Search for: statistical-analysis
Total 81 records
Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 29, Issue 1 , 2010 , Pages 61-70 ; 10219986 (ISSN) ; Bozorghmehry Boozarjomehry, R ; Pishvaie, S. M. R ; Sharif University of Technology
Pore network modeling uses a network of pores connected by throats to model the void space of a porous medium and tries to predict its various characteristics during multiphase flow of various fluids. In most cases, a non-realistic regular lattice of pores is used to model the characteristics of a porous medium. Although some methodologies for extracting geologically realistic irregular networks from pore space images have been presented, these methods require some experimental data which are either unavailable or costly to obtain. 3-dimensional image or 2-dimensional SEM images are among these types of data. In this paper a new irregular lattice algorithm for the construction of these...
Article IEEE Transactions on Communications ; May 2010, Volume 58, Issue 5, P.1589-1598 ; Salehi, J. A ; Sharif University of Technology
Autocorrelation receiver (AcR) is usually used as the general receiver for transmitted reference (TR) communication systems on a quite intuitive basis. In this paper, we apply the principle of statistical invariance to obtain the optimum TR receiver on a decision-theoretic basis, and it is shown that the autocorrelation receiver is optimal only in a special case. Performance of the optimum receiver and the suboptimum AcR for some important modulation schemes is also evaluated. The results imply that allocating a part of the transmitted energy and bandwidth to reference pulses would not help improve the performance of the system and the optimal performance might be achieved via much simpler...
Biodegradation of cyanide by a new isolated strain under alkaline conditions and optimization by response surface methodology (RSM), Article Journal of Environmental Health Science and Engineering ; Vol. 12, issue. 1 , 2014 ; Yaghmaei, S ; Nejad, Z. G ; Sharif University of Technology
Background: Biodegradation of free cyanide from industrial wastewaters has been proven as a viable and robust method for treatment of wastewaters containing cyanide. Results: Cyanide degrading bacteria were isolated from a wastewater treatment plant for coke-oven-gas condensate by enrichment culture technique. Five strains were able to use cyanide as the sole nitrogen source under alkaline conditions and among them; one strain (C2) was selected for further studies on the basis of the higher efficiency of cyanide degradation. The bacterium was able to tolerate free cyanide at concentrations of up to 500 ppm which makes it a good potentially candidate for the biological treatment of cyanide...
Article IEEE Transactions on Aerospace and Electronic Systems ; Volume 53, Issue 4 , 2017 , Pages 2060-2076 ; 00189251 (ISSN) ; Nobahari, H ; Sharif University of Technology
To analyze a highly nonlinear dynamical system, it is necessary to evaluate the time evolution of the probability density function (pdf) of the states. In this paper, a novel Gaussian sum method is proposed to approximate the non-Gaussian pdf of a dynamical system whose nonlinear elements depend only on a single state variable. Using the Chapman-Kolmogorov equation, a set of recursive equations is derived to propagate the mean, covariance, and weight of the Gaussian sum components. There are several multiple integrals in the recursive equations which are analytically reduced to single integrals. As an application, the proposed approach is applied to statistically analyze the engagement of...
Impact of channel estimation errors and power allocation on analog network coding and routing in two-way relaying [electronic resource], Article IEEE Transaction on Vehicular Technology ; Vol. 61, Issue 7, pp. 3223 - 3239, 2012 ; Sadeghi, P ; Hucher, Ch ; Pakravan, Mohammad R ; Sharif University of Technology
In this paper, we study two important transmission strategies in full-duplex two-way relaying in the presence of channel estimation errors. In analog network coding (ANC), the relay transmits the combined signals that were received from both sources, with the aim of achieving better spectral efficiency. However, due to imperfect channel-state information (CSI), sources cannot perfectly cancel their own data in the relayed signal. We derive an achievable information rate for ANC in imperfect-CSI conditions and show how the ANC performance can significantly be degraded as a result. Moreover, we derive cut-set bounds with channel estimation errors for traditional routing (TR), in which time...
M.Sc. Thesis Sharif University of Technology ; Akbari Jokar, Mohammad Reza
With the increase of competition in the world of business and the advent of modern technologies, many companies in the world have turned into integration. The need for flexibility, reduction of costs, establishing close and broad connection among suppliers, producers, and distributors has caused companies to integrate their own systems and organizations so as to survive and keep going in today’s competitive, ever changing environment and finally gain competitive advantage. Supply chain management as a support for essential and operational processes of the organization is not an exception from this integration rule. Despite many views on the integrity of the supply chain, yet there is no...
Identification of the Set of Single Nucleotide Variants in Genome Responsible for the Differentiation of Expression of Genes, M.Sc. Thesis Sharif University of Technology ; Rabiee, Hamid Reza ; Beigi, Hamid
Single nucleotide polymorphs, There are changes caused by a mutation in a nucleotide in the Dena sequence. Mononucleotide polymorphisms are the most common type of genetic variation. Some of these changes have little or no effect on cells, while others cause significant changes in the expression of cell genes that can lead to disease or resistance to certain diseases. Because of the importance of these changes and their effect on cell function, the relationships between these changes are also important. Over the past decade, thousands of single disease-related mononucleotide polymorphisms have been identified in genome-related studies. Studies in this field have shown that the expression of...
