• 상하수도학회지
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• 제22권3호
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• pp.351-358
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• 2008

The modified in-line mixer which was suggested in this study for small water treatment facilities was evaluated on the performance of coagulation. For the objectives of this research, computational fluid dynamics(CFD) simulation was applied for analysis of flow characteristics within the modified in-line mixer. For verifying the results of CFD simulation, wet tests for the pilot plant were conducted. The wet test was to measure the actual coagulant dispersion distribution on the overall cross-section at a distance of 5.5D from the chemical injection point. From the results of CFD simulation and wet test, it was shown that the coagulant dispersion within the modified in-line mixer was occurred more uniformly than within the existing PDM(Pump diffusion Mixer). The results have confirmed the modified in-line mixer had several advantages compared with the existing PDM in terms of dispersion efficiency.

• 전기학회논문지P
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• 제60권1호
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• pp.27-31
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• 2011

In this paper, the electron transport characteristics in $CF_4$ has been analysed over the E/N range 1~300[Td] by a two-term approximation Boltzmann equation method and by a Monte Carlo simulation. The motion has been calculated to give swarm parameters for the electron drift velocity, longitudinal diffusion coefficient, the ratio of the diffusion coefficient to the mobility, electron ionization and attachment coefficients, effective ionization coefficient, mean energy, collision frequency and the electron energy distribution function. The electron energy distribution function has been analysed in $CF_4$ at E/N=5, 10, 100, 200 and 300[Td] for a case of the equilibrium region in the mean electron energy and respective set of electron collision cross sections. The results of Boltzmann equation and Monte Carlo simulation have been compared with experimental data by Y. Nakamura and M. Hayashi. The swarm parameter from the swarm study are expected to serve as a critical test of current theories of low energy electron scattering by atoms and molecules, in particular, as well as crucial information for quantitative simulations of weakly ionized plasmas.

• 한국재료학회지
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• 제12권4호
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• pp.254-258
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• 2002

To realize channel cross-connecting in optical communications systems, a high speed optical matrix switch was fabricated using z-cut $LiNbO_3$. For switch fabrication was design bending structure and coupling length and four $2{\times}2$ directional couplers were integrated on one substrate far construction of a $4{\times}4$ switch. Single-mode optical waveguides were formed by Ti-diffusion at a wet $O_2$ atmosphere. Ti-diffusion profile, refractive index variation and waveguide morphology were analyzed by Prism coupler and optical microscopy, respectively.

• Nuclear Engineering and Technology
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• 제50권1호
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• pp.35-42
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• 2018

This article presents clean core criticality calculations and control rod worth calculations for TRIGA (Training, Research, Isotope production-General Atomics) Mark II research reactor benchmark cores using Winfrith Improved Multi-group Scheme-D/4 (WIMS-D/4) and Program for Reactor In-core Analysis using Diffusion Equation (PRIDE) codes. Cores 133 and 134 were analyzed in 2-D (r, ${\theta}$) and 3-D (r, ${\theta}$, z), using WIMS-D/4 and PRIDE codes. Moreover, the influence of cross-section data was also studied using various libraries based on Evaluated Nuclear Data File (ENDF/B-VI.8 and VII.0), Joint Evaluated Fission and Fusion File (JEFF-3.1), Japanese Evaluated Nuclear Data Library (JENDL-3.2), and Joint Evaluated File (JEF-2.2) nuclear data. The simulation results showed that the multiplication factor calculated for all these data libraries is within 1% of the experimental results. The reactivity worth of the control rods of core 134 was also calculated with different homogenization approaches. A comparison was made with experimental and reported Monte Carlo results, and it was found that, using proper homogenization of absorber regions and surrounding fuel regions, the results obtained with PRIDE code are significantly improved.

• 대한전자공학회논문지SD
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• 제40권11호
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• pp.1-8
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• 2003

본 논문에서는 소스/드레인 및 게이트의 불순물에 따른 실리사이드의 의존성을 면저항과 단면 특성 등의 분석을 통하여 연구하였다. 급속 열처리 후에는 As, P, BF₂, B/sub 11/ 등과 같은 불순물에 대한 먼저항의 차이가 거의 나지 않았다. 하지만 실리사이드 형성 후히 고온 열처리시에 그 특성이 매우 크게 변화하였다. BF₂를 주입한 시편에서의 특성이 가장 좋게 나타난 반면, As를 주입한 실리사이드의 특성이 가장 열화되었다. BF₂를 주입한 시편에서의 실리사이드 특성 향상은 flourine에 의한 니켈의 확산 방지 때문인 것으로 여겨진다. 그러므로 실리사이드의 성능 향상을 위해 Ni의 확산을 방지시키는 것이 매우 필요하다.

• Nuclear Engineering and Technology
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• 제53권11호
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• pp.3543-3562
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• 2021

The methods and performance of a 3D pin-by-pin neutronics code based on the 2D/1D decoupling method are presented. The code was newly developed as an effort to achieve enhanced accuracy and high calculation performance that are sufficient for the use in practical nuclear design analyses. From the 3D diffusion-based finite difference method (FDM) formulation, decoupled planar formulations are established by treating pre-determined axial leakage as a source term. The decoupled axial problems are formulated with the radial leakage source term. To accelerate the pin-by-pin calculation, the two-level coarse mesh finite difference (CMFD) formulation, which consists of the multigroup node-wise CMFD and the two-group assembly-wise CMFD is implemented. To enhance the accuracy, both the discontinuity factor method and the super-homogenization (SPH) factor method are examined for pin-wise cross-section homogenization. The parallelization is achieved with the OpenMP package. The accuracy and performance of the pin-by-pin calculations are assessed with the VERA and APR1400 benchmark problems. It is demonstrated that pin-by-pin 2D/1D alternating calculations within the two-level 3D CMFD framework yield accurate solutions in about 30 s for the typical commercial core problems, on a parallel platform employing 32 threads.

