D. Kourounis¹, L.N. Gergidis¹, A. Charalambopoulos¹

CMES-Computer Modeling in Engineering & Sciences, Vol.28, No.3, pp. 185-202, 2008, DOI:10.3970/cmes.2008.028.185

Abstract The sensitivity of analytical solutions of the direct acoustic scattering problem in prolate spheroidal geometry on the wavenumber and shape, is extensively investigated in this work. Using the well known Vekua transformation and the complete set of radiating "outwards'' eigensolutions of the Helmholtz equation, introduced in our previous work ([Charalambopoulos and Dassios(2002)], [Gergidis, Kourounis, Mavratzas, and Charalambopoulos (2007)]), the scattered field is expanded in terms of it, detouring so the standard spheroidal wave functions along with their inherent numerical deficiencies. An approach is employed for the determination of the expansion coefficients, which is optimal in the sense, that minimizes the… More >

L.N. Gergidis, D. Kourounis, S. Mavratzas, A. Charalambopoulos¹

CMES-Computer Modeling in Engineering & Sciences, Vol.21, No.2, pp. 157-176, 2007, DOI:10.3970/cmes.2007.021.157

Abstract A new complete set of scattering eigensolutions of Helmholtz equation in spheroidal geometry is constructed in this paper. It is based on the extension to exterior boundary value problems of the well known Vekua transformation pair, which connects the kernels of Laplace and Helmholtz operators. The derivation of this set is purely analytic. It avoids the implication of the spheroidal wave functions along with their accompanying numerical deficiencies. Using this novel set of eigensolutions, we solve the acoustic scattering problem from a soft acoustic spheroidal scatterer, by expanding the scattered field in terms of it. Two approaches concerning the determination… More >

T. Jarak¹, J. Sorić¹, J. Hoster¹

CMES-Computer Modeling in Engineering & Sciences, Vol.18, No.3, pp. 235-246, 2007, DOI:10.3970/cmes.2007.018.235

Abstract A meshless computational method based on the local Petrov-Galerkin approach for the analysis of shell structures is presented. A concept of a three dimensional solid, allowing the use of completely 3-D constitutive models, is applied. Discretization is carried out by using both a moving least square approximation and polynomial functions. The exact shell geometry can be described. Thickness locking is eliminated by using a hierarchical quadratic approximation over the thickness. The shear locking phenomena in case of thin structures and the sensitivity to rigid body motions are minimized by applying interpolation functions of sufficiently high order. The numerical efficiency of… More >

Hayder A. Abdulbari ^1,2, Hassan D. Mahammed¹, Z. Hassan, Wafaa K. Mahmood³

FDMP-Fluid Dynamics & Materials Processing, Vol.12, No.2, pp. 86-101, 2016, DOI:10.3970/fdmp.2016.012.086

Abstract An experimental investigation was carried out to study the response of a turbulent pressure drop fluctuations to longitudinal groove riblets, involved two configurations being triangular and spaced triangular grooves with height 600, 800, 1000 μm and peak to peak spacing 1000 μm and 2000 μm respectively. Experiments were therefore performed at free stream velocity up to 0.44 m/sec, which were corresponding to Reynolds number (Re) 53000. The development of the obtained turbulent layer downstream of the grooves was then compared with the results from the corresponding smooth-wall case. To conclude, the effect of the spaced triangular riblets on the turbulent… More >

Wenjie Liu^1,2,*, Yong Xu², James C. N. Yang³, Wenbin Yu^1,2, Lianhua Chi⁴

CMC-Computers, Materials & Continua, Vol.60, No.3, pp. 1237-1250, 2019, DOI:10.32604/cmc.2019.03551

Abstract Privacy-preserving computational geometry is the research area on the intersection of the domains of secure multi-party computation (SMC) and computational geometry. As an important field, the privacy-preserving geometric intersection (PGI) problem is when each of the multiple parties has a private geometric graph and seeks to determine whether their graphs intersect or not without revealing their private information. In this study, through representing Alice’s (Bob’s) private geometric graph G_A (G_B) as the set of numbered grids S_A (S_B), an efficient privacy-preserving quantum two-party geometric intersection (PQGI) protocol is proposed. In the protocol, the oracle operation O_A (O_B) is firstly utilized… More >

