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  • 51.
    Bergman, Bo
    et al.
    Linköping Institute of Technology.
    Klefsjö, Bengt
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    A note on some test statistics against HNBUE1987Ingår i: Annals of the Institute of Statistical Mathematics, ISSN 0020-3157, E-ISSN 1572-9052, Vol. 39, nr 3, s. 483-488Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Some comments and extensions are given to the paper on statistics for testing exponentiality against the HNBUEE property (i.e. {Mathematical expression} ≦μ exp(-t/μ), t≧0) by Basu and Ebrahimi

  • 52. Bergman, Bo
    et al.
    Klefsjö, Bengt
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Legenden Philip Crosby har nyligen avlidit2001Ingår i: Kvalitetsmagasinet, ISSN 1104-1579, nr 4, s. 43-Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 53.
    Bergman, Bo
    et al.
    Linköping Institute of Technology.
    Klefsjö, Bengt
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Letter to the editors1988Ingår i: Reliability Engineering & System Safety, ISSN 0951-8320, E-ISSN 1879-0836, Vol. 21, nr 2, s. 155-160Artikel i tidskrift (Övrigt vetenskapligt)
  • 54. Bergman, Bo
    et al.
    Klefsjö, Bengt
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Recent applications of the TTT-plotting technique1998Ingår i: Frontiers in reliability: a volume commemorating the first 25 years of the Indian Association for Productivity, Quality and Reliability, Singapore: World Scientific and Engineering Academy and Society, 1998, s. 47-61Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 55. Bergman, Bo
    et al.
    Klefsjö, Bengt
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Statistical engineering for quality and productivity improvements1990Ingår i: European Journal of Engineering Education, ISSN 0304-3797, E-ISSN 1469-5898, Vol. 15, nr 3, s. 257-266Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The quality concept is strongly connected with customer satisfaction. One important reason for the quality and productivity success in Japanese industry is a consequent and systematic use of statistical methods during different stages of the production process. The quality challenge of European industry therefore implies claims both on the industry to use more statistical methods and on the teaching of statistics at engineering schools at different levels. The authors discuss the modern quality development and the role of statistical methods in this development. They also emphasize its strong implications for the teaching of statistics at engineering schools (27 refs.)

  • 56.
    Bergman, Bo
    et al.
    Linköpings universitet.
    Klefsjö, Bengt
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Statistics and TQM in industrial continuing education1994Ingår i: International Journal of Continuing Engineering Education, ISSN 0957-4344, Vol. 4, s. 114-121Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The urgent industrial transformation towards total quality management (TQM) and the role of statistics in this transformation are discussed. Implications for the teaching of statistics and TQM principles are drawn. In particular, implications for continuing education are discussed (10 refs.)

  • 57.
    Bergman, Bo
    et al.
    Department of Mathematics, Linköping University.
    Klefsjö, Bengt
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Testing against HNBUE with randomly censored data1985Ingår i: Contributions to probability and statistics in honour of Gunnar Blom, Lund: Lund University. Department of Mathematical Statistics , 1985, s. 49-72Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    The "harmonic new better than used in expectation" (HNBUE) class of life distributions contains all the more familiar classes from reliability theory such as the "increasing failure rate" (IFR) and "new better than used" (NBU), while still allowing one to formulate interesting inequalities comparing such distributions with the memoryless exponential distribution. In this paper test statistics based on the product-limit estimator are derived for testing the hypothesis of HNBUE versus exponentiality given a sample of censored observations from the life distribution of interest. A study of the asymptotic relative efficiency focusses on the loss of information due to censoring.

  • 58.
    Bergman, Bo
    et al.
    Linköping Institute of Technology.
    Klefsjö, Bengt
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    The total time on test concept and its use in reliability theory1984Ingår i: Operations Research, ISSN 0030-364X, E-ISSN 1526-5463, Vol. 32, nr 3, s. 596-606Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    More than 30 years ago, Epstein and Sobel introduced the Total Time on Test (TTT-) concept. During the last 10 years different generalizations of this concept have been defined and studied, e.g. the TTT-transform and the TTT-plot; a basic paper was presented by Barlow and Campo in 1975. Many of these generalizations have proven to be very useful in different areas of reliability, both from a theoretical and a practical point of view. The purpose of this expository paper is to present some of these generalizations and illustrate their value.

