ALBERT

Beschreibung: An improved glucose-sensitive membrane (GSM) was prepared by immobilizing glucose oxidases (GODs) onto silica mesocellular foams and trapping them in a polyacrylamide gel. This gel was then coated on a gold/glass sheet to realize surface plasmon resonance (SPR) sensors. A series of sensing experiments was conducted to obtain the optimized parameters with the improved GSM. The experimental results showed that the improved SPR glucose sensor has a sensitivity of 0.0135 degree/(mg/dL) and a linear range of 0–160 mg/dL. This linear range is twice that obtained with the GSM by immobilizing GODs on SiO 2 nanoparticles.

Beschreibung: Methane is one of the indicative gases in power transformer oil, and the detection of methane dissolved in oil with high accuracy is of great importance for dissolved gases analysis and fault diagnosis inside power transformers. Based on the Beer–Lambert spectral absorption law, dissolved methane detection with tunable diode laser absorption spectrum (TDLAS) is proposed in this paper for the advantages of high sensitivity and resolution. On the basis of wavelength modulation spectroscopy, a specialized TDLAS system was established. To meet the actual needs of field testing, the anti-vibration design of an integrated Herriott cell and a gas pressure (P)/temperature (T) setting are worked out. Photodetector, collimator, and Herriott cell are integrated into one component to reduce the effects of vibration. It is investigated that the temperature has little effect on the second harmonic amplitude in the range of 30 °C ~ 50 °C, and the vacuum pressure is reasonably set at about 1 kPa. Experimental results showed that the resolution of sensitivity could be reached as 6.8 mV/( $mu$ L/L), the maximum deviation was less than $pm 4~mu$ L/L, and the response time is less than 5 min. In the end, field application was also carried out, proving it is a prospective online sensing technique to serve oil-immersed power transformers better.

Beschreibung: This paper presents fixed point operation-based Field Programmable Gate Arrays (FPGA) implementation of Steinhart–Hart Equation (SHHE) for thermistor linearization. FPGA implementation issues of SHHE are presented and their solutions are proposed and experimentally validated in a LabVIEW TM environment. Experimental temperature calibration, performed using a M/S Fluke drywell calibrator, revealed a lowest nonlinearity of 0.11% for an industrial grade thermistor in the input temperature range from −20 °C to 120 °C. Therefore, the main contribution of this work is to demonstrate the lowest nonlinearity for a wider temperature range. This work is expected to be very useful to instrumentation engineers as it employs a time-tested technique, for thermistor linearization in FPGA, leading to the lowest nonlinearity for a larger input temperature range.

Beschreibung: This paper reports on a novel force/moment transducer small enough to replace the root of an artificial tooth. Its dimensions of 4.5 mm in diameter and 16.4 mm in height are identical to the former state-of-the-art design. However, the new design requires a significantly reduced assembly effort and imposes lower demands on the external read-out periphery. The latter improvement facilitates the simultaneous operation of a larger number of force/moment transducers. The novel design was optimized using the finite-element analysis, whose results are experimentally validated. The new design and the former state-of-the-art design are extensively tested with the same test procedure for ranges of ±3 N and ±30 Nmm. The measurement accuracies are measured to be 10, 23, and 64 mN for the forces $f_{x}$ , $f_{y}$ , and $f_{z}$ , respectively, and $161times 10^{-3},,text {Nmm}$ , $302times 10^{-3},,text {Nmm}$ , and $42times 10^{-3},,text {Nmm}$ for the moments $m_{x}$ , $m_{y}$ , and $m_{z}$ . Despite the simpler assembly effort and device handling, the accuracy is better or at least close to former designs. Especially, the more critical force measurements are significantly improved. Long-term stability tests show only little change in measurement performance of the two designs in time.

Beschreibung: This paper illustrates the extension of Rayleigh wave-based surface acoustic wave (SAW) viscosity and density sensor previously developed by the authors for integration with microfluidics and printed circuit board (PCB)-based electronics. The SAW device is first modeled with a microchannel and analyzed using finite-element method (FEM) software. Precise fabrication, alignment, and bonding of polydimethylsiloxane microchannels on diced $Y$ - $Z$ lithium niobate substrates are accomplished. A high-frequency PCB is built to obtain a better performance for SAW device testing. Low glycerin concentrations in deionized (DI) water are analyzed. The FEM simulation results and vector network analyzer measurements of the devices with the microchannel and PCB integration are presented. For low-frequency SAW sensor, a sensitivity of 171.9 Hz/(% glycerin) or 5.57 kHz/(kg/ $text{m}^{2}surd text{s}$ ) in frequency shifts, 0.09°/(% glycerin) or 2.92°/(kg/ $text{m}^{2}surd text{s}$ ) in phase difference, and minimum signal-to-noise ratio of 13.9 dB are achieved at peak frequency of 29.7 MHz. On the other hand, high-frequency (86.1 MHz) SAW sensor provides a sensitivity of 937.5 Hz/(% glycerin) or 37.15 kHz/(kg/ $text{m}^{mathbf {2}}surd text{s}$ ) in absolute frequency shifts, 0.37°/(% glycerin) or 14.7°/(kg/ $text{m}^{mathbf {2}}surd text{s}$ ) in phase difference, and minimum signal-to-noise ratio - f 20.5 dB.

Beschreibung: Distributed Temperature Sensing (DTS) is a technique that uses the interaction of laser pulses with silica to continuously sense temperature along the length of fiber-optic cables. The temporal and spatial resolution of DTS makes it an excellent technique for monitoring the performance of district-scale geothermal exchange borefields. A dynamic, double-ended calibration routine developed in response to site-specific challenges and constraints (i.e., more than 5 km, many splices, different fiber segments, and extended observation periods) is systematically presented and analyzed to provide novel insight on calibration considerations. Results show that different combinations of calibration baths may change calibration accuracy, and over determination in the calculation of calibration parameters provides greater accuracy. Fixing the $gamma $ calibration parameter does not appreciably change accuracy but does provide a buffer against error from variations in calibration bath temperatures. Differential attenuation varied by up to 25% between discrete fiber sections and should be calculated for each array section to prevent errors generated from applying just one attenuation coefficient value for the entire fiber array. Furthermore, dynamically calculated differential attenuation may vary systematically with time and space. In a double-ended configuration, the consideration of whether the forward, reverse, or some combination of all light data is used will affect the robustness of the calibration over time. Each of these results may assist in thoughtful consideration of calibration design at future DTS installations facing similar challenges.

Beschreibung: This paper is conducted to design, fabricate, and characterize a novel high-density large-scale ultrasonic transducer, which is based on a $64times 4$ array of 0.753 MHz piezoelectric micromachined ultrasonic transducer (pMUT) with $100~mu text{m}$ size and $120~mu text{m}$ pitch. The fill factor of the array is 69.4%, which is higher than the other arrays in reports. Sol-gel method with layer-by-layer annealing is used to fabricate isolated piezoelectric lead zirconate titanate elements into a piezoelectric layer. The membrane of the pMUT is released by backside deep silicon etching. The impedance-frequency spectrum of a $4times 5$ subarray of the transducers is characterized by HP 4294A impedance phase analyzer. As a result, the mean value resonant frequency is 0.753 MHz, in reasonable agreement with COMSOL Multiphysics simulation results. And the array shows good uniformity in resonant frequency. The equivalent circuit of the transducer is extracted from the spectrum and the admittance circle deduced from the circuit is in accordance with experimental data. The results show that the present array has a good application prospect on ultrasonic imaging.

Beschreibung: Curvature sensors based on polymer optical fibers (POFs) present some advantages over the conventional technologies for joint angle assessment such as compactness, electromagnetic field immunity, and multiplexing capabilities. However, the polymer is a viscoelastic material, which does not have a constant response with stress or strain. In order to understand and model this effect, this paper presents the dynamic characterization of a POF. The effects of temperature, frequency, and loads on the fiber are analyzed for obtaining the influence of these parameters on the polymer dynamic Young modulus and time constant. Results show that a temperature on the range between 24 °C and 45 °C does not lead to considerable variations on the sensor output. Moreover, it is possible to estimate the storage modulus and loss factor from the frequency and temperature. The polymer time constant is defined on creep recovery experiments. Since the viscoelastic parameters are evaluated in different conditions of temperature, frequency, and load, a model for the stress behavior of the fiber is proposed. Such model leads to a root mean squared error between the modeled and measured results over 15 times lower than the one obtained with the model for bending stress without account the POF viscoelastic behavior.

Beschreibung: Near-infrared spectroscopy (NIRS) is a widely-used noninvasive optical technique for measuring concentration of hemoglobin species in human tissues. Despite its potential, NIRS has seen limited clinical application largely due to a lack of in-vivo standard reference. Hence, cross-validation studies to validate novel NIRS instrumentation against established NIRS devices are needed. This in-vivo study compared a wearable continuous-wave (CW-NIRS) oximeter against a non-wearable frequency-domain (FD-NIRS) oximeter on optical properties and hemoglobin concentrations. To measure absolute coefficients and stoichiometric hemoglobin concentrations, the CW-NIRS oximeter exploits spectral properties of water. Both CW-NIRS and FD-NIRS provided physiologically-valid measurements in skeletal muscles during normoxia, hypoxia, and hyperemia. Although absorption-scattering crosstalk was evident, absorption coefficient $mu _{a}$ and reduced scattering coefficient $mu '_{s}$ at 690nm and deoxyhemoglobin concentration (HbR) were mostly within agreement limits, and the measurements differed principally by a systematic offset. Specifically, CW-NIRS estimated larger $mu '_{s}$ values (+2 cm −1 ) and smaller $mu _{a}$ (from −0.04 to −0.08 cm −1 ) at all wavelengths. The results suggest that lower-cost, wearable CW-NIRS oximeters are a potential alternative to FD-NIRS to measure optical properties and molar concentration of oxyhemoglobin and HbR in skeletal muscles in-vivo as long as the estimated water content is reasonably accurate.

