• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.995-996
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• 2011

전압의 시간적 변동으로 인하여 시각적 혹은 심리적으로 인식되는 불편함을 나타내는 플리커는 인간의 생체심리학적 인지능력과 관련이 있으며, 인간의 눈은 0.3%에서 0.4%의 매우 작은 전압변동에 대하여 5Hz에서 20Hz의 변조 주파수에서 민감하게 반응하며, IEC는 실증시험을 통해 8.8Hz의 전압변동에서 가장 민감하게 인식하는 것을 확인하였다. 이러한 플리커는 시각적 불쾌감과 함께 지속적인 경우 회전기와 같은 기기들에 악영향을 주며, 전자장비, 전구, CRT 장비, UPS 동기상실, 제어설비 및 보호설비의 오동작 발생으로 효과적으로 관리가 필요하다. 현재 국내 전기품질 관리기준은 IEC 국제규격을 바탕으로 제 개정 작업이 진행되고 있어 본 논문에서는 IEC 61000-3-7 국제규격을 국내 적용을 위해 필요한 국내 전력계통의 플리커 전달계수를 제시하였다.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.05a
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• pp.271-275
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• 2006

RFID(Radio Frequency Identification)기술은 초소형 IC 칩에 식별정보를 입력하고 무선주파수를 이용하여 사물, 동물, 사람 등을 인식, 추적, 관리할 수 있는 기술로서 미래 유비쿼터스 환경의 핵심 기술로 대두되고 있다. 본 연구에서는 를 기반으로 한 개별상품의 라이프사이클을 효율적으로 관리하기 위한 통합시스템 설계를 제안한다. 제안되는 통합 시스템은 개별상품의 라이프사이클(제조/물류/유통) 단계에서의 상품 Traceability와 Visibility를 제공하는 EPCglobal 네트워크 기반의 물류(유통), 금융 정보 통합 시스템으로서, 상품 정보 및 이력 데이터를 실시간으로 제공함으로써 Digital Manufacturing과 RTE(Real Time Enterprise)의 인프라를 제공하고, 기존 레거시 시스템(ERP, CRM, SCM)과의 효과적인 정보공유를 가능하게 할 것이다.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06c
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• pp.328-330
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• 2006

유비쿼터스 환경은 모든 사물에 부착된 센서를 통해 정보를 습득하고 관리하는 네트워크를 통해 구현이 가능하다. 그러나 이러한 네트워크의 구현을 위해서는 바코드와 같은 기존의 인식장치보다 좀 더 지능적이고 효율적인 인식장치가 필요하게 되었고 그 최적의 대안이 RFID이다. RFID(Radio Frequency IDentification)란 일정(무선) 주파수 대역을 이용한 자동인식기술로 원거리에서도 대상물을 분석하여 개체의 정보를 읽거나 기록할 수 있는 시스템이다. 본 논문에서는 유비쿼터스 환경을 위한 RFID 미들웨어에 관하여 기술하고, RFID 기반 생산관리시스템을 구현하고자 한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.3
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• pp.7-18
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• 2008

Radio systems decline in the system performances when one system is interfered from the other system. System parameters, which are operating frequency, transmit power, and so on, need to be determined in order that there is no interference between radio systems. We investigate the interference from the sound broadcasting service in the band 87.5-108 MHz to the ILS localizer, one of the aeronautical services, in the band of 108-112 MHz. The results are compared with the interference criteria. And then several system parameters, which are frequency, transmit power, and location, are determined in order to avoid the interference from the FM sound broadcasting service which occupies the frequency band near the band of the aeronautical services. The results of this paper can be applied to set up system parameters of the ILS localizer so that system performance can be maximized. Besides, the result of this paper can be applied for determining spectrum management policy.

