Browsing by Subject "Queueing Theory"

Now showing 1 - 3 of 3

Open Access
Exploiting interclass rules for focused crawling
(IEEE, 2004) Altingövde, I. S.; Ulusoy, Özgür
A baseline crawler was developed at the Bilkent University based on a focused-crawling approach. The focused crawler is an agent that targets a particular topic and visits and gathers only a relevant, narrow Web segment while trying not to waste resources on irrelevant materials. The rule-based Web-crawling approach uses linkage statistics among topics to improve a baseline focused crawler's harvest rate and coverage. The crawler also employs a canonical topic taxonomy to train a naïve-Bayesian classifier, which then helps determine the relevancy of crawled pages.
Open Access
Joint replenishment problem in two echelon inventory systems with transportation capacity
(2006) Büyükkaramıklı, Nasuh Çağdaş
In this study, we examine the stochastic joint replenishment problem in the presence of a transportation capacity. We first study the multi-retailer and singleechelon setting under a quantity based joint replenishment policy. A limited fleet of capacitated trucks is used for the transportation of the orders from the ample supplier in our setting. We model the shipment operations of the trucks as a queueing system, where the customers are the orders and trucks are the servers. Consequently, different transportation limitation scenarios and methods of approach for these scenarios are discussed. We then extend our model to a two-echelon inventory system, where the warehouse also holds inventory. We characterize the departure process of the warehouse inventory system, which becomes the arrival process of the queueing system that models the shipment operations between the warehouse and the retailers. This arrival process is then approximated to an Erlang Process. Several numerical studies are conducted in order to assess the sensitivity of the total cost rate to system and cost parameters as well as the performance of the approximation.
Open Access
M/M/1 polling models with two finite queues
(1995) Daşçı, Abdullah
Polling models are special kinds of queueing models where multiple-customer type single-stage is considered. In this thesis, first an overview and a classification of polling models will be given. Then two-costomer one server M /M /l polling models will be analyzed and the performance of models will be developed for exhaustive, gated, and G-limited service policies. We give analytical methods for a special type of polling model where we solve the system to get mean queue lengths and thruput rates by three methods. The first one is based on solving the steady state distribution of the Markov Process. The second is a decompositon aiming to decrease the size of the problem. The third one is an approximation method that uses the earlier results and it is very accurate. The thesis will be concluded with possible future extensions.