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  • 4501.
    Yella, Siril
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Datateknik.
    Nyberg, Roger G
    Högskolan Dalarna, Akademin Industri och samhälle, Informatik.
    Gupta, Narendra K.
    Edinburgh Napier University.
    Dougherty, Mark
    Högskolan Dalarna, Akademin Industri och samhälle, Datateknik.
    Reliability of manual assessments in determining the types of vegetation on railway tracks2015Inngår i: 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, s. 391-399Konferansepaper (Fagfellevurdert)
    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).

  • 4502.
    Yella, Siril
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Datateknik.
    Nyberg, Roger G.
    Högskolan Dalarna, Akademin Industri och samhälle, Datateknik.
    Payvar, Barsam
    Dougherty, Mark
    Högskolan Dalarna, Akademin Industri och samhälle, Datateknik.
    Gupta, Narendra
    Edinburgh Napier University.
    Machine vision approach for automating vegetation detection on railway tracks2013Inngår i: Journal of Intelligent Systems, ISSN 2191-026X, Vol. 22, nr 2, s. 179-196Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 4503.
    Yella, Siril
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Datateknik.
    Pasha, Sajjad M.
    Dougherty, Mark
    Högskolan Dalarna, Akademin Industri och samhälle, Datateknik.
    Gupta, Narendra K.
    Classifier fusion for condition monitoring of wooden railway sleepers2008Inngår i: Engineer IT, ISSN 1991-5047, s. 31-35Artikkel i tidsskrift (Annet vitenskapelig)
  • 4504.
    Yella, Siril
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Datateknik.
    Shaik, Asif ur Rahman
    Högskolan Dalarna, Akademin Industri och samhälle, Datateknik.
    Dougherty, Mark
    Högskolan Dalarna, Akademin Industri och samhälle, Datateknik.
    Pattern recognition for classifying the condition of wooden railway sleepers2010Inngår i: Multimedia Computing and Information Technology (MCIT), 2010 International Conference on Multimedia Computing and Information Technology, Sharjah, 2010, s. 61-64Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper summarises the results of using a pattern recognition approach for classifying the condition of wooden railway sleepers. Railway sleeper inspections are currently done manually; visual inspection being the most common approach, with some deeper examination using an axe to judge the condition. Digital images of the sleepers were acquired to compensate for the human visual capabilities. Appropriate image analysis techniques were applied to further process the images and necessary features such as number of cracks, crack length etc have been extracted. Finally a pattern recognition and classification approach has been adopted to further classify the condition of the sleeper into classes (good or bad). A Support Vector Machine (SVM) using a Gaussian kernel has achieved good classification rate (86%) in the current case.

  • 4505.
    Yeneneh, Getu Temasgen
    Högskolan Dalarna, Akademin Industri och samhälle, Energiteknik.
    Testing of Apis System Platform in Grid-Connected Photovoltaic System and Comparison with Metrum for Fault Detection and Diagnosis2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    A real time data management web-based software-platform for PV plant monitoring called Apis was tested for fault detection and diagnosis of large scale grid-connected photovoltaic systems. This method was compared with Metrum system which is also another web based monitoring system used in grid connected PV systems. The objective of testing and comparisons were to observe the Apis system performance in large scale PV systems particularly for fault detection, and to identify which of the two systems could give more information to easily identify type of fault and point out the fault location in PV plants.

    The experiment were carried out in the selected two different arrays that have a capacity of 18.4kW and 17.6 kW with four string inverters each, to test three cases at Glava energy center solar park, Sweden. The first demonstrates the response of the systems when the wiring loose or cable disconnection fault occurs in the plant. The second demonstrates the output of the inverters when partial shading is gradually increased and the third demonstrates the output when the fault at components (i.e. at inverter, fuse and circuit breaker) is applied. Both systems collect data from inverters. However, in Apis system, data from individual inverters of the plant could be collected separately in both AC and DC sides while Metrum system was measuring the total output of the whole inverters in the plant.

    During the string disconnection, the Apis monitoring system showed a power drop to zero from the defected strings making it possible to identify them. In the same way during the inverters’ fault the power output of the failed inverter was dropped to zero. However, the normal strings and inverters were still working properly. Meanwhile the Metrum system only displayed a reduced power output which doesn’t directly identify the problem and requires manual inspection. In the case of partial shading there was a persistent difference occurred between the defected string and normal one but it did not dropped to zero at all.

    Apis system is able to differentiate and locate the faults by comparing input and output results of different inverters within the plant, unlike Metrum system which measures the total output of the plant. Nevertheless, Apis system still has less possibility to determine the type of fault further than estimation.

  • 4506. Ylva, Bäckström
    et al.
    Gamrell, Åsa
    Hellqvist, Magnus
    Högskolan Dalarna, Akademin Industri och samhälle, Naturgeografi.
    Ljungqvist, John
    Rapport från arkeologiska utgrävningar vid Mattsgården, Gamla Uppsala, 19981998Rapport (Annet vitenskapelig)
  • 4507.
    Yong, Lim Say
    Högskolan Dalarna, Akademin Industri och samhälle, Miljöteknik.
    Design of a portable powered Stirling engine2005Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    This paper presents a feasibility study of developing a portable solar power Stirling engine. A generator is to be coupled to the Stirling engine to generate electricity. This system is proposed to be used for low power electrical equipments such as laptop computer and battery charging at remote area inaccessible to grid-connected electricity supply. The anticipated power of the system is about 30W. Two main components that are critical for the performance of the system are solar thermal collector and Stirling engine. Therefore, in this study, many possible choices for solar thermal collector and Stirling engine have been reviewed. Fresnel reflector is chosen as the solar thermal collector because it is portable and able to concentrate solar radiation to high temperature. A prototype Fresnel reflector was constructed and tested. Although the Stirling engine has been designed preliminarily, it was not constructed due to time constraints. However, a piece of steel was used as the receiver. The rate of energy absorbed by the steel is calculated by measuring the rate of change of the temperature of the steel. The test has shown that, if selective coating is used, a stagnation temperature of above 500°C is possible to be achieved. Moreover, the reflector can remain unadjusted for a duration of 35 minutes. From the calculation, it is found that the optimum operating temperature of the system is about 200°C. However, with an aperture diameter of 1.05m for the Fresnel reflector, the system can only deliver 18.3W of electrical power at an overall efficiency of 3.417%. The system has to be optimized to meet the expected electrical power of 30W. Testing on the prototype has shown that selective coating should be applied directly onto the receiver’s surface without any adhesive in between for achieving high temperature. On cloudy day or at night, the Stirling engine can be heated by other heat sources such as candles, natural gas, wood fuel etc. The Fresnel reflector can also be used as solar cooker when a cooking pot is placed at the focal point of the reflector.

