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The Global ETD Search service is a free service for researchers
to find electronic theses and dissertations. This service is
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Networked Digital Library of Theses and Dissertations.
Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
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Showing 61 to 62 of 62 (0.018 seconds)Spelling suggestions: "subject:"tysta"" "subject:"nysta""
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Development and study of noise generation from propellers / Utveckling och studie av ljud genererat från propellrarAnton Dunström, Anton, Skjernov, Fredrik January 2022 (has links)
Noise generation from underwater activities propagates into the marine environment.For marine vessels the propulsion system generates the most noise during itsoperations. Naval vessels that want to operate without being detected want to controlthe sound generating properties of the vessel. To control the sound generatingproperties this project has been looking into the existing propeller of the submergedcraft Carrier Seal that is produced by James Fisher Defense. Then a new and bespokenpropeller has been developed with theories applied to minimize its noise generatingproperties. The properties of the propeller that have been altered is the number ofblades, blade area ratio, pitch and skew angle. These properties have been alteredwith aid of the open-source software for Matlab named Openprop. From the finalpropeller design a prototype was later produced, tested and compared to the existingpropeller of the Seal Carrier. To test and compare these two propellers a test procedurewith inspiration from NATO and the Swedish Defense and Research Agency (FOI) wasdeveloped. The results from the comparison show that the sound pressure level fromthe propeller spectrum could be lowered with 3 dB re 1 μP a for the vessels design speedand several blade tones could be eliminated entirely. Simultaneously the efficiency ofthe vessel is increased throughout its speed range.In conclusions the recommendation to JFD is to change their existing propeller tothis bespoken propeller as it has proven itself to better in every way during thesetrials. / Ljud som genererats under vatten sprider sig långt från källan där de uppstått. Frånmarina fartyg är det framdrivningssystemet som står för majoriteten av det genereradeljudet. För militära fartyg som inte vill upptäckas är det av yttersta vikt att minimeraljuden som genereras ombord. För att kontrollera detta har det här projektet riktatin sig på fartyget Carrier Seal som tillverkas utav James Fisher Defense (JFD) ochdess propeller. Den existerande propellern har analyserats och därefter har en nyoch förbättrad propeller utvecklats. Utvecklingen har gjorts genom att tillämpatillgängliga teorier som gått ut på att minska propellerns ljudskapande egenskaper.Propelleregenskaperna som har undersökts är antalet blad som propellern har, dessbladtäckningsgrad, stigning och skevningsvinkel. Dessa egenskaper har varierats medhjälp av mjukvaran Openprop som körs i Matlab för att hitta en kombination somgenererar mindre ljud än sin föregångare. Därefter har en prototyp tillverkats ochtestats för att sedan jämföras med den existerande propellern. Testproceduren somgenomförts har tagits fram med inspiration från liknande procedurer som genomförtsav NATO och FOI. Resultatet från jämförelsen visar att ljudtrycksnivån från propellernhar kunnat minskats med 3 dB re 1 μP a för hela propellerspektrumet vid farkostensmarschfart och flertalet bladtoner kunde elimineras helt och hållet. Samtidigt someffektiviten kunnat förbättras över hela fartområdet.Slutsatsen som kan dras av arbetet är att JFD rekommenderas att byta deras nuvarandepropeller till den förbättrade propellern eftersom den har visat sig avsevärt mycketbättre under dessa tester.
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Tystnaden: Makten, rösten och talet : En analys av tystnaden som kontrollinstrument i Vegetarianen och brun flicka drömmer / Silence: Power, voice and speech : An analysis of silence as an instrument for control in The Vegetarian and brown girl dreamingGuldbacke Lund, Linnéa January 2018 (has links)
Silence, voice and power are the main themes in this essay. The purpose is to analyze how the silence is used as an instrument for control, and how it can be used strategically to take power, but also as a resistance against the power. The novel The Vegetarian by Han Kang and the autobiography novel on verse, brown girl dreaming by Jacqueline Woodson are the core of this essay. This essay focuses on how the characters break the silence, and how they use the silence strategically to find their voice in a society that systematically works to keep women, children and men silent. The silence works in specific ways in all kinds of situations, to explore the complexity of the power dimensions a comparative analysis allows the themes to emerge and enlighten each other’s diversity. With help from Rebecca Solnit in Alla frågors moder, Audre Lorde in Your silence will not protect you and Michel Foucault’s Diskursens ordning, among other voices, the essay aims to search for how the silence can work as a strategy and what it means to speak. The essay shows how the oppressing silence is broken in brown girl dreaming, and how the voice becomes the power, but also how the silence was used in the African-American Civil Rights Movement as an act of resistance. The essays also analyze the female main character in The Vegetarian, who makes a journey from an oppressed woman where the patriarchal men violate her silence and forcing her to speak, to an existence where silence, life and growth thrives. The silence has its own language and sometimes, it’s louder than words.
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