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Kurian, Mathew 1976. "Calibration of a microscopic traffic simulator." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9145.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2000.Includes bibliographical references (leaves 88-90).
A systematic calibration study was performed on a microscopic traffic simulator- MITSIM. An optimization based framework was developed for calibration. Car- Following model parameters were identified for calibration and experimental design methodology was used to determine the set of sensitive parameters. Calibration was performed by minimizing the deviation between the simulated and observed values of speed. Two different objective function forms were formulated for quantifying the deviation between the simulated and observed values. The search space and the optimum parameter values for the two objective function forms were compared. The effect of stochasticity in calibrating the parameter values was also studied. Stochasticity was found to have a significant impact on the optimal parameter values. It was found that though calibration is an intricate process, the performance of the simulator can be substantially improved by an appropriate calibration study.
by Matthew Kurian.
S.M.
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Sterzin, Emily D. 1979. "Modeling influencing factors in a microscopic traffic simulator." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/29398.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004.Includes bibliographical references (p. 93-95).
Microscopic traffic simulation is an important tool for traffic analysis and dynamic traffic management as it enables planners to evaluate traffic flow patterns, predict and evaluate the outcome of various response plans and assists in decision making. It is a vital tool for traffic management centers and can be helpful in developing contingency plans to enhance the safety and security of the transportation system. This thesis investigates the current state-of-the-practice in traffic microsimulation tools. A survey was developed and administered to developers. Results of the survey indicate critical gaps in including influencing external factors beyond the interaction of vehicles, such as incidents, work zones, or inclement weather, in traffic simulators. This thesis introduces a framework for incorporating such factors in existing models. The nature of the influencing factors limits disaggregate trajectory data collection generally needed to estimate driving behavior models. Therefore, an approach using aggregate calibration to refine and enhance existing driving behavior models is formulated. The aggregate calibration methodology is illustrated with a case study incorporating the effects of weather in driving behavior models using a freeway corridor in the Hampton Roads region of Virginia.
(cont.) MITSIMLab, a microscopic traffic simulation laboratory that was developed for evaluating the impacts of alternative traffic management system designs at the operational level, is used for evaluation. The presence of precipitation was found to be significant in reducing speeds in the case study and was incorporated into the driving behavior models with aggregate calibration. This methodology was found to improve the simulation results, by reducing bias and variability. Assessment of the approach is discussed and recommendations for improvement and further study are offered.
by Emily D. Sterzin.
S.M.
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Song, Xiang Ph D. Massachusetts Institute of Technology. "Scenarios discovery : robust transportation policy analysis in Singapore using microscopic traffic simulator." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82852.
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Thesis (S.M. in Transportation)--Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 99-101).
One of the main challenges of making strategic decisions in transportation is that we always face a set of possible future states due to deep uncertainty in traffic demand. This thesis focuses on exploring the application of model-based decision support techniques which characterize a set of future states that represent the vulnerabilities of the proposed policy. Vulnerabilities here are interpreted as states of the world where the proposed policy fails its performance goal or deviates significantly from the optimum policy due to deep uncertainty in the future. Based on existing literature and data mining techniques, a computational model-based approach known as scenario discovery is described and applied in an empirical problem. We investigated the application of this new approach in a case study based on a proposed transit policy implemented in Marina Bay district of Singapore. Our results showed that the scenario discovery approach performs well in finding the combinations of uncertain input variables that will result in policy failure.
by Xiang Song.
S.M.in Transportation
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Dawson, Daniel. "DEVELOPING EMERGENCY PREPAREDNESS PLANS FOR ORLANDO INTERNATIONAL AIRPORT (MCO) USING MICROSCOPIC SIMULATOR WATSIM." Master's thesis, University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2860.
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Emergency preparedness typically involves the preparation of detailed plans that can be implemented in response to a variety of possible emergencies or disruptions to the transportation system. One shortcoming of past response plans was that they were based on only rudimentary traffic analysis or in many cases none at all. With the advances in traffic simulation during the last decade, it is now possible to model many traffic problems, such as emergency management, signal control and testing of Intelligent Transportation System technologies. These problems are difficult to solve using the traditional tools, which are based on analytical methods. Therefore, emergency preparedness planning can greatly benefit from the use of micro-simulation models to evaluate the impacts of natural and man-made incidents and assess the effectiveness of various responses. This simulation based study assessed hypothetical emergency preparedness plans and what geometric and/or operational improvements need to be done in response to emergency incidents. A detailed framework outlining the model building, calibration and validation of the model using microscopic traffic simulation model WATSim (academic version) is provided. The Roadway network data consists of geometric layout of the network, number of lanes, intersection description which include the turning bays, signal timings, phasing sequence, turning movement information etc. The network in and around the OIA region is coded into WATSim with 3 main signalized intersections, 180 nodes and 235 links. The travel demand data includes the vehicle counts in each link of the network and was modeled as percentage turning count movements. After the OIA network was coded into WATSim, the road network was calibrated and validated for the peak hour mostly obtained from ADT with 8% K factor by comparing the simulated and actual link counts at 15 different key locations in the network and visual verification done. Ranges of scenarios were tested that includes security checkpoint, route diversion incase of incident in or near the airport and increasing demand on the network. Travel time, maximum queue length and delay were used as measures of effectiveness and the results tabulated. This research demonstrates the potential benefits of using microscopic simulation models when developing emergency preparedness strategies. In all 4 main Events were modeled and analyzed. In Event 1, occurrence of 15 minutes traffic incident on a section of South Access road was simulated and its impact on the network operations was studied. The averaged travel time under the incident duration to Side A was more than doubled (29 minutes, more than a 100% increase) compared to the base case and similarly that of Side B two and a half times more (23 minutes, also more than a 100% increase). The overall network performance in terms of delay was found to be 231.09 sec/veh. and baseline 198.9 sec/veh. In Event 2, two cases with and without traffic diversions were assumed and evaluated under 15 minutes traffic incident modeled at the same link and spot as in Event 1. It was assumed that information about the traffic incident was disseminated upstream of the incident 2 minutes after the incident had occurred. This scenario study demonstrated that on the average, 17% (4 minutes) to 41% (12 minutes) per vehicle of travel time savings are achieved when real-time traffic information was provided to 26% percent of the drivers diverted. The overall network performance in delay for this event was also found to improve significantly (166.92 sec/veh). These findings led to the conclusion that investment in ITS technologies that support dissemination of traffic information (such as Changeable Message Signs, Highway Advisory Radio, etc) would provide a great advantage in traffic management under emergency situations and road diversion strategies. Event 3 simulated a Security Check point. It was observed that on the average, travel times to Sides A and B was 3 and 5 minutes more respectively compared to its baseline. Averaged queue length of 650 feet and 890 feet worst case was observed. Event 4 determined when and where the network breaks down when loaded. Among 10 sets of demand created, the network appeared to be breaking down at 30% increase based on the network-wide delay and at 15% based on Level of Service (LOS). The 90% increase appeared to have the most effect on the network with a total network-wide delay close to 620 seconds per vehicle which is 3 and a half times compared to the baseline. Conclusions and future scope were provided to ensure continued safe and efficient traffic operations inside and outside the Orlando International Airport region and to support efficient and informed decision making in the face of emergency situations.M.S.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil Engineering
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Tapani, Andreas. "Traffic Simulation Modelling of Rural Roads and Driver Assistance Systems." Doctoral thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-12428.
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Microscopic traffic simulation has proven to be a useful tool for analysis of varioustraffic systems. This thesis consider microscopic traffic simulation of rural roads andthe use of traffic simulation for evaluation of driver assistance systems. A traffic simulation modelling framework for rural roads, the Rural Traffic Simulator(RuTSim), is developed. RuTSim is designed for simulation of traffic on singlecarriageway two-lane rural roads and on rural roads with separated oncoming trafficlanes. The simulated traffic may be interrupted by vehicles entering and leaving themodelled road at intersections or roundabouts. The RuTSim model is applied for analysis of rural road design alternatives.Quality-of-service effects of three alternatives for oncoming lane separation of anexisting Swedish two-lane road are analysed. In another model application, RuTSimis used to simulate traffic on a Dutch two-lane rural road. This application illustratesthat the high level of model detail of traffic micro-simulation may call for use of differentmodelling assumptions regarding driver behaviour for different applications,e. g. for simulation of traffic in different cultural regions. The use of traffic simulation for studies of driver assistance systems facilitateimpact analyses already at early stages of the system development. New and additionalrequirements are however then placed on the traffic simulation model. It isnecessary to model both the system functionality of the considered driver assistancesystem and the driver behaviour in system equipped vehicles. Such requirements canbe analysed using RuTSim. In this thesis, requirements on a traffic simulation model to be used for analysisof road safety effects of driver assistance systems are formulated and investigatedusing RuTSim. RuTSim is also applied for analyses of centre line rumble stripson two-lane roads, of an overtaking assistant and of adaptive cruise control. Thesestudies establish that the assumptions made regarding driver behaviour are crucialfor traffic simulation based analyses of driver assistance systems.
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Damay, Nicolas. "Multiple-objective optimization of traffic lightsusing a genetic algorithm and a microscopic traffic simulator." Thesis, KTH, Skolan för datavetenskap och kommunikation (CSC), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-168413.
