Browsing by Subject "Electromagnetic field effects"

Now showing 1 - 4 of 4

Open Access
Bose-Einstein condensation of noninteracting charged Bose gas in the presence of external potentials
(Elsevier Science Publishers B.V., 2001) Bayındır, Mehmet; Tanatar, Bilal
We investigate thermodynamic properties of noninteracting charged bosons in the presence of externally applied electric and magnetic fields. Using the semiclassical density of states, we obtain the condensate fraction, chemical potential, total energy, and specific heat of a system of finite number of charged Bose particles. We conclude that Bose-Einstein condensation of the charged Bose gas occurs in the crossed electric and magnetic fields.
Open Access
Circular arrays of log-periodic antennas for broadband applications
(IEEE, 2006) Ergül, Özgür; Gürel, Levent
Circular arrays of log-periodic (LP) antennas are designed for broadband applications. A sophisticated electromagnetic simulation environment involving integral equations and fast solvers is developed to analyze the LP arrays both accurately and efficienuy. The resulting matrix equation obtained by the discretization of the electric field integral equation is solved iteratively via the multilevel fast multipole algorithm (MLFMA). Genetic algorithms interacting with MLFMA is employed to optimize the excitations of the array elements to increase the frequency independence and also to add the beam-steering ability to the arrays.
Open Access
An efficient method for electromagnetic characterization of 2-D geometries in stratified media
(IEEE, 2002) Aksun, M. I.; Çalışkan, F.; Gürel, Levent
A numerically efficient technique, based on the spectral-domain method of moments (MoM) in conjunction with the generalized pencil-of-functions (GPOF) method, is developed for the characterization of two-dimensional geometries in multilayer planar media. This approach provides an analytic expression for all the entries of the MoM matrix, explicitly including the indexes of the basis and testing functions provided that the Galerkin's MoM is employed. This feature facilitates an efficient modification of the geometry without the necessity of recalculating the additional elements in the MoM matrix. To assess the efficiency of the approach, the results and the matrix fill times are compared to those obtained with two other efficient methods, namely, the spatial-domain MoM in conjunction with the closed-form Green's functions, and a fast Fourier transform algorithm to evaluate the MoM matrix entries. Among these, the spectral-domain MoM using the GPOF algorithm is the most efficient approach for printed multilayer geometries.
Open Access
Nonplanar trapezoidal tooth log-periodic antennas: design and electromagnetic modeling
(Wiley-Blackwell, 2005) Ergül, Özgür; Gürel, Levent
Nonplanar trapezoidal tooth log-periodic (LP) antennas are investigated by combining the wisdom of theoretical design procedures with the power of accurate numerical simulation environments. Once the theoretical design is completed, electromagnetic simulations employing accurate integral equation solvers are utilized to test and correct the original design. A two-element array of trapezoidal tooth LP antennas is designed. The array features beam-steering ability as a novelty, in addition to frequency independence and higher directivity. Beam steering is achieved by optimizing the excitation coefficients of the two LP antennas.