• Journal of Preventive Medicine and Public Health
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• 제34권1호
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• pp.41-46
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• 2001

Objectives : To investigate the effects of particulate matter (PM), a marker of environmental pollution derived from combustion sources, on lung epithelial cells (A549) and macrophage (RAW 264.7). Methods : The production of reactive radicals from lung cells, the lipid peroxidation of cell membrane, and the cytotoxicity of PM were measured using an in vitro model. The results were compared with a control group. Results : The presence of PM significantly increased the production of reactive oxygen species and reactive nitrogen species with time and in a dose dependent pattern and also increased the malondialdehyde concentration in lung epithelial cells. The cytotoxicity of PM was increased with increasing concentration of PM. Conclusions : It has been suggested that urban particulate matter causes an inflammatory reaction in lung tissue through the production of hydroxyl radicals, nitric oxides and numerous cytokines. The causal chemical determinant responsible for these biologic effects are not well understood, but the bioavailable metal in PM seems to determine the tonicity of inhaled PM.

• 한국수소및신에너지학회논문집
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• 제24권1호
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• pp.12-19
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• 2013

A gasification process with pre-combustion $CO_2$ capture process, which converts coal into environment-friendly synthetic gas, might be promising option for sustainable energy conversion. In the coal gasification for power generation, coal is converted into $H_2$, CO and $CO_2$. To reduce the cost of $CO_2$ capture and to maximize hydrogen production, the removal of CO and the additional production of hydrogen might be needed. In this study, a 2l/min water gas shift system for a coal gasifier has been studied. To control the concentration of major components such as $H_2$, CO, and $CO_2$, MFCs were used in experimental apparatus. The gas concentration in these experiments was equal with syngas concentration from dry coal gasifiers ($H_2$: 25-35, CO: 60-65, $CO_2$: 5-15 vol%). The operation conditions of the WGS system were $200-400^{\circ}C$, 1-10bar. Steam/Carbon ratios were between 2.0 and 5.0. The commercial catalysts were used in the high temperature shift reactor and the low temperature shift reactor. As steam/carbon ratio increased, the conversion (1-$CO_{out}/CO_{in}$) increased from 93% to 97% at the condition of CO: 65, $H_2$: 30, $CO_2$: 5%. However the conversion decreased with increasing of gas flow and temperature. The gas concentration from LTS was $H_2$: 54.7-60.0, $CO_2$: 38.8-44.9, CO: 0.3-1%.

• 에너지공학
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• 제25권2호
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• pp.21-28
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• 2016

본 연구는 국내 상업용 대형 가스오븐 시스템 개발을 목표로 연소기의 연소조건에 대한 수치해석 및 실험을 통해 적정 당량비를 결정한 후 공급열량(20,000 kcal)에 적합한 열교환기를 설계하고 대류 팬 제어방법을 검토하여 상업용 대형 가스오븐 시스템 설계 및 최적운전조건을 도출하는 것이다. 실험결과 당량비는 0.82가 가장 적절하였고 오븐 내부 중앙지점의 온도가 $200^{\circ}C$까지 도달하는데 걸리는 시간은 대류 팬의 회전방향이 반시계방향일 때 시계방향 보다 단축되었다. 또한 오븐 내부의 온도를 균일하게 유지하기 위해서는 대류 팬 제동장치가 필요하였다. 오븐 내부의 승온구간과 온도유지구간 동안 배출되는 배기가스의 열량을 통해 시스템 효율을 비교한 결과 전열면적이 큰 열교환기를 설치한 시스템의 효율이 높게 나타났다.

