• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.4
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• pp.159-164
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• 2002

This paper presents the design and fabrication of a high-Tc superconducting (HTS) power supply for charging of the HTS magnet load, and its characteristics have been analyzed through experiments. HTS power supply consists of two heaters, an electromagnet, a Bi-2223 solenoid and a Bi-2223 pancake magnet load. In this experiment, 331 mH electromagnet and 0.8 A dc heater current were used, and 8.5 sec and 17 sec were used for pumping period. Mechanism of the superconducting switch is used for heater-trigger. In order to measure the pumping-current with respect to the magnet flux changes, hall sensor was installed at the center of the Bi-2223 pancake load. The experimental observations have been compared with the theoretical predictions. In this experiment, the pumping-current has reached about 1.2 A. In computer simulation, the maximum pumping-current of the system has been predicted to be about 2.7 A.

• Progress in Superconductivity and Cryogenics
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• v.15 no.4
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• pp.44-47
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• 2013

We had proposed a winding method so called "Wind-and-Flip", which enables a persistent current operation of an HTS pancake coil without any electrical joint. In order to improve the magnetic field drift characteristics, a prototype HTS coil with the technique was fabricated, and tested under various temperatures. Because the coil doesn't have any electric terminals for current leads, an HTS background magnet was used to induce the persistent current in the coil by field cooling process. A conduction cooling system with a GM cryocooler was prepared to keep the operating temperatures of the prototype coil much below the 77 K. We investigated the magnetic field drift characteristics under the various operating temperatures by measuring the center magnetic field with a cryogenic Hall sensor. The persistent current mode operation at 20 ~ 50K showed a strong possibility of the winding technique for the application such as MRI or NMR.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.12
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• pp.771-777
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• 2000

This paper deals with the design and fabrication of a novel superconducting power supply system, and characteristics have been investigated through experiments. Superconducting power supply consists of rotating and static parts, and superconducting magnet. In this experiment, superconducting foils were placed in parallel within the static part of the machine, pumping currents were measured with respect to rotor speeds and excitation currents. In addition, in order to observe the rotating flux distribution in the superconducting foils, several hall-sensors were placed in it. With the flux distribution acquired, effect of the flux on the superconducting foil during the process of current pumping has been discussed. Also, the general operational characteristics of the superconducting power supply system have been investigated on the basis of the current and voltage data, and magnetic field values acquired through the experiments.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.2 s.233
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• pp.311-317
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• 2005

NC controller parameters are fixed when the controller is combined with a machine. However, the characteristics of controller could be changed as it has being used by the machine or other environmental conditions. Ultimately, it results in tool positioning accuracy changing. The loading torque in servo motor also influences on the positioning accuracy. This study focus on a measuring and analysing method for verifying the angular positioning accuracy of NC servo motor. We used a high resolution A/D converter for acquiring analogue signal of rotary encoder in servo motor. Generating tool path by the combination of axial movements (X,Y,Z) is compared with the encoder signals with the servo motor torque. The current variation signal is also read from the servo motor power using a hall sensor and converted to the motor torque. The method of analysing proposed in this study will be used for determining the gains (tuning) of parameter in NC controller, when the controller is set up at a machine initially or the controller condition is changed during the work.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.362-362
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• 2012

Graphene-based materials have been gaining the unprecedented academic and industrial applications, due to the unique charge transport as a new kind of 2-dimensional materials. The applications incorporate electronic devices, nonvolatile memories, batteries, chemical sensors, etc. based on the electrical, mechanical, structural, optical, and chemical features newly reported. The current work employs thermal chemical vapor deposition involving H2 and CH4, in order to synthesize the 2-dimensional graphene materials. The qualitative/quantitative characterizations of the synthesized graphene materials are evaluated using Raman spectroscopy and Hall Measurements, In particular, the effect of processing variables is systematically investigated on the formation of graphene materials through statistical design of experiments. The optimized graphene materials will be attempted towards the potential applications to flat-panel displays.

