| 1. |
- Barkefors, Annea, et al.
(författare)
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Design and Analysis of Linear Quadratic Gaussian Feedforward Controllers for Active Noise Control
- 2014
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Ingår i: IEEE Transactions on Audio, Speech, and Language Processing. - 1558-7916 .- 1558-7924. ; 22:12, s. 1777-1791
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Tidskriftsartikel (refereegranskat)abstract
- A method for sound field control applied to active noise control is presented and evaluated. The method uses Linear Quadratic Gaussian (LQG) feedforward control to find a Minimal Mean Square Error (MMSE)-optimal linear sound field controller under a causality constraint. It is obtained by solving a polynomial matrix spectral factorization and a linear (Diophantine) polynomial matrix equation. An important component in the design is the control signal penalty term of the criterion. Its use and influence is here discussed and evaluated using measured room impulse responses. The results indicate that the use of a relatively simple, frequency-weighted penalty on individual control signals provides most of the benefits obtainable by the considered more advanced alternative. We also introduce and illustrate several tools for performance analysis. An analytical expression for the attainable performance clearly reveals the performance loss generated by having to use a causal controller instead of the ideal noncausal controller. This loss is largest at low frequencies. Furthermore, we introduce a measure of the reproducibility of the target noise sound field with given control loudspeaker setups and room transfer functions. It describes how well a controller that uses an input subspace of dimension equal to the effective rank of the system is able to reproduce a target sound field. This performance measure can e.g. be used to support the selection of good combinations of placements of control loudspeakers.
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| 2. |
- Barkefors, Annea
(författare)
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Linear Quadratic Gaussian Controllers for Feedforward Active Noise Control : Pushing Performance and Moving Towards Adaptive Control
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Active noise control is a research area focused on using destructive interference of sound fields to attenuate undesired noise. Methods for active noise control are best suited for low frequency noise, as the complexity of the problem grows rapidly with frequency. Coincidentally, passive means of damping have the opposite quality in that they work better for higher frequencies and become bulky and impractical for low frequencies. Applications for active noise control range from fan noise in ducts, noise-cancelling headphones and noise in cars to propeller induced aircraft cabin noise. In this comprehensive summary, the underlying principles of active noise control are presented and the control problem is discussed. Several aspects of the control system are introduced to give an introduction to the research papers that are the basis of this licentiate thesis. The work behind the thesis is focused on a Multiple-Input Multiple-Output (MIMO) Minimal Mean Square Error (MMSE) Linear Quadratic Gaussian (LQG) feedforward controller. This controller is shown to achieve uniform damping in an extended region in space and push the upper frequency that can be controlled. The influence of different design variables has been investigated, and the properties of the control path analyzed with consideration of its ability to suppress noise of prescribed spectral properties over an extended region. In this context, it has been shown how to use the reproducibility of the primary noise path by the control path as an indication of achievable performance for a given control system. Finally, the controller has been adapted to follow changes in the primary noise statistics, an approach that seems promising to considerably raise the performance of the controller.
