Tehran, Iran
Tehran, Iran

The University of Tehran , also known as Tehran University and UT, is Iran's oldest modern university. Based on its historical, socio-cultural and political pedigree, as well as its research and teaching profile, UT has been nicknamed "The mother university of Iran" . It is almost always ranked as the best university in Iran in national and international rankings. It is also the premier knowledge producing institute among all OIC countries. The university offers 111 bachelor degree programs, 177 masters' degree programs, and 156 Ph.D. programs. Many of the departments were absorbed into the University of Tehran from the Dar al-Funun established in 1851 and the Tehran School of Political science established in 1899.The University of Tehran is known as the symbol of higher education in Iran. The main campus of the University is located in the central part of the city. However, other campuses are spread across the city as well as in the suburbs such as the Baghe Negarestan Campus at the central eastern part of the city, the Northern Amirabad Campuses at the central western part of the city and the Abureyhan Campus in the suburb of the capital. The main gate of the University with its specific design and modern architecture is the logo of the University and in a more general sense, a logo of education in Iran. The University is one of the city’s attractions, hosting many international and cultural events attracting academia, foreign tourists as well as local residents. The major festive of Friday Prayers of the capital is held at the University’s main campus every Friday.Admission to the university's renowned undergraduate and graduate programs is very competitive and is limited to the top one percent of students who pass the national entrance examination administered yearly by the Ministry of Science, Research and Technology. Tehran University consistently makes the number one choice of qualifying applicants among all other universities of Iran. Wikipedia.

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Saberi A.A.,University of Tehran | Saberi A.A.,Institute for Research in Fundamental Sciences
Physics Reports | Year: 2015

Percolation is the simplest fundamental model in statistical mechanics that exhibits phase transitions signaled by the emergence of a giant connected component. Despite its very simple rules, percolation theory has successfully been applied to describe a large variety of natural, technological and social systems. Percolation models serve as important universality classes in critical phenomena characterized by a set of critical exponents which correspond to a rich fractal and scaling structure of their geometric features. We will first outline the basic features of the ordinary model. Over the years a variety of percolation models has been introduced some of which with completely different scaling and universal properties from the original model with either continuous or discontinuous transitions depending on the control parameter, dimensionality and the type of the underlying rules and networks. We will try to take a glimpse at a number of selective variations including Achlioptas process, half-restricted process and spanning cluster-avoiding process as examples of the so-called explosive percolation. We will also introduce non-self-averaging percolation and discuss correlated percolation and bootstrap percolation with special emphasis on their recent progress. Directed percolation process will be also discussed as a prototype of systems displaying a nonequilibrium phase transition into an absorbing state. In the past decade, after the invention of stochastic Löwner evolution (SLE) by Oded Schramm, two-dimensional (2D) percolation has become a central problem in probability theory leading to the two recent Fields medals. After a short review on SLE, we will provide an overview on existence of the scaling limit and conformal invariance of the critical percolation. We will also establish a connection with the magnetic models based on the percolation properties of the Fortuin-Kasteleyn and geometric spin clusters. As an application we will discuss how percolation theory leads to the reduction of the 3D criticality in a 3D Ising model to a 2D critical behavior. Another recent application is to apply percolation theory to study the properties of natural and artificial landscapes. We will review the statistical properties of the coastlines and watersheds and their relations with percolation. Their fractal structure and compatibility with the theory of SLE will also be discussed. The present mean sea level on Earth will be shown to coincide with the critical threshold in a percolation description of the global topography. © 2015 Elsevier B.V.

Sadjadi H.M.,University of Tehran
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We consider the spatially flat Friedmann-Lemaitre-Robertson-Walker space-time in the teleparallel model of gravity and assume that the Universe is nearly filled by cold dark matter and a nonminimally coupled scalar field with a power-law potential as dark energy. We investigate the possibility that the Universe undergoes a transition from quintessence to phantom phase. An analytical solution for the scalar field is obtained, and necessary conditions required for such a transition are discussed. © 2013 American Physical Society.