• 전기학회논문지
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• 제66권12호
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• pp.1889-1894
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• 2017

Global automobile manufacturers are developing electric vehicles (EVs) to eliminate the pollutant emissions from internal combustion vehicles and to minimize fossil fuel consumptions for the future generations. However, EVs have a disadvantage of shorter traveling distance than that of conventional vehicles. To answer this shortfall, more batteries are installed in the EV to satisfy the consumer expectation for the driving range. However, as the energy capacity of the battery mounted in the EV increases, the amount of heat generated by each cell also increases. Naturally, a better battery thermal management system (BTMS) is required to control the temperature of the cells efficiently because the appropriate thermal environment of the cells greatly affects the power output from the battery pack. Typically, the BTMS is divided into an active and a passive system depending on the energy usage of the thermal management system. Heat exchange materials usually include gas and liquid, semiconductor devices and phase change material (PCM). In this study, an application of PCM for a BTMS was investigated to maintain an optimal battery operating temperature range by utilizing characteristics of a PCM, which can accumulate large amounts of latent heat. The system was modeled using Dymola from Dassault Systems, a multi-physics simulation tool. In order to compare the relative performance, the BTMS with the PCM and without the PCM were modeled and the same battery charge/discharge scenarios were simulated. Number of analysis were conducted to compare the battery cooling performance between the model with the aluminum case and PCM and the model with the aluminum case only.

• 한국산학기술학회논문지
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• 제10권7호
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• pp.1433-1438
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• 2009

본 논문의 목적은 점화시기의 변화가 LPG/가솔린 겸용차량에 미치는 영향을 살펴보기 위한 것으로 가솔린 전용연료 모드를 LPG 전용연료 모드로 진각시킨 제어시스템을 제안하여 엔진회전수(1500rpm, 2000rpm) 및 점화시기 ($5^{\circ}$,$10^{\circ}$,$15^{\circ}$,$20^{\circ}$)의 변화에 따른 실린더내의 가스압력, 압력상승률 및 열발생률을 측정하였다. 그 결과 실런더내의 가스압력 및 압력상승률은 기관의 회전속도가 1500rpm 및 2000rpm 모두 점화시기가 진각될수록 증가하였으나, $20^{\circ}$부근에서의 압력상승률값만 약간 낮게 나타났다. 또한, 열발생률은 1500rpm에서 점화시기가 진각될수록 증가하였으며 2000rpm의 $20^{\circ}$부근에서 감소하는 경향을 볼 수 있었다.

• 한국가스학회지
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• 제20권1호
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• pp.29-39
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• 2016

폭발성 가스가 존재하는 위험장소에서 사용하는 전기기기는 폭발성 가스의 점화원이 되지 않도록 설계되어야 한다. 내압방폭 구조의 설계는 전기 스파크를 발생시키는 부품을 가진 용기가 내부에서 가스나 증기의 폭발시 최대 압력에 견디고 내부 화염이 외부 가스나 증기 폭발로 전파되지 않도록 설계되어야 한다. 이 논문은 화염 틈새를 통해 외부로 분사되는 연소 생성물의 분사가 외부 가스나 증기를 점화시킬 정도의 온도나 에너지를 가질 수 없도록 하는 MESG(Maximum Experimental Safe Gap)의 중요한 물리적인 메커니즘에 대해 설명하였다. IEC 60079-20-1:2010 기준에 의해 프로판과 아세틸렌의 MESG를 실험하여 MESG 값을 측정하고 가스폭발시의 최대 폭발압력을 측정하였다. 결과로는 최소 MESG가 측정될 때 가스의 농도는 화학당량 농도보다 높고 폭발압력은 최소 MESG에서 가장 높게 나타났다.

• 한국연초학회지
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• 제29권1호
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• pp.23-29
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• 2007

The measurement of physical properties such as apparent density and void fraction of tobacco materials, which is so bulky, is a main theme with regard to tobacco process, quality control, cigarette combustion and smoke generation. Except Solution Impregnation Method, there was no alternative method for measuring those properties in the porous material so far. However, experimental processes of that method are so complicated as to cost much time and labor, the main solution such as mercury to apply to the method is usually very hazard. Therefore, we had developed a new method to determine them easily in our other paper by the mathematical equations derived from the Ergun equation for the purpose of it, and then already evaluated our method through applying some basic data from Muramatsu et at. (1979) with regard to our developed equations. Then, we found our method best fit to experimental one (Oh et al., 2001). In this study we tried to establish our method to conveniently determine those physical properties. Especially, we have focused on the development the easy way to measure surface area and the volume of single shred in a tobacco column. As a result of that, we found that the computer image analyzer was best fit for it. Then, we have finally determined apparent density and void fraction for our domestic tobacco shred.

