Showing papers by "Azarbaijan Shahid Madani University published in 2015"

A Novel High Step-up DC/DC Converter Based on Integrating Coupled Inductor and Switched-Capacitor Techniques for Renewable Energy Applications

Abstract: In this paper, a novel high step-up dc/dc converter is presented for renewable energy applications. The suggested structure consists of a coupled inductor and two voltage multiplier cells, in order to obtain high step-up voltage gain. In addition, two capacitors are charged during the switch-off period, using the energy stored in the coupled inductor which increases the voltage transfer gain. The energy stored in the leakage inductance is recycled with the use of a passive clamp circuit. The voltage stress on the main power switch is also reduced in the proposed topology. Therefore, a main power switch with low resistance $R_{{\rm DS} ({\rm ON})}$ can be used to reduce the conduction losses. The operation principle and the steady-state analyses are discussed thoroughly. To verify the performance of the presented converter, a 300-W laboratory prototype circuit is implemented. The results validate the theoretical analyses and the practicability of the presented high step-up converter.

Optimal Power Dispatch of Multi-Microgrids at Future Smart Distribution Grids

Abstract: In this paper, future distribution network operation is discussed under assumption of multimicrogrids (MMGs) concept. The economic operation of MMGs is formulated as an optimization problem. A stochastically and probabilistic modeling of both small-scale energy resources (SSERs) and load demand at each microgrids (MGs) is done to determine the optimal economic operation of each MGs with minimum cost based on the power transaction between the MGs and main grids. The balance between the total power generation in each MGs and the load demand is determined regarding the sold or purchase power either by MG or by main grid. Based on the results, the mean, standard deviation, and probability density function of each generated power with SSERs is determined considering optimization constraints. A statistical analysis for generated power and costs is given. The power interchange between MGs is considered. The particle swarm optimization is applied to minimize the cost function as an optimization algorithm. Results show that it is possible to regulate the power demand and power transaction between each MGs and the main grid. Moreover, it is indicated that the power sharing between MGs with main grid can reduce the total operation cost of the future distribution network.

An Innovative Scheme of Symmetric Multilevel Voltage Source Inverter With Lower Number of Circuit Devices

Abstract: In this paper, an advanced configuration for a symmetric multilevel voltage source inverter is proposed. The authority of the proposed inverter versus the conventional cascaded H-bridge inverter and those most recently introduced is verified with provided comparisons. The proposed inverter is able to generate the desired voltage levels using a lower number of circuit devices, including power semiconductor switches and related gate driver circuits of switches. As a result, the total cost is considerably reduced, and the control scheme gets simpler. Moreover, the reduced amount of on-state switches in the suggested configuration decreases voltage drops. Furthermore, power losses are diminished. The given simulation results confirm the feasibility of the proposed configuration. To approve the practicability of the proposed inverter, a prototype of the proposed topology has been implemented. Finally, simulation and experimental results are compared, and the provided comparison shows that the obtained results are in good agreement.

Symmetric and asymmetric transformer based cascaded multilevel inverter with minimum number of components

Abstract: In this study, a novel transformer based cascaded multilevel inverter is presented. The proposed inverter can operate in both symmetric and asymmetric topologies. The presented inverter benefits from the advantages such as reduced number of power switches and reduced total peak inverse voltage of the switching components. The numbers of insulated gate driver circuits are also decreased with respect to the power switches. Furthermore, the presented topology requires just a single DC source. In addition, the numbers of on-state switches in the current paths are reduced. Therefore the voltage drops across the switches are mitigated and as a result the efficiency of the presented inverter is improved. The mentioned advantages cause the implementation cost to be reduced. The operation of the converter is discussed thoroughly for both symmetric and asymmetric operations. The feasibility of the presented inverter topology is validated using the simulation results. Experimental results under 1.5 kW are also added to justify the theoretical analyses.

