• 한국지열·수열에너지학회논문집
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• 제16권4호
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• pp.24-30
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• 2020

Ground source heat pump (GSHP) systems are actively introduced as cooling and heating conditioning systems of buildings due to annual stable performance and easily maintenance. However, ground temperature imbalance is occurred when the GSHP is used for a long period. Therefore, in this study, we proposed the operation method of the system that considered the recovery time of heat source temperature. The entering water temperature (EWT) and heat exchange rate (HER) were comparatively analyzed according to the continuous and intermittent operation. Furthermore, the underground thermal environment was evaluated by numerical analysis model. As the result, the intermittent operation was a maximum of 12.3% higher HER during the heating period than the continuous operation. In addition, the overall ground heat source temperature at the intermittent operation was higher than it at the continuous operation.

• 한국가스학회지
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• 제11권3호
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• pp.40-43
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• 2007

스택의 디자인과 운전조건을 최적화하여 PEMFC stack의 성능을 상당히 증진시킬수 있다. 그러한 결과로, 500시간의 DSS(Daily Start-up & Shutdown) 누적 운전후에 일별 운전성능은 조금의 편차가 있었지만 (0.02-0.9%), 스택의 성능은 거의 변화가 없음을 알 수 있었다. 따라서 PEMFC 시스템의 상용화를 위해서는 스택의 수명 및 운전의 신뢰성을 향상시켜야 한다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.134-138
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• 1999

For the stable operation of high speed aerostatic spindle, the low rotational inertia and high damping ratio of spindle shafts as well as high fundamental natural frequency are indispensable. Conventional steel spindles are not appropriate for very high speed operation because of their high rotational inertia and low damping ratio. In this study, the composite spindles with aerostatic bearing were designed and manufactured with carbon fiber/epoxy composite. The fundamental natural frequency of the composite spindle was evaluated through the modal testing.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.368.1-368.1
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• 2014

We proposed amorphous GeSe-based ReRAM device of metal-insulator-metal (M-I-M) structure. The operation characteristics of memory device occured unipolar switching characteristics. By introducing the concepts of valance-alternation-pairs (VAPs) and chalcogen vacancies, the unipolar resistive switching operation had been explained. In addition, the current transport behavior were analyzed with space charge effect of VAPs, Schottky emission in metal/GeSe interface and P-F emission by GeSe bulk trap in mind. The GeSe ReRAM device of M-I-M structure indicated the stable memory switching characteristics. Furthermore, excellent stability, endurance and retention characteristics were also verified.

• 한국통신학회논문지
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• 제33권4A호
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• pp.440-449
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• 2008

본 논문에서는 Inmarsat M4 시스템의 수신기의 실제 구현에 적합한 16-QAM (Quadrature Amplitude Modulation) carrier recovery loop를 제안한다. Inmarsat M4 시스템 규격에서 권고하는 frequency tolerance는 ${\pm}924\;Hz$ (Signal bandwidth: 33.6 kHz) 로서 이러한 상대적으로 큰 주파수 옵셋 환경에서 안정된 동작이 가능한 carrier recovery loop 설계가 요구된다. 일반적인 PLL(Phase Locked Loop) 만을 이용한 carrier recovery loop는 상대적으로 큰 주파수 옵셋 환경에서 안정적인 성능을 보장할 수 없으며, 이에 따라 본 논문에서는 상대적인 주파수 옵셋이 큰 환경에서도 안정적이 동작이 가능한 Inmarsat M4 시스템을 위한 carrier recovery loop 루프를 제안한다. 제안된 carrier recovery loop는 우선 carrier recovery 이전에 UW 신호 detection 을 위해 주파수 옵셋에 강인한 differential filter 기반의 noncoherent 방식의 detector를 이용하여 UW detection을 수행하였으며, 이후 초기 주파수 옵셋 포착을 위해 UW(Unique Word) 신호를 이용한 차동 방식의 CP(Cross Product)-AFC를 적용하였다. 또한 일반적으로 알려진 16-QAM NDA (Non Data Aided) 방식 대신 안정적인 jitter 성능을 위하여 16-QAM DD(Decision Directed) 방식의 PLL 을 적용하여 위상 추적을 수행하였으며, 성능 검증을 통해 제안된 16-QAM carrier recovery loop가 만족스러운 성능과 신뢰성 있는 동작이 가능함을 입증하였다.

