• 에너지공학
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• 제20권2호
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• pp.96-102
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• 2011

본 논문은 2차원 충돌제트 시스템에서 충돌판이 천이영역에 위치할때, 열전달성능이 감소하는 벽면분류영역의 열전달증진을 목적으로 난류촉진체인 정 4각 로드를 평판전열면 앞에 설치하고 로드와 로드사이의 피치(P)를 40 mm로 고정한 후 로드의 폭(W) 변화(4, 6, 8 mm) 및 로드와 전열면사이의 간극(C) 변화(1, 2, 4, 6 mm)에 따른 유동특성과 열전달특성에 대해 실험을 수행하고, 그 결과를 수치해석과 비교 검토하였다. 또한 로드가 설치되지 않은 경우와 정량적으로 비교하여 충돌제트 시스템에서 난류촉진체를 이용한 열전달증진에 관한 기초적 자료를 제공하고자 한다.

• Environmental Engineering Research
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• 제13권4호
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• pp.177-183
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• 2008

Ex-situ reductive dechlorination of carbon tetrachloride (CT) by iron sulfide in a batch reactor was characterized in this study. Reactor scaled-up by 3.5 L was used to investigate the effect of reductant concentration on removal efficiency and process optimization for ex-situ degradation. The experiment was conducted by using both liquid-phase and gas-phase volume at pH 8.5 in anaerobic condition. For 1 mM of initial CT concentration, the removal of the target compound was 98.9% at 6.0 g/L iron sulfide. Process optimization for ex-situ treatment was performed by checking the effect of transition metal and mixing time on synthesizing iron sulfide solution, and by determining of the regeneration time. The effect of Co(II) as transition metal was shown that the reaction rate was slightly improved but the improvement was not that outstanding. The result of determination on the regeneration time indicated that regenerating reductant capacity after $1^{st}$ treatment of target compound was needed. Due to the high removal rates of CT, ex-situ reductive dechlorination in batch reactor can be used for basic treatment for the chlorinated compounds.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제28회 KOSCO SYMPOSIUM 논문집
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• pp.102-111
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• 2004

Partial quenching structure of turbulent diffusion flames in a turbulent mixing layer is investigated by the method of flame hole dynamics to develope a prediction model for the turbulent lift off. The present study is specifically aimed to remedy the problem of the stiff transition of the conditioned partial burning probability across the crossover condition by adopting level-set method which describes propagating or retreating flame front with specified propagation speed. In light of the level-set simulations with two model problems for the propagation speed, the stabilizing conditions for a turbulent lifted flame are suggested. The flame hole dynamics combined with level-set method yields a temporally evolving turbulent extinction process and its partial quenching characteristics is compared with the results of the previous model employing the flame-hole random walk mapping. The probability to encounter reacting' state, conditioned with scalar dissipation rate, demonstrated that the conditional probability has a rather gradual transition across the crossover scalar dissipation rate in contrast to the stiff transition of resulted from the flame-hole random walk mapping and could be attributed to the finite response of the flame edge propagation.

• 한국농촌건축학회논문집
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• 제7권1호
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• pp.88-99
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• 2005

The purpose of this study is to minimize physical obstacles, to propose how we can improve them, and to get the basic information to establish the welfare policy for handicapped students in the university dormitory by studying and analyzing actual conditions of existing facilities and its improving transition which provide most important living accommodation to university students. To carry out this study, they have been surveyed 10 Universities in Korea as a case study which 1 university in Seoul & Kyunggi province, 2 universities in Chungchung province, 5 universities in Jeolla province and 2 universities in Kyungsang province. And they have been studied in relation to the law, theory of the architectural planning & design, and general consideration about handicapped people. As a result the checklist about the facilities was made. The term of survey was in August 2001 and in September 2004. It is concluded that most of universities which have been surveyed were equipped with good facilities for general students without regards for handicapped people at that time. As you can see the result of this research, the facilities of boarding house for handicapped people are very scanty in many universities. So they must be required facilities for handicapped people in the stage of architectural programming, the process of designing the dormitory facility.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권6호
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• pp.489-493
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• 1999

In this paper, an analysis of microstrip-slotline transition is performed using a 3D vector Finite Element Method(FEM). Artificial anistropic absorber technique is employed to implement an matching boundary condition in FEM. On the base of the analysis, power divider/combiner is designed. The structure of the power combiner already developed are Branch-line coupler, Rat-race coupler, Wilkinson coupler, Lange coupler, etc. Which are all planar, If the frequency goes up, the coupling efficiency of these planar couplers is decreased on account of skin loss. Especially, in millimeter-wave band, the efficiency of more than two ways combiner is radically reduced, so that application in power amplifier circuit is almost impossible, Microstrip-slotline transition structure is a power combining technique integrated into wave-guide, so that the loss is small and the efficiency is high. Theoretically, we can mount several transistors into the power-combiner. This makes it possible to develop a high power amplifier. The numerically calculated performances of the device that is, we believe, the best are compared to the experimental results in Ka-Band(26.5GHz-40GHz).

