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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the 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.
11

Effects of Resonant Magnetic Perturbations on the STOR-M Tokamak Discharges

2014 April 1900 (has links)
Studies of resonant magnetic perturbations (RMP) have been an active topic in the tokamak research. The RMP technique involves the use of magnetic perturbations generated by external coils installed on a tokamak device. The resonant interaction between the plasma and RMP has favorable effects on magnetohydrodynamic (MHD) stability and other plasma parameters in tokamaks. The RMP experiments are carried out in the Saskatchewan Torus-Modified (STOR-M) tokamak using (l = 2, n = 1) helical coils carrying a static current pulse. The effect of RMP on the (m = 2, n = 1) magnetic islands is examined during ohmic discharges with high MHD activities. The amplitude and frequency of (2, 1) Mirnov fluctuations are significantly reduced after application of RMP. A phase of improved plasma confinement, characterized by a reduction in the H_alpha emission level and an increase in the soft x-ray (SXR) emission, is induced after application of RMP. It is also observed using the ion Doppler spectroscopy (IDS) that RMP can strongly affect the plasma rotation in STOR-M. It is found that during the RMP pulse, the toroidal velocity of C_III impurities (located at the plasma edge) increases in the co-current direction. However, the toroidal velocities of O_V and C_VI impurities (located near the plasma core) change direction from counter-current to co-current. The reduction of the toroidal flow velocity is accompanied by a reduction of the MHD frequency. It is also found that radial profiles of ion saturation current and floating potential in the edge region can be modified by RMP. An increase in the pedestal plasma density and a more negative electric field are observed at the plasma edge region during the RMP pulse. An internal probe array is assembled and installed in STOR-M to study the RMP penetration and the plasma response to RMP.
12

Comparison study on graph sampling algorithms for interactive visualizations of large-scale networks

Voroshilova, Alexandra January 2019 (has links)
Networks are present in computer science, sociology, biology, and neuroscience as well as in applied fields such as transportation, communication, medical industries. The growing volumes of data collection are pushing scalability and performance requirements on graph algorithms, and at the same time, a need for a deeper understanding of these structures through visualization arises. Network diagrams or graph drawings can facilitate the understanding of data, making intuitive the identification of the largest clusters, the number of connected components, the overall structure, and detecting anomalies, which is not achievable through textual or matrix representations. The aim of this study was to evaluate approaches that would enable visualization of a large scale peer-to-peer video live streaming networks. The visualization of such large scale graphs has technical limitations which can be overcome by filtering important structural data from the networks. In this study, four sampling algorithms for graph reduction were applied to large overlay peer-to-peer network graphs and compared. The four algorithms cover different approaches: selecting links with the highest weight, selecting nodes with the highest cumulative weight, using betweenness centrality metrics, and constructing a focus-based tree. Through the evaluation process, it was discovered that the algorithm based on betweenness centrality approximation offers the best results. Finally, for each of the algorithms in comparison, their resulting sampled graphs were visualized using a forcedirected layout with a 2-step loading approach to depict their effect on the representation of the graphs. / Nätverk återfinns inom datavetenskap, sociologi, biologi och neurovetenskap samt inom tillämpade områden så som transport, kommunikation och inom medicinindustrin. Den växande mängden datainsamling pressar skalbarheten och prestandakraven på grafalgoritmer, samtidigt som det uppstår ett behov av en djupare förståelse av dessa strukturer genom visualisering. Nätverksdiagram eller grafritningar kan underlätta förståelsen av data, identifiera de största grupperna, ett antal anslutna komponenter, visa en övergripande struktur och upptäcka avvikelser, något som inte kan uppnås med texteller matrisrepresentationer. Syftet med denna studie var att utvärdera tillvägagångssätt som kunde möjliggöra visualisering av ett omfattande P2P (peer-to-peer) livestreamingnätverk. Visualiseringen av större grafer har tekniska begränsningar, något som kan lösas genom att samla viktiga strukturella data från nätverken. I den här studien applicerades fyra provtagningsalgoritmer för grafreduktion på stora överlagringar av P2P-nätverksgrafer för att sedan jämföras. De fyra algoritmerna är baserade på val av länkar med högsta vikt, av nodar med högsta kumulativa vikt, betweenness-centralitetsvärden för att konstruera ett fokusbaserat träd som har de längsta vägarna uteslutna. Under utvärderingsprocessen upptäcktes det att algoritmen baserad på betweenness-centralitetstillnärmning visade de bästa resultaten. Dessutom, för varje algoritm i jämförelsen, visualiserades deras slutliga samplade grafer genom att använda en kraftstyrd layout med ett 2-stegs laddningsinfart.
13

