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Efficient full-rate LDCs in correlated Rician fading channel with decoupled decoder
, Article 2012 6th International Symposium on Telecommunications, IST 2012, 6 November 2012 through 8 November 2012 ; November , 2012 , Pages 393-398 ; 9781467320733 (ISBN) ; Azmi, P ; Pilaram, H ; Sharif University of Technology
2012
Abstract
Space-time block codes (STBCs) with orthogonal structures provide full-diversity reception and simple decoupled detection at the receiver. Rate-one orthogonal STBCs (OSTBC) for complex constellations have been found only for two transmit antennas. On the other hand, STBCs' designs are classically based on the assumption of independent and identically distributed (i.i.d.) fading channels. However, poor scattering conditions may have harmful effects on the performance of STBCs. In this paper, we first derive the average of received signal power at the receiver over Rician fading channel, when the signals are coded with linear dispersion code (LDC). Then by using a genetic algorithm (GA), we...
Distributed synchronization and beamforming in uplink relay asynchronous OFDMA CoMP networks
, Article IEEE Transactions on Wireless Communications ; Volume 14, Issue 6 , 2015 , Pages 3471-3480 ; 15361276 (ISSN) ; Kiamari, M ; Khalaj, B. H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
In this paper, we use delay-amplify-and-forward relays in the uplink direction of a coordinated multi-point network based on orthogonal frequency division multiplexing. The key novelty is that we assume delay from users to different base stations (BSs), in general, may exceed cyclic prefix (CP) length as might be the case in large cells and cannot be completely compensated by traditional timing advance strategies. Consequently, interchannel interference and intersymbol interference may arise under such assumptions. We first optimize the adjustable delays added at users, relays and BS nodes in order to reduce the effective delay spread at the receive sites, then we optimize relays' weights...
A lattice-based changeable threshold multi-secret sharing scheme and its application to threshold cryptography
, Article Scientia Iranica ; Volume 24, Issue 3 , 2017 , Pages 1448-1457 ; 10263098 (ISSN) ; Eghlidos, T ; Sharif University of Technology
Sharif University of Technology
2017
Abstract
In this paper, we propose a threshold increasing algorithm for a (t; n) latticebased Threshold Multi-Stage Secret Sharing (TMSSS) scheme. To realize the changeability feature, we use the zero addition protocol to construct a new (t0; n) TMSSS scheme. Therefore, the new scheme enjoys the significant feature of threshold changeability along with the inherited features of being multi-stage, multi-use, and verifiable derived from our previously proposed lattice-based TMSSS scheme. Furthermore, we use the improved TMSSS scheme to propose a threshold decryption algorithm for the Learning With Error (LWE) based public key encryption scheme based on the study of Lindner and Peikert. For threshold...
An efficient lattice based multi-stage secret sharing scheme
, Article IEEE Transactions on Dependable and Secure Computing ; Volume 14, Issue 1 , 2017 , Pages 2-8 ; 15455971 (ISSN) ; Eghlidos, T ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
In this paper, we construct a lattice based (t, n) threshold multi-stage secret sharing (MSSS) scheme according to Ajtai's construction for one-way functions. In an MSSS scheme, the authorized subsets of participants can recover a subset of secrets at each stage while other secrets remain undisclosed. In this paper, each secret is a vector from a t-dimensional lattice and the basis of each lattice is kept private. A t-subset of n participants can recover the secret(s) using their assigned shares. Using a lattice based one-way function, even after some secrets are revealed, the computational security of the unrecovered secrets is provided against quantum computers. The scheme is multi-use in...
A Lattice based Threshold Multi-Secret Sharing Scheme and its Application to Threshold Cryptography
, Ph.D. Dissertation Sharif University of Technology ; Eghlidos, Taraneh (Supervisor)
Abstract
Secret sharing schemes are used for storage and management of sensitive data such as cryptographic keys and bank account numbers. These schemes provide both confidentiality and reliability. Advances in quantum computers have threatened the security of currently used public-key cryptographic algorithms. In this thesis, for designing quantum resistant cryptographic schemes, we construct a lattice based threshold multi-stage secret sharing (TMSSS) scheme. Using a lattice based one-way function, even after some secrets are revealed, the computational security of the unrecovered secrets is provided against quantum computers. The scheme is multi-use and verifiable meaning that the participants can...
