微小卫星整星模块化结构的模态分析

应用有限元软件ANSYS的板单元和梁单元,建立不同的微小卫星整星结构的有限元模型。通过模态仿真分析计算结果讨论,得出微小卫星结构的质量分布对系统的固有频率及振动的影响程度。为后续整星结构有效载荷合理分布提供可靠的依据。

英语习语中的“双子星”结构探究

英语中的"双子星"结构的基本形式是"word A and word B",是英语中一种特殊的习语,在音、形、义及文体等方面具有鲜明的特点。根据词性及word A和word B的相互关系,可以把这种双子星结构分成多种类型。英语中的"双子星"结构具有意义上的统一性、结构上的稳定性、应用上的整体性等特点,并具有形象生动、言简意赅、寓意深刻、加强语气、语义等功能。

一种星–树结构的确定性的小世界网络

在过去的的几十年,人们运用各种机制建构了许多不确定性的和确定性的小世界网络。最近,郭世泽等人通过在星图K1,2上运用一个简单的算法在每个迭代步添加一些边首次形成了一个二叉树结构的确定性的小世界网络。本文通过一个星图K1,6在每个迭代步连接每个树的各祖父节点和它的四个孙子节点,由此构建一个二叉树结构的新的确定性的小世界网络模型。此外,我们给出了一些拓扑属性的分析结果,它表明构建的模型是小世界网络。

新型星-菱形负泊松比蜂窝结构的动态力学特性

为进一步提高蜂窝结构的抗冲击性能和能量吸收能力,通过周期性阵列传统星形胞元和星-菱形胞元,本文构建了内凹星形蜂窝结构(Reentrant star-shaped honeycomb structures,RSH)和新型的面内增强星-菱形蜂窝结构(Enhanced star-rhombic honeycomb structures,ESH)。通过实验和有限元模拟,系统地研究了ESH在不同加载方向的面内力学响应和吸能特性。与RSH相比,准静态压缩下ESH的负泊松比特性减弱,但吸能能力显著提高。此外,结合微拓扑胞元的变形特征,揭示了低速冲击时ESH-y的应力-应变响应呈现双平台特征的变形机制,并讨论了结构参数α、t和b对平台应力的影响规律。基于高速冲击下ESH的周期性逐层坍塌变形特征和动量定理,给出了不同加载方向高速平台应力的理论解,理论结果与有限元结果吻合较好。该研究可为创新设计具有更优力学性能的新型负泊松比结构提供参考。

CO_2加富对黄瓜叶片显微和亚显微结构的影响

以黄瓜为试材 ,研究CO2 加富对叶片显微和亚显微结构的影响。结果表明 :CO2 加富后黄瓜叶片栅栏组织厚度、表皮厚度和叶片厚度增加 ,栅栏组织占叶片总厚度的比例上升 ,栅栏细胞变长 ,排列更加整齐紧密 ;叶片叶绿体数目和大小、淀粉粒数目和大小、基粒及其片层数均增加 ,单位叶绿体含淀粉粒数上升 ,但叶绿体超微结构未见明显伤害。上午以不同浓度CO2 加富 3h效应较小 ,上、下午各以 110 0± 10 0 μL·L-1CO2 加富

华支睾吸虫亚显微结构的研究 Ⅴ 精细胞的分化

目的:研究华支睾吸虫精子的形成。方法：以囊地感染家兔，剖检获取成虫，切取睾丸段做超薄切片，电镜观察。结果：精原细胞分布在睾丸被膜下，睾丸深部分布着不同分化阶段的精母细胞、精细胞和精子，精母细胞行不完全分裂，从而存在细胞质间桥，将32个精母细胞联接在一起，进行同步发育。结论：华支睾吸虫精子的分化分为两个连续的阶段，一、由精原细胞依次向初级精母细胞、次级精母细胞和精细胞分化;二、由精细胞分化、变形，形成精子，本文报告为前一阶段。

