• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.557-562
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• 2004

A surface-piercing barrier model is presented for understanding morphological development in the sheltered region and investigating the main factors causing the severe accumulation. Surface-piercing structures like vertical barriers, surface docks and floating breakwaters are recently favored from the point of view of a marine scenario since they do not in general partition the natural sea. The numerical solutions are compared with experimental data on wave profiles and morphological change rates within a rectangular harbor of a constant depth protected by surface-piercing thin breakwaters as a simplified problem. Our numerical study involves several modules: 1) wave dynamics analyzed by a plane-wave approximation, 2) suspended sediment transport combined with sediment erosion-deposition model, and 3) concurrent morphological changes. Scattering waves are solved by using a plane wave method without inclusion of evanescent modes. Evanescent modes are only considered in predicting the reflection ratio against the vertical barrier and energy losses due to vortex shedding from the lower edge of plate are taken into account. A new relationship to relate the near-bed concentration to the depth-mean concentration is presented by analyzing the vertical structure of concentration. The numerical solutions were also compared with experimental data on morphological changes within a rectangular harbor of constant water depth. Through the numerical experiments, the vortex-induced flow appears to be not ignorable in predicting the morphological changes although the immersion depth of a plate is not deep.

• Nuclear Engineering and Technology
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• v.53 no.7
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• pp.2348-2356
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• 2021

As a relatively new radiation imaging method, the cosmic-ray muon scattering imaging technology can be used to prevent nuclear smuggling and is of considerable significance to nuclear safety. Proposed in this paper is a new reconstruction algorithm based on density clustering, aiming to improve inspection quality with better performance. Firstly, this new algorithm is introduced in detail. Then in order to eliminate the inequity of the density threshold caused by the heterogeneity of the muon flux in different positions, a new flux correction method is proposed. Finally, three groups of simulation experiments are carried out with the help of Geant4 toolkit to optimize the algorithm parameters, verify the correction method and test the inspection quality under shielded condition, and compare this algorithm with another common inspection algorithm under different conditions. The results show that this algorithm can effectively identify and locate nuclear material with low misjudging and missing rates even when there is shielding and momentum precision is low, and the threshold correcting method is universally effective for density clustering algorithms.

• Progress in Medical Physics
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• v.31 no.2
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• pp.9-19
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• 2020

Purpose: This study aims to develop a multi-purpose electron beam irradiation device for preclinical research and material testing using the research electron linear accelerator installed at the Dongnam Institute of Radiological and Medical Sciences. Methods: The fabricated irradiation device comprises a dual scattering foil and collimator. The correct scattering foil thickness, in terms of the energy loss and beam profile uniformity, was determined using Monte Carlo calculations. The ion-chamber and radiochromic films were used to determine the reference dose-rate (Gy/s) and beam profiles as functions of the source to surface distance (SSD) and pulse frequency. Results: The dose-rates for the electron beams were evaluated for the range from 59.16 Gy/s to 5.22 cGy/s at SSDs of 40-120 cm, by controlling the pulse frequency. Furthermore, uniform dose distributions in the electron fields were achieved up to approximately 10 cm in diameter. An empirical formula for the systematic dose-rate calculation for the irradiation system was established using the measured data. Conclusions: A wide dose-rate range electron beam irradiation device was successfully developed in this study. The pre-clinical studies relating to FLASH radiotherapy to the conventional level were made available. Additionally, material studies were made available using a quantified irradiation system. Future studies are required to improve the energy, dose-rate, and field uniformity of the irradiation system.

• Journal of Biosystems Engineering
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• v.31 no.5 s.118
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• pp.389-394
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• 2006

The characteristic of moisture absorption of granular fertilizer was measured at several different opening sizes on the top cover of a hopper in a humid weather. The size of the opening was to represent the degree of looseness of sealing of the top cover of the hopper. The application distribution was characterized by the scattering distance of granular fertilizer with different degree of moisture absorption in a pneumatic granular fertilizer applicator. The moisture absorption rates were 12.92 and 12.26 mg of moisture an hour for one gram of each granular fertilizers of NPK 22-12-12 and 21-17-17, respectively. The moisture absorption increased linearly as the opening size increased. The median value of the scattering distance distribution decreased with time of absorption, however, it decreased very slowly after three hours of absorption.

• Nuclear Engineering and Technology
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• v.24 no.1
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• pp.63-74
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• 1992

The resonant formation rates of muonic molecular ion dtr in the muon-catalyzed fusion are calculated in various fuel temperatures and densities. The elastic scattering cross sections between t$\mu$ and deuterons are obtained by making use of the partial wave method. The transition property of the excited compound molecule [(dt$\mu$)dee]＊ derived by the impulse approximation in the form of a bound-state form factor. The radiative, Auger, and collisional deexcitations are considered as the deexcitation mechanisms of the excited dt$\mu$, and each deexcitation width is calculated as well as back decay width. The resultant reaction widths are used to calculate the formation cross sections of resonant dt$\mu$. The resonant formation rates for dt$\mu$-d and dt$\mu$-t collisions are computed as functions of fuel temperature and density. The calculations show that the resonant formation rates increase with fuel densities and have the maximum values at the particular temperatures where the relative collision energies are equal to the resonant ones.

