液相色谱法同时测定除草剂中乙草胺、异噁草酮和2,4-滴丁酯的含量

目的建立高效液相色谱法同时测定除草剂中异噁草酮、乙草胺和2,4-滴丁酯的含量。方法试样经甲醇溶解,采用ODS-2反相色谱柱,以甲醇/乙腈/氨水溶液(42:42:16,V:V:V)为流动相,对试样中异噁草酮、乙草胺和2,4-滴丁酯进行分离,流速1.0 m L/min,柱温40℃,紫外检测器检测波长为235 nm,外标法定量。结果在测定浓度范围内,乙草胺,异噁草酮和2,4-滴丁酯标准溶液质量浓度与峰面积均呈现出良好的线性关系(r0.9998),对同一样品重复测定5次,变异系数分别为0.33%、0.44%和0.41%,该方法平均加标回收率为98.6%~102.8%,变异系数为0.28%~0.45%。结论该方法简便、快捷、精密度和准确度高、线性关系好,适用于同时测定除草剂中异噁草酮、乙草胺和2,4-滴丁酯含量。     

An improved technology for eliminating nondeterministic latency in the L1 trigger system

Gamma Ray Array Detector(GRAD) is one of external target facility subsystems in the Cooling Storage Ring on the Heavy Ion Research Facility at Lanzhou(HIRFL-CSR).The trigger subsystem of GRAD is required to make a fast L1 trigger decision with a fixed latency for the data acquisition.Because the hit signals from the detector are asynchronous with the local clock of the trigger system,a nondeterministic latency(the value changes between zero and one clock period) is generated when the synchronous receivers of the conventional trigger system process the hit signals.In this paper,an improved trigger logic based on a field-programmable gate array is developed,and comprised of zero-delay broadening circuits as receivers and an improved adding circuit designed for the new receivers.Software simulation and experimental measurement have been conducted.Comparison with the conventional trigger logic,the improved trigger logic has the advantage of eliminating the nondeterministic latency and reducing the total processing latency.     

Effects of environment on dry sliding wear behavior of silver–copper based composites containing tungsten disulfide

Silver based composites containing different amounts of WS₂ were prepared by hot-pressing method and their tribological behaviors were investigated against coin silver under humid air, dry nitrogen and vacuum on a ball-on-disk tester with normal load of 5 N. The components of composites, microstructure of debris and worn surface were characterized using XRD SEM, EDS and XPS. It is demonstrated that environmental conditions significantly affect the tribological behavior of silver based composites. The friction coefficient is the highest in humid air, and the lowest in dry nitrogen. It is found that the friction and wear behavior of the composites are strongly depended on the characteristics of the lubrication film forming in different operating environments, such as thickness and composition. In addition, it is indicated that the dominant wear mechanisms of silver based composites are abrasive wear and delamination under different conditions.     

国外城市街道改造与更新研究述评

从理论和实践两方面通过分析当代国外城市街道改造与更新的发展历程及研究成果,归纳出国外城市街道改造与更新向多样化、人性化、文脉化和可持续化的特色方向发展.总结出街道更新的重点应是保持街道的生机与活力,确保行人的安全与舒适,提高交通的可达与有序,延续街道的文脉与记忆,维持街道的和谐、可持续发展,以期对我国现阶段街道改造与更新研究提供更多的借鉴和启示.     

肝素对金黄色葡萄球菌与血浆蛋白间粘附的阻断作用

金黄色葡萄球菌与宿主细胞粘附是其感染的先决条件。若能阻断粘附环节,金黄色葡萄球菌将无法生长繁殖,即可降低由其引发的疾病的发病率。本研究采用静止粘附技术等实验手段,研究肝素对金黄色葡萄球菌与血浆蛋白粘附的阻断。结果显示,当肝素溶液浓度<1.0 mg/mL时,肝素以浓度依赖的方式阻断。金黄色葡萄球菌粘附血浆蛋白后,淋巴细胞对其吞噬作用减弱;加入肝素后,吞噬作用的强度增强。结果暗示,肝素能够阻断金黄色葡萄球菌与血浆蛋白的粘附,可以作为临床药物开发的靶点。     

蒙特卡罗模拟光子输运中截面数据的拟合

在蒙特卡罗模拟光子运输的过程中,截面一直是一个比较棘手的问题,本文用曲线拟合的最小二乘法来拟合137CS源发出的射线与NaI晶体发生相互作用时其光电截面、康普顿散射截面、总吸收系数,并模拟了137CS源在NaI探测器中的沉积谱.     

房地产企业效率测度实证研究

本文采用不可控制变量DEA模型对2006年我国47家房地产开发上市公司的经营技术效率进行测度。结果表明:我国房地产企业普遍存在规模无效率现象,主要是由于房地产企业多成立于1993～1995之间,成立初期房地产市场供需不平衡,企业多采取规模扩张战略;技术无效率的房地产企业的产出能力不足,在不减少投入的情况下,净利润有很大的提升空间。     

浅谈影像资料在监理工作中的应用和管理

监理工作中的影像资料是信息管理中不可或缺的一个重要组成部分,如实地摄取工程实施中的影像资料是监理工作痕迹最直观和有效的反映之一;影像资料必须按档案管理的要求,工程备案竣工时可将留存的影像资料录成光盘归档.     

网络端到端性能测量模型的研究与实现

与互连网的迅速发展相比,网络性能测量研究领域的标准化工作一直显得滞后,缺乏宏观的体系结构模型,本文针对互连网端到端性能测量的需要,设计了一个可扩展的主动测量模型,该模型采用主动测量技术,通过在网络中配置少量（N)主动测量器,就可测量许多条路径（N2）的端到端性能。文中描述了该测量模型的层次结构,结合海量信息系统测量平台的研究,给出了该模型的具体实现技术和体系结构。