Prospect Of China's New Generation Of Launch Vehicles

INTRODUCTION With the development of science and technology, mankind's space activities have greatly promoted social progress and produced profound and far-reaching effects.Space technology has turned out to be one field of high technology that exerts the most profound influence on modern society.The continuous     

PDM核心业务基础和配置管理标准要求

配置管理是PDM的核心业务基础,本文从论述实现PDM应用中配置管理功能的重要性出发,介绍分析了国际上多种标准对配置管理的基本要求和方法.     

New split-winding doubly salient permanent magnet motor drive

A new split-winding doubly salient permanent magnet (DSPM) motor drive is proposed. This DSPM motor drive offers the advantages of high power density, high efficiency, and wide speed range. The corresponding operation, analysis, implementation, and experimentation are successively presented. Finally, experimental results are used to confirm that the proposed DSPM motor drive offers high efficiency over a wide output power range, exhibits good dynamic performance, and extends the constant-power operation range significantly.     

对当前就业问题的思考

“十五”期间正值我国就业的高峰时期,解决好就业问题,首先要摸清现阶段就业状况及导致失业的原因,提出相应的解决对策,无疑是具有积极意义的。     

Impact of Geoid Improvement on Ocean Mass and Heat Transport Estimates

One long-standing difficulty in estimating the large-scale ocean circulation is the inability to observe absolute current velocities. Both conventional hydrographic measurements and altimetric measurements provide observations of currents relative to an unknown velocity at a reference depth in the case of hydrographic data, and relative to mean currents calculated over some averaging period in the case of altimetric data. Space gravity missions together with altimetric observations have the potential to overcome this difficulty by providing absolute estimates of the velocity of surface oceanic currents. The absolute surface velocity estimates will in turn provide the reference level velocities that are necessary to compute absolute velocities at any depth level from hydrographic data. Several studies have been carried out to quantify the improvements expected from ongoing and future space gravity missions. The results of these studies in terms of volume flux estimates (transport of water masses) and heat flux estimates (transport of heat by the ocean) are reviewed in this paper. The studies are based on ocean inverse modeling techniques that derive impact estimates solely from the geoid error budgets of forthcoming space gravity missions. Despite some differences in the assumptions made, the inverse modeling calculations all point to significant improvements in estimates of oceanic fluxes. These improvements, measured in terms of reductions of uncertainties, are expected to be as large as a factor of 2. New developments in autonomous ocean observing systems will complement the developments expected from space gravity missions. The synergies of in situ and satellite observing systems are considered in the conclusion of this paper. This revised version was published online in August 2006 with corrections to the Cover Date.     

位同步提取环路带宽的自适应控制的研究

本文主要研究数字匹配滤波器在位同步提取环路带宽的自适应控制中的应用。首先，从理论上分析了匹配滤波器的误码性能，定量地推出数字匹配滤波器的误码率计算公式；然后，分析了输入信噪比与数字匹配滤波器输出状态的关系；最后，给出了位同步提取环路带宽的自适应控制的硬件实现方案。     

Effects of modified atmosphere on crop productivity and mineral content.

Wheat, potato, pea and tomato crops were cultivated from seeding to harvest in a controlled and confined growth chamber at elevated CO2 concentration (3700 microL L-1) to examine the effects on biomass production and edible part yields. Different responses to high CO2 were recorded, ranging from a decline in productivity for wheat, to slight stimulation for potatoes, moderate increase for tomatoes, and very large enhancement for pea. Mineral content in wheat and pea seeds was not greatly modified by the elevated CO2. Short-term experiments (17 d) were conducted on potato at high (3700 microL L-1) and very high (20,000 microL L-1) CO2 concentration and/or low O2 partial pressure (approximately 20,600 microL L-1 or 2 kPa). Low O2 was more effective than high CO2 in total biomass accumulation, but development was affected: Low O2 inhibited tuberization, while high CO2 significantly increased production of tubers.     

Investigation of low-energy proton effects on aptamer performance for astrobiological applications

Biochips are promising instruments for the search for organic molecules in planetary environments. Nucleic acid aptamers are powerful affinity receptors known for their high affinity and specificity, and therefore are of great interest for space biochip development. A wide variety of aptamers have already been selected toward targets of astrobiological interest (from amino acids to microorganisms). We present a first study to test the resistance of these receptors to the constraints of the space environment. The emphasis is on the effect of cosmic rays on the molecular recognition properties of DNA aptamers. Experiments on beam-line facilities have been conducted with 2 MeV protons and fluences much higher than expected for a typical mission to Mars. Our results show that this irradiation process did not affect the performances of DNA aptamers as molecular recognition tools.     

新体制卫星导航信号特性与跟踪环路设计

从新体制卫星信号的特性出发,论述新体制卫星导航信号跟踪环路的一种实现方式,即三环双估计器跟踪环路的设计方法,并以一个仿真系统为例给出各项参数推导的详细过程,最终的仿真结果证明所述方法合理可行。     

吸气式脉冲爆震发动机壁温试验

为了探索各频率下管壁温度随时间的变化趋势及爆震管外壁面的温度分布规律,对爆震室内径68mm,长2 000mm,以汽油为燃料、空气为氧化剂的吸气式脉冲爆震发动机进行试验,用热成像仪对稳定工作在10Hz,20Hz,40Hz下的管壁温度进行了监测。结果表明:同一频率下随时间的增加壁面温度增加速度减小;热平衡时壁面温度随频率的增加而增长,10Hz,20Hz,40Hz热平衡时外壁面最高温度分别在726℃,1011.5℃,1159.5℃以上;热平衡前管壁温度的增长速度随频率的增加而增加,管壁温度的增长速度跟频率约成正比;爆震室上沿着压缩波叠加至形成爆震的方向,温度在外壁面上递增分布,在爆震形成区温度最高,从爆震形成区到发动机出口处,温度在外壁面上逐渐降低;各频率下最高温度区位置基本不变,距点火位置1 350mm左右;同一轴向位置上的外壁面温度随频率的增加而增加,温度的增长幅度随频率的增加而减小。