Experimental systems implementation of a hybrid optical-digital correlator

A high-speed hybrid optical-digital correlator system was designed, constructed, modeled, and demonstrated experimentally. This correlator is capable of operation at approximately 3000 correlations/s. The input scene is digitized at a resolution of 512 x 512 pixels and the phase information of the two-dimensional fast Fourier transform calculated and displayed in the correlator filter plane at normal video frame rates. High-fidelity reference template images are stored in a phase-conjugating optical memory placed at the nominal input plane of the correlator and reconstructed with a high-speed acousto-optic scanner; this allows for cross correlation of the entire reference data set with the input scene within one frame period. A high-speed CCD camera is used to capture the correlation-plane image, and rapid correlation-plane processing is achieved with a parallel processing architecture.     

Small optical magnetic-field sensor that uses rare-Earth iron garnet films based on the faraday effect

Highly accurate optical magnetic-field probe sensors that use iron garnet films have been developed. New probe-type sensors were designed with a confocal optical system. A new garnet composition, Bi(0.98)Gd(0.92)La(0.03)Y(1.07)Fe(4.72)Ga(0.28)O(12), was found that shows high temperature stability for a sensitivity of less than 2.0% from -20 to +80 degrees C. The linearity error of the sensor output was within 1.0% for alternating magnetic fields from 0.3 to 42 mT. An optical current transformer that uses the proposed sensor has an ac linearity of 1.0% for input current up to nearly 300 A. The sensor realized high performance in actual use.     

Exchange biasing of magnetoelectric composites

Magnetoelectric composite materials are promising candidates for highly sensitive magnetic-field sensors. However, the composites showing the highest reported magnetoelectric coefficients require the presence of external d.c. magnetic bias fields, which is detrimental to their use as sensitive high-resolution magnetic-field sensors. Here, we report magnetoelectric composite materials that instead rely on intrinsic magnetic fields arising from exchange bias in the device. Thin-film magnetoelectric two-two composites were fabricated by magnetron sputtering on silicon-cantilever substrates. The composites consist of piezoelectric AlN and multilayers with the sequence Ta/Cu/Mn(70)Ir(30)/Fe(50)Co(50) or Ta/Cu/Mn(70)Ir(30)/Fe(70.2)Co(7.8)Si(12)B(10) serving as the magnetostrictive component. The thickness of the ferromagnetic layers and angle dependency of the exchange bias field are used to adjust the shift of the magnetostriction curve in such a way that the maximum piezomagnetic coefficient occurs at zero magnetic bias field. These self-biased composites show high sensitivity to a.c. magnetic fields with a maximum magnetoelectric coefficient of 96 V cm(-1) Oe(-1) at mechanical resonance.     

X-ray colour imaging

A prototype X-ray colour imaging system has been assembled using the principle of tomographic energy-dispersive diffraction imaging (TEDDI). The new system has been tested using samples of nylon-6, aluminium powder and deer antler bone. Non-destructive three-dimensional images of the test objects have been reconstructed on a 300 microm scale with an associated diffraction pattern at each voxel. In addition, the lattice parameters of the polycrystalline material present in the sampled voxels have been determined using full pattern refinement methods. The use of multiple diffracted parallel colour X-ray beams has allowed simultaneous spatially resolved data collection across a plane of the sample. This has simplified the sample scan motion and has improved data collection times by a factor scaling with the number of detector pixels. The TEDDI method is currently limited to thin samples (approx. 1-2mm) with light atoms owing to the very low detection efficiency of the silicon detector at X-ray energies above 25 keV. We describe how these difficulties can be removed by using semiconductor detectors made from heavier atomic material.     

Telemetric Seismic Data-Acquisition System

A system comprising digital telemetry remote stations and an on-line event detection and data recording station has been developed. The remote stations employ time-division multiplexing of up to three seismic sensors operating at sampling rates of 60 samples/s. Higher sampling rates are available if fewer sensors are used per station. The highest single-sensor sampling rate is 240 samples/s. Companding ?-255 law analog-to-digital conversion is performed on-site utilizing an eight-bit transmission format and exhibiting a 72-dB dynamic range. Event detection at a data collection station has been implemented on a microprocessor, which also handles data acquisition and synchronization with a standard-time clock. A slave microprocessor controls data transmission via telephone lines and data recording on magnetic tapes employing a standard format to permit off-line data analysis on a computer. Three digital-to-analog output channels are provided for on-line signal monitoring.     

Optical grating diffraction method: from strain microscope to strain gauge

The grating diffraction method for direct strain measurement is reviewed. Two systems which use this method are presented. The first system is a compact strain microscope. A Leitz optical transmitting microscope with white light source is reconstructed by developing a loading and recording system. Gratings with median density of between 40 and 200 lines/mm are used. With the help of a Bertrand lens, the Fourier spectrum of the grating is formed with high image quality on the CCD sensor plane. Software is developed to precisely, quickly and automatically determine the diffraction spot centroids. The second system is a new strain sensor based on a high-frequency grating and two Position Sensor Detectors (PSDs). The grating, attached to the surface of the specimen, is illuminated by a focused laser beam, generally with a frequency of 1,200 lines/mm. The centroids of diffracted beam spots from the grating are automatically determined using two PSD sensors connected to a personal computer. The shift of diffracted beam spots due to specimen deformation is detected. Strain sensitivity of one micro-strain can be obtained, as can a 0.4 mm spatial resolution for strain measurement. The system can be used for both static and dynamic tests.     

