4,549 research outputs found
Charged gravitational instantons in five-dimensional Einstein-Gauss-Bonnet-Maxwell theory
We study a solution of the Einstein-Gauus-Bonnet theory in 5 dimensions
coupled to a Maxwell field, whose euclidean continuation gives rise to an
instanton describing black hole pair production. We also discuss the dual
theory with a 3-form field coupled to gravity.Comment: 8 pages, plain Te
Validation of a bovine rectal palpation simulator for training veterinary students
No abstract available
An experimental investigation of the hypergolic ignition of some polymeric fuels with oxygen
Hypergolic ignition of polymeric fuels with oxyge
Editorial: Implausible discussions in saturated fat 'research'; definitive solutions won't come from another million editorials (or a million views of one).
The British Journal of Sports Medicine published an opinion editorial advocating a revision of public health guidance on saturated fat.1 Here, we offer a rebuttal, incorporating evidence-based principles absent in the original editorial, focusing on the quality of the evidence presented and we discuss contradictory evidence in relation to saturated fat, low-density lipoprotein cholesterol (LDL-C), specific dietary interventions and cardiovascular disease (CVD) alongside future directions
Drawing a Triangle on the Thurston Model of Hyperbolic Space
In looking at a common physical model of the hyperbolic plane, the authors encountered surprising difficulties in drawing a large triangle. Understanding these difficulties leads to an intriguing exploration of the geometry of the Thurston model of the hyperbolic plane. In this exploration we encounter topics ranging from combinatorics and Pick’s Theorem to differential geometry and the Gauss-Bonnet Theorem
Increased surface flashover voltage in microfabricated devices
With the demand for improved performance in microfabricated devices, the
necessity to apply greater electric fields and voltages becomes evident. When
operating in vacuum, the voltage is typically limited by surface flashover
forming along the surface of a dielectric. By modifying the fabrication process
we have discovered it is possible to more than double the flashover voltage.
Our finding has significant impact on the realization of next-generation micro-
and nano-fabricated devices and for the fabrication of on-chip ion trap arrays
for the realization of scalable ion quantum technology
Towards operational measures of computer security
Ideally, a measure of the security of a system should capture quantitatively the intuitive notion of ‘the ability of the system to resist attack’. That is, it should be operational, reflecting the degree to which the system can be expected to remain free of security breaches under particular conditions of operation (including attack). Instead, current security levels at best merely reflect the extensiveness of safeguards introduced during the design and development of a system. Whilst we might expect a system developed to a higher level than another to exhibit ‘more secure behaviour’ in operation, this cannot be guaranteed; more particularly, we cannot infer what the actual security behaviour will be from knowledge of such a level. In the paper we discuss similarities between reliability and security with the intention of working towards measures of ‘operational security’ similar to those that we have for reliability of systems. Very informally, these measures could involve expressions such as the rate of occurrence of security breaches (cf rate of occurrence of failures in reliability), or the probability that a specified ‘mission’ can be accomplished without a security breach (cf reliability function). This new approach is based on the analogy between system failure and security breach. A number of other analogies to support this view are introduced. We examine this duality critically, and have identified a number of important open questions that need to be answered before this quantitative approach can be taken further. The work described here is therefore somewhat tentative, and one of our major intentions is to invite discussion about the plausibility and feasibility of this new approach
Additive manufacturing: A framework for implementation
As mass production has migrated to developing countries, European and US companies are forced to rapidly
switch towards low volume production of more innovative, customised and sustainable products with high
added value. To compete in this turbulent environment, manufacturers have sought new fabrication techniques
to provide the necessary tools to support the need for increased flexibility and enable economic low volume
production. One such emerging technique is Additive Manufacturing (AM). AM is a method of manufacture
which involves the joining of materials, usually layer-upon-layer, to create objects from 3D model data. The
benefits of this methodology include new design freedom, removal of tooling requirements, and economic low
volumes. AM consists various technologies to process versatile materials, and for many years its dominant
application has been the manufacture of prototypes, or Rapid Prototyping. However, the recent growth in
applications for direct part manufacture, or Rapid Manufacturing, has resulted in much research effort focusing
on development of new processes and materials. This study focuses on the implementation process of AM and is
motivated by the lack of socio-technical studies in this area. It addresses the need for existing and potential
future AM project managers to have an implementation framework to guide their efforts in adopting this new
and potentially disruptive technology class to produce high value products and generate new business
opportunities. Based on a review of prior works and through qualitative case study analysis, we construct and
test a normative structural model of implementation factors related to AM technology, supply chain,
organisation, operations and strategy
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