检索结果-南通市图书馆

Teleconnection between the Indian summer monsoon onset and the Meiyu over the Yangtze River Valley

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china Earth sciences 2008年第7期51卷 1021-1035页

作者： LIU YunYun1,2,3 & DING YiHui2 1 chinese academy of Meteorological sciences, beijing 100081, china 2 National Climate Center, beijing 100081, china 3 Graduate University of chinese academy of sciences, beijing 100049, china chinese academy of Meteorological sciences Beijing China National Climate Center Beijing China Graduate University of chinese academy of sciences Beijing China

Based on the Indian and chinese precipitation data and the NCEP-NCAR reanalysis circulation data, the relationship between the Indian summer monsoon (ISM) onset and the Meiyu over the Yangtze River Valley has been discussed by the methods of correlation analysis and composite analysis. The results show that the date of ISM onset over Kerala in the southwestern coast of the Indian Peninsula is about two weeks earlier than the beginning of the Meiyu over the Yangtze River Valley. After the outbreak of ISM, the teleconnection mode sets up from the western coast of India via the Bay of Bengal (BOB) to the Yangtze River Valley and southern Japan. It is different both in time and space from the telecon- nection mode which is from the northwest of India via the Tibetan Plateau to northern china. The for- mer mode is defined as the "south" teleconnection of the Asian summer monsoon, forming in the pe- riod of ISM onset; while the latter mode is called the "north" teleconnection, mainly occurring in the Asian monsoon culminant period. During the process of the "south" teleconnection’s formation, the Asian monsoon circulation has experienced a series of important changes: ISM onset, the northward movement of the south Asia high (SAH), the onset vortex occurrence, the eastward extension of the stronger tropical westerly belt, and the northeastward jump of the western Pacific subtropical high (WPSH), etc. Consequently, since ISM sets up over Kerala, the whole Asian continent is covered by the upper SAH after about two weeks, while in the mid- and lower troposphere, a strong wind belt forms from the Arabian Sea via the southern India, BOB and the South china Sea (SCS), then along the western flank of WPSH, to the Yangtze River Valley and southern Japan. With the northward moving of the subtropical jet streams, the upper westerly jet stream and the low level jet have been coupled ver- tically over east Asia, while the Yangtze River Valley happens to locate in the ascending motion

关键词： Indian summer monsoon (ISM) the Meiyu over the Yangtze River Valley teleconnection mode

ON COMPLEX DYNAMIC CONTROL SYSTEMS

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science & Complexity 2003年第3期16卷 350-357页

作者： CHENG Daizhan (institute of Systems Science, chinese academy of sciences, beijing 100080, china) institute of Systems Science Chinese Academy of Sciences 北京 100080

This paper presents some recent works on the control of dynamic systems,which have certain complex properties caused by singularity of the nonlinear structures,structure^varyings, or evolution process etc. First, we consider the structure singularity of nonlinear control systems. It was revealed that the focus of researches on nonlinear control theory is shifting from regular systems to singular systems. The singularity of nonlinear systems causes certain complexity. Secondly, the switched systems are considered. For such systems the complexity is caused by the structure varying. We show that the switched systems have significant characteristics of complex systems. Finally, we investigate the evolution systems. The evolution structure makes complexity, and itself is a proper model for complex systems.

关键词： relative degree byrnes-isidori normal form center manifold switchedsystems evolution system

Design of secure operating systems with high security levels

在线全文

学校读者我要写书评

暂无评论

Science in china(Series F) 2007年第3期50卷 399-418页

作者： QING SiHan1,2 & SHEN ChangXiang3 1 institute of Software, chinese academy of sciences, beijing 100080, china 2 School of Software and Microelectronics, Peking University, beijing 102600, china 3 institute of Computing Technology, Navy, beijing 100841, china institute of Software Chinese Academy of Sciences Beijing China School of Software and Microelectronics Peking University Beijing China institute of Computing Technology Navy Beijing China

