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Study the effect of architectural modification on fracture behavior of Al-DRA composite [electronic resource]
, Article Mechanics of Advanced Materials and Structures ; September 2014, Volume 21, Issue 8, pages 662-668 ; Khalili, S ; Bagheri, R ; Simchi, A. (Abdolreza) ; Sharif University of Technology
Abstract
An architectural modification method was utilized to improve fracture toughness of discontinuously reinforced aluminum (DRA) composites. Al-DRA composites having a structure similar to that of reinforced concrete were fabricated. The number of reinforcing DRA rods within Al matrix and volume fraction of SiC particles in DRA were altered to evaluate their effect on fracture behavior of these materials. It was found that architectural modification does not have any destructive influence on elastic modulus and yield strength of the composite. Moreover, the success of this method on toughness improvement strongly depends on the occurrence of debonding between Al and DRA regions upon loading
On the convergence of heterogeneous reinforcement learning private agents to nash equilibrium in a macroeconomic policy game
, Article Australian Journal of Basic and Applied Sciences ; Volume 5, Issue 7 , 2011 , Pages 491-499 ; 19918178 (ISSN) ; Nili, M ; Sadati, N ; Sharif University of Technology
2011
Abstract
A repeated inflation-unemployment game within the linear-quadratic frame-work of Barro and Gordon is studied assuming that the government would like to cheat optimally and the finite heterogeneous population of private agents attempts to learn the government's targets using a reinforcement learning algorithm. Private agents are heterogeneous in their initial expectations of inflation rate but are assumed to utilize an identical anticipatory reinforcement learning process, namely Q-learning. In our heterogeneous setting, the only way for the private agents to achieve a zero value for their loss function, is for all of them to correctly anticipate the Nash equilibrium. It is of particular...
A model for the evolution of concrete deterioration due to reinforcement corrosion
, Article Mathematical and Computer Modelling ; Volume 52, Issue 9-10 , November , 2010 , Pages 1403-1422 ; 08957177 (ISSN) ; Kiani, K ; Hashemian, A ; Sharif University of Technology
2010
Abstract
One of the most crucial factors affecting the service life of reinforced concrete (RC) structures attacked by aggressive ions is reinforcement corrosion. As the steel corrosion progresses, crack propagation in concrete medium endangers the serviceability and the strength of RC structural members. In this study, a nonlinear mathematical model for determining the displacement and stress fields in RC structures subjected to reinforcement corrosion is introduced. For corrosion products, a nonlinear stress-strain relation which has been previously confirmed by experimental data is incorporated in the present analysis. In formulation of the governing equations for steel-rust-concrete composite,...
Preparation of mesh-reinforced cellulose acetate forward osmosis membrane with very low surface roughness
, Article Korean Journal of Chemical Engineering ; Volume 34, Issue 12 , 2017 , Pages 3170-3177 ; 02561115 (ISSN) ; Mousavi, S. A ; Ramazani Saadat Abadi, A ; Sadeghi, M ; Sharif University of Technology
Abstract
Mesh-reinforced cellulose acetate (CA)-based membranes were prepared for forward osmosis (FO) by immersion precipitation. Casting compositions such as CA percent and 1, 4-dioxane/acetone ratio and also preparation conditions such as evaporation time, coagulation bath and annealing temperatures were tested for membranes’ performance. The results were compared with commercially CTA membranes. The best membrane (17.9% polymer and 1, 4-dioxane/acetone ratio of 1.89) showed water flux of 9.3 L/m2h (LMH) and RSF of 0.536 mol NaCl/m2h. Moreover, the membrane structure was reinforced by a polyester mesh, which created micro pores in the back of the membrane. This caused higher water flux and RSF...
Modeling the interphase region in carbon nanotube-reinforced polymer nanocomposites
, Article Polymer Composites ; 2018 ; 02728397 (ISSN) ; Jam, J. E ; Arab, B ; Firouz-Abadi, R. D ; Sharif University of Technology
John Wiley and Sons Inc
2018
Abstract
Carbon nanotubes are regarded as ideal fillers for polymeric materials due to their excellent mechanical properties. Mechanical analysis without consideration of nanotube–matrix interphase, may not give precise predictions. In this work, the impacts of interphase on the behavior of polymer-based nanocomposites are studied. For this purpose, a closed-form micromechanical interphase model considering the diameter of nanotube, the thickness of interphase, and mechanical properties of nanotube and polymer is proposed to estimate the overall mechanical properties of nanotube-reinforced polymer nanocomposites. Furthermore, the effective elastic constants of the nanocomposites for a wide range of...
