Synthesis and analysis of transformer-isolated converters

A systematic and straightforward procedure is developed for the synthesis and analysis of transformer-isolated power converters. The procedure can be used to determine the ranges of duty-ratio over which the transformer-isolated power converters of a given class can be operated without transformer saturation. The procedure can also be used to study the dependence of the power converter switch stresses on duty-ratios. This information is useful in the selection of the transformer-isolated power converter most suitable for a given application and in the design of this power converter with minimum switch stresses, high power density, and low cost     

Correlation of the leakage current and charge pumping in silicon oninsulator gate-controlled diodes

The leakage and charge pumping currents were measured in gate-controlled MOS p-i-n diodes fabricated on thin SIMOX substrates. The efficiencies of the techniques as well as their complementary features are analyzed for various experimental conditions. The interface properties of device-grade SIMOX wafers are characterized and shown to be compatible with VLSI requirements. Special interface coupling effects, which occur only in fully depleted SOI devices and modify the conventional signature of charge pumping and leakage current, are thoroughly investigated     

Optical fiber solitons, their properties and uses

The history and mathematical formulation of solutions are briefly reviewed. Solitons of the nonlinear Schrodinger equation are studied in greater detail because they describe nonlinear pulse propagation on dispersive optical fibers. The proposal by A. Hasegawa and the experiments of L.F. Mollenauer on long distance soliton propagation for use in repeaterless transoceanic fiber transmission cables are described. In 1986, limitations on the distance that can be spanned by a repeaterless link for a given bit rate were shown to exist. It has been shown recently that by proper design these limitations can be overcome, so that newer transoceanic cable designs are likely to utilize solitons. The special properties of solitons make them particularly suited for all optical switching and logic operations. Some recent experiments with such switches are described     

Highly reliable 200 mW AlGaAs laser diode with fundamental transverse mode

A highly reliable 200 mW AlGaAs laser diode with a fundamental transverse mode has been developed, by optimising its structure with a 0.8 mu m thick p-cladding layer, a 1200 mu m long cavity length, and a front facet coating with a low reflectivity of 2%. The maximum output power was 500 mW, and stable fundamental transverse mode operation was obtained up to 350 mW. Stable operation under 200 mW and 50 degrees C was confirmed for more than 1200 h. Optical feedback noise was below 3*10/sup -14/ Hz/sup -1/.<>     

Afterburner [network-independent card for protocols]

Many current implementations of protocols such as the Transmission Control Protocol/Internet Protocol (TCP/IP) are inefficient because data are often accessed more frequently than necessary. Three techniques that reduce the need for memory bandwidth are proposed. The techniques are copy-on-write, page remapping, and single-copy. Afterburner, a network-independent card that provides the services that are necessary for a single-copy protocol stack, is described. The card has 1 MByte of local buffers and provides a simple interface to a variety of network link adapters, including HIPPI and asynchronous transfer mode (ATM). Afterburner can support transfers to and from the link adapter card at rates up to 1 Gbit/s. An implementation of TCP/IP that uses the features provided by Afterburner to reduce the movement of data to a single copy is discussed. Measurements of the end-to-end performance of Afterburner and the single-copy implementation of TCP/IP are presented     

Technology combats disabilities

The author focusses on advances in equipment that offset physically functional limitations. He discusses how disabled and elderly people are using aids that enhance mobility (walking a certain distance, lifting a weight, or climbing stairs) as well as sensory faculties (seeing print, hearing conversation, and speaking intelligibly)     

On the time-domain scattering by a passive classical frequency dependent wedge-shaped region in a lossy dispersive medium

The time-scattering of an electromagnetic wave by a wedge-shaped region in a lossy medium, both with frequency dependent electric characteristics, is analyzed for plane wave and line source illuminations. New exact analytical expressions, satisfying explicitely the causality and allowing useful physical decompositions of the field, are obtained in these cases, using the particularities of the harmonic response in Sommerfeld-Maliuzhinets integral, especially original properties of the spectral function attached to it.     

Fractal error for detecting man-made features in aerial images

A technique is proposed for aiding photointerpreters in detecting man-made features in aerial reconnaissance images. The technique, which uses a metric called fractal error, is based on the observed propensity of natural image features to fit a fractional Brownian motion model. Man-made features usually do not fit this model well, and consequently the fractal error metric may be used as a discriminant function for detecting man-made scene features     

Parametric inference for step-stress models

Applications of the additive accumulation of damages (AAD) or the accelerated failure time (AFT) and the proportional hazards (PH) models in accelerated life testing with step-stresses are discussed. A new model including AAD and PH models is proposed. It is more reasonable than the PH model and wider then the AAD model. Constructing the maximum likelihood function is discussed