Effect of the input coil parameters on the sensitivity threshold of a squid-voltmeter based on high-temperature superconductors

The effect of the parameters of the input coil made of copper wire on the sensitivity threshold of a SQUID-voltmeter, constructed using high-temperature superconducting yttrium ceramic is considered theoretically and determined experimentally. Translated from Izmeritel'naya Tekhnika, No. 11, pp. 48–50. November, 1997.     

Surface-roughness measurement based on the intensity correlation function of scattered light under speckle-pattern illumination

The statistical properties of speckle patterns generated from a rough surface under a fully developed static speckle-pattern illumination are examined. The roughness dependence of the intensity autocorrelation function is studied and utilized to characterize typical engineering surfaces with anisotropic roughness. The speckle patterns under investigation are recorded by use of a CCD technique and are then analyzed by digital image processing algorithms to obtain a parameter that describes the surface roughness. It is shown that an in-process surface inspection can be achieved by this method.     

图像处理方法用于声压敏感核声图的目标定位

利用目标前向散射的扰动声线法适用于在浅水信道对目标进行定位,但所得到的声压敏感核声图的交汇效果易受水底地形不匹配的影响,提出了一种基于图像处理的目标定位方法。首先利用多次的单阈值Otsu方法对多阈值Otsu方法进行改进,确定备选区域;然后从备选区域中选择扰动声线穿过最多的区域并计算重心。仿真结果表明该定位方法不但能够正确定位目标,减小人工判断声图的工作量,而且同样适用于声压敏感核声图交汇效果较差的情况,能够辅助人工判断来减少误判。     

Digital speckle correlation method based on wavelet-packet noise-reduction processing

Despite the advantages of being highly sensitive and nondestructive, the digital speckle correlation method (DSCM) may have difficulties in detecting tiny defects such as delaminations in multilayer ceramic capacitors. This is because the presence of background noise always complicates the data processing. We present a new algorithm, which employs the wavelet-packet noise-reduction process together with the improved DSCM, to improve data processing. Both the computational error and the noise are shown to be reduced successfully by this new algorithm. The accuracy (or precision) of the improved DSCM is increased after operation of the wavelet-packet noise-reduction process. The most important feature of this new algorithm is that it can extract a small hillock signal from a large noisy background in a DSCM deformation result. This helps to save time in the detection of tiny defects, such as delamination, in a miniaturized electronic component.     

基于宽带相关处理的水下运动目标检测

对于水下运动目标的检测,宽带相关处理是一种有效的方法.为了实时实现的需要,选择一类多普勒宽容信号为发射信号,给出了单尺度宽带相关处理器作为运动目标检测器.仿真结果证明,该检测器性能优良,且能够实时实现.     

基于动态响应灵敏度同步反演结构物理参数与输入的算法

提出一种基于动态响应灵敏度概念,仅利用结构少数测点上的动态响应同步反演结构物理参数和输入的方法。首先,将结构的输入力进行正交多项式分解,推导了结构动态响应对输入力的正交系数和结构物理参数的灵敏度计算公式;然后,构造结构参数与输入同步反演的识别方程,并采用阻尼最小二乘法求解方程,同时识别结构物理参数变化与输入力时程;最后,分别利用一个五层平面框架结构和一个九榀三维刚架结构验证了方法的有效性。研究结果表明,该方法可以克服测量噪声和初始模型误差的影响,同步精确地识别结构的输入力和局部损伤引起的结构物理参数变化。     

A multichannel correlation filter based on a photorefractive crystal for the processing of varying speckle fields

A method for the simultaneous processing of speckle fields generated by several single-fiber multimode interferometers is developed. The method uses a multichannel correlation filter based on a single photorefractive crystal. Mutual influence of the neighboring channels is analyzed, and it is shown that the simultaneous processing of several channels can be performed with the help of a single photorefractive crystal, provided that the interchannel spacing is not smaller than half of the size of the optical field pattern formed in the crystal plane.     

Distance measurements by speckle correlation of objective speckle patterns, structured by the illumination

Objective speckles produced by two beams overlapping and interfering on a rough object surface contain information about the angle of incidence of the two beams, and how well they overlap. We obtain the autocovariance function for such a speckle pattern, and demonstrate how the information carried by the objective speckles can be used to probe the distance between the object and the observation plane. From a distance of 75 mm to a distance of 150 mm, and using an angle of 0.3 deg between the two incident beams, we can measure the actual distance with an uncertainty of better than ±0.1% of the full range. As long as the beams overlap at the object surface, the proposed method can measure distance with an uncertainty inversely proportional to the spot size at the object.     

Reduction in correlation-filter sensitivity to background clutter by the automatic spatial frequency selection algorithm

We propose an automatic spatial frequency selection correlation filter that reduces the sensitivity to nonoverlapping noise or background clutter. This is achieved by inclusion of distorted versions of the reference images surrounded by nonoverlapping background clutter. Furthermore, we impose that the window functions of the reference images give response zero-correlation amplitudes. Simulation results are provided in the case of a two-class pattern-recognition problem and show that the results are appreciably increased. The results are compared with a normal automatic spatial frequency selection.     

