• 무역상무연구
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• 제12권
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• pp.495-518
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• 1999

Since the end of World War II, the standby letters of credit have been used as a surety device, serving as a performance bond and guarantee in the world. In Korea, the standby letters of credit have been also being used in international transactions. But there have been a few studies on the standby letters of credit. This study is carrying out to reveal the characteristics of the standby letters of credit and the documentary letters of credit and also between the standby letters of credit and guarantees. Secondly, this study is carrying out to indicate types of practical use of standby letters of credit in international transactions, i.e. bid bonds, performance bonds, advanced payment guarantees etc.. Finally, this study is carrying out to indicate governig rules regarding standby letters of credit, i.e. URCG, URDG, UCP, UN Convention on Independent Guarantees and Standby Letters of Credit, ISP etc..

• 한국건설순환자원학회논문집
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• 제2권2호
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• pp.115-127
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• 2014

Addition of fibers in cement or cement concrete may be of current interest, but this is not a new idea or concept. Fibers of any material and shape play an important role in improving the strength and deformation characteristics of the cement matrix in which they are incorporated. The new concept and technology reveal that the engineering advantages of adding fibers in concrete may improve the fracture toughness, fatigue resistance, impact resistance, flexural strength, compressive strength, thermal crack resistance, rebound loss, and so on. The magnitude of the improvement depends upon both the amount and the type of fibers used. In this paper, locally available waste fibers such as coir fibers, sisal fibers and polypropylene fibers have incorporated in concrete with varying percentages and l/d ratio and their effect on compressive, split, flexural, bond and impact resistance have been reported.

• 대한기계학회논문집
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• 제10권6호
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• pp.830-836
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• 1986

본 연구에서는 이러한 사실에 착안하여 프랑스의 Granjon에 의해 이미 개발된 용접부의 재용성이 탁월한 종래의 정적임플란트(implant)시험기를 정한.고안하여 아아 크용접부의 피로특성에 영향을 미칠 수 있는 제영향인자를 재현하여 간편하게 피로시 험을 할 수 있는 동적 임플란트시험기를 개발하였다. 이러한 시험기를 이용하여 저 온.고압력용강재에 대해서 다음과 같은 항목들을 구명할 목적으로 본 연구는 수행된 것이다.

• 대한치과의사협회지
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• 제51권1호
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• pp.6-11
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• 2013

Dental ceramics is well known to have excellent esthetics, biocompatibility as well as high compressive strength. However, the fragility of ceramics against tensile and shear loads leading to the delayed fracture of micro crack on ceramic surface and the backwardness of ceramic fabrication technique limit the usage of ceramic materials in dentistry. Among all ceramic materials, zirconia has been introduced to overcome the drawback of conventional dental ceramics in the field of dentistry due to the nature of zirconia featuring proper opalescence and high fracture toughness. Also, novel manufacturing techniques enable ceramic materials to prepare high esthetic anterior and posterior all ceramic system. In this paper, it is introduced and discussed that novel techniques characterizing the bond strength between zirconia core and veneering ceramics and analyzing the fluorescence of dental ceramics in order to overcome the gap between the results of basic research and the feasibility of the results in the field of dental clinics.

• Structural Engineering and Mechanics
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• 제19권5호
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• pp.519-533
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• 2005

The numerical simulations on the influence of mesoscopic structures on the macroscopic strength and fracture characteristics are carried out based on that the concrete is assumed to be a three-phase composite composed of matrix (mortar), aggregate and bond between them by using a numerical code named MFPA. The finite element program is employed as the basic stress analysis tool when the elastic damage mechanics is used to describe the constitutive law of meso-level element and the maximum tensile strain criterion and Mohr-Coulomb criterion are utilized as damage threshold. It can be found from the numerical results that the bond between matrix and aggregate has a significant effect on the macroscopic mechanical performance of concrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.715-718
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• 2004

The evaluation of durability of resin concrete was examined through various tests, i.e., compressive strength, absorption, abrasion, chemical attack resistance and bond between general and resin concrete. 2 types of concrete were used such as 40 MPa of general concrete and 90 MPa of resin concrete. The characteristics of resin concrete was more improved than that of general concrete, and especially, resin concrete was most effective on compressive strength, the resistance to $H_2SO_4$ solution attack and absorption. However, abrasion. is almost same between general concrete and resin concrete.

