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

Full item page

Search Results

Now showing 1 - 10 of 12

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.
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.
A second order analysis of the waiting time in the M/G/1 retrial queue
(Asia-Pacific Journal of Operational Research, 2002) Artalejo Rodríguez, Jesús Manuel; Falin, Guennadi I.; López Herrero, María Jesús
We are concerned with the M/G/1 queue with repeated attempts where a customer who finds the server busy leaves the service area and repeats his request after a random amount of time. We concentrate on the study of the waiting time process. Its analysis in terms of Laplace transforms has been discussed in the literature. However, this solution has important limitations in practice. For instance, we cannot calculate the first moments of the waiting time, W, by direct differentiation. This paper supplements the existing work and provides a direct method of computation for the second moment of W. Then the maximum entropy approach is used to estimate the true waiting time distribution.
Analysis of a multiserver queue with setup times
(Queueing Systems, 2005) Artalejo Rodríguez, Jesús Manuel; Economou, Antonis; López Herrero, María Jesús
This paper deals with the analysis of an M/M/c queueing system with setup times. This queueing model captures the major characteristics of phenomena occurring in production when the system consists in a set of machines monitored by a single operator.We carry out an extensive analysis of the system including limiting distribution of the system state, waiting time analysis, busy period and maximum queue length.
A simulation study of a discrete-time multiserver retrial queue with finite population
(Journal of Statistical Planning and Inference, 2007) Artalejo Rodríguez, Jesús Manuel; López Herrero, María Jesús
In this paper, we deal with a discrete-time multiserver retrial queue with finite population. Firstly, we study the Markov chain at the epochs immediately after slot boundaries making emphasis on the computation of its steady-state distribution. Then, the main performance measures are investigated. Besides, we simulate the waiting time of a customer in the retrial group under three different queueing policies. Some numerical examples are given to illustrate the analysis.
Algorithmic approximations for the busy period distribution of the M/M/c retrial queue
(European journal of operational research, 2007) Artalejo Rodríguez, Jesús Manuel; Economou, A.; López Herrero, María Jesús
In this paper we deal with the main multiserver retrialqueue of M/M/c type with exponential repeated attempts. This model is known to be analytically intractable due to the spatial heterogeneity of the underlying Markov chain, caused by the retrial feature. For this reason several models have been proposed for approximating its stationary distribution, that lead to satisfactory numerical implementations. This paper extends these studies by developing efficient algorithmic procedures for calculating the busyperioddistribution of the main approximation models of Wilkinson [Wilkinson, R.I., 1956. Theories for toll traffic engineering in the USA, The Bell System Technical Journal 35, 421–514], Falin [Falin, G.I., 1983. Calculations of probability characteristics of a multiline system with repeated calls, Moscow University Computational Mathematics and Cybernetics 1, 43–49] and Neuts and Rao [Neuts, M.F., Rao, B.M., 1990. Numerical investigation of a multiserver retrial model, Queueing Systems 7, 169–190]. Moreover, we develop stable recursive schemes for the computation of the busyperiod moments. The corresponding distributions for the total number of customers served during a busyperiod are also studied. Several numerical results illustrate the efficiency of the methods and reveal interesting facts concerning the behavior of the M/M/cretrialqueue.
On the distribution of the number of retrials
(Applied Mathematical Modelling, 2007) Artalejo Rodríguez, Jesús Manuel; López Herrero, María Jesús
We consider queuing systems where customers are not allowed to queue, instead of that they make repeated attempts, or retrials, in order to enter service after some time. We obtain the distribution of the number of retrials produced by a tagged customer, until he finds an available server.
Analysis of the busy period for the M/M/c queue: An algorithmic approach
(Journal of Applied Probability, 2001) Artalejo Rodríguez, Jesús Manuel; López Herrero, María Jesús
This paper presents an algorithmic analysis of the busy period for the M/M/c queueing system. By setting the busy period equal to the time interval during which at least one server is busy, we develop a first step analysis which gives the Laplace-Stieltjes transform of the busy period as the solution of a finite system of linear equations. This approach is useful in obtaining a suitable recursive procedure for computing the moments of the length of a busy period and the number of customers served during it. The maximum entropy formalism is then used to analyse what is the influence of a given set of moments on the distribution of the busy period and to estimate the true busy period distribution. Our study supplements a recent work of Daley and Servi (1998) and other studies where the busy period of a multiserver queue follows a different definition, i.e., a busy period is the time interval during which all servers are engaged.
On the busy period of the M/G/1 retrial queue
(Naval Research Logistics (NRL), 2000) Artalejo Rodríguez, Jesús Manuel; López Herrero, María Jesús
The M/G/1 queue with repeated attempts is considered. A customer who finds the server busy, leaves the service area and joins a pool of unsatisfied customers. Each customer in the pool repeats his demand after a random amount of time until he finds the server free. We focus on the busy period L of the M/G/1$ retrial queue. The structure of the busy period and its analysis in terms of Laplace transforms have been discussed by several authors. However, this solution has serious limitations in practice. For instance, we cannot compute the first moments of L by direct differentiation. This paper complements the existing work and provides a direct method of calculation for the second moment of L.
The single server retrial queue with finite population: a BSDE approach
(Operational Research, 2012) Artalejo Rodríguez, Jesús Manuel; López Herrero, María Jesús; Matsatsinis, Nikolaos F.
This paper uses the block-structured state-dependent event (BSDE) approach to generalize the scalar version of the single server retrial queue with finite population. The simple scalar version only involves exponential random variables, which make the underlying Markov chain tractable. However, this is a drawback in applications where the exponentiality is not a realistic assumption and the flows are correlated. The BSDE approach provides a versatile tool to deal with a non-exponential model with correlated flows, but keeping tractable the dimensionality of the block-structured Markov chain. We focus on the investigation of the limiting distribution of the system state and the waiting time. The theory is illustrated by numerical experiments, which demonstrate that the proposed BSDE approach can be applied efficiently