机械系统动态优化设计的灵敏度分析法

本文用变分法理论,统一给出了机械系统动态优化设计中需要的伴随方程、末端条件和灵敏度系数公式。方法统一,形式规范。最后给出了两个实例计算。     

Improving the Dynamic Range of Real-Time X-Ray Imaging Systems via Bayesian Fusion

The performance and reliability of detecting flaws using X-ray techniques are largely conditioned by the dynamic range of the real-time X-ray imaging systems. This paper proposes a software solution to the problem of dynamic range improvement. The idea is to acquire two images of the same object under two different acquisition conditions, and to integrate these two images in order to obtain a more accurate range measurement of signal levels. To do this, a data fusion technique is developed that is based on the Bayesian theory. The Bayesian fusion method is illustrated with the aid of both simulations and exmaples on real images. The study demonstrates the possibility of improving significantly the dynamic range of real-time X-ray imaging systems using data fusion techniques.     

A Homodyne Detection at 100 GHz with a Pyroelectric Detector

Homodyne detection of 100-GHz signals has been accomplished with a PVF2 pyroelectric detector. The minimum detectable power was 4 X 10-15 W using approximately 1-Hz bandwidth. The technique is applicable to active measurements where the signal source can be used as the local oscillator of the homodyne detection.     

Measuring Systems for Thermometer Calibration in Low-Temperature Range

The national temperature standard for the low-temperature range between 13.8033 K and 273.16 K has been established in Poland at the Institute of Low Temperature and Structure Research (INTiBS). The standard consists of sealed cells for realization of six fixed points of the International Temperature Scale of 1990 (ITS-90) in the low-temperature range, an adiabatic cryostat and Isotech water and mercury triple-point baths, capsule standard resistance thermometers (CSPRT), and AC and DC bridges with standard resistors for thermometers resistance measurements. INTiBS calibrates CSPRTs at the low-temperature fixed points with uncertainties less than 1 mK. In lower temperature range??between 2.5 K and about 25 K ?? rhodium?Ciron (RhFe) resistance thermometers are calibrated by comparison with a standard which participated in the EURAMET.T-K1.1 comparison. INTiBS offers a calibration service for industrial platinum resistance thermometers and for digital thermometers between 77 K and 273 K. These types of thermometers may be calibrated at INTiBS also in a higher temperature range up to 550°C. The Laboratory of Temperature Standard at INTiBS acquired an accreditation from the Polish Centre for Accreditation. A management system according to EN ISO/IEC 17025:2005 was established at the Laboratory and presented on EURAMET QSM Forum.     

Measurement of Reflection Coefficient by Means of Slotted Line and Homodyne Detection System

A new method for measuring the complex reflection coefficient in a measurement system with a slotted line and homodyne detector is presented. The measurement involves the investigation of the change of phase angle of wave voltage along the waveguide terminated with the element under test. The principle of measurement and X-band measurement system consisting of waveguide elements are described. The signal fed to the homodyne detector is subject to the rectangular phase modulation which facilitates the construction of the modulator and increases the accuracy of phase determination. The phase shifter used in the system includes a slotted line. The reduction of the influence of residual reflections on the phase shift determination is described. Even with standard waveguide elements the measuring accuracy of amplitude reflection coefficient is found to be approximately 10-3.     

Detection of Ultrasonic Signal Using Polarized Homodyne Interferometer with Avalanche Detector and Electrical Filter

Usually, ultrasonic detection is obtained by conventional contact techniques. In some critical cases such as working at hard environmental conditions (hot oven or nuclear field) or sensitive surfaces, then non-contact optical techniques should be used. However, for all optical techniques, low sensitive ultrasonic detection still a common problem. This paper presents a self building homodyne laser interferometer system which is modified by polarization state to improve the detection performance and to increase the sensitivity limit. The introduced interferometer system has been used to detect ultrasonic signal generated in coated quartz sample around its 10 MHz resonance frequency. He–Ne laser source has been used at 633 nm wavelength with low optical power of 1 μW. The generated ultrasonic signal has been observed by two different photodetectors to investigate the better performance one. Band pass electrical filter with certain specifications has been used to obtain suitable signal to noise ratio as demonstrated through this work.     

Some Design Considerations for Digital Position and Velocity Detecting Systems

Design-type information is presented for a system that uses pattern recognition principles to sense position and velocity of moving objects. Judging from the literature, little or no work has been done on this type of system. It is believed that these systems have potential industrial and military applications, e.g., an optical object finder that identifies objects in addition to locating them, or a process control sensor to detect grain size and other dimensional properties. One of the most important parts of the system is the receptor. Minimum receptor matrix size as a function of pattern shapes, orientation, position, and velocity is considered and results are presented.     

适用于大动态范围场景的自动曝光控制算法

针对数码成像系统在大动态范围场景下存在的对主体曝光不足或曝光过度的问题,本文提出了一种新的自动曝光控制算法.该方法将图像窗口分割成M×N个矩形块,利用大动态范围场景中主体与背景之间所具有的较大的对比度,采用一个主动搜索的过程将主体鉴别出来,随后根据主体与背景之间的亮度关系对光照条件进行判断,并且在计算图像整体亮度水平时赋予主体与背景相应的权重从而更多地反映出主体的信息.实验结果表明,算法对所有的评估场景都做出了正确的光照条件判断,其在大动态范围场景下拍摄的预览帧数和曝光误差分别小于8.8帧和6.56%.     

