• Title/Summary/Keyword: Stochastic field

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Technical Reviews on Ecosystem Modeling Approach and its Applicability in Ecosystem-Based Coastal Management in Saemangeum Offshore and Geum River Estuary (생태계기반 연안관리를 위한 생태모델 개발방향에 대한 기술적 검토 - 새만금 외해역 및 금강 하구역 사례)

  • Kim, Hae-Cheol;Kim, Yong Hoon;Chang, Won-Keun;Ryu, Jongseong
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.18 no.3
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    • pp.233-244
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    • 2015
  • Marine ecosystem modelling has become a more widely used decision-making tool in coastal ecosystem-based management. However, it is not trivial to develop a well calibrated/validated model with potential applicability and practicality because understanding ecological processes with complexities is a pre-requisite for developing robust ecosystem models and this accompanies a great deal of well coordinated efforts among field-going ecologists, laboratory scientists, modelers, stake-holders and managers. This report aims to provide a brief introduction on two different approaches in marine ecological models: deterministic (mechanistic) and stochastic (statistical) approach. We also included definitions, historical overview of past researches, case studies, and contextual suggestions for coastal management in Korea. A long list of references this report included in this study might be used as an introductory material for those who wish to enter ecosystem modelling field.

Statistical Behavior of RC Cooling Tower Shell due to Shape Imperfection (철근콘크리트 냉각탑의 형상불완전에 의한 확률론적 거동)

  • 최창근;노혁천
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.13 no.1
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    • pp.147-158
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    • 2000
  • For the large scale reinforced concrete cooling tower shells, the shape imperfection can be introduced due not only to mistakes in the process of construction but also to the long term behavior of concrete. The shape imperfection evokes the additional responses such as displacements and stresses in addition to the design values. In this study, the statistical behavior of the RC cooling tower shell due to the shape imperfection is investigated using the Monte Carlo simulation. The radius of cooling tower and the shell thickness are adopted as the parameters which cause the shape imperfection. The shape imperfection is modeled as a stochastic field rather than the local one of axisymmetric or bulge type of imperfection. The randomness in the radius is shown to be more affecting the structural responses than the randomness in the shell thickness. In addition to the geometrical randomness, the effect of randomness in the modulus of elasticity on the structural response is also investigated and compared with that of the geometrical ones.

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Effect of spatial variability of concrete materials on the uncertain thermodynamic properties of shaft lining structure

  • Wang, Tao;Li, Shuai;Pei, Xiangjun;Yang, Yafan;Zhu, Bin;Zhou, Guoqing
    • Structural Engineering and Mechanics
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    • v.81 no.2
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    • pp.205-217
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    • 2022
  • The thermodynamic properties of shaft lining concrete (SLC) are important evidence for the design and construction, and the spatial variability of concrete materials can directly affect the stochastic thermal analysis of the concrete structures. In this work, an array of field experiments of the concrete materials are carried out, and the statistical characteristics of thermophysical parameters of SLC are obtained. The coefficient of variation (COV) and scale of fluctuation (SOF) of uncertain thermophysical parameters are estimated. A three-dimensional (3-D) stochastic thermal model of concrete materials with heat conduction and hydration heat is proposed, and the uncertain thermodynamic properties of SLC are computed by the self-compiled program. Model validation with the experimental and numerical temperatures is also presented. According to the relationship between autocorrelation functions distance (ACD) and SOF for the five theoretical autocorrelation functions (ACFs), the effects of the ACF, COV and ACD of concrete materials on the uncertain thermodynamic properties of SLC are analyzed. The results show that the spatial variability of concrete materials is subsistent. The average temperatures and standard deviation (SD) of inner SLC are the lowest while the outer SLC is the highest. The effects of five 3-D ACFs of concrete materials on uncertain thermodynamic properties of SLC are insignificant. The larger the COV of concrete materials is, the larger the SD of SLC will be. On the contrary, the longer the ACD of concrete materials is, the smaller the SD of SLC will be. The SD of temperature of SLC increases first and then decreases. This study can provide a reliable reference for the thermodynamic properties of SLC considering spatial variability of concrete materials.

