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aghapour-hasiri--sajad
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On the Concepts and Roles of Energy and Entropyin Gravitational Physics and Cosmology(Canonical Approaches in Definition of Conserved Quantities in Gravitational Physics)
, Ph.D. Dissertation Sharif University of Technology ; Golshani, Mehdi (Supervisor) ; Jafari, Ghadir (Co-Supervisor)
Abstract
In this thesis, inspired by foundational discussions about the concepts of energy and entropy in the gravitational theory, we study the definitions of these concepts and the roles they play in that theory. The definitions considered in this thesis are derived from canonical formalism. To this end, first of all, the variational principle and the canonical structure in the gravitational theory, especially in situations where the spacetime is bounded, is carefully studied and the boundary and corner actions as well as the canonical structure on the boundaries in three cases of non-null, null and general boundaries are derived. Based on this study, two canonical approaches, namely the...
Determining the Optimal Percentage of Autonomous Trucks to Non-autonomous Trucks in an Intercity Freight System for Stabilizing the Financial Performance: A Case Study of Iran
, M.Sc. Thesis Sharif University of Technology ; Kermanshah, Amir Hassan (Supervisor)
Abstract
Freight transportation by trucks plays a critical role in economic development and shaping human life. A significant portion of the total and operational costs of countries is accounted for by transportation, and efforts to optimize it have always been considered of utmost importance. One of the emerging technologies aimed at transforming traditional transportation is vehicle automation. Due to its more uniform nature compared to urban transportation, road freight transportation has greater potential for adopting this technology. Numerous studies have addressed this issue; however, the assumption of fixed variables and the lack of an optimal program for the gradual transition from...
A Review of Practical Tests of Qantum Mechanics in Macroscopic Domain and its Relevance to the Measurement Problem
, M.Sc. Thesis Sharif University of Technology ; Golshani, Mehdi (Supervisor)
Abstract
The measurement problem is one of the issues that is still under debate about the Quantum theory. A significant part of literature during the recent years includes the standard point of view about this problem (including the separation of microscopic and macroscopic domains) and the criticisms of some major physicists in this context. Among these, alternative theories and interpretations have been getting more attention. Experimental tests of Quantum Mechanics in the macroscopic domain and their comparison with alternative theories have always encountered various difficulties (in particular the decoherence phenomenon). Anyway, towards the end of the last century, with the advances in...
Design and Security Analysis of Broadcast Authentication Schemes
, M.Sc. Thesis Sharif University of Technology ; Mohajeri, Javad (Supervisor)
Abstract
With the increase in the usage of wireless networks and smart grid networks and their applications, need for broadcast transmission has been increased dramatically. In order to use these communication, first we need to secure them by cryptographic methods. As authentication is one of the most important aspect of security, introducing secure broadcast authentication schemes are critical. Because of the resources constrainted nodes of these network, it is important to use light cryptographic methods with high security in these schemes. In this work, after analyzing related works, we introduce a new symmetric broadcast authentication scheme which is more efficient in term of memory consumption...
On variational principle and canonical structure of gravitational theory in double-foliation formalism
, Article Classical and Quantum Gravity ; Volume 36, Issue 1 , 2019 ; 02649381 (ISSN) ; Jafari, G ; Golshani, M ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
In this paper, we analyze the variation of the gravitational action on a bounded region of spacetime whose boundary contains segments with various characters, including null. We develop a systematic approach to decompose the derivative of metric variations into orthogonal and tangential components with respect to the boundary and express them in terms of variations of geometric objects associated with the boundary hypersurface. We suggest that a double-foliation of spacetime provides a natural and useful set-up for treating the general problem and clarifies the assumptions and results in specialized ones. In this set-up, we are able to obtain the boundary action necessary for the variational...
A Machine Learning Approach to Minimize Power Consumption of Smartphones While Satisfying the Gaming Performance
, M.Sc. Thesis Sharif University of Technology ; Sarbazi Azad, Hamid (Supervisor)
Abstract
Today's smartphone devices include several cores, such as CPU, GPU, and different accelerators, in order to maximize user experience. However, due to meeting the power budget and limited capacity battery, power and energy of their cores should be managed using dynamic power management methods such as dynamic voltage and frequency scaling (DVFS). For this purpose, we should find optimal frequency and voltage settings of processing cores for each time, to minimize energy consumption while retaining user experience. Finding this optimal frequency and voltage settings is a challenging problem that depends on many parameters. We propose to use deep reinforcement learning (DRL) method to...
