A theoretical approach for inverse filter design in ultrasonic applications

A comparison between simulation- and measurement-based characterization is provided for the design of one-dimensional, nonadaptive, inverse filters for ultrasonic applications. Both prefiltering and postfiltering are considered by means of two different filtering strategies performed in the time and frequency domains. The results clearly indicate that theoretical methods can be used successfully, provided that the physical limitations of the simulation process are fully appreciated. In some instances, the simulation-based approach is shown to provide superior results, and the reasons for this are explained.     

Quadratic correlation filter design methodology for target detection and surveillance applications

A novel method is presented for optimization of quadratic correlation filters (QCFs) for shift-invariant target detection in imagery. The QCFs are quadratic classifiers that operate directly on the image data without feature extraction or segmentation. In this sense, the QCFs retain the main advantages of conventional linear correlation filters while offering significant improvements in other respects. For example, multiple correlators work in parallel to optimize jointly the QCF performance metric and produce a single combined output, which leads to considerable simplification of the postprocessing scheme. In addition, QCFs also yield better performance than their linear counterparts for comparable throughput requirements. The primary application considered is target detection in infrared imagery for surveillance applications. In the current approach, the class-separation metric is formulated as a Rayleigh quotient that is maximized by the QCF solution. It is shown that the proposed method results in considerable improvement in performance compared with a previously reported QCF design approach and many other detection techniques. The results of independent tests and evaluations at the U.S. Army's Night Vision Laboratory are also presented.     

The design of single crystal materials for magnetic bubble domain applications

The criteria for the existence of stable magnetic bubble domains and their potential in data storage applications are outlined. The development of single crystal materials capable of supporting such domains is reviewed. Particular emphasis is given to both the static and dynamic properties of bubble domains and to how, by careful materials design and preparation, the optimum balance of these properties can be attained.     

Quasi-elliptic dual-band filter design using stepped-impedance resonators and coupling topologies for narrow-to-wide-band applications

Design guidelines are presented for new planar quasi-elliptic dual-band filters in applications requiring high performance, compact size, ease of fabrication and integration with remaining circuitry. Novel coupling topologies between folded stepped-impedance resonators (SIRs) are utilised to generate two narrow or two wide passbands at desired centre frequencies with multiple attenuation poles between passbands. Source? load coupling is employed to place additional attenuation poles within the lower and upper stopband regions. The main feature of these dual-band filters is their approximately symmetrical response, including high selectivity of each passband and controllable fractional bandwidths for either narrowband or wideband coupling schemes, respectively. In addition, the simplicity of the design approach and the use of folded SIR structures result in compact size. Several microstrip dual-band filters in various cascaded SIR configurations with narrow or wide passbands are designed and measured. The measured results are in very good agreement with those obtained from different electromagnetic simulation packages such as Ansoft Designer and IE3D.     

Tunable optical filter for colorimetric applications

A temperature-controlled tunable optical filter for use in the visible range and based on the Christiansen effect, in which the solid particles have been substituted with glass fibers, has been fabricated and tested. The construction of the filter and transmission properties are reported. For an operating temperature of 95°C, the peak wavelength was 509.5 nm, with a peak transmission of 50.8% and a FWHM of 71 nm.     

Holmium-doped optical fiber for filter applications

We consider the properties of holmium-doped fibers in filter applications. We give spectral properties and model filter characteristics. Experiments on filtering of Raman spectra are presented. The fiber filters exhibit strong rejection in the stop band and sharp absorption cutoffs.     

Nanostructural palladium films for sensor applications

The composite films composed of palladium (Pd) nanocrystals and Pd-fullerenes nanocrystals obtained by physical vapor deposition (PVD) method were studied. These types of films can be applied as active material for sensor application.The films were prepared by PVD technique. They were deposited on different substrates and contained Pd in various concentrations. The structure and composition of the Pd films were studied by X-ray diffraction, scanning probe microanalysis, transmission and scanning electron microscopy. It was found that these films were composed of Pd nanocrystals placed in Pd-C₆₀ matrix.Changes of some electric properties of the film upon an influence of a toxic liquid have been characterized by DC electrical measurements. They were performed for different volatile organic compounds (VOCs). At 22 °C the electrical resistance was studied for VOC such as benzene and toluene.     

