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abedi--masoumeh
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Total 148 records
Channel Estimation in mmWave MIMO Systems
, M.Sc. Thesis Sharif University of Technology ; Nasiri Kenari, Masoumeh (Supervisor)
Abstract
Millimeter-wave (mmWave) communication systems exhibit large bandwidth and severe channel attenuations. To maintain the received signal-to-noise ratio on an acceptable level, mmWave systems use large antenna arrays and directional beamforming at both transmitter and receiver. The existence of many antenna elements, however, challenges traditional approaches for pilot transmission and channel estimation wherein the number of pilots linearly scales up with the total number of transmit antennas. For instance, for the uplink channel estimation with a constant coherence interval, adding more antennas to the users comes at the expense of a linear penalty on the number of users, which can...
Dynamical Simulation and Lumbar Spine Control Flexion-Extension Movement
, M.Sc. Thesis Sharif University of Technology ; Vossoughi, Gholamreza (Supervisor) ; Parnianpour, Mohammad (Supervisor)
Abstract
Low back pain (LBP) problems are of concern to many researchers specially physiologists, biomedical engineers and... .biomechanical models can help us to furthering our knowledge of the mechanical characteristics of the spine and its neural control to know more about potential mechanisms of injury. This thesis involves computational model of lumbar spine to generate and control its flexion-extension movement.
Model has involved 7 links: 5 lumbar vertebrae, pelvis and trunk. Desired trajectory has been generated for rhythmic and discrete motion by the central pattern generators (CPGs). And then controller has produced torque of joints to track desired trajectory. CPGs have been...
Model has involved 7 links: 5 lumbar vertebrae, pelvis and trunk. Desired trajectory has been generated for rhythmic and discrete motion by the central pattern generators (CPGs). And then controller has produced torque of joints to track desired trajectory. CPGs have been...
An efficient algorithm for overlay multicast routing in videoconferencing applications
, Article Proceedings - International Conference on Computer Communications and Networks, ICCCN, 3 August 2009 through 6 August 2009, San Francisco, CA ; 2009 ; 10952055 (ISSN); 9781424445813 (ISBN) ; Rabiee, H. R ; Abedi, A ; Ghanbari, M ; Sharif University of Technology
2009
Abstract
The increasing use of multi-party web conferencing applications demands for suitable multicast protocols. Limited bandwidth of typical internet user requires the underlying multicast routing to be efficient. In this paper we present HOMA; an application layer multicast protocol which has been tailored for small-scale multi-party videoconferencing applications. Considering the requirements of such applications, HOMA uses a heuristic routing to construct efficient multicast trees on the application layer. We have evaluated the performance of the proposed routing algorithm through simulations. Experimental results indicate that the proposed algorithm performs better than the related algorithms...
Quantum Black Holes: Conformal Anomaly Effects, Echoes in Gravitational Waves
, Ph.D. Dissertation Sharif University of Technology ; Arfaei, Hessamaddin (Supervisor) ; Afshordi, Niayesh (Co-Advisor)
Abstract
In this thesis by studying the extreme physical conditions near black hole horizons and singularity, we attack intriguing problems in the exciting era of quantum black holes and gravitational wave astronomy. We considered the backreaction of the energy due to quantum fluctuations of the background fields for a Schwarzschild black hole, in semi-classical gravity. We have shown that it results in modification of the horizon and also formation of an inner horizon. The process of the collapse of a thin shell stops before formation of the singularity. After the collapse stops the reverse process takes place. We also demonstrate the existence of a cold remnant for the black hole. We generalized...
Compressed Spectrum Sensing in Cognitive Radio Network
, M.Sc. Thesis Sharif University of Technology ; Nasiri-Kenari, Masoumeh (Supervisor) ; Babayi-Zadeh, Masoud (Co-Advisor)
Abstract
In recent years, the Cognitive Radio Network has received significant attentions due to its high potential for better employment of the spectrum. One of the most important parts of this technology is the spectrum sensing that requires being fast and accurate. The conventional algorithms proposed so far encounter some fundamental challenges at low SNR regimes and in wideband sensing. On the other hand, the compressed sensing algorithms, which take advantages of the sparsity of the signal of interest and utilize measurements instead of the samples, can reduce the sampling rate and thus decrease the complexity associated with the wideband sensing. In this thesis, by exploiting the...
