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Search Results: 1 - 10 of 980 matches for " Mehrdad Asgari "
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Synthesis and Characterization of Nanopowder with Various Chelating Agents
Mehrdad Balandeh,Sirous Asgari
Journal of Nanomaterials , 2010, DOI: 10.1155/2010/695083
Abstract: powders were synthesized with acrylic acid, citric acid, oxalic acid, and triethanolamine (TEA) as a chelating agent. Crystallized was synthesized in air at a calcinations temperature of 500 for 12 hours, when the molar ratio of chelating agents to total metal ion (RPM) was 1.0. The TEA-assisted method had the highest intensity ratio of (003)/(104) peaks of X-ray diffraction (XRD) spectrum. The transmission electron microscopy (TEM) analysis indicates that the sample prepared with triethanolamine obtained the smallest particle size with average particle size of only 12?nm. The results indicate that chelating agents have an important role in the intensity ratio of (003)/(104) peaks of XRD spectrum, size and shape of powders. 1. Introduction Layered oxide LiMO2 ( , Ni, Mg) has been proposed as a cathode material for lithium secondary batteries. Since the commercialization of LiCoO2 by Sony in 1990, many efforts have been exerted to find other layered oxide cathode materials to replace it because of the high toxicity of LiCoO2 [1, 2]. Recently layered oxide LiNiO2 was accepted as an attractive cathode material because of its various advantages such as lower cost, higher discharge capacity, better reversibility, and nontoxicity [3–7]. Transition metal ions such as nickel and cobalt ions are surrounded by six oxygen atoms forming LiNiO2 infinite slabs by edge-sharing of the NiO2 layers in octahedral sites [8]. The ideal layered LiNiO2 structure has a close-packed oxygen array which is slightly distorted from cubic close packing [8]. Therefore, LiNiO2 phase has a rhombohedral structure with an space group, and the parameters of the unit cell are usually defined in terms of the hexagonal setting. However, obtaining synthesized stoichiometric and ordered layered LiNiO2 is difficult because decomposition from LiNiO2 to Li1-xNi1+xO2 ( ) occurs which has a partially disordered cation distribution at the lithium sites. It has been well known that the synthetic condition is important factor to obtain stoichiometric layered LiNiO2 [9]. The use of a solution-chemistry-based technique for synthesizing materials has several advantages. All these approaches yield molecularly homogeneous intermediate precursors. Despite the variation in the reaction chemistry, the precursor can be designed and synthesized to suitable consist of molecular structures closely resembling the final desired oxide. In this study, a sol-gel method has been used for the preparation of stoichiometric layered LiNiO2 with submicron and narrow-size distribution particle. Furthermore, the reduced
Constructing the Critical Curve for the Two-Layer Potts Model Using Cellular Automata
Yazdan Asgari,Mehrdad Ghaemi
Physics , 2006,
Abstract: The critical points of the 3-states two-layer Potts model on square lattice for different interlayer couplings (Kx, Ky,and Kz) are calculated with high precision using probabilistic cellular automata with Glauber algorithm, where Kx and Ky are the nearest-neighbor interactions within each layer in the x and y directions, respectively and Kz is the interlayer coupling. The obtained results are 0.726, 0.807, 0.928, 0.987 and 1.00 for the cases Kz per Kx = 1, 0.5, 0.1, 0.01 and 0.001, respectively. Then, the critical curve has been constructed for this model.
Investigation of Influential Parameters in Deep Oxidative Desulfurization of Dibenzothiophene with Hydrogen Peroxide and Formic Acid
Alireza Haghighat Mamaghani,Shohreh Fatemi,Mehrdad Asgari
International Journal of Chemical Engineering , 2013, DOI: 10.1155/2013/951045
Abstract: An effective oxidative system consisting of hydrogen peroxide, formic acid, and sulfuric acid followed by an extractive stage were implemented to remove dibenzothiophene in the simulated fuel oil. The results revealed such a great performance in the case of H2O2 in the presence of formic and sulfuric acids that led to the removal of sulfur compounds. Sulfuric acid was employed to increase the acidity of media as well as catalytic activity together with formic acid. The oxidation reaction was followed by a liquid-liquid extraction stage using acetonitrile as a polar solvent to remove produced sulfones from the model fuel. The impact of operating parameters including the molar ratio of formic acid to sulfur ( ), hydrogen peroxide to sulfur ( ), and the time of reaction was investigated using Box-Behnken experimental design for oxidation of the model fuel. A significant quadratic model was introduced for the sulfur removal as a function of effective parameters by the statistic analysis. 