• Bulletin of the Korean Chemical Society
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• 제4권2호
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• pp.64-67
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• 1983

NMR shift arising from the electron orbital angular momentum and the electron spin dipolar-nuclear spin angular momentum interactions has been investigated for a $4d^{1}$ system in a strong crystal field of octahedral symmetry. To examine the NMR shif for a $4d^{1}$ system in a strong crystal field of octahedral symmetry, we derive a general expression for ${\Delta}$B/B using a nonmultipole expansion technique. From this expression all the multipolar terms are determined. For the $4d^{1}$ system in a strong crystal field of octahedral symmetry the exact solution for NMR shift, ${\Delta}$B, is compared with the multipolar results. ${\Delta}$B/B for the $4d^{1}$ system is also compared with that for the $3d^{1}$ system. It is found that the $1/R^{7}$ term contributes dominantly to the NMR shift. However, there is good agreement between the nonmultipole and multipolar results for R-values larger than 0.2 nm for the $4d^{1}$ system but for R-values larger than 0.4 nm for the $3d^{1}$ system.

• Bulletin of the Korean Chemical Society
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• 제7권2호
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• pp.89-96
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• 1986

The NMR chemical shift arising from 4d electron angular momentum and 4d electron spin dipolar-nuclear spin angular momentum interaction for a $4d^1$ system in a strong crystal field of octahedral symmetry, when the threefold axis is chosen as the quantization axis, has been investigated. A general expression using a nonmultipole expansion method is derived for the NMR chemical shift. From this expression all the multipolar terms are determined. We find that the nonmultipolar results for the NMR chemical shift ${\Delta}B$, is exactly in agreement with the multipolar results when $R {\ge} 0.20$ nm. It is also found that the 1/$R^7$ term contributes to the NMR chemical shift almost the same as the 1/$R^5$ in magnitude. The temperature dependence analysis of ${\Delta}B$/B(ppm) at various values of R shows that the 1/$T^2$ term has the dominant contribution to the NMR chemical shift but the contributions of other two terms are certainly significant for a $4d^1$ system in a strong crystal field of octahedral symmetry when the threefold axis is chosen to be the axis of quantization.

• Bulletin of the Korean Chemical Society
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• 제5권2호
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• pp.55-60
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• 1984

The NMR shift arising from the electron angular momentum and electron spin dipolar-nuclear spin angular momentum interactions has been investigated for a $4d^1$system in a strong crystal field environment of tetragonal symmetry. A general formula for NMR shift is used to compute the NMR shifts along the (100), (010), (001), (110) and (111) axes. We find that from the computed results, the NMR shift along the (100) and (010) axes is consistent with each other in a strong crystal field environment of tetragonal symmetry, but the NMR shift along the (001) axis is about triply greater in magnitude than those along the (100) and (010) axes and is opposite in sign to those along (100) and (010) axes. In this work, we express the expansion coefficients $a_1^{(i)}$ and $b_1^{(i)}$ of $A_i$ and $B_i$ in terms of $g_m^{(i)}$ and $h_m^{(i)}$ and two matrices $c_{lm}$ and $d_{lm}$ of radial dependence. The NMR shift is also separated into the contributions of multipolar terms. We find that $1/R^3$ term contributes dominantly to the NMR shift along the (100), (010), (001) and (110) axes while along the (111) axis $1/R^5$ term dominantly contributes. However, the contribtions of the other terms may not be negligible.

• 천문학회지
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• 제54권2호
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• pp.71-88
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• 2021

We use N-body/hydrodynamic simulations to study the evolution of the spin of a Milky Way-like galaxy through interactions. We perform a controlled experiment of co-planar galaxy-galaxy encounters and study the evolution of disk spins of interacting galaxies. Specifically, we consider cases where the late-type target galaxy encounters an equally massive companion galaxy, which has either a late or an early-type morphology, with a closest approach distance of about 50 kpc, in prograde or retrograde sense. By examining the time change of the circular velocity of the disk material of the target galaxy from each case, we find that the target galaxy tends to lose the spin through prograde collisions but hardly through retrograde collisions, regardless of the companion galaxy type. The decrease of the spin results mainly from the deflection of the orbit of the disk material by tidal disruption. Although there is some disk material which gains the circular velocity through hydrodynamic as well as gravitational interactions or by transferring material from the companion galaxy, it turns out that the amount of the material is generally insufficient to increase the overall galactic spin under the conditions we set. We find that the spin angular momentum of the target galaxy disk decreases by 15-20% after a prograde collision. We conclude that the accumulated effects of galaxy-galaxy interactions will play an important role in determining the total angular momentum of late-type galaxies.

