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Chinese Physics B 2017年第11期26卷 76-82页

作者： h Farooq M Sarfraz Z Iqbal G Abbas h A Shah Department of Physics Government College University Government College University

The dispersion relations of parallel propagating modes（Langmuir mode, right and left handed circular polarized waves） in the weak magnetic field limit ｜ω-k·v｜〉〉？ are considered for ultra-relativistic arbitrary degenerate electron plasma. The results are presented in terms of moments of Fermi-Dirac distribution. The increase in the electron equilibrium number density from negative large（weakly degenerate） to positive large（highly degenerate） values of μ/Te is observed（where μ is the electron chemical potential and Te is the electron thermal energy）. As a result, shifting of the cutoff points in all the real dispersion branches towards the higher values and increasing in the band gap between unmagnetized longitudinal and transverse modes in k-space are examined. Also, the suppression of the weak magnetic field effects in weakly magnetized right handed and left handed circular polarized waves and a decrease in the longitudinal and transverse screening effects are observed in the graphical patterns due to an increase in the equilibrium number density.

关键词： degenerate Fermi gases relativistic plasmas electromagnetic waves

Existence results for unilateral contact problem with friction of thermo-electro-elasticity

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Applied Mathematics and Mechanics(English Edition) 2015年第7期36卷 911-926页

作者： h.BENAISSA EL-h.ESSOUFI R.FAKhAR Laboratoire de Recherche en Mathématique Informatique et Sciences de l’Ingénieur (MISI) Laboratoire de Science des Matériaux des Milieux et de la Modélisation (LS3M)Université Hassan 1

This work studies a mathematical model describing the static process of contact between a piezoelectric body and a thermally-electrically conductive foundation. The behavior of the material is modeled with a thermo-electro-elastic constitutive law. The contact is described by Signorini＇s conditions and Tresca＇s friction law including the electrical and thermal conductivity conditions. A variational formulation of the model in the form of a coupled system for displacements, electric potential, and temperature is de- rived. Existence and uniqueness of the solution are proved using the results of variational inequalities and a fixed point theorem.

关键词： static frictional contozt thermo-piezoelectric material Signorini's condi-tion Tresca's friction frictional heat generation variational inequality fixed point process

A structural topological optimization method for multi-displacement constraints and any initial topology configuration

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Acta Mechanica Sinica 2010年第5期26卷 735-744页

作者： J. h. Rong J. h. Yi School of Automotive and Mechanical Engineering Changsha University of Science and TechnologyChangsha 410076 China

In density-based topological design, one expects that the final result consists of elements either black （solid material） or white （void）, without any grey areas. Moreover, one also expects that the optimal topology can be obtained by starting from any initial topology configuration. An improved structural topological optimization method for multidisplacement constraints is proposed in this paper. In the proposed method, the whole optimization process is divided into two optimization adjustment phases and a phase transferring step. Firstly, an optimization model is built to deal with the varied displacement limits, design space adjustments, and reasonable relations between the element stiffness matrix and mass and its element topology variable. Secondly, a procedure is proposed to solve the optimization problem formulated in the first optimization adjustment phase, by starting with a small design space and advancing to a larger deign space. The design space adjustments are automatic when the design domain needs expansions, in which the convergence of the proposed method will not be affected. The final topology obtained by the proposed procedure in the first optimization phase, can approach to the vicinity of the optimum topology. Then, a heuristic algorithm is given to improve the efficiency and make the designed structural topology black/white in both the phase transferring step and the second optimization adjustment phase. And the optimum topology can finally be obtained by the second phase optimization adjustments. Two examples are presented to show that the topologies obtained by the proposed method are of very good 0/1 design distribution property, and the computational efficiency is enhanced by reducing the element number of the design structural finite model during two optimization adjustment phases. And the examples also show that this method is robust and practicable.

关键词： Topological optimization Displacement constraint Continuum structure Design space adjustment Rational approximation material model

Analysis of the geometrical dependence of auxetic behavior in reentrant structures by finite elements

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Acta Mechanica Sinica 2016年第2期32卷 295-300页

作者： V.h.Carneiro h.Puga J.Meireles Department of Mechanical Engineering University of Minho

Materials with a negative Poisson＇s ratio（PR）are called auxetics;they are characterized by expansion/contraction when tensioned/*** this counterintuitive behavior,they present very particular characteristics and mechanical *** models have been developed to justify and artificiall reproduce such materials＇ auxetic *** focus of this study is the exploration of a reentrant model by analyzing the variation in the PR of reentrant structures as a function of geometrical and base material *** is shown that,even in the presence of protruding ribs,there may not be auxetic behavior,and this depends on the geometry of each reentrant *** determined for these parameters can be helpful as approximate reference data in the design and fabrication of auxetic lattices using reentrant geometries.

