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  • 1.
    Aalipour, Mojgan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Human Factors Approach for Maintenance Improvement2015Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The purpose of this research work is to explore and describe human factors affectingmaintenance execution. To achieve the purpose of this study, the influencing factors have been identified using a literature survey. They have been categorized into four main groups namely organizational, workplace, job and individual factors. The Analytical Hierarchy Process (AHP) method is employed on data questionnaires to rank the priority of the factors. The interrelationships between these factors have been recognized by theInterpretive Structural Modelling (ISM) model. In the present case studies, MICMAC1analysis technique is also implemented for identifying the driving, dependent, linkage and autonomous factors. The data was collected through a questionnaire survey involving the participation of 16 and 25 maintenance staff and 10 mining experts in Swedish and Iranian mines, respectively. Within the study, it has been identified that the temperature, work layout, tools design and tools availability are the most important factors in both mines related to these categories. However, the significant factors in the organizational and individual categories are different in the selected mines. The effect of workplace factors on the maintainability of mining equipment is discussed and thereafter a methodology for maintainability management in the design and operation phases is developed. In the thirdcase study HEART2 is applied to estimate the probability of human error occurring duringmaintenance execution in an Iranian cable company. This research supports maintenance management to gain knowledge of human factors that affect maintenance execution. Further, this understanding could be useful in the development of strategies to improve the execution of maintenance.Keywords: Human Factors, Maintenance Management, Human Reliability, HumanPerformance, AHP, ISM, MICMAC, HEART

  • 2.
    Aalipour, Mojgan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Ayele, Yonas Zewdu
    Department of Engineering and Safety, UiT The Arctic University of Norway, Tromsø.
    Barabadi, Abbas
    Tromsø University, Department of Engineering and Safety, UiT The Arctic University of Norway, Tromsø.
    Human reliability assessment (HRA) in maintenance of production process: a case study2016Inngår i: International Journal of Systems Assurance Engineering and Management, ISSN 0975-6809, E-ISSN 0976-4348, Vol. 7, nr 2, 229-238 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Human reliability makes a considerable contribution to the maintenance performance, safety, and cost-efficiency of any production process. To improve human reliability, the causes of human errors should be identified and the probability of human errors should be quantified. Analysis of human error is very case-specific; the context of the field should be taken into account. The aim of this study is to identify the causes of human errors and improve human reliability in maintenance activities in the cable manufacturing industry. The central thrust of this paper is to employ the three most common HRA techniques—human error assessment and reduction technique, standardized plant analysis risk-human reliability, and Bayesian network—for estimating human error probabilities and then to check the consistency of the results obtained. The case study results demonstrated that the main causes of human error during maintenance activities are time pressure, lack of experience, and poor procedure. Moreover, the probabilities of human error, obtained by employing the three techniques, are similar and consistent

  • 3.
    Aalipour, Mojgan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Barabadi, Abbas
    Tromsø University, University of Tromsø - The Arctic University of Norway.
    Maintainability management of production facilities in complex and challenging operating conditions2015Inngår i: 2015 IEEE International Conference on Industrial Engineering and Engineering Management (IEEM): Singapore, 6-9 Dec. 2015, Piscataway, NJ: IEEE Communications Society, 2015, 817-820 s., 7385761Konferansepaper (Fagfellevurdert)
    Abstract [en]

    As equipment becomes more complex, repair process becomes more complicated, costly and time-consuming. Maintainability principles are developed to facilitate the repair process. Maintainability principles are applied in design phase and they are characteristic that affects time, accuracy, ease and safety requirements of the repair process. Considering Maintainability principles in the design phase are critical in challenging operational conditions such as Arctic offshore. To have an effective design for maintainability a systematic management approach is required during the design phase. This paper is developed a systematic guideline for maintainability management as an engineering discipline for challenges operational condition

  • 4.
    Aalipour, Mojgan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Barabadi, Abbas
    Tromsø University, University of Tromsø - The Arctic University of Norway.
    Work place factors effect on maintainability in challenging operating conditions2015Inngår i: 2015 IEEE International Conference on Industrial Engineering and Engineering Management (IEEM): Singapore, 6-9 Dec. 2015, Piscataway, NJ: IEEE Communications Society, 2015, 767-771 s., 7385751Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Some industries such as mining industry create complex and challenging work place for maintenance crews. For example in an underground mine, for some machines, heavy maintenance tasks must be performed on site in a limited workspace in a harsh environment, including dust and improper illumination. Such operating conditions can increase the health, safety, and environment (HSE) risk, reduce the availability of the machines and increase the life cycle cost of equipment. A review of current mining equipment design and maintenance procedure confirms that considerable reduction in HSE risk, as well as substantial cost savings, can be achieved by considering human factors. This study discusses the effect of workplace factors on the maintainability of mining equipment. It presents the results from questionnaires on the effect of work place factors on maintainability performance given to maintenance staff at two mines, one in northern Sweden and the other in Iran.

  • 5.
    Aalipour, Mojgan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Singh, Sarbjeet
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Identification of Factors affecting Human performance in Mining Maintenance tasks2014Inngår 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, 71-76 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper investigates the factors affecting humanperformance in maintenance task in mining sector. Theobjective is identify various factors and to classify them asdriving (strong driving power and weak dependence) anddependent factors (weak driving power and strongdependence). The factors were identified through literaturesurvey and are ranked using mean score of data questionnaire.The reliability of measures is pretested by applyingCronbach’s alpha coefficient to responses to a questionnairegiven to maintenance personnel. The interrelationshipsbetween human factors have been recognized by interpretivestructural modeling (ISM). Further, these factors have beenclassified using matrice d'impacts croises-multiplicationappliqué à un classement (MICMAC) analysing. This casestudy will figure out the factors affecting human performancefor deriving maintenance management insights to improveproductivity in the mining sector. Further, this understandingmay be helpful in framing the policies and strategies formining industry. Temperature, lighting, documentation,communication and fitness are driving factors. Moreover,Work layout, tools availability, complex tasks, time pressure,safety, boss decisions, training, fatigue and motivation havestrong driving power as well as high dependencies and itcomes under the category of linkage factors.

  • 6.
    Abbasiverki, Roghayeh
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Betongbyggnad.
    Ansell, Anders
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Betongbyggnad.
    Initial study on seismic analyses of concrete and embankment dams in Sweden2017Rapport (Annet vitenskapelig)
  • 7.
    Abdelmajid, Yezeed
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och geoinformatik.
    Investigation and Comparison of 3D Laser Scanning Software Packages2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Laser scanning technologies has become an important tool in many engineering projects and applications. The output of laser measuring is the point cloud, which is processed in a way that makes it suitable for different applications. Processing of point cloud data is achieved through laser scanning software packages. Depending on the field of application, these packages have many different kinds of functions and methods that can be used. The main processing tasks used on a laser scanning software package include registration, modelling and texture mapping. Investigation and comparison of two laser scanning processing packages (Leica Cyclone and InnovMetric PolyWorks) are performed in this study. The theoretical and mathematical backgrounds of the above functions are presented and discussed. The available methods and functions used by each of the packages for these tasks are addressed and discussed. By using sample data, these functions are trailed and their results are compared and analyzed.

