Wing-Yeong Lee. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 73-75). / Abstracts in English and Chinese. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- The observed data --- p.3 / Chapter 1.3 --- Outline of the thesis --- p.8 / Chapter Chapter 2 --- Modeling using Latent Variable --- p.9 / Chapter Chapter 3 --- Imputation Procedure --- p.16 / Chapter 3.1 --- Introduction --- p.16 / Chapter 3.2 --- Introduction to Metropolis-Hastings algorithm --- p.18 / Chapter 3.3 --- Introduction to Gibbs sampler --- p.19 / Chapter 3.4 --- Imputation step --- p.21 / Chapter 3.5 --- Initialization of the missing values by regression --- p.23 / Chapter 3.6 --- Initialization of the parameters and creating the latent variable and noises --- p.27 / Chapter 3.7 --- Simulation of Y's --- p.30 / Chapter 3.8 --- Simulation of the parameters --- p.34 / Chapter 3.9 --- Simulation of T by use of the Metropolis-Hastings algorithm --- p.41 / Chapter 3.10 --- Distribution of Vij's given all other values --- p.44 / Chapter 3.11 --- Simulation procedure of Vij's --- p.46 / Chapter Chapter 4 --- Data Analysis of the Pollutant Data --- p.48 / Chapter 4.1 --- Convergence of the process --- p.48 / Chapter 4.2 --- Data analysis --- p.53 / Chapter Chapter 5 --- Conclusion --- p.69 / REFERENCES --- p.73

No description available.

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

In view of the worsening air quality in the world, more concerns are focused on the environment. This thesis uses the technique of CFD and develops the computer model to investigate the wind and pollutant transport, as well as the chemistry of reactive pollutants in idealized two-dimensional (2D) street canyons. Three scientific questions are raised in this thesis. The first task is to find out the po- sition with the most favorable pollutant removal along the ground level over 2D idealized street canyon of different building-height-to-street-width (aspect) ratios (ARs). The di- mensionless parameter, C, represents the pollutant removal performance. In the isolated roughness regime, the two local maximum C locate at the reattachment point and the windward corner. In the wake interference regime, C is peaked on the windward side. The number of vertically aligned recirculations depends on the street depth in the skimming flow regime. The sizes of the secondary recirculation upstream and downstream deter- mine how the maximum C shifts from the street centre. After identifying the position of peaked pollutant removal rate at the ground level, the emission source should be placed with the highest constant C in order to remove the pollutants upward more quickly to safeguard the street-level air quality. After understanding the best pollutant removal in the street canyon of different ARs, the second task is to find out what AR is the most favorable for the ventilation and pollutant removal across the roof level. The three parameters, namely friction factor, air exchange rate (ACH) and pollutant exchange rate (PCH), are introduced to quantify the pressure difference to sustain the mean flow, the ventilation and pollutant removal, respectively. The turbulence contributes more than 70% to the total ACH and PCH in all the three flow regimes. By increasing the atmospheric turbulence in building geometry as well as the surface roughness, the ventilation and pollutant removal performance can be improved. The linear relation between the friction factor and ACH demonstrates the larger resistance that in turn promotes the air exchange over the roof level. The physical dispersion is studied; however atmospheric pollutants are seldom in- ert but chemically reactive instead. The last task is to include the three common air pollutants, NO, NO2 and O3, in the simple NOx ?O3 mechanism in terms of the photo- stationary state and reaction rates. The Damkohler numbers of NO and O3, DaNO and DaO3, are parameterized by the concentrations of the sources NO and O3. The normalized mean and fluctuation NO, NO2 and O3 are separately considered. The integrated pho- tostationary state (PSS) in the first canyon increases with DaO3 under the same DaNO. The integrated PSS of the second to the twelveth street canyons are compared with each case, the monotonic increase in the PSS from the second to twelveth canyon is perceived in DaNO/DaO3 1, 0.03, 0.02, 0.001 and 0.000333. Further decreases the DaNO/DaO3 to 0.000143, 0.000125, 0.000118, 0.000111 and 0.0001, the PSS is found to be non-linear and the trough appears in the fourth and fifth canyons. / published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

