A hybrid molecular dynamics/multiparticle collision dynamics algorithm was constructed to model the pressure-driven flow of a compressible fluid through a nanoscopic channel of square cross-sectional area, as well as the effect of this flow on the configuration of a polymer chain that was tethered to the surface of this nanochannel. In the process of simulating channel flow, a new adiabatic partial slip boundary condition was created as well as a modified source/sink inlet and outlet boundary condition that could maintain a specified pressure gradient across the channel without the large entrance effects typically associated with these algorithms. The results of the flow simulations were contrasted with the results from a series solution to the Navier-Stokes equation for isothermal compressible flow, and showed excellent agreement with the results from the series solution when slip-boundary conditions were applied. A finitely extendible non-linear elastic spring and bead polymer chain was used to simulate the effect of flow on the polymer chain configuration under poor solvent and θ solvent conditions. Under θ solvent conditions, the cyclical dynamics that have been previousy observed for tethered polymer chains in pure shear flows were noted, however they were restricted to the end of the polymer chain. Under poor solvent conditions, the polymer adopted a metastable helix configuration as it collapsed to a globule state. The study also examined interchain and intrachain entanglements in polymers using the granny knot and overhand knot. The mechanisms by which these tangles untied themselves were determined. At low flow rates, the tangles unravelled by the end of the chain migrating through the loops of the tangle. At high flow rates, the tangles behaved like an entrained object as they reptated towards the end of the chain.

A hybrid molecular dynamics/multiparticle collision dynamics algorithm was constructed to model the pressure-driven flow of a compressible fluid through a nanoscopic channel of square cross-sectional area, as well as the effect of this flow on the configuration of a polymer chain that was tethered to the surface of this nanochannel. In the process of simulating channel flow, a new adiabatic partial slip boundary condition was created as well as a modified source/sink inlet and outlet boundary condition that could maintain a specified pressure gradient across the channel without the large entrance effects typically associated with these algorithms. The results of the flow simulations were contrasted with the results from a series solution to the Navier-Stokes equation for isothermal compressible flow, and showed excellent agreement with the results from the series solution when slip-boundary conditions were applied. A finitely extendible non-linear elastic spring and bead polymer chain was used to simulate the effect of flow on the polymer chain configuration under poor solvent and θ solvent conditions. Under θ solvent conditions, the cyclical dynamics that have been previousy observed for tethered polymer chains in pure shear flows were noted, however they were restricted to the end of the polymer chain. Under poor solvent conditions, the polymer adopted a metastable helix configuration as it collapsed to a globule state. The study also examined interchain and intrachain entanglements in polymers using the granny knot and overhand knot. The mechanisms by which these tangles untied themselves were determined. At low flow rates, the tangles unravelled by the end of the chain migrating through the loops of the tangle. At high flow rates, the tangles behaved like an entrained object as they reptated towards the end of the chain.

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Detailed and exact collision detection for large amounts of objects has for a long time been a non real-time affair because of the immense amount of computations necessary. This was however not only because of the complexity of the algorithms but also because discussed of the computations would not have had to be done in the first place. This paper has through literature research and empirical testing examined two different broad phase approaches to object culling in a three dimensional environment. The aim of such a broad phase algorithm is to decrease the amount of computation heavy narrow phase collision detection checks and thus enhancing application performance. Potential weaknesses of these approaches were addressed and possible solutions discussed. Performance comparisons were made to give a better overview of what kind of performance enhancements can be expected and to give a theoretical base for further research.

Nowadays, the location technology in the field of the Intelligent Transformation System (ITS) is used generally. Most of location devices on the cars are low-cost GPS, however, it¡¦s not enough if we want to combine with the safe algorithm. Hence, we present a suit of vehicle collision-avoidance system which combined location technology with Intersection-agent in this thesis. The system uses vehicle sensors and GPS information to calculate in Extend Kalman Filter, in order to get the optimal location information. Furthermore, Map-Matching algorithm is used to match the vehicle location on the right road. As to the driver¡¦s safety, laser range scanner¡¦s data are used in fuzzy algorithm and calculate the safe distance between cars. In the intersection area where accident happened most, we also combine with Intersection-agent system to enhance safety. When moving objects cross through the intersection area, Intersection-agent system would use laser range scanner to find the moving objects¡¦ position and velocity, judging whether they can pass the intersection safely or not. Once it¡¦s not safe, system would send out warning signal to the drivers to brake cars, also, passing the position information to car location system by wireless RS-232 transceiver, to decrease location error and let vehicle¡¦s location precision more accurate. In brief, this thesis combines with vehicle location, wireless transmission, car following warning system and Intersection-agent. And make sure this system we developed can fit in with traffic requirement in many experiments.

