Markus Wick, Sebastian Grabmaier, Matthias Juettner and Wolfgang Rucker
The high computational effort of steady-state simulations limits the optimization of electrical machines. Stationary solvers calculate a fast but less accurate approximation…
Abstract
Purpose
The high computational effort of steady-state simulations limits the optimization of electrical machines. Stationary solvers calculate a fast but less accurate approximation without eddy-currents and hysteresis losses. The harmonic balance approach is known for efficient and accurate simulations of magnetic devices in the frequency domain. But it lacks an efficient method for the motion of the geometry.
Design/methodology/approach
The high computational effort of steady-state simulations limits the optimization of electrical machines. Stationary solvers calculate a fast but less accurate approximation without eddy-currents and hysteresis losses. The harmonic balance approach is known for efficient and accurate simulations of magnetic devices in the frequency domain. But it lacks an efficient method for the motion of the geometry.
Findings
The three-phase symmetry reduces the simulated geometry to the sixth part of one pole. The motion transforms to a frequency offset in the angular Fourier series decomposition. The calculation overhead of the Fourier integrals is negligible. The air impedance approximation increases the accuracy and yields a convergence speed of three iterations per decade.
Research limitations/implications
Only linear materials and two-dimensional geometries are shown for clearness. Researchers are encouraged to adopt recent harmonic balance findings and to evaluate the performance and accuracy of both formulations for larger applications.
Practical implications
This method offers fast-frequency domain simulations in the optimization process of rotating machines and so an efficient way to treat time-dependent effects such as eddy-currents or voltage-driven coils.
Originality/value
This paper proposes a new, efficient and accurate method to simulate a rotating machine in the frequency domain.
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Markus Wick, Matthias Jüttner and Wolfgang M. Rucker
The high calculation effort for accurate material loss simulation prevents its observation in most magnetic devices. This paper aims at reducing this effort for time periodic…
Abstract
Purpose
The high calculation effort for accurate material loss simulation prevents its observation in most magnetic devices. This paper aims at reducing this effort for time periodic applications and so for the steady state of such devices.
Design/methodology/approach
The vectorized Jiles-Atherton hysteresis model is chosen for the accurate material losses calculation. It is transformed in the frequency domain and coupled with a harmonic balanced finite element solver. The beneficial Jacobian matrix of the material model in the frequency domain is assembled based on Fourier transforms of the Jacobian matrix in the time domain. A three-phase transformer is simulated to verify this method and to examine the multi-harmonic coupling.
Findings
A fast method to calculate the linearization of non-trivial material models in the frequency domain is shown. The inter-harmonic coupling is moderate, and so, a separated harmonic balanced solver is favored. The additional calculation effort compared to a saturation material model without losses is low. The overall calculation time is much lower than a time-dependent simulation.
Research limitations/implications
A moderate working point is chosen, so highly saturated materials may lead to a worse coupling. A single material model is evaluated. Researchers are encouraged to evaluate the suggested method on different material models. Frequency domain approaches should be in favor for all kinds of periodic steady-state applications.
Practical implications
Because of the reduced calculation effort, the simulation of accurate material losses becomes reasonable. This leads to a more accurate development of magnetic devices.
Originality/value
This paper proposes a new efficient method to calculate complex material models like the Jiles-Atherton hysteresis and their Jacobian matrices in the frequency domain.
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Matthias Jüttner, Andreas Pflug, Markus Wick and Wolfgang M. Rucker
Multiphysics problems are solved either with monolithic or segregated approaches. For accomplishing contrary discretisation requirements of the physics, disparate meshes are…
Abstract
Purpose
Multiphysics problems are solved either with monolithic or segregated approaches. For accomplishing contrary discretisation requirements of the physics, disparate meshes are essential. This paper is comparing experimental results of different interpolation methods for a segregated coupling with monolithic approaches, implemented using a global and a local nearest neighbour method. The results show the significant influence of discretisation for multiphysics simulation.
Design/methodology/approach
Applying disparate meshes to the monolithic as well as the segregated calculation of finite element problems and evaluating the related numerical error is content of the contribution. This is done by an experimental evaluation of a source and a material coupling applied to a multiphysics problem. After an introduction to the topic, the evaluated multiphysics model is described based on two bidirectional coupled problems and its finite element representation. Afterwards, the considered methods for approximating the coupling are introduced. Then, the evaluated methods are described and the experimental results are discussed. A summary concludes this work.
Findings
An experimental evaluation of the numerical errors for different multiphysics coupling methods using disparate meshes is presented based on a bidirectional electro-thermal simulation. Different methods approximating the coupling values are introduced and challenges of applying these methods are given. It is also shown, that the approximation of the coupling integrals is expensive. Arguments for applying the different methods to the monolithic and the segregated solution strategies are given and applied on the example. The significant influence of the mesh density within the coupled meshes is shown. Since the projection and the interpolation methods do influence the result, a careful decision is advised.
Originality/value
In this contribution, existing coupling methods are described, applied and compared on their application for coupling disparate meshes within a multiphysics simulation. Knowing their performance is relevant when deciding for a monolithic or a segregated calculation approach with respect to physics dependent contrary discretisation requirements. To the authors’ knowledge, it is the first time these methods are compared with a focus on an application in multiphysics simulations and experimental results are discussed.
