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نویسندگان: 

Parchami Abbas

اطلاعات دوره: 
  • سال: 

    2023
  • دوره: 

    12
  • شماره: 

    2
  • صفحات: 

    503-512
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    29
  • دانلود: 

    0
چکیده: 

The EM ALGORITHM is a powerful tool and generic useful device in a variety of problems for maximum likelihood estimation with incomplete data which usually appears in practice. Here, the term ``incomplete" means a general state and in different situations it can mean different meanings, such as lost data, open source data, censored observations, etc. This paper introduces an application of the EM ALGORITHM in which the meaning of ``incomplete" data is non-precise or fuzzy observations. The proposed approach in this paper for estimating an unknown parameter in the parametric statistical model by maximizing the likelihood function based on fuzzy observations. Meanwhile, this article presents a case study in the electronics industry, which is an extension of a well-known example used in introductions to the EM ALGORITHM and focuses on the applicability of the ALGORITHM in a fuzzy environment. This paper can be useful for graduate students to understand the subject in fuzzy environment and moreover to use the EM ALGORITHM in more complex examples.

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نویسندگان: 

ZIVKOVIC Z. | KROSE B.

اطلاعات دوره: 
  • سال: 

    2004
  • دوره: 

    -
  • شماره: 

    -
  • صفحات: 

    798-803
تعامل: 
  • استنادات: 

    1
  • بازدید: 

    112
  • دانلود: 

    0
کلیدواژه: 
چکیده: 

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بازدید 112

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عنوان: 
نویسندگان: 

اطلاعات دوره: 
  • سال: 

    1400
  • دوره: 

  • شماره: 

  • صفحات: 

    -
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    26
  • دانلود: 

    0
کلیدواژه: 
چکیده: 

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نویسندگان: 

Azad Mahsa | Sadough Seyed Mohammad Sajad

اطلاعات دوره: 
  • سال: 

    2018
  • دوره: 

    10
  • شماره: 

    1
  • صفحات: 

    62-69
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    190
  • دانلود: 

    0
چکیده: 

In Hierarchical Modulation (HM), the binary data is partitioned into a “ high-priority” (HP) and a “ lowpriority” (LP) bit stream that are separately and independently encoded before being mapped on non-uniformly spaced constellation points. Indeed, HM is a multi-level modulation scheme, proposed for enabling unequal error protection. The HP and LP streams vary in their susceptibility to noise. The basic HP signal is more robust, in other words, heavily protected against noise and interference, whereas the LP stream has much less robustness. In this paper, we propose an improved iterative receiver based on variational Bayesian expectation-maximization (VB-EM) scheme for semi-blind joint channel estimation and data detection based on bit-interleaved coded modulation (BICM), with the aim of improving the bit error rate (BER) of the noisy LP stream. Moreover, the proposed receiver allows us to reduce the pilot symbol overhead compared to the classical HM receivers based on pilot-assisted channel estimation.

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اطلاعات دوره: 
  • سال: 

    2011
  • دوره: 

    2
  • شماره: 

    3
  • صفحات: 

    2-7
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    401
  • دانلود: 

    0
چکیده: 

The relation between single nucleotide polymorphisms (SNPs) and some diseases has been concerned by many researchers. Also the missing SNPs are quite common in genetic association studies. Hence, this article investigates the relation between existing SNPs in DNMT1 of human chromosome 19 with colorectal cancer. This article aims is to presents an imputation METHOD for missing SNPs not at random. In this case-control study, 100 patients suffering from colorectal cancer consulting with the Research Institute for Gastroenterology and Liver Disease of Shahid Beheshti University of Medical Sciences were considered as the case group and 100 other patients consulting with the same research institute were considered as the control group and the genetic test was applied in order to identify the genotype of the 6 SNPs of the DNMT1 of chromosome 19 for all the patients under investigation. The obtained data were analyzed using logistic regression, then a fraction of the data was eliminated both at random and not at random and the imputation was done through the EM ALGORITHM and the logistic regression coefficients variation before and after the imputation was compared. The results of this study implied that in both METHODs, at random and not at random missing SNPs, the estimation of the logistic regression coefficients after the imputation through EM ALGORITHM has a greater correspondence to the results obtained from the complete data in comparison with the METHOD of eliminating the missing values.

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نشریه: 

Scientia Iranica

اطلاعات دوره: 
  • سال: 

    2019
  • دوره: 

    26
  • شماره: 

    1 (Transactions E: Industrial Engineering)
  • صفحات: 

    571-588
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    235
  • دانلود: 

    0
چکیده: 

Discrete Phase-Type (DPH) distributions have one property that is not shared by Continuous Phase-Type (CPH) distributions, i. e., representing a deterministic value as a DPH random variable. This property distinguishes the application of DPH in stochastic modeling of real-life problems, such as stochastic scheduling, in which service time random variables should be compared with a deadline that is usually a constant value. In this paper, we consider a restricted class of DPH distributions, called Mixed Shifted Negative Binomial (MSNB), and show its exibility in producing a wide range of variances as well as its adequacy in tting fat-tailed distributions. These properties render MSNB applicable to represent data on certain types of service time. Therefore, we adapt an Expectation-Maximization (EM) ALGORITHM to estimate the parameters of MSNB distributions that accurately t trace data. To present the applicability of the proposed ALGORITHM, we use it to t real operating room times and a set of benchmark traces generated from continuous distributions as case studies. Finally, we illustrate the e ciency of the proposed ALGORITHM by comparing its results with those of two existing ALGORITHMs in the literature. We conclude that our proposed ALGORITHM outperforms other DPH ALGORITHMs in tting trace data and distributions.

