Design of a Compact Monopole Antenna for UWB Applications

In this paper, a low cost, highly efficient and low profile monopole antenna for ultra-wideband (UWB) applications is presented. A new inverted triangular-shape structure possessing meander lines is designed to achieve a wideband response and high efficiency. To design the proposed structure, three steps are utilized to achieve an UWB response. The bandwidth of the proposed antenna is improved with changing meander lines parameters, miniaturization of the ground width and optimization of the feeding line. The measured and simulated frequency band ranges from 3.2 to 12 GHz, while the radiation patterns are measured at 4, 5.3, 6 and 8 GHz frequency bands. The overall volume of the proposed antenna is 26 × 25 × 1.6 mm3 ; whereas the FR4 material is used as a substrate with a relative permittivity and loss tangent of 4.3 and 0.025, correspondingly. The peak gain of 4 dB is achieved with a radiation efficiency of 80 to 98% for the entire wideband. Design modelling of proposed antenna is performed in ANSYS HFSS 13 software. A decent consistency between the simulated and measured results is accomplished which shows that the proposed antenna is a potential candidate for the UWB applications.     

A CPW-fed wearable antenna at ISM band for biomedical and WBAN applications

Wireless Networks - In this paper, a Mercedes-Benz logo antenna with a metal plate located at an optimized distance from the proposed antenna is introduced as a wearable antenna to operate in the...     

A GDQ approach to thermally nonlinear generalized thermoelasticity of disks

Generalized thermoelasticity response of an annular disk subjected to thermal shock on its inner surface is analyzed in this research. The Lord–Shulman theory, which accounts for one relaxation time in the conventional Fourier law, is used to avoid the infinite speed of thermal wave propagation. Unlike the other available works in which the first law of thermodynamics is linearized, the nonlinearity arising from the temperature change is taken into consideration. The first law of thermodynamics in this case becomes nonlinear and the analysis under such formulation is called thermally nonlinear. Two coupled equations, i.e., the radial displacement wave equation and temperature wave propagation equation are obtained. These equations and the associated boundary conditions are discreted through the generalized differential quadrature method. Solution of the time-dependent system of equations is obtained using the Newmark time marching scheme and the successive Picard method. Numerical results are provided for both thermally linear and thermally nonlinear temperature and radial displacement wave propagations. Parametric studies reveal that at higher temperature levels, thermally nonlinear first law of thermodynamics should be considered instead of thermally linear one. Furthermore, the higher the coupling parameter and/or relaxation time, the higher the divergence of thermally nonlinear-/linear-based results.     

Static and dynamic analysis of an FGM doubly curved panel resting on the Pasternak-type elastic foundation

The static, dynamic, and free vibration analysis of a functionally graded material (FGM) doubly curved panel are investigated analytically in the present paper. The FGM Panel is originated from a rectangular planform and its principle curvatures are considered to be constant. All mechanical properties of the FGM panel are assumed to vary continuously through the thickness according to a power law formulation except Poisson’s ratio, which is kept constant. A Pasternak-type elastic foundation containing damping effects is considered to be in contact with the panel during deformation. The elastic foundation reacts in both compression and tension. Equations of motion are established based on the first order shear deformation and the modified Sanders shell theories. Following the Navier type solution, the established equations are reduced to time-dependent ordinary differential equations. Using the Laplace transform, the time-dependency of the problem is eliminated. The solutions are obtained analytically in the Laplace domain and then are inverted to the time domain following an analytical procedure. Finally, the analytical results are verified with those reported in the literature.     

The Effects of Doping on Crystal Structure, Magnetic and Microwave Properties of SrFe12−2x La x (Mn0.5Zr0.5) x O19 Nanoparticles

M-type hexagonal ferrite powders, SrFe_12?2x La _x (Mn_0.5Zr_0.5) _x O₁₉ (x=0.0, 0.2, 0.4, 0.6, 0.8), have been synthesized by the coprecipitation method. The X-ray diffraction, field emission scanning electron microscope, vibrating sample magnetometer and vector network analyzer all were used to characterize the structure of the samples, their magnetic and microwave properties. The value of the saturation magnetization increased up to x=0.2 and then slowly decreased with increasing doping. A decreasing trend was observed in the value of coercivity with increasing substitution degree, and its value reached a minimum of 2420 Oe for x=0.6 and then increased with further increasing x. The relative complex permittivity and permeability of the composite powders were investigated in the X-band frequency range (8.2–12.4 GHz).     

