Search for: processing-time
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    Approaching complexity by stochastic methods: From biological systems to turbulence

    , Article Physics Reports ; Volume 506, Issue 5 , 2011 , Pages 87-162 ; 03701573 (ISSN) Friedrich, R ; Peinke, J ; Sahimi, M ; Reza Rahimi Tabar, M ; Sharif University of Technology
    This review addresses a central question in the field of complex systems: given a fluctuating (in time or space), sequentially measured set of experimental data, how should one analyze the data, assess their underlying trends, and discover the characteristics of the fluctuations that generate the experimental traces? In recent years, significant progress has been made in addressing this question for a class of stochastic processes that can be modeled by Langevin equations, including additive as well as multiplicative fluctuations or noise. Important results have emerged from the analysis of temporal data for such diverse fields as neuroscience, cardiology, finance, economy, surface science,... 

    Phase-induced intensity noise in digital incoherent all-optical tapped-delay line systems [electronic resource]

    , Article Lightwave Technology, Journal of ; 2006, Volume.24 , Issue. 8, p.3059-3072 Mansouri Rad, M. M. (Mohammad Mehdi) ; Salehi, J. A ; Sharif University of Technology
    In this paper, the authors analyze conditions under which they can be certain on the intensity addition of a given device, such as tapped-delay lines, used in digital incoherent all-optical communication systems. A general expression for phase-induced intensity noise that is applicable to all types of semiconductor lasers is derived by defining an optical self-SNR expression that can be used to analyze and measure phase-induced intensity noise. The result shows that in order to have a minimal phase-induced intensity noise in most digital optical incoherent systems, a large optical self-SNR, e.g., 20 dB or more, is needed. This in turn is shown to place a limit on the maximum rate of... 

    Due date assignment in single machine with stochastic processing times

    , Article International Journal of Production Research ; Volume 51, Issue 8 , 2013 , Pages 2352-2362 ; 00207543 (ISSN) Elyasi, A ; Salmasi, N ; Sharif University of Technology
    This paper considers two different due date assignment and sequencing problems in single machine where the processing times of jobs are random variables. The first problem is to minimise the maximum due date so that all jobs are stochastically on time. It is shown that sequencing the jobs in decreasing service level (DSL) order optimally solves the problem. The results are then extended for two special cases of flow shop problem. The other problem is to minimise a total cost function which is a linear combination of three penalties: penalty on job earliness, penalty on job tardiness, and penalty associated with long due date assignment. The assignment of a common due date and distinct due... 

    A Langevin equation for the rates of currency exchange based on the Markov analysis

    , Article Physica A: Statistical Mechanics and its Applications ; Volume 385, Issue 2 , 2007 , Pages 601-608 ; 03784371 (ISSN) Farahpour, F ; Eskandari, Z ; Bahraminasab, A ; Jafari, G. R ; Ghasemi, F ; Sahimi, M ; Reza Rahimi Tabar, M ; Sharif University of Technology
    We propose a method for analyzing the data for the rates of exchange of various currencies versus the U.S. dollar. The method analyzes the return time series of the data as a Markov process, and develops an effective equation which reconstructs it. We find that the Markov time scale, i.e., the time scale over which the data are Markov-correlated, is one day for the majority of the daily exchange rates that we analyze. We derive an effective Langevin equation to describe the fluctuations in the rates. The equation contains two quantities, D(1) and D(2), representing the drift and diffusion coefficients, respectively. We demonstrate how the two coefficients are estimated directly from the... 

    Characterization of complex behaviors of TCP/RED computer networks based on nonlinear time series analysis methods

    , Article Physica D: Nonlinear Phenomena ; Volume 233, Issue 2 , 2007 , Pages 138-150 ; 01672789 (ISSN) Bigdeli, N ; Haeri, M ; Choobkar, S ; Jannesari, F ; Sharif University of Technology
    Elsevier  2007
    Packet-level observations are representative of the high sensitivity of TCP/RED computer network behavior with respect to network/RED parameter variations. That is, while we do not have any control on network parameters, mis-choosing of the RED parameters results in complex non-periodic oscillations in the router queue length that may damage the Quality of Service requirements. Characterizing the nature of such behaviors, however, helps the network designers to modify the RED design method in order to achieve better overall performance. In this paper, we first investigate the effect of variations in different RED parameters on the network behavior and then seek for the origin of such complex... 

