Analyze of Frequency Selective Surfaces By Hybrid MOM-PO-GTD Method

The intent of this article is to analyze the Diraction phenomena of the incoming waveand provide a new Approach for analyzing the frequency selective surface (Fss) by usinga hybrid method combining Moment Method (MoM), optical physics (PO) with Generaltheory of Diraction (GTD). the frequency selective surface (Fss) is a periodic surfacewith identical two-dimensional arrays of elements arranged on a substrate dielectric. Anincoming plane wave will either be transmitted (bandwidth) or re ected (stopband),completely or partially, depending on the nature of the array element. This happenswhen the frequency of the electromagnetic (EM) wave correspond with the resonantfrequency of the FSS elements. Hence, in free space, and for a certain frequency range,an FSS is capable of transmitting or blocking EM waves; therefore, identied as spa-tial lters. Today, FSSs have been extensively studied and there is tremendous growthin its design and implementation for dierent applications at the microwave to opticalfrequency ranges. In this review article, we present a new hybrid method form on Mo-ment method and GTD for analyzing dierent categories of FSS based on the design ofthe structure, the array elements used, and applications. We also focus on the eectsof diraction, methodology, experimental verications of design examples, as well ason prospects and challenges, particularly in the microwave regime. We highlight theirimportant performance metrics, especially with regard to progress in this area couldfacilitate advanced electromagnetic innovation

Current-induced switching of YIG/Pt bilayers with in-plane magnetization due to Oersted fields

We report on the switching of the in-plane magnetization of thin yttrium iron garnet (YIG)/Pt bilayers induced by an electrical current. The switching is either field-induced and assisted by a dc current, or current-induced and assisted by a static magnetic field. The reversal of the magnetization occurs at a current density as low as $10^5$~A/cm$^{2}$ and magnetic fields of $\sim 40$~$\mu$T, two orders of magnitude smaller than in ferromagnetic metals, consistently with the weak uniaxial anisotropy of the YIG layers. We use the transverse component of the spin Hall magnetoresistance to sense the magnetic orientation of YIG while sweeping the current. Our measurements and simulations reveal that the current-induced effective field responsible for switching is due to the Oersted field generated by the current flowing in the Pt layer rather than by spin-orbit torques, and that the switching efficiency is influenced by pinning of the magnetic domains

Analysis the effect of Diffraction Phenomena by Complex Shapes with Hybrid MOM-GTD Method

This article deals with a hybrid method combining the method of moments (MOM) with the general theory of diffraction (GTD). This hybrid approach is used to analyze antennas located near perfectly Bodies of arbitrary curved shape. Some examples, e.g. an antenna mounted near a perfect conductor cylinder with two plates, demonstrates that the hybrid approach is the most suitable technique for modeling large-scale objects and arbitrary shapes. This approach allows us to resolve the problem, that the other methods can’t solve it alone. Generally, random radiation locates on or near an arbitrary form, can be solved using this technique hence the strong advantages of our method

Unexpected giant elasticity in side-chain liquid-crystal polymer melts: A new approach for the understanding of shear-induced phase transitions

International audienceRecent studies have revealed that high molecular weight liquid crystals typically exhibit shear induced phases within the isotropic melt. From rheo-birefringence measurements, we demonstrate that those shear induced phases are not coupled with conventional orientational-order fluctuations. From rheo-SANS experiments, we show that the polymer chain is deformed at time scales longer than the viscoelastic relaxation time. Finally, careful visco-elastic measurements reveal a strong elastic behaviour; the melt is not a viscoelastic liquid but solid-like at equilibrium one hundred degrees over the glass transition temperature and up to 15°C over the Isotropic-Nematic phase transition. This supra molecular cohesion and its extra long relaxation times may explain the emergence of non-linear phenomena

Identification of finite shear-elasticity at low thickness in the liquid state of molecular (OTP) and polymeric glass formers (PBuA)

International audienceFinite shear elasticity has been identified at low gap in the liquid state of various viscous fluids. The present study is expanded to a van der Waals glass former, the o-Terphenyl and to an ordinary polymer melt, the polybutylacrylate. Elasticity is also identified in these materials at the sub-millimeter scale and far above any phase transition. This macroscopic property is discussed in the frame of the terminal relaxation modes (-process or reptation times) and of their molecular interpretation

Explaining the low-frequency shear elasticity of confined liquids

Experimental observations of unexpected shear rigidity in confined liquids, on very low frequency scales on the order of 0.01-0.1 Hz, call into question our basic understanding of the elasticity of liquids and have posed a challenge to theoretical models of the liquid state ever since. Here we combine the nonaffine theory of lattice dynamics valid for disordered condensed matter systems with the Frenkel theory of the liquid state. The emerging framework shows that applying confinement to a liquid can effectively suppress the low frequency modes that are responsible for nonaffine soft mechanical response, thus leading to an effective increase of the liquid shear rigidity. The new theory successfully predicts the scaling law $G'\sim L^{-3}$ for the low-frequency shear modulus of liquids as a function of the confinement length $L$, in agreement with experimental results, and provides the basis for a more general description of the elasticity of liquids across different time and length scales