  • 4508. Yong, Lim Say
    et al.
    Bales, Chris
    Högskolan Dalarna, Akademin Industri och samhälle, Miljöteknik.
    Design and fabrication of a portable Fresnel reflector2006Inngår i: Eurosun 2006, Glasgow, UK, 2006Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    This paper presents a feasibility study of a portable Fresnel reflector that was designed and constructed using inexpensive materials and then tested. An aluminium plastic laminated reflector was chosen for its cost, reflectance and flexibility. The prototype Fresnel reflector had nine rings of 5 cm width held in place by a lightweight wooden construction, giving a diameter of 1.05 m. All rings and wooden holders can be assembled and disassembled and be stored in a small bag. In the tests, a piece of steel was used as receiver. Two different types of surface on the receiver were tested, namely Maxorb sheet and black paint. The tests showed that the Maxorb achieved a stagnation temperature of above 500 °C while the black paint achieved less than 400 °C. The optical efficiency for both was 0.26. Moreover, the collector could remain unadjusted for a duration of 35 minutes without the receiver temperature dropping lower than 300°C at the center.

  • 4509.
    Youngjo, Lee
    et al.
    Seoul National University.
    Alam, Moudud
    Högskolan Dalarna, Akademin Industri och samhälle, Statistik.
    Noh, Maengseok
    Pukyong National University, Korea.
    Rönnegård, Lars
    Högskolan Dalarna, Akademin Industri och samhälle, Statistik.
    Skarin, Anna
    Swedish University of Agricultural Science, Uppsala.
    Spatial modeling of data with excessive zeros applied to reindeer pellet-group counts2016Inngår i: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 6, nr 19, s. 7047-7056Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We analyze a real data set pertaining to reindeer fecal pellet-group counts obtained from a survey conducted in a forest area in northern Sweden. In the data set, over 70% of counts are zeros, and there is high spatial correlation. We use conditionally autoregressive random effects for modeling of spatial correlation in a Poisson generalized linear mixed model (GLMM), quasi-Poisson hierarchical generalized linear model (HGLM), zero-inflated Poisson (ZIP), and hurdle models. The quasi-Poisson HGLM allows for both under- and overdispersion with excessive zeros, while the ZIP and hurdle models allow only for overdispersion. In analyzing the real data set, we see that the quasi-Poisson HGLMs can perform better than the other commonly used models, for example, ordinary Poisson HGLMs, spatial ZIP, and spatial hurdle models, and that the underdispersed Poisson HGLMs with spatial correlation fit the reindeer data best. We develop R codes for fitting these models using a unified algorithm for the HGLMs. Spatial count response with an extremely high proportion of zeros, and underdispersion can be successfully modeled using the quasi-Poisson HGLM with spatial random effects.

  • 4510. Young-Thelin, Lorna
    et al.
    Boluk, Karla
    Högskolan Dalarna, Akademin Industri och samhälle, Kulturgeografi.
    A case study of human resource practices in small hotels in Sweden2012Inngår i: Journal of Human Resources in Hospitality & Tourism, ISSN 1533-2845, E-ISSN 1533-2853, Vol. 11, nr 4, s. 327-353Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The competitive advantage of organizations in the hotel industry is their human resources. The aim of the authors in this article is to investigate the human resources practices in small hotels in Sweden. They examine the practices of hotels in three main areas of human resource management, namely: hiring, training and performance evaluation. Although the hotels find their human resources important there has been a lack of attention devoted to the development of human resources systems and processes. Accordinly, the implementation and development of human resources systems and procedures depends on the background of the hotel manager or operator and available financial resources. 

  • 4511.
    Yousaf, Naeem
    Högskolan Dalarna, Akademin Industri och samhälle, Maskinteknik.
    Calucaltion of waste heat from hot rolled steel coils at SSAB and its recovery2009Independent thesis Basic level (degree of Bachelor)Oppgave
    Abstract [en]

    Hot rolling process is heat input process. The heat energy in hot rolled steel coils can be utilized. At SSAB Strip Product Borlänge when the hot rolled steel coils came out of the hot rolling mill they are at the temperature range of 500°C to 800°C. Heat energy contained by the one hot rolled steel coil is about 1981Kwh whereas the total heat energy for the year 2008 is 230 GWh/year.The potential of heat is too much but the heat dissipation rate is too slow. Different factors on which heat dissipation rate depends are discussed. Three suggestions are proposed to collect the waste heat from hot rolled steel coils.The 2nd proposal in which water basin is suggested would help not only to collect the waste heat but to decrease in the cooling time.

  • 4512.
    Yribarren, Pedro
    Högskolan Dalarna, Akademin Industri och samhälle, Miljöteknik.
    Evaluation and simulation of a combined system based on heat pump, solar collectors and borehole storage2002Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    The combination of solar collectors with heat pumps and any kind of ground storage offers further possibilities to reduce the electricity demand in buildings significantly compared to standard heat pump systems. On one hand the solar collector enables to deliver higher temperatures to the evaporator of the heat pump and to generate the ground storage much faster, on the other handthe solar heat can be used directly although this requires more advanced system designs and control strategies. In this thesis work the system combination mentioned above has been analysed in two different ways. First, measured data from a system placed in the garden at SERC have been evaluated and second, system simulation with the program TRNSYS have been carried out analysing different designs and configurations for single components in the system. For the evaluation of the measured data files were created that enable to run the whole procedure automatically and to create diagrams for the most important values at the same time. The analysis of the test system at SERC showed that the coefficients of performance of the heat pump for different source and load temperatures do not correspond with the curves from the heat pump company. The simulation work was concentrated mainly on the analysis of the borehole model, further calculations included different system designs for the combination of different solar collectors with a heat pump and borehole storage. In both parts the influence of different parameters on the system performance was analysed regarding as well as energetic values as the temperatures in the ground storage. The advantage of this system combination and the possibilities to increase the system performance were emphasised although it became obvious that further investigations are necessary to open up the whole potential.

  • 4513.
    Yu, Jiaxuan
    Högskolan Dalarna, Akademin Industri och samhälle, Nationalekonomi.
    Factors affecting tourists’ length of stay in Rome2014Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    This thesis documents the design and result of a study on tourists’ length of stay in

    Rome, as a function of age, season and several other factors. Two models are tested. An OLS

    model is developed to examine relation between number of nights stayed in Rome and 15

    factors. A binary logit model is developed and estimated to examine the assumed relationship

    between the probability of staying longer than one week and the same 15 factors. Survey data

    of Rome visitors collected by the Pragma and Doxa consulting firms are used in the analysis.

    The results indicate that travelling by car and remote travel are important for staying longer

    in Rome. Moreover, season, employment status, whether repeated visit, shopping

    opportunities, good tourist information, package holiday and type of accommodation also

    play a role for length of stay.

  • 4514. Yu, Z.
    et al.
    Song, William Wei
    Högskolan Dalarna, Akademin Industri och samhälle, Informatik.
    Zheng, X.
    Chen, D.
    Combining trust propagation and topic-level user interest expansion in recommender systems2016Inngår i: International Journal of Web Services Research, ISSN 1545-7362, E-ISSN 1546-5004, Vol. 13, nr 2, s. 1-19Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    With the development of E-commerce and Internet, items are becoming more and more, which brings a so called information overload problem that it is hard for users to find the items they would be interested in. Recommender systems emerge to response to this problem through discovering user interest based on their rating information automatically. But the rating information is usually sparse compared to all the possible ratings between users and items. Therefore, it is hard to find out user interest, which is the most important part in recommender systems. In this paper, we propose a recommendation method TT-Rec that employs trust propagation and topic-level user interest expansion to predict user interest. TT-Rec uses a reputation-based method to weight users' influence on other users when propagating trust. TT-Rec also considers discovering user interest by expanding user interest in topic level. In the evaluation, we use three metrics MAE, Coverage and F1 to evaluate TT-Rec through comparative experiments. The experiment results show that TT-Rec recommendation method has a good performance. 

