• Interaction and multiscale mechanics
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• 제5권2호
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• pp.157-168
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• 2012

The dilatancy of granular materials has significant influence on its mechanical behaviors. The dilation angle is taken as a constant in conventional associated or non-associated flow rules based on Drucker-Prager yields theory. However, various experimental results show the dilatancy changes during progressive failure of granular materials. A non-associated flow rule with evolution of dilation angle is adopted in this study, and Cosserat continuum theory is used to describe the behaviors of granular materials for considering to some extent the its internal structure. Numerical examples focus on the bearing capacity and localization of granular materials, and results illustrate the capability and performance of the presented model in modeling the effect on failure behavior of granular materials.

• Geomechanics and Engineering
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• 제2권4호
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• pp.281-302
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• 2010

An extended model for the response of a rigid footing on a reinforced foundation bed on super soft soil is proposed by incorporating the rough membrane element into the granular bed. The super soft soil, the granular bed and the reinforcement are modeled as non-linear Winkler springs, non-linear Pasternak layer and rough membrane respectively. The hyperbolic stress-displacement response of the super soft soil and the hyperbolic shear stress-shear strain response of the granular fill are considered. The finite deformation theory is used since large settlements are expected to develop due to deformation of the super-soft soil. Parametric studies quantify the effect of each parameter on the stress-settlement response of the reinforced foundation bed, the settlement and tension profiles.

• 한국입자에어로졸학회지
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• 제19권4호
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• pp.145-154
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• 2023

Granular bed filters are widely used to remove particulate matter in flue gas and are filled with various shapes of packing material. The packing material plays an important role in determining the overall collection performance, such as pressure drop and collection efficiency. The pressure drop of a granular bed filter has been calculated using the Ergun equation, while the collection efficiency has been predicted using the log-penetration equation based on the single sphere theory. However, a prediction equation of collection efficiency for a granular bed filter filled with non-spherical packing materials has not been suggested yet. Therefore, in this study, three different shapes of packing materials (sphere, cylinder, and irregular) were prepared to propose a prediction equation. The pressure drop and collection efficiency in a granular bed filter filled with each shape of packing material were measured experimentally and compared with theoretically predicted values. We found that experimentally measured pressure drops matched well with values theoretically predicted using the Ergun equation considering the shape factor. However, experimental collection efficiencies were higher than theoretical ones predicted by the log-penetration equation using the single sphere theory. We modified the log-penetration equation by employing a shape factor and found a good relationship between experimental and theoretical collection efficiencies.

• 한국지반환경공학회 논문집
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• 제1권1호
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• pp.51-56
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• 2000

조립토 piled raft 시스템은 상부 raft 기초 하부의 연약지반을 조립토 다짐말뚝으로 보강하여 침하를 감소시키고 또한 지지력 증대를 도모하는 효과적인 공법으로 사용되어 왔다. 본 연구에서는, 말뚝 사이의 상호작용 효과 및 말뚝과 raft의 상호작용 효과 등을 고려하고 또한 판이론(plate theory)을 토대로, raft와 기초지반 사이 접촉면에서 발생하는 지점별 불균등 침하량을 예측하기 위한 유한요소 해석기법을 제시하였다. 제시된 해석기법은 조립토 piled raft 시스템의 다양한 배치형태에 대해 지점별 침하량 예측이 가능하며, 제시된 기법의 적합성 확인을 위해 예측된 침하량을 기존 연구결과(김 등, 1999)와 비교 분석하였다. 이외에도 제시된 기법을 이용하여, 조립토 piled raft 시스템의 배치형태별 거동특성 분석이 이루어 졌으며, 또한 침하량 감소효과를 관련 설계변수와 연계하여 분석을 수행하였다.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제16권3호
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• pp.157-162
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• 2016

In this paper, a yield prediction model based on relevance vector machine (RVM) and a granular computing model (quotient space theory) is presented. With a granular computing model, massive and complex meteorological data can be analyzed at different layers of different grain sizes, and new meteorological feature data sets can be formed in this way. In order to forecast the crop yield, a grey model is introduced to label the training sample data sets, which also can be used for computing the tendency yield. An RVM algorithm is introduced as the classification model for meteorological data mining. Experiments on data sets from the real world using this model show an advantage in terms of yield prediction compared with other models.

• Journal of Information Processing Systems
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• 제16권3호
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• pp.663-676
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• 2020

Plant leaf classification is a significant application of image processing techniques in modern agriculture. In this paper, a multi-granular angle description method is proposed for plant leaf classification and retrieval. The proposed method can describe leaf information from coarse to fine using multi-granular angle features. In the proposed method, each leaf contour is partitioned first with equal arc length under different granularities. And then three kinds of angle features are derived under each granular partition of leaf contour: angle value, angle histogram, and angular ternary pattern. These multi-granular angle features can capture both local and globe information of the leaf contour, and make a comprehensive description. In leaf matching stage, the simple city block metric is used to compute the dissimilarity of each pair of leaf under different granularities. And the matching scores at different granularities are fused based on quotient space theory to obtain the final leaf similarity measurement. Plant leaf classification and retrieval experiments are conducted on two challenging leaf image databases: Swedish leaf database and Flavia leaf database. The experimental results and the comparison with state-of-the-art methods indicate that proposed method has promising classification and retrieval performance.

