Showing papers by "University of Tabriz published in 2015"

Fast and fully-scalable synthesis of reduced graphene oxide

Abstract: Exfoliation of graphite is a promising approach for large-scale production of graphene. Oxidation of graphite effectively facilitates the exfoliation process, yet necessitates several lengthy washing and reduction processes to convert the exfoliated graphite oxide (graphene oxide, GO) to reduced graphene oxide (RGO). Although filtration, centrifugation and dialysis have been frequently used in the washing stage, none of them is favorable for large-scale production. Here, we report the synthesis of RGO by sonication-assisted oxidation of graphite in a solution of potassium permanganate and concentrated sulfuric acid followed by reduction with ascorbic acid prior to any washing processes. GO loses its hydrophilicity during the reduction stage which facilitates the washing step and reduces the time required for production of RGO. Furthermore, simultaneous oxidation and exfoliation significantly enhance the yield of few-layer GO. We hope this one-pot and fully-scalable protocol paves the road toward out of lab applications of graphene.

A Single-Phase Cascaded Multilevel Inverter Based on a New Basic Unit With Reduced Number of Power Switches

Abstract: In this paper, a new single-phase cascaded multilevel inverter is proposed. This inverter is comprised of a series connection of the proposed basic unit and is able to only generate positive levels at the output. Therefore, an H-bridge is added to the proposed inverter. This inverter is called the developed cascaded multilevel inverter. In order to generate all voltage levels (even and odd) at the output, four different algorithms are proposed to determine the magnitude of dc voltage sources. Reduction in the number of power switches, driver circuits, and dc voltage sources is the advantage of the developed single-phase cascaded multilevel inverter. As a result, the installation space and cost of the inverter are reduced. These features are obtained by the comparison of the conventional cascaded multilevel inverters with the proposed cascaded topology. The ability of the proposed inverter to generate all voltage levels (even and odd) is reconfirmed by using the experimental results of a 15-level inverter.

Stochastic Scheduling of Renewable and CHP-Based Microgrids

Abstract: Microgrids (MGs) are considered as a key solution for integrating renewable and distributed energy resources, combined heat and power (CHP) systems, as well as distributed energy-storage systems This paper presents a stochastic programming framework for conducting optimal 24-h scheduling of CHP-based MGs consisting of wind turbine, fuel cell, boiler, a typical power-only unit, and energy storage devices The objective of scheduling is to find the optimal set points of energy resources for profit maximization considering demand response programs and uncertainties The impact of the wind speed, market, and MG load uncertainties on the MG scheduling problem is characterized through a stochastic programming formulation This paper studies three cases to confirm the performance of the proposed model The effect of CHP-based MG scheduling in the islanded and grid-connected modes, as well as the effectiveness of applying the proposed DR program is investigated in the case studies

A Nonisolated Multiinput Multioutput DC–DC Boost Converter for Electric Vehicle Applications

Abstract: A new nonisolated multiinput multioutput dc-dc boost converter is proposed in this paper. This converter is applicable in hybridizing alternative energy sources in electric vehicles. In fact, by hybridization of energy sources, advantages of different sources are achievable. In this converter, the loads power can be flexibly distributed between input sources. Also, charging or discharging of energy storages by other input sources can be controlled properly. The proposed converter has several outputs with different voltage levels which makes it suitable for interfacing to multilevel inverters. Using of a multilevel inverter leads to reduction of voltage harmonics which, consequently, reduces torque ripple of electric motor in electric vehicles. Also, electric vehicles which using dc motor have at least two different dc voltage levels, one for ventilation system and cabin lightening and other for supplying electric motor. The proposed converter has just one inductor. Depending on charging and discharging states of the energy storage system (ESS), two different power operation modes are defined for the converter. In order to design the converter control system, small-signal model for each operation mode is extracted. The validity of the proposed converter and its control performance are verified by simulation and experimental results for different operation conditions.

