• Journal of Astronomy and Space Sciences
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• 제31권1호
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• pp.67-72
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• 2014

The next generation small satellite-1 (NEXTSat-1) program has been kicked off in 2012, and it will be launched in 2016 for the science missions and the verification of space core technologies. The payloads for these science missions are the Instrument for the Study of Space Storms (ISSS) and NIR Imaging Spectrometer for Star formation history (NISS). The ISSS and the NISS have been developed by Korea Advanced Institute of Science and Technology (KAIST) and Korea Astronomy and Space science Institute (KASI) respectively. The ISSS detects plasma densities and particle fluxes of 10 MeV energy range near the Earth and the NISS uses spectrometer. In order to verify the spacecraft core technologies in the space, the total of 7 space core technologies (SCT) will be applied to the NEXTSat-1 for space verification and those are under development. Thus, the operation modes for the ISSS and the NISS for space science missions and 7 SCTs for technology missions are analyzed for the required operation time during the NEXTSat-1's mission life time of 2 years. In this paper, the operational concept of the NEXTSat-1's science missions as well as the verification of space core technologies are presented considering constraints of volume, mass, and power after launch.

• 한국세라믹학회지
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• 제42권6호
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• pp.432-436
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• 2005

Nickel powders synthesized by the reduction of hydrazine of nickel salts fiom diethanolamine(DEA) solution, and investigated the morphological characteristics of nickel powders with the addition of hydrazine, reaction temperature, the composition of mixed solvents. The addition of hydrazine in DEA solution largely affected on size control of nickel powders. Under $N_2H_4/Ni^{2+}$ molar ratio= 1.5 and 2.0 conditions, spherical nickel powders in the submicron range obtained, owing to higher the reduction rate. An increase of temperature increased the size of nickel particles. At $220^{\circ}C$ for 40 min, the nickel powders composed of polyhedral particles with high crystalline in the submicron range. The mixed volume ratio of TEA to DEA affected on the increase of particle size and the inhibition of agglomerate between particles.

• 한국의학물리학회지:의학물리
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• 제28권3호
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• pp.77-82
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• 2017

We proposed the objective ROC analysis method based on the setting of threshold value for evaluation of single photon emission computed tomography (SPECT) image. This proposed ROC analysis method uses the quantification computational threshold value to each signal on the SPECT image. The SPECT images for this study were acquired by using Monte Carlo n-particle extended simulation code (MCNPX, Ver. 2.6.0, Los Alamos National Laboratory, USA). The basic SPECT detectors and specific water phantom were realized in the simulation, and we could get the simulation results by the simulation operation. We tried to analyze the reconstructed images using threshold value application based objective ROC method. We can get the accuracy information of reconstructed region in the image. This proposed ROC technique can be helpful when we have to evaluate the weak signal for the NM image. In this study, the proposed threshold value based computational ROC analysis method can provide better objectivity than the conventional ROC analysis method.

• 한국전기전자재료학회논문지
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• 제24권7호
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• pp.589-593
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• 2011

[ $SnO_2$ ]nano powders were prepared by solution reduction method using tin chloride($SnCl_2{\cdot}2H_2O$), hydrazine($N_2H_4$) and NaOH. The $SnO_2$ thick films for gas sensors were fabricated by screen printing method on alumina substrates and annealed at $300^{\circ}C$ in air, respectively. XRD patterns of the $SnO_2$ nano powders showed the tetragonal structure with (110) dominant orientation. The particle size of $SnO_2$ nano powders at the ratio of $SnCl_2:N_2H_4$+NaOH= 1:6 was about 60 nm. The sensing characteristics were investigated by measuring the electrical resistance of each sensor in a test box. Sensitivity of $SnO_2$ gas sensor to 5 ppm $CH_4$gas and 5 ppm $CH_3CH_2CH_3$ gas was investigated for various $SnCl_2:N_2H_4$+NaOH proportion. The highest sensitivity to $CH_4$ gas and $CH_3CH_2CH_3$ gas of $SnO_2$ sensors was observed at the $SnCl_2:N_2H_4$+NaOH= 1:8 and $SnCl_2:N_2H_4$+NaOH= 1:6, respectively. Response and recovery times of $SnO_2$ gas sensors prepared by $SnCl_2:N_2H_4$+NaOH= 1:6 was about 40 s and 30 s, respectively.