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Markus Weder, René M. Rossi, Cyril Chaigneau and Brice Tillmann
The purpose of this investigation is to measure seven different underwears on a sweating torso with differing relative air humidity (30, 50, 80 and 95 per cent RH) and at a fixed…
Abstract
Purpose
The purpose of this investigation is to measure seven different underwears on a sweating torso with differing relative air humidity (30, 50, 80 and 95 per cent RH) and at a fixed ambient temperature of 30°C to determine the influence of the water vapour partial pressure of the environment on the moisture transport properties of various materials.
Design/methodology/approach
All measurements in this investigation were accomplished with the authors' sweating torso which simulates the thermal‐ and humidity release of the human body. Four different sweating rates (50, 75, 100 and 150 g/h*torso) were selected for this investigation.
Findings
It was established that the partial pressure difference did not correlate directly with the evaporative cooling. In general, higher evaporation rates were observed in the dry climate conditions. However, with low‐sweat rates, the highest relative humidity (95 per cent) generally resulted in greater evaporative cooling than the lowest surrounding humidity conditions (30 per cent). In this investigation, a blended fabric made of PES/Vinal exhibited the most efficient evaporative cooling for all the sweat rates, as well as for the four relative humidity conditions chosen.
Research limitations/implications
All received results are based on a surrounding temperature of 30°C (summer climate), for other temperatures the results may be different.
Originality/value
The investigation shows that both the relative humidity and the sweat rate have a major influence on the heat loss.
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Jengchung V. Chen and Yangil Park
Many office workers use computers and the Internet not only to get their daily jobs done but also to deal with their personal businesses. Therefore employers nowadays monitor…
Abstract
Many office workers use computers and the Internet not only to get their daily jobs done but also to deal with their personal businesses. Therefore employers nowadays monitor their employees electronically to prevent the misuse of the company resources. The use of electronic monitoring in organizations causes issues of trust and privacy. This study is dedicated to developing a conceptual model on the two issues under electronic monitoring. Control, considered as the essence of the definition of privacy as well as the foundation of the control model in the theory of procedural justice, plays an important role to people’s privacy concerns and trust. People’s perceived‐self, as essential in the group‐value model in the theory of procedural justice and in the cultural studies, also plays an important role to people’s privacy concerns and trust. This study presents research hypotheses on trust and privacy under electronic surveillance based on the two models of the theory of procedural justice, social identity theory, and cultural studies.
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Dieses Szenario befasst sich mit den wahrscheinli‐chen Entwicklungen von Freizeit und Tourismus in einem Zeithorizont von rund 20 Jahren. Es wird dabei vor allem auf die Situation…
Abstract
Dieses Szenario befasst sich mit den wahrscheinli‐chen Entwicklungen von Freizeit und Tourismus in einem Zeithorizont von rund 20 Jahren. Es wird dabei vor allem auf die Situation in den europäischen Industrieländern Bezug genommen.
Pierre Baret and Vincent Helfrich
Based on a single and innovative case study (Siggelkow, 2007; Yin, 2014), this research aims to identify the main issues of non-financial reporting. They are related to:the…
Abstract
Based on a single and innovative case study (Siggelkow, 2007; Yin, 2014), this research aims to identify the main issues of non-financial reporting. They are related to:
the complexity of the corporate social responsibility (Alcouffe, Berland, Dreveton, & Essid, 2010; Ancori, 2008; Antheaume, 2007; Brichard, 1996; Buritt, 2004; Chan, 2005; Gray & Bebbington, 2001; Herborn, 2005; Savall & Zardet, 2013; Vatn, 2009);
the legislator’s and stakeholders’ expectations (Ancori, 2005; Batifoulier, 2001; Caillaud & Tirole, 2007; Lewis, 1969); and
the company’s expectations (Argyris & Schön, 1978; Chiapello & Gilbert, 2013; David 1998; Grimand, 2012; Moisdon, 1997; Senge, 1992; Wood, 1991).
Symmetrically, it reveals possible pitfalls. Through the study of the way the Rémy Cointreau Group developed its reporting tool, the authors analyze how a company can take the opportunity of a legal obligation to deploy a strategy of non-financial reporting that comes to support and structure a responsible approach. Of course, these results are only replicable under certain conditions related to this singular case.
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Xuan-Hoa Nghiem, Huong Trang Pham, Thu Giang Nguyen and Thi Kim Duyen Nguyen
Climate change has been universally recognized as a major threat to human well-being, necessitating a comprehensive transformation of people's activities. Various measures have…
Abstract
Climate change has been universally recognized as a major threat to human well-being, necessitating a comprehensive transformation of people's activities. Various measures have been proposed to contain climate change among which the green transformation grabs special attention, thanks to its desirable properties. Within the green transformation process, green tourism comes to prominence with huge potential. As one of the largest carbon emitters, the transition towards green tourism may offer substantial benefits not only for tourism companies but also for the whole economy. Yet, most studies tend to focus on the adverse effects of tourism on climate change while overlooking the potential impact of climate change on tourism. This chapter clarifies the feedback relationship between climate change and tourism and makes some recommendations.