Oil Spill Cleanup from Sea Water by Sorbent Materials

Three sorbents were compared in order to determine their potential for oil spill cleanup. Polypropylene nonwoven web, rice hull, and bagasse with two different particle sizes were evaluated in terms of oil sorption capacities and oil recovery efficiencies. Polypropylene can sorb almost 7 to 9 times its weight from different oils. Bagasse, 18 to 45 mesh size, follows polypropylene as the second sorbent in oil spill cleanup. Bagasse, 14 to 18 mesh size, and rice hull have comparable oil sorption capacities, which are lower than those of the two former sorbents. It was found that oil viscosity plays an important role in oil sorption by sorbents. All adsorbents used in this work could remove the oil from the surface of the water preferentially.     

Using hash tables to manage the time-storage complexity in a point location problem: Application to explicit model predictive control

The online computational burden of linear model predictive control (MPC) can be moved offline by using multi-parametric programming, so-called explicit MPC. The solution to the explicit MPC problem is a piecewise affine (PWA) state feedback function defined over a polyhedral subdivision of the set of feasible states. The online evaluation of such a control law needs to determine the polyhedral region in which the current state lies. This procedure is called point location; its computational complexity is challenging, and determines the minimum possible sampling time of the system. A new flexible algorithm is proposed which enables the designer to trade off between time and storage complexities. Utilizing the concept of hash tables and the associated hash functions, the proposed method solves an aggregated point location problem that overcomes prohibitive complexity growth with the number of polyhedral regions, while the storage–processing trade-off can be optimized via scaling parameters. The flexibility and power of this approach is supported by several numerical examples.     

Modelling useful energy demand system as derived from basic needs in the household sector

Inter-fuel substitution in the household sector depends on whether their target energy use is similar or not. To account for the effect of end-use application on energy demand, the concept of useful energy is utilized in which energy carriers are grouped according to their end-use applications. Useful energy is assumed as a commodity demanded to satisfy needs. Therefore, it should possess certain characteristics in accordance with the nature of basic needs. These characteristics were investigated through a two-level budgeting system with demographic variables indicating rural and urban households of Iran. The model has been applied to estimate the behavioural parameters such as income and price elasticities of useful energy demand. The estimated values of income and own-price elasticity show that all categories of useful energy are necessities with a relatively inelastic demand. Among them, cooling and non-substitutable electricity has the highest income and own-price elasticity, while lighting and water heating are ranked as the most necessary types of useful energy due to their low-income elasticity. In addition, small values of cross price elasticities support the idea that different types of useful energy are almost independent. Therefore, the results confirm that useful energy demands could be considered as basic needs.     

Heavy paraffin dehydrogenation and hydrogenation of nitrobenzene to aniline: Effects of operating conditions

Auto-thermal heat exchanger configurations are recognized as a novel concept in process intensification. In the current study, the influence of operating conditions in a novel coupling reactor with radial-flow pattern is investigated for heavy paraffin dehydrogenation process. Catalytic hydrogenation of nitrobenzene to aniline takes place in the exothermic side and supplies the necessary heat for the endothermic dehydrogenation of heavy paraffin reaction. The performance of the reactor is numerically investigated for various key operating variables, such as inlet molar flow rates of exothermic and endothermic streams, number of subsections, and exothermic side angle. The reactor performance is analyzed based on temperature, olefin production rate, and nitrobenzene conversion.     

Corrosion and time dependent passivation of Al 5052 in the presence of H<Subscript>2</Subscript>O<Subscript>2</Subscript>

Corrosion and time–dependent oxide film growth on AA5052 Aluminum alloy in 0.25M Na₂SO₄ solution containing H₂O₂ was studied using electrochemical impedance spectroscopy, potentiodynamic polarization, chronoamperometric and open circuit potential monitoring. It was found that sequential addition of H₂O₂ provokes passivation of AA5052 which ultimately thickens the oxide film and brings slower corrosion rates for AA5052. H2O2 facilitates kinetics of oxide film growth on AA 5052 at 25° and 60 °C which is indicative of formation of a thick barrier film that leads to an increment in the charge transfer resistance. Pitting incubation time increases by introduction of H₂O₂ accompanied by lower pitting and smoother surface morphologies. At short exposure (up to 8 h) to H₂O₂–containing solution, the inductive response at low frequencies predominantly determined the corrosion mechanism of AA5052. On the other hand, at prolonged exposure times (more than 24 h) to 0.25M Na₂SO₄+1vol% H₂O₂ solution, thicker oxide layers resulted in the mixed inductive–Warburg elements in the spectra.     

