운반시간 지연에 의해 저하된 레미콘의 성능회복에 관한 기초적 연구

전충근,文學龍,황인성,양성환,한천구 대한건축학회 2004 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.24 No.1(구조계)

In this paper, availability of deteriorated remicon due to delaying delivery time is discussed. According to test results, fluidity and air content of plain concrete exhibited a tendency to decline with a elapse of time. After 90 minutes since mixed, use of superplasticizer and AE admixture resulted in an increase in fluidity and air content. Adequate dosage of superplasticizer and AE adimixture is found to add with 0.4% and 0.002% respectively to restore the level of original slump and air content from loss one. Setting time of concrete exhibited an acceleration with an increase in leaving time of concrete. Compressive strength of plain concrete is enhanced with and increase of leaving time of concrete. Therefore, it is found that the use of superplasticizer with 0.4% and AE admixture with 0.002% has a desirable effect on restoring the deteriorated quality of concrete related to fluidity, air content and setting time without strength loss caused by delivery time delaying.

성장속도에 따른 대장균 rnpB 유전자 발현의 조절작용

전은순,이학란,이석재,정영환,조명선,정재훈,이영훈,박충웅 全北大學校 基礎科學硏究所 1994 基礎科學 Vol.16 No.-

Growth rate-dependent expression of the rnpB gene encoding M1 RNA, the RNA component of Escherichia coli RNase P, was examined using a hybrid transdcuing λ phage. The hybrid transducing λ phage was constructed carrying the lacZ gene fused to the promoter for the rnpB gene. The amounts of β-galactosidase were analyzed in the E. coli lysogen carrying this transducing phage grown in different growth media to see dependence of the rnpB transcription on growth rate. The synthesis of β-galactosidase from the rnpB-lacZ fusion increased with growth rate. This result suggests that the rnpB promoter activity is dependent on the growth rate.

알코올중독 환자의 예후 예측에 관한 연구(Ⅰ) : 사회문화적 및 심리적 변인을 중심으로

이정균,성상경,전동환 大韓神經精神醫學會 1995 신경정신의학 Vol.34 No.4

Objects : The purpose of the study was to identify the prognosis-predicting indicators in alcoholics by the correlations between prognosis and sociocultural, psychological factors and drinking history. Methods : The subjects were composed of 50 alcoholics including 25 psychiatric inpatients(drinking group) and 25 alcoholics abstinent for 6 months or more after discharge(abstinent group). They were investigated with interview, questionnaire and review of their charts. Results : The results were as follows : 1) Abstinent group showed higher percentage of marriage and more stable martial status than drinking group. 2) Abstinent group got more stable employments before abstinence than drinking group. 3) Abstinent group had been admitted more voluntarily and had therapeutic participation, such as alcoholics anonymous or outpatient care, than drinking group after discharge. 4) Abstinent group had longer maximal length of abstinence than drinking group. Conclusions : With the above results, the authors think that social stability, attitude toward the treatment, therapeutic participation after discharge and maximal length of abstinence could be the important prognosis-predicting indicators for alcoholic.

대뇌 원발성 악성 임파종 1예 : A Case Report

한윤경,오석전,조해동,유영락,김남규,정환영,이중달 대한신경외과학회 1985 Journal of Korean neurosurgical society Vol.14 No.3

Primary malignant lymphoma is very rare and represents less than 1.5 % of all intracranial neoplasms. The authors have experienced a case of primary malignant lymphoma of the brain in a 66 year-old woman who presented with persistent headache, nausea and generalized weakness. Brain CT scan demonstrated typical deep seated tumor masses in the right temporal and left frontal lobes with strong contrast enhancement. We obtained a good result after surgery followed by radiation and chemotherapy and report our case with review of the articles.

Dynamic modeling and simulation of reaction, slag behavior, and heat transfer to water-cooling wall of shell entrained-flow gasifier

Chung Hwan Jeon,Cheol-Oong Kim,김량균,Zelin Wu 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.6

A mathematical model is developed to simulate a pilot Shell entrained-flow coal gasifier. Submodels of specific structures of the gasifier are established to simulate the complicated gasification process. The model includes the total energy conservation equation and mass conservation equations for the gas components, solid flow, and gas flow. It simulates the influence of the gasifier structure and dimensions and can calculate the effects of changing almost every important operation parameter, e.g., the syngas composition, gasification temperature, carbon conversion ratio, walllayer temperature, and slag mass flow rate. The model can predict the syngas composition under a limited residence time condition. Furthermore, it considers the heat transfer coefficient of each layer of the water wall to calculate its heat loss and temperature. Thus, the model also reflects the influence of performance parameters of the gasifier’s water wall. The slag mass flow rate on the wall is calculated using a slag submodel.

