• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.6
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• pp.1123-1129
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• 2003

The noise of maneuvering submarines or vessels can be divided into the tonal signals and broadband ambient noise. Tonal signals are from the revolution of motors and engines of vessels, and broadband ambient noise is from the bubbles which are generated by the propellers and the flow of water around vessels. We can analyze the kinds and the speed of vessels if we analyze the tonal signals and ambient noise. But, it is difficult to divide the tonal signals form the ambient noise when the power of tonal signal is much weaker than the power of ambient noise. In this paper, we detect the direction of arrival(DOA) of the noises generated by vessels with the automatic tracking window(ATW) preprocessing algorithm, and make a beam to the direction of the targets. We suggest a method which can separate weak tonal signals from broadband ambient noise with the ATW algorithm.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.6
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• pp.95-102
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• 2019

As the number of fish keepers increases, fishbowl-related convenience products are on the rise. Existing products are not welcomed by consumers because of their lack of functions or high price. In this paper, we deal with a system that remotely controls sensors and motors of fish bowl based on Raspberry Pi and Arduino. In Android applications, you can use the following functions. firstly, feeding. Second, water changing. Third, it measures, visualizes temperature and pH values including alert function. Through the several experiments, it was verified that the system can be quickly accessed from the outside, and when it is appropriate to change water. This system allows the user to keep the fish more comfortable and safe.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.886-887
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• 2015

There is a growing interest in and demand for power industry acceleration and energy efficiency due to the increased energy consumption, environmental issues. Electronic power IT convergence industries such as intelligent power system has attract attention as new growth engine industry. A large number of sensors and motors are being installed following unmanned, automated in existing incoming panel management system. Observe the operating conditions and rapid response is essential. Despite the need for immediate action to be taken in the event of various later failed to recognize the emergency power can lead to accidents. In this paper, we propose a new architecture of the implementation of incoming panel monitoring system for power monitoring, fault detection, maintenance and system control using open source hardware platform and Wi-Fi networks.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.10
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• pp.516-523
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• 2000

In this paper, intelligent methods using digital protective relay in power supervisory control system is developed in order to protect power systems by means of timely fault detection and diagnosis during operation for induction motor which has various load environments and capacities in power systems. The spectrum pattern of input currents was used to monitor to state of induction motors, and by clustering the spectrum pattern of input currents, the newly occurrence of spectrums pattern caused by faults were detected. For diagnosis of the fault detected, the fuzzy fault tree was derived, and the fuzzy relation equation representing the relation between an induction motor fault and each fault type, was solved. The solution of the fuzzy relation equation shows the possibility of each fault's occurring. The results obtained are summarized as follows: 1) The test result on the basis of KEMC1120 and IEC60255, show that the operation time error of the digital motor protective relay is improved within ${\pm}5%$. 2) Using clustering algorithm by unsupervisory learning, an on-line fault detection method, not affected by the characteristics of loads and rates, was implemented, and the degree of dependency by experts during fault detection was reduced. 3) With the fuzzy fault tree, fault diagnosis process became systematic and expandable to the whole system, and the diagnosis for sub-systems can be made as an object-oriented module.

• Journal of the Korean Ceramic Society
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• v.47 no.1
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• pp.54-60
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• 2010

This paper shortly reviews our recent work on filled skutterudites, which are considered to be one of the most promising thermoelectric (TE) materials due to their excellent power factors and relatively low thermal conductivities. The filled skutterudite system also provides a platform for studying void filling physics/chemistry in compounds with intrinsic lattice voids. By using ab initio calculations and thermodynamic analysis, our group has made progresses in understanding the filling fraction limit (FFL) for single fillers in $CoSb_3$, and ultra-high FFLs in a few alkali-metal-filled $CoSb_3$ have been predicted and then been confirmed experimentally. FFLs in multiple-element-filled $CoSb_3$ are also investigated and anonymous filling behavior is found in a few specific systems. The calculated and measured FFLs, in both single and multiple-filled $CoSb_3$ systems, show good accordance so far. The thermal transport properties can be understood qualitatively by a phonon resonance scattering model, and it seems that a scaling rule may exist between the lattice thermal resistivity and the resonance frequency of filler atoms in filled system. Even though a few things become clear now, there are still many unsolved issues that call for further work.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.10
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• pp.173-179
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• 2014

