oalib

OALib Journal期刊

ISSN: 2333-9721

费用:99美元

投稿

时间不限

2018 ( 1 )

2017 ( 177 )

2016 ( 251 )

2015 ( 764 )

自定义范围…

匹配条件: “ Mohammad Hassan Rahimian” ,找到相关结果约17563条。
列表显示的所有文章,均可免费获取
第1页/共17563条
每页显示
Numerical Simulation of Non-Newtonian Pseudo-Plastic Fluid in a Micro-Channel Using the Lattice Boltzmann Method  [PDF]
Hossein Hamedi, Mohammad Hassan Rahimian
World Journal of Mechanics (WJM) , 2011, DOI: 10.4236/wjm.2011.15029
Abstract: In this paper, the power-law model for a non-Newtonian (pseudo-plastic) flow is investigated numerically. The D2Q9 model of Lattice Boltzmann method is used to simulate the micro-channel flow with expansion geometries. This geometry is made by two squared or trapezoid cavities at the bottom and top of the channel which can simulate an artery with local expansion. The cavities are displaced along the channel and the effects of the displacements are investigated for inline structures and staggered ones (anti-symmetric expansion). The method is validated by a Poiseuille flow of the power-law fluid in a duct. Validation is performed for two cases: The Newtonian fluid and the shear thinning fluid (pseudo-plastic) with n = 0.5. The results are discussed in four parts: 1) Pressure drop; It is shown that the pressure drop along the channel for inline cavities is much more than the pressure drop along the staggered structures. 2) Velocity profiles; the velocity profiles are sketched at the centerline of the cavities. The effects of pseudo-plasticity are discussed. 3) Shear stress distribution; the shear stress is computed and shown in the domain. The Newtonian and non-Newto- nian fluids are discussed and the effect of the power n on shear stress is argued. 4) Generated vortices in the cavities are also presented. The shape of the vortices is depicted for various cases. The results for these cases are talked over and it is found that the vortices will be removed for flows with n smaller than 0.5.
An Unsteady Mixed Convection in a Driven Cavity Filled with Nanofluids Using an Externally Oscillating Lid  [PDF]
Arian Jafari, Mohammad Hassan Rahimian, Alireza Saeedmanesh
Journal of Electronics Cooling and Thermal Control (JECTC) , 2013, DOI: 10.4236/jectc.2013.32008
Abstract: A numerical investigation of an unsteady, periodic, laminar mixed-convection in a cavity utilized with copper-water nanofluid is presented. In this study both top and bottom walls are assumed to be isolated, meanwhile sidewalls are considered under constant temperature condition. We consider a time-dependent oscillating wall on top to fulfill a periodic mixed-convection inside the cavity. In this type of problems both Grashof and Reynolds numbers play a great role in flow pattern and heat transfer characteristics, so we focus our study on four major parameters that can be crucial such as Grashof \"\" and Reynolds\"\"numbers, solid volume fraction \"\" and the non-dimensional lid frequency\"\" . The obtained results show that the augmentation of Reynolds number and Grashof number would enhance the average Nusselt number. It is also found that unlike steady state condition, at high Reynolds numbers, as lid is moving in the negative direction the average Nusselt number on the hot wall becomes higher in respect to the case that lid is moving in the positive direction due to thermal boundary layer disturbance. Lid frequency does not have a significant effect on thermal characteristics at low Reynolds numbers, meanwhile at higher Reynolds numbers, increment of lid frequency results in heat transfer reduction. Moreover, solid volume fraction is found to have better efficiency at higher Grashof numbers.
Numerical Simulation of Single Bubble Deformation in Straight Duct and 90° Bend Using Lattice Boltzmann Method  [PDF]
Hamid Mohammad Mirzaie Daryan, Mohammad Hasan Rahimian
Journal of Electronics Cooling and Thermal Control (JECTC) , 2015, DOI: 10.4236/jectc.2015.54007
