Non-stationary return levels of CMIP5 multi-model temperature extremes     

Linyin Cheng  Thomas J. Phillips  Amir AghaKouchak 《Climate Dynamics》2015,44(11-12):2947-2963

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Axisymmetric interaction of a rigid disc with a transversely isotropic half‐space     

Amir Aabbas Katebi  Ali Khojasteh  Mohammad Rahimian  Ronald Y. S. Pak 《国际地质力学数值与分析法杂志》2010,34(12):1211-1236

A theoretical formulation is presented for the determination of the interaction of a vertically loaded disc embedded in a transversely isotropic half‐space. By means of a complete representation using a displacement potential, it is shown that the governing equations of motion for this class of problems can be uncoupled into a fourth‐order partial differential equation. With the aid of Hankel transforms, a relaxed treatment of the mixed‐boundary value problem is formulated as dual integral equations, which, in turn, are reduced to a Fredholm equation of the second kind. In addition to furnishing a unified view of existing solutions for zero and infinite embedments, the present treatment reveals a severe boundary‐layer phenomenon, which is apt to be of interest to this class of problems in general. The present solutions are analytically in exact agreement with the existing solutions for a half‐space with isotropic material properties. To confirm the accuracy of the numerical evaluation of the integrals involved, numerical results are included for cases of different degrees of the material anisotropy and compared with existing solutions. Further numerical examples are also presented to elucidate the influence of the degree of the material anisotropy on the response. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Deriving snow‐cover depletion curves for different spatial scales from remote sensing and snow telemetry data          下载免费PDF全文

Steven R. Fassnacht  Graham A. Sexstone  Amir H. Kashipazha  Juan Ignacio López‐Moreno  Michael F. Jasinski  Stephanie K. Kampf  Benjamin C. Von Thaden 《水文研究》2016,30(11):1708-1717

During the melting of a snowpack, snow water equivalent (SWE) can be correlated to snow‐covered area (SCA) once snow‐free areas appear, which is when SCA begins to decrease below 100%. This amount of SWE is called the threshold SWE. Daily SWE data from snow telemetry stations were related to SCA derived from moderate‐resolution imaging spectroradiometer images to produce snow‐cover depletion curves. The snow depletion curves were created for an 80 000 km² domain across southern Wyoming and northern Colorado encompassing 54 snow telemetry stations. Eight yearly snow depletion curves were compared, and it is shown that the slope of each is a function of the amount of snow received. Snow‐cover depletion curves were also derived for all the individual stations, for which the threshold SWE could be estimated from peak SWE and the topography around each station. A station's peak SWE was much more important than the main topographic variables that included location, elevation, slope, and modelled clear sky solar radiation. The threshold SWE mostly illustrated inter‐annual consistency. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Origin and kinematics of a basin-scale,non-polygonal,layer-bound normal fault system in the Levant Basin,eastern Mediterranean     

Amir Joffe  Christopher A.-L. Jackson  Josh Steinberg  Rebecca E. Bell  Yizhaq Makovsky 《Basin Research》2023,35(2):662-691

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Effect of foundation flexibility on ductility reduction factors for R/C stack-like structures   总被引：1，自引：1，他引：0  

Amir M.Halabian  Shabnam Kabiri 《地震工程与工程振动(英文版)》2011,10(2):277-290

The most important parameter used to determine force reduction factors in force-based design procedures adopted in the current seismic codes is the structural ductility. For a structure supported on a flexible foundation, the ductility factor could be affected by foundation compliances. The ductility factors given in the current codes are mostly assigned ignoring the effect of SSI and therefore the objective of this research is to assess the signifi cance of SSI phenomenon on ductility factors of stack-like structures. The deformed confi guration of stack-like structures is idealized as an assemblage of beam elements considering nonlinear moment-curvature relations, while a linear sway-rocking model was implemented to model the supporting soil. Using a set of artifi cial records, repeated linear and nonlinear analyses were performed by gradually increasing the intensity of acceleration to a level where the fi rst yielding of steel in linear and nonlinear analyses is observed and a level corresponding to the stack collapse in the nonlinear analysis. The difference between inelastic and elastic resistance in terms of displacement ductility factors has been quantifi ed. The results indicate that foundation flexibility can decrease the ductility of the system and neglecting this phenomenon may lead to erroneous conclusions in the prediction of the seismic performance of flexibly-supported R/C stack-like structures.  相似文献   

