Mg粉/CO2粉末火箭发动机性能分析

从粉末火箭发动机工作性能、影响因素等方面出发,对其性能进行了理论计算。通过分析发现,粉末发动机较传统推进系统的有效比冲高;通过对Mg粉和CO2燃烧性能的计算研究,得到了其受压强、初温、氧燃比等参数的影响规律,为进一步研究奠定了基础。     

Endolithic cyanobacteria in halite rocks from the hyperarid core of the Atacama Desert

In the driest parts of the Atacama Desert there are no visible life forms on soil or rock surfaces. The soil in this region contains only minute traces of bacteria distributed in patches, and conditions are too dry for cyanobacteria that live under translucent stones. Here we show that halite evaporite rocks from the driest part of the Atacama Desert are colonized by cyanobacteria. This colonization takes place just a few millimeters beneath the rock surface, occupying spaces among salt crystals. Our work reveals that these communities are composed of extremely resistant Chroococcidiopsis morphospecies of cyanobacteria and associated heterotrophic bacteria. This newly discovered endolithic environment is an extremely dry and, at the same time, saline microbial habitat. Photosynthetic microorganisms within dry evaporite rocks could be an important and previously unrecognized target for the search for life within our Solar System.     

镁颗粒在CO_2中的点火燃烧特性试验

利用自行设计的氙灯点火燃烧试验装置,采用高分辨率高速成像系统,开展了单个镁颗粒在CO2气体氛围中的点火燃烧试验研究,直接观察到了镁颗粒点火燃烧过程中颗粒和火焰形态。试验结果表明,镁颗粒在CO2中的点火燃烧经历了颗粒熔化、表面化学反应、氧化层破裂、镁蒸气喷射、气相燃烧等物理化学过程,颗粒燃烧过程伴有脉动燃烧现象;环境压强对颗粒表面氧化层疏松度有一定影响,进而会影响到颗粒的点火温度,压强越大,颗粒点火温度越高;燃烧产物是中空的多孔球壳状物质,且外层为白色氧化镁,内层为黑色碳。     

药芯焊丝CO2气体保护焊可行性分析

通过工艺试验证实,药芯焊丝CO2气体保护焊焊接工艺性能好、易操作、飞溅小、焊缝成型光滑美观;熔敷效率高,一般可达75%～85%;焊接接头的力学性能、晶间腐蚀性能及低温冲击性能均较理想;生产率是焊条电弧焊的3～4倍。     

一种高能激光光强测试新方案

为了测试高能CO2激光光强分布,提出利用半导体制冷片作为靶屏,用热像仪测量屏表面温度,通过热像仪的图像回推屏上光强分布.从理论上分析了工作中的制冷片在CO2高能连续激光辐照下热面温度的时空分布,给出回推光强的重构算法.     

Active measures for reducing the global climatic impacts of escalating CO2 concentrations

The buildup of CO₂ by fossil-fuel burning and associated climatic changes have become the subject of intensive investigations. Although the time scale on which significant climatic changes (e.g. mean temperature changes of several degrees, appreciable changes in global and regional rainfalls and winds, etc.) are expected to occur is long, it has been noted that the magnitude of the energy system is so vast that modifications in the primary resource mix should preferably be initiated within a decade or sooner. The notion that the most economical energy source will be replaced globally in response to longterm climate model predictions is probably false. Before policy matters of this type can be discussed reasonably, careful assessments must be made of alternative global measures that do not require curtailments of fossil-fuel applications. This study on active measures for reducing climate changes caused by escalating CO₂ concentrations deals with potentially important areas of research. We find: (a) reductions in the solar input to the Earth by reflecting sunlight directly are prohibitively costly; (b) desired changes in Earth albedo through judicious introduction of small particles can probably be accomplished at acceptable cost through the use of modified combustors on high-flying aircraft.     

几种常见赌博的数学问题

对三类抽奖活动本文利用排列组合与数理统计等知识,进行了分析、揭露,以此告诫人们不要上当受骗.     

