近年来我国存款准备金制度调整的政策效应

在始于2003年下半年的新一轮宏观调控中，素有“巨斧”或“猛药”之称的法定存款准备金被中国人民银行作为一个常规工具来使用，从2003年9月开始，央行连续小幅度地频繁上调准备率，2004年4月开始实施差别存款准备金制度，2003年12月和2005年3月两次单独下调超额存款准备金利率，这些举措对我国的金融与经济产生了深刻的影响。文章主要分析近年来我国法定存款准备金制度调整的特点与政策效应，寻求更好地发挥这一货币政策工具功能的途径。     

涡轮级间燃烧室燃烧性能试验

开展了进口空气马赫数、驻涡区余气系数影响涡轮级间燃烧室燃烧性能的试验研究,获得了燃烧室性能参数的变化规律:随着进口马赫数的增大,总压损失从1.5%增加到7%,流阻系数变化不大,出口温度分布系数OTDF(overall temperature distribution factor)也相应变大;对于不同的进口马赫数,燃烧效率、OTDF随驻涡区余气系数的增大分别为降低和基本不变;燃烧效率大多在70%~85%之间;试验中得到的在燃烧室进口温度为473K时的最大贫油熄火余气系数为9.7.      

直升机起飞性能试飞方法研究

当直升机可用功率不足以维持地效外悬停时,直升机可以利用地面效应增速至一定前飞速度完成起飞。研究了地面效应和前飞速度对直升机剩余功率的影响,阐述了利用剩余功率进行有地效起飞的原理。介绍了3种有地效起飞方式,并使用水平加速—定速爬升法进行了起飞性能飞行试验,得到了水平越障距离随爬升速度的变化曲线,对飞行试验结果进行了分析,得到了有益的结论。     

不同热值生物燃料燃烧特性数值模拟

采用标准k-ε湍流模型、涡耗散湍流燃烧模型、P-1辐射传热模型对二维简化燃烧室燃料甲烷气、沼气、生物质气的燃烧特性进行了数值模拟.通过比较不同截面的燃烧情况,分析燃烧室内的温度分布、NOx质量分数分布、流场结构,研究了不同热值燃料的燃烧特性.结果表明:在入口空气、燃料质量流量相同的条件下,随着燃料热值降低,燃烧温度降低,温度分布更均匀,NOx排放量减少,流动速度降低;适当调节余气系数,能改善燃烧效果,温度分布仍满足高热值燃料燃烧温度高于低热值燃料燃烧温度的规律;在生物燃料混合气中掺入不同热值的可燃成分,可改变混合气的热值,恰当的混合比例能更好地发挥生物燃料的作用.     

直线模拟加载系统的研究进展与发展趋势

直线模拟加载系统是一种用于在实验室条件下模拟承载对象工作时所受直线负载力的半实物仿真系统,可用于模拟各类飞行器关键部件在工作过程中所受的气体阻力载荷。针对目前常用的机械式、电液式和电动式直线模拟加载系统,分析其基本加载原理和研究进展,结合自行研制的电动式直线模拟加载系统进行了深入探讨。针对多余力抑制方法的关键问题,详细论述了直线负载模拟器的结构补偿方法和控制策略。最后,展望了直线模拟加载系统的发展趋势,归纳了电动式直线模拟加载系统的高精度、大载荷发展方向。     

XMM-Newton study of soft excess X-ray emission in clusters of galaxies

We discuss the detection of soft excess X-ray emission in a sample of 19 clusters of galaxies observed by XMM-Newton. In 6/19 clusters evidence for a soft X-ray excess is found. Four of these clusters show soft X-ray and O VII line emission from gas with a temperature of 0.2 keV. The centroid of this oxygen line is consistent with the redshift of the cluster. The intensity and spatial extend of the soft excess agrees with previous PSPC measurements. These observations are interpreted as emission from warm-hot intergalactic medium filaments, with density enhancements near the cluster centers, consistent with theoretical predictions. In the other two soft excess clusters a non-thermal origin is consistent with the data.     

A strategic “viewfinder” for SETI research

One of the most important reasons why unsuccessful results have been obtained so far by the SETI Project is due to the fact that no sure targets to aim at have been available up-to the present state of research. All-sky surveys, even if very accurate and complete, might result to be time-consuming. SETI needs at least one effective “viewfinder” in order that a true targeted research is carried out with a possible success. The best foundation to get this can be identified with the search for the evidence of extraterrestrial astro-engineering activity in form of the Dyson spheres predicted by theory. The existence of such stellar objects can be ascertained by finding the evidence of two main signatures in stars of solar spectral type: infrared excess and anomalous light curves due to transiting artificial objects. These are probably the most powerful viewfinders in order to allow SETI techniques for intelligent signal search to be aimed at more appropriate targets. This paper is not intended to be a research paper but rather a review paper whose goal is not to present calculations and/or operational research but rather to be a research proposal for a more focused research in SETI just using Dyson Spheres as crucial markers.     

Search for high-proper motion objects with infrared excess

The possibility of interstellar migration has been theorized during the past thirty years in the form of “Dysonships” that, using non-relativistic propulsion systems, are able to colonize the Galaxy in a relatively short time compared to the age of the Galaxy and consequently penetrate inside our solar system too. Observational evidence of this can be potentially obtained using the present state of the art of telescopes and related sensors, by following aimed searches and an expanded SETI protocol. Some transient and unrepeated radio signals recorded during standard SETI observations might be due to the transit of high-proper motion artificial sources of extraterrestrial origin, which are expected to show a very weak optical emission, a strong infrared excess and occasional high-energy bursts in the X and Gamma-ray wavelength ranges. Such artificial sources might show an interest to Earth by sending probes to visit it: such a possibility can be investigated scientifically as well.     

无人机用燃料电池阴极供气系统建模与控制

燃料电池因其高效、无污染、噪声小等特点,被认为是未来最具有潜力的无人机（UAV）用动力源,燃料电池阴极供气系统的控制技术是决定燃料电池系统性能和可靠性的关键。针对无人机用质子交换膜燃料电池（PEMFC）阴极供气系统,首先,考虑外界温度、压力、空气密度以及雷诺数等随高度变化的参数,建立了跨高度离心空压机模型并分析了其在不同高度下的工作特性,基于无刷直流电机反电势特征构建了高速空压机驱动电机模型。其次,通过计算燃料电池阴极氧气和氮气的动态分压获取了PEMFC电堆输出电压。设计了基于分数阶PI^λD^μ的过氧比和阴极气压控制方法,驱动电机采用有限集模型预测控制（MPC）实现快速的转矩响应,仿真结果表明设计的控制器可在无人机跨高度运行条件下实现过氧比的快速调节,同时维持阴极气压稳定,满足燃料电池阴极供气需求。     

阶跃型边界平面干涉测量技术

为完成复杂平面样板的测量,提出了一种循环单纯形边缘特征提取及种子填充的数字图像处理技术,解决了复杂平面样板相位复原的问题;应用波长合成技术和小数重合法在相位偏移干涉系统中实现了阶跃型边界平面样板的干涉级次整数部分及小数的测量。在实验中对两种阶跃型平面样板测量的重复性达到了10nm,将其测量结果和三维纳米测量机的测量结果进行了比较,两种仪器测量数据最大偏差8 nm。分析了实验数据的可靠性以及两种测量仪器的优缺点,为复杂平面样板的测量提供了一种新的思路。