Chris McMahon | University of Bristol (original) (raw)

Papers by Chris McMahon

Engineering design reviews, which take place at predetermined phases of the product development p... more Engineering design reviews, which take place at predetermined phases of the product development process, are fundamental elements for the evaluation and control of engineering activities. These meetings are also acknowledged as unique opportunities for all the parties involved to share information about the product and related engineering processes. For product development teams, the knowledge generated during a design review is not as secondary as it may seem; key design decisions, design experiences, and associated rationale are frequently made explicit. Useful work has been carried out on the design review process itself, but little work has been undertaken about the detailed content of the meeting activity; it is argued that understanding the transactions that take place during a meeting is critical to building an effective knowledge-oriented recording strategy. To this effect, an extensive research program based on case studies in the aerospace engineering domain has been carried out. The work reported in this paper focuses on a set of tools and methods developed to characterize and analyze in depth the transactions observed during a number of case studies. The first methodology developed, the transcript coding scheme, uses an intelligent segmentation of meeting discourse transcriptions. The second approach, which bypasses the time consuming transcribing operation, is based on a meeting capture template developed to enable a meeting observer to record the transactions as the meeting takes place. A third method, the information mapping technique, has also been developed to interpret the case study data in terms of decisions, actions, rationale, and lessons learned, effectively generating qualitative measures of the information lost in the formal records of design reviews. Overall, the results generated by the set of tools presented in this paper have fostered a practical strategy for the knowledge intensive capture of the contents of design reviews. The concluding remarks also discuss possible enhancements to the meeting analysis tools presented in this paper and future work aimed at the development of a computer supported capture software for design reviews.

Lecture Notes in Computer Science, 2019

Attributes based on natural language descriptions (Kansei words) are common in affective design q... more Attributes based on natural language descriptions (Kansei words) are common in affective design questionnaire data. Such words are usually inherently vague and exhibit characteristics such as explicitly borderline cases and blurred boundaries between those cases to which the word does and those to which it does not apply. In this paper we propose an integrated treatment of vagueness and uncertainty which combines three value logic and probability by defining a probability distribution over valuations in Kleene's logic. Such an approach naturally results in lower and upper uncertainty measures on the sentences of the language, quantifying the uncertainty that a given sentence is true or that it is not false respectively. Within this framework we propose a representational model for opinions in the form of a graph of conjunctive clauses ordered by precision and weighted according to their respective lower and upper uncertainty measures. Furthermore, by extending the idea of scoring functions to a three valued setting we propose an approach for ranking different designs which takes into account both the level of belief in an opinion and also its relative strength. The potential of this approach is illustrated using a case study involving questionnaire data about Kutani traditional Japanese craft designs.

Energy, 2018

This paper proposes a DC microgrid system based on multiple locally available renewable energy so... more This paper proposes a DC microgrid system based on multiple locally available renewable energy sources in an off-grid rural community, based on a field study carried out in a rural, off-grid village in Nepal. The site has been assessed as suitable for solar and wind power. Using estimated solar data for the site's location, wind data measured locally, household and population data and typical measured domestic demand profiles, a DC microgrid system model has been constructed. Power flow is controlled using modified DC droop control on each individual energy source to enable optimal power sharing with minimum power dissipation across distribution lines.

Product Lifecycle Management in the Era of Internet of Things, 2016

Understanding how users formulate search queries can allow the development of search engines that... more Understanding how users formulate search queries can allow the development of search engines that are tailored to the way users search and thus improve the knowledge discovery process, a key challenge for Product Lifecycle Management (PLM) systems. This paper presents part-of-speech (POS) statistical analysis on two sets of 'Top 500' search query lists in order to compare Internet search with enterprise search with the aim of understanding how enterprise search queries differ from Internet search queries. The Internet queries were obtained from the keyword research company WordTracker.com and covers the month of January 2015. Enterprise search logs were obtained from a large multinational engineering organization and represent the first six months of 2014. The results show enterprise search users are far more likely to search using nouns, with 97 % of queries containing at least one noun. This compares to 89 % for Internet users. 60 % of enterprise queries are single nouns compared to 38 % for Internet search users. In total, enterprise queries fell into 41 lexical classes (noun-noun/adjective-noun/etc.) whilst Internet search contained 95 classes. Of those 41 classes only 12 % contained no nouns, compared to 21 % for Internet search. 80 % of the enterprise search queries can be covered by just four Lexical classes compared to 15 for Internet search. 90 % coverage required 11 classes for enterprise and 44 classes for the Internet. These findings appear to support existing literature in that they show a preference for enterprise searches for specific information using domain specific terms. This paper concludes by considering the implications of these findings for enterprise search systems and PLM in the context of a large engineering organization and in particular proposes two areas of future research.

