Recent emerging gallium nitride (GaN) high electron mobility transistor (HEMT) is expected to be a promising candidate for high frequency power conversion techniques. Due to the advantages of the material, the GaN HEMT has a better figure of merit (FOM) compared to the state-of-the-art silicon (Si) power metal oxide silicon field effect transistor (MOSFET), which allows the GaN HEMT to switch with faster transition and lower switching loss. By applying the GaN HEMT in a circuit design, it is possible to achieve high frequency, high efficiency, and high density power conversion at the same time. To characterize the switching performance of the GaN HEMT, an accurate behavior-level simulation model is developed in this thesis. The packaging related parasitic inductance, including both self-inductance and mutual-inductance, are extracted based on finite element analysis (FEA) methods. Then the accuracy of the simulation model is verified by a double-pulse tester, and the simulation results match well with experiment in terms of both device switching waveform and switching energy. Based on the simulation model, detailed loss breakdown and loss mechanism analysis are made. The cascode GaN HEMT has high turn-on loss due to the body diode reverse recovery of the low voltage Si MOSFET and the common source inductance (CSI) of the package; while the turn-off loss is extremely small attributing to the cascode structure. With this unique feature, the critical conduction mode (CRM) soft switching technique are applied to reduce the dominant turn on loss and increase converter efficiency significantly. The switching frequency is successfully pushed to 5MHz while maintaining high efficiency and good thermal performance. Traditional packaging method is becoming a bottle neck to fully utilize the advantages of GaN HEMT. So an investigation of the package influence on the cascode GaN HEMT is also conducted. Several critical parasitic inductors are identified, which cause high turn on loss and high parasitic ringing which may lead to device failure. To solve the issue, the stack-die package is proposed to eliminate all critical parasitic inductors, and as a result, reducing turn on loss by half and avoiding potential failure mode of the cascode GaN device effectively. Utilizing the proposed stack-die package and ZVS soft switching, the GaN HEMT high frequency, high efficiency, and high density power conversion capability can be further extended to a higher level. / Master of Science

This thesis evaluates the potential recovery of the runway throughput under Wake Turbulence Re-categorization (RECAT) Phase II and Time-based Separation (TBS) with a Runway Occupancy Time (ROT) constraint comparing with RECAT Phase I. This research uses aircraft performance parameters (runway occupancy time, approach speed, etc.) from the Airport Surface Detection Equipment, Model X (ASDE-X) data set. The analysis uses a modified version of the Quick Response Runway Capacity Model (RUNSIM). The main contributions of the study are: 1) identifying the technical buffer between in-trail arrivals and regenerate them in RUNSIM; 2) estimate the percentage of the arrival pairs that have wake mitigation separation times in excess of ROT; 3) developed an additional in-trail arrival separation rule based on ROT; 4) measure the risk of potential go-arounds with and without the additional 95 ROT separation rules. 5) generate a sample equivalent time-based RECAT II. The study results show that the distributions of technical buffers have significant differences for different in-trail groups and strong connectivity to airport elevations. This is critical to estimate runway capacities and safety issues especially when advanced wake mitigation separation rules are applied. Also, with decreasing of wake separations, ROT will become a limiting factor in runway throughput in the future. This study shows that by considering a 95 percentile ROT constrain, one single runway can still obtain 4 or 5 more arrivals per hour under RECAT II but keep the same level of potential go-arounds compared with current operation rules (RECAT I). TBS rules seem to benefit more under strong wind conditions compared to RECAT I, and RECAT II. TBS rules need to be tailored to every airport. / Master of Science / This thesis evaluates the potential recovery of the runway throughputs by re-defining the minimum distance or time separations between successive arrivals. The minimum separation criteria between in-trail arrivals is defined by Federal Aviation Administration to avoid the wake vortex influence produced by the leading aircraft. The main contribution of this thesis lies in estimation of throughput capacity with the reduced minimum separation between arrivals. The study results show that the distributions of buffers added to the minimum separations have significant differences for different in-trail groups and strong connectivity to airport elevations. This is critical to estimate runway capacities and safety issues especially when advanced wake mitigation separation rules are applied. Also, with decreasing of wake separations, runway occupancy time will become a limiting factor in runway throughput in the future. This study shows that by considering a 95 percentile ROT constrain, one single runway can still obtain 4 or 5 more arrivals per hour under reduced minimum separation but keep the same level of potential go-arounds compared with current operation rules.

