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Classification of topolog.cal trivial matter with non-trivial defects

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Science Bulletin 2019年第9期64卷 575-579页

作者： Lokman Tsui Zi-Xiang.Li Yen-Ta Huang.steven g. Louie Dung.Hai Lee Department of Physics University of California Materials Sciences Division Lawrence Berkeley National Laboratory

In this paper, we apply the K-theory to classify topolog.cal trivial fermionic phases which, nonetheless,host symmetry-protected non-trivial defects. An important implication of our work is that the existence of Majorana zero mode in the vortex core is neither a necessary nor a sufficient condition for the superconductor in question being.topolog.cally non-trivial.

关键词： Majorana zero mode Symmetry protected topolog.cal phase Topolog.cal superconductor Topolog.cal defect K-theory

Low rank approximation in g.W0 calculations

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Science China Mathematics 2016年第8期59卷 1593-1612页

作者： SHAO MeiYue LIN Lin YANg.Chao LIU Fang.DA JORNADA Felipe H. DESLIPPE Jack LOUIE steven g. Computational Research Division Lawrence Berkeley National LaboratoryBerkeleyCA 94720USA Department of Mathematics University of California at BerkeleyBerkeleyCA 94720USA School of Statistics and Mathematics Central University of Finance and EconomicsBeijing 100081China Department of Physics University of California at BerkeleyBerkeleyCA 94720USA Materials Science Division Lawrence Berkeley National LaboratoryBerkeleyCA 94720USA NERSC.Lawrence Berkeley National Laboratory Berkeley.CA 94720.USA

The sing.e particle energ.es obtained in a Kohn-Sham density functional theory(DFT) calculation are g.nerally known to be poor approximations to electron excitation energ.es that are measured in transport,tunneling.and spectroscopic experiments such as photo-emission spectroscopy. The correction to these energ.es can be obtained from the poles of a sing.e particle g.een's function derived from a many-body perturbation theory. From a computational perspective, the accuracy and efficiency of such an approach depends on how a self energ. term that properly accounts for dynamic screening.of electrons is approximated. The g.0W_0 approximation is a widely used technique in which the self energ. is expressed as the convolution of a noninteracting.g.een's function(g.0) and a screened Coulomb interaction(W_0) in the frequency domain. The computational cost associated with such a convolution is hig. due to the hig. complexity of evaluating.W_0 at multiple frequencies. In this paper, we discuss how the cost of g.0W_0 calculation can be reduced by constructing.a low rank approximation to the frequency dependent part of W_0. In particular, we examine the effect of such a low rank approximation on the accuracy of the g.0W_0 approximation. We also discuss how the numerical convolution of g.0 and W_0 can be evaluated efficiently and accurately by using.a contour deformation technique with an appropriate choice of the contour.

关键词： density functional theory g.W0 approximation Sternheimer equation contour deformation lowrank approximation

非点源污染模型在土壤侵蚀模拟中的应用及发展动态

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北京林业大学学报 2001年第2期23卷 78-84页

作者：牛志明解明曙孙阁 steven g. 北京林业大学水土保持学院 Southerng.obalChang.Prog.am USDAForestService

近年来 ,随着计算机和地理信息技术的不断发展 ,非点源污染模型在土壤侵蚀研究中得到了广泛的应用 .该文通过对不同模型的背景、功能、应用范围以及优缺点的分析 ,对国外较为常用的 8个土壤侵蚀模型进行了全面综述 .这些模型包括用于预... 详细信息

近年来 ,随着计算机和地理信息技术的不断发展 ,非点源污染模型在土壤侵蚀研究中得到了广泛的应用 .该文通过对不同模型的背景、功能、应用范围以及优缺点的分析 ,对国外较为常用的 8个土壤侵蚀模型进行了全面综述 .这些模型包括用于预测预报的RUSLE ,WEPP和EPIC ,用于流域水文过程模拟的SHE ,CREAMS和ANSWERS等 ,还有用于流域管理措施评价的Ag.PS和SWAT等 .通过对不同模型应用现状的分析 ,提出了土壤侵蚀模拟模型在BMPs评价。

关键词：土壤侵蚀非点源污染模型预测预报模型水文过程模拟流域管理措施评价模型

Hot Ductility Behavior and Slab Crack Performance of Microalloyed Steels During.Continuous Casting

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Hot Ductility Behavior and Slab Crack Performance of Microal...

Spontaneous twisting.of a collapsed carbon nanotube

“第十届中国钢铁年会”暨“第六届宝钢学术年会”

作者： JANSTO steven g. Technical & Market Development Department CBMM North AmericaInc.

This research shows that hig. carbon equivalent microalloyed steels which exhibit inherently lower hot ductility,throug. the hot tensile test as measured by percent reduction in area(%RA),still exhibit sufficient ductility to satisfactorily meet the unbending.stress and strain g.adients existing.in the straig.tening.section of most industrial *** results indicate only 10%

关键词： continuous casting equiaxed-columnar g.ain transition zone hot ductility

来源： cnki会议评论

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Nano Research 2017年第6期10卷 1942-1949页

作者： Hamid Reza Barzeg.r Aiming.Yan Sinisa Coh Eduardo g.acia-Espino Claudia Ojeda-Aristizabal g.briel Dunn Marvin L. Cohen steven g. Louie Thomas Wag.erg.Alex Zettl Department of Physics University of California Berkeley CA 94720 USA Department of Physics Umea University 90187 Umea Sweden Materials Sciences Division Lawrence Berkeley National Laboratory Berkeley CA 94720 USA Kavli Energ. NanoSciences Institute at the University of California Berkeley and the Lawrence Berkeley National Laboratory Berkeley CA 94720 USA

We study the collapsing.and subsequent spontaneous twisting.of a carbon nanotube by in situ transmission electron microscopy （TEM）. A custom-sized nanotube is first created in the microscope by selectively extracting.shells from a parent multi-walled tube. The few-walled, larg.-diameter daug.ter nanotube is driven to collapse via mechanical stimulation, after which the ribbon-like collapsed tube spontaneously twists along.its long.axis. In situ diffraction experiments fully characterize the uncollapsed and collapsed tubes. The experimental observations and associated theoretical analysis indicate that the orig.n of the twisting.is compressive strain.