    The results from registration tests show the same results on both packages for the registration using target methods. Although, the results of cloud-to-cloud registration show some deviation from target registration results, they are more close to each other in both packages than to the target registration results. This indicates the efficiency of cloud-to-cloud methods in averaging the total registration error on all used points, unlike target registration methods.

    The modelling tests show more differences in the accuracy of generated models between the two packages. For both fitting and surface construction methods, PolyWorks showed better results and capabilities for three-dimensional modelling. As a result, the advantages and disadvantages of each package are presented in relation with the used task and methods, and a review of data exchange abilities is presented.

  • 8.
    Abdi, Adel Hirmand
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Contract forms and agreements for operation and maintenance of highways and railways during winter2011Rapport (Annet vitenskapelig)
  • 9.
    Abdi, Adel Hirmand
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Key aspects in winter highway operation and maintenance2010Rapport (Annet vitenskapelig)
  • 10.
    Abdi, Adel Hirmand
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Technical and contractual aspects in winter highway and railway operation and maintenance: a survey of current technical systems and contract forms in Sweden2011Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 11.
    Abdi, Shorash
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad.
    Stedt, Fredrik
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad.
    Utvärdering av Leicas multistations och laserskanners mätosäkerheter2014Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    I nuläget finns det ingen standard för utvärdering av mätosäkerheter för terrester laserskanner (TLS), detta trots att instrumentet funnits på marknaden och använts länge. Eftersom tillverkarens specifikationer inte alltid överensstämmer, är det viktigt att ha kunskap om hur bra instrumentet presterar. Ett flertal studier har under det senaste decenniet tillämpat olika metoder för att undersöka mätosäkerheten på olika TLS.

    Syftet med denna studie var att utvärdera och jämföra mätosäkerheterna mellan Leica ScanStation C10, som är en renodlad TLS, och Leica Nova MS50, som är en totalstation med skanningsfunktion, under två olika väderförhållanden. Osäkerheterna togs fram genom att använda ISO 17123-5:2012, som egentligen är en internationell standard för framtagande av totalstationers mätosäkerheter, för att undersöka om denna standard även kan appliceras på TLS. Undersökningen, som skedde utomhus vid Högskolan i Gävle, genomfördes genom att skanna signaler som ställts upp i en triangelformation från tre stationer. Vid skanning med TLS användes både sfär- och HDS-signaler medan MS50 endast skannade sfärer. Signalerna skannades in fyra gånger från varje instrumentuppställning. Mittpunktskoordinaterna på signalerna togs fram med programvaran Cyclone och därefter beräknades mätosäkerheterna med härledning från ISO-standarden. Resultatet på 3D-osäkerheten för C10 med HDS-signal och sfär blev 2,9 mm respektive 3,5 mm vid soliga förhållanden samt 1,1 mm respektive 1,4 mm i molniga förhållanden. I MS50:s fall blev osäkerheten i sol 3,0 mm och 3,7 i moln. Den höga 3D-osäkerhet som MS50 påvisade under båda väderförhållandena berodde på hög osäkerhet i höjdled. Dessutom genomfördes en hypotesprövning i form av ett chi-två-test på C10 som visade att den beräknade osäkerheten i plan och höjd inte avvek signifikant från tillverkarens specificerade osäkerhet vid användning av HDS-signaler i molnigt väder. Vidare konstaterades det genom ett F-test att det fanns en signifikant skillnad mellan C10 osäkerhet i plan och höjd vid användning av samma signaltyp under olika väderförhållanden medan. I MS50:s fall påvisades ingen signifikant skillnad alls. Av resultatet att döma, blev det en markant förbättring vid skanning under molniga förhållanden. Vår slutsats var att det går att tillämpa standarden som användes i denna studie för att beräkna mätosäkerheter på TLS och ISO bör överväga att använda samma standard för TLS som för totalstation.

  • 12.
    Abdul Al, Fatima
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Urbana och regionala studier.
    Alla barns lekplats: En studie om tillgängligheten på lekplatser2017Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Sverige har länge varit ledande inom tillgänglighet. Genom införandet av begreppen ”tillgänglighet” och ”användbarhet” har man genom Plan- och bygglagen och Boverkets riktlinjer ställt krav på den fysiska miljön.

    Ca 7 000 barn i Sverige är rörelsehindrade. Ungefär hälften av dessa barn använder en rullstol. Trots att alla barn har rätt till lek, är det intressant att undersöka huruvida alla barn ges möjlighet att utnyttja denna rättighet. Efter att ha uppmärksammat Helsingborgs stads kreativa lekplatsbyggen, dök frågan kring huruvida alla barn har möjlighet att leka på dessa lekplatser, upp.

    Syftet med arbetet är att belysa vikten av tillgängliga lekplatser, samt att undersöka hur tillgängligheten på lekplatser kan förbättras och vilka anpassningar som krävs för att förbättra tillgängligheten för rullstolsburna barn.

    I detta arbete görs en litteraturstudie, med fokus på regelverk och litteratur kopplad till tillgänglighet. En fallstudie görs i form av platsbesök på 8 lekplatser i Helsingborg, som underlag för en jämförelse. En intervju görs med Johanna Elgström, landskapsarkitekt på Helsingborgs stad.

    Slutsatsen av detta arbete är att lekplatser där man fokuserat mer på tillgänglighet ofta är mer tillgängliga och användbara för barn i rullstol. Dock krävs incitament för att säkerställa en tillgänglig och användbar lekplatsmiljö, samt tydligare definition av dessa begrepp. Genom att ha en lekplats som är tillgänglig och användbar för de flesta, gynnas den sociala hållbarheten. Slutsatsen av detta arbete blir således att säkerställandet av tillgängliga och användbara lekplatser gynnar rullstolsburna barns möjlighet till socialt samspel.

  • 13.
    Abdula, Sham
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oksman, Dan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Attefallshus som komplementbostadshus: Drömhus eller mardröm?2015Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Den 2 juli 2014 blev det enligt lag tillåtet för en- och tvåbostadshusägare att uppföra en bygglovsbefriad komplementbyggnad på max 25 kvadratmeter på den egna fastigheten. Rapporten undersöker vilket genomslag lagändringen har haft i Stor-Stockholm, Stor-Göteborg och Stor-Malmö. Undersökningen visar att lagändringen ännu inte har haft något stort genomslag. I rapporten undersöks även en utvald del av marknadsaktörers utbud av attefallshus avsett som komplementbostadshus. 

    Ett attefallshus utformas med miljövänligt hållbara material och inspireras av Vitruvius tre principer för god arkitektur. Huset konstrueras med avsikt att uppfylla kraven som ställs i PBL, PBF, BBR och EKS. Målet med de framtagna bygghandlingarna är att få startbesked från byggnadsnämnden i Växjö. 

  • 14.
    Abdulameer, Hasanain
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Byggnadsteknik.
    Chamoun, Kristian
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Byggnadsteknik.
    BIM i små och medelstora anläggningsföretag.2015Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Purpose: The purpose of this bachelor thesis is to improve the usage of BIM in facility projects.

    Method: The methods used for this bachelor thesis are qualitative interviews and literature studies.