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Given the demand for mobility in our society, the cost of building additionalinfrastructures and the increasing concerns about the sustainability of the trafficsystem, traffic managers have to come up with new tools to optimize the trafficconditions within the existing infrastructure. This study considered to optimizethe durations of the green light phases in order to improve several criteria such asthe ability of the network to deal with important demands or the total pollutantemissions. Because the modeling of the problem is difficult and computationally demanding,a stochastic micro-simulator called ’Simulation of Urban MObility’ (SUMO) has been used with a stochastic optimization process, namely a Genetic Algorithm (GA). The research objective of the study was to create a computational frameworkbased on the integration of SUMO and a Multi-Objective Genetic-Algorithm (MOGA).The proposed framework was demonstrated on a medium-size network correspondingto a part of the town of Rouen, France. This network is composed of 11 intersections,168 traffic lights and 40 possible turning movements. The network is monitored with20 sensors, spread over the network. The MOGA considered in this study is basedon NSGA-II. Several aspects have been investigated during the course of this thesis. An initial study shows that the proposed MOGA is successful in optimizing thesignal control strategies for a medium-sized network within a reasonable amount oftime. A second study has been conducted to optimize the demand-related model ofSUMO in order to ensure that the behavior in the simulated environment is close tothe real one. The study shows that a hybrid algorithm composed of a gradient searchalgorithm combined with a GA achieved a satisfactory behavior2 for a medium-sizenetwork within a reasonable time.
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Conran, Charles Arthur. "Modeling Microscopic Driver Behavior under Variable Speed Limits: A Driving Simulator and Integrated MATLAB-VISSIM Study." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/78234.
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Variable speed limits (VSL) are dynamic traffic management systems designed to increase the efficiency and safety of highways. While the macroscopic performance of VSL systems is well explored in the existing literature, there is a need to further understand the microscopic behavior of vehicles driving in VSL zones. Specifically, driver compliance to advisory VSL systems is quantified based on a driving-simulation experiment and introduced into a broader microscopic behavior model. Statistical analysis indicates that VSL compliance can be predicted based upon several VSL design parameters. The developed two-state microscopic model is calibrated to driving-simulation trajectory data. A calibrated VSL microscopic model can be utilized for new VSL control and macroscopic performance studies, adding an increased dimension of realism to simulation work. As an example, the microscopic model is implemented within VISSIM (overriding the default car-following model) and utilized for a safety-mobility performance assessment of an incident-responsive VSL control algorithm implemented in a MATLAB COM interface. Examination of the multi-objective optimization frontier reveals an inverse relationship between safety and mobility under different control algorithm parameters. Engineers are thus faced with a decision between performing multi-objective optimization and selecting a dominant VSL control objective (e.g. maximizing safety versus mobility performance).Master of Science
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Lackey, Nathan. "Simulating Autonomous Vehicles in a Microscopic Traffic Simulator to Investigate the Effects of Autonomous Vehicles on Roadway Mobility." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555072367385629.
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Janson, Olstam Johan. "A model for simulation and generation of surrounding vehicles in driving simulators." Licentiate thesis, Linköping : Linköpings universitet, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-4672.
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Olstam, Johan. "A model for simulation and generation of surrounding vehicles in driving simulators." Licentiate thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-4672.
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Driving simulators are used to conduct experiments on for example driver behavior, road design, and vehicle characteristics. The results of the experiments often depend on the traffic conditions. One example is the evaluation of cellular phones and how they affect driving behavior. It is clear that the ability to use phones when driving depends on traffic intensity and composition, and that realistic experiments in driving simulators therefore has to include surrounding traffic. This thesis describes a model that generates and simulates surrounding vehicles for a driving simulator. The proposed model generates a traffic stream, corresponding to a given target flow and simulates realistic interactions between vehicles. The model is built on established techniques for time-driven microscopic simulation of traffic and uses an approach of only simulating the closest neighborhood of the driving simulator vehicle. In our model this closest neighborhood is divided into one inner region and two outer regions. Vehicles in the inner region are simulated according to advanced behavioral models while vehicles in the outer regions are updated according to a less time-consuming model. The presented work includes a new framework for generating and simulating vehicles within a moving area. It also includes the development of enhanced models for car-following and overtaking and a simple mesoscopic traffic model. The developed model has been integrated and tested within the VTI Driving simulator III. A driving simulator experiment has been performed in order to check if the participants observe the behavior of the simulated vehicles as realistic or not. The results were promising but they also indicated that enhancements could be made. The model has also been validated on the number of vehicles that catches up with the driving simulator vehicle and vice versa. The agreement is good for active and passive catch-ups on rural roads and for passive catch-ups on freeways, but less good for active catch-ups on freeways.
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Burghout, Wilco. "Hybrid microscopic-mesoscopic traffic simulation." Doctoral thesis, KTH, Infrastruktur, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-72.
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Traffic simulation is an important tool for modelling the operations of dynamic traffic systems and helps analyse the causes and potential solutions of traffic problems such as congestion and traffic safety. Microscopic simulation models provide a detailed representation of the traffic process, which makes them most suitable for evaluation of complicated traffic facilities and Intelligent Transportation Systems that often consist of complex traffic management, safety and information systems. Macroscopic and mesoscopic models on the other hand, capture traffic dynamics in lesser detail, but are faster and easier to apply and calibrate than microscopic models. Therefore they are most suitable for modelling large networks, while microscopic models are usually applied to smaller areas. The objective of this thesis is to combine the strengths of both modelling approaches and diminish their individual weaknesses by constructing a hybrid mesoscopic-microscopic model that applies microscopic simulation to areas of specific interest, while simulating a surrounding network in lesser detail with a mesoscopic model. Earlier attempts at hybrid modelling have concentrated on integrating macroscopic and microscopic models and have proved difficult due to the large difference between the continuous-flow representation of traffic in macroscopic models and the detailed vehicle-and driver-behaviour represented in microscopic models. These problems are solved in this thesis by developing a mesoscopic vehicle-based and event-based model that avoids the (dis)aggregation problems of traffic flows at the inter-model boundaries. In addition, this thesis focuses on the general problems of consistency across the entire hybrid model. The requirements are identified that are important for a hybrid model to be consistent across the models at different levels of detail. These requirements vary from network and route-choice consistency to consistency of traffic dynamics across the boundaries of the micro- and mesoscopic submodels. An integration framework is proposed that satisfies these requirements. This integration framework has been implemented in a prototype hybrid model, MiMe, which is used to demonstrate the correctness of the solutions to the various integration issues. The hybrid model integrates MITSIMLab, a microscopic traffic simulation model, and Mezzo, the newly developed mesoscopic model. Both the hybrid model and the new Mezzo model are applied in a number of case studies, including a network in the North of Stockholm, which show their validity and applicability. The results are promising and support both the proposed integration architecture and the importance of integrating microscopic and mesoscopic models.QC 20100520
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Johansson, Fredrik. "Microscopic Simulation of Pedestrian Traffic." Doctoral thesis, Linköpings universitet, Kommunikations- och transportsystem, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-133330.
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There has recently been a renewed interest in planning for pedestrian traffic, primarily in connection to public transport interchange stations, since these are important for public transport to constitute an attractive alternative to car usage. This thesis concerns microscopic simulation of pedestrian traffic, which is a promising tool for analyzing and predicting the traffic situation in a given pedestrian facility; particularly powerful when the traffic is congested. Important applications of microscopic simulation include comparison of possible infrastructure designs such as proposed interchange stations, and evaluations of various traffic management solutions, for example information systems. The purpose of this thesis is to advance the capabilities of pedestrian microsimulation toward a level at which it can be reliably applied for quantitative analysis by practitioners in the field. The work is based on an established microscopic model of pedestrian dynamics, the Social Force Model (sfm), and the advances are made in a number of different areas. To be able to evaluate and compare simulated traffic situations suitable performance measures are needed. A set of local performance measures are proposed that quantifies the local delay rate density and estimates the discomfort perceived by the pedestrians. The sfm is extended to include waiting pedestrians through the introduction of a waiting model, demonstrated to be stable and free from oscillations. The inclusion of waiting pedestrians in the model is critical for accurate modelling of public transport interchange stations, where large groups of waiting pedestrians may hinder passing pedestrians if the design of the station is poor. The relaxation time of the adaptation to the preferred velocity is an important parameter in force based models of pedestrian traffic since it affects several behaviors of the simulated pedestrians, two of which are linear acceleration and turning movements. A comparison of observations of accelerating pedestrians reported in the literature and new observations of turning pedestrians indicates that no value of the relaxation time can give model behavior consistent with both sets of observations. This indicates that modifications of the model is needed to accurately reproduce the observed behavior. An important input to simulations is the preferred speed of the simulated pedestrians. The common assumption that the preferred speed distribution at a location does not vary during the day is tested through observations of pedestrian traffic at Stockholm Central Station. The results demonstrate that the preferred speeds are lower in the afternoon than in the morning, implying that the preferred speed should be treated as a source of uncertainty when applying pedestrian microsimulation. Finally, a sensitivity analysis of a simulation of the lower hall of Stockholm Central Station is performed to find the most important sources of uncertainty in the model predictions, given the available data. The results indicate that the uncertainty related to calibration is the largest of the considered potential error sources.
