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cognition
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Regeneration of stochastic processes: An inverse method
, Article European Physical Journal B ; Volume 47, Issue 3 , 2005 , Pages 411-415 ; 14346028 (ISSN) ; Peinke, J ; Sahimi, M ; Rahimi Tabar, M. R ; Sharif University of Technology
2005
Abstract
We propose a novel inverse method that utilizes a set of data to construct a simple equation that governs the stochastic process for which the data have been measured, hence enabling us to reconstruct the stochastic process. As an example, we analyze the stochasticity in the beat-to-beat fluctuations in the heart rates of healthy subjects as well as those with congestive heart failure. The inverse method provides a novel technique for distinguishing the two classes of subjects in terms of a drift and a diffusion coefficients which behave completely differently for the two classes of subjects, hence potentially providing a novel diagnostic tool for distinguishing healthy subjects from those...
A game-theoretic approach for joint channel and power allocation in downlink of cellular cognitive radio networks
, Article IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC ; 2012 , Pages 1198-1202 ; 9781467325691 (ISBN) ; Khalaj, B. H ; Sharif University of Technology
2012
Abstract
In this paper, we consider a cellular cognitive radio network that uses opportunistic spectrum access for its transmission in the downlink direction from base stations toward cognitive radio users. Since the spectrum is licensed to a primary network, proper resource management should be employed in the secondary network to protect primary users against excessive interference while providing acceptable utilization for secondary users. We use game theory to propose a distributed method for joint frequency and power allocation in the downlink of cognitive radio networks. Earlier works in this area were based on centralized optimization-based approaches, whereas our proposed method solves the...
On the capacity of interference channel with causal and noncausal generalized feedback at the cognitive transmitter
, Article IEEE Transactions on Information Theory ; Volume 58, Issue 5 , 2012 , Pages 2813-2837 ; 00189448 (ISSN) ; Akhbari, B ; Aref, M. R ; Sharif University of Technology
Abstract
In this paper, taking into account the effect of link delays, we investigate the capacity region of the cognitive interference channel (C-IFC), where cognition can be obtained from either causal or noncausal generalized feedback. For this purpose, we introduce the causal C-IFC with delay (CC-IFC-WD) in which the cognitive user's transmission can depend on L future received symbols as well as the past ones. We show that the CC-IFC-WD model is equivalent to a classical causal C-IFC (CC-IFC) with link delays. Moreover, CC-IFC-WD extends both genie-aided and causal cognitive radio channels and bridges the gap between them. First, we derive an outer bound on the capacity region for the arbitrary...
Novel power control algorithms for underlay cognitive radio networks
, Article Proceedings - ICSEng 2011: International Conference on Systems Engineering, 16 August 2011 through 18 August 2011, Las Vegas, NV ; 2011 , Pages 206-211 ; 9780769544953 (ISBN) ; Khalaj, B. H ; Sharif University of Technology
2011
Abstract
Power control mechanisms play a critical role in underlay cognitive radio networks where primary users' quality of service should not be degraded by the secondary users transmission. Consequently, the inflicted interference power of the secondary transmitters on the primary receivers should be less than certain threshold levels that is required to be considered in designing power control algorithms for such networks. In this paper, we first propose a power reduction algorithm for the set of secondary transmitting links in order to guarantee that the members of this set do not violate the interference constraints set by primary users while maintaining their specific SINR quality of service...
Delay-sensitive area spectral efficiency: a performance metric for delay-constrained green networks
, Article IEEE Transactions on Communications ; Volume 65, Issue 6 , 2017 , Pages 2467-2480 ; 00906778 (ISSN) ; Fang, C ; Svensson, T ; Nasiri Kenari, M ; Zorzi, M ; Sharif University of Technology
Abstract
This paper introduces a new metric, referred to as delay-sensitive area spectral efficiency (DASE), to analyze the performance of delay-constrained wireless networks. We study DASE in different point-to-point, spectrum sharing, interference, and Poisson-point process-based dense network configurations and with different levels of channel state information (CSI) at the transmitters. Also, we determine the optimal rates/powers optimizing DASE. Finally, we use some recent results on finite block-length codes to analyze the effect of the codewords length on the network DASE. As demonstrated, DASE is a useful metric for analyzing delay-sensitive green networks. Moreover, adaptive power allocation...
Effects of cognitive load on the amount and temporal structure of postural sway variability in stroke survivors
, Article Experimental Brain Research ; Volume 236, Issue 1 , 2018 , Pages 285-296 ; 00144819 (ISSN) ; Khalaf, K ; Ghomashchi, H ; Taghizadeh, G ; Ebrahimi, I ; Taghavi Azar Sharabiani, P ; Mousavi, S. J ; Parnianpour, M ; Sharif University of Technology
Springer Verlag
2018
Abstract
This study aimed to investigate the variability in postural sway patterns during quiet standing in stroke survivors. The postural sway was measured in 19 stroke survivors, as well as 19 healthy demographically matched participants, at 3 levels of postural difficulty (rigid surface with closed and open eyes, and foam surface with closed eyes), and 3 levels of cognitive difficulty (without a cognitive task, easy and difficult cognitive tasks). Both linear analyses (the amount of postural sway variability, including the standard deviation of the COP velocity in both the anteroposterior (AP) and mediolateral (ML) directions), as well as non-linear analyses [the temporal structure of the COP...
