Computing and information technology in a distributed environment. An overview

Even before the computer was invented, the concept of parallel computation was applied to solving many supercomplex problems manually using large teams of operators. In this overview, the possibility of solving problems in parallel is analyzed and the durability of parallel systems is estimated. As well, parallelization methods, supercomputer unfriendliness, information and access management in distributed environments, distributed systems applied for information simulation and analysis, and establishment of specialized centers are discussed.     

Help desk center operating model as a two-phase queueing system

We consider a two-phase queueing system with a Markovian arrival flow as an operating model for a help desk center. The first phase is a multiserver system with a finite buffer and impatient customers. After getting service in the first phase, a customer either enters the second phase with an infinite buffer or quits the system. Service times at the first and second stages have phase-type distributions with different parameters. We obtain an existence condition for a stationary regime of the system. An algorithm for computing stationary probabilities and basic performance characteristics of the system is presented. Laplace-Stieltjes transforms for the distributions of sojourn and waiting times in the first and second phases are found. Results of numerical experiments are presented. Optimization problem for the system operation is solved numerically.     

Peculiarities in the formation of gold nanoparticles by ion implantation in stabilized zirconia

The investigation of bulk single crystals and sputter-deposited films of yttria-stabilized zirconia (YSZ) upon irradiation by gold (Au) ions with an average energy of 160 keV followed by postimplantation annealing revealed peculiarities in the formation of nanocrystalline metal (nc-M) particles in this matrix. In the case of irradiation to small doses (∼5 × 10¹⁵ cm⁻²), the optical absorption spectra of samples showed evidence of the formation of nanoclusters of matrix cations (nc-Zr). In these samples, postimplantation annealing at temperatures ∼700°C and above leads to the formation of nc-Au particles. Local elemental analysis of individual nc-M particles in the YSZ matrix irradiated to a dose of 4 × 10¹⁶ cm⁻² and annealed at 800°C showed the presence of metal nanoparticles with complex compositions including both implanted Au and matrix Zr atoms.     

Parametric fuzzy model identification based on a hybrid ant colony algorithm

Applying the ant colony algorithm for solving the problem of parametric fuzzy model identification is presented. Transition from continuous optimization to discrete one via constructing a complete oriented decision-search graph is determined. A gradient algorithm is considered as the second optimization step. Experiments for analyzing the performance of the algorithms for optimization and fuzzy system are described.     

Equilibrium states of an ion-beam plasma with magnetized electrons at low pressures

Results are presented of an experimental investigation of an ion-beam plasma with magnetized electrons in the cathode channel of an ion accelerator with an anode layer. New data are reported on the spatial distributions of the local plasma parameters (plasma potential, electron temperature, electron and ion densities) as functions of the external parameters of the discharge (magnetic field strength, anode voltage, and working gas pressure) in regions with strong, nonuniform electric and magnetic fields. Pis’ma Zh. Tekh. Fiz. 24, 33–38 (March 12, 1998)     

Mathematical analysis of the multi-server queueing model for dynamic channel reservation in wireless networks

We consider a multi-server queueing model with two types of customers offered in Y. C. Kim et al. (1999) for modeling dynamic channel reservation based on mobility in wireless networks. Mathematical analysis given contains essential errors what makes some results negligible. We provide a correct analysis of the model     

The internal lagrange ballistic problem for the controlled rate of layered combustion of powder

We have studied the flow of a gas—powder mixture in a discharge, using a moderated propellant with a controlled combustion rate. New gasdynamic effects are detected: formation of combustion waves from a moderated layer of powder grain, formation of a reflected compression wave at the bottom of the piston, etc. The calculated and experimental data are compared for a small-caliber ballistic apparatus and the need to take heat transfer in the barrel wall into account is noted. Institute of Chemical Physics, Russian Academy of Sciences, Chernogolovka 142432. Translated from Fizika Goreniya i Vzyrva, Vol. 30, No. 5, pp. 78–84, September–October, 1994.     

Abrasive wear of protective coatings of thermitic gunite mixtures

The possibility of obtaining protective high-temperature coatings with an elevated resistance to abrasive wear by introducing various functional additions into the initial gunite mixtures is investigated. Technologically admissible additions that decrease the abrasive wear of the coatings by a factor of 2 – 3 are recommended.Translated from Ogneupory, No. 4, p. 18, April, 1995.     

Experimental and Numerical Study of the Formation of Thermophysical Characteristics of Carbon Composite Materials. Part 1. Formation of the thermophysical Characteristics of a Carbon Composite Material

Refractories and Industrial Ceramics - The analysis of a heat transfer mechanism in the bulk of carbon-carbon composite materials was performed. It was experimentally determined that a homogeneous...     

A New Method and Apparatus for High-Resolution γ-Radiographic Introscopy of Bulk Heavy-Metal Products and Blanks. First Application Results

Russian Journal of Nondestructive Testing - A $$\gamma $$-introscopy method and an installation using “electronic focusing” of $$\gamma $$-quanta transmitted through the studied object...