• Journal of the Korean Geotechnical Society
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• v.16 no.5
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• pp.5-17
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• 2000

등가선형이론을 이용한 지진응답해석은 사용의 간편함 때문에 많이 사용되고 있지만, 대부분의 입력 정수들이 경험식에 의해 얻어지고 있어 심각한 오류를 발생시킬 여지가 있다. 입력정수를 실험의 결과로부터 얻을수 없다면 합리적인 방법을 통하여 입력 정수를 결정하여야 하며, 또한 입력 정수들이 해석결과에 어떠한 영향을 미치는지에 대한 고찰이 필요하다. 따라서 본 연구에서는 입력정수가 해석결과에 미치는 영향에 대한 민감도 분석을 실시하였다. 해석은 등가선형화 이론에 기초하여 개발한 액상화 해석프로그램(KLIq)을 이용하였다. 검토된 사항은 전단탄성계수와 감쇠비의 영향, 변형률의 영향, 반복계산에서 유효변형률 결정방법, 최대전자탄성계수의 영향, 변형률 의존곡선(자반의 종류)의 영향, 입력 지질파의 영향 등이다.

• Journal of Ocean Engineering and Technology
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• v.11 no.3
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• pp.116-123
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• 1997

세계적으로 수요가 증대하고 있는 고속선의 설계시 승선감 또는 내항성은 필수적으로 고려되어야 하는 중요요소이다. 고속선은 필연적으로 과도한 운동을 동반하며 그로 인해 승객들은 극심한 멀미와 구토 등 불쾌한 승선감을 경험하게 된다. 근래에 항공 및 육상 교통수단들의 고급화에 따라 해양 운항선사들도 선박품질의 고급화와 괘적한 승선감 확보에 비상한 관심을 보이며 승객 유치 및 승선률 제고를 도모하고 있다. 본 논문은 고속쌍동선에 대한 내항성능을 추정하고 그 해석결과를 실험과 비교하였다. 상하동요 및 종동요 간의 선형 연성 운동방정식을 사용하였고, 규칙파에 대한 상하동요의 응답특성 곡선을 구하였다. 또한 불규칙파에 대한 운동응답을 추정하기 위하여 ITTC파도 스펙트럼을 적용하였으며, 본 고속쌍동선의 운동성능에 미치는 선수 및 선수각의 영향을 고찰하였다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.1
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• pp.255-262
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• 2002

This paper presents a statistical analysis of empirical fragility curves for bridge. The empirical fragility curves are developed utilizing bridge damage data obtained from the 1995 Hyogoken Nanbu(Kobe) earthquake. Two-parameter lognormal distribution functions are used to represent the fragility curves with the parameters estimated by the maximum likelihood method. This paper also presents methods of testing the goodness of fit of the fragility curves and estimating the confidence intervals of the two parameters(median and log-standard deviation) of the distribution. An analytical interpretation of randomness and uncertainty associated with the median is provided.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.6
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• pp.333-342
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• 2022

The blast analysis method entails the use of an empirical equation and application of the pressure-time history curve as an explosive load. Although this method is efficient owing to its simple model and short run time, previous studies indicate that it may not be appropriate for near-field explosions. In this study, we investigated why different results were observed for the analysis method by considering an RC beam under near-field explosion conditions with the scaled distance of 0.4-1.0 as an example. On this basis, we examined the application range of the empirical analysis method by using the finite element analysis program LS-DYNA. The results indicate that the empirical analysis method based on data from far-field explosion tests underestimates the impulse. Thus, the calculated deflection of the RC beam would be smaller than the measured deflection and arbitrary Lagrangian-Eulerian (ALE) analysis result. The ALE analysis method is more suitable for near-field explosion conditions wherein the structural responses are large.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.2
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• pp.1-12
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• 1989

This paper presents a method of minimizing the wave resistance components, due to the linear wave propagating to the far field and the breaking wave in the vicinity of the hull. This method consists of the linear optimization method for the linear wave resistance and the statistical optimization method for the breaking wave resistance through the analysis of the experimental data. For the purpose of the application, a wall-sided model with parabolic waterplane shape was selected as a basic hull form, and two modified hull forms with varied $C_p-curve$ of the fore-body were derived from the linear wave optimization method and the empirical method. The correlation between the linear wave resistance and the breaking wave resistance according to the $C_p-curve$ variation of the fore-body was investigated through the experimental and analytical results for the three hull forms. The fore-body shape optimized by the present method shows the reduction of the wave resistance by 47% comparing to the basic hull form at the design speed($F_n=0.26$).

• Journal of Korean Society of Steel Construction
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• v.18 no.6
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• pp.759-768
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• 2006

The turn-buckle inserted between tension members is a device adjusting a tensile force in tension member. However, the measurement of designed tensile force is impossible and the tensile force is determined based on the experience of field workers. The conventional turn-buckle might be used without any adjustment even though the tensile force has been changed for long term. To improve the disadvantages of conventional turn-buckles a turn-buckle which is measurable the tensile force is developed. In this study, the displacement to the lateral direction is induced by the deformation of curved elements if the tensile force is applied to the new type of turn-buckle that the straight elements are slightly curved. The total lateral displacement could be measured by using the micrometer or vernier-calipers. Trial devices for a measurable turn-buckle were made and tested. An theoretical study was also conducted to show the applicability, and parametric studies were conducted. The appropriate shape and capacity were determined by the parametric study.

