• 상하수도학회지
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• 제33권6호
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• pp.481-489
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• 2019

As aeration is an energy-intensive process, its control has become more important to save energy and to meet strict effluent limits. In this study, predictive aeration control based on the respirometric method has been applied to the sequencing batch reactor (SBR) process. The variation of the respiration rate by nitrification was great and obvious, so it could be a very useful parameter for the predictive aeration control. The maximum respiration rate due to nitrification was about 60 mg O₂/L·h and the maximum specific nitrification rate was about 7.5 mg N/g MLVSS·h. The aeration time of the following cycle of the SBR was daily adjusted in proportion to that which was previously determined based on the sudden decrease of respiration rate at the end of nitrification in the respirometer. The aeration time required for nitrification could be effectively predicted and it was closely related to influent nitrogen loadings. By the predictive aeration control the aerobic period of the SBR has been optimized, and energy saving and enhanced nitrogen removal could be obtained.

• Journal of Advanced Marine Engineering and Technology
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• 제31권5호
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• pp.592-598
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• 2007

The fuel charge is getting higher in navigation cost. Therefore, shipowners try to find the method for reducing oil consumption. ESS(Energy Saving System) is one of he method. ESS is the system consisted with two inverters, ESS control unit and monitoring system. Two inverters control two main sea water cooling pumps. In the ESS control Unit, the control algorithm finds optimized point to decrease a power consumption of main sea water cooling pumps. Monitoring system observes ESS not to work improperly. ESS is experimented in the laboratory with real condition and analyzed in every view. After experiment, the result of the experiment shows that the control algorithm works correctly and safely. ESS has a plan to be operated in the ship soon. In that case, additional devices are needed to connect ESS with cooling system of the vessel. So the development of addition device is needed and being studied.

• Journal of Power Electronics
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• 제12권5호
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• pp.758-768
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• 2012

This paper presents the modeling and position-sensorless vector control of a dual-airgap axial flux permanent magnet (AFPM) machine optimized for use in flywheel energy storage system (FESS) applications. The proposed AFPM machine has two sets of three-phase stator windings but requires only a single power converter to control both the electromagnetic torque and the axial levitation force. The proper controllability of the latter is crucial as it can be utilized to minimize the vertical bearing stress to improve the efficiency of the FESS. The method for controlling both the speed and axial displacement of the machine is discussed. An inherent speed sensorless observer is also proposed for speed estimation. The proposed observer eliminates the rotary encoder, which in turn reduces the overall weight and cost of the system while improving its reliability. The effectiveness of the proposed control scheme has been verified by simulations and experiments on a prototype machine.

• 방사선산업학회지
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• 제9권2호
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• pp.103-109
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• 2015

More recently, companies that have obtained permission to use radioactive materials or radiation device and registered radiation workers have increased by 10% and 4% respectively. The increased use of radiation could have an effect on radiation safety control. However, there is not nearly enough manpower and budget compared to the number of workers and facilities. This paper will suggest a counteroffer thought analyzing pending issues. The results of this paper indicate that there are 47 and 31.3 workers per radiation protection officer in educational and research institutes, respectively. There are 20.1 persons per RPO in hospitals, even though there are 2 RPOs appointed. Those with a special license as a radioisotope handler were ruled out as possible managers because medical doctors who have a special license for radioisotope handling normally have no experience with radiation safety. The number of staff members and budget have been insufficient for safety control at most educational and research institutes. It is necessary to build an optimized safety control system for effective Radiation Safety Control. This will reduce the risk factor of safety, and a few RPOs can be supplied for efficiency and convenience.

• 한국산학기술학회논문지
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• 제21권10호
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• pp.8-15
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• 2020

딥러닝을 사용한 예측 방법은 동일한 예측 모델과 파라미터를 사용한다 하더라도 데이터셋의 특성에 따라 결과가 일정하지 않다. 예를 들면, 데이터셋 A에 최적화된 예측 모델 X를 다른 특성을 가진 데이터셋 B에 적용하면 데이터셋 A와 같이 좋은 예측 결과를 기대하기 어렵다. 따라서 높은 정확도를 갖는 예측 모델을 구현하기 위해서는 데이터셋의 성격을 고려하여 예측 모델을 최적화하는 것이 필요하다. 본 논문에서는 하루 대학 캠퍼스 전력사용량을 1시간 단위로 예측하기 위해 데이터셋의 특성이 고려된 예측 모델이 도출되는 일련의 방법을 단계적으로 제시한다. 데이터 전처리 과정을 시작으로, 이상치 제거와 데이터셋 분류 과정 그리고 합성곱 신경망과 장기-단기 기억 신경망이 결합된 알고리즘(CNN-LSTM: Convolutional Neural Networks-Long Short-Term Memory Networks) 기반 하이퍼파라미터 튜닝 과정을 소개한다. 본 논문에서 제안하는 예측 모델은, 각 시간별 24개 포인트에서 2%의 평균 절대비율 오차(MAPE: Mean Absolute Percentage Error)를 보인다. 단순히 예측 알고리즘만을 적용한 모델과는 달리, 단계적 방법을 통해 최적화된 예측 모델을 사용하여 단일 전력 입력 변수만을 사용해서 높은 예측 정확도를 도출한다. 이 예측 모델은 모바일 에너지관리시스템(Energy Management System: EMS) 어플리케이션에 적용되어 관리자나 소비자에게 최적의 전력사용 방안을 제시할 수 있으며 전력 사용 효율 개선에 크게 기여할 것으로 기대된다.

