• Journal of the Korean Society of Safety
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• v.24 no.2
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• pp.100-104
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• 2009

In this study, the space gamma dose rates in the apartments structured with concrete were measured in accordance with construction year. In addition, the environmental radiation rates coming from the subway platforms and the road tunnels were analyzed in the equivalent dose by multiplying the absorbed dose with the radiation weighting factors. The space gamma dose rates measured in apartments were higher than those of outdoor which was $0.08{\sim}0.11uSv/h$ in the natural conditions. Especially, the older construction year is, the higher becomes space gamma dose rate. The average gamma dose rates in the subway platforms were measured. In the case of Busan and Daegu subway, the earlier the opening year is, the higher becomes dose rate. However, the dose rates of Seoul subway Lines were high overall, regardless of opening year. Seoul subway Line 6 showed the highest value of 0.21uSv/h. The gamma dose rate in road tunnels was higher than one of the outdoor and increased with opening year like as apartment. In dose rate comparison of the concrete structures with the outdoor, therefore, the space gamma dose rate of indoor is higher than one of the outdoor and the older structures have a higher dose rate.

• Journal of Astronomy and Space Sciences
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• v.33 no.4
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• pp.279-285
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• 2016

The space radiation dose over air routes including polar routes should be carefully considered, especially when space weather shows sudden disturbances such as coronal mass ejections (CMEs), flares, and accompanying solar energetic particle events. We recently established a heliocentric potential (HCP) prediction model for real-time operation of the CARI-6 and CARI-6M programs. Specifically, the HCP value is used as a critical input value in the CARI-6/6M programs, which estimate the aviation route dose based on the effective dose rate. The CARI-6/6M approach is the most widely used technique, and the programs can be obtained from the U.S. Federal Aviation Administration (FAA). However, HCP values are given at a one month delay on the FAA official webpage, which makes it difficult to obtain real-time information on the aviation route dose. In order to overcome this critical limitation regarding the time delay for space weather customers, we developed a HCP prediction model based on sunspot number variations (Hwang et al. 2015). In this paper, we focus on improvements to our HCP prediction model and update it with neutron monitoring data. We found that the most accurate method to derive the HCP value involves (1) real-time daily sunspot assessments, (2) predictions of the daily HCP by our prediction algorithm, and (3) calculations of the resultant daily effective dose rate. Additionally, we also derived the HCP prediction algorithm in this paper by using ground neutron counts. With the compensation stemming from the use of ground neutron count data, the newly developed HCP prediction model was improved.

• Journal of Photoscience
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• v.9 no.3
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• pp.37-40
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• 2002

Astronauts are constantly exposed to space radiation at a low-dose rate during long-tenn stays in space. Therefore, it is important to determine correctly the biological effects of space radiation on human health. Space radiations contain various kinds of different energy particles, especially high linear energy transfer (LET) particles. Therefore, we have to study the relative biological effectiveness (RBE) of space radiation under microgravity environment which may change RBE from a stress for cells. Furthermore, the research about space radiation might give us useful information about birth and evolution of life on the earth. We also can realize the importance of preventing the ozone layer from depletion by use of exposure equipment to sunlight at International Space Station (ISS).

• Journal of radiological science and technology
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• v.17 no.2
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• pp.21-27
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• 1994

In this pauper, when the X-ray exposure condition is 70, 90, 110 kV, 10 mAs, FFD 180 cm, FSO $10{\times}10$, $35{\times}35\;cm$, toward the $36{\times}36{\times}15\;cm$ acryl phantom, the free space scatter dose rate at the 15th points in X-ray diagnostic room was measured by electrometer and 1800 co ionization chamber. Therefore, the free space scatter dose distribution profile was drown, and then, the free space scatter dose contribution percentage was Investigated. The obtained results are summarized as following. 1. The X-ray tube leakage dose rate of the experiment generator at the 1 m from focus was measured maximum 85 mR/hr, minimum 20 mR/hr, therefore, this values was appeared below the KS rules, 2. The free space scatter dose become to larger at the primary X-ray beam around area, and lower at the back ward X-ray tube. The maximum values were 3,812 mR/hr at the front Lt 1 m $45^{\circ}$ point, minimum 117 mR/hr at the back ward 1 m $180^{\circ}C$ point. 3. As the more tube voltage and field size increase, the more free space scatter dose contribution percentage become to increase, as to 90 kV from 70 kV, increase to 12 %, to 110 kV from 90 kV, increase to 18 %, and then, become to 11 % at the $10{\times}10\;cm$ and 87 % at the $35{\times}35\;cm$. 4. The 89 % of the total producted scatter ray occured from acryl phantom, at the X-ray tube housing 6 %, at the front side back wall 5 %. 5. The free space scatter dose contribution percentage at the one point build up 80 % from the phanton direction, 14 % from the X-ray tube and collimator direction, 2.2 % from the front wall, 1.8 % from the side wall, 1.7 % the back wall.