Modeling Studies on the Development of a System for Real-Time Magnetic-Field Imaging of Steel Reinforcing Bars Embedded Within Reinforced Concrete

This paper addresses fundamental issues associated with the development of a real-time magnetic-field imaging system for nondestructive testing of prestressed and reinforced concrete. Modeling results have shown that with a square coil of 300 times300 times2.5 mm³, 10-mm rebars can be imaged down to a depth of 100 mm. Studies also indicate that the vertical component of the induced magnetic field is most favorable as it can readily be reconstructed to yield geometry and dimensional information pertaining to the rebar structure.     

The resolving power of magneto-modulation sensors with an amorphous ferromagnetic core

The resolving power of magnetic-field magneto-modulation sensors with an amorphous ferromagnetic core with respect to energy, magnetic flux and induction in the low-frequency range is considered. It is shown that the high energy sensitivity and resolution with respect to the magnetic flux does not always correspond to the lowest sensitivity threshold of the magnetic-induction sensor.     

A New Magnetic Sensor Concept for Nondestructive Evaluation of Deteriorated Prestressing Strand

This article describes proof-of-concept testing of a sensor based on magnetic field detection to estimate the remaining effective cross-sectional area in corroded prestressing strands inside prestressed concrete beams. The primary corrosion mode is rusting of the strand. The magnetic properties of rust are vastly different from those of steel, thus making a magnetic sensor theoretically feasible. An electromagnet system with Hall sensors has been designed. The electromagnet induces a magnetic field in the specimen by magnetizing it from one side, and at a particular distance from the electromagnet's pole face. At near magnetic saturation, for various diameters and distances of up to 2 in from the magnet face, the induced magnetic field is reliably related to the effective cross-section of the steel bar. Experiments with steel rods and prestressing strands of different diameters conducted in a laboratory are presented. Initial results confirm that by using an appropriate electromagnet based on the magnetic-field technique, in-situ detection of remaining effective cross-sectional area is possible. Challenges in making this technique practical are discussed. If the follow-up research confirms the practicality of the proposed magnetic sensor, there is a potential to substantially improve the state-of-the-art in bridge inspection in terms of accuracy and convenience.     

磁轭式磁粉探伤机提升力测量装置的研制

磁粉探伤是一种重要的无损检测方法,在生产实际中得到了广泛应用。磁粉探伤机的性能指标稳定并满足工作要求,是保证其检测结果准确可靠的前提,磁粉探伤机最关键的性能指标就是其磁轭的磁化能力,目前国内常用的磁化能力校验方法是提升力测试法。本文根据磁轭式磁粉探伤机提升力的定义,利用智能传感器和高速数据采集技术,研制出了一种磁粉探伤机提升力测量装置,本装置操作简便,结果直观,不用再使用笨重的提升力测量试块,大大提高了校验效率,取得了良好的社会效益和经济效益。     

Fast computation for generating CGH of a 3D object by employing connections between layers

An approximate method for generating computer-generated holograms (CGH) of a 3D object with six times faster speed than the conventional algorithm is presented. In the conventional algorithm, a 3D object is sliced into many layers and treated as a collection of self-illuminated point light source. The propagation process of a light ray from every point of an object to all the points on the hologram plane is simulated and interfered with by the reference beam to form a CGH. In our proposed method, under the assumption that the depth of a 3D object is much smaller than the recording distance, we just need to calculate the oblique distance between the first layer and the hologram plane, and then the oblique distances from the other layers to the hologram plane can be obtained from a simple relation, thus the computational time is much reduced. The CGH is optically reconstructed and the quality of the reconstructed image agrees well with that from the conventional algorithm.     

Asymmetric giant magnetoimpedance of amorphous microwires under the action of torsional stresses

The effect of torsional stresses on the direct-current-induced asymmetric giant magnetoimpedance in an amorphous microwire with negative magnetostriction has been theoretically studied. The appearance of asymmetry in the dependence of the impedance on the external magnetic field is related to the inter-action of a circular field of the direct current and a helicoidal anisotropy of the wire that is induced by the applied torsional stresses. It is established that torsional stresses significantly influence a threshold value of the current-generated bias field, above which a hysteresis in the dependence of the impedance on the external field disappears. The obtained results can be used for the creation of weak magnetic-field sensors.     

