AC losses in HTS coils for high-frequency and non-sinusoidal currents

2017 ◽  
Vol 30 (9) ◽  
pp. 095006 ◽  
Author(s):  
B J H de Bruyn ◽  
J W Jansen ◽  
E A Lomonova
Keyword(s):  
High Frequency ◽  
Ac Losses ◽  
Sinusoidal Currents

High frequency intergranular AC losses in EuBa2Cu3O7ceramics

1992 ◽  
Vol 5 (1S) ◽  
pp. S268-S271 ◽  
Author(s):  
E Nguyen ◽  
D Castello ◽  
J Fontcuberta ◽  
X Obradors
Keyword(s):  
High Frequency ◽  
Ac Losses

scholarly journals Blocking central pathways in the primate motor system using high-frequency sinusoidal current

2015 ◽  
Vol 113 (5) ◽  
pp. 1670-1680 ◽  
Author(s):  
Karen M. Fisher ◽  
Ngalla E. Jillani ◽  
George O. Oluoch ◽  
Stuart N. Baker
Keyword(s):  
High Frequency ◽  
Primary Motor Cortex ◽  
Cervical Spinal Cord ◽  
System Modeling ◽  
Conduction Block ◽  
Field Potential ◽  
Medial Longitudinal Fasciculus ◽  
Sinusoidal Current ◽  
Sinusoidal Currents

Electrical stimulation with high-frequency (2–10 kHz) sinusoidal currents has previously been shown to produce a transient and complete nerve block in the peripheral nervous system. Modeling and in vitro studies suggest that this is due to a prolonged local depolarization across a broad section of membrane underlying the blocking electrode. Previous work has used cuff electrodes wrapped around the peripheral nerve to deliver the blocking stimulus. We extended this technique to central motor pathways, using a single metal microelectrode to deliver focal sinusoidal currents to the corticospinal tract at the cervical spinal cord in anesthetized adult baboons. The extent of conduction block was assessed by stimulating a second electrode caudal to the blocking site and recording the antidromic field potential over contralateral primary motor cortex. The maximal block achieved was 99.6%, similar to findings of previous work in peripheral fibers, and the optimal frequency for blocking was 2 kHz. Block had a rapid onset, being complete as soon as the transient activation associated with the start of the sinusoidal current was over. High-frequency block was also successfully applied to the pyramidal tract at the medulla, ascending sensory pathways in the dorsal columns, and the descending systems of the medial longitudinal fasciculus. High-frequency sinusoidal stimulation produces transient, reversible lesions in specific target locations and therefore could be a useful alternative to permanent tissue transection in some experimental paradigms. It also could help to control or prevent some of the hyperactivity associated with chronic neurological disorders.

scholarly journals Reduction of Winding AC Losses by Accurate Conductor Placement in High Frequency Electrical Machines

2020 ◽  
Vol 56 (1) ◽  
pp. 183-193 ◽  
Author(s):  
Anuvav Bardalai ◽  
David Gerada ◽  
Dmitry Golovanov ◽  
Zeyuan Xu ◽  
Xiaochen Zhang ◽  
...  
Keyword(s):  
High Frequency ◽  
Electrical Machines ◽  
Ac Losses

scholarly journals Thermal analytical winding size optimization for different conductor shapes

2015 ◽  
Vol 64 (2) ◽  
pp. 197-214 ◽  
Author(s):  
Rafal P. Wojda
Keyword(s):  
High Frequency ◽  
Local Minimum ◽  
Foil Thickness ◽  
Size Optimization ◽  
Temperature Dependent ◽  
3D Finite Element ◽  
Round Wire ◽  
High Frequency Ac ◽  
3D Finite Element Method ◽  
Sinusoidal Currents

Abstract The aim of this paper is to derive an analytical equations for the temperature dependent optimum winding size of inductors conducting high frequency ac sinusoidal currents. Derived analytical equations are useful designing tool for research and development engineers because windings made of foil, square-wire, and solid-round-wire windings are considered. Temperature dependent Dowell’s equation for the ac-to-dc winding resistance ratio is given and approximated. Thermally dependent analytical equations for the optimum foil thickness, as well as valley thickness and diameter of the square-wire and solid-round-wire windings are derived from approximated thermally dependent ac-to-dc winding resistance ratios. Minimum winding ac resistance of the foil winding and local minimum of the winding ac resistance of the solid-round-wire winding are verified with Maxwell 3D Finite Element Method simulations

The Microstructure of Steatite (Protoenstatite)

1985 ◽  
Vol 43 ◽  
pp. 236-237
Author(s):  
W. E. Lee ◽  
A. H. Heuer
Keyword(s):  
High Frequency ◽  
Glass Ceramics ◽  
Magnesium Silicate ◽  
Beam Current ◽  
Glassy Matrix ◽  
Angle Of Incidence ◽  
X Ray ◽  
Mechanical And Electrical Properties ◽  
Argon Ions ◽  
High Temperature Polymorph

IntroductionTraditional steatite ceramics, made by firing (vitrifying) hydrous magnesium silicate, have long been used as insulators for high frequency applications due to their excellent mechanical and electrical properties. Early x-ray and optical analysis of steatites showed that they were composed largely of protoenstatite (MgSiO3) in a glassy matrix. Recent studies of enstatite-containing glass ceramics have revived interest in the polymorphism of enstatite. Three polymorphs exist, two with orthorhombic and one with monoclinic symmetry (ortho, proto and clino enstatite, respectively). Steatite ceramics are of particular interest a they contain the normally unstable high-temperature polymorph, protoenstatite.Experimental3mm diameter discs cut from steatite rods (∼10” long and 0.5” dia.) were ground, polished, dimpled, and ion-thinned to electron transparency using 6KV Argon ions at a beam current of 1 x 10-3 A and a 12° angle of incidence. The discs were coated with carbon prior to TEM examination to minimize charging effects.

Simulations of high-resolution images of amorphous silicon films

1986 ◽  
Vol 44 ◽  
pp. 544-545
Author(s):  
G. Y. Fan ◽  
J. M. Cowley
Keyword(s):  
Electron Microscope ◽  
High Frequency ◽  
Fourier Transformation ◽  
Amorphous Materials ◽  
Low Frequency ◽  
Chromatic Aberration ◽  
Structure Information ◽  
Frequency Components ◽  
High Resolution Images ◽  
Spatial Frequency Spectrum

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.

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