29790094
A branch and bound algorithm to minimize the total weighted flowtime for the two-stage assembly scheduling problem
In this paper, a two-stage assembly scheduling problem is considered with the objective of minimizing the total weighted flowtime. A lower bounding procedure and a dominance criterion are developed and incorporated into a branch and bound procedure. A heuristic procedure is also used to derive an initial upper bound. Computational results of the algorithm are presented.
9604212
A newsboy problem with reactive production
Abstract This paper extends the classic newsboy problem by introducing reactive production . Production occurs in two stages, a anticipatory stage and a reactive stage . In the anticipatory stage, one determines a production level that anticipates the demand, all of which occurs in the reactive stage. There production takes place with full knowledge of the actual demand and, thus, can react to it. The reactive stage contains multiple sources of capacitated production. Demand is continuous and stochastic, and production, holding, and shortage costs are proportional. There are no fixed costs. Shortages are lost. Our model reduces to a single-period model with piecewise-linear convex costs. We obtain an analogue of the well-known critical fractile formula of the classic newsboy model. We also undertake a numerical study that compares our model with (i) the classic newsboy model, and (ii) a model which employs reactive production but uses classic newsboy formulas. Extensive computational experiments with normal demand problems suggest that the costs under our model can be substantially less than the costs under (i) and (ii). Scope and purpose Consider a seasonal product with a long-selling season and a highly volatile stochastic demand. The classic newsboy formulation of this problem assumes that all unsold goods be salvaged at a price that is often far below the production cost. This could lead to unacceptably low service levels since it tends to discourage high stock levels. On the other hand, were management to raise the service level to an acceptable level, the cost of the safety stock might be too great because of the highly volatile demand. To address this difficulty, we modify the classic newsboy problem by allowing management to schedule production in reaction to the demand during the selling period. Such production is possible when the selling period encompasses a long time interval. Our results indicate that this modification can significantly improve both costs and service levels.
13220286
Discovery of Multi-Level Security Policies
With the increasing complexity and dynamics of database systems, it becomes more and more difficult for administrative personnel to identify, specify and enforce security policies that govern against the misuse of data. Often security policies are not known, too imprecise or simply have been disabled because of changing requirements.
9668406
Culturing Evolution Strategies to Support the Exploration of Novel Environments by an Intelligent Robotic Agent
Recently, a lot of attention is paid to the use of evolutionary computing techniques for the development of adaptive robots. This paper presents the use of Cultural Algorithms with Evolution Strategies (ES) to produce optimal solutions to the ball following problem. This involves learning how to find and advance toward a ball. This is a basic skill needed to play robot soccer. Since it is possible that both the ball and the robot can be moving simultaneously this can be a difficult problem to solve. Four different solutions are implemented here. The first is the two member ES with comma strategy, (1,1)-ES. The second is the ES with plus strategy, (1+1)-ES. The third is a cultured version of the (1,1)-ES. The fourth is a cultured version of the (1+1)-ES. In cultural versions, the ES model is the population model for a Cultural Algorithm. The belief space contains generalizations about the individual's ancestral line, e.g. grandparents, in order to guide the modifications. Each of the four systems was tested by loading it into the RAM of a Khpera robot. Each system was then used to learn how to control the direction and speed of the two Khepera robot's wheels in order to direct it to a given ball. The real-time learning results are then compared. The results suggest that simple Evolution Strategies implemented here exhibit a satisfactory level of real-time learning in forwarding and pushing the ball. The cultured version exhibits an improvement in time over this performance as well.
10520928
Development of an interactive multimedia training simulator for responding to abortion clinic bomb threats
This paper describes the development of an interactive multimedia computer program to provide realistic training for responding to bomb threats targeted at abortion clinics. Because the simulator is computer-based, clinic administrators can receive training that might not otherwise be possible due to time, cost or operational limitations.
14748125
Many-Sorted First-Order Logic Database Language
A database languages based on Many-Sorted First-Order Logic (MSFOL) have many advantages over one based on One-Sorted First-Order Logic (OSFOL). The advantages includes ease-of-expressiveness, efficiency, and the abstraction mechanism. Many database researchers have used OSFOL to view the Relational Data Model (RDM) ; however, no RDM has been modelled by MSFOL. This paper first gives a formal definition for MSFOL and then its advantages of expressiveness and of abstraction are illustrated. Two reduction algorithms which can transform an MSFOL-based language into\from an OSFOL-based language are given. The semantic equivalence between languages based on MSFOL and Typed OSFOL is also proved. Recent extensions of RDMs require aggregation, classification, and generalisation/specialisation mechanisms which MSFOL-based languages can provide, but OSFOL-based languages cannot.