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Articles 601 - 630 of 668

Full-Text Articles in Civil and Environmental Engineering

Neural Network Trees And Simulation Databases: New Approaches For Signalized Intersection Crash Classification And Prediction, Piyush Nawathe Jan 2005

Neural Network Trees And Simulation Databases: New Approaches For Signalized Intersection Crash Classification And Prediction, Piyush Nawathe

Electronic Theses and Dissertations

Intersection related crashes form a significant proportion of the crashes occurring on roadways. Many organizations such as the Federal Highway Administration (FHWA) and American Association of State Highway and Transportation Officials (AASHTO) are considering intersection safety improvement as one of their top priority areas. This study contributes to the area of safety of signalized intersections by identifying the traffic and geometric characteristics that affect the different types of crashes. The first phase of this thesis was to classify the crashes occurring at signalized intersections into rear-end, angle, turn and sideswipe crash types based on the traffic and geometric properties of …

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Effects Of Reduced Ras And Volume On Anaerobic Zone Performance For A Septic Wastewater Biological Phosphorous Removal System, Daniel Magro Jan 2005

Effects Of Reduced Ras And Volume On Anaerobic Zone Performance For A Septic Wastewater Biological Phosphorous Removal System, Daniel Magro

Electronic Theses and Dissertations

Enhanced Biological Phosphorous Removal (EBPR) performance was found to be adequate with reduced Return Activated Sludge (RAS) flows (50% of available RAS) to the anaerobic tank and smaller than typical anaerobic zone volume (1.08 hours hydraulic retention time or HRT). Three identical parallel biological nutrient removal (BNR) pilot plants were fed with strong, highly fermented (160 mg/L VFAs), domestic/industrial wastewater from a full scale wastewater treatment facility (WWTF). The pilot plants were operated at 100%, 50%, 40% and 25% RAS (percent of available RAS) flows to the anaerobic tank with the remaining RAS to the anoxic tank. In addition, varying …

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Implementation Strategies For Real-Time Traffic Safety Improvements On Urban Freeways, Jeremy Harvey Dilmore Jan 2005

Implementation Strategies For Real-Time Traffic Safety Improvements On Urban Freeways, Jeremy Harvey Dilmore

Electronic Theses and Dissertations

This research evaluates Intelligent Transportation System (ITS) implementation strategies to improve the safety of a freeway once a potential of a crash is detected. Among these strategies are Variable Speed Limit (VSL) and ramp metering. VSL are ITS devices that are commonly used to calm traffic in an attempt to relieve congestion and enhance throughput. With proper use, VSL can be more cost effective than adding more lanes. In addition to maximizing the capacity of a roadway, a different aspect of VSL can be realized by the potential of improving traffic safety. Through the use of multiple microscopic traffic simulations, …

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The Effect Of Free Chlorine And Chloramines On Lead Release In A Distribution System, Ferdinand Vasquez Jan 2005

The Effect Of Free Chlorine And Chloramines On Lead Release In A Distribution System, Ferdinand Vasquez

Electronic Theses and Dissertations

Total lead release in drinking water in the presence of free chlorine and chloramine residuals was investigated in field, laboratory and fundamental investigations for finished waters produced from ground (GW), surface (SW), saline (RO) and blended (B) sources. Field investigations found more total lead was released in the presence of chloramines than in the presence of free chlorine for RO and blended finished waters; however, there were no statistical differences in total lead release to finished GW and SW. Laboratory measurements of finished waters oxidation-reduction potential (ORP) were equivalent by source and were not affected by the addition of more …

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Numerical Modeling Of Dissimilatory Iron Reduction In Sediments At A Field Site, Chun-Wen Chen Jan 2005

Numerical Modeling Of Dissimilatory Iron Reduction In Sediments At A Field Site, Chun-Wen Chen

