Current Issue : January - March Volume : 2020 Issue Number : 1 Articles : 5 Articles
A fractal absorber based on a metamaterial configuration is proposed for dual-frequency\noperation within the UHF band. The miniaturization skills of the proposed fractal shape are used\nto design a dual-band metamaterial absorber cell with reduced size....................................
The driving necessities of cost reduction and the need to develop fields at ever\nincreasing water depths have led to the use of floating structures. Among\nthese structures are the Floating Production Storage and Offloading (FPSO)\nunits whose motion analysis is considered in this paper. In actual environmental\ncondition, it is required to accurately determine or predict large amplitude\nmotion of the FPSO before any offshore operation. This paper seeks to present\na detailed method of computing the Response Amplitude Operator(s) (RAOs)\nfor the six (6) degrees of freedom using ANSYS AQWA. The results indicate\nfor Heave motion a tendency for the heave peak value to move slightly higher\ndimensionless encounter-frequency as the wave moves from Head sea to Beam\nsea direction. A MATLAB source code was developed to validate the result for\nheave motion at head sea. Although a small difference in predicted heave motion\noccurred, it is pertinent to note that the comparisons between results generated\nin the MATLAB program and ANSYS AQWA demonstrate generally\ngood agreement, and the roll response of the FPSO is noted to be critical....
We present a fourth-order finite difference scheme for the Helmholtz equation\nin polar coordinates. We employ the finite difference format in the interior\nof the region and derive a nine-point fourth-order scheme. Specially,\nghost points outside the region are applied to obtain the approximation for\nthe Neumann boundary condition. We obtain the matrix form of the linear\nsystem and the sparsity of the coefficient matrix is favorable for the computation\nof the Helmholtz equation. The feasibility and accuracy of the method\nare validated by two test examples which have exact solutions....
A consistent physical and mathematical model of the propagation of electromagnetic\nwaves in an inhomogeneous medium with strong discontinuities of\nthe electromagnetic field at the interface of two media, which is a rough surface,\nwas developed. Mathematical modeling of rough surfaces and their profiles\nwas carried out using fractal geometry, which allows us to display the\ntopology of the object as close as possible to reality. For real heterogeneous\nrough structures, we have developed a through-counting method that takes\ninto account the continuity of the total current at the interfaces of adjacent\nmedia, the effect of induced surface charge and surface current. This approach\nlets one avoid the necessity to set surface impedances depending on\nthe structure of the field being determined and on the material properties....
In this work, the Hamiltonian of the four-body problem is considered under\nthe effects of solar radiation pressure. The equations of motion of the infinitesimal\nbody are obtained in the Hamiltonian canonical form. The libration\npoints and the corresponding Jacobi constants are obtained with different\nvalues of the solar radiation pressure coefficient. The motion and its stability\nabout each point are studied. A family of periodic orbits under the effects of\nthe gravitational forces of the primaries and the solar radiation pressure are\nobtained depending on the pure numerical method. This purpose is applied\nto the Sun-Earth-Moon-Space craft system, and the results obtained are in a\ngood agreement with the previous work such as (Kumari and Papadouris,\n2013)....
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