Silicon Carbide (SiC) is a wide-bandgap (WBG) semiconductor materialwhich has several advantages such as higher maximum electric field, lowerON-state resistance, higher switching speeds, and higher maximum allowablejunction operation temperature compared to Silicon (Si). In the 1.2 kV - 1.7kV voltage range, power devices in SiC are foreseen to replace Si Insulatedgatebipolar transistors (IGBTs) for applications targeting high efficiency,high operation temperatures and/or volume reductions. In particular, theSiC Metal-oxide semiconductor field-effect transistor (MOSFET) – which isvoltage controlled and normally-OFF – is the device of choice due to the easeof its implementation in designs using Si IGBTs.In this work the reliability of SiC devices, in particular that of the SiCMOSFET, has been investigated. First, the possibility of paralleling two discreteSiC MOSFETs is investigated and validated through static and dynamictests. Parallel-connection was found to be unproblematic. Secondly, drifts ofthe threshold voltage and forward voltage of the body diode of the SiC MOSFETare investigated through long-term tests. Also these reliability aspectswere found to be unproblematic. Thirdly, the impact of the package on thechip reliability is discussed through a modeling of the parasitic inductancesof a standard module and the impact of those inductances on the gate oxide.The model shows imbalances in stray inductances and parasitic elementsthat are problematic for high-speed switching. A long-term test on the impactof humidity on junction terminations of SiC MOSFETs dies and SiCSchottky dies encapsulated in the same standard package reveals early degradationfor some modules situated outdoors. Then, the short-circuit behaviorof three different types (bipolar junction transistor, junction field-effect transistor,and MOSFET) of 1.2 kV SiC switching devices is investigated throughexperiments and simulations. The necessity to turn OFF the device quicklyduring a fault is supported with a detailed electro-thermal analysis for eachdevice. Design guidelines towards a rugged and fast short-circuit protectionare derived. For each device, a short-circuit protection driver was designed,built and validated experimentally. The possibility of designing diode-lessconverters with SiC MOSFETs is investigated with focus on surge currenttests through the body diode. The discovered fault mechanism is the triggeringof the npn parasitic bipolar transistor. Finally, a life-cycle cost analysis(LCCA) has been performed revealing that the introduction of SiC MOSFETsin already existing IGBT designs is economically interesting. In fact,the initial investment is saved later on due to a higher efficiency. Moreover,the reliability is improved, which is beneficial from a risk-management pointof-view. The total investment over 20 years is approximately 30 % lower fora converter with SiC MOSFETs although the initial converter cost is 30 %higher. / Kiselkarbid (SiC) är ett bredbandgapsmaterial (WBG) som har flera fördelar,såsom högre maximal elektrisk fältstyrka, lägre ON-state resitans, högreswitch-hastighet och högre maximalt tillåten arbetstemperatur jämförtmed kisel (Si). I spänningsområdet 1,2-1,7 kV förutses att effekthalvledarkomponenteri SiC kommer att ersätta Si Insulated-gate bipolar transistorer(IGBT:er) i tillämpningar där hög verkningsgrad, hög arbetstemperatur ellervolymreduktioner eftersträvas. Förstahandsvalet är en SiC Metal-oxidesemiconductor field-effect transistor (MOSFET) som är spänningsstyrd ochnormally-OFF, egenskaper som möjliggör enkel implementering i konstruktionersom använder Si IGBTer.I detta arbete undersöks tillförlitligheten av SiC komponenter, specielltSiC MOSFET:en. Först undersöks möjligheten att parallellkoppla tvådiskretaSiC MOSFET:ar genom statiska och dynamiska prov. Parallellkopplingbefanns vara oproblematisk. Sedan undersöks drift av tröskelspänning ochbody-diodens framspänning genom långtidsprov. Ocksådessa tillförlitlighetsaspekterbefanns vara oproblematiska. Därefter undersöks kapslingens inverkanpåchip:et genom modellering av parasitiska induktanser hos en standardmoduloch inverkan av dessa induktanser pågate-oxiden. Modellen påvisaren obalans mellan de parasitiska induktanserna, något som kan varaproblematiskt för snabb switchning. Ett långtidstest av inverkan från fuktpåkant-termineringar för SiC-MOSFET:ar och SiC-Schottky-dioder i sammastandardmodul avslöjar tidiga tecken pådegradering för vissa moduler somvarit utomhus. Därefter