• Journal of Electrical Engineering and Technology
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• 제13권4호
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• pp.1752-1758
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• 2018

In a low-voltage distribution system, the molded case circuit breaker (MCCB) is a widely used device to protect loads by interrupting over-current; however the hot gas generated from the arc discharge in the interrupting process depletes the dielectric recovery strength between electrodes and leads to re-ignition after current-zero. Even though the circuit breaker is ordinarily tripped and successfully interrupts the over-current, the re-ignition causes the over-current to flow to the load again, which carries over the failure interruption. Therefore, it is necessary to understand the dielectric recovery process and the dielectric recovery voltage of the MCCB. To determine these characteristics, a measuring system comprised of the experimental circuit and source is implemented to apply controllable recovery voltage and over-current. By changing the controllable recovery voltage, in this work, re-ignition is driven repeatedly to obtain the dielectric recovery voltage V-t curve, which is used to analyze the dielectric recovery strength of the MCCB. A measuring system and an evaluation technique for the dielectric recovery strength of the MCCB are described. By using this system and method, the measurement to find out the dielectric recovery characteristics after current-zero for ready-made products is done and it is confirmed that which internal structure of the MCCB affects the dielectric recovery characteristics.

• 한국의류학회지
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• 제23권1호
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• pp.22-29
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• 1999

This paper descrived the changes of peel strength wrinkle recovery and dimensional stability after fusing 4 different wool face fabrics with 3 different fusible interlinings. The fusing condition was conducted by fusing press machine under 4kg.f/cm2 at 15$0^{\circ}C$. To determine the effect of the varous physical properties of the fused fabrics face fabrics and interlinings on the peel strength wrinkle recovery and dimensional stability(hygral expansion and relaxation shrinkage) of fused fabrics correlation among the KES values of fused fabrics face fabrics and interlinings to the peel strength rinkle recovery and dimensional stability of fused fabrics were expeerimentally analyzed,. As the results the peel strength was mainly influenced by the cover factor of face fabric and interlinings. After fusing wrinkle recovery and hygral expansion were decreased. The cover factor wrinkle recovery weight thickness shear rigidity and frictional properties of face fabric and the thickness of fused fabrics were not influence to the wrinkle recovery of fused fabrics. In addition the dimensional stabilities of fused fabrics were mainly influenced by the tensile and frictional properties of the wrinkle recovery of fused fabrics. In addition the dimensional stabilities of fused fabrics were mainly influenced by the tensile and frictional properties of the face fabrics.

• 소성∙가공
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• 제20권6호
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• pp.456-460
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• 2011

A major source of difficulty in die design for high strength steel is the high level of elastic recovery during unloading. The degree of elastic recovery is affected by factors such as material strength, bending angle, punch's corner radius and sheet thickness. Finite Element Method was used in the present work to quantitatively analyze the elastic recovery for various combinations of these parameters. In some cases elastic recovery happened in reverse direction. This phenomenon, which we call spring-go, was explained via changes in stress distribution in the panel occurring in the forming process.

• Computers and Concrete
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• 제24권3호
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• pp.249-258
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• 2019

In order to investigate the strength recovery of fire-damaged concrete after post-fire curing, concrete specimens were heating at $2^{\circ}C/min$ or $5^{\circ}C/min$ to 400, 600 and $800^{\circ}C$, and these exposed specimens were soaked in the water for 24 hours and following by 29-day post-fire curing. The compressive strength and split tensile strength of the high-temperature-exposed specimens before and after post-fire curing were tested. The proportion of split aggregate in the split surfaces was analyzed to evaluate the mortar-aggregate interfacial strength. After the post-fire curing process, the split tensile strength of specimens exposed to all temperatures was recovered significantly, while the recovery of compressive strength was only obvious within the specimens exposed to $600^{\circ}C$. The tensile strength is more sensitive to the mortar-aggregate interfacial cracks, which caused that the split tensile strength decreased more after high-temperature exposure and recovery more after post-fire curing than the compressive strength. The mortar-aggregate interfacial strength also showed remarkable recovery after post-fire curing, and it contributed to the recovery of split tensile strength.

• 한국전문물리치료학회지
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• 제1권1호
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• pp.67-74
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• 1994

Our purpose of this study was to determine the most effective cool-down exercise. The recovery times of dynamic strength after isometric and isotonic cool-down exercise were measured immediately post cool-down exercise, 30 seconds later and 60 seconds later in 30 normal, healthy men from 19 to 29 years, using dumbells(Model, Iron). The recovery time of dynamic strength had a significant positive correlation with isotonic and isometric cool-down exercise using the Chi-square method (p<0.01). Sources of significant differences were determined by the Wilcoxon signed-ranks test (p<0.01). The isometric cool-down exercise significantly shortened the recovery time of dynamic strength. We suggest that the isometric cool-down exercise may be more effective than isotonic cool-down exercise in shortening the recovery time of dynamic strength.

