Due to legislative reasons and environmental concerns the automotive and transport sector are shifting their focus from traditional internal combustion engine (ICE) vehicles to development of battery electric vehicles (BEVs). This brings new challanges to design of cooling systems where axial fans are one of the key components. Axial fans are usually designed with regards to a certain operating condition and outside this region the efficiency of the fan drops drastically. Due to difficulty in specifying the exact operational parameters when placed in a car, post-design optimization may be necessary to ensure maximized performance. This thesis focuses on fan blade shape optimization through mesh morphing using the surrogate based optimization algorithm called Efficient Global Optimization (EGO). The target fans was a 9 bladed prototype fan by Johnson Electric with uneven blade spacing. The optimization uses steady state Reynolds-averaged Navier-Stokes (RANS) simulations to evaluate the fan designs and a Bezier curve parametrization in order to change the fan blade shape together with mesh morphing. The simulation setup was evaluated before peceding with the optimization, and showed good agreement close to intended operational conditions. Differences in turbulence modeling treatments were also evaluated in order to have a satisfactory agreement with measurement data. The EGO algorithm manages to provide fan designs with higher total-to-static efficiency at several different operational conditions. Evaluation of the optimized fan designs was limited to comparison with the provided measurement data and corrensponding simulations. Acoustic evaluation of selected fan designs is also attemped, but further work is required in order for the study to result in a quantitative comparison. / På grund av lagstiftning och miljöpåverkan har bil- och transportindustrin börjat skifta fokus från traditionella förbränningsfordon till utveckling av batteridrivna elbilar. Med detta medföljer nya utmaningar kring kylsystemsdesign där axiella fläktar är en av huvudkomponenterna hos systemet. Axiella fläktar är vanligtvis designade kring ett specifikt drifttillstånd och utanför detta har fläkten avsevärt lägre verkningsgrad. På grund av svårigheter att specificera detta drifttillstånd med hög precision, speciellt när fläkten monteras i en bil, kan efterdesigns-optimering vara nödvändigt för att uppnå maximal prestanda. Denna avhandling fokuserar på form-optimering av fläkt via mesh morphing med hjälp av den surrogat-baserade optimeringsalgoritmen Efficient Global Optimization (EGO). Fläkten som optimerades var en prototypfläkt designad av Johnson Electric med 9 fläktblad och icke-symmetriska mellanrum mellan bladen. I optimeringsprocessen användes icke-tidsberoende Reynolds-averaged Navier-Stokes (RANS) simuleringar för att utvärdera fläktdesignerna och parametrisering med hjälp av Bezier kurvor och mesh morphing för att ändra fläktbladen. Simulerings-uppställningen utvärderades innan optimeringen och bra överensstämning nära avsett driftstillstånd kunde påvisas. Skillnader i turbulens-modelering utvärderades även för att få en tillfredställande överensstämning med mätdata. EGO-algoritmen klarar att förse fläktdesigner med högre total-till-statisk verkningsgrad vid flera olika driftstillstånd. Utvärdering av fläktdesignerna var dock begränsad till jämförelse med mätdata och motsvarande simuleringsdata. En akustik utvärdering av utvalda fläkt-designer försöktes, men mer arbete krävs för att studien ska erhålla en kvantitativ jämförelse.

