Some features of bending of a rod under a strong longitudinal compression

Typical processes of rod bending under strong longitudinal compression are studied. The corresponding dynamic equation of bending is considered as a perturbation of the two-dimensional Laplace equation. It is established that, for these processes, the expantion of domains of rapid increase of bending begins in small neighborhoods of singularity points of solutions of the limiting Laplace equation. The initial stages of these increases are described using the Hardy integral.     

Thermal modelling of laser welding and related processes: a literature review

The main emphasis of this review is on thermal modelling and prediction of laser welding in metals. However as similar techniques are employed to model conventional welding processes such as arc, resistance and friction, as well as related processes such as alloying, cladding and surface hardening, part of this review is given over to the modelling of these processes where appropriate. The time frame of the review is up to the year 2002.     

Plasma synthesis of nanopowders

There is a huge variety of plasma processes for synthesis of nanoparticulate powders. They may be grouped with respect to operating temperature, which is the essential parameter with respect to the properties of the products. In view of industrial production, the highest degree of maturity is found in high temperature processes working under ambient pressure. For products, where well-defined properties are demanded, low temperature microwave plasma processes are best suited. Additionally, these processes allow coating of the produced particles, even with organic phases. Other processes where plasmas are involved, such as laser or flame processes coupled with electric fields have, to some extent, a high potential for development.     

The use of Raman spectroscopy in food processes: A review

Raman spectroscopy is a novel method of food analysis and inspection. It is highly accurate, quick, and noninvasive. The investigation and monitoring of food processing is important because most of the foods humans eat today are processed in various ways. In this article, the use of Raman spectroscopy in food processes, such as fermentation, cooking, processed food manufacturing, and so on, are explored. The characteristics and difficulties of the Raman inspection of these processes are also discussed. According to the various research reports, Raman spectroscopy is a very powerful tool for monitoring these food processes in lab environments and is likely to see usage in situ in the future.     

Influence of the intrinsic dynamics of the magnetisation on the hysteresis loop

We present numeric simulations of switching processes in small ferromagnetic particles. The dynamics of these processes and the influence of the dynamics of the applied and internal fields on the magnetization reversal are studied. In particular, the derivative in time of the effective fields influences the hysteresis of these particles. It is shown that fast switching, as is required in high-speed data storage, reduces the coercive field. A dynamically corrected Stoner–Wohlfarth dependence of the nucleation field is introduced for the limit of high-field rates and low damping. Implications of these findings are discussed for both, numerical simulation of hysteretic properties and the interpretation of experimental data.     

Applications of Singh-Rajput Mes in Recall Operations of Quantum Associative Memory for a Two- Qubit System

Recall operations of quantum associative memory (QuAM) have been conducted separately through evolutionary as well as non-evolutionary processes in terms of unitary and non- unitary operators respectively by separately choosing our recently derived maximally entangled states (Singh-Rajput MES) and Bell’s MES as memory states for various queries and it has been shown that in each case the choices of Singh-Rajput MES as valid memory states are much more suitable than those of Bell’s MES. it has been demonstrated that in both the types of recall processes the first and the fourth states of Singh-Rajput MES are most suitable choices as memory states for the queries ‘11’ and ‘00’ respectively while none of the Bell’s MES is a suitable choice as valid memory state in these recall processes. It has been demonstrated that all the four states of Singh-Rajput MES are suitable choice as valid memory states for the queries ‘1?’, ‘?1’, ‘?0’ and ‘0?’ while none of the Bell’s MES is suitable choice as the valid memory state for these queries also.     

Multi-jet production in hadron collisions

The advent of high-energy hadron colliders necessitates efficient and accurate computation of multi-jet production processes, both as QCD processes in their own right and as backgrounds for other physics. The algorithm that performs these tasks and a brief numerical study of multi-jet processes are presented. Received: 21 February 2002 / Published online: 22 May 2002     

Kinetics of failure of polycrystalline ferroelectric ceramics in mechanical and electric fields

The kinetics of mechanical failure and electrical breakdown in polycrystalline ferroelectric ceramics was studied under the simultaneous action of an electric field and a mechanical load. A kinetic approach is shown to be preferable as compared to the concepts that treat the failure and breakdown as critical phenomena. The mechanical failure and electrical breakdown are shown to be interrelated. It is found that a weak action of one of the fields retards failure caused by the other field and that the simultaneous action of these strong fields accelerates both the mechanical failure and electrical breakdown. Methods for determining the activation characteristics of both processes only from the failure kinetics in one of these processes are developed.     

