• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.6 s.165
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• pp.1001-1010
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• 1999

Thermo-mechanical behavior of discontinuous shape memory alloy(SMA) reinforced polymeric composite has been studied using modified shear lag theory and finite element(FE) analysis with 2-D multi-fiber model. The aligned and staggered models of short-fiber arrangement are employed. The effects of fiber overlap and aspect ratio on the thermomechanical responses such as the thermal expansion coefficient are investigated. It is found that the increase of both tensile stress(resistance stress) in SMA fiber and compressive stress in polymer matrix with increasing aspect ratio is the main cause of low thermal deformation of the composite.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.109-114
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• 2003

The physical model considered here is a horizontal layer of fluid heated below and cooled above with a periodic array of evenly spaced square cylinders placed at the center of the layer, whose aspect ratio here varies from unity to twelve. Periodic boundary condition is employed along the horizontal direction to allow for lateral freedom for the convection cells. Two-dimensional solution for unsteady natural convection is obtained using an accurate and efficient Chebyshev spectral multi-domain methodology for a given Rayleigh numbers of $10^{6}$.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.4
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• pp.1275-1292
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• 2021

As a fine-grained classification problem, aspect-level sentiment classification predicts the sentiment polarity for different aspects in context. To address this issue, researchers have widely used attention mechanisms to abstract the relationship between context and aspects. Still, it is difficult to effectively obtain a more profound semantic representation, and the strong correlation between local context features and the aspect-based sentiment is rarely considered. In this paper, a hybrid attention capsule network for aspect-level sentiment classification (ABASCap) was proposed. In this model, the multi-head self-attention was improved, and a context mask mechanism based on adjustable context window was proposed, so as to effectively obtain the internal association between aspects and context. Moreover, the dynamic routing algorithm and activation function in capsule network were optimized to meet the task requirements. Finally, sufficient experiments were conducted on three benchmark datasets in different domains. Compared with other baseline models, ABASCap achieved better classification results, and outperformed the state-of-the-art methods in this task after incorporating pre-training BERT.

• Structural Engineering and Mechanics
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• v.42 no.6
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• pp.867-882
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• 2012

Analytical (Rayleigh-Ritz method) and numerical studies are carried out and buckling interaction curves are developed for simply supported plates of varying aspect ratios ranging from 1 to 5, under the combined action of in-plane shear and tension. A multi-step buckling procedure is employed in the Finite Element (FE) model instead of a regular single step analysis in view of obtaining the buckling load under the combined forces. Both the analytical (classical) and FE studies confirm the delayed shear buckling characteristics of thin plate under the combined action of shear and tension. The interaction curves are found to be linear and are found to vary with plate aspect ratio. The interaction curve developed using Rayleigh-Ritz method is found to deviate in an increasing trend from that of validated FE model as plate aspect ratio is increased beyond value of 1. It is found that the observed deviation is due to the insufficient number of terms that is been considered in the assumed deflection function of Rayleigh-Ritz method and a convergence study is suggested as a solution.

• Korean Management Science Review
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• v.29 no.3
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• pp.107-120
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• 2012

In this paper we propose an effective genetic algorithm for solving the integrated inventory and routing problem of supply chain composed of multi-warehouses and multi-retailers. Unlike extant studies dealing with integrated inventory and routing problem of supply chain, our model incorporates more realistic aspect such as positive inventory at the multi-warehouses under the assumption of inventory policy of power of two-replenishment-cycle. The objective is to determine replenishment intervals for the retailers and warehouses as well as the vehicles routes so that the total cost of delivery and inventory cost is minimized. A notable feature of our algorithm is that the procedure for evaluating the fitness of objective function has the computational complexity closing to linear function. Computational results show effectiveness of our algorithm.

• Earthquakes and Structures
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• v.16 no.1
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• pp.41-54
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• 2019

Reinforced Concrete (RC) shear walls are widely used in Nuclear power plants as effective lateral force resisting elements of the structure and these may experience nonlinear behavior for higher earthquake demand. Short shear walls of aspect ratio less than 1.5 generally experience combined shear flexure interaction. This paper presents the results of the displacement-controlled experiments performed on six RC short shear walls with varying aspect ratios (1, 1.25 and 1.5) for monotonic and reversed quasi-static cyclic loading. Simulation of the shear walls is then carried out by Finite element modeling and also by macro modeling considering the coupled shear and flexure behaviour. The shear response is estimated by softened truss theory using the concrete model given by Vecchio and Collins (1994) with a modification in softening part of the model and flexure response is estimated using moment curvature relationship. The accuracy of modeling is validated by comparing the simulated response with experimental one. Moreover, based on the experimental work a multi-linear hysteretic model is proposed for short shear walls. Finally ultimate load, drift, ductility, stiffness reduction and failure pattern of the shear walls are studied in details and hysteretic energy dissipation along with damage index are evaluated.

