| 1. |
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| 2. |
- Aldenlöv, Jens
(författare)
-
Exploring Public Procurement of Swedish Railway Infrastructure Maintenance
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In 2002, Sweden started to outsource its railway infrastructure maintenance. Through gradual exposure (i.e. outsourcing one contract area at a time), the Swedish Transport Administration has developed its competence of being a client towards its contractors. The last contract was outsourced in 2014. In the last decade, the development of governance techniques and maintenance cost has not matched the increase in traffic. Due to an increased awareness in environmentally friendlier transportation, traffic is only expected to increase further in the coming years. Governance techniques and maintenance cost ultimately depends on the client-contractor relationship through public procurement. Hence, there is a need to understand public procurement of railway infrastructure maintenance. Therefore, the purpose of this thesis is to contribute to the knowledge of public procurement of railway infrastructure maintenance. Three separate studies were conducted. Study 1 was a literature review to explore and determine the state-of-the-art for the field of public procurement of railway maintenance. Study 2 was a linear regression analysis to examine the relationship between contract design and the output of maintenance in Sweden. Study 3 was an interview study in Sweden that explored what factors that supports or hinders collaboration in railway maintenance.The main results of these studies are that asset knowledge is important for both the client and the contractor. Through reliable asset knowledge, incentives and contracts can be designed to support governance and collaboration. Today, railway infrastructure maintenance is dominated by informal relationships that lack the support of formal partnering activities. When an informal relationship is supported by a formal structure it provides a basis for innovation. This formal structure should be centralized around gaining and sharing asset knowledge. By establishing such a system to increase the asset knowledge and supporting collaboration, public organizations of maintenance can provide a basis for the improvement of maintenance.
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| 3. |
- Aldenlöv, Jens, et al.
(författare)
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Public procurement of railway infrastructuremaintenance : a literature review
- 2017
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Ingår i: Proceedings of the 9th Nordic Conference on Construction Economics and Organization. - Lyngby : Polyteknisk Boghandel og Forlag. - 9788750211259 ; , s. 10-21
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Konferensbidrag (refereegranskat)abstract
- The maintenance of railway infrastructure has in several instances been changed from government-based to being based on public procurement, with varying degrees of flexibility for the contractor to design their maintenance work. The purpose of-giving contractors a larger freedom of choice of how to perform maintenance is to stimulate them to innovate and develop their maintenance processes. Since the contracts differ in between and there are changes in government policies over time that affects both existing and new contracts, a comparison between different contracts becomes challenging. A literature review has been conducted to understand the change in procurement strategy and how to encourage contractors to innovate. The research questions include: What procurement strategies are there? How is maintenance evaluated? How does procurement affect the innovation opportunities for entrepreneurs?The literature review focuses on railway maintenance and contract design between client and contractor. In total, 17 articles matched the search criteria and were selected for the review. To have successful maintenance service, five articles suggested partnering as a strategy with common goals in combination with good communication during the entirety of the contract. When selecting incentive plan, four articles mentions that a focus on performance-based incentives in combination with riskmanagement is better rather than actual payment schemes. The reason being that payment is often themain cause of conflicts between client and contractor. The scientific literature suggests that improvement in incentives improves quality of maintenance, decreases delays and technical failures. The conclusion from the literature review is that partnering in railway maintenance is considered successful. With accurate knowledge about railway assets the incentive plan becomes accurate which reduces costs.The literature review is a part of a research project with an overall goal to develop a model to guide the selection of appropriate type of procurement strategy, contract and control of maintenance for a moresustainable railway system.
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| 4. |
- Bergquist, Bjarne, et al.
(författare)
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A Bayesian analysis of unreplicated two-level factorials using effects sparsity, hierarchy, and heredity
- 2011
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Ingår i: Quality Engineering. - : Informa UK Limited. - 0898-2112 .- 1532-4222. ; 23:2, s. 152-166
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 5. |
- Bergquist, Bjarne, et al.
(författare)
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Alive and kicking–but will Quality Management be around tomorrow? : A Swedish academia perspective
- 2012
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 6. |
- Bergquist, Bjarne, et al.
(författare)
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Alive and kicking–but will Quality Management be around tomorrow? A Swedish academia perspective
- 2012
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Ingår i: Quality Innovation Prosperity. - : Technical University of Kosice, Faculty of Materials, Metallurgy and Recycling. - 1335-1745 .- 1338-984X. ; 16:2, s. 1-18
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 7. |
- Bergquist, Bjarne
(författare)
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Analysis of an unreplicated 2^2 factorial experiment performed in a continuous process
- 2015
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Ingår i: Total Quality Management and Business Excellence. - : Informa UK Limited. - 1478-3363 .- 1478-3371. ; 26:9-10, s. 1083-1094
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Bergquist, Bjarne, et al.
