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  • 4351. Wirtén, Katarina
    et al.
    Hellqvist, Magnus
    Dalarna University, School of Technology and Business Studies, Physical Geography.
    Preliminär insektsanalys. Övergiven gårdsbrunn - en fälla för ekofakter, med ett palaeoentomologiskt bidrag av Magnus Hellqvist1996In: TOR, ISSN 0495-8772, Vol. 26, p. 83-91Article in journal (Other academic)
  • 4352. Wisotzki, L.
    et al.
    Jahnke, K.
    Kuhlbrodt, B.
    van Groningen, Ernst
    Dalarna University, School of Technology and Business Studies, Physics.
    Örndahl, E.
    Spectroscopy and Imaging of QSO Host Galaxies2000In: Stars, Gas and Dust in Galaxies: Exploring the Links, ASP Conference Proceedings / [ed] Olsen, Knut; Galaz, Gaspar; Alloin, Danielle, San Francisco: Astronomical Society of the Pacific, 2000, Vol. 221Conference paper (Other academic)
  • 4353.
    Wokekoro, Victor Dike
    et al.
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    White, Bekibele Onome
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    Intellectual Property Protection: an External Factor that Influences a Foreign Company’s Market Entry Mode into a Prospective Market2010Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [en]

    Intellectual Property Protection is been understood in this paper as IP laws and enforcement of these laws in order to protect intellectual property rights. The goal of this research work is to understand how Swedish companies view issues regarding to Intellectual Property Protection (IPP) and how it influences a foreign company?s market entry mode. In order to achieve this objective, the Nigerian market situation and its? laws that govern IPP will be used to analyzed this issue. This paper argues that IPP is an important factor that influences a company?s entry mode and this argument finds IP laws and enforcement as two variables that influence the market while the market situation influences the foreign company. In carrying out this research literature was reviewed and interviews carried out. The research methodology section has presented a qualitative research and explains the nature of the interview stages that have been used to achieve the goals concerning the findings of the empirical data. A qualitative method was adopted by carrying out in-depth semi-structured interviews. The empirical data collected from the investigation were gathered and analyzed based on the research questions. The findings show that IPP of a host market influences a potential foreign company through the market situation that is also influenced by IP laws and enforcement. The outcome of these findings argues that the Swedish companies that were interviewed in this research will enter the Nigerian market through an intermediary mode. This has been based on the current IPP system of Nigerian.

  • 4354.
    Woldegiorgis, Abraham
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Improved Inverters for Grid Connected PV Systems2004Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    In this thesis work the performances of two inverters are compared. The inverters are connected to a grid-connected PV system located on the roof of the main building of Hogskolan Dalarna. The system totally consists of 72 photovoltaic modules of 45Wp each. One system has 40 modules and an inverter of type SOLWEX 2065, which was functioning starting from 1994. The other system consists of 32 modules and a new inverter of model NT1800. An overall performance evaluation of the inverters was done. The DC current, DC voltage, AC current and AC voltage of the two systems were measured using a data logger and the result was analyzed and compared. Further the output power of the two systems was calculated and the annual yield estimated. It is found out that the old SOLWEX inverter performs below the manufacturer’s specifications. Its efficiency is more than 10% less. It doesn’t always track the maximum power point of the PV array and its threshold power is more than three times higher than the value given by the manufacturer. The new NT 1800 inverter has a wider MPPT voltage range and tracks the maximum power effectively. The daily output of both systems is plotted as a function of daily global irradiation. The new inverter has a better performance for all irradiation levels. Especially for days with low irradiation levels the new inverter gives much higher yield. It is found out that the new inverter connected system delivers 38% more annual yield as compared to the system with old inverter.

  • 4355.
    Woxlin, William C.
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    Perspektiv på HR-arbete vid nedskärningar: - en studie om effekter och handlingar, utifrån tre perspektiv, för den fortsatta överlevnaden2010Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Studien ämnar till att skapa en profil för tre olika empirinära perspektiv, vilka alla spelar en roll före, under och efter en nedskärningsprocess. Dessa tre perspektiv är: ledningsperspektivet, perspektivet för kvarvarande anställda och uppsagda arbetare. Författaren lägger tyngd på den tidigare vetenskapliga forskningen som får agera likt en mall för hur en optimal hantering ska ske under en nedskärningsprocess. Syftet med studien är att detektera bristande överrensstämmelser mellan perspektiven som förhindrar att hanteringen blir optimal för alla parter, samt kunna se om teorin används i det praktiska utövandet. Ledarskapsperspektivet är representerat i två underkategorier: sekundärintervjuer och expertintervjuer. I sekundärintervjuerna så presenteras svar från auktoriteter inom området som förmedlar den erfarenhetsbaserade kunskapen; medan i expertintervjuerna presenteras svar från fyra olika, representerade, företag inom olika branscher i Borlänge. Perspektivet för kvarvarande anställda representeras av en enkätundersökning och en djupare intervju med en kvarvarande anställd. Det tredje empirinära perspektivet, för uppsagda arbetare, representeras av en enkätundersökning och en djupare intervju med en uppsagd arbetare. I resultatet så visar det sig att författaren har kunnat detektera bristande överrensstämmelser på flera punkter, främst inom den uppfattade kommunikationen, mellan perspektiven. Detta tolkas som att de framlagda teorierna inte följs av praktiken och därför råder det ingen optimal situation för något av de representerade perspektiven.

  • 4356.
    Wretlind, Kristoffer
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Separation av resurser i molntjänstarkitekturer: Separation of Resources in Cloud Architectures2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Molnet är ett evolutionärt koncept som erbjuder en konkurrenskraft – och kostnadskontroll för företag

    genom att integrera olika och existerande teknik. Molnet avser både applikationer som levereras som

    tjänst över Internet, och hårdvara – och mjukvara som tillhandahålls i dessa tjänster. För att kunna dra

    nytta av pris – och prestationsfördelar som molnet erbjuder innebär det att resurser är konsoliderade

    mellan flera kunder i samma infrastruktur. Det är med hänsyn till en konsoliderad miljö som isolering

    av kunders resurser är särskilt viktigt att beakta. Syftet med min studie är att identifiera de risker

    gällande separation av resurser som medföljer en molnbaserad infrastruktur, och lyfta fram olika

    mekanismer för att säkert tillgodogöra behovet, samt att belysa homomorfisk kryptering som en

    separationsmekanism. I uppsatsens litteraturstudie presenterar jag de väsentliga risker som gäller

    separation av resurser från andra kunder och från leverantören, och vanligt förekommande logiska

    separationsmekanismer och deras funktioner som riskåtgärder för de presenterade riskerna. Läran om

    kryptografi sammanfattas i syftemål att presentera homomorfisk kryptering och dess anknytning till

    resursseparation. Litteraturstudier och intervjuer med såväl kunder som leverantörer av molntjänster

    har berett mig ett underlag för att kunna utvärdera de presenterade mekanismerna. Studiens resultat

    visade att stark isolering från andra kunder kan uppnås, men att det är problematiskt att fullständigt

    separera resurser från leverantören. Resultatet har dessutom visat att krypteringsalgoritmer som är

    homomorfiska kan vara säkra men brister i dess ineffektivitet att praktiskt kunna tillämpas.

