• Journal of Radiation Industry
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• v.6 no.1
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• pp.23-29
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• 2012

In this study, we investigated the genetic variation in the general of monocot model plant (rice) in response to various ionizing irradiations including gamma-ray, ion beam and cosmic-ray. The non-irradiated and three irradiated (200 Gy of gamma-ray and 40 Gy of ion beam and cosmic-ray) plants were analyzed by AFLP technique using capillary electrophoresis with ABI3130xl genetic analyzer. The 29 primer combinations tested produced polymorphism results showing a total of 2,238 bands with fragments sizes ranged from 30 bp to 600 bp. The number of polymorphism generated by each primer combinations was varied significantly, ranging from 2 (M-CAC/E-ACG) to 158 (M-CAT/E-AGG) with an average of 77 bands. Polymorphic peaks were detected as 1,269 with an average of 44 per primer combinations. By UPGMA (Unweighted Pair Group Method using Arithmetic clustering) analysis method, the clusters were divided into non-irradiated sample and three irradiated samples at a similarity coefficient of 0.41 and three irradiation samples was subdivided into cosmic-ray and two irradiation samples (200 Gy of gamma-ray and 40 Gy of ion beam) at similarity coefficient of 0.48. Similarity coefficient values ranged from 0.41 to 0.55.

• Journal of Astronomy and Space Sciences
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• v.30 no.3
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• pp.133-140
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• 2013

Most of high energy cosmic rays (CRs) are thought to be produced by diffusive shock acceleration (DSA) at supernova remnants (SNRs) within the Galaxy. Fortunately, nonthermal emissions from CR protons and electrons can provide direct observational evidence for such a model and place strong constraints on the complex nonlinear plasma processes in DSA theory. In this study we calculate the energy spectra of CR protons and electrons in Type Ia SNRs, using time-dependent DSA simulations that incorporate phenomenological models for some wave-particle interactions. We demonstrate that the time-dependent evolution of the self-amplified magnetic fields, Alfv$\acute{e}$nic drift, and escape of the highest energy particles affect the energy spectra of accelerated protons and electrons, and so resulting nonthermal radiation spectrum. Especially, the spectral cutoffs in X-ray and ${\gamma}$-ray emission spectra are regulated by the evolution of the highest energy particles, which are injected at the early phase of SNRs. Thus detailed understandings of nonlinear wave-particle interactions and time-dependent DSA simulations of SNRs are crucial in testing the SNR hypothesis for the origin of Galactic cosmic rays.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.17-18
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• 1996

COBE's results on the anisotropy of the cosmic microwave background radiation (CMBR) is discussed. Some ambiguities in the linear GI cosmic perturbation theory are clarified. The problem of the last scattering surface and the deficiencies of the linear cosmic perturbation theory are mentioned. The possible ways to overcome the theoretical difficulties are discussed also.

• Journal of the Korean Society of Radiology
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• v.13 no.1
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• pp.87-93
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• 2019

Recently, the number of passengers using airplanes is rapidly increasing due to the increase of overseas travelers. Therefore, the probability of exposure to natural radiation due to altitude is increasing due to the increase in flight time. Cosmic-ray penetrates the Earth's magnetic field belt Van Allen, which is located at an altitude of 400 km to 1200 km. Most cosmic rays are blocked at Van Allen belt. However, cosmic-ray could be not completely blocked, and a small amount of cosmic-ray affects the earth. In general, if the altitude was increased by 100m, the natural exposure dose increased by 0.03 mSv on the Earth. In this study, I tried to minimize the exposure to natural radiation in airplanes when boarding airplanes. Especially, I was aimed to minimize radiation exposure by protecting the highly sensitive thyroid gland among human organs. According to the results of the study, the designed shielding handkerchief was able to shield cosmic natural radiation dose by more than 70%. In conclusion, the application of the shielding handkerchief made in this study can be effectively shield natural radiation.

• Journal of the Korean Society of Radiology
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• v.16 no.5
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• pp.527-536
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• 2022

The radiation shielding characteristic of neutron shielding material has been studied as the preliminary study in order to design cosmic-ray shielding material. Specially, Soft Magnetic Material, known to be effective in EMP and radiation shielding, has been investigated to check if the material would be applicable to cosmic-ray shielding. In this work, thermal neutron shielding experiment was conducted and the Monte Carlo N-Particle(MCNP) was applied to employ skymap.dat, which is cosmic-ray data embedded in MCNP. As a result, polyethylene, borated polyethylene, and carbon nano tube, containing carbon or hydrogen, have been found to be effective in reduction of neutron flux below 20 MeV (including thermal, epithermal, evaporation). In contrast, the materials composed of iron such as SS316 and Soft Magnetic Material show a good shielding performance in the cascade energy range (above 20 MeV). Since Soft Magnetic Material is consisting of 13% of boron, it can also decrease thermal neutron flux, so it is expected that it would show a significant reduction on the entire range of neutron energy if the Soft Magnetic Material is used with hydrogen and carbon, so called low Z material.