• 한국의학물리학회지:의학물리
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• 제30권4호
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• pp.112-119
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• 2019

Purpose: The advantages of ocular proton therapy are that it spares the optic nerve and delivers the minimal dose to normal surrounding tissues. In this study, it developed a solid eye phantom that enabled us to perform quality assurance (QA) to verify the dose and beam range for passive single scattering proton therapy using a single phantom. For this purpose, a new solid eye phantom with a polymethyl-methacrylate (PMMA) wedge was developed using film dosimetry and an ionization chamber. Methods: The typical beam shape used for eye treatment is approximately 3 cm in diameter and the beam range is below 5 cm. Since proton therapy has a problem with beam range uncertainty due to differences in the stopping power of normal tissue, bone, air, etc, the beam range should be confirmed before treatment. A film can be placed on the slope of the phantom to evaluate the Spread-out Bragg Peak based on the water equivalent thickness value of PMMA on the film. In addition, an ionization chamber (Pin-point, PTW 31014) can be inserted into a hole in the phantom to measure the absolute dose. Results: The eye phantom was used for independent patient-specific QA. The differences in the output and beam range between the measurement and the planned treatment were less than 1.5% and 0.1 cm, respectively. Conclusions: An eye phantom was developed and the performance was successfully validated. The phantom can be employed to verify the output and beam range for ocular proton therapy.

• Journal of Radiation Protection and Research
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• 제20권3호
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• pp.143-154
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• 1995

최근에 정자기장을 사용하는 새로운 기술이 개발되어 인체가 정자기장에 노출될 가능성이 커지게 되어 건강에 영향을 줄 우려도 증가되었다. 여러 나라에서 정부를 비롯한 권위 있는 기관들이 주로 자기공명 영상법(MRI)이나 고에너지물리학에서의 입자가속기와 같은 특수 용도를 위해 노출한도를 제시해 왔다. 산업적인 면과 의학에서의 정자기장의 응용이 앞으로 더 많아져서 직업적이거나 일반공중이거나 간에 노출 가능성이 증가되고, 또 정자기장(static magnetic field)에 영향을 받는 강자성(强磁性) 이식조직 이나 전자장치를 부착한 사람들의 수도 증가하고 있으므로 국제적인 노출한도에 대한 지침이 필요하게 되었다. 본고에서는 비 이온화방사선(NIR)에 대한 국제방사선방어학회/비이온방사선방어위원회(IRPA/ICNIRP)의 제반지침을 검토하기 위하여 이 IRPA/ICNIRP(이전의 INIRC의 것도 포함)의 기본지침 중 정자기장에 대한 노출한도에 관한 지침을 택하여 논하였다.

• 천문학회지
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• 제44권6호
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• pp.217-234
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• 2011

We present two large cosmological N-body simulations, called Horizon Run 2 (HR2) and Horizon Run 3 (HR3), made using $6000^3$ = 216 billions and $7210^3$ = 374 billion particles, spanning a volume of $(7.200\;h^{-1}Gpc)^3$ and $(10.815\;h^{-1}Gpc)^3$, respectively. These simulations improve on our previous Horizon Run 1 (HR1) up to a factor of 4.4 in volume, and range from 2600 to over 8800 times the volume of the Millennium Run. In addition, they achieve a considerably finer mass resolution, down to $1.25{\times}10^{11}h^{-1}M_{\odot}$, allowing to resolve galaxy-size halos with mean particle separations of $1.2h^{-1}$Mpc and $1.5h^{-1}$Mpc, respectively. We have measured the power spectrum, correlation function, mass function and basic halo properties with percent level accuracy, and verified that they correctly reproduce the CDM theoretical expectations, in excellent agreement with linear perturbation theory. Our unprecedentedly large-volume N-body simulations can be used for a variety of studies in cosmology and astrophysics, ranging from large-scale structure topology, baryon acoustic oscillations, dark energy and the characterization of the expansion history of the Universe, till galaxy formation science - in connection with the new SDSS-III. To this end, we made a total of 35 all-sky mock surveys along the past light cone out to z = 0.7 (8 from the HR2 and 27 from the HR3), to simulate the BOSS geometry. The simulations and mock surveys are already publicly available at http://astro.kias.re.kr/Horizon-Run23/.

