• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 1997년도 추계학술대회논문집; 한국과학기술회관; 6 Nov. 1997
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• pp.237-243
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• 1997

Most outdoor sounds go from sources relatively near the ground to receivers near the ground. When either source or receiver are near the ground, interference can occur between the direct sound and that reflected at the ground which travels a slightly longer path. The sound pressure at the receiver is very different depending on the state of ground surface i.e. ground impedance. Ground impedances could be characterized by the value of a single parameter, namely the flow resistivity of the ground surface. This study suggests the measurement method of the flow resistivity using two microphones and predicts the flow resistivities of various ground surfaces.

• Proceedings of the SAREK Conference
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.755-760
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• 2006

The exhaust gas with solid particle goes through the riser in both particle circulating type and circulating fluidized bed type heat exchanger to recover the heat. During heat transfer, gas velocity in vertical riser decreases as viscosity of exhaust gas decreases. In this case, when the particle size is fixed, sometimes the exhaust gas happens to have lower velocity which prohibit them to go out of the riser. In this paper the particle motion in vertical Rayleigh flow was studied. The behavior of heat transfer was investigated by means of velocity and temperature distribution. The result from numerical analysis was validated by the experimental results. Fortran code was used to analyze the particle motion in vertical Rayleigh flow.

• Journal of Korea Multimedia Society
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• 제14권1호
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• pp.133-143
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• 2011

This paper proposes a mobile navigation system which haptically presents the way to go to visually impaired persons. In order to convey the tactile information to the visually impaired persons, we develop a new tactile module with a solenoid, a permanent magnet and an elastic spring. Furthermore, we suggest 2D vibration flow which originates from one point and gradually propagates to other points on a surface of the haptic navigation system. The tactile module and the vibration flow method are incorporated into the proposed haptic navigation system and they stimulate the user's finger pad and palm, respectively. We conduct experiments to investigate that the proposed navigation system haptically provides the direction to the users. From the experimental results, we verify that the proposed system can generate enough tactile sensation to guide the direction to go in real-time.

• Journal of the Korean Society of Propulsion Engineers
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• 제22권6호
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• pp.72-83
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• 2018

In this study, a series of CFD analyses were carried out for a hydrogen rocket combustor with a single shear coaxial injector. A hybrid RANS/LES approach was used for the turbulent combustion analysis with a two-dimensional axisymmetric configuration. Three reaction mechanisms, three spatial discretization methods, and three levels of grid resolution were compared to determine an appropriate CFD approach. The performance of the CFD prediction were investigated by comparing the wall heat flux with experimental data. Investigation of the flow field results provides an insight into the characteristics of the turbulent reacting flow of a rocket combustor with a shear coaxial injector.

• Journal of the Korean Society of Propulsion Engineers
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• 제10권4호
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• pp.34-39
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• 2006

The flow forming has been used to produce long thin walled tube parts, with reduced forming force and enhanced mechanical for a good finished part, compared with other method formed parts. Especially, the flow forming is suitable for making high precision thin walled cylinders, such as rocket motor cases, combustion chamber, hydraulic cylinders and high-pressure vessels and so on. In this paper, finite element analysis of three-roller forward and backward flow forming for combustion chamber is carried out to study effects of forming depth and feed rate on forming force. The axial and radial forming forces of forward flow forming on several forming depth and feed rate conditions are compared with those of backward flow forming.

• Journal of the Korean Home Economics Association
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• 제41권8호
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• pp.213-227
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• 2003

The purpose of this study is to explore a weekly life of Korean high school students, especially focused on their activities, locations, and flow. The data were collected from 116 high school students by the Experiential Sampling Method, employing a cellular-phone as a signaling device. Students reported, in response to the 6964 random signals, that 43.4% of their time was spent for social/leisure activities. An additional 31% percent of time was used for productive activities and the rest of times belonged to maintenance activities. When engaged in productive activities, they usually reported anxiety, while they felt bored for social/leisure activities and flow for maintenance activities. The most pervasive context of their lives was school (42.8％), followed by home (33.3%), public space (24.6%), and educational institutes (9.2%). In general, they experienced flow for the most of the locations, except educational settings in which they felt anxiety. The flow for productive activities varied by gender, pending on where they had productive activities, while others did not show any significant differences in the activity flow by locations.

