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palizi--soheil
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Studying the Problem of Maximum Matching in Stochastic Environments
, M.Sc. Thesis Sharif University of Technology ; Ghodsi, Mohammad (Supervisor)
Abstract
The problem studied in this research is the online stochastic bipartite matching. In this problem the vertices of one side of the given graph arrive in an online manner, with respect to a probability distribution. Also the edges of the graph exist according to a given probability distribution and one should perform queries from an oracle to know about the existence of an edge. The given graph shall be weighted or unweighted. The goal here is to find a maximum matching in the graph that is as close to the omniscient optimum as possible, while the number of queries performed per vertex is limited. In the general case of the problem, there are no specific conditions, but in other versions,...
Bond strength prediction of timber-FRP under standard and acidic/alkaline environmental conditions based on gene expression programming
, Article European Journal of Wood and Wood Products ; Volume 80, Issue 6 , 2022 , Pages 1457-1471 ; 00183768 (ISSN) ; Toufigh, V ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2022
Abstract
Timber is widely used as a construction material; however, the environmental deterioration of timber is a crucial problem for the construction industry. Fiber-reinforced polymer (FRP) has been considered appropriate and beneficial for the repair and rehabilitation of timber. This study proposes three empirical models using a supervised machine learning method called gene expression programming (GEP) to predict the bond strength between timber and FRP under various environmental conditions. The first empirical model is used to predict bond strength under standard conditions. The two other models are proposed to predict the strength reduction in acidic and alkali solutions. The formulation...
Fire-induced damage assessment of cementless alkali-activated slag-based concrete
, Article Construction and Building Materials ; Volume 393 , 2023 ; 09500618 (ISSN) ; Toufigh, V ; Sharif University of Technology
Elsevier Ltd
2023
Abstract
According to recent studies, concrete made with alkali activators and slag is a potential construction material. To ensure the safety and durability of concrete structures after a fire, it is crucial to assess the material properties and determine the extent of the damage. This paper investigated the effect of elevated temperatures (25 °C, 100 °C, 250 °C, 500 °C, 700 °C and 900 °C) on the properties of cementless alkali-activated slag-based concrete. In this regard, 216 cubic samples with eleven mixes were designed according to the literature and then prepared. Two categories of tests were utilized: nondestructive and destructive tests. The nondestructive evaluations included visual...
Post-fire Behavior Evaluation of Slag-Based Geopolymer Concrete
, M.Sc. Thesis Sharif University of Technology ; Toufigh, Vahab (Supervisor)
Abstract
Concrete, a versatile construction material, combines cement, aggregates, and water to form a composite known for its durability and adaptability in various architectural and engineering applications. Its widespread use stems from its ability to efficiently bear heavy loads while maintaining longevity. However, producing concrete's key ingredient, cement, contributes significantly to environmental harm by emitting substantial carbon dioxide during its manufacturing process. This carbon footprint underscores the urgent need for sustainable alternatives and innovative practices in the construction industry to mitigate the detrimental effects on our planet. On the other hand, understanding the...
Critical temperature evaluation of moment frames by means of plastic analysis theory and genetic algorithm
, Article Iranian Journal of Science and Technology - Transactions of Civil Engineering ; 2021 ; 22286160 (ISSN) ; Saedi Daryan, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
Nowadays, deliberate or unwanted fire incidents have created much attention to the behavior of structures against these types of events. Since the properties of structural members are influenced by the increase in the temperature of the members, it is more difficult to predict the general and local behavior of the structures during the fire. In this research, a method has been proposed to calculate the critical temperature in two-dimensional structures at its collapse with desirable accuracy. In this process, the upper-bound theory of plastic analysis is used. The plastic analysis is performed by applying the initial fire scenario to the structure, and its collapse load factor with the...
Critical temperature evaluation of moment frames by means of plastic analysis theory and genetic algorithm
, Article Iranian Journal of Science and Technology - Transactions of Civil Engineering ; Volume 46, Issue 2 , 2022 , Pages 843-856 ; 22286160 (ISSN) ; Saedi Daryan, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2022
Abstract
Nowadays, deliberate or unwanted fire incidents have created much attention to the behavior of structures against these types of events. Since the properties of structural members are influenced by the increase in the temperature of the members, it is more difficult to predict the general and local behavior of the structures during the fire. In this research, a method has been proposed to calculate the critical temperature in two-dimensional structures at its collapse with desirable accuracy. In this process, the upper-bound theory of plastic analysis is used. The plastic analysis is performed by applying the initial fire scenario to the structure, and its collapse load factor with the...
