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Search Results: 1 - 10 of 229578 matches for " John N. Davies "
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Principles of Eliminating Access Control Lists within a Domain
John N. Davies,Paul Comerford,Vic Grout
Future Internet , 2012, DOI: 10.3390/fi4020413
Abstract: The infrastructure of large networks is broken down into areas that have a common security policy called a domain. Security within a domain is commonly implemented at all nodes. However this can have a negative effect on performance since it introduces a delay associated with packet filtering. When Access Control Lists (ACLs) are used within a router for this purpose then a significant overhead is introduced associated with this process. It is likely that identical checks are made at multiple points within a domain prior to a packet reaching its destination. Therefore by eliminating ACLs within a domain by modifying the ingress/egress points with equivalent functionality an improvement in the overall performance can be obtained. This paper considers the effect of the delays when using router operating systems offering different levels of functionality. It considers factors which contribute to the delay particularly due to ACLs and by using theoretical principles modified by practical calculation a model is created. Additionally this paper provides an example of an optimized solution which reduces the delay through network routers by distributing the security rules to the ingress/egress points of the domain without affecting the security policy.
How to Use a Trafficked Woman. The Alliance between Political and Criminal Trafficking Organisations
John Davies,Benjamin Davies
Recherches Sociologiques et Anthropologiques , 2011, DOI: 10.4000/rsa.416
Abstract: The principal argument of this paper is that migrant women with secure mobility rights and supportive social networks can avoid or mitigate many trafficking harms. However the paper contends that some actors have conspired to prevent such circumstances so as to pursue diverse political agendas at the expense of migrant women. The paper’s analysis restructures the trafficking contest from organised criminals versus law enforcement agencies to principally a contest between migrant women and those political agents who benefit from the moral panic associated with trafficking. It is then argued that it is these more sophisticated political actors rather than organised criminals and the clients of sex workers are the most important stakeholders in sustaining or exploiting trafficking harm. Therefore, it is concluded that resolving many trafficking harms in the EEA could be achieved by subverting political traffickers through improving migration policy rather than fighting organised crime.
Part-time undergraduate study in civil engineering – students from the workplace
John Davies
Engineering Education , 2008,
Abstract: This is an investigation of part-time undergraduate degree study in civil engineering based at Coventry University. It aimed to answer the following four questions:How do the experiences of part-time students of civil engineering compare with those for other subject areas reported in the literature?What is the difference in performance of part-time and full-time students?What are the reasons for the differences?What should we learn from this?The study incorporated three elements: scrutiny of data on student numbers, age and performance; a questionnaire to allow comparison of factual information on the circumstances of part-time and full-time students; and interviews with 21 part-time students (in groups of four or five) and three part-time graduates (individually).The interviews gave insights into the experiences of part-time students of civil engineering and allowed comparison with those in other subject areas. A study of performance by part-time and full-time students for four academic years between 2002 and 2006 revealed that part-time students outperformed full-time students in terms of grade of honours and marks in modules (6.4 percentage marks on average in every module). The reasons for the better performance of part-time students were considered and it was concluded that the greatest advantage comes from the skills, attitudes, and motivation that part-time students have developed in the workplace. Recommendations are made in terms of better support for part-time students and ways of benefiting from the potential contributions they can make.
