131,154 research outputs found
A novel ultrawideband FDTD numerical modeling of ground penetrating radar on arbitrary dispersive soils
No full textA novel two-dimensional (2-D) finite-difference timedomain algorithm for modeling ultrawideband pulse propagation in arbitrary dispersive soils is presented. The soil dispersion is modeled by general power law series representation, accounting for multiple higher order dispersive relaxation processes and ohmic losses, and incorporated into the FDTD scheme by using the fractional derivative operators. The dispersive soil parameters are obtained by fitting the reported experimental data. Moreover, dedicated uniaxial perfectly matched layer for matching dispersive media are derived and implemented in combination with the basic time-marching scheme. Examples are given to verify the numerical solution and demonstrate its applications. The proposed technique features a significantly enhanced accuracy in the solution of complex electromagnetic propagation problems typically encountered in geoscience applications
Transparency of Price Conditions in Consumer Credit: The Usage of the APR
No full textThe role of Annual Percentage Rate (APR) in installment plan selection was investigated. The choice of APR was motivated by its wide diffusion due to the mandatory disclosure acts. There have been doubts towards consumer understanding of APR. A sample of 299 consumers were given five series of credit alternatives. The descriptions of the loans were homogeneous and regarded amount borrowed, duration, monthly installment, APR, total of payments, and opportunity cost of capital. Consumers were asked to select a credit option for each series clarifying the motivations of their choice. The ability to select the loan with the highest Net Present Value (NPV) was ascertained. It depends on the awareness of (i) opting for the lowest APR, that is also less than the opportunity cost of capital; and (ii) demanding the extension of the repayment period to improve the convenience of the identified competitive rate. The analysis attested consumer failure to single out the loan with the highest NPV. The reason should be a considerable lack of information about the usage of APR: participants selected the lowest rate but they neglected to consider the opportunity cost of capital and the extension of the repayment period. Furthermore, they often chose the loan contrasting duration and monthly borrowing costs. APR usage may therefore be inapt since employed as a substitute for the monthly installment payment. An overlap between economic convenience and financial sustainability could explain this phenomenon. To improve disclosure, further (or different) borrowing cost measures should be placed in credit advertisements
Fractional-calculus-based FDTD method for solving pulse propagation problems
No full textIn this paper, an accurate finite-difference time-domain (FDTD) scheme for modeling the electromagnetic pulse propagation in arbitrary dispersive media is presented. The main mathematical drawbacks encountered while solving this class of problems by means of the FDTD technique is the approximation of the fractional derivatives appearing in the time-domain permittivity response pertaining such materials. In order to overcome this issue, the proposed scheme solves the Maxwell's equations directly in the time-domain by using the Riemann-Liouville fractional derivative operator. The feasibility of the proposed method is demonstrated by simulating the ultra-wideband wave propagation in general stratified Raicu dispersive media displaying multiple relaxation times response
Solution of the Dirichlet problem for the Laplace equation in general cylinder.
No full textWe consider the Dirichlet problem for the Laplace equation in a bounded cylindrical domain C:=D , where D is a starlike domain of the (x,y)-plane. We show how to construct the solution by using the Fourier series method. We derive some numerical results defining by means of the so called “superformula” introduced by J.Gielis. By using a computer algebra system we find a quite rapid convergence of the approximate solutions to the real one, with only possible exceptions corresponding to singular points in which oscillations recalling Gibbs’ phenomenon appear. Our findings are in agreement with the theoretical results on Fourier series due to L.Carleson
Experimental infrared measurements for hydrocarbon pollutant determination in subterranean waters
Full text linkSubterranean waters are often polluted by industrial and anthropic effluents that are drained in subsoil. To prevent and control pollution, legislations of different developed countries require an online monitoring measurement, especially for detecting organic solvents (chlorinated and unchlorinated ones). Online measurements include both real-time and no real-time measurements. In general, it is difficult to implement real-time measurements in stricto sensu for online acquisitions on aqueous effluents since they need to be processed by a modeling. This research presents an experimental measurement system based on infrared (IR) spectroscopy for aqueous effluents containing hydrocarbons and capable of displaying excellent values of pollutant concentrations even in instable conditions; the system is able to detect pollutants either in laminar or turbulent flow. The results show the possibility of avoiding the use of “Pitot tube” that is employed to create a stagnation point in order to convert kinetic energy into potential one. This conversion allows the transformation of a turbulent flow in a laminar flow making easy measurement of pollutants included in an aqueous effluent. Obviously, “Pitot tube” is also used for other fluid effluents. The obtained results have been compared with those produced by means of sophisticated IR instrumentation for laboratory applications.MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc
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