• 대한수학회논문집
• /
• 제36권4호
• /
• pp.817-827
• /
• 2021

In this paper, we prove that a diffeomorphism f on a normal almost contact 3-manifold M is a CRL-transformation if and only if M is an α-Sasakian manifold. Moreover, we show that a CR-loxodrome in an α-Sasakian 3-manifold is a pseudo-Hermitian magnetic curve with a strength $q={\tilde{r}}{\eta}({\gamma}^{\prime})=(r+{\alpha}-t){\eta}({\gamma}^{\prime})$ for constant 𝜂(𝛄'). A non-geodesic CR-loxodrome is a non-Legendre slant helix. Next, we prove that let M be an α-Sasakian 3-manifold such that (∇_YS)X = 0 for vector fields Y to be orthogonal to ξ, then the Ricci tensor 𝜌 satisfies 𝜌 = 2α²g. Moreover, using the CRL-transformation $\tilde{\nabla}^t$ we fine the pseudo-Hermitian curvature $\tilde{R}$, the pseudo-Ricci tensor $\tilde{\rho}$ and the torsion tensor field $\tilde{T}^t(\tilde{S}X,Y)$.

• Bulletin of the Korean Chemical Society
• /
• 제9권5호
• /
• pp.280-282
• /
• 1988

The structural, electrical and magnetic properties were investigated for the high-Tc superconductor $YBa_2Cu_3O_{7-x}$, where x was 0.13. The results of temperature dependence of the resistivity and the magnetization in $YBa_2Cu_3O_{6.87}$ whose structure and phase are confirmed by arialysis of X-ray powder diffraction pattern have been reported. A very sharp superconductivity transition appears at 92K in the specimen whose chemical composition is determined from redox titration, strongly suggesting that this specimen consists of a single-phase superconductor. From the results of X-ray diffraction analysis, magnetization curves, levitation and resistance measurements, it is suggested that the observed superconductivity is bulk property in nature and that the $YBa_2Cu_3O_{6.87}$ phase is responsible for the superconductivity of the present reproducible specimen.

• Steel and Composite Structures
• /
• 제46권4호
• /
• pp.513-523
• /
• 2023

Buckling and post-buckling behaviors of geometrically perfect double-curvature shells made from smart composites have been investigated. The shell has been supposed to be exposed to transverse mechanical loading and magneto-electro-elastic (MEE) coupling. The composite shell has been made of two constituents which are piezoelectric and magnetic ingredients. Thus, the elastic properties might be variable based upon the percentages of the constituents. Incorporating small scale impacts in regard to nonlocal theory leads to the establishment of the governing equations for the double-curvature nanoshell. Such nanoshell stability will be shown to be affected by composite ingredients. More focus has been paid to the effects of small scale factor, electric voltage and magnetic intensity on stability curves of the nanoshell.

• Bulletin of the Korean Chemical Society
• /
• 제29권6호
• /
• pp.1233-1242
• /
• 2008

The hydration effect on the intrinsic magnetism of natural salmon double-strand DNA was explored using electron magnetic resonance (EMR) spectroscopy and superconducting quantum interference device (SQUID) magnetic measurements. We learned from this study that the magnetic properties of DNA are roughly classified into two distinct groups depending on their water content: One group is of higher water content in the range of 2.6-24 water molecules per nucleotide (wpn), where all the EMR parameters and SQUID susceptibilities are dominated by spin species experiencing quasi one-dimensional diffusive motion and are independent of the water content. The other group is of lower water content in the range of 1.4-0.5 wpn. In this group, the magnetic properties are most probably dominated by cyclotron motion of spin species along the helical π -way, which is possible when the momentum scattering time (${\tau}_k$) is long enough not only to satisfy the cyclotron resonance condition (${\omega}_c{\tau}_k$ > 1) but also to induce a constructive interference between the neighboring double helices. The same effect is reflected in the S-shaped magnetization-magnetic field strength (M-H) curves superimposed with the linear background obtained by SQUID measurements, which leads to larger susceptibilities at 1000 G when compared with the values at 10,000 G. In particular, we propose that the spin-orbital coupling and Faraday's mutual inductive effect can be utilized to interpret the dimensional crossover of spin motions from quasi 1D in the hydrate state to 3D in the dry state of dsDNA.

