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Search Results: 1 - 10 of 92011 matches for " 黄维 "
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金属银凝固与非晶晶化过程的分子动力学模拟
A Study on Solidification and Amorphous Crystallization of Metal Ag by Molecular Dynamics Simulation
 [PDF]

, 梁工英
Applied Physics (APP) , 2013, DOI: 10.12677/APP.2013.36021
Abstract:

文章采用分子动力学方法,以金属银为对象,模拟了面心立方金属的凝固和非晶化过程,借助于体系的内能变化、径向分布函数(RDF)、公共近邻分析(CNA)、原子可视化技术对凝固和晶化形核过程中的结构演变细节进行了描述。模拟结果表明,液态金属中就存在11% bcc结构的短程有序集团,随着液态金属不断过冷,bcc集团逐渐增加,在凝固前达到最高的31%,在非晶形成时,bcc集团大约有24%。当最近邻原子距离相同时,bcc结构单位原子所占体积大于fcc结构,有利于在液态金属和非晶中存在。这些bcc结构作为结晶时的非自发形核的核心,与周围的无序原子一起迅速转变为fcc结构和少量的hcp结构。在过冷液体和非晶系统中并没有发现fcc和hcp的结构,fcc结构为凝固和非晶晶化的很短周期中迅速转变而成。

The melting and solidification of Ag was simulated by molecular dynamics method. The structural transfor- mation of Ag during the metal solidification and amorphous crystallization was analyzed based on the variations of the internal energy, radial distribution function (RDF), common neighbor analysis (CNA), and atomic visualization technique. The simulation results showed that the embryonic crystals similar to body-centered cubic (bcc-like) structure (about 11%) already exist in the liquid metal, the content of bcc increases with cooling and it is up to 31% near the solidifying. About 24% bcc structure has in the amorphous structure. The volume per atom of bcc is larger than that of fcc, which is beneficial in the cooling liquid metal and amorphous structure. In the nucleation process, bcc-like embryonic crystals can be used as the nucleus with disorder atoms near the bcc to transform fcc crystal. There is no fcc and hcp structure in the cooling melt and amorphous structure. They are formed in the solidification directly.

 

Ag-Cu共晶合金非晶转变及晶化的分子动力学模拟
A Molecular Dynamics Study on Amorphous Formation and Crystallization of Ag-Cu Eutectic Alloys
 [PDF]

, 梁工英
Applied Physics (APP) , 2013, DOI: 10.12677/APP.2013.38028
Abstract:

本文采用分子动力学方法研究了Ag-Cu共晶合金的结晶过程。依靠体系内能变化、公共近邻分析和原子可视化技术对Ag-Cu共晶合金的结构演变进行了分析。模拟结果表明,在10%~40%Cu范围内,随着Cu含量的增加,合金形成非晶结构的临界冷却速度减小,玻璃化转变温度增加。公共近邻分析的结果表明,在非晶晶化前的阶段,表征非晶结构的1551、1541和1431键对占据主要部分,但也存在少量的bcc和fcc晶核团簇。其中,表征正二十面体团簇的1551键对,随着Cu含量的增加而增加,表征缺陷二十面体团簇的1541和1431键对则相应减少,这表明,随着Cu含量的增加非晶体系的稳定性增加。与此同时,表征晶体相结构的键对随Cu含量的增加都有所减少,其中,bcc晶核的数量减少较小,但fcc晶核的数量却有较大的下降,从而使非晶晶化的形核核心减少,这也从结构上解释了非晶合金的玻璃化转变温度随成分增加而增加的现象。在非晶晶化以后,虽然体系以fcc结构为主,但仍存在一些无序的非晶态结构,这些结构存在于共晶两相界面,随Cu含量的增加而增加。利用可视化技术,我们可以发现,随着Cu含量的增加,Ag-Cu合金的共晶组织存在从固溶体形、网状共晶到层状共晶的演变。
The crystallization of Ag-Cu alloys was studied by molecular dynamics method (MD) with embedded atom potential (EAM). The structural developments of Ag-Cu alloys were analyzed based on the variations of internal energy, common neighbor analysis (CNA), and atomic visualization technique. The simulation results showed that with the increase in Cu composition, the critical cooling rate of amorphous formation decreased and the glass-transition temperature of amorphous increased under the same heating rate. The results of CNA showed that the amorphous structure is main, and a few crystal clusters (bcc and fcc) are in it. Among the amorphous bond pairs, the pairs 1551 increases with the increase in Cu composition, which is the character of regular icosahedrons cluster. Meanwhile, the pairs 1541 and 1431, which are the character of defect icosahedrons clusters, reduce correspondingly. These show that the stability of amorphous increases. With the increase in Cu composition, the pairs 1441, 1661 and 1421 are all reduced, the 1441 and 1661 decrease little and the 1421 decreases great, which implies that the nuclei reduce during the crystallization of amorphous and the glass-transition temperature increases. After crystallization, the fcc structure is dominant but there are a few defect icosahedrons clusters between the eutectic boundaries. Moreover, the eutectic structure of Ag-Cu alloys can be transformed from solid solution, net-like into the lamellar morphologies with composition during the solidification and crystallization.