关键词： Auxetic Poisson’s ratio Reentrant Finite element analysis Elasticity

Numerical tests of theoretical models describing ionization of h(1s) atom by linearly polarized flat pulse of laser radiation

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Chinese Physics B 2018年第9期27卷 254-261页

作者： Jarostaw h Bauer Min Deng Katedra Fizyki Teoretycznej Wydzial Fizyki i lnformatyki Stosowanej Uniwersytetu LddzkiegoUI.Pomorska 149/153PL-90-236 LddlPoland State Key Laboratory o fLow-Dimensional Quantum Physics Department of PhysicsTsinghua UniversityBeijing 100084China

We derive the well-known Coulomb correction factor for the Gordon-Volkov wave function describing an outgoing electron in the process of ionization in an intense laser field. Although rigorous treatment would limit its use only to laser fields much lower than the so-called barrier-suppression field, it appears that in practice the correction factor may be used also close to and even above this critical value of the laser field. We compare predictions of several analytical expressions describing ionization rate of the hydrogen atom in its ground state in the strong linearly polarized laser field. We also compare ionization probabilities obtained by integrating these ionization rates over a temporal envelope of the laser pulse with predictions based on the exact numerical solution to the time-dependent Schr ¨odinger equation.

关键词： laser fields ionization S-matrix Coulomb-Volkov wave function

Pore Size Distribution as a Soil Physical Quality Index for Agricultural and Pasture Soils in Northeastern Iran

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Pedosphere 2013年第3期23卷 312-320页

作者： h.ShAhAB h.EMAMI G.h.hAGhNIA A.KARIMI Department Soil Science Agriculture Faculty Ferdowsi University of Mashhad

Assessment of soil quality is important for optimum production and natural resources conservation. Agricultural and pasture soil qualities of Deh-Sorkh region located at south of Mashhad, northeastern Iran were assessed using the integrated quality index (IQI) and Nemero quality index (NQI) models in combination with two datasets, i.e., total data set (TDS) and minimum data set (MDS). In this study 6 soil properties considered as MDS were selected out of 18 properties as TDS using principle component analysis. Soil samples were divided into 3 groups based on optimum ranges of 8 soil physical quality indicators. Soil samples with the most indicators at optimum range were selected as group 1 and the samples having fewer indicators at optimum range were located in groups 2 and 3. Optimum ranges of soil pore size distribution functions were also determined as soil physical quality indices based on 8 soil physical quality indicators. Pore size distribution curves of group 1 were considered as the optimum pore size functions. The results showed that relatively high organic carbon contents could improve pore size distribution. Mean comparisons of soil physical quality indicators demonstrated that mean weight diameter of wet aggregates, structural stability index, the slope of moisture retention curve at inflection point, and plant available water content in agricultural land use decreased significantly in relation to pasture land use. In addition, the results demonstrated that the studied MDS could be a suitable representative of TDS. 78% of pasture soils had the optimum pore size distribution functions, while this parameter for agricultural soils was only 13%. In general, the soils of the studied region showed high limitations for plant growth according to the studied indicators.

关键词： integrated quality index land use minimum data set Nemero quality index soil quality

FUNCTIONAL POLYhYDROXYALKANOATES SYNThESIZED BY MICROORGANISMS

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Chinese Journal of Polymer Science 2000年第5期18卷 389-396页

作者： Peter h.Yu Open Laboratory of Chiral Technology Hong Kong Polytechnic University Hong Kong China

