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  • 151.
    Abeysekera, John
    et al.
    Luleå tekniska universitet.
    Lönnroth, Emma-Christin
    Piamonte, Dominic Paul T
    Luleå tekniska universitet.
    Shahnavaz, Houshang
    Welcoming the millennium from a decade of growth and development in ergonomics education and promotion2001Inngår i: International Journal of Industrial Ergonomics, ISSN 0169-8141, E-ISSN 1872-8219, Vol. 27, nr 6, s. 365-Artikkel i tidsskrift (Annet vitenskapelig)
  • 152.
    Abeysekera, John
    et al.
    Luleå tekniska universitet.
    Shahnavaz, Houshang
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Arbetsvetenskap.
    Adaptation to discomfort in personal protective devices: an example with safety helmets1990Inngår i: Ergonomics, ISSN 0014-0139, E-ISSN 1366-5847, Vol. 33, nr 2, s. 137-145Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Discomfort in the use of personal protective devices (PPD) has been one of the chief causes of their non-use. A field trial using industrial helmets was carried out to ascertain whether by training and repeated wearing subjects could experience a significant adaptation to discomfort. Ten subjects took part in the trial in a tropical environment by wearing helmets repeatedly (6 h a day) for one month. Subjective evaluations of discomfort were made at the end of the 1st, 3rd, 5th, 14th and 30th day. It was revealed that complaints of discomfort, viz. hotness, heaviness, bad fit, etc., decreased markedly throughout the 30 day period. Though positive responses of adaptation to discomfort seem to reach an optimum towards 30 days, it is difficult to draw any conclusions on the optimum period of adaptation for each discomfort factor. In relation to inherent discomforts that are extremely difficult to overcome without compromising the protection efficiency of a PPD, the principle of adaptation seems to be a very important facet which has to be developed for an effective PPD programme.

  • 153. Abhale, P.B.
    et al.
    Guha, M
    Nurni, Viswanathan
    Ballal, N.B.
    Prediction of gas flow through layered burden prolies in blast furnace2006Konferansepaper (Fagfellevurdert)
  • 154. Abhale, P.B.
    et al.
    Guha, M.
    Ramna, M.V.
    Nurni, Viswanathan
    Ballal, N.B.
    Prediction of cohesive zone in a blast furnace using wall pressure tap data: modelling appproach2008Konferansepaper (Fagfellevurdert)
  • 155. Abhale, P.B.
    et al.
    Guna, M.
    Ramna, R.V.
    Nurni, Viswanathan
    Investigation of computational aspects in simulation of gas flow in blast furnace2009Konferansepaper (Fagfellevurdert)
  • 156. Abhale, P.B.
    et al.
    Nurni, Viswanathan
    Ballal, N.B.
    Blast furnace modelling2005Konferansepaper (Fagfellevurdert)
  • 157.
    Abhale, P.B.
    et al.
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay.
    Nurni, Viswanathan
    Ballal, N.B.
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay.
    Efficient simulation of gas flow in blast furnace2009Inngår i: Computers, Materials & Continua, ISSN 1546-2218, Vol. 10, nr 2, s. 195-216Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Simulation of gas flow in a multilayered non-isothermal packed bed is useful for blast furnace operators in deciding appropriate charging strategy. While using an anisotropic form of Ergun equation to simulate gas flow through such systems, a new solution methodology for non-isothermal gas with varying density flowing through a layered burden has been proposed. This involves handling non-linearity due to gas density variation with pressure and temperature by solving for the square of pressure instead of pressure directly and handling the non-linearity due to vertical bar nu vertical bar term in the Ergun equation by solving linearized form of Ergun equation and updating vertical bar nu vertical bar iteratively. The proposed scheme is capable of predicting the effect of layer structure on gas flow with economy in number of grid points as well as computation time

