Simulation of thermally induced processes of diffusion and phase formation in layered Fe-Sn and Fe-Zr systems

The simulation results of thermally induced processes of diffusion and phase formation for the Fe-Sn and Fe-Zr layered systems experimentally investigated by M?ssbauer spectroscopy are presented. Simulation has been carried out using the specially designed DIFFUSION program, the basic functional possibilities of which are described in detail. The physical model is based on the phenomenological Darken theory and on the interdiffusion mechanism of components along the continuous diffusion channels of phases in two-phase regions of the system. The simulation results agree well with the experimental data. The character of phase transformations in the investigated layered systems is determined by the change in a local concentration of components during their interdiffusion and corresponds to the features of the equilibrium diagrams for both binary systems.     

Simulation of thermally-induced processes of diffusion and phase formation in layered metal-metalloid systems

A physical model of thermally induced processes of diffusion and phase formation in layered metal-metalloid systems is offered. The software for the model is created, which allows one to quantitatively describe the kinetics of these processes under arbitrary modes of annealing. The results of theoretical computations are compared with the data of experimental studies of a ⁵⁷Fe:O⁺ layered implantation system using the methods of M?ssbauer spectroscopy. The agreement between the numerical and experimental results indicates that the nature of phase transformations in the investigated system is determined by a change in the local concentration of the metalloid during its interstitial diffusion and corresponds to peculiarities of the phase equilibrium diagram of the Fe-O binary system.     

Optically and thermally induced molecular switching processes at metal surfaces

Using light to control the switching of functional properties of surface-bound species is an attractive strategy for the development of new technologies with possible applications in molecular electronics and functional surfaces and interfaces. Molecular switches are promising systems for such a route, since they possess the ability to undergo reversible changes between different molecular states and accordingly molecular properties by excitation with light or other external stimuli. In this review, recent experiments on photo- and thermally induced molecular switching processes at noble metal surfaces utilizing two-photon photoemission and surface vibrational spectroscopies are reported. The investigated molecular switches can either undergo a trans-cis?isomerization or a ring opening-closure reaction. Two approaches concerning the connection of the switches to the surface are applied: physisorbed switches, i.e.?molecules in direct contact with the substrate, and surface-decoupled switches incorporated in self-assembled monolayers. Elementary processes in molecular switches at surfaces, such as excitation mechanisms in photoisomerization and kinetic parameters for thermally driven reactions, which are essential for a microscopic understanding of molecular switching at surfaces, are presented. This in turn is needed for designing an appropriate adsorbate-substrate system with the desired switchable functionality controlled by external stimuli.     

Radiative reactions in two and three nucleon systems

Summary We have reviewed the theoretical and experimental situation regarding radiative processes in two and three nucleon system. There has actually been a lot of recent progress. Data sets from different experiments which agree with one another have now replaced the factor of two discrepancies of just a few years ago for several of the processes. New data on spin observables are now available for a variety of energies. New experiments are in progress for both proton proton and neutron bremsstrahlung. The theorists have not kept up. Although there has been a lot of work, there exists no theory which quantiatively describes all the data for eithern + p d + or forp + d ³He + . Thus there is still a lot to do if we are to fully understand these most basic processes.Invited talk to the symposium Measons and Light Nuclei, Bechyn, Czechoslovakia, May 27–June 1, 1985.Support in part from the Natural Sciences and Engineering Research Council of Canada is gratefully acknowledged.     

Field profiles of bulk plasmon polariton modes in layered systems containing a metamaterial

Electric and magnetic fields in a one-dimensional layered system that alternates air and a metamaterial are investigated. Special attention is devoted to frequencies of electric and magnetic bulk plasmons. It is shown that plasmon polaritons nearby such frequencies display field profiles concentrated in the metamaterial, where the field component parallel to the stacking direction is essentially uniform and dominates the perpendicular one.     

Spatially uniform autowave processes: Global synchronization in systems with transfer and diffusion

We study spatially uniform autowave processes in a generalized model of an active medium. These processes are interpreted as global synchronization in a chain of discrete dynamic systems, which is a discrete analog of a distributed system. We obtain sufficient conditions of global synchronization for different coupling types. Analytical results are illustrated by a numerical experiment carried out for a chain of circuits with individual chaotic dynamics.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 5, pp. 588–596, May, 1996.     

Extrema statistics of Wiener-Einstein processes in one,two, and three dimensions

The maxima and first-passage-time statistics of Wiener-Einstein processes are evaluated analytically in one, two, and three dimensions. We show that the mean square maximum displacement has the same time dependence as the mean square displacement, i.e., it grows linearly with time. The ratio of the mean square maximum to the mean square displacement is shown to decrease with increasing dimensionality. We also calculate the mean first passage time for the process to attain a given absolute displacement and find that it grows as the square of the displacementand is independent of the dimensionality of the process. In addition, we evaluate the dispersion of maxima and of first passage times and discuss their dependence on dimensionality.Supported in part by the National Science Foundation under Grant CHE 75-20624.     

