In some roundabouts, just relying on the "right of way" regulations results in long queues forming along the approaches. This usually happens when a roundabout suffers from unbalanced flow patterns (one or two of the approaches convey much heavier traffic compared to the others). There is an idea that signalization of roundabouts can be useful as a countermeasure for such a problem, especially during peak hours. In that case, signal operation can come in many forms, including full-time control, part-time control, or metering. One problem that seems to be facing engineers when signalizing roundabouts is lacking a general set of patterns or guidelines to choose an appropriate form of signalization and apply it efficiently in different situations. There is also a need for a comprehensive review over the available literature concerning signalization of roundabouts. In this thesis, a review of literature regarding signalization of roundabouts is carried out. Moreover, a roundabout in Stavanger with unbalanced traffic flows is studied in order to find an appropriate signalization scenario which can improve the traffic situation. The network is modeled and simulated in AIMSUN.

Atualmente a medição de energia elétrica para residências em centros urbanos é realizada por meio de medidores eletromecânicos lidos de forma manual. Neste processo uma série de problemas foram observados, dos quais se destacam: erros de leitura, dificuldade de acesso ao ponto de medição, bancos de dados sem atualização, dentre outros. A automação do processo de medição e da leitura, com base nos medidores existentes ou com o uso de medidores eletrônicos da energia elétrica, além de resolver os problemas citados, tem potencialmente uma série de vantagens, que incluem: combate a fraudes e furto de energia, implementação de tarifas diferenciadas em função da hora de consumo (tarifa amarela), corte e religamento remoto de energia, implementação de programas de energia pré-paga, levantamento de curvas de carga e eliminação de erros e custos do processo de leitura manual. Por outro lado observa-se que existem no Brasil cerca de 43 milhões de medidores residenciais instalados, sendo relativamente baixos os custos dos medidores eletromecânicos e do sistema de leitura manual. Desta forma, somente será possível implementar sistemas de automação da medição de energia elétrica residencial se os sistemas ora propostos forem ao mesmo tempo de custo reduzido e altamente confiáveis. O sistema de automação em estudo irá considerar inclusive o aproveitamento dos medidores eletromecânicos existentes, com a instalação de sistemas eletrônicos de coleta dos dados de consumo comunicando-se com concentradores locais, que por sua vez são interligados a sistemas computacionais instalados dentro da concessionária. Os resultados do estudo mostram que hoje existe uma concreta possibilidade de se obter sistemas de automação da medição de energia elétrica residencial seguros e de custos reduzidos. O trabalho ora proposto será desenvolver um sistema automatizado para a medição de energia residencial em centros urbanos, constituído por um módulo concentrador para oito residências, com comunicação deste para um centro de operação da concessionária. Será apresentada a metodologia para a implementação do sistema e considerado um estudo de caso. / In these days, the energy measurement system for residences in urban areas is carried out by eletromechanical meters, which are read manually. Several problems have been observed in this process, which we can emphasize: reading errors, difficulty to access the measurement place, outdated databases, etc. The reading and the measurement automation processes, based in the current eletromechanical meters or with the electronic version of these equipment, besides solving the mentioned problems, have several advantages, such as: minimization of fraud and robbery of energy, implementation of differentiated rates depending on the time of the day (ex:yellow rate), remote energy switch-off and switch-on, implementation of a prepaid system, possibility to get the load curve of each consumer and elimination of error and costs embedded in the manually reading process. On the other hand, we can observe that in Brazil there are an estimated 43 millions residential meters already installed, and the costs for the current measurement system, and also of the meters, are very low. In this scenario, the implementation of a automated system for residential energy measurement is that the proposed system has a very low cost at the same time provides a high reliability. The proposed automation system will consider the reutilization of the current mechanical meters, with the installation of an electronic systems for the consumption data collection, communicating with local concentrators, which in their turn are linked to a computing systems in the energy company. The results of the present work show that, nowadays, there is a real possibility to get, a trustable and cheap automated measurement system for energy in residential urban area. The proposed work is the development of an automated system, for residential energy measurement in urban area. It's composed of a concentrator module for eight residences, with communication from this point to the energy company's operation center. It will be presented a methodology to implement such a system and also a case study.

