Hokyung Shim, Heegon Moon and Semyung Wang
This research aims to present a 3D multi‐objective approach regarding both magnetic and thermal characteristics associated with design of actuators.
Abstract
Purpose
This research aims to present a 3D multi‐objective approach regarding both magnetic and thermal characteristics associated with design of actuators.
Design/methodology/approach
The adjoint variable topology sensitivity equations are derived using the continuum method for 3D optimization. Convection interpolation function is proposed for density method of topologies such that convection term can be taken into consideration for practical design in the process of the optimization. In application of a C‐core actuator, the sensitivity is verified using the finite difference method (FDM). The proposed method is applied to the C‐core actuator and a single‐phase induction motor.
Findings
The thermal field is much more sensitive than electromagnetics that the weighing factor is investigated in the SPIM. Optimal topology result shows that cutting is needed.
Originality/value
A 3D topology optimization for magnetic and thermal systems using the finite element method is proposed.
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Jenam Kang, Chwail Kim and Semyung Wang
This paper presents a probabilistic optimal design for electromagnetic systems. A 2D magnetostatic finite element model is constructed for a reliability‐based topology…
Abstract
This paper presents a probabilistic optimal design for electromagnetic systems. A 2D magnetostatic finite element model is constructed for a reliability‐based topology optimization (RBTO). Permeability, coercive force, and applied current density are considered as uncertain variables. The uncertain variable means that the variable has a variance on a certain design point. In order to compute reliability constraints, a performance measure approach is widely used. To find reliability index easily, the limit‐state function is linearly approximated at each iteration. This approximation method is called the first‐order reliability method, which is widely used in reliability‐based design optimizations. To show the effectiveness of the proposed method, RBTO for the electromagnetic systems is applied to magnetostatic problems.
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Semyung Wang, Seungkyu Park and Jenam Kang
The design of multi‐domain that considers all components of electromagnetic systems such as air, iron, magnet, and coil is investigated using topology optimization, interpolation…
Abstract
The design of multi‐domain that considers all components of electromagnetic systems such as air, iron, magnet, and coil is investigated using topology optimization, interpolation method, and FEM. The design sensitivity equation for topology optimization is derived using the adjoint variable method and the continuum approach. The proposed method is applied to topology optimization of C‐core actuator and shows significant improvement.
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Heon Lee, Heegon Moon, Semyung Wang and Kyungbae Park
Aims to discuss iron loss analysis and experimenting with linear oscillating actuator for linear compressor.
Abstract
Purpose
Aims to discuss iron loss analysis and experimenting with linear oscillating actuator for linear compressor.
Design/methodology/approach
The iron loss analysis of the linear oscillating actuator is performed by using ANSYS and iron loss curves, which is obtained by an Epstein test apparatus.
Findings
The way to calculate the iron loss of the linear oscillating actuator for the linear compressor and the method to experiment the iron loss of that can be studied.
Research limitations/implications
Iron loss analysis of the linear compressor considering the motor part and the structure part is needed.
Originality/value
Each iron loss analysis method examined here can be used to analyze the iron loss of the linear motor.
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Discusses the 27 papers in ISEF 1999 Proceedings on the subject of electromagnetisms. States the groups of papers cover such subjects within the discipline as: induction machines;…
Abstract
Discusses the 27 papers in ISEF 1999 Proceedings on the subject of electromagnetisms. States the groups of papers cover such subjects within the discipline as: induction machines; reluctance motors; PM motors; transformers and reactors; and special problems and applications. Debates all of these in great detail and itemizes each with greater in‐depth discussion of the various technical applications and areas. Concludes that the recommendations made should be adhered to.
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Introduces papers from this area of expertise from the ISEF 1999 Proceedings. States the goal herein is one of identifying devices or systems able to provide prescribed…
Abstract
Introduces papers from this area of expertise from the ISEF 1999 Proceedings. States the goal herein is one of identifying devices or systems able to provide prescribed performance. Notes that 18 papers from the Symposium are grouped in the area of automated optimal design. Describes the main challenges that condition computational electromagnetism’s future development. Concludes by itemizing the range of applications from small activators to optimization of induction heating systems in this third chapter.
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Seung Uk Choi, Hyung Jong Na and Kun Chang Lee
The purpose of this study is to examine the relationship between explanatory language, audit fees and audit hours to demonstrate that auditors use explanatory language in audit…
Abstract
Purpose
The purpose of this study is to examine the relationship between explanatory language, audit fees and audit hours to demonstrate that auditors use explanatory language in audit reports to explain perceived audit risk.
Design/methodology/approach
The authors construct the sentiment value, a novel audit risk proxy derived from audit reports, using big data analysis. The relationship between sentiment value and explanatory language is then investigated. The authors present the validity of their new metric by examining the relationship between sentiment value and accounting quality, taking audit fees and hours into account.
Findings
The authors first find that reporting explanatory language is positively related to audit fees. More importantly, the authors provide an evidence that explanatory language in audit reports is indicative of increased audit risk as it is negatively correlated with sentiment value. As a positive (negative) sentimental value means that the audit risk is low (high), the results indicate that auditors describe explanatory language in a negative manner to convey the inherent audit risk and receive higher audit fees from the risky clients. Furthermore, the relationship is strengthened when the explanatory language is more severe, such as reporting the multiple numbers of explanatory language or going-concern opinion. Finally, the sentiment value is correlated with accounting quality, as measured by the absolute value of discretionary accruals.
