检索结果-南通市图书馆

Ostracod fauna across the Permian-Triassic boundary at Chongyang, Hubei Province, and its implication for the process of the mass extinction

引用

Science china Earth Sciences 2010年第6期53卷 810-817页

作者： LIU Hao1. WANG YongBiao1. YUAN AiHua2. YANG Hao1. SONG HaiJun1.& ZHANG SuXin2. key laboratory of Biogeology and Environmental Geology of Ministry of Education,{2., china 2.state key laboratory of Geological Processes and Mineral Resources,{2., china 1. key {1. of Biogeology and Environmental Geology of Ministry of Education Wuhan 430074 China2. State Key Laboratory of Geological Processes and Mineral Resources Wuhan 430074 China

Thirty species of 1. ostracod genera were identified from 440 fossil specimens isolated through the hot acetolysis of the rock samples collected across the Permian-Triassic boundary at Chongyang section. Twenty species of 6 genera are found to occur in the limestone of Changxing Formation, and 1. species of 7 genera above the main faunal mass extinction horizon. The os-tracod assemblages identified at the Chongyang section are obviously different from those previously reported in the contem-poraneous microbialites in Guangxi and Chongqing regions, not only in the ostracod components but also in the abundance of filter-feeding ostracods relative to the deposit-feeding ostracods, an indicator of the oxygen level of the seawater. This spatial difference in ostracod assemblages might reflect the diversity of oceanic environmental conditions after the end-Permian mass extinction. Ostracods disappear at 2.0 cm below and near the main mass extinction horizon, and on the top of the microbialites, respectively, showing an episodic and gradual collapse process at the Chongyang section. The carbon isotope composition is found to appear at 2.0 cm below the main mass extinction horizon, indicating the initial deterioration of oceanic environment. Fluctuation of the carbon isotope composition is obviously related with the episodic evolution of ostracod species, but not with the abundance of ostracods.

关键词： ostracod microbialite Permian-Triassic mass extinction Chongyang

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Extended multivariate public key cryptosystems with secure encryption function

引用

Science china(Information Sciences) 2011年第6期54卷 1161-1171页

作者： WANG HouZhen 1,2., ZHANG HuanGuo 1,2., WANG ZhangYi 1,2.& TANG Ming 1,2.1 The key laboratory of Aerospace Information Security and Trusted Computing, Ministry of Education, School of Computer, {2. University, {2. 430079, china 2.state key laboratory of Software Engineering, {2. University, {2. 430072. china 1. The key {1. of Aerospace Information Security and Trusted Computing Ministry of Education School of Computer Wuhan University Wuhan 430079 China2. State Key Laboratory of Software Engineering Wuhan University Wuhan 430072 China

Advances in quantum computers pose great threats on the currently used public key cryptographic algorithms such as RSA and ECC. As a promising candidate secure against attackers equipped with quantum computational power, multivariate public key cryptosystems (MPKCs) have attracted increasing attention in recently years. Unfortunately, the existing MPKCs can only be used as a multivariate signature scheme, and it remains unknown how to construct an efficient MPKC enabling secure encryption. Furthermore, some multivariate signature schemes have been shown insecure in recent years, and it is also not trivial to build MPKC which can serve as a secure signature scheme. By employing the basic MQ-trapdoors, this paper proposes a novel MPKC and shows how it can be used as a multivariate signature scheme and a multivariate encryption scheme, respectively. The goal is achieved by incorporating our new hash authentication techniques and some modification methods such as the Shamir's minus method. Thorough analysis shows that our schemes are secure and efficient. Our MPKC gives a positive response to the challenges in multivariate public key cryptography.

关键词： cryptography post-quantum cryptography MQ problem hash function

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

The refined theory of deep rectangular beams based on general solutions of elasticity

引用

Science china(Physics,Mechanics & Astronomy) 2006年第3期49卷 291-303页

作者： GAO Yang1.& WANG Minzhong2.1. College of Science,{1. Agricultural University, Beijing 1.0083,{1. 2. {2. key laboratory for Turbulence and Complex Systems and Department of Mechanics and Engi- neering Science, Peking University, Beijing 1.0871.{1. College of Science China Agricultural University Beijing 100083 China state {1. {2. for Turbulence Complex Systems Department of Mechanics Engineering Science Peking University Beijing 100871 China

The problem of deducing one-dimensional theory from two-dimensional the- ory for a homogeneous isotropic beam is investigated. Based on elasticity theory, the re- fined theory of rectangular beams is derived by using Papkovich-Neuber solution and Lur’e method without ad hoc assumptions. It is shown that the displacements and stresses of the beam can be represented by the angle of rotation and the deflection of the neutral surface. Based on the refined beam theory, the exact equations for the beam without transverse surface loadings are derived and consist of two governing differential equations: the fourth-order equation and the transcendental equation. The approximate equations for the beam under transverse loadings are derived directly from the refined beam theory and are almost the same as the governing equations of Timoshenko beam theory. In two ex- amples, it is shown that the new theory provides better results than Levinson’s beam the- ory when compared with those obtained from the linear theory of elasticity.

