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- Item3D IMAGE ANALYSIS OF CT DATA OF CONCRETE CYLINDER SUNDERGOING DELAYED ETTRINGTIE FORMATION(2019) Shi, Kuo; Amde, Amde M; Livingston, Richard A; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The strains in a concrete caused by delayed ettringite formation (DEF) are conventionally expressed in terms of the one-dimensional linear expansion. However, concrete is not a homogeneous material, and differences in the volume change between the inert aggregates and the reactive cement paste will produce variations in local displacements that cannot be detected by the linear expansion variable. With CT slices offered by Simultaneous neutron and X-ray computed tomography (SNXCT), this thesis applies image analysis algorithms to quantify the distortion of cylinder over time due to delayed ettringite formation. The research reported in this thesis concerned the development of several MATLAB programs to apply image analysis algorithms to quantify the distortion of cylinder over time in terms of summary variables. These included mean radial expansion, deviation from circularity, vertical tilt angle and rotation, void area fraction and the displacement of microbead internal reference points.
- ItemACCESSIBILITY BASED EVALUATION OF COASTAL RURAL COMMUNITIES’ VULNERABILITY TO COASTAL FLOODING AND THEIR ADAPTATION OPTIONS(2022) Yahyazadeh Jasour, Zeinab; Reilly, Allison C; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Global climate change and sea-level rise will cause significant risks to coastal communities. To make inclusive and cost-effective adaptation planning decisions, we need to understand who may be impacted and when. Currently, planning literature generally focuses on housing impacts; when will a house be inundated, and what adaptation strategies are useful to keep a house habitable? Housing, though, is only one of many types of infrastructures people need to reside in an area. Reliable roads are another. This dissertation conducts an analysis of parcel-level impacts of SLR on local residents’ ability to reach key amenities such as emergency services, grocery stores, and schools. Furthermore, it strategically evaluates where road protection should be implemented so that access is maintained in an equitable manner. Next, I use the accessibility analysis to identify the important roads for gathering high-resolution flood data to improve the accuracy of the analysis. I use Dorchester County, Maryland, U.S., as a case study. It is an extremely low-lying rural county and is expected to shrink in half by the end of the century due to SLR. The results from the case study indicate that some parcels are not expected to be inundated by SLR but are expected to experience accessibility impacts. Road protection appears to be a temporary strategy that can buy time for long-term adaptation strategies such as relocation. However, the protection strategies should be cautiously selected based on decision-makers priorities. The insight obtained by this dissertation highlights that when policy and decision-makers are deciding among adaptation strategies, they need to reach some level of consensus about assumptions for which a possible future is planned, and also the trade-off between increasing accessibility levels and balancing the distribution of accessibility among different demographic groups.
- ItemACTIVE RELOCATION AND DISPATCHING OF HETEROGENEOUS EMERGENCY VEHICLES(2014) Sharifi, Elham; Haghani, Ali; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)An emergency is a situation that causes an immediate risk to the property, health, or lives of civilians and can assume a variety of forms such as traffic accidents, fires, personal medical emergencies, terrorist attacks, robberies, natural disasters, etc. Emergency response services (ERSs) such as police, fire, and medical services play crucial roles in all communities and can minimize the adverse effects of emergency incidents by decreasing the response time. Response time is not only related to the dispatching system, but also has a very close relationship to the coverage of the whole network by emergency vehicles. The goal of this dissertation is to develop a model for an Emergency Management System. This model will dynamically relocate the emergency vehicles to provide better coverage for the whole system. Also, when an emergency happens in the system the model will consider dispatching and relocation problem simultaneously. In addition, it will provide real-time route guidance for emergency vehicles. In summary, this model will consider three problems simultaneously: area coverage, vehicle deployment, and vehicle routing. This model is event-based and will be solved whenever there is an event in the system. These events can be: occurrence of an emergency, change in the status of vehicles, change in the traffic data, and change in the likelihood of an emergency happening in the demand nodes. Three categories of emergency vehicle types are considered in the system: police cars, ambulances, and fire vehicles. The police department is assumed to have a homogeneous fleet, but ambulances and fire vehicles are heterogeneous. Advanced Life Support (ALS) and Basic Life Support (BLS) ambulances are considered, along with Fire Engines, Fire Trucks, and Fire Quints in the fire vehicle category. This research attempts to provide double coverage for demand nodes by non-homogenous fleet while increasing the equity of coverage of different demand nodes. Also, the model is capable of considering the partial coverage in the heterogeneous vehicle categories. Two kinds of demand nodes are considered, ordinary nodes and critical nodes. Node demands may vary over time, so the model is capable of relocating the emergency fleet to cover the points with highest demand. In addition, an attempt is made to maintain work load balance between different vehicles in the system. Real-world issues, such as the fact that vehicles prefer to stay at their home stations instead of being relocated to other stations and should be back at their home depots at the end of the work shift, are taken into account. This is a unique and complex model; so far, no study in the literature has addressed these problems sufficiently. A mathematical formulation is developed for the proposed model, and numerical examples are designed to demonstrate its capabilities. Xpress 7.1 is used to run this model on the numerical examples. Commercial software like Xpress can be used to solve the proposed model on small-size problems, but for large-size and real-world problems, an appropriate heuristic is needed. A heuristic method that can find good solutions in reasonable time for this problem is developed and tested on several cases. Also, the model is applied to a real-world case study to test its performance. To investigate the model's behavior on a real-world problem, a very sophisticated simulation model that can see most of the details in the system has been developed and the real case study data has been used to calibrate the model. The results show that the proposed model is performing very well and efficient and it can greatly improve the performance of emergency management centers.
- ItemAdjustment Factors and Applications for Analytic Approximations of Tour Lengths(2021) Choi, Youngmin; Schonfeld, Paul M.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The shortest tour distance for visiting all points exactly once and returning to the origin is computed by solving the well-known Traveling Salesman Problem (TSP). Due to the large computational effort needed for optimizing TSP tours, researchers have developed approximations that relate the average length of TSP tours to the number of points n visited per tour. The most widely used approximation formula has a square root form: √n multiplied by a coefficient β. Although the existing models can effectively approximate the distance for conventional vehicles with large capacities (e.g., delivery trucks) where n is large, approximations that seek to cover large ranges of n, possibly to infinity, tend to yield poorer results for the small n values. Thus, this dissertation focuses on approximation models for the small n values, which are needed for many practical applications, such as for some recent delivery alternatives (e.g., drones). The proposed models show promise in analyzing the real-world problems in which actual tours serve few customers due to limited vehicle capacity and incorporate realistic constraints, such as the effects of a starting point location, geographical restrictions on movements, demand patterns, and service area shapes. The dissertation may open new research avenues for analyzing the new transportation alternatives and provide guidelines to planners for choosing appropriate models in designing or evaluating transportation problems. Approximation models are estimated from the following experiments: 1) a total of 60 cases are developed by considering various factors, such as point distributions and shapes of service areas. 2) Solution methods for TSP instances are compared and chosen. 3) After the TSPs are optimized for each n, the TSP tour lengths are averaged. 4) Lastly, models for the averaged TSP tour lengths are fitted with ordinary least squares (OLS) regression. After the approximations are developed, some possible extensions are explored. First, adjustment factors are designed to integrate the 60 cases within one equation. With those factors, it can be understood how approximation varies with each classification. Next, the approximations considering stochastic customer presence (i.e., probabilistic TSP) are proposed. Third, the approximated tour lengths are compared with the optimal solutions of vehicle routing problem (VRP) in actual rural and urban delivery networks. Here, some additional factors, such as a circuity factor and service zone shape, are discussed. Lastly, the proposed methodology is applied to formulate and explore various types of existing and hypothetical delivery alternatives.