  • 158. Abhale, P.B.
    et al.
    Nurni, Viswanathan
    Ballal, N.B.
    Efficient simulation of gas flow in blast furnace2008Konferansepaper (Fagfellevurdert)
  • 159. Abhale, P.B.
    et al.
    Yadav, V.K.
    Nurni, Viswanathan
    Ballal, N.B.
    Investigation of mal-distribution in blast furnace aerodynamics using a three dimensional simulation model2010Konferansepaper (Fagfellevurdert)
  • 160.
    Abhale, Prakash Bansi
    et al.
    Global R and D, ArcelorMittal, Kolkatta.
    Yadav, Vishal Kumar
    Department of Metallurgy and Materials Engineering (MTM), Katholieke Universiteit, Leuven.
    Nurni, Viswanathan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Ballal, Bharath Nidambur
    Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay.
    Efficient computation of gas flow in blast furnace in 3-D2012Inngår i: 6th Int. Congress on the Science and Technology of Ironmaking 2012, ICSTI 2012: Including Proceedings from the 42nd Ironmaking and Raw Materials Seminar, and the 13th Brazilian Symp. on Iron Ore, 2012, Vol. 1, s. 722-732Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Blast furnace continues to occupy prominent place among iron making technologies as it accounts for more than 90% of the hot metal produced in the world. In India, as a part of initiative from Ministry of Steel, efforts are being made to develop offline as well as online models with an aim to improve blast furnace performance. As a part of this effort, offline comprehensive models simulating the internal state of an operating blast furnace are being developed. Such comprehensive models involve systematic integration of various sub-models for gas flow, solid flow, reaction kinetics, enthalpy balance etc. Unlike in many other systems, these sub-processes are highly interlinked in blast furnace and hence call for large number of iteration among the sub-models which ultimately results in significant computation time. Our efforts in integration of these sub-models have indicated that the gas flow is one of the important bottle necks in achieving faster computation. This has led to a development of new and efficient computation scheme to simulate the gas flow in 2-D [1]. This new scheme provided efficient way of handling complex burden profile in a blast furnace. This paper presents the extension of this 2-D gas flow model to 3-D. Further, the 3-D model has been used to investigate the asymmetry in gas flow which can arise from blanking the tuyeres, asymmetric fusion or cohesive zone or formation scabs or scaffolds in the furnace behavior

  • 161.
    Abid, Fahim
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Busatto, Tatiano
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Rönnberg, Sarah
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Intermodulation due to interaction of photovoltaic inverter and electric vehicle at supraharmonic range2016Inngår i: 2016 17th International Conference on Harmonics and Quality of Power, Piscataway. NJ, 2016, s. 685-690, artikkel-id 7783471Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Advent of power electronic switching is introducing more and more non-linear loads in the low voltage grid. Besides harmonic current generation in the frequency range below 2 kHz, these non-linear loads are also responsible for current emission in the range of 2 kHz to 150 kHz, commonly known as supraharmonic emission. Supraharmonic currents mainly flow between nearby appliances and heavily influence the overall emission of neighboring devices. This paper presents an analysis of supraharmonic interaction between a photovoltaic inverter and an electric vehicle. It has been noticed that intermodulation distortion arises as a result of interaction between different switching frequencies used by the devices. Later, additional household equipment were added to photovoltaic and electric vehicle to observe their effect on intermodulation distortion. All the measurements were conducted in a controlled laboratory environment imitating a domestic customer.

  • 162.
    Abid Musa, Miriam
    Luleå tekniska universitet. Sweco Rail AB.
    Sweco Rail handbok för avbrottsfri kraftförsörjning till Trafikverkets linjebundna signalanläggningar2018Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
  • 163.
    Abiri, Olufunminiyi
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Non-local models in manufacturing simulations2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Ductile fracture presents challenges with respect to material modelling andnumerical simulations of localization. The strain and damage localization maybe unwanted as it indicates a failure in the process or, as in the case ofmachining and cutting, a wanted phenomenon to be controlled. The latterrequires a higher accuracy regarding the modelling of the underlying coupledplastic and fracturing/damage behaviour of the material, metal in the currentcontext as well as the stability and robustness of the simulation procedure.This aim of this work is to develop, evaluate and implement formulations thatcan efficiently and reliably handle localization problems in machiningsimulations. The focus is on non-local models. The non-local models extendthe standard continuum mechanics theory by using non-local continuumtheory in order to achieve mesh independent results when simulating fractureor shear localization.The non-local damage model is implemented and various formulations areevaluated in a Matlab™ based finite element code. The chosen algorithm wasthen implemented in commercial software. The implementations remedy themesh sensitivity problem and gives convergent solution for metal cuttingsimulations with reasonable cost. The length scale associated with the nonlocalmodels are in the current context considered as a numericalregularization parameter. The model has been applied in machiningsimulations and compared with measurements from industry.Keywords: Finite element simulation; Non-local damage; Plasticity; Machining

