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Khmelnytskyi, Ukraine

Goldengorin B.,Khmelnitsky National University | Krushinsky D.,University of Groningen | Slomp J.,University of Groningen
Operations Research

Lately, the problem of cell formation (CF) has gained a lot of attention in the industrial engineering literature. Since it was formulated (more than 50 years ago), the problem has incorporated additional industrial factors and constraints while its solution methods have been constantly improving in terms of the solution quality and CPU times. However, despite all the efforts made, the available solution methods (including those for a popular model based on the p-median problem, PMP) are prone to two major types of errors. The first error (the modeling one) occurs when the intended objective function of the CF (as a rule, verbally formulated) is substituted by the objective function of the PMP. The second error (the algorithmic one) occurs as a direct result of applying a heuristic for solving the PMP. In this paper we show that for instances that make sense in practice, the modeling error induced by the PMP is negligible. We exclude the algorithmic error completely by solving the adjusted pseudo-Boolean formulation of the PMP exactly, which takes less than one second on a general-purpose PC and software. Our experimental study shows that the PMP-based model produces high-quality cells and in most cases outperforms several contemporary approaches. © 2012 INFORMS. Source

Zaspa Y.P.,Khmelnitsky National University
Journal of Friction and Wear

The transition to the condition of autowave motion is illustrated on the example of a dynamic system consisting of weights linked to a pulley moving with friction in the pulley axis under the force of gravity. The coherent interaction between the external modes of nonstationary directed motion and the internal wave modes under the studied conditions induces the effects of negative dynamic friction. The tangential intensification of the counterbody friction in the intervals of positive feedback actuates both the tangential and normal component of the full contact response that has no counterparts in the equilibrium tribodynamics. This effect is explained by the resonance automodulation of contact friction by elastic waves of stresses. The qualitative parameters controlling the changes in external friction conditions are introduced, similar to the Reynolds number in hydroaeromechanics. The general problems of contact tribodynamics and hydroaerodymics of the boundary layer are analyzed in respect to the coherent interaction in the friction system and the wave impulse transfer. © 2012 Allerton Press, Inc. Source

Saumel I.,TU Berlin | Kotsyuk I.,Khmelnitsky National University | Holscher M.,TU Berlin | Lenkereit C.,TU Berlin | And 2 more authors.
Environmental Pollution

Food production by urban dwellers is of growing importance in developing and developed countries. Urban horticulture is associated with health risks as crops in urban settings are generally exposed to higher levels of pollutants than those in rural areas. We determined the concentration of trace metals in the biomass of different horticultural crops grown in the inner city of Berlin, Germany, and analysed how the local setting shaped the concentration patterns. We revealed significant differences in trace metal concentrations depending on local traffic, crop species, planting style and building structures, but not on vegetable type. Higher overall traffic burden increased trace metal content in the biomass. The presence of buildings and large masses of vegetation as barriers between crops and roads reduced trace metal content in the biomass. Based on this we discuss consequences for urban horticulture, risk assessment, and planting and monitoring guidelines for cultivation and consumption of crops. © 2012 Elsevier Ltd. All rights reserved. Source

Pastukh I.M.,Khmelnitsky National University
Technical Physics

Nitriding in a glow discharge is analyzed at the level of its components. A basically new (as compared to the classical) scheme of the process is proposed taking into account the most significant subprocesses. © 2014, Pleiades Publishing, Ltd. Source

Pastukh I.M.,Khmelnitsky National University
Technical Physics

A new model of nitriding is proposed on the basis of the energy initial conditions. © 2016, Pleiades Publishing, Ltd. Source

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