• 한국가족관계학회지
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• 제23권2호
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• pp.67-87
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• 2018

Objectives: The purpose of this study is to critically review the recent discourse on single-person households (SPH) that appeared in Korean newspapers. Specifically, we analyzed articles in five major daily newspapers, which are representative of the media in Korean society, and examined the types of titles, subjects, and contents of articles in which SPH were mentioned. Method: For this purpose, 538 articles on SPH or "living alone" that appeared in the five major Korean newspapers during 2011-2017 were analyzed using content analysis methods. Results: Our analysis revealed eight major topics(living arrangement and household characteristics; financial instruments; food, clothing, and housing culture; policy; welfare; relationships; safety; values and attitudes). The results show that there is a surge of articles portraying neutral images of SPH in Korean newspapers, thereby emphasizing the recent growth in the number of SPH and the information relating to this population group. Although negative images of SPH continue to exist in the discourse, in recent times we found these attitudes to have become less prevalent compared to neutral images or even positive discourse. We also found that the discourse on these topics and arguments can be divided into four themes-the diversity of SPHs, the solo economy for single households, safety issues, and social relationships. Conclusions: Theoretical and policy implications on family studies relating to SPH are discussed.

• 천문학회보
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• 제44권2호
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• pp.48.4-48.4
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• 2019

We studied the metal-distribution of isolated Milky-way mass galaxy using various hydrodynamic solvers and investigated the difference of the result between AMR and SPH codes. In particle-based codes, physical quantities like mass or metallicity defined in each particle are conserved unless being injected explicitly by the effect of the supernova, whereas in the Eulerian codes the diffusion is simply accomplished by hydro-equation. Therefore, without including explicit physics of diffusion on the SPH- codes, the metal mixing in the galaxy or CGM only can be accomplished by the direct motion of the particles, however, the standard-SPH codes depress the instability of the turbulent fluid mixing. In this work, we simulated under common initial conditions, common gas-physics like cooling-heating models, and star-formation feedback using ENZO(AMR) GIZMO and GADGET-2 codes. We additionally included a metal-diffusion algorithm on the SPH-codes, which follows the subgrid-turbulent mixing model investigated by Shen et al. (2010) and compared the effect of the metal-outflow on the halo region of the galaxy in different hydro-solvers. We also found that for the implementation of the diffusion scheme in the SPH-codes, the existence of a sufficient number of the gas-particles, which is the carrier of the metals, is necessary. So we tested a new initial condition for proper implementation of the diffusion scheme on the SPH simulations. By comparing the metal-contamination of the circumgalactic medium with different hydrodynamics models, we quantify the diffusion strength of AMR codes using diffusion parameterization of the SPH codes and also suggest the calibration solutions in the different behavior of codes in metal-outflow.

• 천문학회보
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• 제17권
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• pp.17.1-17.1
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• 1992

• 대한토목학회논문집
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• 제28권3B호
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• pp.261-270
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• 2008

최근 진행된 정밀 수치해석 기법의 비약적인 발전에도 불구하고 SPH 등과 같은 고급수치기법의 수자원 분야에서의 활용은 그리 활발해 보이지 않는다. 대규모 수계를 대상으로 한 flood routing의 경우 비선형 천수방정식으로 대표되는 depth averaged approach가 효과적이나 정밀한 범람고 예단에는 오류가 야기될 수 있다. 본 고에서는 SPH 수치해석 기법의 수자원 분야로의 적용가능성을 모색하기 위해 비교적 수리모형실험자료가 풍부한 제체붕괴로 인한 수리현상을 수치모의하였다 (Martin과 Moyce, 1952). 보다 완벽한 검증을 위해 수로에 장애물이 거치된 경우 (Koshizuka 등, 1995), 수문의 갑작스런 개방으로 인한 수로에서의 수리현상 (Janosi 등, 2004) 등 점진적으로 난이도를 높여 수치모의를 수행하였다. 동수역학 모형 방정식으로는 Navier-Stokes 방정식, 동수역학의 수치적 적분에는 Smoothed Particle Hydrodynamics 기법을 채택하였다. 모의 결과 본 고에서의 수치모의가 기존에 선호되던 VOF, MAC의 수치 기법에 비해 우월한 결과를 보였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권4호
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• pp.390-403
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• 2017

Smoothed Particle Hydrodynamics (SPH) method has a good adaptability for the simulation of free surface flow problems. There are two forms of SPH. One is weak compressible SPH and the other one is incompressible SPH (ISPH). Compared with the former one, ISPH method performs better in many cases. ISPH based on Rankine source solution can perform better than traditional ISPH, as it can use larger stepping length by avoiding the second order derivative in pressure Poisson equation. However, ISPH_R method needs to solve the sparse linear matrix for pressure Poisson equation, which is one of the most expensive parts during one time stepping calculation. Iterative methods are normally used for solving Poisson equation with large particle numbers. However, there are many iterative methods available and the question for using which one is still open. In this paper, three iterative methods, CGS, Bi-CGstab and GMRES are compared, which are suitable and typical for large unsymmetrical sparse matrix solutions. According to the numerical tests on different cases, still water test, dam breaking, violent tank sloshing, solitary wave slamming, the GMRES method is more efficient than CGS and Bi-CGstab for ISPH method.

