• Journal of radiological science and technology
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• v.33 no.3
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• pp.253-260
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• 2010

The primary focus of this study was to explore the variation in dose distributions of electron beams between different types of construction structure of cut-out blocks embodied in electron cones, given that the structure is considered one of the causes of multiple scattered radiation from electrons which may affect dose distributions. For evaluation, two types of cut-out blocks, divergency and straight, manufactured for this study, were compared in terms of area of interval in distribution of dose, and flatness and symmetric state of surface being radiated. The results showed that divergency cut-out blocks reduced the lateral scattering effects on the thickness of cut-out blocks more substantially than straight ones, leading to more uniform dose distribution at baseline depth. Notably in divergency cut-out blocks, the high dose area decreased more significantly, and more uniform dose distribution was observed at the edge of the irradiated field. This points to a need to consider the characteristics of dose distribution of electron beams when setting up radiotherapy planing at the venues. Therefore, this study is significant as an exploratory work for ensuring high accuracy in dose delivery for patients.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.9 no.2
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• pp.113-119
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• 2011

Safe operation and maintenance of engineered dry storage systems for spent fuel from nuclear power plants basically depends on adequately adopted design requirements. The most important design target of the system are those which provide the necessary assurances that spent fuel can be received, handled, stored and retrieved without undue risk to health and safety of workers and the public. To achieve these objectives, the design of the system incorporates features to remove spent fuel residual heat, to provide for radiation protection, and to maintain containment over the lifespan of the system as specified in the design specifications. The features also provide for all possible anticipated operational occurrences and design basis events in accordance with the design basis as guided by the designated regulations. The general performance requirements of a projected storage system are introduced in this paper. The storage system is designed to store fuel assemblies in associated with designated regulatory requirements. Small increases/decreases in maximum burnup can be adjusted with cooling time. These variations are compensated for by a corresponding small site-specific increase/decrease in the design basis-cooling period, as long as the maximum heat load and radioactivity of loaded fuel assemblies are met. Generic design basis events considered for the storage system are summarized. Shielding and radiological requirements along with mechanical and structural are derived in this study.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.2
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• pp.243-260
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• 2018

A literature review on the effects of high temperature and radiation on radiation shielding concrete in Spent Fuel Dry Storage is presented in this study with a focus on concrete degradation. The general threshold is $95^{\circ}C$ for preventing long-term degradation from high temperature, and it is suggested that the temperature gradient should be less than $60^{\circ}C$ to avoid crack generation in concrete structures. The amount of damage depends on the characteristics of the concrete mixture, and increases with the temperature and exposure time. The tensile strength of concrete is more susceptible than the compressive strength to degradation due to high temperature. Nuclear heating from radiation can be neglected under an incident energy flux density of $10^{10}MeV{\cdot}cm^{-2}{\cdot}s^{-1}$. Neutron radiation of >$10^{19}n{\cdot}cm^{-2}$ or an integrated dose of gamma radiation exceeding $10^{10}$ rads can cause a reduction in the compressive and tensile strengths and the elastic moduli. When concrete is highly irradiated, changes in the mechanical properties are primarily caused by variation in water content resulting from high temperature, volume expansion, and crack generation. It is necessary to fully utilize previous research for effective technology development and licensing of a Korean dry storage system. This study can serve as important baseline data for developing domestic technology with regard to concrete casks of an SF (Spent Fuel) dry storage system.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.6
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• pp.487-495
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• 2017

The thermal characteristics of the electrodeless lamp are one of the main factors that determine the design and performance of the lamp. The coupler changes the impedance characteristic by heat and its use temperature is usually within about $150^{\circ}C$. In this study, we observed the phenomenon when the coupler was exposed at a temperature of $150^{\circ}C$ or higher, which has not been discussed so far. Two types of coupler A and coupler B with different spacing between the inner tube and the coupler were analyzed for electrical, thermal and optical properties and deterioration characteristics with different heat and heat shielding conditions. First, the impedance of the system is obtained and used as a criterion for analyzing the electrical characteristics through it. The diameters of the two types of couplers are 1 mm, and the experimental result shows that the coupler diameter is 1 mm, which can cancel out the loss of the magnetic field strength. Therefore, based on these results, when the coupler is exposed to high temperature of about $200^{\circ}C$, the efficient design method corresponding thereto is proposed.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.4
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• pp.434-439
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• 2010

