SEARCH CONTENT

You are looking at 1 - 10 of 13,315 items :

  • Technical and Applied Physics x
Clear All
Principles and Concepts for Enhanced Properties
A Mathematical Introduction

Abstract

This research proposes a novel circularly polarized (CP) reconfigurable microstrip loop antenna for 2.4–2.5 GHz advanced wireless communication using two parasitic patches and two PIN diodes. The reconfigurable antenna can alternate between right hand circular polarization (RHCP) and left hand circular polarization (LHCP) at the main beam by manipulating the ON/OFF status of the PIN diodes. Simulations were carried out for the optimal antenna parameters, and an antenna prototype was fabricated and experiments were undertaken. The simulation and measured results are in good agreement. The antenna achieves an impedance bandwidth of 2.4–2.5 GHz and unidirectional radiation pattern with a maximum gain of 5 dBic and 3-dB axial ratio for both RHCP and LHCP. As a result, the proposed reconfigurable antenna could be utilized to improve wireless communication performance. In essence, the novelty of this research lies in the utilization of parasitic patches and shorted PIN diodes to transform linear to circular polarization; and the reconfigurability of polarization between RHCP and LHCP.

Abstract

In this paper, a tunable balanced-to-balanced in-phase filtering power divider (FPD) is designed, which can realize a two-way equal power division with high selectivity and isolation. A differential-mode (DM) passband with a steep filtering performance is realized by applying microstrip stub-loaded resonators (SLRs). Meanwhile, six varactors are loaded to the SLRs to achieve the center frequency (CF) and bandwidth adjustment, respectively. U-type microstrip lines integrated with stepped impedance slotline resonators are utilized as the differential feedlines, which suppress the common-mode (CM) intrinsically, making the DM responses independent of the CM ones. A tuning center frequency from 3.2 to 3.75 GHz and a fractional bandwidth (12.1–17.6%) with more than 10 dB return loss and less than 2.3 dB insertion loss can be achieved by changing the voltage across the varactors. A good agreement between the simulated and measured results is observed. To the best of authors' knowledge, the proposed balanced-to-balanced tunable FPD is first ever reported.

Abstract

The objective of this work lies in the three-dimensional study of the thermo mechanical behavior of a blade of a centrifugal compressor. Numerical modeling is performed on the computational code "ABAQUS" based on the finite element method. The aim is to study the impact of the change of types of blades, which are defined as a function of wheel output angle β 2, on the stress fields and displacements coupled with the variation of the temperature.

This coupling defines in a realistic way the thermo mechanical behavior of the blade where one can note the important concentrations of stresses and displacements in the different zones of its complex form as well as the effects at the edges. It will then be possible to prevent damage and cracks in the blades of the centrifugal compressor leading to its failure which can be caused by the thermal or mechanical fatigue of the material with which the wheel is manufactured.

Abstract

This study presents an analytical model analysis of reflection/transmission characteristics of long-period fiber Bragg grating (LPFBG) by using coupled mode theory. Reflected signal power is deeply studied against grating length at the optimum operating signal wavelength of 1550 nm for the proposed and previous models. Reflectivity and transmission coefficient are also clarified versus operating wavelength for the previous model and proposed a model with a central wavelength of 1550 nm, Δn = 0.003 and optimum grating length of 30 mm. In the same way, the reflectivity and transmission coefficient are outlined against relative refractive grating difference step at the optimum wavelength of 1550 nm and optimum grating length of 30 mm. The optimum LPFBG can be achieved with the optimum grating length of 30 mm, operating wavelength of 1550 nm and relative refractive grating difference step of 0.3 %.

Abstract

In this paper, 4 × 2 encoder is proposed by combining optical waveguides and the ring resonators. The proposed structure has four input ports, two control input and two output ports. The hexagonal photonic crystal structure has the square lattice of chalcogenide glass rods with the refractive index of 2.1 in air. Maximum bit rate of 10 Tb/s and response time of 0.1 ps is obtained using the proposed cross-layered arrangement of the chalcogenide glass rods with circular inner arrangement. The size of the proposed structure is 18.6 µm x 24.6 µm. Moreover, the contrast ratio of outputs is found to be 28.3 and 48.45 dB. The fundamental structure for the proposed encoder is also designed and analysed for validating the desired bandgap at the resonant wavelength of 1550 nm.

Abstract

This study outlines the distributed feedback laser for signal power amplitude level improvement in the long spectral band of 1550 nm wavelength within supporting pumped wavelength of 1480 nm. The bias and modulation peak currents based distributed feedback laser are varied in order to test the signal power level, peak signal amplitude variations after the fiber-optic channel and light detectors. The signal power level, peak signal amplitude is measured against spectral wavelength and time bit period variations. The study emphasis the signal power level, peak signal amplitude are enhanced for the best selection values of both a bias current at 45 mA and modulation peak current at 0.5 mA.

Abstract

Enormous work has been reported in literature to enhance the performance of metaheuristics by modifying their internal mechanisms via intervening their control equations. Usually, these population based techniques are initiated through random creation of individuals (tentative solutions) to preserve adequate diversity in population and then attempts have been made to maintain a better balance between exploration and exploitation of the problem search space. However, it would be much better if some strategy is employed that could divert tentative solutions toward the promising region. This can be possible if the algorithm has some mechanism to develop certain knowledge (super sense) about the quality of decision variables of the problem. This paper presents super sense genetic algorithm (SSGA) that gradually develops super sense during successive genetic evolutions. The accumulated genetic information so obtained is stored and used to divert individuals near the promising region while preserving adequate diversity. SSGA differs to standard genetic algorithm (GA) only on this aspect. SSGA is applied to solve complex combinatorial network reconfiguration problem of radial distribution systems. The application results highlight the effectiveness of proposed GA.

Abstract

Glass is one of the most important technical surfaces for numerous applications in automotive, optical, and consumer industries. In addition, by producing textured surfaces with periodic features in the micrometre range, new functions can be created. Although laser-based methods have shown to be capable to produce structured materials in a wide amount of materials, due to its transparency large bandgap dielectrics can be only processed in a controlled manner by employing high-power ultra-short pulsed lasers, thus limiting the employable laser sources. In this article, an interference-based method for the texturing of soda-lime glass using a 15 ns pulsed (1 kHz repetition rate) infrared (1053 nm) laser is proposed, which allows fabricating different periodic patterns with micrometre resolution. This method consists on irradiating a metallic absorber (stainless steel) put in direct contact with the glass sample and inducing locally an etching process on the backside of the glass. Then, the produced plasma at the interference maxima positions leads to the local fabrication of well-defined periodic line-like and dot-like surface patterns. The produced patterns are characterised using white light interferometry and scanning electron microscopy.