    Evidence for nonradiative energy transfer in graphene-oxide-based hybrid structures

    , Article Journal of Physical Chemistry C ; Volume 117, Issue 48 , December , 2013 , Pages 25298-25304 ; 19327447 (ISSN) Yeltik, A ; Kucukayan-Dogu, G ; Guzelturk, B ; Fardindoost, S ; Kelestemur, Y ; Demir, H. V ; Sharif University of Technology
    Solution processed graphene variants including graphene oxide (GO) and reduced graphene oxide (RGO) are promising materials for potential optoelectronic applications. To date, efficiency of the excitation energy transfer into GO and RGO thin layers has not been investigated in terms of donor-acceptor separation distance. In the present work, we study nonradiative energy transfer (NRET) from CdSe/CdS quantum dots into single and/or double layer GO or RGO using time-resolved fluorescence spectroscopy. We observe shorter lifetimes as the separation distance between the QDs and GO or RGO decreases. In accordance with these lifetimes, the rates reveal the presence of two different mechanisms... 

    Real-time and MPEG-1 layer III compression resistant steganography in speech

    , Article IET Information Security ; Volume 4, Issue 1 , 2010 , Pages 1-7 ; 17518709 (ISSN) Shirali Shahreza, M. H ; Shirali Shahreza, S ; Sharif University of Technology
    Embedding a secret message into a cover media without attracting any attention, known as steganography, is one of the methods used for hidden communication purposes. One of the cover media that can be used for steganography is speech. In this study, the authors propose a new steganography method in speech signals. In this method, the silence intervals of speech are found and the length (number of samples) of these intervals is changed to hide information. The main feature of our method is robustness to MPEG-1 layer III (MP3) compression. This method can hide information in a speech stream with very low processing time which makes it a real-time steganography method. The hiding capacity of... 

    Applying circular coloring to open shop scheduling

    , Article Scientia Iranica ; Volume 15, Issue 5 , 2008 , Pages 652-660 ; 10263098 (ISSN) Modarres, M ; Ghandehari, M ; Sharif University of Technology
    Sharif University of Technology  2008
    In this paper, a new approach to formulate a class of scheduling problems is introduced, which can be applied to many other discrete problems with complicated structures. The concept of graph circular coloring is applied to develop a model for the special case of an open shop scheduling problem. In this problem, there are some independent jobs to be processed in a shop with dedicated renewable resources. Each job consists of several tasks with no precedence restriction. Each task is processed without preemption. The processing time of the tasks is given. Processing each task requires using some multiple specified types of resource, while no more than one task can use each resource,... 

    Design of a novel HSLA steel with a combination of high strength (140-160 ksi) and excellent toughness

    , Article International Journal of Materials Research ; Volume 112, Issue 10 , 2021 , Pages 800-811 ; 18625282 (ISSN) Nezhad, M. S. A ; Ghazvinian, S ; Amirsalehi, M ; Momeni, A ; Sharif University of Technology
    Walter de Gruyter GmbH  2021
    Three steels were designed based on HSLA-100 with additional levels of Mn, Ni, Cr and Cu. The steels were prepared by controlled rolling and tempered at temperatures in range of 550-700°C. The continuous cooling time curves were shifted to longer times and lower temperatures with the increased tendency for the formation of martensite at lower cooling rates. The microstructures revealed that controlled rolling results in austenite with uniform fine grain structure. The steel with the highest amount of Mn showed the greatest strength after tempering at 750 °C. The top strength was attributed to the formation of Cu-rich particles. The steel with 1.03 wt.% Mn, tempered at 650 °C exhibited the... 

    Dimensional characterization of anesthesia dynamic in reconstructed embedding space

    , Article 29th Annual International Conference of IEEE-EMBS, Engineering in Medicine and Biology Society, EMBC'07, Lyon, 23 August 2007 through 26 August 2007 ; 2007 , Pages 6483-6486 ; 05891019 (ISSN) ; 1424407885 (ISBN); 9781424407880 (ISBN) Gifani, P ; Rabiee, H. R ; Hashemi, M. R ; Ghanbari, M ; Sharif University of Technology
    The depth of anesthesia quantification has been one of the most research interests in the field of EEG signal processing and nonlinear dynamical analysis has emerged as a novel method for the study of complex systems in the past few decades. In this investigation we use the concept of nonlinear time series analysis techniques to reconstruct the attractor of anesthesia from EEG signal which have been obtained from different hypnotic states during surgery to give a characterization of the dimensional complexity of EEG by Correlation Dimension estimation. The dimension of the anesthesia strange attractor can be thought of as a measure of the degrees of freedom or the 'complexity' of the... 