    Findings: Free programs will be available for usage where models can be opened, viewed, examined and studied. The small and medium-sized facility companies will not be forced to use resources to cope with the requirements of Trafikverket.

    Implications: Consequences are that the small and medium-sized civil engineering companies understand and follow the requirements.

    • Using more 3D models to gain more experience and skills in the subject.

    • Attend the Trafikverkets industry days when opportunities arise, the authors believe that it was very instructive.

    • Engage in more BIM projects.

    • Older projects where the drawings are in 2D is converted into 3D.

     

    Limitations: How BIM is used during the management process will not be covered.

    Keywords: Productivity, resource, competence, experience, BIM.

  • 15.
    Abeysekera, John
    et al.
    ndustrial Ergonomics, Work Science Academy (WSA), Linköping.
    Illankoon, Prasanna
    Work Science Academy (WSA), Kandana, Sri Lanka.
    The demands and benefits of ergonomics in Sri Lankan apparel industry2016Inngår i: Work: A journal of Prevention, Assesment and rehabilitation, ISSN 1051-9815, E-ISSN 1875-9270, Vol. 55, nr 2, 255-261 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Apparel exports bring in sizeable foreign income to Sri Lanka. To protect and promote this industry is a paramount need. This can be carried out by applying Human Factors/Ergonomics (HFE) which has proved to control negative effects at work places. This paper reports a case study which describes the demands and benefits of HFE in MAS Holdings which owns a large share of the apparel industry in Sri Lanka.The study consisted of walk through observation survey, a questionnaire survey and ergonomic work place analysis followed by a training programme to selected employees in three companies.Positive responses to questionnaires revealed good ergonomic practices in the work places surveyed. Ergonomically unfit chairs and potential hazards e.g. exposure to noise and hot environment were detected. It is seen that MAS have introduced strategies originated by Toyota Production System viz. 5S, Kaizen, six sigma etc., which are in fact ergonomic methods. A progressive project MAS boast of viz. ‘MAS Operating System’ (MOS) empowers training and development to employees.MAS Holdings has adequately realized the benefits of applying HFE as evident by the number of awards received. Relevant companies were advised to take appropriate corrective measures to control the potential hazards.

  • 16.
    Abrahamsson, Evelina
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för fysisk planering.
    Översvämningsrisker i kustnära städer: Sölvesborg, Karlshamn, Ronneby, Karlskrona2015Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
  • 17.
    Abrahamsson, Lena
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Arbetsvetenskap.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Johansson, Jan
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Arbetsvetenskap.
    Rask, Kjell
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Arbetsvetenskap.
    Fältholm, Ylva
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Arbetsvetenskap.
    Kumar, Uday
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Bergquist, Bjarne
    Projekt: LUPO - globala länkar2010Annet (Annet (populærvitenskap, debatt, mm))
  • 18.
    Ackemo, Sandra
    Högskolan Dalarna, Akademin Industri och samhälle, Byggteknik.
    Hästanpassade vägar: I Leksands Kommun2014Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    I Sverige inträffar ungefär 13 000 personskador per år i samband med ridning och hästhantering. Enligt bestämmelser får ett hästekipage inte använda sig av exempelvis gång- och cykelvägar eller trottoarer, och eftersom många platser kan sakna slingor eller leder anpassade för ridande eller körande hästekipage, så hänvisas de till de motortrafikerade vägarna. Hästen är ett flyktdjur och reagerar olika i olika situationer, och i kombination med exempelvis okunskap hos bilförare så ökar risken för olyckor för hästar i trafiken.Arbetet syftar till att utvärdera om ridsportutövare upplever det problematiskt att vistas i trafiken tillsammans med häst och hur vanligt förekommande det är att de vistas i trafiken med häst. Arbetet syftar också till att ge en översyn av hur väl ridsportutövarna känner till trafikregler berörande hästar i trafiken. Det huvudsakliga syftet med detta examensarbete är dock att ge förslag på hur vägutformningen ska kunna förbättras med hänsyn till trafiksäkerheten, trygghet och framkomlighet för ridsportutövare.

    Studien genomfördes genom en enkätundersökning. Enkäten delades ut till 38 medlemmar på Leksands Ridklubb. Resultatet visar att kunskap om trafikregler skulle kunna ökas hos ridsportsutövare. Tillexempel påpekas det att hästen måste bli en del av samhällsplaneringen och att mer information angående hästar måste ut till de som vistas i trafiken. Andra förslag är sänkta hastigheter för motordriven trafik vid hästtäta passager och övergångar för hästar.

  • 19.
    Acuña, José
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Distributed thermal response tests: New insights on U-pipe and Coaxial heat exchangers in groundwater-filled boreholes2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    U-pipe Borehole Heat Exchangers (BHE) are widely used today in ground source heating and cooling systems in spite of their less than optimal performance. This thesis provides a better understanding on the function of U-pipe BHEs and Investigates alternative methods to reduce the temperature difference between the circulating fluid and the borehole wall, including one thermosyphon and three different types of coaxial BHEs.

    Field tests are performed using distributed temperature measurements along U-pipe and coaxial heat exchangers installed in groundwater filled boreholes. The measurements are carried out during heat injection thermal response tests and during short heat extraction periods using heat pumps. Temperatures are measured inside the secondary fluid path, in the groundwater, and at the borehole wall. These type of temperature measurements were until now missing.

    A new method for testing borehole heat exchangers, Distributed Thermal Response Test (DTRT), has been proposed and demonstrated in U-pipe, pipe-in-pipe, and multi-pipe BHE designs. The method allows the quantification of the BHE performance at a local level.

    The operation of a U-pipe thermosyphon BHE consisting of an insulated down-comer and a larger riser pipe using CO2 as a secondary fluid has been demonstrated in a groundwater filled borehole, 70 m deep. It was found that the CO2 may be sub-cooled at the bottom and that it flows upwards through the riser in liquid state until about 30 m depth, where it starts to evaporate.

    Various power levels and different volumetric flow rates have been imposed to the tested BHEs and used to calculate local ground thermal conductivities and thermal resistances. The local ground thermal conductivities, preferably evaluated at thermal recovery conditions during DTRTs, were found to vary with depth. Local and effective borehole thermal resistances in most heat exchangers have been calculated, and their differences have been discussed in an effort to suggest better methods for interpretation of data from field tests.

    Large thermal shunt flow between down- and up-going flow channels was identified in all heat exchanger types, particularly at low volumetric flow rates, except in a multi-pipe BHE having an insulated central pipe where the thermal contact between down- and up-coming fluid was almost eliminated.

    At relatively high volumetric flow rates, U-pipe BHEs show a nearly even distribution of the heat transfer between the ground and the secondary fluid along the depth. The same applies to all coaxial BHEs as long as the flow travels downwards through the central pipe. In the opposite flow direction, an uneven power distribution was measured in multi-chamber and multi-pipe BHEs.

    Pipe-in-pipe and multi-pipe coaxial heat exchangers show significantly lower local borehole resistances than U-pipes, ranging in average between 0.015 and 0.040 Km/W. These heat exchangers can significantly decrease the temperature difference between the secondary fluid and the ground and may allow the use of plain water as secondary fluid, an alternative to typical antifreeze aqueous solutions. The latter was demonstrated in a pipe-in-pipe BHE having an effective resistance of about 0.030 Km/W.

