• Title/Summary/Keyword: 손상 메커니즘

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Nonlinear Explosion Analyses for Damage Assessments of Reinforced Concrete Structures (비선형 폭발해석에 의한 콘크리트 구조물의 손상도 평가)

  • Huh, Taik Nyung;Kim, Seong Yun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.37 no.1
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    • pp.1-7
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    • 2017
  • In general, the large loads which are applied from explosion, impact, earthquake and wind at a short time caused the materials of structures to large deformations, rotations and strains locally. If such phenomena will be analyzed, hydrocodes which can be considered fluid-structure interaction under computational continuum mechanics are inevitably needed. Also, the explosion mechanism is so complicated, it is reasonable that the behaviors of structure are predicted through explosion analyses and experiment at the same time. But, unfortunately, it is true that explosion experiments are limited to huge cost, large experiment facilities and safety problems. Therefore, in this study, it is shown that the results of explosion analyses using the AUTODYN are agreed with those of existing explosion experiments for reinforced concrete slabs within reasonable error limits. And the explosion damage of the same reinforced concrete slab are assessed for quite different reinforcement arrangement spacings, concrete cover depths, and vertical reinforcements. From the explosion analyses, it is known that the more the ratio of slab thickness to reinforcement arrangement spacing is increased, and small-diameter reinforcements are used than large-diameter reinforcements on the same reinforcement ratio, and vertical reinforcements are used, the more the anti-knock capacities are improved.

Laser Transmission Welding of Flexible Substrates and Evaluation of the Mechanical Properties (플렉서블 기판의 레이저 투과 용접 및 기계적 특성 평가)

  • Ko, Myeong-Jun;Sohn, Minjeong;Kim, Min-Su;Na, Jeehoo;Ju, Byeong-Kwon;Park, Young-Bae;Lee, Tae-Ik
    • Journal of the Microelectronics and Packaging Society
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    • v.29 no.2
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    • pp.113-119
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    • 2022
  • In order to improve the mechanical reliability of next-generation electronic devices including flexible, wearable devices, a high level of mechanical reliability is required at various flexible joints. Organic adhesive materials such as epoxy for bonding existing polymer substrates inevitably have an increase in the thickness of the joint and involve problems of thermodynamic damage due to repeated deformation and high temperature hardening. Therefore, it is required to develop a low-temperature bonding process to minimize the thickness of the joint and prevent thermal damage for flexible bonding. This study developed flexible laser transmission welding (f-LTW) that allows bonding of flexible substrates with flexibility, robustness, and low thermal damage. Carbon nanotube (CNT) is thin-film coated on a flexible substrate to reduce the thickness of the joint, and a local melt bonding process on the surface of a polymer substrate by heating a CNT dispersion beam laser has been developed. The laser process conditions were constructed to minimize the thermal damage of the substrate and the mechanism of forming a CNT junction with the polymer substrate. In addition, lap shear adhesion test, peel test, and repeated bending experiment were conducted to evaluate the strength and flexibility of the flexible bonding joint.

Effect of Heat-Killed Enterococcus faecalis, EF-2001 on C2C12 Myoblast Damage Induced by Oxidative Stress and Muscle Volume Decreased by Sciatic Denervation in C57BL/6 Mice (산화스트레스에 의해 유도된 C2C12 근세포 손상과, 신경절제에 의해 근감소가 유도된 C57BL/6 마우스에서 열처리 사균체 엔테로코커스 패칼리스 EF-2001의 효과)

  • Chang, Sang-Jin;Lee, Myung-Hun;Kim, Wan-Joong;Chae, Yuri;Iwasa, Masahiro;Han, Kwon-Il;Kim, Wan-Jae;Kim, Tack-Joong
    • Journal of Life Science
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    • v.29 no.2
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    • pp.215-222
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    • 2019
  • Muscle dysfunction may arise from skeletal muscle atrophy caused by aging, injury, oxidative stress, and hereditary disease. Powdered heat-killed Enterococcus faecalis (EF-2001) has anti-allergy, anti-inflammatory, and anti-tumor effects. However, its antioxidant and anti-atrophy effects are poorly characterized. In this study, we examined the effects of EF-2001 on muscle atrophy. To determine the protective effect of EF-2001 on oxidative stress, C2C12 myoblasts were treated with $H_2O_2$ to induce oxidative stress. This induced cell damage, which was reduced by treatment with EF-2001. The mechanism of EF-2001's effect was examined in response to oxidative stress. Treatment with EF-2001 reversed the expression of HSP70 and SOD1 proteins. Also, mRNA levels of Atrogin-1/MAFbx and MuRF1 increased under oxidative stress conditions but decreased following EF-2001 treatment. To evaluate muscle volume, two and three dimensional models of the muscles were analyzed using micro-CT. As expected, muscle volume decreased after sciatic denervation and recovered after oral administration of EF-2001. Therefore, EF-2001 is a candidate for the treatment of muscular atrophy, and future discovery of the additional effects of EF-2001 may yield further applications as a functional food with useful activities in various fields.

