• 한국정밀공학회지
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• 제19권7호
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• pp.36-42
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• 2002

This paper presents two actuators for levitation using repulsions of permanent magnet and two magnetic levitation tables using the actuators. Here, one actuator for levitation consists of one fixed magnet and one moving magnet, and the other actuator consists of two fixed magnets and one moving magnet. The moving part of the magnetic levitation table contains the moving magnets. repulsive forces caused by the permanent magnets are linearized, and then the equation of motion of the moving part of the table is derived. Using the equation of motion, stability conditions of the moving part are deduced. The stability conditions are analyzed for positional relations of the moving magnets and the minimum number of active control required for stable system. As a result, in the each case of magnetic levitation tables, the requirements for stabilization are expressed by the positional relations and the number of the active controls.

• Journal of Magnetics
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• 제8권1호
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• pp.70-73
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• 2003

We have developed a new tracking system of jaw movement. The system consists of two permanent NdFeB magnets and 32 elements of two-axial fluxgate sensor array, The two magnets are attached to head portion and front tooth. This system does not need any attachments of the head portion or mouth such as clutch or magnetic field sensor except magnets. The proposed system is applicable for five degree of freedom. Position accuracy within 2]m was achieved. We developed a 3D computer input device by using the above mentioned technique.

• Journal of Magnetics
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• 제16권3호
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• pp.304-307
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• 2011

High performance Nd-Fe-B magnets can be manufactured by both sintering and hot deformation. The corrosion behaviors of the magnets prepared by the two processes were compared. Effect of microstructure on the corrosion resistance of Nd-Fe-B magnets was also investigated. A neutral salt spray test (NSS) was performed for the different-processed magnets. The weight losses of the samples after the corrosion test were measured. The corrosion microstructures were observed using a scanning electron microscope. It shows that the corrosion resistance of hot deformed magnets is much better than that of the sintered ones because the grain size and the distribution of Nd-rich phases of the hot deformed magnets are much finer and more uniform than those of the sintered ones. The different microstructure between the sintered and the hot deformed magnets causes the different corrosion behavior.

• 한국초전도ㆍ저온공학회논문지
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• 제7권4호
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• pp.28-31
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• 2005

To verify the feasibility of bifilar winding type superconducting fault current limiter (SFCL) using BSCCO tape, two types of magnets were fabricated and tested by short-circuit in this research. Even if the FCL using high Tc superconducting (HTS) tape has zero resistance in normal state, it needs to be wound as a bifilar winding for zero inductance. Solenoid type and pancake type bifilar winding magnets are designed and fabricated with the same length of BSCCO tape. The test system consists of AC power supply, transformer, fault switch, load and bifilar winding magnet. The applied AC voltages during fault duration, 0.1s, were from 0.5V to 20V. The test results without bifilar winding magnet were compared with those with each type magnets. The test results include voltage against magnet, transport current and generated resistance curve. Thermal stability, the recovery time, was studied from the results of two type magnets. The pancake type was the most effective to limit fault current but the solenoid type was thermally the most stable. From this research, short-circuit characteristics of the two types were obtained.

• 한국초전도ㆍ저온공학회논문지
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• 제23권4호
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• pp.35-38
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• 2021

Conventional direct current (DC) rotating machines are usually used for crane and press machine using high torque in metal and steel industries, because of a constant output power along variable rotating speed. A general DC motor with permanent field magnets could not increase a magnetic flux density at a gap between armature coils and field magnets. However, a superconducting DC motor has field magnets composed with high temperature superconducting (HTS) coils and it could increase the magnetic flux density at the gap to over 10 times than those of a general DC motor by control the excitation current into HTS coils. The superconducting DC motor could be operated with extremely high torque and constant output power at a low rotational speed. In this paper, a 500 W superconducting DC rotating machine was conceptually designed with a LN₂ (Liquid Nitrogen) cooling method and the operation characteristics results of HTS field magnets were presented. The two no-insulation HTS magnets for a 500 W superconducting DC rotating machine were fabricated. The excitation current for the HTS magnets could be controlled from 0 to 40 A. This test results will be available to design large-sized HTS magnets for a number of hundred kW class superconducting DC rotating machine under LN₂ cooling system.

