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Multi-user opportunistic spectrum access with channel impairments [electronic resource]
, Article AEU - International Journal of Electronics and Communications ; Volume 67, Issue 11, November 2013, Pages 955–966 ; Salehkalybar, S ; Pakravan, M. R ; Sharif University of Technology
Abstract
In this paper, we study the impact of sensing error and channel fading on the decision process of a multiple secondary user network in a primary network whose channel occupancy states are modelled as a Bernoulli process. We present a randomized access strategy to maximize total secondary network throughput. The proposed method guarantees that the probability of collision between primary and secondary users in each channel is less than the predefined value of Pc = ξ. To find the optimal access strategy, we formulate secondary network throughput as an optimization problem. Then, using the KKT method to find the solution, we break the original problem into multiple sub-problems. Then, we employ...
Hegel's ontology of power : the structure of social domination in capitalism
, Book
Cambridge University Press
2020
Optimal Maneuver-Based Motion Planning Over Terrain and Threats Using Heuristic Optimization Approaches
, Ph.D. Dissertation Sharif University of Technology ; Pourtakdoost, Sayyed Hossein (Supervisor)
Abstract
In line with advances in science and technology in the areas of robotics, artificial intelligence, computer and control, unmanned vehicles are being more utilized and focused. On the other hand, development and further advances of these vehicles is highly dependent on the level of their autonomy. Motion planning is one of the most important issues in this regard. Due to high levels of autonomy required for unmanned air vehicles (UAV), the subject of motion planning is of valuable interest in aerospace applications. The goal of the motion planning problem, that is the subject of this research, is to extract an optimal trajectory for the UAV from an initial location toward its target point...
Interruptible Load Contracts and Demand Response Program Implementation in Stochastic Long-Term SCUC with Wind Farm Consideration
, M.Sc. Thesis Sharif University of Technology ; Hosseini, Sayyed Hamid (Supervisor)
Abstract
Providing more choices to customers for determining the cost of their required reliability levels is one of the most important targets of restructured power system. Centralized management of reliability in Vertically Integrated Utility (VIU) applying the same policies to different customers is replaced with decentralized management allowing customers to participate in reliability management based on their required reliability levels. In this thesis, impact of emergency demand response programs, interruptible load contract and wind farms on the long-term security constrained unit commitment has been studied. Random outages of generators and transmission lines, load forecast inaccuracies as...
Lasing without population inversion in an Er 3+-doped YAG crystal
, Article Journal of Modern Optics ; Volume 59, Issue 5 , Nov , 2012 , Pages 446-454 ; 09500340 (ISSN) ; Asadpour, S. H ; Eslami Majd, A ; Sadighi Bonabi, R ; Sharif University of Technology
2012
Abstract
Two atomic models are proposed for an Er 3+-doped YAG crystal with application to lasing with and without population inversion. It is shown how an incoherent pumping field and coherent control coupling field can produce a laser in the presence and absence of population inversion
Cross layer Design in Cognitive Radio Networks
, Ph.D. Dissertation Sharif University of Technology ; Pakravan, Mohammad Reza (Supervisor)
Abstract
In this thesis, the challenges of the PHY and MAC layers in cognitive radio networks are discussed and a plan which considers the cross layer concept between them is presented.In the first part of the thesis, a brief survey on various spectrum sensing techniques is presented. A detector which can improve the network performance is introduced and based on this detector, the important problem of trade-off between spectrum sensing period and the network throughput is considered. For this purpose, first of all, the truncated SPRT detector is presented and for low SNRs the optimal truncation time which leads to maximum network throughput is obtained. In the second part of the thesis,the...
Modeling of cohesive crack growth using an adaptive mesh refinement via the modified-SPR technique
, Article International Journal of Fracture ; Volume 159, Issue 1 , 2009 , Pages 21-41 ; 03769429 (ISSN) ; Moslemi, H ; Majd Ardakany, K ; Barani, O. R ; Azadi, H ; Sharif University of Technology
2009
Abstract
In this paper, an adaptive finite element procedure is presented in modeling of mixed-mode cohesive crack propagation via the modified superconvergent path recovery technique. The adaptive mesh refinement is performed based on the Zienkiewicz-Zhu error estimator. The weighted-SPR recovery technique is employed to improve the accuracy of error estimation. The Espinosa-Zavattieri bilinear cohesive zone model is applied to implement the traction-separation law. It is worth mentioning that no previous information is necessary for the path of crack growth and no region of the domain is necessary to be filled by the cohesive elements. The maximum principal stress criterion is employed for...
