• Journal of the Korean Institute of Telematics and Electronics
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• v.17 no.4
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• pp.45-52
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• 1980

In order to eliminate the phase errors caused by the finite GB product of operational amplifiers, novel integnator circuits are proposed. These circuits are characterized by their positive phase error angles and integrator selectivity. The positive sign of the Q and of the circuits compensates the negative selectivity and phase error angles, inherent in the integrated operational amplifiers. Miller inverting intergrator of a biquad circuit realized by Thomas is replaced by the proposed circuit and the band-pass frequency response of the modified biquad network is experimentally analyzed. A considerable improvement is recognized to such extent that the center frequency of the band-pass filter is allowed to be shifted up to 20KHz, which has been infeasible with conventional biquad networks.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.7
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• pp.1502-1507
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• 2005

The SA filters have a very flexible structure by limiting the maximum subwindow size. This flexible structure presents an effective trade-off between the complexity and performance of the filters. In this paper, experimental results showing the performance variation according to the change of filter order and subfilter type(such as max, min, exclusive-OR, mod) are presented. We designed optimal SA filters minimizing MSE for the various noise conditions. These results show several new properties of SA filters.

• Journal of the Korean Society for Marine Environment & Energy
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• v.5 no.3
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• pp.16-22
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• 2002

The effect and the overall optimal operation of artificial aeration devices for mixing of thermally stratified water reservoir are under study, and its brief introduction is made. The study site is Yeoncho Lake in Geojae island, which is well known for its eutrophication problems in the summer. A few samplings have been made before and after the operation of two types of artificial aerators, and the effect is believed to be positive. Also, design methodology for such artificial aerators is reviewed and a few are applied to the case of Yeoncho Lake. Schladow's[1993] proposal is believed most proper based on the information we have gathered by now. In addition, a simple numerical experiment is also peformed to see the overall effect of the device on the flow and temperature profile.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1377-1384
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• 2015

In this paper, a resource management scheme for preventing the video frame loss in the presence of network congestion is proposed. WiMedia protocol is suitable for the application that supports the real-time multimedia service in the ship area network since it supports high speed data transfer. However, network congestion causes the degradation of video quality, since WiMedia standard discards video frames regardless of importance of video frame. Therefore, a resource management scheme for WiMedia network is proposed in this paper. The proposed technique can intelligently treat the network congestion, and solve the degradation of video quality.

• JOURNAL OF ELECTRICAL WORLD
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• s.350
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• pp.94-97
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• 2006

인구11억명의 무한한 시장‘인도’. 특히 인도는 IT 분야에서 세계 최고의 강국으로 부상하고 있다. 거기에 인도는 10여년간 연평균 GDP 성장률 6%대의 고도성장을 이룩하는 등 중국에 이어 경제강국으로의 탈바꿈을 꿈꾸고 있다. 이처럼 매력적인 시장을 기업들은 놓칠리가 없다. 이미 세계 유수의 기업들은 꿈틀대는 인도 시장을 주목해 왔다. 인도에 법인을 설립, 현지의 값싼 노동력을 이용해 가격 경쟁력을 갖추고 시장을 공략하고 있는가하면, 인도시장에 맞는 저가상품을 적극개발, 공급함으로서 시장점유율을 높이고 있다. 국내기업의 경우 자동차와 가점제품의 경우 비교적 성공적으로 정착한 사례로 꼽히고 있다. 현대자동차, LG전자, 삼성전자 등은 인도 현지에서 호평을 받을 정도로 경쟁력을 확보한 상태다. 하지만 전력 시장에서만큼은 아직까지 뚜렷한 성과를 얻어내지 못하고 있다. 가장 큰 이유는 평균 30% 이상에 달하는 관세율을 극복하지 못하고 있기 때문이다. 그리고 인도 수출의 경우 말처럼 쉽지는 않은 상황이다. 인도의 경우 영국의지배를 받던 국가라 아직까지 ABB, 시멘스 등 유럽업계의 강세가 뚜렷해 타 지역국가 업체들의 인지도가 높지 않은 상황이다. 무엇보다“대금이 들어와야 거래가 성사됐다”라고 말을 할 정도로 대금인수에 어려움을 겪는 사례가 부지기수고, 계약 파기도허다해 계약에들인 노력만큼 성공률이 높지 않은 것도 국내 전력 관련업계의 진출 부진의 한이유다. 그렇다고 인도 시장을 그냥 놓치기에는 너무아깝다. 이에 국내업계의 경우 매력적인 시장을 놓치지 않으려 계속해서 인도 시장 진출추진하고 있다. 인도 전력시장 현황을 소개하고, 수출을 위한 국내 업계의 노력 및 수출시 유의해야 할 사항을 종 합적으로 정리해봤다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.5
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• pp.872-882
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• 1994

