Search results for "binary"
showing 10 items of 833 documents
Hard X-ray Emission from Low Mass X-ray Binaries
2003
In this paper we review our current knowledge of the hard X-ray emission properties of old accreting neutron stars in low mass X-ray binaries, with particular attention to recent results obtained for the brightest sources of this class, the so-called Z sources. While less luminous low mass X-ray binaries often show quite hard spectra, sometimes extending up to energies g 100 keV, the spectra of Z sources are always very soft, dominated by thermal components with characteristic temperatures ∼ 3-6 keV. However, recent broad band observations revealed the presence of a weak hard (power-law) component that is sometimes present in the spectra of these sources. These observations have strengthene…
On Combinatorial Generation of Prefix Normal Words
2014
A prefix normal word is a binary word with the property that no substring has more 1s than the prefix of the same length. This class of words is important in the context of binary jumbled pattern matching. In this paper we present an efficient algorithm for exhaustively listing the prefix normal words with a fixed length. The algorithm is based on the fact that the language of prefix normal words is a bubble language, a class of binary languages with the property that, for any word w in the language, exchanging the first occurrence of 01 by 10 in w results in another word in the language. We prove that each prefix normal word is produced in O(n) amortized time, and conjecture, based on expe…
Nonlinear Modeling of DC/DC Converters Using the Hammerstein's Approach
2007
This paper deals with the modelling of highly nonlinear switching power-electronics converters using black-box identification methods. The duty cycle and the output voltage are chosen, respectively, as the input and the output of the model. A nonlinear Hammerstein-type mathematical model, consisting of a static nonlinearity and a linear time-invariant model, is considered in order to cope with the well-known limitations of the more common small-signal models, i.e. the entity of the variations of the variables around a well-defined steady-state operating point and the incorrect reproduction of the steady-state behavior corresponding to input step variations from the above steady-state operat…
A New Wavelet-Based Texture Descriptor for Image Retrieval
2007
This paper presents a novel texture descriptor based on the wavelet transform. First, we will consider vertical and horizontal coefficients at the same position as the components of a bivariate random vector. The magnitud and angle of these vectors are computed and its histograms are analyzed. This empirical magnitud histogram is modelled by using a gamma distribution (pdf). As a result, the feature extraction step consists of estimating the gamma parameters using the maxima likelihood estimator and computing the circular histograms of angles. The similarity measurement step is done by means of the well-known Kullback-Leibler divergence. Finally, retrieval experiments are done using the Bro…
Spin down of an Accreting Millisecond Pulsar, the case of XTE J1814‐338
2007
We report about a timing analysis performed on the data gathered by RXTE of the accreting millisecond pulsar XTE J1814-338 during its 2003 outburst. The first full orbital solution of this binary system is given. Moreover the evolution of the phase of the pulsed emission reveals that the rotating compact object is spinning down at a rate ν˙ = (-6.7 +/- 0.7) × 10-14 Hz/s, while accreting. This behavior is considered as a result of the braking effect due to the interaction between the magnetosphere and the inner parts of the accretion disc, in the case of an accretion rate low enough to allow the expansion of the magnetospheric radius to the corotation limit. In this context we derive an esti…
Residual Stresses Induced by Cold Expansion of Adjacent and Cut-Out Holes
2012
Fatigue life of fastener holes can be enhanced via a cold-expansion process to introduce a compressive residual stress field around the hole edge and to reduce crack growth propagation. Considering that aerospace components contain multiple rows of holes, the present investigation focuses on the evaluation of the three-dimensional residual stress distribution in adjacent cold-expanded (CE) holes. The redistribution of residual stresses caused by a cut introduced between two adjacent holes was also investigated. Finite element (FE) analysis and experimental technique were used to assess the residual stress distribution in a 6082-T6 aluminum plate with two adjacent holes expanded sequentially…
Vapor–liquid equilibrium of binary mixtures of trichloroethylene with 1-pentanol, 2-methyl-1-butanol and 3-methyl-1-butanol at 100 kPa
1999
Abstract Isobaric vapor–liquid equilibria (VLE) have been obtained for the systems trichloroethylene+1-pentanol, trichloroethylene+2-methyl-1-butanol and trichloroethylene+3-methyl-1-butanol at 100 kPa using a dynamic still. The experimental error in temperature is ±0.1 K, in pressure ±0.1 kPa, and in the liquid and vapor mole fraction ±0.001. The three systems satisfy the point-to-point thermodynamic consistency test. All the systems show positive deviations from ideality. The data have been correlated with the Margules, van Laar, Wilson, NRTL and UNIQUAC equations.
Real-time acquisition of complex optical fields by binary amplitude modulation
2017
We describe, through simulations and experiments, a real-time wavefront acquisition technique using random binary amplitude masks and an iterative phase retrieval algorithm based on the Fresnel propagator. By using a digital micromirror device, it is possible to recover an unknown complex object by illuminating with this set of masks and simultaneously recording the resulting intensity patterns with a high-speed camera, making this technique suitable for dynamic applications.
Disc loss and renewal in A0535+26
1999
This paper presents observations of the Be/X-ray binary system A0535+26 revealing the first observed loss of its circumstellar disc, demonstrated by the loss of its JHK infrared excess and optical/IR line emission. However optical/IR spectroscopy reveals the formation of a new inner disc with significant density and emission strength at small radii; the disc has proven to be stable over 5 months in this intermediate state.
Discovery of a redshifted X-ray emission line in the symbiotic neutron star binary 4U 1700+24
2005
We present the spectral analysis of an XMM-Newton observation of the X-ray binary 4U 1700+24, performed during an outburst in August 2002. The EPIC-PN spectrum above 1 keV can be modeled by a blackbody plus Comptonization model, as in previous observations. At lower energies, however, we detect a prominent soft excess, which we model with a broad Gaussian centered at ~0.5 keV. In the high resolution RGS spectrum we detect a single emission line, centered at 19.19^{+0.05}_{-0.09} \AA. We discuss two possible interpretations for this line: O VIII at redshift z=0.012^{+0.002}_{-0.004} or Ne IX at redshift z~0.4.