Showing papers by "University of Tabriz published in 2012"

A New Multilevel Converter Topology With Reduced Number of Power Electronic Components

Abstract: In this paper, a new topology for cascaded multilevel converter based on submultilevel converter units and full-bridge converters is proposed. The proposed topology significantly reduces the number of dc voltage sources, switches, IGBTs, and power diodes as the number of output voltage levels increases. Also, an algorithm to determine dc voltage sources magnitudes is proposed. To synthesize maximum levels at the output voltage, the proposed topology is optimized for various objectives, such as the minimization of the number of switches, gate driver circuits and capacitors, and blocking voltage on switches. The analytical analyses of the power losses of the proposed converter are also presented. The operation and performance of the proposed multilevel converter have been evaluated with the experimental results of a single-phase 125-level prototype converter.

Characterization of antioxidant chitosan film incorporated with Zataria multiflora Boiss essential oil and grape seed extract

Abstract: Antioxidant chitosan based edible films were developed incorporated with Zataria multiflora Boiss essential oil (ZEO) (5 and 10 g/L) and grape seed extract (GSE) (10 g/L) alone and in combination. The physico-mechanical, wettability, swelling index, color, total phenol and antioxidant characteristics of the films were investigated. Films without any agents were used as control sample. All films, with the exception of 10 g/L GSE + 10 g/L ZEO film, exhibited lower strength and elongation values, and only the addition of 10 g/L ZEO to GSE film improved the water vapor transmission rate of chitosan films. Only GSE containing films had higher swelling index. The incorporation of GSE and ZEO into chitosan film increased the wettability of the surface, total phenol and antioxidant activity. Neat chitosan and ZEO incorporated films had a light yellowish color, whereas GSE + ZEO films were gray.

Modeling and Control of a New Three-Input DC–DC Boost Converter for Hybrid PV/FC/Battery Power System

Abstract: A new three-input dc-dc boost converter is proposed in this paper. The proposed converter interfaces two unidirectional input power ports and a bidirectional port for a storage element in a unified structure. This converter is interesting for hybridizing alternative energy sources such as photovoltaic (PV) source, fuel cell (FC) source, and battery. Supplying the output load, charging or discharging the battery can be made by the PV and the FC power sources individually or simultaneously. The proposed structure utilizes only four power switches that are independently controlled with four different duty ratios. Utilizing these duty ratios, tracking the maximum power of the PV source, setting the FC power, controlling the battery power, and regulating the output voltage are provided. Depending on utilization state of the battery, three different power operation modes are defined for the converter. In order to design the converter control system, small-signal model is obtained in each operation mode. Due to interactions of converter control loops, decoupling network is used to design separate closed-loop controllers. The validity of the proposed converter and its control performance are verified by simulation and experimental results for different operation conditions.

Determining the Main Factors in Declining the Urmia Lake Level by Using System Dynamics Modeling

Abstract: Urmia Lake in Iran is the second largest saline lake in the world. This ecosystem is the home for different species. Due to various socio-economical and ecological criteria, Urmia Lake has important role in the Northwestern part of the country but it has faced many problems in recent years. Because of droughts, overuse of surface water resources and dam constructions, water level has decreased in such a way that one quarter of the lake has changed to saline area in the last 10 years. The purpose of this research is to determine the main factors which reduce the lake’s water level. To this end, a simulation model, based on system dynamics method, is developed for the Urmia Lake basin to estimate the lake’s level. After successful verification of the model, results show that (among the proposed factors) changes in inflows due to the climate change and overuse of surface water resources is the main factor for 65% of the effect, constructing four dams is responsible for 25% of the problem, and less precipitation on lake has 10% effect on decreasing the lake’s level in the recent years. In the future, the model also can be used by managers as a decision support system to find the effects of building new dams or other infrastructures.

Trends in reference evapotranspiration in the humid region of northeast India

Abstract: In the present study, the trends in the reference evapotranspiration (ETO) estimated through the Penman-Monteith method were investigated over the humid region of northeast (NE) India by using the Mann-Kendall (MK) test after removing the effect of significant lag-1 serial correlation from the time series of ETO by pre-whitening. During the last 22 years, ETO has been found to decrease significantly at annual and seasonal time scales for 6 sites in NE India and NE India as a whole. The seasonal decreases in ETO have, however, been more significant in the pre-monsoon season, indicating the presence of an element of a seasonal cycle. The decreases in ETO are mainly attributed to the net radiation and wind speed, which are also corroborated by the observed trends in these two parameters at almost all the times scales over most of the sites in NE India. The steady decrease in wind speed and decline in net radiation not only balanced the impact of the temperature increases on ETO, but may have actually caused the decreases in ETO over the humid region of northeast India. Copyright © 2011 John Wiley & Sons, Ltd.