    Forced convection in the groundwater achieved by injecting nitrogen bubbles was found to reduce the local thermal resistance in U-pipe BHEs by about 30% during heat injection conditions. The temperatures inside the groundwater are homogenized while injecting the N2, and no radial temperature gradients are then identified. The fluid to groundwater thermal resistance during forced convection was measured to be 0.036 Km/W. This resistance varied between this value and 0.072 Km/W during natural convection conditions in the groundwater, being highest during heat pump operation at temperatures close to the water density maximum.

  • 20.
    Adanko, Carina
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsområde Bebyggd miljö.
    Küller, Marianne
    Lunds universitet, LTH, Inst arkitektur och byggd miljö, Miljöpsykologi.
    LED-belysning och brukaren2014Rapport (Annet vitenskapelig)
    Abstract [sv]

    Ljusforskning är om något diversifierad och omfattar teorier och metoder från skilda discipliner som teknik, medicin och samhällsvetenskap. Det finns också en förväntan att erhållna forskningsresultat skall kunna appliceras direkt i verkliga miljöer. I och med introduktionen av LED har många tidigare studier som behandlat glödlampor, lysrör och andra ljuskällor inaktualiserats. Ny kunskap - och ny forskning - krävs.

    En inventering av aktuell humanrelaterad LED-forskning genomfördes under 2013. Med utgångspunkt i detta material har föreliggande forskningsöversikt sammanställts. Totalt omfattar denna drygt 400 artiklar, som redovisas under följande rubriker: Den biologiska klockan; Flimmer och dimring av LED; Energibesparing: dagsljus och ljusstyrning; Färgåtergivning; Bländning och slutligen; Upplevda ljuskvaliteter.

    Såväl bakomliggande teoretiska resonemang som det aktuella kunskapsläget redovisas i de olika avsnitten. Efter varje avsnitt ges också referenser till relevanta forskningspublikationer. Samtliga publikationer har försetts med två eller flera svenska nyckelord, som anger publikationens innehåll. Publikationerna har sedan delars in i kategorier enligt avsnitten ovan. Efter varje avsnitt redovisas de publikationer på vilka texten baserar sig, med nyckelord. I ett slutavsnitt redovisas samtliga LED-publikationer i alfabetisk ordning efter författare och med nyckelord.

  • 21.
    Agnefeldt, Anton
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för fysisk planering.
    Idrottsarenor & Allmänt Intresse: En Fallstudie Över Kalmar Arena2017Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
  • 22.
    Agriam, Pia
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Byggnadsteknik.
    Socialt hållbart boende2016Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Det behövs mer forskning kring vad som ger människan goda förutsättningar till livskvalitet i en bostadsmiljö. Social hållbarhet är ett ämne som arkitekturvärlden värnar om mer än någonsin. Målet är att ta fram ett kunskapsunderlag baserat på erfarenheter från brukare, arkitekt samt beställare som kan användas till gestaltning av bostadsområden med flerbostadshus.

    För att uppnå målet besvaras frågeställningarna ”Hur värderas socialt hållbart boende, enligt arkitekter och beställare, när bostadsområden med flerbostadshus utformas?” samt ”Hur upplevs det som värderas som socialt hållbart, i bostadsområden med nyproducerade flerbostadshus, av brukare?” Frågeställningarna besvaras med hjälp av en enkätundersökning och intervjuer som tillsammans utgör en kvalitativ forskningsmetod.

    Resultatet visar att social hållbarhet kan ses ur olika vinklar. Det är vanligt att se på social hållbarhet ur ett samhällsperspektiv och ur en stads perspektiv i enlighet med vetenskapliga referenser. Som en övergripande sammanfattning är det en byggnads vackra form, utseende och dess funktionsduglighet som vägs in med en rimlig kostnad som skapar ett socialt hållbart boende enligt intervjuer med arkitekt och beställare. Det handlar om en balansgång mellan skönhet, funktion och ekonomi som tillsammans skapar ett boende som håller över tiden och bekräftar människans sociala värdighet. Enligt de som bor på området Nysäter i Mölnlycke som är det studerade objektet, handlar socialt hållbart boende om trivsel, trygghet, privatliv och samhörighet. Tillgång till natur och uteaktiviteter, frisk luft och god grannsämja är andra faktorer som värderas högt. Därmed har socialt hållbart boende kopplingar till både fysiskt greppbara parametrar samt icke fysiska kvaliteter som behöver sammanlänkas med varandra.

    Det sammanfattande resultatet belyser de väsentliga aspekter som bör inbegripas vid planering av ett nytt bostadsområde för att det ska bli socialt hållbart för de boende. Kunskapsunderlaget följer en logisk ordning från att analysera ett orört område med dess kvaliteter till att analysera hur den privata bostaden ska uppfylla människans behov av välbefinnande.

    Rapporten är bred i sitt ämnesval även om den begränsas till människans förhållande till bostaden och bostadsområdet i sociala sammanhang, hur individer upplever sin omgivning både i och utanför bostaden. Ytterligare begränsningar hade gjort att en djupare forskning kring ett specifikt tema hade kunnat genomföras.

  • 23.
    Ahlbäck, Ida
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Detaljplanering: Förslag till exploatering  Del av Sävast 17:42017Independent thesis Basic level (university diploma), 5 poäng / 7,5 hpOppgave
  • 24.
    Ahlroth, Sofia
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö.
    Convergent validity test of structural benefit transfer: the case of water qualityManuskript (preprint) (Annet vitenskapelig)
  • 25.
    Ahlroth, Sofia
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Miljöstrategisk analys.
    Costs and benefits of climate change : a bottom-up analysisManuskript (preprint) (Annet vitenskapelig)
  • 26.
    Ahlroth, Sofia
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Miljöstrategisk analys.
    Finnveden, Göran
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Miljöstrategisk analys.
    Ecovalue08-a new valuation method for environmental systems analysis toolsManuskript (preprint) (Annet vitenskapelig)
  • 27.
    Ahlroth, Sofia
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Miljöstrategisk analys.
    Höjer, Mattias
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö.
    Sustainable energy prices and growth: Comparing macroeconomic and backcasting scenarios2007Inngår i: Ecological Economics, ISSN 0921-8009, E-ISSN 1873-6106, Vol. 63, nr 4, 722-731 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    How do results from the sustainability research world of backcasting relate to the macroeconomic scenarios used for policy evaluation and planning? The answer is that they don't, mostly - they come from different scientific traditions and are not used in the same contexts. Yet they often deal with the same issues. We believe that much can be gained by bringing the two systems of thinking together. This paper is a first attempt to do so, by making qualitative comparisons between different scenarios and highlighting benefits and limitations to each of them. Why are the pictures we get of the energy future so different if we use a macroeconomic model from when using a backcasting approach based on sustainable energy use? It is evident that the methods for producing those two kinds of scenarios differ a lot, but the main reason behind the different results are found in the starting points rather than in the methods. Baseline assumptions are quite different, as well as the interpretations and importance attached to signals about the future. in this paper, it is discussed how those two types of scenarios differ and how they approach issues such as energy prices and growth. The discussion is based on a comparison between Swedish economic and sustainability scenarios. The economic scenarios aim at being forecasts of the future and are used as decision support for long-term policies. But are the assumptions in the economic scenarios reasonable? The sustainability scenarios are explicitly normative backcasting scenarios. They do not take the issue of growth and consumption fully into account. Could they be developed in this respect? The comparison between the scenarios is also used to look closer at the issue of energy prices in a society with sustainable energy use. One of the questions raised is if a low energy society calls for high energy prices. Moreover, the effects of tradable permits versus energy taxes is analysed in the context of how energy use could be kept low in a growing economy.