Two approaches, one using an atmospheric diffusion model and the other an atmospheric tracer, were used to predict the source strength of trace gases from observations of the downwind concentration field. Both approaches do not disturb the prevailing environmental and physical conditions nor the existing biogenic processes. An analytical solution to the advection-diffusion equation was used to back-calculate the source strength from the downwind concentration measurements of (i) single and multipoint (4 and 16 points) trace gas (sulphur hexafluoride (SF6) and methane (CH4)) release experiments conducted over microplots over an open field, and (ii) single point source SF6 release experiments conducted over a forested terrain. Best predictions of the source strength (to within +/-20%) were obtained from concentration observations made along the centreline of the diffusing plumes with the predictions improving when observations at the mean plume height were used. The diffusion model was then used to compute footprint estimates for neutral and unstable conditions, for tower and aircraft based observation platforms above the forest. They showed spatially constrained footprints in the surface layer, due to effective vertical coupling, so that observations from towers and low flying aircraft must be expected to be very site specific, and scaling up to larger areas will have to be done with careful consideration of surface mosaics. Above-canopy sampling of trace gases to determine volatile organic compound emissions were then interpreted in terms of footprint considerations. This was accomplished by defining the upwind canopy areas effectively sampled under the given wind and stability conditions. The analysis demonstrated, for example, that the variability observed in measured isoprene fluxes could be accounted for by varying numbers of randomly distributed clumps of emitter species within a varying footprint. It suggested that heterogeneity of the forest canopy, in ter / Sulphur hexafluoride was also used as an atmospheric tracer in order to estimate CH4 emissions from manure slurry and cattle housed in barns and feedlots. (Abstract shortened by UMI.)

Michel M. Benarie. / Includes bibliographies and indexes.

Three air pollution models are presented which address themselves to the specific problems of 1) pinpointing locations of relative maxima, 2) producing air quality maps efficiently, and 3) presenting. graphic representation of patterns of pollution over a mesoscale region. MAXPOL-A is a semiempirical, source-oriented, microscal0, deterministic, climatological air pollution model which uses a simplex search algorithm to walk, one step at a time, towara the area of maximum concentration. Input parameters govern the length of walk and the precision with which the maximum is located. SIMPLOT is a semiempirical, source-oriented, stochastic, climatological air pollution model and employs the concept of stochastic simulation as well as simulation ! in the usual sense to obtain estimates of air quality. SIMPLOT also uses a technique. called the plume projection procedure which allows it to generate all of the receptors for each eliminating source and meteorological extensive checking. DAMPS condition thus is a dynamic, segmented, source-oriented, deterministic, mesoscale model which keeps track of all air parcels over a 60 by 60 kilometer region. DAMPS updates all receptors hourly and produces three types of graphic output. DAMPS also utilizes the plume projection procedure used in SIMPLOT. Computer programs foe each model are included as are several examples of the use of each model. / Ph. D.

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Mechanical Engineering / Master / Master of Philosophy

by Kwok-Fai Mo. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 74-79). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Statistical Modeling --- p.5 / Chapter 2.1 --- Poisson Regression --- p.5 / Chapter 2.2 --- Overdispersion and Autorrelation --- p.7 / Chapter 2.3 --- Generalized Estimating Equation --- p.9 / Chapter 2.4 --- Zeger's Mehthod --- p.12 / Chapter 2.5 --- Multicollinearity --- p.18 / Chapter 2.5.1 --- The Modified Generalized Estimating Equation --- p.18 / Chapter 2.6 --- Bootstrapping Method --- p.21 / Chapter 2.7 --- The Bootstrap Choice of Ridge Parameter --- p.23 / Chapter 3 --- The Robustness of Zeger's Approach to the Specification of ηt - Simulation Study --- p.26 / Chapter 3.1 --- Introduction --- p.26 / Chapter 3.2 --- Zeger's Algorithm with Varoious Time Series Data --- p.27 / Chapter 3.2.1 --- Data without Multicollinearity --- p.27 / Chapter 3.2.1 --- Data with Multicollinearity --- p.34 / Chapter 3.3 --- Modified Generalized Estimating Equation Approach --- p.40 / Chapter 3.3 --- The Choice of Ridge Paramter in Bootstrap --- p.42 / Chapter 4 --- Real Example --- p.46 / Chapter 4.1 --- Data Structure --- p.46 / Chapter 4.2 --- Model Building --- p.49 / Chapter 4.3 --- Single Pollutant Model --- p.57 / Chapter 4.4 --- Multiple Pollutant Model --- p.62 / Chapter 5 --- Conclusion and Discussion --- p.64 / Appendix --- p.69 / References --- p.74