• 제목/요약/키워드: Strong magnetic field

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Sr-Ferrite와 GC를 이용한 자기연마재 개발 (Development of the Magnetic Abrasive Using Sr-Ferrite and GC)

  • 윤여권;김상백;김희남
    • 한국안전학회지
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    • 제26권2호
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    • pp.13-19
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    • 2011
  • The magnetic polishing is the useful method to finish using magnetic power of magnet. That method is one of precision polishing techniques and has an aim of the clean technology using for the pure of gas and inside of the clean pipe. The magnetic abrasive polishing method is not so common for machine that it is not spreaded widely. There are rarely researcher in this field because of non-effectiveness of magnetic abrasive. Therefore, in this paper deals with development of the magnetic abrasive using Sr-Ferrite. In this development, abrasive grain GC used to resin bond fabricated low temperature. And Sr-Ferrite of magnetic abrasive powder fabricated that Sr-Ferrite was crused into 200 mesh. The XRD analysis result show that only GC abrasive and Sr-Ferrite crystal peaks detected which explains resin bond was not any more chemical reaction. From SEM analysis it is found that GC abrasive and Sr-Ferrite were strong bonding with each other by bond. The magnetic polishing is performed by polishing the surface of pipe by attracting magnetic abrasives with magnetic fields. This can be widely applied for finishing machinery fabrications such as various pipes and for other safety processes. In this paper, we could have investigated in to the changes of the movement of magnetic abrasive grain. In reference to this result, we could have made the experiment which is set under the condition of the magnetic flux density, polishing velocity according to the form of magnetic brush.

인가자장의 크기와 방향을 고려한 고온초전도 다중마그넷의 특성 해석 (Analysis of nested HTS magnets considering the magnitude and orientation of applied magnetic field)

  • 박주경;차귀수;이희준
    • 한국산학기술학회논문지
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    • 제18권11호
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    • pp.23-30
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    • 2017
  • 20T 이상의 높은 자장을 발생시키는 초전도마그넷은 다중 마그넷형태로 제작된다. 주로 저온초전도선재와 고온초전도선재를 혼합하여 제작되며 근래에는 고온초전도선재만을 이용하는 연구도활발하게 진행되고 있다. 고온초전도선재는 외부자계의 방향에 따라 임계상태가 달라지고 임계전류가 달라지는 자계이방성 성질을 가지고 있다. 따라서 고자장용 다중마그넷의 임계전류를 계산할 때에는 적절한 해석기법을 사용해야 한다. 기존에 사용되어왔던 고자장용 다중마그넷의 임계전류 계산방법은 대부분 수직 및 수평각도만을 고려한 부하선 기법이 사용되어왔다. 이 계산방법은 외부자계의 최대수직자장에 의해서 임계전류가 제한되기 때문에 수평자장의 영향이 잘 고려되지 않는 단점이 있다. 본 논문에서는 마그넷의 임계전류를 정밀하게 계산하기위하여 수직 및 수평각도뿐만 아니라 $0{\sim}90^{\circ}$ 사이 모든 각도의 $I_C-B({\Theta})$ 데이터를 고려하였다. 본 논문에서 제시한 해석기법을 사용하여 두 가지 고자장용 다중마그넷 모델을 해석하고 임계전류를 계산하였다. 마그넷에 인가되는 자계분포를 해석하기 위해 전자계수치해석 프로그램을 사용하였으며 진화론적 최적화 알고리즘을 사용하여 중심 자장이 최대로 되는 임계전류를 계산하였다.

