Two magnetars: SGR 1627–41 and 1E 1547–5408

We describe the results obtained with Target of Opportunity observations of the galactic sources SGR 1627–41 and 1E 1547–5408. These two transients show several similarities supporting the interpretation of Anomalous X-ray Pulsars and Soft Gamma-ray Repeaters as a single class of strongly magnetized neutron stars.     

Experimental and theoretical burning of solid rocket propellants near the pressure deflagration limit

Burning of composite solid rocket propellants near the pressure deflagration limit (PDL) was studied experimentally in two different test chambers. The propellant tested was a nonmetallized ammonium perchlorate-based composite propellant (AP 84/CTPB 16). Measurements were taken of the regression rate, oscillations frequency and flame luminosity. Self-sustained oscillations were detected near the PDL that matched reasonably well the predictions of the analytical nonlinear stability theory and of the numerically solved nonlinear mathematical model. Both experimental and numerical results show the burning rate oscillations near the PDL due to statically unstable burning, that is the only combustion regime possible below a certain pressure. When pressure is further reduced the amplitude of the oscillations increases and their frequency decreases, until extinction follows abruptly below a pressure that corresponds to the PDL.     

The spectral and temporal variability of the X-ray transient 4U1630-47

We present the results of four observations made by the European Space Agency's EXOSAT Observatory of the X-ray transient 4U1630-47 during its 1984 outburst. We observed marked spectral changes as the source decayed from a maximum observed intensity of 8×10^–9 erg/cm²/sec (1.5–10 keV). The spectrum could be modelled by a soft thermal-like component with a high energy power-law tail. The relative contribution of the soft to hard component decreased as the total luminosity decreased. We compare these changes with those observed from the black hole candidate Cyg X-1 when it transitions from a high to a low state. In addition we report the discovery of short timescale intensity variations (down to 50 msec) with a characteristic timescale of 20 sec. We present a precise position for this unidentified source.on leave from Università di Roma Dipartimento di Fisica G. Marconi.     

Estimation and classification of FM signals using time frequency transforms

This work deals with electronic warfare: we have to process an intercepted radar-emitted signal assumed to be frequency-modulated (FM). A battery of parametric models being available, we face the two main problems: the parameter estimation, given a model, and the classification, given the battery. For the former, we propose the classical maximum likelihood estimator (MLE) and an original numerical scheme to reach it. For the latter, we construct a test based on the estimated variances cross-ratios. Both perform very efficiently with respect to (w.r.t.) the Cramer-Rao lower bound (CRLB) and the rate of correct classification, respectively, for low signal-to-noise ratios (SNRs).     

和味蕾谈一场恋爱 上海浪漫的情侣餐厅

<正>虽然只要爱对了人,每天都是情人节,但在有纪念意义的节日里,拥有一个难忘的夜晚是每个女孩子的梦想。所以,既然约会去了圣地,那么一家浪漫的情侣餐厅作为后续自然是标准化流程啦。     

Intermittent stellar wind accretion in Pop. I binary systems containing an X-ray pulsar

We review the long term variability properties of accretion powered X-ray pulsars in massive Pop. I binary systems and discuss how their characteristics, in particular the large dynamic range in luminosity of the transient pulsars, can be understood in terms of the interaction of the accreting material with the neutron star magnetosphere. We point out that the X-ray pulsar transient activity in general can be due to the transition between direct wind accretion and a regime in which the centrifugal drag exerted by the pulsar magnetosphere inhibits accretion onto the neutron star surface.