Loading...
Search for:
maximum-likelihood
0.007 seconds
Total 133 records
Estimating a mixed-profile MDCEV: case of daily activity type and duration
, Article Transportation Letters ; 2017 , Pages 1-14 ; 19427867 (ISSN) ; Samimi, A ; Sharif University of Technology
Abstract
Multiple Discrete Continuous Extreme Value (MDCEV) has become popular in the past years. Yet, the model suffers from an ‘empirical identification’ issue that is mainly due to inter-relations between two of its parameters, α and γ. This paper presents a hybrid optimization paradigm (named HELPME) to address this issue in a basic MDCEV formulation and take full advantage of the model by estimating a ‘mixed-profile.’ HELPME benefits from a coarse-to-fine search strategy, in which a customized Electromagnetism-like meta-heuristic precedes a gradient-based approach. The Atlanta Regional Travel Survey (2011) is used to empirically analyze performance of HELPME as well as significance of the...
Constructing and decoding GWBE codes using Kronecker products
, Article IEEE Communications Letters ; Volume 14, Issue 1 , 2010 , Pages 1-3 ; 10897798 (ISSN) ; Faraji, M ; Marvasti, F ; Sharif University of Technology
2010
Abstract
In this letter, we introduce a novel method for constructing large size Generalized Welch Bound Equality (GWBE) matrices. This method can also be used for the construction of large WBE matrices. The advantage of this method is its low complexity for constructing large size matrices and low computational complexity using Maximum Likelihood (ML) decoders for a subclass of these codes. © 2010 IEEE
Expectation maximization based detection for V-BLAST MIMO communication systems and performance evaluation
, Article 2004 IEEE International Symposium on Spread Spectrum Techniques and Applications, ISSSTA 2004, Sydney, 30 August 2004 through 2 September 2004 ; 2004 , Pages 255-259 ; Nasiri Kenari, M ; Sharif University of Technology
2004
Abstract
Maximum likelihood naturally arises as the target criterion for detection in many applications as well as in layered space-time communications. Nevertheless, the existing algorithms for maximum-likelihood decoding have computational complexity that is not feasible for implementation in practical systems. Applying the Expectation-Maximization algorithm to the Maximum Likelihood detection of layered space-time codes, we iteratively maximize the conditional log-likelihood of a single layer, rather than maximizing the intractable likelihood function of all layers. Computer simulations demonstrate the efficiency of the proposed detection scheme, in comparison to the well known nulling and...
Robust video watermarking using maximum likelihood decoder
, Article European Signal Processing Conference, 29 August 2011 through 2 September 2011, Barcelona ; 2011 , Pages 2044-2048 ; 22195491 (ISSN) ; Akhaee, M. A ; Ghaemmaghami, S ; Sharif University of Technology
Abstract
In this paper, a robust multiplicative video watermarking scheme is presented. We segment the video signal into 3-D blocks like cubes, and then apply 3-D wavelet transform to each block. The watermark is inserted through multiplying the low frequency wavelet coefficients by a constant parameter that controls the power of the watermark. The proposed watermark extraction procedure is based on the maximum likelihood rule applied to the watermarked wavelet coefficients
Estimation of weibull parameters for wind energy application in Iran's cities
, Article Wind and Structures, An International Journal ; Volume 21, Issue 2 , 2015 , Pages 203-221 ; 12266116 (ISSN) ; Hannani, S. K ; Boroushaki, M ; Sharif University of Technology
Techno Press
2015
Abstract
Wind speed is the most important parameter in the design and study of wind energy conversion systems. The weibull distribution is commonly used for wind energy analysis as it can represent the wind variations with an acceptable level of accuracy. In this study, the wind data for 11 cities in Iran have been analysed over a period of one year. The Goodness of fit test is used for testing data fit to weibull distribution. The results show that this data fit to weibull function very well. The scale and shape factors are two parameters of the weibull distribution that depend on the area under study. The kinds of numerical methods commonly used for estimating weibull parameters are reviewed. Their...