On endurance of erasure codes in SSD-based storage systems
, Article Computer Architecture and Digital Systems (CADS), 17th CSI International Symposium on ; Article number 6714239 , 2013 , Pages 67-72 ; 9781479905621 ; Miremadi, Gh. (Sayyed Ghassem) ; Asadi, H. (Hossein) ; Sharif Univesity of Technology
2013
Abstract
The wear-out of flash-based Solid-State Drives (SSDs) is a main concern that significantly affects their reliability. One major parameter that accelerates SSD wear-out is the number of write-cycles committed to flash chips. The number of write-cycles in SSD-based disk subsystem is highly dependent on the erasure code implemented in Redundant Array of Independent Disks (RAIDs). In this paper, we investigate the impact of erasure codes and the configuration of storage subsystems (i.e., the number of disks participated in the RAID array and stripe unit size) on the endurance of storage systems. The number of write-cycles is considered as a metric to evaluate the endurance of storage system. We...
Transient Liquid Phase Bonding of AA6061/SiC
, M.Sc. Thesis Sharif University of Technology ; Ekrami, Ali Akbar (Supervisor) ; Sayyed Reyhani, Morteza (Supervisor)
Abstract
Composites are made to obtain several mechanical and physical properties selectively. But joining and manufacturing of complex shapes restricts their usages. Transient liquid phase (TLP) bonding is a novel method for joining of these materials without any defects that occur in other welding methods, such as melting or solid state methods. In this research, temperture gradiant TLP bonding of AA6061/SiC/15p using gallium as interlayer was performed. To obtain the optimum conditions, joining was performed at 260, 310, 360 and 410 ˚C, and pressure of 5 and 10 Mpa with holding time of 5 and 10 minutes, the joined samples then solutionized at 530˚C for 70 minutes. Optical and scanning electron...
Determination of Discharge Coefficient for Sharp-edged Rectangular with Curvature Weirs Experimentally
, M.Sc. Thesis Sharif University of Technology ; Borgheei, Sayyed Mahd (Supervisor) ; Abrishamchi, Ahmad (Co-Advisor)
Abstract
Sharp crested weirs are one of the main and oldest means of measuring discharge in water conveyance systems. Many studies have been done on sharp rectangular weirs and have provided many relationships regarding the effect of geometric parameters and various factors on discharge coefficient of the weirs.In some places, due to existence of obstacles or barriers in the channel, it is impossible to create a symmetrical continuous weir some other cases, multiple or asymmetric or curved weirs should be used, which is the main concept of this project. Since it seems unlikely that a purely mathematical model can review the impact of the multiplicity and asymmetry of these weirs without using...
About Space Time
, M.Sc. Thesis Sharif University of Technology ; Rastegar, Arash (Supervisor)
Abstract
Einstein's general theory of relativity is an admirable successful and unifier geometrical modeling among concepts of space, time and gravity. This theory along with special theory of relativity made a massive change in our physical view and this, especially in its historical context, has deep and interesting consequences in man's philosophical viewpoint which can be studied. Some parts of this thesis relates to these consequences. Some of these interesting consequences may be hidden by computional or mathematical viewpoint and often these equations do not contain enough intuition. in one part, we provide a formulizatin of Einstein's equaion that is intuitional which can be translated in...
Tropical Algebraic Geometry
, M.Sc. Thesis Sharif University of Technology ; Rastegar, Arash (Supervisor)
Abstract
Tropical algebraic geometry is a fairly new branch in geometry which is called so in honor of Brazilian mathematician Imre Simon who was pioneer of this field.The set equipped with the addition and multiplication is a semifield.Algebraic geometry objects like algebraic varieties can be defined over.Polynomials and rational functions are defined over.The functions that they define are piecewise linear and concave functions and the set of points where they are nonlinear is a tropical variety which is a concave polyhedral. Thus, tropical algebraic geometry is a piecewise linear version of algebraic geometry.Another approach to tropical algebraic geometry comes back to the works of Russian...
Evaluating the Effect of Crumb Rubber on the Fracture Properties of Asphaltic Materials Using a Standardized Composite
, M.Sc. Thesis Sharif University of Technology ; Motamed, Arash (Supervisor)
Abstract
Fatigue cracking has a major impact on the performance of flexible pavements. Many test methods have been established to evaluate and estimate the fatigue life of asphaltic materials. Most of these test methods cannot successfully examine the fatigue properties of asphaltic materials. Recent studies demonstrate that using a standardized composite, which consists of glass beads and asphalt binder, can simulate the stress states that binder experiences in the field. This research used standardized composite to investigate the effect of crumb rubber on the fracture properties of asphaltic materials. To validate the test results, the authors conducted fracture tests on the Fine Aggregate Matrix...