  • 4357. Wu, J.
    et al.
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Shen, Jingchun
    University of Nottingham, Ningbo.
    Wu, Y.
    Connelly, K.
    Yang, T.
    Tang, L.
    Xiao, M.
    Xu, P.
    Wang, H.
    A review of thermal absorbers and their integration methods for the combined solar photovoltaic/thermal (PV/T) modules2017In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 75, p. 839-854Article in journal (Refereed)
    Abstract [en]

    Thermal absorbers and their integration methods are critical to solar photovoltaic/thermal (PV/T) modules. These two elements directly influence the cooling effort of PV layers and as a result, the related electrical/thermal/overall efficiency. This paper conducts a critical review on the essential thermal absorbers and their integration methods for the currently-available PV modules for the purpose of producing the combined PV/T modules. A brief overview of different PV/T technologies is initially summarized, including aspects of their structure, efficiencies, thermal governing expressions and their applications. Seven different types of thermal absorbers and four corresponding integration methods are subsequently discussed and summarized in terms of their advantages/disadvantages and the associated application for various PV/T modules. Compared to traditional thermal absorbers, such as sheet-and-tube structure, rectangular tunnel with or without fins/grooves and flat-plate tube, these four types, i.e. micro-channel heat pipe array/heat mat, extruded heat exchanger, roll-bond heat exchanger and cotton wick structure, are promising due to the significant enhancement in terms of efficiency, structure, weight, and cost etc. The appropriate or suitable integration method varies in different cases, i.e. the ethylene-vinyl acetate (EVA) based lamination method seems the best option for integration of PV layer with thermal absorber when compared with other conventional methods, such as direct contact, thermal adhesive and mechanical fixing. Finally, suggestions for further research topics are proposed from five aspects. The overall research results would provide useful information for the assistance of further development of solar PV/T modules with high feasibility for widespread application in energy supply even at district or city-level in the near future. © 2016 Elsevier Ltd.

  • 4358.
    Wuopio, Christina
    Dalarna University, School of Technology and Business Studies, Material Science.
    Kylning av valsar vid spårvalsning2005Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [sv]

    Inom Ruukki Fundia Special Bar finns tre liknande förpar, ett i Smedjebacken och två i Boxholm varav ett i finverket och det andra i mediumverket. Valsarna levereras av Åkers Sweden AB och är av samma kvalité, (gjutna H-SG-P-Mo-48 värmebehandlat-segjärn-perlitisk struktur-molybdenlegerat och med hårdhet 48 Shore) det som skiljer är radien. I mediumverket utsätts valsarna för ett hårt slitage både genom sprickbildning och ojämn yta medan de två andra förparen inte slits lika hårt. Idag används en vals i cirka sex månader, under den tiden sker en omsvarvning. På grund den rikliga sprickbildningen kan bara en omsvarvning ske på grund av att de djupa sprickorna gör att 12-16mm på diametern svarvas bort vid varje tillfälle. En andra omsvarvning gör att valsens radie blir för liten. Företaget vill minimera sprickbildningen för att kunna svarva om valsarna ytterligare en gång och på det sättet förbättra valsekonomin. Syftet med detta examensarbete är att undersöka möjligheter till varför denna sprickbildning och ytojämnhet uppstår. Sprickbildning är en följd av bland annat termiska ojämnheter på valsytan som orsakas växlande uppvärmning från hetan och kylning från kylmedlet. En annan orsak till sprickbildning kan vara överbelastning av valsarna. Temperaturer på valsar, ämne och vatten kommer att undersökas för att få en förståelse för vart problemet kan ligga. Det har gjorts beräkningar på valskrafter och moment för undersökningar i fråga om överbelastning. Programmet Steeltemp har används för att studera temperatur- förändringar i valsen under valsning. Även jämförelser mellan förparen i Smedjebacken och finverket i Boxholm har studerats.

  • 4359.
    Wäckelgård, Ewa
    et al.
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Broman, Lars
    Lindberg, Eva
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Reflection properties of uncoated metal surfaces: A literature study1988Report (Other academic)
  • 4360.
    Wäckelgård, Ewa
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Svedung, Harald
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Optical characterization and modelling of paint top-coatings for low-emittance applications2016In: Infrared physics & technology, ISSN 1350-4495, E-ISSN 1879-0275, Vol. 78, p. 275-281Article in journal (Refereed)
    Abstract [en]

    The study reports on characterization of low-infrared-emittance paint top-coatings for interior building applications in which the thermal radiation becomes important in comparison with thermal conductance. The top-coating that consist of a binder with aluminium flakes has been optically characterized in the infrared wavelength range in order to determine single flake and binder emittance from reflectance measurements. The single flake emittance was found to be 0.12 for non-leafing cornflake. The absorption coefficient that determines the binder emittance as a function of binder thickness was 0.060 [μm]−2 and 0.085 [μm]−2 for Lumiflon and polyester respectively. These results were used as parameters in a simple model of the flake-binder top-coating to investigate how the emittance of the top-coating was influence by the two components and compared with a state-of-art low-emittance commercial paint. It was found from the modelling that replacing the polyester binder with Lumiflon reduces the infrared emittance (at room temperature) from 0.36 to 0.30. Increasing flake reflectance from 0.88 to 0.96 and at the same time reduce flake thickness from 2 to 1 μm gives an emittance of 0.20. However, the real samples prepared with Lumiflon showed a severe degradation caused by the flakes floating up closer to the surface which indicates a viscosity problem that needs to be solved for practical use. Thinner flakes with higher reflectance can be found if vacuum metallised pigments are used instead of ball-milled.

  • 4361.
    Wänn, Anna
    et al.
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    Visone, Daniel
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    Revisorns oberoende: Faktorer som kan påverka uppfattningen om revisornsoberoende2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Lately media has featured many corporate scandals in which the auditors’ actions has beenquestioned. The high-profile scandals have contributed to the deterioration of confidence in the auditindustry. Due to this the requirements for auditor independence has increased.The purpose of this study is to investigate how five different factors influence the perception ofauditor independence. The examined factors are the audit firms economic dependence on the client,whether the audit firm also offers advisory services to the client, the length of audit assignments, thesize of audit firm, and whether the client has an audit committee or not. Through a survey wequestioned business advisors on banks in Dalarna, Sweden. We asked how they perceived that thesefactors affect the auditor's independence. The results shows that the audit firms economicdependence was the factor that most responders considered reduced auditor independence. Offeringof advisory services and having a long audit assignments was also considered by many responders tolead to poor auditor independence. How big the accounting firm was did not affect independenceaccording to most respondents. But those who thought that it did affect believed that a largeaccounting firm gave the auditor greater independence. Most respondents did not know how theauditors’ independence would be affected if the client had an audit committee. The reason for theuncertainty was probably because relatively few of their clients had an audit committee.The results from this study corresponds well with previous studies. Like this study, most previousstudies in this field used the method of questionnaire survey (Beattie et al., 2013; Dart, 2011; Alleyneet al., 2006; Bakar et al., 2005; Beattie et al., 1999; White, 1989; Shockley, 1981). Our surveyincluded some background questions. These show that our respondents often considered and placedgreat importance on auditor independence. Several other studies have turned to similar respondents,consumers of accounting in general and specifically bank advisors (Guiral et al., 2014; Holm &Zaman, 2012; Dart, 2011; Alleyne et al., 2006; Bakar et al., 2005; Alleyne, 2002; White, 1989). Thismeans that our results are well comparable. Previous studies were conducted in countries with anAnglo-Saxon accounting tradition, while Sweden has a continental accounting tradition. Thisdifference does however not appear to have influenced the views of auditor independence.Our study shows that Swedish banking officials' opinions about what affects the auditor'sindependence is consistent with the international opinions. Since the respondents are limited toDalarna, further studies is needed before the results can be generalizes to the whole of Sweden.