    Early detection of apnea-bradycardia episodes in preterm infants based on coupled hidden Markov model

    , Article IEEE International Symposium on Signal Processing and Information Technology, IEEE ISSPIT 2013 ; 2013 , Pages 243-248 Masoudi, S ; Montazeri, N ; Shamsollahi, M. B ; Ge, D ; Beuchee, A ; Pladys, P ; Hernandez, A. I ; Sharif University of Technology
    IEEE Computer Society  2013
    The incidence of apnea-bradycardia episodes in preterm infants may lead to neurological disorders. Prediction and detection of these episodes are an important task in healthcare systems. In this paper, a coupled hidden Markov model (CHMM) based method is applied to detect apnea-bradycardia episodes. This model is evaluated and compared with two other methods based on hidden Markov model (HMM) and hidden semi-Markov model (HSMM). Evaluation and comparison are performed on a dataset of 233 apnea-bradycardia episodes which have been manually annotated. Observations are composed of RR-interval time series and QRS duration time series. The performance of each method was evaluated in terms of... 

    A framework based on the Affine Invariant Regions for improving unsupervised image segmentation

    , Article 2012 11th International Conference on Information Science, Signal Processing and their Applications, ISSPA 2012 ; 2012 , Pages 17-22 ; 9781467303828 (ISBN) Mostajabi, M ; Gholampour, I ; Sharif University of Technology
    Processing time and segmentation quality are two main factors in evaluation of image segmentation methods. Oversegmentation is one of the most challenging problems that significantly degrade the segmentation quality. This paper presents a framework for decreasing the oversegmentation rate and improving the processing time. Significant variations in both color and texture spaces are the main reasons that lead to oversegmentation. We exploit Affine Invariant Region Detectors to mark regions with high variations in both color and texture spaces. The results are then utilized to reduce the oversegmentation rate of image segmentation algorithms. The performance of the proposed framework is... 

    Reducing motion estimation time with skin detection

    , Article 2009 IEEE International Workshop on Imaging Systems and Techniques, IST 2009, Hong Kong, 11 May 2009 through 12 May 2009 ; 2009 , Pages 71-75 ; 9781424434831 (ISBN) Shirali Shahreza, M. H ; Shirali Shahreza, S ; IEEE Instrumentation and Measurement Society ; Sharif University of Technology
    Motion estimation (ME) is one of the key parts of video compression algorithms. But, motion estimation and computation of motion vectors (MVs) are very time con-suming. In this paper, we propose a method for reducing the cost of motion estimation process. During this process, a series of candidate blocks should be searched to find the best motion vectors. In our method, we compare the skin parts of two blocks before comparing all pixel pairs of the two blocks. Having a preprocessing phase, the skin part comparison is performed quickly. This method provides a parameter that can be used to create a balance between the processing time and the motion estimation accuracy. © 2009 IEEE  

    Project completion time in dynamic PERT networks with generating projects

    , Article Scientia Iranica ; Volume 14, Issue 1 , 2007 , Pages 56-63 ; 10263098 (ISSN) Azaron, A ; Modarres, M ; Sharif University of Technology
    Sharif University of Technology  2007
    In this paper, an analytical method is developed to compute the project completion time distribution in a dynamic PERT network, where the activity durations are exponentially distributed random variables. The projects are generated according to a renewal process and share the same facilities. Thus, these projects cannot be analyzed independently. The authors' approach is to transform this dynamic PERT network into a stochastic network and, then, to obtain the project completion time distribution by constructing a proper continuous-time Markov chain. This dynamic PERT network is represented as a network of queues, where the service times represent the durations of the corresponding activities... 

    Digital video stabilization using radon transform

    , Article 2012 International Conference on Digital Image Computing Techniques and Applications, DICTA 2012, 3 December 2012 through 5 December 2012 ; December , 2012 ; 9781467321815 (ISBN) Babagholami Mohamadabadi, B ; Bagheri Khaligh, A ; Hassanpour, R ; Sharif University of Technology
    Digital video stabilization is a category of techniques used to reduce the impact of unintentional camera motion such as jitter, jiggle, and other unsteady motions. These unintentional shakings degrade visual quality of videos and reduce the performance of subsequent processes such as video compression. Digital video stabilization which is performed by post processing the acquired frames, suffers from inaccuracy of motion estimation which is mostly due to the local motions of internal moving objects included in videos, and long processing time which prohibits them from being used in real time applications. In this paper we propose a fast and accurate transform based motion estimation method... 