Photoelectron spectroscopy of two-photon ionisation of rare-gas atoms by multiple high order harmonics

Two-photon ionisation processes of rare-gas atoms produced by a superposition of multiple high order harmonics are studied by using a photoelectron spectroscopy technique. Second-order nonlinearity is confirmed by comparing the intensity-dependent photoelectron yields between the linear and nonlinear processes, and the cross sections of these processes are estimated. We also demonstrate the autocorrelation measurement of harmonic envelopes as a preliminary step toward characterisation of an attosecond pulse train. PACS 32.80.Fb; 32.80.Wr; 42.65.-k     

Scaling of Lévy-Student processes

Student’s t-distributions are widely used in financial studies as heavy-tailed alternatives to normal distributions. As these distributions are not closed under convolution, there exist no Lévy processes with Student’s t-marginals at all points in time. In this article we show that a Student’s t-approximation of these marginals is still suitable, while not exact. Using this approximation, we are able to describe the scaling behavior of such Lévy-Student processes and the parameters of its marginal distributions by a simple analytical scaling law. This scaling law drastically simplifies the use of Lévy-Student processes as a general diffusion process in various interdisciplinary applications. We explicitly provide an application in the context of modelling high-frequency price returns.     

DNA based molecular motors

Most of the essential cellular processes such as polymerisation reactions, gene expression and regulation are governed by mechanical processes. Controlled mechanical investigations of these processes are therefore required in order to take our understanding of molecular biology to the next level. Single-molecule manipulation and force spectroscopy have over the last 15 years been developed into extremely powerful techniques. Applying these techniques to the investigation of proteins and DNA molecules has led to a mechanistic understanding of protein function on the level of single molecules. As examples for DNA based molecular machines we will describe single-molecule experiments on RNA polymerases as well as on the packaging of DNA into a viral capsid—a process that is driven by one of the most powerful molecular motors.     

Gibbs Ensembles of Nonintersecting Paths

We consider a family of determinantal random point processes on the two-dimensional lattice and prove that members of our family can be interpreted as a kind of Gibbs ensembles of nonintersecting paths. Examples include probability measures on lozenge and domino tilings of the plane, some of which are non-translation-invariant. The correlation kernels of our processes can be viewed as extensions of the discrete sine kernel, and we show that the Gibbs property is a consequence of simple linear relations satisfied by these kernels. The processes depend on infinitely many parameters, which are closely related to parametrization of totally positive Toeplitz matrices.     

In Situ Studies on Reaction Mechanisms in Atomic Layer Deposition

During the past decade, atomic layer deposition (ALD) has become an important thin-film deposition method in microelectronics industry, and it has also gained a lot of interest in many other areas, such as nanotechnology. The success of ALD is built on proper surface reactions. In this paper, in situ reaction mechanism studies on ALD processes are reviewed with the aim of building a general understanding on similarities and differences exhibited by various processes and process groups. Also, levels of understanding reaction mechanisms in ALD are discussed. The main methods used to study ALD chemistry in situ under typical process conditions are quadrupole mass spectrometry (QMS), quartz crystal microbalance (QCM), and infrared (IR) spectrometry. These are presented in detail in the review. Various other optical methods, ellipsometry in particular, have been used to study ALD processes too, but they provide little information about the reaction mechanisms. Competent in situ investigations solve the ALD reaction mechanism as balanced equations for the ALD half-reactions. The majority of ALD processes are exploiting ligand exchange reactions, where the ligands of the metal precursor are eliminated by bonding to the Lewis acids of the nonmetal precursors, most commonly hydrogen. These volatile byproducts are usually released during both precursor pulses, and determining their relative amounts is the important task in reaction mechanism studies of such processes. These processes are mechanistically fairly well understood, though some of these also display side-reactions to the ligand exchange reactions. There are also whole groups of processes that are using chemistry almost entirely different from the ligand exchange reactions. The most important such processes involve combustion chemistry, with oxygen, oxygen plasma, or ozone as a precursor or co-reactant. The mechanisms of these processes are complicated and less understood compared with the mechanisms of the ligand exchange reaction processes.     

