Browsing by Author "Dr. Downey Brill, Member"

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    Measurement, Analysis, and Modeling of On-Road Vehicle Emissions Using Remote Sensing
    (1999-05-27) Unal, Alper; Dr. H. Christopher Frey, Chair; Dr. Nagui Rouphail, Member; Dr. Downey Brill, Member
    The main objectives of this research are; to develop on-road emission factor estimates for carbon monoxide (CO) and hydrocarbon (HC) emissions; to collect traffic and vehicle parameters that might be important in explaining variability in vehicle emissions; to develop an empirical traffic-based model that can predict vehicle emissions based upon observable traffic and vehicle parameters. Remote sensing technology were employed to collect exhaust emissions data. Traffic parameters were collected using an area-wide traffic detector, MOBILIZER. During the measurements, license plates were also recorded to obtain information on vehicle parameters. Data were collected at two sites, having different road grades and site geometries, over 10 days of field work at the Research Triangle area of North Carolina. A total of 11,830 triggered measurement attempts were recorded. After post-processing, 7,056 emissions were kept in the data base as valid measurements. After combining with the traffic and license vehicle parameters, a data base has been developed. Exploratory analysis has been conducted to find variables that are important to explain the variability of the emission estimates. Statistical methods were used to compare the mean of the emissions estimates for different sub-populations. For example, multi-comparison analysis has been conducted to compare the mean emissions estimates from vehicles having different model years. This analysis showed that the mean emissions from older vehicles were statistically different than the mean emissions estimates from the recent model year vehicles.One of the contributions of the research was developing an empirical traffic-based emission estimation model. For this purpose, data collected during the study were used to develop a novel model which combines the Hierarchical Tree-Based Regression method and Ordinary Least Squares regression. The key findings from this research include: (1) the measured mean CO emission estimate for Research Triangle park area of North Carolina is estimated as 340 grams/gallon, whereas the mean HC emissions estimate is found to be as 47 grams/gallon (2) inter-vehicle variability in vehicle emissions can be as high as two orders-of-magnitude; (3) intra-vehicle variability is lower compared to the inter-vehicle variability; (4) some vehicle variables such as vehicle model year and vehicle type are important factors in explaining the inter-vehicle variability in emissions estimates; (5) emission estimation model developed in this research can be applied to estimate the emissions from on-road vehicles.
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    Vitri - A Generic Framework for Engineering Decision Support Systems on Heterogeneous Computer Networks
    (2002-02-26) Kumar, Sujay V; Dr. John Baugh Jr, Chair; Dr. Downey Brill, Member; Dr. Ranji Ranjithan, Member; Dr. Purushothaman Iyer, Member
    Vitri is an object-oriented framework implemented in Java for high-performance distributed computing. Using Vitri, applications can engage in cooperativeproblem solving by dividing their tasks among heterogeneous clusters of workstations and PCs. Vitri's features include basic support fordistributed computing and communication, as well as visual tools for evaluating run-time performance, and modules for heuristic optimization. It balances loads dynamically using a client-side task pool, allows theaddition or removal of servers during a run, and provides fault tolerance transparently for servers and networks. Among its more powerful featuresare modules for heuristic optimization and decision support tools such asmodeling to generate alternatives (MGA). Vitri also provides an asynchronous global-parallel genetic algorithm that is particularly suited for coarse-grained tasks executing on processors with large variations in processor speeds. By using dataflow techniques, in which computations areexplicitly based on the availability and forwarding of data, the usual end-of-generation synchronization points are removed from the algorithm. The tools in Vitri are applied to a number of different applicationsfrom the civil engineering domain. The results indicate the adaptability of Vitri to various problems and its utility as a tool for managing engineering decision support systems.