• Journal of Korean Society of Environmental Engineers
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• v.27 no.7
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• pp.686-689
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• 2005

This study was conducted to investigate the effect of ammonium and nitrate nitrogen removal to applied voltage, electrolytic time and activated carbon packing height. Batch bipolar packed bed electrolytic cell reactor was packed with $4{\times}8$ mesh granular activated carbon (GAC). Afterward electrolysis was performed in 20 V for 30 min. As a result, as the filling height adjusted to 80 mm high, the removal efficiency of ammonium nitrogen was 99.9%. and as the electrolytic time varied to 60 min, the removal efficiency of ammonium nitrogen was 97.6%. and in case of continuous electrolytic treatment of ammonium and nitrate nitrogen removal efficiency of total nitrogen was over 80% in bipolar packed bed electrolytic cell reactor for 72 hours as the packing height, sample concentration and input rate of sample adjusted to 280 mm, 30 mg/L, 6.7 mL/min, respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.3
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• pp.60-66
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• 2012

This paper aims to constitute a feedback vibration control system using wireless sensor networks and experiment it on a model structure to verify its effectiveness. For the purpose, we set up a feedback vibration control system composed of a wireless input/output(I/O) sensor node based on bluetooth, a home-made shear type MR damper, a shaker which generates a constant size of sine wave, and a simple beam model structure. The vibration control experiment was performed by shaking the 1/4 point of beam with a shaker. At the moment of shaking, we controled the vibration with MR damper which was placed vertically on the center of beam. Simultaneously, by acquiring acceleration response at the 2/4 point of beam, we evaluated the effectiveness of control capability. The control command was set to send a voltage signal to MR damper when the acceleration response, acquired from the wireless I/O sensor node placed at the center of beam, was more than a certain amount. Although the realtime feedback vibration control system constituted in this paper is effective only within a limited command system, it has been proven that the system was able to effectively decrease the vibration of structure by generating a control command aimed for realtime purpose. The system also showed a possibility to be used as a structural response control system adapting a variety of semi-active control algorithm.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.4
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• pp.143-148
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• 2020

In the case of a system that detects and controls the phase of an alternating voltage, the analog control method compensates the phase offset part by filtering for the detected phase and applies it to the control. However, in the digital control method, precise control cannot be achieved due to an error between the operating frequency of the microprocessor or the microcontroller and the input phase time when controlled using such phase detection. In general, when the method used is a certain time, the accumulated error is compensated and adjusted at random. To solve this problem, a method of detecting a zero point in real time and compensating for the operating frequency of the microprocessor is needed. Therefore, the research to be performed in this paper to reduce these errors and apply them to precise digital control is as follows. 1) Research on how to implement Zero Crossing Detection algorithm through simulation modeling to compensate the zero point to match the operating frequency through detection. 2) A study on the method of detecting zero points in real time through the Zero Crossing Detection design using a microcontroller and compensating for the operating frequency of the microprocessor. 3) A study on the estimation of the rotor position of BLDC motors using the Zero Crossing Detection circuit.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.9
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• pp.1087-1093
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• 2012

In this paper, we implemented a HF-band magnetic-field communication system consisting of an amplitude shift keying(ASK) transmitter, a pair of loop antennas, and an ASK receiver. Especially, we suggested a new ASK transmitter architecture, where a drain bias of class E amplifier is switched alternatively between two voltage levels with respect to input data. A maximum 5 W class E amplifier was designed using a low cost IRF510 power MOSFET at the frequency of 6.78 MHz. A measured sensitivity of the designed ASK receiver is -78 dBm, which consists of a log amplifier, a filter, and a comparator. Maximum communication range of magnetic-wave communication system with loop antennas was calculated using magnetic field equations in both near-field and far-field ranges. Also, in order to verify the calculated values, an indoor propagation loss was measured using a pair of loop antennas whose dimensions are $30{\times}30cm$. Maximum operating range is estimated about 35 m in case of transmitter's output power of 1 W and receiver sensitivity of -70 dBm, respectively. Finally, the communication field test using the designed ASK transmitter and receiver was successfully done at the distance of 5 m.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.3
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• pp.517-531
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• 1999

This paper presents the development of the 2-mode variable gain high power amplifier for a transmitter of INMARSAT-M operating at L-band(1626.5-1646.5 MHz). This SSPA(Solid State Power Amplifier) is amplified 42 dBm in high power mode and 36 dBm in low power mode for INMARSAT-M. The allowable error sets +1 dBm of an upper limit and -2 dBm of a lower limit, respectively. To simplify the fabrication process, the whole system is designed by two parts composed of a driving amplifier and a high power amplifier, The HP's MGA-64135 and Motorola's MRF-6401 are used for driving amplifier, and the ERICSSON's PTE-10114 and PTF-10021 are used the high power amplifier. The SSPA was fabricated by the circuits of RF, temperature compensation and 2-mode gain control circuit in aluminum housing. The gain control method was proposed by controlling the voltage for the 2-mode. In addition, It has been experimentally verified that the gain is controlled for single tone signal as well as two tone signals. The realized SSPA has 42 dB and 36 dB for small signal gain within 20 MHz bandwidth, and the VSWR of input and output port is less than 1.5:1 The minimum value of the 1 dB compression point gets 5 dBm for 2-mode variable gain high power amplifier. A typical two tone intermodulation point has 32.5 dBc maximum which is single carrier backed off 3 dB from 1 dB compression point. The maximum output power of 43 dBm was achieved at the 1636.5 MHz. These results reveal a high power of 20 Watt, which was the design target.the design target.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.6
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• pp.1-14
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• 2007

