DSpace Collection: 2004 Volume 16
http://hdl.handle.net/10525/2110
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Quality Improvement through Experiments with Mixtures
http://hdl.handle.net/10525/2330
Title: Quality Improvement through Experiments with Mixtures<br/><br/>Authors: Vuchkov, I. N.<br/><br/>Abstract: Mixture experiments are typical for chemical, food, metallurgical and other industries. The aim of these experiments is to find optimal component proportions that provide desired values of some product performance characteristics.Comparing Several Methods of Discriminant Analysis on the Case of Wine Data
http://hdl.handle.net/10525/2329
Title: Comparing Several Methods of Discriminant Analysis on the Case of Wine Data<br/><br/>Authors: Vandev, Dimitar; Römisch, Ute<br/><br/>Abstract: The main problem of this European wine project (WINE-DB) is the identification of the geographical origin based on chemico-analytical measurements. At first the type of data collected in preparation of this project will be analysed. Then different procedures of Discriminant analysis are described. Our special attention will be focused to some new techniques as Support Vector Mashines (also known as Kernel Mashines) - procedures from the field of Mashine Learning. We test traditional techniques of Linear, Quadratic and Nonparametric Discriminant Analysis as well as the Support Vector Mashines on the base of our data and comment the results.<br/><br/>Description: 2000 Mathematics Subject Classification: 62H30, 62J20, 62P12, 68T99Interactive Stepwise Discriminant Analysis in Matlab
http://hdl.handle.net/10525/2328
Title: Interactive Stepwise Discriminant Analysis in Matlab<br/><br/>Authors: Vandev, D. L.<br/><br/>Abstract: The program ldagui.m is an interactive tool for linear and quadratic discriminant analysis. The reason for developing such a tool consists in failing of conformity with conventional statistical programs in following aspects: treating of missing data; interaction with the user; testing the quality of obtained models.<br/><br/>Description: 2000 Mathematics Subject Classification: 62-04, 62H30, 62J20Classification of Chenopodium Genus Populations and Species Based on Continuous and Categorical Variables
http://hdl.handle.net/10525/2327
Title: Classification of Chenopodium Genus Populations and Species Based on Continuous and Categorical Variables<br/><br/>Authors: Tsvetanova, Yanka; Grozeva, Neli<br/><br/>Abstract: The estimation of statistical distance between populations arises in many multivariate analysis techniques. Whereas distance measures for continuous data are well developed, those for mixed discrete and continuous data are less so because of the lack of a standard model for such data. Such mixture of variables arise frequently in the field of medicine, biometry, psychology, econometrics and only comparatively few models have been developed for evaluating distance between populations. The subject of our study were data in the field of botany. The aim of the presented investigation was to apply methods for analysis of dissimilarity between 44 populations of 13 species of Ghenopodium genus,presented by 15 variables - 10 continuous and 5 categorical. The previously developed by another authors distance measures between populations presented by mixed attributes turned out not appropriate for the available data of Chenopodium genus. F or that reason a specific distance measures were applied. The matrices with distances between populations and species were used as input for Hierarchical Cluster Analysis to explore the taxonomic structure of the Chenopodium genus.<br/><br/>Description: 2000 Mathematics Subject Classification: 62P10, 62H30Multiple Dipole Source Models for Scalp-Recorded Event-Related Potentials: Example from Complex Visual Processing in the Human Brain
http://hdl.handle.net/10525/2326
Title: Multiple Dipole Source Models for Scalp-Recorded Event-Related Potentials: Example from Complex Visual Processing in the Human Brain<br/><br/>Authors: Tarkka, Ina M.<br/><br/>Abstract: Electrical activity of the human brain can be recorded on the scalp. One of the advantages of the electrical recordings is the high temporal resolution by which e.g. cognitive processes can be followed from millisecond to millisecond. It is not uncommon to record simultaneously 128 electrode sites with high sampling rate and thus advanced mathematical and statistical methodsare needed to sufficiently process the obtained data. Here an example of the analysis of the data recorded during a complex visual processing task is presented. Using advanced methods large amounts of data can be reduced and new information of the function of the human brain can be investigated.<br/><br/>Description: 2000 Mathematics Subject Classification: 62P10, 92C20Simulation and Robust Modifications of Estimates in Branching Processes
