Wang Qing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 72-74). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Literature survey --- p.2 / Chapter 1.2 --- Research carried out in this thesis --- p.4 / Chapter 2 --- Conventional Dynamic Programming --- p.7 / Chapter 2.1 --- Principle of optimality and decomposition --- p.7 / Chapter 2.2 --- Backward dynamic programming --- p.12 / Chapter 2.3 --- Forward dynamic programming --- p.15 / Chapter 2.4 --- Curse of dimensionality --- p.19 / Chapter 2.5 --- Singly constrained case --- p.21 / Chapter 3 --- Surrogate Constraint Formulation --- p.24 / Chapter 3.1 --- Conventional surrogate constraint formulation --- p.24 / Chapter 3.2 --- Surrogate dual search --- p.26 / Chapter 3.3 --- Nonlinear surrogate constraint formulation --- p.30 / Chapter 4 --- Convergent Surrogate Constraint Dynamic Programming: Objective Level Cut --- p.38 / Chapter 5 --- Convergent Surrogate Constraint Dynamic Programming: Domain Cut --- p.44 / Chapter 6 --- Computational Results and Analysis --- p.60 / Chapter 6.1 --- Sample problems --- p.61 / Chapter 7 --- Conclusions --- p.70

Dynamic membranes are considered to be an attractive anti-fouling remedy for membrane filtration, because once fouled, they can be removed and reformed in-situ, thereby prolonging the support membrane???s lifetime. However, large-scale application of dynamic membranes has been limited due to the numerous formation parameters that influence their properties. This thesis provides better understanding of the mechanisms of the dynamic membrane formation process through fundamental formation and characterisation studies of dynamically formed titanium dioxide membranes in laboratory scale dead-end and crossflow systems. The dynamic membranes exhibited water fluxes ranging from 30-1147 L/m2h and dextran (500 kDa) rejections as high as 99.9%. Of the six formation parameters studied, the pH and constant flux conditions had the greatest influence on dynamic membrane properties. The pH affects dynamic membrane properties by changing particle aggregation prior to dynamic membrane formation, while constant flux conditions affect the drag force on particles during deposition thereby altering cake compressibility. The advantage of using the novel concept of constant flux formation over traditional constant pressure formation is that it enables greater control of particle deposition during dynamic membrane formation. Dextran rejection data also suggested the existence of a critical mass loading, above which dynamic membrane flux and rejection properties are reduced. This thesis also demonstrated the utility of a factorial design experiment for preliminary identification and evaluation of the critical factors affecting dynamic membrane formation, a method which could be invaluable for tailoring dynamic membranes for use in specific applications. In addition, cake removal data suggested that more than 80% of the dried cake could be removed providing a high potential for membrane regeneration. For the formation conditions studied, it was concluded that convection was the dominant mechanism governing particle transport during dynamic membrane formation. The fluxes and cake properties of the dynamic membranes were best described by the resistance-in-series model for simple dead-end microfiltration. Furthermore, the higher cake void fraction required to fit the experimental data (at low formation pressure or constant flux conditions) with model predictions suggested that the ratio of shear to convection was an important mechanistic parameter determining dynamic membrane properties.

<p>Report about the final project of Ricardo Ibarra and Pablo de la Iglesia.The project consists in a website built by php and mysql</p>

Agricultural sprayers are used to apply chemical treatments (pesticides and fertilizer) to crops. A sprayer distributes the chemical by employing many nozzles spaced evenly along a boom structure oriented perpendicular to the direction of travel to cover large areas with each machine pass. To maximize spray efficacy, the nozzles must be held a specific distance from the target to be sprayed. With diversification of crop types grown in Western Canada, foliar application of chemical treatments at multiple points during the plants life cycles are now required. This multi-growth-stage application process requires a machine with a large range of vertical adjustment; thus permitting the nozzles to be maintained the correct distance from the target (crop) as it grows. Suspended boom sprayers provide the range of adjustment required.<p> The suspended boom structure consists of three controlled sections which are positioned via use of hydraulic actuators. To reduce the effect of terrain inputs through the carrying frame on the booms orientation, most suspended boom sprayers incorporate a passive suspension system to limit coupling between the carrying frame and boom. By doing this however, a negative effect is created. During typical operation, the operator will use the actuator to reorient one section thereby maintaining the desired distance from the boom to the target; the opposing section will deviate from its desired position due to coupling of the boom sections through the passive suspension system. The quantification of this problem was the basis for this research. <p> A computer simulation model of the boom structure, passive suspension system, hydraulic actuator, and on/off type directional valve was created. Comparisons to experimental data showed the model was applicable for predicting trends in boom performance related to manipulation of actuator velocity profiles. Standardized changes in the actuated sections orientation were used to establish the existing performance baseline and quantify the problem. Alternative commercially available directional valves (proportional and pulse width modulated) were then simulated and used in conjunction with the boom model to determine if boom performance improvements may be realized by defining the actuators acceleration rate during orientation changes. <p> The proportional valve was able to limit the acceleration and deceleration of the actuated section to reduce the coupling effect and improve the non-actuated sections performance. However, the performance of the actuated section degraded more significantly in all trials regardless of input profile. The performance degradation resulted as slower acceleration and deceleration of the actuator required an increased amount of time for the desired orientation of the actuated section to be reached. It was also concluded that performance of the dynamic orientation of the boom structure was equivalent for orientation changes driven wither by pulse width modulation of an on/off valve or a true proportional valve. The boom structures large inertia and low natural frequency acted as a suitable filter for the flow and pressure pulsations introduced by pulse width modulation.

