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In Part I of the paper, analytical field solutions, which account for the fringing flux associated with the finite length of the ferromagnetic armature core in tubular permanent-magnet machines, are established. In Part II, the technique is applied to both slotless and slotted machines, and the results are verified by finite-element calculations. The analytical field solutions enable the resultant cogging force associated with the finite length of the armature to be determined as a function of the armature displacement, for both radially and Halbach magnetized stators. Thus, they not only provide an effective means for evaluating the influence of leading design parameters on the cogging force waveform, but also facilitate its minimization. Index Terms--Cogging force minimization, linear machines, permanent-magnet machines.

This paper extends an analysis developed for tubular permanent-magnet machines to account for the effect of fringing associated with the finite length of the ferromagnetic armature core. The magnetic field distribution, established by using an analytical technique formulated in the cylindrical coordinate system, provides an accurate means of evaluating the effect of the fringing flux on the thrust force and the back-electromotive force. Finite-element calculations confirm the analytically derived results. In Part II of the paper, the analysis is used to predict the cogging force that results from end effects and to facilitate minimization of the force. Index Terms--Linear machines, magnetic field analysis, permanent-magnet machines.

This paper discusses the suitability of four-phase, five-phase, and six-phase modular machines, for use in applications where servo characteristics and fault tolerance are key requirements. It is shown that an optimum slot number and pole number combination exists, for which excellent servo characteristics could be achieved, under healthy operating conditions, with minimum effects on the power density of the machine. To eliminate torque ripple due to residual cogging and various fault conditions, the paper describes a novel optimal torque control strategy for the modular permanent-magnet machines operating in both constant torque and constant power modes. The proposed control strategy enables ripple-free torque operation to be achieved, while minimizing the copper loss under voltage and current constraints. The utility of the proposed strategy is demonstrated by computer simulations on a four-phase fault-tolerant drive system. Index Terms--Fault tolerant, modular machines, optimal control, permanent-magnet machines, servo drives.

We report the first definitive PM and AM noise measurements at 100 GHz of indium phosphide (InP) amplifiers operating at 5 K, 77 K, and room temperature. Amplifier gain ranged from +7 to +30 dB, depending on input RF power levels and operating bias current and gate voltages. The measurement system, calibration procedure, and amplifier configuration are described along with strategies for reducing the measurement system noise floor in order to accurately make these measurements. We compute amplifier noise figure with an ideal oscillator signal applied and, based on the PM noise measurements, obtain NF = 0.8 dB, or a noise temperature of 59 K. Measurement uncertainty is estimated at [+ or -] = 0.3 dB. Results show that the use of the amplifier with an ideal 100-GHz reference oscillator would set a lower limit on rms clock jitter of 44.2 fs in a 20-ps sampling interval if the power into the amplifier were -31.6 dBm. For comparison, clock jitter is 16 fs with a commercial room-temperature amplifier operating in saturation with an input power of -6.4 dBm. Index Terms--AM noise, amplifier noise, jitter, noise figure, noise measurement, 100 GHz, phase modulation noise, spectral analysis.

For high-speed machines, in particular, it is very important to accurately predict natural frequencies of the rotor at the design stage so as to minimize the likelihood of failure. Finite-element analysis and experimental measurements are used to establish the natural frequencies and modes of the rotor of a high-speed permanent-magnet brushless motor, and to assess the influence of leading design parameters, such as the active length, the shaft diameter and extension, the bearings, and the material properties. Index Terms--Brushless motor, high speed, mechanical resonance, permanent-magnet machine, vibration.

