线型聚(N-杂环化)硅烷体系的电子结构与光谱性质的比较研究

用密度泛函理论(DFT)和含时密度泛函理论(TD-DFT)对线型(N-杂环化)硅烷低聚体系与简单聚硅烷的电子结构和吸收光谱性质进行了比较研究。对各体系的基态分子结构在B3LYP/6-31G**水平上进行了全优化,讨论了电荷分布和前线分子轨道性质。在获得基态稳定构型的基础上,应用含时密度泛函理论计算了电子吸收光谱的性质。计算结果显示,当主链硅原子被氮杂环环化后,由于空间位阻作用使相邻硅硅键明显伸长,使主链结构变得松散。但同时改善了分子主链的电子离域范围,增强了分子结构的可塑性。随着氮杂环数目的增加,低聚硅烷的电子吸收光谱发生明显的红移。氮杂环的引入对聚硅烷的最大吸收光谱带影响非常大。     

2-(4-取代苯基)乙烯基吡啶电子光谱的理论研究

对2-(4-取代苯基)乙烯基吡啶系列用密度泛函法(DFT),在B3LYP/6-31+G**冰平上全优化几何构型,探讨苯环对位上不同取代基对分子电荷的转移、前线轨道能量等性质的影响规律.结果,电子由苯环向乙烯链移动,并通过乙烯链再向吡啶环移动;前线轨道能量随着取代基吸电子能力的增加而降低,随着供电子能力的增强而升高.在此基础上采用含时密度泛函(TD-DFT)计算分子第一激发态的电子跃迁能,得到最大吸收波长λmax.计算结果,6个化合物的最强跃迁都由于基态到单重激发态分子的HOMO→LUMO跃迁,由轨道对称性可知为π→π*跃迁.引入上述5种取代基,均导致最大吸收波长红移.     

铁卟啉化合物与氧气分子形成的体系的密度泛函理论研究(英文)

采用密度泛函理论B3LYP方法在6-31G(d)基组水平下对氯化铁(+3)卟啉与氧气分子形成的体系进行了研究,得到了几何构型,电子性质及分子轨道结构等相关数据.对两个体系不同自旋状态下的几何构型参数和电子性质对比发现:受体系立体构型对称性的影响,在两个体系中凡是与卟啉环上N原子相关的几何参数及电子性质均呈现出相同规律性.又采用密度泛函理论UB3LYP/6-311G*//UB3LYP/6-31G*方法对这两个体系不同自旋状态下的能量进行了计算,分析表明自旋多重度越高体系越稳定.然后分别分析了两个体系在最稳定自旋状态下的分子轨道占据情况及中心Fe原子最外层3d轨道的电子分布情况,结果表明Fe原子的3d二和3dxz/3dyz与氧气分子的单占据反键轨道HOMO π*2px/π*2py之间存在相互作用,这种相互作用引起铁卟啉环与O2分子间的电子转移并使O2活化.然而,根据分析在通常状态下铁卟啉对O2分子的活化作用是微弱的.     

1-乙基-3-甲基咪唑和PF-6离子液体的理论研究

采用Hartree-Fock和密度泛函理论方法研究1-乙基-3-甲基咪唑阳离子(EMIM )、PF6-、EMIM -PF6-离子对。氢原子、碳原子、氮原子、氟原子和磷原子在6-31 (d,p)基组水平上,采用Gaussian94软件包给EMIM 、PF6-及12个EMIM -PF6-离子的初始结构做全优化和频率分析。比较研究所优化结构和能量的性质。计算结果表明最低能量结构的EMIM -PF6-阴阳离子对相互作用能,在Hartree-Fock水平上为326.6 kJ／mol、在密度泛函理论上为328.8 kJ／mol。阳离子不对称、阴阳离子间距较大、阴阳离子电荷的分散使①静电作用降低,导致离子液体熔点较低。②EMIM 氢原子的正电荷增加、PF6-氟原子的负电荷增加,导致C-H---F氢键相互作用增强。从而在离子液体中起重要作用。本文着重考察了EMIM 和PF6-相互作用的三种氢键方式。     

1-甲基环丙烯进入α-环糊精分子组装的理论研究(英文)

