scholarly journals Analysis of High-Frequency Dispersion Characteristics of Capacitance and Loss Factor of Aramid Paper Impregnated with Various Dielectric Liquids

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 1063 ◽  
Author(s):  
Stefan Wolny
Keyword(s):  
High Frequency ◽  
Loss Factor ◽  
Frequency Dispersion ◽  
Power Transformers ◽  
Multiple Time ◽  
Dispersion Characteristics ◽  
Time Intervals ◽  
Dielectric Liquids ◽  
High Voltage Insulation ◽  
Natural Ester

This paper presents research results of the loss factor of high voltage insulation samples made of aramid paper impregnated with various types of insulating oil. The analysis was carried out in the high frequency domain in the range of 50 Hz to 1 MHz. The experiments were carried out for three impregnation types: mineral oil, synthetic ester and natural ester. The influence of temperature in the range of 20 °C to 100 °C, which is typical when using this type of insulation in power transformers, was taken into account. In addition, the process of influence of initial aging of aramid paper was simulated by heat soaking the samples before their impregnation at a temperature of 250 °C in multiple time intervals. Based on the analyses of dispersion characteristics of insulation sample loss factors, conclusions and recommendations for further diagnostics of aramid-oil insulations using the method described were delineated.

Magnetic Permeability and Relaxation Frequency in High Frequency Magnetic Materials.

2001 ◽  
Vol 674 ◽  
Author(s):  
M.I. Rosales ◽  
H. Montiel ◽  
R. Valenzuela
Keyword(s):  
High Frequency ◽  
Domain Walls ◽  
Magnetocrystalline Anisotropy ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Anisotropy Constant ◽  
Relaxation Frequency ◽  
Resonance Relaxation ◽  
Frequency Behavior

ABSTRACTAn investigation of the frequency behavior of polycrystalline ferrites is presented. It is shown that the low frequency dispersion (f < 10 MHz) of permeability is associated with the bulging of pinned domain walls, and has a mixed resonance-relaxation character, closer to the latter. It is also shown that there is a linear relationship between the magnetocrystalline anisotropy constant, K1, and the relaxation frequency. The slope of this correlation depends on the grain size. Such a relationship could allow the determination of this basic parameter from polycrystalline samples.

Core loss behavior in high frequency high power transformers—II: Arbitrary excitation

2012 ◽  
Vol 4 (3) ◽  
pp. 033113 ◽  
Author(s):  
E. Agheb ◽  
M. A. Bahmani ◽  
H. K. Høidalen ◽  
T. Thiringer
Keyword(s):  
High Power ◽  
High Frequency ◽  
Core Loss ◽  
Power Transformers

Nycthemeral Rhythm of the Frequency and Biomechanical Energy of High Frequency Intraocular Pressure Fluctuations

2013 ◽  
Author(s):  
Vincent Libertiaux ◽  
William P. Seigfreid ◽  
Massimo A. Fazio ◽  
Juan F. Reynaud ◽  
Claude F. Burgoyne ◽  
...  
Keyword(s):  
Intraocular Pressure ◽  
High Frequency ◽  
Pressure Fluctuations ◽  
Low Frequency ◽  
Pulse Amplitude ◽  
Mean Value ◽  
Multiple Time Scales ◽  
Dynamic Contour Tonometry ◽  
Multiple Time ◽  
Ocular Pulse

The optic nerve head (ONH) is the site of insult in glaucoma, the second leading cause of blindness worldwide. Intraocular pressure (IOP) is commonly regarded as a major factor in the onset and progression of the disease1 and lowering IOP is the only clinical treatment that has been shown to retard the onset and progression of glaucoma2. However, many patients continue to progress even at an epidemiologically-determined normal level of IOP3. This suggests that in addition to the mean value of IOP, IOP fluctuations could be a factor in glaucomatous pathophysiology. The importance of low frequency fluctuations of clinically-measured mean IOP remains controversial. These studies all rely on snapshot measurements of mean IOP at each time point, and those measurements are taken at relatively infrequent intervals (hourly at the most frequent, but usually monthly or longer). Recently however, there has been some interest in ocular pulse amplitude, or the fluctuation in IOP associated with the cardiac cycle, which can be measured by Dynamic Contour Tonometry (DCT). DCT provides continuous measurement of IOP, but only for a period of tens of seconds in which a patient can tolerate corneal contact without blinking or eye movement, which ironically are two of the most common sources of large high frequency IOP fluctuations according to our telemetric data collected from monkeys4 and previous human studies. In a recent report, continuous IOP telemetry was used in three nonhuman primates to characterize IOP dynamics at multiple time scales for multiple 24-hour periods5.

scholarly journals A Rapid and Effective Method to Prolong Pain Relief in Sheep Using Bupivacaine and Intralipid ® Combination

2019 ◽  
Vol 4 (3) ◽  
pp. 1-6
Author(s):  
Farzin Sahebjam
Keyword(s):  
Nerve Block ◽  
Final Concentration ◽  
Noxious Stimulus ◽  
Control Group ◽  
Multiple Time ◽  
Treatment Results ◽  
Time Intervals ◽  
Nerve Blocks ◽  
Duration Of Action ◽  
The Mean

Background : To compare the duration of action of a local anesthetic block using a lipid formulation of bupivacaine to the commercially available aqueous formulation. Bupivacaine 0.5% was mixed with an equal volume of either lipid emulsion (Intralipid, Fresenius Kabi) or normal saline resulting in a final concentration of 0.25% bupivacaine. Eighteen sheep were administered a n erve block of either control or treatment at the metacarpal region of each forelimb to compare the efficacy of the injected formulations. The nociceptive test was determined by applying a blunt noxious stimulus to the foot below the nerve block at multiple time intervals until the sheep responded by withdrawing its foot. The person assessing the response to the noxious stimulus was blinded to the treatment. Results: The Intralipid formulation significantly extended the duration of the nerve block compared to the control group. The mean analgesic period (mean±SD) in the control legs was 4.23±1.8 hr. compared to 5.81±1.78 hr. in the Intralipid injected legs (p=0.013). Conclusions : In conclusion, an Intralipid® - based formulation provided a more prolonged dura tion of local anesthesia after nerve blocks in the sheep metacarpal region compared to aqueous bupivacaine.

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