Dexamethasone (DM) was administered to pregnant ewes as three weekly courses of four injections of 2 mg at 12-h intervals. DM (n = 7) or saline (n = 7) was given starting at 103 days of gestation (dGA; term ~149 days). Fetal femoral arteries (~300-[micro]m internal diameter) were evaluated using wire myography at 119 dGA. DM-exposed fetuses were significantly smaller than saline-exposed fetuses. DM exposure increased maximal contraction to 125 mM KCl, and maximum tension developed along with sensitivity to endothelin-1 and relaxation to bradykinin. Preincubation with the nitric oxide synthase inhibitor [N.sup.G]-nitro-L-arginine methyl ester shifted the dose-response curves to endothelin-1 and acetylcholine to the right in controls but not in the DM-exposed group. Relaxation to acetylcholine and to the nitric oxide donor sodium nitroprusside was similar in both groups. The combination of enhanced endothelin-induced vasoconstriction, abnormal endothelium-dependent relaxation, and normal endothelium-independent relaxation indicates microvessel dysfunction following antenatal DM administration. Because such dysfunction is associated with several forms of adult hypertension, our results indicate the potential for consequences of antenatal glucocorticoid exposure on adult cardiovascular health. wire myography; endothelin-1; nitric oxide; [N.sup.G]-nitro-L-arginine methyl ester; bradykinin; acetylcholine

The application of flux-observer-based sensorless control to permanent-magnet brushless ac motor drives is described. Current methods of speed estimation are assessed, both theoretically and experimentally, and an improved method, which combines the best features of methods in which speed is derived from the differential of rotor position and from the ratio of the electromotive force to excitation flux linkage, is proposed. Its performance is verified experimentally. Index Terms--Brushless ac drives, flux observer, permanent-magnet machines, sensorless control, speed estimation.

Urocortin: a mechanism for the sustained activation of the HPA axis in the late-gestation ovine fetus? Am J Physiol Endocrinol Metab 283: E165-E171, 2002. First published March 19, 2002; 10.1152/ajpendo.00497.2001.--We hypothesized that urocortin might be produced in the pituitary of the late-gestation ovine fetus in a manner that could contribute to the regulation of ACTH output. We used in situ hybridization and immunohistochemistry to identify urocortin mRNA and protein in late-gestation fetal pituitary tissue. Levels of urocortin mRNA rose during late gestation and were associated temporally with rising concentrations of pituitary proopiomelanocortin (POMC) mRNA. Urocortin was localized both to cells expressing ACTH and to non-ACTH cells by use of dual immunofluorescence histochemistry. Transfection of pituitary cultures with urocortin antisense probe reduced ACTH output, whereas added urocortin stimulated ACTH output from cultured pituitary cells. Cortisol infusion for 96 h in chronically catheterized late-gestation fetal sheep significantly stimulated levels of pituitary urocortin mRNA. We conclude that urocortin is expressed in the ovine fetal pituitary and localizes with, and can stimulate output of, ACTH. Regulation of urocortin by cortisol suggests a mechanism to override negative feedback and sustain feed-forward of fetal hypothalamic-pituitary-adrenal function, leading to birth. urocortin; adrenocorticotropic hormone; parturition; hypothalamic-pituitary-adrenal axis

This paper describes the design, analysis, and characterization of a linear permanent-magnet generator and capacitive energy storage system for generating electrical power from a single stroke of a salient-pole armature. It is suitable for applications that require relatively low levels of electrical power, such as remote electronic locks. An electromagnetic analysis of the generator is described, and a design optimization methodology for the system is presented. Finally, the performance of a prototype is validated against measurements. Index Terms--Generators, linear machines, permanent-magnet generators, power conversion.

A general analytical technique predicts the magnetic field distribution in brushless permanent magnet machines equipped with surface-mounted magnets. It accounts for the effects of both the magnets and the stator windings. The technique is based on two-dimensional models in polar coordinates and solves the governing Laplacian/quasi-Poissonian field equations in the airgap/magnet regions without any assumption regarding the relative recoil permeability of the magnets. The analysis works for both internal and external rotor motor topologies, and either radial or parallel magnetized magnets, as well as for overlapping and nonoverlapping stator windings. The paper validates results of the analytical models by finite-element analyses, for both slotless and slotted motors. Index Terms--Electrical machines, magnetic field, permanent magnet.