The Recovery of Two Long-logged Headwaters in Temengor Reservoir,Perak,Malaysia     

Khoo Khay Huat  Mashhor Mansor 《湿地科学》2011,9(2):140-150

A study on water quality of the two long-logged and abandoned headwaters in Temengor Reservoir was conducted to determine their natural recovery.In this study,we used National Water Quality Standards for Malaysia prepared by Malaysian Department of Environment as an indicator for water quality recovery.The parameters measured were dissolved oxygen（mg/L）,water temperature（℃）,pH,conductivity（mS/cm）,total dissolved solids（mg/ L）,water velocity（m/s）,ortho-phosphate（PO₄-P）,nitrite-nitrogen（NO₂-N）,nitrate-nitrogen（NO₃,-N）and alkalinity. In general,water quality in Sungai Enam and Sungai Telang were in ClassⅠ,indicating water quality in both streams have recovered.Based on the t-test,Sungai Enam and Sungai Telang differed significantly in all parameters except for dissolved oxygen,NO₂-N and NO₃-N.In spatial analyses（upper,middle and lower reaches comparisons）, the two-way ANOVA analysis shows that there were significant differences in all studied parameters between the two rivers except for dissolved oxygen,total dissolved solids,NO₂-N and NO₃-N.Stream flow,hydrologic pathways,geomorphology,physical and environmental characteristics are essential elements in understanding the dynamics of water systems in Sungai Enam and Sungai Telang.Due to the recovery,these two headwaters are thus suitable for fish conservation and restoration sites.  相似文献   

Evaluation on the two filling functions for the recovery of forest information in mountainous shadows on Landsat ETM + Image   总被引：1，自引：0，他引：1  

SHAHTAHMASSEBI Amir reza  MOORE Nathan 《山地科学学报》2011,8(3):414-426

In general,topographic shadow may reduce performance of forest mapping over mountainous regions in remotely sensed images.In this paper,information in shadow was synthesized by using two filling techniques,namely,roifill and imfill,in order to improve the accuracy of forest mapping over mountainous regions.These two methods were applied to Landsat Enhanced Thematic Mapper (ETM +) multispectral image from Dong Yang County,Zhejiang Province,China.The performance of these methods was compared with two conventi...  相似文献   

Array Signal Processing for Radio Astronomy   总被引：1，自引：0，他引：1  

Alle Jan Van Der Veen  Amir Leshem  Albert Jan Boonstra 《Experimental Astronomy》2004,17(1-3):231-249

Radio astronomy forms an interesting application area for array signal processing techniques. Current synthesis imaging telescopes consist of a small number of identical dishes, which track a fixed patch in the sky and produce estimates of the time-varying spatial covariance matrix. The observations sometimes are distorted by interference, e.g., from radio, TV, radar or satellite transmissions. We describe some of the tools that array signal processing offers to filter out the interference, based on eigenvalue decompositions and factor analysis, which is a more general technique applicable to partially calibrated arrays. We consider detection of interference, spatial filtering techniques using projections, and discuss how a reference antenna pointed at the interferer can improve the performance. We also consider image formation and its relation to beamforming.  相似文献   

The gravitational-wave spectrum of a non-axisymmetric torus around a rapidly spinning black hole     

Omer Bromberg  Amir Levinson  Maurice van Putten 《New Astronomy》2006,11(8):619-627

The gravitational-wave spectrum emitted by a non-axisymmetric torus rotating at an angular velocity Ω_T, is derived in terms of a structure function representing a combination of sausage-tilt modes in the torus in the limit of an incompressible fluid. The analysis of the gravitational-wave spectrum is then applied to a model proposed recently, in which a highly magnetized torus interacts with a stellar mass, Kerr black hole via poloidal field lines that connect the torus and the horizon. The deformation of the torus results from global magnetic instabilities when the magnetic field strength inside the torus exceeds a few times 10¹⁵ Gauss. The dynamics of the system is illustrated using a non-MHD toy model. It is found that, quite generally, most of the gravitational-wave energy emitted is in the frequency range of sensitivity of LIGO and Virgo.  相似文献   

The Reissner–Sagoci problem for a transversely isotropic half‐space     

Mohammad Rahimian  Amir K. Ghorbani‐Tanha  Morteza Eskandari‐Ghadi 《国际地质力学数值与分析法杂志》2006,30(11):1063-1074

A transversely isotropic linear elastic half‐space, z?0, with the isotropy axis parallel to the z‐axis is considered. The purpose of the paper is to determine displacements and stresses fields in the interior of the half‐space when a rigid circular disk of radius a completely bonded to the surface of the half‐space is rotated through a constant angle θ₀. The region of the surface lying out with the circle r?a, is free from stresses. This problem is a type of Reissner–Sagoci mixed boundary value problems. Using cylindrical co‐ordinate system and applying Hankel integral transform in the radial direction, the problem may be changed to a system of dual integral equations. The solution of the dual integral equations is obtained by an approach analogous to Sneddon's (J. Appl. Phys. 1947; 18 :130–132), so that the circumferential displacement and stress fields inside the medium are obtained analytically. The same problem has already been approached by Hanson and Puja (J. Appl. Mech. 1997; 64 :692–694) by the use of integrating the point force potential functions. It is analytically proved that the present solution, although of a quite different form, is equivalent to that given by Hanson and Puja. To illustrate the solution, a few plots are provided. The displacements and the stresses in a soil deposit due to a rotationally symmetric force or boundary displacement may be obtained using the results of this paper. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献