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  • 20401.
    Zawadzki, Michał
    Jagiellonian University, Kraków, Poland.
    The need for auto-criticism in management sciences2009In: Culture Management/ Kulturmanagement/ Zarządzanie Kulturą, no 2, p. 310-313Article, book review (Other academic)
  • 20402.
    Zawadzki, Michał
    Jagiellonian University, Kraków, Poland.
    The role and place of the "Critical management studies"2012In: Culture Management = Kulturmanagement = Zarządzanie Kulturą, ISSN 2081-4712, Vol. 5, no 4, p. 39-46, 183-192Article in journal (Refereed)
    Abstract [en]

    “Critical Management Studies” is a kind of institutionalized, transdisciplinary critical reflection about management theory and practice. Although this stream is becoming very popular in the Western discourse of management sciences, in Poland it is unrecognized. The aim of the article is to present the most characteristic features of “Critical Management Studies”: reasons of its emergence and the main epistemological, normative and methodological assumptions.

  • 20403.
    Zawadzki, Michał
    Jagiellonian University, Kraków, Poland.
    Tożsamość narracyjna w kontekście zmediatyzowanej rzeczywistości ponowoczesnej [The narrative identity in the context of mediated postmodern reality]2007In: Człowiek a media: obserwacje, wizje, obawy / [ed] W. Gruszczyński & A. Hebda, Warszawa: Oficyna Wydawnicza ASPRA-JR , 2007, p. 183-190Chapter in book (Other academic)
  • 20404.
    Zawadzki, Michał
    Jagiellonian University, Kraków, Poland.
    Typy racjonalności w edukacji menedżerskiej w Polsce: podejście krytyczne [Types of rationality in the management education in Poland: critical approach]2013In: Przedsiębiorczość i Zarządzanie, ISSN 1733–2486, Vol. 14, no 13, cz. 2, p. 221-232Article in journal (Refereed)
    Abstract [en]

    In this paper I make an attempt to critical diagnosis of some key aspects of management education in Poland. In my reflection I use the perspective of the Critical Management Education. The main purpose of my reflection is to indicate the illusion of naturalness of dominance of the instrumental and hermeneutic rationality in management education. I analyze the consequences resulting from this domination on the field of manager’s morality and organizational practice and formulate some propositions of changes connected with the emancipatory direction.

  • 20405.
    Zawadzki, Michał
    Jagiellonian University, Kraków, Poland.
    University as a Panopticon: Disciplinary Power of Performance Management in the Polish Higher Education2015Conference paper (Other academic)
  • 20406.
    Zawadzki, Michał
    Jagiellonian University, Kraków, Poland.
    Życie w trasie: etnografia pracy muzyków [Life on a road: musicians work etnography]2013In: Organizować z polotem: wyobraźnia organizacyjna w praktyce / [ed] M. Kostera, Warszawa: Wydawnictwo Akademickie Sedno , 2013, p. 19-36Chapter in book (Other academic)
  • 20407.
    Zawadzki, Michał
    et al.
    Jagiellonian University, Kraków, Poland.
    Sułkowski, Łukasz
    Jagiellonian University, Kraków, Poland.
    Higher Education – Lower Devastation. Corporate University As A Spectacular Charade2015Conference paper (Refereed)
    Abstract [en]

    The ability of a university to educate students to be responsible and informed citizens in the future has been undercut by the market-inspired, neoliberal attempts to commercialize universities and to turn them into suppliers of proprietary knowledge. The paper focuses on a critique of the ongoing erosion of an important cultural function performed until very recently by the Western universities, which is democratization of social life through development of critical thinking, imagination, and through cultivation of social and humanistic sensibility. We attempt to diagnose the causes of erosion, the consequences of it and to design a possible future social function of a contemporary university as a counterbalancing agency and a testing ground for civic training. The paper opposes a commonly accepted belief that the university should be changed through the corporate market model and presents theoretical research with references to empirical data gathered by other authors.

  • 20408.
    Zawadzki, Michał
    et al.
    Jagiellonian University, Kraków, Poland.
    Ćwikła, Małgorzata
    Jagiellonian University, Kraków, Poland.
    Góral, Anna
    Jagiellonian University, Kraków, Poland.
    "Najciekawsze projekty rodziły się tam, gdzie nie było sztucznych ramek": O urynkowieniu edukacji‚ emancypacyjnej wartości sztuki‚ projektyzacji i zagrożeniach dla dziedzictwa kulturowego z prof. Zygmuntem Baumanem rozmawiają Małgorzata Ćwikła, Anna Góral i Michał Zawadzki2018In: Zarządzanie w Kulturze, ISSN 2084-3976, Vol. 19, no 3, p. 307-319Article in journal (Other (popular science, discussion, etc.))
  • 20409.
    Zdravkovic, Jelena
    et al.
    Department of Computer and Systems Sciences, Stockholm University, Stockholm, Sweden.
    Stirna, Janis
    Department of Computer and Systems Sciences, Stockholm University, Stockholm, Sweden.
    Sandkuhl, Kurt
    Jönköping University, School of Engineering, JTH, Computer Science and Informatics. Institute of Computer Science, Chair of Business Information Systems, University of Rostock, Rostock, Germany.
    Future of capability management2018In: Capability management in digital enterprises / [ed] Kurt Sandkuhl & Janis Stirna, Cham: Springer, 2018, p. 385-396Chapter in book (Refereed)
    Abstract [en]

    Capability management has been the subject of a lot of research during the past years. Many of the results achieved have been presented in the previous chapters. Although the advancements have been substantial, a number of open issues and research questions remain. The chapter gives a summary on the ongoing research in the field and an outlook on future activities. More specifically, we discuss capability management for increasing cyber resilience, supporting digital transformation in organizations, managing big data, as well as carrying out continuous information system development.

  • 20410.
    Zeebari, Zangin
    Jönköping University, Jönköping International Business School, JIBS, Economics, Finance and Statistics.
    A Simulation Study on the Least Absolute Deviations Method for Ridge Regression2012In: Communications in Statistics - Theory and Methods, ISSN 0361-0926, E-ISSN 1532-415XArticle in journal (Refereed)
    Abstract [en]

    Though the Least Absolute Deviations (LAD) method of estimation is robust, there is still the possibility of having strong multicollinearity of the predictors in a linear regression analysis. The paper consists of the application of the LAD estimation instead of the Ordinary Least Squares (OLS) estimation for the ridge regression and a simulation study to assess the performance of some biasing parameters used in the literature with their new LAD versions. The aim is to deal with the cases when the predictors are highly collinear  and the error terms are asymmetric or heavy-tailed, by giving more room to the bias in order to reduce the Mean Squared Error (MSE) of the LAD estimators.

  • 20411.
    Zeebari, Zangin
    Jönköping University, Jönköping International Business School, JIBS, Economics, Finance and Statistics.
    Developing ridge estimation method for median regression2012In: Journal of Applied Statistics, ISSN 0266-4763, E-ISSN 1360-0532, Vol. 39, no 12, p. 2627-2638Article in journal (Refereed)
    Abstract [en]

    In this paper, the ridge estimation method is generalized to the median regression. Though the least absolute deviation (LAD) estimation method is robust in the presence of non-Gaussian or asymmetric error terms, it can still deteriorate into a severe multicollinearity problem when non-orthogonal explanatory variables are involved. The proposed method increases the efficiency of the LAD estimators by reducing the variance inflation and giving more room for the bias to get a smaller mean squared error of the LAD estimators. This paper includes an application of the new methodology and a simulation study as well.

  • 20412.
    Zeebari, Zangin
    Jönköping University, Jönköping International Business School, JIBS, Economics, Finance and Statistics.
    On Median and Ridge Estimation of SURE Models2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This doctoral dissertation is a progressive generalization of some of the robust estimation methods in order to make those methods applicable to the estimation of the Seemingly Unrelated Regression Equations (SURE) models. The robust methods are each of the Least Absolute Deviations (LAD) estimation method, also known as the median regression, and the ridge estimation method. The first part of the dissertation consists of a brief explanation of the LAD and the ridge methods. The contribution of this investigation to the statistical methodology is focused on in the second part of the dissertation, which consists of 5 articles.

