High‐gain waveguide slot antenna using simple parasitic patch's cover

In this article, a way based on using miniature patch cells has been proposed to increase gain and bandwidth of the waveguide slot antenna. In the presented approach, an array of 3 × 3 metal patches has been used as superstrate to create Fabry Perot theorem resonance cavity. The proposed high ‐ gain and simple antenna is composed of a conventional waveguide slot antenna with an extended broad wall, and an array of parasitic patches which are symmetrically placed over slot at a distance of about free ‐ space half wavelength. The slot has been created on a rectangular waveguide WR90 with 22.86 mm × 10.16 mm × 52.5 mm dimension, also extended wall dimension is 2λ₀ (67.5 mm) × 3λ₀ (107 mm). It has been shown that the proposed structure compared with the conventional waveguide slot antenna improves antenna peak gain from 6.5 to 16.5 dBi and, in the same time, antenna bandwidth from 11% to around 16.2%. More important advantage of the proposed antenna is that unlike to other Fabry Perot antenna with the same gain, there is not any dielectric material in the proposed structure. A prototype antenna was simulated, fabricated, and measured for verification.     

A novel green synthesis of zero valent iron nanoparticles (NZVI) using three plant extracts and their efficient application for removal of Cr(VI) from aqueous solutions

In the present study, NZVI particles were synthesized from the plant extracts including Rosa damascene (RD), Thymus vulgaris (TV), and Urtica dioica (UD). The FTIR arspectshowed that polyphenols, proteins and organic acids which serve as reducing and stabilizing agents play a significant role in the synthesis of NPs and reduce the possibility of aggregation of NPs compared to chemical techniques of NPs synthesis. The amount and type of compounds in plant extracts affect the structure and also agglomeration of NPs after adsorption process. Based on the results, the highest removal efficiency occurred at pH 2. With increase in contact time and amount of dose, the percentage removal increases. Inversely, increase of initial concentration of Cr(VI) decreases the removal efficiency of the contaminant. These nanoparticles have a high adsorption capacity. Accordingly, by applying a dose of 0.2 g/l and contact time of 10 min, the three NPs yielded >90% removal efficiency. Also, for 1 min contact time, the percentage removal was 94.87%, 83.48% and 86.8% for RD-Fe, UD-Fe and TV-Fe, respectively. By an increase to 25 min, the removal percentage reached to 100% for TV-Fe and UD-Fe. Moreover, 30 min was required to remove Cr(VI) completely by RD-F.     

Design, optimization and manufacturing of wood–plastic composite pallet

This paper presents the application of an innovative method of optimization to the design of an I-shape profile used in a wood–plastic composite (WPC) pallet. The pallet was made via assembling three WPC extruded profiles manufactured in the extrusion process. The middle profile was considered to be I-shaped, a design which known to have a high load bearing capability. However, due to the characteristics of WPC products, a delicate design and thus optimization is highly required. A multi-objective-optimization program of micro-genetic algorithm was developed in Visual Basic environment to accomplish the optimization task. By specifying the dimensional variables of the profile section and applying finite elements analysis on the profile and then using the optimization program, an optimal profile section was obtained. The objective was to withstand the maximum load while yielding the minimum deflection and mass. The optimized design was used to manufacture a die and then the product was produced to validate the design. The comparison of simulations and experimental results indicted that the given design method is reasonably reliable. The final mass of the produced pallet was less than 20 kg whereas its strength against bending and distributed smooth restraint loading were greater than 500 kg and 2000 kg, respectively.     

Study on the chemical stability of the synthesized TiCx in Ti-Al-C system after immersion in the HF + H2O2 solution

The aim of this study is to investigate the phase stability of the prepared TiC_x in Ti-Al-C system after immersion in the mixture of hydrofluoric acid (HF) and H₂O₂. The powders were immersed in the solution for different period times of 24, 48 and 96?h. The phase change of powders after different immersion times was studied by X-ray diffraction (XRD). The morphology evolution was detected by the field-emission scanning electron (FESEM). Moreover, atomic absorption spectroscopy (AAS) analysis was employed to study the changes in the chemical composition of solutions. The XRD results showed that by increasing the immersion time, gradually, the TiC_x decomposed. It was also found that the selection oxidation aluminum occurred and the Al₂O₃ was the main final product of treatments. The FESEM images also confirmed the XRD results and after immersion of the powders into the solutions the rod-like and sheet-like morphology of the Al₂O₃ particles were obtained.     

Preparation of Ni0.1Mg0.9O nanocrystalline powder and its catalytic performance in methane reforming with carbon dioxide

Ni_0.1Mg_0.9O nanocrystalline powders were prepared by surfactant assisted precipitation method and employed as catalyst in dry reforming. The powders were characterized by using XRD, BET, SEM, TGA/DSC and TPR techniques. The results showed that the surfactant to metal mole ratio affects the textural properties. Increasing in surfactant to metal mole ratio increased the specific surface area and decreased the crystallite and particle size. The Ni_0.1Mg_0.9O with the highest surface area (115.39 m² g^?1) was employed as catalyst in dry reforming. This catalyst showed a high catalytic activity and stability during 122 h time on stream without any decrease in methane conversion.     

An integrated thin-walled steel skeleton structure (two full scale tests)

The increased popularity of cold-formed thin-walled steel sections in housing construction has lead to an increased interest in the development of thin-walled frame buildings in accordance with seismic requirements. This paper investigates appropriate details for the main frame elements of a thin-walled building structure. Some of the proposed details are tested by two full scale one-storey frames under gravity and lateral cyclic loads. The results show that this type of structure offers a good potential for earthquake resistant construction, but more thorough studies are needed.