Application of a multivariable optimiser to the design of CMOS buffers

A multivariable optimiser is used to individually optimise the size of each stage in a CMOS buffer. Then the optimiser is used to minimise the silicon area for a given buffer delay. An area saving of up to 50% is obtained, compared to other types of buffer.<>     

Predicting the dynamic behavior of axial-field actuators

A method is presented for predicting the dynamic behavior of axial-field actuators. This method entails the numerical solution of a system of nonlinear differential equations that govern the dynamics. The theory is applied to a specific actuator geometry, and the predicted results are compared with empirical data     

Numerical diffraction coefficients for surface waves

The numerical uniform theory of diffraction (UTD) is extended to include surface waves. A method for extracting surface wave diffraction coefficients from moment method data is given and Prony's method is applied to the problem of determining surface wave propagation constants. The method is validated through comparison with the exact solution of the problem of surface wave diffraction by a truncated dielectric slab recessed in a conducting surface. Examples are given for scattering from dielectric slabs and frequency-selective surfaces and for radiation from a conformal microstrip antenna with a truncated substrate. The accuracy obtained is demonstrated by comparison with moment method calculations     

A fracture mechanics based fatigue-creep-environment crack growth model for high temperature

This paper deals with the development of a fatigue crack growth model for high temperature complex loading and application to turbine disc conditions. The proposed model is based on an extensive experimental study performed on Astroloy at 650°C, which comprises fatigue with or without hold times, special tests with holds at intermediate loads, fast-slow or slow-fast triangular waves, sequence tests, etc.

The crack growth model is built up in the framework of classical linear elastic fracture mechanics. Its structure is quite simple and is supported by previously developed fatigue crack growth models and a companion study made at École des Mines de Paris (EMP) for the oxidation processes on Astrology.     

Modelling and Simulation of a Direct Contact Rotary Dryer

A mathematical model able to predict solid and drying gas temperature and moisture content axial profiles along a direct contact rotary dryer was developed. The study was focused on the drying kinetics based on phenomenological models. Two different drying mechanisms in the decreasing drying rate period were tested: proponional to the unbound moisture content and moisture diffusion inside the particle. Experimental data collected in a pilot-scale direct contact rotary dryer was used to validate the model. Soya and fish meals were used as drying material.     

Low-noise properties of dry gate recess etched InP HEMTs

Lattice-matched InAlAs-InGaAs HEMTs with dry etched and wet etched gate recesses have been fabricated and both high-frequency and noise measurements have been carried out. The highly selective dry etching process ensures uniform device parameters. The small signal and noise performance shows only minor differences between the two transistor types. There is no evidence of detrimental effects caused by dry etching that reduce the electrical and noise performance of the device at high frequencies. These results show that dry etched InP HEMT's have suitable characteristics for the fabrication of MM-wave integrated circuits