Numerous Internet security incidents have shown that support from secure operating systems is paramount to fighting threats posed by modern computing environments. Based on the requirements of the relevant national and international standards and criteria, in combination with our experience in the design and development of the ANSHENG v4.0 secure operating system with high security level （hereafter simply referred to as ANSHENG OS）, this paper addresses the following key issues in the design of secure operating systems with high security levels： security architecture, security policy models, and covert channel analysis. The design principles of security architecture and three basic security models： confidentiality, integrity, and privilege control models are discussed, respectively. Three novel security models and new security architecture are proposed. The prominent features of these proposals, as well as their applications to the ANSHENG OS, are elaborated. Cover channel analysis （CCA） is a well-known hard problem in the design of secure operating systems with high security levels since to date it lacks a sound theoretical basis and systematic analysis approach. In order to resolve the fundamental difficulties of CCA, we have set up a sound theoretical basis for completeness of covert channel identification and have proposed a unified framework for covert channel identification and an efficient backward tracking search method. The successful application of our new proposals to the ANSHENG OS has shown that it can help ease and speedup the entire CCA process.

关键词： secure operating systems with high security levels architecture security model covert channel analysis

RHEOLOGICAL MODIFICATION OF EPOXY RESINS WITH NANO SILICA PREPARED BY THE SOL-GEL process

在线全文

学校读者我要写书评

暂无评论

chinese Journal of Polymer Science 1999年第3期17卷 253-257页

作者： Xia Wang Jiang Li Cheng-fen Long Yun-zhao Yu PCLCC institute of Chemistry, chinese academy of sciences, beijing 100080, china PCLCC is the Polymer Chemistry Laboratory, chinese academy of sciences and china Petro-Chemica Corporation 中科院化学所高分子化学联合开放实验室北京 100080 中科院化学所高分子化学联合开放实验室北京

Nano silica-modified epoxy resins were synthesized by the sol-gel process, The materials have the morphological structure of nano particales dispersed in the epoxy matrix. The dispersed phase formed a physical network in the resin and thus influenced the rheological behavior greatly. However, the nano silica did not show a significant influence on the mechanical properties of the cured resins.

关键词： epoxy resin nano silica mechanical properties rheology sol-gel process

Follicular growth,differentiation and atresia

在线全文

学校读者我要写书评

暂无评论

chinese Science Bulletin 2003年第17期48卷 1786-1790页

作者： JIN Xuan & LIU Yixun State Key Laboratory of Reproductive Biololgy, institute of Zoology, chinese academy of sciences, beijing 100080, china State Key Laboratory of Reproductive Biololgy Institute of Zoology Chinese Academy of Sciences Beijing 100080 China

Only limited numbers of primordial follicles in mammalian ovary grow and differentiate to reach the stage of dominate follicles and ovulate. 99% of the follicles in the ovary undergo atresia at various stages of development. Regulation of follicular growth, development and atresia is a complex process and involves interactions between endocrine factors and intraovarian regulators. This review summa-rized:ⅰ) FSH may not be a survival factor in regulating slow-growing preantral follicles. Some locally produced growth factors, activin and orphan receptors might play a more important role at this stage. ⅱ) Estrogen, activin/ inhibin and follistatin coordinate with FSH to regulate and control follicle differentiation. ⅲ) There are two types of follicular atresia induced by apoptosis which originates from GC or oocyte, respectively. Early translation of tPA mRNA into tPA protein in oocyte may be associated with oocyte apoptosis.

关键词：哺乳动物原始卵泡卵泡生长粒状细胞细胞分化

Variations of δ^(18)O in precipitation from the Muztagata Glacier, East Pamirs

在线全文

学校读者我要写书评

暂无评论

Science china Earth sciences 2006年第1期49卷 36-42页

作者： LI Zhen1, YAO Tandong1,2, TIAN Lide1,2, XU Baiqing1,2 & Wu Guangjian2 1. Key Laboratory of Cryosphere and Environment, Jointly Established by Cold and Arid Regions Environmental and Engi-neering Research institute and institute of Tibetan Plateau Research, chinese academy of sciences and chinese academy of Meteorological sciences, china Meteorological Administration, CAS, Lanzhou 730000, china 2. Laboratory of Environment and process on Tibetan Plateau, institute of Tibetan Plateau Research, chinese academy of sciences, beijing 100085, china Key Laboratory of Cryosphere and Environment Jointly Established by Cold and Arid Regions Environmental and Engineering Research Institute and Institute of Tibetan Plateau Research Chinese Academy of Sciences and Chinese Academy of Meteorological Sciences China Meteorological Administration Lanzhou China Laboratory of Environment and process on Tibetan Plateau Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing China