An efficient lattice-based threshold signature scheme using multi-stage secret sharing
, Article IET Information Security ; Volume 15, Issue 1 , 2021 , Pages 98-106 ; 17518709 (ISSN) ; Eghlidos, T ; Toluee, R ; Sharif University of Technology
John Wiley and Sons Inc
2021
Abstract
Secret sharing is a cryptographic technique used in many different applications such as cloud computing, multi-party computation and electronic voting. Security concerns in these applications are data privacy, availability, integrity and verifiability, where secret sharing provides proper solutions. The authors address some important features like verifiability and being multi-stage to make it usable in various field of application. Here, the authors propose an anonymous threshold signature scheme based on the trapdoor function introduced by Micciancio and Peikert by sharing the private key using a lattice-based threshold multi-stage secret sharing (TMSSS) scheme. Then, the authors improve...
Distributed Transmission in Relay Coordinated Multi-point (COMP) Networks
, M.Sc. Thesis Sharif University of Technology ; Hossein Khalaj, Babak (Supervisor) ; Behroozi, Hamid (Supervisor)
Abstract
Time offset (TO) at an orthogonal frequency division multiplexing (OFDM) system destroys orthogonality of subcarriers and causes interchannel interference (ICI) and inter symbol interference (ISI). This problem is more challenging in multi-user multi-input multi-output (MU-MIMO) OFDM systems such as coordinated multi-point (CoMP) uplink transmission where joint processing is performed at base stations (BSs) and different delays form users to BSs cannot be compensated by timing strategies. In this thesis, we use delay-amplify and forward relays and post processing at receivers to decrease signal to interference plus noise ratio (SINR) degradation due to large TOs at insufficient cyclic prefix...
Nonlinear interstory drift contours for idealized forward directivity pulses using "modified fish-bone" models
, Article Advances in Structural Engineering ; Volume 18, Issue 5 , May , 2015 , Pages 603-627 ; 13694332 (ISSN) ; Khosravi, H ; Jamnani, H. H ; Sharif University of Technology
Multi-Science Publishing Co. Ltd
2015
Abstract
Four 5-, 10-, 20- and 30-story moment frames, representing low-, mid-, and two high-rise structures, were subjected to a great number of idealized directivity pulses. The amplitudes and periods of pulses vary from 0.02 g to 1.0 g and 0.5 to 12 sec, respectively. Over 1400 nonlinear dynamic analyses of low- to high-rise moment frames were performed which were feasible through using modified fish-bone model. The distribution of interstory drift along the height was studied and two applied contours were proposed: (i) the maximum interstory drift contour, and (ii) the critical story contour. These contours were demonstrated versus the ratio of natural period of the structure to the pulse period...
Analysis of singularities of a 3DOF parallel manipulator based on a novel geometrical method
, Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) ; Sadeghian, H ; Roozbehani, H ; Zohoor, H ; Sharif University of Technology
2006
Abstract
In this article singular points of a parallel manipulator are obtained based on a novel geometrical method. Here we introduce the constrained plain method (CPM) and some of its application in parallel mechanism. Given the definition of constraint plane (CP) and infinite constraint plane (ICP) the dependency conditions of constraints is achieved with the use of a new theorem based on the Ceva geometrical theorem. The direction of angular velocity of a body is achieved by having three ICPs with the use of another theorem. Finally, with the use of the above two novel theorems singularities of the 3UPF_PU mechanism are obtained. It should be emphasized that this method is completely geometrical,...
Melting enthalpy and entropy of freestanding metallic nanoparticles based on cohesive energy and average coordination number
, Article Journal of Physical Chemistry C ; Volume 115, Issue 35 , August , 2011 , Pages 17310-17313 ; 19327447 (ISSN) ; Delavari H., H ; Madaah Hosseini, H. R ; Sharif University of Technology
2011
Abstract
An analytical model is proposed to study the effect of particle size on melting enthalpy and entropy of metallic nanoparticles (NPs). The Mott's and Regel's equations for melting entropy in the combination of core average coordination number (CAC) and surface average coordination number (SAC) of freestanding NPs are considered. Clusters of icosahedral (IC), body centered cubic (BCC), and body centered tetragonal (BCT) structure without any vacancies and defects are modeled. Using the variable coordination number made this model to be in good agreement with experimental and molecular dynamic (MD) results of different crystal structures. The model predicts melting entropy and enthalpy of...
