小型平板CPL蒸发器预热驱动过程研究

分析了小型平板CPL蒸发器毛细多孔芯上下表面温差对启动的影响,建立了蒸发器满液启动的数学模型.结果表明,对不同的金属外壁,多孔芯上下表面平均温差存在一个最大值,铜壁时,温差较小,侧壁效应明显;采用不锈钢壁及上壁铜、侧壁下壁不锈钢时,温差大,侧壁效应小;采用不锈钢外壁时蒸发器加热面的温度过高.上壁采用导热系数大、侧壁下壁为导热系数小的金属对小型平板CPL蒸发器的正常启动以及降低加热表面温度非常有利.     

四旋翼无人机可视化轨迹跟踪仿真系统

为了便于对四旋翼无人机控制算法进行实验仿真和验证,联合Solidworks和Matlab/SimMechanics工具箱设计了一种四旋翼无人机可视化轨迹跟踪仿真系统;利用Solidworks搭建了四旋翼无人机三维实体模型,并通过Solidworks和Matlab转换接口将该实体模型导入到Matlab/SimMechanics中;Matlab/SimMechanics提供了了三维可视化窗口,可以显示无人机的实时仿真状态;仿真平台在Matlab/SimMechanics环境中实现,与Matlab/Simulink通信方便,可方便的将Simulink设计好的控制算法添加到仿真系统中,以进行验证和参数整定,还具有姿态分析和数据分析等功能;轨迹跟踪仿真结果表明,四旋翼无人机可视化轨迹跟踪仿真系统直观可视,准确可靠,能较好地对控制算法进行研究和测试,对四旋翼无人机以及控制算法的研究和开发具有重要价值。     

基于Eclipse图形建模框架的图形化脉冲序列设计软件的实现

采用Eclipse图形建模框架（Graphical Modeling Framework,GMF）技术构建了一个图形化磁共振脉冲序列设计软件．软件具备所见即所得的特点,用户使用拖放方式所画出的脉冲序列与教科书和参考文献上的脉冲序列几乎一样．软件支持核磁共振（Nuclear Magnetic Resonance,NMR）波谱和磁共振成像（Magnetic Resonance Imaging,MRI）的脉冲序列设计,同时提供实验参数管理模块,实现脉冲序列基础上的NMR实验设计和执行预览．得益于GMF完善的模型-视图-控制器模式和强大的代码生成能力,软件开发周期大幅度缩短、扩展能力大幅度提高．     

Multiscale modeling of the effect of carbon nanotube orientation on the shear deformation properties of reinforced polymer-based composites

A combination of molecular dynamics (MD), continuum elasticity and FEM is used to predict the effect of CNT orientation on the shear modulus of SWCNT-polymer nanocomposites. We first develop a transverse-isotropic elastic model of SWCNTs based on the continuum elasticity and MD to compute the transverse-isotropic elastic constants of SWCNTs. These constants are then used in an FEM-based simulation to investigate the effect of SWCNT alignment on the shear modulus of nanocomposites. Furthermore, shear stress distributions along the nanotube axis and over its cross-sectional area are investigated to study the effect of CNT orientation on the shear load transfer.     

多重网格法在燃烧室内流场数值模拟中的应用

多重网格法在燃烧室内流场数值模拟中的应用林文漪，杨彬，周力行（清华大学工程力学系北京１０００８４）关键词：多重网格，数值模拟，湍流一、前言现代燃烧设备多具有复杂的流场结构、多级燃烧的特点及庞大的几何尺寸，无疑地为其数值模拟带来了困难。为了保证计算精度...     

Statistical analyses of electromyographic activity in spasmodic dysphonic and normal control subjects

Heterogeneity in the quality and task sensitivity of vocal symptoms in the spasmodic dysphonia (SD) population contributes to controversy as to whether this is a single disorder or two disorders with different etiologies (neurogenic versus psychogenic). Perceptual and acoustic assessments of vocal symptoms are inadequate to resolve this controversy. However, myoelectric events are intimately proximal to the source of vocal disruption and may be informative. The present report employs statistical modeling of quantitative amplitude measures of electromyographic activity recorded from thyroarytenoid to examine neuromotor bases of vocal symptoms in SD. Consideration of perceptual ratings of the quality and task sensitivity of vocal symptoms in the context of statistical models provides support for the conclusion that the range of vocal symptoms identified as SD represents a single, neurogenic disorder.     

Modeling of MIG/MAG welding with experimental validation using an active contour algorithm applied on high speed movies

This paper investigates some issues in physical modeling of metal inert gas/metal active gas (MIG/MAG) welding process in the short arc mode. In this mode, a metal supply is molten in the arc state and then transferred to the weld pool during the short-circuit state. A hybrid model having two distinct continuous states whose switchings are controlled by two guard conditions is proposed. Due to the complexity of the physical phenomena involved in the welding process, simplifications are used to obtain a model accounting for the main physical contributions but simple enough to yield an efficient, fast and numerically tractable simulator which can be used intensively for evaluating different control strategies. In an attempt to validate the proposed model, different measurements have been made including supply voltage and current sampled synchronously with high speed digital video. In order to extract some relevant quantities representative of the metal transfer from image sequences, an active contour algorithm is developed and tested. The effectiveness of the proposed model in the prediction of major tendencies of a welding process, especially in the arc state, is shown using experimental data. Some limitations of the model during the metal transfer are also stressed and possible remedies are then proposed.     

C 型臂造影系统成像模型和运动模型标定方法研究

C型臂数字造影系统成像原理与相机成像原理类似,但自身机械结构导致其内参随方位改变而变化.提出了一种利用系统提供的方位参数直接计算成像系统内参和外参的新方法,该方法建立在造影系统成像特点和C型臂运动规律的基础上,并利用计算机视觉中的相关理论进行了描述.根据对精度、复杂度和灵活性的不同要求,提出了三种不同层次的模型,模型1用于计算一组特定方位下的系统内参和外参,模型2用于计算发射源到像增强器的距离固定时系统的内外参数,模型3用于计算仟意方位下的系统内外参数.实验结果表明模型1的精度达到亚像素级,可以应用于对精度要求较高的场合;模型2和模型3的精度稍低,但具有较好的灵活性.     

最小方差无失真响应浊音谱建模方法研究

讨论了在语音处理中广泛使用的线性预测模型,分析了线性预测模型在建模语音谱包络方面存在缺点,并分析了线性预测模型过高估计浊音谐波频率处能量以及随着阶数增加线性预测谱逐渐恶化的原因。在此基础上,提出了最小方差无失真响应(MVDR)建模方法,并讨论了通过Toeplitz矩阵的Cholesky分解确定MVDR滤波器系数的方法,通过与线性预测方法进行比较,发现最小方差无失真响应滤波器能提供一个更好的原始语音包络。