• 천문학회보
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• 제44권2호
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• pp.47.2-47.2
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• 2019

Observations indicate that turbulence in molecular clouds of the interstellar medium (ISM) is highly supersonic (M >> 1) and strongly magnetized (β ≈ 0.1), while in the intracluster medium (ICM) it is subsonic (M <~1) and weakly magnetized (β ≈ 100). Here, M is the turbulent Mach number and β is the ratio of the gas to magnetic pressures. Although magnetohydrodynamic (MHD) turbulence in such environments has been previously studied through numerical simulations, some of its properties as well as its consequences are not yet fully described. In this talk, we report a study of MHD turbulence in molecular clouds and the ICM using a newly developed code based the high-order accurate, WENO (Weighted Essentially Non-Oscillatory) scheme. The simulation results using the WENO code are generally in agreement with those presented in the previous studies with, for instance, a TVD code (Porter et al. 2015 &, Park & Ryu 2019), but reveal more detailed structures on small scales. We here present and compare the properties of simulated turbulences with WENO and TVD codes, such as the spatial distribution of density, the density probability distribution functions, and the power spectra of kinetic and magnetic energies. We also describe the populations of MHD shocks and the energy dissipation at the shocks. Finally, we discuss the implications of this study on star formation processes in the ISM and shock dissipation in the ICM.

• 대한안전경영과학회지
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• 제12권4호
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• pp.161-168
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• 2010

RFID has been used as an identification tool substituting bar-code and its application areas are increasing due to its suitability in ubiquitous environment. This paper reviews RFID applications in some areas in which a serious amount of applications were reported such as material handling, physical distribution, and supply chain management of perishable products. The authors try to suggest research issues along with the limitations of RFID.

• 콘크리트학회지
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• 제10권4호
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• pp.135-143
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• 1998

현행 AASHTO 및 AASHTO LRFD 설계기준에는 차선하중에 대한 윤하중분포폭을 차륜하중에 적용되는 윤하중분포폭의 2배를 적용하도록 규정하고 있다. 이에 반해 국내 도로교 표준시방서에는 차선하중에 대한 윤하중분포폭의 규정은 없는 실정이다. 본 연구에서는 연속 철근콘크리트 슬래브 교량에 대한 윤하중분포폭에 관한 연구를 수행하였다. 연속슬래브 교량의 윤하중분포폭에 영향을 미치는 인자들로는 지간길이, 교량폭, 단부보 및 지점조건이 있다. 이들 각 인자들에 대한 유한 요소 모델의 구성 및 해석을 통하여 연속 철근콘크리트 슬래브 교량의 합리적인 윤하중분포폭의 식을 제안하였다. 본 연구에서 제안된 윤하중분포폭의 식은 현행 도로교 표준시방서에 제시되어 있지 않은 철근콘크리트 연속 슬래브 교량의 보다 정확한 설계 및 합리적인 내하력 산정시 매우 효율적으로 사용될 것으로 사료된다.

• 한국정밀공학회지
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• 제16권1호통권94호
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• pp.238-245
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• 1999

For the optimal design of plasma facing components of a fusion reactor, thorough understanding of thermal behavior of high heat. nux components are required. The purpose of this research is to investigate the characteristics of heat flow and thermal stress in divertors which are exposed to high heat load varing with time and space-Numerical simulations of heat now and thermal stress for three types of diverter are performed using finite volume method and finite element method. Respectly, commercial FLUENT code are used in the heat flow simulation, and maximum surface temperature, temperature distribution and cooling rate are calculated. Commercial ABQUS code are used for calculating temperature distribution. thermal stress, strain and displacement. Through this computer simulation. design data for cooling system and Structural provided.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.205-210
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• 2002

This article presents an integrated modeling approach for coupled analysis of heat transfer and microstructure evolution in welding carbon steel. The modeling procedure utilizes commercial [mite element code ABAQUS/Standard as the platform for solving the equation of heat conduction. User subroutines that implement computational thermodynamics and kinetics models are integrated with the FEA code to compute the transient microstructure evolution. In this study, the integrated models are applied to simulate the hot-tap repair welding of carbon steel pipeline. Microstructural components are treated as user output variables. Based on the predicted microstructure and cooling rates, hardness distributions in the welds were also predicted. The predicted microstructure and hardness distribution were found in good agreement with metallographic examinations and hardness measurements. This study demonstrates the applicability of computational models for the development of welding procedure for in-service pipeline repair.

