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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.
1

Statistisk studie av sambandet mellan geostrofisk vind och temperatur i södra Sverige

Höglund, Jonas January 2002 (has links)
Atmosfärisk cirkulation är viktigt vid studier av klimatet både på global och på regional skala. För att studera cirkulationseffekter används olika cirkulationsmodeller. I det här fallet används de geostrofiska vindekvationerna. Två dataserier med månadsmedelvärden för tryck respektive temperatur från tre platser i södra Sverige har använts. I arbetet här studeras först kopplingen mellan medeltemperaturen i södra Sverige och den storskaliga cirkulationen över norra Atlanten (NAO). Det visar sig att storleken på den västliga komponenten klart påverkar temperaturen på så sätt att en stark västlig strömning ger högre temperaturer. Den västliga komponenten under vintern är starkt korrelerad med temperaturen medan den nord-sydliga komponenten är dåligt korrelerad. Motsatt förhållande råder under sommaren, då den nord-sydliga komponenten har stor betydelse för temperaturen i södra Sverige. De härledda cirkulationsmodellerna bestäms med hjälp av statistiska metoder. Enkel och multipel linjär regression används för att förstå sambandet mellan temperatur och cirkulation. Säkerheten i modellerna bestäms genom korrelationskoefficienten och residualvariansen. Modellerna har hög säkerhet under vintern på grund av den västliga strömningen medan de är relativt dåligt bestämda under övriga årstider. Med hjälp av dataserierna och de geostrofiska vindekvationerna har olika regressionsmodeller ställts upp. Det mest intressanta i studien är att ta reda på om de senaste 10-15 årens varma väder kan förklaras av cirkulationen. Genom att använda de uppställda regressionsmodellerna, vilka har kalibrerats för perioden 1873-1975, på de senaste 25 åren med höga temperaturer visar det sig att det blir positiva residualer under vintermånaderna. Under våren blir residualerna också starkt positiva, dessutom signifikant skilda från noll enligt hypotestestet. Slutsatsen är att, de högre temperaturerna under vintern och våren i södra Sverige troligtvis inte enbart kan förklaras av cirkulationsförändringar. / Atmospheric circulation is important in determining the surface climate on both global and regional scale. To quantify its effect, different circulation indices are often used. Here the geostrophic wind equations are applied to obtain circulation information for the south of Sweden on a monthly basis. Monthly means of temperatures have also been used. In this work, the connection between the mean temperature in the south of Sweden and the large-scale circulation in the North Atlantic area is studied. It is shown that flows with a westerly component clearly favour higher temperatures. Moreover, the westerly component is well correlated with the temperature in the winter. The temperature does not correlate with the northerly component for the winter season. In the summer an opposite relationship between the westerly and the northerly components on one hand, and the temperature on the other, as shown. The derived circulation models were established via statistical models. Simple and multiple regressions were used to understand the relationship between temperature and circulation. The accuracy in the models was determined by the correlation coefficient and the residual variance. The accuracy of the models is good during the winter and worse for the rest of the year. Different regression models have been estimated from the two data sets of pressure and temperature using the geostrophic wind equations. The most interesting in this study is to find out if the circulation can explain the increasing temperatures during the latest 10-15 years. By applying the results from the regression models, calibrated on data for the period 1873-1975, to the latest 25 years of high temperatures, it is shown that positive residuals exist during the winter. During the spring the residuals are positive as well. Moreover, the results are significantly differing from zero according to a test of hypothesis. The conclusion of this is that changes on the circulation itself can probably not explain the higher temperatures during the winter and spring.
2

Klassificering av Low Level Jets och analys av den termiska vinden över Östergarnsholm