  • 59. Bergman, Bo
    et al.
    Klefsjö, Bengt
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    TTT transforms and age replacements with discounted costs1983Ingår i: Naval Research Logistics Quarterly, ISSN 0028-1441, Vol. 30, nr 4, s. 631-639Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ordinary age replacement problem consists of finding an optimal age at which a unit, needed in a continuous production process, should be replaced in order to minimize the average long-run cost per unit time. Bergman (1980) introduced a graphical procedure based on the total-time-on-test (TTT) concept for the analysis of the age replacement problem. In this article, that idea is generalized to the situation of discounted costs. The authors also study a more general age replacement problem in which they have a form of imperfect repair (20 refs.)

  • 60.
    Bergman, Bo
    et al.
    Linköping Institute of Technology.
    Klefsjö, Bengt
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    TTT-concept and replacements to extend system life1987Ingår i: European Journal of Operational Research, ISSN 0377-2217, E-ISSN 1872-6860, Vol. 28, nr 3, s. 302-307Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In a number of papers the current authors have illustrated how the Total Time on Test (TTT) concept can be used when analysing the ordinary age replacement problem and different generalization thereof. In this paper we show that the TTT-concept is very useful also when analysing another replacement problem discussed by C. Derman et al. in which the replacements of a vital component, for which there are n space units, are made with the goal of maximizing the expected system life. (12 refs.)

  • 61.
    Bergquist, Bjarne
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Analysis of an unreplicated 2^2 factorial experiment performed in a continuous process2015Ingår i: Total quality management and business excellence (Online), ISSN 1478-3363, E-ISSN 1478-3371, Vol. 26, nr 9-10, s. 1083-1094Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a tentative analysis method for unreplicated factorial designs where regular statistical experimental analysis cannot be used. The methodology is demonstrated through the analysis of an unreplicated two-level, two-factor factorial experiment performed in a continuous production process where the process was not in statistical control and where changes in the experimental design made conventional experimental analysis impossible. The first step of the analyses included screening of the sampled data. Principal component analysis and factor analysis were then used to create an overview of how the various responses and experimental factors were related. Carbon monoxide efficiency was selected as the most important parameter to be analysed further. Elastic net regression was used as a screening tool to remove non-significant factors, interaction, and covariates. Finally, the carbon monoxide efficiency variation was modelled using an intervention analysis. Two experimental factors were found to actively influence the response. The experiment that from other perspectives can be considered to be unanalysable, did thus reveal causal effects. The results imply that for processes where the process dynamics may be monitored, observations of the process dynamics may reduce the needs for repeated experimental runs, thus reducing the experimental costs.

  • 62.
    Bergquist, Bjarne
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Controlling the variation in the PM process1999Ingår i: Joint Nordic Conference in Powder Technology, sintef akademisk forlag, 1999Konferensbidrag (Refereegranskat)
  • 63.
    Bergquist, Bjarne
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Factor analysis of iron-phosphorus PM steel2000Ingår i: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 43, nr 2, s. 143-148Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Alloy design and choice of process parameters are often tasks where different investigations lead in different directions and the process of selecting the best parameter settings is difficult. Multivariate statistics are capable of bringing order in such situations, and here data from four different invesigations on the Fe-P-C system are collected and evaluated. Effects of chemical composition, comapction pressure, sintering time, and sintering temperature on properties including density, tensile strength, impact energy, proof stress, and elongation are studied. The investigation is based on principal factor analysis. Dimensional reduction is presented and discussed. The study compares the different investigations and the results for the Fe-P-C system show how different properties interact.

  • 64.
    Bergquist, Bjarne
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Influence of operating conditions related to physical properties of the iron melt during water atomization1999Ingår i: Joint Nordic Conference in Powder Technology, sintef akademisk forlag, 1999Konferensbidrag (Refereegranskat)
  • 65.
    Bergquist, Bjarne
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    New insights into influencing variables of water atomization of iron1999Ingår i: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 42, nr 4, s. 331-343Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Trace amounts of surfactants have an acute influence on measured surface tension of melts and may influence viscosity. A water atomisation experiment was performed to investigate if variations of these elements could affect quality. Effects of water pressure, melt superheat, and sulphur content, iron scrap oxygen content, and aluminium content were studied. Responses studied were particle size distribution, apparent density, flow, powder chemistry, morphology, green density, and dimensional change. A large sulphur addition reduced the particle size, as a result of a reduction of surface tension, but the largest effect came from changing water pressure. Higher water pressures also resulted in powders with lower apparent density, lower flowrate, and reduced swelling during sintering. An empirical water atomisation model is proposed. Aluminium additions reduced the powder size standard deviation and increased the carbon content of the powder. A reduced powder size standard deviation was seen also for melts with raised superheating.

