| 1. |
- Joffrin, E., et al.
(författare)
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Overview of the JET preparation for deuterium-tritium operation with the ITER like-wall
- 2019
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 59:11
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Forskningsöversikt (refereegranskat)abstract
- For the past several years, the JET scientific programme (Pamela et al 2007 Fusion Eng. Des. 82 590) has been engaged in a multi-campaign effort, including experiments in D, H and T, leading up to 2020 and the first experiments with 50%/50% D-T mixtures since 1997 and the first ever D-T plasmas with the ITER mix of plasma-facing component materials. For this purpose, a concerted physics and technology programme was launched with a view to prepare the D-T campaign (DTE2). This paper addresses the key elements developed by the JET programme directly contributing to the D-T preparation. This intense preparation includes the review of the physics basis for the D-T operational scenarios, including the fusion power predictions through first principle and integrated modelling, and the impact of isotopes in the operation and physics of D-T plasmas (thermal and particle transport, high confinement mode (H-mode) access, Be and W erosion, fuel recovery, etc). This effort also requires improving several aspects of plasma operation for DTE2, such as real time control schemes, heat load control, disruption avoidance and a mitigation system (including the installation of a new shattered pellet injector), novel ion cyclotron resonance heating schemes (such as the three-ions scheme), new diagnostics (neutron camera and spectrometer, active Alfven eigenmode antennas, neutral gauges, radiation hard imaging systems...) and the calibration of the JET neutron diagnostics at 14 MeV for accurate fusion power measurement. The active preparation of JET for the 2020 D-T campaign provides an incomparable source of information and a basis for the future D-T operation of ITER, and it is also foreseen that a large number of key physics issues will be addressed in support of burning plasmas.
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| 2. |
- Christmas, Matthew, et al.
(författare)
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Evolutionary constraint and innovation across hundreds of placental mammals
- 2023
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 380:6643
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Tidskriftsartikel (refereegranskat)abstract
- Zoonomia is the largest comparative genomics resource for mammals produced to date. By aligning genomes for 240 species, we identify bases that, when mutated, are likely to affect fitness and alter disease risk. At least 332 million bases (similar to 10.7%) in the human genome are unusually conserved across species (evolutionarily constrained) relative to neutrally evolving repeats, and 4552 ultraconserved elements are nearly perfectly conserved. Of 101 million significantly constrained single bases, 80% are outside protein-coding exons and half have no functional annotations in the Encyclopedia of DNA Elements (ENCODE) resource. Changes in genes and regulatory elements are associated with exceptional mammalian traits, such as hibernation, that could inform therapeutic development. Earth's vast and imperiled biodiversity offers distinctive power for identifying genetic variants that affect genome function and organismal phenotypes.
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| 3. |
- Isaksson, Ola, 1969, et al.
(författare)
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Design Perspectives, Theories, and Processes for Engineering Systems Design
- 2022
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Ingår i: Handbook of Engineering Systems Design: With 178 Figures and 54 Tables. - Cham : Springer International Publishing. ; , s. 53-99
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Engineering systems are socio-technical systems that provide solutions to fundamental economic and societal challenges. Such systems are complex in both technical and human terms. Engineering systems evolve over time, and uncertainty over time plays a decisive role. Perspectives on design, design theories, and design processes can be used to guide and support designers of engineering systems. This chapter provides an introduction to several well-established perspectives on design, such as design as participatory activity, design as unique mode of thinking, and more. In the same way design theories are introduced, exemplified by C-K theory, axiomatic design, domain theory, and others; and an introduction to well-known processes, including stage-based, agile, and set-based models and many more, is provided. It is explained how each of the discussed approaches offers valuable insights that help to address different aspects of complex systems design. The evolution of the approaches reflects the evolving recognition of users and context when designing engineering systems.
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| 4. |
- Al Handawi, Khalil, et al.
