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Simulation of Unsteady Gas-Particle Flows including Two-way and Four-way Coupling on a MIMD Computer ArchitecturPachler, Klaus, Frank, Thomas, Bernert, Klaus 17 April 2002 (has links) (PDF)
The transport or the separation of solid particles or droplets suspended in a fluid flow is a common task in mechanical and process engineering. To improve machinery and physical processes (e.g. for coal combustion, reduction of NO_x and soot) an optimization of complex phenomena by simulation applying the fundamental conservation equations is required. Fluid-particle flows are characterized by the ratio of density of the two phases gamma=rho_P/rho_F, by the Stokes number St=tau_P/tau_F and by the loading in terms of void and mass fraction.
Those numbers (Stokes number, gamma) define the flow regime and which relevant forces are acting on the particle. Dependent on the geometrical configuration the particle-wall interaction might have a heavy impact on the mean flow structure. The occurrence of particle-particle collisions becomes also more and more important with the increase of the local void fraction of the particulate phase. With increase of the particle loading the interaction with the fluid phase can not been neglected and 2-way or even 4-way coupling between the continous and disperse phases has to be taken into account.
For dilute to moderate dense particle flows the Euler-Lagrange method is capable to resolve the main flow mechanism. An accurate computation needs unfortunately a high number of numerical particles (1,...,10^7) to get the reliable statistics for the underlying modelling correlations. Due to the fact that a Lagrangian algorithm cannot be vectorized for complex meshes the only way to finish those simulations in a reasonable time is the parallization applying the message passing paradigma.
Frank et al. describes the basic ideas for a parallel Eulererian-Lagrangian solver, which uses multigrid for acceleration of the flow equations. The performance figures are quite good, though only steady problems are tackled. The presented paper is aimed to the numerical prediction of time-dependend fluid-particle flows using the simultanous particle tracking approach based on the Eulerian-Lagrangian and the particle-source-in-cell (PSI-Cell) approach. It is shown in the paper that for the unsteady flow prediction efficiency and load balancing of the parallel numerical simulation is an even more pronounced problem in comparison with the steady flow calculations, because the time steps for the time integration along one particle trajectory are very small per one time step of fluid flow integration and so the floating point workload on a single processor node is usualy rather low.
Much time is spent for communication and waiting time of the processors, because for cold flow particle convection not very extensive calculations are necessary. One remedy might be a highspeed switch like Myrinet or Dolphin PCI/SCI (500 MByte/s), which could balance the relative high floating point performance of INTEL PIII processors and the weak capacity of the Fast-Ethernet communication network (100 Mbit/s) of the Chemnitz Linux Cluster (CLIC) used for the presented calculations. Corresponding to the discussed examples calculation times and parallel performance will be presented. Another point is the communication of many small packages, which should be summed up to bigger messages, because each message requires a startup time independently of its size. Summarising the potential of such a parallel algorithm, it will be shown that a Beowulf-type cluster computer is a highly competitve alternative to the classical main frame computer for the investigated Eulerian-Lagrangian simultanous particle tracking approach.
