• Nuclear Engineering and Technology
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• v.11 no.1
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• pp.1-20
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• 1979

Neutron inelastic scattering studies on polycrystalline hydrates, NaBr-2$H_2O$ and BaCl$_2$-2$H_2O$ have been performed to observe librational modes. Assuming all observed peaks are from the $H_2O$ librational origin, the weighted frequency distribution functions are obtained by eliminating the contributions from the higher order processes. All of theoretical frequencies obtained using FG matrix method are dus to highly mixed modes, and therefore the modes identified as significant $H_2O$ librationat modes from their large potential energy distributions are assigned to the observed peaks. The H-bond interactions are estimated using a modified Lippincott Schroeder potential function, and the applicability of the potential function to the H-bond with highly bent or bifurcated configuration is examined on the basis of the shape of $H_2O$ librational potential energies. Some discussions are given on the usefulness of introducing O-H…Y bending terms in addition to the H…Y stretching in similar frequency calculation in order to obtain more information on the nature of H-bond. Also the purity and symmetry properties of the $H_2O$ librational modes are discussed using group theoretical analyses.

• Nuclear Engineering and Technology
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• v.53 no.2
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• pp.423-429
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• 2021

The investigation of the utilization of enriched ²⁰⁸Pb as a coolant to enhance the performance of a long-life fast reactor with a Modified CANDLE (Constant Axial shape of Neutron flux, nuclide densities, and power shape During Life of Energy production) burnup scheme has performed. The analyzes were performed on a reactor with thermal power of 800 MegaWatt Thermal (MWTh) with a refueling process every 15 years. Uranium Nitride (enriched ¹⁵N), ²⁰⁸Pb, and High-Cr martensitic steel HT-9 were employed as fuel, coolant, and cladding materials, respectively. One of the Pb-nat isotopes, ²⁰⁸Pb, has the smallest neutron capture cross-section (0.23 mb) among other liquid metal coolants. Furthermore, the neutron-producing cross-section (n, 2n) of ²⁰⁸Pb is larger than sodium (Na). On the other hand, the inelastic scattering energy threshold of ²⁰⁸Pb is the highest among Na, ^natPb, and Bi. The small inelastic scattering cross-section of ²⁰⁸Pb can harden the neutron energy spectrum. Therefore, ²⁰⁸Pb is a better neutron multiplier than any other liquid metal coolant. The excess neutrons cause more production than consumption of ²³⁹Pu. Hence, it can reduce the initial fuel loading of the reactor. The selective photoreaction process was developing to obtain enriched ²⁰⁸Pb. The neutronic was calculated using SRAC and JENDL 4.0 as a nuclear data library. We obtained that the modified CANDLE reactor with enriched ²⁰⁸Pb as coolant and reflector has the highest k-eff among all reactors. Meanwhile, the ^natPb cooled reactor has the lowest k-eff. Thus, the utilization of the enriched ²⁰⁸Pb as the coolant can reduce reactor initial fuel loading. Moreover, the enriched ²⁰⁸Pb-cooled reactor has the smallest power peaking factor among all reactors. Therefore, the enriched ²⁰⁸Pb can enhance the performance of a long-life Modified CANDLE fast reactor.

• Korean Journal of Metals and Materials
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• v.49 no.7
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• pp.541-548
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• 2011

Thermomechanical fatigue (TMF) behavior of heat resistant austenitic stainless steel was evaluated in the temperature range from 100$^{\circ}C$ to peak temperatures of 600 to 800$^{\circ}C$; The fatigue lives under TMF conditions were plotted against the plastic strain range and the dissipated energy per cycle. In the expression of the inelastic strain range versus fatigue life, the TMF data obtained at different temperature ranges were located close to a single line with a small deviation; however, when the dissipated energy per cycle, calculated from the area of the stress-strain hysteresis loops at the half of the fatigue life, was plotted against the fatigue life, the data showed greater scattering than the TMF life against the inelastic strain range. A noticeable stress relaxation in the stress-strain hysteresis curve took place at the peak temperatures higher than 700$^{\circ}C$, but all specimens in this study exhibited cyclic hardening behavior with TMF cycles. Recrystallization occurred during the TMF cycle concurrent with the formation of fine subgrains in the recrystallized region, which is considered to cause the cyclic hardening of the steel.

• Electrical & Electronic Materials
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• v.9 no.6
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• pp.564-571
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• 1996

We calculated the drift-velocities of electrons and holes of I $n_{0.53}$(A $l_{x}$G $a_{1-x}$ )$_{0.47}$As, which is used for semiconductor materials of high performance HBTs, along with the various doping concentrations and Al mole fractions as well as the electric fields by Monte Carlo experiment. Especially, for the valence bands the accuracy of hole-drift-velocity was improved in the consideration of intervalley scattering due to the inelastic scattering of acoustic phonon. From the results the empirical formulas of the low- and high field mobility of electrons and holes were extracted by using nonlinear least square fitting method. The accuracy of the formulas was proved by comparing the formula of low-field electron mobility as well as drift-velocity of I $n_{0.53}$ G $a_{0.47}$As and of low-field hole mobility of GaAs with the measured values, where the error was below 10%. For the high-field mobilities of electron and hole the results calculated by the formulas were very well matched with the MC experimental results except at the narrow field range where the electrons produced the velocity overshoot and the corresponding error was about 30%.0%. 30%.0%.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.137-137
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• 2000