Electronic Theses and Dissertations

The primary purpose of this study is to identify the 'universal' rate formulations with scaled-dependent parameters for the biological reduction of hematite. Three possible rate formulations were proposed to describe the bioreduction rate of hematite, and two kinds of simulation were conducted to validate the formulations and parameters with both batch and column experimental data: a reaction-based biogeochemical (batch) modeling with BIOGEOCHEM 1.0 and a reactive biogeochemical transport (column) modeling via HYDROGEOCHEM 4.0. Based on the results of simulations, only the dual Monod kinetic with inhibition rate formulation with respect to the concentrations of lactate, ßFeOOH, and Fe2+ under certain …

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Mechanisms Of Nanofilter Fouling And Treatment Alternatives For Surface Water Supplies, Charles Robert Reiss Jan 2005

Mechanisms Of Nanofilter Fouling And Treatment Alternatives For Surface Water Supplies, Charles Robert Reiss

Electronic Theses and Dissertations

This dissertation addresses the role of individual fouling mechanisms on productivity decline and solute mass transport in nanofiltration (NF) of surface waters. Fouling mechanisms as well as solute mass transport mechanisms and capabilities must be understood if NF of surface waters is to be successful. Nanofiltration of surface waters was evaluated at pilot-scale in conjunction with advanced pretreatment processes selected for minimization of nanofilter fouling, which constituted several integrated membrane systems (IMSs). Membrane fouling mechanisms of concern were precipitation, adsorption, particle plugging, and attached biological growth. Fouling was addressed by addition of acid and antiscalent for control of precipitation, addition …

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Three Dimensional Modeling Of Wekiva Springshed With Wash123d, Sandeep Paladagu Jan 2005

Three Dimensional Modeling Of Wekiva Springshed With Wash123d, Sandeep Paladagu

Electronic Theses and Dissertations

This thesis presents a three-dimensional groundwater modeling of Wekia springshed in central Florida using a numerical model, WASH123D. Springs have historically played an important role in Florida's history. The Wekiva River is a spring-fed system associated with about 19 springs connected to the Floridan aquifer. With increased urbanization and population growth in this region, there has been an increased strain on the water levels of Floridan aquifer which is a major source of potable water. Maintaining groundwater recharge to the aquifer is a key factor of the viability of the regional water supply as well as Wekiva ecosystem. Hence, the …

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Safety Issues Of Red-Light Running And Unprotected Left-Turn At Signalized Intersections, Xuedong Yan Jan 2005

Safety Issues Of Red-Light Running And Unprotected Left-Turn At Signalized Intersections, Xuedong Yan

Electronic Theses and Dissertations

Crashes categorized as running red light or left turning are most likely to occur at signalized intersections and resulted in substantial severe injuries and property damages. This dissertation mainly focused on these two types of vehicle crashes and the research methodology involved several perspectives. To examine the overall characteristics of red-light running and left-turning crashes, firstly, this study applied 1999-2001 Florida traffic crash data to investigate the accident propensity of three aspects of risk factors related to traffic environments, driver characteristics, and vehicle types. A quasi-induced exposure concept and statistical techniques including classification tree model and multiple logistic regression were …

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Applying Log-Linear Models And Gis To Study The Safety Of Pedestrians And Bicyclists : A Case Study Of Orange County School Children, Sai Srinivas Chundi Jan 2005

Applying Log-Linear Models And Gis To Study The Safety Of Pedestrians And Bicyclists : A Case Study Of Orange County School Children, Sai Srinivas Chundi

Electronic Theses and Dissertations

Abstract Pedestrian /bicycle safety of school children has been a growing menace that has been attracting attention from transportation professionals, school boards, media and the community all over the country. As such there has been a necessity to identify critical variables and assess their importance in pedestrian/bicycle crashes occurring in and around school zones. The current study is an endeavor in this direction. The literature review identified some studies that were conducted on school zone safety related to pedestrian/bicyclist crashes. Most of the studies pertained to crashes with all age groups. There have been few studies with emphasis only on …

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Evaluation Of Proprietary Stormwater Treatment Devices In Field And Laboratory Conditions, Saheeda Marie Romah Jan 2005

Evaluation Of Proprietary Stormwater Treatment Devices In Field And Laboratory Conditions, Saheeda Marie Romah

