Sonia Leva and Adriano Paolo Morando
To provide a unified analytical tool, based on Park transformation, for the theoretical and practical analysis of a lossy three‐phase transmission line.
Abstract
Purpose
To provide a unified analytical tool, based on Park transformation, for the theoretical and practical analysis of a lossy three‐phase transmission line.
Design/methodology/approach
The results obtained in the study of TEM waves propagation in two‐wire line can be extended to a symmetric m‐wire line by employing the modal analysis. This approach relates the dynamic of m‐wire guided field to the propagation of m modal voltages and currents acting on m single‐wire decoupled transverse electromagnetic (TEM) lines. In the symmetric three‐phase system case, the modal analysis includes, as a particular case for m=3, the symmetric component theory. In previous papers, the authors applied the Park transformation to study the wave propagation of (TEM) three‐phase symmetrical lines. The formulation proposed and tested considers the lossless TEM wave propagation of a three‐phase line without consideration to the dissipations phenomena present in the line itself. Taking into account the obtained results, the extension of the developed approach to the lossy three‐phase transmission line transient analysis is very useful on both theoretical and practical points of view.
Findings
The symmetrical three‐phase line Park model for the lossy transmission line transient analysis, regarded as vector formulation of the line modal analysis, has been presented. The proposed examples highlight how, thanks to the Park model, the dynamic analysis of the three‐phase line in distorted and unsymmetrical systems becomes an integral part of the more general and well‐established power electric system dynamic theory.
Originality/value
The three‐phase transmission line transient analysis presented in this paper emphasizes the conceptual contents, specific to the Park approach. Furthermore, it gives some results very important for the practical analysis of a lossy three‐phase transmission line.
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Francesco Della Torre, Sonia Leva and Adriano Paolo Morando
This paper aims to provide a complete three‐phase distributed constants model of cable‐induction machine systems useful for EMC and overvoltages propagation studies.
Abstract
Purpose
This paper aims to provide a complete three‐phase distributed constants model of cable‐induction machine systems useful for EMC and overvoltages propagation studies.
Design/methodology/approach
The paper considers a three‐phase distributed constants model for the supply cable and a model of the same type for the induction machine. All the magneto‐electric links between phases are considered. The Clarke transform is applied in order to reduce the analytical complexity of the obtained model. A new numerical method is also proposed for the integration of the resulting whole three‐phase model, very similar, in terms of methodology, to the well‐known finite differences models.
Findings
The whole model for the three‐phase drives is used for EMC and overvoltages propagation studies. The proposed examples highlight how, thanks to the Clarke model, the dynamic analysis of the three‐phase drives in case of application of a standard fault source or an equivalent pulse width modulation (PWM) impulse, become easy to implement on a standard PC and with standard software (i.e. Matlab). The obtained results, compared with those that are presented in the literature, confirm the validity of the proposed model and numerical approach.
Originality/value
The developed model is of a three‐phase type because it is not possible to consider a single‐phase equivalent model in case of asymmetric voltage sources (i.e. asymmetric faults or PWM inverter voltage supply). The model also includes all the magneto‐electric couplings between phases that play a fundamental role in the considered applications.
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Sonia Leva and Adriano Paolo Morando
By using the Park‐transformation the three‐phase TEM‐mode is analysed under the two different points of view: circuit and field. The first one leads, in terms of voltage and…
Abstract
By using the Park‐transformation the three‐phase TEM‐mode is analysed under the two different points of view: circuit and field. The first one leads, in terms of voltage and current line‐space vector, to a distributed constants active line. The second one leads, in a formal way, to the deduction of the “Maxwell‐Park equation”. The obtained result brings again, in terms of distributed constants, to the instantaneous sequence components algebra. This result allows a unified analysis, valid for any regime, of the poly‐phase travelling phenomena. This approach is particularly effective in presence of harmonics and sequence components. Under these circumstances, due to the wide spread of this kind of phenomena, the extension of the Park approach, already consolidated for the lumped constants, to the distributed constants case appears an obliged step particularly useful in a conceptual and practical path.
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Francesco Della Torre, Sonia Leva and Adriano Paolo Morando
To provide a unified analytical tool for the theoretical and practical analysis of four‐phase systems under sinusoidal condition but also under dynamic condition and to understand…
Abstract
Purpose
To provide a unified analytical tool for the theoretical and practical analysis of four‐phase systems under sinusoidal condition but also under dynamic condition and to understand the contribution of each sequence components on the energy and air gap field points of view.
