由"龟兔赛跑"想到的

现行高中物理课本很重视与实际问题的联系,直线运动一章后的第42页第5题以"龟兔赛跑"编拟的一道练习题,笔者把该实例应用到速度教学中有以下几点突出作用.     

大口径激光波前测量方法

采用大型透镜阵列对激光波前进行采样，实现了对宽光束的测量。大口径激光束经过大型透镜阵列进行采样形成光斑点阵，通过成像系统，获取点阵图像，得到激光束波前信息，根据激光传输理论和光学系统像差理论，已知激光束的波前函数和强度分布时，可以求出激光束会聚后在焦面处任意位置的光强，因此激光束的波前、发散角、近场分布、远场分布等参数能够通过测量求解得到。     

工程施工中运输网络优化方案

施工工地运输方案的优化设计可以归结为 :按施工期要求设计运输线路或验证已有线路通行能力 ,计算总线路中影响提高流量的关键路段 ,取得最小费用最大流 .本文运用图论理论这一数学工具把实际问题抽象为有向网络 ,进而建立数学模型 .此方法理论上严密 ,解题步聚直观清晰 ,对水利、公路、水路、铁路等其它运输系统有普遍意义 .     

3族新的不含紧优与几乎紧优的有向双环网络无限族

给出了3族新的不含紧优与几乎紧优的有向双环网络.     

Fast-switching SOI-LIGBT with compound dielectric buried layer and assistant-depletion trench

A lateral insulated gate bipolar transistor (LIGBT) based on silicon-on-insulator (SOI) structure is proposed and investigated. This device features a compound dielectric buried layer (CDBL) and an assistant-depletion trench (ADT). The CDBL is employed to introduce two high electric field peaks that optimize the electric field distributions and that, under the same breakdown voltage (BV) condition, allow the CDBL to acquire a drift region of shorter length and a smaller number of stored carriers. Reducing their numbers helps in fast-switching. Furthermore, the ADT contributes to the rapid extraction of the stored carriers from the drift region as well as the formation of an additional heat-flow channel. The simulation results show that the BV of the proposed LIGBT is increased by 113% compared with the conventional SOI LIGBT of the same length L_D. Contrastingly, the length of the drift region of the proposed device (11.2 μ) is about one third that of a traditional device (33 μ) with the same BV of 141 V. Therefore, the turn-off loss (E_OFF) of the CDBL SOI LIGBT is decreased by 88.7% compared with a conventional SOI LIGBT when the forward voltage drop (V_F) is 1.64 V. Moreover, the short-circuit failure time of the proposed device is 45% longer than that of the conventional SOI LIGBT. Therefor, the proposed CDBL SOI LIGBT exhibits a better V_F-E_OFF tradeoff and an improved short-circuit robustness.     

认知无线电网络中利用FEC和DE的多节点频谱感知算法

针对认知无线电网络(CRN)中空闲频谱感知困难的问题,本文提出了基于前向纠错和差分进化算法的多节点频谱感知算法。首先,利用基于差分进化算法的协同检测完成信号感知;然后,研究了信道噪声对频谱感知性能的影响;最后,分析了前向纠错技术在信道存在噪声时对频谱感知性能的影响。仿真实验将纠错和无纠错控制信道的不同信噪比作为依据,采用三种不同的检测方法评估了本文算法。仿真实验结果表明,在存在噪声的认知无线电网络中,本文算法提高了系统的性能和检测概率,且协同感知算法的性能随着节点数目的增加而提高,该算法适合应用于实时性要求较高的应用程序。     

半实物仿真中试验总控软件的设计与实现

试验总控软件是应用于半实物仿真中对参试系统进行管理和控制的一种软件,它可以对半实物仿真中的参试系统进行配置,实现对整个试验仿真的管理和监控。解析各参试系统的数据交互协议是试验总控软件对参试系统进行监控和管理的关键功能。通常试验总控软件解析功能代码完全按照各参试系统数据交互协议开发,这样一旦数据交互协议发生更改,解析功能代码需要根据新协议重新开发导致软件重复开发,影响软件开发效率和通用性。为了解决这个问题,文中提出一种试验总控软件设计框架并采用动态解析数据帧技术将解析代码与数据交互协议隔离,不仅提高软件通用性,同时缩短半实物仿真开发周期,减少人力财力开支。     

k-紧优有向双环网络无限族的构建

本文给出了一种方法用于构造k-紧优双环网络无限族(k≥1),并用此方法构造出了4族3-紧优无限族,3族新的4-紧比无限族,3族5-紧优无限族及2族6-紧优无限族．     

First-principles study of Ga7As7 ionic cluster and influence of multi-charge on its structure

This paper investigates the structures and stabilities of neutral Ga7As7 cluster and its ions in detail by using first-principles density functional theory. Many low energy structures of Ga7As7 cluster are found. It confirms that the ground state structure of neutral Ga7As7 cluster is a pentagonal prism with four face atoms like a basket structure, as reported by previous works. The ground state structures of positive Ga7As7 cluster ions are different from that of the neutral cluster. These investigations suggest that Ga atoms occupy the capping positions more easily than As atoms. Mulliken population analyses also show that Ga atoms can lose or obtain charge more easily than As atoms. It finds that the neutral Ga7As7 cluster can become more stable by gaining one or two additional electrons but further more electrons would cause the decrease of binding energy. The ionisation energy increases with the increase of the number of the removed electrons. These calculated results indicate that the net magnetic moment of the neutral Ga7As7 cluster is zero because all electrons are paired together in their respective molecular orbits. But for the ionic Ga7As7 cluster with odd number of electrons, the net magnetic moment is 1.0 μB due to an unpaired electron.