共查询到20条相似文献，搜索用时 265 毫秒
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基于计算流体力学软件Fluent,运用多相流理论,建立封冻条件下单排桥墩和双排桥墩对桥墩周围流场影响的三维标准湍流数值模型,研究在封冻条件下不同桥墩直径与不同进口水流流速对桥墩附近水流湍动能的影响。结果表明：水流速度对桥墩周围流场的影响较大,水流速度越大,水流的势能转换为动能越多,桥墩周围的湍动能越大;桥墩直径越大,对河道过流断面的挤压就越大,但是桥墩周围湍动能却越小。相对于双排圆形桥墩条件,单排圆形桥墩条件下桥墩附近的流场紊动更剧烈,因而双排桥墩能有效地保护桥墩。 相似文献
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为揭示多级压气机中上下游叶轮对中间叶片叠加气动影响特性,阐述不同叠加干涉情况下下游叶轮进气角度变化,采用数值方法模拟了一级轴流和一级离心组成的组合压气机非定常流场。详细讨论了上游动叶尾迹和下游动叶势流对中间导流叶栅段气流非定常流动的异频和同频叠加干涉特性,依据计算结果,直观地展示了静叶通道中两种干涉间相互激励和抑制作用的位置和时间,与数学公式的推导结果相互印证。研究结果表明:当上下游动叶对中间静叶段异频干涉时,干涉的激励、抑制区域的轴向位置随时间发生变化;当上下游动叶对中间静叶干涉频率相同时,干涉的相互激励、抑制区域的轴向位置不随时间发生变化,但干涉的激励、抑制区域的轴向位置受时序位置影响。另外,上游动叶尾迹与下游离心叶轮势流的不同叠加情况,决定着下游离心叶轮进口相对气流角的大小及波动幅值。 相似文献
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宽尾墩消力池在水利枢纽工程中已经得到广泛的应用,而中高水头宽尾墩消力池内部流场较为复杂,运用物理模型试验结合数值模拟旨在实现水利工程中消能工体型优化的目的。针对物理模型试验难以得到的详细的各项水力学指标,采用RNGk-ε双方程紊流模型和VOF方法对宽尾墩消力池联合消能工的泄洪流场进行三维数值模拟,获得了泄洪流态、流速、水面线、坝面、闸墩和消力池底板压强的分布规律。数值模拟计算和物理模型试验数据的对比分析研究,两者吻合较好,表面数值模拟分析方法能满足工程需求。 相似文献
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为了准确设计高压涡轮盘和叶尖间隙,从概率的角度进行了涡轮盘径向变形的分析。介绍了高精度高效率的非线性动态概率分析的极值响应面方法(Extremum Response Surface Method, ERSM),并建立了其数学模型。考虑材料属性和边界条件的非线性,以及热载荷和离心载荷的动态性,基于ERSM对涡轮盘径向变形进行了非线性动态概率分析,得到了输入输出参数的分布特征和影响涡轮盘径向动态变形的主要因素。最后,通过方法比较,验证了ERSM在保证计算精度的前提下能大大提高计算速度,节约计算时间,改善计算效率。为进行更有效的涡轮盘设计和优化,改善叶尖间隙设计和控制的合理性提供了有效依据。 相似文献
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文章结合某低水头泄水闸设计实际资料,提出了一种新型悬栅消力池,建立了用于研究泄水闸消力池三维紊流的网格模型,利用标准k-ε紊流模型,并采用VOF自由表面追踪法及通过数值模拟,对悬栅消能工和传统SAF型消能效果、流态分布等方面进行对比研究,在此基础上进一步分析了悬栅消力池内流场流态、紊动能分布等水力特性,揭示出悬栅消能工能够应用于底流消力池,并提高低弗氏数水跃消能效率、改善出池流速分布的机理,为今后采用数学模型设计和优化此类工程提供了较好的参考依据。 相似文献
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在本文中介绍了一种用于进行多维的力和力矩测量的六维力传感器。利用Solidworks软件建立了其三维有限元模型,并利用有限元软件进行了静、动态分析,通过分析研究表明了各个参数对弹性体灵敏度以及固有频率综合性能影响的主要次序,从而为优化弹性体结构参数提供了依据,提高了传感器的动、静态特性。 相似文献
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当前,网络的应用已经深入到了家家户户.与此同时,企业的发展也离不开网络的应用.当下,我国使用率最高的网络方式是光纤网络.而我国的网络专家在研究光纤网络的时候更侧重于以下4方面:一是安全性能;二是传输质量;三是传输效率;四是传输技术.本文将对传输技术的现有状况加以改善,让光纤网络能够实现技术的最优化配置,从而更好地给企业及家庭服务. 相似文献
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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。 相似文献
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Milan Grba 《Slavic & East European Information Resources》2017,18(3-4):152-164
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. 相似文献
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《Slavic & East European Information Resources》2013,14(4):25-33
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. 相似文献
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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. 相似文献
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《Slavic & East European Information Resources》2013,14(1-2):123-143
ABSTRACT The article examines the most important periodicals of ethnic minorities in Poland. After 1989, many ethnic groups (e.g., Germans and Romanies) were allowed to publish journals and newspapers for the first time since the end of World War II. The publications examined show the rich cultural life of the various ethnic groups as well as their current status in Poland. In addition to popular titles, some scholarly publications are also discussed. 相似文献
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Jon C. Giullian 《Slavic & East European Information Resources》2013,14(3):278-284
The author answers a reference question on bibliographic sources for the Ukrainian periodical press 1840–1850. Helpful publications include bibliographies, guides, and library catalogs. These potentially make mention of revolutionary developments in Hungary (such as the Twelve Points paragraph of the Demands of the Hungarian Nation in March 1848, the subsequent April Laws, and Hungary's declaration of independence in April 1949), and elsewhere in the Hapsburg Empire. 相似文献
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Josie Barnes Parker 《图书馆管理杂志》2013,53(6):731-737
ABSTRACTIn 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. 相似文献
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Kelly Ahlfeld 《International Information and Library Review》2017,49(4):285-289
Chromebooks and the G Suite group of products, like Google Search, Gmail, and Google Docs, have rapidly expanded in American schools during the past 5 years. The impact of one-to-one Chromebook devices and the pervasive use of Google's software products in American education cannot be overstated. This article explores some of the influences of these products on research, based on the experiences of a librarian and technology coordinator at an elementary education level. The author has several suggestions for effective research with these products in mind. 相似文献
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《Behavioral & Social Sciences Librarian》2013,32(1):49-54
Library historians can learn a great deal from studying the gender of authorship and institutional affiliation of a scholarly journal. The focus of this study is to examine these two aspects of journal production in library history to see who is producing published research in this field. Twenty-three years of Libraries & Culture were chosen as the target volumes. The study reveals that more men than women published in library history as well as locating which institutions were represented. This type of information is usedful to the library historian engaged in the analysis of published scholarship, and more generally to scholars with an interest in patterns of literature production in fields closely related to the social and behavioral sciences. 相似文献
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《Slavic & East European Information Resources》2013,14(1):25-74
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. 相似文献