Owing to the ever-changing developments of battery and electric powertrain, vehicle electrification is the trend in the future. Without the presence of a combustion engine, masking effect from it reduces and noises from other components become perceivable. Among all, the cooling fan is one of the major noise sources. The design of cooling fan modules is usually carried out in the early stage before building prototype vehicles. Therefore, it is essential to come up with a method for selecting optimal fan design without performing complete vehicle testing. This is a Master's degree project in collaboration with Volvo Cars, with a focus on cooling fan noise at the charging state of electric vehicles. The main objective of this thesis is to understand the effects of fan installation. Three different setups of acoustic measurement are carried out, namely free-space, wall-mounted, and in-vehicle measurement. Correlations of these measurements are investigated through comparisons of the measurement results and the installation effects are identified through spectrum difference between free-space and in-vehicle measurement. Moreover, the implementation of spectral decomposition method enables the separation of source strength and propagation effect. Analyses of sound pressure levels are studied by looking into tonal and broadband components. In addition, sound power levels are determined by following ISO standards. Finally, a subjective rating session is held to understand the human perception of cooling fan noise. / Med anledning av den pågående utvecklingen mot elektrifiering där bilarna går mot batterier och elmotorer för framdrivning så ändras ljudbilden. Utan förbränningsmotorer som tidigare maskerade mycket av ljudet från bilarna så framträder nya ljudkällor. En sådan är kylfläkten som allt mer blir en störningskälla. Vanligtvis sker designen av kylfläktsmodulen i en tidig fas innan det finns någon prototypbil att tillgå. Detta gör att det är viktigt att utveckla metoder för att i tidig fas kunna optimera designen av kylfläkten.  Detta är ett examensarbete i samarbete med Volvo Cars med fokus på det ljud som uppstår vid laddning av eldrivna bilar. Uppsatsens huvudsakliga mål är att förstå fläktinstallationens påverkan på ljud genom att korrelera olika typer av mätningar. Detta genomfördes m.h.a tre separata konfigurationer, fritt-upphängd mätning, väggmonterad och installerad i bil. Korrelation undersöktes genom att jämföra mätresultat och analys av spektrumet. Analysen av ljudtrycksnivåerna genom att titta på dels de tonala komponenterna men också på bredbandsnivåerna. Utöver detta fastställs även ljudeffekten genom att följa gängse ISO standard. Slutligen så gjordes en subjektiv utvärdering för att få en förståelse av upplevelsen av ljudet från en kylfläkt.

Ducted fan vehicles possess a superior ability to maximize payload capacity while minimizing vehicle size. Their ability to both hover and fly at high speed is a key advantage for information-gathering missions, particularly when close proximity to a target is essential. However, the ducted fan's aerodynamic characteristics pose difficulties for stable vehicle flight and therefore require complex control algorithms. In particular, they exhibit a large nose-up pitching moment during wind gusts and when transitioning from hover to forward flight. Understanding ducted fan aerodynamic behavior and how it can be altered through flow control techniques are the two prime objectives of this work. This dissertation provides a new paradigm for modeling the ducted fan's nonlinear behavior and new methods for changing the duct aerodynamics using active flow control. Steady and piezoelectric synthetic jet blowing are employed in the flow control concepts and are compared. The new aerodynamic model captures the nonlinear characteristics of the force, moment, and power data for a ducted fan, while representing these terms in a set of simple equations. The model attains excellent agreement with current and legacy experimental data using twelve non-dimensional constants. Synthetic jet actuators (SJA) have potential for use in flow control applications in UAVs with limited size, weight, and power budgets. Piezoelectric SJAs for a ducted fan vehicle were developed through two rounds of experimental designs. The final SJA design attained peak jet velocities in the range of 225 ft/sec (69 m/s) for a 0.03â x 0.80â rectangular slot. To reduce the magnitude of the nose-up pitching moment in cross-winds, two flow control concepts were explored: flow separation control at the duct lip, and flow turning at the duct trailing edge using a CoandÄ surface. Both concepts were experimentally proven to be successful. Synthetic jets and steady jets were capable of modifying the ducted fan flow to reduce pitching moment, but some cases required high values of steady blowing to create significant responses. Triggering leading edge separation on the duct lip was one application where synthetic jets showed comparable performance to steady jets operating at a blowing coefficient an order of magnitude higher. / Ph. D.

As an indirect consequence of increased heat cooling requirements, personal computers (PC) have become noisier due to the increased use of fans. Hard disk drives also contribute to the annoying noise radiated by personal computers, creating a need for the control of computer noise. Due to size constraints, the implementation of passive noise control techniques in PC is difficult. Alternatively, active noise control (ANC) may provide a compact solution to the noise problems discussed above, which is the subject of this work. First, the computer noise sources were characterized. The structure-borne path was altered passively through the decoupling of the vibrating sources from the chassis. Global noise control strategy was then investigated with a hybrid passive/active noise control technique based on folded lined ducts, integrating microphones and speakers, that were added to the PC air inlet and outlet. While the ducts were effective above 1000Hz, the use of a MIMO adaptive feedforward digital controller lead to significant noise reduction at the ducts outlets below 1000Hz. However, global performance was limited due to important airborne flanking paths. Finally, the same type of controller was used to create a zone of quiet around the PC user head location. It was implemented using multimedia speakers and microphones, while the computer was placed in a semi-reverberant environment. A large zone of quiet surrounding the head was created at low frequencies (250Hz), and its size would reduce with increasing frequency (up to 1000Hz). / Master of Science

