http://www.dspace.cam.ac.uk:80/handle/1810/227522 Sun, 19 May 2013 00:54:27 GMT 2013-05-19T00:54:27Z http://www.dspace.cam.ac.uk:80/handle/1810/243633 Title: Modelling the evolution of uncertainty levels during design Authors: Wynn, David C; Grebici, Khadidja; Clarkson, P John Abstract: Design work involves uncertainty that arises from, and influences, the progressive development of solutions. This paper analyses the influences of evolving uncertainty levels on the design process. We focus on uncertainties associated with choosing the values of design parameters, and do not consider in detail the issues that arise when parameters must first be identified. Aspects of uncertainty and its evolution are discussed, and a new task-based model is introduced to describe process behaviour in terms of changing uncertainty levels. The model is applied to study two process configuration problems based on aircraft wing design: one using an analytical solution and one using Monte-Carlo simulation. The applications show that modelling uncertainty levels during design can help assess management policies, such as how many concepts should be considered during design and to what level of accuracy. Description: The final publication is available at www.springerlink.com Thu, 18 Aug 2011 23:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/243633 2011-08-18T23:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/243470 Title: Contact and channel modelling to support early design of technical systems Authors: Albers, Albert; Braun, Thomas; Clarkson, P John; Enkler, Hans-Georg; Wynn, David C Abstract: The early design of mechanical systems is critical because it constrains options later in the design process. In this early stage of the design process, designers must consider customer requirements, how they are related to system functionality and how these requirements and functions are implemented in the physical interactions between components and sub-systems. This paper proposes an approach by which the Contact and Channel Model (C&CM) can be applied to support this stage of embodiment design. The proposed approach is implemented in a computer support tool and illustrated through a simple example. A number of opportunities for further work to extend and evaluate the approach are identified. We argue that our approach offers a unique way to consider the functionality of a design alongside the parts, surfaces and physical effects which embody that functionality, and provides an intuitive representation which could help designers iteratively develop and express this relationship. Description: INTERNATIONAL CONFERENCE ON ENGINEERING DESIGN, ICED'09 24 - 27 AUGUST 2009, STANFORD UNIVERSITY, STANFORD, CA, USA Fri, 31 Jul 2009 23:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/243470 2009-07-31T23:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/243228 Title: The P3 Platform: An approach and software system for developing diagrammatic model-based methods in design research Authors: Wynn, David C; Nair, Seena MT; Clarkson, P John Abstract: Many issues in design and design management have been explored by building models which capture the relationships between different aspects of the problem at hand. These models require computer support to construct and analyse. However, appropriate modelling tools can be time-consuming to develop in a research environment. Reflecting upon five design research projects, this paper proposes that such projects can be facilitated by recognising the iterative and tightly-coupled nature of research and tool development, and by attempting to minimise the effort of solution prototyping within this process. Our approach is enabled by a software platform which can be rapidly configured to implement many conceivable modelling approaches. This configurability is complemented by an emerging library of modelling and analysis approaches tailored to explore design process systems. The platform-based approach enables any mix of modelling concepts to be easily created. We propose it could thus help researchers to explore a wide range of questions without being constrained to existing conventions for modelling – or for model integration. Description: In: Norell Bergendahl, M., Grimheden, M., Leifer, L., Skogstad, P., and Lindemann, U. (eds.) Proceedings of the 17th International Conference on Engineering Design (ICED'09), Vol. 1, pp. 559-570, 2009 Fri, 31 Jul 2009 23:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/243228 2009-07-31T23:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/243227 Title: An Introduction to the Cambridge Advanced Modeller Authors: Wynn, David C; Wyatt, David F; Nair, Seena M T; Clarkson, P John Abstract: Complex products and their development processes may be viewed as systems, whose different aspects can be modelled as networks of interactions between elements in different domains. Many approaches have been proposed to explore, support or improve engineering processes by building such models. Developing these approaches, and applying them to problems of realistic complexity, often requires specialised computer software suitable for manipulating large data sets. However, creating suitable tools can be difficult–because software development is time-consuming and requires skills that many researchers and practitioners do not possess. We developed an approach which aims to address this problem by recognising the iterative nature of modelling research and its often tight coupling with prototype software development, and by reducing the effort of software prototyping and revision within this process. The approach is enabled by, and embodied in, the Cambridge Advanced Modeller (CAM)–a configurable software platform we have developed, refined and applied over several years and through a number of research