Beschreibung: Simultaneous measurement of hydrogen concentration and temperature with high sensitivity and high precision was realized by integrating a photonic crystal fiber (PCF) modal interferometer and a high-birefringence fiber loop mirror (HBFLM). The PCF was coated with sol-gel Pd/WO 3 coating, whose refractive index and volume would be changed along with the variation of surrounding hydrogen concentration or temperature, and then the resonant dip of PCF modal interferometer would shift accordingly. Meanwhile, the resonant dip of the HBFLM has a high sensitivity to surrounding temperature. By integrating PCF modal interferometer and HBFLM together, the two independent resonant dips that can be simultaneously monitored at the output spectrum of the integrated interferometers would all shift with the change of external hydrogen concentration or temperature. Finally, combined with the dual-wavelength matrix method, the hydrogen concentration and temperature could be simultaneously measured. Experimental results showed that the resonant dip of the PCF modal interferometer moved in the short wavelength direction with the increase of hydrogen concentration, and the sensitivity of the hydrogen concentration was −1.12 nm/% within the concentration range from 0% to 1%. In the process of temperature change, the HBFLM realized a higher temperature sensitivity of −1.84 nm/°C. The sensor had high sensitivity, low cost, and simple structure.

Beschreibung: A novel simple and rapid detection method for interferon-gamma (IFN- $gamma$ ) was developed based on a label-free single-stranded DNA (ssDNA) and thioflavin T (ThT). The ssDNA is the aptamer of the IFN- $gamma $ . The aptamer is a G-rich oligonucleotide, and it can fold into a G-quadruplex structure in the presence of ThT, resulting in a high fluorescence emission. Upon the addition of the target, the aptamer combines with its ligand due to higher affinity and specificity, leading to the disruption of the G-quadruplex and the release of ThT. A remarkable decrease of fluorescence was observed. The proposed strategy shows a limit of detection at 1 nM in both buffer and diluted serum. Moreover, the detection of IFN- $gamma $ can be finished in several minutes and it can be used repeatedly.

Beschreibung: This paper presents a microwave angular displacement sensor that consists of a curved two-metal-layer coplanar waveguide (TML CPW) loaded by an electromagnetic bandgap structure (two semi-cylindrical periodic air-gap structures of dielectrics, allocated at the top and bottom of the curved TML CPW). Rotating one of the dielectrics against the other one, produces a variation in the depth of the stopband at the central frequency. The magnitude change is proportional to the angle of the rotation. The curved TML CPW line with the length of 140 mm is fabricated on a $254~mu text{m}$ thick RO3010 Rogers substrate ( $varepsilon _{r} = 10.2$ and $tan delta = 0.0022$ ), which is arched in a semi-cylindrical shape with a radius of 50 mm. The periodic air-gap structures, in order to create the electromagnetic bandgap, are manufactured by laser cutting of an optically transparent polycarbonate ( $varepsilon _{r} = 2.8$ and $tan delta =0.01$ ) in semi-cylindrical shapes. The analysis, finite element method simulation, realization, and measurements have been performed for the sensor with 15 unit cells. An average sensitivity and a dynamic range of about 3 dB/deg and 5° degrees, respectively, have been obtained at 10.2 GHz. The fixed operating frequency and the wide bandwidth of the sensor (>1 GHz) will simplify the design and fabrication of the data readout circuit. The impact of the structure curvature on the sensor response is also investigated as an important practical issue.

Beschreibung: It is well known that the interferometric synthetic aperture radar (InSAR) can be used to realize the reconstruction of digital elevation models. In common InSAR imaging, the signal is considered complete and accurate enough to generate high-quality images. However, only the sparse aperture measurements are available in the actual imaging process, which bring great challenges to the traditional InSAR imaging algorithms. In this paper, a new method for the 3-D InSAR imaging with sparse aperture is proposed. A gradient-based algorithm is adopted to obtain the high-precision reconstructed signal received from each sparse aperture antenna. Then, the 3-D geometric reconstruction of the target can be realized through the interferometric processing on the master and slave images. Finally, the experimental results are given to substantiate the effectiveness of the proposed algorithm.

Beschreibung: A device-free human detection and tracking system using a received signal strength indicator (RSSI) for an indoor environment is presented in this paper. The proposed system has two major functions: a wireless communication system and a human detection and tracking system. The first function is developed for measuring and collecting RSSI signals affected by human presence and movement, while the second function is developed for detecting and tracking the human using a predefined threshold and a zone selection method. The novelty of our proposed system is that the communication protocol can avoid signal interference and packet loss in the network, and the detection and tracking method can specify an actual zone that the human is present by taking an optimal predefined threshold and a level of RSSI variation in each zone into consideration. The proposed system is verified by experiments, and various human movement patterns with different directions and speeds are tested. The experimental results show that the proposed communication protocol can significantly provide communication reliability, and the proposed method can properly detect and track human movements. The packet delivery ratio indicating communication reliability is almost 100%. Detection and tracking accuracy measured by the number of times the method can detect and track the human with the correct zone is almost 100% in all cases of one man movements.

Beschreibung: The use of affordable amendments required increasing the sensitivity and functionality of electrochemical devices is still challenging. Novel scalable, gold nanoparticles-grafted nitrogen-doped graphene nanostructured polyaniline nanocomposites were stupendously developed in this paper. The charge transfer resistance was dramatically decreased from 11000 $Omega $ (for bare fluorine doped tin oxide electrode) down to 115 $Omega $ (for the nanocomposite-modified electrode). The present nanocomposites provided a superb opportunity for the design of electrochemical biosensors with extraordinary performance via enhanced analyte sensitivity for the detection of ascorbic acid (0.640 mM detection limit at signal to noise ratio = 3, and two linear ranges of 0.96–4.66 and 5.06–9.86 mM with the sensitivity of 10.44 and $28.91~mu text{A}$ . mM $^{-1}$ . cm $^{-2}$ , respectively), and high selectivity over electroactive components interfering species, commonly found in real serum samples.

Beschreibung: The ambient assisted living (AAL) technology aims to provide more safety and self-sufficiency, while permitting older persons to live self-dependently in their homes. Monitoring of activities of daily living (ADL) is one of the key ideas of AAL. This becomes an interesting research idea in modern world, where condition monitoring of various ADLs and their automatic classification is a big challenge. This paper proposes a new approach for activity recognition of motion primitives relying on the sparse representation of signals, where signals are represented using a sparse combination of atoms from an over-complete dictionary. This paper intends to investigate the suitability of applying dictionary learning algorithms like K-singular value decomposition (K-SVD), which is usually used to construct an over-complete dictionary, for the effective progress of the ADL monitoring system. This paper proposes to formulate the classification approach by using SRC classifiers, based on the dictionaries learned using K-SVD algorithm. We have validated our proposed approach on a publicly available ADL data set of wrist-worn accelerometer sensor for activity recognition. Performance evaluations demonstrate that the proposed method outperforms several other competing methods.

Beschreibung: In this paper, throughput maximization in a wireless energy harvesting uplink is considered. For fairness, we assume that each node’s throughput cannot drop below what it achieves by direct transmission to the base station. The throughput is maximized using data relaying and by optimally assigning a role to each node, i.e., relay, source (direct transmission), or user (of a relay). Both centralized and decentralized algorithms that find the optimal assignment of each node are proposed and studied. We consider fixed and variable transmit power scenarios and address complexity issues. Our algorithms are shown to have a linear or quadratic complexity compared with the exponential complexity of the brute force approach. Compared with cooperative transmission, our approach maximizes the overall throughput of the network such that no node’s throughput is adversely affected.

Beschreibung: Presents a listing of the editorial board, board of governors, current staff, committee members, and/or society editors for this issue of the publication.

Beschreibung: Nowadays, multi-sensor networks are evolving into large scale networks with limited bandwidth and energy reservoirs. Hence, reducing the number of information exchanges among the sensors is an efficient approach to meet the stringent requirements of bandwidth and energy in the context of multi-sensor state estimation. In this paper, a surprisal-based multi-sensor information filtering is proposed to allow on average a desired number of sensors with most informative measurements to participate in the information exchange, while discarding the sensors with non-informative measurements and outliers. The concept of surprisal is used to facilitate the sensors in the network to independently classify their measurements as informative, non-informative and outliers by setting upper and lower thresholds. Simulation results show that the proposed scheme ensures that on average only a desired number of sensors with the most informative measurements participate in the information exchange and achieves greater estimation accuracy compared to the method, where the sensors are selected randomly for the same number of transmissions.

Beschreibung: Target discrimination plays an important role in the typical synthetic aperture radar (SAR) automatic target recognition (ATR) system. The conventional discrimination features roughly describing the difference between the target and the clutter are useful to discriminate the target from natural clutter, but these features may not well discriminate the target from the artificial clutter. To solve the above problem, a new algorithm for target discrimination is proposed based on the scattering center feature and the K-center one-class classification in this paper. The amplitudes and locations of the scattering centers have not been used as discrimination feature to our best knowledge, even though the distributions of the scattering centers associated with the targets are different from those of the natural clutter and artificial clutter. Then, since the scattering center feature is a typical kind of point set feature, we improve the K-center one-class classification based on Hausdorff distance (HD), where HD is a distance measure for the point set feature. Experimental results based on the measured MiniSAR dataset show that the discrimination performance of the scattering center feature is better than that of the conventional discrimination features, especially for the artificial clutter.

Beschreibung: This paper presents a new analog-to-digital conversion scheme for a second-order $Sigma Delta $ incremental analog to digital converter (ADC) that can be employed in a compressive sensing (CS)-based CMOS image sensor (CIS) as a column-parallel ADC. The conversion scheme removes image distortion from a reconstructed image by making the ADC output codes represent an average of the ADC inputs. In addition, a new multiplexing scheme implementing a compressive sensing matrix helps to reduce hardware complexity and control compression ratio without hardware modifications. A $160times 160$ pixel CS-based CIS fabricated in $0.11~mu text{m}$ CIS process successfully demonstrates the proposed schemes.

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Beschreibung: Presents information on the IEEE Sensor Journal cover/frontispiece competition.

Beschreibung: Variable gas diffusion cell geometries were tested for the extraction of dissolved inorganic carbon (DIC) from a microfluidic (tens to hundreds of microliters) seawater sample. With a focus on optimization of diffusion cell geometry, we compare five unique diffusion cell designs. Using 3-D printing technology to streamline the prototyping and testing process, we were able to conceive, design, fabricate, and thoroughly evaluate each design over the course of about one month. In total, 1043 DIC measurements were carried out in 109 experiments for the five working manifolds. We find that a small diameter, cylindrical diffusion cell design offers several advantages over its planar counterparts and a larger diameter cylindrical cell, most notably the ability to increase the ratio of the exchange membrane’s contact surface area to solution volume (the “aspect ratio”) without sacrificing channel integrity. Multiple designs approached short-term repeatability of <1%, but only the cylindrical diffusion cell design allowed for <0.2% repeatability using less than 200 $mu text{L}$ of sample.

