1,113 research outputs found
A 0535+26: Back in business
In May/June 2005, after 10 years of inactivity, the Be/X-ray binary system A
0535+26 underwent a major X-ray outburst. In this paper data are presented from
10 years of optical, IR and X-ray monitoring showing the behaviour of the
system during the quiescent epoch and the lead up to the new outburst. The
results show the system going through a period when the Be star in the system
had a minimal circumstellar disk and then a dramatic disk recovery leading,
presumably, to the latest flare up of X-ray emission. The data are interpreted
in terms of the state of the disk and its interaction with the neutron star
companion.Comment: Accepted for publication in MNRA
Compact and explicit physical model for lateral metal-oxide-semiconductor field-effect transistor with nanoelectromechanical system based resonant gate
We propose a simple analytical model of a metal-oxide-semiconductor
field-effect transistor with a lateral resonant gate based on the coupled
electromechanical equations, which are self-consistently solved in time. All
charge densities according to the mechanical oscillations are evaluated. The
only input parameters are the physical characteristics of the device. No extra
mathematical parameters are used to fit the experimental results. Theoretical
results are in good agreement with the experimental data in static and dynamic
operation. Our model is comprehensive and may be suitable for any
electromechanical device based on the field-effect transduction
Generation and diffusion of innovations in a district learning system: the case of Ink-Jet Printing
Abstract is included in the paper uploaded
Bivariate Nakagami-m distribution with arbitrary fading parameters
[EN] The bivariate Nakagami-m distribution with arbitrary fading
parameters is derived, obtaining the probability density function (PDF), the
cumulative density function (CDF) and the central moments. Additionally,
limitations of that distribution are discussed.Reig, J.; Rubio Arjona, L.; Cardona Marcet, N. (2002). Bivariate Nakagami-m distribution with arbitrary fading parameters. Electronics Letters. 38(25):1715-1717. doi:10.1049/el:20021124S171517173825Nakagami, M.: ‘Them-distribution—a general formula of intensity distribution of rapid fading’, Hoffman, W.G., Statistical methods in radio wave propagation, (Pergamon 1960)Abramowitz, M., and Stegun, I.A.: ‘Handbook of mathematical functions’, (Dover, New York 1972)Tan, C. C., & Beaulieu, N. C. (1997). Infinite series representations of the bivariate Rayleigh and Nakagami-m distributions. IEEE Transactions on Communications, 45(10), 1159-1161. doi:10.1109/26.63467
Discovery of circular polarization in the Intermediate Polar 1WGA J1958.2+3232
We report on UBVRI polarimetry of the recently identified Intermediate Polar
1WGA J1958.2+3232, carried out on 2000 August, 4-6 at the Nordic Optical
Telescope. Circular polarization was detected in R and I bands with an
increasing absolute mean value with wavelength. There is evidence of possible
modulation of the circular polarization at twice the previously reported white
dwarf spin period, suggesting that it is the true period and that the
modulation in optical and X-ray is dominated by the first harmonic. Indication
of modulation at the orbital period is also present.Comment: 4 pages, 6 figures, accepted by A&A; editing changes onl
Periodicities in the high-mass X-ray binary system RXJ0146.9+6121/LSI+61 235
The high-mass X-ray binary RX J0146.9+6121, with optical counterpart LS I+61°235 (V831 Cas), is an intriguing system on the outskirts of the open cluster NGC 663. It contains the slowest Be type X-ray pulsar known with a pulse period of around 1400 s and, primarily from the study of variation in the emission line profile of Hα, it is known to have a Be decretion disc with a one-armed density wave period of approximately 1240 d. Here we present the results of an extensive photometric campaign, supplemented with optical spectroscopy, aimed at measuring short time-scale periodicities. We find three significant periodicities in the photometric data at, in order of statistical significance, 0.34, 0.67 and 0.10 d. We give arguments to support the interpretation that the 0.34 and 0.10 d periods could be due to stellar oscillations of the B-type primary star and that the 0.67 d period is the spin period of the Be star with a spin axis inclination of 23+10−8 degrees. We measured a systemic velocity of −37.0 ± 4.3 km s−1 confirming that LS I+61°235 has a high probability of membership in the young cluster NGC 663 from which the system's age can be estimated as 20–25 Myr. From archival RXTE All Sky Monitor (ASM) data we further find ‘super’ X-ray outbursts roughly every 450 d. If these super outbursts are caused by the alignment of the compact star with the one-armed decretion disc enhancement, then the orbital period is approximately 330 d
