Design of an Ultra-Wideband Microstrip Patch Antenna Suspended by Shorting Pins

Designing a compact wideband microstrip patch antenna which is composed of a folded-patch feed, a symmetric E-shaped edge and shorting pins is presented in this paper. One pin is applied in order to expand the impedance bandwidth. Two other pins are utilized to miniaturize the size of patch as well. The measured impedance bandwidth ( $\text{ VSWR}\le 2$ ) of the fabricated antenna is more than 90 % in the frequency range 3.92–10.67 GHz for ultra-wideband (UWB) applications. The antenna size is $0.438\lambda _{0}\times 0.365\lambda _{0}\times 0.170\lambda _{0}$ at its center operating frequency. Also, radiation patterns with acceptable stability within the bandwidth are obtained. In addition, the effects of some key parameters are investigated to describe the performance of the proposed design.     

去除牛粪厌氧生物转化过程中的H2S

The main aim of this research was the experimental study at lab scale to check the absorption technology for the in situ removal of H2S from biogas during anaerobic digestion process. The reagent FeCl3 was used to check the removal efficiency of H2S produced from dairy manure during anaerobic bioconversion process. The experiments were conducted under mesophilic conditions. The composition of biogas was analyzed by gas chromatography analyzer equipped with flame photometer and thermal conductivity detectors. Experimental results under the same conditions demonstrate that high concentration of H2S in the form of FeS can be removed totally from the biogas using FeCl3 dosing with in anaerobic batch digester.     

Thin tunnel oxide grown on silicon substrate pretreated by CF4 plasma

High tunneling current and large resistance against stress were the main issue of tunnel oxide for scaling down the operation voltage of EEPROMs. In this letter, thin-tunnel oxides grown on a CF₄ pretreated silicon substrate were prepared and investigated for the first time. The fabricated oxide has about three orders of tunneling current higher than that of control one; furthermore, the stress induced anomalous and low electric field leakage currents were greatly suppressed. The improvement could be contributed to F-incorporation in oxide. This type of oxide is suitable for fabricating low-voltage EEPROMs and less process complexity was added     

Performance and reliability of poly-Si TFTs on FSG buffer layer

A novel and process-compatible scheme for fabricating poly-Si thin-film transistors (TFTs) on an FSG buffer layer was proposed and demonstrated. Experimental results reveal that remarkably improved device performance and uniformity can be achieved with appropriate fluorine concentration. The poly-Si TFTs fabricated on FSG layers have a higher on-current, a lower leakage current, and a higher field-effect mobility compared with the conventional poly-Si TFTs. Furthermore, the incorporation of fluorine also increased the reliability of poly-Si TFTs against hot carrier stressing, which is attributed to the formation of Si-F bonds.     

Elastic buckling of circular annular plate reinforced with carbon nanotubes

The buckling analysis of circular annular plate reinforced by carbon nanotubes (CNTs) subjected to compressive and torsional loads with various axially symmetric boundary conditions are studied in this paper. The developed model is based on the classical laminated plate theory (CLPT). The Mori‐Tanaka method is employed to calculate the effective elastic modulus of composites having aligned oriented straight CNTs. The eigenvalues of the problem are obtained by means of an analytical approach based on the optimized Rayleigh‐Ritz method. The effects of CNTs orientation angles, edge conditions, geometric ratio of plate and agglomeration of the randomly oriented straight CNTs are investigated on the critical buckling loads. Extensive studies validity of the results based on available data have been carried out prior to the presentation of salient results of this analysis. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

A cubic dual band near-field focused array antenna using composite right/left handed transmission lines

This paper proposes a new method for design of a dual-frequency near field-focused (NFF) antenna. A 4 × 4 array of dual-band patches and a dual-band feed network are designed to provide a phase distribution at 2.4 and 5.8 GHz. Rectangular patches with U-shaped slot be used as the double-band patches. The composite right/left handed transmission lines (CRLH TL) are used in design of a dual-band phase distribution network for the patches. Finally, a three-dimensional cubic structure is proposed to isolate the feed network and thereby improve the antenna performance. A prototype of a cubic dual band 4 × 4 near field focused array antenna is fabricated and tested. The measurement results have good agreement with simulation results.     

Effect of the aspect ratio and waviness of carbon nanotubes on the vibrational behavior of functionally graded nanocomposite cylindrical panels

In this study, based on the three‐dimensional theory of elasticity, free vibration characteristics of nanocomposite cylindrical panels reinforced by single‐walled carbon nanotubes (CNTs) are considered. The carbon nanotube‐reinforced (CNTRC) cylindrical panel has smooth variation of CNT fraction in the radial direction, and the material properties are estimated by the extended rule of mixture. In this work, the classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube‐to‐tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. Symmetric and asymmetric volume fraction profiles are provided in this work for comparison. Suitable displacement functions that identically satisfy the boundary conditions at the simply supported edges are used to reduce the equilibrium equations to a set of coupled ordinary differential equation with variable coefficients, which can be solved by a generalized differential quadrature method. The results show that the kind of distribution and volume fraction of CNT have a significant effect on normalized natural frequency.POLYM. COMPOS., 33:2036–2044, 2012. © 2012 Society of Plastics Engineers     

Effects of Nb2O5 Doping on the Microwave Dielectric Properties and Microstructures of Bi2Mo2O9 Ceramics

This study investigated the effects of the addition of Nb₂O₅ and sintering temperature on the properties of Bi₂Mo₂O₉ ceramics. The ceramics were sintered in air at temperatures ranging from 620°C to 680°C. The addition of small amounts of Nb₂O₅ as a dopant significantly affected the crystalline phase and the microwave dielectric properties of the Bi₂Mo₂O₉ ceramics. The secondary phase, γ‐Bi₂MoO₆, was observed when Nb₂O₅ was added. However, unlike the Bi₂Mo₂O₉ ceramic without Nb₂O₅ sintered above 645°C, the ceramics with 3 mol% Nb₂O₅ contained no γ‐Bi₂MoO₆ when sintered at 660°C. The Q × f value and τ_f of the Bi₂Mo₂O₉ ceramics were improved by Nb₂O₅ doping. The Bi₂Mo₂O₉ ceramics doped with 2 mol% Nb₂O₅ exhibited the best microwave dielectric properties, with a permittivity of 36.5, a Q × f value (f = resonant frequency, Q = 1/dielectric loss at f) of 14100 GHz and τ_f of +5.5 ppm/°C after sintering at 620°C.