Voltage-probe-position dependence and magnetic-flux contribution to the measured voltage in ac tansport measurements: Which measuring circuit determines the real losses?

Author(s):  
John R. Clem ◽  
Thomas Pe ◽  
Jason McDonald

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 194
Author(s):  
Michał Marczak ◽  
Józef Zawora

In this article, we present a numerical model of a magnetic abrasive finishing station, which was analyzed using the finite element method (FEM). The obtained results were compared with the real values measured on an experimental station of our own design. The prepared station had the option of adjusting the magnetic flux density inside the machining gap, the width of which could be changed from 10 to 30 mm. The maximum value of the magnetic flux density inside the air gap was 0.8 T. The real distribution of magnetic flux density in the finishing area was also analyzed. A design of experiment was carried out with the following variables: abrasive grain concentration, width of the machining gap, and process duration. The results are presented in the form of regression equations and characteristics for selected roughness parameters.



Author(s):  
A. Christ

After a short recapitulation of the main problems in wet steam turbines, the goal of the measurements is outlined, namely to determine experimentally as accurately as possible the real expansion line in the wet steam region of a 50 MW condensation turbine. These experiments embraced measurement of the steam and water flow withdrawn from the turbine in the water draining system and measurement of the steam wetness after the last runner stage. For this purpose a special probe was built in which a small amount of steam was tapped from the main flow and heated up to saturation. The probe was movable over the blade length of the last runner stage and results are given as local steam wetness as a function of the probe position. A comparison of the results with the findings of modern theory gives some explanation of the experimental facts.



2021 ◽  
Author(s):  
Saul M Dominguez-Nicolas ◽  
Elias Manjarrez

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) may cause low oxygen saturation (SpO2) and respiratory failure in coronavirus disease (COVID-19) patients. Hence the increase of SpO2 levels could be crucial for the quality of life and recovery of these patients. Here we introduce an electromagnetic device termed low-field thoracic magnetic stimulation (LF-ThMS) system. This device was designed to non-invasively deliver a pulsed magnetic field from 100 to 118 Hz and 10.5 to 13.1 mT (i.e., 105 to 131 Gauss) to the dorsal thorax. We show that these frequencies and magnetic flux densities are safe for the patients. We also present a proof-of-concept that a single session of LF-ThMS applied for 30 minutes to the dorsal thorax of 17 COVID-19 patients significantly increases their SpO2 levels. We designed a single-blind, sham-controlled, crossover study on 5 COVID-19 patients who underwent two sessions of the study (real and sham LF-ThMS) and 12 COVID-19 patients who underwent only the real LF-ThMS. We found a statistically significant correlation between magnetic flux density, frequency, or temperature associated with the real LF-ThMS and SpO2 levels in all COVID-19 patients. However, the five patients of the sham-controlled study did not exhibit a significant change in their SpO2 levels during sham stimulation. All the patients did not present adverse events after the LF-ThMS intervention.





2000 ◽  
Vol 179 ◽  
pp. 263-264
Author(s):  
K. Sundara Raman ◽  
K. B. Ramesh ◽  
R. Selvendran ◽  
P. S. M. Aleem ◽  
K. M. Hiremath

Extended AbstractWe have examined the morphological properties of a sigmoid associated with an SXR (soft X-ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S-shaped Hαfilament. The photoheliogram shows flux emergence within an existingδtype sunspot which has caused the rotation of the umbrae giving rise to the sigmoidal brightening.It is now widely accepted that flares derive their energy from the magnetic fields of the active regions and coronal levels are considered to be the flare sites. But still a satisfactory understanding of the flare processes has not been achieved because of the difficulties encountered to predict and estimate the probability of flare eruptions. The convection flows and vortices below the photosphere transport and concentrate magnetic field, which subsequently appear as active regions in the photosphere (Rust & Kumar 1994 and the references therein). Successive emergence of magnetic flux, twist the field, creating flare productive magnetic shear and has been studied by many authors (Sundara Ramanet al.1998 and the references therein). Hence, it is considered that the flare is powered by the energy stored in the twisted magnetic flux tubes (Kurokawa 1996 and the references therein). Rust & Kumar (1996) named the S-shaped bright coronal loops that appear in soft X-rays as ‘Sigmoids’ and concluded that this S-shaped distortion is due to the twist developed in the magnetic field lines. These transient sigmoidal features tell a great deal about unstable coronal magnetic fields, as these regions are more likely to be eruptive (Canfieldet al.1999). As the magnetic fields of the active regions are deep rooted in the Sun, the twist developed in the subphotospheric flux tube penetrates the photosphere and extends in to the corona. Thus, it is essentially favourable for the subphotospheric twist to unwind the twist and transmit it through the photosphere to the corona. Therefore, it becomes essential to make complete observational descriptions of a flare from the magnetic field changes that are taking place in different atmospheric levels of the Sun, to pin down the energy storage and conversion process that trigger the flare phenomena.



2000 ◽  
Vol 179 ◽  
pp. 205-208
Author(s):  
Pavel Ambrož ◽  
Alfred Schroll

AbstractPrecise measurements of heliographic position of solar filaments were used for determination of the proper motion of solar filaments on the time-scale of days. The filaments have a tendency to make a shaking or waving of the external structure and to make a general movement of whole filament body, coinciding with the transport of the magnetic flux in the photosphere. The velocity scatter of individual measured points is about one order higher than the accuracy of measurements.



2000 ◽  
Vol 179 ◽  
pp. 177-183
Author(s):  
D. M. Rust

AbstractSolar filaments are discussed in terms of two contrasting paradigms. The standard paradigm is that filaments are formed by condensation of coronal plasma into magnetic fields that are twisted or dimpled as a consequence of motions of the fields’ sources in the photosphere. According to a new paradigm, filaments form in rising, twisted flux ropes and are a necessary intermediate stage in the transfer to interplanetary space of dynamo-generated magnetic flux. It is argued that the accumulation of magnetic helicity in filaments and their coronal surroundings leads to filament eruptions and coronal mass ejections. These ejections relieve the Sun of the flux generated by the dynamo and make way for the flux of the next cycle.



2000 ◽  
Vol 179 ◽  
pp. 155-160
Author(s):  
M. H. Gokhale

AbstractData on sunspot groups have been quite useful for obtaining clues to several processes on global and local scales within the sun which lead to emergence of toroidal magnetic flux above the sun’s surface. I present here a report on such studies carried out at Indian Institute of Astrophysics during the last decade or so.



Author(s):  
Toshihiko Takita ◽  
Tomonori Naguro ◽  
Toshio Kameie ◽  
Akihiro Iino ◽  
Kichizo Yamamoto

Recently with the increase in advanced age population, the osteoporosis becomes the object of public attention in the field of orthopedics. The surface topography of the bone by scanning electron microscopy (SEM) is one of the most useful means to study the bone metabolism, that is considered to make clear the mechanism of the osteoporosis. Until today many specimen preparation methods for SEM have been reported. They are roughly classified into two; the anorganic preparation and the simple preparation. The former is suitable for observing mineralization, but has the demerit that the real surface of the bone can not be observed and, moreover, the samples prepared by this method are extremely fragile especially in the case of osteoporosis. On the other hand, the latter has the merit that the real information of the bone surface can be obtained, though it is difficult to recognize the functional situation of the bone.



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