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Quantum mechanics

Magnetic Field Design by Using Image Effect from Iron Shield

1998年

作者： mcmurry Sara M.

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Journal of Materials Science & Technology 2004年第1期20卷 125-128页

作者： QuanlingPENG S.M.mcmurry J.M.D.Coey InstituteofHighEnergyPhysics(IHEP) ChineseAcademyofSciencesP.O.Box918-9Beijing100039China DepartmentofPhysics TrinityCollegeDublin2Ireland

Permanent magnet rings are presented, which exploit the image effect in the surrounding circular iron shields. The theory is given for a general permanent ring when the magnetization orientation at each coordinate angle ψ changes by =(n+1)ψ, where n is a positive or negative integer. For the uniformly magnetized case n=-1, the permanent ring produces no field in its bore, and the field is that of a dipole outside. When the ring is surrounded by a soft iron shield, its field becomes uniform in the bore, and zero outside the ring. The field can be varied continuously by moving the iron shield along the magnet axis. A small variable field device was constructed by using NdFeB permanent rings, which produced a field flux density of 0-0.5 T in the central region.

关键词： External magnetic field Internal magnetic field Cylindrical iron shield Permanent magnet ring Easy axis orientation

Approximate Riemann Solvers and Robust High-Order Finite Volume Schemes for Multi-Dimensional Ideal MHD Equations

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Communications in Computational Physics 2011年第2期9卷 324-362页

作者： Franz Georg Fuchs Andrew D.mcmurry Siddhartha Mishra Nils Henrik Risebro Knut Waagan Centre of Mathematics for Applications University of OsloP.O.Box 1053Blindern N-0316 OsloNorway Seminar for Applied Mathematics D-MathETH ZürichHG G.57.2Rämistrasse 101Zürich-8092Switzerland Center for Scientific Computation and Mathematical Modeling The University of MarylandCSCAMM 4146CSIC Building#406Paint Branch Drive College ParkMD 20742-3289USA

We design stable and high-order accurate finite volume schemes for the ideal MHD equations in *** obtain excellent numerical stability due to some new elements in the *** schemes are based on three-and five-wave approximate Riemann solvers of the HLL-type,with the novelty that we allow a varying normal magnetic *** is achieved by considering the semiconservative Godunov-Powell form of the MHD *** show that it is important to discretize the Godunov-Powell source term in the right way,and that the HLL-type solvers naturally provide a stable upwind ***-order versions of the ENO-and WENO-type reconstructions are proposed,together with precise modifications necessary to preserve positive pressure and *** the discrete source term to second order while maintaining stability requires non-standard techniques,which we *** first-and second-order schemes are tested on a suite of numerical experiments demonstrating impressive numerical resolution as well as stability,even on very fine meshes.

关键词： Conservation laws MHD divergence constraint Godunov-Powell source terms upwinded source terms high-order schemes

Finite Volume Methods for Wave Propagation in Stratified Magneto-Atmospheres

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Communications in Computational Physics 2010年第3期7卷 473-509页

作者： Franz Georg Fuchs Andrew D.mcmurry Siddhartha Mishra Nils Henrik Risebro Knut Waagan Centre of Mathematics for Applications(CMA) University of OsloP.O.Box 1053BlindernN-0316 OsloNorway High Altitude Observatory(haO) National Center of Atmospheric ResearchP.O.Box 3000Boulder80307-3000 ColoradoUSA

We present a model for simulating wave propagation in stratified magnetoatmospheres. The model is based on equations of ideal MHD together with gravitational source terms. In addition, we present suitable boundary data and steady statesto model wave propagation. A finite volume framework is developed to simulate thewaves. The framework is based on HLL and Roe type approximate Riemann solversfor numerical fluxes, a positivity preserving fractional steps method for discretizingthe source and modified characteristic and Neumann type numerical boundary conditions. Second-order spatial and temporal accuracy is obtained by using an ENO piecewise linear reconstruction and a stability preserving Runge-Kutta method *** boundary closures are suitably modified to ensure mass balance. The numericalframework is tested on a variety of test problems both for hydrodynamic as well asmagnetohydrodynamic configurations. It is observed that only suitable choices of HLLsolvers for the numerical fluxes and balanced Neumann type boundary closures yieldstable results for numerical wave propagation in the presence of complex magneticfields.

关键词： Solar atmospheres MHD equations finite volume methods non-reflecting boundary conditions

Organic chemistry 5th ed.

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Stationary characteristics in bipolar diffusion charging of aerosols:improving electrical mobility size spectrometers

2000年

作者： mcmurry John. CAL n2005165293# ba0yba0y

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Stationary characteristics in bipolar diffusion charging of ...