  • 4515.
    Yu, Zukun
    et al.
    Zhejiang University.
    Song, William Wei
    Högskolan Dalarna, Akademin Industri och samhälle, Informatik.
    Zheng, Xiaolin
    Zhejiang University.
    Chen, Deren
    Zhejiang University.
    A Recommender System Model Combining Trust with Topic Maps2013Inngår i: World Wide Web: Internet and Web Information Systems: APWeb 2013, 2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Recommender Systems (RS) aim to suggest users with items that they might like based on users' opinion on items. In practice, information about the users' opinion on items is usually sparse compared to the vast information about users and items. Therefore it is hard to analyze and justify users' favorites, particularly those of cold start users. In this paper, we propose a trust model based on the user trust network, which is composed of the trust relationships among users. We also introduce the widely used conceptual model Topic Map, with which we try to classify items into topics for Recommender analysis. We novelly combine trust relations among users with Topic Maps to resolve the sparsity problem and cold start problem. The evaluation shows our model and method can achieve a good recommendation effect.

  • 4516. Yuan, Y
    et al.
    Ouyang, L
    Sun, L
    Cao, X
    Xiang, B
    Zhang, Xingxing
    Högskolan Dalarna, Akademin Industri och samhälle, Energiteknik.
    Effect of connection mode and mass flux on the energy output of a PVT hot water system2017Inngår i: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 158, s. 285-294Artikkel i tidsskrift (Fagfellevurdert)
  • 4517. Yuhan, Z.
    et al.
    Jinshun, W.
    Mu, L.
    Zhang, Xingxing
    Högskolan Dalarna, Akademin Industri och samhälle, Energiteknik.
    Lining, Z.
    Weiya, Z.
    Weijie, Z.
    Jun, W.
    Liang, X.
    Yixuan, W.
    Research on Operation Strategy of Solar Assisted Air Source Heat Pump System2019Inngår i: IOP Conference Series: Materials Science and Engineering, 2019, Vol. 56, nr 1, artikkel-id 012028Konferansepaper (Fagfellevurdert)
  • 4518.
    Yveborg, Zandra
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Grafisk teknik.
    Isaksson, Erik
    Högskolan Dalarna, Akademin Industri och samhälle, Grafisk teknik.
    Kundnytta med JDF-flöde2006Independent thesis Basic level (degree of Bachelor)Oppgave
    Abstract [sv]

    Examensarbetet har gjorts utifrån Företaget AB där kundnyttan med JDF har utretts. Rapporten presenterar de för- och nackdelar med JDF-flöde som framkommit under projektets gång. Man kan välja att utnyttja JDF på olika sätt. I rapporten har tre hypoteser ställts mot varandra där utnyttjandegraden av JDF kontra för- och nackdelar för kunder och tryckeri presenterats.

  • 4519.
    Yvell, Karin
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik. KTH, Materialvetenskap.
    Experimental Studies of Deformation Structures in Stainless Steels using EBSD2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In this thesis, the focus has been the study of deformation structures in stainless steels by using electron backscatter diffraction (EBSD). Via increased knowledge of the evolution of the substructure during deformation, the design and control of the manufacturing process can be improved.

    A relation was found between the active deformation mechanisms, the evolution of low angle boundaries (LABs) and the strain hardening rate. When deformation twinning was an active deformation mechanism in an austenitic stainless steel with lower stacking fault energy (SFE), the strain hardening rate was maintained up to large strains due to formation of LABs. The deformation twin boundaries acted as new obstacles for dislocation slip which in turn increased the formation of LABs even further. During deformation by slip in an austenitic stainless steel with a higher SFE, the strain hardening rate instead decreased when LABs were formed. A high value of SFE promotes dislocation cross slip which in turn increases annihilation of dislocations leading to a minor increase in LAB formation.

    Deformation structures formed in surface grains during in situ tensile tests were found to develop at lower strains than in bulk grains obtained from interrupted conventional tensile tests. This behavior is consistent with the fact that dislocations sources and deformation twinning operate at approximately half the stress on a free surface as compared to the bulk.

    The deformation structures were quantified by measuring size distributions for entities bounded by LABs and high angle boundaries (HABs). The size distributions were found to be well described by bimodal lognormal distribution functions. The average size for the distribution of small grains and subgrains correlated well with the mean free distance of dislocation slip and to the strain hardening.

  • 4520.
    Yvell, Karin
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik. KTH, Materialvetenskap.
    Engberg, Göran
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Deformation structures in a duplex stainless steel2018Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 941, s. 176-181Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The evolution of the deformation structure with strain has been studied using electron backscatter diffraction (EBSD). Samples from interrupted uniaxial tensile tests and from a cyclic tension/compression test were investigated. The evolution of low angle boundaries (LABs) was studied using boundary maps and by measuring the LAB density. From calculations of local misorientations, smaller orientation changes in the substructure can be illustrated. The different orientations developed with strain within a grain, due to operation of different slip systems in different parts of the grain, were studied using a misorientation profile showing substantial orientation changes after a true strain of 0.24. The texture evolution with increasing strain was followed by using inverse pole figures (IPFs). The observed substructure development in the ferritic and austenitic phases could be successfully correlated with the stress-strain curve from a tensile test. LABs were first observed in the different phases when the strain hardening rate changed in appearance indicating that cross slip started to operate as a significant dislocation recovery mechanism. The evolution of the deformation structure is concluded to occur in a similar manner in the austenitic and ferritic phases but with different texture evolution for the two phases.

  • 4521.
    Yvell, Karin
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Engberg, Göran
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Microstructure evolution in an austenitic stainless steel during wire rolling2013Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 753, s. 407-410Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Material characterization is of great importance for example to improve and further develop physically based models for predicting the microstructural evolution in steels during and after hot deformation. The aim of this study was to characterize the microstructure evolution during wire rod rolling of an austenitic stainless steel of type AISI 304L in a wire rod block, consisting of eight pairs of rolls, using electron backscatter diffraction. The investigation showed that the grain size in the center of the bar decreases during the first four passes. The grain size decrease from 6.5 Όm after the first roll pass down to 2 Όm, and only small changes was measured in the overall grain size during the last four passes. The subgrain size adopts an almost constant size of 0.9 Όm from the second until the fifth roll pass. During the first 3 passes almost no recrystallization is observed and strain accumulates. Partial recrystallization then starts and for the last 3 passes the recrystallization is almost complete and the texture is nearly random. © (2013) Trans Tech Publications, Switzerland.