Noise associated with reduction,multiplication and branching processes

We consider noise in particle fluxes which undergo a reduction or a multiplication process, either direct or via branching. It is shown that these processes can be described with the method of addition of independent events, or with a collective procedure. Using the statistical rules for compound and branching processes, general results for the variance of these processes are obtained. In particular, we consider the reduction process associated with the Bernouilli trials, the multiplication process due to geometric variables, some branching processes, and the combined multiplication-reduction process. The results are applied to various cases, such as secondary emission noise, avalanche noise in low voltage breakdown diodes (zener diodes) and in JFETs, cathodoluminescence, noise and interval statistics.     

Investigation of the percolation transition in a nonwetting liquid-nanoporous medium system

The flows of liquid into and out of a nanoporous medium are studied as processes leading to the fluctuation formation and the growth of fractal clusters of filled and empty pores, respectively. The conditions for stable growth of such fluctuations are analyzed as a function of the interfacial energy between the liquid and the porous medium and the surface energy of the liquid. Expressions are obtained for the pressure at which the barrier for fluctuation filling and emptying of the pores vanishes. In general, it is shown for porous media with a pore-size distribution that these processes can be interpreted as a percolation phase transition. The volume and susceptibility of a liquid-porous medium system near the transition points with inflow and outflow of the liquid are calculated. The phenomenon of nonoutflow of a nonwetting liquid from a porous medium and hysteresis of the flow of liquid into and out of a porous medium are explained on the basis of the mechanism considered. The results of an experimental investigation of these processes in the system liquid Wood’s alloy-silochrome 80 and silochrome 120 are presented. The experimental data obtained can be described on the basis of the proposed mechanism.     

Statistical Analysis of the First Passage Path Ensemble of Jump Processes

The transition mechanism of jump processes between two different subsets in state space reveals important dynamical information of the processes and therefore has attracted considerable attention in the past years. In this paper, we study the first passage path ensemble of both discrete-time and continuous-time jump processes on a finite state space. The main approach is to divide each first passage path into nonreactive and reactive segments and to study them separately. The analysis can be applied to jump processes which are non-ergodic, as well as continuous-time jump processes where the waiting time distributions are non-exponential. In the particular case that the jump processes are both Markovian and ergodic, our analysis elucidates the relations between the study of the first passage paths and the study of the transition paths in transition path theory. We provide algorithms to numerically compute statistics of the first passage path ensemble. The computational complexity of these algorithms scales with the complexity of solving a linear system, for which efficient methods are available. Several examples demonstrate the wide applicability of the derived results across research areas.     

Ion diagnostics of deformed regions in solids

This review concerns the processes that occur in deformed areas of the surface when targets of varied composition are bombarded with ions. The results of the scientific research summarized and discussed here are important for understanding the mechanisms behind these processes, as well as for a practical purpose, i.e., for developing a technique for identifying latent deformed areas, for example, removed figures on coins or ground-off markings on a weapon, a car, or a piece of art.     

Application of Fourier Transform Infrared Spectroscopy in the Study of Atmospheric Heterogeneous Processes

Abstract

Atmospheric heterogeneous processes associated with the complex behavior of atmospheric particles may play a crucial role in atmospheric chemistry and global climate change. Many of these heterogeneous processes have been widely investigated in detail over the years, including heterogeneous reactions on the surface of aerosol particles, aerosol hygroscopicity, as well as aerosol chemical compositions. As a fast, sensitive, precise, nondestructive, in situ, and online experimental technique, Fourier transform infrared (FTIR) spectroscopy has played a significant role in investigating atmospheric heterogeneous processes. On the basis of the mechanisms and characteristics of various FTIR techniques, this work presents a review of the applications of in situ FTIR spectroscopy in atmospheric heterogeneous processes study, and future development directions for FTIR spectroscopy are proposed considering current and future research needs for heterogeneous processes.     

Investigation into the processes of thermal and photothermal destruction of F-color centers in alkali-halide crystal phosphors

Using the concept of thermal and photothermal destruction of color centers in alkali-halide phosphors as an ion mechanism, certain formulas are examined which represent these processes. The phenomenon of thermal and photothermal destruction of F-color centers is investigated experimentally for the case of NaCl-Ag. A comparison of the experimental results obtained with the theory enabled an estimate to be made of a number of kinetic characteristics of the processes in question.The results obtained confirm the usefulness of the idea of ion processes in explaining the phenomena of relaxation in alkali-halide crystal phosphors.