• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1583-1586
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• 2005

Grinding process is different from other machining processes such as turning, milling and drilling because the cutting edges in a grinding wheel doesn't have uniformity and acts differently on the workpiece at each grinding. This study focus on predicting the geometric error produced during surface grinding and selecting an optimal grinding condition to reduce the geometric error. To achieve the aim, the Taguchi design of experiments was applied and the S/N ratios of each grinding was used for evaluating the results. The predicted quantities by the S/N ratios were compared with the experimental results.

• Macromolecular Research
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• 제11권6호
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• pp.511-513
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• 2003

Hydroxyl groups were introduced onto the surface of a silicon wafer by O$_2$ plasma treatment. Poly(l-lactide) (1-PLA) was attached onto the surface-modified silicon wafer by the ring-opening polymerization of l-lactide using the hydroxyl group as an initiator. Lamellar single crystals of 1-PLA were grown directly on the 1-PLA-attached silicon wafer from a 0.025% solution in acetonitrile at 5$^{\circ}C$. A well-separated, lozenge-shaped, monolayered lamellar single crystal was prepared because the 1-PLA-attached silicon wafer acts as an initial nucleus.

• 한국공작기계학회논문집
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• 제11권4호
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• pp.68-74
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• 2002

The FD process is analogous to the direct piston extrusion process where the cold feed filament acts as a piston extruding the molten filament from the heated liquefier through a nozzle. The extruded filament is deposited on top of futureless platform, where the liquefier and the nozzle move in X and Y direction control by computer based on the part geometry. After the first layer, the Z platform indexes down and the next layer get deposited on top of the first layer. the layer by layer building process introduces surface problem. This paper describes effect of slice interval of the parts built by fused deposition modelling rapid prototyping system.

• Journal of Mechanical Science and Technology
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• 제14권11호
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• pp.1276-1285
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• 2000

The solubility, the surface concentration and the dissolution behavior of carbon dioxide in deep sea were numerically investigated. Base on the calculations the relations between the surface concentration of liquid carbon dioxide droplet with the hydrate film and the solubility and those between the ambient carbon dioxide concentration in the plume and the dissolution rate were obtained. The result show that a carbon dioxide droplet is released both at 1000 m in depth with the initial droplet diameter of 0.011 m or less and at 1500 m in depth with a diameter of 0.015 m or less, and the droplet is completely dissolved below 500 m in depth. The hydrate film acts as a resistant layer for the dissolution of liquid carbon dioxide, and the effect of the hydrate film on the dissolution of liquid carbon dioxide depended upon the depth.

• 한국정밀공학회지
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• 제15권4호
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• pp.148-155
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• 1998

It is commonly known that, in GMAW, the characteristics of metal transfer and the size of molten drop are highly dependent on the welding current. These changes in the characteristics of metal transfer has a considerable effect on the weld quality, and a lot of studies have been made on metal transfer modes for that reason. In this study, two cases were investigated; the one in which the metal transfer proceeds with gravitational force, surface tension, and no electromagnetic force, and the other in which the process has electromagnetic term in addition, where the current density in the fluid has been assumed to have Gaussian distribution on any given cross-section and it acts vertically. Using fluid flow analysis, this study has observed the whole process of the development and break-up of the molten drop, and it also showed that transitional processes, drop rate, and the drop size in each metal transfer mode can be estimated.

• 한국생산제조학회지
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• 제24권3호
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• pp.302-307
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• 2015

The automobile is an important means of transportation. For this reason, the automotive wheel is also an important component in the automotive industry because it acts as a load support and is closely related to safety. Thus, the wheel design is a very important safety aspect. In this paper, an optimal design for minimizing automotive wheel stress and increasing wheel safety is described. To study the optimal design, a central composite design (CCD) and D-optimal design theory are applied, and the approximate function using the response surface method (RSM) is generated. The optimal solutions using the non-dominant sorting genetic algorithm (NSGA-II) are then derived. Comparing CCD and D-optimal solution accuracy and verified the CCD can deduce more accuracy optimal solutions.

• 한국음향학회지
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• 제6권2호
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• pp.48-53
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• 1987

수면가까이 존재하는 단일주파수 음원에 의한 수심별 sound field에 관하여 수치모델에 의한 결과를 분석하였다. normal mode function의 수심별 특성은 주어진 음속의 기울기에 매우 민감하며 따라서 mode별 특성이 음원으로부터 밀리 떨어진 곳에서의 수심에 따른 변화를 관찰할 수 있다. 특히 양 경계면, 즉 표면과 해저에 가까운 곳에서는 음압이 수심에 따라 일정한 모양의 fluctuation을 하며 해당 주파수 파장의 두배 정도 거리의 상관관계를 나타내었다. 이는 수중음향 관측시에 응용 가능한 결과로써 특히 수중소음 측정시 청음기의 수직거리예측에 활용할 수 있겠다.

• 대한수학회지
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• 제37권3호
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• pp.491-502
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• 2000

The disjoint union of mapping class groups g,1 gives us a braided monoidal category so that it gives rise to a double loop space structure. We show that there exists a natural twist in this category, so it gives us a ribbon category. We show that there exists a natural twist in this category, so it gives us a ribbon category. We explicitly express this structure by showing how the twist acts on the fundamental group of the surface Sg,l. We also make an explicit description of this structure in terms of the standard Dehn twists, as well as in terms of Wajnryb's Dehn twists. We show that the inverse of the twist g for the genus g equals the Dehn twist along the fixed boundary of the surface Sg,l.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2005년도 학술발표논문집
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• pp.423-428
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• 2005

If the load of constructing vehicles during the construction work acts on the road or the ground surface on the soft ground, due to the excess stresses in soils the trafficability of the vehicles influences the constructing efficiency, constructing period and so on. Stress distribution in soils is the very important element to design and to solve the problems of settlement, safety of foundations and trafficability of constructing vehicle in civil engineering. This research represents the comparative estimation of the actual and theoretical measurement on the underground stress of outer layer for each soil after the observation of each top soil layer for its vertical and horizontal stress in (1)homogeneous sand ground (2) weak stratum with the sand soil (3) weak stratum with gravel of the soil model, and it also investigates the effect of subsidence of ground by the repeated load. The underground stress turn out to be different in the value of theoretical and actual measurement after the trial examination of model.

• 대한전자공학회논문지
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• 제27권7호
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• pp.1042-1048
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• 1990

The approximations of charge relationships at normally doped semiconductor interfaces were qualitatively derived basis on electrical neutrality conditions. Effects of ion adsorptions, activation processes, interfacial structures, rectifying phenomena, and effects of surface potential barriers at the p- and n-Si/CsNO3 aqueous electrolytes, and the p-Si/(1HF:3HNO3:6H2O) electrolyte solutions were investigated using a cyclic voltammetric method. The space charge acts the most important role for the pn junction structures, the rectifying phenomena, and the activation processes. The Current-Voltage (I-V) characteristics curves significantly depend on developing of the Helmholtz double layers and charging of the show surface states during the activation processes. A linear Current-Voltage characteristics region was observed at the p-Si/(1HF:3HNO3: 6H2O) electrolyte solution interface.