• Journal of the Korean housing association
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• v.23 no.2
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• pp.15-24
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• 2012

This study aims to examine the transitional process and its effect of Okcheon Jaesa in Yeonghae, Kyoungbook province. Through various bibliographies and Jaesil building in Yeonghae area, the results of this study are as follows: 1) Okcheon Jaesa was established in early 17th century at latest, since then it had been relocated several times. And it was estimated that it was relocated finally to its current location in 1725. 2) Hwasooroo was constructed in 1753, but it was destroyed by a fire in 1811. It is estimated that it was restored next year and remained so far. 3) The closed feeling of space of courtyard in Okcheon Jaesa is estimated as a result of replacing existing lecture hall into the lecture hall with elevated pavilion. 4) Andong-Kweon family affected on building of jaesil each other among their families through mutual exchange and competition. It is estimated to be the influence of Jipheeam of Mooan-Park family that Okcheon Jaesa was changed to Jaesil with elevated pavilion. Since then, Jaesil with elevated pavilion is estimated to have had effect on building Jaesil with low-columned elevated pavilion in Yeonghae area.

• Tribology and Lubricants
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• v.28 no.3
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• pp.130-135
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• 2012

This study presents a new methodology for realtime tool breakage detection by sensor fusion concept of two hall sensor and an acoustic emission (AE) sensor. Spindle induction motor torque of CNC Lathe during machining is estimated by two hall sensor. Estimated motor torque instead of a tool dynamometer was used to measure the cutting torque and tool breakage detection. A burst of AE signal was used as a triggering signal to inspect the cutting torque. A significant drop of cutting torque was utilized to detect tool breakage. The algorithm was implemented on a NI DAQ (Data Acquisition) board for in-process tool breakage detection. The result of experiment showed an excellent monitoring capability of the proposed tool breakage detection system. This system is available tool breakage monitoring through internet also provides this system's user with current cutting torque of induction motor.

• Journal of the Korean Vacuum Society
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• v.8 no.3B
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• pp.346-352
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• 1999

Diamond-like carbon (DLC) lims were deposited by using end hall type ion gun. Benzene gas was used for the generation of carbon ions. In order to systematically control the ion energy, we applied to the substrate DC, pulsed DC or 250 kHz medium frequency bias voltage, DLC films of superior mechanical properties of hardness 39$\pm$4 GPa and elastic mudulus 290$\pm$50GPa (2 to 6 times better than those of the films deposited by plasma assisted CVD method) could be obtained. Deposition rate was much higher than when using Kaufman type ion source, which results from higher ion beam current of end hall type ion gun. The mechanical properties and atomic bond structure were independent of the bias voltage type ion gun. The mechanical properties and atomic bond structure were independent of the bias voltage type but intimately related with the magnitude of the bias voltage. With increasing the negative bias voltage, the structure of the films changed to graphitic one resulting in decreased content of three dimensional inter-links. Degradation of the mechanical properties with increasing bias voltage could be thus understood in terms of the content odf three dimensional inter-links.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.401-401
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• 2011

In this work, we deposited Al2O3doped ZnO (AZO) thin films by direct current (DC) magnetron sputtering method with a $40^{\circ}$ tilted target, for application in the front layer of thin film solar cell. Wet chemical etching behavior of AZO films was also investigated. In order to optimize textured AZO films, oxalic acid ($C_2H_2O_4$)has been used as wet etchant of AZO film. In this experiment we used 0.001% concentration of oxalic acid various etching time, that showed an anisotropy in etching texture of AZO films. Electrical resistivity, Hall mobility and carrier concentration measurements are performed by using the Hall measurement, that are $6{\times}10^{-4}{\Omega}cm$, $20{\sim}25cm^2/V-s$ and $4{\sim}6{\times}10^{20}$, respectively.

• The Journal of Korea Robotics Society
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• v.5 no.3
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• pp.186-196
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• 2010

In this paper, we present a global localization and position error compensation method in a known indoor environment using magnet hall sensors. In previous our researches, it was possible to compensate the pose errors of $x_e$, $y_e$, ${\theta}_e$ correctly on the surface of indoor environment with magnets sets by regularly arrange the magnets sets of identical pattern. To improve the proposed method, new strategy that can realize the global localization by changing arrangement of magnet pole is presented in this paper. Total six patterns of the magnets set form the unique landmarks. Therefore, the virtual map can be built by using the six landmarks randomly. The robots search a pattern of magnets set by rotating, and obtain the current global pose information by comparing the measured neighboring patterns with the map information that is saved in advance. We provide experimental results to show the effectiveness of the proposed method for a differential drive wheeled mobile robot.