Code- division multiple- access techniques in optical fiber networks, part III: optical and gate receiver structure using generalized optical orthogonal codes, Article IEEE Transactions on Communication ; 2006, Vol.54, No.8, PP. 1457-1468 ; Salehi, J. A ; Sharif University Of Technology
In this paper, we present a deep insight into the behavior of optical code-division multiple-access (OCDMA) systems based on an incoherent, intensity encoding/decoding technique using a well-known class of codes, namely, optical orthogonal codes (OOCs). As opposed to parts I and II of this paper, where OOCs with cross-correlation lambda=1 were considered, we consider generalized OOCs with 1leslambdalesw, where w is the weight of the corresponding codes. To enhance the performance of such systems, we propose the use of an optical and logic gate receiver, which, in an ideal case, e.g., in the absence of any noise source, except the optical multiple-access interference, is optimum. Using some...
Two statistical methods for resolving healthy individuals and those with congestive heart failure based on extended self-similarity and a recursive method, Article Journal of Biological Physics ; Volume 32, Issue 6 , 2006 , Pages 489-495 ; 00920606 (ISSN) ; Livari, M. A ; Kaviani, K ; Rahimi Tabar , M. R ; Sharif University of Technology
In this paper we introduce two methods for measuring irregularities in human heartbeat time series (HHTS). First we consider the multi-fractal structure of HHTS to distinguish healthy individuals and from those with congestive heart failure. In this way we modify the Extended Self-Similarity (ESS) method and apply it to HHTS. Our second approach is based on the recursive method, which we use to predict the duration of the next heartbeat by considering a few previous ones. We use standard physiological data and show that these approaches lead to very satisfactory methods to resolve the healthy and CHF individuals. These methods can be used potentially in portable electronic heart alarm...
Article International Conference on Communications (ICC2001), Helsinki, 11 June 2000 through 14 June 2000 ; Volume 5 , 2001 , Pages 1476-1480 ; 05361486 (ISSN) ; Khalaj, B. H ; Sharif University of Technology
Orthogonal frequency division multiplexing (OFDM) has a large peak to mean envelope power ratio (PMEPR), which can result in significant signal distortion in presence of nonlinear amplifiers. In this paper, we will show that peak of the continuous envelope of OFDM signal can be bounded by maximum of corresponding oversampled sequence. This fact is then used as the corner stone of our study in two parts. In the first part, statistical analysis is used to find probability upper bound for complementary cumulative distribution function of PMEPR. It is also proven that for large number of subcarriers, only one redundant bit is necessary to limit PMEPR within %10 of its maximum value. In the...
M.Sc. Thesis Sharif University of Technology ; Farahmand, Farzam ; Parnianpour, Mohammad
Knee pain and injuries are very common in athletes. Anterior cruciate ligament (ACL) injury is one of the most important reason of knee acute and chronic pains. As ACL plays a significant role in knee stability and due to amount of reported ACL related injuries, much effort has been placed on finding proper and on time diagnosis and treatment of these injuries. Arthrometric methods are the most non-invasive reliable diagnosis option; however they are not fully capable of separating partial injuries from intact joint. This weakness can be investigated by quantifying the tests using computer simulations; so far few studies have been conducted toward this goal. In this study a two dimensional...
M.Sc. Thesis Sharif University of Technology ; Hossein Farrahi, Gholam ; Faghidian, Ali
Residual stresses are stress fields that exist in the absence of any external loads. All mechanical processes can cause deformation that may lead to residual stresses. It is well established that virtually no material, no component and no structure of technical importance exists free of residual stresses. However, in practice, the knowledge of the true distribution of exiting residual stress is rare. The residual stress fields are very challenging to evaluate, independent of the measurement techniques. The important aspect about the residual stress determination is that often true distribution is unknown in the engineering specimen. A simple and non-destructive method to measure residual...
M.Sc. Thesis Sharif University of Technology ; Sarvari, Reza
Developing to the sub-micron dimentions reduces the size of integrated circuits, so interconnects and a variations in their characteristics has more effects on circuit performance. Worst case study is the most common method in these systems, but in many cases interconnect lines are independent from eachother. Analysis state that worst case is out of the distribution in many cases (with zero possibility) and result in a pessimistic design. Statistical analysis should replace worst case analysis in multi varient systems. In this titile, statistical analysis will be used to investigate performance of interconnects in new technology. Maximum variation in interconnect parameters are considered...
M.Sc. Thesis Sharif University of Technology ; Goudarzi, Maziar
Process Variation is seen as statistical variations in leakage current and delay of transistors in nano-scale technologies. The amount of process variations increase as the size of transistors decrease by technology scaling such that those effects can be seen in frequency of MPSoC (Multi-Processor System-on-Chip) cores and their leakage power deviation. These variations cause the tasks duration and power consumption fluctuate in different processors in an MPSoC instance. Consequently, some chip instances of the same MPSoC may consume more time and power than their considered limitations. Hence considering the process variation is necessary and required for MPSoC optimization at different...
