• Journal of Welding and Joining
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• 제27권4호
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• pp.73-78
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• 2009

Characterization of the microweld CCFL electrode for the TFT-LCD backlight unit was carried out in terms of the glass beading heat treatment conditions. We evaluate the weld zone and parent metal of the microweld CCFL electrodes that were exposed to simulated glass beading heat treatment. The CCFL electrode was composed of the cup made with pure Ni, the pin made with pure Mo and the lead wire made with Ni-Mn alloy. Each part of the electrode was assembled together by micro spot welding process and then the assembled electrodes were exposed to simulated glass beading temperatures of $700^{\circ}C,\;750^{\circ}C$ and $800^{\circ}C$. The microstructures of the microweld CCFL electrode were observed by using optical microscope, scanning electron microscope and EDS. Micro-tensile and microhardness test were also carried out. The results indicated that the grain coarsening in the HAZs(heat affected zones) for both the cup-pin weld and pin-lead wire were exhibited and the grain coarsening of the HAZ for the cup and the lead wire was more obvious than the HAZ of the pin. The micro-tensile test revealed that the fracture occurred at the cup-pin weld zone for all test conditions. The fracture surface could be classified into two parts such as pin portion and cup portion including weld nugget. The failure was seemed to be initiated from the boundary between nugget and pin through the weld joint. The result of the microhardness measurement exhibited that the relatively low hardness value, about 105HV was recorded at the HAZ of the cup. This value was about 50% less than that of the original value of the cup. The reduction of the microhardness was considered as the cause of the grain coarsening due to welding process. It was also appeared that there was no change in electric resistance for the standard electrodes and heat treated electrodes.

• Restorative Dentistry and Endodontics
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• 제39권1호
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• pp.24-31
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• 2014

Objectives: The purpose of present study was to evaluate the internal adaptation of composite restorations using different adhesive systems. Materials and Methods: Typical class I cavities were prepared in 32 human third molars. The teeth were divided into the following four groups: 3-step etch-and-rinse, 2-step etch-and-rinse, 2-step self-etch and 1-step self-etch system were used. After the dentin adhesives were applied, composite resins were filled and light-cured in two layers. Then, silver nitrate solution was infiltrated, and all of the samples were scanned by micro-CT before and after thermo-mechanical load cycling. For each image, the length to which silver nitrate infiltrated, as a percentage of the whole pulpal floor length, was calculated (%SP). To evaluate the internal adaptation using conventional method, the samples were cut into 3 pieces by two sectioning at an interval of 1 mm in the middle of the cavity and they were dyed with Rhodamine-B. The cross sections of the specimens were examined by stereomicroscope. The lengths of the parts where actual leakage was shown were measured and calculated as a percentage of real leakage (%RP). The values for %SP and %RP were compared. Results: After thermo-mechanical loading, all specimens showed significantly increased %SP compared to before thermo-mechanical loading and 1-step self-etch system had the highest %SP (p < 0.05). There was a tendency for %SP and %RP to show similar microleakage percentage depending on its sectioning. Conclusions: After thermo-mechanical load cycling, there were differences in internal adaptation among the groups using different adhesive systems.

• 박물관보존과학
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• 제11권
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• pp.9-16
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• 2010

국립춘천박물관은 고려 철제석가여래좌상의 부식방지와 상설전시 활용을 위하여 보존처리를 실시하였다. 처리 전 유물의 상태는 부식으로 인한 표면 박락현상이 관찰되었고 가부좌의 오른편 둔부에서 다리부분까지 결손되어 정상적인 전시가 불가능 하였다. 따라서 표면의 이물질을 제거하고 강화·보호 위한 강화처리 작업이 진행되었다. 강화처리 진행에 앞서 국내·외 연구 자료를 바탕으로 micro crystalline wax계를 선정하여 기초 실험을 실시하였다. 그 결과 (주)동남유화의 wax(in xylene) 5wt%가 백화현상과 표면 색상변화가 적으며 작업에 편리성이 높아 강화제로 선택하여 부식을 억제하였다. 결손부분의 복원은 내부 지지대 제작과 함께 epoxy계 수지를 이용하여 탈착이 가능한 복원을 실시하여 전시 효용성을 높였다.

• 열처리공학회지
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• 제21권4호
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• pp.183-188
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• 2008

Hot press forming allows geometrically complicated parts to be formed from sheet and the rapid cooling hardens them to extremely high strength. The main purpose of this research is to characterize Al coated layer in Al coated boron steel during hot press forming. For the hot press hardening experiment, test specimens were heated up to $810{\sim}930^{\circ}C$ and held for 3, 6 and 9 minutes, respectively. And then, some specimens were press hardened and others were air-cooled without any pressing for the comparison purpose. Al coated layer shows four distinct micro-structural regions of interest; diffusion zone, Al-Fe zone(I) low-Al zone(LAZ) and Al-Fe zone(II). Band-like LAZ is clearly shown at temperature ranges of $810{\sim}870^{\circ}C$ and sparsely dispersed at temperature higher than 900oC. The micro-cracking behavior in the Al coated layer during forming were also analyzed by bending and deep drawing tests. The strain concentration in softer LAZ is found to be closely related with micro-cracking and exfoliation in coated layer during forming.