Rajabioun R.,University of Tehran
Applied Soft Computing Journal | Year: 2011

In this paper a novel evolutionary algorithm, suitable for continuous nonlinear optimization problems, is introduced. This optimization algorithm is inspired by the life of a bird family, called Cuckoo. Special lifestyle of these birds and their characteristics in egg laying and breeding has been the basic motivation for development of this new evolutionary optimization algorithm. Similar to other evolutionary methods, Cuckoo Optimization Algorithm (COA) starts with an initial population. The cuckoo population, in different societies, is in two types: mature cuckoos and eggs. The effort to survive among cuckoos constitutes the basis of Cuckoo Optimization Algorithm. During the survival competition some of the cuckoos or their eggs, demise. The survived cuckoo societies immigrate to a better environment and start reproducing and laying eggs. Cuckoos' survival effort hopefully converges to a state that there is only one cuckoo society, all with the same profit values. Application of the proposed algorithm to some benchmark functions and a real problem has proven its capability to deal with difficult optimization problems. © 2011 Elsevier B.V. All rights reserved.

Rafiee R.,University of Tehran
Composite Structures | Year: 2013

The degree to which the non-straight shape of carbon nanotube (CNT) affects the mechanical properties of CNT-based composites is studied. The effective scale of CNT curvature is determined using top-down scanning and then appropriate representative volume element encompassing of several straight and/or non-straight CNTs is defined. A multi-scale modeling relying on bottom-up approach is employed and CNT curvature is taken into account as a random parameter to capture any arbitrary non-straight shapes of CNTs. Comparing obtained results from developed modeling with available experimental data, the developed modeling procedure is validated. The results demonstrate that non-straight shape of CNT considerably reduces its efficiency to reinforce polymer matrix. It is observed that low contents of CNT enhance Young's modulus of polymer more efficiently due to the lower level of CNT waviness and agglomeration. The results exhibit non-linear variations in the Young's modulus of CNT-based composites versus CNT contents which was approved by experimental observations. © 2012 Elsevier Ltd.

Ellenbroek B.A.,Victoria University of Wellington | Ghiabi B.,University of Tehran
Trends in Neurosciences | Year: 2014

Although histamine H3 receptors are predominantly known as presynaptic receptors, regulating the release of neurotransmitters such as dopamine, acetylcholine, and histamine, in the striatal complex the vast majority of these receptors are actually located on the other side, in other words postsynaptically. Given their strategic location, they can crucially affect signaling throughout the basal ganglia. We describe the anatomy and function of H3 receptors within the basal ganglia with a specific focus on their colocalization with dopamine D1 and D2 receptors. Because the basal ganglia are centrally involved in several major neurological and psychiatric disorders, we also discuss the therapeutic potential of drugs targeting H3 receptors in the treatment of Parkinson disease (PD), schizophrenia, and addiction. © 2014 Elsevier Ltd.

Mirzadeh H.,University of Tehran
Mechanics of Materials | Year: 2014

The constitutive behaviors of Mg-Al-Zn magnesium alloys during hot deformation were studied over a wide range of Zener-Hollomon parameters by consideration of physically-based material's parameters. It was demonstrated that the theoretical exponent of 5 and the lattice self-diffusion activation energy of magnesium (135 kJ/mol) can be used in the hyperbolic sine law to describe the flow stress of AZ31, AZ61, AZ80, and AZ91 alloys. The apparent hyperbolic sine exponents of 5.18, 5.06, 5.17, and 5.12, respectively for the AZ31, AZ61, AZ80, and AZ91 alloys by consideration of deformation activation energy of 135 kJ/mol were consistent with the considered theoretical exponent of 5. The influence of Al upon the hot flow stress of Mg-Al-Zn alloys was characterized by the proposed approach, which can be considered as a versatile tool in comparative hot working and alloy development studies. It was also shown that while the consideration of the apparent material's parameters may result in a better fit to experimental data, but the possibility of elucidating the effects of alloying elements on the hot working behavior based on the constitutive equations will be lost. © 2014 Elsevier Ltd. All rights reserved.

