Performance estimation of interior permanent-magnet brushless motors using the voltage-driven flux-MMF diagram

The flux-magnetomotive force (flux-MMF) diagram, or "energy conversion loop," is a powerful tool for computing the parameters of saturated interior permanent-magnet brushless motors, especially when the assumptions underlying classical dq theory are not valid, as is often the case in modern practice. Efficient finite-element computation of the flux-MMF diagram is possible when the motor current is known a priori, but in high-speed operation the current regulator can lose control of the current waveform and the computation becomes "voltage-driven" rather than "current-driven." This paper describes an efficient method for estimating the motor performance-average torque, inductances-by solving the voltage-driven problem. It presents experimental validation for a two-pole brushless interior permanent-magnet motor. The paper also discusses the general conditions under which this method is appropriate, and compares the method with alternative approaches

Reflectance anisotropy spectroscopy of magnetite (110) surfaces

Reflectance anisotropy spectroscopy (RAS) has been used to measure the optical anisotropies of bulk and thin-film Fe3O4(110) surfaces. The spectra indicate that small shifts in energy of the optical transitions, associated with anisotropic strain or electric field gradients caused by the (110) surface termination or a native oxide layer, are responsible for the strong signal observed. The RAS response was then measured as a function of temperature. A distinct change in the RAS line-shape amplitude was observed in the spectral range from 0.8 to 1.6 eV for temperatures below the Verwey transition of the crystal. Finally, thin-film magnetite was grown by molecular beam epitaxy on MgO(110) substrates. Changes in the RAS spectra were found for different film thickness, suggesting that RAS can be used to monitor the growth of magnetite (110) films in situ. The thickness dependence of the RAS is discussed in terms of various models for the origin of the RAS signal

DC-electric-field-induced and low-frequency electromodulation second-harmonic generation spectroscopy of Si(001)-SiO2_2 interfaces

The mechanism of DC-Electric-Field-Induced Second-Harmonic (EFISH) generation at weakly nonlinear buried Si(001)-SiO$_2$ interfaces is studied experimentally in planar Si(001)-SiO$_2$-Cr MOS structures by optical second-harmonic generation (SHG) spectroscopy with a tunable Ti:sapphire femtosecond laser. The spectral dependence of the EFISH contribution near the direct two-photon $E_1$ transition of silicon is extracted. A systematic phenomenological model of the EFISH phenomenon, including a detailed description of the space charge region (SCR) at the semiconductor-dielectric interface in accumulation, depletion, and inversion regimes, has been developed. The influence of surface quantization effects, interface states, charge traps in the oxide layer, doping concentration and oxide thickness on nonlocal screening of the DC-electric field and on breaking of inversion symmetry in the SCR is considered. The model describes EFISH generation in the SCR using a Green function formalism which takes into account all retardation and absorption effects of the fundamental and second harmonic (SH) waves, optical interference between field-dependent and field-independent contributions to the SH field and multiple reflection interference in the SiO$_2$ layer. Good agreement between the phenomenological model and our recent and new EFISH spectroscopic results is demonstrated. Finally, low-frequency electromodulated EFISH is demonstrated as a useful differential spectroscopic technique for studies of the Si-SiO$_2$ interface in silicon-based MOS structures.Comment: 31 pages, 14 figures, 1 table, figures are also available at http://kali.ilc.msu.su/articles/50/efish.ht

Bruising and biochemical measures of stress, dehydration and injury determined at slaughter in sheep transported from farms or markets

abstract: Biochemical measurements of stress and injury were determined in 112 groups of sheep arriving at a commercial abattoir either from farms (71 groups, n=1829), local markets (21 groups, n=2125) or distant markets (20 groups, n=3145). Sheep from farms had significantly fewer bruises (0.08/sheep) than those from local markets (0.20) and sheep from distant markets (0.37). Sheep from distant markets had a significantly greater plasma creatine kinase activity compared with the other 2 groups, suggesting a greater degree of muscle damage. There was no effect of source on the packed cell volume, the plasma concentration of Β-hydroxybutyrate and total protein. Sheep from distant markets had a significantly greater plasma osmolality than those from farms and local markets. Sheep from local markets had a significantly greater plasma cortisol concentration than those from farms. It is suggested that improvements in handling and slaughter near the place of origin can reduce the risk of injury and dehydration

