• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.4
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• pp.535-540
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• 1986

본 연구에서는 소재의 3차원 변형, 즉 평면변형(sidewise spread)과 벌징변형 을 동시에 고려할 수 있는 간단한 동적가용 속도장을 제안하고 이를 클로버(clover) 시편의 업세팅 단조 해석에 적용해보기로 한다. 상계이론에 의한 전체 에너지 소비 율을 최소화시키면서 그때 그때의 높이 감소에 따른 단조 하중과 변형 형상을 구한다. 실험은 SM15C 탄소강을 이용하여 시편의 형상과 윤활조건을 바꿔가면서 상온에서 수행 한다.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10b
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• pp.592-594
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• 2003

이 논문에서는 wavelet과 sobel filter를 사용하여 영상의 객관적인 평가 점수를 계산하는 새로운 기법을 제안한다. 이 기법은 orthogonal wavelet 변환을 기초로 하고 있으며 원본 영상과 처리된 영상 데이터가 모두 가용하다는 것을 전제로 한다. Wavelet을 이용해 주파수에 따라 분할된 영상 정보를 이용해 각각의 부영역 별 차영상을 획득하고 이 획득된 영상의 에너지를 이용해 화질 평가 수치를 계산한다. 부영역 별로 획득된 영상은 일정한 크기의 블록으로 분할되어 동일한 블록 내에서 가용한 영상의 특징에 관한 정보(contrast, edge 영역의 분포 정도) 벡터와 내적하여 새로운 특징 벡터로 사용되고, 이 특징 벡터의 가중치를 최적화하여 높은 상관도의 화질평가 점수를 산출하게 된다.

• Journal of Power System Engineering
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• v.13 no.6
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• pp.22-28
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• 2009

열역학 제 2법칙의 관점의 열역학적 가용에너지인 엑서지 해석법을 적용하여 가솔린, 메탄올, M90 연료를 사용한 전기점화 기관의 성능해석을 수행하였다. 열역학적 사이클 해석을 위하여 사이클을 구성하는 각 과정은 열역학적 모델로 단순화하였고, 크랭크 각도에 따른 실린더의 압력과 작동유체를 구성하는 연료, 공기 및 연소생성물의 열역학적 물성 값들을 이용하여 각 과정에서의 엑서지와 손실 일을 계산하였다. 실험데이터는 단기통 전기점화기관을 가솔린, 메탄올과 M90(메탄을 90%+부탄 10%의 혼합연료)을 연료로 WOT(Wide Open Throttle), MBT(Minimum advanced spark timing for Best Torque), 2500rpm 조건으로 운전하여 측정하였다. 계산에 이용한 자료는 실험으로 측정한 크랭크 각도에 따른 연소실의 압력, 흡입공기와 연료유량, 흡입공기 온도, 냉각수 온도와 배출가스 온도 등이다. 이를 이용하여 각 과정에서의 엑서지와 손실 일을 계산하였으며 각 과정에서의 손실 일은 연소과정에서 가장 크며 팽창과정, 배출과정, 압축과정 및 흡입과정 순으로 크게 나타났다.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10d
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• pp.86-90
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• 2007

WSN는 초기에 센서 노드들이 배치되었을 때 이웃 센서 노드들 간 보안키를 안전하고 효율적으로 설정해야하고 에너지 소비를 최소화해야하며 네트워크의 생존성을 늘리기 위해 불필요한 키 관리 동작을 지양해야한다. 네트워크 레벨의 중앙 집중적인 키 관리는 센서노드 하나에 대한 취약성 공격이 전체 네트워크의 위협으로 가용성보장이 어렵다. 따라서 본 논문에서는 네트워크를 클러스터링 하여 센서노드 노출로 인한 네트워크 전체에 주는 피해를 줄이고자 구의 형태로 클러스터링 함으로써 동일 클러스터내의 노드수의 증가에도 경로키 수를 줄일 수 있게 하여 센서 노드의 에너지 소모를 감소시켜 가용성을 보장하였다.

• New & Renewable Energy
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• v.10 no.1
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• pp.20-29
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• 2014

The present study investigated the effects of thermal pre-treatment on the enhancement of anaerobic biodegradability of waste activated sludge at varied TS concentration levels. The activated sludges were thermally oxidized for 30 minutes at $80{\sim}200^{\circ}C$ with varied TS concentrations (2%, 4% and 6%). and then, sludge characteristics, solubilization efficiency and methane production yield of thermally pre-treated sludges were analyzed. The higher the temperature in the thermal pre-treatment, the higher the concentration levels of dissolved matters such as $SCOD_{Cr}$, $NH_4{^+}$ and VFAs, which indicates that the thermal pre-treatment facilitates the hydrolysis and acid fermentation. Furthermore, the solubilization efficiency was increased in proportion to the temperature rise at all TS concentrations and was reached at 68.9%, 55.6% and 53.1%, respectively, at $200^{\circ}C$. In the BMP test of the pre-treated sludges, higher methane production yields were observed as 0.313. 0.314 and $0.299m^3\;CH_4/kg\;VS_{add}$ at the condition of TS 2% ($160^{\circ}C$), 4% ($160^{\circ}C$) and 6% ($180^{\circ}C$), respectively, and degradation rate was increased by 84%, 79% and 65% compared with non-pretreated waste activated sludge. These findings suggest the effectiveness of thermal pre-treatment of waste activated sludge for anaerobic biodegradable process.