Electronic Theses and Dissertations

Proper stormwater management acknowledges both water quantity and water quality. Historically, stormwater quantity and quality have been separately considered; runoff was routed as quickly as possible into the nearest body of water. Although this alleviates potential flooding concerns, water quality is often compromised. Common stormwater quality problems include gross pollutants, sediment, nutrients, and heavy metals. The chronic elevated presence of these pollutants is detrimental to the environment. As a result, the government has passed legislature to protect waterways. The passage of the National Pollution Discharge Elimination System (NPDES) permit requires that municipalities implement stormwater treatment techniques, known as Best Management …

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Evaluation Of Toxic Cyanobacteria In Central Florida Stormwater Ponds, Robert Miller Jan 2005

Evaluation Of Toxic Cyanobacteria In Central Florida Stormwater Ponds, Robert Miller

Electronic Theses and Dissertations

Algal blooms are a common occurrence in water bodies of all shapes and sizes throughout the United States and countries around the world. The State of Florida is no exception to this phenomenon. Cyanobacteria, or blue-green algae, have proven to be of special concern due to its proliferation and potential to produce toxins that are harmful to humans, livestock and wildlife. A casual drive along the roads and in the neighborhoods of central Florida will confirm algal conditions in many areas. The potential for exposure to harmful and possibly fatal toxins associated with these algal blooms are becoming more evident …

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Finite Element Evaluation Of The Effects Of Lateral Anchorage Strips On The Behavior Of Cfrp-Strengthened Rc Beams, Jose Javier Perez Jan 2005

Finite Element Evaluation Of The Effects Of Lateral Anchorage Strips On The Behavior Of Cfrp-Strengthened Rc Beams, Jose Javier Perez

Electronic Theses and Dissertations

In this thesis, a fully nonlinear finite element study of the flexural behavior of doubly reinforced concrete beams strengthened using different Carbon Fiber Reinforced Polymer (CFRP) composite strengthening configurations has been carried out. Prior to the study, a total of six beams were constructed, pre-cracked, strengthened and tested to failure under a four-point loading condition (Zhao and O'Riordan-Adjah, 2004). Then, for the purpose of this thesis work, detailed three dimensional finite element models were created not only to correlate the results obtained from the experiments, but also to predict the load capacity, failure modes and crack pattern of reinforced concrete …

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The Effect Of Tidal Inlets On Open Coast Storm Surge Hydrographs: A Case Study Of Hurricane Ivan (2004), Michael Salisbury Jan 2005

The Effect Of Tidal Inlets On Open Coast Storm Surge Hydrographs: A Case Study Of Hurricane Ivan (2004), Michael Salisbury

Electronic Theses and Dissertations

Florida's Department of Transportation requires design storm tide hydrographs for coastal waters surrounding tidal inlets along the coast of Florida. These hydrographs are used as open ocean boundary conditions for local bridge scour models. At present, very little information is available on the effect that tidal inlets have on these open coast storm tide hydrographs. Furthermore, current modeling practice enforces a single design hydrograph along the open coast boundary for bridge scour models. This thesis expands on these concepts and provides a more fundamental understanding on both of these modeling areas. A numerical parameter study is undertaken to elucidate the …

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Adapting The Modified Cam Clay Constitutive Model To The Computational Analysis Of Dense Granular Soils, Jose Arvelo Jan 2005

Adapting The Modified Cam Clay Constitutive Model To The Computational Analysis Of Dense Granular Soils, Jose Arvelo

Electronic Theses and Dissertations

The computational constitutive Modified Cam Clay Model (MCCM) was developed at Cambridge to study the behavior of clays and has been proven to be effective. In this study, this model is extended to the case of dense sands to analyze the accuracy of the stress-strain behavior. This analysis is based on triaxial test data applied to remolded and compacted sand samples under drained conditions. The laboratory triaxial tests were performed by the Florida Department of Transportation to research the permeability effect in sandy soils compacted up to 95% of maximum unit weight at the optimum moisture content. Each soil sample …

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Structural Condition Assessment Of Prestressed Concrete Transit Guideways, Robert Zachary Shmerling Jan 2005

Structural Condition Assessment Of Prestressed Concrete Transit Guideways, Robert Zachary Shmerling

