scholarly journals MAGNETIC PROPERTIES AND MAGNETIC STRIP DOMAINS IN MICRO STRIPES PrDyFeCoB

2021 ◽  
pp. 86-93
Author(s):  
D.V. Korolev ◽  
◽  
Yu.V. Stolyankov ◽  
V.P. Piskorsky ◽  
R.A. Valeev ◽  
...  
Keyword(s):  
Hysteresis Loop ◽  
Coercive Field ◽  
Rotation Speed ◽  
Magnetic Phase ◽  
Hysteresis Loops ◽  
Zero Field ◽  
Phase 2 ◽  
Soft Magnetic ◽  
Disk Rotation ◽  
Disk Rotation Speed

The article provides the analysis of PrDyFeCoB magnetic microstripes prepared by extracting material from a melt on a rotating cooling disk. The phases 2-14-1, 1-4-1 and 1-2, α-FeСо were verified in the samples. The division of a hysteresis loop into two strands shows that the coercive field of the α-FeСо phase (500–700 Oe) determines the width of the hysteresis loop near the zero field, while the coercive field of the 2-14-1 phase (10 kOe) corresponds to lateral hysteresis loops. The saturation magnetization increases by 25% with an increase in the disk rotation speed by 3 times together with correspondent acceleration of the cooling rate. This is due to the increase in the proportion of the soft magnetic phase α-FeCo and the increase in the proportion of the amorphous phase with a decrease in the proportion of the main magnetic phase 2-14-1. Strip domains and their dynamics during magnetization were detected using Kerr magneto-optical microscopy.

Exchange Bias Properties in Bulk Ni45Co5Mn38Sn12 Heusler Alloy

2014 ◽  
Vol 875-877 ◽  
pp. 272-276 ◽  
Author(s):  
Chao Jing ◽  
Ye Jun Yang ◽  
Dong Hua Yu ◽  
Zhe Li ◽  
Xiao Long Wang ◽  
...  
Keyword(s):  
Hysteresis Loop ◽  
Exchange Bias ◽  
Heusler Alloy ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
Bias Field ◽  
Magnetic Hysteresis Loop ◽  
Zero Field ◽  
Co Substitution ◽  
Exchange Bias Field

We report the exchange bias properties in the bulk Ni45Co5Mn38Sn12quaternary Heusler alloy. The ferromagnetic (FM) –antiferromagnetic (AFM) interactions get reinforced after the Co substitution for Ni in the Ni-Mn-Sn alloy, which increase the exchange bias field (HE). A maximum shift in hysteresis loops of 306 Oe was observed in the 10 kOe field cooled sample. The origin of this large exchange bias field has been discussed. Magnetic hysteresis loop obtained in the zero field cooled (ZFC) mode shows double-shifted loop, and the reason of this phenomenon has been explained in detail.

On the Instability Mechanisms of a Disk Rotating Close to a Rigid Surface

1995 ◽  
Vol 62 (3) ◽  
pp. 764-771 ◽  
Author(s):  
F. Y. Huang ◽  
C. D. Mote
Keyword(s):  
Rotation Speed ◽  
Maximum Speed ◽  
Film System ◽  
Rigid Surface ◽  
Flow Component ◽  
Flutter Speed ◽  
Disk Rotation ◽  
Viscous Shear ◽  
Air Film ◽  
Disk Rotation Speed

The instability mechanisms of a rotating disk, coupled to a rigid surface through a viscous fluid film at the interface, are investigated analytically. The fluid in the film is driven circumferentially by the viscous shear, and it flows outwards radially under centrifugal forces. The circumferential flow component creates an equivalent viscous damping rotating at one half the disk rotation speed. This film damping dissipates all backward traveling waves where the undamped wave speeds are greater than one half the disk rotation speed. The radial flow component creates a nonsymmetric stiffness in the disk-film system that energizes any wave mode at rotation speeds above its flutter speed. Instabilities in the disk-film system are of two types. A rotating damping instability is caused by the rotating film damping at rotation speeds above a critical value that is less than the flutter speed. A combination instability is caused by the combined effect of the film stiffness and damping at rotation speeds above a threshold that is greater than the flutter speed. The maximum rotation speed of stable disk vibration is bounded above by the lowest onset speed of rotating damping instability. This speed limit is predicted for two wall enclosure designs. The maximum stable rotation speed of a 5.25-inch diameter flexible, memory disk, separated from a rigid surface by a viscous air film, is shown to be more than 15 times greater than the maximum speed of the disk without the air film.