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| 3. |
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| 4. |
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| 5. |
- Brännmark, Lars-Johan, 1974-
(författare)
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Robust Sound Field Control for Audio Reproduction : A Polynomial Approach to Discrete-Time Acoustic Modeling and Filter Design
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is concerned with the design and analysis of robust discrete-time filters for audio equalization and sound field control in real reverberant environments. Inspired by methods in polynomial control theory, a unified framework for acoustic modeling and filter design is developed. The work on modeling is centered around three main themes: First, the acoustic channel between a loudspeaker and a point in space is studied in time, frequency and space, and a polynomial matrix fraction description with diagonal denominator is selected as a physically motivated channel model. As a means for representing channel uncertainties, a probabilistic design model is proposed. Second, the concept of sound field dimensionality, based on the Karhunen-Loève expansion of the sound field, is explored and integrated into the polynomial systems context. Third, a method for spatial interpolation of acoustic transfer functions is proposed and evaluated. Interpolation errors are accounted for by applying the probabilistic uncertainty model to the interpolated data. The work on filter design can be categorized into single- and multichannel methods. The single-channel problem concerns the improvement of the impulse and frequency responses of a single loudspeaker over a region in space, by means of a scalar prefilter. This problem is posed in a SIMO (single-input multiple-output) feedforward control setting, and is solved using polynomial methods. The solution offers several useful insights and results. In particular, new results are derived regarding the adverse pre-ringing problem associated with mixed phase filters. Based on the new results, a refined mixed phase method is proposed that is practically free from pre-ringing artifacts. In the multichannel problem, a desired spatio-temporal sound field is approximated by the joint use of several loudspeakers. This problem is initially formulated and solved by feedforward control over a continuous spatial domain, assuming full knowledge of the spatial field. To obtain a practically feasible design, the control criterion is then spatially discretized, resulting in a standard MIMO(multiple-input multiple-output) linear quadratic feedforward control problem. Since information is generally lost in the discretization process, a robust design based on spatial interpolation and probabilistic error modeling is proposed. The multichannel designs are assessed in an automotive setting, using practical measurements of a nine-channel sound system in a car.
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| 6. |
- Brännmark, Mikael, et al.
(författare)
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A Proposed Model for Evaluating the Sustainability of Continuous Change Programmes
- 2012
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Ingår i: Journal of Change Management. - : Informa UK Limited. - 1469-7017 .- 1479-1811. ; 12:2, s. 231-245
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Tidskriftsartikel (refereegranskat)abstract
- Many studies report that it is difficult to sustain change. This article focuses on how an organization can initiate and sustain a continuous change process. A theoretical model is proposed as a fusion of two previous models for evaluating the sustainability of a change programme; the first is based on analysing stakeholder interest balance as a prerequisite for organizational sustainability, the second on analysing the design of the implementation, indicating whether long-term effects will be achieved. It is argued that the combination of these factors provides a more comprehensive perspective, since it allows us to evaluate both the ‘form’ and the ‘direction’ of the programme. To assess stakeholder interest balance, the goal for the change programme is analysed, utilizing the broad stakeholder interest balance perspective. To assess the design of the implementation, four preconditions for long-term effects should be analysed: management's ownership of the change initiative, professional steering, competent leadership and participation. Reference is given to the management concept Lean Production, which is claimed to engage the organization in continuous change. Application of the model highlights the mismatch between narrowly focused change programmes such as Lean Production and sustainable change.
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| 7. |
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| 8. |
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| 9. |
- Brännmark, Mikael
(författare)
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Implementering av Lean i medelstora företag : En lärande utvärdering om hållbarutveckling
