• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.259-262
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• 2002

This paper provides the experimental verification of a non-destructive time domain approach to examine structural damage. Time histories of the vibration response of structure were used to identify the presence of damage. Damage in a structure cause changes in the physical coefficients of mass density, elastic modulus and damping coefficient. This paper examines the use of beam like structures with PVDF sensor and PZT actuator to perform identification of those physical parameters, and hence to detect the damage. Experimental results are presented from tests on cantilevered composite beams damaged at different location and with damage of different dimensions. It is demonstrated that the method can sense the presence of damage, and characterize the damage to a satisfactory precision.

• Computers and Concrete
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• v.23 no.5
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• pp.321-327
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• 2019

Experimental isotherm compressive tests show that concrete behaviour is dependent on temperature. The aim of such tests is to reproduce how concrete will behave under environmental changes within a moderate range of temperature. In this paper, a novel constitutive elastic damage behaviour law is proposed based on a free energy with an apparent damage depending on temperature. The proposed constitutive behaviour leads to classical theory of thermo-elasticity at small strains. Fixed elastic mechanical characteristics and fixed evolution law of damage independent of temperature and the material volume element size are considered. This approach is applied to compressive tests. The model predicts compressive strength and secant modulus of elasticity decrease as temperature increases. A power scaling law is assumed for specific entropy as function of the specimen size which leads to a volume size effect on the stress-strain compressive behaviour. The proposed model reproduces theoretical and experimental results from literature for tempertaures ranging between $20^{\circ}C$ and $70^{\circ}C$. The effect of the difference in the coefficient of thermal expansion between the mortar and coarse aggregates is also considered which gives a better agreement with FIB recommendations. It is shown that this effect is of a second order in the considered moderate range of temperature.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.10
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• pp.1869-1876
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• 1992

The effect of particle property on FOD(foreign object damage) and strength degradation in structural ceramics especially, silicon carbide was investigated by accelerating a spherical particle having different material and different size. The damage induced showed significant differences in their patterns with increase of impact velocity. Also percussion cone was formed at the back part of specimen when particle size became large and its impact velocity exceeded a critical value. The extent of ring cracks was linearly related to particle size, however the impact of steel particle produced larger ring cracks than that of SiC particle. Increasing impact velocity the residual strength showed different degradation behaviors according to particle and its size. In the region the impact site represents nearly elastic deformation behavior, the residual strength was dependent upon the depth of cone crack regardless of particle size. However in elastic- plastic deformation region, the radial cracks led to rapid drop in residual strength.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.1
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• pp.13-20
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• 2021

In this paper, a new algorithm is proposed to estimate the damage size by combining the reflected area with the reflected position and extracting contours in proportion to the maximum value of pixels from the visible image. The cumulative summation feature vector algorithm is used to obtain the area of the reflected signal. To get the position of the reflected signal, the signal correlation algorithm is used to decompose the reflected signal from the damage. The proposed algorithm is tested and validated for composite panels. Repetitive experiments are performed and it is confirm that the proposed algorithm is reproducible. Further, it is verified that the damage size can be estimated appropriately by the proposed algorithm.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.106-109
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• 2001

In this work, we investigate the toughening mechanism of the rubber-modified epoxy resin. The fracture toughness($K_{IC}$) is measured using CT specimens for three kinds of rubber-modified epoxy resin with different rubber content. The damage zone and rubber particles around a crack tip of a damaged specimen just before fracture are observed by a polarization microscope and an atomic force microscope(AFM). Both the fracture energy($G_{IC}$) and the size of damage zone increase with the rubber content below l5wt%. The size of the rubber particles can be qualitatively correlated with the $G_{IC}$ and the size of damage zone. The cavitation of the rubber particles inside the damage zone is observed, which is expected to be main toughening mechanism by rubber particles. the stress which causes the cavitation of rubber particles is estimated by the Dugdale model.

• Computers and Concrete
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• v.1 no.2
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• pp.169-188
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• 2004

A coupled damage-viscoplasticity model is presented for the analysis of localisation and size effects. On one hand, viscosity helps to avoid mesh sensitivity because of the introduction of a length scale in the model and, on the other hand, enables to represent size effects. Size effects were analysed by means of three-point bending tests. Correlation between the fracture energy parameter measured experimentally and the density fracture energy modelling parameter is discussed. It has been shown that the dependence of nominal strength and fracture energy on size is determined by the ligament length in comparison with the width of the fracture process zone.