- ItemADVANCED DATA ANALYTICS AND MESOSCOPIC DYNAMIC TRAFFIC ASSIGNMENT SIMULATION FOR TRAFFIC IMPACT ANALYSIS OF MARYLAND CASINOS(2019) Donaldson, David; Zhang, Lei; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Three full-service casinos recently opened in Maryland: Live! Casino at the Arundel Mills Mall (June 2012), Horseshoe in Downtown Baltimore (August 2014), and MGM at the National Harbor (December 2016). The increased travel demand associated with such large entertainment complexes prompted an effort to quantify each facility’s impact on regional and local traffic patterns; therefore, a three-pronged analysis was conducted. First, historic vehicle probe data were analyzed to quantify and visualize the observed, local traffic impact for selected months before and after each casino became operational. Subsequently, an open-source mesoscopic DTA simulator named DTALite modeled the regional impact of the before/after scenarios as well as a special event scenario (e.g. Baltimore Ravens’ football game). The paper’s final component explored two innovative trip generation estimation methods to supplement the ITE Manual’s data limitation for casinos by utilizing aggregated mobile device trip data and an origin-demand adjustment system imbedded within DTALite. Ultimately, the data analytics and simulation-based modeling revealed no major traffic impact was generated by any casino. Moreover, upon comparison with ground truth count data, the origin-demand estimation technique out-performed both the ITE-based and location-based trip estimation methods.
- ItemAdvanced Denitrification in Bioretention Systems Usinging Woodchips as a Primary Organic Carbon Source(2013) Peterson, Ian James; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bioretention systems still lack the ability to effectively mitigate nitrogen concentrations from urban stormwater. Column tests were conducted to evaluate the effect of nitrate concentration, stormwater retention time, limestone addition, and woodchip species, size, and mass percentage on the bioretention denitrification process. Denitrification of artificial stormwater appeared to follow pseudo-first-order kinetics. A 0.8 day average retention time showed the highest nitrate removal percentage of 82.4 + 0.4%. Longer retention times correspond to greater removal efficiency. Willow Oak and Red Maple woodchips resulted in the highest total nitrogen removal efficiencies at 61.9 + 0.8% and 61.8%, respectively. Smaller woodchips and higher woodchip mass percentage corresponded to greater nitrate removal efficiencies, but also higher organic nitrogen leaching. Media containing 4.5% 5 mm Willow Oak woodchips by mass represented optimum conditions with a pseudo-first-order denitrification rate of 4.1 + 4.6 day-1 with nitrate concentrations of 1.5 to 4.5 mg/L N.
- ItemAn Agent-Based Model To Examine Housing Price, Household Location Choice, And Commuting Times In Knox County, Tennessee(2007-08-22) Mulbrandon, Matthew; Clifton, Kelly; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The research conducted for this thesis uses an agent-based model (ABM) to simulate housing price, location, and journey to work (JTW) times for households in Knox County, Tennessee. The model is a unique hybrid, combining analytic functions and agents that typically have been used separately for theoretical urban research in very simplified urban landscapes. At the same time it uses data from a real urban area to run and calibrate the model, which is common for statistically-based or gravity models. There are two goals for this simulation; first to examine the feasibility of this approach in urban modeling, second to test the effect of altering transportation times and preferences on agent behavior. Results show this approach can fit real data and represent urban processes reasonably well. In addition several interesting and surprising results are reported from model runs.
- ItemAgent-Based Models of Highway Investment Processes: Forecasting Future Networks under Public and Private Ownership Regimes(2012) Yusufzyanova, Dilya; Zhang, Lei; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The present highway funding system, especially fuel taxes, may become a less reliable revenue source in the future, while the transportation public agencies do not have sufficient financial resources needed to meet the increasing traffic demand. In the last two decades there has been increasing interest in utilizing private sector to develop, finance and operate new and existing roadways in the United States. While transportation privatization projects have shown signs of success, it is not always clear how to measure the true benefits associated with these projects for all stakeholders, including the public sector, the private sector and the public. "Win-win" privatization agreements are tricky to make due to conflicting nature of the various stakeholders involved. Therefore, there is a huge need to study the welfare impacts of various road privatization arrangements for the society as a whole, and the financial implications for private investors and public road authorities. In order to address these needs, first, an empirical analysis is performed to study the investment decision processes of public transportation agencies. Second, the agent-based decision-making model is developed to consider transportation investment processes at different levels of government which forecasts future transportation networks and their performance under both existing and alternative transportation planning processes. Third, various highway privatization schemes currently practiced in the U.S. are identified and an agent-based model for analyzing regulatory policies on private-sector transportation investments is developed. Fourth, the above mentioned models are demonstrated on the networks with grid and beltway topologies to study the impacts of topology configuration on the privatization arrangements. Based on the simulation results of developed models, a number of insights are provided about impacts of ownership structures on the socio-economic performance in transportation systems and transportation network changes over time. The proposed models and the approach can be used in long-run prediction of economic performance intended for describing a general methodology for transportation planning on large networks. Therefore, this research is expected to contribute significantly to the understanding and selecting proper road privatization programs on public networks.