projects. Description: Proceedings of the 1st International Conference on Modelling and Management of Engineering Processes (MMEP 2010). Cambridge, UK, 19-20 July 2010. Wed, 30 Jun 2010 23:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/243227 2010-06-30T23:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/243226 Title: Design project planning, monitoring and re-planning through process simulation Authors: Wynn, David C; Clarkson, P John Abstract: Effective management of design schedules is a major concern in industry, since timely project delivery can have a significant influence on a company’s profitability. Based on insights gained through a case study of planning practice in aero-engine component design, this paper examines how task network simulation models can be deployed in a new way to support design process planning. Our method shows how simulation can be used to reconcile a description of design activities and information flows with project targets such as milestone delivery dates. It also shows how monitoring and re-planning can be supported using the non-ideal metrics which the case study revealed are used to monitor processes in practice. The approach is presented as a theoretical contribution which requires further work to implement and evaluate in practice. Description: INTERNATIONAL CONFERENCE ON ENGINEERING DESIGN, ICED'09 24 - 27 AUGUST 2009, STANFORD UNIVERSITY, STANFORD, CA, USA Fri, 31 Jul 2009 23:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/243226 2009-07-31T23:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/243225 Title: Can change prediction help prioritise redesign work in future engineering systems? Authors: Wynn, David C; Caldwell, Nicholas H M; Clarkson, P John Abstract: Future design environments will necessitate improved management of the propagation and impacts of changes. To ascertain whether change prediction can assist in making better work prioritisation decisions, this paper develops a new simulation approach and applies it to a model of a complex aerospace product, which was elicited from industry. We use an accepted technique to generate potential change propagation trees and apply Monte Carlo methods to generate a sample space within which multiple scheduling policies could be evaluated and compared. The experiments reveal that poor coordination of change activity can result in significant process inefficiencies, that the potential for inefficiency increases for larger change networks, and that a modest ability to accurately predict change propagation in the specific case at hand could have a dramatic effect in reducing unnecessary rework. The experiments also suggest that the capability of predicting multiple steps of change propagation would provide only minimal additional improvement. Description: International Design Conference - DESIGN 2010 Fri, 30 Apr 2010 23:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/243225 2010-04-30T23:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/243224 Title: Modelling iteration in engineering design Authors: Wynn, David C; Eckert, Claudia M; Clarkson, P John Abstract: This paper examines design iteration and its modelling in the simulation of New Product Development (NPD) processes. A framework comprising six perspectives of iteration is proposed and it is argued that the importance of each perspective depends upon domain-specific factors. Key challenges of modelling iteration in process simulation frameworks such as the Design Structure Matrix are discussed, and we argue that no single model or framework can fully capture the iterative dynamics of an NPD process. To conclude, we propose that consideration of iteration and its representation could help identify the most appropriate modelling framework for a given process and modelling objective, thereby improving the fidelity of design process simulation models and increasing their utility. Description: INTERNATIONAL CONFERENCE ON ENGINEERING DESIGN, ICED’07 28 - 31 AUGUST 2007, CITE DES SCIENCES ET DE L'INDUSTRIE, PARIS, FRANCE Tue, 31 Jul 2007 23:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/243224 2007-07-31T23:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/243223 Title: Design of robust service operations using cybernetic principles and simulation Authors: Wynn, David C; Cassidy, Stephen; Clarkson, P John Abstract: Information flows in a service organisation allow business units to co-ordinate their response to changes in the operating environment. Processes and interactions can be designed so that the right information flows to the right people, at the right time to make effective decisions regarding job priorities and allocation of limited resource. This paper develops an analysis framework and simulation approach to identify the internal information flows an organisation needs to “tune itself” for changing conditions, thus making itself more robust to uncertainties. The ideas are developed and illustrated through a case study with a major telecoms company. Description: International Design Conference - DESIGN 2012 Mon, 30 Apr 2012 23:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/243223 2012-04-30T23:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/243209 Title: A cybernetic perspective on methods and process models in collaborative designing Authors: Maier, Anja M; Wynn, David C; Andreasen, Mogens Myrup; Clarkson, P John Abstract: Cybernetic thinking provides a framework to understand the issues in creating and using methods and process models during collaborative designing. It can help understand what takes place while the creation and use is unfolding. This viewpoint allows methods and process models to be framed as aiding human decision-making, and as supporting the organisation of design activities. It casts light on how a team acts and what are they