Improved strained HEMT characteristics using double-heterojunctionIn0.65Ga0.35As/In0.52Al0.48As design

The DC and microwave properties of strained In_0.65Ga _0.35As/In₀₅₂Al_0.48As HEMTs (high electron-mobility transistors) with double-heterojunction design are presented. The high sheet carrier density and good carrier confinement give rise to excellent device performance with very low output conductance. For 1×150-μm² long-gate HEMTs, the measured cutoff frequency f_T and maximum frequency of oscillation f_max are as high as 37 and 66 GHz, respectively     

An experimental superconducting magnetic system with an adjustable winding inductance and a 5 MJ energy capacity

An experimental superconducting magnetic system (MS) with an energy capacity of 5 MJ and an output power of no less than 130 MW is described. The MS winding is sectioned in the axial and radial directions. Owing to sectioning in radial direction, the MS may be used as an adjustable inductance enabling the stabilization of the amperage. The adjustable inductance may also be used as an efficient instrument for leveling the ratio of the active and reactive power in electric mains intended for different purposes (transport, energy industry, and emergency systems).     

Multi-vane expander performance: Breathing characteristics

The throttling of the working fluid flow at the inlet and exhaust port openings of multi-vane expanders leads to power losses. Therefore, a mathematical model has been developed to analyse their breathing characteristics. In particular two existing designs of multi-vane expanders, using refrigerant 113 as the working fluid, were considered. The results obtained indicate that multi-vane expanders exhibit easy-breathing behaviours. Improved breathing characteristics can be achieved by the wise selection of operating conditions for any existing design or by optimising the design parameters for a specific application.     

Instabilities induced in a laminar jet by acoustic hot-wires

Controlled and local excitation of a laminar flow is achieved by means of hot-wires heated periodically by Joule effect and generating acoustic waves. Some preliminary results are presented for the case of a laminar round jet.