Stora barngrupper = stora problem? : En undersökning om förskollärares positiva och negativa uppfattningar om stora barngrupper

Björkhage, Johanna, Forsed Thorsén, Emma January 2015 (has links)
The purpose of this study is to investigate whether large groups of preschool children means lower quality of child development and learning. From six preschool teachers perspective we also wanted to find out the large groups of children positive and negative sides. The reason behind our choice of purposes is both our own experiences of mostly negative opinions of large groups of children among preschool teachers, as well as the news reports about the negative consequences that large groups of preschoolers may cause. The study draws on a approach of the term constructionism in the understanding of the teachers’ perceptions of larger groups of preschoolers. We applied a qualitative method based on interviews with six preschool teachers working on two different preschools. The result of our study shows that the interviewed preschool teachers sees mostly advantages rather than disadvantages with large groups of preschoolers. The preschool teachers describe that to be able to work with large groups of preschoolers there has to be a good structure and organization guaranteeing that the pedagogues have the right competence and that the preschools environment is well designed. The conclusion we have been able to draw is that the preschool teachers in our study is not sharing the same negative view that previous research and media reports have shown. Instead the preschool teachers in our study sees more positive than negative aspects of large groups of preschoolers, as long as there is a good structure and organization.
14

Fractional Order Modeling and Control: Development of Analog Strategies for Plasma Position Control of the Stor-1M Tokamak

Mukhopadhyay, Shayok 01 May 2009 (has links)
This work revolves around the use of fractional order calculus in control science. Techniques such as fractional order universal adaptive stabilization (FO-UAS), and the fascinating results of their application to real-world systems, are presented initially. A major portion of this work deals with fractional order modeling and control of real-life systems like heat flow, fan and plate, and coupled tank systems. The fractional order models and controllers are not only simulated, they are also emulated using analog hardware. The main aim of all the above experimentation is to develop a fractional order controller for plasma position control of the Saskatchewan torus-1, modified (STOR-1M) tokamak at the Utah State University (USU) campus. A new method for plasma position estimation has been formulated. The results of hardware emulation of plasma position and its control are also presented. This work performs a small scale test measuring controller performance, so that it serves as a platform for future research efforts leading to real-life implementation of a plasma position controller for the tokamak.
15

Investigation of Magnetohydrodynamic Fluctuation Modes in the STOR-M Tokamak

Gamudi Elgriw, Sayf 31 July 2009
While magnetohydrodynamic (MHD) instabilities are considered one of the intriguing topics in tokamak physics, a feasibility study was conducted in the Saskatchewan Torus-Modified (STOR-M) tokamak to investigate the global MHD activities during the normal (L-mode) and improved (H-mode) confinement regimes. The experimental setup consists of 32 discrete Mirnov coils arranged into four poloidal arrays and mounted on STOR-M at even toroidal distances. The perturbed magnetic field fluctuations during STOR-M discharges were acquired and processed by the Fourier transform (FT), the wavelet analysis and the singular value decomposition (SVD) techniques. In L-mode discharges, the poloidal MHD mode numbers varied from 2 to 4 with peak frequencies in the range 20-40 kHz. The dominant toroidal modes were reported between 1 and 2 oscillating at frequencies 15-35 kHz. In another experiment, a noticeable MHD suppression was observed during the H-mode-like phase induced by the compact torus (CT) injection into STOR-M. However, a burst-like mode called the gong mode was triggered prior to the H-L transition, followed by coherent Mirnov oscillations. Mirnov oscillations with strong amplitude modulations were observed in the STOR-M tokamak. Correlations between Mirnov signals and soft x-ray (SXR) signals were found.
16

