Loading...
Search for:
log-normal
0.006 seconds
On the BER of multiple-input multiple-output underwater wireless optical communication systems
, Article 2015 4th International Workshop on Optical Wireless Communications, IWOW 2015, 7 September 2015 through 10 September 2015 ; Sept , 2015 , Pages 26-30 ; 9781467377263 (ISBN) ; Salehi, J. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
In this paper we analyze and investigate the bit error rate (BER) performance of multiple-input multiple-output underwater wireless optical communication (MIMO-UWOC) systems. In addition to exact BER expressions, we also obtain an upper bound on the system BER. To effectively estimate the BER expressions, we use Gauss-Hermite quadrature formula as well as approximation to the sum of log-normal random variables. We confirm the accuracy of our analytical expressions by evaluating the BER through photon-counting approach. Our simulation results show that MIMO technique can mitigate the channel turbulence-induced fading and consequently, can partially extend the viable communication range,...
Stochastic qualifier of gel and glass transitions in laponite suspensions
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 81, Issue 6 , Jun , 2010 ; 15393755 (ISSN) ; Jabbari Farouji, S ; Movahed, M. S ; Jafari, G. R ; Rahimi Tabar, M. R ; Sharif University of Technology
2010
Abstract
The existence of the important similarities between gelation and glass transition makes it hard to distinguish between the two types of nonergodic states experimentally. Here, we report on a stochastic analysis of the scattered light intensity through a colloidal particles suspension during the gel and glass formation. In this analysis, we exploit the methods developed for complex hierarchical systems, such as turbulence. Using the multiplicative log-normal cascade models, we provide a criterion to distinguish gels from glasses
Performance characterization of Relay-Assisted Wireless Optical CDMA Networks in Turbulent Underwater Channel
, Article IEEE Transactions on Wireless Communications ; Volume 15, Issue 6 , 2016 , Pages 4104-4116 ; 15361276 (ISSN) ; Akhoundi, F ; Salehi, J. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
Abstract
In this paper, we characterize the performance of relay-assisted underwater wireless optical code division multiple access (OCDMA) networks over turbulent channels. In addition to scattering and absorption effects of underwater channels, we also consider optical turbulence as a log-normal fading coefficient in our analysis. To simultaneously and asynchronously share medium among many users, we assign a unique optical orthogonal code (OOC) to each user in order to actualize OCDMA-based underwater network. The most significant challenge in underwater optical communication is in the ability to extend the short range of its coverage. In order to expand the viable communication range, we consider...
Rate adaptation and power allocation for time-correlated MISO Rayleigh fading channel with delay-limited HARQ
, Article IEEE International Conference on Communications, 10 June 2012 through 15 June 2012 ; 2012 , Pages 3915-3919 ; 15503607 (ISSN) ; 9781457720512 (E-ISBN) ; Vakilinia, S ; Khalaj, B. H ; Sharif University of Technology
Abstract
In this paper, we consider the problem of optimum rate adaptation and power allocation to maximize the delay-limited throughput (DLT) in a time-correlated 2×1 MISO Rayleigh fading channel with Hybrid ARQ in Chase-Combining mode (HARQ-CC). To this aim, we have first formulated the DLT equation based on the outage probability for 2×1 MISO-HARQ channel. We show that exact analytical calculation of the outage probability is not tractable. Therefore, we approximate the outage probability using a log-normal approximation approach. Based on such approximation, optimal rate and power allocations are derived. Finally, using Monte-Carlo simulation, we show that the approximation method provides...
Statistical distribution of intensity fluctuations for underwater wireless optical channels in the presence of air bubbles
, Article IWCIT 2016 - Iran Workshop on Communication and Information Theory, 3 May 2016 through 4 May 2016 ; 2016 ; 9781509019229 (ISBN) ; Khorramshahi, P ; Tashakori, A ; Chizari, A ; Shahsavari, S ; Abdollahramezani, S ; Fazelian, M ; Bahrani, S ; Salehi, J. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
In this paper, we experimentally investigate the statistical distribution of intensity fluctuations for underwater wireless optical channels under different channel conditions, namely fresh and salty underwater channels with and without air bubbles. To do so, we first measure the received optical signal with a large number of samples. Based on the normalized acquired data the channel coherence time and the fluctuations probability density function (PDF) are obtained for different channel scenarios. Our experimental results show that salt attenuates the received signal while air bubbles mainly introduce severe intensity fluctuations. Moreover, we observe that log-normal distribution precisely...