(författare)
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Design Space Exploration and Evaluation Using Margin-Based Trade-Offs
- 2024
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Ingår i: Journal of Mechanical Design - Transactions of the ASME. - 1050-0472. ; 146:6
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Tidskriftsartikel (refereegranskat)abstract
- Design space exploration and margin analysis can inform critical decisions early in engineering design, helping to handle the uncertainties of early design while ensuring design performance. In practice, the complexity of many products makes such decision-making challenging. This paper addresses the challenge with a new design framework that relies on the margin value method to evaluate sets of concepts that are combinatorially generated from an enhanced function-means tree. The basis for concept comparison is the margin value in each design alternative. The margin value method is expanded to address a broad class of design problems by using surrogate models and novel metrics for evaluating different conceptual alternatives. Visualization tools are introduced to support the evaluations. The efficacy of the framework is demonstrated using the design of a structural aeroengine component involving simulation models and uncertain load specifications. Overall, this paper shows how design concepts can be compared objectively and distilled to a set of alternatives that would retain their values throughout product development.
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| 5. |
- Brahma, Arindam, 1987, et al.
(författare)
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A new model for capturing design information with an aim to aid change propagation assessment and subsequent redesign
- 2018
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Ingår i: DS 92: Proceedings of the DESIGN 2018 15th International Design Conference. - : Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Croatia; The Design Society, Glasgow, UK. - 1847-9073.
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Konferensbidrag (refereegranskat)abstract
- A new model is developed to investigate the causes of change propagation and guide the redesign process. The model offers a micro-level perspective on the mechanisms through which changes propagate or are absorbed. Extending the Information Structure Framework (ISF) reported by Ahmad et al. (2013), the model uses a multi-domain approach combined with a reformulated detail design process layer. It is illustrated through a desk-based case study of routine mechanical design. Advantages and limitations are discussed along with possibilities for further work.
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| 6. |
- Brahma, Arindam, 1987, et al.
(författare)
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A study on the mechanisms of change propagation in mechanical design
- 2021
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Ingår i: Journal of Mechanical Design - Transactions of the ASME. - : ASME International. - 1050-0472. ; 143:12
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Tidskriftsartikel (refereegranskat)abstract
- Design changes and change propagation have been recognized as ubiquitous in the engineering design process. But why are some design changes propagated while others are absorbed? This paper reports on a study to investigate the specific properties of a mechanical design that influence whether a change is either propagated or absorbed. Student participants in the study were asked to complete a well-defined mechanical design task and then to introduce several design changes. Analysis of the recorded design processes reveals new insight into the mechanisms of change propagation in terms of properties of the design. The insights suggest avenues for future research to make designs more tolerant to potential future change and to develop improved methods to predict change propagation.
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| 7. |
- Brahma, Arindam, 1987, et al.
(författare)
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Calculating target thresholds for the margin value method using computational tools
- 2020
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Ingår i: Proceedings of the Design Society: DESIGN Conference. - : Cambridge University Press (CUP). - 2633-7762. ; 1
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Konferensbidrag (refereegranskat)abstract
- Overspecification or excess margin in a design can enhance its ability to absorb changes and uncertainty, but also deteriorates performance criteria such as weight and cost. This paper shows how the Margin Value Method (article in review) can be applied in conjunction with CAE tools such as FEA to quantify excess margin where a design is too complex for algebraic analysis. This new application context for the MVM is illustrated using a case study of a flange coupling design, in which topology optimisation is used within the MVM to identify opportunities for design improvement.
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| 8. |
- Brahma, Arindam, 1987, et al.
(författare)
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Circular products: the balance between sustainability and excessive margins in design
- 2024
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Ingår i: Proceedings of the Design Society. - 2732-527X. ; 4, s. 1199-1208
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Konferensbidrag (refereegranskat)abstract
- As the world deals with climate change, it is crucial that new products are designed to be more sustainable. Product design strategies which conform to the Circular Economy principles have recently gained attention, which promote sustainability and resource efficiency. However, such strategies require careful consideration of uncertainties and the ways to mitigate them, e.g. by using margins. The pursuit of circularity can inadvertently lead to overdesign as designers strive to mitigate elevated risks, thereby making a product less sustainable. In this paper, we explore this balance.
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| 9. |
- Brahma, Arindam, 1987, et al.
