• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 가을 학술발표회 논문집
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• pp.556-565
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• 2003

Light losses in optical fibers are investigated by a fiber optic OTDR (Optical Time Domain Reflectometry) sensor system to develop fiber optic probes for structural displacement measurement. The displacement sensitivity was determined by the measurements of fiber-bending loss according to the gage length changes of the displacement sensor. The fiber optic displacement probe was manufactured to verify the feasibility of the structural displacement measurement.

• Earthquakes and Structures
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• 제18권1호
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• pp.97-111
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• 2020

Cylindrical steel tanks are important components of industrial facilities. Their safety becomes a crucial issue since any failure may cause catastrophic consequences. The aim of the paper is to show the results of comprehensive FEM numerical investigation focused on the response of cylindrical steel tanks under mining tremors and moderate earthquakes. The effects of different levels of liquid filling, the influence of non-uniform seismic excitation as well as the aspects of diagnosis of structural damage have been investigated. The results of the modal analysis indicate that the level of liquid filling is really essential in the structural analysis leading to considerable changes in the shapes of vibration modes with a substantial reduction in the natural frequencies when the level of liquid increases. The results of seismic and paraseismic analysis indicate that the filling the tank with liquid leads to the substantial increase in the structural response underground motions. It has also been observed that the peak structural response values under mining tremors and moderate earthquakes can be comparable to each other. Moreover, the consideration of spatial effects related to seismic wave propagation leads to a considerable decrease in the structural response under non-uniform seismic excitation. Finally, the analysis of damage diagnosis in steel tanks shows that different types of damage may induce changes in the free vibration modes and values of natural frequencies.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.651-656
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• 2007

Changes in measured structural responses induced by a damage could be significantly smaller than those by environmental effects such as temperature and temperature gradients. It is highly desirable to develop a methodology to distinguish the changes due to the structural damage from those by the environmental variations. In this study, a novel method to extract the damage-induced deflection under temperature variations is presented using the outlier analysis on the deflections obtained using the modal flexibility matrices. The main idea is that temperature change in a bridge would produce global increase or decrease in deflections over the whole bridge while structural damages may cause local variations in deflections near the damage locations. Hence, the correlation between the deflection measurements may show high abnormality near the damage locations. A series of laboratory tests were carried out on a bridge model with a steel box-girder for 14 days. It has been found that the damage existence assessment and localization can carried out for a case with relatively small damage under the temperature variations

• Structural Engineering and Mechanics
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• 제76권5호
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• pp.653-661
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• 2020

The paper presents a study regarding rubber compressibility behavior. The objective is to analyze the effect of compression degree of rubber on its mechanical properties and propose a new methodology based on reverse engineering to predict compressibility degree based on uniaxial stretching test and Finite Element Analysis (FEA). In general, rubbers are considered to be almost incompressible and Poisson's ratio is close to 0.5. Since this property is intimately related to the rubber packing density, little changes in Poisson's ratio can lead to significant changes regarding mechanical behavior. The deviatory hyperelastic constants were obtained through experimental data fitting by least squares method for the most relevant constitutive models implemented in commercial software Abaqus, such as: Neo-Hooke, Mooney-Rivlin, Ogden, Yeoh and Arruda-Boyce, whereas the hydrostatic part was determined through an optimization algorithm implemented in the Abaqus environment by Python scripting. The simulation results presented great influence of the Poisson's ratio in the rubber specimen mechanical behavior mainly for high strain levels. A conventional pure volumetric compression test was also carried out in order to compare the results obtained by the proposed methodology.

