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On the throughput and outage probability of multi-relay networks with imperfect power amplifiers
, Article IEEE Transactions on Wireless Communications ; Volume 14, Issue 9 , May , 2015 , Pages 4994-5008 ; 15361276 (ISSN) ; Svensson, T ; Eriksson, T ; Nasiri Kenari, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
This paper studies the energy-limited performance of multi-relay networks. Taking the properties of the power amplifiers (PAs) into account, we derive closed-form expressions for the optimal power allocation, the outage probability and the throughput in the cases with a sum consumed energy constraint. Moreover, we analyze the diversity and the multiplexing gains of the PA-aware systems. Finally, we investigate the performance of large-scale multi-relay networks and develop efficient multi-relay systems with low cooperation overhead. The numerical and the analytical results show that the inefficiency of the PAs affects the outage probability and the throughput of the multi-relay systems...
Annealed and quenched disorder in sand-pile models with local violation of conservation
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 92, Issue 2 , August , 2015 ; 15393755 (ISSN) ; Sebtosheikh, M ; Sharif University of Technology
American Physical Society
2015
Abstract
In this paper we consider the Bak, Tang, and Wiesenfeld (BTW) sand-pile model with local violation of conservation through annealed and quenched disorder. We have observed that the probability distribution functions of avalanches have two distinct exponents, one of which is associated with the usual BTW model and another one which we propose to belong to a new fixed point; that is, a crossover from the original BTW fixed point to a new fixed point is observed. Through field theoretic calculations, we show that such a perturbation is relevant and takes the system to a new fixed point
Universal superposition of orthogonal states
, Article Physical Review A ; Volume 96, Issue 5 , 2017 ; 24699926 (ISSN) ; Kianvash, F ; Karimipour, V
Abstract
It is known that no quantum process can produce a predetermined superposition of unknown arbitrary states. It has already been shown that with some partial information about the states, one can produce with some probability such superpositions. In general the success probability of these machines, even for orthogonal states, are less than unity. Here we show that there are specific machines that can produce superpositions of orthogonal qubit states with unit probability. © 2017 American Physical Society
Observation of cosmic rays by Alborz -1 array
, Article Iranian Journal of Physics Research ; Volume 17, Issue 3 , 2017 , Pages 473-484 ; 16826957 (ISSN) ; Sharif University of Technology
Isfahan University of Technology
2017
Abstract
The first phase of the Alborz Observatory Array (Alborz-1) consists of 20 plastic scintillation detectors each one with surface area of 0.25 m2 spread over an area of 40×40 m2 realized to the study of Extensive Air Showers around the knee at the Sharif University of Technology campus. The first stage of the project including construction and operation of a prototype system has now been completed and the electronics that will be used in the array instrument has been tested under field conditions. In order to achieve a realistic estimate of the array performance, a large number of simulated CORSIKA showers have been used. In the present work, theoretical results obtained in the study of...
Effects of loading modes on reliability of cracked structures using FORM and MCS
, Article International Journal of Precision Engineering and Manufacturing ; Volume 18, Issue 1 , 2017 , Pages 63-76 ; 22347593 (ISSN) ; Nazari, S. A ; Sharif University of Technology
SpringerOpen
2017
Abstract
Studying the reliability of cracked structures under different types of failure modes such as a mixture of Mode I and Mode II loadings has been of great importance in many applications. The purpose of this study is to evaluate the effects of different modes of loading, i.e. pure Mode I, pure Mode II and Mixed mode I/II loadings on the reliability of cracked structures via three typical case studies including 1st: through crack in a very wide plate, 2nd: cracked pressurized fuselage and 3rd: cracked fastener holes under actual geometries and loading conditions using the FORM, the fracture toughness and the equivalent SIF for Mixed mode I/II loading which is extracted by the Energy release...
