• 한국구조물진단유지관리공학회 논문집
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• 제25권6호
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• pp.19-26
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• 2021

교량 받침장치부는 상부구조의 수직하중을 지지하여 하부구조에 전달하고, 교량의 붕괴사고를 방지하는 역할을 한다. 하지만, 포항지진에 의하여 총 12개 도로교량의 받침장치 몰탈 파손, 받침장치 파손 및 쐐기 손상이 보고되었다. 본 연구에서는 지진시 교량 받침장치부의 구조 시스템 특성을 고려하여 교각의 코핑부와 무수축몰탈을 포함한 면진받침 장치 실험체의 전단 거동특성 및 손상모드를 평가하였다. 받침장치 쐐기에 대한 영향을 확인하기 위하여 쐐기 설치 유무를 변수로 설정하였으며, 압축-전단 실험을 실시하여 면진장치의 전단 거동특성과 손상모드를 확인하였다. 또한 유한요소해석을 통하여 받침장치의 거동특성 및 각 구성요소별 손상원인을 분석하였다. 실험결과, 쐐기의 충돌 및 손상 발생 이후 급격한 하중변화가 발생하였으며, 받침장치와 무수축몰탈 경계부를 따라 균열이 발생하였다. 쐐기 유무에 따른 쐐기, 앵커 소켓 및 무수축볼탈의 응력거동을 비교함으로써 지진시 교량받침장치부의 손상원인을 규명하였다.

• 한국콘텐츠학회논문지
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• 제9권12호
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• pp.376-384
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• 2009

본 연구는 방사선조사 후 신장 조직의 손상과 방어기전을 알아보고자 생쥐 모델을 이용하여 미세구조를 관찰하였다. 광학현미경(LM)의 관찰 결과; 5Gy 조사 후 10일된 신장 조직에서는 정상조직과 비교하여 사구체가 위축되었으며, 10Gy 관찰에서는 곱슬세관(convoluted tubules)의 막이 파괴되어 세포질이 유출되었다. 투과전자현미경(TEM) 관찰 결과; 5Gy 조사에서는 사립체의 막이 파괴되거나 함몰된 것으로 관찰되었으며, 내부 크리스테의 형태도 소실되었다. 또한 일부에서는 핵막의 파괴도 확인되었다. 10Gy 조사한 조직에서는 기저막의 파괴가 뚜렷하게 관찰되고, 용해소체도 비후 된 것을 관찰하였다. 하지만 프로폴리스 섭식한 실험 군에서는 소기관의 형태가 뚜렷하게 관찰되었고, 핵막과 염색질도 선명하게 관찰되어 방어효과를 확인할 수 있었다.

• 한국터널지하공간학회 논문집
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• 제9권3호
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• pp.299-307
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• 2007

본 논문에서는 터널 숏크리트 라이닝의 장기 화학적 열화에 의한 물리적 손상을 수치적으로 모델링하기 위한 새로운 개념의 해석기법이 제안되었다. 이러한 물리적 손상은 내부균열 발생, 재료 강성과 강도의 저하에 의해 주로 유발되며, 이들은 장기 화학적 열화반응에 의한 체적팽창 및 시멘트질의 침식에 의해 발생된다. 결과적으로, 이러한 숏크리트 라이닝의 손상 메카니즘은 터널내에서 발생할 수 있는 다양한 종류의 열화반응들에서 유사하게 나타난다. 따라서, 본 연구에서는 일련의 화학적 열화 반응에 기인한 물리적 손상 메카니즘을 일반화 하였으며, 열역학에 기반한 수치모델을 수학적으로 유도 하였다. 유도된 수치모델은 3차원 유한요소 프로그램으로 코드화되었으며, 외력과 장기 화학적 열화를 겪고 있는 터널 구조물의 시간의존성 거동 시뮬레이션에 적용된다. 개발된 코드는 몇 개의 예제 수행을 통해 터널설계상에서의 적용성을 검토하였으며, 동일한 열화조건하에서도 주변 지반응력상태에 따라 물리적 손상 속도와 정도가 크게 달라짐을 보였다.