Modeling of photocatalyatic process on synthesized ZnO nanoparticles: Kinetic model development and artificial neural networks

Abstract: The kinetic modeling of organic pollutant photocatalytic degradation on synthesized ZnO nanoparticles was carried out. The photodegradation kinetic characteristics were investigated under different operational parameters including light intensity, initial organic concentration, ZnO content and pH. Based on the elementary photocatalytic reactions, the new kinetic model was established for prediction of photocatalytic degradation efficiency by taking into account the apparent first order rate constant, light intensity, initial organic concentration and ZnO content. The results demonstrated that the kinetic model could predict adequately photodegradation efficiency when high concentration of photo-induced hole-electron was considered. To compare the accuracy of obtained kinetic model, an empirical kinetic model as function of operational parameters and a 3-layer perceptron neural network were developed. The performance of three models was compared with experimental data by error functions and analysis of variance (ANOVA) calculation. The obtained results showed that three developed models are in good agreement with experimental data. It was also found that there is no significant difference among the developed kinetic, empirical kinetic and artificial neural network models. It was concluded that the kinetic model is developed based on the appropriate understanding from determining elementary reactions occurred in photocatalytic degradation of dye.

Elucidating of tool rotational speed in friction stir welding of 7020-T6 aluminum alloy

Abstract: The 7020-T6 aluminum alloy plates of 4 mm thickness were friction stir welded at rotational speeds of 400, 600, 800, and 1000 rpm and constant traverse speed of 100 mm/min. The peak temperatures of the joints were recorded by precise thermocouples. Microstructure, hardness, tensile properties, and fracture surfaces of the joints were analyzed. The results showed that decreasing the tool rotational speed from 1000 to 400 rpm decreased the peak temperature from 311 to 209 °C, and hence caused a lower heat input. In addition, lower rotational speeds result in higher hardness and tensile strengths. The higher hardness and ultimate tensile strength were related to the grain boundary, precipitation, and substructure strengthening mechanisms. In addition, the fracture surfaces of the joints welded at higher heat input conditions showed more ductile mode in comparison with that of welded at lower heat input condition, which confirmed the lower tensile elongation of the joints welded at lower rotational speeds.

A Novel Monolithic MILP Framework for Lot-Sizing and Scheduling of Multiproduct Treelike Pipeline Networks

Abstract: Detailed scheduling of long-distance multiproduct pipelines has received growing attention in the past few years. It helps the planner to reduce the number of pump and segment switches between active and idle conditions to obtain savings on pump operating and maintenance costs. Most contributions on the detailed scheduling of multiproduct pipelines concern networks with a single straight line. Large-scale pipeline networks, however, usually have a treelike configuration, featuring a mainline and several secondary lines, transporting smaller volumes of refined petroleum products over shorter distances. This work addresses the scheduling of a multiproduct treelike pipeline through a continuous-time mixed integer linear programming (MILP) model that allows the execution of simultaneous deliveries from a unique refinery to multiple downstream terminals so as to get a substantial increase in transportation capacity. Contrary to previous contributions on treelike pipeline systems, the new model solves batch siz...

Synthesis of rod-like α-FeOOH nanoparticles and its photocatalytic activity in degradation of an azo dye: Empirical kinetic model development

Abstract: Goethite (α-FeOOH) nanostructures were synthesized using a well-known one-step facile hydrothermal method The X-ray diffraction pattern confirmed the formation of the α-FeOOH with orthorhombic structure The field emission scanning electron microscopy revealed that the synthesized α-FeOOH had rod-like morphology The photocatalytic activity performance of synthesized α-FeOOH was evaluated in the degradation of CI Acid Orange 7 (AO7), as a model organic pollutant The degradation of AO7 in mere photolysis without α-FeOOH and adsorption with α-FeOOH is negligible The degradation of AO7 with α-FeOOH under UVA irradiation was considerable which confirmed the photocatalytic activity of synthesized α-FeOOH The band gap of synthesized nanoparticles was obtained by Tauc-Mott plot and determined around 25 ev The photocatalytic degradation kinetic characteristics were studied by investigation effect of different operational parameters including α-FeOOH dosage, pH and initial AO7 concentration as the effective operational parameters Using the non-linear regression, an empirical kinetic model was developed for predicting the photocatalytic degradation efficiency by taking account into the apparent first order kinetic and operational parameters The predictive capability of developed model was evaluated by comparing the experimental photocatalytic degradation efficiency and calculated ones by model It was found that the developed model fit well with experimental data

pH-Controlled multiple-drug delivery by a novel antibacterial nanocomposite for combination therapy

