Stochastic economic analysis of FACTS devices on contingent transmission networks using hybrid biogeography-based optimization

Electrical Engineering - Flexible AC transmission systems (FACTS) devices have advantages of enhancing AC system controllability and stability, increasing power transfer capability and relieving...     

A game equilibrium model of a retail electricity market with high penetration of small and mid-size renewable suppliers

Game theory has provided a practical tool to model players' strategic behavior in electricity markets, particularly as the world moves towards a more competitive market. A game theoretic approach can be used to find the clearing electricity price in a retail electricity market with a high penetration of small and mid-size renewable suppliers.     

Enhancing the Nucleolytic Resistance and Bioactivity of Functional Nucleic Acids by Diverse Nanostructures through in Situ Polymerization-Induced Self-assembly

Functional nucleic acids (FNAs) are garnering tremendous interest owing to their high modularity and unique bioactivity. Three-dimensional FNAs have been developed to overcome the issues of nuclease degradation and limited cell uptake. We have developed a new facile approach to the synthesis of multiple three-dimensional FNA nanostructures by harnessing photo-polymerization-induced self-assembly. Sgc8 aptamer and CpG oligonucleotide were modified as macro chain-transfer reagents to mediate in situ polymerization and self-assembly. Diverse structures, including micelles, rods, and short worms, afford these two FNAs afford these two FNAs with higher nuclease resistance in serum serum, greater cellular uptake efficiency, and increased bioactivity.     

Modification of electrospun poly(L-lactic acid)/polyethylenimine nanofibrous scaffolds for biomedical application

In this study, modification of poly(L-lactic acid) (PLLA) electrospun nanofibrous scaffolds blending with polyethylenimine (PEI) in different blend ratios was performed. The sample with 85:15 blend ratio revealed most promising results, and was selected for further modification with gelatin. It was found that the presence of PEI could enhanced porosity, mechanical properties, surface/bulk hydrophilicity and also gelatin grafting density about five times with positive effect on cell behavior. The results indicated that the limitations of PLLA electrospun nanofibers for potential application as a functional tissue engineering scaffold (i.e., poor cell adhesion and necrosis of host tissues as a result of providing acidic environment while degradation) could be overcome through blending with PEI and grafting with gelatin.     

Synthesis and Characterization of Novel Heat Resistant,Superparamagnetic Poly(ether-imide) Nanocomposites Containing Xanthene: Representing a Strategy for Improving Thermal Stability of Magnetic Polymer-Based Nanocomposites

Two superparamagnetic and heat resistant xanthene based poly(ether-imide) nanocomposites were successfully synthesized. Field emission scanning electron microscopy, transmission electron microscope, X-ray diffraction, thermal gravimetric analysis, vibrating sample magnetometer, Energy-dispersive X-ray spectroscopy and Fourier-transform infrared (FTIR) techniques were used for studying the morphology, crystalline phase, thermal stability and magnetization properties of the nanocomposites. The neat form of the corresponding poly(ether-imide) was also prepared by thermal imidization method and its structure was confirmed by FTIR, proton nuclear magnetic resonance (¹H NMR), UV–Vis and photoluminescence (PL) spectroscopies. In order to investigate the effects of modifying the surface of Fe₃O₄ nanoparticles on thermal properties of the nanocomposites, the surface of Fe₃O₄ nanoparticles was coated with SiO₂ and polysuccinimide (PSI), sequentially. Then, both the unmodified Fe₃O₄ and surface-modified Fe₃O₄ (Fe₃O₄@SiO₂–PSI) nanoparticles were used as fillers for the polymer matrix. According to the results, the prepared nanocomposites were superparamagnetic and showed higher thermal stability in comparison to the neat poly(ether-imide). Furthermore, poly(ether-imide)/Fe₃O₄@SiO₂–PSI (PIEN 10b) nanocomposite showed higher thermal stability and dispersed better in the polymer matrix [in comparison to poly(ether-imide)/Fe₃O₄ (PIEN 10 a)] due to the presence of imide groups and high hydroxyl content of the functional Fe₃O₄ nanoparticles which caused high interactions between poly(ether-imide) and functional Fe₃O₄. Furthermore, the presence of methyl, ether and bulky xanthene groups in the poly(ether-imide(backbone improved the solubility of the neat polymer in organic solvents. These properties can be very helpful for extending new applications of poly(ether-imide)s.     