• Smart Structures and Systems
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• 제29권2호
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• pp.361-374
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• 2022

As civil infrastructure has continued to age worldwide, its structural integrity has been threatened owing to material deteriorations and continual loadings from the external environment. Structural Health Monitoring (SHM) has emerged as a cost-efficient method for ensuring structural safety and durability. As SHM research has gradually addressed an increasing number of structure-related problems, it has become difficult to understand the changing research topic trends. Although previous review papers have analyzed research trends on specific SHM topics, these studies have faced challenges in providing (1) consistent insights regarding macroscopic SHM research trends, (2) empirical evidence for research topic changes in overall SHM fields, and (3) methodological validations for the insights. To overcome these challenges, this study proposes a framework tailored to capturing the trends of research topics in SHM through a bibliometric and network analysis. The framework is applied to track SHM research topics over 15 years by identifying both quantitative and relational changes in the author keywords provided from representative SHM journals. The results of this study confirm that overall SHM research has become diversified and multi-disciplinary. Especially, the rapidly growing research topics are tightly related to applying machine learning and computer vision techniques to solve SHM-related issues. In addition, the research topic network indicates that damage detection and vibration control have been both steadily and actively studied in SHM research.

• 경영과정보연구
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• 제35권3호
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• pp.1-22
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• 2016

본 연구는 MS-VAR 모형을 이용하여 1971년 1분기부터 2016년 1분기까지 분기별 실질 GDP의 국제적 동조화 및 구조적 변화를 조사하고자 하였다. 본 연구의 주요 결과는 다음과 같다. 첫째, 본 연구에서 실질 GDP에서 모형 또는 개별 시계열에서 발생되는 경기변동현상은 마코프 국면전환 분석으로 파악되었다. 또한 본 연구에서 국가별 실질 GDP를 이용한 MS-VAR 모형의 동조성과 비대칭성을 현저하게 보여 주었다. 둘째, 본 연구에서 부분적으로 차이가 있을지라도 MS-VAR 모형에서 글로벌 오일쇼크위기가 끝나는 1988년 2분기와 글로벌 금융위기가 시작된 2007년 3분기 등에서 경기수축국면(불경기)이 나타나는 구조적 변화가 현저하게 존재하였다. 1988년 2분기 전의 경우 독일과 일본의 상관관계가 가장 높았고 다음으로 미국과 일본, 미국과 독일, 한국과 미국 등의 순으로 높았으며, 이후에는 미국과 독일간의 상관관계가 가장 높았고 미국과 캐나다, 독일과 캐나다, 한국과 일본 등의 순으로 높았다. 셋째, 경기확장과 경기수축국면은 동시적으로 국가간에 대규모로 구조적 변화를 발생시켰다. 1973년과 1974년의 1차의 글로벌 오일쇼크 이후에 동시에 발생한 2차의 전세계 오일쇼크가 대규모의 국제적 실질 GDP의 동조화를 일으킨 주요 원인이었다. 또한 이용되는 G7 국가들이 1997년부터 1999년까지의 아시아의 외환위기 동안에 한국과 관련된 동조화가 미약하게 나타났을지라도 글로벌 금융위기기간인 2007년 말에는 한국과 G7 국가간에 현저한 동조화를 나타내었다. 넷째, 실질 GDP를 이용한 국면전환과 더불어 1973년 이후는 국가별로 발생하는 고유의 충격으로 인해 동시적 상관관계가 높게 나타나는 특징을 보여 주었다. 이러한 결론은 이용가능한 많은 이론적 및 실증적 증거와 일치하였으며, 과거 30년의 거시경제적 변동은 주로 전세계적인 충격에 의해 발생되었다는 것을 확인하였다. 글로벌 경기변동은 대규모의 비대칭적 충격이 일반적 변동으로 인하여 일시적으로 상쇄될 수 있다는 가능성을 배제하지 못할 지라도, 본 연구의 결과는 국가별 고유의 충격으로 인한 주요 국제적 동조화 및 구조적 변화를 보여 주었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.1079-1084
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• 2000

The apartment houses which were constructed in a large quantity are currently being deteriorated and the reuse of them is directly related to the economic and environmental problem of the nation. Therefore, this research approaches to structural planning other than to the materials and/or the repair for the reuse of these deteriorated buildings. The research suggests the structural planning technique which includes the idea for the reinforcement of the structure in a part to improve the structural efficiency by investigating the current condition which includes the structural type of the buildings, examining the plan for the improvement of the structural efficiency, establishing the model of the space reorganization associated to the capability changes for the scale, the use, and the facilities, and checking of the structural efficiency through the structural analysis for the building structure suggested to be replaced.