  • 4362.
    Xi, Xiaochuan
    Dalarna University, School of Technology and Business Studies, Economics.
    A Study on China's Income Inequality and the Relationship with Economic Growth2009Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The purpose of this paper is to study China’s income inequality under rapid economic growth. Does the relationship between economic growth and income inequality in China follow the Kuznets hypothesis? What is the main cause and trend of China’s income inequality? We use data which covers the period 1980-2005 to analyze the overall inequality, and data covering the period 1980-2002 to analyze the inequality inside rural and urban areas. The derived results doubt the validity of Kuznets hypothesis on explaining the relationship between economic growth and income inequality in China. Also we derive the trend of China’s increased income inequality and find that the urban-rural income disparity is the main cause of China’s income inequality.

  • 4363.
    Xiao, Jing
    Dalarna University, School of Technology and Business Studies, Economics.
    The Impact of Foreign Direct Investment on International Trade: An Empirical Study of China2008Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    This paper investigates the impact of inward FDI (Foreign Direct Investment) on international trade of China empirically on the country level by using panel data from 1984 to 2007. Two separate transformed models which are based on the gravity equation and refer to the econometric models of some previous studies, are used in this paper to estimate the effect of FDI inflows on exports and imports respectively. The estimation results confirmed the complementary relationship between FDI inflows and trade of China both on exports and imports, which has also been supported by previous empirical studies.

  • 4364. Xiao, M
    et al.
    Tang, L
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Yu-Fat-Lun, I
    Li, G
    Analysis on cooling technologies of concentrated solar power system: a review2017Conference paper (Refereed)
    Abstract [en]

    The application of the Concentrated Solar Power (CSP) system has attracted an ever-increasing attention with the deepening worldwide energy crisis. Operating temperature is one of the most important factors for CSP system that affects the solar photoelectric conversion efficiency. Reasonable cooling method cannot only decrease the operative temperature, balance flare inhomogeneity, also should display the characteristics of convenient installation, low power consumption and high reliability. Based on a comprehensive literature review, this work conducted a thorough compilation on different cooling techniques of CSP system. It includes the commonly used air cooling and water cooling, also illustrates the promising ground coupled cooling, impinging jet cooling, liquid immersion cooling, microchannel cooling, heat pipe cooling and Phase Change Material systems etc. Besides, the advantages and disadvantages of different cooling technologies are briefly analysed. It is expected that this paper could provide guidance for development and optimization of cooling technologies in CSP system.

  • 4365. Xiao, Manxuan
    et al.
    Tang, Llewelly
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Lun, Isaac Yu Fat
    Yuan, Yanping
    A Review on Recent Development of Cooling Technologies for Concentrated Photovoltaics (CPV) Systems2018In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, no 12, article id 3416Article in journal (Refereed)
    Abstract [en]

    Concentrated Photovoltaics (CPV) technology, as an energy saving method which can directly generate electricity from the Sun, has attracted an ever-increasing attention with the deepening worldwide energy crisis. However, operating temperature is one of the main concerns that affect the CPV system. Excess cell temperature causes electrical conversion efficiency loss and cell lifespan decrease. Thus, reasonable cooling methods should decrease the operating temperature and balance the flare inhomogeneity. They also need to display high reliability, low power consumption, and convenient installation. This paper presented the architectural, commercial, and industrial usage of CPV system, reviewed the recent research developments of different cooling techniques of CPV systems during last few years, including the spectral beam splitting technology, cogeneration power technology, commonly used and promising cooling techniques, active and passive cooling methods. It also analysed the design considerations of the cooling methods in CPV systems, introduced the classification and basic working principles and provided a thorough compilation of different cooling techniques with their advantages, current research limitations, challenges, and possible further research directions. The aim of this work is to find the research gap and recommend feasible research direction of cooling technologies for CPV systems. 

  • 4366.
    Xiao, Yumin
    et al.
    Dalarna University, School of Technology and Business Studies, Statistics.
    Wang, Heng
    Dalarna University, School of Technology and Business Studies, Statistics.
    Aviation accident insurance: actuarial modeling, pricing, and demonstrating the long-term risk via simulation2010Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [en]

    Background: Since the 9.11 air disaster has happened, the degree of concern for aviation accident insurance is higher than before. Having been reformed for several times since 1989, the aviation accident insurance is still dissatisfied with the reality in China. The view that the aviation accident insurance can make huge profits spreads widely. Two obvious defects, huge profits and lack of risk resisting abilities, needs to be solved by the insurers. To understand the problem and propose reasonable strategies, we introduced an actuarial model and did simulations for different scenarios, to see how the premium and risk are connected on the long-term scale. Results: Our simulation results show a monotonic pattern between the yearly premium and the bankruptcy probability for scenarios of 50-200 years periods. Only for the low accident rate of 1/8000000 which is close to the Chinese situation, a yearly premium amount of a single-crash compensation can control the bankruptcy probability to about 5%. Conclusions: The accident rate of the insured airlines needs to be controlled to reduce risk, comprehensive reserve system and reinsurance might also need to be set up.

  • 4367. Xiong, Y
    et al.
    Bo, L
    Qiang, M
    Wu, Y
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology. University of Nottingham.
    Xu, P
    Ma, C
    A characteristic study on the start-up performance of molten-salt heat pipes: Experimental investigation2017In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 82, p. 433-438Article in journal (Refereed)
    Abstract [en]

    This paper reports a fundamental experimental investigation of the start-up characteristics of heat pipes using a dedicated molten-salt mixture as the working fluid. Based on four single salt, i.e. NaNO3(AR), KNO3(AR), LiNO3(AR) and Ca(NO3)2(AR), a quaternary molten-salt working fluid was developed and charged at different masses into four heat pipes with the same dimensions of 980 mm in length and 22 mm in diameter. A parallel comparison on the start-up performance of these heat pipes was then conducted to observe the influence of the charging mass and the inclination angle under the consistent lab-controlled conditions. The experimental results showed the heat pipe with molten-salt charge of 40 g responded much quicker than those with molten salt charge of 60 g, 70 g and 80 g respectively; meanwhile, the molten-salt heat pipe achieved the maximum condensation temperature at inclination angle of 50°. Comparing to the conventional naphthalene heat pipe, the dedicated molten-salt heat pipe had a much shorter start-up time when they were charged with the same amount of 40 g. The overall research result is expected to provide certain guidance for further design and operation of molten-salt heat pipe in high-and-medium-temperature heat transfer and storage scenarios. 

  • 4368.
    Xuyen Pettersson, Sofie
    Dalarna University, School of Technology and Business Studies, Economics.
    Determinants of visitor expenditures: The case of the Nordic World Ski Championships in Falun,Sweden in 20152017Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This paper investigates the effect of the primary determinants of visitors’ total

    expenditure per trip and total daily expenditure at the event by using classic OLS

    regression model and Tobit regression model to individual micro data collected by a

    survey to participants at the The Nordic World Ski Championships in Falun, Sweden in

    2015. It is shown that country of origin and length of stay have effects on both total

    expenditure per trip and total daily expenditure at the event. While accommodation mode,

    transport mode to Falun, local kilometers travelled within Falun affect only total

    expenditure per trip. Visitors’ total daily expenditure at the event are also affected by age.

