Andthe Method Research Articles

A Study on Grammar Teaching at an English Education Department in an EFL Context

This research is the study of Grammar teaching in an English Education Department. The purposes of this study are: to find out the approach used in teaching grammar, to describe the difficulties encountered by students in studying grammar, and to find out the students’ grammar ability. The research was conducted by lecturers and students who are doing research for their graduating paper. The population is students of English Education. Sample was taken using the technique of random according to Krejcie and Morgan table. The instruments used to collect data are tests, observation sheets and questionnaires. The results showed that there are several approaches used in teaching Grammar by the lecturers at the beginning of the semester. They are deductive, inductive, structural and communicative approaches. The problems faced by students in learning grammar are problems related to natural difficulties, mother tongue, students’ aspects, lecturers’ aspects, and the method and timing aspects. The next finding from this study is students’ grammar mastery. It was found out that the grammar mastery of students who have taken all grammar subjects is in fair level. Keywords: grammar, approach, difficulty, mastery

Temperature Dependence of Stability of Copper Clusters

Abstract Previously we have determined the lowest-energy structures and full vibrational spectra of Cu N with N up to 150 atoms by means of an unbiased-structure-optimization approach combined with the analytical formulas of the embedded-atom total-energy method and the harmonic superposition approximation. Here, we extend the earlier T = 0 studies to T ≠ 0 and present the equilibrium thermodynamic properties of copper clusters with N from 2 to 150. Thereby, we calculate the Helmholtz free energy quantum mechanically and examine it as a function of temperature and cluster size. It is shown, that the impact of entropic effects on the stability of the copper clusters is rather small for temperatures less than 300 K, which is about the bulk Debye temperature. For larger temperatures, the influence of the vibrational entropy on the cluster stability becomes stronger so that with increasing temperature the stability of some clusters (most often low-symmetrical) is increased and that of others (most often high-symmetrical) is reduced. For the first time, we demonstrate the existence of new magic copper clusters at elevated temperatures. These have the sizes 80, 88, 104, and 125 and will be called the temperature-dependent magic clusters.

On the homogenization of multicomponent transport

This paper is devoted to the homogenization of weakly coupled cooperativeparabolic systems in strong convection regime with purely periodiccoefficients. Our approach is to factor out oscillations from the solution viaprincipal eigenfunctions of an associated spectral problem and to cancel anyexponential decay in time of the solution using the principal eigenvalue of thesame spectral problem. We employ the notion of two-scale convergence with driftin the asymptotic analysis of the factorized model as the lengthscale of theoscillations tends to zero. This combination of the factorization method andthe method of two-scale convergence is applied to upscale an adsorption modelfor multicomponent flow in an heterogeneous porous medium.

TO THE QUESTION OF THE AIRPLANE CONSTRUCTION DAMAGE BY THE SOIL SOLID PARTICLES IN THE OPERATION

The analysis of the airplane aggregates damage reasons in case of maintenance on soil runwayswas carried out. The damage process of the airplane skin from impacts with flying soil particleswas considered in detail. Possible consequences and applied modern protection methodsof the airplane aggregates were considered. The form of experimental samples was proved andthe method of carrying out pilot studies was offered. For development of protection measures,the approach for determination of the intense deformed skin status after impacts was offered.Also this approach can be used for check of the existing protection methods.

Influence of Processing Parameters on Microstructure of Casting Rolling Semi-Solid AZ91D Magnesium Alloy

Semi-solid AZ91D magnesium slurry was prepared by mechanical stirring method and the evolution of microstructure under different technological parameters such as casting temperature, standing time, stirring time and stirring speed et al were studied. The results show that the technological parameters have great influence on the microstructure of the semi-solid magnesium slurry. Neither too high nor too low stirring speed is a benefit to form the semi-solid state; stirring time is also not too long; higher casting temperature is unfavorable; with the increasing of standing time, the steady-state apparent viscosity of the slurry increases rapidly, the number of nucleation increases and the crystalline structure becomes finer.

Generalization of Fisher Model for Periodically Non-Uniform Grain Boundary

The problem of grain boundary diffusion for a case of boundary grain with periodic heterogeneity diffusion properties is considered. Dependence of Laplace transform images of impurity concentration on various diffusion conductivity places is built. The dimensionless parameters, forming the system of grain boundary diffusion regimes are determined. The space (ln x,lnt,1/T) is divided into areas in which the ratio ln ln ~ ln ln ( / ) ln eff o C r x−k t− Q RT − A is maintained, when the parameters of diffusion regime are constant. The values of parameters , , , eff o r k Q A fully specify the diffusion regimes. On this base the new concept for the definition of grain boundary diffusion regimes is carried out and the method for construction of simplified tracer concentration profile is proposed.

CALCULATION AND ANALYSIS OF THE COST OF PRODUCTION IN BEEKEEPING

Analysis of the cost of production contributes to determining the degree of efficiency of the costs related to the level of production. The efforts of the experts are directed towards finding a system calculation that ensure, on the one side, an operative determination of the unit cost, and on the other side, a possibility of determining the appropriate indicators, necessary to take decisions on short term. Beekeeping is characterized by obtaining more of the products (pollen, propolis, royal jelly, venom, wax, apilarnil) and by highlighting the overall costs of production. Among the methods for calculating the unit cost, the most common are the remaining value method and the coefficients method of distributing costs; the difference between these two methods is represented by the criteria used for sharing costs on products.

