Edge location by use of optical phase variation

Traditional optical methods for locating an edge are based on light intensity variation with respect to a reference triggering level. Since the intensity variation is subject to stray light, the intensity variation of the light source, and the triggering level variation, the exact position of the edge cannot be determined. We describe a method for edge location that uses a phase variation in a modified differential interferometer. The maximal point of the slope of the phase variation across an edge is determined exactly by the relative position between the focused beam spot and the detected edge if the initial intensity ratio of the two single-frequency interference beams is kept unchanged. Therefore the phase variation can be used to locate the edge with high resolution and accuracy. To make practical use of the phase variation, the second derivative of the phase was used as a monotonic zero-crossing signal across the edge. The theoretical and the experimental verification have been conducted in detail. The results of the experiment show the feasibility of edge location when phase variation is used. The scheme is not affected by stray light and the intensity variation of the light source.     

Improving automotive dimensional quality by using principal component analysis

Dimensional quality is a measure of conformance of the actual geometry of products with the designed geometry. In the automotive body assembly process, maintaining good dimensional quality is very difficult and critical to the product. In this paper, a dimensional quality analysis and diagnostic tool is developed based on principal component analysis (PCA). In quality analysis, the quality loss due to dimensional variation can be partitioned into a mean deviation and piece-to-piece variation. By using PCA, the piece-to-piece variation can be further decomposed into a set of independent geometrical variation modes. The features of these major variation modes help in identifying the underlying causes of dimensional variation in order to reduce the variation. The variation mode chart developed in this paper provides the explicit and exact geometrical interpretation of variation modes, making PCA easily understood. A case study using an automotive body assembly dimensional quality analysis will illustrate the value and power of this methodology in solving actual engineering problems in a practical manner.     

Study on Quality Evaluation Model in Multi-station Assembly Processes

Based on features of dimension variation propagation in multi-station assembly processes, a new quality evaluation model of assembly processes is established. Firstly, the error source of multi-station assembly system is analyzed, the relationship of dimension variation propagation in multi-station assembly processes is studied and the state equation for variation propagation is constructed too. Then, the feature parameters which influence variation propagation and accumulation in multi-station assembly processes are found to evaluate quality characteristic of the assembly system. Through the derivation of equation on dimension variation propagation, station coefficient matrices which are combined and conversed to determine the max eigenvalue are educed. The max eigenvalue is multiplied by the weight coefficient to establish the quality evaluation model in multi-station assembly processes. Furthermore, assembly variation indexes are proposed to judge of the assembly technology process. Finally, through the practical example, the application of the model and assembly variation indexes are presented.     

Content Uniformity: Separation and quantitation of sources of dose variation

A propagation of error formula is presented which describes a mathematical relationship between uniformity of dosage units (dose variation) and the individual sources of variability. Using this propagation of error formula and a minor modification of the USP Content Uniformity test procedure, one can assign dose variation to weight variation, blend heterogeneity and assay imprecision without compromising the information required by the USP XXII. This formula separates and quantitates the sources of dose variation and defines the manner in which weight variation, blend heterogeneity and assay imprecision are propagated. By knowing how the dose variation is propagated, specific measures can be taken to improve the uniformity of dosage units.

The propagation of error formula can also be used to calculate a priori estimates of dose variation by choosing reasonable or expected variances for weight variation, blend heterogeneity and assay imprecision. Such calculations can save hours of fruitless effort which attempt to improve the content uniformity without considering how dose variation is propagated and to what extent the expected dose variation can be improved.     

碳纤维的强度及离散的探讨

用韦伯理论评价了碳纤维的抗拉强度和分散,验证了形状参数m和强度离散的关系.同时,探讨了体积效应和碳纤维强度离散,证实了细度离散对强度离散的影响.     

Content Uniformity: Separation and quantitation of sources of dose variation

Abstract

A propagation of error formula is presented which describes a mathematical relationship between uniformity of dosage units (dose variation) and the individual sources of variability. Using this propagation of error formula and a minor modification of the USP Content Uniformity test procedure, one can assign dose variation to weight variation, blend heterogeneity and assay imprecision without compromising the information required by the USP XXII. This formula separates and quantitates the sources of dose variation and defines the manner in which weight variation, blend heterogeneity and assay imprecision are propagated. By knowing how the dose variation is propagated, specific measures can be taken to improve the uniformity of dosage units.

The propagation of error formula can also be used to calculate a priori estimates of dose variation by choosing reasonable or expected variances for weight variation, blend heterogeneity and assay imprecision. Such calculations can save hours of fruitless effort which attempt to improve the content uniformity without considering how dose variation is propagated and to what extent the expected dose variation can be improved.     

