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Effect of Ground Thermal Recovery Using Daily Temperature Difference on Performance of Ground Source Heat Pump
, M.Sc. Thesis Sharif University of Technology ; Hakkakifard, Ali (Supervisor)
Abstract
Ground Source Heat Pumps (GSHP), as a renewable source heating, ventilating, and air conditioning (HVAC) technology, has the highest energy efficiency among different heat pump types. One of the major drawbacks of GSHPs is the long-term ground temperature variations as a result of heat accumulation or depletion in the ground. This contribution puts forward a novel ground thermal recovery system for horizontal ground heat exchangers in a hot climate. The proposed recovery system consists of open-loop horizontal Ground-Air Heat Exchangers (GAHEs) that are buried between the horizontal Ground-Water Heat Exchangers (GWHEs). A fan supplies ambient air to the GAHE pipes when the soil around GWHE...
Detection in Code Division Multiple Access Systems
, Ph.D. Dissertation Sharif University of Technology ; Marvasti, Farokh (Supervisor)
Abstract
In this thesis, detection problem in CDMA systems in overloaded regim is investigated. To thid end, both wireless and optical CDMA systems are considered. In overloaded CDMA systems, if the spreading matrix is invertible and channel is ideal and noiseless, then in the receiver the information of users can be detected without any error. Previusely, it was proven that for limited information symbols space, there are some matrices which are invertible or detecting. However, optimal receiver in these systems is comlex and infeasible. The only case that the optimal receiver can be implemented in a fesible way, is when the spreading matrix is constructed using kronecker technique. Therefore, in...
An Efficient and Secure Attribute-Based Signcryption Scheme for Smart Grid Applications
, M.Sc. Thesis Sharif University of Technology ; Aref, Mohammad Reza (Supervisor) ; Mohajeri, Javad (Co-Advisor)
Abstract
With regards to the development of modern power systems, Smart Grid (SG) as an intelligent generation of electricity networks has been faced with a tremendous attention. Fine-grained data sharing in SG plays a vital role in efficiently managing data flow in the SG. As this data commonly contains sensitive information, design of the secure and efficient privacy preserving schemes for such networks with plenty of resource constrained devices is one of the most controversial issues. In this paper, we propose a Secure Ciphertext-Policy Attribute-Based SignCryption (CP-ABSC) scheme which simultaneously provides the authenticity and privacy of the users by enforcing an arbitrary access control...
Experimental Investigation of ASP Flooding for EOR in Fractured Heavy Oil Reservoirs Using Micromodel Apparatus
, M.Sc. Thesis Sharif University of Technology ; Massihi, Mohsen (Supervisor) ; Ghazanfari, Mohammad Hossein (Supervisor) ; Rashtchian, Davood (Supervisor)
Abstract
Heavy oil reservoirs contain huge amount of initial oil in place in the world. Thus, enhancement of their production attracts lots of attention. Primary and secondary oil recovery methods have just little effects on the production of these reservoirs, thus, using innovative chemical methods which lead them to increase their mobility is recommended to improve their oil recovery efficiency. One of these proper and novel methods which has been established recently to enhance oil recovery is ASP1 flooding that can significantly increase oil recovery from petroleum heavy oil reservoirs. In addition, considerable numbers of reservoirs especially heavy oil reservoirs are fractured reservoirs. In...
Modification of carbohydrate polymers via grafting in air. 1. Ceric-Induced synthesis of starch-g-polyacrylonitrile in presence and absence of oxygen [electronic resource]
, Article Starch - Starke ; Volume 54, Issue 3-4, pages 140–147, April 2002 ; Zohurian Mehr, Mohammad J
Abstract
Monomer grafting, a unique technique for polysaccharide modification, is always performed under inert (e.g., N2) atmosphere. This work is the first report related to evaluating the possibility and efficiency of the grafting of acrylonitrile (AN) onto starch in presence of oxygen. Thus, corn starch (in both granular and gelatinized states) as well as soluble starch were grafted by AN using a ceric-carbohydrate redox initiating system. Graft copolymerizations were performed under nitrogen, air, and oxygen atmospheres at similar conditions. Grafting occurrence was verified using chemical and spectral proofs. The polymerization mechanism and kinetics were investigated by recording the...
Modification of carbohydrate polymers via grafting in Air. 2. Ceric-Initiated graft copolymerization of acrylonitrile onto natural and modified polysaccharides [electronic resource]
, Article Starch - Stärke ; Volume 54, Issue 10, pages 482–488, October 2002 ; Zohuriaan-Mehr, Mohammad J
Abstract
Acrylonitrile (AN) was grafted onto various natural and modified polysaccharides (i.e., gum arabic, gum tragacanth, xanthan gum, sodium alginate, chitosan, sodium carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose) by using ceric-carbohydrate redox initiating system. After overcoming practical problems, mainly from the high viscosity of the aqueous solutions of the different substrates, the graft copolymerization reactions were run either in air or in N2 atmosphere under similar conditions. Grafting was confirmed using chemical and spectral (FTIR) proofs. The reactions were kinetically investigated using semi-empirical expressions and time-temperature profiles. An anomalous...