    The first article is a generalization of the median regression to the estimation of the SURE models. The proposed methodology is compared with each of the Generalized Least Squares (GLS) method and the median regression of individual regression equations.

    The second article generalizes the median regression on the conventional multivariate regression analysis, i.e., the SURE models with the same design matrices of the equations. The results are compared with the median regression of individual regression equations and the conventionally used OLS estimation method for such models (which is equivalent to the GLS estimation, as well).

    In the third article, the author develops ridge estimation for the median regression. Some properties and the asymptotic distribution of the estimator presented are investigated, as well. An empirical example is used to assess the performance of the new methodology.

    In the fourth article, the properties of some biasing parameters used in the literature for ridge regression are investigated when they are used for the new methodology proposed in the third article.

    In the last article, the methodologies of the four preceding articles are assembled in a more generalized methodology to develop the ridge-type estimation of the LAD method for the SURE models. This article has also provided an opportunity to investigate the behavior of some biasing parameters for the SURE models, which were previously used by some researchers in a non-SURE context.

  • 20413.
    Zeebari, Zangin
    et al.
    Department of Public Health Sciences, Karolinska Institute, Stockholm, Sweden.
    Kibria, B. M. G.
    Department of Mathematics and Statistics, Florida International University, Miami, USA.
    Shukur, Ghazi
    Jönköping University, Jönköping International Business School, JIBS, Statistics. Department of Economics and Statistics, Linnaeus University, Växjö, Sweden.
    Seemingly unrelated regressions with covariance matrix of cross-equation ridge regression residuals2018In: Communications in Statistics - Theory and Methods, ISSN 0361-0926, E-ISSN 1532-415X, Vol. 47, no 20, p. 5029-5053Article in journal (Refereed)
    Abstract [en]

    Generalized least squares estimation of a system of seemingly unrelated regressions is usually a two-stage method: (1) estimation of cross-equation covariance matrix from ordinary least squares residuals for transforming data, and (2) application of least squares on transformed data. In presence of multicollinearity problem, conventionally ridge regression is applied at stage 2. We investigate the usage of ridge residuals at stage 1, and show analytically that the covariance matrix based on the least squares residuals does not always result in more efficient estimator. A simulation study and an application to a system of firms' gross investment support our finding.

  • 20414.
    Zeebari, Zangin
    et al.
    Department of Public Health Sciences, Karolinska Institutet, Stockholm, Sweden.
    Lundin, Andreas
    Department of Public Health Sciences, Karolinska Institutet, Stockholm, Sweden.
    Dickman, Paul W.
    Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
    Hallgren, Mats
    Department of Public Health Sciences, Karolinska Institutet, Stockholm, Sweden.
    Are changes in alcohol consumption among swedish youth really occurring 'in concert'?: A new perspective using quantile regression2017In: Alcohol and Alcoholism, ISSN 0735-0414, E-ISSN 1464-3502, Vol. 52, no 4, p. 487-495Article in journal (Refereed)
    Abstract [en]

    Aims: Recent studies of youth alcohol consumption indicate a collective downward drinking trend at all levels of consumption, i.e. reductions occurring 'in concert'. We re-examine the collectivity of drinking theory by applying quantile regression methods to the analysis and interpretation of Swedish youth alcohol consumption.

    Method: Changes in youth alcohol consumption between 2000 and 2014 were assessed using a school-based survey conducted in Stockholm (n = 86,402). Participants were Swedish youth aged 15-18 years. The rate of change in consumption was examined using quantile regression, and compared to Ordinary Least Squares modelling. The hypothesis of parallelism or 'in concert' changes in consumption was assessed using the test of the equality of linear regression slopes corresponding to different quantiles of log consumption.

    Results: In both models, changes in consumption over time did not occur in parallel, contrary to the collectivity of drinking theory. Instead, a clear divergence in the rate of drinking was observed, with most adolescent quantiles reducing consumption, while heavy consuming remained stable.

    Conclusions: Contrary to previous studies, our findings do not support a collectivity of drinking behaviour among Swedish youth. Quantile regression is a robust and appropriate method for analysing temporal changes in alcohol consumption data.

  • 20415.
    Zeebari, Zangin
    et al.
    Jönköping University, Jönköping International Business School, JIBS, Economics, Finance and Statistics.
    Shukur, Ghazi
    Jönköping University, Jönköping International Business School, JIBS, Economics, Finance and Statistics.
    On the least absolute deviations method for ridge estimation of SURE models2014In: Communications in Statistics - Theory and Methods, ISSN 0361-0926, E-ISSN 1532-415XArticle in journal (Other academic)
    Abstract [en]

    In this paper we examine the application of the Least Absolute Deviations (LAD) method for ridge-type parameter estimation of Seemingly Unrelated Regression Equations (SURE) models. The methodology is aimed to deal with the SURE models with non-Gaussian error terms and highly collinear predictors in each equation. Some biasing parameters used in the literature are taken and the efficiency of both Least Squares (LS) ridge estimation and the LAD ridge estimation of the SURE models, through the Mean Squared Error (MSE) of parameter estimators, is evaluated.

  • 20416.
    Zehra, Khizran
    Jönköping University, Jönköping International Business School.
    Jugaar as entrepreneurial resourcefulness2017In: Contextualizing Entrepreneurship in Emerging Economies and Developing Countries / [ed] Marcela Ramírez Pasillas, Ethel Brundin and Magdalena Markowska, Edward Elgar Publishing, 2017, p. 131-145Chapter in book (Refereed)
  • 20417.
    Zehra, Khizran
    Jönköping University, Jönköping International Business School, JIBS, Business Administration.
    Resource mobilization among informal entrepreneurs: A case of event planning industry of Pakistan2018Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This dissertation studies resource mobilization among informal entrepreneurs. It combines the resource mobilization perspective with insights from social capital and human capital theory to understand the resource mobilization activities of informal entrepreneurs, focusing on the founding period and the early years of existence of informal ventures. Empirically the study is based on 15 cases from event planning industry of Pakistan. It primarily uses semi-structured interviews along with observations and secondary documents. The within and cross-case coding are aggregated into a conceptual model that paves the way to understanding inter-organizational gains through informal entrepreneurial networks. These informal entrepreneurial networks are largely based on competitor’s networks that support the exchange of resources, such as the exchange of knowledge, raw material, ideas, opportunities, etc. The new insights contributed from the findings are that resource mobilization is not competitive but rather collaborative among informal entrepreneurs. This collaborative resource mobilization is mainly based on activities like competitor’s collaboration, collaborative knowledge sharing through informal venturing, for the advancement of business goals at founding and in later stages. Collaborative resource mobilization is an alternative to competitive resource mobilization, whereby the flow of resources in the networks remains competitive when it comes to business rivalry. The study contributes to the role of social and human capital in resource mobilizing activities that improve the synergistic effects contributing to the readiness of informal entrepreneurs. Trust and reciprocal exchange of resources among competitors act as a major strengthening factor in promoting collaborative resource mobilization among informal entrepreneurs. It also contributes to the informal entrepreneurship literature and suggests that informal entrepreneurship should not be considered as marginalized activities, but rather a platform where the considerable potential of creative entrepreneurial activity is present.

  • 20418.
    Zehra, Khizran
    et al.
    Jönköping University, Jönköping International Business School, JIBS, Business Administration.
    Achtenhagen, Leona
    Jönköping University, Jönköping International Business School, JIBS, Center for Family Enterprise and Ownership (CeFEO). Jönköping University, Jönköping International Business School, JIBS, Media, Management and Transformation Centre (MMTC).
    Tracking gender in entrepreneurial development processes in Pakistan2011Conference paper (Refereed)
    Abstract [en]

    The main purpose of this paper is to critically assess the context and policy environment for the recent development of women’s entrepreneurship in Pakistan. The paper highlights the fact that Pakistani women have been the passive recipients of various opportunities and programmes related to welfare and development, e.g. related to skill training, but the political commitment needed for achieving a fundamental change of the role of women in society is only slowly emerging. The Pakistani system has traditionally favoured large companies rather than SMEs and entrepreneurs, which has resulted in an economic contribution which is only slowly accelerating. Though there are some positive trends for empowering women entrepreneurs, the gender gap actually appears to be increasing in Pakistan.

