12,888 research outputs found
Optical Turbulence Measurements and Models for Mount John University Observatory
Site measurements were collected at Mount John University Observatory in 2005
and 2007 using a purpose-built scintillation detection and ranging system.
profiling indicates a weak layer located at 12 - 14 km above sea
level and strong low altitude turbulence extending up to 5 km. During calm
weather conditions, an additional layer was detected at 6 - 8 km above sea
level. profiling suggests that tropopause layer velocities are nominally
12 - 30 m/s, and near-ground velocities range between 2 -- 20 m/s, dependent on
weather. Little seasonal variation was detected in either and
profiles. The average coherence length, , was found to be cm for
the full profile at a wavelength of 589 nm. The average isoplanatic angle,
, was arcsec. The mean turbulence altitude,
, was found to be km above sea level. No average in the
Greenwood frequency, , could be established due to the gaps present in the
\vw\s profiles obtained. A modified Hufnagel-Valley model was developed to
describe the profiles at Mount John, which estimates at 6 cm
and at 0.9 arcsec. A series of models were developed, based
on the Greenwood wind model with an additional peak located at low altitudes.
Using the model and the suggested model for moderate ground
wind speeds, is estimated at 79 Hz.Comment: 14 pages; accepted for publication in PAS
Pulsed x-rays dose measurements from a hundred joules plasma focus device
Indexación: Scopus.Present work is aimed to perform dosimetric measurements to characterize dosis obtained from pulsed x-rays emitted from a hundred joules plasma focus device PF-400J using thermoluminescent dosimeters (TLD-100). Two dosimeter arrays (containing 21 dosimeters in each) were used. One of the arrays was kept inside the PF-400J vacuum chamber and other outside the vacuum chamber, simultaneously. It was found that dosis obtained from the inside array (∼200.7 mGy) were hundred times larger than the outside array (∼1.1 mGy) for hundred pulses of x-rays. Later, the vacuum window of PF-400J, which was made of 1 mm aluminum, was replaced by a plastic window and a similar dosimeter array was kept outside the chamber over the plastic window. With this arrangement, the obtained doses (100 pulses of x-rays) were of the same order of magnitude (∼106 mGy) as it was inside the vacuum chamber. Later, a lead piece was inserted inside the hollow anode of PF-400J, which increased dose (∼250 mGy) per hundred pulses of x-ray outside the vacuum chamber using plastic vacuum window. Our results suggest that PF-400J could be a useful device to study low dose pulsed radiation effects on cancer cell lines in in vitro experiments. © Published under licence by IOP Publishing Ltd.The work is supported by grant ACT-1115, CONICYT, Chile.https://iopscience.iop.org/article/10.1088/1742-6596/1043/1/01204
Spectral analysis of Swift long GRBs with known redshift
We study the spectral and energetics properties of 47 long-duration gamma-ray
bursts (GRBs) with known redshift, all of them detected by the Swift satellite.
Due to the narrow energy range (15-150 keV) of the Swift-BAT detector, the
spectral fitting is reliable only for fitting models with 2 or 3 parameters. As
high uncertainty and correlation among the errors is expected, a careful
analysis of the errors is necessary. We fit both the power law (PL, 2
parameters) and cut--off power law (CPL, 3 parameters) models to the
time-integrated spectra of the 47 bursts, and present the corresponding
parameters, their uncertainties, and the correlations among the uncertainties.
The CPL model is reliable only for 29 bursts for which we estimate the nuf_nu
peak energy Epk. For these GRBs, we calculate the energy fluence and the rest-
frame isotropic-equivalent radiated energy, Eiso, as well as the propagated
uncertainties and correlations among them. We explore the distribution of our
homogeneous sample of GRBs on the rest-frame diagram E'pk vs Eiso. We confirm a
significant correlation between these two quantities (the "Amati" relation) and
we verify that, within the uncertainty limits, no outliers are present. We also
fit the spectra to a Band model with the high energy power law index frozen to
-2.3, obtaining a rather good agreement with the "Amati" relation of non-Swift
GRBs.Comment: 16 pages. To appear in MNRAS. Minor changes were introduced in this
last versio
A model to assess customer alignment through customer experience concepts
Business and Information Technology Alignment (BITA) has been one of the main
concerns of IT and Business executives and directors due to its importance to
overall company performance, especially today in the age of digital
transformation. For BITA has been developed several models which in general has
focused in the implementation of alignment strategies for the internal
operation of the organizations and in the measurement of this internal
alignment, but, there is still a big gap in measurement models of the alignment
with the external environment of the organizations. In this paper is presented
the design and application of a maturity measurement model for BITA with the
customers, where the customers are actors of the external environment of the
companies. The proposed model involves evaluation criteria and business
practices which the companies ideally do for improve the relationship with
their customers.Comment: 12 pages, Preprint version, BIS 2019 International Workshops,
Seville, Spain, June 26 to 28, 2019, Revised Paper
On the Structure of Dark Matter Halos at the Damping Scale of the Power Spectrum with and without Relict Velocities
We report a series of high-resolution cosmological N-body simulations
designed to explore the formation and properties of dark matter halos with
masses close to the damping scale of the primordial power spectrum of density
fluctuations. We further investigate the effect that the addition of a random
component, v_rms, into the particle velocity field has on the structure of
halos. We adopted as a fiducial model the Lambda Warm Dark Matter cosmology
with a non-thermal sterile neutrino mass of 0.5 keV. The filtering mass
corresponds then to M_f = 2.6x10^12 M_sun/h. Halos of masses close to M_f were
simulated with several million of particles. The results show that, on one
hand, the inner density slope of these halos (at radii <~0.02 the virial radius
Rvir) is systematically steeper than the one corresponding to the NFW fit or to
the CDM counterpart. On the other hand, the overall density profile (radii
larger than 0.02Rvir) is less curved and less concentrated than the NFW fit,
with an outer slope shallower than -3. For simulations with v_rms, the inner
halo density profiles flatten significantly at radii smaller than 2-3 kpc/h
(<~0.010-0.015Rvir). A constant density core is not detected in our
simulations, with the exception of one halo for which the flat core radius is
~1 kpc/h. Nevertheless, if ``cored'' density profiles are used to fit the halo
profiles, the inferred core radii are ~0.1-0.8 kpc/h, in rough agreement with
theoretical predictions based on phase-space constrains, and on dynamical
models of warm gravitational collapse. A reduction of v_rms by a factor of 3
produces a modest decrease in core radii, less than a factor of 1.5. We discuss
the extension of our results into several contexts, for example, to the
structure of the cold DM micro-halos at the damping scale of this model.Comment: 13 pages, 6 figures, accepted for publication in The Astrophysical
Journa
Business and Information Technology Alignment Measurement -- a recent Literature Review
Since technology has been involved in the business context, Business and
Information Technology Alignment (BITA) has been one of the main concerns of IT
and Business executives and directors due to its importance to overall company
performance, especially today in the age of digital transformation. Several
models and frameworks have been developed for BITA implementation and for
measuring their level of success, each one with a different approach to this
desired state. The BITA measurement is one of the main decision-making tools in
the strategic domain of companies. In general, the classical-internal alignment
is the most measured domain and the external environment evolution alignment is
the least measured. This literature review aims to characterize and analyze
current research on BITA measurement with a comprehensive view of the works
published over the last 15 years to identify potential gaps and future areas of
research in the field.Comment: 12 pages, Preprint version, BIS 2018 International Workshops, Berlin,
Germany, July 18 to 20, 2018, Revised Paper
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