SOPC技术在软件无线电平台中的应用

介绍使用基于NIOSII软核处理器的SOPC技术,并采用基于SOPC的软件无线电技术对一个传统的抗干扰电台进行重新设计,增强了系统功能,改善了系统的灵活性,并提高了其适应不同应用需求的伸缩性。     

Morphological and molecular changes of maize plants after seeds been flown on recoverablf satellite

Dry seeds of Zea mays, heterozygous for Lw₁/lw₁ alleles, sandwiched between nuclear track detectors aboard Chinese satellite for 15 days, were recovered and mutations in morphological characters on plants developed from these seeds, as well as their selected progenies, were investigated. The dosimetric results indicated that 85% of the seeds received at least 1 hit with Z≥20. About 10% of plants developed from flown seeds and 40% of observed selfed lines from the first generation plants showed some morphological changes, such as yellow stripes displayed on leaves, dwarf, anomogensis of floral organs and yellow-green seedlings, when compared with those from ground control. Using yellow stripes on leaves as the main endpoint for evaluating mutation induced in space environment, the frequency of stripe occurrence was 4.6% in the first generation plants, comparable with the results obtained from Long Duration Exposure Facility (LDEF) mission (Mei et al., 1994), but much lower than those from ground based ⁶⁰ Co-gamma treatment at a dose of 100 Gy, which reached 35.5% in the selfed lines of the second generation. One hundred and ten random primers were screened in RAPD analysis to detect the variation on genomic DNA of plants with stripes on leaves. Of these primers, 10.9% were able to generate polymorphic bands between mutated plants and control, also, common band patterns in several progenies with the same mutation phenotype were observed. These results demonstrated that space radiation environment could induce inheritable mutagenic effects on plant seeds, and verified the change in genetic material in the mutants. Further study will be needed for a better understand of the nature and mechanism of this induction of mutation.     

可靠性设计变量样本极值的区间估计法

工程系统设计的变量大且多具有不确定性,它们的极大值和极小值同样也具有不确定性.传统的极值理论尚未很好地解决一组样本的极大值和极小值的区间估计问题.本文从次序统计理论出发,建立了该样本的极大值与极小值的区间估计算法,并对大容量和小容量样本的情况分别进行了讨论,获得了在小样本情况下可用母体均匀分布获得的结果来估计样本极值区间的结论.算例结果表明本文提出的方法可以较好地进行样本极大值与极小值的区间估计.     

可压缩流动转捩的迭代求解

本文叙述了高速可压缩边办流动稳定性和转捩点预报的数值计算方法，特别是Ｒａｙｌｅｉｇｈ反迭代法与边界层渐近匹配方法的配合，有效地提高了计算精度，节省了存储和计算时间，本文给出的评定界层第一模式的稳定性分析和转捩区数值预报结果，与已有的实验结果一致。     

Performance relationships between ground model and space prototype of deployable space antennas

Performance testing is very useful in the design of deployable space antennas. It is arduous and costly to carry out the prototype experiments on the ground because of the large aperture of the antenna and the difficulty of simulating space environments. Thus, a smaller replica of the antenna, called scale model, is used to achieve the performance testing for reasons of economy, convenience, and saving in time. In this paper, a two-step approach is proposed to predict the prototype performance of the antenna in the space environment according to the performance testing of the scale model. The first step is to analyze the similarity between the prototype and the model in the same environment. Different methods are adopted according to the different performance of the antenna. The scaling laws of the driving force of the deployable Astromesh antenna are established through the differential equations on the basis of the deployment dynamic equations, while the scaling laws of frequency are derived by the dimensional analysis method. The second step is to analyze the performance relationships of the scale model in the different environments. Experiments on the scale model can be performed to obtain the performance relationships. Finally, a complete example of the natural frequency analysis is given to illustrate the two-step method.     

Reloading partly recovers bone mineral density and mechanical properties in hind limb unloaded rats

Skeletal unloading results in decreased bone formation and bone mass. During long-term space flight, the decreased bone mass is impossible to fully recover. Therefore, it is necessary to develop the effective countermeasures to prevent spaceflight-induced bone loss. Hindlimb Unloading (HLU) simulates effects of weightlessness and is utilized extensively to examine the response of musculoskeletal systems to certain aspects of space flight. The purpose of this study is to investigate the effects of a 4-week HLU in rats and subsequent reloading on the bone mineral density (BMD) and mechanical properties of load-bearing bones.     

离心压缩机叶片载荷分析

 本文通过对常用叶片载荷型式的分析,推荐一种较理想的叶片载荷型式,并展示高效叶轮的设计实例。 根据欧拉方程,对于理想流体的绝热流动,单位质量流体通过叶轮所获得的功可用理论能量头h_(th)表示:     

溶液法制备PVDF薄膜电活性相方法

为了制备具有电活性相的聚偏氟乙烯(PVDF)薄膜,采用了简单易操作的溶液涂膜方法,并研究了不同前驱体溶液浓度、搅拌时间以及热压工艺对PVDF不同电活性相的晶型结构形成的影响,利用X射线衍射仪、傅里叶变换红外光谱仪(FTIR)对PVDF薄膜的晶型结构进行分析.结果表明:前驱体溶液浓度7%~10%,搅拌时间2~3h都有利于β相的形成,利用红外光谱,可以计算β相的含量,在前驱体溶液浓度7%,搅拌时间2h时得到最大的β相含量81.3%;热压对PVDF薄膜的晶型结构有很大的影响,经过热压处理的PVDF薄膜中γ相转变成更加致密的β相.      

一种基于石墨烯的脉冲星导航X射线探测器

针对脉冲星导航要求X射线探测器具有高能量分辨率和高时间分辨率的需求,研究基于石墨烯电场效应来实现X射线探测的可行性。通过蒙特卡罗方法模拟不同能量X射线和不同厚度探测器基底的相互作用过程,得到不同厚度探测器对X射线的探测效率。利用有限元方法分析X射线在探测器内电离产生载流子的输运过程,验证了X射线入射对石墨烯电学特性的影响。理论分析计算探测器的时间分辨率和能量分辨率等指标参数,结果表明：基于石墨烯电场效应的X射线探测器具有较高的能量分辨率和时间分辨率,是一种潜力巨大的X射线探测方式,可满足未来脉冲星导航的工程应用。