Optimal design method of nonlinear damping system for seismic response control of adjacent structures is studied in this paper. The objective functions of the optimal design are defined by structural response and total amount of the dampers. In order to obtain a solution minimizing two mutually conflicting objective functions simultaneously, multi-objective optimization technique based on genetic algorithm is adopted. In addition, stochastic linearization method is embedded into the multi-objective framework to efficiently estimate the seismic responses of the adjacent structures interconnected by nonlinear hysteretic dampers without performing nonlinear time-history analyses. As a numerical example to demonstrate the effectiveness of the proposed technique, 20-story and 10-story buildings are considered and MR dampers of which hysteretic behaviors vary with the magnitude of the input voltage are considered as nonlinear hysteretic damper interconnecting two adjacent buildings. The proposed approach can provide the optimal number and capacities of the MR dampers, which turned out to be more economical than the uniform distribution system while maintaining similar control performance. The proposed damper system is verified to show more stable performance in terms of the pounding probability between two adjacent buildings. The applicability of the proposed method to the design problem for optimally placing semi-active control system is examined as well.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.6
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• pp.10-16
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• 2013

Ultra-fine planing and micro punching are separately used for improving surface roughness and machining dot patterns, respectively, of metal molds. If these separate machining processes are applied for machining of identical molds, there could be an aligning mismatch between the machine tool and the mold. A hybrid machining system combining ultra-fine planing and micro punching was newly developed in this study in order to solve this mismatch; hybrid process technology was also developed for machining dot patterns on a mirror surface of a metal mold. The hybrid machining system has X, Y, and Z axes, and a cam axis for ultra-fine planing. The cam axis and attachable and removable solenoid actuators for micro punching can make large and small sizes of dot patterns, respectively. Ultra-fine planing was applied in the first place to improve the surface roughness of a metal mold; the measured surface roughness was about 20nm. Then, micro punching was applied to machine dot patterns on the same mold. It was possible to control the diameter of the dot patterns by changing the input voltage of the solenoid actuator. Before machining, severe inhomogeneous plastic deformation around the machined dot patterns was also removed by annealing heat treatment. Therefore, it was verified that metal molds with dots patterns for optical products can be machined using a hybrid machining system and the hybrid process technology developed in this study.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.3
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• pp.60-68
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• 2008

This work describes a re-configurable 10MS/s to 100MS/s, low-power 10b two-step pipeline ADC operating at a power supply from 0.5V to 1.2V. MOS transistors with a low-threshold voltage are employed partially in the input sampling switches and differential pair of the SHA and MDAC for a proper signal swing margin at a 0.5V supply. The integrated adjustable current reference optimizes the static and dynamic performance of amplifiers at 10b accuracy with a wide range of supply voltages. A signal-isolated layout improves the capacitor mismatch of the MDAC while a switched-bias power-reduction technique reduces the power dissipation of comparators in the flash ADCs. The prototype ADC in a 0.13um CMOS process demonstrates the measured DNL and INL within 0.35LSB and 0.49LSB. The ADC with an active die area of $0.98mm^2$ shows a maximum SNDR and SFDR of 56.0dB and 69.6dB, respectively, and a power consumption of 19.2mW at a nominal condition of 0.8V and 60MS/s.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.6
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• pp.30-39
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• 2017

A digital calibration technique based on digital-domain averaging for cyclic ADC is proposed. The proposed calibration compensates for nonlinearity of ADC due to capacitance mismatch of capacitors in 1.5-bit/stage MDAC. A 1.5-bit/stage MDAC with non-matched capacitors has symmetric residue plots with respect to the ideal residue plot. This intrinsic characteristic of residue plot of MDAC is reflected as symmetric A/D transfer functions. A corrected A/D transfer function can be acquired by averaging two transfer functions with non-linearity, which are symmetric with respect to the ideal analog-digital transfer function. In order to implement the aforementioned averaging operation of analog-digital transfer functions, a 12-bit cyclic ADC of this work defines two operational modes of 1.5-bit/stage MDAC. By operating MDAC as the first operational mode, the cyclic ADC acquires 12.5-bits output code with nonlinearity. For the same sampled input analog voltage, the cyclic ADC acquires another 12.5-bits output code with nonlinearity by operating MDAC as the second operational mode. Since analog-digital transfer functions from each of operational mode of 1.5-bits/stage MDAC are symmetric with respect to the ideal analog-digital transfer function, a corrected 12-bits output code can be acquired by averaging two non-ideal 12.5-bits codes. The proposed digital calibration and 12-bit cyclic ADC are implemented by using a $0.18-{\mu}m$ CMOS process in the form of full custom. The measured SNDR(ENOB) and SFDR are 65.3dB (10.6bits) and 71.7dB, respectively. INL and DNL are measured to be -0.30/-0.33LSB and -0.63/+0.56LSB, respectively.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.05a
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• pp.29-33
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• 2004

In this paper, we took the basic experiment in order to explore the characteristics of optical CT(optical current transformer) for measuring high current in a superhigh voltage condition using faraday effect and wrote that. We used the 1,310[nm] Laser Diode for the source of light and PIN-Photodiode for receiver. The transmission line of light was composed of the single-mode fiber of 30[m] which could maintain the state of polarization in the optical fiber. The range of current was from 400[A] to 1300[A]. In addition, the temperature ranged from $20[^{\circ}C}]\;to\;50[^{\circ}C]$. In a same experiment condition, a power magnitude increases in proportion as input current is increasing and temperature become low. The maximum ratio of error in temperature of $50[^{\circ}C]$ appears 0.15[%] and the 0.16[%], 1.24[%] and 0.07[%] is ratio of error in respectively $40[^{\circ}C],\;30[^{\circ}C],\;and\;20[^{\circ}C]$.