Statistical Analysis of Supersonic Downflows in Sunspot Penumbrae

  • Kim, Hyunnam;Solanki, Sami K.;Lagg, Andreas;Kim, Kap-Sung
    • 천문학회보
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    • 제39권1호
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    • pp.75.1-75.1
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    • 2014
  • Sunspot penumbrae show supersonic downflow patches along the periphery. These patches are believed to be the return channels of the Evershed flow. There was previous study to investigate their structure in detail using Hinode SOT/SP observations (M. van Noort et al. 2013) but their data sample was only two sunspots. To make general description it needs to check more sunspot sample. We selected 242 downflow patches of 17 sunspots using Hinode SOT/SP observations from 2006 to 2012. Height-dependent maps of atmospheric parameters of these downflows was produced by using HeLix which was height dependent LTE inversion code of Stokes profiles. The inversion code at high resolution allows for the accurate determination of small scale structures. The recovered atmospheric structure of three layers indicates that regions with very high downflow velocities contain very strong magnetic fields reaching up to 7kG. The higher downflow velocity patches have bigger patch size. Magnetic fields of downflow patches are more vertical while penumbra shows horizontal field and neighbor of downflow patches have opposite polarity. Temperature of downflow patches at highest layer have more strong value than penumbra at deepest layer. The direction of velocity of downflow patches at highest layer have two branches. These result shows that we can expect some heating precess in the middle of layer.

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희토류 자석의 자성이 골모세포 성장인자 수용체의 증가에 미치는 영향에 관한 연구 (Effect of the magnetism(neodymium magnet) on growth factor receptors of osteoblasts)

  • 이상민;이성복;최부병
    • 구강회복응용과학지
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    • 제19권2호
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    • pp.87-96
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    • 2003
  • The purposes of this study were to find out the optimum intensity of magnetic field where magnetism could promote the activity of osteoblast, and to discover the possibility of clinical application in the areas of dental implants and bone grafts by confirming the effect of clinically increasing bone formation. In this experiment, we used the Neodymium magnet, which had magnetic power six times as strong as the current ones and enabled the resistances against the demagnetization up to 20 to 50 times to be minimized with the size of 1mm in sight. In order to culture cells, a specially designed device was used. It was made to adjust the distance and accordingly to control the intensity of the magnetic field, by placing the cell culture plate in the center with a magnet of 1mm long and thick installed on the both ends. Using MC3T3-E1 cell, a kind of osteoblast-like cell, we cultured, for 24 hours, not only the test group which had been cultured under the magnetic fields with different intensity of 5, 10, 50, 100, 500, and 1000 Gauss, but also the control group excluding the influences of the magnetic field. After observing the cell's form and the density of the culture medium through an inverted microscope, we made a series of proceedings needed for the immunofluoroscence staining, such as fixation, normal serum reaction, primary antibody reaction, and secondary antibody reaction. And with a fluorescence microscope, we observed those-above and compared the frequency of expression of IFG-1 receptor. To make a Western immunoblotting analysis, the cells cultured under the same condition as the above had the procedure of the lysis buffer and the acrylamide gel electrophoresis was carried out. Protein transferred into the nitrocellulose membrane and tested on the primary and the secondary antibody reactions was observed and compared. The results were as follows: When observed through an inverted microscope, the nuclear divisions of the cells under the magnetic field of 10 Gauss were the most active, and the density of the cells could be observed the most enormously. As the result of an immunofluoroscence staining of IGF-1 receptor, the expression of IFG-1 was the most frequently observed under the magnetic field of 10 Gauss. On the other hand, few differences of consideration were made between the test group cultured under the magnetic fields of 5, 500, and 1000 Gauss and the control group. In respect of the expression of IFG-1 receptor, the test group cultured under the magnetic fields of 50 and 100 Gauss were higher than the control group, and lower than that cultured under the magnetic field of 10 Gauss.(p<0.05) According to the Western immunoblotting analysis, the band of IFG-1 receptor which had 85KDa of molecular weight was the darkest. Judging from the above-mentioned results, the growth factor receptor of an osteoblast cell which was an important criterion for the bone formation was increased in maximum under the magnetic field of 10 Gauss. Moreover it was observed that the optimum intensity of magnetic field in which magnetism made the activity of the osteoblast cell increase was about 10 Gauss.

