• Journal of Astronomy and Space Sciences
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• 제28권2호
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• pp.123-132
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• 2011

It is generally believed that the occurrence of a magnetic storm depends upon the solar wind conditions, particularly the southward interplanetary magnetic field (IMF) component. To understand the relationship between solar wind parameters and magnetic storms, variations in magnetic field polarity and solar wind parameters during magnetic storms are examined. A total of 156 storms during the period of 1997~2003 are used. According to the interplanetary driver, magnetic storms are divided into three types, which are coronal mass ejection (CME)-driven storms, co-rotating interaction region (CIR)-driven storms, and complicated type storms. Complicated types were not included in this study. For this purpose, the manner in which the direction change of IMF $B_y$ and $B_z$ components (in geocentric solar magnetospheric coordinate system coordinate) during the main phase is related with the development of the storm is examined. The time-integrated solar wind parameters are compared with the time-integrated disturbance storm time (Dst) index during the main phase of each magnetic storm. The time lag with the storm size is also investigated. Some results are worth noting: CME-driven storms, under steady conditions of $B_z$ < 0, represent more than half of the storms in number. That is, it is found that the average number of storms for negative sign of IMF $B_z$ (T1~T4) is high, at 56.4%, 53.0%, and 63.7% in each storm category, respectively. However, for the CIR-driven storms, the percentage of moderate storms is only 29.2%, while the number of intense storms is more than half (60.0%) under the $B_z$ < 0 condition. It is found that the correlation is highest between the time-integrated IMF $B_z$ and the time-integrated Dst index for the CME-driven storms. On the other hand, for the CIR-driven storms, a high correlation is found, with the correlation coefficient being 0.93, between time-integrated Dst index and time-integrated solar wind speed, while a low correlation, 0.51, is found between timeintegrated $B_z$ and time-integrated Dst index. The relationship between storm size and time lag in terms of hours from $B_z$ minimum to Dst minimum values is investigated. For the CME-driven storms, time lag of 26% of moderate storms is one hour, whereas time lag of 33% of moderate storms is two hours for the CIR-driven storms. The average values of solar wind parameters for the CME and CIR-driven storms are also examined. The average values of ${\mid}Dst_{min}{\mid}$ and ${\mid}B_{zmin}{\mid}$ for the CME-driven storms are higher than those of CIR-driven storms, while the average value of temperature is lower.

• 한국수산과학회지
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• 제30권6호
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• pp.948-955
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• 1997

Immunomagnetic separation of virus coupled with .reverse transcription-polymerase chain reaction (IMS-PCR) was performed with infectious hematopoietic necrosis virus (IHNV). A DNA fragment of expected size was synthesized in the RT-PCR with total RNA extracted from IHNV inoculated CHSE-214. In a SDS-PAGE analysis, a protein band of over 70kDa was detected from non-infected cells and cells inoculated with IHNV and infectious pancreatic necrosis virus (IPNV). This protein was detected in the Western blot analysis probably because of non-specific reaction to monoclonal antibody against IHNV nucleocapsid protein. In the immunomagnetic separation, magnetic beads coated with monoclonal antibody against the IHNV nucleocapsid protein was incubated with supernatant from IHNV inoculated CHSE-214 cells. During this process, the non-specifically reacting protein could be removed by washing the magnetic bead with PBS in the presence of an external magnetic field, and viral proteins were detected from the remaining, cleaned magnetic beads. It was necessary to extract viral RNA from the captured virus particles before RT-PCR, and no DNA product was detected when the captured virus was only heated 5 min at $95^{\circ}C$. A PCR-product of expected size was synthesized from IMS-PCR with magnetic beads double coated either by goat anti-mouse IgG antibody -monoclonal antibody or streptavidin - biotin conjugated monoclonal antibody.

• Nuclear Engineering and Technology
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• 제55권9호
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• pp.3485-3492
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• 2023

One of the major topic of tokamak research is the determination of the magnetic profile due to magnetic coil fields and plasma current by mean of data from magnetic probes. The most practical approach is to use the current filament method, which models the plasma column with multiple current carrying filaments and the total current of these filaments is equal to the plasma current. Determining the plasma boundary in Alvand-U tokamak is the main purpose of this paper. In order to determine the magnetic field profile and plasma boundary, information concerning the magnetic coils, their position, and current is required in the computing code. Then, the plasma shape is determined and finally the plasma boundary is extracted by the code. In the conducted research, we discuss how to determine the plasma boundary and the performance of the computing code for extraction of the plasma boundary. The developed algorithm shows to be effective by running it in the regular pc machine with characteristics of Intel (R) core (TM) i3-10100 CPU @3.60 GHz and 8.00 GB of RAM. Finally, we present results of a test run for computing code using a typical experimental pulse.

