• Smart Structures and Systems
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• v.13 no.4
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• pp.615-636
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• 2014

Aluminium Foam Sandwich (AFS) panels are becoming always more attractive in transportation applications thanks to the excellent combination of mechanical properties, high strength and stiffness, with functional ones, thermo-acoustic isolation and vibration damping. These properties strongly depend on the density of the foam, the morphology of the pores, the type (open or closed cells) and the size of the gas bubbles enclosed in the solid material. In this paper, the vibrational performances of two classes of sandwich panels with an Alulight(R) foam core are studied. Experimental tests, in terms of frequency response function and modal analysis, are performed in order to investigate the effect of different percentage of porosity in the foam, as well as the effect of the random distribution of the gas bubbles. Experimental results are used as a reference for developing numerical models using finite element approach. Firstly, a sensitivity analysis is performed in order to obtain a limit-but-bounded dynamic response, modelling the foam core as a homogeneous one. The experimental-numerical correlation is evaluated in terms of natural frequencies and mode shapes. Afterwards, an update of the previous numerical model is presented, in which the core is not longer modelled as homogeneous. Mass and stiffness are randomly distributed in the core volume, exploring the space of the eigenvectors.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.770-771
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• 2005

• Nuclear Engineering and Technology
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• v.54 no.12
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• pp.4560-4570
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• 2022

Dynamic fault tree (DFT) and its related research methods have received extensive attention in safety analysis and reliability engineering. DFT can perform reliability modelling for systems with sequential correlation, resource sharing, and cold and hot spare parts. A technical modelling method of DFT is proposed for modelling ship collision accidents and loss-of-coolant accidents (LOCAs). Qualitative and quantitative analyses of DFT were carried out using the cutting sequence (CS)/extended cutting sequence (ECS) method. The results show nine types of dynamic fault failure modes in ship collision accidents, describing the fault propagation process of a dynamic system and reflect the dynamic changes of the entire accident system. The probability of a ship collision accident is 2.378 × 10^-9 by using CS. This failure mode cannot be expressed by a combination of basic events within the same event frame after an LOCA occurs in a marine nuclear reactor because the system contains warm spare parts. Therefore, the probability of losing reactor control was calculated as 8.125 × 10^-6 using the ECS. Compared with CS, ECS is more efficient considering expression and processing capabilities, and has a significant advantage considering cost.

• Steel and Composite Structures
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• v.42 no.6
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• pp.733-745
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• 2022

This study proposed a robust artificial intelligence (AI) model based on the social behaviour of the imperialist competitive algorithm (ICA) and artificial neural network (ANN) for modelling the deflection of reinforced concrete beams, abbreviated as ICA-ANN model. Accordingly, the ICA was used to adjust and optimize the parameters of an ANN model (i.e., weights and biases) aiming to improve the accuracy of the ANN model in modelling the deflection reinforced concrete beams. A total of 120 experimental datasets of reinforced concrete beams were employed for this aim. Therein, applied load, tensile reinforcement strength and the reinforcement percentage were used to simulate the deflection of reinforced concrete beams. Besides, five other AI models, such as ANN, SVM (support vector machine), GLMNET (lasso and elastic-net regularized generalized linear models), CART (classification and regression tree) and KNN (k-nearest neighbours), were also used for the comprehensive assessment of the proposed model (i.e., ICA-ANN). The comparison of the derived results with the experimental findings demonstrates that among the developed models the ICA-ANN model is that can approximate the reinforced concrete beams deflection in a more reliable and robust manner.

• Nuclear Engineering and Technology
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• v.43 no.6
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• pp.489-498
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• 2011

UK National Nuclear Laboratory's (NNL's) version of the ENIGMA fuel performance code is described, including details of the development history, the system modelled, the key assumptions, the thermo-mechanical solution scheme, and the various incorporated models. The recent development of ENIGMA in the areas of whole core analysis and dry storage applications is then discussed. With respect to the former, the NEXUS code has been developed by NNL to automate whole core fuel performance modelling for an LWR core, using ENIGMA as the underlying fuel performance engine. NEXUS runs on NNL's GEMSTONE high performance computing cluster and utilises 3-D core power distribution data obtained from the output of Studsvik Scandpower's SIMULATE code. With respect to the latter, ENIGMA has been developed such that it can model the thermo-mechanical behaviour of a given LWR fuel rod during irradiation, pond cooling, drying, and dry storage - this involved: (a) incorporating an out-of-pile clad creep model for irradiated Zircaloy-4; (b) including the ability to simulate annealing out of the clad irradiation damage; (c) writing of additional post-irradiation output; (d) several other minor modifications to allow modelling of post-irradiation conditions.

• Structural Engineering and Mechanics
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• v.72 no.2
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• pp.257-273
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• 2019

In this paper, the mechanical behaviour of functionally graded material beams is studied using the 3D Saint-Venant's theory, in which the section is free to warp in and out of its plane (Poisson's effects and out-of-plane warpings). The material properties of the FGM beam are distributed continuously through the thickness by several distributions, such as power-law distribution, exponential distribution, Mori-Tanaka schema and sigmoid distribution. The proposed method has been applied to study a simply supported FGM beam. The numerical results obtained are compared to other models in the literature, which show a high performance of the 3D exact theory used to describe the stress and strain fields in FGM beams.

• Communications of the Korean Mathematical Society
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• v.37 no.1
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• pp.45-56
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• 2022

In this paper, we introduce and study the class of rings in which every ideal consisting entirely of zero divisors is a d-ideal, considered as a generalization of strongly duo rings. Some results including the characterization of AA-rings are given in the first section. Further, we examine the stability of these rings in localization and study the possible transfer to direct product and trivial ring extension. In addition, we define the class of d_E-ideals which allows us to characterize von Neumann regular rings.

• Communications of the Korean Mathematical Society
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• v.38 no.1
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• pp.121-122
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• 2023

In this erratum, we correct a mistake in the proof of Proposition 2.7. In fact the equivalence (3) ⇐ (4) "R is a quasi-regular ring if and only if R is a reduced ring and every principal ideal contained in Z(R) is a 0-ideal" does not hold as we only have Rx ⊆ O(S).

• Geomechanics and Engineering
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• v.32 no.1
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• pp.21-34
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• 2023

In order to analyze the effect of the cyclic lateral loading on the response of a pile-soil system, a full-scale single steel pile was subjected to one-way cyclic loading. The test pile was driven into a bi-layered soil consisting of a normally consolidated saturated clay overlying a silty sandy layer, the site being submerged by water up to one meter above the mudline in order to reproduce the conditions of an offshore pile foundation. The aim of this paper is to present the main results of interpretation of the cyclic lateral tests in terms of pile deflections, bending moment, and cyclic P-Y curves. From these latter an absolute secant reaction modulus E_AS,N was derived and a simple calculation model of the test single pile is proposed based on this modulus. Two applications of the proposed model are carried out, one with a 2D finite element modelling, and the second with a load transfer curves-based method.

• Communications of the Korean Mathematical Society
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• v.38 no.3
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• pp.705-714
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• 2023

Bennis and El Hajoui have defined a (commutative unital) ring R to be S-coherent if each finitely generated ideal of R is a S-finitely presented R-module. Any coherent ring is an S-coherent ring. Several examples of S-coherent rings that are not coherent rings are obtained as byproducts of our study of the transfer of the S-coherent property to trivial ring extensions and amalgamated duplications.