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Number of results: 13
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Abstract

Development and demography of Adalia decempunctata L. were studied under laboratory conditions at seven constant temperatures (12, 16, 20, 24, 28, 32 and 36°C). First instar larvae failed to develop to second instar at 12°С and no development occurred at 36°C. The total developmental time varied from 47.92 days at 16°C to 15.94 days at 28°C and increased at 32°C. The lower temperature thresholds of 11.05 and 9.90°C, and thermal constants of 290.84 day-degree and 326.34 day-degree were estimated by traditional and Ikemoto-Takai linear models, respectively. The lower temperature threshold (Tmin) values estimated by Analytis, Briere-1, Briere-2 and Lactin-2 for total immature stages were 11.99, 12.24, 10.30 and 10.8°C, respectively. The estimated fastest developmental temperatures (Tfast) by the Analytis, Briere-1, Briere-2 and Lactin-2 for overall immature stages development of A. decempunctata were 31.5, 31.1, 30.7 and 31.7°C, respectively. Analytis, Briere-1, Briere-2 and Lactin-2 measured the upper temperature threshold (Tmax) at 33.14, 36.65, 32.75 and 32.61°C. The age-stage specific survival rate (sxj) curves clearly depicted the highest and lowest survival rates at 16 and 32°C for males and females. The age-specific fecundity (mx) curves revealed higher fecundity rate when fed A. gossypii at 24 and 28°C. The highest and lowest values of intrinsic rate of increase (r) were observed at 28 and 16°C (0.1945 d–1 and 0.0592 d–1, respectively). Also, the trend of changes in the finite rate of increase (λ) was analogous with intrinsic rate of increase. The longest and shortest mean generation time (T) was observed at 16 and 28°C, respectively and the highest net reproductive rates (R0) was estimated at 24 and 28°C. According to the results, the most suitable temperature seems to be 28°C due to the shortest developmental time, highest survival rate, and highest intrinsic rate of increase.
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Abstract

By simulating the actual working conditions of a cable, the temperature variation rule of different measuring points under different load currents was analyzed. On this basis, a three-dimensional finite element model (FEM) was established, and the difference and influence factors between the simulation temperature and the experimental measured value were discussed, then the influence of thermal conductivity on the operating temperature of the conductor layer was studied. Finally, combined with the steady-state thermal conductivity model and the experimental measured data, the relation between thermal conductivity and load current was obtained.
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Abstract

Percutaneous RF ablation is one of alternative treatment for non-surgical liver tumors. Ablative changes in hepatic tissue can be successfully estimated using the finite element method. The authors created a 3D model of a multi-tine applicator immersed in liver tissue, and then determined the optimal values of voltage applied to such an RF electrode, which do not exceed the therapeutic temperature range valid during thermal ablation procedure. Importantly, the simulations were carried out for the RF electric probes with 2 to 5 evenly spaced arms. Additionally, the thermal damage of hepatic tissue for multi-armed applicators working at pre-defined limit values of voltages was established based on the Arrhenius model.
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Abstract

Measurement of the perfusion coefficient and thermal parameters of skin tissue using dynamic thermography is presented in this paper. A novel approach based on cold provocation and thermal modelling of skin tissue is presented. The measurement was performed on a person’s forearm using a special cooling device equipped with the Peltier module. The proposed method first cools the skin, and then measures the changes of its temperature matching the measurement results with a heat transfer model to estimate the skin perfusion and other thermal parameters. In order to assess correctness of the proposed approach, the uncertainty analysis was performed.
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Abstract

The paper presents analytical and numerical model calculation results of the temperature distribution along the thermal flow meter. Results show a very good conformity between numerical and analytical model. Apart from the calculation results the experimental investigations are presented. The author performed the test where a temperature of duct wall surface was measured. Therelation between mass flow rate in terms of the duct surface temperature difference was developed.
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Abstract

Based on the theory of heat transfer, the influence of expansion joints on the temperature and stress distribution of ladle lining is discussed. In view of the current expansion joint, the mathematical model of heat transfer and the three dimensional finite element model of ladle lining brick are established. By analyzing the temperature and stress distribution of ladle lining brick when the expansion joints are in different sizes, the thermal mechanical stress caused by the severe temperature difference can be reduced by the suitable expansion joint of the lining brick during the ladle baking and working process. The analysis results showed that the thermal mechanical stress which is caused by thermal expansion can be released through the 2 mm expansion joint, which is set in the building process. So we can effectively reduce the thermal mechanical stress of the ladle lining, and there is no risk of steel leakage, thus the service life of ladle can be effectively prolonged.
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Abstract

