Conformal Antenna Array for Millimeter-Wave Communications: Performance Evaluation

In this paper, we study the influence of the radius of a cylindrical supporting structure on radiation properties of a conformal millimeter-wave antenna array. Bent antenna array structures on cylindrical surfaces may have important applications in future mobile devices. Small radii may be needed if the antenna is printed on the edges of mobile devices and in items which human beings are wearing, such as wrist watches, bracelets and rings. The antenna under study consists of four linear series-fed arrays of four patch elements and is operating at 58.8 GHz with linear polarization. The antenna array is fabricated on polytetrafluoroethylene substrate with thickness of 0.127 mm due to its good plasticity properties and low losses. Results for both planar and conformal antenna arrays show rather good agreement between simulation and measurements. The results show that conformal antenna structures allow achieving large angular coverage and may allow beam-steering implementations if switches are used to select between different arrays around a cylindrical supporting structure.Comment: Keywords: conformal antenna, millimeter-wave communications, patch antenna array. 11 pages, 10 figures, 1 tabl

Effect of alloying elements (Zr, Hf, Co), heat and mechanical treatment conditions on the phase composition and magnetic properties of SmFe11Ti compounds with ThMn12 structure

The results of thermomagnetic, metallographic and X-ray diffraction phase analysis as well as the measurements of specific magnetization (σs), Curie temperature (TC), coercive force (HC) of (Sm,M)(Fe,M)12-xTix alloys samples, where M = Zr, Hf, Co with the ThMn12 main phase structure (1-12) are presented. The effect of the annealing temperature and the cooling rate on the formation of 1-12 phase and its magnetic properties, including the effect of high-energy milling on the magnetic hysteresis properties and alloys structure are described. It was found that the highest magnetic characteristics such as σs = 112.6 emu/g and TC = 600°C are attained in the (Sm0.8Zr0.2)(Fe0.75Co0.25)11.4Ti0.6 alloy after its annealing at 1050 °C and rapid cooling. It is noted that a mechanical milling of the alloy leads to 1-12 phase amorphization which accompanied by an α-(Fe) or metal Co phases impurity formation. © 2018 The Authors, published by EDP Sciences.The work was supported by the State contracts No. 3.6121.2017/ 8.9 between UrFU and the Ministry of Education and Science of Russian Federation and by the Fund of assistance to development of small enterprises in scientific-technical sphere No. 11996GU / 017

SUBSTITUTION OF Co ON THE CRYSTAL STRUCTURE IN THE LiNi1-XCoXPO4 SYSTEM

We present a detailed structural study of the LiNi1-xCoxPO4 (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5) polycrystalline samples using X-ray diffraction (XRD) and Raman scattering.The reported study was funded by RFBR (project No. 19-32-60011)

Spin-glass transition in porous spheres BiFeO3

Magnetic properties of porous spheres BiFeO3 have been studied at temperatures ranging from 2 to 300 K. A transition to cluster spin glass state has been detected in the region of about 100 K. The presence of the transition is confirmed by nonlinear variation of coercive force and the appearance of exchange displacement of magnetic hysteresis loops at temperature below 100 K. Temperature dependence of magnetization for zero-field cooled regime exhibit a maximum at some temperature Tm. The function Tm(H) (H is magneic field) changes in accordance with Almeida-Thouless line. The performed measurements of the frequency dependence of AC susceptibility confirm the behavior of spin glass with spin freezing temperature Tf = 116 K. The critical index zν = 2.5 agrees well with the mean-field theory zν = 2.0. © 2020, ITMO University. All rights reserved.This work was supported by a research program at the Institute of Solid State Chemistry. The authors are grateful to Dr. Maria V. Lukashova (OOO “Tescan”, Saint Petersburg, Russia) for scanning microscopy and 3D FIB-SEM tomography

Refinement of the Crystal Structure LiNi0.1Co0.9PO4

The X-ray diffraction measurement has been carried out to study the Li(Ni,Co)PO4 prepared by the glycerol-nitrate synthesis method. An expansion of the cell volume depends on concentration of the Co-ions and is anisotropic: a, b, c parameters are increases and all obey the Vegard’s law.Исследование выполнено при финансовой поддержке РФФИ в рамках научного проекта № 19-32-60011

Structure and magnetic properties of (Sm1-xZrx)Fe11Ti (x=0-0.2) alloys

Compounds with a tetragonal structure of the ThMn12 type have a high potential for creating on their basis permanent magnets with high energy density and operating temperatures up to 150 - 200 C. In this work, samples of alloys (Sm1-xZrx)Fe11Ti (x = 0 - 0.2) obtained by the rapidly quenching method with subsequent annealing were investigated. Depending on the chemical composition and modes of synthesis in alloys (Sm1-xZrx)Fe11Ti (x = 0 - 0.2) phases of the ThMn12, α-Fe type and a small amount of ZrFe2 are formed, as well as phases with the Th2Zn17 structural type and TbCu7 at high annealing temperatures. The best magnetic properties at room temperature are realized in the alloy (Sm0.9Zr0.1)Fe11Ti after annealing at a temperature of 800 C. © Published under licence by IOP Publishing Ltd.02, 3.6121.2017/8.9The work was supported by MES of RF (contract No. 3.6121.2017/8.9) and Act 211 Government of RF (agreement No. 02.A03.21.0006)

Bandwidth-controlled Mott transition in κ−(BEDT−TTF)2Cu[N(CN)2]BrxCl1−x\kappa-(BEDT-TTF)_2 Cu [N(CN)_2] Br_x Cl_{1-x} I. Optical studies of localized charge excitations

Infrared reflection measurements of the half-filled two-dimensional organic conductors $\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_{2}$]Br$_{x}$Cl$_{1-x}$ were performed as a function of temperature ($5 {\rm K}<T<300$ K) and Br-substitution ($x=0$, 40%, 73%, 85%, and 90%) in order to study the metal-insulator transition. We can distinguish absorption processes due to itinerant and localized charge carriers. The broad mid-infrared absorption has two contributions: transitions between the two Hubbard bands and intradimer excitations from the charges localized on the (BEDT-TTF)$_2$ dimer. Since the latter couple to intramolecular vibrations of BEDT-TTF, the analysis of both electronic and vibrational features provides a tool to disentangle these contributions and to follow their temperature and electronic-correlations dependence. Calculations based on the cluster model support our interpretation.Comment: 12 pages, 12 figure

Magnetic properties of Sr2Ni1-xMgxMoO6 (x = 0.25 and 0.5) double perovskite structure

Sr2Ni1-xMgxMoO6 (x = 0.25 and 0.5) double perovskites were synthesized by pyrolysis of glycerol-salt mixtures and their magnetic properties were investigated. X-ray diffraction was employed to refine crystal structures of these perovskite materials and set sample purity degree. The magnetic ground state of Sr2Ni1-xMgxMoO6 (x = 0.25 and 0.5) has been characterized using magnetic susceptibility measurements. They indicate that Sr2Ni0.75Mg0.25MoO6 is ordered in an antiferromagnetic state below 56 K while Sr2Ni0.5Mg0.5MoO6 is paramagnetic. © Published under licence by IOP Publishing Ltd.3.6121.2017/8.9A03.21.0006, 02.The work was supported by MES of RF (contract No. 3.6121.2017/8.9), and by Act 211 Government of RF (contract No. 02.A03.21.0006), and supported in part y FASO of Russia (theme “Flux” No. AAA-A18-118020190112-8)