N. Takahashi, M. Natsumeda, M. Otoshi and K. Muramatsu
Factors affecting convergence of the simulated annealing method are investigated using an actual model. The convergence characteristics of various optimization methods are…
Abstract
Factors affecting convergence of the simulated annealing method are investigated using an actual model. The convergence characteristics of various optimization methods are examined using the contour line of objective function. Two kinds of combination methods with the simulated annealing method and the Rosenbrock’s method are investigated.
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S. Wiak, A. Pelikant and J. Turowski
Magnetostaic field analysis of 3‐D nonlinear model problem (No.10 ‐ TEAM Workshop) is carried out by the authors using the Reluctance Network Method. The components and resultant…
Abstract
Magnetostaic field analysis of 3‐D nonlinear model problem (No.10 ‐ TEAM Workshop) is carried out by the authors using the Reluctance Network Method. The components and resultant flux density are computed and compared with measurements and results obtained by other authors and shaw reasonable convergence and much less CPU time.
In their now classic book What Do Unions Do? Freeman and Medoff (1984) open their discussion as follows (p. 3): “Trade unions are the principal institution of workers in modern…
Abstract
In their now classic book What Do Unions Do? Freeman and Medoff (1984) open their discussion as follows (p. 3): “Trade unions are the principal institution of workers in modern capitalistic societies. For over 200 years, since the days of Adam Smith, economists and other social scientists, labor unionists, and businessmen and women have debated the social effects of unionism. Despite the long debate, however, no agreed-upon answer has emerged to the question: What do unions do?” In the remainder of the book, the authors provide a coherent answer to this question and, as a result, What Do Unions Do? has become firmly established as a cornerstone for the economic analysis of labor unions. However, since the first publication of the book, developments have emerged that are inconsistent with Freeman and Medoff's predictions regarding the effectiveness of unions. One such development, for example, is the precipitous decline in union density in many countries around the world; another is the growing importance of, and interest in, alternative forms of employee representation.
Mayu Muramatsu, Keiji Yashiro, Tatsuya Kawada and Kenjiro Tarada
The purpose of this study is to develop a simulation method to calculate non-stationary distributions of the chemical potential of oxygen in a solid oxide fuel cell (SOFC) under…
Abstract
Purpose
The purpose of this study is to develop a simulation method to calculate non-stationary distributions of the chemical potential of oxygen in a solid oxide fuel cell (SOFC) under operation.
Design/methodology/approach
The initial-boundary value problem was appropriately formulated and the appropriate boundary conditions were implemented so that the problem of non-stationary behavior of SOFC can be solved in accordance with actual operational and typical experimental conditions. The dependencies of the material properties on the temperature and partial pressure of oxygen were also elaborately introduced to realize actual material responses. The capability of the proposed simulation method was demonstrated under arbitrary operating conditions.
Findings
The steady state calculated with the open circuit voltage condition was conformable with the analytical solution. In addition, the transient states of the spatial distributions of potentials and currents under the voltage- and current-controlled conditions were successfully differentiated, even though they eventually became the same steady state. Furthermore, the effects of dense materials assumed for interconnects and current collectors were found to not be influential. It is thus safe to conclude that the proposed method enables us to simulate any type of transient simulations regardless of controlling conditions.
Practical implications
Although only uniaxial models were tested in the numerical examples in this paper, the proposed method is applicable for arbitrary shapes of SOFC cells.
Originality/value
The value of this paper is that adequate numerical simulations by the proposed method properly captured the electrochemical transient transport phenomena in SOFC under various operational conditions, and that the applicability was confirmed by some numerical examples.
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Eddy currents are investigated in a ferromagnetic bar exposed to a transverse magnetic field. Such an open boundary field problem is analysed applying the Galerkin finite element…
Abstract
Eddy currents are investigated in a ferromagnetic bar exposed to a transverse magnetic field. Such an open boundary field problem is analysed applying the Galerkin finite element method coupled with a separation of variables. A steady state is considered, introducing time periodic conditions. The resultant system of nonlinear equations is solved using an iterative procedure based on Brouwer's fixed‐point theorem referred to the nonlinear material reluctivity. Numerical results are presented for a massive conductor made of cast steel and cast iron. The eddy‐current distribution and characteristics of power losses are illustrated in a graphic form.
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K. Muramatsu, T. Nakata, N. Takahashi, K. Fujiwara and H. Ukita
Recently, rare earth magnets with high coercive force such as Nd‐Fe‐B magnets have been developed. When the magnetic characteristic (M‐H curve) of such a strong magnet is…
Abstract
Recently, rare earth magnets with high coercive force such as Nd‐Fe‐B magnets have been developed. When the magnetic characteristic (M‐H curve) of such a strong magnet is measured, the conventional closed magnetic circuit method using an electromagnet cannot be applicable due to the magnetic saturation of the yoke. Therefore, the open magnetic circuit method has been proposed in which high magnetic fields are generated by using a superconducting or a pulsed magnet. In this method, the correction for demagnetizing field is required. The correction can be done using the demagnetizing factor which is a function of the shape and M‐H curve. The conventional studies take into account only the shape.
Konrad W. Eichhorn Colombo, Peter Schütz and Vladislav V. Kharton
A reliability analysis of a solid oxide fuel cell (SOFC) system is presented for applications with strict constant power supply requirements, such as data centers. The purpose is…
Abstract
Purpose
A reliability analysis of a solid oxide fuel cell (SOFC) system is presented for applications with strict constant power supply requirements, such as data centers. The purpose is to demonstrate the effect when moving from a module-level to a system-level in terms of reliability, also considering effects during start-up and degradation.
