A comprehensive theoretical study of halide perovskites ABX3

Solar cells based on halide perovskites have recently been attractive due to their excellent power conversion efficiency (PCE), lower cost and simple manufacture. Here, a series of halide perovskites (ABX₃: A = CH₃NH₃, CH(NH₂)₂, Cs, Rb; B = Pb, Sn, Ge; X = I, Br, Cl, F) were investigated by Density Functional Theory (DFT) calculations, together with Shockley-Queisser Maximum Solar Cell Efficiency (S-Q) and Spectroscopic Limited Maximum Efficiency (SLME) mathematical models. The results indicate that: the electronic structure of germanium perovskites bears a close similarity to that of lead perovskites with a small energy difference between the nonbonding orbital and antibonding orbitals, but with a large energy difference comparing with that of tin perovskites (0.6–1.7 eV for CsGeI₃ at Z point of the Brillouin zone, 0.7–1.4 eV for CH₃NH₃PbI₃ and 1.4–2.2 eV for CH₃NH₃SnI₃ at R point of the Brillouin zone), which is attributable to the atomic level, where the 4s orbital energy of Ge (−11.5 eV) is close to the 6s orbital energy of Pb (−11.6 eV), but the 5s orbital energy of Sn (−10.1 eV) is significantly high. Therefore, germanium perovskites possess as high absorption coefficient around solar spectrum as lead perovskites, while tin perovskites only have low absorption coefficient, which makes the short-circuit current of CsGeI₃ and CH₃NH₃PbI₃ (0.017 Acm⁻² and 0.016 Acm⁻², simulated by SLME with a 200 nm absorber under AM1.5G) are higher than that of CH₃NH₃SnI₃ (0.015 Acm⁻²) even if the bandgap of CsGeI₃ and CH₃NH₃PbI₃ (1.51 eV and 1.55 eV) are larger than that of CH₃NH₃SnI₃ (1.21 eV). Meanwhile, the effective mass of electrons and holes are approximate for germanium perovskites and lead perovskites (0.14:0.19 for CsGeI₃ and 0.12:0.12 for CH₃NH₃PbI₃), indicating a balanced electrons and holes transport, whereas the electrons transport is much slower than the holes transport for tin perovskites due to the effective mass of electron is much larger than that of hole (0.17:0.04 for CH₃NH₃SnI₃). As a result, the PCE of CsGeI₃ (27.9%) and CH₃NH₃PbI₃ (26.7%) is higher than that of CH₃NH₃SnI₃ (19.9%).     

基于MVC设计模式和J2EE架构的Web信息系统框架研究

介绍了MVC设计模式、J2EE架构、Struts框架和Turbine框架，分析了其优缺点，在此基础上建立了一套高效实用的应用框架AAF。该框架由AAF Application Framework，Business Beans，JSP Pages和AAF Tag Library四部分组成．实现了模型、控制和视图3部分功能。最后对该框架的实际应用效果进行了分析，提高了代码的重用率，增强了程序的可读性．可缩短开发周期、降低开发成本。     

精品课程"数字电子技术"自主学习模式研究与实践

自主学习是当前教学改革中一个重要的研究课题。在自主学习中,教师作为教学过程的主导,学生作为学习过程的主体,只有在教师的指导下,充分发挥学生的主体作用,才能培养学生的自主学习能力,从而促进学生的禀赋和潜能的充分开发,提高教学质量。本文介绍了自主学习的概念,结合教学改革,探索自主学习模式,介绍我校“数字电子技术”课程自主学习实践的具体措施。并就学生的反馈意见,讨论了自主学习改革的效果及进一步改进措施。     

Spirobifluorene Dimers: Understanding How The Molecular Assemblies Drive The Electronic Properties

Spirobifluorene (SBF) is one of the most important scaffolds used in the design of organic semi-conductors (OSCs) for electronics. In recent years, among all the structures developed for these applications, SBF dimers have been highlighted due to their great potential in thermally activated delayed fluorescence and in phosphorescent organic light-emitting diodes. Attaching two SBF units generate 10 dimers, each possessing its own structural specificity, which in turn drives its electronic properties. These ten SBF dimers are gathered herein. Understanding how the molecular assembly determines the electronic properties has been one of the pillars of organic electronics. This is the goal of this article. As positional isomerism is a key tool to design OSCs, defining the design guidelines for the SBF scaffold appears of interest for the future of this building block. Herein, the importance of the two main parameters involved in the electrochemical and photophysical properties, namely the nature of the phenyl linkages and the steric congestion between the two SBF units is discussed. The combination of these two parameters drives the electronic properties but their respective weight is different as a function of the regioisomer involved or of the property considered (frontier orbitals energy level, absorption, fluorescence, phosphorescence).     

微放电检测方法分析

首先分析了微放电的影响,指出了微放电检测的重要性。总结了现有的微放电检测方法,并对其进行分析,结合工程实践总结了各种检测方法的优缺点及适用范围。最后,总结分析了微放电检测方法,并指出了微放电检测方法的研究趋势。     

无磁带化摄制设备研究与应用

目前传统摄录机老化的现状和应用的瓶颈,促进了能给广电、电教摄录带来高效率、低成本制作要求的无磁带化摄制设备的发展,通过对无磁带化摄制过程关键技术的分析,如性能测试、存储介质以及与非线性编辑系统兼容性等方面的研究,提出适应于不同场合的摄制方案。     

In search of computer-aided social support in non-communicable diseases care

Non-communicable diseases burden is well-known and care for these diseases goes beyond patients’ engagement, extending to their family, friends, and acquaintances. The ability of social relations in alleviating the harmful effects of health risks is known as social support. Computing can be used to promote social support to enhance the care of non-communicable diseases. However, it is unclear how computing obtains such enhancement. This paper presents a systematic review, in the form of a mapping study, aiming to answer how computing enhances non-communicable diseases care by using social data and by promoting social support. It also looks for available computing models focused on social support promotion in non-communicable diseases care. The study was guided by a two-phase process review, resulting in 38 reviewed papers from journals, conferences, and chapters in the period from 2010 to 2016. In general, the reviewed papers focus on controlled trials, frameworks and systems, knowledge discovery, simulation models or social media usage analysis. Knowledge discovery was the predominant subject, followed by social media usage analysis, and frameworks and systems.     

高分子PTC材料的进展与发展趋势

介绍高分子PTC材料的历史、结构组成、理论和工艺研究进展,以及国内外的应用和产业化发展情况,并就高分子PTC材料的理论研究和产业化发展提出见解。     

勘测关键技术及其综合应用研究

勘测关键技术及其综合应用研究，系国家“八五”科技攻关２０８－０２－０５专题。该专题研究结合锦屏一、二级等工程，专业面广，应用性强，研究工作难度大，是当前水电工程地质勘探技术中的薄弱环节，是关系到前期工作进展和工程经济效益的重大课题。其研究内容包括：岩心定向技术、砂卵石层取心技术，地应力测试与分析新技术，岩体裂隙结构面的计算机处理系统、岩溶探测新技术、高分辨率工程地震勘探技术、３０００系列测井仪的改     

县级电视台现场直播技术探讨

县级小型电视台没有电视转播车,很难对一些重要的新闻事件或文艺演出等进行现场直播,作者通过多年的实践探索出一套简单实用的方法,在现场直播中,视音频信号处理及传送、导播通信是很关键的环节,对这两个问题进行重点分析并提出具体的解决方案。