• Proceedings of the Korea Water Resources Association Conference
• /
• 2007.05a
• /
• pp.1219-1223
• /
• 2007

수온은 수계에서 가장 중요한 물리적 특성 중 하나로서, 생물 군집, 특히 어류와 무척추 동물에 관련된 많은 수질 인자에 영향을 미친다. 하천의 생태학적 모습을 개선하기 위한 하천 복원 사업 수행에 있어서, 서식처 및 산란처 조건으로서의 수온 조사 및 모델링의 필요성이 점차 증가하고 있는 상황이다. 본 연구는 낙동강의 중상류에 위치한 반변천 합류부에 평면 이차원 비정상 수치모형인 KU-RLMS 모형을 적용하여 수온의 변화 특성을 규명할 목적으로 수행하였다. KU-RLMS 모형은 하천 및 저수지의 국부적인 수리, 수질, 유사이동 해석을 위해 개발된 평면 이차원 비정상 수치모형이다. 직사각형 격자를 사용하는 유한차분법의 단점을 보완하기 위해, 수심적분된 2차원 연속방정식, 운동량방정식, 이송확산방정식을 불규칙한 경계를 현실적으로 모사할 수 있는 직교곡선 좌표계로 변환한 방정식을 사용한다. 이 모형은 흐름, 농도, 지형변화를 조합하여 계산할 수 있는 모형으로서 점착성 및 비점착성 유사의 이동, 보존성 및 비보존성 오염물질의 이동, 수온 변화를 모의할 수 있다. 수치모형 적용을 위한 현황분석으로 안동 및 임하 조정지댐의 방류량, 안동 수위관측소의 수위, 법흥교 및 포진교 지점의 수온 자료를 분석하였다. 이송확산모형의 보정을 위해, 안동대교 지점의 수온 횡분포 측정자료를 사용하여 확산계수에 대한 매개변수 추정 및 검증을 수행하였다. 또한, 안동조정지댐과 임하조정지댐의 방류량 및 방류수온을 고려하여 수치모의조건을 결정하였으며, 각 조건에 대한 수온 변화 특성을 분석하였다.

• Journal of the Society of Naval Architects of Korea
• /
• v.51 no.5
• /
• pp.409-418
• /
• 2014

Simulation of flow past a complex marine structure requires a fine resolution in the vicinity of the structure, whereas a coarse resolution is enough far away from it. Therefore, a lot of grid cells may be wasted, when a simple Cartesian grid system is used for an Immersed Boundary Method (IBM). To alleviate this problems while maintaining the Cartesian frame work, we adopted an Adaptive Mesh Refinement (AMR) scheme where the grid system dynamically and locally refines as needed. In this study, We implemented a moving IBM and an AMR technique in our basic 3D incompressible Navier-Stokes solver. A Volume Of Fluid (VOF) method was used to effectively treat the free surface, and a recently developed Lagrangian Dynamic Subgrid-scale Model (LDSM) was incorporated in the code for accurate turbulence modeling. To capture vortex induced vibration accurately, the equation for the structure movement and the governing equations for fluid flow were solved at the same time implicitly. Also, We have developed an interface by using AutoLISP, which can properly distribute marker particles for IBM, compute the geometrical information of the object, and transfer it to the solver for the main simulation. To verify our numerical methodology, our results were compared with other authors' numerical and experimental results for the benchmark problems, revealing excellent agreement. Using the verified code, we investigated the following cases. (1) simulating flow around a floating sphere. (2) simulating flow past a marine structure.

• Journal of the Korean Institute of Telematics and Electronics S
• /
• v.36S no.9
• /
• pp.1-8
• /
• 1999

In this paper, we propose and analyze a concatenated coding scheme for DS/CDMA systems in asynchronous channels. In the concatenated coding, bandwidth efficient $2^{2L-2}$-state ${\frac{L}{L+1}}$-rate 2-MTCM with biorthogonal signal constellation is used for the inner code, and $(2^{L-1},\;{\lceil}\frac{2^{L-1}}{L/2}{\rceil})$ RS code is use for the outer code. It is shown that we can get considerable performance gain over the uncoded system without sacrificing the data transmission rate. The proposed system can be used as a coding scheme for reliable and high speed integrated information services of mobile communication systems.

• Journal of Ocean Engineering and Technology
• /
• v.29 no.2
• /
• pp.154-162
• /
• 2015

In this study, experimental and numerical methods were applied to observe sloshing impact phenomena. A two-dimensional rectangular tank filled with water and air was considered with a specific excitation condition that induced a hydrodynamic impact without an air pocket at the top corner of the tank. High-speed cameras and a pressure measurement system were synchronized, and a particle image velocimetry (PIV) technique was applied to measure the velocity field and corresponding pressure. The experimental condition was implemented in a numerical computation to solve incompressible two-phase flows using a Cartesian-grid method. The discretized solution was obtained using the finite difference and constraint-interpolation-profile (CIP) methods, which adopt a fractional step scheme for coupling the pressure and velocity. The tangent of the hyperbola for interface capturing (THINC) scheme was used with the weighed line interface calculation (WLIC) method to capture the interface between the air and water. The calculated impact pressures and velocity fields were compared with experimental data, and the relationship between the local velocity and pressure was investigated based on the computational results.

