• Smart Structures and Systems
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• 제3권1호
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• pp.23-49
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• 2007

Wavelet transforms are the emerging signal-processing tools for damage identification and time-frequency localization. A small perturbation in a static or dynamic displacement profile could be captured using multi-resolution technique of wavelet analysis. The paper presents the wavelet analysis of damaged linear structural elements using DB4 or BIOR6.8 family of wavelets. Starting with a localized reduction of EI at the mid-span of a simply supported beam, damage modeling is done for a typical steel and reinforced concrete beam element. Rotation and curvature mode shapes are found to be the improved indicators of damage and when these are coupled with wavelet analysis, a clear picture of damage singularity emerges. In the steel beam, the damage is modeled as a rotational spring and for an RC section, moment curvature relationship is used to compute the effective EI. Wavelet analysis is performed for these damage models for displacement, rotation and curvature mode shapes as well as static deformation profiles. It is shown that all the damage indicators like displacement, slope and curvature are magnified under higher modes. A localization scheme with arbitrary location of curvature nodes within a pseudo span is developed for steady state dynamic loads, such that curvature response and damages are maximized and the scheme is numerically tested and proved.

• Computers and Concrete
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• 제16권5호
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• pp.683-701
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• 2015

When approached using nonlinear finite element (FE) techniques, structural analyses generate, for real RC structures, large complex numerical problems. Damage is a major part of concrete behavior, and the discretization technique is critical to limiting the size of the problem. Based on previous work, the ${\mu}$ damage model has been designed to activate the various damage effects correlated with monotonic and cyclic loading, including unilateral effects. Assumptions are formulated to simplify constitutive relationships while still allowing for a correct description of the main nonlinear effects. After presenting classical 2D finite element applications on structural elements, an enhanced simplified FE description including a damage description and based on the use of multi-fiber beam elements is provided. Improvements to this description are introduced both to prevent dependency on mesh size as damage evolves and to take into account specific phenomena (permanent strains and damping, steel-concrete debonding). Applications on RC structures subjected to cyclic loads are discussed, and results lead to justifying the various concepts and assumptions explained.

• Smart Structures and Systems
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• 제25권3호
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• pp.285-299
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• 2020

Long term structural health monitoring has gained wide attention among civil engineers in recent years due to the scale and severity of infrastructure deterioration. Establishing effective damage indicators and proposing enhanced monitoring methods are of great interests to the engineering practices. In the case of bridge health monitoring, long term structural vibration measurement has been acknowledged to be quite useful and utilized in the planning of maintenance works. Previous researches are majorly concentrated on linear time series models for the measurement, whereas nonlinear dependences among the measurement are not carefully considered. In this paper, a new bridge health monitoring method is proposed based on the use of long term vibration measurement. A combination of the fundamental ARMA model and copula theory is investigated for the first time in detecting bridge structural damages. The concept is applied to a real engineering practice in Japan. The efficiency and accuracy of the copula based damage indicator is analyzed and compared in different window sizes. The performance of the copula based indicator is discussed based on the damage detection rate between the intact structural condition and the damaged structural condition.

• Asian Pacific Journal of Cancer Prevention
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• 제13권6호
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• pp.2961-2966
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• 2012

Extremely low frequency electro magnetic fields (EMFs) have been classified as possibly carcinogenic to humans by the International Agency for Research on Cancer. An increased number of chromosomal alterations in peripheral lymphocytes are correlated with elevated incidence of cancer. The aim of the present study was to assess occupationally induced chromosomal damage in EMF workers exposed to low levels of radiation. We used conventional metaphase chromosome aberration (CA) analysis and the micronucleus (MN) assay as biological indicators of non ionizing radiation exposure. In the present study totally 70 subjects were selected including 50 exposed and 20 controls. Informed written consent was obtained from all participants and the study was performed in accordance with the Declaration of Helsinki and the approval of the local ethical committee. A higher degree of CA and MN was observed in exposed subjects compared to controls, the frequency of CA being significantly enhanced with long years of exposure (P<0.05). Moreover increase in CA and MN with age was noted in both exposed subjects and controls, but was significantly greater in the former. The results of this study demonstrated that a significant induction of cytogenetic damage in peripheral lymphocytes of workers occupationally exposed to EMFs in electric transformer and distribution stations. In conclusion, our findings suggest that EMFs possess genotoxic capability, as measured by CA and MN assays; CA analysis appeared more sensitive than other cytogenetic end-points. It can be concluded that chronic occupational exposure to EMFs may lead to an increased risk of genetic damage among electrical workers.