• Journal of Broadcast Engineering
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• v.16 no.2
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• pp.305-318
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• 2011

Since switched digital video (SDV) provides specific programs only to the subscribers who request the programs, SDV has attracted considerable interest of MSOs for bandwidth efficiency. In North America, MSOs service over 2.3 million households with the SDV for cable networks. In Korea, since demand of HD program, high-speed Internet, VoD, and VoIP is noticeably rising, the SDV is considered as the alternative for bandwidth saving and efficient managing. In this paper, the characteristics, operating structure, and bandwidth saving of the SDV are discussed and technical requirements for the SDV are also introduced. The channel switching performance and stability of the SDV are analyzed through the test-bed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4B
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• pp.704-712
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• 2010

Recently, the lack of the frequency have been emerged due to the use of various wireless terminals. To find solutions for obtaining new frequency resources and for avoiding an interference, a cognitive radio technology have focused on as the new technology that can use the whitespace in TV broadcasting band. In this paper, the Cognitive Radio terminal system for whitespace in TV band is first introduced. The purpose of the CR terminal platform is to evaluate the feasibility of the unlicensed wireless service in the TV band. Then, we design and develop the software for Sensing MAC applied the cognitive radio terminal system. The developed Sensing MAC software based on IEEE 802.22 specification can be aware of using the whitespace in TV band that operates on cognitive radio terminal system. Finally, we have tested for evaluating the sensing MAC module.

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.1
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• pp.44-52
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• 2014

Leakage is an important factor to be considered for the management of underground water supply pipelines in a smart water grid system, especially if the pipelines are aged and buried under the pavement or various structures of a highly populated city. Because the exact detection of the location of such leaks in pipelines is essential for their efficient operation, a new methodology for leak location detection based on frequency band variation, windowing filters, and probability is proposed in this paper. Because the exact detection of the leak location depends on the precision of estimation of time delay between sensor signals due to leak noise, some window functions that offer weightings at significant frequencies are applied for calculating the improved cross-correlation function. Experimental results obtained by applying this methodology to an actual buried water supply pipeline, ~ 253.9 m long and made of cast iron, revealed that the approach of frequency band variation with those windows and probability offers better performance for leak location detection.

• Journal of the Korean Geophysical Society
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• v.6 no.4
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• pp.261-268
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• 2003

Lots of various utilities are buried under the surface. The effective management of underground utilities is becoming the very important subject for the harmonious administration of the city. Ground Penetrating Radar(GPR) survey including other various underground survey methods, is mainly used to detect the position and depth of buried underground utilities. However, GPR is not applicable, under the circumstances of shallow depth and places, where subsurface materials are inhomogeneous and are composed of clay, salt and gravels. The aim of this study is to overcome these limitations of GPR and other underground surveys. High-frequency electromagnetic (HFEM) method is developed for the non-destructive precise deep surveying of underground utilities. The method is applied in the site where current underground surveys are useless to detect the underground big pipes, because of poor geotechnical environment. As a result, HFEM survey was very successful in detecting the buried shallow and deep underground pipes and in obtaining the geotechnical information, although other underground surveys including GPR were not applicable. Therefore this method is a promising new technique in the lots of fields, such as underground surveying and archaeology.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.6
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• pp.437-445
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• 2010

There is increasing interest, on the global basis, in the operation of ocean surface radars for measurement of coastal sea surface conditions to support environmental, oceanographic, meteorological, climatological, maritime and disaster mitigation operations. In south Korea, ocean surface radars are operating to monitoring oil spill, outflow from dike or preventing from safety-accidents in the 6 regions (16 radial sites) by main frequency about 13, 25 and 42 MHz until the present. However, that ocean surface radars have been operated on an experimental spectrum basis. In the results of 3~50 MHz band domestic analysis to improve the regulatory status of the spectrum used by oceanographic radars, it was demonstrated that sufficient frequency bands are available for oceanographic radars on the frequency band above 20 MHz. It is difficult to deploy and operate oceanographic radars in the sub-bands below 20 MHz except for 13 MHz band. For using HF ocean surface radars one should understand the spectrum environment in Korea and should prepare a suitable operating system and data processing techniques.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.4
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• pp.625-632
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• 2022

Gas turbine generators in load-following operation in the domestic power system play a major role in maintaining the rated frequency, but often have poor frequency control. Therefore, after examining the control characteristics of the governor, which is a gas turbine speed control device, and analyzing the failure types, countermeasures were suggested for each case. In addition, it was confirmed through the governor response test that the gas turbine helps in frequency recovery depending on the speed of fuel control, but also acts as a factor impeding stable operation, such as rapid fluctuations in combustion chamber temperature and combustion vibration. Therefore, in order to maintain stable power quality, there was a need for thorough facility management as well as research on the governor control method in which the traditional PID control method and the machine learning algorithm, a core field of the 4th industry, were fused.