Information hiding with maximum likelihood detector for correlated signals
, Article Digital Signal Processing: A Review Journal ; Volume 36, Issue C , January , 2015 , Pages 144-155 ; 10512004 (ISSN) ; Akhaee, M. A ; Sankur, B ; Marvasti, F ; Sharif University of Technology
Elsevier Inc
2015
Abstract
In this paper, a new scaling based information hiding approach with high robustness against noise and gain attack is presented. The host signal is assumed to be stationary Gaussian with first-order autoregressive model. For data embedding, the host signal is divided into two parts, and just one patch is manipulated while the other one is kept unchanged for parameter estimation. A maximum likelihood (ML) decoder is proposed which uses the ratio of samples for decoding the watermarked data. Due to the decorrelating property of the proposed decoder, it is very efficient for watermarking highly correlated signals for which the decoding process is not straightforward. By calculating the...
A maximum likelihood approach to estimate the change point of multistage Poisson count processes
, Article International Journal of Advanced Manufacturing Technology ; Volume 77, Issue 5-8 , March , 2015 , Pages 1443-1464 ; 02683768 (ISSN) ; Akhavan Niaki, S. T ; Asghari Torkamani, E ; Sharif University of Technology
Springer-Verlag London Ltd
2015
Abstract
The difference between the signaling time and the real change point of a process is an important monitoring issue. If the exact time at which the change manifests itself into the process is known, then process engineers can identify and eliminate the root causes of process disturbance efficiently and quickly, resulting in considerable amount of time and cost savings. Multistage count processes that are often observed in production environments must be monitored to assure quality products. In this study, multistage Poisson count processes are first introduced. Then, the process is modeled using a first-order integer-valued autoregressive time series (INAR(1)). For out-of-control signals...
Robust multiplicative watermarking technique with Maximum Likelihood detector
, Article 16th European Signal Processing Conference, EUSIPCO 2008, Lausanne, 25 August 2008 through 29 August 2008 ; 2008 ; 22195491 (ISSN) ; Akhaee, M. A ; Sankur, B ; Marvasti, F ; Canton de Vaud; Interactive Multimodal Information Management (IM); SIMILAR - Network of Excellence; Swiss National Science Foundation (SNSF ; Sharif University of Technology
European Signal Processing Conference, EUSIPCO
2008
Abstract
In this paper, a new multiplicative semi-blind image-adaptive watermarking system has been presented, which exploits human visual model for adapting the watermark data to local properties of the host image. To have a better robustness, the proposed algorithm is implemented on the low-frequency coefficients of the wavelet transform. Moreover, regarding invisibility of the algorithm, the strength factor which controls the watermark power is optimally selected. To extract the watermark data, the Maximum Likelihood (ML) estimator is used. Experimental results confirm the imperceptibility of the proposed method and its high robustness against various attacks such as JPEG compression, noise...
Monotonic change-point estimation of multivariate Poisson processes using a multi-attribute control chart and MLE
, Article International Journal of Production Research ; Vol. 52, issue. 10 , Nov , 2014 , pp. 2954-2982 ; ISSN: 00207543 ; Khedmati, M ; Sharif University of Technology
Abstract
In this paper, a new multi-attribute T2 control chart is initially proposed to monitor multi-attribute processes based on a transformation technique. Then, the maximum likelihood estimator of a multivariate Poisson process change point is derived for unknown changes that are assumed to belong to a family of monotonic changes. Using extensive simulation experiments, the performance of the proposed change-point estimator is compared to the ones derived for step changes and linear-trend disturbances, when the true change types are step change, linear trends and multiple-step changes. We show when the type of the change is not known a priori, the proposed estimator is an appropriate choice,...
Estimating a mixed-profile MDCEV: case of daily activity type and duration
, Article Transportation Letters ; Volume 11, Issue 6 , 2019 , Pages 289-302 ; 19427867 (ISSN) ; Samimi, A ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
Multiple Discrete Continuous Extreme Value (MDCEV) has become popular in the past years. Yet, the model suffers from an ‘empirical identification’ issue that is mainly due to inter-relations between two of its parameters, α and γ. This paper presents a hybrid optimization paradigm (named HELPME) to address this issue in a basic MDCEV formulation and take full advantage of the model by estimating a ‘mixed-profile.’ HELPME benefits from a coarse-to-fine search strategy, in which a customized Electromagnetism-like meta-heuristic precedes a gradient-based approach. The Atlanta Regional Travel Survey (2011) is used to empirically analyze performance of HELPME as well as significance of the...
