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Piezoelectric polarization and quantum size effects on the vertical transport in AlGaN/GaN resonant tunneling diodes

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Chinese Physics B 2016年第6期25卷 483-488页

作者： Dakhlaoui h Almansour S Department of Physics College of Science for GirlsUniversity of Dammam (UOD)

In this work,the electronic properties of resonant tunneling diodes（RTDs） based on GaN-AlxGa（1-x）N double barriers are investigated by using the non-equilibrium Green functions formalism（NEG）.These materials each present a wide conduction band discontinuity and a strong internal piezoelectric field,which greatly affect the electronic transport *** electronic density,the transmission coefficient,and the current–voltage characteristics are computed with considering the spontaneous and piezoelectric *** influence of the quantum size on the transmission coefficient is analyzed by varying GaN quantum well thickness,AlxGa1-xN width,and the aluminum concentration *** results show that the transmission coefficient more strongly depends on the thickness of the quantum well than the barrier;it exhibits a series of resonant peaks and valleys as the quantum well width *** addition,it is found that the negative differential resistance（NDR） in the current–voltage（I–V） characteristic strongly depends on aluminum concentration *** is shown that the peak-to-valley ratio（PVR） increases with xAlvalue *** findings open the door for developing vertical transport nitrides-based ISB devices such as Thz lasers and detectors.

关键词： nitride semiconductor resonant tunneling diode current density

A STABILITY ThEOREM FOR CONSTRAINED OPTIMAL CONTROL PROBLEMS

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Journal of Computational Mathematics 2004年第5期22卷 633-640页

作者： M.h.Farag DepartmentofMathematicsandComputerScienceFacultyofEducation lbriSultanateofOman

This paper presents the stability of difference approximations of an optimal control problem for a quasilinear parabolic equation with controls in the coefficients, boundary conditions and additional restrictions. The optimal control problem has been convered to one of the optimization problem using a penalty function technique. The difference approximations problem for the considered problem is obtained. The estimations of stability of the solution of difference approximations problem are proved. The stability estimation of the solution of difference approximations problem by the controls is obtained.

关键词： Finite difference method Penalty function methods Quasilinear Parabolic equations Stability estimations

ThE FINITE ELEMENT METhOD FOR SEMILINEARPARABOLIC EQUATIONS WITh DISCONTINUOUSCOEFFICIENTS

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Journal of Computational Mathematics 1999年第2期17卷 191-198页

作者： Feng, h Shen, LJ Shenzhen Univ Normal Coll Shenzhen 518060 Peoples R China Inst Appl Phys & Computat Math Lab Computat Phys Beijing 100088 Peoples R China

In this paper we investigate the existence, uniqueness and regularity of the solution of semilinear parabolic equations with coefficients that are discontinuous across the interface, some prior estimates are obtained. A net shape of the finite elements around the singular points was designed in [7] to solve the linear elliptic problems, by means of that net, we prove that the approximate solution has the same convergence rate as that without singularity.

关键词： finite element semilinear parabolic equation discontinuous coefficients

Earthquake-induced landslide displacement attenuation models and application in probabilistic seismic landslide displacement analysis

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Earthquake Engineering and Engineering Vibration 2010年第2期9卷 177-187页

作者： Graeme h.McVerry GNS Science

A landslide displacement (DLL) attenuation model has been developed using spectral intensity and a ratio of critical acceleration coefficient to ground acceleration coefficient. In the development of the model,a New Zealand earthquake record data set with magnitudes ranging from 5.0 to 7.2 within a source distance of 175 km is used. The model can be used to carry out deterministic landslide displacement analysis,and readily extended to carry out probabilistic seismic landslide displacement analysis. DLL attenuation models have also been developed by using earthquake source terms,such as magnitude and source distance,that account for the effects of earthquake faulttype,source type,and site conditions. Sensitivity analyses show that the predicted DLL values from the new models are close to those from the Romeo model that was developed from an Italian earthquake record data set. The proposed models are also applied to an analysis of landslide displacements in the Wenchuan earthquake,and a comparison between the predicted and the observed results shows that the proposed models are reliable,and can be confidently used in mapping landslide potential.

