检索结果-南通市图书馆

Petrogenesis of Indosinian volcanic rocks in Songpan-Garze fold belt of the northeastern Tibetan Plateau:New evidence for lithospheric delamination

引用

Science china Earth Sciences 2010年第9期53卷 1316-1328页

作者： CAI HongMing1,2, ZHANG HongFei1,2, XU WangChun1,2, SHI ZhangLiang1,2 & YUAN HongLin3 1 state key laboratory of Geological Processes and Mineral Resources, Wuhan 430074, china 2 Faculty of Earth Sciences, china university of Geosciences, Wuhan 430074, china 3 state key laboratory of Continental Dynamics, Northwest university, xi’an 710069, china 1. state key laboratory of Geological Processes and Mineral Resources Wuhan 430074 China2. Faculty of Earth Sciences China University of Geosciences Wuhan 430074 China3. State Key Laboratory of Continental Dynamics Northwest University Xi’an 710069 China

In the Songpan-Garze fold belt of the northeastern Tibetan Plateau, an Indosinian lithospheric delamination model has been proposed, based on previous investigation of widespread granitoids. However, this model lacks comparable information from volcanism in the area. During the Indosinian delamination in the Songpan-Garze fold belt, whether partial melting of litho- spheric mantle taken place is debated. This paper reports U-Pb zircon LA-ICP-MS ages, geochemical and Sr-Nd-Hf isotopic compositions from the Aba and Wasai calc-alkaline volcanic rocks in the central Songpan-Garze fold belt. Obtained magma crystallization ages are 210±3 Ma for the Aba andesite and 205±1 Ma for the Wasai andesite. These are consistent with magma crystallization ages of the late Indosinian granitoids in the Songpan-Garze fold belt that formed in a post-collisional tectonic setting. The Aba and Wasai andesites have distinct geochemical singnatures. The former has higher Al2O3, K2O, Rb but lower Na2O, Ba and Sr contents, suggesting differences in their magmatic evolution. The Aba andesites have ISr values of 0.7070-0.7076 and εNd(t) values of -3.9 to -5.3, and the Wasai andesites have ISr values of 0.7075-0.7077 and εNd(t) values of -3.6 to -3.9. Zircons show εHf(t) values of -3.7 to 0.3 for the Aba andesites and -2.7 to 5.5 for the Wasai andesites. Geochemical and Sr-Nd-Hf isotopic compositions indicate that fractional crystallization and crustal assimilation processes are not key roles for their magma evolution, implying that their chemical compositions are those of primary melts. We suggest that the magma of the Aba andesites originated predominantly from a crustal source, with a minor mantle-derived component. The source region of the magma was likely at the crust-mantle boundary. The magma of the Wasai andesites resulted from partial melting of lithospheric mantle, which was probably metasomatized by fluids so that it was amphibole bearing. The petrogenesis of the Aba and Wasai andesite

关键词： volcanism U-Pb dating geochemistry petrogenesis lithospheric delamination Songpan-Garze fold belt

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

Solute Redistribution in Directional Melting Process

引用

Journal of Materials Science & Technology 2000年第5期16卷 514-516页

作者： Wanqi JIE+ and xiping GUO (state key laboratory of Solidification Processing, Northwestern Polytechnical university, xi’an 710072, china) state key laboratory of Solidification Processing Northwestern Polytechnical University Xi'an 710072 China

The solute redistribution in directional melting process is theoretically studied. Based on quantitative evaluations, *** distribution in liquid and a quasi-steady solute distribution in solid are supposed. The discussion on the solute balance comes to a simple model for the solute redistribution in directional melting process. As an example, the variation of liquid composition during melting process of carbon steel is quantitatively evaluated using the model. Results show that the melting of an alloy starts at solidus temperature, but approaches the liquidus temperature after a very short transient process.

关键词： Solute Redistribution in Directional Melting Process

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

Kinetic limit for incubation period of primary phase produced by the combination reaction between two solid heterogeneous pure metals

引用

Science china(Technological Sciences) 2008年第12期51卷 2232-2243页

作者： xiONG JiangTao1,2,LI JingLong1,ZHANG FuSheng1,LIN xin2 & HUANG WeiDong2 1 Shaanxi key laboratory of Friction Welding Technologies,Northwestern Polytechnical university,xi’an 710072,china 2 state key laboratory of Solidification Processing,Northwestern Polytechnical university,xi’an 710072,china Shaanxi key laboratory of Friction Welding Technologies Northwestern Polytechnical University Xi’an 710072 China state key laboratory of Solidification Processing Northwestern Polytechnical University Xi’an 710072 China

An irreversible thermodynamics model was constructed to study the combination reaction of two heterogeneous pure metals in diffusion bonding based on the theorem of minimum entropy production and the Curie *** correlation between the irreversible reaction and diffusion was discussed,which provided the kinetic inevitability of an incubation period of a primary *** analytical descriptions of the incubation period and the kinetically critical grain size of the primary phase were *** of the experimental results of Al/Mo interfacial reaction with the calculations indicated that the performed theoretical analysis was reliable.

