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1 – 10 of 30Andrzej Demenko, Kay Hameyer, Jean-Philippe Lecointe, Ewa Napieralska-Juszczak and Wojciech Pietrowski
Daniel Roger and Ewa Napieralska-Juszczak
High-temperature (HT°) motors are made with inorganic coils wound with a ceramic-coated wire. They must be carefully designed because the HT° insulating materials have a lower…
Abstract
Purpose
High-temperature (HT°) motors are made with inorganic coils wound with a ceramic-coated wire. They must be carefully designed because the HT° insulating materials have a lower breakdown voltages than the polymers used for insulating standard machines.
Design/methodology/approach
The voltage distribution between stator coils is computed with high-frequency (HF) equivalent circuits that consider the magnetic couplings and the stray capacitances. Two time scales are used for getting a fast computation of very short voltage spikes. For the first step, a medium time scale analysis is performed considering a simplified equivalent circuit made without any stray capacitance but with the full PWM pattern and the magnetic couplings. For the second step, a more detailed HF equivalent circuit computes voltage spikes during short critical time windows.
Findings
The computation made during the first step provides the critical time windows and the initial values of the state variables to the second one. The rise and fall time of the electronic switches have a minor influence on the maximum voltage stress. Conversely, the connection cable length and the common-mode capacitances have a large influence.
Research limitations/implications
HF equivalent circuits cannot be used with random windings but only to formed coils that have a deterministic position of turns.
Practical implications
The proposed method can be used designing of HT° machine windings fed by PWM inverter and for improving the coils of standard machine used in aircraft’s low-pressure environments.
Originality/value
The influence of grounding system of the DC link is considered for computing the voltage spikes in the motor windings.
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Rachid Jabbouri, Yann Truong and Helmi Issa
We explore how NGO’s local entrepreneurial initiatives to empower women entrepreneurs can compensate for weak state policies for women in a context of male-dominated…
Abstract
Purpose
We explore how NGO’s local entrepreneurial initiatives to empower women entrepreneurs can compensate for weak state policies for women in a context of male-dominated socio-cultural norms.
Design/methodology/approach
We use the case of a local entrepreneurial initiative launched in the Atlas region of Morocco, the Empowering Women in the Atlas Initiative (EWA). We collected data through 51 semi-structured interviews of women entrepreneurs in three cooperatives which exploit the natural resources of their region to establish a social venture. Our data are longitudinal as they were collected at two time periods: before and after the initiative.
Findings
The findings of this study suggest that local entrepreneurial initiatives can have a significant impact on rural women entrepreneurs’ empowerment. The improved perception of empowerment has not only helped them develop capacities to leverage the business opportunities linked to the natural resources of their region, but it has also increased their status and role within their family and community.
Practical implications
We make recommendations for policymakers to encourage this type of initiative to compensate for the absence of supporting policies geared toward women.
Originality/value
Our study is one of the first to look at empowerment as a policy instrument to develop women entrepreneurial activities in rural areas of developing countries. Our paper uses a unique hierarchical perspective and a multidimensional framework for analyzing social cooperative ventures and rural women entrepreneurs’ empowerment. Our paper unravels interesting insights for women entrepreneurs’ narration strategies.
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Ewa Napieralska-Juszczak, Piotr Napieralski, Krzysztof Komeza and Youcef Zeroukhi
The purpose of this paper is to determine the physical design parameters that influence the total resistance of a twisted conductor (cable). One of the physical parameters…
Abstract
Purpose
The purpose of this paper is to determine the physical design parameters that influence the total resistance of a twisted conductor (cable). One of the physical parameters characterizing this type of structures is the uneven distribution of resistivity due to hardening, which is the result of stress exerted on the wires during the manufacturing process.
Design/methodology/approach
The authors have developed a method to take into account the effect of localized hardening on the inhomogeneous distribution of electrical conductivity in the distorted structures of the conductor. To achieve this goal, the authors have implemented a mechanical-electrical simulation method. The resistance characteristics have been measured as a function of mechanical stress.
Findings
As demonstrated by the results of measurements conducted on various samples and with various cable design parameters, the resistance of a given material (copper or aluminum), expressed as a function of stress, does not depend on the type of force applied. Therefore, the same characteristics may be applied to various cable designs.
Practical implications
The method presented in this paper enables more detailed investigation of the influence of particular design parameters on the total resistance of a cable. It also provides the ability to determine optimal settings of design parameters.
Originality/value
The approach is distinct from similar studies because it takes into account the deformed geometry of the conductor and the uneven distribution of the resistivity within a filament. In the literature, it is sometimes stated that the distribution of resistivity in a compacted cable is uneven, but its measurement is deemed impossible. This paper provides a method for determining such a distribution.
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Marcin Lefik, Krzysztof Komeza, Ewa Napieralska-Juszczak, Daniel Roger and Piotr Andrzej Napieralski
The purpose of this paper is to present a comparison between reluctance synchronous machine-enabling work at high internal temperature (HT° machine) with laminated and solid rotor.
Abstract
Purpose
The purpose of this paper is to present a comparison between reluctance synchronous machine-enabling work at high internal temperature (HT° machine) with laminated and solid rotor.
Design/methodology/approach
To obtain heat sources for the thermal model, calculations of the electromagnetic field were made using the Opera 3D program including effect of rotation and the resulting eddy current losses. To analyse the thermal phenomenon, the 3D coupled thermal-fluid (CFD) model is used.
Findings
The presented results show clearly that laminated construction is much better from a point of view of efficiency and temperature. However, solid construction can be interesting for high speed machines due to their mechanical robustness.
Research limitations/implications
The main problem, despite the use of parallel calculations, is the long calculation time.
