一类含有参数的Euler和的闭形式

将经典的线性和非线性Euler和扩展为一类含有参数的线性和非线性Euler和。并且利用留数定理,我们把这类含有参数Euler和表示成多项式对数函数和黎曼泽塔函数的形式。通过选取不同参数,可以得到一系列新的Euler和。     

计算机安全概述

1.计算机系统面临的威胁和攻击一类是对实体的威胁和攻击;另一类是对信息的威胁和攻击。计算机犯罪和计算机病毒则包括了对计算机系统实体和信息两个方面的威胁和攻击。1.1对实体的威胁和攻击主要指对计算机及其外部设备和网络的威胁和攻击,如各种自然灾害与人为的破坏、设备故障、场地和环境因素的影响、电磁场的干扰或电磁泄漏、战争的破坏、各种媒体的被盗和散失等。     

“A。就是说，B”类句式的语用、篇章考察

从语用和篇章的角度考察“A。就是说,B”这类句式中A和B的表达差异及其成因和对B的表达方式与内容的理解问题。先从正面和反面两个表达角度即肯定和否定的表现形式对句式进行分类。然后,又根据A和B在表达方式上的差别或两者之间的关系分出各种小类。通过分析,认为肯定和否定形式使用的原因,与句式的使用意图和使用缘由直接相关。对于B的表达方式和内容的理解,必须联系上文语境和说话人的意图。     

张Yan教授与我国的植物科学

张Ｙａｎ，植物学家和生物学教育家。中国近代植物学的先驱，现代实验性植物生理学和植物生态学的奠基人。最先自编我国第一套植物学，植物形态学，植物解剖学，种子植物分类学，植物生态学和植物生理学教科书。长期从事科学科的教学和研究工作，为我国的生物科学和教育事业的建立和发展，贡献了自己的一切知识和力量。     

关于选拔大学校长的思索

 大学校长作为社会科学、文化、文明传承和创造的关键角色 ,深受社会的信任和尊重。然而不良的大学校长选拔机制和监督机制 ,则可能使平庸者甚至人格卑劣者混足其中 ,造成大学发展进程的停滞和大学资源的浪费 ,贻误文化和科学事业的发展。因此 ,必须积极地进行大学校长选拔和监督机制的改革和完善。一、大学校长在人们心目中的形象和应有的作为大学校长在人们心目中可以说是极其神圣的 ,其拥有高尚品格和崇高声誉在古今中外可能都一样。因为在任何社会的任何时候 ,大学都是拥有高深知识和学问、拥有高级人才和高雅风气、令人敬仰和神往的地方。而担任大学校长的人 ,自然应该是当时当地声望卓着、学识渊博的学术大师或社会文化名流。     

基于WEB的车牌识别与管理系统设计与实现

为了利用图像处理技术和互联网技术及数据库技术来识别和管理车牌号码,以便最终获得车辆和车主的身份信息,本文设计和实现了一个基于WEB的车牌识别与管理系统,以实现对各类车牌和车主信息的智能化管理和应用。利用基于WEB的车牌识别与管理系统,用户可以实时和方便地识别和获取车牌数据库中车辆和车主的信息。本系统具有很强的实用性和扩展性。     

阿尔茨海默症患者认同维持的叙事研究

利用在自然氛围下的谈话去理解阿尔茨海默症患者的自我意识和认同的产生、维系和保持。认为如果有人和阿尔茨海默症患者进行互动和交流,他们能持续表达他们的自我意识,维持他们的自我认同。运用生命历程模式,人们看到个人生命的主旋律主要取决于目前的选择和模式。这些选择和模式源于同时也基于更早的选择和经历。     

矿山压力及其控制的几个名词的概念

任何学科,都有一套阐述该学科理论的专有名词和术语。因此,建立和统一“矿山压力及其控制”的名词和术语是十分重要的。但是由于学科的理论和实践是不断发展的,特别是即使同一学科,不同学术观点和理论体系的差别,所涉及的名词和术语的范围及其含意也不可能完全一样。因此名词和术语的统一又是相对的,有一个发展和完善的过程。我们的任务首先是讨论和弄清根据不同学术观点和理论体系所提出的一些名词和术语的含意。在此基础上尽可能的把目的相同,含意相似的名词和术语统一起来,赋于“它们”一个更确切的定     