• 한국산업융합학회 논문집
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• 제25권6_3호
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• pp.1199-1206
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• 2022

Fossil fuels are one of the various energy sources used by humans, and industrial development has been achieved by relying on fossil fuels for a long time in the past. In order to respond to the depletion of fossil fuels and climate change, the world is trying to build an eco-friendly energy ecosystem. Research on efficiency improvement using renewable energy and ESS in various ways for energy conversion is being promoted. In this paper, a microgrid for industrial complexes was designed, constructed, and demonstrated. It was operated in two modes: an independent mode that each plant generates and uses independently and a connected operation mode that allows energy sharing between factories. In the case of independent mode, PV and PCS were intermittently stopped and restarted according to the status change of SoC section of each site. But, in the case of the connected operation mode, stable power supply was confirmed through power transaction through the operation of the entire SoC. This paper presented and verified an algorithm to stably supply power to industrial complexes consisting of various consumers with different load characteristics.

• 전기학회논문지
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• 제65권1호
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• pp.73-80
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• 2016

The preliminary test for the dual mode plasma torch system was carried out to explore the operation properties in advance. The dual mode plasma torch system that is able to operate in transferred, non-transferred, or dual mode is very adequate for melting the mixed wastes including nonconductive materials such as concrete, asbestos, etc. since it exploits both the high efficiency of heat transfer to the melt in transferred mode and stable operation in non-transferred mode. Also, system operation including restarting is reliable and very easy. A stationary melter with a refractory structure was designed and manufactured considering the melting behavior of slags to minimize the refractory erosion. The power supply for the dual mode plasma torch system built with high power insulated gate bipolar transistor (IGBT) modules has functions for both current control and voltage control and is sufficient to suppress the harmonics during the operation of the plasma torch. The power supply provides two different voltages for transferred operation and non-transferred. It is confirmed that the operation voltage in transferred is always higher than non-transferred. The dual mode plasma torch system was successfully developed and is under operation for a melting experiment to optimize operation data.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2000년도 제1회 학술대회 논문집
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• pp.105-106
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• 2000

The positive slope of the current-voltage characteristic at pressure up to 850 torr was obtained using the closed microhollow cathode without the individual and/or distributed ballast. This indicates that the stable parallel operation of the discharge was also achieved using the closed microhollow cathode. The parallel operation makes it possible to manufacture de plasma displays with high pressure, small discharge current, and long lifetime.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.703-706
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• 1998

This paper presents an efficient substrate-bias generator(SBG)for low-power, high-density DRAM's The proposed SBG can supply stable voltage with switching the supply voltage of driving circuit, and it can substitude the small capacitance for the large capacitance. The charge pumping circuit of the SBG suffere no VT loss and is to be applicable to low-voltage DRAM's. Also it can reduce the power consumption to make VBB because of it's high pumping efficiency. Using biasing voltage with positive temperature coefficient, VBB level detecting circuit can detect constant value of VBB against temperature variation. VBB level during VBB maintaining period varies 0.19% and the power dissipation during this period is 0.16mw. Charge pumping circuit can make VBB level up to -1.47V using VCC-1.5V, and do charge pumping operation one and half faster than the conventional ones. The temperature dependency of the VBB level detecting circuit is 0.34%. Therefore the proposed SBG is expected to supply a stable VBB with less power consumption when it is used in low power DRAM's.

• KEPCO Journal on Electric Power and Energy
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• 제2권1호
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• pp.83-88
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• 2016

This paper describes the test results of plant minimum stable load (Pmin) for Ilijan Power Plant. The test was conducted on May 13 through 14, 2015 to investigate the plant operating and equipment condition in accordance with "Ilijan Plant Performance Test Procedure on Plant Minimum Stable Load" [1]. This paper also contains the assessment of the impact of Pmin to plant operating parameters and possible technical operating issues when operating at lower loads and to recommend the safe minimum load operation of Ilijan per block. In addition, this paper describes the performance calculation results of efficiency and heat rate depending on the load level.