华支睾吸虫亚显微结构的研究Ⅵ.精子的形成

华支睾吸虫精子的分化可以分为两部分，一是精细胞的发生，二是精子的形成，本文报道的为第二部分。精子的形成首先由精细胞核向细胞的游离端移动，然后出现细胞突起，在突起内可见中心粒和基体，此为分化区，继之胞质突起延伸形成中央突起，并在其两侧出现两个侧突起。细胞核变长，染色质浓缩，核纵断面呈丝状或版层状，核及线粒体分别移入分化区及中央突起内，随之中央突起与两侧突起融合，形成精子的杆状体，分化区的柱状体形成精子头部。最后精子自领状结构的水平与精细胞的胞质间桥分离。

基于遗传算法的农业机械中行星传动机构的优化设计

行星传动机构在水稻插秧机分插机构、拖拉机变速箱、秸秆压块机等诸多农业机械中得到了应用。如何优化设计行星传动结构,以便更好地适应农业机械生产需求,是一项极为重要的工作。为此,介绍了行星传动结构优化设计模型和基本遗传算法的基本原理,在此基础上,将星齿行星传动的最小体积作为优化设计目标,采用遗传算法进行优化设计。实验结果表明,此方法有效减少了星齿行星传动体积,更好地适应了农业机械对于成本和体积的特殊需求。

一种星-箭连接动态界面力的深度学习反演方法

针对于星-箭连接动态界面力无法通过力传感器直接测量,且典型时域动载反演方法难以准确计算界面力的时域变化等难点,提出了基于长短时记忆(LSTM)神经网络的星-箭界面力深度学习反演方法。首先通过卫星地面测试试验得到数据依据,以卫星主体结构的加速度测量数据为输入层,以星-箭界面力测量数据为输出层,利用LSTM神经网络建立输入和输出间的反演映射关系模型,实现卫星在发射过程中较高精度的界面力反演。进而,设计并开展了某典型卫星结构的正弦扫频和随机振动实验,测试LSTM界面力反演方法的可行性。结果分析可知,所提出的基于LSTM深度学习反演方法能够精确地获得动态界面力时程数据,两项性能指标均优于目前典型的载荷反演方法。

力限技术在航天器振动试验中的应用

为了在正弦振动试验中模拟真实的飞行环境,防止因"过试验"而导致航天器结构发生不必要的破坏,需要对试验条件进行下凹控制。在以往的加速度下凹控制方法的基础上,引入力限控制方法可以提高航天器主频处下凹控制的精度和有效性。文章分析了传统加速度下凹控制方法的局限性,并以某结构星力限控制试验为基础,阐述了结构星力限试验条件的制定方法,介绍了力限双控试验平台设计,并分析了试验结果。经分析表明,力限控制具有较高的控制精度,在加速度控制的基础上引入力限控制的"双控"试验方法,能够有效解决航天器振动试验中的"过试验"和"欠试验"问题。

基于模糊聚类法的油气集输系统优化设计

油气集输系统优化设计对地面建设成本控制和保证油田高效生产起着重要作用。以油气集输管网系统投资极小化为目标,综合考虑多级星式管网拓扑结构特点、生产运行参数等多种影响因素,建立了多级星式油气集输系统模糊优化数学模型;并采用模糊c-均值聚类方法对该模型进行优化,得到最优中转站个数、最佳中转站位置、最优网络级数等。通过实例分析与结果对比表明,模糊c-均值法计算结果可靠,能够解决传统优化设计方法中效率与效果不能兼顾的矛盾,有助于油田地面"管-站"部署及优化调整设计,实用性较强。

Crystal structure and fluorescence property of antofloxacin

Antofloxacin free base is prepared from antofloxacin hydrochloride by removing hydrogen chloride. Its crystal is obtained by slow evaporation of an acetonitrile-methanol mixed solution. Single-crystal X-ray diffraction reveals that the crystallography belongs to a triclinic PI space group with cell parameters： a = 0. 663 07（13） nm, b = 0. 898 39（18） nm, c = 1. 569 0（3） nm, α = 75.12（3）°,β = 87.92（3）°, γ = 77.57 （3）°. Antofloxacin shows no fluorescence in solution, but the crystalline state emits strong green light at 510 nm under the excitation of 360 nm, indicating a fluorescence enhancement induced by aggregation. It demonstrates that intermolecular packing and interaction in the crystal lead to the improved fluorescence quantum yield. These results provide important intbrmation for the further exploration of the structure-activity relationship of antofloxacin and the development of new drugs.

