Recent research at the University of Central Florida involving crashes on Interstate-4 in Orlando, Florida has led to the creation of new statistical models capable of determining the crash risk on the freeway (Abdel-Aty et al., 2004; 2005, Pande and Abdel-Aty, 2006). These models are able to calculate the rear-end and lane-change crash risks along the freeway in real-time through the use of static information at various locations along the freeway as well as the real-time traffic data obtained by loop detectors. Since these models use real-time traffic data, they are capable of calculating rear-end and lane-change crash risk values as the traffic flow conditions are changing on the freeway. The objective of this study is to examine the potential benefits of variable speed limit implementation techniques for reducing the crash risk along the freeway. Variable speed limits is an ITS strategy that is typically used upstream of a queue in order to reduce the effects of congestion. By lowering the speeds of the vehicles approaching a queue, more time is given for the queue to dissipate from the front before it continues to grow from the back. This study uses variable speed limit strategies in a corridor-wide attempt to reduce rear-end and lane-change crash risks where speed differences between upstream and downstream vehicles are high. The idea of homogeneous speed zones was also introduced in this study to determine the distance over which variable speed limits should be implemented from a station of interest. This is unique since it is the first time a dynamic distance has been considered for variable speed limit implementation. Several VSL strategies were found to successfully reduce the rear-end and lane-change crash risks at low-volume traffic conditions (60% and 80% loading conditions). In every case, the most successful treatments involved the lowering of upstream speed limits by 5 mph and the raising of downstream speed limits by 5 mph. In the free-flow condition (60% loading), the best treatments involved the more liberal threshold for defining homogeneous speed zones (5 mph) and the more liberal implementation distance (entire speed zone), as well as a minimum time period of 10 minutes. This treatment was actually shown to significantly reduce the network travel time by 0.8%. It was also shown that this particular implementation strategy (lowering upstream, raising downstream) is wholly resistant to the effects of crash migration in the 60% loading scenario. In the condition approaching congestion (80% loading), the best treatment again involved the more liberal threshold for homogeneous speed zones (5 mph), yet the more conservative implementation distance (half the speed zone), along with a minimum time period of 5 minutes. This particular treatment arose as the best due to its unique capability to resist the increasing effects of crash migration in the 80% loading scenario. It was shown that the treatments implementing over half the speed zone were more robust against crash migration than other treatments. The best treatment exemplified the greatest benefit in reduced sections and the greatest resistance to crash migration in other sections. In the 80% loading scenario, the best treatment increased the network travel time by less than 0.4%, which is deemed acceptable. No treatment was found to successfully reduce the rear-end and lane-change crash risks in the congested traffic condition (90% loading). This is attributed to the fact that, in the congested state, the speed of vehicles is subject to the surrounding traffic conditions and not to the posted speed limit. Therefore, changing the posted speed limit does not affect the speed of vehicles in a desirable manner. These conclusions agree with Dilmore (2005).

Detta arbete har utrett möjligheten till att implementera variabelt varvtal hos bulbturbiner. Som utgångspunkt har anläggningar med ett Kaplanlöphjul och en växellåda analyserats där variabelt varvtal ska implementeras med en frekvensomriktare och ett löphjul med fasta skovelblad.  Arbetet har fokuserat på att avgöra vilka huvudkomponenter som krävs till inköp för att kunna implementera variabelt varvtal. Ett ytterligare mål var att avgöra vilken anläggning som kan ge mest producerad energi av en anläggning med fast och variabelt varvtal. Slutligen har lönsamheten för en investering som möjliggör ett variabelt varvtal bedömts. Till grund för beräkningar användes insamlad mätdata från anläggningarna under år 2022 och uppskattningar av verkningsgrad och inköpspris för de olika komponenterna.  Resultatet visar att det är möjligt att implementera variabelt varvtal i anläggningen, både genom att behålla växellådan och genom att bygga bort den. Att behålla växellåda är det alternativ som är enklast att implementera eftersom installationen och ombyggnationen blir mindre omfattande. Vidare kan en anläggning med variabelt varvtal potentiellt leda till en utökning av producerad energi där ökningen är åtminstone 0,8 GWh. Slutligen skulle en investering av denna typ kunna betraktas som lönsam under förutsättningen att man kan få intäkter från stödtjänster.  Dessa slutsatser bygger på en del antaganden som bör valideras med leverantörer. / This work has investigated the opportunities to implement variable speed for bulb turbines. As a reference, facilities with a Kaplan runner and a gearbox have been analyzed were variable speed is introduced with a frequency converter and a runner with non-adjustable blades.  The work has focused on determine which main components are necessary for purchases in order to implement variable speed. Another goal was to determine which facility can produce the most energy comparing a facility with variable and fixed speed. Lastly, the financially profitability of an investment that enable variable speed has been assessed.  The foundation of the calculations were based on measured data from the sites during year 2022 and approximations of efficiency and the price of purchase for the different components. The result shows that it is possible to implement variable speed in the facilities, with and without a gearbox. To keep the gearbox is the alternative that is easiest to implement due to less reconstruction of the facility. Furthermore, a facility with variable could potentially lead to an increase in produced energy where the increase is at least 0.8 GWh. Lastly, an investment of this kind could be considered profitable under the assumption that it is possible to receive revenue from ancillary services.  The conclusions are made on assumptions that needs to be validated with suppliers.