- ItemAir Express Network Design with Hub Sorting(2007-11-05) Ngamchai, Somnuk; Schonfeld, Paul M.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation examines an innovative strategic operation for next day air package delivery. The proposed system, in which some packages are sorted twice at two distinct hubs before arriving at their destinations, is investigated for its potential savings. A two-stage sorting operation is proposed and compared to the currently operated single-stage sorting operation. By considering the endogenous optimization of hub sorting and storage capacities, cost minimization models are developed for both operations and used for performance comparison. Two solution approaches are presented in this study, namely the Column Generation (CG) approach and the Genetic Algorithm (GA) approach. The first method is implemented to optimize the problem by means of linear programming (LP) relaxation, in which the resulting model is then embedded into a branch-and-bound approach to generate an integer solution. However, for solving realistic problem sizes, the model is intractable with the conventional time-space formulation. Therefore, a Genetic Algorithm is developed for solving a large-scale problem. The GA solution representation is classified into two parts, a grouping representation for hub assignment and an aircraft route representation for aircraft route cycles. Several genetic operators are specifically developed based on the problem characteristics to facilitate the search. After optimizing the solution, we compare not only the potential cost saving from the proposed system, but also the system's reliability based on its slack. To provide some insights on the effects of two-stage operation, several factors are explored such as the location of regional hubs, single and multiple two-stage routings and aircraft mix. Sensitivity analyses are conducted under different inputs, including different demand levels, aircraft operating costs and hub operating costs. Additional statistics on aircraft utilization, hub capacity utilization, circuity factor, average transfers per package, and system slack gain/loss by commodity, are analyzed to elucidate the changes in system characteristics.
- ItemAn Algorithm for Crew Scheduling Problem with Bin Packing Features(2008-11-14) Qiao, Wenxin; Haghani, Ali; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This thesis proposes a new approach for solving the traditional crew scheduling problem. The crew scheduling problem is solved with a bin packing approach in polynomial time. Based on the extensive research on the bin packing problem during the past 40 years, an algorithm that is proved to be the most efficient for solving most bin packing problems is selected and modified for application in the crew scheduling problem. A Modified Best-Fit-Decreasing Algorithm is proposed and discussed in this study. A case study is conducted using the proposed algorithm and the results are discussed.
- ItemAn Alignment Optimization Model for a Simple Highway Network(2008-04-07) KANG, MIN WOOK; SCHONFELD, PAUL; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A new highway addition to an existing road network is typically considered for improving traffic performance in that road network. However, finding the new highway that best improves the existing network is a very complex problem since many factors affect the road construction. Besides changes in traffic flow patterns due to the new highway, various costs associated with highway construction as well as design specifications, safety, environmental, and political issues affect such a project. Until recently, many studies have dealt separately with the problems of highway alignment optimization and network design. However, no models have been found that integrate these problems comprehensively and effectively. This dissertation seeks to find a realistic three-dimensional highway alignment that best improves an existing network, while considering its costs, geometric design, and environmental impacts on the study area. To fulfill this objective, an effective network model is developed that can simultaneously optimize (i) highway alignments and (ii) junction points with existing roads. In addition, the model's optimization process considers traffic impacts due to the highway addition as well as factors associated with its construction. This dissertation starts by investigating the major cost components and important constraints in the highway design processes. Next, existing models for optimizing highway alignments are reviewed by assessing their advantages and disadvantages. Effective solution search methods are then developed to help solve the complex optimization problem. Development of the search methods is essential since an equilibrium traffic assignment as well as alignment optimization is undertaken in the proposed network model. Precise formulations of various highway costs and constraints are also developed for evaluating the various candidate alternatives. Cost functions for system improvements that can be obtained from the new highway addition are proposed. These are calculated based on the equilibrium traffic flows found from the assignment process. Complex geographical constraints including user preferences and environmentally sensitive areas are realistically represented, along with design standards required for highways. To represent highway alignments, sets of tangents, circular curves and transition spirals are used; in addition, three-leg structure models are also developed for representing the highway endpoints. Finally, several case studies are conducted to test the performance of the proposed models.