This study fabricated a simulation facility which reduced the structure of a current distribution line to 50:1 in order to analyze the induced lightning shielding effect of a 22.9kV-Y distribution line according to ground resistance capacity, grounding locations, etc. When installing an overhead ground wire, the standard for grounding a distribution line with a current of 22.9kV-Y requires that ground resistance in common use with the neutral line be maintained less than $50\Omega$every 200m span. The reduced line for simulation had 7 electric poles and induced lightning was applied to the ground plane 2m apart from the line in a direction perpendicular to it using an impulse generator. If induced voltage occurred in the line and induced current flowed through the line due to the applied current, the induced voltage and current of the 'A' phase were measured respectively using an oscilloscope. When all 7 electric poles were grounded with a ground resistance of less than $50\Omega$ respectively, the combined resistance of the line was $7.4\Omega$. When an average current of 230A was applied, the average induced voltage and current measured were 1,052V and 13.8A, respectively. Under the same conditions, when the number of grounding locations was reduced, the combined resistance as well as induced voltage and current showed a tendency to increase. When all 7 electric poles were grounded with a ground resistance of less than $100\Omega$, the combined resistance of the line was $14.9\Omega$. When an average current of 236A was applied, the average induced voltage and current of the 'A' phase calculated were 1,068V and 15.6A, respectively. That is, in this case, only the combined resistance was greater than when all 7 electrical poles were grounded, and the induced voltage and current were reduced. Therefore, it is thought that even though ground resistance is slightly higher under a construction environment with the same conditions, it is advantageous to ground all electric poles to ensure system safety.

• Journal of Radiation Protection and Research
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• v.13 no.2
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• pp.9-20
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• 1988

In order to quantify the contribution of cosmic-ray ionizing component to the dose given by natural background radiation, a series of measurement has been carried out using LiF TLDs for about one and a half years on quarterly basis. Three different types of LiF TLDs namely, chips and PTFE based disks of $^{7}LiF$, and the same disks of $^{6}LiF$ for identifying possible contribution of neutron component were used. Measurements were made by placing badge-incased TLDs in a lead castle of 10 to 15cm thick installed in a room on the third floor of a four-story building in CNU Daedeok campus for 5 cycles of 90 days. For comparison a series of spectrometric study was also performed for the energy region over 3MeV using a 3'${\phi}\;{\times}\;3$'NaI(Tl) scintillation detector in association with an MCA of 1024 channels, and it was found that the data obtained by the TLDs placed in the lead castle indicate 75% of the dose given by outdoor cosmic-ray component. The results obtained by the TLDs through correction for shielding loss show that the outdoor dose contribution of ionizing component of cosmic rays at this campus is $34.3{\pm}1.1nGy/h$ which satisfactorily agrees with that expected for our particular location of measurement.

• Journal of Adhesion and Interface
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• v.20 no.1
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• pp.1-8
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• 2019

Fabrication of monolayer is important method for enhancing physical and chemical characteristics such as light shielding and antireflection while maintaining thin film properties. In previous studies, monolayers were fabricated by various methods on small substrates, but processes were complicated and difficult to form monolayers with large area. We used rod coating equipment with a small amount of coating liquid to form a HCP (hexagonal closed packing) coating of PMMA beads on PET(poly(ethylene terephthalate)) substrate with $20cm{\times}20cm$ size. We observed that changes in morphologies of monolayers by using the solvents with different boiling points and vapor pressures, by adapting surfactants on particles and by applying plasma treatment on substrates. The coverage was increased by 20% by optimizing the coating conditions including meniscus of beads, control of the attraction - repulsion forces and surface energy. This result can potentially be applied to optical films and sensors because it is possible to make a uniform and large-scale monolayer in a simple and rapid manner when it is compared to the methods in previous studies.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.24 no.1
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• pp.69-80
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• 2021

