24,139 research outputs found

    CP Violation, an experimental perspective

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    I present a review of current and near-future experimental investigations of CP violation. In this review, I cover limits on particle electric dipole moments (EDMs) and CP violation studies in the K and B systems. The wealth of results from the new B factories provide impressive constraints on the CKM quark mixing matrix elements. Current and future measurements are focusing on processes dominated by loop diagrams, which probe physics at high mass scales in low-energy experiments.Comment: Invited plenary talk, DPF meeting, August 200

    Is agile project management applicable to construction?

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    This paper briefly summarises the evolution of Agile Project Management (APM) and differentiates it from lean and agile production and ‘leagile’ construction. The significant benefits being realized through employment of APM within the information systems industry are stated. The characteristics of APM are explored, including: philosophy, organizational attitudes and practices, planning, execution and control and learning. Finally, APM is subjectively assessed as to its potential contribution to the pre-design, design and construction phases. In conclusion, it is assessed that APM offers considerable potential for application in predesign and design but that there are significant hurdles to its adoption in the actual construction phase. Should these be overcome, APM offers benefits well beyond any individual project

    Analysis of a Helmholtz preconditioning problem motivated by uncertainty quantification

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    This paper analyses the following question: let Aj\mathbf{A}_j, j=1,2,j=1,2, be the Galerkin matrices corresponding to finite-element discretisations of the exterior Dirichlet problem for the heterogeneous Helmholtz equations ∇⋅(Aj∇uj)+k2njuj=−f\nabla\cdot (A_j \nabla u_j) + k^2 n_j u_j= -f. How small must ∄A1−A2∄Lq\|A_1 -A_2\|_{L^q} and ∄n1−n2∄Lq\|{n_1} - {n_2}\|_{L^q} be (in terms of kk-dependence) for GMRES applied to either (A1)−1A2(\mathbf{A}_1)^{-1}\mathbf{A}_2 or A2(A1)−1\mathbf{A}_2(\mathbf{A}_1)^{-1} to converge in a kk-independent number of iterations for arbitrarily large kk? (In other words, for A1\mathbf{A}_1 to be a good left- or right-preconditioner for A2\mathbf{A}_2?). We prove results answering this question, give theoretical evidence for their sharpness, and give numerical experiments supporting the estimates. Our motivation for tackling this question comes from calculating quantities of interest for the Helmholtz equation with random coefficients AA and nn. Such a calculation may require the solution of many deterministic Helmholtz problems, each with different AA and nn, and the answer to the question above dictates to what extent a previously-calculated inverse of one of the Galerkin matrices can be used as a preconditioner for other Galerkin matrices

    Enabling investment for the transition to a low carbon economy: government policy to finance early stage green innovation

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    Rapid transformation to meet the Paris 1.5oC climate target requires greater attention to be given to the role of innovative low carbon early stage businesses and the public sector’s role in addressing finance gaps for longer horizon investment requirements. As entrepreneurs require different forms of finance as their businesses grow and move up the ‘finance escalator’, we explore the role of public sector support for grant, equity, debt and new forms of crowd funding finance. These funds can enable individual sustainability focussed businesses to access finance and encourage finance into new areas through having a demonstration effect. We conclude that a finance ecosystem approach is required that ensures complementary forms of finance for low carbon investment are connected at local, national and international scales, alongside support to build entrepreneurial skills and investment readiness. There is also a need for better evidence of the role of public sector support and where there is greatest impact on climate change

    Measurement of long-range steric repulsions between microspheres due to an adsorbed polymer

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    We have measured the interparticle potential between pairs of micron-sized silica spheres induced by adsorbed polyethylene oxide polymer using a line-scanned optical tweezer. We found this long-range steric repulsion to be exponential over the range of energies (0.1kBT–5kBT) and polymer molecular weights (452 000–1 580 000) studied, and that the potential scaled with the polymer’s radius of gyration RG. The potential’s exponential decay length was about 0.6RG and its range was about 4RG, although both parameters varied significantly from one pair of spheres to another. The potential’s exponential prefactor was greater than mean-field predictions

    Structured Deformations of Continua: Theory and Applications

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    The scope of this contribution is to present an overview of the theory of structured deformations of continua, together with some applications. Structured deformations aim at being a unified theory in which elastic and plastic behaviours, as well as fractures and defects can be described in a single setting. Since its introduction in the scientific community of rational mechanicists (Del Piero-Owen, ARMA 1993), the theory has been put in the framework of variational calculus (Choksi-Fonseca, ARMA 1997), thus allowing for solution of problems via energy minimization. Some background, three problems and a discussion on future directions are presented.Comment: 11 pages, 1 figure, 1 diagram. Submitted to the Proceedings volume of the conference CoMFoS1

    Derivation of linearized transfer functions for switching-mode regulations. Phase A: Current step-up and voltage step-up converters

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    Small-signal models are derived for the power stage of the voltage step-up (boost) and the current step-up (buck) converters. The modeling covers operation in both the continuous-mmf mode and the discontinuous-mmf mode. The power stage in the regulated current step-up converter on board the Dynamics Explorer Satellite is used as an example to illustrate the procedures in obtaining the small-signal functions characterizing a regulated converter

    A microgravity isolation mount

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    The design and preliminary testing of a system for isolating microgravity sensitive payloads from spacecraft vibrational and impulsive disturbances is discussed. The Microgravity Isolation Mount (MGIM) concept consists of a platform which floats almost freely within a limited volume inside the spacecraft, but which is constrained to follow the spacecraft in the long term by means of very weak springs. The springs are realized magnetically and form part of a six degree of freedom active magnetic suspension system. The latter operates without any physical contact between the spacecraft and the platform itself. Power and data transfer is also performed by contactless means. Specifications are given for the expected level of input disturbances and the tolerable level of platform acceleration. The structural configuration of the mount is discussed and the design of the principal elements, i.e., actuators, sensors, control loops and power/data transfer devices are described. Finally, the construction of a hardware model that is being used to verify the predicted performance of the MGIM is described

    Financing Cleantech SME innovation: setting an agenda

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    The need for a clear research and policy agenda to assist early stage Cleantech financing has never been greater. These businesses may hold important keys to unlocking vital globally game changing technologies to tackle climate change. The paper provides an overview of recent academic literature and proposes a research agenda for early stage Cleantech SME finance. With growing interest in how to support innovations that tackle the climate emergency, there is a need for evidence that can assist the private sector, civil society organizations and policymakers in finding more effective ways to encourage impact investing and other finance for early stage Cleantech SMEs. This research agenda will therefore contribute to sustainability transitions in key sectors and the development of a sustainable low carbon economy
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