• Nuclear Engineering and Technology
• /
• v.55 no.5
• /
• pp.1734-1741
• /
• 2023

This work presents the synthesis and preparation of a new glass system described by the equation of (70-x) B₂O₃-5TeO₂ -20SrCO₃-5ZnO -xBi₂O₃, x = 0, 1, 5, 10, and 15 mol. %, using the melt quenching technique at a melting temperature of 1100 ℃. The photon-shielding characteristics mainly the linear attenuation coefficient (LAC) of the prepared glass samples were evaluated using Monte Carlo (MC) simulation N-particle transport code (MCNP-5) at gamma-ray energy extended from 59 keV to 1408 keV emitted by the radioisotopes Am-241, Ba-133, Cs-137, Co-60, Na-22, and Eu-152. Furthermore, we observed that the Bi₂O₃ content of the glasses had a significantly stronger impact on the LAC at 59 and 356 keV. The study of the lead equivalent thickness shows that the performance of fabricated glass sample with 15 mol.% of Bi₂O₃ is four times less than the performance of pure lead at low gamma photon energy while it is enhanced and became two times lower the perforce of pure lead at high energy. Therefore, the fabricated glasses special sample with 15 mol.% of Bi₂O₃ has good shielding properties in low, intermediate, and high energy intervals.

• Publications of The Korean Astronomical Society
• /
• v.32 no.1
• /
• pp.225-230
• /
• 2017

The extragalactic background suggests half the energy generated by stars was reprocessed into the infrared (IR) by dust. At z~1.3, 90% of star formation is obscured by dust. To fully understand the cosmic star formation history, it is critical to investigate infrared emission. AKARI has made deep mid-IR observation using its continuous 9-band filters in the NEP field ($5.4deg^2$), using ~10% of the entire pointed observations available throughout its lifetime. However, there remain 11,000 AKARI infrared sources undetected with the previous CFHT/Megacam imaging (r ~25.9ABmag). Redshift and IR luminosity of these sources are unknown. These sources may contribute significantly to the cosmic star-formation rate density (CSFRD). For example, if they all lie at 1< z <2, the CSFRD will be twice as high at the epoch. We are carrying out deep imaging of the NEP field in 5 broad bands (g, r, i, z, and y) using Hyper Suprime-Camera (HSC), which has 1.5 deg field of view in diameter on Subaru 8m telescope. This will provide photometric redshift information, and thereby IR luminosity for the previously-undetected 11,000 faint AKARI IR sources. Combined with AKARI's mid-IR AGN/SF diagnosis, and accurate midIR luminosity measurement, this will allow a complete census of cosmic star-formation/AGN accretion history obscured by dust.

• International Journal of Contents
• /
• v.7 no.4
• /
• pp.1-5
• /
• 2011

Physics based fluid animation schemes need large computation cost due to tremendous degree of freedom. Many researchers tried to reduce the cost for solving the large linear system that is involved in grid-based schemes. GPU based algorithms and advanced numerical analysis methods are used to efficiently solve the system. Other groups studied local operation methods such as SPH (Smoothed Particle Hydrodynamics) and LBM (Lattice Boltzmann Method) for enhancing the efficiency. Our method investigates this efficiency problem thoroughly, and suggests novel paradigm in fluid animation field. Rather than physics based simulation, we propose a robust boundary handling technique for procedural fluid animation. Our method can be applied to arbitrary shaped objects and potential fields. Since only local operations are involved in our method, parallel computing can be easily implemented.

• Publications of The Korean Astronomical Society
• /
• v.27 no.4
• /
• pp.223-224
• /
• 2012

Understanding the birth and evolution of galaxies, and the history of star formation in them, is one of the most important problems in astronomy. Using the data from the AKARI IRC survey of the Large Magellanic Cloud at 3.2, 7, 11, 15, and $24{\mu}m$, we have constructed a multi-wavelength catalog containing data from the cross-correlation with a number of other databases at different wavelengths. We present the first approach with a Support Vector Machine (SVM)-based method to separate different classes of stars in LMC in the color-color and color-magnitude diagrams.

