The elementary processes of atomic and molecular oxygen over the solid surfaces of graphite and β–cristobalite have been studied theoretically. The aim of the study is to widen the knowledge about the behaviour of materials used as a Thermal Protection Systems in space vehicles during its re-entry on the Earth’s atmosphere. For the oxygen interaction over graphite, a Density Functional Theory study has been carried out for the main heterogeneous elementary processes. Minima and transition states have been characterized for the atomic and molecular adsorption, as also the main features of atomic diffusion and O2 formation via Eley-Rideal and Langmuir-Hinshelwood processes. The rate constants for each of the beforementioned processes have been computed by means of the Transition State Theory and then used in a Kinetic model in order to study the overall effect of the processes occurring at the same time. This model allows estimating the atomic recombination coefficient, widely used in computational fluid dynamics simulations. In order to understand the microscopic mechanism of these processes, a dynamical study has been carried out by means of the quasiclassical trajectory method over several potential energy surfaces (PES). For the atomic interaction with the surface an analytical surface (using the Flexible Periodic Lodon-Eyring-Polanyi-Sato, FPLEPS method) and an interpolated one (using the Modified Shepard method) have been constructed. In the case of two atoms interacting with the surface, a FPLEPS surface has been used. From these calculations, reaction probabilities, scattering angles and other properties has been obtained. The dynamical study of oxygen interacting with β–cristobalite has been completed, specifically for the interaction of an oxygen atom with a precovered surface and for the molecular oxygen over a clean surface. Using these results, the reaction rate constants have been computed and used in a microkinetic model in order to understand the effect of all of the elementary processes considered at the same time. Furthermore, an estimation of the atomic recombination coefficient and the energetic accommodation coefficient has been carried out. / S’ha realitzat un estudi teòric d’alguns dels processos químics elementals de l’oxigen atòmic i molecular sobre les superfícies sòlides del grafit i de la β–cristobalita. La intenció ha sigut la d’ampliar el coneixement sobre quin es el comportament dels materials que s’empren com a sistemes de protecció tèrmica en vehicles espacials durant la seva reentrada a l’atmosfera terrestre. Per entendre millor com tenen lloc aquests processos químics heterogenis sobre la superfície del grafit, s’ha realitzat un estudi a nivell de la Teoria del Funcional de la Densitat sobre la interacció de l’oxigen atòmic i molecular amb aquesta superfície. Així doncs, s’han caracteritzat els principals punts estacionaris (mínims d’adsorció, estats de transició,...) de las reaccions elementals: adsorció atòmica i molecular, difusió, formació de molècules d’O2 a partir de les reaccions d’Eley-Rideal o Langmuir-Hinshelwood,..., observant en tots els casos que són processos energèticament activats. S’han trobat també dos petits mínims de fisisorció per l’àtom i la molècula, amb concordança amb dades experimentals publicades. S’han calculat les constants de velocitat associades a cadascun dels processos elementals a partir de la Teoria de l’Estat de Transició, i s’ha construït un model cinètic (300-1000K), en el que s’han estudiat l’efecte d’aquests processos de forma global, permetent també realitzar una estimació del coeficient de recombinació atòmica. Aquest coeficient, molt emprat en simulacions computacionals de fluids, a resultat ser molt petit a les diferents condicions estudiades. Per a aprofundir en el mecanisme microscòpic dels processos esmentats, s’ha realitzat un estudi de dinàmica molecular mitjançant el mètode de trajectòries quasiclàssiques sobre dos superfícies d’energia potencial , construïdes mitjançant un mètode analític (Flexible Periodic London-Eyring-Polanyi-Sato, FPLEPS) i un mètode d’interpolació (Modified Shepard) per a la interacció de un àtom amb el grafit, i sobre una superfície FPLEPS per a la interacció de dos àtoms amb el grafit. Amb això s’han pogut determinar les probabilitats de reacció per a cadascun dels processos, l’intercanvi energètic entre les espècies en fase gas i la superfície sòlida, angles de dispersió,... obtenint bona concordança d’aquests amb resultats experimentals publicats. S’ha observat que la reflexió atòmica i la adsorció atòmica són els principals processos sobre una superfície sòlida neta. La reacció Eley-Rideal, que produeix molècules d’O2 excitades internament, es produeix sobre una superfície amb O preadsorbit, mentre que la dissociació molecular no s’ha observat pràcticament. S’ha completat l’estudi dinàmic de l’oxigen sobre la superfície de β–cristobalita (001), per als processos de interacció d’un àtom amb la superfície coberta d’oxigen atòmic i per a la col•lisió de l’O2 amb la superfície neta. S’han realitzat també càlculs dinàmics en condicions quasitèrmiques dels processos elementals per obtenir les constants de velocitat associades i poder així construir un model cinètic (700- 1700K), amb el que s’han pogut avaluar els coeficients de recombinació atòmica (γ) i d’acomodació energètica (β). Per al primer s’han obtingut valors propers als experimentals, compresos entre 0.01 i 0.02. En el cas de βO s’han obtingut valors entre 0.75 i 0.8, que difereixen substancialment dels que s’han assumit a simulacions prèvies (βO=1). S’ha demostrat que el procés d’adsorció atòmica es molt més important que la reacció Eley-Rideal en quant a transferència de calor cap a la superfície sòlida.