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Fowler, R. F. "Computer simulation of microscopic liquid drops." Thesis, University of Kent, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371212.
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Kunaka, Charles. "Modelling paratransit services : a microscopic simulation approach." Thesis, University College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243829.
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Paratransit operations in cities in developing countries play an important role in public transport provision. The operations are run within the realm of the infonnal sector and are highly flexible. There are numerous operators running one or two vehicles on a cash basis. This and other issues contribute to the problems with the services that are provided. Poor reliability and stability in supply are the main problems. Despite these serious problems, there has been little research on possible solutions to resolve them. The present study is aimed at improving understanding of the operation of such systems. It assesses the effects on users and operators of different routing, stopping and scheduling regimes. A new model of paratransit operations is developed. The problem of paratransit operations is conceptualised in terms of interactions between demand and supply. The interactions take place in time and geographical space and are shaped by the actions taken by individual users and individual vehicle operators. The model is designed to overcome some of the restrictions on the definitions of time - and in particular space - that are found in existing methodologies. A modelling approach designed to represent the two dimensions as realistically as possible was adopted. Two techniques are central to the construction of the model. Simulation techniques are used to model the temporal processes and a Geographical Information System (GIS) for the spatial processes. The two are complementary to overcome the inherent weaknesses in either approach. Modules are developed to represent demand and supply at a microscopic level. The Model of Paratransit Services (MOPS) involves interfacing a GIS and external modules for dynamic processes. The model was validated against field data collected in Harare, Zimbabwe. Experiments were run for a case study area and the results that were obtained on routing, stopping and scheduling regimes are reported in developing countries.
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Mahanti, Bhanu Prasad 1981. "Aggregate calibration of microscopic traffic simulation models." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28636.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004.Includes bibliographical references (p. 97-101).
The problem of calibration of microscopic simulation models with aggregate data has received significant attention in recent years. But day-to-day variability in inputs such as travel demand has not been considered. In this thesis, a general formulation has been proposed for the problem in the presence of multiple days of data. The formulation considers the day-to-day variability in all the inputs to the simulation model. It has then been formulated using Generalized least squares (GLS) approach. The solution methodology for this problem has been proposed and the feasibility of this methodology has been shown with the help of two case studies. One of them is with an experimental network and the other is with network from Southampton, UK. The results indicate that estimation of day-to-day OD flows is feasible. They also reinforce the importance of having good apriori information on the OD flows and locating the sensors so as to obtain maximum information.
by Bhanu Prasad Mahanti.
S.M.
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Johansson, Fredrik. "Microscopic Modeling and Simulation of Pedestrian Traffic." Licentiate thesis, Linköpings universitet, Kommunikations- och transportsystem, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-101085.
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Walking is an environmentally friendly and important mode of transportation. It constitutes the first and last part of almost any trip, regardless of what the main mode of transport is, and is especially important in connection to public transport trips. When designing public transport stations, and similar facilities with large and varying volumes of pedestrian traffic, it is advantageous to be able to predict the traffic conditions at the facility before it is built; discovering too late that the traffic at the facility is inefficient and perceived as uncomfortable may be very costly. To make these predictions we need accurate quantitative models of pedestrian traffic. The foundation of this thesis is the development of a microsimulation platform for pedestrian traffic, the Pedestrian Traffic Simulation Platform (FTSP). The platform is based on the Social Force Model (SFM) and intended for evaluation of proposed designs of pedestrian facilities. A contribution of this thesis is a thorough documentation of the implementation of the FTSP. An extensive literature review of previous research on the SFM revealed gaps in the methodology used to study the properties of the SFM and to interpret its results. This thesis proposes local performance measures to fill this gap. These measures are based on properties of the SFM, and enable quantitative analyses of the quality of service at pedestrian facilities. The proposed measures are applied to the simulation results of some basic scenarios, which reveal previously unknown properties of the SFM. These properties can be used to test the accuracy of the SFM. Another gap in the literature was how to include waiting behavior in the SFM. This thesis shows that accurate modeling of waiting pedestrians is important for the accuracy of the simulation results, and proposes three different extensions to the SFM to model waiting behavior.
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Yeh, Chun hung. "Diffusion Microscopist Simulator - The Development and Application of a Monte Carlo Simulation System for Diffusion MRI." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00660279.
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Diffusion magnetic resonance imaging (dMRI) has made a significant breakthrough in neurological disorders and brain research thanks to its exquisite sensitivity to tissue cytoarchitecture. However, as the water diffusion process in neuronal tissues is a complex biophysical phenomena at molecular scale, it is difficult to infer tissue microscopic characteristics on a voxel scale from dMRI data. The major methodological contribution of this thesis is the development of an integrated and generic Monte Carlo simulation framework, 'Diffusion Microscopist Simulator' (DMS), which has the capacity to create 3D biological tissue models of various shapes and properties, as well as to synthesize dMRI data for a large variety of MRI methods, pulse sequence design and parameters. DMS aims at bridging the gap between the elementary diffusion processes occurring at a micrometric scale and the resulting diffusion signal measured at millimetric scale, providing better insights into the features observed in dMRI, as well as offering ground-truth information for optimization and validation of dMRI acquisition protocols for different applications.We have verified the performance and validity of DMS through various benchmark experiments, and applied to address particular research topics in dMRI. Based on DMS, there are two major application contributions in this thesis. First, we use DMS to investigate the impact of finite diffusion gradient pulse duration (delta) on fibre orientation estimation in dMRI. We propose that current practice of using long delta, which is enforced by the hardware limitation of clinical MRI scanners, is actually beneficial for mapping fibre orientations, even though it violates the underlying assumption made in q-space theory. Second, we employ DMS to investigate the feasibility of estimating axon radius using a clinical MRI system. The results suggest that the algorithm for mapping the direct microstructures is applicable to dMRI data acquired from standard MRI scanners.
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Narangifard, Ali. "The multislice method in transmission electron microscopy simulation : An implementation in the TEM-simulator software package." Thesis, KTH, Skolan för teknik och hälsa (STH), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-134189.
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This report introduces the multislice method for modeling the interaction between an electron and the atoms in the specimen (electron-specimen interaction). The multislice method is an approximation to the full quantum mechanical model for this interaction. After introducing the theory, we discuss how the multislice method is implemented and integrated into TEM-simulator, a software for simulation of Transmission Electron Microscope (TEM) images.
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Williams, M. L. "Computer simulation of liquids inside microscopic spherical cavities." Thesis, University of Kent, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378359.
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Turley, Carole. "Calibration Procedure for a Microscopic Traffic Simulation Model." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1747.pdf.
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Yang, Qi 1963. "A microscopic traffic simulation model for IVHS applications." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12177.
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Askerud, Caroline, and Sara Wall. "Evaluation of bus terminals using microscopic traffic simulation." Thesis, Linköpings universitet, Kommunikations- och transportsystem, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-139028.
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Traffic simulation is a safe and efficient tool to investigate infrastructural changes as well as traffic conditions. This master thesis aims to analyse a microscopic traffic simulation method for evaluation of bus terminal capacity. The evaluation is performed by investigating a case study of the bus terminal at Norrköping travel centre. The analysed method, referred to as terminal logic in the thesis, uses a combination of time based and event based simulation. Through the combination of time and event, it is possible to capture all movements within the terminal for individual vehicles. The simulation model is built in the software Vissim. A new travel centre for Norrköping is under development. Among the reasons for a new travel centre is the railway project Ostlänken in the eastern part of Sweden. An evaluation of the bus terminal is interesting due to a suspicion of overcapacity and the opportunity of redesigning. To investigate both the terminal capacity and the terminal logic, three scenarios were implemented. Scenario 1: Current design and frequency Scenario 2: Current design with higher frequency Scenario 3: Decreased number of bus stops with current frequency The results from the scenarios confirm the assumption of overcapacity. The capacity was evaluated based on several different measures, all indicating a low utilization. Even so, the utilization was uneven over time and congestion could still occur when several buses departed at the same time. This was also seen when studying the simulation, which showed congestions when several buses departed at the same time. The case study established the terminal logic to be useful when evaluating capacity at bus terminals. It provides a good understanding of how the terminal operates and captures the movements. However, it was time-consuming to adjust the logic to the studied terminal. This is a disadvantage when investigating more than one alternative. The thesis resulted in two main conclusions. Firstly, a more optimised planning of the buses at Norrköping bus terminal would probably be achievable and lead to less congestions at the exits. Secondly, the terminal logic is a good method to use when evaluating bus terminals but it is not straight forward to implement.
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Wolinski, David. "Microscopic crowd simulation : evaluation and development of algorithms." Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1S036/document.