• Journal of the Korean Society of Radiology
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• v.15 no.6
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• pp.813-819
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• 2021

In this study, the shielding rate of L-block-type shielding equipment used for radiation protection when radioactive fluorine is injected into the human body and the dose distribution of the space in the injection room were calculated using the Monte Carlo method. The shielding rate of the body and window parts of the L-block-type shielding equipment was 99.99%. The dose distribution calculated at a distance of 1 m was relatively high at 135°, 45°, 225°, 315°, and 180° of the XZ plane, and was calculated to be very low at 0°, 90°, and 270°. In the YZ plane, it was relatively high at 135°, 180°, and 225°, and was calculated very low at the remaining angles. The AZ and BZ planes also showed similar results to the YZ plane. In addition, it was confirmed that the shielding rate was the best in the range of 225° to 315° through the dose distribution in the horizontal direction of the source and the 45° direction above the source. These results can be used as basic data necessary for radiation protection of radiation workers.

• ETRI Journal
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• v.27 no.4
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• pp.449-452
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• 2005

The electrical characteristics of solid state devices such as the bipolar junction transistor (BJT), metal-oxide semiconductor field-effect transistor (MOSFET), and other active devices are altered by impinging photon radiation and temperature in the space environment. In this paper, the threshold voltage, the breakdown voltage, and the on-resistance for two kinds of MOSFETs (200 V and 100 V of $V_{DSS}$) are tested for ${\gamma}-irradiation$ and compared with the electrical specifications under the pre- and post-irradiation low dose rates of 4.97 and 9.55 rad/s as well as at a maximum total dose of 30 krad. In our experiment, the ${\gamma}-radiation$ facility using a low dose, available at Korea Atomic Energy Research Institute (KAERI), has been applied on two commercially available International Rectifier (IR) products, IRFP250 and IRF540.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.120.1-120.1
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• 2012

The Lunar Reconnaissance Orbiter (LRO) launched on June 16, 2009 has six experiments including of the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) onboard. The CRaTER instrument characterizes the radiation environment to be experienced by humans during future lunar missions. The CRaTER instrument measures the effects of ionizing energy loss in matter specifically in silicon solid-state detectors due to penetrating solar energetic protons (SEP) and galactic cosmic rays (GCRs) after interactions with tissue-equivalent plastic (TEP), a synthetic analog of human tissue. The CRaTER instrument houses a compact and highly precise microdosimeter. It measures dose rates below one micro-Rad/sec in silicon in lunar radiation environment. Forbush decrease (FD) event is the sudden decrease of GCR flux. We use the data of cosmic ray and dose rates observed by the CRaTER instrument. We also use the CME list of STEREO SECCHI inner, outer coronagraph and the interplanetary CME data of the ACE/MAG instrument.We examine the origins and the characteristics of the FD-like events in lunar radiation environment. We also compare these events with the FD events on the Earth. We find that whenever the FD events are recorded at ground Neutron Monitor stations, the FD-like events also occur on the lunar environments. The flux variation amplitude of FD-like events on the Moon is approximately two times larger than that of FD events on the Earth. We compare time profiles of GCR flux with of the dose rate of FD-like events in the lunar environment. We figure out that the distinct FD-like events correspond to dose rate events in the CRaTER on lunar environment during the event period.

• Journal of the Korean Society of Radiology
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• v.11 no.3
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• pp.117-122
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• 2017

With the increase in leisure life, the population of ski resorts is rapidly increasing. The activity at the ski resort is likely to receive a direct chance of natural sunlight or space ray. Because it is located in the mountains where altitude exists. As a general rule, it is widely known that the higher the elevation rate, the more increasing the natural radiation dose. However, the natural radiation dose rate for the ski slopes has not been reported yet. Various ski resorts exist in Korea, but this study had chose 4 ski resorts to measure the natural dose of natural radiation. As a result, the natural radiation dose for the ski slope was measured at a relatively high dose of ordinary living areas. However, the level of natural radiation dose was not worrisome. It is recommended to wear ski wear or goggles to minimize natural radiation exposure at the ski slopes.

• Journal of Astronomy and Space Sciences
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• v.33 no.3
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• pp.229-236
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• 2016

We present proton-induced single event effects (SEEs) and γ-ray-induced total ionizing dose (TID) data for 1 Gbit lowpower double data rate synchronous dynamic random access memory (LPDDR SDRAM) fabricated on a 5 μm epitaxial layer (54 nm complementary metal-oxide-semiconductor (CMOS) technology). We compare our radiation tolerance data for LPDDR SDRAM with those of general DDR SDRAM. The data confirms that our devices under test (DUTs) are potential candidates for space flight applications.

• Journal of radiological science and technology
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• v.23 no.2
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• pp.63-67
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• 2000

The purpose of this study is to survey the present status of portable radiography and the result of free space scattered dose rate when taking a radiography at the general hospital or the university hospital in Taejon city. The results were as follows; 1. The number of cases using portable radiography for three years increased to averages 16.2%, 7.7% per year from January 1st in 1996 to December 31st in 1998. 2. The average of distance of adjacent patients was 219.1 cm at the ward. 3. For portable chest radiography, the free space scattered dose rate was 10.5 mSv/hr at 50 cm distance, 1.8 mSv/hr at 100 cm distance, and 0.2 mSv/hr at 200 cm distance. Therefore, in case of portable chest radiography at the ward, the average of distance of adjacent patients is 219.1 cm, so it does not have influence on the adjacent patients. But during the portable radiography, a guardian who is close to the patient, doctor, nurse and radiologic technologists has to set up the shield to prevent from the unnecessary radiation or the distance should be as great as possible from the mobile X-ray equipment.