• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.810-813
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• 2000

In this study, we fabricated Bi-2223/Ag high temperature superconducting tapes using PIT (Powder-In-Tube) process to apply the superconducting magnet, cable and etc. It's inevitable to deform the superconducting tapes with axial strain for application. Therefore, for the characterization of the strain sensitivity of the superconducting properties, the degradation of Bi-2223/Ag tapes due to axial strain were investigated by measuring the critical current as a function of applied tension strain and external magnetic field. The critical current of Bi-2223/Ag tapes were decreased slightly up to 0.3∼0.4% applied strain but, drastically decreased more than these strains. Superconducting filament cores consisted of brittle ceramic fibers were broken easily by the large strain and current path were decreased simultaneously.

• 자원환경지질
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• 제35권5호
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• pp.421-428
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• 2002

계면활성제를 사용하여 지하수의 표면장력을 인위적으로 감소하였을 때, 감소된 표면장력이 지하수 폭기시의 폭기 영향권 및 VOC 제거 효율에 미치는 영향을 실험실 규모의 실험을 통하여 규명하였다. 내경 9.5 cm, 길이 100 cm의 유리 컬럼에 계면활성제(sodium dodecyl sulfate, SDS) 및 toluene 100 ppm 포함하는 물로 채운 후 일정한 속도로 공기를 주입하였을 때의 toluene의 제거 속도를 측정하였다. 또한 같은 컬럼에 토양(모래)이 채워진 상태에서 동일한 실험을 반복하였다. 토양이 존재하지 않는 상태에서의 stripping에 의한 toluene의 제거 속도는 표면장력의 감소(계면 활성제 농도의 증가)에 따라 증가하는 것으로 나타났으며, 토양이 존재하는 경우에도 비슷한 결과를 나타내었다. 2차원 유리 상자에 모래와 SBS를 포함하는 물을 채운 후 일정한 공기 유속을 유지하였을 때, 폭기의 영향권(공기의 침투영역)은 물의 표면장력 감소에 따라 현저히 증가하는 것으로 나타났다. 특히 SDS의 critical micelle concentration(CMC)보다 훨씬 낮은 농도에서 폭기 영향권이 최대화하는 것으로 밝혀졌다. 본 연구결과는 폭기에 의한 지하수 오염물질 중, 특히 휘발성 유기오염물질의 제거 공정의 효율을 증대하는데 기여할 것으로 생각된다.

• Ocean Systems Engineering
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• 제4권3호
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• pp.215-241
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• 2014

Steel catenary riser (SCR) is a popular/economical solution for the oil/gas production in deep and ultra-deep water. The behavioral characteristics of SCR have a high correlation with the motion of floating production facility at its survival and operational environments. When large motions of surface floaters occur, such as FPSO in 100-yr storm case, they can cause unacceptable negative tension on SCR near TDZ (touch down zone) and the corresponding elastic deflection can be large due to local dynamic buckling. The generation, propagation, and decay of the elastic wave are also affected by SCR and seabed soil interaction effects. The temporary local dynamic buckling vanishes with the recovery of tension on SCR with the upheaval motion of surface floater. Unlike larger-scale, an-order-of-magnitude longer period global buckling driven by heat and pressure variations in subsea pipelines, the sub-critical local dynamic buckling of SCR is motion-driven and short cycled, which, however, can lead to permanent structural damage when the resulting stress is greatly amplified beyond the elastic limit. The phenomenon is extensively investigated in this paper by using the vessel-mooring-riser coupled dynamic analysis program. It is found that the moment of large downward heave motion at the farthest-horizontal-offset position is the most dangerous for the local dynamic buckling.

• International Journal of Advanced Culture Technology
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• 제8권4호
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• pp.207-211
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• 2020

In the global economy, trade is not confined in geological boundaries, enhancing the international relation among countries. However, the trade tension between the largest economy and the second-largest economy raise concerns among the world economies, enhancing the uncertainties around world. In particular, the trade tension between the two countries is highly related with South Korea's trade balance, because the country is highly dependent on the trade with the two countries. Given this, we analyzed the news editorials published in Korean quality newsaper, with related to U.S. and China Trade War by looking at the ideological perspectives of news outlets or journalists to the issue within the framework of critical discourse analysis. In particular we gave a special attention to the attitude to each country in order to investigate their ideological stance to the country, following van Dijk (1998)' ideological square. The results are as follows: first, the Chosun Ilbo emphasized 'their' bad properties directly and aggresively, while the Hankyoreh designated the U.S. as a member of an out-group, thus mitigating 'our' bad quatilies; Second, the two strategies of emphasis and mitigation enabled both newspapers to reinforce in-group homogeneity and out-group exclusion. Thus, we could conclude that the editorial is a clear indicator to show the news outlet's ideological stance to each country in regard to the trade issue.

