29,911 research outputs found
Hollow cathode plasma penetration study Final report
Hollow cathode electron beam discharge for penetrating plasma sheath around reentry vehicl
Doctors who pilot the GMC's Tests of Competence: who volunteers and why?
Background: Doctors who are investigated by the General Medical Council (GMC) for performance concerns may be required to take a Test of Competence (ToC). The tests are piloted on volunteer doctors before they are used in Fitness to Practise (FtP) investigations. Objectives: To find out who volunteers to take a pilot ToC and why. Methods: This was a retrospective cohort study. Between February 2011 and October 2012 we asked doctors who volunteered for a test to complete a questionnaire about their reasons for volunteering and recruitment. We analysed the data using descriptive statistics and Pearson’s chi-square test. Results: 301 doctors completed the questionnaire. Doctors who took a ToC voluntarily were mostly women, of white ethnicity, of junior grades, working in general practice and who held a Primary Medical Qualification from the UK. This was a different population to doctors under investigation and all registered doctors in the UK. Most volunteers heard about the GMC’s pilot events through email from a colleague and used the experience to gain exam practice for forthcoming postgraduate exams. Conclusions: The reference group of volunteers are not representative of doctors under FtP investigation. Our findings will be used to inform future recruitment strategies with the aim to encourage better matching of groups who voluntarily pilot a ToC with those under FtP investigation
PNJL model for adjoint fermions
Recent work on QCD-like theories has shown that the addition of adjoint
fermions obeying periodic boundary conditions to gauge theories on R^3 X S^1
can lead to a restoration of center symmetry and confinement for sufficiently
small circumference L of S^1. At small L, perturbation theory may be used
reliably to compute the effective potential for the Polyakov loop P in the
compact direction. Periodic adjoint fermions act in opposition to the gauge
fields, which by themselves would lead to a deconfined phase at small L. In
order for the fermionic effects to dominate gauge field effects in the
effective potential, the fermion mass must be sufficiently small. This
indicates that chiral symmetry breaking effects are potentially important. We
develop a Polyakov-Nambu-Jona Lasinio (PNJL) model which combines the known
perturbative behavior of adjoint QCD models at small L with chiral symmetry
breaking effects to produce an effective potential for the Polyakov loop P and
the chiral order parameter psi-bar psi. A rich phase structure emerges from the
effective potential. Our results are consistent with the recent lattice
simulations of Cossu and D'Elia, which found no evidence for a direct
connection between the small-L and large-L confining regions. Nevertheless, the
two confined regions are connected indirectly if an extended field theory model
with an irrelevant four-fermion interaction is considered. Thus the small-L and
large-L regions are part of a single confined phase.Comment: 6 pages, 4 figures; presented at INPC 201
Stability of bubble nuclei through Shell-Effects
We investigate the shell structure of bubble nuclei in simple
phenomenological shell models and study their binding energy as a function of
the radii and of the number of neutron and protons using Strutinsky's method.
Shell effects come about, on the one hand, by the high degeneracy of levels
with large angular momentum and, on the other, by the big energy gaps between
states with a different number of radial nodes. Shell energies down to -40 MeV
are shown to occur for certain magic nuclei. Estimates demonstrate that the
calculated shell effects for certain magic numbers of constituents are probably
large enough to produce stability against fission, alpha-, and beta-decay. No
bubble solutions are found for mass number A < 450.Comment: 9 pages and 9 figures in the eps format include
Liquid-Drop Model and Quantum Resistance Against Noncompact Nuclear Geometries
The importance of quantum effects for exotic nuclear shapes is demonstrated.
Based on the example of a sheet of nuclear matter of infinite lateral
dimensions but finite thickness, it is shown that the quantization of states in
momentum space, resulting from the confinement of the nucleonic motion in the
conjugate geometrical space, generates a strong resistance against such a
confinement and generates restoring forces driving the system towards compact
geometries. In the liquid-drop model, these quantum effects are implicitly
included in the surface energy term, via a choice of interaction parameters, an
approximation that has been found valid for compact shapes, but has not yet
been scrutinized for exotic shapes.Comment: 9 pages with 3 figure
Determination of the Joint Confidence Region of Optimal Operating Conditions in Robust Design by Bootstrap Technique
Robust design has been widely recognized as a leading method in reducing
variability and improving quality. Most of the engineering statistics
literature mainly focuses on finding "point estimates" of the optimum operating
conditions for robust design. Various procedures for calculating point
estimates of the optimum operating conditions are considered. Although this
point estimation procedure is important for continuous quality improvement, the
immediate question is "how accurate are these optimum operating conditions?"
The answer for this is to consider interval estimation for a single variable or
joint confidence regions for multiple variables.
In this paper, with the help of the bootstrap technique, we develop
procedures for obtaining joint "confidence regions" for the optimum operating
conditions. Two different procedures using Bonferroni and multivariate normal
approximation are introduced. The proposed methods are illustrated and
substantiated using a numerical example.Comment: Two tables, Three figure
Toward the assessment of the susceptibility of a digital system to lightning upset
Accomplishments and directions for further research aimed at developing methods for assessing a candidate design of an avionic computer with respect to susceptability to lightning upset are reported. Emphasis is on fault tolerant computers. Both lightning stress and shielding are covered in a review of the electromagnetic environment. Stress characterization, system characterization, upset detection, and positive and negative design features are considered. A first cut theory of comparing candidate designs is presented including tests of comparative susceptability as well as its analysis and simulation. An approach to lightning induced transient fault effects is included
Boundary-detection algorithm for locating edges in digital imagery
The author has identified the following significant results. Initial development of a computer program which implements a boundary detection algorithm to detect edges in digital images is described. An evaluation of the boundary detection algorithm was conducted to locate boundaries of lakes from LANDSAT-1 imagery. The accuracy of the boundary detection algorithm was determined by comparing the area within boundaries of lakes located using digitized LANDSAT imagery with the area of the same lakes planimetered from imagery collected from an aircraft platform
Development of computer software to analyze entire LANDSAT scenes and to summarize classification results of variable-size polygons
The Forest Pest Management Division (FPMD) of the Pennsylvania Bureau of Forestry has the responsibility for conducting annual surveys of the State's forest lands to accurately detect, map, and appraise forest insect infestations. A standardized, timely, and cost-effective method of accurately surveying forests and their condition should enhance the probability of suppressing infestations. The repetitive and synoptic coverage provided by LANDSAT (formerly ERTS) makes such satellite-derived data potentially attractive as a survey medium for monitoring forest insect damage over large areas. Forest Pest Management Division personnel have expressed keen interest in LANDSAT data and have informally cooperated with NASA/Goddard Space Flight Center (GSFC) since 1976 in the development of techniques to facilitate their use. The results of this work indicate that it may be feasible to use LANDSAT digital data to conduct annual surveys of insect defoliation of hardwood forests
Quality engineering of a traction alternator by robust design
Robust design is an engineering methodology for improving productivity during research and development so that high-quality products can be developed and produced quickly and at low cost. A large electrical company was developing traction alternators for a diesel electrical engine. Customer requirement was to obtain very high efficiency which, in turn, was influenced by several design parameters. The usual approach of the 'design-build-test' cycle was considered time-consuming and costly; it used to take anywhere from 4 months to 1 year before finalizing the product design parameters as it involved physical assembly and also testing. Instead, the authors used Taguchi's parameter design approach. This approach took about 8 weeks to arrive at optimum design parameter values; clearly demonstrating the cutting edge of this methodology over the traditional design-build-test approach. The prototype built and tested accordingly gave satisfactory overall performance, meeting and even exceeding customer requirements
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