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Dû au grand intérêt porté à la simulation de foules, beaucoup d'algorithmes ont été et sont encore proposés. Toutefois, (1) il n'existe pas de méthode standard pour évaluer le réalisme et la flexibilité de ces algorithmes, et (2) même les algorithmes les plus récents produisent encore des artéfacts évidents. Abordant la première question, nous proposons une méthode visant à évaluer le réalisme des algorithmes de simulation de foules d'une manière objective et impartiale. ''Objective'' grâce à des métriques quantifiant la similitude entre les simulations et des données acquises en situation réelle. ''Impartiale'' grâce à l'estimation de paramètres permettant d'étalonner automatiquement les algorithmes en vue de décrire au mieux les données (par rapport aux métriques), permettant de comparer les algorithmes au mieux de leur capacité. Nous explorons aussi comment ce processus permet d'augmenter le niveau de contrôle d'un utilisateur sur la simulation tout en réduisant son implication. Abordant la deuxième question, nous proposons un nouvel algorithme d'évitement de collisions. Alors que les algorithmes existants prédisent les collisions en extrapolant linéairement les trajectoires des agents, nous allons au-delà grâce à une approche probabiliste et non-linéaire, prenant en compte entre autres la configuration de l'environnement, les trajectoires passées et les interactions avec les obstacles. Nous éliminons ainsi des simulations résultantes des artefacts tels que : les ralentissements et les agglomérats dérangeants d'agents, les mouvements oscillatoires non naturels, ou encore les manœuvres d'évitement exagérées/fausses/de dernière minute. Dans une troisième contribution, nous abordons aussi l'utilisation de notre travail sur l'évaluation et l'estimation de paramètres dans le cadre de systèmes plus larges. Dans un premier temps, nous l'appliquons à la simulation d'insectes, prenant en charge leur comportement local. Après avoir complété le système aux niveaux intermédiaire et global, cette approche basée-données est capable de simuler correctement des essaims d'insectes. Dans un second temps, nous appliquons notre travail au suivi de piétons, construisant un ''méta-algorithme'' servant à calculer la probabilité de transition d'un filtre particulaire, et surpassant les systèmes existantsWith the considerable attention crowd simulation has received, many algorithms have been and are being proposed. Yet, (1) there exists no standard scheme to evaluate the accuracy and flexibility of these algorithms, and (2) even the most recent algorithms produce noticeable simulation artifacts. Addressing the first issue, we propose a framework aiming to provide an objective and fair evaluation of the realism of crowd simulation algorithms. ''Objective'' here means the use of various metrics quantifying the similarity between simulations and ground-truth data acquired with real pedestrians. ''Fair'' here means the use of parameter estimation to automatically tune the tested algorithms to match the ground-truth data as closely as possible (with respect to the metrics), effectively allowing to compare algorithms at the best of their capability. We also explore how this process can increase a user's control on the simulation while reducing the amount of necessary intervention. Addressing the second issue, we propose a new collision-avoidance algorithm. Where current algorithms predict collisions by linearly extrapolating agents' trajectories, we better predict agents' future motions in a probabilistic, non-linear way, taking into account environment layout, agent's past trajectories and interactions with other obstacles among other cues. Resulting simulations do away with common artifacts such as: slowdowns and visually erroneous agent agglutinations, unnatural oscillation motions, or exaggerated/last-minute/false-positive avoidance manoeuvres. In a third contribution, we also explore how evaluation and parameter estimation can be used as part of wider systems. First, we apply it to insect simulation, taking care of local insect behavior. After completing it at the intermediate and global levels, the resulting data-driven system is able to correctly simulate insect swarms. Second, we apply our work to pedestrian tracking, constructing a ''meta-algorithm'', more accurately computing motion priors for a particle-filter-based tracker, outperforming existing systems
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Nezamuddin, Nezamuddin. "DEVELOPING MICROSCOPIC TOLL PLAZA MODEL USING PARAMICS." Master's thesis, University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2867.
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Simulation modeling is the most cost-effective way of studying real life transportation problems, either existing or anticipated, without disturbing the balance of the transportation system. There is a vast suite of simulation models available in market, ready to choose from macroscopic, mesoscopic, or microscopic in nature, to study different transportation system elements like freeways, highways, signalized and un-signalized intersections. However, most of these network simulation models, like PARAMICS, VISSIM, CORSIM … etc, do not come readily available with built in toll plaza models. On the other hand, many researchers have independently developed toll plaza models, which can only model an isolated toll plaza without the road network. These toll plaza models, which are based on queuing theory (and some are macroscopic in nature), do not take into account headway, gap acceptance, or inter-vehicle interaction to follow a lead car or to perform lane changing maneuvers. Vehicles just upstream of the toll plaza are assigned to one of the toll lanes, solely based on the payment method (manual, automatic coin machine, or electronic toll collection) and queue lengths at the toll lanes. For instance, if a vehicle is traveling in the leftmost lane and the rightmost toll lane has the shortest queue length, then the queuing model will assign this vehicle to the rightmost lane, and the vehicle will do unrealistic maneuvering to reach to the assigned toll lane instantly. Microscopic network simulation models simulate the vehicular movements based on lane-changing and car-following rules. If such a model could be customized to serve the purpose of the toll plaza simulation, it will simulate the vehicular movements just upstream and downstream of the toll plaza more realistically. Being a network simulation model, it can also model the road network integrated with the plaza, which can be used to study the entire toll road corridor, unlike the isolated toll plaza models. In addition to being a microscopic network simulation model, PARAMICS has many simulation tools, which can be customized to develop a network model with enhanced toll plaza simulation capabilities. PARAMICS also provides the flexibility of using an aerial picture of the toll plaza and upstream/downstream sections of the road as overlay, to ensure that the toll plaza model operates under similar geometric conditions as the real plaza. Using an overlay, exact details of the transition area can be fed into the model. In real life, there is a smooth transition (in terms of the number of lanes and the width of the roadway) from the uniform free-flowing section of the roadway to the toll plaza. Detailed representation of the transition area, in terms of geometry and curb of the roadway along with the number of lanes, is essential for a realistic toll plaza simulation. This kind of detail is not available in a queuing model. As the roadway approaches the toll plaza, it contains more lanes compared to its upstream segments. However, in a simulation model vehicles have a tendency to maintain the same old lanes, and the newly added lanes remain unoccupied by the vehicles. Next-lane Allocation feature in PARAMICS can be used to map upstream lanes onto downstream lanes, preventing this unrealistic behavior from occurring in the simulation model. It tells the vehicles in a particular upstream lane to choose from one or more of the downstream lanes as per the settings. Next-lane allocation can be used in such a manner that all the downstream lanes are utilized. PARAMICS has several other tools such as Restrictions Manager, Vehicle Type Manager, Lane-choices Rules, HOV Lanes, and Vehicle Actuated (VA) Signals which can be used in combination to build a toll plaza model. A microscopic 'Holland East Plaza - SR408' network model has been developed using PARAMICS V5.1. This model contains the plaza and the downstream section of SR 408 Westbound till I-4 interchange in downtown Orlando. This model has been successfully calibrated and validated for the mainline toll plaza and ramp volumes for year 2004. Several hypothetical incident scenarios were simulated to study an entire corridor from the toll plaza to Interstate 4. It was found that the volumes on I-4 off-ramp and SR 408 mainline were affected the most under incident conditions. Volumes for other ramps were not affected in the same proportions. An incident on mainline toll road affected the throughput of the plaza significantly, but the same is not true for an incident on an off-ramp. Travel times to I-4 off-ramps and SR 408 thru lanes were the most sensitive in each of the incident scenarios. In case of the elimination of tolls during the hurricane evacuation, the throughput of the plaza increased significantly. Travel times for the vehicles coming through the plaza and going to different destinations decreased significantly, while it increased for vehicles using on-ramps, because of their inability to merge in the mainline traffic due to the increased toll road volume. The developed model in this thesis has the potential of transportation network wide applications with multiple toll plazas.M.S.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil Engineering
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Chakraborty, Subhrakanti Chakraborty. "Spectroscopic, microscopic and molecular simulation studies of faujasitic zeolites." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471628140.
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Anwar, Zubair. "Enabling microscopic simulators to perform system-level analysis of viscoelastic flows." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/42943.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 249-261).
State-of-the-art methods for simulating viscoelastic flows couple the conservation equations for mass and momentum with a model from kinetic theory that describes the microstructural state of the polymer. Introduction of appropriate numerical discretization and boundary conditions for these equations leads to a hybrid simulation for studying the dynamic behavior of polymeric liquids in complex geometries. This approach represents a rare example of a successful multiscale solution of a physical problem, as it allows investigation of arbitrary models of kinetic theory. The simulations, however, are not amenable to standard numerical techniques for system-level stability, bifurcation, and control analysis as this requires closed form equations. These simulation either use stochastic descriptions for the polymer microstructure that cannot be reduced to closed form, or involve equations for the evolution of a distribution of polymer conformations, which can only be written in closed form by invoking mathematical closure approximations that can have a significant qualitative impact on the predictive ability of these simulations. The focus of this thesis was to develop a novel numerical method that can enable hybrid simulations to perform system-level analysis of polymeric flows. This numerical approach has been applied directly to kinetic theory models and hybrid simulations to obtain stationary states and associated bifurcations and stability information. The method is general in its applicability in that it treats kinetic theory models and hybrid simulations as black boxes that are then used to obtain system-level information without any modification. The methods developed here are illustrated in a variety of problems.
