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Analysis of effective parameters on ablative PPT performance
, Article Aircraft Engineering and Aerospace Technology ; Volume 84, Issue 4 , 2012 , Pages 231-243 ; 00022667 (ISSN) ; Schönherr, T ; Sharif University of Technology
2012
Abstract
Purpose - The purpose of this paper is to comprehensively review most of the significant works ever done worldwide to study the effects of essential parameters on pulsed plasma thruster (PPT) performance and to analyze the effects of each parameter on PPT performance. Design/methodology/approach - All the important works studying PPT performance are categorized by the parameter they have studied and its effect on the thruster performance, and their works have been reviewed to analyze the influence of each parameter. Findings - The analysis leads to elucidation of the effects of different geometrical parameters including aspect ratio, electrode width, electrode spacing, electrode shape,...
Novel phenomenological discrete bubble model of freely bubbling dense gas-solid fluidized beds: Application to two-dimensional beds
, Article AIChE Journal ; Volume 58, Issue 11 , January , 2012 , Pages 3306-3317 ; 00011541 (ISSN) ; Molaei Dehkordi, A ; Deen, N. G ; van Sint Annaland, M ; Kuipers, J. A. M ; Sharif University of Technology
2012
Abstract
A phenomenological discrete bubble model has been developed for freely bubbling dense gas-solid fluidized beds and validated for a pseudo-two-dimensional fluidized bed. In this model, bubbles are treated as distinct elements and their trajectories are tracked by integrating Newton's equation of motion. The effect of bubble-bubble interactions was taken into account via a modification of the bubble velocity. The emulsion phase velocity was obtained as a superposition of the motion induced by individual bubbles, taking into account bubble-bubble interaction. This novel model predicts the bubble size evolution and the pattern of emulsion phase circulation satisfactorily. Moreover, the effects...
Investigation of particle dispersion and deposition in a channel with elliptic obstructions using lattice Boltzmann method
, Article 2012 7th IEEE International Conference on Nano/Micro Engineered and Molecular Systems, NEMS 2012, 5 March 2012 through 8 March 2012 ; March , 2012 , Pages 523-528 ; 9781467311243 (ISBN) ; Moosavi, A ; Sharif University of Technology
2012
Abstract
Particle transport and deposition in a channel flow with elliptic obstruction is studied. Numerical simulation of fluid flow is performed using two-dimensional lattice Boltzmann method, while one-way coupling Lagrangian method for particle tracking is used. Standard particles are injected in the inlet of the channel. Gravity, Drag force, Brownian forces, and the Saffman lift are considered in equation of particle motion. The influence of geometrical parameter, ellipse aspect ratio, is studied on dispersion and deposition of particles as well as the flow parameters, such as Reynolds number. In addition, the effect of particles size -particles of 0.01-10μm in diameter- on dispersion and...
Effect of carbon-based nanoparticles on the cure characteristics and network structure of styrene-butadiene rubber vulcanizate
, Article Polymer International ; Volume 61, Issue 4 , 2012 , Pages 664-672 ; 09598103 (ISSN) ; Shojaei, A ; Sharif University of Technology
2012
Abstract
The network structure of styrene-butadiene rubber (SBR) in the presence of carbon black (CB) with two different structures and multi-walled carbon nanotubes (MWCNTs) was investigated. Swelling behaviour, tensile properties at various strain rates and cure kinetics were characterized. Experimental data were analysed using the Flory-Rehner model as well as the tube model theory. It is found that the network structure of CB-filled SBR follows a three-phase composite model including rigid particles, semi-rigid bound rubber and matrix rubber. This bound rubber is postulated to be critical for the mechanical and deformational properties, development of crosslinking density in matrix rubber and...
Parametric study of the dynamic response of thin rectangular plates traversed by a moving mass
, Article Acta Mechanica ; Volume 223, Issue 1 , September , 2012 , Pages 15-27 ; 00015970 (ISSN) ; Rofooei, F. R ; Sharif University of Technology
2012
Abstract
The governing differential equation of motion of a thin rectangular plate excited by a moving mass is considered. The moving mass is traversing on the plate's surface at arbitrary trajectories. Eigenfunction expansion method is employed to solve the constitutive equation of motion for various boundary conditions. Approximate and exact expressions of the inertial effects are adopted for the problem formulation. In the approximate formulation, only the vertical acceleration component of the moving mass is considered while in the exact formulation all the convective acceleration components are included in the problem formulation as well. Parametric studies are carried out to investigate the...
