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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:201708.00168 [pdf]

Exact Solution of the Generalized Rabi Model

Degang Zhang
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

The generalized Rabi model is exactly solved by employing the unitary transformation method in the occupation number representation. The analytical expressions for the complete energy spectrum consisting of two sub-energy spectra are presented in the whole range of all the physical parameters. Each energy level possesses twofold degeneracy and is determined by the parameter in the unitary transformation, which obeys a highly nonlinear equation. The corresponding eigenfunction is a convergent infinite series in terms of these physical parameters. Due to the level crossings between the neighboring eigenstates at certain parameter values, such the degeneracies could lead to novel physical phenomena in these quantum systems with the light-matter interaction.

提交时间: 2017-10-18 点击量59, 下载量42

3. 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

4. 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

5. 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

6. 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

7. chinaXiv:201710.00011 [pdf]

基于“一带一路”倡议的数据库供给侧改革探析

张丽英
分类: 图书馆学、情报学 >> 图书馆学

[目的/意义]数据库供需双方存在明显矛盾,亟待供给侧改革破局。[方法/过程]本文在阐述数据库供需双方存在三大矛盾的基础上,引进“一带一路”倡议的主旨和内涵,厘清国人对数据库改革存在的误区,结合供给侧改革“三去一降一补”五大任务提出数据库供给侧结构性改革的具体路径。[结果/结论]供给侧改革是数据商适应国际新形势的主动选择。数据库供给侧改革是一场供需双方的博弈,合作共赢是这场博弈的主旋律。

提交时间: 2017-10-16 点击量211, 下载量27

8. chinaXiv:201710.00008 [pdf]

基于TDTR方法的碳化硅低温导热性能实验研究

张航; 王新伟; 张中印
分类: 动力与电气工程 >> 工程热物理学

低温条件下碳化硅等半导体材料热导率的实验研究极少,数据匮乏,无法满足理论模型的优化需求。现有实验测量以接触式的稳态法导热系数测量为主,实验误差大,且低温测量成本过高。本文通过常规飞秒激光抽运探测热反射法与低温系统的有机结合,完成了4~300 K低温条件下单晶碳化硅热导率的测试及其随温度的变化规律,研究表明单晶碳化硅热导率在100 K左右存在极大值,温度低于100 K时其热导率与温度呈正相关,温度高于100 K时其热导率与温度呈负相关。极值点的位置与理论值的偏差可能是由于样品电子浓度、缺陷分布等因素影响。

提交时间: 2017-10-13 来自合作期刊:《工程热物理学报》 点击量330, 下载量32

9. chinaXiv:201710.00009 [pdf]

轴流压气机等离子体流动控制

吴云; 张海灯; 于贤君
分类: 动力与电气工程 >> 工程热物理学

作者在国际上较早开展了轴流压气机等离子体流动控制研究工作,经过近十年的研究积累,对轴流压气机等离子体流动控制建立了较为深刻的认识。本文首先简要展示了轴流压气机等离子体流动控制的部分研究进展:以压气机叶栅为研究对象,分析了等离子体激励对叶顶泄漏流抑制的规律和机制;通过数值仿真和实验,研究了等离子体激励对高负荷轴流压气机失速的流动控制规律和机制;以高速压气机叶栅为研究对象,探索了吸力面和端壁等离子体激励对高速压气机三维角区分离的流动控制规律;然后介绍了等离子体激励式压气机的概念;最后给出了对未来研究工作的展望。

提交时间: 2017-10-13 来自合作期刊:《工程热物理学报》 点击量316, 下载量28

10. chinaXiv:201710.00010 [pdf]

Chinese Color Nest Project (CCNP)i: Growing Up in China

Ning Yang; Ye He; Zhe Zhang; Hao-Ming Dong; Lei Zhang; Xing-Ting Zhu; Xiao-Hui Hou; Yin-Shan Wang; Quan Zhou; Zhu-QingGong; Li-Zhi Cao; Ping Wang; Yi-Wen Zhang; Dan-Yang Sui; TingXu1; Gao-Xia Wei; Zhi Yang; Lili Jiang; Hui-Jie Li; Ting-YongFeng
分类: 心理学 >> 实验心理学

Abstract: To face the challenges of keeping healthy in increasing population sizes of both ageing and developing people in China, a fundamental request from the public health is the development of lifespan normative trajectories of brain and behavior. This paper introduces the Chinese Color Nest Project (CCNP 2013–2022), a large-scale tenyear program of modeling brain and behavioral trajectories for human lifespan (6–85 years old). We plan to gradually collect the behavioral and brain imaging data at ages across the lifespan on nationwide and depict the normal trajectory of Chinese brain development across the lifespan, based on the accelerated longitudinal design in the coming next 10 years starting at 2013. Various psychiatric disorders have been demonstrated highly relevant to abnormal events during the neurodevelopment regarding their onset ages of first episodes. Therefore, delineation of normative growth curves of brain and cognition in typically developing children is extremely useful for monitoring, early detecting and intervention of various neurodevelopmental disorders. In this paper, we detailed the developing part of CCNP, devCCNP. It tracked 192 healthy children and adolescents (6–18 years old) in Beibei district of Chongqing for the first 5 years of the full CCNP cohort (2013–2017). To demonstrate the feasibility of implementing the longterm follow-up of CCNP, we here comprehensively document devCCNP in terms of its experimental design, sample strategies, data acquisition and storage as well as some preliminary results and data sharing roadmap for future. Specifically, we first describe the accelerated longitudinal sampling design as well as its exact ratio of sample dropping off during the data collection. Second, we present several initial findings such as canonical growth curves of cortical surface areas of a set of well-established large-scale functional networks of the human brain. Finally, together with records generated by many psychological and behavioral tests, we will provide an individual growing-up report for each family participating the program, initiating the potential guidance on the individual academic and social development. The resources introduced in the current work can provide first-hand data for a series of coming Chinese brain development studies, such as Chinese Standard MRI Brain Templates, Normative Growth Curves of Chinese Brain and Cognition as well as Mapping of Language Areas in Chinese Developing Brain. These would not only offer normative references of the atypical brain and cognition development for Chinese population but also serve as a strong force on accelerating the pace of integrating Chinese brain development into the national brain program or Chinese Brain Project.

提交时间: 2017-10-13 点击量321, 下载量28

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