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Sökning: LAR1:umu > Licentiatavhandling

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1.
  • Abdipour, Morteza, 1977- (författare)
  • Arrangement Design Studies : the introduction of the digital wall in domestic environments
  • 2021
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This research focuses on the emergence of 'digital walls' that can project images onto almost all or even the entirety of interior (and perhaps exterior) walls, and what implications this might have for how we arrange our rooms. It demonstrates the arrangement, i.e., the way that domestic products are arranged physically, of rooms changes in the domestic environment in a complex scenario when using large screens. Due to the fast-growing demand for large screens, this product could potentially be available to be used by people in their home environments; however, it does not yet exist in reality at this scale. Constructing large screens can be carried out using different production methods. Here, this concept is called the digital wall, a very thin wall-sized interactive screen. The characteristics of the digital wall will vary to be able to create different scenarios. One such scenario is a space in the home where the surface of the wall is covered with screens, which allows multiple possibilities to experience and interact with digital content. In this research, the social gathering space of homes, nowadays called the living room, is considered as a highly relevant space for installing the digital wall. In this space, the conceptual framework outlines the basic elements of the research and demonstrates the relationships between people’s interactions with the digital wall and domestic products in the domestic environment. I show two examples from design history to understand how arrangement changes impact the home environment: the transformation of the parlor to the living room, and entry of the television into the living room. These two examples are focused on the place in the home where people gather for socializing. The discussion of these examples led to the elaboration of the relationships between the elements in the conceptual framework.I explored relevant design research methodologies to bring this future scenario into the present to understand the relationships between people and the digital wall. I applied research through design and the constructive design research approaches to frame the design research methodology. In this thesis, I set up seven series of design studies in two cluster groups: Supportive studies and Main studies. All of the design studies were conducted in the Design Research Lab, the actual space for carrying out the design experiments, prototyping the digital wall, and the setting of the experiments for user participation. The Lab was fully equipped with relevant technology and allowed me to use multiple methods to collect data while people were experiencing the design study sessions. The Lab was useful as a platform to understand user experiences, barriers for interactions as well as people's experiences in a simulated space of a domestic environment. The main contribution of this research is to understand the forms of arrangement changes when people use the digital wall in homes. The research demonstrates two significant implications that are seen in two forms of arrangements: tangible arrangement and imperceptible arrangement. These findings are useful for both designers and users of the elements of domestic contexts and the relations that can be shaped by the presence of a digital wall in home environments. This understanding may provide design guidelines in future scenarios in which the digital wall is used in homes. The findings are also beneficial for designing the domestic environment, improving the arrangement of space, and raising the requirements for designing domestic products.
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2.
  • Abedan Kondori, Farid, 1983- (författare)
  • Human Motion Analysis for Creating Immersive Experiences
  • 2012
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • From an early age, people display the ability to quickly and effortlessly interpret the orientation and movement of human body parts, thereby allowing one to infer the intentions of others who are nearby and to comprehend an important nonverbal form of communication. The ease with which one accomplishes this task belies the difficulty of a problem that has challenged computational systems for decades, human motion analysis. Technological developments over years have resulted into many systems for measuring body segment positions and angles between segments. In these systems human body is typically considered as a system of rigid links connected by joints. The motion is estimated by the use of measurements from mechanical, optical, magnetic, or inertial trackers. Among all kinds of sensors, optical sensing encompasses a large and varying collection of technologies. In a computer vision context, human motion analysis is a topic that studies methods and applications in which two or more consecutive images from an image sequences, e.g. captured by a video camera, are processed to produce information based on the apparent human body motion in the images. Many different disciplines employ motion analysis systems to capture movement and posture of human body for applications such as medical diagnostics, virtual reality, human-computer interaction etc. This thesis gives an insight into the state of the art human motion analysissystems, and provides new methods for capturing human motion.
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4.