    Determinants such as income, sex, living in Falun, living at home while visiting the

    event, party size, companion age group, paid by others for accommodation, kilometers

    travelled by car to Falun, number of persons if travel by car, distance to Falun, previous

    visit to Falun and visiting family and friend have no effect on both total expenditure per

    trip and total daily expenditure at the event.

  • 4369.
    Yachin, Jonathan Moshe
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    Baking Dalarna's biking cake: Collaboration as a means for destination competitiveness, a case study of “Biking Dalarna"2013Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In the contemporary tourism industry, the competitive game is between destinations. Tourism operations struggle to remain competitive on the international market and their success depends to a large extent on other complementary and competing tourism organizations at the destination. It is the sum of the total tourism offerings at the destination which determines its attractiveness. This research explores tourism collaboration process as a means of generating destination competitiveness. The focus of the research is on the enhancing factors which contribute to the success of the collaboration and to the development of quality tourism products. The research studies the case of Biking Dalarna, a collaboration of different organizations at five biking destinations in Dalarna, Sweden. Its purpose is to develop biking tourism in the region and to make Dalarna into Sweden’s leading biking destination. It is a qualitative research; the empirical data was collected through in depth interviews with representatives of six Biking Dalarna member organizations. The qualitative data collected from the participants provides inside look into the members reflections and experience of collaborating. The findings of this research demonstrate how collaboration has improved the biking product in Dalarna and promoted solutions to development problems. The research finds the good relationship between the collaborating actors and the involvement and leadership of the regional tourism management organization as the most contributing factors to the success of Biking Dalarna. The research also suggests that a third desired outcome of collaboration, improved marketing attributes was yet to be achieved in the case of Biking Dalarna.

  • 4370.
    Yachin, Jonathan Moshe
    Dalarna University, School of Technology and Business Studies, Tourism Studies. Mid-Sweden University.
    The ‘customer journey’: Learning from customers in tourism experience encounters2018In: Tourism Management Perspectives, ISSN 2211-9736, E-ISSN 2211-9744, Vol. 28, p. 201-210Article in journal (Refereed)
    Abstract [en]

    For micro-tourism firms, customers are a readily-accessible and highly important knowledge source that often remains unutilised. This study explores firm–customer encounters along the customer journey as learning opportunities. Based on data collected through participant observations, interviews and a review of user-generated content, this case study provides an in-depth look into the customer journey, with a Swedish micro-tourism firm. The findings suggest that the possibility to generate knowledge about experiential purposes is conditioned by the firm's ability to bestow encounters with an experience-like quality and promote the customers' transformation into participants. This is facilitated by involving customers, adopting an experiential discourse and utilising in-situ supporting moments to socialise. Firms can also learn about customers' subjective perception of value from user-generated content. The study concludes that in the context of learning from customers, small size provides micro-tourism firms with an opportunity to engage in personal relationships with their customers.

  • 4371.
    Yachin, Jonathan Moshe
    Dalarna University, School of Technology and Business Studies, Tourism Studies. Mid Sweden University.
    The entrepreneur–opportunity nexus: discovering the forces that promote product innovations in rural micro-tourism firms2019In: Scandinavian Journal of Hospitality and Tourism, ISSN 1502-2250, E-ISSN 1502-2269, Vol. 19, no 1, p. 47-65Article in journal (Refereed)
    Abstract [en]

    The aim of this study is to investigate what sets in motion the process that results in product innovations in rural micro-tourism firms. The point of departure is to place entrepreneurship as a process that precedes innovations. This approach enables the application of the opportunity-based perspective, on the study of 40 new tourism products. Data were collected through in-depth interviews with owner-managers of micro-tourism firms in rural Sweden. The focus of the analysis is on the formation of the entrepreneur–opportunity nexus. The findings suggest that in forming the nexus, three types of forces are at play: internal, supply chain dynamics and reaction to changes. The notion of triggering forces adds a new dimension to the study of entrepreneurial opportunities. The theoretical contribution of this paper to tourism research is twofold. First, it points at the generating moment as a step towards theorising innovations, and second, the findings contribute to the growing knowledge base about entrepreneurial behaviour in micro-tourism firms in rural areas. Finally, in a practical manner, the findings of this study should encourage tourism entrepreneurs to invest in exploring the value chain, regard tourists as sources of knowledge and be attentive to changes in circumstances.

  • 4372.
    Yah, Fritz Alum
    Dalarna University, School of Technology and Business Studies, Mechanical Engineering.
    Design/Evaluation of A Methodology For Performance Optimization Of Indexable Carbide Inserts2009Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    In this project, two broad facets in the design of a methodology for performance optimization of indexable carbide inserts were examined. They were physical destructive testing and software simulation. For the physical testing, statistical research techniques were used for the design of the methodology. A five step method which began with Problem definition, through System identification, Statistical model formation, Data collection and Statistical analyses and results was indepthly elaborated upon. Set-up and execution of an experiment with a compression machine together with roadblocks and possible solution to curb road blocks to quality data collection were examined. 2k factorial design was illustrated and recommended for process improvement. Instances of first-order and second-order response surface analyses were encountered. In the case of curvature, test for curvature significance with center point analysis was recommended. Process optimization with method of steepest ascent and central composite design or process robustness studies of response surface analyses were also recommended. For the simulation test, AdvantEdge program was identified as the most used software for tool development. Challenges to the efficient application of this software were identified and possible solutions proposed. In conclusion, software simulation and physical testing were recommended to meet the objective of the project.

  • 4373. Yan, Su-Rong
    et al.
    Zheng, Xiao-Lin
    Wang, Yan
    Song, William Wei
    Dalarna University, School of Technology and Business Studies, Information Systems.
    Zhang, Wen-Yu
    A graph-based comprehensive reputation model: exploiting the social context of opinions to enhance trust in social commerce2015In: Information Sciences, ISSN 0020-0255, E-ISSN 1872-6291, Vol. 318, p. 51-72Article in journal (Refereed)
    Abstract [en]

    Social commerce is a promising new paradigm of e-commerce. Given the open and dynamic nature of social media infrastructure, the governance structures of social commerce are usually realized through reputation mechanisms. However, the existing approaches to the prediction of trust in future interactions are based on personal observations and/or publicly shared information in social commerce application. As a result, the indications are unreliable and biased because of limited first-hand information and stake-holder manipulation for personal strategic interests. Methods that extract trust values from social links among users can improve the performance of reputation mechanisms. Nonetheless, these links may not always be available and are typically sparse in social commerce, especially for new users. Thus, this study proposes a new graph-based comprehensive reputation model to build trust by fully exploiting the social context of opinions based on the activities and relationship networks of opinion contributors. The proposed model incorporates the behavioral activities and social relationship reputations of users to combat the scarcity of first-hand information and identifies a set of critical trust factors to mitigate the subjectivity of opinions and the dynamics of behaviors. Furthermore, we enhance the model by developing a novel deception filtering approach to discard "bad-mouthing" opinions and by exploiting a personalized direct distrust (risk) metric to identify malicious providers. Experimental results show that the proposed reputation model can outperform other trust and reputation models in most cases. (C) 2014 Elsevier Inc. All rights reserved.