  • 66.
    Bergquist, Bjarne
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Project: DISIRE2015Övrigt (Övrig (populärvetenskap, debatt, mm))
  • 67.
    Bergquist, Bjarne
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Quality improvement of PM steel processes: a statistical approach2009Bok (Övrigt vetenskapligt)
  • 68.
    Bergquist, Bjarne
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Some ideas why factorial designs are not used in full-scale experiments in continuous processes2015Ingår i: Total quality management and business excellence (Online), ISSN 1478-3363, E-ISSN 1478-3371, Vol. 26, nr 11-12, s. 1242-1254Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents ideas and observations about the infrequent use of factorial experimental designs; although the ideas presented are inspired by a case study, the paper is also conceptual in nature. The ideas build on the experimental practices at a large Swedish process industry manufacturer, where these practices were discussed with engineers using in-depth interviews. Factorial design is not used because, for example, statistical rigor is seldom required and because design of experiments methods are seen as too restrictive to accommodate and adjust to events occurring during long experimental campaigns. The interview results indicate that, while the scepticism of many respondents may be justified, lack of training, interest, and learning time are major obstacles to applying improved methodologies. Some ideas for overcoming these obstacles are suggested.

  • 69.
    Bergquist, Bjarne
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    The importance of experimental design2002Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 328, nr 1-2, s. 348-349Artikel i tidskrift (Övrigt vetenskapligt)
  • 70.
    Bergquist, Bjarne
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Traceability in iron ore processing and transports2012Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 30, s. 44-51Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ability to track and trace products in a production process and in the transportation chain from supplier to customers is important for quality control and process improvements. However, good traceability is often difficult achieve for continuous process products as well as for batch produced products where batches intermix. In this paper, guidelines for improving traceability and setting up a traceability system in the iron ore production process are presented based on two case studies. One case is using process data in a simulation approach for a pellets plant and the other is using RFID methodology to trace pellets in the distribution chain. Results show that simulations can aid short-term traceability, whereas long term traceability is possible through marking pellets with RFID transponders, where the applications are suitable.

  • 71.
    Bergquist, Bjarne
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Tracing granular products using RFID2011Konferensbidrag (Övrigt vetenskapligt)
  • 72.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Albing, Malin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Statistical methods - does anyone really use them?2006Ingår i: Total quality management and business excellence (Online), ISSN 1478-3363, E-ISSN 1478-3371, Vol. 17, nr 8, s. 961-972Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Students taking courses in quality management at Luleå University of Technology receive extensive education in statistical methods. To improve the education and to understand what kind of competence students need when they graduate, a survey was preformed examining how and to what extent the methods Statistical Process Control, Capability Analysis and Design of Experiments are used by organisations hiring the alumni. The result shows that the students employed in the Swedish industrial sector witness a modest use of statistical methods, while use of statistical methods in other sectors hiring the alumni is uncommon. Lack of competence and resources within the organizations are stated as hindrances to expanded use. Conclusions from the study are that implementation techniques must be emphasized in the curriculum and that different types of courses should be given - practical, hands-on courses for engineers, managers and others working in organizations. Furthermore, courses offered at universities must have a strong focus on practical problems such as difficulties randomizing experiments and that graphical methods should be favoured.

  • 73.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Collosimo, Bianca Maria
    Department of Mechanical Engineering Politecnico di Milano .
    The ENBIS‐16 quality and reliability engineering international special issue2017Ingår i: Quality and Reliability Engineering International, ISSN 0748-8017, E-ISSN 1099-1638, Vol. 33, nr 6, s. 1167-1168Artikel i tidskrift (Refereegranskat)
  • 74.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Ericsson, T.
    Division of Engineering Materials, Department Mechanical Engineering, Linköpings universitet.
    Robustness simulation of water atomisation2000Ingår i: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 43, nr 1, s. 37-42Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    One of the main purposes of water atomisation is to keep the powder size distribution within a close range. The process is difficult to monitor and thus the state of today's process control is poor. To investigate this process, both a laboratory scale and an industrial scale atomisation facility were modelled where melt flow and thermal flow were investigated. The results showed that metal temperature is important if stable particle sizes are to be obtained from batch to batch.