  • 164.
    Abiri, Olufunminiyi
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Simplifications of non-local damage models2014Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Ductile fracture presents challenges with respect to material modelling and numerical simulations of localization. The strain and damage localization may be unwanted as it indicates a failure in the process or, as in the case of machining and cutting, a wanted phenomenon to be controlled. The latter requires a higher accuracy regarding the modelling of the underlying coupled plastic and fracturing/damage behaviour of the material, metal in the current context as well as the robustness of the simulation procedure. The focus of this thesis is on efficient and reliable finite element solution of the localization problem through the non-local damage model. The non-local damage model extends the standard continuum mechanics theory by using non-local continuum theory in order to achieve mesh independent results when simulating fracture or shear localization. In this work, the non-local damage model and its various simplifications are evaluated in an in-house finite element code developed using Matlab™. The accuracy, robustness, efficiency and costs of the models are investigated and also compared to a general multi-length scale finite element formulation. A numerical study versus published data is used to demonstrate the validity of the model. The explicit non-local damage variant will be implemented in a commercial finite element code for use in machining simulation

  • 165.
    Abiri, Olufunminiyi
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Non-local damage models in manufacturing simulations2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Localisation of deformation is a problem in several manufacturing processes. Machining is an exception where it is a wanted feature. However, it is always a problem in finite element modelling of these processes due to mesh sensitivity of the computed results. The remedy is to incorporate a length scale into the numerical formulations in order to achieve convergent solutions. Different simplifications in the implementation of a non-local damage model are evaluated with respect to temporal and spatial discretisation to show the effect of different approximations on accuracy and convergence.

  • 166.
    Abiri, Olufunminiyi
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Non-local damage models in manufacturing simulations2015Inngår i: European journal of mechanics. A, Solids, ISSN 0997-7538, E-ISSN 1873-7285, Vol. 49, s. 548-560Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Localisation of deformation is a problem in several manufacturing processes. Machining is an exception where it is a wanted feature. However, it is always a problem in finite element modelling of these processes due to mesh sensitivity of the computed results. The remedy is to incorporate a length scale into the numerical formulations in order to achieve convergent solutions. Different simplifications in the implementation of a non-local damage model are evaluated with respect to temporal and spatial discretisation to show the effect of different approximations on accuracy and convergence.

  • 167.
    Abiri, Olufunminiyi
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Qin, Hao
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Comparison of Multiresolution Continuum Theory and Nonlocal Dame model for use in Simulation of Manufacutring Processes2016Inngår i: International Journal for Multiscale Computational Engineering, ISSN 1543-1649, Vol. 14, nr 1, s. 81-94Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Modelling and simulation of manufacturing processes may require the capability to account for localization behavior, often associated with damage/fracture. It may be unwanted localization indicating a failure in the process or, as in the case of machining and cutting, a wanted phenomenon to be controlled. The latter requires a higher accuracy regarding the modelling of the underlying physics, as well as the robustness of the simulation procedure. Two different approaches for achieving mesh-independent solutions are compared in this paper. They are the multiresolution continuum theory (MRCT) and nonlocal damage model. The MRCT theory is a general multilength-scale finite element formulation, while the nonlocal damage model is a specialized method using a weighted averaging of softening internal variables over a spatial neighborhood of the material point. Both approaches result in a converged finite element solution of the localization problem upon mesh refinement. This study compares the accuracy and robustness of their numerical schemes in implicit finite element codes for the plane strain shear deformation test case. Final remarks concerning ease of implementation of the methods in commercial finite element packages are also given.

  • 168.
    Abiri, Olufunminiyi
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik. University of Johannesburg, South Africa.
    Svoboda, Ales
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Wedberg, Dan
    Controlling Thermal Softening Using Non-Local Temperature Field in Modelling2016Inngår i: Journal of Machining and Forming Technologies, ISSN 1947-4369, Vol. 8, nr 1-2, s. 13-28Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    One of the aims of this work is to show that thermal softening due to the reduced flow strength of a material with increasing temperature may cause chip serrations to form during machining. The other purpose, the main focus of the paper, is to demonstrate that a non-local temperature field can be used to control these serrations. The non-local temperature is a weighted average of the temperature field in the region surrounding an integration point. Its size is determined by a length scale. This length scale may be based on the physics of the process but is taken here as a regularization parameter.

  • 169.
    Abiri, Olufunminiyi
    et al.
    Institute of Intelligent Systems, University of Johannesburg.
    Wedberg, Dan
    AB Sandvik Coromant.
    Svoboda, Ales
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Non-Local Modelling of Strain Softening in Machining Simulations2017Inngår i: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 225, artikkel-id 012053Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Non-local damage model for strain softening in a machining simulation is presented in this paper. The coupled damage-plasticity model consists of a physically based dislocation density model and a damage model driven by plastic straining in combination with the stress state. The predicted chip serration is highly consistent with the measurement results. 