The unchangeable need of securing and locating parts during different manufacturing processes turned the fixtures to key elements in many part production industries. The iterations between design engineers and manufacturing planners because of late collision detection of the part/fixtures with robots cost a lot of time and money. The lead-time can be reduced by developing tools and/or methods for early verification of the fixtures during the simultaneous engineering phase. Different aspects of fixture designing, modeling and simulating is investigated as a base step to recognize the best practice work to do fixture planning in Process Simulate integrated PLM environment. The aim of the project is to use Process Simulate to design and validate modular fixtures at the same time and in a single environment. It also aims to investigate the possibility of adding kinematics, sensors, and actuating signals to the fixtures and utilize them to model the fixture behavior in a larger simulation study. The project narrows down its focus on the fixtures designed for robotic applications specifically in Automotive Body in White lines without losing generality. The document type stated at the title page and in the header of this page is master thesis work.

De krocktester som utförs idag är låsta till det system av styr och draganordningar som byggs upp. Att göra en krocktest därbilarna kan styras individuellt med hjälp av en förarrobot ökar friheten att designa tester. Att krocka två bilar som på bilden på framsidan, med 90 graders vinkel mellan bilarnas färdriktning ställer det mest tidskritiska kravet när de ska träffa varandra. Detta kräver en bra hastighetsreglering vilket är huvuddelen i examensarbetet. I denna rapport redovisas hur ett sådant styrsystem skulle kunna byggas samt tester i en simuleringsmodell för denna typ av krocktest. Simuleringsmodellen är uppbyggd i Matlab/Simulink och eftersträvar att efterlikna ett verkligt sidokollisionstest tillräckligt mycket för att kunna testa styrsystemet. Efter de tester som gjorts kan man konstatera att det är möjligt att konstruera ett sådant styrsystem som kan få två bilar att träffa varandra i en sådan sidokollision som är beskriven ovan.

