• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.209-209
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• 2003

The adventages of Li alloys have attracted the attention of many research groups, many of which have investigated tin-based alloys [1-2], Despite interesting performances of these, the irreversible capacity loss systematically observed on the first cycle for these compounds is a main drawback for their use as anode materials in lithium ion cells. Not only Sn is efficient in forming alloys with Li, Si can also react with Li to form alloys with a high Li/Si ratio, like Li$\_$22/Si$\_$5/ at 400$^{\circ}C$. It corresponds to a capacity of 4200mAh/g. Electrochemical Li-Si reaction occurs between 0 and 0.3 V against Li/Li$\^$+/, so that high-energy density battery can be realized. Despite the high theoretical capacity of elements like Si, however, particles of the alloys crack and fragment due to the repeated alloying and do-alloying which occurs as cell are charged and discharged. The research groups of Muggins [3] and Besenhard [4] have proposed that the volume expansion due to the insertion of Li can be reduced in micro- and submicro-structured matrix alloys. For this reason, the research group of J.R. Dahn investigated Sn/Mo sequential sputter deposition to prepare nanocomposites [5]. In this study, we investigated the characterization and the electrochemical characteristics of sequentially sputtered Si/Mo multilayer for microbattery anode.

• 한국IT서비스학회지
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• 제11권3호
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• pp.49-65
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• 2012

This study aims to investigate the factors influencing followers' continuous usage intention of twitter based on Elaboration Likelihood Model. In particular, central route(information itself) and peripheral route(twitterian's trustworthiness) are tested to reveal which has a more influential role in effecting the continuous usage intention of power-twitter. Furthermore, this study tests the relationship of users' attitude and continuous usage intention. The results indicate that argument quality, accuracy(central route), source expertise and source trustworthiness (peripheral route) have an influence on attitude. However, trustworthy on central route is not significant. Argument quality, trustworthy, accuracy(central route) and source expertise(peripheral route) have an influence on perceived usefulness. But source trustworthiness on peripheral is not significant. Attitude has an influence on perceived usefulness, and attitude and perceived usefulness both have an influence on perceived usefulness. In conclusion, central route is more influential than peripheral route in forming a positive attitude towards arguments, which in turn leads to the perception of twitter's usefulness, and in the end brings the continuous usage intention of twitter.

• 한국융합학회논문지
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• 제11권1호
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• pp.175-180
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• 2020

본 연구에서는 미세패턴 성형이 가능하도록 개발된 초음파 미세패턴 제조시스템을 이용하여 RFID TAG 안테나 형상의 미세패턴 성형기술을 개발하였다. 미세패턴 제조시스템에 종진동 모드의 초음파 공구 혼을 설치하여 절연시트 표면에 RFID TAG 안테나 형상의 미세패턴 안테나 형상을 초음파 압입 성형공정 기술을 개발하였다. 초음파 성형기술은 60kHz 공구 혼을 공진설계 기법을 적용하여 제작하였고, 미세패턴 제조시스템을 이용하여 200㎛ 이하의 절연 시트지에 두께가 25㎛의 코일 와이어를 초음파 압입 성형을 할 수 있다. 초음파 압입 성형 시 코일 와이어의 단선, 박리 및 꼬임 현상 없이 최소선폭 150㎛인 안테나 형상을 성형할 수 있었다.

• 설비공학논문집
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• 제18권6호
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• pp.477-485
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• 2006

A study on frost prevention of fin-tube heat exchanger is experimently performed by spreading antifreezing solution on heat exchanger surface. It is desirable that the antifreezing solution spreads completely on the surface forming thin liquid film to prevent frost nucleation and crystal growth and to reduce the thermal resistance across the liquid film. A small amount of antifreezing solution falls in drops on heat exchanger surface using two types of supplying devices, and a porous layer coating technique is adopted to enhance the wettedness of antifreezing solution on the surface. It is observed that the antifreezing solution liquid film prevents fin-tube heat exchanger from frosting, and heat transfer performance does not degrade through the frosting tests. The concentration of supplied antifreezing solution can be determined by heat transfer analysis of the first row of heat exchanger to avoid antifreezing solution freezing due to dilution by moisture absorption.

• 소성∙가공
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• 제16권1호
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• pp.42-47
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• 2007

LCD-BLU is one of kernel parts of LCD and it consists of several optical sheets: LGP, light source and mold frame. The LGP of LCD-BLU is usually manufactured by etching process and forming numerous dots with $50\sim300{\mu}m$ diameter on the surface. But the surface of the etched dots of LGP is very rough due to the characteristics of the etching process during the mold fabrication, so that its light loss is high along with the dispersion of light into the surface. Accordingly, there is a limit in raising the luminance of LCD-BLU. In order to overcome the limit of current etched dot patterned LGP, optical pattern with continuous microlens was designed using optical simulation CAE. Also, a mold with continuous micro-lens was fabricated by UV-LiGA reflow process and applied to 7 inch size of navigator LCD-BLU in the present study.

