• 한국연소학회지
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• 제9권4호
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• pp.9-21
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• 2004

Stability of laminar premixed planar flames inclined in the gravitational field is asymptotically examined. The flame structure is resolved by a large activation energy asymptotics and a long wave approximation. The coupling between hydrodynamics and diffusion processes is included and near-unity Lewis number is assumed. The results show that as the flame is more inclined from the horizontal plane it becomes more unstable due to not only the decrease of stabilizing effect of gravity but also the increase of destabilizing effect of rotational flow. The obtained dispersion relation involves the Prandtl number and shows the destabilizing effect of viscosity. The analysis predicts that the phase velocity of unstable flame wave depends on not only the flame angle but also the Lewis number. For relatively short wave disturbances, still much larger than flame thickness, the most unstable wavelength is nearly independent on the flame angle and the flame can be stabilized by gravity and diffusion mechanism.

• 한국해양공학회지
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• 제10권3호
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• pp.50-61
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• 1996

The breaking phenomenon of regular periodic waves generated by a numerical wave maker is simulated by finite-difference method which can cope with strong interface motions. The air and water flows are simultaneously solved in the time-marching solution procedure for the Navier-Stokes equation. A density-function technique is devised for the implemenation of the interface conditions. The accuracy is examined and applied to the simulation of two-dimensional breaking phenomena of periodic gravity waves.

• 한국해양공학회지
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• 제10권3호
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• pp.62-73
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• 1996

Numerical simulation is made of the three-dimensional wave breaking motion about a part of a floating offshore structure containing a circular cylinder mounted vertically onto a lower hull in regular periodic gravity wave generated by a numerical wave maker. TUMMAC-VIII finite-difference method is newly developed for such a problem. By use of density-function technique the three-dimensional wave breaking motion is approximately implenented in the framework of rectangular grid system. A porosity technique is devised for the implementation of the no-slip bydy boundary conditions. The generation of breaking waves by the interaction of incident waves with the structure is well simulated and interesting features of breaking waves are revealed with containing degree of quantitative and qualitative accuracy.

• 한국주조공학회지
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• 제9권1호
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• pp.39-48
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• 1989

A basic three dimensional thermal model has been developed to simulate the solidification sequence for gravity die casting process. The finite difference method was used to analyze the solidification process during all the casting cycles. The prediction of die temperature in the quasi-steady state was analyzed by the boundary element method. The influence of die cooling on the heat flow in the cast/mold system was also investigated. Predictions of the computer simulation on temperature profiles and location of shrinkage defects were in good agreement with those observed in experimental die castings. Models of computer simulation which is developed by this work can be useful for the design and process control of die casting.

• 한국연소학회:학술대회논문집
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• 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
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• pp.177-184
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• 2003

Stabilization mechanism of lifted flame in the near field of coflow jets has been investigated experimentally and numerically for methane fuel diluted with nitrogen. Lifted flames were observed only in the near field of coflow jets until blowout occurred in the normal gravity condition. To elucidate the stabilization mechanism for the stationary lifted flames in the near field of coflow jets for the diluted methane having the Schmidt number smaller than unity, the behaviors of the stationary lifted flame in microgravity and unsteady propagation phenomena were investigated numerically at various conditions of jet velocity. It has been founded that the buoyancy plays an important role for flame stabilization of lifted flame in normal gravity and the stabilization mechanism is due to the significant variation of the propagation speed of lifted flame edge compared to the local flow velocity at the edge.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2006년도 추계공동학술대회
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• pp.523-529
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• 2006

Nowadays, a logistics and distribution center plays an important role in all industries. In addition to its traditional functions as a storage and unloading facility the distribution center serves as an assembly place for information, a source of information, and a turning point for the flow of information. On account of the above-mentioned reasons, each and every industry has increasing need of logistics distribution center. At this juncture, the present author thinks that it is necessary to make a study of the establishment and maximization of a ceramics logistics distribution center as a way for activating the ceramics industry.

• 한국안전학회지
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• 제16권4호
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• pp.74-81
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• 2001

A direct numerical simulation (DNS) was applied to nonpremixed counter-flow diffusion flames between oxidizer and fuel ducts. The objective of this study is to evaluate the numerical method for simulation of axisymmetric counterflow diffusion flames. Effects of computational domain size and grid size were scrutinized, and then the method was applied to air-methane diffusion flames. The results at zero gravity conditions were in good agreement with those obtained by the one-dimension flame code OPPDIF. It was confirmed thai the numerical method is applicable to the diffusion flames at the normal gravity conditions since the results clearly showed the effects of buoyancy and velocity ratio.

• 한국주조공학회지
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• 제29권3호
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• pp.138-143
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• 2009

Vacuum suction is applied to the mold during pouring in the inclined gravity die casting to remove defects such as misrun and gas porosity in the brake master cylinder. Casting defects are observed after solidification and their cause is analyzed by using the calculated results with commercial solidification and flow analysis code(ZCAST). The optimum vacuum suction is -2 cmHg, and when the start time of vacuum suction is 3 seconds after pouring, better filled result is obtained by holding it for 15 seconds. Reproducibility test under the optimum conditions attained from the above pouring tests is performed, and it is confirmed that these pouring conditions can be applied to the mass production immediately.

• 산업공학
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• 제20권2호
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• pp.121-132
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• 2007

The facility layout problem (FLP) involves the positioning of facilities within a given workplace in order to minimize the material flow distance between facilities. In this paper, we focus on the FLP in which the each facility has a rectangular shape and an input and output points. We develop a heuristic algorithm in which the facilities are arranged according to the layout algorithm using center of gravity and then simulated annealing algorithm is applied to improve the solution. A comparison of the computational results with exiting algorithms shows that the proposed algorithm provides better solutions in reasonable range of computational time.

• 무역학회지
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• 제46권3호
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• pp.1-24
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• 2021

The Belt and Road Initiative (BRI) is designed to intensify bilateral trade between China and the BRI countries through the improvement of transportation connections. However, little research has empirically investigated the impacts of this policies on the trade patterns. This paper attempts to evaluate the impacts of BRI on the trade patterns of Tanzania. Our study extends the original gravity model of bilateral trade by adding GDP per capita, population and proximity as the explanatory variables. According to our research, we observed that the BRI significantly impacted the Tanzania's trade patterns, as it led to the increase of bilateral trade flow between Tanzania and China more importantly between Tanzania and its adjacent countries. It indicates that the Belt and Road Initiative (BRI) has boosted Tanzania's trade exclusively, hence the Tanzania's export sector earns greater trading potential with the adjacent countries.