• 소성∙가공
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• 제28권5호
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• pp.281-286
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• 2019

The plastic strain ratio is one of the factors of the deep drawability of metal sheets. The plastic strain ratio of Al sheet is low value. Therefore, it is necessary to increase the plastic strain ratio in order to improve the deep draw ability of the Al sheet. This study investigated the increase of the plastic strain ratio and the texture change of AA3003 sheet after the hot asymmetric rolling. The average plastic strain ratio of the initial AA3003 sheets was 0.69. After 83% hot asymmetric rolling at $200^{\circ}C$, the average plastic strain ratio was 0.83. The average plastic strain ratio of the 83% hot asymmetrically rolled AA3003 sheet at $200^{\circ}C$ is 1.2 times higher than that of the initial AA3003 sheet. The ${\mid}{\Delta}R{\mid}$ of 83% hot asymmetrically rolled AA3003 sheet at $200^{\circ}C$ is 0.83 times lower than that of the initial AA3003 sheet. This result is due to the development of the intensity of ${\gamma}-fiber$ texture and reduces the intensity of {001}<110> and {001}<100> textures after hot asymmetric rolling of AA3003 sheet.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2012년도 추계 학술논문 발표대회
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• pp.47-49
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• 2012

Under this study, the characteristics of concrete intensity condition following the curing method under the extremely low temperature environment have been contemplated, and as a result, in the event of insulation + heat cable curing, the intensity and accumulated temperature accomplishment period is required for two times of requiring initial frost damage prevention than the case of heating + heat insulation curing method due to the insufficient calories supplied in general.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1997년도 추계학술대회 논문집
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• pp.120-126
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• 1997

This paper examines the crack growth behavior of 7075-T651 aluminum alloy under high-low block loading condition. The cantilever beam type specimen with a chevron notch is used in this study. The crack growth and closure are investgated by compliance method. The applied initial stress ratios are R=-0.5, R=0.0 and R=0.25 Crack length($\alpha$), effective stress intensity factor range(ΔKeff), ratio of effective stress intensity factor range(U) and crack growth rate(d$\alpha$/dN) etc. are inspected fracture mechanics estimate.

• 한국생산제조학회지
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• 제7권2호
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• pp.54-61
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• 1998

This paper examines the crack growth behavior of 7075-T651 aluminum alloy for small tensile overload under high-low block loading condition. The cantilever beam type specimen with a chevron notch is used in this study. The crack growth and closure are investigated by compliance method. The applied initial stress ratios are R=-0.5 R=0.0 and R=0.25 Crack length, effective stress intensity factor range, ratio of effective stress intensity factor range and crack growth rate etc, are inspected with fracture mechanics estimate.

• 한국지반공학회논문집
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• 제28권6호
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• pp.63-70
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• 2012

저강도 강우상태에서 투수계수가 일반적인 절토사면의 흡인력 분포와 안정성에 어떤 영향을 주는지를 평가하였다. 지하수면 위의 불포화 지층의 초기 흡인력을 15 kPa로 가정하였다. 강우 지속시간 증가에 따른 절토사면의 안정성을 평가하기 위해 유한요소법과 한계평형법을 사용하였다. 유한요소 침투해석 결과, 저강도 강우상태에서는 불포화 지층이 계속해서 불포화 상태로 유지되는 현상을 보였다. 또한, 침윤선(wetting front)이 불포화 지층에 남아있는 경우에는 사면의 안정성에 사실상 변화가 없었으나, 침윤선(wetting front)이 지하수면에 도달하는 경우에는 지하수면이 높아짐에 따라 사면안정성이 크게 저하되었다.

• 생명과학회지
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• 제8권4호
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• pp.373-380
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• 1998

A considerable change observed in X-ray diffraction during the muscle contraction was that the movement of myosin head and conformational change of contractile monecules were occurred in the muscle contraction. Time slice requires tension peak after the onset of stimulation and the height of tension peak depends on the number of twitch cycle. The intensity of I$_{11}$, I$_{10}$, 143${\AA}$ reflection is measured with 5ms time resolution and is recorded in isometric tension. The peak height of I$_{11}$ and 143${\AA}$ intensity is changed after the onset of a stimulation I$_{i}$, and the length of twitch is shortened by successive twitches in the case of stimulation TI$_{i}$. On the other hand, the peak height of I$_{11}$ and 215${\AA}$ intensity starts to decrease at the 1st twitch and remains constant at low peak hight without appreciable recovery during the contraction term. In the case of uccessive twitch stimulation, the myosin heads of muscle are once moved from their resting position and never returned to their initial position.