With the use of a discourse psychology approach, this study has intended to highlight and analyze the nature of the Swedish digitalized football fan culture on Instagram, which previously hasn't been studied within the field of research in Sweden. The collection of data has been gathered through a non-participatory netnographic approach, from which comments of hate speech are expressed on Instagram, regarding the first 6 rounds of the 2024 season of Allsvenskan. The three discourses (1) to discriminate, (2) fans authenticity, and (3) masculinity, has been the base of the analysis. The results demonstrate that the terms stooge, hobo, and bastard, are the three characteristics that are particularly important regards to maintaining and reinforce the use of hate speech, as well as the use of GIFs and likes. Football fans' utilization of superiority, subordination, and the othering of opposing fans, have proven to permeate the comments, especially in protecting one's fandom and team. Moreover, the results indicate Instagram as a platform which furthers online hate speech opportunities. Lastly, the study's theoretical framework has been proven to be of relevance for the results. / Studien har nyttjat ett diskurspsykologiskt angreppsätt i syfte att belysa och analysera den digitaliserade svenska fotbollssupporterkulturen på Instagram, något som inte tidigare gjorts inom det svenska forskningsfältet. Studiens datainsamlingsmetod består av en icke- deltagande netnografisk ansats, där kommentarer som gett uttryck för hat på Instagram, rörande Allsvenskans första sex omgångar under säsongen 2024, har inhämtats för en diskurs-psykologisk analys. Analysen har utgått ifrån de tre diskurserna (1) att diskriminera, (2) supportrars äkthet, och (3) maskulinitet. Resultaten visar på att de tre benämningarna dräng, luffare och horunge är synnerligen utmärkande för upprätthållandet och förstärkande av studiens hatuttryck, likaså brukandet av GIFs och gilla-markeringar. Supportrars markerande av över- och underordningar liksom andrafiering av motståndssupportrar har påvisat vara genomsyrande i kommentarerna, i synnerhet i termer av att skydda sitt supporterskap och tillhörande fotbollslag. Därtill indikerar även resultaten på att Instagram som plattform främjar tillfällen för hatuttryck online. Slutligen har de teoretiska utgångspunkterna konstaterats ha en betydande förklaringskraft för resultaten.

Considérant l’environnement numérique qui se caractérise par la convergencedes modes et des formes discursifs, à quels cadres les auteurs et les lecteurs héritiers de la bande dessinée se référent-ils et de quelle manière s’y réfèrent-ils ? Il s'agit de comprendre comment des auteurs confrontés à de nouveaux dispositifs de publication produisent le sens commun nécessaire à la création de récits numériques dont les lecteurs parviennent à partager les standards de transcription, tirent des routines d’usage pour leur interprétation, et jugent attrayante la sélection et la mise en forme des évènements racontés. Après avoir présenté lecontexte dans lequel ont émergé les premiers récits identifiés comme des « bandes dessinées numériques de création », l'étude porte sur l'analyse indexicale d'entretiens conduits auprès des auteurs et des lecteurs de deux de ces récits. L'analyse fait apparaître l'originalité des assemblages de cadres de références opérés par les auteurs et reconnus de leurs lecteurs. Cette étude montre ainsi l'importance des dynamiques de production de sens dans l'invention et l'adoption de nouvelles formes narratives. Le retour critique sur ce travail soulève plusieursquestions méthodologiques, notamment quant à la place du chercheur en tant qu'acteur engagé dans la production de sens, mais aussi quant à la prépondérance accordée au mot dans ce type d'étude, et enfin quant aux modalités d'entretien les plus favorables à la recherche et à l'élucidation des marques indexicales par lesquelles s'expriment les cadres de référence des acteurs. / What are the frames to which authors inspired by the comics legacy refer inthe digital environment, characterized by the convergence of media and discursive forms ? How do they refer to such frames in order to make sense and to tell digital stories from which readers are able to share the standards of translation, find routines for their interpretation, and feel entertained by the selection and the arrangement of events ? After setting the context in which emerged the first accounts identified as « original digital comics », the study focuses on the indexical analysis of interviews with authors and readers of two such stories. The analysis reveals the originality of the frames arrangements made by the authors and recognized by their readers. This study shows the importance of sensemaking activities for the invention and adoption of new narrative forms. The critical review of this work raises several methodological issues, particularly regarding the place of the scientist as an actor engaged in the sensemaking activity, but also about the the importance given to words in this kind of researches, and finally about the appropriate interview methods in order to find and explain indexical marks leading to the actors' frames

This thesis discusses the optical diagnostics of electrical motor parts using a 3D scanner. It describes the construction of electrical induction motors, their heat losses, cooling and refrigeration systems that may be used by such motors. It approaches the possibilities of heat recording and briefly explains the 3D scanner’s principal. It also introduces the simulation program ANSYS which uses the finite element method. This thesis shows the post processing of the digitalized object and the simulations and compares the simulation and measurement results. The final part is devoted to the analysis of the obtained results.