• Journal of Korean Society of Water and Wastewater
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• 제25권5호
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• pp.699-706
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• 2011

This study has a purpose of examining technical feasibility of supplying the in-stream flow for the Gyobang cheon by using treated water from small wastewater treatment facilities as a decentralized option. To do this, the water and contaminant flow in study areas of the Gyobang cheon are defined from the context of the integrated urban water cycle, and analyzed by using the Urban Volume and Quality (UVQ) model. First, the UVQ model was built for the study areas of the Gyobang cheon and calibrated with observation data. Second, the decentralized options of the in-stream flow was explored with consideration of availability of water sources. The UVQ simulation then led to selecting the best option which would meet the criteria of water quantity and quality. It was finally concluded that using water sources out of study areas 1 and 2, adjoining the upper part of the Gyobang cheon, in the decentralized manner can be a feasible option for in-stream flow. It also seems that the UVQ model is useful to understand the water cycle in study areas of the Gyobang cheon.

• 한국해양학회지
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• 제30권5호
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• pp.467-479
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• 1995

To investigate the current structures and diffusion characteristics in Youngil Bay, a systematic field observations of current velocity, drogue tracking, dye diffusion experiment and aerial photographing were performed. The flow patterns in the surface layer of the bay depend more strongly on the wind and ocean current than the tidal current, and the patterns in the middle are predominated by the ocean current. The residual currents in the surface generally flow toward the inner bay through the western and central areas of the bay, and then the currents go toward the ocean along the eastern shore of the bay with anti-clock-wise circulation. The residual currents in the surface of the eastern cease are not nearly influenced by the wind, and the currents always move northward to northeastward. However, the currents in the western shore depend strongly on the wind and the outflow of the Huntsman River, that is, the residual currents go northward to northeastward when the southerly to westerly winds blow or a large amount of flow from the river discharge. The residual currents in the middle layer flow toward the inner bay along the western shore of the bay, and the incomed currents go out to the ocean along the eastern shore with anticlockwise circulation. The diffusion of dye patch by the instantaneous point source shows a similar pattern to the drogue trajectory, and the apparent diffusion coefficients of the dye patch by Fick's theory is 1.14${\times}$10$^4$ cm$^2$/s. The behavior of the river discharges in flood shows a band type's effluent pattern toward the outer bay along the western coast.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제33권6호
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• pp.2473-2481
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• 2013

The two characteristics of two-lane-and-two-way traffic flow are platoon and overtaking triggered by low-speed vehicle. It is crucial to develop a robust model which simultaneously generates the behaviors of platoon by low-speed vehicle and overtaking using opposite lane. Hence, a microscopic two-lane and two-way vehicle model was introduced (B. Yoon, 2011), which is based on CA (Cellular Automata) which is one of discrete time-space models, in Korea. While the model very reasonably explains the behaviour of overtaking low-speed vehicle in stable traffic flow below critical density, it has shortcomings to the overtaking process in unstable traffic flow above the critical density. Therefore, the objective of this study is to develope a vehicle model to more realistically explain overtaking process in unstable traffic flow state based on the model developed in the previous study. The experimental results revealed that the car-following model robustly generates the various macroscopic relationships of traffic flow generating stop-and-go traffic flow and the overtaking model reasonably explains the behaviors of overtaking under the conditions of both opposite traffic flow and stochastic parameter to consider overtaking in unstable traffic flow state. The vehicle model presented in this study can be expected to be utilized for the analysis of two-lane-and-two-way traffic flows more realistically than before.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.269-273
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• 2011

In present paper focused on the influence of the inlet-outlet area ratio of counter flow manifold on the flow distribution and pressure drop characteristics of a tubular heat exchanger. The characteristics of flow distribution and pressure loss can be obtained depending on the inlet-outlet area ratio. In this paper, a tubular heat exchanger can be designed with minimum flow mal-distribution and better characteristic of pressure loss by choosing the optimum inlet-outlet area ratio.