Ultrasonic pulse velocity for mechanical properties determination of wood
, Article Wood Material Science and Engineering ; Volume 18, Issue 6 , 2023 , Pages 1966-1977 ; 17480272 (ISSN) ; Toufigh, V ; Ramezanpour kami, M ; Sharif University of Technology
Taylor and Francis Ltd
2023
Abstract
Wood is a widely used material in various industries, and its mechanical properties are crucial to determine the final product's performance. Modulus of elasticity (MOE) is one of the most important mechanical properties of wood, which measures its stiffness and ability to resist deformation under applied loads. The objective of this research was to create robust models for predicting the moduli of elasticity (MOE) of wood species in three principal directions under varying moisture levels, using the ultrasonic pulse velocity (UPV) technique. The study employed three modeling techniques, namely multivariable linear regression (MLR), artificial neural network (ANN), and support vector...
Size and layout optimum design of frames with steel plate shear walls by metaheuristic optimization algorithms
, Article Structures ; Volume 48 , 2023 , Pages 657-668 ; 23520124 (ISSN) ; Salari, M ; Palizi, S ; Farhoudi, N ; Sharif University of Technology
Elsevier Ltd
2023
Abstract
Optimization of a structure refers to a design procedure that results in the most economical structure in terms of materials and sizing of sections. In structures with steel plate shear walls, finding the best layout of the walls in a frame is also of priority in designing a structure with the minimum weight. Finding the least weight of a structure while all design provisions according to codes and standards are satisfied is a challenging task that is hard to perform with the existing design methods. Metaheuristic optimization algorithms are robust computational tools used for solving complex problems, which are used widely in many engineering fields, especially structural engineering. This...
Modelling of Frictional Cracks by the Extended Finite Element Method Considering the Effect of Singularity
, M.Sc. Thesis Sharif University of Technology ; Khonsari, Vahid (Supervisor) ; Mohammadi, Soheil (Co-Advisor)
Abstract
When a crack is subjected to a compression field, it will close and its edges will get into contact with each other. Depending on the direction and magnitude of the loads and also the coefficient of friction, ‘stick’ or ‘slip’ situationsbetween the edges will occur. This type of crack is known as ‘frictional crack.’ In this project, first these cracks are studied analytically and the order of singularity is derived using asymptotic analysis and also the analytical fields are determined for both ‘isotropic’ and ‘orthotropic’ materials. Then, numerical simulations are carried out using extended finite element method which is considered as the most powerful means for analyzing the problems...
Theoretical and Numerical Analysis of Shock Waves Propagation in Porous Medium
, Ph.D. Dissertation Sharif University of Technology ; Ahmadi, Mohammad Mehdi (Supervisor) ; Mohammadi, Soheil ($item.subfieldsMap.e)
Abstract
Particulate porous mateials have always been of interest in terms of reducing shock waves effects in different protective applications. Therefore, the physics governing the flow in porous media is especially significant for which different models have been presented by the researchers. The complexities of these media have caused many existing models to be unable to properly predict the behavior of granular media under shock loadings. On the other hand, the complexity of the equations makes the numerical solution of them cumbersome and costly in a way that many researchers do not solve the whole coupled equations and reduce their number. In addition, current high-resolution TVD solutions of...
Reducing the Number of Elements in Order to Enhance the Speed of the Ultrasound Tomographic Imaging Systems
, M.Sc. Thesis Sharif University of Technology ; Kavehvash, Zahra (Supervisor) ; Hakakzadeh, Soheil (Co-Supervisor)
Abstract
Transmission-mode ultrasound computed tomography (USCT) has emerged as a novel, safe, and cost-effective method for quantitative imaging of biological tissues, especially in breast screening. Despite technological advancements, challenges such as reduced accuracy in heterogeneous media, incomplete acoustic field coverage, sensitivity to initial conditions, and phenomena like cycle skipping still limit image quality and reconstruction speed in these systems. In this thesis, aiming to improve the speed and performance of USCT imaging, three reconstruction algorithms have been designed, implemented, and evaluated: a travel-time-based Gauss-Newton method, frequency-domain full waveform inversion...