(cont) Steady state results have been obtained for the non-interacting rigid dumbbell model in steady shear, and for the free-draining bead-spring chain model in both steady shear and uniaxial elongation that are in excellent agreement with previous studies and steady state computed from direct integration. The method is also applied to a hybrid simulation for the pressure-driven flow of non-interacting rigid dumbbells in a planar channel with a linear array of equally spaced cylinders. The computed steady state is in agreement with direct integration and qualitatively matches previous computations with closed models. Bifurcation analysis has been performed for the Doi model at equilibrium with the Onsager excluded volume potential. This analysis agrees with previous studies and accurately predicts the isotropic-nematic transition and turning point for the unstable to stable transition on the prolate solution branch. Bifurcation analysis has also been performed for the Doi model in the weak shear flow limit for the Maier-Saupe excluded volume potential. It is found that stable stationary solutions are lost at a limit point beyond which time-periodic tumbling orbits are the only stable solution. This transition occurs via an infinite period global bifurcation, while the limit point approaches a threshold value as the shear rate approaches zero. This result matches a recently published scaling analysis and demonstrates the ability of the method to provide general bifurcation analysis of kinetic theory models. Stability analysis of the fiber-spinning process for polymeric fluids has also been performed by using a hybrid simulation that couples the one-dimensional conservation equations for mass and momentum with a stochastic description for the configuration fields of the Hookean dumbbell model. The steady-state velocity profiles are in good agreement with previous studies with the Oldroyd-B model.
(cont) The analysis predicts onset of the draw resonance instability via a Hopf bifurcation and subsequent stabilization via second Hopf bifurcation in draw ratio parameter space. This result is in good agreement with experimentally observed behavior during polymer fiber-spinning.
by Zubair Anwar.
Ph.D.
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Holbrook, Owen. "Simulation of energy filtered electron microscopy." Thesis, University of Bath, 1998. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266475.
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Sultan, Beshr. "The study of motorway operation using a microscopic simulation model." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322018.
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Morgan, Daniel J. (Daniel John) 1977. "A microscopic simulation laboratory for advanced public transportation system evaluation." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/84807.
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Wang, Tianjiao. "Study of pedestrian-vehicle interaction behaviour by microscopic simulation modelling." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/348871/.
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Walking is healthy, environmentally beneficial and sustainable to human society. Travellers increasingly are being encouraged to walk more. However, pedestrians’ interaction with motorised vehicles is a major constraint to their movement. Many innovative treatments have been developed to balance the two modes. Proper methods are required to evaluate and compare performances of different treatments to support decision making. Micro-simulation is a useful supplementary tool for such evaluation and comparison studies for its cost-effectiveness and non-intrusiveness. However, there is a significant gap between capabilities of existing simulation models and practical needs. New understandings of the Pedestrian-Vehicle Interaction (PVI) behaviour and corresponding micro-simulation models are required to conduct micro-simulation studies of the interaction process between the two modes to derive new knowledge of the mixed traffic. This dissertation presents the development and application of a micro-simulation model, PVISIM (Pedestrian-Vehicle Interaction SIMulation), to study PVI behaviour in a range of circumstances in an urban street environment. Key contributions relate to the collection of a substantial data base, development and validation of the model, an appreciation of the value of the approach and new understandings of PVI behaviour. A series of studies to measure behaviour based on the data collected in Beijing, China have been detailed. Intra vehicle and pedestrian behaviour models were developed and validated separately, incorporating the best available understandings from existing published studies and in accordance with the specific local data. The two modes were integrated by interpreting new findings from the study of microscopic interaction behaviour of the two modes. The complete model was validated against field data independent of those used in model development, covering a number of typical scenarios, including both unsignalised and signalised situations. The validated model was applied to study a typical unsignalised scenario by analysing system performances under different combinations of vehicular traffic and pedestrian crossing demand, in terms of efficiency, safety and environmental impact. Also, operations of different treatments including no-control, Zebra crossing, fixed-time signal crossing and Puffin crossing at two typical types of locations were compared. Interpretations and recommendations were given for each application. The results can be used to supplement existing guidelines for pedestrian related problems, and also contribute to the knowledge base to incorporate pedestrians into current micro-simulation tools in a more realistic way.
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Kang, Wei. "Molecular dynamics simulations and microscopic hydrodynamics of nanoscale liquid structures." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22597.
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Thesis (Ph. D.)--Physics, Georgia Institute of Technology, 2008.Committee Chair: Landman, Uzi; Committee Member: Chou, Mei-Yin; Committee Member: Gao, Jianping; Committee Member: Glezer, Ari; Committee Member: Luedtke, W. D.
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Hui, Hui. "Contribution to a Simulator of Arrays of Atomic Force Microscopes." Thesis, Besançon, 2013. http://www.theses.fr/2013BESA2031/document.
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Dans cette thèse, nous établissons un modèle à deux échelles à la fois pour desmatrices de cantilevers unidimensionnels et bidimensionnels en régime de fonctionnementélastodynamique avec des applications possibles aux réseaux de microscopesà force atomique (AFM). Son élaboration est basée sur une analyseasymptotique pour les structures minces élastiques, une approximation à deuxéchelles et une mise à l’échelle utilisée pour l’homogénéisation des milieux fortementhétérogènes. Nous complétons la théorie de l’approximation à deux échellespour les problèmes aux limites du quatrième ordre posés dans des domaines mincespériodiques connexes seulement dans certaines directions. Notre modèle reproduitla dynamique globale du support ainsi que les mouvements locaux des cantilevers.Pour simplifier la suite du travail, nous concentrons nos travaux à l’étude de matricesde leviers constituées de lignes découplées en régime dynamique. Comme lesupport des leviers est élastique, l’effet du couplage entre levier est pris en compte.La vérification du modèle est soigneusement réalisée. Nous montrons que chaquemode propre peut être décomposé en produits d’un mode de base avec un modede levier. Nous présentons une méthode de discrétisation du modèle et effectuonssa vérification numérique en la comparant avec des résultats de simulation paréléments finis du problème d’élasticité tridimensionnel. Par ailleurs, nous avonsélaboré de nouveaux outils d’aide à la conception de réseaux d’AFM. Une boîte àoutils d’optimisation robuste est interfacée avec le modèle permettant d’optimiserun design avant micro-Fabrication. Un algorithme d’estimation de l’état statiquecombinant la mesure de déplacements mécaniques par interférométrie et le modèlea été introduit. Nous avons également synthétisé un régulateur quadratiquelinéaire (LQR) pour un réseau de cantilevers en mode dynamique comprenant actionneurset capteurs régulièrement espacées. Dans le but de mettre en oeuvre lecontrôle en temps réel, nous proposons une approximation semi-Décentralisée quipeut être réalisé par un circuit électronique distribué analogique. Plus précisément,notre processeur analogique peut être réalisé par un réseau périodique derésistances (PNR). La méthode d’approximation de commande est basée sur deuxconcepts généraux, à savoir sur un calcul fonctionnel (c’est-À-Dire des fonctionsd’opérateurs) et sur la formule de représentation d’une fonction d’opérateur deDunford-Schwartz. Cette méthode d’approximation est étendue pour la résolutiond’un problème de filtrage optimal robuste de type H∞ de la dynamique d’un réseaude leviers couplés avec sources aléatoires de bruitIn this dissertation, we establish a two-Scale model both for one-Dimensionaland two-Dimensional Cantilever Arrays in elastodynamic operating regime withpossible applications to Atomic Force Microscope (AFM) Arrays. Its derivationis based on an asymptotic analysis for thin elastic structures, a two-Scale approximationand a scaling used for strongly heterogeneous media homogenization. Wecomplete the theory of two-Scale approximation for fourth order boundary valueproblems posed in thin periodic domains connected in some directions only. Ourmodel reproduces the global dynamics as well as each of the cantilever motion. Forthe sake of simplicity, we present a simplified model of mechanical behavior of largecantilever arrays with decoupled rows in the dynamic operating regime. Since thesupporting bases are assumed to be elastic, cross-Talk effect between cantileversis taken into account. The verification of the model is carefully conducted. Weexplain not only how each eigenmode is decomposed into products of a base modewith a cantilever mode but also the method used for its discretization, and reportresults of its numerical validation with full three-Dimensional Finite Element simulations.We show new tools developed for Arrays of Microsystems and especiallyfor AFM array design. A robust optimization toolbox is interfaced to aid for designbefore the microfabrication process. A model based algorithm of static stateestimation using measurement of mechanical displacements by interferometry ispresented. We also synthesize a controller based on Linear Quadratic Regulator(LQR) methodology for a one-Dimensional cantilever array with regularly spacedactuators and sensors. With the purpose of implementing the control in real time,we propose a semi-Decentralized approximation that may be realized by an analogdistributed electronic circuit. More precisely, our analog processor is made by PeriodicNetwork of Resistances (PNR). The control approximation method is basedon two general concepts, namely on functions of operators and on the Dunford-Schwartz representation formula. This approximation method is extended to solvea robust H∞ filtering problem of the coupled cantilevers for time-Invariant systemwith random noise effects
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Belaidi, Sophie. "Microscopie à force électrostatique : étude fondamentale et simulation numérique." Montpellier 2, 1997. http://www.theses.fr/1997MON20222.
