| 1. |
- Ekengren, Jens, 1976-
(författare)
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Estimating inclusion content in high performance steels
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Non-metallic inclusions in steel pose a major problem for the fatigue resistance, especially regarding fatigue at very long lives corresponding to low cyclic stress levels, as well as being detrimental to material toughness and polishability.The largest inclusions are quite rare, which makes conventional detection methods timeconsuming if reliable results are to be obtained. Based on surface scanning using light or electron microscopes, these methods provide results that have to be converted to reflect the statistical volume distribution of inclusions.Very high cycle fatigue (in the order of 109 cycles or more) using ultrasonic fatigue at 20 kHz has been found efficient at finding the largest inclusions in volumes of about 300 mm3 per specimen. The inclusions found at the fatigue initiation site can then been used to estimate the distribution of large inclusions using extreme value statistics.In this work, a new method for estimating the volume distribution of large inclusions is presented as well as a suggested ranking variable based on the volume distribution.Results from fatigue fractography and area scanning methods are compared to the endurance limit at 109 cycles for a number of batches from two high performance steels.In addition, the extreme value distributions of fatigue initiating inclusions in six high performace steels, produced by different routes, are presented. It is shown that all modes of the Generalized Extreme Values distribution can be found in different materials. This result shows that the assumption of mode I distribution, also known as Gumbel or Largest Extreme Value distribution, must be substantiated.
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| 2. |
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| 3. |
- Khodadad, Davood
(författare)
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Combined Digital Holography and Speckle Correlation for Rapid Shape Evaluation
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In manufacturing industry there is a high demand for on line quality control to minimize the risk of incorrectly produced objects. Conventional contact measurement methods are usually slow and invasive, meaning that they cannot be used for soft materials and for complex shapes without influencing thecontrolled parts. In contrast, interferometry and digital holography in combination with computers become faster, more reliable and highly accurate as an alternative non-contact technique for industrial shape evaluation. In digital holography, access to the complex wave field and the possibility tonumerically reconstruct holograms in different planes introduce a new degree of flexibility to optical metrology. With digital holography high resolution and precise three dimensional (3D) images of the manufactured parts can be generated. This technique can also be used to capture data in a single exposure,which is important when doing measurements in a disturbed environment.The aim of this thesis is to perform online process control of free-form manufactured objects by measuring the shape and compare it to the CAD-model. To do this, a new technique to measure surface gradients and shape based on single-shot dual wavelength digital holography and image correlation of speckle displacements is demonstrated. Based on an analytical relation between phase gradients and speckle displacements it is shown that an object is retrieved uniquely to shape and position without the unwrapping problems that usually appear in dual wavelength holography. The method is firstdemonstrated using continues wave laser light from two temperature controlled laser diodes operating at 640 nm. Further a specially designed dual core diode pumped fiber laser that produces pulsed light with wavelengths close to 1030 nm is used. One significant problem when using the dual wavelength single-shot approach is that phase ambiguities are built in to the system that needs to be corrected. An automatic calibration scheme is therefore required. The intrinsic flexibility of digital holography gives a possibility to compensate these aberrations and to remove errors, fully numerically without mechanical movements. In this thesis I present a calibration method which allows single-shot online shape evaluation in a disturbed environment. It is shown that phase maps and speckle displacements can be recovered free of chromatic aberrations. This is the first time that a single-shot dual wavelength calibration is reported by defining a criteria to make an automatic procedure.By the results of the presented work, it is experimentally verified that the single-shot dual wavelength digital holography and numerically generated speckle images can be used together with digital speckle correlation to retrieve and evaluate the object shape. The proposed method is also robust to large phasegradients and large movements within the intensity patterns. The advantage of the approach is that, using speckle displacements, the shape measurement can be done even though the synthetic wavelength is out of the dynamic range of the height variation of the object.
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| 4. |
- Liang, Yuli, 1985-
(författare)
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A study of multilevel models with block circular symmetric covariance structures
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerns the study of multilevel models with specific patterned covariance structures and addresses the issues of maximum likelihoodestimation. In particular, circular symmetric hierarchical datastructures are considered.In the first paper (Paper I), we consider so-called dihedral block symmetrymodels and extend them to models which covariance structures reflects both circularity and exchangeability present in the data. The main contribution of Paper I are two derived patterns of the covariancematrices which characterizes models under consideration. The relationship between these two patterned covariance matrices was investigatedand it has been verified they are similar matrices. New expressions for the eigenvalues of block circular symmetric matrices are obtained which take into account the block structure. Paper II deals with estimation ofbalanced multilevel models with block circular symmetric covariance matrices. The spectral properties of such patterned covariance matrices are established. Maximum likelihood estimation is considered through the spectral decomposition of the patterned covariance matrix. The main results of Paper II concern the spectrum of the covariance matrix inthe model of interest and the existence of explicit maximum likelihood estimators for the covariance parameters.
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| 5. |
- Ågerup, Karl, 1972-
(författare)
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L'esthétique didactique de Yasmina Khadra
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Based on three novels by the contemporary Algerian novelist Yasmina Khadra, the study discusses didactic and aesthetic features of the literary text. While essentially set in the Arab world, Khadra’s fiction links to western encyclopaedia and journalistic discourse. In relating to this part of the reader’s experience, the novels produce an impression of proximity to the peripheral real, and a sense of responsibility. It is suggested that this interdiscursivity be viewed not as a deviation from literature but as inherent to literary discourse itself; the text comments and constitutes simultaneously. Emphasising the hybridity of literary means and didactical drive, the study proposes that Khadra’s work be labelled “didafiction”.