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Denna rapport är ett av delresultaten från det interaktiva forskningsprojektet Produktionslyftet, inom HELIX VINN Excellence Centre. Projektet genomförs i samarbete med Produktionslyftet, ett nationellt program för spridande av managementkonceptet Lean produktion. Syftet med forskningsprojektet är att öka kunskapen om hur hållbart utvecklingsarbete kan bedrivas, både utifrån ett program- och företagsperspektiv. Rapporten beskriver två delstudier, en kvalitativ och en kvantitativ, som genomförts i samarbete med elva av företagen i Produktionslyftet, tio av dem pilotföretag för programmet. Den första delstudien genomfördes under sommaren 2008, genom en intervjustudie med programmets pilotföretag, medan den andra genomfördes under våren 2009, i formen av en enkätstudie med sju av företagen i programmet. Då en interaktiv forskningsansats har använts, så har i båda fallen den insamlade empirin från de båda delstudierna återkopplats till representanter från Produktionslyftet, samt programmets finansiärer, och en gemensam tolkning och analys av empirin har gjorts. Denna gemensamma tolkning har sedan analyserats utifrån modeller kring hållbart utvecklingsarbete och resultatet från detta arbete har sedan sammanfattats i två arbetsrapporter, som har återkopplats till programmet och dess finansiärer. Resultaten i delstudierna, samt den gemensamma tolkningen och analysen av empirin, fokuserar Produktionslyftets coacher, samt deras arbete med företagen. Dels spelar coacherna uppenbarligen en central roll i programmets arbete med företagen, och dels är coacherna mycket uppskattade av företagen. Coachernas arbetssätt, samt hur deras arbete påverkar möjligheten för företagen att skapa en hållbar utveckling, upptar också en central del i rapporten. Detta kan sammanfattas, som att om coacherna driver på arbetet för hårt, få finns det risk att det uppstår problem för företagen, men om coacherna inte är pådrivande så finns risken att åtminstone vissa av företagen inte tar sitt ansvar för Lean-arbetet. Med andra ord, coachernas arbete med företagen utgör en svår balansgång mellan att uppfylla företagens målsättningar med Lean-arbetet, i vägning mot Produktionslyftets mål och syfte. Men resultaten pekar också på vikten av att företagen har ett tydligt ägarskap och driv i utvecklingsarbetet. Slutsatsen i denna rapport blir därför att om programmets utvecklingsarbete skall bli hållbart, så hänger det troligen på dels att man har duktiga och kompetenta coacher, men också att man har en väl fungerande företagsrekryteringsprocess, där företag med ett internt driv för Lean-arbetet väljs till programmet.
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| 10. |
- Brännmark, Mikael, et al.
(författare)
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Implementing Lean in Swedish Municipalities and Hospitals : Initial effects on the work system
- 2011
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Ingår i: FALF2011:Det nya arbetslivet. - Luleå : FALF.
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Konferensbidrag (refereegranskat)abstract
- This paper is the first preliminary product of a three year interactive research project, studying the effects of Lean when introduced in Swedish municipalities and hospitals. Focus of the paper is the implementation process (more specifically, employee participationand facilitated learning) and changes in the work system (focusing on work content, organization and work environment). The empirical data has been collected through interviews and group interviews in three municipalities and one hospital. These results, together with the discussion and analysis, shows firstly that the implementation processes of the studied units are characterized by a medium or high level of opportunities for employee participation and learning, although this is produced in different ways. Second, the changes in the work systems mostly affect the organization of the work, through reorganization and redistribution of the work tasks, rather than changes in how the work tasks are performed.This has lead to more orderly and structured work processes. Lastly, the employees’ reactions to these changes have been mostly positive, although not exclusively so. However, it is important to stress that the employee reactions are most likely as much a result of the implementation process, as of the changes in the work systems. Longitudinal studies are therefore needed to study the long term changes in the work system and the effects on employee health, which will be the next step of this research project.
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| 11. |
- Brännmark, Mikael
(författare)
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Interaktiv forskning : Gemensamt kunskapande för allas nytta
- 2010
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Ingår i: FALF2010. - Malmö : FALF.
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Konferensbidrag (refereegranskat)abstract
- Utvärdering är ett mycket vanligt redskap för kontroll och uppföljning inom olika verksamheter, exempelvis projekt och program. Den traditionella ”summativa” utvärderingen har dock ett flertal brister, som gjort att intresset för formativa utvärderingar ökat. Ett exempel på dessa är de s.k. lärande utvärderingarna, men också forskning i olika former kan användas för att utvärdera projekt och program. I det offentliga programmet Produktionslyftet har det förekommit ett flertal utvärderingsformer, bl.a. två summativa måluppföljelseutvärderingar och ett interaktivt forskningsprojekt. I detta paper presenteras en fallstudie kring dessa utvärderingsformer, samt vilka interna respektive externa spridningseffekter (av programmets erfarenheter), samt också vilken form av utvecklingsstöd, som dessa har möjliggjort för Produktionslyftet. Resultaten pekar på att ett summativa utvärderingsprojekt kan användas för både intern spridning av erfarenheter och för att skapa utvecklingsstöd, förutsatt att halvtidsutvärderingar används. Detta kan också ett interaktivt forskningsprojekt bidra med, samt en lärande utvärdering, men det interaktiva forskningsprojektet tycks vara överlägset när det gäller extern spridning av resultaten från programmet – även om det också är den mest resurskrävande formen av utvärdering. Uttryckt på ett annat sätt, så skapar det interaktiva forskningsprojektet underlag för gemensam diskussion, reflektion och analys för programmet, samt gör också programmet/projektet mer transparent, genom extern spridning av gjorda erfarenheter.
