Information cut for clustering using a gradient descent approach

We introduce a new graph cut for clustering which we call the Information Cut. It is derived using Parzen windowing to estimate an information theoretic distance measure between probability density functions. We propose to optimize the Information Cut using a gradient descent-based approach. Our algorithm has several advantages compared to many other graph-based methods in terms of determining an appropriate affinity measure, computational complexity, memory requirements and coping with different data scales. We show that our method may produce clustering and image segmentation results comparable or better than the state-of-the art graph-based methods.     

Robust estimation for circular data

The problems arising when there are outliers in a data set that follow a circular distribution are considered. A robust estimation of the unknown parameters is obtained using the methods of weighted likelihood and minimum disparity, each of which is defined for a general parametric family of circular data. The class of power divergence and the related residual adjustment function is investigated in order to improve the performance of the two methods which are studied for the Von Mises (circular normal) and the Wrapped Normal distributions. The techniques are illustrated via two examples based on a real data set and a Monte Carlo study, which also enables the discussion of various computational aspects.     

小型腔式微波离子源的研制

研制了１种用在离子束细胞刻蚀装置中的小型腔式微波离子源，它由石英放电管、同轴谐振腔和封装在管一端的二电极引出系统组成。该源由同轴腔激发起的表面波在石英管内产生等离子体柱。为了提高柱末端等离子体离子引出流密度，选用了在内径７．０ｍｍ直管的一端加上一内径５．０ｍｍ衬管的放电管。在微波频率为２．４５ＧＨｚ，输入功率为９３Ｗ下，氮的引出流密度分别为４８．４ｍＡ／ｃｍ２和９１．７ｍＡ／ｃｍ２。这种表面波放电等离子体源体积小、结构简单，可在较宽的压强范围内产生重复性好、工作稳定的等离子体柱。     

激光冲击处理提高铝合金性能的研究

研究了高功率密度激光冲击处理对Ｌｙ１２ＣＺ铝合金力学性能的影响，研究结果表明激光冲击处理可大幅度提高铝合金的疲劳寿命，疲劳寿命的提高是由于微观组织中位错密度的明显增加，使得材料表层的强度和硬度也明显增加所致。     

双能X射线骨密度仪测定技术研究

以Ｌｕｎａｒ公司ＤＰＸ－Ｌ型双能Ｘ射线骨密度仪为例，研究引起测量误差的主要因素并提出质控措施。用自检模块、腰椎体膜评定仪器的体外测量精度好于１％。对１０位志愿者重复２次测量，体内精度对腰椎，ＭＰＤ（平均百分差）为０．４６，ＣＶ（变异系数）为０．７５；对股骨颈，ＭＰＤ为１．２６、ＣＶ为０．４７；Ｗａｒｄ’ｓ三角区ＭＰＤ为２．０１、ＣＶ为１．１４；大转子ＭＰＤ为１．６６、ＣＶ为０．７２。扫描图像由２位     

快中子零功率反应堆(DF-VI)的临界事故概率分析

本文应用故障树分析方法,对快中子零功率堆(DF-Ⅵ)在启动过程中发生临界事故的可能性做了初步的定量估计。结果表明,该堆每次启动发生临界事故的概率约为10~(-6)量级,得出确保装置启动安全的首要因素是选配合格的操作人员的结论,并对设备的改进提出了一些建议.     

High-Pressure (up to 140 MPa) Dynamic Viscosity of the Methane and Toluene System: Measurements and Comparative Study of Some Representative Models

The dynamic viscosity of toluene and methane mixtures containing 25.03, 37.19, 49.95, 64.11, and 95.00 mol% methane has been measured using a falling-body viscometer. The measurements (280 data points) have been performed in the temperature range 293.15 to 373.15 K and at pressures up to 140 MPa. The data have been discussed in the framework of recent representative models (hard-sphere scheme, friction theory, and free-volume model) as well as with simple mixing laws and empirical models (particularly the LBC model and the self-referencing model) used in the literature. This comparative study shows that the average absolute deviation of the models is between 4.9 and 26.8%, and the maximum deviation is between 11.6 and 49.5%.     

沥青输送泵的选型计算

液体沥青是铝用阳极的重要原料之一,其不同温度下的密度、粘度特性和流量、扬程等直接决定了沥青泵的选型,本文以具体的铝用阳极生产为例,对沥青输送泵尤其是齿轮泵的参数选取进行了科学的计算与合理的分析。     

Density of Carier in YBCO Superconductors with (Ca,Th) Doping

ＩｔｈａｓｂｅｎｗｅｌｋｎｏｗｎｔｈａｔｓｏｍｅｌａｎｔｈａｎｉｄｅｓｃａｎｒｅｐｌａｃｅｙｔｒｉｕｍｉｎＹＢＣＯｓｕｐｅｒｃｏｎｄｕｃｔｏｒｓｗｉｔｈｏｕｔａｐｐｒｅｃｉａｂｌｅｃｈａｎｇｉｎｇｔｈｅｔｒａｎｓｉｔｉｏｎｔｅｍｐｅｒａｔｕｒｅ．Ｎ...     

HDPE／PA6共混型塑料阻隔材料

以自制接枝聚乙烯为增容剂，高密度聚乙烯为基材，尼龙６为阻隔材料，用挤出法，制取ＨＤＰＥ／ＰＡ６共混材料。ＭＰＥ的加入，增大了相间的粘接改善了力学性能，使材料具有良好的阻渗性能。