  • 75.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Foley, K.
    Garvare, Rickard
    Johansson, Peter
    Third generation quality managemet2007Ingår i: New Perspectives on the Theories and Practices of Organizational Excellence: Proceedings of 6th MAAOE International Conference. The Multinational Alliance For The Advancement Of Organizational Excellence, University of Versailles Sain-Quentin-En-Yvelines , 2007Konferensbidrag (Refereegranskat)
  • 76.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Foley, Kevin
    Sydney University of Technology.
    Garvare, Rickard
    Johansson, Peter
    Reframing quality management2008Ingår i: The Theories and Practices of Organization Excellence: New Perspectives, Sydney: SAI Global , 2008, s. 501-538Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 77.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Fredriksson, Maria
    Svensson, Magnus
    TQM: terrific quality marvel or tragic quality malpractice2005Ingår i: TQM Magazine, ISSN 0954-478X, E-ISSN 1758-6887, Vol. 17, nr 4, s. 309-321Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose - Total quality management has seen a tremendous rise of popularity in the 1980s and 1990s. Aims to question the effectiveness, utility and use of TQM among many people - practitioners, as well as academics. Design/methodology/approach - Discusses the lack of common interpretations of TQM based on literature study. The answer to the question whether TQM is a marvel or malpractice depends on several factors, for instance, in what kinds of organizations TQM is applied, what interpretation of TQM is made, and what input the theorists and practitioners have, i.e. their earlier environment, culture and values. Often respondents and opponents use the same word but mean different things. Findings - TQM should not be rejected as a whole if one or even, many applications fail. TQM should, however, be applied with considerable consideration of the specifics of the target organization, the purpose of the organization, and the purpose of applying TQM. Originality/value - The paper emphasizes the lack of common interpretations of TQM.

  • 78.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Garvare, Rickard
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Evaluating Quality of Higher Education by Assessing its Output: The Swedish Example2013Ingår i: 16th QMOD-ICQSS Proceedings: Quality Management and Organizational Development Conference / [ed] Su Mi Dahlgaard Park, Moderna Organizacija , 2013, s. 216-222Konferensbidrag (Refereegranskat)
  • 79.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Garvare, Rickard
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Eriksson, Henrik
    Chalmers University of Technology.
    Hallencreutz, Jacob
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle.
    Langstrand, Jostein
    Linköpings universitet.
    Vanhatalo, Erik
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Zobel, Thomas
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Alive and kicking – but will Quality Management be around tomorrow?: A Swedish academia perspective2012Ingår i: Quality Innovation Prosperity, ISSN 1335-1745, E-ISSN 1338-984X, Vol. 16, nr 2, s. 1-18Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The purpose of this article is to describe how Quality Management (QM) is perceived today by scholars at three Swedish universities, and into what QM is expected to develop into in twenty years. Data were collected through structured workshops using affinity diagrams with scholars teaching and performing research in the QM field. The results show that QM currently is perceived as consisting of a set of core of principles, methods and tools. The future outlook includes three possible development directions for QM are seen: [1] searching for a “discipline X” where QM can contribute while keeping its toolbox, [2] focus on a core based on the traditional quality technology toolbox with methods and tools, and [3] a risk that QM, as it is today, may seize to exist and be diffused into other disciplines.

  • 80.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Garvare, Rickard
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Eriksson, Henrik
    Chalmers tekniska högskola, Teknikens ekonomi och organisation.
    Hallencreutz, Jacob
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle.
    Langstrand, Jostein
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Avdelningen för Kvalitetsteknik.
    Vanhatalo, Erik
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Zobel, Thomas
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Alive and kicking–but will Quality Management be around tomorrow?: A Swedish academia perspective2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Purpose: There is a lack of a recognized conception of quality management (QM) comprises of, as well as a clear roadmap of where QM is heading. The purpose of this article is to investigate how QM is perceived today by scholars at three Swedish universities, but also how and into what QM is expected to develop into in twenty years.Methodology: Data have been collected through three structured workshops using affinity diagrams with scholars teaching and performing research in the QM field affiliated with three different Swedish universities.Findings: The results indicate that current QM is perceived similarly among the universities today, although the taxonomy differs slightly. QM is described as a fairly wide discipline consisting of a set of core of principles that in turn guide which methods and tools that currently by many are perceived as the core of the discipline. The outlook for the future differs more where three possible development directions for QM are seen: [1] searching for a “discipline X” where QM can contribute while keeping its toolbox, [2] focus on a core based on the traditional quality technology toolbox with methods and tools, and [3] a risk that QM, as it is today, may seize to exist and be diffused into other disciplines. Originality/value: This article contributes with a viewpoint on QM today and its future development from the academicians’ perspective.