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| 12. |
- Brännmark, Mikael
(författare)
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Is Lean No Longer Mean? : A Study of the Consequences for Working Conditions in Companies Implementing Lean
- 2010
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Ingår i: FALF2010. - Malmö : FALF.
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Konferensbidrag (refereegranskat)abstract
- Lean is today becoming increasingly popular in Swedish manufacturing industry, and the concept has also started to spread to other sectors, such as administration, healthcare and the municipal sector. However, previous studies have suggested that Lean can become “mean”, creating working conditions that are bad for the employees. Conversely, other studies instead suggest that this has less to do with Lean, than with the implementation of Lean. Thus, this paper aims at studying the implementation of Lean in eight medium sized companies over a two year period, using qualitative and quantitative data. First, the results from the qualitative data suggest that these companies implementation of Lean is characterized by Lean coordinators, pilot projects and improvements groups, while the Lean tools mostly used are 5S, SMED, standardization and means to improve the production flow. Second, the perceived effects on working conditions, based on the quantitative data, suggest an improvement in the working environment, an increase in the work with safety and some degree of increase in stress for the workers. Consequently, the implementation structure of these companies does not indicate a “mean” production system, although the long term effects on working conditions cannot be determined, based on these data.
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| 13. |
- Brännmark, Mikael
(författare)
-
Lean administration : En litteraturgenomgång av lean när konceptet implementeras i kommuner
- 2011
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Ingår i: FALF2011: Det nya arbetslivet. - Luleå : FALF.
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Konferensbidrag (refereegranskat)abstract
- Lean blir allt vanligare i svensk offentlig förvaltning. Litteraturstudier har tidigare genomförts inom sjukvård och service. Denna litteraturgenomgång fokuserar istället på kommuner. Fokus ligger på vilka former som lean-konceptet tar, hur det implementeras, vilka effekter som uppnås, samt vilka svårigheter som man stött på. Sökningar gjordes i två omgångar i fyra olika databaser under i maj 2010. Endast empiriska artiklar i peer-reviewadetidsskrifter inkluderades; studier som inom vård- eller industriliknande kontexterexkluderades. Totalt resulterade sökningen och urvalsprocessen i fem publikationer, som beskriver lean i elva verksamheter. Slutsatserna från genomgången av dessa är de studerade lean-implementeringar i hög grad utgår från en ansats som påminner om värdeflödeskartläggningar. Fokus för lean-arbetet ligger på verktyg och system för förbättringsarbete. De upplevda problemen i lean-arbetet är framför allt associerade med implementeringsansatsen, snarare än konceptet eller kontexten. Verksamheternas arbete med lean har gett mestadels positiva verksamhetseffekter, framför allt rörande effektivitet och produktivitet. Hur kunderna, och framför allt personalen, påverkats är dock osäkrare.
