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  • Open Access

    ARTICLE

    Emerging Trends in Terahertz Metamaterial Applications

    Balamati Choudhury1, Sanjana Bisoyi1, Pavani Vijay Reddy1, Manjula S.1 and R. M. Jha1

    CMC-Computers, Materials & Continua, Vol.39, No.3, pp. 179-215, 2014, DOI:10.3970/cmc.2014.039.179

    Abstract The terahertz spectrum of electromagnetic waves is finding its position in various applications of day to day life because of its unique properties, including the penetration through opaque materials. Naturally occurring materials in this range are rare due to the display of a natural breakpoint of both electric, and magnetic resonances in these materials. However recent advances in artificially engineered materials, which show resonance in this region are able to harness desirable properties in the terahertz region. In this paper, terahertz design and fabrication issues have been explored along with their applications. A brief review of metamaterial terahertz applications has… More >

  • Open Access

    ARTICLE

    A Sliding Mode Control Algorithm for Solving an Ill-posed Positive Linear System

    Chein-Shan Liu1

    CMC-Computers, Materials & Continua, Vol.39, No.2, pp. 153-178, 2014, DOI:10.3970/cmc.2014.039.153

    Abstract For the numerical solution of an ill-posed positive linear system we combine the methods from invariant manifold theory and sliding mode control theory, developing an affine nonlinear dynamical system with a positive control force and with the residual vector as being a gain vector. This system is proven asymptotically stable to the zero residual vector by using an argument from the Lyapunov stability theory. We find that the system fast tends to the sliding surface and then moves with a sliding mode, such that the resultant sliding mode control algorithm (SMCA) is robust against large noise and stable to find… More >

  • Open Access

    ARTICLE

    A Plastic Damage Model with Stress Triaxiality-Dependent Hardening for Concrete

    X.P. Shen1,2, X.C. Wang1

    CMC-Computers, Materials & Continua, Vol.39, No.2, pp. 135-152, 2014, DOI:10.3970/cmc.2014.039.135

    Abstract Emphases of this study were placed on the modelling of plastic damage behaviour of prestressed structural concrete, with special attention being paid to the stress-triaxiality dependent plastic hardening law and the corresponding damage evolution law. A definition of stress triaxiality was proposed and introduced in the model presented here. Drucker-Prager -type plasticity was adopted in the formulation of the plastic damage constitutive equations. Numerical validations were performed for the proposed plasticity-based damage model with a driver subroutine developed in this study. The predicted stress-strain behaviour seems reasonably accurate for the uniaxial tension and uniaxial compression compared with the experimental data… More >

  • Open Access

    ARTICLE

    Rupture and Instability of Soft Films due to Moisture Vaporization in Microelectronic Devices

    Linsen Zhu1, Jiang Zhou2, Xuejun Fan2

    CMC-Computers, Materials & Continua, Vol.39, No.2, pp. 113-134, 2014, DOI:10.3970/cmc.2014.039.113

    Abstract In this paper, a damage mechanics-based continuum theory is developed for the coupled analysis of moisture vaporization, moisture absorption and desorption, heat conduction, and mechanical stress for a reflow process in microelectronic devices. The extremely compliant film has been used in wafer level lamination process. Such a soft film experiences cohesive rupture subjected to moisture absorption during reflow. The numerical simulation results have demonstrated that vapor pressure due to moisture vaporization is the dominant driving force for the failures. The correlation between the vapor pressure evolution and the film rupture observed from the experiments have been established through two case… More >

  • Open Access

    ARTICLE

    A Stochastic Multi-Scale Model for Prediction of the Autogenous Shrinkage Deformations of Early-age Concrete

    S. Liu1, X. Liu2,3, Y. Yuan2, P. F. He1, H. A. Mang2,4

    CMC-Computers, Materials & Continua, Vol.39, No.2, pp. 85-112, 2014, DOI:10.3970/cmc.2014.039.085

    Abstract Autogenous shrinkage is defined as the bulk deformation of a closed, isothermal, cement-based material system, which is not subjected to external forces. It is associated with the hydration process of the cement paste. From the viewpoint of engineering practice, autogenous shrinkage deformations result in an increase of tensile stresses, which may lead to cracking of early-age concrete. Since concrete is a multi-phase composite with different material compositions and microscopic configurations at different scales, autogenous shrinkage does not only depend on the hydration of the cement paste, but also on the mechanical properties of the constituents and of their distribution. In… More >

