检索结果-南通市图书馆

Superconductivity of topological matters induced via pressure

在线全文

学校读者我要写书评

暂无评论

Frontiers of physics 2012年第2期7卷 193-199页

作者： Jun-liang Zhang (1) (2) Si-jia Zhang (1) Hong-ming Weng (1) Wei Zhang (1) Liu-xiang Yang (1) Qing-qing Liu (1) Pan-pan Kong (1) Jie Zhu (1) Shao-min Feng (1) Xian-cheng Wang (1) Ri-cheng Yu (1) Lie-zhao Cao (2) Shoucheng Zhang (3) (4) Xi Dai (1) Zhong Fang (1) Chang-qing Jin (1) 1. Beijing National Laboratory for Condensed Matter Physics & Institute of Physics Chinese Academy of Sciences Beijing 100190 China2. Department of Physics University of Science & Technology of China Hefei 230026 China3. Department of Physics McCullough Building Stanford University Stanford CA 94305-4045 USA4. Center for Advanced Study Tsinghua University Beijing 100084 China

By applying pressure on the topological insulator Bi2Te3 single crystal, superconducting phase was found without a crystal structure phase transition. The new superconducting phase is under the pressure range of 3 GPa to 6 GPa. The high pressure Hall effect measurements indicated that the superconductivity caused by bulk hole pockets. The high pressure structure investigations with synchrotron X-ray diffraction indicated that the superconducting phase is of similar structure to that of ambient phase structure with only slight change with lattice parameter and internal atomic position. The topological band structures indicate the superconducting phase under high pressure remained topologically nontrivial. The results suggested that topological superconductivity can be realized in Bi2Te3 due to the proximity effect between superconducting bulk states and Dirac- type surface states. We also discussed the possibility that the bulk state could be a topological superconductor.

关键词： topological insulator high pressure

Generation of cell-type-specific gene mutations by expressing the sgRNA of the CRISPR system from the RNA polymerase II promoters

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Protein & Cell 2015年第9期6卷 689-692页

作者： Jiaqiang Wang (1) Xin Li (1) (2) Yanhua Zhao (1) Jingyu Li (1) Qi Zhou (1) (2) Zhonghua Liu (1) 1.College of Life Sciences Northeast Agricultural University Harbin 150030 China 2.State Key Laboratory of Reproductive Biology Institute of Zoology Chinese Academy of Sciences Beijing 100101 China

Recently, the CRISPR/Cas9 system is emerging as a powerful tool for genome editing （Chang et al., 2013; Li et al., 2013; Niu et al., 2014; Shen et al., 2013; Wan et al., 2015; Wang et al., 2013） and genetic screening （Konermann et al., 2015）, and holds great promise for biomedical applications in disease modeling and gene therapy by in vivo genome editing （Mad- dalo et al., 2014; Xue et al., 2014）.

关键词：

An analytical model for Network-on-Chip with finite input buffer

在线全文

学校读者我要写书评

暂无评论

Frontiers of Computer Science 2011年第1期5卷 126-134页

作者： Jian Wang (1) wangjian3630@*** Yu-bai Li (1) Chang Wu (1) Univ elect Sci & Technol China Didital Signal Proc Lab Sch Commun & Informat Engn Chengdu 610054 Peoples R China

An analytical model is proposed for input buffer router architecture Network-on-Chip （NoC） with finite size buffers. The model is developed based on M/G/ 1/K queuing theory and takes into consideration the restriction of buffer sizes in NoC. It analyzes the packet＇s sojourn time in each buffer and calculates the packets average latency in NoC The validity of the model is verified through simulation. By comparing our analytical outcomes to the simulation results, we show that the proposed model successfully captures the performance characteristics of NoC, which provides an efficient performance analysis tool for NoC design.

关键词： analytical model finite buffer Network-on-Chip (NoC) queue system

Quantum spin Hall effect in inverted InAs/GaSb quantum wells

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of physics 2012年第2期7卷 200-207页

作者： Ivan Knez (1) Rui-Rui Du (1) 1. Department of Physics and Astronomy Rice University Houston TX 77251-1892 USA

We review the recent experimental progress towards observing quantum spin Hall effect in inverted InAs/GaSb quantum wells （QWs）. Low temperature transport measurements in the hybridization gap show bulk conductivity of a non-trivial origin, while the length and width dependence of con- ductance in this regime show strong evidence for the existence of helical edge modes proposed by Liu et al. [Phys. Rev. Lett., 2008, 100： 236601]. Surprisingly, edge modes persist in spite of compa- rable bulk conduction and show only weak dependence on magnetic field. We elucidate that seeming independence of edge on bulk transport comes due to the disparity in Fermi-wave vectors between the bulk and the edge, leading to a total internal reflection of the edge modes.

关键词： quantum spin Hall effect InAs/GaSb quantum wells topological insulators

Influence of particle composition on thorium scavenging in the marginal China seas

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Oceanologica Sinica 2009年第2期28卷 45-53页

作者： YANG Weifeng CHeN Min CAO Jianping QIU Yusheng ZHANG Run MA Qiang TONG Jinlu YANG Junhong YANG Zhi LUe e Department of Oceanography Xiamen University Xiamen 361005 China State Key Laboratory of Marine environmental Science Xiamen University Xiamen 361005 China

Thorium-234 and particle composition （organic matter, biogenic silica, carbonate and lithogenic component） were examined in the east China Sea （eCS） and the northern South China Sea （NSCS） in order to constrain the particle types scavenging thorium isotopes. Good positive correlations between particulate organic matter （POM） or carbonate and thorium-234 in suspended particulate matter （SPM） indicates that POM and carbonate are efficient to scavenge thorium-234. No relationship between biogenic silica and thorium-234 suggests that geochemical behavior of thorium-234 may be not influenced by biogenic silica. A simple model was used to evaluate the affinity of thorium-234 to different particle components. The results show that POM is the most efficient scavenger for thorium-234 in the eCS and the NSCS, followed by carbonate. The authors＇ results lend support to the utility of thorium-234 as a proxy of POC and carbonate in the upper layer. However, the strong dependence of thorium scavenging on particle composition challenges thorium-230 as a constant flux proxy.

