集群系统中央控制器信令/调度单元的设计

这篇文章以自行研制的“多信道共用通信与报警系统”为例,对系统中央控制器的信令/调度单元做了比较全面的介绍,阐述了利用单片机实现系统信令/调度单元的控制过程,给出了系统信令/调度单元软件控制流程。     

连续液相烧结钨基高比重合金板的密度分布

采用阿基米德排水法，测量了连续液相烧结钨基高比重合金板的密度，并对其在长度和宽度方向上的密度分布进行了研究。结果表明，连续液相烧结得到的钨基高比重合金板密度在烧结试样行进方向上产生梯度分布。定量金相分析表明，密度分布不均是由于钨相在烧结试样行进方向上分布不均所致。而钨的定向浓差扩散是导致钨相分布不均的直接原因。     

Content-Based 3-D Model Retrieval: A Survey

As the number of available 3D models grows, there is an increasing need to index and retrieve them according to their contents. This paper provides a survey of the up-to-date methods for content-based 3D model retrieval. First, the new challenges encountered in 3D model retrieval are discussed. Then, the system framework and some key techniques of content-based 3D model retrieval are identified and explained, including canonical coordinate normalization and preprocessing, feature extraction, similarity match, query representation and user interface, and performance evaluation. In particular, similarity measures using semantic clues and machine learning methods, as well as retrieval approaches using nonshape features, are given adequate recognition as improvements and complements for traditional shape-matching techniques. Typical 3D model retrieval systems and search engines are also listed and compared. Finally, future research directions are indicated, and an extensive bibliography is provided.     

基于RSD的脉冲放电系统主回路仿真与试验

研究了基于RSD开关的脉冲放电主回路,应用ATPDraw软件仿真了不同主电容、主电压、负载电阻条件下的输出电流波形,并在测试平台上进行了相应的开通试验.试验研究了不同叠片片数和不同主电压下磁开关的输出电压波形,为其配合RSD使用、保证合适延迟时间提供了依据.进行了直径40mm的RSD管芯极限通流试验,200μs脉宽下获得峰值电流42kA,与经验公式吻合.计算和试验结果都反映了RSD开通电压随峰值电流增大而增大的趋势.     

Sub-molecular features of single proteins in solution resolved with scanning tunneling microscopy

Scanning tunneling microscopy (STM) can be used to image individual biological molecules, such as proteins, in vacuum or air. This requires sample dehydration and thus may not reflect the native state of the molecule. Extensive efforts have been made to image single proteins in solution using STM; however, the images have revealed only round or oval shapes with no sub-molecular details. Here, we present the sub-molecular features of streptavidin proteins under physiological conditions using a homebuilt low-leakage-current and highstability liquid phase STM. The N-lobe, C-lobe, and C-terminal tail of the epidermal growth factor receptor kinase domains were also resolved in solution. Our results demonstrate that the structure, morphology, and dynamics of a protein molecule can be examined under physiological conditions by the STM.

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Nonlinear discriminant clustering based on spectral regularization

Owing to sparseness, directly clustering high-dimensional data is still a challenge problem. Therefore, obtaining their low-dimensional compact representation by dimensional reduction is an effective method for clustering high-dimensional data. Most of existing dimensionality reduction methods, however, are developed originally for classification (such as Linear Discriminant Analysis) or recovering the geometric structure (known as manifold) of high-dimensional data (such as Locally Linear Embedding) rather than clustering purpose. Hence, a novel nonlinear discriminant clustering by dimensional reduction based on spectral regularization is proposed. The contributions of the proposed method are two folds: (1) it can obtain nonlinear low-dimensional representation that can recover the intrinsic manifold structure as well as enhance the cluster structure of the original high-dimensional data; (2) the clustering results can also be obtained in the dimensionality reduction procedure. Firstly, the desired low-dimensional coordinates are represented as linear combinations of predefined smooth vectors with respect to the data manifold, which are characterized by a weighted graph. Then, the optimal combination coefficients and the optimal cluster assignment matrix are computed by maximizing the ratio between the between-cluster scatter and the total scatter simultaneously as well as preserving the smoothness of the cluster assignment matrix with respect to the data manifold. Finally, the optimization problem is solved in an iterative procedure, which is proved to be convergent. Experiments on UCI data sets and real world data sets demonstrated the effectiveness of the proposed method for both clustering and visualization high-dimensional data set.     

基于DLL技术和COM组件技术实现LabVIEW和MATLAB混合编程

LabVIEW和MATLAB混合编程应用日益广泛,然而大多数开发软件在客户端应用时需要同步安装MATLAB,大大限制了软件的推广应用。针对LabVIEW和MATLAB混合编程开发软件发布后独立于MATLAB运行的要求,从LabVIEW和MATLAB共同支持的数据接口技术出发,论述LabVIEW调用MATLAB计算代码的方法,比较每种接口技术的优势和缺点。通过实例实现了基于DLL(动态链接库)技术和COM(基于组件对象模型)组件技术的LabVIEW与MATLAB混合编程。成功实现了应用程序独立运行并明显改善了执行效率。     

大型热网加热器管板堆焊工艺

介绍大型热网加热器管板堆焊工艺和如何通过控制焊接顺序及方向解决堆焊变形问题的。     

Performance evaluation of high g accelerometers

A numerical model for the split Hopkinson bar fly-away technique is presented to evaluate the performance of accelerometers measuring large amplitude pulses. Simulation results based on the numerical model indicate that the rise time of the incident stress pulse in the incident bar and the disk length are of appropriate lengths for the disk response to be accurately approximated as a rigid-body motion. Strain-time histories demonstrate that the incident strain pulse is non-dispersive. The rigid-body acceleration of the disk is derived from analytical models with stress at the incident bar/disk interface, incident strain-time data, and particle velocity on the free end of the disk calculated from numerical results. Thus, accelerations measured using the accelerometer and those derived from the models can be compared. These acceleration-time pulses show good agreement. The numerical model of the split Hopkinson bar fly-away technique can be used to calibrate high g accelerometers.     

油酸钠对半水硫酸钙晶须的稳定化机理

采用SEM，FT-IR，XRD等测试方法分析了油酸钠稳定化处理前后半水硫酸钙晶须的表面形貌、表面基团、物相组成，在此基础上研究了油酸钠对半水硫酸钙晶须的稳定化机理。结果表明，油酸钠在半水硫酸钙晶须表面的吸附状态随其用量的不同而不同，油酸钠对半水硫酸钙晶须表面活性点钙离子的封闭作用、对晶须表面离子的阻溶作用以及对晶须表面性质的改变是油酸钠使半水硫酸钙晶须保持稳定的根本原因。