燃烧加热污染空气对超燃冲压发动机性能影响研究

针对燃烧加热地面试验设备存在的工质污染问题,采用数值模拟方法研究了燃烧加热污染空气对氢燃料超燃冲压发动机性能的影响。以飞行马赫数Ma=6.5,当量油气比ER=0.6为计算基准状态,分别对纯净空气和污染空气来流下氢燃料超燃冲压发动机的整机流场和性能进行了对比计算分析。燃烧化学反应模拟采用了改进的H₂/O₂七组分八方程模型,湍流模型为标准的 k-ε模型,并采用直连式燃烧室试验数据进行了数值方法的验证。研究结果表明:(1)相对于纯净空气来流,污染空气来流下的超燃冲压发动机推力和比冲均有所下降。(2)采用酒精燃烧加热器的前提下,来流参数匹配静温、静压、马赫数时,发动机性能与纯净空气来流下的结果最为接近,而匹配总温、总压、马赫数时相差最大。(3)来流参数匹配总焓、静压、马赫数的前提下,采用氢燃烧加热器时发动机性能与纯净空气来流下的结果最为接近,而采用甲烷燃烧加热器时相差最大。      

超大跨预应力混凝土梁的施工监测与分析

文章通过对某47m跨后张有粘结预应力混凝土梁张拉过程进行实时监测,并且对监测结果进行了初步的整理和分析,得到了预应力钢筋的伸长值、梁的跨中挠度、控制截面的应力以及预应力总损失等结果,与理论值做对比,提出竖向构件侧向刚度对预应力总损失的影响,希望对今后的大跨度预应力混凝土梁的设计和施工有所帮助。     

浴火猛龙 DSI进气道介绍与使用机型分析

进气道是指飞机发动机所需空气的进口和通道。进气道设计是战斗机设计的关键之一,在整个飞行包线内,由于战斗机需要在很宽的速度和高度范围内以及高机动条件下飞行,进入发动机的空气流量变化很大,因此进气道设计需要在所有情况下为发动机提供足够的和高质量的空气以保证压气机和燃烧室正常工作。进气道的设计对飞机性能也有一定的影响,进气道总压恢复系数如果提高1％,可使发动机推力提高1．3％～1．5％;进气道和发动机的匹配优劣直接关系到飞行的安全,进气道的设计还关系到进气道的流场是否会紊乱;     

壁面马赫数分布规律可控的新型内收缩基准流场设计方法

根据有旋特征线理论,设计出了沿程马赫数下降规律可控的轴对称基准流场,分析了基准流场的几何参数(前缘压缩角及中心体半径)的影响规律,发现选取较小的前缘压缩角和中心体半径有利于得到性能优良的基准流场;然后在设计状态Ma=6时研究了三种典型的马赫数下降规律对这种轴对称流场性能的影响。最后考虑了粘性的影响,并进行了粘性修正探索,结果表明,采用附面层位移厚度修正方法后,基准流场的壁面压力分布和无粘情况吻合良好。      

H2O/CO2污染对煤油燃料超声速燃烧影响数值研究

在纯净空气与H₂O/ CO₂污染空气来流对比试验结果基础上,采用数值计算方法和化学动力学方法,研究了H₂O和CO₂污染组分对煤油燃料超声速燃烧的影响,获得了试验手段难以得到的燃烧室流场参数和性能数据。完成了相应的煤油燃料超声速燃烧室二维数值计算,其中匹配了进口总温、总压、马赫数、氧气摩尔分数和工作当量油气比。将数值计算结果与相应试验测量值进行了对比分析,并结合燃烧室流场数据、性能参数分析了H₂O和CO₂污染的动力学影响、以及对燃烧室性能的影响。研究表明:(1)数值计算结果与实验测量值总体上吻合,两种手段均体现了纯净空气来流时不同煤油当量油气比的燃烧室性能,并反映了一致的“污染效应”影响趋势;(2) H₂O污染、H₂O+ CO₂污染的存在降低了煤油燃料超声速燃烧室性能,体现在燃烧诱导压升、燃烧效率、流向冲量增量的下降,而且随着污染组分含量的增加,燃烧室性能下降越加显著。      

关于专利引文分析中的引文数据修正

专利引文分析是专利情报分析的重要组成部分,但由于引文分析方法本身的特点,如需要对不同年份、不同领域、不同地点授权的专利的被引数据进行对比,单纯利用从数据库中检索出来的原始被引数据将会使分析结果出现很大偏差,因此有必要对专利引文数据进行修正以确保专利引文分析的有效性.本文首先分析了引起偏差的各种因素,它们分别是专利被引年限的人为切断,专利技术领域的不同,以及专利数量、引文数量的不断上升.在偏差因素分析的基础上,介绍了两种对被引数据进行修正的方法--固定效果修正及准结构化修正.前者简单剥离所有偏差因素对专利被引数据的影响,后者则能有选择地消除某种偏差因素的作用.     