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Cette these presente, tout d'abord, les resultats issus d'un modele numerique : le modele des charges equivalentes pour calculer la force electrostatique s'appliquant sur une pointe de microscope a force atomique. Ce modele nous permet de determiner les limites des approximations habituellement utilisees pour le cas d'une pointe conductrice en face d'un plan conducteur. Puis, nous determinons l'importance des differents composants du capteur en mode resonant et statique. Plus particulierement, nous montrons, en accord avec l'experience, l'effet predominant du levier pour de grandes distances pointe - echantillon et determinons les moyens de corriger ce phenomene. Enfin, au moyen de la methode des charges equivalentes et de celle des elements finis, nous simulons le balayage au-dessus de surfaces comportant diverses heterogeneites electriques et topographiques. Ces simulations nous permettent d'etablir des relations existant entre la resolution spatiale, les caracteristiques geometriques de la pointe et la distance pointe - echantillon en microscopie a force electrostatique.
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Soyez, Thomas. "Étude du glissement des dislocations dans le zirconium." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP053.
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Les alliages de zirconium sont utilisés dans l’industrie nucléaire pour la fabrication des assemblages combustibles (tube guides, gaines et grilles). Afin de correctement prédire le comportement de ces alliages au cours de leur utilisation, il est nécessaire de connaître leur comportement mécanique. La déformation des métaux s’effectue généralement par glissement des dislocations et par maclage. Le zirconium présentant une structure hexagonale compacte, le développement de la déformation plastique est anisotrope. Pour une sollicitation suivant la direction du cristal, le mode de déformation principal correspondant au glissement de dislocations de vecteur de Burgers ne permet pas d’accommoder la déformation et le glissement de dislocations à vecteur de Burgers ou le maclage doit s’activer. Cette thèse a pour but d’étudier les propriétés de ces dislocations en se basant sur deux approches complémentaires, des observations en microscopie électronique à transmission (MET) et des simulations atomiques.Les observations MET ont permis de mettre en évidence le système de glissement des dislocations : ces dernières ne glissent que dans des plans pyramidaux de première espèce. Le glissement dévié est fréquemment observé entre plans pyramidaux de première espèce. Les dislocations apparaissent rectilignes et orientées préférentiellement dans leur orientation , soit l’intersection entre le plan de glissement et le plan de base. Lors d’essais de traction in situ en MET, le glissement de ces dislocations a été observé et un glissement plus difficile de la dislocation dans son orientation a été démontré. Deux types de glissement ont été observés : un glissement rigide où la dislocation avance en bloc dans son plan de glissement et un glissement visqueux des segments conduisant à la création de macro décrochements.Les simulations atomiques ont permis d’expliquer le glissement dans le plan pyramidal de première espèce via une étude des fautes d’empilement dans les plans possibles de glissement et via la détermination de la structure de cœur de la dislocation vis dans son état fondamental. Cette structure est pilotée par une dissociation en deux partielles non équivalentes dans le plan pyramidal de première espèce. L’étude de l’évolution de la structure de cœur dans son état fondamental sous une contrainte appliquée met en évidence une contrainte de Peierls différente en fonction du sens de la contrainte et démontre un glissement difficile de la dislocation avec une contrainte de Peierls trente fois plus élevée que celle nécessaire pour le glissement de la dislocation . L’activation thermique est donc nécessaire pour permettre à la dislocation vis d’avancer. En température, un glissement par germination de double décrochements a été observé dans des simulations de dynamique moléculaire et a été décrit par une loi thermiquement activée. La dislocation alignée dans une direction présente, quant à elle, une structure non planaire, se dissociant dans son plan de glissement pyramidal, mais également dans un second plan. La nature de ce second plan de dissociation, basal ou prismatique, varie avec le modèle énergétique choisiZirconium alloys are used in the nuclear industry as fuel cladding tubes and structural components of the fuel assemblies. In order to properly predict the mechanical behavior of those alloys throughout their usage time, it is necessary to understand the physical mechanisms controlling plasticity. Deformation in metals is usually accommodated by dislocation glide and twinning. Zirconium has a hexagonal close packed structure and its plastic deformation is anisotropic. For a mechanical loading along the axis of the crystal, the principal deformation mode corresponding to dislocation glide cannot accommodate the deformation and dislocation glide and twinning have to be activated. This thesis aims to study properties of dislocations based on two complementary approaches, Transmission Electron Microscopy (TEM) observations and atomic simulations.TEM observations underlined the glide system of the dislocations, which exclusively glide in first order pyramidal planes even, with cross slip between different first order pyramidal planes being activated at room temperature. dislocations appear rectilinear, with a preferential orientation along the direction which is the intersection between the glide plane and the basal plane. TEM in situ tensile test experiments show that this orientation glide with difficulty. Two types of glide mechanism were observed: a rigid motion where the dislocation keeps its shape while gliding and a viscous motion of these segments leading to the creation of macro-kinks.Atomic simulations rationalize the glide of dislocations in first order pyramidal plane with the existence of stacking faults in the possible glide planes and with a ground state structure of the screw dislocation which dissociates in two non-equivalent partial dislocations in a first order pyramidal plane. The evolution of this structure under an applied stress allowed to obtain the Peierls stress which depends on the direction of the applied stress and underlined a difficult glide: the Peierls stress of this screw dislocation is thirty times greater than the one of the dislocation. Thermal activation appears therefore necessary for dislocation glide. Molecular dynamics simulations evidence a glide of the screw dislocation operating by double kinks nucleation. The structure of the dislocation oriented in its direction is dissociated in its glide plane, i.e. a first order pyramidal plane, and also a secondary plane whose nature varies with the energetic model. This secondary dissociation is expected to explain the difficult glide of this orientation
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Huang, Zhen. "Dynamic Emission Prediction Platform and It's Integration with Microscopic Traffic Simulation." Thesis, Uppsala University, Department of Information Technology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-108012.
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With the increase of traffic congestion and vehicle emission, environmental pollutionbecomes an important concern for traffic policy makers and traffic planners in theirdecision-making process. In order to study and reduce road transport emissions, anaccurate estimation of emission amount is crucial for traffic planning and management purposes.
The emission value from the traffic on a given road section depends strongly on thestate of vehicles. The basis for a detailed estimation is therefore the emit rate as afunction of instantaneous vehicle state such as speed, acceleration etc.
In this thesis, an application is built by integrating emission simulation with the trafficsimulator at KTH-TPMA, which is a real time application for imitating real trafficsituations, to predict emission value. The approach adopted is based on vehicle datafrom traffic simulations which serve as real world traffic data provider. With thisapplication, traffic simulation and emission simulation could be executed with adistributed computing approach. The thesis investigates how these twosimulations are implemented in a computer simulation system and theirperformance and accuracy.
The major contribution of this thesis is its integrating traffic simulation with emissionsimulation to estimate reasonable emission values. It illustrates how these twosimulation applications could be integrated to provide a tool for making policy andplanning.
Key Words: Emission Model Simulation, Traffic Simulator (KTH-TPMA), Distributedcomputing, CORBA and Web Service.
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Kim, Seung-Jun. "Simultaneous calibration of a microscopic traffic simulation model and OD matrix." Texas A&M University, 2006. http://hdl.handle.net/1969.1/4409.
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With the recent widespread deployment of intelligent transportation systems
(ITS) in North America there is an abundance of data on traffic systems and thus an
opportunity to use these data in the calibration of microscopic traffic simulation models.
Even though ITS data have been utilized to some extent in the calibration of microscopic
traffic simulation models, efforts have focused on improving the quality of the
calibration based on aggregate form of ITS data rather than disaggregate data.
In addition, researchers have focused on identifying the parameters associated
with car-following and lane-changing behavior models and their impacts on overall
calibration performance. Therefore, the estimation of the Origin-Destination (OD)
matrix has been considered as a preliminary step rather than as a stage that can be
included in the calibration process.
This research develops a methodology to calibrate the OD matrix jointly with
model behavior parameters using a bi-level calibration framework. The upper level seeks
to identify the best model parameters using a genetic algorithm (GA). In this level, a
statistically based calibration objective function is introduced to account for disaggregate
form of ITS data in the calibration of microscopic traffic simulation models and, thus,
accurately replicate dynamics of observed traffic conditions. Specifically, the
Kolmogorov-Smirnov test is used to measure the "consistency" between the observed
and simulated travel time distributions. The calibration of the OD matrix is performed in
the lower level, where observed and simulated travel times are incorporated into the OD
estimator for the calibration of the OD matrix. The interdependent relationship between travel time information and the OD matrix is formulated using a Extended Kalman filter
(EKF) algorithm, which is selected to quantify the nonlinear dependence of the
simulation results (travel time) on the OD matrix.
The two test sites are from an urban arterial and a freeway in Houston, Texas.
The VISSIM model was used to evaluate the proposed methodologies. It was found that
that the accuracy of the calibration can be improved by using disaggregated data and by
considering both driver behavior parameters and demand.
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Cottman, Nicholas James. "Modelling the impacts of intelligent transport systems using microscopic traffic simulation /." [St. Lucia. Qld.], 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17339.pdf.
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Li, Lian, and 李煉. "Microscopic study and numerical simulation of the failure process of granite." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31242005.
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Zheng, Pengjun. "A microscopic simulation model of merging operation at motorway on ramps." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289589.
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Anvari, Bani. "A new microscopic model for the simulation of shared space schemes." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/33123.