On the temperature and residual stress field during grinding
, Article WCE 2010 - World Congress on Engineering 2010, 30 June 2010 through 2 July 2010 ; Volume 2 , 2010 , Pages 1196-1200 ; 9789881821072 (ISBN) ; Farrahi, G. H ; Ghadbeigi, H ; Sharif University of Technology
2010
Abstract
Grinding is widely used for manufacturing of components that require fine surface finish and good dimensional accuracy. In this study a thermo-mechanical finite element analysis is conducted to find out how grinding parameters can affect temperature and residual stress distribution in the workpiece. Results of parametric study presented in this work indicate, by carefully selecting the grinding parameters, minimum thermal and mechanical damage can be achieved. Higher workpiece velocities produce higher surface residual stress. By increasing depths of cut, depth of tensile residual stresses increases. Convection heat coefficient does not have any considerable effect on surface residual stress...
A new lattic LP-based post filter for adaptive noise cancellers in mobile and vehicular applications
, Article Proceedings of the 8th IEEE International Symposium on Signal Processing and Information Technology, ISSPIT 2008, 16 December 2008 through 19 December 2008, Sarajevo ; 2008 , Pages 407-412 ; 9781424435555 (ISBN) ; Sameti, H ; Veisi, H ; Abutalebi, H. R ; Sharif University of Technology
2008
Abstract
Adaptive Noise Cancellation (ANC) is a well-known technique for background noise reduction in automobile and vehicular environments. The noise fields in automobile and other vehicle interior obey the diffuse noise field model closely. On the other hand, the ANC does not provide sufficient noise reduction in the diffuse noise fields. In this paper, a new multistage post-filter is designed for ANC as a solution to diffuse noise conditions. The designed post-filter is a single channel Linear Prediction (LP) based speech enhancement system. The LP is performed by an adaptive lattice filter and attempts to extract speech components by using intermediate ANC signals. The post-filter has no...
Finite element analysis of shot-peening effect on fretting fatigue parameters
, Article Tribology International ; Volume 44, Issue 11 , 2011 , Pages 1583-1588 ; 0301679X (ISSN) ; Alvandi Tabrizi, Y ; Farrahi, G. H ; Majzoobi, G. H ; Ghadbeigi, H ; Sharif University of Technology
2011
Abstract
Shot peening is widely used to improve the fretting fatigue strength of critical surfaces. Fretting fatigue occurs in contacting parts that are subjected to fluctuating loads and sliding movements at the same time. This paper presents a sequential finite element simulation to investigate the shot peening effects on normal stress, shear stress, bulk stress and slip amplitude, which are considered to be the controlling parameters of fretting damage. The results demonstrated that among the modifications related to shot peening, compressive residual stress has a dominant effect on the fretting parameters
Boundary control design for vibration suppression and attitude control of flexible satellites with multi-section appendages
, Article Acta Astronautica ; Volume 173 , 2020 , Pages 22-30 ; Salarieh, H ; Nejat Pishkenari, H ; Jalili, H ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Attitude and vibration control of a general form of flexible satellites is addressed in this paper. Partial differential dynamic equations are derived considering new details such as multi sectioned solar panels and elastic connections between main hub and solar panels. Boundary control approach is adopted to eliminate simplification errors of discrete models, using just one actuator in the hub. Asymptotic stability of attitude dynamics is proved for a group of boundary controllers and necessary conditions for asymptotic stability of vibrations are discussed. Being independent of modeling accuracy and using easily measurable feedbacks are among advantages of the proposed class of...
Characterization and calcination behavior of a low-grade manganese ore
, Article Materials Today Communications ; Volume 25 , 2020 ; Becker, H ; Eftekhari, H ; Yoozbashizadeh, H ; Safarian, J ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Characterization and calcination behavior of a low-grade manganese ore, as a part of Mn ferroalloys production, was studied by XRF, ex-situ XRD, in-situ XRD, and SEM-EDS techniques. Calcination experiments were carried out at and up to 900 °C (1173 K) in air and argon atmospheres. The samples were in particles and powder forms. The results indicated that both quartz and calcite phases in the ore exhibit a bimodal spatial distribution; as relatively large regions and finely distributed in the Mn- and Fe-containing phases. By Rietveld analysis of the in-situ XRD data, the reactions occurring upon heating during the calcination process were deduced. Thermal decomposition and reactive diffusion...