Seismic retrofit of large-scale reinforced concrete columns by prestressed high-strength metal strips
, Article Proceedings of the 2009 Structures Congress - Don't Mess with Structural Engineers: Expanding Our Role, 30 April 2009 through 2 May 2009, Austin, TX ; 2009 , Pages 2863-2872 ; 9780784410318 (ISBN) ; Samadi, M ; Sharif University of Technology
2009
Abstract
This paper presents the results of an experimental study on the application of pre-stressed high strength metal strips in retrofit of RC columns. Six 2/3 scale were deliberately designated with insufficient transverse reinforcement details and tested under constant axial and cyclic lateral load reversals. The level of axial load and the pattern of strengthening were parameters of this study. It was observed that the technique has been capable to enhance the lateral behavior of columns significantly, in terms of ductility. Very ductile behavior was obtained. The height-wise variations of lateral strain on confining strips are studied. The analysis of the fiber-based model of tested columns...
Modeling the interphase region in carbon nanotube-reinforced polymer nanocomposites
, Article Polymer Composites ; Volume 40, Issue S2 , 2019 , Pages E1219-E1234 ; 02728397 (ISSN) ; Jam, J. E ; Arab, B ; Firouz Abadi, R. D ; Sharif University of Technology
John Wiley and Sons Inc
2019
Abstract
Carbon nanotubes are regarded as ideal fillers for polymeric materials due to their excellent mechanical properties. Mechanical analysis without consideration of nanotube–matrix interphase, may not give precise predictions. In this work, the impacts of interphase on the behavior of polymer-based nanocomposites are studied. For this purpose, a closed-form micromechanical interphase model considering the diameter of nanotube, the thickness of interphase, and mechanical properties of nanotube and polymer is proposed to estimate the overall mechanical properties of nanotube-reinforced polymer nanocomposites. Furthermore, the effective elastic constants of the nanocomposites for a wide range of...
Optimum design of sunken reinforced enclosures under buckling condition
, Article Applied Sciences (Switzerland) ; Volume 10, Issue 23 , 2020 , Pages 1-14 ; Kashyzadeh, K. R ; Rahimian Koloor, S. S ; Petrů, M ; Amiri, N ; Sharif University of Technology
MDPI AG
2020
Abstract
Increasing the lifetime and improving the performance of structures through redesign and optimization are important, especially in marine structures. In general, there are two main groups of marine structures: onshore and offshore structures. Most marine structures are offshore, and these are divided into two categories: floating or sunken. One of the important parameters in the design of sunken structures is the critical load resulting from the buckling of walls, which can cause damage to the structure. In the present paper, three rectangular aluminum and steel compartments of different conditions and sizes were modeled using design analysis methods. Then, different finite element analyses...
Reinforcement learning based on active learning method
, Article Proceedings - 2008 2nd International Symposium on Intelligent Information Technology Application, IITA 2008, 21 December 2008 through 22 December 2008, Shanghai ; Volume 2 , 2008 , Pages 598-602 ; 9780769534978 (ISBN) ; Bagheri Shouraki, S ; Khasteh, H ; Kiaei, A. A ; Sharif University of Technology
2008
Abstract
In this paper, a new reinforcement learning approach is proposed which is based on a powerful concept named Active Learning Method (ALM) in modeling. ALM expresses any multi-input-single-output system as a fuzzy combination of some single-input-singleoutput systems. The proposed method is an actor-critic system similar to Generalized Approximate Reasoning based Intelligent Control (GARIC) structure to adapt the ALM by delayed reinforcement signals. Our system uses Temporal Difference (TD) learning to model the behavior of useful actions of a control system. The goodness of an action is modeled on Reward-Penalty-Plane. IDS planes will be updated according to this plane. It is shown that the...
Application of actor-critic reinforcement learning method for control of a sagittal arm during oscillatory movement
, Article Biomedical Engineering - Applications, Basis and Communications ; Volume 16, Issue 6 , 2004 , Pages 305-312 ; 10162372 (ISSN) ; Lucas, C ; Parnianpour, M ; Sharif University of Technology
Institute of Biomedical Engineering
2004
Abstract
Numerous disciplines are engaged in studies involving motor control. In this study, we have used a single link system with a pair of muscles that are excited with alpha and gamma signals to achieve an oscillatory movement with variable amplitude and frequency. The system is highly nonlinear in all its physical and physiological attributes. The major physiological characteristics of this system are simultaneous activation of a pair of nonlinear muscle-like-actuators for control purposes, existence of nonlinear spindle-like sensors and Golgi tendon organ-like sensor, actions of gravity and external loading. Transmission delays are included in the afferent and efferent neural paths to account...