Interference Alignment in Wireless Networks
, M.Sc. Thesis Sharif University of Technology ; Nasiri Kenari, Masoumeh (Supervisor) ; Hosseini Khalaj, Babak (Supervisor)
Abstract
In this thesis, we derive an achievable Degrees of Freedom (DoF) region for a MIMO channel that models uplink transmission in a cellular network of two interfering cells with two users in each cell, under two different genie-aided cognitive scenarios; a cognitive cell together with a primary cell, and a cognitive transmitter with a primary transmitter in each cell. Most of the previous works dealt with networks with only two transmitters. Here, we study the effect of increase in the number of transmitters on nullifying and aligning the interference. In each scenario, an outer bound on the DoF region is derived. Then, we evaluate how cognition can improve the maximum achievable DoF by...
Appropriate MAC Sub-layer Algorithms for Body Area Networks and Related Analysis
, M.Sc. Thesis Sharif University of Technology ; Nasiri-Kenari, Masoumeh (Supervisor) ; Vosougi Vahdat, Bijan (Co-Advisor)
Abstract
WBAN , as one of the most important wireless networks in the near future, has received significant attentions in recent years. The most important designing challenge in these networks is the scarcity of energy resources especially in their sensor nodes. Additionally, special characteristics of these networks have led the other network’s designs, especially the general sensor network protocols to be inefficient for the WBAN. Among others, the existences of recurring patterns in each sensor channel fading and the high correlation among different sensor channels are some of the most important characteristics of WBANs. Considering these characteristics, in this thesis, the MAC sub-layer of...
Efficient Methods for Transmission and Reception of Information in Molecular Communication Systems
, M.Sc. Thesis Sharif University of Technology ; Nasiri-Kenari, Masoumeh (Supervisor) ; Gohari, Amin (Supervisor)
Abstract
This thesis studies on diffusion-based molecular communication channel between two nano-machines. The effect of the amount of memory on performance is characterized, and a simple memory-limited decoder is proposed and its performance is shown to be close to that of the best possible decoder (without any restrictions on the computational complexity or its functional form), using Genie-aided upper bounds. This effect is studied for the case of Molecular Concentration Shift Keying; it is shown that a four-bits memory achieves nearly the same performance as infinite memory. Then a general class of threshold decoders is considered and shown not to be optimal for a Poisson channel with memory,...
Energy Efficient Policies for TDMA based Wireless Body Area Network (WBAN)
, M.Sc. Thesis Sharif University of Technology ; Nasiri-Kenari, Masoumeh (Supervisor) ; Ashtiani, Farid (Supervisor)
Abstract
Recent advancements in wireless communication along with the urgent need for new care systems for the patients, has attracted the attention of many communication researchers to Wireless Body Area Networks (WBANs), which has led to IEEE 802.15.6 and IEEE 802.15.4j standards, accordingly. The main goal of such networks, is to send the vital data of the associate, through the over/in-body-implanted sensors, to one central node. One of the key features of these networks is the limited energy sources of the sensors, transmit the data. Meanwhile, on-time error-free transmission of the data is also of great importance. Therefore, designing a proper algorithm, satisfying the aforementioned...
Computation in Wireless Cooperative Networks
, M.Sc. Thesis Sharif University of Technology ; Nasiri-Kenari, Masoumeh (Supervisor) ; Ashtiani, Farid (Co-Advisor)
Abstract
In this thesis, we consider Compute and Forward schemes in relay assisted cooperative communication networks. The main problem associated with the compute and Forward scheme is the possible dependency of the relayed equations to the destination, which leads to the outage and thus the very low achievable rate. We propose several approaches to deal with this problem. In the first part of the thesis, we consider a cooperative network consisting of multi users, multi relays, and one common destination with no direct links between the users and the destination. We propose three strategies to lessen the aforementioned problem associated with the conventional compute and forward relaying scheme,...
