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Search Results: 1 - 10 of 53160 matches for " 兰宏 "
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麂属rDNA限制性位点多态性及其系统进化

科学通报 , 1993,
Abstract: 核糖体RNA基因家族(rRNA gene或rDNA)是一类中等重复的DNA序列,每个重复单元由非转录间隔区(nontranscribed spacer,NTS)、转录间隔区(internal transcri-bed spacer,ITS)和三种rRNA(18S RNA,5.8S RNA,28S RNA)基因编码区组成.由于rDNA遵循协同进化(concerted evolution)模式,种内个体间重复单元的序列差异不
麂属rDNA限制性位点多态性及其系统进化

科学通报 , 1993,
Abstract: 核糖体RNA基因家族(rRNAgene或rDNA)是一类中等重复的DNA序列,每个重复单元由非转录间隔区(nontranscribedspacer,NTS)、转录间隔区(internaltranscri-bedspacer,ITS)和三种rRNA(18SRNA,5.8SRNA,28SRNA)基因编码区组成.由于rDNA遵循协同进化(concertedevolution)模式,种内个体间重复单元的序列差异不
Ag嵌入ZnO(10 0)表面的第一性原理研究
Ag Incorporation on ZnO(10 0) Surface: First Principles Study
 [PDF]

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Applied Physics (APP) , 2014, DOI: 10.12677/APP.2014.48018
Abstract:
基于密度泛函理论,采用第一性原理计算了Ag嵌入ZnO(10 0)面的几何结构和导电性以及电子结构,分析了Ag掺杂ZnO(10 0)面的表面结构弛豫和Ag嵌入ZnO (10 0)不同层的形成能情况。计算结果表明:和纯净ZnO(10 0)相比,Ag嵌入ZnO(10 0)受结构弛豫影响比较明显。同时发现,Ag嵌入ZnO(10 0)第一层的形成能最低,因此,Ag嵌入在第一层的情况最稳定,这表明Ag原子更容易集中在表面层,而不是占据体内位置。通过对纯净和掺杂体系的态密度图分析发现,Ag嵌入ZnO(10 0)表面表现为p型特征,有利于p型的制备。然而,Ag嵌入ZnO(10 0)第一层的离化能较高,不利于p型导电。
Based on the density function theory, we have performed first principles calculations of energetic stability and conductive properties and electronic structure of Ag incorporation on ZnO (10 0) surface, and after calculations, we have analyzed the relaxation of the structure and formation energy of Ag incorporation on ZnO (10 0) surface at different layers. Our results show that com-pared with pure ZnO (10 0), there is an obvious effect on the relaxation of the structure for Ag incorporation on ZnO (10 0) surface. Simultaneously, we found that the formation energy of the Ag incorporation on the first layer is the lowest in all cases. Therefore, Ag incorporation on the first layer is the most stable, which indicates that Ag atom prefers to collect in the surface layer instead of the bulk. And we found that the system for Ag incorporation on ZnO (10 0) surface demonstrates as p-type, which is in favors of fabricating p-type material. However, the ionization of Ag incorporation on ZnO (10 0) surface is much higher, which hinders the electronic ionize.

N-S共掺ZnO的电子结构和光学性质的第一性原理研究
First-Principles Investigation of Electronic Structure and Optical Properties in N-S Codoping ZnO
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Applied Physics (APP) , 2014, DOI: 10.12677/APP.2014.44007
Abstract:

为了分析纯净ZnO和N元素的掺入对S掺杂ZnO的电子结构和光学性质的影响,基于密度泛函理论采用第一性原理计算方法,我们研究了各种复合体的缺陷形成能、离化能、态密度、导电率、介电函数和吸收系数。结果发现:3N-S共掺ZnO不仅能提高N受主溶解度,而且可以引起浅受主能级。这表明3N-S共掺能够得到高质量稳定p型ZnO。同时,随着N原子的增加,体系的离化能迅速降低,而体系的导电率增强。另外,通过对介电函数和吸收系数的计算,结果表明3N-S共掺ZnO在低能区有非常奇特的特性。希望不久我们的理论结果能够为实验提供理论依据。
To analyze the electronic structures and optical properties of pure-ZnO and N-S codoped ZnO, the defect formation and ionization energy, density of states, conductivity, dielectric constant and adsorption coefficient of varies complexes were calculated by the first-principles calculation methods based on Density Functional Theory (DFT). It is found that 3N-S codoping in ZnO not only enhances N acceptor solubility, but also leads to shallower acceptor energy, demonstrating that 3N-S codoping can obtain a high-quality and more stable p-type ZnO. Furthermore, as the incorporation of N atoms is increasing, the ionization energies of the complexes are sharply decreasing, and the conductivity of the system is enhanced. In addition, the calculation of the dielectric functions and adsorption spectrum shows that 3N-S codoped ZnO has interesting characteristic in the low-energy region. We expect that this theory study might be helpful for the experimental results.

