• Journal of Ocean Engineering and Technology
• /
• v.6 no.2
• /
• pp.35-40
• /
• 1992

A recently developed new technique for measuring the fraction of wetted area has applied to pool boiling of water. The basis of the new applied technique of ultrasonic makes use of the reflection of ultrasonic from the vapour surface to measure the fraction of wetted area values. The results are the measured fraction of wetted area values in nucleate and transition boiling and the pool boiling curve for water under steady state conditions. The measurement of this paper shows a fraction of wetted areaf around 0.98 at the critical heat flux for water.

• Journal of KIISE:Computing Practices and Letters
• /
• v.9 no.4
• /
• pp.439-446
• /
• 2003

In this paper, a single sign-on system has been designed and implemented. The purpose of the proposed system is that a user logs in once using a single password and gets authenticated access to all the servers that he is authorized to use without sending any passwords over the network. The proposed system involves the use of digital signature and cryptographic authentication protocols. For its implementation, a public-key infrastructure is also designed and implemented. To view the behavior of the proposed system, message sequence charts and state transition diagrams have been

• Journal of Advanced Marine Engineering and Technology
• /
• v.13 no.4
• /
• pp.40-53
• /
• 1989

Boiling heat transfer phenomena is widely applied to BWR and electrical heating system because of its high heat transfer coefficient. In these systems, steady state heat transfer is dependent on nucleate boiling. When the heat generating rate is sharply increased or the cooling capacity of coolant is sharply decreased, sharp wall temperature rise is occurred under the critical heat flux(CHF) condition. This paper presents the simple wall temperature fluctuation model of transition mechanism in the repeating process of overheating and quenching, when coalescent bubble passes relatively slowly on the wall and simultaneously the transition from nucleate boiling to film boiling is carried at especially onset of the CHF state. The values calculated by the present model are resulted comparatively good with the measured.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.683-683
• /
• 2013

박막태양전지의 일종인 CIGS 태양전지는 직접천이형 반도체로 광흡수계수가 $1{\times}10^5cm^{-1}$로 매우 높고, 전기광학적 안정성이 우수하여 실리콘 결정질 태양전지를 대체할 고효율 태양전지로 각광받고 있다. CIGS 태양전지는 광흡수층 공정방법에 따라 다양한 결정구조 및 효율 차이가 나타난다. 본 실험에서는 Sputtering방법으로 금속전구체를 증착하고, Sequential process를 이용하여 고온에서 셀렌화 열처리를 수행하였다. Soda-lime glass 기판에 배면전극으로 Mo를 증착하고, 1단계로 CuIn0.7Ga0.3 조성비의 타겟을 이용하여 Sputtering법으로 $1.0{\sim}1.2{\mu}m$두께의 CIG 전구체를 증착하였다. 2단계로 CIG 전구체에 분자빔증착기를 이용하여 Se를 증착하고, 열처리를 통하여 CIGS 화합물 구조의 박막을 형성시켰다.증착된 CIGS 박막은 광전자분광분석기로 원소의 화학적 결합상태를 확인하고, in-situ 엑스선회절분석을 통해 Se층의 증착두께와 열처리 온도 변화에 따른 CIGS 층의 결정구조 및 결정화도 변화를 분석하였다.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.62 no.8
• /
• pp.1074-1079
• /
• 2013

Demand response(DR) is potential generation alternative to improve the reliability indices of system and load points. However, when demand resources scheduled in DR market fail to reduce demand, it can create new problems associated with maintaining a reliable supply. In this paper, a reliability model of demand resource is constructed considering customers' behaviors in the same form as conventional generation units, where availability and unavailability are associated with the simple two-state model. As a result, the generalized reliability model of demand resources is represented by multi-state model.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.40 no.3
• /
• pp.299-307
• /
• 1991

This paper deals with the determination of a firing sequence of transitions in the reachability problem of Safe Petri Net. The determination problem of a firing sequence is very important from the point of practical view, especially in the control of the discrete systems modelled by Safe Petri Net. The determination method of a firing sequence of transitions by means of the matrix equation for the discrete systems modelled by Safe Petri Net is proposed. First, a construction method of the indicence matrix and the firing rule for Safe Petri Net with self-loop are presented by defining the permissive arc in place of self-loop. Next, we develop a method that can find the enable transitions of Safe Petri Net by means of the matrix equation of Safe Petri Net. Finally, by using this method, we propose an algorithm that determines the firing sequence of transitions of Safe Petri Net.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.28A no.11
• /
• pp.855-865
• /
• 1991

A simple method for analysis of serial search burst-format direct-sequence spread-spectrum (DS-SS) code acquisition system had been recently proposed, and therein, the effect of the code autocorrelation sidelobes on the performance of DS-SS code acquisition system has been assessed [4],[5]. In this paper, a new hybrid scheme which combines the serial search with maximum likelihood search is proposed to eliminate the deleterious effect of code autocorrelation sidelobes, and the performance is analyzed for the additive withe Gaussian noise (AWGN) channels. To analyze the performance of this system, we have generalized the method used in [4],[5] to arbitrary burst-format DS-SS acquisition schemes. The results show that a new hybrid scheme has good immunity against the effect of code autocorrelation sidelobes. Thevalidity of the presented approach has been confirmed form the results of simulation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2009.11a
• /
• pp.253-256
• /
• 2009

In the present paper, experimental and numerical fundamental analyses of the occurrence of lateral force in overexpanded thrust nozzle were carried out. Investigation of the lateral force fluctuations in an thrust nozzle for the shutdown transient was presented. Wall pressure distribution and Schlieren Photographs as NPR were presented. Pressure peak is observed during transition of RSS to FSS.

• Korean Journal of Environment and Ecology
• /
• v.13 no.4
• /
• pp.392-403
• /
• 2000

지리산국립공원 거림계곡 식물군집구조를 파악하기 위하여 거림계곡 내 등산로를 따라 66개(6,600m2)의 방형구를 설정하였으며 DCA 기법을 이용하여 분석한 결과 해발고 740-950m 의 조사구는 졸참나무군집(군집I) 해발 950-1,340m의 조사구는 신갈나무군집(군집II) 해발 1,340-1,390m의 조사구는 구상나무-거제수나무군집(군집III)으로 분류되었다 상대우점치 흉고직경급별 분포 분석결과 각 군집의 우점종인 졸참나무 신갈나무 구상나무가 우점하는 군집으로 계속유지될것으로 판단되었으며 특히 관목층은 조랫대의 밀도가 높아 천이진행에 영향을 주는 동시에 종다양도가 낮은 것으로 판단되었다 한편 3개 군집간의 유사도지수는 낮은 상태로 해발고에 따라 식생구분이 명확하였다

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.1 no.1
• /
• pp.20-27
• /
• 1990

This paper presents an efficient method to estimate the induced current by the external electromagnetic wave when the line system is composed of cascaded transmission lines. To solve this phenomena, we apply the state variable method to the nonhomogeneous differential equation. This new method is the way of transferring the sources at a different point by the Ch- aracteristics of the transition matrix. Using this method, we investigate the characteristics of the induced power of the transmission line above the perfectly conducting ground plane.