• Proceedings of the KSME Conference
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• 2001.06d
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• pp.348-353
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• 2001

Experimental schemes that enable characterization of phase-change phenomena in the micro scale regime is essential for understanding the phase-change kinetics. Particularly, monitoring rapid vaporization on a submicron length scale is an important yet challenging task in a variety of laser-processing applications, including steam laser cleaning and liquid-assisted material ablation. This paper introduces a novel technique based on Michelson interferometry for probing the liquid-vaporization process on a solid surface heated by a KrF excimer laser pulse (${\lambda}=248nm,\;FWHM=24\;ns$) in water. The effective thickness of a microbubble layer has been measured with nanosecond time resolution. The maximum bubble size and growth rate are estimated to be of the order of $0.1{\mu}m\;and\;1\;m/s$, respectively. The results show that the acoustic enhancement in the laser induced vaporization process is caused by bubble expansion in the initial growth stage, not by bubble collapse. This work demonstrates that the interference method is effective for detecting bubble nucleation and microscale vaporization kinetics.

• Korean Journal of Materials Research
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• v.14 no.7
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• pp.477-481
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• 2004

High quality polycrystalline silicon is very critical part of the high quality thin film transistor(TFT) for display devices. Metal induced lateral crystallization(MILC) is one of the most successful technologies to crystallize the amorphous silicon at low temperature(below $550^{\circ}C$) and uses conventional and large glass substrate. In this study, we observed that the MILC behavior changed with abrupt variation of the amorphous silicon active pattern width. We explained these phenomena with the novel MILC mechanism model. The 10 nm thick Ni layers were deposited on the glass substrate having various amorphous silicon patterns. Then, we annealed the sample at $550^{\circ}C$ with rapid thermal annealing(RTA) apparatus and measured the crystallized length by optical microscope. When MILC progress from narrow-width-area(the width was $w_2$) to wide-width-area(the width was $w_1$), the MILC rate decreased dramatically and was not changed for several hours(incubation time). Also the incubation time increased as the ratio, $w_1/w_2$, get larger. We can explain these phenomena with the tensile stress that was caused by volume shrinkage due to the phase transformation from amorphous silicon to crystalline silicon.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.1
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• pp.115-121
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• 2005

Micromachines are extremely novel artifacts with a variety of special characteristics. Utilizing their tiny dimensions ranging roughly from 10 to $10^3$ micro-meters, the micromachines can perform tasks in a revolutionary manner that would be impossible for conventional artifacts. Micromachines are in general related to various coupled physical phenomena. They are required to be evaluated and designed considering the coupled phenomena. This paper describes finite element analysis (FEA) simulation of practical behaviors for the micro actuator. Especially, electric field modeling in micro actuators has been generally restricted to in-plane two-dimensional finite element analysis because of the complexity of the micro actuator geometry. However, in this paper, the actual three-dimensional geometry of the micro actuator is considered. The starting torque obtained from the in-plane two-dimensional analytical solutions were compared with that of the actual three-dimensional FE analysis results. The starting torque is proportional to $V^2$, and that the two-dimensional analytical solutions are larger than the three- dimensional FE ones. It is found that the evaluation of micro actuator has to be considered electrical leakage phenomenon.

• Smart Structures and Systems
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• v.6 no.1
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• pp.1-16
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• 2010

This paper presents a novel smart MEMS accelerometer which employs a hybrid control algorithm and an estimator. This scheme is realized by adding a sliding-mode controller to a conventional PID closed loop system to achieve higher stability and higher dynamic range and to prevent pull-in phenomena by preventing finger displacement from passing a maximum preset value as well as adding an adaptive nonlinear observer to a conventional PID closed loop system. This estimator is used for online estimation of the parameter variations for MEMS accelerometers and gives the capability of self testing to the system. The analysis of convergence and resolution show that while the proposed control scheme satisfies these criteria it also keeps resolution performance better than what is normally obtained in conventional PID controllers. The performance of the proposed hybrid controller investigated here is validated by computer simulation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.8
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• pp.1140-1147
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• 2001

Experimental schemes that enable characterization of phase-change phenomena in the microscale regime are essential for understanding the phase-change kinetics. Particularly, monitoring rapid vaporization on a submicron length scale is an important yet challenging task in a variety of laser-processing application, including steam laser cleaning and liquid-assisted material ablation. This paper introduces a novel technique based on Michelson interferometry for probing the liquid-vaporization process on a solid surface heated by a KrF excimer laser pulse(λ=248nm, FWHM=24ns) in water. The effective thickness of a microbubble layer has been measured with nanosecond time resolution. The maximum bubble size and growth rate are estimated to be of the order of 0.1㎛ and 1m/s, respectively. The results show that the acoustic enhancement in the laser induced vaporization process is caused by bubble expansion in the initial growth stage, not by bubble collapse. This work demonstrates that the interference method is effective for detecting bubble nucleation and microscale vaporization kinetics.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.1045-1048
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• 2002