Preparation of alumina/polystyrene core-shell composite powder via phase inversion process for indirect selective laser sintering applications

Indirect selective laser sintering (SLS) is one of the promising additive manufacturing (AM) methods that can process conventionally difficult or even impossible materials such as ceramics. In this work, an innovative phase inversion technique is used to fabricate spherical alumina particles coated with a thin layer of polystyrene (PS). Then, indirect SLS is used to fabricate green parts from the 6 wt% PS coated alumina particles via a Nd:YAG laser. The assessed SLS process parameters were the scan speed, laser power, scan spacing, pulse frequency, and pulse width. The characterization of the AL₂O₃/PS core-shell composite particles was described using techniques including SEM (for morphology), FT-IR (for chemical bonding at the interfaces), TGA (for mass loss), and DSC (for glass transition temperature, T_g). 3D green parts were then fabricated using proper process parameters as a proof of the feasibility of using SLS technique for AL₂O₃/PS core-shell composite powder. The results showed that using a Nd:YAG laser with less absorption by alumina and PS provides greater penetration through a powder bed. In addition, the possibility of sound connections among particles in every direction was observed due to the uniformity of the coating process in spite of a minimal amount of binder. In addition, green part density measurements show high values compared to previously reported results.     

Synthesis and characteristics of fly ash and bottom ash based geopolymers–A comparative study

The research was carried out to develop geopolymers mortars and concrete from fly ash and bottom ash and compare the characteristics deriving from either of these products. The mortars were produced by mixing the ashes with sodium silicate and sodium hydroxide as activator solution. After curing and drying, the bulk density, apparent density and porosity, of geopolymer samples were evaluated. The microstructure, phase composition and thermal behavior of geopolymer samples were characterized by scanning electron microscopy, XRD and TGA-DTA analysis respectively. FTIR analysis revealed higher degree of reaction in bottom ash based geopolymer. Mechanical characterization shows, geopolymer processed from fly ash having a compressive strength 61.4 MPa and Young's modulus of 2.9 GPa, whereas bottom ash geopolymer shows a compressive strength up to 55.2 MPa and Young's modulus of 2.8 GPa. The mechanical characterization depicts that bottom ash geopolymers are almost equally viable as fly ash geopolymer. Thermal conductivity analysis reveals that fly ash geopolymer shows lower thermal conductivity of 0.58 W/mK compared to bottom ash geopolymer 0.85 W/mK.     

Chemical Looping Steam Methane Reforming via Ni-ferrite Supported on Cerium and Zirconium Oxides

Pure hydrogen was produced by means of chemical looping steam methane reforming with novel oxygen carriers. Ni-ferrite, Ni-ferrite-ZrO₂, and Ni-ferrite-CeO₂ were synthesized as oxygen carriers and characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, scanning electron microscopy (SEM), dynamic light scattering (DLS), and hydrogen temperature-programmed reduction (H₂-TPR). The performances of the as-synthesized oxygen carriers in the cyclic oxidation-reduction were investigated in the packed-bed microreactor at a defined temperature range and under atmospheric pressure. Ni_0.39Fe_2.61O₄-ZrO₂ exhibited the best performance and maximum methane conversion among the other oxygen carriers. In addition, high selectivities for H₂ and CO were reached.     

Non-catalytic conversion of wheat straw,walnut shell and almond shell into hydrogen rich gas in supercritical water media

Agricultural wastes as lignocellulosic biomasses are known as the major resources of bioenergy. These valuable resources can be converted into useful environmental friendly fuels and chemicals. Wheat straw, walnut shell and almond shell are the main agricultural wastes in Kurdistan province, Iran. This study investigates the hydrogen-rich gas production via gasification of these biomasses in supercritical water media. Experiments were performed first, in the base case condition using a stainless steel batch micro reactor system. Then, the effect of reaction time on the total gas yield and yield of hydrogen, were investigated. It was seen that the total gas yields and gasification efficiencies increased by increasing the reaction time to 30 min and then the total gas yield was approximately remained constant. Among three used feed stocks, wheat straw with higher amount of cellulose and lower amount of lignin had the highest total gas and hydrogen yields in shorter reaction times. The maximum hydrogen yields of 7.25, 4.1 and 4.63 mmol per gram of wheat straw, almond shell and walnut shell occurred at 10, 15 and 20 min of reaction time, respectively.