• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.47 no.8
• /
• pp.541-548
• /
• 2019

In this paper, the required amount of heat for an anti-icing system of a Flush Air Data Sensing(FADS) system is predicted. For an efficient prediction during the early stage of a design process, a handbook method is used. A program of which inputs are flight conditions is developed to predict the required amount of heat. A CFD analysis is conducted to compute the water catch efficiency which is one of the core parameters used in the handbook method. Kriging method, one of well-known regression mothods, is utilized to construct a surface contour database to evaluate impingements of droplets. To predict the trajectories of droplets, the database of a flow field around the surface is built using Kriging method as well.

• Journal of Korean Society of Water and Wastewater
• /
• v.19 no.2
• /
• pp.161-172
• /
• 2005

Recently, water treatment methods utilizing microbubbles such as DAF and EF are gaining interest and being studied. Current study is focused on the fundamental research of electroflotation by examining the characteristics of microbubbles and particles. The objects of this research consist of two things; (1) theoretical modeling of microbubble-particle collision, (2) the experimental investigation of removal efficiency of turbidity in electroflotation. From investigation, the mechanism of electroflotation can be explained not only by the characteristics of microbubbles and particles but also the chemistry of aluminum dissolved from aluminum electrode during the electroflotation experiment.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.10 no.3
• /
• pp.395-402
• /
• 2015

In this paper, we propose an efficient gait trajectory generation method for the static stair climbing of a quadruped robot with mechanism of insectile legs, which has no collision with staris. First, we derive the kinematic and inverse models of a quadruped robot using the algebraic and geometrical methods, respectively. In the proposed method, we generate the stair locomotion trajectory of a sine wave after lifting a leg from the start position, and then determine the coefficient of the generated trajectory to avoid the collision with stairs. In addition, we make the gait sequence for the stable stair locomotion. Finally, we verify the effectiveness and applicability of the proposed stair locomotion method through computer simulations.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.411-411
• /
• 2010

Cavity mode Whistler wave를 사용하는 자화유도결합플라즈마 (Magnetized Inductively Coupled Plasma, MICP)의 제반 특성을 비등방성 수송계수를 가지는 Drift-Diffusion 근사, 에너지 보존 방정식 및 유도전자계를 self-consistent 하게 고려하여 계산하였다. 이러한 접근법은 비충돌성 전자가열현상을 고려하지 못하는 단점에도 불구하고, 반도체 장비설계에 필수적인 전자온도, 밀도, 플라즈마 전위, 시스템의 임피던스 특성에 대한 경향성 파악에 매우 유용하다. 뿐만 아니라 전자밀도분포가 공간내에 형성되는 R-wave mode에 미치는 영향을 분석할 수 있다. 직경 320 mm를 가지는 작은 반응기에서 시뮬레이션과 실험결과를 비교하여 본 모델링 방법의 타당성을 검증한 후, 450 mm wafer가공에 적합한 대면적 플라즈마 반응기에서 플라즈마 특성을 연구하였다. 수 mTorr의 공정압력에서 약 10 Gauss전후의 약한 자장이 인가됨으로서 반경방향의 전자밀도 균일성이 대폭 향상되었다. 플라즈마 및 안테나의 대면적화에 수반되는 높은 Q값이 자장의 인가로 큰 폭으로 감소함으로서 임피던스메칭의 안정성이 비약적으로 개선되었고 전력전달 효율 또한 크게 증가함을 알 수 있었다. 본 연구 결과는 차세대 450 mm 반도체 공정장비의 개발에 있어 자화유도결합플라즈마가 매우 유용하게 사용될 수 있음을 보여준다.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.3 no.4
• /
• pp.44-50
• /
• 1999

For the prediction of combustion performance of the Unlike Impinging Quadlet Injector (OOOF type), mixing efficiency, mixing characteristic velocity, and efficiency of mixing characteristic velocity were obtained from the cold test. Water/kerosene were used for simulants, The momentum ratio of oxidizer and fuel were mixing correlating parameter. Orifice discharge coefficient, spray pattern and mass distribution were measured. As a result, invasion-depth had strong effect on mixing efficiency, mixing characteristic velocity, and efficiency of mixing characteristic velocity. Mixing efficiency and efficiency of mixing characteristic velocity showed maximum value for momentum ratio 1.67(TMR = 2.5), and fuel rich state showed larger decreasing ratio than oxidizer rich state.

