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No. of bitstreams: 1 20180705 - Operacoes-Marmo-Dissertacao_final.pdf: 4751437 bytes, checksum: aa09035b7b8668a465698d55769d6bfc (MD5) Previous issue date: 2018-06-13 / O presente estudo trata o tema sobre estratégias para o gerenciamento da capacidade e demanda em serviços de transportes que possuem restrições de capacidade e limitações operacionais. Nesse sentido, apresenta e discute as diferentes práticas encontradas na literatura com a aplicação específica em um sistema aquaviário de transporte de passageiros no estado de São Paulo. Para tanto, utilizou como modelo a análise do eventual impacto da aplicação de tais práticas de gestão da capacidade e demanda nos serviços oferecidos. Atualmente, o desequilíbrio entre oferta e demanda e a falta de incentivos para a diversificação da matriz modal de transportes nos grandes centros urbanos acabam impactando diretamente na qualidade dos serviços de transportes prestados em todos os modais. O sistema aquaviário de transporte de passageiros do estado de São Paulo não destoa do cenário nacional descrito, em que a diferença entre oferta e demanda acaba por sobrecarregá-lo em rotas específicas e causa redução na qualidade do serviço prestado, dessa forma, traduzindo-se em extensas filas aos usuários. Considerando as particularidades da oferta e demanda do serviço de balsas, bem como o elevado custo fixo e a estrutura tarifária pouco flexível, surgiu o seguinte questionamento desta pesquisa: como a aplicação de estratégias específicas de gestão da capacidade e demanda pode impactar na qualidade percebida pelos usuários de uma rota do sistema de travessias litorâneas? Objetivando, então, alcançar uma resposta, este estudo intencionou compreender quais estratégias poderiam impactar na qualidade percebida pelos usuários, com enfoque no tempo de espera, de uma rota específica do sistema. Para isso, o trabalho adotou uma abordagem qualitativa, baseada na estratégia de estudo de caso aplicado, fundamentada pela análise de documentos do sistema de travessias litorâneas e análise de conteúdo das entrevistas. O resultado do estudo indicou quais estratégias podem apresentar um impacto positivo na qualidade da rota, com redução do tempo de fila, além de individuar eventuais desafios, restrições e práticas que auxiliem na futura aplicação dessas estratégias. / The present study aims to address strategies for capacity and demand management in transportation services which have restrictions and operational limitations. It presents and discusses the different practices found in literature with specific application to a passengers waterway transportation system in São Paulo State. For this, it uses as model the impact’s analysis of such practices application of capacity and demand management in the offered services. Nowadays, the unbalance between supply and demand plus lack of incentives to diversify the modal matrix of transport in large urban centers, have a direct impact on transport services quality provided in all modal. The waterway passengers transportation system of São Paulo State does not deviate from described national scenario, where the difference between supply and demand end up overloading it on specific routes, causing service’s quality reduction and translating into extensive queues to users. Considering the particularities of supply and demand of ferries’ service, as well as the high fixed cost and the inflexible tariff structure, emerged the following question of this study: how the specifics strategies application from capacity and demand management can impact the quality perceived by users of a coastal crossing system route? In order to reach an answer, this study aimed to understand which strategies could impact the quality perceived by users, focusing on waiting time, in an specific route of the system. For this, the work adopted a qualitative approach, based on the strategy of applied case study, grounded on documental analysis of the coastal crossing system and interviews content analysis. The outcome of the study indicated which strategies may have a positive impact on route quality, with a reduction in queuing time, besides identifying possible challenges, restrictions and practices that may help in future application of these strategies.

