• Earthquakes and Structures
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• 제15권2호
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• pp.155-164
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• 2018

Design of structures subjected to blast loads are usually carried out through nonlinear inelastic dynamic analysis followed by imposing acceptance criteria specified in design codes. In addition to comprehensive aspects of inelastic dynamic analyses, particularly in analysis and design of structures subjected to transient loads, they inherently suffer from convergence and computational cost problems. In this research, a strategy is proposed for design of steel moment resisting frames under far range blast loads. This strategy is inspired from performance based seismic design concepts, which is here developed to blast design. For this purpose, an algorithm is presented to calculate the capacity modification factors of frame members in order to simplify design of these structures subjected to blast loading. The present method provides a simplified design procedure in which the linear dynamic analysis is preformed, instead of the time-consuming nonlinear dynamic analysis. Nonlinear and linear analyses are accomplished in order to establish this design procedure, and consequently the final design procedure is proposed as a strategy requiring only linear structural analysis, while acceptance criteria of nonlinear analysis is implicitly satisfied.

• 한국건축시공학회지
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• 제15권6호
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• pp.569-577
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• 2015

구조물 내진설계에 대한 개념이 사양중심설계에서 성능기반설계로 변화하고 있다. 구조물 목표성능을 직접 부여하여 설계하는 성능기반설계를 위해서는 구조물 실제 거동을 정확히 예측하기 위한 비탄성 구조해석이 필요하다. 이에 본 연구에서는 KBC2009 기준으로 설계한 5층 철근콘크리트 모멘트-저항골조 시스템 구조물을 대상으로 푸쉬오버해석을 수행하여 내진성능을 평가한 후 직접공사비를 산출하여 경제성을 분석하였다. 분석 결과 보통 및 중간모멘트골조는 요구성능설계기준을 만족하며 직접공사비 또한 유사한 것으로 평가되었다. 하지만, 강 기둥-약 보 기준이 적용되는 특수모멘트골조는 요구성능설계기준을 만족하나 다른 골조시스템 보다 비경제적인 것으로 평가되었다. 따라서 IBC2012에서는 내진설계범주 D 중간모멘트골조 적용을 제한하고 있지만 5층 철근콘크리트 모멘트-저항골조 구조물의 경우, 특수모멘트골조 보다 보통 및 중간모멘트골조로 설계하는 것이 합리적이라고 판단된다.

• Korean Chemical Engineering Research
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• 제53권6호
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• pp.723-729
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• 2015

고성능액체크로마토그래피(high-performance liquid chromatography, HPLC)에서 C18(octadecyl silica, ODS) 칼럼에서 고리형 아데노신 일인산(cyclic adenosine monophosphate, cAMP)의 크로마토그램을 얻은 후, 모멘트 분석을 수행하였다. 일반속도 모델(general rate model, GR model)을 기반으로 first absolute moment와 second central moment를 계산하였다. 모멘트 분석의 중요한 세 가지 계수인 분자확산계수(molecular diffusivity, $D_m$), 외부물질전달계수(external mass transfer coefficient, $k_f$), 입자내부확산계수(intra-particle diffusivity, $D_e$)는 각각 Wilke-Chang 식, Wilson-Geankoplis 식을 이용하고 이론단수(theoretical plate number) 식과 van Deemter 식을 비교하여 계산하였다. 실험은 각각 세 가지의 이동상 조성, 용질 농도, 유량 조건에서 수행하였다. Van Deemter 그래프를 그려 모멘트 분석결과를 정성적으로 정리했으며, 이론단 상당높이(height equivalent to a theoretical plate, HETP, $H_{total}$)에 $H_{ax}$, $H_f$, $H_d$가 미치는 영향을 알아보기 위해 van Deemter coefficient를 비교했다. HETP에 가장 큰 영향을 주는 요인은 입자내부확산($H_d$)이었으며 외부물질 전달($H_f$)는 그 영향이 매우 작았다.

• Steel and Composite Structures
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• 제25권5호
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• pp.617-624
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• 2017

In this study, a new empirical method is presented to obtain Dynamic Increase Factor (DIF) in nonlinear static analysis of structures against sudden removal of a gravity load-bearing element. In this method, DIF is defined as a function of minimum ratio of difference between maximum moment capacity ($M_u$) and moment demand ($M_d$) to plastic moment capacity ($M_p$) under unamplified gravity loads of elements. This function determines the residual strength of a damaged building before amplified gravity loads. For each column removal location, a nonlinear dynamic analysis and a step-by-step nonlinear static analysis are carried out and the modified empirical DIF formulas are derived, which correspond to the ratio min $[(M_u-M_d)/M_p]$ of beams in the bays immediately adjacent to the removed column, and at all floors above it. Therefore, the new DIF can be used with nonlinear static analysis instead of nonlinear dynamic analysis to assess the progressive collapse potential of a moment frame structure. The proposed DIF formulas can estimate the real residual strength of a structure based on critical member.

• 대한통합의학회지
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• 제5권4호
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• pp.41-48
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• 2017

Purpose : The purpose of this study was to verify the relationships among the knee adduction moment, hip rotation range, strength of hip rotators, and Foot Posture Index of healthy young adults. Method : Thirty-two healthy adults(24 male, 8 females) participated in this study. Subjects performed 5 walking trials to evaluate the knee adduction moments using a three-dimensional motion analysis system. Hip rotation ranges and hip rotator strengths were measured using a standard goniometer and a handheld dynamometer, respectively. The mean of three trials of clinical tests was used for data analysis. Results : The first peak knee adduction moment was significantly correlated with the hip rotation ranges and hip rotator strengths (P<.05). The second peak knee adduction moment was showed significant correlations with hip external rotation and rotation ratio. There were no correlations between Foot Posture Index and all knee adduction moments (P>.05). Conclusion : This study suggests that imbalances of the range of motion and strength of the internal and external rotation of the hip joint can affect knee adduction moments. The impact may exacerbate musculoskeletal disorders such as osteoarthritis of the knee. Therefore, further studies should be conducted to evaluate the effects of clinical interventions to correct these imbalances on the reduction of the knee adduction moments in patients with knee osteoarthritis.