CURRENT STATUS OF SHOCK ACCELERATION THEORY

  • DRURY LUKE O'C
    • 천문학회지
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    • 제37권5호
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    • pp.393-398
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    • 2004
  • This paper describes some recent developments in our understanding of particle acceleration by shocks. It is pointed out that while good agreement now exists as to steady nonlinear modifications to the shock structure, there is. also growing evidence that the mesoscopic scales may not in fact be steady and that siginficant instabilties associated with magnetic field amplification may be a feature of strong collisionless plasma shocks.

Alfvenic Turbulence in Pulsar/Black Hole Magnetospheres

  • Cho, Jungyeon
    • 천문학회보
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    • 제38권2호
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    • pp.99-99
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    • 2013
  • If the magnetic field is extremely strong, as in pulsar/black hole magnetospheres, the Alfven speed approaches to the speed of light and we need relativity to describe interactions of Alfvenic waves. In this poster, we discuss physics of Alfvenic turbulence in this limit. We first discuss interaction of Alfvenic wave packets and scaling relations of resulting turbulence. Then we show results of numerical simulations. Finally we compare relativistic Alfvenic turbulence and its Newtonian counterpart.

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22.9[kV] 배전선로 주변의 전장과 자장의 분포 (Profiles of Electric and Magnetic Fields around 22.9[kV] Distribution Lines)

  • 이복희;박종순;길형준
    • 조명전기설비학회논문지
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    • 제13권2호
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    • pp.46-54
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    • 1999
  • 최근 전자환경은 가전 제춤의 보급과 전력소비의 증가와 더불어 변화되고 잇다. 대부분 관심이 집중되고 있는 자료들은 전력 주파수의 전장과 자장의 노출된 인체에 미치는 영향에 대해 많은 관심이 집중되고 있으며, 이에 대한 정확한 측정과 분석이 요구되고 있다 본 논문에서는 22.9[kV] 배전선로에 발생하는 극저주파 영역의 전장과 자장의 측정과 분석이 수행되었고, 배전선로를 가로지르는 방법으로 측정하였으며, 측정값과 비교를 위해 FIELDS 프로그램을 사용하여 이론적으로 계산하였다. 전장과 자장의 세기는 배전선로 아래에서 강하였고, 횡방향 거리에 반비례하여 감소하였다. 전장의 분포곡선은 M자형태이고 자장은 $\bigcap$자 형태이었으며, 측정값은 이론값고 거의 흡사한 양상을 보였다. 그리고, 전장과 자장의 세기는 모두 측정높이가 증가함에 따라 강하게 나타남을 알 수 있었다. 전장의 분포는 3상 도체의 배치에 의해 영향을 받으며 자장의 분포 특성은 상전류의 불평형에 의해 최대값이 중앙점으로부터 이동되는 것을 알았다.

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MAGNETIC HELICITY PUMPING BY TWISTED FLUX TUBE EXPANSION

  • CHAE JONGCHUL;MOON Y.-J.;RUST D. M.;WANG HAIMIN;GOODE PHILIP R.
    • 천문학회지
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    • 제36권1호
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    • pp.33-41
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    • 2003
  • Recent observations have shown that coronal magnetic fields in the northern (southern) hemisphere tend to have negative (positive) magnetic helicity. There has been controversy as to whether this hemispheric pattern is of surface or sub-surface origin. A number of studies have focused on clarifying the effect of the surface differential rotation on the change of magnetic helicity in the corona. Meanwhile, recent observational studies reported the existence of transient shear flows in active regions that can feed magnetic helicity to the corona at a much higher rate than the differential rotation does. Here we propose that such transient shear flows may be driven by the torque produced by either the axial or radial expansion of the coronal segment of a twisted flux tube that is rooted deeply below the surface. We have derived a simple relation between the coronal expansion parameter and the amount of helicity transferred via shear flows. To demonstrate our proposition, we have inspected Yohkoh soft X-ray images of NOAA 8668 in which strong shear flows were observed. As a result, we found that the expansion of magnetic fields really took place in the corona while transient shear flows were observed in the photosphere, and the amount of magnetic helicity change due to the transient shear flows is quantitatively consistent with the observed expansion of coronal magnetic fields. The transient shear flows hence may be understood as an observable manifestation of the pumping of magnetic helicity out of the interior portions of the field lines driven by the expansion of coronal parts as was originally proposed by Parker (1974).