• 한국게임학회 논문지
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• 제11권6호
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• pp.193-199
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• 2011

고 밀집 상태의 군중 시뮬레이션은 객체 수에 따라 복잡도와 제작 비용이 크게 증가함으로 사실적인 움직임을 표현하는데 어려움이 있다. 본 논문에서는 고 밀집 군중 시뮬레이션 시 사실적인 움직임을 표현하기 위해 Smoothed Particle Hydrodynamics (SPH) 기법을 도입하였다. 본 연구에서는 유체 시뮬레이션에 사용되는 SPH 모델을 응용하여 객체 움직임에 필요한 회피력, 거리 유지력, 그룹 응집력을 새로이 제안하였다. 제안된 객체 운동 수식은 고 밀집 상태에서 유체와 같이 자연스런 객체 움직임을 표현하는데 효과적이다. 실험 결과, 본 시스템은 밀집도 높은 군중 시뮬레이션을 실시간으로 생성 가능함을 보였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권3호
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• pp.638-651
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• 2014

Main aim of this paper is to find the best combination of numerical schemes for 2-D SPH simulation of wedge water entry. Diffusion term is considered as laminar, turbulent, and artificial viscosity. Density filter that seriously affects the pressure distribution is investigated by adopting no filter, first order filter, and second order filter. Validation of the results indicates that turbulent model and first order density filter can lead to more reasonable solutions. This simulation was then conducted for wedge water entry with wide range of deadrise angles including 10 degrees, 20 degrees, 30 degrees, 45 degrees, 60 degrees and 81 degrees, with extreme deadrise angles of 10 degrees, 60 degrees and 81 degrees being considered. Comparison of SPH results with BEM solutions has displayed favorable agreement. In two particular cases where experimental data are available, the SPH results are shown to be closer to the experiments than BEM solution. While, accuracy of the obtained results for moderate deadrise angles is desirable, numerical findings for very small or very large deadrise angles are also very reasonable.

• Nuclear Engineering and Technology
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• 제53권3호
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• pp.752-762
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• 2021

The Smoothed Particle Hydrodynamics is one of the most widely used mesh-free numerical method for thermo-fluid dynamics. Due to its Lagrangian nature and simplicity, it is recently gaining popularity in simulating complex physics with large deformations. In this study, the 3D single/two-phase numerical simulations are performed on the Liquid Metal Reactor (LMR) centralized sloshing benchmark experiment using the SPH parallelized using a GPU. In order to capture multi-phase flows with a large density ratio more effectively, the original SPH density and continuity equations are re-formulated in terms of the normalized-density. Based upon this approach, maximum sloshing height and arrival time in various experimental cases are calculated by using both single-phase and multi-phase SPH framework and the results are compared with the benchmark results. Overall, the results of SPH simulations show excellent agreement with all the benchmark experiments both in qualitative and quantitative manners. According to the sensitivity study of the particle-size, the prediction accuracy is gradually increasing with decreasing the particle-size leading to a higher resolution. In addition, it is found that the multi-phase SPH model considering both liquid and air provides a better prediction on the experimental results and the reality.

• 천문학회지
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• 제34권4호
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• pp.261-263
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• 2001

Numerical simulations based on the smoothed particle hydrodynamics (SPH) is performed to investigate the dynamical properties of barred galaxies that have nuclear rings. The nuclear ring morphology depends on the relative strength of bar potentials. Nuclear rings form between the two ILRs and align perpendicular to the bars unless the bar potentials are strong enough to allow the x1 orbits near the ILRs. Shock dissipation plays a critical role in the formation of nuclear rings.

• 천문학회지
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• 제27권1호
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• pp.13-29
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• 1994

We have constructed a 3-dim hydrodynamics code called BTSPH. The fluid dynamics part of the code is based on the smoothed particle hydrodynamics (SPH), and for its Poisson solver the binary tree (BT) scheme is employed. We let the smoothing length in the SPH algorithm vary with space and time, so that resolution of the calculation is considerably enhanced over the version of SPH with fixed smoothing length. The binary tree scheme calculates the gravitational force at a point by collecting the monopole forces from neighboring particles and the multipole forces from aggregates of distant particles. The BTSPH is free from geometric constraints, does not rely on grids, and needs arrays of moderate size. With the code we have run the following set of test calculations: one-dim shock tube, adiabatic collapse of an isothermal cloud, small oscillation of an equilibrium polytrope of index 3/2, and tidal encounter of the polytrope and a point mass perturber. Results of the tests confirmed the code performance.