• Progress in Superconductivity
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• v.13 no.2
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• pp.105-110
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• 2011

SQUID sensor-based ultra low-field magnetic resonance apparatus with ${\mu}T$-level measurement field requires a strong prepolarization magnetic field ($B_p$) to magnetize its sample and obtain magnetic resonance signal with a high signal-to-noise ratio. This $B_p$ needs to be ramped down very quickly so that it does not interfere with signal acquisition which must take place before the sample magnetization relaxes off. A MOSFET switch-based $B_p$ coil driver has current ramp-down time ($t_{rd}$) that increases with $B_p$ current, which makes it unsuitable for driving high-field $B_p$ coil made of superconducting material. An energy cycling-type current driver has been developed for such a coil. This driver contains a storage capacitor inside a switch in IGBT-diode bridge configuration, which can manipulate how the capacitor is connected between the $B_p$ coil and its current source. The implemented circuit with 1.2 kV-tolerant devices was capable of driving 32 A current into a thick copper-wire solenoid $B_p$ coil with a 182 mm inner diameter, 0.23 H inductance, and 5.4 mT/A magnetic field-to-current ratio. The measured trd was 7.6 ms with a 160 ${\mu}F$ storage capacitor. trd was dependent only on the inductance of the coil and the capacitance of the driver capacitor. This driver is scalable to significantly higher current of superconducting $B_p$ coils without the $t_{rd}$ becoming unacceptably long with higher $B_p$ current.

• Journal of the Korean Institute of Gas
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• v.22 no.2
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• pp.29-33
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• 2018

Accident likelihood is growing due to a correlation for gas and electricity installed in the area of dense energy consumption like traditional market and underground shopping center. In order to prevent and respond accident risks related to gas and electricity in this area, it should be monitored and predicted for factors of gas leak or electricity by developing safety management system. This study is about accident prediction model development considering fire risk factor related to gas accident. The temperature variation characteristic near a gas burner was analyzed. Also, accident prediction algorithm and related module were developed to prevent fire in the area of dense energy consumption.

• Journal of Advanced Navigation Technology
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• v.21 no.1
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• pp.99-106
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• 2017

In this paper, an energy harvesting and profiling system is designed for smart video devices in internet of things environments without dedicated power source. The energy harvesting module provides the harvested energy from solar panel to the smart video device. The energy profiling module measures the battery outflow current and the battery voltage of the smart video device and the consumed energy of processes, and calculate the harvested energy from the energy harvesting module to the smart video device and the total energy consumption of the smart video device. The accuracy of the harvested energy measured by the device energy profiling module is validated by comparing with the calculated energy using the regional solar radiation provided by Korea Meteorological Administration. Energy harvesting data from the designed energy harvesting and profiling system can be used to design the perpetual operation of smart video devices or Internet of Things sensors.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.3
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• pp.667-673
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• 2015

A laser diode(LD) has been studied in many fields what medical, industrial processing, sensor, advertising equipment, printing equipment. And the LD is being used in industry. However, LD will require precision handling. Therefore, the actual use of LD is limited to areas of specialization. In this study, attend to the characteristics of the LD what weak to electrostatic and physical impact, current and heat. And will make a sample module that use comfortably a various wavelength LD. Furthermore, Furthermore, through the printing CTP(Computer to Plate) equipment used the 128-channel LD-Driver, compares it with a 64-channel CTP device about the print speed and resolution. And will solved the problem of delay between the dot and the dot. Finally, consider the potential of the 256-channel LD-Driver.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.7
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• pp.339-345
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• 2000

This paper deals with the displacement estimation of magnetically suspended simple 1 DOF(degree of freedom) system without the displacement sensor. Inherently electro-magnet for control has two natural feedback loops. One is the transfer function which represents the dependance of the amount of the magnetic flux on the gap displace-ments. The other is the transfer function expressing the properties that the back electromotive force is derived from the time derivative of the magnetic flux. Through these two feedback loops, information about the gap length can be represented by the magnetic flux and the coil current. This means that the gap length can be detected from these two states variables of the electromagnet without a displacements sensor(self-sensing). The displacement can be estimated with the magnetic flux subtracted by the coil current. In this paper we use a balance beam in order to deal with the displacement sensorless estimation of the magnetic bearing system. For the stable estimation of the gap displacements by using the method of self-sensing simple PD controller is used. We first show the mathematical model of the balance beam, and then we show the effectiveness of the current and flux feedback for making stable estimation of the gap displacements for the balance beam. Simulation results show the effectiveness of the current and flux feedback for good estimation of the displacement without using displacement sensor.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.6
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• pp.575-580
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• 2010

