Preparation and investigation of properties of deproteinized natural rubber nanocomposites incorporating functionalized nano-alumina by in situ emulsion polymerization

The present study reports the preparation, characterization, and investigation of properties of DNR/f-Al₂O₃ nanocomposites through an in situ emulsion polymerization technique. The method consists of the dispersion of pretreated nano-alumina (f-Al₂O₃ NPs) onto deproteinized natural rubber (DNR) latex, followed by the polymerization reaction with the K₂S₂O₈/K₂S₂O₅ redox initiation system, after deproteinization of natural rubber using urea in the presence of a surfactant. To improve the compatibility and reactivity of the nanofillers with DNR latex, the nano-alumina surface was treated with 3-methacryloxypropyltrimethoxysilane (MPS) to produce f-Al₂O₃ NPs. The thermo-gravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy approved that the MPS was bound onto the surface of Al₂O₃ NP. The resulting nanocomposites were characterized using standard techniques for physical properties and structural morphology, including X-ray diffraction (XRD) analysis, FTIR spectroscopy, scanning electron microscopy (SEM), and TGA. The SEM images showed a homogeneous distribution of f-Al₂O₃ NPs throughout DNR matrix. Due to such monodisperse particles, the DNR/f-Al₂O₃ nanocomposite films revealed significant enhancement in thermal stability with increasing nano-alumina loading as compared with the neat DNR.     

The Bioactivity and Toxicological Actions of Carvacrol

Carvacrol is a monoterpenic phenol produced by an abundant number of aromatic plants, including thyme and oregano. Presently, carvacrol is used in low concentrations as a food flavoring ingredient and preservative, as well as a fragrance ingredient in cosmetic formulations. In recent years, considerable research has been undertaken in an effort to establish the biological actions of carvacrol for its potential use in clinical applications. Results from in vitro and in vivo studies show that carvacrol possess a variety of biological and pharmacological properties including antioxidant, antibacterial, antifungal, anticancer, anti-inflammatory, hepatoprotective, spasmolytic, and vasorelaxant. The focus of this review is to evaluate the existing knowledge regarding the biological, pharmacological, and toxicological effects of carvacrol.     

Numerical analysis of the nonlinear performance of concentrically braced frames under cyclic loading

Concentrically braced frames (CBFs) are widely used as lateral-load resisting system in steel structures. This study examines the effects of different parameters especially those associated with connections, on the behavior of CBFs. A single bay, singlestory frame is used to evaluate the interaction between structural members. Nonlinear analyses using a detailed inelastic finiteelement model (FEM) are carried out to study the behavior of frames subjected to cyclic loading. Models are designed based on seismic codes and analyzed to evaluate the performance of both SCBFs and OCBFs. The equivalent plastic strain concept is used to determine the ductility capacity and to predict fracture and failure in these models. Results show that the seismic performance of CBFs, which are designed according to current provisions can be improved by configuring the details of gusset plate connections in a way that inelastic demands are balanced in middle of brace and gusset plate corners.     

Reducing CO2 emission from exhaust gases using molten carbonate fuel cells: a new approach

The aim of this study is to couple molten carbonate fuel cell (MCFC) stack with integrated gasification combined cycle fed by refinery residues, to remove CO₂ from gas turbine exhaust gases that have CO₂ emission rate of 14,200 ton/year. By applying multi-objective optimisation (MOO) using genetic algorithm, the optimal values of operating load and the corresponding values of objective functions are obtained. The MOO of the MCFC system regarding two scenarios is performed. The first scenario is minimisation of cost of electricity (COE) and CO₂ emission rate. Objective functions of the second scenario are the same as in the first scenario while CO₂ tax is taken into account. Results show that the second scenario has 29.5% lower average optimal COE and 2.5% lower average emission rate in comparison with the first scenario. A sensitivity analysis is also performed to study the effect of fuel price and CO₂ tax variations on optimal solutions.     