Evaluating the performance of artificial neural network model in downscaling daily temperature, precipitation and wind speed parameters
, Article International Journal of Environmental Research ; Vol. 8, issue. 4 , 2014 , p. 1223-1230 ; Abbaspour, M ; Soltaniyeh, M ; Hosseinzadeh, F ; Abedi, Z ; Sharif University of Technology
2014
Abstract
Numerous studies yet have been carried out on downscaling of the large-scale climate data using both dynamical and statistical methods to investigate the hydrological and meteorological impacts of climate change on different parts of the world. This study was also conducted to investigate the capability of feedforward neural network with error back-propagation algorithm to downscale the provincial segmentation of Iran (30 provinces) on a daily scale. This model was proposed for the downscaling daily temperature, precipitation and wind speed data, and it was calibrated and verified by using the daily outputs derived from the National Center for Environmental Prediction (NCEP) database...
Utilization of analytical hierarchy process in contingency ranking
, Article 2009 IEEE/PES Power Systems Conference and Exposition, PSCE 2009, Seattle, WA, 15 March 2009 through 18 March 2009 ; 2009 ; 9781424438112 (ISBN) ; Ehsan, M ; Ghofrani Jahromi, Z ; Masjed Jamei, M ; Sharif University of Technology
2009
Abstract
Contingency screening and ranking is one of the most important issues for security assessment in the field of power system operation. The objective of contingency screening and ranking is to quickly and accurately select a short list of critical contingencies from a large list of potential contingencies and rank them according to their severity. Then suitable preventive control actions can be implemented considering contingencies that are likely to affect the power system performance. In this paper a novel approach is presented for contingency ranking based on static security assessment (SSA). This method uses weighted performance index with the application of Analytical Hierarchy Process...
Axisymmetric and three-dimensional flow simulation of a mixed compression supersonic air inlet
, Article Propulsion and Power Research ; Volume 9, Issue 1 , 2020 , Pages 51-61 ; Askari, R ; Sepahi Younsi, J ; Soltani, M. R ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
The flow through an axisymmetric supersonic mixed-compression air inlet has been simulated numerically to investigate the effects and the necessity of the three-dimensional (3D) modeling in comparison with the axisymmetric one. For this purpose, a supersonic inlet has been simulated numerically via axisymmetric and 3D CFD solvers, using the steady state Reynolds-averaged Navier-Stokes equations along with the SST k-ω turbulence model, for a free-stream Mach number of 2.0 and at zero degrees angle of attack. The grid for the 3D cases was a 14.4-degree sector, instead of a 360-degree domain one, with rotational periodic boundary condition for the side boundaries. The results show that both...
Environmental parametric cost model in oil and gas EPC contracts
, Article Sustainability (Switzerland) ; Volume 10, Issue 1 , 2018 ; 20711050 (ISSN) ; Toutounchian, S ; Dana, T ; Abedi, Z ; Toutounchian, S ; Sharif University of Technology
MDPI AG
2018
Abstract
This study aims at identifying the parameters that govern the environmental costs in oil and gas projects. An initial conceptual model was proposed. Next, the costs of environmental management work packages were estimated, separately and were applied in project control tools (WBS/CBS). Then, an environmental parametric cost model was designed to determine the environmental costs and relevant weighting factors. The suggested model can be considered as an innovative approach to designate the environmental indicators in oil and gas projects. The validity of variables was investigated based on Delphi method. The results indicated that the project environmental management's weighting factor is...
In situ postweld heat treatment of transformation induced plasticity steel resistance spot welds
, Article Science and Technology of Welding and Joining ; Volume 23, Issue 1 , 2018 , Pages 71-78 ; 13621718 (ISSN) ; Pouranvari, M ; Abedi, A ; Ghaderi, A. A ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
Transformation-induced plasticity (TRIP) steel resistance spot welds are delicate to low-energy interfacial failure via crack propagation through martensitic fusion zone during cross-tension (CT) loading. This paper addresses the effect of three different types of in situ postweld heat treatment (PWHT) on the mechanical properties of TRIP steel resistance spot welds. Depending on the post weld second pulse current level, three different strengthening mechanisms were found including (i) martensite tempering with reduced hardness, (ii) refining of martensite packets with improved toughness and (iii) nugget re-melting/enlargement combined with possible reduction of grain boundary impurity...