undersöks kortslutningsbeteende för tre typer (bipolärtransistor,junction-field-effect transistor och MOSFET) av 1.2 kV effekthalvledarswitchargenom experiment och simuleringar. Behovet att stänga avkomponenten snabbt stöds av detaljerade elektrotermiska simuleringar för allatre komponenter. Konstruktionsriktlinjer för ett robust och snabbt kortslutningsskyddtas fram. För var och en av komponenterna byggs en drivkrets medkortslutningsskydd som valideras experimentellt. Möjligheten att konstrueradiodlösa omvandlare med SiC MOSFET:ar undersöks med fokus påstötströmmargenom body-dioden. Den upptäckta felmekanismen är ett oönskat tillslagav den parasitiska npn-transistorn. Slutligen utförs en livscykelanalys(LCCA) som avslöjar att introduktionen av SiC MOSFET:ar i existerandeIGBT-konstruktioner är ekonomiskt intressant. Den initiala investeringensparas in senare pågrund av en högre verkningsgrad. Dessutom förbättrastillförlitligheten, vilket är fördelaktigt ur ett riskhanteringsperspektiv. Dentotala investeringen över 20 år är ungefär 30 % lägre för en omvandlare medSiC MOSFET:ar även om initialkostnaden är 30 % högre. / <p>QC 20170524</p>

Background and purpose. The purpose of the study was to determine the costs incurred on the average length of stay (ALOS) on patients with Human Immunodeficiency Virus (HIV) and Acquired Immune Deficiency Syndrome (AIDS) related illnesses admitted in hospital and whether there are any other significant costs involved. Method. A quantitative approach was used to collect data; analysed; interpretation and report writing. Purposive sampling and data collection was done using data collection sheet. This was a retrospective cost analysis data from in-patients records (record review) of ages from 15 years to 49 years both gender. Data analysis and presentation of information was presented by the use of tables; different types of graphs and the interpretation thereof. Results. The study found that males (63%) with HIV Human Immunodeficiency Virus (HIV) and Acquired Immune Deficiency Syndrome (AIDS) related illnesses had longer average length of stay in a hospital compared to females. However, females illustrated higher in-patient costs but majority of patients had costs of between R0–R17 500. Patients with longer hospital stay (>3 days of hospitalisation) had higher in-patient costs. Conclusion. The findings also showed that in-patient care costs were directly proportional to length of stay with higher costs for HIV and AIDS patient management care. Our findings are consistent with other studies regarding higher economic implications of care for HIV infected persons being almost as twice as people who are HIV negative due to longer periods of hospitalisation. / Health Studies / M.A. (Public Health)

<div>This research analyzes over 60,000 awarded highway contracts from 18 states throughout the United States. Analysis was performed on the state and aggregate level. The contracts were awarded from the years 2008 through 2018. Statistical analysis utilizing Pearson's Correlation and Ordinary Least Squares regression for each sample was performed to identify each variables relationship between the budget and awarded values.</div><div>The research examined effects of economic indicators, contractor descriptors and yearly/seasonal adjustments These variables included DBE Participation Goal, Number of Bidders, Project Dollar Value, Project Duration, Unemployment Rate, S&P 500 Index, Volatility Index, quarter, and year of project award. The results were examined by using a combination of simple statistical summaries and econometric coefficients called a cost vector. <br></div><div>Summary statistics observed Bid Difference at 8.5% below the Engineer's Estimate. The study observed DBE Participation Goals averaged 3.74% of the value of contracts, with an observed average of 4.5 bidders per contract. <br></div><div>The research determined that 55% of observed states had a positive significant correlation with DBE Participation Goal and Bid Difference. This correlation translated to nearly $80 million in additional cost. In addition, the research determined that all 19 groups in this study had a negative significant correlation with the Number of Bidders. The correlation translated to a savings of nearly $500 million. <br></div>