Beschreibung: Due to the continuous improvement of solid-state lighting technologies, multispectrum, multicolor LEDs have been used as transmitters for wavelength division multiplexing visible light communication (WDM-VLC) techniques. Although the multispectrum LEDs can emit light with different wavelengths for multichannel transmission, the overlapped spectra across the WDM channels could cause high interband multichannel interferences (IBMCI). Accordingly, the large-scale filter-array detectors (LFDs) have been adopted to WDM-VLC techniques and shown high capability for the IBMCI rejection using the maximum signal-to-interference-plus-noise ratio (SINR) combining (MSC) method. However, in the MSC method, it requires 100% filter array usage ratio, which would potentially result in costly computational complexity. In this paper, we propose two approaches, namely, conjugate gradient (CG) algorithm approach and binary particle swarm optimization (BPSO) algorithm approach, for sparse filter selection. According to both simulation and experimental results, the proposed CG algorithm approach can significantly reduce the filter array usage ratio by up to 70% while maintaining a good detector output SINR. The proposed BPSO algorithm approach can provide a near optimal detector output SINR while maintaining a good reduction of filter array usage ratio.

Beschreibung: Milk adulteration is one of the most dishonest food preparation, which not only reduces the nutritional value but also causes various diseases to human. Some of the common adulterants are detergents, ammonium sulphate [(NH 4 ) 2 SO 4 ], sodium hydroxide (NaOH), sodium-bi-carbonate (NaHCO 3 ), and common salt (NaCl). The aim of this paper is to identify the minimum detectable limit for the above five adulterants in milk. An impedance sensor is used, which is sensitive to the ionic concentration of the measuring medium and gives different phase angle of the impedance, when immersed in different adulterated/unadulterated milk. Signal transduction circuit is designed to convert the phase angle to voltage and for display in liquid crystal display. By this detection system, the limit of detection of adulterants in milk with different fat % (from 1.5% to 20%) is studied. Commercial packet milk, ultra high temperature milk, and raw-milk (directly collected from the milk collection center) are used for the experiment. Experimental results are plotted in origin software and statistical analysis method analysis of variance is applied on experimental data for verification of the result and to check the data consistency.

Beschreibung: In induction home appliances, the characterization of the physical properties of the vessel allows for better control strategies and new cooking functionalities. Current modelling techniques calculate a simple ${R}$ – ${L}$ equivalent circuit that models the inductor impedance taking into account all the physical coupling parameters, but these techniques do not allow to directly extract the physical parameters, such as vessel material. In this paper, a new methodology for online detection of the pot material is presented. On this approach, the inductor included in the hob simultaneously serves as heating element and sensor. First, harmonic impedances are calculated by spectral estimation from the currents and voltages waveforms recorded at the inductor. Then, a feature set, including four harmonic impedances and the power factor, is processed by machine learning algorithms for the identification of the pot material. The material identification system is implemented onto an embedded processor similar to those included in current induction hobs; thus, smart sensing features are incorporated onto a domestic cooker without using additional sensors, at no additional cost.

Beschreibung: Multi-scale geometric analysis, one of the most often-used multi-sensor image fusion (MSIF) techniques, can offer outstanding performance during extracting the features of source image. Interval type-2 fuzzy sets (Type-2 FS) have a good prospect in image fusion field, because it can effectively address the uncertain and fuzzy problem in image fusion for selecting the high-quality pixels or coefficients of source images. We try to extend the application fields of Type-2 FS and improve the performance of MSIF; therefore, this paper presents a hybrid method by combining the local spatial frequency (LSF) with interval Type-2 FS in nonsubsampled shearlet transform (NSST) domain. NSST is used to decompose source images, and interval Type-2 FS and LSF is employed to extract the regional features of source images; so it can extract and fuse the detailed features of different source images accurately. First, NSST is performed to decompose the source images into low frequency and high frequency sub-images. Second, LSF-based fusion rule is applied to fuse low frequency sub-images. Thirdly, a novel fusion process based on interval Type-2 FS is designed to fuse high frequency sub-images. At last, inverse NSST2 (INSST) is implemented to reconstruct the fused images. The experimental and contrastive results of different image sets show that the proposed method is an effective MSIF scheme, which can achieve better fusion effect than the existing representative methods.

Beschreibung: A high-performance fiber-optic relative humidity (RH) sensor was prepared by layer-by-layer self-assembly of polycation, poly (4-vinylpyridinium chloride), and polyanion, sodium alginate, on the surface of a thin-core fiber modal interferometer. The process of layer-by-layer self-assembly was monitored by UV-vis spectroscopy and surface profilometer. The morphology of the fabricated multilayer film was characterized by atomic force microscopy and field emission scanning electron microscopy. A fast, reversible, and linear response to RH with a high resolution of 0.1 nm/1% RH has been experimentally demonstrated by the proposed fiber-optic sensor.

Beschreibung: A small-period long-period grating (LPG) with a period of $40mu text{m}$ fabricated in a single-mode fiber by femtosecond laser direct writing has been demonstrated. A series of high-order Bragg resonant peaks of Bragg grating and attenuation bands of LPG can be observed simultaneously in the broadband spectrum range that exhibited different responses to surrounding refractive index, temperature, and axial strain. Meanwhile, we provided a sensitivity matrix to correct the errors caused by temperature in measurements of refractive index and strain to achieve a dual-parameter fiber sensor at high temperature.

Beschreibung: In this paper, we propose a simple nonlinear equation to describe the cross-sensitivity between temperature and refractive index in fiber Bragg grating refractometers. A numerical analysis using Comsol Multiphysics software was performed to understand how the effective index changes with the temperature and refractive index. The sensor response to refractive index (from 1.33 to 1.45) and temperature (from 15 °C to 45 °C) was fitted using a surface equation. Even though the refractive index range considered being significantly large, and the sensor response being nonlinear, proper concordance between computer simulations and experiments point out that this multivariable equation is suitable to describe the Bragg wavelengths as a function of temperature and refractive index. When applied to multimode fiber Bragg gratings, the proposed equation can be used to construct a system of equations to calculate temperature and refractive index from the measured Bragg wavelengths.

Beschreibung: Phase fraction of oil–water two-phase flow is important to the process control and optimization. In this paper, a prediction model based on the mechanism of ultrasound attenuations in oil–water mixture is presented to estimate the phase fraction. This model consists of physical parameters of the two-phase flow and ultrasound frequency, by incorporating the scattering and attenuation of ultrasound in different flow patterns of the oil–water two-phase flow. The nonlinear relationship between ultrasound attenuation coefficient and phase fraction is corrected. An array of 16 ultrasonic transducers with 1-MHz center frequency and 20-Vpp sine acoustic signal is presented to implement this method, and a measuring system was designed and tested on a multiphase flow loop with actual flow experiments. The proposed prediction model showed a good agreement with the online phase fraction calibration in the flow experiments. The average error is 2.3% in water continuous flow, while in 2.8% in oil continuous flow. These findings and the mechanism prediction model provide basic foundations for the phase fraction estimation of oil–water two-phase flow by using the ultrasound attenuation technique.

Beschreibung: Compared with the original backprojection (BP) algorithm, the fast factorized BP algorithm accelerates enormously. As it is known to all, 2-D image interpolations are always utilized to raise the accuracy, yet leadings to the tradeoff with the efficiency. In this paper, a novel factorized BP algorithm based on Cartesian coordinate without interpolation, is proposed for high-resolution spotlight SAR with much better efficiency and accuracy. The innovative idea is achieved by establishing two spectrum compressing filters to decrease the cross-range Nyquist sampling rate enormously, thus avoid spectrum aliasing. The proposed algorithm, termed as the Cartesian factorized BP (CFBP) algorithm, can produce images with the similar quality as the BP does, but is better than FFBP, where the interpolations accumulate errors to some extent. The CFBP is designed for spotlight mode working in both the linear and curved trajectories. Simulation results and real-data processing validate the superiorities of CFBP by the comparisons with FFBP and the original BP individually.

Beschreibung: Compressed sensing (CS) for sparse backscattering field recovery from very limited measurements has received increasing attention among the radar imaging community. The chirp (i.e., linear frequency modulated) waveform, benefiting from a large time-bandwidth product, is widely utilized in imaging radars, such as synthetic aperture radars (SARs) and inverse SARs (ISARs). In this paper, the influence of sub-Nyquist sampling jamming on ISAR with chirp waveform is investigated, where the CS-based dechirping (CS-D) algorithm is applied to achieve range compression of the under-sampled jamming signals. The jamming signals, formed by the intercepted radar signals under the sub-Nyquist sampling theorem and scattered by the moving targets, are collected by ISAR to form a (2-D) array and the azimuth compression is done via conventional Fourier transform. The main novelty of this framework is twofold: 1) the CS-D range compression of the under-sampled jamming signals is characterized and 2) the potential of sub-Nyquist sampling jamming is demonstrated against ISAR with the CS-D range compression. Simulated trials and real data of a Yak-42 plane are used to validate the correctness of the analyses and finally, the well-focused false-target images greatly support the effectiveness of the sub-Nyquist sampling jamming idea in the countermeasures of chirp-ISAR with the CS-D range compression.

Beschreibung: Wire-mesh sensors produce 3-D data of void fraction distribution at high resolution thus being an appropriate tool to investigate two-phase gas-liquid flows. Slug flow is typically found in petroleum production lines. This type of flow is characterized by the intermittent occurrence of gas bubbles and liquid slugs along the pipe. An important issue of these flows is the existence of a variety of regimes, depending on the flow rates of gas and liquid. The quantitative and qualitative information about shapes of the bubble nose and tail allows to study and to model the flow characteristics in order to increase safety and efficiency of oil production operations. In this paper, we describe two methods to estimate typical bubble shape from wire-mesh sensor data, which are based on ensemble mean and median approaches. Results from a set of two-phase flow experiments in inclined tubes, show that both approaches produce similar estimations, however since median is a type of robust estimator, contours of bubbles are better defined. 3-D images of typical bubbles, for eight different operational conditions, were generated and reveal some details about bubble shape. In addition, the bubble identification was validated by measuring the gas flow rate in comparison with reference instrumentation.

Beschreibung: Non-contact displacement measurement based on the phase-based microwave interferometry technology has attracted growing interest in recent years. In this paper, aiming to exploit the frequency-modulated continuous wave (FMCW) radar-based vibration monitoring technique, the principle and detailed procedure for extracting the displacement time series of vibration movement are illustrated. The approximate maximum likelihood approach is proposed to extract the phase history of beat signals across multiple sweep periods. Moreover, the measurement accuracy of vibration displacement extraction and several practical issues of this technique are evaluated and concerned. Both simulated and experimental validations are provided to show the effectiveness and robustness of the proposed method and approach.

