• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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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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• 제23권5호
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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.

• 대한기계학회논문집
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• 제16권10호
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• pp.1869-1876
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• 1992

본 연구에서는 고온에서 높은 강도특성을 유지하면서 동시에 내마모성이 뛰어 나 가스터어빈의 부재로서의 사용이 기대되는 탄화규소(SiC) 세라믹에 대하여, 고체입 자의 충격에 의해 생기는 손상에 미치는 입자의 재질 및 크기의 영향을 조사하였다. 또 각 형태의 손상발생 임계치와 강도저하에 미치는 입자크기의 영향에 관해서도 검토 하였다.

• 한국항공우주학회지
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• 제49권1호
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• pp.13-20
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• 2021

본 논문에서는 반사된 면적 결과와 반사된 위치 결과를 중첩하고, 가시화된 이미지에서 픽셀의 최대값에 대한 비율로 윤곽선을 추출하여 손상 크기를 추정하는 알고리즘을 제안하였다. 반사된 신호의 면적을 구하기 위해서 누적함수 특성벡터 알고리즘을 사용하였고, 반사된 신호의 위치를 구하기 위해서 신호 상관관계를 이용해서 측정신호로부터 손상 신호를 분리하였다. 그리고 제안한 손상크기 추정 알고리즘을 복합재 평판에서 실험 수행하여 검증하였다. 임의의 위치에서 반복 실험을 수행해서 제안된 알고리즘이 반복에 따른 재현성이 있음을 검증하였고, 손상크기 변화에 따라 손상 크기를 추정하고 분별할 수 있음을 검증하였다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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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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• 제1권2호
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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.

• 대한본초학회지
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• 제36권1호
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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.

• 한국군사과학기술학회지
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• 제15권6호
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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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• 제31권6호
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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.

• 대한본초학회지
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• 제33권1호
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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.