자성 및 발광 특성이 조절 가능한 다기능 코어/중간체/쉘 나노 입자 합성 (Synthesis of the Multifunctional Core/Intermediate/Shell Nanoparticles: Tunable Magnetic and Photoluminescence Properties)

  • 김문경;김세윤;문경석;신원호;정형모
    • 한국분말재료학회지
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    • 제26권6호
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    • pp.463-470
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    • 2019
  • Fe3O4/SiO2/YVO4:Eu3+ multifunctional nanoparticles are successfully synthesized by facile stepwise sol-gel processes. The multifunctional nanoparticles show a spherical shape with narrow size distribution (approximately 40 nm) and the phosphor shells are well crystallized. The Eu3+ shows strong photoluminescence (red emission at 619 nm, absorbance at 290 nm) due to an effective energy transfer from the vanadate group to Eu. Core-shell structured multifunctional nanoparticles have superparamagnetic properties at 300 K. Furthermore, the core-shell nanoparticles have a quick response time for the external magnetic field. These results suggest that the photoluminescence and magnetic properties could be easily tuned by either varying the number of coating processes or changing the phosphor elements. The nanoparticles may have potential applications for appropriate fields such as laser systems, optical amplifiers, security systems, and drug delivery materials.

Tiny Pores Observed by New Solar Telescope and Hinode

  • 조경석;봉수찬;채종철;김연한;박영득
    • 천문학회보
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    • 제36권1호
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    • pp.37.2-37.2
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    • 2011
  • Our previous study on tiny pores (R < 2") observed by HINODE/Solar Optical Telescope (SOT) revealed that the plasma in the pores at the photosphere is always moving down and the pores are surrounded by the strong downward motions (highly red-shifted) of neighboring granulations. From this study, we speculated that the flow motions above the pore should be related with the motions at the photosphere, since the pore is strong magnetic field region. Meanwhile, SNU and KASI installed Fast Imaging Solar Spectrograph (FISS) in the Cude room of the 1.6 m New Solar Telescope (NST) at Big Bear Solar Observatory. FISS is a unique system that can do imaging of H-alpha and Ca II 8542 band simultaneously, which is quite suitable for studying of dynamics of chromosphere. To get some clue on the relationship between the photospheric and low-chromospheric motions at the pore region, we took a coordinate observation with NST/FISS and Hinode/SOT for new emerging active region (AR11117) on October 26, 2010. In the observed region, we could find two tiny pores and two small magnetic islands (SMIs), which have similar magnetic flux with the pores but does not look dark. Magnetic flux density and Doppler velocities at the photosphere are estimated by applying the center-of-gravity (COG) method to the HINODE/spectropolarimeter (SP) data. The line-of-sight motions above the photosphere are determined by adopting the bisector method to the wing spectra of Ha and CaII 8542 lines. As results, we found the followings. (1) There are upflow motion on the pores and downflow motion on the SMIs. (2) Towards the CaII 8542 line center, upflow motion decrease and turn to downward motion in pores, while the speed of down flow motion increases in the SMIs. (3) There is oscillating motion above pores and the SMIs, and this motion keep its pattern along the height. (4) As height increase, there is a general tendency of the speed shift to downward on pores and the SMIs. This is more clearly seen on the other regions of stronger magnetic field. In this talk, we will present preliminary understanding of the coupling of pore dynamics between the photosphere and the low-chromosphere.

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