Satellite Constellation Design for Complex Coverage

Most traditional satellite constellation design methods are associated with a simple zonal or global, continuous or discontinuous coverage connected with a visibility of points on the Earth's surface. A new geometric approach for more complex coverage of a geographic region is proposed. Full and partial coverage of regions is considered. It implies that, at any time, the region is completely or partially within the instantaneous access area of a satellite of the constellation. The key idea of the method is a two-dimensional space application for maps of the satellite constellation and coverage requirements. The space dimensions are right ascension of ascending node and argument of latitude. Visibility requirements of each region can be presented as a polygon and satellite constellation as a uniform moving grid. At any time, at least one grid vertex must belong to the polygon. The optimal configuration of the satellite constellation corresponds to the maximum sparse grid. The method is suitable for continuous and discontinuous coverage. In the last case, a vertex belonging to the polygon should be examined with a revisit time. Examples of continuous coverage for a space communication network and of the United States are considered. Examples of discontinuous coverage are also presented.

Evaluation of coverage of self-assembled polyaniline-analogue monolayer by capacitance measurements

A method is developed to estimate the coverage of an electropolymerizable aniline-analogue monolayer (mixture of 2- and 3-aminophenols, 2/3-ATP) by measuring the charge capacitance of the electrode (theta = 81%). The technique of filling the uncovered area (defect sites) of the aniline-analogue monolayer with alkanethiols with long alkane chains (1-decanethiol, 1-DT) has been used to determine the coverage. The dielectric constant (permittivity) of the PANI-analogue monolayer was determined to 8.4. Adsorption kinetics of 1-DT was also studied, and the value of the rate constant of the secondary adsorption was measured to 0.9 mol(-1) dm(3) s(-1).

CO adsorption and correlation between CO surface coverage and activity/selectivity of preferential CO oxidation over supported Ag catalyst: an in situ FTIR study

In situ IR measurements for CO adsorption and preferential CO oxidation in H-2-rich gases over Ag/SiO2 catalysts are presented in this paper. CO adsorbed on the Ag/SiO2 pretreated with oxygen shows a band centered around 2169 cm(-1), which is assigned to CO linearly bonded to Ag+ sites. The amount of adsorbed CO on the silver particles ( manifested by an IR band at 2169 cm(-1)) depends strongly on the CO partial pressure and the temperature. The steady-state coverage on the Ag surface is shown to be significantly below saturation, and the oxidation of CO with surface oxygen species is probably via a non-competitive Langmuir Hinshelwood mechanism on the silver catalyst which occurs in the high-rate branch on a surface covered with CO below saturation. A low reactant concentration on the Ag surface indicates that the reaction order with respect to Pco is positive, and the selectivity towards CO2 decreases with the decrease of Pco. On the other hand, the decrease of the selectivity with the reaction temperature also reflects the higher apparent activation energy for H-2 oxidation than that for CO oxidation.

环球滑翔飞行及其地表投影的近似计算方法

定义了通过滑翔实现环球飞行的概念,并提出了以椭圆轨道理论和分段常滑翔角方法相结合的飞行器环球滑翔飞行地表投影的近似算法。计算和分析表明,初始投送方向角是决定环球滑翔飞行地表投影的关键因素。最后给出的算例验证了该近似计算方法的有效性。

Surface Stress Induced By Adatoms Adsorption On Solid Surfaces

Based on the statistical thermodynamics theory, a theoretical model of adsorbate induced surface stress of adatoms adsorption on solid surface is presented. For the low coverage, the interaction between the adsorbed molecules is entirely negligible and the adsorption induced surface stress is found to be the function of the coverage and the adsorption energy change with strain. For the high coverage, the adsorbate-adsorbate interaction contributes to the adsorption-induced surface stress effectively. In the case of carbon adsorption on the Ni(100) surface, the value of 0.5 is obtained as a characteristic coverage to decide whether to take the interaction between the adsorabtes into consideration and the results also show that the adsorption induces a compressive surface stress.