On the influence of centerline strain on the stability of a bimorph piezo-actuated microbeam
, Article Scientia Iranica ; Volume 18, Issue 6 , December , 2011 , Pages 1246-1252 ; 10263098 (ISSN) ; Kamali Eigoli, A ; Zohoor, H ; Vossoughi, G ; Sharif University of Technology
2011
Abstract
The nonlinear equation of motion for pre-stretched EulerBernoulli beams is derived. The effect of pre-tension and pre-compression in EulerBernoulli beams is studied. It is shown that compressive strain affects the bending stiffness much more than tensile strain. Based on the derived equation, the dynamic model of bimorph piezo-actuated beams, which is accurate, yet simple, is then developed. Afterwards, the critical voltage, which makes the piezo-actuated microbeam unstable, is numerically investigated. It is shown that the strain of the centerline is proportional to the beam's aspect ratio squared. Results show that the more the aspect ratio, the less the critical voltage. In addition, it...
Visual technique for detection of gas-liquid two-phase flow regime in the airlift pump
, Article Journal of Petroleum Science and Engineering ; Volume 75, Issue 3-4 , January , 2011 , Pages 327-335 ; 09204105 (ISSN) ; Ghanbarzadeh, S ; Saidi, M. H ; Sharif University of Technology
Abstract
Simplicity of manufacturing and high reliability of airlift pumps have promoted these pumps to be used in different industries, such as petrochemical and oil industries, especially in oil recovery from dead wells. One of the main parameters affecting the performance of these pumps is two-phase flow regime in the main pipe of the pump. In this research, experimental data are utilized to investigate the influence of the flow regimes on the performance of an airlift pump. The data are obtained for air-water two-phase flow in a vertical pipe with a diameter of d = 50. mm and an aspect ratio of L/d = 120. In this study, the gas liquid upward two-phase flow regime in the upriser pipe is...
Seismic assessment of unanchored steel storage tanks by endurance time method
, Article Earthquake Engineering and Engineering Vibration ; Volume 10, Issue 4 , 2011 , Pages 591-603 ; 16713664 (ISSN) ; Estekanchi, H. E ; Sharif University of Technology
Abstract
Liquid storage tanks are essential structures that are often located in residential and industrial areas; thus an assessment of their seismic performance is an important engineering issue. In this paper, the seismic response of unanchored steel liquid storage tanks is investigated using the endurance time (ET) dynamic analysis procedure and compared to responses obtained for anchored tanks under actual ground motions and intensifying ET records. In most cases, the results from ground motions are properly obtained with negligible differences using ET records. It is observed that uplifting of the tank base, which is closely related to the tank aspect ratio, has the greatest significance in the...
Numerical investigation of the swirling air diffuser: Parametric study and optimization
, Article Energy and Buildings ; Volume 43, Issue 6 , June , 2011 , Pages 1329-1333 ; 03787788 (ISSN) ; Saidi, M. H ; Mohebbian, A ; Sharif University of Technology
2011
Abstract
During the recent decade, high induction diffusers have become more appealing in applications which require relatively high ventilation airflow rates, such as clean rooms. In this research, the effect of geometric parameters on the performance of a specific type of swirling air diffuser is investigated numerically. The results show that although the diffuser slots geometry, namely their angle and aspect ratio, is impressive on the diffuser performance, it is not as important as the swirling blade angle and the performance is almost constant in a wide range of slots specifications. The results also demonstrate that the diffuser performance and the resultant indoor airflow distribution highly...
Development of a penetration model for an erosive long rod considering strength effects of colliding materials
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 225, Issue 4 , August , 2011 , Pages 965-973 ; 09544062 (ISSN) ; Vahedi, K ; Zohoor, H ; Sharif University of Technology
2011
Abstract
In this article a simple penetration model for the terminal ballistic of long rod penetrators is developed. The model is to predict the crater depth of a projectile penetrating into a semi-infinite target. A principle objective was to take an account of strength properties of colliding materials using erosive phenomena. The entire velocity regime from low to hypervelocity is analysed. The effect of the penetrator aspect ratio is also considered in the model. The model developed here is based on the steady-state penetration process and is used to compare with existing experimental measurements. The results of the comparison show very good agreement with experimental investigations of other...