doing to solve design problems, by considering that they react to changes in the perceived solution state or goal state. Cybernetics thus provides an articulation of mechanisms for doing design. By identifying virtues that support creation and use of methods and process models during designing, cybernetics could thus help teams to design more effectively. This article considers the creation and use of process models and methods in design from a cybernetic perspective. We suggest that a process model and method are similar in nature, in that they both give guidance for progressing the design according to the circumstances encountered. Cybernetic principles are interpreted to help understand the role of modelling and method use in design process evolution. Description: International Design Conference - DESIGN 2012 Mon, 30 Apr 2012 23:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/243209 2012-04-30T23:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/242457 Title: How can PD process modelling be made more useful? An exploration of factors which influence modelling utility Authors: Wynn, David C; Maier, Anja M; Clarkson, P John Abstract: In what sense is PD process modelling useful? and how can the utility of modelling be improved? In this paper, we approach these questions through an analysis of PD process modelling ‘utility’ – which in broad terms we consider to be the degree to which a model-based approach or modelling intervention benefits practice. We view the utility of modelling as a composite characteristic which depends both on the properties of models and on the way they are applied. The paper draws upon established principles of cybernetic systems in an attempt to explain the role played by process modelling in operating and improving PD processes. We use this framework to identify eight key factors which influence the utility of modelling in the context of use. Further, we indicate how these factors can be interpreted to identify opportunities to improve modelling utility. Description: International Design Conference - DESIGN 2010 Fri, 30 Apr 2010 23:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/242457 2010-04-30T23:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/241996 Title: Redesigning the design process through interactive simulation: A case study of life-cycle engineering in jet engine conceptual design Authors: Kerley, Warren; Wynn, David C; Eckert, Claudia M; Clarkson, P John Abstract: Many aerospace companies are currently making the transition to providing fully-integrated product-service offerings in which their products are designed from the outset with life-cycle considerations in mind. Based on a case study at Rolls-Royce, Civil Aerospace, this paper demonstrates how an interactive approach to process simulation can be used to support the redesign of existing design processes in order to incorporate life-cycle engineering (LCE) considerations. The case study provides insights into the problems of redesigning the conceptual stages of a complex, concurrent engineering design process and the practical value of process simulation as a tool to support the specification of process changes in the context of engineering design. The paper also illustrates how development of a simulation model can provide significant benefit to companies through the understanding of process behaviour that is gained through validating the behaviour of the model using different design and iteration scenarios. Description: Post-print Sat, 01 Jan 2011 00:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/241996 2011-01-01T00:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/241944 Title: Simulating intertwined design processes that have similar structures: a case study of a small company that creates made-to-order fashion products Authors: Wynn, David C; Eckert, Claudia M; Clarkson, P John Abstract: The authors use simulation to analyse the resource-driven dependencies between concurrent processes used to create customised products in a company. Such processes are uncertain and unique according to the design changes required. However, they have similar structures. For simulation, a level of abstraction is chosen such that all possible processes are represented by the same activity network. Differences between processes are determined by the customisations that they implement. The approach is illustrated through application to a small business that creates customised fashion products. We suggest that similar techniques could be applied to study intertwined design processes in more complex domains. Description: Post-print Sat, 01 Jan 2011 00:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/241944 2011-01-01T00:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/241703 Title: R/BHC: fast Bayesian hierarchical clustering for microarray data Authors: Savage, Richard S; Heller, Katherine; Xu, Yang; Ghahramani, Zoubin; Truman, William M; Grant, Murray; Denby, Katherine J; Wild, David L Abstract: Abstract Background Although the use of clustering methods has rapidly become one of the standard computational approaches in the literature of microarray gene expression data analysis, little attention has been paid to uncertainty in the results obtained. Results We present an R/Bioconductor port of a fast novel algorithm for Bayesian agglomerative hierarchical clustering and demonstrate its use in clustering gene expression microarray data. The method performs bottom-up hierarchical clustering, using a Dirichlet Process (infinite mixture) to model uncertainty in the data and Bayesian model selection to decide at each step which clusters to merge. Conclusion Biologically plausible results are presented from a well studied data set: expression profiles of A. thaliana subjected to a variety of biotic and abiotic stresses. Our method