Beschreibung: This paper gives a solution to solve the interference problem of electronic nose (e-nose), which is ill-posed due to the uncertainty and unpredictability of its instable behavior. Traditional methods for interference suppression are component correction frameworks, which are laborious or little efficient. With interference (especially background interference and sensor drift), the distribution of test data obtained in practical application is different from that of the previous training data. From the viewpoint of machine learning, a novel domain correction and adaptive extreme learning machines (DC-AELM) framework with transferring capability is proposed to solve the serious interference problem in e-nose. The framework consists of two parts: 1) DC, which makes the distributions of two domains close and 2) AELM, which realizes the knowledge transfer at the decision level and makes the robustness of the prediction model improved. This method is motivated by the idea of transfer learning, especially from the perspective of domain correction and decision-making, to realize the knowledge transfer for interference suppression. A background interference data set obtained by our designed e-nose and a public benchmark sensor drift data set are used to verify the effectiveness of the proposed DC-AELM method.

Beschreibung: In this paper, we propose a generalized co-prime multiple-input multiple-output (MIMO) configuration for direction of arrival estimation. Compared with the conventional co-prime MIMO radar that requires prototype co-prime arrays for transmitter and receiver, the proposed configuration enlarges the inter-element spacing of transmitter with an integer expansion factor. By vectorizing the sample covariance matrix, the generalized sum and difference coarray (GSDC) concept is defined for exploiting the advantages of proposed configuration. The analytical expressions for the expansion factor, the maximum consecutive lags, and the number of unique lags are derived carefully. It is verified that GSDC can obtain more degrees of freedom (DOFs) with the increase of expansion factor. Specifically, with $mathcal {O}(M+N)$ sensors, GSDC can provide $mathcal {O}(M^{2}N^{2})$ DOFs, whereas the conventional one only has $mathcal {O}(MN)$ DOFs. Simulation results demonstrate the usefulness of proposed configuration utilizing both spatial smoothing and sparse representation algorithms.

Beschreibung: A switched-capacitor sigma–delta ( $Sigma Delta $ ) CMOS interface circuit for the closed-loop operation of a micromechanical capacitive accelerometer is presented in this paper. A distributed-feedback and feedforward topology is proposed to combine with a high-Q sensor element to obtain a sub- $mu text{g}/surd $ Hz noise floor. The loop stability is implemented by damping the high-Q sensor element in the operation of electrostatic feedback force and heavy phase compensation, which introduces an extra zero to compensate the loop. Besides, the low-frequency loop gain is controlled by off-chip adjusting of distributed-feedback factor to keep the balance between the loop stability and noise shaping ability. The interface circuit is designed and fabricated in a standard 0.5- $mu text{m}$ CMOS process. The chip consumes 10 mW from a single 5-V supply. The measurement results show that the noise level is lower than 400 ng/ $surd $ Hz, and the average noise equivalent acceleration density is 200 ng/ $surd $ Hz over a 700-Hz bandwidth. The input range of the accelerometer is ±0.7 g resulting in a dynamic range of 125 dB over 1-Hz bandwidth. The measured sensitivity of 2.5 V/g is shown with a dc nonlinearity of 0.17%, and the bias instability is $19~mu text{g}$ .

Beschreibung: Intrusion localization plays a significant role in a perimeter system. A precise intrusion localisation method using fiber Bragg grating (FBG) sensors is proposed in this paper. Based on the fixed-simply supported beam theory, FBG strain data are used to establish the intrusion deflection distribution. The intrusion localisation and force identification are realized by deflection curve analysis. In order to optimize the identifying result, an improved particle swarm optimization algorithm is introduced. The experiments and simulation results show that the proposed algorithm performs better than the traditional algorithms in detection precision and stability for intrusion signal identifying.

Beschreibung: Taste sensor with five all-solid-state electrodes (ASSE) III (third version) was used for qualitative and quantitative analysis of selected tonic waters (J.Gasco, Kinley, Jurajski, Jurajski with citrus flavor, Carrefour, Schweppes Indian Tonic, and Schweppes Bitter Lemon). The results obtained by this taste sensor analyzed with principal component analysis, agglomerative hierarchical clustering methods show that this sensor can be applied for discrimination of tonic waters with respect to their composition. Based on sensor’s results, two models for prediction of the content of quinine hydrochloride and total saccharides in selected tonic waters were developed using multivariate linear regression. The results obtained by this analysis in comparison to nominal data (experimentally determined and obtained from manufacturers’) are consistent (range of 0.1%–1.8%). It means that taste sensor with five ASSE III may be a useful tool for the qualitative and quantitative analysis of selected tonic waters.

Beschreibung: A quasi-coaxial system consisting of a central current carrying copper rod and five symmetric return paths takes up to 20 kA. The installation provides a homogeneous magnetic field $mathbf {B_{varphi }}$ to a Taylor–Couette flow. One challenging part of the system is the design of the current distributor, which is supposed to divide the return current into several equally weighted lines. The individual components like the copper rods as well as all electrical contacts provide a characteristic resistance, each in the same magnitude of several $ {mu }Omega $ . By initial installation this will support an imbalance in the current distribution affecting the symmetry of the magnetic field. So the adjustment of current distribution becomes mandatory to ensure maximum field homogeneity. Controlling the outflow temperature of the required water cooling offers an indirect access to set the current by thermostatically operated valves with CO 2 adsorption charge in conjunction with the temperature dependent branch resistance. A numerical investigation proves that a stable current distribution can be achieved by a couple of paralleled thermal controlled heater valves with proportional characteristics. Finally, recent ironless Hall-effect current sensors help to calibrate the system so that the current homogeneity differs less than 1% from optimal state in a wide range of currents.

Beschreibung: Activity classification in smartphones helps us to monitor and analyze the physical activities of the user in daily life and has potential applications in healthcare systems. This paper proposes a descriptor-based approach for activity classification using built-in sensors of smartphones. Accelerometer and gyroscope sensor signals are acquired to identify the activities performed by the user. In addition, time and frequency domain signals are derived using the collected signals. In the proposed approach, two descriptors, namely, histogram of gradient and centroid signature-based Fourier descriptor, are employed to extract feature sets from these signals. Feature and score level fusion are explored for information fusion. For classification, we have studied the performance of multiclass support vector machine and $k$ -nearest neighbor classifiers. The proposed approach is evaluated on two publicly available data sets, namely, UCI HAR data set and physical activity sensor data. Our experimental results show that the feature level fusion provides better performance than the score level fusion. In addition, our approach provides considerable improvement in classifying different activities as compared with the existing works. The average activity classification accuracy achieved using the proposed method is 97.12% as against the existing work, which provided 96.33% on UCI HAR data set. On the second data set, the proposed approach attained 96.83% classification accuracy, whereas the existing work achieved 90.2%.

Beschreibung: A wireless and passive (battery free) temperature sensor that can be embedded inside an orthopedic implant, such as an interference screw, was developed. The sensor is based on an inductive–capacitive–resistive resonant circuit that is inductively powered so the temperature at the implant can be measured wirelessly. A potential application of this sensor is to monitor internal wound temperature for the diagnosis of local infection at the implant site. Infections pose a significant risk to patients, who receive orthopedic implants, often lead to adverse conditions including implant failure, tissue necrosis, and amputation. Current approaches for diagnosing orthopedic implant-associated infections, such as blood tests, radiographic imaging, and histological study are slow, tedious, and nonspecific. In recent years, thermographic imaging has been used to monitor local temperature at the external surgical site as a means to detect infection, but its applications are limited to surface or near-surface wounds. The described sensor will serve as an useful research tool to investigate using temperature as an indication of deep-tissue orthopedic implant infection. When fully developed, this sensor may also improve orthopedic care by allowing simple, early detection of infection at an implant site. This paper describes the design and fabrication of the sensor, as well as characterizes its performance. Experimental results indicate the temperature response of the sensor is reproducible within the tested range of 30–42 °C.

Beschreibung: Recognition of movement is a crucial process to assist humans in activities of daily living, such as walking. In this work, a high-level method for the simultaneous recognition of locomotion and gait phases using wearable sensors is presented. A Bayesian formulation is employed to iteratively accumulate evidence to reduce uncertainty, and to improve the recognition accuracy. This process uses a sequential analysis method to autonomously make decisions, whenever the recognition system perceives that there is enough evidence accumulated. We use data from three wearable sensors, attached to the thigh, shank, and foot of healthy humans. Level-ground walking, ramp ascent and descent activities are used for data collection and recognition. In addition, an approach for segmentation of the gait cycle for recognition of stance and swing phases is presented. Validation results show that the simultaneous Bayesian recognition method is capable to recognize walking activities and gait phases with mean accuracies of 99.87% and 99.20%. This process requires a mean of 25 and 13 sensor samples to make a decision for locomotion mode and gait phases, respectively. The recognition process is analyzed using different levels of confidence to show that our method is highly accurate, fast, and adaptable to specific requirements of accuracy and speed. Overall, the simultaneous Bayesian recognition method demonstrates its benefits for recognition using wearable sensors, which can be employed to provide reliable assistance to humans in their walking activities.

Beschreibung: The deployment of Wi-Fi fingerprint-based indoor positioning systems is severely hindered by the lack of an efficient and low-cost way to establish a signal fingerprint database. In this paper, we present a novel fingerprinting method, slide , that can collect fingerprints in a fast and accurate way. Slide uses a commodity flashlight and a smartphone to achieve linear positioning . This allows automatic mapping from the received signal strength to the position on a line, serving as a building block for fingerprinting in general environments. Slide also features a channel-based scanning method, which acquires fingerprint location after each Wi-Fi channel scanning, to mitigate the fingerprint misalignment problem found in the general mobile fingerprinting. Quantitative analysis and experimental results show that slide is faster than the manual fingerprinting method by up to an order of magnitude with comparable positioning accuracy, and is also more efficient than state-of-the-art mobile fingerprinting methods.

Beschreibung: Feature extraction for fault signals is critical and difficult in all kinds of fault detection schemes. A novel simple and effective method of faulty feeder detection in resonant grounding distribution systems based on the continuous wavelet transform (CWT) and convolutional neural network (CNN) is presented in this paper. The time-frequency gray scale images are acquired by applying the CWT to the collected transient zero-sequence current signals of the faulty feeder and sound feeders. The features of the gray scale image will be extracted adaptively by the CNN, which is trained by a large number of gray scale images under various kinds of fault conditions and factors. The features extraction and the faulty feeder detection can be implemented by the trained CNN simultaneously. As a comparison, two faulty feeder detection methods based on artificial feature extraction and traditional machine learning are introduced. A practical resonant grounding distribution system is simulated in power systems computer aided design/electromagnetic transients including DC, the effectiveness and performance of the proposed faulty feeder detection method is compared and verified under different fault circumstances.