液体推进剂运输中常见事故的处理

根据液体火箭推进剂腐蚀性强、毒性大等特点，提出了液体火箭推进剂运输过程中应注意的事项，以各类常见事故的处理和人员中毒的防护与急救措施，以最大程度地保障液体火箭推进剂的运输安全。     

几种常见赌博的数学问题

对三类抽奖活动本文利用排列组合与数理统计等知识，进行了分析、揭露，以此告诫人们不要上当受骗。     

Determination of vibrational CO2 distributions in thermodynamically-nonequilibrated rarefied flows by use of radiational characteristics in the 15 μm band

A method for determination of the vibrational distributions and populations of individual vibrational levels of vibrationally-nonequilibrated carbon dioxide in bend-stretch manifold and asymmetric stretching mode was developed and substantiated. The method is based on the measurements of integrated radiation intensity in the wide spectral intervals of the 15 μm CO₂ band and total emissivities of its appropriate Q-branches. Computations of radiation intensities and emissivities in P and R-branches were performed by using vibrational-rotational band models and in Q-branches by the direct “line-by-line” integration.It was shown that vibrational temperature of CO₂ asymmetric stretching mode may be determined from the measurements of integrated radiation intensity of the 15 μm band. The populations of individual levels of the bend-stretch manifold may be obtained from the measurements of total emissivities of some Q-branches of the 15 μm band.The procedure of the CO₂ lower vibrational levels populations determination under the conditions typical of 18 μm and 9–11 μm CO₂ laser cavities is described.     

成都区域管制室常用管制英语通话用法

随着成都空域逐步对外开放,越来越多的国外航班飞越、起降成都机场,航空管制用语将逐步向英语过渡,这样我们使用管制英语的机会将越来越多。所以,运用好管制英语是我们管制工作好坏的基本     

英语应用能力B级考试翻译常见错误分析

翻译是大学英语教学的重要部分,英译汉是高等学校英语应用能力B级考试的考核内容之一,可是由于学生翻译能力较差,丢分严重.论文结合教学实践,针对学生考试中的常见翻译错误进行具体分析,并简要提出了相应的教学策略,以提高学生的英汉翻译能力和B级考试成绩.     

预测：今后十年全球卫星市场将大幅增长

欧洲咨询公司6月8日宣布．据其最新发布的《2018年前将建造和发射的卫星全球市场预测》报告估计．2009～2018年全球将建造和发射1185颗卫星．比前10年（1999～2008年）增加近50％,卫星制造和发射市场收入预计将以同样的幅度增长,达到1780亿美元。该公司空间与通信部门主任、报告编辑雷切尔．维兰称．政府和商业部门都将是市场增长的推动力量．     

PETS 口语考试常见问题及对策

我国对外开放的深入和对外交往的扩大需要越来越多的英语人才,过去的英语考试模式已经不能满足社会经济发展的要求,这就需要用PETS考试代替过去比较封闭单一、脱离社会需求的英语考试模式,从而扭转英语教学的被动局面。文章从PETS口语考试的形式、评分标准入手,对考生在考试的每个环节中常见的问题进行了分析,并提出了一些有效的应对措施。     

系统级EMC实验中常见虚假信号的分析与验证

对系统级电磁兼容性试验中常见的虚假信号的产生原因和特点进行了理论分析,并通过软件仿真和试验予以验证,证明虚假信号是低噪声放大器（LNA）等设备在大功率信号的作用下,由于其非线性特性引起的,而实际上并不存在。文章最后给出了虚假信号的判别方法,即通过加减衰减器观察信号幅值的变化,可判断检测信号的真伪。同时,对系统级EMC试验的测试系统给出了改进建议。     

空管建设项目中几个常见问题的分析与思考

"十一五"规划期间(2006—2010年),长江三角洲、京津冀地区、成渝地区及东北老工业基地等国家规划工作中亟待增强之薄弱环节被放在突出重要的位置,成为新     

在常规小风洞中实现大风洞中的气动力实验

就风洞尺寸要多大才比较合理以及小风洞的改造和挖潜等问题进行了讨论。认为风洞尺寸不是越大越好,而是在不同速度范围存在着一组相对适中的带某种唯一性的风洞尺寸。这种风洞尺寸,既能满足航天器研制的需要,又具有合理的经费开支。文中推荐了不同速度下一组较合适的且能满足需要的风洞尺寸,供人们参考。同时本文还认为,在一定的风洞条件下,实验数据的精准度与风洞尺寸的大小无关,只要相似模拟的条件正确,就能给出同样精准度的实验数据。就这一观点,列举了在北京空气动力研究所的FD 02小风洞中做出的几种实验。     

用换面法与直角三角形法求一般位置平面实形的比较

介绍了用直角三角形法求一般位置平面实形的方法.该方法与教材介绍的换面法相比较,具有直观、易于理解、节约课时等优点.可满足机械制图求一般位置平面的要求.     

LM-2F for Tiangong 2 in General Assembly

<正>The general assembly work for the first,second core stages and the boosters of LM-2F planned for launching the Tiangong 2 target spacecraft is being conducted smoothly.The carrier rocket will enter the testing phase after the completion of the assembly work in early August and is scheduled to launch the Tiangong 2target spacecraft next year.The Capital Aerospace Machinery Corporation worked out 19 measurements including production preparation,organization,