  • 4374.
    Yang, Bowen
    Dalarna University, School of Technology and Business Studies, Microdata Analysis.
    Ranking hotels for recommendation via generalized linear mixed model and Box-Cox model: A case of Stockholm rating data from booking.com2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis is aimed at recommending suitable hotels to the customers using the data collected from the website booking.com. In this thesis, data from Stockholm is chosen as an example, and statistical modeling is applied. We propose recommended hotels based on their rankings in terms of the scores of the hotels. The ranking score is derived by using eneralized linear mixed models. Box-Cox transformation is applied further to improve the previous analysis. Separate group analysis indicates that the ranks between different reviewer groups are significantly different. Model evaluation is executed via Cross-validation method by calculating the classification accuracies for all models. The best model is found based on theclassification accuracy, and we recommend the top 10, top 15 and top 20 hotels from the best model in this thesis.

  • 4375.
    Yang, Jinseok
    et al.
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    Wittenberg, Philip
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    Perceived Work-related Factors and Turnover Intention: - A Case Study of a South Korean Construction Company2016Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Purpose – Employee turnover entails considerable costs and is a major problem for the construction industry. By creating an extensive framework, this study aims to examine whether perceived work-related factors affect turnover intention in South Korean construction companies.

    Research design – The paper is based on the results of a questionnaire of 136 employees that was conducted and provided by a Korean construction company. Research hypotheses were tested via correlation analyses. The most influencing work-related factors, as well as differences among job levels, were determined by multiple regression analyses.

    Findings Communication, immediate leaders, organizational commitment, and organizational pride substantially affect turnover intentions. All of these factors can be considered as relational factors. The most influencing factors differ among job levels.

    Discussion/practical implications Immediate leaders should be aware of their role in retaining employees and enhance communication, organizational commitment and pride. This study shows how the importance of certain variables differs for groups of employees.

    Theoretical implications/limitationsThis study is based on a sample of employees from a Korean construction company. Therefore, the generalizability of the findings has to be tested. Future research should test the proposed framework with other factors or resources.

    Originality/value This study shed light on the turnover subject in the South Korean construction industry. It shows that different factors can influence turnover intention among job levels. A framework was created, which is based on 16 work-related factors including organizational factors, HRM practices and job attitudes.

  • 4376.
    Yang, Jinseok
    et al.
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    Wittenberg, Philip
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    Perceived Work-related Factors and Turnover Intention: A Case Study of a South Korean Construction Company2016Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Purpose – Employee turnover entails considerable costs and is a major problem for the construction industry. By creating an extensive framework, this study aims to examine whether perceived work-related factors affect turnover intention in South Korean construction companies.

    Research design – The paper is based on the results of a questionnaire of 136 employees that was conducted and provided by a Korean construction company. Research hypotheses were tested via correlation analyses. The most influencing work-related factors, as well as differences among job levels, were determined by multiple regression analyses.

    Findings Communication, immediate leaders, organizational commitment, and organizational pride substantially affect turnover intentions. All of these factors can be considered as relational factors. The most influencing factors differ among job levels.

    Discussion/practical implications Immediate leaders should be aware of their role in retaining employees and enhance communication, organizational commitment and pride. This study shows how the importance of certain variables differs for groups of employees.

    Theoretical implications/limitationsThis study is based on a sample of employees from a Korean construction company. Therefore, the generalizability of the findings has to be tested. Future research should test the proposed framework with other factors or resources.

    Originality/value This study shed light on the turnover subject in the South Korean construction industry. It shows that different factors can influence turnover intention among job levels. A framework was created, which is based on 16 work-related factors including organizational factors, HRM practices and job attitudes.

  • 4377.
    Yarmukhamedov, Sherzod
    Dalarna University, School of Technology and Business Studies, Economics.
    Trade effects of exchange rate fluctuations: Evidence from Sweden2007Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    An overview of the theoretical literature for the last two decades suggests that there is no clear-cut relationship one can pin down between exchange rate volatility and trade flows. Analytical results are based on specific assumptions and only hold in certain cases. Especially, the impact of exchange rate volatility on export and import activity investigated separately leads also to dissimilar conclusions among countries studied. The general presumption is that an increase in exchange rate volatility will have an adverse effect on trade flows and consequently, the overall heath of the world economy. However, neither theoretical models nor empirical studies provide us with a definitive answer, leaving obtained results highly ambiguous and inconsistent (Baum and Caglayan, 2006). We purposed to empirically investigate trade effects of exchange rate fluctuations in Sweden from the perspective of export and import in this research. The data comprises period from January 1993 to December 2006, where export and import volumes are considered from the point of their determinants, including exchange rate volatility, which has been measured through EGARCH model. The results for the case of Sweden show that short run dynamics of volatility negatively associated with both export and import, whereas considered from the case of previous period volatility it exhibits positive relationship. These results are consistent with the most findings of prior studies, where the relationship remained ambiguous.

  • 4378.
    Yaseen, Muhammad Usman
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Identification of cause of impairment in spiral drawings, using non-stationary feature extraction approach2012Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Parkinson’s disease is a clinical syndrome manifesting with slowness and instability. As it is a progressive disease with varying symptoms, repeated assessments are necessary to determine the outcome of treatment changes in the patient. In the recent past, a computer-based method was developed to rate impairment in spiral drawings. The downside of this method is that it cannot separate the bradykinetic and dyskinetic spiral drawings. This work intends to construct the computer method which can overcome this weakness by using the Hilbert-Huang Transform (HHT) of tangential velocity. The work is done under supervised learning, so a target class is used which is acquired from a neurologist using a web interface. After reducing the dimension of HHT features by using PCA, classification is performed. C4.5 classifier is used to perform the classification. Results of the classification are close to random guessing which shows that the computer method is unsuccessful in assessing the cause of drawing impairment in spirals when evaluated against human ratings. One promising reason is that there is no difference between the two classes of spiral drawings. Displaying patients self ratings along with the spirals in the web application is another possible reason for this, as the neurologist may have relied too much on this in his own ratings.

  • 4379. Yazdanshenas, Eshagh
    et al.
    Furbo, Simon
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Theoretical comparison between solar combisystems based on bikini tanks and tank-in-tank solar combisystems2008In: Eurosun 2008, Lisbon, 2008Conference paper (Other academic)
    Abstract [en]

    Theoretical investigations have shown that solar combisystems based on bikini tanks for low energy houses perform better than solar domestic hot water systems based on mantle tanks. Tank-in-tank solar combisystems are also attractive from a thermal performance point of view. In this paper, theoretical comparisons between solar combisystems based on bikini tanks and tank-in-tank solar combisystems are presented. The investigations are carried out for different designs and sizes of the two solar heating system types installed in different houses. The investigations show which types of solar combisystems are suitable for low energy houses, new houses built according to the building codes and old houses.