  • 20419.
    Zehra, Khizran
    et al.
    Jönköping University, Jönköping International Business School, JIBS, Business Administration.
    Nordqvist, Mattias
    Jönköping University, Jönköping International Business School, JIBS, Center for Family Enterprise and Ownership (CeFEO).
    Informal Entrepreneurship and Dynamic Governance Mechanisms: Role of Entrepreneurial Resourcefulness2015In: Academy of Management Proceedings, January 2015 (Meeting Abstract Supplement) 16786, 2015 / [ed] John Humphreys, 2015Conference paper (Refereed)
    Abstract [en]

    Drawing on perspective of real governance this paper examines the informal and formal governance mechanisms of small informal-semi formal entrepreneurial firms. Empirically this study has been conducted in Pakistan and sample firms have been drawn from event planning industry. They are mostly young and small informal or semi-formal firms and have strongly emerged against core competition contributed by traditional hotel and catering industry. Findings improved our understanding of everyday governance i.e. real governance and elaborated the concept of entrepreneurial resourcefulness in un-favored institutionalized environment. As we found resourcefulness perspective be supportive in the process of generation and evolution of governance patterns.

  • 20420. Zeidlitz, Andreas
    et al.
    Wallin, Tina
    Jönköping University, Jönköping International Business School, JIBS, Economics.
    Flyttströmmar till och från Jönköpings kommun2013Report (Other academic)
  • 20421.
    Zellweger, Thomas M.
    et al.
    University of St. Gallen, Switzerland.
    Nason, Robert S.
    Babson College, Boston, USA.
    Nordqvist, Mattias
    Jönköping University, Jönköping International Business School, JIBS, Center for Family Enterprise and Ownership (CeFEO).
    Brush, Candida G.
    Babson College, Arthur M. Blank Center for Entrepreneurship.
    Why Do Family Firms Strive for Nonfinancial Goals? An Organizational Identity Perspective2013In: Entrepreneurship: Theory & Practice, ISSN 1042-2587, E-ISSN 1540-6520, Vol. 37, no 2, p. 229-248Article in journal (Refereed)
    Abstract [en]

    This paper develops an organizational identity-based rationale for why family firms strive for nonfinancial goals. We show that the visibility of the family in the firm, the transgenerational sustainability intentions of the family, and the capability of the firm for self-enhancement of the family positively influence the importance of identity fit between family and firm as well as the family's concern for corporate reputation. We suggest that the concern for corporate reputation leads the family to pursue nonfinancial goals to the benefit of nonfamily stakeholders. We also discuss reinforcing feedback loops in these processes.

  • 20422.
    Zellweger, Thomas
    et al.
    University of St Gallen.
    Nason, Robert
    Babson College.
    Nordqvist, Mattias
    Jönköping University, Jönköping International Business School, JIBS, Center for Family Enterprise and Ownership (CeFEO). Jönköping University, Jönköping International Business School, JIBS, ESOL (Entrepreneurship, Strategy, Organization, Leadership).
    From Longevity of Firms to Transgenerational Entrepreneurship of Families: Introducing Family Entrepreneurial Orientation2012In: Family Business Review, ISSN 0894-4865, E-ISSN 1741-6248, Vol. 25, no 2, p. 136-155Article in journal (Refereed)
    Abstract [en]

    Whereas existing research on the longevity of family firms has focused on the survival of firms, this article investigates transgenerational entrepreneurship of families. By building on the transgenerational entrepreneurship research framework, the authors argue that by shifting from firm to family level of analysis, one gains a deeper understanding of family firms’ ability to create value across generations. The authors find evidence for their argument in that such a level shift reveals extended entrepreneurial activity, which is missed when focusing exclusively on the firm level. The study introduces and empirically explores the construct of family entrepreneurial orientation, which may serve as an antecedent to transgenerational value creation by families.

  • 20423. Zellweger, Thomas
    et al.
    Nordqvist, Mattias
    Jönköping University, Jönköping International Business School, JIBS, Center for Family Enterprise and Ownership. Jönköping University, Jönköping International Business School, JIBS, EMM (Entrepreneurship, Marketing, Management).
    Nason, Robert
    Why do firms strive for non-pecuniary performance outcomes?2008In: Annual Meeting of the Academy of Management, 2008Conference paper (Refereed)
  • 20424.
    Zellweger, Thomas
    et al.
    University of St Gallen.
    Nordqvist, Mattias
    Jönköping University, Jönköping International Business School, JIBS, Center for Family Enterprise and Ownership. Jönköping University, Jönköping International Business School, JIBS, EMM (Entrepreneurship, Marketing, Management).
    Nason, Robert
    Babson College.
    Brush, Candida
    Babson College.
    Why Do Firms Strive for Non-Pecuniary Performance Outcomes: The Case of the Family Firm2009Conference paper (Refereed)
  • 20425.
    Zeng, Zhaocheng E.
    et al.
    McMaster University, Hamilton, ON, Canada.
    Honig, Benson
    McMaster University, Hamilton, ON, Canada.
    How should entrepreneurship be taught to students with diverse experience? A set of conceptual models of entrepreneurship education2016In: Models of start-up thinking and action: Theoretical, empirical and pedagogical approaches / [ed] Jerome A. Katz , Andrew C. Corbett, Emerald Group Publishing Limited, 2016, p. 237-282Chapter in book (Refereed)
    Abstract [en]

    Entrepreneurship education has been largely treated as a pedagogical "black box." Despite the emergence of popular entrepreneurship models such as business planning, the lean startup, or business model canvas, neither theoretical nor pedagogical foundations are typically evident. This limits the accumulation of useful evidence that could inform better teaching practices. In this chapter, we develop a set of conceptual models anchored in learning theory regarding how entrepreneurship education should be taught to students. These conceptual models are built on the techniques of entrepreneurship pedagogy such as experiential education. They are developed for three groups of students: students without any, entrepreneurship experience, students with previous entrepreneurship experience, and students who are currently running their start-ups. A set of potential variables that could be used for course evaluation purposes is also included. The proposed models meet the needs of students with different levels of entrepreneurship experience. Theoretically, we demonstrate that entrepreneurship students should not be treated as a homogeneous group, as they have different levels of startup experience and different educational needs. Lecturers of entrepreneurship programs could choose the suitable model proposed in this chapter in teaching based on the characteristics of their students. The chapter provides novel insights with regard to how entrepreneurship programs should be designed for students with different levels of entrepreneurship experience.

  • 20426.
    Zeng, Zhaocheng
    et al.
    McMaster University, Hamilton, ON, Canada.
    Honig, Benson
    McMaster University, Hamilton, ON, Canada.
    A study of living wage effects on employees' performance-related attitudes and behaviour2017In: Canadian Journal of the Administrative Sciences, ISSN 0825-0383, E-ISSN 1936-4490, Vol. 34, no 1, p. 19-32Article in journal (Refereed)
    Abstract [en]

    Despite the surge of interest in living wage research, most studies pay little attention to the effect of living wages on employee attitudes and behaviour. We examine the differences between living wage and minimum wage workers on three attitudinal and behavioural outcomes: affective commitment, organizational citizenship behaviour (OCB), and turnover intention. We also examine the effects of training and benefits on the three outcomes. Results show that living wage workers have higher affective commitment and lower turnover intention. Training and benefits also improve workers' attitudinal and behavioural outcomes variously.

