• Korean Journal of Optics and Photonics
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• v.8 no.6
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• pp.506-509
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• 1997

A novel narrowband wavelength bandpass filter with a large side-lobe suppression was proposed in vertical coupler structure using coupling variation in propagation direction. Combination of a half sinusoidal distributed and a slow coupling schmes was used for narrow bandwidth and small side-lobes. Simulation showed 1.5 nm passband at 1.5507 $\mu\textrm{m}$ and the side-lobes were suppressed more than 20 dB which is two times larger than that of a constant coupling filter. A monolithic two-channel wavelength demultiplexer was proposed and theoretically investigated.

• IEIE Transactions on Smart Processing and Computing
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• v.2 no.4
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• pp.189-196
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• 2013

This paper presents a two-stage approach to detect pedestrians in video sequences taken from a moving vehicle. The first stage is a preprocessing step, in which potential pedestrians are hypothesized. During the preprocessing step, a difference image is constructed using a global motion estimation, vertical and horizontal edge maps are extracted, and the color difference between the road and pedestrians are determined to create candidate regions where pedestrians may be present. The candidate regions are refined further using the vertical edge symmetry features of the pedestrians' legs. In the next stage, each hypothesis is verified using the integral channel features and an AdaBoost classifier. In this stage, a decision is made as to whether or not each candidate region contains a pedestrian. The proposed algorithm was tested on a range of dataset images and showed good performance.

• Journal of the Korean Society of Visualization
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• v.6 no.1
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• pp.53-58
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• 2008

We carried out the experiments which controled the periodic jet in front of the fence to alter the fence wake. The experiments were performed in circulating water channel and the vertical fence was submerged in the boundary layer. The frequency, jet nozzle distance and speed of jet passing the slit were investigated. Each case divided into 20 phases and phase-averaged results were compared with uncontrolled fence flow. From the results, we found the specific frequency and nozzle distance which were good for reducing the reattachment length. In this case, the reattachment length was decreased 35% compared with the uncontrolled fence flow.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.468-478
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• 2020

The wave interaction problem with a vertical slotted breakwater, consisting of impermeable upper, lower parts and a permeable middle part, has been studied theoretically. An analytical model was presented for the estimation of reflection and transmission of monochromatic waves by a slotted breakwater. The far-field solution of the wave scattering involving nonlinear porous boundary condition was obtained using eigenfunction expansion method. The empirical formula for drag coefficient in the near-field, representing energy dissipation across the slotted barrier, was determined by curve fitting of the numerical solutions of 2-D channel flow using CFD code StarCCM+. The theoretical model was validated with laboratory experiments for various configurations of a slotted barrier. It showed that the developed analytical model can correctly predict the energy dissipation caused by turbulent eddies due to sudden contraction and expansion of a slotted barrier. The present paper provides a synergetic approach of the analytical and numerical modelling with minimum CPU time, for better estimation of the hydrodynamic performance of slotted breakwater.

• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.6
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• pp.773-779
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• 1986

In this paper, we discuss fabrication and characteristics of the Vertical Double diffused MOS(VDMOS) transistor. The epi layers of starting wafers are 18~22\ulcorner in thickness and 8~12\ulcornercm in resistivity. The channel regions are defined through the self-aligned double diffusion process. The characteristics of the fabricated VDMOS are breakdown voltage of 240V, threshold voltage of 2V, on-resistance of 226\ulcornerand transconductance of 3x10**-3 mho.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.2
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• pp.67-74
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• 2015

In this study, analysis and experiments were carried out on temperature distributions and thermal deformations in a dry vacuum pump with vertical screws for safe operation. When a vacuum pump is working, it is necessary to get rid of the heat generated by the friction of bearings and the compression of air to prevent the vacuum pump from being damaged by interference between two screws and housing through thermal deformation. Additional cooling was proposed by using oil flow through the inner channel of the rotating axis for lower temperature control of the vacuum pump. Analysis and experimental results were compared in terms of temperature distribution and thermal deformation of the vacuum pump, and two sets of results matched reasonably well. These results for a dry vacuum pump with vertical screws can be used in similar model development and can minimize errors in design and manufacture by providing reasonably accurate prediction in advance.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.1
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• pp.24-29
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• 2000

We propose a simple method to control the crystallization depth of amorphous silicon (a-Si) deposited by PECVD or LPCVD during the excimer laser annealing (ELA). Employing the new method, we have formed poly-Si/a-Si double film and fabricated a new poly-Si TFT with vertical a-Si offsets between the poly-Si channel and the source/drain of TFT without any additional photo-lithography process. The maximum leakage current of the new poly-Si TFT decreased about 80% due to the highly resistive vertical a-Si offsets which reduce the peak electric field in drain depletion region and suppress electron-hole pair generation. In ON state, current flows spreading down through broad a-Si cross-section in the vertical a-Si offsets and the current density in the drain depletion region where large electric field is applied is reduced. The stability of poly-Si TFT has been improved noticeably by suppressing trap state generation in drain region which is caused by high current density and large electric field. For example, ON current of the new TFT decreased only 7% at a stress condition where ON current of conventional TFT decreased 89%.

• Journal of Industrial Technology
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• v.30 no.A
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• pp.17-23
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• 2010

Recently, a large number of open-pit mines are planning to change their mining method to underground types because the environmental concerns and legal regulations are increased with a rise in the standard of living. The K silica mine, which is one of them and located in Kyunggi province, is planning the establishment of a vertical shaft which will be used for ore-pass channel in their new glory hole mining method. This vertical shaft will be designed to join with a horizontal gangway excavated from the ground level. In this new mining system, the excavated ore particles will be stored inside a shaft and transported out with a help of a conveyor belt. Therefore the hang-up of ore particles in a shaft, the control of gate at the bottom of a shaft, the installation of dog-leg at the gate should be investigated identically. In this study, the PFC-2D code which is one of the discrete element numerical methods has been applied to simulate the particle flow mechanism in a shaft, and the optimum mine design has been proposed to maximize the productivity and to minimize the system damage.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2007.12a
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• pp.125-126
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• 2007

In this paper, the floating body with vertical plate is introduced with a study on the flow patterns and characteristics in around the floating body by using 2 frame particle tracking method. This paper introduce an analysis method to predict the characteristics if flow around the neighboring fields if Floating Body with vertical plate in order to investigate a high performance model. Flow visualization has conducted in a drcu1ating water channel by a high speed camera and etc. Flow phenomena according to turbulence intensity distribution and flow separation around the floating body with vertical plate were obtained by two-dimensional PIV system.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.10
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• pp.698-703
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• 2014

The structures of fresh water plume depending on estuarine geometries and wind directions (upwelling, onshore, downwelling, and offshore winds) were studied using the Regional Ocean Modeling System (ROMS). Four idealized estuaries, which are different in bathymetry, were considered. The results showed that the fresh water plume was restricted close to the shore line where a river was connected to the sloping shelf rather than the flat shelf due to the fast momentum exchanges from x, y to z momentums on the sloping shelf. Mild upwelling and offshore winds (${\mid}{\tau}_{\omega}{\mid}=0.01Pa$) enhanced stratification on the contrast to previous studies which showed that winds destroyed stratification by enhanced vertical mixing. However, downwelling and onshore winds had similar effects on the vertical structure of the fresh water plume as in previous studies enhancing vertical mixing. The plume was confined above the underneath submarine channel, thus the plume path was directly affected by the direction of the submarine channel on the shelf.