A Review of Molecular Mechanisms Involved in Toxicity of Nanoparticles

Abstract: In recent decades, the use of nanomaterials has received much attention in industrial and medical fields. However, some reports have mentioned adverse effects of these materials on the biological systems and cellular components. There are several major mechanisms for cytotoxicity of nanoparticles (NPs) such as physicochemical properties, contamination with toxic element, fibrous structure, high surface charge and radical species generation. In this review, a brief key mechanisms involved in toxic effect of NPs are given, followed by the in vitro toxicity assays of NPs and prooxidant effects of several NPs such as carbon nanotubes, titanium dioxide NPs, quantum dots, gold NPs and silver NPs.

Reduction of Power Electronic Elements in Multilevel Converters Using a New Cascade Structure

Abstract: In this paper, a new structure for cascade multilevel converters is presented. The proposed structure is based on a cascaded connection of submultilevel converters. The proposed cascade structure can generate a large number of levels with reduced numbers of insulated-gate bipolar transistors, gate drivers, antiparallel diodes, dc voltage sources, and blocked voltage by switches. For the proposed cascade converter, a new algorithm to determine dc source values is presented. In addition, the optimal structures are presented for different goals. The suggested structure is compared with conventional cascade and other topologies. The performance and operation of the suggested submultilevel and cascade structures is verified by experimental and simulation results. Validation of the analytical conclusions is done using MATLAB/Simulink software.

Photocatalytic degradation of ciprofloxacin by synthesized TiO2 nanoparticles on montmorillonite: Effect of operation parameters and artificial neural network modeling

Abstract: TiO 2 /MMT nanocomposite was synthesized and characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray fluorescence (XRF) and Brunauer–Emmett–Teller (BET) techniques. The average size of TiO 2 nanoparticles was decreased from 60–80 nm to 40–60 nm through the immobilization on MMT. The main influential factors such as the TiO 2 /MMT dose, ciprofloxacin (CIP) concentration, pH of the solution, UV light regions, reusability of the catalyst and electrical energy determination were studied. The addition of radical scavengers (e.g. chloride, iodide, sulfate and bicarbonate) and enhancers (e.g. hydrogen peroxide, potassium iodate and peroxydisulfate) on the degradation efficiency was studied. The predicted data from the designed artificial neural network model were found to be in a good agreement with the experimental data ( R 2 = 0.9864). The main intermediates of CIP degradation were determined by GC–Mass spectrometry.

Reliability Evaluation of Conventional and Interleaved DC–DC Boost Converters

Abstract: Obviously for the correct operation of conventional boost converters, all components should work correctly. Interleaved boost converters having several stages, can be used to increase the reliability. So in this paper, a reliability comparison is done between the conventional boost converter and the interleaved structure. Two different operation modes are defined for the interleaved boost converter: half-power and full-power operation modes. The reliability calculation is based on the Markov model of the converters. The power loss effect of converter components on their failure rates, and therefore, on the reliability of converter has been assessed. For the first time different failure rates have been considered for different operation modes. Also a laboratory prototype of a two-stage interleaved boost dc–dc converter has been built up and the failure rate of components in different operation modes are calculated practically. Results show that in addition to other benefits, interleaved structure has higher reliability and as the power increases, there will be a decrease in the reliability.

Effect of probiotic fermented milk (kefir) on glycemic control and lipid profile in type 2 diabetic patients: a randomized double-blind placebo-controlled clinical trial.

