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#### Renormalization of entanglement in the anisotropic Heisenberg (XXZ) model

, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 77, Issue 3 , 2008 ; 10502947 (ISSN) ; Jafari, R ; Langari, A ; Sharif University of Technology
2008

Abstract

We have applied our recent approach to study the quantum-information properties of the anisotropic s=1/2 Heisenberg chain. We have investigated the underlying quantum-information properties such as the evolution of concurrence, entanglement entropy, nonanalytic behaviors, and the scaling close to the quantum critical point of the model. Both the concurrence and the entanglement entropy develop two saturated values after enough iterations of the renormalization of coupling constants. These values are associated with the two different phases, i.e., Néel and spin liquid phases. The nonanalytic behavior comes from the divergence of the first derivative of both measures of entanglement as the...

#### Renormalization of concurrence: The application of the quantum renormalization group to quantum-information systems

, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 76, Issue 6 , 20 December , 2007 ; 10502947 (ISSN) ; Jafari, R ; Langari, A ; Sharif University of Technology
2007

Abstract

We have combined the idea of renormalization group and quantum-information theory. We have shown how the entanglement or concurrence evolve as the size of the system becomes large, i.e., the finite size scaling is obtained. Moreover, we introduce how the renormalization-group approach can be implemented to obtain the quantum-information properties of a many-body system. We have obtained the concurrence as a measure of entanglement, its derivatives and their scaling behavior versus the size of system for the one-dimensional Ising model in transverse field. We have found that the derivative of concurrence between two blocks each containing half of the system size diverges at the critical point...

#### Efficient Compression of ECG Signals based on two dimensional wavelet transform and DCT decimation

, Article IWSSIP 2005 - 12th International Workshop on Systems, Signals and Image Processing(SSIP-SPI, 2005), Chalkida, 22 September 2005 through 24 September 2005 ; 2005 , Pages 317-322 ; 0907776205 (ISBN); 9780907776208 (ISBN) ; Rabiee, H. R ; Ghanbari, M ; Sharif University of Technology
2005

Abstract

An ECG signal is composed of many similar beats which makes it to behave semi-periodic. This paper deals with beat variation periods and exploits the correlation between cycles (inter-beat) and correlation within each cycle (intra-beat) for compression. For efficient compression a 2-dimensional array is constructed from the one dimensional ECG signal using decimation and interpolation in the discrete cosine transform (DCT) domain. Since reasonable results in image compression have been achieved by means of set partitioning in hierarchical trees (SPIHT) algorithm, we use SPIHT algorithm to code the 2-D wavelet transform of the ECG signals. Experimental results on selected records of ECG from...

#### Investigation of a protein complex network

, Article European Physical Journal B ; Volume 41, Issue 1 , 2004 , Pages 113-121 ; 14346028 (ISSN) ; Ramezanpour, A ; Karimipour, V ; Sharif University of Technology
2004

Abstract

The budding yeast Saccharomyces cerevisiae is the first eukaryote whose genome has been completely sequenced. It is also the first eukaryotic cell whose proteome (the set of all proteins) and interactome (the network of all mutual interactions between proteins) has been analyzed. In this paper we study the structure of the yeast protein complex network in which weighted edges between complexes represent the number of shared proteins. It is found that the network of protein complexes is a small world network with scale free behavior for many of its distributions. However we find that there are no strong correlations between the weights and degrees of neighboring complexes. To reveal...