TIME DOMAIN INVERSE SCATTERING OF A TWO-DIMENSIONAL HOMOGENOUS DIELECTRIC OBJECT WITH ARBITRARY SHAPE BY PARTICLE SWARM OPTIMIZATION

This paper presents a computational approach to the two- dimensional time domain inverse scattering problem of a dielectric cylinder based on the finite difference time domain (FDTD) method andthe particle swarm optimization (PSO) to d etermine the shape, location and permittivity of a dielectric cylinder. A pulse is incident upon a homogeneous dielectric cylinder with unknown shape and d ielectric constant in free space andthe scatteredfieldis record ed outside. By using the scattered field, the shape and permittivity of the dielectric cylinder are reconstructed. The subgridding technique is implemented in the FDTD code for modeling the shape of the cylinder more closely. In order to describe an unknown cylinder with arbitrary shape more effectively, the shape function is expandedby closedcubic- spline function insteadof frequently usedtrigonometric series. The inverse problem is resolvedby an optimization approach, andthe global searching scheme PSO is then employedto search the parameter space. Numerical results demonstrate that, even when the initial guess is far away from the exact one, goodreconstruction can be obtained . In addition, the effects of Gaussian noise on the reconstruction results are investigated. Numerical results show that even the measured scattered E fields are contaminated with some Gaussian noise, PSO can still yield goodreconstructedquality.

Shock Compaction of WC-Co Powder in Metallic Tube

The tungsten carbide - cobalt, (WC-Co) powder is compacted and bonded to on a stainless steel (SUS304) rod by using explosives. In this research, the experiments are conducted using two methods. They are the method of making the pressure of the explosive act directly on the powder and the method of explosively driving a metal pipe with high speed to create high pressure acting on powder. Crack free bulk material was recovered. Heat-treatment was performed on the recovered sample. After heat treatment, the value of hardness was increased compared with commercial material.

Theoretical Analysis and Simulation of Airflow of Super High-Speed Grinding Wheel

The airflow field of super-high speed grinding was analyzed in the paper and the method of computing and analyzing the distribution of the field has been brought forward by applying boundary layer theory. Adopting the method of finite element, the model of airflow field in the 3-D grinding zone has been built up by using software; the solving strategy and the boundary conditions has been defined, where artificial viscosity coefficient in the repetitive and continuous analysis and the method by applying inertia relaxation have been discussed, which helped to revolve stability. The results of simulation was given and analyzed, which can be validated with experiment by using the equipment of PIV (particle image of velocity).

Slow-Wave Characteristics of Elliptical Corrugated Waveguideswith a Concentric Circular Hole

We present the formulation of elliptical corrugated waveguideswith a concentric circular hole using the field-matching method andthe addition theorem for Mathieu functions. The dispersion equation andthe mean interaction impedance of this structure are derivedseparately. The numerical results, which are generally based on thecurrent approach, agree well with the results obtained by thecommercial software package CST. As a slow-wave structure, thisstructure has potential applications in high power microwave amplifiersand possibly filtering structures.

Optimal placement of sensors for structural health monitoring using improved geneticalgorithms

The global optimization of sensor locations for structural health monitoring systems isstudied in this paper. First, the performance function based on damage detection ispresented. Then, genetic algorithms (GAs) are adopted to search for the optimal locationsof sensors. However, the simple GAs can result in infeasible solutions to the problem. Someimproved strategies are presented in this paper, such as crossover based on identificationcode, mutation based on two gene bits, and improved convergence. The analytical resultsfrom the improved genetic algorithm are compared with the penalty function method andthe forced mutation method. It is concluded that the convergence speed with the proposedimproved genetic algorithm is faster than that with the penalty function methodand the forced mutation method, and the result of placement optimization isbetter.

Investigation of the feasibility of amplitude-modulated dipolardecoupling in magic-angle spinning solid-state nuclear magneticresonance

The feasibility of using periodic amplitude-modulated radio-frequency (RF)irradiation under `magic-angle spinning' for heteronuclear dipolardecoupling in solid-state nuclear magnetic resonance is addressed.The RF waveforms used are tailored to satisfy the theoretical criterionfor decoupling which calls for an irradiated spin propagator which iscyclic in the sense that it equals the identity matrix irrespective of thestrength and orientation of the chemical shift and dipolar couplingtensors. This requirement is met by using the Floquet formalism toprovide insight into the influence of an arbitrary waveform on thedynamics of the irradiated spin-½nuclei and invoking perturbation methods todesign particular modulation functions which impose the requiredcyclicity on the propagator. Simple RF modulations which are synchronizedwith the sample spinning are thus derived analytically. Finally, thevalidity of the scheme is explored in simple test experiments and thedecoupling performance is compared with the traditional `continuous-wave' method andthe recently developed technique of `two-pulse phase modulation'.

