国外鱼雷防御问题评述(二)水面舰艇鱼雷防御系统中鱼雷报警纵览

鱼雷防御是从对来袭鱼雷的识别报警开始的,所有鱼雷防御系统的基础是其对鱼雷的检测、分类和定位能力。为了有效地对抗鱼雷攻击,各国海军正在努力提升其声纳的鱼雷目标检测、定位和识别性能。文章对国外鱼雷报警系统的现状和发展趋势进行了分析和评述。鱼雷报警功能可以利用专门的鱼雷报警声纳来实现,也可以集成在一个被动拖线阵里。但通常由一个主被动联合拖曳阵声纳和舰壳声纳构成一个完整的系统,共同完成鱼雷辐射噪声的被动检测、分类和主动回波信号的分析,每个声纳都为鱼雷这个高速小目标的检测定位进行了优化。这样的系统由于可以采用基元数众多长线阵、更好地利用声场条件等,可以实现对鱼雷目标的远距离识别、定位和全方位覆盖。系统部分组成通常也是反潜战能力的组成部分,而将鱼雷检测和水声对抗结合正成为一种新的发展趋势,一些拖曳阵可以作为软杀伤对抗措施欺骗其检测到的鱼雷目标。     

Rapid analyte recognition in a device based on optical sensors and the olfactory system

We report here the development of a new vapor sensing device that is designed as an array of optically based chemosensors providing input to a pattern recognition system incorporating artificial neural networks. Distributed sensors providing inputs to an integrative circuit is a principle derived from studies of the vertebrate olfactory system. In the present device, primary chemosensing input is provided by an array of fiber-optic sensors. The individual fiber sensors, which are broadly yet differentially responsive, were constructed by immobilizing molecules of the fluorescent indicator dye Nile Red in polymer matrices of varying polarity, hydrophobicity, pore size, elasticity, and swelling tendency, creating unique sensing regions that interact differently with vapor molecules. The fluorescent signals obtained from each fiber sensor in response to 2-s applications of different analyte vapors have unique temporal characteristics. Using signals from the fiber array as inputs, artificial neural networks were trained to identify both single analytes and binary mixtures, as well as relative concentrations. Networks trained with integrated response data from the array or with temporal data from a single fiber made numerous errors in analyte identification across concentrations. However, when trained with temporal information from the fiber array, networks using "name" or "characteristic" output codes performed well in identifying test analytes.     

Characterization of Wire Rope Defects with Gray Level Co-occurrence Matrix of Magnetic Flux Leakage Images

Magnetic flux leakage (MFL) techniques are used extensively for non-intrusively detecting and characterizing wire rope defects. Traditionally, MFL signals are captured with induction coil sensors. However, the output of coil sensors is related to the wire rope speed, and they can only provide the axial distribution along the wire rope. Hall sensors array are designed due to the limitation of coil sensors. In this paper, a Hall sensors array was designed to capture the MFL signals both axially and circumferentially. 30-channel data from Hall sensors are processed to compose a MFL image. A digital image process technique is introduced to preprocess the MFL image, the MFL images from different types of defects show different texture characteristics. Gray level co-occurrence matrix is utilized for feature extraction of the texture in the MFL image. Five typical eigenvalues (contrast, correlation, energy, homogeneity and entropy) are used as the inputs of back propagation (BP) networks. After training with typical samples, the BP networks show good performance in the quantitative recognition of different defects. The result of this work shows that texture analysis method for MFL image is suitable for feature extraction and quantitative detection of wire rope defects.     

Intrinsic fiber-optic ultrasonic sensor array using multiplexed two-wave mixing interferometry

An intrinsic multiplexed laser interferometer is presented that allows for the simultaneous detection of acoustic waves by an array of fiber-optic sensors. The phase-modulated signals from each sensor are demodulated by use of an adaptive two-wave mixing setup. The light from each sensing fiber in the array is mixed with a reference beam in a single photorefractive crystal (PRC), and the output beams from the PRC are imaged onto separate photodetectors to create a multiplexed two-wave mixing (MTWM) system. The sensing fibers are embedded in graphite-epoxy composite panels, and detection of both acoustic emission and ultrasonic signals in these materials is demonstrated. The intrinsic MTWM system is an effective tool for the simultaneous demodulation of signals from a large fiber sensor array. Also, the adaptive nature of the MTWM setup obviates the need for active stabilization against ambient noise.     