  • 20427.
    Zetterlind, Madelene
    et al.
    Jönköping University, School of Engineering.
    Keller, Christina
    Jönköping University, Jönköping International Business School, JIBS, Business Informatics.
    Vetenskaplig metod på nätet: Att dela digitala lärobjekt inom en högskola2010Conference paper (Other academic)
    Abstract [sv]

    Syfte och mål med projektet: Syftet med projektet var att skapa en modell för gemensam utveckling och användning av ämnesövergripande nätbaserade kurser vid Högskolan i Jönköping. Digitala lärobjekt för helt eller delvis nätbaserad undervisning i kurser om vetenskaplig metod prioriterades som ett viktigt område för högskolan.

    Metod eller tillvägagångssätt: Projektet inleddes i början av 2008 och bedrivs som ett samarbetsprojekt mellan fackhögskolorna vid Högskolan i Jönköping. I projektet medverkar representanter för Resurscentrum för flexibelt lärande, Högskolebiblioteket, Hälsohögskolan, Tekniska Högskolan, Internationella Handelshögskolan och Högskolan för lärande och kommunikation. Ett trettiotal lärare har bidragit till att utforma innehållet tillsammans med bibliotekarier, TV-pedagoger och översättare. Kursresursen innehåller en introducerande del samt följande kursmoduler:

    1. Vetenskapsteoretisk och vetenskapshistorisk orientering
    2. Informationssökning
    3. Att skriva vetenskapliga rapporter
    4. Forskningsprocessen
    5. Forskningsmetoder och tekniker för datainsamling
    6. Metoder för dataanalys

    De digitala lärobjekten som har skapats i projektet består av inspelade föreläsningar, intervjuer och rundabordssamtal, powerpoint-presentationer och annat textbaserat material. Lärobjekten har samlats i två kurser i högskolans lärplattform. En svensk och en engelskspråkig version av kursresursen har utarbetats. Kursresursen innehåller också en utvärderingsdel med student- respektive lärarutvärdering.

    Resultat: Från november 2008 till juni 2009 har kursresursen använts i tio kurser och under hösten 2009 och vårterminen har hittills 19 kurser fått tillgång den. Kursresursen har använts av samtliga fackhögskolor, mestadels på kandidatnivå men även på masterutbildningar. Sex av kurserna har använt den engelskspråkiga kursresursen. Kursresursen har hittills mest använts i campuskurser men under hösten 2009 används den även i ren distansutbildning. Skälen för att använda kursresursen har bl. a. varit att möjliggöra att minska antalet föreläsningstimmar till förmån för seminarier, att erbjuda variation, fördjupning och breddade perspektiv, att använda som stöd vid uppsatsskrivning och ge ökad möjlighet till flexibilitet i tid och rum för studenterna.

    Från de lärar- och studentutvärderingar som har gjorts framkommer både för och nackdelar. De digitala lärobjekten, som är avsedda för användning inom många ämnesdiscipliner, upplevs ibland av studenterna som för löst kopplade till den aktuella kursen. Av samma skäl har lärare ibland svårt att anpassa användandet av lärobjekten till kursens nivå – grund eller avancerad. För att komma tillrätta med det här krävs det att lärare arbetar aktivt med att foga ihop lärobjekten till en sammanhängande kurs med en klar struktur och nivåinriktning. Studenter uppger att de största fördelarna är att de inspelade föreläsningarna kan stoppas, spolas tillbaka och tas om samt flexibiliteten i tid och rum ökar.

  • 20428. Zhan, Y.
    et al.
    Karlsson, Ida K.
    Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
    Karlsson, R.
    Tillander, A.
    Reynolds, C. A.
    Pedersen, Nancy L.
    Hägg, S.
    Exploring the Causal Pathway from Telomere Length to Coronary Heart Disease: A Network Mendelian Randomization Study2017In: Circulation Research, ISSN 0009-7330, E-ISSN 1524-4571, Vol. 121, no 3, p. 214-219Article in journal (Refereed)
    Abstract [en]

    Rationale: Observational studies have found shorter leukocyte telomere length (TL) to be a risk factor for coronary heart disease (CHD), and recently the association was suggested to be causal. However, the relationship between TL and common metabolic risk factors for CHD is not well understood. Whether these risk factors could explain pathways from TL to CHD warrants further attention.

    Objective: To examine whether metabolic risk factors for CHD mediate the causal pathway from short TL to increased risk of CHD using a network Mendelian randomization design.

    Methods and Results: Summary statistics from several genome-wide association studies were used in a 2-sample Mendelian randomization study design. Network Mendelian randomization analysis - an approach using genetic variants as the instrumental variables for both the exposure and mediator to infer causality - was performed to examine the causal association between telomeres and CHD and metabolic risk factors. Summary statistics from the ENGAGE Telomere Consortium were used (n=37 684) as a TL genetic instrument, CARDIoGRAMplusC4D Consortium data were used (case=22 233 and control=64 762) for CHD, and other consortia data were used for metabolic traits (fasting insulin, triglyceride, total cholesterol, low-density lipoprotein cholesterol, fasting glucose, diabetes mellitus, glycohemoglobin, body mass index, waist circumference, and waist:hip ratio). One-unit increase of genetically determined TL was associated with -0.07 (95% confidence interval, -0.01 to -0.12; P=0.01) lower log-transformed fasting insulin (pmol/L) and 21% lower odds (95% confidence interval, 3-35; P=0.02) of CHD. Higher genetically determined log-transformed fasting insulin level was associated with higher CHD risk (odds ratio, 1.86; 95% confidence interval, 1.01-3.41; P=0.04).

    Conclusions: Overall, our findings support a role of insulin as a mediator on the causal pathway from shorter telomeres to CHD pathogenesis.

  • 20429. Zhang, H.
    et al.
    Xu, Weili
    Aging Research Center.
    Dahl, Anna
    Jönköping University, School of Health and Welfare, HHJ. Ageing - living conditions and health. Jönköping University, School of Health and Welfare, HHJ, Institute of Gerontology.
    Xu, Z.
    Wang, H-X.
    Qi, X.
    Relation of socio-economic status to impaired fasting glucose and Type 2 diabetes: findings based on a large population-based cross-sectional study in Tianjin, China2013In: Diabetic Medicine, ISSN 0742-3071, E-ISSN 1464-5491, Vol. 30, no 5, p. 157-162Article in journal (Refereed)
    Abstract [en]

    Aims: Studies on the relationship between socio-economic status and Type 2 diabetes mellitus in the Chinese population are sparse. We aimed to examine the relation of socio-economic status as represented by income, education and occupation to impaired fasting glucose, Type 2 diabetes, and the control of Type 2 diabetes in a large Chinese population.

    Methods: This study included 7315 individuals who were aged 20-79 years and living in Tianjin, China. Impaired fasting glucose and Type 2 diabetes were ascertained according to the 1999 World Health Organization criteria. Data were analysed using multinomial and binary logistic regression, with adjustment for potential confounders.

    Result: Among all participants, 532 (7.3%) persons had impaired fasting glucose, 688 (9.4%) persons had Type 2 diabetes, including 288 (3.9%) previously undiagnosed Type 2 diabetes. In fully adjusted multinomial logistic regression, compared with higher income (≥ 2000 yuan, $243.3/month), lower income (< 1000 yuan, $121.70/month) showed odds ratios (95% confidence intervals) of 3.31 (2.48-4.41) for impaired fasting glucose, 4.50 (3.07-6.61) for undiagnosed Type 2 diabetes and 4.56 (3.20-6.48) for diagnosed Type 2 diabetes. These results remained significant in the analysis stratified by education and occupation. Furthermore, persons who were retired were more likely to have impaired fasting glucose [odds ratio 1.91 (1.40-2.45)], undiagnosed Type 2 diabetes [odds ratio 2.01) 1.40-2.89] and diagnosed Type 2 diabetes [odds ratio 3.02 (2.12-4.22)]. Among the patients with Type 2 diabetes previously diagnosed, lower education (less than senior high school), non-manual work and unemployment were related to worse glycaemic control (fasting blood glucose level > 8.5 mmol/l).