  • 170. Abitew, Aymiro
    Hydro-Geotechnical Study of Tailings at Aitik Mine: Emphasis on Hydraulic Conductivity of the Deposit2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The main objective of this study is to characterize the tailings deposit at Aitik Mine in terms of its hydro geotechnical properties with more emphasis on hydraulic conductivity and present their vertical and horizontal distribution. In this study, relationship between each parameter has also been identified. The investigation has been done in three sections which cover approximately 3km2 of area and 4-5meters vertically. 3-5 test pits have been excavated in each section and disturbed and undisturbed samples are collected from various levels. Apart from in situ tests like balloon density, laboratory investigations have been done on the collected samples. These tests includes: Proctor compaction, particle density termination, grain size analysis, and permeability. Evaluation of existing empirical relations between grain size analysis and hydraulic conductivity were also one of the aims of this thesis work.The horizontal hydraulic conductivity has been found to have a good correlation to fine fraction and void ratio. Similar to the results of Jantzer et al (2008), the increased void ratio did not correspond to vertical hydraulic conductivity. Based on evaluation of Hazen (1911) and Chapuis et al (2003) formulas using the samples collected, conclusions have been made. Therefore, Hazen formula (1911) has given 25 and 45 times the measured values of vertical and horizontal hydraulic conductivity respectively. On the other hand, Chapuis et al (2003) has not been succeeded for prediction of hydraulic conductivity of undisturbed samples. However, it has given comparatively good prediction of hydraulic conductivity for disturbed samples which are compacted to their field dry density. Particle density, porosity and void ratio results are in agreement with the range determined by Yunxin (2001), Shamsai (2007), and Jantzer et al (2008) on different tailings deposit. Ice layers are encountered exactly above layers with higher silt and clay contents. Silty SAND is discovered to be the predominant soil type in the investigated area.Because the study was able to cover only part of the whole deposit, further detailed investigation covering the whole area and depth of the deposit is recommended to be done in the future. Additionally, monitoring and continuous measurements are important to minimize uncertainty that could be caused by seasonal tailings property changes.

  • 171. Abitew, Aymiro
    et al.
    Zeinali, Amin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Hydraulic conductivity of tailings deposit used as dam construction material at Aitik mine in Sweden2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Distribution of vertical and horizontal hydraulic conductivity and their correlation to geotechnical parameters affecting the hydraulic conductivity of tailings deposit at Aitik mine have been determined. The investigation was carried out along three sections which cover approximately 3km2 of area and 4-5meters of thickness. 3-5 test pits have been excavated in each section and samples are collected from various levels. The horizontal hydraulic conductivity has been found to have a good relation with fraction of fine particles in the deposit and void ratio. However, similar to the results of Jantzer et al (2008) from the same mine, the vertical hydraulic conductivity did not correspond to void ratio. According to evaluation of existing empirical relations to estimate hydraulic conductivity from particle size analysis, Hazen formula (1911) gives 25 and 45 times the measured values of vertical and horizontal hydraulic conductivity respectively. On the other hand, Chapuis et al (2003) has not been succeeded for prediction of hydraulic conductivity of undisturbed samples from the investigated area. However, it gives comparatively good prediction of hydraulic conductivity for disturbed samples which are compacted to their field dry density.

  • 172. Abitew, Aymiro
    et al.
    Zeinali, Amin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Hydraulic conductivity of tailings sand used for dam construction at Aitik mine in Sweden2012Inngår i: SWEMP 2012: International symposium on Environmental Issues and Waste Management in Energy and Mineral Production, 2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Distribution of vertical and horizontal hydraulic conductivity and their correlation to geotechnical parameters affecting the hydraulic conductivity of tailings deposit at Aitik mine have been determined. The investigation was carried out along three sections which cover approximately 3km2 of area and 4-5meters of thickness. 3-5 test pits have been excavated in each section and samples are collected from various levels. The horizontal hydraulic conductivity has been found to have a good relation with fraction of fine particles in the deposit and void ratio. However, similar to the results of Jantzer et al (2008) from the same mine, the vertical hydraulic conductivity did not correspond to void ratio. According to evaluation of existing empirical relations to estimate hydraulic conductivity from particle size analysis, Hazen formula (1911) gives 25 and 45 times the measured values of vertical and horizontal hydraulic conductivity respectively. On the other hand, Chapuis et al (2003) has not been succeeded for prediction of hydraulic conductivity of undisturbed samples from the investigated area. However, it gives comparatively good prediction of hydraulic conductivity for disturbed samples which are compacted to their field dry density.