(författare)
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Concepts of change propagation analysis in engineering design
- 2023
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Ingår i: Research in Engineering Design - Theory, Applications, and Concurrent Engineering. - : Springer Science and Business Media LLC. - 1435-6066 .- 0934-9839. ; 34:1, s. 117-151
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Tidskriftsartikel (refereegranskat)abstract
- Interest in change propagation analysis for engineering design has increased rapidly since the topic gained prominence in the late 1990s. Although there are now many approaches and models, there is a smaller number of underlying key concepts. This article contributes a literature review and organising framework that summarises and relates these key concepts. Approaches that have been taken to address each key concept are collected and discussed. A visual analysis of the literature is presented to uncover some trends and gaps. The article thereby provides a thematic analysis of state-of-the-art in design change propagation analysis, and highlights opportunities for further work.
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| 10. |
- Brahma, Arindam, 1990, et al.
(författare)
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Margin value method for engineering design improvement
- 2020
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Ingår i: Research in Engineering Design - Theory, Applications, and Concurrent Engineering. - : Springer Science and Business Media LLC. - 1435-6066 .- 0934-9839. ; 31:3, s. 353-381
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Tidskriftsartikel (refereegranskat)abstract
- Margin occurs where a design is overspecified with respect to the minimum required. Margin may be desirable to mitigate risk and absorb future changes, but at the same time, may be undesirable if the overspecification deteriorates the design’s performance. In this article, the margin value method (MVM) is introduced to analyse an engineering design, localise the excess margin, and quantify it considering change absorption potential in relation to design performance deterioration. The method provides guidance for improving a design by prioritising excess margin that provides relatively little advantage at high cost, and that could, therefore, be eliminated to improve design performance. It shows how the value of excess margin depends on its localisation in the design parameter network, the importance of design performance parameters, and the importance of absorbing potential future changes. The method is applied to a belt conveyor design. This case indicates that the method is practicable, reveals implications, and suggests opportunities for further work.
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| 11. |
- Brahma, Arindam, 1990, et al.
(författare)
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Use of Margin to Absorb Variation in Design Specifications: An Analysis Using the Margin Value Method
- 2022
-
Ingår i: Proceedings of the Design Society. - : Cambridge University Press (CUP). - 2732-527X. ; 2, s. 323-332
-
Konferensbidrag (refereegranskat)abstract
- Predicting the impact of changes in a design can be challenging, especially for complex designs. Margins are often built into the designs which can absorb the knock-on effect of such changes, erroneously allocating which can however, lead to propagation. A method for localising and sizing margins in an incremental design context is the Margin Value Method. This paper adapts MVM in the context of uncertainty in input specifications. It discusses possible ways to allocate them in a design such that undesirable effects of margins are minimised while preventing change propagation.
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| 12. |
- Saurer, Matthias, et al.
(författare)
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Spatial variability and temporal trends in water-use efficiency of European forests
- 2014
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 20:12, s. 3700-3712
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Tidskriftsartikel (refereegranskat)abstract
- The increasing carbon dioxide (CO2) concentration in the atmosphere in combination with climatic changes throughout the last century are likely to have had a profound effect on the physiology of trees: altering the carbon and water fluxes passing through the stomatal pores. However, the magnitude and spatial patterns of such changes in natural forests remain highly uncertain. Here, stable carbon isotope ratios from a network of 35 tree-ring sites located across Europe are investigated to determine the intrinsic water-use efficiency (iWUE), the ratio of photosynthesis to stomatal conductance from 1901 to 2000. The results were compared with simulations of a dynamic vegetation model (LPX-Bern 1.0) that integrates numerous ecosystem and land-atmosphere exchange processes in a theoretical framework. The spatial pattern of tree-ring derived iWUE of the investigated coniferous and deciduous species and the model results agreed significantly with a clear south-to-north gradient, as well as a general increase in iWUE over the 20th century. The magnitude of the iWUE increase was not spatially uniform, with the strongest increase observed and modelled for temperate forests in Central Europe, a region where summer soil-water availability decreased over the last century. We were able to demonstrate that the combined effects of increasing CO2 and climate change leading to soil drying have resulted in an accelerated increase in iWUE. These findings will help to reduce uncertainties in the land surface schemes of global climate models, where vegetation-climate feedbacks are currently still poorly constrained by observational data.
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