• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.901-905
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• 2012

In this study, we investigated the pure geometrical effect of porous materials in gas adsorption using the grand canonical Monte Carlo simulations of primitive gas-pore models with various pore geometries such as planar, cylindrical, and random pore geometries. Although the model does not possess atomistic level details of porous materials, our simulation results provided many insightful information in the effect of pore geometry on the adsorption behavior of gas molecules. First, the surface curvature of porous materials plays a significant role in the amount of adsorbed gas molecules: the concave surface such as in cylindrical pores induces more attraction between gas molecules and pore, which results in the enhanced gas adsorption. On the contrary, the convex surface of random pores gives the opposite effect. Second, this geometrical effect shows a nonmonotonic dependence on the gas-pore interaction strength and length. Third, as the external gas pressure is increased, the change in the gas adsorption due to pore geometry is reduced. Finally, the pore geometry also affects the collision dynamics of gas molecules. Since our model is based on primitive description of fluid molecules, our conclusion can be applied to any fluidic systems including reactant-electrode systems.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1395-1398
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• 2007

MgO thin films were deposited by e-beam evaporator using the 2-step method for alternate current plasma display panels (AC-PDPs). Glancing angle deposition (GLAD) method was employed to produce various surface geometry of the thin film; the bottom layer was deposited on a substrate by normal e-beam evaporation method and the top layer was deposited on bottom layer with $85^{\circ}$ by GLAD method. Results show that firing and sustain voltages improved as the sharpness of surface and isolated columnar structures increases, respectively.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.757-762
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• 2002

Many reports have been shown that the buoyancy, electromagnetic force, surface tension, and gas shear stress are the driving forces of weld pool circulation in arc welding. Among them, the surface tension of molten metal plays an important role in the flow in weld pool, which are clarified by the specially designed experiments with small particles as well as the numerical simulations. The surface tension is also related to the penetration in arc welding. Therefore, a quantitative evaluation of surface tension is demanded for the development of materials and arc process control. However, there are few available data published on the surface tension of molten metals, since it depends on the temperature and the composition of materials. In this study, a new method was proposed for the evaluation of surface tension and its temperature dependence, in which it is evaluated by the equilibrium condition of acting forces under a given surface geometry, especially back surface. When this method was applied to the water pool and to the back surface of molten pool in the stationary gas tungsten arc welding of thin plate, following results were obtained. In the evaluation of surface tension of water, it was shown that the back surface geometry was very sensitive to the evaluation of surface tension and the evaluated value coincided with the surface tension of water. In the measurement of molten pool in the stationary gas tungsten arc welding, it was also shown that the comparison between the surface tension and temperature distribution across the back surface gave the temperature dependent surface tension. Applying this method to the mild steel and stainless steel plates, the surface tension with negative gradient for temperature is obtained. The evaluated values are well matched with ones in the published papers.

• Journal of the Korean Mathematical Society
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• v.33 no.4
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• pp.1139-1171
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• 1996

The purpose of our research is to understand geometric and topological aspects of real projective structures on surfaces. A real projective surface is a differentiable surface with an atlas of charts to $RP^2$ such that transition functions are restrictions of projective automorphisms of $RP^2$. Since such an atlas lifts projective geometry on $RP^2$ to the surface locally and consistently, one can study the global projective geometry of surfaces.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.10a
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• pp.181-185
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• 2002

The modeling of realistic water-jet geometry is needed in order to facilitate the design modifications. The present paper proposes a method of generating inlet geometry. Inlet duct was represented by NURBS method which utilized the skinning and local cubic interpolation scheme. Three test examples are presented demonstrating the effectiveness of the methods of skinning and local cubic interpolation. Computational examples associated with practical configurations have shown the usefulness of the present method.

• Tribology and Lubricants
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• v.11 no.1
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• pp.27-36
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• 1995

Maximum allowable PV values of oilless composite bearing materials (70% epoxy-resin/30% Graphite) were measured and compared at various types of test rigs that have different contact geometry and the operating conditions. Test results showed that material failure was mainly characterized by the sharp increase in both coefficient of friction and surface temperature, and different PV values were measured under different Contact geometry. The discrepancy in measurement of PV values was analyzed in the light of theoretical frictional heating analysis. Results show that surface temperature rise depends on its contact geometry, and PV values could be overestimated in the testing conditions of high sliding velocity. Test data of different contact geometry were normalized by using a normalized contact pressure and sliding velocity; it showed a good correlation. This work suggests that normalized PV values could be more effective in evaluating bearing materials than conventional PV values for a design parameter of journal bearings.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.500-503
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• 2003

The tool geometry parameters and cutting process have complex relationships. Until now, various cutting test were needed to acquire optimal design of end mill for the purpose of high speed machining, due to the insufficient knowledge about cutting process in high speed machining. Using various tools with different geometry, relationships between tool geometry parameter (rake angle, clearance angle, length of cutter) and cutting process (cutting force, surface accuracy, surface roughness) have been studied. Acquired data can be used to design optimal tool for high speed machining

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.419-431
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• 2007

The track and rail surface geometry is of prime importance on the requirement for track dynamic stiffness, particularly for the speed of 350 km/h, for which both the requirement for fatigue and tensile strength limits require a lower stiffness than 100 kN/mm, which is near the value for ballasted track. However, the track quality has been considered as being the same for 350 km/h as that for 300 km/h, and based on ballasted track, and the track geometry may be kept in better condition with a slab track(probably more similar to the medium quality track geometry of ballasted track). In conclusion, under the condition that the track geometry quality provided by the concrete slab system is fairly good, and that the required maintenance is applied to the rail surface, there would be no safety risk if the fastening system point stiffness reaches 160 kN/mm for 300 km/h operation, and 110 N/mm at 350 km/h.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.485-491
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• 1999

A burr is formed in every corner of parts as a result of machining, which produces undesirable edge geometry and influence deeply to surface quality of workpiece. Therefore these burrs must be removed certainly. The cost of removing these burrs is directly proportional to their size. Burrs have been among the most troublesome obstruction to high productivity and automation of machining processes. The proper selection of cutting condition and tool geometry will be helpful to reduce the occurrence of burrs. In paper will observe burr formation along helix angle in end milling and certificate experimentally mechanics relation of helix angle and burr formation.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.4 s.148
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• pp.440-450
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• 2006

In this paper, we suggest a design concept of defining the propeller geometry by stacking up the blade sections aligned with propeller surface streamlines. Numerical and experimental propeller open water(P.O.W.) characteristics of a newly designed propeller are presented. The surface streamlines for a propeller are obtained by using the panel method. Redefinition of the blade sections aligned with the streamlines is provided together with 8-spline modeling, by which we manufacture model propellers. We carried out the P.O.W, tests in a towing tank in order to show the effect of the present method on P.O.W. characteristics.