• 콘크리트학회논문집
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• 제15권5호
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• pp.747-758
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• 2003

The moment-curvature envelope describes the changes in the flexural capacity with deformation during a nonlinear analysis. Therefore, the moment-curvature analysis for reinforced concrete columns, indicating the available flexural strength and ductility, can be conducted providing the stress-strain relation for the concrete and steel are known. The moments and curvatures associated with increasing flexural deformations of the column may be computed for various column axial loads by incrementing the curvature and satisfying the requirements of strain compatibility and equilibrium of forces. Clearly it is important to have accurate information concerning the complete stress-strain curve of confined high-strength concrete in order to conduct reliable moment-curvature analysis that assesses the ductility available from high-strength concrete columns. However, it is not easy to explicitly characterize the mechanical behavior of confined high-strength concrete because of various parameter values, such as the confinement type of rectilinear ties, the compressive strength of concrete, the volumetric ratic and strength of rectangular ties. So a stress-strain model is developed which can simulate complete inelastic moment-curvature relations of high-strength concrete columns.

• 대한토목학회논문집
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• 제14권3호
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• pp.487-493
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• 1994

강절(剛節) 뼈대 구조물(構造物)의 해석(解析)에 적용하는 모멘트 분배법은 총조정(總調整) 모멘트라는 개념을 이용하여 연립방정식(聯立方程式)으로 간단히 표현된다. 이 방정식(方程式)은 간단한 손계산기(hand calculator)로 직접 작성되고 쉽게 풀어질 수 있다. 이 방정식(조정방정식(調整方程式))은 무한번의 분배 과정을 완료한 상태를 나타내며 그 해는 소거법(消去法)으로 풀 수도 있으나 일종의 이완방정식(弛緩方程式)으로써 되풀이 산법을 사용하면 간단히 풀어진다. 이 방법이 연속량(連續梁)의 휨 모멘트 계산이나 영향선(影響線) 해석(解析)에 어떻게 이용될 수 있는 지를 두개의 예제로서 설명하였다. 특히 영향선의 해법은 전산에 편리하도록 행렬(行列)로 표현하였다.

• 대한기계학회논문집A
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• 제30권8호
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• pp.985-992
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• 2006

Many methods for reliability analysis have been studied and one of them, a moment method, has the advantage that it doesn't require sensitivities of performance functions. The moment method for reliability analysis requires the first four moments of a performance function and then Pearson system is used for the probability of failure where the accuracy of the probability of failure greatly depends on that of the first four moments. But it is generally impossible to assess them analytically for multidimensional functions, and numerical integration is mainly used to estimate the moment. However, numerical integration requires many function evaluations and in case of involving finite element analyses, the calculation of the first fo 따 moments is very time-consuming. To solve the problem, this research proposes a new method of approximating the first four moments based on kriging metamodel. The proposed method substitutes the kriging metamodel for the performance function and can also evaluate the accuracy of the calculated moments adjusting the approximation range. Numerical examples show the proposed method can approximate the moments accurately with the less function evaluations and evaluate the accuracy of the calculated moments.

• 한국강구조학회 논문집
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• 제8권3호통권28호
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• pp.127-137
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• 1996

Connections as basic elements and an integrated part of a steel frame has an effect on the frame's performance. Conventional analysis and design techniques are based on either idealized fixed or pinned conditions. In fact, the use of rigid or pinned connection model in steel frame analysis serves the purpose of simplifying the analysis and design processes, but all connections used in current pratice possess stiffness and transfer moment which fall between the extreme cases of fully rigid and ideally pinned. To predict the behavior of the semi-rigid steel frames, it is necessary to predict the moment-rotation behavior of the beam-to-column connections. In this research, prediction equation for moment-rotation behavior of the beam-to-column connection is suggested and the effect of design parameters has investigated. Prediction model, in a nondimensional form shows the moment-rotation characteristic for connections. It is composed of the curve fitting power function using standardization constant K and 4 parameter $KM_o$, ${\theta}_0$, b, n based on the pretest result about moment-rotation behavior of connection.

• Biotechnology and Bioprocess Engineering:BBE
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• 제7권1호
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• pp.16-20
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• 2002

Parameter estimations were made for the reversed-phase adsorption of perillyl alcohol (POH), a potent anti-cancer agent, on octadecylsilyl-silica gel (ODS). The average particle diameter of ODS was about $15\;{\mu}m$, and the particles were packed in the column $(3.9\;\times\;300mm)$. The mobile phase used was a mixture of acetonitrile and water, in which the acetonitrile ranged between 50 and $70\;(v/v\;\%)$. The first absolute moment and the second central moment were determined from the chromatographic elution curves by moment analysis. Experiments were carried out using POH solutions within the linear adsorption range. The fluid-to-particle mass transfer coefficient was estimated using the Wilson-Geankoplis equation. The axial dispersion coefficient and the intra particle diffusivity were determined from the slope and intercept of a plot of H vs $1/u_0$, respectively. The contributions of each mass-transfer step were axial dispersion, fluid-to-particle mass transfer, and intraparticle diffusion.