• Tribology and Lubricants
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• 제21권3호
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• pp.114-121
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• 2005

As fuel cell system is environmental friendly generator, its performance depends on its air supply system. Because, fuel cell stack generates electrical energy by electron and the electron is generated by reacting between air and hydrogen. So, more and more compressed air is supplied, more and more the energy can be obtained. In this study, turbo-expander supported by air foil bearing is introduced as the air supply system used by fuel cell systems. The turbo-expander is a turbo machine which operates at high speed, so air foil bearings suit its purpose for the bearing elements. Analysis for confirming the stability and endurance is conducted. Based on FDM and Newton-Raphson method, characteristics of air foil bearing, dynamic coefficients, pressure field and load capacity, are obtained. Using the characteristics of air foil bearing, the rotordynamic analysis is performed by finite element method. The analysis (stability analysis and critical speed map) shows that turbo-expander is stability at running speed. After the analysis, the test process and results are presented. The goals of test are running up to 90,000 RPM, flow rate of 150 $m^3/h$ and pressure ratio of 1.15. The test results show that the aerodynamic performance and stability of turbo-expander are satisfied to the primary goals.

• Asian Pacific Journal of Cancer Prevention
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• 제16권8호
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• pp.3533-3538
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• 2015

Background: Multiple primary malignancies (MPM) have become increasingly prevalent worldwide. This investigation was aimed at establishing the clinicopathological characteristics of MPM patients and evaluating the impact of the living environment on MPM in the Taiwanese population. Materials and Methods: From January 2009 to December 2013, a total of 8,268 cancer patients were identified in our institutional center. Of these, 125 were diagnosed as MPM and thus enrolled. Data for clinicopathological features and treatment approaches for these MPM patients living in urban or suburb zone were obtained. Findings for the air pollution status in Taiwan were also collected. Results: The most common cancer match of MPM was esophageal cancer with hypopharyngeal cancer (12.8%), followed by colorectal cancer with gastric cancer (6.4%) and colorectal cancer with breast cancer (5.6%). The air quality was significantly worse in the urban than in the suburban zone and there was a remarkably higher portion of MPM patients in the urban zone suffering from grade III and IV post-chemotherapeutic neutropenia (30.8% vs 15.1%, P=0.036). Conclusions: The tumor frequency and site distribution should be taken into the clinical evaluation because there is a relatively high risk of developing MPM. This study also highlighted the potential influence of environmental factors on post-chemotherapeutic neutropenia for patients with MPM.

• 한국대기환경학회지
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• 제32권1호
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• pp.21-31
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• 2016

Organic carbon (OC) and elemental carbon (EC) in $PM_{2.5}$ were measured with Sunset OC/EC Field Analyzer at Taehwa Research Forest (TRF) near Seoul metropolitan area from May 2013 to April 2014. During the study period, the mean concentrations of OC and EC were $5.0{\pm}3.2{\mu}gC/m^3$ and $1.7{\pm}1.0{\mu}gC/m^3$, respectively. They showed clear seasonality reaching their maximum in winter ($6.5{\mu}gC/m^3$ and $1.9{\mu}gC/m^3$) and minimum in wet summer ($2.5{\mu}gC/m^3$ and $1.4{\mu}gC/m^3$). While OC showed greater seasonal variation, the diurnal variation was more noticeable for EC through all seasons with a clear maximum in the morning, which reveals the influence of vehicle emissions. In contrast, OC exhibited a broad second peak in the afternoon during May~June, when biological activities were the highest. Using the morning peaks of EC and OC, primary OC/EC ratio was assessed, which was assumed to be anthropogenic origin. It was the greatest in winter followed by spring and the lowest in wet summer. The seasonal difference in primary OC/EC ratio implies the influence of non-local sources of OC at the Mt. Taehwa.

• 한국대기환경학회지
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• 제17권1호
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• pp.97-104
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• 2001

Decomposition of trichloroethlyene(TCE) in electron beam irradiation was examined on order to obtain information on the treatment of VOC in air. Air containing vaporized TCE has been studied in a flow reactor with different reaction environments, at various initial TCE concentration and in the presence and absence of water vapor. Maximum decomposition was observed in oxygen reaction environment and the degree of decomposition was about 99% at 20kGy for 2,000ppm initial TCE. The concentration of TCE exponentially decreased with dose in air and pure oxygen. The effect of water vapor on TCE decomposition efficiency was examined. The decomposition rate of TCE in the presence of water vapor (5,600 ppm) was approximately 10% higher than that in the absence of water vapor. Dichloroacetic acid, dichloroacethyl chloride and dichloroethyl ester acid were identified as primary products of this reaction adn were decomposed and oxidized to yield CO and $CO_2$. Perchloroethylene, hexachloroethane, chloroform and carbon tetrachloride were also observed as highly chlorinat-ed by products.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제24회 KOSCO SYMPOSIUM 논문집
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• pp.3-10
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• 2002

In this work, numerical parametric studies on spray combustion have been conducted. In simulation of turbulence, RNG ${\kappa}-{\varepsilon}model$ is adopted. Initial spray distribution is specified by Rosin-Rammler distribution function. Eddy break-up model is adopted as a combustion model. The parameters considered are inlet air temperature, swirl number, and SMD. With higher inlet air temperature, the axial velocities are increased and penetration of primary jet is stronger than that of lower inlet air temperature and temperature at the exit of combustor is more uniform. Combustion efficiency is improved with high inlet air temperature. The effect of swirl number on flow field is not significant. It affect only recirculation zone. So temperature at upstream of combustor is influenced. Combustion efficiency deteriorate as SMD of fuel spray increase.

