核医学成像技术中计算机的应用

由于计算机和核医学的结合,各种成像方法的计算机化医学图像层析技术正在迅速发展,并开始广泛应用。本文介绍各类成像技术中计算机的应用,特别评述其最近进展,并提出了今后的展望。     

A new simplified two-dimensional model for the threshold voltage ofMOSFET's with nonuniformly doped substrate

A new simplified two-dimensional model for the threshold voltage of MOSFETs is derived in terms of simple characteristic functions. These characteristic functions are transformed from the exact series solution of the two-dimensional Poisson's equation, in which the effects of a nonuniformly doped substrate and a finite graded source-drain junction depth are included. In this model, charge-screening effects are proposed to account for the weak dependence of the threshold voltage on the substrate bias for short-channel MOSFETs, and exact source and drain boundary potentials can be approximated by their equivalent power functions. The accuracy of the simplified 2-D model is verified by 2-D numerical analysis. Moreover, comparisons between the simplified 2-D model and the experimental results are made, and good agreement is obtained for wide ranges of channel lengths, applied substrate, and drain biases     

用三十六臂井径成像测井技术评价套损情况

对油水井套管损伤情况的检测是工程测井的主要内容之一,36臂成像井径测井能较准确判断套管弯曲、变径、变形等情况。介绍了36臂井径成像测井仪器、解释方法,并给出测井实例。36臂井径通过独立臂的硬接触提供36条井径测井曲线,提供套管的质量状况,成果图图象直观、准确,可形成立体图、井壁展开成像图、井壁截面图。     

基于HMM方法的动态手势轨迹训练性能研究

基于HMM(Hidden Markov Model,隐形马尔可夫模型)对动态手势轨迹的训练是手势识别的关键技术之一。本文对HMM的模型训练采用Baum.Welch算法,并分别从迭代次数,样本个数选取,以及模型初值选取等方面对动态手势轨迹的训练性能进行了研究。实验结果表明HMM方法对具有时空特性的动态手势轨迹识别是非常有效的。     

三平板剪切干涉仪自动测试系统

三平板剪切干涉仪是环路剪切干涉仪中最简单的一种,它具有基本等光程、剪切量连续可调、两出射光束恒相互平行等特点。利用三平板剪切干涉仪对激光器出射波面质量进行检测,探讨了由剪切干涉图复原原始波面的1阶微分法,编制了专家辅助软件系统,为光机型的三平板剪切干涉仪配置了实时图像采集、处理系统,实现了光、机、电、算相结合,融硬、软件于一体的数字波面剪切干涉仪,并通过实验验证了方法的重复性精度。     

多媒体教学课件的网上发布

主要介绍AUTHORWARE下多媒体教学课件的网上发布技术路线与实践     

Co-evolution as a computational and cognitive model of design

Co-evolutionary design has been developed as a computational model that assumes two parallel search spaces: the problem space and the solution space. The design process iteratively searches each space using the other space as the basis for a fitness function when evaluating the alternatives. Co-evolutionary design can also be developed as a cognitive model of design by characterizing the way in which designers iteratively search for a design solution, making revisions to the problem specification. This paper presents the computational model of co-evolutionary design and then describes a protocol study of human designers looking for evidence of co-evolution of problem specifications and design solutions. The study shows that co-evolutionary design is a good cognitive model of design and highlights the similarities and differences between the computational model and the cognitive model. The results show that the two kinds of co-evolutionary design complement each other, having strengths in different aspects of the design process. Electronic Publication     

Microstructure and thermal behavior of Sn-Zn-Ag solders

The microstructure and thermal behavior of the Sn-Zn-Ag solder were investigated for 8.73–9% Zn and 0–3.0% Ag. The scanning electron microscopy (SEM) analysis shows the Ag-Zn compound when the solder contains 0.1% Ag. X-ray diffraction (XRD) analysis results indicate that Ag₅Zn₈ and AgZn₃ become prominent when the Ag content is 0.3% and above. Meanwhile, the Zn-rich phase is refined, and the Zn orientations gradually diminish upon increase in Ag content. The morphology of the Ag-Zn compound varies from nodular to dendrite structure when the Ag content increases. The growth of the Ag-Zn compounds is accompanied by the diminishing of the eutectic structure of the Sn-9Zn solder. Differential scanning calorimetry (DSC) investigation reveals that the solidus temperature of these solders exists at around 198°C. A single, sharp exothermic peak was found for the solders with Ag content less than 0.5%. Liquidus temperatures were identified with the DSC analysis to vary from 206°C to 215°C when the Ag content ranges from 1.0% to 3.0%     

Mössbauer effect studies and X-ray diffraction analysis of cobalt ferrite prepared in powder form by thermal decomposition method

Cobalt ferrite (Co_xFe_3?xO₄) is prepared in powder form by thermal decomposition of iron and cobalt salts and is analysed by X-ray diffraction and Mössbauer spectroscopic techniques. The variation of Mössbauer parameters, lattice parameters and crystallite size of the products formed with variation in the composition of Fe and Co ratios are studied. The studies confirm the formation of nano-size cobalt ferrite particles with defect structure and it is found to be maximum for the Fe : Co = 60 : 40 ratio of the initial precursor oxides.