#### Three-parameter correlation functions for the calculation of thermal conductivity of gases, liquids, and refrigerants over wide temperature-pressure ranges

, Article High Temperatures - High Pressures ; Volume 35-36, Issue 3 , 2003 , Pages 313-319 ; 00181544 (ISSN) ; Najafi, B ; Daneshmand, E ; Parsafar, G. A ; Sharif University of Technology
2003

Abstract

Two new correlation functions with three adjustable parameters for the calculation of thermal conductivity of gases, liquids, and refrigerants over wide temperature-pressure ranges are presented. It is shown that by using suitable mathematical expressions for the correlation functions, the number of adjustable parameters can be limited to three, which is less than for similar functions. The average and maximum deviation of the correlation compared with the measured data is about 1% and 8%, respectively

#### Generating correlated networks from uncorrelated ones

, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 67, Issue 4 2 , 2003 , Pages 461071-461076 ; 1063651X (ISSN) ; Karimipour, V ; Mashaghi, A ; Sharif University of Technology
2003

Abstract

The characteristics of correlated networks, generated from uncorrelated networks, were studied. New correlated networks with a considerable clustering were obtained from the line graphs of uncorrelated network. The transformation by which random graphs were converted to their line (edge-dual) graphs was explained. The solution for site percolation on the transformed graphs was also studied

#### General reaction-diffusion processes with separable equations for correlation functions

, Article Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics ; Volume 66, Issue 4 , 2002 , Pages 9- ; 1063651X (ISSN) ; Sharif University of Technology
2002

Abstract

We consider general multispecies models of reaction diffusion processes and obtain a set of constraints on the rates which give rise to closed systems of equations for correlation functions. Our results are valid in any dimension and on any type of lattice. We also show that under these conditions the evolution equations for two point functions at different times are also closed. As an example we introduce a class of two species models that may be useful for the description of voting processes or the spreading of epidemics. © 2002 The American Physical Society

#### Geometry selects highly designable structures

, Article Journal of Chemical Physics, Woodbury, NY, United States ; Volume 113, Issue 15 , 2000 , Pages 6437-6442 ; 00219606 (ISSN) ; Ejtehadi, M. R ; Sharif University of Technology
American Inst of Physics
2000

Abstract

The designability of structures in a two-dimensional hydrophobic-polar (HP) pair contact lattice model in a wide range of intermonomer interaction parameters was studied by considering HP constraints. The designability of all structures was clarified by enumerating all sequences of length 20. Results confirm that changing the intermolecular interactions affects the structure designability and also chooses the search space of the native state but the set of HDSs is invariant

#### Simply decoded efficient full-rate space-time block codes over correlated Rician fading channels

, Article IET Communications ; Volume 8, Issue 10 , 3 July 2014 , Pages 1684-1695 ; Pilaram, H ; Mohammadi, A ; Sharif University of Technology
Abstract

A novel technique is presented to design efficient full-rate space-time block codes (STBCs) over correlated Rician fading channels. The authors first derive a formula for the achievable information rate of a linear dispersion coded multi-input single-output system as a function of correlation at the transmitter in a Rician fading channel. In addition, the authors obtain the bit-error-rate (BER) equations for this system, when multiple phase shift keying and multiple quadrature amplitude modulation schemes are used at the transmitter. Therefore with regard to derived formulae and using a genetic algorithm, a method is presented to construct STBCs over correlated Rician fading channels. The...

#### Exact ground states for two new spin-1 quantum chains, new features of matrix product states

, Article European Physical Journal B ; Volume 62, Issue 2 , 2008 , Pages 159-169 ; 14346028 (ISSN) ; Karimipour, V ; Memarzadeh, L ; Sharif University of Technology
2008

Abstract

We use the matrix product formalism to find exact ground states of two new spin-1 quantum chains with nearest neighbor interactions. One of the models, model I, describes a one-parameter family of quantum chains for which the ground state can be found exactly. In certain limit of the parameter, the Hamiltonian turns into the interesting case H=∑ i (S i· S i+1) 2. The other model which we label as model II, corresponds to a family of solvable three-state vertex models on square lattices. The ground state of this model is highly degenerate and the matrix product states is a generating state of such degenerate states. The simple structure of the matrix product state allows us to determine the...