    Conclusions: Lower income and retirement are associated with increased odds of impaired fasting glucose and Type 2 diabetes in Tianjin, China. Education and occupation may play a role in glycaemic control among patients with Type 2 diabetes.

  • 20430.
    Zhang, Tingting
    et al.
    Department of Information Technology and Media, Mid Sweden University.
    Jennehag, Ulf
    Department of Information Technology and Media, Mid Sweden University.
    Xu, Youzhi
    Department of Information Technology and Media, Mid Sweden University.
    Numerical modeling of transmission errors and video quality of MPEG-22001In: Signal processing. Image communication, ISSN 0923-5965, E-ISSN 1879-2677, Vol. 16, no 8, p. 817-825Article in journal (Refereed)
    Abstract [en]

    To efficiently combat the signal loss of MPEG-2 transmission over unreliable networks, priority encoding transmission, unequal packet loss protection and priority dropping techniques have been studied in many papers. Those studies are based on the qualitative analysis of different importance of signals, without quantitative investigation of signal loss effect on video quality. In this paper, MPEG-2 packet loss effect on video quality is quantitatively investigated, a temporal layered signal model is described and evaluated, a quality measure for reconstructed pictures called macroblock impairment ratio is suggested and defined. The investigation and the model are specified for MPEG-2, but the principles and the methods are suitable for any layered video. These are useful for the development of efficient schemes and protocols for packet video transmission over unreliable networks.

  • 20431.
    Zhang, Tingting
    et al.
    Department of Information Technology and Media, Mid Sweden University.
    Österberg, Patrik
    Department of Information Technology and Media, Mid Sweden University.
    Xu, Youzhi
    Jönköping University, School of Engineering, JTH. Research area Robust Embedded Systems. Jönköping University, School of Engineering, JTH, Computer and Electrical Engineering.
    Multicast-Favorable Max-Min Fairness: A General Definition of Multicast Fairness2005In: Proceedings - First International Conference on Distributed Frameworks for Multimedia Applications, DFMA '05, Besancon, France, 6-9 Feb. 2005., IEEE , 2005, p. 239-245Conference paper (Refereed)
  • 20432.
    Zhang, Yafan
    et al.
    KTH/Acreo.
    Belov, Ilja
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing - Surface technology.
    Bakowski, Mietek
    Acreo.
    Nee, Hans-Peter
    KTH.
    Leisner, Peter
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing - Surface technology.
    Investigation of a finned baseplate material and thickness variation on thermal performance of a SiC power module: Key-note presentation2014In: Proceedings of the 15th Int. Conference IEEE EuroSimE 2014; April 7-9 2014, Ghent, Belgium, IEEE, 2014Conference paper (Refereed)
  • 20433.
    Zhang, Yafan
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing - Surface technology.
    Belov, Ilja
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing - Surface technology.
    Bakowski, Mietek
    Acreo / KTH.
    Sarius, Niklas G.
    Nee, Hans-Peter
    KTH.
    Leisner, Peter
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing - Surface technology.
    Thermal evaluation of a liquid/air cooled integrated power inverter for hybrid vehicle applications2013In: 14th international conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Micro-Systems, IEEE, 2013Conference paper (Refereed)
    Abstract [en]

    A thermal design of an integrated double-side cooled SiC 50kW-1200V-200A power inverter for hybrid electric vehicle applications has been proposed to enable cooling in two different automotive operating environments: under-hood and controlled temperature environment of passenger compartment. The power inverter is integrated with air/liquid cooled cold plates equipped with finned channels. Concept evaluation and CFD model calibration have been performed on a simplified thermal prototype. Computational experiments on the detailed model of the inverter, including packaging materials, have been performed for automotive industry defined application scenarios, including two extreme and one typical driving cycles. For the studied application scenarios the case temperature of the SiC transistors and diodes have been found to be below 210°C. The maximum steady-state temperature of the DC-link capacitor has been below 127 °C for the worst-case scenario including liquid cooling, and up to 140 °C for the worst-case scenario with air-cooling.

  • 20434.
    Zhang, Yafan
    et al.
    Department of Netlab, RISE Acreo, Kista, Sweden.
    Hammam, Tag
    Department of Joining Technology, Swerea KIMAB, Kista, Sweden.
    Belov, Ilja
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Sjögren, Torsten
    Department of Structural and Solid Mechanics, SP Technical Research Institute of Sweden, Borås, Sweden.
    Bakowski, Mietek
    Department of Netlab, RISE Acreo, Kista, Sweden.
    Nee, Hans-Peter
    Department of Electric Power and Energy Systems, KTH Royal Institute of Technology, Stockholm, Sweden.
    Thermomechanical Analysis and Characterization of a Press-Pack Structure for SiC Power Module Packaging Applications2017In: IEEE Transactions on Components, Packaging, and Manufacturing Technology, ISSN 2156-3950, E-ISSN 2156-3985, Vol. 7, no 7, p. 1089-1100Article in journal (Refereed)
    Abstract [en]

    This paper presents an experimental methodology for the characterization of thermomechanical displacement and friction properties in a free-floating press-pack structure, and evaluation of the tensile stress on the semiconductor die through simulation of different mechanical and thermal loading conditions. The press-pack structure consists of a single silver-metallized (1 μm) silicon carbide die (400 μm) in contact with rhodium-coated (0.4 μm) molybdenum square plates. The thermomechanical displacements in the press-pack structure have been obtained using the digital image correlation technique, and the mean random error has been $± $0.1 μm, which is approximately 10 ppm of the measured length (10.5 mm). The developed experimental method has led to an analytical estimation of friction coefficients on the interfaces' silicon carbide-molybdenum and molybdenum-copper. The results demonstrate that the thin silver layer behaves as a solid film lubricant. A 2-D finite-element model representing the experimental setup has been implemented. The difference in displacement between measurement and simulation is less than 8%. Furthermore, the coinfluence of the design parameters on the thermomechanical performance of the stacked structure has been analyzed through simulations. Finally, design guidelines to reduce the tensile stress on the silicon carbide die have been proposed regarding free-floating press-pack power electronics packaging.

  • 20435.
    Zhang, Yafan
    et al.
    Acreo AB, Department of NetLab, Kista, Sweden.
    Nee, Hans Peter
    The Royal Institute of Technology (KTH), School of Electrical Engineering, Stockholm, Sweden.
    Hammam, Tag
    Swerea KIMAB AB, Department of Joining Technology, Kista, Sweden.
    Belov, Ilja
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Ranstad, Per
    GE Power Sweden AB, Department of Electrical Energy Conversion, Vaxjo, Sweden.
    Bakowski, Mietek
    Acreo AB, Department of NetLab, Kista, Sweden.
    Multiphysics Characterization of a Novel SiC Power Module2019In: IEEE Transactions on Components, Packaging, and Manufacturing Technology, ISSN 2156-3950, E-ISSN 2156-3985, Vol. 9, no 3, p. 489-501Article in journal (Refereed)
    Abstract [en]

    This paper proposes a novel power module concept specially designed for highly reliable silicon carbide power devices for medium- and high-power applications. The concept consists of two clamped structures: 1) a press-pack power stage accommodating silicon carbide power switch dies, and 2) perpendicularly clamped press-pack heatsinks, in which, the heatsinks are in contact with electrically insulated case plates of the power stage. The concept enables bondless package with symmetric double-sided cooling of the dies and allows for an order of magnitude higher clamping force on the heatsinks than what can be applied on the dies. The concept has been evaluated in a first demonstrator (half-bridge configuration with ten paralleled silicon carbide dies in each position). Experimental methodologies, setups, and procedures have been presented. The commutation loop inductance is approximately 9 nH at 78 kHz. The junction-to-case thermal resistance is approximately 0.028 K/W. Furthermore, a simplified 3D finite element thermomechanical model representing the center unit of the demonstrator, has been established for the purpose of future optimization. The accuracy of the simulated temperatures is within 4 % compared to the measurements. Finally, a 3D thermomechanical stress distribution map has been obtained for the simplified model of the demonstrator. 

