فیلترها/جستجو در نتایج    

فیلترها

سال

بانک‌ها




گروه تخصصی











متن کامل


اطلاعات دوره: 
  • سال: 

    1401
  • دوره: 

    52
  • شماره: 

    3
  • صفحات: 

    205-215
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    136
  • دانلود: 

    23
چکیده: 

Distance-based clustering methods categorize samples by optimizing a global criterion, finding ellipsoid clusters with roughly equal sizes. In contrast, density-based clustering techniques form clusters with arbitrary shapes and sizes by optimizing a local criterion. Most of these methods have several hyper-parameters, and their performance is highly dependent on the hyper-parameter setup. Recently, a Gaussian Density Distance (GDD) approach was proposed to optimize local criteria in terms of distance and density properties of samples. GDD can find clusters with different shapes and sizes without any free parameters. However, it may fail to discover the appropriate clusters due to the interfering of clustered samples in estimating the density and distance properties of remaining unclustered samples. Here, we introduce Adaptive GDD (AGDD), which eliminates the inappropriate effect of clustered samples by adaptively updating the parameters during clustering. It is stable and can identify clusters with various shapes, sizes, and densities without adding extra parameters. The distance metrics calculating the dissimilarity between samples can affect the clustering performance. The effect of different distance measurements is also analyzed on the method. The experimental results conducted on several well-known datasets show the effectiveness of the proposed AGDD method compared to the other well-known clustering methods.

شاخص‌های تعامل:   مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

بازدید 136

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesدانلود 23 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesاستناد 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesمرجع 0
نویسندگان: 

RAHIMZADEH MITRA | KAVEHIE BEHROOZ

اطلاعات دوره: 
  • سال: 

    2016
  • دوره: 

    2
  • شماره: 

    2
  • صفحات: 

    68-75
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    247
  • دانلود: 

    0
چکیده: 

Background & Aim: In the survival data with Long-term survivors the event has not occurred for all the patients despite long-term follow-up, so the survival time for a certain percent is censored at the end of the study. Mixture cure model was introduced by Boag, 1949 for reaching a more efficient analysis of this set of data. Because of some disadvantages of this model non-mixture cure model was introduced by Chen, 1999, which became well-known promotion time cure model. This model was based on the latent variable distribution of N. Non mixture cure models has obtained much attention after the introduction of the latent activating Scheme of Cooner, 2007, in recent decades, and diverse distributions have been introduced for latent variable.Methods & Materials: In this article, generalized Poisson-inverse Gaussian distribution (GPIG) will be presented for the latent variable of N, and the novel model which is obtained will be utilized in analyzing long-term survival data caused by skin cancer. To estimate the model parameters with Bayesian approach, numerical methods of Monte Carlo Markov chain will be applied. The comparison drawn between the models is on the basis of deviance information criteria (DIC). The model with the least DIC will be selected as the best model.Results: The introduced model with GPIG, with deviation criterion of 411.775, had best fitness than Poisson and Poisson-inverse Gaussian distribution with deviation criterion of 426.243 and 414.673, respectively.Conclusion: In the analyzing long-term survivors, to overcome high skewness and over dispersion using distributions that consist of parameters to estimate these statistics may improve the fitness of model. Using distributions which are converted to simpler distributions in special occasions, can be applied as a criterion for comparing other models.

شاخص‌های تعامل:   مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

بازدید 247

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesدانلود 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesاستناد 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesمرجع 0
اطلاعات دوره: 
  • سال: 

    2024
  • دوره: 

    13
  • شماره: 

    2
  • صفحات: 

    13-32
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    12
  • دانلود: 

    0
چکیده: 

Recently, Alizadeh and Shafaei (2023) introduced some estimators for varentropy of a continuous random variable. The present article applies these estimators and construct some tests of fit for Inverse Gaussian distribution. Percentage points and type I error of the new tests are obtained and then power values of the proposed tests against various alternatives are computed. The results of a simulation study show that the tests have a good performance in terms of power. Finally, a real data set is used to illustrate the application of the proposed tests.

شاخص‌های تعامل:   مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

بازدید 12

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesدانلود 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesاستناد 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesمرجع 0
مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
نویسندگان: 

اطلاعات دوره: 
  • سال: 

    0
  • دوره: 

    8
  • شماره: 

    4
  • صفحات: 

    412-429
تعامل: 
  • استنادات: 

    1
  • بازدید: 

    205
  • دانلود: 

    0
کلیدواژه: 
چکیده: 

شاخص‌های تعامل:   مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

بازدید 205

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesدانلود 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesاستناد 1 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesمرجع 0
اطلاعات دوره: 
  • سال: 

    2024
  • دوره: 

    13
  • شماره: 

    1
  • صفحات: 

    71-84
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    15
  • دانلود: 

    0
چکیده: 

The Inverse Gaussian (IG) distribution is widely used to model positively skewed data. In this article, we examine goodness of fit tests for the Inverse Gaussian distribution based on the empirical distribution function. In order to compute the test statistics, parameters of the Inverse Gaussian distribution are estimated by maximum likelihood estimators (MLEs), which are simple explicit estimators. Critical points and the actual sizes of the tests are obtained by Monte Carlo simulation. Through a simulation study, power values of the tests are compared with each other. Finally, an illustrative example is presented and analyzed.

