On line fatiguemeter: a large experiment in French nuclear plants

During operation of PWR plants, thermal transients occur and induce fatigue stresses at critical locations in the nuclear steam supply system. Assessment of cumulative usage factor at these locations is one the major concerns regarding plant life extension.A system based on real time fatigue monitoring his been developed by EDF. The principle of the system, that records plant operating parameters and calculate thermohydraulic conditions, local stresses and usage factor resulting from each individual transient, is firstly presented.Demonstration experiments, concerning two higly stressed locations of reactor coolant system (charging line nozzle and surge line), carried out in two 900 MW units are then described.Finally, analysis of these experiment results is commented. The system allows automatic transients book keeping and usage factor assessment. EDF intends to equip all its PWR units with such fatigue monitoring systems.     

Novel permanent magnet motor drives for electric vehicles

Novel permanent magnet (PM) motor drives have been successfully developed to fulfil the special requirements for electric vehicles such as high power density, high efficiency, high starting torque, and high cruising speed. These PM motors are all brushless and consist of various types, namely rectangular-fed, sinusoidal-fed, surface-magnet, buried-magnet, and hybrid. The advent of novel motor configurations lies on the unique electromagnetic topology, including the concept of multipole magnetic circuit and full slot-pitch coil span arrangements, leading to a reduction in both magnetic yoke and copper, decoupling of each phase flux path, and hence an increase in both power density and efficiency. Moreover, with the use of fractional number of slots per pole per phase, the cogging torque can be eliminated. On the other hand, by employing the claw-type rotor structure and fixing an additional field winding as the inner stator, these PM hybrid motors can further provide excellent controllability and improve efficiency map. In the PM motors, by purposely making use of the transformer EMF to prevent the current regulator from saturation, a novel control approach is developed to allow for attaining high-speed constant-power operation which is particularly essential for electric vehicles during cruising. Their design philosophy, control strategy, theoretical analysis, computer simulation, experimental tests and application to electric vehicles are described     

Spectral analysis of a new six-phase pole-changing induction motor drive for electric vehicles

In this paper, a new six-phase pole-changing induction motor drive is proposed to extend the constant-power operating range for electric vehicle application. The double Fourier series is newly employed to analyze the spectra of the motor phase voltage and current. Consequently, the harmonic expression of the inverter DC-link current can be derived. In order to reduce the DC-link harmonics, a new sinusoidal pulsewidth-modulation strategy is developed for the proposed six-phase inverter. Experimental results, particularly the spectra of the phase current and the DC-link current, are given to verify the theoretical analysis.     

High-speed InP/InGaAs heterojunction bipolar transistors

Very-high-performance common-emitter InP/InGaAs single heterojunction bipolar transistors (HBTs) grown by metalorganic molecular beam epitaxy (MOMBE) are reported. They exhibit a maximum oscillation frequency (f_T) of 180 GHz at a current density of 1×10⁵ A/cm². this corresponds to an (R_BC_BC)_eff=f _T/(8πf²_max) delay time of 0.12 ps, which is the smallest value every reported for common-emitter InP/InGaAs HBTs. The devices have 11 μm² total emitter area and exhibit current gain values up to 100 at zero base-collector bias voltage. The breakdown voltage of these devices is high with measured BV_CEO and BV_CEO of 8 and 17 V, respectively     

Fracture of shear bands in atactic polystyrene

Thick shear bands in polystyrene formed by compression could cause fracture or the formation of cracks by intersecting with themselves, by relaxing after the removal of the load, by propagating all the way to the side surfaces and by subsequent tensile deformation. The microstructural mechanisms involved in all these fracture processes are discussed.     

Accumulation and depuration of tetramethyllead by rainbow trout

Tetramethyllead was found very toxic especially to juvenile rainbow trout (Salmo gairdneri). It was accumulated rapidly from the water by the fish and the highest concentration was found in the lipid layer of the intestine. Depuration of Me₄Pb from the fish organs was initially quite rapid, followed by a slower decrease and eventually reaching residual levels. Environmental concentrations of Me₄Pb detected in the fishery products thus represent a balance between uptake and depuration of this compound in fish.In conjunction with this study, a dosing system for exposing rainbow trout to Me₄Pb was developed.