Expeditions to Muztagata (in the eastern Pamirs) during the summer seasons of2002 and 2003 collected precipitation samples and measured their oxygen isotopes. The δ^(18)O inprecipitation displays a wide range, varying from -17.40per thousand to +1.33per thousand inJune—September 2002 and from -22.31per thousand to +4.59per thousand in May—August 2003. Theδ^(18)O in precipitation correlates with the initial temperature of precipitation during theobserving periods. The positive correlation between δ^(18)O and temperature suggests that δ^(18)Ocan be used as an indicator of temperature in this region. The δ^(18)O values in fresh-snow samplescollected from two snow events at different elevations on the Muztagata Glacier show a strong''altitude effect'', with a ratio of nearly -0.40per thousand per 100 m from 5500 m to 7450 m.

关键词： Muztagata, δ18O, temperature, altitude effect.

PROBABILISTIC ANALYSIS OF GALERKIN-LIKE METHODS FOR THE FREDHOLM EQUATION OF THE SECOND KIND

在线全文

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 1998年第5期16卷 445-456页

作者： Tian-zi Jiang (School of Mathematics, The University of New South Wales, Sydney 2052, Austmlia National Laborutory of Pattern Recognition, institute of Automation,chinese academy of sciences, beijing 100080, china) 中科院自动化所北京

This paper deals with the approximate solution of the Fredholm equation u TKu = f of the second kind from a probabilistic point of view. With Wiener typemeasures on the set of kernels and free terms we determine statistical features of the approximation process, i.e., the most likely rate of convergence and the dominating individual behavior. The analysis carried out for a kind of Galerkin-like method.

关键词： Probabilistic analysis fredholm equation galerkin-like method abstract wiener space

Observation of the Turbulent Burst near ASheared Air-Water Interface

在线全文

学校读者我要写书评

暂无评论

Communications in Nonlinear Science and Numerical Simulation 1999年第2期4卷 94-99页

作者： Shuangfeng WANG Fu JIA Zhennan NIU Zhangzhi WU(institute of Mechanics, chinese academy of sciences, beijing 100080, china)(State Key Laboratory for Turbulence Research, Peking University, beijing 100871,china) institute of Mechanics Chinese Academy of Sciences Beijing 100080 China

The turbulent burst under a sheared air-water interface was experimentally investigated using hydrogen bubble visualization technique. The surface shear wasimposed by an airflow over the water flow which was kept free from surface waves. Resultsshow that the wind shear has the main influence on the bursting events. At relativelyhigh shear rates, the flow near the interface is dominated primarily by intermittent bursting events. The general features of bursting processes are described in some detail. Theobserved bursting events show qualitative similarities with those occurring in near-wallturbulence. However, a few distinctive phenomena were also observed, including the existence of vertical vortices and thickening process of the boundary layer, which appear tobe associated with the Characteristics of air-water interface.

关键词： air-water interface turbulent burst flow-visualization

Dislocations in the Crystallites of Nanocrystalline α-Fe—A Molecular Dynamics Study

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 1996年第6期12卷 476-478页

作者： Zhiying CHEN and Jiaqans DING (Lab. on Non-linear Mechanics of Continuous Media, institute of Mechanics, chinese academy of sciences,beijing 100080, china)(To whom correspondence should be addressed) Lab. on Non-linear Mechanics of Continuous Media Institute of Mechanics Chinese Academy of Sciences Beijing 100080 China

Molecular dynamics simulations are carried out in order to Study the atomic structure of crystalline component of nanocrystalline α-Fe when it is consolidated from small grains. A two-dimensional computational block is used to simulate the consolidation process. All the preset dislocations in the original grains glide out of them in the consolidation process, but new dislocations can generate when the grain size is large enough. It shows that dislocations exist in the consolidated material rather than in the original grains. Whether dislocations exist in the crystalline component of the resultant model nano-material depends upon grain size. The critical value of grain size for dislocation generation appears to be about 9 nm. This result agrees with experiments qualitatively.

关键词： Fe A Molecular Dynamics Study Dislocations in the Crystallites of Nanocrystalline