• 대한기계학회논문집B
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• 제27권2호
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• pp.236-242
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• 2003

Thermal bubbles find their diverse application areas in the MEMS (MicroElectroMechanial Systems) technology, including bubble jet printers, microactuators, micropumps, etc.. Especially, microactuators and micropumps, which use a microbubble growing by a controlled heat input, frequently involve mechanical and thermal interaction of the bubble with a solid structure, such as a cantilever beam and a membrane. Although the concept is experimentally verified that an internal pressure of the bubble can build up high enough to deflect a thin solid plate or a beam, the physics of the entire process have not yet been thoroughly explored. This work reports the experimental study of the growth of a thermal bubble while deflecting a thin cantilever beam. A physical model is presented to predict the elastic response of the cantilever beam based on the experimental measurements. The scaling law constructed through this work can provide a design guide for micro- and nano-systems that employ a thermal bubble for their actuation/pumping mechanism.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
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• pp.345-350
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• 1999

The effectiveness of software error compensation for thermally induced machine tool errors relies on the prediction accuracy of the pre-established thermal error models. The selection of optimal sensor locations is the most important in establishing these empirical models. In this paper, a methodology for the selection of optimal sensor locations is proposed to establish a robust linear model which is not subjected to collinearity. Correlation coefficient and time delay are used as thermal parameters for optimal sensor location. Firstly, thermal deformation and temperatures are measured with machine tools being excited by sinusoidal heat input. And then, after correlation coefficient and time delays are calculated from the measured data, the optimal sensor location is selected through hard c-means clustering and sequential selection method. The validity of the proposed methodology is verified through the estimation of thermal expansion along Z-axis by spindle rotation.

• 한국산학기술학회논문지
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• 제12권6호
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• pp.2644-2651
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• 2011

본 연구의 목적은 촉각과 온각 자극에 따른 악력, 상지 기민성, 그리고 손 기능 변화의 차이 를 비교 분석하여 움직임에 가장 영향력 있는 자극의 종류를 규명하는 것이었다. 건강한 성인 남성 40명을 대상으로 하였고 신체적 특성을 파악한 뒤 악력과 상지 기민성 및 손 기능을 측정하였다. 이 후 부드러운 솔을 이용하여 촉각 입력을 발현한 뒤 재측정 하였으며 다음날 핫팩을 이용하여 온각 자극 발현 뒤 재측정하였다. 연구 결과 악력과 상지 기민성 검사의 모든 변인에서 통계적으로 유의한 차이가 나타났고(p<.001), Lifting small objects를 제외한 모든 손 기능 변인에서 통계적으로 유의한 차이가 나타났다(p<.01). 결론적으로 자극의 입력은 악력, 기민성, 그리고 손 기능을 증가시킨다. 또한 자극의 종류에 따른 영향에서 온각 자극 입력은 촉각 자극 입력보다 악력, 기민성, 그리고 손 기능을 더욱 증가시킨다. 따라서 재활치료 및 산업 현장에서 상지와 손의 기능 촉진을 위해서는 적절한 자극의 적용이 도움이 될 것이며 앞으로 자극의 빈도와 강도에 대한 연구가 더욱 필요할 것으로 생각된다.

• 대한기계학회논문집B
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• 제36권11호
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• pp.1073-1079
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• 2012

본 논문은 나노유체를 적용하여 써모사이폰 열전달 성능 특성 변화를 실험적으로 규명하는 것을 목적으로 하고 있다. 이를 위하여, 증발부 내부체적을 공유하는 3 개의 독립된 파이프를 가지는 써모사이폰을 제작하였으며 증류수, Ag 나노유체 그리고 $TiO_2$ 나노유체에 대하여 충진량, 증발부에 가해지는 입력열량 그리고 농도변화에 따른 써모사이폰 성능특성 변화를 고찰하였다. 증류수를 작동유체로 사용하는 경우 써모사이폰의 최적충진량은 30%로 결정되었고, $TiO_2$ 나노유체를 적용하는 써모사이폰 열저항이 Ag 나노유체를 적용한 경우에 비하여 평균 18.1% 감소하였다. 또한, 300W 입력열량 및 $TiO_2$ 나노유체 농도 1%에서 써모사이폰의 열전달 성능은 가장 우수하였다.