Scheduling has always been an indispensable part of resource allocation in wireless networks. Accurate information about channel-state is assumed as a modeling simplification. However, in a real-life network ,e.g., Long Term Evolution(LTE) or IEEE 802.16e WiMAX, the channel-state information feedback to the transmitter can have uncertainty. The primary reason being that although resource allocation is done at the finer granularity of a Physical Resource Block (PRB), channel-state information is still feedback at the coarser granularity of a sub band, which is a group of PRBs. This is done to reduce the feedback traffic from the users to the Base Station. However, this averaging causes information loss and hence, the resulting uncertainty at the scheduler. Moreover, uncertainty might be present in the channel-estimates because of the very process of estimation. In the first part of the thesis, we model the channel-estimate in accuracy and characterize the network stability region. Compared to earlier works, we allow the channel estimates to have dependence among themselves, which is a more realistic situation in a modern LTE or WiMax network. We then propose two simple Max Weight based scheduling schemes that achieve any rate in the interior of the stability region. We also derive an asymptotically tight upper bound on the mean queueing delay in our system under one of the throughput-optimal policies we propose. The above policies ensure stability of the network and we have also obtained bounds on the mean queueing delays. However, different applications may require certain quality of service which may not be satisfied by these policies. Thus, we also propose a throughput-optimal policy for the network under traffic with heterogeneous QoS constraints and present some numerical results studying its performance. In the second part of the thesis, we study the problem of energy-efficient scheduling under average delay constraint. For wireless access technologies, the largest power consumer is the Base Station(BS). Any reduction in the power consumption in a BS will reduce carbon footprint from the Information and Communication Technology sector. We concentrate on the problem of minimizing the total non-renewable power consumed in a Green BS, that is powered by renewable energy sources ,e.g., solar/wind energy and may also be connected to the power grid or diesel generators. Specifically, we consider the problem of minimizing the average grid power consumption of a Green BS downlink in scheduling multiple users with average delay constraints. We have a packetized model for the data packets (i.e., the packets cannot be fragmented) which is a more realistic model for packet-switched networks. The power function is a non-decreasing convex function of the queue-lengths and only one user is allowed to transmit in a slot. We prove the existence of a power optimal policy under delay constraints for multiple users. We analyse the problem and provide some structural results for the optimal policy.

En viktig del av passagerartillfredsställelsen utgörs av hur smidiga köpprocesserna är. I denna studie analyseras delprocesser hos KING SEAWAYS med mål om att skapa ett optimerat förbättringsförslag till de studerade processerna. Den nuvarande processen gällande fartygets tid i hamn innefattar delprocesser som körs beroende och oberoende av varandra. Fokus i studien är på de sista delprocesserna innan fartygets avgång från det att passageraren ankommer till check-in fram till dem står parkerade på bildäcket. Kundundersökningen visar ett missnöje bland passagerarna gällande väntetid på kajen. Efter att ha analyserat passagerarbeteendet och genom att göra några resonabla antaganden för att förenkla uträkningarna gällande köer, är det uppenbart att det finns betydande flaskhalsar i processen som kan åtgärdas. Att applicera köteori i varje steg, skapar en klar bild av att förändringar kan skapa förutsättningar för reducerade kostnader samt en förhöjd kundnöjdhet.   Förbättringsförslaget som framkom efter analys av den nuvarande processen och kundernas upplevelse var att nyttja tiden på kajen till att förbereda inför ombordkörning och placera bilar efter layout ombord på fartyget. Med detta kan bilarna på kajen hanteras som en homogen grupp, snarare än enskilda enheter och då öka effektiviteten i processen. Förslaget bör även ge ett positivt utfall på kundtillfredsställelsen.   