• 운동영양학회지
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• 제24권4호
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• pp.28-33
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• 2020

[Purpose] This study aimed to investigate the effects of branched-chain amino acid (BCAA) supplement on delayed onset muscle soreness (DOMS) by analyzing the maximum muscle strength and indicators of muscle damage. [Methods] Twelve men with majors in physical education were assigned to the BCAA group and placebo group in a double-blinded design, and repeated measurements were conducted. DOMS was induced with an isokinetic exercise. Following BCAA administration, the changes in the knee extension peak torque, flexion peak torque, aspartate aminotransferase (AST), creatine kinase (CK), and lactate dehydrogenase (LDH) concentrations were analyzed. The maximum knee muscle strength was measured at the baseline (pre-D0) following BCAA administration for 5 days before exercise (-D5, -4D, -3D, -2D, -1D). In contrast, the post-treatment measurements (D3) were recorded after BCAA administration for 3 days (post-D0, D1, D2). Blood samples were obtained before (pre-D0), immediately after (post-D0), 24 h (D1), 48 h (D2), and 72 h (D3) after the exercise to analyze the indicators of muscle strength. BCAA was administered twice daily for 8 days (5 days and 3 days before inducing DOMS and during the experimental period, respectively). [Results] There was no difference in the flexion peak torque between the groups. However, the BCAA group showed a significantly higher extension peak torque at D3 (second isokinetic exercise), compared to the placebo group (p<.05). There was no difference in AST changes between the groups. Nonetheless, the CK and LDH were significantly reduced in the BCAA group, compared to the placebo group. There was no correlation between the extension peak torque and flexion peak torque. However, the CK and LDH increased proportionately in DOMS. Moreover, their concentrations significantly increased with a decreasing peak torque (p<.01). [Conclusion] An exercise-induced DOMS results in a decrease in the peak torque and a proportional increase in the CK and LDH concentrations. Moreover, the administration of BCAA inhibits the reduction of the extension peak torque and elevation of CK and LDH concentrations. Therefore, BCAA might be administered as a supplement to maintain the muscle strength and prevent muscle damage during vigorous exercises that may induce DOMS in sports settings.

• 자원ㆍ환경경제연구
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• 제23권4호
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• pp.689-718
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• 2014

본 연구는 홍수피해가 관련 산업부문의 자본을 감소시킬 경우 국가경제에 미치는 파급효과를 완전예측형 동태CGE모형을 이용하여 2010년을 기준연도로 분석하였다. 여러 홍수피해 항목들 중에서 통계자료가 확보될 수 있는 농경지, 선박, 공공시설의 물적 피해 항목에 분석을 한정하였다. 홍수피해의 시나리오는 1991년~2010년 기간 홍수피해를 2010년 기준으로 불 변화하여 항목별 홍수피해의 평균과 최대로 각각 채택하였다. 분석 결과, 산업별 생산의 경우에는 자본스톡이 직접적으로 감소하는 수산업+운송업의 생산 감소율이 가장 크고 다음으로 농임 업의 생산감소율이 큰 것으로 나타났다. GDP는 충격 기준연도에 벤치마크 해 대비로는 0.001%~0.057% 그리고 초기 자본감소 대비로는 약 11% 감소하는 것으로 분석되었다. 동태적으로는 GDP는 말기로 가정된 2030년까지 서서히 감소하는 것으로 분석되어서 홍수피해가 자본을 감소시킬 경우 국가경제에 미치는 영향력은 오래 지속되는 것으로 나타났다.

• Geomechanics and Engineering
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• 제20권5호
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• pp.461-474
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• 2020

Analysing the incompatible deformation and damage evolution around the tunnels in mixed strata is significant for evaluating the tunnel stability, as well as the interaction between the support system and the surrounding rock mass. To investigate this issue, confined compression tests were conducted on upper-soft and lower-hard strata specimens containing a circular hole using a rock testing system, the physical mechanical properties were then investigated. Then, the incompatible deformation and failure modes of the specimens were analysed based on the digital speckle correlation method (DSCM) and Acoustic Emission (AE) data. Finally, numerical simulations were conducted to explore the damage evolution of the mixed strata. The results indicate that at low inclination angles, the deformation and v-shaped notches inside the hole are controlled by the structure plane. Progressive spalling failure occurs at the sidewalls along the structure plane in soft rock. But the transmission of the loading force between the soft rock and hard rock are different in local. At high inclination angles, v-shaped notches are approximately perpendicular to the structure plane, and the soft and hard rock bear common loads. Incompatible deformation between the soft rock and hard rock controls the failure process. At inclination angles of 0°, 30° and 90°, incompatible deformations are closely related to rock damage. At 60°, incompatible deformations and rock damage are discordant due that the soft rock and hard rock alternately bears the major loads during the failure process. The failure trend and modes of the numerical results agree very well with those observed in the experimental results. As the inclination angles increase, the proportion of the shear or tensile damage exhibits a nonlinear increase or decrease, suggesting that the inclination angle of mixed strata may promote shear damage and restrain tensile damage.

