Blind Feedforward Symbol-Timing Estimation With PSK Signals: A Constant-Modulus Approach

In this letter, the problem of blind symbol-timing estimation with M-ary phase-shift keying (M-PSK) signals is considered. An estimator exploiting the constant modulus (CM) property of M-PSK constellations and the structure of the received signal when the convolution of the transmitter's signaling pulse and the receiver filter satisfies the Nyquist criterion is proposed. Since the derived estimator, termed the CM estimator, requires a maximization with respect to a continuous variable, a closed-form approximate CM (ACM) algorithm, suitable for digital implementation, is proposed. Computer simulation results show that with small excess bandwidth factors, the derived ACM algorithm outperforms previously proposed algorithms at moderate and high signal-to-noise ratios     

Detection of internal defects using phase shifting holographic interferometry

Phase shifting holographic interferometry is shown to be a useful tool for detection of internal defects in materials by observing strain anomalies in a stressed object. The pos-t recording signal processing includes smoothing of the measured deformation by means of data polynomial fitting, a derivation process taken from computer vision edge detection algorithms, which makes use of a Gaussian derivative and a cubic spline interpolation, a second smoothing, a regular numeric derivative and final smoothing. Defects, ie weak areas of the sample, are detected in the second derivative of the sample deformation, which is proportional to the stress map of the sample surface. The second derivative provides information about the defect dimensions and its severity and location. A theoretical model forthe loading of a sample containing a defect is presented as well as results based on it. Good correlation between experiment and theory was found.     

Real-time optical spectrum analyser based on chirped fibre Bragggratings

A real-time fibre optic spectrum analyser for optical pulses is realised. It is based on a chirped fibre Bragg grating and the formation of a time domain analogue of the Fraunhofer diffraction regime. The spectrum of a modelocked diode laser was measured, with a resolution of 0.3 nm, which can be easily improved to 0.06 nm     

Non-data-aided carrier-frequency offset estimation for pulse-shaping OFDM/OQAM systems

In this paper we consider the problem of blind carrier-frequency offset (CFO) estimation for pulse-shaping orthogonal frequency-division multiplexing (OFDM) systems based on offset quadrature amplitude modulation (OQAM). In particular, under the assumption of low signal-to-noise ratio, three maximum-likelihood (ML) CFO estimators for non-dispersive channels are derived. Due to their significant computational complexity a more feasible closed-form CFO synchronization algorithm is considered. The performance of the derived blind estimators is assessed via computer simulations and compared with that of a blind CFO estimator previously proposed in the literature, exploiting the second-order cyclostationarity property of the OFDM/OQAM signal.     

South Africa's rapid electrification programme: Policy,institutional, planning,financing and technical innovations

This paper documents South Africa's electrification programme from the late 1980s to the present. The primary aim of the paper is to present the reader with an overview of the policy, institutional, planning, financing and technological developments and innovations that resulted in more than 5 million households receiving access to electricity between 1990 and 2007. Key aspects include the way in which a period of political change and policy disruption were essential to the programme's initiation, and the critical role played by organisations and individuals outside of national government in helping shape new electrification policies and strategies. In addition, the paper identifies the contribution of technology development in cost reduction and achieving the social aims of the programme. Several lessons may be drawn from the institutional and planning arrangements that the South African programme has developed, the significance of the development of appropriate cost-driven technical innovations and standards, and the acknowledgement of the social function of electrification and its funding from the fiscus (rather than through cross-subsidies).     

Abstracts of Papers Deposited at Viniti

Journal of Engineering Physics and Thermophysics -