#### Numerical analysis of the swirl intensity decay rate for internal turbulent swirling flow

, Article 2007 5th Joint ASME/JSME Fluids Engineering Summer Conference, FEDSM 2007, San Diego, CA, 30 July 2007 through 2 August 2007 ; Volume 1 SYMPOSIA, Issue PART B , August , 2007 , Pages 1987-1995 ; 0791842886 (ISBN); 9780791842881 (ISBN) ; Mousavian, S. M ; Saidi, M. H ; Sharif University of Technology
2007

Abstract

In this research the trend of swirl decay and factors influencing the turbulent swirl flows have been investigated in a fixed pipe. In this regard, turbulent swirling decay flow with solid body rotation has been numerically surveyed using different flow conditions at the pipe inlet. The numerical results have been validated and compared with the existing mathematical relations having satisfactory agreement. Results show that the swirl intensity decay rate has strong dependency on the Reynolds number. On this basis, correlations have been proposed which improves predictions of swirl intensity decay rate at upstream regions and those with high swirl intensity. In addition, analyses have been...

#### Calculation of thermodynamic properties of simple fluids using a new derived pair correlation function

, Article Fluid Phase Equilibria ; Volume 254, Issue 1-2 , 2007 , Pages 138-143 ; 03783812 (ISSN) ; Parsafar, G. A ; Najafi, B ; Sharif University of Technology
2007

Abstract

Based on a new derived radial distribution function (RDF) for potentials with a hard-core we have presented in this paper a method to apply the derived RDF for calculating thermodynamic properties of real fluids up to moderate densities. In order to use the derived RDF for real fluids, one of the potential parameters is chosen in such a way that the RDF behaves more like that for a real fluid. Hence we have been able to calculate all thermodynamic properties of a simple fluid analytically. We have then applied our procedure to a Lennard-Jones fluid and compared the results with simulation data. The agreement is good up to moderate densities, i.e. ρ* ≤ 0.6, which lies in the liquid range of...

#### Entanglement and optimal strings of qubits for memory channels

, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 74, Issue 6 , 2006 ; 10502947 (ISSN) ; Memarzadeh, L ; Sharif University of Technology
2006

Abstract

We investigate the problem of enhancement of mutual information by encoding classical data into entangled input states of arbitrary length and show that while there is a threshold memory or correlation parameter beyond which entangled states outperform the separable states, resulting in a higher mutual information, this memory threshold increases toward unity as the length of the string increases. These observations imply that encoding classical data into entangled states may not enhance the classical capacity of quantum channels. © 2006 The American Physical Society

#### A multifractal detrended fluctuation description of Iranian rial-US dollar exchange rate

, Article Physica A: Statistical Mechanics and its Applications ; Volume 367 , 2006 , Pages 328-336 ; 03784371 (ISSN) ; Rahmani, B ; Sharif University of Technology
2006

Abstract

The miltifractal properties and scaling behaviour of the exchange rate variations of the Iranian rial against the US dollar from a daily perspective is numerically investigated. For this purpose the multifractal detrended fluctuation analysis (MF-DFA) is used. Through multifractal analysis, the scaling exponents, generalized Hurst exponents, generalized fractal dimensions and singularity spectrum are derived. Moreover, contribution of two major sources of multifractality, that is, fat-tailed probability distributions and nonlinear temporal correlations are studied. © 2005 Elsevier B.V. All rights reserved

#### CIROLS: Codec independent recovery of lost speech packets

, Article 2007 9th International Symposium on Signal Processing and its Applications, ISSPA 2007, Sharjah, 12 February 2007 through 15 February 2007 ; 2007 ; 1424407796 (ISBN); 9781424407798 (ISBN) ; Manzuri Shalmani, M. T ; Aghatabar, M. M ; Sharif University of Technology
2007

Abstract

In this paper, we have focused on finding an error resilient method for discontinuity-less transmission of speech signals in the internet. Our proposed method creates artificial correlation between speech samples that pre-distorts the speech signal. The receiver uses this correlation to reconstruct the lost speech packets. A discrete Fourier transform (DFT)-based speech enhancement technique is designed for the reduction of the processing error in the recovered speech caused by the speech codecs. The SegSNR results show the superiority of our proposed method over a recently proposed speech enhancement technique. ©2007 IEEE