- ItemALL ABOUT CONGESTION: MODELING DEPARTURE TIME DYNAMICS AND ITS INTEGRATION WITH TRAFFIC MODELS(2011) Xiong, Chenfeng; Zhang, Lei; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This thesis comprehensively studies departure time choice models, and analyzes the consequent system-level peak spreading effects. In modeling, the school of discrete choice models successfully reveals the user heterogeneity. A mixture logit model and a latent class model based on the notion of carpooling preference have been estimated. Then a novel positive approach has been developed, which avoids the assumptions of rationality and focuses on how individuals actually make departure time decisions. Following this positive theory, we specify Bayesian learning, empirically estimate search start and stopping conditions that vary among users, and empirically derive search and decision rules from a joint reveal/stated-preference survey dataset. This innovative behavioral model is integrated with a traffic simulation model for a real-world study. Findings from this application reveal the potential of the proposed model to capture network dynamics and behavioral reactions. This integrated framework also provides a valuable tool for the evaluation of new transportation infrastructures, policies, and operation strategies.
- ItemAlternative Dynamic Testing by Active Control(2012) Wagman, Nicholas Alexander; Chang, Peter C; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As the general public becomes increasingly aware of the seismic risk to structures, Americans expect assurance from structural engineering professionals that building designs are safe and reliable. Increasing public scrutiny places even greater emphasis on the need for research and validation of performance-based earthquake engineering designs. Current methods for experimental validation of designs with full-scale tests (e.g. shake table and pseudo dynamic testing) can be extremely expensive and the facilities necessary are not available at many universities. This thesis proposes an Alternative Dynamic Test which uses a properly scaled model test specimen and a desktop shake table to perform accurate experimental validation of structural designs. The methodology and laboratory setup of this testing method are discussed including the motor characterization and power requirements. Error approximation and practical implementation of the Alternative Dynamic Test are also addressed.
- ItemANALYSES OF INFLUENTIAL FACTORS FOR ACCURATE DETERMINATION OF PEAK RATE FACTORS AND TIMES TO PEAK OF UNIT HYDROGRAPHS(2017) Zhao, Tianming; McCuen, Richard H.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Despite the availability of a number of sophisticated hydrologic models, the unit hydrograph (UH) is still one of the most widely used models for computing runoff hydrographs. The two-parameter gamma UH can be fully characterized by two parameters: the peak rate factor (PRF) and the time to peak (tpUH). Currently, obtaining accurate estimates of UH parameters is still a problem, especially for ungauged watersheds. The goal of this research was to analyze factors that influence estimates of UH parameters and to develop general guidelines that can assist in estimating UH parameters more accurately. A calibration model was developed for evaluating PRFs and tpUHs simultaneously from rainfall-runoff data. The effects of various influential factors were identified and investigated based on analyses of both synthetic and measured rainfall-runoff data. Results showed that the accuracy of calibrated UH parameters is affected by the rainfall characteristics, the time offset, the nonuniformity of rainfall, the extent of nonlinear watershed processes, and the flexibility of the gamma probability distribution function. Guidelines were developed to assist UH users in interpreting the calibration results and calibrating UH parameters more accurately.