No description available.

Fans and fandoms are ever more salient aspects of our everyday lives offline and linked to the Internet's growing influence also online, particularly on social media. While fans have generally been pathologized via mass media but also early academic representations especially prior to the founding of the interdisciplinary Fan Studies in the 1970s/1980s, which sought to actively counter negative fan representations and foreground fans' creative productivity, nowadays, even though many types of fans have been 'mainstreamed' and are generally accepted, specific fan types are still systematically discriminated against - even within Fan Studies - along the lines of socio-demographic variables. These marginalised fans are predominantly female, young, queer and non-white. Moreover, even though Fan Studies define fan identity as one of their focal concerns, linguistic research on fan identity, particularly regarding its narrative and interactive construction, has widely been neglected. However, as narrative interaction and specifically small stories (as propsed within the small story paradigm by Bamberg & Georgakopoulou, 2007/8) have been found to play a very important role in the construction of identity, the investigation of how fan identity is constructed via small stories and - given the centrality of collective fandoms for fans - specifically shared (group) stories can severely contribute to fan (identity) research. Thus, combining decidedly linguistic research on narrative fan identity construction and the inclusion of previously marginalised fan communities, this thesis focuses on the construction of fan identity of Taylor Swift fans (Swifties) - a predominantly female and young fandom that has been ridiculed by mass media and dominant discourses - via shared stories. More specifically this study analyses the construction of Swiftie fan identity via shared stories both online in nicknames on Tumblr and Twitter and face to face in the form of a positioning analysis investigating the interactions of a Zoom focus group made up of five German Swifties. This research finds that within Swiftie nicknames Swiftie fan identity is centrally constructed by means of variously highly condensed, combined and/or personalised references (to shared stories of the overarching Swiftie community). The focus group interactions then reveal various positioning practices that are strongly intertwined with (often) more elaborate shared stories, which are 'shared' by the Swiftie participants both with regards to experiences on the story level and their interactive co-construction on the level of interaction. Despite their diverging local manifestations both within the investigated Swiftie nicknames and focus group interactions shared stories are centrally utilised to construct and communicate Swiftie fan identity as a particularly collectively experienced and defined ingroup identity that confers belonging and further functions as a shield against outgroup discrimination. Further research should then enlarge the present investigative focus to include also other online platforms and fan communicative acts, supplementary and also offline implemented focus groups and field studies, more heterogenous participants with regard to often neglected socio-demographic variables (next to age and gender) as well as other (marginalised) fandoms outside of the Swiftie community.

The revolutionisation of international economies and monetary systems has been taking place since the early 1970s. This occurred due to the diminishing fixed exchange rate systems of, initially, the Gold Standard and subsequently the Bretton Woods System. The collapse of these systems, especially the Bretton Woods System, led to the almost free movement of exchange rates. The lack of restriction placed on the movement of currencies created volatile markets; which, in turn, gave rise to an innumerable amount of risks. In Correia, Holman and Jahreskog (2012) it was determined that an astonishing 74% of non-financial firms in South Africa hedge foreign exchange risk (the risk of currency movement). The 10% of firms which did not hedge any risks declared it was due to the lack of exposure to foreign exchange risks and that the cost of acquiring a hedging contract, in many cases, exceeded the contract’s benefits. In the aforementioned study it was also established that the extractive sector of South Africa is one of the industries referring from the use of hedges. The intention of this study is to improve the effectiveness of derivative instruments for companies in the extractive sector of South Africa exporting to the United States of America. South Africa is a large exporter and importer of goods, making it extremely important for market participants to determine the movement of the exchange rates. This estimates the amount of risk a company is willing to take and the amount of hedges they will use to protect themselves against inauspicious and adverse movements in the markets. Therefore, incorporated in this study is the use of risk management tools from the technical analysis to predict the exchange rates at which companies should have set their hedging contracts on specific dates. This analysis could enable companies to perform an internal control that is inexpensive and which reduces risks of foreign exporting. / MCom (Management Accountancy), North-West University, Potchefstroom Campus, 2014