Many bacteria have been found to synthesize a family of polyesters termed polyhydroxyalkanoate, abbreviated as PhA. Some interesting physical properties of PhAs such as piezoelectricity, non-linear optical activity, biocompatibility and biodegradability offer promising applications in areas such as degradable packaging, tissue engineering and drug delivery. Over 90 PhAs with various structure variations have been reported and the number is still increasing. The mechanical property of PhAs changes from brittle to flexible to elastic, depending on the side-chainlength of PhA. Many attempts have been made to produce PhAs as biodegradable plastics using various microorganisms obtained from screening natural environments, genetic engineering and mutation. Due to the high production cost, PhAs still can not compete with the nondegradable plastics, such as polyethylene and polypropylene. Various processes have been developed using low cost raw materials for fermentation and an inorganic extraction process for PhA purification. however, a super PhA production strain may play the most critical role for any large-scale PhA production. Our recent study showed that PhA synthesis is a common phenomenon among bacteria inhabiting various locations, especially oil-contaminated soils. This is very important for finding a suitable bacterial strain for PhA production. In fact, PhA production strains capable of rapid growth and rapid PhA synthesis on cheap molasses substrate have been found on molasses contaminated soils. A combination of novel properties and lower cost will allow easier commercialization of PhA for many applications.

关键词： polyhydroxybutyrate polyhydroxyalkanoate biopolymer polyester

Bunching and Antibunching in Cavity QED

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Communications in Theoretical Physics 2011年第7期56卷 134-138页

作者： h.Jabri h.Eleuch Dpartement de Physique Facult des Sciences de Tunis Institute for Quantum Studies Texas A & M UniversityCollege Station Texas University of Carthage

We study the statistics of the emitted filed from Rydberg atom confined inside a microcavity and interacting with a pump laser in the strong coupling regime. We explore the manifestation of the antibunching in connect... 详细信息

关键词： quantum fluctuations quantum noise photon statistics cavity quantum electrodynamics

Plant conservation in the Anthropocene-Challenges and future prospects

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Plant Diversity 2017年第6期39卷 314-330页

作者： Vernon h.heywood School of Biological Sciences University of Reading

Despite the massive efforts that have been made to conserve plant diversity across the world during the past few decades, it is becoming increasingly evident that our current strategies are not sufficiently effective to prevent the continuing decline in biodiversity. As a recent report by the CBD indicates,current progress and commitments are insufficient to achieve the Aichi Biodiversity Targets by *** species lists continue to grow while the world's governments fail to meet biodiversity conservation goals. Clearly, we are failing in our attempts to conserve biodiversity on a sufficient *** reasons for this situation are complex, including scientific, technical, sociological, economic and political factors. The conservation community is divided about how to respond. Some believe that saving all existing biodiversity is still an achievable goal. On the other hand, there are those who believe that we need to accept that biodiversity will inevitably continue to be lost, despite all our conservation actions and that we must focus on what to save, why and where. It has also been suggested that we need a new approach to conservation in the face of the challenges posed by the Anthropocene biosphere which we now inhabit. Whatever view one holds on the above issues, it is dear that we need to review the effectiveness of our current conservation strategies, identify the limiting factors that are preventing the Aichi goals being met and at the same time take whatever steps are necessary to make our conservation protocols more explicit, operational and efficient so as to achieve the maximum conservation effect. This paper addresses the key issues that underlie our failure to meet agreed targets and discusses the necessary changes to our conservation approaches. While we can justifiably be proud of our many achievements and successes in plant conservation in the past 30 years, which have helped slow the rate of loss, unless we devise a more coherent, consisten

关键词： Plant conservation Anthropocene Aichi targets Biodiversity governance Protected areas

Efficiency of DNA barcodes for species delimitation:A case in Pterygiella Oliv.(Orobanchaceae)

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Journal of Systematics and Evolution 2011年第3期49卷 189-202页

作者： Alexandra h.WORTLEY Royal Botanic Garden Edinburgh

DNA barcoding is becoming an increasingly popular means to identify *** obscure discrimination in the genus Pterygiella calls into question the re-assessment of the criterion for species *** collected 20 individuals,representing all five described species of this genus in its distributional *** aim was to use three proposed barcode DNA regions(rbcL,matK,and ITS) to diagnose Pterygiella species,and examine which barcode is more suitable for discerning the congeneric and related *** results showed that the core barcodes matK and rbcL were comparatively less ***,the ITS region,especially ITS-1 and ITS-2,successfully identified all species in the ***,the secondary structure of ITS-2 RNA,especially compensatory base changes,appears complementary to classical primary sequence analysis for DNA barcoding.

关键词： compensatory base changes(CBCs) DNA barcode ITS-2 non-monophyletic species Pterygiella Oliv. secondary structure.