关键词： incubation period primary phase interfacial reaction irreversible thermodynamics

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 microtine distribution and its environmental significance since the Middle Pleistocene in Zhangping Caves of the Qinling Mountains

引用

Science china Earth Sciences 2008年第2期51卷 294-299页

作者： LI Yongxiang1 & XUE xiangXu1,2 1 state key laboratory of Continental Dynamics, Department of Geology, Northwest university, Institute of Cenozoic Geology and Environment, xi’an 710069, china 2 Institute of Earth Environment, state key laboratory of Loess and Quaternary Geology, Chinese Academy of Sciences, xi’an 710075, china 1. state key laboratory of Continental Dynamics Department of Geology Northwest University Institute of Cenozoic Geology and Environment Xi’an 710069 China 2. Institute of Earth Environment State Key Laboratory of Loess and Quaternary Geology Chinese Academy of Sciences Xi’an 710075 China

Three microtine species are recovered from the Zhangping Caves of the Qingling Mountains, namely Microtus oeconomus, Caryomys inez and Caryomys eva. They are climate-sensitive ones with different ecological habits, therefore their distribution well corresponds to environmental variations. Statistical comparison of the distribution of fossil microtines and their counterparts nowadays displays that the climate variation of the studied area and its contiguity since the middle Pleistocene are: warm and humid at 493 ka ago, cool and humid at 259 ka ago―cold and humid at 205 ka ago―cool and humid at 28 ka ago, and warm and dry at present.

关键词： environmental variation since Middle Pleistocene microtine fossils Zhangping Caves of the Qinling Mountains

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

Paleoenvironments indicated by the fossil mammalian assemblages from red clay-loess sequence in the Chinese Loess Plateau since 8.0 Ma B.P.

引用

Science china Earth Sciences 2006年第5期49卷 518-530页

作者： XUE xiangxu1,2, ZHANG Yunxiang1,2 & YUE Leping1,2 1. state key laboratory of Continent Dynamics (Northwest university), Institute of Cenozoic Geology and Environment, De- partment of Geology, Northwest university, xi’an 710069, china 2. Institute of Earth Environment, state key laboratory of Loess and Quaternary Geology, Chinese Academy of Sciences, xi’an 710075, china 1. state key laboratory of Continent Dynamics (Northwest university) Institute of Cenozoic Geology and Environment Department of Geology Northwest University Xi’an 710069 China 2. Institute of Earth Environment State Key Laboratory of Loess and Quaternary Geology Chinese Academy of Sciences Xi’an 710075 China

Information from eleven profiles of eolian earthy red silty clay and loess of the middle of the Late Miocene to Holocene age have been studied and correlated. A complete summary profile with projected isotopic ages and fossil-bearing beds has been assembled. The profile is subdivided into 12 stratigraphic units proceeding from the lower (older) to the upper (younger) one. The character of mammalian assemblages contained in each unit was analyzed and the corresponding pa- leo-climatic environments were deduced. The environmental character of each period and the change from the middle of the Late Miocene at about 8.0 Ma B.P. up to the Holocene progressed from the hot semiarid and semi-moist, warmer-moist, warm-moister of the Late Miocene. To slightly less warm moist, cool-dry, slight-warmer-moister of the Pliocene; later the cool to cold dry periods alternated frequently with the mild semiarid and semi-moist periods of the Quaternary. Vegetation progressed from the grasslands with sparse woods, wooded shrub-grasslands and subtropical forest-grasslands of the Late Miocene age to sparse grasslands and dry grasslands of the Pliocene; and to sparse grasslands, dry grasslands and tundras of the Quaternary. The climate changes in the Neogene were of low-amplitute in a generally warm-humid background. Those of the Quaternary were of higher am- plitude with a longer phase. Cool or cold dry and slightly warm semiarid and semi-moist climates al- ternated on a generally cool-dry background. The tendency since the start of the Quaternary was the change to more northern and western shift in the Loess Plateau, with progressively cooler and dryer conditions. The dramatic uplift of the Qinghai-xizang (Tibet) Plateau and the forming and expansion of the Arctic ice sheet might be the main reasons of the more pronounced changes in the Quaternary.