  • 4522.
    Yvell, Karin
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Grehk, T. M.
    Engberg, Göran
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Microstructure characterization of 316L deformed at high strain rates using EBSD2016Inngår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 122, s. 14-21Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Specimens from split Hopkinson pressure bar experiments, at strain rates between ~ 1000–9000 s− 1 at room temperature and 500 °C, have been studied using electron backscatter diffraction. No significant differences in the microstructures were observed at different strain rates, but were observed for different strains and temperatures. Size distribution for subgrains with boundary misorientations > 2° can be described as a bimodal lognormal area distribution. The distributions were found to change due to deformation. Part of the distribution describing the large subgrains decreased while the distribution for the small subgrains increased. This is in accordance with deformation being heterogeneous and successively spreading into the undeformed part of individual grains. The variation of the average size for the small subgrain distribution varies with strain but not with strain rate in the tested interval. The mean free distance for dislocation slip, interpreted here as the average size of the distribution of small subgrains, displays a variation with plastic strain which is in accordance with the different stages in the stress-strain curves. The rate of deformation hardening in the linear hardening range is accurately calculated using the variation of the small subgrain size with strain.

  • 4523.
    Yvell, Karin
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Grehk, T. M.
    Hedström, P.
    Borgenstam, A.
    Engberg, Göran
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    EBSD analysis of surface and bulk microstructure evolution during interrupted tensile testing of a Fe-19Cr-12Ni alloy2018Inngår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 141, s. 8-18Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract The microstructure evolution in both surface and bulk grains in a pure Fe-19Cr-12Ni alloy has been analyzed using electron backscatter diffraction after tensile testing interrupted at different strains. Surface grains were studied during in situ tensile testing performed in a scanning electron microscope, whereas bulk grains were studied after conventional tensile testing. The evolution of the deformation structure in surface and bulk grains displays a strong resemblance but the strain needed to obtain a similar deformation structure is lower in the case of surface grains. Both slip and twinning are observed to be important deformation mechanisms, whereas deformation-induced martensite formation is of minor importance. Since the stacking fault energy (SFE) is low, 17mJ/m2, dynamic recovery by cross slip of un-dissociated dislocations is unfavorable. This reduces the annihilation of dislocations which in turn leads to a significant increase of low angle boundaries with increasing strain. The low SFE also favors formation of deformation twins which reduces the slip distance, leading to a hardening similar to the Hall-Petch relation. The combination of a low ability for cross-slip and a reduced slip distance caused by twinning is concluded to be the main reason for maintaining a high strain-hardening rate up to strains close to necking.

  • 4524.
    Yvell, Karin
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Grehk, T. M.
    Hedström, P.
    Borgenstam, A.
    Engberg, Göran
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Microstructure development in a high-nickel austenitic stainless steel using EBSD during in situ tensile deformation2018Inngår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 135, nr Supplement C, s. 228-237Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Plastic deformation of surface grains has been observed by electron backscatter diffraction technique during in situ tensile testing of a high-nickel austenitic stainless steel. The evolution of low- and high-angle boundaries as well as the orientation changes within individual grains has been studied. The number of low-angle boundaries and their respective misorientation increases with increasing strain and some of them also evolve into high-angle boundaries leading to grain fragmentation. The annealing twin boundaries successively lose their integrity with increasing strain. The changes in individual grains are characterized by an increasing spread of orientations and by grains moving towards more stable orientations with 〈111〉 or 〈001〉 parallel to the tensile direction. No deformation twins were observed and deformation was assumed to be caused by dislocation slip only.

  • 4525.
    Yvell, Karin
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    Lindgren, Michael
    Bexell, Ulf
    Högskolan Dalarna, Akademin Industri och samhälle, Materialteknik.
    A microstructural investigation of roll formed austenitic stainless steel2013Inngår i: Sheet metal 2013: Key engineering metals, 2013, Vol. 549, s. 364-371Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Due to high production rates and the possibility to form complex geometries roll forming has become an increasingly popular forming process for sheet metal. Increasing quantities of high strength steels are used today but can be difficult to form due to their low ductility. One way to partly overcome this problem is to heat the steel in the forming area thus locally increasing the ductility. In the present study partially heated cold rolled high strength AISI 301 type austenitic stainless steel was investigated using electron backscattered diffraction (EBSD), and the results were compared to microhardness measurements. The results show that partial heating will give an almost complete reverse martensite transformation, i.e. martensite (alpha') transforms to austenite (gamma), close to the surfaces and grain growth in the middle of the steel sheet. The extension of the heat affected zone can be determined using either microhardness or EBSD measurements. Both these measurements can be used to determine the position of the neutral layer after roll forming. The hardness measurement cannot distinguish between microstructural features but the results are in good agreement with the EBSD results for volume fraction of alpha'-martensite. A major advantage of using EBSD is the possibility to characterize and follow the microstructural development when heating and roll forming.

  • 4526.
    Zager, Merle
    Högskolan Dalarna, Akademin Industri och samhälle, Turismvetenskap.
    Rättvik – This is where it happens!?: Enhancing stakeholder collaboration for rural tourismdevelopment with the help of nearby mega sport events2015Independent thesis Advanced level (degree of Master (Two Years)), 10 poäng / 15 hpOppgave
    Abstract [en]

    The presented study investigates how rural tourism destinations can benefit from a mega sport event that is hosted in a city nearby. This is done by examining the case study of Camp Norway, an initiative of the municipality of Rättvik, which was hosted during the FIS Nordic Ski World Championship in Falun 2015. For this purpose semi-structured interviews were conducted with several key stakeholders and members of the steering committee of the project. The research aimed to answer what the concept was actually about, what the stakeholders expected, how they collaborated and how they evaluate the project. It was explored that a main intention of the project was to bring the tourism stakeholders of the municipality together and thus enhance their collaboration for the future. Although the expectations concerning visitor numbers and economic benefits were too high and have not been met, the overall concept evaluation is still very positive. This is due to the fact that the actors have recognised the importance of close stakeholder collaborations especially in the rural tourism industry and have successfully established a common ground for future projects in Rättvik. The case of Camp Norway can be taken as an example also for other rural tourism destinations, how to improve local stakeholder collaboration by innovatively benefitting from nearby events.

  • 4527.
    Zakrisson, Emma
    Högskolan Dalarna, Akademin Industri och samhälle, Datateknik.
    En granskning av personuppgifters flöde genom Falu kommuns gymnasiala Vuxenutbildning i enlighet med General Data Protection Regulation, GDPR2018Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    On May 25, 2018, the EU's new data protection regulation will come into force throughout the EU. The English name of this regulation is the Data Protection Regulation which is shortened GDPR. The purpose of the new data protection regulation is to ensure people's right to protection of their personal data, which will strengthen personal integrity in an increasingly digitized world. This will be done by establishing rules for the free flow of personal data within the EU. The Data Protection Regulation will place high demands on organizations that have to undergo major change efforts to comply with the regulatory requirements.

    One of the aims of this study has been to investigate whether the operation of the adult education within the municipality of Falun is sustainable in view of the requirements of the new data protection regulation. With this as a starting point, a review of the handling of personal data has been identified. One of the study's issues has been to identify critical points in the adult education activities where personal data incidents could occur. In the study, mixed techniques have been used to gather the necessary information in relation to the questions. Literature studies have been conducted in the field of data protection regulation and information security in general. In addition, gathering of empirical data has been done through oral and written interviews with selected key persons in the organization. Based on this information, a mapping and analysis has been made, which has resulted in an evaluation of the organizations processes in which personal data are handled. With that as a starting point, the questions have been as critical points have been identified and recommended working methods have been presented.