    Joint process and quality control of a continuously stirred tank reactor with non-Gaussian process noise

    , Article IET Control Theory and Applications ; Volume 6, Issue 5 , 2012 , Pages 651-661 ; 17518644 (ISSN) Afshar, P ; Nobakhti, A ; Wang, H ; Sharif University of Technology
    This study proposes a multi-objective control algorithm for simultaneous process and quality control in non-Gaussian stochastic batch processes. The objective is to control a non-Gaussian process so that each batch is delivered within a pre-specified time. During each batch, the process is controlled by a fixed-parameter PI controller. Between any two adjacent batches the controller parameters are updated by a differential evolution algorithm so that the integral squared of tracking error, entropy of tracking error, integral of absolute processing time error and entropy of processing time error are minimised. the proposed algorithm is applied to a batch continuously stirred tank reactor... 

    Robust timing and frequency synchronization for OFDM systems

    , Article IEEE Transactions on Vehicular Technology ; Volume 60, Issue 8 , Oct , 2011 , Pages 3646-3656 ; 00189545 (ISSN) Abdzadeh Ziabari, H ; Shayesteh, M. G ; Sharif University of Technology
    This paper deals with timing and frequency synchronization in orthogonal frequency-division multiplexing (OFDM) systems. A robust multistage scheme that works in the time domain, independent of the preamble structure, is proposed. After coarse-timing estimation, joint timing and integer frequency synchronization is performed. Then, fractional frequency correction is carried out, and finally, fine-timing estimation completes the synchronization process. The new timing estimation method is flexible and can be adjusted according to the degree of channel distortion. Furthermore, frequency synchronization is efficiently accomplished with an estimation range that is as large as the bandwidth of... 

    A simulation optimization approach to un-paced assembly line balancing problem-II with additional reworking issue

    , Article 2011 4th International Conference on Modeling, Simulation and Applied Optimization, ICMSAO 2011, 19 April 2011 through 21 April 2011 ; April , 2011 , Page(s): 1 - 6 ; 9781457700057 (ISBN) Noushabadi, M. E ; Bahalke, U ; Dolatkhahi, K ; Yolmeh, A. M ; Sharif University of Technology
    This paper investigates the problem of assembly line balancing problem, in which the products in the production line may undergo to be reworked on the current task. Since the real manufacturing systems deal with the stochastic nature of the items in production lines, this paper considers the simple assembly line balancing problem type 2 (SALBP-II) under the conditions of stochastic processing time of tasks and the element of reworking system. Exposing to the stochastic conditions encouraged us to handle the problem via simulation optimization procedure, which uses the well known genetic algorithm as an optimization tool. Results show the adaptation and effectiveness of GA to considered... 

    Mixed analog-digital crossbar-based hardware implementation of sign-sign LMS adaptive filter

    , Article Analog Integrated Circuits and Signal Processing ; Volume 66, Issue 1 , 2011 , Pages 41-48 ; 09251030 (ISSN) Merrikh Bayat, F ; Bagheri Shouraki, S ; Sharif University of Technology
    Recently announcement of a physical realization of a fundamental circuit element called memristor by researchers at Hewlett Packard (HP) has attracted so much interest worldwide. Combination of this newly found element with crossbar interconnect technology, opened a new field in designing configurable or programmable electronic systems which can have applications in signal processing and artificial intelligence. In this paper, based on the simple memristor crossbar structure, we will propose a new mixed analog-digital circuit as a hardware implementation of the sign-sign least mean square (LMS) adaptive filter algorithm. In this proposed hardware, any multiplication and addition is performed... 

    Process patterns for MDA-based software development

    , Article 8th ACIS International Conference on Software Engineering Research, Management and Applications, SERA 2010, 24 May 2010 through 26 May 2010, Montreal, QC ; 2010 , Pages 190-197 ; 9780769540757 (ISBN) Asadi, M ; Esfahani, N ; Ramsin, R ; Sharif University of Technology
    Information systems are expected to satisfy increasingly ambitious requirements, while reducing time-to-market has become a primary objective. This trend has necessitated the advent of development approaches that are better equipped and flexible enough to cope with modern challenges. Model-Driven Architecture (MDA) and Situational Method Engineering (SME) are approaches addressing this requirement: MDA provides promising means for automating the software process, and revitalizes the role of modeling in software development; SME focuses on project-specific methodology construction, mainly through assembling reusable method fragments (process patterns) retrieved from a method base. We provide...