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301.
苏德慧 《大连理工大学学报》1994,34(2):235-239
通过浅水风波试验,探讨了浅水波高、波周期的分布形式,重点分析了水深因素对波高、波周期分布的影响,给出了浅水波高、波周期分布的表达式,并确定了浅水特征波高间的关系。 相似文献
302.
介绍了由两只偏振器和波晶片组成的PCP平面偏振光干涉系统对各种光偏振态检验的原理及其方法. 相似文献
303.
苏文希 《汕头大学学报(自然科学版)》1994,9(2):47-52
LoutsH.Y.Chen在文[1]中应用测度论的方法,证明标准正态随机向量的一个充分条件.本文指出它也是必要条件.同时将它推广到一般多元正态分布的情形,从而得到几个一般性结论. 相似文献
304.
PAC中氧化铝和盐基度的测定 总被引:2,自引:0,他引:2
本文研究了铝矾土经酸溶制备聚合氯化铝中溶出杂质对氧化铝和盐基度分析的影响,采用硝酸铅标准溶液返滴定EDTA测定氧化铝,消除了Ca2+的干扰,采用酸度计直接指示试液pH值测定盐基度,避免了杂质硅酸在氟化钾法中的副反应,实验结果准确可靠. 相似文献
305.
首先分析了辽河油田L46块的地质特征,然后分析和介绍了开发前的油藏工程,主要包括前期准备井的部署原则,实施要求,指出该块必须采用注水补充能量的开发方式进行开发,给出了合理的井冈井距、即合理井距为300m,采用正方形并网,确定了油井产能为平均单井产油10t/d,最后予测了年产原油6.6×104t/d,采油速度为2.20%. 相似文献
306.
本文着重阐述了有机体能量代谢过程中ATP—CP系统、有氧氧化和无氧酵解三大供能系统的偶联反应。并对ATP恢复的影响因素作了分析,同时介绍了作者对ATP的再认识和理解。 相似文献
307.
308.
Improving the precision of the keyword-matching pornographic text filtering method using a hybrid model 总被引:1,自引:0,他引:1
With the flooding of pornographic information on the Internet, how to keep people away from that offensive information is becoming one of the most important research areas in network information security. Some applications which can block or filter such information are used. Approaches in those systems can be roughly classified into two kinds: metadata based and content based. With the development of distributed technologies, content based filtering technologies will play a more and more important role in filtering systems. Keyword matching is a content based method used widely in harmful text filtering. Experiments to evaluate the recall and precision of the method showed that the precision of the method is not satisfactory, though the recall of the method is rather high. According to the results, a new pornographic text filtering model based on reconfirming is put forward. Experiments showed that the model is practical, has less loss of recall than the single keyword matching method, and has higher precision. 相似文献
309.
The enantioselective assay for S(+)- and R(-)-propafenone (PPF) in human urine that developed in this work involves extraction of propafenone from human urine and using S(+)-propafenone as internal standard, chiral derivatization with 2,3,4,6-tetra-O-beta-D-glucopranosyl isothiocyanate, and quantitation by an RP-HPLC system with UV detection (lambda=220 nm). A baseline separation of propafenone enantiomers was achieved on a 5-microm reverse phase ODS column, with a mixture of acetic acid (25:12:0.02,v/v) as mobile phase. There was good linear relationship from 24.9 ng/ml to 1875.0 ng/ml for both of enantiomers. The regression equations of the standard curves based on C(S-PPF) (or C(R-PPF)) versus ratio of A(S-PPF)/A(S) (or A(R-PPF)/A(S)) were y=0.0032x-0.081, (r=0.999) for S-PPF and y=0.0033x+0.0039, (r=0.998) for R-PPF, respectively. The method's limit of detection was 12.5 ng/ml for both enantiomers, and the method's limit of quantitation was 28.2+/-0.52 ng/ml for S-PPF, 30.4+/-methanol:water:glacial 0.53 ng/ml for R-PPF (RSD<8%, n=5). The analytical method yielded average recovery of 98.9% and 100.4% for S-PPF and R-PPF, respectively. The relative standard deviation was no more than 6.11% and 6.22% for S-PPF and R-PPF, respectively. The method enabled study of metabolism of S(+)- and R(-)-propafenone in human urine. The results from 7 volunteers administered 150 mg racemic propafenone indicated that propafenone enantiomers undergo stereoselective metabolism and that in the human body, S(+)-propafenone is metabolized more extensively than R(-)-propafenone. 相似文献
310.
Widespread use of antimalarial agents can profoundly influence the evolution of the human malaria parasite Plasmodium falciparum. Recent selective sweeps for drug-resistant genotypes may have restricted the genetic diversity of this parasite, resembling effects attributed in current debates to a historic population bottleneck. Chloroquine-resistant (CQR) parasites were initially reported about 45 years ago from two foci in southeast Asia and South America, but the number of CQR founder mutations and the impact of chlorquine on parasite genomes worldwide have been difficult to evaluate. Using 342 highly polymorphic microsatellite markers from a genetic map, here we show that the level of genetic diversity varies substantially among different regions of the parasite genome, revealing extensive linkage disequilibrium surrounding the key CQR gene pfcrt and at least four CQR founder events. This disequilibrium and its decay rate in the pfcrt-flanking region are consistent with strong directional selective sweeps occurring over only approximately 20-80 sexual generations, especially a single resistant pfcrt haplotype spreading to very high frequencies throughout most of Asia and Africa. The presence of linkage disequilibrium provides a basis for mapping genes under drug selection in P. falciparum. 相似文献