Practical implications
The obtained simulation and experimental results show the possibility of building a machine operating at a much higher ambient temperature than it was previously produced for example in the vicinity of the aircraft turbines.
Originality/value
The paper presents the application of fully three-dimensional coupled electromagnetic and thermal analysis of new machine constructions designed for elevated temperature.
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Paola Migliorini, Alexander Wezel, Eve Veromann, Carola Strassner, Dominika Średnicka-Tober, Johannes Kahl, Susanne Bügel, Teresa Briz, Renata Kazimierczak, Hélène Brives, Angelika Ploeger, Ute Gilles, Vanessa Lüder, Olesa Schleicher-Deis, Natalia Rastorgueva, Fabio Tuccillo, Liina Talgre, Tanel Kaart, Diana Ismael and Ewa Rembiałkowska
To clarify needs and requests of the young generation to the contemporary and future education on food systems, this paper aims to examine the following issues: students’…
Abstract
Purpose
To clarify needs and requests of the young generation to the contemporary and future education on food systems, this paper aims to examine the following issues: students’ background knowledge, students’ behaviour as consumers and food citizenship, most interesting topics of SFS for students and students’ preferences and expectations in developing different skills, topics and preferences in teaching/learning methods.
Design/methodology/approach
This study was performed as an online-survey amongst eight European Universities in seven European Union (EU) countries to which 1,122 students responded. Data was analysed with descriptive and multivariate statistical analyses.
Findings
Taste and Health are the most important values and motives that influence students’ food buying and consumption decisions, but significant differences were found amongst students from different universities and countries. The most important topics for students for future teaching courses are “organic food”, “fair trade”, “organic agriculture” and most important skills to learn are “ability to make a judgement and justify decisions” and the “ability to create and innovate”. Excursions and field trips as teaching methods was given the highest ranks.
Research limitations/implications
Different study programmes and cultural backgrounds of the participating students in the different universities could be a limiting factor for the interpretation of some results.
Originality/value
These results provide a basis for improvement of higher education in the EU towards sustainable food systems based on experiential learning/teaching methods.
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Ewa Bulzacka, Jeanne Vilain, Franck Schürhoff, Alexandre Méary, Marion Leboyer and Andrei Szöke
Subjective measurements of cognition have seldom been used in schizophrenia. This is mainly due to the assumption that such measurements lack sensitivity in a disorder…
Abstract
Subjective measurements of cognition have seldom been used in schizophrenia. This is mainly due to the assumption that such measurements lack sensitivity in a disorder characterized by poor insight. We investigated the capacity of BRIEF-A (Behavior Rating Inventory of Executive Function - Adult Version: a self-administered, ecological questionnaire) to identify executive deficits in adults with schizophrenia. The global score and each domain-specific score was significantly lower in patients than in healthy controls. BRIEF-A could be a useful complement to objective measurements, providing a subjective assessment of everyday consequences of executive dysfunction in patients with schizophrenia.
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Nabil Hihat, Krzysztof Komęza, Ewa Napieralska‐Juszczak, Jean‐Philippe Lecointe and Tadeusz Niewierowicz
The purpose of this paper is to present a comparative analysis concerning the influence of eddy currents on the distribution of the magnetic flux density in the laminated…
Abstract
Purpose
The purpose of this paper is to present a comparative analysis concerning the influence of eddy currents on the distribution of the magnetic flux density in the laminated anisotropic structures.
Design/methodology/approach
The influence of the magnetic flux normal to the lamination surface is particularly analysed. Several models containing internal air gaps and overlapping are tested. For every structure, the eddy currents are first taken into account and then, they are neglected. At last, the 3D simulation of the anisotropic conductivity permits to analyse separately the longitudinal and normal flux in the structure and the eddy currents induced by those fluxes.
Findings
The study leads to a more realistic numerical model with conducting laminations. The results show that the normal flux does not turn at once on lamination. The normal and longitudinal fluxes induce eddy currents which modify the flux distribution in the laminated structure.
Practical implications
The results of the presented simulations make it possible to elaborate a more realistic numerical model of homogenized characteristics taking into account eddy currents.
Originality/value
The eddy currents induced by the fluxes modifies the field distribution in the structure and should be taken into account. The internal air‐gaps higher than 0.1 mm have an influence on the field distribution; the isolation between the laminations of 0.01 mm has a smaller but not negligible effect on the magnetic flux. The direction of the normal flux from one sheet to another one does not change immediately after the entrance of the lamination, the transition is progressive.
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Dariusz Siemieniako, Krzysztof Kubacki, Ewa Glińska and Katarzyna Krot
Earlier studies into consumer ethnocentrism focused on identification of the level of ethnocentric tendencies in different countries and their investigation for various categories…
Abstract
Purpose
Earlier studies into consumer ethnocentrism focused on identification of the level of ethnocentric tendencies in different countries and their investigation for various categories of products. This research contributes to a wider understanding of that phenomenon, aiming to explore the characteristics of Polish consumers' national and regional ethnocentric attitudes and behaviours, especially symptoms of those attitudes in relationship with locally produced brands of beer.
Design/methodology/approach
All the data were collected on a university campus in Poland in late autumn 2007 in a group of ten university students. Purposive sampling was used to establish two focus groups within the industry's main target market age group, each of which met on two occasions, three weeks apart.
Findings
The main identified issues broadly covered two main categories: national ethnocentrism and regional ethnocentrism. The findings point to the relative importance of elements such as brand image (based on Polish culture and referring to its symbols), local brands as contributors to local identities and the form of their expression, as well as a moral obligation to buy local brands.
Originality/value
Indicative findings suggest that several areas need to be further investigated in future research in order to better understand the characteristics of national and regional ethnocentric tendencies, and the contribution they make to local identities.
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