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Shared space is an innovative streetscape design which seeks minimum separation between vehicle traffic and pedestrians. Urban design is moving towards space sharing as a means of increasing the community texture of street surroundings. Its unique features aim to balance priorities and allow cars and pedestrians to co-exist harmoniously without the need to dictate behaviour. There is, however, a need for a simulation tool to model future shared space schemes and to help judge if they might represent suitable alternatives to traditional street layouts. This thesis presents a microscopic mathematical model to simulate pedestrians and 4-wheeled motorised vehicles in shared space schemes. The complete development of the model is addressed: mathematical formulation of three interrelated layers based on the Social Force Model (SFM), software implementation, calibration and validation using the case studies from New Road (Brighton) and Exhibition Road (London). Microscopic pedestrian, vehicle and mixed traffic models are reviewed and evaluated with respect to their ability to reproduce behavioural phenomena, resulting in the SFM being adopted as the most suitable basis for this thesis. The behavioural patterns of shared space users are analysed to identify specific manoeuvres that need consideration. These patterns are realised in a three-layer model: The first layer introduces the flood fill algorithm to define intermediate destinations for agent's path around obstacles to the final destination. The second layer explains how the SFM is modified for pedestrians and vehicles. The third layer describes conflict avoidance with minimal change of speed and direction. The new mathematical model is calibrated and validated according to defined performance indicators using real data from the two case study sites. The results show that this model is suitable to simulate shared space users but that the physical parameters depend on how a shared space scheme is realised compared to the original philosophy. The achievements of this thesis can be beneficial to urban planners and councils considering the implementation of a new shared space scheme.
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Machumu, Kelvin S. "Enhancing the Existing Microscopic Simulation Modeling Practice for Express Lane Facilities." UNF Digital Commons, 2017. http://digitalcommons.unf.edu/etd/758.
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The implementation of managed lanes (MLs), also known as dynamically priced express lanes, to improve freeway traffic flow and personal throughput is on the rise. Congestion pricing is increasingly becoming a common strategy for congestion management, often requiring microscopic simulation during both planning and operational stages. VISSIM is a recognized microscopic simulation software used for analyzing the performance of managed lanes (MLs). This thesis addressed two important microscopic simulation issues that affect the evaluation results of MLs.
One of the microscopic simulation issues that has not yet been addressed by previous studies is the required minimum managed lane routing decision (MLRD) distance upstream of the ingress point of MLs. Decision distance is an optimal upstream distance prior to the ingress at which drivers decide to use MLs and change lanes to orient on a side of MLs ingress. To answer this question, this study used a VISSIM model simulating I-295 proposed MLs in Jacksonville, Florida, United States (U.S), varying the MLRD point at regular intervals from 500 feet to 7,000 feet for different levels of service (LOS) input. Three measures of effectiveness (MOEs) - speed, the number of vehicles changing lanes, and following distance - were used for the analysis. These MOEs were measured in the 500 feet zone prior to the ingress. The results indicate that as the LOS deteriorates, speed decreases, the number of vehicles changing lanes increases, and the following distance decreases. When the LOS is constant, the increase in the MLRD distance from the ingress point was associated with the increase in the speed at the 500 feet zone prior to the ingress, less number of lane changes, and the increase in following vehicle gap. However, the MOEs approached constant values after reaching a certain MLRD distance. LOS D was used to determine the minimum MLRD distance to the ingress of the MLs. The determined minimum MLRD distances were 4,000 and 3,000 feet for 6 and 3 lane segments prior to the ingress point, respectively.
Another issue addressed in this thesis is the managed lane evaluation (MLE) outputs, which include speed, travel time, density, and tolls. In computing the performance measures, the existing VISSIM managed lane evaluation (EVMLE) tool is designed to use the section starting at the point when vehicles are assigned to use MLs, also known as the MLRD point, which is located upstream of the ingress. The longer the MLRD distance from the ingress, the more the EVMLE tool uses the traffic conditions of the MLs traffic before entering the ML in its computations. This study evaluates the impact of the MLRD distance on the EVMLE outputs and presents a proposed algorithm that addresses the EVMLE shortcomings. In order to examine the influence of the MLRD distance on the outputs of the above-mentioned two algorithms, simulation scenarios of varying MLRD distances from 500 ft to 7,000 feet from the ingress were created. For demonstration purposes, only the speed was used to represent other performance measures. The analysis of variance (ANOVA) test was performed to determine whether there was a significant difference in the speed results with the change in the MLRD distance. According to the ANOVA results, the EVMLE tool produced ML speeds that are MLRD dependent, yielding lower speeds with an increased MLRD distance. On the other hand, the ML speed results from the proposed algorithm were fairly constant, regardless of the MLRD distance.
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Crouzier, Loïc. "Développement d'une nouvelle approche hybride combinant AFM et MEB pour la métrologie dimensionnelle des nanoparticules." Thesis, Poitiers, 2020. http://www.theses.fr/2020POIT2260.
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Afin de bénéficier des propriétés uniques des nanomatériaux liés à leur taille mais aussi d'évaluer leurs risques potentiels associés, les acteurs du secteur industriel ont besoin de s’appuyer sur des méthodes de mesure fiables, robustes et permettant d’obtenir l’ensemble des informations dimensionnelles requises. Cependant, il n’existe pas d’instrument capable de mesurer une nanoparticule dans les trois dimensions de l’espace avec une incertitude contrôlée. L’objectif de ces travaux est de combiner les mesures de diamètre par microscopie électronique à balayage (MEB) avec celles de hauteur par microscopie à force atomique (AFM). L’utilisation de particules de silice, supposée sphériques permet de valider cette approche hybride combinant AFM et MEB.Le bilan d’incertitudes associé à la mesure de nanoparticules par MEB a d’abord été établi. Nous avons mis en évidence que la principale contribution au bilan d’incertitudes est la taille du faisceau électronique, difficilement mesurable. Deux méthodes, fondées sur la modélisation Monte Carlo, ont été mises en place pour évaluer l’influence de ce paramètre sur la mesure MEB. La première est fondée sur la comparaison entre les signaux expérimentaux et simulés. La seconde repose sur la segmentation des images MEB en utilisant un point remarquable, non influencé par les dimensions du faisceau électronique. Ces deux méthodes ont permis de montrer que l’erreur liée à la taille du faisceau était largement surestimée en utilisant les outils de segmentation d’images classiques. À partir de ces résultats, une comparaison directe des mesures AFM et MEB a été réalisée sur les mêmes particules. Un écart systématique est observé entre les deux techniques pour les plus petites particules lié à leur non-sphéricité. L’utilisation d’une troisième technique, la microscopie électronique en transmission (MET) permet de confirmer ces observations. Enfin, l’approche de métrologie hybride a été mise en œuvre pour la mesure des trois dimensions caractéristiques de nanoparticules de formes complexes dont la morphologie était éloignée de celle de la sphèreIn order to take advantages of remarkable properties of the nanomaterials related to their size but also assess their potential risks, industrial actors need to rely on robust measurement methods that provide all the required dimensional information. However, there is no instrument capable of measuring a nanoparticle in all three dimensions of space with controlled uncertainty. The aim of this work is to combine diameter measurements by scanning electron microscopy (SEM) with height measurements by atomic force microscopy (AFM). The use of silica particles, supposedly spherical, allows to validate this hybrid approach combining AFM and SEM. First, the uncertainty budget associated with the measurement of nanoparticles by SEM was established. We have demonstrated that the main contribution to the uncertainty budget is the size of the electron beam, which is difficult to measure. Two methods, based on Monte Carlo modelling, have been developed to evaluate the influence of this parameter on the SEM measurement. The first is based on the comparison between experimental and simulated signals. The second is based on the segmentation of the SEM images using a remarkable point, not influenced by the dimensions of the electron beam. These two methods have shown that the error related to the beam size is largely overestimated using conventional image segmentation tools. From these results, a direct comparison of AFM and SEM measurements was performed on the same particles. A systematic discrepancy was observed between the two techniques for the smallest particles related to their non-sphericity. The use of a third technique, transmission electron microscopy (TEM), confirms these observations. Finally, the hybrid approach has been implemented for measuring the three characteristic dimensions of the complex-shaped nano-objects with very non-spherical morphology
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Bart, Graeme. "Bridging the Microscopic and Macroscopic Realms of Laser Driven Plasma Dynamics." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/38187.
Full textAbstract:
The physical processes shaping laser plasma dynamics take place on length scales ranging from the microscopic (1 ångström) to the macroscopic realms (µm). Microscopic field fluctuations due to the motions of individual plasma charges evolve on an atomic scale. Collisional effects influencing thermalization and ionization processes depend on the plasma fields on an atomic level. Simultaneously, collective processes such as plasma oscillations take place on a mesoscopic length scale of many-nm. The macroscopic realm is ultimately determined by the laser which typically spans hundreds of nm to a few µm.
Consequently, ab-initio modelling of laser plasma dynamics requires the resolution of length scales from 1Å to multiple µm. As such, in order to bridge the microscopic and macroscopic length scales of light-matter interaction, in is necessary to account for the individual motions of up to ~10^11 particles. This is a not an insignificant undertaking.