关键词： POC biogenic silica thorium carbonate particle composition

Fuzzy c-means clustering with non local spatial information for noisy image segmentation

在线全文

学校读者我要写书评

暂无评论

Frontiers of Computer Science 2011年第1期5卷 45-56页

作者： Feng Zhao (1) add_zf1119@*** Licheng Jiao (1) Hanqiang Liu (1) Xidian Univ Key Lab Intelligent Percept & Image Understanding Minist Educ China Inst Intelligent Informat Proc Xian 710071 Peoples R China

As an effective image segmentation method, the standard fuzzy c-means （FCM） clustering algorithm is very sensitive to noise in images. Several modified FCM algorithms, using local spatial information, can overcome this problem to some degree. However, when the noise level in the image is high, these algorithms still cannot obtain satisfactory segmentation performance. In this paper, we introduce a non local spatial constraint term into the objective function of FCM and propose a fuzzy c- means clustering algorithm with non local spatial information （FCM_NLS）. FCM_NLS can deal more effectively with the image noise and preserve geometrical edges in the image. Performance evaluation experiments on synthetic and real images, especially magnetic resonance （MR） images, show that FCM NLS is more robust than both the standard FCM and the modified FCM algorithms using local spatial information for noisy image segmentation.

关键词： image segmentation fuzzy clustering algo-rithm non local spatial information magnetic resonance(MR) image

Multi-isotopic system geochronology of low temperature eclogite from Huangzhen,Southern Dabie Terrain

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China earth Sciences 2004年第10期47卷 931-942页

作者： CHeN Daogong1, e. Deloule2, CHeNG Hao1, XIA Qunke1 & WU Yuanbao1 1. School of earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China 2. CRPG-CNRS Nancy, 54501, France School of earth and Space Sciences University of Science and Technology of China Hefei China CRPG-CNRS Nancy France

Zircon U-Pb thermal ionization mass-spectrometer (TIMS) and secondary ion mass-spectrometer (SIMS) dating, mica and amphibole 40Ar-39Ar dating and mineral Sm-Nd isotopic compositions of Huangzhen low temperature eclogite and country granitic gneiss are carried out. The zircon U-Pb weighted average SIMS age is (231.6?9.7) Ma for one eclogite. The mica 40Ar-39Ar isochron age is (232.6?2.1) Ma and the lowest plateau age is (221.7?2.4) Ma from same sample. U-Pb TIMS concordant ages from other eclogite zircons are from (221.3?1.4) Ma to (222.5?2.3) Ma. U-Pb SIMS low intercept age from country granitic gneiss is (221?35) Ma. The retrograde amphibole 40Ar-39Ar isochron age is (205.9?1.0) Ma. except for mica, which may contain excess 40Ar, all the ages represent peak and retrograde metamorphism of low temperature eclogites. It is indicated that the Huangzhen low temperature eclogites differ from Xiongdian low temperature eclogites of north of the Northern Dabie Terrain in metamorphic ages. Huangzhen low temperature eclogites share one coherent HP-UHP terrain with high temperature eclogites from Southern Dabie Terrain and they may have differences in subduction depth and cooling rates during exhumation.

关键词： low temperature eclogite, multi-isotopic dating, HP-UHP metamorphism, Dabieshan.

Tuning the Fermi level in Bi2Se3 bulk materials and transport devices

在线全文

学校读者我要写书评

暂无评论

Frontiers of physics 2012年第2期7卷 160-164页

作者： Zhi-yong Wang (1) Peng Wei (1) Jing Shi (1) Department of Physics & Astronomy University of California Riverside USA

Bi2Se3 has been predicted to be a three-dimensional （3D） topological insulator （TI） with Dirac fermions residing on the two-dimensional （2D） surface. Unique transport properties such as high carrier mobility due to the suppressed backscattering are expected for the Dirac fermions. In order to eliminate the contribution of the bulk carriers, therefore, to place the Fermi level in the band gap of Bi2Se3, we first introduce various amounts of Ca dopants into the crystal to realize the bulk insulating state. Then by avoiding uncontrolled heating and electron beam irradiation in the nanofabrication process, we maintain the insulating state in thin devices. By sweeping the gate voltage, we have observed a conductivity minimum that is expected for the Dirac fermions in the band gap of 3D TIs.

关键词： topological insulators Bi2Se3 transport properties nano-devices

Theoretical analysis of some problems in the measurement of beam divergence angle for eAST neutral beam injector

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2011年第S2期54卷 300-304页

作者： YongJian Xu (1) ChunDong Hu (1) 1. Institute of Plasma Physics Chinese Academy of Sciences Hefei 230031 China

Beam angular divergence is one of the indicators to evaluate the beam quality. Operating parameters of the beam extraction system could be adjusted to gain better beam quality following the measurement results, which will be helpful not only to study the transmission characteristics of the beam and the power distribution on the heat load components, but also to understand the real-time working condition of the ion source and beam extraction system. This study includes: (1) the theoretical analysis of beam extraction pulse duration for measurement of beam angular divergence; (2) the theoretical analysis of beam intensity distribution during beam transmission for experimental Advanced Superconducting Tokomak (eAST) neutral beam injector. Those theoretical analyses could point the way to the measurement of beam divergence angle for eAST neutral beam injector.

关键词： neutral beam beam divergence angle beam intensity pulse duration