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    Spectral controllability of some singular hyperbolic equations on networks

    , Article Journal of Dynamical and Control Systems ; 2016 , Pages 1-22 ; 10792724 (ISSN) Fotouhi, M ; Salimi, L ; Sharif University of Technology
    Springer New York LLC  2016
    Abstract
    The purpose of this paper is to address the question of well-posedness and spectral controllability of the wave equation perturbed by potential on networks which may contain unbounded potentials in the external edges. It has been shown before that in the absence of any potential, there exists an optimal time T∗ (which turns out to be simply twice the sum of all length of the strings of the network) that describes the spectral controllability of the system. We will show that this holds in our case too, i.e., the potentials have no effect on the value of the optimal time T∗. The proof is based on the famous Beurling-Malliavin’s Theorem on the completeness interval of real exponentials and on a... 

    Spectral controllability of some singular hyperbolic equations on networks

    , Article Journal of Dynamical and Control Systems ; Volume 23, Issue 3 , 2017 , Pages 459-480 ; 10792724 (ISSN) Fotouhi, M ; Salimi, L ; Sharif University of Technology
    Abstract
    The purpose of this paper is to address the question of well-posedness and spectral controllability of the wave equation perturbed by potential on networks which may contain unbounded potentials in the external edges. It has been shown before that in the absence of any potential, there exists an optimal time T∗ (which turns out to be simply twice the sum of all length of the strings of the network) that describes the spectral controllability of the system. We will show that this holds in our case too, i.e., the potentials have no effect on the value of the optimal time T∗. The proof is based on the famous Beurling-Malliavin’s Theorem on the completeness interval of real exponentials and on a... 

    Externalities and fairness

    , Article 2019 World Wide Web Conference, WWW 2019, 13 May 2019 through 17 May 2019 ; 2019 , Pages 538-548 ; 9781450366748 (ISBN) Seddighin, M ; Saleh, H ; Ghodsi, M ; Amazon; Bloomberg; Criteo AI Lab; et al.; Google; Microsoft ; Sharif University of Technology
    Association for Computing Machinery, Inc  2019
    Abstract
    One of the important yet insufficiently studied subjects in fair allocation is the externality effect among agents. For a resource allocation problem, externalities imply that the share allocated to an agent may affect the utilities of other agents. In this paper, we conduct a study of fair allocation of indivisible goods when the externalities are not negligible. Inspired by the models in the context of network diffusion, we present a simple and natural model, namely network externalities, to capture the externalities. To evaluate fairness in the network externalities model, we generalize the idea behind the notion of maximin-share (MMS) to achieve a new criterion, namely,... 

    A low-power complex active-RC filter for low-IF receivers using a new class-AB operational amplifier

    , Article 2007 International Symposium on Integrated Circuits, ISIC, Singapore, 26 September 2007 through 28 September 2007 ; 2007 , Pages 309-312 ; 1424407974 (ISBN); 9781424407972 (ISBN) Abrishamifar, A ; Zanbaghi, R ; Mehrmanesh, S ; Lahiji, G. R ; Sharif University of Technology
    2007
    Abstract
    The design of a complex active-RC filter for low-IF Wireless applications is described. Fifth-order complex Butterworth filter is designed using Class-AB operational amplifier architecture. This new structure makes the filter suitable for low power applications with high dynamic range. Simulation results show that the filter provides more than 40 dB image rejection ratio (IIR) and dynamic range of 82dB. The complete filter including on-chip tuning circuit consumes only 4.3mW with 1.8V single supply voltage. © 2007 IEEE  

    Design for scalability in enterprise SSDs

    , Article Parallel Architectures and Compilation Techniques - Conference Proceedings, PACT ; 24-27 August , 2014 , p. 417-429 ; ISSN: 1089795X ; ISBN: 9781450328098 Tavakkol, A ; Arjomand, M ; Sarbazi-Azad, H ; Sharif University of Technology
    Abstract
    Solid State Drives (SSDs) have recently emerged as a high speed random access alternative to classical magnetic disks. To date, SSD designs have been largely based on multi-channel bus architecture that confronts serious scalability problems in high-end enterprise SSDs with dozens of flash memory chips and a gigabyte host interface. This forces the community to rapidly change the bus-based inter-flash standards to respond to ever increasing application demands. In this paper, we first give a deep look at how different flash parameters and SSD internal designs affect the actual performance and scalability of the conventional architecture. Our experiments show that SSD performance improvement... 

