3,338 research outputs found
Rotational properties of the binary and non-binary populations in the Trans-Neptunian belt
We present results for the short-term variability of Binary Trans-Neptunian
Objects (BTNOs). We performed CCD photometric observations using the 3.58 m
Telescopio Nazionale Galileo, the 1.5 m Sierra Nevada Observatory telescope,
and the 1.23 m Centro Astronomico Hispano Aleman telescope at Calar Alto
Observatory. We present results based on five years of observations and report
the short-term variability of six BTNOs. Our sample contains three classical
objects: 2003MW12, or Varda, 2004SB60, or Salacia, and 2002 VT130; one detached
disk object: 2007UK126; and two resonant objects: 2007TY430 and 2000EB173, or
Huya. For each target, possible rotational periods and/or photometric
amplitudes are reported. We also derived some physical properties from their
lightcurves, such as density, primary and secondary sizes, and albedo. We
compiled and analyzed a vast lightcurve database for Trans-Neptunian Objects
(TNOs) including centaurs to determine the lightcurve amplitude and spin
frequency distributions for the binary and non-binary populations. The mean
rotational periods, from the Maxwellian fits to the frequency distributions,
are 8.63+/-0.52 h for the entire sample, 8.37+/-0.58 h for the sample without
the binary population, and 10.11+/-1.19 h for the binary population alone.
Because the centaurs are collisionally more evolved, their rotational periods
might not be so primordial. We computed a mean rotational period, from the
Maxwellian fit, of 8.86+/-0.58 h for the sample without the centaur population,
and of 8.64+/-0.67 h considering a sample without the binary and the centaur
populations. According to this analysis, regular TNOs spin faster than
binaries, which is compatible with the tidal interaction of the binaries.
Finally, we examined possible formation models for several systems studied in
this work and by our team in previous papers.Comment: Accepted for publication in Astronomy and Astrophysics (June 26th,
2014); minor changes with published version; 21 pages, 17 figures, 7 table
Regionalizing telecommunications reform in West Africa
In recent years, there has been an increasing recognition that significant welfare gains could be realized through deep forms of regional integration which entail harmonization of legal, regulatory and institutional frameworks. Reforms that reduce cross-border transaction costs and improve the performance of “backbone” infrastructure services are arguably even more important for the creation of an open, unified regional economic space than trade policy reforms narrowly defined. This paper assesses the potential gains from regionalized telecommunications policy in West Africa. To this end, the paper: (i) discusses how regional cooperation can overcome national limits in technical expertise, enhance the capacity of nations credibly to commit to stable regulatory policy, and ultimately facilitate infrastructure investment in the region; (ii) identifies trade-distorting regulations that inhibit opportunities for regional trade and economic development, and so are good candidates for regional trade negotiations to reduce indirect trade barriers; and (iii) describes substantive elements of a harmonized regional regulatory policy that can deliver immediate performance benefits.E-Business,Environmental Economics&Policies,ICT Policy and Strategies,Transport Economics Policy&Planning,Emerging Markets
Aerodynamic interference effects on tilting proprotor aircraft
The Green's function method was used to study tilting proprotor aircraft aerodynamics with particular application to the problem of the mutual interference of the wing-fuselage-tail-rotor wake configuration. While the formulation is valid for fully unsteady rotor aerodynamics, attention was directed to steady state aerodynamics, which was achieved by replacing the rotor with the actuator disk approximation. The use of an actuator disk analysis introduced a mathematical singularity into the formulation; this problem was studied and resolved. The pressure distribution, lift, and pitching moment were obtained for an XV-15 wing-fuselage-tail rotor configuration at various flight conditions. For the flight configurations explored, the effects of the rotor wake interference on the XV-15 tilt rotor aircraft yielded a reduction in the total lift and an increase in the nose-down pitching moment. This method provides an analytical capability that is simple to apply and can be used to investigate fuselage-tail rotor wake interference as well as to explore other rotor design problem areas
Pairwise Well-Formed Modes and Transformations
One of the most significant attitudinal shifts in the history of music
occurred in the Renaissance, when an emerging triadic consciousness moved
musicians towards a new scalar formation that placed major thirds on a par with
perfect fifths. In this paper we revisit the confrontation between the two
idealized scalar and modal conceptions, that of the ancient and medieval world
and that of the early modern world, associated especially with Zarlino. We do
this at an abstract level, in the language of algebraic combinatorics on words.
