Time filter

Source Type

United Kingdom

Guttmann W.,University of Ulm | Struth G.,University of Shefield | Weber T.,University of Cambridge
CEUR Workshop Proceedings | Year: 2011

We have implemented a repository of algebraic structures and theorems in the theorem proving environment Isabelle/HOL. It covers variants of Kleene algebras and relation algebras with many of their models. Most theorems have been obtained by automated theorem proving within Isabelle. Main purposes of the repository are the engineering of algebraic theories for computing systems and their application in formal program development. This paper describes the present state of the repository, illustrates its potential by a theory engineering and a program verification example, and discusses the most important directions for future work. Source

Lee P.J.,University of Liverpool | Lee P.J.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Kang J.,University of Shefield
Acta Acustica united with Acustica | Year: 2015

Street geometry is one of main issues on urban design which influence sound environment as well as urban climate in a street canyon. A parametric study was performed in order to investigate the influence of height-to-width ratio (H/W) on sound fields in urban streets in terms of sound pressure level (SPL), reverberation time (T30), and early decay time (EDT). A computer simulation technique based on a hybrid method combining ray tracing and image source modeling was adopted, and an omnidirectional sound source was used. Four typical idealized urban streets were modeled, with street widths of 6 m, 13 m, 20 m, and 27 m, respectively. The H/W ratio was then changed in seven steps with varying building heights while the widths of streets were fixed. Comparisons with experimental studies showed that the computer simulation models produce reliable results for SPL and T30. It was found that the variation of SPL was afected by the H/W ratio only for narrow urban streets, and the T30 and EDT increased with an increase in the H/W ratio for both narrow and wide streets. It was also observed that the T30 decreased with increasing scattering coeficients, and the EDT significantly increased as scattering coeficients increased for H/W of 3 and 6. A line source representing road trafic noise was found to produce diferent tendencies in SPL and EDT, showing that SPL and EDT were relatively constant along the length. © S. Hirzel Verlag • EAA. Source

Couto N.,University of Manchester | Couto N.,University of Shefield | Malys N.,University of Manchester | Malys N.,University of Warwick | And 3 more authors.
Journal of Proteome Research | Year: 2013

Glutathione reductase (Glr1) is a low abundance protein involved in defense mechanisms against reactive oxygen species. Expressed on cytosolic ribosomes, the same gene, GLR1, uses alternative start codons to generate two forms of Glr1. Translation from the first AUG codon generates the mitochondrial form incorporating a presequence necessary for import; translation from the second AUG codon yields the cytosolic counterpart. Proteomic strategies were used to analyze the N-terminal sequences and the turnover of Saccharomyces cerevisiae Glr1. The N-terminus of cytosolic Glr1 was found normally to be N-acetylserine. When a Glr1-overproducing strain was employed, unprocessed mitochondrial Glr-1 with N-terminal acetylmethionine also accumulated in the cytosol. The processed mitochondrial Glr1 was surprisingly found to have three alternative N-termini, none of them acetylated. Mitochondrial Glr1 was turned over faster than the cytosolic form by a factor of about 2, consistent with the importance of redox homeostasis in the mitochondria. These experiments also allowed us to estimate the extent of "leaky scanning" in the synthesis of Glr1. Surprisingly, the second AUG appears to be responsible for most of the cellular Glr1. This is the first report of protein turnover measurements of a low-abundance protein distributed in different compartments of a eukaryotic cell. © 2013 American Chemical Society. Source

Caicedo-Nunez C.H.,University of Southampton | Veres S.M.,University of Shefield
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2013

Problems dealing with coordination of autonomous vehicles usually assume that the agents share a universal orientation in their local reference frames. Although the sensing requirements to satisfy this assumption can sometimes be low, they cannot always be guaranteed. The basic problem of frame alingment is studied here, in the absence of orientation sensors, by exploiting the notions of rigidity, visibility and communication graphs. First the relationship is examined between geometric rigidity of a formation and the agents' ability to agree on a shared orientation to their local frames. Our main results are then formulated in terms of visibility and communication graphs using cyclic graph coverage. Cases when only distances are measurable are also investigated, in which case the motion capabilities of the agents need to be exploited to resolve ambiguity caused by symmetry. © 2013 IFAC. Source

Han L.,University College London | Hipwell J.H.,University College London | Tanner C.,ETH Zurich | Taylor Z.,University of Shefield | And 4 more authors.
Physics in Medicine and Biology | Year: 2012

Physically realistic simulations for large breast deformation are of great interest for many medical applications such as cancer diagnosis, image registration, surgical planning and image-guided surgery. To support fast, large deformation simulations of breasts in clinical settings, we proposed a patient-specific biomechanical modelling framework for breasts, based on an open-source graphics processing unit-based, explicit, dynamic, nonlinear finite element (FE) solver. A semi-automatic segmentation method for tissue classification, integrated with a fully automated FE mesh generation approach, was implemented for quick patient-specific FE model generation. To solve the difficulty in determining material parameters of soft tissues in vivo for FE simulations, a novel method for breast modelling, with a simultaneous material model parameter optimization for soft tissues in vivo, was also proposed. The optimized deformation prediction was obtained through iteratively updating material model parameters to maximize the image similarity between the FE-predicted MR image and the experimentally acquired MR image of a breast. The proposed method was validated and tested by simulating and analysing breast deformation experiments under plate compression. Its prediction accuracy was evaluated by calculating landmark displacement errors. The results showed that both the heterogeneity and the anisotropy of soft tissues were essential in predicting large breast deformations under plate compression. As a generalized method, the proposed process can be used for fast deformation analyses of soft tissues in medical image analyses and surgical simulations. © 2012 Institute of Physics and Engineering in Medicine. Source

Discover hidden collaborations