• 대한가정학회지
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• 제44권12호
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• pp.53-64
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• 2006

The purpose of this study was to investigate the variables on employees' retirement expectations divided into imposed frustration, new beginning, transition to rest, and continuing. Independent variables were individual(gender, age, occupation, income, education, and health condition), psychological(self-esteem, locus of control, attitude of leisure, and attitude of family), and job-related variables(job attitude, job satisfaction, and job stability). In order to achieve this purpose, a survey was conducted with 515 employees from Daegu and Kyungpook. Retirement expectations were measured with questionnaire based on several studies. The data analyzed by frequency, percentage, mean, factor analysis, Cronbach's $\alpha$, correlation, and multiple regression. The major findings were as follows. First, imposed frustration was affected by income, self-esteem, locus of control, job satisfaction, job attitude, and job stability. Second, new beginning was affected by self-esteem, locus of control, attitude toward leisure and family, and job stability. Individual variables were not statistically significant predictors of new beginning. Third, transition to rest was affected by locus of control, attitude toward family, job satisfaction, job attitude, and job stability. Individual variables were not statistically significant predictors of transition to rest. Finally, continuing was affected by age, education, job satisfaction. Psychological variables were not statistically significant predictors of continuing.

• Journal of Mechanical Science and Technology
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• 제15권12호
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• pp.1816-1821
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• 2001

Two-dimensional blow-down type supersonic wind tunnel was designed and built to investigate the transient behavior of the startup of a supersonic flow from rest. The contour of the divergent part of the nozzle was determined by the MOC calculation. The converging part of the nozzle, upstream of fille throat was contoured to make the flow uniform at the throat. The flow characteristics of the steady supersonic condition were visualized using the high-speed schlieren photography. The Mach number was evaluated from the oblique shock wave angle on a sharp wedge with halt angle of 5 degree. The measured Mach number was 2.4 and was slightly less than the value predicted by the design calculation. The initial transient behavior of the nozzle was recorded by a high-speed digital video camera with schlieren technique. The measured transition time from standstill to a steady supersonic flow was estimated by analyzing the serial images. Typical transition time was approximately 0.1sec.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.355-359
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• 2003

In this paper, we investigated the wear lift, wear rate, and its transition on the Hertz pressure. In the experiment, we used TiAlCrN coating deposited by the sputtering technique and ball diameter of 10mm, 7.94mm and 4.76mm for the various Hertz pressure. Ball-on-disk sliding tests wire performed under the unlubricated condition. As the diameter of a ball decreased, the failure load of TiAlCrN coating decreased. However, a good correlation was observed between the wear life and Hertz pressure, and all ball specimens showed the infinite wear life at about 450MPa. In measurement of wear rate, as the diameter of the ball inclosed, the wear transition appeared in bigger load. However, a good correlation was observed between the wear rate and Hertz pressure. The transition appeared in the range from 550MPa to 600MPa at all ball speimens.

• 한국지하수토양환경학회지:지하수토양환경
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• 제20권3호
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• pp.51-64
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• 2015

In the present study, we develop two history matching techniques based on Markov chain Monte Carlo method where radial basis function and Gaussian distribution generated by unconditional geostatistical simulation are employed as the random walk transition kernels. The Bayesian inverse methods for aquifer characterization as the developed models can be effectively applied to the condition even when the targeted information such as hydraulic conductivity is absent and there are transient hydraulic head records due to imposed stress at observation wells. The model which uses unconditional simulation as random walk transition kernel has advantage in that spatial statistics can be directly associated with the predictions. The model using radial basis function network shares the same advantages as the model with unconditional simulation, yet the radial basis function network based the model does not require external geostatistical techniques. Also, by employing radial basis function as transition kernel, multi-scale nested structures can be rigorously addressed. In the validations of the developed models, the overall predictabilities of both models are sound by showing high correlation coefficient between the reference and the predicted. In terms of the model performance, the model with radial basis function network has higher error reduction rate and computational efficiency than with unconditional geostatistical simulation.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2005년도 학술발표논문집
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• pp.97-101
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• 2005

High strength concretes utilizing EVA with micro particles were prepared by varying polymer/binder mass ratio and curing conditions with a constant water/binder mass ratio of 0.3. The EVA modified concretes on the compressive and flexural strength, microstructure, ultrapulse modulus in curing condition(dry and water curing) were studied. Also, scanning electron microscope analysis(SEM) was performed to reveal the presence of polymer film and cement hydrates in the concrete. The compressive strength of the EVA modified concretes cured at water conditions ere higher than that of the EVA modified concretes cured at dry conditions. But, the flexural strength of the specimens cured at dry conditions were higher than that of the specimens cured at water conditions. Due to the interaction of the cement hydrates and polymer film, an interpenetrating network originated in which the aggregates were embedded. The curing of the polymer modified concrete involves two step of cement hydrates and polymer modification, and cement hydrates was promoted in water conditions and polymer film formation take place when water evaporates and was thereby was favored in dry conditions. By SEM analysis, influences of polymer modification was strengthening of the transition zone between the aggregate and the paste, and the porosity of transition zone decreases. By spring analysis, it could known that polymer film affects in porosity decrease and strengthening of transition zone.