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Vad som engagerar användare på Facebook : Vad gillar du och varför? En undersökning om användarnas krav på innehåll samt vad företag kan förvänta sig av sin marknadsföring i sociala medier. / What does engage users on FacebookAronsson, Linda January 2017 (has links)
Syftet med studien är att ge företag och organisationer kunskaper i hur de skapar relevant innehåll som intresserar deras kunder och hur de ska arbeta med sin marknadsföring på Facebook. Metoder som används är en kvalitativ studie bestående av enskilda intervjuer med experter inom området för marknadsföring i sociala medier. Därtill har en kvantitativ studie genomförts för att mäta interaktionen på tre kommersiella Facebooksidor. Resultatet visar att det är viktigt att tänka efter vad som är målet och vilken utgång som marknadsföringen på Facebook kommer generera. Vidare är det inte ett ändamål i sig att få högt engagemang. Det krävs en kontinuerlig närvaro samt att företaget visar ett intresse och ger kunderna uppmärksamhet. Idag är användarna på Facebook mer anonyma än tidigare och det har blivit ovanligare att följa sidor. Att skapa innehåll som inbjuder till att samskapa och möjligheten att träffas utanför sociala medier visar på högt engagemang hos följarna i studiens kvantitativa undersökning. Implikationen är därför att användarna har blivit vana vid att innehållet riktas direkt till dem samt att det har hög kvalité och relevans. Innehåll utformas efter en specifik målgrupp som når dem vid rätt tidpunkt för att ge den ett så relevant innehåll som möjligt. Studien är begränsad till det sociala mediet Facebook och deras användare. Studien omfattar marknadsföring på Facebook via företagssidor. / Purpose – The purpose of this study is to give companies and organization's knowledge on how to create relevant content that interests their customers and how they can work with their marketing on Facebook. Method – Methods used in this study are a qualitative study including interviews with experts in the field of marketing in social media. Furthermore, a quantitative study was made through measuring the interaction on three business sites on Facebook. Findings – Findings show that it is important to focus on the purpose and goal for the marketing, and what it will result in. Furthermore, it is not a goal itself to have high engagement. Today, the Facebook users are more anonymous online than earlier, and it has become unusual for them to follow a business site. Creating content that invites the users to co-create and to meet outside social media results in high interaction among the followers in the quantitative study. Lastly, continuous presence is required along with a genuine interest towards the costumers, and that the company gives their customer's attention. Implications – The implication is therefore that users have become more used to that content is directed directly towards them with a high quality and relevance. The content is designed for a specific target group that reaches them at the right time to give them as relevant content as possible. Limitations – The study is limited to the social media Facebook and its users. Furthermore, the study is focused towards marketing on Facebook for business sites.
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Network Coding for Wirless Relaying and Wireline NetworksVijayvaradharaj, T M January 2014 (has links) (PDF)
Network coding has emerged as an attractive alternative to routing because of the through put improvement it provides by reducing the number of channel uses. In a wireless scenario, in addition, further improvement can be obtained through Physical layer Network Coding (PNC), a technique in which nodes are allowed to transmit simultaneously, instead of transmitting in orthogonal slots. In this thesis, the design and analysis of network coding schemes are considered, for wireless two-way relaying, multi-user Multiple Access Relay Channel (MARC) and wireline networks.
In a wireless two-way relay channel with PNC, the simultaneous transmissions of user nodes result in Multiple Access Interference (MAI) at there lay node. The harmful effect of MAI is the presence of signal set dependent deep channel fade conditions, called singular fade states, under which the minimum distance of the effective constellation at the relay become zero. Adaptively changing the network coding map used at the relay according to channel conditions greatly reduces the impact of this MAI. In this work, we obtain these adaptive PNC maps, which are finite in number ,by completing partially filled Latin Squares and using graph vertex coloring. Having obtained the network coding maps, the set of all possible channel realizations is quantized into a finite number of regions, with a specific network coding map chosen in a particular region and such a quantization is obtained analytically for 2λ-PSK signal set. The performance of the adaptive PNC scheme for two-way relaying is analyzed and tight high SNR upper bounds are obtained for the average end-to-end symbol error probability, in terms of the average error probability of a point-to-point fading channel. The adaptive PNC scheme is generalized for two-way relaying with multiple antennas at the nodes.
As an alternative to the adaptive PNC scheme for two-way relaying, a Distributed Space Time Coding (DSTC) scheme is proposed, which effectively re-moves the effect of singular fade states at the transmitting nodes itself without any Channel State Information at the Transmitter (CSIT), and without any need to change the PNC map as a function of channel fade conditions. It is shown that the singular fade states can be viewed equivalently as vector subspaces of C2, which are referred to as the singular fade subspaces. DSTC design criterion to minimize the number of singular fade subspaces and maximize the coding gain is formulated and explicit low decoding complexity DSTC designs are provided.
For the K-user MARC, in which K source nodes want to transmit messages to a destination node D with the help of are lay node R, a new PNC scheme is proposed. Use of a many-to-one PNC map with conventional minimum squared Euclidean distance decoding at D, results in a loss of diversity order due to error propagation from the relay node. To counter this, we propose a novel low complexity decoder which offers the maximum diversity order of two.
Next, we consider wire line networks and explore the connections between linear network coding, linear index coding and discrete polymatroids, which are the multi-set analogue of matroids.