  • Adjeiwaah, Mary, 1980- (författare)
  • Quality assurance for magnetic resonance imaging (MRI) in radiotherapy
  • 2017
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Magnetic resonance imaging (MRI) utilizes the magnetic properties of tissues to generate image-forming signals. MRI has exquisite soft-tissue contrast and since tumors are mainly soft-tissues, it offers improved delineation of the target volume and nearby organs at risk. The proposed Magnetic Resonance-only Radiotherapy (MR-only RT) work flow allows for the use of MRI as the sole imaging modality in the radiotherapy (RT) treatment planning of cancer. There are, however, issues with geometric distortions inherent with MR image acquisition processes. These distortions result from imperfections in the main magnetic field, nonlinear gradients, as well as field disturbances introduced by the imaged object. In this thesis, we quantified the effect of system related and patient-induced susceptibility geometric distortions on dose distributions for prostate as well as head and neck cancers. Methods to mitigate these distortions were also studied.In Study I, mean worst system related residual distortions of 3.19, 2.52 and 2.08 mm at bandwidths (BW) of 122, 244 and 488 Hz/pixel up to a radial distance of 25 cm from a 3T PET/MR scanner was measured with a large field of view (FoV) phantom. Subsequently, we estimated maximum shifts of 5.8, 2.9 and 1.5 mm due to patient-induced susceptibility distortions. VMAT-optimized treatment plans initially performed on distorted CT (dCT) images and recalculated on real CT datasets resulted in a dose difference of less than 0.5%. The magnetic susceptibility differences at tissue-metallic,-air and -bone interfaces result in local B0 magnetic field inhomogeneities. The distortion shifts caused by these field inhomogeneities can be reduced by shimming.  Study II aimed to investigate the use of shimming to improve the homogeneity of local  B0 magnetic field which will be beneficial for radiotherapy applications. A shimming simulation based on spherical harmonics modeling was developed. The spinal cord, an organ at risk is surrounded by bone and in close proximity to the lungs may have high susceptibility differences. In this region, mean pixel shifts caused by local B0 field inhomogeneities were reduced from 3.47±1.22 mm to 1.35±0.44 mm and 0.99±0.30 mm using first and second order shimming respectively. This was for a bandwidth of 122 Hz/pixel and an in-plane voxel size of 1×1 mm2.  Also examined in Study II as in Study I was the dosimetric effect of geometric distortions on 21 Head and Neck cancer treatment plans. The dose difference in D50 at the PTV between distorted CT and real CT plans was less than 1.0%.In conclusion, the effect of MR geometric distortions on dose plans was small. Generally, we found patient-induced susceptibility distortions were larger compared with residual system distortions at all delineated structures except the external contour. This information will be relevant when setting margins for treatment volumes and organs at risk.  The current practice of characterizing MR geometric distortions utilizing spatial accuracy phantoms alone may not be enough for an MR-only radiotherapy workflow. Therefore, measures to mitigate patient-induced susceptibility effects in clinical practice such as patient-specific correction algorithms are needed to complement existing distortion reduction methods such as high acquisition bandwidth and shimming.
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6.
  • Adlerborn, Björn, 1975- (författare)
  • Parallel Algorithms and Library Software for the Generalized Eigenvalue Problem on Distributed Memory Computer Systems
  • 2016
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • We present and discuss algorithms and library software for solving the generalized non-symmetric eigenvalue problem (GNEP) on high performance computing (HPC) platforms with distributed memory. Such problems occur frequently in computational science and engineering, and our contributions make it possible to solve GNEPs fast and accurate in parallel using state-of-the-art HPC systems. A generalized eigenvalue problem corresponds to finding scalars y and vectors x such that Ax = yBx, where A and B are real square matrices. A nonzero x that satisfies the GNEP equation is called an eigenvector of the ordered pair (A,B), and the scalar y is the associated eigenvalue. Our contributions include parallel algorithms for transforming a matrix pair (A,B) to a generalized Schur form (S,T), where S is quasi upper triangular and T is upper triangular. The eigenvalues are revealed from the diagonals of S and T. Moreover, for a specified set of eigenvalues an associated pair of deflating subspaces can be computed, which typically is requested in various applications. In the first stage the matrix pair (A,B) is reduced to a Hessenberg-triangular form (H,T), where H is upper triangular with one nonzero subdiagonal and T is upper triangular, in a finite number of steps. The second stage reduces the matrix pair further to generalized Schur form (S,T) using an iterative QZ-based method. Outgoing from a one-stage method for the reduction from (A,B) to (H,T), a novel parallel algorithm is developed. In brief, a delayed update technique is applied to several partial steps, involving low level operations, before associated accumulated transformations are applied in a blocked fashion which together with a wave-front task scheduler makes the algorithm scale when running in a parallel setting. The potential presence of infinite eigenvalues makes a generalized eigenvalue problem ill-conditioned. Therefore the parallel algorithm for the second stage, reduction to (S,T) form, continuously scan for and robustly deflate infinite eigenvalues. This will reduce the impact so that they do not interfere with other real eigenvalues or are misinterpreted as real eigenvalues. In addition, our parallel iterative QZ-based algorithm makes use of multiple implicit shifts and an aggressive early deflation (AED) technique, which radically speeds up the convergence. The multi-shift strategy is based on independent chains of so called coupled bulges and computational windows which is an important source of making the algorithm scalable. The parallel algorithms have been implemented in state-of-the-art library software. The performance is demonstrated and evaluated using up to 1600 CPU cores for problems with matrices as large as 100000 x 100000. Our library software is described in a User Guide. The software is, optionally, tunable via a set of parameters for various thresholds and buffer sizes etc. These parameters are discussed, and recommended values are specified which should result in reasonable performance on HPC systems similar to the ones we have been running on.
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7.
  • Adolfsson, Lena, 1955- (författare)
  • Attityder till naturvetenskap : Förändringar av flickors och pojkars attityder till biologi, fysik och kemi 1995 till 2007
  • 2011
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • I den här avhandlingen beskrivs hur hög- och lågpresterande flickors och pojkars attityder till biologi, fysik och kemi har förändrats från 1995 till 2007. Data från den svenska delen av TIMSS-studierna för årskurs 8 i Sverige används. För att definiera hög- och lågpresterande används resultatet på matematikprovet från TIMSS och attityderna undersöks med hjälp av fyra frågor från elevenkäterna. Resultatet diskuteras utifrån olika perspektiv som kan bidra till förståelsen av den komplexa bilden av olika faktorers betydelse för elevers attityder till naturvetenskap. Det första resultatet, pojkar är mer positiva till fysik och kemi och flickor till biologi, diskuteras utifrån ämnenas genuskodning. På ett symboliskt plan är fysik och kemi mer förknippade med maskulinitet än biologi. Det andra resultatet, högpresterande elever och särskilt pojkar, är mindre positiva till de tre ämnena 2007 än 1995. Det resultatet diskuteras mot bakgrund av ungdomars identitet och identitetskonstruktion. Det verkar som om unga människor i dag inte tycker att utbildningar och arbeten inom det naturvetenskapliga och tekniska området ger dem möjligheter att använda sina talanger, kreativitet och självförverkligande. Resultatet diskuteras också utifrån de förändringar av arbetsmetoder som har skett i svensk skola där det individuella arbetet har ökat och lärarledda genomgångar har minskat. Kan det ha påverkat de högpresterande eleverna så att de har blivit mindre stimulerade och fått färre utmaningar och på så sätt blivit mindre positiva till de naturvetenskapliga ämnena? Det tredje resultatet, en större andel hög- och lågpresterande pojkar tycker att de tre ämnena är tråkiga 2007 jämfört med 1995, diskuteras utifrån begreppen "antipluggkultur" och att vara "cool". Kan resultatet från denna studie indikera att det är viktigare för pojkar 2007 att ha en attityd att visa sig ”cool” och att inte plugga. Kan detta ha påverkat attityderna till de naturvetenskapliga ämnena negativt? Slutligen visar resultaten att lågpresterande flickor och pojkar tycker att de presterar bättre 2007 än 1995 och det diskuteras mot bakgrund av förändringarna av arbetsmetoder i den svenska skolan. Mer tid ägnas åt individuellt arbete vilket kan innebära att de lågpresterande eleverna väljer att inte arbeta med svårare uppgifter och att de därför upplever att de presterar bättre. Avhandlingen avslutas med mina egna reflektioner kring undervisningen i de naturvetenskapliga ämnena i grundskolan, kring förändringarna av flickors och pojkars attityder till naturvetenskap utifrån resultaten från denna studie och kring mina erfarenheter som lärare i dessa ämnen.