#### Thermal entanglement of spins in the Heisenberg model at low temperatures

, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 70, Issue 5 A , 2004 , Pages 052307-1-052307-5 ; 10502947 (ISSN) ; Karimipour, V ; Sharif University of Technology
2004

Abstract

The entanglement between two spins in the ferromagnetic Heisenberg chain at low temperatures was calculated. It was shown that if a magnetic field is applied to a ferromagnetic Heisenberg chain, then pairwise entanglement develops between spins at arbitrary given states. It was also shown that the entanglement profile is a Gaussian with a characteristic length depending on the temperature and the coupling between spins only when the ground state and the one-particle states are populated. The magnetic field was shown to affect only the amplitude of the profile and not its characteristic length

#### Effects of confining walls on laminar natural convection from a horizontal cylinder

, Article Proceedings of the Intersociety Energy Conversion Engineering Conference ; Volume 2 , 2000 , Pages 1261-1267 ; 0146955X (ISSN) ; Razi, Y. P ; Sharif University of Technology
2000

Abstract

The laminar natural convection from an isothermal horizontal cylinder confined between vertical walls is investigated by experimental and numerical methods. The experimental and numerical data are well correlated, independently, to equations which give the average Nusselt number in terms of the wall spacing to cylinder diameter ratio, t/D, and the Rayleigh number, Ra, for two different values of the wall height to cylinder diameter ratios, H/D=7 and 15.2. For the low Rayleigh numbers considered (Ra<1000), there are certain conditions for the confining walls under which heat transfer from the cylinder is maximum. Results are compared with the reported numerical and/or experimental results...

#### Numerical and Semi-Empirical Investigation of Pulsating Heat Pipe

, M.Sc. Thesis Sharif University of Technology ; Shafii, Mohammad Behshad (Supervisor) ; Saboohi, Yadollah (Supervisor)
Abstract

Thermal management of electronics is a contemporary issue which is increasingly gaining importance in line with the advances in packaging technology. Immediate and consistent multi-disciplinary research is needed to cater to the prevailing trends of net power and flux levels of upcoming microelectronics products. Material science, packaging concepts, fabrication technology and novel cooling strategies are some of key areas requiring synchronal research for successful thermal management. Focusing on the latter area, this thesis attempts to describe the complex thermo-hydrodynamics of Closed Loop ...

#### A method for determination of harmonics responsibilities at the point of common coupling using data correlation analysis

, Article IET Generation, Transmission and Distribution ; Volume 8, Issue 1 , 2014 , Pages 142-150 ; ISSN: 17518687 ; Mokhtari, H ; Sharif University of Technology
Abstract

In this study, a new method is proposed to evaluate the utility harmonic impedance and the harmonics responsibilities at the point of common coupling. The former task is accomplished by involving the harmonic phase angles in the data correlation method, and the latter one is done using an approach based on the fluctuation of the background harmonic voltage. An important advantage of the method is to take the load harmonic impedance into account in appropriate manner. The performance of the proposed method is verified using simulation studies for different cases and also field measurements. Long-term measurement data are used to determine the harmonic contribution of the industrial customers...

#### Probabilistic optimal power flow in correlated hybrid wind-PV power systems: A review and a new approach

, Article Renewable and Sustainable Energy Reviews ; Vol. 41 , 2014 , pp. 1437-1446 ; ISSN: 13640321 ; Rashidinejad, M ; Firuz-Abad, M. F ; Sharif University of Technology
Abstract

Hastening the power industry reregulation juxtaposed with the unprecedented utilization of uncertain renewable energies (REs), faces power system operation with sever uncertainties. Consequently, uncertainty assessment of system performance is an obligation. This paper reviews the probabilistic techniques used for probabilistic optimal power flow (P-OPF) studies and proposes a novel and powerful approach using the unscented transformation (UT) method. The heart of the proposed method lies in how to produce the sampling points. Appropriate sampling points are chosen to perform the P-OPF with a high degree of accuracy and less computational burden compared with features of other existing...