Optical pre-nova identification for the X-ray Nova GRO J0422+32 (Nova Persei, 1992)

The X-ray Nova GRO J0422+32 in its low brightness has been identified with a B 21 ^m , R20 ^m star on Palomar Sky Survey glass copies. The scans obtained with an automatical microdensitometer along with our special PC program were used. The resulting outburst amplitude 8 ^m is one of similarity features for the class of the low mass X-ray Novae, black hole candidates.     

X-ray and optical observations of Nova Muscae 1983 during its nebular stage

The detection of X-rays from Nova Muscae 1983 (discovered on January 18, 1983) constitutes the first detection of X-rays from a classical nova during outburst. X-ray observations were carried out on 1984 April 20 and July 14 when Nova Mus had entered the nebular stage. During both observations no significant flux was observed with the medium energy detectors (2–50 keV). The source was detected with the low energy detector (.04–2 keV) using 3000 Å Lexan and Parlene- N-Aluminium filters; counting rates of (3.4 ± 1.2) × 10³ and (3.7 ± 1.2 × 10^-3 counts/sec were measured with the respective filters. The source was detected again on July 14 with about the same intensity. Either a shocked shell of circumstellar gas emitting 10⁷ thermal bremsstrahlung at 10³⁵ erg/sec intensity or a white dwarf remnant emitting 3.5 × 10⁵ blackbody radiation at 10³⁷ erg/sec luminosity are compatible with the measurements.Spectra taken in the visual spectral range show strong forbidden coronal emission lines of [FeVII] 6085, [FeX] 6374, and as never observed before in such a strength, [FeXIV] 5303 requiring excitation temperatures of 2 × 10⁶ °K.     

Optimum and Suboptimum Synchronizer for Binary FSK Communication Systems

This paper considers a binary frequency-shift-keying (FSK) communication system with an adaptive receiver. Partially coherent detection is accomplished exploiting phase and bit synchronization directly extracted from the information-bearing waveform. The optimum (maximum a posteriori probability criterion) estimators of the relevant channel parameters are found along with some suboptimum realizations. It turns out that these schemes are decision-directed tracking systems that may be implemented using standard circuitry.     

Effects of a Finite-Width Decision Threshold on Binary CPSK and FSK Communication Systems

The function of the receiver in a binary digital communication system is to make a binary (?space?, ?mark? or ?"0?, ?1?) decision by comparing the signal values from the mark and space filters (or correlators) at known successive time intervals (?bit? or ?baud? time intervals). When the signal value out of the mark filter is greater than that out of the space filter, it is decided that mark or 1 is transmitted, and vice versa. It is of fundamental importance to know the exact instant of time at which the two filter outputs are to be compared. This is the problem of synchronization between the transmitter and the receiver. In this paper, we assume a system that is perfectly synchronized. In a practical system, the difference between the two filter outputs must differ from a threshold by some finite amount in order to cause the device to respond reliably. The examination of the effects of this dead zone (finite-width decision threshold) on digital transmission systems is of important practical interest. Its effects on binary differentially coherent phase-shift-keying, and m-level phase-shift-keying systems have been investigated previously. In this paper we consider its effects on binary coherent phase-shift-keying (CPSK), coherent orthogonal (CFSK), and noncoherent orthogonal (NCFSK) systems. The probability of bit error and the channel capacity of each system is obtained in terms of the dead zone threshold.     

The Effect of Spectral Shape on the Probability of Error in Laser Binary Communication Systems

The effect of spectral bandwidth and spectral shape upon laser binary communication systems is investigated. The probability of error is plotted as a function of bandwidth for Lorentzian and Gaussian shaped spectra. The results show that even when the average noise power and the signal-to-noise ratio are held constant, the probability of error varies considerably as a function of spectral bandwidth.     