• The KIPS Transactions:PartB
• /
• v.12B no.4 s.100
• /
• pp.379-386
• /
• 2005

This paper provides a rigorous theory for analysis of quantization effects and optimum filter bank design in quantized multidimensional subband filter banks. Even though subband filter design has been a hot topic for last decades, a few results have been reported on the subband filter with a quantizer. Each pdf-optimized quantizer is modeled by a nonlinear gain-plus-additive uncorrelated noise and embedded into the subband structure. Using polyphase decomposition of the analysis/synthesis filter banks, we derive the exact expression for the output mean square quantization error. Based on the minimization of the output mean square error, the technique for optimal filter design methodology is developed. Numerical design examples for optimum nonseparable paraunitary and biorthogonal filter banks are presented with a quincunx subsampling lattice. Through the simulation, $10\~20\;\%$ decreases in MSE have been observed compared with subband filter with no quantizers especially for low bit rate cases.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2005.10a
• /
• pp.289-295
• /
• 2005

LMTT (Linear Motor-based Transfer Techn-ology) is a horizontal transfer system for the yard automation This system is based on PMLSM (Permanent Magnetic Linear Synchronous Motor) toot consists of stator modules on the rail and shuttle car. In this research, the kriging interpolation method with sequential sampling find the optimum design of mover in LMTT. The design variables are considered as the transverse, longitudinal and wheel beam's thicknesses. The objective function is set up as weight, while the constant function are set up as the stresses generated by four loading conditions. The objective function is set up as weight. The optimum results obtained by the suggested method are compared with those by the GENESIS.

• 한국해양학회지
• /
• v.30 no.6
• /
• pp.565-583
• /
• 1995

We have used a nonlinear quasi-geostrophic model to study effects of lateral friction and bottom topography on the motion of warm eddies. The two empirical orthogonal functions of the stream function, accounting for the vertical structure, represent the barotropic and first baroclinic dynamic modes. This model is integrated 360 days on a 1000 km ${\times}$ 1000 km domain with a resolution of 10 km ${\times}$ 10 km including both the thermocline and idealized topography of the East Sea. Prescribed inflow through the Korea Strait is compensated by outflow through the Tsugaru Strait. The balance between the nonlinear advection term and the planetary ${\beta}$-effect tends to make northward movement of warm eddy over a flat bottom. The motion of a warm eddy over a sloping topography can be dominated by the nonlinear advection, while nonlinearity plays a secondary role over a flat topography. For eddies dispersing over topography, the nonlinear tendency is a function of time. For a strong warm eddy, northward propagation can occur. For intermediate strength of eddies one might expect a balance between the nonlinear term and the topographic ${\beta}$-effect. As nonlinearity decreases with eddy dispersion, southward motion along the slope may occur by such as a topographic Rossby wave. Our numerical simulations have confirmed the importance of lateral friction on eddy motions, in such a way that the northward penetration of the warm eddy increases drastically by the decrease of the lateral friction. The northward motion of warm eddy can be prevented by reducing the Reynolds number sufficiently. We have also demonstrated the crucial role of topographic effects in the eddy motion process.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2007.05a
• /
• pp.1214-1218
• /
• 2007