Quantification Analysis Problem using Mean Field Theory in Neural Network (평균장 이론을 이용한 전량화분석 문제의 최적화)

  • Jo, Gwang-Su
    • The Transactions of the Korea Information Processing Society
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    • v.2 no.3
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    • pp.417-424
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    • 1995
  • This paper describes MFT(Mean Field Theory) neural network with continuous with continuous variables is applied to quantification analysis problem. A quantification analysis problem, one of the important problems in statistics, is NP complete and arises in the optimal location of objects in the design space according to the given similarities only. This paper presents a MFT neural network with continuous variables for the quantification problem. Starting with reformulation of the quantification problem to the penalty problem, this paper propose a "one-variable stochastic simulated annealing(one-variable SSA)" based on the mean field approximation. This makes it possible to evaluate of the spin average faster than real value calculating in the MFT neural network with continuous variables. Consequently, some experimental results show the feasibility of this approach to overcome the difficulties to evaluate the spin average value expressed by the integral in such models.ch models.

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Relationship between fracture distribution and the acidity of mine drainage at the Il-Gwang Mine (일광광산의 절리분포 특성과 광산배수 산성도의 관계)

  • Choi, Jae-Young;Um, Jeong-Gi;Kwon, Hyun-Ho;Shim, Yon-Sik
    • The Journal of Engineering Geology
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    • v.20 no.4
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    • pp.425-436
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    • 2010
  • We established a stochastic 3-D fracture network system for fractured rock masses located in Il-Gwang Mine, Busan, to explore the relationship between the acidity of mine drainage and fracture geometry. A field scanline survey and borehole image processing were performed to estimate the best probability distributions of fracture geometry parameters. The stochastic 3-D fracture network system constructed for the rock masses was validated and deemed to be successful. The 3-D fracture network model was suitable for developing conceptual ideas on fluid flow in fractures at a field experimental site. An injection well and three observation wells were drilled at the field experimental site to monitor the acidity of mine drainage induced by the injection of fresh water. The field experiment, which was run for 29 days, yielded a significant relationship (with a high coefficient of determination) between the fracture geometry parameters and the acidity of mine drainage. The results show that pH increased with increasing relative frequency of fracture strike, and decreased with increasing fracture density. The concentration of $SO^{2-}_4$ decreased with increasing relative frequency of fracture strike, and increased with increasing fracture density.

Assessment of Slope Stability With the Uncertainty in Soil Property Characterization (지반성질 불확실성을 고려한 사면안정 해석)

  • 김진만
    • Proceedings of the Korean Geotechical Society Conference
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    • 2003.03a
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    • pp.123-130
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    • 2003
  • The estimation of key soil properties and subsequent quantitative assessment of the associated uncertainties has always been an important issue in geotechnical engineering. It is well recognized that soil properties vary spatially as a result of depositional and post-depositional processes. The stochastic nature of spatially varying soil properties can be treated as a random field. A practical statistical approach that can be used to systematically model various sources of uncertainty is presented in the context of reliability analysis of slope stability Newly developed expressions for probabilistic characterization of soil properties incorporate sampling and measurement errors, as well as spatial variability and its reduced variance due to spatial averaging. Reliability analyses of the probability of slope failure using the different statistical representations of soil properties show that the incorporation of spatial correlation and conditional simulation leads to significantly lower probability of failure than obtained using simple random variable approach.