  • 81.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Garvare, Rickard
    Klefsjö, Bengt
    Quality management for tomorrow2007Ingår i: Quality management and organizational excellence: oxymorons, empty boxes, or significant contributions to management thought and practice? / [ed] Kevin J. Foley; Douglas A. Hensler; Jan Jonker, Sydney: SAI Global , 2007, s. 253-286Konferensbidrag (Refereegranskat)
  • 82.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Hjortsberg, E.
    Chalmers University of Technology.
    Filling induced density variations in metal powder2002Ingår i: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 45, nr 2, s. 146-153Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Filling induced density variations is a problem that has long been overlooked by powder metallurgy scientists. In this paper,densityvariations are addressed, both why they occur and what problems they may cause. A test method, including a test rig, is presented that is able to link several different factors to resulting powder densities. The relations are analysed and several density affecting mechanisms are suggested. These mechanisms could be used either to minimise density differences within parts or to control density by directing powder to critical areas.

  • 83.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Kvarnström, Björn
    Tracing granular products using RFID2010Konferensbidrag (Övrigt vetenskapligt)
  • 84.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Kvarnström, Björn
    Tracking and tracing products in continuous processes2011Ingår i: International Congress on Productivity, Quality, Reliability, Optimization and Modelling: ICPQROM 2011, Indian Statistical Institute , 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Traceability is important for quality control and process improvements, but it is often difficult to track or trace products in continuous process production, since products and product lots are difficult to separate. In the past, engineers have had to rely on coarse calculations for tracing products, but new possibilities emerge as new technology and models are being used. In this paper, we present experiences from applying chemical and RFID tracers to achieve traceability in continuous flows, with examples taken from the minerals processing sector.

  • 85.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Lovén, Erik
    Olsson, Thomas
    Luleå tekniska universitet.
    The one-hour design of experiments course2006Ingår i: Quality Management Journal, ISSN 1068-6967, Vol. 13, nr 1, s. 26-32Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A one-hour introductory course in design of experiments (DOE) is described that has been designed to attract high school students to study science and engineering in general and quality management in particular. The course is inspired by the Pepsi Challenge and is evaluated on the basis of "Seven Good Principles to Achieve Good Learning." Results show it is possible to covey the benefits of statistical thinking to students with limited knowledge of mathematics and statistics within a short period of time.

  • 86.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Söderholm, Peter
    Trafikverket.
    Control charts for assessment of linear asset condition using both temporal and spatial information2012Ingår i: Proceedings of the 2nd International Workshop & Congress on eMaintenance: Dec 12-14 Luleå, Sweden : eMaintenace: trends in technologies and methodologies, challenges, possibilities and applications / [ed] Ramin Karim; Aditya Parida; Uday Kumar, Luleå: Luleå tekniska universitet, 2012, s. 145-152Konferensbidrag (Refereegranskat)
  • 87.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Söderholm, Peter
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Control Charts supporting Condition-Based Maintenance of Linear Railway Infrastructure Assets2015Ingår i: International Journal of COMADEM, ISSN 1363-7681, Vol. 18, nr 2, s. 7-16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a control chart approach for monitoring, diagnostics and prognostics to support condition-based maintenance (CBM) using condition data of linear railway infrastructure assets. The condition data were obtained from regular inspections done by a railway track measurement wagon. The condition data were statistically analysed by using two different control charts to evaluate the possibility for earlier detection of derailment hazardous faults using both temporal and spatial information.The study indicates that that the proposed control chart approach can be used for condition assessment of track and thereby provides valuable decision support for CBM. The control chart for condition information in the temporal domain supports diagnostics, while the control chart for condition information in the spatiotemporal domain also supports prognostics. The two proposed control charts give earlier fault warnings compared to the traditional approach. This facilitates decisions regarding CBM actions with an extended planning horizon and gives the possibility to increase the operational availability of track.

  • 88.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Söderholm, Peter
    Trafikverket.
    Control Charts supporting Condition-Based Maintenance of Linear Railway Infrastructure Assets2014Ingår i: Proceedings of the 3rd international workshop and congress on eMaintenance: June 17-18 Luleå, Sweden : eMaintenance, Trends in technologies & methodologies, challenges, possibilites and applications / [ed] Uday Kumar; Ramin Karim; Aditya Parida; Philip Tretten, Luleå: Luleå tekniska universitet, 2014, s. 101-107Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a control chart approach for monitoring,diagnostics and prognostics to support condition-basedmaintenance (CBM) using condition data of linear railwayinfrastructure assets. The condition data were obtained fromregular inspections done by a railway track measurement wagon.The condition data were statistically analysed by using twodifferent control charts to evaluate the possibility for earlierdetection of derailment hazardous faults using both temporal andspatial information. The study indicates that that the proposedcontrol chart approach can be used for condition assessment oftrack and thereby provide valuable decision support for CBM. Thecontrol chart for condition information in the temporal domainsupports diagnostics, while the control chart for conditioninformation in the spatiotemporal domain also supportsprognostics. The two proposed control charts give earlier faultwarnings compared to the traditional approach. This facilitatesdecisions regarding CBM actions with an extended planninghorizon and gives the possibility to increase the operationalavailability of track.

