mW power. The overall system sensing resolution is limited by electrical interferences coupled through long interconnect traces between a GRSA and an electronic sensing module. Dynamic and static pressure testing shows the prototype system functionality achieving a gait ground velocity sensing resolution of 100 $mu{rm m/s}$ .

Description: Electromagnetic induction systems have proven to be very effective in detecting subsurface metallic and magnetic objects. Such systems often employ separate transmit and receive coils, and thus it is desirable for the transmit and receive coils in these systems to have minimal mutual coupling. It is also desirable for the product of the fields generated by the transmit and receive coils to be as large as possible to maximize the detection depth. We demonstrate that a pair of spiral coils can be optimized to achieve these desired properties. A mathematical representation is chosen for the coils, which allows the coil pair to be optimized using an iterative convex method, which, due to its convexity, is very fast. We then present results showing a pair of nonuniformly wound spiral coils created with this optimization.

Description: The comparison of bundle sensor performance between 16 concentric receiving fiber (RF) and 1000 hemicircular RF probes is reported. A theoretical analysis is developed for 1000 RF to support the experimental findings, which uses an electromagnetic Gaussian beam approach to determine the transfer function of the probe. Three linear ranges of the displacement profile can be obtained from each probe, namely, the front slope, the first back slope, and the second back slope. The highest sensitivity obtained by the 16 concentric RF at the front slope range is 5.8148 mV/mm with a resolution ${>}{rm 0.3}~mu{rm m}$ . Its lowest sensitivity at the second back slope region is 0.06 mV/mm with an initial resolution of 26 $mu{rm m}$ . The 16 RF probe produces a better sensor performance both at the front slope and the first back slope region, whereas at the second back slope region, the 1000 RF exhibits a higher sensitivity. Furthermore, a wider linear range is realized through the 1000 RF whereby the front slope and the first back slope are 1.45 and 4.75 mm, respectively. The second back slope of the 16 RF, however, provides a longer linear range 3.0 mm. The latter sensor probe has many potential applications in the longer displacement range, such as position control, micro-displacement sensing in hazardous regions, and automated monitoring control.

Description: Giant magnetoresistance (GMR) sensors are assumed as an important role in magnetic field sensing applications because of their small size, high sensitivity, large frequency response, low power consumption, and relatively low cost. In all these applications, it is very important to estimate and possibly reduce the measurement uncertainty related to the use of these sensors. In this paper, the metrological characterization of GMR magnetometers highlights the contributions to measurement uncertainty of hysteresis, nonlinearity, and operating temperature. Starting from this knowledge, an automatic procedure for calibration and adjustment of GMR magnetometers is setup. This procedure, based on a mixed hardware-software solution, allows a meaningful reduction of the measurement uncertainty for both ac and dc magnetic field amplitude measurements using GMRs.

Description: We demonstrate the feasibility of using optical coherence tomography (OCT) to image and detect 2.8 $mu{rm m}$ diameter microparticles (stationary and moving) on a highly-reflective gold surface both in clear media and under skin in vitro. The OCT intensity signal can clearly report the microparticle count, and the OCT response to the number of microparticles shows a good linearity. The detect ability of the intensity change $(2.9%pm 0.5%)$ caused by an individual microparticle shows the high sensitivity of monitoring multiple particles using OCT. An optical sensing method based on this feasibility study is described for continuously measuring blood sugar levels in the subcutaneous tissue, and a molecular recognition unit is designed using competitive binding to modulate the number of bound microparticles as a function of glucose concentration. With further development, an ultra-small, implantable sensor might provide high specificity and sensitivity for long-term continuous monitoring of blood glucose concentration.

Description: Interest has grown for using acoustic Doppler current profilers (ADCPs) to measure suspended solids concentrations (SSC) in aqueous environments because of the ability to make simultaneous unobtrusive long-term multipoint measurements with high spatial and temporal resolutions. The acoustic backscatter intensity (ABS) measured by ADCPs is a function of the particle size distribution, concentration, and incident acoustic signal strength and thus provides the theoretical basis for measuring SSC. The applicability of using ABS from a 2400-kHz ADCP to estimate SSC in units of volume concentration over variable particle size distributions is evaluated in a controlled laboratory study. Results from this research show a log-linear relationship between ABS and volume concentrations over variable size distributions. Volume concentrations predicted from the sonar equation using measured ABS and empirically derived response coefficients compare well with the measured concentrations over the full range of concentrations and particle size distributions tested. The ABS response is shown to be linear with the theoretical Rayleigh scattering target strength, calculated from the empirical particle size distribution, and thus explains the observed linearity over a variable particle size distribution. These results indicate that ABS can be used to provide meaningful volume concentration estimates for characteristically variable colloidal suspensions.