Effects of Land Use on Greenhouse Gas Flux in Playa Wetlands and Associated Watersheds in the High Plains, USA

第一届全国环境化学青年学者论坛

作者： Xiaotong Chen Peter H.mcmurry Jingkun Jiang 清华大学环境学院

＜正＞Electrical mobility size spectrometers are widely used to measure particle number size distributions（PNSD） in the range of 1-1000 nm [1,2]（Wang and Flagan 1990;Jiang et al.2011）.These instruments condition t...

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Agricultural Sciences 2019年第2期10卷 181-201页

作者： Dale W. Daniel Loren M. Smith Scott T. mcmurry Brian A. Tangen Charles F. Dahl Ned H. Euliss Jr. Ted LaGrange Department of Integrative Biology Oklahoma State University Stillwater OK USA U.S. Geological Survey Northern Prairie Wildlife Research Center Jamestown ND USA Nebraska Game & Parks Commission Wetlands Program Lincoln NE USA

In the High Plains, U.S., native prairie conversion to cropland agriculture has resulted in a loss of service delivery capabilities from most depressional wetlands as a result of sedimentation. Restoring historic hydrological conditions to affected wetlands may rejuvenate some services, however, there may be tradeoffs due to emissions of CH4 and N2O. We evaluated the influence of two predominant conservation programs (Wetlands Reserve Program, WRP and Conservation Reserve Program, CRP) on gas emissions (CO2, CH4, N2O) from 42 playas and uplands in the High Plains of Nebraska. Because playa restoration through the WRP is most prevalent in the Rainwater Basin (RWB), we studied 27 playas/uplands among reference condition, cropland, and WRP land uses. We studied 15 playas/uplands within native grassland, cropland, and CRP land uses in the Western High Plains (WHP) of Nebraska. Emissions were collected bi-weekly from April-October of 2012 and 2013 from four landscape positions extending outward from the wetland center into upland. In RWB playas, CH4 and N2O emissions were similar among land uses but CO2 was 28% higher in cropland than WRP wetlands. Cropland uplands emitted 648% more N2O than reference and WRP uplands. Overall, net CO2-equiv emissions were lower in playas/uplands in WRP, suggesting that benefits of playa restoration may include climate mitigation services as well as increased water storage capacity and biodiversity provisioning. In the WHP, cropland and grassland playas emitted 46 and 23 times more CH4, respectively, than CRP in 2013. Playas in CRP emitted 43% less N2O than cropland playas. In 2013, net emissions for cropland and native grassland playas were 75% and 39% greater, respectively, than CRP playas. In the WHP, the benefits of lower gas emissions must be appropriately weighted against tradeoffs of ecosystem services related to shorter hydroperiods as a result of reduced runoff into playas in CRP.

关键词： Conservation Reserve Program Depressional Wetlands Ecosystem Services Global Climate Change Wetlands Reserve Program Wetland Restoration

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野生扬子鳄种群及栖息地现状研究

生物多样性 2001年第2期9卷 102-108页

作者：丁由中王小明何利军邵民谢万树 Thorbjarnarson B John Mc Murry T Scott 华东师范大学生物学系上海200062 安徽扬子鳄繁殖研究中心宣州242000 TheWildlifeConservationSociety newyorkusa10460 Texas Tech University Health Sciences Center texasusa79416

1999年 7～ 8月及 2 0 0 0年 8～ 9月 ,利用GPS、激光测距仪等 ,采用夜间灯光照射计数方法 ,对有野生扬子鳄(Alligatorsinensis)存在的安徽省宣州、泾县、广德、郎溪、南陵等 5县市的 2 6个地点进行了调查 ,包括扬子鳄国家级自然保护区... 详细信息

1999年 7～ 8月及 2 0 0 0年 8～ 9月 ,利用GPS、激光测距仪等 ,采用夜间灯光照射计数方法 ,对有野生扬子鳄(Alligatorsinensis)存在的安徽省宣州、泾县、广德、郎溪、南陵等 5县市的 2 6个地点进行了调查 ,包括扬子鳄国家级自然保护区的 13个指定保护点。结果发现 :目前野生扬子鳄主要生存在第一类栖息地 (1999年 5 0 .7%、2 0 0 0年40 .0 % ) ,面积为 17.38hm2 ;其他两类栖息地的野生扬子鳄分布比率较小 (各为 1999年 2 4.0 %、2 0 0 0年 30 .9%、1999年 2 5 .3%、2 0 0 0年 2 9.1% ) ,面积分别为 2 2 .0 4hm2 、19.0 3hm2 。两年的平均生态密度分别为 1.2 8条 /hm2和 1.79条 /hm2 ,野生扬子鳄种群数量为 145条。其种群已明显分为至少 18个数量不等且相互隔离的地方种群。建议恢复足够大的栖息地 ,并放饲养鳄于其中以重新建立有效野生种群。

关键词：野生扬子鳄种群数量栖息地