• Journal of Astronomy and Space Sciences
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• v.36 no.2
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• pp.45-60
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• 2019

The Earth's outer radiation belt has long received considerable attention mainly because the MeV electron flux in the belt varies often dramatically and at various time scales. It is now widely accepted that the wave-particle interaction is one of the major mechanisms responsible for such flux variations. The wave-particle interaction can accelerate electrons to MeV energies, explaining the observed flux increase events, and can also scatter the electrons' motion into the loss cone, resulting in atmospheric precipitation and thus contributing to flux dropouts. In this paper, we provide a review of the current state of research on relativistic electron scattering and precipitation due to the interaction with electromagnetic ion cyclotron (EMIC) waves in the inner magnetosphere. The review is intended to cover progress made over the last ~15 years in the theory and simulations of various issues, including quasilinear resonance diffusion, nonlinear interactions, nonresonant interactions, effects of finite normal angle on pitch angle scattering, effects due to rising tone emission, and ways to scatter near-equatorial pitch angle electrons. The review concludes with suggestions of a few promising topics for future research.

• Advances in nano research
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• v.14 no.4
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• pp.313-327
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• 2023

Zinc metal organic framework (MOF_Zn)-loaded goad nanoparticles (AuNPs) sol (Au@MOF_Zn), which was characterized by TEM, Mapping, FTIR, XRD, and molecular spectrum, was prepared conveniently by solvothermal method. The results indicated that Au@MOF_Zn had a very strong catalytic effect with the nanoreaction of AuNPs formation between sodium oxalate (SO) and HAuCl4. AuNPs in the new indicator reaction had a strong resonance Rayleigh scattering (RRS) signal at 370 nm. The indicator AuNPs generated by this reaction, which had the most intense surface enhanced Raman scattering (SERS) peak at 1621 cm -1. The new SERS/RRS indicator reaction in combination with specific aptamer (Apt) to fabricate a sensitive and selective Au@MOF_Zn catalytic amplification-aptamer SERS/RRS assay platform for carbendazim (CBZ), with SERS/RRS linear range of 0.025-0.5 ng/mL. The detection limit was 0.02 ng/mL. Similarly, this assay platform has been also utilized to detect oxytetracycline (OTC) and profenofos (PF).

• Journal of applied mathematics & informatics
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• v.27 no.5_6
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• pp.1017-1031
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• 2009

The problem of interaction of surface water waves by small undulation at the bottom of a laterally unbounded sea is treated on the basis of linear water wave theory for both normal and oblique incidences. Perturbation analysis is employed to obtain the first order corrections to the reflection and transmission coefficients in terms of integrals involving the shape function c(x) representing the bottom undulation. Fourier transform method and residue theorem are applied to obtain these coefficients. As an example, a patch of sinusoidal ripples is considered in both the cases as the shape function. The principal conclusion is that the reflection coefficient is oscillatory in the ratio of twice the surface wave number to the wave number of the ripples. In particular, there is a Bragg resonance between the surface waves and the ripples, which is associated with high reflection of incident wave energy. The theoretical observations are validated computationally.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.1
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• pp.25-39
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• 2018

In this paper, an integrated analysis model for evaluating the underwater acoustic performance of the multilayered acoustic coatings containing visco-elastic composite layers with hollow glass microspheres is described. The model uses the effective medium theory considering the acoustic scattering and resonance effects of the inclusions. Also, the model incorporates the compressive deformation mechanism associated with hydrostatic pressure. The technique developed in this work was used as the acoustic layer design and performance analysis tools for the practical hull coatings and acoustic baffles in Korean next generation submarines.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.5
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• pp.123-128
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• 2022

Applying rigorous modal transmission-line theory (MTLT), the properties of resonant diffraction gratings under conical light incidence is investigated. The mode vectors pertinent to resonant diffraction under conical mounting vary less with incident angle than those associated with diffraction gratings in classical mounting. Furthermore, as the evanescent diffracted waves drive the leaky modes responsible for the resonance effects, the conical mounting imbues diffraction gratings with larger angular tolerance than their classical counterparts. Based on these concepts, the angular-spectral and wavelength-spectral performance of resonant diffraction gratings in conical and classical mounts by numerical calculations with spectra found for conical incidence are quantified. These results will be useful in various applications demanding resonant diffraction gratings that are efficient and physically sparse.

• The Journal of the Acoustical Society of Korea
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• v.10 no.2
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• pp.36-43
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• 1991

Acoustic backscattering from a buble column in water was studied theoretically and experimentally. For theoretical analysis a general scattering theory was used by assuming the bubble column to be lumped element scatterer which can be characterized by its shape, void fraction and dimensions. When the void fraction is less than 1% and the incident frequency is higher than individual bubble resonance frequencies, the experimental results show that the acoustic backscattering from a bubble column depends mainly on the void fraction rather than the individual bubble sizes. It was also theoretically and experimentally observed that the acoustic backscattering levels were increased and their peaks moved to the lower frequency regin by raising the void fraction of bubble column.