• Journal of the Korean Magnetics Society
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• v.23 no.2
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• pp.54-61
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• 2013

Ferromagnetic material's residual magnetization is remained because of the interaction between domains from external apply field, so the electrical and electronic industry and area of defense development request deperm protocol which makes the residual magnetization to 0. But the deperm protocols which are used theses days are developed by using only experience and experiment, so we have to develop deperm protocol considering hysteresis curve. In this paper, Anhysteretic Deperm, Deperm-ME, Flash-Deperm were analyzed using two dimensional finite element method and Preisach model that was formulated by property of magnetic materials. From that analysis, the relations between hysteresis curve and deperm variable are compared by analyzing the trace of Preisach plane. Also, an efficient current ratio of deperm protocol, is proposed.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.370-370
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• 2023

수자원이란 인간의 생활이나 경제활동 및 자연환경 유지 등을 하는데 이용할 수 있는 자원으로서의 물을 말하며 효율적인 수자원의 활용을 위해서는 수문조사가 필수적이라고 할 수 있다. 수문조사는 강수량, 수위, 유량, 유사량, 증발산량, 토양수분량을 측정, 조사, 분석하는 것이라고 할 수 있으며 이 중 유량은 강우-유출 관계 규명, 이수, 치수 등을 위해 높은 정확도의 관측자료가 필요하다. 그러나 하천유량은 장기간 연속적으로 관측하는 것이 어려우므로 특성 횟수의 유량조사를 통해 수위-유량관계곡선식(Rating curve)을 개발하여 수위로부터 연속적인 유량을 산정하여 활용하고 있어 이를 개선하기 위해 전자파표면유속계를 활용한 자동유량측정장치를 개발하였으며 측정자료 분석 및 알고리즘 고도화를 통해 신뢰도 높은 유량을 산정하고자 하였다. 운동하는 물체에 의하여 산란된 전자파의 주파수가 변하게 되는 현상을 도플러 효과라고 하며 이때의 주파수의 변화량을 도플러 주파수라고 한다. 전자파표면유속계는 하천 수면으로 전자파를 발사한 후 물 표면에서 반사되는 전자파의 도플러 효과를 이용하여 표면유속을 측정하는 것으로 전자파표면유속계를 교량 상류 방향으로 고정시켜 설치하였으며 측정된 자료는 유량관측 시스템에서 저장, 관리되고 물리적, 통계적 방법이 적용된 알고리즘을 통해 유량을 산정한다. 산정된 유량의 정확도 확보를 위해 바람 영향, 최적 환산계수 재산정, 통계분석 등을 통해 시스템의 유량산정 알고리즘 개선 방안을 도출하였으며 개선된 알고리즘이 적용된 유량은 NSE(Nash Sutcliffe Efficiency), PBIAS(Percent Bias), RSR(RMSE-observations standard edviation ratio)을 통해 평가하였다. 바람 영향은 유량 관측 고도화 매뉴얼(일본 토목연구소)의 경험식과 현장에서 관측된 풍향·풍속을 활용하여 분석하였으나 개선효과가 미미한 것으로 나타났으며 자동으로 관측된 유량자료에 포함된 무작위적인 변화량을 감소시키기 위해 경향성 분석을 병행하여 이동평균 방법을 적용하였다. 또한 ADCP 등을 활용한 유량측정성과와 수위-유량관계곡선식과의 비교·분석을 통해 수위별 최적 환산계수를 산정하여 유량산정 알고리즘에 적용한 결과 NSE는 0.980, PBIAS는 1.580, RSR은 0.142로 모두 Very Good(높은 상관성)으로 분석되어 유량자료의 정확도를 확보하였다.

• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.3
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• pp.354-362
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• 2018

Periogen is a new caries activity test using real-time polymerase chain reaction. The aim of this study was to assess the validity of Periogen by evaluating the correlation with dmft, dmfts indices and comparing with Cariview and caries risk assessment tool (CAT). 83 children under 6 participated in this study. Dmft, dmfts indices and CAT were collected through an examination of oral health status. Plaque samples for Periogen and Cariview were collected and manipulated according to the manufactures' instructions. The correlation coefficient of Periogen, Cariview and CAT with the dmfts index were 0.38, 0.56 and 0.66 in each (p < 0.01). The sensitivity of Periogen, Cariview and CAT were 43%, 76% and 95% and specificity were 80%, 72% and 74% respectively. Area under curve under the receiver operating characteristic curves in each method indicated 0.69, 0.81 and 0.85. CAT and Cariview were more effective in evaluation the risk of dental caries than Periogen so far. To be used Periogen clinically, more improvements for higher validity were needed.

• Geophysics and Geophysical Exploration
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• v.17 no.1
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• pp.11-20
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• 2014

To reveal shear-wave velocities ($v_s$) and site characterization of Wonju, Korea, Rayleigh waves were recorded at 78 sites of lower altitude using 12 to 24 4.5-Hz vertical geophones for 20 days during the period of February to September 2013. Dispersion curves of the Rayleigh waves obtained by the extended spatial autocorrelation method were inverted using the damped least-squares method to derive $v_s$ models. From these 1-D models, the average $v_s$ to a depth of 30 m ($v_s30$), $v_s$ of weathered rocks, depths to these basement rocks, and average $v_s$ of the overburden layer were derived to be $16.3{\pm}0.7m$, $576{\pm}8m/s$, $290{\pm}7m/s$, and $418{\pm}13m/s$, respectively, in the 95% confidence range. To determine adequate proxies for $v_s30$, we computed correlation coefficients of $v_s30$ with topographic slope (r = 0.46) and elevation (r = 0.43). An empirical linear relationship is presented as a combination of individually estimated $v_s30$ with weighting factors of 0.45, 0.45, and 0.1 for topographic slope, elevation, and mapped lithology, respectively. Due to a weak correlation between $v_s30$ obtained from inversion of dispersion curves and the proxy-based estimation (r = 0.50), however, the relatively large error range should be considered for applications of this relationship.