• 전력전자학회:학술대회논문집
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• 전력전자학회 1997년도 전력전자학술대회 논문집
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• pp.386-392
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• 1997

Recently, according to developing industry and life style, power consumption have been increased year after year. Currently these much power demand from power consumer is weakening the allowable power reserve margin in summer. As one of the remedies about this problem, the small scale utility interactive photovoltaic system(UIPVS) is considered for auxiliary power source. For this system one of problems to be solved technically, system operating power factor. Generally in case of small scale system, system is operated in unity power factor. But this unity power factor operating mode decrease power factor viewed from utility because UIPVS supply active power to utility. Therefore this paper propose UIPVS with power factor correcting function and this system is analyzed.

• Korean Circulation Journal
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• 제54권7호
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• pp.382-394
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• 2024

Background and Objectives: Fractional flow reserve (FFR) is an invasive standard method to identify ischemia-causing coronary artery disease (CAD). With the advancement of technology, FFR can be noninvasively computed from coronary computed tomography angiography (CCTA). Recently, a novel simpler method has been developed to calculate onsite CCTA-derived FFR (CT-FFR) with a commercially available workstation. Methods: A total of 319 CAD patients who underwent CCTA, invasive coronary angiography, and FFR measurement were included. The primary outcome was the accuracy of CT-FFR for defining myocardial ischemia evaluated with an invasive FFR as a reference. The presence of ischemia was defined as FFR ≤0.80. Anatomical obstructive stenosis was defined as diameter stenosis on CCTA ≥50%, and the diagnostic performance of CT-FFR and CCTA stenosis for ischemia was compared. Results: Among participants (mean age 64.7±9.4 years, male 77.7%), mean FFR was 0.82±0.10, and 126 (39.5%) patients had an invasive FFR value of ≤0.80. The diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of CT-FFR were 80.6% (95% confidence interval [CI], 80.5-80.7%), 88.1% (95% CI, 82.4-93.7%), 75.6% (95% CI, 69.6-81.7%), 70.3% (95% CI, 63.1-77.4%), and 90.7% (95% CI, 86.2-95.2%), respectively. CT-FFR had higher diagnostic accuracy (80.6% vs. 59.1%, p<0.001) and discriminant ability (area under the curve from receiver operating characteristic curve 0.86 vs. 0.64, p<0.001), compared with anatomical obstructive stenosis on CCTA. Conclusions: This novel CT-FFR obtained from an on-site workstation demonstrated clinically acceptable diagnostic performance and provided better diagnostic accuracy and discriminant ability for identifying hemodynamically significant lesions than CCTA alone.

• 전기학회논문지
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• 제65권6호
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• pp.969-978
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• 2016

Around the world are increasing the demand for ESS. Currently, the domestic is expected to benefit by operating ESS. In the domestic, it is expected to benefit from operations of the installed ESS because of the introduction of ESS less capacity. However ESS capacity to the maximum profit occurs is unknown. ESS is different from the charge-discharge characteristics and the reserve to replace, depending on the application. Therefore, it should be established in accordance with the ESS optimal capacity according to the purpose used because it can maximize the quality and efficiency of the electric energy. To the ESS optimal capacity estimation by the purpose used, It should compare the investment cost caused by ESS facility installation and operation cost caused by operating ESS. In this paper, the operation mathematical model for estimating marginal operation costs established. In operation mathematical model, operating cost is considered fuel cost and no-load cost start-up cost. Because no-load cost and start-up cost are not related to cost and power plant output, there are expressed an integer variable costs as a step function.

• 융합정보논문지
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• 제10권11호
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• pp.324-331
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• 2020

본 연구는 의료기관 회계정보 공시시스템에 등록된 29개 지방의료원의 재무정보를 이용하여 지방의료원들이 경영활동 운영자금 조달방법별 조달비율과 이들이 당기순이익에 어떠한 영향을 미치는지를 분석하였다. 연구결과, 지방의료원들의 경영활동 운영자금 조달비율은 의료수익 83.50%, 의료부대수익9.53%, 기부금수익 4.54%, 기타 의료외 수익 4.42%, 감가상각비 1.21%, 고유목적사업준비금 전입액 0.73%이었다. 지방의료원들의 경영활동 운영자금 조달방법들이 당기순이익에 미치는 영향을 살펴본 결과 의료수익, 의료부대수익, 기부금수익, 기타 의료외수익에 의한 운영자금 조달비율이 당기순이익에 긍정적인 영향을 미쳤으며, 고유목적사업준비금 전입액에 의한 조달비율이 당기순이익에 부정적인 영향을 미치는 것으로 확인되었다. 따라서 지방의료원들이 바람직한 경영활동을 위해서는 비용관리에 있어서 자체발생수익, 내부에 유보할 수 있는 자금 등을 고려할 필요성이 제기된다.