This thesis presents a performance assessment of flight operations in the North Atlantic Organized Track System (OTS) using the Global Oceanic Model. The main contributions of the study are: a) improvements to the logic of the Global Oceanic Model; b) prediction of benefits among various aircraft separation minima and operational policies to assign flights to tracks in the OTS system; and c) forecast of OTS traffic over North Atlantic from 2020 to 2040. The preliminary results show that a concept of operation with longitudinal separation minima of 15 nm and information of the flight cost matrix provides average fuel savings of 93 kilograms per flight using 2020 traffic. The fuel savings increase to 170 kilograms per flight using traffic levels expected in the year 2040. A new operational track assignment routine is developed and it could save around 40 kilograms per flight compared with the current concept of operations. The study results show a shortage of capacity of the Organized Track System in the future. The analysis shows that the OTS configuration used today and in 2020 is unable to accommodate the traffic projected in 2040. The analysis concludes that more tracks will be needed to maintain an acceptable level of service. / MS

Det globala energibehovet ökar ständigt och i takt med detta ökar även faran för global uppvärmning bortom en hanterbar nivå och därför stramas kraven åt gällande minskade utsläpp av växthusgaser. EU har som följd av detta enats om en uppsättning klimatmål som benämns 20/20/20-målen som syftar till att minska växthusgasutsläppen med 20 procent, jämfört med 1990 års nivåer, sänka energianvändningen med 20 procent, höja andelen förnybar energi samt höja andelen biobränsle i transportsektorn med 10 procent.  Sektorn bostäder och service står enligt energimyndigheten för nära 40 procent av Sveriges totala energianvändning och blir därför ett område som är mycket intressant när det gäller att implementera energieffektiviseringsåtgärder.  Det kommunala företaget AB Gavlegårdarna ska under perioden 2016-2018 renovera ett tiotal punkthus i stadsdelen Östra Sätra i Gävle. Husen är typiska miljonprogramshus och beroende på val av effektiviseringsåtgärder kommer behovet av köpt värme samt el att förändras, dvs deras lastprofiler på det energisystemet. Dessa förändringar kommer i föreliggande arbete att simuleras och studeras i simuleringsprogrammet IDA ICE (IDA Indoor Climate and Energy) version 4.6.2, där resultaten jämförs och valideras med befintlig statistik.  Husen som berörs av upprustningen är av typen punkthus som definieras som friliggande hus med trapphus i mitten med lägenheter runt om.  Punkthusen var vanliga på 1940 talet och byggdes då oftast med 4-5 våningar. Även om huskropparna står fritt är de oftast placerade i grupp för att skapa en områdeskänsla. De aktuella byggnaderna är i stort lika varandra där avsaknad av källarplan hos vissa av husen är den tydligaste skillnaden, i övrigt består konstruktionen av markplan plus 4 våningsplan och ett vindsutrymme. Hus med källarplan rymmer totalt 29 lägenheter medan de övriga rymmer 27. Energisystemmodellen validerades samt modifierades att passa de renoverade husen. Resultatet har sedan använts för att beräkna områdets lastprofil gällande fjärrvärme vilket kan ses i nedanstående figur. Diagrammet visar lastkurvan både före och efter de energieffektiviserande åtgärderna implementerats.  Med hjälp utav de erhållna effektkurvorna kan områdets totala energianvändning jämföras före och efter implementering av energieffektiviseringsåtgärder. Resultatet visar att värmebehovet sjunker med 1,39 GWh. Appliceras detta på kraftvärmeproduktionen resulterar minskningen i 0,55 GWh lägre elproduktion som måste importeras till systemet. Importeras elen från kolkondens kan detta ge upphov till ökade koldioxidutsläpp med 512 ton koldioxidekvivalenter per år jämfört med 2,13 ton CO2 ekvivalenter om elen tas från svensk elmix.

This diploma thesis deals with the question of simulation models. It is divided into the theoretical and practical part. The aim of the opening part, in which the fundamental theory is defined, is to familiarize the readers with the ideas and advantages which simulation models can offer. In its practical part the work already focuses on the particular simulation project which should point out the possibilities of utilization of these models in practice. The subject of this project is the simulation of the course of the cultural event in the O2 Arena stadium. The main goal of this project is creation of the authentic simulation model which would on the basis of the later analysis enable the elimination or optimalization of the predefined major problems that are connected with organizing big cultural events in this arena.

