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.

댄스스포츠 트레이닝이 여대생의 심폐기능과 신체구성 및 혈중 콜레스테롤에 미치는 영향

정진욱 ( Jin Wook Chung ),전태원 ( Tae Won Jun ),김연수 ( Yeun Soo Kim ),김은경 ( Eun Kyung Kim ),김광준 ( Kwang Jun Kim ),이경영 ( Kyoung Yung Lee ),박성태 ( Sung Tae Park ),전병환 ( Byeong Hwan Jeon ) 한국운동생리학회 2003 운동과학 Vol.12 No.1

Chung, S.T., Jun, T.W., Chung, Y.S., Lee, D.K, Park, I.R., Eom, W.S., Woo, J.H., Kim, K.L The Study of Fitness and Health Consciousness for Big City Company Employee`s. Exercise Science, 12(1): 133-152, 2003. The purpose of this study is to examine closely big city company employee`s relationship between fitness and health consciousness. Research targets were 130 men and women in ages of 30-50 of 3 organizations that were chosen randomly in 3 districts (gu)`s of Seoul area and they took the survey about health consciousness, basic physical test. Ran χ^2 test between society-population factor and each questions by doing cross-tab method to get the statical analysis and used independent-test between society-population factor and other subordinate factor(about fitness and health consciousness) to see the significant level. Got the following results after taking the surveys and physical tests. First, man appeared that man has higher employment rate than woman does. Second, woman was more exposed to weight loss effort than man did. Third, man`s weight loss hope region was waist while woman was abdomen area. Fourth, in man`s case about cause of corpulence was exposed due to lack of exercise and imbalance of food in the case of woman. Fifth, weight control system was exercising in ages of 30 and food control by people in ages of 50. Sixth, most of the men were smokers but only a few women were smokers. Seventh, smoking period of man was more than 10 years mainly and while smoking period was less than 1 year in woman`s case. Eighth, in average man usually drinks 3 times a week and 1 time a week in woman`s case. Ninth, man drinks 7 - 9 bottles and woman drinks about 4 bottles in averages. Tenth, about stress cause, man appeared to be as company problems, that woman receives stress from economical problem mainly. Eleventh, people with high education levels did relaxation(이완??) method to treat stress but people`s with less than high school levels got rid of stress by exercise. Twelfth, exercise number decreased as people gets older. Thirteenth, man`s average exercise time was about 2 - 4 hours per week, and 60 - 90 minutes in a week for woman. Fourteenth, man prefers jogging and health-club exercise, and woman prefers also health-club exercises and swimming. Fifteenth, man exercises mainly at leisure times but woman usually does not exercise during spare time. Sixteenth, man has higher muscle strength, muscle endurance, cardio-respiratory function than woman has. However, woman has higher value on flexibility and % body fat than man has.

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.

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

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

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

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.

선박용 엔진의 텀블형상 및 내부유동 특성에 관한 수치 해석적 연구

전충환(Chung-Hwan Jeon),이병화(Byoung-Hwa Lee),김호성(Ho-Sung Kim) 한국마린엔지니어링학회 2007 한국마린엔지니어링학회 학술대회 논문집 Vol.2007 No.-

Many researches have been studied on in-cylinder flow as one of dominant effects for an engine combustion. Specially because the combustion flame speed is mainly determined by the turbulence at the end of compression process. Tumble and Turbulence ahead of combustion is changed according to combustion figure, compression ratio, RPM like this kind of operation condition, and it has much influence on combustion stability. As this phenomenon make research certainly, combustion stability and effectivity will be improve. This paper describes analytical results of the tumble flow, intensity, turbulence inside the cylinder of maritime engine. 3-D computation has been performed by using STAR-CD v3.26 solver and es-ice.