• Journal of KIISE:Computing Practices and Letters
• /
• v.8 no.3
• /
• pp.328-335
• /
• 2002

When we want to transfer video streaming data through computer networks, we will have to be allocated a larger bandwidth compared to a general application. In general, it causes a serious network overload inevitably due to the limited bandwidth. In this paper, in order to resolve the problem, we haute taken a method for transmitting video streaming data using RTP and RTCP. With RR(Receiver Report) packet in RTCP we will test it to check whether the traffic in a network has occurred or not. If it happened, we haute tried to reduce the overall network traffic by dynamically changing the quantization factor of the Motion JPEG that is one of the encoding styles in JMF. When the ratio of the average of transmission for each session to the average of overall transmission is greater than 7%, we should adjust the amount of data to be transmitted for each session to reach the session mean values. The experimental results show that the proposed method taken here reduces the overload effectively and therefore improves the efficiency for transmitting video streaming data.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.14 no.6
• /
• pp.1365-1373
• /
• 1994

A Monte-Carlo simulation model, developed to predict size distribution of air bubbles in turbulent shear flow, is applied to a laboratory-scale problem. Sensitivity to various numerical and physical parameters of the model is analyzed. Practical applicability of the model is explored through comparisons of results with experimental measurements. Bubble size increases with air-water discharge ratio and friction factor. Bubble size decreases with increasing mean flow velocity, but the total bubble surface area in the aeration region remains fairly constant. The effect on bubble size distribution of the longitudinal length increment in the simulation model is negligible. A larger radial length increment yields more small and large bubbles and fewer in between. Bubble size distribution is significantly affected by its initial distribution and the location of air injection. Collision efficiency is introduced to explain the discrepancy between collisions with and without coalescence.

• Journal of ILASS-Korea
• /
• v.11 no.4
• /
• pp.220-227
• /
• 2006

Experimental studies has been conducted to investigate the effect of orifice diameter ratio on the mixing characteristics of the split element of doublet and triplet elements. The spray characteristics of non-reacting immiscible liquids have been investigated using a patternator. The local volume fraction is measured by use of mean value of each component. This volume measurement represents the mixing characteristics of the liquid, which affect the overall combustion efficiency. The ratio of the orifice diameter, ranging from 1 to 1.5, and that of the jet-momentum, ranging from 0.5 to 6.0, we used. The jet impinging behavior with use of various ratios exhibits substantially different mixing characteristics. Mixing efficiency is maximized when the jet-momentum ratio is increased; this behavior is particularly prominent when the orifice diameter ratio is greater than unity. The split of the triplet element yields better mixing characteristics and is more effective than that of the doublet element in regard to achieving high combustion efficiency. The optimum mixing factor for the triplet element is found to be 0.75, according to our measurement.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.12 no.2
• /
• pp.120-131
• /
• 2009

This study measured the centripetal force and effective scope of the population spread from urban center and subcenters in order to diagnose the urban spatial structure of the formation of a multicentric city structure in Busan. The study analyzed the variability of the determination coefficient value (R square) with a negative exponential function derived from the population density model by extending the circular region into 5-km units. The aim of this study was to measure changes in the effective scope of the population centripetal force of the urban center and subcenter in 5-year intervals from 1995 to 2005 using census data. The explanatory adequacy of the population density function was examined with the bias of the function to calculate the distance error between the real location of the urban center and the optimal location, according to the population density function. To summarize the results, the value for the area of Jungangdong showed a continuous reduction, whereas Seomyeon (Bujeondong) maintained explanatory adequacy without a large change. As a whole, Busan was in the process of continuous diversification, in spite of its reduced population. Therefore, it appears necessary to strengthen the function of the urban center and subcenter and to supply adequate dwelling zones close to downtown to form a more efficient urban spatial structure. The results of the present study will be utilized as basic data for the formulation of a political approach to the efficient reorganization of spatial structure by correlating concrete spatial information with the population variability of Busan's urban center and subcenter.

• Journal of the Korea Convergence Society
• /
• v.11 no.5
• /
• pp.175-182
• /
• 2020

The calculation of the optimal trajectory of the stepped top-down robot was made using a genetic algorithm and a computational torque controller. First, the total energy efficiency was minimized using the Red-Cold Generic Algorithm (RCGA) consisting of reproductive, cross, and mutation. The reproducibility condition related to the position assembly of the start and end of the stride and the joints, angles, and angular velocities are linear constraints. Next, the unequal constraint accompanies the condition for preventing the collision of the swing leg at the corner with the outer surface of the stairs, the condition of the knee joint for preventing kinematic peculiarity, and the condition of no moment in safety in the traveling direction. Finally, the angular trajectory of each joint is defined by fourth-order polynomial whose coefficient is to approximate chromosomes. This is to approximate walking. In this study, the energy efficiency of the optimal trajectory was analyzed by computer simulation through a biped robot with seven degrees of freedom composed of seven links.