Hysteresis Loops and Coercivity Mechanisms in Sintered and Nanocrystalline Permanent Magnets

1999 ◽  
Vol 577 ◽  
Author(s):  
H. Kronmüller ◽  
D. Goll ◽  
I. Kleinschroth ◽  
A. Zern
Keyword(s):  
Coercive Field ◽  
Permanent Magnets ◽  
Spontaneous Magnetization ◽  
Hysteresis Loops ◽  
Mesh Size ◽  
High Coercivity ◽  
Exchange Constant ◽  
Soft Magnetic ◽  
Wall Width ◽  
Model Calculations

ABSTRACTThe hysteresis loops of nanocrystalline (nc) permanent magnets (pms) produced by the melt-spin technique have been investigated for compositions based on the intermetallic compounds R2Fe14B (R = Nd, Pr) and the carbides Sm2Fe17−xGaxCy. The following three types of pms have been studied: 1) High-coercivity pins with exchange decoupled grains. 2) High-remanence exchange-spring pms. 3) High-coercive-high-remanence composite pins with exchange coupled soft and hard magnetic grains. The temperature dependence of the coercive field μ0Hc for all three types ofpms obeys a relation for a modified nucleation field, Hc = (2K1/Js)α - Neff Ms (K1 = first anisotropy constant, Ms = spontaneous magnetization). For an analysis of the characteristic differences between the microstructural parameters a and Neff as obtained for the three types of pms, computational micromagnetism on the basis of the Finite Element Technique is applied. This powerful method allows a quantitative analysis of the role of grain size, grain boundaries (gbs), texture of easy directions and of soft magnetic phases in composite materials. In order to obtain satisfactory results, a self-adapting algorithm has been developed where the mesh size is adapted to the gradients of the direction cosines of the spontaneous magnetization. It turns out that excellent magnetic properties of composite pms can only be obtained if the gbs are as ideal as possible. Remanence and coercive field are found to decrease linearly with a corresponding reduction of both, the crystal anisotropy and the exchange constant within the gbs. In composite pins the diameters of the soft magnetic grains should be smaller than twice the domain wall width, of the hard magnetic phase in order to obtain a remarkable remanence enhancement. From these model calculations general rules for the development of optimized nc pms with large remanences and large coercivities are derived.

Effect of Warp on the Multiple Equilibria of a Hydrodynamically Coupled Flexible Disk

2006 ◽  
Author(s):  
Nikhit N. Nair ◽  
Grant M. Warner
Keyword(s):  
Manufacturing Process ◽  
Shooting Method ◽  
Multiple Equilibria ◽  
Rotation Speed ◽  
Coupled System ◽  
Instability Phenomenon ◽  
Disk Rotation ◽  
Hybrid Formulation ◽  
Flexible Disk ◽  
Disk Rotation Speed

In this paper, a hydrodynamically coupled flexible disk rotating in a thin housing is mathematically modeled and an attempt is made to explain the jump instability phenomenon that occurs when the disk rotation speed is varied slightly. The disk is assumed to have an initial warped profile due to slight imperfections in the manufacturing process. After non-dimensionalization of the participating variables, a hybrid formulation is carried out. Radial flows above and below the disk are taken into consideration. The deflection and pressure equations form a coupled system, and a solution is attempted using the shooting method. The deflections obtained are plotted to obtain the deflected disk profile and appropriate conclusions are drawn.

scholarly journals Design and study of seeding devices for small selection seeding machines

2019 ◽  
Vol 126 ◽  
pp. 00008
Author(s):  
Vladimir Nemtinov ◽  
Nikolai Kryuchin ◽  
Alexandr Kryuchin ◽  
Yulia Nemtinova
Keyword(s):  
Linear Dependence ◽  
Rotation Speed ◽  
Rotation Frequency ◽  
Field Studies ◽  
Disk Rotation ◽  
Seed Supply ◽  
Computer Technologies ◽  
Laboratory Results ◽  
Agricultural Plants ◽  
Disk Rotation Speed

In this paper, it is proposed to use a self-propelled pneumatic mini-seeder with replaceable mechanical sowing devices designed and manufactured using computer technologies, advanced software and threedimensional printing for seeds selection. As a result of the research, hightech operating devices for a grain-drill feed with screw and disk-pin continuous seed metering are designed and manufactured. Grain-drill feeds allow sowing of free-flowing and non-free-flowing seeds, when used as seed meters on self-propelled pneumatic mini-seeders for selection sowing of grass seeds. Analysis of laboratory results of and field studies of the proposed grain-drill feeds allowed to determine the qualitative indicators of their performance: at a disk rotation speed of up to 15 rpm a linear dependence of the seed supply on the rotation frequency is provided; in the field studies, the instability of bluegrass seeding did not exceed 8%. The highest performance of the screw is obtained at the angle of choke inclination of 30...35 degrees with the seeding instability indicator of 2.5...3.5%. The developed grain-drill feed will significantly reduce the range of seeders and expand the set of sown seeds of various agricultural plants with one brand of a grain-drill feed.

scholarly journals Inverted Hysteresis Loops in the Fe73.5Cu1Nb3Si13.5B9 Alloy With Small Coercivity