This thesis focuses on evaluating the appropriate speed at which vehicles should travel under different traffic conditions on freeways and its impact on crash frequency. The common belief is that the lower speed results in fewer crashes as reduced speed provides drivers with more time to react effectively and avoid collisions. However, this perspective overlooks the interplay among traffic speed, average spacing between consecutive vehicles, and the distance available for stopping a vehicle. Hence, we propose a safety parameter termed ‘Safety Correlate' (SCORE), which is defined as the proportion of average spacing relative to the stopping distance. To determine the relationship between SCORE and crash frequency, data from 366 4-lane urban freeway segments located in Virginia was analyzed and a Random-effects Poisson Lognormal model was developed. The obtained result indicated that the safety parameter SCORE is negatively associated with the annual hourly crash frequency, implying that the lesser the average spacing as a proportion of the stopping distance while traffic flow remains constant, the more frequent will be the crashes. Additionally, this research presents an application of SCORE in setting variable speed limits under various traffic flows. Overall, the study results provide valuable insights by investigating SCORE to improve traffic safety. Also, this research would help practitioners and policymakers to incorporate safety aspects while setting variable speed limits on freeways.

No description available.

In this dissertation, a novel two-phase switched reluctance machine (SRM) with a stator comprised of E-core structure having minimum stator core iron is presented for low-cost high-performance applications. In addition, three new magnetic structures for the E-core SRM comprising two segmented stator cores or a monolithic stator core are proposed for good manufacturability, mechanically robustness, ease of assembly, and electromagnetic performance improvement. Each E-core stator in the segmented structure has three poles with two small poles at the ends having windings and a large center pole containing no copper windings. The common stator pole at the centers in the segmented E-core is shared by both phases during operation. Other benefits of the common poles contributing to performance enhancement are short flux paths, mostly flux-reversal-free-stator, constant minimum reluctance around air gap, and wide pole arc equal to one rotor pole pitch. Therefore, two additional common poles in the monolithic E-core configuration are able to significantly improve efficiency due to more positive torque and less core loss by the unique design. Using a full MEC analysis, the effect of the common-pole structure on torque enhancement is analytically verified. Efficiency estimated from the dynamic simulation is higher by 7% and 12% at 2000 rpm and by 3% and 7 % at 3000 rpm for the segmented and single-body SRMs, respectively, compared to a conventional SRM with four stator poles and two rotor poles. The new E-core SRMs are suitable for low-cost high-performance applications which are strongly cost competitive since all the new E-core SRMs have 20% cost savings on copper and the segmented E-core SRMs have 20% steel savings as well. Strong correlation between simulated and experimentally measured results validates the feasibility of the E-core common-pole structure and its performance. A simple step-by-step analytical design procedure suited for iterative optimization with small computational effort is developed with the information of the monolithic E-core SRM, and the proposed design approach can be applied for other SRM configurations as well. For investigating thermal characteristics in the two-phase single-body E-core SRM, the machine is modeled by a simplified lumped-parameter thermal network in which there are nine major parts of the motor assembly. / Ph. D.

The Switched Reluctance Motors(SRM) have gained considerable attention in the variable speed drive market mainly due to the simple construction of the motor and the possibility of developing low cost converters and controllers. As these machines are under development, a considerable amount of research effort is directed to the experimental performance evaluation of the SRM drives. System efficiency, electromagnetic torque, torque ripple, output and losses are some of the required measurements. / Master of Science

During the last decades the road traffic has increased tremendously leading to congestion, safety issues and increased environmental impacts. As a result, many countries are continuously trying to find improvements and new solutions to solve these issues. One way of improving the traffic conditions is by the use of so called intelligent transport systems, where information and communication technologies are being used for traffic management and control. One such system commonly used for traffic management purposes are variable speed limit systems. These systems are making use of signs to show speed limits adjusted to the prevailing road or traffic conditions. The rapid development in telecommunication technologies has enabled communication between vehicles, and between vehicles and the infrastructure, so called cooperative systems. This opens up for  the possibility to further improve the performance of a standard variable speed limit system by adding cooperative system features. The overall aim of this thesis is to investigate the potential benefits of incorporating infrastructure to vehicle communication and autonomous control to an existing variable speed limit system. We show how such a cooperative variable speed limit system can be modeled and evaluated by the use of microscopic traffic simulation. Results from the evaluation indicate increased flow harmonization in terms of narrowing of the acceleration rate distribution and reduced exhaust emissions. Further, we compare four control algorithms for deciding on speed limits in variable speed limit systems. Differences in the resulting traffic performance between the control algorithms are quantified by the use of microscopic traffic simulation. It is concluded that the dened objective for the algorithms have a decisive influence on the effects of the variable speed limit system. The results from this thesis are useful for further development of variable speed limit systems, both with respect to incorporating cooperative features and by improving the speed setting control algorithms.