• Nuclear Engineering and Technology
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• v.52 no.8
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• pp.1817-1825
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• 2020

Background: Cosmic ray-induced particles can lead to failure of semiconductors packaged for export during air transport. This work performed MCNP 6.2 simulations to optimize shielding against neutrons and protons induced by cosmic radiation Methods and materials: The energy spectra of protons and neutrons by incident angle at the flight altitude were determined using atmospheric cuboid model. Various candidates for the shielding materials and the geometry of the Unit Load Device Container were evaluated to determine the conditions that allow optimal shielding at all sides of the container. Results: It was found that neutrons and protons, at the flight altitude, generally travel with a downward trajectory especially for the particles with high energy. This indicated that the largest number of particles struck the top of the container. Furthermore, the simulation results showed that, among the materials tested, borated polyethylene and stainless steel were the most optimal shielding materials. The optimal shielding structure was also determined with the weight limit of the container in consideration. Conclusions: Under the determined optimal shielding conditions, a significantly reduced number of neutrons and protons reach the contents inside the container, which ultimately reduces the possibility of semiconductor failure during air transport.

• Nuclear Engineering and Technology
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• v.36 no.1
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• pp.1-11
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• 2004

Two approximate methods for a cosmic radiation shielding calculation in low earth orbits were developed and assessed. Those are a sectoring method and a chord-length distribution method. In order to simulate a change in cosmic radiation environments along the satellite mission trajectory, IGRF model and AP(E)-8 model were used. When the approximate methods were applied, the geometrical model of satellite structure was approximated as one-dimensional slabs, and a pre-calculated dose-depth conversion function was introduced to simplify the dose calculation process. Verification was performed with mission data of KITSAT-1 and the calculated results were also compared with detailed 3-dimensional calculation results using Monte Carlo calculation. Dose results from the approximate methods were conservatively higher than Monte Carlo results, but were lower than experimental data in total dose rate. Differences between calculation and experimental data seem to come from the AP-8 model, for which it is reported that fluxes of proton are underestimated. We confirmed that the developed approximate method can be applied to commercial satellite shielding calculations. It is also found that commercial products of semi-conductors can be damaged due to total ionizing dose under LEO radiation environment. An intensive shielding analysis should be taken into account when commercial devices are used.

• Journal of Astronomy and Space Sciences
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• v.13 no.2
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• pp.149-162
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• 1996

The results of space radiation experiments carried out on board the first two Korean technology demonstration microsatellites are presented in this paper. The first satellite, KITSAT-1, launched in August 1992, carries a radiation monitoring payload called cosmic ray experiment(CRE) for characterizing the low-earth orbit(LEO) radiation environment. The CRE consists of two sub-systems: the cosmic particle experiment (CPE) and the total dose experiment(TDE). In addition, single event upset(SEU)rates of the program memory and the RAM disk are also monitored. The second satellite, KITSAT-2, launched in September 1993, carries a newly developed 32-bit on-board computer(OBC), KASCOM(KAIST satellite computer in addition to OBC186. SEUs ocurred in the KASCOM, as well as in the program memory and RAM disk memory, have been monitored since the beginning of the satellite operation. These two satellites, which are very similar in structures but different in orbits, provide a unique opportunity to study the effects of the radiation environment characterized by the orbit.

• Annals of Occupational and Environmental Medicine
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• v.34
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• pp.5.1-5.10
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• 2022

Background: Some epidemiological studies have estimated exposure among flight attendants with and without breast cancer. However, it is difficult to find a quantitative evaluation of occupational exposure factors related to cancer development individually in the case of breast cancer in flight attendants. That is, most, if not all, epidemiological studies of breast cancer in flight attendants with quantitative exposure estimates have estimated exposure in the absence of individual flight history data. Case presentation: A 41-year-old woman visited the hospital due to a left breast mass after a regular check-up. Breast cancer was suspected on ultrasonography. Following core biopsy, she underwent various imaging modalities. She was diagnosed invasive ductal carcinoma of no special type (estrogen receptor positive in 90%, progesterone receptor positive in 3%, human epidermal growth factor receptor 2/neu equivocal) with histologic grade 3 and nuclear grade 3 in the left breast. Neoadjuvant chemotherapy was administered to reduce the tumor size before surgery. However, due to serious chemotherapy side effects, the patient opted for alternative and integrative therapies. She joined the airline in January, 1996. Out of all flights, international flights and night flights accounted for 94.9% and 26.2, respectively. Night flights were conducted at least four times per month. Moreover, based on the virtual computer program CARI-6M, the estimated dose of cosmic radiation exposure was 78.81 mSv. There were no other personal triggers or family history of breast cancer. Conclusions: This case report shows that the potentially causal relationship between occupational harmful factors and the incidence of breast cancer may become more pronounced when night shift workers who work continuously are exposed to cosmic ionizing radiation. Therefore, close attention and efforts are needed to adjust night shift work schedules and regulate cosmic ionizing radiation exposure.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.41-42
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• 1996

A possible cosmic X-ray background(XRB) radiation related to original antimatter is considered. If the universe is made of separating domains of antimatter and matter, the photons produced by the annihilation of electron-positron and proton-antiproton on the last scattering surface would reach us in the energy $\~$0.45 keV and $\~$60 keV respectively because of the redshift. The spectrums of X-ray radiation from annihilation are deduced and a possible observational figure is described also.