XMM-Newton observation of the persistent Be/NS X-ray binary pulsar RX J0440.9+4431
Many X-ray accreting pulsars have a soft excess below 10 keV. This feature
has been detected also in faint sources and at low luminosity levels,
suggesting that it is an ubiquitous phenomenon. In the case of the high
luminosity pulsars (Lx > 10^36 erg/s), the fit of this component with thermal
emission models usually provides low temperatures (kT < 0.5 keV) and large
emission regions (R > a few hundred km); for this reason, it is referred to as
a `soft' excess. On the other hand, we recently found that in persistent,
low-luminosity (Lx ~ 10^34 erg/s) and long-period (P > 100 s) Be accreting
pulsars the observed excess can be modeled with a rather hot (kT > 1 keV)
blackbody component of small area (R < 0.5 km), which can be interpreted as
emission from the NS polar caps. In this paper we present the results of a
recent XMM-Newton observation of the Galactic Be pulsar RX J0440.9+4431, which
is a poorly studied member of this class of sources. We have found a best-fit
period P = 204.96(+/-0.02) s, which implies an average pulsar spin-down during
the last 13 years, with dP/dt ~ 6x10^(-9) s/s. The estimated source luminosity
is Lx ~ 8x10^(34) erg/s: this value is higher by a factor < 10 compared to
those obtained in the first source observations, but almost two orders of
magnitude lower than those measured during a few outbursts detected in the
latest years. The source spectrum can be described with a power law plus
blackbody model, with kTbb = 1.34(+/-0.04) keV and Rbb = 273(+/-16) m,
suggesting a polar-cap origin of this component. Our results support the
classification of RX J0440.9+4431 as a persistent Be/NS pulsar, and confirm
that the hot blackbody spectral component is a common property of this class of
sources.Comment: 8 pages, 6 figures, 2 tables. Accepted for publication by Astronomy
and Astrophysic
XMM-Newton observation of the persistent Be/NS X-ray binary pulsar RX J1037.5-5647 in a low luminosity state
The spectra of several X-ray binary pulsars display a clear soft excess,
which in most cases can be described with a blackbody model, above the main
power-law component. While in the high-luminosity sources it is usually
characterized by low temperature (kT
100 km), in the two persistent and low-luminosity pulsars 4U 0352+309 and RX
J0146.9+6121 this component has a high temperature (kT > 1 keV) and a smaller
radius (R < 0.5 km), consistent with the estimated size of the neutron-star
polar cap. Here we report on the timing and spectral analysis of RX
J1037.5-5647, another low-luminosity persistent Be binary pulsar, based on the
first XMM-Newton observation of this source. We have found a best-fit period P
= 853.4(+/-0.2) s, that implies an average pulsar spin-up dP/dt ~ -2E-8 s/s in
the latest decade. The estimated source luminosity is Lx ~ 10^34 erg/s, a value
comparable to that of the other persistent Be binary pulsars and about one
order of magnitude lower than in most of the previous measurements. The source
spectrum can be described with a power law plus blackbody model, with kTbb =
1.26(+0.16/-0.09) keV and Rbb = 128(+13/-21) m, suggesting a polar-cap origin
of this component. These results strengthen the hypothesis that, in addition to
low luminosities and long periods, this class of sources is characterized also
by common spectral propertiesComment: 9 pages, 8 figures, 2 tables. Accepted for publication by Astronomy
and Astrophysic
Modelling driving behaviour and its impact on the energy management problem in hybrid electric vehicles
