Priority queues have been extensively studied by several researchers (see for example Jaiswal [33] and Takagi [55] for detailed analysis, and Gross and Harris [31] for pre, liminaries). In such queueing systems, arriving customers are classified as belonging to different priorities. The one with highest priority has better access to the service counter than those with lower priorities. Classification into different levels of priority helps in reducing customer impatience. As an example consider a clinic where patients queue up for appointment with physicians. Patients, while waiting in the system, may become seriously ill (priority generation). At this epoch, any physician who is examining an 'ordinary' patient leaves him to be of service to the emergency (priority) case. At the time of arrival of the customer if one 'of lower priority is going service then the customer in service may be pushed out to accomodate the one just arrived, provided there is no other customer of priority equal to or greater than that tagged to the present arrival. This manner of pushing out a customer of lower priority in service is reffered to as pre-emptive priority. The customer who was pushed out will be taken for service only when the system does not have a customer of higher priority waiting. On the other hand, the service of a lower priority customer may continue even after the arrival of a higher priority customer and the latter is taken for service only after the present service is completed. This type of service discipline is reffered to as non-pre-emptive service. The pre-emptive case can be further divided into pre-emptive resume and pre-emptive repeat services. In pre-emptive ressume, the customer of lower priority will continue getting the remaining part of the service; whereas in the latter case service starts from scratch.
In this article, we report a new implicit difference method of ) ( 3 1 2 l l l h kh h k O + + − on a variable mesh based on arithmetic average discretization for the solution of non-linear parabolic partial differential equation ε ) , , , , ( t x xx u u u t x f u = , 00 subject to appropriate initial and Dirichlet boundary conditions prescribed, where ε>0 is a small real constant and k>0, hl >0 are grid sizes in timeand space-directions, respectively. We also derive a new explicit variable mesh method of ) ( 3 l l h kh O + for the estimates of ) / ( x u ∂ ∂ . In both cases, we require only 3-spatial variable grid points. The proposed methods are directly applicable to problems in polar coordinates and we do not require any fictitious points to handle the singular point. The proposed method when applied to a linear parabolic equation is shown to be unconditionally stable. Numerical results are provided to demonstrate the utility of the proposed variable mesh methods derived.
Successes with kernel-based classification methods have spawned recent efforts to kernelize clustering algorithms for object data. Here we extend the kernelization to relational data clustering by proposing a kernelized form of the nonEuclidean relational fuzzy c-means algorithm. A numerical test result is included
In this work an intelligent web service environment for managing hydroponics cultivation processes is proposed. The environment is called HydroNet and includes information and personalized support to hydroponics’ interested groups. The aim is to give the producer the opportunity to access for the first time hydroponics consulting services that meet his/her particular needs over the web. The environment consists of an underlying web services infrastructure. It supports training, support and recommendation services, adaptive web and user interaction services, remote online access services and GIS support services. The web services are coupled with smart mechanisms such as dynamic information flow, interface adaptation and intelligent web structure reorganization. The exploitation of various state of the art technologies takes place, in order to achieve a user centric approach for the collection, presentation and dissemination of data. Overall the environment aims at encouraging the development of hydroponics in Greece.