Investigation of Magnetohydrodynamic Fluctuation Modes in the STOR-M Tokamak

Gamudi Elgriw, Sayf 31 July 2009 (has links)
While magnetohydrodynamic (MHD) instabilities are considered one of the intriguing topics in tokamak physics, a feasibility study was conducted in the Saskatchewan Torus-Modified (STOR-M) tokamak to investigate the global MHD activities during the normal (L-mode) and improved (H-mode) confinement regimes. The experimental setup consists of 32 discrete Mirnov coils arranged into four poloidal arrays and mounted on STOR-M at even toroidal distances. The perturbed magnetic field fluctuations during STOR-M discharges were acquired and processed by the Fourier transform (FT), the wavelet analysis and the singular value decomposition (SVD) techniques. In L-mode discharges, the poloidal MHD mode numbers varied from 2 to 4 with peak frequencies in the range 20-40 kHz. The dominant toroidal modes were reported between 1 and 2 oscillating at frequencies 15-35 kHz. In another experiment, a noticeable MHD suppression was observed during the H-mode-like phase induced by the compact torus (CT) injection into STOR-M. However, a burst-like mode called the gong mode was triggered prior to the H-L transition, followed by coherent Mirnov oscillations. Mirnov oscillations with strong amplitude modulations were observed in the STOR-M tokamak. Correlations between Mirnov signals and soft x-ray (SXR) signals were found.
17

Ordförståelse i förskolan : Pedagogers syn på arbetet med yngre barns utveckling av ordförståelse i en stor barngrupp med blandad språkbakgrund / Vocabulary in Preschool : Teachers' Views on the Work of Young Children's Development of Vocabulary in a Large Group of Children of Mixed Language Backgrounds

Petersson, Elin January 2014 (has links)
Syftet med studien är att synliggöra förskollärares syn på arbetet med ordförståelse för yngre barn i större barngrupper där barnen har blandad språkbakgrund. Frågeställningarna är hur förskollärarna arbetar med att introducera nya ord, vad de tror påverkar inlärningen och hur utvecklingen av språket påverkas av faktorerna kring barngruppen. Kvalitativa intervjuer har genomförts med två förskollärare som arbetar med barn i åldrarna tre till fem år på förskolor i större städer i Mellansverige. Studien visar att organisation och planering är en viktig del i arbetet i en stor barngrupp. Pedagogens förhållningssätt och goda förebilder hos både pedagoger och andra barn är en viktig del i hur barnen lär sig nya ord. Bilder, sagor och teman är viktiga pedagogiska verktyg för att introducera nya ord för yngre barn. / The purpose ofthis studyis to highlight thepreschool teachers'views on thedevelopment of thevocabularyforyoung childreninlargergroups, where children havemixedlanguagebackground. The questions is howpreschool teachersworking tointroduce newwords, whatthey thinkaffectslearning andhow the development oflanguageis influencedby the factorssurrounding thechildgroup. Qualitative interviews were conducted withtwopreschool teachersworking withchildren aged 3-5yearsinpreschoolsin larger cities incentral Sweden.The study shows thatorganization and planningisan important part ofthe work of alargegroup of children. The teachers'attitudes androle modelsof botheducatorsand other childrenisan important part ofhowchildren learnnew words.Pictures,stories andin themes are important educational tool to introducenew wordsfor younger children.
18

Student-generated representations in Algodoo while solving a physics problem / Studentgenererade representationer i Algodoo vid lösningen av en fysikuppgift

