• 제목/요약/키워드: magnetic core

검색결과 964건 처리시간 0.035초

Ag@Fe3O4 코어-쉘 나노입자의 광학적 특성 (Optical Properties of Ag@Fe3O4 Core-Shell Nanoparticles)

  • 송윤성;고광락;김규정;이재범
    • 한국광학회지
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    • 제28권3호
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    • pp.97-102
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    • 2017
  • 본 논문에서는 플라즈모닉 코어와 자성 쉘로 구성된 $Ag@Fe_3O_4$ 나노입자의 흥미로운 광학적 특성에 대해 연구를 하였다. 기존의 60 nm의 지름을 갖는 은 나노입자의 표면에 높은 굴절률을 갖는 $Fe_3O_4$ 쉘이 형성됨에 따라 국소 표면 플라즈몬 공명(Localized surface plasmon resonance; LSPR) 파장이 420 nm에서 650 nm로 이동하는 red-shift 현상을 관찰 할 수 있었고, 또한, 세 가지 시뮬레이션 모델들 ($Ag@Fe_3O_4$ 나노입자, $Fe_3O_4$ 쉘 나노입자, 은 나노입자)을 통해서 410 nm 파장의 peak이 60 nm의 두께를 가진 $Fe_3O_4$ 쉘에 의해 발생하는 산란이 주된 원인이라는 것을 규명하였다. 이 결과는 비슷한 종류의 나노입자를 이용한 추후 다양하고 복잡한 나노어셈블리의 광학적 현상을 이해하는데 사용될 것이다.

태양광 모듈형 전력조절기를 위한 양방향 벅-부스트 포워드 컨버터 (Bi-Directional Buck-Boost Forward Converter for Photovoltaic Module type Power Conditioning System)

  • 김경탁;전영태;박종후
    • 전력전자학회논문지
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    • 제21권4호
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    • pp.335-342
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    • 2016
  • This paper proposes an energy storage-assisted, series-connected module-integrated power conversion system that integrates a photovoltaic power conditioner and a charge balancing circuit. In conventional methods, a photovoltaic power conditioner and a cell-balancing circuit are needed for photovoltaic systems with energy storage devices, but they cause a complex configuration and high cost. Moreover, an imbalanced output voltage of the module-integrated converter for PV panels can be a result of partial shading. Partial shading can lead to the fault condition of the boost converter in shaded modules and high voltage stresses on the devices in other modules. To overcome these problems, a bidirectional buck-boost converter with an integrated magnetic device operating for a charge-balancing circuit is proposed. The proposed circuit has multiple secondary rectifiers with inductors sharing a single magnetic core, which works as an inductor for the main bidirectional charger/discharger of the energy storage. The secondary rectifiers operate as a cell-balancing circuit for both energy storage and the series-connected multiple outputs of the module-integrated converter. The operating principle of the cell-balancing power conversion circuit and the power stage design are presented and validated by PSIM simulation for analysis. A hardware prototype with equivalent photovoltaic modules is implemented for verification. The results verify that the modularized photovoltaic power conversion system in the output series with an energy storage successfully works with the proposed low-cost bidirectional buck-boost converter comprising a single magnetic device.

Interferometric Monitoring of Gamma-ray Bright AGNs: S5 0716+714

  • Lee, Sang-Sung;Lee, Jee Won;Hodgson, Heffrey A.;Kim, Dae-Won;Algaba, Juan-Carlos;Kang, Sincheol;Kang, Jiman;Kim, Sungsoo S.
    • 천문학회보
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    • 제42권1호
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    • pp.28.3-29
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    • 2017
  • We present the results of very long baseline interferometry (VLBI) observations of gamma-ray bright blazar S5 0716+714 using the Korean VLBI Network (KVN) at the 22, 43, 86, and 129 GHz bands, which are part of the KVN key science program known as the Interferometric Monitoring of Gamma-ray Bright AGNs (iMOGABA). Multi-frequency VLBI observations were conducted in 29 sessions from January 16, 2013 to March 1, 2016. The source was detected and imaged in all available frequency bands. For all observed epochs, the source is compact on the milliarcsecond (mas) scale, yielding a compact VLBI core dominating the synchrotron emission on the mas scale. Based on the multi-wavelength data at 15 and 230 GHz, we found that the source shows multiple prominent enhancements of the flux density at the centimeter (cm) and millimeter (mm) wavelengths, with mm enhancements leading cm enhancements with a time lag of $18{\pm}5$ days. Turnover frequency is found to vary over our observations between 22 to 69GHz. Taking into account the synchrotron self-absorption model of the relativistic jet in S5 0716+714, we estimated the magnetic field strength in the mas emission region to be 0.4-66 mG during the observing period, finding that the magnetic field strength is strongly correlated with the turnover frequency and the relatively strong magnetic field (e.g., B > 40 mG) is correlated with flux enhancements at mm wavelengths (e.g., 86 GHz).