The effects of 24 h water deprivation when associated with some aspects of transportation on the behaviour and blood chemistry of sheep

abstract: In a 2×2 factorial experiment, groups of 6 sheep were moved from individual pens where they had access to hay and water to environmental chambers kept at either 14°C or 21°C. Within each chamber, half the sheep had access to water but they were all kept at a space allowance of 0.41 m²/sheep without feed. After 24 h they were returned to their individual pens and offered hay and water. Behaviour and a range of biochemical measurements of dehydration and feed restriction were recorded before, during and after the treatment period. During the treatment period there was no evidence of dehydration, and sheep with access to water drank less than they did before the treatment. The plasma concentration of free fatty acids increased during fasting and, post-treatment, the intake of hay was greater than before treatment. The rapid post-treatment intake of dry feed was associated with some evidence of dehydration, as indicated by increased plasma osmolality and plasma vasopressin concentration. It is suggested that following provision and consumption of large quantities of feed after a period without access to feed and water during transportation, sheep must be allowed sufficient time to drink before a subsequent journey is undertaken

Effect of lairage during 24 h of transport on the behavioural and physiological responses of sheep

abstract: Suffolk × Greyface lambs, 16 weeks of age, weighing 30-40 kg, were transported by road, confined on a stationary vehicle or received no treatment (controls). The effects of 24 h continuous transport or confinement were compared with those of 12 h treatment followed by 12 h lairage, 3 h lairage or 3 h access to feed and water without unloading, followed by another 12 h transport or confinement. After 3 h of treatment, plasma cortisol concentration was higher in transported sheep than in confined sheep and controls (P<0.05) and after 24 h transport cortisol concentration was still higher that of controls. There was an increase in plasma free fatty acids after 12 h and β-hydroxybutyrate after 24 h in transported sheep. There was no biochemical evidence of dehydration during the journey, although sheep transported for 24 h had a greater water intake after transport than controls. Sheep given hay and water on the vehicle had a lower water intake than sheep in lairage and a greater water intake after transport than any other group. Plasma cortisol concentration was higher during the 2nd part of the journey in sheep that were given hay and water but not unloaded than in lairaged sheep. There was no difference between lairage treatments in the time spent lying down during the first and second 12-h treatment period. There were fewer potentially traumatic events (falls, loss of balance, butting etc.) during the second 12 h of transport than during the first 12 h with no difference between lairage treatments

Effect of space allowance during transport on the behavioural and physiological responses of lambs during and after transport

abstract: Behavioural observations and physiological measurements were made on weaned lambs (35 kg) before, during and either after stationary confinement or transport for 12 h at 4 space allowances (0.22, 0.27, 0.31 and 0.41 m²/sheep). Two groups were not loaded (a control group with access to food anf water, and a group with no food or water for 12 h). During the confinement and transport period, the proportion of scans spent lying or ruminating were significantly less than than before treatment (P0.05). Under these experimental conditions, sheep with a live weight of 35 kg can be transported for 12 h at space allowances of between 0.22 and 0.41 m²/sheep without major physiological changes indicating injury or dehydration. The sheep appeared to be hungry after 12 h without food and showed a cortisol and heart rate reponse to transport, indicating that some aspect of transport was acting as a stressor. A space allowance of 0.22 m²/sheep cannot be recommended for 35 kg sheep as there is insufficient space for most sheep to lie down during transport. A space allowance of 0.27 m²/ sheep does allow most sheep sufficient space to lie down