4,746 research outputs found
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Towards a change process planning tool
The relationship between a product and its design process is generally complex and not fully understood. When modifying a product, industry still rarely considers the implementation process and its consequences for other design activities in the company, which is hard to assess with conventional planning methods. Although change processes are highly constrained, product and process constraints are not usually considered together or traded off against each other when planning the change. Inadequate assessment and planning of the change implementation process can lead to costly knock-on effects across the product and the design process. This paper argues for a combination of change and process research and discusses requirements for a change process planning tool. It proposes a system for the analysis of the impact of change on the product as well as other company activities. Then, a more informed selection between change alternatives is possible
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Parameter trails
Successful communication is vital for the success of any design project. However, communication often fails, adversely affecting design process efficiency and product quality.understand the connections between different aspects of design and don–t know where to find out more information or who to talk to. This paper presents a new model, developed from current project planning techniques, which supports communication using parameter-specific data. It enables designers to question information, inform their colleagues pro-actively and assess the impact of changing parameter values on subsequent design tasks. Such interaction is critical in allowing designers to see how their own tasks fit into the overall product design
Galaxy correlations and the BAO in a void universe: structure formation as a test of the Copernican Principle
A suggested solution to the dark energy problem is the void model, where
accelerated expansion is replaced by Hubble-scale inhomogeneity. In these
models, density perturbations grow on a radially inhomogeneous background. This
large scale inhomogeneity distorts the spherical Baryon Acoustic Oscillation
feature into an ellipsoid which implies that the bump in the galaxy correlation
function occurs at different scales in the radial and transverse correlation
functions. We compute these for the first time, under the approximation that
curvature gradients do not couple the scalar modes to vector and tensor modes.
The radial and transverse correlation functions are very different from those
of the concordance model, even when the models have the same average BAO scale.
This implies that if void models are fine-tuned to satisfy average BAO data,
there is enough extra information in the correlation functions to distinguish a
void model from the concordance model. We expect these new features to remain
when the full perturbation equations are solved, which means that the radial
and transverse galaxy correlation functions can be used as a powerful test of
the Copernican Principle.Comment: 12 pages, 8 figures, matches published versio
A functional analysis of change propagation
A thorough understanding of change propagation is fundamental to effective change management during product redesign. A new model of change propagation, as a result of the interaction of form and function is presented and used to develop an analysis method that determines how change is likely to propagate. The analysis produces a Design Structure Matrix, which clearly illustrates change propagation paths and highlights connections that could otherwise be ignored. This provides the user with an in-depth knowledge of product connectivity, which has the potential to support the design process and reduce the product's susceptibility to future change
Locally extracting scalar, vector and tensor modes in cosmological perturbation theory
Cosmological perturbation theory relies on the decomposition of perturbations
into so-called scalar, vector and tensor modes. This decomposition is non-local
and depends on unknowable boundary conditions. The non-locality is particularly
important at second- and higher-order because perturbative modes are sourced by
products of lower-oder modes, which must be integrated over all space in order
to isolate each mode. However, given a trace-free rank-2 tensor, a locally
defined scalar mode may be trivially derived by taking two divergences, which
knocks out the vector and tensor degrees of freedom. A similar local
differential operation will return a pure vector mode. This means that scalar
and vector degrees of freedom have local descriptions. The corresponding local
extraction of the tensor mode is unknown however. We give it here. The
operators we define are useful for defining gauge-invariant quantities at
second-order. We perform much of our analysis using an index-free
`vector-calculus' approach which makes manipulating tensor equations
considerably simpler.Comment: 13 pages. Final version to appear in CQ
Efficient optimisation of structures using tabu search
This paper presents a novel approach to the optimisation of structures using
a Tabu search (TS) method. TS is a metaheuristic which is used to guide local
search methods towards a globally optimal solution by using flexible memory
cycles of differing time spans. Results are presented for the well established
ten bar truss problem and compared to results published in the literature. In
the first example a truss is optimised to minimise mass and the results
compared to results obtained using an alternative TS implementation. In the
second example, the problem has multiple objectives that are compounded into a
single objective function value using game theory. In general the results
demonstrate that the TS method is capable of solving structural optimisation
problems at least as efficiently as other numerical optimisation approaches
Randomized Extended Kaczmarz for Solving Least-Squares
We present a randomized iterative algorithm that exponentially converges in
expectation to the minimum Euclidean norm least squares solution of a given
linear system of equations. The expected number of arithmetic operations
required to obtain an estimate of given accuracy is proportional to the square
condition number of the system multiplied by the number of non-zeros entries of
the input matrix. The proposed algorithm is an extension of the randomized
Kaczmarz method that was analyzed by Strohmer and Vershynin.Comment: 19 Pages, 5 figures; code is available at
https://github.com/zouzias/RE
Characteristics of changeable systems across value chains
Engineering changes (ECs) are inevitable for businesses due to increasing innovation, shorter lifecycles, technology and process improvements and cost reduction initiatives. The ECs could propagate and cause further changes due to existing system dependencies, which can be challenging. Hence, change management (CM) is a relevant discipline, which aims to reduce the impact of changes. EC assessment methods form the basis of CM that support in assessing system dependencies and the impact of changes. However, there is limited understanding of which factors influence the change-ability across value chains (VCs). This research adopted a VC approach to EC assessment. Dependencies in products and processes were captured, followed by the risk (i.e. likelihood x impact) assessment of ECs using change prediction method (CPM). Four case studies were conducted from two industries (automotive, furniture) to identify design (product) and manufacturing (process) elements with high risk to be affected by ECs. Based on the case results, characteristics were identified that influence change-ability across VC. This contributed to the CM domain while businesses could also use the results to assess ECs across VC, and improve the design of products and processes by increasing their changeability across VC e.g. by proactive decoupling or reactive handling of system dependencies.Department for Business, Energy and Industrial Strategy (BEIS), UK under Advanced Manufacturing Supply Chain Initiative (AMSCI
Combined Reconstruction and Registration of Digital Breast Tomosynthesis
Digital breast tomosynthesis (DBT) has the potential to en-
hance breast cancer detection by reducing the confounding e ect of su-
perimposed tissue associated with conventional mammography. In addi-
tion the increased volumetric information should enable temporal datasets
to be more accurately compared, a task that radiologists routinely apply
to conventional mammograms to detect the changes associated with ma-
lignancy. In this paper we address the problem of comparing DBT data
by combining reconstruction of a pair of temporal volumes with their reg-
istration. Using a simple test object, and DBT simulations from in vivo
breast compressions imaged using MRI, we demonstrate that this com-
bined reconstruction and registration approach produces improvements
in both the reconstructed volumes and the estimated transformation pa-
rameters when compared to performing the tasks sequentially
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