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Damped electrostatic ion acoustic solitary wave structures in quantum plasmas with Bohm potential and spin effects

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Chinese Physics B 2019年第1期28卷 460-465页

作者： s hussain h hasnain Mahnaz q.haseeb Theoretical Physics Division(TPD) Department of Physics COMSATS University

Nonlinear properties of ion acoustic solitary waves are studied in the case of dense magnetized plasmas. The degenerate electrons with relative density effects from their spin states in the same direction and from equally probable up and down spinning states are taken up separately. quantum statistical as well as quantum tunneling effects for both types of electrons are taken. The ions have large inertia and are considered classically, whereas the electrons are degenerate. The collisions of ions and electrons with neutral atoms are considered. We derive the deformed Korteweg de–Vries(DKdV)equation for small amplitude electrostatic potential disturbances by employing the reductive perturbation technique. The Runge–Kutta method is applied to solve numerically the DKdV equation. The analytical solution of DKdV is also presented with time dependence. We discuss the profiles for velocity, amplitude, and time variations in solitons for the cases when all the electrons are spinning in the same direction and for the case when there is equal probability of electrons having spin up and spin down. We have found that the wave is unstable because of the collisions between neutral gas molecules and the charged plasmas particles in the presence of degenerate electrons.

关键词： degenerate plasma collisions spin-up spin-down

Comparing Ordinary Kriging and Regression Kriging for soil Properties in Contrasting Landscapes

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Pedosphere 2010年第5期20卷 594-606页

作者： q.ZhU h.s.LIN Department of Crop and soil sciences 116 ASI BuildingThe Pennsylvania State UniversityUniversity ParkPA 16802(USA)

The accuracy between ordinary kriging and regression kriging was compared based on the combined consideration of sample size,spatial structure,and auxiliary variables(terrain indices and electromagnetic induction surveys) for a variety of soil properties in two contrasting landscapes(agricultural ***).When spatial structure could not be well captured by point-based observations(e.g.,when the ratio of sample spacing over correlation range was > 0.5),or when a strong relationship existed between target soil properties and auxiliary variables(e.g.,their R2 was > 0.6),regression kriging(RK) was more accurate for interpolating soil properties in both landscapes ***,ordinary kriging(OK) was *** depth and wetness condition did not appear to affect the selection of kriging for soil moisture interpolation,because they did not significantly change the ratio of sample spacing over correlation range and the relationship with the auxiliary *** of a smaller ratio of elevation change over total study area(E/A = 1.2) and multiple parent materials in the agricultural land,OK was generally more accurate in that *** contrast,a larger E/A ratio of 6.8 and a single parent material led to RK being preferable in the steep-sloped forested *** results from this study can be useful for selecting kriging for various soil properties and landscapes.

关键词： geostatistics soil moisture spatial interpolation spatial structure

Low Frequency Electromagnetic Instability in Unmagnetized Inhomogeneous Dusty Plasmas

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Chinese Physics Letters 2001年第3期18卷 402-404页

作者： s.Mahmood q.haque h.saleem NPD PINsTECh P.O.NiloreIslamabadPakistan

The low frequency electromagnetic wave instability in an unmagetized inhomogeneous dusty plasma has been pointed *** has been noticed that there exists a stable mode if the propagation of the wave vector along the density gradient is ***,the mode becomes unstable by including the propagation of the wave in the opposite direction of the density gradient.

关键词： wave inhomogeneous opposite

MAKING DUCTILE CAsT IRON WITh EsR PROCEss

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Acta Metallurgica sinica(English Letters) 1998年第3期11卷 169-174页

作者： s.J.Chu h.h.Lou q.Niu Univ of science and Technology Beijing Beijing China

Making ductile cast iron with EsR process under D.C. condition without adding spheroidizing inoculant alloys has been studied in laboratory. The key operation of EsR for cast iron is increasing the silicon content in unrefined consumable electrodes of flake graphite cast iron and using CaF2-based slags containing rare-earth or basic oxides and magnesium fluoride. The samples excel ductile cast iron produced by general technological process in fatigue strength and sealing performance.