Frost, Lisa January 2004 (has links)
Syftet med den här studien är att studera vindprofiler och klassificera Low Level Jets (LLJ) och även analysera den termiska vinden över Östergarnsholm. Östergarnsholm är en liten ö som ligger 4 kilometer öster om Gotland. Viseringar och sonderingar från åren 1995 till 2001 samt år 2003 har använts. Det kriteriet som har använts för att klassificera LLJs är att det ska finnas ett vindhastighetsmaximum under 500 meters höjd. De undersökta orsakerna till uppkomsten av en LLJ är sjöbris, tröghetssvängning och termisk vind. För att kunna ta ut LLJs orsakade av sjöbris har vindprofiler över hela dygn använts. Vindens vridning vid marken, under dagen, jämfört med den överlagrade vindens riktning vid 2000 meters höjd har undersökts. LLJs som uppkommit på grund av tröghetssvängning har analyserats. Metoden för tröghetssvängning bygger på att analysera den geostrofiska vindens hastighet och vindriktning för att sedan kunna räkna ut hur vinden har blåst och var en eventuell LLJ skulle kunna bildas. Här har vindriktningar mellan 20º – 220º använts eftersom det medför att vinden då blåser från havet. Resterande vindriktningar medför att vinden har blåst över Gotland vilket resulterar i att en eventuell tröghetssvängning skulle störas och en LLJ skulle försvinna innan den når Östergarnsholm. Vindhastigeter och vindriktningar har jämförts med teoretiskt uträknade värden från tryckmätningar. Från alla 245 viseringar fanns 103 vindprofiler med LLJs. Utav dessa var 27 stycken, under 12 dygn, orsakade av sjöbris. Hur många LLJs som bildats av tröghetssvängning är oklart. Detta eftersom olika resultat erhålles beroende på om vindhastigheter och vindriktningar tas från viseringarna eller är beräknade från tryckmätningar, samt om beräkningarna av transporttiden sker med raka eller krökta trajektorier. Totalt hittades 9 LLJs som orsakats av tröghetssvängning. Metoden som använts för att analysera tröghetssvängning ger förmodligen bättre resultat över land än över hav. Detta eftersom det är svårt att mäta de exakta vindförhållandena längs luftens transport över hav. Den geostrofiska vindens ändring med höjden över ön, det vill säga den termiska vinden, har analyserats genom att undersöka alla vindprofiler, även de utan LLJs. Dessa har jämförts med den geostrofiska vinden beräknad från tryckmätningar, som representerar vinden vid marken, för att se om det uppkommer termiska vindar över Östergarnsholm. En LLJ som orsakats av termisk vind uppkommer när den geostrofiska vinden avtar med höjden, det vill säga vid negativ termisk vind. Antalet fall där den geostrofiska vinden avtar med höjden och där vinden är konstant med höjden var ungefär lika många. Däremot fanns något fler fall där den geostrofiska vinden ökade med höjden, dessa uppgick även till högre hastigheter än när vinden avtog med höjden. Det finns inget samband för vindvridningen med höjden då det förekommer LLJs på grund av termisk vind. Däremot finns ett tydligt samband mellan den negativa termiska vindens u- och v-komponent och den geostrofiska vindens u- respektive v-komponent. I båda fallen så tenderar vinden att gå mot noll med höjden. Totalt hittades 41 LLJs som var orsakade av termisk vind. Vid ungefär 50% av alla vindprofiler, både när den geostrofiska vinden avtog och ökade med höjden, var den termiska vindens nord-sydliga komposant positiv och den ost-västliga komposanten negativ. Detta ger att den varmare luften finns i nordost. / The aim of this study is to classify Low Level Jets (LLJ) and analyze the thermal wind over Östergarnsholm. Östergarnsholm is a small island that is situated 4 kilometres east of Gotland in the Baltic Sea. Pibal trackings and soundings from 1995 to 2001 and 2003 have been used in the study. The criteria that have been used to classify the LLJs is that there must be a maximum of the wind speed below 500 meters. Wind profiles from a specific day have been used to determine if the LLJs is caused by sea breeze. The shift of wind direction at ground level, during the day, compared to the geostrophic wind at 2000 meters has been analyzed. LLJs caused by internal oscillation have been analyzed. In the used method the geostrophic wind speed and wind direction have been analyzed to determine how the wind has blown and where a LLJ possibly could be formed. Only wind directions between 20º and 220º have been used to avoid that the wind should have passed Gotland. If the winds have passed Gotland the internal oscillation has been disturbed and no LLJ can appear. Measured wind speeds and directions have been compared to theoretical values from pressure measurements. 103 wind profiles with LLJs were found from all pibal trackings. In 27 of these pibal trackings, from 12 days, were LLJs caused by sea breeze. It is difficult to say how many LLJs that are caused by an internal oscillation. This due to the different results obtained when using wind speeds and wind directions from pibal trackings or pressure measurements. Also using straight line trajectories or trajectories following the isobars gives different results. Totally 9 LLJs were found, caused by an internal oscillation. Probably this way of analyze the internal oscillations is a better method for measurements over land than over sea. This due to the difficulties in measuring the exact wind speed and wind direction over the whole traveling distance over sea. The thermal wind over the island has been analyzed by studying all pibal trackings, even those without LLJs. The pibal trackings have been compared to the geostrophic wind calculated from pressure measurements to determine if thermal winds occur over Östergarnsholm. A LLJ caused by thermal wind occur when the geostrophic wind decreese with height, i.e. negative thermal wind. There was no difference in the amount of negative thermal winds and cases with no thermal wind. There were a few more positive thermal winds and they had higher wind speeds than the negative ones. There is no connection in the shift of wind direction when there is a LLJ caused by thermal wind. But there is a significant connection between the u- and v-component of the negative thermal winds and the u- and v-component of the geostrophic wind. In both cases the geostrophic wind tends to decreese towards zero with height. 41 of all LLJs were caused by thermal winds. About 50% of both negative and positive thermal winds have a positive v-component and a negative u-component. This means that the warmer region is in the north east.
3