    The study's results show that the municipality of Falun has begun adaptation work to meet the requirements of the new data protection regulation. However, the work has started so late that you still have a lot of work left to implement in the organization. The Data Protection Regulation was adopted on April 27, 2016, which means that in practice they have had at least two years to prepare. For Falun municipality to meet the new requirements of the Data Protection Regulation, key factors are the management's commitment and understanding, as well as the implementation of custom education for all staff in the organization. The study also shows that the adaptation to the new data protection regulation is a continuous work, which should be achieved systematically over time.

    In the environmental surveillance of other municipalities, many have begun their work with an adaptation to the new data protection regulation. These are, like the municipality of Falun, far from fully prepared for the data protection regulation to enter into force on May 25, 2018.

  • 4528. Zalakeviciute, R.
    et al.
    Rybarczyk, Yves
    Högskolan Dalarna, Akademin Industri och samhälle, Mikrodataanalys. Intelligent and Interactive Systems Lab (SI2 Lab) Universidad de Las Americas (UDLA), Ecuador.
    Granda-Albuja, M. G.
    Diaz Suarez, M. V.
    Alexandrino, K.
    Chemical characterization of urban PM10 in the Tropical Andes2019Inngår i: Atmospheric Pollution Research, ISSN 1309-1042, E-ISSN 1309-1042, Vol. 11, nr 2, s. 343-356Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Complex inhalable particles have become one of the main causes to trigger health problems worldwide. While the level of concern depends on the chemical composition of these particles, some regions are poorly studied, particularly, the Andes. In this work, the chemical characterization of atmospheric PM10 filter samples, collected between January and October of 2017, was carried out for the first time in the world's highest capital, Quito, Ecuador. This study investigates PM10 relation with meteorological variables and criteria pollutants. Average PM10 concentrations ranged from 24.9 μg m−3 to 26.2 μg m−3, with some alarming peaks during the episodes of fires and New Year's celebration. The major elements at study sites were Ca, Na, S, Mg, P, K, Fe, Si and Al, while the major water-soluble ion was SO42−. Meteorology plays an important role at this complex terrain city. Factor analysis showed natural dust and soil resuspension as the main source of particulate matter. Moreover, two less urbanized sites showed evidence of industrial activities or airport emissions, while the central city site showed a very strong signal of traffic-related pollution. These results are compared with representative cities around the world. As is the case in developing countries, low-quality diesel fuel is recognized for emitting large amounts of heavy metals, resulting in higher levels of those tracers in traffic flow areas. This work demonstrates the problems facing a midsize city, such as the lack of stricter regulations and, thus compromised air quality. This may imply serious respiratory and cardiovascular health effects.

  • 4529. Zan, Yanjun
    et al.
    Sheng, Zheya
    Lillie, Mette
    Rönnegård, Lars
    Högskolan Dalarna, Akademin Industri och samhälle, Statistik. SLU.
    Honaker, Christa F
    Siegel, Paul B
    Carlborg, Örjan
    Artificial selection response due to polygenic adaptation from a multilocus, multiallelic genetic architecture2017Inngår i: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 34, nr 10, s. 2678-2689Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ability of a population to adapt to changes in their living conditions, whether in nature or captivity, often depends on polymorphisms in multiple genes across the genome. In-depth studies of such polygenic adaptations are difficult in natural populations, but can be approached using the resources provided by artificial selection experiments. Here, we dissect the genetic mechanisms involved in long-term selection responses of the Virginia chicken lines, populations that after 40 generations of divergent selection for 56-day body weight display a 9-fold difference in the selected trait. In the F15 generation of an intercross between the divergent lines, 20 loci explained >60% of the additive genetic variance for the selected trait. We focused particularly on fine-mapping seven major QTL that replicated in this population and found that only two fine-mapped to single, bi-allelic loci; the other five contained linked loci, multiple alleles or were epistatic. This detailed dissection of the polygenic adaptations in the Virginia lines provides a deeper understanding of the range of different genome-wide mechanisms that have been involved in these long-term selection responses. The results illustrate that the genetic architecture of a highly polygenic trait can involve a broad range of genetic mechanisms, and that this can be the case even in a small population bred from founders with limited genetic diversity.

  • 4530.
    Zare, Kourosh Abbas
    Högskolan Dalarna, Akademin Industri och samhälle, Energiteknik.
    Development of a Predictive Control Model for a Heat Pump System Based on Artificial Neural Networks (ANN) approach2019Independent thesis Advanced level (degree of Master (Two Years)), 10 poäng / 15 hpOppgave
  • 4531.
    Zarzycka, Aleksandra
    Högskolan Dalarna, Akademin Industri och samhälle, Turismvetenskap.
    Young tourist’s preferences in context of cultural tourism in Podlasie´s region2017Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    The present paper constitutes a review of the results of a study concerning cultural tourism conducted on a group of students from selected higher education institutions in Bialystok. The aim of this paper is to analyze young tourists' preferences in Podlasie's region in terms of cultural tourism: their choice of activities and attractions, as well as trip related characteristics in contrast to the preferences of young non-cultural tourists. Quantitative research approach has been applied in the study in order to meet the objective of this paper, as the quantitative methods allow to summarize vast sources of information and facilitate comparisons across categories and over time (Kruger, 2003, p.18-19). An online survey was used as a technique to carry out the research. The main results indicate that students, as cultural tourists, prefer a variety of activities (both cultural and non-cultural) in diverse locations and do not limit themselves to any dominant attractions. The work has its value within the cultural tourism literature, as it discusses the potential of the tourist youth market in the developing rural area of post-communist country, Poland. The paper offers suggestions on a more in-depth further research.

  • 4532.
    Zatyko, Judit
    Högskolan Dalarna, Akademin Industri och samhälle, Miljöteknik.
    Solar Radiation from Sisimiut2004Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    The topic of this project was to deal with measured solar radiation and other weather data from Asiaq station 515, sisimiut, Greenland in spring 2004 to make investigations and determinations about the available solar energy in high latitudes; determine the solar radiation on tilted surfaces from radiation on horizontal with the help of different solar radiation models for the test period, and compare the results to the measurements, Determine the ground reflectance during the test period.

  • 4533.
    Zelenková, Iveta
    et al.
    Masaryk University.
    Vyhlídal, Jiří
    Masaryk University.
    Klimplová, Lenka
    Högskolan Dalarna, Akademin Industri och samhälle, Företagsekonomi. Masaryk University.
    Hodnocení možnosti uplatnění vybraných prvků švédského monitoringu potřeb trhu práce v podmínkách ČR2015Inngår i: Fórum sociální politiky, ISSN 1802-5854, Vol. 9, nr 4, s. 2-8Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of the paper is to describe an adapted Swedish qualitative way of monitoring employers' needs on a local or regional labour market and to evaluate its functionality and applicability in environment of Czech public employment services.