http://hdl.handle.net/10525/2325
Title: Simulation and Robust Modifications of Estimates in Branching Processes<br/><br/>Authors: Stoimenova, V.; Atanasov, D.; Yanev, N.<br/><br/>Abstract: This study is focused on the comparison and modification of different estimates arising in the branching processes. Simulations of models with or without migration are put through. Due to the complexity of the computations the algorithms are designed with the language of technical computing MATLAB. Using the simulations, estimates of the o spring mean of the generated processes are calculated. It is well known in the literature that under certain conditions the asymptotic distribution of the estimates is proved to be normal. Using the asymptotic normality a modified method of maximum likelihood is proposed. The aim is to obtain trimmed maximum likelihood estimates based on several sample paths with the same number of generations. Thus in a natural way the observations, inconsistent with the aprior information about the asymptotic normality are excluded from the model. The computation of the standard error allows the comparison of different types of estimates.Application of Two-Phase Regression to Geotechnical Data
http://hdl.handle.net/10525/2324
Title: Application of Two-Phase Regression to Geotechnical Data<br/><br/>Authors: Stoimenova, E.; Datcheva, M.; Schanz, T.<br/><br/>Abstract: A method for estimating a transition parameter in two-phase regressionis described. The two phases are fitted and simultaneously the transitionpoint is estimated. Practical application of the method is demonstrated onthe data for determining soil hydraulic properties.<br/><br/>Description: 2000 Mathematics Subject Classification: 62F10, 62J05, 62P30Total Progeny in a Subcritical Branching Process with two Types of Immigration
http://hdl.handle.net/10525/2323
Title: Total Progeny in a Subcritical Branching Process with two Types of Immigration<br/><br/>Authors: Slavtchova-Bojkova, M.; Becker-Kern, P.; Mitov, K. V.<br/><br/>Abstract: We consider subcritical Bellman-Harris branching processes with two types of immigration - one appears whenever the process hits zero state and an other one is in accordance of an independent renewal process. The law of large numbers (LLN) for the total progeny of these processes and Anscombe's type central limit theorem (CLT) for the total number of particles in the cycles completely finished by the moment t are obtained.<br/><br/>Description: 2000 Mathematics Subject Classification: 60J80, 60F05A Statistical Approach for Multilingual Document Clustering and Topic Extraction from Clusters
http://hdl.handle.net/10525/2322
Title: A Statistical Approach for Multilingual Document Clustering and Topic Extraction from Clusters<br/><br/>Authors: Silva, Joaquim; Mexia, Joao; Coelho, Carlos A.; Lopes, Gabriel<br/><br/>Abstract: This paper describes a statistics-based methodology for document unsupervised clustering and cluster topics extraction.For this purpose, multiword lexical units (MWUs) of any length are automatically extracted from corpora using the LiPXtractor extractor - a language independent statistics-based tool. The MWUs are taken as base-features to describe documents. These features are transformed and a document similarity matrix is constructed. From this matrix, a reduced set of features is selected using an approachbased on Principal Component Analysis. Then, using the Model Based Clustering Analysis software, it is possible to obtain the best number of clusters. Precision and Recall for document-cluster assignment range above 90%. Most important MWUs are extracted from each cluster and taken as document cluster topics. Results on new document classification will just be mentioned.<br/><br/>Description: 2000 Mathematics Subject Classification: 62H30On the Equality of Sharp and Germ - Fields for Gaussian Processes and Fields
http://hdl.handle.net/10525/2321