• The Korean Journal of Physiology and Pharmacology
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• 제28권1호
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• pp.1-10
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• 2024

Type 2 diabetes mellitus (T2DM) is characterized by hyperglycemia and dyslipidemia. Carvacrol (CAR) has demonstrated the potential to mitigate dyslipidemia. This study aims to investigate whether CAR can modulate blood glucose and lipid levels in a T2DM rat model by regulating short-chain fatty acids (SCFAs) and the GPR41/43 pathway. The T2DM rat model was induced by a high-fat diet combined with low-dose streptozocin injection and treated with oral CAR and/or mixed antibiotics. Fasting blood glucose, oral glucose tolerance, and insulin tolerance tests were assessed. Serum lipid parameters, hepatic and renal function indicators, tissue morphology, and SCFAs were measured. In vitro, high glucose (HG)-induced IEC-6 cells were treated with CAR, and optimal CAR concentration was determined. HG-induced IEC-6 cells were treated with SCFAs or/and GPR41/43 agonists. CAR significantly reduced blood lipid and glucose levels, improved tissue damage, and increased SCFA levels in feces and GPR41/43 expression in colonic tissues of T2DM rats. CAR also attenuated HG-induced apoptosis of IEC-6 cells and enhanced GPR41/43 expression. Overall, these findings suggest that CAR alleviates blood lipid and glucose abnormalities in T2DM rats by modulating SCFAs and the GPR41/43 pathway.

• Journal of Ginseng Research
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• 제45권2호
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• pp.295-304
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• 2021

Background: Acute promyelocytic leukemia (APL) is a hematopoietic malignancy driven by promyelocytic leukemia-retinoic acid receptor A (PML-RARA) fusion gene. The therapeutic drugs currently used to treat APL have adverse effects. 20(S)-ginsenoside Rh2 (GRh2) is an anticancer medicine with high effectiveness and low toxicity. However, the underlying anticancer mechanisms of GRh2-induced PML-RARA degradation and apoptosis in human APL cell line (NB4 cells) remain unclear. Methods: Apoptosis-related indicators and PML-RARA expression were determined to investigate the effect of GRh2 on NB4 cells. Z-VAD-FMK, LY294002, and C 87, as inhibitors of caspase, and the phosphatidylinositol 3-kinase (PI3K) and tumor necrosis factor-α (TNF-α) pathways were used to clarify the relationship between GRh2-induced apoptosis and PML-RARA degradation. Results: GRh2 dose- and time-dependently decreased NB4 cell viability. GRh2-induced apoptosis, cell cycle arrest, and caspase3, caspase8, and caspase9 activation in NB4 cells after a 12-hour treatment. GRh2-induced apoptosis in NB4 cells was accompanied by massive production of reactive oxygen species, mitochondrial damage and upregulated Bax/Bcl-2 expression. GRh2 also induced PML/PML-RARA degradation, PML nuclear bodies formation, and activation of the downstream p53 pathway in NB4 cells. Z-VAD-FMK inhibited caspase activation and significantly reversed GRh2-induced apoptosis and PML-RARA degradation. GRh2 also upregulated TNF-α expression and inhibited Akt phosphorylation. LY294002, an inhibitor of the PI3K pathway, enhanced the antitumor effects of GRh2, and C 87, an inhibitor of the TNF-α pathway, reversed NB4 cell viability, and GRh2-mediated apoptosis in a caspase-8-dependent manner. Conclusion: GRh2 induced caspase-dependent PML-RARA degradation and apoptosis in NB4 cells via the Akt/Bax/caspase9 and TNF-α/caspase8 pathways.

• 산업융합연구
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• 제21권12호
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• pp.55-62
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• 2023