本文用密度泛函理论(DFT)和PM3方法研究了1-甲基环丙烯(1-MCP)与α-环糊精(α-CD)包合物形成机理。用B3LYP/6-31G*法优化了α-CD和1-MCP的几何结构,并用PM3方法优化了所有包合物的初始几何结构,结果得到了1-MCP从2个不同端口进入α-CD形成包合物的2个能量最低的结构。在B3LYP/6-31G*水平对这2个能量最低结构的能量、氢键相互作用、Mulliken电荷转移、前线分子轨道进行了分析。结果表明,1-MCP从大口端进入α-CD空腔能量更低。最后,用B3LYP/6-31G*法计算了包合物的红外光谱。     

新型咔唑衍生物密度泛函理论的研究

运用量子化学中的密度泛函和含时密度泛函理论法,计算1种新型咔唑衍生物,以探讨其几何构型、电子结构、前线分子轨道和电子光谱性质。计算结果表明当2-(4-吡啶基)乙烯基的反式构型与咔唑环作用时比顺式稳定,引入取代基后使化合物的HOMO和LUMO之间的能隙降低,吸收光谱红移。电子被激发时,电子从咔唑环向吡啶环转移,说明新型咔唑类化合物具有很好的光学性能,可以作为空穴传输材料。     

N-乙基吡啶溴盐离子液体分子结构和光谱性质的量子化学计算

离子液体以其独特性质广受关注,人们对其潜在的利用价值做了大量的研究。本文采用密度泛函(DFT)B3LYP/6-31G+(d)方法和从头算(ab initio)HF/6-31G+(d)方法计算了N-乙基吡啶溴盐([EPy]Br)离子液体的结构性质和光谱性质,对比阳离子及形成阴阳离子对后的结构变化。通过自然键轨道(NBO)...     

4种类胡萝卜素抗氧化性质的量化计算

类胡萝卜素分子结构中含有一个共轭大π键,可能是这种特殊的结构使它容易与自由基起反应,形成无害的产物,或通过破坏自由基链反应,将自由基清除。运用密度泛函理论方法(density functional theory,DFT)在B3LYP/6-31(d)水平上对虾青素、β-胡萝卜素、玉米黄素和叶黄素四种类胡萝卜素分子进行了优化计算,之后在B3LYP/6-311(d)水平上进行了单点能(single pointenergy,SPE)计算。文章从分子的几何结构、总能量、原子的NBO电荷值、以及前线轨道结构方面详细讨论了它们性质。研究表明,分子的共轭效应使C-C单双键的键长均匀化,同时降低了分子的能量,最高占据轨道与最低空轨道能级间隔ΔE(LUMO-HOMO)变小,光谱移至可见区,从而显出多种颜色。从原子的NBO电荷值,前线轨道ΔE方面分析可见,抗氧化活性理论上虾青素>玉米黄素≈β-胡萝卜素>叶黄素。玉米黄素和叶黄素结构中的羟基的亲水性会增强其与水溶性或脂溶性氧化物反应,导致其清除体内自由基的能力大于β-胡萝卜素。     

MoS_2薄膜电子性质随层数变化的理论研究

本文采用基于密度泛函理论的第一性原理方法计算了体相和1-10层3R-MoS_2的几何结构和电子结构。计算获得了体相3R-MoS_2的几何结构参数,与实验值相一致,表明了计算方法和参数设置的可靠性。随后,分别计算了1-10层3R-MoS_2的几何结构和电子性质。可以看到,优化后的结构参数c随层数增加而线性增加;计算得到的带隙值随着层数的增加而呈现出减小趋势,并趋于稳定值。     

3-甲基-7-二乙氨基-1,4-氧氮杂萘-2-酮的波谱性质量子化学从头计算

以合成的重要荧光材料3-甲基-7-二乙氨基-1,4-氧氮杂萘-2-酮为例子,进行了一些有机含氮杂环化合物的红外、核磁性质Hartree-Fock(HF)和密度泛函(DFT)量子化学从头计算研究。通过系统构象搜寻,对低能量稳定构象进行了红外振动频率和1H、13C-NMR及偶合常数等光谱学性质的计算,并对计算结果进行详细的归属和解析。在化学位移计算方面,HF／631g(d)和DFT／BG3LYP／6311 g(2d,p)方法计算结果相当。但对于自旋偶合常数的计算,用HF／631g(d)方法不能得到准确的结果,只能用密度泛函大基组的方法才能得到比较准确的结果。计算结果表明有机分子光谱性质的理论计算尤其是核磁性质的计算是一种非常有效的辅助结构确定方法。     

煤矿井下安全监控分站的设计及其仿真实现

为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.     

