Reducing of heat loss of rubber compound using natural zeolite filler: effect of partially substitution of fillers on compound properties

The main objective of this work was reducing the heat loss of styrene butadiene rubber by partial substitution of carbon black with natural zeolite as a filler. Reducing the usage of carbon black in the rubber industry is a good strategy to decrease fossil fuel usage and global warming. There are different mineral fillers like silica and clay to be used instead of carbon black. Effect of application of natural zeolite on reducing the heat loss of rubber compound based on SBR was investigated by melt mixing of natural zeolite in rubber matrix in an internal mixer. Natural zeolite was selected as 5, 10, 15, and 20 phr. Carbon black was partially substituted with zeolite and the effect of natural zeolite content and structure on different aspects of the compound including heat buildup, hardness, elongation, and modulus were evaluated. It was shown that although cross-link density and mechanical properties of the compounds decreased a little, but a significant improvement was observed in the fatigue resistance of the compounds beside a favorable decrease in the heat buildup and abrasion loss with an increase in the natural zeolite loading. The rate of improvement in properties was slowed down at zeolite contents higher than 5 phr.     

An improved mechanism for capacity payment based on system dynamics modeling for investment planning in competitive electricity environment

Many countries have experienced restructuring in their electric utilities. This restructuring has presented the power industries with new challenges, the most important of which is long-term investment planning under uncertain conditions. This paper presents an improved mechanism for capacity payment. The mechanism has been investigated based on system dynamic modeling. In our proposed mechanism, generators will recover a part of their investment through capacity payment. While the payment for any plant remains constant during the operation period, it depends on the investment needed to build it. The main factors affecting long-term planning have been considered in our model. The approach can be used to investigate the effects of fixed as well as variable capacity payment in market investment. We used the probability density function of load as a new concept to calculate average market price. Delays in unit constructions, estimation of demand, and market capacity growth during construction periods have been included in the proposed algorithm as parameters, which affect the regulator's decision for changing capacity payment. The model can be used by regulators to investigate strategies that may affect the fluctuations in the market.     

Synthesis and thermal stability of polystyrene and poly(vinyl chloride) coated with polythiophene and modified with Fe2O3 nanoparticles

In this study, polystyrene and poly(vinyl chloride) particles were coated successfully with polythiophene in aqueous media. These nanocomposites were prepared in situ by polymerization of thiophene in the presence of FeCl₃ as an oxidant and poly(vinyl pyrrolidone) as a surfactant. The effect of Fe₂O₃ nanoparticles on the characteristics of products such as thermal stability and morphology was investigated. The chemical structure, morphology, and thermal stability of these core‐shell nanocomposites were studied by Fourier‐transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, and thermogravimetric analysis. Thermal stability of the nanocomposites was compared and indicated that the thermal stability of polythiophene/polystyrene was better than the polythiophene/poly(vinyl chloride) nanocomposite. Also, the presence of Fe₂O₃ nanoparticles can drastically increase the thermal stability of polythiophene nanocomposites. J. VINYL ADDIT. TECHNOL. 20:212–217, 2014. © 2014 Society of Plastics Engineers     

Iterative step‐by‐step procedure for optimal placement and design of viscoelastic dampers to improve damping ratio

In this study, an iterative step‐by‐step procedure is proposed for optimal placement and design of viscoelastic dampers in order to achieve a target damping ratio based on simple equations and quick estimation. Through the procedure, the dampers are placed one by one in stories with maximum interstory drift at each sequence. Effect of lateral stiffness of added dampers and consequent changes in frequency of the structure as well as changes in damping characteristic of the structure after adding each damper are also considered at each sequence. In order to achieve an economical design, dampers are designed according to the lateral stiffness at each story of the main structure instead of using identical dampers in all stories. During the whole procedure, a time‐history analysis is performed at each sequence. Two numerical examples, including an 8‐story and a 15‐story building, are presented. The results indicate that optimal arrangement of dampers has a considerable influence on reduction of roof displacement up to 25% compared to uniformly distributed arrangement of dampers. In addition, with optimal arrangement, the number of dampers needed to achieve a specific interstory drift is significantly reduced, and the structural damping ratio is improved to a target value, reflecting global optimality of the proposed method.     

Sustainability in highrise building design and construction

This paper presents a review of the recent literature on sustainability in construction and design with a focus on highrise buildings. The paper is divided into the following main sections: energy consumption, environmental effects and green practices for highrise buildings. A number of concepts in sustainable design are reviewed including passive solar design, renewable energy resources, cogeneration and tri‐generations, embodied energy reduction, net zero energy building, carbon emission reduction, envelope environment quality, green materials, efficient mechanical design and innovative structural systems. Their applications in a dozen signature and iconic structures are described. In order to achieve net zero energy in a new highrise building, first, multiple green solutions need to be evaluated using two categorical solutions: passive solar and envelop environment design and renewable energy resources along with efficient energy generators. Next, a robust optimization algorithm should be used to select the optimum set of solutions. This is worth pursuing in future sustainable design of highrise buildings because they are massive and complex structures with many components. Copyright © 2016 John Wiley & Sons, Ltd.     