  • 89.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Söderholm, Peter
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Data Analysis for Condition-Based Railway Infrastructure Maintenance2015Ingår i: Quality and Reliability Engineering International, ISSN 0748-8017, E-ISSN 1099-1638, Vol. 31, nr 5, s. 773-781Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Condition assessment is crucial to optimize condition-based maintenance actions of assets such as railway infrastructure, where a faulty state might have severe consequences. Hence, railways are regularly inspected to detect failure events and prevent the inspected item (e.g. rail) to reach a faulty state with potentially safety critical consequences (e.g. derailment). However, the preventive measures (e.g. condition-based maintenance) initiated by the inspection results may cause traffic disturbances, especially if the expected time to a faulty state is short. The alarm limits are traditionally safety related and often based on geometrical properties of the inspected item. Maintenance limits would reduce the level of emergency, producing earlier alarms and increasing possibilities of planned preventive rather than acute maintenance. However, selecting these earlier maintenance limits in a systematic way while balancing the risk of undetected safety-critical faults and false alarms is challenging. Here, we propose a statistically based approach using condition data of linear railway infrastructure assets. The data were obtained from regular inspections done by a railway track measurement wagon. The condition data were analysed by a control chart approach to evaluate the possibility for earlier detection of derailment hazardous faults using both temporal and spatial information. The study indicates that that the proposed approach could be used for condition assessment of tracks. Control charts led to earlier fault warnings compared to the traditional approach, facilitating planned condition-based maintenance actions and thereby a reduction of track downtime

  • 90.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Söderholm, Peter
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Improved Condition Assessment through Statistical Analyses: Case Study of Railway Track2017Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Traditional practice within railway maintenance is based on engineering knowledge and practical experience, which are documented in regulations. This practice is often time-based, but can also be condition-based by combining time-based inspections with condition-based actions depending on the inspection results. However, the logic behind the resulting regulation is seldom well documented, which makes it challenging to optimise maintenance based on factors such as operational conditions or new technologies, methodologies and best practices. One way to deal with this challenge is to use statistical analysis and build models that support fault diagnostics and failure prognostics. This analysis approach will increase in importance as automated inspections replace manual inspections. Specific measurement equipment and trains are not the only ones producing automated measurements; regular traffic is increasingly often producing measurements. Hence, there will not be any lack of condition data, but the challenge will be to use this data in a correct way and to extract reliable information as decision support. In this context, it is crucial to balance the risks of false alarms and unrecognised faults, but also to estimate the quality of both data and information. The purpose of this work is to use statistics in order to support improved asset management, by building statistical models as a complement to physical models and engineering knowledge. The resulting models combine theories from the field of time-series analysis, statistical process control (SPC) and measurement system analysis. Charts and plots present results and have prognostic capabilities that allow necessary track possession times to be included in the timetable. 

  • 91.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Söderholm, Peter
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Measurement System Analysis of Railway Track Geometry Data using Secondary Data2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we use secondary data to make a partial measurement system analysis of railway measurement cars and their obtained track geometry data. When a measurement car passes the same track section shortly after the previous passage, such as returning in the other direction after reaching a railway endpoint, the repeated measurements hold information of the measurement uncertainty of that car. Reasons for the measurement uncertainty can be sought in other variables that also are stored in the database, such as the individual car identity, the type of car, the speed of the car during measurement, and the travelled direction of the car. By also considering other known factors during the time of measurement as regressors, such as ground frost periods, enhanced modelling may be achieved and also indicate if such periods should be avoided to improve the measurement data quality.The results of this study suggest that the type of car had the largest influence on measurement variation out of the studied regressors. If the variation of a track geometry property on a track section is studied, the variation component belonging to the type of car can be deducted, improving data quality. We suggest that the method could also be used to find track sections that are prone to large seasonal variation, such as due to ground frost.