M.Sc. Thesis Sharif University of Technology ; Nourani, Amir
Auxetic materials have a negative Poisson ratio (NPR), which is their most distinguishable characteristic as compared to regular materials. Test specimens were made of conventional polyurethane (PU) foams according to ASTM ; then, with a thermo-mechanical process, the foam was converted to auxetic PU foam. The reproducibility of specimens' fabrication was checked with CoV= for the final foam thickness. With regard to the fact that changing loading conditions can vary Poisson's ratio, in this study, the variations occurred in Poisson's ratio due to changing loading conditions are investigated. The applied strain and strain rate were altered in experiments and statistical analysis was...
Equilibrium sorption of crude oil by expanded perlite using different adsorption isotherms at 298.15 k, Article International Journal of Environmental Science and Technology ; Volume 7, Issue 3 , June , 2010 , Pages 591-598 ; 17351472 (ISSN) ; Taghikhani, V ; Safekordi, A. A ; Bastani, D ; Sharif University of Technology
During the past decades, a significant increase occurred in accidental oil spill in the aquatic environments. In this regard, oil spill in Marine freshwater is still considered as a major environmental hazard. In this research, the experimental data on the sorption capacity of expanded perlite to crude oil were correlated with the equilibrium isotherm of Langmuir, Freudlich, Tempkin and the three parameter Redlich-Peterson isotherms. The results obtained from each specified isotherms were compared and accuracy of the models were favorably discussed. Accuracy of each model using the error function were evaluated. Moreover, the effect of type of objective function on the final results was...
Scour hole depth prediction around pile groups: review, comparison of existing methods, and proposition of a new approach, Article Natural Hazards ; Volume 88, Issue 2 , 2017 , Pages 977-1001 ; 0921030X (ISSN) ; Beheshti, A. A ; Ataie Ashtiani, B ; Sharif University of Technology
A dataset of 365 laboratory tests for scour hole depth (SHD) around pile groups (PGs) under unidirectional aligned flow is compiled, and the performances of the existing equations are comparatively evaluated on the dataset using several statistical indices. A formulation based on a correction of HEC-18 equation provides the best estimate with a correlation factor of 0.58. The test durations of the considered data ranged between 4 and 389 h. A time factor (Kt) is proposed to take into account the temporal variation of the SHD around different PGs. Among the datasets, 51 long-duration experiments are scrutinized to show the temporal variation of scour depth toward equilibrium state. The time...
Article Journal of Seismology ; Volume 22, Issue 5 , 2018 , Pages 1249-1261 ; 13834649 (ISSN) ; Bakhshi, A ; Sharif University of Technology
Springer Netherlands 2018
The present research focuses on the statistical evaluation of Iranian plateau aftershocks from an engineering perspective and presents probabilistic models applicable for generating random earthquake scenarios. Accordingly, a comprehensive earthquake data catalog including the period from 1964 to 2016 is prepared. Data are declustered into 37 separate mainshock-aftershock sequences by considering the completeness moment magnitude of the database. The well-known modified Omori occurrence rate formula is adopted to determine the recurrence time of the events, considering the effect of secondary aftershocks. In addition to computing the probability density functions of the parameters of the...
Article Scientia Iranica ; Volume 13, Issue 1 , 2006 , Pages 50-59 ; 10263098 (ISSN) ; Akhavan Niaki, S. T ; Sharif University of Technology
Sharif University of Technology 2006
In this paper, two methods to solve multi-response statistical problems are presented. In these methods, desirability function, genetic algorithm and simulation methodology are applied. The desirability function is responsible for modeling the multi-response statistical problem, the genetic algorithm tries to optimize the model and, finally, the simulation approach generates the required input data from a simulated system. The methods differ from each other in controlling the randomness of the problem. In the first method, replications control this randomness, while, in the second method, the randomness is controlled by a statistical test. Furthermore, these methods are compared by designed...
Estimating ground-level PM2.5 concentrations by developing and optimizing machine learning and statistical models using 3 km MODIS AODs: case study of Tehran, Iran, Article Journal of Environmental Health Science and Engineering ; Volume 19, Issue 1 , 2021 ; 2052336X (ISSN) ; Arhami, M ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH 2021
Purpose: In this study we aimed to develop an optimized prediction model to estimate a fine-resolution grid of ground-level PM2.5 levels over Tehran. Using remote sensing data to obtain fine-resolution grids of particulate levels in highly polluted environments in areas such as Middle East with the abundance of brightly reflecting deserts is challenging. Methods: Different prediction models implementing 3 km AOD products from the MODIS collection 6 and various effective parameters were used to obtain a reliable model to estimate ground-level PM2.5 concentrations. In this regards, the linear mixed effect model (LME), multi-variable linear regression model (MLR), Gaussian process model (GPM),...