  • 173. Abizadeh, Nastaran
    Adoption of franchising: cultural barriers and pitfalls in Iran2010Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    As the result of globalization, today’s business environment is undergoing a fundamental transformation. Franchising, as a business format for market penetration, has become an accepted strategy for business growth, job creation and economic development. It helps companies to expand into foreign market. It also helps companies to adapt to different cultures and business rules. This thesis focuses on cultural obstacles of franchising in Iran. To identify the cultural barriers, an interview guide was designed based on Hofstede’s cultural model. The interview was conducted among owners, managers and employees of two of the biggest franchising companies that are already working in Iran. For analyzing the data gathered during the interviews, Grounded Theory was used in its three different coding levels, to translate the data and discover the main cultural barriers facing by franchising companies in Iran

  • 174. Abolghasemi Kordestani, Arash
    A conceptual framework for marketing strategy in SMEs regarding export performance as an independent variable: case of Iran2008Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this research a framework has been developed for food exporters, because there were only few strong frameworks in exporting and there were not good ones for Iranian exporters. In this dissertation effects of export performance on organizational commitment to export and also its hidden effect on marketing strategy definition have been considered in order to develop the framework. A new view on export performance has been taken which considers export performance as an independent variable compare to previous ones, also one important consideration which has been chosen is that there is not a pure strategy like standardization or adaptation but it is a matter of degree between these two strategies. After meetings with experts in university and industry and doing pilot test data were collected from Iranian exporter food SMEs from provinces of Iran in order to verify the questions of this research. Results confirmed these hypotheses and some strategies were standardized while some of them were adaptive. Moreover important variables in commitment to export and in marketing strategy have been discussed and it is found that satisfaction with prior year export performance results decrease the commitment of firm in the current year. One of the aims is to show importance and results of export performance in previous year as an independent variable on marketing mix strategy while others considered it as a dependent variable and worked on inverse relationship. These effects have been proved mostly. Also other important variables on defining marketing mix strategy have been shown and effects of export market competition and export market development have been investigated. Finally this framework with help of these factors was developed and has been confirmed with food exporter SMEs questionnaires.

  • 175.
    Abolmasoumi, Amirhossein
    et al.
    Department of Electrical Engineering, Faculty of Engineering, Arak University.
    Sayyaddelshad, Saleh
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Observer design for a class of nonlinear delayed systems with unknown inputs and Markovian jump parameters2012Inngår i: ICCAS 2012: 12th International Conference on Control, Automation and Systems, 2012, s. 1848-1852Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The problem of full-order observer design for a class of delayed nonlinear systems with unknown inputs and Markovian jumping parameters is considered. The design method is formulated as solving a set of linear matrix inequalities (LMI's). Extending the results of nonlinear observer design to Markovian jump systems with time-varying delays is the main advantages of this paper. The sufficient LMI conditions are dependent on both the upper and lower bounds of delay. The effectiveness of the proposed method is shown via an illustrative example.

  • 176. Abongwa, Paul Wanka
    Mineral texture and composition of magnetite in the Sahavaara IOCG deposit, Pajala area: a mineral processing approach2009Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Stora Sahavaara is one of several iron (Cu-Au) deposits of economic potential in the Pajala-Kolari area and it is currently developed for mining by Northland Resources Inc. These deposits are hosted by 2.3-2.0 Ga Karelian greenstones and occur as magnetite-rich lenses at certain stratigraphical positions and often in association with carbonate rocks. They contain various amounts of skarn minerals with serpentine, pyroxene, and amphibole as the most important gangue minerals. The Stora Sahavaara iron occurrence was previously considered as belonging to a broad group of magnetite-dominated, Ca-Mg- and Mg-silicate skarn-hosted deposits, which occur throughout northern Sweden, within a Karelian volcano-sedimentary domain. Several deposits considered to be of the same type also occur and have been well studied in the Finnish part of the Lappland, in the Kolari district. These deposits, which are interpreted to be epigenetic Fe-Cu + Au deposits, occur within the same structures as the Stora Sahavaara deposit. They are suggested to belong to the increasingly important group of iron- oxide-copper-gold (IOCG) deposits. A characteristic feature of the Stora Sahavaara magnetite is the high Mg content of its concentrate which is suggested to be lattice bound. In some cases the recovery (magnetite) is poor, or the concentrates are not clean, which is clearly indicated by a high SiO2 content in the concentrate. Also, significant inclusions/intergrowths of sulphides in magnetite grains could cause the final iron ore concentrate to have high S content, for example. Alternatively, the grade may be lower than predicted due to silicate or other gangue carrying finely disseminated magnetite in some textural ore types. The general purpose of this work is to apply the mineralogy and geology of the Stora Sahavaara deposit in order to better understand the metallurgical processing characteristics of the ore. For the mineral processing of the ore and the properties and quality of the final products, the texture of magnetite, its impurities and its chemistry is of great importance. According to the data presented, the principal ore minerals of the Stora Sahavaara magnetite deposit are Mgt-Po-Py-Ccp. The main ore mineral magnetite contains high amounts of Mg, bound to the crystal lattice only in cases where coarse-grained textures of the first generation occur and where serpentine skarn dominates. The dominant sulphide is pyrrhotite which exists in both monoclinic and hexagonal crystal forms. The monoclinic crystal form of pyrrhotite is the principal factor behind some S-bearing concentrates as it turns to report with magnetite. All other metal oxides such as SiO2+Al2O3, TiO2 and vanadium, which have upper acceptable limits in the Direct Reduction Ironmakers (DRI) pellets, which is the pellet towards which Northland’s efforts are primarily directed, are within acceptable ranges. This study shows that the Stora Sahavaara magnetite composition is suitable for the DRI type of pellets, most especially considering blending. It gives a detailed characterization of the magnetite, and will hopefully serve as a useful manual during the mining process.

