With the expansion of the Internet and an increasing fraction of consumers having broadband connections, more and more content is finding its way on-line. Video content is becoming one of the most popular types of media content on the Internet. Traditional media content providers, such as television networks, are placing their content on the Internet in order to gain a broader audience. On-demand websites such as kanal5play.se allow viewers to view the multimedia content they want at the time of their choice. While this gives viewers flexibility in their viewing, it creates resource problems for content providers. Statistics from Kanal5 AB show that, even with individual viewers requesting content when they want, there are still patterns in which multiple viewers watch the same content at the same time. This means there are correlations in the demand for content. With unicast distribution this leads to spikes in requirements for bandwidth to the viewers. These peaks lead to high costs for network and server resources to deliver the requested content, but these resources have low average utilization. This thesis project investigates how a content provider can make use of each viewer’s own resources to deliver content to other users using peer-to-peer techniques. The thesis evaluates what methods can be used in order to reduce the content provider’s resource requirements during peak hours by exploiting copies of contents that have already been delivered to viewers who requested this same content earlier. A prototype was made to evaluate the suggested design using Java Remote Method Invocation (RMI), which is built on top of the Transfer Control Protocol (TCP). Experiments show that an initial delay of several seconds is reached on a network with a simulated delay of 100ms, while a minimal initial delay was observed on a network with low delay, i.e. ideal conditions. The throughput results of the prototype show that the suggested solution is adequate for delivering on-demand content supplied by Kanal5 AB. However, the relatively poor startup performance of this solution argues for tuning the application to better work with the TCP protocol or to utilize another transport protocol - especially if the round-trip delay is large as TCP’s 3-way handshake and flow control algorithm limit the performance of the prototype system. / Med utbyggnaden av Internet och en ökande andel konsumenter med bredband, mer och mer innehåll hittar sin väg på nätet. Video innehåll blir en av de mest populära typer av media på Internet. Innehållsleverantörer som använder sig av traditionella medier, exempelvis tv-nät, lägger sitt innehåll på Internet för att nå en bredare publik. On-demand webbplatser som kanal5play.se låter tittarna se multimediainnehållet de vill, när de vill. Även om detta ger tittarna flexibilitet i sitt tittande så skapar det resursproblem för innehållsleverantörer. Statistik från Kanal5 AB visar att även med enskilda tittare som begär innehåll när de vill så finns det fortfarande mönster där flera tittare tittar på samma innehåll på samma gång. Detta innebär att det finns samband i efterfrågan på innehåll. Med unicast distribution leder detta till sprikar i krav på bandbredd till tittarna. Dessa toppar leda till höga kostnader för nät-och server för att leverera det efterfrågade innehållet, men dessa resurser har låga genomsnittliga utnyttjanden. Detta examensarbete undersöker hur en innehållsleverantör kan använda sig av varje tittares egna resurser för att leverera innehåll till andra användare med hjälp av peer-to-peer-teknik. Avhandlingen utvärderar vilka metoder kan användas för att minska innehållsleverantörens resursbehov under rusningstid genom att utnyttja kopior av innehåll som redan har levererats till tittarna som begärde samma innehåll tidigare. En prototyp gjordes för att utvärdera den föreslagna konstruktionen med Java Remote Method Invocation (RMI), som är byggd ovanpå Transfer Control Protocol (TCP). Experiment visar en uppstartsfördröjning på flera sekunder på ett nätverk med en simulerad fördröjning på 100 ms, samtidigt som en minimal uppstartsfördöjning observerades på ett nätverk med låg fördröjning, dvs idealiska förhållanden. Resultaten för genomströmningshastigheten hos prototypen visar att den föreslagna lösningen är tillräcklig för att leverera on-demand innehåll som tillhandahålls av Kanal5 AB. De relativt dåliga uppstartsresultaten för denna lösning säger dock att förbättringar bör göras i applikationen så att den kan arbeta bättre med TCP protokollet, eller att ett annat protokoll används - särskilt om nätverksfördröjningen är stor, då TCP:s 3-vägs handskakning och flödeskontroll algoritm begränsar prestandan hos det föreslagna systemet.

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Sewage, agricultural runoff, and atmospheric deposition have greatly increased the amount of nutrients (largely nitrogen (N) and phosphorus (P)) in surface water nationwide. Excess nutrients are associated with algal blooms and dissolved oxygen depletion in many water bodies, but linkages between nutrients and dissolved oxygen have been largely correlative. Biochemical oxygen demand (BOD) is a regulated water quality parameter that is aimed at describing the amount of oxygen consumed during the decomposition of organic matter. Despite the awareness that excess nutrients are linked to dissolved oxygen in rivers, few studies in the nutrient criteria literature discuss BOD measurements or how nutrients may impact BOD. Accordingly, I used factorial experiments to test the effect of inorganic nutrients (as N, P and N+P) and dissolved organic carbon on BOD measurements in Utah streams. The study was carried out from January through summer baseflow in 2011, allowing me to evaluate the effects of spatial and temporal variation of ambient nutrient concentration on oxygen demand. The study design included measurements in streams above and below nutrient point-sources (publicly owned treatment works) and several reference sites. I used classification and regression trees to identify thresholds of TN and TP that separate BOD response to nutrients into statistically distinct groups. My results show that seasonal variation affected BOD levels. As temperatures rose and water levels increased during peak runoff, I observed the highest BOD response to nutrient additions. I also found a significant correlation between BOD and ambient nutrient concentrations during that time period. I identified potential nutrient-related thresholds that could be used to assign numeric criteria that would protect designated uses. The threshold values I found for TN and TP were 0.56 mg/L and 0.09 mg/L, respectively. My results suggest that BOD may be sensitive to nutrient inputs and my experimental approach could be used as one line of evidence to support nutrient criteria related to aquatic life uses.