댐 하류로 탁수를 선택적으로 배제하기 위해서는 방류 탁수가 하류에 미치는 영향을 정확히 예측할 수 있는 하천 탁도 예측 및 관리시스템 구축이 필요하다. 낙동강과 반변천의 합류부에서의 이차원적인 혼합에 관한 수치해석 결과는 완전혼합을 가정하는 일차원 수질모델링의 초기 입력자료에 사용됨으로써 낙동강 본류 전체구간의 탁도 모의결과의 정확성을 높이는 데 사용될 수 있다. 본 연구는 낙동강의 중상류에 위치한 반변천 합류부에 평면 이차원 비정상 수치모형인 KU-RLMS 모형을 적용하여 탁도 변화 특성을 규명할 목적으로 수행하였다. KU-RLMS 모형은 하천 및 저수지의 국부적인 수리, 수질, 유사이동 해석을 위해 개발된 평면 이차원 비정상 수치모형이다. 직사각형 격자를 사용하는 유한차분법의 단점을 보완하기 위해, 수심적분된 2차원 연속방정식, 운동량방정식, 이송확산방정식을 불규칙한 경계를 현실적으로 모사할 수 있는 직교곡선 좌표계로 변환한 방정식을 사용한다. 이 모형은 흐름, 농도, 지형변화를 조합하여 계산할 수 있는 모형으로서 점착성 및 비점착성 유사의 이동을 모의할 수 있다. 수치모형 적용을 위한 현황분석으로 안동 및 임하 조정지댐의 방류량, 안동 수위관측소의 수위, 법흥교 및 포진교 지점의 탁도 자료를 분석하였다. 이송확산모형의 보정을 위해, 안동대교 지점의 탁도 횡분포 측정 자료를 사용하여 확산계수에 대한 매개변수 추정 및 검증을 수행하였다. 또한, 안동조정지댐과 임하조정지댐의 방류량 및 방류탁도을 고려하여 수치모의조건을 결정하였으며, 각 조건에 대한 탁도 변화 특성을 분석하였다.된 주변국이 될 수밖에 없을 것이다. 21세기 문화산업에서 우리가 판단하게 될 디자인의 가치는 계몽의 원리에 대한 '역사성'과 '현재성'의 변증법에 달려있는 것이며, 새로운 철학, 새로운 문명, 새로운 세계를 열어가는 것이다.r$ (地理志)에는 추현리와 이미 외리를 언급하면서 상주의 자기제작의 위상을 짐작하는 기록이 언급되면서 전국의 상품의 절반을 담당하고 있었음을 알 수 있었다. $\ulcorner$경상도지리지$\lrcorner$(慶尙道地理志)에는 상주가 8곳으로 1/3의 자기 생산을 담당하고 있었다. $\ulcorner$경상도지리지$\lrcorner$(慶尙道地理志)에는 $\ulcorner$세종실록$\lrcorner$(世宗實錄) $\ulcorner$지리지$\lrcorner$(地理志)와 동년대에 동일한 목적으로 찬술되었음을 알 수 있다. $\ulcorner$경상도실록지리지$\lrcorner$(慶尙道實錄地理志)에는 $\ulcorner$세종실록$\lrcorner$(世宗實錄) $\ulcorner$지리지$\lrcorner$(地理志)와의 비교를 해보면 상 중 하품의 통합 9개소가 삭제되어 있고, $\ulcorner$동국여지승람$\lrcorner$(東國與地勝覽) 에서는 자기소와 도기

• Korean Journal of Remote Sensing
• /
• v.11 no.3
• /
• pp.1-21
• /
• 1995

The characteristics of the Asian summer monsoon have been investigated for the periods of 1993/1994, the contrasting years in a view of the summer monsoon precipitation. In order to investigate the monsoon features over the eastern Asian monsoon region, the cloudiness(using the extensive data derived by the geostationary meteorological satellite), the condition of underlying surface including sea-surface temperature, and the summer rainfall are analyzed and some comparisons with 1993 and 1994 are also made and the characteristic differences are discussed. An analysis of the 2-degree latitude-longitude gridded 5-day mean high cloud amount data shows the detailed movement and persistence of the convective activities. In order to describe the spatial and temporal structures of the intraseasonal oscillation for the movement and evolution of the monsoon cloud, the extended empirical orthogonal fnction analysis with the twenty-day window size is used for the each year. Also, in order to find out the periodicity of the equatorial convective cluster, Fourier harmonic analysis is applied to the each year. The most prevailing intraseasonal oscillations of high cloud amount are 61 day mode and 15day mode in the equatorial and the subtropical oceans. However it was found that the most prevailing modes over the equatorial western Pacific and Indian Ocean were different for each year, hence raising the possibillity that the contrasting monsoon presipitation may be more fundamentally related to the interaction of intraseasonal oscillations and seasonal variation of convective activities over the lower latitude ocean.

• Clean Technology
• /
• v.28 no.3
• /
• pp.249-257
• /
• 2022

The adsorption equilibria of nitrogen on a region of nanoporous carbonaceous adsorbent with local molecular orientation (LMO) were calculated by grand canonical Monte Carlo simulation at 77.16 K. Regions of LMO of identical size were arranged on a regular lattice with uniform spacing. Microporosity was predominately introduced to the model by removing successive out-of-plane domains from the regions of LMO and tilting pores were generated by tilting the basic structure units. This pore structure is a more realistic model than slit-shaped pores for studying adsorption in nanoporous carbon adsorbents. Their porosities, surface areas, and pore size distributions according to constrained nonlinear optimization were also reported. The adsorption in slit shaped pores was also reported for reference. In the slit shaped pores, a clear hysteresis loop was observed in pores of greater than 5 times the nitrogen molecule size, and in capillary condensation and reverse condensation, evaporation occurred immediately at one pressure. In the LMO pore model, three series of local condensations at the basal slip plane, armchair slip plane and interconnected channel were observed during adsorption at pore sizes greater than about 6 times the nitrogen molecular size. In the hysteresis loop, on the other hand, evaporation occurred at one or two pressures during desorption.