• Journal of Platform Technology
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• 제8권1호
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• pp.24-32
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• 2020

본 논문은 SMT라인의 핵심 기술인 칩마운터의 보급을 위해 교육연구용이나 샘플제작을 목적으로 사용이 가능한 3D 프린터 기술기반의 칩마운터를 설계하고 제작하였다. 저가형 구동부 설계를 위해 오픈루프제어가 가능한 스텝모터를 사용하였다. 스텝모터 사용으로 발생하는 모터의 진동, 탈조 등의 특성상 단점은 마이크로스텝제어 방법을 이용하여 보완하였다. 칩마운터 실험은 제작한 소형 칩마운터에 거버파일을 생성하고 실제 크기로 프린트하여 샘플보드 제작과 동일한 방법으로 HASL 처리되어 있는 PCB에 솔더크림을 프린팅한 후 부품을 실장하여 여러 번 반복해서 수행하였다. 실험결과 2012 미소부품과 달리 보정이 필요한 SOIC, TQFP 등의 부품은 부품 실장 시간이 2배정도 길었지만 비교적 정확히 실장되는 것을 확인할 수 있었다. 또한, 초기 위치에 대한 오차를 총 10회에 반복하여 측정한 결과 약 0.110mm의 비교적 적은 오차가 발생함을 확인할 수 있었다.

• Design & Manufacturing
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• 제17권4호
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• pp.42-51
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• 2023

In this study, we investigated the injection molding technology of thick-walled light guides, which are parts that control the light source of automotive lamps. Through injection molding analysis, the gate position that can minimize product shrinkage and deformation was selected, and a mold reflecting the analysis results was manufactured to evaluate the effect of injection speed and holding pressure on transferability during micro-pattern molding through experiments. When designing an injection mold for products with varying thicknesses, it was found that installing the gate on the side of the thicker part was advantageous for reducing volume shrinkage and deformation. It was found that the effect of shrinkage due to thickness may be greater than the position of the gate on pattern transferability. The pattern transfer error decreased as the injection speed and holding pressure increased, and it was found that increasing the injection speed was relatively effective.

• 한국문화재보존과학회:학술대회논문집
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• 한국문화재보존과학회 2004년도 제20회 발표논문집
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• pp.137-153
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• 2004

We have analyzed the ingredients of 17 pieces of Bronze Age bronze ware, and an additional 22 pieces of Koryo and Chosun dynasty bronze ware. We have also conducted analysis of the extraction sites where these bronze ware items were found. For analyzing the main ingredient the bronze ware items have been divided into 3 groups - Cu-Sn(70?75:20), Cu-Pb-Sn(70:10:10), Cu-Pb-Sn(60:10:20) type respectively. In tile cases of the Cu-Pb-Sn groups the division comes down to differences in the Cu content as the main component, and elements such as Ni, Fe, Co contribute as a micro ingredient. The geographical and periodic characteristics of ancient bronze ware items show that theircompositional element changes from Cu:Sn to Cu:Pb:Sn and the Cu content decreases with the period,while the Pb content increases with the period. Bronze ware items from Suchon Ri, Gongju (that were used in 3 B.C.) form very different categories from 3rd ${\~}$ 2nd B.C.. They additionally formed very different categories from those bronze ware items analyzed in this research. These bronze ware itemsare shown to be geographically close and periodically overlapped, but made of a new elemental composition. This shows an inflow of a production technical culture present in the new bronze wares. The main component content of Cu is lower, and the Co and Fe contents (as microelements) are much higher than that of other bronze ware items. Such facts showthat those bronze ware items used completely different materials from bronze ware items in other cultural areas, or that there were differences in smelting techniques In the places where ancient bronze ware items have been extracted, it is presumed that the materials originated from the southern parts of Korea andnorthern parts and southern parts of China. .As more bronze ware scientific research is compiled one can conclude that that there will be enough scientific evidence to study the Bronze Age culture of Koreasystematically.