The detection of transient-like signals in the presence of a spatially inhomogeneous,nonstationary noise field

We will consider the problem of detecting transient-like signals by means of a spatially distributed array of sensors embedded in an inhomogeneous, nonstationary noise field. If each element of the array has an independent, uncorrupted reference sensor to estimate the noise statistics, then conventional adaptive noise cancellation algorithms can be used to improve the detection process. However, because of practical real-world constraints, independent, uncorrupted reference sensors for the noise might not be available. Thus, the applicability of conventional adaptive noise cancellation techniques is in question. This paper will discuss the development of a knowledge-based signal-processing system that uses Artificial Intelligence (Al) methodologies to adaptively cancel inhomogeneous, nonstationary noise from a distributed array of passive sensors that is constrained to have no noise-reference sensors.     

Optical multibead arrays for simple and complex odor discrimination

A fiber optic bead-based sensor array platform has been employed to discriminate between six different odors and air carrier gas. Six different bead sensor types, with over 250 replicates of each, were monitored before, during, and after odor exposure to produce time-dependent fluorescence response patterns that were unique for each sensor-analyte combination. A total of 2,683 sensors were analyzed with respect to changes in their fluorescence, and signals from identical sensor beads were averaged to improve signal-to-noise ratios. Analyte classification rates of 100% were achieved for three complex (coffee bean) odors and three pure (simple) odors (toluene, acetone, 1,3-dinitrotoluene) measured at their highest relative concentrations. When lower odor concentrations were employed, the system exhibited better than 85% classification rates for analyte discrimination. Sensor response repeatability to these odor stimuli has also been quantified statistically, which is vital in defining the detection limit of the overall system. These results demonstrate, for the first time, the utility of our bead array technology for discriminating between different odor types at various dilution levels.     

Design of a fiber-optic quasi-distributed strain sensors ring network based on a white-light interferometric multiplexing technique

A fiber-optic quasi-distributed strain sensors ring network has been designed based on a Mach-Zehnder optical paths interrogator. The optical paths matching for each sensor are discussed, and the optical power budgetary analysis is performed. The relation between the number of sensors and the intensity of the signals of the ring network is given for evaluation of the multiplexing capacity. Experimentally, a seven-sensor array ring network was realized under the condition of light source power 35 microW at 1310 nm, and the distribution strain test was also demonstrated.     

Combination of grating lenses for color splitting and imaging

A pair of planar reflection gratings is proposed and discussed for use in a color-splitting and imaging system, such as a projection-type color-scanner head. Red, green, and blue light reflected from a color subject are split by a color-splitting grating lens and imaged by an image-correction grating, consisting of three segments, onto three line sensors arranged in parallel. The phase-shift function of the image-correction grating was optimized for each color by numerical iteration with the ray-tracing method to suppress aberrations resulting from the wide view angle and the three different wavelengths. Gratings were designed and fabricated, and aberration suppression was experimentally confirmed.     

Time-resolved step-scan infrared imaging system utilizing a linear array detector

A time-resolved infrared (IR) imaging system combined with a multichannel IR microscope, which utilizes a 16 channel linear array (LA) detector, and step-scan Fourier transform infrared (FT-IR) microscope was developed. The LA detector integrates a readout circuit on each detector element, so the detected signals can be read simultaneously. Thus, this system can perform high speed imaging using the step-scan method, similar to a single channel detector. To verify the capabilities of this system, a reflective sample was examined whose position was altered using a piezo actuator activated by an alternating voltage. In addition, the localization of relaxation dynamics for the liquid crystal (LC) molecules in an LC cell under oscillating electric field conditions was detected by this system.     

通过PVDF阵列测量阶梯梁体积位移的实验

以阶梯梁为例,通过一组阵列式压电薄膜(Polyvinylidene fluoride,PVDF)测量阶梯梁的体积位移。在梁表面均匀布置一组相同形状的矩形PVDF阵列,通过测量PVDF与激励力之间的频率响应函数,然后利用伪逆方法结合截断奇异值法(The truncated singular value decomposition,TSVD)设计这组PVDF阵列的加权系数,从而得到阶梯梁体积位移。实验结果表明,该方法能够准确测量到阶梯梁的体积位移,具有不需计算结构模态、附加质量小、与激励力位置无关等优点。     

The development of a portable spectrophotometer for noncontact color measurement

A portable spectrophotometer for noncontact color measurement was developed to display spectral distribution and tristimulus values of a color simultaneously. It comprises electronic control circuits, control firmware, and an optical mechanism with a photo detector array. Essentially, a light beam is reflected or transmitted by a measured object into a device that disperses the light beam into its spectrum on a photo detector array. Then, the photo detector module generates a series of signals as functions of light intensity and produces their corresponding digital values reflecting light intensity. These digital data are processed by the electronic control circuits and control firmware to directly provide the spectral distribution and standard color values. The measured results of the developed system were also compared with those obtained by a similar instrument on the market.     