Abstract: Nanoparticle-based combination therapies have shown several unique features that are untenable in traditional chemotherapy. The present attempt intends to prepare a novel smart multifunctional drug delivery system based on cationic silica based polymer–clay nanocomposites for combination cancer therapy. The intercalation of silica based copolymers into montmorillonite (MMT) was achieved through an ion exchange process. The structure of the resulting nanocomposites was characterized by means of XRD, FT-IR, TG-DTA and SEM. This nanocomposite was used for multiple drug delivery of two anticancer drugs doxorubicin (DOX) and methotrexate (MTX) and an antibacterial agent ciprofloxacin (CIP). The in vitro antimicrobial activity of nanocomposites and CIP loaded nanocomposites was tested in growth inhibition of Escherichia coli and Pseudomonas aeruginosa bacteria by the MIC method. Furthermore, the potential antitumoral activity of this combined therapy system was evaluated against T47D cell lines by MTT assay and qRT-PCR. XRD results proved successful interaction of MMT with the cationic silica based copolymer. The nanocomposites showed an encapsulation efficiency of about 95% for the mentioned drugs. The cumulative in vitro release of the DOX/MTX/CIP-loaded nanocomposites revealed that the individual drug can undergo controlled release with the ability to distinguish between tumor tissues. Cell viability tests additionally confirmed that the dual-administration of DOX with MTX had a higher cytotoxicity to the mentioned cells in comparison with free dual drug forms. The in vitro antimicrobial results revealed good antimicrobial activities of both the blank nanocomposite and CIP loaded nanocomposite. Therefore, the dual anticancer drug-loaded antibacterial smart nanocomposite has the potential to be used for combination cancer therapy.

Facile Synthesis Optimization and Structure Characterization of Zinc Tungstate Nanoparticles

Abstract: The study involves a direct precipitation method developed for the facile and efficient synthesis of ZnWO4 nanoparticles. Effects of various parameters such as zinc and tungstate ion solution concentrations, flow rate of reagent addition, and reactor temperature on diameter of synthesized zinc tungstate nanoparticles were investigated experimentally by the aid of orthogonal array design. The findings of the study revealed that the diameter of the produced ZnWO4 nanoparticles can be fine-tuned through the adjustment of the reaction parameters, including zinc and tungstate ion solution concentrations and the reaction temperature, and at optimum conditions of synthesis procedure, the size of the produced zinc tungstate particles was about 33 nm. Finally, scanning electron microscopy, X-ray diffraction, FTIR, and photoluminescence techniques were used for structural and morphological characterization of the product, so as to monitor the role of the mentioned parameters on the targeted properties in the product.

Geodesic deviation equation in f(T) gravity

Abstract: In this work, we show that it is possible to study the notion of a geodesic deviation equation in $f(T)$ gravity, in spite of the fact that in teleparallel gravity there is no notion of geodesics, and the torsion is responsible for the appearance of gravitational interaction. In this regard, we obtain the general relativity equivalent equations for $f(T)$ gravity, which are in the modified gravity form such as $f(R)$ gravity. Then, we obtain the geodesic deviation equation within the context of this modified gravity. In this way, the obtained geodesic deviation equation will correspond to the $f(T)$ gravity. Eventually, we extend the calculations to obtain the modification of the Mattig relation.

A new approach for decreasing energy in wireless sensor networks with hybrid LEACH protocol and fuzzy C-means algorithm

Abstract: The optimum use of energy in wireless sensor networks WSNs is very important. The recent researches show that organising the network nodes in some clusters leads to higher efficiency of energy and finally it increases the lifetime of the network. So, controlling the number and the location of the clusters head CHs and also the size of the clusters about the node number leads to a balance in energy use of the CHs and increasing the lifetime of the network. Clustering-based routing protocols are energy-efficient protocols that improve the lifetime of a wireless sensor network. The objective of the clustering is to minimise the total transmission power by aggregating into a single path for prolonging the network lifetime. In this paper, fuzzy C-means FCM algorithm is used for the optimum number of the CHs and their location. Using FCM in WSNs helps changing the LEACH protocol parameters while execution. The results show that the hybrid algorithm increases the lifetime of the network in comparison to the LEACH algorithm.