• 복식문화연구
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• 제12권5호
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• pp.737-742
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• 2004

The purpose of this study is restoration for tearing strength of the durable press (DP) finished 100% cotton fabric by enzymatic treatment. Dimethylol Dihydroxy Ethylene Urea (DMDHEU) was used as a DP finish chemical. Enzymes (cellulase, pectinase, protease, lipolase) were selected based on their specific reaction activities. Ideal application of the enzymes for this work was to remove cross-links created by DMDHEU on the surface of the fibers to offer migration property between microstructures of cellulose, yet cross-links that exist inside of the fibers are still remained to impart effect of wrinkle resistance. Physical characteristics (tearing strength, wrinkle recovery, FT-IR) of enzyme treated samples were measured and compared. It was found out that, in case of enzyme treatment, most of enzymes didn't have a great effect on tearing strength, but, in case of Protease, tearing strength increased at DMDHEU 2% treatment. As a result of an experiment on wrinkle recovery of the textiles treated with enzyme making density of DMDHEU different whenever respective experiment was made, it was discovered that density of DMDHEU increased as wrinkle recovery increased and, in the relation to enzyme treatment especially in Lipase enzyme treatment, the lesser density of DMDHEU, the more wrinkle recovery increased.

• Journal of Welding and Joining
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• 제26권2호
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• pp.69-74
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• 2008

590MPa grade weldable steels were gas metal arc welded with flux cored wires. Welding parameters such as current, voltage, and speed were varied independently. Effects of each parameter on the strength and chemical composition of weld metal were investigated. Increase of voltage caused decrease of weld metal tensile strength due to the low recovery of alloying elements such as carbon and manganese. On the contrary, increase of current and speed resulted in increase of weld metal strength because of higher recovery of the alloying elements.

• 한국군사과학기술학회지
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• 제17권4호
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• pp.413-421
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• 2014

Since the structural temperature of a flight vehicle flying at high speed rises rapidly due to aerodynamic heating, it is necessary for optimum structural design to obtain proper material properties at high temperature by taking into account of its operational environment. For a special alloy, analysis data on strength change due to exposure time to high temperature are very limited, and most of them are for an exposure time longer than 30 minutes for long term operations. In this study, base and weld metal samples of Ti-6Al-4V alloy had been prepared and high temperature tensile tests with induction heating were performed, and then high temperature strength characteristics and strength recovery characteristics through cooling have been analyzed. Pre-tests to determine maximum heating rate were performed, and response characteristics for temperature control were confirmed. As a result, high temperature tensile strength appeared to be lower than that of room temperature, but it was higher than that of high temperature of 30 minite exposure listed in MMPDS. In strength recovery through cooling Ti-6Al-4V alloy has shown higher recovery rate compared with other alloys.

• 한국의류학회지
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• 제11권3호
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• pp.57-65
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• 1987

The purpose of this study was to investigate the optimum treatment [condition for the Durable press finish of viscose rayon fabrics. Three types of commercial N-methylol crosslinking agents were applied to the fabric utilizing the pad-dry-cure technique. Changes in physical properties were evaluated for the various resin and catalyst concentrations. For DMU, the effect of different catalysts, $MgCl_2$ and $NH_4Cl$, were also compared. DMU treated fabrics showed in crease recovery angle, tensile strength and tearing strength but drastic decrease in abrasion resistance. DMDHEU and MDMDHEU treated fabrics were similar in most physical properties. However, DMDHEU treated fabrics were better in crease recovery angle and stiffness, and MDMDHEU treated fabrics were better in tensile strength, tearing strength and abrasion resistance. For a given resin system, crease recovery angle, tensile strength and stiffness increased with a increase in resin concentration. Tearing strength showed very little change, while abrasion resistance was decreased significantly as the crease recovery angle was increased. For the treatment of DMU, $MgCl_2$ catalyst was much better than $NH_4Cl$ in all physical properties. When $NH_4Cl$ catalyst was used, strength reduction and discoloration were observed. As the catalyst concentration increased, crease recovery angle, stiffness were increased. Tensile strength and tearing strength were increcased than control but at high catalyst concentration, the strength were decreased and abrasion resistance was significantly lowered. DMDHEU and MDMDHEU were more sensitive to catalyst concentrations than DMU.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 춘계학술발표대회 논문집
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• pp.18-21
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• 2003

The effect of interface bonding strength on the recovery force of SMA wire reinforced polymer matrix composites was investigated by pullout test. Firstly, the recovery forces and transformation temperatures of various prestrained SMA wires were measured and 5% prestrained SMA wires were prepared for the reinforcements of composites. EPDM incorporated with 20vol% silicon carbide particles(SiCp) of 6, 12, $60{mutextrm{m}}$ size were used as matrix. Pullout test results showed that the interface bonding strength increased when the SiCp size decreased due to the increase of elastic modulus of matrix. Cyclic test of composites was performed through control of DC current at the constant displacement mode. The abrupt decrease of recovery force during cycle test at high current was occurred by thermal degradation of matrix. This was in good agreement with temperature related in the thermal degradation of matrix. The hysteresis of recovery force with respect to the temperature was compared between wire and composite and the hysterisis of composites was smaller than the wire due to less thermal conduction.