• Asian Journal of Atmospheric Environment
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• 제1권1호
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• pp.9-13
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• 2007

Various aspects of the air quality problems caused by ambient particles in and around the city of Seoul are discussed. First, the trend of the air quality in Seoul over time is investigated along with the types and quantities of energy consumption in Seoul. It was found that the general air quality in Seoul has improved over the last twenty years because of a change in the primary fuel used in Korea. However, the visibility in Seoul, a representation of the ambient particle concentration, is still worse than in other cities in Korea. In the air around Seoul, secondary particle generation might be as important as particles directly emitted from within the city or transported from outside.

• Asian Journal of Atmospheric Environment
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• 제2권1호
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• pp.34-46
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• 2008

Emissions inputs for use in air quality modeling of Korea were generated with the emissions inventory data from the National Institute of Environmental Research (NIER), maintained under the Clean Air Policy Support System (CAPSS) database. Source Classification Codes (SCC) in the Korea emissions inventory were adapted to use with the U.S. EPA's Sparse Matrix Operator Kernel Emissions (SMOKE) by finding the best-matching SMOKE default SCCs for the chemical speciation and temporal allocation. A set of 19 surrogate spatial allocation factors for South Korea were developed utilizing the Multi-scale Integrated Modeling System (MIMS) Spatial Allocator and Korean GIS databases. The mobile and area source emissions data, after temporal allocation, show typical sinusoidal diurnal variations with high peaks during daytime, while point source emissions show weak diurnal variations. The model-ready emissions are speciated for the carbon bond version 4 (CB-4) chemical mechanism. Volatile organic carbon (VOC) emissions from painting related industries in area source category significantly contribute to TOL (Toluene) and XYL (Xylene) emissions. ETH (Ethylene) emissions are largely contributed from point industrial incineration facilities and various mobile sources. On the other hand, a large portion of OLE (Olefin) emissions are speciated from mobile sources in addition to those contributed by the polypropylene industry in point source. It was found that FORM (Formaldehyde) is mostly emitted from petroleum industry and heavy duty diesel vehicles. Chemical speciation of PM2.5 emissions shows that PEC (primary fine elemental carbon) and POA (primary fine organic aerosol) are the most abundant species from diesel and gasoline vehicles. To reduce uncertainties in processing the Korea emission inventory due to the mapping of Korean SCCs to those of U.S., it would be practical to develop and use domestic source profiles for the top 10 SCCs for area and point sources and top 5 SCCs for on-road mobile sources when VOC emissions from the sources are more than 90% of the total.

• 대한기계학회논문집B
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• 제23권11호
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• pp.1464-1472
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• 1999

Design and operation of $1MW_{th}$ pulverized coal combustion testing facility are described. Also the influence of air staging on NOx emission and burnout of coal flames was investigated in this facility. The test facility consisted of coal feeding system, firing system and flue gas treatment system. A top-fired externally air staging burner was adopted in order to avoid influence of gravity on the coal particles and for easy maintenance. Distribution of temperature and chemical species concentration of coal flames could be measured in vertical pass of furnace. Main fuel was pulverized (83.4% less than $80{\mu}m$) Australian high bituminous coal. From variety of test conditions, overall excess air ratio was selected at 1.2(20% excess air). Tho study showed that increasing the staged air resulted in lower NOx omission, and it was suggested to be more than 40% of the total combustion air for the substantial NOx reduction. Sufficient burnout was not achievable when NOx emission was less than 500ppm. Also, the amount of core air did not influence tho NOx reduction.

• 한국대기환경학회지
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• 제34권1호
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• pp.1-15
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• 2018

Nation-wide systematic and comprehensive measurements of air quality criteria species have been made over 340 sites currently in Korea since 1990. Using these data, temporal and spatial trends of $SO_2$, $PM_{10}$, $NO_2$, $O_3$, CO and $O_x(NO_2+O_3)$ were analyzed to characterize and evaluate implementing efficiency of air quality policy and regulations. Due to strict and effective policy to use cleaner fuels in late 1980s and 1990s, the primary pollutants, such as $SO_2$, CO, and $PM_{10}$ decreased sharply by early 2000s in all parts of Korea. After this period, their concentrations declined with much lower rates in most parts of Korea. In addition, isolated but noticeable numbers of places, especially in major ports, newly developing towns and industrial parks, sustained high levels or even showed further degradation. Despite series of emission control strategies were enforced since early 1990s, $NO_2$ concentrations haven't changed much till 2005, due to significant increase in number of automobiles. Nevertheless, we confirmed that the staggering levels of $NO_2$ and $PM_{10}$ improved evidently after 2005, especially in Seoul Metropolitan Area (SMA), where enhanced regulations for $NO_2$ and $PM_{10}$ emissions was imposed to automobiles and large emission sources. However, their decreasing trends were much lessened in recent years again as current air quality improvement strategies has been challenged to revise further. In contrast to these primary species, annual $O_3$, which is secondary product from $NO_2$ and volatile organic compounds (VOCs), has increased consistently with about 0.6 ppbv per year in every urban part of Korea, while yearly average of daily maximum 8-hour $O_3$ in summer season had a much higher rate of 1.2 ppbv per year. Increase of $O_3$ can be explained mainly by reductions of NO emission. Rising background $O_3$ in the Northeast Asia and increasing oxidizing capacity by changing photochemistry were likely causes of observed $O_3$ increase. The future air quality policy should consider more effective ways to lower alarming level of $O_3$ and $PM_{10}$.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권2호
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• pp.1155-1158
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• 2007

To reduce acoustic noise level of an AV projector, primary noise sources of AV projector were analyzed. Based on the analyzed result, methods to control each source are presented and tried. Structure-borne noise can be controlled by anti vibration design of mounting system, and air-borne noise by reducing flow resisitvity.