噪声测量值的修正探讨

文章在给出背景噪声定义的同时,举例说明背景噪声监测的必要性。在探讨噪声测量值修正时指出：当测量值与背景值相差3dB（A）～10dB（A）时,为避免出现偏差,应采用公式计算法进行修正;差值小于3dB（A）时,首次给出定性结果判断方法,为环境执法提供技术支持。     

期刊影响因子的偏差分析与修正

本文通过对期刊影响因子产生偏差的因素进行分析，提出了修正偏差的看法。以便影响因子更公正有效的对论文和科研绩效进行评价。     

石溪变电站10kv侧线路导线选择

在变电站建设过程中,线路导线的选择具有重要意义.按新建石溪66kV变电站最终规模考虑,根据负荷预测和从经济性的角度,按经济电流密度选择导线,使网络处于最佳经济运行状态,得出导线经济电流密度及各个需求的参数,并通过校验电压损耗,修正导线电阻,线路功率损耗,最终得出的导线截面的方案符合现场,设计的造价经济合理.     

网络求助的心理代价

网络求助往往引发超出预想心理代价,导致了所谓的“网络暴民”的出现。“网络暴民”侵害公民隐私权和名誉权,引发出不可小觑的“蝴蝶效应”,鉴于此,我们应该通过报纸等媒体对网络道德监督偏差来进行修正。     

British Writings on Romania: From Travel Accounts to Studies

This article surveys a sample of sources of the information about Romania available to British readers in nineteenth century British newspapers and periodicals. It traces first contacts between the Romanian lands and Britain after the union of the principalities of Wallachia and Moldavia in 1859, then after their independence from the Ottoman Empire. The article highlights an increased Romanian interest in British periodicals, which reported and reviewed Romanian literature and scholarship. The article concludes that nineteenth century British newspapers and periodicals offer a great variety and wealth of new material previously unavailable or unknown to researchers. It also states that only a portion of a large quantity of this material has been indexed and is therefore available via the bibliographic sources mentioned in the article. The author argues for the need of a new and updated British-Romanian bibliography, which can draw on new online resources offering access to thousands of new newspapers and periodical records.     

Slavic Approval Plans: What Works and What Doesn't

ABSTRACT

The paper looks at library approval plans for material published in Slavic, East European, and Eurasian countries from the selector's point of view. Reasons why a selector would or would not want one are examined. Success with approval plans requires monitoring receipts, as well as good and ongoing communication among the selector, the acquistions department, and the vendor. A preliminary list of vendors offering approval plans for the countries of the region appears in the appendix.     

由“资源集聚”向“需求导向”转变——对武汉科技信息服务平台建设的思考

为进一步提升武汉科技信息共享服务平台使用效率,本文从平台资源建设、资源应用、供需对接方式和供需特点等方面分析了武汉科技信息资源服务现状;基于需求和利用的角度,结合平台管理实践和走访用户、问卷调查等研究方法,从信息资源需求主体和平台自身建设管理两个维度,找出制约科技资源供需对接的主要因素;以市场化和制度化为创新理念,从政策创新、机制创新、市场化服务、环境营造、人才培养等方面提出平台建设由“资源集聚”向“需求导向”转变的对策建议.     

Politicking for the Public Library

ABSTRACT

In today's current political environment raising support for millage renewals, bond campaigns or even millage continuations for public libraries is affected by national politics, and a tendency towards tax aversion on principle across the country. The lessons we can learn from the governing boards of small and rural public libraries are worth raising up to a greater national consciousness. Board governance, community consciousness, and facilities management are clear and logical tools that elected boards of public libraries can use to politick for support of libraries.     