Mahboub V.,University of Tehran
Journal of Geodesy | Year: 2012

In this contribution, it is proved that the weighted total least-squares (WTLS) approach preserves the structure of the coefficient matrix in errors-in-variables (EIV) model when based on the perfect description of the dispersion matrix. To achieve this goal, first a proper algorithm for WTLS is developed since the quite recent analytical solution for WTLS by Schaffrin and Wieser is restricted to the condition P A=P 0⊗P x (where ⊗ is used to denote the Kronecker product) for the weight matrix of the coefficient matrix in the EIV model. This situation can be seen in the case of an affine transformation where the univariate approach can be an appropriate alternative to the multivariate WTLS approach, which has been applied to the affine transformation by Schaffrin and Felus, resp. Schaffrin and Wieser with restrictions similar to P A=P 0⊗P x. In addition, this algorithm for WTLS can be interpreted well in the geodetic literature since it is based on the perfect description of the inverse dispersion matrix (or variance-covariance). By using the algorithm of WTLS, one obtains more realistic results in some applications of transformation where a high precision is needed. Some empirical examples, resp. simulation studies give insight into the efficiency of the procedure. © 2011 Springer-Verlag.

Complex coacervation driven by associative electrostatic interactions was studied in mixtures of exfoliated sodium-montmorillonite (Na(+)-MMT) nanoplatelets and fish gelatin, at a specific mixing ratio and room temperature. Structural and viscoelastic properties of the coacervate phase were investigated as a function of pH by means of different complementary techniques. Independent of the technique used, the results consistently showed that there is an optimum pH value at which the coacervate phase shows the tightest structure with highest elasticity. The solid-like coacervates showed an obvious shear-thinning behavior and network fracture but immediately recovered back into their original elastic character upon removal of the shear strain. The nonlinear mechanical response characterized by single step stress relaxation experiments revealed the same trend for the yield stress and isochronal shear modulus of the coacervates as a function of pH with a maximum at pH 3.0 and lower values at 2.5 and 3.5 pHs, followed by a very sharp drop at pH 4.0. Finally, small-angle X-ray scattering (SAXS) data confirmed that at pHs lower than 4.0 the coacervate phases were dense and structured with a characteristic length scale (ξ(SAXS)) of ~7-9 nm. Comparing the ξ(SAXS) with rheological characteristic length (ξ(rheol)) estimated from low-frequency linear viscoelastic data and network theory, it was concluded that both the strength of the electrostatic interactions and the conformation of the gelatin chains before and during of the coacervation process are responsible for the structure and rigidity of the coacervates.

Soroudi A.,University of Tehran
Energy | Year: 2013

This paper proposes a robust optimization model for optimal self scheduling of a hydro-thermal generating company. The proposed model is suitable for price taker Gencos which seeks the optimal schedule of its thermal and hydro generating units for a given operating horizon. The uncertainties of electricity prices are modeled using robust optimization approach to make it more practical. It considers various technical constraints like water balance and water traveling time between cascaded power stations and emission allowance. Finally, different case studies are analyzed to demonstrate the strength of the proposed model. © 2013 Elsevier Ltd.

Mohseni Sadjadi H.,University of Tehran
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

We consider modified teleparallel gravity (f(T) gravity), as a framework to explain the present accelerated expansion of the universe. The matter component is assumed to be cold dark matter. To find the explicit form of the function f, we utilize generalized Noether theorem and use generalized vector fields as variational symmetries of the corresponding Lagrangian. We study the cosmological consequences of the obtained results. © 2012 Elsevier B.V.

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