51,972 research outputs found
Reliability of vocational assessment: an evaluation of level 3 electro-technical qualifications
Testing the Role of Technical Information in Public Risk Perception
It is widely believed that more detail about health effects and likely exposure routes is apt to reduce citizens\u27 concerns about low-probability Risks. The authors\u27 study suggests that providing such detail may not be as useful as, e.g., addressing public concerns and keeping citizens current on officials\u27 actions
MillerâUrey spark-discharge experiments in the deuterium world
We designed and conducted a series of primordial-soup Miller-Urey style experiments with deuterated gases and reagents to compare the spark-discharge products of a âdeuterated worldâ with the standard reaction in the âhydrogenated worldâ. While the deuteration of the system has little effect on the distribution of amino acid products, significant differences are seen in other regions of the product-space. Not only do we observe about 120â
new species, we also see significant differences in their distribution if the two hydrogen isotope worlds are compared. Several isotopologue matches can be identified in both, but a large proportion of products have no equivalent in the corresponding isotope world with ca. 43â
new species in the D world and ca. 39â
new species in the H world. This shows that isotopic exchange (the addition of only one neutron) may lead to significant additional complexity in chemical space under otherwise identical reaction conditions
The effectiveness of thin films in lieu of hyperbolic metamaterials in the near field
We show that the near-field functionality of hyperbolic metamaterials (HMM),
typically proposed for increasing the photonic local density of states (LDOS),
can be achieved with thin metal films. Although HMMs have an infinite density
of internally-propagating plane-wave states, the external coupling to nearby
emitters is severely restricted. We show analytically that properly designed
thin films, of thicknesses comparable to the metal size of a hyperbolic
metamaterial, yield a LDOS as high as (if not higher than) that of HMMs. We
illustrate these ideas by performing exact numerical computations of the LDOS
of multilayer HMMs, along with their application to the problem of maximizing
near-field heat transfer, to show that thin films are suitable replacements in
both cases.Comment: 5 pages, 3 figure
Timed Fault Tree Models of the China Yongwen Railway Accident
Safety is an essential requirement for railway transportation. There are many methods that have been developed to predict, prevent and mitigate accidents in this context. All of these methods have their own purpose and limitations. This paper presents a new useful analysis technique: timed fault tree analysis. This method extends traditional fault tree analysis with temporal events and fault characteristics. Timed Fault Trees (TFTs) can determine which faults need to be eliminated urgently, and it can also provide a safe time window to repair them. They can also be used to determine the time taken for railway maintenance requirements, and thereby improve maintenance efficiency, and reduce risks. In this paper, we present the features and functionality of a railway transportation system based on timed fault tree models. We demonstrate the applicability of our framework via a case study of the China Yongwen line railway accident
A probabilistic model checking approach to analysing reliability, availability, and maintainability of a single satellite system
Satellites now form a core component for space
based systems such as GPS and GLONAS which provide
location and timing information for a variety of uses. Such
satellites are designed to operate in-orbit and have lifetimes of
10 years or more. Reliability, availability and maintainability
(RAM) analysis of these systems has been indispensable in
the design phase of satellites in order to achieve minimum
failures or to increase mean time between failures (MTBF)
and thus to plan maintainability strategies, optimise reliability
and maximise availability. In this paper, we present formal
modelling of a single satellite and logical specification of
its reliability, availability and maintainability properties. The
probabilistic model checker PRISM has been used to perform
automated quantitative analyses of these properties
Optimization of sharp and viewing-angle-independent structural color
Structural coloration produces some of the most brilliant colors in nature
and has many applications. However, the two competing properties of narrow
bandwidth and broad viewing angle have not been achieved simultaneously in
previous studies. Here, we use numerical optimization to discover geometries
where a sharp 7% bandwidth in scattering is achieved, yet the peak wavelength
varies less than 1%, and the peak height and peak width vary less than 6% over
broad viewing angles (0--90) under a directional illumination. Our
model system consists of dipole scatterers arranged into several rings;
interference among the scattered waves is optimized to yield the
wavelength-selective and angle-insensitive response. Such designs can be useful
for the recently proposed transparent displays that are based on
wavelength-selective scattering
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