Agricultural sprayers are used to apply chemical treatments (pesticides and fertilizer) to crops. A sprayer distributes the chemical by employing many nozzles spaced evenly along a boom structure oriented perpendicular to the direction of travel to cover large areas with each machine pass. To maximize spray efficacy, the nozzles must be held a specific distance from the target to be sprayed. With diversification of crop types grown in Western Canada, foliar application of chemical treatments at multiple points during the plants life cycles are now required. This multi-growth-stage application process requires a machine with a large range of vertical adjustment; thus permitting the nozzles to be maintained the correct distance from the target (crop) as it grows. Suspended boom sprayers provide the range of adjustment required.<p> The suspended boom structure consists of three controlled sections which are positioned via use of hydraulic actuators. To reduce the effect of terrain inputs through the carrying frame on the booms orientation, most suspended boom sprayers incorporate a passive suspension system to limit coupling between the carrying frame and boom. By doing this however, a negative effect is created. During typical operation, the operator will use the actuator to reorient one section thereby maintaining the desired distance from the boom to the target; the opposing section will deviate from its desired position due to coupling of the boom sections through the passive suspension system. The quantification of this problem was the basis for this research. <p> A computer simulation model of the boom structure, passive suspension system, hydraulic actuator, and on/off type directional valve was created. Comparisons to experimental data showed the model was applicable for predicting trends in boom performance related to manipulation of actuator velocity profiles. Standardized changes in the actuated sections orientation were used to establish the existing performance baseline and quantify the problem. Alternative commercially available directional valves (proportional and pulse width modulated) were then simulated and used in conjunction with the boom model to determine if boom performance improvements may be realized by defining the actuators acceleration rate during orientation changes. <p> The proportional valve was able to limit the acceleration and deceleration of the actuated section to reduce the coupling effect and improve the non-actuated sections performance. However, the performance of the actuated section degraded more significantly in all trials regardless of input profile. The performance degradation resulted as slower acceleration and deceleration of the actuator required an increased amount of time for the desired orientation of the actuated section to be reached. It was also concluded that performance of the dynamic orientation of the boom structure was equivalent for orientation changes driven wither by pulse width modulation of an on/off valve or a true proportional valve. The boom structures large inertia and low natural frequency acted as a suitable filter for the flow and pressure pulsations introduced by pulse width modulation.

Our group has recently described a new form of kinetic isotope effect that arises from dynamic selectivity in the bifurcation of a reaction pathway on the slope of an energy surface. Since the selection between products does not occur at a potential energy saddle point, we proposed that the isotope effect is decided by dynamic factors that are not necessarily related to zero point energy effects on the surface. As an alternative explanation, it has recently been suggested that variational transition state theory can account for these isotope effects. The dynamic explanation and variational transition state theory explanation make distinct predictions as to the temperature dependence of these isotope effects. I describe here my studies of the temperature dependence of the intramolecular isotope effects for the reaction of singlet oxygen with gemtetramethylethylene- d6. The selectivity observed for this reaction across a broad temperature range is clearly a non-Eyring distribution and thus the mechanism cannot be adequately described solely using transition state theory or even some variation of it. After using these results to evaluate competing theories it was concluded that this mechanism could only be properly understood using a dynamic explanation.

Report about the final project of Ricardo Ibarra and Pablo de la Iglesia.The project consists in a website built by php and mysql

No description available.

No description available.

No description available.