Originality/value
Contrary to previous research, the authors’ findings suggest that auditors disclose audit risks of client firms by including explanatory language in audit reports. In addition, the authors demonstrate that their new metric effectively identifies the audit risk outlined qualitatively in audit report. To the best of the authors’ knowledge, this is the first study that establishes a connection between sentiment analysis and audit-related textual data.
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Seung Uk Choi, Kun Chang Lee and Hyung Jong Na
The paper aims to estimate abnormal audit fees more precisely than the traditional audit fee model by applying an artificial intelligence (AI) method.
Abstract
Purpose
The paper aims to estimate abnormal audit fees more precisely than the traditional audit fee model by applying an artificial intelligence (AI) method.
Design/methodology/approach
The AI technique employed in this paper is the deep neural network (DNN) model, which has been successfully applied to a wide variety of decision-making tasks. The authors examine the ability of the classic ordinary least squares (OLS) and the DNN models to describe the effects of abnormal audit fees on accounting quality based on recent research that demonstrates a systematic link between accruals-based earnings management and abnormal audit fees. Thus, the authors seek to imply that their new method provides a more precise estimate of abnormal audit fees.
Findings
The findings indicate that abnormal audit fees projected using the DNN model are substantially more accurate than those estimated using the classic OLS model in terms of their association with earnings management. Specifically, when abnormal audit fees predicted using the DNN rather than the OLS are incorporated in the accruals-based earnings management model, the adjusted R2s are larger. Additionally, the DNN-estimated coefficient of abnormal audit fees is more favorably associated to earnings management than the classic OLS-estimated coefficient. Additionally, the authors demonstrate that the DNN outperforms OLS in terms of explanatory power in a negative discretionary accruals subsample and a Big 4 auditor subsample. Finally, abnormal audit fees projected using the DNN method provide a better explanation for audit hours than those estimated using the OLS model.
Originality/value
This is the first approach that utilized a machine learning technology to estimate abnormal audit fees. Because more precise measurement yields more credible research results, the findings of this study imply a significant advancement in calculating unusually higher audit fees.
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Taegoo Terry Kim, Osman M. Karatepe and Ung Young Chung
The purpose of this study is to propose a research model in which political skill (PS) exerts a direct effect on role stress, job tension, work engagement and service performance…
Abstract
Purpose
The purpose of this study is to propose a research model in which political skill (PS) exerts a direct effect on role stress, job tension, work engagement and service performance and buffers the deleterious impact of role stress on job tension. The model also investigates the interrelationships of role stress, job tension, work engagement and service performance.
Design/methodology/approach
The sample was drawn from 261 customer-contact employees in 15 casual restaurants in South Korea. Structural equation modeling was used to assess the aforementioned relationships.
Findings
The findings illustrate that PS alleviates role stress and job tension, while it fosters work engagement and service performance. PS is a panacea to the deleterious impact of role stress on job tension. As expected, role stress heightens job tension, while job tension mitigates work engagement. The findings further reveal that work engagement exerts a positive impact on service performance.
Practical implications
Training interventions can be used to develop employees’ PS. Management should hire the individuals with high PS because such employees can work in harmony with the organizational culture and experience lower role stress and job tension.
Originality/value
The extant hospitality research implicitly demonstrates that very little is known about the outcomes of PS and its moderating role on the relationship between role stress and job tension. The current work set out to fill in this gap.
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Bilquis Bibi Safoorah Mohamodhosen, Frederic Gillon, Mounaim Tounzi and Loïc Chevallier
The purpose of this paper is to propose a methodology to seek the optimal topology of electromagnetic devices using the density method while taking into account the non-linear…
Abstract
Purpose
The purpose of this paper is to propose a methodology to seek the optimal topology of electromagnetic devices using the density method while taking into account the non-linear behaviour of ferromagnetic materials. The tools and methods used are detailed and applied to a three-dimensional (3D) electromagnet for analysis and validation. Resulting topologies with and without the non-linear behaviour are investigated.
Design/methodology/approach
The polynomial mapping is used with the density method for material distribution in the optimisation domain. To consider the non-linear behaviour of the materials, an analytical approximation based on the Marrocco equation is used and combined with the polynomial mapping to solve the problem. Furthermore, to prevent the occurrence of intermediate materials, a weighted sum of objectives is used in the optimisation problem to eliminate these undesired materials.
Findings
Taking into account the non-linear materials behaviour and 3D model during topology optimisation (TO) is important, as it produces more physically feasible and coherent results. Moreover, the use of a weighted sum of objectives to eliminate intermediate materials increases the number of evaluations to reach the final solution, but it is efficient.
Practical implications
Considering non-linear materials behaviour yields results closer to reality, and physical feasibility of structures is more obvious in absence of intermediate materials.
Originality/value
This work tackles an obstacle of TO in electromagnetism which is often overlooked in literature, that is, non-linear behaviour of ferromagnetic materials by proposing a methodology.