• E2M - 전기 전자와 첨단 소재
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• 제8권1호
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• pp.27-34
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• 1995

The analysis of nonlinear equivalent circuit and the resonance characteristics of input current and output voltage were simulated, and their electrical properties are discussed in the transverse-type piezoelectric ceramic transformer. The nonlinear resonance characteristics of input current and output voltage showed by the thermal effect due to a higher driving current, the nonlinearity increased greatly as driving current increased. When load resistor was 100[M.ohm.], the nonlinear coefficient was -1.3. The nonlinear resonance curve of input current and output voltage for a variation of input voltage and load resistor agreed with the discussed theory. The output voltage increased nearly proportioned to input voltage when load resistors were below 50[M.ohm.], the voltage step-up ratio decreased when a load resistor was 100[M.ohm.] and their maximum value was 950.

• KIEAE Journal
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• 제15권4호
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• pp.105-110
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• 2015

Purpose: This study aimed at finding the optimal input variables of the artificial neural network-based predictive model for the optimal controls of the indoor temperature environment. By applying the optimal input variables to the predictive model, the required time for restoring the current indoor temperature during the setback period to the normal setpoint temperature can be more precisely calculated for the cooling season. The precise prediction results will support the advanced operation of the cooling system to condition the indoor temperature comfortably in a more energy-efficient manner. Method: Two major steps employing the numerical computer simulation method were conducted for developing an ANN model and finding the optimal input variables. In the first process, the initial ANN model was intuitively determined to have input neurons that seemed to have a relationship with the output neuron. The second process was conducted for finding the statistical relationship between the initial input variables and output variable. Result: Based on the statistical analysis, the optimal input variables were determined.

• Journal of Welding and Joining
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• 제9권1호
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• pp.32-39
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• 1991

A 200W pulsed Nd: YAG laser for fine welding was developed. The important laser parameters such as laser peak power, average power, pulse width, and pulse energy for welding were studied. In order to obtain the sufficient laser power density for welding, thermal lensing effects were analyzed and a laser resonator with laser beam divergence was designed. The power supply unit was designed to support up to 7kW input. The pulse control unit was developed using a GTO thyristor and could control over 100kW input power to obtain 3.5kW peak power laser. Also due to the GTO thyristor the pulse width could be varied continuously from 0.1 to 20 msec and maximum repetition rate was as high as 300pps.

• 한국생산제조학회지
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• 제19권6호
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• pp.826-833
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• 2010

Electric-thermal-structural actuated compliant mechanisms are mechanisms onto which electric voltage drop is applied as input instead of force. This mechanism is based on thermal expansion of material while being heated. Compliant mechanisms are designed subjected to electric charge input using BESO(bi-directional evolutionary structural optimization) method. Reliability-based topology optimization (RBTO) is applied to the topology design of actuators. performance measure approach (PMA), which has probabilistic constraints that are formulated in terms of the reliability index, is adopted to evaluate the probabilistic constraints. In this study, BESO method is used to obtain optimal topology of compliant mechanisms from initial design domain. PMA approach is used to evaluate reliability index. The procedure has been tested in numerical applications and compared with the results obtained by other methods to validate these approaches.

• Smart Structures and Systems
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• 제6권9호
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• pp.1041-1056
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• 2010

This paper investigates the possibility of a strategy for an automatic full recover of a structural component undergoing loading-unloading (fatigue) cycles: full recover means here that no replacement is required at the end of the mission. The goal is to obtain a material capable of self healing earlier before the damage becomes irreversible. Attention is focused on metallic materials, and in particular on shape memory alloys, for which the recovering policy just relies on thermal treatments. The results of several fatigue tests are first reported to acquire a deep understanding of the physical process. Then, for cycles of constant amplitude, the self-healing objective is achieved by mounting, on the structural component of interest, a suitable microcontroller. Its input, from suitable sensors, covers the current stress and strain in the alloy. The microcontroller elaborates from the input the value of a decisional parameter and activates the thermal process when a threshold is overcome.

• 한국태양에너지학회 논문집
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• 제28권6호
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• pp.64-69
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• 2008

In this study the thermal performance and economic analysis program of solar heating system for district heating was developed. This program, named SOLAN-DHS and based on TRNSYS, consisted of four modules like as user's interface for system input/output, library, and utilities and a calculating engine. SOLAN-DHS simplifies user's input data through the database of most system engineering data including weather data of 17 areas in Korea. Five different types of solar systems which can be applicable to district heating system were presented in this program. Due to the user-friendly layout, all design parameters can be changed quickly and easily for the influence on system efficiency. The reliability of SOLAN-DHS was finally verified by the experiments.