• 천문학회보
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• 제41권2호
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• pp.41.2-41.2
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• 2016

We perform three statistical studies on the physical properties and oscillations in the confined plasma such as a photospheric sunspot and confined coronal loop. From the statistical studies on the sunspot umbra and its oscillation, we find that (1) the total magnetic flux inside the umbra for the three groups increases proportionally with the powers of the umbral area and the power indices in the three groups significantly differ from each other; (2) the three groups have different characteristics in their umbral area, intensity, magnetic field strength, and Doppler velocity as well as their relationships; (3) the mean frequency of the umbral oscillations increases with the umbral mean magnetic field strength and height; (4) the time delay of the core intensity of Fe I absorption line relative to the continuum which are de-convolved with the frequency range higher than 3.5 mHz is mostly positive, implying that the photospheric umbral oscillations are likely upwardly propagating; (5) the umbral mean plasma beta ranges approximately 0.6-1.1 and does not vary significantly from pores to mature sunspots. From the comparative study on the quasi-periodic pulsations (QPPs) in the solar and stellar flares, (6) we find that the power index of the periods scaling the damping times observed in the stellar QPPs is consistent with that observed in the solar QPPs, suggesting that physical mechanisms responsible for the stellar QPPs are likely the magneto-hydrodynamic oscillation of solar coronal loops.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2005년도 춘계학술대회 논문집
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• pp.299-303
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• 2005

본 연구는 MHD(Magnetohydrodynamics)방식의 전자기력을 이용하여 선박사고 등으로 인하여 해상에 유출된 기름을 분리하는 새로운 방법에 대한 설계 및 정식화를 이끌어 내었다. MHD분리방식은 최근에 연구되고 있는 자기파우더를 이용한 분리방식보다도 더욱 친환경적이고 분리가 용이하다는 강점을 가지고 있다. 여기서는 기름을 대신하여 고분자 입자를 넣은 해수를 가정하여 유체내의 전류, 자기장, 유속에 대한 분리율(분리측 입장의 질량/전 입자의 질량)을 수치시뮬레이션을 이용하여 그 특성을 검토하였다.

• 천문학회보
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• 제37권1호
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• pp.91.2-91.2
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• 2012

Kokubun (1983) reported the local time variation of normalized amplitude of sudden commencement (SC) with a strong day-night asymmetry at geosynchronous orbit with 81 SC events. Further careful inspection of Kokubun's local time distribution reveals that the normalized SC amplitudes in the prenoon sector are larger than those in the postnoon sector. That is, there is a morning-afternoon asymmetry in the normalized SC amplitudes. Until now, however, there are no studies on this SC-associated morning-afternoon asymmetry at geosynchronous orbit. Motivated by this previous observation, we investigate a large data set (422 SC events in total) of geosynchronous SC observations and confirm that the geosynchronous SC amplitudes is larger in the morning sector than in the afternoon sector. This morning-asymmetry is probably caused by the enhancement of partial ring current, which is located in the premidnight sector, due to solar wind dynamic pressure increase. We also examine the latitudinal and seasonal variations of the normalized SC amplitude. We find that the SC-associated geosynchronous magnetic field perturbations are dependent on the magnetic latitude and season of the year. This may be due to the location of the magnetopause and cross-tail currents enhanced during SC interval with respect to geosynchronous spacecraft position.

• 지구물리와물리탐사
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• 제5권3호
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• pp.157-168
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• 2002

Magsat 인공위성의 자력계로부터 관측된 동아시아 (동경90도-50도, 남위10도-북위50도) 암권의 자기이상을 추출하기 위한 연구를 수행하였다. 이를 위해 ring current correction, ionospheric correction, pass-by-pass correlation등을 실시하였고, 위성트랙 잡음을 효율적으로 제거하기 위한 spectral reconstruction을 실시하였다. 최종적으로 추출된 자기이상의 신뢰도를 검증하기 위해 항공자기이상과 대비하였고, 이를 위해 항공자기이상에 low-pass필터를 적용하여 인공위성 고도에서 관측 불가능한 고주파성분을 제거하였다. 결과적으로 위성자기이상과 항공자기이상은 0.243의 비교적 낮은 상관관계를 보이나 연구지역내 많은 부분에서 양(+)의 상관관계를 갖고 있음이 밝혀졌다. 일반적으로 낮은 상관계수는 각 주파수별 성분의 양과 음의 장관계수가 혼합되어 나타나며, 따라서 본 연구와 같은 포텐셜상의 경우에는 이상체의 심도 및 누중 때문에 양과 음의 상관관계를 갖는 이상체를 분류하는 것이 매우 어렵다. 본 연구에서는 인공위성 자력계 관측값으로부터 연구지역 암권의 자기이상을 성공적으로 추출하였으며 항공자기이상과도 양호한 상관관계를 갖고 있음이 밝혀졌다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 1999년도 추계학술발표회 초록집
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• pp.49-49
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• 1999

