• 전기학회논문지
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• 제64권4호
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• pp.529-536
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• 2015

With the growing interest of microgrid all over the world, many studies on microgrid operation are being carried out. The battery energy storage system(BESS) is a key equipment for effective operation of the microgrid. In this paper, we analyze the characteristics of the charge and discharge output voltage of the battery and the characteristics of the life-span variation and the investment cost when the state-of-charge (SOC) changes. The formulas to represent the quality of the charge and discharge output voltage of the battery and the economics due to the life-span variation and the investment cost according to DOD(Depth of Discharge) are derived. The methodology of determining the proper operation ranges of the battery SOC with varying the weighting of the quality of its charge and discharge output voltage of the battery and the economics due to its life-span variation and the investment cost is presented using these formulas.

• 한국추진공학회지
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• 제25권3호
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• pp.14-25
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• 2021

개도에 따른 핀틀 분사기의 분무특성에 대한 실험적 연구를 수행하였다. 분사조건에 따른 핀틀 분사기의 유량계수를 확인하였으며, 분무 이미지 촬영을 통해 분무각을 측정하였다. 유량계수 측정 결과 바깥쪽 분사기는 실험조건에 걸쳐 유량계수 변화가 크지 않았지만 안쪽 분사기는 유량에 따른 유량계수 변화가 큰 것을 확인하였다. 분무각 측정결과 분무가 완전 발달되는 조건에서는 분무각의 변화가 크지 않았으나 낮은 유량에서 분무가 완전 발달되지 않는 경우가 있었다. 이를 통해 핀틀 분사기의 추력조절 가능성을 확인하였다.

• 전기전자학회논문지
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• 제28권1호
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• pp.14-19
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• 2024

주택용 BESS에 적용하기 위한 재활용 셀 성능을 파악하기 위해 지난 5년 동안 사용한 셀을 선택하였다. 시험에 사용된 셀의 기본 사양은 공칭 전압이 3.7[V], 공칭 용량이 2,200[mAh], 충전 전압이 4.05[V], 연속방전전류가 1[C](2,200[mA]), 연속충전전류가 0.5[C](1,100[mA]) 이다. 새 셀의 경우 내부저항은 21.3±1[mΩ]인데, 재활용 셀의 경우 평균 내부저항이 25.38[mΩ]로 나타나 약 19.1[%] 상승하였다. 충·방전 용량은 새 셀에 비해 약 18.9~19.3[%] 정도 낮게 나타났다. 내부저항과 충·방전 용량이 셀의 노화에 상호 밀접하게 연관되어 있으므로 BESS에 적용할 셀은 초기 내부저항보다 1.5배 이하이고 70[%] 이상의 충·방전 용량 성능을 갖는 제품을 사용할 필요가 있다.

• 한국농공학회지
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• 제10권1호
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• pp.1394-1408
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• 1968

The tidal discharge is defined as the quantity of water flowing through a certain cross-section per unit of time, in contrast to river discharges, tidal discharges change periodically in magnitude and direction. Thus the total volumes of water flowing into again out of the system-called flood volume and ebb volume, respectively, depend on both the tidal and the river discharges. To ditermine the tidal discharge and the flood and ebb volumes of the Yong-san river, the discharges were measured at spring, mean and neap tide and simultaneous gage reading were taken at Samhak-do, Lower Myo-do, Myongsan-ni and Naju. The general procedure for measuring the tidal discharges was as follows. First, several cross-sections were measured and one of them was chosen. First, several cross-sections were measured and one of them was chosen. Then verticals were serected in the chosen cross section. Because comparatively few verticals should be representative of the discharge distribution over the river profile, the selection was done in accordance with the somtimes irregular bottom profile. The velocities were measured with the same current meters. The observations which included water level readings were continued for a period of about 13 hours. The current direction meter, a pyramid shaped resistance body, suspend in the water on a thin wire. The bubble in a circular tilting level fixed to the wire indicates the direction of the current. Reading were taken at intervals of 1m for depths of 10m or less, and for depths over 10m at intervals of 2m, going downwards and upwards. The averages of the two velocities were used for the computation of the discharges. The discharges and the flood and ebb volumes were ditermined by a graphical method. The mean velocities, corrected for their direction when necesary, were ditermined for each time interval and each vertical, and these velocities were plotted against the time. The resulting curves show possible mistakes very clearly, and the effect of observation errors could be reduced. The corrected velocities read from the curve at half-hour intervals were multiplied by the depth at the virtical at the corresponding time. The discharges thus found were ploted against the position of the vertical in the transit and joined by a smooth curve, integration of the curve rendered the total discharges as they occurred of half-hour intervals. Plotting these total discharges against the time yeilded during the day. The flood and ebb volumes were obtained by integration of the total discharge curve.

