2,762 research outputs found
Kinetic energy release in electron-induced decay reactions of molecular ions: C3H8+ and C3H7+
We have measured the kinetic energy release (KER) distributions for electron-induced dissociation of mass-selected molecular parent and fragment ions of propane. They are compared with distributions determined for spontaneous (metastable) dissociation. The average KER for induced dissociation of C3H8+ into C3H7+ is 13.2 +/- 1.2 meV, about 42% larger than for the spontaneous reaction. This large difference is attributed to the dramatically reduced time at which the induced reaction can be sampled. In contrast, the KER for dissociation of C3H7+ into C3H5+, which is characterized by a large reverse activation energy, is hardly affected by the experimental time scale. (C) 2000 American Institute of Physics. [S0021-9606(00)00826-6]
Design of a Scalable Modular Production System for a Two-stage Food Service Franchise System
The geographically distributed production of fresh food poses unique challenges to the production system design because of their stringent industry and logistics requirements. The purpose of this research is to examine the case of a European fresh food manufacturerâs approach to introduce a scalable modular production concept for an international twoâstage gastronomy franchise system in order to identify best practice guidelines and to derive a framework for the design of distributed production systems that perform in a highly dynamic environment. The design framework was developed by creating a theoretical model through literature review and the thorough analysis of an industrial case. Information was collected through multiple site visits, workshops and semiâstructured interviews with the companyâs key staff of the project, as well as examination of relevant company documentations. By means of a scenario for the Central European market, the model was reviewed in terms of its development potential and finally approved for implementation. However, research through case survey requires further empirical investigation to fully establish this approach as a valid and reliable design tool
High-resolution kinetic energy release distributions and dissociation energies for fullerene ions C(n)(+), 42 \u3c= n \u3c= 90
We have measured the kinetic energy released in the unimolecular dissociation of fullerene ions, C(n)(+)--\u3eC(n-2)(+)+C(2), for sizes 42less than or equal tonless than or equal to90. A three-sector-field mass spectrometer equipped with two electric sectors has been used in order to ensure that contributions from isotopomers of different masses do not distort the experimental kinetic energy release distributions. We apply the concept of microcanonical temperature to derive from these data the dissociation energies of fullerene cations. They are converted to dissociation energies of neutral fullerenes with help of published adiabatic ionization energies. The results are compared with literature values. (C) 2004 American Institute of Physics
THE IFC FILE FORMAT AS A MEANS OF INTEGRATING BIM AND GIS: THE CASE OF THE MANAGEMENT AND MAINTENANCE OF UNDERGROUND NETWORKS
Abstract. The construction sector is undergoing an important digital revolution. The integration between Building Information Modeling (BIM) and Geographical Information System (GIS) is a key component of this revolution and is increasingly discussed. Although benefits are already recognised, several challenges still remain. The purpose of this paper is to present the method proposed by the GEOBIMM project to overcome the existing barriers towards the integration between BIM and GIS domains and to present the first results applied to the maintenance of underground networks. The results are a set of guidelines essential for the integration of BIM files in GIS platforms within the GEOBIMM domain, to ensure: the appropriate geometric description of the elements; the correct georeferencing; the geospatial semantic and topological interoperability between the two systems; the appropriate definition of the information parameters. These pillars are further used to develop a guideline for planners and construction companies supporting them in developing compliant BIM models
High resolution measurements of kinetic energy release distributions of neon, argon, and krypton cluster ions using a three sector field mass spectrometer
Using a newly constructed three sector field mass spectrometer (resulting in a BE1E2 field configuration) we have measured the kinetic energy release distributions of neon, argon, and krypton cluster ions. In the present study we used the first two sectors, B and E1, constituting a high resolution mass spectrometer, to select the parent ions in terms of mass, charge, and energy, and studied the decay of those ions in the third field free region. Due to the improved mass resolution we were able to extend earlier studies carried out with a two sector field machine, where an upper size limit arose from the fact that several isotopomers contribute to a decaying parent ion beam when the cluster size exceeds a certain value. Furthermore we developed a new data analysis. It allows us to model also fragment ion peaks that are a superposition of different decay reactions and thus we can determine the average kinetic energy release for all decay reactions of a given cluster ion. In a further step we used these results to determine the binding energies of cluster ions Rg(n) (ngreater than or equal to10) by applying finite heat bath theory. The smaller sizes have not been included in this analysis, because the validity of finite heat bath theory becomes questionable below napproximate to10. The present average kinetic energy releases and binding energies are compared with other experiments and various calculations. (C) 2004 American Institute of Physics
Mechanisms and dynamics of the metastable decay in Ar-2(+)
A detailed experimental as well as theoretical investigation of the properties of the metastable dissociation Ar-2(+)--\u3eAr++Ar is presented. The mass-analyzed ion kinetic energy (MIKE) scan technique has been performed using a three sector field mass spectrometer. The possible mechanisms of the metastability of Ar-2(+) have been examined and the observed decay process is assigned to the II(1/2)(u)--\u3eI(1/2)(g) bound to continuum radiative transition, in agreement with earlier work. The calculation of the theoretical shape of the kinetic energy release distribution of fragment ions allowed us to construct the theoretical MIKE peak and compare it with the raw experimental data. The accuracy of various sets of potential energy curves for Ar-2(+) is discussed, as well as the way of production of the metastable Ar-2(+)[II(1/2)(u)] electronic state by electron impact. Excellent agreement between the experimental data and theoretical model has been observed. (C) 2004 American Institute of Physics
Kinetic-energy release in Coulomb explosion of metastable C3H52+
C3H52+, formed by electron impact ionization of propane, undergoes metastable decay into C2H2++CH3+. We have monitored this reaction in a magnetic mass spectrometer of reversed geometry that is equipped with two electric sectors (BEE geometry). Three different techniques were applied to identify the fragment ions and determine the kinetic-energy release (KER) of spontaneous Coulomb explosion of C3H52+ in the second and third field free regions of the mass spectrometer. The KER distribution is very narrow, with a width of about 3% [root-mean square standard deviation]. An average KER of 4.58+/-0.15 eV is derived from the distribution. High level ab initio quantum-chemical calculations of the structure and energetics of C3H52+ are reported. The activation barrier of the reverse reaction, CH3++C2H2+ (vinylidene), is computed. The value closely agrees with the experimental average KER, thus indicating that essentially all energy available in the reaction is partitioned into kinetic energy. (C) 2003 American Institute of Physics
The peculiar source XSS J12270-4859: a LMXB detected by FERMI ?