In this study, $Cl_2/BCI_3$ magnetized inductively coupled plasmas (MICP) were used to etch GaN and the effects of magnetic confinements of inductively coupled plasmas on the GaN etch characteristics were investigated as a function of $Cl_2/BCI_3$. Also, the effects of Kr addition to the magnetized $Cl_2/BCI_3$ plasmas on the GaN etch rates were investigated. The characteristics of the plasmas were estimated using a Langmuir probe and quadrupole ma~s spectrometry (QMS). Etched GaN profiles were observed using scanning electron microscopy (SEM). The small addition of $Cl_2/BCI_3$ (10-20%) in $Cl_2$ increased GaN etch rates for both with and without the magnetic confinements. The application of magnetic confinements to the $Cl_2/BCI_3$ inductively coupled plasmas (ICP) increased GaN etch rates and changed the $Cl_2/BCI_3$ gas composition of the peak GaN etch rate from 10% $BCI_3$ to 20% $BCI_3$. It also increased the etch selectivity over photoresist, while slightly reducing the selectivity over $Si0_2$. The application of the magnetic field significantly increased positive $BCI_2{\;}^+$ measured by QMS and total ion saturation current measured by the Langmuir probe. Other species such as CI, BCI, and CI+ were increased while species such as $BCl_2$ and $BCI_3$ were decreased with the application of the magnetic field. Therefore, it appears that the increase of GaN etch rate in our experiment is related to the increased dissociative ionization of $BCI_3$ by the application of the magnetic field. The addition of 10% Kr in an optimized $Cl_2/BCI_3$ condition (80% $Cl_2/$ 20% $BCI_3$) with the magnets increased the GaN etch rate about 60%. More anisotropic GaN etch profile was obtained with the application of the magnetic field and a vertical GaN etch profile could be obtained with the addition of 10% Kr in an optimized $Cl_2/BCI_3$ condition with the magnets.

• 대한전기학회논문지
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• 제41권4호
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• pp.379-384
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• 1992

The Fe-base amorphous ribbons with 15mm width and about 20x10S0-6Tm thickness, (FeS179-xTCrS1xT)BS116TSiS15T and (FeS181-xTMnS1xT) BS112TSiS17T (x:0-6), were prepared melt spinner. The thickness of the ribbons followed by PFC (Planar Flow Casting). The initial permeability and total core losses were measured as a function of additive elements (Cr, Mn) and annealing conditions in high frequency for the purpose of using these materials as a core of magnetic amplifier and switched mode power supplies. The initial permeabilities were enhanced and core losses were decreased by non-magnetic field annealing in proper conditions. The lowest core loss in 0.2T/10kHz was measured at 3% Cr addition amorphous ribbon, and the loss was 5.6W/kg. The permeability of the ribbon at 10kHz was about 9000.

• 한국초전도ㆍ저온공학회논문지
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• 제22권1호
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• pp.12-16
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• 2020

As high homogeneity in magnetic field is required to increase the resolution of MRI magnets, various shimming methods have been researched. Using one of them, the design of the superconducting active zonal shim coil for MRI magnets is discussed in this paper. The magnetic field of the MRI magnet is expressed as the sum of spherical harmonic terms, and the optimized current density of shim coils capable of removing higher-order terms is calculated by the Tikhonov regularization method. To investigate all potential designs derived from calculated current density, 4 sweeping parameters are selected: (1) axial length of shim coil zone; (2) radius of shim coils; (3) exact axial position of shim coils; and (4) operating current. After adequate designs are determined with constraints of critical current margin and homogeneity criterion, the total wire length required for each is calculated and the design with a minimum of them is chosen. Using the superconducting wire length of 9.77 km, the field homogeneity over 50 cm DSV is improved from 24 ppm to 1.87 ppm in the case study for 9.4 T whole-body MRI shimming. Finally, the results are compared with the finite element method (FEM) simulation results to validate the feasibility and accuracy of the design.