Architectures of Knowledge and Literary Tradition: A History of the Almanac in Croatia

ABSTRACT

The history of the almanac in Croatia is reconstructed through primary research in bibliographic and archival sources. The almanac is a vehicle for knowledge communication in informal contexts, engaging both oral tradition and literary forms traceable to medieval literacy and ways of structuring knowledge. The history of the almanac in Croatia reflects the changing context of the book trade, literacy, and the evolution of language. Four main stages are identified: (1) the beginning of the annual almanac in the seventeenth century; astrological almanacs reflecting the sensibility of the Baroque period; (2) the Enlightenment's stimulation of almanac publishing in the spirit of contemporary secular reforms in agriculture and education; (3) nineteenth-and twentieth-century almanac trade, showing complex and overlapping networks for the production, distribution and appropriation of printed almanacs;(4) roughly the end of World War II, when the almanac slowly moved out of the role of a popular mass medium and into specialized niches represented by regional, diaspora, and religious almanacs.     

基于文献时间特征的学科主题演化分析方法研究 ——以图书情报学领域为例

在分析文献在不同研究阶段用词时间特征的倾向性基础上,提出一种基于主题模型的研究发展阶段识别方法。重点阐述该方法的构建过程,包括时间特征抽取、发展阶段界定、主题冷热变化分析等步骤。为验证该方法的有效性,针对词频统计法和主题模型方法在主题演化分析中的效果进行比较分析。结果表明,该方法能在识别主题热点和发展趋势的同时,有效地区分不同主题所反映的研究发展阶段。     

How Digital Content Resellers are Impacting Trade Book Publishing

Some key questions for publishers in today’s market are: Could Amazon’s recent merger and acquisitions strategy create a disruptive or paradigm shifting business model in the publishing industry? Do their recent actions post mergers and acquisitions illustrate a predicable pattern of behaviour that publishers can strategize around? This paper will explore these questions and look at some of the possible reasons behind Amazon’s business practices and the possible consequences to publishers.     

Germany's New Culture of Welcome—Our Libraries are an Essential Part of it

ABSTRACT

German authorities are expecting more than 1 million refugees by the end of 2015. These people come to Germany to seek protection and assistance and to build a new life, therefore it is important to welcome them and to assist them in their integration as soon as possible. This situation creates a versatile and perfectly fitting opportunity for cultural and educational programs, including libraries, which can play a vital role in this integration process. The key to integration is the knowledge of the German language, and the most important challenge now is to teach the necessary language skills to as many asylum-seekers as possible.     

Syndicating Rich Bibliographic Metadata Using MODS and RSS

Abstract

Many libraries use RSS to syndicate information about their collections to users. A survey of 65 academic libraries revealed their most common use for RSS is to disseminate information about library holdings, such as lists of new acquisitions. Even though typical RSS feeds are ill suited to the task of carrying rich bibliographic metadata, great potential exists for developing applications that can exploit metadata exposed to Web services via RSS. Using the MODS metadata format, entire catalog records can be seamlessly embedded in RSS 2.0 feeds. Existing tools, such as Library of Congress Java toolkits and XSLT stylesheets, can facilitate this process, while a new XSLT stylesheet may be used to create the RSS feeds complete with MODS records. As an example of the added functionality these MODS/RSS feeds can offer, records from a MODS-enriched RSS feed can be ingested into a non-RSS application such as Zotero. As more emerging library technologies use Web services architectures to handle data objects, the ability to syndicate catalog records will become more critical to providing innovative library Web services.     

Selling Women on PDAs from “Simply Palm” to “Audrey”: How Moore's Law Met Parkinson's Law in the Kitchen

This essay investigates key moments in the history of personal digital assistant (PDA) marketing to women. Analyzing promotional texts for three PDAs that received considerable press coverage from 1999 to 2001, this essay explores the cultural significance of the convergence of anxieties about women's place in the gendered division of labor with the computer industry's changing marketing imperatives. Drawing on an array of promotional texts, including news articles, press releases, promotional Web sites, and ads appearing in newspapers and magazines, this paper tells the story of how the computer industry aimed to sell smaller, faster computing devices to women while promising to mediate and thus reproduce women's overwork as paid and familial laborers. After experimenting with the PDA as a sexy fashionable gadget for working women, marketers approached women as mothers with “Audrey,” an Internet appliance designed for the kitchen.