Characterization of zinc sulfide (ZnS) nanoparticles Biosynthesized by Fusarium oxysporum

A variety of chemical and physical procedures could be used for the synthesis of metal sulfide nanoparticles. However, these methods suffer from some disadvantages including the use of toxic solvents, generation of hazardous by-products, and high energy consumption. In this work, zinc sulfide (ZnS) nanoparticles were synthesized through an environmentally and economically friendly method using the fungus Fusarium oxysporum. The ZnS nanoparticles were characterized using UV–visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Fluorescence spectroscopy. The obtained results demonstrated the presence of ZnS nanoparticles. Transmission electron microscopy (TEM), also determined their morphology as spherical, and their average size to be about 42 nm.     

A novel thermal decomposition method for the synthesis of ZnO nanoparticles from low concentration ZnSO4 solutions

In this research work, ZnO nanoparticles were prepared by direct thermal decomposition method with Zn₄(SO₄)(OH)₆·0.5 H₂O as a precursor. The precursor was calcinated in air for 1 h at 825 °C. Samples were characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), infrared spectrum (IR), and scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The XRD, EDS, and IR results indicated that the ZnO nanoparticles were pure. The average crystallite and particle size of the ZnO nanoparticles were estimated to be 87 nm and 92 nm by XRD and TEM, respectively. The SEM and TEM images showed that the ZnO nanoparticles were of spherical shape. The simplicity of the present method suggests its potential application at industrial scale as a cheap and convenient way to produce pure ZnO nanoparticles from low concentration ZnSO₄ solutions.     

Timoshenko beam model for buckling of piezoelectric nanowires with surface effects

This paper investigates the buckling behavior of piezoelectric nanowires under distributed transverse loading, within the framework of the Timoshenko beam theory, and in the presence of surface effects. Analytical relations are given for the critical force of axial buckling of nanowires by accounting for the effects of surface elasticity, residual surface tension, and transverse shear deformation. Through an example, it is shown that the critical electric potential of buckling depends on both the surface stresses and piezoelectricity. This study may be helpful in the characterization of the mechanical properties of nanowires and in the calibration of the nanowire-based force sensors.     

Investigation of the thermal comfort properties of knitted fabric produced from Estabragh (Milkweed)/cotton-blended yarns

In this research, the thermal comfort properties of a newly known fiber called Estabragh (Milkweed) have been investigated. Estabragh is a natural hollow fiber which is expected to provide excellent insulation properties due to their individual characteristics. Thermal comfort is one of the important fabric properties especially in the area of sport application which is considered in this research. For investigating this, 50–50% Estabragh/cotton-blended spun yarns was produced using short-staple spinning system. Two different sets of interlock-knitted samples using 100% cotton and Estabragh/cotton-blended yarns were produced individually on a flat knitting machine. Heat transfer rate, water vapor transmission, air permeability, and capillary absorption of produced fabrics were measured and compared. The results revealed that the vapor transmission rate through the knitted samples produced from Estabragh/cotton-blended yarns was 66.4% which is higher than that of the 100% cotton samples as 60.22%. It was also found that 100% cotton samples exhibited less moisture transfer rate than cotton/Estabragh samples. As far as heat transfer is concerned, it was concluded that the heat transfer ability of 100% cotton samples is higher than that of the Estabragh/cotton samples by about 47%. It was also shown that the capillary absorption of samples produced from Estabragh/cotton-blended yarns was higher than that of the 100% cotton samples. Compared to the 100% cotton samples, air permeability of Estabragh/cotton-knitted structures was found to be relatively low. The results totally proved that Estabragh fibers have a lot of advantages in order to be used in different fields of applications especially in sport areas.     

STUDY ON THE ACETYLENE HYDROGENATION PROCESS FOR ETHYLENE PRODUCTION: SIMULATION,MODIFICATION, AND OPTIMIZATION

In this study, an industrial acetylene hydrogenation unit is simulated utilizing three available kinetic models. The results are compared against six-day experimental data and the best model is selected. Effects of feed temperature and the amount of injected hydrogen on ethylene selectivity are also studied. According to the simulation results, the unit is not working under its optimum conditions. Furthermore, by reduction of the hydrogen flow rate to 52 kg/h, process selectivity is increased. In addition, a new approach is proposed to modify the hydrogenation process and reduce undesired by-products. In the simulation of the modified process, hydrogenation reactors temperature, hydrogen flow rate, and H-1/H-2 ratio were regulated as adjustable parameters for the process optimization. The simulation shows that ethylene selectivity increases by 12%, while acetylene concentration and hydrogenation reactor temperature remains within acceptable ranges. Such selectivity could be achieved at the hydrogen flow rate of 50 kg/h with H-1/H-2 ratio of 0.1/0.9.     