För småhusägare finns ekonomiska incitament till att sänka det årliga energibehovet för värme och tappvarmvattenberedning, då det utgör huvudparten av det totala årliga energibehovet för bostäder i Sverige. Valet av värmesystem är därför ett viktigt då det kan medföra mer eller mindre gynnsamma ekonomiska konsekvenser sett över längre tidsperioder,då den mängd köpt energi som systemet kräver kan medföra besparingar som viktas mot den ekonomiska investeringen av systemet.Syftet med denna studie har därför varit att skapa ett referensunderlag över fyra olika värmesystem med jämförelser mot småhus av olika storlek, geografisk placering samt olikaisoleringsstandard, där det eller de mest ekonomiskt gynnsamma värmesystemen, sett över en 50-årsperiod, kan utläsas utifrån dessa parametrar.De småhus som studien har jämfört har bestått av enplanshus med tre antagna areor, 89,7/120/150,3 m2. Dessa har jämförts för Malmö, Stockholm, Sundsvall samt Luleå, varpå varje area har innefattat tre olika antagna genomsnittliga värmegenomgångskoefficienter, Umedelvärden. Studien har genomförts med energiberäkningar enligt gradtimmemetoden, och den ekonomiska analysen genom beräknade livscykelkostnader, LCC, för de olika systemkonstellationerna. Fyra värmesystem har undersökts: Fjärrvärme, bergvärmepump, luft-vattenvärmepump samt frånluftsvärmepump. Frånluftsvärmepumpen har inkorporerats som ett FX-ventilationssystem, frånluftsventilation med värmeåtervinning. De övriga tre systemen har för studien kombinerats med ett FTX-ventilationssystem, från- och tilluftsventilation med värmeåtervinning.Resultaten har påvisat att FTX-system, i jämförelse med FX-system, sänker för samtliga studerade byggnader i Malmö det årliga värmeenergibehovet, den energi som måste tillsättas byggnaden, med 36–71%, medan det i Luleå sänks med 32–61%. Den årliga energianskaffningen, den energi som måste köpas för att värmesystemen skall generera erfordrad värmeenergi och tappvarmvattenberedning, är genomgående lägst för systemkonstellationen bergvärmepump i kombination med FTX. Den systemkonstellationenmed studiens genomgående högsta andel köpt energi, är fjärrvärme i kombination med FTX.Vid jämförelse av livscykelkostnader, LCC, har påvisats att fjärrvärme i kombination med FTX är mest ekonomiskt gynnsam endast då det årliga behovet av köpt energi är mycket litet, och att det vid högre behov istället blir det dyraste alternativet. Frånluftsvärmepump utgör ett ekonomiskt gynnsamt alternativ vid majoriteten av analyserade fall, tack vare lägre investeringskostnader som väger upp de högre värmeenergibehov som ventilationstypen medför. Bergvärme i kombination med FTX, utgör det dyraste alternativet i de flesta fall därdet årliga behovet av köpt energi är lågt, men påvisar ekonomisk gynnsamhet vid höga energibehov. Luft-vattenvärmepump i kombination med FTX, är relativt likvärdig bergvärmepump men har ej påvisats vara det billigaste alternativet i något studerat fall. Vid jämförelse mellan frånluftsvärmepump och bergvärmepump i kombination med FTX, har påvisats att för studiens samtliga analyserade objekt är den största prisskillnaden, utslaget på 50 år, mindre än 1.800 kr/år.Utifrån de parametrar som presenterats, har påvisats genomförbarhet i att skapa ett referensunderlag över optimal gynnsamhet för värme- och ventilationssystem hos småhus, vilket avläses utifrån husets storlek, U-medelvärde samt geografiska placering. / For homeowners, there are economic incentives to reduce the annual energy demand for heating and domestic hot water preparation, as these constitute the main part of the total annual energy demand for houses in Sweden. The choice of heating system is therefore important as it can have more or less favorable economic consequences over longer periods of time, as the amount of purchased energy required by the system can lead to savings that weigh against the economic investment in the system. The purpose of this study has therefore been to create a reference framework for four different heating systems, comparing them across houses of different sizes, geographical locations, and insulation standards, to identify the most economically beneficial heating systems over a 50-year period, that can be interpreted based on these parameters. The houses compared in the study were single-story houses with three assumed sizes: 89.7/120/150.3 m². They have been compared in Malmö, Stockholm, Sundsvall and Luleå, with each size having three different assumed average thermal transmittance values, average U-values. The study was conducted using energy calculations based on the degree-hour method, and the economic analysis was performed using calculated life cycle costs, LCC, for