Apathy exacerbates postural control impairments in stroke survivors: The potential effects of cognitive dual-task for improving postural control
, Article Neuropsychologia ; Volume 174 , 2022 ; 00283932 (ISSN) ; Mehdizadeh, H ; Azad, A ; Cheraghifard, M ; Jamali, S ; Davoudi, M ; Shokouhyan, S. M ; Taghizadeh, G ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Apathy is a stressor and debilitating common condition for both stroke survivors and their caregivers. However, its effects on the postural control of these patients have not yet been investigated. Improved postural stability through withdrawing attention from postural control by concurrent cognitive task (i.e. dual-task condition) has been reported previously, but the effect of apathy, as a confounding factor, remains unknown. This study aimed to examine the effects of apathy and dual-task condition on postural control of chronic stroke survivors from biomechanical and neurophysiological perspectives. Twenty non-apathetic stroke survivors, 20 apathetic stroke survivors, and 20 sex-, age-,...
Interference Avoidance Algorithms in Cognitive Radio Networks and Performance Analysis
, M.Sc. Thesis Sharif University of Technology ; Nasiri Kenari, Masoumeh (Supervisor)
Abstract
Cognitive radio faces specific challenges due to its special spectrum access scheme. Providing required QoS and preventing irrecoverable interference on the primary users is among the crucial requirements. Beam forming is one of the interference avoidance schemes utilized in MIMO networks. Most of the studies on this scheme assume that each symbol is transmitted via vectors in order to grant desired beam forming and specific combinations in the receiver. Since transmitting multiple symbols at every transmission can provide higher data rates, it seems necessary to exploit beam forming through matrixes instead of vectors. In this thesis, by neglecting the interference of the secondary user,...
Rendezvous Algorithms for Cognitive Radio Networks
, M.Sc. Thesis Sharif University of Technology ; Pakravan, Mohammadreza (Supervisor)
Abstract
In the present thesis we will design and study some rendezvous algorithms for cognitive radio networks. In cognitive radio networks, secondary users try to access the spectrum of primary users in an opportunistic manner. Each secondary user constructs a channel list of accessible resources by channel sensing. These resources are not necessarily the same for different users; therefore, in order to make a connection in absence of a fixed control channel, different secondary users should find each other properly and quickly after entering the network. This is known as the blind rendezvous problem. We will develop and examine a new sequence based algorithm for blind rendezvous. Moreover, some...
Designing an Efficient Algorithm for Group Recommender Systems based
on Group Profile
,
M.Sc. Thesis
Sharif University of Technology
;
Movaghar Rahimabadi, Ali
(Supervisor)
Abstract
Recommender Systems have become an attractive field within the recent decade since they facilitate users’ selection process in limited time. Conventional recommender systems have proposed numerous methods with a focus on recommending to individual users. Recently, due to a significant increase in the number of users, studies in this field have shifted to properly identify groups of people with similar preferences and provide a list of recommendations for each group. Because, offering a recommendations list to each individual undergoes computational cost and sometimes is not possible. So far, most of the previous studies requires the restrictive assumptions such as: (1) limited number of...
Investigating Ethical Consequences of the Information and Communication Technologies (ICT) with Respect to Luciano Floridi’s Philosophy and Ethics of Information
, M.Sc. Thesis Sharif University of Technology ; Taghvai, Mostafa (Supervisor)
Abstract
The main purpose of this dissertation is to give an ethical evaluation of one of the consequences of ICT. Since these technologies are present in every corner of our personal and social life, recognizing their ethical and social consequences are of vital importance. The present dissertation, which is set up in 3 chapters, is allocated for evaluating one of these consequences. In the first chapter which is the first step of our overall argument indeed, one of recent theories in Cognitive Psychology and memory studies, namely Working Memory will be introduced. In the second chapter, introducing another theory in Cognitive Psychology namely Cognitive Load Theory, the role of Working Memory in...
Energy-Aware Routings in Cognitive Wireless Sensor Network
, M.Sc. Thesis Sharif University of Technology ; Hemmatyar, Ali Mohammad Afshin (Supervisor)
Abstract
Wireless Sensor Networks (WSNs) has been a research topic for more than a decade, and the range of potential applications has spanned beyond the military domain into commercial domains. A key feature of current WSN solutions is operation in unlicensed frequency bands, for instance, the worldwide available 2.4 GHz band. However, the same band is shared by other wireless applications, such as Wi-Fi and Bluetooth, as well as other proprietary technologies. There is evidence that unlicensed spectrum is becoming overcrowded, to solve this problem, concept of cognitive radio has been introduced.
A main challenge for routing in cognitive radio wireless sensor networks is the collaboration...
A main challenge for routing in cognitive radio wireless sensor networks is the collaboration...
