Pliska Studia Mathematica Bulgarica

Volume 20, 2011



Many Facet, Common Latent Trait Polytomous IRT Model and Em Algorithm
Dimitar Atanasov

2000 Mathematics Subject Classification: 91E45
Key words: item response theory, many facets, EM algorithm.

Densities With Spherical Level Sets in the Gauss-Exponential Domain
Guus Balkema

2000 Mathematics Subject Classification: 60F05, 60B10
Key words: Gauus-exponential, high risk scenario, hyperbolic metric, level set, spherical, unimodal.

About the Oral Health of Bulgarian Population over 20 Years Old
Nina Daskalova
Boyko Bonev

2000 Mathematics Subject Classification: 62P10, 62J12.
Key words: epidemiological research, caries, statistical data analysis, generalized linear models, logistic regression.

Em Estimation of the Offspring Distribution in Mutitype Branching Processes - a Model in Cell Kinetics
Nina Daskalova

2000 Mathematics Subject Classification: 60J80, 60J85, 62P10, 92D25.
Key words: multitype branching processes, offspring distribution, maximum likelihood estimation, expectation maximization, stochastic context-free grammars, inside-outside algorithm, cell kinetics modelling.

Single-Server Queueing System with Markov-Modulated Arrivals and Service Times
Mitko Dimitrov

2000 Mathematics Subject Classification: 60K25.
Key words: Markov-modulated queues, waiting time, heavy traffic.

Estimation of the Offspring and Immigration Mean Vectors for Bisexual Branching Processes with Immigration of Females And Males
M. Gonzalez
M. Molina
M. Mota
I. del Puerto

2000 Mathematics Subject Classification: 60J80, 62M05.
Key words: Bisexual branching processes, immigration, moment method, least squares method, asymptotic properties.

Two-Type Age-Dependent Branching Processes with Inhomogeneous Immigration as Models of Renewing Cell Population
Ollivier Hyrien
Nikolay M. Yanev

2000 Mathematics Subject Classification: 60J80, 60J85, 92C37.
Key words: Age-dependent branching processes, immigration, cell proliferation models, limiting moments and correlation.

Maximal Number of Successors in a Nginar(1)Process
Pavlina K. Jordanova
Ivan K. Mitov

2000 Mathematics Subject Classification: 60J80, 60J20, 60J10, 60G10, 60G70, 60F99.
Key words: Markov chains; NGINAR process; Branching processes; Processes of maxima; Stationary sequences.

Risk Measures for Classical and Perturbed Risk Processes - a Survey
Ekaterina T. Kolkovska

2000 Mathematics Subject Classification: 60B10, 60G17, 60G51, 62P05.
Key words: Classical risk process, α-processes, ruin probability, severity of ruin, expected discounted penalty Gerber-Shiu function.

Some Contributions to the Class of Two-Sex Branching Processes Depending on the Number of Couples in the Population
Shixia Ma
Manuel Molina
Yongsheng Xing

2000 Mathematics Subject Classification: 60J80.
Key words: Two-sex branching processes, limiting behavior.

Analysing and Monitoring Surveillance Data of Mumps in Bulgaria
M. Mitova-Bobcheva
M. Slavtchova-Bojkova
M. Kojouharova
A. Kurchatova

2000 Mathematics Subject Classification: 62P10.
Key words: Bayesian approach, Outbreak, Surveillance of Infectious Diseases.

Subcritical Randomly Indexed Branching Processes
Kosto V. Mitov
Georgi K. Mitov

2000 Mathematics Subject Classification: 60J80, 62P05.
Key words: Galton-Watson branching process; Random time change; Moments; Extinction; Limit theorems

Nonlinear Normalization in Limit Theorems for Extremes
E. I. Pancheva
K. V. Mitov
S. Nadarajah

2000 Mathematics Subject Classification: 60G70, 60F05.
Key words: Extreme values, Nonlinear normalization, Limit theorems, Domain of attraction.

Optimization Problem in a Class of Linear System. Application to Multiple Drug Administration
Krasimira Prodanova

2000 Mathematics Subject Classification: 62H15, 62P10.
Key words: optimal control, application to medical science.

Robust Estimation in Multitype Branching Processes Based on their Asymptotic Properties
Vessela Stoimenova
Dimitar Atanasov

2000 Mathematics Subject Classification: 60J80.
Key words: Trimmed likelihood, multitype branching process, asymptotic properties, para- meter estimation.

Properties of the Bellman Gamma Distribution
Evelina Veleva

2000 Mathematics Subject Classification: 62H10.
Key words: exact distribution, sample covariance matrix, monotone missing data, Wishart distribution.

Characterizations of Exponential Distribution via Conditional Expectations of Record Values
George P. Yanev

2000 Mathematics Subject Classification: 62G30, 62E10.
Key words: characterizations, exponential distribution, record values.

Weak Ergodicity of Mt /Mt /N /N + R Queue
Alexander Zeifman
Anna Korotysheva

2000 Mathematics Subject Classification: 60J27, 60K25.
Key words: nonstationary birth and death processes, rate of convergence, Mt/Mt/N/N + R queue.