土壤侵蚀的3个基本动力学过程

简要介绍了土壤侵蚀的基本特征,将土壤侵蚀过程概括为3个基本的动力学过程,即降雨导致的坡面产流过程、表面流对土壤颗粒的剥蚀过程,以及表面流的汇集和输沙过程。进一步对3个基本过程的基本内容和涉及的科学问题进行了分析和概括,并由此讨论了土壤侵蚀动力学研究的发展趋势。     

Bi2Te3基热电材料的电输运性能研究进展

Bi2Te3基化合物是热电领域的代表性材料之一,被广泛应用于余热发电、固态制冷、温度探测等方面.该类材料具有复杂的能带结构,利用强自旋轨道和能带反转,有望对Bi2Te3基材料的热电性能实现优化.通过分析对比近些年Bi2Te3基材料的能带结构计算数据与部分实验结果,总结了Bi2Te3、N型Bi2Te3-x Sex和P型B...     

非平衡格林函数在电子输运问题中的应用

简单讨论了非平衡格林函数理论,并利用非平衡格林函数理论推导了电子相互作用体系的电流公式,获得了一些一般性的结果。     

Mean waiting time approximation for a real time polling system

This paper considers a novel polling system with two classes of message which can experience an upper bounded time before being served. The station serves these two classes with mixed service discipline, one class with exhaustive service discipline, and the other with gated service discipline. Using iterative method, we have developed an approximation method to obtain the mean waiting time for each message class. The performance of approximation has been compared with the simulation results. The expression for the upper bound of waiting time is given too.     

基于结构化Gossip协议的网格服务发现

在动态的网格环境中分布着大量不同类型的服务和资源.快速、准确地进行资源与服务发现,是影响网格计算性能的关键因素,因此,建立了一种基于消息扩散的网格服务发现机制.提出了一种新型的结构化Gossip消息扩散算法,简称为S-Gossip,此算法具有良好的冗余性和完备性.我们详细的描述了此算法及其协议的实现,并在此基础上建立了层次化的服务发现模型.     

排队系统的非平衡动态指派模型及战时维修应用

战时装备抢修的任务调度问题是跟排队论、任务指派与动态规划有关的交叉问题,具有一定的代表性,可归结为排队系统的非平衡动态任务指派问题.该问题目前尚无简便有效的求解方法.结合动态规划与匈牙利算法的优势,提出了剖面降维、补项截余、消元归简的三步法,将原命题逐步分解转换为已知求解方式的问题,简化了运算过程.最后,以坦克团的一次进攻战斗为实例,利用Matlab软件实现的装备战损及抢修仿真,验证了此法的可用性和有效性.     

基于耐心阈值下联络中心放弃率的仿真研究

顾客放弃率是衡量联络中心服务水平的一项重要指标.传统呼叫中心的顾客遵循先到先服务的原则,但考虑到顾客的耐心程度,会有部分顾客在排队过程中流失.通过设置顾客时耐心阈值并考虑为会员顾客增加特定的座席渠道,或在原有的人力下调整座席渠道数量,在传统呼叫中心模型的基础上建立新型的联络中心排队模型.运用ProModel仿真软件对顾...     

川西拗陷雷口坡组输导体及其组合特征

探讨川西拗陷中三叠统雷口坡组输导体特征及其对油气成藏的贡献.综合利用野外露头、钻井岩心、地震解释、有机地球化学等资料对雷口坡组输导体类型、特征及组合方式进行剖析,提出了4种典型输导体和4种典型输导体组合模式,并讨论了其对天然气成藏的意义.4种典型输导体是:断层及其破碎带输导体、优质(内幕)储层输导体、风化壳输导体、褶皱...     

基于交换式消息调度算法的FlexRay网络优化研究

汽车电子设备水平的提升对车载总线网络提出了很高的要求。而FlexRay网络因为其高速率、可靠性等特点成为了流行的车载通信协议。为满足网络发展的需求,设计了一种基于交换式FlexRay网络的调度算法,提出了一种可以准确计算静态段和动态段最坏情况响应时间的计算方法。通过仿真实验,验证了所提算法的网络传输速率提升了26%,时隙数量减少了44%,总线占用率降低了23%。从而进一步优化了FlexRay网络。     

Short- and medium-chain carnitine acyltransferases and acyl-CoA thioesterases in mouse provide complementary systems for transport of β-oxidation products out of peroxisomes

Peroxisomes metabolize a variety of lipids, acting as a chain-shortening system that produces acyl-CoAs of varying chain lengths, including acetyl-CoA and propionyl-CoA. It is, however, still largely unknown how β-oxidation products exit peroxisomes and where they are further metabolized. Peroxisomes contain carnitine acetyltransferase (CRAT) and carnitine octanoyltransferase (CROT) that produce carnitine esters for transport out of peroxisomes, together with recently characterized acyl-CoA thioesterases (ACOTs) that produce free fatty acids. Here we have performed tissue expression profiling of the short- and medium-chain carnitine acyltransferases Crat, Crot and the short- and medium-chain thioesterases (Acot12) and (Acot5), and show that they are largely expressed in different tissues, suggesting that they do not compete for the same substrates but rather provide complementary systems for transport of metabolites across the peroxisomal membrane. These data also explain earlier observed tissue differences in peroxisomal production of acetyl-CoA/acetyl-carnitine/acetate and underscores the differences in peroxisome function in various organs. Received 18 December 2007; received after revision 18 January 2008; accepted 22 January 2008