• 지반과기술
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• v.6 no.2
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• pp.71-71
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• 2009

• Composites Research
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• v.25 no.6
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• pp.211-216
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• 2012

FBG sensor peaks could be split due to polarization by shear strain, when the fiber optic sensors embedded or attached to the structure. For the fiber optic sensor packages, sensor grating has to be protected from shear strains. Also, pretension has to be applied to the sensor because compressive strain must be measured. Without pretension of sensor, the sensor does not show any change of signal until it is stretched. In order to mesure compressive and tensile strains, two fixing point and prestressed sensor need. In the fixing point, just holding the optical fiber cause slip between core and cladding in the fiber. A Fixation method of prestressed FBG sensors fixed with partially stripped fibers was developed. The sensor package has the prestress controllable fixtures at the fixing points. Prestress to the sensor imposed by controlling the two fixed points with bolts and nuts make it easy to measure compressive strain as well as tensile strain. The fiber optic sensor packages applied to the actual structure and the structural monitoring system using the package can be applied to safety through surveillance.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.6
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• pp.607-613
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• 2008

A monitoring system for the subway structures using prestrained FBG sensors fixed with partially stripped fibers was developed. The sensor packages had pre-strain controllable fixtures. Tensile and compressive strain of the structure could be measured without slip. The FBG sensor system was applied to the concrete lining structure in Taegu subway. Near the structure, the narrow tunnel construction, for the electric power cables and telecommunication cables, started. We wanted to measure the deformations of the subway structures due to the construction by the FBG sensor. The applied sensors had the gauge length of 1 meter to overcome the inhomogeneity of the concrete material with enough length. In order to fix tightly to the structure, the partially stripped parts of the sensor glued to the package and slip phenomenon between fiber and acrylate jacket was prevented. Prestrain of the sensor was imposed by controlling the two fixed points with bolts and nuts in order to measure compressive strain as well as tensile strain. The behavior of subway lining structure could be monitored very well.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.149-152
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• 2008

FBG sensor system is applied to the concrete lining structure in Taegu subway. Near the structure, the power cable tunnel construction started. We wanted to measure the deformation of the structure due to the construction by the FBG sensor. The applied sensor has the gauge length of 1 meter to overcome the inhomogeneity of the concrete material with enough length. In order to fix tightly to the structure, the partially stripped parts of the sensor glued to the package and slip phenomenon between fiber and acrylate jacket was prevented. Prestrain of the sensor was imposed by controlling the two fixed points with bolts and nuts in order to measure compressive strain as well as tensile strain. The behavior of subway lining structure could be monitored very well

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.700-709
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• 2009

FBG sensor system is applied to the concrete lining structure in Taegu subway. Near the structure, the power cable tunnel construction started. We wanted to measure the deformation of the structure due to the construction by the FBG sensor. The applied sensor has the gauge length of 1 meter to overcome the inhomogeneity of the concrete material with enough length. In order to fix tightly to the structure, the partially stripped parts of the sensor glued to the package and slip phenomenon between fiber and acrylate jacket was prevented. Prestrain of the sensor was imposed by controlling the two fixed points with bolts and nuts in order to measure compressive strain as well as tensile strain. The behavior of subway lining structure could be monitored very well.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.20-25
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• 2000

In order to study the impact fracture behavior of brittle materials, a steel-ball-impact experiment was Performed. Five kinds of materials were used in this study : soda-lime glass plates, glass/epoxy prepreg-one layer-bonded and unbonded glass plates, glass/epoxy prepreg-three layers-bonded and unbonded glass plates. Fracture patterns, the maximum stress and absorbed fracture energy were observed according to various impact velocities 40-120m/s. With increasing impact velocity, ring crack, cone crack, radial crack and lateral crack took place in the interior of glass plates. The generation of such cracks was largely reduced with glass/epoxy prepreg coating. Consequently, it is thought that the characteristics of the dynamic Impact fracture behavior could be evaluated using the absorbed fracture energy and the maximum stress measured at the back surface of glass plates.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.4
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• pp.353-360
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• 2010