• 한국진공학회지
• /
• 제20권1호
• /
• pp.57-62
• /
• 2011

열처리 방식을 통하여 형성된 FePt 나노 입자를 사용하는 자기 양자점 소자를 제작하고, 전기적 및 자기적 특성을 연구하였다. FePt 자기 양자점 터널링 소자는 p 형 Si 기판 상부에 약 20 nm의 $SiO_2$ 터널 절연막을 형성하고 FePt 박막을 3 nm 두께로 증착한 후에 열처리 방식을 이용하여 8~15 nm 크기의 양자점을 갖는 구조이다. 터널링 소자의 전류-전압 특성을 자기장과 온도 변화에 따라 관찰하였고 특히, 저온에서 비선형적인 전류-전압 곡선을 확인하였으며 이러한 단전자 수송현상을 전자의 hopping 모델과 양자점의 터널링 현상을 이용하여 설명하였다. FePt 양자점 터널링 소자는 20 K에서 터널링 현상을 보였으며, 양단에 가해준 전압과 관계없이 외부 자기장이 증가할수록 음의 자기저항이 커지는 현상을 관찰하였고, 9,000 G에서 약 26.2 %의 자기저항 비를 확인하였다.

• 한국자기학회지
• /
• 제23권3호
• /
• pp.98-103
• /
• 2013

NiFe/Cu/NiFe/IrMn/NiFe/Cu/NiFe 이중 거대자기저항-스핀밸브(GMR-SV) 박막의 진공 후열처리 온도의존성을 조사하여 강자성층 자화용이축을 유도하였다. 자유층과 고정층의 자화용이축에 의존하는 이중 스핀밸브 박막의 자기저항곡선은 외부자기장 각도를 다르게 하면서 측정하였다. 열처리온도가 $105^{\circ}C$일 때, $0^{\circ}$와 $90^{\circ}$ 사이 임의 측정 각도에서 약 2.0 %/Oe인 자장감응도 특성을 얻었다. 이러한 결과는 면상 강자성층과 자유층을 면상에서 서로 직교한 자화방향 유도를 통하여 이중구조 GMR-SV 박막이 고감도 바이오센서로 사용할 가능성을 제시하였다.

• 천문학회보
• /
• 제36권2호
• /
• pp.86.2-86.2
• /
• 2011

We investigate the evolution of coronal loop emission in the context of the coronal magnetic field topology. New modeling techniques allow us to investigate the magnetic field structure and energy release in active regions (ARs). Using these models and high-resolution multi-wavelength coronal observations from the Transition Region and Coronal Explorer and the X-ray Telescope on Hinode, we are able to establish a relationship between the light curves of coronal loops and their associated magnetic topologies for NOAA AR 10963. We examine loops that show both transient and steady emission, and we find that loops that show many transient brightenings are located in domains associated with a high number of separators. This topology provides an environment for continual impulsive heating events through magnetic reconnection at the separators. A loop with relatively constant X-ray and EUV emission, on the other hand, is located in domains that are not associated with separators. This result implies that larger-scale magnetic field reconnections are not involved in heating plasma in these regions, and the heating in these loops must come from another mechanism, such as smallscale reconnections (i.e., nanoflares) or wave heating. Additionally, we find that loops that undergo repeated transient brightenings are associated with separators that have enhanced free energy. In contrast, we find one case of an isolated transient brightening that seems to be associated with separators with a smaller free energy.

• 한국초전도저온공학회:학술대회논문집
• /
• 한국초전도저온공학회 2002년도 학술대회 논문집
• /
• pp.277-280
• /
• 2002

It is well known that the critical current of a HTS tape has anisotropic characteristic in magnetic field. We are interested in critical current density distribution of a HTS tape. We assumed the experimentally obtained Ic-B curves do represent the local properties of HTS tapes and calculated the critical current density distribution of HTS tapes using numerical method. Also we predicted the critical current of the tapes.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1989년도 추계학술대회 논문집 학회본부
• /
• pp.58-62
• /
• 1989

Magnetic levitation railway is being developed as an advanced ground transport system which is high speed and has less environmental pollution. In this paper, the effectiveness of the proposed controller is proved by a vehicle body's curvature running characteristics. We select two types of transition curves for investigation, namely clothoid and sine.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.52-54
• /
• 2005

This paper describes an exciting current calculation method for transformers by finite element method. In case of a special case such as air-gap presence, one can not calculate exciting current accurately using exciting power curves due to flinging effect, magnetic saturation and so on. Transient analysis with external circuit is performed with a 2D model and compared to a test result.