NORMAL MODES OF FLUID-STRUCTURE INTERACTION IN INTERNAL FLOWS

As an important cornerstone, the methodology of normal modal analysis plays a quite important role in dynamic analyses of linear vibrating systems, and makes much easy to access an understanding of frequency-domain characteristics of the systems. However, most reported work on fluid-structure interaction (FSI) in liquid-filled pipes has been directly carried out in the time domain. When needed, information in the frequency domain has been deduced by the discrete Fourier transforms. In this paper, an analysis is undertaken directly to get modal information of FSI in internal flows and has the advantage of enabling dispersive and dissipative terms to be included in a fully coupled manner. The development used herein highlights common features of the analysis in the frequency domain. The method is validated by comparison with an exact analytical solution, with the results obtained by the discrete Fourier transform from an analysis using the method of characteristics and by comparison with measured data fr     

季风气候区极端水文事件分析——中国洪汝河

１９７５年８月，一场特大暴雨袭击了中国河南省洪汝河流域，导致流域内两座水库大坝漫顶冲毁，整个流域经受了一场严重的洪水灾害，由于大坝冲毁，改变了流域的水文特性，所以要用多种方法研究洪以量的重现期，年极序列法（ＡＭＳ）局部历时离列法（ＰＤＳ）和地区综合分析法，三种不同的分析方法对１９７５年水文事件的洪充量给出不同的重要现期，这就发生一个以概率为基础的方法是否适用于特大水文事件计算的疑问，本次分析计算，     

有介质球的孔径天线的辐射

对于分析有介质球的终端开路波导的辐射方向图,本文介绍了一种更加系统和精确的分析方法。这个分析方法基于以前推导的关于球面矢量波函数径向传播的公式。另外叙述了一个实验程序,证明该分析方法是正确的。     

InSb与化学汽相淀积SiO_2间界面的X射线光电子能谱研究

一、引言窄禁带材料的MOS工艺需要寻找击穿特性合适的、化学稳定性好的高质量介质膜。但是大多数III—V族化合物半导体的原生氧化物化学计量比不稳定,组分不均匀,易水解。因此,近来大量的工作致力于发展与这些半导体的化学性质相适宜的淀积介质膜。低温化学汽相淀积(LTCVD)技术是制备这种介质膜的特别有希望的方法。在InSb单晶衬底上淀积SiO_2得到的化学系统,近来被推荐用于制备红外CCD成象列阵。SiO_2的稳定性、纯度加之工艺简单使这种介质膜颇具吸引力。研究得出的结论是,电性活泼的表面态仍然是因淀积时淀积物与原生氧化物之间的相互作用而引起的。文中采用x射线光电子能谱和较为缓和的化学腐蚀作纵向剖面分布,从而研究考察这种相互作用的化学本质。     

絲网印刷中的问题及解决方法

厚膜电路的制造从丝网印刷开始,丝网印刷是厚膜电路制造的最初工序,它给后面的工序带来重要影响。由于印刷不良而引起的缺陷都是在电路制成后才被发现的,所以丝网印刷     

40nm工艺在军事应用中的风险和机遇

随着芯片制造技术向尺寸更小的新工艺技术节点迈进,芯片制造商和数字设计人员都需要做出有一定风险的决定。而设计人员需要的是功能和性能的提高能够抵消复杂的设计工艺和芯片交付进度所带来的风险。这些要求促使厂商加速开发40nm芯片,为军事用户提供密度更高、速度更快的收发器技术。     

Temporal occurrence of immature skeletal muscle fibers in the sciatic nerve matrix regenerating within the silicone chamber after nerve transection in the normal rat

We examined by light and electron microscopy the immature skeletal muscle fibers in the rat sciatic nerve regenerating within the silicone chamber 14 days after nerve transection. Small myelinated and nonmyelinated nerve fibers associated with Schwann cells from the proximal stump began to approach the midportion of the interstump zone. In the middle segment, fibroblasts or fibroblast-like mesenchymal cells and macrophages were observed everywhere in the newly formed matrix filled with exuded erythrocytes and fibrin clots. In addition to some fibroblast-like mesenchymal cells were closely apposed to each other. However, the proximal and distal segments contained immature muscle fibers with various amount of myofilaments and one or plural centrally located nuclei, thus indicating various phases of the early differentiation of skeletal muscle fibers similar to those observed during an early stage of developing muscle fibers. However, the precise origin of these skeletal muscle fibers remains to be determined.     

Computer-aided diagnosis of solid breast nodules: use of an artificial neural network based on multiple sonographic features

A computer-aided diagnosis (CAD) algorithm identifying breast nodule malignancy using multiple ultrasonography (US) features and artificial neural network (ANN) classifier was developed from a database of 584 histologically confirmed cases containing 300 benign and 284 malignant breast nodules. The features determining whether a breast nodule is benign or malignant were extracted from US images through digital image processing with a relatively simple segmentation algorithm applied to the manually preselected region of interest. An ANN then distinguished malignant nodules in US images based on five morphological features representing the shape, edge characteristics, and darkness of a nodule. The structure of ANN was selected using k-fold cross-validation method with k = 10. The ANN trained with randomly selected half of breast nodule images showed the normalized area under the receiver operating characteristic curve of 0.95. With the trained ANN, 53.3% of biopsies on benign nodules can be avoided with 99.3% sensitivity. Performance of the developed classifier was reexamined with new US mass images in the generalized patient population of total 266 (167 benign and 99 malignant) cases. The developed CAD algorithm has the potential to increase the specificity of US for characterization of breast lesions.     

Role of blood shear stress in the regulation of vascular smooth muscle cell migration

Smooth muscle cell (SMC) migration from the media to the intima of blood vessels contributes to neointimal formation and atherogenesis. Here, we demonstrate how blood shear stress regulates vascular SMC migration in the encapsulating tissue of a micro-cylinder implanted in the center of the rat vena cava with the micro-cylinder perpendicular to blood flow. In this model, the micro-cylinder was exposed to a laminar flow with a known shear stress field in the leading region and a vortex flow in the trailing region. After surgery, the micro-cylinder was encapsulated by a thrombus-like tissue within one day, followed by SMC migration from the vena cava to the encapsulating tissue from day 3 to 20. SMC migration was time-dependent with a peak migration speed at day 5. At each given time (excluding day 1), blood shear stress exerts an inhibitory effect on SMC migration with significantly suppressed SMC migration in the laminar flow region than in the stagnation, separation, and vortex flow regions. SMCs were relatively parallel to the shear stress direction in high shear stress regions, whereas perpendicular to the shear stress direction in low shear stress regions. These results suggest that blood shear stress plays a role in regulating SMC migration and orientation in this model.     

电力电子系统应用的时间域网络解析器的精确度和速度

本文通过比较5个商业软件包的精确度和执行时间，研究了具有固定时间和变换时间的网络仿真方法的性能差异。包含了多个三相二极管整流器和一个PWM电压源逆变器的一系列基准实例显示：对于线性电路来说，固定时间步长法的仿真时间更短一些；然而，为了得到精确的结果，即使对于低开关频率的PWM应用都可能需要非常小的时间步长。否则，如果使用的时间步长过大，即使波形看起来是正确的，PWM逆变器控制信号也可能有严重的错误。