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Second Order Fluid Glow Discharge Model Sustained by Different Source Terms

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Plasma Science and Technology 2011年第5期13卷 583-590页

作者： D.GUENDOUZ A.hamid A.HENNAD Institute of Maintenance and Industrial Security University of Oran Electrical Engineering Department Oran University of Sciences and Technology

Behavior of charged particles in a DC low pressure glow discharge is studied. The electric properties of the glow discharge in argon, maintained by a constant source term with uni- form electron and ion generation, between two plane electrodes or by secondary electron emission at the cathode, are determined. A fluid model is used to solve self-consistently the first three moments of the Boltzmann equation coupled with the Poisson equation. The stationary spatial distribution of the electron and ion densities, the electric potential, the electric field, and the electron energy, in a two-dimensional （2D） configuration, are presented.

关键词： glow discharge Boltzmann equation Poisson equation electron temperature

Electroencephalography studies of hypoxic ischemia in fetal and neonatal animal models

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Neural Regeneration Research 2020年第5期15卷 828-837页

作者： hamid Abbasi Charles P.Unsworth Department of Engineering Science the University of Auckland

Alongside clinical achievements,experiments conducted on animal models (including primate or non-primate) have been effective in the understanding of various pathophysiological aspects of perinatal hypoxic/ ischemic encephalopathy (HIE).Due to the reasonably fair degree of flexibility with experiments,most of the research around HIE in the literature has been largely concerned with the neurodevelopmental outcome or how the frequency and duration of HI seizures could relate to the severity of perinatal brain injury,following HI *** survey concentrates on how EEG experimental studies using asphyxiated animal models (in rodents,piglets,sheep and non-human primate monkeys) provide a unique opportunity to examine from the exact time of HI event to help gain insights into HIE where human studies become difficult.

关键词： animal models automatic detection clinical EEG fetal HIE hypoxic-ischemic encephalopathy neonatal non-human primates review seizure

Development of fragility curves by incorporating new spectral shape indicators and a weighted damage index:case study of steel braced frames in the city of Mashhad,Iran

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Earthquake Engineering and Engineering Vibration 2017年第2期16卷 383-395页

作者： hamid Kazemi Mohsen Ghafory-Ashtiany Alireza Azarbakht Department of Civil Engineering Science and Research Branch Islamic Azad University Tehran Iran International Institute of Earthquake Engineering and Seismology (IIEES) Tehran Iran Department of Civil Engineering Faculty of Engineering Arak University Arak Iran

In this study, strong ground motion record （SGMR） selection based on Eta （~/） as a spectral shape indicator has been investigated as applied to steel braced flame structures. A probabilistic seismic hazard disaggregation analysis for the definition of the target Epsilon （ε） and the target Eta （η） values at different hazard levels is presented, taking into account appropriately selected SGMR＇s. Fragility curves are developed for different limit states corresponding to three representative models of typical steel braced frames having significant irregularities in plan, by means of a weighted damage index. The results show that spectral shape indicators have an important effect on the predicted median structural capacities, and also that the parameter r/is a more robust predictor of damage than searching for records with appropriate c values.

关键词： vulnerability spectral shape indicator incremental dynamic analysis damage index hazard disaggregation record selection

Study of effective parameters for enhancement of methane gas production from natural gas hydrate reservoirs

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Green Energy & Environment 2019年第4期4卷 453-469页

作者： hamid Aghajari Moien Habibi Moghaddam Mehdi Zallaghi Azad University Omidiyeh BranchIran Isfahan Oil Refinery Co. Iran Science and Research Azad University of Tehran Iran Tehran Petroleum Research Center Petroleum University of TechnologyIran

Natural gas hydrate resources have become the major source of energy in the second half of 21st *** production and fluid behavior in natural gas hydrate reservoirs are different from conventional *** are three major methods for methane decomposition such as depressurization,thermal stimulation and inhibitor ***,CO2 substitution can also be introduced as an alternative method to inject in sediments containing gas *** these methods tend to imbalance equilibrium condition via temperature and pressure variation in order to fulfill hydrate decomposition *** study aims to simulate depressurization method for gas production from a hydrate gas bearing ***,a sensitivity analysis of reservoir parameters includes porosity,permeability,hydrate saturation,hydrate thickness layer;pressure and temperature of single well hydrate model were investigated to determine how these parameters impact on gas *** show that depressurization is an efficient method for gas production from hydrate bearing *** sensitivity analysis,it has been concluded that if properties of a hydrate layer such as porosity and permeability become greater,methane production will be increased ***,results investigate that the rate of hydrate dissociate is strongly dependent on pressure reduction,and it has a reverse relationship with bottomhole pressure and reservoir temperature.

关键词： Gas hydrate Depressurization Sensitivity analysis Simulation study Hydrate dissociation Methane formation Thermodynamic equilibrium

Bifurcation in a 3-DOF Airfoil with Cubic Structural Nonlinearity

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Chinese Journal of Aeronautics 2011年第3期24卷 265-278页

作者： Saied IRANI hamid SARRAFZADEH Mohammad Reza AMOOZGAR Department of Aerospace Engineering K.N.Toosi University of Technology

Limit cycle oscillations （LCOs） as well as nonlinear aeroelastic analysis of a 3-DOF aeroelastic airfoil motion with cubic restoring moments in the pitch degree of freedom are investigated. Aeroelastic equations of an airfoil with control surface in an incompressible potential flow are presented in the time domain. The harmonic balance （HB） method is utilized to calculate the LCO frequency and amplitude for the airfoil. Also the semi-analytical method has revealed the presence of stable and unstable limit cycles, along with stability reversal in the neighborhood of a Hopf bifurcation. The system response is determined by nu- merically integrating the governing equations using a standard Runge-Kutta algorithm and the obtained results are compared with the HB method. Also the results by the third order HB （HB3） method for control surface are consistent with the other numerical solution. Finally, by combining the numerical and the HB methods, types of bifiarcation, be it supercritical, subcritical, or diver- gent flutter area are identified.