(författare)
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Cleaning of Railway Track Measurement Data forBetter Maintenance Decisions
- 2019
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Ingår i: Proceedings of the 5<sup>th</sup> International Workshop and Congress on eMaintenance. - : Luleå University of Technology. ; , s. 9-15
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Konferensbidrag (refereegranskat)abstract
- Data of sufficient quality, quantity and validity constitute a sometimes overlooked basis for eMaintenance. Missing data, heterogeneous data types, calibration problems, or non-standard distributions are common issues of operation and maintenance data. Railway track geometry data used for maintenance planning exhibit all the above issues. They also have unique features stemming from their collection by measurement cars running along the railway network. As the track is a linear asset, measured geometry data need to be precisely located to be useful. However, since the sensors on the measurement car are moving along the track, the observations’ geographical sampling positions come with uncertainty. Another issue is that different seasons and othertime restrictions (e.g. related to the timetable) prohibit regular sampling. Hence, prognostics related to remaining useful life (RUL) are challenging since most forecasting methods require a fixed sampling frequency.This paper discusses methods for data cleaning, data condensation and data extraction from large datasets collected by measurement cars. We discuss missing data replacement, dealing with autocorrelation or cross-correlation, and consequences of not fulfilling methodological pre-conditions such as estimating probabilities of failures using data that do not follow the assumed distributions or data that are dependent. We also discuss outlier detection, dealing with data coming from multiple distributions, of unknown calibrations and other issues seen in railway track geometry data. We also discuss the consequences of not addressing or mishandling quality issues of such data.
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| 9. |
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| 10. |
- Bergquist, Bjarne, et al.
(författare)
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Control Charts supporting Condition-Based Maintenance of Linear Railway Infrastructure Assets
- 2015
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Ingår i: International Journal of COMADEM. - 1363-7681. ; 18:2, s. 7-16
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 11. |
- Bergquist, Bjarne, et al.
(författare)
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Control Charts supporting Condition-Based Maintenance of Linear Railway Infrastructure Assets
- 2014
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Ingår i: Proceedings of the 3rd international workshop and congress on eMaintenance. - Luleå : Luleå tekniska universitet. - 9789174399721 - 9789174399738 ; , s. 101-107
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 12. |
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| 13. |
- Bergquist, Bjarne, et al.
(författare)
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Data Analysis for Condition-Based Railway Infrastructure Maintenance
- 2015
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Ingår i: Quality and Reliability Engineering International. - : Wiley. - 0748-8017 .- 1099-1638. ; 31:5, s. 773-781
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Tidskriftsartikel (refereegranskat)abstract
- 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
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| 14. |
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| 15. |
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| 16. |
- Bergquist, Bjarne
(författare)
-
Factor analysis of iron-phosphorus PM steel
- 2000
-
Ingår i: Powder Metallurgy. - : Informa UK Limited. - 0032-5899 .- 1743-2901. ; 43:2, s. 143-148
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 17. |
- Bergquist, Bjarne, et al.
(författare)
-
Improved Condition Assessment through Statistical Analyses : Case Study of Railway Track
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 18. |
- Bergquist, Bjarne, et al.
(författare)
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In-situ measurement in the iron ore pellet distribution chain using active RFID technology
- 2020
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Ingår i: Powder Technology. - : Elsevier. - 0032-5910 .- 1873-328X. ; 361, s. 791-802
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Tidskriftsartikel (refereegranskat)abstract
- The active radio frequency identification (RFID) technique is used for in-situ measurement of acceleration and temperature in the distribution chain of iron ore pellets. The results of this paper are based on two experiments, in which active RFID transponders were released into train wagons or product bins. RFID exciters and readers were installed downstream in a harbour storage silo to retrieve data from the active transponders. Acceleration peaks and temperatures were recorded. The results imply that in-situ data can aid the understanding of induced stresses along the distribution chain to, for example, reduce pellet breakage and dusting. In-situ data can also increase understanding of product mixing behaviour and product residence times in silos. Better knowledge of stresses, product mixing and residence times are beneficial to process and product quality improvement, to better understand the transportation process, and to reduce environmental impacts due to dusting.
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| 19. |
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| 20. |
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| 21. |
- Bergquist, Bjarne, et al.
(författare)
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Measurement System Analysis of Railway Track Geometry Data using Secondary Data
- 2016
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 22. |
- Bergquist, Bjarne, et al.