• Tunnel and Underground Space
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• v.32 no.5
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• pp.327-343
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• 2022

The standard work report for trucks was developed that records data on truck haulage operations in open-pit and underground mines, and to evaluate the performance of haulage operations. Work reports used in 5 mines in Korea was secured and analyzed, and items to be included in the standard work report were determined. By analyzing the formulas for key performance indicators (KPIs) proposed by the Global Mining Guidelines Group (GMG), it was possible to determine how to record time-related data. After selecting a limestone underground mine as a research area, the performance of haulage operations was evaluated using a standard work report. As a result, in terms of truck availability, uptime was 46.7%, and both physical and mechanical availability were 100%. In the case of utilization, use of availability was 88.2%, the asset utilization was 41.1%, and operating and effective utilization were 88.2% and 79.2%, respectively. Also, in terms of efficiency, operating efficiency was found to be 89.9%.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.46-48
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• 2020

본 논문에서는 전기자동차용 배터리의 충방전 시 단자전압이 배터리의 상하한 전압에 도달하지 않는 최대 가용 출력 전류 추정 알고리즘을 제안한다. 제안하는 알고리즘은 SOC에 따라 변화하는 내부 파라미터를 고려하여 일정 시간동안 배터리가 출력 가능한 최대의 전류를 추정함으로써 해당 시간 동안 배터리의 출력을 보장하고 배터리의 가용 에너지를 극대화한다. 알고리즘을 검증하기 위하여 전기자동차용 배터리를 이용한 실험 및 시뮬레이션을 진행한다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.12
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• pp.1573-1581
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• 2004

Thermodynamic principles are described with a new point of view. In present study, the interaction between two systems is focused instead of the behavior of a system in conventional thermodynamics. The state change of a system cannot occur by itself but it is the result of the interaction between systems. However, the interaction itself is also the result of another kind of interaction, the interaction between two interactions. To reconstruct thermodynamics with such a point of view, the reversible world is imagined, in which conservations and measurements are discussed. There exists a conserved quantity for each mode of reversible interaction. The conserved transferring quantity in the interaction between interactions is the effective work, which is supposed to be measurable and conserved in reversible world. Effective work is the primary concepts of energy. It is the key factor to explain measurements, energy conservation and energy dissipation. The concepts developed in reversible world are applied to the real world in which irreversible phenomena may occur. Irreversibility is the result of effective energy dissipation, in which effective work irreversibly changes into entropy. A quantitative relation between the disappearing effective work and the generated entropy is dissipation equation which is given by experiments. A special temperature scale to give a very simple type of the dissipation equation is the absolute temperature scale, which gives the conventional conservation of energy.

• Journal of IKEEE
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• v.19 no.2
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• pp.210-218
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• 2015

In this paper an auto-switching energy harvesting circuit using vibration and thermoelectric energy is proposed. Since the maximum power point of a thermoelectric generator(TEG) output and a vibration device(PEG) output is 1/2 of their open-circuit voltage, an identical MPPT controller can be used for both energy sources. The proposed circuit monitors the outputs of the TEG and PEG, and chooses the energy source generating a higher output voltage using an auto-switching controller, and then harvests the maximum power from the selected device using the MPPT controller. The proposed circuit is designed in a $0.35{\mu}m$ CMOS process and its functionality has been verified through extensive simulations. The designed chip occupies $1.4mm{\times}1.2mm$ including pads.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.2
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• pp.90-95
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• 2009

Sludge pre-treatment utilizing cavitation is one of the commercialized methods at present. Cavitation can be generated by two different methods, sonotrode and hydrodynamic principle, and there has been no direct comparison between the two methods. In this study, solubilization efficiency, changes in sludge size distribution, and the methane production potential after pre-treatment by the two methods were compared. The maximum solubilization efficiency per unit energy input with the two methods was similar, and was 302 mg ${\Delta}SCOD/g$ TS at the energy input of 0.18 kWh/L. Break-up of sludge flocs were dominant during the early period of pre-treatment, while cell disintegration continued through the pre-treatment with the increase in the number of particles with less than 1 ${\mu}m$. BMP test results indicated that the methane potential increased up to 24.3% without differences between the two pre-treatments, and the increase in methane potential did not proportional to energy input. Although the energy efficiency of the two methods was quite similar, hydrodynamic methods might be a better choice for field application considering the operation and maintenance cost, and its potential improvement in energy efficiency.