Until recently, approaches to numerical modelling of light-matter interactions were limited to MD and PIC, each with their own limitations. MicPIC has been developed to fill the gap left by MD and PIC but so far has not been adapted for scalable parallel processing on large distributed memory machines. Thus, its full potential was not able to be fully realized until now.
This thesis presents the massively parallel MicPIC method capable of bridging the micro- and macroscopic realms. A wide range of applications that have heretofore not been accessible to theory or, at best, had limited applicability are now open for thorough investigation. Among these are nonlinear nanophotonics, quantum nanophotonics, laser machining, ab-initio dynamics of strongly coupled plasmas, high-harmonic generation, electron and x-ray sources, and optical switching. Two of the first applications of parallel MicPIC to a selection of such problems are shown and discussed below, demonstrating the applicability of the method to a wide variety of newly accessible strong field laser-plasma physics phenomena.
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Oricchio, Valerio. "Microscopic Simulation Model of Traffic Operations at intersections in Malfunction Flash Mode." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16161.
Full textAbstract:
When a malfunction occurs in a traffic signal controller cabinet, the signal is automatically placed into malfunction flash mode as a safety precaution. During this event, drivers are presented with one of two possible scenarios: flashing yellow on the major street and flashing red on the minor street, or flashing red on all the approaches. Volumes and percentages of car stopping were collected at fifty-one study intersections in the Atlanta regions. By means of the VISSIM microsimulation software a sample of intersections was simulated under the two malfunction scenarios and the signalized one. Based on output data such as delay and queue, the performances of each simulated intersection is compared and recommendations on which mode of flash must be used in case of malfunction are provided.
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Grumert, Ellen. "Cooperative Variable Speed Limit Systems : Modeling and Evaluation using Microscopic Traffic Simulation." Licentiate thesis, Linköpings universitet, Kommunikations- och transportsystem, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-106926.
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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.
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Chatterjee, Indrajit Edara Praveen K. "Replication of freeway work zone capacity values in a microscopic simulation model." Diss., Columbia, Mo. : University of Missouri--Columbia, 2008. http://hdl.handle.net/10355/6287.
Full textAbstract:
Title from PDF of title page (University of Missouri--Columbia, viewed on Feb. 12, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Thesis advisor: Dr. Praveen K. Edara. Includes bibliographical references.
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Scariza, Joseph R. (Joseph Ralph) 1979. "Evaluation of coordinated and local ramp metering algorithm using microscopic traffic simulation." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/16921.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003.Includes bibliographical references (p. 105-108).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Ramp meters are special traffic signals at the end of a freeway on-ramp that regulate the flow of traffic onto the mainline. The main purpose of ramp meters is to keep the mainline of the freeway from becoming overly congested, and to maximize the efficient use of freeway capacity. The first use of ramp metering was in Chicago, in 1963, and today ramp meters are becoming more popular in both the US and in Europe. Although the original ramp metering controllers used pre-timed ramp meters, nearly all modern ramp metering algorithms are traffic responsive. Traffic responsive ramp meters can be divided into two categories: local or coordinated. Local ramp metering algorithms only take into account traffic conditions near a single ramp, while coordinated algorithms try to optimize traffic over an area. Four algorithms are evaluated in this thesis. ALINEA is a local ramp metering algorithm. ALINEA / Q is a local algorithm based on ALINEA, but handles ramp queues in a more efficient manner. FLOW is a coordinated algorithm that tries to keep the traffic at a predefined bottleneck below capacity. The Linked Algorithm is a coordinated algorithm that seeks to optimize a linear-quadratic objective function. Each of these four algorithms was tested on the M27 Motorway near Southampton, UK. Because none of the algorithms showed any significant benefits, different scenarios were tested, both on the M27 network, and on a generic network. The effect of four variables was studied: total demand, ramp spacing, proportion of traffic using ramps, and traffic distribution among ramps. A regression analysis was performed on each algorithm to determine the sensitivity to each variable. The most significant result was that ramp metering, especially the coordinated algorithms, was only effective when the ramps are spaced closely together. It was also observed that ramp metering was only effective at relatively high demand levels, and that ALINEA / Q and the coordinated algorithms were more effective than regular ALINEA when the volume was extremely high.
by Joseph R. Scariza.
S.M.
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Hasan, Masroor 1970. "Evaluation of ramp control algorithms using a microscopic traffic simulation laboratory, MITSIM." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/40017.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1999.Includes bibliographical references (p. 77-80).
Ramp metering has emerged as an effective freeway control measure to ensure efficient freeway operations. A number of algorithms have been developed in recent years to ensure an effective use of ramp metering. As the performance of ramp metering depends on various factors (e.g. traffic volume, downstream traffic conditions, queue override policy etc), these algorithms should be evaluated under a wide range of traffic conditions to check their applicability and performance and to ensure their successful implementation. In view of the expenses of and confounding effects in field testing, simulation plays an important role in the evaluation of such algorithms. This thesis presents an evaluation study of two ramp metering algorithms: ALINEA and FLOW. ALINEA is a local control algorithm and FLOW is an area wide coordinated algorithm. The purpose of the study is to use microscopic simulation to evaluate systematically how the level of traffic demand, queue spillback handling policy and downstream bottleneck conditions affect the performance of the algorithms. It is believed that these variables have complex interactions with ramp metering. MITSIM microscopic traffic simulator is used to perform the empirical study. It is argued that an explicit modeling of merging behavior is necessary for an appropriate evaluation of ramp control algorithms and therefore, a microscopic simulation model should be used. The study consists of two stages. In the first stage, key input parameters for the algorithms were identified and calibrated. The calibrated parameters were then used for the second stage, where the performance of the algorithms were compared with respect to three traffic variables mentioned above using an orthogonal fraction of experiments. It was observed that for many of the scenarios, particularly at low demands, metering significantly increased system travel time. However, with proper calibration, the algorithms improved mainline as well as ramp conditions at high demands. A ramp queue storage length smaller than the physical length of the ramp was found to produce better performance. Regression analysis was used to identify the impacts of some of the interactions among experimental factors on the algorithms' performance, which is not otherwise possible with a tabular analysis. These results provide insights which may be helpful for design and calibration of more efficient ramp control algorithms.
by Masroor Hasan.
S.M.
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Cuneo, David J. (David Joseph) 1972. "A system-wide evaluation of a traffic control system using microscopic simulation." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/10104.
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Gao, Yu. "Calibration and Comparison of the VISSIM and INTEGRATION Microscopic Traffic Simulation Models." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/35005.
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Microscopic traffic simulation software have gained significant popularity and are widely used both in industry and research mainly because of the ability of these tools to reflect the dynamic nature of the transportation system in a stochastic fashion. To better utilize these software, it is necessary to understand the underlying logic and differences between them. A Car-following model is the core of every microscopic traffic simulation software. In the context of this research, the thesis develops procedures for calibrating the steady-state car-following models in a number of well known microscopic traffic simulation software including: CORSIM, AIMSUN, VISSIM, PARAMICS and INTEGRATION and then compares the VISSIM and INTEGRATION software for the modeling of traffic signalized approaches.
The thesis presents two papers. The first paper develops procedures for calibrating the steady-state component of various car-following models using macroscopic loop detector data. The calibration procedures are developed for a number of commercially available microscopic traffic simulation software, including: CORSIM, AIMSUN2, VISSIM, Paramics, and INTEGRATION. The procedures are then applied to a sample dataset for illustration purposes. The paper then compares the various steady-state car-following formulations and concludes that the Gipps and Van Aerde steady-state car-following models provide the highest level of flexibility in capturing different driver and roadway characteristics. However, the Van Aerde model, unlike the Gipps model, is a single-regime model and thus is easier to calibrate given that it does not require the segmentation of data into two regimes. The paper finally proposes that the car-following parameters within traffic simulation software be link-specific as opposed to the current practice of coding network-wide parameters. The use of link-specific parameters will offer the opportunity to capture unique roadway characteristics and reflect roadway capacity differences across different roadways.
Second, the study compares the logic used in both the VISSIM and INTEGRATION software, applies the software to some simple networks to highlight some of the differences/similarities in modeling traffic, and compares the various measures of effectiveness derived from the models. The study demonstrates that both the VISSIM and INTEGRATION software incorporate a psycho-physical car-following model which accounts for vehicle acceleration constraints. The INTEGRATION software, however uses a physical vehicle dynamics model while the VISSIM software requires the user to input a vehicle-specific speed-acceleration kinematics model. The use of a vehicle dynamics model has the advantage of allowing the model to account for the impact of roadway grades, pavement surface type, pavement surface condition, and type of vehicle tires on vehicle acceleration behavior. Both models capture a driverâ s willingness to run a yellow light if conditions warrant it. The VISSIM software incorporates a statistical stop/go probability model while current development of the INTEGRATION software includes a behavioral model as opposed to a statistical model for modeling driver stop/go decisions. Both software capture the loss in capacity associated with queue discharge using acceleration constraints. The losses produced by the INTEGRATION model are more consistent with field data (7% reduction in capacity). Both software demonstrate that the capacity loss is recovered as vehicles move downstream of the capacity bottleneck. With regards to fuel consumption and emission estimation the INTEGRATION software, unlike the VISSIM software, incorporates a microscopic model that captures transient vehicle effects on fuel consumption and emission rates.Master of Science