Preparation of ZIF-8—Pebax 1657 nanocomposite membranes for n-hexane/nitrogen separation as a representative of gasoline vapour recovery

Gasoline vapour emission is hazardous to both human health and the ecosystem and also results in capital loss, altogether revealing the necessity of its recovery. Some ZIF-8–Pebax flat nanocomposite membranes were fabricated by the method of solution casting and used for gasoline vapour recovery as represented by n-hexane vapour/nitrogen separation. Microporous ZIF-8 nanoparticles were synthesized and characterized by Fourier transform infrared (FTIR) and Brunauer–Emmett–Teller (BET) analysis. BET results revealed specific surface area, total volume, and average pore diameter of 940.8 m² · g⁻¹, 0.36 cm³ · g⁻¹, and 1.54 nm, respectively. Pure nitrogen and n-hexane vapour/nitrogen gas mixture permeabilities were measured through the membranes. There was a decline in both permeation rate and selectivity up to 5.0 wt.% of ZIF-8 loading and the next increment at their higher loadings to considerably more values that the pristine membrane. The maximum n-hexane vapour permeability and selectivity at 10.0 wt.% loading of ZIF-8 nanoparticles, the feed flow rate of 173 mL · min⁻¹, and permeate side pressure of −200 mbar were observed as 280.1 Barrer and 106.7, respectively, revealing 60.0% and 36.9% improvements compared with those of the pristine Pebax membrane. Observed 86%–92% n-hexane vapour recovery approves the successful application of the ZIF-8–Pebax nanocomposite membranes for n-hexane/nitrogen separation. The long-term separation performance of 5.0 wt.% ZIF-8 loaded nanocomposite membrane was improved by 76.5% compared with that of the pristine Pebax membrane.     

Highly selective ratiometric fluorescence determination of Eu3+ ion based on (4E)-4-(2-phenyldiazenyl)-2-((E)-(2-aminoethylimino)methyl)phenol

(4E)-4-(2-phenyldiazenyl)-2-((E)-(2-aminoethylimino)methyl)phenol (PAMP) was synthesized for the first time and used as a ratiometric fluorescent chemosensor for recognition of Eu³⁺ ions in acetonitrile solution. PAMP shows a fluorescent emission at 536 nm. When it forms a complex with Eu³⁺ ion, two new fluorescent enhancements at 418 and 496 nm appeared. In acetonitrile solution, the blue shift of fluorescent emission upon europium binding is due to the formation of a 1:1 metal ligand complex. The chemosensor shows a linear response toward Eu³⁺ in the range of 8.3 × 10^? 8 M to 8.3 × 10^? 6 M. The new fluorescent probe exhibits high selectivity toward Eu³⁺ ions over a large number of interfering cations.     

Autoregressive Filters for the Identification and Replacement of Bad Data in Power System State Estimation

The quadratic cost function J(x?) and the normalized residuals rN are used conventionally for identifying the presence and location of bad measurements in power system state estimation. These are "post estimation" tests and therefore require the complete re-estimation of system states whenever bad data is identified. This paper presents a pre-estimation filter for detection and identification of gross measurement errors. The basic function of this filter is to compare the measured value of a system variable with its predicted value obtained using an autoregressive (AR) model. If the difference exceeds a pre-determined threshold, the measured value is discarded in favor of the predicted value. Each measurement is processed by an AR filter before being used in the state estimation. The performance of the AR filter is tested against that of the J(x?) and rN tests and the results are reported in this paper. The principal advantage of the AR filtering scheme is its speed in bad data identification. Furthermore, it can be used to complement other bad data processing methods.     

Microwave nondestructive detection and evaluation of voids in layered dielectric slabs

A microwave nondestructive testing technique is discussed for detection and evaluation of voids in layered dielectric media backed by a conducting plate. This technique utilizes the phase properties of the effective reflection coefficient of the medium as a microwave signal penetrates inside the dielectric layers and is reflected by the conducting plate. Properties of the difference between this phase in the absence and presence of an air gap is investigated as a function of the void thickness, frequency, and dielectric properties of the layers. Utilizing a simple experimental apparatus measurements were also conducted, the results of which were compared with the theoretical predictions.