GLR detector for coded signals in noise and interference
, Article Scientia Iranica ; Volume 15, Issue 2 , 2008 , Pages 170-174 ; 10263098 (ISSN) ; Derakhtian, M ; Nayebi, M. M ; Aref, M. R ; Sharif University of Technology
Sharif University of Technology
2008
Abstract
In this paper, the detection of a coded signal in additive white Gaussian noise and the interference is studied, where there is no knowledge about the correlation between the received symbols and about the noise and interference parameters. The Maximum Likelihood (ML) estimates of the unknown parameters are found, they are substituted in the probability density functions of the observation and the Generalized Likelihood Ratio (GLR) detector is derived. This detector can also be used for the activity detection of a signal in unknown Inter-Symbol Interference (ISI). In this case, the interference is modeled as the unknown correlation between the received symbols. Simulation examples are...
Linear decoupled and quasi-decoupled space-time codes
, Article IEEE Transactions on Communications ; Volume 55, Issue 1 , 2007 , Pages 54-59 ; 00906778 (ISSN) ; Khalaj, B. H ; Shamsi, M ; Sharif University of Technology
2007
Abstract
Space-time transmit diversity results in coupling of transmitted symbols across different antennas, which increases the complexity of maximum-likelihood decoding. Symbol coupling can be completely or partially avoided if the space-time code (STC) satisfies specific decoupling conditions; examples of such codes are orthogonal space-time block codes and quasi-orthogonal codes. In this letter, we study decoupling conditions for a linear full-diversity STC. Quasi-decoupled codes are proposed as a partially decoupled full-diversity STC of any rate for any number of transmit antennas with minimum decoding delay. By optimizing the coding gain of quasi-decoupled codes, it is shown that...
DGSAN: Discrete generative self-adversarial network
, Article Neurocomputing ; Volume 448 , 2021 , Pages 364-379 ; 09252312 (ISSN) ; Alihosseini, D ; Soleymani Baghshah, M ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Although GAN-based methods have received many achievements in the last few years, they have not been entirely successful in generating discrete data. The most crucial challenge of these methods is the difficulty of passing the gradient from the discriminator to the generator when the generator outputs are discrete. Despite the fact that several attempts have been made to alleviate this problem, none of the existing GAN-based methods have improved the performance of text generation compared with the maximum likelihood approach in terms of both the quality and the diversity. In this paper, we proposed a new framework for generating discrete data by an adversarial approach in which there is no...
Detecting and estimating the time of a step-change in multivariate Poisson processes
, Article Scientia Iranica ; Volume 19, Issue 3 , June , 2012 , Pages 862-871 ; 10263098 (ISSN) ; Khedmati, M ; Sharif University of Technology
2012
Abstract
In multi-attribute process monitoring, when a control chart signals an out-of-control condition indicating the existence of a special cause, knowing when the process has really changed (the change point) accelerates the identification of the source of the special cause and makes the corrective measures to be employed sooner. This, of course, results in a considerable amount of savings in time and money. Since many real world multi-attribute processes are Poisson and most process changes are step-change, a new method is proposed, in this paper, to derive the maximum likelihood estimator of the time of a step-change in the mean vector of multivariate Poisson processes. In this method, two...
Distribution independent blindwatermarking
, Article Proceedings - International Conference on Image Processing, ICIP, 7 November 2009 through 10 November 2009, Cairo ; 2009 , Pages 125-128 ; 15224880 (ISSN); 9781424456543 (ISBN) ; Akhaee, M. A ; Marvasti, F ; IEEE Signal Processing Society; The Institute of Electrical and Electronics Engineers ; Sharif University of Technology
IEEE Computer Society
2009
Abstract
In this paper, a new blind scaling based watermarking approach is presented. The host signal is assumed to be stationary Gaussian with first-order autoregressive model. Partitioning the host signal into two separate parts, the data is embedded in one part and the other is kept unchanged for blind parameter estimation. Driving the distribution of the decision variable we have suggested a maximum likelihood decoding algorithm which is independent of the host signal distribution and can be applied for any transform domains. The proposed algorithm is applied to both artificial Gaussian autoregressive signals as well as various test images. Experimental results confirm the independence of the...
