Browsing by Author "Liu, Yang"

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    Aspects of linking CAD and cost estimation software
    (Stellenbosch : Stellenbosch University, 2001-12) Liu, Yang; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH ABSTRACT: This thesis describes a module that links AutoCAD and CeDeas (cost estimation software which was developed by Department of Mechanical Engineering, University of Stellenbosch). CeDeas is intended for estimating the direct manufacturing cost of simple welded assemblies in a batch production environment. It is aimed at use during late concept design or early detail design. The link module was developed in Borland C++ Builder. By using COM (Component Object Model) technology, the link module employs the methods and the properties of the AutoCAD automation interface to extract manufacturing information that is required by CeDeas. The link module prompts the user to pick objects in an AutoCAD drawing and then determines the values required by CeDeas to estimate the manufacturing cost. The user can choose between a "direct select method" (which uses the properties of geometric entities already in the drawing) and a "user define method" (whereby the user defmes temporary entities or combines aspects of existing entities in the AutoCAD drawing). With these results and some non-geometric inputs, the user can get a cost estimate of components and assemblies. After design changes, the link module can provide CeDeas with updated values with minimal user interaction in situations where the "direct select method" was used. The designer can therefore easily use the cost estimates to compare design alternatives to optimise the design. Validation studies demonstrated the numerical accuracy of the use of the link module. The link module can be regarded as an extension of CeDeas. At present it only supports AutoCAD R14, but can be extended to support AutoCAD 2000 and Mechanical Desktop.
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    A flexible distributed design assistance tool in early design phases
    (Stellenbosch : Stellenbosch University, 2007-12) Liu, Yang; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH ABSTRACT: The globalisation is increasing the complexity of product development in terms of product variants and the range of technologies implemented. It emphasises the requirement for developing various design information support systems for the world market. However, small and medium enterprises that employ a wide range of design procedures may not be able to afford customised information support systems, with the result that there is a need for flexible, i.e. easily adaptable, design support tools. Four case studies were carried out to investigate the requirements for an information support system aimed at the design process and design documents. They indicated that a design information support system aimed at supporting design teams in the pre-detail mechanical design phases should be able to adapt various design methods and handle design information in a flexible way. Flexible here means being applicable over a wide range of contexts and extendable without affecting data already captured. Ontology based approaches are widely applied where diverse information has to be handled. The development of the Internet today also makes a distributed design approach more and more popular for mechanical design. An internet-based design support system called DiDeas II (Distributed Design assistant) was developed here with an ontologybased approach implemented to provide distributed and flexible assistance during concept generation in small companies. The DiDeas II has separate server side and client side programs, which communicate through a TCP/IP connection. DiDeas II allows design teams to manage their design information according to various design methods, to decrease time-delays and to improve communication between team members. These benefits were confirmed in two case studies carried out to evaluate DiDeas II. Keywords: Distributed design; ontology; concept design, web-based system.
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    Inferring the number of COVID-19 cases from recently reported deaths
    (2020) Jombart, Thibaut; Van Zandvoort, Kevin; Russell, Timothy W.; Jarvis, Christopher I.; Gimma, Amy; Abbott, Sam; Clifford, Sam; Funk, Sebastian; Gibbs, Hamish; Liu, Yang; Pearson, Carl A. B.; Bosse, Nikos I.; Centre for the Mathematical Modelling of Infectious Diseases COVID-19 Working Group; Eggo, Rosalind, M.; Kucharski, Adam J.; Edmunds, W. John
    We estimate the number of COVID-19 cases from newly reported deaths in a population without previous reports. Our results suggest that by the time a single death occurs, hundreds to thousands of cases are likely to be present in that population. This suggests containment via contact tracing will be challenging at this point, and other response strategies should be considered. Our approach is implemented in a publicly available, userfriendly, online tool.