  • 177.
    Abou-Chakra, Bisan
    Luleå tekniska universitet, Institutionen för konst, kommunikation och lärande.
    En påhittad arabvärld: En studie av hur andra generationens invandrare ser på hur den arabiska kulturen och dess länder framställs i västerländska TV-serier.2019Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Denna studie utfördes med syfte att studera hur andra generationens invandrare i Sverige upplever representationen i västerländska TV-serier och huruvida deras verklighetsbild kring landet överstämde med det fiktiva. Studien analyseras utifrån ett postkolonialt perspektiv med teorier som inkluderar Orientalism, representation och stereotyper. Frågeställningen grundade sig i huruvida dessa intervjupersoner kände sig representerade och om bilden av kulturen och landet var rättvist gestaltad samt hur de upplevde serierna kontra verkligheten. Metoden som användes för att besvara frågeställningen var kvalitativa intervjuer där resultatet visade att intervjupersonernas verklighet upplevelser inte stämde överens med vad som visats i serierna då mycket utav det som framställt var enligt deras tolkningar konstruerade stereotyper.

  • 178. Aboudrar, Abderahim
    et al.
    Johansson, Anders
    Betongbalkar förstärkta med kolfiberkomposit: en undersökning av böj- och tvärkraftskapacitet1998Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
  • 179. Abrahamsson, Anders
    et al.
    Furu, Henrik
    Faktorer för mjukvarukvalitet: vad är viktigt för slutanvändaren?2004Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
  • 180. Abrahamsson, Anders
    et al.
    Furu, Henrik
    Viktiga strategier vid implementering av beslutsstödjande system2004Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
  • 181. Abrahamsson, Carolina
    et al.
    Olsen, Anette
    God gemenskap: med hjälp av gruppstärkande övningar?2009Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
  • 182. Abrahamsson, David
    et al.
    Jonsson, Henrik
    Spectroscopic characterization and development of technique for high-pressure synthesis of carbon based nano-structural materials2007Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    To be able to study high pressure properties and synthesis of carbon nanostructures, we built a pressure control box to regulate and fine tune pressure to our membrane diamond anvil cell (MDAC). Using ruby fluorescence method, we calibrated the pressure in the membrane against the generated pressure in the cell. This resulted in both a pre-indentation pressure curve for hardened stainless steel gaskets and in a calibration curve for pressure in the membrane against generated pressure in the MDAC. Raman spectroscopy was used to characterize carbon nanostructures. Two kinds of carbon nanotubes (CNTs) were examined, one HiPCO and one Arc- discharged produced sample, with the purpose to see how side-wall functionalization affects their spectra. Spectra were acquired from pristine and functionalized samples with 532 nm (2,33 eV) and 632,8 nm (1,96 eV) excitations and compared. Both metallic and semiconducting tubes are being probed, and we can see that metallic- and small diameter semiconducting tubes are more affected compared to semiconducting tubes with larger diameters. Different types of polymeric fullerene samples were also characterized in order to determine their structure. Spectra from 1D and one kind of 2D polymeric fullerene samples were found. Multi wall CNT (MWNT) - epoxy composites, manufactured by SiCOMP, were examined with Raman spectroscopy to see how well the MWNT interacted with the epoxy matrix and to get an estimation of how well dispersed the MWNTs were in the matrix. Spectra were acquired from epoxy and MWNTs separately, and then compared with spectra acquired from the composites. We could not see any sign of interaction between the epoxy and the MWNTs, and the tubes do not seem to be that well dispersed in the matrix.

