Loading...
Search for:
fazel-mojtahedi--farid
0.217 seconds
Total 110 records
Investigation of Ardabil Plain Subsidence with Respect to Changes in Groundwater Level and Climate Fluctuations
, M.Sc. Thesis Sharif University of Technology ; Khosravi, Ali (Supervisor)
Abstract
The subsidence phenomenon in the past years has caused many problems and issues for the agricultural lands, roads, power transmission lines, energy etc., due to different reasons including over use of groundwater resources and changes in climate. This phenomenon has been observed in different plains of the country including the Khorasan, Kerman, Hamedan, Ghazvin and Isfahan plains and has caused many damages to infrastructure and agricultural products in the mentioned regions. In this research the main factors which have affected the subsidence phenomenon especially reduced ground water table and climate changes in Ardebil plain, are taken into account and some studies which comprise...
Numerical finite element analysis of laterally loaded fin pile in sandy soil
, Article Innovative Infrastructure Solutions ; Volume 4, Issue 1 , 2019 ; 23644176 (ISSN) ; Hanaei, F ; Fazel Mojtahedi, S. F ; Rezaee, M ; Sharif University of Technology
Springer
2019
Abstract
In the present study, the behavior of fin pile under lateral loading was investigated by ABAQUS software. First, the generated model was verified against an available experimental small-scale test in the literature. Having conducted verification, a study was carried out on the fin pile dimensions under lateral loading. Different parameters, such as pile diameter, fin’s length, and width, were studied. Moreover, a study on the fin’s aspect ratio by setting fin’s area constant was conducted, and then, optimum fin’s ratio was obtained. The results indicated that both fin’s length and width could improve pile efficiency under lateral loading, yet fin’s length had a more critical impact, and...
Failure procedure in epoxy adhesive joining composite plates
, Article Iranian Journal of Science and Technology - Transactions of Mechanical Engineering ; 2020 ; Kadivar, M. H ; Zohoor, H ; Farid, M ; Hematiyan, M. R ; Sharif University of Technology
Springer
2020
Abstract
In this paper, several numerical simulations are performed to study the failure of epoxy adhesive joining composite plates. Different geometries for the joint and its edge are considered, and the effects of these geometries on the failure load are investigated. Moreover, the joints are subjected to different types of loading in order to determine the failure load. The failure theories of composite materials are implemented into the finite element software ABAQUS, and the failure propagation in the joint is studied. © 2020, Shiraz University
The ∑ 1-Provability Logic of Intuitionistic Arithmetic
, Ph.D. Dissertation Sharif University of Technology ; Ardeshir, Mohammad (Supervisor)
Abstract
In this dissertation, we study (first-order) arithmetical interpretations for propositional (modal and non-modal) logics. More precisely, the following results are included in this dissertation: an axiomatization for provability logic of Heyting Arithmetic, HA, and its self-completion HA := HA + PrHA(⌜A⌝) ! A for 1-substitutions is provided, and their arithmetical completeness theorems are proved. We also show that they are decidable. The de Jongh property for Basic Arithmetic BA, HA and HA + □ are proved
Optimization of Pressure Leaching of Chalcopyrite Concentrate with Oxygen and Kinetics Study of the Process in Sulfuric Acid Solution
, M.Sc. Thesis Sharif University of Technology ; Yoozbashizadeh, Hossein (Supervisor)
Abstract
The enormous benefits of hydrometallurgical processes have led to the progressive metals extraction industry. Many studies are carried out on the application of these processes in the copper extraction industry. In this research, the oxygen pressure leaching of chalcopyrite concentrate was studied. Experiments were carried out under conditions of the solid-liquid ratio of 0.1, agitation speed of 750 rpm, and sulfuric acid concentration of 2M in a stainless-steel autoclave system. Central composite design (CCD) was used to design experiments, and three factors of temperature, time, and pressure of oxygen, were selected as design variables. The obtained model for %Cu includes parameters of...
Assessment of Water and Sewage Facilities of Kish Island and Offering Solutions in Emergency Conditions (A Case Study on Kish Island)
, M.Sc. Thesis Sharif University of Technology ; Hashemian, Jamal (Supervisor)
Abstract
Vulnerability of water and sewage infrastructure in Kish Island survey versus natural and unnatural threats. It is important to know what to do when crisis or unpredicted event occurs in the Island. Decision makers and master managers of the Island, as the main custodians make suitable and effective reactions and decisions so that the impact of threats is reduced to minimum. According to the threats, there are short term and long term solutions. These solutions can be applied when the Island is encountered with crisis
Pressure leaching of chalcopyrite concentrate with oxygen and kinetic study on the process in sulfuric acid solution
, Article Transactions of the Indian Institute of Metals ; Volume 73, Issue 4 , 6 March , 2020 , Pages 975-987 ; Rasouli, S ; Yoozbashizadeh, H ; Sharif University of Technology
Springer
2020
Abstract
In this research work, the pressure leaching of chalcopyrite concentrate with oxygen was studied. Experiments were carried out under conditions of the solid–liquid ratio of 0.1, agitation speed of 750 rpm, and sulfuric acid concentration of 2 M in a stainless-steel autoclave system under 0.6 to 1 MPa oxygen gas. Central composite design was used to design experiments, and three factors of temperature, time, and oxygen pressure were selected as the design variables. A linear model for %Cu and a quadratic model for %Fe were proposed by Minitab Software. The results showed that temperature is the most effective factor in chalcopyrite leaching. Under optimal conditions, 93.08% of copper with the...