Electronic Theses and Dissertations

Objective condition assessment is essential to make better decisions for safety and serviceability of existing civil infrastructure systems. This study explores the condition of an existing transit guideway system that has been in service for thirty-five years. The structural system is composed of six-span continuous prestressed concrete bridge segments. The overall transit system incorporates a number of continuous bridges which share common design details, geometries, and loading conditions. The original analysis is based on certain simplifying assumptions such as rigid behavior over supports and simplified tendon/concrete/steel plate interaction. The current objective is to conduct a representative study for a more …

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Right Turn Split: A New Design To Alleviate Weaving On Arterial Streets, Khaled Shaaban Jan 2005

Right Turn Split: A New Design To Alleviate Weaving On Arterial Streets, Khaled Shaaban

Electronic Theses and Dissertations

While weaving maneuvers occur on every type of roadway, most studies have focused on freeway maneuvers. Weaving occurring on non-freeway facilities, such as arterial streets, can cause significant operational problems. Arterial streets weaving typically occur when vehicles coming from a side street at an upstream intersection attempt to enter the main street from one side to reach access points on the opposite site at a downstream intersection by crossing one or more lanes. This dissertation investigates the type of problems occurring on arterial streets due to the weaving movements and recommends a new design to alleviate weaving on arterial streets. …

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Assessing Crash Occurrence On Urban Freeways Using Static And Dynamic Factors By Applying A System Of Interrelated Equations, Rajashekar Pemmanaboina Jan 2005

Assessing Crash Occurrence On Urban Freeways Using Static And Dynamic Factors By Applying A System Of Interrelated Equations, Rajashekar Pemmanaboina

Electronic Theses and Dissertations

Traffic crashes have been identified as one of the main causes of death in the US, making road safety a high priority issue that needs urgent attention. Recognizing the fact that more and effective research has to be done in this area, this thesis aims mainly at developing different statistical models related to the road safety. The thesis includes three main sections: 1) overall crash frequency analysis using negative binomial models, 2) seemingly unrelated negative binomial (SUNB) models for different categories of crashes divided based on type of crash, or condition in which they occur, 3) safety models to determine …

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Infrared Thermography And High Accuracy Gps For Automated Asphalt Crack Detection, Tarek M. Abdel-Monem Jan 2005

Infrared Thermography And High Accuracy Gps For Automated Asphalt Crack Detection, Tarek M. Abdel-Monem

Electronic Theses and Dissertations

Roads are major public assets. The USA spends billions of dollars each year on road construction and maintenance. To keep these roads in a healthy condition and for better planning and allocation of maintenance budgets, knowledge of distressed locations is needed. Roads develop cracks when they are subjected to stresses that exceed their designed criteria or their materials properties. Early detection and repair of cracks has proven to be the most cost-effective strategy in limiting the damage to roads and reducing expenditures. Various methodologies of crack detection were developed and significant techniques were made in the last few years. One …

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Effects Of Bedding Void On Internal Moment Increase In Concrete Pipes, Jad Kazma Jan 2005

Effects Of Bedding Void On Internal Moment Increase In Concrete Pipes, Jad Kazma

Electronic Theses and Dissertations

Large diameter concrete pipes have been used in many areas of central Florida to carry pressured sewage flow. These pipes have been typically located at six feet below finished roadway elevation, and ranges in diameter from thirty six to sixty inches. The water table is typically located at shallow depth below finished roadway elevation, and generally fluctuates between five to ten feet depending on the relative roadway elevation to mean sea level. These pipes are under pressure when carrying the sewage flow, but return to normal atmospheric pressures when the flow stops. Since the water table encases most of the …

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Evaluating Ramp Metering And Variable Speed Limits To Reduce Crash Potential On Congested Freeways Using Micro-Simulation, Albinder Dhindsa Jan 2005

Evaluating Ramp Metering And Variable Speed Limits To Reduce Crash Potential On Congested Freeways Using Micro-Simulation, Albinder Dhindsa