• Nuclear Engineering and Technology
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• 제52권7호
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• pp.1347-1354
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• 2020

To improve the efficiency of MC criticality calculation, an acceleration method of fission source convergence which gives an improved initial fission source is proposed. In this method, the MC global homogenization is carried out to obtain the macroscopic cross section of each material mesh, and then the nonlinear iterative solution of the SP3 equations is used to determine the fission source distribution. The calculated fission source is very close to the real fission source, which describes its space and energy distribution. This method is an automatic computation process and is tested by the C5G7 benchmark, the results show that this acceleration method is helpful to reduce the inactive cycles and overall running time.

• 천문학회보
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• 제39권2호
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• pp.45.1-45.1
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• 2014

structure of matters of Lambda cold dark matter (CDM) cosmology on detailed numerical simulations. To accomplish our research goal, we have added the following baryonic physics on the existing cosmological hydrodynamic code, Gadget-2: 1) radiative heating and cooling, 2) reionization of the Universe and UV shielding, 3) star formation, 4) energy and metallicity feedback by supernova. In addition, we included cluster formation to distinguish clustered star formation inside the very high density gas clumps from the field star formation. Our simulations cover a cubic box of a side length 4Mpc/h with 130 million particles. The mass of each particles is $3.4{\times}104Msun$, thus the GCs can be resolved with more than hundreds particles. We discuss various properties of the GCs such as mass function, specific frequency, baryon-to-dark matter ratio, metallicity, spatial distribution, and orbit eccentricity distribution as functions of redshift. We also discuss how the formation and evolution of the GCs are affected by UV shielding.

• 대한전기학회논문지:시스템및제어부문D
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• 제55권8호
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• pp.397-400
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• 2006

An optimized iron core structure of stimulating coil are presented in order to control the induced electric field distribution using the Continuum Design Sensitivity Analysis (CDSA) combined with a commercially available generalized finite element code (OPERA). The results show that a Figure-Of-Eight (FOE) coil as well as a circular coil with the proposed iron core structure can increase induced electric field intensity by more than two times and make better field localization, compared with those of existing stimulation coil with a air core. After considering manufacturing constraints, a practical iron core structure based on the proposed optimized one is proposed and its performance is analyzed.

• Nuclear Engineering and Technology
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• 제52권11호
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• pp.2415-2421
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• 2020

The axial heterogeneous void distribution in a fuel channel is a relevant and important issue during nuclear reactor analysis for LWR, especially for boiling water channel-type reactors. Variation of the coolant density in fuel channel has an effect on the neutron spectrum that will in turn have an impact on the values of absolute reactivity, the void reactivity coefficient, and the fuel isotopic compositions during irradiation. This effect is referring to as the history effect in light water reactor calculations. As the void reactivity effect is positive in RBMK type reactors, the underestimation of water density heterogeneity in 3D reactor core numerical calculations could cause an uncertainty during assessment of safe operation of nuclear reactor. Thus, this issue is analysed with different cross-section libraries which were generated with WIMS8 code at different reference water densities. The libraries were applied in single fuel model of the nodal code of QUABOX-CUBBOX/HYCA. The thermohydraulic part of HYCA allowed to simulate axial water distribution along fuel assembly model and to estimate water density history effect for RBMK type fuel.

• Journal of Mechanical Science and Technology
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• 제18권7호
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• pp.1177-1186
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• 2004

In this paper, the spray atomization characteristics of a gasoline direct-injection injector were investigated experimentally and numerically. To visualize the developing spray process, a laser sheet method with a Nd :YAG laser was utilized. The microscopic atomization characteristics such as the droplet size and velocity distribution were also obtained by using a phase Doppler particle analyzer system at the 5 ㎫ of injection pressure. With the experiments, the calculations of spray atomization were conducted by using the KIVA code with the LISA-DDB breakup model. Based on the agreement with the experimental results, the prediction accuracy of LISA-DDB breakup model was investigated in terms of the spray shapes, spray tip penetration, SMD distribution, and axial mean velocity. The results of this study provides the macroscopic and microscopic characteristics of the spray atomization, and prediction accuracy of the LISA-DDB model.