Vädrets påverkan på byggarbetsplatsen

Müller, Henrik, Villamil, Jair, Andersson, Jonas January 2008 (has links)
<p>This exam report contains studies about how the weather affects the construction site from a planning and productivity perspective. In 1960’s the contractors started to build during the winter, since then the demands to obtain a good construction has been higher on both the contractor and then promoter.</p><p>In this report you will see how the different actors at the construction site handle the weather problems. By several interviews of the actors at the construction site there have been opinions about the weather situation which has been collected. </p><p>To get a wide perspective of the problem, field studies from four different construction sites been made.</p><p>Weather statistics over Halmstad is a mayor part of this report. Wind, temperature and precipitation will be presented in diagrams and tables divided over all months. The point with these tables and diagrams are ment to be a help during the projecting and timetable planning of the construction project. </p><p>In this report we came up with the following; that weather is a big negative factor on the construction site. The losses related to productivity are mayor, especially during framework. If no consideration is taken to the weather, productivity losses for one year will be significant. From interviews and weather statistics the final result has been that April and May are the most productive months of the year.</p>
4

Vädrets påverkan på byggarbetsplatsen

Müller, Henrik, Villamil, Jair, Andersson, Jonas January 2008 (has links)
This exam report contains studies about how the weather affects the construction site from a planning and productivity perspective. In 1960’s the contractors started to build during the winter, since then the demands to obtain a good construction has been higher on both the contractor and then promoter. In this report you will see how the different actors at the construction site handle the weather problems. By several interviews of the actors at the construction site there have been opinions about the weather situation which has been collected. To get a wide perspective of the problem, field studies from four different construction sites been made. Weather statistics over Halmstad is a mayor part of this report. Wind, temperature and precipitation will be presented in diagrams and tables divided over all months. The point with these tables and diagrams are ment to be a help during the projecting and timetable planning of the construction project. In this report we came up with the following; that weather is a big negative factor on the construction site. The losses related to productivity are mayor, especially during framework. If no consideration is taken to the weather, productivity losses for one year will be significant. From interviews and weather statistics the final result has been that April and May are the most productive months of the year.
5

Fuktvariationer i uteluftsventilerade vindsutrymmen / Moisture variations in outdoor air ventilated attics

Angerstig, Kristofer, Eidenstedt, Olle January 2002 (has links)
<p>NR 20140804</p>
6

