7,163 research outputs found
Application of a truncated normal failure distribution in reliability testing
Statistical truncated normal distribution function is applied as a time-to-failure distribution function in equipment reliability estimations. Age-dependent characteristics of the truncated function provide a basis for formulating a system of high-reliability testing that effectively merges statistical, engineering, and cost considerations
Perceptions of time in relation to climate change
Time is at the heart of understanding climate change, from the perspective of both natural and social scientists. This article selectively reviews research on time perception and temporal aspects of decision making in sociology and psychology. First we briefly describe the temporal dimensions that characterize the issue of climate change. Second, we review relevant theoretical approaches and empirical findings. Then we propose an integration of these insights for the problem of climate change and discuss mismatches between the human mind, surrounding social dynamics, and climate change. Finally, we discuss the implications of this article for understanding and responding to climate change, and make suggestions on how we can use the strengths of the human mind and social dynamics to communicate climate change in its temporal context.This article is categorized under:
Climate, History, Society, Culture > Ideas and Knowledge
Perceptions, Behavior, and Communication of Climate Change > Perceptions of Climate Change
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A dimension-breaking phenomenon for water waves with weak surface tension
It is well known that the water-wave problem with weak surface tension has
small-amplitude line solitary-wave solutions which to leading order are
described by the nonlinear Schr\"odinger equation. The present paper contains
an existence theory for three-dimensional periodically modulated solitary-wave
solutions which have a solitary-wave profile in the direction of propagation
and are periodic in the transverse direction; they emanate from the line
solitary waves in a dimension-breaking bifurcation. In addition, it is shown
that the line solitary waves are linearly unstable to long-wavelength
transverse perturbations. The key to these results is a formulation of the
water wave problem as an evolutionary system in which the transverse horizontal
variable plays the role of time, a careful study of the purely imaginary
spectrum of the operator obtained by linearising the evolutionary system at a
line solitary wave, and an application of an infinite-dimensional version of
the classical Lyapunov centre theorem.Comment: The final publication is available at Springer via
http://dx.doi.org/10.1007/s00205-015-0941-
MRI changes in psoriatic dactylitisextent of pathology, relationship to tenderness and correlation with clinical indices
Objectives. To quantify the extent of inflammation in psoriatic dactylitis and to examine the relationship between clinical and magnetic resonance imaging (MRI) data in both tender and non-tender dactylitis.
Methods. Seventeen patients with psoriatic dactylitis underwent clinical assessment for 6 months after change of treatment, usually to methotrexate. Measures of dactylitis included the Leeds Dactylitis Index, the assessment tool used in the Infliximab in Psoriatic Arthritis Clinical Trial (IMPACT), a simple count of tender dactlylitic digits and a count of all dactylitic digits, both tender and non-tender. MRI scans of the affected hand or foot were performed before and after treatment using a 1.5T Siemens scanner pre- and post-contrast.
Results. All patients improved clinically, as did their respective dactylitis scores and MRI images. The findings on MRI in both dactylitic and non-dactylitic digits were profound and widespread. The difference between tender and non-tender dactylitis was quantitative rather than qualitative. Synovitis and soft-tissue oedema were the most frequent abnormalities being present in 69 of tender dactylitic digits but bone oedema and flexor tenosynovitis were also frequently seen. Soft-tissue oedema was circumferential and enhancing and not limited to association with the flexor or extensor tendons. None of the clinical indices of dactylitis showed a close relationship to the extent of MRI abnormalities.
Conclusions. MRI images demonstrate widespread abnormalities in digits of people with psoriatic arthritis. Tender dactylitic digits have more abnormalities than other digits but the relationship between clinical and MRI scores is not strong
Avalanche noise characteristics of single Al/sub x/Ga/sub 1-x/As(0.3
Avalanche multiplication and excess noise have been measured on a series of Al/sub x/Ga/sub 1-x/As-GaAs and GaAs-Al/sub x/Ga/sub 1-x/As (x=0.3,0.45, and 0.6) single heterojunction p/sup +/-i-n/sup +/ diodes. In some devices excess noise is lower than in equivalent homojunction devices with avalanche regions composed of either of the constituent materials, the heterojunction with x=0.3 showing the greatest improvement. Excess noise deteriorates with higher values of x because of the associated increase in hole ionization in the Al/sub x/Ga/sub 1-x/As layer. It also depends critically upon the carrier injection conditions and Monte Carlo simulations show that this dependence results from the variation in the degree of noisy feedback processes on the position of the injected carriers
Dust in dwarf galaxies: The case of NGC 4214
We have carried out a detailed modelling of the dust heating and emission in
the nearby, starbursting dwarf galaxy NGC 4214. Due to its proximity and the
great wealth of data from the UV to the millimeter range (from GALEX, HST, {\it
Spitzer}, Herschel, Planck and IRAM) it is possible to separately model the
emission from HII regions and their associated photodissociation regions (PDRs)
and the emission from diffuse dust. Furthermore, most model parameters can be
directly determined from the data leaving very few free parameters. We can fit
both the emission from HII+PDR regions and the diffuse emission in NGC 4214
with these models with "normal" dust properties and realistic parameters.Comment: 4pages, 3 figures. To appear in 'The Spectral Energy Distribution of
Galaxies' Proceedings IAU Symposium No 284, 201
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