3 resultados para Sen, Amartya Kumar

em Dalarna University College Electronic Archive


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I detta arbete har jag intervjuat fyra kvinnor vilka alla har varit beroende av alkohol eller droger. Mitt syfte har varit att fokusera på dessa missbrukskarriärers brytpunkter, det som lett till att kvinnorna lämnat sitt missbruk. Jag har studerat likheter och skillnader gällande vilka faktorer som varit betydelsefulla för dessa kvinnor under deras väg tillbaka till ett drogfritt och nyktert liv.Jag har i arbetet antagit en narrativ ansats, och kvinnorna och deras historier har getts mycket utrymme i min uppsats. Jag har använt mig av tematiska intervjuer då jag samlat in mitt arbetsmaterial. Jag har försökt att i möjligaste mån låta kvinnornas berättelser genomlysa mitt arbete, och jag hoppas jag gett dem rättvisa.De slutsatser jag kom fram till efter att ha bearbetat mitt insamlade material var att det aldrig var endast en enskild händelse som ledde till att de intervjuade kvinnorna beslutade sig för att lämna missbruket bakom sig. Beslutet föranleddes hos alla kvinnor av flera händelser som tillsammans gjorde att de valde att gå en annan väg.

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The submerged entry nozzle (SEN) is used to transport the molten steel from a tundish to a mould. The main purpose of its usage is to prevent oxygen and nitrogen pick-up by molten steel from the gas. Furthermore, to achieve the desired flow conditions in the mould. Therefore, the SEN can be considered as a vital factor for a stable casting process and the steel quality. In addition, the steelmaking processes occur at high temperatures around 1873 K, so the interaction between the refractory materials of the SEN and molten steel is unavoidable. Therefore, the knowledge of the SEN behaviors during preheating and casting processes is necessary for the design of the steelmaking processes  The internal surfaces of modern SENs are coated with a glass/silicon powder layer to prevent the SEN graphite oxidation during preheating. The effects of the interaction between the coating layer and the SEN base refractory materials on clogging were studied. A large number of accretion samples formed inside alumina-graphite clogged SENs were examined using FEG-SEM-EDS and Feature analysis. The internal coated SENs were used for continuous casting of stainless steel grades alloyed with Rare Earth Metals (REM). The post-mortem study results clearly revealed the formation of a multi-layer accretion. A harmful effect of the SENs decarburization on the accretion thickness was also indicated. In addition, the results indicated a penetration of the formed alkaline-rich glaze into the alumina-graphite base refractory. More specifically, the alkaline-rich glaze reacts with graphite to form a carbon monoxide gas. Thereafter, dissociation of CO at the interface between SEN and molten metal takes place. This leads to reoxidation of dissolved alloying elements such as REM (Rare Earth Metal). This reoxidation forms the “In Situ” REM oxides at the interface between the SEN and the REM alloyed molten steel. Also, the interaction of the penetrated glaze with alumina in the SEN base refractory materials leads to the formation of a high-viscous alumina-rich glaze during the SEN preheating process. This, in turn, creates a very uneven surface at the SEN internal surface. Furthermore, these uneven areas react with dissolved REM in molten steel to form REM aluminates, REM silicates and REM alumina-silicates. The formation of the large “in-situ” REM oxides and the reaction of the REM alloying elements with the previously mentioned SEN´s uneven areas may provide a large REM-rich surface in contact with the primary inclusions in molten steel. This may facilitate the attraction and agglomeration of the primary REM oxide inclusions on the SEN internal surface and thereafter the clogging. The study revealed the disadvantages of the glass/silicon powder coating applications and the SEN decarburization. The decarburization behaviors of Al2O3-C, ZrO2-C and MgO-C refractory materials from a commercial Submerged Entry Nozzle (SEN), were also investigated for different gas atmospheres consisting of CO2, O2 and Ar. The gas ratio values were kept the same as it is in a propane combustion flue gas at different Air-Fuel-Ratio (AFR) values for both Air-Fuel and Oxygen-Fuel combustion systems. Laboratory experiments were carried out under nonisothermal conditions followed by isothermal heating. The decarburization ratio (α) values of all three refractory types were determined by measuring the real time weight losses of the samples. The results showed the higher decarburization ratio (α) values increasing for MgO-C refractory when changing the Air-Fuel combustion to Oxygen-Fuel combustion at the same AFR value. It substantiates the SEN preheating advantage at higher temperatures for shorter holding times compared to heating at lower temperatures during longer holding times for Al2O3-C samples. Diffusion models were proposed for estimation of the decarburization rate of an Al2O3-C refractory in the SEN. Two different methods were studied to prevent the SEN decarburization during preheating: The effect of an ZrSi2 antioxidant and the coexistence of an antioxidant additive and a (4B2O3 ·BaO) glass powder on carbon oxidation for non-isothermal and isothermal heating conditions in a controlled atmosphere. The coexistence of 8 wt% ZrSi2 and 15 wt% (4B2O3 ·BaO) glass powder of the total alumina-graphite refractory base materials, presented the most effective resistance to carbon oxidation. The 121% volume expansion due to the Zircon formation during heating and filling up the open pores by a (4B2O3 ·BaO) glaze during the green body sintering led to an excellent carbon oxidation resistance. The effects of the plasma spray-PVD coating of the Yttria Stabilized Zirconia (YSZ) powder on the carbon oxidation of the Al2O3-C coated samples were investigated. Trials were performed at non-isothermal heating conditions in a controlled atmosphere. Also, the applied temperature profile for the laboratory trials were defined based on the industrial preheating trials. The controlled atmospheres consisted of CO2, O2 and Ar. The thicknesses of the decarburized layers were measured and examined using light optic microscopy, FEG-SEM and EDS. A 250-290 μm YSZ coating is suggested to be an appropriate coating, as it provides both an even surface as well as prevention of the decarburization even during heating in air. In addition, the interactions between the YSZ coated alumina-graphite refractory base materials in contact with a cerium alloyed molten stainless steel were surveyed. The YSZ coating provided a total prevention of the alumina reduction by cerium. Therefore, the prevention of the first clogging product formed on the surface of the SEN refractory base materials. Therefore, the YSZ plasma-PVD coating can be recommended for coating of the hot surface of the commercial SENs.

