31Tuberculosis (TB) is still a serious public health problem in various countries. One of the long-

The capability of predicting the adhesion forces between a rough particle and surface including the van der Waals force and capillary force is important for modeling various processes involving particle surface retention and resuspension. On the basis of the fractal theory describing the behavior of multiple roughness scales and the Gaussian roughness distribution, a set of mathematical models for the van der Waals force and capillary force is proposed. The proposed models provide the adhesion force predictions in good agreement with the existing experimental data and converge to the previous classical solutions of the adhesion forces between a smooth particle and surface as the roughness goes to zero. The influences of roughness for the combination of particle and surface, relative humidity (RH), contact angle, and Hurst exponent toward the adhesion forces are examined using the proposed models. The decline mode of the adhesion force with surface roughness and contact angle, as well as the increase mode with RH and the Hurst exponent are reasonably predicted by the proposed models. The comparison between the proposed models and those from the existing studies is also performed, which shows the similarities and differences between the proposed models and the existing models.

The compositions of food wastes and their co-gasification producer gas were compared with the existing data of sewage sludge. Results showed that food wastes are more favorable than sewage sludge for co-gasification based on residue generation and energy output. Two decentralized gasification-based schemes were proposed to dispose of the sewage sludge and food wastes in Singapore. Monte Carlo simulation-based cost-benefit analysis was conducted to compare the proposed schemes with the existing incineration-based scheme. It was found that the gasification-based schemes are financially superior to the incineration-based scheme based on the data of net present value (NPV), benefit-cost ratio (BCR), and internal rate of return (IRR). Sensitivity analysis was conducted to suggest effective measures to improve the economics of the schemes.

Long-term exposure to airborne particulate matter (PM) indoors can cause adverse health effects to the occupants. Such exposure can be influenced by human-walking-induced particle resuspension (HWIPR). Several factors affecting HWIPR were investigated experimentally. The resuspension rates during walking were calculated based on the mass balance model, and the power law was applied to fit the resuspension rate data. The resuspension rate was further normalized for investigating the effects of various factors on HWIPR. It was found that the normalized resuspension rate of PM10 was about 2.5 times that of PM2.5 for both carpet and wood polyvinyl chloride (PVC). The normalized resuspension rate from carpet was about twice as much as the rates from wood PVC and four times that from vinyl. For both carpet and vinyl, the resuspension rates under the low relative humidity (RH) (41%) were three times that under the medium RH (63%) and 3.5 times that under the high RH (82%). The experimental results suggest that the addition of the mechanical mechanism is critical for HWIPR. Based on the power law relationship, an airborne particle concentration model was developed for HWIPR. The modelled concentration profiles were consistent with the experimentally determined particle concentrations associated with HWIPR. The proposed airborne particle concentration model provides a new way of predicting human exposure to airborne particles due to HWIPR.

Particle number concentration, particle size distribution, and size-dependent chemical compositions were measured at a bus stop, alongside a high way, and at an industrial site in a tropical city. It was found that the industry case had 4.93×10-7.23×10 and 3.44×10-3.69×10#/m higher concentration of particles than the bus stop and highway cases in the range of 0.25-0.65μm and 2.5-32μm, respectively, while the highway case had 6.01×10 and 1.86×10#/m higher concentration of particles than the bus stop case in the range of 0.5-1.0μm and 5.0-32μm, respectively. Al, Fe, Na, and Zn were the most abundant particulate inorganic elements for the traffic-related cases, while Zn, Mn, Fe, and Pb were abundant for the industry case. Existing respiratory deposition models were employed to analyze particle and element deposition distributions in the human respiratory system with respect to some potential exposure scenarios related to bus stop, highway, and industry, respectively. It was shown that particles of 0-0.25μm and 2.5-10.0μm accounted for around 74%, 74%, and 70% of the particles penetrating into the lung region, respectively. The respiratory deposition rates of Cr and Ni were 170 and 220 ng/day, and 55 and 140ng/day for the highway and industry scenarios, respectively. Health risk assessment was conducted following the US EPA supplemented guidance to estimate the risk of inhalation exposure to the selected elements (i.e. Cr, Mn, Ni, Pb, Se, and Zn) for the three scenarios. It was suggested that Cr poses a potential carcinogenic risk with the excess lifetime cancer risk (ELCR) of 2.1-98×10 for the scenarios. Mn poses a potential non-carcinogenic risk in the industry scenario with the hazard quotient (HQ) of 0.98. Both Ni and Mn may pose potential non-carcinogenic risk for people who are involved with all the three exposure scenarios.