Projektering av vindkraftspark i Juddhult, Småland

Pettersson, Daniel, Svantesson, Per January 2008 (has links)
<p>The aim with this study was to collect fundamental information, and to plan, a wind</p><p>power farm in Juddhult , Småland in southern Sweden. The goal is to collect the best</p><p>available projecting planning support. The pieces of this projecting planning support</p><p>that will be presented is; Environmental Consequence Description (MKB), production</p><p>calculations, comparisons between different plant types, economic calculations, evaluate</p><p>the economy and give some farm design suggestions. The imagined wind farm will be</p><p>located in forest environment and which may cause a number of new problems. Special</p><p>interest that will be affected, where special consideration because of the forest</p><p>environmental is requested is, hunting, wetlands, ancient monuments and wind</p><p>turbulence. To perform calculations of expected energy transformation, sound-, shadowand</p><p>landscape influence the program WindPro has been used for these calculations. The</p><p>economic calculation methods used in this project is the annual method and electricity</p><p>price prognosis. Among the results some interesting KPI (Key Performince Indicator) for</p><p>the wind farm is presented. To be able to do a risk analysis three scenarios has been</p><p>created, the worst case scenario, the most likely scenario and the best possible scenario.</p>
7

Utvärdering av energianvändningen i ett produktionskök på Svartsö i Stockholms skärgård : Undersökning av förutsättningarna för ett PV-vind hybridsystem och energibesparande lösningar

Khoshlahge-Yazdi Jöhnemark, Behroz, Spinelli Scala, Robin January 2015 (has links)
The EU Directive 20-20-20 places high demands on new buildings and activities designed with a focus on sustainability with low climate impact. The use of renewable energy technologies are becoming increasingly important to lower carbon emissions and ensuring a sustainable and environmentally friendly energy supply. This becomes especially important in energy-intensive activities like office buildings or commercial kitchens which are characterized by high internal heat generation from appliances, machinery and people. By providing the business with electricity from renewable energy sources and recovering excess heat both money and the environment can be saved. The starting point of this study was to investigate a planned commercial kitchen on Svartsö in the Stockholm archipelago that is supposed to produce organic fresh baby food. The company behind the business wishes to profile their activities climate and environmentally friendly. The purpose of the study was to investigate the electricity production potential for a PV-wind hybrid systems on Svartsö and examine how much of this electricity can be integrated directly in the business. The building's energy need was calculated by a constructed model in the energy calculation program VIP-Energy. To estimate the production potential of the renewable micro-generation simulations of a PV-wind hybrid system with location-specific weather data from SMHI was designed and performed in Matlab. The study provides analysis and reflections of the results. The conclusion is that the electricity usage profile of the business correlates well with the production profile of solar power while wind power is expensive in relation to solar power.
8

Projektering av vindkraftspark i Juddhult, Småland

Pettersson, Daniel, Svantesson, Per January 2008 (has links)
The aim with this study was to collect fundamental information, and to plan, a wind power farm in Juddhult , Småland in southern Sweden. The goal is to collect the best available projecting planning support. The pieces of this projecting planning support that will be presented is; Environmental Consequence Description (MKB), production calculations, comparisons between different plant types, economic calculations, evaluate the economy and give some farm design suggestions. The imagined wind farm will be located in forest environment and which may cause a number of new problems. Special interest that will be affected, where special consideration because of the forest environmental is requested is, hunting, wetlands, ancient monuments and wind turbulence. To perform calculations of expected energy transformation, sound-, shadowand landscape influence the program WindPro has been used for these calculations. The economic calculation methods used in this project is the annual method and electricity price prognosis. Among the results some interesting KPI (Key Performince Indicator) for the wind farm is presented. To be able to do a risk analysis three scenarios has been created, the worst case scenario, the most likely scenario and the best possible scenario.
9

Utmaningar med att projektera höga trähus / Challenges in Designing Tall Timber Buildnings