    Pancyclicity of OTIS (swapped) networks based on properties of the factor graph

    , Article Information Processing Letters ; Vol. 111, Issue 23-24 , 15 December , 2011 , pp. 1114-1119 ; ISSN: 200190 Malekimajd, M ; Hoseiny-Farahabady, M. R ; Movaghar, A ; Sarbazi-Azad, H ; Sharif University of Technology
    Abstract
    The plausibility of embedding cycles of different lengths in the graphs of a network (known as the pancyclicity property) has important applications in interconnection networks, parallel processing systems, and the implementation of a number of either computational or graph problems such as those used for finding storage schemes of logical data structures, layout of circuits in VLSI, etc. In this paper, we present the sufficient condition of the pancyclicity property of OTIS networks. The OTIS network (also referred to as two-level swapped network) is composed of n clones of an n-node original network constituting its clusters. It has received much attention due to its many favorable... 

    A novel hardware implementation for joint heart rate, respiration rate, and gait analysis applied to body area networks

    , Article Proceedings - IEEE International Symposium on Circuits and Systems ; 2013 , Pages 1889-1892 ; 02714310 (ISSN) ; 9781467357609 (ISBN) Khazraee, M ; Zamani, A. R ; Hallajian, M ; Ehsani, S. P ; Moghaddam, H. A ; Parsafar, A ; Shabany, M ; Sharif University of Technology
    2013
    Abstract
    Continuous and remote monitoring of vital health-related and physical activity signs of a patient is one of the most important technology-oriented applications to monitor the health-care of ill individuals. In this paper, an innovative framework for a wireless Body Area Network (BAN) system, based on the IEEE 802.15.6 standard, with three types of sensors is proposed and implemented. These include Electrocardiogram (ECG), Force Sensitive Resistor (FSR) and Gyroscope. The proposed design is a novel implementation of an embedded system for the real-time processing and analyzing of the ECG signal, gait phases, and detection of the respiration rate from the ECG signal, by means of small... 

    Upper bounds for the 2-hued chromatic number of graphs in terms of the independence number

    , Article Discrete Applied Mathematics ; Volume 160, Issue 15 , 2012 , Pages 2142-2146 ; 0166218X (ISSN) Dehghan, A ; Ahadi, A ; Sharif University of Technology
    Elsevier  2012
    Abstract
    A 2-hued coloring of a graph G is a coloring such that, for every vertex v∈V(G) of degree at least 2, the neighbors of v receive at least two colors. The smallest integer k such that G has a 2-hued coloring with k colors is called the 2-hued chromatic number of G, and is denoted by χ2(G). In this paper, we will show that, if G is a regular graph, then χ2(G)-χ(G)≤2log 2(α(G))+3, and, if G is a graph and δ(G)<2, then χ2(G)-χ(G)≤1+4 Δ2δ-1⌉(1+log 2Δ(G)2Δ(G)-δ(G)(α(G))), and in the general case, if G is a graph, then χ2(G)-χ(G)≤2+min α′(G),α(G)+ω(G)2  

    Pancyclicity of OTIS (swapped) networks based on properties of the factor graph

    , Article Information Processing Letters ; Volume 111, Issue 23-24 , 2011 , Pages 1114-1119 ; 00200190 (ISSN) Malekimajd, M ; Hoseiny Farahabady, M. R ; Movaghar, A ; Sarbazi Azad, H ; Sharif University of Technology
    2011
    Abstract
    The plausibility of embedding cycles of different lengths in the graphs of a network (known as the pancyclicity property) has important applications in interconnection networks, parallel processing systems, and the implementation of a number of either computational or graph problems such as those used for finding storage schemes of logical data structures, layout of circuits in VLSI, etc. In this paper, we present the sufficient condition of the pancyclicity property of OTIS networks. The OTIS network (also referred to as two-level swapped network) is composed of n clones of an n-node original network constituting its clusters. It has received much attention due to its many favorable... 

    Preventing black hole attack in AODV through use of hash chain

    , Article 2011 19th Iranian Conference on Electrical Engineering, ICEE 2011, 17 May 2011 through 19 May 2011 ; May , 2011 , Page(s): 1 ; 9789644634284 (ISBN) Shoja, M. K ; Taheri, H ; Vakilinia, S ; Sharif University of Technology
    2011
    Abstract
    Wireless ad hoc networks are vulnerable against many types of attacks including black hole. In this paper we investigate the effect of this attack on ad hoc networks. Furthermore, we use hash chain to prevent this type of attack in a network that uses AODV as a routing protocol and results of applying this method has been investigated. Simulation results using OPNET simulator indicates that packet delivery ratio, in the presence of malicious nodes, reduces remarkably and proposed approach can prevent the effect of black hole attacks  

