• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.133-140
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• 2019

The effects of thermal cycle conditions on the bonding strength and crack propagation behaviors in electroplated Cr/electroplated Ni-P coatings were systematically evaluated. 1^st heat treatment was performed at 500℃ for 3 hours after electroplating Ni-P, and then, 2^nd heat treatment was performed at 750℃ for 6 hours after electroplating Cr. The measured bonding strength by ASTM C633 were around 25.6 MPa before thermal cycling, while it increased to 47.6 MPa, after 1,000 cycles. Increasing thermal cycles led to dominant fail mode with cohesive failure inside adhesive, which seemed to be closely related to the increasing bonding strength possibly not only due to higher Cr surface roughness, but also to penetrated channeling crack density. Also, increasing density of penetrated channeling cracks in electroplating Cr layer led to slightly stronger bonding strength due to mechanical interlocking effects of adhesive inside channeling cracks.

• Korea journal of population studies
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• v.20 no.2
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• pp.5-42
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• 1997

This study contributes to understanding women's labor market behavior by focusing on a particular set of labor force transitions - labor force withdrawal and entry during the period surrounding the first birth of a child. In particular, this study provides a dynamic analyses, using longitudinal data and event history analysis, to conceptualize labor force behaviors in a straightforward way. The main research question addresses which factors increase or decrease the hazard rates of leaving and entering the labor market. This study used piecewise Gompertz model, following the guide of the non-parametric analysis on the hazard rates, which allowed relatively detailed description on the distribution of timing of leave and entry to the labor market as parameters of interest. The results show that preferences and structural variables, as well as economic considerations, are very important factors to explain the labor market behavior of women in the period surrounding childbirth.

• Korean Journal of Materials Research
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• v.8 no.10
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• pp.938-944
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• 1998

$MoSi_2$/W composites were fabricated by vacuum hot press at $1600^{\circ}C$ under 30MPa for 3 hrs. The effects of the amount of tungsten in the composites was explained in terms of the microstructure and mechanical properties. Although tungsten was mainly substituted to Mo atoms forming a complete solid solution of (Mo.W).Si, (x= 1, 5, y=2, 3). the grain size of composites became smaller with the increase of tungsten added. Vickers hardness was increased with the increase of tungsten content due to the solid-solution hardening. On the other hand, toughness of composites decreased sharply by increasing the amount of tungsten. Optimum tungsten amount was determined to be a 10 vol% of composite. Indentation fracture toughness was calculated to be 4.5MPa\sqrt{m}$ in this composites, compared with $2.7MPa\sqrt{m}$ in pure $MoSi_2$.

• Journal of Biomedical Engineering Research
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• v.22 no.6
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• pp.511-518
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• 2001

In vitro corrosion resistance of the commercially used 76.5wt.%Pd-17.6%Cu-7.2%Ga and 77.3%Pd-6.0%Ga dental Prostheses high-Palladium system alloys in cast, degassing and porcelain-firing heat treatment conditions were evaluated by the potentiodynamic polarization technique in the de-aerated 0.9%NaCl and a modified Fusayama electrolyte. From the corrosion rate experimental results, we found that there is a small difference in the corrosion resistance depending on the microstructure. However. it was so small that there is no significant problem as a dental material. The 77.3%Pd-6.0%Ga showed better corrosion resistance than the 76.5%Pd-11.6%Cu-7.2%Ga dental Prostheses high-palladium system alloys. These experimental observations in 76.5%Pd-11.6%Cu-7.2%Ga alleys are mainly due to a rapid quenching and Cu in the alloy which accelerate the eutectic reaction with a segregation and Precipitates in the microstructure. On the ocher hand, 77.3%Pd-6.0%Ga alloys, which are solid-solution matrix, show much better col·lesion resistance compared with that of 76.5%Pd-11.6%Cu-7.2%Ga alloys.

