• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7B
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• pp.411-421
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• 2007

It is well known that the biggest problem of wireless sensor networks is power conservation. There have been two major approaches to efficiently use energy in wireless sensor networks. One is to use a dynamic power management scheme and the other is to use energy efficient protocols. In the former, the power manager is responsible for managing the proper power state of CPU and each I/O with respect to the events, but the power manager does not concern about the internal operation of the underlying network protocols. Thus such conventional power managers can waste unpredicted power during communication period. On the other hand, the energy efficient protocols are just focused on the power saving operation of the radio PHY. In this paper, we introduce an energy-efficient power saving mechanism that can significantly reduce unwanted power consumption of wireless sensor nodes through the communication event-driven power management. We show that our scheme improves the energy conservation in the entire network through simulations.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.34-42
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• 2012

This paper analyses the energy saving basic power models in core IP networks, and proposes the adaptive buffer and burst scheme which is a possible energy saving method, and its implementation algorithm in core IP networks. Especially this paper describes the adaptive buffer and burst scheme dynamically varying the buffering interval B according to the input traffic volume of ingress router, and explains the operation principle of proposed scheme. This method is to adjust the buffering interval B according to input traffic volume of ingress router, that is increasing the interval B when input traffic volume is low, and decreasing the interval B when input traffic volume is high between some given interval regions. This method can gets the high energy saving effect as decreasing the transition number of idle/active in networks when input traffic volume is low, and decreasing the transition number of idle/active by the continuous of burst packets in transit router when input traffic volume is high. This paper shows the increasing of asleep rate for the energy saving of core IP networks and confirms the energy saving of core IP networks by the computer simulation. We confirmed that proposed method can be save the energy of IP networks by properly trade off network performances.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.1
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• pp.195-201
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• 2010

In this paper, a cooling system of high-power propulsion motor with Energy Saving System(ESS) is described. Normally, the cooling system for ship consists of fresh water pump, sea water pump, 3-way valve and cooler. In the cooling system, F.W(Fresh Water) and S.W(Sea Water) pump is operated on rated rpm, and the 3-way valve is controlled for preventing over-cooling. So, the consumption power of pump's motor is changed according to a sea water temperature. In the proposed cooling system, F.W. pump and S.W pump is controlled by inverter, and it is can be reduced the consumption power. Also, it is proved with simulation.

• Journal of Power Electronics
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• v.17 no.5
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• pp.1211-1222
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• 2017

In order to decrease the parameter sensitivity of deadbeat direct torque control (DB-DTC), an improved deadbeat direct torque control method for surface mounted permanent-magnet synchronous motor (SPMSM) drives is proposed. First, the track errors of the stator flux and torque that are caused by model parameter mismatch are analyzed. Then a sliding mode observer is designed, which is able to predict the d-q axis currents of the next control period for one-step delay compensation, and to simultaneously estimate the model parameter disturbance. The estimated disturbance of this observer is used to estimate the stator resistance offline. Then the estimated resistance is required to update the designed sliding-mode observer, which can be used to estimate the inductance and permanent-magnetic flux linkage online. In addition, the flux and torque estimation of the next control period, which is unaffected by the model parameter disturbance, is achieved by using predictive d-q axis currents and estimated parameters. Hence, a low parameter sensitivity DB-DTC method is developed. Simulation and experimental results show the validity of the proposed direct control method.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.5
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• pp.376-383
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• 2012

Owing to rapid development of power device and inverters, most of submarines adopt an eletric propulsion system. Although PMPM(Permanent Magnet Propulsion Motor) propulsion system has relatively higher power, energy conversion efficiency and smaller volume than engine propulsion system, it also produces large amount of heat due to current flowing inside motor coils and change of magnetic field induced by iron core. The produced heat in stator and inverter largely affects motor efficiency and bearing lubrication and causes thermal aging while the system is on operation. So, we analyze the existing cooling system and submarine ESS (Energy Saving System) cooling system whose power consumption is reduced. HILS(Hardware In the Loop System) technique is used for the modelling of the submarine cooling system. To confirm the ESS cooling system characteristic, HILS is simulated using LabVIEW with hardware. As a result, the ESS cooling system has the characteristic of better temperature stability and less power consumption than the existing one.