Traditionally, research on cross‐country skiing biomechanics is based mainly on experimental testing alone. Trying a different approach, this thesis explores the possibilities of using computational musculoskeletal biomechanics for cross‐country skiing. As far as the author knows, this has not been done before. Cross‐country skiing is both fast and powerful, and the whole body is used to generate movement. Consequently, the computational method used needs to be able to handle a full‐body model with lots of muscles. This thesis presents several simulation models created in the AnyBody Modeling System, which is based on inverse dynamics and static optimization. This method allows for measurementdriven full‐body models with hundreds of muscles and rigid body segments of all major body parts. A major result shown in the thesis is that with a good simulation model it is possible to predict muscle activation. Even though there is no claim of full validity of the simulation models, this result opens up a wide range of possibilities for computational musculoskeletal biomechanics in cross‐country skiing. Two example of new possibilities are shown in the thesis, finding antagonistic muscle pairs and muscle load distribution differences in different skiing styles. Being able to perform optimization studies and asking and answering “what if”‐questions really gives computational methods an edge compared to traditional testing. To conclude, a combination of computational and experimental methods seems to be the next logical step to increase the understanding of the biomechanics of crosscountry skiing. / Traditionellt har biomekaniska forskningsstudier av längdskidåkning baserats helt och hållet på experimentella metoder. För att prova ett annat angreppssätt undersöks i denna avhandling vilka möjligheter som beräkningsbaserad biomekanik kan ge för längdskidåkning. Så vida författaren vet, har detta inte gjorts tidigare. Längdskidåkning innehåller snabba och kraftfulla helkroppsrörelser och därför behövs en beräkningsmetod som kan hantera helkroppsmodeller med många muskler. Avhandlingen presenterar flera simuleringsmodeller skapade i AnyBody Modeling System, som baseras på inversdynamik och statisk optimering. Denna metod tillåter helkroppsmodeller med hundratals muskler och stelkroppssegment av de flesta kroppsdelarna. Ett resultat som avhandlingen visar är att med en bra simuleringsmodell är det möjligt att förutsäga muskelaktiviteten för en viss rörelse och belastning på kroppen. Även om ingen validering av simuleringsmodellen ges, så visar ändå resultatet att beräkningsbaserad biomekanik ger många nya möjligheter till forskningsstudier av längdskidåkning. Två exempel visas, hur muskelantagonister kan hittas samt hur lastfördelningen mellan musklerna förändras då skidåkaren förändrar stilen. Att kunna genomföra optimeringsstudier samt fråga och svara på ”vad händer om”‐ frågor ger beräkningsbaserad biomekanik en fördel i jämförelse med traditionell testning. Slutsatsen är att en kombination av beräkningsbaserade och experimentella metoder borde vara nästa steg för att addera insikt om längdskidåkningens biomekanik. / <p>Report code: LIU‐TEK‐LIC‐2008:4. On the day of the defence date the status of article V was: Submitted.</p>

Este trabalho está voltado à avaliação dos problemas do transporte intermodal sob efeito de restrições sazonais que, usualmente, não são consideradas na fase de planejamento e dimensionamento da frota. E, considerando a sobreposição de dois fatores sazonais restritivos ao longo da cadeia de transportes - a variação na produção de grãos ao longo do ano e a sazonalidade das cotas de nível d\'água nas hidrovias -, um modelo de simulação de eventos discretos mostra as impedâncias sofridas no sistema pela junção de fatores restritivos bem fortes. É possível avaliar o impacto dessas restrições não só no nível de utilização dos silos intermediários e silagem do porto, mas também no número de veículos necessários para fazer o transporte de commodities na região Centro-Oeste do Brasil. Em um sistema de transporte composto pelos modais rodoviário, hidroviário e marítimo, no qual o modelo de simulação abrange desde a produção nas fazendas, passando pelo transporte de caminhão até os armazéns intermediários, posteriormente com o transporte fluvial com destino ao porto para exportação. O presente estudo traz uma série de comparações entre cenários para avaliação dos gargalos existentes neste sistema de transporte intermodal, especialmente avaliando cenários com e sem as restrições sazonais, assim como análises de sensibilidade de performance de equipamentos de carregamento e descarregamento, nos quais a frota e os estoques necessários são substancialmente diferentes se a sazonalidade não for considerada. / This work focuses on the evaluation of the intermodal transport problems under the influence of seasonal constraints that are not usually considered on the phase of planning and sizing the fleet. Considering the superposition of two different seasonal factors along the transportation chain - first one the variation on grain production and the second one the level of water in the waterways throughout the year -, a discrete event simulation model was built to show the real effects of those constraints in the grain supply chain. So, it is possible to evaluate the impact of those constraints not only on the usage level of storages in this system, but also the number of vehicles required to transport this commodities from the Midwest of Brazil to the port. In a complex multimodal transportation system, the simulation model in this work includes roadways, waterways and seaways to transport all the cargo from farms to the final costumer. This study is composed by a number of scenarios to evaluate the bottlenecks in this intermodal transportation system, specially analyzing scenarios with and without seasonal constraints, as well as analysis of sensitivity of performance of equipment of loading and unloading, in which the fleet and the required stocks are substantially different if seasonality is not considered. In other words, it is possible to evaluate the risks involved when managers are making decisions if they do not take in consideration any of those seasonal constraints.

