16,087 research outputs found
Choosing effective methods for design diversity - How to progress from intuition to science
Design diversity is a popular defence against design faults in safety critical systems. Design diversity is at times pursued by simply isolating the development teams of the different versions, but it is presumably better to "force" diversity, by appropriate prescriptions to the teams. There are many ways of forcing diversity. Yet, managers who have to choose a cost-effective combination of these have little guidance except their own intuition. We argue the need for more scientifically based recommendations, and outline the problems with producing them. We focus on what we think is the standard basis for most recommendations: the belief that, in order to produce failure diversity among versions, project decisions should aim at causing "diversity" among the faults in the versions. We attempt to clarify what these beliefs mean, in which cases they may be justified and how they can be checked or disproved experimentally
The experimental study of the surface current excitation under the influence of a relativistic electron electromagnetic field
The problem of the surface current excitation in a conductive targets by a
relativistic electron electric field as the origin of such radiation mechanisms
as diffraction and transition radiation of relativistic electron was considered
in frame of both surface current and pseudo-photon methods. The contradiction
between these viewpoints in respect to the surface current on the target
downstream surface necessitated the experimental test of this phenomenon. The
test performed on electron beam of the 6 MeV microtron showed, that not any
surface current is induced on the target downstream surface under the influence
of a relativistic electron electromagnetic field in contrast to the upstream
surface. This is important implication for the understanding of the forward
transition and diffraction radiation nature.Comment: Was Presented at the symposium Channeling 2008 (Charged and Neutral
Particles Channeling Phenomena), October 25 - November 1, 2008 Erice (Trapani
- Sicily), Italy, and was accepted for publication in proceedings of
symposiu
Dressing Symmetries of Holomorphic BF Theories
We consider holomorphic BF theories, their solutions and symmetries. The
equivalence of Cech and Dolbeault descriptions of holomorphic bundles is used
to develop a method for calculating hidden (nonlocal) symmetries of holomorphic
BF theories. A special cohomological symmetry group and its action on the
solution space are described.Comment: 14 pages, LaTeX2
On Systematic Design of Protectors for Employing OTS Items
Off-the-shelf (OTS) components are increasingly used in application areas with stringent dependability requirements. Component wrapping is a well known structuring technique used in many areas. We propose a general approach to developing protective wrappers that assist in integrating OTS items with a focus on the overall system dependability. The wrappers are viewed as redundant software used to detect errors or suspicious activity and to execute appropriate recovery when possible; wrapper development is considered as a part of system integration activities. Wrappers are to be rigorously specified and executed at run time as a means of protecting OTS items against faults in the rest of the system, and the system against the OTS item's faults. Possible symptoms of erroneous behaviour to be detected by a protective wrapper and possible actions to be undertaken in response are listed and discussed. The information required for wrapper development is provided by traceability analysis. Possible approaches to implementing “protectors” in the standard current component technologies are briefly outline
Multidimensional Worldline Instantons
We extend the worldline instanton technique to compute the vacuum pair
production rate for spatially inhomogeneous electric background fields, with
the spatial inhomogeneity being genuinely two or three dimensional, both for
the magnitude and direction of the electric field. Other techniques, such as
WKB, have not been applied to such higher dimensional problems. Our method
exploits the instanton dominance of the worldline path integral expression for
the effective action.Comment: 22 pages, 13 figure
Improving the Hydrogen Yield of Microbial Electrolysis Cell with Facilitated Electron Transfer Using Mediators, Choice of Environmental Conditions and Anode Treatment with Conductive Materials
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