  • 4380.
    Ybrahim, Rawan
    Dalarna University, School of Technology and Business Studies, Human Resource Management.
    Kränkande särbehandling i arbetslivet: En kvalitativ intervjustudie om hur kränkande särbehandling uppstår i organisationer med utredningsfokus2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this study is to investigate why victimization occurs in organizations and to create an understanding for how working groups perceive faktaundersökning (a Norwegian investigation method for victimization). The method used is a qualitative interview study in which three investigators and three clients of the investigation method faktaundersökning were individually interviewed. Three reports from the investigations has also been analysed and later used in the result. Four different cases in three different organizations has been investigated for this study in total. The study shows that all organizations had an insufficient working environment with multiple factors that were the underlying cause of the emerge of victimization, bullying and conflicts. These factors were later able to be categorized as; communication, leadership and roles, organizational structure and culture, policies, understanding and values. The study thus showed that the individuals who performed the negative interpersonal actions were the result of an insufficient organizational and social work environment. Furthermore, the study showed that the respondents experienced the faktaundersökning as dry, direct and hard to go through for both the different parties, but also the working groups and the organizations. The study showed that it is important that all parties are offered emotional support as soon as possible in order for the parties to feel fairly treated and thus become more willing to cooperate in the investigations. According to the respondents, trust and impartiality between investigators and the parties were an important aspect for the investigation to generate in such a true result as possible, where the right of reply plays a crucial role in the legal certainty of the investigation.

  • 4381.
    ye, yanfang
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    defining a unified scale for a test battery for Parkinson Patients2010Independent thesis Basic level (degree of Bachelor)Student thesis
  • 4382.
    Yella, Siril
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    A.I. Techniques for the Automating Railway Sleeper Inspections2006Licentiate thesis, monograph (Other academic)
  • 4383.
    Yella, Siril
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Expert system for predicting slipperiness on winter roads in the province of Dalarna, Sweden2003Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Friction plays a key role in causing slipperiness as a low coefficient of friction on the road may result in slippery and hazardous conditions. Analyzing the strong relation between friction and accident risk on winter roads is a difficult task. Many weather forecasting organizations use a variety of standard and bespoke methods to predict the coefficient of friction on roads. This article proposes an approach to predict the extent of slipperiness by building and testing an expert system. It estimates the coefficient of friction on winter roads in the province of Dalarna, Sweden using the prevailing weather conditions as a basis. Weather data from the Road Weather Information System, Sweden (RWIS) was used. The focus of the project was to use the expert system as a part of a major project in VITSA, within the domain of Intelligent Transport Systems.

  • 4384.
    Yella, Siril
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Pattern recognition approach for the automatic classification of data from impact acoustics2006In: IASTED International Conference on Artificial Intelligence and Soft Computing, Palma de Mallorca, 2006Conference paper (Other academic)
    Abstract [en]

    This paper addresses and deals with the problem of automating condition monitoring of wood in the transportation domain. Current day condition monitoring applications involving wood are mostly carried out through visual inspection and if necessary some impact acoustic examination is carried out. These inspections are mostly done intuitively by skilled personnel. Hence, it is desired to automate such intuitive human skills for the development of more robust and reliable testing methods. Data resulting from impact acoustics tests made on wooden beams has been used. The relation between condition of the wooden beam and their respective emissions has been analyzed experimentally applying different feature extraction techniques. Combining the usage of traditional frequency extraction techniques like the magnitude of the signal together with famous speech recognition techniques like Cepstral Coefficients, Linear Predictive Coding yield good results. Effect of using classifiers like Gaussian Mixture Models and Learning Vector Quantization has been tested and compared. In the current case Gaussian mixture model seem to achieve higher classification rates than Learning Vector Quantization model.

  • 4385.
    Yella, Siril
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Pattern recognition for automating condition monitoring of wooden railway sleepers2008Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The thesis aims to investigate the current state of railway sleeper inspection and proposes automatic testing procedures based on pattern recognition for future inspections concerning the condition of the sleeper. Wooden railway sleeper inspections in Sweden are currently done by hand. That is to say, a human inspector in charge of the maintenance activities visually examines each structure in turn for the presence of cracks on the sleeper. Where necessary some deeper inspection may be carried out on site, for example using an axe to hit and judge the condition of the sleeper by listening to the sound produced. Though the manual procedure uses non-destructive testing methods (visual and sound analysis), decision making is largely based on intuition; moreover the process is rather slow, expensive and also requires skilled and trained staff. Maintaining an even quality standard is another serious issue. In order to be able to fulfil the aims of the thesis, emphasis on the likely factors concerning sleeper condition was a key issue. Studies based on emulation of the human inspection process have been considered a promising route of enquiry. The emulation process is achieved by selecting and evaluating two non-destructive testing methods. The first method (impact acoustic analysis) aims to build an automatic procedure to replace the usage of an axe for distinguishing sounds; which can be described qualitatively as a crisp sound in case of a good sleeper and a dull thud on their bad counterparts. The second method (vision analysis) is to develop an appropriate machine vision algorithm to replicate the visual examination. Data were collected for each of the above methods and appropriate features were extracted. Frequency based features and crack based features have been extracted in the case of impact acoustics and machine vision methods respectively. Pattern recognition has been mainly researched for further classification work concerning the condition (good or bad) of the sleeper. Research conducted on the usage of the inspection methods such as impact acoustic and machine vision analysis show that the methods can form the basis of an automatic sleeper condition monitoring procedure. Further, two more non-destructive testing methods namely electrical resistivity analysis and ultrasound analysis have also been tested. Usage of such methods did not yield success in the current case, but they have contributed in adding knowledge to the domain in cases of relevant problems. Initially, work has pursued data from only one inspection method at a time. Given that data from a single method (or sensor) seems not to be adequate to make a reliable judgement; data fusion was investigated with an aim of achieving more reliable and robust results. Data fusion has been investigated at three different levels namely sensor-level fusion, feature-level fusion and classifier-level fusion. Results achieved by fusion in the current thesis demonstrate an overall efficiency of around 90% when compared to a human operator. This can be regarded as a good result, given that even humans disagree on certain judgements; and destructive testing can be seen as the only way to resolve such disagreements.

  • 4386.
    Yella, Siril
    et al.
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Baskar, Jayalakshmi
    Dougherty, Mark
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Machine vision for analysing the position of fastening nails on wooden railway sleepers2011In: Signal and Image Processing, 2011 / [ed] Rao, K.R., Dallas, Texas, USA, 2011Conference paper (Refereed)
    Abstract [en]

    Wooden railway sleeper inspections in Sweden and to a large extent elsewhere are carried out manually by a human operator; visual inspection being the most common approach. Manually inspecting railway sleepers is slow and time consuming. Machine vision algorithms investigating surface cracks on the sleeper and sinking of the metal plate have been studied for the purpose of automating the task. In this particular article, information concerning how far the fastening nail has lifted out of position is investigated with an aim of using such information while assessing the condition of the sleeper. Laser beams incident on the sleeper have been used to highlight the geometrical form of the sleeper/plate/nail complex. Digital images of the nail were acquired mimic human visual capabilities. Appropriate image analysis techniques were applied to further process the images and necessary features were extracted. Results of unsupervised learning, achieved in the current work indicate that expectation maximization algorithm produced reliable results.

  • 4387.
    Yella, Siril
    et al.
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Dougherty, Mark
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Automatically detecting the number of logs on a timber truck2013In: Journal of Intelligent Systems, ISSN 2191-026X, Vol. 22, no 4, p. 417-435Article in journal (Refereed)
    Abstract [en]

    This article describes a method of automatically detecting, counting and classifying logs on a timber truck using a photograph (taken by the driver). An image-processing algorithm is developed to process the photograph to calculate an estimate of the number of logs present and their respective diameters. The algorithm uses color information in multiple color spaces as well as geometrical operators to segment the image and extract the relevant information. This information enables the sawmill to better plan internal logistics and production in advance of the truck’s arrival time. The algorithm is robust with respect to external factors such as varying lighting conditions and camera angle, but some inaccuracies remain, mainly caused by logs being occluded or covered in mud or snow.

