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Characteristics of pressure gradient force errors in a terrain-following coordinate

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Atmospheric and Oceanic Science Letters 2016年第3期9卷 211-218页

作者： li jin-xi li Yi-Yuan WANG Bin State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of Sciences College of Earth Science University of Chinese Academy of Sciences Ministry of Education Key Laboratory for Earth System Modeling and Center for Earth System Science Tsinghua University

A terrain-following coordinate （a-coordinate） in which the computational form of pressure gradient force （PGF） is two-term （the so-called classic method） has significant PGF errors near steep terrain. Using the covariant equations of the a-coordinate to create a one-term PGF （the covariant method） can reduce the PGF errors. This study investigates the factors inducing the PGF errors of these two methods, through geometric analysis and idealized experiments. The geometric analysis first demonstrates that the terrain slope and the vertical pressure gradient can induce the PGF errors of the classic method, and then generalize the effect of the terrain slope to the effect of the slope of each vertical layer （φ）. More importantly, a new factor, the direction of PGF （a）, is proposed by the geometric analysis, and the effects of φ and a are quantified by tan φ.tan a. When tan φ.tan a is greater than 1/9 or smaller than -10/9, the two terms of PGF of the classic method are of the same order but opposite in sign, and then the PGF errors of the classic method are large. Finally, the effects of three factors on inducing the PGF errors of the classic method are validated by a series of idealized experiments using various terrain types and pressure fields. The experimental results also demonstrate that the PGF errors of the covariant method are affected little by the three factors.

关键词： Terrain-following coordinatepressure gradient forceerrors direction of pressuregradient slope of eachvertical layer nonlinearvertical pressure gradient pressure gradient alongvertical layer

Pressure gradient errors in a covariant method of implementing theσ-coordinate:idealized experiments and geometric analysis

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Atmospheric and Oceanic Science Letters 2016年第4期9卷 270-276页

作者： li jin-xi li Yi-Yuan WANG Bin State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina College of Earth Science University of Chinese Academy of SciencesBeijingChina Ministry of Education Key Laboratory for Earth System Modeling and Center for Earth System ScienceTsinghua UniversityBeijingChina

A new approach is proposed to use the covariant scalar equations of the a-coordinate （the covariant method）, in which the pressure gradient force （PGF） has only one term in each horizontal momentum equation, and the PGF errors are much reduced in the computational space. In addition, the validity of reducing the PGF errors by this covariant method in the computational and physical space over steep terrain is investigated. First, the authors implement a set of idealized experiments of increasing terrain slope to compare the PGF errors of the covariant method and those of the classic method in the computational space. The results demonstrate that the PGF errors of the covariant method are consistently much-reduced, compared to those of the classic method. More importantly, the steeper the terrain, the greater the reduction in the ratio of the PGF errors via the covariant method. Next, the authors use geometric analysis to further investigate the PGF errors in the physical space, and the results illustrates that the PGF of the covariant method equals that of the classic method in the physical space; namely, the covariant method based on the non-orthogonal a-coordinate cannot reduce the PGF errors in the physical space. However, an orthogonal method can reduce the PGF errors in the physical space. Finally, a set of idealized experiments are carried out to validate the results obtained by the geometric analysis. These results indicate that the covariant method may improve the simulation of variables relevant to pressure, in addition to pressure itself, near steep terrain.

关键词： Pressure gradient forceerrors covariant scalarequations of the o-coordinate steep terrain computational andphysical space geometricanalysis non-orthogonala-coordinate

Is short-term therapy really sufficient to eradicate Helicobacter pylori infection?

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2010年第9期11卷 690-701页

作者： Ning ZHOU Wei-xing CHEN WeiZHANG Lan li xi jin You-ming li Department of Gastroenterology the First Affiliated Hospital School of Medicine Zhejiang University Hangzhou 310003 China

Objective:The aim of our study was to perform a systematic review and meta-analysis of the efficacy of short-term protocols for Helicobacter pylori eradication and to review the safety and adverse profiles of these eradication ***:literatures were located through electronic searches by PubMed,Medline,ISI Web of Knowledge,and Cochrane library using the relevant *** of important meetings were searched manually in some journal *** bibliographies were identified from the reference lists of identified *** independent reviewers systemically identified randomized controlled trials(RCTs) comparing short-duration protocols vs.7-d proton pump inhibitor(PPI)-based triple protocols,as well as studies reporting eradication rates of short-duration protocols for *** effect size was calculated as relative risk(RR) and 95% confidence intervals(CI) using Review Manager 4.2,and Plightly fewer adverse-effects were found in short-term ***:Although more economical,short-duration protocols are inferior to 7-d PPI-based triple protocols with regarding to eradication rate of *** of more than 3 d,however,may be equivalent to 7-d protocols.