The field fluctuational model of thermally stimulated processes in ferroelectric LiNbO3

The thermally stimulated processes in the x-irradiated LiNbO₃ crystals were studied by the fractional glow technique. The trap ionization with unusually high values of the mean activation energy and the effective frequency factor as well as decreasing the activation energy of the traps when the temperature increased from 150–180 K were observed. We suggest that all these effects are due to the ion-fluctuation process (the electric field generated by thermal reorientation of dipoles.     

Generation of electric potentials during heterogeneous combustion in systems containing VI group elements

The behavior of frontally burning heterogeneous systems containing chromium, molybdenum, and tungsten, which are used in the self-propagating high-temperature synthesis of complex oxide materials, was studies by the potentiometric method. It was revealed that the peak emf between the combustion wave front and the synthesis products can be as high as 2 V, depending on the chemical composition of the initial stock. A mobile registering probe moving with the velocity of combustion wave propagation makes it possible to substantially increase the time of emf recording     

Infrared behaviour of metallic systems in one,two and three dimensions

A simple approximate expression for the electron lifetime() in metals is rederived and discussed for different dimensions. In the 3D-case we get the well known Drude behaviour, i.e. a constant. In one dimension() is strongly frequency-dependent in the IR. The 2D-case is intermediate to the preceding ones. These results are essentially due to the different form of the Fermi surface for an electron gas in one, two and three dimensions.     

Infrared behaviour of metallic systems in one, two and three dimensions

A simple approximate expression for the electron lifetime() in metals is rederived and discussed for different dimensions. In the 3D-case we get the well known Drude behaviour, i.e. a constant. In one dimension() is strongly frequency-dependent in the IR. The 2D-case is intermediate to the preceding ones. These results are essentially due to the different form of the Fermi surface for an electron gas in one, two and three dimensions.     

Pattern formation in reaction diffusion systems: a Galerkin model

Reaction diffusion systems are extremely useful for studying pattern formation in biological systems. We carry out a Lorenz like few mode truncation of a reaction diffusion system and show that it not only gives the same qualitative behaviour as the more complicated systems but also indicates of the existence of a Hopf-bifurcation in the turing region. Received 10 May 2000 and Received in final form 14 March 2001     

Properties of interfaces in the two and three dimensional Ising model

To investigate order-order interfaces, we perform multimagnetical Monte Carlo simulations of the 2D and 3D Ising model. Following Binder we extract the interfacial free energy from the infinite volume limit of the magnetic probability density. Stringent tests of the numerical methods are performed by reproducing with high precision exact 2D results. In the physically more interesting 3D case we estimate the amplitudeF ₀ ^s of the critical interfacial tensionF ³=F ₀ ^s t to beF ₀ ^s =1.52±0.05. This result is in good agreement with a previous MC calculation by Mon, as well as with experimental results for related amplitude ratios. In addition, we study in some details the shape of the magnetic probability density for temperatures below the Curie point.     

Anomalous transport and diffusion phenomena induced by biharmonic forces in deformable potential systems

We study transport properties of an inertial Brownian motor which moves in a deformable Remoissenet-Peyrad periodic potential and is subjected to both a static bias force and time periodic driving biharmonic force. By modifying the shape of the potential, the anomalous transport is identified for a particular set of the system parameters. For a particular potential shape, the mean velocity of a particle is modified by going from negative to positive values according to the external bias force. These features also depend on both the biharmonic parameter and the phase-lag of two signals. A remarkable transition of the negative velocity depending on the shape of the potential is observed. We also focus on the efficiency of the motor and discuss velocity fluctuation. In addition, within selected system parameters, different types of diffusion particle such as subdiffusion, superdiffusion, normal diffusion, ballistic diffusion, hyperdiffusion and dispersionless transport phenomena are generated in the system.     

ICP-AES法测定两个等级的三种绿茶中九种矿物质元素含量

绿茶含有多种人体必需的营养成分,是传统的健康饮品之一.采用lCP-AES法测定了两个等级三个品种的绿茶中Ni,Ba,Fe,Mn,Cr,Mg,Ca,Cu和Al九种元素含量,结果表明小同品种绿茶中各种矿物质元素含量存在一定的差异,同一品种不同等级的绿茶矿物质元素含量也有所不同.研究结果不仅对人们日常饮茶的选择提供了一定科学...