• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.104-107
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• 2005

Recently, according to the development of semiconductor industry, needed to high-integration and high-functionality. These changes are required for silicon wafer of large scale diameter and precision of TTV (Total Thickness variation). So, in this research, suggest that the method of monitoring system is using motor current. This method is needed for observation of silicon wafer grinding process. Motor current sensor is consisted of hall sensor. Hall sensor is known to catching of change of current. Received original signal is converted to the diginal, then, it is calculated RMS values, and then, it is analysed in computer. Generally, the change of force is relative to the change of current, So this reason, in this research tried to monitoring of motor current change, and then, it will be applied to analysis for silicon wafer grinding process. using motor current sensor.

• Progress in Superconductivity and Cryogenics
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• v.6 no.2
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• pp.29-34
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• 2004

The linear type flux pump aims to compensate a little bit decremental persistent current of the HTS magnet in NMR and MRI spectrometers. The flux pump mainly consists of DC bias coil, 3-phase AC coil and Nb foil. The persistent current in closed superconductive circuit can be easily adjusted by the 3-phase AC current, its frequency and the DC bias current. In the experiment, it has been investigated that the flux pump can effectively charge the current in the load coil of 543 mH for various frequencies in 18 minutes under the DC bias of 10 A and the AC of 5 $A_{rms}$. The maximum magnitudes of pumping current and load magnet voltage are 0.72 A/min and 20 ㎷, respectively. Based on simulation results by the FEM are proved to nearly agree with experimental ones.

• The Korean Journal of Archival Studies
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• no.43
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• pp.71-102
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• 2015

The present study aims at investigating the current usage patterns of Korean Standard Records Management System. The Korean Standard Records Management System has been designed and distributed by the National Archives Korea in order to support records management of public agencies. An email survey has been sent to 4 types of public agencies: central government agencies, provincial governments, provincial education offices as well as city and county offices. While all agencies are included in the survey for the first three types, only two provincial districts are selected for city and county offices, Out of 101 email questionnaires sent, 65 are returned(63.73%). The results show the usage patterns of 240 functionalities aligned to 9 main functions: accession from records creators, preservation, appraisal, accession to the national archives, reference management, access and tracking, retrieval and use, system management as well as freedom of information management by public institutions. Since its launch in 2007, the system has been distributed to 707 public agencies as of late 2014. The problem is that there has been no attempt to evaluate the functionalities and usabilities of the system. Only grievances from those agencies implemented the system have never been ceased. The present study is expected to offer the levelled ground for productive discussion between the national archives and the agencies.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.961-963
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• 2002

When high temperature superconducting(HTS) tapes are wound on former for HTS cable application, their critical characteristics are likely to be degraded seriously because of mechanical stress. In this study, prior to fabricate prototype HTS cables, we investigated the variation of critical characteristics of HTS tapes according to their pitch angles. For this work, we prepared the samples of HTS tapes on the former of which diameter is 3cm. Pitch angles of HTS tapes are $0^{\circ}$, $00^{\circ}$, $20^{\circ}$, $30^{\circ}$, $40^{\circ}$, respectively. We applied current up to 160 $A_{rms}$ to HTS tapes and investigated E-I characteristics. The critical current of HTS tapes was decreased as pitch angle increased. In addition, when the applied current was beyond their critical current, the rate of resistance increase of HTS tapes was in proportion to their critical current. Finally, We concluded that the pitch angles affected resistance increase of HTS tapes as well as critical current.

• Journal of the Optical Society of Korea
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• v.2 no.2
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• pp.74-79
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• 1998

The use of a fiber Fabry-Perot interferometer (FFPI) as an optical current transducer is demonstrated. A conventional inductive pickup coil converts the time-varying current I(t) being measured to a voltage waveform V(t) applied across a piezeolectric strip to which the FFPI is bonded. The strip experiences a longitudinal expansion and contraction, resulting in an optical phase shift ${\phi}(t)$ in the fiber proportional to V(t). This phase shift is measured using a frequency-modulated semiconductor light source, photodiodes to monitor the reflected light from the FFPI and the laser power, and a digital signal processor. Calibration routines compute V(t) and I(t) from the measured phase shift at a l KHz rate. Response to 60 Hz ac over the design range 0-1300A rms is characterized Transient response of the FFPI transducer is also measured.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.390-394
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• 2001

A dynamic simulation model for the brush less dc (BLDC) motor drives using Matlab is presented. In this model, an entire BLDC motor drive, including power conversion unit, BLDC motor, and speed/torque control system, is investigated. Especially, the PWM inverter is modeled using switching function concept, so that the detailed voltage and current waveforms, such as line-to-line voltages, inverter input current, ac line current, and switch/diode currents, can be obtained and average/rms ratings of the components can be easily calculated. Also, the proposed model is made into modular blocks and it can be easily extended to other ac motor applications with a little modification. The detailed modeling method is explained and its actual implementation is described. The validity of the proposed model is verified by various simulation results.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.3
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• pp.331-338
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• 2014

A charge-pump circuit using a current-bypass technique, which suppresses charge sharing and reduces the sub-threshold currents, helps to decrease phase-locked loop (PLL) jitter without resorting to a feedback amplifier. The PLL shows no stability issues and no power-up problems, which may occur when a feedback amplifier is used. The PLL is implemented in 0.11-${\mu}m$ CMOS technology to achieve 0.856-ps RMS and 8.75-ps peak-to-peak jitter, which is almost independent of ambient temperature while consuming 4 mW from a 1.2-V supply.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.30-35
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• 2003

Recently, with the rapid growth of information technology, many studies have been performed to implement web-based manufacturing system. Such technologies are expected to meet the need of many manufacturing industries those want to adopt E-manufacturing system for the construction of globalization, agility, digitalization to cope with the rapid changing market requirements. In this research, areal-time web-based machine tool and machining process monitoring system is developed as a first step fur implementing I-manufacturing system. In this system, main spindle motor current and feed current are measured using hall sensors. And the relationship between the cutting force and the spindle motor RMS current at various spindle rotational speed is obtained. Also, a rule-based expert system is developed in order to monitor the machining process effectively. Finally, developed system is applied to real machining process to verify the effectiveness.

• Journal of the Korean Solar Energy Society
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• v.30 no.1
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• pp.7-12
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• 2010

As many grid-connected photovoltaic power conditioning systems (PVPCS)are installed in many residential areas simultaneously, these have raised potential problems of network protection on electrical power system. One of the numerous problems is an Islanding phenomenon. In this paper, active frequency drift (AFD) method, one of the anti-islanding methods which is analyzed by current magnitude compensation and calculation of the fundamental component. Both harmonic component and RMS value of the output current for THD analysis are provided and verified by simulation.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.252-256
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• 2000

We investigated resistance development in Au/YBCO thin film meander lines during quench. The meander lines were fabricated by coating YBCO films insitu with a gold layer and patterning them by photolithography. The center stripe quenched fastest even though the flux flow resistance that appeared upon the current passing the critical current was uniform. Quench started at an area of the center stripe and propagate both through the gold layer and the sapphire substrate. Quench propagation speed was uniform and 60 cm/s at 30 V$_{rms}$.