1. Introduction Deep desulfurization of diesel fuel has become an important issue due to the legislative regulations to reduce sulfur content in most countries (e.g., 15?ppmw since 2006 in the US and 10?wppm since 2008 in the EU) [1, 2]. Hydrodesulfurization (HDS) is the process most widely used in refineries to remove sulfur compounds from liquid hydrocarbons by transforming them to hydrogen sulfide. This process is catalytically carried out in the presence of hydrogen under severe reaction conditions such as high temperature and high pressure [3]. However, it has been recognized that the achievement of almost zero values of sulfur in fuels has to be done through the combination of HDS process with complementary reactions. Studies reveal that sulfur compounds remaining in diesel fuel after HDS process, at sulfur level lower than 0.1% wt., are generally thiophene, benzothiophene, dibenzothiophene, and their derivatives. These compounds exhibit low HDS reactivity because of the strict hindrance for the interaction between sulfur and active sites on the catalyst [3]. As a result, to remove refractory sulfur compounds with HDS, more severe operating conditions are needed, including higher temperature and pressure, more active catalysts, and longer residence time, which lead to large hydrogen consumption and reduction of catalyst life. To solve the shortcomings of the HDS process to remove refractory sulfur compounds, several new processes including oxidative desulfurization (ODS), selective adsorption, and biodesulfurization have been developed as alternative or complementary
Calculation of The Critical Point for Two-Layer Ising and Potts Models Using Cellular Automata
Yazdan Asgari,Mehrdad Ghaemi,Mohammad Ghasem Mahjani
Physics , 2004,
Abstract: The critical points of the two-layer Ising and Potts models for square lattice have been calculated with high precision using probabilistic cellular automata (PCA) with Glauber algorithm. The critical temperature is calculated for the isotropic and symmetric case (Kx=Ky=Kz=K), where Kx and Ky are the nearest-neighbor interactions within each layer in the x and y directions, respectively, and Kz is the interlayer coupling. The obtained results are 0.310 and 0.726 for two-layer Ising and Potts models, respectively, that are in good agreement with the accurate values reported by others.
Computer Simulation Study of the Levy Flight Process
Mehrdad Ghaemi,Zahra Zabihinpour,Yazdan Asgari
Statistics , 2010, DOI: 10.1016/j.physa.2008.12.071
Abstract: Random walk simulation of the Levy flight shows a linear relation between the mean square displacement and time. We have analyzed different aspects of this linearity. It is shown that the restriction of jump length to a maximum value (lm) affects the diffusion coefficient, even though it remains constant for lm greater than 1464. So, this factor has no effect on the linearity. In addition, it is shown that the number of samples does not affect the results. We have demonstrated that the relation between the mean square displacement and time remains linear in a continuous space, while continuous variables just reduce the diffusion coefficient. The results are also implied that the movement of a levy flight particle is similar to the case the particle moves in each time step with an average length of jumping . Finally, it is shown that the non-linear relation of the Levy flight will be satisfied if we use time average instead of ensemble average. The difference between time average and ensemble average results points that the Levy distribution may be a non-ergodic distribution.
Lattice Gas Automata Simulation of 2D site-percolation diffusion: Configuration dependence of the theoretically expected crossover of diffusion regime
Mehrdad Ghaemi,Nasrollah Rezaei-Ghaleh,Yazdan Asgari
Physics , 2010,
Abstract: Theoretical analysis of random walk on percolation lattices has predicted that, at the occupied site concentrations of above the threshold value, a characteristic crossover between an initial sub-diffusion to a final classical diffusion behavior should occur. In this study, we have employed the lattice gas automata model to simulate random walk over a square 2D site-percolation lattice. Quite good result was obtained for the critical exponent of diffusion coefficient. The random walker was found to obey the anomalous sub-diffusion regime, with the exponent decreasing when the occupied site concentration decreases. The expected crossover between diffusion regimes was observed in a configuration-dependent manner, but the averaging over the ensemble of lattice configurations removed any manifestation of such crossovers. This may have been originated from the removal of short-scale inhomogeneities in percolation lattices occurring after ensemble averaging.