Title: On the Equality of Sharp and Germ - Fields for Gaussian Processes and Fields<br/><br/>Authors: Robeva, Raina S.; Pitt, Loren D.<br/><br/>Abstract: We investigate the relationship between the sigma-field and the infinitesimal or germ sigma-field.<br/><br/>Description: 2000 Mathematics Subject Classification: 60G15, 60G60; secondary 31B15, 31B25, 60H15A Stochastic Approach for Finding of Semantically Related Words
http://hdl.handle.net/10525/2320
Title: A Stochastic Approach for Finding of Semantically Related Words<br/><br/>Authors: Noncheva, Veska; Gamallo, Pablo; Agustini, Alexandre; Lopes, Gabriel<br/><br/>Abstract: Semantically related words are modelled as words having the same probability distribution on the set of syntactic contexts occurring in text corpora. A learning algorithm for finding of clusters of semantically related words is developed. In that algorithm Chi-Squared statistics is used as a performance measure.<br/><br/>Description: 2000 Mathematics Subject Classification: 62P99, 68T50An Estimate of the Probability Pr(X<Y)
http://hdl.handle.net/10525/2319
Title: An Estimate of the Probability Pr(X<Y)<br/><br/>Authors: Nadarajah, Saralees; Mitov, Georgi K.; Mitov, Kosto V.<br/><br/>Abstract: In the area of stress-strength models there has been a large amount of work as regards estimation of the probability R = Pr(X<Y) when X and Y are independent random variables belonging to the same univariate family of distributions. In this paper we propose an estimate of this quantity based on a simple property of the uniform distribution. We illustrate the use of the estimate with bootstrap confidence intervals for four commonly known distributions (normal, exponential, gamma and beta).<br/><br/>Description: 2000 Mathematics Subject Classification: 33C90, 62E99Discrete Time Bisexual Branching Processes in Varying Environments
http://hdl.handle.net/10525/2318
Title: Discrete Time Bisexual Branching Processes in Varying Environments<br/><br/>Authors: Molina, Manuel; Mota, Manuel; Ramos, Alfonso<br/><br/>Abstract: This paper concerns with the bisexual branching process in varying environments introduced in [16]. For such a model a survey of results is provided. Previously, brief descriptions about the bisexual branching process and some bisexual models derived from it are given.<br/><br/>Description: 2000 Mathematics Subject Classification: 60J80Limiting Distributions for Lifetimes in Alternating Renewal Processes
http://hdl.handle.net/10525/2317
Title: Limiting Distributions for Lifetimes in Alternating Renewal Processes<br/><br/>Authors: Mitov, Kosto V.; Yanev, Nikolay M.<br/><br/>Abstract: The spent life time and the residual life time are well investigated characteristics of an ordinary renewal process. In the present paper a generalization of these lifetime processes associated with an alternating renewal process is considered. Limiting distributions are presented in the case of in finite mean renewal periods.<br/><br/>Description: 2000 Mathematics Subject Classification: 60K05A Modified Model of Risk Business
http://hdl.handle.net/10525/2316
Title: A Modified Model of Risk Business<br/><br/>Authors: Minkova, Leda D.<br/><br/>Abstract: We consider the risk model in which the claim counting process {N(t)} is a modified stationary renewal process. {N(t)} is governed by a sequence of independent and identically distributed inter-occurrence times with a common exponential distribution function with mass at zero equal to ρ>0. The model is called a Polya-Aeppli risk model. The Cramer-Lundbergapproximation and the martingale approach of the model are given.<br/><br/>Description: 2000 Mathematics Subject Classification: 60K10, 62P05Gait Measurements and Motor Recovery after Stroke
http://hdl.handle.net/10525/2315
Title: Gait Measurements and Motor Recovery after Stroke<br/><br/>Authors: Mateev, Plamen S.; Tarkka, Ina M.; Titianova, Ekaterina B.<br/><br/>Abstract: Gait analysis is one of the methods used for estimation of the degree of restoration of motor recovery after stroke. The purpose of the present study was to examine the diagnostic value of the footprint parameters and their relationship with the functional ambulation profile (FAP) scores provided automatically by the pressure sensor walkway system for gait examination. The patterns of walking were studied in a group of 23 patients with chronic unilateral stroke and 72 healthy subjects. Among the measured gait variables the peak times of the footprints were found as most informative parameters. Their predictive value was compared with some other gait indicatorsfor motor recovery after stroke.<br/><br/>Description: 2000 Mathematics Subject Classification: 62P10, 92C20