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영양소분지에 분포하는 경상누층군에 대한 고지자기 연구 (Paleomagnetism of the cretaceous sedimentary rocks in the Yongyang Sub-Basin)

  • 도성재
    • 자원환경지질
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    • 제32권2호
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    • pp.189-201
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    • 1999
  • Paleomagnetic and rock magnetic investigations have been carried out for the Cretaceous Hanyang Group, exposed in the Yongyang Sub-Basins within the Kyeongsang Basin, eastern South Korea. A total of 452 oriented core samples was drilled from 31 sits for the study. The in-situ site mean direction is more dispersed than the mean direction after bedding correction, indicating that the fold test is positive at 95% confidence level. In addition, the stepwise unfolding of the characteristic remanent magfold test is positive at 95% confidence level. In addition, the stepwise unfolding of the characteristic remanent magnetization reveals that a maximum value of k is observed at 90% unfolding. Furthermore, the rock magnetic investigations and electron microscope observations of the representative samples show that the main magnetic carrier of the Hayang Group is the detrital specular hematite of single and pseudo-single domain sizes with negligible contribution of pigmentary hematite grains. These results collectively imply that the ChRM direction is the primary component acquired at the time of the formation of the strata. Provided the primary nature of the ChRM, a magnetostratigraphic correlation between polarities of the studied formation and the Geomagnetic Time Scale indicates that the Hayang Group in the Yongyang Sub-Basin can be correlated to the Cretaceous Long Normal superchron. The paleomagnetic pole position from this study is significantly different from those of the Hayang group in the Euiseong the Milyang sub-Basins. Rather the paleomagnetic pole position of the Hayang Group of the study area is closer to that of the Quaternary period or present time of the Korean Peninsula. It is hypothesized that the study area might be rotated about 25$^{\circ}$ aticlockwise with respect to the Euiseong and Milyang Sub-Basins after the formation of the strata and aquisition of the ChRM, although there is not enough geologic evidence supporting the rotation hypothesis.

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경상분지 남서부 진교-사천 지역 전기백악기 퇴적암에 대한 고자기 연구 (Palaeomagnetism of Early Cretaceous Sedimentary Rocks in Chingyo-Sach'ŏn Area, Southwestern Kyŏngsang Basin)

  • 김인수;강희철;이현구
    • 자원환경지질
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    • 제26권4호
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    • pp.519-539
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    • 1993
  • A total of 264 independently oriented core samples were collected from 26 sites in the southwestern part (the Naktong Trough) of the Cretaceous $Ky{\check{o}}ngsang$ Basin in south Korea. The sampled formations comprise the sedimentary Shindong and the Hayang Groups of the Lower Cretaceous age. Alternating field and thermal demagnetizations were conducted. Characteristic remanent magnetization (ChRM) was relatively easily isolated in each formation except in the Chinju formation, from which only remagnetization circles were observed. Even though an extensive use of the fold test was not possible due to the nearly homoclinal nature of the strata in the area, we believe that the ChRM of each formation is of primary origin based on the following grounds: The in-situ ChRM direction of each formation is different from the present geomagnetic field direction. Fisherian precision parameter becomes enhanced through the tilt correction in all formations, closely to the values required for a positive fold test. Three out of the five studied formations pass the reversal test. The mean palaeomagnetic pole position from the studied area is found to be statistically different from the contemporary pole from the Chinese block exclusive of the Shandong area. The difference in magnetic declination suggests a $14.5^{\circ}$ (${\pm}10.5^{\circ}$) clockwise rotation of the studied area relative to the Chinese block comprising the west of the Tan-Lu fault. On the other hand, any significant difference in magnetic inclination and concurrent palaeolatitude is not observed between the studied area and China as well as the other area (Taegu-Andong area) in the $Ky{\check{o}}ngsang$ Basin. The dual nature of the magnetic polarity confirmed in all formations suggests an older than 124 Ma (Neocomian or older) age of the studied sedimentary strata.

