University of Bath

About: University of Bath is a education organization based out in Bath, Bath and North East Somerset, United Kingdom. It is known for research contribution in the topics: Population & Photonic-crystal fiber. The organization has 15830 authors who have published 39608 publications receiving 1358769 citations. The organization is also known as: Bath University.

Tracking with prescribed transient behaviour

Abstract: Universal tracking control is investigated in the context of a class S of M-input, M-output dynamical systems modelled by functional differential equations. The class encompasses a wide variety of nonlinear and infinite-dimensional systems and contains – as a prototype subclass – all finite-dimensional linear single-input single-output minimum-phase systems with positive high-frequency gain. The control objective is to ensure that, for an arbitrary -valued reference signal r of class W 1,∞ (absolutely continuous and bounded with essentially bounded derivative) and every system of class S, the tracking error e between plant output and reference signal evolves within a prespecified performance envelope or funnel in the sense that for all t ≥ 0, where φ a prescribed real-valued function of class W 1,∞ with the property that φ(s) > 0 for all s > 0 and . A simple (neither adaptive nor dynamic) error feedback control of the form $u(t)=- \alpha ({\varphi}(t)\|e(t)\|)e(t)$ is introduced which achieves the objective whilst maintaining boundedness of the control and of the scalar gain .

Genetics and evolution of pigment patterns in fish

Abstract: Vertebrate pigment patterns are both beautiful and fascinating. In mammals and birds, pigment patterns are likely to reflect the spatial regulation of melanocyte physiology, via alteration of the colour-type of the melanin synthesized. In fish, however, pigment patterns predominantly result from positioning of differently coloured chromatophores. Theoretically, pigment cell patterning might result from long-range patterning mechanisms, from local environmental cues, or from interactions between neighbouring chromatophores. Recent studies in two fish genetic model systems have made progress in understanding pigment pattern formation. In embryos, the limited evidence to date implicates local cues and chromatophore interactions in pigment patterning. In adults, de novo generation of chromatophores and cell-cell interactions between chromatophore types play critical roles in generating striped patterns; orientation of the stripes may well depend upon environmental cues mediated by underlying tissues. Further genetic screens, coupled with the routine characterization of critical gene products, promises a quantitative understanding of how striped patterns are generated in the zebrafish system. Initial 'evo-devo' studies indicate how fish pigment patterns may evolve and will become more complete as the developmental genetics is integrated with theoretical modelling.

Further analysis of multilevel Monte Carlo methods for elliptic PDEs with random coefficients

Abstract: We consider the application of multilevel Monte Carlo methods to elliptic PDEs with random coefficients. We focus on models of the random coefficient that lack uniform ellipticity and boundedness with respect to the random parameter, and that only have limited spatial regularity. We extend the finite element error analysis for this type of equation, carried out in Charrier et al. (SIAM J Numer Anal, 2013), to more difficult problems, posed on non-smooth domains and with discontinuities in the coefficient. For this wider class of model problem, we prove convergence of the multilevel Monte Carlo algorithm for estimating any bounded, linear functional and any continuously Frechet differentiable non-linear functional of the solution. We further improve the performance of the multilevel estimator by introducing level dependent truncations of the Karhunen---Loeve expansion of the random coefficient. Numerical results complete the paper.

Knowledge management in engineering design: personalization and codification

Abstract: Knowledge management is one of the key enabling technologies of distributed engineering enterprises. It encompasses a wide range of organizational, management and technologically orientated approaches that promote the exploitation of an organizations' intellectual assets. Knowledge management approaches may be divided into personalization approaches that emphasize human resources and communication, and codification approaches that emphasize the collection and organization of knowledge. This distinction is used to explore the application of knowledge management in engineering design, after first outlining the engineering circumstances that have led to the current emphasis on the application. The paper then gives an overview of approaches to knowledge management through personalization, including human and organizational approaches, concentrating on the establishment of communities of practice. The role of information technology is explained both in terms of personalization (communication and team support t...