We define a discrete polymatroidal network and show that a fractional vector linear solution over a field Fq exists for a network if and only if the network is discrete polymatroidal with respect to a discrete polymatroid representable over Fq.An algorithm to construct networks starting from certain class of discrete polymatroids is provided. Every representation over Fq for the discrete polymatroid, results in a fractional vector linear solution over Fq for the constructed network.
It is shown that a linear solution to an index coding problem exists if and only if there exists a representable discrete polymatroid satisfying certain conditions which are determined by the index coding problem considered. El Rouayheb et. al. showed that the problem of finding a multi-linear representation for a matroid can be reduced to finding a perfect linear index coding solution for an index coding problem obtained from that matroid. Multi-linear representation of a matroid can be viewed as a special case of representation of an appropriate discrete polymatroid. We generalize the result of El Rouayheb et. al. by showing that the problem of finding a representation for a discrete polymatroid can be reduced to finding a perfect linear index coding solution for an index coding problem obtained from that discrete polymatroid.
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Nouvelle technique de grilles imbriquées pour les équations de Saint-Venant 2D / New nested grids technique for 2D shallow water equationsAltaie, Huda 17 December 2018 (has links)
Les écoulements en eau peu profonde se rencontrent dans de nombreuses situations d’intérêts : écoulements de rivières et dans les lacs, mais aussi dans les mers et océans (courants de marée, tsunami, etc.). Ils sont modélisés par un système d’équations aux dérivées partielles, où les inconnues sont la vitesse de l’écoulement et la hauteur d’eau. On peut supposer que la composante verticale de la vitesse est petite devant les composantes horizontales et que ces dernières sont indépendantes de la profondeur. Le modèle est alors donné par les équations de shallow water (SWEs). Cette thèse se concentre sur la conception d’une nouvelle technique d’interaction de plusieurs grilles imbriquées pour modèle en eau peu profonde en utilisant des méthodes numériques. La première partie de cette thèse comprend, La dérivation complète de ces équations à partir des équations de Navier- Stokes est expliquée. Etudier le développement et l’évaluation des méthodes numériques en utilisant des méthodes de différences finies et plusieurs exemples numériques sont appliqués utilisant la condition initiale du niveau gaussien pour 2DSWEs. Dans la deuxième partie de la thèse, nous sommes intéressés à proposer une nouvelle technique d’interaction de plusieurs grilles imbriquées pour résoudre les modèles océaniques en utilisant quatre choix des opérateurs de restriction avec des résultats de haute précision. Notre travail s’est concentré sur la résolution numérique de SWE par grilles imbriquées. A chaque niveau de résolution, nous avons utilisé une méthode classique de différences finies sur une grille C d’Arakawa, avec un schéma de leapfrog complété par un filtre d’Asselin. Afin de pouvoir affiner les calculs dans les régions perturbées et de les alléger dans les zones calmes, nous avons considéré plusieurs niveaux de résolution en utilisant des grilles imbriquées. Ceci permet d’augmenter considérablement le rapport performance de la méthode, à condition de régler efficacement les interactions (spatiales et temporelles) entre les grilles. Dans la troisième partie de cette thèse, plusieurs exemples numéériques sont testés pour 2DSWE avec imbriqués 3:1 et 5:1. Finalement, la quatrième partie de ce travail, certaines applications de grilles imbriquées pour le modèle tsunami sont présentées. / Most flows in the rivers, seas, and ocean are shallow water flow in which the horizontal length andvelocity scales are much larger than the vertical ones. The mathematical formulation of these flows, so called shallow water equations (SWEs). These equations are a system of hyperbolic partial differentialequations and they are effective for many physical phenomena in the oceans, coastal regions, riversand canals. This thesis focuses on the design of a new two-way interaction technique for multiple nested grids 2DSWEs using the numerical methods. The first part of this thesis includes, proposing several ways to develop the derivation of shallow water model. The complete derivation of this system from Navier-Stokes equations is explained. Studying the development and evaluation of numerical methods by suggesting new spatial and temporal discretization techniques in a standard C-grid using an explicit finite difference method in space and leapfrog with Robert-Asselin filter in time which are effective for modeling in oceanic and atmospheric flows. Several numerical examples for this model using Gaussian level initial condition are implemented in order to validate the efficiency of the proposed method. In the second part of our work, we are interested to propose a new two-way interaction technique for multiple nested grids to solve ocean models using four choices of higher restriction operators (update schemes) for the free surface elevation and velocities with high accuracy results. Our work focused on the numerical resolution of SWEs by nested grids. At each level of resolution, we used explicit finite differences methods on Arakawa C-grid. In order to be able to refine the calculations in troubled regions and move them into quiet areas, we have considered several levels of resolution using nested grids. This makes it possible to considerably increase the performance ratio of the method, provided that the interactions (spatial and temporal) between the grids are effectively controlled. In the third part of this thesis, several numerical examples are tested to show and verify twoway interaction technique for multiple nested grids of shallow water models can works efficiently over different periods of time with nesting 3:1 and 5:1 at multiple levels. Some examples for multiple nested grids of the tsunami model with nesting 5:1 using moving boundary conditions are tested in the fourth part of this work.