To smooth the substrate depositions of DC magnetron sputter (MS), such that the supplementary electrical and mechanical adjustment efforts can be alleviated, a refinement scheme that can be applied directly to the existing DC MS will be introduced. By properly controlling the magnetic and electric fields inside the vacuum chamber, trajectories of those atoms that are sputtered from the target surface can be more spread out. In addition, with the resultant higher plasma density, chance of collisions among the sputtered atoms and those Ar ions in the plasma will also be increased, hence the resulting distributions of target atoms deposited on the substrate surface will certainly be evened out. To further confirm such concepts, a rational emulating process that can explore both the atom sputtering process from the target and those collisions at the chamber with different three-dimensional magnetic and electric field environments is also developed. Thus the associated performance investigations on the DC MS with different magnetron arrangements can then be conveniently carried out.

Driven by the ambition for ubiquitous networking, wireless networks had gained substantial technical advances in recent years. Using radio signals in air as data links, wireless networks can get rid of the tangling of wired cables. However, due to the inherent limitations of wireless channels and legacy protocol design, users of wireless networks today still suffer from the problems on low bandwidth and high error rates. The seven-layer Open System Interconnection (OSI) model was originally designed with wired network environments in mind. Following the seven-layer OSI model, each layer is responsible for handling specific tasks without communicating with each other. Due to the relative stability of wired channels, the strictly-layered approach works well in wired network environments. However, its adequacy is a controversy in wireless environments, since wireless networks have completely different characteristics from its wired counterparts. In wireless environments, channel conditions are highly time-varying and are affected by many factors. External interference or signal degradation may lead to severe packet loss. Even signal-to-noise ratios are fine, transmissions may still fail due to collisions when contention-based MAC protocols are adopted. Conventional protocols developed with wired network environments in mind cannot appropriately response to the characteristics of wireless channels and may make wrong reactions. For these reasons, a flexible framework to capture the rapid change conditions of wireless channels and respond to them immediately is necessary. In this dissertation, we design a cross-layer framework with the consideration of wireless network characteristics. By the coordination between the involved layers, the cross-layer framework can adapt to wireless channel conditions and significantly improve QoS in wireless networks. In order to reduce collision probabilities in wireless networks, we propose a novel protocol named Wait-and-Transmit, which effectively alleviates contentions in wireless networks. By reducing collision probabilities of wireless networks, transmission delays can be shortened and throughputs can be significantly improved. Aiming at the transmission paths containing at least one wireless link, a flexible and efficient cross-layer transmission scheme is also present in this dissertation, which separates the rapid change conditions such as collision probabilities from the relatively stable conditions and well responds to these changes. The proposed approaches significantly improve the performance of wireless networks. We believe that these approaches can contribute to the development of wireless networking.

Bridges with low clearance are vulnerable to collision with overheight vehicles. Collisions of overheight vehicles can cause fatalities and injuries to the drivers and passengers of the overheight vehicles, and damage to bridge girders. The repair of the damaged bridges can be costly and time consuming. This research investigates the feasibility of developing a bridge bumper that minimizes the physical injuries and the likelihood of fatalities and protects the structural elements of bridges by absorbing the impact energy. The thesis describes a small-scale impact experiment using the proposed bridge bumper with several options of energy absorbing materials to protect a reinforced concrete beam. A finite element analysis is done to simulate the small-scale impact experiments. Optimization of the finite element model is carried out for the response quantities of interest with respect to the geometrical parameters and the material properties of the proposed bridge bumper. Such analysis can guide the design of an optimal bridge bumper that maximizes the energy dissipation and minimizes the damage to the bridge girder and the likelihood of fatalities and injuries.

As the progress of computer, virtual reality has become a more and more widespread technology and is applied extensively in entertainment, training, or medical science. To increase the interaction and reality of the virtual technology, the development of haptic feedback improves rapidly in recent years. This paper focuses on judgment existing collision detection algorithms, virtual wall models, and friction models from the view point of man-machine interface. A virtual environment interface with force feedback by using a joystick for computer game as a haptic device is established. A virtual environment is also built by employing the DirectX, a 3D computer graphic software developed by Microsoft Corp. Three virtual wall models are compared and four operational experiments are conducted to explore the influence of force feedback on operation task in virtual environment.