Macro- and Microemulsion Silicone Softeners on Polyester Fibers: Evaluation of Different Physical Properties

In this research, polyester fabrics were treated with three concentrations (10, 20 and 30 g/L) of macro- and microemulsions of silicones in water at 30 °C by the padding method. The treated fabrics were then dried/cured at 130 °C for 40 s. Some of the physical and chemical properties of the samples are discussed. The drapeability of treated samples was lower and found to depend on the silicone particle size. Moisture absorbency of treated samples was also lower. Colorimetric properties of softener treated fabrics were evaluated with a reflectance spectrophotometer. Scanning electron microscope (SEM) examinations showed an aggregation of silicone particles on the fiber surface.

Palladium Nanoparticles Supported on Poly(2-hydroxyethyl methacrylate)/KIT-6 Composite as an Efficient and Reusable Catalyst for Suzuki–Miyaura Reaction in Water

Pd nanoparticle-poly(2-hydroxyethyl methacrylate)/KIT-6 (Pd-PHEMA/KIT-6) composite was fabricated through in situ polymerization method and was evaluated as a novel heterogeneous catalyst in Suzuki–Miyaura cross coupling reactions of aryl halides and phenylboronic acid in an aqueous medium. The catalyst was characterized by XRD, FT-IR, UV–Vis, TG, BET, and TEM techniques. The results revealed that the supported catalyst Pd-PHEMA/KIT-6 exhibited excellent catalytic activity for the coupling of aryl iodides, aryl bromides, and aryl chlorides. This heterogeneous catalyst could be reused at least nine times without any decrease in activity.     

Assay of Total Mercury in Commercial Food Supplements of Marine Origin by Means of DLLME/ICP-AES

In this work, we have developed a sensitive and cost-effective preconcentration and quantification methodology for total mercury (Hg) at trace levels in food supplements of marine origin. Dispersive liquid–liquid microextraction was successfully employed for the preconcentration of mercury at trace levels prior to inductively coupled plasma atomic emission spectrometry. The mercury was extracted as mercury-1, 5-diphenyl-3-formazathiol complex, at pH 1.0 mediated by multidroplet formation of microextraction solvent assisted by disperser solvent. The lower limit of detection obtained under the optimal conditions was 0.24 μg L⁻¹. The calibration graphs were linear up to 500 μg L⁻¹. The precision of the method in terms of relative standard deviation was 4.8% for the concentration of 100 μg L⁻¹. In order to validate the proposed method, a certified reference material RTC-QCI-049 was analyzed with the proposed procedure. Moreover, potential interference by 20 species was also evaluated.     

Effect of pulsed plasma nitriding on mechanical and tribological performance of Ck45 steel

We studied the mechanical properties and wear performance of AISI 1045 (Ck45) carbon steel under the influence of pulsed plasma nitriding. The treatments were performed at temperatures of 500 and 550 degrees C in N2:H2 gas ratios of 1:3 and 3:1 and the working pressure of 10 mbar for 1 to 4 hours. Samples were examined by X-ray diffraction, optical, electron and atomic force microscopy, microhardness tests, roughness measurements and wear tests. Nitride layers were mainly composed of epsilon-(Fe2-3N) or gamma'-(Fe4N) depending on the gas ratio and/or temperature and time. When the nitriding time is increased, the composition of the compound layer varies from monophase gamma'-(Fe4N) to the two phase of epsilon-(Fe2-3N) and gamma'-(Fe4N). The highest thickness and hardness of the layers were obtained at 550 degrees C in the N2:H2 gas ratios of 3:1 for 4 h. The topographical evolution and surface roughness of the samples showed that all the roughness parameters increase with increasing the temperature. The friction coefficient of all samples was higher than that of untreated material. Wear performance of all nitrided samples was significantly better than that of untreated material.