the different system configurations. Four heating systems were investigated: district heating, geothermal heat pump, air-to-water heat pump, and exhaust air heat pump. The exhaust air heat pump was incorporated as an MEVHR ventilation system, mechanical exhaust air ventilation with heat recovery, while the other three systems were combined with an HRVventilation system, mechanical exhaust and supply air ventilation with heat recovery. The results have shown that HRV systems, compared to MEVHR systems, reduce the annual heating energy demand, the amount of energy that must be supplied to the building, for all studied buildings in Malmö by 36-71%, while in Luleå it is reduced by 32-61%. The annual energy procurement, the amount of energy that must be purchased for the heating systems to generate the required heating energy and domestic hot water preparation, is consistently lowest for the geothermal heat pump system combined with the HRV. The system configuration with the highest proportion of purchased energy throughout the study is district heating combined with HRV. When comparing life cycle costs, LCC, it was found that district heating combined with HRVis the most economically beneficial system only when the annual demand for purchased energy is very low, and becomes the most expensive option at higher demands. The exhaust air heat pump is a cost-effective option in the majority of analyzed cases, thanks to lower investment costs that offset the higher heating energy demand induced by this type of ventilation. Geothermal heat pump combined with the HRV is the most expensive option in most cases when the annual demand for purchased energy is low but shows economic advantages at high energy demands. The air-to-water heat pump combined with the HRV is relatively similar to the geothermal heat pump but has not been shown to be the cheapest option in any of the studied cases. When comparing the exhaust air heat pump with the geothermal heat pump combined with the HRV, it is found that for all objects analyzed in the study, the largest price difference is, averaged over 50 years, less than 1,800 SEK/year. Based on the presented parameters, the feasibility of creating a reference framework for the cost-effectiveness of heating and ventilation systems in houses has been demonstrated, which can be assessed based on the house size, U-value, and geographical location.

This thesis addresses the three principal questions concerning the development of CT urography for investigating haematuria and each question is the subject of a separate chapter. The questions are: What is the reasoning behind using CT urography? What is the optimum diagnostic strategy using CT urography? What are the problems with using CT urography and how may solutions be provided? Haematuria can signify serious disease such as urinary tract stones, renal cell cancer, upper tract urothelial cancer (UTUC) and bladder cancer (BCa). CT urography is defined as contrast enhanced CT examination of kidneys, ureters and bladder. The technique used here includes unenhanced, nephrographic and excretory-phases for optimized diagnosis of stones, renal masses and urothelial cancer respectively. The reasoning behind using excretory-phase CT urography for investigating haematuria is based on results showing its high diagnostic accuracy for UTUC and BCa. Patients with haematuria are classified as low risk or high risk for UTUC and BCa, by a risk score, determined by the presence/absence of risk factors: age > 50 years, visible or nonvisible haematuria, history of smoking and occupational exposure. The optimum diagnostic strategy for patients at high risk for urothelial cancer, uses CT urography as a replacement test for ultrasonography and intravenous urography and as a triage test for flexible and rigid cystoscopy, resulting in earlier diagnosis and potentially improving prognosis. For patients at low risk, ultrasonography, unenhanced and nephrographic-phase CT urography are proposed as initial imaging tests. Problems with using CT urography include false positive results for UTUC, which are eliminated by retrograde ureteropyelography-guided biopsy, an innovative technique, for histopathological confirmation of diagnosis. Recommendations for the NHS and possible future developments are discussed. CT urography, including excretory-phase imaging, is recommended as the initial diagnostic imaging test before cystoscopy for patients with haematuria at high risk for urothelial cancer.