This thesis presents a novel, low cost, high precision , and efficient design for an electro-hydrostatic circuit for single rod hydraulic cylinders. The design is the main contribution of candidate to fulfill the regiments of PhD degree. The challenge of existing deigns of electro-hydrostatic circuits for single-rod cylinders is using one pump to control the cylinder under switching (resistive-assistive) loads. The proposed circuit utilizes off-the-shelf industrial elements. It uses two counterbalance valves to manage switching loads and one on/off solenoid valve to redirect the differential flow of the single rod cylinder to tank. A set of simulation studies is conducted using Simhydraulic tools of Matlab in order to study performances of the proposed circuit and compare it with existing designs. Pump-controlled hydraulic circuit for double rod cylinders was developed and is widely used by industry. It is used as the benchmark for simulation studies. As well, the proposed circuit and two major existing pump-controlled circuits for single rod cylinders are compared to the benchmark circuit. Evaluations are conducted by comparing chamber pressure responses as well as pressure vs position of the cylinder end-effector for each individual circuit. Results indicate that the proposed circuit performed as well as the benchmark circuit by controlling pressures to both sides of the cylinder at the same time. Moreover, the load in the proposed circuit is more controllable compared to the benchmark circuit. Experimental results, obtained from the developed test rig, validate accuracy of the simulation model. Maximum steady state position error of 0.06 mm applications is experimentally observed when the test rig is tested under different loading conditions with various amplitudes and frequencies. The circuit consumes up to 20% of the energy that is required by a valve controlled circuit given the same sinusoidal tracking signal. The relative efficiency of the proposed circuit over a valve xii controlled circuit depends on the pattern and frequency of the tracking signal. In all the experiments, a simple proportional controller, which uses readings of a linear position transducer, is employed. The use of the proportional controller makes the proposed circuit easy to implement and shows it is good candidate for industrial applications. The accuracy of the position response of the proposed circuit indicates, it is a good candidate for robotic applications too. / May 2016

Call number: LD2668 .T4 1986 R43 / Master of Science / Biological and Agricultural Engineering

A presente dissertação aborda a avaliação de três sistemas fotovoltaicos de bombeamento, que compreendem duas configurações com equipamentos dedicados à tecnologia fotovoltaica e um com equipamentos alternativos com potências entre 0,75 CV e 1,0 CV. Os resultados mostram que a configuração alternativa apresenta menor eficiência diária do sistema motobomba. A avaliação econômica revela a competitividade da configuração alternativa frente aos sistemas importados dedicados à tecnologia fotovoltaica. Alia-se a isso a disponibilidade dos equipamentos de condicionamento de potência e a facilidade de reposição. Verificou-se também que a configuração alternativa, conversor de freqüência WEG CFW08 e motobomba SOMAR de 1,0 CV e 8 estágios, trabalha com eficiência diária próxima aos 30% na faixa de operação de 20 a 40 metros de coluna dágua. Portanto, com uma adequada escolha da motobomba para a configuração alternativa, podem-se obter desempenhos semelhantes aos obtidos com sistemas importados dedicados à tecnologia fotovoltaica. Para 30 metros, a configuração alternativa bombeou somente 1% a menos do que o sistema Grundfos. O custo do volume bombeado para 30m de altura manométrica total do sistema alternativo é 22% menor do que o sistema Grundfos e 51% mais econômico do que o sistema Solarjack (Sun Pumps). / The present dissertation shows the evaluation of three Photovoltaic Pumping Systems, which involves two configurations: the equipment dedicated to the photovoltaic technology and the alternative equipment with nominal powers between 0.75 CV and 1.0 CV. The results show that the alternative configuration attained minor daily efficiency of the motopump system. The economic evaluation reveals the competitiveness of the alternative configuration in comparison with imported photovoltaic technology dedicated systems. It also should be considered the availability of equipment for power conditioning and the facility of replacement. It was also verified that the alternative configuration, variable speed drive WEG CFW08 and 1.0 CV SOMAR motor pump with 8 stages, works with daily efficiency near 30% in the 20 to 40 meters operation range. Therefore, with an adequate choice of the motor pump for the alternative configuration, performances similar to the imported photovoltaic technology dedicated systems can be obtained. For 30 meters, the alternative configuration pumped only 1% less than the Grundfos system. The cost of pumped volume for 30 meters of manometer total height of the alternative system is 22% cheaper than the system Grundfos and 51% cheaper than the system Solarjack (Sun Pumps).