Beschreibung: Gesturing is an instinctive way of communicating to present a specific meaning or intent. Therefore, research into sign language interpretation using gestures has been explored progressively during recent decades to serve as an auxiliary tool for deaf and mute people to blend into society without barriers. In this paper, a smart sign language interpretation system using a wearable hand device is proposed to meet this purpose. This wearable system utilizes five flex-sensors, two pressure sensors, and a three-axis inertial motion sensor to distinguish the characters in the American sign language alphabet. The entire system mainly consists of three modules: 1) a wearable device with a sensor module; 2) a processing module; and 3) a display unit mobile application module. Sensor data are collected and analyzed using a built-in embedded support vector machine classifier. Subsequently, the recognized alphabet is further transmitted to a mobile device through Bluetooth low energy wireless communication. An Android-based mobile application was developed with a text-to-speech function that converts the received textinto audible voice output. Experiment results indicate that a true sign language recognition accuracy rate of 65.7% can be achieved on average in the first version without pressure sensors. A second version of the proposed wearable system with the fusion of pressure sensors on the middle finger increased the recognition accuracy rate dramatically to 98.2%. The proposed wearable system outperforms the existing method, for instance, although background lights, and other factors are crucial to a vision-based processing method, they are not for the proposed system.

Beschreibung: Automatic fall detection is an active research area since several years. Basically, this is motivated by the impact that falls have, in terms of mortality, morbidity, and social costs, which make them comparable to road traffic injuries. The early detection of a fall can be critical to reduce the mortality rate and to limit the associated health consequences. Technological solutions designed to automatically detect and notify a fall may be classified into wearable and non-wearable. Among the former ones, the use of specific devices to be worn by the subject is a very common assumption, but it fails to address user’s acceptability issues. In fact, the position of the sensor or its visibility may be perceived as a stigma associated with the primary function of fall detection. To address such an issue, this paper presents a methodology for fall detection that relies on a pair of smart shoes, equipped with force sensors and a tri-axial accelerometer, able to detect a fall and notify it to a supervising system. The instrumented footwear enables the analysis of the subject’s motion and foot orientation, recognizing abnormal configurations. The developed algorithm is not computationally intensive, and therefore, can be easily executed on board the wearable device. Laboratory tests provided satisfactory performances in falls detection and correct classification: on 544 falls and 136 activities of daily living, performed by 17 healthy subjects, a 97.1% accuracy has been achieved. Further experiments involving two elderly users demonstrate the effectiveness of the proposed method in a real-life scenario.

Beschreibung: Experimental study presented in “Delay Compensation of Tilt Sensors Based on MEMS Accelerometer Using Data Fusion Technique” by M. Ghanbari and M. J. Yazdanpanah is commented. It seems that some of the reported results are affected by errors related to mechanical imperfections of the applied test apparatus, what might have influenced determination of parameters of models of the applied complementary and Kalman filters. Appropriate modifications of the test apparatus are proposed. An alternative method of processing the experimental data is suggested.

Beschreibung: The real-time electromagnetic tracking method has been widely applied, despite its limitations such as a high computational cost and complex hardware components. In this paper, a simple and efficient electromagnetic tracking approach, with both 3-D and 6-D pose tracking, is proposed. This approach utilizes the geomagnetic field and the magnetic field generated by the 2.5-kHz sinusoidal signal from a uniaxial transmitting coil. By extracting both the alternating current (AC) and direct current (DC) components from the outputs of a miniature tri-axial magneto-resistive sensor, the position and orientation parameters of the sensor can be computed by using the combination of the geomagnetic orientation algorithm and the magnetic dipole model-based localization algorithm. Since the implementation of the tracking algorithm is based on a sextic equation, this proposed approach is simple and fast. Experimental results show that the root-mean-square value of the position error is 2.6±0.79 mm and the orientation error is 1.4±0.61°. This tracking approach has simple structures of both software and hardware but promising performance and applicability.

Beschreibung: This paper deals with the capability characterization of a recently developed novel fiber optical tip force sensing needle. The needle can directly measure the axial force required to penetrate a tissue at its tip, which can then be used for in vivo identification of tissues through either a robotic or a manual needle procedure. To characterize the needle’s force sensing capability, ex- vivo experiments are conducted using both phantom human tissues and swine belly tissues. Various factors relevant to tissue identification are investigated, including needle advancing rate and displacement, automated and manual modes of needle insertion, needle-tissue frictional force, and types of tissues. Furthermore, data of forces versus types of tissue are obtained for tissue identification, based on phantom and swine tissue insertions. By means of this database, two tissue identification experiments are performed, which are a multiple layered tissue and swine muscle with neoplasm tissue with the insertion being repeated 15 times per tissue. The result shows that 66.7% of the multiple layered tissue and 86.7% of the neoplasm tissue are successfully identified.

Beschreibung: With the increase of large outdoor advertising boards, the issues of public safety raised by the collapse of outdoor advertising boards have attracted great public concern. In this paper, a wireless sensor network (WSN) monitoring system is designed for the structural health monitoring of large outdoor advertising boards. By using the WSN technology, this system can judge the security of the outdoor advertising boards and give early warnings when the boards are being in danger. The monitoring system consists of two subsystems, one is the WSN structure system based on ZigBee wireless sensor nodes with a six-axis MEMS motion sensor integrated to capture the movement information, and the other is the monitoring center system controlled by ARM microcontroller for data processing and long-distance wireless communications with remote server through a GPRS module. The simulation model of outdoor advertising board is also built to analyze the deformed shape of the advertising board structure under wind load, and the early warning judgment standard is proposed. The performance of the monitoring system is evaluated through several experiments under the condition of laboratory in different aspects of the comparison experiments. The experimental results indicate that the WSN monitoring system can real timely and accurately monitor the state of the outdoor advertising boards.

Beschreibung: Arthritis remains a disabling and painful disease, and involvement of finger joints is a major cause of disability and loss of employment. Traditional arthritis measurements require labour intensive examination by clinical staff. These manual measurements are inaccurate and open to observer variation. This paper presents the development and testing of a next generation wireless smart glove to facilitate the accurate measurement of finger movement through the integration of multiple IMU sensors, with bespoke controlling algorithms. Our main objective was to measure finger and thumb joint movement. These dynamic measurements will provide clinicians with a new and accurate way to measure loss of movement in patients with rheumatoid arthritis. Commercially available gaming gloves are not fitted with sufficient sensors for this particular application, and require calibration for each glove wearer. Unlike these state-of-the-art data gloves, the inertial measurement unit glove uses a combination of novel stretchable substrate material and nine degree of freedom inertial sensors in conjunction with complex data analytics to detect joint movement. Our novel iSEG-Glove requires minimal calibration and is therefore particularly suited to the healthcare environment. Inaccuracies may arise for wearers who have varying degrees of movement in their finger joints, variance in hand size or deformities. The developed glove is fitted with sensors to overcome these issues. This glove will help quantify joint stiffness and monitor patient progression during the arthritis rehabilitation process.

Beschreibung: Wireless body area networks are being deployed for an ever increasing number of applications. The main research challenges are still related to the quality of the communication link and to the energy consumption. Since WBAN on-body communication channels’ quality varies over time, it is not appropriate to use a static and pre-defined transmission power level (TPL). Nowadays, the vast majority of WBANs use transmission power control (TPC) mechanisms aiming to minimize energy waste during on-body communications, radio interferences, and the energy specific absorption rate (SAR). These goals are achieved by continuously adjusting and updating the TPL. This paper proposes a novel TPC mechanism that employs a hybrid operation principle (closed-loop control together with posture and motion detection) targeting resource constrained devices. This mechanism uses the on-body communication RSSI values to approximate the fading signal during the user’s gait cycle and, simultaneously, the acceleration signal (from inertial sensors) is used to determine the position within the gait cycle. Experimental results shows that the proposed TPC mechanism is capable to achieve up to 35% energy save per packet transmitted compared with the transmissions performed at maximum TPL. Furthermore, the additional traffic overhead is significantly smaller than those verified in other TPCs addressed in the literature. This research shows that all WBAN application requirements identified by IEEE 802.15.6 TG can be ensured in an energy-efficient way without sacrificing reliability and latency.

Beschreibung: This paper proposes a distributed localization algorithm in wireless sensor networks. The algorithm considers the position uncertainty of reference nodes, which have been ignored in the past research, in which imperfect position information of reference nodes intensifies the error accumulation phenomenon. The algorithm calculates position uncertainty by the dilution of precision and presents a balance point between range errors and position errors by applying the modified spring mass method. We verify the feasibility of the proposed algorithm by changing multiple parameters under various circumstances. The result proves that the overall performance of localization is enhanced by considering the position uncertainty.

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Beschreibung: A novel fluorescence probe based on ZnTe quantum dots (QDs) modified by 3-Mercaptopropionic acid had been constructed for the selective and sensitive detection of paeoniflorin. ZnTe QDs were successfully synthesized via a simple method in aqueous solutions. The average size of ZnTe QDs was 12 nm and characterized by transmission electron microscopy and X-ray diffractograms. Upon addition of paeoniflorin into the system, the fluorescence intensity was significantly quenched in buffer solution. This proposed fluorescence sensor can be used to detect paeoniflorin under certain conditions, which pH was 7.5, temperature was 25 °C and incubation time was 20 min. Additionally, the quenching procedure was presumed to be static and the mechanism was proved by the rate constant $K_{q},(9.70 times 10^{11}text {L}cdot text {mol}^{-1}cdot text {s}^{-1})$

Beschreibung: A room temperature reversible ammonia (NH 3 ) gas sensor based on the resistive transduction mechanism comprising of thin film of nickel doped cryptomelane octahedral molecular sieves of K-OMS-2 nanofibers is developed. Ni-OMS2 demonstrated excellent and persistent sensing toward the low concentration of ammonia in air at room temperature. The sensor showed strong response of 20% and 57% for 10 and 50 ppm of NH 3 . No heating was required either for sensing or recovery. Doping concentration of Ni significantly affect the ammonia sensing properties of nanofibers. Low doping of 0.11 Ni +2 in K-OMS-2 resulted in the major improvement in recovery time during ammonia sensing to 40s from 87s in undoped nanofibers. However, higher amount of Ni doping showed no response for ammonia sensing.