关键词： flutter bifurcation cubic nonlinearity limit cycle oscillations harmonic balance method

An accurate model for the thin film flow

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Acta Mechanica Sinica 2008年第4期24卷 375-380页

作者： hamid Ait Abderahmane Georgios H.Vatistas Department of Mechanical and Industrial Engineering Concordia University 1455 de Maisonneuve Blvd West Montreal OC H3G 1M8 Canada

This paper deals with the linear stability of a liquid film flowing down an inclined plane. The Navier-Stokes equations were reduced into four evolution equations that describe the development of the film depth, the flow rate, the free surface velocity, and the wall shear stress, using the Karman-Polhausen boundary layer integral method. Thus, we were able to determine the stability threshold and approach well the critical wave number for long waves. The obtained results were found to be in good agreement with the experiments of Liu et al.

关键词： Liquid film Linear stability Flow model

Fabrication and characterization of nanocrystalline Al/Al_(12)(Fe,V)_3Si alloys by consolidation of mechanically alloyed powders

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International Journal of Minerals,Metallurgy and Materials 2014年第7期21卷 711-719页

作者： hamid Ashrafi Rahmatollah Emadi Mohammad Hosein Enayati Department of Materials Engineering Isfahan University of Technology

The aim of this study was to produce bulk nanocrystalline Al/Al12（Fe,V）3Si alloys by mechanical alloying （MA） and subsequent hot pressing （HP） of elemental powders. A nanostructured Al-based solid solution was formed by MA of elemental powders for 60 h. After HP of the as-milled powders at 550℃ for 20 min, the Al12（Fe,V）3Si phase was precipitated in a nanocrystalline Al matrix. Scanning electron microscopy （SEM） images of the bulk samples represented a homogeneous and uniform microstructure that was superior to those previously obtained by rapid solidification-powder metallurgy （RS-PM）. Nanostructured Al-8.5Fe-1.3V-1.7Si and Al-11.6Fe-1.3V-2.3Si alloys ex-hibited high HV hardness values of～205 and～254, respectively, which are significantly higher than those reported for the RS-PM counter-parts.

关键词： aluminum alloys nanostructured materials mechanical alloying hot pressing hardness

An investigation on the ground motion parameters and seismic response of underground structures

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Earthquake Science 2012年第3期25卷 253-261页

作者： hamid Reza Nejati Morteza Ahmadi hamid Hashemolhosseini Rock Mechanics Department School of Engineering Tarbiat Modares University Tehran 14117-13116 Iran Mining Engineering Department Isfahan University of Technology Isfahan 84156-83111 Iran

Peak ground acceleration (PGA), frequency content and time duration are three fundamental parameters of seismic loading. This study focuses on the seismic load frequency and its effect on the underground structures. Eight accelerograms regarding different occurred earthquakes that are scaled to an identical PGA and variation of ground motion parameters with ratio of peak ground velocity (PGV) to PGA, as a parameter related to the load frequency, are considered. Then, concrete lining response of a circular tunnel under various seismic conditions is evaluated analytically. In the next, seismic response of underground structure is assessed numerically using two different time histories. Finally, effects of incident load frequency and frequency ratio on the dynamic damping of geotechnical materials are discussed. Result of analyses show that specific energy of seismic loading with identical PGA is related to the seismic load frequency. Furthermore, incident load frequency and natural frequency of a system have influence on the wave attenuation and dynamic damping of the system.

关键词： ground motion parameter load frequency PGA dynamic analysis wave attenuation

Seismic progressive-failure analysis of tall steel structures under beam-removal scenarios

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Frontiers of Structural and Civil Engineering 2019年第4期13卷 904-917页

作者： Behrouz BEHNAM Fahimeh SHOJAEI hamid Reza RONAGH School of Civil and Environmental Engineering Amirkabir University of Technology Tehran 13496 Iran Independent Researcher Earthquake Engineer Parand 37611 Iran Centre for Infrastructure Engineering Western Sydney University NSW 2751 Australia

Investigating progressive collapse of tall structures under beam removal scenarios after earthquake is a complex subject because the earthquake damage acts as an initial condition for the subsequent scenario. An investigation is performed here on a 10 story steel moment resisting structure designed to meet the life safety level of performance when different beam removal scenarios after earthquake are considered. To this end, the structure is first subjected to the design earthquake simulated by Tabas earthquake acceleration. The beam removal scenarios are then considered at different locations assuming that both ends connections of the beam to columns are simultaneously detached from the columns;thus the removed beam falls on the underneath floor with an impact. This imposes considerable loads to the structure leading to a progressive collapse in all the scenarios considered. The results also show that the upper stories are much more vulnerable under such scenarios than the lower stories. Hence, more attention shall be paid to the beam-to-column connections of the upper stories during the process of design and construction.

关键词： progressive collapse tall steel moment-resisting frames non-linear dynamic analysis beam-removal scenario impact