• Smart Structures and Systems
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• v.21 no.1
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• pp.65-74
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• 2018

In this article, an analytic non-classical model for the free vibrations of nanobeams accounting for surface stress effects is developed. The classical continuum mechanics fails to capture the surface energy effects and hence is not directly applicable at nanoscale. A general beam model based on Gurtin-Murdoch continuum surface elasticity theory is developed for the analysis of thin and thick beams. Thus, surface energy has a significant effect on the response of nanoscale structures, and is associated with their size-dependent behavior. To check the validity of the present analytic solution, the numerical results are compared with those obtained in the scientific literature. The influences of beam thickness, surface density, surface residual stress and surface elastic constants on the natural frequencies of nanobeams are also investigated. It is indicated that the effect of surface stress on the vibrational response of a nanobeam is dependent on its aspect ratio and thickness.

• Smart Structures and Systems
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• v.19 no.2
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• pp.115-126
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• 2017

In this paper, size dependent bending and free flexural vibration behaviors of functionally graded (FG) nanobeams are investigated using a nonlocal quasi-3D theory in which both shear deformation and thickness stretching effects are introduced. The nonlocal elastic behavior is described by the differential constitutive model of Eringen, which enables the present model to become effective in the analysis and design of nanostructures. The present theory incorporates the length scale parameter (nonlocal parameter) which can capture the small scale effect, and furthermore accounts for both shear deformation and thickness stretching effects by virtue of a hyperbolic variation of all displacements through the thickness without using shear correction factor. The material properties of FG nanobeams are assumed to vary through the thickness according to a power law. The neutral surface position for such FG nanobeams is determined and the present theory based on exact neutral surface position is employed here. The governing equations are derived using the principal of minimum total potential energy. The effects of nonlocal parameter, aspect ratio and various material compositions on the static and dynamic responses of the FG nanobeam are discussed in detail. A detailed numerical study is carried out to examine the effect of material gradient index, the nonlocal parameter, the beam aspect ratio on the global response of the FG nanobeam. These findings are important in mechanical design considerations of devices that use carbon nanotubes.

• The Journal of Korea Robotics Society
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• v.12 no.2
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• pp.161-172
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• 2017

Foot mechanisms play the role of interface between the main body of robotic systems and the ground. Biomimetic design of the foot mechanism is proposed in the paper. Specifically, multi-chained and multiple contact characteristics of general foot mechanisms are analyzed and their advantages are highlighted in terms of impulse. Using Newton-Euler based closed-form external and internal impulse models, characteristics of multiple contact cases are investigated through landing simulation of an articulated leg model with three kinds of foot. It is shown that in comparison to single chain and less articulated linkage system, multi-chain and articulated linkage system has superior characteristic in terms of impulse absorption as well as stability after collision. The effectiveness of the simulation result is verified through comparison to the simulation result of a commercialized software.

• Journal of the Korean Society of Industry Convergence
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• v.3 no.1
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• pp.53-59
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• 2000

단섬유 보강 복합재료의 종횡비(aspect ratio)를 변화시키며 기계적 특성(탄성계수, 인장강도)을 평가하였다. 2차원 다중 파이버(multi-fiber) 모델을 이용하여 엇갈린(staggered) 배열과 규칙적(aligned) 배열에 대해 유한요소 해석을 하였다. 단섬유 복합재료의 유효탄성계수 및 인장강도는 섬유와 기지의 탄성계수비, 섬유 배열상태, 그리고 단섬유 종횡비의 함수로 표현되었으며, 해석결과의 탄성계수와 인장강도는 이론 모델의 결과와 사출 성형된 PEEK 복합재료 시험편의 결과와 비교하였다. 시험결과는 낮은 종횡비에서 이론 모델 결과와 일치함을 보였다. 단섬유 보강 복합재료의 배열 및 종횡비 변화에 따른 섬유보강 효과에 따른 계면응력 상태는 기계적 특성 결정에 중요한 영향을 보였다.