Design/methodology/approach
In-house experimental data on a system-level are used to capture the behavior during start-up and normal operation, including drifts of the operation point due to degradation. The system is assumed to allow replacement of stacks during operation, but a minimum number of stacks in operation is needed to avoid complete shutdown. Experimental data are used in conjunction with a physics-based performance model to construct the failure probability function. A dynamic program then solves the optimization problem in terms of time and replacement requirements to minimize the total negative deviation from a given target reliability.
Findings
Results show that multi-stack SOFC systems face challenges which are only revealed on a system- and not on a module-level. The main finding is that the reliability of multi-stack SOFC systems is not sufficient to serve as sole power source for critical applications such as data center.
Practical implications
The principal methodology may be applicable to other modular systems which include multiple critical components (of the same kind). These systems comprise other electrochemical systems such as further fuel cell types.
Originality/value
The novelty of this work is the combination of mathematical modeling to solve a real-world problem, rather than assuming idealized input which lead to more benign system conditions. Furthermore, the necessity to use a mathematical model, which captures sufficient physics of the SOFC system as well as stochasticity elements of its environment, is of critical importance. Some simplifications are, however, necessary because the use of a detailed model directly in the dynamic program would have led to a combinatorial explosion of the numerical solution space.
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Lichao Wang, Fuyan Ding, Dongbo Yang, Ke Wang, Biaoqiang Jiao and Qian Chen
This paper aims to provide a new method of generating relatively accurate and smooth saturated B-H curves based on reliable measurement data to improve the accuracy and efficiency…
Abstract
Purpose
This paper aims to provide a new method of generating relatively accurate and smooth saturated B-H curves based on reliable measurement data to improve the accuracy and efficiency of electromagnetic simulation.
Design/methodology/approach
The characteristics of different B-H curve extrapolation models are summarized, and an improved method is proposed. The fitting procedure in low fields and extrapolation procedure in high fields are presented in detail. The saturated B-H curves generated by various methods are compared and discussed. Finally, a simulation case study proved the advantages of the new method in terms of simulation accuracy and efficiency.
Findings
The B-H curve created by the new method avoids extrapolation from a single point and simultaneously smoothens the entire B-H curve, thereby improving the simulation accuracy and efficiency. The low magnetic potential requirements for closed measurements and the small deviation with open measurements indicate that this method is well-suited for implementation.
Research limitations/implications
The results are applicable for materials subject to such excitation levels that saturation has to be taken into account.
Originality/value
While some extrapolation models of B-H curves have been investigated in reference papers, there is still room for improvement in accuracy and smoothness. The new method processes low fields and high fields magnetization data and then connects them based on third-order boundary equations for the first time. This method can generate saturated B-H curves with good accuracy and smoothness while retaining outstanding operability.
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Deepika Kishor Nagthane and Archana M. Rajurkar
One of the main reasons for increase in mortality rate in woman is breast cancer. Accurate early detection of breast cancer seems to be the only solution for diagnosis. In the…
Abstract
Purpose
One of the main reasons for increase in mortality rate in woman is breast cancer. Accurate early detection of breast cancer seems to be the only solution for diagnosis. In the field of breast cancer research, many new computer-aided diagnosis systems have been developed to reduce the diagnostic test false positives because of the subtle appearance of breast cancer tissues. The purpose of this study is to develop the diagnosis technique for breast cancer using LCFS and TreeHiCARe classifier model.
Design/methodology/approach
The proposed diagnosis methodology initiates with the pre-processing procedure. Subsequently, feature extraction is performed. In feature extraction, the image features which preserve the characteristics of the breast tissues are extracted. Consequently, feature selection is performed by the proposed least-mean-square (LMS)-Cuckoo search feature selection (LCFS) algorithm. The feature selection from the vast range of the features extracted from the images is performed with the help of the optimal cut point provided by the LCS algorithm. Then, the image transaction database table is developed using the keywords of the training images and feature vectors. The transaction resembles the itemset and the association rules are generated from the transaction representation based on a priori algorithm with high conviction ratio and lift. After association rule generation, the proposed TreeHiCARe classifier model emanates in the diagnosis methodology. In TreeHICARe classifier, a new feature index is developed for the selection of a central feature for the decision tree centered on which the classification of images into normal or abnormal is performed.
Findings
The performance of the proposed method is validated over existing works using accuracy, sensitivity and specificity measures. The experimentation of proposed method on Mammographic Image Analysis Society database resulted in classification of normal and abnormal cancerous mammogram images with an accuracy of 0.8289, sensitivity of 0.9333 and specificity of 0.7273.
Originality/value
This paper proposes a new approach for the breast cancer diagnosis system by using mammogram images. The proposed method uses two new algorithms: LCFS and TreeHiCARe. LCFS is used to select optimal feature split points, and TreeHiCARe is the decision tree classifier model based on association rule agreements.
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Andrzej Patecki, Sławomir Stępień and Grzegorz Szymański
Presents 3D method for the computation of the winding current distribution and power losses of the electromagnetic gear. For a prescribed current obtained from measurement, the…
Abstract
Presents 3D method for the computation of the winding current distribution and power losses of the electromagnetic gear. For a prescribed current obtained from measurement, the transient eddy current field is defined in terms of a magnetic vector potential and an electric scalar potential. From numerically obtained potentials the power losses are determined. The winding power losses calculation of an electromagnetic gear shows that a given course of the current generates skin effect and significantly changes the windings resistances. Also presents the designing method for reducing power losses.