合金元素对圆环链用钢强韧性的影响——矿用高强度圆环链用钢的设计与开发之一

本文测定了高韧性。高强度矿用圆环链用钢在淬火和不同温度回火后的强度和冲击韧性。通过逐步回归分析,得出了实验钢的成份和强度。韧性的回归方程。运用X射线衍射和透射电镜。电子衍射研究了合金元素对钢的组织和性能的影响。     

汉韩翻译教学中的词汇教学问题

韩国语词汇是韩国族学生和其他一些将韩国语作为第2语言的习得者在学习和翻译过程中出现偏差和误译较多的领域。韩国语词汇来源较复杂，难掌握。这是韩国语作为黏着语的一个突出的特点。词汇中较难分辨的是多义词和同义词的掌握和使用。并且不同事物和语境对应要求的词汇甄别和筛选也成为众多教师和翻译工作者的一道难关。本文主要通过词汇的2大分类的分析，以此探索出词汇教学方法。     

非均匀泵浦的半经典自洽场激光理论

将半经典自洽场激光理论扩展至非均匀泵浦,并对一维不均匀泵浦发光半导体的第一域值进行理论推导和计算.计算结果显示,第一激光域值D(1)th与泵浦区域x0成反比,在半导体外强度为常数,即光通量守恒.     

用光泵浦法评价AlGaAs/GaAs/AlGaAs双异质结外延片

本文提出了采用光泵浦法评价掩埋异质结构(BH)激光器的一次外延片质量的技术。该评价技术简便易行,对样片无破坏性,且可由其测量结果预言激光器发射波长和阈值等特性。     

半导体加热器性能的优化分析

应用非平衡态热力学及有限时间热力学理论导出半导体加热器在导热、热漏及焦耳热等三种主要不可逆因素影响下的供热率和供热系数,并由此讨论了加热器的优化性能,得到一些对半导体加热器的最佳设计和运行均有指导意义的结论。     

Recent developments in compact ultrafast lasers

Ultrafast lasers, which generate optical pulses in the picosecond and femtosecond range, have progressed over the past decade from complicated and specialized laboratory systems to compact, reliable instruments. Semiconductor lasers for optical pumping and fast optical saturable absorbers, based on either semiconductor devices or the optical nonlinear Kerr effect, have dramatically improved these lasers and opened up new frontiers for applications with extremely short temporal resolution (much smaller than 10 fs), extremely high peak optical intensities (greater than 10 TW/cm2) and extremely fast pulse repetition rates (greater than 100 GHz).     

Energy-transfer pumping of semiconductor nanocrystals using an epitaxial quantum well

As a result of quantum-confinement effects, the emission colour of semiconductor nanocrystals can be modified dramatically by simply changing their size. Such spectral tunability, together with large photoluminescence quantum yields and high photostability, make nanocrystals attractive for use in a variety of light-emitting technologies--for example, displays, fluorescence tagging, solid-state lighting and lasers. An important limitation for such applications, however, is the difficulty of achieving electrical pumping, largely due to the presence of an insulating organic capping layer on the nanocrystals. Here, we describe an approach for indirect injection of electron-hole pairs (the electron-hole radiative recombination gives rise to light emission) into nanocrystals by non-contact, non-radiative energy transfer from a proximal quantum well that can in principle be pumped either electrically or optically. Our theoretical and experimental results indicate that this transfer is fast enough to compete with electron-hole recombination in the quantum well, and results in greater than 50 per cent energy-transfer efficiencies in the tested structures. Furthermore, the measured energy-transfer rates are sufficiently large to provide pumping in the stimulated emission regime, indicating the feasibility of nanocrystal-based optical amplifiers and lasers based on this approach.     