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| 14. |
- Brännmark, Mikael
(författare)
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Lean i kommuner och myndigheter : En översikt över existerande empirisk forskningslitteratur
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Denna litteraturgenomgång avser att studera det empiriska underlaget om lean i kommuner och myndigheter (exklusive sjukvård) utifrån den forskningslitteratur som finns. Sökningar har gjorts i sex forskningsdatabaser under oktober 2011. Relevanta frågor för studien är hur lean används i kommuner och myndigheter, varför organisationerna väljer att arbeta med lean och vilka resultat man har uppnått.Totalt hittades 48 publikationer, men efter sortering återstod endast 17 empiriska artiklar av relevans för den här rapporten. De studier som valdes bort var antingen för diskuterande eller redogjorde inte tydligt för hur man har samlat in sin empiri. De 17 studierna som används är av skiftande kvalitet och utformning och det empiriska underlaget är varierat. En majoritet av de inkluderade publikationerna är publicerade efter 2005. Tio av de 17 publikationerna innehåller totalt 18 fallstudier. Utifrån detta, är det rimligt att hävda att den empiriska forskningen om lean i kommuner och myndigheter är ett relativt nytt fenomen. Fallstudierna föranleder flera slutsatser, även om det bör betonas att det empiriska underlaget är tunt och studierna är av starkt varierande kvalitet och utformning. Därför bör slutsatserna endast ses som tentativa, men det innebär samtidigt att det finns flera frågor som kan vara av stort intresse för fortsatt forskning.För det första, när det gäller vilka former lean-arbetet tar, så tycks värdeflödeskartläggning och slöserireducering utgöra centrala inslag i kommuner och myndigheters arbete med lean. Ofta verkar det handla om punktinsatser. Lean-program som omfattar hela organisationen är relativt ovanliga. Andra lean-verktyg förekommer också, men det är mindre vanligt. För det andra, när det gäller målen med lean-arbetet, verkar det i hög grad initieras med syfte att öka produktiviteten, även om andra skäl också förekommer, som exempelvis behov av kostnadssänkningar. För det tredje, när det gäller resultat av lean-arbetet, framför allt då värdeflödeskartläggningarna, verkar ökad produktivitet vara det vanligaste resultatet. Samtidigt leder arbetet också ofta till minskade problem och störningar för de anställda, vilket ofta uppskattas. Däremot tycks effekterna för personalen vara mer varierade än verksamhetseffekterna. De lean-verktyg som emellanåt verkar ge negativa konsekvenser är bland annat standardisering, visualisering och kundkontakt. Kundeffekterna är dock svårare att uttala sig om eftersom det ofta saknas empiri om detta i studierna.Slutligen bör det betonas att utifrån de inkluderade studiernas utformning och metodik är det mycket svårt att uttala sig om de långsiktiga effekterna av arbetet med lean, eftersom det finns empiri i publikationerna som väcker frågetecken om hur hållbart lean-arbetet är, till exempel deltagarnas känsla av att arbetet är avklarat efter genomförda förbättringsworkshops.
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| 15. |
- Brännmark, Mikael, et al.
(författare)
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Lean production and work-related musculoskeletal disorders: overviews of international and Swedish studies
- 2012
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Ingår i: Work. - : IOS Press. - 1051-9815 .- 1875-9270. ; 41, s. 2321-2328
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Tidskriftsartikel (refereegranskat)abstract
- This paper aimed at summarizing the knowledge of the relationship between Lean and work related musculoskeletal disorders (WMSD), and WMSD risk factors, in manufacturing companies. Literature search processes identified 23 publications studying this, in scientific journals. Eight included measurements of WMSD; three were mostly negative, two showed mixed results, one showed no results and two were mostly positive. Eighteen publications included measurements of WMSD risk factors; seven showed mostly negative results, eight snowed mixed results, two showed mostly positive results and one was inconclusive. Three literature reviews were identified, which studied this question; two were mostly negative, while the third was inconclusive. Also, 12 publications of grey literature studying Lean and WMSD risk factors in Swedish organizations were identified; nine showed mixed results, two showed mostly positive results and one showed mostly negative results. Due to the varying quality and study design of the publications, together with the few identified studies, it is difficult to compare them. The context and the implementation also likely affect the results. The general conclusion was that a Lean implementation may increase the risk of WMSD and risk factors for WMSD, if it is not accompanied with an ergonomic intervention.
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| 16. |
- Brännmark, Mikael
(författare)
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Lean Working Environments : An Empirical Study of 24 CompaniesImplementing Lean
- 2010
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Ingår i: NES2010: Proactive Ergonomics. - Stavanger.
