• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.451-454
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• 2007

This paper presents the pattern characteristic using the electrostatic drop-on-demand ink-jet printing system. In order to achieve the pattern characteristic of electrostatic inkjet printing, the capillary inkjet head system is fabricated using capillary tube, Pt wire and electrode, and is packaged by acrylic board for the accurate alignment between wire and electrode-hole. The applied DC voltage of 1.4 $\sim$ 2.0 kV used for the observation of electrostatic droplet ejection. Electrostatic droplet ejection is directly observed using a high-speed camera. For investigated pattern characteristic, conductive inkjet silver ink used. The higher voltage has a good condition which has micro dripping mode. Also, the droplet size decreases with increasing the supplied DC voltage. This paper shows the pattern which is formed by about 300um. Also, capillary inkjet head system will be applied industrial area comparing conventional electrostatic inkjet head system.

• Journal of Advanced Marine Engineering and Technology
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• 제27권7호
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• pp.872-878
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• 2003

As the results of recent industrial development, many industrial plants and marine structures are exposed to severe corrosion environment than before. Especially, under the wet environment, crevice corrosion damage problems necessarily occur and encourage many interests to prevent them. In this study, the electrochemical polarization test was carried out to study characteristics of crevice corrosion for AISI 304 stainless steel in various solution temperatures. The results are as follows ; 1) as the solution temperature increased in IN $\textrm{H}_2\textrm{SO}_4$, the passive current density and critical current density were increased, whereas corrosion potential and break down potential were nearly constant, 2) as the solution temperature increased. the induced time for initiation of crevice corrosion was shortened. 3) The potential range in the crevice was -220mV/SCE to -380mV/SCE according to the distance from the crevice opening, which is lower than that of external surface of -200mV/SCE.

• Korean Chemical Engineering Research
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• 제56권4호
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• pp.585-591
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• 2018

미세액적 유동반응기 공정에서 제조된 나노구조 $SiO_2:Zn$ 원환형 입자의 특성을 밴드갭 에너지와 표면 반응성의 관점에서 고찰하였다. $SiO_2:Zn$ 원환형 입자를 단일 공정에서 연속적이며 합리적인 생산 효율로 첨가제인 THAM (tris(hydroxymethyl)-aminomethane)과 도핑되는 $Zn^{2+}$ 이온의 농도 변화에 따라 성공적으로 제조할 수 있었다. 그리고 $Zn^{2+}$ 이온의 도핑은 $Si^{4+}$ 이온의 conduction band 보다 에너지 레벨이 낮은 $Zn^{2+}$ 이온의 acceptor level을 형성함으로써 $SiO_2:Zn$ 원환형 입자의 밴드갭 에너지를 줄일 수 있었다. 또한, 입자의 원환형 구조는 $SiO_2:Zn$ 입자의 밴드갭 에너지를 감소시키는데 기여하였다. 따라서 $Zn^{2+}$ 이온이 도핑된 $SiO_2:Zn$ 원환형 입자는 표면에 SiO-H의 형성과 산소 결함의 생성으로 표면 반응성을 증대시킬 것으로 사료되었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.263-268
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• 2001

MCPs means Micro Cellular Plastics. The micro-cells are generated in the products by the difference of dissolution through the pressure drop after super critical fluid of CO2 or N2 dissolves into polymer. We have developed injection molding process adopting MCPs and applied it to a broad range of injection molded thermoplastic materials and applications. It can prevent the leakage of impact strength and increase the thermal conductivity, moreover regulate the thermal conductivity. Then we can develop the high strength foaming plastics. Also, it can be gained a competitive advantage by utilizing its processing benefits, e.g. the lightweight products and significant reductions in material consumption.

• 한국기계가공학회지
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• 제4권4호
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• pp.34-38
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• 2005

This is a widespread requirement for low cost lightweight thermal imaging sensors for both military and civilian applications. Today, a large number of uncooled infrared detector developments are under progress due to the availability of silicon technology that enables realization of low cost IR sensor. System prices are continuing to drop, and swelling production volume will soon drive process substantially lower. The feasibility of micromechanical optical and infrared (IR) detection using microcantilevers is demonstrated. Microcantilevers provide a simple Structurefor developing single- and multi-element sensors for visible and infrared radiation that are smaller, more sensitive and lower in cost than quantum or thermal detectors. Microcantilevers coated with a heat absorbing layer undergo bending due to the differential stress originating from the bimetallic effect. This paper reports a micromachined silicon uncooled thermal imager intended for applications in automated process control. This paper presents the design, fabrication, and the behavior of cantilever for thermomechanical sensing.