Microsatellites underestimate genetic divergence in the Green-backed Tit (Parus monticolus)

Although a growing number of both sequence-based and microsatellite nuclear loci have been used to infer genetic structures, their relative efficiencies remain poorly understood. In our study, we used the Green-backed Tit (Parus monticolus) to explore the resolving ability of these two types of markers. The south-western and central mitochondrial DNA (mtDNA) phylogroups were divergent to some extent in sequence-based nuclear data, while mixed together in microsatellites data. The F ST values among clades were about four times lower in microsatellite loci than those in sequence-based nuclear loci. We are of the opinion that size homoplasy may have contributed to the inability of microsatellites to uncover differentiation. Our results suggest that sequence-based nuclear loci outperformed microsatellite loci in detecting population structures, especially those focused on populations with large effective population sizes. There was no significant correlation between F ST values and allelic size variability, which suggested that the efficiency of microsatellite loci in detecting genetic structure may be independent of their polymorphism. F ST is better than R ST in detecting intraspecific divergence due to the high variance of R ST . In agreement with sequence-based nuclear loci, microsatellite loci did resolve the genetic distinctness of the Taiwan Residents phylogroup. The genetic differentiation between the Taiwan Residents and continental clades may involve allopatric divergence without gene flow.

Implementation and comparative testing of turn-based algorithm for logit network loading

In order to evaluate the practicality and effectiveness of the turn-based algorithm for logit loading （TALL）, the TALL is implemented using C＋＋, and it is compared with a combination of the network-expanding method and the Dial algorithm based on the analysis of algorithm procedures. The TALL uses the arc-labeling shortest path searching, bidirectional star and the deque structure to directly assign the traffic flow, while the Dial algorithm should be used in an expanded network. The test results over realistic networks of eight cities show the superior performance of the TALL algorithm over the combination of the network-expanding method and the Dial algorithm, and the average processing time is reduced by 55. 4%. Furthermore, it is found that the operational efficiency of the TALL relates to the original densities of the cities. The average processing time is reduced by 65. 1% when the original density is about 14%, but the advantage of the TALL is not obvious with the increase in the original density.

Fabrication of Monodisperse ＂Core-Satellite＂ Nanostructures by DNA-Programming： a Novel Class of Superstructured Building Blocks for Hierarchical Nanoassembly

Monodisperse nanoparticle assembly with tunable structure, composition and properties can be taken as a superstructured building block for the construction of hierarchical nanostruc tures from the bottom up, which also represents a great challenge in nanotechnology. Here we report on a facile and controllable method that enables a high yield fabricatioa of uniform gold nanoparticle （AuNP） coresatellites with definable number （in average） of the satellite particles and tunable coretosatellite distance. The formation of the coresatellite nanostruc tures is driven by programmable DNAbasepairing, with the resulting nanocomplexes being isolatable via gel electrophoresis. By rationally controlling the DNA coverages on the core and shell particles, high production yields are achieved for the assembly/isolation process. As well, benefiting from a minimum DNA coverage on the satellite AuNPs, a strong affinity is observed for the asprepared coresatellites to get adsorbed on proteincoated graphene ox ide, which allows for a twodimensional hierarchical assembly of the coresatellite structures. The resulting hierarchical nanoassemblies are expected to find applications in various areas, including plasmonics, biosensing, and nanocatalysis. The method should be generalizable to make even more complicated and higherorder structures by making use of the structural programmability of DNA molecules.

Genetic diversity and population structure of a Sichuan sika deer(Cervus sichuanicus) population in Tiebu Nature Reserve based on microsatellite variation

Cervus sichuanicus is a species of sika deer （Cervus nippon Group）. To date, research has mainly focused on quantity surveying and behavior studies, with genetic information on this species currently deficient. To provide scientific evidence to assist in the protection of this species, we collected Sichuan sika deer fecal samples from the Sichuan Tiebu Nature Reserve （TNR） and extracted DNA from those samples. Microsatellite loci of bovine were used for PCR amplification. After GeneScan, the genotype data were used to analyze the genetic diversity and population structure of the Sichuan sika deer in TNR. Results showed that the average expected heterozygosity of the Sichuan sika deer population in TNR was 0.562, equivalent to the average expected heterozygosity of endangered animals, such as Procapra przewalsldi. Furthermore, 8 of 9 microsatellite loci significantly deviated from the Hardy-Weinberg equilibrium and two groups existed within the Sichuan sika deer TNR population. This genetic structure may be caused by a group of Manchurian sika deer （Cervus hortulorum） released in TNR.

