• 지구물리와물리탐사
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• 제11권1호
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• pp.60-67
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• 2008

이 논문에서 우리는 해저용 수신기들과 이동하는 전기적 양극송신기의 한 조로 이루어진 전형적인 해양 인공송신 전자탐사 (MCSEM) 방법에 의해 얻어진 자료 해석에 전자탐사 구조보정법의 적용을 다룬다. 이 연구에서와 같이 다중 송신기와 다중 수신기를 이용해 획득된 자료는 방대한 컴퓨터 계산을 요하기 때문에 MCSEM자료의 3차원적 해석은 매우 도전적인 문제이다. 이와 동시에, 우리는 조밀하게 송신 및 수신기를 위치 시켜야 하는 이 MCSEM시스템은 구조보정법의 적용에 아주 적합하다는 것을 보여줄 것이다. 구조보정장 계산의 속도를 증가시키기 위해 우리는 직접 개발한 다중격자 준선형 (MGQL) 근사법에 기초한 적분방정식 해의 빠른 형태를 적용시켰다. 이 논문에서 공식화된 구조보정 영상 원리는 전형적인 해저 석유 저류층 모델에 적용되어 시험 되었다.

• 한국초전도ㆍ저온공학회논문지
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• 제25권3호
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• pp.18-21
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• 2023

Pollution of the environment by micro-plastics is now a worldwide problem. Plastics are difficult to decompose and put a great load on the marine environment. Especially a plastic with a size of 5 mm or less is defined as micro-plastic and are carried by ocean currents over long distances, causing global pollution. These are not easily decomposed in the natural environment. In this paper, we aimed to experimentally demonstrate that micro-plastics in seawater can be continuously separated by electromagnetic Archimedes force. Using polyethylene particles of 3 mm in diameter as the separation target, a flow channel was fabricated and separation conditions were investigated by particle trajectory calculations for separation experiments. Based on the calculation results, a solenoid-type superconducting magnet was used as a source of magnetic field to conduct separation experiments of micro-plastics in seawater. Although a high separation rate was assumed in the simulation results, the experimental results did not show any significant improvement in the separation rate due to the electromagnetic Archimedes force. It was found that the gas generated by the electrolytic reaction may have inhibited the migration of the particles.

• 지구물리와물리탐사
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• 제1권2호
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• pp.87-91
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• 1998

쓰레기 매립장 부근지역에 대해 전자탐사, GPR 탐사, 전기탐사 등 물리탐사를 실시하여 이들을 통한 토양오염의 조사 및 평가에 대한 적용가능성을 연구하였다. 연구결과 전자탐사법은 오염지 역의 수평적 분포현황 및 오염경로 파악에 탁월한 효과를 보이며 그 방법의 간편성 및 신속성에 비추어 볼 때 최우선적으로 적용해야 할 탐사법으로 판단된다. 전기탐사법은 오염지역의 수직적 분포 현황 파악에 효과적이다. 경계면의 정량적 해석 및 기초 지질구조,지하수면 등의 파악 가능성,탐사수행의 간편성 등을 고려할 때 천부조사에는 GPR 탐사법이 유리할 것으로 판단되나 심부 정보를 얻기 위해서는 두 탐사법을 동시에 적용하면 좋을 것이다.

• 한국전자파학회논문지
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• 제30권5호
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• pp.356-364
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• 2019

최근 정부는 주파수의 효율적 이용을 위하여 이용자에게 주파수의 경제적 가치를 부과하겠다는 정책을 발표한 바있다. 이에 따라 다양한 용도의 주파수에 대한 경제적 가치를 측정하려는 시도가 있을 것으로 예상된다. 이러한 측면에서 본 연구는 주파수 공용통신 용도의 주파수의 경제적 가치를 최소비용대안 방식으로 측정하고자 하였다. 이 경우, 주파수의 가치는 해당 주파수가 주어지지 않을 경우 다른 방법으로 동 서비스를 제공하는데 들어가는 비용으로 측정할 수 있으며, 주파수 공용통신의 경우 이는 LTE 망을 통하여 제공하는데 소요되는 비용이 된다. 즉, TRS 용 주파수의 가치를 LTE 망 이용대가, 설비투자비용, 단말기 보조금, 보상금 등의 합계로 추정해 보았다. 본 연구의 결과는 향후 다른 용도의 주파수 이용대가 산정에도 시사점을 제공할 수 있을 것으로 기대된다.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
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• pp.321-327
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• 2003