• 천문학회보
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• 제44권1호
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• pp.34.3-34.3
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• 2019

We report our discovery of observational evidence for the coherence between galaxy rotation and the average motion of neighbors. Using the Calar Alto Legacy Integral Field Area (CALIFA) survey data analyzed with the Python CALIFA STARLIGHT Synthesis Organizer (PyCASSO) platform, and the NASA-Sloan Atlas (NSA) catalog, we estimate the angular momentum vectors of 445 CALIFA galaxies and build composite maps of their neighbor galaxies on the parameter space of velocity versus distance. The composite radial profiles of the luminosity-weighted mean velocity of neighbors show striking evidence for dynamical coherence between the rotational direction of the CALIFA galaxies and the average moving direction of their neighbor galaxies. The signal of such dynamical coherence is significant for the neighbors within 800 kpc distance from the CALIFA galaxies with a confidence level of $3.5{\sigma}$, when the angular momentum is measured at the outskirt ($Re<R{\leq}2Re$) of each CALIFA galaxy. We also find that faint or kinematically misaligned galaxies show stronger coherence with neighbor motions than bright or kinematically well-aligned galaxies do. Our results show that the rotation of a galaxy, particularly at its outskirt, may be significantly influenced by recent interactions with its neighbors.

• Bulletin of the Korean Chemical Society
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• 제6권5호
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• pp.255-259
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• 1985

The NMR chemical shift arising from 4d electron orbital angular momentum and 4d electron spin dipolar-nuclear Spin angular momentum interactions for a $4d^2$ system in a strong crystal field environment of octahedral symmetry has been investigated when the four fold axis is taken as the quantization axis. The NMR results are comparted with the multipolar shift at various R-values and we find that the exact results are in agreement with the multipolar shift when $R{\geqslant}0.20 nm.$ We also separate the NMR shift into the contribution of the $1/R^5$ and $1/R^7$ terms. It is found that the contribution of the $1/R^5$term to the NMR shift is dominant than the contribution of the $1/R^7$ term. Temperature dependence analysis shows that the $1/T^2$ term is the dominant contribution to the NMR shift for a $4d^2$ system but the contribution of the 1/T term may not negligible. The similar results are obtained for a $4d^1$ system from the temperature dependence analysis.

• 천문학회보
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• 제46권1호
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• pp.56.3-57
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• 2021

We use N-body/hydrodynamic simulations to study the evolution of the spin of a Milky Way-like galaxy through interactions. We perform a controlled experiment of co-planner galaxy-galaxy encounters and study the evolution of disk spins of interacting galaxies. Specifically, we consider the cases where the late-type target galaxy encounters an equally massive companion galaxy, which has either a late or an early-type morphology, with the closest approach distance of about 50 kpc, in prograde or retrograde sense. By examining the time change of the circular velocity of the disk material of the target galaxy from each case, we find that the target galaxy tends to lose the spin through prograde collisions but hardly through retrograde collisions, regardless of the companion galaxy type. The decrease of the spin results mainly from the deflection of the orbit of the disk material by tidal disruption. It is found that the spin angular momentum of the disk of the target galaxy decreases by 15 - 20% after a prograde collision. We conclude that the accumulated effects of galaxy-galaxy interactions will play an important role in determining the angular momentum of late-type galaxies at current stage.