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Konferensbidrag (refereegranskat)abstract
- This paper studies the perceived effects on the working conditions in 24 medium sized manufacturing companies, approximately 1.5 year into their implementation of Lean. This is studied quantitatively based on four stakeholders’ perceptions (the workers, the managers, the production supervisors and the white-collar workers), based on three factors; changes in the working environment, work with safety for the personnel and level of stress. The results indicate that the physical work environments have improved and the workers and production supervisors report a slight increase in stress. Lastly, all groups report an increase in the work with safety for the personnel.
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| 17. |
- Brännmark, Mikael, et al.
(författare)
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Leaninspirerade förändringar och personalens upplevelser
- 2013. - 1
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Ingår i: Lean i arbetslivet. - Stockholm : Liber. - 9789147105601 ; , s. 103-121
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- De anställdas upplevelser av hur de kommer att påverkas av ett förändringskoncept är en avgörande faktor för om konceptet kommer att få reellt genomslag eller inte. Det här kapitlet behandlar denna centrala aspekt av leankonceptet – hur personalen upplever leaninspirerade förändringar. Just denna fråga finns det mycket lite empirisk forskning kring, så väl internationellt som i Sverige.I kapitlet redovisas en studie av personalens erfarenheter från leanarbetet i medelstora svenska tillverkningsföretag som ingått i det nationella programmet Produktionslyftet. Programmet kan ses som ett exempel på en ”svensk tolkning” av lean. Produktionslyftet har fått stort genomslag i den svenska diskussionen om lean, men samtidigt har konsekvenserna av lean ur ett arbetsmiljöperspektiv inte utvärderats på ett genomgripande sätt.
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| 18. |
- Brännmark, Mikael, et al.
(författare)
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Packages of participation : Swedish employees´experience of Lean depends on how they are involved
- 2013
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Ingår i: IIE Transactions on Occupational Ergonomics and Human Factors. - : Informa UK Limited. - 2157-7323 .- 2157-7331. ; 1:2, s. 93-108
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Tidskriftsartikel (refereegranskat)abstract
- Background: Lean production is a dominant approach in Swedish and global manufacturing and service industries. Studies of Lean’s employee effects are few and contradictory. Purpose: Employee effects from Lean are likely not uniform. This article investigates the effect of employees’ participation on their experiences of Lean. Method: This study investigated how different packages of employee participation in Lean affected manufacturing workers’ experiences of Lean. During 2008–2011, qualitative and quantitative data were collected from Swedish manufacturing companies participating in the national Swedish Lean production program Produktionslyftet. Data from 129 surveys (28 companies), 39 semi-structured interviews, and 30 reports were analyzed. In the main analysis, comparisons were made of the survey-reported Lean experiences of employees in three groups: temporary group employees (N = 36), who participated in Lean mostly through intermittent projects; continuous group employees (N = 69), who participated through standing improvement groups; and combined group employees (N = 24), who participated in both ways. Results: Continuous group employees had the most positive experience of Lean, followed by the combined group. Temporary group employees had the least positive experiences, being less likely than their counterparts to report that Lean improved teamwork; occupational safety; and change-related learning, decision making, and authority. Conclusions: These findings support the importance of continuous, structured opportunities for participation but raise the possibility that more participation may result in greater workload and role overload, mitigating some benefits of employee involvement. Consequently, companies should consider involving employees in change efforts but should attend to the specific design of participation activities.
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| 19. |
- Brännmark, Mikael, et al.
(författare)
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Patient Quality Effects from Lean Healthcare : An Empirical Investigation
- 2012
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Ingår i: NES2012 Proceedings.. - Stockholm : KTH Royal Institute of Technology. - 9789163711503
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Konferensbidrag (refereegranskat)abstract
- The use of Lean in healthcare settings has become common in Swedish hospitals. However, the effects from Lean on patients have not been studied extensively. This paper contributes to our understanding of this question, based on 24 semi-structured interviews in three municipal care units and three units in hospitals. The results indicate that there may be a positive link between Lean activities and quality of care. However, it is plausibly a weak link, heavily modulated by non-Lean factors. Thus, we need more empirical research to understand the causal link between patient safety and quality of care from Lean Healthcare.
