• Journal of computational fluids engineering
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• v.17 no.1
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• pp.70-77
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• 2012

In this paper, diagonal implicit harmonic balance method with overset grid technique is applied to analyze helicopter rotor blade flow in hover and forward flight condition. The chimera grid need interpolation time with sub-grid and background grid in moving problem such as forward flight on every time step. Present method is available enough to reduce the grid module interpolation time. In order to demonstrate present method, Caradonna & Tung's and AH-1G rotor blades are used and the results are compared to other researchers' result and experimental data.

• Journal of Navigation and Port Research
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• v.28 no.8
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• pp.753-757
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• 2004

The free-surface flow is simulated to make clear the viscous interaction of stem waves and the sub-breaking phenomena around a high speed vehicle. The Navier-Stokes equation is solved by a finite difference method where the body-fitted coordinate system, the wall function and the triple-grid system are invoked They are applied to study precisely on the stem flow of S-103 as to which extensive experimental data are available. Computations are extended to the submerged revolutional body. The numerical result shows that the gradient of M/Us is greatly influenced by the submerged depth And the stem wave is influenced by the separation due to the bow wave.

• Nuclear Engineering and Technology
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• v.54 no.3
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• pp.860-866
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• 2022

An accurate prediction of the pressure drop along the flow paths is crucial in the design of advanced passive systems cooled by heavy liquid metal coolants. To date, a generic pressure drop correlation over spacer grids by Rehme has been applied extensively, which was obtained from substantial experimental data with multiple types of components. However, a few experimental studies have reported that the correlation may give large discrepancies. To provide a more reliable correlation for ring-type spacer grids, the current numerical study aims at figuring out the most critical factor among four hypothetical parameters, namely the flow area blockage ratio, number of fuel rods, type of fluid, and thickness of the spacer grid in the flow direction. Through a set of computational fluid dynamics simulations, we observed that the flow area blockage ratio dominantly influences the pressure loss characteristics, and thus its dependence should be more emphasized, whereas the other parameters have little impact. Hence, we suggest a new correlation for the drag coefficient as C_B = C_ν,m/ε^2.7, where C_ν,m is formulated by a nonlinear fit of simulation data such that C_ν,m = -11.33 ln(0.02 ln(Re_b)).

• Journal of Internet Computing and Services
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• v.9 no.4
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• pp.143-156
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• 2008

Grid-based PACS can provide an advanced medical information services such as remote image file transfer, collaboration, remote diagnosis, and virtual hospital. In this paper, we have implemented Grid-PACS which guarantees both storage safety and extendability for virtual large scale storage system. The experimental results showed that the virtual storage system provided more efficient and faster data transfer than the conventional PACS. The proposed Grid data management system can be utilized to improve the effectiveness of the PACS data management and transmission between medical institutions.

• Carbon letters
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• v.28
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• pp.55-59
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• 2018

Transition-metal-embedded carbon nanotubes (CNTs) have been accepted as a novel type of sensing material due to the combined advantage of the transition metal, which possesses good catalytic behavior for gas interaction, and CNTs, with large effective surface areas that present good adsorption ability towards gas molecules. In this work, we simulate the adsorption of $O_2$ and $O_3$ onto Rh-doped CNT in an effort to understand the adsorbing behavior of such a surface. Results indicate that the proposed material presents good adsorbing ability and capacities for these two gases, especially $O_3$ molecules, as a result of the relatively large conductivity changes. The frontier molecular orbital theory reveals that the conductivity of Rh-CNT would undergo a decrease after the adsorption of two such oxidizing gases due to the lower electron activity and density of this media. Our calculations are meaningful as they can supply experimentalists with potential sensing material prospects with which to exploit chemical sensors.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.450-465
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• 2021

In this study, an attempt has been made to investigate the water-entry characteristics of the high-speed parallel projectile numerically. The shear stress transport k-𝜔 turbulence model and the Zwart-Gerber-Belamri cavitation model based on the Reynolds-Averaged Navier-Stokes method were used. The grid independent inspection and grid convergence index is carried out and verified. The influences of the parallel water-entry on flow filed characteristics, trajectory stability and drag reduction performance for different values of initial water-entry speed (𝜈₀ = 280 m/s, 340 m/s, 400 m/s) and clearance between the parallel projectiles (L_p = 0.5D, 1.0D, 2.0D, 3.0D) are presented and analyzed in detail. Under the condition of the parallel water-entry, it can be found that due to the intense interference between the parallel projectiles, the distribution of cavity is non-uniform and part of the projectile is exposed to water, resulting in the destruction of the cavity structure and the decline of trajectory stability. In addition, the parallel projectile suffers more severe lateral force that separates the two projectiles. The drag reduction performance is impacted and the velocity attenuation is accelerated as the clearance between the parallel projectiles reduces.

