Real-time dynamic modeling of hydrogen PEMFCs

A control-oriented dynamic model of proton exchange membrane fuel cells (PEMFCs) has been developed in this paper. It aims to generate system dynamics with real-time performance for the micro-chip controller design. A unified bond graph approach was employed that integrates physical and chemical domains in the fuel cell operation, including fluid dynamics, heat transfer, and electrochemistry effects. In this paper, two major bond graphs, one for thermofluids, the other for the electrochemical system, were constructed. They are inter-connected to interpret the highly nonlinear transport and reaction system dynamics. The nonlinear simulation on a personal computer (PC) is about four times faster than the realistic operation. A step response test shows that the start-up time of an example PEMFC is about 5 s from ambient conditions. Further frequency-response test in the operation region shows that the bandwidth is near 2 rad/s.     

光诱导淀粉质体向叶绿体转化过程中光合特性的研究

本文以马铃薯(Solanum tuberosum.L.)块茎为材料,研究了不同光诱导期间块茎近表皮内淀粉质体向叶绿体转化过程中叶绿素的形成和积累,光系统Ⅰ和光系统Ⅱ复合物的出现和发育,以及相应光化学活性的变化。结果表明:光诱导淀粉质体转化为叶绿体的过程,不仅是叶绿体不断发育,叶绿素和蛋白质成分不断形成、组装,使其光合机构不断完善的过程,也是相应光合功能不断完善的过程。在转化初期,叶绿素a的形成速度较快,光系统Ⅰ的发育较光系统Ⅱ快。     

降水资源有效化与旱地农业

本文针对旱地水资源生产潜力可控性分析,探讨了旱地农业高产的可能性,根据研制出的水雨有效化渗水地膜,提出了降水资源有效化是旱地农业突破口的观点,并建立起渗水地膜保小雨、微地形打孔集大雨和孔洞灌溉节约用水的新技术体系。经过大面积试验取得了极其显著的增产效果,从而证实了这套新技术体系的有效性。最后,提出了利用这套技术体系实施全省旱地降水资源有效化工程的建议。     

固定化离子液体的制备及其在气体分离中的应用研究

离子液体具有独特的气体选择性溶解与吸收性能.为气体的分离与纯化提供了新的途径.将离子液体固定到聚合物或多孔无机载体材料中.得到的固定化离子液体兼具离子液体和载体材料的优势.用于分离过程时有利于提高气体吸收与脱吸速率.增大气体吸收量甚至选择性,更易工业化,因而具有良好的应用前景.本文综述了固定化离子液体——离子液体颗粒和离子液体膜的制备及其在气体分离与纯化中的应用研究进展.     

连续循环亲和提取过程的分离纯化特性

将前人提出的连续循环亲和提取（ＣＡＲＥ）过程扩展到利用超滤膜的系统，即考虑超滤膜对料液中各组分的截留作用，建立了该过程的数学模型，对该过程的分离纯化性能──浓缩因子（ＣＦ），纯化因子（ＰＦ）和回收率（ＲＥＣ）──进行理论分析。结果表明：随膜截留率的增大，ＣＦ和ＲＥＣ增大，而ＰＦ降低；增大洗脱液和循环液的流速虽可提高回收率，但却使纯化因子降低，表明存在最佳的操作条件使该过程的分离纯化性能最好。     

浅谈建筑膜结构技术

膜结构是近几十年国际上正在研究并逐渐发展的一种新型空间结构形式。为了便于设计师在今后的建筑设计中能更好地应用和推广膜结构,本文详细介绍了膜结构和膜材料的特点、分类,膜结构的设计计算、连接构造、制作、安装与验收。     

剖宫产427例原因分析

目的:探讨剖宫产率上升原因,寻找降低剖宫产率的可能途径。方法:统计1999-3-12～2000-4-8在张家口医学院第一附属医院427例剖宫产病历,分析各种剖宫产原因及所占比例。结果:胎儿因素197例(46.1％),其中胎儿宫内窘迫86例(20.1％);母体因素104例(24.4％),其中胎膜早破37例(8.796);母儿因素72例(16.9％);社会因素54例(12.6％)。结论:胎儿因素是剖宫产率上升的主要原因,要求剖宫产也占了很大比例,要降低剖宫产率需要医生和社会共同提高认识。     

渗透胁迫对玉米幼苗膜脂过氧化及过氧化氢酶活性的影响

本实验以三个玉米品种新实多2号、东单7号、中原单32为实验材料,采用PEG 6000模拟土壤干旱条件,研究渗透胁迫下不同玉米品种M DA(丙二醛)含量、CAT(过氧化氢酶)活性以及膜相对透性间的相互关系,结果表明,渗透胁迫下三个玉米品种M DA含量和质膜相对透性均随胁迫强度的增加而增加,而CAT活性则随胁迫强度的增加而减少,CAT活性与M DA含量、质膜相对透性均呈显著或极显著负相关关系,且品种间存在差异,通过分析比较,可初步判断三个玉米品种幼苗的抗渗透胁迫能力为新实多2号优于中原单32和东单7号.     

充气膜结构的优化设计

比较了张拉膜和充气膜的异同。基于非线性有限元UL格式,进行充气膜的形态分析和荷载分析,分析中考虑了充气膜的特殊之处。建立了充气膜的优化设计模型,以工程造价为目标函数进行优化。编制了相应程序,算例表明本文的分析方法是可行的。     

Effect of antioxidants and antibiotics on levels of seminal oxidative stress in leukocytospermic infertile men

Defective sperm function is the most common cause of infertility. A prospective study was carried out to correlate the concentration of nitrite (the stable metabolite of nitric oxide) in seminal plasma with leukocytospermia, and sperm membrane integrity. Total Fifty-seven normozoospermic subjects with and without leukocytospermia visiting the Infertility clinic at KH and MRC, Karad, were included in the present study. Semen samples were checked for sperm concentration, total sperm count, sperm motility, seminal leukocyte concentration and sperm membrane integrity as Hypoosmotic Swelling Test. Similarly the concentration of nitrite in seminal plasma was measured by Griess reaction and total antioxidant power measured as ferric reducing ability of plasma. The concentration of nitrite in seminal plasma was found to be raised with significantly increased leukocyte concentration in semen. Also significantly lowered levels of total antioxidant power along with defective sperm function was observed. Our results suggest that supplementary treatment of antioxidants with antibiotic for leukocytospermic infertile male patients may improve the sperm membrane integrity.