Proceedings of the Institution of Mechanical Engineers, 1995

Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2005

Many organizations are increasingly relying on design simulation rather than expensive and time-c... more Many organizations are increasingly relying on design simulation rather than expensive and time-consuming prototype testing for product evaluation. However, uncertainties in analytical and computational methods need to be understood in order to improve confidence in their use, and models need to be validated. This paper presents a case study of a MacPherson strut automotive suspension analysis, and evaluates the uncertainties in the modelling of this complex dynamic problem using a simplified analytical model and a complex computational model. In both cases, variability in design variables is characterized using probabilistic design methods. As a first step, the model variables are described by assumed datasets, which are collated from several sources such as tolerances specified in drawings, expert opinion, published data, etc. Measurement of the properties of the suspension system components is then performed (spring stiffness, damping coeffcient, etc.), and the statistical parame...

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 1997

This article is concerned with part representation and reasoning algorithms for automatic process... more This article is concerned with part representation and reasoning algorithms for automatic process planning in CADCAM (computer aided design and manufacture). Process planning involves the translation of a part description into instructions for a sequence of operations for the manufacture of the part. Part representations in CADCAM are reviewed, and a hierarchical representation is introduced which describes parts as the set-theoretic union of positive (protrusion) features, with the set-theoretic union of negative (depression) features subtracted. The model information hierarchy also incorporates topological relationships among features (adjacency, ownership and intersection), tolerances and links to a boundary representation (B-rep) geometric model. The hierarchical part representation is used as the basis for a reasoning scheme that uses topological relationships between features to restrict the search space of operation sequences. A recursive algorithm produces candidate operatio...

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2008

Key characteristics (KCs) play a significant role in product lifecycle management (PLM) and in co... more Key characteristics (KCs) play a significant role in product lifecycle management (PLM) and in collaborative and global product development. Over the last decade, KCs methodologies and tools have been studied and practiced in several domains of the product lifecycle, and many world-class companies have introduced KCs considerations into their product development practices. However, there has been no systematic survey of KCs techniques, methodologies, and practices in this respect. This paper aims to give a comprehensive survey of KCs methodologies, and practices from the perspective of enterprise integration and PLM. The paper firstly presents a holistic framework of KCs methodologies and practices through the product lifecycle, and summarizes the fundamentals of KCs including their definition and classification, KC flowdown, and the identification and selection of KCs. A review of the KCs methods and practices in the product lifecycle is then presented, particularly in engineering ...

International Journal of Fatigue, 2001

Residual stresses, which can be produced during the manufacturing process, play an important role... more Residual stresses, which can be produced during the manufacturing process, play an important role in an industrial environment. Residual stresses can and do change in service. In this paper, measurements of the statistical distribution of the initial residual stress in shot blast bars of En15R steel are presented. Also measured was the relaxation of the residual stresses after simple tensile

Computer-Aided Design, 1992

Abstract A parametric program may use rules and algorithms to define the relationships between di... more Abstract A parametric program may use rules and algorithms to define the relationships between dimensions and elements of designs, and it may thus generate variants of a design. Programs currently in use have technical limitations in their ability to handle time-varying and imprecise data, the search for suitable existing designs and their maintainability. The paper suggests how these and other limitations can be overcome to widen the field of application of parametric programs.

decomposition A categorisation of the the Design Information and Knowledge (DIAK) domain has been... more decomposition A categorisation of the the Design Information and Knowledge (DIAK) domain has been established. This highlights 8 major areas that may be grouped into four views on the domain. This categorisation may be used to communicate and integrate the issues, to work globally and to plan and identify critical research areas. The information centric view arguably represents the overall information life cycle. The approach deals with not only the information life cycle but also user issues, technology issues and generic issues. The issue of ‘quality ’ in information is an emerging new area and will be a critical part of new research initiatives. The various domain views illustrate the cross functional nature of the issues of managing design information and knowledge. The overall aim is to enable the development of a unified theory of design information and knowledge that will underpin and support the provision of appropriate and accurate information to engineering designers who a...

This paper describes an approach to viewpoint-dependent feature-based modelling in computer-aided... more This paper describes an approach to viewpoint-dependent feature-based modelling in computer-aided design developed for the purposes of supporting design automation. The approach uses a combination of a multi-level modelling approach and two stages of mapping between models. The multi-level model approach is implemented in a three-level architecture involving (1) a feature-based description for each viewpoint, comprising a combination of form features and other features such as loads and constraints for analysis, (2) an executable representation of the feature model, for example, in the form of an executable macro file or object model and (3) an “evaluation” of the feature model obtained by executing the representation defined in (2) in a CADCAM system. The mappings involved in the system comprise firstly, mapping between the level (1) feature representations associated with different viewpoints, for example for the geometric simplification and addition of boundary conditions associa...