(författare)
-
Measurement Systems Analysis of Railway Measurement Cars
- 2016
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 23. |
- Bergquist, Bjarne
(författare)
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Multivariate analysis of iron-phosphorus PM steel
- 1998
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Ingår i: Proceedings of 1998 Powder Metallurgy World Congress. - Shrewsbury : European powder metallurgy association. - 1899072098
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Konferensbidrag (refereegranskat)
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| 24. |
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| 25. |
- Bergquist, Bjarne, et al.
(författare)
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Networking to boost lean six sigma potential
- 2008
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Ingår i: Third international Conference on Sex Sigma. - Glasgow : University of Strathclyde. - 9780947649326 ; , s. 488-500
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Konferensbidrag (refereegranskat)abstract
- 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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| 26. |
- Bergquist, Bjarne, et al.
(författare)
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Networking to make improvements sustainable : an SME success factor?
- 2009
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Ingår i: Proceedings 7th ANQ Congress Tokyo 2009. ; , s. 522-531
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Konferensbidrag (refereegranskat)abstract
- I mars 2008 beslutade tre svenska mindre företag att öka takten i sitt förbättringsarbete och anställde gemensamt en förbättringskonsult på heltid. Detta dokument beskriver företagens arbete och presenterar resultat från en undersökning baserad på Ajzen's teori om planerat beteende, riktad till samtliga anställda och genomförd efter nio månader. Resultaten visar att arbetstagarnas avsikt att genomföra förbättringsarbete var korrelerade med tron på den egna förmågan att utföra förbättringsarbete, och med ledningens normer. Således kan nyckeln till ett framgångsrikt förbättringsarbete för dessa företag ses ligga i att ha en engagerad ledning och erbjuda anställda utbildning och handledning.
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| 27. |
- Bergquist, Bjarne
(författare)
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New insights into influencing variables of water atomization of iron
- 1999
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Ingår i: Powder Metallurgy. - : Informa UK Limited. - 0032-5899 .- 1743-2901. ; 42:4, s. 331-343
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 28. |
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| 29. |
- Bergquist, Bjarne, et al.
(författare)
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Power Analysis of Methods for Analysing Unreplicated Factorial Experiments
- 2013
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 30. |
- Bergquist, Bjarne, 1965-, et al.
(författare)
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Prediction Models for Track Deterioration
- 2019
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Ingår i: <em>Proceedings of the International Heavy Haul Conference</em>.
-
Konferensbidrag (refereegranskat)abstract
- The Swedish Iron ore line is subjected to sub-arctic weather conditions, high axle loads and a large yearly tonnage. These operational conditions challenge the usefulness of existing deterministic deterioration models for railway infrastructure that are validated in other contexts. However, more frequent and higher precision of condition measurements, combined with statistically based prediction methods, may offer a viable solution. Here, we study remaining useful life predictions of railway track geometry properties based on recursively updated time series. We discuss how data-driven models are affected by measurement errors of track properties, such models’ ability to detect seasonal effects, and how they are affected by irregular sampling. The prediction abilities and uncertainty measures for different modelling approaches are also compared.
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| 31. |
- Bergquist, Bjarne, et al.
(författare)
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Predictive Modelling for Estimation of Railway Track Degradation
- 2016
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Ingår i: Current Trends in Reliability, Availability, Maintainability and Safety. - Cham : Encyclopedia of Global Archaeology/Springer Verlag. - 9783319235967 - 9783319235974 ; , s. 331-347
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Konferensbidrag (refereegranskat)abstract
- 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
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| 32. |
- Bergquist, Bjarne
(författare)
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Project: DISIRE
- 2015
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Annan publikation (populärvet., debatt m.m.)
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| 33. |
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| 34. |
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| 35. |
- Bergquist, Bjarne
(författare)
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Property variation in sintered steel : design of experiments
- 1997
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Ingår i: International journal of powder metallurgy (1986). - 0888-7462. ; 33:2, s. 30-40
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Tidskriftsartikel (refereegranskat)abstract
- To reduce dimensional and mechanical property variations in a component manufactured from a phosphorus alloyed P/M steel, a design of experiments approach was used to identify the most important green compact variations. Responses evaluated were unnotched Charpy impact energy total dimensional change, and sintered density. The experimental array was defined using a fractional factorial design, and the variables investigated were: phosphorus content; median particle size of Fe[3]P-powder; iron powder fines content; added graphite content; green density; and sintering temperature. The design of experiments proved powerful in detecting the most important variables; it pinpointed graphite and phosphorus content, and green density variations as being detrimental.
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| 36. |
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| 37. |
- Bergquist, Bjarne, et al.