  • 183.
    Abrahamsson, Filip
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Leaching of Pyrrhotite from Nickel Concentrate2017Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Non-oxidative acid leaching of pyrrhotite from Kevitsa’s Ni-concentrate and methods to recover by-products, have been investigated. Selective dissolution of pyrrhotite (Fe1-xS, 0<x<0.25) can enrich the content of the valuable metals, such as Ni and Co, in the final concentrate and will reduce the amount of Fe and S sent to the smelters. The pyrometallurgical smelting of leached concentrate will thus give less formation of smelter by-products in form of slag and SO2. The leaching was studied through an experimental design plan with parameter settings of  38.8% to 57.8% H2SO4 and temperatures from 60 to 100°C. The best results were obtained in experiments carried out at the lower experimental range. Leaching at 60°C with an initial acid concentration of 38.8% H2SO4 was found sufficient to selectively dissolve most of the pyrrhotite; leaving an enriched solid residue. A QEMSCAN analysis of the solid residue confirmed that most of the pyrrhotite had been dissolved and showed that pentlandite was still the main Ni-mineral. Chemical assays showed that more than 95% of the Ni, Co, and Cu remained in the final residue.

       The utilized leaching process generates by-products, in the form of large quantities of Fe2+ in solution and gaseous H2S. To recover Fe2+, crystallization of iron(ii) sulfate (FeSO4∙nH2O) from leach solution through cooling have been studied. The crystallized crystals were further dehydrated into the monohydrate (FeSO4∙H2O) through a strong sulfuric acid treatment (80%H2SO4). XRD analysis confirmed that FeSO4∙H2O was the main phase in the final crystals, and a chemical analysis showed a Fe content of about 30%, 1.5% Mg, 0.4% Ca, and 0.2% Ni.

       The possibility to leach the concentrate by circulating the acidic solution from the crystallization stage has been tested. The recirculation of the solution showed no negative effects, as the recoveries of elements and chemical assays of the final solid residue were found to be similar to the obtained assay when the concentrate was leached in a fresh solution.

  • 184. Abrahamsson, Fredrik
    et al.
    Lundberg, Stina
    Arbetsuppgiftens påverkan på motivation och presation2008Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
  • 185. Abrahamsson, Helena
    et al.
    Nordsten, Ann-Louise
    Återanvändning av komponenter: skillnad i mognadsnivå mellan utveckling av standardprogramvara och skräddarsydd programvara2000Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
  • 186. Abrahamsson, Jan-Tony
    et al.
    Forsgren, Thomas
    Lundgren, Håkan
    Sport sponsorship as a marketing communication tool2003Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Sport sponsorship has grown to be an important part of the marketing communication mix for companies over the past decades and it is also an important source of income for sports entities. This thesis aims to look at sports sponsorship as marketing communication tool, regarding the issues of the objectives with the sponsorship, selection of sports entity to sponsor and effect measuring of the sponsorship.

  • 187. Abrahamsson, Jan-Tony
    et al.
    Kairento, Peter
    Varför sprids inte EVA bland svenska företag: en studie ur företags- och konsultperspektiv2010Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
  • 188. Abrahamsson, Jan-Tony
    et al.
    Lundgren, Håkan
    The use of web sites in integrated marketing communication2004Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    Internet and the use of web sites has grown during the past decade to become more and more important as a marketing communication tool, in today’s rapidly changing business environment. Furthermore it is also an important source of income. This thesis aims to investigate how web sites are used as an integrated marketing communications tool regarding issues such as objectives, reaching and communicating with target audiences, what types of integrated marketing communication tools used and how to measure the effectiveness of using web sites as an integrated marketing communications tool.

  • 189. Abrahamsson, Jerker
    et al.
    Enbom, Jonathan
    Potentialen av skogsbiomassa i Sverige: En metaanalys2016Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The objective with the thesis was to make a comprehensive review of scientific articles and other studies on the potential of woody biomass in Sweden. Furthermore, the impact different approaches, restrictions and type of study have had on the reported outcome from the different studies have been examined. The method is based on a meta-analysis using ordinary least square (OLS) regression estimations. The theoretical framework is based on optimal harvesting rates of renewable resources and a supply and demand model of woody biomass, identifying the factors that affect the supplied amount of woody biomass. The results imply that the choice of restrictions (economical, technical, ecological and theoretical), as expected, had a large impact on the estimated potential of woody biomass. However, the result for using economical restrictions suggests an increased potential, which was unexpected. Conclusively, the thesis suggests that there is further potential to increase the utilization of woody biomass in Sweden.

