A separate two-stage pulse tube cooler working at liquid helium temperature

A novel 4 K separate two-stage pulse tube cooler (PTC) was designed and tested. The cooler consists of two separate pulse tube coolers, in which the cold end of the first stage regenerator is thermally connected with the middle part of the second regenerator. Compared to the traditional coupled multi-stage pulse tube cooler, the mutual interference between stages can be significantly eliminated. The lowest refrigeration temperature obtained at the first stage pulse tube was 13.8 K. This is a new record for singlestage PTC. With two compressors and two rotary valves driving mode, the separate two-stage PTC obtained a refrigeration temperature of 2.5K at the second stage. Cooling capacities of 508mW at 4.2K and 15W at 37.5K were achieved simultaneously. A one-compressor and one-rotary valve driving mode has been proposed to further simplify the structure of separate type PTC.     

Selective Smoothed Finite Element Method

The paper examines three selective schemes for the smoothed finite element method (SFEM) which was formulated by incorporating a cell-wise strain smoothing operation into the standard compatible finite element method (FEM). These selective SFEM schemes were formulated based on three selective integration FEM schemes with similar properties found between the number of smoothing cells in the SFEM and the number of Gaussian integration points in the FEM. Both scheme 1 and scheme 2 are free of nearly incompressible locking, but scheme 2 is more general and gives better results than scheme 1. In addition, scheme 2 can be applied to anisotropic and nonlinear situations, while scheme 1 can only be applied to isotropic and linear situations. Scheme 3 is free of shear locking. This scheme can be applied to plate and shell problems. Results of the numerical study show that the selective SFEM schemes give more accurate results than the FEM schemes.     

用具有零权的平差方法求解秩亏自由网的研究

以秩亏自由网平差的法方程系数阵的特征根作为虚拟权 ,构造两组虚拟误差方程 ,其中一组具有零权 ,从而用具有零权的平差思想 ,导出求解秩亏自由网待估参数平差值及其协因数的公式 ,并指出 ,此结果与用主成分估计法求解秩亏自由网的结果完全一致。     

基于遗传算法的模糊聚类方法

针对模糊c 均值算法容易收敛于局部极小点的缺陷 ,将遗传算法应用于模糊c 均值算法的优化计算中 .算法采用实数编码 ,提高了试验精度 .实验证明基于遗传算法的模糊聚类方法能够在一定程度上克服初值的影响 ,跳出局部极小点 ,在大样本的聚类方面有较大的优势 .     

一个虚拟手原型的实现

以５ＤＴ 公司生产的数据手套作为手势输入设备,开发了一个虚拟手原型．它以手的运动学模型为基础,采用层次结构法构造手的几何模型,极大地方便了虚拟手的图形显示和实时更新的实现．根据人手的运动约束关系得到各关节弯曲角度的相对比例关系,就能从数据手套得到的７ 个传感数据获得整个手的运动情况,并用静态碰撞检测法处理虚拟手与其他物体的碰撞检测,在运行期间不断地对用户手势进行手势映射计算找到最匹配的手势,执行与该手势对应的动作．本原型简单易行,便于增加手势,最后给出了实现结果．     

灯盏乙素对大鼠肝线粒体氧化损伤的抑制作用

运用Fe^2 -Vc损伤体系诱导大鼠肝线粒体氧化损伤，并研究了灯盏乙素的抑制作用，采用分光光度法测定脂质过氧化物丙二醛（MDA）含量，膜蛋白巯基含量及线粒体肿胀度，利用荧光染料Rhodamine123对线粒体进行标记，跟踪线粒体膜电位的变化，研究发现20－50μmol/L的灯盏乙素能抑制MDA的生成并促使膜巯基含量下降，对线粒体肿胀和膜电位的降低都有一定的抑制作用，并呈剂量依赖关系，结果表明灯盏乙素是一种有效的抗氧化剂，能抑制活性氧诱导的线粒体氧化损伤。μ     

基于H263/TMN8的前后景码率分配及控制

在H263ZI‘MN8的控制技术基础上,提出可控的前后景码率分配算法、前景区优先编码策略以及优化的量化编码次序．可以仅使用一个控制参数来控制前后景的码率分配,并且编码后码流仍符合标准I-t263码流．试验结果表明,该算法在低比特率的情况下视频图像的主观质量要优于TMN8,非常适合窄信道视频通信的应用．     

基于互联网的过程控制系统的安全性设计

分析了远程控制系统安全性设计要解决的两个方面问题：为防止未授权用户恶意破坏控制系统,提出了对付网络入侵者恶意操作控制系统的安全措施;为保证实时数据传输的快速性和安全性,将高级数据加密标准AES与网络通信加密协议SSL相结合,实现了适合于实时控制系统的数据加密算法,并通过测量实时数据加密传输的网络时延来验证该算法的有效性．     

Optical properties of NdxGd1−xAl3(BO3)4 crystal

The optical properties of Nd x Gd 1-x Al\-3(BO\-3)\-4 (NGAB) crystal are reported. The refractive index of it were mesured by V_prism method. The absorption spectra and the flourescence specra of NGAB were also obtained. The optical parameters of NGAB were calculated following J_O theory, the three optical parameters are Ω 2 =1 805×10 -20 , Ω 4=1 85×10 -20 , Ω 6=3 793×10 -20 (RMS=1 4×10 -7 ) and β c( 4F 3/2 → 4I 11/2 ) is about 0 53.     

准噶尔盆地南缘构造物理模拟实验

根据准噶尔盆地南缘地质构造特征和相似理论 ,成功地设计并进行了两组实验 :①利用砂箱模拟了该区剖面中可见的三排背斜带以及背斜紧闭、向斜开阔的特征 ;②利用湿粘土模拟了南缘几排背斜带与边界断裂斜交成“入”字型的平面特征 ,对西南缘存在东、西分段性的形成机制给予了很好的解释。模拟实验结果表明 ,压扭性走滑作用可以产生准噶尔盆地南缘的复杂构造现象 ,在右行压扭的区域动力学背景下可以产生与主位移带呈高角度斜交的张扭性断裂 ,以此可以解释南缘地区东、西分带的原因