A operação de adubação responde por parte significativa dos custos de produção agrícola. Melhorar a qualidade dessa operação acarreta benefícios econômicos e ambientais. O processo de adubação normalmente é realizado a uma taxa média, representativa de uma área, no entanto, propriedades químicas do solo podem variar consideravelmente dentro dessa área. Desse modo, alguns locais poderão receber fertilizantes e/ou corretivos em excesso, enquanto outros poderão receber quantidades insuficientes. A alternativa à taxa média é a realizar a aplicação à taxa variada, que se caracteriza por aplicar os insumos de acordo com as necessidades específicas dentro da área. Para que essa aplicação aconteça, mecanismos dosadores controlam a aplicação. O objetivo deste estudo é avaliar os mecanismos dosadores de uma carreta adubadora de arrasto, comportas e esteiras, atendem as prescrições de doses previstas no mapa de recomendação de adubação. Para avaliar a uniformidade da operação utilizou-se o controle estatístico do processo. De acordo com os resultados obtidos pode-se afirmar que os mecanismos dosadores não atenderam a condição de realizar a aplicação à taxa variável de maneira uniforme. / The operation fertilization accounts for a significant portion of the costs of agricultural production. Improve the quality of this operation entails economic and environmental benefits. The process of fertilization is usually performed at an average rate representative of an area, however, the chemical properties of soil can vary considerably within the area. Thus, some locations may receive fertilizer and / or lime in excess, while others may receive insufficient amounts. The alternative is to average the application to perform variable rate, characterized by applying inputs according to the specific requirements within the area. For this application happens, metering mechanisms control the application. The aim of this study is to evaluate the dosing mechanisms of a truck hauling fertilizer, locks and mats, meet the requirements of the prescribed dose map fertilizer recommendation. To evaluate the uniformity of operation used the statistical process control. According to the obtained results it can be stated that the meter mechanism did not meet the condition to perform variable rate application to uniformly.

The ongoing Smart Grid (SG) initiative proposes several modifications to the existing power grid in order to better manage power demands, reduce CO2 emissions and ensure reliability through several new applications. One part of the SG initiative that is currently being implemented is the Advanced Metering Infrastructure (AMI) which provides two-way communication between the utility company and the consumers' smart meters (SMs). The AMI can be built by using a wireless mesh network which enables multi-hop communication of SMs. The AMI network enables collection of fine-grained power consumption data at frequent intervals. Such a fine-grained level poses several privacy concerns for the consumers. Eavesdroppers can capture data packets and analyze them by means of load monitoring techniques to make inferences about household activities. To prevent this, in this dissertation, we proposed several privacy-preserving protocols for the IEEE 802.11s-based AMI network, which are based on data obfuscation, fully homomorphic encryption and secure multiparty computation. Simulation results have shown that the performance of the protocols degrades as the network grows. To overcome this problem, we presented a scalable simulation framework for the evaluation of IEEE 802.11s-based AMI applications. We proposed several modifications and parameter adjustments for the network protocols being used. In addition, we integrated the Constrained Application Protocol (CoAP) into the protocol stack and proposed five novel retransmission timeout calculation functions for the CoAP in order to increase its reliability. Upon work showing that there are inconsistencies between the simulator and a testbed, we built an IEEE 802.11s- and ZigBee-based AMI testbed and measured the performance of the proposed protocols under various conditions. The testbed is accessible to the educator and researchers for the experimentation. Finally, we addressed the problem of updating SMs remotely to keep the AMI network up-to-date. To this end, we developed two secure and reliable multicast-over-broadcast protocols by making use of ciphertext-policy attribute based signcryption and random linear network coding.

Venturi flowmeters have been used to measure flow in piped systems for over 100 years (Finnemore & Franzini, 2006). There has been much research on the performance of Venturi flowmeters and for that reason they have become popular flowmeters used in various municipal and industrial applications. Venturi flowmeters can be calibrated in a laboratory setting to find their performance characteristics. In order for the flowmeter to achieve optimum performance, the flowmeter should be installed with sufficient length of straight pipe immediately upstream of the flowmeter. Often Venturi flowmeters that are not installed in ideal conditions produce errors and uncertainty is introduced to the flow measurement. This study used multiple tap sets on Venturi flowmeters in order to reduce error and uncertainty when a Venturi flowmeter is installed in non-ideal conditions. The multiple taps sets were used to measure an average of the hydraulic pressure within the flowmeter.

<p>In some roundabouts, just relying on the "right of way" regulations results in long queues forming along the approaches. This usually happens when a roundabout suffers from unbalanced flow patterns (one or two of the approaches convey much heavier traffic compared to the others). There is an idea that signalization of roundabouts can be useful as a countermeasure for such a problem, especially during peak hours. In that case, signal operation can come in many forms, including full-time control, part-time control, or metering. One problem that seems to be facing engineers when signalizing roundabouts is lacking a general set of patterns or guidelines to choose an appropriate form of signalization and apply it efficiently in different situations. There is also a need for a comprehensive review over the available literature concerning signalization of roundabouts. In this thesis, a review of literature regarding signalization of roundabouts is carried out. Moreover, a roundabout in Stavanger with unbalanced traffic flows is studied in order to find an appropriate signalization scenario which can improve the traffic situation. The network is modeled and simulated in AIMSUN.</p>

