• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2001년도 추계 기술심포지움
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• pp.146-150
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• 2001

Microwave model and high-frequency measurement of the ACF flip-chip interconnection was investigated using a microwave network analysis. S-parameters of on-chip and substrate were separately measured in the frequency range of 200 MHz to 20 GHz using a microwave network analyzer HP8510 and cascade probe. And the cascade transmission matrix conversion was performed. The same measurements and conversion techniques were conducted on the assembled test chip and substrate at the same frequency range. Then impedance values in ACF flip-chip interconnection were extracted from cascade transmission matrix. ACF flip chip interconnection has only below 0.1nH, and very stable up to 13 GHz. Over the 13 GHz, there was significant loss because of epoxy capacitance of ACF. However, the addition of SiO$_2$filler to the ACF lowered the dielectric constant of the ACF materials resulting in an increase of resonance frequency up to 15 GHz. High frequency behavior of metal Au stud bumps was investigated. The resonance frequency of the metal stud bump interconnects is higher than that of ACF flip-chip interconnects and is not observed at the microwave frequency band. The extracted model parameters of adhesive flip chip interconnects were analyzed with the considerations of the characteristics of material and the design guideline of ACA flip chip for high frequency applications was provided.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.379.1-379.1
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• 2016

Recently, new types of wearable devices such as textile electronics are considered as the next generation wearable electronics. To realize the textile electronics, conductive fibers are required to supply the power and for signal processing. Conventionally, silver nanowires (Ag NWs) have been attracted as one of the conductive additives in the fibers, however, using the Ag NWs may lead to high production cost since it is a noble metal. Many researches have been done to replace the Ag NWs into a cheaper materials such as copper nanowires (Cu NWs). Here, we synthesized ultra-long Cu NWs for a conductive filler material in conductive fibers, taking advantages of their structural features. To investigate the effect of capping agents on the aspect ratio of the synthesized Cu NWs, we used various capping agents such as hexadecylamine, butylamine, ethylenedilamine and oleylamine in the Cu NW synthesis. In this research, the effects of capping agents on the structure and the synthesis of Cu NWs are presented.

• Composites Research
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• 제30권5호
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• pp.303-309
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• 2017

Organo-montmorillonite (OMMT) has attracted much attention for fiber-reinforced polymer composites as a filler material due to high aspect ratio and low charge density. The present study focused on the fabrication of nanocomposites using Vinyl ester and Jute fabric as matrix and reinforcement respectively. The OMMT was uniformly dispersed in vinyl ester resin at 1, 2 and 3 wt%, loading through high speed mechanical stirrer at room temperature and further nanocomposites were manufactured through vacuum assisted resin infusion (VARI) technique. Effects of OMMT on the mechanical properties of vinyl ester/Jute composites were carefully investigated through tensile, bending and Izod impact tests, which revealed significant improvement in mechanical properties. The morphology of the nanocomposites after tensile test was investigated by SEM which affirmed that OMMT filled nanocomposites has improved interactions with the host matrix than the pure composites. Based on the nature and flame retardancy mechanism, the OMMT slightly improved the flammability property which was clearly explained by horizontal burning test.

• Journal of Welding and Joining
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• 제15권4호
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• pp.166-177
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• 1997

The high strength AlZnMgCu0.5 alloy is a light metal with good age hardenability, and has a high tensile and yielding strength. Therefore, it can be used for structures requiring high speciple strength. Even though high strength AlZnMgCu alloy has good mechanical properties, it has a lot of problems in TIG and MIG welding processes. Since lots of high heat absorption is introduced into the weldment during TIG and MIG processes, the microstructural variation and hot cracks take place in heat affected zone. Therefore, the mechanical properties of high strength AlZnMgCu0.5 alloy can be degraded in weldment and heat affected zone. Welding process utilizing high density heat source such as electron beam should be developed to reduce pore and hot cracking, whichare usually accompanied by MIG and TIG welding processes. In this work, electron beam welding process were used with or without AlMg4.5Mn as filler material to avoid the degradation of mechanical properties. Mechanical and metallurgical characteristics were also studied in electron beam weldment and heat affected zone. Moreover hot cracking mechanism was also investigated.

• Restorative Dentistry and Endodontics
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• 제9권1호
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• pp.127-132
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• 1983

The purpose of this study was to examine the sealing ability of the vitapex, when used with gutta-percha cone, as a root canal filling material. Fourty five canals from extracted human maxillary and mandibular teeth were randomly selected and instrumented in a conventional method with k-file. After instrumentation and dry the canal with paper points, the canals were divided into three groups and fifteen canals in each group were filled with the following materials; Vitapex, Vitapex in combination with gutta-percha cone, and Gutta-percha cone and Zinc-oxide Eugenol Cement. All the specimens were immersed in 2% methylenblue dye solution and the depth of dye penetration into the canals were evaluated by macroscope at the intervals of 1 day, 2days and 7days. The following results were obtained; 1. All the materials experimented showed varying degrees of dye penetration. 2. The canals filled with Vitapex and Vitapex in combination with gutta perch a cone revealed sudden increase of dye penetration with time passage compared to the canals obturated with Gutta-percha cone and Zinc-oxide eugenol cement. 3. In the canals filled with Vitapex, the mean dye penetration was 1.6mm at 1day, but the specimen exposed to the dye for 7days showed mean dye penetration of 9.2mm. 4. In the canals obturated with Vitapex and gutta-percha cone, the mean dye penetration was 2mm at 1day, 2.2mm at 2days, and 8mm at 7days.