Outage probability and power allocation of amplify and forward relaying with channel estimation errors
, Article IEEE Transaction on Wireless Communications ; Volume 10, Issue 1, Article number 5618893 , January , 2011 , Pages 124-134 ; Sadeghi, P ; Pakravan, M. R. (Mohammad Reza) ; Sharif University of Technology
Abstract
This paper studies the statistical properties of the signal-to-noise ratio (SNR) of the dual-hop relaying link in a cooperative wireless communication system in the presence of channel estimation errors for fixed-gain (FG) and variable-gain (VG) relays. The SNR expression is derived and three different analytical approaches with different simplifying assumptions are proposed to obtain the probability distribution function of the SNR and the outage probability in each mode. All but one approach result in closed-form expressions for the outage probability. The simplest approach in each mode has been used to find an optimum power allocation scheme for pilot and data symbols transmission at the...
Compressed sensing encryption: compressive sensing meets detection theory
, Article Journal of Communications ; Volume 13, Issue 2 , February , 2018 , Pages 82-87 ; 17962021 (ISSN) ; Ghanizade Bafghi, H ; Seyfe, B ; Sharif University of Technology
Engineering and Technology Publishing
2018
Abstract
Since compressive sensing utilizes a random matrix to map the sparse signal space to a lower dimensional transform domain, it may be possible to apply this matrix at the same time for encrypting the signal opportunistically. In this paper, a compressed sensing based encryption method is considered and the secrecy of measurement matrix of compressive sensing is analysed from the detection theory perspective. Here, the detection probability of intended and unintended receivers are compared by applying the Neyman-Pearson test. We prove that the detection probability of eavesdropper will be reduced significantly because he does not know the transform domain subspace. Furthermore, in some...
Monitoring multinomial logistic profiles in phase I using log-linear models
, Article International Journal of Quality and Reliability Management ; Volume 35, Issue 3 , 2018 , Pages 678-689 ; 0265671X (ISSN) ; Noorossana, R ; Akhavan Niaki, T ; Sharif University of Technology
Emerald Group Publishing Ltd
2018
Abstract
Purpose: The purpose of this paper is to apply Poisson generalized linear model (PGLM) with log link instead of multinomial logistic regression to monitor multinomial logistic profiles in Phase I. Hence, estimating the coefficients becomes easier and more accurate. Design/methodology/approach: Simulation technique is used to assess the performance of the proposed algorithm using four different control charts for monitoring. Findings: The proposed algorithm is faster and more accurate than the previous algorithms. Simulation results also indicate that the likelihood ratio test method is able to detect out-of-control parameters more efficiently. Originality/value: The PGLM with log link has...
Investigating the fluctuations of solar and wind energy
, Article Iranian Journal of Physics Research ; Volume 19, Issue 2 , 2019 , Pages 249-261 ; 16826957 (ISSN) ; Madanchi, A ; Absalan, M. R ; Anvari, M ; Sharif University of Technology
Isfahan University of Technology
2019
Abstract
A time series study of the electrical energy generated by wind turbines and solar cells shows that the energy produced has a lot of fluctuations due to the geographic conditions. These ups and downs have caused not only the share of these sources to be marginal, but also they lead to the volatility of electric power plants. By examining several different data from different countries and regions with the frequency of second and minute, we show that different scale behaviors exist at different time intervals and reveal their other random and nonlinear characteristics. We also compare the non-Gaussian behavior of these regions together, showing that studying the properties of such data helps...
The effects of viscous dampers on the reliability of steel structures using a PIF index
, Article Proceedings of the Institution of Civil Engineers: Structures and Buildings ; Volume 172, Issue 4 , 2019 , Pages 289-300 ; 09650911 (ISSN) ; Bakhshi, A ; Sharif University of Technology
ICE Publishing
2019
Abstract
A new comparative performance measure based on a structure's seismic fragility curve is introduced. This factor, called the performance improvement factor (PIF), was used to compare the seismic performance and reliability of two structures. Using the PIF, the efficiency of viscous dampers on the behaviour of a weak mid-rise steel structure was investigated. A prototype five-span 12-storey steel frame was equipped with three patterns of viscous dampers and their seismic performance was studied. The distribution of dampers along the height of the structure was optimised in three hazard levels using a genetic algorithm and the structure was subjected to 12 ground motion records scaled to levels...