• 대한기계학회논문집A
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• 제27권11호
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• pp.1986-1996
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• 2003

Methodology based on the elastic-plastic fracture mechanics has been widely accepted in predicting the critical crack length(CCL) of pressure tubes of CANDU nuclear plants. A conservative estimate of CCL is obtained by employing the J-resistance curves measured with the specimens satisfying plane strain condition as suggested in the ASTM standard. Due to limited thickness of the pressure tubes the curved compact tension(CT) specimens taken out from tile pressure tube have been used in obtaining J-resistance curves. The curved CT specimen inevitably introduce slant fatigue crack during precracking. Hence, effect of specimen geometry and slant crack on J-resistance curve should be explored. In this study, the difference of J integral values between the standard CT specimens satisfying plane strain condition and the nonstandard curved CT with limited thickness (4.2mm) is estimated using finite element analysis. The fracture resistance curves of Zr-2.5Nb obtained previously by other authors are critically discussed. Various finite element analysis were conducted such as 2D analysis under plane stress and plane strain conditions and 3D analysis for flat CT, curved CT with straight crack and curved CT with slant crack front. J-integral values were determined by local contour integration near the crack tip, which was considered as accurate J-values. J value was also determined from the load versus load line displacement curve and the J estimation equation in the ASTM standard. Discrepancies between the two values were shown and suggestion was made for obtaining accurate J values from the load line displacement curves obtained by the curved CT specimens.

• 한국응용과학기술학회지
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• 제31권1호
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• pp.7-13
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• 2014

양이온 에스테르형 계면활성제인 N-2-hydroxy-3-(2-hydroxyacetoxy)proply-N,N-dimethyl dodecylaminium chloride (HPDA)를 합성하였고, FT-IR 과 $^1H$-NMR 분석으로 확인하였다. 합성화합물의 묽은 수용액에 대하여 표면장력을 측정하고, 임계미셀농도를 산정하였다. 표면장력은 $10^{-3}{\sim}10^{-2}mol/L$ 농도 범위에서 33~34 dyne/cm 이었고, 표면장력법에 의해 산정한 임계미셀농도는 $8.5{\times}10^{-3}mol/L$ 이었다. 합성 계면활성제인 HPDA와 SLS, TTAB의 유화특성을 시험하였다. 그 결과 HPDA가 우수한 유화제로 확인되었다. 그리고 Ross-Miles 방법으로 기포력과 기포안정성도 측정하였다.

• 공업화학
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• 제30권2호
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• pp.241-246
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• 2019

본 실험에서 반응성 계면활성제는 비이온성 계면활성제인 polyoxyethylene(23) lauryl ether(Brij 35)와 polyoxyethylene(20) stearyl ether(Brij S20)를 acrylic acid 또는 3-butenoic acid를 사용하여 합성하였다. 계면활성제는 FT-IR과 $^1H$-NMR로 확인하였으며, 물성은 임계미셀농도, 유화력, 기포력을 측정하였다. 합성한 반응성 계면활성제의 표면장력과 임계미셀 농도는 35 dyne/cm~41 dyne/cm에서 $1.0{\times}10^{-4}mol/L{\sim}9.7{\times}10^{-5}mol/L$의 값을 가진다. 또한, 계면활성제의 유화력은 대두유, 벤젠, 모노머에서 측정하였으며, 기포의 초기 높이 및 5 min 후의 높이를 측정하여 비교하였다.

• 공업화학
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• 제23권5호
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• pp.433-439
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• 2012

본 연구에서는 도데실 글리시딜 에테르와 아미노에탄올을 반응시킨 후 디메틸 설페이트로 4급화시켜 분자 내에 2개의 라우릴기, 3개의 히드록실기를 가진 양이온 계면활성제 BHMAS (N,N-bis-(3'-n-dodecyloxy-2'-hydroxypropyl)-N-methyl-2-hydroxyethylammonium methyl sulfate)를 합성하였고, 생성물의 분자구조는 $^{1}H-NMR$, FT-IR 등의 기기분석을 통하여 확인하였다. 합성한 계면활성제의 CMC (critical micelle concentration)는 $9.12\;{\times}\;10^{-4}$ mol/L이며, CMC에서의 표면장력은 28.71 mN/m이었다. Maximum bubble pressure tensiometer를 사용하여 동적 표면장력을 측정한 결과, 공기와 수용액의 계면이 계면활성제 단분자에 의하여 포화되는 데 비교적 오랜 시간이 소요되었다. 1 wt% 계면활성제 수용액과 n-decane 사이의 계면장력은 0.045 mN/m이며, 평형에 도달하는 데 약 5 min의 시간이 소요되었다. 합성된 계면활성제의 흡착 특성이 매우 우수하였으며, 합성한 양이온 계면활성제가 섬유표면에 효과적으로 흡착되어 유연효과를 나타낼 수 있음을 확인하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.265-266
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• 2006

Superconductor is developed for applications in high-power devices such as power-transmission cables, transformers, motor and generators. In such applications, HTS tapes are subjected to various kinds of stress or strain. In the fabrication of the devices, the critical current (Ic) of the high temperature superconductor degrades due to many reasons including the tension applied by bending, twist and thermal contraction. In particular manufactured HTS cable, we need pitch angle controls. This paper is analyzed that Ic characteristics is changed pitch angle of HTS tape. These results will amount the most important basis data in HTS cable.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.55-60
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• 2004

In this study, the configuration and tension of a towing cable for side-scan sonar are predicted in an ambient flow and at an unsteady towing condition. The governing equation of three-dimensional dynamic analysis for a flexible cable is solved using a finite difference method. We successfully predict the configuration and tension of a side-scan sonar and designed the towing system. It is found in static analyses that the side-scan sonar must be towed to keep a its stable depth at a reasonable speed. The study also reveals in the transient analyses that the dominant component affecting the top tension is the tangential drag force for the larger towing speed than the critical speed, and the self weight of a towed instrument for the smaller towing speed than. It should be maneuvered for a towing vessel with good consideration for the impact effect in a cable due to tension peak when a towing speed is suddenly increase. The developed program can be applicable for three-dimensional dynamic analysis of a towing system for various marine survey instruments.