圆柱体涡激振动缩尺实验的相似关系研究
Study on the Similarity Relation of Model Test of Vortex-Induced Vibration on Circular Cylinders
 [PDF]

周阳,
International Journal of Fluid Dynamics (IJFD) , 2014, DOI: 10.12677/IJFD.2014.23004
Abstract:
提出了一种基于雷诺相似的圆柱体涡激振动(VIV)实验方法。涡旋的泄放模式与雷诺数Re密切相关,目前圆柱体涡激振动的研究中,缩尺模型实验往往基于弗汝德相似而雷诺数不相似,因此,模型与原型的涡泄模式不同,由此可以推断,模型的涡激振动响应与原型不相似。这就意味着基于弗汝德相似准则的模型实验结果不能准确地预测原型的涡激振动响应。对基于雷诺数相似的模型与原型的涡激振动实验相似关系进行了推导,采用CFD方法对原型和3种不同相似准则条件下的缩尺模型进行了涡激振动仿真计算, 同时引入实验进行对比。数模结果表明,仅满足雷诺数相似的模型与原型的涡泄模式相似,这个结果与弗汝德数和雷诺数均相似的结果一致,而仅弗汝德数相似条件下,模型与原型之间的涡泄模式和尾流场完全不同。实验结果表明,仅满足雷诺数相似时,模型与原型涡泄周期满足相应缩尺比,而仅满足傅汝德数相似时,模型与原型涡泄周期不满足相应缩尺比。因此,缩尺实验中仅满足傅汝德数相似模型的涡激振动特性不可能与原型相似,应采用雷诺相似准则。
An experimental method, based on Reynolds number similarity, of the vortex-induced vibration (VIV) of circle cylinders is proposed to achieve VIV similarity between prototype and tested model. The VIV response of a circle cylinder is closely related to Reynolds number because the mode of vortex shedding highly depends on Re. However, the scaled model test of circle cylinder’s VIV is designed based on Froude number similarity but Reynolds number is not similar under the same fluid for both model and prototype. Therefore, the VIV response of tested model is not similar to that of the prototype because they have different vortex shedding modes. It means that the test results can not be used to predict the VIV response of the prototype according to the scaling law based on Froude number similarity. The prototype and three scaled models with different simi-larity schemes have been simulated using CFD to validate the method and at the same time, expe-riments are compared. The numerical results show that the similarity between prototype and model is satisfying by Reynolds number similarity, and it is in accordance with both Froude number and Reynolds number similarity. But the similarity between prototype and model is not satisfying by Froude number similarity. The experimental results show that the similarity of period of the vortex shedding is satisfying by Reynolds number similarity but not satisfying by Froude number similarity. As a result, Reynolds number similarity should be used in the scale model test instead of Froude number similarity when studying the characteristics of VIV.
心理契约违背对反生产行为的影响作用研究——以心理资本为调节变量
Study on the Effect of Psychological Contract Violation on Counter-Productive Behavior——With Psychological Capital as a Moderator
 [PDF]

, 王琛,
Advances in Psychology (AP) , 2012, DOI: 10.12677/ap.2012.21004
Abstract: 企业员工反生产行为及其后果的严重性引起了国内外学者的重视,本研究通过对167名国企员工的有效调查样本进行分析发现:1) 员工的心理契约违背感受对其反生产行为的发生程度有显著的正向预测作用;2) 员工的心理资本对其反生产行为的发生程度有显著的负向预测作用;3) 员工的心理资本对其心理契约违背感受和反生产行为之间的关系起到显著的负向调节作用。
Counter-productive behavior and its serious consequences of employees have attracted the atten- tion of domestic and foreign scholars. This study analyzed 167 valid samples from state-owned companies and the results showed that: 1) Psychological contract violation of employees had a significant positive im- pact on the occurrence of counter-productive behavior; 2) Psychological capital of employees predicted nega- tively the occurrence of counter-productive behavior; 3) Psychological capital of employees played a signi- ficant negative moderating effect on the relationship between psychological contract violation and counter- productive behavior.
医疗机构员工满意度与经营绩效相关性之实证研究
An Empirical Study on the Relationships between Job Satisfaction and Organizational Performance in Healthcare Settings
 [PDF]