• 한국광학회지
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• 제35권5호
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• pp.218-227
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• 2024

펨토초 레이저 펄스를 이용한 테이블 탑(table-top) 규모의 THz파 광원은 주로 전자가 가진 전하량의 시공간적인 변화를 기반으로 한다. 본 해설논문에서는 전자가 가진 스핀 각운동량이 THz파 발생에 기여하는 새로운 방식에 대해 소개한다. 우선 강자성체(ferromagnet)에서의 레이저 유도 스핀 전류 발생에 초점을 맞추어 나노미터 두께의 강자성체/비자성체 복합 박막에서의 고출력, 광대역, 편광 자유도 등 우수한 특성을 설명한다. 또한 나노미터 두께의 박막을 기반으로 반도체 결합 소자 개발, 대면적 광 소자 개발, 플렉시블 광 소자 개발 등의 다양한 응용 기술 연구를 소개한다. 이를 통해 스핀트로닉 THz파 발생 원리를 이해하고, 차세대 THz 광 소자로서 주목받고 있는 전자의 스핀을 활용한 다양한 응용 연구를 수행하는 데 도움을 주고자 한다.

• 한국지구과학회지
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• 제45권4호
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• pp.292-303
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• 2024

We study quasi-spherical, supersonic accretion flows around black holes using high-accuracy numerical simulations. We describe a code, the Lagrangian Total Variation Diminishing (TVD), and a remap routine to address a specific issue in the Advection Dominated Accretion Flow (ADAF) that is, appropriately handling the angular momentum even near the inner boundary. The Lagrangian TVD code is based on an explicit finite difference scheme on mass-volume grids to track fluid particles with time. The consequences are remapped on fixed grids using the explicit Eulerian finite-difference algorithm with a third-order accuracy. Test results show that one can successfully handle flows and resolve shocks within two to three computational cells. Especially, the calculation of a hydrodynamical accretion disk without viscosity around a black hole shows that one can conserve nearly 100% of specific a ngular momentum in one-and two-dimensional cylindrical coordinates. Thus, we apply this code to obtain a numerically similar ADAF solution. We perform simulations, including viscosity terms in one-dimensional spherical geometry on the non-uniform grids, to obtain greater quantitative consequences and to save computational time. The error of specific angular momentum in Newtonian potential is less than 1% between r~10r_s and r~10⁴ r_s, where r_s is sink size. As Narayan et al. (1997) suggested, the ADAFs in pseudo-Newtonian potential become supersonic flows near the black hole, and the sonic point is r_sonic~5.3r_g for flow with α =0.3 and γ=1 .5. Such simulations indicate that even the ADAF with γ=5/3 is differentially rotating, as Ogilvie (1999) indicated. Hence, we conclude that the Lagrangian TVD and remap code treat the role of viscosity more precisely than the other scheme, even near the inner boundary in a rotating accretion flow around a nonrotating black hole.

• 한국운동역학회지
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• 제16권4호
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• pp.153-164
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• 2006

This thesis is focused on kinematical and kinematical analysis of each types(Type #1 : use both swing of arm and reaction of knee, Type #2 : Use only swing of arm, not reaction of knee, type #3 : Neither use of swing of arm nor reaction of knee) of vertical jumps according to gender of High School Students. The subjects of this study is High School Student's male and female, 5 each, for analyzation of actions 3D image analyzing and GRF machines were used. To identify the differences of analyzed variables, an independent T-test on gender, an One-way ANOVA on types were used. Summery of the results are stated below. first of all, female students showed differences on Hip Joint angle and Joint Velocity from male students on Kimentic Variable. So training on hip joint force of flection and extension of female students is needed. Both male and female students showed relatively bigger result of arm's Angular Momentum than thigh's Angular Momentum on Type #1. This is regarded of faster Joint Velocity of Arm. Bigger result of female students of arm's contribution on Type #1 than male students can be said as Female student's weaker hip joint's angular muscle force than male student's, so the dependency of arm is heavier than male students. In Kinetic variable, GRF showed bigger result on male students than female students. So female students need to enhance joint's torque to increase GRF than male students. On vertical Impulse, high numeric data of last two reaction of tiptoe of vertical GRF and antero-posterior GRF helped increasing impulse by extending action time of force.