• 한국도로학회논문집
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• 제16권6호
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• pp.137-147
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• 2014

PURPOSES : Daejeon is basically divided into an old downtown and a new downtown, and the recent relocation of the Chungcheongnam-do Provincial Government of Republic of Korea from the old downtown and the opening of governmental buildings in the new downtown as well have made this new downtown only densely populated with industrial and business facilities. Such changes in the downtowns have promoted the conditions of the new downtown while, consequently, dragging down the old downtown. Out of concern for those unbalanced developments of the two downtowns, Daejeon is now carrying out several city projects to revive the old downtown. In the light of that, as a part of the project to promote the old downtown, this study aims to conduct an evaluation on landscape of the culture and arts street in Daeheungdong which was built upon those ideas of a theme street project by Daejeon. METHODS : Based on the findings from the questionnaire not only on the components that would design the streetscape of the culture and arts street but also on the public satisfaction with the streetscape, the study defined how those changes in the components affect emotional factors of the pedestrians. In order to achieve the research goal, the study made changes in D/H ratio of the street structural components as well as the roadside trees. In terms of the questionnaire method, the study used the SD scale, and proceeded with its investigation through the frequency analysis, the principal component analysis (the factor analysis) and the structural equation model. RESULTS : According to the results from the factor analysis and the regression analysis, of those three factors, such as the openness, the comfortable sensation and the safety, the openness followed by the comfortable sensation and the safety was determined to have the most positive influence on the total satisfaction. The structural model analysis reported that the D/H and the structural components of the roadside trees and planting have a positive effect on the emotional image, and this emotional image also appeared to be positively related to the total satisfaction. CONCLUSIONS : This study looked into how the changes in the street structural components of the culture and arts street in Daeheungdong would affect the satisfaction with the streetscape, and finally confirmed that the D/H and the planting are what would have a positive effect on this satisfaction. What has been learned from this study will be the basic data to figure out how to promote and improve the culture and arts street in Daeheung-dong as this data will also help designing and developing of those specialized streets in other regions.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1971-1973
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• 1999

Monolayers of azo-benzene group containing fatty acids(8A5H) were made by spreading and compressing on the water surface. These monolayers were optically stimulated by illuminating the lights of 365[nm] and 450[nm] from X-non lamp, and the structural changes of the molecules were measured by the displacement current method. Also, the dynamic behaviors of these monolayers were measured by the $\pi-A$ isotherms when changing the temperatures of the water surface. As results, when the monolayers were stimulated by 365[nm] light, the positive currents which were generated by the structural changes from trans to cis were measured. But the negative currents of the structural changes from cis to trans were too weak to detect. When the temperatures of the water surface were increased, surface pressures of the monolayers increased early because of the thermal activations of the molecules, and the double liquid film phase were disappeared upon $40[^{\circ}C]$.

• Journal of Acupuncture Research
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• 제27권3호
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• pp.93-104
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• 2010

Objectives : The purpose of this study is to observe the effects of work environment and low back pain on the structural and muscle strength changes in lumbar spine to helpful for preventation and cure of low back pain. Methods : Through measuring of lumbosacral angle, lumbar lordotic angle, lumbar gravity line ratio analyzed structure of lumbar spine and using Trunk Extension Flexion Program of CYBEX NORM System(cybex770+TMC, USA) analyzed Flex. PT, Ext. PT, E/F ratio of lumbar spine of company employees given a medical examination. Results : According to work environment, lumbar gravity line ratio is higher in white collar group than in blue collar group, Ext. PT is significantly lower in white collar group than in blue collar group. According to low back pain or not, lumbar gravity line ratio, Ext. PT is lower in low back pain group than in non-low back pain group. Conclusions : Work environment and low back pain effects on the structural and muscle strength changes in lumbar spine.