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1. chinaXiv:201710.00016 [pdf]

Organization and Exploration Fined-grained Historical Knowledge on Contemporary China Based on Semantic Mining

Zhang, Zhixiong; Wang, Ying; Sun, Hui; Lei, Feng
分类: 图书馆学、情报学 >> 图书馆学

China has a huge volume of historical resources on its contemporary history. Lots of valuable knowledge are hidden in those resources and cannot be utilized easily. It is an urgent problem to mine the implicit semantic knowledge scattered in a large number of historical resources and to reorganize the historical knowledge and facts in a fined-grained manner, so that can help user to explore the historical knowledge for research and education. This paper proposes a method, which is called “Mining down, Organizing up”, to semantically represent and organize historical knowledge on contemporary China hidden in historical encyclopedia text. Based on the proposed historical ontology of contemporary Chinese, this method extracts knowledge objects and facts from the unstructured historical text items by utilizing text mining technologies, represents the historical knowledge in semantically enriched way, and interlinks the related historical knowledge objects and facts to form a historical knowledge network of the contemporary China. By mining the historical facts and the historical knowledge network, the authors get more valuable patterns from the historical knowledge which could be used to form the new organization scheme to reorganize the historical knowledge in a more vivid way. Based on this method, the authors developed a system which can represent and organize historical knowledge of contemporary China in a fined-grained manner, support user to explore historical knowledge by providing functions such as semantic retrieval, historical objects and facts clustering, visualization navigation, association analysis, and chronicle facts reconstruction etc.

提交时间: 2017-10-20 点击量6, 下载量1

2. chinaXiv:201710.00012 [pdf]

Four new ent-kaurene diterpene glucosides from Mikania micrantha

Dong, Limei; Jia, Xuchao; Luo, Qingwen; Peng, Yiming; Zhang, Qiang; Luo, Bi; Tan, jianwen
分类: 化学 >> 应用化学

Phytochemical study on the aerial parts of Mikania micrantha led to the isolation of four new ent-kaurene diterpene glucosides, β-D-glucopyranosyl-15α-(3-hydroxy-3-methylbutanoyloxy)-9β-hydroxy-ent-16-kauren-19-oate (1), β-D-glucopyranosyl-15α-(3-methylbutanoyloxy)-9β-hydroxy-ent-16-kauren-19-oate (2), β-D-glucopyranosyl-15α-(2-methylbutanoyloxy)-9β-hydroxy-ent-16-kauren-19-oate (3), β-D-glucopyranosyl-15α-(3-methyl-2-butenoyloxy)-9β-hydroxy-ent-16-kauren-19-oate (4), along with a known one, β-D-glucopyranosyl-15α-(3-hydroxy-3-methylbutanoyloxy)-ent-16-kauren-19-oate (5). Their structures were elucidated on the basis of extensive spectroscopic analysis. Compounds 1–4 are a group of C-9 hydroxylated ent-kaurene diterpene glucosides which is relatively rare in nature. These compounds selectively showed in vitro antibacterial activity against four assayed Gram-(+) and three Gram-(-) bacteria. In addition, the in vitro growth inhibitory activity of these compounds against human cancer cell lines Hela, A549, HepG-2 and MCF-7, were also tested.

提交时间: 2017-10-17 点击量580, 下载量285

3. chinaXiv:201710.00013 [pdf]

金属泡沫中填充石蜡的相变换热特性实验研究

张嘉杰; 屈治国
分类: 动力与电气工程 >> 工程热物理学

本文对金属铜泡沫填充石蜡的相变换热特征进行了实验研究,通过测试试件加热面及内部的温度响应曲线,分析了金属泡沫填充及自然对流对石蜡非稳态相变换热过程的影响。研究结果表明,采用顶部加热方式时,石蜡内部的换热以纯导热为主,而采用底部加热时,液态石蜡内的自然对流作用使相界面移动速度更快,试件内部温度一致性更好,同时在相变对流区可实现对加热面的温度控制。金属泡沫的填充可强化石蜡内的导热但抑制液态石蜡的自然对流,前者使得试件加热面温升减缓,相界面移动加快,后者则导致底部加热时石蜡的相变区分为相变导热区和相变对流区。金属泡沫的导热强化能力在试件换热中占据主导作用。

提交时间: 2017-10-17 来自合作期刊:《工程热物理学报》 点击量318, 下载量27

4. chinaXiv:201710.00014 [pdf]

聚光光伏与甲醇重整热化学互补发电系统性能研究

李文甲(1,2); 郝勇(1)
分类: 动力与电气工程 >> 工程热物理学

本文提出了太阳能光伏电池与甲醇中低温重整反应相结合的发电系统;通过太阳能的梯级利用以及物理能与化学能之间的品位耦合,太阳能净发电效率较单一光伏或甲醇热化学发电方式获得显著提升。热力学分析表明,在100~250℃C的系统运行温度范围内,系统的理论太阳能净发电效率达43.6%~44.3%(已考虑光学损失),显著高于光伏系统(22.5%)及热化学系统(32.7%)。系统约50%的太阳净发电量来自甲醇重整产物氢气,以化学能形式实现了太阳能的高效储能,且光伏、热化学发电随温度变化的相反趋势间互补达到了稳定输出的效果。此外,系统产生的电能中约25%来自太阳能,高于单一太阳能甲醇热化学发电系统的14%,对化石能源的依赖度降低。光伏与热化学互补发电为太阳能高效综合利用提供了新的思路。

提交时间: 2017-10-17 来自合作期刊:《工程热物理学报》 点击量319, 下载量26

5. chinaXiv:201710.00015 [pdf]

大功率半导体激光器散热研究综述

邓增(1,2); 沈俊(1); 戴巍(1)
分类: 动力与电气工程 >> 工程热物理学

近年来,半导体激光器功率不断提高,由之引发的散热问题已成为限制半导体激光器发展的瓶颈。芯片温度升高引起激光器性能下降,要使激光器在大功率条件下依然保持良好特性就必须强化对激光器芯片的散热。通过分析激光器芯片温度对激光器各项性能指标的影响,说明了降低芯片温度对保证激光器正常工作的重要性。鉴于流体侧的对流传热热阻在总热阻起主导作用,重点分析半导体激光器散热结构中流体侧的散热方法,并将其分为传统散热方法和新型散热方法,传统散热方法包括平板热沉散热、大通道水冷等,新型散热方法包括微通道散热、喷雾冷却、射流冲击、热管散热和液态金属散热。总结了各种方法的优缺点,从热流密度和温差两个指标评价各种散热方法,探讨其在激光器散热上的应用前景。

提交时间: 2017-10-17 来自合作期刊:《工程热物理学报》 点击量325, 下载量35

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