关键词： Helicobacter pylori Eradication therapy Short-term Meta-analysis Adverse effects

Metaphors Enhance Creativity in Writing

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Sino-US English Teaching 2007年第2期4卷 48-51,68页

作者： li jin-xi Tianmu Xueyuan Zhejiang Forestry College Lin ＇an Zhejiang 311300 China

Metaphor, a rhetoric device which involves both stylistics as well as cognition, is really a hot theme in recent years of academic research. Thus this paper thinks that metaphor may help the language learners to write... 详细信息

关键词： metaphor creativity writing

维普期刊数据库评论

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基于认知的异构无线网络信道借用策略

北京邮电大学学报 2009年第5期32卷 20-23页

作者：李希金纪红泛网无线通信教育部重点实验室(北京邮电大学) 北京100876

为解决频谱资源日益紧张的问题,基于IEEE802.11无线局域网(WLAN)和时分同步码分多址(TD-SCDMA)技术构建的异构网络模型,考虑了异构无线网络下信道借用的条件,提出了一种新的基于预测的信道垂直借用方案及其算法.该算法在借鉴信道水平借... 详细信息

为解决频谱资源日益紧张的问题,基于IEEE802.11无线局域网(WLAN)和时分同步码分多址(TD-SCDMA)技术构建的异构网络模型,考虑了异构无线网络下信道借用的条件,提出了一种新的基于预测的信道垂直借用方案及其算法.该算法在借鉴信道水平借用策略的基础上,引入信道预留机制并增加了信道借用预测算法.仿真结果表明,该方案可有效降低呼叫阻塞率,改善系统性能.

关键词：异构无线网络信道分配信道借用呼叫阻塞率

铝酸盐溶液对TiAl合金微弧氧化膜生长和膜层特性的影响

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表面技术 2019年第7期48卷 97-103页

作者：李夕金薛文斌河南大学物理与电子学院河南开封475004 北京师范大学核科学与技术学院北京100875

目的改善TiAl合金表面结构,提高其力学性能。方法利用微弧氧化(MAO)方法,在NaAlO2电解液中制备了TiAl合金表面的陶瓷膜,分析微弧氧化过程中不同阶段的膜层生长特点,并研究铝酸盐溶液对微弧氧化膜生长速率的影响。通过硬度测试和显微划... 详细信息

目的改善TiAl合金表面结构,提高其力学性能。方法利用微弧氧化(MAO)方法,在NaAlO2电解液中制备了TiAl合金表面的陶瓷膜,分析微弧氧化过程中不同阶段的膜层生长特点,并研究铝酸盐溶液对微弧氧化膜生长速率的影响。通过硬度测试和显微划痕测试方法,评价膜层对基体硬度的影响和膜/基结合力的变化。利用扫描电子显微镜(SEM)分析不同厚度膜层的结构,结合能谱仪(EDS)分析膜层中元素的分布变化。使用X射线衍射仪(XRD)分析膜层相结构的变化。结果铝酸盐溶液中微弧氧化膜的厚度随着微弧氧化时间增加,可以达到57μm。微弧氧化过程分为明火花和暗火花生长两个阶段:前30min是明火花生长阶段,生长速率可达1μm/min;后续时间为暗火花生长阶段,生长速率约为0.23μm/min。膜层包括致密内层和疏松外层。致密层中孔隙较少,Al、Ti含量较低;外层有较大的孔隙,Al含量较高,Ti含量较低。扫描电子显微镜结果显示,膜的内层与基体结合良好。显微划痕实验测得膜/基结合力达到45N。陶瓷膜的相成分是Rutile-TiO2和Al2TiO5,且随着膜层变厚,Al2TiO5的相对含量上升。陶瓷膜的显微硬度随着膜厚度的增加而增加,120min膜的显微硬度值可达1450HV,是基体硬度的3倍多。结论在NaAlO2中对TiAl合金进行微弧氧化处理,可以制备55μm的陶瓷层。该膜层与基体间有优异的结合力,可以有效改善基体的表面结构,提高材料的硬度,改善其耐磨性能。