Effects of Haematococcus pluvialis supplementation on antioxidant system and metabolism in rainbow trout (Oncorhynchus mykiss)

Abstract: Effects of commercial source for astaxanthin (Haematococcus pluvialis) (Hp) on antioxidant power, specific marker enzymes, and some metabolites were examined in rainbow trout (Oncorhynchus mykiss) Fish were fed on diets containing 1, 3, and 10 g microalga kg(-1) feed for 30 days Serum total antioxidant activity and lipid peroxidation product, indicated by malondialdehyde (MDA), significantly enhanced with different doses of administration, indicating the elevated antioxidant status in all treatment groups In group fed with high dose of alga, significantly elevated aspartate aminotransferase activity (AST) was noted, indicating damage of normal liver function in this group Alkaline phosphatase (ALP) and alanine aminotransferase (ALT) were not affected in all groups Although serum total protein remained unaffected, serum glucose level was decreased significantly in lower doses of administration Furthermore, triglyceride and cholesterol levels showed significant decrease in 3 g kg(-1) microalga group by modulation of lipid metabolism in this group On the other hand, in highest dose, significant increase in lipids was observed, indicating the slight dysfunction in lipid metabolism in this treatment group The present study suggests that Haematococcus pluvialis especially in dose of 3 g kg(-1) feed administration may effectively enhance the antioxidant system and some biochemical parameters in rainbow trout

Bivariate drought frequency analysis using the copula method

Abstract: Droughts are major natural hazards with significant environmental and economic impacts. In this study, two-dimensional copulas were applied to the analysis of the meteorological drought characteristics of the Sharafkhaneh gauge station, located in the northwest of Iran. Two major drought characteristics, duration and severity, as defined by the standardized precipitation index, were abstracted from observed drought events. Since drought duration and severity exhibited a significant correlation and since they were modeled using different distributions, copulas were used to construct the joint distribution function of the drought characteristics. The parameter of copulas was estimated using the method of the Inference Function for Margins. Several copulas were tested in order to determine the best data fit. According to the error analysis and the tail dependence coefficient, the Galambos copula provided the best fit for the observed drought data. Some bivariate probabilistic properties of droughts, based on the derived copula-based joint distribution, were also investigated. These probabilistic properties can provide useful information for water resource planning and management.

Heterogeneous photocatalytic degradation of 4-nitrophenol in aqueous suspension by Ln (La3+, Nd3+ or Sm3+) doped ZnO nanoparticles

Abstract: Lanthanide doped ZnO nanoparticles with different Ln (Ln = La, Nd and Sm) contents were synthesized by polymer pyrolysis method and characterized by various techniques such as XRD, UV–vis, SEM, TGA, and TEM. The XRD results revealed that Ln 3+ is uniformly dispersed on ZnO nanoparticles in the form of small Ln 2 O 3 cluster. From SEM and TEM images it was found that the particle size of La-doped ZnO is much smaller as compared to that of pure ZnO. The photocatalytic activity of La-doped ZnO in the degradation of 4-nitrophenol (4-NP) was studied. The effects of the type and amount of loadings on the photocatalytic activity of Ln-doped ZnO were studied and the results were compared with pure ZnO. It was observed that the rate of degradation of 4-NP over Ln-doped ZnO increases with increasing La, Nd and Sm loading up to 4, 4 and 8 wt% and then decreases. It was found that the doping of Ln in ZnO helps to achieve complete mineralization of 4-NP within a short irradiation time. Among the catalysts, the 4 wt% Nd-doped ZnO was the most active and showing high photocatalytic activity for the degradation of 4-NP.