Description: An all-metal double metal diaphragm-based optical fiber accelerometer with low transverse sensitivity is proposed and experimentally demonstrated. The theoretical analysis is given based on the electro-mechanical theory. Finite element modal analysis shows that the proposed accelerometer has low transverse sensitivity. Calibration results show that axis responsivity is 41 dB $({rm re}!:~0~{rm dB},=,1~{rm rad}/{rm g})$ with a fluctuation ${pm}{rm 2}~{rm dB}$ in frequency bandwidth of 5–400 Hz. The transverse sensitivity is ${sim}{rm 3}~{rm dB}~({rm re}!:~0~{rm dB},=,1~{rm rad}/{rm g})$ with a fluctuation ${pm}{rm 1.5}~{rm dB}$ . A transverse sensitivity of about ${-}{rm 40}~{rm dB}$ is achieved. The fluctuation of the acceleration responsivity for the three accelerometers is within ${pm}{rm 2.5}~{rm dB}$ , which shows good consistency of the proposed accelerometer. The minimum phase demodulation detection accuracy of the phase-generated carrier is $10^{-5}~{rm rad}/{rm Hz}^{1/2}$ , and the minimum detectable acceleration can be 90 ${rm ng}/{rm Hz}^{1/2}$ theoretically. With an all-metal structure, the proposed accelerometer is expected to improve the reliability of long-term use in harsh environment. These desirable features show that the proposed optical fiber accelerometer is promising for seismic wave monitoring in oil and gas exploration.

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Description: Provides a listing of current staff, committee members and society officers.

Description: Provides a listing of current committee members and society officers.

Description: The inertial magnetoelectric velocity sensor is widely used in the fields of vibration control and measurement. The frequency response in the low frequency range is, however, limited by high frequency resonance because of the characteristic of second order high pass filter of the structure. A frequency-selected network for amplitude-frequency characteristic compensation to improve the performance of the frequency response is presented. The frequency-selected network, which is composed of amplifiers, resistors, and capacitances, is connected to the output port of the sensor in cascade without any modification of the sensor's structure. After compensation, the frequency band of the sensor is flattened and frequency response still has the characteristic of second order high pass filter, whereas the resonant frequency decreases from ${sim}{10}$ to 0.93 Hz. Meanwhile, it keeps the transducer in small size and light weight. The experimental results have shown that the sensor after been compensated has good performance in the low frequency range.

Description: We report the fabrication and characterization of a pH sensor made with titanium dioxide $({rm TiO}_{2})$ /multiwall carbon nanotube (MWCNT)/cellulose hybrid nanocomposite. The ${rm TiO}_{2}$ -coated MWCNTs are synthesized by hydrothermal process. The X-ray diffraction and Raman spectra observations show that high anatase crystalline ${rm TiO}_{2}$ nanoparticles are well formed on the surface of MWCNTs. After blending the ${rm TiO}_{2}$ /MWCNTs with cellulose solution, the TiO/MWCNT/cellulose hybrid nanocomposite is made and used for the pH sensor. This nanocomposite pH sensor exhibits two linear regions in its conductance between pH 1 and 12. Large surface area of the hybrid nanocomposite increases adsorption sites of ions so as to increase the pH sensitivity as well as sensing range. The long-term stability test and reusable test demonstrate that this hybrid nanocomposite pH sensor is useful for many practical applications. The pH sensing mechanism of this hybrid nanocomposite pH sensor is also discussed in this paper.

Description: A wide variety of tactile (touch) sensors exist today for robotics and related applications. They make use of various transduction methods, smart materials and engineered structures, complex electronics, and sophisticated data processing. While highly useful in themselves, effective utilization of tactile sensors in robotics applications has been slow to come and largely remains elusive today. This paper surveys the state of the art and the research issues in this area, with the emphasis on effective utilization of tactile sensors in robotic systems. One specific with the use of tactile sensing in robotics is that the sensors have to be spread along the robot body, the way the human skin is—thus dictating varied 3-D spatio–temporal requirements, decentralized and distributed control, and handling of multiple simultaneous tactile contacts. Satisfying these requirements pose challenges to making tactile sensor modality a reality. Overcoming these challenges requires dealing with issues such as sensors placement, electronic/mechanical hardware, methods to access and acquire signals, automatic calibration techniques, and algorithms to process and interpret sensing data in real time. We survey this field from a system perspective, recognizing the fact that the system performance tends to depend on how its various components are put together. It is hoped that the survey will be of use to practitioners designing tactile sensing hardware (whole-body or large-patch sensor coverage), and to researchers working on cognitive robotics involving tactile sensing.

Description: In this paper, we describe a low cost optical sensor of water level based on fiber bending effect associated to the use of an elastomeric membrane. The sensor proposed has a particular design to be simple, reliable, and low cost. It is suitable to be used in tubes of embankment dams, tanks, and reservoirs. The sensor uses a standard single mode fiber and can measure the water levels up to 10 m or more, choosing the appropriate membrane. This paper describes the development of the sensor, a theoretical modeling, and the results of laboratory and field tests. Seven sensors were installed in an embankment dam where they have been used in a real time monitoring system based in optical time domain reflectometry.

