• Journal of Astronomy and Space Sciences
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• 제35권2호
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• pp.67-74
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• 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.

• 천문학회보
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• 제39권2호
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• pp.45.1-45.1
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• 2014

structure of matters of Lambda cold dark matter (CDM) cosmology on detailed numerical simulations. To accomplish our research goal, we have added the following baryonic physics on the existing cosmological hydrodynamic code, Gadget-2: 1) radiative heating and cooling, 2) reionization of the Universe and UV shielding, 3) star formation, 4) energy and metallicity feedback by supernova. In addition, we included cluster formation to distinguish clustered star formation inside the very high density gas clumps from the field star formation. Our simulations cover a cubic box of a side length 4Mpc/h with 130 million particles. The mass of each particles is $3.4{\times}104Msun$, thus the GCs can be resolved with more than hundreds particles. We discuss various properties of the GCs such as mass function, specific frequency, baryon-to-dark matter ratio, metallicity, spatial distribution, and orbit eccentricity distribution as functions of redshift. We also discuss how the formation and evolution of the GCs are affected by UV shielding.

• 한국환경성돌연변이발암원학회지
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• 제7권2호
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• pp.103-111
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• 1987

The effects of LET (linear energy transfer) of radiation on the induction of somatic chromosome mutations or gene mutations of Drosophila melanogaster were studied. For detecting somatic chromosome mutations and gene mutations, Drosophila wing spot system and eye-color spot system were used, respectively. The frequencies of somatic chromosome mutations or gene mutations induced after third instar larval treatment with 23 MeV neutrons, thermal neutrons, X-rays were examined. From these data, the RBE(relative biological effectiveness) values of 23 MeV neutrons relative to X-rays for induction of somatic chromosome mutations or gene mutations were calculated. The present results suggest that high LET radiations are efficient than X-ray in producing not only somatic chromosome mutations but also gene mutations.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.517-523
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• 2010

Recently, the rapid evolution of computational fluid dynamics (CFD) has enabled its key role in industries and predictive sciences. From diverse research disciplines, however, are there strong needs for integrated analytical tools for multi-phenomena beyond simple flow simulation. Based on the concurrent simulation of multi-dynamics, multi-phenomena beyond simple flow simulation. Based on the concurrent simulation of multi-dynamics, multi-physics and multi-scale phenomena, the multi-phenomena CFD technology enables us to perform the flow simulation for integrated and complex systems. From the multi-phenomena CFD analysis, the high-precision analytical and predictive capacity can enhance the fast development of industrial technologies. It is also expected to further enhance the applicability of the simulation technique to medical and bio technology, new and renewable energy, nanotechnology, and scientific computing, among others.

• Journal of the Optical Society of Korea
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• 제5권4호
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• pp.136-139
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• 2001

We investigated a high-output ower, periodically poled lithium niobate(PPLN) optical parametric oscillator(OPO) pumped by a Q-switched Nd:YAG laser. Given the low optical damage threshold and the limited aperture (0.5mm thick) of PPLN, we tried to maximize the signal output power in a linear cavity consisting of two flat mirrors with a loosely focused pump beam. It is found that this simple cavity structure allowed a robust OPO operation, which was not sensitive to alignment compared with the conventional ones using concave mirrors. A maximum energy of 100$\mu$J/pulse was achieved for the signal at 1.36${\mu}{\textrm}{m}$, while the oscillation threshold was 0.3 mJ/pulse for the pump at 1064 nm.

• 천문학회보
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• 제42권1호
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• pp.35.1-35.1
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• 2017

We present the characteristics and the performance of the new CCD camera system, SNUCAM-II (Seoul National University CAMera system II) that was installed on the Lee Sang Gak Telescope (LSGT) at the Siding Spring Observatory Australia in 2016. SNUCAM-II consists of a deep depletion chip covering a wide wavelength from $0.3{\mu}m$ to $1.1{\mu}m$ with high sensitivity (QE at 90%). It is equipped with SDSS ugriz filters and 13 medium band width (50nm) filters. On LSGT, SNUCAM-II covers $15.7{\times}15.7arcmin$ FOV at pixel scale of 0.92 arcsec and a limiting magnitude of g = 19.91 AB mag at $5{\sigma}$ with 180s exposure time. SNUCAM-II will enable us to study Spectral Energy Distributions (SEDs) of diverse objects from extragalactic sources to solar objects in the southern hemisphere for research and education activities.

• 한국세라믹학회지
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• 제40권7호
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• pp.615-619
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• 2003

Temperature and frequency dependence of dielectric and electrical properties was investigated in cerium and manganese doped Sr$\_$0.6/Ba$\_$0.4/Nb$_2$O$\_$6/(60SBN) ceramic system. Structural deformation of 60SBN by dopants did not appeared. 1350$^{\circ}C$-10 h sintered specimen had higher densification than 1250$^{\circ}C$-10 h sintered one, to which dielectric properties are related. That the feature of dielectric maxima peaks was typical Diffusive Phase Transition (DPT), it was explained by "random-field Ising model". Even though 60SBN has large dielectric loss at high frequency above 100 ㎑, it is desirable for optical applications because of low dielectric loss at low frequency. From Arrhenius plot of temperature, the activation energy was calculated to 0.45-0.49 eV.

• Nuclear Engineering and Technology
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• 제46권6호
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• pp.863-868
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• 2014

The evaluation of thermal properties of actinide oxide fuels is a problem of high importance for the development of new generation reactors. In the present study, an expression obtained for n-dimensional Debye functions is used to derive a simple analytical expression for the specific heat capacity of nuclear fuels. To test the validity and reliability of this expression, the analytical expression is applied to $UO_2$, $NpO_2$, $ThO_2$, and $PuO_2$. It is seen that the formula was in agreement with the experimental and theoretical results reported in the literature.

• Nuclear Engineering and Technology
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• 제50권5호
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• pp.751-757
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• 2018

In this article, a UV sensor that is an appropriate tool for fire detection has been designed and constructed. The structure of this UV sensor is an air-filled single-wire detector that is able to operate under normal air condition. A reflective CsI photocathode is installed at the end of the sensor chamber to generate photoelectrons in the ion chamber. An electric current is produced by accelerating photoelectrons to the anode in the electric field. The detector is able to measure the intensity of the incident UV rays whenever the current is sufficiently high. Therefore, the sensitivity coefficient of this sensor is found to be $7.67{\times}10^{-6}V/photons/sec$.

• Nuclear Engineering and Technology
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• 제54권8호
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• pp.2877-2882
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• 2022

The paper presents the main results of computational and experimental optimization of the automatic power control system (AC) of the IBR-2M pulsed reactor in the presence of a high level of oscillatory instability. Optimization of the parameters of the AC made it possible to significantly reduce the influence of random and deterministic oscillations of reactivity on the noise of the pulse energy, as well as to sharply reduce the manifestation of the oscillatory instability of the reactor. As a result, the safety and reliability of operation of the reactor has increased substantially.