    An energy-aware methodology for mapping and scheduling of concurrent applications in MPSoC architectures

    , Article 2011 19th Iranian Conference on Electrical Engineering, ICEE 2011, 17 May 2011 through 19 May 2011 ; May , 2011 , Page(s): 1 ; ISSN : 21647054 ; 9789644634284 (ISBN) Rajaei, R ; Hessabi, S ; Vahdat, B. V ; Sharif University of Technology
    2011
    Abstract
    Mapping and Scheduling are two central and critical steps in design flow of the Networks on Chips (NoCs). They deal with implementation of the applications on NoCs. In this paper a novel energy aware algorithm, called EAMS, for mapping and scheduling of concurrent applications to NoC platforms is developed. It is considered that, the NoC architecture consists of a set of heterogeneous IP cores. The introduced algorithm finds a mapping of the tasks of the application to available IP cores so that the overall energy consumption, meeting task deadlines, is minimized  

    Business process-based modeling of enterprise communication network

    , Article 2014 International Congress on Technology, Communication and Knowledge, ICTCK 2014, 26 November 2014 through 27 November 2014 ; 2015 ; 9781479980215 (ISBN) Hosseinioun, M. H ; Houshmand, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Abstract
    Communications in organizations have been one of the most important issues. To run the business processes, the company needs communication between units and customers. We provide a framework which can be used by network designers in an organization. The outcome of the framework is value for three QoS parameters: delay, loss and availability. The organizations business processes are used as a basis for the framework We used UML as the tool to model the business processes in the organization. First, the process is modeled with UML activity, sequence and class diagrams. Then, a three-step analysis has been conducted on the models to find the specifications of the business process. The analysis... 

    O-TF and O-FTF, optical fault-tolerant DCNS

    , Article Proceedings - 26th Euromicro International Conference on Parallel, Distributed, and Network-Based Processing, PDP 2018 ; 6 June , 2018 , Pages 639-642 ; 9781538649756 (ISBN) Akbari Rokn Abadi, S ; Koohi, S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    Performance of a data center is a function of three features; bandwidth, latency, and reliability. By adopting optical technology in data center network, bandwidth increment, in addition to reduction of transmission latency and power consumption, is achieved. Unfortunately, fault tolerance of the optical networks has raised less attention so far. So in this paper, we propose a fault-tolerant, scalable, and high-performance optical architecture built upon previously proposed O-TF network, with the goal of redundancy optimization and reducing the minimum number of wavelength channels required for non-blocking functionality of the network. Moreover, reducing network diameter, in O-FTF network... 

    Distributed Primary and secondary power sharing in a droop-controlled lvdc microgrid with merged AC and DC characteristics

    , Article IEEE Transactions on Smart Grid ; Volume 9, Issue 3 , 2018 , Pages 2284-2294 ; 19493053 (ISSN) Peyghami, S ; Mokhtari, H ; Loh, P. C ; Davari, P ; Blaabjerg, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    In an ac microgrid, a common frequency exists for coordinating active power sharing among droop-controlled sources. A common frequency is absent in a dc microgrid, leaving only the dc source voltages for coordinating active power sharing. That causes sharing error and poorer voltage regulation in dc microgrids, which in most cases, are solved by a secondary control layer reinforced by an extensive communication network. To avoid such an infrastructure and its accompanied complications, this paper proposes an alternative droop scheme for low-voltage dc microgrid with both primary power sharing and secondary voltage regulation merged. The main idea is to introduce a non-zero unifying frequency... 

    Exploitation of wavelength, hardware, and path redundancies in fault-tolerant all-optical DCNs

    , Article Optical Fiber Technology ; Volume 51 , 2019 , Pages 77-89 ; 10685200 (ISSN) Akbari Rokn Abadi, S ; Koohi, S ; Sharif University of Technology
    Academic Press Inc  2019
    Abstract
    Data center performance is affected by three main factors; bandwidth, latency, and reliability of intra-data center interconnection network. Bandwidth and latency are definitely improved by adopting optical technology for intra-data center communication, but fault tolerance of the corresponding optical networks has been raised less. Recently, we introduced two Torus-based, all-optical, and non-blocking networks, i.e. O-TF and O-FTF, addressing reliability of optical networks, and now, in this paper, to address the scalability problem, we propose a novel Optical Clos-based architecture which reduces minimum number of required wavelength channels, as well as, the switch size in each node.... 