Whole-exome Sequencing Efficiently Detects Rare Mutations in Autosomal Recessive Nonsyndromic Hearing Loss

Abstract: Identification of the pathogenic mutations underlying autosomal recessive nonsyndromic hearing loss (ARNSHL) is difficult, since causative mutations in 39 different genes have so far been reported. After excluding mutations in the most common ARNSHL gene, GJB2, via Sanger sequencing, we performed whole-exome sequencing (WES) in 30 individuals from 20 unrelated multiplex consanguineous families with ARNSHL. Agilent SureSelect Human All Exon 50 Mb kits and an Illumina Hiseq2000 instrument were used. An average of 93%, 84% and 73% of bases were covered to 1X, 10X and 20X within the ARNSHL-related coding RefSeq exons, respectively. Uncovered regions with WES included those that are not targeted by the exome capture kit and regions with high GC content. Twelve homozygous mutations in known deafness genes, of which eight are novel, were identified in 12 families: MYO15A-p.Q1425X, -p.S1481P, -p.A1551D; LOXHD1-p.R1494X, -p.E955X; GIPC3-p.H170N; ILDR1-p.Q274X; MYO7A-p.G2163S; TECTA-p.Y1737C; TMC1-p.S530X; TMPRSS3-p.F13Lfs*10; TRIOBP-p.R785Sfs*50. Each mutation was within a homozygous run documented via WES. Sanger sequencing confirmed co-segregation of the mutation with deafness in each family. Four rare heterozygous variants, predicted to be pathogenic, in known deafness genes were detected in 12 families where homozygous causative variants were already identified. Six heterozygous variants that had similar characteristics to those abovementioned variants were present in 15 ethnically-matched individuals with normal hearing. Our results show that rare causative mutations in known ARNSHL genes can be reliably identified via WES. The excess of heterozygous variants should be considered during search for causative mutations in ARNSHL genes, especially in small-sized families.

Charged system search for optimal design of frame structures

Abstract: The charged system search (CSS) algorithm is utilized for design of frame structures. The algorithm is inspired by the laws in physics. The CSS utilizes a number of charged particles which influence each other based on their fitness values and their separation distances considering the governing law of Coulomb. A comparison between the characteristics of the CSS algorithm and other well-known meta-heuristics is performed to indicate their similarities and differences. Some benchmark frame examples are optimized with the CSS algorithm. Comparison of the results of CSS with some other meta-heuristic algorithms shows the robustness of the new algorithm.

Symmetric multilevel inverter with reduced components based on non-insulated dc voltage sources

Abstract: Multilevel inverters have an important portion in power processing in power systems. These inverters have some inherent advantages such as ability to operate with high power and voltage, improved output waveform quality and flexibility which make them attractive and more popular. This study proposes a new topology based on the non-insulated dc voltage sources for multilevel inverter with reduced number of switching devices. As a result, it reduces control complexity and gate driver circuits. The proposed topology is a general topology which can be easily extended to a desired number of voltage levels. All of the desired output voltage levels (both odd and even) can be achieved using the proposed topology. The validity of the proposed multilevel inverter is verified with both computer simulation and experimental results from a 15-level laboratory prototype.

Coupled eagle strategy and differential evolution for unconstrained and constrained global optimization

Abstract: The performance of an optimization tool is largely determined by the efficiency of the search algorithm used in the process The fundamental nature of a search algorithm will essentially determine its search efficiency and thus the types of problems it can solve Modern metaheuristic algorithms are generally more suitable for global optimization This paper carries out extensive global optimization of unconstrained and constrained problems using the recently developed eagle strategy by Yang and Deb in combination with the efficient differential evolution After a detailed formulation and explanation of its implementation, the proposed algorithm is first verified using twenty unconstrained optimization problems or benchmarks For the validation against constrained problems, this algorithm is subsequently applied to thirteen classical benchmarks and three benchmark engineering problems reported in the engineering literature The performance of the proposed algorithm is further compared with various, state-of-the-art algorithms in the area The optimal solutions obtained in this study are better than the best solutions obtained by the existing methods The unique search features used in the proposed algorithm are analyzed, and their implications for future research are also discussed in detail

INVESTIGATING THE EFFECTS OF EDM PARAMETERS ON SURFACE INTEGRITY, MRR AND TWR IN MACHINING OF Ti–6Al–4V

Abstract: Ti–6Al–4V is a kind of difficult-to-cut material with poor machinability by traditional machining methods, while electrical discharge machining (EDM) is suitable for machining titanium alloys. In this paper, three input machining parameters including pulse current, pulse on time and open circuit voltage were changed during EDM tests. To investigate the output characteristics; material removal rate (MRR), tool wear ratio (TWR) and different aspects of surface integrity for Ti–6Al–4V samples such as topography of machined surface, crack formation, white layer (recast layer) thickness and microhardness were considered as performance criteria. The variations of MRR and TWR versus input machining parameters were investigated by means of main and interaction effect plots and also verified by ANOVA results. The effect of pulse energy based on pulse on time and pulse current variations against recast layer thickness and microhardness was studied. The possibility of forming different chemical elements and compound...