Review of Failure Mechanisms on the Semiconductor Devices under Electromagnetic Pulses (고출력전자기파에 의한 반도체부품의 고장메커니즘 고찰)

  • Kim, Dongshin;Koo, Yong-Sung;Kim, Ju-Hee;Kang, Soyeon;Oh, Wonwook;Chan, Sung-Il
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.6
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    • pp.37-43
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    • 2017
  • This review investigates the basic principle of physical interactions and failure mechanisms introduced in the materials and inner parts of semiconducting components under electromagnetic pulses (EMPs). The transfer process of EMPs at the semiconducting component level can be explained based on three layer structures (air, dielectric, and conductor layers). The theoretically absorbed energy can be predicted by the complex reflection coefficient. The main failure mechanisms of semiconductor components are also described based on the Joule heating energy generated by the coupling between materials and the applied EMPs. Breakdown of the P-N junction, burnout of the circuit pattern in the semiconductor chip, and damage to connecting wires between the lead frame and semiconducting chips can result from dielectric heating and eddy current loss due to electric and magnetic fields. To summarize, the EMPs transferred to the semiconductor components interact with the chip material in a semiconductor, and dipolar polarization and ionic conduction happen at the same time. Destruction of the P-N junction can result from excessive reverse voltage. Further EMP research at the semiconducting component level is needed to improve the reliability and susceptibility of electric and electronic systems.

Toxicity Monitoring and Assessment of Nanoparticles Using Bacteria (박테리아를 이용한 나노입자의 독성평가 및 탐지)

  • Hwang, Ee-Taek;Lee, Jung-Il;Sang, Byoung-In;Gu, Man-Bock
    • KSBB Journal
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    • v.22 no.6
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    • pp.414-420
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    • 2007
  • Nanomaterials have been applied to various fields due to their advantageous characteristics such as high surface area, rapid diffusion, high specific surface areas, reactivity in liquid or gas phase, and a size close to biomacromolecules. Up to date, increased manufacturing and frequently use of the materials, however, revoke people's concerns on their hazard impact including toxicity the materials. Many research groups have carried out different protocols to evaluate toxic effects of nanomaterilas on different organisms, and consequently, nanomaterials are known to cytotoxicity. In this paper, we reviewed some of the most reports on toxic effects of several nanoparticles specifically on bacteria. There are numbers of reports focused on antibacterial effect of nanoparticles based on bacterial cell viability. Therefore, the application of each nanomaterial should be concerned with its toxicity and its toxic effect should be evaluated in terms of concentrations and sizes of the nanomaterials used, prior to use of a nanomaterial.

Application of Laser Surface Treatment Technique for Adhesive Bonding of Carbon Fiber Reinforced Composites (탄소복합재 접착공정을 위한 CFRP의 레이저 표면처리 기법의 적용)

  • Hwang, Mun-Young;Kang, Lae-Hyong;Huh, Mongyoung
    • Composites Research
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    • v.33 no.6
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    • pp.371-376
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    • 2020
  • The adhesive strength can be improved through surface treatment. The most common method is to improve physical bonding by varying the surface conditions. This study presents the effect of laser surface treatment on the adhesive strength of CFRP. The surface roughness was patterned using a 1064 nm laser. The effects of the number of laser shots and the direction and length of the pattern on the adhesion of the CFRP/CFRP single joint were investigated through tensile tests. Tests according to ASTM D5868 were performed, and the bonding mechanism was determined by analyzing the damaged surface after a fracture. The optimized number of the laser shots and the optimized depth of the roughness should be required to increase the bonding strength on the CFRP surface. When considering the shear stress in the tensile direction, the roughness pattern in the direction of 45° that increases the length of the fracture path in the adhesive layer resulted in an increase of the adhesive strength. The surface treatment of the bonding surface using a laser is a suitable method to acquire a mechanical bonding mechanism and improve the bonding strength of the CFRP bonding joint. The study on the optimized laser process parameters is required for utilizing the benefits of laser surface processing.

Green Synthesis of Nanoceria and the Mechanism Behind Their Antibacterial Activity (나노세리아의 친환경 합성과 항균 활성 메커니즘)

  • Maheshkumar Prakash Patil;Yong-Suk Lee;Mi Jeong Jo;Yong Bae Seo;Gun-Do Kim
    • Journal of Life Science
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    • v.34 no.9
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    • pp.647-655
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    • 2024
  • The synthesis of cerium oxide nanoparticles (nanoceria, CeO2) has received significant attention across scientific and technological disciplines in the last decade. This article explores an overview of the green synthesis method and the antibacterial activity of nanoceria. The utilization of biological materials, such as plants and microorganisms, in the synthesis of nanoceria, has gained attention as an ecofriendly approach. Plants are rich in phytochemicals, including alkaloids, flavonoids, phenols, proteins, and other nutritious components. Likewise, microorganisms generate bioactive metabolites, pigments, enzymes, proteins, acids, and antibiotics. The phytochemicals and metabolites are involved in the reduction of metal salt into nanoceria and provide stability to synthesized nanoparticles. Nanoceria synthesis using plants and microorganisms is facile and ecofriendly, and synthesized nanoceria are biocompatible. Many biomedical applications of nanoceria have been reported, including those that are anticancer, anti-inflammatory, larvicidal, enzyme inhibiting, antibiofilm, and antimicrobial. However, in this review, we focused on and described in detail the antibacterial potential of nanoceria. The antibacterial activity of nanoceria occurs due to excessive reactive oxygen species generation, the impairment of the cell membrane, and the inhibition of cellular mechanisms. Ultimately, this review's primary goal is to provide readers with a logical understanding of the significant achievements of nanoceria as a cutting-edge therapeutic agent for treating a range of microbial pathogens and combating other diseases.