Over the past ten years, more than 4,000 genome-wide association studies (GWAS) have helped to shed light on the genetic architecture of complex traits and diseases. In recent years, phenotyping of the samples has often gone beyond single traits and it has become common to record multi- to high-dimensional phenotypes for individu- als. Whilst these rich datasets offer the potential to analyse complex trait structures and pleiotropic effects at a genome-wide level, novel analytic challenges arise. This thesis summarises my research into genetic associations for high-dimensional phen- otype data. First, I developed a novel and computationally efficient approach for multivari- ate analysis of high-dimensional phenotypes based on linear mixed models, com- bined with bootstrapping (LiMMBo). Both in simulation studies and on real data, I demonstrate the statistical validity of LiMMBo and that it can scale to hundreds of phenotypes. I show the gain in power of multivariate analyses for high-dimensional phenotypes compared to univariate approaches, and illustrate that LiMMBo allows for detecting pleiotropy in a large number of phenotypic traits. Aside from their computational challenges in GWAS, the true dimensionality of very high-dimensional phenotypes is often unknown and lies hidden in high-dimen- sional space. Retaining maximum power for association studies of such phenotype data relies on using an appropriate phenotype representation. I systematically ana- lysed twelve unsupervised dimensionality reduction methods based on their per- formance in finding a robust phenotype representation in simulated data of different structure and size. I propose a stability criteria for choosing low-dimensional phen- otype representations and demonstrate that stable phenotypes can recover genetic associations. Finally, I analysed genetic variants for associations to high-dimensional cardiac phenotypes based on MRI data from 1,500 healthy individuals. I used an unsuper- vised approach to extract a low-dimensional representation of cardiac wall thickness and conducted a GWAS on this representation. In addition, I investigated genetic associations to a trabeculation phenotype generated from a supervised feature ex- traction approach on the cardiac MRI data. In summary, this thesis highlights and overcomes some of the challenges in per- forming genetic association studies on high-dimensional phenotypes. It describes new approaches for phenotype processing, and genotype to phenotype mapping for high-dimensional datasets, as well as providing new insights in the genetic structure of cardiac morphology in humans.

No gerenciamento de recursos hídricos, a bacia hidrográfica é considerada a unidade natural de gestão. Suas características físicas definem um espaço onde a água converge para uma saída comum. O desenvolvimento integrado de uma bacia, bem como os possíveis conflitos ocasionados por demandas concorrentes do mesmo recurso, devem ser administrados respeitando esse conceito de unidade. No caso específico da bacia hidrográfica do Rio Jaguari, existe uma crescente preocupação relacionada aos usos múltiplos da água superficial. O rio Jaguari, importante afluente do Paraíba do Sul no estado de São Paulo, tem suas águas represadas para geração de energia elétrica e regularização de vazões. Nos últimos anos, tem-se constatado um crescente rebaixamento dos níveis operacionais da represa do Jaguari. Segundo estudos da sociedade civil organizada local, a tendência é de esgotamento do reservatório em poucos anos. Este trabalho aborda a questão do rebaixamento dos níveis de Jaguari através da aplicação do software DHI Mike Basin 2000. Trata-se de um simulador genérico para sistemas de recursos hídricos, de ampla aplicação. A bacia do Jaguari é representada em um modelo matemático e são simulados quatro cenários distintos de usos de água na bacia. Verifica-se que o problema é real e requer uma intervenção multi-institucional para ser solucionado. / In the management of water resources, basin is naturally considered the administration unit. Its physical properties define a land space where water flows on the way to a common outlet. The integrated development of a basin, as well as potential conflicts resulted by divergent users should be managed under this unit concept. On Jaguari river basin, in state of São Paulo, Brazil, there is an emergent concern related to the multiplicity of water uses. Jaguari river, an important branch of Paraíba do Sul river in state of São Paulo is dammed for the generation of electricity and stream flow regulation. In last years, it has been observed an increasing reduction in Jaguari reservoir operational levels. According to local organizations\' studies, the reservoir trends to collapse in few years. The present dissertation holds a discussion about the reduction of water level trend in Jaguari reservoir, through the application of DHI MIKE BASIN 2000 software. It is a generic, very useful simulator for water resources systems. The Jaguari basin is represented by a mathematic model, simulated for four different water use scenarios. It is shown that the problem is real, and requires a multi-institutional intervention to be solved.

The thesis deals with the use of cloud computing to solve computationally intensive task. Simulation methods are employed to analyze the operation of the proposed system before putting it into operation. Cloud computing makes the functionality of modern data centers accessible to small businesses, cloud allows scaling up and scaling down of resource usage on an as-needed basis; moreover, without high initial investments and long-term commitments. The paper examines in detail the ways to adapt the currently most popular cloud environment of Amazon's Elastic Compute Cloud to the specific requirements of custom applications and suggests ways to automate the process of creation and customization of instance images. The automation and management of running applications in cloud environment is demonstrated on the example of geographic data processing and map generation application. The simulation model for running applications in the cloud is built and exploited to verify the ability of the proposed solutions to succeed in a production deployment.