Artificial Magnetic Conductor as Planar Antenna for 5G Evolution

A 5G wireless system requests a high-performance compact antenna device. This research work aims to report the characterization and verification of the artificial magnetic conductor (AMC) metamaterial for a high-gain planar antenna. The configuration is formed by a double-side structure on an intrinsic dielectric slab. The 2-D periodic pattern as an impedance surface is mounted on the top surface, whereas at the bottom surface the ground plane with an inductive narrow aperture source is embedded. The characteristic of the resonant transmission is illustrated based on the electromagnetic virtual object of the AMC resonant structure to reveal the unique property of a magnetic material response. The characteristics of the AMC metamaterial and the planar antenna synthesis are investigated and verified by experiment using a low-cost FR4 dielectric material. The directional antenna gain is obviously enhanced by guiding a primary field radiation. The loss effect in a dielectric slab is essentially studied having an influence on antenna radiation. The verification shows a peak of the antenna gain around 9.7 dB at broadside which is improved by 6.2 dB in comparison with the primary aperture antenna without the AMC structure. The thin antenna profile of λ/37.5 is achieved at 10 GHz for 5G evolution. The emission property in an AMC structure herein contributes to the development of a low-profile and high-gain planar antenna for a compact wireless component.     

A heuristic‐based design of robust SMES controller taking system uncertainties into consideration

In this paper, a heuristic‐based design of robust superconducting magnetic energy storage (SMES) controller is proposed taking system uncertainties into consideration. The SMES model with active and reactive power controllers is used. In addition, the effect of SMES coil current is also included in the model. The power system and the SMES unit with the designed controller are formulated as an optimization problem. The proposed objective function considers both the damping performance index and the robust stability index. In particular, the robust SMES controller is designed to enhance the system damping performance and robustness against system uncertainties such as various load and system parameter changes. The robust stability margin is guaranteed in terms of the multiplicative stability margin (MSM). In the proposed method, the robust SMES active and reactive power controllers are designed systematically by using hybrid tabu search and evolutionary programming, so that the desired damping performance and the best obtainable MSM are acquired. Finally, the designed SMES controller is examined under different situations to evaluate and confirm the effectiveness and robustness via eigenvalue analysis and nonlinear simulations. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Combination Inhibition Activity of Nisin and Ethanol on the Growth Inhibition of Pathogenic Gram Negative Bacteria and Their Application as Disinfectant Solution

Nisin and ethanol have been used as antimicrobial agents in food industry. However, nisin alone could not inhibit the growth of gram‐negative bacteria, except in combination with a chelating agent, EDTA, or organic acid. This research aimed to study the survival of Escherichia coli O157: H7, Salmonella Typhimurium TISTR 292 and Salmonella Enteritidis DMST 17368 after treatment with nisin at 100, 200, 300, 500, 800, or 1000 IU/mL and ethanol at 70%, 50%, 30%, 20%, or 10% (v/v) alone and in combination. None of all nisin concentrations could reduce the growth of target strains. While 20% ethanol (v/v) having no negative effect on human health, could slightly reduce the growth of target strains. However, the combination of nisin at 500, 800 or 1000 IU/mL and 20% ethanol displayed significant growth reduction at 15 min were below 1 log CFU/mL. Thus, the minimum inhibitory concentration of nisin and ethanol was 500 IU/mL and 20% (v/v), respectively. The release of fatty acid, genetic materials and scanning electron microscope suggested that nisin‐ethanol treated cells have altered permeability causing bacterial growth inhibition. Comparison treatment of combined solution and commercial chloride based sanitizer were done for all target strains on stainless steel surface. Survivals of three target strains were below 1 log CFU/mL. The result suggested that combined solution of nisin and ethanol may be a beneficial sanitizer for food industry to inhibit the growth of E. coli O157:H7 and Salmonella sp.     

Effects of Process Parameters on Mechanical Adhesion of Thermal Oxide Scales on Hot-Rolled Low Carbon Steels

The present work investigated the effects of process parameters in a hot-rolling line, finishing and coiling temperatures, on mechanical adhesion of scale on low carbon steel substrate using a tensile test. Modification of our previous model to quantify mechanical adhesion energy was proposed for a system consisting of a cracked scale on a metallic substrate by introducing a distribution function of stress in scale. When a linear distribution was assumed, the quantified mechanical adhesion energy lay in the range of 40–890 J m^?2. Higher finishing temperature had a prominent role on increasing final scale thickness and weakening scale adhesion. For scale with similar thickness, the mechanical adhesion energy was lowered for the sample subjected to higher temperature gradient between finishing and coiling temperatures. This was considered to be from the increased water vapour in atmosphere due to the higher amount of water used to cool down the steel strip. The mechanical adhesion test was further conducted to attest this assumption. It was found that humidified atmosphere during oxidation weakened the scale adhesion to low carbon steel substrate measured at room temperature.     

High Temperature Oxidation of Micro-alloyed Steel and Its Scale Adhesion

The present work investigated the high temperature oxidation behaviour of the micro-alloyed steel and the adhesion of thermal oxide scale to its steel substrate. Oxidation testing was conducted at 815 °C in oxygen without and with 17.9% v/v water vapour. The oxidation kinetics in the two atmospheres were parabolic with similar rate constants, i.e. 1.13 × 10^?9 and 1.17 × 10^?9 g² cm^?4 s^?1 for the sample oxidised in oxygen without and with water vapour, respectively. The XRD peaks for wustite, magnetite, Ti-doped magnetite and titanium carbide were detected for the sample oxidised in oxygen. For the sample oxidised in the humidified atmosphere, Ti-doped magnetite was dominantly observed, additionally with titanium carbide. A tensile testing machine equipped with an optical lens was used to monitor scale failure during straining. For the sample oxidised for 1 min, the strain initiating the first spallation of the steel oxidised in the humidified oxygen was 1.74 ± 0.14%. This strain was higher than the strain initiating the first spallation of the steel oxidised in oxygen which was 1.00 ± 0.04%, indicating the improved adhesion of scale formed in the atmosphere containing water vapour. Mechanisms of water vapour effect on scale adhesion are discussed.