• 농약과학회지
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• 제16권1호
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• pp.11-20
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• 2012

식량증산을 위해 농약사용량이 증가함에 따라, 식품 중 잔류농약의 안전성 문제에 대한 관심은 날로 증가하고 있지만 효율적인 잔류농약 저감화 방법은 보급되지 못하고 있는 것이 현실이다. 최근에 기체 플라즈마에 의한 오염물질 제거는 고효율성과 환경친화성으로 많은 주목을 받고 있다. 특히 플라즈마는 수질 및 고체 표면 중 유기인계살충제, 페놀, 벤조산, 염료, 니트로벤젠과 같은 오염물질의 제거에 큰 효과가 있는 것으로 알려지고 있다. 본 연구는 플라즈마를 이용하여 농식품 중에 잔류되는 농약의 제거 가능성을 알아보고자 대기압 및 감압플라즈마 플라즈마 발생 상태에서 60종의 농약을 대상으로 분해양상을 파악해보고자 시도하였다. 시험용 농약을 유리판에 도포 후 대기압 및 감압 플라즈마 발생기에서 5분간 조사 후 잔류량을 확인 한 결과 대조구의 회수 분석결과가 70% 미만인 18종을 제외한 41종의 농약 분해율이 66.88-100%를 나타내었고, clothianidin은 감압플라즈마하에서 26.9%이 분해율을 보였다.

• 한국군사과학기술학회지
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• 제21권5호
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• pp.665-674
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• 2018

In this paper, we propose a development results of a D-type non-rechargeable lithium battery($Li/SOCl_2$) on improvement in a low cost protection circuit of discharge for domestic military power source. According to this study, we describe a new design and product with 8-bit microcontroller in the protection circuit which can estimate state of health of the battery regardless of occurring an initial voltage delay. Also this paper discuss and facilitate development as solution to a safety about the non-rechargeable lithium batteries. As a result, we verified a quality of the protection circuit by a development test and evaluation(DT&E) process.

• 한국농공학회논문집
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• 제51권6호
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• pp.91-96
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• 2009

This study describes a zero discharge and reuse system developed for rural areas. The purpose of the system is decontamination of used irrigation water for down-stream usage and reuse of wastewater in rural villages for preventing water shortage problem expected to happen in near future. The system consists of anoxic, FES (Ferrous Electricity System), Oxic, Cralifier processes. The main feature of the system is to remove phosphorous by using Fe-ionizing module. Indoor experiments were undertaken with a trial product of the system to test its performance. The removal capacities of T-P, T-N, and BOD were examined. Also the proper time for the replacement of iron plate module was tested as well as the efficiency of T-P removal rate based on the usage of an automatic washing system for the iron plate. As results, the system showed very good water purification performances through obtaining the results of over 90% removal rates from T-P, BOD, and 67% from T-N. The proper time period for replacement of iron plate was maximum 2 years, and also efficiency of T-P removal rate found to be greatly influenced by the usage of an automatic washing system from the test.

• Journal of Astronomy and Space Sciences
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• 제35권2호
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• pp.93-103
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• 2018

Non-specular, vertically upward transit, fast-moving radar echoes are observed in the summer polar upper mesosphere near 90 km using 52 MHz VHF radar at Esrange, Sweden. By resolving maximum echo power movement, the unusual meteor trails propagate vertically upward with taking horizontal displacements at an initial speed of 10 km/s exponentially decreasing with increasing height from 85-89 km, lasting for 3.5 sec. Another upward transit is observed as following a downward transit echo target in about ~1 sec, lasting over 5 sec. The upward motion cannot be explained with the dynamics of penetrating meteors or by atmospheric dynamics. The observation proposes that secondary produced plasma jets occurring from meteor trail are possibly responsible for upward fast moving echoes. The long-lasting (3-5 sec), ascending meteor trails at speeds of a few $10^4m/s$ are distinctive from any previous occurrences of meteors or upper atmospheric electrical discharges in the aspect of long-lasting upward/downward motions. This result possibly suggests a new type of meteor-trail leader discharge occurring in the summer polar upper mesosphere and lower thermosphere.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.1176-1179
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• 2003

Low-Pressure inductively coupled RF discharge sources have important industrial applications mainly because they can provide a high-density electrodeless plasma source with low ion energy and low power loss. In an inductive discharge, the RF power is coupled to the plasma by an electromagnetic interaction with the current flowing in a coil. In this paper, the experiments have been focussed on the electric characteristic and carried out using a single Langmuir probe. The internal electric characteristics of inductively coupled Ar RF discharge at 13.56 [MHz] have been measured over a wide range of power at gas pressure ranging from $1{\sim}70$ [mTorr].

• 환경위생공학
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• 제23권4호
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• pp.65-71
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• 2008

To drive efficiently total water pollution load management, needs to calculate the exact load emissions, pollution load allocation and implementation evaluation in each unit area of watershed and accurate and regular flow of data. For these reasons, the Nakdong River TMDL Research Center has produced directly or indirectly in the average interval of eight days (30 times or more / year) 41 points for unit area of the total water pollution load management and 8-point of municipal requirement for a total of 49 branches as a flow data in 2004 from August. This acquired the survey flow is evidence of trends and changes each point in the Nakdong River based on time, such as 10 years based on average design flow available to the foundation of the summit as the major water policy is to be utilized. This study was performed on actual discharge measuring data and introduced performance results each drainage basin of Nakdong River from 2004 to 2008 over the total of past five years.