Modeling of in Plane Behavior of Retrofitted Adobe Walls with Finite Element Method under Cyclic Loading
, M.Sc. Thesis Sharif University of Technology ; Bakhshi, Ali (Supervisor) ; Ghannad, Mohammad Ali (Co-Advisor)
Abstract
Statistical studies indicate the fact that in Iran, like many other developing countries, a significant percentage of buildings are made of traditional materials and most of them are adobe buildings especially in rural areas. Furthermore, geological data indicates that Iran is located in alps-Himalayas seismic zone and exposed by destructive earthquakes and adobe buildings suffer the most damages comparing with other type of the structures. According to these explanations, this research deals with adobe buildings behavior and provides solutions for reinforcing them and improving the seismic response of these buildings. These studies include numerical modeling with finite elements methods by...
Silica chloride/wet SiO2 as a novel heterogeneous system for the deprotection of acetals under mild conditions [electronic resource]
, Article Phosphorus, Sulfur, and Silicon and the Related Elements ; Volume 178:2667-2670, Issue 12, 2003 ; Pourjavadi, Ali ; Zolfigol, Mohammad Ali ; Bamoniri, Abdolhamid
Abstract
A combination of silica chloride and wet SiO2 was used as an effective deacetalizating agent for the conversion of acetals to their corresponding carbonyl derivatives under mild and heterogeneous condition
Distributed Fault-tolerant Computation for Massive Data
, M.Sc. Thesis Sharif University of Technology ; Maddah-Ali, Mohammad Ali (Supervisor)
Abstract
In this thesis we consider the problem of distributed computation by many processors.We mainly concentrate on matrix multiplication problem in this thesis because of its importance. A distributed system consists of N worker processors and one master processor. The master processor should distribute the computation between workers and after computation in each of them, collect the results. In this thesis, we are going to mitigate the effect of straggler processors by using coding methods. Straggler processors can cause delays in the computation time.In this thesis, we firstly introduce a method to multiply any number of matrices in each other. The proposed method occurred in one shot without...
Improving Fault Tolerance in Safety-Critical Distributed Automotive Communication Networks
, Ph.D. Dissertation Sharif University of Technology ; Miremadi, Ghassem (Supervisor)
Abstract
Nowadays, distributed embedded systems are extensively employed in safety-critical automotive applications, e.g. Steer-By-Wire and Brake-By-Wire. Moreover, according to the present and future needs of the automotive industry of Iran, in this Ph.D. thesis, fault tolerance in safety-critical distributed automotive communication networks has been improved. This thesis consists of three research layers. In the first layer, several comprehensive studies on all automotive communication protocols and their architectures have been done. Among the protocols, the FlexRay communication protocol has been selected to employ in safety-critical distributed embedded systems. In the second layer, the fault...
Categorizing and analysis of activated faults in the flexray communication controller registers
, Article Proceedings of the 14th IEEE European Test Symposium, ETS 2009, 25 May 2009 through 29 May 2009, Sevilla ; 2009 , Pages 121-126 ; 9780769537030 (ISBN) ; Miremadi, G ; Sharif University of Technology
2009
Abstract
FlexRay communication protocol is expected becoming the de-facto standard for distributed safetycritical systems. In this paper, transient single bit-flip faults were injected into the FlexRay communication controller to categorize and analyze the activatedfaults. In this protocol, an activated fault results in one or more error types which are Boundary violation, Conflict, Content, Freeze, Synchronization, and Syntax. To study the activated faults, a FlexRay bus network, composed of four nodes, was modeled by Verilog HDL; and a total of 135,600 transient faults were injected in only one node, where 9,342 (6.9%) of the faults were activated. The results show that the Synchronization error is...
A low-cost on-line monitoring mechanism for the flexray communication protocol
, Article Proceedings - 2009 4th Latin-American Symposium on Dependable Computing, LADC 2009, 1 September 2009 through 4 September 2009, Joao Pessoa ; 2009 , Pages 111-118 ; 9780769537603 (ISBN) ; Miremadi, G ; Sharif University of Technology
2009
Abstract
Nowadays, communication protocols are used in safety-critical automotive applications. In these applications, fault tolerance is a main requirement and the existence of single points of failure is a serious threat to system failures. Among the communication protocols, FlexRay is expected to become the communication backbone for future automotive systems. In this paper, we identify single points of failure in the FlexRay protocol by injecting a total of 135,600 single-bit transient faults into all accessible registers of the FlexRay communication controller. The results showed that about 1.2% of all injected faults caused the controller to freeze immediately. Based on these results and...
Incomplete Reduction of Iron Ore in a Fluidized Bed Reactor
, M.Sc. Thesis Sharif University of Technology ; Halali, Mohammad (Supervisor)
Abstract
The main goal of current investigation was partial reduction of Fe2O3 available in Hematite-rich ore to Magnetite by Fludization Bed method. The reductive gas, CO, was produced by incomplete combustion of Acetylene and Airmixed in inappropriate ratio. X-Ray Diffraction and X-Ray Florescence analyses were implemented in order to conducting qualitative analysis of present phases before and after reduction of the ore. Quantitative analysis of the same phases was also conducted by Titration. The latter analysis revealed the precise magnitude of available iron in each of the oxide containing phases. The chemical composition of the reactor gas was also determined before and after reduction...
