基于单片机的智能小车避障循迹系统设计

本设计是以STC89C52为核心,根据超声波等感测模块传输的路面信息,检测信号识别障碍物并及时调整小车行驶走向,实现了小车自适应行驶、避障的功能。智能小车自适应行驶的成功研究有助于智能车辆的研制与开发,同时也为交通工具的智能化发展提供了一个合理可行的方向。     

The Full Cost of Cryptanalytic Attacks

An open question about the asymptotic cost of connecting many processors to a large memory using three dimensions for wiring is answered, and this result is used to find the full cost of several cryptanalytic attacks. In many cases this full cost is higher than the accepted complexity of a given algorithm based on the number of processor steps. The full costs of several cryptanalytic attacks are determined, including Shanks method for computing discrete logarithms in cyclic groups of prime order n, which requires n^1/2+o(1) processor steps, but, when all factors are taken into account, has full cost n^2/3+o(1). Other attacks analyzed are factoring with the number field sieve, generic attacks on block ciphers, attacks on double and triple encryption, and finding hash collisions. In many cases parallel collision search gives a significant asymptotic advantage over well-known generic attacks.     

基于webots的机器人避障及物体识别仿真

本文运用webots对机器人在家庭环境下物体识别可能遇到的问题进行了模拟仿真,验证其可行性.主要完成了对家庭环境和机器人模型的搭建及控制程序的编写并以此实现机器人避障和物体识别.仿真结果表明,此方法可行.为今后的算法改进奠定了基础.     

RC4的密钥碰撞

RC4加密算法是密码学家RonRivest在1987年设计的序列密码算法,其密钥长度可变,接受1字节至256字节。RC4在二十世纪八十年代得到了大力发展,广泛应用于商业密码产品中,包括LotusNotes,苹果计算机的AOCE和Oracle安全SQL数据库。RC4的核心部分为可变的S盒。研究了RC4的密钥编制算法,从密钥的碰撞层面研究了RC4的密钥脆弱性,描述了在S盒为256字节时,两组不同密钥KI、K2怎样经过密钥编制算法生成了相同的初始状态,即发生了“密钥碰撞”。     

钻柱与井壁碰撞的非线性有限元分析

根据连续介质力学和非线性有限元理论,给出了钻柱碰撞井壁过程中钻柱的控制方程,并建立了相应的有限元列式。采用显式时间积分方法求解了基于拉格朗日算法的碰撞动力学方程。计算实例与分析表明,钻柱与井壁碰撞时所造成的最大第一主应力达到308MPa,其结果远远大于人们的估计;碰撞是造成钻柱先期失效的首要原因。采用显式非线性有限元技术可以对钻柱与井壁碰撞的过程进行成功的数值仿真分析,钻柱与井壁碰撞的整个时间历程得以全面细致地模拟再现。     

带有天线转换开关的车用毫米波雷达

车用雷达作为汽车防碰撞系统以及自适应巡航控制系统的关键组成部件之一,拥有广阔的市场前景。但由于造价高昂,体积偏大而一直没有得到广泛的应用。带有天线转换开关的毫米波雷达,通过两个模拟开关分别控制3个发射天线和3个接收天线,在获得了超过20°的水平方位探测角以及小于2°的方位分辨率的同时,有效地降低了雷达的造价,减小了雷达的体积。     

Distributed Power Control for Energy Conservation in Hybrid Cellular Network with Device-to-Device Communication

Device-to-Device （D2D） com- munication has been proposed as a promising implementation of green communication to benefit the existed cellular network. In order to limit cross-tier interference while explore the gain of short-range communication, we devise a series of distributed power control （DPC） schemes for energy conservation （EC） and enhancement of radio resource utilization in the hybrid system. Firstly, a constrained opportunistic power control model is built up to take advantage of the interference avoidance methodology in the presence of service requirement and power constraint. Then, biasing scheme and admission control are added to evade ineffective power consumption and maintain the feasibility of the system. Upon feasibility, a non-cooperative game is further formulated to exploit the profit in EC with minor influence on spectral efficiency （SE）. The convergence of the DPC schemes is validated and their performance is confirmed via simulation results.     

Radio resource management scheme and outage analysis for network-assisted multi-hop D2D communications

In a cellular network it's very difficult to make spectrum resource more efficiently. Device-to-Device (D2D) technology enables new service opportunities, and provides high throughput and reliable communication while reducing the base station load. For better total performance, short-range D2D links and cellular links share the same radio resource and the management of interference becomes a crucial task. Here we argue that single-hop D2D technology can be used to further improve cellular networks performance if the key D2D radio resource management algorithms are suitably extended to support multi-hop D2D communications. Aiming to establish a new paradigm for the analysis and design of multi-hop D2D communications, We propose a radio resource allocation for multi-hop D2D routes based on interference avoidance approach in LTE-A networks. On top of that, we investigate the outage probability of D2D communication. We first introduce a new definition of outage probability by considering the maximum distance to be allowable for single-hop transmission. Then we study and analyze the outage performance of a multi-hop D2D route. We derive the general closed form expression of outage probability of the multi-hop D2D routes. The results demonstrate that the D2D radio, sharing the same resources as the cellular network, provide higher capacity compared to pure cellular communication where all the data is transmitted through the base station. They also demonstrate that the new method of calculation of D2D multi hop outage probability has better performance than classical method defined in the literature.     

时隙式随机争用多址系统分析方法研究

本文给出一种新的平均周期分析方法,并对时隙式随机争用多址系统进行了分析,得到了系统的信息分组发送成功的平均长度公式、信息分组发生碰撞的平均长度公式和空闲时隙的平均长度公式,并在讨论了系统的冲突分解特性后,给出了系统的吞吐量。     

直升机防撞系统的电力线检测方法

使用防撞系统探测电力线,对低能见度条件下直升机的低空飞行安全至关重要。通过理论分析,介绍了电力线的布拉格散射特征。在静态条件下,利用毫米波收发系统对电力线的散射特性进行了试验验证。在运动条件下进行运动补偿,将电力线的布拉格散射回波和输电铁塔的强回波峰进行图像累积,并利用霍夫变换进行电力线提取。试验结果可清晰地检测到电力线,证明了处理模型和方法的正确性。