Beschreibung: Parallel arrays of silicon nanowire transistors are novel types of transducers under study for chemical and biochemical sensing that exploit the high surface-to-volume ratio of nanowires for sampling of low analyte concentrations and yet provide high output conductance. To investigate the applicability and practical sensitivity of parallel nanowire sensor devices, here, we study their signal-to-noise behavior. Parallel arrays of nominally un-doped Si-nanowires with intruded Ni silicide contacts were characterized by capacitance–voltage, current–voltage, and noise measurements. The power spectral density (PSD) shows a high noise level, which is strongly gate-voltage-dependent. The normalized PSD decreases with the square root of the amount of channel charge, which indicates that the $1/f$ -noise is uncorrelated. Therefore, Hooge’s model can be applied, and $alpha _{mathrm {mathbf {H}}}$ between 7E-1 and 3E-2 is extracted. The input-referred voltage noise of 100 $mu $ VHz $^{{mathbf {-0.5}}}$ and a charge noise of 1000 eHz $^{{mathbf {-0.5}}}$ are obtained at 1 Hz for parallel arrays of approximately 100 nanowires with a 7.4 $mu text{m}$ long conduction channel. It is found that the smallest input referred noise level is obtained when operating the device directly at the threshold voltage $text{V}_{mathrm {mathbf {th { }}}}$ independent of the device gate length. Using Al 2 O 3 as io- -sensitive dielectric, the presented devices are employed as pH-sensors. It is found that the Ag/AgCl reference electrode is adding a large level of correlated drift, when used in continuous voltage sweeping mode, which dominates the low-frequency noise.

Beschreibung: A new, non-contact, planar spiral coil-based inductive displacement sensor is presented in this paper. The proposed sensor employs a fixed planar coil and a movable $U$ -shaped magnetic core. The sensor is designed such a way that the shape of inductance versus displacement $x$ is sinusoidal. Due to this feature, the value of $x$ is obtained easily from the inductance measured without the need of a look-up table, which is not the case for most of the planar coil-based sensors. The proposed sensor has very low sensitivity to vertical misalignment of the core. A phase-sensitive detector-based measurement scheme is employed to measure the inductance. The inductance characteristic of the proposed sensor is symmetric with respect to the center of the coil. A simple capacitive detection scheme to distinguish the position of the core between the two halves of the coil is proposed in this paper. This method enables to extend the sensor range with multiple coils connected in series. A prototype of the proposed sensor has been developed and tested. The sensor has a worst case error of 0.6%. A modified sensor using two coil sets has been developed. The modified sensor has high sensitivity over its entire range, unlike the first prototype. It has a worst case error of 0.2% and a resolution of 6.5 $mu text{m}$ . The low-cost sensor developed will be useful for many industrial linear position sensing applications.

Beschreibung: This paper presents an analytical model for a recently introduced class of 2-D directional anemometers based on fluidic structures capable of averaging the differential pressure developed by the wind across distinct diameters of the transverse cross-section of a single cylinder. In previous works, it was found that performing the average over a proper set of diameters produces a differential pressure that depends on the wind direction according to a cosine law, allowing simple direction estimation. This fact, which was not investigated in previous articles, is explained in this paper taking into account symmetry and angular spectral properties of the pressure distribution. Besides analyzing previously proposed devices, this paper introduces several new configurations, which are classified according to the type of average and number of diameters involved. Comparison of the estimated performances with the experimental results obtained in earlier works clearly shows that prototypes proposed so far were far from achieving the best theoretical accuracy, suggesting that significant improvements can be obtained by re-design of the fluidic structures.

Beschreibung: Results are presented for the design and testing of a vibration energy harvesting device that converts ambient mechanical vibration into electricity. The working principal of the device is based upon internal resonance—a nonlinear dynamic response in which vibration modes of a structure can couple when their natural frequency ratios occur as integer multiples. The resulting response enables the harvester to generate power over an extended frequency range in comparison to linear-dynamics-based harvesters when subject to harmonic external excitation. Measurements of displacement and power generated from a prototype demonstrate this behavior. The prototype is also shown to the generated maximum power under random base excitation when the ratio of the first two natural frequencies is closest to 2:1.

Beschreibung: Dissolved oxygen (DO) is essential for aquatic life, but is consumed during the decomposition process of the organic matter in water. It is used as a primary indicator of water quality, and is also crucial for the efficiency of the waste water treatment process. Hence, a sensitive, long term reliable, in-line DO sensor is essential for sustainability of water ecosystems and management of water resources. This paper introduces a low-cost, all-solid state DO sensing device by the integration of polyhemin-based DO sensitive electrode and Pd/H reference electrode. Low cost electrodeposition techniques are applied in both the DO sensitive electrode and the Pd/H reference electrode synthesis. First, the operation parameters of the Pd/H reference electrode was characterized to obtain the adequate lifetime and response time of reference for DO sensing application. The regeneration procedure of the reference electrode is also investigated to achieve multi-usage of this Pd/H electrode. Consequently, this DO sensing device has a sensitivity of 1.3 ( $mu text{A}$ /cm 2 )/(mg/L) over a DO concentration range of 1.5 – 20 mg/L. The DO sensing applications in various water samples including tap water, simulated surface water and wastewater are also demonstrated. The all solid-state feature allows this sensing device to be applied as a long-term DO sensor for continuous, in-situ water monitoring.

Beschreibung: The electronic properties and the adsorption behavior of n-butylamine on B 40 borospherene molecular device are studied using the density functional theory in combination with the non-equilibrium Green’s function method. The device density of states spectrum demonstrates the variation in peak maxima, and the molecular orbitals between the borospherene base material and the target vapor show the transfer of electrons. $I - V$ characteristics confirm the variation in the current upon adsorption of n-butylamine vapor molecules on borospherene device. The findings from the quantum chemical studies infer that borospherene molecular device may be used to detect n-butylamine vapors in the trace level.

Beschreibung: Pristine and different amounts of praseodymium oxide (Pr 6 O 11 )-functionalized tin oxide (SnO 2 ) flower-like architectures were synthesized by a facile one-step hydrothermal method. Their crystal structure, surface morphology, and chemical compositions were analyzed by XRD, SEM, TEM, and XPS. Measured results showed that Pr existing was in the form of Pr 6 O 11 . Compared with pristine SnO 2 architectures, the gas sensing properties toward acetone of Pr 6 O 11 -functionalized SnO 2 architectures could significantly be enhanced under different working temperatures. The response of the as-synthesized Pr 6 O 11 /SnO 2 (Pr (mol) :Sn (mol) = 1:50) sensor to 100 ppm acetone was about 27, which was about three times higher than that of pristine SnO 2 architectures. The response/recovery time was 2/36 s at 200 °C. When acetone concentration was down to 1 ppm, Pr 6 O 11 /SnO 2 (Pr (mol) :Sn (mol) = 1:50) sensor also exhibited an obvious response. Meanwhile, the enhanced gas sensing mechanism of Pr 6 O 11 -functionalized SnO 2 architectures was discussed, and the results indicated that the architectures are promising candidates for the practical acetone sensing.

Beschreibung: The majority of circuits used to sense magnetic tunnel junction devices are clocked (i.e., a clock signal triggers a read operation). However, there are applications in which a continuous read is the desired functionality. We characterize a binary output resistance-to-voltage read circuit designed to continuously sense the state of a magnetic tunnel junction device. It uses a current conveyor architecture, thereby keeping the voltage across the device stable. This allows for greater resilience to load capacitance (e.g., in the device connections). Empirical results measured from a test chip fabricated in a 3M2P 0.5- $mu text {m}$ process are presented, including the demonstration of functional correctness, static properties, and dynamic properties.

Beschreibung: Fullerenes (C60) exhibits many advantageous properties but its poor solubility seriously restricts its applications. In this paper, C60 is dissolved in graphene oxide (GO) aqueous solution homogenously. This water-soluble composite material of GO/C60 is used for making a capacitive humidity sensor. This sensor shows a sensitivity of three times larger than that of the sensor based on C60 film. The possible reason is that C60 is uniformly adsorbed on the surface of GO, thus reducing the agglomeration of C60. This is supported by TEM, FTIR, and complex impedance test.

Beschreibung: Fabrication and characterization of a highly sensitive fiber-optic cholesterol sensor utilizing cholesterol oxidase (ChOx) have been carried out. The operation of the sensor is based on combined phenomenon of localized and propagating surface plasmons. Two different immobilization schemes of enzyme ChOx have been used. In one, the enzyme is entrapped in the hydrogel and in second the enzyme is immobilized over the graphene oxide (GO) nanosheets. The synthesis of GO is confirmed by XRD, TEM, and Raman spectroscopy and the binding between ChOx and GO is verified through the Raman spectroscopy and Fourier transform infrared spectroscopy techniques. Following three types of probes having different configurations are fabricated and compared: 1) enzyme entrapped gel layer over silver coated unclad fiber; 2) enzyme immobilized over silver and GO coated unclad fiber; and 3) enzyme immobilized over silver, GO, and silver nanoparticles coated unclad fiber. The performance of all these probes have been compared in terms of operating range, sensitivity and limit of detection. The sensors have many advantages, such as compact size, modest cost, high sensitivity, high selectivity, and capability of remote sensing.

Beschreibung: In this paper, for the first time, we introduce a simple and low cost hydrazine sensor based on a commercial junction field-effect transistor (JFET). The transistor was mechanically treated, isolated, and used as an ion sensitive FET (ISFET) for hydrazine detection, after the electrodeposition of the sensing membrane on its metal gate surface. Copper hexacyanoferrate nanoparticles as suitable sensing membrane were electrodeposited on the copper metal gate of transistor from a solution containing K 4 Fe(CN) 6 by a cyclic voltammetry method. The prepared sensor showed a super-Nernstian response of 94.8 mV pHyd −1 over a linear concentration range of $1.17times 10^{-5}$ – $2.15times 10^{-2}$ M, a very low drift of 0.04 mV h −1 , and the detection limit of $3.16~mu text{M}$ . Also, the various ISFET characteristics of the prepared sensor were studied and discussed.

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Beschreibung: Presents the front cover for this issue of the publication.