The research which sees the wild animals back with the system for the penetration prevention, when the wild animals approaches with the infrared ray sensor which composes a proposed system to use radiation department and the solar heat which occur and to make lead in the spiral which informs a guard to application of power department and back the edge where uses the battery of the application of power department which supplies all the member and the outside minute electric current to do in order to maximize a warning utterance or a luminous effect, an utterance department and the light for a prevention and about the system which restrains the wild animals is a thing. The proposed system which sees the express highway and the national road, with region degree establishes back the same wild animals appears and disappears frequently a day and night and between in circumference and goes without question appears and disappears the penetration of the wild animals which prevents and the animal the vehicle and prevents the damage which collides, joins in and driver and is the ecosystem of natural environment protects preserves.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.179-179
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• 2008

$BaTiO_3$를 기본조성으로 하는 PTC 써미스터는 Curie 온도이상에서 저항이 급격히 상승하는 산화물 반도체 세라믹이다. 이러한 성질을 이용하여 degaussing 소자, 정온 발열체, 온도센서, 전류 제한소자 등 상업적으로 여러 분야에서 연구되고 있다. 또한 원가절감 등을 위하여 Ni 내부전극을 사용하여 환원 분위기에서 소결하는 칩 타입에 대한 연구가 진행되고 있다. 본 연구에서는 Sm 함량(0.1at%~1.0at%)을 달리한 $BaTiO_3$(Si, Mn, Ca) 계를 선택하여 3%$H_2/N_2$ 분위기에서 1200~$1260^{\circ}C$, 2h 소결한 후 공기 중에서 재산화 처리하고 재산화 시간에 따른 PTC 특성 변화에 대하여 고찰하였다. 재산화 온도와 시간은 각각 $800^{\circ}C$와 0.5h~10h으로 하였다. Sm 함량을 달리하여 환원 분위기에서 소결한 시편의 미세구조와 PTC 특성과의 상관관계를 관찰한 결과, 소결온도가 낮을수록 PTC 특성은 좋아졌으며, 상온 비저항은 Sm 함량이 높아질수록 낮아졌다. 또한 Sm 함량이 높아질수록 jumping ratio$(R_{max}/R_{25^{\circ}C})$는 낮아졌다. 재산화 시간에 따른 PTC 특성은 다소 떨어졌지만 소결온도에 따라 달리 나타났다. Jumping ratio$(R_{max}/R_{25^{\circ}C})$는 Sm을 0.7 at% 첨가한 계에서 재산화를 1시간 처리한 시편에서 가장 우수하였다.

• Journal of the Korean Chemical Society
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• v.48 no.5
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• pp.491-498
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• 2004

The response characteristics of the bioelectrode developed by the co-immobilization of black goat liver tissue and ferrocene in a carbon paste matrix for the amperometric determination of hydrogen peroxide were evaluated. In the range of electrode potential examined ($-0.3{\sim}+0.0\;V$ vs. Ag/AgCl), the response time was relatively short (t95%=12 s) and it responded in the wide range of pH. The detection limit was 2.25${\times)10^{-6}M$ and a relative standard deviation of the measurements which were repeated 15 times using 1.0${\times}10^{-2 }$M hydrogen peroxide was 1.87%. The bioelectrode sensitivity decreased to 50% of the original value in 19 days of continuous use.

• Journal of the Korean Magnetics Society
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• v.8 no.1
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• pp.21-26
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• 1998

The temperature dependence of the magnetoimpedance (MI) effect is important both for scientific study and for thermal stability of MI sensor. We have performed the measurement of MI effect in amorphous $Co_{66}Fe_1Ni_1B_{14}Si_{15}$ (Metglas 2714 A) ribbon from a cryogenic chamber where the temperature of the sample can vary from 10 K to 300 K. The ac current was fixed at 10 mA for all measured frequencies ranging from 100 KHz to 10 MHz. The magnetoimpedance ratio (MIR) was revealed the drastic increment as a function of MIR (T) = MIR (0) exp(cT$^2$) where c is a constant. The measured MIR values at room temperature are usually 2-3 times larger than the data measured at 10 K for all measured frequencies. However, the shapes of the MIR curves are remained. This result shows the potential application of the MI effect for a temperature sensor. The frequency dependence of MIR has shown the typical tendency where the maximum values of MIR are increasing ans also the shapes of MIR curves are getting broader as the measured frequency increases.

• Korean Journal of Optics and Photonics
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• v.21 no.1
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• pp.16-20
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• 2010

In this study, we have fabricated a fiber-optic dosimeter using an organic scintillator and a plastic optical fiber. The dosimeter measure skin dose and percentage depth dose in a build-up region for an incident high energy photon beam. The scintillating light generated in the organic sensor probe embedded in a solid water phantom is guided by 30 m plastic optical fiber to a light-measuring device such as a PMT or an electrometer. In addition, using a fiber-optic dosimeter or a GAFCHROMIC EBT film, skin dose and percentage depth dose in the build-up region are measured and compared.