On the essential instabilities caused by fractional-order transfer functions
, Article Mathematical Problems in Engineering ; Volume 2008 , 2008 ; 1024123X (ISSN) ; Karimi Ghartemani, M ; Sharif University of Technology
2008
Abstract
The exact stability condition for certain class of fractional-order (multivalued) transfer functions is presented. Unlike the conventional case that the stability is directly studied by investigating the poles of the transfer function, in the systems under consideration, the branch points must also come into account as another kind of singularities. It is shown that a multivalued transfer function can behave unstably because of the numerator term while it has no unstable poles. So, in this case, not only the characteristic equation but the numerator term is of significant importance. In this manner, a family of unstable fractional-order transfer functions is introduced which exhibit...
Capillary pressure estimation using statistical pore size functions
, Article Chemical Engineering and Technology ; Volume 30, Issue 7 , 2007 , Pages 862-869 ; 09307516 (ISSN) ; Rashtchian, D ; Kharrat, R ; Vossoughi, S ; Sharif University of Technology
2007
Abstract
Capillary pressure curves, which have been employed for a long period of time by researchers interested in pore size distribution, are commonly obtained from experimental measurements. The dynamic capillary pressure that influences the flow is affected by many factors including the pore size characteristics and pore scale dynamics. Hence, it is important to investigate the variation of the estimated pore size distribution with capillary number. In this study, a glass type micromodel is considered as the porous media sample. A parametric probability density function is proposed to express the pore size distribution of the porous model, which is also measured using an image analysis technique....
Multicolored trees in complete graphs
, Article Journal of Graph Theory ; Volume 54, Issue 3 , 2007 , Pages 221-232 ; 03649024 (ISSN) ; Alipour, A ; Sharif University of Technology
Wiley-Liss Inc
2007
Abstract
A multicolored tree is a tree whose edges have different colors. Brualdi and Hollingsworth [5] proved in any proper edge coloring of the complete graph K2n(n > 2) with 2n -1 colors, there are two edge-disjoint multicolored spanning trees. In this paper we generalize this result showing that if (a1,..., ak) is a color distribution for the complete graph Kn, n ≥ 5, such that 2 ≤ a1 ≤ a2 ≤ ⋯ ≤ ak ≤ (n + 1)/2, then there exist two edge-disjoint multicolored spanning trees. Moreover, we prove that for any edge coloring of the complete graph Kn with the above distribution if T is a non-star multicolored spanning tree of Kn, then there exists a multicolored spanning tree T′ of Kn such that T and T′...
Short-term prediction of medium-and large-size earthquakes based on Markov and extended self-similarity analysis of seismic data
, Article Lecture Notes in Physics ; Volume 705 , 2006 , Pages 281-301 ; 00758450 (ISSN) ; 3540353739 (ISBN); 9783540353737 (ISBN) ; Sahimi, M ; Ghasemi, F ; Kaviani, K ; Allamehzadeh, M ; Peinke, J ; Mokhtari, M ; Vesaghi, M ; Niry, M. D ; Bahraminasab, A ; Tabatabai, S ; Fayazbakhsh, S ; Akbari, M ; Sharif University of Technology
2006
Abstract
We propose a novel method for analyzing precursory seismic data before an earthquake that treats them as a Markov process and distinguishes the background noise from real fluctuations due to an earthquake. A short time (on the order of several hours) before an earthquake the Markov time scale tM increases sharply, hence providing an alarm for an impending earthquake. To distinguish a false alarm from a reliable one, we compute a second quantity, T1, based on the concept of extended self-similarity of the data. T1 also changes strongly before an earthquake occurs. An alarm is accepted if both tM and T1 indicate it simultaneously. Calibrating the method with the data for one region provides a...