Pipelining method for low-power and high-speed SAR ADC design
, Article Analog Integrated Circuits and Signal Processing ; Volume 87, Issue 3 , 2016 , Pages 353-368 ; 09251030 (ISSN) ; Saeedi, S ; Atarodi, M ; Sharif University of Technology
Springer New York LLC
2016
Abstract
A low power analog to digital converter (ADC), based on a pipelining method employed in successive approximation register (SAR) architecture is presented. This structure is a two-stage pipeline SAR ADC with asymmetrical time interleaved (TI) channels, aimed to reach sampling rate as high as about threefold of a conventional SAR ADC while benefiting from its low power consumption and small area. Passive residue conversion without inter-stage amplifier and symphonic collaboration of stages are employed to design a low power, high speed, and accurate converter. In the proposed architecture, every signal sample experiences equal comparator offset during its conversion due to the applied novel...
Development of a device for measuring air–water flow characteristics
, Article International Journal of Civil Engineering ; Volume 15, Issue 2 , 2017 , Pages 195-203 ; 17350522 (ISSN) ; Fazelian, M ; Sarkardeh, H ; Sharif University of Technology
Springer International Publishing
2017
Abstract
Air–water flow is a complex and challenging subject in many engineering fields as well as hydraulic engineering; and discovery of its characteristics can help the engineers to predict and analyze a probable phenomenon. In the present paper, development of a device capable of measuring the flow velocity, air concentration, diameter and counts of bubbles in air–water flows is described. The heart of the present device is two resistive probes with a novel configuration. Being pressure and corrosion resistant and also having negligible resistivity in the flow are some of the unique features of the employed needles. Moreover, sampling frequency and time can be adjusted for the intended...
A Low-power clock generator with a wide frequency tuning range and low temperature variation: analysis and design
, Article Journal of Circuits, Systems and Computers ; Volume 29, Issue 1 , 2020 ; Shokrekhodaei, M ; Atarodi, M ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2020
Abstract
This paper presents a quadrature-clock generator based on a novel low-power ring oscillator with a wide frequency tuning range and low temperature variations. The proposed ring oscillator consists of two differential delay cells with a new controllable capacitive load of an MOS transistor. The wide tuning range is achieved due to transistor utilization in different regions and considering its resistance not to narrow down the frequency range. Delay cells are biased with a minimum possible value of a proportion to absolute temperature current to decrease frequency variations to temperature while the power consumption is kept low. The validation of the proposed methods is proved by circuit...
A system-level design method for RF receiver front-end with low power consumption
, Article Analog Integrated Circuits and Signal Processing ; 2021 ; 09251030 (ISSN) ; Atarodi, M ; Sadughi, S ; Sharif University of Technology
Springer
2021
Abstract
Due to wireless communication’s rapid growth, the need for low power integrated transceivers is increasing. The receiver power is a major limiting factor, and the radio frequency (RF) front-end is often its significant power consuming part. Therefore, system-level design in which the overall specifications are distributed among RF front-end building blocks such that the minimum total power is consumed is crucial. A complete system-level design method for a low power RF front-end is presented in this paper. For this purpose, the performance of each block is modeled by its current and overdrive voltage. An analytical associated with a search-based optimization technique is employed to derive...
Throughput Analysis in Multi Hop Cellular Networks
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
OFDMA multi-hop cellular network (MCN) is the topic of a wide range of research today. In this thesis, we analyse this type of networks, regarding shadowing status, mobility patterns and different service requirements. In the multi-hop (MH) scenario, six fixed relays are set up in each cell, which split the cell into seven subcells. For mobility modeling, each subcell is split into several sub-regions. Mobile nodes are able to maintain at each sub-region with a random time distribution and migrate from it to one of its neighboring sub-regions. We also consider three types of services requiring specific number of subcarriers with specific BERs. The set of subcarriers is distributed among...