关键词： displacement landslide intensity measures deterministic analysis probabilistic analysis

Investigation of optoelectronic properties of pure and Co substituted α-Al_2O_3 by hubbard and modified Becke–Johnson exchange potentials

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Chinese Physics B 2015年第9期24卷 430-435页

作者： h.A.Rahnamaye Aliabad Department of Physics Hakim Sabzevari University

Advanced GGA ＋ U（hubbard） and modified Becke–Johnson（mBJ） techniques are used for the calculation of the structural, electronic, and optical parameters of α-Al2-x CoxO3（x = 0.0, 0.167） compounds. The direct band gaps calculated by GGA and m BJ for pure alumina are 6.3 eV and 8.5 eV, respectively. The m BJ approximation provides results very close to the experimental one（8.7 eV）. The substitution of Al with Co reduces the band gap of alumina. The wide and direct band gap of the doped alumina predicts that it can efficiently be used in optoelectronic devices. The optical properties of the compounds like dielectric functions and energy loss function are also calculated. The rhombohedral structure of theα-Al2-x CoxO3（x = 0.0, 0.167） compounds reveal the birefringence properties.

关键词： density functional theory hubbard U modified Becke–Johnson exchange potential optoelectronic properties

AN OUTLINE OF ThE VARIETIES OF ThE SECOND-ORDER SYSTEMS SCIENCES

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Journal of Systems Science and Systems Engineering 2017年第3期26卷 383-412页

作者： Karl h. Muller International Academy for Systems Science and Cybernetics Steinbeis Transfer Center New Cybernetics Vienna Austria

The systems sciences are based on a universal language of systems which can be used within most academic disciplines in their endeavors for exploring the world. Currently, systems sciences cover a wide variety of different approaches like complex adaptive systems, resilient systems or systems engineering. One of the future extensions of the systems sciences comes through the applications of second-order systems science as a new field of reflexive studies on first-order systems science. This article provides a general background on the relations of first-order science and second-order science in general and then goes on to sketch a basic outline for the second-order systems sciences and their potentials for quality control and for innovations for the first-order systems sciences.

关键词： Optimization

MODIFIED DISCREPANCY PRINCIPLES WITh PERTURBED OPERATORS AND NOISY DATA

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Journal of Computational Mathematics 1996年第2期14卷 108-119页

作者： Chen, h hou, ZY WUhAN UNIV DEPT MATHWUHAN 430072PEOPLES R CHINA FUDAN UNIV INST MATHSHANGHAI 200433PEOPLES R CHINA

We investigate a class of a posterior parameter choice for iterated Tikhonov regularization with perturbed operators and noisy data by using modified Arcangeli's method. The rate of convergence of regularization appro... 详细信息

关键词： Ill posed problems Computational mathematics Approximation Linear transformations

Fabrication of porous titanium carbide ceramics by gelcasting process

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Rare Metals 2022年第9期41卷 3220-3227页

作者： h.Foratirad M.G.Maragheh h.R.Baharvandi Materials and Nuclear Fuel Research School Nuclear Science and Technology Research InstituteTehran14155-1339Iran Department of Materials Science and Engineering MUTTehran15875-1774Iran

Titanium carbide ceramics with high porosity were fabricated by gelcasting process with methacrylamide as a chain forming monomer,methylenebisacrylamide as a cross-linker monomer and tetramethylammonium hydroxide as a *** stability of suspension,mechanical properties,phase composition and micro structure were investigated by zeta potential,bending and compressive strengths,X-ray diffraction and scanning electron microscopy(TEM) analyses,*** results show that the optimal concentration of dispersant for the best homogeneous unagglomerated microstructures is 0.4 wt%at ph *** highest green strength of 33 MPa is obtained from the suspension with 40 vol% solid loading and25 wt% *** porosity increases with the increase in monomer content and the decrease in solid ***,the strength of porous TiC ceramic decreases with the content of pores increasing in the sintered ceramics.

关键词： Titanium carbide Porous ceramic Gelcasting Bending strength

Plasmonic Nanostructured Electromagnetic Materials

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Chinese Physics Letters 2012年第9期29卷 133-137页

作者： h.Sadeghi h.Khalili M.Goodarzi Department of Physics Faculty of ScienceArak UniversityArak 8349-8-38156Iran

We study the materials that are composed of metals and *** plasmonic and non-plasmonic materials are ordered in geometric arrangements with dimensions that are fractions of the wavelength of light.A theoretical model is developed to simulate the refractive index of these nano-structured electromagnetic materials which support surface plasmon *** contributing to the refractive index sensitivity are explored *** with size parameters smaller by much less than 1 have optical properties accurately predicted by the quasi-electrostatic theory while particles with larger size parameters necessitate *** simulate a type of refractive index material composed of metal and insulating dielectric nano-spheres,which are able to sustain the propagation of infrared or visible frequency electromagnetic waves known as surface plasmon polaritons.

关键词： refractive size arrangement