• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.44 no.4
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• pp.99-107
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• 2012

In this study, the lumen loading technology for preparing magnetic papers were evaluated. The rice husk fiber, softwood kraft pulp, hardwood kraft pulp were applied and the morphological properties of pits on the those fibers were investigated with SEM. The softwood kraft pulp had the bigger size of pits, $3{\sim}5{\mu}m$ in diameter, which resulted in higher loading amount. The comparison of two methods for lumen loading such as the low concentration method with the disintegrator and the high concentration method with the Hobart mixer showed the Hobart mixer could resulted in the higher efficiency. The conditions of lumen loading process such loading time, addition amount of metal particles and addition of PEI were also evaluated. The magnetic hysteresis loop of handsheet samples made of lumen loaded fiber with $Fe_3O_4$ and $Fe_2O_3$ were examined. The differences in magnetic properties could be found according to the ferrite types.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.12
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• pp.71-77
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• 2021

An impeller identification technique that is essential for adding viscosity measurement functions to overhead stirrers is presented in this study. Previous studies have revealed that using magnets facing the same poles arranged in a row can aid in distinguishing the types of impellers by detecting the number of magnets in a non-contact manner. However, as these previous studies measured the magnetic fields using analog Hall sensors, a converting circuit for the digital signals is required that can interface with the MCU. In this study, it was demonstrated that the number of magnets can be distinguished without using a separate conversion circuit by using a Hall sensor with a digital output. Owing to the unique hysteresis characteristics of digital Hall sensors, it was confirmed through experiments that the complex and diverse outputs appear depending on the direction of the magnetic field, the arrangement of magnetic poles, and the moving direction of the magnet. The measurement of the magnetic field showed that an edge signal equal to the number of magnets inserted into the impeller was detected when the radial direction was used, and the south pole was first approached.

• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1715-1721
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• 2013

Magnetic properties of magnetite ferrofluid are studied by measuring magnetic weights under different magnetic fields with a conventional electronic balance. Magnetite nanoparticles of 11 nm diameter are synthesized to make the ferrofluid. Magnetization calculated from the magnetic weight reveals the hysteresis and deviates from the Langevin function at high magnetic fields. Magnetic weight shifts instantaneously with magnetic field change by Neel and Brown mechanism. When high magnetic field is applied to the sample, slower change of magnetic weight is accompanied with the instantaneous shift via agglomeration of nanoparticles. The slow change of the magnetic weight shows the stretched exponential kinetics. The temporal change of the magnetic weight and the magnetization of the ferrofluid at high magnetic fields suggest that the superparamagnetic sample turns into superspin glass by strong magnetic interparticle interactions.

• Progress in Superconductivity
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• v.6 no.1
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• pp.84-88
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• 2004

The polycrystalline superconductor $SmBa_2$$Cu_3$$O_{x}$ is fabricated, and intergranular magnetic properties are investigated using the critical state model, from which some useful parameters such as the critical current density and the intergranular volume fraction are obtained. The curve fitting for M-H hysteresis loop shows that the intergranular critical current density of $SmBa_2$$Cu_3$$O_{x}$ / decreases in the form of ($1-T/T_{c}$ )$^{1.5}$ . The intergranular volume fraction is influenced by granular morphology. From SEM image, the grains of $SmBa_2$$Cu_3$$O_{x}$ are found to be randomly shaped. This mean:; that the intergranular volume fraction of $SmBa_2$$Cu_3$$O_{x}$ / should be smaller than those of superconductors, of which grains are plate-shaped such as Tl-based superconductor.

• Journal of the Korean Magnetics Society
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• v.25 no.4
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• pp.123-128
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• 2015

The iron is an element having a high yield strength, mechanical hardness, good electrical conductivity, and also it has been used in various fields because of ease machining. In bridges have been used tendon made of a steel wire for large loads and light weight. Tension measurement of tendon employed in PreStressed Concrete (PSC) bridge is very important for the bridge safety check. NDT (Non-Destructive Testing) is essential for the safety check, however, magnetic NDT is difficult to apply due to the non-linear magnetization curve and hysteresis loop in the magnetic properties. In this work, for basic study of magnetic NDT application, we have constructed a B-H loop measuring system for 7-strand tendon of which diameter is 15.5 mm, and which can apply tensile stress up to 2.0 GPa. We have measured hysteresis loops of two kinds of tendons under different tensile stress. Amplitude permeability and maximum magnetic induction near knee show the most sensitive and high linearity depends on tensile stress. Relative amplitude permeability was decreased from 500 to 200 and maximum magnetic flux density changed 0.6 T.

• 한국초전도학회:학술대회논문집
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• 2008.08a
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• pp.40-40
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• 2008

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1183-1184
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• 2006

Core loss of soft magnetic powder cores have been focused on to achieve high efficiency of power supplies. In this study the effects of crystal grain size on core loss were investigated by changing heat treatment conditions. It was found that core loss is influenced by crystal grain size because eddy current loss decreased and hysteresis loss increased by making crystal grain size smaller, and it is also influenced by particle size.

• Proceedings of the Korean Magnestics Society Conference
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• 2017.05a
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• pp.220-220
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• 2017

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1177-1178
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• 2006

Magnetic Properties of dust cores made of mixtures of atomized pure iron powder and pure alumina powder has been investigated in the temperature range from 673 to 1073K. The effect of annealing on coercivity has been positive effect up to 973K and thus coercivity is gradually reduced form 280A/m (as-compressed) to 160A/m (973K). However, dust cores annealed at 1073K displayed a 15% increasing of coercivity by annealing at 973K. Hysteresis loss shows a tendency similar to coercivity. Microstructure observation of specimens shows grain refinement by recrystallization in the temperature range from 773 to 1073K.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.2
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• pp.165-170
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• 2013

This paper presents the iron loss prediction of rotating electric machines taking account of the vector hysteretic properties of electrical steel sheet. The E&S vector hysteresis model is adopted to describe the vector hysteretic properties of a non-oriented electrical steel sheet, and incorporated into finite element analysis (FEA) for magnetic field analysis and iron loss prediction. A permanent magnet synchronous generator is taken as a numerical model, and the analyzed magnetic field distribution and predicted iron loss by using the proposed method is compared with those from a conventional method which employs an empirical iron loss formula with FEA based on a non-linear B-H curve. Through the comparison the effectiveness of the presented method for the iron loss prediction of the rotating machine is verified.