CO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>-free hydrogen and carbon nanofibers production by methane decomposition over nickel-alumina catalysts

Nickel catalysts supported on mesoporous nanocrystalline gamma alumina with various nickel loadings were prepared and employed for thermocatalytic decomposition of methane into CO _x -free hydrogen and carbon nanofibers. The prepared catalysts with different nickel contents exhibited mesoporous structure with high surface area in the range of 121.3 to 66.2m²g^?1. Increasing in nickel content decreased the pore volume and increased the crystallite size. The catalytic results revealed that the nickel content and operating temperature both play important roles on the catalytic performance of the prepared catalysts. The results showed that increasing in reaction temperature increased the initial conversion of catalysts and significantly decreased the catalyst lifetime. Scanning electron microscopy (SEM) analysis of the spent catalysts evaluated at different temperatures revealed the formation of intertwined carbon filaments. The results showed that increasing in reaction temperature decreased the diameters of nanofibers and increased the formation of encapsulating carbon.     

Silica aerogel/epoxy nanocomposites: Mechanical,vibrational, and morphological properties

The present study was an attempt to examine the effects that adding silica aerogel (SA) nanoparticles to epoxy would exert on its mechanical, vibrational, and morphological properties. Neat epoxy was consecutively combined with 1, 2, and 4 wt% of SA nanoparticles. A number of tests of mechanical properties were then performed on the samples, including tests of tensile, bending, compressive, dynamic mechanical thermal, hardness, and Izod impact. Vibration and water uptake tests were also conducted on the samples. The highest modulus and strength values were found in the nanocomposite sample with 4 wt% of SA, and the highest toughness and elongation values were detected in the sample with 1 wt% of SA. Furthermore, adding the SA nanoparticles to the epoxy improved the energy absorption and hardness of the epoxy matrix. The findings from the tests of dynamic mechanical thermal and vibration properties demonstrated that, with an increase in the nanoparticles content in the samples, the values of storage modulus and natural frequency increased while the values of tan δ and damping ratios decreased. A comparison between the values of natural frequency from the vibration test and the values from the Euler–Bernoulli beam theory showed a good agreement between the theoretical and experimental results.     

Impact of innovation programs on development of energy system: Case of Iranian electricity-supply system

The paper presents further experiments with an extended version of a comprehensive model for assessment of energy technologies and research and development (R&D) planning to evaluate the impact of innovation programs on development of Iranian electricity-supply system. This analytical instrument is a model of energy R&D resource allocation with an explicit perspective of developing countries which has been linked to a bottom-up energy-systems model. Three emerging electricity generation technologies of solar PV, wind turbine and gas fuel cell are considered in the model and the impact of innovation programs on cost-reducing innovation for them is examined. The main results provided by the modeling approach include optimal allocation of R&D resources, induced capacity expansion policies to guarantee the effectiveness of R&D activities, competitive cost of emerging technologies, impact of innovation programs on optimal structure of electricity-supply system and benefits of innovation programs in the long-run.     

Investigation on Microstructure,Wear Behavior and Microhardness of Al−Si/SiC Nanocomposite

Aluminum matrix nano-composites have been widely used in various fields such as aerospace, automobile, and packing industries. In this study, the effect of nano-SiC content on the microst-ructure, wear resistance and micro-hardness of Al–Si/SiC nano-composite was investigated. In this regard, Al–Si matrix was reinforced by different amounts of nano-SiC: 0, 0.5, 1, 1.5, 3, 5, 10 wt %. The results showed that with increasing the nano-SiC weight ratio, nano-particles are agglomerated and unsuitable sintering increases the porosity, as pores and cavities. For more than 1.5% weight ratio of nano-SiC in the matrix, the wear resistance and the micro-hardness decreased. The results of the wear test, scanning electron microscopy, energy dispersive X-ray spectroscopy and worn surfaces showed that the dominant wear mechanism is controlled by nano-SiC contents. This study indicated that with adding nano-SiC particles more than the optimal content, wear resistance and micro-hardness of Al–Si/SiC nano-composite increased more than twice.