Effect of Process Parameters on Microstructure and Micro-hardness of AZ91/Al2O3 Surface Composite Produced by FSP

In this article, the effects of three different sizes of Al₂O₃ particles in the friction stir processing on grain size, cluster size, microstructure, and micro-hardness of as-cast magnesium alloy AZ91 were investigated. Moreover, the effects of two types of tool geometries and number of passes on the mentioned parameters were considered. Effect of mentioned parameters on microstructure, grain refinement, and micro-hardness profile in the friction stirred zone of the specimens was compared by as-cast received form and also friction stir processed (FSPed) specimens without particles. Microstructural characterization of the materials revealed reasonably uniform distribution of Al₂O₃ reinforcement and significant grain refinement. Hardness studies revealed that the incorporation of nano- and micro-size Al₂O₃ particulates in magnesium matrix led to a simultaneous increase in hardness.     

Damping and microstructure of fly ash-based geopolymers

As environmentally-friendly materials, geopolymers have the potential to replace ordinary Portland cement (OPC) for the construction of railway sleepers and multi-flue chimneys, where the vibration control capabilities of the material must be considered. The critical damping value (ξ) is the main parameter in relation to vibration reduction. In this study, the traditional logarithmic decrement technique was used to measure the ξ of geopolymers. Geopolymers were prepared by activating fly ash using alkali solutions with different SiO₂/Na₂O ratios. The results show that the ξ of the geopolymers is similar to that of the OPC counterpart. Finite element analysis (FEM) based on the Rayleigh damping model was conducted to replicate the test results, and scanning electron microscopy and mercury-intrusion porosimetry were used to study the microstructure of the geopolymers. A discussion of the possible damping mechanisms based on the microstructural investigation and the FEM analysis is presented.     

Optimizing parameters affecting synthetize of CuBTC using response surface methodology and development of AC@CuBTC composite for enhanced hydrogen uptake

CuBTC, a widely studied metal-organic framework, is a promising candidate for industrial applications owing to its easy synthesis procedure and excellent textural properties. In this research CuBTC was synthesized by solvothermal method with the purpose of hydrogen uptake. Response surface methodology (RSM) was employed in order to determine the optimum synthesis condition with the highest hydrogen capacity. Amount of ligand, volume of solvent, synthesis temperature, and synthesis time were chosen as independent variables, while the amount of hydrogen uptake was selected as the response. Subsequently, activated carbon (AC) was incorporated within the optimized CuBTC structure as a “void space filling agent” and adsorption behavior of AC@MOF composite was evaluated from the view point of different AC contents. It was observed that the hydrogen uptake of AC@CuBTC composite was increased compared to bare CuBTC samples. This finding could be attributed to effective utilization of micropore volume of CuBTC structure by AC incorporation.     

Review of materials and manufacturing options for large area flexible dye solar cells

This review covers the current state of the art related to up-scaling and commercialization of dye solar cells (DSC). The cost analysis of the different components and manufacturing of DSC gives an estimate on the overall production costs. Moreover, it provides an insight in which areas improvement is needed in order to reach significant cost reductions. As a result of the cost analysis, transferring the technology to flexible substrates and employment of simple roll-to-roll production methods were found the key issues. The focus of this work was set accordingly. In this work, appropriate materials along with their unique fabrication processes and different design methods are investigated highlighting their advantages and limitations. The basic goal is to identify the best materials and preparation techniques suitable for an ideal roll-to-roll process of flexible dye solar module fabrication as well as the areas where further development is still needed.     

A comprehensive approach in green space site planning: an application of a three-stage multi-criteria decision support system

ABSTRACT

To green space site planning, this paper deals with ‘Regional Park site planning’, and presents a concept of ‘criteria screening and selection’. Through a three-stage decision support system, this paper, firstly, identifies general criteria for green space site planning and then comes up with specific criteria for Regional Park site planning within Shiraz metropolitan area. The paper contributes to the literature by improving the existing approaches of criteria selection, and points out that the list of selection criteria aggregated from literature should be adapted to case specific characteristics before being used to select a new location for public green spaces.     

Effect of modified whey protein concentrates on empirical and fundamental dynamic mechanical properties of frozen dough

Dairy byproduct proteins are considered natural functional additives having the ability to interact with the starch and gluten network in a dough system and thus behave as dough improvers. Native whey proteins have negative effect in bread making so whey protein concentrates modified to increase viscosity in solution (mWPC) might overcome undesirable weakening of the gluten network which usually occurs in frozen dough products during prolonged times in frozen storage. The objective of this research project was to determine the effect of mWPC on empirical and fundamental dynamic rheological properties of wheat flour dough. The results for empirical rheological studies showed that addition of mWPC had significant effects on mixographic parameters and also increased values of mixing time and peak height percentage. The results for the fundamental mechanical properties of the frozen dough revealed an increase in the values of G′ with the increase in the frequency, along with an upward trend with increasing temperature, but the highest values were obtained after cooling. Addition of mWPC in the dough treatments induced softening in the dough system, as shown by the decrease in the values of the viscoelastic moduli. Rheological and textural changes in the bakery products made from frozen dough could be imparted by the incorporation of modified whey protein concentrates as dough improvers.