Abstract: The paper aims to give a comprehensive investigation of the two dimensional deformation of a single bubble in a straight duct and a 90° bend under the zero gravity condition. For this, the two phase flow lattice Boltzmann equation (LBE) model is used. An averaging scheme of boundary condition implementation has been applied and validated. A generalized deformation benchmark has been introduced. By presenting and analyzing the shape of the bubbles moving through the channels, the effects of the all important nondimensional numbers on the bubble deformation are examined thoroughly. It is seen that by increasing the Weber number the rate of the deformation enhances. Besides, because of the velocity dissimilarity between the particles constructing the bubble, the initial coordinates and the diameter of the bubble play a great role in the future behavior of the bubble. The density ratio has a little effect on the shape of the bubble within the assumed range of the density ratio. Moreover, as the Reynolds number or the viscosity ratio is decreased, higher rate of deformation is exhibited. Finally it is found that there is an inverse proportionality between the amplitude and frequency of the bubble deformation.
Intertidal scale worms (Polychaeta, Polynoidae and Sigalionidae) from the northern coasts of the Persian Gulf and Gulf of Oman
Alieh Bonyadi Naeini,Hassan Rahimian
ZooKeys , 2009, DOI: 10.3897/zookeys.31.127
Abstract: Sampling of Polychaeta has been performed in the Persian Gulf and Gulf of Oman during December 2006 to October 2007. So far, 10 species belonging to six genera from two families have been identified. Seven species from the family Polynoidae (Lepidonotus natalensis, L. purpureus, Parahalosydnopsis arabica, Harmothoe hirsuta, H. liaoi, Paralepidonotus ampulliferous) and one species from the family Sigalionidae (Sthenelais boa) are new records for the Gulf of Oman. Thormora jukesii and H. marerubrum (Polynoidae) are new records for the Persian Gulf. Lepidonotus tenuisetosus could be recorded for both gulfs. The most diverse genera in the area are Lepidonotus and Harmothoe with each of them represented by three species. The most common species was Lepidonotus tenuisetosus, which was collected from 25 locations. The highest diversity of polychaetes species could be observed in rocky habitats containing stones covered with algae.
THE STUDY OF BARRIERS TO ENTREPRENEURSHIP IN MEN AND WOMEN
Mohammad Bagher Gorji,Paria Rahimian
Australian Journal of Business and Management Research , 2011,
Abstract: The present study aims to investigate the barriers to individual entrepreneurship as well as comparing them in men and women population. This study was applied, correlation-survey method. Using field method, the data are collected from 113 men entrepreneurs and 65 women entrepreneurs. One questionnaire whose validity and reliability is verified by content and Cranach’s methods is also used to collect the research data. To analyze the data, T-test and ANOVA are used. The results indicated that there is a meaningful difference between individual and environmental barriers to entrepreneurship and order of effectiveness of barriers in men and women.
Learning without Recall: A Case for Log-Linear Learning
Mohammad Amin Rahimian,Ali Jadbabaie
Mathematics , 2015,
Abstract: We analyze a model of learning and belief formation in networks in which agents follow Bayes rule yet they do not recall their history of past observations and cannot reason about how other agents' beliefs are formed. They do so by making rational inferences about their observations which include a sequence of independent and identically distributed private signals as well as the beliefs of their neighboring agents at each time. Fully rational agents would successively apply Bayes rule to the entire history of observations. This leads to forebodingly complex inferences due to lack of knowledge about the global network structure that causes those observations. To address these complexities, we consider a Learning without Recall model, which in addition to providing a tractable framework for analyzing the behavior of rational agents in social networks, can also provide a behavioral foundation for the variety of non-Bayesian update rules in the literature. We present the implications of various choices for time-varying priors of such agents and how this choice affects learning and its rate.
Numerical Analysis of Electromagnetic Control of the Boundary Layer Flow on a Ship Hull  [PDF]
Mohammad Bakhtiari, Hassan Ghassemi
Open Journal of Fluid Dynamics (OJFD) , 2014, DOI: 10.4236/ojfd.2014.41006