Throughput Analysis of a Cognitive Multi-hop Wireless Network Overlaid on a Cellular Network
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
In this thesis, we evaluate the maximum stable throughput of a cognitive multi-hop IEEE 802.11-based WLAN overlaid on a cellular network. In the considered scenario, the secondary users operate in the downlink or uplink frequency band of primary network and transmit their data in free primary channels using OFDM technique. The activity of primary nodes is modeled independently by ON-OFF alternating states. To model the scenario, each secondary user is modeled with an open queueing network. The queueing network can model the transmission of data as well as the effect of primary users. By writing the traffic equations of the queueing network and applying the stability conditions, we are able...
Network Coding-based Packet Relaying in Wireless Networks
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
In this thesis, we propose two new network coding-based packet relaying schemes suitable for multiple unicast scenarios in a random access network. In such networks the channels may have memory dependent upon the random access scheme. Thus, the optimal scheme for memoryless channels reported recently in the literature is not necessarily optimal in random access networks. In our proposed schemes, we convert a multiple unicast scenario to a combination of multiple anycast and a few multicast scenarios. By such an approach, we exploit the channels between relay node and the other nodes, instead of using only one channel at each packet transmission, for as many as possible. By simple analytical...
Analysis of the Effect of Frame Aggregation in IEEE 802.11 Standard
, M.Sc. Thesis Sharif University of Technology ; Ashtiyani, Farid (Supervisor)
Abstract
In this thesis the effect of frame aggregation mechanism in maximizing throughput in Wireless Local Area Networks (WLANs) have been investigated. Frame aggregation has become a part of the IEEE 802.11 standard as the amendment IEEE 802.11n. First, we have a quick review on access control layer in IEEE 802.11 standard then illustrate the necessity of frame aggregation. Afterwards, we propose an analytical model for the analysis of an IEEE 802.11n network comprised of an Access Point (AP) and several conventional nodes, all in the coverage area of each other. This analytical model focuses on downlink throughput; therefore only AP uses frame aggregation and the other nodes use basic IEEE 802.11...
Performance Analysis of Cognitive Radio Networks With Capability of Spectrum Mobility
, M.Sc. Thesis Sharif University of Technology ; Ashtinani, Farid (Supervisor)
Abstract
In cognitive radio networks, secondary users try to use empty channels that primary users provide for transmitting data. First, the secondary users sense the target channels. If the selected channel is empty, they send their data. When the primary user returns, the secondary user has to find another empty channel for transmitting data. The process of changing channel is called hand off. In recent years, there are challenges in the spectrum mobility of for reducing delay time of secondary users packet. In this thesis, we assume that the secondary users network is an ad-hoc network. We use contestation based method for reducing collision between secondary users. In this thesis, we present an...
Content Distribution Service Analysis in Vehicular Ad-Hoc Networks
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
Car accident damages take about 7 percent of GPD of Iran every year. As a result of car accidents, the economy of the country is damaging irreparably. The amount of road casualties equals casualties in a complete war. Considering the aforementioned conditions, the researchers are thinking about new technologies to reduce the cost of the accidents. So the use of Vehicular ad-hoc Networks (VANET) is inevitable in the near future. Content distribution service is one of the emerging services of VANETs. This service is used in both safety and comfort related applications. Content distribution describes delivery of media content such as Video, Audio, Image, Text, Software, and Video Games over...
Energy Harvesting in Wireless Communication Networks
, Ph.D. Dissertation Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
In this dissertation, we focus on two types of EH cooperative networks. In the first type, the source and relay nodes access a shared channel according to a random access protocol. Also, they harvest energy from non-RF environmental resources. The relay node has data and energy buffers to store the packets of the source and the harvested energy, respectively. Our main goal is to find the optimal relaying protocol at the relay node. In this regard, the first type of the EH cooperative networks are investigated in two different scenarios. In the first one, the MAC channels of the nodes are independent of the applied policy at the relay node, and thus the throughput of the network is fixed....
Cooperative Networks from the MAC Layer Viewpoint
, Ph.D. Dissertation Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
Cooperative networks have attracted much attention in the last decade. Being introduced to mitigate the inefficiencies in the physical layer, cooperation can also be beneficial in upper layers, such as MAC layer. Using cooperative communications is specifically more challenging in the random access networks, where collision is a main concern. Delay, as one of the main performance metrics in random access networks, can decrease significantly by using cooperative communications. Transmission delay, i.e., the required time for delivering one packet form its source to destination, is an important metric in many communication networks, such as the networks in which each node generates and...
Analysis of Age of Information in Multisource Communication Networks
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
In this thesis, we investigate the age of information in multisource networks. To this end, in the first phase of this thesis, we evaluate the Age of Information (AoI) in slotted ALOHA network. Regarding the interactions among the nodes in such a network, we model the memory of this network with a Trellis and find the peak Age of Information (PAoI) by using this Trellis. Then, we evaluate Age of Information-constrained regions and achievable throughput regions in the slotted ALOHA network and optimize Age of information in a symmetric case. In the second phase, we propose an efficient prioritizing scheme from AoI point of view and find the distribution of AoI and PAoI in such a scheme with...