Mechanically activated synthesis of single crystalline MgO nanostructures
, Article Journal of Alloys and Compounds ; Volume 506, Issue 2 , September , 2010 , Pages 715-720 ; 09258388 (ISSN) ; Yoozbashizadeh, H ; Askari, M ; Kobatake, H ; Fukuyama, H ; Sharif University of Technology
2010
Abstract
One-dimensional (1D) MgO structures were successfully synthesized via carbothermic reduction of mechanically activated mixture of MgO and graphite. Mechanical activation of source materials before carbothermic reduction can substantially enhance the formation of MgO products at a temperature (1000 °C) relatively lower than that required in previous approaches (≥1200 °C). However, the morphology of MgO formed is dependent on the degree of mechanical activation and the condition of the subsequent carbothermic reduction. Two distinctive morphologies were found for MgO products synthesized using our method: single crystalline nanorods with rectangular cross-sections whose diameters range from 50...
Minimizing the error of time difference of arrival method in mobile networks
, Article 2005 International Conference on Wirelessand Optical Communications Networks, Dubai, 6 March 2005 through 8 March 2005 ; 2005 , Pages 328-332 ; 0780390199 (ISBN); 9780780390195 (ISBN) ; Aghababa, H ; Radfar, M. H ; Khalaj, B. H ; Sharif University of Technology
2005
Abstract
Estimating the position of a mobile set is of great importance in new mobile services. However, in most cases, the accuracy should be less than 100 meters. This accuracy is hard to reach especially in urban areas. The main problem is that there are a lot of obstacles like buildings between the BTS and the mobile set. Thus the time measured between BTS and the mobile set is somehow greater than the time it takes the wave to travel directly between two points. This paper introduces an optimized solution for TDOA as one of the most efficient ways for finding the location of a mobile phone. Considering the standards and limitations of both GSM and UMTS, the Authors present a solution for...
A fast and novel method of pattern synthesis for non-uniform phased array antennas
, Article Proceedings International Radar Symposium, 24 June 2015 through 26 June 2015 ; Volume 2015-August , 2015 , Pages 924-929 ; 21555753 (ISSN) ; 9783954048533 (ISBN); 9783954048533 (ISBN); 9783954048533 (ISBN) ; Sebt, M. A ; Nayebi, M. M ; Behroozi, H ; Rohling, H ; Rohling, H ; Rohling, H ; Sharif University of Technology
IEEE Computer Society
2015
Abstract
Weighting elements to achieve radiation patterns with desired characteristics is a classical work in phased array antennas. These characteristics can be low sidelobe level, narrow beamwidth, high directivity, pattern nulling in special angle and etc. For each of these characteristics, different methods have been introduced. Most of methods have been presented for uniform arrays, however there are lots of methods to obtain a desired pattern for antennas with non-uniform element distances. The problem with these methods is complexity or not very good results. In this paper, fast and easy methods based on Least Square Error that leads to good results are presented. In addition, weighting of...
Size-dependent interaction of an edge dislocation with an elliptical nano-inhomogeneity incorporating interface effects
, Article International Journal of Solids and Structures ; Volume 49, Issue 5 , March , 2012 , Pages 759-770 ; 00207683 (ISSN) ; Ahmadzadeh Bakhshayesh, H ; Gutkin, M. Y
2012
Abstract
The elastic behavior of an edge dislocation, which is positioned outside of a nanoscale elliptical inhomogeneity, is studied within the interface elasticity approach incorporating the elastic moduli and surface tension of the interface. The complex potential function method is used. The dislocation stress field and the image force acting on the dislocation are found and analyzed in detail. The difference between the solutions obtained within the classical-elasticity and interface-elasticity approaches is discussed. It is shown that for the stress field, this difference can be significant in those points of the inhomogeneity-matrix interface, where the radius of curvature is smaller and which...
Identification of an aspidospermine derivative from borage extract as an anti-amyloid compound: A possible link between protein aggregation and antimalarial drugs
, Article Phytochemistry ; Volume 140 , 2017 , Pages 134-140 ; 00319422 (ISSN) ; Ashrafian, H ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
A number of human diseases, including Alzheimer's and Parkinson's have been linked to amyloid formation. To search for an anti-amyloidogenic product, alkaloid enriched extract from borage leaves was examined for anti-amyloidogenic activity using Hen Egg White Lysozyme (HEWL) as a model protein. After isolation of the plant extract using rHPLC, only one fraction indicated a significant bioactivity. TEM analysis confirmed a remarkable reduction of amyloid fibrils in the presence of the bioactive fraction. To identify the effective substance in the fraction, mass spectrometry, FTIR, and NMR were performed. Our analyses determined that the bioactive compound as...