关键词： deep rectangular beams,the refined theory,Papkovich-Neuber solution,Lur'e method,governing equation

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

A Hybrid Genetic Algorithm for Reduct of Attributes in Decision System Based on Rough Set Theory

引用

wuhan University Journal of Natural Sciences 2002年第3期7卷 285-289页

作者： Dai Jian\|hua 1,2., Li Yuan\|xiang 1,2.,Liu Qun 3 1. state key {2. of Software Engineering, wuhan University, wuhan 430072. Hubei,china 2. School of Computer, wuhan University, wuhan 430072. Hubei, china 3. School of Computer Science, wuhan University State Key Laboratory of Software Engineering Wuhan Hubei China (GRID:grid.49470.3e) (ISNI:***) wuhan University School of Computer Wuhan Hubei China (GRID:grid.49470.3e) (ISNI:***) Chongqing University of Posts & Telecommunications School of Computer Science Chongqing China (GRID:grid.411587.e) (ISNI:***)

Knowledge reduction is an important issue when dealing with huge amounts of data. And it has been proved that computing the minimal reduct of decision system is NP-complete. By introducing heuristic information into genetic algorithm, we proposed a heuristic genetic algorithm. In the genetic algorithm, we constructed a new operator to maintaining the classification ability. The experiment shows that our algorithm is efficient and effective for minimal reduct, even for the special example that the simple heuristic algorithm can’t get the right result.

关键词： rough set reduction genetic algorithm heuristic algorithm

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

The refined theory of transversely isotropic piezoelectric rectangular beams

引用

Science china(Physics,Mechanics & Astronomy) 2006年第4期49卷 473-486页

作者： GAO Yang1.& WANG Minzhong2.1. College of Science,{1. Agricultural University, Beijing 1.0083,{1. 2. {2. key laboratory for Turbulence and Complex Systems and Department of Mechanics and Engi- neering Science, Peking University, Beijing 1.0871.{1. 1. College of Science China Agricultural University Beijing 100083 China 2. {1. key {2. for Turbulence and Complex Systems and Department of Mechanics and Engineering Science Peking University Beijing 100871 China

The problem of deducing one-dimensional theory from two-dimensional theory for a transversely isotropic piezoelectric rectangular beam is investigated. Based on the piezoelasticity theory, the refined theory of piezoelectric beams is derived by using the general solution of transversely isotropic piezoelasticity and Lur'e method without ad hoc assumptions. Based on the refined theory of piezoelectric beams, the exact equations for the beams without transverse surface loadings are derived, which consist of two governing differential equations: the fourth-order equation and the transcendental equation. The approximate equations for the beams under transverse loadings are derived directly from the refined beam theory. As a special case, the governing differential equations for transversely isotropic elastic beams are obtained from the corresponding equations of piezoelectric beams. To illustrate the application of the beam theory developed, a uniformly loaded and simply supported piezoelectric beam is examined.

关键词： rectangular beams, the refined theory, piezoelectric, transversely isotropic.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Preparation of MWNTs/Al_2._3 composites and their mechanical and electrical properties

引用

Science china(Technological Sciences) 2005年第6期48卷 622-631页

作者： FAN Jinpeng1.2. ZHAO Daqing1.2. XU Zening1.2.& WU Minsheng1.2.1. Department of Mechanical Engineering, Tsinghua University, Beijing 1.0084, china 2. key {2. for Advanced Manufacturing by Materials Processing technology, Tsinghua University, Beijing 1.0084, china 1. Department of Mechanical Engineering Tsinghua University 100084 Beijing China 2. {1. laboratory for Advanced Manufacturing by Materials Processing {2. Tsinghua University 100084 Beijing China

The mechanical and electrical properties of MWNTs/Al2.3 composite prepared fabricated by hot pressing are investigated. The relation between properties and microstructure of composites is also discussed. With 4wt% MWNTs as reinforcement, the fracture toughness of composite obtained reaches 5.55 MPa·m1.2. which is 80% higher than that of pure Al2.3 obtained in the same conditions. The main toughening mechanism is CNTs’ pinning alumina grain boundaries, and the pullout of CNTs takes effect also. Through adding 2.t% MWNTs and altering the mix method, the fracture toughness of the composite obtained is 3.97 MPa·m1.2. Furthermore, the electrical resistivity is as low as 8.4×1.?3 ?·m, decreasing by 1. orders of magnitude compared with pure alumina ceramics. The function of CNTs in composite is related to the distribution state of CNTs in composite, and the distribution state of CNTs in matrix is dependent on preparation procedures.

