• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 추계학술대회 논문집
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• pp.254-259
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• 2003

The 4-probe method with a voltage tap on terminals has been used for the measurement of the critical current of multi-strand high-Tc superconducting (HTS) cables. And the critical current of cables is obtained as the measured total current divided by the number of conductor when the terminal voltage exceeds the predetermined criterion of critical current. However, because of the non-uniform current distribution due to the different critical current, shapes, and other characteristics of each conductor this is not applicable method to the multi-strand HTS cable. To determine the critical current of multi-strand HTS cable the critical current of each conductor must be measured with different method. In this paper, the current distribution and the critical current of each conductor in multi-strand cable were measured with specially made pick-up coils and voltage taps. It is presented that the real critical current of multi-strand is smaller than sum of each conductors. The main cause of non-uniform current distribution is the different resistances appeared in each HTS wires.

• International Journal of Concrete Structures and Materials
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• 제9권3호
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• pp.369-379
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• 2015

Friction in a post-tensioning system has a significant effect on the distribution of the prestressing force of tendons in prestressed concrete structures. However, attempts to derive friction coefficients using conventional electrical resistance strain gauges do not usually lead to reliable results, mainly due to the damage of sensors and lead wires during the insertion of strands into the sheath and during tensioning. In order to overcome these drawbacks of the existing measurement system, the Smart Strand was developed in this study to accurately measure the strain and prestressing force along the strand. In the Smart Strand, the core wire of a 7-wire strand is replaced with carbon fiber reinforced polymer in which the fiber Bragg grating sensors are embedded. As one of the applications of the Smart Strand, friction coefficients were evaluated using a full-scale test of a 20 m long beam. The test variables were the curvature, diameter, and filling ratio of the sheath. The analysis results showed the average wobble and curvature friction coefficients of 0.0038/m and 0.21/radian, respectively, which correspond to the middle of the range specified in ACI 318-08 in the U.S. and Structural Concrete Design Code in Korea. Also, the accuracy of the coefficients was improved by reducing the effective range specified in these codes by 27-34 %. This study shows the wide range of applicability of the developed Smart Strand system.

• 대한수의학회지
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• 제31권3호
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• pp.329-335
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• 1991

The filter elution technique was used to assay $^{60}Co$ $\gamma$ ray-induced DNA strand breaks(SB) in EL4 mouse leukemia cell and mouse spleen lymphocyte. The lymphocytes were stimulated with lipopolysaccharide (LPS, $20{\mu}g/ml$) to label $[^3H]$ thymidine. EL4 cells and lymphocytes in suspension were exposed at $0^{\circ}C$ to 0Gy, 1Gy, 5Gy, 10Gy or l5Gy for DNA single strand breaks(SSB) assay and 0Gy, 25Gy, 50Gy, 75Gy or 100Gy for DNA double strand breaks(DSB) assay of $^{60}Co$ radiation and elution procedure was performed at pH12.1 and 9.6. The number of DNA strand breaks increased with increasing doses of r rays. The strand scission factor(SSF) was estimated in each experiment (eluted volume 21ml). The slope of SSB EL4 cells was $0.01301{\pm}0.00096Gy^{-1}$ (n=5), the slope of SSB for lymphocytes was $0.01097{\pm}0.00091Gy^{-1}$ (n=5) and the slope of DSB for lymphocytes was $0.001707{\pm}0.0000573Gy^{-1}$ (n=5). Thus EL4 cells were more sensitive to induction of DNA SSB by ionizing radiation than lymphocytes (p<0.005). The ratio of slope of dose-response relationship (SSF versus dose) of lymphocytes DNA SSB as compared with the slope of DNA DSB was 6.4.

• 한국전산구조공학회논문집
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• 제21권3호
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• pp.287-294
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• 2008

이 연구에서는 교량 상부구조물의 보수 보강에 많이 사용되는 7연 강연선의 공용중 긴장력 관리를 위한 새로운 방법은 제안하였다. 제안된 스마트 강연선은 기존 강연선의 중앙 킹와이어를 강제튜브로 대체하고, 강제튜브의 내부에 FBG 광섬유센서를 설치하여 강연선의 변형률을 측정할 수 있도록 하였다. 내장된 센서를 통하여 이 스마트 강연선의 변형률을 쉽게 측정할 수 있으므로, 공용중 강연선의 긴장력을 모니터링할 수 있다. 본 연구에서 제안된 장력 모니터링 방법의 효용성을 증명하기 위하여 FBG센서 2개가 내장된 길이 7.0m인 스마트 강연선을 제작하고, 이를 길이 6.4m, 높이 0.6m인 RC T형 모형거더에 외장형 텐던으로 적용하였다. 그리고 이 시험거더에 대한 재하-제하시험을 실시하고 로드셀에서 계측된 긴장력과 스마트 강연선을 이용하여 예측한 긴장력을 비교하였다. 비교 결과, 제안된 스마트 강연선은 긴장력이 작용된 강연선의 장력을 정확하게 모니터링 하는데 유용함을 확인할 수 있었다.