Pseudo-critical slowing down within the cluster variation method andthe path probability method

The pseudo critical slowing down phenomenon reported for an order-disordertransition of the first order is reproduced by the path probability methodcalculations on a L10 ordered phase. The slowing down takes place towardsthe instability temperature of the metastable ordered phase ratherthan the transition temperature. In order to clarify the thermodynamicorigin of the pseudo critical slowing down, the temperature dependency ofgeneralized susceptibilities are calculated for the L10 ordered phase as afunction of v2,2/v2,1, where v2,n is the nthnearest neighbour effective pair interaction energy. The diverging behaviouris observed towards the instability temperature through the transitiontemperature. This is pronounced, as the second-order character is emphasized.It is confirmed that the pseudo-critical slowing down phenomenon is caused bythe flattening of the free energy surface, leading to the loss of thethermodynamic driving force for relaxation. The first-principles calculationof the susceptibility is attempted for Cu-Au system at a 1:1 stoichiometriccomposition. A sharp rise is confirmed near the transition temperature.

Resource Accounting in Measures of Unsustainability: Challenging the World Bank's Conclusions

The World Bank has recently published acomprehensive study of environmental and resourceaccounting, covering 103 countries (World Bank1997a). The study concludes that many Sub-Saharan,Northern African and Middle East countries have hadnegative `genuine' saving rates over the last 20years and therefore fail to pass the test of weaksustainability. This paper argues that the Bank'sconclusions depend on a method for computing usercosts from resource exploitation that is challengedby two competing ones (the `El Serafy'-method andthe method of Repetto et al.) and is inferior to oneof its rivals. Resource rents are re-computed usingthe `El Serafy'-method for 14 countries and theSub-Saharan and Northern African and Middle Eastregions. The results are that both regions andalmost all countries either stop exhibiting signs ofunsustainability or their unsustainability can beexplained without having recourse to resourceaccounting. However, for Congo, Ecuador, Gabon,Nigeria, Mauritania and Trinidad and Tobago there isa lesson: These countries did not adequately use theopportunities they were given through their naturalresource endowments and should learn from theirmistake for the future depletion of their remainingreserves of natural resources.

A new piezodriven precision micropositioning stage utilizing flexurehinges

A precision micropositioning system with a high displacement resolution and widemotion range has been required for industrialized applications for a long time. This paper discussesthe design and the characteristics of a new piezodriven precision micropositioning stage utilizingflexure hinges. Two-grade amplifying and a monolithic symmetrical mechanism are adopted in thedesign. An analytical model is presented and a series of formulae for the static and dynamicbehaviour of the stage are derived. Based on the theoretical analysis, the optimum design schema isput forward. The experimental demonstration to study the performance of the stage is described, andthe method for reducing nonlinearity errors is proposed. The experimental results are in closeagreement with those predicted by the theoretical analysis.

Voltage Dependence of Resistivity in Semiconducting Ceramics

Voltage dependence of resistivity(VDR)is a widely existing phenomenon insemiconducting ceramics, but there is no quantitative study on this phenomenon. Inthis note, the quantitative results of voltage dependence of resistivity insemiconducting ceramics are obtained from the grain boundary barrier model, andthe methods to decrease the voltage dependence of resistivity in sendconductingceramics are proposed.

Generalization of the static mechanical properties of plasticized polyamide-12 and polyamide-6

Generalization of the static mechanical properties of plasticized PA-12 andthe method of reduced variables over a wide temperature range has yielded a discrete series of values of the effective activation energy corresponding to the main relaxation processes. The character of change in effective activation energy with strain is regarded as a relaxation transition similar to that occuring on exposure to temperature. A scheme of the temperature-strain transitions in polymers is proposed.

Regularization and linear boundary value problems

The method of regularization is used in a general setting to obtain least squares solutions of thelinear equation Lx = y, permitting applications to linear boundary value problems of ordinary and partial differential equations. In regularization the functional is minimized over the domain , where L is assumed to be aclosed densely defined linear operator from a Hilbert space X into a Hilbert space Y, α is a nonzero parameter, and T is a linearoperator from X into a Hilbert space Z with . Under suitable conditions on L and T, it is shown that Gα achieves a minimum at a unique point xα in , and by using the alternative method the xα are shown to converge to a least squares solution of Lx = y with rate of convergence of order α2 . The regularization method is also recast as a least squares process. Finally, the important special case Z = X and T = I is examined in detail, andthe method is applied to the numerical solution of some model boundary value problems.

STUDY ON OPTICAL REMOTE SENSING ATMOSPHERIC AEROSOL AND WATER VAPOUR CONTENT

With the multichannel radiometer of visible and infrared band, ground-based observationsof the intensity of solar spectrum and the atmospheric optical thickness have been made andthe method of remote sensing atmospheric aerosol and water vapour content have been studied.With the radiometer(seven channels of 0.5--1.06μ), observations have been made for morethan one year in Beijing. The atmospheric water vapour content obtained from remote sensingis in accord with that from radiosonde data. In this paper, the characteristics of atmosphericaerosol and total water vapour content are discussed, and the influences of aerosol and thewater vapour on the atmospheric optical thickness and the relationship between them in thewater absorption region are also treated with.