University of Shefield

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University of Shefield

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Vivarelli G.,University of Shefield | Qin N.,University of Shefield | Shahpar S.,Rolls-Royce
AIAA SciTech Forum - 55th AIAA Aerospace Sciences Meeting | Year: 2017

Mesh adaptation has proven to enable engineers to obtain a much improved solution and reduce uncertainty in parameters of interest with a limited size grid. However, it is scarcely utilised within industry, partly due to the complexity of the problems that have to be analysed. In fact, within the literature there is a limited number of intricate geometries being considered under the flow conditions of interest to developers. Providing evidence of the capabilities of grid adaptation strategies to handle elaborate configurations, demonstrates how industrial environments can improve their design turnaround times. This paper will utilise feature-based approaches to automatically improve an initial mesh that did not allow evaluation of the adjoint solution. The possibility of determining this, permits to adopt the more sophisticated error estimation approach. Therefore, it will be shown that even for a test-case with elaborate flow behaviour, such as a transonic compressor blade, it will be possible to evaluate the adjoint solution with a coarse mesh. The final results will be compared with significantly finer grids as a benchmark, showing comparable results with a much reduced mesh node count. © 2017 by Rolls-Royce plc.

Mahajan S.,University of Southern California | Alameer A.,University of Southern California | McMinn P.,University of Shefield | Halfond W.G.J.,University of Southern California
ISSTA 2017 - Proceedings of the 26th ACM SIGSOFT International Symposium on Software Testing and Analysis | Year: 2017

A consistent cross-browser user experience is crucial for the success of a website. Layout Cross Browser Issues (XBIs) can severely undermine a website's success by causing web pages to render incorrectly in certain browsers, thereby negatively impacting users' impression of the quality and services that the web page delivers. Existing Cross Browser Testing (XBT) techniques can only detect XBIs in websites. Repairing them is, hitherto, a manual task that is labor intensive and requires significant expertise. Addressing this concern, our paper proposes a technique for automatically repairing layout XBIs in websites using guided search-based techniques. Our empirical evaluation showed that our approach was able to successfully fix 86% of layout XBIs reported for 15 different web pages studied, thereby improving their cross-browser consistency. © 2017 ACM.

Hollom J.,University of Shefield | Qiny N.,University of Shefield
18th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference, 2017 | Year: 2017

Gradient-free multi-point optimization of subsonic natural laminar flow airfoils is undertaken to assess robustness of drag to variations in surface quality, leading edge contamination, and machining defects. These are modeled via the reduc- tion of transition amplification factor, or critical N-factor, used in the linear stability theory based eN transition model. Drag minimization of the NLF0416, NLF0215F and NLF0115 airfoils over a range of weighted design points is carried out using a Genetic Algorithm implemented via the Distributed Evolutionary Algorithms in Python (DEAP) package. Simulation of the flow is done using the XFOIL potential flow solver. The airfoils are deformed using a perturba- tion profile, parametrized using the Class Shape Transformation method. The results of this study show that robustness of an airfoil’s drag to critical N-factor varies over its entire polar. Improvements obtained locally will result in losses elsewhere. The gradient of the transition location with changing lift coefficient can be used to provide some insight into robustness as this is found to have a strong effect on its strength and distribution. © 2017 American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

Zhong Q.-C.,Illinois Institute of Technology | Zhong Q.-C.,University of Shefield | Boroyevich D.,Virginia Polytechnic Institute and State University
IEEE Access | Year: 2016

It is well known that droop control is fundamental to the operation of power systems and now the parallel operation of inverters, while phase-locked loops (PLLs) are widely adopted in modern electrical engineering. In this paper, it is shown at first that droop control and PLLs structurally resemble each other. This bridges the gap between the two communities working on droop control and PLLs. As a result, droop controllers and PLLs can be improved and further developed via adopting the advancements in the other field. This finding is then applied to operate the conventional droop controller for inverters with inductive output impedance to achieve the function of PLLs, without having a dedicated synchronization unit. Extensive experimental results are provided to validate the theoretical analysis. © 2013 IEEE.

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.

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.

Sudholt D.,University of Shefield
GECCO 2015 - Companion Publication of the 2015 Genetic and Evolutionary Computation Conference | Year: 2015

Insight into probabilistic models underlying ACO and PSO. How design choices and parameters affect (bounds on) running times. How simple ACO algorithms optimize unimodal functions and plateaus. Results for ACO in combinatorial optimization. First analyses of basic PSO algorithms in discrete and continuous spaces.

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.

Vere J.,University of Shefield | Joshi R.,University of Shefield
The International journal of oral & maxillofacial implants | Year: 2012

PURPOSE: The aim of this systematic review was to assess the methodologic and statistical quality of prospective case series of treatment interventions of dental implant surgery and prosthodontics published between 2004 and 2008.MATERIALS AND METHODS: Prospective case series were identified following detailed searches of the Medline, EMBASE, and CINAHL databases. Identified studies were independently assessed by two nonblinded reviewers for 10 key methodologic and statistical domains. Information was collected using a customized data collection sheet.RESULTS: The initial search yielded 1,484 studies. Following application of inclusion criteria, 31 prospective case series reports that did not present the same patient material were identified for this review. Interexaminer agreement was assessed for all domains (median kappa score, 0.84). All disagreements were resolved by discussion. The source of funding was unclear in 20 studies (65%). Treatment protocol was adequately described in 21 studies (68%), and eligibility criteria were adequately reported in 24 studies (77%). Only two studies (6.5%) tested the intraexaminer/interexaminer reliability of at least one outcome of interest. Inferential statistical analysis was presented in 21 studies. However, this analysis was only considered appropriate in 12 studies (57%). Confidence intervals were reported in four studies (13%).CONCLUSIONS: Prospective case series of treatment interventions of dental implant surgery and Prosthodontics are poorly analyzed and rarely test the reliability of outcome measures. These particular studies have limited external validity and appear to provide little unbiased evidence to support clinical decision-making.

Mazumdar S.,University of Shefield | Zhang Z.,University of Shefield
CEUR Workshop Proceedings | Year: 2016

This paper describes an extension of the TableMiner+ sys- tem, an open source Semantic Table Interpretation system that annotates Web tables using Linked Data in an effective and efficient approach. It adds a graphical user interface to TableMiner+, to facilitate the visualization and correction of automatically generated annotations. This makes TableMiner+ an ideal tool for the semi-automatic creation of high-quality semantic annotations on tabular data, which facilitates the publication of Linked Data on the Web.

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