Denna rapport berör endast ett fartyg i DFDS totala flotta om cirka 50 fartyg, men tankarna som lett fram till resultat och slutsats bör även vara applicerbart på flertalet andra fartyg i flottan. Bara för fartyget KING SEAWAYS skulle en förändring om en minskad tid i hamn, om 15 minuter dagligen, innebära en bränslebesparing årligen om 1,7 miljoner danska kronor. Med en snabb beräkning gällande besparingar av resurser visar förbättringsförslaget att det kan komma att handla om flertalet miljoner. Med nöjdare kunder skaps även konkurrenskraft och det är en förutsättning för att DFDS även i framtiden behålla sin marknadsposition. / An important factor in passenger satisfaction is queue management. In this study processes at KING SEAWAYS are analyzed with the aim of creating a proposal for improvement and optimization. The current process of the vessels turnaround includes sub-processes that run dependent and independent of each other. The focus in this study deals with the final sub-processes before departure, from the time that the passenger arrives at the check-in until they are parked on the car deck. The customer survey shows dissatisfaction among passengers regarding waiting time on the dock. After analyzing the behavior of passengers and by taking a couple of reasonable assumptions, it becomes obvious that bottlenecks could be reduced. Applying queuing theory in each step creates a clear picture that changes can create conditions for reduced costs as well as increased condition for customer satisfaction.   The improvement proposal that emerged after analyzing the current process and customer experience was to utilize time on the quay to prepare for boarding and place cars according to the ship layout. With this, the cars on the dock can be handled as a homogeneous group, rather than individual units, and then increase the efficiency of the process. The proposal should also give a positive outcome to customer satisfaction.   This report deals with one vessel in DFDS' total fleet of about 50 vessels, but the thoughts that led to the results and conclusion could be applicable to most of the other fleet vessels. For KING SEAWAYS only, a reduced turnaround time of 15 minutes corresponds to fuel saving of 1.7 million Danish kroner per year. With a quick estimation on resource savings the proposal for improvement shows that improvements could have a considerable impact on DFDS bottom line. Satisfied customers are also a prerequisite for DFDS to maintain its market position in the future.

Aux futurs collisionneurs linéaires et circulaires, la présence d’un halo autour du faisceau est susceptible de fortement limiter les performances, et peut également activer, voire endommager, les composants de l’accélérateur. Le halo doit par conséquent est contrôlé par un système de collimateurs efficace. Pour évaluer l’impact sur les expériences de physique des particules ainsi que les efficacités de collimation, une bonne compréhension des mécanismes physiques générateurs de halo est essentielle, pour par exemple prédire les distributions de probabilité de manière fiable. Pour ce faire, une investigation systématique ont été menée à l’Accelerator Test Facility (ATF) du KEK dans le cadre de cette thèse, d’abord à travers une analyse théorique des principales sources de halo dans ATF, puis moyennant le développement et l’implémentation de diagnostiques dédiés aux mesures du halo, dont les résultat sont ensuite présentés et comparés aux prédictions théoriques. Le halo produit par la diffusion des particules du faisceau sur les noyaux des molécules du gaz résiduel dans la chambre à vide (« Beam Gas Scattering » - BGS) est d’abord estimé analytiquement, avec certaines approximations, puis moyennant une simulation Monte-Carlo. Un nombre considérable de particules de halo BGS est prédit, ainsi qu’une dépendance dans la pression de gaz résiduel. Pour étudier la possible formation d’un halo par le mécanisme de diffusion intra-paquet à grand angle dit de « Touschek » en présence d’une dispersion optique résiduelle, le taux de cette diffusion a été estimé en fonction de plusieurs paramètres faisceau pertinents. Une simulation Monte-Carlo de la diffusion intra-faisceau à petit angle (IBS) et de « Touschek » est aussi en cours de développement. Pour tester les prédictions théoriques, les performances d’un détecteur de halo déjà existant basé sur un capteur diamant ont été améliorées moyennant une technique de repondération qui a permis d’en augmenter la gamme dynamique jusqu’à 10⁵. Afin de disposer d’un instrument complémentaire pour mesurer le halo, un moniteur YAG/OTR a aussi été conçu, construit et installé dans la ligne d’extraction d’ATF. Il a pu être montré que la gamme dynamique et la résolution de ce moniteur