Description: This paper presents a non-linear framework employing a robust polynomial filter for accomplishing enhancement of mammographic abnormalities outcoming from biomedical instrumentation, i.e., X-rays instrumentation. The approach proposed in this paper uses a linear combination of Type-0 and Type-II polynomial filters as a generalized filtering solution to achieve enhancement of mammographic masses and calcifications irrespective of the nature of background tissues. A Type-0 filter provides contrast enhancement, suppressing the ill-effects of background noise. On the other hand, Type-II filter performs edge enhancement leading to preservation of finer details. Contrast improvement index is used as a performance measure to quantify the degree of improvement in contrast of the region-of interest. In addition, estimation of signal-to-noise ratio (in terms of PSNR and ASNR) is carried out to account for the suppression in background noise levels and over-enhancements of the processed mammograms. These measures are used as a mechanism to optimally select the filter parameters and also serve as a quantifying platform to compare the performance of the proposed filter with other non-linear enhancement techniques to be used for diverse biomedical image sensors.

Description: This paper reports an analysis of the design and potential of a fiber optic-based sensor designed to monitor lateral pressure, and with the birefringence characteristics of a polarization-maintaining fiber, enabling the measurement of a transverse force applied to the fiber. This evaluation involves the consideration of several key parameters of the system, including the effect of the fiber structure, the magnitude and the direction of the applied external force that can be sensed, and the fiber length used, a combination of which determines the pressure sensitivity of the fiber when it is used as a pressure sensor. In the system design, to interrogate the birefringence variation of the sensor when it is subjected to the force causing the transverse pressure variation, the fiber loop mirror technique is employed following the results of an analysis using mode-coupling theory. The design created in this paper is based on sound theoretical principles and is generic and thus suitable for use with any fiber structure with high birefringence, for sensor applications. The data obtained from this design study are in good agreement with those from an experimental verification carried out, demonstrating its suitability for measurements of pressure and applied forces through an appropriate and tailored sensor based around exploiting the properties of high birefringence fibers.

Description: A new technique is proposed to detect and locate wire faults using the impedance spectroscopy and a model-based approach. A modeling approach for transmission lines is developed, in which every cable part having the same characteristic impedance is represented analytically by a frequency-dependent ABCD model. The model parameter extraction is resolved by global optimization techniques based on genetic algorithms leading to a robust convergence behavior and excellent accuracy. This novel method enables the location of hard and soft faults and the identification of types of wire faults. The bandwidth of the developed transmission line model fits to experimental results, so that influence effects such as losses, dispersion, and frequency-dependent signal propagation can be precisely modeled. The calculation time is not proportional to the wiring length or dependent on cable system complexity by numerical methods such as FDTD.

Description: A micro-electromechanical-systems (MEMS) three-axis Lorentz force magnetometer based on a 0.24 $,times,$ 0.4 ${rm mm}^{2}$ MEMS resonator that is the smallest Lorentz force sensor reported to date is presented in this paper. A magnetic field can be detected in two axes using a single MEMS structure. Placing two structures perpendicular to each other in a single die makes three-axis sensing possible. Sensing is performed by exciting the MEMS resonator at its in-plane and out-of-plane mechanical resonant frequencies of 40.5 and 107.4 kHz, respectively. A modest die-level vacuum packaging results in in-plane and out-of-plane mechanical quality factors of 110 and 310, respectively. The sensor has a bandwidth of 184 Hz for $z$ -axis and 189 Hz for $x/y$ -axis magnetic field. With an excitation power of 2 mW, the sensor resolution is 285 ${rm nT}/surd{rm Hz}$ for $z$ -axis magnetic field inputs and 344 ${rm nT}/surd{rm Hz}$ for $x/y$ -axis magnetic field inputs. The resolution is limited by Brownian noise in the $z$ -axis whereas the $x/y$ -axis resolution is limited by electronic noise. With an averaging time of 288 s, the sensor shows an offset stability of 23 nT.

Description: We report for the first time the application of turnaround-point long period fiber gratings for wavelength encoded detection of automobile fuel adulteration. The demonstrated high sensitivity of 0.96 nm/% change of kerosene in petrol up to 10% adulteration is significantly high compared with previously published values. These specialty gratings can easily detect the presence of 1% contamination of kerosene in petrol and thus provide opportunities for development of portable fuel adulteration sensors.

Description: In this paper, a novel method is proposed to recover and extract the original signal parameters from the saturated multifrequency sinusoid wave signals. It makes use of the zero-crossing characteristics of the multifrequency sinusoid signals, to collect valid samples in unsaturated parts of the signals. On these valid samples, the amplitudes and phases of the specific original ac sensing signals can be linearly computed by applying the least square method. The simulation results show that the proposed method has satisfactory accuracy even with very large saturation ( ${sim}{10}$ times of the saturation limit) and large dc offset, which frees us from the restriction to avoid the signal saturation problem in the signal acquisition. The method is realized by the software algorithm, and no longer requires the common used hardware—the phase sensitive detection circuit. Hence when it is applied to the magnetic coupling system, we will obtain much simpler system composition, higher accuracy, and high execution speed.