Electronic Theses and Dissertations

Recent research at UCF into defining surrogate measures for identifying crash prone conditions on freeways has led to the introduction of several statistical models which can flag such conditions with a good degree of accuracy. Outputs from these models have the potential to be used as real-time safety measures on freeways. They may also act as the basis for the evaluation of several intervention strategies that might help in the mitigation of risk of crashes. Ramp Metering and Variable Speed Limits are two approaches which have the potential of becoming effective implementation strategies for improving the safety conditions on congested …

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Hydrogen Sulfide Flux Measurements And Dispersion Modeling From Constr, Sangho Eun Jan 2004

Hydrogen Sulfide Flux Measurements And Dispersion Modeling From Constr, Sangho Eun

Electronic Theses and Dissertations

Odor problems are a common complaint from residents living near landfills. Many compounds can cause malodorous conditions. However, hydrogen sulfide (h2s) has been identified as a principal odorous component from construction and demolition (c&d)debris landfills. Although several studies have reported the ambient concentrations of h2s near c&d landfills, few studies have quantified emission rates of h2s. The most widely used and proven technique for measuring gas emission rates from landfills is the flux chamber method. Typically the flux chamber is a cylindrical enclosure device with a spherical top which limits the gas emission area. Pure zero grade air is introduced …

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Nitrification Investigation And Modeling In The Chloraminated Drinking Water Distribution System, Suibing Liu Jan 2004

Nitrification Investigation And Modeling In The Chloraminated Drinking Water Distribution System, Suibing Liu

Electronic Theses and Dissertations

This dissertation consists of five papers concerning nitrification in chloraminated drinking water distribution systems in a one and a half year field study. Seven finished waters were produced from different treatment processes and distributed to eighteen pilot distribution systems (PDSs) that were made pipes taken from actual distribution systems. Unlined cast iron (UCI), galvanized steel (G), lined cast iron (LCI), and PVC pipes were used to build the PDSs. All finished waters were stabilized and chloraminated before entering the PDSs. This dissertation consists of five major parts. (1) System variations of nitrates, nitrites, DO, pH, alkalinity, temperature, chloramine residuals and …

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Evaluation Of The Impacts Of Its Information Strategies On I-4 Corridor, Yueliang Zuo Jan 2004

Evaluation Of The Impacts Of Its Information Strategies On I-4 Corridor, Yueliang Zuo

Electronic Theses and Dissertations

This study evaluated the impacts of ITS information strategies under incident conditions in Interstate 4 (I-4) corridor of Orlando. The analysis was performed using DYNASMART-P software package. The ITS information strategies range from pre-trip information, en-route information, and variable message signs. Simulation covered one hour during the morning peak period. The impacts of ITS information strategies on mobility were evaluated by simulating the performance of various ITS information components (pre-trip information, en-route information, and variable message signs) under incident conditions for the I-4 corridor and comparing the results with the corresponding scenarios in the absence of these components. The traffic …

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Analysis Of Type And Severity Of Traffic Crashes At Signalized Intersections Using Tree-Based Regression And Ordered Probit Models, Joanne Marie Keller Jan 2004

Analysis Of Type And Severity Of Traffic Crashes At Signalized Intersections Using Tree-Based Regression And Ordered Probit Models, Joanne Marie Keller

Electronic Theses and Dissertations

Many studies have shown that intersections are among the most dangerous locations of a roadway network. Therefore, there is a need to understand the factors that contribute to traffic crashes at such locations. One approach is to model crash occurrences based on configuration, geometric characteristics and traffic. Instead of combining all variables and crash types to create a single statistical model, this analysis created several models that address the different factors that affect crashes, by type of collision as well as injury level, at signalized intersections. The first objective was to determine if there is a difference between important variables …

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Investigation Of Ground Penetrating Radar For Detection Of Leaking Pipelines Under Roadway Pavements And Development Of Fiber-Wrapping Repair Technique, Pedro F. Suarez Jan 2004

Investigation Of Ground Penetrating Radar For Detection Of Leaking Pipelines Under Roadway Pavements And Development Of Fiber-Wrapping Repair Technique, Pedro F. Suarez