In this paper, an efficient algorithm is established in order to estimate the plastic properties of power-law hardening bulk specimen materials with one simple spherical indentation impression test. This work is based on a new formulation of representative strain and, therefore, compare to the preceding approaches the fitting parameters are significantly reduced. Moreover, the new definition of representative strain endowed more physical meaning to the representative strain. In order to verify the reliability of the reverse analysis, we have studied a broad set of materials whose property ranges cover essentially all engineering metals and alloys. Based on the indentation force-displacement P-${\delta}$ curves obtained from numerical simulations, the characteristics of the indentation response and material elastoplastic properties are bridged via explicit functions. Next, through the procedure of reverse analysis the yield stress and power-law hardening exponent of bulk specimen materials can be determined. Finally, good agreement between the result from reverse analysis and initial input data from experiment can be observed.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.5
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• pp.79-86
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• 2009

With the substantial increase of the size of structure, the management of excavation becomes more difficult. Therefore, massive collapses which are related to retaining wall recently increase. However, since the study on measuring and monitoring the pre-stressing force of anchor is insufficient, behavior of anchor may not be predicted and monitored appropriately by the existing strain gauge and load cell type monitoring system. FBG Sensor, which is smaller than strain gauge and has better durability and does not have a noise from electromagnetic waves, is adapted to measure the strain and pre-stressing force of 7-wire strand, so called smart tendon. A series of pullout tests were performed to verify the feasibility of smart tendon and find out the load transfer mechanism around the steel wire tendon fixed to rock with grout. Distribution of measured strains and estimated shear stresses are compared with those predicted by theoretical solutions. It was found that developed smart tendon can be used effectively for measuring strain of 7-wire strand anchor and theoretical solutions underestimate the magnitude of shear stress and load transfer depth.

• Journal of the korean veterinary medical association
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• v.32 no.4
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• pp.206-219
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• 1996

동물의 전염성 해면형 뇌증에는 양과 염소의 스크래피, 사슴과 엘크의 만성소모형, 밍크의 전염성 밍크 뇌증, 소 및 소과 야생동물의 소 해면형 뇌증 그리고 고양이의 고양이 해면형 뇌증등이 알려져 있다. 전염성 해면형 뇌증의 원인은 알려져 있지 않으며, 스트레인간의 차이는 숙주의 프리온 유전자에 있어서의 대립유전자의 차이에 의존되는 것으로 추정되고 있다. 이러한 동물의 전염성 해면형 뇌증들은 우리나라에서의 발생보고가 없는 해외 가축전염병이며 현재 영국에서 문제되고 있는 소 해면형 뇌증 즉 일명 광우병은 영국에서 1986년 최초로 확인된 새로운 가축전염병으로서 사람의 크로이츠휄트-야콥병과의 어떤 연관 가능성 때문에 수의학계의 관심의 대상이 되고 있는 질병이다. 영국정부 보건장관 스티픈 도렐은 최근(1996년 3월 20일)에 과거 10년 동안 영국의 소에 감염되어 온 소 해면형 뇌증이 사람의 희귀한 뇌 질환인 크로이츠휄트-야콥병의 새로운 스트레인과 관련성이 있는 증거가 있을 수 있는 것으로 과학자문위원회가 믿고 있다고, 영국하원에서 보고한 바 있다. 한편, 영국의 농업장관 더글러스 호그는 영국에서 30개월 이상된 소를 도살할 때에는 모든 뼈를 제거하여야 하며, 모든 포유동물의 조직은 농업용 사료로 사용해서는 아니된다는 새로운 규정을 공표하였다. 그러나 영국의 쇠고기는 안심하고 먹을 수 있다고 발표하면서 만일 문제가 된다면, 영국에서 사육하는 1천 1백만 마리의 소를 전부 도살할 용의가 있다고 하였다. 이러한 영국정부 견해는 다음 날 CNN News 등 세계 각 매스컴을 통하여 보도되었으며, 아직까지 과학적인 증거가 확립된 바는 없지만, 수의학이나 의학적인 사실 확인의 여부를 떠나, 사회 경제적인 문제로 큰 놀라움과 많은 의문사항을 남겨둔 채, 영국산 소와 쇠고기의 수입금지 조치 등 국제적인 문제로 확대되었다. 본편에서는 동물의 전염성 해면형 뇌증에 대하여 종합적으로 고찰해 보고자 한다.