Jinlan Xu¹, Ningning Sun¹, Laixin Shu¹, Timon Rabczuk², Gang Xu^1,*

CMC-Computers, Materials & Continua, Vol.60, No.2, pp. 615-632, 2019, DOI:10.32604/cmc.2019.04464

Abstract Trimming techniques are efficient ways to generate complex geometries in Computer-Aided Design (CAD). In this paper, an improved integration for trimmed geometries in isogeometric analysis (IGA) is proposed. The proposed method can improve the accuracy of the approximation and the condition number of the stiffness matrix. In addition, comparing to the traditional approaches, the trimming techniques can reduce the number of the integration elements with much fewer integration points, which improves the computational efficiency significantly. Several examples are illustrated to show the effectiveness of the proposed approach. More >

Muhammad Shoaib Arif¹, Mairaj Bibi², Adnan Jhangir³

CMC-Computers, Materials & Continua, Vol.54, No.2, pp. 181-195, 2018, DOI:10.3970/cmc.2018.054.181

Abstract This communique is opted to study the approximate solution of the Algebraic Lyapunov equation on the manifold of positive-definite Hermitian matrices. We choose the geodesic distance between -AHX - XA and P as the cost function, and put forward the Extended Hamiltonian algorithm (EHA) and Natural gradient algorithm (NGA) for the solution. Finally, several numerical experiments give you an idea about the effectiveness of the proposed algorithms. We also show the comparison between these two algorithms EHA and NGA. Obtained results are provided and analyzed graphically. We also conclude that the extended Hamiltonian algorithm has better convergence speed than the… More >

Haolong Chen^1,2, Bo Yu¹, Huanlin Zhou^1*, Zeng Meng¹

CMC-Computers, Materials & Continua, Vol.53, No.4, pp. 271-290, 2017, DOI:10.3970/cmc.2017.053.271

Abstract The cuckoo search algorithm (CS) is improved by using the conjugate gradient method(CGM), and the CS-CGM is proposed. The unknown inner boundary shapes are generated randomly and evolved by Lévy flights and elimination mechanism in the CS and CS-CGM. The CS, CGM and CS-CGM are examined for the prediction of a pipe’s inner surface. The direct problem is two-dimensional transient heat conduction in functionally graded materials (FGMs). Firstly, the radial integration boundary element method (RIBEM) is applied to solve the direct problem. Then the three methods are compared to identify the pipe’s inner surfacewith the information of measured temperatures. Finally,… More >

Qunfeng Liu^1,2, Liang Wang¹, gping Shen¹

CMC-Computers, Materials & Continua, Vol.46, No.2, pp. 105-123, 2015, DOI:10.3970/cmc.2015.046.105

Abstract Molecular dynamics simulations have been performed to investigate the effects of cross section geometry and shape on the mechanical behaviors of silicon nanowires (Si NWs) under tensile loading. The results show that elasticity of <100> rectangular Si NWs depends on their cross section aspect ratios while the elastic limits of <110> and <111> wires show geometry independence. Despite the significant influence of axial orientation, both yield stress and Young's Modulus show the remarkable shape dependence for wires with various regular cross sections. Additionally, underlying mechanism for the geometry and shape effects on mechanical behavior are discussed based on the fundamental… More >

G. M. Kulikov¹, S. V. Plotnikova¹

CMC-Computers, Materials & Continua, Vol.23, No.3, pp. 233-264, 2011, DOI:10.3970/cmc.2011.023.233

Abstract This paper presents a robust non-linear piezoelectric exact geometry (EG) four-node solid-shell element based on the higher-order 9-parameter equivalent single-layer (ESL) theory, which permits one to utilize 3D constitutive equations. The term EG reflects the fact that coefficients of the first and second fundamental forms of the reference surface are taken exactly at each element node. The finite element formulation developed is based on a new concept of interpolation surfaces (I-surfaces) inside the shell body. We introduce three I-surfaces and choose nine displacements of these surfaces as fundamental shell unknowns. Such choice allows us to represent the finite rotation piezoelectric… More >