Scalable coordination of distributed in-memory transactions

Phd ThesisCoordinating transactions involves ensuring serializability in the presence of concurrent data accesses. Accomplishing it in an scalable manner for distributed in-memory transactions is the aim of this thesis work. To this end, the work makes three contributions. It first experimentally demonstrates that transaction latency and throughput scale considerably well when an atomic multicast service is offered to transaction nodes by a crash-tolerant ensemble of dedicated nodes and that using such a service is the most scalable approach compared to practices advocated in the literature. Secondly, we design, implement and evaluate a crash-tolerant and non-blocking atomic broadcast protocol, called ABcast, which is then used as the foundation for building the aforementioned multicast service. ABcast is a hybrid protocol, which consists of a pair of primary and backup protocols executing in parallel. The primary protocol is a deterministic atomic broadcast protocol that provides high performance when node crashes are absent, but blocks in their presence until a group membership service detects such failures. The backup protocol, Aramis, is a probabilistic protocol that does not block in the event of node crashes and allows message delivery to continue post-crash until the primary protocol is able to resume. Aramis design avoids blocking by assuming that message delays remain within a known bound with a high probability that can be estimated in advance, provided that recent delay estimates are used to (i) continually adjust that bound and (ii) regulate flow control. Aramis delivery of broadcasts preserve total order with a probability that can be tuned to be close to 1. Comprehensive evaluations show that this probability can be 99.99% or more. Finally, we assess the effect of low-probability order violations on implementing various isolation levels commonly considered in transaction systems. These three contributions together advance the state-of-art in two major ways: (i) identifying a service based approach to transactional scalability and (ii) establishing a practical alternative to the complex PAXOSiii style approach to building such a service, by using novel but simple protocols and open-source software frameworks.Red Ha

