Stormwater (SW) runoff in urban areas represents a major pathway for pollutant transfer to receiving waters. Best management practices (BMP) were introduced in the 1970s to help mitigate the negative effects of SW. In the 1990s, Stormwater management (SWM) ponds were established as a BMP to help increase the water quality of SW effluent. Many SWM ponds do not provide sufficient water quality treatment. Information on the internal processes influencing the reduction of total phosphorus (TP), soluble reactive phosphorus (SRP) and total suspended solid (TSS) concentrations in SWM ponds with different designs is lacking. Knowledge of the processes affecting TP, SRP and TSS retention can help improve the design of SWM ponds to enhance their treatment performance. The purpose of this thesis is to provide an assessment of the internal chemical processes that affect the trap efficiency (TE) and spatial and temporal variability of TP, SRP and TSS concentrations at two structurally different SWM ponds (Pond 45; conventional and Pond 33; hybrid extended detention) in Waterloo, ON. Water samples were collected at the inflow and outflow at the two SWM ponds during six storm events and 30 baseflow periods. A mass balance approach was used to quantify the TE of TP, SRP and TSS concentrations at each pond. Pond 33 had a TE of 24.3%, 26.7% and 66.8% for baseflow and stormflow samples of TP, SRP and TSS. Pond 45 performed much better with TE of 93.8%, 94.2% and 98% for TP, SRP and TSS concentrations. Pond 33 was a source of TP, SRP and TSS for 3, 4 and 2 storm events sampled during the field season, respectively. Pond 45 was a sink for all parameters on all storm events samples. The spatial and temporal variability of TP, SRP and TSS concentrations were examined to improve knowledge of external factors and internal processes that influence the TE of SWM ponds. The effects of storm magnitude, seasonality and vegetation growth and senescence on effluent water quality were investigated. Additionally, the role of sediment on P cycling in the ponds was evaluated by determining grain size distribution, porewater SRP concentrations, sediment geochemistry and mineralogy, and the sediment P buffering capacity. Vegetation senescence, anoxic conditions, porewater SRP concentrations, sediment characteristics and buffering capacity influenced the poor TE at Pond 33. Pond 45 had more favourable water column conditions, i.e. higher dissolved oxygen concentrations, therefore allowed greater amounts of P to adsorb onto sediment. Design and maintenance considerations are described to help improve the performance at Pond 33. Continual water quality monitoring of SW effluent will identify changes in quality and mitigation measures can be implemented to increase a SWM ponds performance.

Stormwater (SW) runoff in urban areas represents a major pathway for pollutant transfer to receiving waters. Best management practices (BMP) were introduced in the 1970s to help mitigate the negative effects of SW. In the 1990s, Stormwater management (SWM) ponds were established as a BMP to help increase the water quality of SW effluent. Many SWM ponds do not provide sufficient water quality treatment. Information on the internal processes influencing the reduction of total phosphorus (TP), soluble reactive phosphorus (SRP) and total suspended solid (TSS) concentrations in SWM ponds with different designs is lacking. Knowledge of the processes affecting TP, SRP and TSS retention can help improve the design of SWM ponds to enhance their treatment performance. The purpose of this thesis is to provide an assessment of the internal chemical processes that affect the trap efficiency (TE) and spatial and temporal variability of TP, SRP and TSS concentrations at two structurally different SWM ponds (Pond 45; conventional and Pond 33; hybrid extended detention) in Waterloo, ON. Water samples were collected at the inflow and outflow at the two SWM ponds during six storm events and 30 baseflow periods. A mass balance approach was used to quantify the TE of TP, SRP and TSS concentrations at each pond. Pond 33 had a TE of 24.3%, 26.7% and 66.8% for baseflow and stormflow samples of TP, SRP and TSS. Pond 45 performed much better with TE of 93.8%, 94.2% and 98% for TP, SRP and TSS concentrations. Pond 33 was a source of TP, SRP and TSS for 3, 4 and 2 storm events sampled during the field season, respectively. Pond 45 was a sink for all parameters on all storm events samples. The spatial and temporal variability of TP, SRP and TSS concentrations were examined to improve knowledge of external factors and internal processes that influence the TE of SWM ponds. The effects of storm magnitude, seasonality and vegetation growth and senescence on effluent water quality were investigated. Additionally, the role of sediment on P cycling in the ponds was evaluated by determining grain size distribution, porewater SRP concentrations, sediment geochemistry and mineralogy, and the sediment P buffering capacity. Vegetation senescence, anoxic conditions, porewater SRP concentrations, sediment characteristics and buffering capacity influenced the poor TE at Pond 33. Pond 45 had more favourable water column conditions, i.e. higher dissolved oxygen concentrations, therefore allowed greater amounts of P to adsorb onto sediment. Design and maintenance considerations are described to help improve the performance at Pond 33. Continual water quality monitoring of SW effluent will identify changes in quality and mitigation measures can be implemented to increase a SWM ponds performance.