    OMUX: Optical multicast and unicast-capable interconnection network for data centers

    , Article Optical Switching and Networking ; Volume 33 , 2019 , Pages 1-12 ; 15734277 (ISSN) Nezhadi, A ; Koohi, S ; Sharif University of Technology
    Elsevier B.V  2019
    Abstract
    Exponential growth of traffic and bandwidth demands in current data center networks requires low-latency high-throughput interconnection networks, considering power consumption. By considering growth of both multicast and unicast applications, power efficient communication becomes one of the main design challenges in today's data center networks. Addressing these demands, optical networks suggest several benefits as well as circumventing most disadvantages of electrical networks. In this paper, we propose an all-optical scalable architecture, named as OMUX, for communicating intra-data centers. This architecture utilizes passive optical devices and enables optical circuit switching without... 

    Missing low-rank and sparse decomposition based on smoothed nuclear norm

    , Article IEEE Transactions on Circuits and Systems for Video Technology ; Volume 30, Issue 6 , 2020 , Pages 1550-1558 Azghani, M ; Esmaeili, A ; Behdin, K ; Marvasti, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    Abstract
    Recovering low-rank and sparse components from missing observations is an essential problem in various fields. In this paper, we have proposed a method to address the missing low-rank and sparse decomposition problem. We have used the smoothed nuclear norm and the L1 norm to impose the low-rankness and sparsity constraints on the components, respectively. Furthermore, we have suggested a linear modeling for the corrupted observations. The problem has been solved with the aid of alternating minimization. Moreover, some simplifications have been applied to the relations to reduce the computational complexity, which makes the algorithm suitable for large-scale problems. To evaluate the proposed... 

    Derivation of a vector model for a Brushless Doubly-Fed Machine with multiple loops per nest

    , Article 2008 IEEE International Symposium on Industrial Electronics, ISIE 2008, Cambridge, 30 June 2008 through 2 July 2008 ; 2008 , Pages 606-611 ; 1424416655 (ISBN); 9781424416653 (ISBN) Barati, F ; Oraee, H ; Abdi, E ; McMahon, R ; Sharif University of Technology
    2008
    Abstract
    The paper presents a vector model for a Brushless Doubly-Fed Machine (BDFM). The BDFM has 4 and 8 pole stator windings and a nested-loop rotor cage. The rotor cage has six nests equally spaced around the circumference and each nest comprises three loops. All the rotor loops are short circuited via a common end-ring at one end. The vector model is derived based on the electrical equations of the machine and appropriate vector transformations. In contrast to the stator, there is no three phase circuit in the rotor. Therefore, the vector transformations suitable for three phase circuits can not be utilised for the rotor circuit. A new vector transformation is employed for the rotor circuit... 

    A clock boosting scheme for low voltage circuits

    , Article 15th IEEE International Conference on Electronics, Circuits and Systems, ICECS 2008, St. Julian's, 31 August 2008 through 3 September 2008 ; 2008 , Pages 21-24 ; 9781424421824 (ISBN) Behradfar, A ; Zeinolabedinzadeh, S ; HajSadeghi, K ; Sharif University of Technology
    2008
    Abstract
    Limitations in operation of analog switches at very low voltages have caused many problems in design of these types of switched capacitor circuits and data converters. In this paper by modifying a recently proposed clock boosting circuit, we could obtain a new structure with better performance for very low voltage circuits. This method requires simpler digital circuits in comparison with previously reported structures, as well as less number of transistors and smaller chip area. This method can be used for sampling the full swing signals with supply voltages as low as 0.4 volt. © 2008 IEEE  

    Load balancing in UTRAN by bipartite graphs

    , Article 4th European Conference on Circuits and Systems for Communications, ECCSC '08, Bucharest, 10 July 2008 through 11 July 2008 ; 2008 , Pages 301-306 ; 9781424424207 (ISBN) Javan, M. R ; Bouzari, S. M ; Tabandeh, M ; Sharif University of Technology
    2008
    Abstract
    3g wireless communication is the next version of mobile networks. Load balancing in networks causes efficient using of network resources. In this paper, we propose an efficient algorithm for load balancing of Radio Network Controllers (RNCs) in Radio Access Networks (RANs). As the characteristics of connections between RNCs and BTSs in a RAN are similar to those of graphs, we make use of graphs to solve our problem. The algorithm is based on the finding a path by which the RNCs could exchange their overloads. By using these paths the algorithm load balances the RNCs in an efficient and fast way. By testing our algorithm on networks with different topology and comparing the results, the...