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NAND flash-based Solid State Devices (SSDs) provide high performance and energy efficiency and at the same time their capacity continues to grow at an unprecedented rate. As a result, SSDs are increasingly being used in high end computing systems such as supercomputing clusters. However, one of the biggest impediments to large scale deployments is the limited erase cycles in flash devices. The natural skewness in I/O workloads can results in Wear imbalance which has a significant impact on the reliability, performance as well as lifetime of the cluster. Current load balancers for storage systems are designed with a critical goal to optimize performance. Data migration techniques are used to handle wear balancing but they suffer from a huge metadata overhead and extra erasures. To overcome these problems, we propose an endurance-aware write off-loading technique (EWO) for balancing the wear across different flash-based servers with minimal extra cost. Extant wear leveling algorithms are designed for a single flash device. With the use of flash devices in enterprise server storage, the wear leveling algorithms need to take into account the variance of the wear at the cluster level. EWO exploits the out-of-place update feature of flash memory by off- loading the writes across flash servers instead of moving data across flash servers to mitigate extra-wear cost. To evenly distribute erasures to flash servers, EWO off-loads writes from the flash servers with high erase cycles to the ones with low erase cycles by first quantitatively calculating the amount of writes based on the frequency of garbage collection. To reduce metadata overhead caused by write off-loading, EWO employs a hot-slice off-loading policy to explore the trade-offs between extra-wear cost and metadata overhead. Evaluation on a 50 to 200 node SSD cluster shows that EWO outperforms data migration based wear balancing techniques, reducing up to 70% aggregate extra erase cycles while improving the write performance by up to 20% compared to data migration. / Master of Science / Exponential increase of Internet traffic mainly from emerging applications like streaming video, social networking and cloud computing has created the need for more powerful data centers. Datacenters are composed of three main components- compute, network and storage. While there have been rapid advancements in the field of compute and networking, storage technologies have not advanced as much in comparison. Traditionally, storage consists of magnetic disks with magnetic parts which are slow and consume more power. However, Solid State Disks (SSDs) offer both better performance and lower energy. With the price of these SSDs being comparable to magnetic disks, they are increasingly being used in storage clusters. However, one of the biggest drawback of SSDs is the limited program erase (P/E) cycles. There is a need to ensure the uniform wearing of blocks in a SSD. While solutions for this do exist for a single SSD device, usage of these devices in a cluster poses new problems. This work introduces EWO which is a wear balancing algorithm that balances wear in a flash storage cluster. It carried out load balancing in a flash storage cluster while incorporating the wear characteristics as a cost function. EWO carries out lazy data migration also referred to as write offloading. To alleviate the metadata overhead, the migration is performed at the slice level. To evaluate EWO, a distributed key value store emulator was built to simulate the behavior of an actual flash storage cluster.

[pt] Este trabalho apura os custos do escoamento de óleo na operação de exploração e produção da Petrobrás na Bacia de Campos. O desenvolvimento do tema está baseado na forma que a operação é executada, tanto por navios aliviadores quanto por dutos submarinos; e os custos são tratados ao longo da operação, alinhados com as estruturas das organizações envolvidas com o escoamento, também chamado offloading. O objetivo deste trabalho é propor uma metodologia de cálculo do custo de escoamento, relacionando as operações desenvolvidas com as várias parcelas no processo de escoamento, dentro da aplicação da técnica de Custo Baseado na Atividade - ABC Costing. Tal técnica propõe que as atividades sejam determinadas através da análise das etapas do processo e assim os componentes dos custos são identificados para se chegar ao todo. Não faz parte do escopo desse estudo a comparação entre os modais, embora, ao final do estudo, sejam apresentados os custos por volume de óleo transferido, tanto através de dutos como por navios. A opção de investimentos, por um ou outro modal de transporte, obedece, algumas vezes, a fatores intangíveis, contemplados dentro do plano estratégico da Petrobras, apenas mencionados por estarem fora do alcance e da proposta desse estudo. A expectativa é que, ao final, o leitor possa ter uma compreensão dos componentes de formação dos custos de escoamento, tanto através de dutos quanto por navios aliviadores, e a contribuição que a técnica de Custo Baseado na Atividade pode oferecer nos cálculos desses custos para avaliação de futuros projetos. / [en] This study disserts about the costs of oil offloading in the exploration and production operation - E and P - of Petrobras in Campos` Basin. The development of the subject is based on the way the operation is performed, as much for shuttle tankers as for sub-sea pipelines; depicting the way costs were treated along the operation, aligned with the organizations structures involved in the offloading process. The core objective of this work is to offer a methodology to calculate the total offloading operation cost value, assigning each developed operation with its related cost components, using an Activity-Based Costing - ABC - approach. This approach considers that activities should be determined through the analysis of all stages. Once all activities are outlined, related cost components are assigned to each activity, calculating total oil offloading cost. It is not a target of this study to compare modals, though costs for volume of transferred oil, for pipelines and ships are presented at the end of the study. Sometimes, the choice for investments in one or another transport modal, might be based on intangible variables, or strategic decisions, contemplated on the Petrobras Strategic Plan. The expectation, at the end of this study, is to give the reader an understanding of the offloading costs and the contribution that the Activity Based Costing approach provides to calculate these costs for future projects evaluations.