, 许恒韶
Modern Management (MM) , 2012, DOI: 10.12677/MM.2012.24026
Abstract: 本研究目的在了解医疗机构中员工的工作满意度对经营绩效之影响。将员工需求及建议作分析,并谋求预防性策略管理,让病患、员工及医院产生良性循环互动,达医院永续经营。研究对象为医院员工,且为实证调查研究。研究结果显示:1) 两年度员工工作满意度:a) 皆以离家近、同事相处融洽、宗教理念相符为员工愿意留在医院服务之主因。b) 工作本身与领导沟通之构面满意度均达六成。c) 员工对工作满意度偏低之变项为护理人员、服务年资介于2~5年者、非主管职、宗教信仰为道教、月收入较低者;2) 第二年度较第一年度工作满意度略为提高;3) 第二年度较第一年度经营绩效之医疗服务量增加。

The purpose was to study the relationships between the job satisfaction and organizational performance. The substantial suggestions of employees and the potential factors of turnover were thoroughly analyzed in this study. Moreover, the managerial strategy to deal with turnover rate and to establish the good compromise between healthcare consumers and providers will be the key concept for the healthcare settings. Therefore, Organizational culture, internal customers’ satisfaction, turnover reduction and healthcare quality are the critical issues needed to be investigated. The research samples were drawn from a certain regional hospital in southern Taiwan. The research design was structured survey study. The significant findings in this study were following: 1) for job satisfaction: a) distances from home, harmony with colleague and religion motivation were the three critical factors to encourage employee to stay b) both job characteristics and leadership/communication were more satisfied rate c) for the dissatisfied staffs, nurses with working experience 2 - 5 years, non-administrative position, non-catholic religion, and low income were dominant subjects; 2) for overall job satisfaction in different years: more satisfaction in the 2nd year than the first year; 3) for organizational

竺可桢同志与我国热带和海南岛的科学研究(一) 我国热带、亚热带界线问题

地理研究 , 1984,
Abstract: 竺可桢同志逝世,忽忽已十更寒暑。他生前在中国科学院任副院长二十多年,对我国热带的研究抱着很大热忱。我国自然条件复杂,但热带面积不大。利用如此有限的热带,对全国经济可以挹注有无,截长补短,起到很重要的作用。从五十年代中期开始,他曾积极组织琼雷和滇南的综合考察,他自己亦数度跋涉于湿热的环境中。1963年我随他去滇南考察,他
经贸型MIS的开发策略

计算机系统应用 , 1993,
Abstract: 经贸型企业置身社会面向市场,企业对市场的快速应变和决策能力,是企业在市场竞争中立于不败之地的 决定因素。而建立一个充满活力的企业自适应的MIS,是企业达到此目的的有力手段。本文介绍经贸型企业MIS 的开发策略。
“社科项目"信息处理系统的应用开发

计算机系统应用 , 1992,
Abstract:
一些模型问题高阶离散格式的低阶预条件

科学通报 , 1992,
Abstract: 一、引言 偏微分方程的高阶(离散)格式能以较少的节点而获得高精度的离散解,但所形成的代数系统却非常病态和具有许多的非零元。为了有效地求解此代数系统,Wong提出了使用低阶预条件的一种预条件共轭梯度法。其主要技术是利用同一微分方程的低阶格式构物造预条件
核磁共振谱在有机化学中的应用

科学通报 , 1960,
Abstract: 核磁共振谱是在1946年由Purcell和Bloch两个学派同时发现的,经过十多年来的发展,在分子结构的测定及化学动力学方面都得到广泛的应用。尤其是在最近五六年来,由于广泛测定了各类有机化合物的核磁共振谱,积累了大量数据,所以核磁共振谱的测定已经成为有机化学研究中最重要的方法之一。按照古典的说法,具有磁矩的原子核好象一个小磁铁,在外加强磁场中磁矩绕外场方向进动,进动的角频率ω随外加磁场的大小决定,这个进动的角频率又称为Larmor频率,可用下式表示,即:
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