• International Journal of Precision Engineering and Manufacturing
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• 제9권2호
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• pp.3-7
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• 2008

Vibratory conveyors are widely used in industry to transport granular materials and products. A theoretical point mass model for vibratory conveying was studied. The results agreed well with experimental observations. The model theory included the resting, sliding and flight states of the material. Each state was considered separately when determining the equations of motion. For the coefficients of restitution, values of zero for the normal component and 0.8 for the tangential component were found to be appropriate for modeling the collisions of the granular particles with the conveying surface. The vibration angle had a large influence on the mode and rate of transport. There was an optimum vibration angle for a given set of conditions. The optimum vibration angle decreased and was better defined as the coefficient of friction increased. The results suggest the existence of an optimum dimensionless track acceleration (throw number), which does not support general industrial practice in which the track acceleration is limited when the feed cycle becomes erratic and unstable.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.129-136
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• 2004

Anisotropic characteristics of deformation are important to understand the particular behavior in the pre-failure state of soils. Recent experiments shows that cross-anisotropic moduli of granular soils can be expressed by functions of normal stresses in the corresponding directions, which is closely linked to micromechanical characteristics of particles. Granular soils are composed of a number of particles so that the force-displacement relationship at each contact point governs the macroscopic stress-strain relationship. Therefore, the micromechanical approach in which the deformation of granular soils is regarded as a mutual interaction between particle contacts is one of the best ways to investigate the anisotropic deformation of soils. In this study, a numerical program based on the theory of micromechanics is developed. Modified Hertz-Mindlin model is adopted to represent the force-displacement relationship in each contact point for the realistic prediction of anisotropic moduli. To evaluate the model parameters, a set of analytical solutions of anisotropic moduli is derived in the isotropic stress condition. By comparing the analytical solutions with exact values, we confirm that the analytical solutions can be utilized to evaluate model parameters within the acceptable range of error of 10%.

• 한국산학기술학회논문지
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• 제19권9호
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• pp.420-426
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• 2018

데니스 게이버(Dennis Gabor)의 음향 양자(Acoustic Quanta) 이론은 음향 합성법의 하나인 그래뉼러 합성법(Granular Synthesis)의 이론적 토대가 되어 많은 컴퓨터 음악 작곡가들과 사운드 디자이너들에게 영감을 주었다. 음향 양자는 1에서 100 ms의 지속시간을 가진, 시간적으로 더 이상 짧게 분해될 수 없는 소리를 뜻한다. 그래뉼러 합성법은 원음을 매우 짧은 시간 간격으로 분할하여 소리 입자들(Sound Grain)로 만든 다음, 이 소리 입자들을 조합하여 새로운 음악 또는 음색을 구현하는 방법이다. 음향 양자 개념은 그래뉼러 합성법의 소재가 되는 소리 입자의 이론적 근거가 되었다. 기존 음향 합성법과는 전혀 다른 음색의 사운드를 만들어 낼 수 있는 그래뉼러 합성법은 사운드 디자인 분야에서 다양한 용도로 사용 가능하다. 본 논문에서는 게이버의 음향 양자 개념을 소개하고 이를 그래뉼러 합성법에 적용하여 활용 가능한 사운드 디자인 방법, 특히 동기식(Synchronous) 그래뉼러 방식에 의한 신디사이저(Synthesizer) 제작 가능성과 그 응용에 대하여 논하였다. 연구결과 가청주파수를 감안한 음향 양자의 지속시간은 0.239에서 33.367 ms 사이가 되어야하기 때문에 음향 양자의 본래 개념과는 차이가 있었다.

• Nuclear Engineering and Technology
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• 제54권7호
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• pp.2367-2375
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• 2022

In this work, we propose a new mechanistic model for the treatment of helium behaviour at the grain boundaries in oxide nuclear fuel. The model provides a rate-theory description of helium inter-granular behaviour, considering diffusion towards grain edges, trapping in lenticular bubbles, and thermal resolution. It is paired with a rate-theory description of helium intra-granular behaviour that includes diffusion towards grain boundaries, trapping in spherical bubbles, and thermal re-solution. The proposed model has been implemented in the meso-scale software designed for coupling with fuel performance codes SCIANTIX. It is validated against thermal desorption experiments performed on doped UO₂ samples annealed at different temperatures. The overall agreement of the new model with the experimental data is improved, both in terms of integral helium release and of the helium release rate. By considering the contribution of helium at the grain boundaries in the new model, it is possible to represent the kinetics of helium release rate at high temperature. Given the uncertainties involved in the initial conditions for the inter-granular part of the model and the uncertainties associated to some model parameters for which limited lower-length scale information is available, such as the helium diffusivity at the grain boundaries, the results are complemented by a dedicated uncertainty analysis. This assessment demonstrates that the initial conditions, chosen in a reasonable range, have limited impact on the results, and confirms that it is possible to achieve satisfying results using sound values for the uncertain physical parameters.