Modified fringe-adjusted joint transform correlation to accommodate noise in the input scene

A modified fringe-adjusted joint transform correlator is proposed that is able to accommodate noise in the input scene. The effect of noise in the input scene on the performance of the joint transform correlator is analyzed and quantified. When the target is embeddedin aseverely noise-corrupted input scene, it is shown that the proposed modified fringe-adjusted filter joint transform correlator delivers a better correlation performance and the capacity to accommodate this noise than does the fringe-adjusted filter-based correlator. When the power spectra of the input image and the reference image are subtracted from the power spectrum of the joint-input image, it is found that the noise effect on the output plane is independent of the objects in the input scene and originates from the convolution of the reference image and noise in the input scene.     

基于辐照度测量法的火焰检测研究

火焰检测的核心问题是用于火焰检测中的传感器特性评估.本文提出以黑体标定红外传感器.在一定条件下,将标准火光谱辐射出射度特性传递到电光源,以电光源取代标准火的标定方法,采用标准传感器对被检标准火焰辐照度进行量值传递,构造了火焰测量装置并进行了实验.实验结果表明,采用标准传感器在一定精度下实现对标准火焰光谱辐照度进行量值传递是可行的,所引入的不确定度小于1%,为建立人工电光源提供了基本设计参数.     

Modelling the effects of input correlation in iterative software

This paper deals with the dependability evaluation of software programs of an iterative nature. In this work we define a model that is able to account for both dependencies between input values of successive iterations and the effects of sequences of consecutive software failures on the reliability of the controlled system. Differently from previously proposed models, some effort is devoted to address the problem of how to get accurate estimates for the basic parameters. A model is thus proposed that, requiring the designers or users to provide information usually obtainable by experimental techniques, e.g. testing, is more useful and more generally applicable. A thorough analysis is then performed to highlight the effects of the different parameters on the dependability attributes. This analysis allows us to appreciate which effects (and their extent) have variations of both correlation between successive inputs and different structural characteristics of the software at hand. Moreover, the robustness of the model against imprecise assessments of the starting parameters is also shown.     

High sensitivity to humidity of an element based on a carbon-nanotube bundle

The results of development and studies of humidity-sensitive elements based on a carbon-nanotube bundle are presented. It has been demonstrated that arrays of nanotubes grown by the low-temperature plasma-chemical method on planar silicon structures have exceptional sensitivity to humidity. The ratio of the structure resistance in dry and humid states is more than 10⁵-fold. Such a high relative resistance change is caused by the character of changes in conductivity of the charge carriers between individual tubes of the bundle upon adsorption of water molecules.     

Estimation of a dense velocity field based on the statistics of dynamic speckle

This article presents a new technique for flow velocity estimation from ultrasound image sequences. The method is based on the analysis of the temporal statistics of the speckle pattern in motion. We demonstrate that the biased local temporal variance (LTV) of a single pixel within an image of dynamic speckle is related to velocity. This allows us to estimate the total velocity magnitude without the requirement of neither block matching nor autocovariance estimation. A new estimator, asymptotically without bias, called LTV is presented. Results conducted on experimental B mode sequences (40 MHz) of blood mimicking fluid with calibrated velocities are presented. Performances of the estimator are studied and results show good agreement with the statistical model. Magnitude of the 3D velocity vector in the range of 0.1–2 mm/s have been estimated with a standard deviation error of less than 12%. The validity of the method and its limitations are then discussed. © 2010 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 20, 268‐276, 2010     

Optical correlation: influence of the coding of the input image

We analyze the influence of different optical coding methods of the input image in optical correlators. The noise robustness and the optical efficiency of the correlator are investigated. We show in particular that the signal-to-noise ratio is greatly dependent on the coding method. It decreases drastically for large phase modulation.     

On the reconstruction of polycrystalline microstructures from two-point correlation statistics

An exhaustive branching technique is introduced for reconstructing discrete microstructures from two-point statistic occurrences. It is shown that two-point statistics control microstructure, to the extent that exact replicas of discrete microstructures are produced when sufficient two-point statistic occurrences are matched. Efficiency comparisons between simulated-annealing methods and the exhaustive branching method are made on polycrystalline structures and some discussion on advancing the exhaustive branching method is given.     

Multivariate sensitivity analysis to measure global contribution of input factors in dynamic models

Many dynamic models are used for risk assessment and decision support in ecology and crop science. Such models generate time-dependent model predictions, with time either discretised or continuous. Their global sensitivity analysis is usually applied separately on each time output, but Campbell et al. (2006 [1]) advocated global sensitivity analyses on the expansion of the dynamics in a well-chosen functional basis. This paper focuses on the particular case when principal components analysis is combined with analysis of variance. In addition to the indices associated with the principal components, generalised sensitivity indices are proposed to synthesize the influence of each parameter on the whole time series output. Index definitions are given when the uncertainty on the input factors is either discrete or continuous and when the dynamic model is either discrete or functional. A general estimation algorithm is proposed, based on classical methods of global sensitivity analysis.The method is applied to a dynamic wheat crop model with 13 uncertain parameters. Three methods of global sensitivity analysis are compared: the Sobol'-Saltelli method, the extended FAST method, and the fractional factorial design of resolution 6.