  • 4534.
    Zeng, Wenjie
    Högskolan Dalarna, Akademin Industri och samhälle, Turismvetenskap.
    Ready to Cope with the Sharing Economy in Tourism Service: Small and Medium-Sized Travel Agencies in China2016Independent thesis Advanced level (degree of Master (Two Years)), 10 poäng / 15 hpOppgave
    Abstract [en]

    This thesis work investigates the response of China’s SME travel agencies to the growth of

    the sharing economy in travel and tourism services, with the aim to formulate practical

    recommendations for industry insiders. Through in-depth interviews conducted in the city of

    Shanghai, the thesis produces an outline of how the SME travel agencies perceive sharing

    economy in Chinese context. The aspects of business performance are studied for both

    incumbent travel agencies and those emerging sharing start-ups. The key concepts of sharing

    economy are focused and used to examine the sharable potential of SME travel agencies in

    order to achieve the aim of this thesis. It is revealed that SME travel agencies in Shanghai

    have adopted various new practices in response to market changes. It appears that the gradual

    development of their proactive “collaborative activities” interprets the tenets propagated by

    the sharing economy advocates. As sharing propensity becomes formidable, it is

    recommended that SME travel agencies should focus in line with key principles of the

    sharing economy on sharable potential in their products, distribution channels and sales

    personnel.

  • 4535.
    Zetterström, Denise
    Högskolan Dalarna, Akademin Industri och samhälle, Företagsekonomi.
    Revisionsberättelsen & bokslutsrapporten: Små bolags redovisningsalternativ efter avskaffande avrevisionsplikten2015Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Revisionsplikten för små aktiebolag i Sverige avskaffades år 2010. Efter avregleringen harledningen för de små bolagen flera handlingsalternativ för att ändå vara trovärdiga införintressenter. Bolagen kan frivilligt välja mellan att anlita en revisor, låta en auktoriseradredovisningskonsult skapa en bokslutsrapport eller ta hand om den finansiella redovisningenpå egen hand.Studiens syfte är att skapa förståelse och kunskap om bokslutsrapporter ochrevisionsberättelser, om de utifrån kreditgivares synvinkel kan bidra till att öka företagenskreditvärdighet samt förtroende och legitimitet till företagens finansiella redovisning.Resultatet visar att en ren revisionsberättelse ger större trovärdighet hos kreditgivare och ökarföretagens kreditvärdighet jämfört med bokslutsrapporter. Både bokslutsrapporten ochrevisionsberättelsen kan bidra eller stärka företagens legitimitet. Dock ses revisorn ochrevisionsberättelsen som mer vedertaget. Kreditgivarna känner till hur revisorn arbetar, vilkalagar, regler, standarder och normer revisorn följer i sin granskning. Att revisorn ståroberoende till det företag som granskas gör räkenskaperna mer trovärdiga för kreditgivarna.Revisionsberättelsen och revisorn är därför den typ av kontroll som bidrar mest till attkreditgivarna finner förtroende till företaget.Studiens teoretiska referensram används för att tolka och förstå insamlad empirisk data samtstudiens syfte och problemställning. Den teoretiska referensramen består av intressentteorin,principal – agentteorin, legitimeringsteori samt tidigare forskning som kan beröra ämnet.Empiriska data samlades in med semistrukturerade intervjuer. Fyra kreditchefer och fyraföretagsrådgivare från olika banker i Sverige deltog som respondenter. Med hjälp av denteoretiska referensramen och insamlad empiri genomfördes en analys som slutligenresulterade i studiens slutsatser.

  • 4536.
    Zhang, Baoxin
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    How the different time steps weather data affect the simulation results of solar combisystems2009Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    The hourly time step weather data are very common used in the field of evaluations and predictions of the performance of solar heating systems, especially in the computer simulation area. However, studies in [3] states that using the hourly weather data in simulation of solar systems may ignore the variations of solar radiation during one hour, it will cause a inaccurate simulation results. Using the smaller time step weather data instead can resolve this problem and make the simulation results very close to the fact. In this paper, the variations of solar radiation during hourly will be found through comparison of the same weather data based on different time steps (hourly and 6min). A whole weather data reference year based on 6min, 12min, 18min, 30min and 60min in Borlänge, Sweden will be built. Then the total radiation on a sloped surface, clearness index and solar utilizability based on these different time steps weather data will be calculated and compared with each other respectively. The results show that same weather data based on different time steps do not affect the calculation results of total radiation on a sloped surface (collector surface) but they may affect the beam and diffuse fractions and estimate of collector performance. After that all the weather based on different time steps will be used in the simulations of three different solar combisystems. As the result shows, using the hourly weather data leads to relative conservative estimate of solar heating systems compare with that based on shorter time step weather data, although the difference is very limited.

  • 4537.
    Zhang, Fan
    Högskolan Dalarna, Akademin Industri och samhälle, Energiteknik.
    A hybrid structured deep neural network with Word2Vec for construction accident causes classification2019Inngår i: International Journal of Construction Management, ISSN 1562-3599Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    According to the latest fatal work injury rates reported by the Bureau of Labors Statistics, construction sites remain the most hazardous workplaces. In the construction sector, fatality investigation summary reports are available for past accidents and by investigating such reports, valuable insights can be gained. In this study, text mining algorithms are explored for automatic construction accident causes classification. To be more specific, Word2Vec skip-gram model is utilized to learn word embedding from a domain-specific corpus and a hybrid structured deep neural network is proposed by incorporating the learned word embedding for accident reports classification. Dataset from Occupational Safety and Health Administration (OSHA) is employed in the experiment to evaluate the performance of the proposed approach. Besides, five baseline models: support vector machine (SVM), linear regression (LR), K-nearest neighbor (KNN), decision tree (DT), Naive Bayes (NB) are employed to compare with the proposed approach. Experiment results show that the proposed model achieves the highest average weighted F1 score among all models considered in this study. The result also proves the effectiveness of applying Word2Vec skip-gram algorithm for semantic information augmentation. As a result, robustness of the model is improved when classifying cases of low support values.

  • 4538.
    Zhang, Fan
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Energiteknik.
    Fleyeh, Hasan
    Högskolan Dalarna, Akademin Industri och samhälle, Datateknik.
    A Review of Single Artificial Neural Network Models for Electricity Spot Price Forecasting2019Inngår i: European Energy Market 2019, 2019Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Electricity price forecasting plays a crucial role in a liberalized electricity market. In terms of forecasting approaches, computational intelligence based models have been widely used with respect to electricity price forecasting and among all computation intelligence based models, artificial neural networks are most popular among researchers due to their flexibility and efficiency in handling complexity and non-linearity. However, a review of recent applications of neural networks for electricity price forecasting is not found in the literature. The motivation of this paper is to fill this research gap. In this study, existing approaches are analyzed and a summary of the strengths and weaknesses of each approach is presented. Besides, each neural network model is briefly summarized, followed by reviews of the corresponding studies of each neural network with respect to electricity forecasting from year 2010 onwards. Major contributions, datasets adopted as well as the corresponding experiment results are analyzed for each reviewed study. Apart from the review of existing studies, the advantages and disadvantages of each type of neural network model are discussed in details. Compared with neural networks based hybrid models, a single neural network model is easier to be implemented, less complex and more efficient. Scope of the review is the application of non-hybrid neural network models. It is found that most literature focuses on short term electricity price forecasting while medium and long term forecasting still remain relatively uncovered.