شاخص‌های تعامل:   مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

بازدید 15

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesدانلود 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesاستناد 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesمرجع 0
نویسندگان: 

SEDGHI TOHID | SHAFEI SHAHIN

اطلاعات دوره: 
  • سال: 

    2013
  • دوره: 

    2
  • شماره: 

    7
  • صفحات: 

    16-23
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    285
  • دانلود: 

    0
کلیدواژه: 
چکیده: 

We have examined the convergence behavior of the LSCMA in some simple environments. Algorithms such as Multi Target CMA, Multistage CMA, and Iterative Least Squares with Projection can be used for this purpose. The results presented here can form a basis for analysis of these multi-signal extraction techniques. Clearly, the variance and distribution of output SINR obtained with the LSCMA is also an important area for investigation. We finally comment on the hard-limit non-linearity. For high SIR, the hard-limiter is the optimal non-linearity when the desired signal has a constant envelope. However, at low SIR other non-linearities can yield greater SIR gain. Thus, it is possible that non-linear functions other than the hard-limit can be used to develop blind adaptive algorithms, which converge faster for low initial SINR.

شاخص‌های تعامل:   مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

بازدید 285

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesدانلود 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesاستناد 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesمرجع 0
مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
اطلاعات دوره: 
  • سال: 

    1399
  • دوره: 

    17
  • شماره: 

    1 (پیاپی 43)
  • صفحات: 

    61-77
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    855
  • دانلود: 

    271
چکیده: 

آنالیز تصاویر چهره انسان به دلیل کاربردهای فراوان آن در جراحی های چهره دارای اهمیت زیادی است. وجود ابزارهای سخت افزاری و نرم افزاری در زمینه آنالیز جراحی های چهره کمک شایانی را می تواند به متخصصان جراحی های چهره در قبل و بعد عمل جراحی داشته باشد. در این راستا، نیاز به دانستن آنتروپومتری های موردنظر در آنالیز جراحی های چهره و استخراج ویژگی هستیم. جهت استخراج کانتور نمای جانبی چهره و ناحیه گوش برای آنالیز در جراحی های رینوپلاستی و اتوپلاستی از مدل کانتور فعال مبتنی بر توزیع گوسین مکانی (مدل LGDF) استفاده شده است. در جراحی های اشاره شده، ابتدا کانتور ناحیه موردنظر را با استفاده از مدل LGDF استخراج کرده و در مرحله بعد با اعمال گوشه یاب هریس نقاط شاخص موردنظر جهت آنالیز آنتروپومتری موردنظر آشکارسازی شده اند. دقت الگوریتم پیشنهادی در جراحی رینوپلاستی برای پایگاه داده دانشگاه سهند بالای %90 بوده و در جراحی اتوپلاستی دقت الگوریتم پیشنهادی برای پایگاه داده AMI جهت اندازه گیری طول، عرض و زاویه خارجی گوش به ترتیب 432/96%، 423/97% و 546/85% هستند.

شاخص‌های تعامل:   مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

بازدید 855

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesدانلود 271 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesاستناد 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesمرجع 0
اطلاعات دوره: 
  • سال: 

    2025
  • دوره: 

    14
  • شماره: 

    1
  • صفحات: 

    1-22
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    7
  • دانلود: 

    0
چکیده: 

The Inverse Gaussian distribution finds application in various fields, such as finance, survival analysis, psychology, engineering, physics, and quality control. Its capability to model skewed distributions and non-constant hazard rates makes it a valuable tool for understanding a wide range of phenomena. In this paper, we present a goodness-of-fit test specifically designed for the Inverse Gaussian distribution. Our test uses an estimate of the Gini index, a statistical measure of inequality. We provide comprehensive details on the exact and asymptotic distributions of the newly developed test statistic. To facilitate the application of the test, we estimate the unknown parameters of the Inverse Gaussian distribution using maximum likelihood estimators. Monte Carlo methods are utilized to determine the critical points and assess the actual sizes of the test. A power comparison study is conducted to evaluate the performance of existing tests. Comparing its powers with those of other tests, we demonstrate that the Gini index-based test performs favorably. Finally, we present a real data analysis for illustrative purposes.

شاخص‌های تعامل:   مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

بازدید 7

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesدانلود 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesاستناد 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesمرجع 0
نویسندگان: 

FALLAH NEZHAD MOHAMMAD SABER | RASTI BATUL

اطلاعات دوره: 
  • سال: 

    2015
  • دوره: 

    8
  • شماره: 

    18
  • صفحات: 

    1-12
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    333
  • دانلود: 

    0
چکیده: 

In this paper, a Bayesian approach is proposed for shift point detection in an inverse Gaussian distribution. In this study, the mean parameter of inverse Gaussian distribution is assumed to be constant and shift points in shape parameter is considered. First the posterior distribution of shape parameter is obtained. Then the Bayes estimators are derived under a class of priors and using various loss functions. We assumed uniform, Jeffreys, exponential, gamma and chi square distributions as prior distributions. The squared error loss function (SELF), entropy loss function (ELF), linex loss function (LLF) and precautionary loss function (PLF), are used as loss functions. We attempt to find out the best estimator for shift point under various priors and loss functions. The proposed Bayesian approach can be adapted to any similar problem for shift point detection. Simulation studies were done to investigate the performance of different loss functions. The results of simulation study denote that the Jeffrey prior distribution under PLF has the most accurate estimation of shift point for sample size of 20, and the gamma prior distribution under SELF has the most accurate estimation of shift point for sample size of 50.

شاخص‌های تعامل:   مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

بازدید 333

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesدانلود 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesاستناد 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesمرجع 2
نویسنده: 

PANAHI HANIEH | JAFARI FATEMEH

اطلاعات دوره: 
  • سال: 

    2016
  • دوره: 

    4
تعامل: 
  • بازدید: 

    316
  • 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.

شاخص‌های تعامل:   مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

بازدید 316

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesدانلود 0
litScript
telegram sharing button
whatsapp sharing button
linkedin sharing button
twitter sharing button
email sharing button
email sharing button
email sharing button
sharethis sharing button