Validation of Spectral and Broadband UV-B (290 - 325 nm) Irradiance for Canada  [PDF]
Jacqueline Binyamin, John Davies, Bruce McArthur
Atmospheric and Climate Sciences (ACS) , 2011, DOI: 10.4236/acs.2011.13008
Abstract: Stratospheric ozone depletion, as a result of increasing chlorofluorocarbons in the stratosphere, allows more UV-B irradiance (290 - 325 nm) to reach the earth’s surface with possible detrimental biological effects. Be-cause there are few UV-B radiation stations, irradiance models are useful tools for estimating irradiances where measurements are not made. Estimates of spectral and broadband irradiances from a numerical model are compared with Brewer spectrophotometer measurements at nine Canadian stations (Alert, Resolute Bay, Churchill, Edmonton, Regina, Winnipeg, Montreal, Halifax and Toronto) and 26 years of data. The model uses either the discrete ordinate radiative transfer (DISORT) or the delta-Eddington algorithms to solve the radiative transfer equation for a 49-layer, vertically inhomogeneous, plane-parallel atmosphere, with cloud inserted between the 2 and 3 km heights. Spectral calculations are made at 1 nm intervals. The model uses extraterrestrial spectral irradiance, spectral optical properties for each atmospheric layer for ozone, air mole-cules, and aerosol and surface albedo. A fixed broadband cloud optical depth of 27 was satisfactory for cal-culating cloudy sky irradiances at all stations except in the arctic. Comparisons are made both for daily totals and for monthly averaged spectral and broadband irradiances. The delta-Eddington method is shown to be unsuitable for calculating spectral irradiances under clear skies, at wavelengths less than 305 nm where absorption by ozone is high, and at large solar zenith angles. The er-rors are smaller for overcast conditions. The method is adequate for daily total and monthly averaged spec-tral (? 305 nm) and broadband calculations for all sky conditions, although consistently overestimating ir-radiances. There is a good agreement between broadband measurements and calculations for both daily totals and monthly averages with mean bias error mainly less than 5% of the mean measured daily irradiance and root mean square error less than 25%, decreasing to below 15% for monthly averages.
Comparison of UV-B Broadband Brewer Measurements with Irradiances from Surface-Based and Satellite-Based Models  [PDF]
Jacqueline Binyamin, John Davies, Bruce McArthur
Atmospheric and Climate Sciences (ACS) , 2011, DOI: 10.4236/acs.2011.13016
Abstract: UV-B irradiance can be estimated from surface meteorological data or from satellite measurements. This paper compares irradiance estimates from the Davies surface-based radiation model and the Canada Centre for Remote Sensing (CCRS) satellite model with Brewer spectrophotometer measurements for all sky conditions at six Canadian stations (Edmonton, Regina, Winnipeg, Montreal, Halifax and Toronto). The Davies model is applied with both the discrete ordinate radiative transfer (DISORT) and the delta-Eddington algorithms to solve the radiative transfer equation. Both models’ estimates are compared with instantaneous Brewer measurements. Both perform similarly with mean bias errors within 6% of the mean measured irradiance for the measurement period and root mean square errors between 25% and 30%.
Recovery of the Decorin-Enriched Fraction, Extract (D), From Human Skin: An Accelerated Protocol
Denys N. Wheatley,Emma Graham,R. Shannon McMaster,Ian F. K. Muir,John D. Holmes,Michaela Davies
Journal of Biomedicine and Biotechnology , 2004, DOI: 10.1155/s1110724304308089
Abstract: The original extraction procedure of Engel and Catchpole [1] has often been used to recover decorin-enriched material from the skin. This material has a strong inhibitory effect on fibroblast proliferation, and clearly suppresses it in skin except after the first 5–6 days of wounding when new scaffold material is required. The aim of our present study has been to find and evaluate the product of a faster recovery method, and to check its consistency as a more reliable means of regularly obtaining sufficient material for topical application in wounds that might become hypertrophic. Modifications of the original Toole and Lowther [2] extraction procedure have been carefully evaluated in an attempt to cut preparation time without compromising biological activity of the inhibitory extract. We have devised a faster recovery procedure without compromising biological activity, even if initial recovery has been somewhat reduced. The latter problem could be offset by repeated cycles of the final extraction step. The main inhibitory activity is shown to be within the decorin-enriched “extract D,” as the core protein and DSPG II. Adjustment of the extract towards neutrality after dialysis against water keeps most of the extracted protein in solution and yielded a decorin-enriched preparation that had a specific activity equivalent to that of the old method. It also yielded a fraction that was readily lyophilised to give a small amount of material that could be stored indefinitely without loss of activity and readily redissolved in aqueous solution. A reliable and relatively quick method is presented for the production, from human skin, of a decorin-enriched preparation that has strong fibroblast inhibitory action. The value of the procedure is that it is inexpensive and can produce the quantities that might be used topically in reducing hypertrophic scarring of wounds.