  • 4539.
    Zhang, Fan
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Energiteknik.
    Fleyeh, Hasan
    Högskolan Dalarna, Akademin Industri och samhälle, Datateknik.
    A review on electricity price forecasting using neural network based models2018Rapport (Annet (populærvitenskap, debatt, mm))
  • 4540.
    Zhang, Fan
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Energiteknik.
    Fleyeh, Hasan
    Högskolan Dalarna, Akademin Industri och samhälle, Datateknik.
    Hybrid Artificial Neural Networks Based Models for Electricity Spot Price Forecasting - A Review2019Inngår i: 2019 16th European Energy Market Conference (EEM 19), 2019, artikkel-id 8916245Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Electricity price forecasting plays a crucial role in aliberalized electricity market. In terms of forecasting approaches,artificial neural networks are the most popular amongresearchers due to their flexibility and efficiency in handlingcomplexity and non-linearity. On the other hand, a single neuralnetwork presents certain limitations. Therefore, in recent years,hybrid models that combine multiple algorithms to balance outthe advantages of a single model have become a trend. However,a review of recent applications of hybrid neural networks basedmodels with respect to electricity price forecasting is not found inthe literature and hence, the motivation of this paper is to fill thisresearch gap. In this study, methodologies of existing forecastingapproaches are briefly summarized, followed by reviews of neuralnetwork based hybrid models concerning electricity forecastingfrom year 2015 onwards. Major contributions of each study,datasets adopted in experiments as well as the correspondingexperiment results are analyzed. Apart from the review ofexisting studies, the novelty and advantages of each type of hybridmodel are discussed in detail. Scope of the review is theapplication of hybrid neural network models. It is found that theforecast horizon of the reviewed literature is either hour ahead orday ahead. Medium and long term forecasting are notcomprehensively studied. In addition, though hybrid modelsrequire relatively large computational time, time measurementsare not reported in any of the reviewed literature.

  • 4541.
    Zhang, Fan
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Energiteknik.
    Fleyeh, Hasan
    Högskolan Dalarna, Akademin Industri och samhälle, Datateknik.
    Short Term Electricity Spot Price Forecasting Using CatBoost and Bidirectional Long Short Term Memory Neural Network2019Inngår i: 19th European Energy Market Conference (EEM 19), 2019Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Electricity price forecasting plays a crucial role in liberalized electricity markets. Generally speaking, short term electricity price forecasting is essential for electricity providers to adjust the schedule of production in order to balance consumers’ demands and electricity generation. Short term forecasting results are also utilized by market players to decide the timing of purchasing or selling to gain maximized profit. Among existing forecasting approaches, neural networks are regarded as the state of art method. However, deep neural networks are not studied comprehensively in this field, thus the motivation of this study is to fill this research gap. In this paper, a novel hybrid approach is proposed for short term electricity price forecasting. To be more specific, categorical boosting (Catboost) algorithm is used for feature selection and a bidirectional long short term memory neural network (BDLSTM) serves as the main forecasting engine. To evaluate the effectiveness of the proposed approach, two datasets from the Nord Pool market are employed in the experiment. Moreover, the performance of multi-layer perception (MLP) neural network, support vector regression (SVR) and ensemble tree models are evaluated and compared with the proposed model. Results show that the proposed approach outperforms the rest models in terms of mean absolute percentage error (MAPE).

  • 4542.
    Zhang, Fan
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Energiteknik.
    Fleyeh, Hasan
    Högskolan Dalarna, Akademin Industri och samhälle, Datateknik.
    Wang, X.
    Lu, M.
    Construction site accident analysis using text mining and natural language processing techniques2019Inngår i: Automation in Construction, ISSN 0926-5805, E-ISSN 1872-7891, Vol. 99, s. 238-248Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Workplace safety is a major concern in many countries. Among various industries, construction sector is identified as the most hazardous work place. Construction accidents not only cause human sufferings but also result in huge financial loss. To prevent reoccurrence of similar accidents in the future and make scientific risk control plans, analysis of accidents is essential. In construction industry, fatality and catastrophe investigation summary reports are available for the past accidents. In this study, text mining and natural language process (NLP) techniques are applied to analyze the construction accident reports. To be more specific, five baseline models, support vector machine (SVM), linear regression (LR), K-nearest neighbor (KNN), decision tree (DT), Naive Bayes (NB) and an ensemble model are proposed to classify the causes of the accidents. Besides, Sequential Quadratic Programming (SQP) algorithm is utilized to optimize weight of each classifier involved in the ensemble model. Experiment results show that the optimized ensemble model outperforms rest models considered in this study in terms of average weighted F1 score. The result also shows that the proposed approach is more robust to cases of low support. Moreover, an unsupervised chunking approach is proposed to extract common objects which cause the accidents based on grammar rules identified in the reports. As harmful objects are one of the major factors leading to construction accidents, identifying such objects is extremely helpful to mitigate potential risks. Certain limitations of the proposed methods are discussed and suggestions and future improvements are provided.

  • 4543.
    ZHANG, LEI
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Nationalekonomi.
    YOU, XI
    Högskolan Dalarna, Akademin Industri och samhälle, Nationalekonomi.
    The Choice of STIGA Table Tennis Blades: Evidence from China2010Independent thesis Basic level (degree of Bachelor)Oppgave
    Abstract [en]

    The purpose of this paper is to investigate how individuals with different characteristics make their choice-decisions when consuming STIGA table tennis blades, which are combinations of various attributes, such as price, control, attack, etc. It is expected that the general trend of choice behavior on this special commodity can be, at least to some extent, revealed. Data were collected using questionnaires sent to registered members of a table tennis club in China. The questionnaires included information and questions about individuals’ monthly income levels, ages, technique styles, etc. A multinomial logit model was then applied to analyze factors determining Chinese consumers’ choice behavior on STIGA table tennis blades. The results indicated that the main element influencing Chinese consumers’ choice of STIGA ping-pong blades was the technique style and other variables did not seem to influence the choice of table tennis blades. These results might be explained by the limited sample size as well as unmeasured and immeasurable factors. Thus, a more extensive research is needed to be conducted in the future.

  • 4544.
    Zhang, Liming
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Statistik.
    Han, Yang
    Högskolan Dalarna, Akademin Industri och samhälle, Statistik.
    Detecting Major Genes Controlling Robustness of Chicken Body Weight Using Double Generalized Linear Models2010Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    Detecting both the majors genes that control the phenotypic mean and those controlling phenotypic variance has been raised in quantitative trait loci analysis. In order to mapping both kinds of genes, we applied the idea of the classic Haley-Knott regression to double generalized linear models. We performed both kinds of quantitative trait loci detection for a Red Jungle Fowl x White Leghorn F2 intercross using double generalized linear models. It is shown that double generalized linear model is a proper and efficient approach for localizing variance-controlling genes. We compared two models with or without fixed sex effect and prefer including the sex effect in order to reduce the residual variances. We found that different genes might take effect on the body weight at different time as the chicken grows.