Utility companies (electricity, gas, and water suppliers), governments, and researchers recognize an urgent need to deploy communication-based systems to automate data collection from smart meters and sensors, known as Smart Metering Infrastructure (SMI) or Automatic Meter Reading (AMR). A smart metering system is envisaged to bring tremendous benefits to customers, utilities, and governments. The advantages include reducing peak demand for energy, supporting the time-of-use concept for billing, enabling customers to make informed decisions, and performing effective load management, to name a few. A key element in an SMI is communications between meters and utility servers. However, the mass deployment of metering devices in the grid calls for studying the scalability of communication protocols. SMI is characterized by the deployment of a large number of small Internet Protocol (IP) devices sending small packets at a low rate to a central server. Although the individual devices generate data at a low rate, the collective traffic produced is significant and is disruptive to network communication functionality. This research work focuses on the scalability of the transport layer functionalities. The TCP congestion control mechanism, in particular, would be ineffective for the traffic of smart meters because a large volume of data comes from a large number of individual sources. This situation makes the TCP congestion control mechanism unable to lower the transmission rate even when congestion occurs. The consequences are a high loss rate for metered data and degraded throughput for competing traffic in the smart metering network. To enhance the performance of TCP in a smart metering infrastructure (SMI), we introduce a novel TCP-based scheme, called Split- and Aggregated-TCP (SA-TCP). This scheme is based on the idea of upgrading intermediate devices in SMI (known in the industry as regional collectors) to offer the service of aggregating the TCP connections. An SA-TCP aggregator collects data packets from the smart meters of its region over separate TCP connections; then it reliably forwards the data over another TCP connection to the utility server. The proposed split and aggregated scheme provides a better response to traffic conditions and, most importantly, makes the TCP congestion control and flow control mechanisms effective. Supported by extensive ns-2 simulations, we show the effectiveness of the SA-TCP approach to mitigating the problems in terms of the throughput and packet loss rate performance metrics. A full mathematical model of SA-TCP is provided. The model is highly accurate and flexible in predicting the behaviour of the two stages, separately and combined, of the SA-TCP scheme in terms of throughput, packet loss rate and end-to-end delay. Considering the two stages of the scheme, the modelling approach uses Markovian models to represent smart meters in the first stage and SA-TCP aggregators in the second. Then, the approach studies the interaction of smart meters and SA-TCP aggregators with the network by means of standard queuing models. The ns-2 simulations validate the math model results. A comprehensive performance analysis of the SA-TCP scheme is performed. It studies the impact of varying various parameters on the scheme, including the impact of network link capacity, buffering capacity of those RCs that act as SA-TCP aggregators, propagation delay between the meters and the utility server, and finally, the number of SA-TCP aggregators. The performance results show that adjusting those parameters makes it possible to further enhance congestion control in SMI. Therefore, this thesis also formulates an optimization model to achieve better TCP performance and ensures satisfactory performance results, such as a minimal loss rate and acceptable end-to-end delay. The optimization model also considers minimizing the SA-TCP scheme deployment cost by balancing the number of SA-TCP aggregators and the link bandwidth, while still satisfying performance requirements.

Understanding how swirl flows can be applied to processes in the oil and gas industry and how problems might hinder them, are the focus of this thesis. Three application areas were identified: wet gas metering, liquid loading in gas wells and erosion at pipe bends due to sand transport. For all three areas, Computational Fluid Dynamics (CFD) simulations were performed. Where available, experimental data were used to validate the CFD results. As a part of this project, a new test loop was conceived for the investigation of sand erosion in pipes. The results obtained from CFD simulations of two-phase (air-water) flow through a pipe with a swirl-inducing device show that generating swirl flow leads to separation of the phases and creates distinct flow patterns within the pipe. This effect can be used in each of the three application areas of interest. For the wet gas metering application, a chart was generated, which suggests the location of maximum liquid deposition downstream of the swirling device used in the ANUMET meter. This will allow taking pressure and phase fraction measurements (from which the liquid flow rate can be determined) where they are most representative of the flow pattern assumed for the ANUMET calculation algorithms. For the liquid loading application, which was taken as an upscaling of the dimensions investigated for the wet gas metering application, the main focus was on the liquid hold-up. This parameter is defined as the ratio of the flowing area occupied by liquid to the total area. Results obtained with CFD simulations showed that as the water rate increases, the liquid hold-up increases, implying a more effective liquid removal. Thus, it was concluded that the introduction of a swirler can help unload liquid from a gas well, although no investigation was carried out on the persistance of the swirl motion downstream of the device. For the third and final application, the erosion at pipe bends due to sand transport, the main focus was to check the erosion rate on the pipe wall with and without the introduction of a swirler. The erosion rate was predicted by CFD simulations. The flow that was investigated consisted of a liquid phase with solid particles suspended in it. The CFD results showed a significant reduction in erosion rate at the pipe walls when the swirler was introduced, which could translate into an extended working life for the pipe. An extensive literature review performed on this topic, complemented by the CFD simulations, showed the need for a dedicated multiphase test loop for the investigation of sand erosion in horizontal pipes and at bends. The design of a facility of this type is included in this thesis. The results obtained with this work are very encouraging and provide a broad perspective of applications of swirl flows and CFD for the oil and gas industry.