Raman injection laser

Stimulated Raman scattering is a nonlinear optical process that, in a broad variety of materials, enables the generation of optical gain at a frequency that is shifted from that of the incident radiation by an amount corresponding to the frequency of an internal oscillation of the material. This effect is the basis for a broad class of tunable sources known as Raman lasers. In general, these sources have only small gain (approximately 10(-9) cm W(-1)) and therefore require external pumping with powerful lasers, which limits their applications. Here we report the realization of a semiconductor injection Raman laser designed to circumvent these limitations. The physics underlying our device differs in a fundamental way from existing Raman lasers: it is based on triply resonant stimulated Raman scattering between quantum-confined states within the active region of a quantum cascade laser that serves as an internal optical pump--the device is driven electrically and no external laser pump is required. This leads to an enhancement of orders of magnitude in the Raman gain, high conversion efficiency and low threshold. Our lasers combine the advantages of nonlinear optical devices and of semiconductor injection lasers, and could lead to a new class of compact and wavelength-agile mid-and far-infrared light sources.     

Single-nanowire electrically driven lasers

Electrically driven semiconductor lasers are used in technologies ranging from telecommunications and information storage to medical diagnostics and therapeutics. The success of this class of lasers is due in part to well-developed planar semiconductor growth and processing, which enables reproducible fabrication of integrated, electrically driven devices. Yet this approach to device fabrication is also costly and difficult to integrate directly with other technologies such as silicon microelectronics. To overcome these issues for future applications, there has been considerable interest in using organic molecules, polymers, and inorganic nanostructures for lasers, because these materials can be fashioned into devices by chemical processing. Indeed, amplified stimulated emission and lasing have been reported for optically pumped organic systems and, more recently, inorganic nanocrystals and nanowires. However, electrically driven lasing, which is required in most applications, has met with several difficulties in organic systems, and has not been addressed for assembled nanocrystals or nanowires. Here we investigate the feasibility of achieving electrically driven lasing from individual nanowires. Optical and electrical measurements made on single-crystal cadmium sulphide nanowires show that these structures can function as Fabry-Perot optical cavities with mode spacing inversely related to the nanowire length. Investigations of optical and electrical pumping further indicate a threshold for lasing as characterized by optical modes with instrument-limited linewidths. Electrically driven nanowire lasers, which might be assembled in arrays capable of emitting a wide range of colours, could improve existing applications and suggest new opportunities.     

关于连抽带喷的理论分析

本文深入讨论了利用惯性使抽油机连抽带喷的有关要素及其计算方法,并从理论上推导了连抽带喷的喷量表达式,从而得出了连抽带喷井的泵效计算式。为设计抽汲参数创造了条件,为油井连抽带喷,提高系统效率提供了理论依据。     

可重构游梁式抽油机的设计和仿真分析

借助于可重构制造系统的基本思想 ,论述了可重构抽油机的基本概念、特点及可重构的理论依据 ,并对可重构抽油机的关键环节模块的划分思路进行了探讨。给出了模块划分方案 ,分析了可重构游梁式抽油机的拼装特性。为了对可重构抽油机的性能进行验证 ,提出了将虚拟样机技术应用于抽油机的可重构设计 ,并利用虚拟样机技术软件ADAMS对APIC 32 0D 2 5 6 12 0抽油机进行了运动学和动力学分析 ,验证了虚拟样机技术应用于可重构抽油机设计的可行性。利用游梁式抽油机的可重构设计 ,可以实现抽油机的模块化生产 ,用户可根据需要对抽油机进行重构 ,从而实现了对抽油机传统生产和使用理念的变革     

新型双变径天轮式抽油机的设计

利用机构选型中的组合原理设计了一种新型天轮式长冲程抽油机。该新型抽油机由曲柄摇杆机构与双变径增程天轮机构组成 ,可以通过对现有的游梁式抽油机进行改造而制得。按照逐步优化设计思想 ,对该抽油机主参数进行了多目标优化设计和动态静力分析。现场试验和理论分析表明 ,该抽油机具有节能、结构紧凑、曲柄扭矩峰值较低、负扭矩小、扭矩变化平缓等优点。用该机构作为主机构的抽油机 ,其减速箱扭矩具有与双驴头抽油机类似的特性。与常规抽油机相比 ,其扭矩可以下降 10 %～ 15 % ,平衡效果好 ,平衡力矩有较大幅度降低。该机采用双变径天轮 ,提高了整机的动力性能 ;采用导向轮让位方式 ,改善了柔性件和支架的受力。由于该机选用了柔性件传动 ,在设计时必须考虑提高柔性件的寿命