  • 28.
    Ahlroth, Sofia
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Miljöstrategisk analys.
    Nilsson, Måns
    SEI.
    Finnveden, Göran
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Miljöstrategisk analys.
    Hjelm, Olof
    Linköpings universitet.
    Hochschorner, Elisabeth
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Miljöstrategisk analys.
    Weightning and valuation in environmental systems analysis toolsManuskript (preprint) (Annet vitenskapelig)
  • 29.
    Ahmadi, Alireza
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Aircraft scheduled maintenance programme development: decision support methodologies and tools2010Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The air transport business is large in its operations, integrated, automated and complex. Air carriers are constantly striving to achieve high standards of safety and simultaneously to attain an increased level of availability performance at minimal cost. This needs to be supported through an effective maintenance programme which has a major impact on the availability performance and which ultimately can enhance the aircraft’s capability to meet market demands at the lowest possible cost. The development of a maintenance programme is challenging, but can be enhanced by supporting methodologies and tools. The purpose of this study is to develop decision support methodologies and tools for aircraft scheduled maintenance programme development within the framework of Maintenance Review Board (MRB) process. To achieve the purpose of the research, literature studies, case studies, and simulations have been conducted. Empirical data have been collected through document studies, interviews, questionnaires, and observations from the aviation industry. For data analysis, theories and methodologies within risk, dependability and decision making have been combined with the best practices from the aviation industry. One result of the research is the identification of potential areas for improving the use of MSG-3 methodology in aircraft scheduled maintenance development. Another result is the development of a systematic methodology guided by the application of an Event Tree Analysis (ETA) for the identification and quantification of different operational risks caused by aircraft system failures, to support decision making for maintenance task development. A third result is a proposed methodology, based on a combination of different Multi-Criteria Decision Making (MCDM) methodologies, for selecting the most effective maintenance strategy for aircraft scheduled maintenance development. Finally, the fourth result is a proposed Cost Rate Function (CRF) model supported by a graphical approach. The approach can be used to identify the optimum maintenance interval and frequencies of Failure Finding Inspection (FFI) and to develop a combination of FFI and restoration tasks for the aircraft’s repairable items which are experiencing aging. These results are related to some of the specific industrial challenges, and are expected to enhance the capability of making effective and efficient decisions during the development of maintenance tasks. The results have been verified through interaction with experienced practitioners within major aviation manufacturers and air operators.

  • 30.
    Ahmadi, Alireza
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    An assessment of operational consequences of failures to support aircraft scheduled maintenance program development2007Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    A majority of the direct and indirect maintenance costs in the life cycle of aircraft stems from the consequences of decisions taken during the initial maintenance program development. In particular, the preventive and corrective maintenance requirements, which greatly influence both the system availability and life cycle cost, need to be defined in order to perform only those preventive actions that are absolutely necessary and costeffective. Reliability-Centered Maintenance (RCM) is a systematic methodology used to identify the preventive maintenance tasks that are necessary to realize the inherent reliability of equipment at the lowest possible cost. Developing a scheduled maintenance program by means of RCM consists of identifying those preventive tasks which are both applicable (technically feasible) and effective (worth doing). An applicable maintenance task must satisfy the requirements of the type of failure to restore the item's initial performance capability. To be effective, a preventive maintenance task must lead to a reduced risk (or expected loss) of the consequence classes to a level which is acceptable to the user. In the design development phase, in order to identify the most cost effective solution, a design trade-off study is needed. This involves choosing the correct balance of the cost of consequences of failure and its correction, with their cost of prevention. However, during initial aircraft maintenance program development, lack of a methodology that supports the assessment of the operational consequences of failures has made the costeffectiveness analysis of maintenance tasks a challenging issue. This might reduce the accuracy of the analysis, which results in higher maintenance costs and may decreases the punctuality of operation, which ultimately increases the total aircraft life cycle cost. The purpose of this study is to develop a methodology for identifying different operational consequences and associated costs caused by aircraft system failure, in order to facilitate and enhance the capability of taking correct and efficient decisions when analyzing the cost-effectiveness of maintenance tasks. Some empirical studies of possible scenarios involving aircraft failures and their operational consequences for a commercial airline have been performed. Empirical data were extracted through document studies and interviews, guided by the application of an Event Tree Analysis (ETA). The analysis was performed together with experienced practitioners from both an aircraft manufacturer and commercial airlines, which contributed to a continuous verification of the outcomes of the study. Finally, the study has also estimated the associated cost of the identified operational consequences of failures. In order to quantify the operational consequences of failures, in the absence of adequate and reliable data, a methodology using pair-wise comparison technique has been applied to extract judgments of experts efficiently

  • 31.
    Ahmadi, Alireza
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    ArastehKhouy, Iman
    Kumar, Uday
    Schunnesson, Håkan
    Selection of maintenance strategy, using analytical hierarchy process2009Inngår i: Communications in Dependability and Quality Management, ISSN 1450-7196, Vol. 12, nr 1, 121-132 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Selection of appropriate maintenance strategy is key to economic viability of aviation and manufacturing industries. The study discusses and presents an approach to facilitate the selection of the most appropriate maintenance strategy on the basis of the cost-benefit analysis by using Analytical Hierarchical Process (AHP). The goal is to select the most cost-effective alternative, among Run-To-Failure (RTF), Preventive Maintenance (PM), incorporating Prognostic Health Management(PHM) capability, or any possible Design-Out Maintenance (DOM) strategies, which positively affects on aircraft operational availability. In this paper we proposed a stepwise algorithm to guide the selection process, based on two criteria of operational availability (benefit) and cost of failure.