[ $CO_2$ ] sequestration in oil reservoirs can be one of the most effective strategies for long-term removal of greenhouse gas from atmosphere. This paper presents an advantage of the localized nonlinear approximation of integral equation solutions for inverting crosswell electromagnetic data, which are observed as a part of pilot project of $CO_2$ flooding at the Lost Hills oil field in central California, U.S.A. To monitor the migration of $CO_2$, we have used 2-D cylindrically symmetric and 2.5-D tomographic inversion methods. These two schemes produce nearly the same images if the borehole separation is large compared with the skin depth. However, since the borehole separation is much less than five skin depths in this $CO_2$ injection experiment, the 2.5-D model seems to be more reliable than the 2-D model. In fact, the pre-injection 2.5-D image is more successfully compared with induction logs observed in the two wells than the 2-D model. From the time-lapse crosswell imaging, we can confirm the replacement of brine with $CO_2$ makes a decrease of conductivity.

• Journal of Power Electronics
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• 제19권5호
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• pp.1303-1314
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• 2019

This paper studies the harmonic characteristics of ship electric propulsion systems and their treatment methods. It also adopts effective measures to suppress and prevent ship power systems from affecting ship operation due to the serious damage caused by harmonics. Firstly, the harmonic characteristics of a ship electric propulsion system are reviewed and discussed. Secondly, aiming at problems such as resonant frequency and filter characteristics variations, resonance point migration, and unstable filtering performances in conventional passive filters, a method for fully tuning of a passive dynamic tunable filter (PDTF) is proposed to realize harmonic suppression. Thirdly, to address the problems of the uncontrollable inductance L of traditional air gap iron core reactors and the harmonics of power electronic impedance converters (PEICs), this paper proposes an electromagnetic coupling reactor with impedance transformation and harmonic suppression characteristics (ECRITHS), with the internal filter (IF) designed to suppress the harmonics generated by PEICs. The ECRITHS is characterized by both harmonic suppression and impedance change. Fourthly, the ECRITHS is investigated. This investigation includes the harmonic suppression characteristics and impedance transformation characteristics of the ECRITHS at the fundamental frequency, which shows the good performance of the ECRITHS. Simulation and experimental evaluations of the PDTF are carried out. Multiple PDTFs can be configured to realize multi-order simultaneous dynamic filtering, and can effectively eliminate the current harmonics of ship electric propulsion systems. This is done to reduce the total harmonic distortion (THD) of the supply currents to well below the 5% limit imposed by the IEEE-519 standard. The PDTF also can eliminate harmonic currents in different geographic places by using a low voltage distribution system. Finally, a detailed discussion is presented, with challenges and future implications discussed. The research results are intended to effectively eliminate the harmonics of ship electric power propulsion systems and to improve the power quality of ship power systems. This is of theoretical and practical significance for improving the power quality and power savings of ship power systems.

• Journal of Electrical Engineering and Technology
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• 제12권5호
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• pp.2021-2030
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• 2017

In this paper, the unipolar corona-needle charger was developed and its capabilities were both numerically and experimentally investigated. The experimental corona discharges and particle losses in the charger were obtained at different corona voltage, aerosol flow rate and particle diameter for positive and negative coronas. Inside the charger, the electric field and charge distribution and the transport behavior of the charged particle were predicted by a numerical simulation. The experimental results yielded the highest ion number concentrations of about $1.087{\times}10^{15}ions/m^3$ for a positive corona voltage of about 3.2 kV, and $1.247{\times}10^{16}ions/m^3$ for a negative corona voltage of about 2.9 kV, and the highest $N_it$ product for positive and negative coronas was found to about $7.53{\times}10^{13}$ and $8.65{\times}10^{14}ions/m^3$ s was occurred at the positive and negative corona voltages of about 3.2 and 2.9 kV, respectively, and the flow rate of 0.3 L/min. The highest diffusion loss was found to occur at particles with diameter of 30 nm to be about 62.50 and 19.33 % for the aerosol flow rate of 0.3 and 1.5 L/min, respectively, and the highest electrostatic loss was found to occur at particles with diameters of 75 and 50 nm to be about 86.29 and 72.92 % for positive and negative corona voltages of about 2.9 and 2.5 kV, respectively. The numerical results for the electric field distribution and the charged particles migration inside the charger were used to guide the description of the electric field and the behavior of charged particle trajectories to improve the design and refinement of a unipolar corona-needle charger that otherwise could not be seen from the experimental data.