Polymorphisme du dioxotriplomb (II) tetraoxosulfate (VI) Pb3O2(SO4) a basse temperature. II - Etude structurale de la phase ferroelastique gamma-Pb3O2 (SO4) par diffraction neutronique sur poudres a 2 et 45K

Full-profile neutron powder diffraction structure refinements of dioxotrilead(II)tetraoxosulfate(VI) at 2 and 45K reveal that both the alpha- and the gamma-Pb₃O₂ (SO₄) polymorphs have to be refined simultaneously at these temperatures. Accordingly, the paraelastic alpha phase is trapped in the ferroelastic gamma phase, yielding thus mixtures of both compounds in a nearly 1:1 molar ratio. Both structures are essentially similar. The slight variations of the lead-oxygen distances in the infinite edge-sharing tetrahedral (Pb₃ O₂)n double-chains force the sulfate group to adopt nearly C3v and C2v site symmetries respectively in the alpha and gamma phases. The present work is a good example of the behaviour of the DBW3.2 program (1) when mixtures of very similar structures are refined simultaneously (high correlation between some structural parameters).     

Decentralized Networked Control System Design Using Takagi-Sugeno (TS) Fuzzy Approach

This paper proposes a new method for control of continuous large-scale systems where the measures and control functions are distributed on calculating members which can be shared with other applications and connected to digital network communications.At first, the nonlinear large-scale system is described by a Takagi-Sugeno(TS) fuzzy model. After that, by using a fuzzy LyapunovKrasovskii functional, sufficient conditions of asymptotic stability of the behavior of the decentralized networked control system(DNCS),are developed in terms of linear matrix inequalities(LMIs). Finally, to illustrate the proposed approach, a numerical example and simulation results are presented.     

Structure cristalline de la phase haute temperature de PbSO4.2PbO A 973K

Full profile X-ray powder diffraction structure refinements have been performed on the two polymorphs of the PbSO₄.2PbO phase. Both structures can be described as infinite double-chains of edge-sharing OPb₄ tetrahedra linked by the sulfate groups and running parallel to the (010) direction for the low temperature phase, and parallel to the (001) direction for the high temperature one. The mechanism of the phase transition may be described as a rotation of the sulfate group about one of its pseudo-ternary axis. The space group adopted for the refinement of the structure of the high temperature phase is Cmcm.     

The crystal structures of PbO.PbXO4 (X = S,Cr, Mo) at 5K by neutron powder profile refinement

The structures of PbO.PbXO₄ monobasic lead oxide- lead sulphate, chromate and molybdate have been determined at 5K by neutron powder profile refinement. They are all isostructural with Lanarkite (the sulphate), being based on the red PbO structure with PbO₂^2? and its lone pair electrons replaced by XO₄^2?. A similar mechanism apparently produces the di-basic and tetra-basic oxides nPbO.PbXO₄. These materials are of relevence to solid state reactions in lead — acid battery electrodes.     

Design of a compact size tag antenna based on split ring resonator for UHF RFID application

In this article, a new design of miniaturized split‐ring resonator antenna using a meander line technique with a simple impedance matching method applicable to UHF‐RFID tags is presented. The new approach is based on the integration of a meander line into the radiating element of SRR to reduce the electrical tag size and a theoretical demonstration to calculate the conjugate impedance matching and directly attach the antenna with the chip. The new SRR antenna, which is printed on the flexible substrate Arlon CuClad 250LX, is designed using Alien Higgs 3 RFID ASIC whose input impedance is 25‐j190. The prototype antenna has a low‐cost compact size (18.28 mm × 18.28 mm) with a read range higher than 4 m within the RFID UHF band and with a roughly 4.2‐m peak range at 915 MHz. As a proof of behavior, a tag prototype is fabricated and measured to operate at a UHF RFID band. Based on some works' results, an optimized design is obtained with a 48% size reduction compared with the classic split ring resonator antenna and with a good impedance matching the antenna with RFID ASIC without the need for any external matching network.     

Hybrid rectenna and monolithic integrated zero-bias microwave rectifier

In this study, we have developed a hybrid sensitive rectenna (rectifier + antenna) system at 2.45 GHz. To achieve this system, we have first optimized and validated a zero-bias microwave sensitive rectifier using commercial Schottky diodes. We have then optimized and achieved a 2/spl times/2 patch antenna array, which is associated to the microwave rectifier in order to validate the rectenna system, where an RF-dc conversion efficiency of 56% has been observed experimentally. In order to minimize the rectenna dimensions, we have conducted a study using the OMMIC ED02AH 0.20-/spl mu/m GaAs pseudomorphic high electron-mobility transistor process to develop and achieve a monolithic rectifier at 2.45 GHz with RF-dc conversion efficiency of 65%.     

New Design of Multi-Band PIFA Antenna with Reduced SAR for Mobile and Wireless Applications

Wireless Personal Communications - In this paper, a new multi-band PIFA antenna covering four frequency bands (GSM, Wifi/Bluetooth, 4G LTE and WIMAX) is presented. The proposed method in this work...     

Iterative technique for analysis and design of circular leaky‐wave antenna for the 2.45‐GHz radio‐frequency identification applications

This paper suggests a new miniaturized antenna for radio‐frequency identification (RFID) applications of 2.45 GHz. Our structure consists of a circular microstrip patch antenna which incorporates two concentric annular slots is printed on a multilayer substrates. The bandwidth, one of the most important characteristics of antenna, can be significantly improved by using a multilayer dielectric configuration. we aim by this study to show that the effect of radiating structure loaded by annular rings for the patch size reduction as well as the advantage of this structure being to create a circular polarisation in the direction of maximal radiation pattern. The wave concept iterative procedure is used to analyse this new antenna. Using the proposed procedure, less computing time and memory are needed to calculate the electromagnetic parameters of our design. The validation of the results of our developed model was verified with known commercial software called “CST Microwave Studio Software” followed by an experimental test. According to the reached results, we can judge that our new design antenna is suitable for RFID applications in the 2.45 GHz band.     

Influence of split ring resonators on the properties of propagating structures

The study of a 50 Omega microstrip line and microstrip resonators loaded with resonant elements called split-ring resonators (SRRs) is presented. The two different filtering phenomena observed lead to make an analogy with those observed when waveguides are loaded with these elements. So, in order to make this analogy, the different results obtained with the SRRs loaded in a propagating and an under cut-off waveguide are shown. Then, another technique to achieve and even improve these results is presented. The technique consists of using, respectively, a 50 Omega microstrip line and capacitive-gap-coupled microstrip resonators instead of the propagating and under cut-off waveguides. The numerical and experimental results obtained with the two structures (waveguides and microstrip lines) are compared and discussed. This study shows that the combination of SRRs with guiding structures helps in the design of compact structures, but an enhancement of the performances needs a better fabrication accuracy     

Design of a Dual-Polarized UWB 5G NR Antenna

Wireless Personal Communications - In this paper, we propose a compact, planar, eight-port/four-resonator slot antenna array with a dual-polarized function for multiple-input-multiple-output (MIMO)...