Real-Time Ultrasound Image-Guidance and Tracking in External Beam Radiotherapy

Background and Purpose - To evaluate the accuracy of Clarity (clinical version) system by using ultrasound phantom and some probe position. - To evaluate the intrafraction motion of prostate by collecting and analyzing ultrasound monitoring data from some patients. - To evaluate the accuracy of Clarity (Anticosti) system by using 3D phantom programmed with sinusoidal and breathing movement patterns to simulate computer-controlled based breath-hold phases interspersed with spontaneous breathing. - To evaluate the clinical applicability of Clarity (Anticosti) system for liver cases in healthy volunteers. The tracking results of healthy volunteers were compared to surface marker. - To evaluate the intrafraction motion during breath-hold in liver case by collecting and analyzing US monitoring data from some patients. Material and Methods The accuracy of Clarity (clinical version) system was evaluated using ultrasound phantom and some probe position. Two different probes were used: transabdominal ultrasound (TAUS) and transperineal ultrasound (TPUS) probe. Two positions of the phantom were used for TPUS, the vertical and the horizontal position. Intrafraction motion assessment of the prostate was based on continuous position monitoring with a 4D US system along the three directions; left(+)-right (LR), anterior(+)-posterior (AP), and inferior(+)-superior (SI). 770 US monitoring sessions in 38 prostate cancer patients’ normo-fractionated VMAT treatment series were retrospectively evaluated. The overall mean values and standard deviations (SD) along with random and systematic SDs were computed. The tracking accuracy of the research 4D US system was evaluated using two motion phantoms programmed with sinusoidal and breathing patterns to simulate free breathing and DIBH. The clinical performance was evaluated with 5 healthy volunteers. US datasets were acquired in computer-controlled DIBH with varying angular scanning angles. Tracked structures were renal pelvis (spherical structure) and portal/liver vein branches (non-spherical structure). An external marker was attached to the surface of both phantoms and volunteers as a secondary tracked object by an infrared camera for comparison. Residual intrafractional motion of DIBH tracking target relative to beginning position in each breath-hold plateau region was analysed along three directions; superior-inferior (SI), left-right (LR) and anterior-posterior (AP). 12 PTVs of 11 patients with primary/secondary liver tumours or adrenal gland/spleen metastases of diverse primaries were irradiated with SBRT in DIBH. Real time tracking of target or neighbouring surrogate structures was performed additionally using 4D US system during CBCT acquisition after permission of local IRB. Results The geometric positioning tolerance for Clarity-Sim and Clarity-Guide is 1 mm according to the manufacturer’s specifications. The results showed that all phantom and probe combinations met this criterion. The mean duration of each prostate monitoring session was 254s. The mean (μ), the systematic error () and the random error (σ) of intrafraction prostate motion were μ=(0.01, -0.08, 0.15)mm, =(0.30, 0.34, 0.23)mm and σ=(0.59, 0.73, 0.64)mm in LR, AP and SI direction, respectively. The percentage of treatments for which prostate motion was 2mm was present in about 0.67% of the data. The percentage increased to 2.42%, 6.14%, and 9.35% at 120s, 180s and 240s, respectively. The phantom measurements using Clarity (Anticosti) system showed increasing accuracy of US tracking with decreasing scanning range. The probability of lost tracking was higher for small scanning ranges (43.09% (10°) and 13.54% (20°)).The tracking success rates in healthy volunteers during DIBH were 93.24% and 89.86% for renal pelvis and portal vein branches, respectively. There was a strong correlation between the motion of the marker and the US tracking for the majority of analyzed breath-holds. 84.06% and 88.41% of renal pelvis target results and 82.26% and 91.94% of liver vein target results in AP and SI direction, the Pearson correlation coefficient was between 0.71 and 0.99. For evaluation of the intrafraction motion during breath-hold, 680 individual BHs during 93 treatment fractions were analysed. On visual control of tracking movies, target was lost in 27.9% of tracking, leaving a total of 490 BHs with optimal tracking. During these BHs, mean(+SD) target displacement were 1.7(+0.8)mm, 0.9(+0.4)mm, 2.2(+1.0)mm and 3.2(+1.0)mm for SI, LR, AP and 3D vector, respectively. Most of target displacement was below 2mm with percentage of 64.6%, 88.1% and 60.5% for SI, LR and AP, respectively. Data percentage of large target displacement increased with added BH time. At 5s, 3D vector of target displacement >10mm could be observed in 0.1% of data. Percentage values increased to 0.2%, 0.6%, and 1.1% at 10s, 15s and 20s, respectively. Conclusions The 4D US system offers a non-invasive method for online organ motion monitoring without additional ionizing radiation dose to the patient. The magnitudes of intrafraction prostate motion along the SI and AP directions were comparable. On average, the smallest motion was in the LR direction and the largest in AP direction. Most of the prostate displacements were within a few millimeters. However, with increased treatment time, larger 3D vector prostate displacements up to 18.30 mm could be observed. Shortening the treatment time can reduce the intrafractional motion and its effects and US monitoring can help to maximize treatment precision particularly in hypofractionated treatment regimens. For organ monitoring during BH application, the 4D US system showed a good performance and tracking accuracy in a 4D motion phantom when tracking a target that moves in accordance to a simulating breathing pattern. A 30°scanning range turned out to be an optimal parameter to track along with respiratory motion considering the accuracy of tracking and the possible loss of the tracked structure. The ultrasound tracking system is also applicable to a clinical setup with the tested hardware solution. The tracking capability of surrogate structures for upper abdominal lesions in DIBH is promising but needs further investigation in a larger cohort of patients. Ultrasound motion data show a strong correlation with surface motion data for most of individual breath-holds. Further improvement of the tracking algorithm is suggested to improve accuracy along with respiratory motion if using larger scanning angles for detection of high-amplitude motion and non-linear transformations of the tracking target. The exact quantification of residual motion impact requires an in-depth analysis of time spent at every position, nevertheless mean residual motion during DIBH is low and predominant direction is SI and AP. Only infrequently larger displacements of 3D vector >1 cm were observed, for short periods. Beam interruption at predefined thresholds could take DIBH treatments close to perfection. Key words: Medical Physics, 4D ultrasound, IGRT (image-guided radiotherapy), prostate motion, stereotactic body radiotherapy (SBRT), deep inspiratory breath-hold (DIBH)