关键词： multi-walled carbonnanotube collapsed carbon nanotube in situ TEM electron diffraction twisting g.aphene nanoribbons

The Development and Operational Testing.of an Underwater Bait Setting.System to Prevent the Mortality of Albatrosses and Petrels in Pelag.c Long.ine Fisheries

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Open Journal of Marine Science 2015年第1期5卷 1-12页

作者： g.aham Robertson Phillip Ashworth Peter Ashworth Ian Carlyle steven g. Candy Australian Antarctic Division Kingston Australia Amerro Eng.neering Warana Australia

Long.ine fisheries for tunas and tuna-like species present an existential threat to many populations of albatrosses and petrels worldwide. To prevent this form of mortality we developed a new technolog. desig.ed to deploy baited hooks underwater beyond the dive depths of?seabirds (6 - 10 m for the species most commonly caug.t). The underwater bait setter is a stern-mounted, hydraulically-operated and computer-controlled?device that catapults?baited hooks underwater in a steel capsule?connected to hydraulic winches by Spectra®.rope. Baits are flushed from the capsule by water pressure throug. a spring.loaded bait release door. The chief eng.neering.challeng.s in the developmental stag.swere ensuring.?1) bait delivery?to targ.t depths with cycle times (time from release to recovery) that were practical for fishing.operations;?2) bait retention in the capsule (no drop-outs) on the descent phase of the cycle;?3) baits, upon?release at targ.t depth, were not drawn up the water column on the capsule recovery phase (from possible hook-ups and/or suction);and?4) the retention of baits?on?hooks post-release from the capsule was not affected by the mechanical release underwater. Operational trials with the final version of the capsule yielded?satisfactory cycle times to depths of 6 - 10 m. All baits were retained?in the capsule on the descent and?released as required?at targ.t depths (n = 606 deployments). Bait retention on hooks post release from the capsule and retention on hooks hand-set at the surface (the conventional method) were statistically indisting.ishable.?The underwater bait setter is modular in construction and can be fitted to all types of vessel sterns.

关键词： Seabird Bycatch Long.ine Fisheries Underwater Setting Marine Eng.neering Innovation Co-Operative Research

Serg. Lang. 1927--2005 （I）

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数学译林 2011年第2期30卷 136-146页

作者： Jay Jorg.nson steven g. Krantz 高燕芳(译) 赵振江(校)

这是一篇分两部分文章的第1部分．^1）第2部分将在后面的期刊刊出，当中作者将谈Serg. Lang.塞尔日·兰）的数学成就以及这些成果的影响．

关键词： Serg. Lang 塞尔日.兰数学人物介绍

Net Nitrog.n Mineralization in Natural Ecosystems across the Conterminous US

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International Journal of g.osciences 2013年第9期4卷 1300-1312页

作者： LeeAnna Y. Chapman steven g. McNulty g. Sun Yang.Zhang Department of Marine Earth and Atmospheric Sciences North Carolina State University Raleigh USA Eastern Forest Environmental Threat Assessment Center United States Department of Agriculture—Forest Service Raleigh USA

Nitrog.n is the primary nutrient limiting.ecosystem productivity over most of the US. Althoug. soil nitrog.n content is important, knowledg. about its spatial extent at the continental scale is limited. The objective of this study was to estimate net nitrog.n mineralization for the conterminous US (CONUS) using.an empirical modeling.approach by scaling.up site level measurements. Net nitrog.n mineralization and total soil nitrog.n data across the CONUS were obtained from three different ecosystems: low elevation forests, hig. elevation forests, and g.asslands. Equations to predict net nitrog.n mineralization were developed throug. stepwise linear reg.ession using.total Kjeldahl nitrog.n, air temperature, precipitation, and nitrog.n deposition as predictor variables for four categ.ries: low elevation hig. temperature forests (coefficient of determination, R2 = 0.83), low elevation low temperature forests (R2 = 0.74), hig. elevation forests (R2 = 0.80), and g.asslands (R2 = 0.88). A map of net nitrog.n mineralization was developed in g.S using.these equations and national-scale databases for the CONUS. The result shows that net nitrog.n mineralization varies widely across the US. g.asslands were predicted to have the lowest net nitrog.n mineralization, while low elevation forests in the east had the hig.est. Mean values were 14.3 kg.ha-1·yr-1 for g.asslands, 22.6 kg.ha-1·yr-1 for hig. elevation forests, 58 kg.ha-1·yr-1 for low elevation low temperature forests, and 82.9 kg.ha-1·yr-1 for low elevation hig. temperature forests. This continental scale estimation of net nitrog.n mineralization provides a means of comparing.net nitrog.n mineralization across reg.ons, and the databases developed from this study are useful for accounting.for nitrog.n limitations in larg. scale ecosystem modeling.

关键词： Nitrog.n Limitation Total Kjeldahl Nitrog.n Forest g.assland Linear Reg.ession Plant Available Nitrog.n

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复分析作为催化剂

数学译林 2009年第3期28卷 214-230页

作者： steven g. Krantz

0．开场白众所周知，我是复分析专家，但我从未修过复变理论课程。我的教育中的这个空白或许会影响我思考这个论题的方式．

关键词：复分析催化剂理论课程