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L’Association des Nations de l'Asie du Sud-Est (ASEAN) : Contribution à l’étude du processus d’institutionnalisation dans le droit international public / The Association of Southeast Asian Nations (ASEAN) : Contribution to the study of institutionalization in International Public LawTran, Thi Phuong Nhung 23 July 2014 (has links)
L’Association des nations de l’Asie du sud-est (ASEAN) est l’une des organisationsrégionales les plus anciennes en Asie. Créée en 1967 par la Déclaration de Bangkok, une déclarationinterétatique, l’ASEAN n’avait pas un statut juridique clair jusqu’en 2007, date de l’adoption de saCharte constitutive. A défaut d’une base conventionnelle, l’ASEAN ne manquait pourtant pas descaractéristiques d’une organisation internationale. Pendant les quarante années qui ont suivi sacréation, elle avait choisi un mode de fonctionnement fondé principalement sur les relations(relationship-based) et non sur les règles de droit. La prédominance du politique dans lefonctionnement de l’ASEAN a donc laissé aux règles de droit une place secondaire voire ambigüe.Cette spécificité, appelée ASEAN way, a fait de l’ASEAN une organisation au service des intérêtsindividuels de ses membres. En 2007, l’ASEAN s’est dotée d’une Charte constitutive, qui tente à latransformer en une organisation fondée sur des règles (rule-based). Cette Charte qui a ouvert unenouvelle ère pour l’ASEAN, l’a mise au rang d’organisation internationale, sujet dérivé du droitinternational. Elle semble remettre en cause la place du politique dans le fonctionnement de cetteorganisation. Néanmoins, la Charte a renforcé l’ASEAN way, ce qui démontre les limites de l’ASEAN.L’étude de l’institutionnalisation de l’ASEAN vise à démontrer les causes de la prééminence del’ASEAN way sur le droit et ses répercussions sur les relations entre les Etats. Cette présente étudeprocède à l’examen de l’articulation entre les objectifs et principes comme cadre axiologique del’ASEAN, son système institutionnel et son ordre juridique. / The Association of Southeast Asian Nations (ASEAN) is one of the most ancient regionalorganizations in Asia. Created in 1967 by the Bangkok Declaration, an interstate declaration, ASEANdid not have a clear legal status until 2007, date of its constituent Charter adoption. Lacking aconventional basis, ASEAN however did not lack the characteristics of an international organization.During the 40 years following its creation, it had chosen a mode of functioning mainly based onrelationship and not on rules of law. The political predominance in the ASEAN functioning therefore leftonly a secondary place to the rules of law, somewhat ambiguous. This particularity, so-called ASEANway, has made ASEAN an organization geared towards the individual interests of its members. In2007, ASEAN adopted a constituent Charter, whose aim is to transform ASEAN into a rule-basedorganization. This Charter, opening a new era for ASEAN, raised it to the rank of internationalorganization – derived subject of international law. It seems to call into question the place of politics inits functioning. The Charter nevertheless reinforced the ASEAN way, which shows the limits of ASEAN.The study of the ASEAN institutionalization aims at proving the cause of the predominance of ASEANway on the law and its repercussions on interstate relationships. This present study carries out theexamination of the link between the aims and the principles as an axiomatical framework of ASEAN, ofits institutional system and its legal order.