Pavements encompass a significant component of the total civil infrastructure investment. In Ontario, the Ministry of Transportation (MTO) is responsible for the maintenance and construction of approximately 39,000 lane-kilometres of highway. In 2004, the province estimated the value of the total highway system at $39 billion dollars. Thus, managing this asset is an important factor to ensure a high level of service to the traveling public. One of the most important indicators of level of service for a road network is safety. Each year, thousands of motorists across North America are involved in motor vehicle collisions, which result in property damage, congestion, delays, injuries and fatalities. The MTO estimated that in 2002, vehicle collisions in Ontario cost nearly $11 billion. Despite the importance of highway safety, it is usually not considered explicitly in the pavement management framework or maintenance analysis. A number of agencies across North America collect skid data to assess the level of safety at both the project and network level (Li et al, 2004). However, a number of transportation agencies still do not collect friction data as part of their regular pavement data collection programs. This is related to both liability concerns and lack of knowledge for how this data can be effectively used to improve safety. The transportation industry generally relies on information such as collision rates, black-spot locations and radius of curvature to evaluate the level of safety of an alignment (Lamm et al., 1999). These are important factors, but the use of complementary skid data in an organized proactive manner would also be beneficial. In preparation for a considered Long Term Area Maintenance Contract, a project was initiated by the MTO to collect network level friction data across three regions in the Province of Ontario. This project represents the first time friction data was collected at the network level in Ontario. In 2006, approximately 1,800 km of the MTO highway network was surveyed as a part of this study. This research utilized the network level skid data along with collision data to examine the relationships and model the impacts of skid resistance on the level of safety. Despite the value of collecting network level skid data, many Canadian transportation agencies still do not collect network level skid data due to the costs and potential liability associated with the collected data. The safety of highway networks are usually assessed using various levels of service indicators such as Wet-to-Dry accident ratio (W/D), surface friction (SN), or the collision rate (CR). This research focused on developing a framework for assessing the level of safety of a highway network in terms of the risk of collision based on pavement surface friction. The developed safety framework can be used by transportation agencies (federal, state, provincial, municipal, etc.) or the private sector to evaluate the safety of their highway networks and to determine the risk or probability of a collision occurring given the level of friction along the pavement section of interest. As a part of the analysis, a number of factors such as Region, Season of the Year, Environmental Conditions, Road Surface Condition, Collision Severity, Visibility and Roadway Location were all investigated. Statistical analysis and modeling were performed to developed relationships which could relate the total number of collisions or the collision rate (CR) to the level of available pavement friction on a highway section. These models were developed using over 1,200 collisions and skid test results from two Regions in the Province of Ontario. Another component of this study examined the Wet-to-Dry accident ratio and compared it to the Skid Number. A number of Transportation Agencies rely on the Wet-to-Dry accident ratio to identify potential locations with poor skid resistance. The results of the comparison further demonstrated the need and importance of collecting network level skid data. Another component of this study was to evaluate the effectiveness of various preservation treatments used within the Long Term Pavement Performance (LTPP) study. In addition, modeling was performed which examined the historical friction trends over time within various environment zones across North America to investigate skid resistance deterioration trends. The results of the analysis demonstrated that commonly used preservation treatments can increase skid resistance and improve safety. The cost effectiveness of implementing preservation and maintenance to increase the level of safety of a highway using Life Cycle Cost Analysis (LCCA) was evaluated. A Decision Making Framework was developed which included the formulation of a Decision Matrix that can be used to assist in selecting a preservation treatment for a given condition. The results of this analysis demonstrate the savings generated by reducing the number of collisions as a result of increasing skid resistance. The results of this research study have demonstrated the importance of network level friction testing and the impact of skid resistance on the level of safety of a highway. A review of the literature did not reveal any protocol or procedures for sampling or minimum test interval requirements for network level skid testing using a locked-wheel tester. Network level friction testing can be characterized as expensive and time-consuming due to the complexity of the test. As a result, any reduction in the required number of test points is a benefit to the transportation agency, private sector (consultants and contractors) and most importantly, the public. An analysis approach was developed and tested that can be used to minimize the number of required test locations along a highway segment using common statistical techniques.

In recent years, researchers have developed virtual environments, which allow more realistic human-computer interactions and have become increasingly popular for engineering applications such as computer-aided design and process evaluation. For instance, the demand for product service, remanufacture, and recycling has forced companies to consider ease of assembly and disassembly during the design phase of their products. Evaluating these processes in a virtual environment during the early stages of design not only increases the impact of design modifications on the final product, but also eliminates the time, cost, and material associated with the construction of physical prototypes. Although numerous virtual environments for assembly analysis exist or are under development, many provide only visual feedback. A real-time haptic simulation test bed for the analysis of assembly and disassembly operations has been developed, providing the designer with force and tactile feedback in addition to traditional visual feedback. The development such a simulation requires the modeling of collisions between virtual objects, which is a computationally expensive process. Also, the demands of a real-time simulation incorporating haptic feedback introduce additional complications for reliable collision detection. Therefore, the first objective of this work was to discover ways in which current collision detection libraries can be improved or supplemented to create more robust interaction between virtual objects. Using the simulation as a test bed, studies were then conducted to determine the potential usefulness of haptic feedback for analysis of assembly and disassembly operations. The following significant contributions were accomplished: (1) a simulation combining the strengths of an impulse-based simulation with a supplemental constraint maintenance scheme for modeling object interactions, (2) a toolkit of supplemental techniques to support object interactions in situations where collision detection algorithms commonly fail, (3) a haptic assembly and disassembly simulation useful for experimentation, and (4) results from a series of five experimental user studies with the focus of determining the effectiveness of haptic feedback in such a simulation. Additional contributions include knowledge of the usability and functionality of current collision detection libraries, the limitations of haptic feedback devices, and feedback from experimental subjects regarding their comfort and overall satisfaction with the simulation.

