• Aerospace Engineering and Technology
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• v.6 no.2
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• pp.171-179
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• 2007

The Test Equipment for the upper stage of KSLV-I has following functions via umbilical cable interface; external power supply, command output such as discrete and analog, data acquisition, CS-I interface simulation for first stage of KSLV-I and RS-422 serial communication for PDU. The main purpose of UTE is the experiment or function verification of system-level upper stage. To realize this system, we used PXI control system. The UTE is consisted of the PXI control system, power supply, terminal block, internal harness, connector panel and so on. The software functions of UTE are classified by four blocks. These are Discrete/Analog I/O control, PDU RS-422 serial communication control, power supply GPIB control and UTE remote control. In this paper, we will describe the design on the hardware and software of UTE.

• Journal of the Institute of Convergence Signal Processing
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• v.15 no.2
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• pp.64-69
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• 2014

Ultrasound system is one of the complex wireless signal processing systems that are widely used in the fields of modern industry such as medical diagnostics, underwater communications, and sensor-networks. Miniaturization of ultrasound system has been raging recently. In this paper, a hybrid LNA that is suitable for miniaturization and mobile diagnostic ultrasound system has been developed. The proposed LNA has low noise figure of less than 5dB, and the feedback resistor is designed to be electrically adjusted in order to attain the impedance-matching for various ultrasound transducers. It supports the whole ultrasound frequencies from 10KHz to 150MHz frequency band and also provides sleep modes. A gain from -18.8 to -29.5 dB is achieved by adjusting each transducer to fit the system character. Power consumption can be reduced up to 90% in similar performance as compared to the existing LNA.

• Proceedings of the Korean Society of Computer Information Conference
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• 2018.07a
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• pp.509-512
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• 2018

최근 미세먼지에 대한 관심이 높아지고 있으며, 미세먼지를 줄이기 위한 다양한 기술이 연구되고 있다. 본 연구에서는 기존 가솔린 이륜차의 단점을 극복하고 미세먼지 발생을 줄일 수 있는 배터리 교환식 이륜차 및 IoT 기반 지원시스템을 소개한다. 전기 이륜차에 탑재되는 IoT Edge device에서는 배터리 잔량, 배터리 ID, 위치 정보 등의 정보를 LTE-M 통신을 통해 IoT 클라우드에 전송하고, 배터리 교환이 필요한 경우 주변의 배터리 교환기 위치 및 교환 가능한 배터리 정보 전달 받을 수 있다. 현재 전기이륜차에 탑재될 IoT Edge device 및 사용자용 스마트폰앱을 개발하고 있으며, 배터리 교환기 및 클라우드 서비스 개발도 수행될 예정이다.

• Journal of Broadcast Engineering
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• v.25 no.6
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• pp.994-1003
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• 2020

In this paper, we investigated the current issues on the KPAS(Korean Public Alert Service) by News analysis. News articles, from May 15, 2005 to April 30, 2020, were collected with the key word of 'KPAS' through the News Big-Data System provided by the Korea Press Foundation. The results of the content analysis are as follows. First, the issues on alert presentation were categorized by alarm sound, message content, alert level, transmission frequency, delay, reception range, time of alert, and language. Issues on inability to receive KPAS messages were categorized into authority, mobile, sending standard, mobile communication infra, etc. For the last two to three years, news on the inability issues had decreased, while news on the presentation issues had increased. This tells us that the public demand for improvement in the KPAS lies in the presentation issues. The demand for societal resolutions to the presentation issues especially on message content, transmission frequency, and reception range has soared.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.4
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• pp.205-211
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• 2014

With a development of modern industry, demand for electric power is rapidly increasing and the capacity of power transfer is required to become bigger and bigger. At power station, the high-voltage power cable is used as the only method in order to transfer electric power. In this paper, we have analyzed the deterioration characteristics of 6.6kV power cable systems in operation. For the time duration of 2000 days, we have measured the cable in operation in order to extract the data for the deterioration characteristics. By analyzing the data by means of several steps of filtering processes, we could obtain the linear relations of insulation resistances as a function of time. Furthermore, we can verify that the progress characteristics in deterioration process of 6.6kV power cable systems follows the process of heat deterioration.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2B
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• pp.232-243
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• 2010

In this paper, various physiological signals of humans were measured and analyzed to inference their psychological state and biological information, and Bio-Signal Context aware system (BSC), which recognizes the current context of its users as well as the information of exterior environment and offers the service appropriate for them, was designed and implemented. The BSC extracts and analyzes the features from bio-signals, such as the measured electroencephalogram (EEG), electrocardiogram (ECG), and galvanic skin response (GSR), with its different sensors, has the input of the analyzed results, and discriminates four psychological states of rest, concentration, tension and melancholy. In addition to the results of the discriminated psychological states, the information of biological condition analyzed from the user's bio-signals, for example, heart rate variability (HRV), Galvanic skin response (GSR) and body temperature, and the information of external environment related to the user's are collected to offer the service fit for the user's present biological condition by inferring and recognizing the user's present situation.

• 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.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.5
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• pp.91-97
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• 2012

Recently, the performances of electrical and electronic devices are improving while the sizes are becoming smaller. As sound-generating systems, the two-dimensional speakers have been developed in place of conventional three-dimensional ones. Piezoelectric materials show the mechanical vibrations due to the voltage applied from outside the materials. The early film speakers had a limitations of output power in that it was not easy to make the conducting macromolecular films on the surfaces of the materials due to the internal chemical properties of materials. We have adopted the corona surface treatment in order to improve the output characteristics by increasing the adhesion of the coating material on to the surface of the center material of piezo film. The results showed the improvement of output power in the wider range of operating frequencies.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.6
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• pp.105-112
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• 2010

Recently, wireless communication systems have been developed and the circuits which operate with the broad-band for multiband uses were introduced. However, broad-band circuits have problems that inevitably increase the size. Dual-band circuit operates only two frequency, therefore, it will be able to miniaturize through unnecessary decreased elements. The Wilkinson power divider is the one of the most commonly used components in wireless communication system for power division. Nowaday, the Wilkinson power divider is also demanded dual-band. In this paper, I propose miniaturized dual-band Wilkinson power divider operating at 2.45 GHz and 5.2 GHz for IEEE 802.11n standard. Proposed dual-band Wilkinson power divider is used in parallel stub line. The design is accomplished by transforming the electrical length and impedance of the quarter wave sections of the conventional Wilkinson power divider into dual band ${\pi}$-shaped sections.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.5
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• pp.199-208
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• 2017

Lithium polymer batteries are used in energy storage systems (ESS), electric vehicles (EVs), etc. due to their high safety, fast charging and long lifecycle, and now they are used in agricultural drones. However, when overcharging and overdischarging, the lithium-polymer battery is destroyed in the gap structure in the lithium-ion battery and the battery life is reduced. In order to prevent overcharge and overdischarge, uneven cell voltage Cell balancing system is needed. In this paper, a fuzzy controller suitable for nonlinear systems is proposed by detecting the unbalanced cells by detecting the voltage difference between charging and discharging of each cell, and suggesting the applied cell balancing algorithm. In this paper, we have designed the cell balancing of the battery pack of agricultural drones by fuzzy control and it is designed for equal control between cells. As a final result, we checked whether cell balancing is good, and when there are two cells, Cell balancing was confirmed. We tested whether it could be used for other products. As a result, we confirmed that cell balancing is good regardless of the number of cells used.