avoids several limitations of traditional methods, for example how many clusters there should be and how to choose a principled distance metric. Description: RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are. Wed, 05 Aug 2009 23:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/241703 2009-08-05T23:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/240739 Title: Efficient Alternatives to the Ephraim and Malah Suppression Rule for Audio Signal Enhancement Abstract: Audio signal enhancement often involves the application of a time-varying filter, or suppression rule, to the frequency-domain transform of a corrupted signal. Here we address suppression rules derived under a Gaussian model and interpret them as spectral estimators in a Bayesian statistical framework. With regard to the optimal spectral amplitude estimator of Ephraim and Malah, we show that under the same modelling assumptions, alternative methods of Bayesian estimation lead to much simpler suppression rules exhibiting similarly effective behaviour. We derive three of such rules and demonstrate that, in addition to permitting a more straightforward implementation, they yield a more intuitive interpretation of the Ephraim and Malah solution. Description: RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are. Sun, 07 Sep 2003 23:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/240739 2003-09-07T23:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/240505 Title: Particle Filtering Applied to Musical Tempo Tracking Abstract: This paper explores the use of particle filters for beat tracking in musical audio examples. The aim is to estimate the time-varying tempo process and to find the time locations of beats, as defined by human perception. Two alternative algorithms are presented, one which performs Rao-Blackwellisation to produce an almost deterministic formulation while the second is a formulation which models tempo as a Brownian motion process. The algorithms have been tested on a large and varied database of examples and results are comparable with the current state of the art. The deterministic algorithm gives the better performance of the two algorithms. Description: RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are. Sun, 07 Nov 2004 00:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/240505 2004-11-07T00:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/240504 Title: Particle Filtering for Joint Symbol and Code Delay Estimation in DS Spread Spectrum Systems in Multipath Environment Abstract: We develop a new receiver for joint symbol, channel characteristics, and code delay estimation for DS spread spectrum systems under conditions of multipath fading. The approach is based on particle filtering techniques and combines sequential importance sampling, a selection scheme, and a variance reduction technique. Several algorithms involving both deterministic and randomized schemes are considered and an extensive simulation study is carried out in order to demonstrate the performance of the proposed methods. Description: RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are. Sun, 07 Nov 2004 00:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/240504 2004-11-07T00:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/240503 Title: Joint Tracking of Manoeuvring Targets and Classification of Their Manoeuvrability Abstract: Semi-Markov models are a generalisation of Markov models that explicitly model the state-dependent sojourn time distribution, the time for which the system remains in a given state. Markov models result in an exponentially distributed sojourn time, while semi-Markov models make it possible to define the distribution explicitly. Such models can be used to describe the behaviour of manoeuvring targets, and particle filtering can then facilitate tracking. An architecture is proposed that enables particle filters to be both robust and efficient when conducting joint tracking and classification. It is demonstrated that this approach can be used to classify targets on the basis of their manoeuvrability. Description: RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are. Sun, 07 Nov 2004 00:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/240503 2004-11-07T00:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/240502 Title: Editorial Description: RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are. Sun, 07 Nov 2004 00:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/240502 2004-11-07T00:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/239300 Title: Digital Audio Effects Description: RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are. Tue, 22 Feb 2011 00:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/239300 2011-02-22T00:00:00Z http://www.dspace.cam.ac.uk:80/handle/1810/237810 Title: Atomic Layer Deposition of ZnO on Multi-walled Carbon Nanotubes and Its Use for Synthesis of CNT–ZnO Heterostructures Abstract: Abstract In this article, direct coating of ZnO on PECVD-grown multi-walled carbon nanotubes (MWCNTs) is achieved using atomic layer deposition (ALD). Transmission electron microscopy investigation shows that the deposited ZnO shell is continuous and uniform, in contrast to the previously reported particle morphology. The ZnO layer has a good crystalline quality as indicated by Raman and photoluminescence (PL) measurements. We also show that such ZnO layer can be used as seed layer for subsequent hydrothermal growth of ZnO nanorods, resulting in branched CNT–inorganic hybrid nanostructures. Potentially, this method can also apply to the fabrication of ZnO-based hybrid nanostructures on other carbon nanomaterials. Description: RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are. Fri, 06 Aug 2010 23:00:00 GMT http://www.dspace.cam.ac.uk:80/handle/1810/237810 2010-08-06T23:00:00Z