• 한국전기전자재료학회논문지
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• 제18권12호
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• pp.1152-1158
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• 2005

New conductor is developed by using high strength nonmagnetic steel(NM) wire as the core of overhead conductor. This conductor is called ACNR overhead conductor(Aluminum Conductor Nonmagnetic Steel Reinforced). Formed by the combination of aluminum alloy wire and high strength nonmagnetic steel wire, it has about the same weight and diameter as conventional ACSR overhead conductor. To enhance properties beneficial in an electrical and mechanical conductor during the process of high strength nonmagnetic steel wire, we made a large number of improvements and modifications in the working process, aluminum cladded method, and other process. ACNR overhead conductor, we successfully developed, has mechanical and electrical properties as good as or even better than conventional galvanized wire. Microstructure of raw material M wire was austenite and then deformed martensite after drawing process. Strength at room temperature is about $180kgf/mm^2\~200kgf/mm^2$. NM wire developed as core of overhead conductor shows heat resistant characteristics higher than that of HC wire used as core of commercial ACSR overhead conductor, Strength loss was not occur at heat resistant test below $600^{\circ}C$. Fatigue strength of vibration fatigue is about $32kgf/mm^2\~35kgf/mm^2$ and that of tension-tension fatigue is $90kgf/mm^2\~120kgf/mm^2$ which is $50\~65\%$ of tensile strength.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.227-228
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• 2010

경량콘크리트의 유동성과 압축강도에 대한 경량잔골재 치환율의 영향을 평가하기 위해 경량잔골재치환율을 주요변수로 5배합의 경량콘크리트가 배합되었다. 실험결과 경량잔골재의 치환율이 증가할수록 슬럼프 손실 기울기는 증가하였으며, 압축강도 발현율에는 큰 영향이 없었다.

• International Journal of Concrete Structures and Materials
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• 제6권1호
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• pp.3-18
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• 2012

Observed wall damage in recent earthquakes in Chile and New Zealand, where modern building codes exist, exceeded expectations. In these earthquakes, structural wall damage included boundary crushing, reinforcement fracture, and global wall buckling. Recent laboratory tests also have demonstrated inadequate performance in some cases, indicating a need to review code provisions, identify shortcomings and make necessary revisions. Current modeling approaches used for slender structural walls adequately capture nonlinear flexural behavior; however, strength loss due to buckling of reinforcement and nonlinear and shear-flexure interaction are not adequately captured. Additional research is needed to address these issues. Recent tests of reinforced concrete coupling beams indicate that diagonally-reinforced beams detailed according to ACI 318-$11^1$ can sustain plastic rotations of about 6% prior to significant strength loss and that relatively simple modeling approaches in commercially available computer programs are capable of capturing the observed responses. Tests of conventionally-reinforced beams indicate less energy dissipation capacity and strength loss at approximately 4% rotation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.628-631
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• 2004

In this paper, mechanical properties of concrete incorporating CKD are discussed with W/B and fluidity. For setting properties, an increase in W/B retarded setting time greatly in $5^{\circ}C$, while accelerated in $20^{\circ}C$. For fluidity, an increase in slump delayed the setting time with dosage of SP agent. The presence of CKD has little influence on setting time compared with plain concrete. For compressive strength, an increase in maturity enhanced compressive strength. Fluidity had no relation to compressive strength. At low curing temperature, concrete with CKD has slight strength loss compared with plain concrete. However, remarkable strength loss at low curing temperature in early stage was not found, which can be applicable to low temperature environment concrete placing.

• 한국농공학회논문집
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• 제46권2호
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• pp.59-66
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• 2004

This study was performed to evaluate the freezing and thawing properties of the high strength concrete using recycled coarse aggregate. The recycled coarse aggregate replaced natural crushed aggregate by 0%, 25%, 50%, 75% and 100%. The compressive strength of the concrete using recycled coarse aggregate showed more than 300 kgf/$cm^2$ at the curing age 28 days. The mass loss ratio by freezing and thawing was less than 1% at all mix type. The relative dynamic modulus of elasticity was decreased with increasing the freezing and thawing cycles. Also, the durability factor by the freezing and thawing was decreased with increasing the content of recycled coarse aggregate. But, the recycled concrete except 100% recycled coarse aggregate showed 60 or more durability factor in the freezing and thawing 300 cycles. Accordingly, these recycled coarse aggregate can be used for high strength concrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.425-428
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• 2006

In order to estimate the reduction of laodbearing capacity, followed by the attributive change of heat while high strength concrete structure is revealed on fire it is necessary to evaluate, it is necessary to evaluate the property of material under high temperature such as thermal conductivity, specific heat, compressive strength, modulus of rigidity and diminution figure. Therefore, this study is for the purpose of presenting evaluation data for the analysis of thermal behavior about the high strength concrete material under high temperature, through the experiment by manufacturing concrete(40, 50, 60, 80, 100 MPa) commonly used in the construction field. As a result of the study, in the case of physical attribute, it demonstrates a greater fluctuation of change than the one of 30 MPa concrete. In case of specific heat, the high strength concrete, shown the serious diminution between $500{\sim}600^{\circ}C$, presents the thermal change area corresponding to the change of high strength concrete. In compressive strength, regardless of intensity of concrete, all of them show the first intensity loss between normal temperature and $100^{\circ}C$, the dramatic loss beyond $400^{\circ}C$. The concrete weighing above 50 MPa shows a twice lower dramatic intensity loss than the one weighing $30{\sim}40MPa$. The concrete ranging from $60{\sim}80MPa$, shows the biggest diminution of modulus of elasticity under $400^{\circ}C$, which implies the structural unstability of temperature.