Sequential Competitive Facility Location In Continuous Geometric Space
, M.Sc. Thesis Sharif University of Technology ; Abam, Mohammad Ali (Supervisor)
Abstract
Abstract The problem of competetive facility location can be defined as follows: There are a number of customers in the form of points in space, and two players arrange a number of facilities in the form of points in space, given some limitations, respectively. Each customer’s connection to each facility has a cost for the customer and an advantage for the facility, and each customer wants to be connected to at most one of the facilities which has the lowest cost for him. The goal is to find the strategy of placing the facilities and determining the cost which the facility receives from the customer, in such a way that the player’s profit is maximised.In this thesis, we first sought to...
Distributed Verifiable Computing: Algorithms and Analysis
, M.Sc. Thesis Sharif University of Technology ; Maddah Ali, Mohammad Ali (Supervisor)
Abstract
Zero knowledge proofs allow a person (prover) to convince another person (verifier) that he has performed a specific computation on a secret data correctly, and has obtained a true answer, without having to disclose the secret data. QAP (Quadratic Arithmetic Program) based zkSNARKs (zero knowledge Succinct Non-interactive Argument of Knowledge) are a type of zero knowledge proof. They have several properties that make them attractive in practice, e.g. verifier's work is very easy. So they are used in many areas such as Blockchain and cloud computing. But yet prover's work in QAP based zkSNARKs is heavy, therefore, it may not be possible for a prover with limited processing resource to run...
Privacy Preserving Communication Schemes for Light Clients in Blockchain Networks: Algorithms and Analysis
, M.Sc. Thesis Sharif University of Technology ; Pakravan, Mohammad Reza (Supervisor) ; Maddah Ali, Mohammad Ali (Co-Supervisor)
Abstract
Lightweight clients are a type of blockchain users who do not store all the blocks in the blockchain due to limited resources. These users store only a small part of each block and when needed, request transactions from full nodes that store the entire blockchain. These users have no role in block validation and only want to receive transactions related to their addresses with proof of the inclusion in the block from full nodes.Since light clients rely on full nodes for receiving transactions, their privacy against full nodes is important. The current implementation of Bitcoin uses Bloom filters for privacy, but this offers very little privacy to the users.In this thesis, we study the...
The Effect of Soli-Structure Interaction on Dynamic Characteristics of Structures with Embedded Fondation
, M.Sc. Thesis Sharif University of Technology ; Ghannad, Mohammad Ali (Supervisor)
Abstract
Soil-structure interaction has significant effect on dynamic behavior of the super structure. This effect is usually investigated in two separate parts, i.e., the Kinematic Interaction effect and the Inertial Interaction effect. The first modifies the input ground motion to the foundation as a result of difference in soil and foundation stiffness. The later, i.e., the II effect, introduces the effect of soil flexibility and radiation of waves into the supporting medium on the response of the structure. These effects are usually considered by introducing a replacement oscillator with modified natural period and damping ratio subjected...
Perusing Metal Perusing Metal Insulator Transistors with in the Dynamical Field Approximation at Finite Temperature
, Ph.D. Dissertation Sharif University of Technology ; Vesaghi, Mohammad ALi (Supervisor)
Abstract
The aim of this work is to investigate some theoretical models developed in recent years for describing electronic correlation and apply them to some special problems and metallicity and insulating behavior of one type of paramagnetic systems. One of the vast‐applied and effective routines for investigating the strongly correlated electron systems is Dynamical Mean Field Theory (DMFT). In the first part, the equations of DMFT are solved on nearly real frequency axis with a effective and more reliable solver a little parameter γ above the real axis. This approach appears fine structures that can’t be captured with the ...
On a Bounded Budget Network Creation Game
, M.Sc. Thesis Sharif University of Technology ; Safari, Mohammad Ali (Supervisor)
Abstract
In this thesis, we consider a network creation game in which, each player (vertex) has a limited budget to establish links to other players. In our model, each link has a unit cost and each agent tries to minimize its cost which is its local diameter or its total distance to other players in the (undirected) underlying graph of the created network. Two variants of the game are studied: in the MAX version, the cost incurred to a vertex is the maximum distance between that vertex and other vertices, and in the SUM version, the cost incurred to a vertex is the sum of distances between that vertex and other vertices. We prove that in both versions pure Nash equilibria exist, but the problem of...
Power System Load Frequency Control Considering Renewable Energy Sources
, M.Sc. Thesis Sharif University of Technology ; Ranjbar, Ali Mohammad (Supervisor)
Abstract
Power system frequency regulation entitled load frequency control (LFC) has been one of the important control problems in electric power system design and operation. Off-normal frequency can directly impact on power system operation and system reliability. A large frequency deviation can damage equipment, degrade load performance, cause the transmission lines to be overloaded and can interfere with system protection schemes, ultimately leading to an unstable condition for the power system . On the other hand, the increasing need for electrical energy in the 21st century, as well as limited fossil fuel reserves and the increasing concerns with environmental issues for the reduction of carbon...