Impact of maximum back-EMF limits on the performance characteristics of interior permanent magnet synchronous machines

Interior permanent magnet (IPM) synchronous machines are vulnerable to uncontrolled generator (UCG) faults at high speed that can damage the inverter. One approach to reducing this risk is to impose limits on the maximum machine back-EMF voltage at top speed. This paper presents the results of a comparative design study that clarifies the nature and extent of the penalties imposed on the IPM machine metrics and performance characteristics as a result of imposing progressively tighter values of back-EMF voltage limits. As an alternative to limiting back-EMF and penalizing machine designs, this paper also investigates the effectiveness of the system-side protection approach to the same UCG fault problem.Seok-hee Han, Thomas M. Jahns, Metin Aydin, Mustafa K. Guven, Wen L. Soon

Delayed presentation of symptomatic breast cancers in Hong Kong: Experience in a public cancer centre

Objective Delayed presentation is an important obstacle to improving cancer treatment outcomes. We aimed to study the magnitude of this problem in Hong Kong and the factors associated with delayed presentation of patients with symptomatic breast cancers. Design Retrospective study using self-administered questionnaires. Setting Clinical Oncology Department in a regional public hospital in Hong Kong. Patients A total of 158 Chinese women with breast cancer referred to our hospital between October 2006 and December 2007 consented to participate in this study. Among these, 59 (37%) patients were referred after having surgery in private sector. Results The mean total delay (from first symptom to treatment) was 22 weeks. The mean patient delay (from first symptom to first consultation) was 13 weeks, constituting the largest component (60%) of the total delay. After symptom onset, the delay exceeded 12 weeks for consulting a doctor in 29%, and for receipt of treatment in 52% of them. Low family income (<HK$5000 per month; P<0.001) and surgery in public hospitals (P=0.013) were both independent predictors of patient delay. Surgery in public hospitals (P=0.006) and low family income (P=0.005) were the only predictors of doctor/system delay and total delay, respectively. Conclusions Delayed presentation and treatment of symptomatic breast cancer remains an important issue in Hong Kong. Apart from socio-economic factors, limited access to public medical care was likely an important contributing factor in delays related to patients as well as to doctor/system.published_or_final_versio

Design and experimental verification of a 50 kW interior permanent magnet synchronous machine

This paper presents the design details for an IPM machine designed to deliver 50 kW constant power over a 5:1 speed range extending from 850 rpm to 4250 rpm, with a gradual reduction in the required output power up to 8000 rpm (25 kW). Electromagnetic, thermal, and structural considerations have been included in the design optimization process. The resulting machine is designed with two magnet layers per pole and a distributed stator winding. Special features of the machine include its deep stator slots and four-layer winding, made necessary by the desire to minimize the machine's moment of inertia. Test results available to date demonstrate that the machine is capable of delivering the required output torque and power, and the agreement between the predicted and measured machine parameters is generally quite good. Calculated iron losses for high-speed flux-weakening operation are presented in the final section of the paper, illustrating the challenges associated with minimizing the impact of high-frequency harmonic flux density components.Jahns, T.M.; Seok-Hee Han; El-Refaie, A.M.; Jei-Hoon Baek; Aydin, M.; Guven, M.K.; Soong, W.L

Measurement of the Transverse-Longitudinal Cross Sections in the p (e,e'p)pi0 Reaction in the Delta Region

Accurate measurements of the p(e,e?p)pi0 reaction were performed at Q^2=0.127(GeV/c)^2 in the Delta resonance energy region. The experiments at the MIT-Bates Linear Accelerator used an 820 MeV polarized electron beam with the out of plane magnetic spectrometer system (OOPS). In this paper we report the first simultaneous determination of both the TL and TL? (``fifth" or polarized) cross sections at low Q^{2} where the pion cloud contribution dominates the quadrupole amplitudes (E2 and C2). The real and imaginary parts of the transverse-longitudinal cross section provide both a sensitive determination of the Coulomb quadrupole amplitude and a test of reaction calculations. Comparisons with model calculations are presented. The empirical MAID calculation gives the best overall agreement with this accurate data. The parameters of this model for the values of the resonant multipoles are |M_{1+}(I=3/2)|= (40.9 \pm 0.3)10^{-3}/m_pi, CMR= C2/M1= -6.5 \pm 0.3%, EMR=E2/M1=-2.2 \pm 0.9%, where the errors are due to the experimental uncertainties.Comment: 10 pages, 3 figures, minor corrections and addition

Adaptive evolution of the vertebrate skeletal muscle sodium channel

Tetrodotoxin (TTX) is a highly potent neurotoxin that blocks the action potential by selectively binding to voltage-gated sodium channels (Nav). The skeletal muscle Nav (Nav1.4) channels in most pufferfish species and certain North American garter snakes are resistant to TTX, whereas in most mammals they are TTX-sensitive. It still remains unclear as to whether the difference in this sensitivity among the various vertebrate species can be associated with adaptive evolution. In this study, we investigated the adaptive evolution of the vertebrate Nav1.4 channels. By means of the CODEML program of the PAML 4.3 package, the lineages of both garter snakes and pufferfishes were denoted to be under positive selection. The positively selected sites identified in the p-loop regions indicated their involvement in Nav1.4 channel sensitivity to TTX. Most of these sites were located in the intracellular regions of the Nav1.4 channel, thereby implying the possible association of these regions with the regulation of voltage-sensor movement

Stress-induced alterations in parkin solubility promote parkin aggregation and compromise parkin's protective function

10.1093/hmg/ddi413Human Molecular Genetics14243885-389