Piezoelectric composites for sensor and actuator applications

In the last 25 years, piezoelectric ceramic-polymer composites have been conceptualized, prototyped, fabricated, and implemented in an array of applications encompassing medical imaging and military missions, among others. A detailed snapshot of the materials used, and a detailed account of the major innovative methods developed in making various piezoelectric ceramic-polymer composites are presented. The salient aspects of processing of such composites are summarized, and structure-processing-property relations are described using connectivity as the unifying central concept. Computer-aided design (CAD)-based fabrication methods, which result in composites whose structural complexity surpass that of composites obtained with traditional methods, are described to introduce the reader to novel concepts in processing of piezocomposites. A brief survey of some recent advances made in modeling of (0-3), (1-3), and (2-2) composites also is provided.     

Hybrid approach for rugate filter design

Fourier techniques and direct optimization are applied to the synthesis of complex rugate filters. A hybrid approach is presented. The design strategies are illustrated numerically for different spectral shapes.     

A novel sensor for X-ray imaging applications

In this study, a novel direct X-ray conversion electronic sensor for X-ray imaging, aimed at the enhancement of the signal characteristics of a cadmium zinc telluride (CdZnTe) detector substrate, is proposed. CdZnTe substrates are promising candidates in detector technology since they have a high stopping power. The novelty of the sensor lies in the material of use as well as in the signal collector design, which exhibits “Frisch-grid” capabilities. As a result, the proposed technology provides an effective mode to shield the electron-collecting electrode from the charge induced on it from moving positive ions and trapped charge. Overall, this technology would allow for a decreased sensor thickness, accompanied with a high collector efficiency, and consequently improved signal characteristics. Therefore, the signal quality of an imaging sensor as applied to medical detector technology, radio astronomy, aviation security, surveillance and nondestructive inspection, and other industrial areas will be significantly improved     

Adaptive key pre-distribution model for distributed sensor networks

In this paper, a key pre-distribution model with the concept of key pool generation in distributed sensor networks (DSNs) is proposed. In this scheme, additional information is inserted into each group during key pool generation. The nodes in the DSNs can use this extra information to increase system performance. A concrete example is given to clarify this concept and prove that the added information in the scheme can greatly improve connectivity between nodes even if node deployment is sparse or non-uniform. In addition, high connectivity decreases the energy consumption of wireless communication between sensor nodes and extends the life of these nodes.     

基于被动式传感器的目标跟踪算法研究

仅有角度量测的被动式单传感器跟踪搜索系统有广泛的应用前景,但现有的针对性跟踪算法并不能很好的处理实际问题,失跟现象常常发生。本文对现有算法所存在的问题进行了深入研究,并提出了相应的改进算法。通过对机动目标运动分析,总结出角度向量在时间域中的变化规律,通过引入新的计算向量,对原算法残差计算进行了修正。它对基于单个被动传感器的纯方位跟踪问题的处理提供了新的思路。仿真实验及实际应用已证明了该算法有效性。     

A flow intensification model for granular filter applications

A flow intensification model was proposed for calculation of the initial collector efficiency of a granular filter. In this model, the flow acceleration within voids of granular media is taken into account with an intensification factor β. Simple physical argument gives an estimation of β, which should be close to 1/ε. Creeping flow is assumed and Happel model is used to represent the granular media. After obtaining the flow field, the initial collector efficiency η₀ is calculated from trajectory analysis and compared with experimental data. The reasonably good agreement between the theory and experiments suggests that the current model is physically plausible and potentially useful for granular filter performance prediction if further theoretical development is implemented.     

Double-wavelength technique for surface plasmon resonance measurements: basic concept and applications for single sensors and two-dimensional sensor arrays

A new technique for on-line monitoring of analyte binding to sensor surfaces by surface plasmon resonance (SPR) detection is described. It is based on differential measurements using two wavelengths provided by two diode lasers. The technique is as simple and robust as the conventional SPR detection measuring the reflected radiation at fixed incidence angle, but it has the advantage of being nonsensitive to variations of the resonance width and providing essentially higher signal/noise ratios. The paper presents the first four channel prototype system for parallel 2D-monitoring at four different spots. One channel is always used as a reference to compensate temperature fluctuations and nonspecific adsorptions. Calibration with sucrose solutions revealed an absolute sensitivity of Deltan approximately 5 x 10(-6). The new technique is tested with a biotin-streptavidin binding and with hybridization/denaturation of DNA. Biotin binding to a streptavidin monolayer is detected with a signal/noise ratio of about 5, which demonstrates the high potential of the new technique for applications in drug discovery. Applications to gene analysis are tested with short oligonucleotides of the sequences used for genotyping human hepatitis C viruses. A selective response to complementary oligonucleotides is observed. The high reproducibility in subsequent cycles of hybridization/denaturation (by formamide or by heating) points out potential applications of the technique in medical diagnostics, food industry, genomics, and proteomics too.     

