Microstrip Antenna with High Gain and Strong Directivity Loaded with Cascaded Hexagonal Ring-Shaped Metamaterial

A new cascaded hexagonal ring-shaped metamaterial element is designed, which is arranged periodically and placed on the top of a traditional microstrip antenna to optimize the performance of the traditional antenna. The simulation results show that the new metamaterial microstrip antenna works at near 10 GHz, the impedance bandwidth is extended by 0.25 GHz and the gain is increased by 113.6% compared with a traditional microstrip antenna. Cross-shaped slots are etched on the ground plate of the microstrip antenna to widen the impedance bandwidth. It is shown that the impedance bandwidths at the resonant frequencies of 10 GHz and 14 GHz are broadened by 0.06 GHz and 0.56 GHz, respectively, and the gain of the slot-etched antenna is 13.454 dB. After the metamaterial unit structure is optimized, a nested double-hexagon ring-shaped electromagnetic metamaterial unit structure is proposed. The metamaterial slot microstrip antenna operates in two frequency bands of 10 GHz and 14 GHz; the relative bandwidths are increased to 16.9% and 19.4% with two working bandwidths of 1.74 GHz and 4.98 GHz, respectively; and the gain and directivity are also improved compared with the traditional microstrip antenna. The metamaterial unit structure proposed in this paper is of certain reference value for the variety of metamaterial and the application of metamaterial in traditional microstrip antennas.

A previously unknown cyclic alkanolamine and molecular ranking using the pair distribution function

A new six-membered cyclic alkanolamine with chemical formula C6H15N3O3 was synthesized by the reaction of glycolaldehyde with gaseous ammonia. The molecular structure, characterized by a hexagonal ring of alternating carbon and nitrogen atoms with three hydroxymethyl groups attached to the carbon atoms, could not be unambiguously determined by elemental analysis and 1H/13C/15N NMR. The molecular structure and conformation were further determined using a combination of vibrational spectroscopy (IR and Raman) and real-space pair distribution function (PDF) analysis. The crystal structure was determined ab initio from laboratory X-ray powder diffraction (XRPD) with orthorhombic space group Ama2 (No. 40) and unit-cell parameters a = 12.1054 (2) Å, b = 13.5537 (2) Å and c = 5.20741 (8) Å. Consistent structure models could be obtained by symmetry-independent PDF and PDF-Rietveld co-refinements. Independent local structure refinements indicate that the most likely deviations from the average structure consist of small tilting and translational distortions of hydrogen-bonded molecular stacks. Thermal analysis (TG/DTA) and temperature-dependent XRPD measurements were also performed to determine the thermal behavior.

Facile and Rapid Synthesis of Durable SSZ-13 Catalyst Using Choline Chloride Template for Methanol-to-Olefins

In this study, a facile and rapid synthesis approach for SSZ-13 catalyst was proposed using choline chloride (CC) as template. The optimal synthesis condition was explored, and the catalytic performance for methanol-to-olefins (MTO) was examined. Results revealed that the appropriate ratio of soft template could meet the condition for rapid and ordered growth of catalyst crystals. Using environmentally friend and cheaper CC as template could greatly accelerate the formation of bi-hexagonal ring structure in SSZ-13 framework, and it could shorten the synthesis cycle to within 4 h. With a proper amount of CC addition (i.e., m(CC)/m(SiO2) = 0.14), uniform and homogeneously distributed cubic SSZ-13 crystals were obtained with relatively lower aggregation. The catalyst synthesized with m(CC)/m(SiO2)=0.14 demonstrated excellent porous features with a total specific surface area and mesopore volume of 641.706 m2.g-1 and 0.0377 cm3.g-1, respectively. The optimized strong and weak acid sites on the SSZ-13 were obtained by regulating the m(CC)/m(SiO2). As a typical acid catalytic reaction, the SSZ-13 catalyst with strong and weak acid sites exhibited bi-functional role. The lower amount of strong acid sites and larger amount of weak acid sites in the synthesized catalyst were conducive to the catalytic performance for MTO under relatively lower reaction temperature (450 oC). Consequently, the synthesized SSZ-13 showed a better conversion rate and lifetime than that of purchased one. The methanol conversion rate using synthesized catalyst was maintained over 95% within 120 min, and its lifetime was achieved to 172 min. The appropriate acidity and well-developed pore structure of synthesized SSZ-13 could slow down the carbon deposition rate and significantly increase the lifetime of the catalyst. Moreover, the initial selectivity of light olefin could maintain above 50% within 160 min. Eventually, the desirable features of synthesized SSZ-13 catalyst were thought be with good potential for industrial application.

A 5-Channel DWDM Demultiplexer in C Band on Silicon Photonic Crystal Slab: Design and Numerical Analysis

In this work we propose a novel design of 5-channel DWDM demultiplexer and, numerical analysis of its optimal design parameters and device performance is presented. Photonic crystal hexagonal ring resonators of airholes on a silicon slab are used as channel drop filters. Wavelength controlling is achieved by fine tuning of coupling holes outside each ring resonator. For the proposed design, the resolved wavelengths are in the range of 1535 to 1539nm, where Erbium Doped Fiber Amplifiers are applicable. The average coupling efficiency and cross talk are found to be 72.4% and -18.31dB, respectively. Photonic bandgap computation is performed by using plane wave expansion method and spectral characteristics are obtained by applying 3D finite difference time domain method.

Design of CPW-fed Star-Shaped Monopole Antenna for UWB Applications using Transmission Line Model

This article presents a structure of coplanar waveguide (CPW)-fed star-shaped monopole antenna (SSMA) with a pair of quarter-circular-slit (QCS) and partly-hexagonal-ring-slit (PHRS) defected ground structure. By inserting a pair of QCS and PHRS on the rectangular ground plane, an excellent impedance bandwidth is achieved i.e., 139 % (from 2.2--12.21 GHz). The dimension of the SSMA is about 0.286λ l ×0.216λ l mm 2 , where λ l is the wavelength in free space at the lowest operating frequency i.e, 2.2 GHz. The transmission line model (TLM) of the SSMA is presented and it shows the antenna behavior based on the effect of each element. It is observed that the characteristics of the TLM model are close to the simulation result using the CST simulator. From the results, it is observed that the proposed ultra-wideband (UWB) antenna close to omnidirectional radiation patterns and suitable for UWB Applications.