• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권12호
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• pp.6000-6017
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• 2018

This paper presents a new descriptor, named Histograms of Prominent Edge Directions (HPED), for the recognition of facial expressions in a person-independent environment. In this paper, we raise the issue of sampling error in generating the code-histogram from spatial regions of the face image, as observed in the existing descriptors. HPED describes facial appearance changes based on the statistical distribution of the top two prominent edge directions (i.e., primary and secondary direction) captured over small spatial regions of the face. Compared to existing descriptors, HPED uses a smaller number of code-bins to describe the spatial regions, which helps avoid sampling error despite having fewer samples while preserving the valuable spatial information. In contrast to the existing Histogram of Oriented Gradients (HOG) that uses the histogram of the primary edge direction (i.e., gradient orientation) only, we additionally consider the histogram of the secondary edge direction, which provides more meaningful shape information related to the local texture. Experiments on popular facial expression datasets demonstrate the superior performance of the proposed HPED against existing descriptors in a person-independent environment.

• 대한원격탐사학회지
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• 제20권5호
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• pp.289-305
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• 2004

Atmospheric correction of Landsat Visible and Near Infrared imagery (VIS/NIR) over aquatic environment is more demanding than over land because the signal from the water column is small and it carries immense information about biogeochemical variables in the ocean. This paper introduces two methods, a modified dark-pixel substraction technique (path--extraction) and our spectral shape matching method (SSMM), for the correction of the atmospheric effects in the Landsat VIS/NIR imagery in relation to the retrieval of meaningful information about the ocean color, especially from Case-2 waters (Morel and Prieur, 1977) around Korean peninsula. The results of these methods are compared with the classical atmospheric correction approaches based on the 6S radiative transfer model and standard SeaWiFS atmospheric algorithm. The atmospheric correction scheme using 6S radiative transfer code assumes a standard atmosphere with constant aerosol loading and a uniform, Lambertian surface, while the path-extraction assumes that the total radiance (L/sub TOA/) of a pixel of the black ocean (referred by Antoine and Morel, 1999) in a given image is considered as the path signal, which remains constant over, at least, the sub scene of Landsat VIS/NIR imagery. The assumption of SSMM is nearly similar, but it extracts the path signal from the L/sub TOA/ by matching-up the in-situ data of water-leaving radiance, for typical clear and turbid waters, and extrapolate it to be the spatially homogeneous contribution of the scattered signal after complex interaction of light with atmospheric aerosols and Raleigh particles, and direct reflection of light on the sea surface. The overall shape and magnitude of radiance or reflectance spectra of the atmospherically corrected Landsat VIS/NIR imagery by SSMM appears to have good agreement with the in-situ spectra collected for clear and turbid waters, while path-extraction over turbid waters though often reproduces in-situ spectra, but yields significant errors for clear waters due to the invalid assumption of zero water-leaving radiance for the black ocean pixels. Because of the standard atmosphere with constant aerosols and models adopted in 6S radiative transfer code, a large error is possible between the retrieved and in-situ spectra. The efficiency of spectral shape matching has also been explored, using SeaWiFS imagery for turbid waters and compared with that of the standard SeaWiFS atmospheric correction algorithm, which falls in highly turbid waters, due to the assumption that values of water-leaving radiance in the two NIR bands are negligible to enable retrieval of aerosol reflectance in the correction of ocean color imagery. Validation suggests that accurate the retrieval of water-leaving radiance is not feasible with the invalid assumption of the classical algorithms, but is feasible with SSMM.

• 대한기계학회논문집B
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• 제36권12호
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• pp.1141-1150
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• 2012

이 논문은 선박에서 자세 안정용 양방향 축류펌프에 대한 임펠러 블레이드의 형상최적설계를 설명한 것이다. 양방향 축류펌프용 블레이드는 대칭형 익형을 사용하므로 효율이 기존의 단방향 축류펌프보다 낮다. 이러한 양방향 축류펌프의 단점을 최소화 하고 효율을 증가시키기 위해 최적설계기법을 사용하였다. 양방향 축류펌프의 성능 개선을 위해 상용 CFD 프로그램인 ANSYS CFX v.13 을 이용하여 유동해석을 수행하였다. 직교배열표, 분산분석과 직교다항식을 이용한 대리모델기반 최적설계방법은 최적 설계변수를 결정하고 주효과를 찾는데 사용하였다. 최적설계 결과로부터, 임펠러 블레이드의 유효한 설계변수를 확인하고 이의 최적해와 설계요구조건 만족에 대한 유용성을 설명하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.637-640
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• 2005

The mechanical properties of bellows, such as the extensibility and the strength can be changed depending on the shape. For the shipbuilding material, it is favorable that the fatigue lift is long due to the elastic property and the reduction of thermal stress in piping system. Nowadays, the domestic production and design of bellows are based on the E.J.M.A Code. Therefore, the design standard is in need because of much errors and lack of detailed analysis. In this study, it is attempted to find out the optimal shape of U-type ship's bellows that is applied to design of experiment using the finite element method. The effective factors, mountain height, length, thickness, and number of mountains and the length of joint are considered and the proper values are chosen for the simulation. The number of mountains are increased, the volume increases above the standard volume and the stress obviously increases. In addition, the effect of the thickness of bellows on the stress is very large. Both of the volume and stress are decreasing at a certain lower value region.