• Journal of Microbiology
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• 제37권2호
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• pp.59-65
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• 1999

RecA protein can promote strand assimilation, homologous pairing, and strand exchange. All these reactions require DNA-dependent ATP hydrolysis by recA protein, and the activities of recA protein are affected by the ionic environment. In this experiment, DNA-dependent ATPase activity showed different sensitivity to anionic species. ATP hydrolysis and strand exchange were relatively sensitive to salt in the reactions with NaCl, strongly inhibited at 100 mM NaCl. However, the inhibition by sodium acetate or sodium glutamate was not observed at 50∼100 mM concentration. Addition of sodium glutamate to the standard reaction condition increased the apparent efficiency of ATP hydrolysis during strand exchange. The condition including 50∼100 mM sodium-glutamate might be similar to the physiological condition.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2012년도 추계 학술논문 발표대회
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• pp.167-168
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• 2012

Analysis on structural effects which are reduction of friction coefficient and increase of tendon area by HDPE greased and large size strand in post-tensioning system of reactor containment building was carried out. Effective ratio of tendon force increases 67% to 83% by HDPE greased strand and vertical, horizontal internal section forces increased maximum 51%, 41% respectively. Tendon quantity could be reduced 30% by large size and HDPE greased strand that can maintain safety of ultimate internal pressure same as at present.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2012년도 추계 학술논문 발표대회
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• pp.169-170
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• 2012

It is analyzed that constructability of post-tensioning system applying HDPE greased strand that is greased and coated by high density polyethylene on a bare strand in reactor containment building. The improvement of corrosion resistance by greasing and HDPE coating on a strand makes transportation, handling and installation of tendon to be easier. Therefore, serial and repetitive process of post-tensioning composed of construction preparation, tendon installation, stressing and anchoring, grease injection could be improved parallel and lumping process of installation and grouting, stressing and anchoring.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.765-767
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• 1992

A superconducting multistranded cable is used to realize high current capacity for AC use. The critical current value of the cable to be less than the simple summation of individual critical current value of each strand. The causes for such a degradation of the critical current value have not been revealed. This paper investigates the current distribution in multistrands before and after their quenching by using 7-strand superconducting cable. The following experimental results are derived. (1)The quenching is initiated at one strand in the cable, (2)The current in the quenched strand is transferred into the other strands, (3) An avalanche of quenching is induced among the strands, (4)The central strand is quenched finally among the strands.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.37-38
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• 2009

이 논문은 한국형 PS정착구의 하중전달 성능에 관한 실험적 연구로 기존에 사용하고 있는 1860MPa 강연선과 포스코, 고려제강등을 통해 새로 개발되는 2200MPa급 강연선에 대하여 이루어졌다. 하중전달성능은 ETAG 기준에 따라 이루어졌으며 실험결과 1860MPa 강연선이 적용되는 구조물의 경우 모든 시험체가 실험기준을 만족하고 있음을 확인하였다. 한편, 2200MPa급 강연선이 적용될 경우 일부 정착구의 경우 허용기준을 만족하였지만 대부분은 적합하지 않은 것으로 나타났다. 따라서 2200MPa급 이상의 강연선에 대해서는 전용 정착구의 개발이 요구된다.

• Structural Engineering and Mechanics
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• 제50권2호
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• pp.231-240
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• 2014

In the present research, fatigue behavior of chopped strand mat/epoxy composites has been studied with two different techniques. First, the normalized stiffness degradation approach as a well-known model for unidirectional and laminated composites was utilized to predict the fatigue behavior of chopped strand mat/epoxy composites. Then, the capability of the fatigue damage accumulation model for chopped strand mat/epoxy composites was investigated. A series of tests has been performed at different stress levels to evaluate both models with the obtained results. The results of evaluation indicate a better correlation of the normalized stiffness degradation technique with experimental results in comparison with the fatigue damage accumulation model.