二进码的复制特性

本文基于复制理论的思想,分析了有关的二进码,指出了二进码本身具有的某种复制特性,并且根据组合思想提出了新的二进码—K码,根据平移复制和对称复制的等效性,证明了K码和自然码的关系,揭示了K码的物理意义.     

The COS-B X-ray observations of X-ray binaries

The observational information on X-ray binaries that was collected with the 80 cm² auxiliary X-ray detector onboard the COS-B gamma-ray satellite is reviewed. The results illustrate that in the study of X-ray binaries observations of long duration are extremely effective, even when using a small instrument.     

Optimum Adaptive Reception for Binary Sequences

The a posteriori probability density function p(?|X1, X2,...,Xk), where the Xi, i=1, 2, ..., K, represent Kvector-valued observations statistically related to the random vector ?, appears in many applications of the methods of statistical inference to problems in pattern recognition and statistical communication theory. In this paper, it is shown that for equally likely binary sequences (M= 2) of anticorrelated patterns for signals observed in additive Gaussian noise, a device that computes p?|X1, X2, XK) can be synthesized from a correlator, a simple instantaneous nonlinearity, and a multiplier. These results are used to derive some equally simple structures for various optimum nonsupervised estimators, pattern recognition machines, and signal detectors.     

X-ray Reflection

Material irradiated by X-rays produces backscattered radiation which is commonly known as the Reflection Spectrum. It consists of a structured continuum, due at high energies to the competition between photoelectric absorption and electron scattering enhanced at low energies by emission from the material itself, together with a complex line spectrum. We briefly review the history of X-ray reflection in astronomy and discuss various methods for computing the reflection spectrum from cold and ionized gas, illustrated with results from our own work reflionx. We discuss how the reflection spectrum can be used to obtain the geometry of the accretion flow, particularly the inner regions around black holes and neutron stars.     

解构二元对立 建构社会乌托邦

库切的代表作《耻》是一部寓意丰富,思想深刻的小说。文章将从解构主义文学理论来颠覆传统的二元对立关系即黑人与白人,男人与女人,人类与动物,粉碎西方文明中的白人中心主义,男人中心主义和人类中心主义,揭示库切对人类生存状态的忧虑、人道主义的关怀和创建乌托邦的理想。     

A Comparison of Binary Delay-Lock Tracking-Loop Implementations

The delay-lock loop is a device for tracking the delay difference between two correlated waveforms. It is used as a synchronizing loop for binary communications and tracking. The delay tracking performance is derived for various radio-frequency implementations of the binary delay-lock loop. Amplitude and biphase modulation by pseudorandom sequences are considered. Three types of receivers are analyzed for each modulation: envelope correlation, phase-coherent correlation, and phase-lock demodulation followed by video correlation.     

Programmed-Amplitude Binary Signaling with Decision and Information Feedback

A sequential detection scheme with combined decision and information feedbacks, where the signal amplitude at each iteration may be properly programmed, is analyzed. This approach allows a remarkable gain in transmission rate and a significant reduction in the peak-to-average power ratio, relative to the nonsequential scheme with constant signal amplitude.     

On the Acquisition Behavior of Binary Delay-Lock Loops

The acquisition problem for binary delay-lock loops is re-examined. Previous results obtained by Spilker and Gill on the maximum allowable search rate are shown to be in error. New results are given for the 2-? loop with video correlation and the 1-? loop with video and envelope correlation.     

Feedback Transmission of Binary Data with Automaton Receiver

Feedback transmission of binary data over a discrete-time additive Gaussian white noise channel is considered. The effect of some specific finite memory structure at the receiver is investigated. The whole communication scheme is the discrete analog of the one previously analyzed by Khas'minskii. The resulting average transmission time is increased by only about 20 percent of the theoretical limit in the low signal-to-noise ratio region. Numerical results are also shown.     

二进制乘法器的面—时平方复杂性研究

讨论了n位二进制整数乘法下界面－时平方复杂性问题,给出了一种树型布局的乘法器网络模型,并分析了它的AT~2复杂性