• Journal of Astronomy and Space Sciences
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• 제37권3호
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• pp.171-185
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• 2020

This paper presents a methodology for Initial Orbit Determination (IOD) based on a modification of the Laplace's geocentric method. The orbital elements for Near-Earth asteroids (1864) Daedalus, 2003 GW, 2019 JA8, a Hungaria-type asteroid (4690) Strasbourg, and the asteroids of the Main Belt (1738) Oosterhoff, (2717) Tellervo, (1568) Aisleen and (2235) Vittore were calculated. Input data observations from the Minor Planet Center MPC database and Astronomical Observatory of the Technological University of Pereira (OAUTP; MPC code W63) were used. These observations cover observation arcs of less than 22 days. The orbital errors, in terms of shape and orientation for the estimated orbits of the asteroids, were calculated. The shape error was less than 53 × 10^-3 AU, except for the asteroid 2019 JA8. On the other hand, errors in orientation were less than 0.1 rad, except for (4690) Strasbourg. Additionally, we estimated ephemerides for all bodies for up to two months. When compared with actual ephemerides, the errors found allowed us to conclude that these bodies can be recovered in a field of vision of 95' × 72' (OAUTP field). This shows that Laplace's method, though simple, may still be useful in the IOD study, especially for observatories that initiate programs of minor bodies observation.

• 한국해양환경ㆍ에너지학회지
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• 제11권1호
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• pp.35-41
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• 2008

월파형 파력발전장치는 월류된 파랑으로 인하여 발생한 수두차를 이용하여 터빈을 구동하는 일종의 파랑에너지 변환장치로써 파랑에너지를 전기 에너지로 변환하는 장치이다. 본 연구에서는 먼저 상용 CFD코드 인 Fluent를 사용하여 수치조파수조를 구현하고, Reynolds-Averaged Navier-Stokes 방정식과 VOF 모델을 이용하여 2차원 수치 선형 규칙파를 생성한 후 이를 계산 결과와 비교 검증을 수행하였다. 다음으로 월류 성능의 최적 설계점과 파력발전 장치의 월류 충전량을 고찰하기 위하여 여러 가지 파랑조건과 형상변수들에 대하여 계산을 수행 하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.373-376
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• 2006

The ring rolling design for a large-scale Ti-6Al-4V alloy ring was performed with a calculation method and FEM simulation. The ring rolling design includes geometry design and optimization of process variables. The calculation method was to determine geometry design such as initial billet and blank size, and final rolled ring shape. A commercial FEM code, SHAPE was used to simulate the effect of process variables in ring rolling on the distribution of the internal state variables such as strain, strain rate and temperature. In order to predict the forming defects during ring rolling, the process-map approach based on Ziegler's instability criterion was used with FEM simulation. Finally, an optimum process design to obtain sound Ti-6Al-4V rings without forming defects was suggested through combined approach of Ziegler's instability map and FEM simulation results.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.253-254
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• 2003

Computations of the mean and turbulence flows over three-dimensional hill of conical shape have implemented. Beside the standard ${\kappa}-{\varepsilon}$ , two other modifications proposed by Detering & Etling and Duynkerke for atmospheric applications were also considered. These predictions were compared with the data of a wind tunnel experiment. From the comparison, it was concluded that all three models predict the mean flow velocities equally well while only the Duynkerke's model accurately predicts the turbulence data statistics. It also concluded that there are large discrepancies between model predictions and the measurements near the ground surface. The flow field, which was obtained by using the Duynkerke's modification, was used to simulate gas dispersion from an upwind source. The calculation results are verified based on the measurement data. Modifications of the turbulent Schmidt number were carried out in order to match the measured results. The code was used to investigate the influence of the recirculation zone behind a building of cubical shape on the transport and dispersion of pollutant. For a stack behind and near the obstacle, some conclusions about the effect of the stack height and stack location were derived.

• Wind and Structures
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• 제22권3호
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• pp.307-328
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• 2016

This paper describes an investigation of the net wind loads on solar panels and wind loads on the underlying roof surface for panels mounted parallel to pitched roofs of domestic buildings. Typical solar panel array configurations were studied in a wind tunnel and the aerodynamic shape factors on the panels were put in a form appropriate for the Australian/New Zealand Wind Actions Standard AS/NZS 1170.2:2011. The results can also be used to obtain more refined design data on individual panels within an array. They also suggest values for the aerodynamic shape factors on the roof surface under the panels, based on a gust wind speed at roof height, of ${\pm}0.5$ for wind blowing parallel to the ridge, and ${\pm}0.6$ for wind blowing perpendicular to the ridge. The net loads on solar arrays in the middle portion of the roof are larger than those on the same portion of the roof without any solar panels, thus resulting in increased loads on the underlying roof structure.

• Journal of the Optical Society of Korea
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• 제13권2호
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• pp.251-255
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• 2009

In the non-contact 3-dimensional (3D) shape measurements, the fringe pattern projection method based on the phase-shifting technique has been considered very effective for its high speed and accuracy. The digital fringe projector in particular has great flexibility in generating fringe patterns since the patterns can be controlled easily by the computer program. In this work, we have developed a high-speed digital laser grating projection system using a laser diode and a polygon mirror, and evaluated its performance. It has been demonstrated that all the optical measurements required to find out the profile of a 3D object could be carried out within 31 ms, which confirmed the validity of our 3D measurement system. The result implies the more important fact that the speed in 3D measurement can be enhanced remarkably since, in our novel system, there is no device like a LCD or DMD whose response time limits the measurement speed.