In scale theory the juxtaposition is between well-formed and pairwise
well-formed scales and modes, expressed in terms of Christoffel words or
standard words and their conjugates, and the special Sturmian morphisms that
generate them. Pairwise well-formed scales are encoded by words over a
three-letter alphabet, and in our generalization we introduce special positive
automorphisms of , the free group over three letters.Comment: 12 pages, 3 figures, paper presented at the MCM2017 at UNAM in Mexico
City on June 27, 2017, keywords: pairwise well-formed scales and modes,
well-formed scales and modes, well-formed words, Christoffel words, standard
words, central words, algebraic combinatorics on words, special Sturmian
morphism
Improvements in Space Geodesy Data Discovery at the CDDIS
The Crustal Dynamics Data Information System (CDDIS) supports data archiving and distribution activities for the space geodesy and geodynamics community. The main objectives of the system are to store space geodesy and geodynamics related data products in a central data bank. to maintain information about the archival of these data, and to disseminate these data and information in a timely manner to a global scientific research community. The archive consists of GNSS, laser ranging, VLBI, and DORIS data sets and products derived from these data. The CDDIS is one of NASA's Earth Observing System Data and Information System (EOSDIS) distributed data centers; EOSDIS data centers serve a diverse user community and arc tasked to provide facilities to search and access science data and products. Several activities are currently under development at the CDDIS to aid users in data discovery, both within the current community and beyond. The CDDIS is cooperating in the development of Geodetic Seamless Archive Centers (GSAC) with colleagues at UNAVCO and SIO. TIle activity will provide web services to facilitate data discovery within and across participating archives. In addition, the CDDIS is currently implementing modifications to the metadata extracted from incoming data and product files pushed to its archive. These enhancements will permit information about COOlS archive holdings to be made available through other data portals such as Earth Observing System (EOS) Clearinghouse (ECHO) and integration into the Global Geodetic Observing System (GGOS) portal
Математическое моделирование взаимодействия верхового лесного пожара с противопожарным разрывом конечных размеров
Analysis of dependence of the critical dimensions of fire ruptures on the main characteristics of forests and wind speed. As a result of the numerical integration of fields was obtained the temperature distribution, oxygen concentration and volatile combustible pyrolysis products
Functional Relaxation and Guided Imagery as Complementary Therapy in Asthma: A Randomized Controlled Clinical Trial
Background: Asthma is a frequently disabling and almost invariably distressing disease that has a high overall prevalence. Although relaxation techniques and hypnotherapeutic interventions have proven their effectiveness in numerous trials, relaxation therapies are still not recommended in treatment guidelines due to a lack of methodological quality in many of the trials. Therefore, this study aims to investigate the efficacy of the brief relaxation technique of functional relaxation (FR) and guided imagery (GI) in adult asthmatics in a randomized controlled trial. Methods: 64 patients with extrinsic bronchial asthma were treated over a 4-week period and assessed at baseline, after treatment and after 4 months, for follow-up. 16 patients completed FR, 14 GI, 15 both FR and GI (FR/GI) and 13 received a placebo relaxation technique as the control intervention (CI). The forced expiratory volume in the first second (FEV 1) as well as the specific airway resistance (sR(aw)) were employed as primary outcome measures. Results: Participation in FR, GI and FR/GI led to increases in FEV 1 (% predicted) of 7.6 +/- 13.2, 3.3 +/- 9.8, and 8.3 +/- 21.0, respectively, as compared to -1.8 +/- 11.1 in the CI group at the end of the therapy. After follow-up, the increases in FEV 1 were 6.9 +/- 10.3 in the FR group, 4.4 +/- 7.3 in the GI and 4.5 +/- 8.1 in the FR/GI, compared to -2.8 +/- 9.2 in the CI. Improvements in sR(aw) (% predicted) were in keeping with the changes in FEV 1 in all groups. Conclusions: Our study confirms a positive effect of FR on respiratory parameters and suggests a clinically relevant long-term benefit from FR as a nonpharmacological and complementary therapy treatment option. Copyright (C) 2009 S. Karger AG, Base
Flux calibration of medium-resolution spectra from 300 nm to 2500 nm: Model reference spectra and telluric correction
While the near-infrared wavelength regime is becoming more and more important
for astrophysics there is a marked lack of spectrophotometric standard star
data that would allow the flux calibration of such data. Furthermore, flux
calibrating medium- to high-resolution \'echelle spectroscopy data is
challenging even in the optical wavelength range, because the available flux
standard data are often too coarsely sampled. We will provide standard star
reference data that allow users to derive response curves from 300nm to 2500nm
for spectroscopic data of medium to high resolution, including those taken with
\'echelle spectrographs. In addition we describe a method to correct for
moderate telluric absorption without the need of observing telluric standard
stars. As reference data for the flux standard stars we use theoretical spectra
derived from stellar model atmospheres. We verify that they provide an
appropriate description of the observed standard star spectra by checking for
residuals in line cores and line overlap regions in the ratios of observed
(X-shooter) spectra to model spectra. The finally selected model spectra are
then corrected for remaining mismatches and photometrically calibrated using
independent observations. The correction of telluric absorption is performed
with the help of telluric model spectra.We provide new, finely sampled
reference spectra without telluric absorption for six southern flux standard
stars that allow the users to flux calibrate their data from 300 nm to 2500 nm,
and a method to correct for telluric absorption using atmospheric models.Comment: Reference spectra available at CDS. Published in A&A 568, A9, 201
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