检索结果-南通市图书馆

Periodic,quasiperiodic and chaotic discrete breathers in a parametrical driven two-dimensional discrete diatomic Klein-Gordon lattice

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2009年第6期18卷 2469-2474页

作者：徐权田强 department of Physics Daqing Normal University department of Physics Beijing Normal University

We study a two-dimensional （2D） diatomic lattice of anhaxmonic oscillators with only quartic nearest-neighbor interactions, in which discrete breathers （DBs） can be explicitly constructed by an exact separation of their time and space dependence. DBs can stably exist in the 2D discrete diatomic Klein-Gordon lattice with hard and soft on-site potentials. When a parametric driving term is introduced in the factor multiplying the harmonic part of the on-site potential of the system, we can obtain the stable quasiperiodic discrete breathers （QDBs） and chaotic discrete breathers （CDBs） by changing the amplitude of the driver. But the DBs and QDBs with symmetric and anti-symmetric profiles that are centered at a heavy atom are more stable than at a light atom, because the frequencies of the DBs and QDBs centered at a heavy atom are lower than those centered at a light atom.

关键词： discrete breather quasi-periodic discrete breather chaotic discrete breather two-dimensional discrete diatomic Klein-Gordon lattice

Effect of process parameters on SPRC35 spot welded automotive panels

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2010年第3期23卷 185-190页

作者： M.Balasubramanian V.Balasubramanian department of Mechanical Engineering Velammal Engineering College department of Manufacturing Engineering Annamalai University

This paper presents an experimental study on the resistance spot weldability of SPRC35（steel plate re-phosphorised cold rolled） *** sheets were joined by using resistance spot welding as lap *** weld nugget diameter and tensile shear force were ***-shear tests were applied to the welded specimens to understand the tensile shear force that the joint can *** relationships were developed for both nugget diameter and tensile shear *** of automatic mode, will increase the dependence on the use of equations to predict the nugget *** developed models have been checked for their adequacy and significance by the F test and t test *** results obtained from the empirical relationships have been optimized and also tested using conformity test runs.

关键词： Resistance spot welding SPRC35 steel

Numerical Model for the Characterization of Retro-reflective Materials Behavior in an Urban Street Canyon

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2018年第5期27卷 456-462页

作者： VALLATI Andrea MAURI Luca COLUCCI Chiara DE LIETO VOLLARO Roberto department of DIAEE Sapienza University of Rome department of Mechanical Engineering University of Roma Tre

In this work, a preliminary numerical model of the behavior of retro-reflective materials used as envelope coatings on street canyon buildings facades has been tested. Retro-reflective materials have a surface finish that allows to reflect the solar radiation back in the same direction of the incident radiation. In the last years this kind of materials has been studied as buildings envelope coating for their potentials in the reduction of the UHI effect. As a matter of fact, the angular dependence of their optical-radiative response would help to mitigate the phenomenon of radiative entrapment due to the urban fabric environment. For this reason, an urban canyon was selected as the most common urban architecture to perform the analysis. A virtual retroreflective material has been simulated considering its response as almost diffusive but in the same direction of the incident radiation. The assessment of the energy advantages of the adoption of a virtual retro-reflective material as envelope coating is investigated by means of a numerical model developed in MATLAB and based on the Gebhart factors theory. The final purpose of the numerical model is the evaluation of the surfaces solar loads by a comparison between perfectly diffusive materials and RR materials used as fa？ades coating.