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Denna studie har till syfte att beskriva tre lärares erfarenheter av digitala hjälpmedel inom sfi-undervisningen med fokus riktat på iPad. Studien är kvalitativ och ger svar på frågor kring lärarnas erfarenhet av litteracitetsutveckling, motivation och det individuella arbetet i klassrummet. Metoden omfattas av intervjuer som bygger på tre frågeställningar. Hur upplever lärarna litteracitetsutveckling och motivation hos de studerande vid användning av iPad och ett annat digitalt hjälpmedel? Hur ser lärarna på de enskilda studenternas behov vid användning av iPad och ett annat digitalt hjälpmedel? Vilken utveckling ser lärarna med iPad i framtida perspektiv? . Resultatet har analyserats och diskuterats i relation till tidigare forskning kring litteracitet, digitala hjälpmedel i undervisningen samt en rapport om iPad i skolan. I den första frågeställningen är lärarna överens om att litteracitetsutvecklingen med iPad relateras till vilken nivå de studerande uppnått. Ju lägre skriftspråksutvecklingsnivå ju lämpligare är språkinlärning med iPad som digitalt hjälpmedel. Detta på grund av dess enkla användarvänlighet. Lärarna anser också att enkelheten och den snabba responsen som de studerande får har en motiverande effekt. De som uppnår en högre skriftspråksutvecklingsnivå i svenska och som behöver mer utvecklande skrivövningar använder i föreliggande undersökning dator. I andra frågan diskuteras den individuella aspekten kring användning av iPad. De tre lärarna i studien anser att iPaden är ett bra verktyg och de har positiva erfarenheter om de studerandes individuella arbete och kan på ett enkelt sätt tillgodose individuella önskemål och behov hos de studerande. I den tredje frågan diskuteras iPad i ett framtida perspektiv. De tre lärarna ser iPaden som ett bra verktyg i en vidare utveckling av sfi. De menar att Skolverkets krav tillgodoses på ett lämpligt sätt med detta digitala hjälpmedel.