A polygon mesh, or a 3D mesh, consisting of a collection of vertices, edges, and polygons in three-dimensional space, is the standard way of representing 3D objects. In practice, polygon meshes acquired from the 3D scanning process fail to meet the quality requirements for most practical applications. Mesh defects like holes, duplicate elements, non-manifold elements are introduced during the scanning process, which lowers the quality of the output meshes. In this thesis, we describe a complete mesh-repairing process that fixes all defects within a polygon mesh. This process is divided into two parts: the mesh-cleaning part and the hole-filling part. In the mesh-cleaning part, we describe the ways of repairing different types of mesh defects. In the hole-filling part, we discuss two main hole-filling approaches: the surface-based method and the volumetric. In addition, we present a hybrid algorithm by combining the surface-based approach and the volumetric approach. We compare the meshes created by different hole-filing algorithms and show that the new algorithm is a good alternative to the existing ones. / Thesis (Master, Computing) -- Queen's University, 2013-09-11 23:45:08.591

Multiple-resource satellite scheduling problem (MuRRSP) is a complex and difficult scheduling problem, which schedules a large number of task requests onto ground-station antennas in order to communicate with the satellites. We first examined several exact algorithms that were previously implemented in the machine scheduling field. They are column generation and logic-based Benders decomposition. A new hybrid approach that combines both column generation and logic-based Benders decomposition is proposed. The hybrid performed well when there is a large number of machines. Next, we presented a connection between the parallel machine scheduling problem and MuRRSP in order to solve MuRRSP with exact algorithms. Furthermore, we proposed a strengthened cut in the sub-problem of the logic-based Benders decomposition. The resulting algorithm proved to be very effective. Barbulescu’s benchmark problems were solved and proved optimal with an average run-time less than one-hour. To the best of our knowledge, previous efforts to solve MuRRSP were all heuristic based and no optimal schedules existed.

Multiple-resource satellite scheduling problem (MuRRSP) is a complex and difficult scheduling problem, which schedules a large number of task requests onto ground-station antennas in order to communicate with the satellites. We first examined several exact algorithms that were previously implemented in the machine scheduling field. They are column generation and logic-based Benders decomposition. A new hybrid approach that combines both column generation and logic-based Benders decomposition is proposed. The hybrid performed well when there is a large number of machines. Next, we presented a connection between the parallel machine scheduling problem and MuRRSP in order to solve MuRRSP with exact algorithms. Furthermore, we proposed a strengthened cut in the sub-problem of the logic-based Benders decomposition. The resulting algorithm proved to be very effective. Barbulescu’s benchmark problems were solved and proved optimal with an average run-time less than one-hour. To the best of our knowledge, previous efforts to solve MuRRSP were all heuristic based and no optimal schedules existed.

A pre-optimizer has been developed which modifies existing turbomachinery blades to create new geometries with improved selected aerodynamic coefficients calculated using a linear panel method. These blade rows can then be further refined using a Navier-Stokes method for evaluation. This pre-optimizer was developed in hopes of reducing the overall CPU time required for optimization when using only Navier-Stokes evaluations. The primary method chosen to effect this optimization is a parallel evolutionary algorithm. Variations of this method have been analyzed and compared for convergence and degree of improvement. Test cases involved both single and multiple row turbomachinery. For each case, both single and multiple criteria fitness evaluations were used.

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The aim of this thesis is to investigate the development and control of electro-pneumatic actuators in a haptic teleoperation system. For controlling the mass flow rate of such actuators, two types of valve technology are sudied, i.e. solenoid (on/off) valve and proportional servovalve. The servovalves have found widespread applications in which high accuracy of force/position control are needed. They are however typically expensive due to the requirements of high-precision manufacturing. Therefore, the low-cost solenoid valves can be an alternative to the servovalves for achieving acceptable-performance pneumatic control. Generally, the highly nonlinear of the pneumatic actuator is heightened when it uses on/off solenoid valves instead of servovalves. In this case, precise control is challenging due to the discrete-input nature of the system. Our first objective is to demonstrate that it is possible to design an acceptable performance teleoperation system using master-slave robots that have pneumatic actuators equipped with only inexpensive on/off solenoid valves. To control efficiently the switching valves, several control approaches have been proposed, namely pulse width modulation (PWM), hybrid algorithm, and sliding mode control. A hybrid control theory, which includes more switching control modes, than PWM, allows to reduce the chattering problem and improve the energy consumption of the valves. Another strategy (i.e. a sliding mode control), which does not depend on the pneumatic model, is proposed. This control stratgy allows to perform not only the transparent analysis but also the stability analysis. In order to improve the dynamic performance and reduce the chattering problem in solenoid valve actuated pneumatic teleoperation systems, a five-mode sliding control scheme has been used, which can be considered as an extension of the three-mode sliding controller. Our study demonstrates that by increasing the number of possible control actions for the valves, we can reduce the valves' switching activities, hence improving the valve's life times at no cost to teleoperation transparency. The second objective of the thesis involves in implementing the proportional servovalves on the pneumatic teleoperation system. A comparison related to the teleoperation performance between an on/off valve and a servovalve is carried out. In experiments, it is observed that with the bilateral teleoperation architecture employing solenoid valves or servovalves, satisfactory force and position tracking between the master and the slave is obtained. In bilateral teleoperation control, force sensors are often omitted to save cost and to lessen weight and volume. Therefore, another aspect of our work consists in using observers for an estimation of operator and environment forces. Experimental results show that acceptable teleoperation transparency based on a simple Nicosia observer and a tangent linear control approach can be achieved.

In this thesis an image-space and geometry hybrid algorithm for portal rendering is con- structed and evaluated in terms of correctness and performance. A number of tests are de ned and out of these three are selected and executed. Based on the results of these tests, the con- clusion is that a hybrid approach to portal rendering is a valid option for increasing the speed without sacri cing the correctness of an image-space portal rendering algorithm.

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Šiame darbe nagrinėjama negiljotininio, dvimačio, stačiakampių pjaustymo uždavinio atliekų minimizavimo problema ir jos sprendimo metodai. Dėl uždavinio kombinatorinio sudėtingumo neįmanoma tiksliai ir visais atvejais pateikti optimalų jo sprendinį, todėl pasirinkti apytiksliai sprendimo metodai. Uždavinys sprendžiamas metaeuristiniais hibridiniais genetiniu ir modeliuojamo atkaitinimo algoritmais apjungtais su euristiniais „Žemiausio kairėn užpildymo“ ir „Žemiausio tarpo“, kuris yra originali „Geriausiai tinkamo“ metodo modifikacija. Taip pat realizuojami minėti euristiniai algoritmai atskirai nuo hibridinių. Atliekama šių metodų lyginamoji analizė bei jų parametrų ir pradinių sąlygų parinkimo įtakos tyrimas sprendinio kokybei. Suformuojama ir pateikiama metodika pjaustymo uždavinių sprendimui. / A non – guillotinable, two – dimensional, rectangular cutting stock problem is being introduced in this paper and its solving methods either. Due to the combinatorial complexity of a problem, it is impossible to solve it optimally for every instance. Consequently an aproximate methods have been chosen. The problem is solved by metaheuristic genetic and simulated annealing methods hybridised with heuristic „Bottom Left Fill“ and „Lowest Gap“, which is an originally modified version of „Best Fit“ algorithm. The same heuristic algorithms are implemented separately from hybridised ones. A comparation analysis of these methods is done and the influence on solution quality depending on the selection of algorithms parameters and its initial conditions is considered. The methodology of solving cutting stock problems is being formulated and presented.