共查询到20条相似文献，搜索用时 62 毫秒
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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。 相似文献
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《中国科技资源导刊 (中国信息导报)》2004,(12)
我国科学家积极研制"原创"科研设备 近年来,中国科学院积极支持创新性科研设备研制,初步走出了一条科研设备原创之路。 世界上第一台包含3个独立光学微机械手的纳米光镊系统、我国第一座用于超燃冲压模型发动机的地面实验装置、紫外共振拉曼光谱仪等一批原创的科技装备在中科院诞生,让世界同行为之侧目。 相似文献
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极速狂飙美国空军X-51A验证机的研制与发展 总被引：1，自引：0，他引：1
5月26日上午,美国空军第419飞行中队的一架B-52H轰炸机从爱德华空军基地起飞,携带着X-51A验证机,执行首次飞行试验任务。大约10时10分,X-51A验证机从载机的左侧机翼下脱离,经过助推和分离阶段后,顺利实现了超燃冲压发动机的点火和加速,总共持续飞行了200秒,使飞行速度达到了马赫数5。此次试飞实现了以超燃冲压发动机为动力的飞行器迄今为止最长的飞行时间,成为超燃冲压发动机研制与发展历程中的一个重要里程碑。 相似文献
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超音速燃烧冲压发动机是一种新型的吸气式发动机,装置了这种发动机的飞行器将大大突破现有的速度和高度极限,使飞行马赫数(运动速度与音速之比)达到6～25,从而实现人类航空航天史上一个新的突破。 由西北工业大学出版社出版的《超音速燃烧与超音速燃烧冲压发动机》一书,是作者(刘陵教授等)多年在航空航天高等院校和研究所从事教学、科研工作,在对该领域进行跟踪分析、数值模拟、理论与实验研究的基础上撰写出来的一部学术专著。 相似文献
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天然气汽车因其具有节能及环保等优点获得极大的关注与推广,而作为汽车心脏的发动机,性能在很大程度上取决于其燃气喷射电控系统是否能对空燃比、点火能量和点火提前角等实现精确控制。天然气发动机汽车作为重点推广的清洁汽车,开展其强鲁棒性及自适应空燃比控制系统的研究是汽车发动机电控技术的重要发展方向。 相似文献
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新型三维编织碳/碳化硅复合材料存在较强的各向异性,而各个方向的性能数据积累不足,复合材料的强度计算方法尚不完善,为了发现新型三维编织碳/碳化硅复合材料在冲压发动机喷管中应用可能遇到的问题,并找到相应地解决措施,开展了这种复合材料应用于冲压发动机喷管的承压强度计算和承压实验研究。对承压实验中出现的低压破坏情况进行了分析,分析了低压破裂的原因,提出了改进措施。分析结果表明:C/SiC喷管喉部密度较低,导致强度较低,承载能力下降,是首次强度验证实验过程中该局部破坏的原因;为提高喷管强度,需要通过其形状设计并控制沉积流场,保证其喉部的沉积密度达到1.9g/cm3以上。对改进后的喷管进行了实验验证,实验结果与计算结果基本一致,满足要求。因此,在实际应用中应对喷管喉部和纵向密度的分布进行工业CT无损检测,确保喷管密度的分布均匀。 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
8.
本文采用内容分析的方法,运用二维测量框架理论,对2010年4月至11月《纽约时报》对上海世博会的报道进行统计分析。本文分析其时空框架的构建及变化特点,在此基础上提出相关建议。 相似文献
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本文主要讨论了网格计算的概念,介绍了国内外网格计算与网格体系架构的主要研究进展,并在此基础上研究了基于网格计算的地理信息系统——网格GIS的概念。文章在开放网格服务结构OGSA的基础上初步提出了包括资源层、中间件层、网格服务层和应用层的网格GIS体系结构,并以科学数据中心群网络设计体系为例,对网格GIS的体系结构进行深入探究。 相似文献
11.
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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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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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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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