Study of encapsulation and transport of 3DTV by satellite

The project was developed in EADS ASTRIUM Toulouse in the framework of the MUSCADE project with the latest technologies in 3DTV. Currently most of the research in satellite broadcasting field is focused in 3DTV transmission as the following of HDTV. MUSCADE is a European project funded by the 7th Framework Program whose objective is to demonstrate a complete multiview 3DTV live chain over wireline, wireless and satellite networks. This project aims to set up a satellite testbed to validate the 3D content format defined by MUSCADE in an emulated satellite environment. The document’s first chapter describes the environment where the internship has taken place and a brief overview of the EADS Company. After, a short description of the whole MUSCADE project can be found in section 5. This allows the reader to achieve a global vision of all the technological concepts involved in the project even if this internship is focused in satellite transmission. Section 6 describes the internship development. By means of conclusion, the new skills achieved, the knowledge applied and a professional and personal balance could be found at the end of this report.Ingeniería de TelecomunicaciónTelekomunikazio Ingeniaritz

DeMMon Decentralized Management and Monitoring Framework

The centralized model proposed by the Cloud computing paradigm mismatches the decentralized nature of mobile and IoT applications, given the fact that most of the data production and consumption is performed by end-user devices outside of the Data Center (DC). As the number of these devices grows, and given the need to transport data to and from DCs for computation, application providers incur additional infrastructure costs, and end-users incur delays when performing operations. These reasons have led us into a post-cloud era, where a new computing paradigm arose: Edge Computing. Edge Computing takes into account the broad spectrum of devices residing outside of the DC, closer to the clients, as potential targets for computations, potentially reducing infrastructure costs, improving the quality of service (QoS) for end-users and allowing new interaction paradigms between users and applications. Managing and monitoring the execution of these devices raises new challenges previously unaddressed by Cloud computing, given the scale of these systems and the devices’ (potentially) unreliable data connections and heterogenous computational power. The study of the state-of-the-art has revealed that existing resource monitoring and management solutions require manual configuration and have centralized components, which we believe do not scale for larger-scale systems. In this work, we address these limitations by presenting a novel Decentralized Management and Monitoring (“DeMMon”) system, targeted for edge settings. DeMMon provides primitives to ease the development of tools that manage computational resources that support edge-enabled applications, decomposed in components, through decentralized actions, taking advantage of partial knowledge of the system. Our solution was evaluated to amount to its benefits regarding information dissemination and monitoring capabilities across a set of realistic emulated scenarios of up to 750 nodes with variable failure rates. The results show the validity of our approach and that it can outperform state-of-the-art solutions regarding scalability and reliabilityO modelo centralizado de computação utilizado no paradigma da Computação na Nuvem apresenta limitações no contexto de aplicações no domínio da Internet das Coisas e aplicações móveis. Neste tipo de aplicações, os dados são produzidos e consumidos maioritariamente por dispositivos que se encontram na periferia da rede. Desta forma, transportar estes dados de e para os centros de dados impõe uma carga excessiva nas infraestruturas de rede que ligam os dispositivos aos centros de dados, aumentando a latência de respostas e diminuindo a qualidade de serviço para os utilizadores. Para combater estas limitações, surgiu o paradigma da Computação na Periferia, este paradigma propõe a execução de computações, e potencialmente armazenamento de dados, em dispositivos fora dos centros de dados, mais perto dos clientes, reduzindo custos e criando um novo leque de possibilidades para efetuar computações distribuídas mais próximas dos dispositivos que produzem e consomem os dados. Contudo, gerir e supervisionar a execução desses dispositivos levanta obstáculos não equacionados pela Computação na Nuvem, como a escala destes sistemas, ou a variabilidade na conectividade e na capacidade de computação dos dispositivos que os compõem. O estudo da literatura revela que ferramentas populares para gerir e supervisionar aplicações e dispositivos possuem limitações para a sua escalabilidade, como por exemplo, pontos de falha centralizados, ou requerem a configuração manual de cada dispositivo. Nesta dissertação, propõem-se uma nova solução de monitorização e disseminação de informação descentralizada. Esta solução oferece operações que permitem recolher informação sobre o estado do sistema, de modo a ser utilizada por soluções (também descentralizadas) que gerem aplicações especializadas para executar na periferia da rede. A nossa solução foi avaliada em redes emuladas de várias dimensões com um máximo de 750 nós, no contexto de disseminação e de monitorização de informação. Os nossos resultados mostram que o nosso sistema consegue ser mais robusto ao mesmo tempo que é mais escalável quando comparado com o estado da arte