关键词： paleoenvironment, mammalian fossils, eolian red clay-loess sequence, Loess Plateau.

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

key Technologies for High Speed WLAN

引用

ZTE Communications 2006年第2期4卷 19-22页

作者： Chen Yanhui (state key Lab of integrated Service networks, xidian university, xi’an 710071, china)

The rapid development of Wireless Local Area network (WLAN) has not yet broken the bottleneck that the low transmission speed hinders the further development of WLAN. Now, some key technologies for next generation mobile communications can solve the problem by supporting high-speed transmission and ensuring reliable performance. IEEE 802.11n has made general amendment to 802.11. Based on IEEE 802.11n, the transmission speed can be doubled by the application of Orthogonal Frequency Division Multiplexing (OFDM) and Multiple Input Multiple Output (MIMO) technologies on the physical layer. In addition, the enhanced Medium Access Control (MAC) system performance, optimized data frame and improved network throughput can all be achieved by the adoption of frame convergence, Transmission Opportunity (TXOP) and block-acknowledge technologies on the MAC layer. A new error correction method, called Low Density Parity Check Code (LDPC), can also be adopted for the receiver to enjoy low Bit Error Ratio (BER) with low S/N, thus improving signal coverage.

关键词： key Technologies for High Speed WLAN IEEE LDPC TXOP MIMO MAC OFDM STBC MPDU

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

Microstructures and mechanical properties of directionally solidified multi-element Nb-Si alloy

引用

Progress in Natural Science:Materials International 2011年第2期21卷 146-152页

作者： Qiang HUANG~(1,2),xi-ping GUO~2,Yong-wang KANG~1,Jin-xia SONG~1,Shi-yu QU~1,Ya-fang HAN~1 1.National key laboratory of Science and Technology on Advanced High Temperature Structural Materials, Beijing Institute of Aeronautical Materials,Beijing 100095,china 2.state key laboratory of Solidification Processing,Northwestern Polytechnical university,xi'an 710072,china [a] National key laboratory of Science and Technology on Advanced High Temperature Structural Materials Beijing Institute of Aeronautical Materials Beijing 100095 China [b] state key laboratory of Solidification Processing Northwestern Polytechnical University Xi'an 710072 China

Nb-Si system in-situ composites with nominal composition of Nb-21Ti-16Si-7Cr-3Al-2Hf（mole fraction,%） were prepared by directional solidification technology in an optical floating zone furnace at the growth rates of 3,5,8 and 12 mm/*** microstructures and mechanical properties were investigated as a function of the growth *** results show that the solidification microstructures consist of Nb solid solution（Nbss）,α-Nb5Si3andβ-*** with high aspect ratio grow continuously and straightly when the growth rate is 5mm/h;lower or higher growth rates are disadvantageous for the formation of favorable directional *** compressive strength at 1 250℃and room-temperature fracture toughness of the specimen with the growth rate of 5 mm/h that exhibits excellent mechanical properties are 415 MPa and 22.4 MPa·m1/2,respectively.

关键词： Nb-Si system in-situ composite directional solidification microstructure mechanical property

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

Chosen Ciphertext Secure Identity-Based Broadcast Encryption in the Standard Model

引用

Journal of Shanghai Jiaotong university(Science) 2011年第6期16卷 672-676页

作者：孙瑾胡予濮张乐友 key laboratory of Computer network and Information Security Xidian University Department of Application Mathematics Xi'an University of Technology

To give concurrent consideration both the efficiency and the security(intensity of intractable problem) in the standard model,a chosen ciphertext secure identity-based broadcast encryption is *** the chosen ciphertext security model,by using identity(ID) sequence and adding additional information in ciphertext,the self-adaptive chosen identity security(the full security) and the chosen ciphertext security are gained *** reduction of scheme's security is the decisional bilinear Diffie-Hellman(BDH) intractable assumption,and the proof of security shows that the proposed scheme is indistinguishable against adaptive chosen ciphertext attacks in the standard model under the decisional BDH intractable *** the security level is improved,and it is suitable for higher security environment.

