In this work, we propose a low-profile single-layer coplanar waveguide (CPW)-fed metasurface (MTS) antenna with broadband circular polarization radiation. With the help of characteristic mode ...analysis (CMA), a 3 × 4 metasurface is analyzed to reveal the useful modes supported by the structure. Consequently, two modes with orthogonal current distribution, broadside radiation, and nearly 90° phase difference over a wide frequency band are chosen as operation modes. Moreover, the modal near-field of the aforementioned modes shows that, unlike conventional microstrip patches, the entire proposed metasurface supports two kinds of extraordinary TM modes namely e- TM 30 and e-TM 04 . Accordingly, a rotated CPW feeding line is used to excite the two modes without adding an extra layer as reported in the literature, making the design simpler and easier to manufacture. Based on that, a low profile antenna of 0.058λ 0 has been designed and fabricated. The measured results show an impedance bandwidth (IBW) of 25% (4.87-6.26 GHz), 3-dB axial ratio band (AR) of 19.42% (5.30-6.44 GHz), and a maximum gain of 8 dBi.
A compact circularly polarized (CP) implantable antenna working at 915 MHz, at the industrial, scientific, and medical (ISM) band, is developed in this article. The proposed radiator is based on a ...fully planar and low-profile patch antenna with a ground plane and different slots but without any via holes, which makes the structure a good candidate for implantable devices. The circular polarization is achieved by means of introducing a surrounding and asymmetrical U-shaped structure. A meander line has been included in the inside of the U-shaped structure to increase the electrical length of the antenna without increasing its mechanical dimensions. An impedance bandwidth of 18.9% from 810 to 980 MHz and an axial ratio of 17.2% from 850 to 1010 MHz have been achieved. The proposed antenna has a compact size of <inline-formula> <tex-math notation="LaTeX">5.2\times 5.6\times0.25 </tex-math></inline-formula> mm 3 , which seems to be the smallest antenna over the recently reported implantable antennas. In addition, the proposed antenna achieves a relatively high gain value of −23 dBi.
This paper proposes a new triple-band monopole antenna based on Complementary Split Ring Resonators (CSRR) perturbing the ground plane (GND). The antenna consists of an inverted-L-shaped monopole fed ...by a modified microstrip line with two CSRRs cut out of the ground plane. The operational bands are independently controlled by the CSRR unit cell parameters. In addition, the antenna presents a dual-polarization performance (vertical polarization at 2.4 GHz band and horizontal polarization at both 3.6 and 5.9 GHz bands). The designed antenna is fully planar and low profile avoiding the vias with the ground plane and covering the WLAN, WiMAX, and IEEE 801.11p bands at 2.45, 3.6, and 5.8 GHz. A compact prototype (<inline-formula> <tex-math notation="LaTeX">{0.32\lambda _{0}}\times {0.32\lambda _{0}} </tex-math></inline-formula> being <inline-formula> <tex-math notation="LaTeX">\lambda _{0} </tex-math></inline-formula> is the wavelength corresponding to the lowest resonance frequency) has been fabricated and measured showing good agreement between simulations and measurements. The measured impedance bandwidths are 10% (2.38-2.63 GHz), 2.5% (3.54-3.63 GHz), and 20% (5.83-7.12 GHz) whereas the measured gains are 1.34, 0.68, and 2.65 dBi at 2.4, 3.6, and 5.9 GHz respectively.
In this paper, we present a novel design of a compact miniaturized dual-band antenna for industrial, scientific, and medical (ISM) implantable applications working at 915 MHz and 2.4 GHz. The ...proposed antenna has a compact size of (Formula Omitted mm3). The antenna shows a wide bandwidth of 12.6% at the lowest frequency and 12.8% at the highest frequency and gain values of −21.8 dBi and −19.2 dBi at 915 MHz and 2.4 GHz, respectively which are relatively high for implantable applications. The design has been done for healthy and unhealthy tissues (adenocarcinoma). Furthermore, the fabricated prototype has been tested in minced pork as a suitable real tissue to validate the simulated results. Finally, a comparison with the recently published state-of-the-art solutions is provided showing good results in terms of size, bandwidth and gain.
Cet article présente les résultats d’une recherche expérimentale visant à étudier la dégradation de la surface des pales d’éoliennes situées dans des zones arides causée par les impacts de particules ...de sable et l’influence qui en résulte sur leur performance énergétique. Les essais sont effectués dans une sableuse à érosion puis dans la soufflerie pour la pale en fibre de verre / polyester non revêtue sous différents angles et durées d’impact. Les forces aérodynamiques sur les profiles NACA 4412 sont déterminées expérimentalement. Tous les profiles (AR = 0,571) sont testés dans une soufflerie à une vitesse de l’air de 10 m/s au nombre de Reynolds 6.5×10
5
. Les résultats montrent les différences de comportement détectées pour les échantillons avec T = 160s, T = 240s et T = 340s (quand Ra augmente) en les comparant avec l’échantillon lisse (T = 0s, Ra = 0,94). Les coefficients de force (CL et CD) montrent des changements significatifs qui conduisent à une diminution du rapport portance-traînée et donc une perte de performance notable.
l’amélioration de la durée de vie des pales éoliennes opérant dans une région aride au-delà de sa durée de vie habituelle de 20 ou 25 ans oblige leur propriétaire à augmenter le nombre des ...inspections dans le cadre de la maintenance préventive sachant que les coûts de maintenance et d’arrêt d’une d’éolienne ont un impact direct sur la production totale et peuvent représenter jusqu’à 25% de l’énergie produite. Sachant que dans une région poussiéreuse, les pales sont soumises à une usure érosive qui contribue à la modification de la forme aérodynamique du bord d’attaque et réduit ainsi les performances de l’éolienne. Ce papier décrive et propose une nouvelle méthode de maintenance CBM pour améliorer la durée de vie d’une pale éolienne. Les résultats expérimentaux montrent que l’utilisation de cette méthode est très efficace pour détecter toute dégradation provoquée par l’usure érosive à la surface d’une pale pendant son service.
This experimental study aims to investigate the effect of the closed cycle of air circulation on the thermal performance of the solar air collector with attached fins in the site of Laghouat in ...Algeria, under climatic conditions. Our experimental procedure includes two types of cycles: open cycle and closed cycle. For each cycle, we have considered two tilt angle: 0 and 30 degree. Moreover, the solar collector is oriented in a southerly direction with a definite angle of inclination. The flow rate used in experiment is equal to 0.0129402 m3/s. Then, by comparing the experimental and theoretical results, we observe that the maximum temperature difference between the outlet and inlet air for the open cycle (27 °C, at 14h30) is higher than that of the close cycle (17 °C, at 14h00). The maximum efficiencies obtained for the open cycle for the both configurations were η (30 degrees) = 25.29 % and η (0 degree) = 35.71 % at 4 pm. These values are higher than those of the maximum efficiencies of the closed cycle with η (30 degrees) = 7.86 % at 4 pm and η (0 degree) = 13.31% at 12h00, respectively
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