Tissue, among the highest value added paper products, finds extensive application in modern society. Continued efforts are being made to further improve tissue properties, such as strength, softness and water absorbency. Besides the efforts on characterizing facial tissue softness, this study focuses on tissue quality improvement through chemical means. The application of a wet strength resin, Kymene1500 and a debonding agent, Softrite7516 onto cellulose fibers is considered. First, the adsorption kinetics of the two chemical additives onto cellulose fibers was studied. The adsorption mechanisms were proposed and validated by kinetic data. A novel apparatus was designed in this study, and represented the first in the field to collect real-time data, which has the potential to be applied to the adsorption kinetic study of other types of paper additives. Second, the effects of Kymene1500 and Softrite7516 on various sheet properties were studied. The results provide quantitative information on tissue additives effects on sheet properties. It is shown that the combined application of the additives can overcome the disadvantages of individual species and produce sheets with both wet strength and softness. Finally, environmental-benign debonding agents with polyoxyethylene chains were applied to the sheets, and the effects of two design parameters, i.e., fatty acid and degree of ethoxylation, on tissue properties were investigated.

The purpose of this thesis is to fabricate 12-layer In0.75Ga0.25As quantum dot-in-a-well (In0.1Ga0.9As) structures grown by molecular-beam epitaxy (MBE) on GaAs substrate, and analyze the optical properties of laser devices for optical fiber communication systems. For the laser structures, larger Al content AlGaAs cladding layer enhance the optical confinement, but encounter much challenges to improve the quality. After we simulate and fabricate different Al content laser structures, we find the best cladding layer composition - Al0.2Ga0.8As which performs a best material gain. In the active layer, 12 layers In0.75Ga0.25As quantum dots (QDs) and QDs in a well (DWell) structure, and DWell with Be-doping in the well structure are included in this study. The well structure slows down the hot carriers speed and Be-doping decrease the carrier life time and increases the electron-hole pair recombination rate. We increase the QDs deposition coverage to move the emission wavelength to 1.3£gm, but the high temperature cladding layer growth process indirectly anneal the QDs and result in the emission wavelength blue shift to 1.24£gm. In the laser fabrication, to transport the light wave in smaller dispersion loss single mode waveguide, wet etching photolithography processes are adapted in this study to fabricate 2£gm width ridge waveguide. The as-cleaved facets are used as Fabry-Perot laser mirrors in ridge waveguide lasers. Finally, the current density of QD Laser(C528) lasing in CW mode is 581A/cm2, slope efficiency of 510mW/A and maximum power/facet of 65mW are obtained.Then the current density of DWELL+PD Laser(C540) lasing in CW mode is 880A/cm2, slope efficiency of 430mW/A and maximum power/facet of 34mW are obtained.