• Journal of Climate Change Research
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• v.7 no.1
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• pp.95-101
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• 2016

This study measured the amount of electricity consumed by the vending machines installed on campus and aim to come up with measures to address excessive consumption of electricity. We chose 10 universities located in the city of Seoul and Gyeonggi province and measured electricity consumption of 10 vending machines installed in each university. We then calculated annual electricity consumption of the machines based on previously calculated electricity consumption of 100 samples. According to the result of the calculation, it is estimated that the machines studied on consume 700 KWh a year. This amount could translate into approximately 3,000 tons of annual carbon emissions and 640 million KRW in annual electricity bills. It was also found that there is a significant difference between ordinary vending machines and machines certified for being eco-friendly and energy efficient, in terms of electric power consumption. It is expected that, if the ordinary machines are replaced with the eco-friendly and high-efficient machines, 640 KWh of electricity, 300 kg of carbon, and 61,640 KRW in electricity bills would be saved, which means 28% saving in energy, emissions and bills. In conclusion, we determined that, as one of the ways to reduce electric power consumption and carbon emissions, old vending machines on campus could be replaced with eco-friendly and high-efficient machines.

• Journal of the Korean Solar Energy Society
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• v.40 no.3
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• pp.21-31
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• 2020

The government mandates gradually zero energy building and Photovoltaic power generation systems installed in buildings are emerging as the most realistic alternative to increase the independence rate of building energy. In this study, we propose a method to reduce the power consumption of households by increasing the PV capacity of balconies and applying the method used the charged electric power stored in batteries after sunset. In order to evaluate the electric power energy savings of the residential BESS, a balcony PV 1.2 kW and a battery pack 2 kWh were installed for 9 houses in 4 apartments in Seoul and Gyeonggi-do. The BESS is charged when the balcony PV is generated electric power, and when solar power generation is finished, it supplies power to the electric appliances connected to the load. As a result of installing the solar PV module 1.2 kW and 2 kWh class BESS for 3 households located in Seoul and Gyeonggi-do, the average electric power consumption saving rate was 40%. The reduction in electricity consumption in the case of zero generation surplus power by maximizing the utilization rate of BESS has been improved to about 53%. Therefore, in order to increase the self-sufficiency rate of electric energy in apartment houses, it is effective to increase the solar photovoltaic capacity of the balcony and apply the residential BESS. In the future, it is believed that the balcony PV and home BESS will play a key role in achieving mandatory zero-energy housing.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.6
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• pp.439-446
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• 2022

Efforts to reduce carbon dioxide(CO₂) emissions are being carried out due to climate environmental problems. Eco-friendly ships are also being developed, and various energy saving measures have been developed and applied. In ships, researches have been conducted in various fields such as electric propulsion system and energy saving devices. In addition, the development of ships using various renewable energy, such as kite using wind power and wind power generation, has been carried out. This paper proposes a plan to use renewable energy for ships by applying wave generators to small ships. In 2016, 130 small domestic ships drifted by sea due to discharge of starting storage batteries, and discharge cases accounted for the largest portion of the causes of domestic ship accidents. This is due to the excessive use of storage batteries for starting the main engine by departing in a weak storage battery state for small ships. Accordingly, two type wave power generators - opened flow wave power generator and enclosed vibrator type wave power generator - are developed for charging a starting storage battery when the ships are stationary at sea or port. Opened flow wave power generator utilizes the flow of fluid in the ship by using wave induced ship motion. Enclosed vibrator type wave power generator utilizes the pendulum kinetic energy located in a ship due to wave induced ship motion.

• The Transactions of the Korean Institute of Power Electronics
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• v.2 no.3
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• pp.37-43
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• 1997

Microstepping control of two phase hybrid step motors provides high step resolution as well as smoothness of operation at low speed, and removes most of the resonance phenomena which is undesirable. This paper focuses on the development of a microstepping driver with enhanced performance. The developed microstepping driver can divide one step(l.8 degree) into 128 microsteps and supports current saving mode to remove the thermal problems which results from long time operation.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.25-27
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• 2004

Power Saving는 Portable 무선 기기 전반에 걸쳐 중요한 연구 과제로서, 에너지 절감을 위해 많은 protocol들이 제안되고 있다. 한편 에너지의 절감은 송수신 성능의 감소라는 문제점을 갖기 때문에 PS(Power Saving) protocol 설계상의 주요 과제는 이 trade-off에 대하여 송수신성능의 희생을 최소화 하면서 에너지 절감율을 대폭 향상 시키는 데에 있다. 본 논문에서는 저자들이 [1]에서 이미 제안한 바 있는 SPFAI(Synchronized Periodically-Fully-Awake-Interval ) Protocol을 개선하여 한층 더 효율적인 PS protocol을 제시하고 기존 SPFAI과의 성능비교를 위하여 대표적인 공개 network simulator인 NS2[2]를 이용하여 제안된 protocol의 성능을 검증한다.