Study of Structural and Magnetic Properties of Superparamagnetic Fe3O4–ZnO Core–Shell Nanoparticles

In this work, Fe₃O₄–ZnO core–shell nanoparticles have been successfully synthesized using a simple two-step co-precipitation method. In this regard, Fe₃O₄ (magnetite) and ZnO (zincite) nanoparticles (NPs) were synthesized separately. Then, the surface of the Fe₃O₄ NPs was modified with trisodium citrate in order to improve the attachment of ZnO NPs to the surface of Fe₃O₄ NPs. Afterwards, the modified magnetite NPs were coated with ZnO NPs. Moreover, the influence of the core to shell molar ratio on the structural and magnetic properties of the core–shell NPs has been investigated. The prepared nanoparticles have been characterized utilizing transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and vibrating sample magnetometer (VSM). The results of XRD indicate that Fe₃O₄ NPs with inverse spinel phase were formed. The results of VSM imply that the Fe₃O₄–ZnO core–shell NPs are superparamagnetic. The saturation magnetization of prepared Fe₃O₄ NPs is 54.24 emu/g and it decreases intensively down to 29.88, 10.51 and 5.75 emu/g, after ZnO coating with various ratios of core to shell as 1:1, 1:10 and 1:20, respectively. This reduction is attributed to core–shell interface effects and shielding. TEM images and XRD results imply that ZnO-coated magnetite NPs are formed. According to the TEM images, the estimated average size for most of core–shell NPs is about 12 nm.     

Analytical layerwise free vibration analysis of circular/annular composite sandwich plates with auxetic cores

In the present research, free vibration of circular and annular sandwich plates with auxetic (negative Poisson’s ratio) cores and isotropic/orthotropic face sheets is investigated for different combinations of the boundary conditions. To ensure that the results are accurate and reliable, a global–local layerwise plate theory is employed instead of the traditional equivalent single-layer theories. The governing equations are derived based on Hamilton’s principle and solved using a Taylor transform whose center is located at the outer radius of the plate. Due to this hint, the resulting semi-analytical solution can be employed for both circular and annular sandwich plates. After investigation of vibration behavior of a single-layer annular auxetic plate, a comprehensive parametric study including evaluation of effects of the auxeticity for sandwich plates with isotropic and orthotropic face sheets, symmetric and asymmetric layups, different core to sheet thickness, radius to thickness, and inner to outer radius ratios, and various boundary conditions, is carried out. Results show that unlike the single-layer auxetic plates that exhibit a transition state, the auxeticity may considerably increase the natural frequencies and rigidities of the circular/annular sandwich plates, especially when the boundary conditions induce higher rigidity in the plate or when the fibers are along the radial direction. Accuracy of results of the employed layerwise theory and the proposed semi-analytical solution is verified by comparing the results with those of the three-dimensional theory of elasticity extracted from the ABAQUS software.     

A semi-analytical solution for free vibration of variable thickness two-directional-functionally graded plates on elastic foundations

The present paper investigates free vibration of variable thickness two-directional-functionally graded circular plates, resting on elastic foundations. The results are obtained for clamped, free, and simply supported edge conditions. Variations of the material and geometrical parameters are monitored by five distinct exponential functions. Therefore, the resulted non-dimensional solution may be used for a wide range of the practical problems. Mindlin’s plate theory and the differential transformation technique are used to obtain the governing equations of the natural frequencies of the circular plates. Effects of variations of the material properties in the radial and thickness directions, geometric parameters (e.g., the thickness-to-radius ratio in the center of the plate), stiffness parameters of the foundation, and various boundary conditions on the natural frequencies are investigated. Results reveal that by choosing a suitable combination of the material properties, the free vibration behavior of the thick plates may be enhanced without the need to change the geometric parameters.     

Parkinson’s Disease Detection Using Biogeography-Based Optimization

In recent years, Parkinson's Disease (PD) as a progressive syndrome of the nervous system has become highly prevalent worldwide. In this study, a novel hybrid technique established by integrating a Multi-layer Perceptron Neural Network (MLP) with the Biogeography-based Optimization (BBO) to classify PD based on a series of biomedical voice measurements. BBO is employed to determine the optimal MLP parameters and boost prediction accuracy. The inputs comprised of 22 biomedical voice measurements. The proposed approach detects two PD statuses: 0-disease status and 1- good control status. The performance of proposed methods compared with PSO, GA, ACO and ES method. The outcomes affirm that the MLP-BBO model exhibits higher precision and suitability for PD detection. The proposed diagnosis system as a type of speech algorithm detects early Parkinson’s symptoms, and consequently, it served as a promising new robust tool with excellent PD diagnosis performance.     

Laser-assisted preparation of C3N4/Fe2O3/Au nanocomposite: a magnetic reusable catalyst for pollutant degradation

Clean Technologies and Environmental Policy - Assorted common contaminants namely organic dyes and nitro compounds are generated by various industries and have caused alarming problems for the...