  • Open Access

    ARTICLE

    Electronic Structure and Magnetic Properties of New Rare-earth Half-metallic Materials AcFe2O4 and ThFe2O4: Ab Initio Investigation

    Jingguo Yan1, Xudong Wang1, Man Yao1,2, Ning Hu3,4

    CMC-Computers, Materials & Continua, Vol.39, No.1, pp. 73-84, 2014, DOI:10.3970/cmc.2014.039.073

    Abstract Electronic structure and magnetism of the rare-earth metals Ac and Th doped Fe3O4 Fe1-xRexFe2-yReyO4(Re=Ac, Th; x=0, 0.5, 1; y=0, 0.5, 1.0, 1.5, 2.0) are investigated by first-principle calculations. AcFe2O4, FeAc2O4 and ThFe2O4 are found to be II B-type half-metals. The large bonding-antibonding splitting is believed to be the origin of the gap for AcFe2O4, FeAc2O4 and ThFe2O4, resulting in a net magnetic moment of 9.0μB, 4.0μB and 8.1μB, respectively, compared with 4.0μB of Fe3O4. Also, the conductance of AcFe2O4 and ThFe2O4 are both slightly larger than that of Fe3O4. It can be predicted that the new rare-earth half-metals AcFe2O4 and… More >

  • Open Access

    ARTICLE

    A Novel Approach to Identify the Thermal Conductivities of a Thin Anisotropic Medium by the Boundary Element Method

    Y.C. Shiah1, Y.M. Lee2, T.C. Huang2

    CMC-Computers, Materials & Continua, Vol.39, No.1, pp. 49-71, 2014, DOI:10.3970/cmc.2014.039.049

    Abstract A common difficulty arises in characterizing the anisotropic properties of a thin sheet of anisotropic material, especially in the transverse direction. This difficulty is even more phenomenal for measuring its mechanical properties on account of its thickness. As the prelude of such investigation, this paper proposes a novel approach to identify the thermal conductivities of an unknown thin layer of anisotropic material. For this purpose, the unknown layer is sandwiched in isotropic materials with known conductivities. Prescribing proper boundary conditions, one may easily measure temperature data on a few sample boundary points. Therefore, the anisotropic thermal conductivities can be calculated… More >

  • Open Access

    ARTICLE

    Change of Scale Strategy for the Microstructural Modelling of Polymeric Rohacell Foams

    J. Aubry1, P. Navarro1, S. Marguet1, J.-F. Ferrero1, O. Dorival2, L. Sohier3, J.-Y. Cognard3

    CMC-Computers, Materials & Continua, Vol.39, No.1, pp. 21-47, 2014, DOI:10.3970/cmc.2014.039.021

    Abstract In this paper a numerical model dedicated to the simulation of the mechanical behaviour of polymeric Rohacell foams is presented. The finite elements model is developed at the scale of the microstructure idealized by a representative unit cell: the truncated octahedron. Observations made on micrographs of Rohacell lead to mesh this representative unit cell as a lattice of beam elements. Each beam is assigned a brittle linear elastic mechanical behaviour in tension and an elastoplastic behaviour in compression. The plasticity in compression is introduced as a way to mimic the buckling of the edges of the cells observed in experimental… More >

  • Open Access

    ARTICLE

    Dynamic Instability of Rectangular Composite Plates under Parametric Excitation

    Meng-Kao Yeh1, Chia-Shien Liu2, Chien-Chang Chen3

    CMC-Computers, Materials & Continua, Vol.39, No.1, pp. 3-20, 2014, DOI:10.3970/cmc.2014.039.003

    Abstract The dynamic instability of rectangular graphite/epoxy composite plates under parametric excitation was investigated analytically and experimentally. In analysis, the dynamic system of the composite plate, obtained based on the assumedmodes method, is a general form of Mathieu’s equation, including parametrically excited terms. The instability regions of the system, each separated by two transition curves, were found to be functions of the modal parameters of the composite plate and the position and the excited amplitude of the electromagnetic device on the composite plates. The fiber orientation, the aspect ratio and the layer numbers of the composite plates were varied to assess… More >

  • Open Access

    ARTICLE

    Review of "The Theory of Materials Failure" by Prof. Richard M. Christensen, Stanford University Published by: Oxford University Press, 2013, 277 pages

    Satya N. Atluri1

    CMC-Computers, Materials & Continua, Vol.39, No.1, pp. 1-2, 2014, DOI:10.3970/cmc.2014.039.001

    Abstract This article has no abstract. More >

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