Abstract
This paper considers the single machine scheduling problem with linear earliness and quadratic tardiness costs, and no machine idle time. Several dispatching heuristics are proposed, and their performance is analysed on a wide range of instances. The heuristics include simple scheduling rules, as well as a procedure that takes advantage of the strengths of these rules, Linear early/quadratic tardy dispatching rules are also considered, as well as a greedy-type procedure. Extensive experiments are performed to determine appropriate values for the parameters required by some of the heuristics. The computational tests show that the best results are given by the linear early/quadratic tardy dispatching rule. This procedure is also quite efficient, and can quickly solve even very large instances. [Received 15 December 2006; Revised 20 July 2007; Accepted 24 July 2007]

Abstract
The apparent tardiness cost heuristic is one of the best performing dispatch rules for the weighted tardiness scheduling problem. This heuristic uses a lookahead parameter that has previously been set at a fixed value. We propose two different approaches for determining an appropriate value for this parameter. In the first approach, a function is used to map several instance statistics into an adequate value. The second method uses the characteristics of the current workload to determine an appropriate value each time a scheduling decision is to be made. The computational results show that the new procedures outperform the fixed value approach over a wide range of test instances and workload characteristics. The new versions are therefore suited for application in scheduling systems, since they are capable of adjusting themselves to changes in the workload, and provide important savings over the current fixed value implementations.

Abstract
In this paper, we consider the single machine earliness/tardiness scheduling problem with release dates and no unforced idle time. We analyse the performance of a varied set of heuristics. This set includes simple scheduling rules, early/tardy dispatching heuristics, a greedy procedure and a decision theory heuristic. Two different approaches are considered to calculate a lookahead parameter used in the early/tardy dispatching heuristics, and extensive experiments were performed to determine an appropriate value for this parameter. We also propose an improvement procedure that uses some dominance rules to improve the solution obtained by the heuristics. The computational results show that the use of the improvement step is recommended, since it reduces the objective function value with little additional computational effort. The best results were given by the decision theory heuristic, but this procedure is computationally expensive and therefore limited to small and medium size instances. For large instances, one of the early/tardy dispatching heuristics is then the heuristic of choice.

Abstract
In this paper, we consider the single machine earliness/tardiness scheduling problem with job-independent penalties, and no machine idle time. Several dispatching heuristics are proposed, and their performance is analysed on a wide range of instances. The heuristics include simple scheduling rules, as well as a procedure that takes advantage of the strengths of each of those rules. We also consider early/tardy dispatching procedures, and a heuristic method based on existing adjacent precedence conditions. An improvement procedure that can be used to improve the schedules generated by the heuristics is also proposed. The computational tests show that the best results are given by the early/tardy dispatching rules. These heuristics are also quite fast, and are capable of quickly solving even very large instances. The use of the improvement procedure is recommended, since it improves the solution quality, with little additional computational effort.

Abstract
An iterative numerical technique has been developed to simulate in detail the dynamics of a shallow-layer gravity settler. Currently acknowledged models apply only to specific equipments at steady-state and laboratory scale [Jeelani SAK, Hartland S. The continuous separation of liquid/liquid dispersions. Chem Eng Sci 1993;48(2):239-54]. To our knowledge, no study has ever addressed the dynamic simulation of a gravity settler. In this paper a direct numerical technique is presented for computing the thickness and drop-size composition of the dispersion band formed in a shallow-layer settler under steady-state and transient conditions. This technique is an extension for the settler of the one used on the stirred vessel by Ribeiro [Ribeiro LM. Simulacao Dinamica de Sistemas Liquido-Liquido, Urn novo Algoritmo com Potencialidades de Aplicao em Controlo. PhD thesis, Universidade do Minho, Portugal; 1995].

Abstract
This paper presents a topic map approach to PubMed in order to create a knowledge representation for this information system. PubMed is a free search engine that gives very full coverage of the related biomedical sciences. With more than 17 millions of citations since 1865, PubMed users have several problems to find the papers desired. So, it is necessary to organize these concepts in a semantic network. To achieve this objective, we use the Metamorphosis system, choosing the keywords from MeSH ontology. This way, we obtain an ontological index for PubMed, making easier to find specific papers. Copyright © 2007 Giovani Rubert Librelotto, Henrique Tamiosso Machado, Mirkos Martins, Pedro Gabriel Dias Ferreira, José Carlos Ramalho, and Pedro Rangel Henriques.