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مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
اطلاعات دوره: 
  • سال: 

    2004
  • دوره: 

    11
تعامل: 
  • بازدید: 

    187
  • دانلود: 

    0
چکیده: 

AUTOMATIC SEGMENTATION OF BRAIN TISSUES IS CRUCIAL TO MANY MEDICAL IMAGING APPLICATIONS. ACCURATE AND FAST BRAIN TISSUE SEGMENTATION IS NEEDED FOR MANY MEDICAL DIAGNOSTIC AND THERAPEUTIC PROCEDURES. WE USE A MULTI-RESOLUTION ANALYSIS AND A POWER TRANSFORM TO EXTEND THE WELL-KNOWN GAUSSIAN MIXTURE MODEL EXPECTATION MAXIMIZATION BASED ALGORITHM FOR SEGMENTATION OF WHITE MATTER, GRAY MATTER, AND CEREBROSPINAL FLUID FROM T1-WEIGHTED MAGNETIC RESONANCE IMAGES (MRI) OF THE BRAIN. EXPERIMENTAL RESULTS WITH NEAR 4000 SYNTHETIC AND REAL IMAGES ARE INCLUDED. THE RESULTS ILLUSTRATE THAT THE PROPOSED METHOD OUTPERFORMS SIX EXISTING METHODS.

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نویسندگان: 

AZIZI AFSANEH | SAYYAREH ABDOLREZA

اطلاعات دوره: 
  • سال: 

    2019
  • دوره: 

    18
  • شماره: 

    1
  • صفحات: 

    133-155
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    174
  • دانلود: 

    0
چکیده: 

In recent years, bivariate lifetime distributions are often used to model reli-ability and survival data. In this paper, we introduce a bivariate Burr III distribution, so that the marginals have Burr III distributions. It is observed that the joint probabil-ity density function, the joint cumulative distribution function and the joint survival distribution function can be expressed in compact forms. We suggest to use the ECM ALGORITHM to compute the maximum likelihood estimators of the unknown parame-ters. We report some simulation results and perform one data analysis for illustrative purposes.

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اطلاعات دوره: 
  • سال: 

    1398
  • دوره: 

    4
  • شماره: 

    2
  • صفحات: 

    201-210
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    830
  • دانلود: 

    416
چکیده: 

برآورد پارامتر توزیع های آماری از بحث های مهم استنباط آماری است. با توجه به کاربردهای توزیع لوماکس در تجارت، اقتصاد، علوم آماری، نظریه صف، مدل بندی ترافیکی اینترنت و غیره در این مقاله پارامتر­ های توزیع لوماکس تحت داده های سانسور نوع دوم با استفاده از الگوریتم EM و تقریب لیندلی برآورد می شوند. از آن جا که انتخاب توزیع های پیشین و توابع زیان، نقش مهمی در برآورد بیزی ایفا می کند. از این رو، برآورد بیزی با انتخاب توزیع پیشین مناسب تحت توابع زیان میانگین مربع خطا، لاینکس و آنتروپی ارائه می شود. از آن جاکه معادلات نرمال به دست آمده از روش های برآورد، توابع صریح از پارامترها نیستند، اقدام به برآورد پارامترها با استفاده از روش های خطا، از جمله الگوریتم و تقریب لیندلی خواهد شد. و در پایان با استفاده از ملاک میانگین توان دوم خطا، براوردگرها مقایسه و نتایج حاصل از شبیه سازی نشان می دهد که برآوردگر بیزی بهتر از برآورد بیشینه ی درست نمایی عمل می کند و با افزایش حجم نمونه در حالی که تعداد شکست ثابت است، دقت برآوردگر بیش تر می شود.

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نویسنده: 

PANAHI HANIEH | JAFARI FATEMEH

اطلاعات دوره: 
  • سال: 

    2016
  • دوره: 

    4
تعامل: 
  • بازدید: 

    317
  • دانلود: 

    0
چکیده: 

THE MOST IMPORTANT STEP IN FINANCIAL RISK IS TO FIND A GOOD MODEL FOR THE ANALYSES AND ESTIMATE THE RISK MEASURES. THE NORMAL INVERSE GAUSSIAN (NIG) DISTRIBUTION IS THE MOST USED TOOL FOR THE MODELING OF FINANCIAL DATA. THE NIG DISTRIBUTION IS ABLE TO MODEL SYMMETRIC AND ASYMMETRIC DISTRIBUTIONS WITH POSSIBLY LONG TAILS IN BOTH DIRECTIONS. MOREOVER, THE NIG DISTRIBUTION POSSESSES A NUMBER OF ATTRACTIVE THEORETICAL PROPERTIES, AMONG OTHERS ITS ANALYTICAL TRACTABILITY. MOREOVER CHOOSING THE BEST METHOD FOR ESTIMATING THE PARAMETERS OF DISTRIBUTION IS ONE OF THE IMPORTANT ASPECTS IN STATISTICAL VIEWPOINT. ONE STRENGTH OF OUR APPROACH IS THAT WE INTRODUCE AN EXPECTATION–MAXIMIZATION (EM) ALGORITHM TO COMPUTE THE MAXIMUM LIKELIHOOD ESTIMATES OF PARAMETERS WHICH INVOLVES TWO STEPS. A DATA SET OF THE TEHRAN STOCK EXCHANGE INDEX IS USED TO ILLUSTRATE THE PROPOSED RESULTS. WE ALSO APPLY THE NIG DISTRIBUTION TO EVALUATION OF THE TEHRAN STOCK EXCHANGE DATA IN VALUE-AT-RISK FRAMEWORK.

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