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8.
  • Alger, Susanne, 1967- (författare)
  • Licence to drive : the importance of reliability for the validity of the Swedish driving licence test
  • 2019
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Background: The Swedish driving licence test is a criterion-referenced test resulting in a pass or fail. It currently consists of two parts - a theory test with 65 multiple-choice items and a practical driving test where at least 25 minutes are spent driving in traffic. It is a high-stakes test in the sense that the results are used to determine whether the test-taker should be allowed to drive a car without supervision. As the only other requirements for obtaining a licence is a few hours of hazard education (and a short introduction if you intend to drive with a lay instructor) it is important that the test result, in terms of pass or fail, is reliable and valid. If this is not the case it could have detrimental effects on traffic safety. Examining all relevant aspects is beyond the scope of this licentiate thesis so I have focused on reliability.Methods Reliability for both the theoretical and practical test results was examined. As these are very different types of tests the types of reliability examined also differed. In order to examine inter-rater reliability of the driving test 83 examiners were accompanied by one of five selected supervising examiners for a day of tests. All in all 535 tests were conducted with two examiners assessing the same performance. At the end of the day the examiners compared notes and tried to determine the reason for any inconsistencies. Both examiners and students also filled in questionnaires with questions about background and preparation. As for studying decision consistency and decision accuracy of the theory test, three test versions (a total of around 12,000 tests) were examined with the help of methods devised by Subkoviak (Subkoviak, 1976, 1988) and Hanson & Brennan (Brennan, 2004; Hanson & Brennan, 1990).Results The results from two research studies concerning reliability were presented. Study I focused on inter-rater reliability in the driving test and in 93 per cent of cases the examiners made the same assessment. For the tests where their opinions differed there was no correlation to any of the background variables or other variables examined except for three, which had logical explanations and did not constitute a problem. Although there were cases where the differences were due to different stances on matters of interpretation the most common suggested cause was the placement in the car (back seat vs. front seat). Although the supervising examiners gave both praise and criticism as to how the test was carried out the study does not answer the question whether the tests were equal in terms of composition and difficulty.In Study II the focus was on decision consistency and decision accuracy in the theory test. Three versions of the theory tests were examined and, on the whole, found to be fairly similar in terms of item difficulty and score distribution, but the mean was so close to the cut-score (i.e. the score required to pass) that the pass rate differed somewhat between versions. Agreement coefficients were around .80 for all test versions (between .79 and .82 depending on method). Classification accuracy indicated an .87 probability of a correct classification.Conclusion It is important to examine the reliability and validity of the driving licence test since a misclassification can have serious consequences in terms of traffic safety. In the studies included here the rate of agreement between examiners is deemed as satisfactory. It would be preferable if the classification consistency and classification accuracy, as estimated by the methods used, were higher for the theory test, given its importance.While reliability in terms of agreement between raters/examiners or consistency and accuracy of classification are routinely examined in other contexts, such as large-scale educational testing, this is not often done for the driving licence tests. At the same time, the methods used here can be transferred to contexts where such properties are generally not examined. Collecting information about test-takers and examiners, like in Study I, can provide evidence concerning possible bias.Examining to what extent decisions are consistent is one important aspect of collecting evidence that shows that test results can be used to draw conclusions about driver competence. Still, regardless of outcome, validation is a process that never ends. There is always reason to examine various aspects and make further improvements. There are also many other relevant aspects to examine. A prerequisite for the validity of the score interpretation of a criterion-referenced test like this one is that the cut-score is appropriate and the content relevant. This should therefore be the subject of further research as the validation process continues.
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9.
