scholarly journals A peculiarity of the magnetization of a ferromagnet by an alternating field

2020 ◽  
pp. 35-47
Author(s):  
Yu. Ya. Reutov ◽  
Keyword(s):  
External Field ◽  
Surface Effect ◽  
Internal Field ◽  
Demagnetizing Field ◽  
Magnetic Poles ◽  
Magnetizing Field

It has been experimentally established that the demagnetizing field of the magnetic poles formed at the ends of an open ferromagnetic cylinder decreases with increasing frequency of the magnetizing field due to a decrease in their size under the influence of the surface effect. For this reason, as the frequency of the magnetizing external field increases, the internal field in a ferromagnetic cylinder near the surface approaches it in amplitude. In addition, it has been found that the field on the surface of a ferromagnetic rod magnetized by an alternating field significantly exceeds the latter in strength with increasing frequency of this field.

scholarly journals Isolating internal secular variation in Geomagnetic Virtual Observatory time series using Principle Component Analysis

2021 ◽  
Author(s):  
William Brown ◽  
Ciarán Beggan ◽  
Magnus Hammer ◽  
Chris Finlay ◽  
Grace Cox
Keyword(s):  
Time Series ◽  
External Field ◽  
Local Time ◽  
Secular Variation ◽  
Large Scale ◽  
Time Series Data ◽  
Geomagnetic Latitude ◽  
Component Analysis ◽  
Internal Field ◽  
Series Data

<p>Geomagnetic Virtual Observatories (GVOs) are a method for processing magnetic satellite data in order to simulate the observed behaviour of the geomagnetic field at a fixed location. As low-Earth orbit satellites move at around 8 km/s and have an infrequent re-visit time to the same location, a trade-off must be made between spatial and temporal coverage, typically averaging over half the local time orbit precession period, within a radius of influence of 700 km. The annual differences (secular variation, SV) of residuals between GVO time series data and an internal field model at a single GVO location will be strongly correlated with its neighbours due to the influence of large-scale external field sources and the effect of local time precession of the satellite orbit. Using Principal Component Analysis we identify and remove signals related to these noise sources to better resolve internal field variations on sub-annual timescales.</p><p>We apply our methodology to global grids of monthly GVOs for the Ørsted, CHAMP, CryoSat-2 and Swarm missions, covering the past two decades. We identify common principle components representing orbit precession rate dependent local time biases, and major external field sources, for all satellites. We find that the analysis is enhanced by focussing on regions of geomagnetic latitude where different external field sources dominate, identifying distinct influences in polar, auroral and low-to-mid latitude regions. Annual differences are traditionally used to calculate SV so as to remove annual and semi-annual external field signals, but these signals can be re-introduced if our corrected SV is re-integrated. We find that by representing secular variation with monthly first differences, rather than annual differences, we can identify and remove annual and semi-annual external field variations from the SV, which then improves the use of re-integrated main field GVO time series. By better accounting for contaminating signals from correlated external fields and aliasing, we are able to produce a global grid of GVO time series which better represents internal secular variation at monthly time resolution.</p>

Research on the correlation of mechanical properties of BN–graphene–BN/BN vertically-stacked nanostructures in the presence of interlayer sp3 bonds and nanopores with temperature

2020 ◽  
Vol 22 (10) ◽  
pp. 5920-5928 ◽  
Author(s):  
Wenjuan Yao ◽  
Lei Fan
Keyword(s):  
Mechanical Properties ◽  
External Field ◽  
Internal Field ◽  
Field Strain ◽  
Field Defect

In this study, we investigate the coupling of an internal field (defect field-sp3 bonds and nanopores) and an external field (strain and temperature).

Archeomagnetism of a 19th century pottery kiln near Jordan, Ontario

1980 ◽  
Vol 17 (9) ◽  
pp. 1275-1285 ◽  
Author(s):  
David J. Dunlop ◽  
Murray B. Zinn
Keyword(s):  
External Field ◽  
Deep Sea ◽  
Remanent Magnetization ◽  
Internal Field ◽  
Natural Remanent Magnetization ◽  
Shape Anisotropy ◽  
Blocking Temperature ◽  
Fabric Anisotropy ◽  
Pottery Kiln ◽  
Drilling Project

