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991.
992.
以LD端面泵浦的固体激光器为例,讨论了泵浦光源在激光晶体中的分布模型,计算了泵浦速率分布函数的归一化,并对分布函数进行了数值模拟。 相似文献
993.
基于DBMS的元数据管理策略* 总被引:3,自引:1,他引:2
海量存储系统的元数据一般采用层次结构或哈希法来管理,存在元数据修改和查询目录等操作所需时间和空间开销大等问题,严重影响了系统的性能。通过引入二维表保存元数据信息,提出了一种基于DBMS的新型元数据管理策略。分析了将基于DBMS元数据管理策略用于管理海量存储系统中的元数据信息时,所需的时空开销以及管理元数据的灵活性。验证了基于DBMS元数据管理策略能有效地减少查询和更新所需的时空开销,实现高效、灵活的元数据管理功能,从而有效地提高海量存储系统的性能。 相似文献
994.
钢绞线(丝)网-聚合砂浆加固技术是一项新型加固工艺,具有耐火、耐腐蚀、耐老化等优点.在以往试验研究的基础上,采用换算截面法计算加固梁的等效刚度,推导出加固梁正常使用阶段在集中荷载作用下跨中挠度的计算公式,并通过46根加固梁的80组试验数据对其验证,吻合良好,结果可为实际工程加固设计提供参考,同时也为进一步研究加固梁的力学性能建立理论基础. 相似文献
995.
兰州市大气环境质量影响因素多元统计模型研究 总被引:2,自引:0,他引:2
有别于其他文献从单方面讨论城市大气环境的成因和影响因素,在统计分析软件SPSS12.0的技术支持下,选择兰州市作为代表,对经济发展、能源消耗等与城市大气环境质量相关的诸多影响因子进行了综合数理统计分析并建立模型.结果表明: 影响兰州市大气环境质量的因素可归纳为两类,第一类主要包含社会经济发展、能源消耗以及空气污染因素;第二类主要包括气象因素.兰州市大气环境质量主要受机动车数量、国内生产总值GDP、GDP增长率、工业总产值和万元工业废气量等因素影响;并给出了概率水平为0.05的情况下的兰州市空气污染综合指数的回归方程. 相似文献
996.
Tao Zhang JunHong Jin DaYong Hu ShengLin Yang Guang Li JianMing Jiang 《中国科学E辑(英文版)》2009,52(4):906-909
The effect of coagulation temperature on the morphology, microstructures and mechanical properties of dihydroxy poly(p-phenylene benzobisoxazole) (DHPBO) fibers was investigated during dry-jet wet-spinning process, in which the coagulation
bath concentration and drawn ratio were kept as 10 wt% of PPA in water and 1.7, respectively. The structures and mechanical
properties of the as-spun DHPBO fibers were characterized by FTIR, XRD, SEM, and single fiber tensile testing. The results
indicated that in PPA/H2O coagulation system, when the coagulation temperature was 25°C, highly crystallized DHPBO as-spun fibers possessing fine
crystallites, circular and smooth morphology, and excellent mechanical properties could be achieved.
Supported by the National Natural Science Foundation of China (Grant No. 50673017), Shanghai Leading Academic Discipline Project
(Grant No. B603) and the Program of Introducing Taleuts of Discipline to University of People’s Republic of China (“111” Program)
(Grant No. 111-2-04) 相似文献
997.
ZHANG Tao JIN JunHong HU DaYong YANG ShengLin LI Guang & JIANG JianMing State Key Laboratory for Modification of Chemical Fibers Polymer Materials College of Material Science Engineering Donghua University Shanghai China 《中国科学E辑(英文版)》2009,(4)
The effect of coagulation temperature on the morphology, microstructures and mechanical properties of dihydroxy poly(p-phenylene benzobisoxazole) (DHPBO) fibers was investigated during dry-jet wet- spinning process, in which the coagulation bath concentration and drawn ratio were kept as 10 wt% of PPA in water and 1.7, respectively. The structures and mechanical properties of the as-spun DHPBO fibers were characterized by FTIR, XRD, SEM, and single fiber tensile testing. The results indicated that in PPA/H2... 相似文献
998.
HongBo Lan YuCheng Ding HongZhong Liu YeRong Que WeiWei Tao HanSong Li BingHeng Lu 《中国科学E辑(英文版)》2009,52(2):294-302
UV-nanoimprint lithography (UV-NIL) using a soft mold is a promising technique with low cost and high throughput for producing the submicron scale large-area patterns. However, the deformations of the soft mold during imprinting process which can cause serious consequences have to be understood for the practical application of the process. This paper investigated the deformation of the soft mold by theoretical analyses, numerical simulations, and experimental studies. We simulated the mold deformation using a simplified model and finite element method. The simulation and the related experimental results agree well with each other. Through the investigation, the mechanism and affected factors of the mold deformation are revealed, and some useful conclusions have been achieved. These results will be valuable in optimizing the imprinting process conditions and mold design for improving the quality of transferred patterns. 相似文献
999.
Introduction of fluorin into PBO polymer chains: Toward higher thermal stability and lower dielectric constant 总被引:1,自引:0,他引:1
Tao Zhang DaYong Hu JunHong Jin ShengLin Yang Guang Li JianMing Jiang 《中国科学E辑(英文版)》2009,52(1):232-237
A series of novel fluorinated benzoxazole polymers (6FPBO's) with high thermal stability and low dielectric constant were synthesized by copolymerization of 1,3-diamino-4, 6-dihydroxybenzene dihy-drochloride (DAR), 1,4-benzenedicarboxylic acid (PTA) and various amount of 4'4- (hexafluoroisopro-pylidene) bis (benzoic acid) (BIS-B-AF) in the medium of polyphosphoric acid (PPA). 6FPBO fibers were then obtained via dry-jet wet-spinning technique and characterized by means of Fourier transform infrared (FTIR) spectra, thermogravimetric analysis (TGA), single fiber tensile testing machine and scanning electron microscopy (SEM). FTIR spectrum of 6FPBO fibers indicated that the fluorine groups had been incorporated into PBO molecular chains successfully. TGA curves revealed that 6FPBO fibers possessed high thermal stability just as pure PBO fibers. Moreover, dielectric constant spectrum of 6FPBO exhibited that the polymers had low dielectric constant, especially in the range of high- frequency. 相似文献
1000.
The electronic structures of kinks in the [100](010) and 1/2[111](−110) edge dislocations in bcc iron containing hydrogen
are investigated by means of the first-principles DMol method and the discrete variational method. The effects of hydrogen
on the kinks are discussed. The results show that hydrogen forms weak bonding states with its neighboring host atoms, and
since hydrogen draws charge from its neighboring host atoms, the interactions between most of the host atoms are weakened
compared with those of the corresponding atomic pairs in the clean kinks. This indicates that the migration of kink, i.e.
the motion of dislocation, is easier in the doping hydrogen kink than in the clean kink, which may be the solid solution softening
effect resulting from the impurity hydrogen.
Supported by the National Basic Research Program of China (Grant No. 2006CB605102) and Science Foundation of Central South
University of Forestry & Technology (Grant No. 06y016) 相似文献