• The Korea Journal of Herbology
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• v.36 no.1
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• pp.51-57
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• 2021

Objects : In this study, I aimed to determine the size and administration Method of pills preparation in Treatise on Cold Damage Diseases. Methods : I investigated the Treatise on Cold Damage Diseases, Newly Revised Materia Medica, Variorum of the Classic of Materia Medica, The Korean Herbal Pharmacopoeia, and recent studies. Results : There were four kinds of pills preparation. Each size of pill preparation was equal to the Odongja, Tanwhan, Yolk, and quarter of daily dosage of Decoction. One pill of Tanwhan was equivalent to 16 pills of Odongja, and one Yolk was equal to 40 pills of Odongja. The Diameter of Odongja was 6.5 mm, Tanwhan was 16.37897 mm, and Yolk was 22.11484 mm. Jeodangwhan was equal to one quarter daily dosage of Jeodangtang. Maximum size to swallow with water was Odongja and daily dosage, which was 16 pills, includes one square-inch-spoon of powder preparation. When we made the pill preparation, it is difficult to make 16 pills using one square-inch-spoon of powder. Therefore, Zhang Zhongjing made one dosage started from 10 pills to 20 pills to find out optimum dose. Due to the difficulty of making precise size of pills and considerable amount of daily dosage, there was no smaller size than Odongja. When the size of Pill preparation was larger than Odongja, it was ground or boiled slightly to make suspensions. Conclusions : These results suggest that the sizes of Pill preparation in the Treatise on Cold Damage Diseases were true compared with reality.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.6
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• pp.738-745
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• 2012

Aircraft battle damage repair(ABDR) is emergency repair method for the damaged aircraft in battle field. The main purpose of the ABDR is to increase the readiness of fighter aircraft during wartime. While many studies have been conducted to develop ABDR method, few efforts have focused on evaluation of damage and determination of the size of hole caused by enemy's anti-aircraft artillery attack. The aim of this study is essentially to quantify damage of aircraft wing attacked by anti-aircraft artillery. The computer simulations was performed to accomplish this goal. A number of simulations have been carried out to compare size of damages under various attack conditions. In conclusion, it was revealed that the size of damage varied depending on the type and direction of cannonball. Furthermore, in this paper, the proper path sizes are suggested for different damage conditions.

• Smart Structures and Systems
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• v.31 no.6
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• pp.573-583
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• 2023

Although unmanned aerial vehicles have been used to overcome the limited accessibility of human-based visual inspection, unresolved issues still remain. Onsite inspectors face difficulty finding previously detected damage locations and tracking their status onsite. For example, an inspector still marks the damage location on a target structure with chalk or drawings while comparing the current status of existing damages to their previous status, as documented onsite. In this study, an augmented-reality-based structural inspection system with onsite damage information marking was developed to enhance the convenience of inspectors. The developed system detects structural damage, creates a holographic marker with damage information on the actual physical damage, and displays the marker onsite via an augmented reality headset. Because inspectors can view a marker with damage information in real time on the display, they can easily identify where the previous damage has occurred and whether the size of the damage is increasing. The performance of the developed system was validated through a field test, demonstrating that the system can enhance convenience by accelerating the inspector's essential tasks such as detecting damages, measuring their size, manually recording their information, and locating previous damages.

• The Korea Journal of Herbology
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• v.33 no.1
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• pp.65-70
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• 2018

Objectives : The purpose of this study was to assume the size of one piece and decocting method of Asini Corii Colla in Treatise on Cold Damage Diseases written at the Eastern han Dynasty. Methods : I assumed the size of one piece and decocting method based on Treatise on Cold Damage Diseases and Prescriptions of the Gold Chamber, Essential Skill to Benefit the People, Classified Emergency Materia Medica, Illustration and Consideration of Plant's Name and Reality, Essential Prescriptions Worth a Thousand Gold, and other articles about Asini Corii Colla. And I compared these results with current merchandize in China, Dong-e E-jiao, China Resuorces DongeEjiao, and Furen Medicine Group Co., LTD. Results : Asini Corii Colla was made of the skin of cattle in Treatise on Cold Damage Diseases written at the Eastern han Dynasty. The weight of one Asini Corii Colla is equal to 6.5 g, which is equal to one rayng of Treatise on Cold Damage Diseases. The size of it is 3.5 cm in width, 9.0 cm in length and 0.17 cm in height. The specific gravity of it was 1.24. The general daily dose was two rayng and also melted in solution. Conclusions : It was easy to measure daily dose two rayng due to weight of one Asini Corii Colla, one rayng is equal to 6.5 g, and also to melt in solution becauase of its rectangular shape and 0.17 cm thickness.