• Journal of Mechanical Science and Technology
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• 제18권12호
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• pp.2294-2302
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• 2004

The objective of this study is to obtain detailed information for the micro fabrication of lead frames by applying spray technology to wet etching process. Wet etching experiments were performed with different etching parameters such as injection pressure, distance from nozzle tip to etched substrate, nozzle pitch and etchant temperature. The characteristics of single and twin spray were measured to investigate the correlation between the spray characteristics and the etching characteristics. Drop size and velocity were measured by Phase-Doppler Anemometer (PDA). Four liquids of different viscosity were used to reveal the effects of viscosity on the spray characteristics. The results indicated that the shorter the distance from nozzle tip and the nozzle pitch, the larger etching factor became. The average etching factor had good positive correlation with average axial velocity and impact force. It was found that the etching characteristics depended strongly on the spray characteristics.

• 대한기계학회논문집B
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• 제25권12호
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• pp.1784-1792
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• 2001

Numerical analysis on a parallel flow heat exchanger(PFHE) is performed using 2 dimensional turbulent porous modeling. This modeling can consider three-dimensional configuration of passage (flat tube with micro-channels), and the stability and accuracy of numerical results are improved. The geometrical parameters(e.g., the position of separators, inlet/outlet, and porosity of passages of a PFHE) are varied in order to examine the flow and thermal characteristics and flow distribution of the single phase multiple passages system. The flow non-uniformities along the paths of the PFHE are observed to evaluate the thermal performance of the heat exchanger. The location of inlet affects the heat transfer, and the location of outlet affects the pressure drop. The porosity with the optimum thermal performance is around 0.53.

• 한국분무공학회지
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• 제8권4호
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• pp.39-45
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• 2003

The Objective of this study is to investigate the effect of internal swiller angle and swirl chamber aspect ratio of nozzle on spray characteristics for application of spray system in micro fabrication process. The macro-spray characterictics such as the spray angle and breakup process were obtained by photographs illustrating atomization. The micro-spray characteristics such as droplet size and axial velocity were measured by using PDA with swirler angle and swirl chamber aspect ratio. The swiller angles were $13.5^{\circ},\;27^{\circ},\;and\;40.5^{\circ}$. The swirl chamber aspect ratios were 1.2, 1.6, and 2.0. It was found that the smaller swirl chamber aspect ratio was, the larger axial velocity and drop size were.

• 설비공학논문집
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• 제11권1호
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• pp.10-17
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• 1999

The present work presents condensation heat transfer and pressure drop data for the flow of R-12 in flat extruded aluminum tubes with small hydraulic diameters. The tube outside dimensions are $18mm(width){\times}1.7mm(height)$. Three types of internal geometry with the same outside dimensions are tested : sample 1 (7 tube holes), sample 2 (13 tube holes) and sample 3 (7 tube holes, micro-fin). The overall heat transfer coefficient is obtained for air-to-refrigerant heat transfer, and the Wilson plot method is used to determine the heat transfer coefficient for refrigerant flow. The sample 2 and sample 3 show significantly higher performance than sample 1. The heat transfer rates for the sample 2 and sample 3 are 9% and 12% higher, respectively, than sample 1. The friction factors for the sample 2 and sample 3 are 11.9% and 2.4% higher, respectively, than sample 1.

• 설비공학논문집
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• 제25권12호
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• pp.654-659
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• 2013

This paper presents a numerical optimization of louvered fins to enhance the JF factor in terms of the design parameters, including the fin pitch, the number of louvers, the louver angle, the fin thickness, and the re-direction louver length. We carried out a parametric study to select the three most important parameters affecting the JF factor, which were the fin pitch, number of louvers, and the louver angle. We optimally designed the louvered fin by using 3rd-order full factorial design, the kriging method, and a micro genetic algorithm. Consequently, the JF factor of the optimum model increased by 16% compared to that of the base model. Moreover, the optimum model reduced the pressure drop by 17% with a comparable heat transfer rate.