  • 92.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Söderholm, Peter
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Measurement Systems Analysis of Railway Measurement Cars2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Purpose: The presentation proposes ways to understand and quantify the variation component due to the measurement system of railway track properties using subsequent runs from measurement cars.Background: Railway infrastructure conditions are commonly inspected by using measurement cars. The measurements are performed with some regularity, and the inspection frequencies could for instance be set taking into account the common train axle loads, railway speed or load bearing classification, number of trains passing, the known railway condition, or the availability of the measurement cars. By combining different inspections of the same track section, it is also possible to monitor the degradation of the infrastructure over time. Often, the railway system is inspected by many measurement cars, and for single tracks, measurements can be obtained from the car travelling in different directions. The measurements are performed at different speeds, related to random variation, but also to the maximum speeds at which the measurement cars operate. The measurements are also afflicted by external variation sources, some of which are acting with a known direction, such as the wear of the track which increases property variation. Maintenance usually (but not always) result in reduced property variation, whereas other sources such as climate related properties such as spring thaw may induce variation over time, but also induce variation that show a periodic behavior with periods with increasing as well as decreasing property variation. This presentation aims to devise a model for how these variation sources may be separated, with the main aim to classify measurement error, but also to estimate the magnitude of other variation sources.Method: No statistically significant differences were found between repeated measurements of cars travelling back and forth on the single track found at the Swedish Iron ore line. These measurements contain measurement error as well as error due to short term degradation and variation due to measurement. As measurement variance is added, it was concluded that the measurement variation could not be larger than the variation shown by repeat measurements. By comparing repeated measurements over time and subtracting variation due to wear, measurement variation for different cars, measurement speeds and measurement directions was estimated using Generalized Linear Models regression analysis. Co-variation between measurement cars and measurement speeds were accounted for using Ridge regression and Elastic Net regression.Results: The regression analysis shows that whereas both measurement speed and the measurement car individuals correlate with the measurement variation obtained, regularized regression points to the measurement cars as the major variation factor and that different measurement cars have different measurement precisionDiscussion and conclusion: The study demonstrates how repeated measurements from regular process data and thus not obtained using the regular and systematic experimental procedures of measurement system analysis can be used for estimation of the variation components of the measurement system. As a side effect, the sizes of other variation sources, external to the measurement system, can be estimated.

  • 93.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Söderholm, Peter
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Predictive Modelling for Estimation of Railway Track Degradation2016Ingår i: Current Trends in Reliability, Availability, Maintainability and Safety: An Industry Perspective / [ed] Uday Kumar; Alireza Ahmadu; Ajit Kumar Verma; Prabhakar Varde, Encyclopedia of Global Archaeology/Springer Verlag, 2016, s. 331-347Konferensbidrag (Refereegranskat)
    Abstract [en]

    The degradation processes affecting railway track condition depends both on the resistance of the track and on the stresses subjected to it. Regarding the stresses, both their magnitudes and cycles are of importance when considering the degradation. Furthermore, the stresses have some regularity and variability in the time domain, while the degradation resistance of a track has some spatial regularity as well as variability. In addition, the condition measurements of track may be both irregular and contain measurement errors. Hence, it is challenging to model the condition of track to enable predictions and condition-based maintenance. However, wear prediction models could help to change large parts of the maintenance practice from predominantly corrective to preventive if both the deterministic and the stochastic components of the wear process can be estimated with sufficient accuracy. In this study, one-step-ahead predictions have been used for establishing prognostic models based on repeated measurements of railway track geometry to estimate track wear properties, degradation rates and stochastic behaviour including measurement errors. The prognostic models have then been used for condition assessment and state predictions. Repeated sampling allows for estimations of measurement errors, but the irregular sampling need to be accounted for by interpolation in the time series modelling approach

  • 94.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Söderholm, Peter
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Projekt: Förbättrad tillståndsbedömning genom statistisk analys2015Övrigt (Övrig (populärvetenskap, debatt, mm))
  • 95.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Söderholm, Peter
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Eriksson, Per-Erik
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Innovation och Design.
    Karrbom Gustavsson, Tina
    Arkitektur och samhällsbyggnad, KTH, Sverige.
    Projekt: Offentlig upphandling av järnvägsunderhåll2015Övrigt (Övrig (populärvetenskap, debatt, mm))
  • 96.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Söderholm, Peter
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi. Trafikverket.
    Kauppila, Osmo
    University of Oulu.
    Vanhatalo, Erik
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Cleansing Railway Track Measurement Data for Better Maintenance Decision2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    Data of sufficient quality, quantity and validity constitute asometimes overlooked basis for eMaintenance. Missing data,heterogeneous data types, calibration problems, or non-standarddistributions are common issues of operation and maintenancedata. Railway track geometry data used for maintenance planningexhibit all the above issues. They also have unique featuresstemming from their collection by measurement cars runningalong the railway network. As the track is a linear asset, measuredgeometry data need to be precisely located to be useful. However,since the sensors on the measurement car are moving along thetrack, the observations’ geographical sampling positions comewith uncertainty. Another issue is that different seasons and othertime restrictions (e.g. related to the timetable) prohibit regularsampling. Hence, prognostics related to remaining useful life(RUL) are challenging since most forecasting methods require afixed sampling frequency.

