• Journal of the Korean Society for Environmental Technology
• /
• v.19 no.6
• /
• pp.493-502
• /
• 2018

The purpose of this study was to develop EM media for water treatment and to remove nitrogen and phosphorus which cause water algae boom in water system. The ideal mixing ratio of raw material such as clay: zeolite: vermiculite: activated carbon for manufacturing the EM media was 10: 2.5: 0.1: 2, and the calcination temperature was $700^{\circ}C$. The comparison of the physical properties of manufactures using distilled water and EM activated liquid as the material mixture are as follows. Porosity and density of EM media were 39.98 % and $1.13kg/m^3$, adsorption efficiencies of nitrogen and phosphorus were 69.3 % and 38.9 %. In contrast, porosity and density of distilled water media were 37.80 % and $1.11kg/m^3$, and adsorption efficiencies of nitrogen and phosphorus were 62.5 % and 37.8 %. The adsorption rate of nitrogen and phosphorus in the EM media was higher than that of the distilled water made one by 6.8 % and 1.1 %, respectively. The adsorption characteristics of the media to nitrogen and phosphorus could be expressed by the Freudlich adsorption isotherm. The change of calcination time did not affect the adsorption efficiency of phosphorus and nitrogen when EM media was formed, but it was considered that it affects the strength of media. Nitrogen removal efficiency was the best record in 4 hours of calcination time and 3 hours of calcination time in phosphorus removal efficiency.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.12 no.5
• /
• pp.424-431
• /
• 2007

This thesis proposed H-Bridge Multi-Level Inverter for Fluidized Bed Combustion Boiler Secondary Air Fan in 200MW thermal power plant. The adjustable speed drive systems improve the efficiency in lightly load condition and extend the life span of motor by limiting the over current at starting. H-Bridge Multi-level Inverter is composed of the several series low voltage power cell inverters, which have the independent isolated do link, in each phase. KEPRI(Korea Electric Power Research Institute) has successfully completed to develop, install, and commission H-Bridge Multi-level Inverter(6.6kV, 1MVA). This thesis gives a full detail about H-Bridge Multi-level Inverter, proposed boiler DCS(Distributed Control System) logic, and commissioning test result.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.1B
• /
• pp.125-130
• /
• 2006

In this research, possibility of sand capping was experimentally evaluated to control phosphorus release from lake sediment into water body. Three acrylic columns without and with 40 and 80 mm of sand capping were prepared. Phosphorus concentrations of overlying water in these columns were measured. Performances of sand capping were evaluated for 0, 40, and 80 mm of capping thickness by measuring DO, ORP, TP, and $PO_4$-P. For the case without capping, the releasing rate of total phosphorus was higher and dissolved oxygen decreased faster, comparing with those of columns with capping. Total phosphorus concentrations in overlying water were inversely proportional to capping thickness, while phosphate concentration showed no significant differences between both cases. The experiment results suggested that sand capping is effective to retard total phosphorus release from sediment.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.10
• /
• pp.7043-7052
• /
• 2015

This study divides subjects into people with metabolically healthy obesity and those with metabolically unhealthy obesity to identify the physical activities and nutrients influencing adults with obesity. Participants in the sixth Korea National Health and Nutrition Examination Survey conducted from January through December 2013 were selected as the subjects, and an analysis of complex survey samples was conducted with them. It was found that the number of days of a flexibility exercise (Odds ratio (OR)=1.18, 95% confidence interval (95% CI)=1.01-1.38), water intake (OR=1.04, 95% CI=1.01-1.06) and protein intake (OR=1.07, 95% CI=1.02-1.13) for one week were higher in people with metabolically healthy obesity than in those with metabolically unhealthy obesity, while their fat intake (OR=0.99, 95% CI=0.98-1.00)and carbohydrate intake (OR=0.98, 95% CI=0.97-0.99) were lower. Based on the results of this study, it was found that nursing intervention for obesity would need an approach according to the metabolic condition of obesity.

• Journal of the Korea Convergence Society
• /
• v.13 no.5
• /
• pp.389-400
• /
• 2022

This study was conducted to identify factors influencing mental health of one-person household members. Using data from the 2019 Korea National Health and Nutrition Examination Survey, 768 subjects were included. The SPSS/Win 21.0 program was used, and the complex sample design data were analyzed by Rao-Scott 𝑥² test and multiple logistic regression analysis. Of the subjects, 29.9% perceived high stress, 16.2% felt depressed, and 8.2% had suicidal ideation. The influencing factors of stress perception were age and subjective health status(p<.001). Factors influencing depressed mood were household income, subjective health status, and perceived stress(p<.001). Factors influencing suicidal ideation were age, household income, subjective health status, perceived stress, and depressed mood(p<.001). The results of this study can be used as basic data for improving mental health services of one-person household members.