  • Ali-Eldin, Ahmed, 1985- (författare)
  • Capacity Scaling for Elastic Compute Clouds
  • 2013
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • AbstractCloud computing is a computing model that allows better management, higher utiliza-tion and reduced operating costs for datacenters while providing on demand resourceprovisioning for different customers. Data centers are often enormous in size andcomplexity. In order to fully realize the cloud computing model, efficient cloud man-agement software systems that can deal with the datacenter size and complexity needto be designed and built.This thesis studies automated cloud elasticity management, one of the main andcrucial datacenter management capabilities. Elasticity can be defined as the abilityof cloud infrastructures to rapidly change the amount of resources allocated to anapplication in the cloud according to its demand. This work introduces algorithms,techniques and tools that a cloud provider can use to automate dynamic resource pro-visioning allowing the provider to better manage the datacenter resources. We designtwo automated elasticity algorithms for cloud infrastructures that predict the futureload for an application running on the cloud. It is assumed that a request is either ser-viced or dropped after one time unit, that all requests are homogeneous and that it takesone time unit to add or remove resources. We discuss the different design approachesfor elasticity controllers and evaluate our algorithms using real workload traces. Wecompare the performance of our algorithms with a state-of-the-art controller. We ex-tend on the design of the best performing controller out of our two controllers anddrop the assumptions made during the first design. The controller is evaluated with aset of different real workloads.All controllers are designed using certain assumptions on the underlying systemmodel and operating conditions. This limits a controller’s performance if the modelor operating conditions change. With this as a starting point, we design a workloadanalysis and classification tool that assigns a workload to its most suitable elasticitycontroller out of a set of implemented controllers. The tool has two main components,an analyzer and a classifier. The analyzer analyzes a workload and feeds the analysisresults to the classifier. The classifier assigns a workload to the most suitable elasticitycontroller based on the workload characteristics and a set of predefined business levelobjectives. The tool is evaluated with a set of collected real workloads and a set ofgenerated synthetic workloads. Our evaluation results shows that the tool can help acloud provider to improve the QoS provided to the customers.
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10.
  • Allard, Ingrid (författare)
  • Achieving building energy performance : requirements and evaluation methods for residential buildings in Sweden, Norway, and Finland
  • 2015
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Building energy performance has always been important in the cold climate of Sweden, Norway and Finland. To meet the goal that all new buildings should be nearly zero-energy buildings by 2020, set in the EU directive 2010/31/EU [1] on the energy performance of buildings (EPBD recast), the building sector in Europe now faces a transition towards buildings with improved energy performance. In such a transition, a discussion is needed about the objective of the improvement – why, or to what end, the building energy performance should be improved. The objective of improving building energy performance is often a political decision, but scientific research can contribute with knowledge on how the objectives can be achieved.This thesis addresses how the indicators used in the requirements used to achieve building energy performance in Sweden, Norway, and Finland, and the methods used to evaluate these requirements, reflect building energy performance. It also addresses difficulties in achieving comparable and verifiable indicators in evaluations of building energy performance. The research objective has two parts: to review, compare, and discuss (i) requirements and (ii) evaluation methods used to achieve energy performance of residential buildings in Sweden, Norway and Finland. The work in this thesis includes reviews of the requirements used in national building codes and passive house criteria to achieve building energy performance, of methods used to evaluate compliance with such requirements, and of methods used specifically to evaluate the indicator Envelope Air Tightness. The results show that different sets of indicators are used to achieve building energy performance in the studied building codes and passive house criteria. The methods used to evaluate compliance with requirements used to achieve building energy performance are also different, but calculation methods are generally more often used than measurement methods. The calculation- and measurement methods used are often simple. A methodology to analyze the deviation between predictions- and measurements of building energy performance (the performance gap) was developed, to investigate the effects of different evaluation methods on different indicators used to achieve building energy performance. The methodology was tested in a case-study. This study indicated that the choice of method affects which parts of the performance gap reflected in the indicators Supplied Energy (see Terminology), Net Energy (see Terminology), and Overall U-value. Among the reviewed methods to evaluate air tightness, the Fan/Blower Door Pressurization is well known and preferred by professionals in the field. The results in this thesis may be useful when choosing indicators and evaluation methods to achieve different objectives of improving building energy performance and in the quest towards comparable and verifiable indicators used to achieve building energy performance.
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