• Journal of the Korean Magnetic Resonance Society
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• v.3 no.2
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• pp.84-89
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• 1999

The 87Rb quadrupole coupling constants (e2qQ/h) and the asymmetry parameters (η) in RbMnCl3 were determined from a nonlinear least-squares fit to the 87Rb NMR powder spectra. The spectra were acquired in the temperature range from 260K to 330K. An important feature in this work is the determination of the quadrupole coupling constants and the asymmetry parameters for two physically nonequivalent Rb sites, Rb(I) and Rb(II), as a function of temperature. In addition, a structural phase transition at room temperature was conformed with the changes in the quadrupole coupling constant and the asymmetry parameter of Rb(II) site.

• Journal of the Korean Magnetic Resonance Society
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• v.7 no.1
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• pp.16-24
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• 2003

Nuclei with the spin quantum number not smaller than unity have not only the nuclear magnetic moment but also the electric quadrupole moment. The quadrupole moment couples with the electric field gradient (EFG) to produce the nuclear quadrupole interaction. It is well known that two independent parameters, i.e. the quadrupole coupling constant (QCC) and the asymmetry parameter ($\eta$) together with the principal axis directions can fully describe the interaction and are very sensitive to the local symmetry and structure of the solid. In order to obtain quantitative estimates of the EFG tensor for various simple ionic configurations surrounding the nucleus under consideration, we employ the simple point charge approximation and apply the calculated results to some real crystals. General agreement is rather satisfactory.

• Journal of the Korean Magnetic Resonance Society
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• v.8 no.2
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• pp.70-76
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• 2004

ZORA-DFT calculations of $^{11}$B EFG (electric field gradient) tensors for lithium borates, LiB$_3O_5$ (LBO) and Li$_2B_4O_7$ (LTB), were performed. The calculated values of 11B quadrupole coupling constant and asymmetry parameter are in good agreement with the experimental values. The sign of the quadrupole coupling constant for the tetrahedral boron site was deduced from the distortion from the ideal tetrahedral symmetry.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.861-864
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• 2006

In general, 4-pole parameter and three-point method are used for predicting transmission loss which is one of characteristics of Muffler using CAE tools. However, these mehtods show different results from experiment when the flow effects are presented in practical model. In this parer, to overcome these problems, both Fluent and.Sysnoise are used to analyze the performance of extended inlet/outlet muffler including flow effects with varying flow velocity at inlet of duct. Flow fields and quadrupole source is calculated by Fluent. And Sysnoise is used to analyze acoustic performances of muffler with quadrupole source data extracted from Fluent. Finally, the variation of transmission loss is estimated according to various inlet flow velocity.

• Journal of The Korean Astronomical Society
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• v.38 no.2
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• pp.175-178
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• 2005

We show that next-generation galaxy surveys such as KAOS (the Kilo-Aperture Optical Spectro-graph)will constrain dark energy even if the baryon oscillations are missing from the monopole power spectrum and the bias is scale- and time-dependent KAOS will accurately measure the quadrupole power spectrum which gives the leading anisotropies in the power spectrum in redshift space due to peculiar velocities, the finger of God effect, as well as the Alcock-Paczynski effect. The combination of monopole and quadrupole power spectra powerfully breaks the degeneracy between the bias parameters and dark energy and, in the complete absence of baryon oscillations ($\Omega$b = 0), leads to a roughly $500\%$ improvement in constraints on dark energy compared with the monopole spectrum alone. As a result, for KAOS the worst case with no oscillations has dark energy errors only mildly degraded relative to the ideal case, providing insurance on the robustness of KAOS constraints on dark energy. We show that nonlinear effects are crucial in correctly evaluating the quadrupole and significantly improving the constraints on dark energy when we allow for multi-parameter scale-dependent bias.

• Journal of the Korean Magnetics Society
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• v.9 no.6
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• pp.271-277
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• 1999