A multi sender attribute-based broadcast authentication scheme
, Article 2016 8th International Symposium on Telecommunications, IST 2016, 27 September 2016 through 29 September 2016 ; 2017 , Pages 78-83 ; 9781509034345 (ISBN) ; Ameri, M. H ; Mohajeri, J ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
Multi sender attribute-based broadcast authentication scheme for the network containing resource constrained nodes is the main focus of this research. In this paper, we proposed a framework in which each element of a set of authorized users whose attributes satisfy a special sign control policy can generate a valid signature. In this framework, there exists a trusted server who receives and verifies the validity of the generated attribute-based signatures and broadcast the intended message through the nodes of the network in an efficient and authenticated manner. We also proposed a new symmetric-based broadcast authentication scheme which is used for broadcasting the authenticated messages...
Hardware Design for Cold Plasma Characterization Chamber
, M.Sc. Thesis Sharif University of Technology ; Rashidian, Bijan (Supervisor) ; Faez, Rahim (Supervisor)
Abstract
Cold plasma due to its special properties has many applications in the microelectronics industry. At the beginning of this study, a few examples of widely used plasmas and the requirements for driving their power sources have been investigated. To generate and characterize plasma, various topologies of DC power supply construction, including high-voltage low-current power supplies called multipliers and low-voltage high-voltage power supplies called converters, have been reviewed and compared.Circuit for pulse generating for plasma application has also been proposed and investigated. In the simulation section, after introducing, reviewing, and compareing the common types of simulators, the...
Solving High Dimensional PDEs with Machine Learning Methods and Its Application in Option Pricing
, M.Sc. Thesis Sharif University of Technology ; Arian, Hamid Reza (Supervisor) ; Zamani, Shiva (Supervisor)
Abstract
differential equations. These methods have extensive applications in the financial domain, including in risk hedging and derivative pricing. One of the main advantages of using deep learning methods in this area is their high capability to solve high-dimensional problems. Despite the introduction of these new methods, some of them have not performed well in certain problems. In this research, efforts have been made to improve the efficiency of these methods by enhancing the neural network architecture and modifying the learning process
Adversarial Attack to Deep Learning Networks via Imperceptible Sparse Perturbation
, M.Sc. Thesis Sharif University of Technology ; Ghaemmaghami, Shahrokh (Supervisor) ; Marvasti, Farokh (Supervisor) ; Amini, Sajad (Co-Supervisor)
Abstract
Nowadays, methods based on deep learning networks are the most effective artificial in telligence methods. Although they have achieved success in various fields (such as machine vision and object recognition), practical and experimental cases show the fragility of deep learning networks against perturbations and unwanted changes of the input pattern. All these perturbations must be in a way that the main class of the perturbed input pattern can be rec ognized by human, but the network makes a mistake in recognizing its correct class. This thesis seeks a more accurate evaluation by designing adversarial attacks such that the main class of the adversarial pattern is detectable by human...
A Bayesian-based classification framework for financial time series trend prediction
, Article Journal of Supercomputing ; Volume 79, Issue 4 , 2023 , Pages 4622-4659 ; 09208542 (ISSN) ; Manzuri, M. T ; Aghapour, A ; Karimi, A ; Rabiee, A ; Shalmani, S. M ; Sharif University of Technology
Springer
2023
Abstract
Financial time series have been extensively studied within the past decades; however, the advent of machine learning and deep neural networks opened new horizons to apply supercomputing techniques to extract more insights from the underlying patterns of price data. This paper presents a tri-state labeling approach to classify the underlying patterns in price data into up, down and no-action classes. The introduction of a no-action state in our novel approach alleviates the burden of denoising the dataset as a preprocessing task. The performance of our labeling algorithm is experimented with using machine learning and deep learning models. The framework is augmented by applying the Bayesian...
Dynamic response of metal foam FG porous cylindrical micro-shells due to moving loads with strain gradient size-dependency
, Article European Physical Journal Plus ; Volume 134, Issue 5 , 2019 ; 21905444 (ISSN) ; Forsat, M ; Barati, M. R ; Abdella, G. M ; Mohasel Afshari, B ; Hamouda, A. M. S ; Rabby, S ; Sharif University of Technology
Springer Verlag
2019
Abstract
The dynamic characteristics of functionally graded (FG) metal foam cylindrical micro-scale shells in contact with a moving load will be analyzed thorough this paper accounting for strain-gradient size-dependency. In the material structure of a metal foam, pores can diffuse uniformly or non-uniformly. Based upon Laplace transform, the dynamical governing equations of the first-order micro-shell model can be established in a new domain. In order to go back into the time domain, an inverse Laplace transform will be required. Thus, on can express the time response or dynamic deflection of the micro-shell under moving load. In the presented results, it is easy to see the prominence of...