Development of fragility curves for existing residential steel buildings with concentrically braced frames
, Article Scientia Iranica ; Volume 26, Issue 4A , 2019 , Pages 2212-2228 ; 10263098 (ISSN) ; Soltanieh, H ; Sharif University of Technology
Sharif University of Technology
2019
Abstract
The objective of this study is to develop analytical fragility curves for an ensemble of existing 3-to 6-story residential steel buildings with concentrically braced frames in 2 directions, designed during 2010 to 2015 in Qazvin, Iran. The buildings were modeled three-dimensionally in OpenSees considering braces buckling behavior. Maximum Inter-story Drift Ratio (.MIDR) and spectral acceleration at. fundamental period of the structure with 5% viscous damping (Sa(7,5%)) were considered as Damage Index (DI) and Intensity Measure (/M), respectively. Limit states were specified as discussed in FEMA 356. Ground motion record selection and uncertainties assessment were carried out based on FEMA...
Development of fragility curves for existing residential steel buildings with concentrically braced frames
, Article Scientia Iranica ; Volume 26, Issue 4A , 2019 , Pages 2212-2228 ; 10263098 (ISSN) ; Soltanieh, H ; Sharif University of Technology
Sharif University of Technology
2019
Abstract
The objective of this study is to develop analytical fragility curves for an ensemble of existing 3-to 6-story residential steel buildings with concentrically braced frames in 2 directions, designed during 2010 to 2015 in Qazvin, Iran. The buildings were modeled three-dimensionally in OpenSees considering braces buckling behavior. Maximum Inter-story Drift Ratio (.MIDR) and spectral acceleration at. fundamental period of the structure with 5% viscous damping (Sa(7,5%)) were considered as Damage Index (DI) and Intensity Measure (/M), respectively. Limit states were specified as discussed in FEMA 356. Ground motion record selection and uncertainties assessment were carried out based on FEMA...
A method for improving power distribution characteristics of space time block codes
, Article China Communications ; Volume 17, Issue 6 , 2020 , Pages 223-234 ; Shayesteh, M. G ; Sharif University of Technology
Editorial Department of China Communications
2020
Abstract
Improving power distribution characteristics of space time block codes (STBCs), namely peak to average power ratio (PAPR), average to minimum power ratio (Ave/min), and probability of transmitting 'zero' by antenna, makes easier their practical implementation. To this end, this study proposes to multiply full diversity STBC with a non-singular matrix in multiple input multiple output (MIMO) or multiple input single output (MISO) systems with linear or maximum likelihood (ML) receivers. It is proved that the obtained code achieves full diversity and the order of detection complexity does not change. The proposed method is applied to different types of STBCs. The bit error rate (BER) and power...
World city mode choice: Choice of rail public transportation
, Article Scientia Iranica ; Volume 11, Issue 4 , 2004 , Pages 320-331 ; 10263098 (ISSN) ; Tabatabaee, N ; Kermanshah, M ; Aashtiani, H. Z ; Toobaei, S ; Sharif University of Technology
Sharif University of Technology
2004
Abstract
The choice of technology to transport passengers in large metropolitan areas is an important issue everywhere. There are many factors involved in this choice. This paper deals with the possibility of the objective use of available information in the analysis of the suitability of a rail public transport system for a city. A database has been made from publications on public city transportation and country level information. Logit models of choice have been calibrated by the maximum likelihood and nonlinear least square methods based on the acquired information. Each city is treated as an "individual", choosing rail or non-rail modes for its trips. Only cities with a population of more than...
Estimating a Mixed Profile MDCEV:Case of Daily Activity Type and Duration
, M.Sc. Thesis Sharif University of Technology ; Samimi, Amir (Supervisor)
Abstract
The closed-form formulation of MDCEV has become popular in past years, as it accounts for satiation effects through a novel consumption-based utility structure. The model, however, suffers from an “empirical identification” problem. The problem is mainly due to entangled roles of two model parameters in capturing satiation effects. Thus far, the best known solution to the problem is fixing either or both of the parameters to pre-defined values and estimate a restricted satiation profile. This paper, presents a new hybrid optimization algorithm (named HEMPME) to eliminate the need for imposing such restrictions, and disentangle the two effects through estimating a “mixed profile” model....