Geometric algorithms for the conformational analysis of long protein loops

The efficient filtering of unfeasible conformations would considerably benefit the exploration of the conformational space when searching for minimum energy structures or during molecular simulation. The most important conditions for filtering are the maintenance of molecular chain integrity and the avoidance of steric clashes. These conditions can be seen as geometric constraints on a molecular model. In this article, we discuss how techniques issued from recent research in robotics can be applied to this filtering. Two complementary techniques are presented: one for conformational sampling and another for computing conformational changes satisfying such geometric constraints. The main interest of the proposed techniques is their application to the structural analysis of long protein loops. First experimental results demonstrate the efficacy of the approach for studying the mobility of loop 7 in amylosucrase from Neisseria polysaccharea. The supposed motions of this 17-residue loop would play an important role in the activity of this enzyme.     

Trajectory Modeling of Robot Manipulators in the Presence of Obstacles

This paper presents two different strategies for the problem of the optimal trajectory planning of robot manipulators in the presence of fixed obstacles. The first strategy is related to the situation where the trajectory must pass through a given number of points. The second strategy corresponds to the case where only the initial and final points are given. The optimal traveling time and the minimum mechanical energy of the actuators are considered together to build a multiobjective function. The trajectories are defined using spline functions and are obtained through offline computation for online operation. Sequential unconstrained minimization techniques (SUMT) have been used for the optimization. The obstacles are considered as three-dimensional objects sharing the same workspace performed by the robot. The obstacle avoidance is expressed in terms of the distances between potentially colliding parts. Simulation results are presented and show the efficiency of the general methodology used in this paper.     

免调试固体激光器的研究

描述了一种新型的免调试激光装置.它采用定向棱镜作为谐振腔的全反镜,在固体激光器中安装后不经调试就能实现激光运行,它具有抗失调能力强、远场光场能量集中、发散角小的特点,角度失调允量±20°,棒轴平移量为D/4,发散角小于3mrad.在100Hz高重复频率运行时,单脉冲Cr4+:YAG晶体被动调Q输出能量达到300mJ,且光场分布均匀.     

Mathematical Justification of the Obstacle Problem in the Case of a Shallow Shell

This paper deals with the asymptotic formulation and justification of a mechanical model for a shallow shell in frictionless unilateral contact with an obstacle. The first three parts of the paper concern the formulation of the equilibrium problem. Special attention is paid to the contact conditions, which are usual within two or three dimensional elasticity, but which are not so usual in shell theories. Lastly the limit problem is formulated in the main part of the paper and a convergence result is presented. Two points are worth stressing here. First, we point out that unlike classical bilateral shell models justifications, the functional framework of the present analysis involves cones. Secondly, while the cones result from a positivity condition on the boundary as long as the thickness parameter is finite, leading to a Signorini problem in the Sobolev space H ¹, the cone results from a positivity condition in the domain, giving rise to a so-called obstacle problem in the Sobolev space H ² at the limit.      

直升机毫米波防撞雷达的发展与应用

首先简要描述了直升机毫米波防撞雷达的发展历程,然后重点介绍国外已经装备和正在研制的几种典型的直升机毫米波防撞雷达,最后指出了直升机毫米波防撞雷达技术的未来发展趋势。     

遗传算法在船舶转向避碰幅度决策中的应用研究

针对船舶避碰决策系统中的船舶运动趋势和避碰时机,应用遗传算法模型,实时预测各目标船相对于本船在下一时刻的运动参数,预估目标船相对于本船的最近会遇距离（DCPA）和最近会遇时间（TCPA）。同时,应用遗传算法模型预测避碰最优角度问题。仿真结果表明,该方法能有效提高船舶海上航行的灵活性和安全可靠性,达到提前预警和帮助驾驶员提前做好避碰准备等目的。     

低轨卫星通信系统干扰分析及策略研究

卫星通信技术日益进步,低轨卫星通信系统已然成为新的发展趋势.由于频谱资源受限,低轨卫星通信系统可能面临自身及与外部地面和卫星系统的同频干扰问题.文章指出从外部系统对低轨卫星通信系统干扰、低轨卫星通信系统对外部系统干扰以及低轨卫星通信系统内部干扰3个方面进行了系统干扰场景分析,在此基础上,根据不同的干扰情况分别给出了外部...     

空间机器人捕获卫星操作基于柔顺装置的无源模糊避撞柔顺控制

讨论了漂浮基空间机器人在轨捕获非合作卫星过程避免关节受冲击及过载破坏的避撞柔顺控制问题。在关节电机与机械臂之间配置了一种柔顺装置——旋转型串联弹性执行器(RSEA),其作用一是在捕获阶段,通过其内置弹簧的变形来缓冲捕获过程中被捕获卫星对空间机器人关节产生的冲击能量;二是在捕获完成后的镇定运动阶段,结合所设计的避撞柔顺策略来适时开关关节电机以保证关节冲击力矩受限在安全范围。首先,根据拉格朗日法及牛顿-欧拉法分别建立了含柔顺装置空间机器人与目标卫星系统的动力学方程;之后,结合整个系统动量守恒关系、系统运动几何及位置约束关系,建立了捕获操作后两者形成混合体系统的动力学方程。在此基础上,针对捕获操作后不稳定的混合体系统,提出了一种基于无源性理论的避撞柔顺模糊控制方案以实现其镇定控制。最后,通过仿真实验验证了所提避撞柔顺策略的有效性。     

Small Cell在LTE网络中的应用及频谱分配策略研究

详细分析了Smal Cel 的技术特点和优势,探讨了在LTE网络中的应用场景,并针对不同环境设计了兼顾干扰避免和容量提升的Smal Cel 与宏蜂窝的频谱分配方案。     

A hotspot mitigation protocol for ad hoc networks

Hotspots represent transient but highly congested regions in wireless ad hoc networks that result in increased packet loss, end-to-end delay, and out-of-order packets delivery. We present a simple, effective, and scalable hotspot mitigation protocol (HMP) where mobile nodes independently monitor local buffer occupancy, packet loss, and MAC contention and delay conditions, and take local actions in response to the emergence of hotspots, such as, suppressing new route requests and rate controlling TCP flows. We use analysis, simulation, and experimental results from a wireless testbed to demonstrate the effectiveness of HMP in mobile ad hoc networks. HMP balances resource consumption among neighboring nodes, and improves end-to-end throughput, delay, and packet loss. Our results indicate that HMP can also improve the network connectivity preventing premature network partitions. We present analysis of hotspots, and the detailed design of HMP. We evaluate the protocol’s ability to effectively mitigate hotspots in mobile ad hoc networks that are based on on-demand and proactive routing protocols.