Postharvest processing of grain is an important step in the overall grain production process. It makes possible not only quantitative and qualitative preservation of the harvest, but also ensures maximum profit from its sale at the most favorable market conditions. Convective heat treatment (drying, cooling) guarantees commercial harvest conservation, prevents its loss, and in some cases improves the quality of the finished product. The necessity of intensification and automation of technological processes of postharvest grain processing requires the development of methods of mathematical modeling of energy-intensive processes of convective heat treatment. The determination and substantiation of optimum modes and parameters of equipment operation to ensure the preservation of grain quality is possible only when applying mathematical modeling techniques. In this work, a mathematical model of particulate material drying is presented through a system of differential equations in partial derivatives of which the variable in time and space relationship between heat and mass transfer processes in the material and a drying agent is reflected. The aim of the research was to determine the dynamics of the interrelated fields of unsteady temperature and moisture content of the material and the drying agent on the basis of mathematical models of heat and mass transfer in the layer of particulate material in convective heat approach or heat retraction. The implementation of the mathematical model proposed in the standard mathematical set allows analyzing efficiency of machines and equipment for the convective heat treatment of particulate agricultural materials in a dense layer, according the determinant technological parameters and operating modes.
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Abstract

The paper presents the results of numerical computations performed for the furnace chamber waterwalls of a supercritical boiler with a steam output of 2400 × 103 kg/h. A model of distributed parameters is proposed for the waterwall operation simulation. It is based on the solution of equations describing the mass, momentum and energy conservation laws. The aim of the calculations was to determine the distribution of enthalpy, mass flow and fluid pressure in tubes. The balance equations can be brought to a form where on the left-hand side space derivatives, and on the right-hand side – time derivatives are obtained. The time derivatives on the right-hand side were replaced with backward difference quotients. This system of ordinary differential equations was solved using the Runge-Kutta method. The calculation also takes account of the variable thermal load of the chamber along its height. This thermal load distribution is known from the calculations of the heat exchange in the combustion chamber. The calculations were carried out with the zone method.
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Abstract

In thermosfluid dynamics, free convection flows external to different geometries, such as cylinders, ellipses, spheres, curved walls, wavy plates, cones, etc., play major role in various industrial and process engineering systems. The thermal buoyancy force associated with natural convection flows can play a critical role in determining skin friction and heat transfer rates at the boundary. In thermal engineering, natural convection flows from cylindrical bodies has gained exceptional interest. In this article, we mathematically evaluate an entropy analysis of magnetohydrodynamic third-grade convection flows from permeable cylinder considering velocity and thermal slip effects. The resulting non-linear coupled partial differential conservation equations with associated boundary conditions are solved with an efficient unconditionally stable implicit finite difference Keller-Box technique. The impacts of momentum and heat transport coefficients, entropy generation and Bejan number are computed for several values of non-dimensional parameters arising in the flow equations. Streamlines are plotted to analyze the heat transport process in a two-dimensional domain. Furthermore, the deviations of the flow variables are compared with those computed for a Newtonian fluid and this has important implications in industrial thermal material processing operations, aviation technology, different enterprises, energy systems and thermal enhancement of industrial flow processes.
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Abstract

In the paper, the mathematical model of coupled electromagnetic and thermal phenomena in the pulse transformer taking into account the magnetic hysteresis is presented. For the mapping of magnetic hysteresis, Jiles-Atherton model is applied. In order to solve field equations, the finite element method (FEM), "step-by-step" procedure and Newton-Raphson algorithm are used. Software elaborated on this basis is used for analysis of hysteresis loss in the core. Selected results of investigations are shown.
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Abstract

The transient thermal model of the permanent magnet linear actuator (PMLA) has been considered. The characteristics of heating have been calculated including the main subdomains of the actuator. The carcasses from various materials have also been considered. The calculations have been verified experimentally and a good conformity was obtained.
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Abstract

According to the analysis of the current state of the knowledge shows that there is little information on the process of phase transformations that occur during the cooling Cu-Al-Fe-Ni hypo-eutectoid bronzes with additions of Cr, Mo and/or W, made additions individually or together, for the determination of: the type of crystallizing phases, crystallizing phases, order and place of their nucleation. On the basis of recorded using thermal and derivative analysis of thermal effects phases crystallization or their systems, analysis of the microstructure formed during crystallization - observed on the metallographic specimen casting ATD10-PŁ probe, analysis of the existing phase equilibrium diagrams forming elements tested Cu-Al-Fe-Ni bronze, with additions of Cr, Mo, W and/or Si developed an original model of crystallization and phase transformation in the solid state, the casting of high quality Cu-Al-Fe-Ni bronze comprising: crystallizing type phase, crystallizing phase sequence, place of nucleation.
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Abstract

The paper presents an FE model of coupled electromagnetic and thermal phenomena in Line Start Permanent Magnet Synchronous Motors (LSPMSMs). An algorithm for solving equations of a discrete model using the FEM has been presented. On the basis of this algorithm the author’s personally developed software for the analysis of coupled electromagnetic-thermal phenomena in the LSPMS motors was elaborated. This software was used to analyze the start-up process of motors with identical stator and rotor magnetic circuits and different materials of the starting cage. The start-up process of motors with the squirrel-cage made of aluminum and copper was considered. The influence of temperature on the start-up process has been taken into account. The results of simulation tests were compared with the results of measurements.
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