⎯We consider a single server retrial queue with batch arrivals, two phases of heterogeneous service and multiple vacations with Npolicy. The primary arrivals find the server busy or doing secondary job (vacation) will join orbit (group of repeated calls). If the number of repeated calls in orbit is less than N, the server does the secondary job repeatedly until the retrial group size reaches N....

The present investigation deals with performance analysis of single server preemptive priority retrial queue with immediate Bernoulli feedback. There are two types of customers are considered, which are priority customers and ordinary customers. The priority customers do not form any queue and have an exclusive preemptive priority to receive their services over ordinary customers. After complet...

introduction: this study aims to compare the cognitive performance of patients with multiple sclerosis (ms) in the field of autobiographical, prospective and working memory compared to normal people. method: in a causal-comparative study using convenience sampling 200 patients with ms (100 were affected less and 100 were affected more than 2 years (and 100 healthy individuals were matched regar...

The effects of working hours on health were examined taking psychological job strain into account. White-collar workers employed at the main office of a Japanese manufacturing company provided data for analysis done in 1997. The eligible subjects were 286 workers aged 20-39. Causal relationships between working hours, health, and psychological job strain were examined by covariance structure an...

As a generalization of classic queueing models with vacations,the working vacation queues were introduced in 2002, where the server serves customers at a lower rate rather than completely stopping service during the vacation period. This type of vacation models can be applied in performance evaluation of optical communication networks, production and service systems, and other fields. In recent...

This paper treats two-threshold policies for an M/G/1 queue with two types of generally distributed random vacations: type 1 (long) and type 2 (short) vacations. Upon returning from a vacation, the server observes the queue length. If this is less than the lower threshold, the server takes a type 1 vacation; if it is between the two thresholds, the server takes a type 2 vacation; and if it is a...