• Journal of Positioning, Navigation, and Timing
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• 제12권2호
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• pp.177-184
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• 2023

In order to reserve frequency bands for stable operation of the Korean Positioning System (KPS), it must be demonstrated that the impact of interference caused by KPS on other services operating in the same bands is tolerable. The International Telecommunication Union (ITU) provides the radio regulations and a compatibility assessment methodology for the coexistence of different services in limited frequency resources. The purpose of this paper is to investigate the radio regulations regarding the compatibility issues between the KPS and other services sharing the same frequency bands. The results of the investigation show that the RNSS system can be operated in the L5-band under the condition that the Power Flux Density (PFD) and Aggregated Equivalent PFD (AEPFD) thresholds specified in the radio regulations are met. In addition, the ITU recommends that the interference-to-noise ratio (INR) protection criteria be met to prevent degradation of the performance of radar systems operating in the L2/L6-band. In the case of the S-band, coordination of allocations for RDSS space stations with respect to terrestrial services is not required if the PFD does not exceed regulated thresholds regulated by ITU.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.374-375
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• 2006

전력시장이 경쟁체제로 바뀜에 따라 전력거래소는 적정예비력을 에너지 시장과 분리된 예비력 시장을 통해 확보해야 한다. 발전사업자는 두 시장에서 이득을 얻을 수 있으므로 이득을 고려하여 전략적인 입찰함수를 결정한다. 본 연구에서는 에너지 시장과 예비력 시장을 모형화하고 lemke 알고리즘을 사용하여 경쟁으로 나타나는 균형점을 해석한다. 또한 균형상태의 시장실적을 분석하여 발전사업자의 전략적인 행태를 분석한다. 마지막으로 예비력 시장과 에너지 시장의 참여유인을 한계이득과 관련지어 분석한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.216-217
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• 2006

This paper presents development of program for generator maintenance scheduling. The maintenance scheduling of generating units is a dynamic discrete combinatorial optimization problem with constraints to determine the optimal maintenance periods of each generating units for a given planning periods. The developed program is designed so as to provide the maintenance schedule satisfying the operating reserve margin levelization and the procurement of proper reliability. In order to verify the effectiveness of the developed program, the numerical study has been performed with the practical data in 2005.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.642-644
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• 2004

DLC(Direct Load Control) program has been introduced and operated for the stabilization of power demand. DLC program takes effect in accordance with political judgment of government (operating reserve ratio etc), which is controlled by DLC system mechanism. So we would improve understanding of DLC program participant introducing about control procedure in detail and also propose direction of development about control system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.284-285
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• 2015

발전설비의 불시정지, 예상치 못한 전력수요 급증 등 전력수요와 공급의 불확실성에 대비하기 위해 예비력을 운영 하고 있다. 최근 풍력발전원의 지속적인 증가로 풍력발전 출력값과 예측값의 차이인 예측오차에서 기인하는 풍력발전출력의 불확실성 또한 예비력 산정 시 고려할 주요 요소로 논의되고 있다. 본 논문에서는 발전력의 상당 부분을 풍력발전원이 담당하는 전력시스템에서 산정된 운영예비력의 적정성을 평가하는 방안을 제시하였다. 기존의 전력수요 예측오차, 발전기 불시정지 뿐만 아니라 풍력발전원의 불확실성을 모두 고려해 산정된 운영 예비력의 적정성을 평가한다.

• 한국막학회:학술대회논문집
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• 한국막학회 1997년도 심포지움시리즈 Jan-97 수처리용 분리막 기술 및 응용
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• pp.111-130
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• 1997

The lack of water resources is becoming worse due to water pollution with accelerated industrialzation and regional unbalanced distribution of water resources. In recent, the production water quality is decreasing because of the increased organic matters and soluble solids in the water sources for power plants. The purpose of this paper discribes the ststus and prospect of membrane application in electric power industry. So this study lies in developing a process which can produce high purity water by appluing RO(Reserve Osmosis) ahead of the IX(Ion Exchange) tower and evaluating the product water quality and the cost effectiveness. The capital and operating cost for the treatment of brackish water, sea water by RO were presented as a reference for the review on securing water source for the new plant site.