• 한국조명전기설비학회지:조명전기설비
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• 제7권6호
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• pp.42-50
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• 1993

본 논문에서는 플랜트 모델에 불확실성이 존재하는 경우에도 강인 안정도를 보장하는 제어기 설계 문제를 연구하였다. 먼저 강인 안정도 및 감도 특성을 특이치 한계를 이용하여 기술하고 이들 설계 조건을 만족하는 제어기 설계 기법을 Diophantine 방정식과 감도 평가 함수의 최소화에 의해 제시하였다. Diophantine 방정식의 해를 구하기 위해 칼만 필터의 설계와 필터의 주파수 역 특성을 조사하였고, 원하는 특이치 형성을 통해 저감도 특성을 만족하는 특성 다항식 행렬을 구하였다. 그리고 제어기에 설계 자유도를 주어 감도 평가 함수를 최소화하는 제어기 매개 변수 계산 방법을 Routh 배열을 이용하여 제시하였다.제안된 강인한 제어기 설계 기법을 모델에 적용하여 검토해 본 결과 만족스러운 결과를 얻을 수 있었다.

• Transactions on Electrical and Electronic Materials
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• 제15권2호
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• pp.77-80
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• 2014

The effect of reactive diluents on the ac electrical treeing in epoxy/nanosilicate systems was studied, in a needle-plate electrode geometry. Diglycidyl ether of bisphenol A (DGEBA) type epoxy was used as a base resin, and layered silicate was used as a nano-sized filler. Polyglycol (PG) or 1,4-butanediol diglycidyl ether (BDGE) was introduced as a reactive diluent to the DGEBA/nanosilicate system, in order to decrease the viscosity of the nanocomposite system. PG acted as a flexibilizer, and BDGE acted as a chain extender, after the curing reaction. To measure the treeing propagation rate, a constant alternating current (ac) of 10 kV/4.2 mm (60 Hz) was applied to the specimen, in a needle-plate electrode arrangement, at $30^{\circ}C$ of insulating oil bath. When 10 kV/4.2 mm (60 Hz) was applied, the treeing propagate rate in the DGEBA system was $1.10{\times}10^{-3}$ mm/min, and that in the DGEBA/PG system was $1.05{\times}10^{-3}$ mm/min. As 1.5 wt% of nanosilicate was added to the DGEGA/PG system, the propagation rate was $0.33{\times}10^{-3}$ mm/min. This meant that the nano-sized layered silicates would act as good barriers to treeing propagation. The effect of chlorine content was also studied, and it was found that chlorine had a bad effect on the electrical insulation property of the epoxy system.

• Advances in concrete construction
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• 제5권3호
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• pp.241-255
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• 2017

Concrete is known to be the most used construction material worldwide. The environmental and economic aspects of Ordinary Portland Cement (OPC) containing concrete have led research studies to investigate the possibility of incorporating supplementary cementitious materials (SCMs) in concrete. Metakaolin (MK) is one SCM with high pozzolanic reactivity generated throughout the thermal activation of high purity kaolinite clay at a temperature ranging from $500^{\circ}C$ to $800^{\circ}C$. Although many studies have evaluated the effect of MK on mechanical properties of concrete and have reported positive effects, limited articles are considering the effect of MK on durability properties of concrete. Considering the lifetime assessment of concrete structures, the durability of concrete has become of particular interest recently. In the present work, the influences of MK on mechanical and durability properties of concrete mixtures are evaluated. Various experiments such as slump flow test, compressive strength, water permeability, freeze and thaw cycles, rapid chloride penetration and surface resistivity tests were carried out to determine mechanical and durability properties of concretes. Concretes made with the incorporation of MK revealed better mechanical and durability properties compared to control concretes due to combined pozzolanic reactivity and the filler effect of MK.

• Advances in materials Research
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• 제1권3호
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• pp.221-231
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• 2012

In this study, the physical and mechanical properties of bamboo fiber reinforced epoxy composites were studied. Composites were fabricated using short bamboo fiber at four different fiber loading (0 wt%, 15 wt%, 30 wt% and 45 wt%). It has been observed that few properties increases significantly with respect to fiber loading, however properties like void fraction increases from 1.71% to 5.69% with the increase in fiber loading. Hence, in order to reduce the void fraction, improve hardness and other mechanical properties silicon carbide (SiC) filler is added in bamboo fiber reinforced epoxy composites at four different weight percentages (0 wt%, 5 wt%, 10 wt% and 15 wt%) by keeping fiber loading constant (45 wt%). The significant improvement of hardness (from 46 to 57 Hv) at 15 wt%SiC, tensile strength (from 10.48 to 13.44 MPa) at 10 wt% SiC, flexural strength (from 19.93 to 29.53 MPa) at 5 wt%SiC and reduction of void fraction (from 5.69 to 3.91%) at 5 wt%SiC is observed. The results of this study indicate that using particulate filled bamboo fiber reinforced epoxy composites could successfully develop a composite material in terms of high strength and rigidity for light weight applications compared to conventional bamboo composites. Finally, SEM studies were carried out to evaluate fibre/matrix interactions.

• Journal of Welding and Joining
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• 제34권5호
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• pp.26-32
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• 2016

In this study, Hot-wire laser welding (HWLW) without keyhole which deposits filler material by feeding hot wire into the process zone has been performed to increase process performance. From the analysis of High Speed Imaging (HSI), for higher voltage, the process is prone to arc formation and drop transfer, which is disagreeable transfer mode. It is necessary that arc formation and drop (globular) transfer should be avoided by lower voltage. Therefore, continuous wire melting and transfer mode is preferred when adopting this process. The HWLW technique has high potential in terms of performance, precision, robustness and controllability for thick section of narrow gap.