  • 4388.
    Yella, Siril
    et al.
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Dougherty, Mark
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Philosophical challenges concerning education and career orientation in the ITS area2005In: 10th Euro Working Group in Transportation, Poznan, Poland: Proc 10th Euro Working Group in Transportation , 2005Conference paper (Other academic)
  • 4389.
    Yella, Siril
    et al.
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Dougherty, Mark
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Gupta, N K
    Artificial Intelligence techniques for the automatic interpretation of data from non-destructive testing2006In: Insight (Northampton), ISSN 1354-2575, E-ISSN 1754-4904, Vol. 48, no 1, p. 10-20Article in journal (Other academic)
    Abstract [en]

    This paper attempts to summarise the findings of a large number of research papers deploying artificial intelligence (AI) techniques for the automatic interpretation of data from non-destructive testing (NDT). Problems in the rail transport domain are mainly discussed. However, a majority of the emphasis in this paper is laid on rail inspection problems, since it was believed that the review would provide a perfect ground to the authors in pursuing further work within the rail inspection area. NDT is a broad name for a variety of methods and procedures concerned with all aspects of uniformity, quality and serviceability of materials and structures, without causing damage to the material that is being inspected. During the past several years, problems concerning the automatic interpretation of data from NDT have received good attention and have stimulated interests in other areas like transportation, for making key assessments within some of its subject areas. Rail, air and marine industries together with bridge inspection and pavement maintenance are good examples of such areas where a considerable amount of work has been done. Such work neatly splits into two schools. The first school investigates the classical usage of data by an experienced human operator to determine the condition of the inspected material or structure. The other school focuses attention on the automatic interpretation of NDT data using AI techniques, in determining the result of inspection. The scope of this paper is only limited to the automatic interpretation of data from NDT, with the goal of assessing embedded flaws as quickly and accurately as possible in a cost effective fashion. AI techniques such as neural networks, machine vision, knowledge-based systems and fuzzy logic were applied to a wide spectrum of problems in the area. A secondary goal was to provide an insight into possible research methods concerning railway sleeper inspection by automatic interpretation of data. A brief introduction is provided for the benefit of the readers unfamiliar with the techniques.

  • 4390.
    Yella, Siril
    et al.
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Dougherty, Mark
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Gupta, Narendra
    Fuzzy logic approach for automating visual condition monitoring of railway sleepers2007In: IICAI, Indian International Conference on Artificial Intelligence, Pune, India, 2007Conference paper (Other academic)
  • 4391.
    Yella, Siril
    et al.
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Dougherty, Mark
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Gupta, Narendra K.
    Condition monitoring of wooden railway sleepers2009In: Transportation Research Part C: Emerging Technologies, ISSN 0968-090X, E-ISSN 1879-2359, Vol. 17, no 1, p. 38-55Article in journal (Refereed)
    Abstract [en]

    Wooden railway sleeper inspections in Sweden are currently performed manually by a human operator; such inspections are to large extent based on visual analysis. In this paper a machine vision based approach has been considered to emulate the visual abilities of the human operator to enable automation of the process. Digital images from either ends (left and right) of the sleepers have been acquired. A pattern recognition approach has been adopted to classify the condition of the sleeper into classes (good or bad) and thereby achieve automation. Appropriate image analysis techniques were applied and relevant features such as the number of cracks on a sleeper, average length and width of the crack and the condition of the metal plate were determined. Feature fusion has been proposed in order to integrate the features obtained from each end for the classification task which follows. The effect of using classifiers like multi-layer perceptron and support vector machines has been tested and compared. Results obtained from the experiments show that multi-layer perceptron and support vector machines have achieved encouraging results, with a classification accuracy of 90%; thereby exhibiting a competitive performance when compared to a human operator.

  • 4392.
    Yella, Siril
    et al.
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Dougherty, Mark
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Gupta, Narendra K.
    Data fusion for automating condition monitoring of wooden railway sleepers2008In: Insight (Northampton), ISSN 1354-2575, E-ISSN 1754-4904, Vol. 50, no 7, p. 356-363Article in journal (Other academic)
    Abstract [en]

    Wooden railway sleeper inspections in Sweden are currently done by hand. That is to say, a human inspector in charge of the maintenance activities visually examines each structure in turn for the presence of cracks on the sleeper. Where necessary some deeper inspection may be carried out on site, for example using an axe to hit and judge the condition of the sleeper by listening to the sound produced. Though the manual procedure uses non-destructive testing methods (visual and sound analysis), decision-making is largely based on intuition; moreover the process is rather slow, expensive and also requires skilled and trained staff. Maintaining an even quality standard is another serious issue. Hence, it is desired to automate the human inspection process by proposing automatic testing procedures for future inspections concerning the condition of the sleeper. Studies based on emulation of the human inspection process have been considered a promising route of enquiry for automation. Such an emulation process is achieved by selecting and evaluating two non-destructive inspection methods. The first method (impact acoustic analysis) aims to build an automatic system to replace the usage of an axe for distinguishing sounds. The second method (visual analysis) is to develop an appropriate machine vision algorithm to replicate the visual examination. Further, the above-mentioned methods were fused (data fusion) to generate a single output condition concerning the condition of the sleeper. In the current work, fusion has been achieved in mainly three levels, namely sensor-level, feature-level and classifier-level. Experimental results achieved in this work indicate that data fusion has achieved superior performance when compared with using data from one method at a time.

  • 4393.
    Yella, Siril
    et al.
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Ghiamati, Samira
    Dougherty, Mark
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Condition monitoring of wooden railway sleepers using time-frequency techniques and pattern classification2009In: Systems, Man and Cybernetics, 2009. SMC 2009. IEEE International Conference on Systems, San Antonio, Texas, USA, 2009, p. 4164-4169Conference paper (Refereed)
    Abstract [en]

    Railway sleepers are a key engineering element of all railways. Lack of much sophistication in monitoring railway sleepers makes it a key problem within the rail transportation domain. Current day condition monitoring applications involving wooden railway sleepers are mostly carried out through visual inspection and if necessary some impact acoustic examination is carried out. Decision making is largely based on intuition; moreover the process of manually inspecting sleepers is rather slow and expensive. Maintaining an even quality standard is another serious issue. In this article, a pattern recognition and classification approach is taken to automate such intuitive human skills for the development of more robust and reliable testing methods. Features were extracted from the impact acoustic emissions of wooden sleepers and were used for pattern classification. Time-frequency based feature extraction techniques such short-time Fourier transform and discrete wavelet transform yielded good results. Multi-layer perceptron, radial basis function neural networks and support vector machine classifiers have been tested and compared. Further classifier fusion was investigated by considering the output of single best classifiers as input to a new classifier with an aim of improving performance. Results obtained experimentally demonstrate a classification accuracy of around 84%.

