• Structural Monitoring and Maintenance
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• 제11권3호
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• pp.219-234
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• 2024

The strength reduction factor spectrum is traditionally obtained from a single-degree-of-freedom (SDOF) system with a constant damping coefficient. However, according to the principle of Rayleigh damping, the damping coefficient matrix of a system changes with the stiffness matrix, and the damping coefficient of an equivalent SDOF system changes with the tangent stiffness coefficient. In view of that, this study proposes an equivalent SDOF system with an adaptive damping coefficient and derives a standardized reaction balance equation. By iteratively adjusting the strength reduction factor, the corresponding spectrum with an equivalent ductility factor is obtained. In addition, the ratio between the strength reduction factor that considers adaptive damping and the traditional strength reduction factor, denoted by η, is determined, and the η-μ-T relationship is obtained. Seismic records of Classes C, D, and E sites are selected as excitations. Moreover, a nonlinear response time-history analysis is performed to establish the relationship between the η and T values for the equivalent ductility factor μ. Further, by exploring the effects of the site class, ductility factor, second-order stiffness coefficient, and period T on the mean value of η, a simplified calculation equation of mean η is derived, and η is used as a modified value for the traditional strength reduction factor R spectrum.

• The Korean Journal of Ecology
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• 제12권3호
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• pp.191-202
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• 1989

This study was carried out to investigate the relationship between soil mites(Acarina:Cryptostigmata) and vegetation in sampled area. From July 1984 to June 1985, samples were taken monthly from coniferous forests; a pinenut (Pinus koraiensis S. et Z.) forest (site C-1), a whitepine(Pinus strobus L.) forest (site C-2), a needle fir tree(Abies holophyla Max.) forest (site C-3), and three broad-leaved forests; site B-1, B-2, and B-3 in Cholanamdo province, southerm part of Korea. Vascular plants of 152 species belonging to 115 genera (53 families) were identified. The flora in the coniferous forests were more diverse than in the broad-leaved forest. Similarity coefficient to the flora was shown highly between the neighbouring sites. The oribatid species in the coniferous forests were more diverse than those in the broadleaved forests. The similarity index suggested that oribatid mites in those surveying sites could be divided into "coniferous forest type" and "broad-leaved forest type".d forest type".uot;.

• 한국세라믹학회지
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• 제33권10호
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• pp.1131-1137
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• 1996

The dielectric properties and phase stabilities of Pb(Zn0.6Mg0.4)1/3Nb2/3O3 [PZMN]system were investigated into substitution of A-site with Ba, Sr and Ca ions. The A-site substitutions led to the complexity of components of perovskite phase and then DPT coefficient increased. The A-site substitutions of Ba or Sr ion perovskite single phase could be easily formed by columbite process due to increase of perovskite phase stability. The variation of lattice parameters in specimen obeyed Vegard's law and curie temperature and dielectric constant of specimen decreased linearly. But Ca substitution led to perovskite phae instability. The lattice parameter dielectric constant and curie temperature of specimens drasticaly decreased with formation of pyrochlore phase.

• Journal of Radiation Protection and Research
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• 제28권4호
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• pp.337-342
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• 2003

On a basis of the washout model and concentrations of anthropogenic tritium in rainwater around the Wolsong site, the washout coefficients of tritium by rainwater were calculated, and the validity of washout deposition model are estimated. As the result of that, the washout coefficients in 10 sampling stations around Wolsong site were in the range of $2.9{\times}10^{-5}\;-\;16{\times}10^{-5}\;s^{-1}$ with the mean value of $7.21{\times}10^{-5}\;s^{-1}$. The validity of the washout deposition model was confirmed by comparing the observed data with the calculated ones.

• 한국대기환경학회지
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• 제30권4호
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• pp.378-386
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• 2014

The use of bus stop in the center lane has reduced the emissions of exhaust gas on the road due to the improvement of the traffic speed but has caused a health problem for the citizens who are waiting for the bus in the platform, and thus the air pollution control of bus stop in the center lane is emerging as a more important part. This study was conducted to investigate the air pollution degree for the center lane-bus stops in four regions using mobile air measuring vehicle, and to evaluate the characteristics of air pollution by comparing with the data measured at the urban air monitoring site close to the bus stops. In addition, the correlation analysis was performed to analyze the impact to neighboring region by vehicle exhaust gas. The regional mean concentration of nitrogen dioxide in the center lane-bus stops ranged from 0.025 to 0.043 ppm which shows from 2.5 times to 5.3 times higher than the values of urban air monitoring site selected as a control group. The regional mean concentration of ozone in the center lane-bus stops ranged from 0.023 to 0.034 ppm which shows from 3% to 28% lower than the values of urban air monitoring site selected as a control group. The concentrations of nitrogen dioxide and ozone for the sampling regions did not exceed one hour-air quality environmental standard (0.1 ppm). The mean concentration of particulate matter for four center lane-bus stops was $28{\mu}g/m^3$ which shows about 27% higher than the values of urban air monitoring site selected as a control group, and that of particulate matter did not exceed one day-air quality environmental standard ($100{\mu}g/m^3$). In the results of correlation analysis between data from center lane-bus stops and data from urban air monitoring sites, the correlation coefficient (r) of nitrogen dioxide was relatively low as 0.316 to 0.416, and the correlation coefficient was high as the distance was close and vice versa. However, the correlation coefficient of ozone ranged from 0.167 to 0.658 and the correlation coefficient was high as the distance was far and vice versa.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.1015-1023
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• 2010