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리니어 왕복운동 제어시스템 구동용 가동코일형 리니어 액츄에이터의 설계제작 및 제어정수 도출 (Design and Extraction of Control Parameters of a Moving-Coil-Type Linear Actuator for Driving of Linear Reciprocating Motion Control Systems)

  • 장석명;정상섭;박희창;문석준;박찬일;정태영
    • 대한전기학회논문지:전기기기및에너지변환시스템부문B
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    • 제48권5호
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    • pp.241-248
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    • 1999
  • Recently, many linear motion generators and motors are rapidly finding applications that ranges from short stroke linear motion vibrators, such as dynamic cone type loudspeakers to stirling engine driven linear reciprocating alternators, compressors, textile machines etc. The stroke-length may go up to 2m, and the maximum speed is in the range of 5 to 10m/s with oscillating frequency as high as 15 kHz. Therefore, the linear oscillating actuators(LOAs) may be considered as variable speed drivers of precise controller with stoke-length and reversal periods during the reciprocating motion. In this paper, the design, fabrication, experiments, and extraction of control parameters of a moving coil type LOA for driving of linear reciprocating motion control systems, are treated. The actuator consists of the NdFeB permanent magnets with high specific energy as the stator produced magnetic field, a coil-wrapped nonmagnetic hollow rectangular bobbin structure, and an iron core as a pathway for magnetic flux. Actually, the design is accomplished by using FEM analysis for the basic configuration of a magnetic circuit, and characteristic equations for coil design. In order to apply as the drivers of a linear motion reciprocating control system, the control parameters and circuit parameters, such as input voltage-stoke, exciting frequency-stoke, coil inductance and so on, are extracted from the analysis and experiments on concerning a fabricating LOA.

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페라이트 코어와 칩캐패시터의 주기적 연결구조에서 발생하는 자기유도파 (Magneto-inductive Wave in Periodic Chain of Ferrite Cores and Chip Capacitors)

  • 신광호
    • 한국자기학회지
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    • 제25권1호
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    • pp.22-26
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    • 2015
  • 이 논문에서 Ni-Zn 페라이트 코어와 칩캐패시터를 이용하여 제작한 주기적인 연결구조에서 발생하는 자기유도파(magneto-inductive wave)에 대한 실험적 결과를 보고 한다. 주기적 연결구조는 동일한 공진주파수를 가진 LC공진기(LC resonator)로 되었으며, 개별 공진기는 도선과 칩캐패시터로 구성되었다. 인접하는 공진기들은 패라이트코어를 통해서 자기적으로 결합되었다. 제작된 주기적 구조의 특성을 검토하기 위해서 네트워크 아날라이저를 이용한 S-파라미터를 분석하여 신호전송특성을 평가하였다. 5개의 LC공진기를 1차원적으로 연결하여 제작한 주기구조의 신호전송 중심주파수는 32 MHz~38 MHz였으며, 이는 인가자계의 크기에 의해서 조정할 수 있었다.

동적전압보상기를 위한 정합 변압기의 돌입전류 제어 (Inrush Current Control of Matching Transformer for Dynamic Voltage Restorer)

  • 서일동;전희종;손진근
    • 전력전자학회논문지
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    • 제11권4호
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    • pp.340-348
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    • 2006
  • 본 논문에서는 동적전압보상기 (DVR)를 구성하기 위한 정합 변압기의 돌입전류 제어기법을 제안하였다. DVR 시스템은 배전계통에서 발생하는 순시적 전압강하를 보상하기 위한 직렬전압 주입장치로서, 임의의 전압을 생성하는 PWM 인버터와 전압 평활용 LC 수동필터 및 절연을 위한 정합 변압기 등으로 구성된다. 그러나 정합 변압기의 사용은 변압기내에서 자속 포화현상에 의하여 정격의 수배에 달하는 돌입전류가 발생하여 시스템의 절연파괴를 초래하고 이 때문에 변압기의 정격용량을 2 배 정도로 초과하여 사용하게 한다. 따라서 본 연구에서는 정합 변압기의 자속 포화현상에 따른 돌입전류의 크기를 분석할 수 있는 새로운 모델링 분석기법 및 돌입전류의 크기를 제한하는 자화전류 제어기법을 제안하였다. 모의실험 및 실험을 통하여 제안된 DVR 제어기법의 타당성을 입증하였다.