• Nuclear Engineering and Technology
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• v.51 no.8
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• pp.2018-2025
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• 2019

This study systematically compared two hybrid deterministic/Monte Carlo transport codes, ADVANTG/MCNP and MAVRIC, in solving a difficult shielding problem for a real-world spent fuel storage cask. Both hybrid codes were developed based on the consistent adjoint driven importance sampling (CADIS) methodology but with different implementations. The dose rate distributions on the cask surface were of primary interest and their predicted results were compared with each other and with a straightforward MCNP calculation as a baseline case. Forward-Weighted CADIS was applied for optimization toward uniform statistical uncertainties for all tallies on the cask surface. Both ADVANTG/MCNP and MAVRIC achieved substantial improvements in overall computational efficiencies, especially for gamma-ray transport. Compared with the continuous-energy ADVANTG/MCNP calculations, the coarse-group MAVRIC calculations underestimated the neutron dose rates on the cask's side surface by an approximate factor of two and slightly overestimated the dose rates on the cask's top and side surfaces for fuel gamma and hardware gamma sources because of the impact of multigroup approximation. The fine-group MAVRIC calculations improved to a certain extent and the addition of continuous-energy treatment to the Monte Carlo code in the latest MAVRIC sequence greatly reduced these discrepancies. For the two continuous-energy calculations of ADVANTG/MCNP and MAVRIC, a remaining difference of approximately 30% between the neutron dose rates on the cask's side surface resulted from inconsistent use of thermal scattering treatment of hydrogen in concrete.

• Korea-Australia Rheology Journal
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• v.14 no.3
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• pp.115-119
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• 2002

In this paper, a rheo-optical methodology based on small angle light scattering and polarimetry is applied to investigate in-situ and on a time resolved basis the flow-induced structures in aqueous biopolymeric blends. Water-dextran-gelatin is chosen as an example. It is verified to what extent the laws and scaling relations, originally developed for synthetic polymer blends, are valid for the morphology development in this aqueous biopolymeric mixture. It was observed that under low shear rate conditions, the biopolymeric emulsion can be regarded as a conventional emulsion. However, at high shear rates flow induced homogenization occurs.

• Journal of the Korean Society of Radiology
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• v.2 no.1
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• pp.31-34
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• 2008

The neutron capture spectrum for the light nuclide was very useful to study the nuclear structure. In the present study, the capture gamma-ray from the 27-keV resonance of $^{19}F(n,g)^{20}F$ reaction were measured with an anti-Compton NaI(Tl) spectrometer and the 3-MV Pelletron accelerator of the Research Laboratory for Nuclear Reactors at the Tokyo institute of technology. A neutron Time-of-Flight method was adopted with a 1.5 ns pulsed neutron source by the $^7Li(p,n)^7Be$ reaction. In the present experiment, a Teflon(($CF_2$)n) sample was used The sample was disk with a diameter of 90mm. The thickness of sample was determined so that reasonable counting rates could be obtained and the correction was not so large for the self-shielding and multiple scattering of neutrons in the sample, and was 5mm. The primary gamma-ray transitions were compared with previous measurement of Kenny.

• Progress in Superconductivity and Cryogenics
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• v.17 no.4
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• pp.12-15
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• 2015

We report on the infrared spectroscopic studies of the normal-state electronic response of rare-earth ternary platinum germanide superconductor $La_2Pt_3Ge_5$. We analyzed the temperature-dependent optical conductivity spectra using the Drude-Lorentz oscillator model. We found that the two Drude responses with distinct scattering rates are required to explain the charge dynamics at 10 K while a single Drude mode could reproduce the far-infrared conductivity at higher temperatures. Our results indicated the two-band character of the electronic structure and highlighted the disparate temperature evolution of the electrodynamics of the two electronic states.

• Journal of Biosystems Engineering
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• v.34 no.3
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• pp.147-154
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• 2009

Suitable rapeseed cultivation techniques of domestic agriculture are essential for stable security, supply and demand of rapeseed. This research developed a rapeseed seeder for bio-diesel and analyzed the seeding performance improving an existent granule fertilizer applicator. The relational expression of metering groove size and discharge rate per time displayed high correlation with a coefficient of determination of 0.988. Also, the scattering types were analyzed by forwarding speed and discharge rate. Validity application width was decided as 7.0 m by analyzing application uniformity at application widths of 7.6 m, 6.6 m, 5.6 m. All average coefficients of variation values were less than 20%. The best application uniformity was obtained in the condition of a work speed of 1.3 m/s and a sowing rate of 19.0 g/s. It was better average coefficient of variation values under 10% at superposition application of rapeseed seeder. Also, scattering amount rates of right and left were within 0.89${\sim}$1.0.