Public transit agencies often struggle with service reliability issues; when a bus or train does not arrive on time, passengers become frustrated and may be less likely to choose transit for future trips. To address reliability problems, transit authorities increasingly provide real-time vehicle location and arrival information to riders via web-enabled and mobile devices. Although prior studies have found several benefits of offering this information to passengers, researchers have had difficulty determining if real-time information affects ridership levels. Therefore, the objective of this dissertation is to quantify the impact of real-time information on public transit ridership. Statistical and econometric methods were used to analyze passenger behavior in three American cities that share a common real-time information platform: New York City, Tampa, and Atlanta. New York City was the setting for a natural experiment in which real-time bus information was gradually launched on a borough-by-borough basis over a three year period. Panel regression techniques were used to evaluate route-level bus ridership while controlling for changes in transit service, fares, local socioeconomic conditions, weather, and other factors. In Tampa, a behavioral experiment was performed with a before-after control group design in which access to real-time bus information was the treatment variable and web-based surveys measured behavior changes over a three month period. In Atlanta, a methodology to combine smart card fare collection data with web-based survey responses was developed to quantify changes in transit travel of individual riders in a before-after study. In summary, each study utilized different data sources and quantitative methods to assess changes in transit ridership. The results varied between cities and suggest that the impact of real-time information on transit travel is greatest in locations that have high levels of transit service. These findings have immediate implications for decision-makers at transit agencies, who often face pressure to increase ridership with limited resources.

In recent years Ethernet has cought the attention of the real-time community. the main reason for this is that it has a high data troughput, 10Mbit/s and higher, and good EMI characteristics. As a protocol that might be used in real-time anvironments such as control systems for cars etc, it seems to fulfil the rquirements. TTEthernet is a TDMA extention to normal Ethnernet, designed to meet the hard deadlines required by real-time networks. This thesis describes how TTEthernet handles frames and the mathematical formulas to calculate shuffle delay of frames in such a network. Open problems related to TTEthernet are also discussed.

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Real-time systems are those whose correctness depends not only on logical results of computations, but also on the time at which the results are produced. This thesis provides a formal definition for real-time systems and includes the following original contributions on real-time scheduling algorithms. The first topic studied in the thesis is minimizing the total penalty to be paid in scheduling a set of soft real-time tasks. The problem is NP-hard. We prove the properties of any optimal scheduling algorithm. We also derive a number of heuristic algorithms which satisfy the properties obtained. Moreover, we obtain a tight upper bound for the optimal solution to the problem. Numerical results that compare the upper bound with the optimal solution and the heuristic algorithms are provided. In the second part of this thesis, we study the problem of minimizing the number of processors required for scheduling a set of periodic preemptive independent hard real-time tasks. We use a partitioning strategy with an EDF scheduling algorithm on each processor. The problem is NP-hard. We derive lower and upper bounds for the number of processors required to satisfy the constraints of the problem. We also compare a number of heuristic algorithms with each other and with the bounds derived in this research. Numerical results demonstrate that our lower bound is very tight. In the third part of the thesis, we study the problem of uplink scheduling in telecommunication systems with two dimensional resources. Our goal is to maximize the total value of the packets sent in uplink subframe such that system constraints and requirements are satisfied. The packets have various QoS requirements and have either soft or hard deadlines. We take two approaches, namely 0-1 and fractional approaches, to model the problem. Considering the properties of the application, we derive globally optimal solutions in polynomial time for the models. We also present a method to fine-tune the models. Numerical results are provided to compare the performance of the various optimal algorithms each corresponding to a model. / Thesis (Ph.D, Computing) -- Queen's University, 2009-04-24 08:22:04.238

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Market based generation dispatch is becoming the industry norm in advanced electrical jurisdictions. Due to the continuous evolution of markets and their potential impacts on system operation, studies are performed from economic and social perspectives in order to gauge the effects of any changes before implementation into live systems. In addition, it is essential to verify the effect of changes in market design on power systems from a technical perspective. The main objective of this thesis is to develop a real-time power system simulator for use in the investigation of market designs and automatic generation control schemes. The scope of this thesis is the mathematical algorithms used in the simulator, hardware and software implementation, and validation of the implemented simulator. The simulator is based on a modified version of the power flow calculation using an innovative combination of a standard numerical technique implemented on a readily available computing hardware platform. The result is a significant decrease in computation time. The power flow is performed repeatedly, with frequency being calculated between time steps to provide system dynamics. Frequency is calculated using a modified version of the generic generator swing equation. Generator and load models and their respective control systems are provided for the purposes of simulator validation and testing, although do not fall within the scope of the simulator itself.

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Thesis (M.S.)--University of Texas at Dallas, 2007. / Includes vita. Includes bibliographical references (leaves 70-72)