• 대한치과교정학회지
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• 제48권2호
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• pp.90-97
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• 2018

Objective: The aim of this study was to assess the analgesic effect of a single application of low-level laser therapy (LLLT) on spontaneous pain and pain on chewing after placement of initial archwires. Methods: Forty-two patients (26 women, 16 men) were randomly recruited for this split-mouth randomized clinical trial. Each patient received super-elastic nickel-titanium (NiTi) initial archwires (0.012, 0.014, 0.016, and 0.018-inch [in]) in the maxilla for leveling and alignment for an interval of 4 weeks between archwires. One side of the mouth was randomly designated as experimental, while the other side served as placebo. After insertion of each archwire, the experimental side was irradiated with a diode laser for 3 seconds each on 5 points facially and palatally per tooth, from the central incisor to first molar. On the placebo side, the laser device was held the same way but without laser application. A numerical rating scale was used to assess the intensity of spontaneous and masticatory pain for the following 7 days. The Mann-Whitney U test was used to compare pain scores between sides. Results: Patients in the LLLT group exhibited significantly lower mean scores for spontaneous pain after insertion of the initial two archwires (0.012-in and 0.014-in NiTi; p < 0.05), while there was no significant difference for 0.016-in and 0.018-in wires between the LLLT and placebo groups. LLLT significantly reduced chewing pain scores (p < 0.05) for all archwires. Conclusions: A single dose of LLLT considerably lessened postoperative pain accompanying the placement of super-elastic NiTi wires for initial alignment and leveling.

• 한국안전학회지
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• 제5권1호
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• pp.19-29
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• 1990

The objective of this paper is to investigate the effect of residual stresses on the $\Delta$K$\sub$th/ and fatigue crack growth behavior of butt weldments. For this purpose, transverse butt sutmerged arc welding was performed on SM50A steel plate and CT(compact tension) specimens which loading direction is perpendicular to weld bead were selected. Welding residual stresses distribution on the specimen was determined by hole drilling method. The case of crack located parallel to weld bead, the states of as weld and PWHT, $\Delta$K$\sub$th/ of specimens(HAZ, weld zone) was higher than that of the base metal probably because of the compressive residual stresses of crack tip. In low $\Delta$K region, it is estimated that the effects of residual stresses for da/dN are great. In region II, the da/dN of weldments in as weld state was lower than that of the base metal. Though da/dN of Weldments in PWHT state was similar to that of the base metal. The constant of power law, m in two states consisted with the base metal. Therefore , it is estimated that the value of m is not affected by residual stresses. Fatigue crack growth behavior of weldments consisted with the base metal considering the effective stress intensity factor range($\Delta$K$\sub$eff/) included the effect of initial residual stress(Kres). Thus, we can predict the fatigue crack growth behavior of weldment by knowing the distribution of initial residual stress at the crack tip.

• 한국의류학회지
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• 제23권6호
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• pp.853-863
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• 1999

the change of physical properties (thickness, weight, air permeability) and mechanical properties(abrasion resistance breaking load and displacement) of samples were determined after heat exposure by a RPP tester. The effect of exposure time and heat flux intensity on the changes and the relationship between physical properties and mechanical properties were investigated. FR treated cotton Kevlar/PBI and Nomex with different structureal characteristics were chosen for specimens. The changes of physical properties and mechanical properties were calculated based on their initial values before heat exposure. The longer exposure time and the high heat flux intensity the more changes of those properties. Heat flux intensity was more effective on the changes, The showed to be affected by an interplay of shrinkage and pyrolysis products loss. The changes of thickness and abrasion resistance showed to be higher for plain weave fabric and those of air permeabiliyt and breaking load and displacement for twill weave fabric. While FR treated cotton which have high RPP value experienced serious and detrimental changes after heat exposure Kevlar/PBI which has low RPP value showed no high changes. In conclusion it could be confirmed that when total performance of a protective clothing is estimated retention capability of physical and mechanical properties after heat exposure as well as RPP value must be considered.

• Journal of the Optical Society of Korea
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• 제18권3호
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• pp.217-224
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• 2014

A major advantage of wavefront reconstruction based on a series of diffracted intensity images using only single-beam illumination is the simplicity of setup. Here we propose a fast-converging algorithm for wavefront calculation using single-beam illumination. The captured intensity images are resampled to a series of intensity images, ranging from highest to lowest resampling; each resampled image has half the number of pixels as the previous one. Phase calculation at a lower resolution is used as the initial solution phase at a higher resolution. This corresponds to separately calculating the phase for the lower- and higher-frequency components. Iterations on the low-frequency components do not need to be performed on the higher-frequency components, thus making the convergence of the phase retrieval faster than with the conventional method. The principle is verified by both simulation and optical experiments.