• Structural Engineering and Mechanics
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• 제8권6호
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• pp.561-578
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• 1999

The response of a reinforced concrete structure to loading is both immediate and time-dependent. Under a sustained load, the deflections caused by creep and shrinkage may be several times their instantaneous values. The paper describes a general finite element procedure, based on the so-called layered model, to analyse reinforced concrete members, and shows in particular how the simple Step by Step Method may be incorporated into this procedure. By invoking the Modified Newton Raphson Method as a solution procedure, the accuracy of the finite element method is verified against independent test results, and then applied to a variety of problems in order to demonstrate its efficacy. The method forms a general method for analysing highly indeterminate concrete structures in the time domain.

• Bulletin of the Korean Chemical Society
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• 제13권4호
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• pp.398-404
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• 1992

We have investigated the kinetics of diffusion-influenced bimolecular reactions in which one reactant has an internal mode, called the gating mode, that activates or deactivates its reactivity intermittently. The rate law and an expression for the time-dependent rate coefficient have been obtained from the general formalism based on the hierarchy of kinetic equations involving reactant distribution functions. The analytic expression obtained for the steady-state reaction rate constant coincides with the one obtained by Szabo et al., who derived the expression by employing the conventional concentration-gradient approach. For the time-dependent reaction rate coefficient, we obtained for the first time an exact analytic expression in the Laplace domain which was then inverted numerically to give the time-domain results.

• Geomechanics and Engineering
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• 제1권4호
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• pp.307-321
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• 2009

The paper employs a feed forward neural network with back-propagation algorithm for modeling time dependent swell in clays containing carbonate in the presence of sulfuric acid. The oedometer swell percent is estimated at a nominal surcharge pressure of 6.25 kPa to develop 612 data sets for modeling. The input parameters used in the network include time, sulfuric acid concentration, carbonate percentage, and liquid limit. Among the total data sets, 280 (46%) were assigned to training, 175 (29%) for testing and the remaining 157 data sets (25%) were relegated to cross validation. The network was programmed to process this information and predict the percent swell at any time, knowing the variable involved. The study demonstrates that it is possible to develop a general BPNN model that can predict time dependent swell with relatively high accuracy with observed data ($R^2$=0.9986). The obtained results are also compared with generated non-linear regression model.

• 대한수학회지
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• 제56권4호
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• pp.1017-1029
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• 2019

In this paper, blows-up and global solutions for a class of nonlinear divergence form parabolic equations with the abstract form of $({\varrho}(u))_t$ and time dependent coefficients are considered. The conditions are established for the existence of a solution globally and also the conditions are established for the blow up of the solution at some finite time. Moreover, the lower bound and upper bound of the blow-up time are derived if blow-up occurs.

• Communications for Statistical Applications and Methods
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• 제29권2호
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• pp.225-238
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• 2022

In this paper, we propose a clustering method for advanced metering infrastructure (AMI) data in Korea. As AMI data presents non-stationarity, we consider time-dependent frequency domain principal components analysis, which is a proper method for locally stationary time series data. We develop a new clustering method based on time-varying eigenvectors, and our method provides a meaningful result that is different from the clustering results obtained by employing conventional methods, such as K-means and K-centres functional clustering. Simulation study demonstrates the superiority of the proposed approach. We further apply the clustering results to the evaluation of the electricity price system in South Korea, and validate the reform of the progressive electricity tariff system.

• 한국ITS학회 논문지
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• 제11권5호
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• pp.38-45
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• 2012

시간 종속적 가로망에 대한 최단경로 탐색은 ITS분야의 경로 일정계획과 실시간 내비게이션 시스템에서 중요한 부분을 차지한다. 본 연구에서는 매시간간격 변동적인 링크 통행속도를 고려하는 one-to-one 시간 종속적 최단시간 경로 알고리즘을 제시한다. 이를 위해, 먼저 기존의 일반적인 최단거리 경로 알고리즘 중에서 실제 도로망에서 비교적 빠르고 효율적인 알고리즘으로 알려져 있는 3가지의 알고리즘들, 즉, two queues 구조를 가진 Graph growth 알고리즘, approximate buckets 구조를 가진 Dijkstra 알고리즘, double buckets 구조를 가진 Dijkstra 알고리즘이 선택되었다. 이 알고리즘들은 모두 네트워크 내 하나의 노드에서 모든 노드(one-to-all)로의 최단거리 경로를 빠르게 탐색하기위해 개발되었다. 선택된 알고리즘들은 시간 종속적 도로망에 대해 하나의 출발노드에서 하나의 목적노드(one-to-one)로의 최단시간 경로 탐색이 가능하도록 확장된다. 또한, 제안된 3가지의 시간 종속적 최단시간 경로탐색 알고리즘들은 미국의 Anaheim, Baltimore, Chicago, Philadelphia 4개 도시의 실제 가로망에 적용하여 검증 평가된다. 결과적으로, 도시부 가로망을 대상으로 한 시간 종속적 최단시간 경로탐색 알고리즘으로 double buckets 구조를 가진 확장된 Dijkstra 알고리즘이 추천된다.

