Chih-Chung Wen

A complementary mild-slope equation derived using higher-order depth function for waves obliquely propagating on sloping bottom

In this paper a complementary mild-slope equation (CMSE) is derived in order to investigate the transformation of progressive waves obliquely propagating over the sloping bottom more realistically. We introduce a new depth function which includes the wave refraction and the influence of the bottom slope α, perturbed to the second-order in the integral equation. A new depth-integrated mild-slope equation is derived, by using the above mentioned depth function, to model a time-harmonic motion of small amplitude waves in varying water depth. The simulated results reveal that the proposed model provides a significant improvement in the calculation of the wavenumber and the group velocity at different bottom slopes. With the increasing bottom slope, the discrepancies in the reflection coefficient of Bragg scattering between the analytical solution and the one calculated from the conventional mild-slope equation (MSE) and the modified MSE (MMSE) are seen to steadily increase. The group velocity of the waves, wh...

Concentrations of nano and related ambient air pollutants at a traffic sampling site

A micro-orifice uniform deposit impactor (MOUDI) and a nano-MOUDI were used to measure the atmospheric coarse (PM2.5- 10), fine (PM2.5), ultrafine (PM0.056 - 1) and nano (< 0.056 μm) particle concentrations and size distributions at a traffic sampling site in winter in central Taiwan, from November 2004 to January 2005. Concentrations of metallic elements (Fe, Mg, Cr, Zn, Pb, Cu) and major ion (SO2 - 4; NO- 3; NH+ 4) in particles of various sizes (nano, ultrafine, fine and coarse) were measured. Ambient air particulates generally exhibited a bimodal size distribution in the range 0.056-10 mm. The results show that the concentrations followed the order, Fe-Mg-Cr-Zn-Pb-Cu in PM10, fine, ultrafine and nano-sized particles. Moreover, the data showed that the average metallic elements Fe and Zn have similar concentration distributions: the concentration decreased as the particle size fell in the nano size range.

Development of Appropriate Statistical Equations for Ambient Air Particulates and Pollutants at a Traffic Sampling Site

This study monitored the atmospheric pollutants at the WuChi traffic (WT) sampling site from March 2004 to January 2005 near the Taiwan Strait in central Taiwan. The distributions of the particle concentrations between the total suspended particulates and the particulate matter around roads (fine particles and inhaled particles) at the WT sampling site were also determined. The variations in the concentrations of metallic elements (Fe, Mg, Cr, Cu, Zn, Mn, and Pb) and ions species (Cl−, NO3 −, SO4 2 −, NH4 +, Mg2+, Ca2+ and Na+) in those particles were also analyzed with reference to meteorological conditions. A nonparametric (Spearman) correlation analysis indicated that the meteorological conditions are closely correlated with the largest total suspended particulates at the WT sampling site. The results also indicated that the temperature importantly affected the particulate matter and was more closely correlated with particulate matter than other meteorological parameters such as wind speed, relative humidity, and atmospheric pressure. Finally, the regression equations between the pollutants and the meteorological parameters are shown.