Effects of Ethanol Extract from Lathyrus palustris on Anti-inflammation Response of RAW 264.7 Cell (RAW 264.7 대식세포 염증반응에 대한 털연리초 에탄올 추출물의 항염증 효과)

  • Nam, Jung Hwan
    • Korean Journal of Plant Resources
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    • v.33 no.4
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    • pp.287-292
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    • 2020
  • Lathyrus palustris often used as a treatment for inflammation of the kidneys in Korean traditional medication. Generally, drugs for arthritis have anti-inflammatory and antinociceptive properties. However, the validity of the anti-inflammatory effect has not been scientifically investigated so far. Therefore, the purpose of the research was to investigate the latent anti-inflammatory ability of L. palustris using the ethanol extract. To evaluate the anti-inflammatory activities, we examined the inflammatory arbitrators such as a nitric oxide (NO) and prostaglandin E2 (PGE2) on RAW 264.7 cells. Our results indicated that ethanol extract significantly inhibited the lipopolysaccharide E (LPS) derived PGE2 production in RAW 264.7 cell. The inhibitory activity of ethanol extract for PGE2 tests with inhibition ratio showed in 40 ㎍/mL. Overall, PGE2 tests had a higher inhibitory effect on inflammation than NO tests. This result anticipated that the ethanol extract from L. palustris is a good candidate for developing the origin of anti-inflammatory agents.

EM Algorithm and Two Stage Model for Incomplete Data (불완전한 자료에 대한 보완기법(EM 알고리듬과 2단계(Two Stage) 모델))

  • 박경숙
    • Korea journal of population studies
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    • v.21 no.1
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    • pp.162-183
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    • 1998
  • This study examines the sampling bias that may have resulted from the large number of missing observations. Despite well-designed and reliable sampling procedures, the observed sample values in DSFH(Demographic Survey on Changes in Family and Household Structure, Japan) included many missing observations. The head administerd survey method of DSFH resulted in a large number of missing observations regarding characteristics of elderly non-head parents and their children. In addition, the response probability of a particular item in DSFH significantly differs by characteristics of elderly parents and their children. Furthermore, missing observations of many items occurred simultaneously. This complex pattern of missing observations critically limits the ability to produce an unbiased analysis. First, the large number of missing observations is likely to cause a misleading estimate of the standard error. Even worse, the possible dependency of missing observations on their latent values is likely to produce biased estimates of covariates. Two models are employed to solve the possible inference biases. First, EM algorithm is used to infer the missing values based on the knowledge of the association between the observed values and other covariates. Second, a selection model was employed given the suspicion that the probability of missing observations of proximity depends on its unobserved outcome.

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Free radical scavenging activity and protective effect of three glycyrrhiza varieties against hydrogen peroxide-induced oxidative stress in C6 glial cells (종류별 감초의 라디칼 소거능 및 H2O2에 의한 C6 glial 세포의 산화적 스트레스 개선 효과)

  • Kim, Ji Hyun;Cho, Min Ji;Park, Chan Hum;Cho, Eun Ju;Kim, Hyun Young
    • Journal of Applied Biological Chemistry
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    • v.63 no.4
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    • pp.327-334
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    • 2020
  • Oxidative stress is common cause of neurodegenerative diseases. The purpose of this study is to investigate the in vitro free radical scavenging activity and protective effect of three Glycyrrhiza species including Glycyrrhiza uralensis, G. glabra, and a new variety of Glycyrrihza (Shinwongam, SW) against hydrogen peroxide-induced oxidative stress in C6 glial cells. In vitro assays, radical scavenging activities of G. uralensis, G. glabra, and SW against 2,2-diphenyl-1-picrylhydrazyl, ·OH, and O2- increased as concentration-dependent manner. In addition, the SW was found to contain the highest polyphenol and flavonoid contents. The treatment of H2O2 to C6 glial cell induced oxidative stress, whereas G. uralensis, G. glabra, and SW significantly increased the cell viability as dose-dependent manner. In particular, SW exerted stronger protective effect on H2O2-induced cytotoxicity, than G. uralensis and G. glabra. Furthermore, reactive oxygen species (ROS) formation was significantly elevated by H2O2 in C6 glial cells. However, treatments of G. uralensis, G. glabra, and SW decreased ROS formation. In addition, SW decreased pro-inflammatory related protein expression levels such as inducible nitric oxide synthase and cyclooxygenase-2, compared to H2O2-treated control group. These results indicated that G. uralensis and G. glavra, especially SW, may be useful for preventing from oxidative stress-induced neuronal damage by regulating inflammatory reaction.