• 한국수자원학회논문집
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• 제42권6호
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• pp.445-455
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• 2009

본 논문에서는 연구대상 지역의 150 mm 주철 상수관로의 첫 번째 파손으로부터 일곱 번째 파손사건에 대한 비례 위험모형을 구축하였다. 모형의 구축과정에서 공변수의 위험률에 대한 비례위험 가정을 검사하여 이를 위배할 경우 시간종속형 공변수로 모형화하였다. 그 결과 첫 번째 파손에 대해서는 관로의 제원 및 연결 방식과 급수인구가, 그리고 두 번째 파손 사건에 대해서는 급수인구의 영향이 시간에 따라 변하는 것으로 나타났다. 각 생존시간군의 기저위험률에 대한 분석으로부터 첫 번째와 두 번째 파손에 대해서는 대체적으로 파손 위험률이 시간에 따라 계속해서 증가하는 것으로 나타났으며, 세 번째 파손으로부터 일곱번째 파손사건에 대해서는 파손 위험률이 감소하다가 시간이 지나면 증가하는 욕조 모양으로 추정되었다. 또한 시간과 파손횟수에 따른 기저위험률의 변화 및 각 생존시간군의 중간생존시간으로부터 연구대상 상수관로들은 파손횟수가 증가할수록 전반적인 관로의 상태가 악화되는 것으로 판단된다. 추정된 공변수의 회귀계수와 위험비율을 이용하여 관로파손에 미치는 인자와 그 시간적 영향에 대하여 분석하였으며, 구축된 모형의 이탈잔차를 이용하여 모형의 적합도를 검증하였다.

• Molecules and Cells
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• 제21권1호
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• pp.121-128
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• 2006

Maitotoxin (MTX) is known as one of the most potent marine toxins involved in Ciguatera poisoning, but intracellular signaling pathways caused by MTX was not fully understood. Thus, we have investigated whether intracellular reactive oxygen species (ROS) are involved in MTX-induced cellular responses in human umbilical vein endothelial cells. MTX induced a dose-dependent increase of intracellular [$Ca^{2+}$]. MTX stimulated the production of intracellular ROS in a dose- and time-dependent manner, which was suppressed by BAPTA-AM, an intracellular $Ca^{2+}$ chelator. Ionomycin also elevated the ROS production in a dose-dependent manner. MTX elevated transamidation activity in a time-dependent manner and the activation was largely inhibited by transfection of tissue transglutaminase siRNA. The activation of tissue transglutaminase and ERK1/2 by MTX was suppressed by BAPTA-AM or ROS scavengers. In addition, MTX-induced cell death was significantly delayed by BAPTA-AM or a ROS scavenger. These results suggest that [$Ca^{2+}$]-dependent generation of intracellular ROS, at least in part, play an important role in MTX-stimulated cellular responses, such as activation of tTGase, ERK phosphorylation, and induction of cell death, in human umbilical vein endothelial cells.

• Bulletin of the Korean Chemical Society
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• 제33권3호
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• pp.1029-1036
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• 2012

Push-pull-type copolymers - low-band-gap copolymers of electron-rich fused-ring units (such as cyclopentadithiophene; CPDT) and electron-deficient units (such as benzothiadiazole; BT) - are promising donor materials for organic solar cells. Following a design principles proposed in our previous study, we investigate the electronic structure of a series of new CPDTBT derivatives with various electron-withdrawing groups using the time-dependent density functional theory and predict their power conversion efficiency from a newlydeveloped protocol using the Scharber diagram. Significantly improved efficiencies are expected for derivatives with carbonyl [C=O], carbonothioyl [C=S], dicyano [$C(CN)_2$] and dicyanomethylene [C=$C(CN)_2$] groups, but these polymers with no long alkyl side chain attached to them are likely to be insoluble in most organic solvents and inapplicable to low-cost solution processes. We thus devise several approaches to attach alkyl side chains to these polymers while keeping their high efficiencies.

• Geomechanics and Engineering
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• 제21권5호
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• pp.489-501
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• 2020

This paper conducts a complicated coupled effective stress analysis of X-section-in-place concrete (XCC) pile installation and consolidation processes using the dual-stage Eulerian-Lagrangian (DSEL) technique incorporating the modified Cam-clay model. The numerical model is verified by centrifuge data and field test results. The main objective of this study is to investigate the shape effect of XCC pile cross-section on radial total stress, excess pore pressure and time-dependent strength. The discrepancies of the penetration mechanism and set-up effects on pile shaft resistance between the XCC pile and circular pile are discussed. Particular attention is placed on the time-dependent strength around the XCC pile shaft. The results show that soil strength improved more significantly close to the flat side compared with the concave side. Additionally, the computed ultimate shaft resistance of XCC pile incorporating set-up effects is 1.45 times that of the circular pile. The present findings are likely helpful in facilitating the incorporation of set-up effects into XCC pile design practices.