烧结温度对低压ZnO压敏陶瓷显微结构及电性能的影响

利用ＸＲＤ，ＳＥＭ等技术，研究了ＺｎＯ－Ｂｉ２Ｏ３－ＴｉＯ３系低压压敏电阻材料的相民及显微组织，并对不同烧结温度下的电性能进行了研究。结果表明，在１１５０－１２００℃范围内，可通过改变烧结温度调材料的压敏电压值，而材料的非线性系数ａ变化不大。     

硫鎓盐引发环氧树脂光交联反应

本文用BDS·2PF_6为引发剂,对双酚A型环氧树脂(E_(44))及E_(44)-丙烯酸酯混杂体系的紫外光交联反应进行了研究。凝胶率法、硬度法和红外光谱测定的结果表明,光交联反应速度随涂膜厚度的增加而下降;光照停止后,即使在较低的温度下反应仍可继续进行;对于E_(44)-丙烯酸酯的混杂体系,环氧基的反应活性较双键的高,且两种反应是互相影响、互相制约的,在适当配比下有协同效应,体系的反应活性和性能与组成有关。     

苯与乙烯在ZSM－5上的烷基化反应（Ⅲ）固定床反应器行为的化较

给出了低浓度乙烯和苯在ＺＳＭ－５型分子筛催化剂上的宏观动力学方程。建立了中试固定床反应器模型。模型值与中试结果相一致。化较了单段绝热床、等温床和多段绝热床反应器行为。结果表明：在达到乙烯９５％转化率时，苯生成乙苯和乙烯生成乙苯的选择性为等温床要化单段绝热床好；四段绝热床可达到与等温床相当的指标。考虑到绝热床投资少，操作简单，可变性强，四段绝热床反应器应该是首选的反应装置。     

仙人掌,绿色之翼

在渺无人烟的沙漠里，一棵仙人掌就是生命的希望；在冰雪漫天的寒冬里，一棵仙人掌就是绿色的春天…… 仙人掌是掌类植物的一种。仙人掌、叶仙人掌、仙人球、仙人柱等都属于仙人掌科。这是一个有200多属、2000多个品种的大家庭。仙人掌耐干旱，喜阳光，一般生长在沙漠等干旱地区．为灌丛状肉质植物。有的品种小如鸟蛋．有的却大若高楼。据说最大的仙人掌可以长到15米以上，重达十几吨。一般意义上的仙人掌节片扁平。绿色。卵形或长椭圆形。有黄褐色或暗褐色刺。花一般为黄色。而果实一般为红色或紫色。花期夏季。果熟期秋季。仙人掌的原产地在南、北美洲。我国西南部也有野生仙人掌。随着科学的进步，人们对仙人掌的研究不断深入。仙人掌不仅可以药用，对多种疾病的治疗起到一定功效。同时还可以作为美味佳肴摆上餐桌。[编者按]     

Dielectric properties of (Ba0.95Ca0.05)(Ti1-yCay)O3-y ceramics

Calcium doped barium titanate ceramics with composition (Ba_0.95Ca_{0. 05}) (Ti_1-yCa_y)O_3-y prepared by a liquid mixing technique were used to measure the dielectric properties. The pure barium titanate and lightly-Ca-doped materials obey a Curie Weiss law when the temperature is above the Curie temperature. It has been found that the average cubic-tetragonal phase transition temperature moves downward when the octahedrally-coordinated Ca concentration increases, and heavily-Ca-doped barium titanate ceramics show relaxor behavior with a diffuse phase transition characteristic (DPT). Above the average transition temperature T_av the dielectric properties for heavily doped materials do not obey the Curie Weiss law, but can be described by a quadratic relation over a wide range of temperature. Experiments have shown that there exists an extra K(T) peak attributable to the existence of separate microregions of Ba_0.95Ca_0.05TiO₃ in a matrix of (Ba_0.95Ca_0.05) (Ti_1-yCa_y)O_3-y (where y ≤ 2%).     

计量圆光栅动态精度的检测技术

本文探讨了计量圆光栅的精度检测问题，提出了一种新的动态检测方法。它不同于目前普遍采用的标准多面棱体静态检测法，后者只能得到圆光栅静止于圆周内若干等分位置的静态误差，而前者采用频谱分析方法、借助计算机处理，实现对圆光栅动态地、连续测量，最终得到其误差函数Ｒ（θ）。本方法采用软件修正技术剔除安装偏心等系统误差，硬件系统使用了高精度的脉冲计数电路，使得检测系统的精度大为提高，并且排除了测量过程中，环境或人为因素对检测精度的影响。本文对这种光栅动态检测技术的原理及应用进行了研究，并给出此方法的精度估计     

Monoclonal origin of multicentric Kaposi's sarcoma lesions

BACKGROUND: Kaposi's sarcoma has features of both hyperplastic proliferation and neoplastic growth. Multiple lesions, in which spindle cells are prominent, often arise synchronously over widely dispersed areas. We tested the hypothesis that the spindle cells in these multicentric lesions originate from a single clone of precursor cells. METHODS: To determine whether Kaposi's sarcoma is a monoclonal disorder, we assessed the methylation patterns of the androgen-receptor gene (HUMARA) in multiple lesions from women with the acquired immunodeficiency syndrome. In polyclonal tissues, about half the copies of each HUMARA allele are methylated, whereas in cells derived from a single clone all the copies of only one allele are methylated. To minimize contamination by normal DNA, we used microdissection to isolate areas composed primarily of spindle cells, the putative tumor cells. RESULTS: Eight patients with a total of 32 tumors were studied. Of these tumors, 28 had highly unbalanced methylation patterns (i.e., predominant methylation of one HUMARA allele). In all the tumors that had unbalanced methylation from a given patient, the same allele predominated. CONCLUSIONS: These data indicate that Kaposi's sarcoma is a disseminated monoclonal cancer and that the changes that permit the clonal outgrowth of spindle cells occur before the disease spreads.     

Searching for Flash Movies on the Web: A Content and Context Based Framework

The phenomenal growth of online Flash movies in recent years has made Flash one of the most prevalent media formats on the Web. The retrieval and management issues of Flash, vital to the utilization of the enormous Flash resource, are unfortunately overlooked by the research community. This paper presents the first piece of work (to the best of our knowledge) in this domain by suggesting an integrated framework for the retrieval of Flash movies based on their content characteristics as well as contextual information. The proposed approach consists of two major components: (1) a content-based retrieval component, which explores the characteristics of Flash movie content at compositional and semantic levels; and (2) a context-based retrieval component, which explores the contextual information including the texts and hyperlinks surrounding the movies. An experimental Flash search engine system has been implemented to demonstrate the feasibility of the suggested framework. The work described in this paper was supported substantially by a grant (Project No. 7001457), and partially by another grant (Project No. 7001564), both from CityU of Hong Kong.