• 대한기계학회논문집B
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• 제30권5호
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• pp.405-412
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• 2006

In order to realize a stably propagating flame in a narrow channel, flame instabilities resulting from flame-wall interaction should be avoided. In particular flame quenching is a significant issue in micro combustion devices; quenching is caused either by excessive heat loss or by active radical adsorptions at the wall. In this paper, the relative significance of thermal and chemical effects on flame quenching is examined by means of quenching distance measurement. Emphasis is placed on the effects of surface defect density on flame quenching. To investigate chemical quenching phenomenon, thermally grown silicon oxide plates with well-defined defect distribution were prepared. ion implantation technique was used to control defect density, i.e. the number of oxygen vacancies. It has been found that when the surface temperature is under $300^{\circ}C$, the quenching distance is decreased on account of reduced heat loss; as the surface temperature is increased over $300^{\circ}C$, however, quenching distance is increased despite reduced heat loss effect. Such abberant behavior is caused by heterogeneous surface reactions between active radicals and surface defects. The higher defect density, the larger quenching distance. This result means that chemical quenching is governed by radical adsorption that can be parameterized by oxygen vacancy density on the surface.

• 유기물자원화
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• 제19권4호
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• pp.60-65
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• 2011

실록산은 유기규소화합물로서 혐기성소화조에서 생산되는 바이오가스로 휘발되며, 이러한 실록산은 바이오가스로 이용되는 가스 연소 엔진 고장의 원인이 된다. 따라서, 바이오가스 내의 실록산을 저감시킬 수 있는 방안이 필요하며 우선적으로 실록산의 발생특성에 대한 조사가 필요하다. 이에 본 연구는 음식물류폐기물폐수의 혐기성소화조에서 발생되는 바이오가스에 함유되어 있는 실록산의 농도 특성을 조사하였다. 총 실록산의 농도는 평균적으로 $9.5mg\;siloxane/m^3$로 나타났으며, 고리 구조 D4의 실록산 농도는 $4.0mg\;siloxane/m^3$로 가장 높게 나타났다. 고리구조 및 선형구조 실록산의 농도는 각각 D4>D5>D6 및 L4>L3>L5>L2의 순서로 나타났다. 1월 2월 및 3월의 실록산 농도 측정 결과에서 1월의 총 실록산 농도가 가장 낮게 나타났으며, 3월의 총 실록산 농도가 가장 높게 나타났다.

• 한국환경농학회지
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• 제38권1호
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• pp.10-16
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• 2019

BACKGROUND: Coal ashes generated from thermal power plants have been known as beneficial materials for agricultural use because of their nutrient elements. However, there is limitation to recycle them due to their alkalinity. The objective of this study was to evaluate the effectiveness or safety of the coal ashes for their heavy metals on agricultural recycling when adjusted to pH of 5 with sulfuric acid. METHODS AND RESULTS: Concentration of hydrogen which is needed to adjust pH of coal ash was estimated by using a buffering curve and then the amount of sulfuric acid was changed by the estimation before incubation. Each of fly ash (FA) and bottom ash (BA) was collected from both thermal plants of Yeongdong (YD) and Yeongheung (YH). The pH values of coal ashes increased to 4.76 (from 4.34) after incubation with sulfuric acid for 56 days, closer to the targeted pH. Coal ashes also increased the contents of available phosphorus by 2-fold (165 mg/kg) and 11-fold (1,137 mg/kg) for YDBA and YDFA, respectively, compared to the control. CONCLUSION: The utilization of coal ash with its acidity regulation would be very beneficial to agriculture sector and further suggest promising environmental safety against heavy metals.