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Bytový dům Panoráma Boskovice - dopravní řešení / Panorama Boskovice Apartment Hose - design of transportWerner, David January 2019 (has links)
The diploma thesis deals with the project of transport solution for new buildings of BD Panorama Boskovice. The project documentation elaborates the design of the road, sidewalks and parking spaces to the proposed 4 apartment buildings in Boskovice The work corresponds to the extent of the design documentation for construction (PDPS).
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Listen Up! : A study of how teachers in SLA approach the listening skill within upper secondary schools in SwedenAndersson, Julia, Lagerström, Elin January 2020 (has links)
Listening comprehension and listening strategies plays a crucial role in the process of acquiring a language. This study aims to investigate to what extent the listening skill is practised in upper secondary schools in the south of Sweden. Research studies within the field of listening are few which indicates that the listening skill is not considered as essential in second language teaching as the other three skills: reading, writing and speaking. Previous studies indicate that teachers should educate students metacognitive awareness when teaching listening. The results summarize the teachers’ answers, reflections and attitudes conducted from semi-structured interviews. The analysis of the results focuses on the four categories distinguished from the teachers’ answers: Teaching Approaches, National Exams, The Individual Student and Metacognitive Awareness. Some of the teachers do not possess the knowledge of how to teach listening that develops students' listening proficiency. As a conclusion, the study shows that a hierarchy exists among the four skills to which teachers adjust to, and this may be detrimental in achieving educational aims.
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Simulation of Unsteady Gas-Particle Flows including Two-way and Four-way Coupling on a MIMD Computer ArchitecturPachler, Klaus, Frank, Thomas, Bernert, Klaus 17 April 2002 (has links)
The transport or the separation of solid particles or droplets suspended in a fluid flow is a common task in mechanical and process engineering. To improve machinery and physical processes (e.g. for coal combustion, reduction of NO_x and soot) an optimization of complex phenomena by simulation applying the fundamental conservation equations is required. Fluid-particle flows are characterized by the ratio of density of the two phases gamma=rho_P/rho_F, by the Stokes number St=tau_P/tau_F and by the loading in terms of void and mass fraction.
Those numbers (Stokes number, gamma) define the flow regime and which relevant forces are acting on the particle. Dependent on the geometrical configuration the particle-wall interaction might have a heavy impact on the mean flow structure. The occurrence of particle-particle collisions becomes also more and more important with the increase of the local void fraction of the particulate phase. With increase of the particle loading the interaction with the fluid phase can not been neglected and 2-way or even 4-way coupling between the continous and disperse phases has to be taken into account.
For dilute to moderate dense particle flows the Euler-Lagrange method is capable to resolve the main flow mechanism. An accurate computation needs unfortunately a high number of numerical particles (1,...,10^7) to get the reliable statistics for the underlying modelling correlations. Due to the fact that a Lagrangian algorithm cannot be vectorized for complex meshes the only way to finish those simulations in a reasonable time is the parallization applying the message passing paradigma.
Frank et al. describes the basic ideas for a parallel Eulererian-Lagrangian solver, which uses multigrid for acceleration of the flow equations. The performance figures are quite good, though only steady problems are tackled. The presented paper is aimed to the numerical prediction of time-dependend fluid-particle flows using the simultanous particle tracking approach based on the Eulerian-Lagrangian and the particle-source-in-cell (PSI-Cell) approach. It is shown in the paper that for the unsteady flow prediction efficiency and load balancing of the parallel numerical simulation is an even more pronounced problem in comparison with the steady flow calculations, because the time steps for the time integration along one particle trajectory are very small per one time step of fluid flow integration and so the floating point workload on a single processor node is usualy rather low.
Much time is spent for communication and waiting time of the processors, because for cold flow particle convection not very extensive calculations are necessary. One remedy might be a highspeed switch like Myrinet or Dolphin PCI/SCI (500 MByte/s), which could balance the relative high floating point performance of INTEL PIII processors and the weak capacity of the Fast-Ethernet communication network (100 Mbit/s) of the Chemnitz Linux Cluster (CLIC) used for the presented calculations. Corresponding to the discussed examples calculation times and parallel performance will be presented. Another point is the communication of many small packages, which should be summed up to bigger messages, because each message requires a startup time independently of its size. Summarising the potential of such a parallel algorithm, it will be shown that a Beowulf-type cluster computer is a highly competitve alternative to the classical main frame computer for the investigated Eulerian-Lagrangian simultanous particle tracking approach.