  • 190. Abrahamsson, Johan
    et al.
    Johnsson, Pär
    Är det värt mödan?: Ett examensarbete om ljud och tal som informationsbärare2012Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    In (traditional) radio there are three types of information carriers/channels speech, sound and music. The purpose of this thesis is to examine which type of information that is best suited for the channels speech and sound. This was achieved through measuring the information loss during a listening test where we used the channels speech and sound. We also took noise (auditive information which competes with the message, for example sounds that occurs while driving) into consideration and measured which media had the biggest noise tolerance.The result showed that there are differences between the channels and different types of information, generally it might be said that speech had a higher efficacy while sound was more tolerant to noise. The central point of our study is that the channels contribute with different attributes, speech is the essential information carrier whilst sound adds feeling. Our conclusion is thereby that despite the higher demands on the production that sound means, it is worth the effort.

  • 191.
    Abrahamsson, Kenneth
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Arbetsvetenskap.
    Activity: European conference on promoting workplace health2006Konferansepaper (Annet (populærvitenskap, debatt, mm))
  • 192.
    Abrahamsson, Kenneth
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Arbetsvetenskap.
    Activity: International Conference on Vocational Education and Training Reform: comments on current policies and development2005Konferansepaper (Annet (populærvitenskap, debatt, mm))
  • 193. Abrahamsson, Kenneth
    Adult education in Sweden and the United States: Working Life in Sweden No. 381990Rapport (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    All young persons in Sweden have to complete 9 years of basic compulsory schooling. More than 95 percent opt for an additional 2 or 3 years of upper secondary school, after which they have free access to further education. The system of adult education is designed to bridge the gaps between generations and to provide opportunities for recurrent, lifelong education. The traditionally strong position of adult education is partly tied to the large number of providers. Formal adult education comprises basic education operated by authorities through government grants and municipal adult education. Popular adult educational activities are studies at folk high schools or under the aegis of adult educational associations. Labor market training takes the form of specially organized vocational training or uses the regular educational system. Personnel education and inservice training are educational activities aimed at employees and organized on the employers' terms and at their expense in companies and national or local authorities. The government has tried to establish the necessary preconditions for adult educational activities, including adult education in all municipalities, educational financing, educational leave, studies as part of the renewal of working life, and adult education as an expression of general welfare policy

  • 194. Abrahamsson, Kenneth
    Adult literacy and basic skills in Sweden: an overview of policy issues and research needs1990Rapport (Annet (populærvitenskap, debatt, mm))
  • 195. Abrahamsson, Kenneth
    Adult participation in Swedish higher education: a study of organizational structure, educational design and current policies1986Bok (Annet vitenskapelig)
  • 196.
    Abrahamsson, Kenneth
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Arbetsvetenskap.
    Aktivitet: EDEN 2005 Annual Conference: reflections on overeducation, underlearning and anorectic work organisations2005Konferansepaper (Annet (populærvitenskap, debatt, mm))
  • 197.
    Abrahamsson, Kenneth
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Arbetsvetenskap.
    Arbetslivsforskningen och parterna har vänt varandra ryggen2006Inngår i: TCO-tidningen, ISSN 0346-2935, nr 5, s. 10-Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 198. Abrahamsson, Kenneth
    Arbetstiden som forskningsfält1998Inngår i: Arbetstiden, jobben & framtiden, Stockholm: Arbetsmiljöfonden , 1998, s. 15-21Kapittel i bok, del av antologi (Annet (populærvitenskap, debatt, mm))
  • 199. Abrahamsson, Kenneth
    Arbetstider i olag1998Inngår i: Arbetstiden, jobben & framtiden, Stockholm: Arbetsmiljöfonden , 1998, s. 7-14Kapittel i bok, del av antologi (Annet (populærvitenskap, debatt, mm))
  • 200.
    Abrahamsson, Kenneth
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Arbetsvetenskap.
    Banbrytare, livsberättelser och lärande: en efterskrift2007Inngår i: Det krokiga lärandet, Stockholm: NTG-lärprojektet : Paraplyprojektet , 2007, s. 150-175Kapittel i bok, del av antologi (Annet (populærvitenskap, debatt, mm))
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