A probability-based instruction combining method for scheduling in VLIW processors
, Article IEEE International Conference on Computer Systems and Applications, 2006, Sharjah, 8 March 2006 through 8 March 2006 ; Volume 2006 , 2006 , Pages 673-679 ; 1424402123 (ISBN); 9781424402120 (ISBN) ; Sarbazi Azad, H ; Sharif University of Technology
IEEE Computer Society
2006
Abstract
In this paper, we show that by considering the factor of usage in instruction bundles in VLIW processors and using the slots filled with NOPs in bundles, we can improve the overall performance by reducing the total execution time of the program. By our proposed scheme, Combined Bundle Scheduling (CBS), we have gained better performance compared to that for the PDT scheme (Predicted Decision Tree scheduling) which is the best scheduling strategy known so far. © 2006 IEEE
Time-variant reliability-based prediction of COVID-19 spread using extended SEIVR model and Monte Carlo sampling
, Article Results in Physics ; Volume 26 , 2021 ; 22113797 (ISSN) ; Mahsuli, M ; Sioofy Khoojine, A ; Hosseini, V. R ; Sharif University of Technology
Elsevier B.V
2021
Abstract
A probabilistic method is proposed in this study to predict the spreading profile of the coronavirus disease 2019 (COVID-19) in the United State (US) via time-variant reliability analysis. To this end, an extended susceptible-exposed-infected-vaccinated-recovered (SEIVR) epidemic model is first established deterministically, considering the quarantine and vaccination effects, and then applied to the available COVID-19 data from US. Afterwards, the prediction results are described as a time-series of the number of people infected, recovered, and dead. Upon introducing the extended SEIVR model into a limit-state function and defining the model parameters including transmission, recovery, and...
Biased random satisfiability problems: From easy to hard instances
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 71, Issue 6 , 2005 ; 15393755 (ISSN) ; Moghimi Araghi, S ; Sharif University of Technology
2005
Abstract
In this paper we study biased random K-satisfiability (K-SAT) problems in which each logical variable is negated with probability p. This generalization provides us a crossover from easy to hard problems and would help us in a better understanding of the typical complexity of random K-SAT problems. The exact solution of 1-SAT case is given. The critical point of K-SAT problems and results of replica method are derived in the replica symmetry framework. It is found that in this approximation αcp-(K-1) for p→0. Solving numerically the survey propagation equations for K=3 we find that for p
MgB2 under pressure and plane strain: a DFT study
, Article Computer Physics Communications ; Volume 179, Issue 6 , 15 September , 2008 , Pages 385-390 ; 00104655 (ISSN) ; Tavana, A ; Akhavan, M ; Sharif University of Technology
2008
Abstract
Full potential density functional theory (DFT) calculations have been performed for the MgB2 superconductor. Results show that applying positive (negative) pressure leads to a decrement (increment) in the DOS at the Fermi level that this calculations suggest a decrement in Tc under application of positive pressure. In the Γ - A path of momentum space, the band which has the dominant role in conduction properties, moves upward when c increases or a decreases, and moves downward when c decreases or a increases. By relaxation of the system under the plane strain, we have studied the behavior of axial lattice parameter c. Our results show that changes in the axial lattice constant c is one third...
Zero tension Kardar-Parisi-Zhang equation in (d + 1)-dimensions
, Article Journal of Statistical Physics ; Volume 116, Issue 5-6 , 2004 , Pages 1521-1544 ; 00224715 (ISSN) ; Tabei, S. M. A ; Masoudi, A. A ; Shahbazi, F ; Rahimi Tabar, M. R ; Sharif University of Technology
2004
Abstract
The joint probability distribution function (PDF) of the height and its gradients is derived for a zero tension d + 1-dimensional Kardar-Parisi-Zliang (KPZ) equation. It is proved that the height's PDF of zero tension KPZ equation shows lack of positivity after a finite time tc. The properties of zero tension KPZ equation and its differences with the case that it possess an infinitesimal surface tension is discussed. Also potential relation between the time scale tc and the singularity time scale tc,v→0 of the KPZ equation with an infinitesimal surface tension is investigated. © 2004 Springer Science+Business Media, Inc
Relations between belief propagation on erasure and symmetric channels
, Article Proceedings - 2004 IEEE International Symposium on Information Theory, Chicago, IL, 27 June 2004 through 2 July 2004 ; 2004 , Pages 209- ; 21578097 (ISSN) ; Sharif University of Technology
2004
Abstract
We give an upper bound on the performance of the belief propagation algorithm in decoding a code over a binary-input output-symmetric channel in terms of the decoding threshold of the code over the erasure channel. Using this upper bound, we obtain the overhead of fountain codes on the erasure channel, provided that they are capacity-achieving on a symmetric channel. The upper bound is similar to a lower bound proved by Khandekar. The lower bound will be used to bound from above the reception overhead of fountain codes on symmetric channels