A simulation algorithm for crystal size distribution dynamics in a continuous crystallizer was developed using the method of lines. Dimensionless crystal sizes, in vector form, were used as state variables. Simulation results using this algorithm satisfied stability criteria for continuous crystallizers, which had been developed previously using different methods. The use of a state space representation of the algorithm permits the use of well-known theoretical and numerical approaches to the modeling of an experimental R-z crystallizer and for design of a proportional controller for a continuous crystallizer system. Boundary conditions defined by the nucleation/growth rate kinetics were separately written as an auxiliary function so that other kinetics can be substituted without any change of the main algorithm. This implies that the algorithm is applicable for any growth-type particulate system. CSD dynamics from an experimental crystallizer were satisfactorily modelled using this algorithm with reasonable parameters: e.g. the recycle ratios of the fines dissolver and the product classifier, crystal sizes at the upper cut size of the dissolver and at the lower cut size of the classifier, initial CSD, and the form of the upset. Algorithms for controller design using pole placement and optimization techniques were applied to develop a proportional matrix controller for an R-z crystallizer. It was evident that pole placement is a better method than optimization to design a controller for this crystallizer system. The system poles are concentrated at a point and it is necessary to assign the controller poles further apart to obtain appropriate control. To summarize controller design using the pole placement method, a schematic flow diagram of a system controller using the minimum order Luenberger observer was illustrated. In this example, only a few population densities need to be measured to drive the controller.

In the thesis, we fabricated the quantum dots lasers of 2D photonic crystal microcavity structures by E-beam lithography. The Al0.5Ga0.5As sacrificing layer beneath the Dwells structure is used for the purpose of suspending the active layer by air. Therefore, it has a high refractive index contrast in vertical direction to confine energy. Finally, we could fabricate a low threshold current photonic crystal laser. We can judge the epitaxy quality by the Microdisk (MD) process before the photonic crystal device process. For the 2D photonic crystal microcavity, we design different kinds of window to support the photonic crystal membrane cavity. We use dry and wet etching technique and metal mask to fabricate MD and photonic crystal membrane cavity. We use £g-PL to measure MD cavity resonant mode for the device of diameter 3£gm at room temperature. In addition, we design three kinds of defects (L3, H2, H3) of photonic crystal membrane structures using the sample C488. We measure resonant mode with H3 structure. The H3 structure measured resonant wavelength 1.26£gm, with Q =503.

Thesis--Ph. D., University of Hong Kong, 1984.

Thesis--M. Phil., University of Hong Kong, 1982.

published_or_final_version / Physics / Master / Master of Philosophy

published_or_final_version / Physics / Doctoral / Doctor of Philosophy

No description available.

No description available.

No description available.

No description available.