Beschreibung: In this paper, we have developed a miniaturized a chemical sensor based on a new nanostructured Co-phthalocyanine (Co(II)Pc-PAA) derivative functionalized Au microelectrodes for perchlorate ClO − 4 detection. The morphological properties of the sensitive layer have been characterized by contact angle measurement. The response of the obtained sensor-based CoPc/Au microelectrodes has been investigated by electrochemical impedance spectroscopy measurements. The experimental impedance data of the sensor device were analyzed by an equivalent electrical circuit using a modified Randles model for better understanding the phenomena present at the sensing membrane/electrolyte interface. Therefore, under optimized working conditions in terms of polarization and frequency, best performances have been achieved when compared with those obtained in the literature for Au electrodes-based devices functionalized with the same molecule. The present chemical sensor has provided a lower detection limit (17.3 pM), the lowest achieved until now to our knowledge, with a larger linear range from 1.73 10 −11 to 10 −1 M. The selectivity of the sensor has been also studied by evaluating the response towards ClO − 4 with other interfering anions. The measurement were stable after ten days of the chemical sensor storage at room temperature. This is very promising for environmental application using rapid analyses and low-cost chemical sensors. Perspectives for a potentiometric sensor at higher concentrations were also assessed.

Beschreibung: Presents the table of contents for this issue of the periodical.

Beschreibung: A two-port local resonating (TPLR) method for thin-film Lamb wave sensor is proposed. Based on properties of multi-modes analyzed by numerical simulation and experimental measurement, the TPLR method is able to generate the second-order flexural mode $A_{02}$ ( $A_{0i}$ , $i = 2$ ). Density and sound velocity of liquid solutions can be decoupled based on the first-order flexural mode $A_{01}$ ( $A_{0i}$ , $i=1$ ) and the $A_{02}$ mode, and solutions with the same density, such as CH 3 CH 2 OH and CH 3 OH, can be successfully distinguished on a single Lamb wave device. When the phase velocity of $A_{02}$ mode is close to the sound velocity of liquid, compared with the traditional delay-line configuration, smaller period of interdigital transducers and device miniaturization by the TPLR method can be realized. Generation of new modes with the TPLR method demonstrates an alternative for multi-parameters sensing of Lamb wave sensors.

Beschreibung: Vanadium pentoxide xerogel films deposited onto gold microelectrodes were micropatterned by thermally induced conversion into crystalline $alpha $ -V 2 O 5 , using optical lithography written at the focus of a confocal Raman microscope. The laser scribing process improved the electric contact and promoted the $n$ -doping of the film with $V^{mathrm {IV}}$ ions. In this way, a field effect transistor like device was constructed and successfully applied as humidity sensor, where the combined lithographic design and the application of a negative back gate field ( $V _{mathrm {G}} = -10.0$ V) boosted the source–drain current by a hundred times, leading to a large gain in sensitivity.

Beschreibung: Force sensors using strain gauge have been widely applied in mechanical systems. They usually possess a structure consisting of a simple cantilever beam and two strain gauges attached to two opposite beam surfaces. However, this structure shows severely distorted stress in the implementation of smart robot grippers with lateral offsets, which is usual in limited-space applications. In order to overcome the limitation and to reduce the nonlinearity of the gauge sensor, a novel hinged-joint cantilever beam sensor structure is proposed. An analytical model is derived to predict the force sensitivity and force linearity. The simple cantilever beam sensor and the hinged-joint sensor are analyzed and compared with the conducting finite-element-method simulation. Signal processing circuits are designed and implemented. A hinged-joint prototype force sensor is fabricated for calibration and testing. Experiments show that the proposed hinged-joint sensor possesses a high quality of linearity and excellent sensitivity, which can be applied to diverse fields including smart robot grippers.

Beschreibung: An optical magnetic field sensor based on electrogyratory and electrooptic compensation is proposed and experimentally demonstrated. Besides natural birefringence and optical activity, single quartz crystal simultaneously exhibits the magnetooptical Faraday effect, electrooptic Pockels effect, electrogyratory effect, and so on. For the intensity-modulated light sensing signal, the Faraday rotation angle can be compensated by both electrogyratory angle and electrooptic phase retardation. The 50-Hz ac magnetic flux density has been measured within 267 Gs by using a block of single quartz crystal, and typical compensating voltage is about ~ $0.725 text {V}cdot$ Gs −1 . Advantages of the proposed magnetic field sensor mainly include closed-loop optical measurement of magnetic field or current, low compensating voltage, moderate temperature dependence of electrooptic and electrogyratory effects, a solid sensing unit, and low cost.

Beschreibung: An integrated and miniaturized micro-gas chromatography (GC) with real-time imaging capability for simultaneous chemical separation and detection was developed. Surface plasmon resonance imaging (SPRi) was used as a sensitive and real-time imaging-based detector for various gaseous chemical mixtures, and good gas chromatographs were obtained. The system integrated a home-made miniaturized molecular sieve packed spiral microchannel column with the SPRi chip and real-time chemical separation and detection were demonstrated using alkanes. The chemical separation processes were simulated using COMSOL and matched well with the experimental results. The system enabled the study of chemical separation processes in real-time by miniaturizing and integrating the micro-GC separation and detection units. This approach can be expanded to multidimensional GC development.

Beschreibung: The temperature drift of the current sensor with an air gap limits its measurement accuracy, so a ferromagnetic design is presented to improve the temperature characteristics of the current sensor by an air-gapped magnetic field intensity self-compensation. In this paper, the magnetostriction and thermal expansion are introduced into a hysteresis model within the temperature range from 258 to 358 K, and the relationship between the permeability and the air-gapped length of amorphous alloy is analyzed. The results show that the air-gapped length increases as the temperature increases, resulting in the air-gapped magnetic field intensity weakened. Moreover, the permeability of amorphous alloy increases as the temperature increases, resulting in the air-gapped magnetic field intensity strengthened. Hence, the air-gapped magnetic field intensity can be self-compensated with the amorphous alloy. The effectiveness of the design is verified experimentally with 1–10 mm air-gapped amorphous cores. In addition, in order to analyze the air-gapped magnetic field intensity changes more accurately, a new hysteresis modeling method is proposed, which can overcome the disadvantages of a J-A model for the minor hysteresis curve simulations and a Preisach model for the major hysteresis curve simulations.

Beschreibung: The measurement accuracy of the Larmor frequency of the Overhauser magnetic sensor directly determines the magnetic accuracy of the Overhauser magnetometer. We propose a multichannel interpolation method for marine magnetic measurements, addressing specifically the deficiencies in traditional measurement methods. The quantization error of the count value of the standard signal is greatly reduced using the delay chain interpolation technique. Also the influence arising from the phase error is weakened through channel expansion. In addition, we also design a test platform and conduct two sets of field contrast tests, the test results showing that the proposed method not only improves the precision of the frequency measurement by about three times but also improves the resolution and lowers the noise level of the system.

Beschreibung: It is evident that surface electromyography (sEMG)-based sensing approach for human–machine interfaces has some inherent limitations for applications requiring morphological changes information of deep-layered muscles, such as dexterous prosthetic hands. In this paper, the design, simulation, fabrication, and evaluation for a series of novel structured ultrasound transducers are conducted in order to develop a type of A-mode ultrasound transducers that overcome the drawbacks of the sEMG-based sensing. The transducers cover single-frequency and dual-frequency types. Their key parameters, the acoustic impedance and thickness of the matching layer, are simulated and verified by PZFlex. The parameters are designed as 0.3 times of the 1–3 composite piezoelectric’s acoustic impedance and 0.25 times of the wavelength, respectively. The characterizations of the dual-frequency transducers significantly outperform single-frequency transducers. The experiments of recognizing dexterous hand gesture are designed to detect morphological changes information of deep-layered muscles. The classification accuracy improvements with linear discrimination analysis are 7.3% and 4.7%, and with support vector machine are 14.1% and 13.4% for the horizontal stacked and annulus array. This preliminary study concludes that the dual-frequency transducers have huge potential for applications that need contraction information of deep-layered muscles over the single-frequency transducers, letting alone sEMG-based sensors.

Beschreibung: This paper describes the design and development of a system of gas sensors based on quartz crystal microbalances (QCMs) to be used for the measurement of gas, vapors, and their mixtures. This system’s architecture manages an array composed of eight QCMs with a resonance frequency of about 32 MHz. Custom oscillator circuits were designed and built to drive the QCMs. A data acquisition stage was developed to collect the output frequencies of the QCMs array and to visualize and store the data. The QCMs have been functionalized with eight different types of anthocyanins, using two different techniques. Three of the QCMs composing the array have been tested, and their performance is compared to a previous array based on 20-MHz QCMs. One of the QCMs, covered via drop casting, when tested in a calibration experiment, shown an improved performance consisting in a ratio of 4.92 between 32- and 20-MHz sensitivities. This number confirmed the ratio of 5.76 theoretically calculated using Sauerbrey’s law. The other two QCMs tested were covered via spray casting, giving resolution of tens of ppb, comparable with the previous release.

Beschreibung: To develop the differential piezoresistive sensor made of carbon nanotube filled silicone rubber composite with concise configuration, a coplanar-electrodes-based differential structure is designed. The structure includes two composite films with high carbon nanotube content (12 vol.%) and two composite films with low carbon nanotube content (4 vol.%). All the electrodes for the four composite films are located in the same encapsulation layer (i.e., all the electrodes are located on the same side of the composite films), which can simplify the configuration of the sensor probe. The electrical resistance of the composite film with high/low carbon nanotube content decreases/increases with the increase of the compressive pressure and increases with the increase of the temperature. The two composite films with high carbon nanotube contents are placed on the two diagonal arms of an electrical bridge, and the other two composite films with low carbon nanotube contents are placed on the other two diagonal arms of the bridge. The experimental results verify the feasibility of using the coplanar-electrodes-based differential structure to reduce the output drift induced by the temperature and improve the sensitivity.

Beschreibung: In this paper, mechanical thermal noise in micro-machined levitated two-axis rate gyroscopes (MLG) is comprehensively studied. Taking into account the gyroscopic nature and a type of electromagnetic levitation employed in MLG, effective damping coefficients are obtained for two cases corresponding to positive and negative angular position stiffness. According to obtained coefficients, expressions for the spectral density of the gyroscope noise floor and its angular random walk are derived. Moreover, an investigation of the response of an ideal levitated gyroscope to the fluctuating torque within the entire frequency domain shows a restriction of the detection of the measuring rate in order to preserve the same angular position stiffness. This response, a form of Johnson noise, provides an explanation of the mechanism of constraints in gyroscope resolution, which in turn limits the current performance of levitated gyroscopes. Also, using the Ising criterion, an alternative qualitative means to estimate the resolution is obtained. By joining the Johnson noise and Ising criterion techniques, a confidence range for the gyroscope resolution is proposed.