Pem fuel cell modeling and converters design for a 48 v dc power bus

Fuel cells (FC) are electrochemical devices that directly convert the chemical energy of a fuel into electricity. Power systems based on proton exchange membrane fuel cell (PEMFC) technology have been the object of increasing attention in recent years as they appear very promising in both stationary and mobile applications due to their high efficiency, low operating temperature allowing fast startup, high power density, solid electrolyte, long cell and stack life, low corrosion, excellent dynamic response with respect to the other FCs, and nonpolluting emissions to the environment if the hydrogen is obtained from renewable sources. The output-voltage characteristic in a PEMFC is limited by the mechanical devices which are used for regulating the air flow in its cathode, the hydrogen flow in its anode, its inner temperature, and the humidity of the air supplied to it. Usually, the FC time constants are dominated by the fuel delivery system, in particular by the slow dynamics of the compressor responsible for supplying the oxygen. As a consequence, a fast load transient demand could cause a high voltage drop in a short time known as oxygen starvation phenomenon that is harmful for the FC. Thus, FCs are considered as a slow dynamic response equipment with respect to the load transient requirements. Therefore, batteries, ultracapacitors or other auxiliary power sources are needed to support the operation of the FC in order to ensure a fast response to any load power transient. The resulting systems, known as FC hybrid systems, can limit the slope of the current or the power generated by the FC with the use of current-controlled dc-dc converters. In this way, the reactant gas starvation phenomena can be avoided and the system can operate with higher efficiency. The purpose of this thesis is the design of a DC-DC converter suitable to interconnect all the different elements in a PEMFC-hybrid 48-V DC bus. Since the converter could be placed between elements with very different voltage levels, a buck-boost structure has been selected. Especially to fulfill the low ripple requirements of the PEMFCs, but also those of the auxiliary storage elements and loads, our structure has inductors in series at both its input and its output. Magnetically coupling these inductors and adding a damping network to its intermediate capacitor we have designed an easily controllable converter with second-order-buck-like dominant dynamics. This new proposed topology has high efficiency and wide bandwidth acting either as a voltage or as a current regulator. The magnetic coupling allows to control with similar performances the input or the output inductor currents. This characteristic is very useful because the designed current-controlled converter is able to withstand shortcircuits at its output and, when connected to the FC, it facilitates to regulate the current extracted from the FC to avoid the oxygen starvation phenomenon. Testing in a safe way the converter connected to the FC required to build an FC simulator that was subsequently improved by developing an emulator that offered real-time processing and oxygen-starvation indication. To study the developed converters and emulators with different brands of PEMFCs it was necessary to reactivate long-time inactive Palcan FCs. Since the results provided by the manual reactivation procedure were unsatisfactory, an automatic reactivation system has been developed as a complementary study of the thesis.En esta tesis se avanzo en el diseño de un bus DC de 48 V que utiliza como elemento principal de generación de energía eléctrica una pila de combustible. Debido a que la dinámica de las pilas de combustible están limitadas por sus elementos mecánicos auxiliares de control una variación rápida de una carga conectada a ella puede ocasionar daños. Es por esto que es necesario utilizar elementos almacenadores de energía que puedan suministrar estas rápidas variaciones de carga y convertidores para que gestionen de una forma controlada la potencia del bus DC. Durante la realización de pruebas de los convertidores es de gran importancia utilizar emuladores o simuladores de pilas de combustibles, esto nos permite de una forma económica y segura realizar pruebas criticas antes de conectar los convertidores a la pila. Adicionalmente una nueva topologia de convertidor fue presentada y ésta gestionará la potencia en el bu

Intelligent instrumentation, control and monitoring of precision motion systems

Ph.DDOCTOR OF PHILOSOPH

Estudio y evaluación de plataformas de distribución de cómputo intensivo sobre sistemas externos para sistemas empotrados.