In this paper, the Low Noise Amplifier(LNA) is designed and fabricated to include a band pass filter characteristics considering the antenna system characteristics according to the transmitting and receiving signal level of communication satellite transponder. As an example, a 2-stage low noise amplifier and a 4-stage amplifier and designed, fabricated and measured at 14,0~14.5GHz of receiving frequency band. This fabricated LNA has shown the gain with very good flatness within pass-band, and its gain decreases rapidly out of band resulting in supperssion of the transmitting signal power leakage. It has shown the 20.3dB +- 0.1dB of pass-band gain, the 1.44dB +-0.04dB of noise figure and the 14dB rejection out of band(12.25~12.75GHz). The gain flatness, noise figure and group delay of this 2-stage LNA satisfactorily met the simulation results. And the fabricated 4-stage amplifier has shown the more than 42dB of pass-band gain, the +-0.25dB of flatness and the 28dB of the rejection effect for transmitting power leakage. The 2-stage LNA and 4-stage amplifier, in this paper, will bring a design margin for the input filter and also result in the system cost reduction.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.6
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• pp.473-476
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• 2018

Herein, a $2{\times}2$ subarray antenna is designed to implement a VHF band active electronically scanned array. The Yagi-Uda antenna is used as a radiating element. The bandwidth enhancement and miniaturization of the Yagi-Uda antenna are achieved by optimizing the diameter of a driven element and the length of a director. In addition, the grid reflector is utilized to improve the front-to-back ratio(FBR) and to reduce both the wind resistance and overall system weight. The fabricated $2{\times}2$ subarray antenna fully covers the VHF target band($0.98{\sim}1.02f_c$). The measured maximum gain is 10.61 dBi and the FBR is larger than 26 dB.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.4
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• pp.672-678
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• 2017

In this paper, we studied a design method for a broadband quasi-Yagi antenna (QYA) for terrestrial digital television (DTV) reception. The proposed antenna is composed of a dipole driver, a rectangular patch type director close to the dipole, and a ground reflector printed on an FR4 substrate. A balun between a microstrip line and a coplanar strip (CPS) line is a rectangular patch inserted along the center of the CPS. The end of the balun is connected to the CPS line through a shorting pin. An antenna, as an design example for the proposed antenna, is designed for the operation in the frequency band of 470-806 MHz for terrestrial DTV, and the characteristics of the designed antenna are examined. The antenna has a good performance such as a frequency band of 430-842 MHz for a voltage standing wave ratio < 2, a gain > 3.7 dBi, and a front-to-back ratio > 7.4 dB.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.2
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• pp.245-252
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• 2016

In this paper, the design of a double-dipole quasi-Yagi antenna (DDQYA) with a gain over 7 dBi at 1.70-2.70 GHz band is studied. The proposed DDQYA consists of two strip dipoles with different lengths and a ground reflector, which are connected trough a coplanar stripline. The length of the second dipole is adjusted to increase the gain in the low frequency band, whereas a rectangular patch director is appended to the DDQYA to enhance the gain in the middle and high frequency band. The effects of the length of the second dipole, and the length and width of the director on the antenna performance are analyzed, and final design parameters to obtain a gain over 7 dBi are obtained. A prototype of the proposed DDQYA is fabricated on an FR4 substrate, and the experimental results show that the antenna has a frequency band of 1.60-2.86 GHz for a VSWR < 2, and measured gain ranges 7.2-7.6 dBi at 1.70-2.70 GHz band.

• Explosives and Blasting
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• v.21 no.1
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• pp.41-47
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• 2003

A large scale blasting is necessary for the construction or road, harbor or ground foundation of building and it is common that the blasting work is performed by a specialist subcontracted from the construction company who is originally responsible for the project. Sometimes the latter do not agree with the former in total amount of blasted rock. They try to find out real work amount as precisely as possible. The estimation is sometimes carried out by an entrusted person when it is impossible to come to an agreement with each other. There are several methods in estimating the blasted rock volume; a calculation by prescribed equivalents of explosive before construction, a calculation by specific charge per unit volume of rock, and a calculation by rock volume per detonator. In this study, the last method is reviewed and recommended as most reliable one.