关键词： TiAl合金微弧氧化液相等离子沉积铝酸盐溶液结构硬度

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供应链部分整合对制造商渠道入侵的影响

管理科学学报 2024年第5期27卷 76-92页

作者：李金溪易余胤苏州城市学院数字经济与管理学院苏州215104 暨南大学管理学院广州510632

过去研究渠道入侵问题主要聚焦于集中和分散的供应链,但在实际的商业实践中部分整合的供应链十分普遍.供应链部分整合分为部分前向整合(供应链上游企业持有下游企业的部分股份,记为PFI)以及部分后向整合(供应链下游企业拥有上游企业的... 详细信息

过去研究渠道入侵问题主要聚焦于集中和分散的供应链,但在实际的商业实践中部分整合的供应链十分普遍.供应链部分整合分为部分前向整合(供应链上游企业持有下游企业的部分股份,记为PFI)以及部分后向整合(供应链下游企业拥有上游企业的部分股份,记为PBI).本研究在这两种不同的整合方式下研究制造商线上渠道入侵问题,研究发现:在PFI下,入侵总是制造商的占优策略,但不一定有利于零售商.仅当制造商持有股份较小且直销成本较大时,制造商入侵会带来双赢(win-win).然而,在PBI下入侵并不总是制造商的占优策略,尤其是在零售商持有股份较大且直销渠道效率不高时入侵更要慎重.此外,当制造商入侵但不销售(只展示产品信息)时,在PFI下入侵总是对制造商有利对零售商不利,从而形成win-lose的局面,而在PBI下则会导致win-win,win-lose,lose-win三种结果.

关键词：供应链部分整合制造商入侵博弈论

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壳聚糖涂膜对樱桃番茄贮藏品质的影响

湖北农业科学 2011年第21期50卷 4454-4456页

作者：李西进临沂大学实验中心山东临沂276005

以樱桃番茄（Lycopersicum esculentum ***）千禧作为试验材料,在低温条件下采用不同浓度的壳聚糖醋酸溶液（pH 5.5~5.8）对其进行涂膜处理,测定其总糖、维生素C含量、硬度和腐烂率的变化。结果表明,壳聚糖涂膜处理能明显降低其腐烂率,... 详细信息

以樱桃番茄（Lycopersicum esculentum ***）千禧作为试验材料,在低温条件下采用不同浓度的壳聚糖醋酸溶液（pH 5.5~5.8）对其进行涂膜处理,测定其总糖、维生素C含量、硬度和腐烂率的变化。结果表明,壳聚糖涂膜处理能明显降低其腐烂率,延缓果实硬度、总糖含量和维生素C含量的下降,质量分数1.5%的壳聚糖醋酸溶液涂膜处理保鲜效果较好。

关键词：壳聚糖樱桃番茄(Lycopersicum esculentum var.cerasiforme) 贮藏品质

Local magnetic moment oscillation around an Anderson impurity on graphene

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Science China(Physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 192-201页

作者： Shuai li Zhen Ma jin-Hua Gao School of Science Hebei University of Science and Technology School of Electronics and Information Zhengzhou University of Light Industry School of Physics and Wuhan National High Magnetic Field Center Huazhong University of Science and Technology

We theoretically investigate the spin resolved Friedel oscillation （FO） and quasiparticle interference （QPI） in graphene induced by an Anderson *** the impurity becomes magnetic,the resulted FO becomes spin dependent,which gives rise to a local magnetic moment oscillation with an envelop decaying as r-2in real space in the doping ***,at half filling,the electron density and local magnetic moment will not oscillate but decay as *** spin resolved FO has both sublattice and spin ***,the local magnetic moment decay at half filling only occurs at one sublattice of graphene,which is quite like the phenomenon observed in the STM experiment (***ález-Herrero et al.,Science 352,437 （2016）).We further give an analytic formula about such spin dependent FO based on the stationary phase ***,we study the interference of quasiparticles around the magnetic impurity by calculating the spin dependent Fourier-transformed local density of states （FT-LDOS）.Our work gives a comprehensive understanding about the local magnetic moment oscillation around an Anderson impurity on graphene.

关键词： Friedel oscillation local magnetic moment graphene Anderson impurity