Design/methodology/approach
Starting from the general procedures of analysis for the n‐phase symmetric systems, the analysis of four‐phase system is first developed in the phasorial domain, then, with reference to the asymmetrical sinusoidal conditions in terms of symmetric components. As a complement to what is already present in the literature, finally a formalization of the four‐phase systems in an instantaneous form based on the Lyon and Clarke‐Park vectors is proposed. Furthermore, a particular emphasis will be given to the physical meaning of the involved quantities, to their link with the three‐phase quantities and to the instantaneous energetic interpretation.
Findings
Four phase system presents the existence of the pseudozero‐sequence component which is an additional descriptive variable of the four‐phase configuration, absent in the three‐phase system. Pseudozero‐sequence component results completely independent on the need for a neutral wire. Knowledge of the Park vector is as much as necessary to generate the field in the air gap.
Practical implications
The four‐phase systems methodological analysis presented in this paper is very helpful for the formalization of the theoretical and applicative methodologies necessary for the development of four‐phase systems in a systematic and unified way.
Originality/value
The four‐phase systems analysis is presented in this paper both for the sinusoidal and the variable conditions. Furthermore, the role of the pseudozero‐sequence component, not present in three‐phase case, and its implications in circuital terms have been investigated with attention. Finally, the energetic side and the definition of the correspondent instantaneous and average powers have been investigated as well.
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Gives introductory remarks about chapter 1 of this group of 31 papers, from ISEF 1999 Proceedings, in the methodologies for field analysis, in the electromagnetic community…
Abstract
Gives introductory remarks about chapter 1 of this group of 31 papers, from ISEF 1999 Proceedings, in the methodologies for field analysis, in the electromagnetic community. Observes that computer package implementation theory contributes to clarification. Discusses the areas covered by some of the papers ‐ such as artificial intelligence using fuzzy logic. Includes applications such as permanent magnets and looks at eddy current problems. States the finite element method is currently the most popular method used for field computation. Closes by pointing out the amalgam of topics.
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Jahanzeb Marwat, Suresh Kumar Oad Rajput, Sarfraz Ahmed Dakhan, Sonia Kumari and Muhammad Ilyas
The current study aims to achieve two targets. First, examine empirically that whether corporate managers use tax avoidance to influence short-term profitability? Second…
Abstract
Purpose
The current study aims to achieve two targets. First, examine empirically that whether corporate managers use tax avoidance to influence short-term profitability? Second, investigate the impact of tax avoidance on the value of firms. The tax accounts provide the opportunity to influence temporary/permanent profitability but empirical studies overlooking this matter, particularly in emerging economies.
Design/methodology/approach
First, the authors identified unexpected fluctuations of tax avoidance and then examine whether it impacts the profitability signal and firms' value? The unbalanced panel data of 189 non-financial firms for the period 2000–2018 are used for empirical analysis. The estimation biases and results consistency are verified by using two different econometric models including generalized least square and two-stage least square
Findings
The study identifies that managers manipulate the profitability signal through tax avoidance. Tax avoidance practices help in earning management and earning smoothing to avoid negative signals in the stock market. In line with the behavioral finance view, tax avoidance has a positive impact on current stock returns because investors focus on profitability without a detailed screening of cash flows.
Originality/value
A limited number of studies investigate the use of tax avoidance for manipulation of the short-term earning signal. Identifying gaps and limitations in the literature, this study provides invaluable insights into tax avoidance and its association with the profitability and value of firms. The findings are important for investors, managers and policymakers in making portfolio decisions and corporate policies.
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Ted Ladd, Katarzyna Bachnik, Amanda Nimon-Peters and Sonia Scrocchi
This study examined the relationship between pedagogical self-efficacy and student course evaluations among an international sample of management education faculty. We also…
Abstract
Purpose
This study examined the relationship between pedagogical self-efficacy and student course evaluations among an international sample of management education faculty. We also investigated gender’s moderating role in this relationship and its impact on the development of pedagogical self-efficacy.