YAGOTR sont, respectivement, autour de 10⁵ et inférieure à 10 μm. Grâce aux diagnostiques développés pour mesurer le halo du faisceau d’ATF, les distributions transverses et en énergie ont pu être étudiées. L’accord satisfaisant obtenu entre les prédictions théoriques et les mesures, ainsi qu’une dépendance importante dans la pression de gaz résiduel, ont permis de montrer que la distribution verticale du halo est dominée par le mécanisme BGS. Par contre, la distribution horizontale est bien supérieure aux prédictions BGS, et est par ailleurs asymétrique. L’asymétrie observée peut être en partie reliée à la qualité du champ de l’élément pulsé servant à l’extraction du faisceau d’ATF, ainsi qu’à certaines aberrations dans le transport optique. La distribution de probabilité du halo en fonction de l’énergie a par ailleurs pu être mesurée, grâce à une technique nouvelle d’ajustement de la dispersion optique dans le plan vertical, et a été trouvée compatible qualitativement avec le mécanisme de diffusion « Touschek ». Un scénario plausible de génération du halo dans le plan horizontal a ainsi pu être suggéré. / At future linear and circular colliders, beam halo can strongly limit machine performances, cause as well component damage and activation, and should, therefore, be controlled by an efficient collimation system. To evaluate the impact on particle physics experiments and collimation efficiencies, a clear understanding of beam halo formation mechanisms is essential, e.g., to predict halo distribution reliably. For this purpose, systematic investigations have been carried out at the Accelerator Test Facility (ATF) of KEK. In this dissertation, the theoretical analysis of the primary halo sources at ATF and the development of dedicated halo diagnostics are presented. Measurements of beam halo at ATF are also described and compared with the theoretical predictions. Beam halo arising from Beam-Gas Scattering (BGS) in the damping ring was firstly estimated through analytical approximations and a Monte Carlo simulation. A considerable amount of halo particles generated by BGS and the corresponding vacuum dependence have been predicted. To explore the probability of beam halo formation from Touschek scattering in the presence of dispersion, the Touschek scattering rate was estimated with respect to relevant beam parameters. Furthermore, a Monte Carlo simulation of Intra-Beam Scattering (IBS) and Touschek scattering is under development. To probe the theoretical predictions, the performance of an already existing diamond sensor detector was optimized via a data rescaling technique to increase the dynamic range to 1×10⁵. For a complementary diagnostics of beam halo, a YAG/OTR monitor was also designed and installed in the extraction section of ATF2. The dynamic range and resolution of the YAG/OTR monitor have been shown to be around 1×10⁵ and less than 10 μm, respectively. Thanks to the halo monitors developed at ATF2, the transverse halo and momentum tail have been studied. Satisfactory agreement between numerical predictions and measurements as well as a significant vacuum dependence indicate that the BGS process dominates the vertical halo. On the other hand, the horizontal halo appeared to be higher than the prediction from BGS, and moreover asymmetric. The observed asymmetry was shown to be related to the quality of the extraction kicker field and optical aberration. Finally, the momentum tail was for the first time observed by implementing a novel scheme of vertical dispersion adjustment and was found to be qualitatively consistent with the presence of Touschek scattering. A possible scenario for horizontal beam halo formation from Touschek scattering was also suggested.

The main objective of this work is to design and implement an application that can be used as an aid for the education of programming essentials. Particularly, the attention focuses on the domain of dynamic data structures. The target application will be implemented with the use of web technologies so that it can be run in an ordinary WWW browser. First of all, a brief introduction recapitulates the data structures to be covered. Then the work summarizes the usable technologies available within the web browsers with the focus on the particular technology (which is DHTML) that will become the target platform. The most significant part of this work then discusses the design of the final application. This rather theoretical part is then followed by the description of the practical implementation. A short user manual is also included.

No description available.