While various PCPT-based methods for the analysis of consolidation were developed, additional laboratory test is needed to estimate the coefficient of consolidation. In this paper, hyperbolic method using PCPT dissipation curve for the estimation of coefficient of consolidation was proposed. To verify proposed method, field settlement test data and PCPT dissipation test data at same site were collected and analyzed. It is observed that proposed method shows good agreement with measured field settlement data.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.1051-1060
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• 2010

In this study, the pressuremeter test (PMT) and the standard penetration test (SPT) were performed on the lateral pile loading tests site to evaluate the coefficient of subgrade reaction, which is used for load-deformation behavior analysis of laterally loaded piles by elastic subgrade reaction method. As a result, widely used empirical formulas of the coefficient of subgrade reaction by N values of SPT is evaluated conservatively lateral behavior of piles. While the method of directly used PMT results and evaluation method of the coefficient of subgrade reaction considering deformation moduli of soil and a pile diameter that is able to estimate very similar to actual load-deformation behavior of laterally loaded piles in deformation range of 0.5%-1.0% of a pile diameter.

• 한국유체기계학회 논문집
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• 제12권2호
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• pp.31-38
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• 2009

The valve performance has been evaluated from the theoretical equation based on design information such as packing thrust, spring preload and friction coefficient(${\mu}$). The accuracy of those data can be lower than that of vendor's initial design data. Especially, the friction coefficient can be degraded with time than the original condition and the valve performance calculated using the previous friction coefficient can not be available. Accordingly, this paper is describing a new performance evaluation method of valve based on diagnostic test data which are acquired from a site valve tested in static and dynamic conditions. Especially, this paper provides a new method using friction coefficient(${\mu}$) which is derived from the diagnostic test data acquired in the valve's design basis condition.

• 한국지반환경공학회 논문집
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• 제16권1호
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• pp.17-27
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• 2015

최근 우리 정부는 안전한 대한민국이라는 슬로건 아래 지진재해를 포함한 자연재해피해를 최소화하는데 많은 노력을 집중하고 있으며, 이를 위해 산사태 위험도와 액상화 위험도와 같은 지진 시 지반피해 GIS 시스템 데이터가 구축되고 있는 실정이다. 우리나라 전역을 포함하는 지진 시 액상화 위험도를 작성하기 위해서는 수많은 지반시추정보에 대한 적용성 검토가 필요하다. 본 연구에서는 액상화 위험도 작성을 위해 인구밀도가 높은 광역지역의 지반증폭계수를 검토하였으며 이를 위해 S시 522개 시추공지반 정보를 수집하여 지반응답해석을 수행하였다. 이때 지반분류는 지반정보의 불확실성을 고려하고자 현행 내진 설계기준에서 제안하고 있는 시추종료 깊이 이후의 지반 정보를 30m로 가정하는 경우와 지반정보의 오리지널 데이터 값만을 이용하는 경우로 나누어 비교하였으며, 타당성 검토 시에는 지반응답해석 결과에 대한 확률분포와 통계분석을 이용하여 수행하였다. 최종적으로 정규분포를 통한 신뢰도 50%, 70%, 90%에 대한 지반증폭계수를 도출하여 액상화 위험도를 도시하였으며, 이를 지반응답해석을 통해 도시한 LPI 액상화 위험도와 비교하여 가장 유사한 값을 추천하였다. 연구결과 제안된 지반증폭계수가 향후 국내 액상화에 대한 연구와 중진지역의 광역지역 액상화 위험도 작성에 큰 도움이 될 수 있을 것으로 기대한다.

• 한국지진공학회논문집
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• 제10권2호
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• pp.63-71
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• 2006

동반논문(II-지반분류 개선방법)에서는 지반의 고유주기를 기준으로 지반을 분류하는 방법이 국내 지반조건에 적합한 지반분류 방법으로 제시하였다. 그러나, 지반분류 방법을 개선하여도 해석결과의 평균 스펙트럼 가속도 값과 재산정된 응답스펙트럼과 차이가 나타나는 부분이 존재한다. 이는 설계응답스펙트럼을 작성에 필요한 증폭계수를 계산하는 방법을 변경해야 해결할 수 있다. 본 논문에서는 국내 지반조건에 적합하도록 증폭계수를 재산정하기 위한 적분구간 변경에 대하여 검토하였다. 검토 결과 장주기 영역의 증폭계수 $F_v$의 적분구간은 현재 주기 0.4초${\sim}$2.0초에서 주기 0.4초${\sim}$1.5초로 변경할 경우 해석결과의 평균 스펙트럼 가속도 값과 설계응답스펙트럼이 비교적 잘 일치하는 결과를 얻을 수 있었고, 기존의 방법보다 국내 지반특성에 더 적합한 설계응답스펙트럼을 작성할 수 있었다.