• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.05a
• /
• pp.47-51
• /
• 2001

The structural properties of varistors surface studied by fractal phenomenon were investigated to verify the relations of electrical characteristics. The SEM photograph of varistors surface were changed by binary code and the grain shape of that were analyzed by fractal dimension. The void of varistors surface was found by fractal program. The relation between grain density and electrical properties depend on fractal dimension. The grain size in varistors surface was decreased by increasing of oxide antimony addition. The grain size of devices by oxide antimony addition were from 5 to $10[{\mu}m]$. The fractal dimension and electrical properties of varistors surface was related to between grain boundary and grain density. The grain size was decreased by increasing of fractal dimensions.

• The KSFM Journal of Fluid Machinery
• /
• v.2 no.3 s.4
• /
• pp.37-44
• /
• 1999

In a screw-type centrifugal pump, the pump head deteriorates from single-phase flow to the choke due to an increased air entrainment at a wide tip clearance compared to that of a narrow tip clearance. Moreover, at a narrow tip clearance, the pump head became partially higher in a two-phase flow than that of a single-phase flow near the best efficiency point in low void fraction region. Therefore, we observed the internal flow pattern by using a stroboscope and we measured the mean size of bubbles from the images obtained with a high speed camera. Then, we investigated the influences of the mean size of bubbles, tip clearances and flow patterns on pump performance.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.30 no.4
• /
• pp.79-84
• /
• 1998

The process of double coating consists of bottom coating using relatively coaser pigments to improve characteristics of base paper and top coating using finer pigments to cover unevenness of the bottom coating and to give various function of the coated paper. The structure of precoating is influenced not only by its components, but also characteristics of base paper, Moreover pore size and its size distribution of precoating are expected to influence the top coating properties, but this is not well understood. Coating and printing operations involve the application of pigmented fluid on top of a porous substrate. The porosity of the substrate has been shown to influence the properties of the coating, but a good understanding of the mechanisms is lacking in the literature. The role of pore size and void volume on top coating structure is unclear.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.1
• /
• pp.51-59
• /
• 2008

In this study, cyclic shear characterics of sand-clay mixtures were analyzed. In order to perform cyclic triaxial tests on sand clay mixtures, natural clays with activity and silica sand were mixed variously to reproduce soils with wide range of grain size compositions. Test specimens with various fines contents were prepared by the moisture compaction and pre-consolidation methods, while paying attention to the void ratio expressed in terms of the sand structure and clay structures, and undrained cyclic shear tests were performed. In the test results, cyclic shear strength decreased with increasing of sand granular void ratio below 20% of fine contents. When the granular void ratio of the test specimen exceeded the maximum void ratio of the silica sand, the clay matrix dominated the soil structure, and soil structures were not influenced by compaction energy. It was observed that, the matrix structure of the coarse particles has great effect on the undrained cyclic shear strength characteristics for sand-clay mixtures, and therefore, it is more appropriate to pay more attention to the density of the sand structure, rather than to the fines content.

• International Journal of Concrete Structures and Materials
• /
• v.18 no.2E
• /
• pp.117-124
• /
• 2006

Porous concrete has been used recently for the purpose of decreasing the load on the earth environment. It consists solely of cement, water and coarse aggregate of uni form size. Its fundamental properties are considerably affected by the physical properties of aggregate because the aggregate is the main material for the most part in its mix proportion. Because of this reason, this study carried out an investigation of the influence of the size and type of aggregate on the fundamental properties of porous concrete. It is shown that the fundamental properties of porous concrete was seldom affected by the size of aggregate except for the case of using $2.5{\sim}5mm$ aggregate but varied significantly by the type of aggregate. In particular, the compressive strength of porous concrete using $2.5{\sim}5mm$ aggregate was much higher than that using other aggregate, and its void ratio and coefficient of permeability was lower. Moreover, the capacity to maintain the permeability of porous concrete was found to vary by the size and type of aggregate. Of particular notice was that it decreased greatly when $2.5{\sim}5mm$ aggregate was used. Unlike ordinary concrete, porous concrete exhibited very high dynamic modulus of elasticity at early age and continued to increase but slowly afterwards.

• Journal of the Korean GEO-environmental Society
• /
• v.9 no.1
• /
• pp.27-31
• /
• 2008

In this study, evaluation of samples' reflection of in-situ condition was performed for those by 225 mm KICT large sampler and NX size piston sampler. Disturbance analysis was conducted for the clay sampled by two kinds of sampler throughout consolidation tests, uniaxial tests and triaxial test, under the same condition. From the analysis it can be seen that not only the initial void ratio and preconsolidation pressure from KICT large sampler but strength parameters from both uniaxial and triaxial compression tests are also about 10% higher than those of NX size piston sampler's.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.10b
• /
• pp.1303-1308
• /
• 2000