A neural network applied to estimate Burr XII distribution parameters
, Article Reliability Engineering and System Safety ; Volume 95, Issue 6 , June , 2010 , Pages 647-654 ; 09518320 (ISSN) ; Hosseinifard, S. Z ; Coit, D. W ; Sharif University of Technology
2010
Abstract
The Burr XII distribution can closely approximate many other well-known probability density functions such as the normal, gamma, lognormal, exponential distributions as well as Pearson type I, II, V, VII, IX, X, XII families of distributions. Considering a wide range of shape and scale parameters of the Burr XII distribution, it can have an important role in reliability modeling, risk analysis and process capability estimation. However, estimating parameters of the Burr XII distribution can be a complicated task and the use of conventional methods such as maximum likelihood estimation (MLE) and moment method (MM) is not straightforward. Some tables to estimate Burr XII parameters have been...
The effect of brine salinity on water-in-oil emulsion stability through droplet size distribution analysis: A case study
, Article Journal of Dispersion Science and Technology ; 2017 , Pages 1-13 ; 01932691 (ISSN) ; Ayatollahi, S ; Sharif University of Technology
Abstract
Water-in-oil emulsion usually forms during waterflooding in some heavy oil reservoirs. The composition and salinity of the injected water critically affect the w/o emulsion droplet size distribution, which control the emulsion stability and emulsion flow in porous media. The aim of the present work is to assess the effect of different sea water salinities on w/o emulsion stability through microscopic imaging. Therefore, w/o emulsions were prepared with different sea water samples, which were synthesized to resemble Persian Gulf, Mediterranean, Red Sea, and North Sea water samples. The results showed that log-normal distribution function predicts very well the experimental data to track the...
Predicting crash frequency for multi-vehicle collision types using multivariate poisson-lognormal spatial model: a comparative analysis
, Article Accident Analysis and Prevention ; Volume 118 , 2018 , Pages 277-288 ; 00014575 (ISSN) ; Sahebi, S ; Zamzuri, Z. H ; Shukri Yahaya, A ; Ismail, N ; Sharif University of Technology
Abstract
According to crash configuration and pre-crash conditions, traffic crashes are classified into different collision types. Based on the literature, multi-vehicle crashes, such as head-on, rear-end, and angle crashes, are more frequent than single-vehicle crashes, and most often result in serious consequences. From a methodological point of view, the majority of prior studies focused on multivehicle collisions have employed univariate count models to estimate crash counts separately by collision type. However, univariate models fail to account for correlations which may exist between different collision types. Among others, multivariate Poisson lognormal (MVPLN) model with spatial correlation...
The effect of brine salinity on water-in-oil emulsion stability through droplet size distribution analysis: a case study
, Article Journal of Dispersion Science and Technology ; Volume 39, Issue 5 , 2018 , Pages 721-733 ; 01932691 (ISSN) ; Ayatollahi, S ; Sharif University of Technology
Taylor and Francis Inc
2018
Abstract
Water-in-oil emulsion usually forms during waterflooding in some heavy oil reservoirs. The composition and salinity of the injected water critically affect the w/o emulsion droplet size distribution, which control the emulsion stability and emulsion flow in porous media. The aim of the present work is to assess the effect of different sea water salinities on w/o emulsion stability through microscopic imaging. Therefore, w/o emulsions were prepared with different sea water samples, which were synthesized to resemble Persian Gulf, Mediterranean, Red Sea, and North Sea water samples. The results showed that log-normal distribution function predicts very well the experimental data to track the...
Proposed 2D and 3D geometries intended for smart antenna applications, including direction finding and beamforming implementation
, Article IET Radar, Sonar and Navigation ; Volume 13, Issue 5 , 2019 , Pages 673-681 ; 17518784 (ISSN) ; Farzaneh, F ; Sharif University of Technology
Institution of Engineering and Technology
2019
Abstract
Novel two-dimensional (2D) and three-dimensional (3D) antenna array geometries for smart antenna application are introduced. Minimum mean square error beamforming algorithm, using these arrays, in presence of signal, noise and interferences is implemented. Beamforming approach is used for every type of array assuming uniform and log-normal distributions for the interference amplitudes. Equal volume cylindrical or prism type arrays with circular, hexagonal, triangular, square and star cross-sections with equal number of elements are considered. Novel geometries consisting of rotated cross-sections are studied as well. In each case, the relative signal-to-interference ratios (SIRs) are...
