• Journal of Biomedical Engineering Research
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• v.18 no.1
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• pp.87-96
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• 1997

A pixel profile in the conventional DANTE sequence is so poor that the excited area by DANTE sequence is a small portion of a pixel. This causes poor signal to noise ratio in DANTE image. In this paper, a frequency modulated(FM) DANTE imaging sequence is proposed to improve pixel profile in DANTE image. A DANTE pulse train is shaped by an FM function so that all the spins within a pixel are excited, thereby improving the signal to noise ratio. It also shows that the pixel profiles are dependent on the sweep in FM signal. Computer simulations and experimental result obtained using a 7.0 T NMR imaging system are presented.

• Journal of Ocean Engineering and Technology
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• v.10 no.2
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• pp.53-60
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• 1996

Many studies on the plastic spin have been done, but it is still an opened subject. It is essential for the modelling of plastic spin to understand its origin and governing parameters. For the task, it is helpful to know the hehavior of sigle crystal. This study gives the interpretations for the plastic spin of a B.C.C(body centered cubic crystal) by numerical simulation. It is discussed that the different levels of shear stresses induced on each slip pair in crystallographic slip systems and the nonlinear relationship between shear stress and slip velocity are the fundamental mechanisms of plastic spins. Finally some comments are provided on the plastic spin of polycrystal.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.4
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• pp.89-95
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• 2005

This paper intends to identify experimentally the relationship between transverse vibration behavior of a spinning disk and high-frequency fluctuation in the driving torque. A testrig has been developed using a CD-ROM disk, a driving motor with torque-varying capability and a power transmission belt and a laser vibrometer was employed to measure the transverse vibration displacements of the disk for a certain range of the spinning speed. The results show that the spinning speed and the magnitude and frequency of the torque fluctuation affect the stability of the disk. In other word, the torque fluctuation causes the instability of the disk at several ranges of the spinning speed below the critical speed and its effects become larger as the disk spins faster or the magnitude of torque fluctuation becomes bigger. The experimental results are found to be in good agreement with analytical estimation.

• Journal of Magnetics
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• v.10 no.1
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• pp.36-39
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• 2005

We report element-resolved and interface-sensitive magnetization reversals investigated from an oppositely exchange-biased NiFe/FeMn/Co structure by employing soft x-ray resonant Kerr rotation measurements. We have found not only switchable uncompensated antiferromagnetic regions with its sizable thicknesses at both interfaces of the FeMn layer but also their strong coupling to the individual ferromagnetic layers. These experimental results provide a better insight into experimentally observed reductions in exchange-bias field on the basis of an interface-proximity model proposed in this work.

• Proceedings of the Korean Magnestics Society Conference
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• 2011.12a
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• pp.55-56
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• 2011

We have carried out spectroscopic studies on the physical properties of graphite tiles modified by electron and proton irradiation. While increase in local order was observed in the electron-irradiated sample, structural disorder and amorphization were revealed in the proton-irradiated sample, with considerably decreased electrical conductivity. Besides, C-OH bond with a sp3 configuration was identified in the proton-irradiated sample, apparently giving rise to a narrow ESR peak ascribed to localized spins.

• The Korean Journal of Ceramics
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• v.6 no.4
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• pp.405-407
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• 2000

Polycrystalline films of Ni- and Co-ferrites films are prepared from aqueous solution at $90^{\circ}C$ by ferrite plating, which are subjected to Fe$^57$ conversion electron Mossbauer spectroscopy in backscatter mode. The average angle of Fe spins relative to the film plane is evaluated as 18 degree and 82 degree for the Ni- and Co-ferrite films, respectively, indicating a prominent magnetic anisotropy parallel and perpendicular to the film plane. It was also verified by the magnetization measurements.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.791-798
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• 2001

As the form factor of the disk drive is decreased, many mechanical issues that are negligible in larger form factors, should be considered for the design of the miniature drives. This paper deals with basic research on vibration characteristics and design considerations of small disks and actuators. The natural frequencies of micro-sized disks with polycabonate and glass substrates are experimentally measured, being compared to FEM results. In order to investigate the effects of rotating speeds, airflow and disk size on power consumption. we measure power imposed to spindle motor when different optical disks are spins in vacuum chamber. Finally, The vibration characteristics of the micro actuator used in a IBM Microdrive are experimentally studied for the application to the basic design of micro optical disks.

• Journal of Magnetics
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• v.12 no.2
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• pp.77-80
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• 2007

Recently there was a proposal for a spin filter by using the spin superlattice structure. In a certain energy range, the proposed structure exhibits a high spin filtering efficiency close to 100%. Unfortunately such energy range turns out to be narrow. In this paper, we report a method to widen the energy range by using an analogy to optical anti-reflection coating. In optics, it is well known that a stack of alternating layers of two dielectric materials can function as a highly transmissive or reflective filter for wide range of wavelength. Since electrons also have wave character as light, it would be possible to make an electronic analog of an optical filter. We demonstrate that alternating layers of two materials with different g-factors can function as a spin filter that allows electrons to be transmitted only when their spins point towards a certain particular direction. This spin-superlattice-based spin filter operates in wide energy ranges, curing the problem in the previous proposal.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.73.1-73.1
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• 2019

We investigate the evolution of the galactic spin of spiral galaxies in various dynamical situations using the N-body/SPH simulations. To do this we first construct a Milky Way-like galaxy model. Then we perform both prograde and retrograde encounters between the spiral galaxy pair. We also conduct a simulation with our galaxy model in isolation for comparison. We find that the circular motion of the disk stars in the inner region of the galaxy decrease clearly when the galaxy experiences strong prograde interactions. Such decrease has not found when the galaxy experiences weak or no interactions. We compare our simulation results with recent observational studies on the galactic spins.

• Journal of Photoscience
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• v.9 no.2
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• pp.70-73
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• 2002

A cyanobacteria-like organism Aaryochloris marina performs oxygenic photosynthesis with near far-red light by the use of chlorophyll d. Reaction center chlorophyll (Chl) of Photosystem (PS) II of A. marina was studied by analysis of millisecond-delayed fluorescence. Delayed fluorescence is emitted by Chi d indicating efficient energy transfer between antenna Chi d molecules and the unknown primary electron donor of PS II. P740 a reaction center Chl of PS I of A. marina is shown to give a dimer type cation, and triplet state with a D value of 245xlO$\^$-4/ cm$\^$-l/ in contrast to the 280-290 xlO$\^$-4/cm$\^$-l/ values of P700 suggesting triplet spins interacting at a 5% larger distance in P740 than in P700.