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Search Results: 1 - 10 of 13 matches for " Sadoullah Ebrahimnejad "
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Bi-objective supply chain problem using MOPSO and NSGA-II
Hassan Javanshir,Sadoullah Ebrahimnejad,Samaneh Nouri
International Journal of Industrial Engineering Computations , 2012,
Abstract: The increase competition and decline economy has increased the relevant importance of having reliable supply chain. The primary objective of many supply chain problems is to reduce the cost of services and, at the same time, to increase the quality of services. In this paper, we present a multi-level supply chain network by considering multi products, single resource and deterministic cost and demand. The proposed model of this paper is formulated as a mixed integer programming and we present two metaheuristics namely MOPSO and NSGA-II to solve the resulted problems. The performance of the proposed models of this paper has been examined using some randomly generated numbers and the results are discussed. The preliminary results indicate that while MOPSO is able to generate more Pareto solutions in relatively less amount of time, NSGA-II is capable of providing better quality results.
A Primal-Dual Simplex Algorithm for Solving Linear Programming Problems with Symmetric Trapezoidal Fuzzy Numbers  [PDF]
Ali Ebrahimnejad
Applied Mathematics (AM) , 2011, DOI: 10.4236/am.2011.26089
Abstract: Two existing methods for solving a class of fuzzy linear programming (FLP) problems involving symmetric trapezoidal fuzzy numbers without converting them to crisp linear programming problems are the fuzzy primal simplex method proposed by Ganesan and Veeramani [1] and the fuzzy dual simplex method proposed by Ebrahimnejad and Nasseri [2]. The former method is not applicable when a primal basic feasible solution is not easily at hand and the later method needs to an initial dual basic feasible solution. In this paper, we develop a novel approach namely the primal-dual simplex algorithm to overcome mentioned shortcomings. A numerical example is given to illustrate the proposed approach.
Trapping of three-dimensional Holstein polarons by various impurities
Hadi Ebrahimnejad,Mona Berciu
Physics , 2012, DOI: 10.1103/PhysRevB.85.165117
Abstract: We study the bound states of a three-dimensional Holstein polaron near various kinds of single impurities, using the momentum average approximation. We show that the electron-phonon coupling is responsible for a strong renormalization of the impurity potential, resulting in an effective potential with significant retardation effects, which describes essential physics ignored by "instantaneous" approximations. The accuracy of our approximation is gauged by comparison with results from Diagrammatic Monte Carlo for the case of an impurity that modifies the on-site energy of the electron. We also discuss impurities that modify the local strength of the electron-phonon coupling, as well as isotope substitutions that change both the electron-phonon coupling and the phonon frequency, and contrast and highlight the difference between these cases.
Binding carriers to a non-magnetic impurity in a two-dimensional square Ising antiferromagnet
Hadi Ebrahimnejad,Mona Berciu
Physics , 2013, DOI: 10.1103/PhysRevB.88.104410
Abstract: A hole in a two-dimensional Ising antiferromagnet was believed to be infinitely heavy due to the string of wrongly oriented spins it creates as it moves, which should trap it near its original location. Trugman showed that, in fact, the hole acquires a finite effective mass due to contributions from so-called {\it Trugman loop} processes, where the hole goes nearly twice around closed loops, first creating and then removing wrongly-oriented spins, and ending up at a different lattice site. This generates effective second- and third-nearest-neighbor hopping terms which keep the quasiparticle on the sublattice it was created on. Here, we investigate the trapping of the quasiparticle near a single attractive non-magnetic impurity placed at one lattice site. We consider the two cases with the quasiparticle and impurity being on the same versus on different sublattices. The main result is that even though the quasiparticle can not see the bare disorder in the latter case, the coupling to magnons generates an effective renormalized disorder on its own sublattice which is strong enough to lead to bound states, which however have a very different spectrum than when the quasiparticle and impurity are on the same sublattice.