Novel View Synthesis Using Light Field Camera
, M.Sc. Thesis Sharif University of Technology ; Amini, Arash (Supervisor)
Abstract
In the last two decades, novel view synthesis has become increasingly important in the movie and game industries. The new generated views correspond to virtual viewpoints, where no real camera has taken snapshot. Depending on the amount of available information from the scene, different approaches have been proposed to create novel views. If the depth information is available, then by knowing camera relative motion, novel views can be constructed. The conventional cameras only record the intensity of the captured scene, and discard the depth information. In the recent concept of light field cameras, by locating an array of micro-lenses between the camera sensor and the main lens, one can...
Developing a New Method to Evaluate and Quality Control of Chip Seal
, M.Sc. Thesis Sharif University of Technology ; Motamed, Arash (Supervisor)
Abstract
Chip seal is one of the most economical pavement maintenance practice that extends pavement life. To ensure chip seal good performance several quality control methods have been developed. However, most of these methods are qualitative and only measure the stone loss under a certain number on loading. This research developed a new method for quality control of chip seal, based on the assumption that characteristics of the bond between chips and pavement surface play a key role in chip seal performance. To validate this test method, the authors used a wheel track loading test. The results from this research clearly showed that the characteristics of the bond between chips and pavement surface...
Investigating the Effect of Various Additives on the Curing Time of Chip Seal and Chip Seal Treatments in Different Climate Conditions.
,
M.Sc. Thesis
Sharif University of Technology
;
Motamed, Arash
(Supervisor)
Abstract
Recently, a new method to investigate chip seal performance has developed by a research team at Sharif University of Technology. This study investigates the effect of various additives such as CRM, SBR Latex, Hydrated Lime and Ordinary Portland Cement (OPC), on the curing time of chip seal by this method. In addition, the chip seal treatments were investigated in different climate conditions like Wet and Wet-Freeze zones. The overall performance of mixture specimens evaluated using creep loading test. In fact, the bonding properties between aggregates and surface of Hot Mix Asphalt measured. The test results were analyzed by using of the work and time parameters. These parameters were...
Brandom’s Conception of Trust
, M.Sc. Thesis Sharif University of Technology ; Abazari, Arash (Supervisor)
Abstract
A Spirit of Trust results from Brandom's thirty-year effort to give a pragmatistic reading of Hegel's Phenomenology of Spirit. In A Spirit of Trust, Brandom reformulates Hegel's arguments in the language of contemporary Analytical Philosophy and gives a unique interpretation of Hegel's key concepts. In this Thesis, we will examine one of its key concepts, namely, Trust; We will pursue the following questions: First, What is Trust? And what is its connection to other aspects of Brandom's philosophy? Second, How does Trust help us in overcoming Alienation? Third, Are Confession and Forgiveness, which are the constitutive concepts of Trust, psychologistic or normative? Fourth, What is the...
Design of Stress Absorbing Membrane Interlayer (Sami) and Overlay to Reduce Reflective Cracking
, M.Sc. Thesis Sharif University of Technology ; Motamed, Arash (Supervisor)
Abstract
Cracks or construction joints in an overlayed pavement can propagate into the overlay over time due to various factors, the most important of which are traffic and temperature loading, and cause premature failure of pavement. This propagated cracks are called reflective cracks and the phenomenon of crack propagation into the overlay is called reflective cracking. Use of stress-absorbing membrane interlayers (SAMI) is one of the ways can reduce the occurrence of reflective cracking and/or delay it. One of the most common SAMIs is an asphalt mixture consists of bitumen and aggregate layed down between the old and the veneer layers. The function of the SAMI depends on several factors such as...
An Investigation on the Effect of Filler Type and Content on the Performance of Asphaltic Materials
, M.Sc. Thesis Sharif University of Technology ; Motamed, Arash (Supervisor)
Abstract
The objective of this research is evaluating the effect of filler type and content on the characteristics of asphaltic materials. The properties of the asphalt mixture are greatly influenced by its components. As asphalt mixtures are composed of two prominent components, aggregates and binder, the change in type and contents of these materials may lead to altering the performance of asphalt mixtures. Aggregates in the asphalt mixtures are categorized into three groups based on their particle sizes: coarse aggregate, fine aggregate and mineral filler. The effect of filler on the characteristics of asphalt mixtures can be examined by changing the type and content of filler and holding the...
The Analysis of HDR Video Reconstruction Methods
, M.Sc. Thesis Sharif University of Technology ; Amini, Arash (Supervisor)
Abstract
The conventional cameras and displays do not have the ability to record and display the full brightness of the world around us. These deficiencies have led to the development of methods known as High Dynamic Range Imaging. Most of the work done in this field falls into two groups: compression of the light range and its expansion. In compression, the brightness range is intended to display content with a high dynamic range in simple displays. But the goal of expanding the brightness range is to reconstruct HDR content from a low dynamic range one. In addition to the above classification, this field is also categorized based on the type of content (image or video). In this study, the...