关键词： retro-reflective materials numerical model Gebhart factors radiative trapping urban street canyon

Characterization of Microstructural and Morphological Properties in As-deposited Ta/NiFe/IrMn/CoFe/Ta Multilayer System

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2014年第4期30卷 359-364页

作者： Ramis Mustafa ksoglu Umut Sarac Mustafa Yildirm Hakan inar department of Materials Sciences and Engineering University of Anadolu department of Elementary Education University of Bartin

Surface morphology and its relationship with microstructure in Ta/NiFe/IrMn/CoFe/Ta multilayer system deposited by pulsed DC magnetron sputtering have been investigated in dependence of Ta buffer and NiFe seed layer thicknesses using atomic force microscopy. The structural parameters such as grain size, dislocation density, texture and strain were calculated. For each surface, a self-affinity behavior with mean fractal dimensions in the range of 2.03-2.18 was found. Additionally, it was also observed that the surface of all samples has locally smooth textured surface structure in the short range. The texture aspect parameter and texture direction index have been obtained for isotropy/anisotropy surface texture. A significant relationship between the surface texture and the strength of the 〈111〉 texture in IrMn layer has been found. The analysis indicated that the surface roughness is strongly affected by the thicknesses of the NiFe seed and Ta buffer layers.

关键词： Pulsed DC magnetron sputtering Surface roughness Strain and texture

Vector meson's spin alignments in high energy reactions

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 5-20页

作者： Jin-Hui Chen Zuo-Tang Liang Yu-Gang Ma Xin-Li Sheng Qun Wang Key Laboratory of Nuclear Physics and Ion-beam Application (MoE) Institute of Modern PhysicsFudan University Institute of Frontier and Interdisciplinary Science Key Laboratory of Particle Physics and Particle Irradiation (MOE)Shandong University INFN-Firenze department of Modern Physics University of Science and Technology of China School of Mechanics and Physics Anhui University of Science and Technology

The global spin alignment of vector mesons has been observed by the STAR collaboration at the Relativistic Heavy Ion Collider （RHIC） at Brookhaven National Laboratory （BNL）.It provides a unique opportunity to probe the correlation between the polarized quark and antiquark in the strongly coupled quark-gluon plasma （sQGP） produced in relativistic heavy ion collisions,opening a new window to explore the properties of s *** addition,spin alignments of vector mesons have also been observed in other high-energy particle collisions such as e+e-annihilations at high energies where hadron production is dominated by quark fragmentation *** results obtained are quite different from those obtained in heavy ion collisions where quark coalescence/combination mechanism dominates suggesting strong dependence on hadronization *** comprehensive studies in different hadronization processes are *** this article,we present a brief review of theoretical and experimental advances in the study of vector meson’s spin alignments in a variety of high-energy particle collisions,with emphasis on hadronization mechanisms.

关键词： vector meson spin alignment global polarization relativistic heavy ion collisions fragmentation

CONTINUOUS STIFFNESS MODE NANOINDENTATION RESPONSE OF POLY(METHYL METHACRYLATE) SURFACES

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2013年第8期31卷 1096-1107页

作者： T. Iqbal B.J. Briscoe S. Yasin P.F. Luckham Chemical Engineering department University of Engineering & Technology Chemical Engineering department Imperial College

Indentation is a comparatively simple and virtually nondestructive method of determining mechanical properties of material surfaces by means of an indenter inducing a localized deformation. The paper present experimental results of the load-displacement curves, the hardness and the elastic modulus data, and associated analysis for poly（methyl methacrylate）（PMMA） surfaces as a function of contact displacement. The experimental results include continuous stiffness indentations performed using constant loading rate and constant displacement rate experiments. The continuous stiffness indentation involves continuous calculation of a material stiffness, and hence hardness and elastic modulus of surfaces, during discrete loading-unloading cycles, as in a conventional indentation routine, and in a comparatively smaller time constant, The dependence of the compliance curves, the hardness, the elastic modulus and the plasticity index upon the imposed penetration depth, the applied normal load and the deformation rate are described. Tip area and load frame calibrations for the continuous stiffness indentation are also reported. The paper includes practical considerations encountered during indentation of polymers specifically at low penetration depths. The experimental results show a peculiarly harder response of PMMA surfaces at the submicron （near to surface） layers.

关键词： Nanoindentation PMMA Hardness Modulus Continuous stiffness.

