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991.
通过对移相控制全桥零电压开关变换器的运行过程的详细分析,研究了超前桥臂与滞后桥臂的开关互换动作在变换器功率传输过程中所起的作用,另外,由于变换器的输出滤波部分与Buck变换器类似,因此,可将在Buck变换器闭环控制设计中获得成功应用的滑膜控制引入移相控制全桥零电压开关变换器中,仿真结果表明,滑膜控制的变换器闭环系统对输入电源扰动具有较好的鲁棒性,对负载扰动的瞬态响应特性也较为理想。 相似文献
992.
993.
A series of adeno-associated viral vectors containing a mutation of human factor Ⅸ (hFⅨR338A) with different regulation elements were constructed and used to transduce cell lines. The plasmids and the stable transduction cell clones with high expression level of hFⅨR338A were obtained by selecting and optimizing, and then, the recombinant adeno-associated viral vector with hFⅨR338A was prepared via novel rHSV/AAV hybrid virus packaging system on a large scale, which contained the capsid protein genes. A method for producing rAAV-hFⅨR338A viral stocks on a large scale and higher titer was established, which can be used for industrial purpose. The titer of rAAV-hFⅨR338A was more than 1.25×1012 particle/mL, and then, a mammalian cell line, C2C12 and the factor Ⅸ knock-out mice were transfected with the rAAV-hFⅨR338A in vitro and in vivo. The results show that the high-level expression of rAAV-hFⅨR338A was achieved in cell line and hemophilia B mice. It reached at (2551.32±92.14) ng·(106 cells)-1·(24 h)-1 in C2C12 cell in vitro and had a peak concentration of 463.28 ng/mL in mice treated with rAAV-hFⅨR338A, which was as high as the expression of rAAV-hFⅨ-wt (2565.76±64.36) ng·(106 cells)-1·(24 h)-1 in C2C12 and 453.92 ng/mL in the mice treated with rAAV-hFⅨ-wt) in vitro and in vivo, there is no any difference between two groups, but the clotting activity of hFⅨR338A is about 2.46 times higher than that of hFⅨ-wt. It was first reported that a mutation of human factor Ⅸ was used into gene therapy research for hemophilia B, meanwhile, a novel packaging system, rAAV/HSV was used for preparation of rAAV-hFⅨR338A on a large scale, which laid the foundation of industrial production for applying rAAV viral stocks to gene therapy clinical trial for hemophilia B mediated with rAAV-hFⅨ. 相似文献
994.
Magnetostratigraphy and pavleo-environmental record of Tertiary deposits of Lanzhou Basin 总被引:1,自引:0,他引:1
Leping Yue F. Heller Zhanxiang Qiu Li Zhang Guangpu Xie Zhuding Qiu Yunxiang Zhang 《科学通报(英文版)》2001,46(9):770-773
The Tertiary deposits of the Yongdeng section, the Lanzhou Basin were studied by means of magnetostrati-graphy. The magnetostratigraphic sequences from Paleocene to Miocene were established, and the time scale for the corresponding stratigraphy and mammalian faunas was also established by referring to their correlation to the GPTS of BKSA95 (The geomagnetic polarity time scale which was thoroughly revised and updated by Berggreen et al. in 1995). In the end the paleoenvironmental records and their relationship with the uplifting of the Tibetan Plateau were discussed. The results are as follows. The top boundary of the Xiliugou Formation is dated to be 51 Ma, i.e. Eocene. TheYehucheng Formation covers the time span of 51-31.5 Ma, i.e. from late Early Eocene to early Early Oligocene. The Xianshuihe Formation covers the time span of 31.5-15 Ma, i.e. from Early Oligocene to Middle Miocene. The lower member of the Xianshuihe Formation spans from 31.5 to 20.0 Ma, i.e. from Early Oligocene to early Early Miocene. The middle member is from 20.0 to 16.5 Ma, i.e. in the middle Early Miocene. 相似文献
995.
聚L-丙交酯的制备及其热稳定性能的研究 总被引:5,自引:0,他引:5
对聚丙交酯的合成和热稳定性进行了研究。单体重结晶次数、辛酸亚锡浓度、聚合时间等条件均是影响聚合物特性粘数的重要因素。热稳定剂对聚丙交酯的分子量几乎没有影响。优化聚合条件可以获得粘均分子量大于200000的聚丙交酯材料,聚合结果具有良好的重复性。实验表明在高于聚合物熔点温度以上,聚丙交酯表现出热不稳定性。热稳定剂ULTRONOX 626A能够有效降低聚丙交酯的热降解幅度。 相似文献
996.
通过观察、统计、分析 ,揭示了远距离投篮不中球的反弹落点趋势 ,以及球的不同反弹方向和距离所呈现的进攻、防守队争获三分篮板球的成功比率。 相似文献
997.
采用紫外线和二氧化氮的协同杀菌作用对冻虾仁中的副溶血性弧菌进行控制,微生物学检验表明,紫外线和二氧化氯的协同作用比单独的紫外线和二氧化氯杀菌效果好,在协作作用中,消毒剂是主体,消毒剂的浓度和作用时间起主导作用,紫外线起协同作用。 相似文献
998.
指出了浙江省贝类养殖业存在的一些问题,并从改善养殖环境、防治贝类病害,提高贝类种质等几方面提出了相应的对策,为浙江省贝类养殖业的可持续发展提供了科学依据。 相似文献
999.
采用NaCl-KCl熔盐法制备了纯钙钛矿相结构的(1-x)PMN-xPT陶瓷,研究了他们的电致应变及其温度稳定性,结果表明,随着PT含量的增加,PMN基陶瓷的最大电致应变逐渐增大,且具有较大的电致应变,最大应变达0.1%以上,但(1-x)PMN-xPT陶瓷的电致应变温度稳定性很差,其最大Tsmax比Tm约低20度。 相似文献
1000.