Bengtz, Oskar January 2018 (has links)
Fysiklärare möter ofta den svåra uppgiften att representera abstrakta, väldefinierade egenskaper hos den fysiska världen (så som krafter eller energier) för studenter som går bortom ekvationer, grafer eller diagram. I denna studie tittar jag två fall av universitetsstudenter som löser en fysikalisk uppgift, användandes det digitala programmet Algodoo på en stor pekskärm för att undersöka hur studenter naturligt använder sig av sådan teknologi för att återskapa dessa representationer själva. Jag finner att när studenter skapar scener i Algodoo prioriterar de att behålla en viss mått av likhet från den fysiska världen, vilket går bortom den formella behandlingen av uppgifter som studenter kan ha fått lära sig i fysikundervisningen. Vidare, när studenterna använder sig av fysikaliska ekvationer vid lösandet av problemet, verkar de använda Algodoo som ett facit för att se huruvida deras numeriska lösning, uträknad på en klassisk whiteboard, stämmer. På detta sätt - vilket har föreslagits i tidigare forskning - ser jag hur Algodoo, och liknande digitala lärmiljöer, fungerar som en bro mellan studenternas konceptuella förståelse av den fysiska världen, och den mer formella, matematikbaserade beskrivningen vilket används inomfysiken. / Physics teachers are often faced with the difficult task of representing abstract, formally-defined properties of the physical world (such as forces or energy) for students in a way which goes beyond equations, graphs, and diagrams. In this study, I investigate two cases of university students solving a physics problem while using the digital software, Algodoo, on a large touch screen to examine how students might naturally leverage such technology to create such representations of their own. I find that as student draw scenes in Algodoo, they tend to prioritze a degree of resemblance to the physical world which goes beyond the formal treatment of problems they might have been taught in physics classes. Additionally, as the students recruit physics equation into their solution of the problem, they appear to use Algodoo as a conceptual check for the numerical answer they calculate on the normal whiteboard. In this way - and as has been hypothesized in previous research - I see the potential for Algodoo and similar digital learning environments to act as a bridge between students’ conceptual intuitions of the physical world and the more formal, mathematically-based descriptions used in physics.
19

Hela Tyskland i nationellt festrus tacke vare dåren hitler! : En undersökning av fem olika dagstidningar före och under andra världskriget

Lindén, Max, Forshage, Andreas January 2018 (has links)
Arbetet handlar om hur olika tidningar i Sverige framställer nazistregimen i Tyskland före och under andra världskriget i sina rubriker. Syftet är att ta reda på vilka skillnader och likheter som finns mellan lokala tidningar, tidningarna själva över tid, lokala tidningar över tid, lokal respektive rikstidning och lokal respektive rikstidning över tid. Materialet som ligger till grund för undersökningen är fyra lokala tidningar samt en rikstidning. Därutöver har vi konstruerat en analysmodell med inspiration från Asp (2011) mediernas betydelse, valet 2010och Lundgren (1999) Nyheter- att läsa tidningstext. Undersökningen visar på att det finns skillnader och även likheter mellan de olika lokaltidningarna. Dessutom påvisar undersökningen att det finns skillnader över tid mellan vissa lokaltidningar och att vissa lokaltidningar också förändrar sig över tid. Undersökningen påvisar också skillnader mellan lokaltidningar och rikstidningen.
20

Specialist på det oförutsedda? : Anestesisjuksköterskans roll vid stora olyckor och katastrofer / Specialist in the unexpected? : The role of the nurse anaesthetist at major accidents and disasters

Hantoft, Linda January 2020 (has links)
Bakgrund: För att upprätthålla en så normal kvalitet på vården som möjligt och minska det psykiska och fysiska lidandet vid stora olyckor och katastrofer måste resurserna ledas och fördelas på ett annat sätt än i sjukvårdens vardagsorganisation. Detta medför en omställning i sättet att bedriva sjukvård på till katastrofmedicinsk metodik. Anestesisjuksköterskan är en viktig del i den katastrofmedicinska beredskapen men hur anestesisjuksköterskan själv uppfattar sin roll är ett sparsamt utforskat område. Syfte: Syftet med denna studie var att beskriva anestesisjuksköterskans uppfattning om sin roll vid stora olyckor och katastrofer. Metod: En kvalitativ metod användes, där 10 semistrukturerade intervjuer med anestesisjuksköterskor har analyserats med en kvalitativ innehållsanalys. Resultat: Efter analys framkom fyra kategorier; vara en del i något större, vara närmast patienten, genom sin profession känna trygghet och medvetenhet och få förutsättningar att fungera i sin roll. Det genomgående temat i anestesisjuksköterskans uppfattningar är att genom sin profession vara en livsviktig nyckelfunktion med vilja att verka i den på bästa sätt. Konklusion: Anestesisjuksköterskan har en betydelsefull och komplex roll i den katastrofmedicinska beredskapsorganisationen men efterfrågar kunskap och utbildning för att kunna verka effektivt och säkert. Den katastrofmedicinska beredskapen måste lyftas och medvetandegöras i verksamheten.

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