Along with playing an ever-increasing role in the integration of other communication networks and expanding in application diversities, the current Internet suffers from serious overuse and congestion bottlenecks. Efficient congestion control is fundamental to ensure the Internet reliability, satisfy the specified Quality-of-Service (QoS) constraints and achieve desirable performance in response to varying application scenarios. Active Queue Management (AQM) is a promising scheme to support end-to-end Transmission Control Protocol (TCP) congestion control because it enables the sender to react appropriately to the real network situation. Analytical performance models are powerful tools which can be adopted to investigate optimal setting of AQM parameters. Among the existing research efforts in this field, however, there is a current lack of analytical models that can be viewed as a cost-effective performance evaluation tool for AQM in the presence of heterogeneous traffic, generated by various network applications. This thesis aims to provide a generic and extensible analytical framework for analyzing AQM congestion control for various traffic types, such as non-bursty Poisson and bursty Markov-Modulated Poisson Process (MMPP) traffic. Specifically, the Markov analytical models are developed for AQM congestion control scheme coupled with queue thresholds and then are adopted to derive expressions for important QoS metrics. The main contributions of this thesis are listed as follows: iii ¿ Study the queueing systems for modeling AQM scheme subject to single-class and multiple-classes Poisson traffic, respectively. Analyze the effects of the varying threshold, mean traffic arrival rate, service rate and buffer capacity on the key performance metrics. ¿ Propose an analytical model for AQM scheme with single class bursty traffic and investigate how burstiness and correlations affect the performance metrics. The analytical results reveal that high burstiness and correlation can result in significant degradation of AQM performance, such as increased queueing delay and packet loss probability, and reduced throughput and utlization. ¿ Develop an analytical model for a single server queueing system with AQM in the presence of heterogeneous traffic and evaluate the aggregate and marginal performance subject to different threshold values, burstiness degree and correlation. ¿ Conduct stochastic analysis of a single-server system with single-queue and multiple-queues, respectively, for AQM scheme in the presence of multiple priority traffic classes scheduled by the Priority Resume (PR) policy. ¿ Carry out the performance comparison of AQM with PR and First-In First-Out (FIFO) scheme and compare the performance of AQM with single PR priority queue and multiple priority queues, respectively.

An investigation into the impact of generalised maximum entropy solutions on the study of queues with or without arrival balking and their applications to congestion management in communication networks Keywords: Queues, Balking, Maximum Entropy (ME) Principle, Global Balance (GB), Queue Length Distribution (QLD), Generalised Geometric (GGeo), Generalised Exponential (GE), Generalised Discrete Half Normal (GdHN), Congestion Management, Packet Dropping Policy (PDP) Generalisations to links between discrete least biased (i.e. maximum entropy (ME)) distribution inferences and Markov chains are conjectured towards the performance modelling, analysis and prediction of general, single server queues with or without arrival balking. New ME solutions, namely the generalised discrete Half Normal (GdHN) and truncated GdHN (GdHNT) distributions are characterised, subject to appropriate mean value constraints, for inferences of stationary discrete state probability distributions. Moreover, a closed form global balance (GB) solution is derived for the queue length distribution (QLD) of the M/GE/1/K queue subject to extended Morse balking, characterised by a Poisson prospective arrival process, i.i.d. generalised exponential (GE) service times and finite capacity, K. In this context, based on comprehensive numerical experimentation, the latter GB solution is conjectured to be a special case of the GdHNT ME distribution. ii Owing to the appropriate operational properties of the M/GE/1/K queue subject to extended Morse balking, this queueing system is applied as an ME performance model of Internet Protocol (IP)-based communication network nodes featuring static or dynamic packet dropping congestion management schemes. A performance evaluation study in terms of the model’s delay is carried out. Subsequently, the QLD’s of the GE/GE/1/K censored queue subject to extended Morse balking under three different composite batch balking and batch blocking policies are solved via the technique of GB. Following comprehensive numerical experimentation, the latter QLD’s are also conjectured to be special cases of the GdHNT. Limitations of this work and open problems which have arisen are included after the conclusions