- ItemAnalysis and behavior investigations of box girder bridges(2010) Begum, Zakia; Fu, Chung C; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Due to efficient dissemination of congested traffic, economic considerations, and aesthetic desirability horizontally curved steel box girder bridges have become increasingly popular nowadays in modern highway systems, including urban interchanges. Although significant research has been underway on advanced analysis for many years to better understand the behavior of all types of box-girder bridges, however, the results of these various research works are scattered and unevaluated. Hence, a clear understanding of more recent work on straight and curved box-girder bridges is highly desired. The non-composite steel section must support both the fresh concrete and the entire construction loads hence steel box girders are at their critical stage during construction. In the current study, non composite straight and curved steel boxes are analyzed with beam and shell elements using the three dimensional finite element analysis and their behavior is investigated. The present research addresses comparison using beam and shell element models of the straight and curved box girder bridge. This task involves examining the stress patterns obtained using static three-dimensional finite element modeling. Comparisons are made between stresses obtained for the straight and curved box girder bridges, from the beam element model and shell element model for each. Further, the finite element results are compared to the BEST center program DESCUS-II results. Finally, the parametric investigations are performed on the curved steel box model to evaluate the effects of several important parameters on the behavior of the girder.
- ItemANALYSIS AND SIMULATION OF ENERGY USE AND COST AT A MUNICIPAL WASTEWATER TREATMENT PLANT(2011) Feng, Yilu; Brubaker, Kaye L; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The cost of electricity, a major operating cost of municipal wastewater treatment plants, is related to influent flow rate, power price, and power load. With knowledge of inflow and price patterns, plant operators can manage processes to reduce electricity costs. Records of influent flow, power price, and load are evaluated for Blue Plains Advanced Wastewater Treatment Plant. Diurnal and seasonal trends are analyzed. Power usage is broken down among treatment processes. A simulation model of influent pumping, a large power user, is developed. It predicts pump discharge and power usage based on wet-well level. Individual pump characteristics are tested in the plant. The model accurately simulates plant inflow and power use for two pumping stations [R2 = 0.68, 0.93 (inflow), R2 =0.94, 0.91(power)]. Wet-well stage-storage relationship is estimated from data. Time-varying wet-well level is added to the model. A synthetic example demonstrates application in managing pumps to reduce electricity cost.
- ItemANALYSIS OF ACTIVITY CHOICE: THE ROLE OF ACTIVITY ATTRIBUTES AND INDIVIDUAL SCHEDULES(2009) Akar, Gulsah; Clifton, Kelly J; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Activity-based approaches have taken hold in transportation research over the last several decades. The foundation of the activity-based approach is to view travel as a result of our activity choices and scheduling decisions. Therefore, better understanding of activity choice, planning time horizons, and activity attributes will lead to more accurate demand forecasts. This dissertation extends the current activity choice modeling framework by incorporating the characteristics of the individuals' schedules, planning time horizons and focusing on the salient attributes of the activities. This study consists of three parts which are linked to one another by their conceptual and empirical findings. The first part identifies the determinants of the planning time horizons - defined as when people decide about performing their activities. Several household and individual characteristics, and activity attributes are tested for their association with planning times. The activity attributes which have significant impacts on the planning time horizons of the activities are used in the second part for generating new activity groups. The second part clusters activities based on their salient attributes, such as duration, frequency, number of involved people and flexibilities, rather than their functional types (work, leisure, household obligations, etc.) and creates activity groups such as "long, infrequent, personally committed activities", "quick, spatially fixed, temporally flexible activities" etc. The activity groups generated in this part inform the activity choice modeling structure developed in the third part. The main analytical techniques used in this research are the Principal Components Analysis (PCA) and discrete choice models. PCA is used to define the new activity groups. The analysis of the planning time horizons and activity choice are performed by mixed logit models. The model results reveal the significant relationships between socio-demographics, temporal characteristics, travel, and characteristics of the schedules on activity choice. The findings of these models could be integrated in the activity choice modules of the existing activity-travel simulation models by either applying the comprehensive model (which may face limitations due to the availability of data) or integrating the findings of the models in the decision rules.