关键词： MWNTs, alumina, composite, fracture toughness, electrical properties.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Numerical simulation of the influences of sinker weight on the deformation and load of net of gravity sea cage in uniform flow

引用

Acta Oceanologica Sinica 2006年第3期25卷 125-137页

作者： LI Yucheng 1.2. , ZHAO Yunpeng 1., GUI Fukun 1., TENG Bin 1., DONG Guohai 1.1. {1. key {2. of Coastal and Offshore Engineering, Dalian University of technology, Dalian 1.602., china 2. R&D Center of Civil Engineering technology, Dalian University, Dalian 1.662., china state {1. {2. of Coastal and Offshore Engineering Dalian University of Technology Dalian 116024 China

A numerical model for determining fishing net configuration and load is developed, based on the lumped masses method. The model is used to analyze the influences on the net of gravity sea cage by different sinker weights in uniform flow. The net of gravity sea cage is simulated under different current velocities and sinker weights. In order to verify the validity of the numerical results, model test results made by Lader and Enerhaug are cited and compared with the numerical ones. The results of numerical simulation agree well with the experimental ones and the agreement is within an error range of 1.% under different velocities and sinker weights. The numerical results indicate that increasing the sinker weight can effectively reduce the net deformation, but the total drag force on the net will increase accordingly. Results will give references for better knowledge of the hydrodynamic behavior of gravity sea cage.

关键词： sea cage numerical simulation lumped mass method sinker weight

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Semi-Supervised Classification based on Gaussian Mixture Model for remote imagery

引用

Science china(Technological Sciences) 2010年第S1期53卷 85-90页

作者： XIONG Biao1.ZHANG XiaoJun1.& JIANG WanShou1.2.1.{1. key {2. of Information Engineering in Surveying,Mapping and Remote Sensing,wuhan University,wuhan 430079,china 2.{1. key {2. of Remote Sensing Science,Beijing,china 1. state {1. {2. of Information Engineering in Surveying Mapping and Remote Sensing Wuhan University Wuhan 430079 China2. State Key Laboratory of Remote Sensing Science Beijing China

Semi-Supervised Classification (SSC),which makes use of both labeled and unlabeled data to determine classification borders in feature space,has great advantages in extracting classification information from mass *** this paper,a novel SSC method based on Gaussian Mixture Model (GMM) is proposed,in which each class’s feature space is described by one *** show the proposed method can achieve high classification accuracy with small amount of labeled ***,for the same accuracy,supervised classification methods such as Support Vector Machine,Object Oriented Classification,*** be provided with much more labeled data.

关键词： remote sensing image classification Semi-Supervised Classification Gaussian Mixture Model EM algorithms

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Preparation of InSb nanocrystals embedded in SiO_2.thin films

引用

Chinese Science Bulletin 1998年第19期43卷 1610-1615页

作者： ZHU Kaigui 1. SHI Jianzhong 1. WEI Yanfeng 2.and ZHANG Lide 1.1. Institute of Solid {1. Physics, Chinese Academy of Science, Hefei 2.0031. china 2. {1. key laboratory of Surface Physics, Fudan University, Shanghai 2.0433, china Institute of Solid state Physics Chinese Academy of Science Hefei China state {1. {2. of Surface Physics Fudan University Shanghai China

InSb nanocrystals embedded in SiO 2.thin films were prepared by rf magnetron cosputtering technique. THe observation by transmission electron microscope showed that InSb nanocrystals dispersed uniformly in SiO-2.matrices. InSb nanocrystals with different sizes can be obtained by changing the annealing condition. The average size of InSb nanocrystals depended on annealing temperature and time, but not on the t 1.3 rules. X-ray photoelectron spectroscopy and X-ray diffraction were also applied to the analyses of the composite thin films.

关键词： InSb nanocrystals radio-frequency sputtering quantum confinement.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Preparation and Microstructural Analysis of Ti_2.lC/TiAl(Nb) Composite

引用

Journal of wuhan University of {1.(Materials Science) 2007年第1期22卷 7-11页

作者：岳云龙 Shod of Materials Science and technology Jinan University

By using the spark plasma sintering process, Ti2.lC/TiAlcomposite with the addition of Niobium （Nb） was prepared in-situ and the microstructure of Ti2.lC/TiAl （Nb） composite was investigated by means of transmission electron microscopy （TEM） and high-resolution electron microscopy （HREM）. The results indicate that new-formed Ti2.IC particles disperse with a high degree of uniformity and well combine with the matrix. In the area of phase interface the d-spaces of Ti2.lC （1.0） and TiAI （1.0） were measured as 0.2.48 nm and 0.2.91.nm,respectively. The atom arrangement beside the interface was only partly corresponding, existing in semicoherent state. On the contrary, in the area of grain interface the d-spaces of TiAl （1.0） and TiAl （1.0） were measured as 0.2.62.nm and 0.2.31.nm,respectively and the atom arrangement beside the interface was almost corresponding, existing in coherent state.

关键词： Ti2.lC/TiAl CNb) composite interface semicoherent structure coherent structure

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：