喷管潛入对固体火箭稳定性的影响

通常用计算燃烧室内部小振幅振荡的增长或衰减速率来确定固体推进剂火箭燃烧室的线性稳定性。用纯增一衰系数αgd 表示燃烧室压力扰动状态的通用表达式为:P_1(z,t)-P(z)e~(αgdt) e~(iωt) (1)此表达式中,以系数αgd 的符号确定扰动的增衰。可证明,αgd 能以下列关系表示:     

Real time confocal laser scanning microscopy: potential applications in space medicine and cell biology

Photodynamic therapy (PDT), in which tissues may be rendered fatally light-sensitive represents a relatively novel treatment for cancer and other disorders such as cardiovascular disease. It offers significant application to disease control in an isolated environment such as space flight. In studying PDT in the laboratory, low energy lasers such as HeNe lasers are used to activate the photosensitized cellular target. A major problem associated with these studies is that events occurring during actual exposure of the target cells to the system cannot be examined in real time. In this study HeLa cells were photosensitized and photodynamic activation was accomplished using the scanning microbeam from a confocal laser scanning microscope. This form of activation allowed for simultaneous photoactivation and observation and facilitated the recording of events at a microscopic level during photoactivation. Effects of photodynamic activation on the target cells were monitored using the fluorophores rhodamine 123 and ethidium homodimer-1. Potential applications of these forms of analyses to space medicine and cell biology are discussed.     

First results from experiments performed with the ESA Anthrorack during the D-2 Spacelab mission

In 1993 four astronauts performed physiological experiments on the payload "Anthrorack" during the second German Spacelab mission D-2. The Anthrorack set-up is a Spacelab double rack developed under the management of the European Space Agency. It consists of an ECHO machine, a respiratory monitoring system (gas analyzer with flow meter), a blood centrifuge, an ergometer, a finger blood pressure device, ECG, body impedance measurement device and a respiratory inductance plethysmograph. Experiment-specific equipment was used as well. Nineteen investigators performed experiments in the cardiovascular, pulmonary, fluid-renal and nutritional physiology area. Results on central venous pressure, ocular pressure, vascular resistance, cardiac output, tissue thickness and orthostatic intolerance are presented in the cardiovascular area. In the pulmonary area first results are mentioned on O2 transport perfusion and ventilation distribution and breathing pattern. From the fluid-renal experiments, data from diuresis, sodium excretion and hormonal determinations are given. Finally results from glucose metabolism and nitrogen turnover experiments are presented.     

浅谈企业文化与建设

企业文化,是企业员工共有的价值体系,是维系企业与员工的纽带,也是建设和谐社会、促进企业健康发展不可替代的一项重要内容。当我们遇到困难和问题时,企业文化能够为我们提供正确的途径来约束员工的行为--什么是我们该做的,什么是我们不该做的——并对问题进行概念化、定义、分析和解决。企业文化的内涵极其广泛,可以说渗透于经营管理活动的方方面面,任何一个企业,无论人员的多寡,规模的大小,都有自己的企业文化。只不过有些企业文化是经过人为的修饰与引导的,而有些企业的文化是自发形成的。企业文化对于企业来说,是一把典型的双刃剑。优秀…     

数字频率合成的新途径

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GE公司为支线飞机研制改型发动机

GE公司已正式着手CF34-8C涡扇发动机的全尺寸研制计划,该发动机已选装加拿大庞巴迪公司计划的CRJ-X,这是一种50座CRJ的加长型,有70个座位。-8C的推力为57.8千牛,是装CRJ的CF34-3B的改型。目前庞巴迪公司还未正式开始飞机计划,据飞机公司说,他们希望今年末启动这项计划。在5月份召开的支线航空协会会议上,GE公司小型商用涡扇发动机部的总经理汤姆森说,研制进度将保证发动机在1998     

测量参数时间延迟对气动导数辨识结果的影响

主要讨论了测量参数间的时间延迟对飞机气动导数辨识结果的影响。通过对飞机仿真数据的计算表明,为了保证气动导数辨识的准确性,必须对测量参数间的延迟时间作一定的限制。结果表明,飞机的主要导数对时间延迟不敏感,而一些小值导数则较敏感。文中还根据实际计算经验对测量参数间的延迟时间给出了适当的限制。这些结果可为工程应用提供理论参考。     

改进的高加速度,高性能固态加速度计

本文介绍了具有毫ｇ性能的单块固态晶体石英１２００ｇ振梁加速度计目前研制所取得的成就。做到这些意味着将类似应用领域中的仪表性能提高两个数量级。这项工程是为了支持美军导弹司令部先进动能导弹（ＡｄＫＥＭ）研制计划，这种微型捷联战术导航优质加速度计的性能目标包括：从２０ｇ软发射阶段、１２００ｇ助推阶段到低ｇ巡航阶段的加速度数据。本文在分析改进后的第二阶段仪表的物理特点、机械结构、应力分析、设计特点、装配问     

厦门机场雷暴风切变的预报

本文通过对1997年1月至2004年10月发生在厦门机场的雷暴风切变进行了分类，并就导致这一天气现象的天气背景进行了分析。在此基础上，结合卫星云图显示的云状和云顶的TBB，运用统计分析的方法建立回归方程，供短期预报参考。其中将雷暴风切变归纳为以下三种类型：锋面型雷暴、西太平洋副热带高压系统型雷暴、热力型雷暴等。