The Jordan pottery kiln near St. Catharines, Ontario, was last fired about 1840–1841. Bricks from the kiln floor have intense NRM's (natural remanent magnetizations) in the range 0.2 × 10−2 to 3.7 × 10−2 emu cm−3 which are directionally stable against alternating field (AF) demagnetization to 1000 Oe (7.96 × 104 A/m). Of 31 specimens tested by the modified Thellier double-heating method, 27 yielded reliable paleofield intensities averaging 1.166 ± 0.092 times the present field intensity. Natural remanent magnetization directions are "streaked" in inclination and shallower than expected. Their average, D = 359.4°, I = 71.3 °(α95 = 2.2°, k = 310, N = 15 samples), differs significantly from both 1845 and 1979 fields in the area. Upon thermal demagnetization to 520 or 540 °C, streaking disappears and remanence vectors systematically steepen. The thermally cleaned mean direction, D = 357.8°, I = 73.7 °(α95 = 1.5°, k = 635, N = 15 samples), is indistinguishable at the 95% confidence level from the 1845 field, but differs significantly from the 1979 field.Part of the "inclination error" and streaking of NRM directions could result from fabric anisotropy or tilting of the bricks, but the greater part probably results from shape anisotropy of the strongly magnetic kiln floor, which deflects the internal field away from the external field and into the plane of the floor during cooling. The internal field is also weaker than the external field as a result of this self-demagnetization. The stronger the NRM, the greater the inclination error and the weaker the apparent paleofield intensity recorded. Thus, high-blocking-temperature fractions of NRM should record a less magnetically refracted (i.e., a steeper) paleofield, as observed. Also observed is approximate correlation between the spatial variation of NRM intensity in the kiln floor and variations in inclination and apparent paleointensity. The shape anisotropy of strongly magnetized horizontal sheets is a probable source of shallow inclinations, scattered directions, and weak apparent paleointensities in many submarine lavas sampled by the Deep Sea Drilling Project.

scholarly journals The magneto-caloric effect and other magnetic phenomena in iron

1934 ◽  
Vol 146 (857) ◽  
pp. 362-387 ◽  
Keyword(s):  
External Field ◽  
Specific Heat ◽  
Unit Volume ◽  
Spontaneous Magnetization ◽  
Internal Field ◽  
The Body ◽  
Adiabatic Process ◽  
Total Field ◽  
Apparent Increase ◽  
Caloric Effect

According to the Weiss theory a ferromagnetic body is composed of a number of “domains” each magnetized even in the absence of an external field to an intensity dependent on the temperature. At absolute zero this spontaneous magnetization (σ 0 ) is equal to the saturation intensity (σ ∞ ) whilst at any other temperature (T) the value of σ 0 /σ ∞ is dependent only on the ratio T/θ where θ is the Curie temperature. This is known as the law of corresponding states. At low temperatures the apparent increase in magnetization, accompanying the application of the external field H, is due merely to alignment of the directions of spontaneous magnetization of the various domains. As the temperature rises, however, σ 0 becomes much less than σ ∞ , and the effect of an external field is twofold—(1) an apparent increase of magnetization due to alignment, and (2) a true increase in the degree of magnetization of each domain. Magnetization of a specimen is accompanied by a decrease of magnetic energy and if the experiment is carried out adiabatically a rise in temperature results. This phenomenon is known as the magneto-caloric effect. Weiss and Forrer have shown that this temperature increase is given by the equation where ch is the specific heat at constant external field H, ρ the density, J the mechanical equivalent of heat, and σ the intensity per unit volume. This equation was arrived at thermodynamically without reference to the hypothesis of the intramolecular field. The intramolecular field theory has been attacked by Honda who develops an equation identical with (1) but in which he states that H is the total field (external + intramolecular). If this were so, equation (1) would be in complete quantitative disagreement with the experiments of Weiss and Forrer on nickel. Honda’s argument depends on the use of the equation d W = pdv + v H d σ, where v H d σ is the work done on the body by the field. Honda assumes that H is the total field, but since work can hardly be done on a body by its own internal field, it appears to the writer that the H in Honda’s formula is the external field, giving then an equation identical with that of Weiss and Forrer. Equation (1) is further justified by being in excellent agreement with the experimental results of Weiss and Forrer, and with those of the writer given below. Weiss and Forrer have further shown that the rise of temperature is related to the change in the magnetization by the equation d T = H + H'/J ρcσ d σ, (2) where H' is the internal field, c σ the specific heat at constant magnetization, and d σ the change in volume-intensity accompanying the application of an external field H. This involves no assumption as to the nature of H', but follows from the statement that the change of energy of the substance per unit volume can be expressed as d U = J ρcσ d T — H' d σ, where this equation may be considered as the definition of H'. In addition the work ( d W) done on the body by the external field is = H d σ. Since in an adiabatic process the heat d Q communicated to the specimen is zero we have d Q — d U — d W = 0 thus leading immediately to equation (2).

scholarly journals The Exercise Vibration Wave Principle in Physical Rehabilitation of Children with Musculoskeletal System Disorders

2021 ◽  
Vol 9 (SPE3) ◽  
Author(s):  
Nikolai Nikolaevich Efimenko ◽  
Volodymyr Vyktorovych Biesieda ◽  
Mykhailo Vyctorovych Litvyakov
Keyword(s):  
External Field ◽  
Acoustic Wave ◽  
Musculoskeletal System ◽  
Aquatic Environment ◽  
Internal Field ◽  
Physical Rehabilitation ◽  
Physical Exercises ◽  
Wave Effects ◽  
Vibration Wave ◽  
Methodological Aspects