• Journal of the Korea Convergence Society
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• v.11 no.9
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• pp.359-366
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• 2020

The purpose of this study was to find out the differences in the teaching methods of elementary, middle and high school physical education teachers for online physical education classes and the improvement of online education. To this end, an online questionnaire was conducted for 166 physical education teachers belonging to the Busan Metropolitan Physical Education Research Association community, and cross-analysis were conducted. There search results are as follows. First, there was no difference in gender, starting with online school. Second, there were differences in the method sand motivation so online physical education classes according to the type of employment, and there was no difference in improvement. Third, there was significant difference in the motivation for online physical education classes according to the teaching career. Based on these research results, it is expected that various efforts will be needed to promote the adaptation and improvement of education and teachers for online physical education classes.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.236-236
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• 2010

알루미늄 자체에 대한 질화 기술의 어려움 때문에 현재까지는 AlN 분말을 이용한 소결 공정을 통하여 주요 부품의 제작이 되어 왔으며. Al 질화 기술보다는 아노다이징과 같은 표면 산화 공정 또는 도금과 같은 기술이 선호되어 왔다. 알루미늄 질화 기술이 잘 사용되지 않았던 이유는 알루미늄 표면에 2 5 nm 두께로 존재하는 치밀한 산화층의 높은 안정성 때문에 질화반응이 어렵기 때문이다. 이 알루미늄 산화물의 안정성은 질화물에 비교하여 5 배까지 높으며, 이런 경향은 온도가 높아짐에 따라 더욱 커지기 때문이다. 특히, 알루미늄의 낮은 기계적 물성을 향상시키기 위해서는 충분히 깊은 두께로 형성되어야 할 필요성이 높으나 알루미늄에 대한 질소의 고용도가 거의 없고 확산 계수가 매우 낮기 때문에 충분히 두꺼운 질화층의 형성이 어렵기 때문이다. 결국, 알루미늄 질화가 가능하기 위해서는 표면의 산화층을 없애야 하며, 알루미늄이 AlN이 되려는 속도는 $Al_2O_3$를 만드려는 속도보다 매우 느리므로, 잔존 산소량을 최소화 할 필요성이 있어서 고진공 분위기에서 처리되어야 한다. 일반적으로 알루미늄 질화를 위해서는 $10^{-6}\;torr$ 이하의 고진공도의 챔버가 필요하며 고순도의 반응 가스를 사용하여야 한다. 그러나 이러한 고진공하에서는 낮은 이온밀도 때문에 신속질화가 기존의 공정시간인 20시간동안, AlN층이 5um이하로 형성되었다. 본 연구에서, 알루미늄의 질화에 있어서, 표면층에 높은 전류를 걸어주어, 용융상태로 만들어주는 것이 좋다는 연구 결과를 얻었으며, 이를 토대로 신속질화를 위하여 전류밀도(전력량)에 따라 알루미늄 질화층의 형성 정도를 연구하였다. SEM, EDS, XRD등을 통해 Al의 표면에 플라즈마 질화를 통해 Al에 질소의 함유량이 증가하는 것을 확인하였으며 광학현미경을 통해 질화층의 두께와 표면조직을 확인하였다. Al 시편의 표면을 효과적으로 활성화할 수 있는 $400^{\circ}C$ 이상의 온도에서 전류밀도(전력량)와 시간의 변화에 따라 질화층이 효과적으로 형성되는 조건과 시간에 따라 두께가 증가하는 경향을 확인할 수 있었다. 이러한 신속 질화 공정을 통해 2시간 이내의 질화를 통해 40um이상의 AlN층을 형성할 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.165-165
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• 2013