- ItemANALYSIS OF LIDAR DATA FOR FLUVIAL GEOMORPHIC CHANGE DETECTION AT A SMALL MARYLAND STREAM(2008) Gardina, Vincent Joseph; Brubaker, Kaye L.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Numerous detailed topographic measurements, which must be periodically repeated, are required to characterize stream bank and channel geometry. Light Detection and Ranging (LiDAR) is becoming more widely used, but its accuracy for change detection in and around small streams is not well quantified. Two LiDAR and one ground-surveyed elevation data sets are compared for a thickly vegetated riparian area in the Maryland Piedmont. Interpolated surfaces (prediction maps) and estimates of their uncertainty (standard error maps) are created from the point data using kriging. The LiDAR 2006 elevations are compared to ground-survey to evaluate accuracy. LiDAR 2002 and 2006 elevations are compared to evaluate the potential for change detection. When the estimated LiDAR system error is included in hypothesis testing, no statistically significant elevation differences are found between 2002 and 2006. Conclusions about geomorphic change based on LiDAR scenes should account for error and uncertainty in the data collection and processing.
- ItemAn Analysis of Pedestrian-Vehicular Crashes Near Public Schools in the City of Baltimore, Maryland(2005-05-04) Fults, Kandice Kreamer; Clifton, Kelly J; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In previous research, children have been shown to be involved in pedestrian-vehicular crashes in high numbers due to improper pedestrian behaviors. Little research has been conducted to examine the relationship between schools and pedestrian crashes. This study analyzes pedestrian-vehicular crashes in the City of Baltimore, Maryland to determine any relationships that may exist between crashes near public schools and the physical and social attributes of these schools. It was found that the presence of a driveway decreases crash occurrence and severity. A setback from the road will decrease crash occurrence but increase the severity of the crashes. The presence of off-street parking was shown to increase the severity of a crash, particularly for children ages 16-18. Recreational facilities are shown to increase the crash occurrence and severity of crashes. This study however, is limited as it does not include pedestrian demand data and the results should be interpreted as such.
- ItemAN ANALYSIS OF PHARMACEUTICAL COUNTERFEITING: ASSESSING SCREENING FACTORS AND THEIR INFLUENCE ON COUNTERFEITING(2015) Rahaman, Faiad; Baecher, Gregory; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The United States pharmaceutical supply chain is one of the safest and most secure systems in the world. However, in recent years, an increasing number of drug counterfeit products were detected in it. This increase in documented incidents greatly concerns the pharmaceutical industry, and state and federal regulatory bodies. The repercussions of a tainted drug supply chain are potentially economically devastating and detrimental to the health and well-being of the public. Decision makers face a challenge keeping the drug supply chain safe from these influences, specifically assessing the risk of drug counterfeiting. With the problems posed by counterfeit, the identification of the right counterfeit attributes and the development of models to help supply chain managers determine the probability of counterfeit drugs are vital. Known drug counterfeiting research and studies are limited in scope; and despite increasing trends in counterfeiting, empirical research in this area is scarce. This research undertakes an in-depth examination of literature to identify counterfeit attributes and factors as well as to develop a drug counterfeit model to assess the probability of the drug counterfeiting. The identification of drug counterfeiting attributes resulted from a comprehensive review of the literature and a survey of experts. Data were subsequently collected on the attributes identified through literature, case studies, and experts. The findings of this research led to these substantive outcomes: * The identification of 10 key counterfeit attributes: Average Price, Drug Class, Medication Class, Product Type, Volume, Product Complexity, Product Location, Region, Previous Product Counterfeiting, and Product Shortage. * Using exploratory factor analysis, a model emerged with three distinct factors: Market, Product History, and Supply Chain Characteristics. * A process and a model are developed to assess the probability of drug counterfeiting. This is the first known model developed to assess the probability of drug counterfeiting. Decision makers can assess products in an objective and robust way to determine which products are of greater risk of counterfeiting, and to develop policies and strategies to mitigate or minimize counterfeit drugs in the legitimate supply chain