• 대한한의학회지
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• 제22권3호
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• pp.1-10
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• 2001

Objectives : The water extract of Nueihyuljunbang (NHJB) has long been used for treatment of ischemic brain damage in Oriental Medicine. However, little is known about the mechanism by which the water extract of NHJB recovers brain cens from ischemic damage. Methods : To elucidate the protective mechanism on ischemic induced cytotoxicity, we investigated the regulation of lipopolysaccharide (LPS) and phorbol-12-myristate-13-acetate (PMA)-induced inducible nitric oxide synthase (iNOS) expression in C6 glial cells. Results : LPS combined PMA treatment for 72 hours in C6 glial cells markedly induced nitric oxide (NO), but treatment of the cells with the water extract of NHJB decreased dose-dependently nitrite formation. In addition, LPS combined PMA treatment for 72 hours induced severe celt death and lactate dehydrogenase (LDH) release in C6 glial cells. However, treatment of the celts with the water extract of NHJB did not induce significant change compared to control cells. Furthermore, the protective effects of the water extract of NHJB were mimicked by the treatment of NGMMA, a specific inhibitor of NOS. LPS combined PMA induced iNOS activation in C6 glial cells caused chromosomal condensation and fragmentation of the nuclei by caspase activation. The treatment of C6 glial cells with the water extract of NHJB might suppress apoptosis via caspase inhibition by regulation of iNOS expression. Conclusions : From the results, we suggest that the protective effects of the water extract of NHJB against ischemic brain damage may be mediated by regulation of iNOS during ischemic condition.

• Coupled systems mechanics
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• 제8권4호
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• pp.315-338
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• 2019

The numerical investigations have been carried out on reinforced concrete slab against blast loading to demonstrate the accuracy and effectiveness of the finite element based numerical models using commercial package ABAQUS. The response of reinforced concrete slab have been studied against the influence of weight of TNT, standoff distance, boundary conditions, influence of air blast and surface blast. The results thus obtained from simulations were compared with the experiments available in literature. The inelastic behavior of concrete and steel reinforcement bar has been incorporated through concrete damage plasticity model and Johnson-cook models available in ABAQUS were presented. The predicted results through numerical simulations of the present study were found in close agreement with the experimental results. The damage mechanism and stress response of target were assessed based on the intensity of deformations, impulse velocity, von-Mises stresses and damage index in concrete. The results indicate that the standoff distance has great influence on the survivability of RC slab against blast loading. It is concluded that the velocity of impulse wave was found to be decreased from 17 to 11 m/s when the mass of TNT is reduced from 12 to 6 kg. It is observed that the maximum stress in the concrete was found to be in the range of 15 to $20N/mm^2$ and is almost constant for given charge weight. The slab with two short edge discontinuous end condition was found better and it may be utilised in designing important structures. Also it is observed that the deflection in slab by air blast was found decreased by 60% as compared to surface blast.

• Smart Structures and Systems
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• 제31권4호
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• pp.365-381
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• 2023

The existing vision-based techniques for inspection and condition assessment of civil infrastructure are mostly manual and consequently time-consuming, expensive, subjective, and risky. As a viable alternative, researchers in the past resorted to deep learning-based autonomous damage detection algorithms for expedited post-disaster reconnaissance of structures. Although a number of automatic damage detection algorithms have been proposed, the scarcity of labeled training data remains a major concern. To address this issue, this study proposed a semi-supervised learning (SSL) framework based on consistency regularization and cross-supervision. Image data from post-earthquake reconnaissance, that contains cracks, spalling, and exposed rebars are used to evaluate the proposed solution. Experiments are carried out under different data partition protocols, and it is shown that the proposed SSL method can make use of unlabeled images to enhance the segmentation performance when limited amount of ground truth labels are provided. This study also proposes DeepLab-AASPP and modified versions of U-Net++ based on channel-wise attention mechanism to better segment the components and damage areas from images of reinforced concrete buildings. The channel-wise attention mechanism can effectively improve the performance of the network by dynamically scaling the feature maps so that the networks can focus on more informative feature maps in the concatenation layer. The proposed DeepLab-AASPP achieves the best performance on component segmentation and damage state segmentation tasks with mIoU scores of 0.9850 and 0.7032, respectively. For crack, spalling, and rebar segmentation tasks, modified U-Net++ obtains the best performance with Igou scores (excluding the background pixels) of 0.5449, 0.9375, and 0.5018, respectively. The proposed architectures win the second place in IC-SHM2021 competition in all five tasks of Project 2.

• 한국의사학회지
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• 제27권2호
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• pp.99-120
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• 2014