Stening, Eric, Wall, Erik January 2017 (has links)
Detta arbete har utförts för att ta fram de utmaningar som kan uppstå när höga trähus ska projekteras. Höga trähus kan vara en viktig del i ett hållbart byggande ur flera aspekter. Höga hus har i detta arbete definierats till byggnader med minst åtta våningar. I samarbete med WSP Örebro har avdelningschefen på byggprojektering bistått med hjälp och tips samt givit kontaktinformation till relevanta aktörer inom ämnet och även varit drivande i att kontakta flera aktörer på egen hand. För att få fram information har litteratur studerats samt intervjuer utförts med erfarna aktörer inom byggprojektering. Flertalet aktörer var inriktade inom trähus. Under arbetets intervjumoment har det framkommit att utmaningarna för höga trähus i regel grundas av 5 områden. • Fukt • Krympning • Akustik • Vind • Brand Under resultat tas varje område upp och sammanfattas till den del som svarar på frågeställningen. Den främsta utmaningen är hur vind kan påverka höga trähus eftersom trä är ett lätt material. I slutsatsen visas att ett högt trähus bör stå i många år för att kunna visa hur pass bra det är. / This thesis have been executed to address the challenges that may emerge when tall timber buildings are to be designed. Tall timber buildings can be an important part for sustainable construction from several aspects. In this thesis, tall buildings have been defined as buildings with at least eight floors. In collaboration with WSP Örebro, the Head of Department on Construction Engineering has assisted with support and tips, and provided contact information to relevant actors in the subject, and has also been contacting several actors by own hand. In order to obtain the information, literature has been studied and interviews conducted with experienced actors in construction design. Most actors were oriented in timber buildings. During the interview, it has been found that the challenges for tall timber buildings are usually based on 5 areas. • Moisture • Shrinkage • Acoustics • Wind • Fire Under results, each area is summarized to the part that answers the question. The main challenge is how wind can affect tall timber buildings since wood is a lightweight material. In the conclusion, it is shown that a tall timber building should stand for many years in order to show what a good quality of a structure the tall timber building is.
10

Vetenskapen : - En Forskningsstation i Tarfala / The Research Station in Tarfala

Zickerman, Linnéa January 2016 (has links)
Utan att forskarna riktigt kunde förklara varför stod det helt klart under 1900-talets första hälft att isarna blev mindre. På hela norra halvklotet blev glaciärerna allt mindre och denna storlekförändring sattes i samband med den temperaturökning som skett under samma tid. Glaciärerna krympte och man sökte den exakta kopplingen mellan klimatets förändring och smältande glaciärer. Professor Ahlman, glaciolog vid Stockholms universitet beslutade att Storglaciären i Tarfaladalen var platsen där mätningar skulle ske och sedan 1946 har Stockholms Universitet bedrivit verksamhet vid Tarfala Forskningsstation. Stationen fungerar som en plattform för glaciologer och används kontinuerligt av forskare och studentgrupper från SU men även av internationella forskare och studenter. Mätstudierna som utförs i Tarfala är betydelsefullt underlag för glaciologiska och klimatologiska studier, såväl nationellt som internationellt. Verksamheten och forskningsgruppen har med åren vuxit och är idag i stort behov av en större och mer komplex byggnad för att kunna bedriva forskning på världsledande nivå. I mitt examensarbete har jag undersökt platsen, vinden och forskningsverksamheten. / In the beginning of the 20th century the glaciers in the world got smaller. Scientists couldn’t explain why but tried to find a connection between climate change and melting glaciers. One of them, V. Schytt, made a ski journey between Abisko and Kebnekaise to find the most suitable glacier in Sweden for measuring mass balance. He faced the windy, rough but beautiful valley “Tarfaladalen”. He viewed over ”Storglaciaciaren” and realized that this site is optimal for a glacier research center. Since 1946 the Stockholm University founded a research station where both national researcher as well as international visits and uses as a platform. The data that is collected around this area is important information for glacier studies around the world. We are facing huge climate changes in the world and the Department of Geological Science in Tarfala are in need of a more complex building adapted to the extreme environment that gives the best support to practise science and research at an international high level. During my thesis project I have analyzed the site, the wind and the organisation Department of Geological Science in Tarfala.

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