Falta palabras claveNowadays, the capabilities of current embedded systems are constantly increasing, having a wide range of applications. However, there are a plethora of intensive computing tasks that, because of their hardware limitations, are unable to perform successfully. Moreover, there are innumerable tasks with strict deadlines to meet (e.g. Real Time Systems). Because of that, the use of external platforms with sufficient computing power is becoming widespread, especially thanks to the advent of Cloud Computing in recent years. Its use for knowledge sharing and information storage has been demonstrated innumerable times in the literature. However, its core properties, such as dynamic scalability, energy efficiency, infinite resources... amongst others, also make it the perfect candidate for computation off-loading. In this sense, this thesis demonstrates this fact in applying Cloud Computing in the area of Robotics (Cloud Robotics). This is done by building a 3D Point Cloud Extraction Platform, where robots can offload the complex stereo vision task of obtaining a 3D Point Cloud (3DPC) from Stereo Frames. In addition to this, the platform was applied to a typical robotics application: a Navigation Assistant. Using this case, the core challenges of computation offloading were thoroughly analyzed: the role of communication technologies (with special focus on 802.11ac), the role of offloading models, how to overcome the problem of communication delays by using predictive time corrections, until what extent offloading is a better choice compared to processing on board... etc. Furthermore, real navigation tests were performed, showing that better navigation results are obtained when using computation offloading. This experience was a starting point for the final research of this thesis: an extension of Amdahl’s Law for Cloud Computing. This will provide a better understanding of Computation Offloading’s inherent factors, especially focused on time and energy speedups. In addition to this, it helps to make some predictions regarding the future of Cloud Computing and computation offloading

An intelligent power management system for unmanned earial vehicle propulsion applications

Electric powered Unmanned Aerial Vehicles (UAVs) have emerged as a promi- nent aviation concept due to the advantageous such as stealth operation and zero emission. In addition, fuel cell powered electric UAVs are more attrac- tive as a result of the long endurance capability of the propulsion system. This dissertation investigates novel power management architecture for fuel cell and battery powered unmanned aerial vehicle propulsion application. The research work focused on the development of a power management system to control the hybrid electric propulsion system whilst optimizing the fuel cell air supplying system performances. The multiple power sources hybridization is a control challenge associated with the power management decisions and their implementation in the power electronic interface. In most applications, the propulsion power distribu- tion is controlled by using the regulated power converting devices such as unidirectional and bidirectional converters. The amount of power shared with the each power source is depended on the power and energy capacities of the device. In this research, a power management system is developed for polymer exchange membrane fuel cell and Lithium-Ion battery based hybrid electric propulsion system for an UAV propulsion application. Ini- tially, the UAV propulsion power requirements during the take-off, climb, endurance, cruising and maximum velocity are determined. A power man- agement algorithm is developed based on the UAV propulsion power re- quirement and the battery power capacity. Three power states are intro- duced in the power management system called Start-up power state, High power state and Charging power state. The each power state consists of the power management sequences to distribute the load power between the battery and the fuel cell system. A power electronic interface is developed Electric powered Unmanned Aerial Vehicles (UAVs) have emerged as a promi- nent aviation concept due to the advantageous such as stealth operation and zero emission. In addition, fuel cell powered electric UAVs are more attrac- tive as a result of the long endurance capability of the propulsion system. This dissertation investigates novel power management architecture for fuel cell and battery powered unmanned aerial vehicle propulsion application. The research work focused on the development of a power management system to control the hybrid electric propulsion system whilst optimizing the fuel cell air supplying system performances. The multiple power sources hybridization is a control challenge associated with the power management decisions and their implementation in the power electronic interface. In most applications, the propulsion power distribu- tion is controlled by using the regulated power converting devices such as unidirectional and bidirectional converters. The amount of power shared with the each power source is depended on the power and energy capacities of the device. In this research, a power management system is developed for polymer exchange membrane fuel cell and Lithium-Ion battery based hybrid electric propulsion system for an UAV propulsion application. Ini- tially, the UAV propulsion power requirements during the take-off, climb, endurance, cruising and maximum velocity are determined. A power man- agement algorithm is developed based on the UAV propulsion power re- quirement and the battery power capacity. Three power states are intro- duced in the power management system called Start-up power state, High power state and Charging power state. The each power state consists of the power management sequences to distribute the load power between the battery and the fuel cell system. A power electronic interface is developed with a unidirectional converter and a bidirectional converter to integrate the fuel cell system and the battery into the propulsion motor drive. The main objective of the power management system is to obtain the controlled fuel cell current profile as a performance variable. The relationship between the fuel cell current and the fuel cell air supplying system compressor power is investigated and a referenced model is developed to obtain the optimum compressor power as a function of the fuel cell current. An adaptive controller is introduced to optimize the fuel cell air supplying system performances based on the referenced model. The adaptive neuro-fuzzy inference system based controller dynamically adapts the actual compressor operating power into the optimum value defined in the reference model. The online learning and training capabilities of the adaptive controller identify the nonlinear variations of the fuel cell current and generate a control signal for the compressor motor voltage to optimize the fuel cell air supplying system performances. The hybrid electric power system and the power management system were developed in real time environment and practical tests were conducted to validate the simulation results