  • 32.
    Ahmadi, Alireza
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Block, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Garmabaki, Amir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Project: Efficient Performance Based Air Vehicle Maintenance, Supported by VINNOVA (NFFP-6), Luleå University of Technology, Saab Support and Services, SAAB Aeronautics2014Annet (Annet (populærvitenskap, debatt, mm))
  • 33.
    Ahmadi, Alireza
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Block, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Garmabaki, Amir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Project: Enhanced Life Cycle Assessment for Performance-Based Logistics, Supported by Vinnova (NFFP-5), Saab Support Service and Luleå University of Technology2014Annet (Annet (populærvitenskap, debatt, mm))
  • 34.
    Ahmadi, Alireza
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Block, Jan
    Kumar, Uday
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Risk based maintenance deferral for components subject to hidden failure2012Inngår i: 2012 proceedings: Annual Reliability and Maintainability Symposium (RAMS 2012) : Reno, Nevada 23-26 Jan. 2012, Piscataway, NJ: IEEE Communications Society, 2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In the aviation industry, it may be necessary to employ a combination of Failure Finding Inspection (FFI) and a scheduled discard task at a specific threshold, when a component is aging and its failures are hidden and exert a “safety effect”. This is to ensure an adequate level of availability of hidden functions, and to reduce the risk of multiple failures to an acceptable level. However, in some situations, operators prefer to extend the discard life of components beyond their recommended life limit, due to operational needs or logistic issues. This necessitates the definition of an optimal Failure Finding Inspection interval for the extended life period. The main purpose of this paper is to develop analytical and graphical methodologies to identify the optimal FFI interval for extension of the discard life of aircraft components. The paper considers repairable components which are periodically tested. The methodology assumes that the inspection and repair actions lead to as-bad-as-old (ABAO) reliability characteristics.The graphical approach proposed in this paper considers inspection and repair times, as well as the costs associated with accidents, inspection, and repair, and it takes into account the opportunity losses due to the maintenance downtime. The analytical approach for calculating the unavailability of the hidden function is based on the Mean Fractional Dead Time (MFDT).

  • 35.
    Ahmadi, Alireza
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Franson, Torbjörn
    Saab Aerosystems, Linköping.
    Crona, Anneli
    Saab Aerosystems, Linköping.
    Klein, Markus
    Saab Aerosystems, Linköping.
    Söderholm, Peter
    Integration of RCM and PHM for the next generation of aircraft2009Inngår i: 2009 IEEE Aerospace Conference: Big Sky, Montana, USA, 7 - 14 March 2009, Piscataway, NJ: IEEE Communications Society, 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    With global cuts in defense budgets, air forces have to sustain the same level of readiness with a reduced number of aircraft. To succeed with this challenge, it is not sufficient to improve current maintenance concepts, but new ones also have to be introduced.Traditionally, the development of on-board functions and maintenance concepts has been performed rather independently. The new approach is to focus on an integration of these two developments and to adapt a life cycle view together with a disregard of organizational boundaries.To facilitate the necessary change, a study is performed by Saab and Luleå University of Technology. The study focuses on the possibilities to integrate RCM and PHM in a cost-effective way. The aim is to reduce the workload of maintenance development and to find out how to combine RCM and PHM to achieve a joint development of the aircraft and its maintenance program throughout the aircraft's whole life cycle.The paper describes some similarities and differences between RCM and PHM. Furthermore, the paper describes some aspects of how RCM and PHM are complementing each other and what kind of adaptations that has to be done to achieve a successful integration. For example, a good application of RCM early in system design might generate a pull for PHM-technology integration and motivate design changes of the aircraft. Simultaneously, available PHM-technologies might strongly affect the selection of applicable and effective maintenance tasks in the development of the initial maintenance program. PHM might also support a surveillance of the maintenance program's performance. The description is highlighted with examples and experiences from the Swedish Gripen fighter aircraft. Finally, the paper also outlines some suggestions for further research.

  • 36.
    Ahmadi, Alireza
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Garmabaki, Amir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Ghodrati, Behzad
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Kumar, Uday
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Optimum inspection interval for hidden functions during extended life2015Inngår i: International Journal of COMADEM, ISSN 1363-7681, Vol. 18, nr 3, 45-49 s.Artikkel i tidsskrift (Fagfellevurdert)
  • 37.
    Ahmadi, Alireza
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Ghodrati, Behzad
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Garmabaki, Amir Soleimani
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Kumar, Uday
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Optimum inspection interval for hidden functions during extended life2014Konferansepaper (Fagfellevurdert)
  • 38.
    Ahmadi, Alireza
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Ghodrati, Behzad
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Rantatalo, Matti
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Optimum Failure Finding Inspection During Extended Operation Life2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In a complex system such as railway and aviation equipment’s, it may be necessary to employ a combination of Failure Finding Inspection (FFI) and a scheduled discard task, as suggested by Reliability-Centered Maintenance (RCM). This strategy ensures an adequate level of availability of hidden functions, as well as the reduction of the risk of multiple failures to an acceptable level. However, in some situations, operators prefer to extend the discard life of components beyond their recommended life limit, due to the operational restrictions. This necessitates the definition of an optimal Failure Finding Inspection interval for the extended life period. This paper aims to provide a mathematical model for defining optimal FFI interval, during the extended period of the replacement life. A cost function (CF) is developed to identify the cost per unit of time associated with different FFI intervals, for the proposed extended period of life, i.e. postponement period. The proposed method concerns as-bad-as-old (ABAO) inspection and repairs (due to failures found by inspection). It considers inspection and repair times, and takes into account the costs associated with inspection and repair, the opportunity cost of lost production due to maintenance downtime created by inspection and repair actions, and also the cost of accidents due to the occurrence of multiple failure

  • 39.
    Ahmadi, Alireza
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Gupta, Suprakash
    Banaras Hindu University, Varanasi.
    Ghodrati, Behzad
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Galar, Diego
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Estimation of economic consequences of aircraft system failures2012Inngår i: Communications in Dependability and Quality Management, ISSN 1450-7196, Vol. 15, nr 1, 39-49 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A large portion of the direct and indirect aircraft operational costs stems from the consequences of decisions made during the maintenance program development. Decision on maintenance task selection for non-safety category of failures, is based on the cost effectiveness, in which the cost of preventive maintenance should be less than the costs associated with the corrective action and failure consequence. Although the assessment of the direct cost for preventive and corrective maintenance is quiet straightforward, however quantification and estimation of the cost associated with the consequence of failure is a great challenge. This is due to a long list of contributory factors and lack of adequate data regarding the cost headings. This study attempts to estimate the economic consequences of aircraft system failures which lead to a technical delay. The paper considers financial losses, mostly due to the additional unexpected costs related to the flight crew, passengers, aircraft itself, ramp and airport, when one of the cost headings, e.g. the pre-fixed crew cost is known. The experience of the field experts has been used following a pairwise comparison technique to compare the cost headings, and to estimate the contribution of each one to the total cost of a delay. The study shows that the proposed model can be a tool to assess the cost of failure consequences in aircraft operation, when there is a limited data and information regarding the cost headings.

  • 40. Ahmadi, Alireza
    et al.
    Gupta, Suprakash
    Banaras Hindu University, Varanasi.
    Karim, Ramin
    Kumar, Uday
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Selection of maintenance strategy for aircraft systems using multi-criteria decision making methodologies2010Inngår i: International Journal of Reliability, Quality and Safety Engineering (IJRQSE), ISSN 0218-5393, Vol. 17, nr 3, 223-243 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper, proposes the Multi-Criteria Decision Making (MCDM) methodology for selection of a maintenance strategy to assure the consistency and effectiveness of maintenance decisions. The methodology is based on an AHP-enhanced TOPSIS, VIKOR and benefit-cost ratio, in which the importance of the effectiveness appraisal criteria of a maintenance strategy is determined by the use of AHP. Furthermore, in the proposed methodology the different maintenance policies are ranked using the benefit-cost ratio, TOPSIS and VIKOR. The method provides a basis for consideration of different priority factors governing decisions, which may include the rate of return, total profit, or lowest investment. When the preference is the rate of return, the benefit-cost ratio is used, and for the total profit TOPSIS is applied. In cases where the decision maker has specific preferences, such as the lowest investment, VIKOR is adopted. The proposed method has been tested through a case study within the aviation context for an aircraft system. It has been found that using the methodology presented in the paper, the relative advantage and disadvantage of each maintenance strategy can be identified in consideration of different aspects, which contributes to the consistent and rationalized justification of the maintenance task selection. The study shows that application of the combined AHP, TOPSIS, and VIKOR methodologies is an applicable and effective way to implement a rigorous approach for identifying the most effective maintenance alternative.