    This paper discusses methods for data cleaning, data condensationand data extraction from large datasets collected by measurementcars. We discuss missing data replacement, dealing withautocorrelation or cross-correlation, and consequences of notfulfilling methodological pre-conditions such as estimatingprobabilities of failures using data that do not follow the assumeddistributions or data that are dependent. We also discuss outlierdetection, dealing with data coming from multiple distributions,of unknown calibrations and other issues seen in railway trackgeometry data. We also discuss the consequences of notaddressing or mishandling quality issues of such data.

  • 97.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Vanhatalo, Erik
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Power Analysis of Methods for Analysing Unreplicated Factorial Experiments2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Several methods for formal analysis of unreplicated factorial type experiments have been proposed in the literature. Based on a simulation study, five formal methods found in the literature based on the effect sparsity principle have been studied. The simulation included 23 and 24 type factorials with one, two, or four active effects. The simulated signal-to-noise ratios for the effects were all between two and four, and the Type I and Type II errors of the analysis methods were analysed. Preliminary results show that Bayesian models are more powerful in these contexts, especially if informative priors based on the effect heredity and effect hierarchy principles are used.

  • 98.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Vanhatalo, Erik
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Using Active RFID for In-Situ Measurement of Temperature and Acceleration in the Distribution Chain of Iron Ore PelletsIngår i: Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This article describes how active radio frequency identification (RFID) technique can be used to measure accelerations and temperature that iron ore pellets endure along parts of their distribution chain. Increased knowledge about the accelerations and temperature can help the mining company reduce pellets breakage and dusting. In this work we have studied the distribution chain between the pelletizing plant and the harbour. The article reports on two experiments with active RFID transponders released into the product flow after the pelletizing plant. The transponders measured the temperature and peak accelerations. Transponder data were then captured by RFID readers in the harbour. The results show that active RFID technique can be used for in-situ measurements of accelerations and temperature in the pellets distribution chain although further research is needed to study the segregation behaviour of the active transponders

  • 99.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Vanhatalo, Erik
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle.
    Nordenvaad, Magnus Lundberg
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    A Bayesian analysis of unreplicated two-level factorials using effects sparsity, hierarchy, and heredity2011Ingår i: Quality Engineering, ISSN 0898-2112, E-ISSN 1532-4222, Vol. 23, nr 2, s. 152-166Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This article proposes a Bayesian procedure to calculate posterior probabilities of active effects for unreplicated two-level factorials. The results from a literature survey are used to specify individual prior probabilities for the activity of effects and the posterior probabilities are then calculated in a three-step procedure where the principles of effects sparsity, hierarchy, and heredity are successively considered. We illustrate our approach by reanalyzing experiments found in the literature.

  • 100.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Westerberg, Mats
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Innovation och Design.
    Networking to boost lean six sigma potential2008Ingår i: Third international Conference on Sex Sigma / [ed] Jiju Antony; Maneesh Kumar; Chidebere Ogbu, Glasgow: University of Strathclyde, 2008, s. 488-500Konferensbidrag (Refereegranskat)
    Abstract [en]

    At the beginning of 2008 three SMEs in a small town in Sweden started a network project inspired by the Six Sigma programme, and hired a full-time Black Belt to lead the improvement activities. Three months into the project, we interviewed the top management of the participating companies and the Black Belt, to pinpoint success factors as well as risks of the cooperation project. Results show that statistical methods were unused in favour of methods associated with lean manufacturing such as 5S. Accordingly, the expectations of the CEOs were related to production improvements and flow rather than quality. Both the Black Belt and the CEOs stated that management commitment was vital for the success of the partnership, but also that the visibility of this commitment could be improved. Despite this, all interviewees agreed that the project had gotten a good start and the managers had high expectations for its progress.

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