The use of small satellites is rapidly growing, especially satellites with masses between 1 and 10 kg and few litres of volume. The main reasons are due to the low development time and cost. Electronics miniaturization and high density integration is enabling the small satellites class to perform more and better tasks and at a lower cost. When deployable structures are required for the missions, the actual paradigm is that there are very few that have been successfully developed and flown. It is usually not possible to scale down existing deployable structures from larger satellites. Power and attitude control is also very limited in small satellites thus, completely new deployable structures, low mass and with high packaging ratio (yet large and with adequate mechanical properties when deployed) must be developed. Furthermore, such new structures are usually made of very thin and light materials which complicates the on-ground tests prior the launch. Therefore, advances in modelling and simulation deployable structures such as booms are also of great interest for the scientific community. This thesis and the papers included herein focus on the finite element modelling of a meter-class passively deployable boom – based on the SIMPLE boom by Thomas W. Murphey – and deployment simulations. Experimental tests were also carried on a boom prototype suspended from a gravity off-loading system. An analytical model produced certain parameters which are used for validation of the finite element model. The strain energy stored in the boom prior to deployment and spacecraft displacements during deployment agreed well. The deployment time, however, have discrepancies: the models predicted a deployment time six times faster than the experimental tests. For that reason the deployment simulations cannot be compared with the tests. The reason of the discrepancies are believed to be due to the actual material model and the contacts formulation used in the finite element model. The finite element simulations, however, shows a reasonable behaviour given the nature of the deployment thus, despite the necessary improvements, we believe that future improvements in the material and friction models will provide us more realistic results. / Användningen av små satelliter ökar snabbt, särskilt satelliter med en vikt på mellan 1 och 10 kg och bara några liters volym. De främsta orsakerna till detta är den korta utvecklingstiden och den låga kostnaden. Elektronikminiatyrisering och hög integreringsdensitet möjliggör för små satelliter att utföra fler och bättre uppgifter till en lägre kostnad. När utfällbara strukturer krävs för uppdragen är nuvarande läge att det är få som utvecklats och flugits framgångsrikt. Det är inte heller alltid möjligt att skala ner utfällbara strukturer som utformats för användning i större satelliter. I små satelliter är den tillgängliga elektriska energin och volymen starkt begränsade faktorer och därmed måste helt nya passivt utfällbara strukturer med låg vikt och liten packningsvolym, men ändå rätt storlek och mekaniska egenskaper när de är utfällda, utvecklas. Dessa strukturer är vanligen tillverkade av mycket tunna och lätta material, som komplicerar tester innan uppskjutningen p.g.a. tyngdkraften. Därför är det av stort intresse att noggrant kunna modellera och simulera ett tyngdlöst utfällningsförlopp. Denna licentiatuppsats och bilagda artiklar i fokuserar på finit elementmodellering och utfällningssimuleringar av en 1 meter lång passivt utfällbar bom baserad på SIMPLE-bommen som utformats av Thomas W. Murphey. Utfällningsexperiment har utförts på en prototyp av bommen upphängd i ett tyngdkraftskompenserande system. Analytiska modeller har använts för att validera simuleringarna och töjningsenergin som lagrats i bommen innan utfällning och rymdfarkostens förflyttning efter utfällning överensstämmer väl. Utfällningstiden avviker dock och båda modellerna predikterar en utfällningstid som är sex gånger snabbare än den tiden som observeras i experimenten. Anledningen till skillnaderna antas delvis bero på begränsningar i den använda materialmodellen och i algoritmer för hantering av kontakt i den finita elementmodellen. De finite elementsimuleringarna visar dock ett rimligt dynamisk beteende hos bommen baserat på vad som observerats i experimenten och även om modellen är i behov av förbättring så finns det stora förhoppningar att åstadkomma en mer realistisk modell genom införande av förbättrade kontakalgoritmer och nogrannare modellering av dämpning och friktion. / <p>QC 20130506</p>

