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비선형 부하 계통에서 진상 무효전력 및 고조파 발생에 따른 S-PFC와 DCB의 한계 및 보상 전략에 관한 연구
이재천,이태호,서원수,김태규 한국산학기술학회 2025 한국산학기술학회논문지 Vol.26 No.12
This study analyzed the parallel resonance characteristics of low-voltage power systems containing nonlinear loads using field measurements and MATLAB simulations. The Power Factor Correction (PFC) circuit of nonlinear loads generates leading reactive power (Q < 0) because the input current leads the voltage. Consequently, parallel resonance occurs near the 13th harmonic (≈ 775 Hz) when a Standard Power Factor Correction bank (S-PFC) was applied. When a 5.7 % Detuning Capacitor Bank (DCB) was introduced, the resonance point shifted to approximately the 4.2nd harmonic order (≈ 251 Hz), mitigating resonance and reducing harmonic current injection into the capacitor bank. Nevertheless, the compensation performance of S-PFC and DCB was limited when the displacement power factor (PFdisp) approached unity or became leading. Under these conditions, the combined use of an Active Harmonic Filter (AHF), Static Var Generator (SVG), or Shunt Reactor (SR) was more effective. The proposed analysis clarifies the relationship between the leading reactive power and harmonic resonance in nonlinear systems, providing practical and implementable guidelines for optimal reactive power compensation and harmonic resonance mitigation according to the PFdisp and THDi conditions.
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이재천,유경근,정진기,손정수,윤호성,안종관,장종신,안승천 한국자원공학회 2007 한국자원공학회지 Vol.44 No.2
The patents were searched to investigate the trend and the direction of technologies about chalcopyrite metallurgy. Database was collected using WIPS site, and supported by USPTO, PAJ, EPO and KIPRIS. Among the database collected using chalcopyrite as keyword, after the patents related with semiconductor were deleted, 127 patents were selected investigating abstracts. The patents from 1974 to 2004 were analyzed according to countries, international patent classification (IPC), companies, and technologies. Unite states has the most patents among countries investigated and the most companies to apply the patents about chalcopyrite metallurgy. Patents about bacterial leaching is the most among patents of leaching technologies. 황동광 제련에 대한 관련 기술의 추이 및 동향을 조사하기 위하여 특허 출원 검색을 실시하였다. 특허 검색 데이터베이스는 국내 WIPS사의 특허검색 사이트를 이용하였으며, 미국의 USPTO, 일본의 PAJ, 유럽의 EPO 그리고 한국의 KIPRIS를 참고하여 보완하였다. 검색 키워드는 황동광과 chalcopyrite로 하였으며, 반도체(semiconductor)와 관련된 특허를 제외한 후, 특허 요약문을 분석하여 127건을 선정하였다. 특허 분석은 1974년부터 2004년까지의 특허를 주요 국가별, IPC 분류별, 주요 출원인(회사)별 그리고 관련 기술별로 분류하여 분석하였다. 특허출원국 및 출원인 국적 분석에서 미국이 가장 많은 특허출원 건수를 나타내고 있으며, 침출기술 중에서는 미생물 침출기술이 가장 많았다.
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Japanese Cedar (Cryptomeria japonica) Pollinosis in Jeju, Korea: Is It Increasing?
이재천,이근화,이혜숙,홍성철,김정홍 대한천식알레르기학회 2015 Allergy, Asthma & Immunology Research Vol.7 No.3
Jeju is an island in South Korea located in a temperate climate zone. The Japanese cedar tree (JC) has become the dominant tree species while used widely to provide a windbreak for the tangerine orchard industry. An increase in pollen counts precedes atopic sensitization to pollen and pollinosis, but JC pollinosis in Jeju has never been studied. We investigated JC pollen counts, sensitization to JC pollen, and JC pollinosis. Participants were recruited among schoolchildren residing in Jeju City, the northern region (NR) and Seogwipo City, the southern region (SR) of the island. The JC pollen counts were monitored. Sensitization rates to common aeroallergens were evaluated by skin prick tests. Symptoms of pollinosis were surveyed. Among 1,225 schoolchildren (49.6% boys, median age 13 years), 566 (46.2%) were atopic. The rate of sensitization to Dermatophagoides pteronyssinus (35.8%) was highest, followed by D. farinae (26.2%), and JC pollen (17.6%). In the SR, 156 children (23.8%) were sensitized to JC pollen; this rate was significantly higher than that in the NR (59 children, 10.4%, P<0.001). A significant increment in the sensitization rate for JC pollen with increasing school level was observed only in the SR. JC pollen season in the SR started earlier and lasted longer than that in the NR. JC pollen season in Jeju was defined as extending from late January to mid-April. The prevalence of JC pollinosis was estimated to be 8.5%. The prevalence differed significantly between the NR and SR (5.3% vs 11.3%, P<0.001), mainly due to the difference in sensitization rates. JC pollen is the major outdoor allergen for early spring pollinosis in Jeju. JC pollen season is from late January to mid-April. Warmer weather during the flowering season scatters more JC pollen in the atmosphere, resulting in a higher sensitization rate in atopic individuals and, consequently, making JC pollinosis more prevalent.
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