  • 20436.
    Zhang, Zuotai
    et al.
    Royal Institute of Technology, Sweden.
    Matsushita, Taishi
    Royal Institute of Technology, Sweden.
    Li, Wenchao
    Seetharaman, Seshadri
    Royal Institute of Technology, Sweden.
    Investigation of wetting characteristics of liquid iron on dense MgAlON-based ceramics by x-ray sessile drop technique2006In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 37, no 3, p. 421-429Article in journal (Refereed)
    Abstract [en]

    The wetting characteristics of liquid iron on dense MoAlON-based composite ceramics were investigated using X-ray sessile drop technique. The contact angles were measured on substrates of different composites as functions of temperature and varying partial pressures of oxygen. The results with pure argon gas showed that contact angles kept almost constant in the temperature range 1823 to 1873 K. The contact angle was found to show a slight increase with increasing boron nitride (BN) content in MgAlON-BN composites. These are attributed to the higher contact angle between BN substrate and liquid iron drop compared with that obtained for MgAlON substrate. When the CO-CO2-Ar gas mixtures were introduced into the system, the contact angle showed an initial quick decrease followed by a slow decrease and then a period of nearly constant contact angle at a given temperature corresponding to the steady-state condition. Even in this case, BN seemed to cause an increase in the equilibrium contact angle. The equilibrium contact angle was found to decrease with increasing temperature. XRD results indicated that the substrate was oxidized and the oxidation products combined with FeO formed by the oxidation of the iron drop to form FeAl2O4 and Mg1-xFexO. These were likely to form a ternary FeO-Al2O3-MgO slag or a quaternary slag by combining with B2O3. An interesting observation is that the iron drop moved away from the original site, probably due to the Marangoni effect.

  • 20437.
    Zhang, Zuotai
    et al.
    Royal Institute of Technology, Sweden.
    Matsushita, Taishi
    Royal Institute of Technology, Sweden.
    Li, Wenchao
    Seetharaman, Seshadri
    Royal Institute of Technology, Sweden.
    Reactions between MgAlON-BN Composites and CaO-SiO2-Al2O3-MgO-“FeO” Slag2007In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 38, no 2, p. 231-241Article in journal (Refereed)
    Abstract [en]

    The reactions between MgAlON and MgAlON-BN composites and synthetic CaO-SiO2-Al2O3-MgO-“FeO” slag at different temperatures were investigated under stagnant condition using the ‘‘finger’’ experiment as well as X-ray sessile drop methods. The corrosion rate was denoted by the radius difference between the initial radius of the specimen rod and the unreacted core at definite time intervals. The experimental results showed that the radius difference is linear with the square root of time. This indicated that the diffusion of ions in the slag through the product layer is the rate-determining step. One product layer was observed between the unreacted core and slag. X-ray images showed that gas bubbles were generated during the slag penetration. The slag penetration process depends strongly on the temperature. The apparent activation energy was evaluated to be 376.4 kJ/mol. The FeO addition into slag increased the slag corrosion rate. This is most probably due to the decrease of the slag viscosity, because the Fe+2 generally behaves as a network breaker. Furthermore, MgAlON and boron nitride (BN) can be oxidized by FeO, which also increased the slag corrosion rate. The slag corrosion rate decreased with increasing BN content. This can be explained by the fact that the grain boundary interfacial energy decreases with the increase of BN content and nonwetting of BN by molten slag compared to pure MgAlON.

  • 20438.
    Zhen, Rong
    et al.
    Högskolan i Skövde, Institutionen för informationsteknologi.
    Riveiro, Maria
    Högskolan i Skövde, Institutionen för informationsteknologi.
    Jin, Yongxing
    Merchant Marine College, Shanghai Maritime University, Shanghai, China.
    A novel analytic framework of real-time multi-vessel collision risk assessment for maritime traffic surveillance2017In: Ocean Engineering, ISSN 0029-8018, E-ISSN 1873-5258, Vol. 145, p. 492-501Article in journal (Refereed)
    Abstract [en]

    Multi-vessel collision risk assessment for maritime traffic surveillance is a key technique to ensure the safety and security of maritime traffic and transportation. This paper proposes a framework of real-time multi-vessel collision assessment that combines a spatial clustering process (DBSCAN) for detecting clusters of encounter vessels and a multi-vessel collision risk index model for encounter vessels within each cluster from the large amounts of monitored vessels in a surveyed sea area. First, the vessels monitored are clustered using DBSCAN to obtain the clusters of encounter vessels, filtering out the relatively safe vessels. Then, the dynamic motion relation between encounter vessels within each cluster is modeled to obtain DCPA and TCPA. The semantic and mathematical relationship of vessel collision risk index for each cluster of encounter vessels with DCPA and TCAP is constructed using a negative exponential function. To illustrate the effectiveness of the framework proposed, an experimental case study has been carried out within the west coastal waters of Sweden. The results show that our framework is effective and efficient at detecting and ranking collision risk indexes between encounter vessels within each duster, which allows an automatic risk prioritization of encounter vessels for further investigation by operators. Hence, this framework can improve the safety and security of vessel traffic transportation and reduce the loss of lives and property.

  • 20439.
    Zhou, Haoyong
    et al.
    Keele Management School, Staffordshire, UK.
    He, Fan
    Department of Finance, School of Business, Central Connecticut State University, New Britain, CT, United States.
    Wang, Yangbo
    SKK Graduate School of Business, Seoul, South Korea.
    Did family firms perform better during the financial crisis?: New insights from the S&P 500 firms2017In: Global Finance Journal, ISSN 1044-0283, E-ISSN 1873-5665, Vol. 33, p. 88-103Article in journal (Refereed)
    Abstract [en]

    This paper provides new evidence on whether family firms performed better during the global financial crisis (2008–2010). Using the dataset of the S&P 500 nonfinancial firms during the period 2006–2010, we find that family firms outperformed nonfamily firms during the crisis. Among family firms, the ones that contributed to the outperformance were those where the founder was still present. We also find that during the global financial crisis, founder firms invested significantly less and had better access to the credit market than nonfamily firms. Our analysis suggests that the superior performance of founder firms is largely caused by their having less incentive to overinvest in order to boost short-term earnings during the crisis. 

  • 20440.
    Zhou, Heng
    et al.
    School of Earth and Planetary Sciences, Curtin University, Perth, Australia.
    Xia, Jianhong
    School of Earth and Planetary Sciences, Curtin University, Perth, Australia.
    Norman, Richard
    School of Public Health, Curtin University, Perth, Australia.
    Hughes, Brett
    Department of Transport, Perth, Australia.
    Nikolova, Gabi
    Department of Transport, Perth, Australia.
    Kelobonye, Keone
    School of Earth and Planetary Sciences, Curtin University, Perth, Australia.
    Du, Kai
    School of Earth and Planetary Sciences, Curtin University, Perth, Australia.
    Falkmer, Torbjörn
    Jönköping University, School of Health and Welfare, HHJ. CHILD. School of Occupational Therapy and Social Work, Curtin University, Perth, Australia.
    Do air passengers behave differently to other regional travellers? A travel mode choice model investigation2019In: Journal of Air Transport Management, ISSN 0969-6997, E-ISSN 1873-2089, Vol. 79, article id 101682Article in journal (Refereed)
    Abstract [en]

    This research aims to investigate travel mode choices and behaviours of air passengers and community respondents in regional Western Australia. Multinomial logit and Nested logit models were used for the mode choice analysis based on Stated-Preference survey data. The results indicate that travel cost, journey time, service frequency and seat comfort played important roles in affecting travellers' mode choices. For business trips, air passengers are willing to pay more to reduce journey time and increase seat comfort and service frequency compared to community respondents. While for non-business trips, these differences were much smaller. The findings will provide some insights in understanding people's mode choice behaviours and therefore guide policy makers and airlines in developing policies and practice. 