Perfect knowledge of future driving conditions can be rarely assumed on real applications when optimally splitting power demands among different energy sources in a hybrid electric vehicle. Since performance of a control strategy in terms of fuel economy and pollutant emissions is strongly affected by vehicle power requirements, accurate predictions of future driving conditions are needed. This paper proposes different methods to model driving patterns with a stochastic approach. All the addressed methods are based on the statistical analysis of previous driving patterns to predict future driving conditions, some of them employing standard vehicle sensors, while others require non-conventional sensors (for instance, global positioning system or inertial reference system). The different modelling techniques to estimate future driving conditions are evaluated with real driving data and optimal control methods, trading off model complexity with performance.Guardiola García, C.; Plá Moreno, B.; Blanco Rodriguez, D.; Reig Bernad, A. (2014). Modelling driving behaviour and its impact on the energy management problem in hybrid electric vehicles. International Journal of Computer Mathematics. 91(1):147-156. doi:10.1080/00207160.2013.829567S147156911Ericsson, E. (2001). Independent driving pattern factors and their influence on fuel-use and exhaust emission factors. Transportation Research Part D: Transport and Environment, 6(5), 325-345. doi:10.1016/s1361-9209(01)00003-7Q. Gong, P. Tulpule, V. Marano, S. Midlam-Mohler, and G. Rizzoni,The role of ITS in PHEV performance improvement, 2011 American Control Conference, June–July, San Francisco, CA, 2011, pp. 2119–2124.C. Guardiola, B. Pla, S. Onori, and G. Rizzoni,A new approach to optimally tune the control strategy for hybrid vehicles applications, IFAC Workshop on Engine and Powertrain Control, Simulation and Modeling E-COSM’12, October, Rueil-Malmaison, France, 2012.Johannesson, L., Asbogard, M., & Egardt, B. (2007). Assessing the Potential of Predictive Control for Hybrid Vehicle Powertrains Using Stochastic Dynamic Programming. IEEE Transactions on Intelligent Transportation Systems, 8(1), 71-83. doi:10.1109/tits.2006.884887Liu, S., & Yao, B. (2008). Coordinate Control of Energy Saving Programmable Valves. IEEE Transactions on Control Systems Technology, 16(1), 34-45. doi:10.1109/tcst.2007.903073Paganelli, G. (2001). General supervisory control policy for the energy optimization of charge-sustaining hybrid electric vehicles. JSAE Review, 22(4), 511-518. doi:10.1016/s0389-4304(01)00138-2Rizzoni, G., Guzzella, L., & Baumann, B. M. (1999). Unified modeling of hybrid electric vehicle drivetrains. IEEE/ASME Transactions on Mechatronics, 4(3), 246-257. doi:10.1109/3516.789683Control of hybrid electric vehicles. (2007). IEEE Control Systems, 27(2), 60-70. doi:10.1109/mcs.2007.338280L. Serrao, S. Onori, and G. Rizzoni,ECMS as realization of Pontryagin's minimum principle for HEV control, 2009 American Control Conference, June, Saint Louis, MO, 2009, pp. 3964–3969.Serrao, L., Onori, S., & Rizzoni, G. (2011). A Comparative Analysis of Energy Management Strategies for Hybrid Electric Vehicles. Journal of Dynamic Systems, Measurement, and Control, 133(3). doi:10.1115/1.4003267Stockar, S., Marano, V., Canova, M., Rizzoni, G., & Guzzella, L. (2011). Energy-Optimal Control of Plug-in Hybrid Electric Vehicles for Real-World Driving Cycles. IEEE Transactions on Vehicular Technology, 60(7), 2949-2962. doi:10.1109/tvt.2011.2158565Sundström, O., Ambühl, D., & Guzzella, L. (2009). On Implementation of Dynamic Programming for Optimal Control Problems with Final State Constraints. Oil & Gas Science and Technology – Revue de l’Institut Français du Pétrole, 65(1), 91-102. doi:10.2516/ogst/2009020O. Sundström and L. Guzzella,A generic dynamic programming Matlab function, 18th IEEE International Conference on Control Applications Part of 2009 IEEE Multi-conference on Systems and Control, July, Saint Petersburg, 2009, pp. 1625–1630.R. Wang and S.M. Lukic,Review of driving conditions prediction and driving style recognition based control algorithms for hybrid electric vehicles, Vehicle Power and Propulsion Conference (VPPC), 2011 IEEE, September 6–9, Raleigh, NC, 2011, pp. 1–7
FDG-PET studies of the effect of MDMA in rat brain
[Abstract] The 10th International Conference on Functional Mapping of the Human Brain, June 13-17, 2004, Budapest, HungaryAlterations of the human brain due to MDMA use are a focus of ongoing research. MDMA abuse produces both
short and long-term effects on brain; MDMA-induced functional alterations of the serotonergic system are
reported to alter local energy metabolism of cortical and subcortical structures. Presently, there are no FDG-PET
experimental studies reported in animals. The aim of this study is to assess these brain glucose metabolism
changes after a single dose of MDMA in rats by using FDG-PETPublicad
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