Syftet med den föreliggande studien var att undersöka huruvida arbetsrelaterade krav och arbetsrelaterade resurser kunde predicera utmattning hos förskolepersonal (N = 114). Studien genomfördes med en korrelationell design där de validerade enkäterna COPSOQ III och KUS-26 användes för att samla in data. Analysen genomfördes med tre hierarkiska multipla regressionsanalyser som visade att arbetsrelaterade krav och arbetsrelaterade resurser tillsammans kunde predicera utmattning. Arbetsrelaterade krav kunde predicera utmattning med ett positivt samband, medan arbetsrelaterade resurser inte på egen hand kunde predicera utmattning när de förekom i samma modell som arbetsrelaterade krav. Känslomässiga krav och kvantitativa krav var de typer av arbetsrelaterade krav som positivt kunde predicera utmattning. Socialt stöd från överordnad var den enda typen av resurs som kunde predicera utmattning med ett negativt samband. Sammanfattningsvis visade den föreliggande studien att arbetsrelaterade krav tycks vara en större riskfaktor än bristande arbetsrelaterade resurser när det kommer till utmattningsproblematik hos svensk förskolepersonal. / The aim of this study was to investigate whether job-demands and resources could predict exhaustion in Swedish preschool personnel (N = 114). The study was done using a quantitative method where the validated questionnaires COPSOQ III and KUS-26 were used to gather the data. Using 3 hierarchical multiple regression analyzes the present study showed that job-demands and resources could predict exhaustion. Job demands could positively predict exhaustion. However, job resources could not on its own predict exhaustion when occurring in the same model as job demands. The present study showed that emotional and quantitative demands were the types of demands that could positively predict exhaustion. Social support from supervisor was the only type of resource that could negatively predict exhaustion. In conclusion, the study showed that for Swedish preschool personnel, high job demands are a greater risk factors for exhaustion than lacking job resources.

Electric power systems are undergoing a paradigm shift where an increasing number of variable renewable energy resources such as wind and solar power are being introduced to all levels of existing power grids. At the same time consumers are gaining a more active role where self energy production and home automation solutions are no longer uncommon. This challenges traditional power systems which were designed to serve as a centralized top-down solution for providing electricity to consumers. Demand response has risen as a promising solution to cope with some of the challenges that this shift is creating. In this thesis, control and scheduling studies using demand response, and consumer load models adapted to environments similar to Sweden are proposed and evaluated. The studies use model predictive control approaches for the purpose of providing ancillary and financial services to electricity market actors using thermal flexibility from detached houses. The approaches are evaluated on use-cases using data from Sweden for the purpose of reducing power imbalances of a balance responsible player and congestion management for a system operator. Simulations show promising results for reducing power imbalances by up to 30% and managing daily congestion of 5-19 MW using demand response. Moreover, a consumer load model of an office building is proposed using a gray-box modeling approach combining physical understanding of buildings with empirical data. Furthermore, the proposed consumer load model along with a similar model for detached houses are packaged and made freely available as MATLAB applications for other researchers and stakeholders working with demand response. The applications allow the user to generate synthetic electricity load profiles for heterogeneous populations of detached houses and office buildings down to 1-min resolution. The aim of this thesis has been to summarize and discuss the main highlights of the included articles. The interested reader is encouraged to investigate further details in the second part of the thesis as they provide a more comprehensive account of the studies and models proposed. / <p>QC 20171011</p>

The housing market is one of the most important markets for many economic agents. Large differences in the local market across Sweden suggest regional heterogeneity, however. This study aims to answer if the price and income elasticities of demand for small houses vary between different types of Swedish municipalities. This answer is explored in the light of the central place theory and location theory to see if they follow a hierarchal structure across space. To test this empirically, the 290 municipalities were grouped based on the Swedish Association of Local Authority and Regions’ definitions and tested group-wise using a log-log fixed-effect average hedonic price model using data for 2013-2020. The main findings indicate some differences in the estimates of price and income elasticities between different types of municipalities, but mixing results whether they follow a hierarchal relationship. The conclusions changes depending on which scale one measure, which indicate how local the housing market is.

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Municipal water suppliers are increasingly faced with implementing programs to address temporary water shortages in the United States. Having reliable estimates for the effectiveness of these programs will help in water supply planning. This dissertation estimates the reductions in residential water-use for voluntary and mandatory water-use restrictions used in Virginia during the 2002 drought. These restrictions were evaluated using both a conventional approach (single-dummy variable for each) and non-conventional approach where program intensity was accounted for. Program intensity was measured by information dissemination for voluntary restrictions, and by information dissemination and enforcement efforts for mandatory restrictions. An unbalanced panel with data from 21 municipal water suppliers was used in the analysis. Under the conventional approach, voluntary restrictions had no significant effect on water-use and mandatory restrictions showed a small to moderate effect. However, program intensity was found to have a significant influence on the magnitude of the water-use reductions in the non-conventional approach. These reductions ranged from 0-7% for voluntary restrictions, and from 0-22% for mandatory restrictions. Moreover, these reductions followed a pattern of increasing program effectiveness with higher levels of information and enforcement. This result indicates that water supply planners need to give considerable attention to the manner in which drought management programs are implemented. Price was also found to have an important effect on residential water-use. A moderate price increase of $3 per 1000 gallons would be expected to reduce water-use by almost 15%. Thus combining mandatory restrictions (implemented at high intensity) with a moderate to high price increase could result in water-use savings approaching 40% based on estimates from this analysis. Other important findings included: a) consumers were responding to a mix of pure marginal price and fixed fees/previous block rates, b) apartment accounts were found to be included in most of the localities residential data and had a significant impact on water-use, and c) the income parameter was measuring more than a pure income effect. / Ph. D.