  • 20441.
    Zhou, Shoujin
    et al.
    Peking University, China.
    Caccamo, Marta
    University of International Business and Economics, China.
    Review And Revision: Theory And Practice of Corporate Philanthropy in China2013In: Journal of International Business Ethics, ISSN 1940-1485, Vol. 6, no 1/2, p. 42-56Article in journal (Refereed)
    Abstract [en]

    Corporate philanthropy has played an indispensable role in public welfare areas 1 in China since its emergence in the 1990s. As an "emerging philanthropic market" (Michon & Tandon, 2012) where entrepreneurship or corporate citizenship is still to be entrenched in the society, the progress of corporate philanthropy in China is crucial for cultivating the philanthropic spirit of society and fostering the growth of civil society. Therefore, it is worthwhile to pay more attention and make more investigation into the theory and practice of corporate philanthropy in China (Lu, 2002; Ge, 2007). The present paper aims to make a general review of the state of this particular area and to discuss potential ways to optimize current frameworks.

  • 20442.
    Zhu, Baiwei
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Casting and anodising of Al alloys- Alloy design, manufacturing process and material properties2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Casting and semi-solid metal (SSM) casting are widely used to manufacture near-net-shape components of Al-Si alloys in the automotive and electronic industries. In such applications, casting components need to meet the combined requirements of good mechanical properties and corrosion and wear resistance. Hence, a good understanding of the relevant aspects such as material design, manufacturing and surface treatments have a significant impact on the final performance of the component. The objective of this thesis is to understand the interaction among manufacturing and surface treatments and how their combination impacts the microstructure and final properties. The results will accordingly highlight the potential for improving the mechanical and anodising properties of rheocast components.

    The influence of the most relevant alloying elements has been investigated in this study. It is found that Si and Fe have a significant influence on anodising. During anodising, Si particles are oxidised at a much lower rate than Al phase and embedded in the oxide layer. Due to the presence of Si particles and their morphology, residual metallic Al phase and cracks are introduced in the oxide layer. A reduced number of residual metallic Al phase, as well as defects, can be obtained by changing the Si particle morphology to disconnected fibrous by Sr modification. On the contrary, Fe-rich intermetallics could be partly dissolved during anodising, leaving vacancies or voids as defects in the oxide layer. So, it was proved that by modifying Si particles and removing Fe-rich intermetallics from the surface, the defects in the oxide layer are reduced, and better corrosion protection is achieved.

    The SSM process increases the microstructural inhomogeneity such as transverse macrosegregation and longitudinal macrosegregation in the cast component. The results show that the presence of surface liquid segregation (SLS) layer by transverse macrosegregation does not have a significant impact on the corrosion resistance and hardness of the oxide layer of as-cast surfaces compared to liquid casting. The longitudinal macrosegregation influences the corrosion protection provided by the anodised layer but does not affect the hardness of the rheocast component before or after anodising. In this study, it is also found that, during the casting of Al-Si alloys, the surface of the component can be enriched in Fe-rich intermetallics due to the SLS or interaction with the die material. Despite this affects only the very superficial thickness, it has a big impact on the corrosion resistance and hardness of the oxide layer.

    This study has revealed that the high value of the oxide layer thickness, as well as the hydrothermal sealing, is not a guarantee for improving the corrosion resistance of the oxide layer. An increase of the oxide layer thickness by increasing applied voltage or anodising time decreases both the corrosion resistance and hardness of the oxide layer. Moreover, the hydrothermal sealing after anodising significantly decreases the corrosion protection provided by the anodised layer in Al-Si alloys due to cracks formation.

    This study has observed that the casting defects such as oxide film, cold shots and the solute-rich layer which are related to the casting process dominate the fatigue behaviours of the SSM cast components. The fractographic examination indicates that the oxide film, cold shots and solute-rich layer act as crack initiation points during fatigue testing. Therefore, it was found that, in these conditions, the anodising does not have an evident impact on fatigue properties, despite the anodising process adds a brittle anodised layer on the surface.

  • 20443.
    Zhu, Baiwei
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Persson, Per (Contributor)
    Jarfors, Anders (Contributor)
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Leisner, Peter (Contributor)
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing - Surface technology.
    Zanella, Caterina (Contributor)
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing - Surface technology.
    Effect of Si particle modification on the growth and microstructure of anodised aluminium oxide2016Other (Other academic)
  • 20444.
    Zhu, Baiwei
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    On the influence of Si on anodising and mechanical properties of cast aluminium alloys2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The combination of two cost-effective processes, i.e. casting and anodising, would be an interest for the aluminium component applications. However, there are some obstacles in the application of anodising on cast Al alloys. The challenges mostly relate to the alloying elements especially Si and the surface quality. With the development of casting process, cast aluminium alloys with low Si content can be casted, and a complex geometry component with reasonably good surface finish can be achieved. This study aims to identify the influence of Si on anodising and mechanical properties of Al-Si alloys.

    In this study, six Al-Si alloys with three different Si level and two different Sr level were investigated. Sr acts as a modifier to change the morphology of Si particles. The directional solidification technology was used to vary the microstructure coarseness by controlling the cooling rate to study the influence of Si level, Si particle morphology and cooling rate on mechanical properties, oxide layer formation and corrosion protection performance in cast Al-Si alloys.

    This study has observed that Si has a significant influence on anodising. During anodising, Si particles are anodised at a lower rate than the Al phase. The presence of Si particles in eutectic phase make the oxide layer locally thinner and more defected due to the low oxide growth rate in eutectic phase. This study observed the presence of residual metallic Al phase beneath or between Si particles. Due to their presence and their geometry, Al can be shielded by Si particles and prevented from oxidation. Si particles also act as a key role in the corrosion protection of oxide layer in Al-Si alloys. The corrosion attack propagates along Si particles as well as oxide defects to the Al substrate.

    It is found that the morphology of Si particles has a significant influence on the oxide layer formation and corrosion protection performance of the oxide layer on cast Al-Si alloys. A substantially improvement the corrosion resistance of anodised layer on Al-Si alloys is attributed to the morphology change from interconnected flakes to disconnected Si fibres when Sr is added, with less oxide defects and better oxide distribution.

    The Si level governs the mechanical properties of Al-Si based alloys. An increase of Si content in Al alloys improves the mechanical properties such as ultimate tensile and yield strength as well as hardness of the materials, but decreases the ductility. However, an increase of Si level in Al alloys decreases the thickness of oxide layer, and thereby, the corrosion protection of the oxide layer is deteriorated.

  • 20445.
    Zhu, Baiwei
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Fedel, Michele
    Department of Industrial Engineering, University of Trento, Trento, Italy.
    Andersson, Nils-Eric
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Leisner, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. SP-Technical Research Institute of Sweden, Borås, Sweden.
    Deflorian, Flavio
    Department of Industrial Engineering, University of Trento, Trento, Italy.
    Zanella, Caterina
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Effect of Si content and morphology on corrosion resistance of anodized cast Al-Si alloys2017In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, no 7, p. C435-C441Article in journal (Refereed)
    Abstract [en]

    This paper investigates the influence of Si content and Si particle morphology on the corrosion protection of anodized oxide layers on Al-Si alloys. Two Al alloys with low Si concentrations (2.43 wt-% and 5.45 wt-%, respectively) were studied and compared with 6082-T6 via electrochemical impedance spectroscopy (EIS) in 3 wt-% NaCl solution prior to oxide layer sealing. Si particles were also modified by the addition of Sr to study the influence of Si particle morphology on the corrosion protection of the oxide layer. The EIS showed that the corrosion protection provided by the oxide layer on Al-Si alloys is significantly affected by the presence of Si particles. Si particles make the oxide layer locally thinner and more defective in the eutectic region, thereby increasing the ease of substrate corrosion attack. However, the addition of Sr can improve the corrosion protection of anodized Al-Si alloys significantly. Furthermore, it was proved that higher Si level influences negatively the anodized oxide corrosion protection due to the higher amount of cracks and defects, but Sr modification is efficient in preventing this negative effect.