Prediction for Dynamic Characteristics of Ring-Plate Planetary Indexing Cam Mechanism

This paper is aimed to propose an approach to predict the dynamic characteristics of ring-plate planetary indexing cam mechanism, which is a novel type of indexing mechanism that employs internal planetary transmission structure. Firstly, the geometry and structure of the mechanism are discussed and the kinematic practicability is simulated with virtual prototype design. Then a 3D finite element model of the ring-plate planetary indexing cam mechanism is developed with the commercial software of MATLAB and ANSYS. Through the finite element analysis, the natural frequencies and the corresponding mode shapes are predicted in one motion cycle. On the basis of the virtual prototype design and finite element analysis, an experimental prototype is made and tested to validate the prediction of the dynamic characteristics. The agreement between experimental results and the finite element analysis testifies that the finite element model developed is applicable to the prediction of the dynamic characteristics of this type of mechanism.

集群通信系统中微波多工器的应用研究

微波多工器对于解决集群通信系统中电磁兼容问题具有重要作用。文章全面介绍了现代微波多工器的各种设计方案,包括定向耦合器、星点式结构、多头线多工器、环形器耦合、可调相位器等方案,并对各种方案的优缺点进行了对比分析,最后重点讨论了UHF频段星点式可调多工器的设计方法。

Genetic diversity and genetic structure of the Daurian Partridge(Perdix dauuricae) in China,assessed by microsatellite variation

The Daurian Partridge(Perdix dauuricae) is a kind of hunting bird with high economic value.Genetic diversity and structure in the Daurian Partridge were studied by analyzing eight microsatellite loci in 23 populations found throughout the range of the species in China.The objectives were to evaluate the consequences on genetic diversity and differentiation of Daurian Partridge populations and to obtain a profound genetic insight for future management decisions and for effective measures to protect and exploit Daurian Partridges.The results showed that microsatellites were polymorphic in all Daurian Partridge populations,with a high level of genetic diversity over all the loci,especially in the Qaidam Basin populations which have the highest level of diversity.Significant genetic divergence was observed among different groups as well as between populations within the same group;most pairwise FST values were highly significant.Both phylogenetic trees and Bayesian clustering analyses revealed clear differentiation among the 23 populations of the Daurian Partridge,which were classified into two genetically differentiated groups.A bottleneck analysis indicated that Daurian Partridge populations have experienced a recent bottleneck.Our study argues that the Qaidam populations,North China populations,JN population,ZJC population,and Liupan Mountain populations should be paid special attention in order to retain adequate population sizes for maintaining genetic diversity.

Dynamic Connectivity in Cislunar Communication Networking Based on Geosynchronous Orbit Relay Satellites

The architecture of cislunar multi-hop communication networks, which focuses on the requirements of lunar full-coverage and continuous cislunar communications, is presented on the basis of Geosynchronous Orbit (GEO) satellite network relays. According to the geographical distribution of the forthcoming Chinese Deep Space Measuring and Controlling Network (DSMCN), two networking schemes are proposed and two elevation angle optimization models are established for locating GEO relay satellites. To analyze the dynamic connectivity, a dynamic network model is constructed with respect to the time-varying characteristics of cislunar trunk links. The advantages of the two proposed schemes, in terms of the Connectivity Rate (CR), Interruption Frequency (IF), and Average Length of Connecting Duration (ALCD), are corroborated by several simulations. In the case of the lunar polar orbit constellation case, the gains in the performance of scheme I are observed to be 134.55%, 117.03%, and 217.47% compared with DSMCN for three evaluation indicators, and the gains in the performance of scheme II are observed to be 238. 22%, 240.40%, and 572.71%. The results validate that the connectivity of GEO satellites outperforms that of earth facilities significantly and schemes based on GEO satellite relays are promising options for cislunar multi-hop communication networking.