Detection of square shape voids with size 30$\times$20$\times$5cm and 20$\times$20$\times$20cm in concrete were carried out by ultrasonic image processing technique. The advantages and limitations of this technique for non-destructive inspection of square shape voids in concrete are investigated. In this study, it has been verified that the semi-direct measurement method is more effective than the other methods for detecting the voids in concrete using ultrasonic image processing method.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.6 no.3
• /
• pp.118-125
• /
• 2011

The size and distribution of concrete void was one among the factor determining durability of concrete. Recently, there was a lot of researches related to the High-Fludity Concrete(HFC) with field applications. However, the research about the void structure having an effect on durability of concrete is insufficient. Therefore, in this research, Conventional Concrete(CC) and HFC using lime stone powder and fly-ash of 30 MPa range was manufactured and observed the void structure of CC and HFC. Experimental results showed that average pore diameter in the case of the 30 MPa range HFC was to be lower than CC and SEM analyzed result, HFC was firmer inner structure than CC.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2016.11a
• /
• pp.128-128
• /
• 2016

Cu 배선폭 미세화 기술은 반도체 디바이스의 성능 향상을 위한 핵심 기술이다. 현재 배선 기술은 lithography, deposition, planarization등 종합적인 공정 기술의 발전에 따라 10x nm scale까지 감소하였다. 하지만 지속적인 feature size 감소를 위하여 요구되는 높은 공정 기술 및 비용과 배선폭 미세화로 인한 재료의 물리적 한계로 인하여 배선폭 미세화를 통한 성능의 향상에는 한계가 있다. 배선폭 미세화를 통한 2차원적인 집적도 향상과는 별개로 chip들의 3차원 적층을 통하여 반도체 디바이스의 성능 향상이 가능하다. 칩들의 3차원 적층을 위해서는 별도의 3차원 배선 기술이 요구되는데, TSV(through-Si-via)방식은 Si기판을 관통하는 via를 통하여 chip간의 전기신호 교환이 최단거리에서 이루어지는 가장 진보된 형태의 3차원 배선 기술이다. Si 기판에 $50{\mu}m$이상 깊이의 via 및 seed layer를 형성 한 후 습식전해증착법을 이용하여 Cu 배선이 이루어지는데, via 내부 Cu ion 공급 한계로 인하여 일반적인 공정으로는 void와 같은 defect가 형성되어 배선 신뢰성에 문제를 발생시킨다. 이를 해결하기 위해 각종 유기 첨가제가 사용되는데, suppressor를 사용하여 Si 기판 상층부와 via 측면벽의 Cu 증착을 억제하고, accelerator를 사용하여 via 바닥면의 Cu 성장속도를 증가시켜 bottom-up TSV filling을 유도하는 방식이 일반적이다. 이론적으로, Bottom-up TSV filling은 sample 전체에서 Cu 성장을 억제하는 suppressor가 via bottom의 강한 potential로 인하여 국부적 탈착되고 via bottom에서만 Cu가 증착되어 되어 이루어지므로, accelerator가 없이도 void-free TSV filling이 가능하다. Accelerator가 Suppressor를 치환하여 오히려 bottom-up TSV filling을 방해한다는 보고도 있었다. 본 연구에서는 유기 첨가제의 치환으로 인한 TSV filling performance 저하를 방지하고, 유기 첨가제 조성을 단순화하여 용액 관리가 용이하도록 하기 위하여 suppressor만을 이용한 TSV filling 연구를 진행하였다. 먼저, suppressor의 흡착, 탈착 특성을 이해하기 위한 연구가 진행되었고, 이를 바탕으로 suppressor만을 이용한 bottom-up Cu TSV filling이 진행되었다. 최종적으로 $60{\mu}m$ 깊이의 TSV를 1000초 내에 void-free filling하였다.

• KIEAE Journal
• /
• v.10 no.3
• /
• pp.89-96
• /
• 2010

In comparison with ordinary or heavy-weight concrete, light-weight air void concrete has the good aspects in optimizing super tall structure systems for the process of design considering wind load and seismic load by lightening total dead load of buildings and reducing natural resources used. Light-weight air void concrete has excellent properties of heat and sound insulating due to its high amount porosity of air voids. So, it has been used as partition walls and the floor of Ondol which is the traditional Korean floor heating system. Under the condition of which the supply of light-weight aggregates are limited, the development of light-weight concrete using air voids is highly required in the aspects of reduced manufacturing prices and mass production. In this study, we investigated the physical properties and thermal behaviors of specimens that applied different mixing ratios of foaming agent to evaluate the possibility of use in the structural elements. We proposed the estimating equation for compressive strength of each mix having different ratio of foaming agent. We also confirmed that the density of cement matrix is decreased as the mixing amount of foaming agent increase up to 0.6% of foaming agent mixing ratio which was observed by SEM. Based on porosity and compressive strength of control mortar without foaming agent, we built the estimating equations of compressive strength for mortars with foaming agent. The upper limit of use in foaming agent is about 0.6% of the binder amount. Each air void is independent, and size of voids range from 50 to $100{\mu}m$.