A perturbational study of the lifetime of a Holstein polaron in the presence of weak disorder
Hadi Ebrahimnejad,Mona Berciu
Physics , 2012, DOI: 10.1103/PhysRevB.86.205109
Abstract: Using the momentum average (MA) approximation, we find an analytical expression for the disorder-averaged Green's function of a Holstein polaron in a three-dimensional simple cubic lattice with random on-site energies. The on-site disorder is assumed to be weak compared to the kinetic energy of the polaron, and is treated perturbationally. Within this scheme, the states at the bottom of the polaron band are found to have an infinite lifetime, signaling a failure of perturbation theory at these energies. The higher-energy polaron states have a finite lifetime. We study this lifetime and the disorder-induced energy shift of these eigenstates for various strengths of disorder and electron-phonon coupling. We compare our findings to the predictions of Fermi's golden rule and the average T-matrix method, and find a significant quantitative discrepancy at strong electron-phonon coupling, where the polaron lifetime is much shorter than Fermi's golden rule prediction. We attribute this to the renormalization of the on-site potential by the electron-phonon coupling.
Usage of Template Matching for Lung Nodule Detection in CT Images
Jvad Ebrahimnejad,Rasoul Amirfattahi,Farzaneh Shayegh
Majlesi Journal of Electrical Engineering , 2008, DOI: 10.1234/mjee.v2i3.91
Abstract: In this paper we describe the lung nodule detection through image processing methods. Therefore, in the preprocessing stage, we use a medical-like method to omit all objects that surely they are not nodule. In this way nodule candidates are obtained. Therefore, false positives decay, while rate of main process does not increase. Finally, nodule candidates are selected through these suspicious regions. In the first step, we extracted candidate areas of the lung using synchronous thresholding in consecutive slices, medical decision implementation and also morphology methods. We divided the preprocessing stage into two phases for detecting all of lung nodules more accurately, depend on the nodule is connected to lung wall or vessel or it is an alone nodule.Here, template matching and maximum similarity method have used for nodule detection. The used database comes from LIDC database images that consist of 7 patients' CT scans. All of nodules are completely detected and there are 3 FP/slice. Value of similarity has been computed for all of points (pixels) that determined in preprocessing stage. Indeed, the limited search area makes the optimum (i.e. direct search) algorithm as fast as other sub-optimal search methods. Indeed, this method is faster than other methods that don’t have enough attention to information of CT scan slices.
The dynamics of a doped hole in cuprates is not controlled by spin fluctuations
Hadi Ebrahimnejad,George A. Sawatzky,Mona Berciu
Physics , 2014, DOI: 10.1038/nphys3130
Abstract: Twenty seven years after the discovery of high-temperature superconductivity \cite{BedMu}, consensus on its theoretical explanation is still absent. To a good extent, this is due to the difficulty of studying strongly correlated systems near half-filling, needed to understand the behaviour of one or few holes doped into a CuO$_2$ layer. To simplify this task it is customary to replace three-band models \cite{Emery} describing the doping holes as entering the O $2p$ orbitals of these charge-transfer insulators \cite{ZSA} with much simpler one-band Hubbard or $tJ$ models \cite{rev1,rev2}. Here we challenge this approach, showing that not only is the dynamics of a doped hole easier to understand in models that explicitly include the O orbitals, but also that our solution contradicts the long-held belief that the quantum spin fluctuations of the antiferromagnetic (AFM) background play a key role in determining this dynamics. Indeed, we show that the correct, experimentally observed dispersion is generically obtained for a hole moving on the O sublattice, and coupled to a N\'eel lattice of spins without spin fluctuations. This marks a significant conceptual change in our understanding of the relevant phenomenology and opens the way to studying few-holes dynamics without finite-size effect issues \cite{BayoB}, to understand the actual strength of the "magnetic glue".
Differences in the quasiparticle dynamics for one-band and three-band cuprate models
Hadi Ebrahimnejad,George A. Sawatzky,Mona Berciu
Physics , 2015,
Abstract: We study the quasiparticles of the one-band $t$-$J$ and $t$-$t'$-$t"$-$J$ models using a variational approximation that includes spin fluctuations in the vicinity of the hole. We explain why the spin fluctuations and the longer range hopping have complementary contributions to the quasiparticle dynamics, and thus why both are essential to obtain a dispersion in agreement with that measured experimentally. This is very different from the three-band Emery model in the strongly-correlated limit, where the same variational approximation shows that spin fluctuations have a minor effect on the quasiparticle dynamics. This difference proves that these one-band and three-band models describe qualitatively different quasiparticles, and therefore they they cannot both be suitable to describe the physics of underdoped cuprates.