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Easing the transition from block-based programming in education : Comparing two ways of transitioning from block-based to text-based programming and an alternative way to solve the transition problem / Att underlätta övergången från blockbaserad programmering inom utbildningAbdinur Iusuf, Joakim, Nordling, Edvin January 2023 (has links)
Many learners find the transition from block-based programming to text-based programming difficult. Consequently, research has investigated how block-based languages support learners when making the transition to text-based programming. It categorized the way in which block-based languages support the transition into one-way transition, dual-modality and hybrid environments. This research investigates how one-way transition environments compare to dual-modality environments with regards to learning a text-based language, and how the two modalities differ with regards to the motivational factors satisfaction, enjoyment and easiness. The results show that dual-modality environments could be a better alternative than one-way transition environment when learners make the transition from block-based to text-based programming. The results also show that solving a problem in dual-modality environments could be easier than solving them in one-way transition environments, which could potentially mean that learners experience more motivation when making the transition in a dual-modality environment. This study also investigated if there is an alternative to one-way transition, dual-modality and hybrid environments when helping learners transition from block-based to text-based programming, and what a learning activity in this alternative solution could look like. It found that Blockly Games is an alternative, and describes a learning activity built in Blockly Games. Future research should aim at gaining a deeper understanding of the differences between one-way transition, dual-modality and hybrid environments, and investigate if the approach taken by Blockly Games is a better alternative. / Många elever tycker att övergången från blockbaserad programmering till textbaserad programmering är svår. Följaktligen har forskning undersökt hur blockbaserade språk stödjer elever när de gör övergången till textbaserad programmering. En studie fann att blockbaserade språk stöder denna övergång med hjälp av one-way transition miljöer, dual-modality miljöer och hybrid miljöer. Denna forskning undersöker hur one-way transition miljöer jämför sig med dual-modality miljöer när det kommer till att lära sig ett textbaserat språk, och hur de två modaliteterna skiljer sig åt med avseende på motivationsfaktorerna tillfredsställelse, njutning och lätthet. Resultaten visar att dual-modality miljöer kan vara ett bättre alternativ än one-way transition miljöer när eleverna gör övergången från blockbaserad till textbaserad programmering. Resultaten visar också att det kan vara lättare att lösa ett problem i dual-modality miljöer än att lösa dem i one-way transition miljöer, vilket potentiellt kan innebära att eleverna upplever mer motivation när de gör övergången i en dual-modality miljö. Denna studie undersökte också om det finns ett alternativ till one-way transition miljöer, dual-modality miljöer och hybrid miljöer när elever ska övergå från blockbaserad till textbaserad programmering, och hur en inlärningsaktivitet i denna alternativa lösning skulle kunna se ut. Den fann att Blockly Games är ett alternativ och beskriver en inlärningsaktivitet byggd i Blockly Games. Framtida forskning borde försöka få en djupare förståelse för skillnaderna mellan one-way transition miljöer, dual-modality miljöer och hybrid miljöer, och undersöka om det tillvägagångssätt som Blockly Games använder är ett bättre alternativ.
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Self-locking Brake used in Reversible Sailboat Winches : Development of a self-locking braking system that will be used to allow sailboat winches to reverseAndersson, Lukas January 2022 (has links)
Sailboat winches are used to help sailors manipulate the control lines that control the position and shape of the sails. Unlike most winches sailboat winches usually only have the ability to winch in the rope, but not to reverse. To reverse the line a sailor needs to manually manipulate it, this is both inconvenient and can also be a safety hazard. This master’s thesis will focus on the development of a self-locking braking system that will be used to allow a sailboat winch to reverse. The goal of the thesis is to design a braking system that works with a modified version of the E40i winch produced by Seldén. The braking system that was developed during this thesis is made up of two main parts, a one-way mechanism and a brake. The type of one-way mechanism that was chosen was an overrunning roller clutch. For the brake a wet disk brake was chosen with an outer diameter of 50mm and an inner diameter of 28.8mm. A 3D model of the braking system has been generated and materials have been selected so that the system is ready for prototyping and physical testing.
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