Abstract: Background: Diabetes is a global health problem in the world. Probiotic food has anti-diabetic property. The aim of this trial was to determine the effect of probiotic fermented milk (kefir) on glucose and lipid profile control in patients with type 2 diabetes mellitus. Methods: This randomized double-blind placebo-controlled clinical trial was conducted on 60 diabetic patients aged 35 to 65 years.Patients were randomly and equally (n=30) assigned to consume either probiotic fermented milk (kefir) or conventional fermented milk (dough) for 8 weeks. Probiotic group consumed 600 ml/day probiotic fermented milk containing Lactobacillus casei, Lactobacillus acidophilus and Bifidobacteria and control group consumed 600 ml/day conventional fermented milk.Blood samples tested for fasting blood glucose, HbA1C, triglyceride (TG), total cholesterol, HDL-C and LDL-C at the baseline and end of the study. Results: The comparison of fasting blood glucose between two groups after intervention was statistically significant (P=0.01). After intervention, reduced HbA1C compared with the baseline value in probiotic fermented milk group was statistically significant (P=0.001), also the HbA1C level significantly decreased in probiotic group in comparison with control group (P=0.02) adjusting for serum levels of glucose, baseline values of HbA1c and energy intake according to ANCOVA model. Serum triglyceride, total cholesterol, LDL-cholesterol and HDL- cholesterol levels were not shown significant differences between and within the groups after intervention. Conclusion: Probiotic fermented milk can be useful as a complementary or adjuvant therapy in the treatment of diabetes.

Characterization of hot-pressed graphene reinforced ZrB2 -SiC composite

Abstract: In this paper, the hot pressing of monolithic ZrB2 ceramic (Z), ZrB2–25 vol% SiC composite (ZS), as well as 5 wt% graphene reinforced ZrB2–25 vol% SiC composite (ZSG) is investigated. The hot pressing at 1850 1C for 60 min under a uniaxial pressure of 20 MPa resulted in a near fully-dense ZSG composite (499% relative density). In addition, the influence of graphene reinforcement on the sintering process, microstructure, and mechanical properties (Vickers hardness and fracture toughness) of ZrB2–SiC composite is discussed. It was disclosed that the grain growth of the ZrB2 matrix was effectively stopped by SiC particles and graphene nano-platelets. The fracture toughness of ZSG composite (6.4 MPa m 1/2 ) was strongly enhanced by incorporating the mentioned reinforcements into the ZrB2 matrix, which is higher than that of Z ceramic (1.8 MPa m 1/2 ) and ZS composite (4.3 MPa m 1/2 ). After the hot pressing process, the fractographical outcomes revealed that some graphene nano-platelets were kept in the composite microstructure, apart from SiC grains, which lead to the toughening of the composite through graphene nano-platelets wrapping and pull out, crack deflection, and crack bridging. & 2014 Elsevier B.V. All rights reserved.

A review of technological and clinical aspects of robot-aided rehabilitation of upper-extremity after stroke

Abstract: Cerebrovascular accident (CVA) or stroke is one of the leading causes of disability and loss of motor function. Millions of people around the world are effected by it each year. Stroke results in disabled arm function. Restoration of arm function is essential to regaining activities of daily living (ADL). Along with traditional rehabilitation methods, robot-aided therapy has emerged in recent years. Robot-aided rehabilitation is more intensive, of longer duration and more repetitive. Using robots, repetitive dull exercises can turn into a more challenging and motivating tasks such as games. Besides, robots can provide a quantitative measure of the rehabilitation progress. This article overviews the terms used in robot-aided upper-limb rehabilitation. It continues by investigating the requirements for rehabilitation robots. Then the most outstanding works in robot-aided upper-limb rehabilitation and their control schemes have been investigated. The clinical outcomes of the built robots are also given that demonstrates the usability of these robots in real-life applications and their acceptance. This article summarizes a review done along with a research on the design, simulation and control of a robot for use in upper-limb rehabilitation after stroke. Implications for Rehabilitation Reviewing common terms in rehabilitation of upper limb using robots Reviewing rehabilitation robots built up to date Reviewing clinical outcomes of the mentioned rehabilitation robots.

