• 한국염색가공학회지
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• 제9권1호
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• pp.15-22
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• 1997

The alkali treated and black dyed PET fabrics were sputter etched under Ar gas atmosphere. The color depth of PET fabrics were increased with sputter etching time only under some limits of discharge power. And above that limits of discharge power the color depth of PET fabrics was decreased by increasing discharge power and treatment time. Minute cracks were made by sputter etching in the whole surface of fabrics to the direction of perpendicular to the longitudinal side of yarns. The fineness and density of minute crack were increased with lowering discharge power. And the size of crack was far smaller than that of microcrater which was obtained by alkali treatment. It is considered that the increase of color depth is related to the minute crack. The water permeation time of sputter etched fabrics was increased with increasing discharge power and treating time. The increase of color depth attained by sputter etching was fully kept through repeated laundering.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.311-314
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• 2005

This research aims to analyze of prestressed composite hollow-core slab and box type steel beam. The smeared crack model used in abaqus for the modeling of hollow core reinforced concrete, including cracking of the concrete, rebar and concrete interaction using the tension stiffening concept, and rebar yield. The structure modeled is a simply supported hollow core spancrete slab subjected spa-h beams and prestressed in one direction. The hollow core spancrete slab is subjected to four-point bending. The concrete-rebar interaction that occur as the concrete begins to crack are of major importance in determining the spancrete slab's response between its initial, deformation and its collapse. This smeared crack model used in analysis involved non-liner concrete analysis concept.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.577-580
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• 2003

Problem of repairing by boring is that it deteriorates stabelety and durability of structure by permeation of seawater from underneath after damage and repair of reinforcing rod regarding of spot. The purpose of this study is to improve the porblem by using the repair method of general boring to mend the of large mat basis. Direction of thes experiment is to apply the new repair material and the method to control the blazing fire factor caused by the crack from the foundation of large mat and also to estimate it's integrity. New method of construction is method of contruction that do speace scurity in vertical drilling and bottom useing water jet. New material used bantonite and rubberized asphalt. Test result existent repair method of construction large size mat basis perforation is difficult and reinforcing rod can be damaged coule there were a lot of problems with re-water leakage of crack repair region, but overcomes existent short coming by method that apply in this study.

• Elastomers and Composites
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• 제32권3호
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• pp.179-185
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• 1997

In solution and melting state, SiOD prepolymer was prepared by cured excess DDM with epoxy-terminated siloxane oligomers to control phase separation when DGEBA was blended with PDMS. DGEBA/SiOD prepolymer was also cured at $150^{\circ}C$ for 3hrs. Mechanical and thermal properties of the cured prepolymer specimen were investigated. DGEBA/SiOD60 specimen blended SiOD prepolymer had the best flexural strength, modulus and impact strength. To show crack-formation procedure to morphology, DGEBA/DDM neat specimen was flowed homogeneously in direction of crack energy, whereas DGEBA/SiOD$(30{\sim}60)$ specimen showed heterogeneously dispersed particles and scattered domain of crack energy, but DGEBA/SiOT specimen showed homogeneous phase.

• International Journal of Precision Engineering and Manufacturing
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• 제2권4호
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• pp.40-46
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• 2001

Bulging is a forming method to shape die cavity by using hydraulic pressure in tube or vessel. Bulging machine and die were developed in order to produce vessel for keeping warm. Bulging machine is a double type with two horizontal cylinders for bulging of two pieces at the same time. The developed die system has one bulging die and two drawing dies for necking at both ends of the tube. The diameter of tube expands by hydraulic pressure in tube. At the same time, thrust at both ends of the tube pushes tube in the direction of expansion to obtain high expansion rate with no crack. In this study, the bulging properties were investigated to solve tube crack and necking in manufacturing vessel by combining bulging and drawing. As a result, high expanding rate of tube radius without crack, precision necking and high productivity were obtained.

• 대한기계학회논문집A
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• 제25권7호
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• pp.1155-1162
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• 2001

Sihs minimum strain energy density criterion(SED) often used in the mixed mode problem has the ambiguity of the choice of minimum values. In this paper, as the method to solve the problem of SED, maximum minimum strain energy density criterion is proposed that the crack propagates in the direction of having the maximum among the minimum values of modified strain energy density factor(MS), i.e., sign($\sigma$(sub)$\theta$).Smin.

• 한국정밀공학회지
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• 제22권2호
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• pp.120-125
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• 2005

Effect of transverse electric fields on fracture behavior in ferroelectric ceramics under purely electrical loading is investigated. It is shown that the shape and size of the domain switching zone depend strongly on the ratio of the transverse electric field to the coercive electric field as well as the direction of the applied electric field. Under small-scale conditions, the crack-tip mode I and II stress intensity factors induced by ferroelectric domain switching are numerically obtained. The crack kinking in ferroelectric ceramics is also discussed.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2003년도 춘계학술발표대회 개요집
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• pp.263-265
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• 2003

The transverse crack, a type of cold crack, occurs perpendicular to the axis of the weld interface, longitudinal residual stresses ($\sigma$k direction) are more important in transverse crack occurrence from my own experience. Specimens were fabricated and welded under actual construction conditions, and then residual stresses of longitudinal stresses were measured for different welding conditions with SAW and FCAW process. The residual stress values for the specimen welded Interpass temperature below 30$^{\circ}C$ was higher than the specimen welded interpass temperature of 100～120$^{\circ}C$. And also the residual stress values for a specimen measured at weld surface, as welded condition, was higher than that of longitudinal residual stresses that was measured from a small test piece, due to the residual stress was relieved in the process of the cutting and machining. Transverse weld cracks were detected in the area of the maximum residual stresses both SAW and FCAW process.

• 한국전산구조공학회논문집
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• 제12권2호
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• pp.161-169
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• 1999

이방성체의 평면내 직선균열에 대한 균열선단부근의 응력과 변위의 분포는 어떠한 균열체의 형상 및 하중조건에 대해서도 응력확대계수라는 하나의 매개변수로서 나타낼 수 있다고 하는 것이 파괴역학에서 보편화되어 있다. 그러나 많은 경우에 있어서 급수전개식의 이어지는 항은 정량적으로 중요하다. 따라서 본 연구에서는 이러한 항을 유도하고 이것이 균열진전방향에 미치는 영향에 대하여 검초하였다. 이를 위하여 단축하중을 받는 직방성균열체의 해석을 수행하며 재료는 균질이방성체라고 가정하였다. 급수전개식에서 2차항의 영향을 고려하기 위하여 균열선단에서의 응력의 분포를 재해석하였으며, 2차항의 사용은 정확한 균열진전방향의 결정을 위해서 매우 중요함을 보였다. 초기균열진전각도의 결정을 위해서 수직응력비이론을 적용하였다.

• 한국지반환경공학회 논문집
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• 제9권3호
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• pp.5-9
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• 2008

하수관거는 지중에 매설되기 때문에 균열발생 시 오염원이 빠르게 지하로 침투되어 오염을 야기한다. 본 연구에서는 하수관거 균열발생 시의 오염원의 확산에 대한 수치모델링을 수행하였다. 모델링 수행 결과를 이용하여 오염원의 이동경로를 예측해보았으며, 다음과 같은 결론을 얻었다. 오염원의 이동방향은 지표면의 지형경사에 따른 흐름과 비슷한 경향을 보이는 것으로 나타났으며, 지하방향으로는 약 8~10m 깊이까지 침투되는 것으로 나타났다. 본 연구를 통하여 장래 하수관거 관리에 효율성을 제공할 것으로 기대된다.