Transport firms that daily pickup or deliver commodities encounter a plethora of problems relating to their Vehicle Routing and Scheduling (VRS) activities. To make decisions about Routing and Scheduling during special events is even more complicated process. During the Athens Olympic Games 2004 in Athens, the Vehicle Routing and Scheduling problem was very keen. Actually, the commodities transportation had to be done within strictly defined time-periods and under many security and traffic restrictions [2], [8]. "Xenios" is a specific DSS that was developed to assist the daily VRS activities of Greek transport firms during special events. This system incorporated essential functions of GIS, database systems and model management techniques to support overall routing, scheduling and decisionmaking processes for VRS problems encountered during the Athens 2004 Olympic Games (ATHENS 2004).Our work aimed at the successful setting up of DSS "Xenios" so that it could cover a wide range of variations of the VRS problem, especially problems with hard time-windows in the route generation [15], [17].The first step in the development of any specific DSS is the identification of the applying problem dimensions [3], [7], [10]. In order to make easier the development procedure, we tried to classify the most significant VRS problem dimensions that have common characteristics in groups. According to our consideration, this work could accelerate and ease the development of the specific DSS.
In this paper, we examine the zero-fourth cumulant approximation that was applied to fluctuating velocity components of homogeneous and isotropic turbulence by M.D. Millionschikov. Since the publication of the remarkable paper of Millionschikov, many authors have applied this hypothesis to solve the closure problem of turbulence. We discuss here various studies by the other authors on the developments of this hypothesis and their applications to the incompressible velocity temperature, hydrodynamic and magnetohydrodynamic fluctuating pressure fields and the general magnetohydrodynamic turbulence field. Lastly, we discuss broadly the computational difficulties that arise in turbulence problems and their possible refinements. We include also some enlightments of the process of future work that could be undertaken in this field of research.
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