In this paper, a motor parameter identification system has been implemented to improve the performance of the position sensorless stroke controller for linear compressors. In order to control the cooling capability of a refrigerator or an air conditioner in which linear compressors are applied, the piston speed should be controlled. The piston speed control can be obtained by adjusting the frequency or the stroke of linear motors. The dynamic performance of linear compressors depends on how accurately the stroke or the piston amplitude is estimated. The merits and demerits of Constant method and PIM (Parameter Identification Method) concerning the needed memory space and the stroke error are discussed and verified via some experimental studies.

• Journal of IKEEE
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• v.22 no.2
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• pp.258-265
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• 2018

This paper proposes an algorithm for reducing the starting current when the single-phase induction motor starts and analyzes its operation. Generally, the single-phase induction motors require several starters to generate the starting torque due to their structural characteristics. In this paper, a capacitor-start / capacitor-run method of the single-phase induction motor is basically adopted. This conventional method is efficient and has a large starting torque, but it generates about 5 ~ 6 times of inrush current at startup. As a result, the freezer starting device and peripheral devices are damaged and life time may be reduced. To reduce the inrush current, the current control algorithm based on the virtual dq model is presented to control the starting current. In addition, it validates the proposed algorithm through experiments to smooth transit from start-up operation to the rated operating region.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.7
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• pp.706-712
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• 2014

The inverters used to drive Brushless DC motors (BLDC) include switching devices such as FETs and the faults in FETs cause severe performance degradation in systems where a BLDC acts as actuator. This paper presents a fault detection and isolation method for the FETs of an inverter for BLDC motor control systems, which is based on the EKF (Extended Kalman filter). Firstly, an equivalent circuit model for a BLDC motor plus its inverter system was derived. Secondly, a state-space equation was established, where the on-resistance of the FETs is expressed as a state variable and the EKF equation estimates the on-resistance. If the estimated resistance differs greatly from the known value, it can be asserted that there is a fault on that FET. Thirdly, the local convergence of the established EKF was proved. Finally, through the experiments, the performance of the proposed method was verified. The results show that the on-resistance is estimated close to the value specified in the FET data sheet in normal operation, whereas the estimated resistance is a much larger value than the normal one in case an FET fault occurs. Therefore, it is confirmed that the proposed fault detection and isolation method works appropriately in real systems.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.3
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• pp.156-163
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• 2014

In this paper, a phase control system has been implemented to improve the dynamic performance of the stroke response for linear compressors. In order to control the cooling capability of a refrigerator or an air conditioner in which liner compressors are applied, the piston speed should be controlled. The piston speed control can be obtained by adjusting the frequency or the stroke of linear motors. The dynamic performance of linear compressors depends on how accurately the stroke or the piston amplitude is estimated. A phase control system is added to the stroke control loop and the superior performance of the phase control system is verified via some simulation studies.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.10
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• pp.955-962
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• 2016

In this paper, we propose a design method for speed controller, current control of a Brushless Direct Current(: BLDC) motor using disturbance rejection techniques. Disturbance assumes a back electromotive force occurring in the electrical system and the variation of the load acting on the rotary shaft from the outside of the motor. And it assumed to be constant during the time interval and the Luenberger's observer design. So that the error of the observer about the system status can converge to zero show how to set the appropriate gain. Further, to stabilize the whole system, and proposes a method for setting the appropriate PI gain control to improve the tracking performance. By applying the proposed controller to 120W BLDC motors were tested for the ability to follow the velocity and current reference. Since the simulation results of the steady state error is within 0.1%, we were able to show the usefulness of the tracking performance of the proposed controller.