• Journal of the Korean Magnetics Society
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• v.10 no.1
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• pp.22-29
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• 2000

The effective linewidth was measured using the conventional cavity perturbation method at 9.43 GHz in room temperature for Ca-Zr substituted yttrium iron garnet plate. The experimental set-up consists of the network analyzer, the electromagnet and the cylimdrical TE001 cavity. Measurement was performed in the static magnetic field perpendicular to the sample plane. The real and imaginary parts of diagonal component of the microwave susceptibility tensor are obtained from the resonance frequency and the quality factor Q of the cavity. Variations of the effective linewidth was qualitatively explained with the spin wave scattering theory.

• Journal of The Korean Astronomical Society
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• v.47 no.5
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• pp.187-193
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• 2014

Recent cosmological observations indicate that the reionized universe may have started at around z = 6, where a significant suppression around $Ly{\alpha}$ has been observed from the neutral intergalactic medium. The associated neutral hydrogen column density is expected to exceed $10^{21}cm^{-2}$, where it is very important to use the accurate scattering cross section known as the Kramers-Heisenberg formula that is obtained from the fully quantum mechanical time-dependent second order perturbation theory. We present the Kramers-Heisenberg formula and compare it with the formula introduced in a heuristic way by Peebles (1993) considering the hydrogen atom as a two-level atom, from which we find a deviation by a factor of two in the red wing region far from the line center. Adopting a representative set of cosmological parameters, we compute the Gunn-Peterson optical depths and absorption profiles. Our results are quantitatively compared with previous work by Madau & Rees (2000), who adopted the Peebles approximation in their radiative transfer problems. We find deviations up to 5 per cent in the Gunn-Peterson transmission coefficient for an accelerated expanding universe in the red off-resonance wing part with the rest wavelength ${\Delta}{\lambda}{\sim}10{\AA}$.

• Journal of the Optical Society of Korea
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• v.18 no.3
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• pp.274-282
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• 2014

In this study, closely spaced Au nanoparticles which are arranged in nanocluster (heptamer) configurations have been employed to design efficient plasmonic subwavelength devices to function at the telecommunication spectrum (${\lambda}$~1550 nm). Utilizing two kinds of nanoparticles, the optical properties of heptamer clusters composed of Au rod and shell particles that are oriented in triphenylene molecular fashion have been investigated numerically, and the cross-sectional profiles of the scattering and absorption of the optical power have been calculated based on a finite-difference time-domain (FDTD) method. Plasmon hybridization theory has been utilized as a theoretical approach to characterize the features and properties of the adjacent and mutual heptamer clusters. Using these given nanostructures, we designed a complex four-branch ($1{\times}4$) Y-shape splitter that is able to work at the near infrared region (NIR). This splitter divides and transmits the magnetic plasmon mode along the mutual heptamers arrays. Besides, as an important and crucial parameter, we studied the impact of arm spacing (offset distance) on the guiding and dividing of the magnetic plasmon resonance propagation and by calculating the ratio of transported power in both nanorod and nanoshell-based structures. Finally, we have presented the optimal structure, that is the four-branch Y-splitter based on shell heptamers which yields the power ratio of 23.9% at each branch, 4.4 ${\mu}m$ decaying length, and 1450 nm offset distance. These results pave the way toward the use of nanoparticles clusters in molecular fashions in designing various efficient devices that are able to be efficient at NIR.

• Nuclear Engineering and Technology
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• v.52 no.3
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• pp.461-468
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• 2020

The improvements of the DeCART/MUSAD code system for uncertainty analysis of HTGR neutronic parameters are presented in this paper. The function for quantifying an uncertainty of critical-spectrumweighted few group cross section was implemented using the generalized adjoint B₁ equation solver. Though the changes between the infinite and critical spectra cause a considerable difference in the contribution by the graphite scattering cross section, it does not significantly affect the total uncertainty. To reduce the number of iterations of the generalized adjoint transport equation solver, the generalized adjoint B₁ solution was used as the initial value for it and the number of iterations decreased to 50%. To reflect the implicit uncertainty, the correction factor was derived with the resonance integral. Moreover, an additional correction factor for the double heterogeneity was derived with the effective cross section of the DH region and it reduces the difference from the complete uncertainty. The code system was examined with the MHTGR-350 Ex.II-2 3D core benchmark. The k_eff uncertainty for Ex.II-2a with only the fresh fuel block was similar to that of the block and the uncertainty for Ex.II-2b with the fresh fuel and the burnt fuel blocks was smaller than that of the fresh fuel block.