Preparation of magnetic pH-sensitive microcapsules with an alginate base as colon specific drug delivery systems through an entirely green route

Abstract: The aim of this work was to prepare pH-sensitive drug carriers for colon specific drug delivery through a completely green and environmentally friendly route (without using any organic solvents, hazardous chemicals and even a harsh procedure). To achieve this, natural biopolymers (sodium alginate, chitosan and carboxymethylcellulose sodium) were used. Naproxen (as a model drug) and magnetic nanoparticles were encapsulated into the alginate microcapsules by formation of an alginate–Ca2+ complex. To overcome the drawbacks of the alginate microcapsules like porosity and burst drug release, they were coated with chitosan and carboxymethylcellulose sodium by a layer-by-layer technique that led to the formation of polyelectrolyte complexes through inter-ionic interactions between oppositely charged biopolymers. After coating with these natural polymers, porosity was reduced and burst drug releases were modified. The prepared magnetic microcapsules were characterized by FT-IR, DSC and SEM to study their structures and the roles that each polymeric layer plays. The swelling ratios and in vitro drug release profiles of the microcapsules were studied in both enzyme-free simulated gastric (SGF, pH 1) and simulated colonic fluids (SCF, pH 7.4). These microcapsules could be driven by means of an external magnet and also the results show that these coated microcapsules are completely pH-sensitive and potentially can be used as stimuli responsive carriers for colon specific drug delivery.

Sensing properties of pristine, Al-doped, and defected boron nitride nanosheet toward mercaptans: a first-principles study

Abstract: The adsorption of mercaptans on pristine, Al-doped, and mono-vacancy and Stone–Wales defected hexagonal boron nitride (h-BN) nanosheets was studied by the density functional theory method at the wB97X-D/6-311G(d) level of theory. Two types of mercaptans (i.e., methyl and ethyl mercaptan) were chosen as the adsorbates. No adsorption was observed on the pristine and defected h-BN nanosheet except for the B-vacancy defected h-BN nanosheet of which the adsorption was exothermic. In the case of the Al-doped h-BN nanosheet with substituted boron and nitrogen defect sites, not only was adsorption observed for both methyl and ethyl mercaptan but also the adsorption was exothermic. It was suggested that the Al-doped h-BN nanosheet and B-vacancy defected h-BN nanosheet could be a potential resource for adsorbing mercaptans. The electronic properties of all kinds of the studied h-BN nanosheets and the adsorption configuration of mercaptans on them were reported.

Synthesis, characterisation and sustained release properties of layered zinc hydroxide intercalated with amoxicillin trihydrate

Abstract: The intercalation of amoxicillin trihydrate (AMOX) into layered zinc hydroxide (LZH) has been achieved via ion-exchange method. The resulted nanocomposite (AMOX-LZH) has been thoroughly characterised by a number of techniques including powder X-ray diffraction (PXRD), FT-IR spectroscopy, TGA/DTG analysis and scanning electron microscopy (SEM). The PXRD results showed that the gallery height of LZH was expanded from 9.57 to 11.97 A, indicating that the AMOX anions were successfully intercalated into the interlayer space of LZHs. The increased thermal stability of nanocomposite was confirmed by TGA/DTG analyses. Improved antibacterial activity and minimum inhibitory concentration of AMOX-LZH nanocomposite was evaluated against Gram-positive bacteria Staphylococcus aureus, Klebsiella pneumonia and Gram- negative Escherichia coli using the disk diffusion technique. The sustained release of amoxicillin drug from the AMOX-LZH nanocomposite was also verified.