Incorporating multiscale micromechanical approach into PLSNs with different intercalated morphologies
, Article Journal of Applied Polymer Science ; Volume 119, Issue 6 , September , 2011 , Pages 3347-3359 ; 00218995 (ISSN) ; Bagheri, R ; Kazeminezhad, M ; Heidarian, D ; Sharif University of Technology
2011
Abstract
The objective of the present study is to predict Young's modulus of polymer-layered silicate nanocomposites (PLSNs) containing fully intercalated structures. The particular contribution of this article is to consider the changes in structural parameters of different intercalated morphologies in vicinity of each other. These parameters include aspect ratio of intercalated stacks, number of silicate layers per stack, d-spacing between the layers, modulus of the gallery phase, and volume fraction of each intercalated morphology. To do this, the effective particle concept has been employed and combined with the Mori-Tanaka micromechanical model. It has been shown that the simultaneous effects of...
Free vibration of generally laminated plates with various shapes
, Article Polymer Composites ; Volume 32, Issue 3 , FEB , 2011 , Pages 445-454 ; 02728397 (ISSN) ; Kargarnovin, M. H ; Hosseini Hashemi, S. H ; Sharif University of Technology
Abstract
This article is focused on a simple approach for determining the natural frequency and mode shape of laminated angle-ply plates with various shapes by rectangular orthotropy. Since the boundary of the domain for all shapes are not natural to the material coordinate axes it seems appropriate to express the plate displacement amplitude in terms of a polynomial and a general shape function multiplication in the x and y coordinates. The boundary conditions considered are clamped and simply supported edges. The effect of the fiber orientation, layer number, and lamination sequence on the natural frequencies of plates is also considered. The natural frequency determinant has been generated using...
Non-linear vibration analysis of laminated composite plates resting on non-linear elastic foundations
, Article Journal of the Franklin Institute ; Volume 348, Issue 2 , March , 2011 , Pages 353-368 ; 00160032 (ISSN) ; Fesanghary, M ; Ahmadian, M. T ; Sharif University of Technology
2011
Abstract
In this study, the homotopy analysis method (HAM) is used to obtain an approximate analytical solution for geometrically non-linear vibrations of thin laminated composite plates resting on non-linear elastic foundations. Geometric non-linearity is considered using von Karman's straindisplacement relations. Then, the effects of the initial deflection, ply properties, aspect ratio of the plate and foundation parameters on the non-linear free vibration is studied. Comparison between the obtained results and those available in the literature demonstrates the potential of HAM for the analysis of such vibration problems, whose governing differential equations include the quadratic and cubic...
A depthwise averaging solution for cross-stream diffusion in a Y-micromixer by considering thick electrical double layers and nonlinear rheology
, Article Microfluidics and Nanofluidics ; Volume 19, Issue 6 , 2015 , Pages 1297-1308 ; 16134982 (ISSN) ; Sadeghi, A ; Saidi, M. H ; Sharif University of Technology
Springer Verlag
2015
Abstract
Both nonlinear rheology and finite EDL thickness effects on the mixing process in an electroosmotically actuated Y-sensor are being investigated in this paper, utilizing a depthwise averaging method based on the Taylor dispersion theory. The fluid rheological behavior is assumed to obey the power-law viscosity model. Analytical solutions are obtained assuming a large channel width to depth ratio for which a 1-D profile can efficiently describe the velocity distribution. Full numerical simulations are also performed to determine the applicability range of the analytical model, revealing that it is able to provide accurate results for channel aspect ratios of ten and higher and quite...
Frequency-dependent energy harvesting via magnetic shape memory alloys
, Article Smart Materials and Structures ; Volume 24, Issue 11 , October , 2015 ; 09641726 (ISSN) ; Askari Farsangi, M. A ; Sharif University of Technology
Institute of Physics Publishing
2015
Abstract
This paper is focused on presenting an accurate framework to describe frequency-dependent energy harvesting via magnetic shape memory alloys (MSMAs). Modeling strategy incorporates the phenomenological constitutive model developed formerly together with the magnetic diffusion equation. A hyperbolic hardening function is employed to define reorientation-induced strain hardening in the material, and the diffusion equation is used to add dynamic effects to the model. The MSMA prismatic specimen is surrounded by a pickup coil, and the induced voltage during martensite-variant reorientation is investigated with the help of Faraday's law of magnetic field induction. It has been shown that, in...