关键词： the standard model provably secure broadcast encryption the chosen ciphertext security the self-adaptive chosen identity security

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

Geochemistry of the high-Mg andesites at Zhangwu, western Liaoning: Implication for delamination of newly formed lower crust

引用

Science china Earth Sciences 2007年第12期50卷 1773-1786页

作者： HUANG Hua1,GAO Shan1,2,HU ZhaoChu1,LIU xiaoMing2 & YUAN HongLing2 1 state key laboratory of Geological Processes and Mineral Resources,china university of Geosciences,Wuhan 430074,china 2 state key laboratory of Continental Dynamics,Department of Geology,Northwest university,xi’an 710069,china 1. state key laboratory of Geological Processes and Mineral Resources China University of Geosciences Wuhan 430074 China 2. state key laboratory of Continental Dynamics Department of Geology Northwest University Xi’an 710069 China

Ten volcanic samples at Zhangwu,western Liaoning Province,North china were selected for a sys-tematic geochemical,mineralogical and geochronological study,which provides an opportunity to ex-plore the interaction between the continental crust and mantle beneath the north margin of the North china *** one basalt sample(SiO2= 50.23%),the other nine samples are andesitic with SiO2 contents ranging from 53% to 59%.They have relatively high MgO(3.4%―6.1%,Mg#=50―64) and Ni and Cr contents(Ni 27×10?6―197×10?6,Cr 51×10?6―478×10?6).Other geochemical characteristics of Zhangwu high-Mg andesites(HMAs) include strong fractionation of light rare earth elements(LREE) from heavy rare earth elements(HREE),and Sr from Y,with La/Yb greater than 15,and high Sr/Y(34― 115).Zircons of andesite YX270 yield three age groups with no Precambrian age,which precludes ori-gin of the Zhangwu HMAs from the partial melting of the Precambrian *** oldest age group peaking at 253 Ma is interpreted to represent the collision of the Siberia block and the North china block,resulting in formation of the Central Asian orogenic belt by closure of the Mongol-Okhotsk *** intermediate age group corresponds to the basalt underplating which caused the wide-spread coeval granitoids in the North china craton with a peak 206Pb/238U age of 172 *** youngest age group gives a 206Pb/238U age of 126±2 Ma,which is interpreted as the eruption age of the Zhangwu *** high 87Sr/86Sri(126 Ma)>0.706 and low εNd(t)= ?6.36―?13.99 of the Zhangwu HMAs are distinct from slab *** common presence of reversely zoned clinopyroxene phenocrysts in the Zhangwu HMAs argues against the origin of the Zhangwu HMAs either from melting of the water saturated mantle or melting of the lower *** light of the evidence mentioned above,the envisaged scenario for the formation of the Zhangwu HMAs is related to the basaltic underplating at the base of the crust,which led to the thickening of the lower crust and

关键词： Zhangwu HMAs, basalt underplating, newly formed lower crust, delamination, North china craton

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

Binary particle swarm optimization with multiple evolutionary strategies

引用

Science china(Information Sciences) 2012年第11期55卷 2485-2494页

作者： ZHAO Jing1,HAN ChongZhao1 & WEI Bin2 1Ministry of Education key Lab For Intelligent networks and network Security,state key laboratory for Manufacturing Systems Engineering,Institute of integrated Automation,School of Electronics and Information Engineering,xi'an Jiaotong university,xi'an 710049,china 2Institute of System Engineering,School of Electronics and Information Engineering,xi'an Jiaotong university,xi'an 710049,china 1. Ministry of Education key Lab For Intelligent networks and network Security State Key Laboratory for Manufacturing Systems Engineering Institute of Integrated Automation School of Electronics and Information Engineering Xi’an Jiaotong University Xi’an 710049 China2. Institute of System Engineering School of Electronics and Information Engineering Xi’an Jiaotong University Xi’an 710049 China

This paper introduces a novel variation of binary particle swarm optimization(BPSO) algorithm and a further extension to improve its ***,mimicking the behaviors of some creatures group,multiple evolutionary strategies BPSO(MBPSO) is introduced which takes different evolutionary strategies for various particles according to their ***,on the basis of MBPSO,a new strategy is discussed to improve the performance of the MBPSO(M2BPSO) which adopts the concept of the mutation operator aiming to overcome the premature convergence and slow convergent speed during the later stages of the *** proposed two algorithms are tested on seven benchmark functions and their results are compared with those obtained by other *** results show that our methods outperform the other algorithms.

关键词： binary particle swarm optimizer evolutionary strategies swarm intelligence

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

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：