Steady-Flow Characteristics and Its Influence on Spray for Direct Injection Diesel Engine

Jeon, Chung-hwan,Park, Seung-hwan,Chang, Young-june The Korean Society of Mechanical Engineers 2002 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.16 No.7

Flow and spray characteristics are critical factors that affect the performance and exhaust emissions of a direct injection diesel engine. It is well known that the swirl control system is one of the useful ways to improve the fuel consumption and emission reduction rate in a diesel engine. However, until now there have only been a few studies on the effect of flow on spray. Because of this, the relationship between the flow pattern in the cylinder and its influence on the behavior of the spray is in need of investigation. First, in-cylinder flow distributions for 4-valve cylinder head of DI (Direct Injection) Diesel engine were investigated under steady-state conditions for different SCV (Swirl Control Valve) opening angles using a steady flow rig and 2-D LDV (Laser Doppler Velocimetry). It was found that swirl flow was more dominant than that of tumble in the experimented engine. In addition, the in-cylinder flow was quantified in terms of swirl/tumble ratio and mean flow coefficient. As the SCV opening angle was increased, high swirl ratios more than 3.0 were obtained in the case of SCV -70° and 90°. Second, spray characteristics of the intermittent injection were investigated by a PDA (Phase Doppler Anemometer) system. A Time Dividing Method (TDM) was used to analyze the microscopic spray characteristics. It was found that the atomization characteristics such as velocity and SMD (Sauter Mean Diameter) of the spray were affected by the in-cylinder swirl ratio. As a result, it was concluded that the swirl ratio improves atomization characteristics uniformly.

정적연소실내 메탄-공기 혼합기의 가연한계 및 연소특성에 관한 실험적 연구

전충환(Chung-hwan Jeon),양인규(In-gyu Yang),김현규(Hyunkyu Kim),송주헌(Ju-hun Song),장영준(Young-june Chang) 한국마린엔지니어링학회 2010 한국마린엔지니어링학회 학술대회 논문집 Vol.2010 No.4

Natural gas is a promising alternative fuel to meet strict engine emission regulations in many countries. The development of natural gas engines requires low emissions along with the demand for better fuel consumption and increased power ratings. In this study, a cylindrical Constant Volume Combustion Chamber(CVCC) was used to investigate the combustion characteristics under different ambient pressure and equivalence ratio. The maximum combustion pressure, heat release rate and mass fraction of burned gas was evaluated in particular by ambient pressure and equivalence ratio. It also show that variation of flammability limits according to existence of pre-chamber. This result could provide lean bum condition by analyzing combustion characteristics with ambient condition.

TMA를 이용한 국내 발전용 탄의 용융점 변화에 대한 연구

전충환 ( Chung Hwan Jeon ),이순호 ( Soon Ho Lee ),임호 ( Ho Lim ),김상도 ( Sang Do Kim ) 한국화학공학회 2014 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.52 No.2

석탄 연소 시 발생하는 회가 보일러 벽면에 부착되어 일어나는 슬래깅 현상은 보일러의 열효율을 감소시키고 보일러 안정성에도 악영향을 준다. 이러한 슬래그의 유동 특성은 회의 용융 특성과 관련이 있는데 이는 회의 화학적 조성에 영향을 받는다. 본 연구에서는 회의 용융특성을 TMA(Thermo-Mechanical Analysis) 장비를 이용하여 분석하였다. 이 테스트는 회의 수축률에 따른 용융온도(T25%, T50%, T75%, T90%)를 정량적으로 측정 하는 방법이다. TMA에서측정된 각각의 온도는 용융단계별 특성을 나타낸다. TMA로 분석된 결과 값에 XRF 장비를 이용하여 분석한 회의 성분 조성이 미치는 영향을 분석하였다. 회에 포함된 성분 중 refractory, fluxing contents가 회분의 용융온도에 미치는 영향을 확인할 수 있었다. Refractory contents 성분인 SiO2, Al2O3의 함량이 많을수록 전체적인 용융온도가 올라가며SiO2/Al2O3가 커질수록 고온에서의 용융온도인 T75%, T90%가 낮아지는 것을 알 수 있었다. 이와 달리 fluxing contents성분인 Fe2O3, K2O, CaO의 함량이 많아질수록 전체적인 용융온도가 낮아지며 이중 K2O, CaO는 초기 용융 온도인T25%를 낮추는데 큰 역할을 하는 것으로 판단되었다. TMA 분석과 회의 조성 비교를 통하여 회의 용융 특성을 예측하고 설명할 수 있었다. The slagging which generated from ash deposition on furnace wall and tube in boiler reduces the heat transfer efficiency and damages to safety of boiler. The slag flow behavior in boiler is affected by melting temperature which is related to ash compositions. In this study, the behavior of slag is researched by using ash fusibility test, called TMA (Thermo-Mechanical Analysis). The technique measures the percentage shrinkage as the function of temperature, T25%, T50%, T75%, T90%. These temperatures indicate different stages of melting. Then, the effect of ash chemical compositions measured from XRF (X-ray Fluorescence Spectrometer) to ash fusion temperatures is discussed. Among the chemical compositions, refractory and fluxing influence on ash fusibility is described. High levels of refractory component and limited amount of fluxing components (Fe2O3, K2O, CaO) increase overall melting temperatures. High SiO2/Al2O3 ratio decrease high melting temperatures (T75%, T90%). Meanwhile, the presence of reasonable levels of fluxing components reduces overall melting temperature. A presence of fluxing component such as K2O and CaO is found to decrease the T25% values significantly. From this research, it is possible to make a reasonable explanation and prediction of ash fusion characteristic from analysis of TMA results and ash chemical compositions.