• Advances in concrete construction
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• 제7권1호
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• pp.11-22
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• 2019

A comprehensive assessing approach for durability of reinforced concrete structures dealing with the corrosion process of rebar subjected to the attack of aggressive agent from environment was proposed in this paper. Corrosion of rebar was suggested in the form of combination of global corrosion and pitting. Firstly, for the purposed of considering the influence of rebar's radius, a type of Plane Corrosion Model (PCM) based on uniform corrosion of rebar was introduced. By means of FE simulation approach, global corrosion process of rebar regarding PCM and LCM (Linear Corrosion Model) was regressed and compared according to the data from Laboratoire $Mat{\acute{e}}riaux$ et $Durabilit{\acute{e}}$ des Constructions (LMDC). Secondly, pitting factor model of rebar in general descend law with corrosion degree was introduced in terms of existing experimental data. Finally, with the comprehensive numerical simulation, the durability of an existing arch bridge was studied in depth in deterministic way, including diffusion process and sectional strength of typical cross section of arch, crossbeam and deck slab. Evolution of structural capacity considering life-cycle rehabilitation strategy indicated the degradation law of durability of reinforced arch bridges.

• Nuclear Engineering and Technology
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• 제51권7호
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• pp.1721-1728
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• 2019

The advanced node core code CORCA-3D is one of the independent developed codes of NPIC for the nuclear reactor core design. CORCA-3D code can calculate the few-group cross section, solve the 3D diffusion equations, consider the thermal-hydraulic feedback, reconstruct the pin-by-pin power. It has lots of functions such as changing core status calculation, critical searching, control rod value calculation, coefficient calculation and so on. The main theory and functions of CORCA-3D code are introduced and validated with a lot of reactor measured data and the SCIENCE system. Now, CORCA-3D code has been applied in ACP type reactor nuclear cores design.

• 한국음향학회지
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• 제21권3호
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• pp.245-255
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• 2002

5.1채널 스피커 시스템을 이용하여 음향을 재현시 나타나는 현상인 크로스토크를 제거하여 청취자에게 보다 입체적인 음을 재현하는 방법에 관한 것이다. 본 논문에서는 크로스토크를 제거하기 위하여 자유음장 모델을 사용하였다. 이것을 구현함에 있어 주파수 영역에서 심리음향에 기초한 바크 스케일 (bark scale)을 사용한 복소이득 보상을 실시하였으며, 서라운드 채널에 관해서는 밴드패스 필터를 추가하여 주파수 제한적인 음질 보상을 실시하였다. 정면 채널과 서라운드채널의 음원을 제작하여 기존의 2채널 및 5.1 시스템에서 제시하는 음원과 비교하여 객관적인 음질 평가 및 청취자를 대상으로 한 주관 평가를 실시하였다. 제안된 방법에 따라 측정한 결과에 따르면 ±30°의 정면 스피커를 배치한 돌비 표준 스피커 배치에서 38 dB이상의 분리도를 얻었으며 확산감에 대해 전문가를 대상으로 한 주관 평가는 5점 평가를 기준으로 0.4점이 향상되었다.

• 재무관리연구
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• 제25권1호
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• pp.23-49
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• 2008

본 논문의 목적은 과거의 산업 포트폴리오 수익률이 확률추세로부터 어떻게 전체 주식시장과 두 가지 거시경제 변수인 경기동행지수와 산업생산 등을 예측할 수 있는 지를 알아보는 데에 있다. 이를 위하여 본 연구에서는 연구모형을 설정한 후 세 가지 검정절차를 제시하고 이를 실증적으로 분석하였다. 당월의 전체 주식시장 수익률은 과거의 시차를 지닌 특정 산업부문 포트폴리오 수익률에 대하여 양(+)의 상관관계를 유지하고 있다는 '예측 1'과 전체 주식시장의 수익률은 특정산업부문의 수익률에 대하여 선행성을 지닐 수 없다는 '예측 2'에 대한 검정 결과는 '예측 1'과 '예측 2'가 지지되고 있음을 파악할 수 있었다. 그리고 산업별 포트폴리오 수익률과 거시경제변수 간의 높은 상관관계를 토대로 하여 전체 주식시장 수익률 예측을 가능하게 하는 업종 정보의 점진적 확산 현상이 발생하게 되는가를 검토하기 위하여 각 산업들의 포트폴리오 수익률과 전체 주식시장 수익률이 VAR 모형을 토대로 볼 경우 Granger 인과관계를 갖고 있는 지를 분석하였다. 분석결과 21개 업종은 각 산업별 포트폴리오 수익률이 전체 주식시장 수익률을 5% 수준에서 통계적으로 유의한 영향을 주고 있음을 알 수 있었다. 이들 21개의 산업별 포트폴리오 수익률은 경제적으로도 중요한 의미를 지니고 있어 산업제품의 가격 상승과 하락이 경제에 미치는 영향을 파악할 수 있다. 특히 음료 업종에서 전체 주식시장 수익률과 상호간의 인과성을 나타내었으며, 인터넷과 화장품 업종에서는 전체 주식시장 수익률이 이들 업종에 대하여 일방적인 영향을 보이고 있음을 알 수 있었다.