Physically Meaningful Rendering using Tristimulus Colours

In photorealistic image synthesis the radiative transfer equation is often not solved by simulating every wavelength of light, but instead by computing tristimulus transport, for instance using sRGB primaries as a basis. This choice is convenient, because input texture data is usually stored in RGB colour spaces. However, there are problems with this approach which are often overlooked or ignored. By comparing to spectral reference renderings, we show how rendering in tristimulus colour spaces introduces colour shifts in indirect light, violation of energy conservation, and unexpected behaviour in participating media. Furthermore, we introduce a fast method to compute spectra from almost any given XYZ input colour. It creates spectra that match the input colour precisely. Additionally, like in natural reflectance spectra, their energy is smoothly distributed over wide wavelength bands. This method is both useful to upsample RGB input data when spectral transport is used and as an intermediate step for corrected tristimulus‐based transport. Finally, we show how energy conservation can be enforced in RGB by mapping colours to valid reflectances.     

基于分布参数的煤矿井下直流杂散电流研究

直流杂散电流是引起井下瓦斯爆炸的重要原因之一,对煤矿安全生产具有很大威胁。针对这一问题,从杂散电流的产生机理着手,建立了井下直流杂散电流的分布参数模型;在该模型的基础上,仿真分析了各个参数对杂散电流的影响,得出了如下结论:随着机车电流的增加、供电区间的延长及轨道电阻的增大,杂散电流也会线性增加,可通过减小机车电流、缩短供电区间长度及减小轨道电阻来减小杂散电流;轨道与大地间过渡电阻低于安全值时会造成杂散电流急剧增大,保证轨道与地之间的绝缘是限制杂散电流的一种有效措施。     

基于Modbus RTU的虚拟仪器风洞电机温度监控系统开发

为监测风洞运行过程中动力系统电机温升状态,使其工作性能和绝缘等级处于合理范围,应用研华ADAM-4015模块对置于风洞6 KV高压电机相绕组与前后轴内的Pt100热电阻进行测量,本地PLC通过串口ModbusRTU协议与研华模块通讯获得电机实时温度,上位机虚拟仪器LabVIEW软件通过以太网OPC通讯实时获得PLC内电机温度值,实现了高压电机安全精确的隔离测量,以及本地、远程多个节点的温度实时监控、报警和安全联锁;实验结果表明,系统在-50～150℃内,可达到±0.1％精度,对最大功率下动力系统温升数据和特性曲线的获取实现了工作状态的分析预测,为安全互镇提供了控制依据.     

基于ASI的高速数据传输接口的设计

介绍了一种基于ASI编码的高速数据传输接口设计方案。该传输接口利用NS公司的CLC007和CLC014芯片进行发送驱动和接受均衡,利用CYPRESS公司的CY78923和CY78933芯片进行编码和解码,采用ALTERA的FPGA实现数据缓冲与转换的功能,并通过对数据的分组打包和解包校验的方法,保证数据的完整性及正确性。编码产生的数据利用50n阻抗匹配的同轴电缆进行传输,传输速率最高可达400Mbps,传输距离最远可达200m。     

基于De Bruijn图的De Novo序列组装软件性能分析

随着新一代测序技术的发展,一些新的全基因组组装算法应运而生,特别是针对第三代高通量测序仪产生的海量短序列的组装软件被不断开发出来,这些组装软件渐渐走向市场。但是,由于这些组装软件的适用性和其性能的差别,选择一款性能优良的组装工具或者开发并行高吞吐的组装工具成为了当前面临的一大难题。本文选取基于 De Bruijn 图算法开发的 4 款 De Novo 组装的软件（Velvet、SOAPdenovo、IDBA、ABySS）对 4 种物种的基因组的模拟数据进行测试,并从软件的算法、组装性能和组装质量 3 个方面分析这 4 个软件的性能,同时根据其算法特点推断影响这些软件性能的关键因素,并给出软件的使用建议以及开发并行序列组装工具来组装超大规模的基因数据应该注意的问题。     

Analysis of distribution time of multiple files in a P2P network

Peer-to-Peer (P2P) file sharing attracts much attention due to its scalability and robustness. One important metric in measuring the performance of a P2P file sharing system is the amount of time required for all peers to get the files. We refer this time as the file distribution time. Researchers have proposed protocols to minimize the file distribution time under different situation. However, most works are based on the single-file scenario. On the other hand, there are studies showing that in a file sharing application, users may download multiple files at the same time. In this paper, we analyze the minimum time needed to distribute multiple files. We develop an explicit expression for the minimum amount of time needed to distribute multiple files in a heterogeneous P2P fluid model. Unlike the single-file scenario, we demonstrate that the theoretical lower bound in multi-file is not always achievable. With a comprehensive consideration of all the configurations, we elaborate how to partition the bandwidth capacities of both seeds and leechers for a particular file such that the finish time is optimal.     

校园网安全分析及安全防范

网络技术的不断发展和普及,许多学校都建立了校园网络。随着校园网应用的深入,网络的安全问题也越来越引起关注。本文就威胁校园网安全的因素及维护网络安全的策略两个方面,进行了分析和探讨。     

larbin网络爬虫的体系结构

本文通过对larbin网络爬虫的研究后总结出了larbin网络爬虫的体系结构。然后结合该爬虫详细介绍了整个体系结构的工作过程．最后介绍了larbin网络爬虫的特点。     

基于MQP模型的电离图参数反演解析算法研究

针对现今普遍采用的偏导迭代电离图反演算法存在的求解依赖于初值选择的不足,给出了一种初值选择准则,保证了该算法的收敛性。同时,利用该准则,以及在对电离图虚高表达式进行合理近似的基础上,提出了一种新的电离图参数反演算法,该方法实现电离图参数反演的解析计算,较偏导迭代法计算量大大减少,更好满足工程实时性要求。