• 폴리머
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• 제33권6호
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• pp.581-587
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• 2009

PLA와 PEG를 사용하여 용융블렌드 방법으로 PLA/PEG 블렌드 섬유를 제조한 후 in vitro 환경조건인 pH7.4, 온도 $37\;^{\circ}C$의 완충용액에서 1~8주 동안 가수분해한 다음 무게감량률 및 인장강도 등에 미치는 영향을 검토하였다. 가수분해 시간이 1주에서 8주까지 증가함에 따라 블렌드 시간은 10~30분으로, PEG 함량은 5~30 wt%로 증가할수록 PLA/PEG 블렌드 섬유의 무게감량률은 증가하는 경향이, 인장강도 및 인장탄성률은 감소하는 경향이 현저하게 나타남을 확인하였다. 결론적으로 가수분해 시간 2주까지는 PLA/PEG 블렌드 섬유의 무게 감량률은 약 0.9% 이내이고 강도유지율은 약 90% 이상을 나타냄으로써 임계상처치유기간 중 양호한 강도가 유지될 수 있음을 확인하였다.

• Membrane and Water Treatment
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• 제12권1호
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• pp.37-41
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• 2021

This paper presents the multiscale calculation results of the very fast volume transport in micro/nano cylindrical tubes with the wall slippage. There simultaneously occurs the adsorbed layer flow and the intermediate continuum fluid flow which are respectively on different scales. The modeled fluid is water and the tube wall is somewhat hydrophobic. The calculation shows that the power loss on the tube no more than 1.0 Watt/m can generate the wall slippage even if the fluid-tube wall interfacial shear strength is 1 MPa; The power loss on the scale 104 Watt/m produces the volume flow rate through the tube more than one hundred times higher than the classical hydrodynamic theory calculation even if the fluid-tube wall interfacial shear strength is 1 MPa. When the wall slippage occurs, the volume flow rate through the tube is in direct proportion to the power loss on the tube but in inverse proportion to the fluid-tube wall interfacial shear strength. For low interfacial shear strengths such as no more than 1 kPa, the transport in the tube appears very fast with the magnitude more than 4 orders higher than the classical calculation if the power loss on the tube is on the scale 104 Watt/m.

• 한국의류학회지
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• 제30권8호
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• pp.1323-1332
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• 2006

Lyocell is a regenerated cellulose fiber manufactured by an environmentally-friendly process. Since the fiber has more crystalline region compared to rayon, lyocell shows higher wet-strength than rayon. Although fibril generation of lyocell is lower than that of rayon because of the reason, the fibril generated during the wet process deteriorates the smooth look and soft touch of the fabric. The efficient way to remove the fibril yet retain the strength property was investigated in this work. In order to scour and remove the fibril from the fabric, cellulase enzymes were introduced and the traditional scouring was carried to be compared. Weight loss, dye-ability, and strength of treated fabric were measured after the treatments. Scanning electron microscopy was used to observe the surface of the fiber. Among the cellulases used in this work, Denimax 992L showed the best results for removal of fibril with low weight loss and tensile strength loss. The optimal conditions for the enzymatic treatment could be chosen depending on a characteristic for final purpose of the lyocell product.

• Geomechanics and Engineering
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• 제10권6호
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• pp.827-836
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• 2016

The rate of softening is an important factor to determine whether the failure occurs along localized shear band or in a more diffused manner. In this paper, strength loss and softening rate effect depending on sensitivity are investigated for weakly cemented clays, for both artificially cemented high plasticity San Francisco Bay Mud and low plasticity Yolo Loam. Destructuration and softening behavior for weakly cemented sensitive clays are demonstrated and discussed through multiple vane shear tests. Artificial sensitive clays are prepared in the laboratory for physical modeling or constitutive modeling using a small amount of cement (2 to 5%) with controlled initial water content and curing period. Through test results, shear band thickness is theoretically computed and the rate of softening is represented as a newly introduced parameter, ${\omega}_{80%}$. Consequently, it is found that the softening rate increases with sensitivity for weakly cemented sensitive clays. Increased softening rate represents faster strength loss to residual state and faster minimizing of shear band thickness. Uncemented clay has very low softening rate to 80% strength drop. Also, it is found that higher brittleness index ($I_b$) relatively shows faster softening rate. The result would be beneficial to study of physical modeling for sensitive clays in that artificially constructed high sensitivity (up to $S_t=23$) clay exhibits faster strain softening, which results in localized shear band failure once it is remolded.