  • 20446.
    Zhu, Baiwei
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Fedel, Michele
    Department of Industrial Engineering, University of Trento, Trento, Italy.
    Andersson, Nils-Eric
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Leisner, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. RISE Research Institute of Sweden, Borås, Sweden.
    Deflorian, Flavio
    Department of Industrial Engineering, University of Trento, Trento, Italy.
    Zanella, Caterina
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Influence of the Sr modification and post-treatment on corrosion resistance of oxide layer of cast Al-(low)Si alloys2017In: EUROCORR 2017 - The Annual Congress of the European Federation of Corrosion, 20th International Corrosion Congress and Process Safety Congress 2017, Asociace koroznich inzenyru z.s.- AKI - Czech Association of Corrosion Engineers , 2017, p. 27-39Conference paper (Refereed)
    Abstract [en]

    The current development of casting process makes it possible to cast low Si content aluminium alloys, which open the gate for the application of anodising on cast aluminium components. This paper aims to investigate the influence of Sr modification as well as the post-treatment on corrosion resistance of oxide layer of low Si content cast Al alloys. In the present study, designed Al-Si alloys with 5.45 wt-% Si were studied by performing electrochemical impedance spectroscopy (EIS) in 3 wt-% NaCl solution. The morphology of Si particle was determined by controlling the level of Sr. The microstructure features were evaluated by optical microscopy and scanning electron microscopy (SEM). Furthermore, focus ion beam-SEM (FIB-SEM) equipped with energy-dispersive X-ray spectroscopy (EDXS) was applied to exam the corrosion morphology and the anodised layer with Si rich eutectic phases. The EIS study revealed that the corrosion resistance of the oxide layer on cast Al alloys can be significantly influenced by the morphology of Si particle and the post-treatment. It was found that the change of Si particle morphology from flake-like to fibrous by Sr addition can substantially improve the corrosion resistance of the oxide layer in the unsealed condition due to the formation of the more compacted oxide layer with less defects. Normally, the application of a sealing step such as the hydrothermal sealing can improve the corrosion protection of the oxide layer. However, in the current study, it was found the hydrothermal sealing step leads to a significant reduce of the corrosion protection due to the generation of cracks into the oxide layer, and the hydrothermal sealing step can counteract the improvement of the corrosion protection by Sr addition.

  • 20447.
    Zhu, Baiwei
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Leisner, Peter
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing - Surface technology.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Jarfors, Anders E.W.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Influence of Si and cooling rate on microstructure and mechanical properties of Al-Si-Mg cast alloys2015In: Proceedings of the 7th Symposium of Aluminium Surface Science and Technology, 2015Conference paper (Refereed)
    Abstract [en]

    This paper aims to investigate the effect of Si-content and microstructure on mechanical properties of Al-Si-Mg alloys with the purpose of to develop high strength cast aluminum alloys that are anodizable. The Si-content was 2.5, 3.5 and 5.5 wt% Si and both Sr-modified and unmodified conditions were used. The samples were produced using the gradient solidification furnace to generate a well-controlled microstructure. The resulting secondary dendrite arm spacing was 10µm and 20µm. The microstructural features were evaluated by employing SEM/EDS, and optical microscopy. Furthermore, CT-scan technology was used to provide a 3-D view of high density phases in the microstructure. The mechanical properties of these alloys were studied by means of tensile and hardness testing where the latter were performed on the macro- and micro-level. The results demonstrate clearly how the Si growth in the microstructure is restricted by increased cooling rate and modification and its role in strength development in Al-Si alloys. Additionally, the CT-scan visualized the morphology of intermetallics as well as supported in identifying the oxide layer growth as a result of the anodizing process.

  • 20448.
    Zhu, Baiwei
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Leisner, Peter
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing - Surface technology.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Jarfors, Anders E.W.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Influence of Si and cooling rate on microstructure and mechanical properties of Al–Si–Mg cast alloys2016In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 48, no 8, p. 861-869Article in journal (Refereed)
    Abstract [en]

    This paper aims to investigate the effect of Si-content and microstructure on mechanical properties of Al–Si–Mg alloys with thepurpose of to develop high-strength cast aluminum alloys that are anodizable. The Si-content was 2.5, 3.5 and 5.5wt% Si, andboth Sr-modified and unmodified conditions were used. The samples were produced using the gradient solidification furnaceto generate awell-controlled microstructure. The resulting secondary dendrite armspacingwas 10 and 20μm. Themicrostructuralfeatures were evaluated by employing SEM/EDS and optical microscopy. Furthermore, computed tomography (CT) scan technologywas used to provide a 3D view of high-density phases in the microstructure. The mechanical properties of these alloys werestudied by means of tensile and hardness testing where the latter was performed on the macrolevel and microlevel. The resultsdemonstrate clearly how the Si growth in the microstructure is restricted by increased cooling rate and modification and its rolein strength development in Al-Si alloys. Additionally, the CT scan visualized the morphology of intermetallics and supported inidentifying the oxide layer growth as a result of the anodizing process.

  • 20449.
    Zhu, Baiwei
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing - Surface technology.
    Leisner, Peter
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing - Surface technology.
    Zanella, Caterina
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing - Surface technology.
    Persson, Per O.Å.
    Linköpings universitet.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Jarfors, Anders E. W.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    A study of formation and growth of the anodized surface layer on Al-Si casting alloys based on different analytical techniques2015Conference paper (Refereed)
  • 20450.
    Zhu, Baiwei
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Leisner, Peter
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing - Surface technology. SP-Technical Research Institute of Sweden.
    Zanella, Caterina
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing - Surface technology. SP-Technical Research Institute of Sweden; University of Trento, Dept of Industrial Engineering.
    Persson, Per
    Thin Film Physics Division, Department of Physics, Chemistry and Biology, Linköping University.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Jarfors, Anders E.W.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    A study of formation and growth of the anodised surface layer on Al-Si casting alloys based on different analytical techniques2015Conference paper (Refereed)
    Abstract [en]

    One of the major limitations in the application of anodizing of aluminum casting alloys is the non-uniform thickness of the oxide layer. Previous researches have studied the formation of the oxide film during anodizing in detail. These investigations have mainly been limited to aluminum and wrought aluminum alloys, and only a few papers have given some insights about the formation of the oxide layer on cast aluminum alloys. The majority of cast aluminum alloys contains relatively higher amounts of Si and other elements (e.g. Cu and Fe) than wrought alloys. This paper aims to investigate the mechanisms of formation and growth of the anodized surface layer on Al-Si casting alloys by applying different analytical techniques such as optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray computer tomography (X-ray CT) scanning. Three different Al alloys with various Si content (2.4%, 3.5% and 5.5%) were investigated. Si morphological modification by Sr addition, as well as gradient solidification was used to vary the microstructural coarseness in a controlled manner to study the influence of these parameters on the growth of the oxide layer. The microstructure features of the anodized layer and the interface between matrix and the oxide layer were studied, employing optical microscopy (figure 1), and SEM/EDS (figure 2). X-Ray CT-scanning (figure 3) was used to examine the high density phases (Fe and Cu bearing phases) and also to give a 3-D view of the anodized oxide surface. Furthermore, TEM was used to examine the general filming behavior of anodized layer and the local effects associated with Si particles in the matrix.

    It was found that: (i) during anodizing, the oxide front grew around the Si particles and tends to engulf them; (ii) the oxide front grew inwards but did expand in other directions in the eutectic areas; (iii) a scalloped interface between substrate and oxide indicated different anodizing rates in dendrites and eutectic phases. The oxide front was moving faster in the primary dendrite Al-phase than in the eutectic, and the growth rate was particularly slow in larger eutectic areas; (iv) different anodizing rates in dendrite and eutectic phases resulted in thinner layers in specimens with lower SDAS (secondary dendrite arm spacing); and (v) a more uniform layer thickness in Sr-modified specimens illustrates that oxide growth speed was faster in modified eutectic phase. However, diffusion of Si or long distance between Si particles after modification could even results in the adverse situation with a bad anodized surface appearance. 

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