• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.4
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• pp.73-79
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• 2003

Fatigue test is conducted to see the effect of pre-indentation on the fatigue crack retardation of Al5052-H18 plate. Metallographic observation is introduced to deduce the relationship between fatigue crack retardation and fracture appearance with indentation. The grain size of the specimen becomes smaller with the increase of indentation force and the plastic zone is formed with the decrease of grain size. The fatigue striations are appeared densely as the Indentation force becomes higher. Metallographic observation and fatigue test results show that the indentation force has the limited value in improving fatigue crack retardation. Important point to retard the fatigue crack growth is that the crack growth path should pass through the indented area.

• The Journal of Korean society of community based occupational therapy
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• v.1 no.1
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• pp.41-47
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• 2011

Objective : We try to show the necessity of crafts and arts comparing visual perception of autism with that of mental retardation using craft programmes. Methods : We applied a visual perception programme after sorting 10 autism and 10 mental retardation according to criteria. A used craft programmes are consulted and produced by specialist who are applying crafts as treatment or have experienced applying crafts. The items included potter, mobile art, wheat flour kneading, clay, corrugated cardboard work and color mix work. We applied the programmes twice a week during 4 weeks and used motor-free visual perception test-third edition(MVPT-3) to investigate the effect before and after treatments. Results : First, craft programmes had effect on both autism and mental retardation. Second, craft programmes had more effect on mental retardation. Conclusion : We could know that craft programmes influenced on visual perceptional development of autism and mental retardation.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.119-124
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• 2003

In this study, retardation behavior of fatigue crack under single overloading of the mixed mode I+II state was experimentally investigated. To produce single overload in the mixed mode I+II state, the compact tension shear (CTS) specimen and loading device were used. The propagation tests for fatigue crack were performed under mode I loading overloading afterwards. We examined the observed deformation aspects, variation of fatigue life and crack propagation rate, and the aspects of retardation behavior from tests. The retardation effect of mixed-mode single overload on fatigue crack propagation behavior was smaller than that of mode I single overload. It has been confirmed that the retardation behavior did not immediately appear and the retardation length was short when the component of mixed-mode overload was changed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.2
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• pp.93-98
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• 2015

This study focuses on simulation technology in the injection molding process for plastic optic lenses. The CAE program 3D TIMON was used to predict retardation, flow patterns and warpage deformation. The results were compared to the results of optic lenses as measured using the WPA-100 retardation measurement device with injection molding CAE for retardation predictions. According to the analysis and measured results, the distributions of retardation between the CAE results and the measurement results were similar. It was also confirmed that varying the injection speed had an effect on the injection pressure, warpage deformation and retardation distribution. As the injection speed increases, the injection pressure also increases and warpage deformation decreases. However, as the injection speed increases, the retardation distribution deteriorates.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.2
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• pp.126-136
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• 1999

We studied on crack growth retardation in single overloading condition. Crack tip branching which as the second mechanism on crack growth retardation was examined. Crack tip branching was observed to kinked type and forked type. It was found that the branching angle range was from 25 to 53 degree. The variations of crack driving force with branching angle were calculated with finite element method The variation of {{{{ KAPPA _I}}}}, {{{{ KAPPA _II}}}} and total crack driving force(K) were examined respectively So {{{{ KAPPA _I}}}}, {{{{ KAPPA _II}}}} and K mean to mode I, II and total crack driving force. Present model(Willenborg's model) for crack growth retardation prediction was modified to take into consideration the effects of crack tip branching When we predicted retardation with modified model. it was confirmed that predicted and experimental results coincided with well each other.

• Journal of Information Display
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• v.9 no.4
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• pp.1-5
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• 2008

This paper investigates the effect of the electrode edge of a patterned vertical alignment (PVA) liquid crystal (LC) device on the viewing angle characteristics. In general, a transmissive LCD applies an LC layer with half-wave retardation for a bright state and with zero retardation for a dark state. The retardation of the LC layer would be distorted in each point, however, when a voltage is applied because of the non-uniform voltage distribution in the electrode edge effect. In this paper, the feasibility of the full effect of the electrode edge on the viewing angle property is considered, and the optical viewing angles of the VA LCD with a uniform half-wave LC layer and the PVA LCD with a practical non-uniform LC layer are compared.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.4
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• pp.670-679
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• 1989

The constant amplitude loading and 100% single overloading fatigue studies of domestic high tensile 7075-T73 aluminum alloy were performed to exmine the effect of specimen thickness and its mechanisms on fatigue crack growth behavior. The stage II fatigue crack growth rates tend to increase with decreasing specimen thickness under constant amplitude loading condition and this has relation with stress intensity factors and plastic zone size. The amount of retardation by an overload increased with decreasing specimen thickness when the crack depth and baseline stress intensity factors were constant. The crack depth is one of major factors which affect retardation phenomena by an overload and the amount of retardation increase with decreasing the crack depth. Its main mechanisms are crack closure and decreasing of K at the crack tip by branching and deflection of crack. And they are affected by near surface more severely than central portion of specimen.

• Korean Journal of Food Science and Technology
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• v.51 no.1
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• pp.48-51
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• 2019

The purpose of this study was to investigate the retardation effect of commercial wheat flours on starch retrogradation using a model system, the rice cake (garaetteok). Rice cakes were prepared with four different commercial wheat flours in various concentrations (0.1-0.7%). The rice cakes were vacuum-packed and stored for 4 days at room temperature. The rice cakes containing > 0.3% wheat flour were not able to maintain their original appearance due to enzymatic decomposition, whereas the rice cakes containing 0.1% wheat flour did not reveal any retrogradation-retardation effect. Garaetteok containing 0.2% wheat flour maintained its shape well and showed considerably lower hardness than that of the control, thereby demonstrating a retrogradation-retardation effect. The commercial wheat flours clearly showed the retardation effect on starch retrogradation, and thus, it is important to use a proper amount. On the other hand, the retrogradation-retardation effect of the different wheat flours was not significantly altered possibly due to the same origin of wheat grain.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1186-1192
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• 1990

It is well known that the fatigue crack growth retardation following overloads can be estimated reasonably well by the models of Wheeler and Willenborg. These models, however, can not explain the delayed-retardation revealed by every experimental result. This means that they necessarily have some qualitative defects in themselves despite of a fair approximation of quantity. In fact, they did not take into account the effects of the compressive portion of the overload cycle such as the change of reversed plastic zone size. The present study is focused on the acceleration effect in the reversed plastic zone in order to analyze qualitatively delayed-retardation phenomenon following single peak overload on the fatigue crack growth behavior using 2024-T3 aluminum alloy.

• Korean Journal of Pharmacognosy
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• v.13 no.3
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• pp.116-121
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• 1982

In order to investigate the side-effects of crude drugs, twenty drugs have been tested for the teratogenic effect in rats. Among seven drugs contained alkaloid as their ingredients, no one showed teratogenic effect, but Veratri rhizoma showed embryo-toxic as revealed by severe retardation in growth of the fetuses. The other thirteen drugs which have been used freguently in oriental medicines exhibited no teratogenic effect. Cyclophosphamide used as a reference compound showed severe malformation and retardation in the growth of rat fetuses. These findings suggest that the drug extracts adopted for the study might have no teratogenic effect in the rats.