Neuromuscular control of sagittal ARM during repetitive movement by actor-critic reinforcement learning method
, Article Intelligent Automation and Control Trends, Principles, and Applications - International Symposium on Intelligent Automation and Control, ISIAC - Sixth Biannual World Automation Congress, WAC 2004, Seville, 28 June 2004 through 1 July 2004 ; 2004 , Pages 371-376 ; 1889335223 (ISBN) ; Lucas, C ; Parnianpour, M ; Sharif University of Technology
2004
Abstract
In this study, we have used a single link system with a pair of muscles that are excited with alpha and gamma signals to achieve an oscillatory movement with variable amplitude and frequency. This paper proposes a reinforcement learning method with an Actor-Critic architecture instead of middle and low level of central nervous system (CNS). The Actor in this structure is a two layer feedforward neural network and the Critic is a model of the cerebellum. The Critic is trained by State-Action-Reward-State-Action (SARSA) method. The system showed excellent tracking capability and after 280 epochs the RMS error for position and velocity profiles were 0.02, 0.04 radian and radian/sec,...
Active learning method to solve bin packing problems
, Article Proceedings of the IASTED International Conference on Neural Networks and Computational Intelligence, Grindelwald, 23 February 2004 through 25 February 2004 ; 2004 , Pages 263-268 ; Shouraki, S. B ; Sharif University of Technology
2004
Abstract
Previous researches have shown the success of using reinforcement learning in solving combinatorial optimization problems. The main idea of these methods is to learn (near) optimal evaluation function to improve local searches and find (near) optimal solutions. Stage algorithm introduced by Boyan & Moore, is one of the most important algorithm in this area. In the other hand fuzzy methods have been used in all fields of science to solve problems but still never used in combinatorial optimization problems. In this paper we focus on Bin Packing Problem. We introduce two basic fuzzy algorithms (ALM and IDS) and then solve our problem with these fuzzy algorithms. We run ALM and IDS algorithms on...
Influence of confining hoop flexural stiffness on behavior of high-strength lightweight concrete columns
, Article ACI Structural Journal ; Volume 98, Issue 5 , 2001 , Pages 657-664 ; 08893241 (ISSN) ; Bozorgzadeh, A ; Sharif University of Technology
2001
Abstract
This paper presents the behavior of high-strength lightweight concrete columns confined with small size diameter hoop reinforcement. The concrete had a strength of up to 87.2 MPa (12,500 psi). The experimental program consisted of axial load tests on eight column specimens. The cross-sectional shape of the column specimens was elliptical, with dimensions of 152 × 229 mm (6 × 9 in.) and height of 762 mm (30 in.). The only longitudinal reinforcements used were four 4.52 mm (0.178 in.) diameter wires that were tack-welded to the lateral reinforcement to maintain the desired configuration of the lateral reinforcement. The influencing parameters included concrete strength and amount and spacing...
Effect of geotextile reinforcement on the mechanical behavior of sand
, Article Geotextiles and Geomembranes, Exeter, United Kingdom ; Volume 18, Issue 6 , 2000 , Pages 385-402 ; 02661144 (ISSN) ; Noorzad, R ; Oskoorouchi, A. M ; Sharif University of Technology
Elsevier Science Ltd
2000
Abstract
Laboratory triaxial compression tests were carried out in order to determine the stress-strain and dilation characteristics of geotextile-reinforced dry beach sand. The mechanical behavior of the composite material was investigated through varying the number of geotextile layers, type of geotextile, confining pressure, and geotextile arrangement. In order to study the effect of sample-size on the results, tests were performed on samples with two different diameters. The results demonstrated that geotextile inclusion increases the peak strength, axial strain at failure, and ductility. However, it reduces dilation. Such improvements in the behavior of reinforced sand are more pronounced for...
Assessment of fiber-reinforcement and foam-filling in the directional energy absorption performance of a 3D printed accordion cellular structure
, Article Composite Structures ; Volume 297 , 2022 ; 02638223 (ISSN) ; Mahdi Ashrafian, M ; Behravesh, A. H ; Kaveh Hedayati, S ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
This paper presents an evaluation of two distinct techniques to improve energy absorption capability of an accordion cellular structure with close-to-zero Poisson's ratio. For this purpose, fiber-reinforcement and foam-filling methods were employed to address the material enhancement and to obtain light and tough structures with high specific energy absorption. Employing an innovated additive manufacturing based on material extrusion process, specimens of glass fiber-reinforced PLA were produced in both in-plane directions to compare with the un-reinforced counterpart. In continue, some of the 3D printed samples were strengthened by means of polyurethane foam in their hollow structure. The...