Design of n-tier multilevel interconnect architectures by using carbon nanotube interconnects
, Article IEEE Transactions on Very Large Scale Integration (VLSI) Systems ; Volume 23, Issue 10 , October , 2015 , Pages 2128-2134 ; 10638210 (ISSN) ; Sarvari, R ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
In this paper, n-tier methodology is developed to design multilevel interconnect architecture of macrocells using single-wall carbon nanotube (SWCNT) bundles. Upper limit of low-bias voltage of SWCNT bundle interconnects is derived and its dependence on temperature, SWCNTs' diameter, and interconnect length is studied. Possibility of using SWCNT bundles as local interconnects at 7.5-nm technology node is discussed, and it is shown that SWCNT bundles with 1 nm diameter cannot be used at the first interconnect metal level. Using Cu and SWCNT bundles, multilevel interconnect architecture of a 7.5-nm ASIC macrocell is designed which reduces the number of metal levels by 27% and power dissipation...
Investigation of Thermomechanical Properties of UHMWPE/Graphene Oxide Nanocomposites Prepared by in situ Ziegler-Natta Polymerization
, Article Advances in Polymer Technology ; Volume 34, Issue 4 , February , 2015 ; 07306679 (ISSN) ; Ramazani, A.S.A ; Kheradmand, A ; Shafiee, M ; Baniasadi, H ; Sharif University of Technology
John Wiley and Sons Inc
2015
Abstract
The graphene-based Ziegler-Natta catalyst has been used to prepare ultrahigh molecular weight polyethylene/graphene oxide (UHMWPE/GO) nanocomposite via in situ polymerization. The morphological investigations have been conducted using X-ray diffraction patterns and scanning electron microscopy method. The obtained results indicated that no diffraction peak is detected in a GO pattern, which could be due to the exfoliation of graphene nanosheets in the UHMWPE matrix. Morphological investigations indicated that GO nanosheets are dispersed almost uniformly in polymeric matrix, and that there should exist a good interaction between nanofillers and matrix. The mechanical properties of the...
Thermal buckling analysis of piezoelectric functionally graded plates with temperature-dependent properties
, Article Mechanics of Advanced Materials and Structures ; Volume 22, Issue 10 , Nov , 2015 , Pages 864-875 ; 15376494 (ISSN) ; Fereidoon, A ; Khaksari Nouri, M ; Mareishi, S ; Sharif University of Technology
Taylor and Francis Inc
2015
Abstract
In this study, the thermal buckling analysis of hybrid laminated plates made of two-layered functionally graded materials (FGMs) that are integrated with surface-bonded piezoelectric actuators referred to as (P/FGM)s are investigated. Material properties for both substrate FGM layers and piezoelectric layers are temperature-dependent. Uniform temperature rise as a thermal load and constant applied actuator voltage are considered for this analysis. By definition of four new analytic functions, the five coupled governing stability equations, which are derived based on the first-order shear deformation plate theory, are converted into fourth-order and second-order decoupled partial differential...
Interaction curves for in-plane and out-of-plane behaviors of unreinforced masonry walls
, Article Journal of Earthquake Engineering ; Volume 19, Issue 1 , 2015 , Pages 60-84 ; 13632469 (ISSN) ; Aref, A. J ; Whittaker, A. S ; Sharif University of Technology
Taylor and Francis Ltd
2015
Abstract
Different types of macro-elements have been proposed to simulate the behavior of unreinforced masonry (URM) structures under seismic loads. In many of these, macro-elements URM walls are replaced with beam elements with different hysteretic behaviors. The effect of out-of-plane loading or change of gravity load due to the overturning moment is usually not considered in the behavior of these macro-elements. This article presents interaction curves for bidirectional loadings of unreinforced masonry walls to investigate the importance of these factors. Two parameters are systematically changed to derive the interaction curves for a wall with specific dimensions, including compressive traction...
Performance analysis and optimization of high capacity pulse tube refrigerator
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010 ; Volume 1 , 2010 , Pages 257-263 ; 9780791849156 (ISBN) ; Roshanghalb, F ; Jahanbakhshi, R ; Saidi, M. H ; Kazemzadeh Hannani, S ; Sharif University of Technology
Abstract
High capacity pulse tube refrigerator (HCPTR) is a new generation of cryocoolers tailored to provide more than 250 W of cooling power at cryogenic temperatures. The most important characteristics of HCPTR when compared with other types of pulse tube refrigerators are a powerful pressure wave generator, and an accurate design. In this paper the influence of geometrical and operating parameters on the performance of a double inlet pulse tube refrigerator (DIPTR) is studied. The DIPTR is modeled applying the nodal analysis technique, using mass, momentum and energy conservation equations. The model is able to compute instantaneous flow field throughout the system and calculate cooling capacity...