Description: Cyclosporine, a powerful immunosuppressive agent, is used to prevent allograft rejection. This paper describes a simple, rapid, and cost effective method based on a quartz crystal nanobalance for the detection of cyclosporine. Measurement is based on the frequency shifts of a methyl phenyl silicon, 75% phenyl (OV25)-coated quartz crystal because of the adsorption of analytes. The frequency shift of sensor is linear related to the concentration of cyclosporine in solution. Linear calibration curve is obtained in the range of 2–8 ${rm mg}~{rm L}^{-1}$ . The correlation coefficient and the lower limit detection are 0.993 and 0.94 ppm, respectively.

Description: In this paper, a novel nondestructive method based on magnetic field sensing is proposed for underground power cable operation-state monitoring and energization-status identification. The magnetic field distribution of the cable is studied using finite element method (FEM) for the power cable operating in different states, i.e., current-energized state (the cable is energized and carries load current) and voltage-energized state (the cable is energized but carries no load current). This innovative method can reconstruct all the source parameters of the cable based on a set of measured magnetic field values. Stochastic optimization technique is applied to realize the reconstruction based on the measured magnetic field. The technology is developed with an artificial immune system algorithm that is able to find out the global optimum with high probability even if very little knowledge about objective function is provided. Application of this method is demonstrated on an 11 kV cable with metallic outer sheath. The results highly match with the actual source parameters of the cable. For application in practice, possible limitations introduced by the nonidealistic of magnetoresistive sensor on magnetic field measurement are discussed and corresponding solutions are suggested. An experimental setup is constructed and the test results are used for the demonstration of this method. This paper shows that the proposed method is able to monitor the operation states of an underground power cable with high accuracy. Engineers can also correctly identify the energization status of the target cable during onsite maintenance. This method is adaptable to other kinds of power cables simply by updating the geometrical and material parameters of the cable in the FEM computation. Moreover, this is an entirely passive method and does not need any active signal injection into the cable.

Description: Feeding by sucking is one of the first activities of daily life performed by infants. Sucking plays a fundamental role in neurological development and may be considered a good early predictor of neuromotor development. In this paper, a new method for ecological assessment of infants' nutritive sucking behavior is presented and experimentally validated. Preliminary data on healthy newborn subjects are first acquired to define the main technical specifications of a novel instrumented device. This device is designed to be easily integrated in a commercially available feeding bottle, allowing clinical method development for screening large numbers of subjects. The new approach proposed allows: 1) accurate measurement of intra-oral pressure for neuromotor control analysis and 2) estimation of milk volume delivered to the mouth within ${〈} 2%$ variation between estimated and reference volumes.

Description: This letter presents a novel complementary metal-oxide-semiconductor (CMOS) micromachined capacitive flow sensor for respiratory monitoring. Airflow induces a pressure change on the suspended sensing plate and causes a capacitance change with respect to the bottom electrode. The microstructure fabricated by post-CMOS metal etch occupies an area of 190 $,times,$ 190 $mu{rm m}^{2}$ and possesses a sensing capacitance of 180 fF. Output waveform of consecutive breaths is successfully measured with an output noise of 14 $mu{rm V}$ for a measuring bandwidth of 0.5 Hz, which is equivalent to a minimum detectable capacitance change and airflow velocity of 0.13 aF and 0.2 mm/sec, respectively.

Description: Chitosan-based sensor thin films were fabricated to detect trace amounts of lead ion using surface plasmon resonance (SPR) optical sensor. The gold surface used for SPR measure- ments was modified with chitosan and chitosan-tert-butylcalix[4]arene-tetrakis(N,N-dimethylthioacetamide) (chitosan-BCAT). Both chitosan and chitosan-BCAT layers were deposited on the gold surface by spin coating technique. The experiment has been carried out to monitor the SPR signals for lead ion with sensitive enhancement by chitosan and chitosan-BCAT layers. For both layers, the change in resonance angle $(Deltatheta)$ is directly proportional to the concentration of lead ion solution. The higher amounts of $Deltatheta$ were obtained for chitosan-BCAT film due to a specific binding of BCAT with lead ion. The chitosan-BCAT film enhanced the sensitivity of detection down to 0.03 ppm. Data analysis also has been done by Matlab software using Fresnel formula for multilayer system.

Description: Based on the observed temperature information of arch dam, the mathematical and mechanical methods are combined usually with dam engineering theory to capture in real time and evaluate in time the developing status and space-time distribution of arch dam temperature, and implement the back analysis for temperature control measures. It is an important step for dam construction and safe operation. Some methods, namely transient temperature-field simulation, thermodynamic parameters back-calculation, and model correction, are used synthetically to solve the above problem. A method is proposed to back calculate the thermodynamic parameters of arch dam by use of the temperature data obtained by the distributed optical fiber temperature sensor (DTS). A problem is studied to couple the simulated temperature field by finite element method (FEM) and the observed temperature field by the DTS. A method is presented to update dynamically the FEM model on the basis of the observed temperature field. An actual engineering is analyzed by the proposed method. It is shown that the DTS system can implement the real-time observation of concrete arch dam temperature field. According to the observed temperature field by the DTS and the updated numerical simulation model of the temperature field, scientific guidance can be given during the pouring process of the arch dam, and reliable data can be provided to analyze and evaluated arch dam safety.

