• Proceedings of the KSR Conference
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• 2000.11a
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• pp.157-164
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• 2000

This study is about predicting the interior pressure level of the korean high speed train using ray acoustic method. The motor car and the motor and passenger cabin are investigated under the environment of passing open countryside and inside tunnel of 350 km/hr. Calculated sound levels are compared with the proposed sound levels and suggestions about the transmission Joss values of isolating panels inside motor car and the guide lines of allowed sound power limit of motor equipments are provided. Results of TPI car show calculated interior sound level is below the proposed values for both cases of open countryside running and inside tunnel. Since ray acoustic method calculated only air borne noise component, real sound level of the motor car may be higher than prediction. Passenger cabins of TMI, TM5 show higher sound level than the proposed values, so window method was carried out to find the contribution of each panel components and point out the remedy of transmission path. Reduction of sound power of motor equipments should be condisered at the same time.

• Water for future
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• v.23 no.2
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• pp.227-237
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• 1990

For a detailed understanding of groundwater flow in rock mass, the effect of major fractures, topography and coefficent of permeability has been evaluated. The numerical model of GFFP-WT was used for the purpose. The results indicate that in the granite porphyry layer with a small permeability, the direction of flow path changes due to convergence of equipotential lines, while the travel time changes due to the presence of fractured in rock masses.

• Transactions of The Korea Fluid Power Systems Society
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• v.5 no.1
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• pp.20-26
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• 2008

Various types of hydraulic shock absorbers are widely used in many fields because of its numerous advantages. However, in order to design adequate damping characteristics, accurate flow data near the orifices are required essentially. In this paper, a commercial computational fluid dynamics(CFD) code, FLUENT is adopted to investigate the flow characteristics near orifices of a shock absorber. Static pressure and velocity vector distributions, fluid path lines are presented for compression/tension strokes and various piston speeds. In order to validate the result of analysis, the numerically obtained damping forces are compared with those of analytical estimations obtained by modified Bernoulli equation. The results reported herein will provide better understanding of the detailed flow fields within shock absorber, and the CFD analysis method proposed in this paper can be used in the design of other types of hydraulic shock absorber.

• Journal of the Korean Society of Combustion
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• v.7 no.2
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• pp.24-33
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• 2002

The morphology of deposits on $15-{\mu}m$ thin SiC filaments has been investigated with SEM in a co-flowing, propane/air laminar diffusion flame. The average size of mature soot particles deposited in the luminous flame edge is strongly dependent on their axial position in a typical heavily sooting flame. The surface growth of liquid-phase PAHs molecules and the transition to soots from fully-developed precursors could be observed in the radial deposition of the flame. Two sooting regimes were found: one is the transition from the condensed-phase precursors; the other is the aggregation of smaller soot particles (or chains of them) to be carried along particle path lines. In the high temperature flame edge outside the soot luminous flame surface, the very thin fiber-like structures, which are about 10 nm thick, were found.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.11a
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• pp.485-490
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• 2004

Airborne laser mapping is the latest and fastest method for generating 3D data. By now, elevation data was mainly acquired using air photos. But this way takes long time from land control surveying to digital visualization. Airborne laser mapping does not need any ground control after system calibration. In this paper, power line and electric tower areas were measured. And using the 3D laser result and digital camera images, contour lines and mosaic images was generated and the accuracy was presented. Airborne laser mapping and digital camera have a full capacity to substitute existing methods for electric and landscape works.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.11
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• pp.637-642
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• 2000

IEEE 1149.1 boundary scan architecture is used as a standard in board-level system testing. The simplicity of this architecture is an advantage in system testing, but at the same time, it it makes a limitation of applications. Because of several problems such as 3-state net conflicts, or ambiguity issues, interconnect testing for multi-drop multi-board systems is more difficult than that of single board systems. A new approach using IEEE 1149.1 boundary scan architecture for multi-drop multi-board systems is developed in this paper. Adding boundary scan cells on backplane bus lines, each board has a complete scan-chain for interconnect test. This new scan-path insertion method on backplane bus using limited 1149.1 test bus less area overhead and mord efficient than previous approaches.

• Korean Journal of Digital Imaging in Medicine
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• v.5 no.1
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• pp.130-136
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• 2002

One of current trends of medical technology is analog to digital. Moreover, The Government put a premium on PACS(Picture Archiving and Communication System) for Medical Insurance in November, 1999. Therefore many hospitals are installing(or planning to install) PACS facilities on their buildings. However most of hospitals didn't consider PACS facilities in the beginning of construction. In particular, the Networking is one of the most difficult things for PACS installation. There is no space for network equipments, and no path for network lines, etc. To solve these problems, wireless network is proposed. The wireless network is divided to three parts mainly. One is the wireless communication for Local Area Network, another is the data transmission through a satellite for Tele-Radiology, and the last one is the technology using Bluetooth for each sub-system of PACS. But there are other problems in wireless systems, i.e., network bandwidth, system stability, interference with other devices. The purpose of this paper is to suggest the future and new trend of PACS including all the problems.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.55.2-55.2
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• 2013

We present the observational study of parsec-scale jets from YSOs reaching lengths of several arc-minutes. The medium-resolution spectroscopic data were obtained between 6000 - $7000{\AA}$ with BOAO long-slit spectrograph. By performing multi-position observation, we investigated the physical variation of the jets and the ambient gas along the whole path of the jets. The flux, electron density, ionization fraction, and electron temperature are discussed with the estimated line ratios between from [OI], [NII], $H{\alpha}$ and [SII] emission lines. This study carried out with more than 8 jets of YSOs including low- to intermediate-mass stars. We also briefly discuss the kinematics of the outflows using spatial and spectroscopic data.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.2
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• pp.78-84
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• 2000

This paper introduces a method of determining the maximum real power transfer limit of interface lines, which connect two areas of a power system, using locally parameterized continuation algorithm. This method traces the path of power flow solutions as interface flow is gradually increased under a certain load demand condition and finds the steady state voltage stability limit, the interface flow limit. Voltage stability index is used to indicate how close the maximum limit is reached. Also, this study presents a procedure to determine the security-constrained interface flow limit using the above method. Contingency ranking index is proposed to identify the severity of contingencies. The case study is performed according to the suggested procedure.

• Journal of Electrical Engineering and Technology
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• v.7 no.6
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• pp.1023-1033
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• 2012

An underwater planar covering problem is studied where the coverage region consists of polygonal cells, and line sweep motion is used for coverage. In many subsea applications, sidescan sonar has become a common tool, and the sidescan sonar data is meaningful only when the sonar is moving in a straight line. This work studies the optimal line sweep coverage where the sweep paths of the cells consist of straight lines and no turn is allowed inside the cell. An optimal line sweep coverage solution is presented when the line sweep path is parallel to an edge of the cell boundary. The total time to complete the coverage task is minimized. A unique contribution of this work is that the optimal sequence of cell visits is computed in addition to the optimal line sweep paths and the optimal cell decomposition.