• 대한토목학회논문집
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• 제30권2C호
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• pp.85-93
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• 2010

전단 강성은 지반 거동을 이해하기 위한 필수적인 요소로 인식되고 있으며, 특히 탄성계수 및 간극비는 구조물의 기본적인 설계 정수로서 그 중요성이 점차 증가하고 있다. 본 연구의 목적은 전단파와 압축파 같은 탄성파 및 전기비저항 측정이 가능한 현장 탄성파 및 전기비저항 측정 장비(FVRP)를 개발하고, 이를 이용하여 대상지반의 탄성계수 및 간극비를 산정하는 것이다. 압축파 및 전단파는 각각 피에조 디스크 엘리먼트와 벤더 엘리먼트를 이용하여 측정하였다. 그리고 전기비저항은 소형 전기비저항 측정 프로브를 제작하여FVRP 선단에 설치하여 측정하였다. 개발된 장비는 실내의 대형토조와 현장에 적용되었다. 대형 토조실험의 경우, 모래와 점토를 슬러리 상태에서 혼합하여 지반을 조성한 후 상재하중을 가하여 조성된 지반을 압밀 시킨 후 진행되었으며, 탄성파 및 전기비저항의 측정은 매 심도 1cm 간격으로 수행되었다. 현장 실험은 남해안 지역에서 수행되었으며, 탄성파 및 전기비저항 측정은 관입심도 6m부터 20m까지 10cm 간격으로 수행하였다. 토조 및 현장 실험을 통해 측정된 탄성파와 전기비저항은 이론적인 관계식을 이용하여 탄성계수 및 간극비로 환산되었다. 탄성파와 전기비저항을 이용한 간극비는 부피를 이용하여 산정한 간극비와 유사한 값을 나타내었다. 본 연구에서 개발된 탄성파와 전기비저항을 동시에 측정할 수 있는 FVRP는 연약지반의 탄성계수 및 간극비 산정에 유용한 장비가 될 수 있음을 보여준다.

• 지구물리와물리탐사
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• 제9권1호
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• pp.44-49
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• 2006

이 연구에서는 $CO_2$ 주입 모니터링에서의 전기비저항 토모그래피(ERT)의 분해능에 대해 조사한다. $CO_2$ 주입체 양쪽의 케이싱 없는 시추공에서 단극자 및 양극자 전극 배열이 사용된다. 주입 전 및 주입에 따른 3단계 모델에 대한 반응이 계산되고, 잡음이 더해진 후의 이론 값들이 L1 과 L2 norm을 사용해 역산된다. 역산결과는 어느 정도 수준이상의 $CO_2$ 부피가 확실히 감지됨을 보여준다. 대부분의 경우에 L1 norm의 경우가 L2에 비해 우월함이 판명되었다. 역산 결과를 주입 전 모델의 역산결과로 정규화하면 전기비저항이 변화하는 부분의 훌륭한 영상을 보여주며, 비저항의 전체적인 변화를 통합해서 판단하면 전체 주입된 부피에 대한 타당한 측정이 이루어짐이 입증된다.

• 지구물리
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• 제6권1호
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• pp.13-23
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• 2003

본 연구 대상 지역은 석면 및 콘크리트 잔해물을 포함한 다량의 건축폐기물이 매립되어 있는 곳으로서, 건축 폐기물의 매설량과 매설된 범위를 파악하기 위하여 쌍극자배열전기비저항탐사 및 지반투과레이다탐사를 실시하였다. 전기비저항탐사는 총 6개의 측선에 대해 전극간격을 2, 2.5 및 5m로 설정하여 실시하였고, GPR탐사는 225Mhz송‧수신기 안테나를 이용하여 연속 모드 기법으로 총 12개의 측선에서 실시하였다. 전기비저항탐사 결과 매립된 구간 및 충적층에서는 10~수백ohm-m, 원지반에서는 1,000~5,000 ohm-m의 전기비저항을 나타내며 그 경계는 지상에서 5 m 깊이 안쪽에 위치하는 것으로 확인되었다. GPR탐사를 통하여 원지반과 매립층을 포함한 충적층의 경계 면이 지하 2 m 깊이 내외에 존재함을 확인하였고 이것을 토대로 건축 폐기물의 매립 구간과 심도를 추정한 후 이것을 매설 영역내 13곳을 굴착하여 육안으로 확인하였다. 이러한 결과를 토대로 산출한 매설된 영역의 면적과 부피는 각각 약 3,953$m^2$및 4,033$m^3$ 으로 나타났다.

• 한국재료학회지
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• 제12권8호
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• pp.661-668
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• 2002

A study was made to examine the electrical, compositional, structural and morphological properties of Ag thin films deposited by DC magnetron sputtering in $O_2$ atmosphere with deposition temperature from room temperature to 15$0^{\circ}C$ using in-line sputter system. The Ag films deposited at temperature above $100^{\circ}C$ in oxygen atmosphere gave a similar specific resistivity to and even lower oxygen content than those deposited using pure Ar sputter gas The Ag films deposited with pure Ar gas was mainly composed of crystallites with [111] preferred orientation, while, for those deposited in oxygen atmosphere, more than 50% of the volume was composed of crystallites with [100] orientation. The difference in the micro structure did not cause any difference in the specific resistivity of Ag films. The results showed that the transparent conducting oxide films and the Ag films could be processed sequentially in the same deposition chamber with careful control of deposition temperature, which might result in a cost reduction for constructing the large scale in-line deposition system.

