TCP协议在卫星网络中的问题研究

由于TCP协议直接应用到卫星网络中将可能会导致网络性能下降,因此针对卫星网络的特点,分析了传播时延、高误码率、非对称连接方式等特点对TCP协议性能的影响,对主要解决方法进行了分析、比较现有的几种解决方法利弊,应根据具体应用采用相应的解决方案.     

Olfactory Responses of the Predatory Mites (N eoseiulus cucumeris) and Insects (O rius strigicollis ) to Two Different Plant Species Infested with Onion Thrips (T hrips tabaci)

Responses of Neoseiulus cucumeris (a predatory mite) and the predatory insect Orius strigicollis to volatiles associated with two different plant species infested with onion thrips, Thrips tabaci, were examined in a Y-tube olfactometer. Both predators species showed a significant preference for volatiles from infested cucumber leaves without T. tabaci over clean air. However, they were not attracted to volatiles from uninfested cucumber leaves, artificially damaged cucumber leaves, or volatiles from T. tabaci plus their visible products collected from cucumber leaves. These results suggest that both predator species are capable of exploiting herbivore-induced volatiles from T. tabaci-infested cucumber leaves as a foraging cue. Neither predator was attracted to volatiles from uninfested spring onion leaves, infested spring onion leaves without T. tabaci, or volatiles from T. tabaci plus their visible products collected from spring onion leaves. Interestingly, they avoided volatiles from artificially damaged spring onion leaves. A possible explanation for the non-significant olfactory responses of the predator species to spring onion plants with infestation damage of T. tabaci is discussed.     

Local collision avoidance of multiple robots using avoidability measure and relative distance

This paper presents a new method driving multiple robots to their goal position without collision. To consider the movement of the robots in a work area, we adopt the concept of avoidability measure. The avoidability measure figures the degree of how easily a robot can avoid other robots considering the velocity of the robots. To implement the concept to avoid collision among multiple robots, relative distance between the robots is proposed. The relative distance is a virtual distance between robots indicating the threat of collision between the robots. Based on the relative distance, the method calculates repulsive force against a robot from the other robots. Also, attractive force toward the goal position is calculated in terms of the relative distance. These repulsive force and attractive force are added to form the driving force for robot motion. The proposed method is simulated for several cases. The results show that the proposed method steers robots to open space anticipating the approach of other robots. In contrast, since the usual potential field method initiates avoidance motion later than the proposed method, it sometimes fails preventing collision or causes hasty motion to avoid other robots. The proposed method works as a local collision-free motion coordination method in conjunction with higher level of task planning and path planning method for multiple robots to do a collaborative job.     

A Review of:“The Remembering Self: Construction and Accuracy in the Self-narrative”, edited by ULRIC NEISSER and ROBYN FIVUSH,Cambridge University Press,New York (1994), pp. x + 301, £30.00, ISBN 0-521-43194-8

Driving is a task that requires the timely detection of critical events and relevant changes in traffic circumstances. Adaptation of speed and safety margins allows drivers to control the time available to react to potential hazards. One of the basic safety margins in driving is the time headway preserved with respect to cars ahead. To avoid rear-end collisions, drivers have to detect decelerations of lead cars. It can be assumed that fast or abrupt decelerations of the lead car are detected faster than slow or gradual decelerations. Moreover, expected decelerations are presumably detected faster than unexpected decelerations. Drivers' responses to rather abrupt and more gradual decelerations of the lead were investigated in a driving simulator. Situational traffic cues were used to manipulate the driver's expectations. Drivers adjusted the timing of their responses very well to the level of deceleration of the lead car. If cues in the environment indicated that the lead car was likely to decelerate, drivers reacted faster. Moreover, drivers increased their headway before the lead car actually started to decelerate, which can be considered an anticipatory response. In general, anticipation allows drivers to maintain their preferred headway and control time pressure in driving.     

基于早期随机检测(RED)算法的拥塞避免策略

RED算法采用随机丢弃策略,避免传统尾部丢弃方式而引起的TCP全局同步,同时通过控制队列的长度来抑制拥塞的发生     

Learning to make errors: evidence from a driving task simulation

Human errors represent a mismatch between the demands of an operational system and what the operator does. If they cannot be reversed, their consequences may be severe. Errors are frequently classified as design-or operator-induced. A third class of errors may also be identified, namely process-induced errors. Such errors arise out of on-going processes which typically extend over time. One such process is that of learning. In relation to the acquisition of skills, for example, learning frequently involves a trial-and-error component. Accidents by inexperienced drivers may represent a severe consequence of such errors. Errors may also arise out of particular learning experiences which provide a distorted underestimate of objective risk and/or motivate high risk behaviour. These phenomena are investigated in a computer simulation of the driving task. The relationship is discussed between various kinds of learning experience and the development of situations in which the possibility of error recovery declines. Some suggestions for reducing the frequency of irreversible errors and for increasing the data base for human error in vehicle driving are made.     

Development of a lane departure monitoring and control system

The lane departure avoidance systems have been considered promising to assist human drivers in AVCS (Advanced Vehicle Control System). In this paper, a lane departure monitoring and control system is developed and evaluated in the hardware-in-the-loop simulations. This system consists of lane sensing, lane departure monitoring and active steering control subsystems. The road image is obtained based on a vision sensor and the lane parameters are estimated using image processing and Kalman Filter technique. The active steering controller for avoiding the lane departure is designed based on the lane departure metric. The proposed lane departure avoidance system is realized in a steering HILS (hardware-in-the-loop simulation) tool and its performance is evaluated with a driver in the loop.     

基于AI技术的固定翼无人机集群分布式规避控制系统研究与设计

固定翼无人机集群是由多个固定翼无人机组成的群体,在飞行任务中协同工作。相比于单个无人机,固定翼无人机集群具有更高的综合性能和更广阔的应用前景。但由于固定翼无人机在恶劣环境作业过程中存在着很多风险,例如障碍物撞击、相邻无人机碰撞等,威胁无人机的安全性。故设计了基于AI技术的固定翼无人机集群分布式规避控制系统。系统硬件单元主要包括AI视觉传感器设计单元、激光雷达传感器设计单元、控制器设计单元与无线通信网络设计单元,通过上述硬件设备提供实时的环境信息,控制无人机飞行姿态,实现信息共享。软件模块基于AI技术解算无人机位置和姿态,计算障碍物位置实现形状感知,完成无人机集群分布式规避控制。通过硬件与软件的协同作业,实现了固定翼无人机集群的分布式规避控制。实验结果显示:应用设计系统获得的无人机位置感知结果、障碍物位置感知结果与实际位置相同,路径总偏离量数值为4m,充分证实了设计系统控制性能较佳。     

基于BIM的机电自动管线综合优化技术研究与应用

本文针对目前BIM技术在机电管道综合排布中应用不充分、未能较好发挥其功能、严重依赖工程师经验的问题,提出了自动化的解决方案。由管道通用避让原则、典型碰撞场景标识、典型碰撞解决方案、基于模型信息的场景自动识别、专业化碰撞检查等主要技术组成机电自动管综技术,实现管道碰撞问题的快速检测和分类,并自动完成碰撞问题的调整。本文通过Revit二次开发完成机电自动管综插件,介绍了各项主要技术的原理和实现方法,通过案例测试了软件的使用效果,并提出了进一步优化的关键方法和步骤。对软件适用的范围和时机作出了限制,并提出了改进方案。