Description: This paper presents a prototype machine-to-machine (M2M) healthcare solution that combines mobile and IPv6 techniques in a wireless sensor network to monitor the health condition of patients and provide a wide range of effective, comprehensive, and convenient healthcare services. A low-power embedded wearable sensor measures the health parameters dynamically, and is connected, according to the concept of IPv6 over low-power wireless personal area network, to the M2M node for wireless transmission through the internet or external IP-enabled networks via the M2M gateway. A visualization module of the server program graphically displays the recorded biomedical signals on Android mobile devices used by patients and doctors at the end of the networks in real-time. Our approach for a global M2M healthcare solution is managed to process the large amount of biomedical signals through the extended network combining IPv6 technique and mobile technology for daily lifestyle to users appropriately.

Description: A mobile ad hoc network is a dynamic wireless network, which does not have fixed infrastructure. This paper presents a new multicast algorithm to increase the lifetime of node and network in the mobile ad hoc network. Here, it considers two metrics, namely residual-battery-capacity of the node and relay-capacity of the node to do multicasting from the source to a group of destination nodes. The proposed model is simulated using network simulator-2.33 and is tested under various conditions. The proposed model is compared with the existing algorithms such as multicast-incremental-power, lifetime-aware-multicast-tree, multicast-ad-hoc-on-demand-distance-vector protocol and multiple-path-multicast-ad-hoc on-demand vector. The proposed model shows the best results in terms of node lifetime, network lifetime and throughput.

Description: New optical probes are developed for carotid distention waveform measurements, in order to assess the risk of cardiovascular diseases. The probes make use of two distinct photodetectors: planar and avalanche photodiodes. Their performance is compared for visible and infrared (IR) light wavelengths. The test setup designed for the evaluation of the probes simulates the fatty deposits commonly seen in the obese people, between skin and the artery. The performed tests show that the attenuation of the signal is lower for the IR light, with higher penetration and better resolution in the captured distension waveform, with higher definition in morphological features on the wave and higher signal-to-noise ratio when compared to the visible source signals. The probes show good overall performance in the test setup with a root mean square error lower than 8%. In vivo, the IR probes allow easier waveform detection, even more relevant with the increasing deposit structures.

Description: A compact fiber sensor based on fiber Bragg grating (FBG) embedded in a fiber modal interferometer (MI) for simultaneous measurement of strain and temperature is proposed. Because the total length of the sensor is 12 mm and can be further reduced, the spatial resolution of the sensor is improved. Due to the different responses of the fiber MI and the FBG to strain and temperature, the simultaneous measurement at the same point is achieved. For 0.01-nm wavelength resolution, the resolution of the sensor is 5.96 ${mu}{varepsilon}$ and 0.31 $^{circ}{rm C}$ in strain and temperature, respectively.

Description: The transduction of a biological event into a readable electronic signal generally occurs as a result of modulation of amplitude of either an optical, electrical, or mechanical signal. Several limitations occur as a result of amplitude modulation, like limitation of sensitivity due to amplitude noise and difficulty of multiplexing. In the electronics industry, the modulation of frequency or phase of the signal is widely used and offers many advantages such as extraction of signals buried in amplitude noise, or detection of multiple codes on a single line, and several other advantages. Here we introduce a novel method involving the use of gratings in the sidewalls of microchannels for coding a signal in phase in addition to amplitude. The use of this technique allows for several advantages such as improvement in signal-noise ratio, and also allows for the possibility of using a single line for simultaneous multiplex measurement of biological events.

Description: High-Q sensory microsystems are desirable especially in low noise applications. However this makes implementation of the closed-loop control a great challenge. An in-depth investigation into high-performance closed-loop interface circuit design for high-Q capacitive microaccelerometers is presented. Focus is placed on an analogue force feedback scheme with proportional-derivative compensation. Such an approach is differing from the commonly used electromechanical $Delta,Sigma$ technique, since the latter one often suffers severe problems in balancing between the loop stability and other essential characteristics in the presence of high-Q sensing element. A comprehensive analysis concerning the system linearity and bandwidth is conducted, aiming for performance optimization. The adverse impact arising from several electronic noise sources in the system is studied in order for minimization. Accordingly, a prototype interface circuit is designed and fabricated in a commercial 0.35- $mu{rm m}$ CMOS process. The chip measures 2.5 $,times,$ 2.5 ${rm mm}^{2}$ and operates from a single 5 V supply. The quiescent current is about 10 mA. The test results show that it offers a full scale acceleration of ${pm}{rm 1.2}~{rm g}$ correspondingly with integrated non-linearity (INL) of 6.6%, wide-band noise equivalent acceleration of nearly 1 $mu{rm g}/surd{rm Hz}$ over a signal bandwidth of about 1.2 kHz.

