相对极小模型

In the modal of computing elevation angle and azimuth angle of satellite,we ignore the impact of precession,nutation and pole shift in the process of coordinate system transformation due to their small effects.

在卫星俯仰角和方位角的计算模型中，针对岁差、章动和极移的影响相对于卫星位置是二阶小量，因此在坐标系转换过程中忽略岁差、章动和极移的影响。

To solve this problem, based on the concept of graph theory we give a few models and arithmetic designs of virtual backbone in the environment of different application, and propose the corresponding routing mechanism with these virtual backbones. The major achievements are outlined as follows:The state of host's power or the time of host's online plays an important role in keeping stability of a virtual backbone. With a view to this feature, the paper introduces a simple and efficient heuristic algorithm for calculating the virtual backbone by seeking a minimum connected dominating set with maximal weight. The maximality of the weight-based choice of backbone nodes guarantees that the most suitable nodes have been chosen for the role of backbone nodes so that they can properly coordinate all the other nodes and keep stability of the virtual backbone in the network.

为了解决这个问题，本文利用网络图论中的一些理论，在不同的应用环境下给出几种虚拟骨干网的模型、构建及基于稳定性和节能的算法设计，并针对这些骨干网提出相应的分层路由机制，主要研究内容和贡献如下：考虑到主机的功率大小和在线时间长短对虚拟骨干中心的相对稳固性的影响，提出用基于极大权的最小连通支配集模拟虚拟骨干网；并给出其数学模型和相应的启发式算法，确保了性能强的主机担任骨干节点；通过优化规则确保骨干网的极小性，有效地减小了控制分组转发开销；最后进行了仿真验证。

However, as the name（read－only memory）implies, CD disks cannot be written onorchanged in any way.

然而，正如其名字所指出的那样，CD盘不能写，也不能用任何方式改变其内容。

Galvanizes steel pallet is mainly export which suits standard packing of European Union, the North America. galvanizes steel pallet is suitable to heavy rack. Pallet surface can design plate type, corrugated and the gap form, satisfies the different requirements.

镀锌钢托盘多用于出口，替代木托盘，免薰蒸，符合欧盟、北美各国对出口货物包装材料的法令要求；喷涂钢托盘适用于重载上货架之用，托盘表面根据需要制作成平板状、波纹状及间隔形式，满足不同的使用要求。