New and improved approaches for shared-path protection in WDM mesh networks

This paper investigates the problem of dynamic survivable lightpath provisioning in optical mesh networks employing wavelength-division multiplexing (WDM). In particular, we focus on shared-path protection because it is resource efficient due to the fact that backup paths can share wavelength links when their corresponding working paths are mutually diverse. Our main contributions are as follows. 1) First, we prove that the problem of finding an eligible pair of working and backup paths for a new lightpath request requiring shared-path protection under the current network state is NP-complete. 2) Then, we develop a heuristic, called CAFES, to compute a feasible solution with high probability. 3) Finally, we design another heuristic, called OPT, to optimize resource consumption for a given solution. The merits of our approaches are that they capture the essence of shared-path protection and approach to optimal solutions without enumerating paths. We evaluate the effectiveness of our heuristics and the results are found to be promising.     

Globally optimal transmitter placement for indoor wireless communication systems

A global optimization technique is applied to solve the optimal transmitter placement problem for indoor wireless systems. An efficient pattern search algorithm - DIviding RECTangles (DIRECT) of Jones et al.- has been connected to a parallel three-dimensional radio propagation ray tracing modeler running on a 200-node Beowulf cluster of Linux workstations. Surrogate functions for a parallel wideband code-division multiple-access (WCDMA) simulator were used to estimate the system performance for the global optimization algorithm. Power coverage and bit-error rate are considered as two different criteria for optimizing locations of a specified number of transmitters across the feasible region of the design space. This paper briefly describes the underlying radio propagation and WCDMA simulations and focuses on the design issues of the optimization loop.     

氧差对烟火药光辐射强度的影响

采用闪光有效光强测定仪和非接触式红外测温仪,对一系列不同氧差的硝酸钡、镁粉和酚醛树脂烟火药反应体系进行了试验研究.结果表明:在负氧情况下,随着氧差绝对值的增大,光辐射强度、燃烧温度和燃速也随之增大,当达到一定程度时,则随着氧差的增大而减小;当氧差为-24g时达到最大值,此时对应的光强为44.81kcd,燃烧温度为1 379.9℃,燃速为13.93mm·s-1.     

PEG/增塑剂共混物相容性的分子动力学模拟和介观模拟

为解决含能钝感增塑剂应用于硝酸酯增塑聚醚(NEPE)推进剂的问题,研究了增塑剂三羟甲基乙烷三硝酸酯(TMETN)、硝化甘油(NG)、1,2,4-丁三醇三硝酸酯(BTTN)与粘合剂预聚物聚乙二醇(PEG)的相容性。采用分子动力学模拟计算了PEG、TMETN、NG、BTTN四种纯物质的溶度参数及分子内和分子间径向分布函数,得到相容性优劣顺序为:TMETN/PEGBTTN/PEGNG/PEG。BTTN分子中的亚甲基和TMETN的结构削弱了自身分子间作用、降低了与PEG溶度参数的差值;分析了共混物的结合能及分子间径向分布函数,认为增塑剂与PEG相容的本质为"分子间以非键作用相结合,范德华作用占主要比重"。此外,增塑剂与PEG分子的极性越相近、范德华作用的占比越大;通过介观模拟得到体系的介观形态演变过程,发现NG/PEG及BTTN/PEG易发生相分离、TMETN/PEG仅发生轻微的同相归并。最终得出:含能钝感增塑剂TMETN与PEG的相容性优于BTTN及NG,可以考虑将其代替或部分代替NG、降低NEPE推进剂的感度,为低易损战术武器的发展提供依据。     

提高低燃速丁羟推进剂力学特性研究

大量粗粒度AP和降速剂的添加很难实现低燃速丁羟推进剂高强度的技术要求。研究以静态燃速不高于5.1 mm/s(20℃,6.0 MPa)低燃速丁羟推进剂作为基础配方,通过优选HTPB规格、键合剂组合和添加新型扩链剂的方法提高推进剂力学特性。结果表明,采用新型扩链剂SX,使70℃推进剂的抗拉强度高于1.0 MPa,伸长率大于10%。     

惯性平台稳定回路控制律对稳定精度的影响分析

以单轴稳定平台为对象,研究分析不同类型外界干扰力矩作用下,惯性平台稳定回路控制律形式对平台稳定精度的影响.采用高阶型控制律,更有利于实现对干扰力矩的抑制,尤其是在有较大过载变化的应用环境,或存在较大偏心不易精确平衡的情况下,需要适当提高控制律的阶次来提高平台的稳定精度.仿真结果说明,在与过载有关的干扰力矩作用下,稳定回路控制律的积分校正阶次越高,平台的稳定精度越高.     

低温感包覆火药装药的内弹道势平衡理论模拟

为了进一步研究低温感包覆火药装药的内弹道特征及其内弹道数值计算方法,运用内弹道势平衡理论,对制式装药和低温感包覆火药装药的势平衡点参数进行了比较。分析了低温感包覆火药装药势平衡点处燃去火药相对量ψE随装填密度变化的原因,并拟合了低温感包覆火药装药的实际燃气生成函数。在此基础上利用势平衡方程对内弹道过程进行了数值模拟。结果表明,计算曲线与实验曲线基本一致,应用内弹道势平衡理论描述低温感包覆火药装药的膛内燃烧规律可行。     

弹底过载存储记录仪

为获取弹丸在膛内的加速度,设计了一种能承受高压、高过载的微小型存储测试仪。它由单片机和CPLD作为主控芯片、高速FIFO作为缓存与NAND flash为存储介质,以橡胶作为电路模块与外壳的缓冲材料。采用有限元软件ANSYS/LSDYNA对冲击过程进行了数值模拟,并经155mm火炮实测验证。记录仪成功获取了膛内弹底加速度,并承受住了弹丸出口31000g的过载。     

某燃气发生器用双基推进剂包覆设计及工艺研究

针对某型燃气发生器内弹道性能试验中,出现实测曲线偏离设计基准的问题,通过分析试验数据,并结合包覆材料性能及阻燃机理,确定原因为原包覆材料硝基油漆布在包覆粘接后使推进剂出现了硝化甘油迁移现象,从而影响了推进剂能量与燃速,使产品内弹道性能发生变化。改进设计采用一种聚氨酯材料及浇注包覆工艺对推进剂进行包覆,并进行产品内弹道性能测试,结果表明包覆材料及工艺更改后内弹道曲线更接近设计曲线,产品可靠性更高。