Person:
López Herrero, María Jesús

First Name

María Jesús

Last Name

López Herrero

URI

https://hdl.handle.net/20.500.14352/77420

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Estudios estadísticos

Department

Estadística y Ciencia de los Datos

Area

Estadística e Investigación Operativa

Identifiers

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Now showing 1 - 10 of 49

A maximum entropy approach for the busy period of the M/G/1 retrial queue
(Annals of Operations Research, 2006) López Herrero, María Jesús; Boros, Endre
This paper concerns the busy period of a single server queueing model with exponentially distributed repeated attempts. Several authors have analyzed the structure of the busy period in terms of the Laplace transform but, the information about the density function is limited to first and second order moments. We use the maximum entropy principle to find the least biased density function subject to several mean value constraints. We perform results for three different service time distributions: 3-stage Erlang, hyperexponential and exponential. Also a numerical comparative analysis between the exact Laplace transform and the corresponding maximum entropy density is presented.
The SIS and SIR stochastic epidemic models: A maximum entropy approach
(Theoretical population biology, 2011) Artalejo Rodríguez, Jesús Manuel; López Herrero, María Jesús
We analyze the dynamics of infectious disease spread by formulating the maximum entropy (ME) solutions of the susceptible-infected-susceptible (SIS) and the susceptible-infected-removed (SIR) stochastic models. Several scenarios providing helpful insight into the use of the ME formalism for epidemic modeling are identified. The ME results are illustrated with respect to several descriptors, including the number of recovered individuals and the time to extinction. An application to infectious data from outbreaks of extended spectrum beta lactamase (ESBL) in a hospital is also considered.
Stochastic epidemic models: new behavioral indicators of the disease spreading
(Applied Mathematical Modelling, 2014) Artalejo Rodríguez, Jesús Manuel; López Herrero, María Jesús
The purpose of this paper is to propose new indicators of the dynamics of infectious disease spread in stochastic epidemic models, including both global system-oriented descriptors (e.g. the final size measured as the number of individuals infected on a least one occasion during an outbreak) and individual-oriented descriptors (e.g. the time to reach an individual run of infections). We focus on birth-and-death models and the basic SIR epidemic model but the methodology remains valid for other nonlinear stochastic epidemic models. The theory is illustrated by numerical experiments which demonstrate that the proposed behavioral indicators can be applied efficiently
Distribution of the number of customers served in an M/G/1 retrial queue
(Journal Of Applied Probability, 2002) López Herrero, María Jesús; Taylor, Peter
We present a recursive method of computation for the probability that at most k customers were served during the busy period of an M/G/1 retrial queue
On the single server retrial queue with balking
(INFOR. Information systems and operational research, 2000) Artalejo Rodríguez, Jesús Manuel; López Herrero, María Jesús
We are concerned with the M/G/1 retrial queue with balking. The ergodicity condition is first investigated making use Of classical mean drift criteria. The limiting distribution of the number of customers in the system is determined with the help of a recursive approach based on the theory of regenerative processes. Many closed form expressions are obtained when we reduce to the M/M/1 queue for some representative balking policies.
Algorithmic analysis of the maximum queue length in a busy period for the M/M/c retrial queue
(INFORMS Journal on Computing, 2007) Artalejo Rodríguez, Jesús Manuel; Economou, A.; López Herrero, María Jesús
This paper deals with the maximum number of customers in orbit (and in the system) during a busy period for the M/M/c retrial queue. Determining the distribution for the maximum number of customers in orbit is reduced to computation of certain absorption probabilities. By reducing to the single-server case we arrive at a closed analytic formula. For the multi-server case we develop an efficient algorithmic procedure for computation of this distribution by exploiting the special block-tridiagonal structure of the system. Numerical results illustrate the efficiency of the method and reveal interesting facts concerning the behavior of the M/M/c retrial queue.
Low retrial analysis of multiserver queues with repeated attempts due to impatience
(Simulation in Industry´2000, 2000) Artalejo Rodríguez, Jesús Manuel; López Herrero, María Jesús; Moller, DPF
We consider a multiserver queueing system where customers may become impatient and then retry for service after some random time. The study of this queueing model is motivated by the existence of exchange distributed operating systems with a time-out mechanism (Boyer et al. 1988). In this paper, we concentrate on the system performance under low retrial rate.
Numerical analysis of (s, S) inventory systems with repeated attempts
(Annals of Operations Research, 2006) Artalejo Rodríguez, Jesús Manuel; Krishnamoorthy, A.; López Herrero, María Jesús
This paper deals with a continuous review (s, S) inventory system where arriving demands finding the system out of stock, leave the service area and repeat their request after some random time. This assumption introduces a natural alternative to classical approaches based either on lost demand models or on backlogged models. The stochastic model formulation is based on a bidimensional Markov process which is numerically solved to investigate the essential operating characteristics of the system. An optimal design problem is also considered.
Cellular mobile networks with repeated calls operating in random environment
(Computers and Operations Research, 2010) Artalejo Rodríguez, Jesús Manuel; López Herrero, María Jesús
Many of the Currently used cellular networks have been constructed on the premise trial me retrial phenomenon is negligible and the operating environment is static. However. a proper modeling of the mobile cellular network cannot ignore the existence of repeated calls. Moreover, real systems often operate in varying environment conditions. In this paper, we show how the matrix-analytic formalism gives one the ability to construct and study versatile cellular mobile networks with user retrials operating in random environment. More concretely, we investigate two four-dimensional. Markovian models which allow us to represent two different options for the use of the guard channel concept. We put emphasis on the numerical evaluation of the redial behavior and the environmental factors on the system performance. This implies the performance analysis of a variety of descriptors including blocking probabilities (handover and fresh calls), mean average analysis, and waiting time in orbit.
Performance analysis of a cellular mobile networkwith retrials and guard channels using waiting and first passage time measures
(European Transactions on Telecommunications, 2009) Economou, Antonis; López Herrero, María Jesús; Xu, Changqiao
Most studies of modern cellular mobile networks concern performance measures directly computable from the stationary state probabilities such as the blocking probability and the mean traffic rates of the various kinds of calls. In this paper, we consider a cellular mobile system with retrials and guard channels for the handover calls, but we concentrate on performance measures related to the waiting and first passage times of the system. More concretely, we first build a Markovian model representing a station of the network and then we study the waiting time of a customer, the idle times of the guard channels and the time between successive lost calls. These measures shed light on the behaviour of the system and quantify the quality of service from both points of view of the customer and the administrator. Several numerical results illustrate the effect of the system parameters in its performance.