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Analysis of Filtration Performance by Brownian Dynamics (Brownian Dynamics 를 이용한 입자 포집 과정 및 여과 성능 해석)

  • Bang, Jong-Geun;Yoon, Yoong-Sup
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.10
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    • pp.811-819
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    • 2009
  • In the present study, deposition of discrete and small particles on a filter fiber was simulated by stochastic method. Trajectory of each particle was numerically solved by Langevin equation. And Lattice Boltzmann method (LBM) was used to solve flow field around the filter collector for considering complex shape of deposit layer. Interaction between the flow field and the deposit layer was obtained from a converged solution from an inner-loop calculation. Simulation method is properly validated with filtration theory and collection efficiency due to different filtration parameters are examined and discussed. Morphology of deposit layer and its evolution was visualized in terms of the particle size. The particle loaded effect on collection efficiency was also discussed.

Simulation of particle filtration by Brownian dynamics (Brownian dynamics 를 이용한 입자 포집 모사)

  • Bang, Jong-Geun;Yoon, Yoong-Sup
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.1922-1927
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    • 2008
  • In the present study, deposition of discrete and small particles, which diameter is less than $1{\mu}m$, on a filter element was simulated by stochastic method. Trajectory of each particle was numerically solved by Langevin equation and Brownian random motion was treated by Brownian dynamics. Lattice Boltzmann method (LBM) was used to solve flow field around the filter collector and deposit layer. Interaction between flow field and deposit layer was obtained from a converged solution from an inner-loop calculation. Simulation method is properly validated and collection efficiency due to different filtration parameters are examined and discussed. Morphology of deposit layer and its evolution was visualized in terms of the particle size. The particle loaded effect on collection efficiency was also discussed.

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Adaptive Active Noise Control of Single Sensor Method (단일 센서 방식의 적응 능동 소음제어)

  • 김영달;장석구
    • Journal of KSNVE
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    • v.10 no.6
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    • pp.941-948
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    • 2000
  • Active noise control is an approach to reduce the noise by utilizing a secondary noise source that destructively interferes with the unwanted noise. In general, active noise control systems rely on multiple sensors to measure the unwanted noise field and the effect of the cancellation. This paper develops an approach that utilizes a single sensor. The noise field is modeled as a stochastic process, and an adaptive algorithm is used to adaptively estimate the parameters of the process. Based on these parameter estimates, a canceling signal is generated. Oppenheim assumed that transfer function characteristics from the canceling source to the error sensor is only a propagation delay. This paper proposes a modified Oppenheim algorithm by considering transfer characteristics of speaker-path-sensor This transfer characteristics is adaptively cancelled by the proposed adaptive modeling technique. Feasibility of the proposed method is proved by computer simulations with artificially generated random noises and sine wave noise. The details of the proposed architecture. and theoretical simulation of the noise cancellation system for three dimension enclosure are presented in the Paper.

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A Sigma-Coordinate Scalar Transport Model Coupled with Boussinesq Equations (${\sigma}$-좌표계 기반의 혼합 모형과 Boussinesq Equations 모형의 연계)

  • Kim, Dae-Hong;Lynett, Patrick
    • Proceedings of the Korea Water Resources Association Conference
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    • 2010.05a
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    • pp.218-222
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    • 2010
  • 본 연구에서는 ${\sigma}$-좌표계를 기반으로 하는 3차원의 이송확산 모형과 depth-integrated eddy simulation 모형을 결합한 효율적인 3차원 근역 (near-field) 해석모형을 제시하였다. 흐름 모형은 Boussinesq-type equations과 stochastic backscatter model을 기본으로 하고 있다. 이 흐름 모형은 수면의 변화와 바닥으로부터 발생하는 전단력과 파랑의 유동으로부터 발행하는 수심방향의 유속분포를 예측할 수 있다. 이와 같은 흐름 정보를 3차원 ${\sigma}$-좌표계의 이송확산모형에 제공하고 scalar의 이송과 확산에 대한 거동을 계산한다. 기본적인 이송과 이송-확산에 대한 검증 및 개수로에서 정량적 검증과 정성적 검증을 수행하였다. 전반적으로 타당한 결과가 도출되어 모형의 적합성이 있음을 확인하였다.

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