High Dynamic Range SQUID Readout for Frequency-Domain Multiplexers

A 16-SQUID array has been designed and fabricated, which shows 0.12 μΦ ₀ Hz^−1/2 flux noise at 4.2 K. The readout amplifier based on a cryogenic silicon-germanium bipolar transistor employs short-delay negative flux feedback and reaches 7 MHz bandwith for a 1 Φ _0p-p signal. The −1 dB compression is reached approximately at 4.2 Φ _0p-p amplitude when the signal frequency is 1 MHz. In the feedback mode the flux noise is anomalously increased to 0.35 μΦ ₀ Hz^−1/2.      

Adaptive Forecast-Based Monitoring for Dynamic Systems

Several forecast-based monitoring methods have been developed for autocorrelated data. One effective method is to use the forecasts based on the exponentially weighted moving average (EWMA). However, during the transition period of dynamic systems, the forecast-based monitoring procedure becomes inadequate due to its use of constant time series model parameters. In this article we present an adaptive forecast-based monitoring approach that performs well on dynamic systems. We examine two competing procedures: the adaptive time series model and the adaptive EWMA. We use a plastic extrusion process with first-order dynamics to illustrate the application of these two procedures, and we also evaluate the performance of the two procedures via simulation.     

Wood Derived Composites for High Sensitivity and Wide Linear‐Range Pressure Sensing

Natural wood possesses a unique 3D microstructure containing hierarchical interconnected channels along its growth direction. This study reports a facile processing strategy to utilize such structure to fabricate carbon/silicone composite based flexible pressure sensors. The unique contribution of the multichannel structure on the sensor performance is analyzed by comparing the pressure response of the vertically cut and horizontally cut composite structures. The results show that the horizontally cut composite based sensors exhibit much higher sensitivity (10.74 kPa^?1) and wider linear region (100 kPa, R² = 99%), due to their rough surface and largely deformable microstructure. Besides, the sensors also show little hysteresis and good cycle stability. The overall outstanding sensing properties of the sensors allow for accurate continuous measurement of human pulse and respiration, benefiting the real‐time health signal monitoring and disease diagnoses.     

非亏损对称系统的子结构灵敏度综合方法

本提出了一种利用子结构灵敏度综合对非亏损对称系统进行特征对灵敏度分析的方法。本利用固定界面模态综合和子结构约束模态以及约束主模态的二阶灵敏度，实现了非亏损对称系统的重特征值灵敏度分析。算例表明了本的方法是行之有效的。     

A Wide Dynamic Range Analog-to-Digital Conversion System for GCMS Applications

An analog-to-digital conversion system is described which utilizes three parallel integrators of different sensitivities in front of a 12-bit analog-to-digital converter (ADC) to achieve a wide dynamic range, high linearity, and noise reduction. Gain ranging decisions are made by the hardware using a novel method of checking the ADC serial data output, with a minimal amount of logic circuitry. Applications to gas chromatography mass spectrometry (GCMS) are described.     

Homodyne tomography of classical and non-classical light

Abstract

States with explicit quantum character, such as squeezed vacuum and bright squeezed light, as well as coherent states and incoherent superpositions of coherent states were generated and analysed by tomographical methods. Wigner functions, photon-number distributions, density matrices and phase distributions were reconstructed with high accuracy. Features such as photon number oscillations, sub-Poissonian and super-Poissonian photon statistics, bifurcations of the phase distribution, and loss of coherence were observed, demonstrating the usefulness of quantum state reconstruction as an analysing tool in quantum optics experiments.     

Probability of Detection and Optimal Sensor Placement for Threshold Based Detection Systems

This paper provides a probabilistic analysis of simple detection systems which are based on thresholding feature values extracted from a sensor signal. For such systems, this paper explains how to calculate the probability of detection as a function of range from the sensor to the object of interest. This function is important in that it enables optimal positioning of a group of sensors, either maximizing detection rates for a given number of sensors or informing the minimum number of sensors necessary to achieve a desired probability of detection throughout an area. An example case study is presented, based on a novel approach to passive acoustic diver detection in noisy environments.      

非保守系统特征灵敏度分析直接法

当结构动力学系统的阻尼矩阵不能同时通过质量和刚度矩阵对角化时,线性振动系统的特征值问题就转化为二次特征值方程,相应的特征值和特征值向量以及它们的导数都成为复空间内的量.针对非保守系统的二次特征值问题,通过求解非齐次线性方程组,直接导出非保守系统特征值和特征向量的一阶灵敏度.提出的方法不需要非保守系统的全部模态,因此,适用于大型复杂结构的特征灵敏度分析.     

一类动力系统的稳定性及镇定

本文定义了一类新的动力系统-HCTD系统,利用矩阵迹的不等式理论研究了这类系统的稳定性,并给出了该系统稳定的充分必要条件。讨论了当Lyapunov方程的解P是HCTD阵时,动力系统稳定的充分条件。提出了用解矩阵迹的不等式设计动力系统镇定控制器的一种新方法。