Levantamento de percursos em transportes públicos usando Wi-Fi

Mestrado em Engenharia de Computadores e TelemáticaAn important aspect in improving public transport efficiency is collecting information regarding traveler routes, usually represented as an OriginDestination (OD) matrix. Most public transportation systems implement fare collection systems that can provide the accurate origins of traveler routes but not accurate destinations. In this dissertation we look at WiFi, more specifically 802.11 data-link layer, as a candidate to provide OD matrix estimations. We present an algorithm capable of collecting information regarding Wi-Fi capable devices inside the bus complemented with positioning and time. A system is also presented to implement this concept using minimal requirements. An implementation of this system was deployed in a public bus to collect data for several weeks. This resulted on over 15000 traveler routes collected in 9 different days. This data was contextualized and mapped to an OD system in order to demonstrate how it can be used to generate OD matrix estimations.Um aspecto importante na melhoria da eficiência de transportes públicos consiste na recolha de percursos de passageiros, frequentemente representados na forma de matrizes Origem-Destino (OD). Grande parte dos sistemas de transportes públicos implementa sistemas de bilhética que são capazes de fornecer com precisão a origem dos percursos efectuados pelos passageiros, mas não o destino. Nesta dissertação foi selecionada a tecnologia Wi-Fi como um candidata a fornecer leituras de precisão para estimar matrizes OD. Apresentamos um algoritmo capaz de recolher informação sobre dispositivos que suportam Wi-Fi, dentro de um autocarro público, acoplada com informação sobre posicionamento e tempo. É também apresentado um sistema que implementa este conceito ao usar requisitos mínimos. Uma implementação deste sistema foi colocada num autocarro público para efectuar recolha de dados durante várias semanas. Mais de 15000 percursos foram recolhidos em 9 dias diferentes. Estes dados foram contextualizados e mapeados num sistema OD para demonstrar como podem ser usado para estimar matrizes OD

Proceedings of the Fifth International Mobile Satellite Conference 1997

Satellite-based mobile communications systems provide voice and data communications to users over a vast geographic area. The users may communicate via mobile or hand-held terminals, which may also provide access to terrestrial communications services. While previous International Mobile Satellite Conferences have concentrated on technical advances and the increasing worldwide commercial activities, this conference focuses on the next generation of mobile satellite services. The approximately 80 papers included here cover sessions in the following areas: networking and protocols; code division multiple access technologies; demand, economics and technology issues; current and planned systems; propagation; terminal technology; modulation and coding advances; spacecraft technology; advanced systems; and applications and experiments