Polycyclic aromatic hydrocarbons (PAHs) are one of major classes of organic pollutants. As semi-volatile organic compounds, PAHs can be transported in the atmosphere and scavenged according to various processes (dry and wet deposition). Atmospheric deposition is an important pathway for the transfer of pollutants from atmosphere to the terrestrial and water surfaces. The objective of this research is to quantify the dry and wet deposition of the atmospheric PAHs in the Kaohsiung coastal area. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were also performed with diagnostic ratios to determine the potential sources of PAHs. The mean dry and wet deposition fluxes of atmospheric total suspended particles (TSP) during the study period (January-December 2010) were estimated to be 44.3 (6.60-384) and 211 (56.1-738) mg/m2d, respectively. The annual mean total PAH fluxes in dry and wet deposition were 1500 (749-3760) and 8470 (2280-46000) ng/m2d, respectively. Both concentrations and dry deposition fluxes of TSP were much higher during dust storm. During Ghost Month, however, they were comparable with other sampling events. By comparing with literatures, the total PAH concentrations of TSP were relatively low during Ghost Month, suggesting that wind direction and precipitation might be plausible. The ratio of PM2.5/PM10 had a relatively low value during dust storm, indicating that coarse particle might be predominant. In addition, during dust storm, both TSP dry deposition velocity and total PAH dry deposition velocity were higher than other sampling events. Our findings in this study showed that previous attempts in literature to estimate total PAH dry deposition fluxes by using TSP dry deposition velocity and PAH concentrations could lead to overestimate fluxes in the field. TSP dry deposition fluxes were positively correlated with atmospheric total TSP concentrations and TSP dry deposition velocity, but were correlated negatively with intensity of precipitation. In addition, TSP dry deposition velocity showed a positive correlation with TSP concentrations. Total PAH dry deposition fluxes were correlated positively with atmospheric total particulate concentrations and total PAH dry deposition velocity, but negatively with intensity of precipitation and temperature. However, TSP and total PAH fluxes in wet deposition were both correlated positively with intensity of precipitation. Diagnostic ratios showed that diesel exhaust was the main source of combustion-derived PAHs in the study. HCA and PCA analysis indicated that emissions from the ships and vehicles, and fuel used were the main sources of combustion-derived PAHs, while during special events, such as dust storm and Ghost Month, suggesting a different source of PAHs.

Twin-screw multiphase pumps experience a severe decrease in efficiency, even the breakdown of pumping function, when operating under wet gas conditions. Additionally, field operations have revealed significant vibration and thermal issues which can lead to damage of the pump internals and expensive repairs and maintenance. There are limited models simulating the performance of twin-screw pump under these conditions. This project develops a pump-user oriented simulator to model the performance of twin-screw pumps under wet gas conditions. Experimental testing is conducted to verify the simulation results. Based on the simulations, an innovative solution is presented to improve the efficiency and prevent the breakdown of pumping function. A new model is developed based upon a previous Texas A&M twin-screw pump model. In this model, both the gas slip and liquid slip in the pump clearances are simulated. The mechanical model is coupled with a thermodynamic model to predict the pressure and temperature distribution along the screws. The comparison of experimental data and the predictions of both isothermal and non-isothermal models show a better match than previous models with Gas Volume Fraction (GVF) 95% and 98%. Compatible with the previous Texas A&M twin-screw pump model, this model can be used to simulate the twin-screw pump performance with GVF from 0% to 99%. Based on the effect of liquid viscosity, a novel solution is investigated with the newly developed model to improve the efficiency and reliability of twin-screw pump performance with GVF higher than 94%. The solution is to inject high viscosity liquid directly into the twin-screw pump. After the simulations of several different scenarios with various liquid injection rates and injection positions, we conclude that the volumetric efficiency increases with increasing liquid viscosity and injecting liquid in the suction is suggested.

A simple and high efficient wet etching technique for fabricating pyramid textures on (100) Si wafer is proposed. Conventionally, pyramid textures were formed on Si wafers to reduce reflections using KOH anisotropic etching. Isopropyl Alcohol (IPA) is often added to the solution to abate the bubbling effect caused by hydrogen released form the Si surfaces during reaction. In this study, a metal net with proper opening dimension was used as a shelter to trap the hydrogen from leaving the surfaces of Si, and therefore turns the hydrogen gas into a gas-type etching mask during the anisotropic etching. In this way, pyramid textures with dimensions range from 3µm to 8µm were successfully fabricated. The measured average reflectivity of the texture for incident optical wave length from 400nm to 1000nm is less than 18%.

No description available.