A surface-acoustic-wave comb spectrum oscillator for sensor applications

A surface-acoustic-wave comb spectrum oscillator (SAWCSO) for sensor applications employing a long delay line is described. It generates low jitter narrow pulses in the kHz range. The relative sensitivity to velocity changes is close to the theoretical maximum and at least twice as high as in single mode oscillators.     

Improved zinc oxide film for gas sensor applications

Zinc oxide (ZnO) is a versatile material for different commercial applications such as transparent electrodes, piezoelectric devices, varistors, SAW devices etc because of its high piezoelectric coupling, greater stability of its hexagonal phase and its pyroelectric property. In fact, ZnO is a potential material for gas sensor applications. Good quality ZnO films were deposited on glass and quartz substrates by a novel CVD technique using zinc acetate as the starting solution. X-ray diffraction confirmed the crystallinity of the zinc oxide film and SEM study revealed uniform deposition of fine grains. Undoped ZnO films were used for detection of dimethylamine (DMA) and H₂ at different temperatures by recording the change in resistivity of the film in presence of the test gases. The response was faster and the sensitivity was higher compared to the earlier reported ZnO based sensors developed in our laboratory. The main objective of this work was to study the selectivity of the ZnO film for a particular gas in presence of the others. The operating temperature was found to play a key role in the selectivity of such sensors.     

Indium tin oxide overlayered waveguides for sensor applications

The use of indium tin oxide (ITO) thin films as electrodes for integrated optical electrochemical sensor devices is discussed. The effect of various thicknesses of ITO overlayers exhibiting low resistivity and high transparency on potassium ion-exchanged waveguides fabricated in glass substrates is investigated over the wavelength range 500-900 nm. ITO overlayers are formed by reactive thermal evaporation in oxygen, followed by annealing in air to a maximum temperature of 320 degrees C. With air as the superstrate, losses in the waveguides were found to increase dramatically above 30-nm ITO thickness for TE polarization and above 50-nm thickness for TM. Losses were increased over the whole wavelength range for a superstrate index close to that of water. A one-dimensional, multilayer waveguide model is used in the interpretation of the experimental results.     

A strain gauge tactile sensor for finger-mounted applications

This paper describes a strain gauge-based sensor used for measuring finger force. The theory, design, and sensor construction details are presented. It was constructed using metallic strain gauges and a carefully designed structure which has a protection device that impedes the sensor damage when forces higher than 100 N are applied. Its dimensions are suitable for measuring thumb force, but the same design can be used for constructing smaller sensors for other fingers. It is rugged, presents linear response, good repeatability, resolution of 0.3 N, low hysteresis, and sensitivity of 0.12 V/N. It can be useful in rehabilitation engineering, biomechanics, robotics, and medicine     

Optimal design of CMOS pseudoactive pixel sensor (PAPS) structure for low-dark-current and large-array-size imager applications

In this paper, a pixel structure called the optimal pseudoactive pixel sensor (OPAPS) is proposed and analyzed for the applications of CMOS imagers. The shared zero-biased-buffer in the pixel is used to suppress both dark current of photodiode and leakage current of pixel switches by keeping both biases of photodiode and parasitic pn junctions in the pixel bus at zero voltage or near zero voltage. The factor of photocurrent-to-dark-current ratio per pixel area (PDRPA) is defined to characterize the performance of the OPAPS structure. It is found that a zero-biased-buffer shared by four pixels can achieve the highest PDRPA. In addition, the column sampling circuits and output correlated double sampling circuits are also used to suppress fixed-pattern noise, clock feedthrough noise, and channel charge injection. An experimental chip of the proposed OPAPS CMOS imager with the format of 352/spl times/288 (CIF) has been designed and fabricated by using 0.25-/spl mu/m single-poly-five-level-metal (1P5M) N-well CMOS process. In the fabricated CMOS imager, one shared zero-biased-buffer is used for four pixels where the PDRPA is equal to 47.29 /spl mu/m/sup -2/. The fabricated OPAPS CMOS imager has a pixel size of 8.2/spl times/.2 /spl mu/m, fill factor of 42%, and chip size of 3630/spl times/3390 /spl mu/m. Moreover, the measured maximum frame rate is 30 frames/s and the dark current is 82 pA/cm/sup 2/. Additionally, the measured optical dynamic range is 65 dB. It is found that the proposed OPAPS structure has lower dark current and higher optical dynamic range as compared with the active pixel sensor (APS) and the conventional passive pixel sensor (PPS). Thus, the proposed OPAPS structure has high potential for the applications of high-quality and large-array-size CMOS imagers.