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Charge distribution and electroluminescence in cross-linked polyethylene under dc field
The intent of this paper is to cross-correlate the information obtained by space charge distribution analysis and electroluminescence (EL) detection in cross-linked polyethylene samples submitted to dc fields, with the objective to make a link between space charge phenomena and energy release as revealed by the detection of visible photons. Space charge measurements carried out at different field levels by the pulsed electro-acoustic method show the presence of a low-field threshold, close to 15-20 kV mm-1, above which considerable space charge begins to accumulate in the insulation. Charges are seen to cross the insulation thickness through a packet-like behaviour at higher fields, starting at about 60-70 kV mm-1. EL measurements show the existence of two distinct thresholds, one related to the continuous excitation of EL under voltage, the other being transient EL detected upon specimen short circuit. The former occurs at values of field corresponding to charge packet formation and the latter to the onset of space charge accumulation. The correspondence between pertinent values of the electric field obtained through space charge and EL analyses provides support for the existence of degradation thresholds in insulating materials. Special emphasis is given to the relationship between charge packet formation and propagation, and EL. Although the two phenomena are observed in the same field range, it is found that the onset of continuous EL follows the formation at the electrodes of positive and negative space charge regions that extend into the bulk prior to the propagation of charge packets. Charge recombination appears to be the excitation process of EL since oppositely charged domains meet in the material bulk. To gain an insight into specific light-excitation processes associated with charge packet propagation, EL has been recorded for several hours under fields at which charge packet dynamics were evidenced. It is shown that current and luminescence oscillations are detected during charge packet propagation, and that they are in phase. The mechanisms underlying EL and charge packets are further considered on the basis of these results
Heavy ion irradiation of crystalline water ice
Under cosmic irradiation, the interstellar water ice mantles evolve towards a
compact amorphous state. Crystalline ice amorphisation was previously monitored
mainly in the keV to hundreds of keV ion energies. We experimentally
investigate heavy ion irradiation amorphisation of crystalline ice, at high
energies closer to true cosmic rays, and explore the water-ice sputtering
yield. We irradiated thin crystalline ice films with MeV to GeV swift ion
beams, produced at the GANIL accelerator. The ice infrared spectral evolution
as a function of fluence is monitored with in-situ infrared spectroscopy
(induced amorphisation of the initial crystalline state into a compact
amorphous phase). The crystalline ice amorphisation cross-section is measured
in the high electronic stopping-power range for different temperatures. At
large fluence, the ice sputtering is measured on the infrared spectra, and the
fitted sputtering-yield dependence, combined with previous measurements, is
quadratic over three decades of electronic stopping power. The final state of
cosmic ray irradiation for porous amorphous and crystalline ice, as monitored
by infrared spectroscopy, is the same, but with a large difference in
cross-section, hence in time scale in an astrophysical context. The cosmic ray
water-ice sputtering rates compete with the UV photodesorption yields reported
in the literature. The prevalence of direct cosmic ray sputtering over
cosmic-ray induced photons photodesorption may be particularly true for ices
strongly bonded to the ice mantles surfaces, such as hydrogen-bonded ice
structures or more generally the so-called polar ices.Comment: 22pages, 11 figures, accepted in A&
Radioscience simulations in General Relativity and in alternative theories of gravity
In this communication, we focus on the possibility to test GR with
radioscience experiments. We present a new software that in a first step
simulates the Range/Doppler signals directly from the space time metric (thus
in GR and in alternative theories of gravity). In a second step, a
least-squares fit of the involved parameters is performed in GR. This software
allows one to get the order of magnitude and the signature of the modifications
induced by an alternative theory of gravity on radioscience signals. As
examples, we present some simulations for the Cassini mission in
Post-Einsteinian gravity and with the MOND External Field Effect.Comment: 4 pages; Proceedings of "Les Rencontres de Moriond 2011 - Gravitation
session
Rhythms of walking : history and presence in a city street
Peer reviewedPostprin
Hadron Energy Reconstruction for the ATLAS Calorimetry in the Framework of the Non-parametrical Method
This paper discusses hadron energy reconstruction for the ATLAS barrel
prototype combined calorimeter (consisting of a lead-liquid argon
electromagnetic part and an iron-scintillator hadronic part) in the framework
of the non-parametrical method. The non-parametrical method utilizes only the
known ratios and the electron calibration constants and does not require
the determination of any parameters by a minimization technique. Thus, this
technique lends itself to an easy use in a first level trigger. The
reconstructed mean values of the hadron energies are within of the
true values and the fractional energy resolution is . The value of the ratio
obtained for the electromagnetic compartment of the combined calorimeter is
and agrees with the prediction that for this
electromagnetic calorimeter. Results of a study of the longitudinal hadronic
shower development are also presented. The data have been taken in the H8 beam
line of the CERN SPS using pions of energies from 10 to 300 GeV.Comment: 33 pages, 13 figures, Will be published in NIM
Mobile encounters:bus 5A as a cross-cultural meeting place
The paper explores modes of encounters in the everyday practice of bus travel. Particularly, it addresses cross-cultural encounters located in the tension between familiarity and difference, between inclusion and exclusion. The paper is located in contemporary thoughts, approaching public transport not only as a moving device but also as a social arena. Furthermore, the bus is simultaneously perceived as a public space, at once composite, contradictory and heterogeneous, and as a meeting place involving âThrowntogethernessâ. The encounters analysed are bodily, emotional charged and outspoken meetings between passengers, with the socio-materiality of the bus and drivers as co-riders and gatekeepers
Developing a sense of place toolkit: Identifying destination uniqueness
It has long been recognised that the tangible and intangible characteristics that make a location distinctive and memorable, contribute significantly to destination image. How this destination feel is communicated, has largely been the domain of place branding and destination marketing, which have the potential to miss stakeholder voices. Recently though, practitioners are starting to carefully consider âsense of placeâ; that is an emotional attachment to place, which is defined more carefully in the literature review of this article, and which corresponds with long-running academic discussions. This paper attempts to identify some of these and bridge the gap between academic theory on sense of place and practice. In the UK, many rural areas are now seeking to operationalise sense of place through toolkit documents that might inform landscape interpretation and destination branding. A scenario echoed internationally, where local distinctiveness features in both rural and urban planning. However, sense of place in a tourism context, and more specifically the development of these toolkits, has received limited academic attention. Hence, this paper presents the case of Morecambe Bay, and the development of a dedicated sense of place toolkit. The subsequent case emerges from a collaboration between academics and practitioners and draws on participant observation, semi-structured interviews and document analysis. Specifically, the paper outlines a series of workshop activities developed with destination stakeholders and identifies how these inform subsequent toolkit design. It offers a critical analysis of the benefits and potential pitfalls of employing this approach. This case is of value to academics and destination stakeholders interested in identifying and communicating the uniqueness and emotional tone of the destination. Key lessons and recommendations are identified for those engaging in similar toolkit development initiatives
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