• 한국세라믹학회지
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• 제28권9호
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• pp.689-695
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• 1991

Dielectric properties of Ba1-$\chi$Sr$\chi$Ti1-yCayO3-y ceramics, where Sr and Ca were doped to Ba-site and Ti-site within the range of 0 x 0.24 and 0 y 0.05, respectively, were investigated. The substitution of Ca for Ti, which maintained the high resistivity of these formulations after sintering in a reducing atmosphere, was confirmed. Ca addition decreased the tetragonality c/a, increased the unit cell volume, and lowered Curie temperature, which were attributed to the occupancy of Ca2+ ions on Ti-sites. The lowering of Curie temperature by Ca addition was affected by the substitution of Sr for Ba-site; within 2 mol% of Ca, Curie temperature was lowered at a rate of 2$0^{\circ}C$ and 16$^{\circ}C$ per mol% of Ca at x=0 and x=0.08, respectively. Whereas the resistivity of the formulations without Ca was reduced to 107 {{{{ OMEGA }}cm, when sintered at low oxygen partial pressure of 10-9 MPa, the resistivity value higher than 1011 {{{{ OMEGA }}cm was maintained for the formulations containing Ca more than 0.5 mol%. Dielectric loss factor, tan$\delta$, was about 1% for most formulations.

• 한국염색가공학회지
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• 제24권1호
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• pp.79-90
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• 2012

This study surveys the characteristics of the PU/MWNT foaming film according to foaming conditions. For this purpose, firstly, 16 kinds of PU/MWNT forming films were prepared with 4 kinds of dispersion solutions (IPA/MWNT, DMF/MWNT, MEK/MWNT, and Toluene/MWNT) and 4 kinds of blowing agents (organic I, organic II, capsule, and inorganic). The electrical resistivity of these PU/MWNT foaming films according to the dispersion solutions and blowing agents were analysed and discussed with surface profile and cell morphology of measured by SEM. And secondly, 24 kinds of PU/MWNT foaming films were also prepared with 2 kinds of IPA dispersion solution contents and 3 kinds of blowing agents with variation of the blowing temperatures and film thickness. The physical properties of the PU/MWNT foaming films such as electrical resistivity (surface and volume) and triboelectricity with cell morphology were measured and discused through the quantities of IPA, blowing agent added and also physical conditions(temperature, thickness so on) for establishing optimum foaming conditions with good electrostatic dissipation.

• Transactions on Electrical and Electronic Materials
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• 제13권6호
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• pp.267-272
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• 2012

Considering the properties of the carbon nano tubes (CNT), their inclusion into the polymer matrix vastly increases the properties of the resultant composite. However, this is not the case due to the poor interfacial adhesion of the CNT and the polymer matrix. The present approach focuses on increasing the interaction between the polymer matrix and the CNT through the chemical modification of the CNT resulting in allyl ester functionalized carbon nanotubes (ACNT) and silane functionalized carbon nano tubes (SCNT) which are capable of reacting with the polymer matrix during the curing reaction. The addition of ACNT/SCNT into unsaturated polyester resin (UPR) resulted in the improvement of the electrical properties of resulted nanocomposites in comparison to the CNT. The surface resistivity, volume resistivity, dielectric strength, dry arc resistivity, and the comparative tracking index of the nanocomposites were significantly improved in comparison to CNT. The chemical modification of CNT was confirmed via spectroscopy.

• 한국초전도ㆍ저온공학회논문지
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• 제9권4호
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• pp.37-40
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• 2007

As power demands increase, development of the superconducting fault current limiter (SFCL) is being watched with interest. Many types of SFCLs using various superconducting materials have been developed. Especially, the FCL using coated conductor (CC) has been investigated actively at present. CCs have many advantages for the FCL application. YBCO materials used in CCs have a high n-value, and it is relatively easy to choose a matrix of the CC for high resistivity. If the CC has high resistivity, high voltage can be applied to the CC. Then total length of the CC used in SFCL, which has effects on total price and volume of the SFCL, can be reduced. Short circuit tests of two different types of CCs in the liquid nitrogen bath and its sub-cooled condition were performed and analyzed. An effect of high resistivity of the CC and cooling methods on fault current limiting characteristics could be verified in this paper.

• 한국세라믹학회지
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• 제39권1호
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• pp.21-25
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• 2002

Effect of abnormal grain growth and heat treatment time on the electrical properties of donor-doped semiconductive BaTiO$_3$ceramics was examined. La-doped BaTiO$_3$ceramics was sintered at 134$0^{\circ}C$ for different times from 10 to 600 min in order to change the volume fraction of the abnormal grains in samples. As a result, samples with different volume fraction of abnormal grain growth from 22 to 100% were prepared. The samples were annealed at 120$0^{\circ}C$ for various times. The resistivity of the sam-ples at room and above Curie temperature was examined. The complex impedance measurement as functions of the volume fraction of abnormal grains and annealing time was conducted. Separation of complex impedance semicircle was observed in a sample in which abnormal and fine grains coexist. The results are discussed from a viewpoint of microstructure-property relationship.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기물성,응용부문
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• pp.230-232
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• 2004

In this paper, we investigated dielectric and insulation characteristics of epoxy resin which includes elastomers to improve mechanical property, as varied additive elastomer contents with 5[phr], 10[phr], 15[phr], and 20[phr]. We measured permittivity and tan $\delta$ at 1kHz of signal frequency and room temperature. And we also measured BVD(break-down voltage) and volume resistivities. According to the experimental results, it is appeared that when the additive elastomer contents are increasing, permittivity, volume resistivity, BVD and volume resistance are decreasing because elastomer remains inferior to epoxy resin on electrical properties.