LFR 장치를 이용한 입자 크기 변화에 따른 저열량 아역청 미분탄의 연소특성에 관한 실험적 연구

전충환(Chung-Hwan Jeon),김용균(Yong-Gyun Kim),김재동(Yong-Gyun Kim),김규보(Gyu-Bo Kim),송주헌(Ju-Hun Song) 대한기계학회 2010 大韓機械學會論文集B Vol.34 No.3

본 연구는 아역청탄의 미분탄 연소특성에 있어서, 입자크기가 미치는 영향을 알고자 실험을 통해 고찰한 것이다. 본 연구를 위하여, 온도 및 온도 상승률을 고려해 볼 때, 실제 미분탄 연소로의 환경을 잘 구현할 수 있는 층류반응기를 설계하고 이용하였다. 크기가 다른 미분탄 입자들이 탈 때 형성되는 화염구조 및 길이를 본 반응기를 이용해 조사하였다. 육안으로 관찰된 화염구조로부터 석탄연소과정들을 분명하게 구분할 수 있었다. 입자의 크기변동은 휘발분 점화개시점에 미치는 영향이 큰 반면, 휘발분의 연소시간에 미치는 영향은 가장 적었다. 입자의 크기가 커질수록 촤의 화염길이도 증가하였다. 화염불안정성 역시 입자가 커짐에 따라 증대되었다. 일정한 체류시간 간격내에서의 촤의 소비율은 거의 일정하였다. In this study, the effect of particle size on the combustion characteristics of pulverized sub-bituminous coal was experimentally investigated. A laminar-flow-entrained reactor was designed and implemented to realize the desired heating ratio and temperature corresponding to the combustion atmosphere of a pulverized-coal-fueled furnace. The flame length and structure of burning particles according to different sizes were investigated. Coal combustion processes were clearly distinguished by direct visual observation of the flame structure. The onset point of volatile ignition is greatly affected by changes in the particle size, and the burning time of the volatiles is least affected by changes in the particle size. The length and instability of char flame also increase with the increase of the particle size. However, the char consumption rate within the residential time remains nearly constant.

보문 : 에너지/환경,신재생에너지,폐기물처리/자원화기술 ; 탈휘발화 과정에서 혼탄의 반응률과 열적 거동에 관한 연구

전충환 ( Chung Hwan Jeon ),유광일 ( Kwang Il Ryu ),김량균 ( Ryang Gyoon Kim ),이동방 ( Dong Fang Li ),오택림 ( Ze Lin Wu ) 한국화학공학회 2013 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.51 No.1

본 연구 목적은 탈휘발화 과정에서의 역청탄과 아역청탄의 혼탄 열중량 곡선을 예측 하는 것이다. TSL (Thermal Shock Large) TGA를 통하여 실험을 수행 하였으며, 반응속도상수 분석은 Coats-redfern 방법을 이용하였다. 도출된 반 응속도상수를 기반으로 단일탄의 Sum Method에 대한 일차적 검증을 하였으며, 혼탄시의 TG curve를 WSM(Weight Sum Method)와 저자가 제시한 MWSM (Modified Weight Sum Method)를 사용하여 예측 및 비교하였다. WSM 및 MWSM를 통한 예측결과와 TG curve 실험결과의 정량적인 비교를 위해 Linear least square method를 사용하였다. TG curve 상에서 서로 다른 기울기를 가지는 경우와 많은 휘발분의 방출로 인한 급격한 질량감소가 나타나는 구간의 경우 MWSM이 WSM 보다 실험결과에 더 정확한 결과를 예측함을 확인하였다. 탈휘발 과정에서의 혼탄의 열적 거동은 단 일탄의 특성에서부터 예측할 수 있음을 확인할 수 있었다. The objective of this research is to predict the TG curve of blends of bituminous coal and sub-bituminous coal during devolatilization. TSL (Thermal Shock Large) TGA was used for Experiments, and Coats-redfern method was used for reaction order calculation. Based on reaction order, sum method was verified to be suitable for a single coal, then, prediction and comparison of TG curve of coal blends was conducted using both of WSM (Weight Sum Method) and MWSM (Modified Weight Sum Method), where the latter was developed in this research. The presented experiment results and WSM & MWSM were showed to be reasonable using linear least square method. MWSM performed more accurately than WSM for the case that TG curve had different slopes and the case that sharp weight loss happened due to release of volatile matter. The results showed that it`s possible to predict the thermal behavior of coal blends during devolatilization based on the thermal behavior of single coals