Numerous studies on Queueing systems, such as Internet traffic flows, have shown to be bursty, self-similar and/or long-range dependent, because of the heavy (long) tails for the various distributions of interest, including intermittent intervals and queue lengths. Other studies have addressed vacation in no-customers’ queueing system or when the server fails. These patterns are important for capacity planning, performance prediction, and optimization of networks and have a negative impact on their effective functioning. Heavy-tailed distributions have been commonly used by telecommunication engineers to create workloads for simulation studies, which, regrettably, may show peculiar queueing characteristics. To cost-effectively examine the impacts of different network patterns on heavy- tailed queues, new and reliable analytical approaches need to be developed. It is decided to establish a brand-new analytical framework based on optimizing entropy functionals, such as those of Shannon, Rényi, Tsallis, and others that have been suggested within statistical physics and information theory, subject to suitable linear and non-linear system constraints. In both discrete and continuous time domains, new heavy tail analytic performance distributions will be developed, with a focus on those exhibiting the power law behaviour seen in many Internet scenarios. The exposition of two major revolutionary approaches, namely the unification of information geometry and classical queueing systems and unifying information length theory with transient queueing systems. After conclusions, open problems arising from this thesis and limitations are introduced as future work.

År 2024 upplevde Sverige längre väntetider och sämre tillgänglighet inom både primär- och specialiserad vård jämfört med andra länder. Detta ledde till ökat tryck på akutmottagningar då många patienter sökte sig dit för vård som annars kunde hanterats på ordinära mottagningar om tillräcklig personal funnits tillgänglig. Denna studie fokuserar på att undersöka patientflöden vid Danderyds sjukhus genom att identifiera flaskhalsar inom akutmottagningen. Studiens syfte var att hitta flaskhalsar som kan åtgärdas för att minska väntetiderna och förbättra resursanvändningen genom att använda matematiska modeller och diskret händelsesimulering. Analysen baseras på data insamlad under det första kvartalet för åren 2022, 2023 och 2024. Resultaten från simuleringarna visar kritiska statistiska mått som är avgörande för att förstå systemets kapacitet och prestanda under varierande belastningar. Dessa resultat belyser även nödvändigheten av resursallokering och förväntade väntetider för patienter. Studien bidrar inte bara till en bra förståelse av de nuvarande processerna utan presenterar även strategier för att effektivt hantera de utmaningar akutmottagningarna står inför. Slutsatserna diskuterar de teoretiska och praktiska implikationerna med betoning på hur simuleringarna kan användas för att utforska nya arbetsmetoder för akutmottagningar framöver. Denna forskning lägger grunden för framtida innovationer inom sjukvårdens arbetsflöden och resursallokering, vilket kan leda till förbättrad patientvård och effektivare sjukhusdrift. / In 2024, Sweden experienced longer wait times and reduced accessibility in both primary and specialized care compared to other countries. This led to increased pressure on emergency departments, as many patients sought care there that could have been managed at regular clinics if sufficient staff were available. This study focuses on examining patient flows at Danderyd Hospital by identifying bottlenecks within the emergency department. The aim of the study was to find bottlenecks that can be addressed to reduce wait times and improve resource utilization through the use of mathematical models and discrete event simulation. The analysis is based on data collected during the first quarter of the years 2022, 2023, and 2024. The results from the simulations reveal critical statistical measures that are essential for understanding the system's capacity and performance under varying loads. These results also highlight the need for resource allocation and expected wait times for patients. The study not only contributes to a better understanding of the current processes but also presents strategies for effectively addressing the challenges faced by emergency departments. The conclusions discuss the theoretical and practical implications, emphasizing how the simulations can be used to explore new working methods for emergency departments in the future. This research lays the foundation for future innovations in healthcare workflows and resource allocation, which can lead to improved patient care and more efficient hospital operations.