<p>This thesis presents a solution enabling lower losses in hydraulic actuator systems. A mobile fluid power system often contains several different actuators supplied with a single load sensing pump. One of the main advantages is the need of only one system pump. This makes the fluid power system compact and cost-effective.</p><p>A hydraulic load often consists of two ports, e.g. motors and cylinders. Such loads have traditionally been controlled by a valve that controls these ports by one single control signal, namely the position of the spool in a control valve. In this kind of valve, the inlet (meter-in) and outlet (meter-out) orifices are mechanically connected. The mechanical connection makes the system robust and easy to control, at the same time as the system lacks flexibility. Some of the main drawbacks are</p><p><strong> </strong></p><p><strong>The fixed relation </strong>between the inlet and outlet orifices in most applications produce too much throttling at the outlet orifice under most operating conditions. This makes the system inefficient.</p><p><strong> </strong></p><p><strong>The flow directions </strong>are fixed for a given spool position; therefore, no energy recuperation and/or regeneration ability is available.</p><p>In this thesis a novel system idea enabling, for example, recuperation and regeneration is presented. Recuperation is when flow is taken from a tank, pressurized by external loads, and then fed back into the pump line. Regeneration is when either cylinder chambers (or motor ports) are connected to the pump line. Only one system pump is needed. Pressure compensated (load independent), bidirectional, poppet valves are proposed and utilized.</p><p>The novel system presented in this thesis needs only a position sensor on each compensator spool. This simple sensor is also suitable for identification of mode switches, e.g. between normal, differential and regenerative modes. Patent pending.</p><p>The balance of where to put the functionality (hardware and/or software) makes it possible to manoeuvre the system with maintained speed control in the case of sensor failure. The main reason is that the novel system does not need pressure transducers for flow determination. Some features of the novel system:</p><p><strong>Mode switches </strong>The mode switches are accomplished without knowledge about the pressures in the system</p><p><strong>Throttle losses </strong>With the new system approach, choice of control and measure signals, the throttle losses at the control valves are reduced</p><p><strong>Smooth mode switches </strong>The system will switch to regenerative mode automatically in a smooth manner when possible</p><p><strong>Use energy stored in the loads </strong>The load, e.g. a cylinder, is able to be used as a motor when possible, enabling the system to recuperate overrun loads</p><p>The system and its components are described together with the control algorithms that enable energy efficient operation. Measurements from a real application are also presented in the thesis.</p>

Solar photovoltaics have received government support in the form of rebates, tax credits and net metering tariff mechanisms. The intended goal of these incentives is to encourage innovation in the manufacturing and installation of these systems, which is expected to eventually help overcome the high cost barrier for the adoption of the technology. These systems have the advantages of abundant availability of the solar resource, low environmental footprint, and the possibility of onsite installation, reducing the need for additional generation and transmission capacity. Since millions of dollars have been invested in these incentive programs, there is an interest in tracking the progress in the cost and capacity installed. In the first part of this thesis, I analyzed the trends in costs and adoption of solar PV by residential and commercial customers in the city of Austin. This is accomplished by tabular and graphical analysis of data on PV installations from 2004, when Austin Energy’s rebate program started, to early 2010. In the second part of the thesis, I used technology diffusion models to analyze and forecast the diffusion of residential PV systems in Austin. Three types of models were used to model the adoption trends: Logistic growth model, Bass model without price effects and Bass model including price effects. In the final part of the thesis, I analyzed the net metering tariff mechanism in Austin and studied the difference between the current and an alternative tariff. The alternative tariff uses actual ‘grid usage’ to calculate the energy charge (cost of providing distribution service) instead of the ‘net energy consumed’ that is currently in use. Using simulated PV generation data and ERCOT load profile data, I calculated the difference in revenue for Austin Energy with the alternative tariff. The results indicate that the alternative tariff adds little revenue to Austin Energy’s energy charge revenues at the current level of penetration of solar PV. However, at a higher penetration level of PV, the alternative tariffs might result in significant additional revenue for the utility. The thesis concludes with a discussion on the possible rationale for the alternative tariff and directions for future research. / text