• 한국해양공학회지
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• 제14권2호
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• pp.84-88
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• 2000

The main objectives of this study are to compare the obtained mechanical characteristics of reduced-scale model materials with those of the prototype and to provide the information on the best selection of materials. Manufacturing techniques on the micro-concrete and reduced reinforcement are introduced. The test results of these materials are shown to be satisfactory with regard to the similitude requirement. The simple beam tests were performed to verify similitude in the bond behavior between micro-concrete and reduced reinforcement. Those results also prove that these manufacturing and experimental techniques are useful and reliable for reduced-scale model tests.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 가을 학술논문 발표대회
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• pp.17-18
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• 2021

In the present study, Al-Zn coating was deposited by Arc thermal (AT) and plasma arc thermal (PAT) spray processes, and their corrosion characteristics were studied in 3.5% NaCl through electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM) and mechanical tests. The bond adhesion result showed that plasma arc sprayed coating had a higher value attributed to compact, dense, and less porous coating compared to arc thermal spray coating which contains defects/pores and uneven morphology as revealed by scanning electron microscope analysis. Electrochemical results revealed that the plasma arc sprayed coating had a high polarization resistance at early stage of immersion, suggesting its excellent corrosion protection performance.

• 대한소아치과학회지
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• 제38권4호
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• pp.348-354
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• 2011

침식 법랑질의 표층은 건전 법랑질과는 물리화학적 성상이 다르므로 침식 법랑질면에 대한 복합레진의 결합력을 증가시키기 위한 대안으로, 법랑질 내층으로의 침투력이 탁월한 infiltrant resin을 응용하는 방법을 생각하게 되었다. 본 연구는 다양한 정도로 인공 침식이 유발된 법랑질면을 대상으로, infiltrant resin과/또는 기존의 접착제를 적용한 경우의 복합레진 결합강도를 비교 분석할 목적으로 시도되었다. 건전한 순면을 가진 발거된 상악 유전치를 대상으로, 인공침식 유발 횟수 및 infiltrant resin과/또는 기존의 접착제를 적용한 방법에 따라 각 20개씩의 시료를 제작하였으며, 각 군의 미세인장 결합강도를 측정하고, 파절면의 파절 양상을 평가하여 다음과 같은 결과를 얻었다. 법랑질 표면의 침식 유발 횟수가 늘어날수록 결합강도가 낮았다(p<0.05). 기존의 접착제 상부에 infiltrant resin을 추가 적용한 군, infiltrant resin만 적용한 군, 접착제만 적용한 군의 순으로 미세인장결합강도가 높게 나타났다(p<0.05). 파절 양상의 관찰에서는 인공 침식 유발 횟수가 적은 군 및 infiltrant resin을 적용한 군에서 응집파절의 비율이 높게 나타났다. 결론적으로, 법랑질의 침식도가 클수록 복합레진 수복물과의 결합 강도는 감소하였으며, infiltrant resin으로 기존의 적찹제를 대체하거나 첨가함으로써 결합강도를 보완시킬 수 있을 것으로 판단되었다.

• 한국도로학회논문집
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• 제18권3호
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• pp.75-86
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• 2016

PURPOSES : The purpose of this study is to investigate characteristics of crack spacing and crack width and their relationship in continuously reinforced concrete pavement (CRCP) based on the data obtained from long-term field observations. METHODS : The crack spacings and crack widths are measured periodically over 10 years at two different CRCP sections: one with asphalt bond breaker beneath concrete slab, and the other with bonded lean concrete base beneath concrete slab. The effects of steel ratio, type of underlying layer, terminal treatment method, and seasonal temperature change on the crack characteristics are evaluated by analyzing the measured data. RESULTS : The CRCP with lean concrete base shows smaller crack spacings than those of the CRCP with asphalt bond breaker. As the steel ratio increases, both the crack spacing and crack width tend to decrease. The crack width becomes larger as the crack age increases, but once the crack age is over a certain value the crack width tends to converge. When the terminal anchor lug system is not used and the expansion joints are employed at the terminals, the crack spacings and crack widths increase near the terminal sections. The crack spacing and crack width seem to be proportional each other, but not necessarily linearly, and their relationship is more distinguished in the summer when the crack widths become smaller. CONCLUSIONS : The steel ratio, underlying layer type, terminal treatment method, and seasonal temperature change affect the characteristics of cracks and the crack spacing and crack width are related to each other.