Description: In this paper, we simulate a refractive index sensor based on the 2-D photonic crystal using finite difference time domain methods. The sensor which is called double-hole defect sensor, consists of two waveguides and two-point defect microcavities when the lattice constant is $a=440~{rm nm}$ . In the optimum structure, the sensitivity of the sensor is $s=500~{rm nm/ RIU}$ (refractive index unit), whereas the refractive index resolution is very small and $Delta n=0.0001$ (i.e., resonance wavelength shifts up by 0.05 nm).

Description: This paper reports a soft fiber optic sensor based on polymer fiber Bragg gratings (PFBGs) for simultaneous measurement of shear and normal stresses. The sensor comprises two PFBGs embedded in soft polydimethylsiloxanes (PDMS) matrix, and one of them is horizontally placed while the other is tilted. The transduction principle is that applied normal and/or shear stresses lead to deformation of the matrix and induce strains on gratings. Finite element simulation reveals non-uniform strain distribution along two fibers for direct imbedding that is verified by theoretical analysis, and therefore four gaskets are used to stretch polymer optical fibers from two ends and to produce strains on gratings. The fabricated sensor is tested by concurrently applying normal and shear forces, and Bragg wavelength shifts of two gratings were found to be linearly dependent on stresses in two directions. The measured pressure sensitivity is 0.8 pm/Pa in the range of 2.4 kPa and the shear stress sensitivity is 1.3 pm/Pa for a full range of 0.6 kPa. Such soft sensors are especially suitable for high precision measurement of contact stresses involving human skins and tissues because they are similar in Young's modulus to the used PDMS.

Description: In this paper, we address a new photoplethysmography (PPG) signal-sensing method using a wristwatch-type PPG array sensor. According to the development of the ubiquitous health care system, the many types of medical equipment and treatments have been improved. In conventional PPG signal-sensing approaches, the finger-type PPG probe has been used. However, the finger-type PPG probe requires tight fitting that restricts movement, meaning that patients should endure dome discomfort while wearing it. To solve this problem, we propose a novel PPG array sensor module with a wristwatch-type design. The proposed module measures the PPG signal from the radial artery and the ulnar artery of the wrist, whereas previous methods obtained it from the capillaries of the skin. Moreover, we place phototransistors and infrared-emitting diodes in an array form to improve the PPG signal sensitivity and level of accuracy. Various arrays are considered for optimization, and a conductive rubber wristband is employed to reduce external noise. In the experiments, the proposed module is assessed and compared with the commercial product. This comparison between the commercial finger-type probe dataset and the PPG array module wrist-type probe dataset shows that the degree of similarity between the two signals is greater than 91.2%.

Description: An easily implementable signal conditioning circuit for resistive humidity and temperature sensors is presented. It is based on a relaxation oscillator in which both the frequency and the duty-cycle of the square-wave output signal simultaneously carry information from two different types of sensors. The output frequency is linearly related to the resistive unbalance of an active bridge, whereas the duty-cycle is independently controlled by a thermal sensor for controlling temperature error of the humidity sensor (RH). The design, analysis, and experimental characterization of the circuit and its application to a sol-gel thin film porous $gammahbox{-}{rm Al}_{2}{rm O}_{3}$ -based humidity sensor and resistance temperature detector are reported. Experimental results confirm the theoretical value predicted. The circuit covering wide resistance measurement range has the potential for remotely monitoring measurement parameters accurately.

Description: A novel in-fiber refractometer based on a compact Hi-Bi fiber tip working on reflection is proposed and experimentally demonstrated. The fiber sensing head is composed of a short section of PANDA-type Hi-Bi fiber with a length of 0.15 m. The fringe contrast of the interferometer is extremely sensitive to ambient refractive index (RI) variation when the Hi-Bi fiber tip is immersed in water–glycerin solutions with different mass concentration for different RIs. The experimental results show that the proposed sensing device provides a high RI sensitivity of ${-}{rm 35.34}~{rm dB/RI}$ unit for resolutions with RI values near 1.33, making it a good candidate for sensing in chemical and biological applications.

Description: This paper presents the design and characterization of a microelectromechanical system (MEMS)-based intraoperative monitoring system for improving lumbar surgery safety. A MEMS pressure-sensing module is designed and incorporated into a nerve root retractor tip to directly monitor pressure exerted on a nerve root during a lumbar surgery. Animal experiments are conducted for intraoperative pressure monitoring to investigate effects of nerve root retraction during a surgery. Amplitude and latency of electrophysiological response of a nerve root are measured during different time intervals after retraction under various retraction magnitude and duration conditions. Correlation between exerted pressure on a retracted nerve root and its electrophysiological response is investigated. The relationship between intraoperative pressure and alteration of neural tissue structure is analyzed by morphological observation. Experimental results indicate that a nerve root injury is strongly related to the magnitude and duration of its retraction. The prototype MEMS-based intraoperative monitoring system can potentially alert surgeons about risk factors associated with nerve root injury during a lumbar surgery as well as provide critical surgical guidelines. The system can also serve as a basis for implementing an intelligent robotically controlled closed-loop lumbar surgical operating system in the future.

