激光多普勒测速仪使用时圆柱管壁影响的分析计算

本文分析计算了使用前向式激光多普勒测速仪测定圆管中流体介质速度时圆柱管壁的影响。由于圆柱管壁的影响,提高了发射光轴方向的空间分辨率,但引起发射系统和接收系统移动时不同步,降低信号质量和增加信号噪声。接收系统相对发射光轴的偏角应控制在15°之内。     

计算机综合自动化制造系统CIMS的结构与概念

ＣＩＭＳ是近来发展起来、在制造业中的一种计算机应用系统，它把各种有关的子系统有机地综合成一个完整的系统，从而更有效地提高制造过程的质量与效率。它是一种多层次，多阶段和多模式的复杂系统，不仅对系统中的物质流进行有效地控制，还对信息流进行综合与控制，并把系统优化空间扩展到设计、检验和市场。传统方法和人工智能相结合是处理这种复杂系统的有效方法。     

有机钴胺素的合成及光谱研究

本文使用Schrauzer法合成了多种有机钴胺素,测定了紫外-可见吸收光谱,提出了判断有机钴胺素生成的光谱证据。     

新型立式弯水管双层炉排锅炉的研制

小容量低压锅炉量大面广,如何改进结构和改善燃烧以节约燃料和保护环境有着十分重大的意义。本文介绍新型立式弯水管双层炉排锅炉的设计研制工作。作者针对现有小锅炉存在燃烧效率低和环境污染严重等问题,设计新产品时在结构、燃烧与通风方式以及受热面布置诸方面采取新的有效技术措施。试验结果和二年多的运行实践表明,该新产品的节能和环保性能指标均达到国内先进水平,同时操作简便,运行安全,煤种适应性广,具有更换同容量旧有锅炉的推广价值。它现已在江、皖、浙、沪投产,广泛用于生产、生活,经济效益显著。     

微电极上镍的电结晶研究

人们试图通过研究单核的形成和生长来探索电结晶规律。已经表明,由于受到浓度场的限制,单位面积基体上的晶核数目是个有限值,例如锌电结晶的最大晶核数度为1×10~6cm~(-2)。可见,采用面积小于10~(-6)cm~2的电极有可能实现单核生长的条件。本     

金属中缺陷对电化学渗氢的影响

金属中缺陷用缺陷密度G_i、陷阱能量E_i和频率因子V_i表示,氢扩散系数同这些参数的关系由简单的位能曲线模型导出.缺陷对电化学渗氢暂态的影响通过数值方法进行分析.结果表明,缺陷的存在会延迟渗氢暂态电流的出现,减小渗氢电流的变化速度.这些结论可用于解释若干异常的渗氢实验现象.文中还讨论了氢扩散系数的Arrhenius关系.     

Inequality in mutation rates of the two strands of DNA

As the mechanisms for replicating the two strands of duplex DNA differ it is, in principle, possible for the mutation rates to differ depending on which strand is being copied. In the absence of selection this would lead to a difference in the measured rate of a particular base substitution, such as T to C, depending on which DNA strand was analysed to determine the rate. Thus a change such as T to C on one DNA strand results from either a direct T-to-C mutation on that strand or an A-to-G mutation on the complementary strand; for the other strand the situation is reversed, and it can be seen that different processes are responsible for the two cases, allowing for asymmetry in substitution rate. We have tested whether such asymmetry indeed occurs by studying equivalent sequences from the beta-globin complexes of six species of primate. Our results reveal an asymmetry in substitution rates consistent with predictions based on strand-inequalities in mutation rates. Our sequence comparisons also allow us to make predictions about the positions of replication origins and the replication error rates of one strand relative to the other.     

The genome sequence and structure of rice chromosome 1

The rice species Oryza sativa is considered to be a model plant because of its small genome size, extensive genetic map, relative ease of transformation and synteny with other cereal crops. Here we report the essentially complete sequence of chromosome 1, the longest chromosome in the rice genome. We summarize characteristics of the chromosome structure and the biological insight gained from the sequence. The analysis of 43.3 megabases (Mb) of non-overlapping sequence reveals 6,756 protein coding genes, of which 3,161 show homology to proteins of Arabidopsis thaliana, another model plant. About 30% (2,073) of the genes have been functionally categorized. Rice chromosome 1 is (G + C)-rich, especially in its coding regions, and is characterized by several gene families that are dispersed or arranged in tandem repeats. Comparison with a draft sequence indicates the importance of a high-quality finished sequence.     

医学科研选题的原则及技巧

科研选题是科研工作的关键环节。科研选题应根据学科专业的特点，把握需求性原则、创新性原则、科学性原则与可行性原则，采用恰当的方法技巧，确定高水平、高质量的选题。     

Mlgebraic Attack on Filter-Combiner Model Keystream Generators

Algebraic attack was applied to attack Filter-Combiner model keystream generators. We proposed thetechnique of function composition to improve the model, and the improved model can resist the algebraic attack. A new criterion for designing Filter-Combiner model was also proposed: the total length L of Linear Finite State Machines used in the model should be large enough and the degree d of Filter-Combiner function should be approximate [L/2].