Pt–CeO2/reduced graphene oxide nanocomposite for the electrooxidation of formic acid and formaldehyde

Abstract: The Pt–CeO2/reduced graphene oxide nanocomposite on the carbon-ceramic electrode (Pt–CeO2/RGO/CCE) was prepared by a two-step electrodeposition process. RGO was deposited on the CCE through a simple electrochemical method using graphene oxide and CCE as the precursor and electrode substrate, respectively. Then, RGO/CCE was used as a support for the Pt–CeO2 nanoparticle deposition by another electrochemical process to form the nanocomposite based electrocatalyst; Pt–CeO2/RGO/CCE. The obtained electrocatalyst was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and cyclic voltammetric techniques. The electrocatalytic activity of the Pt–CeO2/RGO/CCE toward the oxidation of formic acid and formaldehyde was investigated by cyclic voltammetry and chronoamperometry in 0.1 M H2SO4 solution. It was found that the Pt–CeO2/RGO/CCE is electrocatalytically more active than the Pt–CeO2/CCE, Pt/RGO/CCE and Pt/CCE electrocatalysts. The increased electrocatalytic efficiency of Pt in Pt–CeO2/RGO/CCE is likely to result from its combination with CeO2 to form Pt–CeO2 nanoparticles and their deposition on/in the RGO layers at the CCE surface. From the obtained results, it could be concluded that the Pt–CeO2/RGO/CCE can be used as a potential and effective electrocatalyst for direct liquid fuel cell applications.

Cytotoxicity, Antioxidant Activity and Phenolic Content of Eight Fern Species from North of Iran

Abstract: Background: Although ferns possess great potential because of some interesting medicinal properties, the phytochemical potential of ferns is relatively unexplored. Due to the lack of scientific evidence to support the traditional use of fern species in Iran, the present work focuses on evaluating the phenolic content, cytotoxicity and antioxidant properties of these plants. Methods: Toxicity of extracts was assessed by the brine shrimp test. Screening of antioxidant capacity of the rhizome and aerial parts of eight fern species was carried out using DPPH and ABTS radical scavenging assays. The total phenol content (TPC) of the methanol extracts were determined using the Folin-Ciocalteu method. Results: Compared to podophyllotoxin (with LC50 of 30 µg/ml), Athyrium filix-femina and Pteris cretica demonstrated a significant cytotoxic activity (with LC50 of 6.1 and 15.5 µg/ml, respectively). The methanol extract of Polystichum aculeatum was found to have significant antioxidant properties with IC50 value of 0.45 ± 0.02 µg/ml. Athyrium filix-femina exhibited the strongest ABTS radical scavenging activity (29.85 ± 1.39 µmol Trolox/g plant). Conclusion: Rhizome parts generally had higher DPPH scavenging capacity and showed better ABTS scavenging activity than aerial parts. Results showed that these ferns could be used for discovery of new and biologically active natural compounds.

pH-sensitive, polymer modified, plasma stable niosomes: promising carriers for anti-cancer drugs.

Abstract: The aim of this study was the design and evaluation of a novel plasma stable, pH-sensitive niosomal formulation of Mitoxantrone by a modified ethanol injection method. Cholesterol hemisuccinate was added instead of cholesterol in order to produce pH-sensitivity property and using PEG-Poly (monomethyl itaconate)-CholC6 (PEG-PMMI-CholC6) copolymer introduced simultaneously pH-sensitivity and plasma stability properties in prepared niosomes. The pH-sensitivity and cytotoxicity of Mitoxantrone niosomes were evaluated in vitro in phosphate buffer with different pHs as well as using human ovarian cancer cell line (OVCAR-3), human breast cancer cell line (MCF-7) and human umbilical vein endothelial cells (HUVEC). Results showed that both cholesterol derivatives bearing formulations had pH-sensitive property and were found to release their contents under mild acidic conditions rapidly. In addition, the PEG-PMMI-CholC6-based niosomes could reserve the pH-sensitivity after incubation in plasma. Both Mitoxantrone-loaded pH-sensitive niosomes showed higher cytotoxicity than the conventional niosomes on OVCAR-3 and MCF-7 cell lines. However, both pH-sensitive niosomes exhibited lower cytotoxic effect on HUVEC cell line. Plasma stable, pH-sensitive niosomes could improve the cytotoxic effect and reduce the side effects of anti-tumor drugs.