DDetection of Variation Sources in a Serial Production System

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Impact of SOI thickness fluctuation on threshold voltage variation in ultra-thin body SOI MOSFETs

Threshold voltage variation due to quantum confinement effect in ultra-thin body silicon-on-insulator (SOI) MOSFETs is examined. It is experimentally demonstrated that threshold voltage variation drastically increases when SOI layer is thinned down to 3 nm. A percolation model is used to estimate the contribution of surface roughness to V/sub th/ variation. The method to suppress the threshold voltage variation is also proposed, and around 15% reduction in threshold voltage variation is experimentally demonstrated by applying substrate bias. The reason of the suppression can be explained by quantum confinement effect induced by substrate bias.     

卷筒包装材料的张力分析

以卷筒包装材料的收放卷过程为例，分析包装机械工作过程中柔性包装材料的张力。通过变质量构件的动力学分析，得出张力控制力矩随卷筒直径变化的计算公式。此外，由于张力还受张力还受许多不确定因素的影响，其变化是一个随机过程。当统计图上出现不正常变化时，调节控制力矩需加一个附加值。     

Modeling of nonphase mechanisms in ultrasonic modulation of light propagation

While phase variation due to ultrasonic modulation of coherent light has been extensively studied in acousto-optical imaging, fewer groups have studied nonphase mechanisms of ultrasonic modulation, which may be important in exploring ultrasonic modulation of incoherent light for imaging. We have developed a versatile Monte Carlo based method that can model not only phase variation due to refractive index changes and scatterer displacement in tissue or tissue-like phantoms, but also amplitude and exit location variations due to the changes in optical properties and refractive index under ultrasonic modulation, in which the exit location variation has not, to the best of our knowledge, been modeled previously. Our results show that the modulation depth due to the exit location variation is three orders of magnitude higher than that due to amplitude variation, but two to three orders of magnitude lower than that due to phase variation for monochromatic light. Furthermore it is found that the modulation depth in reflectance due to the exit location variation is larger than that in transmittance for small source-detector separations.     

Variation transmission analysis and diagnosis of multi-operational machining processes

In a Multi-operational Machining Process (MMP), final product variation is an accumulation, or stack-up of variations generated at all the manufacturing operations. In this paper, variation transmission in the MMP is analyzed by relating part variations to operational errors from machine tools, fixtures and datums. At each operation, total part variation is separated into several components corresponding to different variation sources. The result can be applied in both process design and diagnosis. A methodology is developed to identify faulty operations. Process diagnosability is also discussed. A case study is provided to illustrate the developed diagnostic methodology.     

A Robustness Approach to Reliability

Reliability of products is here regarded with respect to failure avoidance rather than probability of failure. To avoid failures, we emphasize variation and suggest some powerful tools for handling failures due to variation. Thus, instead of technical calculation of probabilities from data that usually are too weak for correct results, we emphasize the statistical thinking that puts the designers focus on the critical product functions. Making the design insensitive to unavoidable variation is called robust design and is handled by (i) identification and classification of variation, (ii) design of experiments to find robust solutions, and (iii) statistically based estimations of proper safety margins. Extensions of the classical failure mode and effect analysis (FMEA) are presented. The first extension consists of identifying failure modes caused by variation in the traditional bottom–up FMEA analysis. The second variation mode and effect analysis (VMEA) is a top–down analysis, taking the product characteristics as a starting point and analyzing how sensitive these characteristics are to variation. In cases when there is sufficient detailed information of potential failure causes, the VMEA can be applied in its most advanced mode, the probabilistic VMEA. Variation is then measured as statistical standard deviations, and sensitivities are measured as partial derivatives. This method gives the opportunity to dimension tolerances and safety margins to avoid failures caused by both unavoidable variation and lack of knowledge regarding failure processes. Copyright © 2012 John Wiley & Sons, Ltd.     

Effect of Nb on long-term creep life of JIS SUS304HTB and JIS SUS347HTB steels – heat-to-heat variation and life assessment of stainless steels

Heat-to-heat variation in creep life has been investigated for the 9 heats of JIS SUS 304HTB (18Cr–8Ni steel) and also for the 9 heats of JIS SUS 347HTB (18Cr–12Ni–Nb steel) in the NIMS Creep Data Sheets, mainly taking the effect of Nb into account. The heat-to-heat variation in creep life of 304HTB is mainly caused by the variation in precipitation hardening due to fine NbC carbides at short times, while it is mainly caused by the variation in available nitrogen concentration, defined as the concentration of nitrogen free from AlN and TiN, at long times. The heat-to-heat variation in creep life of 347HTB is mainly explained by the variation of boron concentration, 3–27 ppm, but not by the variation of solution temperature, Nb/C atomic ratio and phosphorus concentration. Boron reduces the coarsening rate of fine M₂₃C₆ carbides along grain boundaries, which enhances the grain boundary precipitation hardening.     