We investigate charmonium production in the hot medium created by heavy-ion collisions by setting up a framework in which in-medium charmonium properties are constrained by thermal lattice QCD (lQCD) and subsequently implemented into kinetic approaches. A Boltzmann transport equation is employed to describe the time evolution of the charmonium phase space distribution with the loss and gain term accounting for charmonium dissociation and regeneration (from charm quarks), respectively. The momentum dependence of the charmonium dissociation rate is worked out. The dominant process for in-medium charmonium regeneration is found to be a 3-to-2 process. Its corresponding regeneration rates from different input charmquark momentum spectra are evaluated. Experimental data on J/[psi] production at CERN-SPS and BNL-RHIC are compared with our numerical results in terms of both rapidity-dependent inclusive yields and transverse momentum (pt) spectra. Within current uncertainties from (interpreting) lQCD data and from input charm-quark spectra the centrality dependence of J/[psi] production at SPS and RHIC (for both mid-and forward rapidity) is reasonably well reproduced. The J/[psi] pt data are shown to have a discriminating power for in-medium charmonium properties as inferred from different interpretations of lQCD results.

Kinodynamic motion planning is an important problem in robotics. It consists of planning the dynamic motion of a robotic system taking into account its kinematic and dynamic constraints. For this class of problems, high dimensionality is a major difficulty and finding an exact time optimal robot motion trajectory is proven to be NP-hard. Probabilistic approximate techniques have therefore been proposed in the literature to solve particular problem instances. These methods include Randomized Potential Field Planners (RPP), Probabilistic Roadmaps (PRM) and Rapidly Exploring Random Trees (RRT). When physical obstacles and differential constraints are added to the problem, applying RPPs or PRMs encounter difficulties. In order to handle these difficulties, RRTs have been proposed. In this study, we consider a multiple camera industrial inspection problem where the concurrent motion of these cameras needs to be planned. The cameras are required to capture maximum number of defect locations while globally avoiding collisions with each other and with obstacles. Our approach is to consider a solution to the kinodynamic planning problem of multiple camera inspection by making use of the RRT algorithm. We explore and resolve issues arising when RRTs are applied to this specific problem class. Along these lines, we consider the cases of a single camera without obstacles and then with obstacles. Then, we attempt to extend the study to the case of multiple camera where we also need to avoid collisions between cameras. We present simulation results to show the performance of our RRT based approach to different instrument configurations and compare with existing deterministic approaches.

This thesis focuses on the development of guidance algorithms in order to avoid a prescribed obstacle primarily using the Collision Cone Method (CCM). The Collision Cone Method is a geometric approach to obstacle avoidance, which forms an avoidance zone around the obstacles for the vehicle to pass the obstacle around this zone. The method is reactive as it helps to avoid the pop-up obstacles as well as the known obstacles and local as it passes the obstacles and continue to the prescribed trajectory. The algorithm is first developed for a 2D (planar) avoidance in 3D environment and then extended for 3D scenarios. The algorithm is formed for the optimized CCM as well. The avoidance zone radius and velocity are optimized using constraint optimization, Lagrange multipliers with Karush-Kuhn-Tucker conditions and direct experimentation.

<p>The purpose of the present study was to examine effects of driver, vehicle, and environment characteristics on Collision Warning System (CWS) design. One hypothesis was made that the capability of collision avoidance would not be same among a driver, vehicle, and environment group with different characteristics. Accident analysis and quantitative analysis was used to examine this hypothesis in terms of ‘risk’ and ‘safety margin’ respectively. Rear-end collision had a stronger focus in the present study. </p><p>As a result of accident analysis, heavy truck showed a higher susceptibility of the fatal rear-end accidents than car and light truck. Also, dry road surface compared to wet or snow, dark condition compared to daylight condition, straight road compared to curved road, level road compared to grade, crest or sag, roadway having more than 5 travel lanes compared to roadway having 2, 3 or 4 travel lanes showed a higher susceptibility of the fatal rear-end accidents. Relative rear-end accidents involvement proportion compared to the other types of collision was used as a measure of susceptibility. </p><p>As a result of quantitative analysis, a significant difference in terms of Required Minimum Warning Distance (RMWD) was made among a different vehicle type and braking system group. However, relatively small difference was made among a different age, gender group in terms of RMWD. Based on the result, breaking performance of vehicle should be regarded as an input variable in the design of CWS, specifically warning timing criteria, was concluded.</p>

<p>This Master’s thesis is a pilot study that investigates different systems to drive autonomous and non-autonomous vehicles simultaneously on test tracks. The thesis includes studies of communication, positioning, collision avoidance, and techniques for surveillance of vehicles which are suitable for implementation. The investigation results in a suggested system outline.</p><p>Differential GPS combined with laser scanner vision is used for vehicle state estimation (position, heading, velocity, etc.). The state information is transmitted with IEEE 802.11 to all surrounding vehicles and surveillance center. With this information a Kalman prediction of the future position for all vehicles can be estimated and used for collision avoidance.</p>