• Korean Journal of Microbiology
• /
• v.38 no.2
• /
• pp.113-118
• /
• 2002

Laboratory experiments were aimed to evaluate the effect of nitrate as a electron acceptor during the biological phosphorus uptake and to investigate the microbial community. Anaerobic-anoxic sequencing batch reactor (SBR) compared the removal behaviour to anaerobic-oxic SBR, both SBRs maintained lower effluent quality with 1.0 mgp/1. Anaerobic-anoxic SBR was able to remove additional 5.0 to 7.0 mg (P+N)/ι than other biological nutrient removal (BM) system. Therefore, it was proposed that the anaerobic-anoxic SBR was more effective at weak sewage. From the results of the maicrobial community analysis, it can be inferred that denitrifying bacteria and polyphosphate accumulating bacteria coexist in anaerobic-anoxic SBR during stable condition for removing the nitrogen and phosphorus. Particularly, it was suggested that the Zoogloea ramigera in the $\beta$-subclass of proteobacteria and the Alcaligenes defragrans of the Rhodocyclus group in the $\beta$-subclass of proteobacteria played a major role for removing the nitrogen and phosphorus as dPAOs (denitrifying phosphate accumulating organisms).

• Proceedings of the KIPE Conference
• /
• 2013.07a
• /
• pp.522-523
• /
• 2013

본 논문에서는 1인승 전기차량 구동을 위한 병렬형 3상 인버터를 제안 하였다. 제안된 인버터는 전기차량의 부하 상태에 따라 하나 또는 두개의 인버터를 병렬로 사용하여 부하가 분담된 패턴으로 제어한다. 인버터의 전체적인 제어 방식으로는 유도 전동기를 위한 벡터제어와 공간벡터 변조방식을 적용 하였다. 본 연구의 타당성은 PSIM 시뮬레이션을 통하여 검증을 하고자 한다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.17 no.1
• /
• pp.45-53
• /
• 2003

For the improvement of welding performance, high-efficiency inverter system was designed and applied that system to the conventional large scale Flashbutt welder. The inverter systems are consists of full bridge PWM power control system and DSP controller. This inverter system has increased switching frequency of power control system of Flashbutt welder. For the test of application effects, we compared an our inverter control system with a conventional thyristor control system. In the results, we confirmed that our system has decreased the welding spatter amouts and improved welding performance.

• Korea Petroleum Association Journal
• /
• no.7 s.249
• /
• pp.66-76
• /
• 2005

●2004년 세계 석유 소비는 8천75만7천 b/d로 전년대비 3.4% 증가하여 1978년 이래 최고상승률을 기록했다. 소비 비중은 미국이 전체의 24.9%를 점유하여 1위를 차지했고 중국(8.2%), 일본(6.4%), 러시아연방(3.4%), 독일(3.3%), 인도(3.2%), 한국(2.8%)순으로 나타났다. ●석유소비증가량은 중국이 전년대비 무려 15.8%인 246만 3천b/d증가하였고 미국은 2.8%인 48만 4천 b/d 증가한 반면 일본은 3.0%인 16만 7천 b/d감소하는 등 전체적으로 246만 7천 b/d증가하였다. ●세계석유생산은 8천 26만 b/d로 전년대비 4.5% 증가하였고 생산량 순으로는 사우디아리비아가 전체의 13.1%를 점유하여 1위를 차지하였고, 러시아연방(11.9%), 미국(8.5%), 이란(5.2%), 멕시코(4.9%), 중국(4.5%) 순으로 나타났다. ●세계석유매장량은 1조 1,886억 배럴로 가채년수는 405년이며 국가별로는 사우디아라비아가 전체의 22.1%를 점유하여 1위를 차지하였고 이란(11.1%), 이라크(9.7%), 쿠웨이트(8.3%), UAE(8.2%), 베네수엘라(6.5%), 러시아연방(6.1%) 순으로 나타났다. ●세계정제능력은 8천 459만 2천b/d로 전년대비 0.8% 증가하였다. 국가별로는 미국이 전체의 20.1%를 점유하여 1위를 차지하였고 중국(6.9%), 러시아연방(6.4%), 일본(5.4%), 한국(3.1%) 순으로 나타났다.

• Electric Engineers Magazine
• /
• v.216 no.8
• /
• pp.9-13
• /
• 2000

수용가의 수전전력은 개개의 설비의 소비전력이 합성된 것으로 시시각각 변화하고 있으나 시간적인 변동사항을 나타낸 것이 부하곡선이며 1일분을 30분 또는 1시간마다의 평균전력으로 나타낸 것이 일부하곡선이다.