Proposed 2D and 3D geometries intended for smart antenna applications, including direction finding and beamforming implementation
, Article IET Radar, Sonar and Navigation ; Volume 13, Issue 5 , 2019 , Pages 673-681 ; 17518784 (ISSN) ; Farzaneh, F ; Sharif University of Technology
Institution of Engineering and Technology
2019
Abstract
Novel two-dimensional (2D) and three-dimensional (3D) antenna array geometries for smart antenna application are introduced. Minimum mean square error beamforming algorithm, using these arrays, in presence of signal, noise and interferences is implemented. Beamforming approach is used for every type of array assuming uniform and log-normal distributions for the interference amplitudes. Equal volume cylindrical or prism type arrays with circular, hexagonal, triangular, square and star cross-sections with equal number of elements are considered. Novel geometries consisting of rotated cross-sections are studied as well. In each case, the relative signal-to-interference ratios (SIRs) are...
A distribution-free tracking interval for model selection: application in the strength of brittle materials
, Article Communications in Statistics - Theory and Methods ; 2020 ; Sayyareh, S ; Sharif University of Technology
Bellwether Publishing, Ltd
2020
Abstract
In the literature of model selection, Vuong’s test and Akaike information criterion aim to find the best statistical model. Both of them are related to the expectation of the log-likelihood function of the rival models, but they are not sensitive to the small difference between rival models. The goal of this study is to develop a simple model selection approach which does not assume a true distribution for data. We have introduced a nonparametric tracking interval in the context of model selection. We have shown that this interval is compatibale with the known Vuong’s test results, but here we let the magnitude of the data enhance the performance of statistical inference. Simulation study...
Particles Size Distribution effect on 3D packing of nanoparticles into a bounded region
, Article International Journal of Engineering, Transactions A: Basics ; Volume 20, Issue 3 , 2007 , Pages 281-291 ; 17281431 (ISSN) ; Salehpoor, P ; Esmaielzadeh Kandjani, A ; Vaezi, M. R ; Sadrnezhaad, S. K ; Sharif University of Technology
Materials and Energy Research Center
2007
Abstract
In this paper, the effects of two different Particle Size Distributions (PSD) on packing behavior of ideal rigid spherical nanoparticles using a novel packing model based on parallel algorithms have been reported. A mersenne twister algorithm was used to generate pseudorandom numbers for the particles initial coordinates. Also, for this purpose a nanosized tetragonal confined container with a square floor (300 * 300 nm) were used in this work. The Andreasen and the Lognormal PSDs were chosen to investigate the packing behavior in a 3D bounded region. The effects of particle numbers on packing behavior of these two PSDs have been investigated. Also the reproducibility and the distribution of...
A distribution-free tracking interval for model selection: application in the strength of brittle materials
, Article Communications in Statistics - Theory and Methods ; Volume 51, Issue 16 , 2022 , Pages 5607-5637 ; 03610926 (ISSN) ; Sayyareh, S ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
In the literature of model selection, Vuong’s test and Akaike information criterion aim to find the best statistical model. Both of them are related to the expectation of the log-likelihood function of the rival models, but they are not sensitive to the small difference between rival models. The goal of this study is to develop a simple model selection approach which does not assume a true distribution for data. We have introduced a nonparametric tracking interval in the context of model selection. We have shown that this interval is compatibale with the known Vuong’s test results, but here we let the magnitude of the data enhance the performance of statistical inference. Simulation study...
Estimating the four parameters of the Burr III distribution using a hybrid method of variable neighborhood search and iterated local search algorithms
, Article Applied Mathematics and Computation ; Volume 218, Issue 19 , 2012 , Pages 9664-9675 ; 00963003 (ISSN) ; Abbasi, B ; Niaki, S. T. A ; Abdi, M ; Sharif University of Technology
2012
Abstract
The Burr III distribution properly approximates many familiar distributions such as Normal, Lognormal, Gamma, Weibull, and Exponential distributions. It plays an important role in reliability engineering, statistical quality control, and risk analysis models. The Burr III distribution has four parameters known as location, scale, and two shape parameters. The estimation process of these parameters is controversial. Although the maximum likelihood estimation (MLE) is understood as a straightforward method in parameters estimation, using MLE to estimate the Burr III parameters leads to maximize a complicated function with four unknown variables, where using a conventional optimization such as...