Amorphous $Fe_{83}B_9Nb_7Cu_1$ alloy has been studied by M$\"{o}$ssbauer spectroscopy. Revised Vincze method was used and distributions of hyperfine field, isomer shift, and quadrupole line broadening of the sample at various temperatures have been evaluated and Curie temperature and $H_{hf}\;(0)$ were calculated to be 393 K and 231 kOe, respectively. Temperature variation of reduced average hyperfine field shows a flattered curvein comparison with the Brillouin curve for S=1. This behavior can be explained on the basis of Handrich molecular field model, in which the parameter Δ, which is a measure of fluctuation in exchange interactions, is assumed to have the temperature dependence ${Delta}=0.75-0.64{\tau}+0.47{\tau}^2$ where $\tau$ is $T/T_C$. At low temperature, the average hyperfine field can be fitted to $H_{hf}\;(T)=H_{hf}\;(0)\;[1-0.44\;(T/T_C)^{3/2}-0.28(T/T_C)^{5/2}-… ]$, which indicates the presence long wave length spin wave excitations. At temperature near TC, reduced average hyperfine field varies as $1.00\;[1-T/T_C]^{0.39}$. It is also found that half-width of the hyperfine field distribution was 102 kOe (3.29 mm/s) at 13 K and decreased monotonically as temperature increased. Above the Curie temperature, an average quadrupole splitting value of 0.43 mm/s was found. Average line broadening due to quadrupole splitting distribution was 0.31 mm/s at 13 K and decreases monotonically to 0.23 mm/s at 320 K, whereas that due to the isomer shift distribution is 0.1 mm/s at 13 K and 0.072 mm/s at 320 K, which is much smaller than that of both hyperfine field and quadrupole splitting. The temperature dependence of the isomer shift can be fitted within the harmonic approximation to a Deybe model with a Debye temperature ${Theta}_D=424{\pm}5K$.TEX>.

• 한국가시화정보학회:학술대회논문집
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• 2004.04a
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• pp.1-7
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• 2004

When a vortex diffracts upon encountering a vortex, many strong and weak waves are produced in the course of interaction. They are the cause of shock wave attenuation and noise production. This phenomenon is fundamental to understanding the more complex supersonic turbulent Jet noise. In this paper we have reviewed the research on shock-vortex interaction we have carried on last seven years. We have computationally investigated the parameter effect. When a shock is strong, shock diffraction pattern becomes complex since the slip lines from the triple points on Mach stem curl into the vortex, causing an entropy layer. When the vortex is unstable, vortexlets are brought about each of which make shock diffraction of a reduced intensity. Strong vortex produces quadrupole noise as it impinges into a vortex. Elementary interaction models such as shock splitting, shock reflection, and shock penetration are presented based on shock tube experiment. These models are also verified by computational approach. They easily explain production and propagation of the aforementioned quadrupole noise, Diverging acoustics are explained in terms of shock-vortexlet interactions for which a computational model Is constructed.

• Journal of the Korean Magnetics Society
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• v.17 no.1
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• pp.26-29
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• 2007

Fe-based powders, Fe-M(M=Cr, Mn, Cu, Zn), were prepared in Ar gas by mechanical alloying and their crystallographic and magnetic properties were investigated. X-ray diffraction indicates that the cubic lattice parameter increases for the M substitution. The distance of closest approach around M can explained the increase of lattice constant in Fe-M powders. $M\"{o}ssbauer$ spectroscopy measurements on Fe-M samples indicates the coexistence of ferromagnetic phases and paramagnetic phase that are created by the distribution of local environment M on Fe atom. On the other hand, The spread of line-width on $M\"{o}ssbauer$ spectra can be explained by the distribution of hyperfine magnetic fields. The results of quadrupole shift and isomer shift revealed that M substitutions in Fe-M powders didn't change both structure and the local charge distribution around Fe atom severely.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.715-721
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• 2008

공동주택에서의 음환경 성능은 실내환경의 질과 연관시켜 설계단계부터 충분한 검토가 필요한 성능항목이다. '국토해양부'는 '공통주택 성능등급 표시제도'에서 Air Duct를 통해 상하층간 전파되는 소음을 제어하기 위한 대책을 요구하고 있다. 이에 화장실에 적합한 구조 및 재질로 소음 저감기를 개발하고, 소음기 성능평가 장치를 구성하여 이론과 비교평가하고, 실제 현장에 설치 시 적용효과를 분석하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.8 s.239
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• pp.921-926
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• 2005

In the idealized model problem of the interaction between a planar travelling shock and a symmetric vortex, the physics of shock distortion and quadrupole sound generation are well known to many researchers. However, the authors have distinguished the weak waves reflected and transmitted by the complicated photograph images obtained from a shock tube experiment. In this paper, we introduces a parametric study based on Navier-Stokes simulation and Rankin vortex model to see the difference of shock deformation shapes. Four combination of the strength of shock and vortex are respectively selected from a parameter plane of shock and vortex strength extended to the strong vortex region. The result shows clearly discernable wave morphology for the main parameters, which is not yet explicitly mentioned by other researchers.