Bulk Power HVDC transmission schemes over distances of up to 2000 km are currently under planning for various large hydropower stations in India and China. Ultra high dc voltage (UHVDC) up to 800 kV is the preferred dc voltage level for these applications. Currently world-wide existing HVDC schemes are limited to maximum voltage levels of 500 kV to 600 kV. Therefore, the impact of increased ste...

Rsing agricultural productivity is central to economic development and has been studied by the historians of many countries. Much has been learned about their separate histories, but long-term, cross-national comparisons remain elusive. Crop yields have received considerable attention,' and progress has been made in understanding their evolution. However, labour productivity is arguably a more ...

PREFACE This publication presents a state-of-the-art survey of public-key cryptography circa 1988-1990. In doing so, it covers a number of different topics including: 1. The theory of public-key cryptography. 2. Comparisons to conventional (secret-key) cryptography. 3. A largely self-contained summary of relevant mathematics. 4. A survey of major existing public-key systems. 5. An exploration o...

A new UV submersible spectroradiometer has been employed to determine the diffuse attenuation coefficient for irradiance in the clearest natural waters [K(w)(lambda)] with emphasis on the spectral region from 300 to 400 nm. K(w)(lambda) can be related to the inherent optical properties of pure water, in particular the total absorption coefficient a(w)(lambda) and the molecular scattering coeffi...

Constraining the history of seawater (234U/238U) is important because this ratio is used to assess the validity of U/ Th ages, and because it provides information about the past rate of physical weathering on the continents. This study makes use of U-rich slope sediments from the Bahamas in an attempt to reconstruct seawater (234U/238U) for the last 800 kyr. For the last 360 kyr, U/Th dating of...

Erico L. Rempel1,†, Abraham C.-L. Chian1,2,3, Axel Brandenburg4,5, Pablo R. Muñoz1 and Shawn C. Shadden6 1Institute of Aeronautical Technology (ITA), World Institute for Space Environment Research (WISER), 12228–900 São José dos Campos – SP, Brazil 2Observatoire de Paris, LESIA, CNRS, 92190 Meudon, France 3National Institute for Space Research (INPE), WISER, P.O. Box 515, 12227–010 São José dos...

Mobile agent technology offers a new computing paradigm in which a program, in the form of a software agent, can suspend its execution on a host computer, transfer itself to another agent-enabled host on the network, and resume execution on the new host. The use of mobile code has a long history dating back to the use of remote job entry systems in the 1960's. Today's agent incarnations can be ...

It is a decade since Professors David Milner and Richard Beard produced data to show that 39% of babies born at 25 weeks' gestation and 16% of those born at 24 weeks' gestation were surviving in the major neonatal intensive care units (NICUs) in Britain.' Translated into birth weight, this and other contemporaneous data suggested that at least 20-30% of babies weighing 600-800 g were surviving ...