• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.1076-1079
• /
• 1997

A new 3D micromachining method, called Hole Area Modulation(HAM), has been introduced and experimentally confirmed its feasibility. In this method, information on the depth of machining is converted to the sizes of small holes in the mask. The machining is carried out with a simple 2D movement of the workpiece. This method can be applied for machining various kinds of microcavities in various materials. In this paper, a mathematical model for excimer laser micromachining based on HAM and also determination of the optimal laser ablation conditions(width, Hole radius, step size, path, etc.) is completed by employing using Genetic Algorithm(GA).

• 한국정보디스플레이학회:학술대회논문집
• /
• 2002.08a
• /
• pp.243-252
• /
• 2002

We propose a new concept: that of photonic crystal phosphors (PCPs) for display and phosphor related applications. It is well known that microcavities with dimensions comparable to the emitting wavelength strongly enhance light-matter interactions, resulting in a significant increase in spontaneous emission rate, which can be directly translated into enhancement in phosphor efficiency. In recent simulations we have demonstrated that when a microcavity is formed in a nano-phosphor structure, the luminescence band is modified, and can be made spectrally sharp and tunable by engineering the geometry/material properties of the cavity and the surrounding photonic crystal lattice. New phosphor material structures based on photonic crystals are proposed. Applications to thin film EL phosphors and particle phosphors are discussed. Additionally, economic methods of synthesizing and incorporating PCPs into current display applications are proposed.

• The Journal of Engineering Geology
• /
• v.9 no.3
• /
• pp.243-251
• /
• 1999

Granitic rock, by its nature, contains numerous micro-discontinuities including grain boundary, microcracks, microcavities and mineral cleavages. The brittle fracture of rock is a progressive procedure in which the failure occurs with prior microcracking. In this paper, initiation, propagation and interaction of microcracks are considered to be the dominant, controlling micromechanisms of macroscopic failure. The authors show a few patterns of microcrack initiation and propagation by using sequential photographs of water-saturated granite taken under triaxial compressive state. The failure process was observed directly and continuously by a newly developed triaxial compressive test system.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.11 no.6
• /
• pp.17-23
• /
• 2002

A new 3D micromachining method called Hole Area Modulation(HAM), has been introduced to enhance the current micromachining technology. In this method, information on the depth of machining is converted to the sizes of small holes in the mask. The machining is carried out with a simple 2D movement of the workpiece. This method can be applied for machining various kinds of microcavities in various materials. In this paper, a machematical model for excimer laser micromachining based on HAM and also determination of optimal laser ablation conditions(width hole radius, step size, path, etc.) is performed by Genetic Algorithm(GA).

• Korean Journal of Optics and Photonics
• /
• v.27 no.5
• /
• pp.181-187
• /
• 2016

We report on the parameter-dependent optical characteristics of the unidirectional single-mode lasing square ring cavities. Using the taper-step section in the square cavities, the resonant direction can be selected and we characterize the optical losses by changing the taper lengths. Various kinds of square ring cavities are fabricated, based on InGaAsP/InGaAs multiple quantum well semiconductor materials. From the experimental results we obtain the optimized taper length for a given device structure, while maintaining unidirectional single-mode lasing.

• Journal of Korea Foundry Society
• /
• v.19 no.5
• /
• pp.427-432
• /
• 1999

Most investment castings contain some porosities and microcavities. In this study, we investigated the elimination trends of various internal defects in IN738LC investment castings for industrial gas turbine blade by hot isostatic pressing. The results showed that cylindrical defects which are under $0.6mm{\Phi}{\times}7mm$ size are mostly eliminated and aspect ratio of defects is more sensitive factor than their cross section shape in removing these defects. Increasing hot isostatic pressure and holding time doesn't affect the elimination trend of cylindrical defects over $0.6mm{\Phi}{\times}7mm$ size because first step(plastic deformation) of HIP densification doesn't occur under these HIPping conditions.