Optimal cut-off of homeostasis model assessment of insulin resistance (HOMA-IR) for the diagnosis of metabolic syndrome: third national surveillance of risk factors of non-communicable diseases in Iran (SuRFNCD-2007)
Alireza Esteghamati, Haleh Ashraf, Omid Khalilzadeh, Ali Zandieh, Manouchehr Nakhjavani, Armin Rashidi, Mehrdad Haghazali, Fereshteh Asgari
Nutrition & Metabolism , 2010, DOI: 10.1186/1743-7075-7-26
Abstract: Data of the third National Surveillance of Risk Factors of Non-Communicable Diseases, available for 3,071 adult Iranian individuals aging 25-64 years were analyzed. MetS was defined according to the Adult Treatment Panel III (ATPIII) and International Diabetes Federation (IDF) criteria. HOMA-IR cut-offs from the 50th to the 95th percentile were calculated and sensitivity, specificity, and positive likelihood ratio for MetS diagnosis were determined. The receiver operating characteristic (ROC) curves of HOMA-IR for MetS diagnosis were depicted, and the optimal cut-offs were determined by two different methods: Youden index, and the shortest distance from the top left corner of the curve.The area under the curve (AUC) (95%CI) was 0.650 (0.631-0.670) for IDF-defined MetS and 0.683 (0.664-0.703) with the ATPIII definition. The optimal HOMA-IR cut-off for the diagnosis of IDF- and ATPIII-defined MetS in non-diabetic individuals was 1.775 (sensitivity: 57.3%, specificity: 65.3%, with ATPIII; sensitivity: 55.9%, specificity: 64.7%, with IDF). The optimal cut-offs in diabetic individuals were 3.875 (sensitivity: 49.7%, specificity: 69.6%) and 4.325 (sensitivity: 45.4%, specificity: 69.0%) for ATPIII- and IDF-defined MetS, respectively.We determined the optimal HOMA-IR cut-off points for the diagnosis of MetS in the Iranian population with and without diabetes.Insulin resistance, which represents a reduced physiological response of the peripheral tissues to the action of the normal levels of insulin, is amajor finding in several metabolic disorders, including type 2 diabetes and metabolic syndrome (MetS) [1]. Therefore, a reliable measure of insulin resistance is important for investigating the link between insulin resistance and MetS. Furthermore, given that insulin resistance is an important risk factor for development of type 2 diabetes and incident cardiovascular diseases, identification of subjects with insulin resistance is a strategy for identifying high-risk people f
Third national surveillance of risk factors of non-communicable diseases (SuRFNCD-2007) in Iran: methods and results on prevalence of diabetes, hypertension, obesity, central obesity, and dyslipidemia
Alireza Esteghamati, Alipasha Meysamie, Omid Khalilzadeh, Armin Rashidi, Mehrdad Haghazali, Fereshteh Asgari, Mandana Kamgar, Mohammad Gouya, Mehrshad Abbasi
BMC Public Health , 2009, DOI: 10.1186/1471-2458-9-167
Abstract: The results of this study are extracted from the third national Surveillance of Risk Factors of Non-Communicable Diseases (SuRFNCD-2007), conducted in 2007. A total of 5,287 Iranian citizens, aged 15–64 years, were included in this survey. Interviewer-administered questionnaires were applied to collect the data of participants including the demographics, diet, physical activity, smoking, history of hypertension, and history of diabetes. Anthropometric characteristics were measured and serum biochemistry profiles were determined on venous blood samples. Diabetes (fasting plasma glucose ≥ 126 mg/dl), hypertension (systolic blood pressure ≥ 140 mmHg, diastolic blood pressure ≥ 90 mmHg, or use of anti-hypertensive drugs), dyslipidemia (hypertriglyceridemia: triglycerides ≥ 150 mg/dl, hypercholesterolemia: total cholesterol ≥ 200 mg/dl), obesity (body mass index ≥ 30 kg/m2), and central obesity (waist circumference ≥ 80 cm in females and ≥ 94 cm in males) were identified and the national prevalence rates were estimated.The prevalence of diabetes, hypertension, obesity, and central obesity was 8.7% (95%CI = 7.4–10.2%), 26.6% (95%CI = 24.4–28.9%), 22.3% (95%CI = 20.2–24.5%), and 53.6% (95%CI = 50.4–56.8%), respectively. The prevalence of hypertriglyceridemia and hypercholesterolemia was 36.4% (95%CI = 34.1–38.9%) and 42.9% (95%CI = 40.4–45.4%), respectively. All of the mentioned prevalence rates were higher among females (except hypertriglyceridemia) and urban residents.We documented a strikingly high prevalence of a number of chronic non-communicable diseases and their risk factors among Iranian adults. Urgent preventive interventions should be implemented to combat the growing public health problems in Iran.Chronic non-communicable diseases (NCDs) such as cardiovascular disease and diabetes are the leading cause of death worldwide [1], having comprised 60% of all deaths in 2005. Approximately 80% of NCD-attributable deaths are occurring in low and middle-income countries
Learning and Teaching Ethics through Stories: A Few Examples from the Buddhist Tradition  [PDF]
Mehrdad Massoudi
Creative Education (CE) , 2010, DOI: 10.4236/ce.2010.11004
Abstract: The art of storytelling, similar to poetry, takes us to a different realm, yet always bringing us back to where we are. In many traditional societies, ethical concerns were taught through stories. A few stories from the Buddhist tradition have been selected to convey some basic teachings of the Buddha on ethical issues. This does not mean that these few stories capture the whole of Buddhist ethics. Furthermore, it is understood that similar stories can be found in other traditions, and therefore the same technique can be used in other religions as well. The universalities of these stories provide a means to teach ethics in a multi-cultural context.
Many-body effects in low dimensional electron liquids
R. Asgari
Iranian Journal of Physics Research , 2008,
Abstract: This review article is about the role of electron-electron interactions in low dimensional systems and its transport properties in nano-structures. It begins with a review of the pair-distribution function theory of electron liquid systems taking into account the electron-electron interactions. We extend the theory for highly correlated system such two- and one-dimensional electron liquids. We then review the microscopic theory of the local-field factors and calculate the quasiparticle properties in two-dimension electron liquid and compare our results with those measured by recent experiments. The physics of two-dimension bilayer structures are revised and are immediately applied to the study of charged Coulomb drag effects in a bilayer electron-electron system and results are compared with experimental data. As a final application, the Luttinger theory is discussed and we compare our recent calculations with those obtained from quantum Monte Carlo simulation for one dimensional electron liquid.
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