The Long-Term Dynamical Evolution of Planetary Systems
Melvyn B. Davies,Fred C. Adams,Philip Armitage,John Chambers,Eric Ford,Alessandro Morbidelli,Sean N. Raymond,Dimitri Veras
Physics , 2013, DOI: 10.2458/azu_uapress_9780816531240-ch034
Abstract: This chapter concerns the long-term dynamical evolution of planetary systems from both theoretical and observational perspectives. We begin by discussing the planet-planet interactions that take place within our own Solar System. We then describe such interactions in more tightly-packed planetary systems. As planet-planet interactions build up, some systems become dynamically unstable, leading to strong encounters and ultimately either ejections or collisions of planets. After discussing the basic physical processes involved, we consider how these interactions apply to extrasolar planetary systems and explore the constraints provided by observed systems. The presence of a residual planetesimal disc can lead to planetary migration and hence cause instabilities induced by resonance crossing; however, such discs can also stabilise planetary systems. The crowded birth environment of a planetary system can have a significant impact: close encounters and binary companions can act to destabilise systems, or sculpt their properties. In the case of binaries, the Kozai mechanism can place planets on extremely eccentric orbits which may later circularise to produce hot Jupiters.
Feedback through student essay competitions: what makes a good engineering lecturer?
Kate Collins,John Davies
Engineering Education , 2009,
Abstract: The Engineering Subject Centre of the Higher Education Academy has run student essay competitions for some years. In 2007/08 the title was ‘What makes a good engineering lecturer?’. This paper presents an analysis of the 43 submissions, carried out to identify the most commonly cited attributes and to present quotes that convey the spirit of the essays. The same title had been used for the first competition in 2003/04, and the outcomes of the 2007/08 competition are compared with those previously published for the 2003/04 award. The attributes most commonly identified across both sets of essays are use of real-world examples, approachability, enthusiasm, diversity of media, and good communication.
HeartSmartTM: A New Method of Assessing Hydration in Neurosurgical Patients  [PDF]
Kenneth James Warring-Davies, John Martin Bland
Surgical Science (SS) , 2012, DOI: 10.4236/ss.2012.311108
Abstract: Background: Maintenance of normal fluid homeostasis is challenging in neurosurgical patients. Consequently, we studied hydration assessment in neurosurgical intensive care patients. Methods: Pulmonary artery catheter thermodilution (PACTD) is the conventional method for measuring cardiac index (CI) and mean pulmonary artery occlusion (MPAOP) or wedge pressure (MPWP). We compared values from this technique with those derived from continuous cardiac dynamic monitoring (CCDM)-HeartSmart?, a new, less invasive, software-based technique. Over 4 years, we undertook an audit of 101 paired sets of data from 21 patients with sub-arachnoid hemorrhage who had pulmonary artery flotation catheters inserted as part of their treatment. Measured values of CI and MPWP were obtained retrospectively from patients’ charts and compared with values calculated using CCDM-HeartSmart? software. Results: Using the Bland-Altman method for comparing two measurement techniques, there was good agreement between measured and calculated MPWP (mean of differences –1.81, SD 3.97, SE 0.39, 95% CI –2.59 to 2.04 l/min/m2; two-sided p < 0.0001). The measured and calculated values of CI were also in good agreement (mean of differences 0.36, SD 1.30, SE 0.13, 95% CI 0.109 - 0.619; two-sided p = 0.0055, 95% limits of agreement –2.1 to 2.91 l/min/m2). This indicates that, when estimating CI and MPWP in critically ill neurosurgical patients, CCDM-HeartSmart? provides values close to those generated using PACTD. Conclusions: The CCDM-HeartSmart? could prove invaluable for optimizing response to fluid replacement and for guiding cardiovascular support in neurosurgical patients. This new, simple technology may help to facilitate routine adoption of perioperative optimization of blood flow using early goal-directed therapy.
Convergence of eigenvalues for a highly non-self-adjoint differential operator
E. B. Davies,John Weir
Mathematics , 2008, DOI: 10.1112/blms/bdp120
Abstract: In this paper we study a family of operators dependent on a small parameter $\epsilon > 0$, which arise in a problem in fluid mechanics. We show that the spectra of these operators converge to N as $\epsilon \to 0$, even though, for fixed $\epsilon > 0$, the eigenvalue asymptotics are quadratic.
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