희토류 발광 물질은 4f 껍질에 위치하는 전자의 독특한 특성 때문에 발광 소자와 디스플레이에 그 응용성을 확장하고 있다. 본 연구에서는 고효율의 적색과 주황색 형광체를 합성하기 위하여 모체 격자 CaNb2O6에 희토류 이온인 유로퓸과 사마륨을 치환 고용하여 최적의 합성 조건을 조사하였다. Ca1-1.5xNb2O6:REx3+ (RE=Eu, Sm) 형광체 분말 시료는 고상반응법을 사용하여 활성제 이온인 Eu3+와 Sm3+의 농도비를 0, 0.01, 0.05, 0.10, 0.15, 0.20 mol 로 변화시키면서 합성하였다. 초기 물질 CaO, Nb2O5, Eu2O3와 Sm2O3을 화학 적량으로 측정하고, 400 rpm의 속도로 24시간 밀링 작업을 수행한 후에, 건조기 $60^{\circ}C$에서 28시간 건조하고, 시료를 막자 사발에서 갈아 세라믹 도가니에 담아 튜브형 전기로에서 분당 $5^{\circ}C$의 비율로 승온시켜 $500^{\circ}C$에서 5시간 동안 하소와 $1,100^{\circ}C$에서 6시간 소결하여 합성하였다. Eu3+가 도핑된 경우에, 발광 스펙트럼은 Eu3+ 이온의 농도비에 관계없이 강한 적색 발광 스펙트럼이 616 nm에서 관측되었다. 이외에도, 596 nm와 708 nm에서 상대적으로 발광 세기가 약한 주황색 발광과 적색 발광 신호가 검출되었으며, 541 nm에서는 매우 약한 녹색스펙트럼이 관측되었다. Eu3+ 이온의 농도비에 0.01 mol에서 0.15 mol로 증가함에 따라 주발광 신호의 세기는 점점 증가하였으며, 0.15 mol에서 최대 발광 세기를 나타내었다. Eu3+ 이온의 농도비가 0.20 mol 로 더욱 증가함에 따라 주 피크의 세기는 농도 소강 현상에 의하여 현저히 감소함을 보였다. 한편, 주된 흡광 스펙트럼은 279 nm에서 나타났는데, 이것은 전하전달밴드 신호이다. Sm3+가 도핑된 형광체 분말의 발광 스펙트럼은 모든 시료의 경우에 613 nm에서 강한 적주황색 발광 스펙트럼이 관측되었고, 상대적으로 세기가 약한 570 nm와 660 nm에 피크를 갖는 황색과 적색 발광 스펙트럼이 발생하였다. 흡광과 발광 스펙트럼의 최대 세기는 0.05 mol에서 나타났으며, Sm3+ 이온의 농도비가 더욱 증가함에 따라 흡광과 발광 세기는 급격하게 감소하였다.

• Journal of the Korean Society for Library and Information Science
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• v.51 no.1
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• pp.69-102
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• 2017

In this study, the Department of Library & Information Science's Students are including their cognitive for the employment prospects of library information, it wants to know satisfaction with current curriculum, job preparation, and requirements for job - related programs. The result, first of all, the students of the field of employment hope was that the library was the field of employment and the public library was the highest one of them. Second, areas of employment were that the Seoul Gyeonggi-do Province showed the highest regardless of the location of the university. Third, the satisfaction of the university curriculum is high, It appeared to be desirable that was field - based employment program. Fourth, The difficulty in preparing for employment was the lack of employment information. Fifth, The factors influencing job choice were working conditions, retirement benefits, welfare benefits, and remuneration. Therefore, to increase the employment rate of students, it was required by the establishment of job information system, reinforcement of field - based training courses, and improvement of local employment conditions and the environment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.2545-2552
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• 2014

This study is aiming to suggest the effective thermal management system design technologies for the high voltage and capacity battery system of the electricity driven vehicles and introduce the theoretical designing methods. In order to investigate the effective operation of the battery system for the electricity driven vehicles, the heat generation model for Li-ion battery system using the chemical reaction while charging and discharging was suggested and the thermal loads of the heat sources (air or liquid) for cooling and heating were calculated using energy balance. Especially, the design methods for the cooling and heating of the battery system for maintaining the optimum operation temperature were investigated under heating, cooling and generated heat (during charging and discharging) conditions. The battery thermal management system for the effective battery operation of the electricity driven vehicles was suggested reasonably depending on the variation of the season and operation conditions. In addition, at the same conditions under summer season, the cooling method using the liquid and active cooling technique showed a relatively high capacity, while cooling method using the passive cooling technique showed a relatively low capacity.

• Journal of the Korean Electrochemical Society
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• v.22 no.2
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• pp.60-68
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• 2019

High-voltage operation of the lithium ion battery is one of the advantageous approaches to obtain high energy capacity without changing the conventional cell components and structure. However, operating at harsh condition inevitably results in severe side reactions at the electrode surface and structural disintegration of active material particles. Herein we coated layers composed of $Al_2O_3$ and ZnO on the electrode based on NCM using atomic layer deposition (ALD). Thicker layers of novel Al-doped ZnO (AZO) coating compared to conventional ALD coated layers are prepared. Cathode based on NCM with the varying AZO coating thickness are fabricated and used for coin cell assembly. Effect of ALD coating thickness on the charge-discharge cycle behavior obtained at high-voltage operation was investigated.