• 소성∙가공
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• 제16권1호
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• pp.48-53
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• 2007

LCD-BLU(Liquid Crystal Display - Back Light Unit) consists of several optical sheets: LGP(Light Guiding Plate), light source and mold frame. The LGP of LCD-BLU is usually manufactured by etching process and forming numerous dots with $50{\mu}m$ in diameter on the surface. But the surface roughness of LGP with etched dots is very high, so there is much loss of light. In order to overcome the limit of current etched dot patterned LGP, optical pattern design with microlens of $50{\mu}m$ diameter was applied in the present study. The microlens pattern fabricated by modified LiGA with thermal reflow process was applied to the optical design of LGP and optical simulation was carried out to know tendency of microlens patterned LGP simultaneously. The attention was paid to the effects of different aspect ratio(i.e. $0.2\sim0.5$) of optical pattern conditions to the brightness distribution of BLU with microlens patterned LGP. Finally, high aspect ratio microlens patterned LGP showed superior results to the one made by low aspect ratio in average luminance.

• 한국전기전자재료학회논문지
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• 제16권6호
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• pp.510-514
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• 2003

We have studied the alignment of liquid crystals (LCs) on homeotropic polymeric surface that is scanned using an atomic force microscope (AFM) tip by optical polarizing microscopy and computer simulation. The scanned areas on one substrate are 5 $\mu\textrm{m}$ ${\times}$ 5 $\mu\textrm{m}$, 10 $\mu\textrm{m}$ ${\times}$ 10 $\mu\textrm{m}$, and 20 $\mu\textrm{m}$ ${\times}$ 20 $\mu\textrm{m}$ and this substrate is assembled to another substrate coated. with homeotropic polymer. The fabricated micro-LC cell using two substrates does not show any hysteresis and disclination lines inside the nano-rubbing areas, while changing voltage up and down. This indicates that the pretilt angle exists in the areas, thereby forming a hybrid LC configuration. From the experimental and computer simulation results, we can understand that the AFM rubbing clearly changes surface status of homeotropic alignment layer and causes the pretilt angle to an initial scanning direction.

• 소성∙가공
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• 제16권8호
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• pp.614-620
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• 2007

Deformation characteristics and damage evolution during warm backward extrusion of bulk AZ31 Mg alloy were investigated using finite element analyses. AZ31 Mg alloy was assumed as a hardening viscoplastic material. The tensile tests of AZ31 Mg alloy in previous experimental works showed the ductile fracture even at the warm temperature of $175^{\circ}C$. In this study, damage evolution model proposed by Lee and Dawson, which was developed based on the growth of micro voids in hardening viscoplastic materials, was combined into DEFORM 2D. Effects of forming temperature, punch speed, extrusion ratio and size of work piece on formability in warm backward extrusion as well as on mechanical properties of extruded products were examined. In general, finite element predictions matched the experimental observations and supported the analyses based on experiments. Distributions of accumulated damage predicted by the finite element simulations were effective to identify the locations of possible fracture. Finally, it was concluded that the process model, DEFORM2D combined with Lee & Dawson#s damage evolution model, was effective for the analysis of warm backward extrusion of AZ31 Mg alloys.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.209-210
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• 2006

We have successfully termed brown colored patterns inside of a transparent borosilicate glass generally known as BK7, laying the focus of near infrared Ti: sapphire femtosecond laser beam in the bulk BK7 glass. It is important to keep the laser power well below the damage threshold of BK7 in forming the color center. Thanks to the low laser power, there was no laser induced mechanical damage such as cracks or threads in the color formed area. From the absorbance spectrum and its gaussian fitting, we found the band gap of BK7, 4.21eV, and three absorption edges.

• Nuclear Engineering and Technology
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• 제46권5호
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• pp.675-680
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• 2014

Pulverization of two different sized micro-$B_4C$ particles (${\sim}10{\mu}m$ and ${\sim}150{\mu}m$) was investigated using a STS based high energy ball milling system. Shapes, generation of the impurities, and reduction of the particle size dependent on milling time and initial particle size were investigated using various analytic tools including SEM-EDX, XRD, and ICP-MS. Most of impurity was produced during the early stage of milling, and impurity content became independent on the milling time after the saturation. The degree of particle size reduction was also dependent on the initial $B_4C$ size. It was found that the STS nanoparticles produced from milling is strongly bounded with the $B_4C$ particles forming the $B_4C$/STS composite particles that can be used as a neutron absorbing nanocomposite. Based on the morphological evolution of the milled particles, a schematic pulverization model for the $B_4C$ particles was constructed.