The surface collective modes of thin K films deposited on Al(111) have been investigated using frequency dependent photoyield measurements and momentum resolved inelastic electron scattering. Jellium based theoretical calculations have predicted a richer set of features in the thin films than for the surface of a semi-infinite solid because there are th interference between two interfaces (substrate-film and film-vacuum) and heavy damping on the substrate. The use of an optical probe and electron scattering has allowed us to draw a more complete picture of the dynamic screening in thin films. The number, dispersion, damping and optical activity of the collective modes of the thin films have been measured as a function of K film thickness. New overlayer-induced excitations are observed : At qII=0, they correspond to the antisymmetric slab mode and the multipole surface plasmon. At finite qII=0, these modes undergo a transition towards the K multipole and monopole surface plasmons. With increasing coverage, the overlayer excitations turn into the collective modes of semi-infinite K. For a consistent interpretation of photoyield and electron energy loss spectra it is crucial to account for the non-analytic dispersion of the overlayer modes at small parallel wave vectors and for the finite angular resolution of the detector. The observed dispersions confirm predictions based on the time-dependent density functional approach.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.88.2-88.2
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• 2014

The symbiotic star V1016 Cygni shows the Raman scattered O VI features at $6825{\AA}$ and $7088{\AA}$. These are formed through inelastic scattering of O VI 1032, 1038 by atomic hydrogen. They exhibit characteristic double peak profiles with a stronger red peak, which is explained by the accretion flow around the white dwarf. In addition, the two Raman features have different profiles in such a way that the blue part of the Raman 7088 feature is relatively more suppressed than the Raman 6825 counterpart. We produced the Doppler maps of the two Raman features in order to trace the origin of the disparate profiles. We conclude that the profile difference is due to various O VI 1032 to O VI 1038 flux ratios in the accretion region. This is consistent with the picture where the slow stellar wind from the giant interacts with the accretion flow around the white dwarf.

• Progress in Superconductivity
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• v.13 no.3
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• pp.146-150
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• 2012

We solve the momentum resolved d-wave Eliashberg equation employing the magnetic excitation spectrum from the inelastic neutron scattering on the LSCO superconductors reported by Vignolle et al. The magnetic excitation spectrum exhibits 2 peaks: a sharp incommensurate peak at 18 meV at momentum (${\pi}$, ${\pi}{\pm}{\delta}$) and (${\pi}{\pm}{\delta}$, ${\pi}$) and another broad peak near 40~70 meV at momentum (${\pi}$, ${\pi}$). Above 70 meV, the magnetic excitation spectrum has a long tail that is shaped into a circle centered at (${\pi}$, ${\pi}$) with ${\delta}$. The sign of the real part of the self-energy is determined by the momentum position of the peaks of the magnetic excitation spectrum and bare dispersion. We will discuss the effects of the each component of the magnetic excitation spectrum on the self-energy, the pairing self-energy.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.61-61
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• 2010

By using high resolution x-ray photoelectron spectroscopy, we show that inelastic scattering of photoelectron at low temperature (30K~50K) generates two kinds of oxygen species on Pt (111) surface. Intense synchrotron radiation source dissociates oxygen molecules into chemisorbed atomic oxygen and induces the formation of PtO on surface. Estimated coverage of dissociated atomic oxygen is 0.5 ML, suggesting possible formation of p($2{\times}1$) surface structure, while PtO coverage shows saturation coverage of 0.5 ML. Molecular oxygen dosed at 30 K undergoes thermally activated transition from physisorbed to chemisorbed state at around 40K.

• Nuclear Engineering and Technology
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• v.35 no.1
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• pp.35-44
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• 2003

The neutron induced nuclear data for Eu-153, Gd-155 and Cd-157 are calculated and evaluated in the high energy region. The evaluation procedure for deformed nuclei is setup by using Ecis-Empire codes. The energy dependent optical model potential parameters are searched based on the recent experimental data and applied up to 20 MeV. Optical model, full featured Hauser-Feshbach model and multistep direct and multistep compound model are used in the calculation. The direct-semidirect capture model and the direct coupled-channels contribution to discrete levels are introduced to improve the capture and inelastic scattering cross sections. The theoretically calculated cross sections are compared with the experimental data and the evaluated files. The model-calculated total and capture cross sections are in good agreement with the reference experimental data. The evaluated cross section results are compiled to ENDF-6 format and are expected to improve the ENDF/B-Vl.

• Journal of Magnetics
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• v.8 no.4
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• pp.153-156
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• 2003

The values of crystalline-electric-field parameters $A_{nm}$ for $RFe_{11}$Ti $H_{x}$ (R=Tb,Ho) (x=0,l) are obtained by fitting calculations to the magnetization curves along the crystal axes at 4.2 K and higher temperatures. The insertion of H element in RFe$_{11}$Ti significantly affects CEF parameters $A_{nm}$ . By using exchange field 2${\mu}$$_{B}$ $H_{ex}$ derived by inelastic neutron scattering and fitted $A_{nm}$ , the calculations reproduce the experimental curves well.