Parametric study of strain rate effects on nanoparticle-reinforced polymer composites
, Article Journal of Nanomaterials ; Volume 2016 , 2016 ; 16874110 (ISSN) ; Haji Gholami, I ; Masajedian, S ; Mertiny, P ; Sameoto, D ; Taheri, F ; Sharif University of Technology
Hindawi Publishing Corporation
2016
Abstract
Crashworthiness, energy absorption capacity, and safety are important factors in the design of lightweight vehicles made of fiber-reinforced polymer composite (FRP) components. The relatively recent emergence of the nanotechnology industry has presented a novel means to augment the mechanical properties of various materials. As a result, recent attempts have contemplated the use of nanoparticles to further improve the resiliency of resins, especially when resins are used for mating FRP components. Therefore, a comprehensive understanding of the response of nanoreinforced polymer composites, subjected to various rates of loading, is of paramount importance for developing reliable structures....
Finite element analysis of a CFRP reinforced retaining wall
, Article Geomechanics and Engineering ; Volume 10, Issue 6 , 2016 , Pages 757-774 ; 2005307X (ISSN) ; Toufigh, V ; Desai, C ; Toufigh, V ; Saadatmanesh, H ; Sharif University of Technology
Techno Press
Abstract
Soils are usually weak in tension therefore different materials such as geosynthetics are used to address this inadequacy. Worldwide annual consumption of geosynthetics is close to 1000 million m2, and the value of these materials is probably close to US$1500 million. Since the total cost of the construction is at least four or five times the cost of the geosynthetic itself, the impact of these materials on civil engineering construction is very large indeed. Nevertheless, there are several significant problems associated with geosynthetics, such as creep, low modulus of elasticity, and susceptibility to aggressive environment. Carbon fiber reinforced polymer (CFRP) was introduced over two...
Effect of thermal cycles on mechanical response of pultruded glass fiber reinforced polymer profiles of different geometries
, Article Composite Structures ; Volume 223 , 2019 ; 02638223 (ISSN) ; Ashrafi, H ; Bazli, M ; Ozbakkaloglu, T ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
This study investigates the effect of Thermal cycles on the mechanical properties of GFRP pultruded profiles with different geometries. Bending specimens consisted of I-shaped and U-channel profiles that were tested in three-point bending along their both principal weak and strong axes, whereas box profiles and laminates were used in compression and tension tests, respectively. Each specimen was exposed to a range of thermal cycles, between −20 °C and 20 °C. The failure modes of the profiles were closely investigated at both major and minor scales. Results were analyzed using ANOVA to determine the influence of each factor and a model was developed to predict the strength retention of...
The tensile performance of FRP bars embedded in concrete under elevated temperatures
, Article Construction and Building Materials ; Volume 211 , 2019 , Pages 1138-1152 ; 09500618 (ISSN) ; Vatani Oskouei, A ; Khaneghahi, M. H ; Shoaei, P ; Ozbakkaloglu, T ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
In this research, the mechanical properties of glass and carbon fiber reinforced polymer (FRP) bars with epoxy resin matrices embedded in concrete were investigated under an extensive range of elevated temperatures (i.e., 25–800 °C). Embedded FRP bars with various bar diameters were studied in order to determine bar diameter influence on the results. In addition, analysis of variance (ANOVA) was performed on the experimental results to investigate the contribution of exposure temperature and bar diameter to the tensile behavior of embedded in concrete FRP bars at elevated temperatures. The results show that the tensile strength of embedded FRP bars generally decreases with increasing...
Seismic behavior of concrete moment frame reinforced with GFRP bars
, Article Composites Part B: Engineering ; Volume 163 , 2019 , Pages 324-338 ; 13598368 (ISSN) ; Khaloo, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
In this research, four types of concrete moment frame were designed with glass fiber reinforced polymer (GFRP) bars according to ACI 440.1R-15 and the seismic behavior was assessed using pushover analysis. The frames were three and five stories with two and three bays. A computer code was developed to calculate the amount of fiber reinforced polymer bars in beams of the frames. In order to evaluate nonlinear behavior in plastic hinge regions, sections of beams and columns were analyzed on the basis of moment-curvature diagram and also P-M interaction curve for columns. Performance levels of frames were determined considering ATC-40 criteria. Behavior of concrete moment frames reinforced with...