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| 7. |
- Alklind Taylor, Anna-Sofia
(författare)
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Coaching by Gaming : An Instructor Perspective of Game-based Vocational Training
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Military organisations have a long history of using games for training. Over the years, they have developed training practices involving role-play, simulations, puckstering and gaming. Most researchers in serious games, i.e. games used for non-entertainment purposes, focus their studies on the learners. This licentiate thesis, instead, takes a closer look on the roles of instructors in game-based training situations, specifically at the Swedish Land Warfare Centre. Through a mix of theoretical and empirical studies, training practices were scrutinised, resulting in a framework for game-based vocational training. A key element of this framework is the coaching by gaming perspective in which instructors give un-intrusive, formative feedback through role-play and gameplay. Another important aspect of the framework involves dynamic debriefing. These insights points to specific needs for system support for instructors involved in game-based training. They also emphasise the fact that serious gaming is a highly contextualised activity made up of more than the game and the players.
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| 9. |
- Carlborg, Per
(författare)
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Extending the Service Innovation Concept : Realization and Productivity
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this study is to contribute to a better understanding of service innovation by exploring realization as a part of service innovation. Service innovation can be described as something that creates value for customers through new service offerings or service processes while realization refers to the actual use or deployment of the service.My research approach is based on a multiple case study, that focuses on three international firms with origins in Sweden. Empirical material has been gathered through interviews and focus groups. A literature review that tracks the evolution of service innovation further contributes to the exploration of the service innovation concept.Innovation has traditionally been connected to new technology and new products. However the present study has found that service innovation has evolved into a multifaceted concept. Specifically, service innovation is not restricted to the development of new products and services in the shape of new offerings, it also becomes relevant to consider the actual usage of the service offerings. In order to fully understand the process of service innovation, it is important to include the usage of a service offering in the service innovation concept. This realization occurs when the service offering is introduced and used in the customer’s processes, and typically involves both the customer and the provider.This research illustrates how realization requires resources from both the provider and the customer. In general, the realization part of the service innovation process requires more participation from the customer than the development of new offerings. However, this can vary depending on the customer’s competence, intention to interact and level of commitment. Considering an active or recipient customer role and also whether the service offering is directed at the products or the customer processes, this study shows how these different service offerings will have different impacts on service innovation realization, for example, in terms of different resources being required.The extended view of the service innovation concept, includes realization, and is therefore not limited to developing new offerings. This view implies that new areas of innovation that do not necessary need to include new technology, but contribute in other ways to customer value creation must be propelled into focus. Productivity improvements in customer processes are becoming important since they help create customer value (reduced costs, improved quality, reduced down-time etc.). Empirical evidence shows how service offerings that emphasize improvements in customer processes have become more important. This thesis discusses how this view of productivity can result in important benefits for customers, as consideration is given to both customer satisfaction and the use of customer resources. In this respect, productivity becomes a part of the extended service innovation concept.Extending the service innovation concept by adding realization implies an increased emphasis on deployment, and implicitly on customer value creation. Thus, service innovation becomes critical for gaining long-term sustainable competitive advantages through service.
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| 10. |
- Dag, Munir, 1968-
(författare)
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Unga människor med rörelsehinder utanför arbetsmarknaden : om barriärer, sociala relationer och livsvillkor
- 2003
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Syftet med studien har varit att beskriva de specifika barriärer som individer med rörel-sehinder i åldrarna 20-35 år upplever att de möter i sin strävan att komma in på arbets-marknaden. Syftet har också varit att beskriva individernas livssituation under arbets-löshet och jämföra detta med livssituationen i någon form av sysselsättning. Metoden som har använts är kvalitativ, intervjuer med 12 individer med rörelsehinder.Resultaten från intervjuerna visar att individer med rörelsehinder möter barriärer inom olika områden. Barriärerna uppkommer via ett komplext samspel mellan den so-ciala och fysiska miljön, regelsystemen och individen. Studien tyder på olika orsaker till att individer med rörelsehinder möter barriärer i sina försök att få arbete. Exempel på sådana hinder är själva funktionshindret, graden av anpassning i den fysiska miljön, samhällets fördomar och rådande lagar. Utifrån detta har studien kunnat särskilja tre huvudkategorier av barriärer - individrelaterade, miljörelaterade och regelrelaterade.Resultatet visar att barriärer på individnivå är låg utbildning, avsaknad av yrkeserfa-renhet, lång period av arbetslöshet och dåliga kunskaper i regelsystemet. Ytterligare barriärer på individnivå är låg motivation att söka arbete.De miljörelaterade barriärer som identifieras är främst dåligt anpassade arbetslokaler, avsaknad av tekniska hjälpmedel och dåligt fungerade färdtjänst, bristande information samt rådande attityder om funktionshindrade i samhället. Dessa aspekter innebär di-rekta hinder för anställning av rörelsehindrade.Studien tyder också på att regelsystemen kan fungera som barriärer. Dels uppger un-dersökningsgruppen att de har bristande kunskaper i gällande regler, dels uppges att det inte är lönsamt att arbeta, eftersom inkomsten inte förbättras med ett arbete.
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