The frozen state in the liquid phase of side-chain liquid-crystal polymers

International audienceQuenched isotropic melts of side-chain liquid-crystal polymers reveal surprisingly an anisotropic polymer conformation. This small-angle neutron-scattering (SANS) result is consistent with the identification of a macroscopic, solidlike response in the isotropic phase. Both experiments (rheology and SANS) indicate that the polymer system appears frozen on millimeter length scales and at the time scales of the observation. This result implies that the flow behavior is not the terminal behavior and that cross-links or entanglements are not a necessary condition to provide elasticity in melts

Mendil et al Reply

International audienceIn the preceding Comment [1], Collin and Martinoty claim that a conventional flow behavior (G' ~ f2 , G'' ~ f) is obtained at 20 $\mu$m gap thickness, for a LC-polymer (LCP105) in the nematic phase, using a filling with a capillary, whereas a solidlike behavior (G' ~ Cst, G" ~ Cst) is observed by approaching two parallel surfaces to the sample (as we apply in our experiment). Our observations of a terminal solidlike behavior are thus interpreted by Collin and Martinoty as an anomaly induced by compression effects. We clearly refute this interpretation. We note that, on Fig. 13 and 14 of a previous paper written by Collin and Martinoty [2], they report no more a conventional flow but an elastic behavior at lower temperature using the capillary filling and the same polymer (LCP105). Their previous observations are thus in contradiction with their present purpose; i.e., a terminal flow behavior

Studying Dispersed Phase Holdup in a Pilot Plant Agitated Liquid–liquid Mixer by Developing Online Expanded Laser Beam based Technique

Expanded Laser Transmission Technique (E-LTT), where a laser beam is used in conjunction with a beam expander large enough to cover the average drop size up to a few millimeters in the path of the laser in a liquid–liquid dispersion mixture, has been applied for online continuous measurement and investigation in a non-invasive manner of the drop phase volume fraction in an agitated flow mixer of a pilot plant scale. The limitations of beam scattering by the drops through the dispersion path were overcome by having liquids of matching refractive indices enabled by the temperature control system. This study reports for the first time the continuous measurements of the line averaged dispersed phase holdup for a pilot plant scale liquid–liquid mixer equipped with a commercial design mixer, where the measurements have no limitations to the geometrical aspects. Experimental results from a cubic mixing tank with a dispersion depth of 30cm were discussed. Online measurements were carried out in the presence of a revolving impeller and transmission of the expanded laser beam. The net volume of the mixer was 20.42liter, and the dispersed phase holdup that was successfully measured ranged between 0.15 and 0.75. In this work, arrangement of the laser setup was made to scan and measure continuously the line average dispersed phase holdup along the height of the pilot plant scale of the flow agitated liquid–liquid mixer. The E-LTT measurements were validated by comparing their results with those obtained from the mixer by shut-down procedure

Burdur ilinde karayollarının yakınından toplanan bazı karayosunu örneklerinde ağır metal seviyelerinin belirlenmesi

The main sources of atmospheric heavy metals deposition are agricultural activities, fossil fuels, central heating stations and the exhaust gases of motor vehicles. In this study, the total of 29 mosses samples were collected from contaminated points near the Isparta-Antalya, Burdur-Denizli, Burdur-Afyonkarahisar, Burdur-Fethiye (Muğla) and Burdur-Antalya highways (2-20m) and uncontaminated areas in 2012. Samples were analyzed by flame and graphite furnace atomic absorption spectrometry (AAS) later microwave digestion methods. The highest accumulation levels detected as µg.g−1 Fe (1419.02)>Zn (158.44)>Mn (362.77)>Ni (109.53)>Cr (60.51)>Pb (30.38)>Cd (35.866)>Cu (25.17) for mosses. Element levels are differ depending on moss species and the location of collecting localities.Atmosferik Ağır metal birikiminin ana kaynakları, tarımsal faaliyetler, fosil yakıtlar, merkezi ısıtma istasyonları ve bölgedeki motorlu taşıtların egzoz gazlarıdır. Bu çalışmada, 2012 yılında Isparta-Antalya, Burdur-Denizli, Burdur-Afyonkarahisar, Burdur-Fethiye (Muğla) ve Burdur-Antalya karayollarının yakınından (2-20m) kirlenmiş bölgeden ve bu yollara uzak noktalardan temiz bölgeden 29 karayosunu örneği toplanmıştır. Örnekler mikrodalga çözünürleştirme sonrasında alev ve grafit fırın atomik absorpsiyon spektrometresi (AAS) metodu ile analiz edilmiştir. Karayosunları için en yüksek birikim seviyeleri µg.g−1 olarak şu şekilde tespit edildi; Fe (1419.02)>Mn (362.77)>Zn (158.44)>Ni (109.53)>Cr (60.51)>Pb (30.38)>Cd(35.866)>Cu (25.17). Element seviyesi, karayosunu türlerine ve toplanma lokalitelerinin durumuna bağlı olarak farklıdır