• Structural Engineering and Mechanics
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• 제32권2호
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• pp.193-212
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• 2009

The resilience of a city confronted with a terrorist bomb attack is the background of the paper. The resilience strongly depends on vital infrastructure and the physical protection of people. The protection buildings provide in case of an external explosion is one of the important elements in safety assessment. Besides the aspect of protection, buildings facilitate and enable many functions, e.g., offices, data storage, -handling and -transfer, energy supply, banks, shopping malls etc. When a building is damaged, the loss of functions is directly related to the location, amount of damage and the damage level. At TNO Defence, Security and Safety methods are developed to quantify the resilience of city infrastructure systems (Weerheijm et al. 2007b). In this framework, the dynamic response, damage levels and residual bearing capacity of multi-storey RC buildings is studied. The current paper addresses the aspects of dynamic response and progressive collapse, as well as the proposed method to relate the structural damage to a volume-damage parameter, which can be linked to the loss of functionality. After a general introduction to the research programme and progressive collapse, the study of the dynamic response and damage due to blast loading for a single RC element is described. Shock tube experiments on plates are used as a reference to study the possibilities of engineering methods and an explicit finite element code to quantify the response and residual bearing capacity. Next the dynamic response and progressive collapse of a multi storey RC building is studied numerically, using a number of models. Conclusions are drawn on the ability to predict initial blast damage and progressive collapse. Finally the link between the structural damage of a building and its loss of functionality is described, which is essential input for the envisaged method to quantify the resilience of city infrastructure.

• Structural Engineering and Mechanics
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• 제81권6호
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• pp.665-675
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• 2022

The safety problems of giant hydraulic structures such as dams caused by terrorist attacks, earthquakes, and wars often have an important impact on a country's economy and people's livelihood. For the national defense department, timely and effective assessment of damage to or impending damage to dams and other structures is an important issue related to the safety of people's lives and property. In the field of damage assessment and vulnerability analysis, it is usually necessary to give the damage assessment results within a few minutes to determine the physical damage (crack length, crater size, etc.) and functional damage (decreased power generation capacity, dam stability descent, etc.), so that other defense and security departments can take corresponding measures to control potential other hazards. Although traditional numerical calculation methods can accurately calculate the crack length and crater size under certain combat conditions, it usually takes a long time and is not suitable for rapid damage assessment. In order to solve similar problems, this article combines simulation calculation methods with machine learning technology interdisciplinary. First, the common concrete gravity dam shape was selected as the simulation calculation object, and XFEM (Extended Finite Element Method) was used to simulate and calculate 19 cracks with different initial positions. Then, an LSTM (Long-Short Term Memory) machine learning model was established. 15 crack paths were selected as the training set and others were set for test. At last, the LSTM model was trained by the training set, and the prediction results on the crack path were compared with the test set. The results show that this method can be used to predict the crack propagation path rapidly and accurately. In general, this article explores the application of machine learning related technologies in the field of mechanics. It has broad application prospects in the fields of damage assessment and vulnerability analysis.

• 한국건축시공학회지
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• 제24권3호
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• pp.297-308
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• 2024

본 연구에서는 화재로 손상된 콘크리트의 손상 깊이 판정방법을 제안하고자 하였다. 고온에 노출된 콘크리트의 경우 내부 조직이 팽창하여 건전한 부위보다 손상부위의 공극이 다량 발생하고 미세균열이 발생됨에 따라 흡수율이 더 높아져 수중 침치후 건조를 하는과정에서 건전부위보다 손상부위의 늦은 건조속도와 이에 따른 명도차이에 의한 색상차이를 이용하여 손상 깊이를 측정하는 것이다. 수중 침지방법의 경우 배합별로 각각 38.7 및 37.5mm로 나타났는데, 기존 페놀프탈레인에 의한 중성화 측정 방법보다 손상깊이를 깊게 추정하는 것을 알 수 있었다. 이는 Portlandite(Ca(OH)₂)의 존재여부에 따라 발색이 되는 페놀프탈레인법에 비해 조직이완에 따른 흡수율 원리를 이용한 손상 깊이를 측정하는 방법이 더 민감도가 높아 얻어진 결과로 사료된다.