Nanostructured Materials Utilized in Biopolymer-based Plastics for Food Packaging Applications

Abstract: Most materials currently used for food packaging are nondegradable, generating environmental problems. Several biopolymers have been exploited to develop materials for ecofriendly food packaging. However, the use of biopolymers has been limited because of their usually poor mechanical and barrier properties, which may be improved by adding reinforcing compounds (fillers), forming composites. Most reinforced materials present poor matrix-filler interactions, which tend to improve with decreasing filler dimensions. The use of fillers with at least one nanoscale dimension (nanoparticles) produces nanocomposites. Nanoparticles have proportionally larger surface area than their microscale counterparts, which favors the filler-matrix interactions and the performance of the resulting material. Besides nanoreinforcements, nanoparticles can have other functions when added to a polymer, such as antimicrobial activity, etc. in this review paper, the structure and properties of main kinds of nanostructured materials which have been studied to use as nanofiller in biopolymer matrices are overviewed, as well as their effects and applications.

Up regulation of Bax and down regulation of Bcl2 during 3-NC mediated apoptosis in human cancer cells

Abstract: Recently, we have reported the induction of apoptosis by 2-amino-4-(3-nitrophenyl)-3-cyano-7-(dimethylamino)-4H-chromene (3-NC) in HepG2, T47D and HCT116 cells with low nano molar IC50 values. In this study, anti-proliferative effects of modified 4-aryle-4H-chromenes derivatives; 2-amino-4-(3-bromophenyl)-3-cyano-7-(dimethylamino)-4H-chromene (3-BC), 2-amino-4-(3-trifluoromethylphenyl)-3-cyano-7-(dimethylamino)-4H-chromene (3-TFC) and 2-amino-4-(4,5-methylenedioxyphenyl)-3-cyano-7-(dimethylamino)-4H-chromene (4, 5-MC) were investigated in three human cancer cell lines. Compared to 3-NC none of the compounds displayed better anti-proliferative effect, although 3-BC appeared somewhat similar. Therefore 3-NC was selected for further studies. Treatment of HepG2, T47D and HCT116 cells with this compound induced apoptosis as visualized by fluorescence microscopic study of Hoechst 33258 stained cells. Induction of apoptosis was quantified by Annexin V/PI staining using flow cytometry. Western blot analysis also revealed that 3-NC down-regulated the expression of anti-apoptotic protein Bcl2 and up-regulated pro-apoptotic protein Bax, in all of the cell lines. Nonetheless, HepG2 cell line was the most responsive to 3-NC as Bax and Bcl2 showed the most dramatic up and down regulation. Our previous finding that 3-NC down regulates Inhibitor of Apoptosis Proteins (IAPs) and the present observation that Bax is upregulated and Bcl2 is down regulated upon 3-NC treatment, this chromene derivative has the potential to overcome chemotherapy resistance caused by up regulation of these proteins.

Microstructural development and mechanical properties of hot pressed SiC reinforced TiB2 based composite

Abstract: The present work is focused on investigating the effect of SiC addition (0, 15, 20, 25 and 30 vol.%) on microstructural features, phase evolution and mechanical properties of the vacuum hot pressed TiB 2 at 1850 °C/2 h/20 MPa. Hardness measurements revealed an initial increase in hardness from 14.2 GPa for nominally pure TiB 2 to 20.8 GPa for TiB 2 –15 vol.% SiC and a subsequent decrease with further increase in the SiC addition. Also the TiB 2 –30 vol.% SiC showed an improved indentation fracture toughness of 5.76 MPa m 1/2 which was mostly attributed to the addition of the SiC particles that could activate toughening mechanisms such as crack deflection, crack branching and grain breaking. The microstructure of the sintered samples was characterized by XRD and FESEM, which indicated that SiC reacted with and removed oxide impurities (TiO 2 and B 2 O 3 ) that were present on the particle surfaces. Elimination of such impurities promoted densification by minimizing grain coarsening and in composite contain 30 vol.% SiC the reaction led to in situ formation of TiC. Hence, the results indicated that sinterability of TiB 2 -based composites was remarkably improved by addition of SiC compared to the single phase TiB 2 ceramic.