(författare)
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Quality management for tomorrow
- 2007
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Ingår i: Quality management and organizational excellence. - Sydney : SAI Global. - 1921093307 ; , s. 253-286
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Konferensbidrag (refereegranskat)
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| 38. |
- Bergquist, Bjarne, et al.
(författare)
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Reframing quality management
- 2008
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Ingår i: The Theories and Practices of Organization Excellence. - Sydney : SAI Global. - 192109351X ; , s. 501-538
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 39. |
- Bergquist, Bjarne, et al.
(författare)
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Robust sinter steel by robust design experimentation
- 1996
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Ingår i: Advances in Powder Metallurgy and Particulate Materials. - Princeton, NJ : Metal powder industries federation. - 1878954598 ; , s. 317-328
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Konferensbidrag (refereegranskat)
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| 40. |
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| 41. |
- Bergquist, Bjarne, et al.
(författare)
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Robustness simulation of water atomisation
- 2000
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Ingår i: Powder Metallurgy. - : Informa UK Limited. - 0032-5899 .- 1743-2901. ; 43:1, s. 37-42
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 42. |
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| 43. |
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| 44. |
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| 45. |
- Bergquist, Bjarne
(författare)
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Some ideas why factorial designs are not used in full-scale experiments in continuous processes
- 2015
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Ingår i: Total Quality Management and Business Excellence. - : Informa UK Limited. - 1478-3363 .- 1478-3371. ; 26:11-12, s. 1242-1254
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 46. |
- Bergquist, Bjarne
(författare)
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Statistical approaches to PM steel process improvements
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Increased performance:cost ratios for PM steel components is vital if current growth rate of market shares of such components versus competing technology is to be sustained. Both performance and cost of components are affected by variation of component properties. This work focuses on variation; where major variation sources lie and measures to circumvent problems that could be taken.A design-of-experiments approach was used to identify the most important green compact variations and interactions of a Fe-P alloy. The results show that the highest impact energies are obtained for high green densities, and without graphite addition. It is concluded that sintered density is the reason for the observed impact energies. Variation sources controlling phosphorus content and added graphite content are of concern since they affect the dimensional stability. Prospects for a robust sintering operation of same alloy is investigated. The objective is to find a setting of the variables investigated to maintain high tensile strength and proof stress without loss of dimensional stability, tensile elongation or impact energy. In the study, an endothermic sintering atmosphere was better for the robustness of the tested properties. A mechanism for the occasionally brittle behavior of the system is concluded to be loss of grain boundary cohesion due to decarburization.Possibilities for improved particle size distribution of water atomized powder are studied experimentally and by simulations. The most important variable for all studied responses is water pressure. Higher melt temperatures reduce particle size due to decreased viscosity. Large sulfur additions reduce particle size and this is an effect of reduced surface tension. Narrower size distributions were obtained for powder atomized with aluminum additions and for increased melt temperatures. A model for particle size for water atomization is presented and used in simulations.
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| 47. |
- Bergquist, Bjarne, et al.
(författare)
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Statistical methods - does anyone really use them?
- 2006
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Ingår i: Total Quality Management and Business Excellence. - : Informa UK Limited. - 1478-3363 .- 1478-3371. ; 17:8, s. 961-972
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 48. |
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| 49. |
- Bergquist, Bjarne, et al.
(författare)
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Testing for motivation to engage in improvements : a conceptual framework and an initial empirical test
- 2014
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Ingår i: Total Quality Management and Business Excellence. - : Informa UK Limited. - 1478-3363 .- 1478-3371. ; 25:11-12, s. 1224-1235
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Tidskriftsartikel (refereegranskat)abstract
- This paper aims to develop a conceptual framework for testing the motivation to engage in improvement work. The framework is based on Ajzen's theory of planned behavior (TPB), that we suggest can be used to facilitate the implementation of improvement programmes. By using the model and probing intentions, attitudes, norms and perceived ability related to improvement work, we believe hindrances for implementation of improvement programmes will be exposed. When operationalising the framework we developed a survey instrument based on TPB and then made an initial empirical test by distributing it to 124 employees (response rate 67%) of three manufacturing small- and medium-sized enterprises. Factor analysis and regression were used to analyse the survey and follow-up interviews with employees and managers were used to validate the results. This initial test of the instrument showed that it has sound measurement properties, indicated by clear factor structure and good internal consistency. Interview data also validated that the instrument was able to capture important aspects related to implementation of improvement work. Based on the result, we conclude that TPB may be useful for guiding management actions. However, since our study only draws on a limited empirical sample, future research is needed to test the contextual validity.
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