Purpose : There are two types of sleep disturbance: inability to sleep (不眠) and somnolence (多眠). This study is to examine treatments of the two types of sleep disturbance in the Books of Cold Damage and how those theories were established and formed. Methods : 1. Verses including the words related to inability to sleep and somnolence were extracted from "Treatise on Cold Damage Diseases" (傷寒論). 2. Among the Books on Cold Damages that are classified according to the symptoms, 17 books with contents related to inability to sleep and somnolence were selected to collect and classify data in three perspectives: mechanism of disease (病機), method of treatment (治法) and disease pattern (病證). 3. Data collected through the above methods were compared and diagramed. Results & Conclusions : 1. On Cold Damage, inability to sleep is mostly rooted when human body lacks yin energy while having excessive yang energy (陽盛陰虛) due to fire and heat (火熱). The reason could be misuse of perspiration inducing method (汗法) or purgation (下法) on the doctors' part. 2. On Cold Damage, somnolence is rooted when pathogen (邪氣) is spread to yin meridians (陰經) and the human body lacks yang while having excessive yin energy (陰盛陽虛) or when heat (熱邪) is invaded into interior parts (裏部). 3. Many scholars of Cold Damage in later periods had copied the "Treatise on Cold Damage Diseases" for treatments of sleep disturbance but many others have applied the verses from "Treatise on Cold Damage Diseases" or added new treatments. Do jeol-am (陶節庵) and Wang Geung-dang (王肯堂) particularly had deep understanding on "Treatise on Cold Damage Diseases" and utilized the content freely or suggested new remedies because they had thorough knowledge on relating formula as well.

• Geomechanics and Engineering
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• 제22권3호
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• pp.255-264
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• 2020

With the ongoing development of deep mining of coal resources, some coal mine dynamic disasters have exhibited characteristics of both coal-gas outbursts and rockbursts. Therefore, research is required on the mechanism of rockburst-outburst coupling disaster. In this study, the failure characteristics of coal-rock combination structures were investigated using lab-scale physical simulation experiments. The energy criterion of the rockburst-outburst coupling disaster was obtained, and the mechanism of the disaster induced by the gas-solid coupling instability of the coal-rock combination structure was determined. The experimental results indicate that the damage of the coal-rock structure is significantly different from that of a coal body. The influence of the coal-rock structure should be considered in the study of rockburst-outburst coupling disaster. The deformation degree of the roof is controlled by the more significant main role of the gas pressure and the difference in the strength between the rock body and the coal body. The outburst holes and spall characteristics of the coal body after the failure of the coal-rock structure are strongly affected by the difference in strength between the roof and the coal body. The research results provide an in-depth understanding of the mechanism of rockburst-outburst coupling disasters in deep mining.

• 비파괴검사학회지
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• 제19권1호
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• pp.25-33
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• 1999

콘크리트는 다상(multi-phase)의 재료로서 구성되어지는 복합재료의 일종으로써 준취성(quasi-brittle)적인 재료적 특성을 가지고 있기 때문에 실제 복잡한 미시적 파괴특성을 나타낸다. 따라서 콘크리트 구조물의 안전성 확보를 위해서는 먼저 하중의 증가에 따른 콘크리트 내부의 변형특성 및 미시적 파손기구를 파악하여야 하며, 특히 실제 구조물에 있어서는 이들 특성들을 비파괴적으로 상시 (on-line) 모니터링 하여야 할 필요가 있다. 따라서 본 연구에서는 3점 굽힘 하중을 받는 콘크리트 부재의 미시적 파손기구 및 각 파손기구에 대한 AE 특성을 명확히 함으로써 콘크리트 부재의 미시적 손상 및 파괴 특성을 비파괴적으로 평가하고 AE 발생원 위치 추정 기법을 이용하여 균열 발생 및 진전거동을 평가하였다.

• 한국미생물·생명공학회지
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• 제48권2호
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• pp.148-157
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• 2020

Eucalyptus oil is a rich source of bioactive compounds with a variety of biological activities and is widely used in traditional medicine. Eucalyptus citriodora is cultivated for the production of essential oils. However, the mode of antibacterial action of essential oils from E. citriodora is not well-known. This study aimed to determine the chemical components, microbial inhibitory effect, and mechanism of action of the essential oil from E. citriodora. The oil was extracted from E. citriodora leaves by hydro-distillation and the chemical components were analyzed using gas chromatography-mass spectrometry. The antibacterial activities of eucalyptus oil against gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus, and Staphylococcus intermedius) and gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) were screened by disc diffusion method and quantitative analysis was conducted by the microdilution method. The mechanism of action of the extracted essential oil was observed using SEM and analyzed by SDS-PAGE. The major components of E. citriodora oil were citronellal (60.55 ± 0.07%), followed by dl-isopulegol (10.57 ± 0.02%) and citronellol (9.04 ± 0.03%). The antibacterial screening indicated that E. citriodora oil exhibited prominent activity against all tested strains. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against B. subtilis were 0.5% and 1.0%, respectively. The MIC and MBC concentrations against S. aureus, S. intermedius, E. coli, and P. aeruginosa were 1% and 2%, respectively. As observed by SEM, the antibacterial mechanism of E. citriodora oil involved cell wall damage; SDS-PAGE revealed decrease in protein bands compared to untreated bacteria. Thus, E. citriodora oil showed significant antimicrobial properties and caused cellular damage.