Electronic Theses and Dissertations

Nowadays, it has become a common practice to observe urban roadways undergo severe distress characterized by substantial depressions. In some cases, these pavement depressions are caused by leakages in the connecting joints of sewage pipelines laid beneath the roadway pavement. Manual inspection of pipe leakages has become costly and complex since sewage pipes with relative small diameters do not allow inspection from inside and digging may be required. On the other hand, pipes with large diameters, in which inspection can be made from pipe interior, inspector can not remain inside of the pipe for long periods of time because of …

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Modeling Of Membrane Solute Mass Transfer In Ro/Nf Membrane Systems, Yu Zhao Jan 2004

Modeling Of Membrane Solute Mass Transfer In Ro/Nf Membrane Systems, Yu Zhao

Electronic Theses and Dissertations

Five articles describing the impact of surface characteristics, and development of mass transfer models for diffusion controlled membrane applications are published in this dissertation. Article 1 (Chapter 3) describes the impact of membrane surface characteristics and NOM on membrane performance for varying pretreatment and membranes during a field study. Surface charge, hydrophobicity and roughness varied significantly among the four membranes used in the study. Membrane surface characteristics, NOM and SUVA measurements were used to describe mass transfer in a low pressure RO integrated membrane system. Inorganic and organic solute and water mass transfer coefficients were systematically investigated for dependence on …

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Biostability In Drinking Water Distribution Systems Study At Pilot-Scale, Michael Le Puil Jan 2004

Biostability In Drinking Water Distribution Systems Study At Pilot-Scale, Michael Le Puil

Electronic Theses and Dissertations

Biostability and related issues (e.g. nitrification) were investigated for 18 months in 18 pilot distribution systems, under various water quality scenarios. This study specifically investigated the impact of steady-state water changes on HPC levels in chlorinated and chloraminated distribution systems. Chlorination was more effective than chloramination in reducing HPC levels (1-2 log difference). There was a rapid increase in HPC corresponding to the change in steady-state water quality, which was observed in all PDS. Modeling effort demonstrated that HPC levels reached a maximum within five days after water quality change and return to initial level ten days after the change. …

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Effects Of The Soil Properties On The Maximum Dry Density Obtained Fro, Andres Arvelo Jan 2004

Effects Of The Soil Properties On The Maximum Dry Density Obtained Fro, Andres Arvelo

Electronic Theses and Dissertations

In the construction of highways, airports, and other structures, the compaction of soils is needed to improve its strength. In 1933 Proctor developed a laboratory compaction test to determine the maximum dry density of compacted soils, which can be used for specifications of field compaction. The Compaction of soils is influenced by many factors, the most common are the moisture content, the soil type and the applied compaction energy. The objective of this research is the analysis of the maximum dry density values based on the soil classification and characterization. The method of choice in the determination of the maximum …

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Predicting Air Quality Near Roadway Intersections Through The Applicat, Brian Kim Jan 2004

Predicting Air Quality Near Roadway Intersections Through The Applicat, Brian Kim

Electronic Theses and Dissertations

With substantial health and economic impacts attached to many highway-related projects, it has become imperative that the models used to assess air quality be as accurate as possible. The United States (US) Environmental Protection Agency (EPA) currently promulgates the use of CAL3QHC to model concentrations of carbon monoxide (CO) near roadway intersections. This model uses steady-state and macroscopic methods to model the physical phenomena (e.g., emission rates, atmospheric dispersion, etc.) occurring at intersections. These methods are not straightforward and unintuitive for the users. Therefore, this project investigated the possibility of developing a model that is theoretically more realistic and flexible …

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Modeling Crash Frequencies At Signalized Intersections In Central Flor, Smitha Kowdla Jan 2004

Modeling Crash Frequencies At Signalized Intersections In Central Flor, Smitha Kowdla

Electronic Theses and Dissertations

A high percentage of highway crashes in the United States occur at intersections. These crashes result in property damage, lost productivity, injury, and even death. Identifying intersections associated with high crash rate is very important to minimize future crashes. The purpose of this study is to develop efficient means to evaluate intersections, which may require safety improvements. The area covered by the analysis in this thesis includes Orange and Seminole Counties and the City of Orlando. The aforementioned counties and city thus represent Central Florida. Each County/City provided data that consisted of signalized intersection drawings that were either in the …

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