  • 41.
    Ahmadi, Alireza
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Gupta, Suprakash
    Kumar, Uday
    Assessment of the cost of operational consequences of failures in aircraft operation2007Inngår i: Proceedings of 3rd International Conference on Reliability and Safety, 2007Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Maintenance decisions regarding aircraft require consideration of the operational impact of failures. The cost of the operational impact of failure is difficult to assess due to the influence of a large number of contributory factors. This study attempts to assess the cost of operational consequences of failures using the expertise of the field experts following a pairwise contribution technique. The study shows that the proposed model can be a tool to assess the cost of operational consequences of failures in aircraft operation, when there is not sufficient and reliable data

  • 42. Ahmadi, Alireza
    et al.
    Karim, Ramin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Barabady, Javad
    Prerequisites for a business-oriented fleet availability assurance program in aviation2010Inngår i: Proceedings of the 1st international workshop and congress on eMaintenance, Luleå: Luleå tekniska universitet, 2010, 168-175 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The air transport business is a large, integrated, automated and complex domain with high requirements on safety, security and dependability. In order to achieve customer satisfaction and gain a global competitive advantage, provision of services is essential. In air transport business with an extensive competition, the consequences of unreliable services become more critical which may increase cost of operation and reduce productivity. Furthermore, occurrence of unreliable services might also lead to annoyance, inconvenience and a lasting customer dissatisfaction that can create serious problem with regarding the responsible company‟s marketplace position. Hence, it is crucial for air transport companies to continuously improve the quality of the services they provide to customer. In the context of air transport, maintenance process and maintenance-related services have a high impact on effectiveness, productivity and costs. Maintenance departments are required to ensure that their fleet is expected to meet, or continues to meet, airline‟s established availability performance goals (e.g. operational readiness, dispatch reliability and cost affectivity) and to ensure that demands for deliveries will met. One way to align maintenance decisions and business objectives and at the same time highlight where the potential weakness in the systems and maintenance performance can be expected, is through Fleet Availability Assurance Program (FAAP). However, an effective implementation of FAAP needs adaptation to the usage context. Hence, the purpose of this paper is to present an availability assurance program in airline industries, in which the essential functional elements of such a program are discussed. The paper also proposes an integrated information logistic infrastructure for this management system.

  • 43.
    Ahmadi, Alireza
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Kumar, Uday
    Cost based risk analysis to identify inspection and restoration intervals of hidden failures subject to aging2011Inngår i: IEEE Transactions on Reliability, ISSN 0018-9529, E-ISSN 1558-1721, Vol. 60, nr 1, 197-209 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The analytical model presented in this paper aims to study possible maintenance strategies considering risk constrains, to preserve or assure availability of hidden functions of a repairable unit in aircraft systems considering ageing effect. The paper discusses two known strategies for hidden failure management aviation and other high risk industries, namely Failure Finding Inspection (FFI), and a combination of a series of FFI and restoration after a specific number of FFI cycles ( i.e., FFI-Rs strategy). Based on discussions, the paper introduces a new approach named Dynamic Failure Finding Inspection strategy (DFFI) to assure the acceptable level of risk and also the unit's hidden function availability continuously . The paper presents analytical methods to estimate optimal FFI, and optimal thresholds for restoration of degradation (refreshing risk level) within FFI-Rs strategy. It also discusses criteria used to select appropriate thresholds to change the FFI intervals within DFFI strategy, i.e. reducing inspection intervals after specific thresholds, to reduce the risk. The method is based on the mean proportion of time i.e. (Mean Functional Dead Time, MFDT) that the unit is not functioning during the inspection intervals and the average unavailability behavior within the restoration/discard period. The proposed method considers inspection, repair, and restoration times, and takes in to account costs associated with inspection, repair, restoration, potential losses due to non-availability of aircraft due to maintenance downtime or accident often caused multiple failures.

  • 44. Ahmadi, Alireza
    et al.
    Kumar, Uday
    Ghodrati, Behzad
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Risk based maintenance decision for periodically tested repairable components subject to hidden failure2011Inngår i: Proceedings of 2nd International Conference on Reliability, Safety and Hazard - ICRESH 2010: Mumbai Dec 15-16, 2010 / [ed] P V Varde, Piscataway, NJ: IEEE Communications Society, 2011, 197-204 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper aims to develop a graphical method to facilitate the identification of risk and cost of postponement of restoration for repairable components which are periodically tested and whose failures are hidden, i.e, are detectable by inspection or upon demand. The paper focuses on the items which are under aging, however, the methodology is flexible to implement for any aging pattern. The paper considers Failure Finding Inspection (FFI) with restoration actions (FFI+Res), for the “safety effect” categories of hidden failures. As-bad-as-old (ABAO) inspection effectiveness and as-good-as-new (AGAN) restoration effectiveness are considered. In case of repair due to findings by inspection, as-bad-as-old repair effectiveness is considered. The graphical methodology proposed in this paper considers inspection and repair times, as well as the costs associated with accident, inspection, repair, and restoration, and takes into account the opportunity losses due to the maintenance downtime. The analytical approach is based on the Mean Fractional Dead Time. In the case of an operational limit, when it is not possible to remove the unit for restoration, or one needs to use the unit longer than the expected operating time, the paper introduces an approach to analyzing the possibility of and conditions for providing an extension to the restoration interval that satisfies the risk constraints and the business requirements at the same time.

  • 45.
    Ahmadi, Alireza
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Kumar, Uday
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Söderholm, Peter
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    On aircraft scheduled maintenance program development2010Inngår i: Journal of Quality in Maintenance Engineering, ISSN 1355-2511, E-ISSN 1758-7832, Vol. 16, nr 3, 229-255 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose – The purpose of this paper is to present issues and challenges of scheduled maintenance task development within the maintenance review board (MRB) process, and to find potential areas of improvement in the application of the MSG-3 methodology for aircraft systems. Design/methodology/approach – The issues and challenges as well as potential areas of improvement have been identified through a constructive review that consists of two parts. The first part is a benchmarking between the Maintenance Steering Group (MSG-3) methodology and other established and documented versions of reliability-centred maintenance (RCM). This benchmarking focuses on the MSG-3 methodology and compares it with some RCM standards to identify differences and thereby find ways to facilitate the application of MSG-3. The second part includes a discussion about methodologies and tools that can support different steps of the MSG-3 methodology within the framework of the MRB process. Findings – The MSG-3 methodology is closely related to the RCM methodology, in which the anticipated consequences of failure are considered for risk evaluation. However, MSG-3 considers neither environmental effects of failures nor operational consequences of hidden failures. Furthermore, in MSG-3, the operational check (failure-finding inspection) is given priority before all other tasks, whereas in RCM it is considered as a default action, where there is no other applicable and effective option. While RCM allows cost-effectiveness analysis for all failures that have no safety consequences, MSG-3 just allows it for failures with economic consequences. A maintenance program that is established through the MRB process fulfils the requirements of continuous airworthiness, but there is no foundation to claim that it is the optimal or the most effective program from an operator’s point-of-view. The major challenge when striving to achieve a more effective maintenance program within the MRB process is to acquire supporting methodologies and tools for adequate risk analysis, for optimal interval assignments, and for selection of the most effective maintenance task. Originality/value – The paper presents a critical review of existing aircraft scheduled maintenance program development methodologies, and demonstrates the differences between MSG-3 and other RCM methodologies.