Variation of defect density and its influence on yield extrapolation for integrated circuits

Using the example of stress tests for dielectric breakdown, the close relation between the local variation of defect density on the one hand and the area dependence of yield is verified directly. There is appreciable real variation of defect density (in addition to purely statistical fluctuation) even within individual wafers, but also additional variation between wafers processed together in groups and further variation again between groups of wafers processed separately. Correspondingly, the dependence of yield on area differs progressively more from the Poisson model as more (different) data are summarized in a single average yield. The local variation of defect density also depends on stress level, and hence on the defect considered.     

基于Hilbert-Huang变换的心率变异信号分析

提出一种基于Hilbert-Huang变换(HHT)的心率变异信号分析的新方法。心率变异分析被广泛应用于评估心脏自律功能以及疾病诊断领域。为获得更多心率信号内在特征,首先利用经验模态分解(Empirical Mode Decomposi-tion,EMD)方法将信号分解为一组固有模态函数(Intrinsic Mode Function,IMF),运用Hilbert变换计算并分析各层IMF的瞬时频率和瞬时幅值,从而获取信号所包含的内在信息、心率变异突发时刻和变化趋势。结合积分脉冲频率调制(Inte-gral Pulse Frequency Modulation,IPFM)模型模拟出的心率信号以及真实的心率信号,利用小波分析方法以及HHT方法对心率信号进行对比分析,实验结果证明了HHT方法的可行性,显示了该方法相对于小波分析方法的优势。     

有限元──迭代法

本文提出基于有限元分析结构变更后的迭代法，文中导出了迭代公式，讨论了收敛速度并附有算例，用本文方法计算变更后的新结构，不论结构刚度变化区域大小均可节约计算时间，从而克服了广义结构变更定理应用中的局限性。     

散斑干涉条纹图的总变分去噪方法

去除散斑条纹图中的噪声是电子散斑干涉测量技术的关键问题.提出将总变分图像去噪方法应用于电子散斑干涉条纹图滤波过程中,并对保真系数进行了改进.用总变分模型定义图像的能量函数,利用变分法求得满足能量函数的最优解,将图像去噪过程转化为求解偏微分方程的过程.分别对计算机模拟的条纹图和实验获得的条纹图进行了测试,定性和定量分析的结果表明该技术能够在显著滤波的同时保持条纹的对比度.     

Speckle reduction in optical coherence tomography by adaptive total variation method

An adaptive total variation method based on the combination of speckle statistics and total variation restoration is proposed and developed for reducing speckle noise in optical coherence tomography (OCT) images. The statistical distribution of the speckle noise in OCT image is investigated and measured. With the measured parameters such as the mean value and variance of the speckle noise, the OCT image is restored by the adaptive total variation restoration method. The adaptive total variation restoration algorithm was applied to the OCT images of a volunteer’s hand skin, which showed effective speckle noise reduction and image quality improvement. For image quality comparison, the commonly used median filtering method was also applied to the same images to reduce the speckle noise. The measured results demonstrate the superior performance of the adaptive total variation restoration method in terms of image signal-to-noise ratio, equivalent number of looks, contrast-to-noise ratio, and mean square error.     

The dynamic influence of genetic variation on the susceptibility of sheep to gastrointestinal nematode infection.

The interaction between sheep and the nematode Teladorsagia circumcincta is one of the best understood of all host-parasite interactions. Following infection, there is considerable variation among lambs in the number of nematode eggs produced, the number of early fourth-stage larvae and the number of adult worms in the mucosa. These traits have a high variance to mean ratio (i.e. they are overdispersed or aggregated among hosts), they are skewed and approximately negative binomially distributed. The sources of overdispersion are differences among lambs in the ingestion of infective larvae and the immune response. Both forces can produce aggregation but their relative importance is unknown. The key components of variation can be identified by variance analysis. The sum of the average effects of polymorphic genes is known as additive genetic variation and this increases essentially from zero at one month of age to quite high values at six months of age. The major mechanism underlying genetic variation appears to be the differences among individuals in immune responses. Two of the major sources of variation in immune responses are differences in antigen recognition and differences in the type of cytokines produced. Genes that influence both these sources of variation are associated with differences in resistance to nematode infection. Therefore, much of the heterogeneity among animals in parasite transmission appears to be due to genetic variation in immune responsiveness.     

Effects of applied magnetic field on twin-wire indirect arc shapes

Research on regularity of indirect arc shapes change with variation of applied magnetic field is studied. Results show that indirect arc would be elongated or compressed in XOZ plane with variation of applied transverse magnetic field’s direction and intensity, while the indirect arc would be deflected with the application of longitude magnetic field in YOZ plane, and the deflection degree and direction will be also changed by the variation of longitude magnetic field’s intensity and direction. It is considered that change of arc shapes is caused by variation of arc forces. The influence of Ampere force on indirect arc deformation and deflection is analyzed in this paper.