Browsing by Author "Van Wijck, W."

Now showing 1 - 8 of 8
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    3D-feature recogntion from measured data
    (Department of Industrial Engineering, Stellenbosch University, 1999) Janssens, M.; Van Wijck, W.; Du Preez, N. D.
    ENGLISH ABSTRACT: This paper presents a method to automatically extract analytical entities like planes, spheres and cylinders from a file containing a cloud of points. The method facilitates the manipulation and reduction of large data sets and the evaluation of it. It can be used as a design tool, a quality control tool, data-processing tool or a data reduction tool. From a database of points, the user can automatically extract a subset of points belonging to an analytical entity of interest, within a predefined but adjustable level of confidence. If necessary, the dimensional parameters of the entity can also be calculated. The method is based on the subtle statistical properties of the least-squares technique that makes it compliant with the strict regulations in the co-ordinate measuring arena. Its robustness guarantees the applicability to less accurate environments than precision engineering.
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    Constraint programming and university timetabling
    (SAIIE, 2002) Groves, G. W.; Van Wijck, W.
    ENGLISH ABSTRACT: The technology of Constraint Programming is rapidly becoming a popular alternative for solving large-scale industry problems. This paper provides an introduction to Constraint Programming and to Constraint Logic Programming (CLP), an enabler of constraint programming. The use of Constraint Logic Programming is demonstrated by describing a system developed for scheduling university timetables. Timetabling problems have a high degree of algorithmic complexity (they are usually NP-Complete), and share features with scheduling problems encountered in industry. The system allows the declaration of both hard requirements, which must always be satisfied, and soft constraints which need not be satisfied, though this would be an advantage.
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    A cost optimised process mean set point for two sided specifications
    (SAIIE, 1999) Van Wijck, W.; Von Benecke, M.
    ENGLISH ABSTRACT: This paper describesthe derivationof cost minimisingexpressions to optimallyset the processmeanof a manufacturing processrestrictedby a double-sidedspecification. Two scenariosare considered. For the first scenario,multiplereworkingiterationsare possible,while in the second,only one rework opportunityis allowed. A numericalexampleis also presented. Resultswere obtainedby numerical solutionand are presentedin graphicalformat.
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    An effective scheduling scheme for lift clubs
    (SAIIE, 1998) Van Wijck, W.
    ENGLISH ABSTRACT: This paper describes a formula for scheduling the day-to-day operation of a lift club. The formula is remarkably simple, and can easily be implemented on a spreadsheet. It is also extremely flexible and can cater for almost any peculiarity that may arise. Much like a business, the lift club is viewed as an entity in its own right, rather than as a collection of individuals. The scheme can be used to generate interesting statistics such as percentage utilization of each member, average percentage utilization of all members, effective size of the lift club, etc. In addition, a graph, depicting each member's liability towards the club against time, can be generated. Finally, every member can obtain a record of his/her trip data over any specific period, which may be handy for income tax purposes.
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    An introduction to rapid casting : development and investigation of process chains for sand casting of functional prototypes
    (SAIIE, 2007) Dimitrov, D.; Van Wijck, W.; De Beer, N.
    ENGLISH ABSTRACT: This paper discusses the results obtained from studies on different Rapid Tooling process chains in order to improve the design and manufacture of foundry equipment that is used for sand casting of prototypes in final material. These prototypes are intended for functional and pre-production tests of vehicles. The Three Dimensional Printing process is used as core technology. Subsequently, while considering aspects such as time, cost, quality (accuracy and surface roughness), and tool life, a framework is presented for the evaluation and selection of the most suitable process chain in accordance with specific requirements. This research builds on an in-depth characterisation of the accuracy and repeatability of a 3D printing process.
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    A Non-zero sampling plan for the moderation of examination papers
    (SAIIE, 2007) Van Wijck, W.
    ENGLISH ABSTRACT: The moderation of examination answer books is an area where quality assurance is essential, and should be employed to ensure that an examination paper’s standard, content and span, marking, etc. are fair and reasonable. A scientific procedure is given for finding the minimum number of answer books to moderate (sample size) so that the statement – that no answer book in a set will contain more than a prespecified proportion of errors – can be made with a pre-specified confidence. The procedure is an extension and enhancement of previous research [7], and guarantees a statistical statement in all cases.
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    Simply optimal - beyond EOQ for a popular class of inventory problems
    (SAIIE, 1999) Van Wijck, W.
    ENGLISH ABSTRACT: True optimal solution s to real life problems are normally only achievable at the expense of great complexity. Every now and then however, one is almost stunned by the simplicity of a good solution to a practical problem. This paper discusses a relatively simple method for determining the joint optimum order quantity and reorder point for the case where service level is specified as a desired fraction of demand to be satisfied directly from stock. Separate solutions were derived for complete backorders and lost sales, and the method is equally applicable to fixed order quantity and periodic review inventory problems . Demand during the lead time is assumed to be normally distributed. The intent of the paper is to focus on the findings and the application of the method, rather than the mathematical derivation of the formulae itself.
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    A zero sampling plan for the moderation of examination papers
    (SAIIE, 2005) Van Wijck, W.; Dirkse van Schalkwyk, T.
    ENGLISH ABSTRACT: Quality assurance within local educational institutions has been under the spotlight in recent years. In particular these institutions are increasingly subjected to minimum standards specified by controlling bodies such as the Higher Education Quality Committee and others. The moderation of examination papers is an important quality assurance activity to ensure that an examination paper’s standard, content, span and marking are fair and reasonable. This paper describes a sampling plan to determine the number of answer books to be checked to confirm that individual marks were awarded correctly. The sampling procedure relates the confidence that marks awarded in a set of examination books meets a specified minimum standard to the number of books moderated.