Micromachines are extremely novel artifacts with a variety of special characteristics. Utilizing their tiny dimensions ranging roughly from 10 to $1O^3$ micro-meters, the micromachines can perform tasks in a revolutionary manner that would be impossible for conventional artifacts. Micromachines are in general related to various coupled physical phenomena. They are required to be evaluated and designed considering the coupled phenomena. This paper describes finite element analysis (FEA) simulation of practical behaviors for the micro actuator. Especially, electric field modeling in micro actuators has been generally restricted to in-plane two-dimensional finite element analysis because of the complexity of the micro actuator geometry. However, in this thesis, the actual three-dimensional geometry of the micro actuator is considered. The starting torque obtained from the in-plane two-dimensional analytical solutions were compared with that of the actual three-dimensional FE analysis results. The starting torque is proportional to $V^2$, and that the two-dimensional analytical solutions are larger than the three-dimensional FE ones. It is found that the evaluation of micro actuator has to be considered electrical leakage phenomenon.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.6
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• pp.308-312
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• 2006

Partial Discharge (PD) phenomena occurred by different nature of insulating defects has been regarded as a random process by which Phase Resolved Partial Discharge Analysis(PRPDA) has been proposed and then commercially accepted for the diagnosis of the power apparatus since more than three decades. Moreover, for the same purpose, a novel approach based on the Chaotic Analysis(CAPD) has been proposed since 2000, in which Partial Discharge(PD) phenomena is suggested to be considered as a deterministic dynamical process. In this work, for the diagnosis of Gas Insulated Transformer(GITr), four different types of specimen were fabricated as a model of the possible defects that might possibly cause its sudden failures such as turn to turn insulation, inter coil insulation, free moving particle and protrusion. For this purpose, these defects are introduced into the Gas Insulated Transformer(GITr) mock-up and experimental investigations have been carried out in order to analyze the related Partial Discharge(PD) patterns by means of both Phase Resolved Partial Discharge Analysis(PRPDA) and Chaotic Analysis(CAPD) respectively and then their comparisons are made systematically.

• Membrane Journal
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• v.12 no.2
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• pp.55-66
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• 2002

fouling phenomena of ion exchange membranes were reviewed for improved design and operation of electodialysis. The membrane fouling index for electrodialysis (EDMFI) was defined for the quantitative analysis of fouling potential as an analogy to the pressure-driven membrane process. fouling phenomena were compared in the electrodialysis experiments with inorganic foulant (silica sol) and organic foulants (humate and bovine serum albumin (BSA)), and their fouling potentials were analyzed using the fouling index. The comparison showed that the EDMFI could be used as a quantitative measure of the fouling tendency in electrodialysis processes. As a novel fouling mitigation method, square wave power was reported to be effective in electrodialysis with organic foulants. The square wave powers having the pulsed electric field enabled to reduce the membrane fouling significantly at an optimal frequency.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2060-2062
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• 2005

Partial Discharge (PD) phenomena occurred by different nature of insulating defects has been regarded as a random process by which Phase Resolved Partial Discharge Analysis (PRPDA) has been proposed and then commercially accepted for the diagnosis of the power apparatus since more than three decades. Moreover, for the same purpose, a novel approach based on the Chaotic Analysis(CAPD) has been proposed since 2000, in which PD phenomena is suggested to be considered as a deterministic dynamical process. In this work for the diagnosis of GITr, four different types of specimen were fabricated as a model of the possible defects that might possibly cause its sudden failures such as turn to turn insulation, inter coil insulation, free moving particle and protrusion. For this purpose, these defects are introduced into the GITr mock-up and experimental investigations have been carried out in order to analyze the related PD patterns by means of both PRPDA and CAPD respectively and then their comparisons are made systematically.

• Journal of Physiology & Pathology in Korean Medicine
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• v.28 no.5
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• pp.465-477
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• 2014

In Korean Medicine (KM), the Yin-Yang doctrine is still used as a theoretical tool for understanding and explaining the clinical experiences. However, as the traditional culture declined in East Asia and the scientific culture took over, there was an increased negative view on the Yin-Yang doctrine, and thus a heightened distrust over KM. For KM to survive in an unfamiliar culture of science, a novel outlook on the Yin-Yang doctrine is needed. In this sense, I consider a thoroughly medical take on the Yin-Yang doctrine to be most important. The focus needs to be on the goals of medicine: this includes riddance of any discourses on Yin-Yang that cannot contribute to the goals, and an enhancement of the Yin-Yang concept as a rational and scientific terminology. One way to achieve this is by understanding Yin-Yang as a type of metaphor. The Yin-Yang doctrine that is utilized in KM corresponds well to the conceptual metaphor suggested by Lakoff and Johnson. As a metaphor, the Yin-Yang concept plays a role in structuring the target domain, that is life phenomena, metaphorically. Through the Yin-Yang metaphors, the life phenomena are understood as the Yin-Yang phenomena, and are systematically organized by the subcategories contained in the Yin-Yang doctrine. Understanding Yin-Yang as a metaphor is a good way to enhance the Yin-Yang concept and doctrine as a rational terminology and method.