• KEPCO Journal on Electric Power and Energy
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• 제1권1호
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• pp.9-13
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• 2015

Energy storage systems (ESS) can be used to provide frequency regulation services in a power system to replace traditional frequency regulation power plants. Battery ESS, in particular, can provide "fast-responding frequency regulation," wherein the facility can respond immediately and accurately to the frequency regulation signal sent by the system operator. This paper presents the development and the trial run results of a frequency regulation control system that uses large-scale ESS for use in a large power system. The control system was developed initially for the 4 MW ESS demonstration facility in Jocheon Jeju Island, and was further developed for use in the 28 MW ESS facility at the Seo-Anseong substation and the 24 MW ESS facility at the Shin-Yongin substation to provide frequency regulation services within mainland Korea. The ESS facility in Seo-Anseong substation responds to a sudden drop in frequency via governor-free control, while the ESS facility in Shin-Yongin responds via automatic generator control (AGC).

• 대한의용생체공학회:의공학회지
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• 제15권4호
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• pp.383-388
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• 1994

일정한 단속 주파수(triggering frequency)를 지닌 청각자극의 반송 주파수(carrier ferquency, pure tone)를 1kHz에서 3kHz까지 0.5kHz단위로 증가시키면서, 이에 반응하는 뇌전위를 디지탈 EEG측정장치를 이용하여 총 7초 동안 1kHz의 sampling frequency로 컴퓨터로 전송하였다. 먼저 신호의 pseudo-phase space분석을 통해 뇌전위의 진폭특성을 파악하였다. 이러한 해석은 생리학적으로 밝져진 소리의 반송주파수와 소리의 크기 인지사이의 상관관계와 잘 일치함이 확인되었다. 또한 이 신호외 Lyapunov exponent 분석을 통해 신호의 발산 특성을 물리적으로 파악하고, 이러한 특성을 이미 여러가지 접근법에 의해 밝혀져 있는 생리학적 실험결과와 관련지어 해석함으로써 반송 주파수에 반응하는 뇌의 mechanism을 뇌전위 측정에 의해서 검출이 가능함을 확인할 수 있었다.

• 대한의용생체공학회:의공학회지
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• 제28권1호
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• pp.24-28
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• 2007

Presuming that firing neurons have motions inside the MRI magnet due to the interaction between the neuronal magnetic field and the main magnetic field, we applied motion encoding gradients to dissected snail ganglia to observe faster responding MRI signal than the BOLD signal. To activate the snail ganglia in synchronization with the MRI pulse sequence, we used electrical stimulation with the frequency of 30 Hz and the pulse width of 2s. To observe the fast responding signal, we used the volume selected MRI sequence. The magnetic resonance signal intensity, measured with 8 ms long motion encoding gradient with a 20mT/m gradient strength, decreased about $3.46{\pm}1.48%$ when the ganglia were activated by the electrical stimulation.

• Journal of Power Electronics
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• 제18권1호
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• pp.195-203
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• 2018

In the variable speed Wind Turbine based on ElectroMagnetic Coupler (WT-EMC), a synchronous generator is coupled directly to the grid. Therefore, like conventional power plants, WT-EMC is able to inherently support grid frequency. However, due to the reduced inertia of the synchronous generator, WT-EMC is expected to be controlled to increase its output power in response to a grid frequency drop to support grid frequency. Similar to the grid frequency support control of Type 3 or Type 4 wind turbine, inertial control and droop control can be used to calculate the WT-EMC additional output power reference according to the synchronous generator speed. In this paper, an experimental platform is built to study the grid frequency support from WT-EMC with inertial control and droop control. Two synchronous generators, driven by two induction motors controlled by two converters, are used to emulate the synchronous generators in conventional power plants and in WT-EMCs respectively. The effectiveness of the grid frequency support from WT-EMC with inertial control and droop control responding to a grid frequency drop is validated by experimental results. The selection of the grid frequency support controller and its gain for WT-EMC is analyzed briefly.

• 한국소음진동공학회논문집
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• 제16권5호
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• pp.521-528
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• 2006

The vibration fatigue is suitable case of fatigue problem that system is exposed to the random or other irregular sources. Even some kinds of effort using power spectral density (PSD) and statistical concept was presented to cope with the intangible force signal, it is still lack of providing a reasonable solution when its exciting frequency is near or beyond of first eigenvalue. In this paper, energy approach method is presented to calculate a vibration induced fatigue damage in frequency domain. Since the corresponding damage become much larger than nominal case when the vibration is coupled with a mode shape of given structure, the new technique compensate the characteristics of structure with a measured frequency response function (FRF) between forcing acceleration and responding stress.