N掺杂ZnO (100)表面对其电学性质的影响
Influence of N Doping on Electronic Properties of ZnO Surface
 [PDF]

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Advances in Condensed Matter Physics (CMP) , 2014, DOI: 10.12677/CMP.2014.34007
Abstract:
基于密度泛函理论的第一性原理计算了N掺杂ZnO (100)表面的形成能和电学性质。首先,我们分析了N掺杂ZnO (100)表面不同层时的结构弛豫情况,接着计算了N掺杂表面的形成能和电子结构。结果表明N掺杂后体系发生较大的晶格畸变。N掺杂块体ZnO的形成能比掺杂表面时的形成低。结果表明N很容易聚集在体内而不是表面。从N掺杂ZnO (100)表面的电子结构中得知,体系的费米能级向价带移动,这主要归因于N-p态,同时体系表现为p型特征。
A theory of formation energy and electronic properties of N doping ZnO (100) surface is proposed on the first principles based on density function theory. First, we have analyzed the relaxation of the structure of N doping ZnO (100) surface at different layers. Later, we have calculated the formation energy and electronic structure of N doping ZnO (100) surface. The results show that there is a large lattice distortion after N doping. And the formation energy is lowest in the bulk ZnO when N is doped in the bulk ZnO. The results show that N atom easily accumulates in the body instead on the surface layers. The calculated electronic structure shows that the Fermi level shifts into the valence band which is contributed by N-p states, and the system after doping demonstrates as p-type.
PHYLOGENETIC RELATIONSHIPS AMONG GIANT PANDA AND RELATED SPECIES BASED ON RESTRICTION SITE VARIATIONS IN rDNA SPACERS
大熊猫及其近缘种rDNA序列变异和系统进化关系

,王文
动物学研究 , 1998,
Abstract: In this study, non radioactive Digoxigenin labeled ribosomal DNA(rDNA) probes were used for Southern blotting analysis to study the molecular phylogeny of the giant panda and related species. Restriction maps in the regions of rDNA spacers were compared between giant panda( Ailuropoda melanoleuca ), lesser panda( Ailurus fulgens ), Asiatic black bear( Selenarctos thibetanus ), sun bear( Helarctos malayanus ), raccoon( Procyon lotor ) and lynx( Felis lynx ). Phylogenetic trees for these species were constructed using maximum likelihood and parsimony method. The results show that in respect to rDNA RFLPs, the giant panda is more closely related to bear than to lesser panda; while the lesser panda is slightly related to the raccoon.
争论是物理学发展的动力

现代物理知识 , 2001,
Abstract: 普朗克曾经说过:“在科学史中,一个新概念从来都不会是一开头就以其完整的最后形式出现,像古希腊神话雅典娜一下子从宙斯的头脑里跳出来那样”。的确,物理学的基本理论是在许多物理学家反复研究和论证的基础上,经过千锤百炼才逐渐形成的。对同一物理问题,由于客观事物的复杂性,研究者看问题角度的不同,思想方法的不同等等,往往同时存在多种不同的看法。这必然导致研究者之间的争论,并促使研究者千方百计地从理论和实践方面寻求解决问题的办法,从而加速了物理学发展的进程。 一、蛙腿论战 1780年的一天。意大利解剖学教授伽伐…
凹凸棒土增强聚丙烯复合材料冲击断裂韧性的研究

高压物理学报 , 1996, DOI: 10.11858/gywlxb.1996.01.010
Abstract: 用Charpy冲击实验装置研究凹凸棒土(AT)增强聚丙烯(PP)复合材料的断裂韧性。测量AT含量为10wt%~40wt%试样的断裂韧性。结果显示,在AT含量为10wt%~30wt%范围内,复合材料的断裂韧性(Gc)高于纯基体PP.这说明,在一定条件下,加入AT可以改善PP的断裂韧性。
工程科学前沿的拓荒者——郑哲敏

力学进展 , 2013, DOI: 10.6052/1000-0992-13-033
Abstract: 郑哲敏先生是著名力学家,我国爆炸力学的奠基人和开拓者,2012年度国家最高科学技术奖获得者.本文回顾了郑哲敏先生在过去60多年中非常丰富的科研活动,特别是他在爆炸加工、地下核爆、爆炸排淤、穿破甲、煤与瓦斯突出、水合物开采、水弹性动力学、材料力学行为等方面的杰出学术贡献.这些工作闪耀着鲜明的工程科学特点,即着眼国家重大需求,从错综复杂的问题中概括提炼关键物理因素,创新理论,进而指导实践.郑哲敏先生的科学贡献和学术思想,对于力学学科发展,有着重要的现实意义和参考价值.
水产品中组胺的测定方法研究

食品科学 , 2000,
Abstract: ?组胺为一种生物胺,可在许多动、植物中发现。由于它是由微生物作用于其前体-组胺酸而产生的,普遍认为食物中存在着组胺。一些国家的政府建议用组胺作为鱼和水产品中微生物腐败的指标[1]。目前在国内由组胺引起的食物中毒也时有发生,因此应对食品中的组胺开展检测。食品中组胺测定的方法有生物学法、薄层层析法、荧光法和hplc法[2]。我国用于鱼体中组胺测定的方法为正戊醇提取稀盐酸反卒取,再用具有致癌性的对硝基苯胺重氨化显色法[3]。本文采用三氯醋酸提取样品中的组胺,直接与安全的氨基苯磺酸钠重氮化反应的方法测定水产品中的组胺。方法快速、简便且重现性好,去掉有了毒的有机溶剂,是组胺测定较为理想的方法。
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