Nano-thermal transport array: An instrument for combinatorial measurements of heat transfer in nanoscale films

The nano-Thermal Transport Array is a silicon-based micromachined device for measuring the thermal properties of nanoscale materials in a high-throughput methodology. The device contains an array of thermal sensors, each one of which consists of a silicon nitride membrane and a tungsten heating element that also serves as a temperature gauge. The thermal behavior of the sensors is described with an analytical model. The assumptions underlying this model and its accuracy are checked using the finite element method. The analytical model is used in a data reduction scheme that relates experimental quantities to materials properties. Measured properties include thermal effusivity, thermal conductivity, and heat capacity. While the array is specifically designed for combinatorial analysis, here we demonstrate the capabilities of the device with a high-throughput study of copper multi-layer films as a function of film thickness, ranging from 15 to 470 nm. Thermal conductivity results show good agreement with earlier models predicting the conductivity based on electron scattering at interfaces.     

Development of alternative plasma sources for cavity ring-down measurements of mercury

We have been exploring innovative technologies for elemental and hyperfine structure measurements using cavity ring-down spectroscopy (CRDS) combined with various plasma sources. A laboratory CRDS system utilizing a tunable dye laser is employed in this work to demonstrate the feasibility of the technology. An in-house fabricated sampling system is used to generate aerosols from solution samples and introduce the aerosols into the plasma source. The ring-down signals are monitored using a photomultiplier tube and recorded using a digital oscilloscope interfaced to a computer. Several microwave plasma discharge devices are tested for mercury CRDS measurement. Various discharge tubes have been designed and tested to reduce background interference and increase the sample path length while still controlling turbulence generated from the plasma gas flow. Significant background reduction has been achieved with the implementation of the newly designed tube-shaped plasma devices, which has resulted in a detection limit of 0.4 ng/mL for mercury with the plasma source CRDS. The calibration curves obtained in this work readily show that linearity over 2 orders of magnitude can be obtained with plasma-CRDS for mercury detection. In this work, the hyperfine structure of mercury at the experimental plasma temperatures is clearly identified. We expect that plasma source cavity ring-down spectroscopy will provide enhanced capabilities for elemental and isotopic measurements.     

Multiplexing of optical fiber gas sensors with a frequency-modulated continuous-wave technique

We report on the use of a frequency-modulated continuous-wave technique for multiplexing optical fiber gas sensors. The sensor network is of a ladder topology and is interrogated by a tunable laser. The system performance in terms of detection sensitivity and cross talk between sensors was investigated and found to be limited by coherent mixing between signals from different channels. The system performance can be improved significantly by use of appropriate wavelength modulation-scanning coupled with low-pass filtering. Computer simulation shows that an array of 37 acetylene sensors with a detection accuracy of 2000 parts in 10(6) for each sensor may be realized. A two-sensor acetylene detection system was experimentally demonstrated that had a detection sensitivity of 165 parts in 10(6) for 2.5-cm gas cells (or a minimum detectable absorbance of 2.1 x 10(-4)) and a cross talk of -25 dB.     

Robot gripper control system using PVDF piezoelectric sensors

A novel robot gripper control system is presented that uses PVDF (polyvinylidene fluoride) piezoelectric sensors to damp exerted force actively. By monitoring the current developed by the PVDF sensor, an output proportional to the rate of change of the force exerted by the gripper is obtained. The signals from the PVDF sensor and strain-gauge force sensor are arranged in a proportional and derivative control system for the control of force. The control system was tested on an instrumented Rhino XR-1 manipulator hand. The capabilities of the control system are analyzed and are verified experimentally. The results for this particular gripper indicate that the additional sensory feedback can decrease the force step response rise time by 88% while maintaining a monotonic zero-overshoot response. The inclusion of the rate feedback increases the damping ratio of the dominant poles while maintaining the step response rise time.     