• 전력전자학회논문지
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• 제21권3호
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• pp.231-237
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• 2016

Recently, the interest in DC systems to achieve more efficient connection with renewable energy sources, energy storage systems, and DC loads has been growing extensively. DC systems are more advantageous than AC systems because of their low conversion losses. However, the DC-link voltage is variable during operation because of different random effects. This study focuses on DC voltage stabilization applied in stand-alone DC microgrids by means of voltage ranges, power management, and coordination scheme. The quality and stability of the entire system are improved by keeping the voltage within acceptable limits. In terms of optimized control, the maximum power should be tracked from renewable resources during different operating modes of the system. The ESS and VSDG cover the power shortage after all available renewable energy is consumed. Keeping the state of charge of the ESS within the allowed bands is the key role of the control system. Load shedding or power generation curtailment should automatically occur if the maximum tolerable voltage variation is exceeded. PSIM-based simulation results are presented to evaluate the performance of the proposed control measures.

• KIEAE Journal
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• 제17권5호
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• pp.69-76
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• 2017

Purpose: This study aimed at developing an Artificial Neural Network (ANN) model for predicting the amount of cooling energy consumption of the variable refrigerant flow (VRF) cooling system by the different set-points of the control variables, such as supply air temperature of air handling unit (AHU), condenser fluid temperature, condenser fluid pressure, and refrigerant evaporation temperature. Applying the predicted results for the different set-points, the control algorithm, which embedded the ANN model, will determine the most energy efficient control strategy. Method: The ANN model was developed and tested its prediction accuracy by using matrix laboratory (MATLAB) and its neural network toolbox. The field data sets were collected for the model training and performance evaluation. For completing the prediction model, three major steps were conducted - i) initial model development including input variable selection, ii) model optimization, and iii) performance evaluation. Result: Eight meaningful input variables were selected in the initial model development such as outdoor temperature, outdoor humidity, indoor temperature, cooling load of the previous cycle, supply air temperature of AHU, condenser fluid temperature, condenser fluid pressure, and refrigerant evaporation temperature. The initial model was optimized to have 2 hidden layers with 15 hidden neurons each, 0.3 learning rate, and 0.3 momentum. The optimized model proved its prediction accuracy with stable prediction results.

• Nuclear Engineering and Technology
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• 제56권1호
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• pp.70-77
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• 2024

A low energy ion irradiation system based on the deuterium arc ion source with a high perveance of 1 µP for a single extraction aperture has been successfully developed for the investigation of ion irradiation on plasma-facing components including the first mirror of plasma optical diagnostics system. Under the optimum operating condition for mirror testing, the ion source has a beam energy of 200 eV and a current density of 3.7 mA/cm². The ion source comprises a magnetic cusp-type plasma source, an extraction system, a target system with a Faraday cup, and a power supply control system to ensure stable long time operation. Operation parameters of plasma source such as pressure, filament current, and arc power with D₂ discharge gas were optimized for beam extraction by measuring plasma parameters with a Langmuir probe. The diode electrode extraction system was designed by IGUN simulation to optimize for 1 µP perveance. It was successfully demonstrated that the ion beam current of ~4 mA can be extracted through the 10 mm aperture from the developed ion source. The target system with the Faraday cup is also developed to measure the beam current. With the assistance of the power control system, ion beams are extracted while maintaining a consistent arc power for more than 10 min of continuous operation.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1613-1616
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• 2008

A Transcutaneous Energy Transmission System (TET) has been developed for the wireless energy transmission with two magnetically coupled coils. A resonance circuit is used to raise the induced voltage and current of the secondary coil. Its resonance frequency depends on the internal resistance of circuit and the transferred energy. Because the transferred energy usually changes in wide range, the output voltage is unstable and the energy transferring efficiency decrease. A push-pull class E amplifier is usedto generate high frequency AC voltage. To maintain proper resonance frequency, the voltage output of the amplifier was continuously monitored and adjusted to the optimized resonance frequency. Because of its high frequency (370 kHz), a phase lockedloop circuit and a comparator are used to monitor the output waveform. The results of experimentaldata show that the PLL circuit can increase the transmission efficiency and stabilize the output voltage of TET.

• 전기학회논문지
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• 제68권1호
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• pp.129-139
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• 2019

In order for a gun-launched guided projectile to glide to the maximum range, when to deploy the fin and start flight with guidance and control should be considered in range optimization process. This study suggests a solution to the optimal guidance problem for flight range maximization of the flight model of a guided projectile in vertical plane considering the aerodynamic properties. After converting the nonlinear Multi-Phase Optimal Control Problem to Two-Point Boundary Value Problem, the optimized guidance command and the best fin deployment timing are calculated by the proposed numerical method. The optimization results of the multiple flight rounds with various initial velocity and launch angle indicate that determining specific launch condition incorporated with the guidance scheme is of importance in terms of mechanical energy consumption.