Browsing by Author "Uang, Shi-Nian"

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Measurements of ultrafine particle concentrations and size distribution in an iron foundry
(2008-10-01)
Cheng, Yu-Hsiang
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Chao, Yen-Chi
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Wu, Cheng-Han
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Tsai, Chuen-Jinn
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Uang, Shi-Nian
The number and surface area concentration of ultrafine particles in an iron foundry is of interest as freshly generated ultrafine particles are produced by metal melting, pouring and molding processes. This study measured the number and surface area concentrations of ultrafine particles and their size distributions in an iron foundry using a scanning mobility particle sizer (SMPS). The 10-100 nm ultafine particle number concentrations (NC0.01-0.1) and surface area concentrations (SC0.01-0.1) measured at the iron foundry were 2.07 x 10(4) to 2.82 x 10(5) particles cm(-3) and 67.56 to 2.13 x 10(3) mu m(2) cm(-3), respectively. The concentrations changed dramatically depending on on-site manufacturing conditions. The NC0.01-0.1 levels in the iron foundry were approximately 4.5 times higher on average compared with those in the outdoor ambient environment. These measurement results indicate that the presence of extra particles in the workplace air is within the ultrafine range. Additionally, the analytical results suggest that the number mode diameter can be used to estimate the SC0.01-0.1 levels using the NC0.01-0.1 levels. Moreover. the ultrafine particle number mode diameter was found to be about 46.1 nm in the iron foundry. (C) 2008 Elsevier B.V. All rights reserved.
Novel Active Personal Nanoparticle Sampler for the Exposure Assessment of Nanoparticles in Workplaces
(2012-04-17)
Tsai, Chuen-Jinn
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Liu, Chun-Nan
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Hung, Shao-Ming
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Chen, Sheng-Chieh
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Uang, Shi-Nian
A novel active personal nanoparticle sampler (PENS), which enables the collection of both respirable particulate mass (RPM) and nanoparticles (NPs) simultaneously, was developed to meet the critical demand for personal sampling of engineered nanomaterials (ENMs) in workplaces. The PENS consists of a respirable cyclone and a micro-orifice impactor with the cutoff aerodynamic diameter (d(pa50)) of 4 mu m and 100 nm, respectively. The micro-orifice impactor has a fixed micro-orifice plate (137 nozzles of 55 mu m in the inner diameter) and a rotating, silicone oil-coated Teflon filter substrate at 1 rpm to achieve a uniform particle deposition and avoid solid particle bounce. A final filter is used after the impactor to collect the NPs. Calibration results show that the d(pa50) of the respirable cyclone and the micro-orifice impactor are 3.92 +/- 0.22 mu m and 101.4 +/- 0.1 nm, respectively. The d(pa50) at the loaded micro-Al2O3 mass of 0.36-3.18 mg is shifted to 102.9-101.2 nm, respectively, while it is shifted to 98.9-97.8 nm at the loaded nano-TiO2 mass of 0.92-1.78 mg, respectively. That is, the shift of d(pa50) due to solid particle loading is small if the PENS is not overloaded. Both NPs and RPM concentrations were found to agree well with those of the IOSH respirable cyclone and MOUDI. By using the present PENS, the collected samples can be further analyzed for chemical species concentrations besides gravimetric analysis to determine the actual exposure concentrations of ENMs in both RPM and NPs fractions in workplaces, which are often influenced by the background or incident pollution sources.
The Effect of Nanoparticle Convection-Diffusion Loss on the Transfer Function of an Aerosol Particle Mass Analyzer
(2014)
Lin, Guan-Yu
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Liao, Bo-Xi
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Tzeng, Neng-Jiun
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Chen, Chun-Wan
;
Uang, Shi-Nian
The existing theoretical response spectra of APM-3600 agree well with the experimental data for submicron particles larger than 100nm in the electrical mobility diameter but not for nanoparticles. In this study, a 2-D numerical model was developed to predict the transfer function and response spectra of APM-3600 based on the detailed simulation of flow and particle concentration fields. It was found that recirculation flows existed in the annular classifying region and APM\'s inlet and outlet regions, which led to enhanced convection-diffusion loss of nanoparticles compared to that without considering flow recirculation. As a result, the APM underestimates the mass of naonoparticles due to the shift of the peak position of the transfer function to a larger diameter than the targeted diameter. The response spectra calculated with the simulated transfer function agree well both in shapes and peak values with the experimental data present in a previous study for both nanoparticles and submicron particles larger than 100 nm. The predicted particle masses also agree well with the PSL\'s experimental data of the article.Copyright 2014 American Association for Aerosol Research