The article describes the methodical and methodological possibilities of the vibration-wave principle of physical exercises in the context of its use in the physical rehabilitation of children with musculoskeletal disorders both in the conditions of the hall for movement therapy and in the aquatic environment using the example of hydrokinesis therapy. The analysis of the well-known healing properties of vibration on the human body, which can be used in the physical rehabilitation of children with musculoskeletal system disorders, is given. The known possibilities of acoustic wave effects on the musculo-fascial and skeletal systems of people are analyzed. The unique possibilities of applying the phenomena of vibration and waves not only on land but also in an aquatic environment, in conditions of hydrokinesis therapy in a pool are considered. The properties of a longitudinal elastic (acoustic) wave and its effect on the musculoskeletal system of children are characterized. The authors proposed a new concept in physical rehabilitation - "correctional acoustic internal field" on land and "correctional hydroacoustic external field" (in water). The methodological aspects of the varieties of using these fields in an autoactive (independent, conscious) version and in an imperative (forced, directing from the outside) version are considered.

scholarly journals A Dynamo Model for the Large Scale Fields

1971 ◽  
Vol 43 ◽  
pp. 780-782
Author(s):  
I. K. Csada
Keyword(s):  
Magnetic Field ◽  
Periodic Solution ◽  
External Field ◽  
Large Scale ◽  
Internal Field ◽  
Dynamo Model ◽  
Central Meridian ◽  
Coupling Tensor ◽  
Characteristic Features ◽  
The Magnetic Field

The expansion of the magnetic field in a series of force-free constituents for the internal field and that of ‘semi’ force-free constituents for the external field results in the skew symmetry of the coupling tensor of a magnetohydrodynamic dynamo. The periodic solution which exists in this case is deduced by the method of eigenvalues. Based on the numerical results a dynamo model is proposed to draw up the characteristic features of the magnetographic observations carried along the central meridian and at the polar areas.

The Effect of Pentosan Polysulphate (SP54) on the Fibrinolytic Enzyme System - A Human Volunteer and Experimental Animal Study

1985 ◽  
Vol 54 (04) ◽  
pp. 833-837 ◽  
Author(s):  
N A Marsh ◽  
P M Peyser ◽  
L J Creighton ◽  
M Mahmoud ◽  
P J Gaffney
Keyword(s):  
Plasminogen Activator ◽  
Surface Effect ◽  
Ex Vivo ◽  
Vena Cava ◽  
Tissue Type ◽  
Similar Response ◽  
Small Contribution ◽  
Thrombosis Model ◽  
Pentosan Polysulphate

SummaryPentosan polysulphate causes an increase in plasminogen activator activity in plasma both after oral ingestion and after subcutaneous injection. The effect is greatest after 3 h and has disappeared by 6 h. Repeat doses by mouth over 5 days elicit a similar response. The recorded increase in activity is due largely to the release of tissue-type plasminogen activator (tPA) from the endothelium according to the antigen assay although there could be a small contribution from Factor XH-related “intrinsic” fibrinolysis induced in vitro. SP54 enhances activity ex vivo by a non-specific surface effect, and this phenomenon may contribute the increased levels of activity seen in vitro. Administration of SP54 to animals elicits a similar increase in activator activity, the intramuscular route being slightly more effective. Results with an inferior vena cava thrombosis model in the rat suggest that pentosan polysulphate may induce a thrombolytic effect.

UJI TARIK HIDRODINAMIKMODEL KAPAL BERSAYAP WiSE DENGAN LAMBUNG DASAR BERSTEP

2013 ◽  
Vol 12 (3) ◽  
Author(s):  
Iskendar Iskendar ◽  
Andi Jamaludin ◽  
Paulus Indiyono
Keyword(s):  
Comparative Study ◽  
Model Test ◽  
Hydrodynamic Model ◽  
Surface Effect ◽  
Center Of Gravity ◽  
Test Results ◽  
Flat Bottom ◽  
Towing Tank ◽  
Test Models ◽  
Wetted Surface Area

This paper describes hydrodynamic model tests of Wing in Surface Effect (WiSE) Craft. These craft  was fitted with  stephull  form in different location on longitudinal flat bottom (stepedhull planning craft) to determine the influences of sticking and porpoising motion performances. These motions are usually occured when the craft start to take-off from water surfaces. The test models with scale of 1 : 7 were comprised of 4 (four) stephull models and 1 (one) non-stephull model  as a comparative study. The hydrodynamic  tests were performed with craft speed of 16 – 32 knots (prototype values) in Towing Tank at UPT. Balai Pengkajian dan Penelitian Hidrodinamika (BPPH), BPPT, Surabaya. The resistance (drag) was measured by dynamo meter and the trim of model (draft changing at fore and aft  of model due to model speed) was measured by trim meter. By knowing the value of model trim, the wetted surface area can be determined. Then, the lift forces were calculated based on these measured values. The model test results were presented on tables and curves.  Test results show that models  with step located far away from center of gravity of the WiSE craft tend to porpoising and sticking condition, except if the step location on the below of these center of gravity. While model without step tends to sticking conditions.

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