Call for Papers The 6^th International Conference on Grid and Cooperative Computing

Recent years have seen rapid advances in various grid-related technologies, middleware, and applications. The GCC conference has become one of the largest scientific events worldwide in grid and cooperative computing. The 6th international conference on grid and cooperative computing (GCC2007) Sponsored by China Computer Federation (CCF),Institute of Computing Technology, Chinese Academy of Sciences (ICT) and Xinjiang University ,and in Cooperation with IEEE Computer Soceity ,is to be held from August 16 to 18, 2007 in Urumchi, Xinjiang, China.     

View-based model-driven architecture for enhancing maintainability of data access services

In modern service-oriented architectures, database access is done by a special type of services, the so-called data access services (DAS). Though, particularly in data-intensive applications, using and developing DAS are very common today, the link between the DAS and their implementation, e.g. a layer of data access objects (DAOs) encapsulating the database queries, still is not sufficiently elaborated, yet. As a result, as the number of DAS grows, finding the desired DAS for reuse and/or associated documentation can become an impossible task. In this paper we focus on bridging this gap between the DAS and their implementation by presenting a view-based, model-driven data access architecture (VMDA) managing models of the DAS, DAOs and database queries in a queryable manner. Our models support tailored views of different stakeholders and are scalable with all types of DAS implementations. In this paper we show that our view-based and model driven architecture approach can enhance software development productivity and maintainability by improving DAS documentation. Moreover, our VMDA opens a wide range of applications such as evaluating DAS usage for DAS performance optimization. Furthermore, we provide tool support and illustrate the applicability of our VMDA in a large-scale case study. Finally, we quantitatively prove that our approach performs with acceptable response times.     

A pragmatic multi-method investigation of discrepant technological events: Coping,attributions, and ‘accidental’ learning

Discrepant technological events or situations that entail a problem, a misunderstanding or a difficulty with the Information Technology (IT) being employed, are common in the workplace, and can lead to frustration and avoidance behaviors. Little is known, however, about how individuals cope with these events. This paper examines these events by using a multi-method pragmatic approach informed by coping theory. The results of two studies – a critical incident study and an experiment – serve to build and test, respectively, a theoretical model that posits that individuals use a variety of strategies when dealing with these events: they experience negative emotions, make external attributions, and adopt engagement coping strategies directed at solving the event, eventually switching to a disengagement coping strategy when they feel they have no control over the situation. Furthermore, users’ efforts may result in ‘accidental’ learning as they try to overcome the discrepant IT events through engagement coping. The paper ends with a discussion of the results in light of existing literature, future opportunities for research, and implications for practice.     

The Distributed Time-Triggered Simulation Scheme: Core Principles and Supporting Execution Engine

Distributed real-time simulation is a young technology field but its practice is under increasing demands. In recent years the author and his collaborators have been establishing a new approach called the distributed time-triggered simulation (DTS) scheme which is conceptually simple and easy to use but widely applicable. The concept was initiated in the course of developing a new-generation object-oriented real-time programming scheme called the time-triggered message-triggered object (TMO) programming scheme. Some fundamental issues inherent in distributed real-time simulation that were learned during recent experimental studies are discussed along with some approaches for resolving the issues. An execution engine developed to support both the TMOs engaged in control computation and the TMOs engaged in DTS is also discussed along with its possible extensions that will enable significantly larger-scale DTSs.     

Software-Konfigurationsmanagement in großen Softwareprojekten

Zusammenfassung Mit zunehmender Größe der Softwaresysteme verschärfen sich die für die Software-Herstellung typischen Probleme: Beherrschen großer Objektmengen, Erhalten der Systemkonsistenz, Kontrolle der ständigen Änderungseinflüsse und Gewährleisten einer langen Lebensdauer. Die Disziplin Konfigurationsmanagement bildet den methodischen Ansatz, diese Probleme besser zu beherrschen. Software-Konfigurationsmanagement faßt die Herstellung von Softwaresystemen als eine Abfolge von kontrollierten Änderungen an gesicherten Zwischen- und Endergebnissen auf. Dargestellt werden die Objekte und Funktionen des Software-Konfigurationsmanagements sowie die hierfür in großen Software-Projekten benötigten Methoden, Instanzen und Hilfsmittel.     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and     

Editorial:Brain-machine interface(BMI) and cyborg intelligence

正Brain-machine interfaces(BMIs)aim at building a direct communication pathway between the brain and an external device,and represent an area of research where significant progress has been made during the past decade.Based on BMIs,mind information can be read out by neural signals to control     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and overseas to the world’s scientific circles,especially to stimulate     

SCIENCE CHINA Information Sciences SUBJECT INDEX TO VOLUME 57(2014)

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