Multiplexing Scheme for Self-Interfering Long-Period Fiber Gratings Using a Low-Coherence Reflectometry

A novel multiplexing scheme based on a low-coherence reflectometry (LCR) is proposed for a sensing array (in parallel) of self-interfering long-period fiber gratings (SI-LPGs). Each SI-LPG sensor consists of an LPG and a section of fiber with a highly reflective end (mirror). The spectral information of each LPG is sensitive to some parameters of the surrounding measurand and can be reconstructed from the corresponding subreflectograms (obtained by the LCR) through a fast Fourier transformation. The sensing signals of multiple SI-LPG sensors can be multiplexed if the length of the fiber section in each sensor is set to a different value. Experiments of measuring the surrounding temperature at different sensors are demonstrated to show the good performance of our multiplexing system.     

Gas discrimination in an air-conditioned system

In this work, an identification system based on an array of semiconductor tin dioxide gas sensors has been developed. This system has provided a good success rate in the discrimination of carbon dioxide, forane R134a or their mixtures without a sensor dedicated to carbon dioxide. After a characterization of the five-sensor array, pretreatment was tested on the collected data to select the most representative parameters. Then the information contained in the resulting look-up table was analyzed with PCA, but no significant result was observed. Discriminant factorial analysis was then used and has shown a better separation of the different clusters. Next, unknown data were taken to validate the classification. The results show that a reliable system can be designed using nondedicated chemical semiconductor gas sensors     

Optoelectronic parallel-matching architecture: architecture description, performance estimation, and prototype demonstration

We propose an optoelectronic parallel-matching architecture (PMA) that provides powerful processing capabilities in global processing compared with conventional parallel-computing architectures. The PMA is composed of a global processor called a parallel-matching (PM) module and multiple processing elements (PE's). The PM module is implemented by a large-fan-out free-space optical interconnection and a PM smart-pixel array (PM-SPA). In the proposed architecture, by means of the PM module each PE can monitor the other PE's by use of several kinds of global data matching as well as interprocessor communication. Theoretical evaluation of the performance shows that the proposed PMA provides tremendous improvement in global processing. A prototype demonstrator of the PM module is constructed on the basis of state-of-the-art optoelectronic devices and a diffractive optical element. The prototype is assumed for use in a multiple-processor system composed of 4 x 4 PE's that are completely connected through bit-serial optical communication channels. The PM-SPA is emulated by a complex programmable device and a complementary metal-oxide semiconductor photodetector array. On the prototype demonstrator the fundamental operations of the PM module were verified at 15 MHz.     

Charge-Based Capacitive Sensor Array for CMOS-Based Laboratory-on-Chip Applications

In this paper, we present a capacitive sensor array for highly integrated lab-on-chip (LoC) applications using the charge-based capacitance measurement method (CBCM). The core-CBCM sensor chip is designed and implemented in 0.18 micron CMOS process featuring an array of capacitive sensors; an offset cancellation module and a low complexity analog-to-digital converter (ADC). This sensor chip is incorporated with a microfluidic channel using direct-write fabrication process. We demonstrate the testing results using chemical solvents with known dielectric constants in order to show the viability of the proposed sensor chip for LoCs.     

SnO/sub 2/ gas sensing array for combustible and explosive gas leakage recognition

A gas-sensing array with ten different SnO/sub 2/ sensors was fabricated on a substrate for the purpose of recognizing various kinds and quantities of indoor combustible gas leakages, such as methane, propane, butane, LPG, and carbon monoxide, within their respective threshold limit value (TLV) and lower explosion limit (LEL) range. Nano-sized sensing materials with high surface areas were prepared by coprecipitating SnCl/sub 4/ with Ca and Pt, while the sensing patterns of the SnO/sub 2/-based sensors were differentiated by utilizing different additives. The sensors in the sensor array were designed to produce a uniform thermal distribution along with a high and differentiated sensitivity and reproducibility for low concentrations below 100 ppm. Using the sensing signals of the array, an electronic nose system was then applied to classify and identify simple/mixed explosive gas leakages. A gas pattern recognizer was implemented using a neuro-fuzzy network and multi-layer neural network, including an error-back-propagation learning algorithm. Simulation and experimental results confirmed that the proposed gas recognition system was effective in identifying explosive and hazardous gas leakages. The electronic nose in conjunction with a neuro-fuzzy network was also implemented using a digital signal processor (DSP).