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Article
Publication date: 18 September 2018

Ethan M. Moon and Vadim V. Yakovlev

This paper aims to introduce and illustrate a computational technique capable of determining the geometry and complex permittivity of a supplementary dielectric insert…

130

Abstract

Purpose

This paper aims to introduce and illustrate a computational technique capable of determining the geometry and complex permittivity of a supplementary dielectric insert making distributions of microwave-induced dissipated power within the processed material as uniform as possible.

Design/methodology/approach

The proposed technique is based on a 3D electromagnetic model of the cavity containing both the processed material and the insert. Optimization problem is formulated for design variables (geometrical and material parameters of the insert) identified from computational tests and an objective function (the relative standard deviation [RSD]) introduced as a metric of the field uniformity. Numerical inversion is performed with the method of sequential quadratic programming.

Findings

Functionality of the procedure is illustrated by synthesis of a dielectric insert in an applicator for microwave fixation. Optimization is completed for four design variables (two geometrical parameters, dielectric constant and the loss factor of the insert) with 1,000 points in the database. The best three optimal solutions provide RSD approximately 20 per cent, whereas for the patterns corresponding to all 1,000 non-optimized (randomly chosen) sets of design variables this metric is in the interval from 27 to 136 per cent with the average of 78 per cent.

Research limitations/implications

As microwave thermal processing is intrinsically inhomogeneous and the heating time is not a part of the underlying model, the procedure is able to lead only to a certain degree of closeness to uniformity and is intended for applications with high heating rates. The initial phase of computational identification of design variables and their bounds is therefore very important and may pre-condition the “quality” of the optimal solution. The technique may work more efficiently in combination with advanced optimization techniques dealing with “smart” (rather than random) generation of the data; for the use with more general microwave heating processes characterized by lower heating rates, the technique has to use the metric of non-uniformity involving temperature and heating time.

Practical implications

While the procedure can be used for computer-aided design (CAD) of microwave applicators, a related practical limitation may emerge from the fact that the material with particular complex permittivity (determined in the course of optimization) may not exist. In such cases, the procedure can be rerun for the constant values of material parameters of the available medium mostly close to the optimal ones to tune geometrical parameters of the insert. Special manufacturing techniques capable of producing a material with required complex permittivity also may be a practical option here.

Originality/value

Non-uniformity of microwave heating remains a key challenge in the design of many practical applicators. This paper suggests a concept of a practical CAD and outlines corresponding computational procedure that could be used for designing a range of applied systems with high heating rates.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 37 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 31 January 2020

Petra Kumi, Stephanie A. Martin, Vadim V. Yakovlev, Martin S. Hilario, Brad W. Hoff and Ian M. Rittersdorf

The paper introduces and illustrates the use of numerical models for the simulation of electromagnetic and thermal processes in an absorbing ceramic layer (susceptor) of a…

95

Abstract

Purpose

The paper introduces and illustrates the use of numerical models for the simulation of electromagnetic and thermal processes in an absorbing ceramic layer (susceptor) of a new millimeter-wave (MMW) heat exchanger. The purpose of this study is to better understand interaction between the MMW field and the susceptor, choose the composition of the ceramic material and help design the physical prototype of the device.

Design/methodology/approach

A simplified version of the heat exchanger comprises a rectangular block of an aluminum nitride (AlN) doped with molybdenum (Mo) that is backed by a thin metal plate and irradiated by a plane MMW. The coupled electromagnetic-thermal problem is solved by the finite-difference time-domain (FDTD) technique implemented in QuickWave. The FDTD model is verified by solving the related electromagnetic problem by the finite element simulator COMSOL Multiphysics. The computation of dissipated power and temperature is based on experimental data on temperature-dependent dielectric constant, loss factor, specific heat and thermal conductivity of the AlN:Mo composite. The non-uniformity of patterns of dissipated power and temperature is quantified via standard-deviation-based metrics.

Findings

It is shown that with the power density of the plane wave on the block’s front face of 1.0 W/mm2, at 95 GHz, 10 × 10 × 10-mm blocks with Mo = 0.25 – 4% can be heated up to 1,000 °C for 60-100 s depending on Mo content. The uniformity of the temperature field is exceptionally high – in the course of the heating, temperature is evenly distributed through the entire volume and, in particular, on the back surface of the block. The composite producing the highest level of total dissipated power is found to have Mo concentration of approximately 3%.

Research limitations/implications

In the electromagnetic model, the heating of the AlN:Mo samples is characterized by the volumetric patterns of density of dissipated power for the dielectric constant and the loss factor corresponding to different temperatures of the process. The coupled model is run as an iterative procedure in which electromagnetic and thermal material parameters are upgraded in every cell after each heating time step; the process is then represented by a series of thermal patterns showing time evolution of the temperature field.

Practical implications

Determination of practical dimensions of the MMW heat exchanger and identification of material composition of the susceptor that make operations of the device energy efficient in the required temperature regime require and expensive experimentation. Measurement of heat distribution on the ceramic-metal interface is a practically challenging task. The reported model is meant to be a tool assisting in development of the concept and supporting system design of the new MMW heat exchanger.