• Applied Microscopy
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• 제42권3호
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• pp.136-141
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• 2012

Diversification and individualization are pursued to fulfill the increasing human desire for beauty. There are many methods to change human appearances; of these, a permanent wave is often applied to improve beauty. A permanent wave uses physical and chemical methods to break and reform the bonds of natural hair. Thus, research into the optimized conditions for permanent waves is necessary to minimize hair damage and improve the efficiency of the treatment. The object of this study is to examine the effect of varying the alkalinity (8%, 12%, and 16%) of the permanent wave treatment on the wave efficiency, degree of hair damage via tensile strength, and degree of hair protein release. The results indicate that the treatment with the highest alkalinity (16%) is more effective than that with 8% alkalinity; however, the degree of hair damage when treated with the 16% alkalinity wave is higher than with the 8% alkalinity wave. Additionally, hair proteins increasingly dissolve with increasing alkalinity of the permanent wave.

• Smart Structures and Systems
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• 제6권2호
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• pp.115-133
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• 2010

A modal filter is a tool used to extract the modal coordinates of each individual mode from a system's output. This is achieved by mapping the response vector from the physical space to the modal space. It decomposes the system's responses into modal coordinates, and thus, on the output of the filter, the frequency response with only one peak corresponding to the natural frequency to which the filter was tuned can be obtained. As was shown in the paper (Deraemecker and Preumont 2006), structural modification (e.g. a drop in stiffness or mass due to damage) causes the appearance of spurious peaks on the output of the modal filter. A modal filter is, therefore, a great indicator of damage detection, with such advantages as low computational effort due to data reduction, ease of automation and lack of sensitivity to environmental changes. This paper presents the application of modal filters for the detection of stiffness changes. Two experiments were conducted: the first one using the simulation data obtained from the numerical 7DOF model, and the second one on the experimental data from a laboratory stand in 4 states of damage.

• 한국실내디자인학회논문집
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• 제25권3호
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• pp.82-89
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• 2016

This study investigated the preservation status of wooden architectural heritages, designated as Chungcheongbuk-do designated heritage in Jecheon. The purpose of this paper is to find the damage cause and the preservation method of wooden architectural heritages. It was conducted using the research methods of the existing literature and field survey to compare a current status of wooden architectural heritages. The result are as followings. Firstly, it was found the problems of a break, a damage, etc. in the platform and the problems of a cracking, an exfoliation, a corrosion, a warp, etc. in the wall. And, it was found a cracking of the beam(梁) and a roof tile(瓦), a falling of Angto(仰土), a sagging roof, etc. in the roof. Secondly, the damage causes of wooden architectural heritages were mostly caused by the physical limitations of the materials. And, it was caused by a rainwater, a subsidence of ground settlement, a destruction of waterproof membrane, etc. Lastly, the repair methods are making a quicklime layer in the soil mound on a cracking and an exfoliation part, a resin treatment or strut operation on a corrosion part of column, etc.

• 한국콘텐츠학회논문지
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• 제13권8호
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• pp.152-159
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• 2013

사회가 발전해 감에 따라 범죄가 급속도로 증가함과 동시에 청소년들이 저지르는 비행도 급속하게 늘어가고 있다. 최근 발생하는 청소년들의 비행은 잔인화 흉폭화 심각화됨으로 인하여 주변의 청소년들은 비행에 대한 두려움을 느끼고 있다. 특히, 폭력의 경우 청소년이 받게 되는 피해가 크기 때문에, 폭력비행에 의한 두려움은 피해청소년 및 주변청소년에게 신체적 피해 뿐 만 아니라 심각한 형태의 정신적 피해를 준다고 많은 선행연구에서 증명하고 있다. 따라서, 이 연구에서는 학교폭력에 의하여 발생하는 두려움이 피해 청소년의 반응에 미치는 영향을 살펴보기 위한 목적을 가지고 있다. 학교폭력에 의하여 발생하는 두려움은 직 간접적인 피해경험과 교내 외 무질서로 설정하였으며, 비행으로 인한 두려움의 반응은 회피적 행위 방어적 행위로 설정하여 대구지역의 일반 남자고등학생을 대상으로 설문조사를 실시한 뒤 가설을 검증한 결과, 학교폭력에 대한 두려움에서 간접적인 피해경험은 방어적 행위를 하는데 있어서 유의미한 영향을 미치는 것으로 나타났으며, 직접적인 피해경험은 회피적 행위를 하는데 있어서 유의미한 영향을 미치는 것으로 나타났다.