Using Game Theory to Battle Jammer in Control Channel of Ad-hoc Cognitive Radio Networks
, M.Sc. Thesis Sharif University of Technology ; Salehi, Javad (Supervisor)
Abstract
Due to both dynamic and opportunistic spectrum access, Cognitive radio networks is a promising solution for spectrum scarcity problem. In cognitive radio networks, users need to have a control channels in order to cooperate for sharing the sensing information, channel sharing and etc. In Ad-hoc cognitive radio networks because of the absence of infrastructure and central nodes, every user runs a distributed algorithm to create a common control channel. If the control channel gets jammed, network’s performance degrades dramatically, therefore the jammer’s target in cognitive radio networks is the control channels to disturb the networks’ performance. The traditional solution to confront...
Examining the Relationship Between Post-choice Attitude Change and Framing Effects
, M.Sc. Thesis Sharif University of Technology ; Fatemi, Farshad (Supervisor) ; Bahrami, Bahador (Supervisor)
Abstract
In economics, choice or behavior is considered as a result of utility optimization. However, there’s much theoretical and experimental evidence that shows human beings suffer from decision-making and judgment errors. This research aiming at examining the relationship between post-choice attitude changes and framing effects as the two instances of those errors designed and implemented a 2 by 2 between-subject lab experiment. The subjects were randomly assigned to one of these four groups. The two treatment groups made their decision after they rated the objects one time and the two control groups did this after they evaluated the objects two times. Another intervention was to manipulate...
Explaining the Concept of Civilization by using Theory of Constructive Perceptions with Emphasis on Knowledge and Technology as Components of Civilization
, M.Sc. Thesis Sharif University of Technology ; Taghavi, Mostafa (Supervisor)
Abstract
The purpose of writing this thesis is to arrive at the concept of civilization. And in this process, using the constructive perception. My approach in constructive perception is different with approach of Allameh tabatabaei in constructive perception. In first chapter defining constructive perception as the perception that mind by analogy between two consepts makes the non-real relations and attributes it deliberated to the reality (the parties). Meanwhile, should have been constructive perception is the intermediary that stimulation our sense abut reality. These feelings can be tenderness or hatred or fear and hope and ... . In the second chapter we will show that the use of technology...
Identification of Influence Mechanisms of Executive/non-executive Board Composition on Board’s Attribution Style
, M.Sc. Thesis Sharif University of Technology ; Alavi, Babak (Supervisor)
Abstract
The influence mechanisms of executive/non-executive board compostion on board’s attribution style have been explored. In two case studies, I have examined boards’ causal interpretation about a critical incident which had a significant impact on firm performance. A qualitative research approach has been taken in the case studies. Data was gathered through semi-structured interviews with all board members and was analyzied with the theme analysis method. According to the results, board of directors’ collective attribution formation process can be devided into three stages of members’ expression of information and facts at board meetings, forming the individual judgements of members and at...
Effective Implementation of Wide-band Spectrum Sensing
, M.Sc. Thesis Sharif University of Technology ; Shabany, Mahdi (Supervisor) ; Fakharzadeh, Mohammad (Supervisor)
Abstract
Ever increasing demand for higher data rate in wireless communication in the face of limited or underutilized spectral resources has motivated the introduction of cognitive radio for dynamic access to spectrum. In dynamic spectrum access a new type of users called secondary users measure the spectrum to see if it is occupied by licensed users (primary users or PU). When channel is empty secondary users can use it to transmit signal. This approach is called spectrum sensing. Hidden PU problem can severely defect detection ability of non-cooperativ spectrum sensing systems. Cooperative spectrum sensing (CSS) uses spatial diversity of spectrum sensors to tackle this problem. There are two kinds...
, M.Sc. Thesis Sharif University of Technology ; AliReza (Supervisor)
Abstract
After positivists, that argue the structure and growth of scientific knowledge is rational, and constructivists, that argue science is based on irrational basis, analysis of structure and growth of scientific knowledge, in few decades ago, has developed from cognitive perspective. In this approach, i.e cognitive phase of philosophy of science, the role of concepts, that organized around hierarchies, become important. In current dissertation, we have considered views of paul Thagard, the cognitive scientist, about conceptual systems, and structure of science from cognitive approach. Thagard, postulating the truth of scientific developments, describes mental representations and processes in...
Spectrum Sensing Based on Cyclostationary Detector with the Use of Transmission Period in Cognitive Radio Networks
, M.Sc. Thesis Sharif University of Technology ; Salehi, Javad (Supervisor)
Abstract
The different methods of spectrum sensing to identify the presence of signal transmission are as follows: Energy detectors, Cyclostationary detectors and Matched-filter detectors. Energy detectors are simple and easy to implement but they are unable to differentiate interference from primary users and noise. They also have a very poor performance in low SNR. Matched-filtering is the optimum method for detection of primary users and can achieve a certain detection performance in a short time but its implementation complexity is too high and requires perfect knowledge of primary user’s signaling features that makes its usage in cognitive radios infeasible. Among these detectors Cyclostationary...
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...