Proposal of a uniform color scale for virgin olive oils

A new color scale was developed from a broad data set of 1700 virgin olive oil samples over four crop seasons, which can be considered highly representative of the whole color range of virgin olive oils available in Spain. This color scale provides a new set of 60 color standards, improving the results achieved by the old 60-color standards proposed by the bromthymol blue method. Seeking the greatest possibility of including a near match between colors of virgin olive oils and proposed standards, we developed our new color scale using a recent uniform color space, with standards placed in a regular rhombohedral lattice like the one employed by the Uniform Color Scales of the Optical Society of America. The average color difference between each of the 1700 virgin olive oils and its nearest standard is reduced from 8.17 CIELAB units, using the bromthymol blue standards, to 3.99 CIELAB units using the new standards. Within a color tolerance of 7.0 CIELAB units, 93.2% of our virgin olive oils can be classified with the new standards, but only 59.1% with the bromthymol blue ones. In the interest of future adoption, the performance of the new color standards should be tested by industry and researchers.     

A self‐commutated back‐to‐back system and its performance under a single line‐to‐ground fault condition

This paper deals with a self‐commutated BTB (Back‐To‐Back) system for the purpose of power flow control and/or frequency change in transmission systems. Each BTB unit consists of two sets of 16 three‐phase voltage‐source converters, and their AC terminals are connected in series to each other via 16 three‐phase transformers. Hence, the BTB unit uses totally 192 switching devices capable of achieving gate commutation. This results in a great reduction of voltage and current harmonics without performing PWM control. Simulation results verify the validity of the proposed system configuration and control scheme not only under a normal operating condition but also under a single line‐to‐ground fault condition. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(3): 68–78, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10124     

西北—华中联网背靠背直流工程一次系统设计

介绍了我国第一个背靠背直流工程西北—华中联网工程的系统条件、构成、运行方式和运行参数以及主设备的型式和各主要子系统的设计要求、方案 ,为我国今后背靠背直流工程乃至更大规模直流工程的系统设计和设备成套设计提供重要的参考。     

基于跳转轨迹的分支目标缓冲研究

现代计算机体系结构受两个方面的困扰:性能和能耗。为降低嵌入式处理器日益增长的功耗,提出基于跳转轨迹的分支目标缓冲结构(TG-BTB)。与传统分支目标缓冲每次提取指令时需要查询分支目标缓冲不同,TG-BTB只在执行轨迹预测为跳转时才查询分支目标缓冲。该结构通过在程序执行过程中动态分析跳转轨迹行为,可以实现只在轨迹跳转时查询分支目标缓冲,从而降低功耗。在动态分析过程中首先提取记录两条跳转分支指令之间的指令间隔,然后将提取的指令间隔存储在TG-BTB中,最后根据存储在TG-BTB中的指令间隔决定是否需要查询BTB。基于基准测试向量进行模型验证和性能测试,实验结果表明TG-BTB降低了81%的BTB查询能耗。     

Voltage balancing control of chain link converter application to interconnection system

An application of the chain link converter (CLC) system, which consists of multiple single‐phase voltage source converters (VSCs) connected in parallel or series, is studied as interconnection systems. In a CLC‐high voltage direct current transmission (HVDC) system, single‐phase converters must be connected in series on the DC side to make the DC voltage high, and the DC voltage of each converter must be controlled to the same value to get an appropriate capacity. This paper describes a DC voltage balancing control (DVBC) method between series converters. Simulations and simulator tests in steady states and in transient states were carried out to confirm behaviors of the CLC‐HVDC system. Those results confirmed the viability of CLC applications to interconnection systems. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

动态分支预测技术分析与量化研究

随着现代微处理器的流水线变得越来越深,指令发射宽度越来越大,预测失败所带来的时间代价和空间(功能部件)有效利用率损失也越来越大,预测准确率对流水线的性能的影响也越来越重要。为了量化研究不同动态分支预测技术的准确率,采用计算机体系结构模拟软件Simple Scalar和SPEC 2000 Benchmark,对2bC,GAg,PAg,GAp,PAp,G-share六种动态预测技术的分支方向和分支地址预测准确率进行了性能模拟与测试,最后对模拟结果进行统计分析,得出预测准确率与硬件实现复杂度之间的量化关系,为设计出具有高准确率和低复杂度的动态分支预测器提供了参考。     

中国—俄罗斯背靠背联网工程500kV交流出线具有自动重合闸的直流控制策略

为提高中俄直流联网黑河换流站跨国联网工程运行的可靠性,提出了修改故障期间直流控制策略的方案,以使工程原设计方案中未设置的自动重合闸功能恢复使用。采用EMTDC仿真软件建立模型进行典型工况计算,并对重合闸期间产生的交流母线过电压、交流母线避雷器和阀避雷器的耐受能力进行了校核比较。仿真结果表明,新的控制策略应限制故障期间功率水平在300MW(标幺值为0.4)以内。修改后的控制策略在黑河换流站实施后,通过兴福变至黑河变(兴黑线)故障后重合闸的实践检验,证明了策略的可行性和可靠性。所得出的直流控制策略对研究弱交流系统条件下换流站仅有1回交流出线时采用自动重合闸功能有重要指导意义。     

灵宝换流站顺序控制和联锁

基于换流站控制保护系统的引进技术研究了西北—华中直流联网背靠背工程灵宝换流站的顺序控制和联锁,提出的实施方案(包括功能、性能及步骤的规定)通过了成套设计审查,由厂家根据成套设计方案生产设备,并通过了在北京的联合功能及性能测试。     

灵宝背靠背直流工程系统调试中的关键技术分析

灵宝背靠背直流联网输电工程是我国直流输电国产化的示范工程,该工程的系统调试是第一次依靠国内技术力量调试全部国产化设备。介绍了系统调试中几个关键技术问题的分析和解决过程：系统调试方案的编写过程;在换流站两侧均为单回交流进线的情况下交流系统单相瞬时故障点的选择和试验方法;最后断路器跳闸功能的原理、配置原则及软件和硬件的完善;换流站阀冷却变频器控制保护功能的完善。这几个关键技术问题的解决保证了系统调试的完成以及该工程的顺利投入运行。     

BTB索引散列算法的研究与设计

分支误预测是影响高性能处理器性能进一步提升的一个主要因素.现代处理器采用分支目标缓存(branch target buffer,BTB)预测分支指令的目标地址,BTB的预测精度受限于其命中率.由于程序中分支指令的分布并不均匀,传统的BTB索引方式无法充分利用BTB资源,从而造成不必要的冲突缺失,影响分支目标地址的预测精度,采用散列索引方式优化访问映射关系是有效解决方法之一.当前大量文献研究了cache的访问方式,但对BTB的散列索引算法的专门探讨则显不足.为了消除分支指令的分布空洞,离散分支指令和BTB条目的固有映射关系,设计了用于BTB索引的XOR散列算法和优化的bit-select索引算法,使用概率方法对BTB单组最大映射数期望的上界作了估计,并对这两种散列索引算法的效果进行了模拟评估.实验结果表明,散列映射方式能够较好地避免BTB冲突缺失造成的预测失败,XOR散列算法的离散效果更好.