The X-ray source XSS J12270-4859 has been first suggested to be a magnetic
cataclysmic variable of Intermediate Polar type on the basis of its optical
spectrum and a possible 860 s X-ray periodicity. However further X-ray
observations by the Suzaku and XMM-Newton satellites did not confirm this
periodicity but show a very peculiar variability, including moderate repetitive
flares and numerous absorption dips. These characteristics together with a
suspected 4.3 h orbital period would suggest a possible link with the so-
called "dipping sources", a sub-class of Low-Mass X-ray Binaries (LMXB). Based
on the released FERMI catalogues, the source was also found coincident with a
very high energy (0.1-300 GeV) VHE source 2FGL J1227.7-4853. The good
positional coincidence, together with the lack of any other bright X-ray
sources in the field, makes this identification highly probable. However, none
of the other standard LMXBs have been so far detected by FERMI. Most galactic
VHE sources are associated with rotation-powered pulsars. We present here new
results obtained from a 30 ksec high-time resolution XMM observations in
January 2011 that confirm the flaring-dipping behaviour and provide upper
limits on fast X-ray pulsations. We discuss the possible association of the
source with either a microquasar or an accreting rotation powered pulsar.Comment: To appear in the Proceedings of "The Golden Age of Cataclysmic
Variables (Palermo 2011)", in Mem. Soc. Astron. It. (4 pages, 2 figures
Rapid variability of accretion in AM Herculis
We present the last pointed observation of AM Her carried out during the life
of the BeppoSAX satellite. It was bright at the beginning of the observation,
but dropped to the lowest X-ray level ever observed so far. The X-ray emission
during the bright period is consistent with accretion occurring onto the main
pole of the magnetized white dwarf. The rapid change from the active state to
the low deep state indicates a drop by a factor of 17 in the accretion rate and
hence that accretion switched-off. The short timescale (less than one hour) of
this variation still remains a puzzle. Optical photometry acquired
simultaneousy during the low state shows that the white dwarf remains heated,
although a weak emission from the accretion stream could be still present.
Cyclotron radiation, usually dominating the V and R bands, is negligible thus
corroborating the possibility that AM Her was in an off-accretion state. The
X-ray emission during the inactive state is consistent with coronal emission
from the secondary late type star.Comment: 6 pages A&A-Latex, 6 Figures, accepted for publication in A&
The X-ray spectra and spectral variability of intermediate type Seyfert galaxies: ASCA observations of NGC 4388 and ESO 103-G35
The X-ray spectra of two intermediate type Seyfert galaxies are investigated
using ASCA observations separated by more than a year. Both NGC 4388 and ESO
103-G35 exhibit strong, narrow Fe K alpha line emission and absorption by cold
neutral gas with a column density ~ 10^23 cm^-2, characteristic of the X-ray
spectra of type 2 Seyfert galaxies. The power law continuum flux has changed by
a factor of 2 over a time-scale of ~ 2 years for both objects, declining in the
case of NGC 4388 and rising in ESO 103-G35. No variation was observed in the
equivalent width of the Fe K alpha line in the spectra of NGC 4388, implying
that the line flux declined with the continuum. We find that the strength of
the line cannot be accounted for by fluorescence in line-of-sight material with
the measured column density unless a `leaky-absorber' model of the type favored
for IRAS 04575-7537 is employed. The equivalent width of the Fe K alpha
emission line is seen to decrease between the observations of ESO 103-G35 while
the continuum flux increased. The 1996 observation of ESO 103-G35 can also be
fitted with an absorption edge at 7.4 0.2 keV due to partially ionized
iron, and when an ionized absorber model is fitted to the data it is found that
the equivalent column of neutral hydrogen rises to 3.5 x 10^23 cm^-2. The Fe K
alpha line flux can be accounted by fluorescence in this material alone and
this model is also a good representation of the 1988 and 1991 Ginga
observations. There is then no requirement for a reflection component in the
ASCA spectra of ESO 103-G35 or NGC 4388.Comment: 45 pages, 5 tables, 11 figures. Accepted for publication in the
Astrophysical Journa
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