关键词： ductile cast iron electroslag remelting nodulizing element

EMBRITTLEMENT OF A Cr-Mo LOW-ALLOY sTEEL DUE TO LOW-TEMPERATURE NEUTRON IRRADIATION

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Acta Metallurgica sinica(English Letters) 2006年第1期19卷 20-26页

作者： s.h. song L. q. Weng Department of Materials science and Engineering Shenzhen Graduate School HarbinInstitute of Technology Shenzhen 518055 China

Embrittlement of a Cr-Mo2.25CrlMo steel stemming from neutron irradiation at 270℃ is studied by virtue of small punch testing in conjunction with scanning electron microscopy. The ductile-brittle transition temperature determined by the small punch test is much lower than that determined by the standard Charpy test. There is some irradiation-induced embrittlement effect after the steel is irradiated for 46 days with a neutron dose rate of 1.05×10^18dpa/s （displacement per atom per second）.

关键词： irradiation embrittlement segregation low alloy steels pressure vessel

Generation of unsteady waves by concentrated disturbances in an inviscid fluid with an inertial surface

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Acta Mechanica sinica 2008年第3期24卷 267-275页

作者： D.q.Lu s.q.Dai shanghai Institute of Applied Mathematics and Mechanics Shanghai University200072 ShanghaiChina shanghai Key Laboratory of Mechanics in Energy and Environment Engineering 200072 ShanghaiChina

The surface waves generated by unsteady concentrated disturbances in an initially quiescent fluid of infinite depth with an inertial surface are analytically investigated for two- and three-dimensional cases. The fluid is assumed to be inviscid, incompressible and homogenous. The inertial surface represents the effect of a thin uniform distribution of non-interacting floating matter. Four types of unsteady concentrated disturbances and two kinds of initial values are considered, namely an instantaneous/oscillating mass source immersed in the fluid, an instantaneous/oscillating impulse on the surface, an initial impulse on the surface of the fluid, and an initial displacement of the surface. The linearized initial-boundary-value problem is formulated within the framework of potential flow. The solutions in integral form for the surface elevation are obtained by means of a joint Laplace-Fourier transform. The asymptotic representations of the wave motion for large time with a fixed distance- to-time ratio are derived by using the method of stationary phase. The effect of the presence of an inertial surface on the wave motion is analyzed. It is found that the wavelengths of the transient dispersive waves increase while those of the steady-state progressive waves decrease. All the wave amplitudes decrease in comparison with those of conventional free-surface waves. The explicit expressions for the freesurface gravity waves can readily be recovered by the present results as the inertial surface disappears.

关键词： Waves Inertial surface Concentrated disturbances Asymptotic representation

Mechanical properties of cocoons constructed consecutively by a single silkworm caterpillar,Bombyx mori

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Acta Mechanica sinica 2008年第2期24卷 151-160页

作者： s.q.h.ang h.P.Zhao X.q.Feng W.Cui Z.Lin M.q.Xu Department of Engineering Mechanics FML Tsinghua University Beijing 100084 China Department of sericulture Shandong Agriculture University Tai'an 271018 China Department of Landscape Architecture Human Environment-Biological Polytechnic College. Hengyang 421005 China

Most animals have the ability to adapt, to some extends and in different ways, the variation or disturbance of environment. In our experiments, we forced a silkworm caterpillar to spin two, three or four thin cocoons by taking it out from the cocoon being constructed. The mechanical properties of these cocoons were studied by static tensile tests and dynamic mechanical thermal analysis. Though external disturbances may cause the decrease in the total weight of silk spun by the silkworm, a gradual enhancement was interestingly found in the mechanical properties of these thin cocoons. scanning electron microscopy observations of the fractured specimens of the cocoons showed that there exist several different energy dissipation mechanisms occurred simultaneously at macro-, meso-, and micro-scales, yielding a superior capacity of cocoons to adsorb the energy of possible attacks from the outside and to protect efficiently its pupa against damage. Through evolution of millions of years, therefore, the silkworm Bombyx mori seems to have gained the ability to adapt external disturbances and to redesign a new cocoon with optimized protective function when its first cocoon has been damaged for some reasons.