Antibiotic Resistance of Kidney Stones and Urine from the Patients Under Going Nephrolithotomy
Shahande Z,Sadighian F,Shafi H,Ebrahimnejad A
Medical Laboratory Journal , 2011, DOI: http://www.goums.ac.ir/mljgoums/index.php?slc_lang=en&sid=1
Abstract: Background and objectives: Infection stones are the directly due topersistent or recurrent infection with Urease producing bacteria. they may beexacerbated by urinary obstruction or stasis. Also, some drug components likeciprofloxacin can be the cause of stone formation. We aimed at studingantibiotic resistance of bacteria isolated form kidney stones and Urinary tractinfection(UtI).Material and Methods: This descriptive study, during 2008-2010,weobtained kidney stones and urine of 45 patients under gone nephrolithotomy inshahid Beheshti hospital of Babol, Iran. The stones were transferred tomicrobiology Lab in a strile Condition, after grinding, cultured on Blood Agarand Eosin-Methylene Blue(EMB) media. In Addilion, urin Samples werecultured on the for mentioned media. The Positive cultures were qualitativelyevaluated and then, antibiogram was done by using Kirby Bauer method.Results: The resulte show that 10 kidney stone specimens and 8 urine sampleswere infected by bacteria, mostly by E.coli. In one stone sample and two urinesamples, we can isolate more than one bacteria. The bacteria isolated in thestone and urine samples of six patients was the same. We could find two casesof staphylococcus inurine and one in stone culture. The bacteria isolated fromstone are resistance to oflaxacin(80%) , which is higher than that to the otherantibiotics.Conclusion: Based on the results, there is no relationship between the kind ofkidney stone and type of bacteria. Further study needs to be done to prove thisrelation.Key words: Kidney stone, Antibiogram, E.coli, Infected stone.
Effective and Ineffective Resistance Genes and Resistance Reaction of Promising Barley Lines to Puccinia striiformis f. sp. hordei in Iran
Safar Ali Safavi,S.M. Atahusaini,Sh. Ebrahimnejad
Asian Journal of Plant Sciences , 2012,
Abstract: Barley stripe rust, caused by Puccinia striiformis f. sp. hordei, is an important disease of cultivated barley in several parts of world and sometimes, it causes yield losses due to sever epidemics. In order to prevent disease epidemics and decrease of yield losses; determining of effective genes, use and production of resistant cultivars/lines, particularly durable resistance, will be the best control method. Thus, for these purposes 31 barley genotypes including differential sets and promising lines, were evaluated during 2007-2010 cropping years. This study was subdivided into two experiments. The experiment-1 was conducted in three parts of Iran; Ardabil, Sari, Mashhad, by monitoring of virulence factors on differential sets during 2007-2009. But the experiment-2 was conducted on promising barley lines by measuring of Disease Severity (DS), Coefficient of Infection (CI) and relative Area under Disease Progress Curve (rAUDPC) in Ardabil during 2009-2010 cropping seasons. The results of virulence and avirulence monitoring in Ardabil showed presence of virulence for Rps2, Rps1.b, Rps3 and RpsI5 but in Mashhad virulence was observed for Rps2, Rps1.b and Bancroft. In Sari, except for Topper cultivar, virulence for resistance genes was not observed. In this study it was also concluded that RpsEm1, RpsEm2, RpsHF, Rps4, Rps1.c, RpsVa1, RpsVa2, RpsAst were effective resistance genes. The effective genes can be used in breeding programs, e.g., pyramiding resistance genes. Among promising lines, except for EC-81-15, EC-82-11 and EW-80-13 which had low CI and rAUDPC, the rest lines had moderately susceptible or susceptible reaction to barley stripe rust in Ardabil.
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