一种空间匹配的高速飞行目标轨迹估计方法

针对低空高速飞行目标轨迹估计问题,提出了一种利用多阵列进行空间匹配的轨迹估计方法。该方法首先对探测范围内的空间点进行划分,计算其相对于阵列参考坐标的真实方位角与俯仰角并建立字典进行存储。将传感器阵列接收到的信号进行分帧处理,对每一帧数据计算波达方位。理论上,在探测范围内,高速运动目标为直线运动。在理想情况下,对于单个阵列,每一帧数据得到的方向矢量与参考坐标所构成的直线均处于同一平面。对每一帧数据估计得到的波达方位在字典上进行匹配,找到误差最小的N个空间点,进行直线拟合。再对由两帧以上数据得到的直线进行空间平面拟合,得到估计平面。两个阵列所得的估计平面的相交直线即为高速飞行目标的估计轨迹。仿真结果验证了高速飞行目标的轨迹估计算法的有效性。     

Magnetic Field for Radiating and Receiving Loops Placed on Parallel Planes

In the calibration of radio receivers and field-intensity meters, a radiating loop and a receiving loop under test are mainly located either in a coaxial or coplane to each other. A formula to obtain the average magnetic-field strength incident on a receiving loop is derived for the case where the radiating and receiving loop antennas have a certain deviation on a parallel plane from the coaxial or coplanar alignment of the loops. In order to expand the uniform region of the magnetic field around the test point, the distribution of the magnetic field is investigated by using this formula for some alignments where the four (or less) radiating loops and a receiving loop lie on parallel planes to each other. It is obvious that the uniform regions are improved by factors of about 10 or 16 by increasing a radiating loop to two or four loops, respectively.     

Improving the Frequency Characteristics of RF Standard Magnetic-Field Generator Employing Loop Antenna

In the HF and VHF region, the standard magnetic-field generator having a loop antenna has been generally used for the calibration of a radio receiver or a field-strength meter. Presented are new standard magnetic field generators which are able to produce a constant magnetic field over a wide band frequency range by means of measuring the loop current through a compensation transmission line and a compensation thermination resistor. A magnetic-field generator in which a thermistor was used as both a compensation resistor and a current sensor was constructed and examined over the frequency range 10 to 50 MHz. The measured values were agreed with theoretical values within ±0.1 dB.     

油品含水率多点实时监测系统的研制

提出了润滑系统油品含水率多点在线实时监测系统的实现方法,设计了基于变介电常数式电容传感器的润滑油品含水率变送器,根据高速线材厂液压循环润滑系统的特点,利用组态王软件,实现对液压系统的润滑油含水率进行多点实时监测.通过在高速线材厂液压循环系统的使用证明,该系统能够准确、快速地测出润滑油品的含水率并及时报警,从而避免了润滑失效所带来的潜在危害.     

Broad-Band Remote-Sensing Magnetometer

A broad-band remote-sensing magnetometer system has been developed for measuring fast-rising pulsed magnetic fields. Broad frequency response is achieved by frequency modulating a 1.5-GHz microwave carrier for transmission from the sensor to a remotely located receiver. The primary field probe is a ferrite-loaded coil, which produces a current proportional to the magnetic-field intensity. This current is used to frequency modulate a YIG-tuned transistor oscillator in the sensor. A traveling-wave amplifier in the receiver provides carrier amplification and amplitude limiting because it is operated in saturation mode. A new type of FM discriminator, which offers multiple-octave bandwidth potential, converts the frequency-modulated carrier to an amplitude-modulated carrier. The signal is finally detected and amplified for oscilloscope display. While the present system achieves a 50-MHz bandwidth, the system concept should be capable of extension to several times this bandwidth.     

Integrated transmission lines for magnetic thin film memories

The pulse transmission properties of integrated strip lines are examined for a structure that has been proposed for application in a large capacity, high-speed magnetic film memory. The lines are vacuum-deposited onto an insulated ground plane and are characterized by low impedances. Previous analyses, such as those given by Eastman and Chang, McQuillan, and Harloff, examine the effects of skin-depth losses in lines which are assumed to be perfectly terminated. In general, this type of analysis is insufficient for lines which are lossy and which have resistive terminations. The present analysis considers skin-effect losses in the ground plane and in the strip conductors separately and also includes the effect of reflections from resistive terminations. The influence of heavy magnetic loading of the transmission line due to the presence of magnetic film devices is examined in detail. A computer program, similar to the one described by Bertin, has been used to obtain numerical results for the pulse response of the transmission lines. Data are presented which demonstrate the influence of line geometry and material properties.     

Minimizing data collection for field calibration of steady-state virtual sensors for HVAC equipment

The paper presents an algorithm to minimize the amount of data collection for calibration of steady-state virtual sensors when obtained during normal operation of HVAC equipment in the field. If virtual sensors were calibrated using laboratory data, the amount of the calibration data could be minimized using design of experiment techniques. However, these techniques are not applicable to data from field operating equipment since most of the operating conditions are not controllable (e.g., ambient temperature, loads). In this paper, an algorithm to minimize the data collection period for calibration of steady-state virtual sensors is developed based on sensor accuracy, reliability and applicability. Application of the method is demonstrated for calibration of hourly electricity consumption virtual sensors for 3 packaged air conditioners that are serving a small commercial building, and the method terminated the calibration process after about 3 weeks of data collection for all units with very accurate estimates of electricity consumption.