Theory of phonon-modulated electron spin relaxation time based on the projection reduction method

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2014年第8期23卷 436-443页

作者： Nam Lyong Kang Sang Don Choi department of Applied Nanoscience Pusan National University department of Physics Kyungpook National University

This paper introduces a new method for a formula for electron spin relaxation time of a system of electrons interacting with phonons through phonon-modulated spin-orbit coupling using the projection-reduction method. The phonon absorption and emission processes as well as the photon absorption and emission processes in all electron transition processes can be explained in an organized manner, and the result can be represented in a diagram that can provide intuition for the quantum dynamics of electrons in a solid. The temperature （T） dependence of electron spin relaxation times （T1） in silicon is T1 ∝ T-1.07 at low temperatures and T1 ∝ T-3.3 at high temperatures for acoustic deformation constant Pad = 1.4 × 10^7 eV and optical deformation constant Pod = 4.0 × 10^17 eV/m. This means that electrons are scattered by the acoustic deformation phonons at low temperatures and optical deformation phonons at high temperatures, respectively. The magnetic field （B） dependence of the relaxation times is T1 ∝ B-2.7 at 100 K and T1 ∝ B-2.3 at 150 K, which nearly agree with the result of Yafet, T1 ∝ B-3.0- B -2.5.

关键词： electron spin resonance spin-orbit coupling projection-reduction method phonon scattering

Effect of substitution group on dielectric properties of 4H-pyrano [3,2-c] quinoline derivatives thin films

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2016年第7期25卷 440-449页

作者： H M Zeyada F M El-Taweel M M El-Nahass M M El-Shabaan department of Physics Faculty of Science Damietta University department of Chemistry Faculty of Science Damietta University department of Physics Faculty of Education Ain Shams University

The AC electrical conductivity and dielectrical properties of 2-amino-6-ethyl-5-oxo-4-（3-phenoxyphenyl）-5,6-dihydro-4H-pyrano[3, 2-c]quinoline-3-carbonitrile（Ph-HPQ） and 2-amino-4-（2-chlorophenyl）-6-ethyl-5-oxo-5,6-dihydro-4H-pyrano [3, 2-c] quinoline-3-carbonitrile（Ch-HPQ） thin films were determined in the frequency range of 0.5 k Hz–5 MHz and the temperature range of 290–443 K. The AC electrical conduction of both compounds in thin film form is governed by the correlated barrier hopping（CBH） mechanism. Some parameters such as the barrier height, the maximum barrier height, the density of charges, and the hopping distance were determined as functions of temperature and frequency. The phenoxyphenyl group has a greater influence on those parameters than the chlorophenyl group. The AC activation energies were determined at different frequencies and temperatures. The dielectric behaviors of Ph-HPQ and Ch-HPQ were investigated using the impedance spectroscopy technique. The impedance data are presented in Nyquist diagrams for different temperatures. The Ch-HPQ films have higher impedance than the Ph-HPQ films. The real dielectric constant and dielectric loss show a remarkable dependence on the frequency and temperature. The Ph-HPQ has higher dielectric constants than the Ch-HPQ.

关键词： thin films quinoline derivatives dielectrical properties correlated barrier hopping

Vibration characteristics of FGM circular cylindrical shells filled with fluid using wave propagation approach

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2009年第11期30卷 1393-1404页

作者： Zafar Iqbal Muhammad Nawaz Naeem Nazra Sultana Shahid Hussain Arshad Abdul Ghafar Shah department of Mathematics University of Sargodha department of Mathematics G. C. University Faisalabad department of Mathematics University of Sargodha department of Mathematics The Islamia University of Bahawalpur

The vibration characteristics of a functionally graded material circular cylindrical shell filled with fluid are examined with a wave propagation approach. The shell is filled with an incompressible non-viscous fluid. Axial modal dependence is approximated by exponential functions. A theoretical study of shell vibration frequencies is analyzed for simply supported-simply supported, clamped-simply supported, and clamped-clamped boundary conditions with the fluid effect. The validity and the accuracy of the present method are confirmed by comparing the present results with those available in the literature. Good agreement is observed between the two sets of results.

关键词： functionally graded material Love's shell theory cylindrical shell volumefraction law natural frequency wave propagation