CPLD在多路定时信号处理中的应用

本文主要介绍了CPLD在多路定时信号处理中的应用。针对大型核物理实验中的符合测量、多路时间测量系统中的门控快定时信号等应用的需要,设计了一种多路延迟/脉宽调节电路.主要功能是对输入的多路快信号进行延迟和脉宽调节,支持NIM负信号输入和输出,在系统主时钟频率为100MHz的时候,延迟和脉宽调节的最小步进精度为10ns。我们采用复杂可编程逻辑器件CPLD来构建系统的主要电路,具有较小的延迟和脉宽调节误差,和常规逻辑器件相比其特点是:元件少且成本低,功耗小,稳定性好。

毛细管式的靶-离子源系统在线实验研究

讨论了在线同位素分离器使用激光离子源的必要性 ,分析研究了毛细管式激光离子源对电离器的要求及热毛细管电离器的工作原理 ,并给出了在线实验的结果 .为了在较低温度下形成等离子体鞘势和降低热电离效率 ,采用了低电子逸出功的耐高温材料Nb作毛细管材料 .在线实验获得成功 ,使用毛细管式的靶 -离子源的在线同位素分离器的总效率约达 0 2 % ,满足了激光离子源电离器和靶室的工作要求

Abnormal phenomenon of the dependence of the retention factors for uncharged species on applied voltage in capillary electrochromatography

Polymethacrylate-based monolithic columns were prepared for capillary electrochromatography (CEC) by in situ copolymerization of butyl methacrylate (BMA), 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), and ethylene dimethacrylate (EDMA) in the presence of a porogen in fused-silica capillaries of 100 mum I.D. The abnormal phenomenon that retention factors for neutral species decreases with applied voltage in CEC was observed. Capillary electrophoresis (CE) instruments usually require a period of time to increase voltage from 0 kV to desired value, which is called as ramp time. Such ramp time and any error in the determination of dead time should be taken into account during the accurate calculation of retention factors. After the correction of the retention factors, the plots of the corrected factors for alkylbenzene versus applied voltage were made, the absolute value of the plot slopes are less than 1.8 X 10(-4), Which indicates that the corrected retention times for neutral species do not show any dependence on applied voltage. Further, the plots of the corrected retention times for acidic and basic compounds versus the reciprocal of applied voltage were drawn, where the target compounds were eluted in neutral form. The very nice linearity of the plots was obtained. The linear correlation coefficients are over 0.999. Here, the slopes of the plots represent

Combination of CH4 oxidative coupling reaction with C2H6 oxidative dehydrogenation by CO2 to C2H4

A new process has been suggested for converting natural gas to ethylene by combining oxidative coupling of methane with ethane dehydrogenation to provide an efficient method for the utilization of thermicity and CO2. From their thermodynamics, it is clear that the exothermicity from CH4 oxidative coupling reaction (DeltaH(800degreesC) = -174.3 kJ mol(-1)) can support C2H6 dehydrogenation by CO2 (DeltaH(800degreesC) = + 180.2 kJ mol(-1)). Meanwhile, the two reactions can be conducted under the same reaction conditions, such as the reaction temperature and reaction pressure as well as space velocity. In addition, the CO2 yielded from CH4 oxidative coupling reaction can be directly used for C2H6 dehydrogenation. Two kinds of catalyst are developed for this combined process with an achievement, from which C2H4 content in tail gas can reach attractively 16.4%, which can be used directly to produce ethylbenzene by the alkylation of benzene. (C) 2002 Elsevier Science Ltd. All rights reserved.

黄土高原旱地施肥对小麦与苜蓿土壤水分养分含量的影响

研究黄土高原旱地小麦(Wheat)和苜蓿(Alfalfa)连作20年后的产量、土壤水分及养分的变化。结果表明:磷肥对小麦增产不显著,而对苜蓿则增产显著(增产183.5%);施肥可以延缓苜蓿的衰老,提高产草量;苜蓿地土壤干燥化明显,施用氮磷有机肥后小麦地也出现干燥化趋势;长期施磷肥有利于改善土壤磷素有效性,其中苜蓿地全磷和有效磷含量,增加了13.6%和83.8%,小麦土壤增加了22.9%和367.9%;苜蓿土壤全氮和速效氮均呈增加,而小麦地则减少;平衡施用氮磷有机肥能培肥土壤,使产量大幅度提高;在该区采取合理的轮作方式和培肥措施能有效地改善农田生态系统的生产力。

农田生态系统微量元素循环研究进展

微量元素含量很低,但对生物却有着重要的生物学效应,因而微量元素研究的重要性也逐渐被人们所认同,许多人对土壤中微量元素的形态、有效性进行了研究。从农田生态系统中微量元素的含量、影响循环效率的因素及前人研究概况等方面对农田生态系统微量元素循环方面的研究进行了综述,同时指出了未来的研究方向。

人工湿地除磷研究进展

从人工湿地除磷机理着手,综述了国内外有关湿地基质、湿地植物及微生物强化除磷的研究机理以及进展。深入研究多种基质组合对磷素的吸附与解析机理,可以从理论上推进诸多高效除磷基质的实际应用进程;植物间接净化作用及其与湿地水力停留时间的关系,是影响湿地植物选种和种植的重要依据;植物根际微环境以及植物与微生物的耦合作用可能是人工湿地除磷的主要途径之一;强调湿地的污水净化功能而忽视其生态服务功能,是湿地运行中普遍存在的认识错误。最后指出:湿地运行应采取高水力负荷、低污染负荷的方式,强调强化一级处理的重要性。

Carbazole-based hole-transporting materials for electroluminescent devices

Two kinds of carbazole-based molecules connected with diphenylamine and carbazole are synthesized by modified Ullmann reaction. Comparative study on their thermal stability, redox behavior, hole injection and transport properties are present. The results demonstrate that the carbazole-based molecules are very promising hole-transporting materials for electroluminescent devices.

聚酰亚胺基体树脂的新发展

本文介绍了一系列新型异构的芳香四酸二酐,并以此制备了异构的热塑和热固性聚酰亚胺树脂,研究了它们的热性能、机械性能、高温流变以及动态力学上的差异.异构的聚酰亚胺(3,3′和3,4′-)较传统的4,4′-相连的聚酰亚胺,具有更高的玻璃化转变温度、热性能及溶解性;3,4′-相连的聚酰亚胺具有较低的复合粘度及较宽的加工窗口.

Application of 2D Raman correlation spectroscopy to studing the effect of rare-earth Eu3+ on hemoglobin

The effect of rare-earth ion Eu3+ on hemoglobin (Hb) was studied by using two-dimensional Raman correlation spectroscopy. The results show that with the variation of Eu3+ concentrations as perturbation, the oxidation state of Hb and its spin state are both sensitive to the perturbation. Eu3+ added to Hb affects the oxidation and spin state synchronously. The four structure-sensitive bands of Hb are more accessible to the Eu3+ than other bands.