Abstract: In this article, electromagnetic control of turbulent boundary layer on a ship hull is numerically investigated. This study is conducted on the geometry of tanker model hull. For this purpose, a combination of electric and magnetic fields is applied to a region of boundary layer on stern so that produce wall parallel Lorentz forces in streamwise direction as body forces in stern flow. The governing equations including RANS equations with SST k-ω turbulent model coupled with electric potential equation are numerically solved by using Ansys Fluent codes. Accuracy of this turbulent model of Fluent in predicting Turbulent flow around a ship is also tested by comparing with available experimental results that it shows a good agreement with experimental data. The results obtained for ship flow show that by applying streamwise Lorentz forces that are large enough, flow is accelerated. The results are caused to delay or avoid the flow separation in stern, increase the propeller inlet velocity, create uniform flow distribution behind the ship’s hull in order to improve the propeller performance, and finally decrease the pressure resistance and total resistance.
First record of the family Pseudocerotidae (Platyhelminthes, Polycladida, Cotylea) from the Persian Gulf, Iran
Zahra Khalili,Hassan Rahimian,Jamile Pazooki
ZooKeys , 2009, DOI: 10.3897/zookeys.31.136
Abstract: In this paper, two species of cotylean Platyhelminthes are recorded for the first time from Qeshm Island, Persian Gulf, Iran. Pictures are taken from living specimens to illustrate shape and colour, and stained sections and drawings are used to describe shape and organisation of some organs. Morphological characters of Persian Gulf specimens of Tytthosoceros lizardensis Newman & Cannon, 1996 are compared to those of the type specimens of this species.
Learning without Recall by Random Walks on Directed Graphs
Mohammad Amin Rahimian,Shahin Shahrampour,Ali Jadbabaie
Mathematics , 2015,
Abstract: We consider a network of agents that aim to learn some unknown state of the world using private observations and exchange of beliefs. At each time, agents observe private signals generated based on the true unknown state. Each agent might not be able to distinguish the true state based only on her private observations. This occurs when some other states are observationally equivalent to the true state from the agent's perspective. To overcome this shortcoming, agents must communicate with each other to benefit from local observations. We propose a model where each agent selects one of her neighbors randomly at each time. Then, she refines her opinion using her private signal and the prior of that particular neighbor. The proposed rule can be thought of as a Bayesian agent who cannot recall the priors based on which other agents make inferences. This learning without recall approach preserves some aspects of the Bayesian inference while being computationally tractable. By establishing a correspondence with a random walk on the network graph, we prove that under the described protocol, agents learn the truth exponentially fast in the almost sure sense. The asymptotic rate is expressed as the sum of the relative entropies between the signal structures of every agent weighted by the stationary distribution of the random walk.
Detection and Isolation of Failures in Directed Networks of LTI Systems
Mohammad Amin Rahimian,Victor M. Preciado
Mathematics , 2014,
Abstract: We propose a methodology to detect and isolate link failures in a weighted and directed network of identical multi-input multi-output LTI systems when only the output responses of a subset of nodes are available. Our method is based on the observation of jump discontinuities in the output derivatives, which can be explicitly related to the occurrence of link failures. The order of the derivative at which the jump is observed is given by $r(d+1)$, where $r$ is the relative degree of each system's transfer matrix, and $d$ denotes the distance from the location of the failure to the observation point. We then propose detection and isolation strategies based on this relation. Furthermore, we propose an efficient algorithm for sensor placement to detect and isolate any possible link failure using a small number of sensors. Available results from the theory of sub-modular set functions provide us with performance guarantees that bound the size of the chosen sensor set within a logarithmic factor of the smallest feasible set of sensors. These results are illustrated through elaborative examples and supplemented by computer experiments.
第1页/共17563条
每页显示


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.