Design/methodology/approach
We conducted semi-structured interviews with 20 professors at an international business school, identifying three subdomains of pedagogical self-efficacy: course design, classroom management, and feedback provision. We designed a 25-question faculty survey to measure pedagogical self-efficacy, administered it to 84 faculty members, and analyzed the data alongside 20,000 student course evaluations.
Findings
All three pedagogical self-efficacy domains significantly predicted student course evaluations. The self-efficacy of female faculty had a positive relationship with course evaluations across all subdomains. In contrast, the self-efficacy of male faculty had a negative relationship with course evaluations on the course design subdomain. Student evaluations of courses taught by women were 10% lower than those taught by males and male faculty had significantly higher self-efficacy ratings than their female counterparts.
Practical implications
The results suggest that interventions designed to boost pedagogical self-efficacy can enhance student learning, irrespective of faculty gender. However, given biases in how students perceive female faculty, it is likely that female and male faculty members develop self-efficacy differently.
Originality/value
This study is the first to examine how pedagogical self-efficacy affects course evaluations, focusing on gender as a potential moderator. We also added an international higher education perspective to self-efficacy theories.
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This chapter briefly discusses the postmodern critique of developmental psychology and then presents a Vygotskian-influenced alternative understanding of development as a…
Abstract
This chapter briefly discusses the postmodern critique of developmental psychology and then presents a Vygotskian-influenced alternative understanding of development as a non-linear, relational, improvised activity engaged in by groupings of people. This reconstruction of development was the basis of a professional development project in which early childhood teachers participated in a 6-week improv workshop. The goal of the project was to reconnect the teachers with their ability to improvise or to participate in process-oriented, meaning-making activity. The project was based on the hypothesis that developing teachers’ ability to improvise would give them an alternative to relating to children as being on, or off, a developmental trajectory.
Sonia Akrimi, Sophie Raynor, Richard Johnson and Ann Wylie
Many barriers to health and emotional well‐being for children are prevalent within inner‐city communities, and often result in negative consequences for education. Health…
Abstract
Many barriers to health and emotional well‐being for children are prevalent within inner‐city communities, and often result in negative consequences for education. Health promotion strategies have previously cited mentoring schemes as interventions through which targeted pastoral support can be effectively provided to children. This paper draws on detailed focus group interviews in order to evaluate SHINE ‐ Make Every Child Count, a student‐led charity operating five mentoring programmes across the London boroughs of Southwark and Lambeth. Following content analysis, this paper identifies six themes associated with mentor support: rapport; emotional well‐being and development; social behaviour; enabling; emerging ambition; and attitudinal development. Results show participant children have gained considerable enjoyment from mentor support. Successful friendships are built and emotional well‐being supported, with children actively including mentors as part of their support network. Children recognise the impact of a mentor on relationships with peers, behaviour within the classroom and social responsibility, in addition to direct educational support. Children also show an increased interest in learning, and evidence of considering ‐ often for the first time ‐ their own future aspirations. Findings demonstrate the impact of the mentoring programmes, as perceived by participant children. Evaluation can be used to inform future development of the programmes, as well as expansion to further schools, with the organisation working towards achieving long‐term sustainability.
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José Castro Oliveira, João M. Lopes, Luís Farinha, Sónia Silva and Mónica Luízio
The Paris agreement for climate changes brought new attention to the themes of reduce carbon emissions, green ecosystems, the circular economy and the need to ensure the emergence…
Abstract
Purpose
The Paris agreement for climate changes brought new attention to the themes of reduce carbon emissions, green ecosystems, the circular economy and the need to ensure the emergence of sustainable entrepreneurial ecosystems. This study aims to investigate entrepreneurship from the perspective of circular economy and waste collection in the Portuguese context.
Design/methodology/approach
Following a quantitative approach, the sample comprises 2,690 firm-year observations related to 354 firms from different industries within the waste from electric and electronic equipment (WEEE) scope.
Findings
The results show that a large part of SMEs started to comply with waste management regulations as of 2006 and are still not prone to innovation. Regulatory compliance is expected to have a positive impact on innovation, with a significant and positive change in the number of patents and the value of intangibles after companies comply with the waste management regulation.
Originality/value
This paper is original because it addresses equally to entrepreneurial ecosystems and circular economy (studies that address these two aspects are rare), with the Portuguese context in an embryonic stage with an extensive path to follow in the applicability of circular economy to business.