关键词： silk silkworm cocoon Mechanical property Biomimetics

Macroscopic and microscopic mechanical behaviors of climbing tendrils

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Acta Mechanica sinica 2019年第3期35卷 702-710页

作者： q.Guo J.J.Dong Y.Liu X.h.Xu q.h.qin J.s.Wang Tianjin Key Laboratory of Modern Engineering Mechanics Department of MechanicsTianjin UniversityTianjin 300054China state Key Laboratory of Nonlinear Mechanics (LNM) Institute of MechanicsChinese Academy of ScienceBeijing 100080China Research school of Engineering Australian National UniversityCanberraACT 2601Australia

Tendril-bearing climbing plants must recur to the tendril helices with chiral perversion or dual chirality for climbing and to obtain sun exposure. Despite researchers' prolonged fascination with climbing tendrils since Darwin's time and even earlier, why the soft and slender tendrils can bear heavy loads such as the self-weight of a plant or additional load caused by rain remains elusive. In this paper, we take towel gourd tendrils as an example and investigate the macroscopic and microscopic mechanical behaviors of tendrils through experiments and simulations. Our study indicates that the tendril filament exhibits rubber-like hyperelastic behaviors and can particularly endure large elongation, which is mainly attributed to the superelasticity of the cellulose fibril helix contained in the cell wall. Combination of the tendril helical structure with dual chirality or chiral perversion at a macroscale and a cellulose filament helix at a subcellular level creates superior elasticity for biological species relying on support and climbing. This study provides deep insight into the structure-property relationship of climbing tendrils, and the relationship is useful for the bioinspired design of composite systems with superior elasticity.

关键词： Climbing tendril Mechanical behaviors structure-property relationship Large elongation

Influence of Fe Addition on Products of self-Propagating high-Temperature synthesis Reaction in 3Ti-si-2C system

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稀有金属材料与工程 2009年第A3期38卷 113-118页

作者： Guan q L Wang h Y Li s L si W P Jiang q C Key Laboratory of Automobile Materials of Ministry of Education Jilin University Changchun 130025 China

Influence of Fe addition on products of self-propagating high-temperature synthesis (shs) reaction in 3Ti-si-2C system was investigated in the present study. Without Fe addition, Ti5si3 and TiC are the dominant phases along with a small amount of Ti3siC2 phase and unreacted C left in the final products. As Fe content ranges from 10% to 30%, the products consist of TiC, Ti5si3, Fe2Ti and unreacted C, but no trace of Ti3siC2 phase is detected. Furthermore, the amounts of both Fe2Ti and C phases increase with Fe content increasing. Addition of Fe has a great effect on the reaction route and significantly restrains the formation of Ti3siC2 during the combustion synthesis process, and therefore, the shs is not an effective fabrication technique to synthesize the ternary Ti3siC2 ceramic in either 3Ti-si-2C or Fe-3Ti-si-2C system. Besides, without Fe addition, Ti5si3 presents as the coarse irregular appearance with an obviously sintered morphology. In contrast, the shape of Ti5si3 exhibits more and more spherical (cobblestone-like) and the surface becomes increasingly smooth, because the amount of liquids formed during the shs reaction increases with the increase of Fe content. On the other hand, with Fe content increasing from 0 to 30 wt.%, the particulate size of TiC decreases from more than 5 μm to 1 μm or less, mainly due to the fact that the combustion temperature decreases with the increase of Fe content in the preforms.

关键词：复合材料铁含量燃烧过程物理性能