激光熔凝覆盖率对材料表面力学性能影响的模拟

通过有限元方法，模拟了接触载荷下，激光熔覆盖率对材料表层循环应力幅值和表层裂纹CTOD的影响，从而预测了熔凝覆盖率对材料接触疲劳寿命的影响。文中考虑了不同熔凝覆盖率的材料表面微结构形状的差异，不同熔凝覆盖率摩擦副的摩擦系数一样和发生变化两种情况。结果显示，熔凝覆盖率为20％左右的材料表层强韧化性能最好。

基于土壤水分平衡原理的毛乌素沙地草地种植咨询系统

本研究初步建立了基于土壤水分平衡原理的毛乌素沙地草地种植咨询系统“ASSG”，该系统用于进行毛乌素地区沙地草地利用和种植管理咨询，并可进行更新知识库和存储有关咨询结果的操作。该系统适用于田间工作者、农场管理者、有关科研人员以及任何对生态科学和自然资源管理感兴趣者。 在文中描述了该咨询系统的开发过程，即系统的需求分析、设计、实现和运行，该系统实现了专家系统和仿真模型的结合，该模型即基于水分平衡的最佳植被覆盖率模型，有如下初步结论产生：土壤水分的平衡随植被覆盖率变化的情况（上升或下降）取决于立地条件的差异，笼统地讲“植被覆盖率越高越好”或“植被覆盖率一概不宜太高”未免失之偏颇。 在解决复杂的生态学问题时人工智能／专家系统技术的应用以及在定性模型和方法（如专家系统）的应用中使用定量模型（如仿真模型）正处于发展之中，本系统的实现是应用专家系统与仿真模型结合的方法解决实际生态学问题的又一个例子。

内蒙古多伦典型草原植物多样性与生产力的关系及其对水分梯度的响应

为了研究草地群落发展的初期阶段物种多样性和生产力的关系及对降雨梯度的响应，同时确定草地群落面对降雨量的波动时物种多样性和地上生物量稳定性的关系，我们在2004-2005年在内蒙古草原进行一个为期二年的实验。我们在降雨梯度内（增雨、对照、减雨）模拟群落物种丰富度（4种，8种和14种）。我们的结果表明，在草地群落早期阶段观测到的物种丰富度及地上生物量的关系不同于群落发展成熟稳定时的关系。我们发现：1）无论是在群落水平还是功能群水平，盖度相对物种丰富度都是一个决定群落地上生物量的重要因素； 2）不同植物功能群表现出不同的物种丰富度-地上生物量的关系。这可能是因为不同功能群植物的横向扩展能力不同导致；3）在群落水平和豆科固氮功能群，地上生物量随着土壤含水量的增加而增加，但禾本功能群和非豆科非禾本功能群的关系不显著；4）降雨量变化对物种多样性和地上生物量的关系影响不大；5）在我们实验中，具有较高的物种丰富度植物群落的地上生物量比那些物种丰富度低的群落较为稳定，我们的研究结果因此支持“保险假说”；6）土壤含氮量和含碳量呈现非常显著的正相关关系。 为了补充2004-2005年实验结果，我们在2006年同一个实验样地进行了另一个实验。2006年实验土壤经过翻耕平整，然后选择植物幼苗移载。在这种情况下，我们发现：1）物种组成是决定地上生物量一个关键因素；2）降雨量变化对物种多样性和地上生物量的关系影响不大; 3）混合群落表现出超产效应，物种丰富度高的群落超产的比例较高；4）在三个水分处理梯度都没有发现物种丰富度和群落可靠度存在相关关系；5）在所有水分处理样方都发现地上生物量和土壤含氮量呈现非常显著的负相关关系；6）土壤含氮量和土壤含碳量与土壤湿度呈现非常显著的正相关关系；7）土壤含氮量和含碳量呈现非常显著的正相关关系。