Description: A taxel device on flexible substrates based on the electrical contact resistance (ECR) variation mechanism is developed. The proposed taxel device consists of one top and one bottom substrates, which are coated with conductive polymer then face-to-face assembled. The device is tested with different substrate materials to show the viability of the ECR variation mechanism. It is found that when paper is used as the substrate material, because of its exclusive features of surface roughness and material compressibility, the ECR variation mechanism is greatly enhanced and the device exhibits higher sensitivity and larger working pressure range. Practical applications are investigated in elasticity measurement on phantom samples and biological tissues. The results are promising with our taxel device made on flexible substrates being capable of integration onto surgical tools and the potential to realize the psychical property of biological tissues.

Description: MEMS force sensors embedded in flexible polyimide substrates are reported, motivated by the need to monitor force and pressure on nonplanar surfaces for structural health monitoring. Details of the fabrication, measured preliminary results, and figures of merit are described. The sensors showed an average piezoresistive gauge factor of 1.75. The average value of normalized Hooge noise coefficient ${rm K}_{1/{rm f}}$ was found to be $1.89times 10^{-10}$ . The sensitivity was measured to the range from 0.266 to 2.248 V/N with an average sensitivity of 1.25 V/N. The noise equivalent force was calculated to the range from 8.83 to 46.56 $mu{rm N}$ with an average value of 20.47 $mu{rm N}$ for the force sensors in a noise frequency bandwidth from 1 to 8 Hz.

Description: Flexible sensors that can be integrated into clothing to measure everyday functional performance is an emerging concept. It aims to improve the patient's quality of life by obtaining rich, real-life data sets. One clinical area of interest is the use of these sensors to accurately measure knee motion in, e.g., osteoarthritic patients. Currently, various methods are used to formally calculate joint motion outside of the laboratory and they include electrogoniometers and inertial measurement units. The use of these technologies, however, tends to be restricted, since they are often bulky and obtrusive. This directly influences their clinical utility, as patients and clinicians can be reluctant to adopt them. The goal of this paper is to present the development process of a patient centered, clinically driven design for an attachable clothing sensor (ACS) system that can be used to assess knee motion. A pilot study using 10 volunteers was conducted to determine the relationship between the ACS system and a gold standard apparatus. The comparison yielded an average root mean square error of ${sim}{1}^{circ}$ , a mean absolute error of ${sim}{3}^{circ}$ , and coefficient of determination above $(R^{2})$ 0.99 between the two systems. These initial results show potential of the ACS in terms of unobtrusive long-term monitoring.

Description: For linear discrete-time stochastic systems measured by multiple sensors, where different sensors are subject to mixed uncertainties of random delays, packet dropouts and/or uncertain observations, the centralized fusion linear optimal estimators in the linear minimum variance sense are presented via the innovation analysis approach, which is a general and useful tool to find the optimal linear estimate. The stability of the proposed estimators is analyzed. A sufficient condition for the existence of the centralized fusion steady-state estimators is given. For a single sensor case, the proposed estimators have the simpler forms and the lower computational cost compared to the existing literature, since a lower dimension parameterized system is constructed and the colored noise is avoided. A simulation example verifies the effectiveness of the proposed estimators.

Description: Noninvasive real time visual monitoring systems are more demanding in the field of automation because of their high reliability, robustness, fast execution time, portability, and flexibility. In this paper, a novel architecture of detection algorithm has been developed to identify the geometrical and statistical features of position of the pointer's image from the captured image of indicating type meters in real time. In our view, a real time visual monitoring system has the following stages: 1) image acquisition; 2) image pre-processing; 3) segmentation; 4) feature extraction; 5) feature matching; and 6) display of result into graphical user interface window along with controlling decision. The geometrical, statistical, and wavelet-based image features were used to recognize the indicated value using feature matching algorithm. Also, the system controller compares the recognized value with the set value of parameters and if, it is found beyond the specified limit, it generates various alarms and controlling or tripping signals for the final control elements.

Description: This paper addresses the problem of detecting minute concentrations (nano to pico-molar) of analyte in a fluid flow chamber using an array of surface-based sensors. It is shown that in the mass-transport influenced case, when the rate of transport of analyte is comparable to or smaller than the intrinsic reaction rates at the sensor surface, substantial improvements in the response rate can be obtained from an array of spaced small sensor surfaces relative to a single large surface. Advection-diffusion-reaction models are developed to predict the response of such sensor arrays, which are compared to individual sensor surfaces of the same total area. Formulas are derived for quantifying the improvement in performance and optimal size of the sensors in the array. The results of the model are compared with experimental data obtained for an ion-channel switch biosensor and a surface plasmon resonance biosensor.