• Journal of Medicine and Life Science
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• 제21권1호
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• pp.1-10
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• 2024

The purpose of this study is to determine the issues of supplementation and improvement to prepare for the outbreak of new infectious diseases such as new variants of coronavirus disease 2019 (COVID-19) to guide work for a strategic new response to infectious disease. Public officials of Jeju Special Self-governing Province and health personnel responding to COVID-19, working at six public health centers in Jeju-do region were administered a survey about additional preparations to be made in the future, based on the period when COVID-19 was treated legally as a first-class infectious disease. Frequency analysis was conducted on the collected data. The Likert 5-point scale and Kruskal-Wallis test were used to compare the scores for effective response to emerging infectious diseases according to demographics. Among the important factors identified for effective response to new infectious diseases, 'facilitation of cooperation with public institutions' and 'facilitation of cooperation with private institutions' had the highest scores. In the future, when a patient presents with a new infectious disease, the step that needs to be supplemented in each phase of the public health center's response is 'immediate response team operation'. Further, public health centers responded that 'expansion of dedicated personnel related to infectious diseases' needs to be improved to respond to new infectious diseases. Along with the results of this study, considering the difficulties experienced by health personnel responding to new infectious diseases in preparation for future outbreaks of new infectious diseases, and to respond effectively, detailed and clear guidelines for responding to quarantine of patients of new infectious diseases will be needed.

• 생태와환경
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• 제37권3호통권108호
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• pp.304-312
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• 2004

수 생태계 내에서 흔히 볼 수 있는 3영양단계 먹이사슬 구조를 이루는 종들이 밀도비 의존 모델로써 구현 될 때 외부 환경에 대해서 어떻게 반응하는지를 연구하였다. 환경 요인은 주기적 요인과 일반적 노이즈 두 부분으로 나누었다. 주기적 요인이 온도로써 대표되었을 때 온도변이를 바이어스와 주기로 나누었고, 기타 복합적인 노이즈는 가우스 분포로 나타내었다. 온도변이 바이어스 ${\varepsilon}$, 온도주기 ${\Omega}$, 및 가우스 노이즈 크기 ${\'{O}}$가 서로 결합하여 3영양단계 먹이사슬에서 개체군 멸절을 포함한 다양한 개체군 동태를 보여 주었다. 변수의 적절한 값에 따라 '안정된 제한 사이클'이나 '이상한 끌개'를 보여 주었으며, 전체적으로 개체군 동태는 환경 변수에 따라 민감하게 반응하였고, 포식자 및 최상위포식자 개체군의 멸절시간이 조절되었다.

• Journal of Power Electronics
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• 제19권4호
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• pp.956-967
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• 2019

This paper introduces a virtual signal injected maximum torque per ampere (MTPA) control strategy for direct-torque-controlled five-phase interior permanent magnet synchronous motor (IPMSM) drives. The key of the proposed method is that a high frequency signal is injected virtually into the stator flux linkage. Then the responding stator current is calculated and regulated to compensate the amplitude of the flux linkage. This is done according to the relationship between the stator current and the stator flux linkage. Since the proposed method does not inject any real signals into the motor, it does not cause any of the problems associated with high-frequency signals, such as additional copper loss and extra torque ripple. Simulation and experimental results are offered to verify the effectiveness of the proposed method.

• 전기학회논문지
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• 제67권5호
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• pp.617-625
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• 2018

Since FERC order 755 was published, each frequency regulation market rules of the North American ISO/RTO have been revised in many parts. In 2016, the domestic CBP market has also changed its market rules to allow ESS to participate in the frequency regulation reserve services(Governor Free and Automatic Generation Control). This paper compares and analyzes the changed North American ISP/RTO market and domestic CBP market rules. In particular, we compare PJM and CAISO frequency regulation market pricing mechanism and settlement rules with the settlement rules of the domestic CBP market and compare the factors of each market used to compensate the participating resources in terms of resource dependency and accuracy.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1122-1127
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• 2004

an isolated droplet combustion exposed to pressure perturbations in stagnant gaseous environment is numerically conducted. Governing equations are solved for flow parameters at gas and liquid phases separately and thermodynamic parameters at the interfacial boundary are matched for problem closure. For high-pressure effects, vapor-liquid interfacial thermodynamics is rigorously treated. A series of parametric calculations in terms of mean pressure level and wave frequencies are carried out employing a n-pentane droplet in stagnant gaseous air. Results show that the operating pressure and driving frequency have an important role in determining the amplitude and phase lag of a combustion response. Mass evaporation rate responding to pressure waves is amplified with increase in pressure due to substantial reduction in latent heat of vaporization. Phase difference between pressure and evaporation rate decreases due to the reduced thermal inertia at high pressure. In addition to this, augmentation of perturbation frequency also enhances amplification of vaporization rate because the time period for the pressure oscillation is much smaller than the liquid thermal inertia time. The phase of evaporation rate shifts backward due to the elevated thermal inertia at high acoustic frequency.