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| 20. |
- Brännmark, Mikael, et al.
(författare)
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Researching Lean: Methodological Implications of Loose Definitions
- 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. 35-48
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Tidskriftsartikel (refereegranskat)abstract
- Recently, Lean Production (Lean) has become a prevailing management concept in Sweden. However, previous research seems to show that the Lean concept and the impact of Lean vary considerably between organizations. This paper illustrates some key methodological issues that need to be considered when researching loosely defined management concepts such as Lean. The paper is based on a review of the literature and five comparative Swedish cases studies. Our study indicates that Lean has changed over time and that operationalization and interpretations of the concept vary considerably. This study concludes that future Lean studies should include a thorough assessment of the Lean interventions, study settings, and in particular non-Lean factors mediating the outcomes of Lean-inspired change programs.
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| 21. |
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| 22. |
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| 23. |
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| 24. |
- Gunnarsson, Viktor
(författare)
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Binaural Modeling for High-Fidelity Spatial Audio
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The enjoyment of reproduced sound and music is a prime pleasure for many, and the high-fidelity reproduction of binaural audio is integral to many applications in augmented and virtual reality. This thesis introduces a framework for binaural headphone auralization of sound systems, together with an in-depth analysis and proposed solutions to address sources of coloration within the signal chain.The framework includes a novel method for binaural auralization of microphone array impulse responses. Employing a hybrid parametric approach, it utilizes causal multichannel Wiener filtering to synthesize the directional response of the ear, as described by head-related transfer functions (HRTFs), using the microphone array and a model of its acoustic properties. A time-domain polynomial matrix framework is employed for filter computations and direct and reflected sound is treated separately. Results demonstrate a small perceptual difference to reference measured binaural room impulse responses. Additionally, the thesis addresses the impact of binaural measurement uncertainty and proposes a new measurement technique for HRTFs and headphone transfer functions (HpTFs). The method is based on a cardioid microphone array for open ear canal measurements. Results indicate that the method significantly reduces measurement uncertainty compared to omnidirectional measurements in the ear canal. Moreover, a phase pre-processing method for HRTFs is introduced that reduces spatial phase variability of the HRTF set at high frequencies while retaining correct interaural coherence for diffuse sound. It is demonstrated that the HRTF phase pre-processing greatly reduces spectral coloration in headphone simulation of amplitude panning on virtual speakers. The method also improves performance in binaural rendering of microphone array recordings. Finally, the thesis presents a comprehensive model for addressing coloration at the ear-signal level inherent in amplitude panning on speaker arrays. The analysis focuses on pairwise panning on symmetrical speaker setups and monaural correction filters are proposed that are robust to head movements around the sweet spot. The proposed filters are found to mitigate the phantom source elevation effect in stereophonic panning and enhance the perceived spectral similarity between discrete and panned sound sources, with effectiveness contingent on the speaker setup geometry.
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| 25. |
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| 26. |
- Johansson, Mathias, et al.
(författare)
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Sound field control using a limited number of loudspeakers
- 2009
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Ingår i: 36th Audio Engineering Society International Conference 2009: Automotive Audio - Sound in Motion, Dearborn, Michigan. - Red Hook, NY : Audio-Engineering Society. - 9781615673377
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Konferensbidrag (refereegranskat)
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| 27. |
- Lindskog, Pernilla, et al.