Description: This review article discusses various techniques of environmental monitoring (EM) systems and what is required for the variations in hardware implementation and/or algorithmic logic. This review presents an overview of the existing state-of-the-art practices of environmental monitoring systems and is mainly focused on energy-efficient and low-cost environment monitoring systems. The following are some of the major factors that usually rule the development of EM systems, namely, energy efficiency, cost of the overall system, response time of the sensor module, good accuracy of the system, adequate signal-to-noise ratio, radio frequency interference/electromagnetic interference (RFI/EMI) rejection during varying atmospheric conditions and in inhomogeneous environments, a user friendly interface with the computer, and complexity of computation. The above concerns are also recognized by reference to research articles on environmental monitoring systems. Emphasis is on the necessity of robust systems that address all or most of the above mentioned criteria.

Description: In this paper, we first derive an analytical formulation for capacitance prediction of multi-conductor and multi-dielectric system. A simulation model based on this formulation is then developed. By introducing the effective capacitance, we also propose a new methodology to measure the capacitance for multi-conductor system. Results from simulated model are compared with measurement data. It shows that our model can make reasonable predictions of capacitive sensors in the environment of multi-conductor/dielectrics. This simulated model is subsequently used to evaluate the input/output linearity of the radial displacement capacitance sensor that our newly proposed. It shows that the linearity coefficient between the input torsion angle and output differential capacitance of this new device is within 0.3% of perfect straight.

Description: In this paper, the ${rm RuO}_{2}$ sensing film is fabricated by the sputtering system, and the miniature reference electrode is fabricated by the screen printed technique for integrating the ${rm RuO}_{2}$ thin film in the array flexible sensor. Furthermore, the computer numerical control technique is used to fabricate the stainless model of the fluidic channel, and polydimethylsiloxane is used as the material of the fluidic channel. Finally, the array flexible sensor is integrated fluidic channel to form the potentiometric biosensor of the fluidic. The property of the fluidic channel is analyzed by differential pressure meter to measure the pressure drop and discuss the effect of related factors. In this paper, the ${rm RuO}_{2}$ based pH sensor can obtain a higher sensing value at 61.3 mV/pH with super-Nernstian response. Besides, due to silver's excellent stability and conductivity, the miniature reference electrode is fabricated by screen printed technique to fix silver at the polyethylene terephthalate substrate. The sensitivities of the sensor of 61.31, 59.65, and 56.45 mV/pH with flow rates of 10, 20, and 30 ml/min, respectively, are obtained. The experimental result demonstrates that the potentiometric biosensor can be applied to detect the fluidic concentration.

Description: A fiber Bragg grating (FBG) sensor employing an interrogation scheme based on erbium-doped fiber (EDF) edge detection filter, with enhanced detection bandwidth and intrinsic temperature insensitivity, is proposed and experimentally demonstrated. The edge filter is based on the spectral dependence of absorption in EDF with the possibility of tailoring the absorption profile using appropriate lengths of EDF. A wide filter bandwidth of about 10 nm and a slope detection sensitivity of 1.0 dB/nm in the C-band is demonstrated and validated by simulation results. The proposed scheme is versatile and allows for simultaneous interrogation of multiple FBGs.

Description: A novel method to fabricate a composite material made by compressing Zinc Oxide (ZnO) crystals and cellulose fibers is reported. The fabricated material shows electrical photoconductivity changes when exposed to ultraviolet (UV) light. Mixing cellulose fibers with ZnO yields a higher photosensitivity than the one obtained from devices mainly made of ZnO. The structural, electrical, and photosensitivity tests are performed for these mixtures with the goal to determine the mechanisms enhancing their sensitivity as well as finding an optimal ZnO–cellulose composition for the fabrication of sensors. A device made from a mixed 50–50 wt% composition of ZnO and cellulose yields the best sensitivity to UV, suggesting that the enhancement could be because of the higher oxygen permeability of the cellulose matrix facilitating the ${rm O}_{2}$ adsorption–desorption processes on the ZnO surface.

Description: The detection of terpene vapors, a group of biomarker vapors emitted by plants during their growth process, is an efficient way to monitor plant growth status and control plant pests and disease. In this study, a gas sensor based on the localized surface plasma resonance (LSPR) of Au nanoparticles (Au NPs) is proposed for the terpene vapors detection. Au ion sputtering method is used to deposit Au NPs on transparent glass substrates. The dependence of transmission spectra on the morphology of Au NPs prepared by different sputtering conditions is investigated. In order to enhance the sensitivity and selectivity of the sensor, thiolate modification is applied to form the selective soluble monolayer on the surface of Au NPs. The results indicate that different thiolates could form different steric capping layers, and the responding ability of the LSPR sensor is verified by a red-shift of the minimum transmittance in wavelength $(Deltalambda_{min})$ and a decrease in the minimum transmittance $(Delta{rm T}_{min})$ upon exposure to terpene vapors.