• Design & Manufacturing
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• 제14권4호
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• pp.71-77
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• 2020

Various manufacturing technologies, including over-molding and insert-injection molding, are used to produce hybrid plastics and metals. However, there are disadvantages to these technologies, as they require several steps in manufacturing and are limited to what can be reasonably achieved within the complexities of part geometry. This study aims to determine a practical approach for producing metal/plastic hybrid components by combining plastic injection molding and metal die casting to create a new hybrid metal/plastic molding process. The integrated metal/plastic hybrid injection molding process developed in this study uses the proven method of multi-component technology as a basis to combine plastic injection molding with metal die casting into one integrated process. In this study, the electrical conductivity and ampacity were verified to qualify the new process for the production of parts used in electronic devices. The electrical conductivity was measured, contacting both sides of the test sample with constant pressure, and the resistivity was measured using a micro ohmmeter. Also, the specific conductivity was subsequently calculated from the resistivity and contact surface of the conductor path. The ampacity defines the maximum amount of current a conductive path can carry before sustaining immediate or progressive deterioration. The manufactured hybrid multi-components were loaded with increasing currents, while the temperature was recorded with an infrared camera. To compare the measured infrared images, an electro-thermal simulation was conducted using commercial CAE software to predict the maximum temperature of the power loaded parts. Overall, during the injection molding process, it was demonstrated that multifunctional parts can be produced for electric and electronic applications.

• Journal of Plant Biotechnology
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• 제35권3호
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• pp.235-243
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• 2008

본 연구에서는 배추 원형질체 배양에 있어 다양한 처리의 효과를 구명함으로써 배추 원형질체 배양을 통한 재분화 체계를 확립하고자 하였다. 배추 원형질체 분리 수율은 효소액, 사용된 조직 및 효소액 처리 시간에 따라 달리 나타났는데, 효소액 처리 약 7시간 이후부터는 분리되는 원형질체의 수가 크게 증가하지 않았다. 따라서 효소 자체에 의한 부정적 영향을 고려하였을 때 최장 7시간 동안 효소처리를 하는 것이 적정한 것으로 판단하였다. 떡잎유래 원형질체를 2,4-D 1.0 mg/L, NAA 0.5 mg/L 및 BA 1.0 mg/L 첨가 액체배지에서 배양하였을 때 초기 세포분열과 이어지는 micro-callus 생장이 가장 양호하였다. 다양한 배추 인자형에 대한 검토 결과 본 연구의 배양조건 하에서는 초기 세포분열과micro-callus 생장이 배추 인자형에 따라 뚜렷하게 영향을 받는 것으로 나타났다. 노랑봄 품종의 떡잎에서 분리한 원형질체로부터 생장한 micro-callus 현탁액을 zeatin 0.2 mg/L외 spermidine 0.1 mM이 첨가된 반고체 MS 배지에 plating하였을 때 가장 왕성하게 callus colony가 형성 및 생장하였다. 이들 callus colony는 BA 5.0 mg 및 NAA 1.0 mg/L가 첨가된 배지에서 4.3%의 빈도로 재분화 신초가 유도되었다 얻어진 신초는 PGR 무첨가 MS배지에서 손쉽게 발근하였고 발근된 식군체는 기외에서 정상 식물체로 생장하였다. 본 연구의 결과는 배추 단독 원형질체 배양을 통한 고빈도 식물체 재분화 연구에 중요한 정보를 제공함으로써 유용하게 활용될 것으로 사료된다.

• Composites Research
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• 제31권5호
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• pp.209-214
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• 2018

본 연구에서는 친환경적이고 공급이 안정적인 소재를 찾기 위하여, Bio waste인 쌀겨와 조개 껍질에서 활용하여 마이크로 사이즈의 미세 입자를 추출하고, 추출한 입자의 크기와 형상을 분석한 후 CFRP에 첨가하여 물성의 변화를 관찰하였다. 쌀겨와 탄화 쌀겨의 주요구성성분은 탄소, 산소, 규소로 이루어졌으며 탄화과정을 거치면서 탄소와 규소의 비율이 증가함을 확인하였고, 조개 껍질 분말에서는 탄소 산소와 칼슘이 검출되었으며 이는 조개 껍질의 주요구성물질인 탄산칼슘의 영향으로 보인다. 쌀겨 분말의 면적평균은 $6.19{\mu}m$ 체적평균은 $14.77{\mu}m$으로 FE-SEM을 통하여 막대형상의 입자가 관찰되며 이는 쌀겨가 가지고 있던 껍질부분의 주름이나 표면의 털이 남아있는 형상으로 보인다. 탄화쌀겨의 분말은 면적평균은 $1.55{\mu}m$ 체적평균은 $8.20{\mu}m$ 조개 껍질 분말은 면적평균은 $2.53{\mu}m$ 체적평균은 $5.79{\mu}m$로 분석되었으며 쌀겨분말의 경우 막대(Rod)형상의 입자들이 관찰되었고, 조개 껍질 분말의 경우 판상(Plate)의 형상을 가지는 것으로 관찰되었다. CFRP에 첨가하였을 경우 첨가량에 비례하여 물성의 하락이 관찰되었는데 그 폭이 쌀겨분말의 경우가 가장 컸으며, 조개 껍질 분말의 경우 물성하락을 거의 유발하지 않음을 확인하였다.