최근 등장하는 랜섬웨어들은 다양한 공격 기법과 다양한 경로를 통해 공격을 수행하고 있어 조기 탐지와 방어에 많은 어려움을 겪고 있으며, 그 피해 규모도 날로 증가하고 있다. 따라서 본 논문에서는 효과적인 랜섬웨어 탐지를 위하여 파일 암호화와 암호화 패턴을 머신러닝 기반으로 하는 감지 기법을 제안한다. 파일 암호화는 랜섬웨어가 공격하는데 필수적으로 사용하는 기능으로 암호 행위와 암호화 패턴을 분석함으로써 랜섬웨어를 탐지하고 랜섬웨어의 특정 변종이나 새로운 유형의 랜섬웨어를 탐지할 수 있기 때문에 랜섬웨어 공격을 식별하고 차단하는 데 매우 효과적이다. 제안한 머신러닝 기반의 암호화 행위 감지 기법은 암호화 특성과 암호화 패턴 특성을 추출하여 머신러닝 기반의 분류기를 통해 각각 학습을 시켜 해당 행위에 대한 탐지를 진행하고 최종 결과는 두 분류기의 평가 결과를 기반으로 앙상블 분류기에서 랜섬웨어 유무를 판별하여 좀 더 정확도를 높였다. 또한, 제안한 기법을 numpy와 pandas, 파이썬의 사이킷런 라이브러리를 사용하여 구현하여 평가지표를 사용한 성능를 평가한 결과 평균적으로 94%,의 정확도와 95%의 정밀도, 93%의 재현률과 95%의 F1 스코어가 산출되었다. 성능 평가 결과를 보면 암호화 행위 감지를 통해 랜섬웨어 탐지가 가능하다는 것을 확인할 수 있었고 랜섬웨어의 사전 탐지를 위해 제안한 기법의 성능을 높이기 위한 연구도 계속해서 진행되어야 한다.

• 한국식품위생안전성학회지
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• 제28권2호
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• pp.146-151
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• 2013

t-BHP는 대표적인 산화스트레스에 의한 간 손상 모델이며, 본 연구자는 랫드에 기능성이 강화된 기능성 들깻잎 추출물(P. frutescens leaf extract, PLE)을 250, 500 또는 1000 mg/kg body weight (b.w.)으로 6일간 경구 투여하고 t-BHP의 복강 주사로 간 손상을 일으킨 후 기능성 들깻잎 추출물이 간에서 산화스트레스를 얼마나 억제하여 주는지를 혈액의 간 손상 지표인 lactate dehydrogenase (LDH), aspartate aminotransferase (AST) 그리고 alanine aminotransferase (ALT)를 측정하였으며, 간 조직에서 항산화 바이오 마커인 reduced glutathione (GSH), 지질과산화물의 척도인 malondialdehyde (MDA)를 통해서 측정하였다. 산화스트레스에 의한 간 손상시 GSH는 아무것도 처리하지 않은 정상 대조군($146.0{\pm}5.4$ mM GSH/g protein)에 비해 t-BHP로 산화스트레스를 유발한 그룹에서 $128.6{\pm}6.8$ mM GSH/g protein로 감소하였다. 반면 기능성 들깻잎 추출물을 250, 500 그리고 1000 mg/kg b.w. 을 투여한 그룹에서는 $129.3{\pm}2.6$ mM GSH/g protein, $151.9{\pm}6.8$ mM GSH/g protein, $171.9{\pm}5.2$ mM GSH/g protein로 농도 의존적으로 GSH 함량이 회복되는 경향을 나타내며, 500 mg/kg b.w. 투여군부터 정상 대조군의 GSH 함량과 비슷한 수준을 나타내었다. 또한, 간 조직에서 산화스트레스에 의하여 발생된 지질과산화물을 측정하였을 때 t-BHP에 의하여 산화스트레스만 유발한 그룹은 $834.0{\pm}154.7{\mu}M/g$ protein 로 정상 대조군의 $385.6{\pm}39.7{\mu}M/g$ protein 보다 2.17배 높은 MDA를 생성한 것으로 지질과산화가 많이 일어난 것을 확인하였으나, 기능성 들깻잎 추출물을 투여한 그룹의 MDA의 생성량은 $669.2{\pm}145.0$, $595.1{\pm}142.6$, $415.9{\pm}133.8{\mu}M/g$ protein 로 농도에 따라 감소하는 경향을 확인하였다. 랫드의 간 조직에서, 독성을 유발하는 t-BHP를 복강 투여 후 기능성 들깻잎 추출물을 경구 투여하였을 때 지질과산화의 지표인 MDA의 감소와 항산화의 지표인 GSH 함량이 증가하였다. 조직병리학적 확인을 위하여 간 조직을 H&E 염색 후 광학현미경으로 관찰하였을 때, t-BHP만 처리한 음성 대조군의 경우 간 세포의 괴사와 조직의 변형을 확인할 수 있었지만 기능성 들깻잎 추출물을 처리하였을 경우 모두 정상 상태의 조직을 관찰할 수 있었다. 위의 결과들을 종합하였을 때, t-BHP가 간에서 산화스트레스를 유발하여 간 손상을 야기시키고, 간 조직의 인지질 막 손상을 줄 수 있으며, 기능성 들깻잎 추출물은 간 손상에 대한 보호 효과가 있음을 확인하였다.