A simple parallelization technique with MPI for ocean circulation models

This paper proposes a comparatively simple technique based on overlapping domain decomposition for the transformation of serial computational algorithms of ocean circulation models into parallel ones. The advantage of the proposed technique is that only additional procedures using basic MPI functionality are required instead of a significant transformation of serial code. The method is fairly efficient for computations on comparatively inexpensive clusters, which are usually affordable for small companies. The impacts of various factors, which may affect the method efficiency are studied.     

A helical-radial magnetic cumulation fast-growing current pulse generator

A design-experimental study of a magnetic cumulation generator (further referred to as generator) with flat helical is performed. This generator combines advantages of both spiral-cylindrical and disk generators. As to speed of operation, the spiral-radial generator is equivalent to the disk generator, but can operate in high-impedance loads. To calculate characteristics of spiral-radial generators, including external-excitation generators, a semiempirical procedure for determining laws of variations of the inductances and mutual inductance of helical of the generator is developed. The procedure is based on measuring the current oscillation frequency in the course of the magnetic-field compression, while the helix is loaded into a small capacitance. A satisfactory compliance of the experimental data and semiempirical calculations is obtained. The experimental effective time values of the current buildup of the spiral-radial generators do not exceed the same characteristic for spiral-cylindrical generators with an axial charge initiation of the explosive material. A possibility of further decreasing the effective time is shown for the plane-parallel throwing of liner plates.     

Induction of chromosome aberrations is non-linear within the low dose region and depends on dose rate

The low dose region was evaluated for meristem cells of spring barley. A study of the cytogenetic damage in the low dose range was carried out to determine the genuine shape of the dose curve. The relationship between the frequency of aberrant cells and the absorbed dose is shown to be non-linear with a site at low doses within which the cytogenetic damage exceeds the control level significantly and does not depend on dose value. Within the tested exposure region, the aberrant cell frequency is found to decrease with increasing dose rate, but the shape of the dose curve remained invariable. The piecewise linear model fits the experimental data much better than the linear one.     

EPECUR setup for the search for narrow baryon resonances in pion-proton scattering

The EPECUR experimental setup has been designed to search for narrow resonant states by precisely measuring differential and total reaction cross sections for pion-nucleon interactions with 1-MeV pion energy steps. Over the 5 years that passed from the submission of the idea of the experiment to the start of data taking in April 2009, a non-magnetic spectrometer with a liquid hydrogen target based on the large-aperture multiwire drift chambers with a hexagonal structure has been built at the universal beamline 322 of the U-10 proton synchrotron at the Alikhanov Institute for Theoretical and Experimental Physics. Owing to the unique properties of the beamline, the beam particle momentum can be measured with an accuracy of 0.1% or better using 1-mm-pitch proportional chambers located at the first focus of the beamline. The design of numerous subsystems of the setup is based on modern electronic components including microprocessors and field programmable gate arrays. All the subsystems have been tuned and tested both individually and as parts of the whole setup. The distributed data acquisition system is based on the widely spread USB and Ethernet protocols, which help achieve high performance characteristics and take full advantage of the industrial solutions.     

Comparison of the phase behaviour of the liquid-crystalline polymer/poly(methyl methacrylate) and poly(vinyl acetate)/poly(methyl methacrylate) blends

The phase behaviour of blends of a liquid-crystalline polymer (LCP) and poly(methyl methacrylate) (PMMA), as well as the phase state of blends of PMMA and poly(vinyl acetate) (PVA) has been investigated using light scattering and phase-contrast optical microscopy. The blends of LCP and PMMA have been obtained by coagulation from ternary solutions. The cloud point curves were determined. It was established that both pairs demix upon heating, ie have an LCST. In the region of intermediate composition, the phase separation proceeds according to a spinodal mechanism; however for LCP/PMMA blends, the decomposition proceeds according to a non-linear regime from the very onset. In the region of small amounts of LCP, the phase separation follows a mechanism of nucleation and growth. For PMMA/PVA blends, the spinodal decomposition proceeds according to a linear regime, in spite of the molecular mobility that PVA chains develop at lower temperatures. Only after prolonged heat treatment does the process transit to a non-linear regime. The data show a similarity between the phase behaviour of blends of liquid-crystalline and of flexible amorphous polymers. The distinction consists of the absence of a linear regime of decomposition for LCP-PMMA blends. © 1999 Society of Chemical Industry     

Filler effect on polymerization kinetics and phase separation in polymer blends formed in situ

The kinetics of formation of a mixture of two polymers [poly(methyl methacrylate) and polyurethane] in situ in the course of two simultaneously proceeding reactions was studied in the presence of various amount of a filler (fumed silica). It was shown that the filler affects the rates of both reactions. In addition, the filler exerts an influence on the phase separation induced by the chemical reaction increasing the amount of a filler increases the time for the onset of phase separation. The effects observed may be explained both by the increase in the viscosity of the reaction system due to introduction of a filler and by selective adsorption of reaction system components at the interface with filler particles. In all cases, phase separation in the early stages of reaction proceeds in a four‐component system (two polymers formed and two initial compounds) and obeys the spinodal mechanism. It is also shown that the final morphology is determined far from the end of the reaction and before establishing the equilibrium state. © 2003 Society of Chemical Industry