• Nuclear Engineering and Technology
• /
• v.49 no.7
• /
• pp.1505-1512
• /
• 2017

Because accelerator-based boron neutron capture therapy (BNCT) systems are planned for use in hospitals, entry into the medical room should be controlled as hospitals are generally assumed to be public and safe places. In this paper, computational investigation of the medical staff effective dose during BNCT has been performed in different situations using Monte Carlo N-Particle (MCNP4C) code and two voxel based male phantoms. The results show that the medical staff effective dose is highly dependent on the position of the medical staff. The results also show that the maximum medical staff effective dose in an emergency situation in the presence of a patient is ${\sim}25.5{\mu}Sv/s$.

• Journal of The Korean Astronomical Society
• /
• v.37 no.5
• /
• pp.465-470
• /
• 2004

I address the issue of nonthermal processes in the large scale structure of the universe. After reviewing the properties of cosmic shocks and their role as particle accelerators, I discuss the main observational results, from radio to $\gamma$-ray and describe the processes that are thought be responsible for the observed nonthermal emissions. Finally, I emphasize the important role of $\gamma$-ray astronomy for the progress in the field. Non detections at these photon energies have already allowed us important conclusions. Future observations will tell us more about the physics of the intracluster medium, shocks dissipation and CR acceleration.

• Publications of The Korean Astronomical Society
• /
• v.15 no.spc2
• /
• pp.53-56
• /
• 2000

We investigate the critical issue on how the BBF (bursty bulk flow) is related to the substorm current wedge formation. Observationally, after analysing data sets from Geotail spacecraft at near tail and many ground magnetic observatories for 9 months period of 1996, we find three BBF events that clearly occurred at the center of the wedge with region I type FAC (field-aligned current), and two other BBF events that were seen outside the wedge sector. Theoretically, we suggest that the substorm current wedge generation by BBF is most likely when the h' VB contribution is dominant in the well-known MHD $J_{II}$ expression (Vasyliunaus, 1984) or when the divergence of the cross-tail current carried by the particle's gradient/curvature drift is predominantly sufficient at the moment of the BBF arrival at near tail.

• The Bulletin of The Korean Astronomical Society
• /
• v.38 no.2
• /
• pp.93.2-93.2
• /
• 2013

Polarization of the light scattered by the lunar surface contains information on the mean particle size of the lunar regolith, which gradually decreases by continued micro-meteoroid impact over a long period and thus is an age indicator of the surface. We performed multi-band (U, B, V, R and I) polarimetric observations toward the whole near side of the Moon at the Lick observatory using a 15-cm reflecting telescope with 1.1km/pixel spatial resolution at the center of the lunar disk. We analyze the color dependence of the polarization properties of the lunar regolith and discuss its implication for the study of lunar swirls.

• Journal of Astronomy and Space Sciences
• /
• v.35 no.2
• /
• pp.67-74
• /
• 2018

Higgs boson enables the Standard Model (SM) to be established. However, we do not know much about dark matter which occupies approximately six times of the SM particles in universe besides having mass. The interactions of dark matter is much weaker than that of the SM. Further, its mass range is very wide, from the order of eV to PeV. Therefore, many experiments have contributed to search for dark matter by indirect, direct and accelerator research. This paper reviews researches on dark matter using accelerator, especially the $e^+e^-$ collider, from the viewpoint of experimental high energy physicists.

• Proceedings of the Korean Society of Medical Physics Conference
• /
• 2002.09a
• /
• pp.171-173
• /
• 2002

Present status of the proton therapy project at the Wakasa Wan Energy Research Center, Japan, is reported. Construction of the accelerator system was finished in 2001, followed by some trials of the production of the flat clinical irradiation field for the clinical usage. After the patient positioning system with X-ray CT was verified, the first clinical trial was started for two patients with prostate cancer.