  • 4545. Zhang, Nan
    et al.
    Chen, Xiangjie
    Su, Yuehong
    Zheng, Hongfei
    Ramandan, Omar
    Zhang, Xingxing
    Högskolan Dalarna, Akademin Industri och samhälle, Energiteknik.
    Chen, Hongbin
    Riffat, Saffa
    Numerical investigations and performance comparisons of a novel cross-flow hollow fiber integrated liquid desiccant dehumidification system2019Inngår i: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 182, s. 1115-1131Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The heat and mass transfer process of a novel cross-flow hollow fiber integrated liquid desiccant dehumidification system is analysed numerically. Compared with other porous media or packing towers in dehumidification applications, hollow fibre membranes have significant advantages including low weight, corrosion resistant and no liquid droplet carryover. A novel air-KCOOH cross-flow dehumidification system was designed and manufactured, with 5500 hollow fibres formed into a circular module. The variations of the dehumidification effectiveness and moisture removal rates were studied numerically and validated against experimental results under the incoming air mass flow rates of 0.08-0.26kg/s and relative humidity from 55% to 75%. The dehumidification performance comparisons for the proposed system using CaCl2, LiCl and KCOOH as the desiccants have been conducted as well. The results demonstrated that under the same m*(ratio between solution mass flow rate to the air mass flow rate), the proposed system using 62% KCOOH could achieve approximately the same latent effectiveness compared with 40% CaCl2 and 32% LiCl, with the at least 3.1% sensible effectiveness increased by. Therefore, it could be concluded that the proposed system using KCOOH as desiccant could be more applicable for dehumidification purpose compared with other systems using conventional liquid desiccants.

  • 4546.
    Zhang, Pengcheng
    Högskolan Dalarna, Akademin Industri och samhälle, Nationalekonomi.
    Is there wage premium to computer use in Sweden2005Independent thesis Basic level (degree of Bachelor)Oppgave
    Abstract [en]

    This paper examines the wage premium to computer use in Sweden in the early 1990’s. I use simple regression model and interaction terms in my paper to examine the effect of computer use at work. Although the data is only one-year cross-section data, my results clearly show a wage premium to computer use in Sweden. There are also interesting findings in my paper by using Swedish data. From the results, I find wage premium to be related to intensity of computer use at work.

  • 4547. Zhang, S.
    et al.
    Song, William Wei
    Högskolan Dalarna, Akademin Industri och samhälle, Informatik.
    Ding, M.
    Hu, P.
    A multi-semantic classification model of reviews based on directed weighted graph2016Inngår i: 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, s. 424-435Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Semantic and sentimental analysis plays an important role in natural language processing, especially in textual analysis, and has a wide range of applications in web information processing and management. This paper intends to present a sentimental analysis framework based on the directed weighted graph method, which is used for semantic classification of the textual comments, i.e. user reviews, collected from the e-commerce websites. The directed weighted graph defines a formal semantics lexical as a semantic body, denoted to be a node in the graph. The directed links in the graph, representing the relationships between the nodes, are used to connect nodes to each other with their weights. Then a directed weighted graph is constructed with semantic nodes and their interrelationships relations. The experimental results show that the method proposed in the paper can classify the semantics into different classification based on the computation of the path lengths with a threshold. © Springer International Publishing AG 2016.

  • 4548.
    Zhang, Sheng
    et al.
    Nanchang Hangkong Univ, Sch Informat Engn, Nanchang, Peoples R China.;Dalarna Univ, Business Intelligence & Informat, Borlange, Sweden..
    Liu, Xiaodong
    Nanchang Hangkong Univ, Sch Informat Engn, Nanchang, Peoples R China..
    Bao, Xiaoling
    Nanchang Hangkong Univ, Sch Informat Engn, Nanchang, Peoples R China..
    Song, William Wei
    Högskolan Dalarna, Akademin Industri och samhälle, Informatik.
    Multilayer and multi-agent data fusion in WSN2015Inngår i: Web Information Systems Engineering – WISE 2014 Workshops: 15th International Workshops IWCSN 2014, Org2 2014, PCS 2014, and QUAT 2014, Thessaloniki, Greece, October 12-14, 2014, Revised Selected Papers / [ed] Boualem Benatallah, Azer Bestavros, Barbara Catania, Armin Haller, Yannis Manolopoulos, Athena Vakali, Yanchun Zhang, 2015, Vol. 9051, s. 211-225Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In the wireless sensor networks, the hardware limitations of sensor nodes cause high transmission failure rate. We usually increase the density of nodes to improve the quality of information transmission. However, it is difficult for the limited energy supply, storage, and communication bandwidth to transfer large amount of redundant sensory data. So we use data fusion technology to remove the redundant data as much as possible before the data transmission. Data fusion becomes a research hotspot in recent years. In this paper we propose a multilayer and multi-agent data fusion mode, and analyze the proposed mode performance in three aspects: hops, energy consumption and network delay. The simulation experiments show that, if reasonably suitable parameters, such as the network scale, the number and size of agents, the data processing cost, are selected, the mobile agent mode is much better than the client/server mode.

  • 4549.
    Zhang, Sheng
    et al.
    Nanchang Hangkong Univ, Sch Informat Engn, Nanchang, Peoples R China..
    Wang, Xin
    Nanchang Hangkong Univ, Sch Informat Engn, Nanchang, Peoples R China..
    Yao, Minghui
    Nanchang Hangkong Univ, Sch Informat Engn, Nanchang, Peoples R China..
    Song, William Wei
    Högskolan Dalarna, Akademin Industri och samhälle, Informatik. Dalarna Univ, Business Intelligence & Informat, Borlange, Sweden..
    Community-based message transmission with energy efficient in opportunistic networks2016Inngår i: Web Information Systems Engineering – WISE 2016: 17th International Conference, Shanghai, China, November 8-10, 2016, Proceedings, Part II, 2016, Vol. 10042, s. 411-423Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An Opportunistic Networks is a wireless self-organized network, in which there is no need to build a fixed connectivity between source node and destination node, and the communication depends on the opportunity of node meeting. There are some classical message transmission algorithms, such as PRoPHET, MaxProp, and so on. In the Opportunity Networks with community characteristic, the different message transmission strategies can be sued in inter-community and intra-community. It improves the message successful delivery ratio significantly. The classical algorithms are CMTS and CMOT. We propose an energy efficient message forwarding algorithm (EEMF) for community-based Opportunistic Networks in this paper. When a message is transmitted, we consider not only the community characteristic, but also the residual energy of each node. The simulation results show that the EEMF algorithm can improve the message successful delivery ratio and reduce the network overhead obviously, in comparison with classical routing algorithms, such as PRoPHET, MaxProp, CMTS and CMOT. Meanwhile the EEMF algorithm can reduce the node's energy consumption and prolong the lifetime of network.

  • 4550.
    Zhang, Xiaoxue
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Sun, Qiao
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Performance Evaluation of a Grid-connected PV system in Falun2009Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    The photovoltaic system of 150WP in Falun is on the sloped roof which is 14 degree with east and west orientations. A calibration of the radiation sensors has been done in order to correct the voltage drop caused by the extended cable length. The radiation sensors are calibrated by comparing the measured irradiance of the PV system with the reference irradiance which is measured by a portable data logger system. The annual performance of the system is evaluated over one year from April 08 to March 09 according to IEC 61724. Two other PV systems are compared with Falun system based on the annual performance of each system. The total system energy production of one year is about 96 MWh and the performance ratio PR is 0.817.

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