• 한국의학물리학회지:의학물리
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• 제28권2호
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• pp.67-75
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• 2017

Prior to the introduction of a medical apparatus based on heavy-ion medical accelerator in Korea, a study is needed on quality control in clinical operation for the safe and appropriate usage of the instrument. Data relevant for the study were obtained via information sharing sessions and visits by the Particle Therapy Co-Operative Group (PTCOG) and other related academic associations. Furthermore, investigative analysis of the European and Japanese performance evaluation guidelines for heavy ion, as well as research on relevant literature, were conducted. In addition, instrumental standards were analyzed through an investigation of the current usage status of the heavy-ion medical accelerator, and further analysis was conducted on the evaluation methods for the performance, safety, and significance of the instrument. Based on these analyses, regular quality control procedures for heavy-ion medical accelerators in hospitals and other institutes were extrapolated. It is hoped that the results of this study will facilitate hospitals that have introduced heavy-ion medical accelerators, or are considering the implementation of the instrument, in their understanding of the fundamental standards and capabilities of the treatment system, as well as in establishing and carrying out quality control procedures for clinical operations such that it will contribute to the safety of patients and the efficiency of medical practitioners.

• Nuclear Engineering and Technology
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• 제48권3호
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• pp.785-794
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• 2016

The Argonne National Laboratory of the United States and the Kharkov Institute of Physics and Technology of the Ukraine have been collaborating on the design, development and construction of a neutron source facility at Kharkov Institute of Physics and Technology utilizing an electron-accelerator-driven subcritical assembly. The electron beam power is 100 kW using 100-MeV electrons. The facility was designed to perform basic and applied nuclear research, produce medical isotopes, and train nuclear specialists. The biological shield of the accelerator building was designed to reduce the biological dose to less than 5.0e-03 mSv/h during operation. The main source of the biological dose for the accelerator building is the photons and neutrons generated from different interactions of leaked electrons from the electron gun and the accelerator sections with the surrounding components and materials. The Monte Carlo N-particle extended code (MCNPX) was used for the shielding calculations because of its capability to perform electron-, photon-, and neutron-coupled transport simulations. The photon dose was tallied using the MCNPX calculation, starting with the leaked electrons. However, it is difficult to accurately tally the neutron dose directly from the leaked electrons. The neutron yield per electron from the interactions with the surrounding components is very small, ~0.01 neutron for 100-MeV electron and even smaller for lower-energy electrons. This causes difficulties for the Monte Carlo analyses and consumes tremendous computation resources for tallying the neutron dose outside the shield boundary with an acceptable accuracy. To avoid these difficulties, the SOURCE and TALLYX user subroutines of MCNPX were utilized for this study. The generated neutrons were banked, together with all related parameters, for a subsequent MCNPX calculation to obtain the neutron dose. The weight windows variance reduction technique was also utilized for both neutron and photon dose calculations. Two shielding materials, heavy concrete and ordinary concrete, were considered for the shield design. The main goal is to maintain the total dose outside the shield boundary less than 5.0e-03 mSv/h during operation. The shield configuration and parameters of the accelerator building were determined and are presented in this paper.

• Transactions on Electrical and Electronic Materials
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• 제18권1호
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• pp.46-50
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• 2017

The Zn1-xMnxO ($0.00{\leq}x{\leq}0.06$) samples have been synthesized in the form of powder by the coprecipitation method at low temperature using $Zn(CH_3COO)_2$. $2H_2O$ and $Mn(CH_3COO)_2$. $4H_2O$ powders, as well as HCl and $NH_4OH$ solutions as starting materials. Characterization was conducted using XRD, TEM, XRF, FTIR and VSM. The result shows that the $Zn_{(1-x)}Mn_xO$ ($0.00{\leq}x{\leq}0.06$) nanoparticles have the wurtzite phase with a hexagonal structure and particle sizes ranging from 17.48 to 118.83 nm. In a qualitative analysis of XRF, the peaks that confirm the existence of the manganese element in Mn-doped ZnO samples were observed. Meanwhile, FTIR test result shows that there are peaks at around $500cm^{-1}$ and $400cm^{-1}$ in the FTIR spectra for Mn doped ZnO samples which clearly reveal the existence of the (Zn, Mn)-O strain mode. The (Zn, Mn)-O absorption peak positions have shifted to a lower wave number with increasing Mn doping content. The peak intensity is also lower if compared to that of the ZnO sample without doping. From the VSM test, it is shown that $Zn_{(1-x)}Mn_xO$ ($0.00{\leq}x{\leq}0.06$) nanoparticles are all paramagnetic having monotonically increased susceptibility as increasing Mn content.