Originality/value

While exploitation of a finite element model (e.g. in COMSOL Multiphysics environment) of the scenario in question would require excessive computational resources, the reported FDTD model shows operational capabilities of solving the coupled problem in the temperature range from 20°C to 1,000°C within a few hours on a Windows 10 workstation. The model is open for further development to serve in the ongoing support of the system design aiming to ease the related experimental studies.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 39 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 1 March 2005

Vadim V. Yakovlev, Ethan K. Murphy and E. Eugene Eves

To outline different versions of a novel method for accurate and efficient determining the dielectric properties of arbitrarily shaped materials.

Abstract

Purpose

To outline different versions of a novel method for accurate and efficient determining the dielectric properties of arbitrarily shaped materials.

Design/methodology/approach

Complex permittivity is found using an artificial neural network procedure designed to control a 3D FDTD computation of S‐parameters and to process their measurements. Network architectures are based on multilayer perceptron and radial basis function nets. The one‐port solution deals with the simulated and measured frequency responses of the reflection coefficient while the two‐port approach exploits the real and imaginary parts of the reflection and transmission coefficients at the frequency of interest.

Findings

High accuracy of permittivity reconstruction is demonstrated by numerical and experimental testing for dielectric samples of different configuration.

Research limitations/implications

Dielectric constant and the loss factor of the studied material should be within the ranges of corresponding parameters associated with the database used for the network training. The computer model must be highly adequate to the employed experimental fixture.

Practical implications

The method is cavity‐independent and applicable to the sample/fixture of arbitrary configuration provided that the geometry is adequately represented in the model. The two‐port version is capable of handling frequency‐dependent media parameters. For materials which can take some predefined form computational cost of the method is very insignificant.

Originality/value

A full‐wave 3D FDTD modeling tool and the controlling neural network procedure involved in the proposed approach allow for much flexibility in practical implementation of the method.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 24 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 5 April 2019

Vadim Marshev

During the first quarter of the twentieth century in Russia rapidly developed management thought, generated by many reasons, including socio-economic and political…

Abstract

Purpose

During the first quarter of the twentieth century in Russia rapidly developed management thought, generated by many reasons, including socio-economic and political transformations, the results of scientific and practical activities of domestic and foreign experts in management. The purpose of this paper is, first, to acquaint readers with some of factors of the development of the history of Russian Management Thought in nineteenth century and at the beginning of twentieth century and, second, to present the most striking results of the formation of the History of Soviet Management Thought (SMT) in post-revolutionary Russia in the form of the movement of the so-called “The scientific organization of labor” (SOL), including “The scientific organization of managerial labor” (or SOML).

Design/methodology/approach

The review and causal analysis of the process of formation of the SMT and historiography of the SMT, a brief description of the institutions of SOL and SOMT and a comparative analysis of little-known works of some Russian authors on management topics of nineteenth century are chosen as research methods.

Findings

The paper emphasizes the action of objective historical inertia (or “non-Markoviness”) of the process of development of managerial thought, manifested, on the one hand, in the stable action of some management paradigms but, on the other hand, in identifying paradigmatic anomalies, in identifying the need for constant development of managerial thought, in the development of sought-after ideas and concepts of management, and even in the institutionalization of applied scientific research in the field of management throughout the country (in the form of SOL and SOML).

Originality/value

The paper attempts to attract the attention of researchers to the little-known Russian and Soviet authors and their little-known works in the field of management thought.

Details

Journal of Management History, vol. 25 no. 3
Type: Research Article
ISSN: 1751-1348

Keywords

Article
Publication date: 1 May 1991

Abu F. Dowlah and John E. Elliott

Gorbachev′s vision of democratic, decentralised and market‐orientedsocialism has generated diverse and controversial perceptions in theSoviet Union. Gorbachev′s claim that…

Abstract

Gorbachev′s vision of democratic, decentralised and market‐oriented socialism has generated diverse and controversial perceptions in the Soviet Union. Gorbachev′s claim that the USSR is not retreating from socialism but advancing towards it, having dismantled the Stalinist Command model, is assessed.

Details

International Journal of Social Economics, vol. 18 no. 5/6/7
Type: Research Article
ISSN: 0306-8293

Keywords

Article
Publication date: 1 May 1993

John P. Willerton

Operating out of a Slavophile tradition, Aleksandr Solzhenitsynoffers a critique of both Soviet and Western societies that iscomprehensive and damning. A review of his…

Abstract

Operating out of a Slavophile tradition, Aleksandr Solzhenitsyn offers a critique of both Soviet and Western societies that is comprehensive and damning. A review of his writings reveals a profound rejection of many core values and practices of Western civilization. What is viewed as an aberrant Soviet experience is understood as but a logical extension of developments in the West. Solzhenitsyn′s prescription for an identified Soviet and Western moral bankruptcy draws on past Russian Orthodox thinking and practices. Playing to Russian collectivist and conservative instincts, he venerates an idyllic Russian rural setting; but that setting has little relevance to contemporary Soviet reality. Ironically, Solzhenitsyn′s strong reformist inclinations are not unlike those of many reformers now championing change in a post‐Soviet Russia. But his stated political and economic preferences place him solidly in the ranks of contemporary Russian nationalist extremists, making him a leading figure for those promoting a return to earlier authoritarian Russian practices.

Details

International Journal of Social Economics, vol. 20 no. 5/6/7
Type: Research Article
ISSN: 0306-8293

Keywords

Content available
Article
Publication date: 15 February 2013

Olga Tretyak

339

Abstract

Details

Journal of Business & Industrial Marketing, vol. 28 no. 3
Type: Research Article
ISSN: 0885-8624

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