Analysis of Image Distortion on Magnetic Resonance Diffusion Weighted Imaging

  • Cho, Ah Rang;Lee, Hae Kag;Yoo, Heung Joon;Park, Cheol-Soo
    • Journal of Magnetics
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    • 제20권4호
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    • pp.381-386
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    • 2015
  • The purpose of this study is to improve diagnostic efficiency of clinical study by setting up guidelines for more precise examination with a comparative analysis of signal intensity and image distortion depending on the location of X axial of object when performing magnetic resonance diffusion weighted imaging (MR DWI) examination. We arranged the self-produced phantom with a 45 mm of interval from the core of 44 regent bottles that have a 16 mm of external diameter and 55 mm of height, and were placed in 4 rows and 11 columns in an acrylic box. We also filled up water and margarine to portrait the fat. We used 3T Skyra and 18 Channel Body array coil. We also obtained the coronal image with the direction of RL (right to left) by using scan slice thinkness 3 mm, slice gap: 0mm, field of view (FOV): $450{\times}450mm^2$, repetition time (TR): 5000 ms, echo time (TE): 73/118 ms, Matrix: $126{\times}126$, slice number: 15, scan time: 9 min 45sec, number of excitations (NEX): 3, phase encoding as a diffusion-weighted imaging parameter. In order to scan, we set b-value to $0s/mm^2$, $400s/mm^2$, and $1,400s/mm^2$, and obtained T2 fat saturation image. Then we did a comparative analysis on the differences between image distortion and signal intensity depending on the location of X axial based on iso-center of patient's table. We used "Image J" as a comparative analysis programme, and used SPSS v18.0 as a statistic programme. There was not much difference between image distortion and signal intensity on fat and water from T2 fat saturation image. But, the average value depends on the location of X axial was statistically significant (p < 0.05). From DWI image, when b-value was 0 and 400, there was no significant difference up to $2^{nd}$ columns right to left from the core of patient's table, however, there was a decline in signal intensity and image distortion from the $3^{rd}$ columns and they started to decrease rapidly at the $4^{th}$ columns. When b-value was 1,400, there was not much difference between the $1^{st}$ row right to left from the core of patient's table, however, image distortion started to appear from the $2^{nd}$ columns with no change in signal intensity, the signal was getting decreased from the $3^{rd}$ columns, and both signal intensity and image distortion started to get decreased rapidly. At this moment, the reagent bottles from outside out of 11 reagent bottles were not verified from the image, and only 9 reagent bottles were verified. However, it was not possible to verify anything from the $5^{th}$ columns. But, the average value depends on the location of X axial was statistically significant. On T2 FS image, there was a significant decline in image distortion and signal intensity over 180mm from the core of patient's table. On diffusion-weighted image, there was a significant decline in image distortion and signal intensity over 90 mm, and they became unverifiable over 180 mm. Therefore, we should make an image that has a diagnostic value from examinations that are hard to locate patient's position.

통가 EEZ내 TA25 해저산에서 채취한 열수광체의 암석자기학적 특성 연구 (Rock-magnetic Properties of Chimneys from TA25 Seamount in the Tofua Arc, Southwest Pacific)

  • 김원년;박상준;이경용;문재운;김현섭;최선기
    • 자원환경지질
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    • 제46권3호
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    • pp.207-214
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    • 2013
  • 2012년 통가해저열수광상 개발 사업의 일환으로 통가아크 해저산 TA25에서 ROV와 GTV를 이용하여 열수황화물광체를 채취하였다. 채취된 광체 중 본 연구에서는 약 $200^{\circ}C$의 열수분출을 보인 고온성 활성침니(ROV01), $80^{\circ}C$의 열수분출을 보인 저온성 활성침니(GTV01), 그리고 비활성침니(ROV02)를 이용하여, 암석자기학적 특성을 규명하고 이를 바탕으로 광체의 진화과정을 알아보고자 하였다. ROV01의 자기적 특성은 주로 자류철석에 의해 나타나며, GTV01의 경우 광체내부는 자류철석이 주로 나타나지만 외곽으로 갈수록 자류철석과 적철석이 혼재하게 된다. 비활성침니인 ROV02는 오랜 산화작용으로 인해 외곽에서 적철석뿐만 아니라 침철석이 자류철석과 함께 나타나고, 최외곽에서는 magnetotactic bacteria의 작용에 의해 자철석이 존재한다. 포화잔류자화(saturation magnetic remanent magnetization, SIRM), 비자기이력잔류자화(anhysteretic remanent magnetization, ARM)/SIRM으로 나타낸 자성광물의 함량과 입자크기 변화는 침니의 특성에 따라 뚜렷한 차이가 난다. 고온의 ROV01에서 가장 적은 함량과 작은 입자크기를 보이며, 저온의 GTV01에서 점차 증가하다가 비활성침니인 ROV02에서 가장 높은 함량과 큰 입자크기를 나타내게 된다. 이러한 결과는 자성광물의 종류, 함량, 입자크기 변화 등의 암석자기학적 특성을 이용하여 기존 광물학적 접근방법으로 추적에 한계가 있었던 열수황화물광체의 진화과정에 대한 정보를 획득할 수 있을 것으로 판단된다.