(författare)
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Managerial Challenges in Creating Sustainable Development Work (Lean) : An interactive case study from socio-technical perspectives
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Purpose - At present, healthcare organizations are facing both quality and financial challenges. Consequently, organizations in this sector have started to introduce Lean inspired production concepts in order to become more efficient and effective. The implementation of Lean in healthcare is not unproblematic, especially not within psychiatry, the context of which differs greatly from other sectors where it is more usual to see Lean implemented. The aim of this article is to identify managerial preconditions for the implementation of a sustainable Lean organization at a psychiatry division in a Swedish university hospital.Design/methodology/approach – An interactive case study approach was chosen with the purpose of gaining deeper knowledge and understanding of the first-line managers’ role during implementation of Lean. Focus group interviews together with 24 first-line managers were conducted. In the analysis, a socio-technical perspective was used due to the characteristics of the psychiatry healthcare context but also from a sustainability perspective. The empirical data from the focus group interviews were also complemented with a semi-structured interview with a key actor.Findings – Development work is context dependent and so is the implementation of Lean. This particular case study points out that clarity of the organizational structures within the Lean work, i.e. objectives and roles, affects the level of participation and consequently the sustainability of the Lean implementation. The empirical findings also show that a managerial lack of power and authority make it difficult for first-line managers (the majority being nurses) to prioritize engagement and time spent in Lean work.Originality/value – At present there are few studies on the implementation of Lean within the psychiatry healthcare sector and in a socio-technical context. In this article a model is presented, visualizing managerial preconditions for sustainable Lean in the context presented.
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| 28. |
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| 29. |
- Vänje, Annika, Docent, 1963-, et al.
(författare)
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Walking around the pyramids : Managers’ shop-floor activities in Lean-inspired organizations
- 2017
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Ingår i: Economic and Industrial Democracy. - : Sage Publications. - 0143-831X .- 1461-7099. ; 38:3, s. 495-512
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Tidskriftsartikel (refereegranskat)abstract
- The approach in this article is to study leadership activities from the shop-floor workers’ perspectives during the implementation of a Lean-inspired production concept – an angle of approach that corresponds to a need for a deeper knowledge of the interactions between organizational structures and the physical work environment. The empirical findings are from a national R&D program called the Production Leap and collected through different methods: semi-structured interviews carried out at eight manufacturing companies, the open-ended part of a longitudinal survey, and participative observations. Lean leadership practices at these companies do not enable the possibilities of developing the technical systems or work relationships between the managers and the shop-floor workers. Instead, they provide the means and activities to circumvent coordination problems and create a feeling of participation. The results here indicate that leadership activities and coordination of work do not, as it is sometimes argued by the proponents of Lean, ‘turn the pyramid’ of power upside down. One reason for this is the lack of social structures in the organization.
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| 30. |
- Widmark, Simon, 1984-
(författare)
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Causal MMSE Filters for Personal Audio : A Polynomial Matrix Approach
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is devoted to the study of synthesis of causal filters for generating personal sound zones. Personal sound zones, personal audio or personal sound is the theory and practice of steering sound in such a way that it is amplified in one region and suppressed in another. In lower frequencies, this is accomplished by designing filters that control the complex pattern of constructive and destructive interference that a set of sound sources gives rise to. There are many ways of designing such filters and the field of personal audio has been rather active in the last few decades. As the algorithms approach actual production line implementation, the aspects of realisability gain in importance. It has been noted in the literature that filters that are causal by design solve many of the problems associated with implementability and may increase the subjective sound quality in the bright zone. However, the problem of synthesis of causal filters for personal audio has received less attention than that of non-causal filters. In this thesis, synthesis of causal filters for personal audio with emphasis on implementability is explored. Several different approaches, with varying formulations of the personal audio problem, are investigated and discussed. The majority of these designs are also implemented and tested in real systems.Practical designs that are studied include a weighted sound field synthesis design, drawing from the previous sound field synthesis literature, and a design with a constraint on the acoustic power transmitted into the quiet region. A design with constrained power difference between the quiet and the non-quiet (bright) region is also proposed and investigated. As an auxiliary result, a method for incorporating quadratic power constraints in the rational matrix filter approach to synthesis of Infinite Impulse Response Wiener filters is proposed. An expansion to include robustness to uncertainties in the systems under investigation is also investigated. General guidelines for the use of the different proposed methods are sought, but the problems are very complex. Over all, a user-centric approach is developed, where emphasis is placed on practical design and analysis of the optimization problems at hand.
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