  • 4394.
    Yella, Siril
    et al.
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Gupta, Naredra K.
    Dougherty, Mark
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Automating condition monitoring of wooden railway sleepers2007In: EngineerIT, ISSN 1991-5047, Vol. 2, no 10Article in journal (Other academic)
  • 4395.
    Yella, Siril
    et al.
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Gupta, Naren
    Dougherty, Mark
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Condition monitoring using pattern recognition techniques on data from acoustic emissions2006In: ICMLA 2006: 4th International Conference on Machine Learning and Applications, Proceedings, 2006Conference paper (Other academic)
    Abstract [en]

    Condition monitoring applications deploying the usage of impact acoustic techniques are mostly done intuitively by skilled personnel. In this article, a pattern recognition approach is taken to automate such intuitive human skills for the development of more robust and reliable testing methods. The focus of this work is to use the approach as a part of a major research project in the rail inspection area, within the domain of Intelligent Transport Systems. Data from impact acoustic tests made on wooden beams have been used. The relation between condition of the wooden beams and respective sounds they make when struck, has been analyzed experimentally. Features were extracted from the acoustic emissions of wooden beams and were used for pattern classification. Features such as magnitude of the signal, natural logarithm of the magnitude and Mel-frequency cepstral coefficients, yielded good results. The extracted feature vectors were used as input to various pattern classifiers for further pattern recognition task. The effect of using classifiers like Support vector machines and Multi-layer perceptron has been tested and compared. Results obtained experimentally, demonstrate that Support vector machines provide good detection rates for the classification of impact acoustic signals in the NDT domain.

  • 4396.
    Yella, Siril
    et al.
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Gupta, Narendra
    Dougherty, Mark
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Comparison of pattern recognition techniques for the classification of impact acoustic emissions2007In: Transportation Research Part C: Emerging Technologies, ISSN 0968-090X, E-ISSN 1879-2359, Vol. 15, no 6, p. 345-360Article in journal (Refereed)
    Abstract [en]

    Current day condition monitoring applications involving wood are mostly carried out through visual inspection and if necessary some impact acoustic examination is carried out. These inspections are mainly done intuitively by skilled personnel. In this paper, a pattern recognition approach has been considered to automate such intuitive human skills for the development of robust and reliable methods within the area. The study presents a comparison of several pattern recognition techniques combined with various stationary feature extraction techniques for classification of impact acoustic emissions. Further issues concerning feature fusion are discussed as well. It is hoped that this kind of broad analysis could be used to handle a wide spectrum of tasks within the area, and would provide a perfect ground for future research directions. A brief introduction to the techniques is provided for the benefit of the readers unfamiliar with the techniques. Pattern classifiers such as support vector machines, etc. are combined with stationary feature extraction techniques such as linear predictive cepstral coefficients, etc. Results from support vector machines in combination with linear predictive cepstral coefficients delivered good classification rates. However, Gaussian mixture models delivered higher classification rates when feature fusion is proposed.

  • 4397.
    Yella, Siril
    et al.
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Nyberg, Roger G.
    Dalarna University, School of Technology and Business Studies, Information Systems.
    Assessing the quality and reliability of visual estimates in determining plant cover on railway embankments2016In: Web Information Systems Engineering – WISE 2016: 17th International Conference, Shanghai, China, November 8-10, 2016, Proceedings, Part II / [ed] Wojciech Cellary, Mohamed F. Mokbel, Jianmin Wang, Hua Wang, Rui Zhou, Yanchun Zhang, 2016, Vol. 10042, p. 404-410Conference paper (Refereed)
    Abstract [en]

    This study has investigated the quality and reliability of manual assessments on railway embankments within the domain of railway maintenance. Manually inspecting vegetation on railway embankments is slow and time consuming. Maintenance personnel also require extensive knowledge of the plant species, ecology and bio-diversity to be able to recommend appropriate maintenance action. The overall objective of the study is to investigate the reliable nature of manual inspection routines in favour an automatic approach. Visual estimates of plant cover reported by domain experts’ have been studied on two separate railway sections in Sweden. The first study investigated visual estimates using aerial foliar cover (AFC) and sub-plot frequency (SF) methods to assess the plant cover on a railway section in Oxberg, Alvdalsbanan, Sweden. The second study investigated visual estimates using aerial canopy cover method on a railway section outside Vetlanda, Sweden. Visual estimates of the domain experts were recorded and analysis-of-variance (ANOVA) tests on the mean estimates were investigated to see whether if there were disagreements between the raters’. ICC(2, 1) was used to study the differences between the estimates. Results achieved in this work indicate statistically significant differences in the mean estimates of cover (p < 0.05) reported by the domain experts on both the occasions.

  • 4398.
    Yella, Siril
    et al.
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Nyberg, Roger G
    Dalarna University, School of Technology and Business Studies, Information Systems.
    Gupta, Narendra K.
    Edinburgh Napier University.
    Dougherty, Mark
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Reliability of manual assessments in determining the types of vegetation on railway tracks2015In: Web Information Systems Engineering – WISE 2015: 16th International Conference, Miami, FL, USA, November 1-3, 2015, Proceedings, Part II / [ed] Wang, J., Cellary, W., Wang, D., Wang, H., Chen, S.-C., Li, T., Zhang, Y., Springer, 2015, Vol. 9149, p. 391-399Conference paper (Refereed)
    Abstract [en]

    Current day vegetation assessments within railway maintenance are (to a large extent) carried out manually. This study has investigated the reliability of such manual assessments by taking three non-domain experts into account. Thirty-five track images under different conditions were acquired for the purpose. For each image, the raters’ were asked to estimate the cover of woody plants, herbs and grass separately (in %) using methods such as aerial canopy cover, aerial foliar cover and sub-plot frequency. Visual estimates of raters’ were recorded and analysis-of-variance tests on the mean cover estimates were investigated to see whether if there were disagreements between the raters’.  In tra-correl ation coefficient was used to study the differences between the estimates. Results achieved in this work revealed that seven out of the nine analysis-of-variance tests conducted in this study have demonstrated significant difference in the mean estimates of cover (p < 0.05).

  • 4399.
    Yella, Siril
    et al.
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Nyberg, Roger G.
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Payvar, Barsam
    Dougherty, Mark
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Gupta, Narendra
    Edinburgh Napier University.
    Machine vision approach for automating vegetation detection on railway tracks2013In: Journal of Intelligent Systems, ISSN 2191-026X, Vol. 22, no 2, p. 179-196Article in journal (Refereed)
    Abstract [en]

    The presence of vegetation on railway tracks (amongst other issues) threatens track safety and longevity. However, vegetation inspections in Sweden (and elsewhere in the world) are currently being carried out manually. Manually inspecting vegetation is very slow and time consuming. Maintaining an even quality standard is also very difficult. A machine vision-based approach is therefore proposed to emulate the visual abilities of the human inspector. Work aimed at detecting vegetation on railway tracks has been split into two main phases. The first phase is aimed at detecting vegetation on the tracks using appropriate image analysis techniques. The second phase is aimed at detecting the rails in the image to determine the cover of vegetation that is present between the rails as opposed to vegetation present outside the rails. Results achieved in the current work indicate that the machine vision approach has performed reasonably well in detecting the presence/absence of vegetation on railway tracks when compared with a human operator.

  • 4400.
    Yella, Siril
    et al.
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Pasha, Sajjad M.
    Dougherty, Mark
    Dalarna University, School of Technology and Business Studies, Computer Engineering.
    Gupta, Narendra K.
    Classifier fusion for condition monitoring of wooden railway sleepers2008In: Engineer IT, ISSN 1991-5047, p. 31-35Article in journal (Other academic)
85868788899091 4351 - 4400 of 4530
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