• 한국초전도ㆍ저온공학회논문지
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• 제18권2호
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• pp.21-24
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• 2016

In recent years, the iron-dominated high-temperature superconductor (HTS) quadrupole magnets are being developed for heavy ion accelerators. Field analyses for iron-dominated quadrupole magnets were based on the normal-conducting (NC) quadrupole magnet early in the development for accelerators. Some conclusions are still in use today. However, the magnetic field of iron-dominated HTS quadrupole magnets cannot fully follow these conclusions. This study established an HTS quadrupole magnet model and an NC quadrupole magnet model, respectively. The harmonic characteristics of two magnets were analyzed and compared. According to the comparison, the conventional iron-dominated quadrupole magnets can be designed for maximum field gradient; the HTS quadrupole magnet, however, should be considered with varying field gradient. Finally, the HTS quadrupole magnet was designed for the changing field gradient. The field quality of the design was improved comparing with the result of the previous study. The new design for the HTS quadrupole magnet has been suggested.

• Journal of Magnetics
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• 제21권3호
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• pp.364-373
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• 2016

The article presents the results and findings obtained through the assembly of opposing linear Halbach arrays from two magnet layers using large magnetic blocks from permanent NdFeB magnets, especially concerning the distribution of magnetic induction in an air gap. The use of these large blocks has led to a significant expansion of the area of magnetic field with a substantially higher value of magnetic induction in comparison with similar linear Halbach arrays composed of small magnets. The paper also discusses the determined dependences of magnetic induction on the parameters of the x, y, z coordinate system and indicates the possibilities of achieving an even stronger magnetic field in a larger volume of an air gap for application for instance in equipment for magnetic separation of raw materials, in instrument technologies and in other areas.

• 한국주조공학회지
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• 제17권1호
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• pp.67-75
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• 1997

The semisolid processing of two Al-Si alloys, A356 and Al-25wt%Si, was studied with using the rotor composed of permanent magnets. The semisolid slurry was agitated by the electromagnetic force induced from the rotating permant magnets. The round shaped primary ${\alpha}$ phases were formed in A356 alloy as a result of agitation. In Al25wt%Si alloy, spherodization of primary Si particles was not observed with the rotation of the magnets. The primary Si particles were segregated to the outer surface area of sample, which became pronounced with increasing the rotating speed of magnets.

• International Journal of Precision Engineering and Manufacturing
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• 제9권2호
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• pp.34-38
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• 2008

Commercially available magnetic barrel machines equipped with permanent magnets have certain limitations: work can only be finished effectively in limited areas of the container because permanent magnets are arranged two-dimensionally on the magnet disk. We overcame this problem by developing a new magnetic barrel machine equipped with a three-dimensional magnet arrangement. The effectiveness of the new machine has already been reported; this study improved the machine's polishing ability by changing the polarity of magnets on a magnet block. Polishing experiments confirmed the most effective arrangement of magnets on the magnet block. An alternating arrangement of north and south poles produced far superior polishing characteristics than a uniform arrangement of the same pole facing outward. Alternating polarity probably causes increased quantities of barrel media to work together. Finally, we introduced stronger permanent magnets to the magnet block, and found that the increased magnetic field also improved polishing ability.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제21권4호
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• pp.336-340
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• 2018

Foreign body ingestions pose a significant health risk in children. Neodymium magnets are high-powered, rare-earth magnets that is a serious issue in the pediatric population due to their strong magnetic force and high rate of complications. When multiple magnets are ingested, there is potential for morbidity and mortality, including gastrointestinal fistula formation, obstruction, bleeding, perforation, and death. Many cases require surgical intervention for removal of the magnets and management of subsequent complications. However, we report a case of multiple magnet ingestion in a 19-month-old child complicated by gastroduodenal fistula that was successfully treated by endoscopic removal and supportive care avoiding the need for surgical intervention. At two-week follow-up, the child was asymptomatic and upper gastrointestinal series obtained six months later demonstrated resolution of the fistula.