Computer simulation model of the structure of ion implanted impurities in semiconductors

A system of ion implanted impurities in a semiconductor is described by a Monte Carlo simulation of a non-equilibrium system of random distributed hard spheres. The radial distribution function of this system is found. The comparison is made with the fluid hard sphere case. The assumption that the absence either of annealing or diffusion of the impurities after the implantation process is also made.     

Dynamics of a multilink mechanism containing rotational kinematic pairs

Mechanics Institute, Ukrainian Academy of Sciences, Kiev. Translated from Prikladnaya Mekhanika, Vol. 26, No. 3, pp. 92–96, March, 1990.     

Effects of Coulomb interaction on charge transport in a silicon-based nanocluster array

The effects of Coulomb interaction on charge transport in a model of light emission from an array of silicon nanoclusters are studied by Monte Carlo simulations. The array is sandwiched between a p-type and an n-type doped silicon crystals and electrons and holes are driven into the array by an applied electric field. Radiative recombinations of electrons and holes take place near the center of the array producing the emission of red light, and the total emission power is approximately proportional to the current injected into the system. It is found that the carrier-carrier interaction plays a crucial role in charge transport. Specifically, the self-interaction of charges inside each nanocluster is found to be the dominant interaction term for the semiclassical Hamiltonian considered. In addition, it drastically limits the current in the device giving rise to a strong non-linear relation between current and density of free carriers in the doped silicon crystals.     

Rational irreducible plane continua without the fixed-point property

We define rational irreducible continua in the plane that admit fixed-point-free maps with the condition that all of their tranches have the fixed-point property. This answers in the affirmative a question of Hagopian. The construction is based on a special class of spirals that limit on a double Warsaw circle. The closure of each of these spirals has the fixed-point property.

     

Compressive Stress Dependence of Magnetic Properties of Co66Fe4Ni1B14Si15 Alloy

The influence of compressive stresses on magnetic properties of Co₆₆Fe₄Ni₁B₁₄Si₁₅ amorphous alloy rings was investigated. In spite of low magnetostriction the stress sensitivity is significant. New method of applying stresses to a ring core is presented.     

Nonlinear rescaling vs. smoothing technique in convex optimization

We introduce an alternative to the smoothing technique approach for constrained optimization. As it turns out for any given smoothing function there exists a modification with particular properties. We use the modification for Nonlinear Rescaling (NR) the constraints of a given constrained optimization problem into an equivalent set of constraints.?The constraints transformation is scaled by a vector of positive parameters. The Lagrangian for the equivalent problems is to the correspondent Smoothing Penalty functions as Augmented Lagrangian to the Classical Penalty function or MBFs to the Barrier Functions. Moreover the Lagrangians for the equivalent problems combine the best properties of Quadratic and Nonquadratic Augmented Lagrangians and at the same time are free from their main drawbacks.?Sequential unconstrained minimization of the Lagrangian for the equivalent problem in primal space followed by both Lagrange multipliers and scaling parameters update leads to a new class of NR multipliers methods, which are equivalent to the Interior Quadratic Prox methods for the dual problem.?We proved convergence and estimate the rate of convergence of the NR multipliers method under very mild assumptions on the input data. We also estimate the rate of convergence under various assumptions on the input data.?In particular, under the standard second order optimality conditions the NR method converges with Q-linear rate without unbounded increase of the scaling parameters, which correspond to the active constraints.?We also established global quadratic convergence of the NR methods for Linear Programming with unique dual solution.?We provide numerical results, which strongly support the theory. Received: September 2000 / Accepted: October 2001?Published online April 12, 2002     

In vitro evaluation of the antioxidant and antimicrobial activity of DIMBOA [2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one]

The aim of this study was to evaluate the in vitro antioxidant and antimicrobial properties of the natural cyclic hydroxamic acid: 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA). Antioxidant activity of the isolated DIMBOA was examined using DPPH, FRAP and ABTS tests. It was found that DIMBOA exhibits a potent free-radical scavenging activity and a weaker iron (III) ions reducing activity. Antimicrobial activity against selected G(+), G(–) bacterial strains and against yeasts-like reference strains of fungi was investigated using disk-diffusion method. It has been shown that DIMBOA possess growth inhibitory properties against many strains of studied bacteria and fungi, such as Staphylococcus aureus, Escherichia coli as well as against Saccharomyces cerevisiae.