The new town in Korea, developed as a large-scale housing plan, has created urban ecological corridors to provide habitat and movement routes to wildlife and to promote natural ecological flow. This study aimed to investigate the use of wildlife in 10 ecological corridors in Gwanggyo New Town through camera trap technology and confirm effectiveness by identifying environmental factors affecting the use of wildlife's urban ecological corridors. Our researchers installed 20 unmanned sensor cameras at each the entrance and exit of the ecological corridors, and monitored urban wildlife for 10 weeks. According to the monioring results, the main species in Gwanggyo New Town were identified not only raccons, cats, water deer, korean hare and avain but also magpies, dove, eurasian tree sparrow, ring-necked pheasant, and eurasian jay. The number of uses ecological corridors of urban residents was 801(13.49%), as high as that of urban wildlife (1,140, 19.20%), which was judged to have disturbed the use of ecological corridors by wildlife. However, most dominant species of urban wildlife are nocturnal so that, it was judged that they share home range with urban residents at a time interval. In addition, according to the correlation analysis results between the mammal using rate of the urban ecological corridors and environmental factors(ecological corridor-specific length, ecological corridor-specific width, cover degree, shielding degree, connected green area, separation of movement routes, and presence of streetlights), environmental factors were not statistically significant. However, the more the area of green space connected to ecological corridors, the more increasing the mammal using rate of ecological corridor(r=0.71, p<0.05). Therefore, the area of green space connected to the ecological corridors that is associated with rate of wildlife using corridors should be considered as a priority when developing an urban ecological corridors. In the future, this study will extend the observation period of the ecological corridors and continuously accumulate data by adding the number of observation cameras. Furthermore, it is expected that the results of this study can be used as basic data for the standards for urban ecological corridors installation.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.6
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• pp.226-231
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• 2020

Polyvinyl pyrrolidone nanofibers including nickel, zinc, and iron precursors were fabricated via the electrospinning method. To convert as-spun nanofibers to Ni0.5Zn0.5Fe2O4 oxide nanof ibers which is capable of shielding an electromagnetic wave, heat treatment conditions were optimized. To obtain the heat treatment condition that can exclude amorphous carbon black and secondary crystal phase, samples were taken at each temperature while the calcination process and analyzed. According to the X-ray diffraction (XRD) analysis, the Ni0.5Zn0.5Fe2O4 crystal phase started to appear from 300℃, but it was confirmed through energy dispersive spectroscopy (EDS) analysis that heat treatment of 500℃ or more was required to remove most of the carbon black. When the calcination temperature exceeds 650℃, crystal nuclei starts to grow and the fiber surface condition becomes rough, so it was confirmed that the heat treatment conditions should be selectively determined according to the application field.

• Journal of the Korean Society of Radiology
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• v.16 no.3
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• pp.273-279
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• 2022

In order to reduce the absorbed dose given to the patient during dental radiography, a sensor that inserts a shield into the intraoralsensor was designed. Using the designed sensor, the change in absorbed dose depending on whether or not a shield was used was evaluated. The system used to evaluate the absorbed dose is VEX-S300C from Vatech, and the energy spectrum of X-rays was obtained through SPEKTR simulation based on the irradiation conditions of 65 kV, 3 mA, and 0.15 sec, and the number of photons for each energy was derived. After designing the system through Genat4 Application for Tomographic Emission(GATE) simulation, the energy spectrum obtained was used as a radiation source to calculate the absorbed dose. Lead was used for the shield, and simulations were performed at 0.1 mm thickness intervals from 0.1 mm to 0.5 mm was evaluated. In the case of using an X-ray field with a diameter of 60 mm, the decrease in absorbed dose according to the presence or absence of a shield decreased exponentially as the thickness of the shield increased. In addition, when a 20 mm × 30 mm field was used, the absorbed dose was significantly reduced even when no shield was used, and it was confirmed that the absorbed dose was further reduced when a shield was used.