• Atmosphere
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• v.24 no.2
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• pp.245-251
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• 2014

Statistical trajectory analysis has been widely used to identify potential source regions for chemically and radiatively important chemical species in the atmosphere. The most widely used method is a statistical source-receptor model developed by Stohl (1996), of which the underlying principle is that elevated concentrations at an observation site are proportionally related to both the average concentrations on a specific grid cell where the observed air mass has been passing over and the residence time staying over that grid cell. Thus, the method can compute a residence-time-weighted mean concentration for each grid cell by superimposing the back trajectory domain on the grid matrix. The concentration on a grid cell could be used as a proxy for potential source strength of corresponding species. This technical note describes the statistical trajectory approach and introduces its application to estimate potential source regions of $CO_2$ enhancements observed at Korean Global Atmosphere Watch Observatory in Anmyeon-do. Back trajectories are calculated using HYSPLIT 4 model based on wind fields provided by NCEP GDAS. The identified $CO_2$ potential source regions responsible for the pollution events observed at Anmyeon-do in 2010 were mainly Beijing area and the Northern China where Haerbin, Shenyang and Changchun mega cities are located. This is consistent with bottom-up emission information. In spite of inherent uncertainties of this method in estimating sharp spatial gradients within the vicinity of the emission hot spots, this study suggests that the statistical trajectory analysis can be a useful tool for identifying anthropogenic potential source regions for major GHGs.

• Journal of the Korean Graphic Arts Communication Society
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• v.29 no.3
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• pp.17-30
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• 2011

The polarizer is an important optical element used in a variety of applications. Nano-wire grid polarizers in the form of sub-wavelength metallic gratings are an attractive alternative to conventional polarizers, because they provide high extinction ratio. This study has been carried out to fabrication of the 17inch area size nano-wire grid polarizer(NWGP) The master for NWGPs with a pitch of 200nm and the area size $730mm{\times}450mm$ were fabricated using laser interference lithography and aluminum sputtering and wet etching. And The NWGP fabrication process was using by the Roll to-Roll UV imprinting and was applied to flexible PET film. The results were a transmission of light (Tp) 46.7%, reflectance (Rs) 40.1% and Extinction ratio of above 16 for the visible light range.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.979-981
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• 2004

여러 과학 및 공학 응용 프로그램에서 다루는 그래프 데이터는 종종 그 크기가 너무 커서 컴퓨터의 주 메모리에 다 들어 갈 수 없는 경우가 많다. 이러한 방대한 크기의 자료를 처리하면서 입출력의 빈도가 자연적으로 커지게 되고 전체 계산에서 주요한 병목 요인으로 작용한다. 본 논문은 solid grid 그래프를 위한 입출력 복잡도 (I/O-complexity)가 O(sort(N))인 depth-first search (DFS) 알고리즘을 제안한다. 여기서, N=｜V｜+｜E｜이고 Sort(N)=Θ((N/B)logM/B(N/B)) 이다. 이 전까지 알려진 가장 좋은 알고리즘은 적절한 Sub-grid 입출력을 바탕으로 한 전통적 DFS 알고리즘으로 그 입출력 복잡도는 O((N/B)$B^{1}$2/) 이다.

• Journal of Korean Society for Atmospheric Environment
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• v.17 no.2
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• pp.147-155
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• 2001

ISCLT3 model was applied in Seoul metropolitan area to investigate the source-receptor relationships among 17 cities in the Kyonggi Province. For the purpose of the model simulation, emission rates of NO$_2$, SOx, and PM(sub)10 were prepared for grid scale with 1$\times$1 km, and receptors were located on every 2$\times$2 km grid. Meterological data for the last 10 years(88~97) were used as input data. According to our study, NO$_2$ concentration of the cities ranged from 10 to 45 ppb with the highest value appearing from Puchon city. The concentrations of SOx and PM(sub)10 concentrations fell in the range of 5~20 ppb and 20~70$\mu\textrm{g}$/㎥, respectively. It was also found out that air quality in one city can be affected greatly by the air pollutants originating from other cities.