­^¤åºK­n In the wet wafer cleaning process, the wafer surfaces are washed with toxic solutions such as ammonia and sulfuric acid which was not to allow to enter the surroundings i.e. clean room. Therefore, common practice is to reduce the pressure differential between the wet bench and the surroundings to a very low pressure difference level while maintaining a high exhaust flow rate for toxic fumes. In such a case, the isolation of process area from the surrounding area may be compromised i.e. there is a danger that the surrounding air was suctioned to the process area. Conceptually, this dilemma can be solved by creating an air buffer between the wafer process area and the surrounding area. This study aims to determine/prove-in the optimal operational conditions and geometries of such design by both CFD analysis and experimental verification. This thesis includes three parts. First, the detailed experimental data to a bio-clean bench installed with the guide-vane design are conducted. The data are then used to verify the feasibility/accuracy of the CFD model. Second, the optimal operational conditions and geometries of a full-scale isothermal wet bench with the guide-vane design are determined by CFD simulation that takes most influential factors into account. These influential factors include exhaust pressures, length of the guide- vane, guide-vane angle and downward face velocity of the filter etc. The results show that the air curtain created by the guide-vane is able to isolate the process area from surrounding area, and vise-versa. Third, the thermal effect of ammonia solution on the distribution of ammonia vapor are examined. The shape of the thermal plume that encounters the downward air stream of the filter is discussed intensively. In general, this thesis provides significant information in improving the isolation effect of wet benches by the air-curtain design.

The objectives of this research were to obtain the optimum operating conditions for a catalytic wet air process and to investigate their reaction kinetics. Either the ferrouscyanide (Fe(CN)64¡Ð) or the 2,4-dichlorophenol (2,4-DCP) solution was treated by the catalytic wet air oxidation (CWAO) process using three metal ions (Cu2+, Ce3+, and Mn2+) as catalysts or with the Mn/Ce composite oxide catalysts, respectively. In addition, the biodegradability of the effluent derived from the CWAO (2,4-DCP) process was studied. Results show that the effect of addition of the Cu2+ ion on the wet air oxidation (WAO) of Fe(CN)64¡Ð solution is significant because the Cu2+ ion plays in a role of catalyst, which may lower the activation energy (Ea) during the first-stage of the CWAO process. However, either the Ce3+ or Mn2+ ion did an adverse effect on the Fe(CN)64¡Ð removal, even they had a worse removal than that did by the WAO run without any catalyst addition. The Ea value of the first-stage in the WAO of the Fe(CN)64¡Ð solution process was calculated to be 40.5 KJ mol¡Ð1. On the other hand, the Ea values of the CWAO process with an addition of the Cu2+, Ce3+, or Mn2+ ion, were reduced to 14.1, 16.0, and 20.4 KJ mol¡Ð1, respectively. Obviously, the values of Ea can be reduced to promote the pollutants removal by an addition of suitable catalysts into the WAO process. It was observed that 2,4-DCP is difficult to be decomposed in the thermal pyrolysis process, but the conversion of 2,4-DCP is significant in the WAO process. With an application of the Mn/Ce composite oxide catalyst in the CWAO process to treat the 2,4-DCP solutions resulted in a better removal than that did by the WAO process. The higher the reaction temperature was applied, the higher 2,4-DCP removal was obtained. Also, the catalyst in a higher Mn/Ce molar ratio would increase the removal of 2,4-DCP during the CWAO runs, while the catalyst in a Mn/Ce molar of 7:3 showed the best 2,4-DCP removal of 96.5%. It is suggested that the reaction temperature of the CWAO process could be controlled 40 K lower than that required in the WAO run to reach an equivalent 2,4-DCP removal efficiency. The Ea value of the WAO of 2,4-DCP process performed in a semi-batch type reactor were 13.6 and 23.7 KJ mol¡Ð1, respectively, for the first-stage and the second-stage reactions. However, the Ea values of the both reaction stages in the CWAO of 2,4-DCP run were reduced to 9.1 and 5.7 KJ mol¡Ð1, respectively. If the CWAO of 2,4-DCP was performed in an up-flowing fixed -bed reactor, a second-order formula was found. Also, the activation energy and the frequency constant of the CWAO of 2,4-DCP run were calculated to be 11.9 KJ mol¡Ð1 and 0.96 sec¡Ð1. In the Microtox® toxicity tests, the TUa,15 values of the effluent from the CWAO run were below 8.26, when the CWAO process was operated at 433 K and at a space velocity of less than 11.0 hr¡Ð1, and the Mn/Ce (7:3) composite oxide as a catalyst. On the other hand, the toxicity of the 2,4-DCP could be reduced greatly by being treated in the CWAO process over the Mn/Ce (7:3) composite oxide catalyst. It is possible to treat the 2,4-DCP solution in a concentration less than 500 mg L¡Ð1 to meet the discharging regulation standards using a CWAO run, and followed by an activated sludge unit in which the retention time of the wastewater could be sorter than twelve hours.