Beschreibung: Optical feedback interferometry (OFI)-based flow-metry enables simple, robust, self-aligned, and low-cost systems to measure the fluid flow velocity with reasonable accuracy. The particle concentration in the fluid causes significant changes in the signal of OFI sensors. While the spectral analysis of the particle induced Doppler shift remains as the most usual approach to determine the flow properties, different processing algorithms have been proposed in order to evaluate the average flow velocity within the measurement volume. In this paper, the validity of the commonly used methods with regards to particle concentrations and flow rates is verified.

Beschreibung: In this paper, we have explored Parylene-C (PC) as a sensing material for its unique signature and selectivity for explosive sensing. We have used a bi-layer deposition process to fabricate bottom-gate-top-contact organic field effect transistor (OFET) structures. Opening of dangling bonds on subjecting PC to plasma oxidation (POPC) renders these molecules to be employed as a receptor material in sensing vapors of both explosives and non-explosives, such as Trinitrotoulene (TNT), 1,3,5 trinitro-1,3,5-triazacyclohexane(RDX), PETN, Dinitrobenzene (DNB), Nitrobenzene (NB), Benzoquinone (BQ), and Benzophenone (BP). The change in: 1) the vibrational modes of the molecule by infrared spectroscopy; 2) surface potential of POPC by Kelvin probe force microscopy (KPFM); and 3) electrical characterization by I–V measurements of PC-based OFET on exposing to vapors have been systematically studied. Different signatures for all the analytes have been observed while exact and perfect selectivity for TNT, RDX were found from I–V studies and for PETN by KPFM studies. Thus, the OFET device-based chemical sensors demonstrated here with improved sensitivity and excellent selectivity, stand as promising candidates for explosives detection.

Beschreibung: A thermal THz detector based on commercial CMOS technology working in room temperature is proposed. The THz electromagnetic wave is first selectively absorbed by an on-chip $lambda /4$ dipole antenna realized in the metallization layer. The absorbed wave energy is then converted to Joule heat energy via a polysilicon resistor. The heat-generated temperature rise is finally detected by a proportional to absolute temperature sensor. The theoretical analysis and physical modeling of the detector including the mechanism of the electromagnetic energy absorption, the thermal conversion, and the electrical circuit response, are presented. The detectors at three typical THz frequencies of 1, 2.9, and 28.3 THz are designed in standard 0.18- $mu text{m}$ CMOS technology and post-simulated to illustrate the detector’s frequency-selective capability in the whole THz range. The simulated detector’s voltage responsivity is 18.0 V/W at 1 THz, 18.9 V/W at 2.9 THz, and 18.6 V/W at 28.3 THz, respectively. The noise equivalent power is $1.7~mu text{W}/surd $ Hz at the three frequencies.

Beschreibung: The cameras of a close-range photogrammetry system must be calibrated to find their positions and optical properties. This is a crucial step in ensuring the performance of the complete system, especially if micrometric precision over a large field of view and long-term reproducibility is required. The target positions within the images for camera calibration and measurements are perturbed if stability between images is not achieved. This paper aims to evaluate the optimal conditions to guarantee the stability of the target images during measurements and calibration. The effect of temperature on the target positions is estimated to be about 0.1 pixels during a camera warm-up period of 20 min or more. This effect is reduced to about 0.02 pixels after a warm-up period of less than 10 min by developing a controller for the camera’s pixel clock. Additionally, an approximately 22% variation of illumination intensity is found to cause a small, but clearly measurable effect between images. Other aspects studied here are the illumination angle and the target characteristics. A 180° movement of the illumination source with respect to the camera produces a 0.3 pixel change in the target locations when masked retroreflective targets are involved. In contrast, this effect is diminished by a factor of about ten with the use of larger, opaque targets.

Beschreibung: Measurement of transformer oil quality plays an important role in health condition monitoring of a transformer. The breakdown voltage of transformer oil is influenced by both water content and temperature variation. Therefore, accurate assessment of water content in transformer oil and variation of breakdown voltage due to change in temperature are essential for health condition monitoring of a transformer. It helps to estimate the life expectancy of a transformer. This paper presents a polymer optical fiber sensor based instrumentation system (POFSBIS) to measure the water content in transformer oil of a transformer. Furthermore, the POFSBIS is also used to detect the effect of transformer oil breakdown under controlled laboratory environment. Ultraviolet visual spectrophotometer has been employed to study the changing temperature effect and voltage breakdown effect on transformer oil. The instrumentation system measures the water content in transformer oil as well as provides the online information about the breakdown occurrence in transformer oil which helps to prevent the catastrophic losses of a transformer.

Beschreibung: We report on the implementation of an automated platform for detecting the presence of an antibody biomarker for human papillomavirus-associated oropharyngeal cancer from a single droplet of serum, in which a nanostructured photonic crystal surface is used to amplify the output of a fluorescence-linked immunosorbent assay. The platform is comprised of a microfluidic cartridge with integrated photonic crystal chips that interfaces with an assay instrument that automates the introduction of reagents, wash steps, and surface drying. Upon assay completion, the cartridge interfaces with a custom laser-scanning instrument that couples light into the photonic crystal at the optimal resonance condition for fluorescence enhancement. The instrument is used to measure the fluorescence intensity values of microarray spots corresponding to the biomarkers of interest, in addition to several experimental controls that verify correct functioning of the assay protocol. In this paper, we report both dose-response characterization of the system using anti-E7 antibody introduced at known concentrations into serum and characterization of a set of clinical samples from which results were compared with a conventional enzyme-linked immunosorbent assay performed in microplate format. The demonstrated capability represents a simple, rapid, automated, and high-sensitivity method for the multiplexed detection of protein biomarkers from a low-volume test sample.

Beschreibung: In this paper, we propose fast, highly sensitive, and wide-dynamic-range fiber-optic probe-type biosensors to detect pH and glucose. The operation principle of the proposed biosensors is based on the Fabry–Perot interferometry technique. Three pH-sensitive dyes (methyl orange, methyl red, and thymol blue) and three solvatochromic dyes (Nile red, rhodamine-B, and 4-amino-N-methylphthalimide) were individually mixed with polymers to obtain five pH- and three glucose-sensitive sensing membranes. These membranes were subsequently deposited on eight gold nanoparticles coated on fiber-optic probes to obtain five pH and three glucose fiber-optic probe sensors. To ascertain the effectiveness of the sensors, various concentrations of pH buffer solutions and glucose solutions were tested. The proposed fiber-optic pH and glucose probe sensors showed sensitivities of 1.95 nm/pH and 3.25 nm/mM, respectively, with high-sensing stability with the relative standard deviation about 2.5%. The proposed sensors offer a linear sensing ability over wide ranges of pH (2–12) and glucose ( $1~mu text{M}$ –1 M) with an R 2 value of approximately 0.996. The response and recovery times of the proposed sensors were approximately 8 and 9 s, respectively. Finally in this paper, we compared the performance of the proposed fiber-optic probe sensors with that of other pH and glucose sensors and determined that the proposed sensors achieve better sensing performance.

Beschreibung: This paper presents the utilization of optical fiber Bragg gratings (FBGs) embedded into a carbon fiber reinforced polymer transtibial prosthesis to evaluate the user’s gait, and its own performance. Static mechanical tests were performed to characterize the sensors. Vertically and horizontally positioned FBGs within the structure have been used for load and strain force evaluation during real-time experiments with a candidate at different speeds on a treadmill. For simplicity, one non-amputee candidate performed the experiments using a mechanical adaptation. Distinctive patterns of response of the FBGs located at different points within the prosthetic structure enabled the differentiation between slow and fast motion gait cycle and the force distribution during the tread. This optical instrumentation contributes to the development of a new tool for the evaluation of prosthesis design and amputee patients rehabilitation and to the assessment of the performance of athletes during training or competition.

Beschreibung: We investigate and compare the $varphi $ -optical time domain reflectometry (OTDR) and OTDR-interferometry methods, both using phase demodulation, for distributed acoustic sensing. By theoretical analysis and experiments we show that, while both $varphi $ -OTDR and OTDR-interferometry give proper instantaneous amplitude, frequency, and phase properties of the acoustic signal, OTDR-interferometry produces larger signals and offers higher sensitivity, better signal-to-noise-ratio, and larger demodulated signal width than $varphi $ -OTDR due to the introduction of the interferometer. This work enables the selection of the better method for distributed acoustic sensing for different situations of surface, seabed, and downhole environments.

Beschreibung: This paper presents the development of a novel 2-D fiber Bragg grating (FBG)-based micro-force sensing design for detection of catheter tip-tissue interaction forces. A miniature and symmetrical force-sensitive flexure-based catheter distal sensor has been prototyped, and four optical fibers inscribed with one FBG element each have been mounted on it for force and temperature decoupling and detection. The axial property of the tightly suspended fiber configuration has been utilized with a pre-tensioned force, and the embedded FBG element can be stretched and compressed to sense the force-induced and temperature-caused strain variations. The proposed configuration can achieve an improved resolution and sensitivity than the light intensity modulation-based approaches, and avoid the limitations closely associated with the commonly direct FBG-pasting methods, such as chirping failure and low repeatability. Finite-element modeling (FEM)-based simulation has been implemented to investigate the flexure performance and improve the design. The decoupling approach has been proposed based on the simulation results and implemented to separate and determine the force and temperature. The force-sensing flexure prototype has been calibrated to achieve a resolution of around 4.6 mN within the measurement range of 0 ~ 3.5 N. Both static calibration experiments and in-vitro dynamic experiments have been performed to prove the feasibility of the proposed design. The decoupling capacity of force and temperature will benefit its broad implementations in generalized intravascular catherization procedures.

Beschreibung: In this paper, a novel single color camera stereo vision system is proposed. Two planar mirrors are used to create double views (blue and red views). A dichroic filter (DF) is used to combine them and eliminate their interference. The double views can then be captured by a color camera through blue and red channels. When the DF transmits the red light, refraction would occur. During calibration, we separate the calibration process: calibrate the virtual red camera and the virtual blue camera in order, and then calibrate their pose relationship. The refraction is removed in this process. Moreover, when computing the 3-D position of a point, the measurement error caused by the refraction is also considered. In this experiment, the interference between the blue- and red-channels is shown to be negligible. We verified the proposed vision system on the standard spherical and cylindrical surfaces. It is shown that the measurement accuracy is improved when the effect of refraction is considered. In addition, the noise robustness of this proposed system is also tested. The measurement accuracy would not be affected severely, if the standard deviation of the uniformly distributed random noise is less than 0.035. Finally, the proposed system is employed to measure the profile of a flower model. The proposed system has potential industrial applications.