高温处理对T300级炭纤维结构及性能的影响

为了研究炭纤维在复合材料数次高温处理过程中的性能变化,选取1种国产和1种进口T300级炭纤维,进行3次2 500℃高温处理,研究了高温处理及处理次数对纤维微观形貌、线密度、晶格参数及灰分含量等性能的影响,讨论了不同的高温处理次数对不同纤维及不同性能的影响.实验结果表明,2种炭纤维的各项性能在3次高温热处理中的变化趋势相...     

基于Web Services的J2EE和.NET架构比较

在文章中,我们将简单的比较两种可用来构造商业XML Web Services的平台,分别是Sun Microsystems所提供的Java 2 Enterprise Edition(J2EE)以及Microsoft所提供的.NET平台。     

电子器件系统维护的优化模型

本利用变分法原理给出复杂联接状态下电子器件系统维护的优化模型，寻求维护时刻间的最优值，并得到最优的平均维护时间周期。     

低速风洞设计中的导流片损失问题

低速回流式风洞中拐角部位的流动损失占总损失的比重很大，该位置导流片绕流的流动状况对于流动损失有明显的影响。与常规的工程估算方法不同，风洞实验与数值计算相结合，并通过正交优化能够对不同工作条件下导流片流动及其性能指标的变化规律进行研究，对特定的导流片找到了最佳的工作条件。     

建筑产品价格问题商榷

建筑产品价格如何确定，是造价管理体制改革中的热点问题，笔者对目前存在的三种意见进行分析后提出，应按照国际惯例，由建筑安装企业自行编制建筑安装产品的价格，参与市场竞争。     

开口圆管气体的非线性振荡研究及雾化应用

主要研究开口圆管内的非线性振荡，圆管受迫端由一活塞驱动，活塞为小谐波振荡，另一端为完全开口状态。理论和实验均发现存在非线性现象，实验中还发现活塞激振频率和管内气体的固有频率接近时会发生共振，有强烈的非线性效应，同时在管口附近产生强烈的整波效应，发现利用此效应对水流有较好的雾化功能。     

带有启动费用与维持费用的动态批量问题

建立了带启动费用与维持费用的多产品动态批量问题模型，讨论了最优解的存在性及其特征，提出有效地解决上问题的分枝定界法。     

Ultrastructural and geochemical characterization of Archean-Paleoproterozoic graphite particles: implications for recognizing traces of life in highly metamorphosed rocks

Abundant graphite particles occur in amphibolite-grade quartzite of the Archean-Paleoproterozoic Wutai Metamorphic Complex in the Wutaishan area of North China. Petrographic thin section observations suggest that the graphite particles occur within and between quartzite clasts and are heterogeneous in origin. Using HF maceration techniques, the Wutai graphite particles were extracted for further investigation. Laser Raman spectroscopic analysis of a population of extracted graphite discs indicated that they experienced a maximum metamorphic temperature of 513 +/- 50 degrees C, which is consistent with the metamorphic grade of the host rock and supports their indigenicity. Scanning and transmission electron microscopy revealed that the particles bear morphological features (such as hexagonal sheets of graphite crystals) related to metamorphism and crystal growth, but a small fraction of them (graphite discs) are characterized by a circular morphology, distinct marginal concentric folds, surficial wrinkles, and complex nanostructures. Ion microprobe analysis of individual graphite discs showed that their carbon isotope compositions range from -7.4 per thousand to -35.9 per thousand V-PDB (Vienna Pee Dee Belemnite), with an average of -20.3 per thousand, which is comparable to bulk analysis of extracted carbonaceous material. The range of their size, ultrastructures, and isotopic signatures suggests that the morphology and geochemistry of the Wutai graphite discs were overprinted by metamorphism and their ultimate carbon source probably had diverse origins that included abiotic processes. We considered both biotic and abiotic origins of the carbon source and graphite disc morphologies and cannot falsify the possibility that some circular graphite discs characterized by marginal folds and surficial wrinkles represent deflated, compressed, and subsequently graphitized organic-walled vesicles. Together with reports by other authors of acanthomorphic acritarchs from greenschist-amphibolite-grade metamorphic rocks, this study suggests that it is worthwhile to examine carbonaceous materials preserved in highly metamorphosed rocks for possible evidence of ancient life.     

影响中国北方航空公司员工工作积极性的因素分析

激发人的积极性,发掘人的潜能和价值,是人力资源管理的关键。通过对中国北方航空公司值机部门人员进行了问卷调查分析,找出影响员工工作积极性的显著因素,关尝试运用需要层次理论、期望理论、公平理论以及领导理论等,对如何激发员工的工作积极性进行了探讨,提出了一些建议。