Abstract The aim of this thesis is to propose an array of novel cooperative content delivery (CCD) methods and related incentive mechanisms for future fifth-generation (5G) and beyond networks. CCD using multiple air interfaces is a powerful solution to mitigate the problem of congestion in wireless networks, in which the available multiple air interfaces on smart devices are utilized intelligently to distribute data content among a group of users that are in the vicinity of one another. The requirements for higher capacity, reliability, and energy efficiency in the 5G networks have warranted the development of methods focusing on CCD. Moreover, critical to the efficiency of a CCD process are incentive mechanisms to induce cooperation among the mobile users engaged in CCD. The first part of the thesis studies an ideal condition of reliable and error-free distribution of content using cellular and short-range links. The main contribution is to introduce different device selection CCD methods that take into account only the link quality of the devices’ primary (cellular) interfaces. The proposed methods provide frequency carrier savings for the operator while allowing users to enjoy higher downlink rates. The second part of the thesis studies a more realistic CCD situation where users with low data rate wireless links can be a bottleneck in terms of CCD performance. The main contribution is to propose a novel device selection CCD method that considers the link quality of both primary (cellular) and secondary (short-range) interfaces of the devices. Additionally, a carrier aggregation-based incentive mechanism for the proposed method is introduced to address the challenge of selfish deviating users. The proposed mechanism maximizes individual and network payoffs, and is an equilibrium against unilateral selfish deviations. The third part of the thesis addresses the adverse selection problem in CCD scenarios. The operator is assumed to have incomplete information about the willingness of the users to participate in CCD. The main contribution is to introduce contract-based methods through which the operator could motivate users to reveal their true willingness towards participation. The proposed methods incentivize users according to their willingness and improve system performance in terms of the utility of the operator and the users. / Tiivistelmä Tämän väitöskirjan tavoitteena on kehittää menetelmiä yhteistyössä tapahtuvaan sisällön jakamiseen (cooperative content delivery, CCD) sekä siihen liittyviä kannustinmekanismeja viidennen sukupolven (5G) ja sen jälkeisille matkaviestinverkoille. CCD:n käyttö hyödyntämällä älylaitteessa olevia useita ilmarajapintoja on tehokas ratkaisu välttää langattomien verkkojen ruuhkautumista. CCD-menetelmissä laiteen ilmarajapintoja käytetään älykkäästi datan jakamiseen käyttäjäryhmälle, kun käyttäjät ovat lähellä toisiaan. 5G-verkkojen vaatimukset korkeammalle kapasiteetille, luotettavuudelle ja energiatehokkuudelle ovat motivoineet CCD-menetelmien kehitystyötä. Erityisen tärkeää CCD-menetelmien tehokkuudelle on kannustinmekanismien kehittäminen mahdollistamaan yhteistyö mobiilikäyttäjien välillä. Väitöskirjatyön ensimmäinen osuus käsittelee ideaalista tilannetta luotettavalle ja virheettömälle sisällön jakamiselle hyödyntämällä solukkoverkkoa ja lyhyen kantaman linkkejä. Tässä osuudessa päätuloksena on kehitetty käyttäjien valinnalle menetelmiä, jotka huomioivat linkin laadun solukkoverkon ilmarajapinnassa. Ehdotetut menetelmät tuovat operaattorille säästöjä taajuusresurssien käytön osalta ja käyttäjät saavuttavat korkeampia laskevan siirtotien datanopeuksia. Työn toinen osuus tutkii todenmukaisempaa CCD-tilannetta, jossa alhaisen datanopeuden linkkien käyttäjät voivat olla pullonkaula CCD:n suorituskyvylle. Päätulos tässä on uusi käyttäjien valintamenetelmä, joka ottaa huomioon linkkien laadun sekä solukkoverkossa että lyhyen kantaman linkeissä. Lisäksi esitellään eri taajuuksien yhdistämistä hyödyntävä kannustinmenetelmä, joka ottaa huomioon itsekkäiden käyttäjien aiheuttamat ongelmat. Ehdotettu mekanismi maksimoi yksittäisen käyttäjän ja verkon hyödyt ja saavuttaa tasapainotilan käyttäjien yksipuolista itsekkyyttä vastaan. Väitöskirjan kolmannessa osuudessa tutkitaan haitallisen valikoitumisen mahdollisuutta CCD:ssä. Operaattorilla oletetaan olevan epätäydellistä tietoa käyttäjien halukkuudesta osallistua yhteistyöhön CCD:ssä. Tämän osuuden päätulos on esitellä sopimuksiin perustuvia kannustinmenetelmiä, joiden avulla operaattori voi motivoida käyttäjiä paljastamaan heidän todellinen tahtotilansa osallistua yhteistyöhön. Ehdotetut menetelmä kannustavat käyttäjiä heidän todellisen tahtotilan perusteella ja parantavat järjestelmän suorituskykyä operaattorin ja käyttäjien saavuttamien hyötyjen osalta.