Microstructure and failure behavior of dissimilar resistance spot welds between low carbon galvanized and austenitic stainless steels
, Article Materials Science and Engineering A ; Volume 480, Issue 1-2 , 2008 , Pages 175-180 ; 09215093 (ISSN) ; Pouranvari, M ; Amirabdollahian, S ; Abedi, A ; Goodarzi, M ; Sharif University of Technology
2008
Abstract
Resistance spot welding was used to join austenitic stainless steel and galvanized low carbon steel. The relationship between failure mode and weld fusion zone characteristics (size and microstructure) was studied. It was found that spot weld strength in the pullout failure mode is controlled by the strength and fusion zone size of the galvanized steel side. The hardness of the fusion zone which is governed by the dilution between two base metals, and fusion zone size of galvanized carbon steel side are dominant factors in determining the failure mode. © 2007 Elsevier B.V. All rights reserved
Performance Analysis of Ultra-Wide Band (UWB) Communication with a Relay Node
, Ph.D. Dissertation Sharif University of Technology ; Nasiri Kenari, Masoumeh (Supervisor) ; Azhang, Behnaam (Supervisor)
Abstract
In recent years, there has been an increased interest on employing low-cost, high-speed, low-latency wireless links for short range communications (< 10m). Ultra-wideband (UWB) radio is a promising technology to meet this interest. However, due to the limitation on its transmitted power level, UWB system faces major challenges to achieve an adequate system performance. Therefore, it is greatly necessary to find some efficient methods to enhance the system performance. Recently, cooperative diversity has emerged as an effective scheme to overcome multipath fading and thus to improve the quality of service in the physical layer of wireless networks without increasing the transmission power of...
Optimal Relay Location in Wireless Networks
, M.Sc. Thesis Sharif University of Technology ; Golestani, Jamaloddin (Supervisor) ; Nasiri-Kenari, Masoumeh (Co-Advisor)
Abstract
According to the wide range of applications and numerous implementations, wireless networks are considered as a prominent means of providing data services, and have attracted the attention of many researches in recent years. Performance enhancement of these networks can be very beneficial to industry and wireless data service providers. Manipulation of relays, have been always considered as a proper means for improvement of network performance measures throughput and outage probability.In order to design relay networks efficiently, one should address two following problems: 1- determining transmission policy, and 2- relay location. In this research work, having in mind the optimality of...
UEP CodesBased Cooperative Network With Different User Priorities Approach and Their Analysis
, M.Sc. Thesis Sharif University of Technology ; Nasiri-kenari, Masoumeh (Supervisor) ; Behroozi, Hamid (Supervisor)
Abstract
In recent years, coded cooperation has been considered as one of the best methods to cope with fading and at the same time to achieve channel coding gain. There is a special case of cooperative networks that provide different level of user priority. Among all methods for creating user priority our motivation is to use of UEP codes for this propose. UEP codes are a special case of channel codes that provide different level of protection for message. It means that some part of message that has more protection it has less error. First we review all type of UEP codes and compare them in term of probability of bit error on the AWGN channel. And best code will be choosing for applying to this...
Uncertainty Modeling in Practical Molecular Communication Transmitters and their Effects on Rate
, M.Sc. Thesis Sharif University of Technology ; Aminzadeh Gohari, Amin (Supervisor) ; Nasiri Kenari, Masoumeh (Co-Advisor)
Abstract
Molecular communication (MC), is a new way of communication among nanomachines.its applications are typically in cases which the conditions of transfer such as size, nature of the medium and nature or type of the original signal, is consistent with molecules such as medicine, health care, industrial and environmental applications.In this thesis, we first review different models of molecular transmitters. In most of them, storage capacity and molecule generation rate are not considered. we try to propose practical transmitter models considering these limitations. for high storage capacity transmitters, we propose Fixed and Linear transmission methods. assuming that channel is without...