  • 46. Ahmadi, Alireza
    et al.
    Kumar, Uday
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Söderholm, Peter
    Risk of operational consequences of aircraft system failure2010Inngår i: International Journal of Pedagogy, Innovation and New Technologies, ISSN 0973-1318, E-ISSN 2392-0092, Vol. 6, nr 2, 149-158 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The purpose of this paper is to describe a methodology for identifying different operational consequences and associated costs caused by aircraft system failure, in order to facilitate and enhance the capability of taking correct and efficient decisions when analyzing the cost-effectiveness of maintenance tasks. The paper focuses on the operational consequences of failures that lead to delay. To identify the operational consequences of aircraft system failures, Empirical studies of possible scenarios involving aircraft failures and their operational consequences for a commercial airline have been performed. Empirical data were extracted through document studies and interviews, guided by the application of an Event Tree Analysis (ETA). In order to effectively utilize the knowledge of field experts in the assessment process, a pairwise comparison technique was adopted for quantifying the contribution of different factors to the operational. The work was performed together with experienced practitioners from both an aircraft manufacturer and commercial airlines, which contributed to a continuous verification of the outcome of the study.The study shows that the proposed methodology based on ETA and pairwise comparison can be used to identify and quantify the cost of operational consequences of failures in aircraft operation, when there is no sufficient and reliable data.

  • 47.
    Ahmadi, Alireza
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Soleimanmeigouni, Iman
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Block, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Letot, Christophe
    University of Mons.
    Optimum failure management strategy for periodically inspected units with imperfect maintenance2016Inngår i: IFAC PAPERSONLINE, ISSN 2405-8963, Vol. 49, nr 12, 799-804 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this paper is to develop a reliability-based cost model for periodically inspected units subject to hidden functions, with imperfect restoration (overhaul) action after a certain number of inspections. In the model, effectiveness of the consecutive restoration actions is considered, and possible alternative maintenance strategies are identified and compared. The method is based on the Total Cost and identifies the optimum interval and frequency of inspections, as well as restoration that minimize the total life cycle cost. In the proposed model, repair due to failures found by inspection is considered as minimal repair, and restoration/overhaul action is considered as normal repair. The result also shows that for a specific value of restoration effectiveness (θ0), when θ> θ0, the behavior of alternatives tends to as-bad-as-old and for θ< θ0 tends to an as-good-as-new. It is also observed that when the cost of accident is high it is needed to perform inspections at smaller intervals.

  • 48.
    Ahmadi, Alireza
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Soleimanmeigouni, Iman
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Letot, Christopher
    Machine Design and Production Engineering Unit, Research Institute for the Science and Manage ment of Risks, University of Mons.
    Block, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Inspection Optimization under imperfect maintenance performance2017Inngår i: Proceedings of MPMM 2016: 6th International Conference on Maintenance Performance Measurement and Management, 28 November 2016, Luleå, Sweden / [ed] Diego Galar, Dammika Seneviratne, Luleå: Luleå tekniska universitet, 2017, 139- s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Scheduled maintenance and inspection development is one of the main requirements for emergency equipment and safety devices. These types of devices have hidden functions which are used intermittently or infrequently, so their failure will not be evident to the operating crew. The analytical model presented in this paper deals with the periodically tested units with overhauls (preventive maintenance) after certain number of inspections and a renewal after a series of overhauls. The cost based optimization method presented in this paper identifies the optimum interval and frequency of Failure Finding Inspection (FFI) and restoration. In the proposed model, repair due to failures found by inspection makes the unit As Bad As Old, and restoration/overhaul action rejuvenates the unit to any condition between As Good As New and As Bad As Old. As Good As New effectiveness also is considered for renewal action. It considers inspection and repair times, and takes into account the costs associated with inspection, repair, restoration, and also the cost of accidents due to the occurrence of multiple failure. The results show that when the unit is not under aging process, the optimal alternative for each inspection interval is the one with highest possible number of inspection without restoration. Finally, it is observed that when the cost of accident is quite high it is needed to perform inspections at smaller intervals to control the risk of accident.

  • 49. Ahmadi, Alireza
    et al.
    Söderholm, Peter
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Assessment of the operational consequences of aircraft failures: using event tree analysis2008Inngår i: 2008 IEEE Aerospace Conference: 1-8 March 2008 : [Big Sky, Montana]., Piscataway, NJ: IEEE Communications Society, 2008, 1-14 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The purpose of this paper is to describe a methodology that supports an assessment of the operational consequences of failures in aircraft systems and its associated costs, in order to facilitate a correct and efficient decision-making during cost-effectiveness analysis of maintenance tasks within scheduled aircraft maintenance program development. The paper is based on empirical studies of possible scenarios from aircraft failure to operational consequences in commercial airlines. Empirical data was extracted through document studies and interviews, guided by the application of an Event Tree Analysis (ETA). The analysis was performed together with experienced practitioners from both an aircraft manufacturer and commercial airlines, which contributed to a continuous verification of the outcomes of the study. The proposed methodology, which is based on ETA, is considered as a valuable support in the assessment of the operational consequences of failures within a MSG-3 framework. The proposed methodology focuses on assessing the operational consequences of failures and associated economical losses. Hence, in order to enable an estimation of the maintenance tasks' cost-effectiveness, the methodology should be further developed to include a cost assessment of the applicable maintenance tasks. The proposed methodology could be adapted as a support to those involved in the development of aircraft maintenance program. The operational consequences and the probabilities of the proposed event tree can be quantified by the aid of historical data or expert judgment.

  • 50.
    Ahmadi, Alireza
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Söderholm, Peter
    Kumar, Uday
    An overview of trends in aircraft maintenance program development: past, present, and future2007Inngår i: Risk, Reliability and Societal Safety: Pproceedings of the European Safety and Reliability Conference 2007 (ESREL 2007), Stavanger, Norway, 25 - 27 June 2007 / [ed] Terje Aven; Jan Erik Vinnem, London: Taylor and Francis Group , 2007, 2067-2076 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The purpose of this paper is to describe the trends in aircraft maintenance program development during the last 50 years, including the reasons for the aircraft industry to change its view of maintenance. The major milestones and fundamental reasons for such development are also discussed and illustrated in relation to a flow diagram, which shows the logical and chronological order of the trends. Finally, the paper describes some possibilities and challenges as regards applying Information & Communication Technology (ICT) within the emerging approach of e-Maintenance in order to enhance the surveillance of aircraft maintenance program performance.

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