Search results for "difference [rapidity]"
showing 10 items of 82 documents
Design of Yagi-like printed antennas for WLAN applications
2007
A directive broadband printed Yagi-like antenna design is presented. We have focused on the 2.45 GHz WLAN band, at which some designs have been carried out. For the design and the modelling processes, we made use of FDTD based in-house developed algorithms. Some selected prototypes have then been fabricated onto a low-cost printed circuit board dielectric substrate and tested successfully. Bandwidths higher than 10% and moderate to high (>7 dBi) gains can be obtained this way. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2174–2178, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22655
Full-wave FDTD design and analysis of wideband microstrip-to-waveguide transitions
2003
Wideband transitions are designed and analysed by using two different approaches of the finite-difference time-domain (FDTD) method, in combination with the theory of nonuniform transmission lines. These transitions consist of a ridged waveguide-based taper between a shielded microstrip and a standard X-band rectangular waveguide. In the first step, a full-wave 2D-FDTD scheme is used to calculate the dispersion characteristics, as well as the geometry dependence of the impedance in the double ridged waveguide. Once these design curves have been obtained, the stepped transmission line transformer theory is used to design the tapers. In a former step, the nonuniform 3D-FDTD technique is appli…
Calculation of the characteristic impedance of microstrips using a full-wave 2-D FDTD scheme
1997
The frequency dependence of the characteristic impedance of microstrip lines has been investigated by many authors using 3D-FDTD formulations. In the present letter, a two-dimensional FDTD scheme is used to calculate both the propagation constant and the characteristic impedance of the fundamental quasi-TEM mode in a microstrip which, in fact, is a hybrid mode. Because of the substantial reduction of computer resources required for the calculations, this method can be used as a design tool. © 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 16: 58–60, 1997.
Finite-Difference Time-Domain Simulation of Towers Cascade Under Lightning Surge Conditions
2015
In this paper, the simulation of towers cascade under lightning surge conditions is presented. Finite-difference time-domain method is used to solve both the Maxwell's and telegraph equations. Maxwell's equations and the time-domain resistivity model of Darveniza are used to simulate the nonlinear behavior of the grounding system. Telegraph equations are used to describe the propagation in the overhead lines. Multiple ionizations, on different grounding electrodes belonging to various towers, can be implemented simultaneously, without making assumptions on the shape of the ionized areas.
Evaluation of radiated EMI in 42 V vehicle electrical systems by FDTD simulation
2007
In this paper a full 3D numerical scheme, based on the finite difference time domain method, is used to predict the electromagnetic radiated interference generated by 42 V vehicle power electronic driven electrical loads. An experimental set-up has been arranged on purpose in order to validate the proposed simulation tool. To this aim, the features of a semi-anechoic electromagnetic chamber have been exploited in order to operate in a shielded test site for the measurement of near field radiated emissions. Two different three-dimensional geometrical configurations of realistic vehicle installations of the loads, are studied. A comparative analysis among measured and computed results is perf…
Finite difference time domain simulation of earth electrodes soil ionisation under lightning surge condition
2008
The non linear effects of soil ionisation on the behaviour of earth electrodes are investigated by a finite difference time domain numerical scheme. A time variable soil resistivity is used in order to simulate the soil breakdown; step by step the resistivity value is controlled by the local instantaneous value of the electric field compared with the electrical strength, fixed for the soil. No a priori hypothesis about the geometrical shape of the ionised zone around the electrodes has to be enforced. Simulation results related to complex earth electrodes of limited extension are reported. The model has been validated by comparing the computed results with data available in technical litera…
School-age vaccination, school openings and Covid-19 diffusion
2022
This article investigates the relationship between school openings and Covid-19 diffusion when school-age vaccination becomes available. The analysis relies on a unique geo-referenced high frequency database on age of vaccination, Covid-19 cases and hospitalization indicators from the Italian region of Sicily. The study focuses on the change of Covid-19 diffusion after school opening in a homogeneous geographical territory (i.e., with the same control measures and surveillance systems, centrally coordinated by the Regional Government). The identification of causal effects derives from a comparison of the change in cases before and after school opening in the school year 2020/21, when vaccin…
A tale of two trade-offs: Effects of opening pathways from vocational to higher education
2021
Abstract This paper studies the effects of a vocational secondary school reform implemented in Finland between 1999 and 2001. The reform extended vocational two-year programs to three years and made all graduates eligible to apply for university. For identification, we exploit the gradual implementation of the reform, and use a differences-in-differences approach and administrative register data up to 13 years after the reform. We find no long-term effect on enrollment in further education or labor market outcomes. However, our results illustrate that the reform increased the dropout probability. Thus, the benefits of opening pathways from vocational to higher education may be outweighed by…
The Electoral Effects of Offshoring-Induced Mass-Layoffs: Germany in Comparative Perspective
2012
How does globalization’s impact on the labor market affect political preferences? This study takes up the strategy of a recent contribution (Margalit 2011a) and studies the local electoral effects of regional job losses due to offshoring. By applying the analytical strategy to German national elections in 2005 and 2009, it studies whether and how the finding on U.S. presidential elections travels to other contexts. Theoretically, the contribution adds a perspective suggested by previous research on the individual level political consequences of the globalization-labor market link that addresses the likely social policy preferences of globalization’s losers. Preliminary empirical results ind…
Tīmekļa lapu veidošanas metožu efektivitātes salīdzinājums
2020
Mūsdienās ir dažnedažādi veidi kā veidot tīmekļa lapas, taču bieži tehnoloģijas tiek izvēlētas pēc gatavo veidņu pieejamības, ietvariem. Tiek dota priekšroka tīmekļa tehnoloģijām, kas ne būt nav efektīvākās lejupielādes laika ziņā. Protams viss ir atkarīgs no tīmekļa lapas mērķa. Vai ir svarīgs resursu lietojums, vai var atļauties neekonomēt resursus. Darbā ir apskatīta HTML, PHP un JS tīmekļa lapu veidošanas tehnoloģiju efektivitāte -lejupielādes laika ziņā pie vienādas funkcionalitātes tīmekļa pārlūkprogrammā.