نتایج جستجو برای: روش lda

تعداد نتایج: 375270  

Journal: :IEEE Trans. Pattern Anal. Mach. Intell. 2001
Marco Loog Robert P. W. Duin Reinhold Häb-Umbach

ÐWe derive a class of computationally inexpensive linear dimension reduction criteria by introducing a weighted variant of the well-known K-class Fisher criterion associated with linear discriminant analysis (LDA). It can be seen that LDA weights contributions of individual class pairs according to the Euclidian distance of the respective class means. We generalize upon LDA by introducing a dif...

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه شهرکرد - دانشکده علوم پایه 1391

نظریه تابعی چگالی یکی از روش های بررسی دستگاه های بس ذره ای است. معروف ترین تقریب هایی که برای جمله تبادلی- همبستگی در این نظریه مطرح است، تقریب چگالی موضعی (lda) و تقریب شیب تعمیم یافته (gga) هستند. اما این دو تقریب برای دستگاه های با الکترون جایگزیده f و d جواب های دقیقی بدست نمی دهند. پس باید سراغ تقریب بهتری به نام lda+u رفت که شکل تصحیح شده تقریب lda است. پارامتر هابارد در این تقریب را می ...

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه فردوسی مشهد - دانشکده فنی 1393

مشکلات موجود در طبقه بند جداساز خطی (lda) از قبیل حساسیت به داده های پرت، فرض اولیه تک مدی بودن توزیع کلاس ها و معکوس ناپذیری ماتریس پراکندگی داخل کلاس انگیزه ای برای ارائه طبقه بندی جدید در این طرح شد. البته در تحقیقات گذشته راهکارهایی همچون استفاده از گراف همسایگی، استفاده از نرم یک و وزنی نمودن طبقه بند برای کاهش حساسیت به داده های پرت، روش هایی مانند کاهش ابعاد، بکارگیری پارامتر تنظیم ساز و...

2009
Viet Ha-Thuc Padmini Srinivasan

Relevance-based language models operate by estimating the probabilities of observing words in documents relevant (or pseudo relevant) to a topic. However, these models assume that if a document is relevant to a topic, then all tokens in the document are relevant to that topic. This could limit model robustness and effectiveness. In this study, we propose a Latent Dirichlet relevance model, whic...

2014
Annalisa De Girolamo Salvatore Cervellieri Angelo Visconti Michelangelo Pascale

Fourier-transform-near infrared (FT-NIR) spectroscopy has been used to develop quantitative and classification models for the prediction of deoxynivalenol (DON) levels in durum wheat samples. Partial least-squares (PLS) regression analysis was used to determine DON in wheat samples in the range of <50-16,000 µg/kg DON. The model displayed a large root mean square error of prediction value (1,97...

Journal: :The Journal of clinical endocrinology and metabolism 2017
Rose G Radin Lindsey A Sjaarda Neil J Perkins Robert M Silver Zhen Chen Laurie L Lesher Noya Galai Jean Wactawski-Wende Sunni L Mumford Enrique F Schisterman

Context Among women with a single, recent pregnancy loss, daily preconception low-dose aspirin (LDA) increased the live birth rate with no effect on pregnancy loss. Ovulation is a potential mechanism underlying this effect. Objective We estimated the effect of LDA on the per-cycle risk of anovulation among eumenorrheic women. Design Multicenter, randomized, double-blind, placebo-controlled ...

2015
Yuji Shimada Akihito Nagahara Mariko Hojo Daisuke Asaoka Hitoshi Sasaki Hiroya Ueyama Kenshi Matsumoto Sumio Watanabe

Background. We investigated the prevalence, symptoms, and QOL impact of esophageal (EI), gastric (GI), and duodenal mucosal injury (DI) individually between low-dose aspirin (LDA) users and nonusers to reveal the clinical features of LDA-related mucosal injury. Methods. Data were extracted from the records of subjects who underwent upper gastrointestinal endoscopy at our department between Apri...

Journal: :Pattern Recognition 2008
Jing-Hao Xue D. M. Titterington

For two-class discrimination, Ref. [1] claimed that, when covariance matrices of the two classes were unequal, a (class) unbalanced dataset had a negative effect on the performance of linear discriminant analysis (LDA). Through re-balancing 10 realworld datasets, Ref. [1] provided empirical evidence to support the claim using AUC (Area Under the receiver operating characteristic Curve) as the p...

2010
Mark Johnson

This paper establishes a connection between two apparently very different kinds of probabilistic models. Latent Dirichlet Allocation (LDA) models are used as “topic models” to produce a lowdimensional representation of documents, while Probabilistic Context-Free Grammars (PCFGs) define distributions over trees. The paper begins by showing that LDA topic models can be viewed as a special kind of...

2016
Qihua Liu

The hidden topic model of Chinese text, which possesses complicated semantics, is urgently needed, since China has occupied an increasingly significant role during the booming development of globalization over recent years. This paper details and elaborates the basic process of extracting latent Chinese topics by demonstrating a Chinese topic extraction schema based on Latent Dirichlet Allocati...

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