A Complete Experimental Investigation on The Rheological Behavior of Silver Oil Based Nanofluid

In this study, thermo‐physical properties including thermal conductivity, viscosity, density and specific heat capacity of an oil based nanofluid including silver as to be nanoparticles have been experimentally studied. The results indicate an enhancement in thermal conductivity which was depended on bulk temperature and volume fraction of utilized nanofluids. Viscosity data show a significant increment through volume fraction increasing. In addition, the specific heat capacity and density of nanofluids were studied experimentally and it was found that, all measured rheological properties of these nanofluids, were not in agreement to published correlations.     

A comparative study for synthesis methods of nano-structured (9Ni–2Mg–Y) alloy catalysts and effect of the produced alloy on hydrogen desorption properties of MgH2

9Ni–2Mg–Y alloy powders were prepared by arc melting, induction melting, mechanical alloying, solid state reaction and subsequent ball milling processes. The results showed that melting processes are not suitable for preparation of 9Ni–2Mg–Y alloy due to high losses of Mg and Y. Therefore, 9Ni–2Mg–Y alloy powder was prepared by three methods including: 1) mechanical alloying, 2) mechanical alloying + solid state reaction + ball milling, and 3) mixing + solid state reaction + ball milling. The prepared 9Ni–2Mg–Y alloy powders were compared for their catalytic effects on hydrogen desorption of MgH₂. It is found that 9Ni–2Mg–Y alloy powder prepared by mechanical alloying + solid state reaction + ball milling method has a smaller particle size (1–5 μm) and higher surface area (1.7 m² g⁻¹) than that of other methods. H₂ desorption tests revealed that addition of 9Ni–2Mg–Y alloy prepared by mechanical alloying + solid state reaction + ball milling to MgH₂ decreases the hydrogen desorption temperature of MgH₂ from 425 to 210 °C and improves the hydrogen desorption capacity from 0 to 3.5 wt.% at 350 °C during 8 min.     

Al2O3–Water nanofluid heat transfer and entropy generation in a ribbed channel with wavy wall in the presence of magnetic field

In this article, a parametric study is conducted to evaluate heat transfer enhancement in a ribbed channel containing Al₂O₃–Water nanofluid with wavy wall. The physical domain is under the influence of the magnetic field that creates a negative force against the working fluid to move. Nanofluid with higher temperature enters the cool ribbed duct and heat is exchanged along the walls of channel. The effects of the dominant parameters including number of the blocks, solid volume fractions of nanofluid, Hartmann number, Reynolds number, and different states of amplitude sine waves are numerically tested on the local and average Nusselt number, skin friction, and total entropy generation. Excellent agreement between present study and previous literature is observed. It is found that, an augmentation in magnetic field will result in higher values of both local and average Nusselt number accompanying with bigger values of skin friction and entropy generation. Computations illustrate that, increasing the solid volume fraction of the Al₂O₃ nanoparticles will raise the Nusselt number and total entropy generation rate but its effect on the skin friction is negligible. Also, numerical results imply that increasing amplitude sine waves of the geometry has incremental effect on the Nusselt number and skin friction but its effect on the total entropy generation rate is not so clear. Moreover, by adding number of the used blocks in the presence of magnetic field, the local Nusselt number experiences more jumps but it does not increase the average Nusselt number, necessarily. In addition, using more blocks increases skin friction but it has a reverse effect on the total entropy generation rate.     

Evaluation of hydrogen permeation through standalone thermally sprayed coatings of AISI 316L stainless steel

This research evaluates hydrogen permeation and its diffusion characteristics through standalone thermally sprayed coatings of AISI 316L stainless steel. The effects of various charging currents and other parameters on hydrogen diffusion coefficient were scrutinized using electrochemical hydrogen permeation tests. Hydrogen permeation through the thermally sprayed coatings displayed anomalous behavior such that a maximum pinnacle was observed in the permeation curves, attributed to heavily trapped hydrogen atoms in the delayed surface cracks. Therefore, new diffusion parameters were defined for modeling of the anomalous permeation curves. The fitted diffusion parameters were consistently identified, and hence, the model perfectly explained experimental data. The results showed that the increase in charging current caused fast activation and development of surface cracks. The measured diffusion coefficient of hydrogen in the stainless steel thermally sprayed coating was relatively high because the microstructure of the coating contained some ferritic phases and dense dendritic structure, which configure fast diffusion paths.