2021 ◽  
Vol 8 ◽  
Author(s):  
P. P. Shen ◽  
Y. T. Wang ◽  
B. A. Sun
Keyword(s):  
Hysteresis Loop ◽  
Magnetization Curve ◽  
Room Temperature ◽  
Hysteresis Loops ◽  
Superconducting Magnet ◽  
Structural Inhomogeneity ◽  
Physical Origin ◽  
Soft Magnetic ◽  
Field Range ◽  
The Past

The phenomenon of inverted hysteresis loop has been observed in many materials for the past decades. However, the physical origin of the inverted hysteresis loop has long been debated. Here, we report the completely inverted hysteresis loop with a clockwise cycle in the soft-magnetic nanocrystalline Fe73.5Cu1Nb3Si13.5B9 alloy and amorphous Fe73.5Cu1Nb3Si13.5B9 alloy at room temperature. The negative remanence and positive coercivity were observed in the descending branch of magnetization curve when the scan field range was above 1 KOe. By comparing the results with that of the standard Pd sample, we found that the net coercivities of the nanocrystalline Fe73.5Cu1Nb3Si13.5B9 alloy and standard Pd sample are almost equal for the different scanning field ranges. Therefore, it is confirmed that the phenomenon of completely inverted hysteresis loop is caused by the remanence of superconducting magnet rather than the structural inhomogeneity effects. Our results suggest that special care should be taken during the measurement of hysteresis loops using MPMS 3, especially for the materials with small coercivity.

scholarly journals Results of laboratory and bench-scale studies of seed dispensers with an electric drive of working tools

2021 ◽  
Vol 34 (06) ◽  
pp. 1761-1767
Author(s):  
Anatoly Ivanovich Zavrazhnov ◽  
Aleksandr Vladimirovich Balashov ◽  
Sergey Petrovich Strygin ◽  
Nikita Yurievich Pustovarov ◽  
Andrey Anatolyevich Zavrazhnov
Keyword(s):  
Control System ◽  
Electric Drive ◽  
Rotation Speed ◽  
Soybean Seeds ◽  
Seeding Rate ◽  
Linear Speed ◽  
Bench Scale ◽  
Disk Rotation ◽  
Trajectory Length ◽  
Disk Rotation Speed

Mechanical and pneumatic seed drills of both domestic and foreign production are used in Russian farms. They are equipped with a mechanical drive of working tools and an electronic seeding control system. Due to the slipping of the wheels or the breakage of the chains, the sowing of seeds in individual seed dispensers interrupts. According to the results of laboratory and bench-scale studies in respect to soybean seeds, the required power for the electric drive of one seed dispenser was determined, which, depending on the disk rotation speed from 10 to 60 rpm, ranged from 30 to 120 W. By calculation, using the analytical expression, the power, required for the fan drive of a 12-row seed drill, was determined, which, depending on the disk rotation speed, ranged from 1.6 to 2.47 kW. A condition is formulated, which will eliminate the probability of shifting and rolling seeds along the furrow after their fall out of the sowing disc rotating in the opposite direction to the movement of the seeder unit, provided correspondence of the linear speed of the sowing disc and the speed of the seeder unit (the effect of zero overlaps). In this case, the trajectory length of the seeds falling to the furrow should be consistent with the speed of the seeder unit and the seeding rate according to the proposed expression.

scholarly journals Characterization of the Transverse Distribution of Fertilizer in Coffee Plantations

Agronomy ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 601
Author(s):  
Alan Delon Andrade ◽  
Gabriel Araújo e Silva Ferraz ◽  
Murilo Machado de Barros ◽  
Rafael De Oliveira Faria ◽  
Fábio Moreira da Silva ◽  
...  
Keyword(s):  
Rotation Speed ◽  
Fertilizer Application ◽  
Production Costs ◽  
Distribution Profile ◽  
Transverse Distribution ◽  
Operating Modes ◽  
Disk Rotation ◽  
Coffee Plants ◽  
The Impact ◽  
Disk Rotation Speed

Considering the impact of fertilizers on coffee production costs, the search for greater efficiency in the use of these inputs has an important role. Accordingly, the aim of the present study is to evaluate the transverse distribution of fertilizer by a centrifugal spreader in a coffee plantation and to compare two operating modes: fertilizer application on one side (FA1), or both sides (FA2) of the coffee plants. In addition, three doses (200, 300 and 400 kg ha−1) of monoammonium phosphate and three spreading disk rotation speeds (240, 375 and 750 rpm) were tested. To characterize fertilizer distribution profiles, collectors were placed under the canopy of coffee plants, and the collected fertilizer was weighed. From the data obtained, distribution profile histograms were constructed, and coefficients of variation were calculated for each treatment. Distribution profiles with higher uniformity were related to the morphologic characteristics of the coffee plants. Regarding the operating modes evaluated, FA1 presented better results with a disk rotation speed of 750 rpm (FA1-W3); FA2 produced the best results with a disk rotation speed of 240 rpm. By relating these results with information on root morphology, FA1-W3 was found to be the most appropriate application method.

Sign in / Sign up

Export Citation Format

Share Document