• 한국의류산업학회지
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• 제10권3호
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• pp.385-388
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• 2008

Four kinds of PET fabrics were coated with Copper and Nickel by electroless chemical plating, and the electromagnetic wave shielding effectiveness for those samples have been examined. The shielding effectiveness showed between 90 dB and 70 dB, and it related to the fabric structure, such as cover factor and cloth density. The dense fabric structure showed the better shielding effect.

• 조명전기설비학회논문지
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• 제27권10호
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• pp.30-40
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• 2013

In this study the method based on flux linkage in cell was introduced in calculation of eddy currents by cell method. According to this method eddy current distribution and the loss can be evaluated and since the shielding effectiveness by flux cancelation of eddy current can be analyzed, this method is applicable to design of conductive shield. And also the formula of shielding factor were so deduced as to be applicable to finite-width infinite-length shielding sheets and infinite-length underground cable shield. These formula are adaptable to magnetic materials as well as conductive materials. As the results of calculation in model shields are follows. In case of finite-width infinite-length shielding sheet, shielding effectiveness increases with increasing of conductivity. In case of infinite-length underground cable shield, the effectiveness become higher with increasing of permeability. Especially the effectiveness is very high in materials with both high conductivity and permeability in underground cable shield.

• Computers and Concrete
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• 제17권2호
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• pp.281-294
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• 2016

The increased awareness of electromagnetic wave hazards has prompted studies on electromagnetic shielding using conductive materials in the construction industry. Previous studies have explored the effects of the types of conductive materials and their mix proportions on the electromagnetic shielding performance; however, there has been insufficient research on the effect of the geometry of the conductive materials on the electromagnetic shielding performance. Therefore, in this study, the dependence of the electromagnetic shielding performance on the cross-sectional geometry, diameter and length of fibers was investigated. The results showed that the electromagnetic shielding performance improved when the fiber length increased or the diameter decreased, but the effect of the cross-sectional geometry of the fibers was smaller than the effect of the fiber spacing factor.

• Nuclear Engineering and Technology
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• 제54권2호
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• pp.449-455
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• 2022

The rapid rise in the application of novel treatment techniques, such as intensity-modulated radiotherapy (IMRT), motivated us to survey the status of Korea's radiation safety management and the shielding designs of facilities employing medical linear accelerators (LINACs). To this end, a questionnaire was used to collect information on LINAC facilities and treatments, workload, shielding design, shielding management, and path of obtaining shielding information. Out of 100 domestic institutions, 52 responded to the survey. Approximately 70% of the institutions utilized IMRT for more than 60% of their cases, and an IMRT factor of 5 was adopted by 75% of these institutions. Over 80% of the institutions accounted for the applied time-averaged dose rate per week and instantaneous dose equivalent rates in their shielding designs. Approximately 45% of the institutions obtained important shielding information via a radiation shielding design company and the NCRP-151 report. Overall, most facilities were shown to follow the standards recommended by the relevant international agencies. However, the requirement to establish standardized shielding design information and clarify ambiguous paths for information acquisition was also highlighted. Therefore, the study's results can be used as a foundation for establishing a safety control system and for creating adequate shielding designs.

• 한국의학물리학회지:의학물리
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• 제29권1호
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• pp.42-46
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• 2018

The purpose of this study was to perform a survey of the radiation shielding design goals (P) and workload (W) based on the radiation safety reports concerned with structural shielding design for the IMRT treatment technique in Tomotherapy vaults. The values of the P and W factors as well as of a verified concrete thickness of the ceiling, bottom, sidewalls (sidewall-1 and sidewall-2), and door have been obtained from radiation safety reports for a total of 16 out of 20 vaults. The recommended and most widely used report for P values was the NCRP No. 151 report, which stated that the P factor in controlled and uncontrolled areas was 0.1 and 0.02 mSv/week, respectively. The range of the W factor was 600~14,720 Gy/week. The absorbed dose delivered per patient was 2~3 Gy. The maximum number of patients treated per day was 10~70. The quality assurance (QA) dose was 100~1,000 Gy/week. Fifteen values of the IMRT factor (F) were mostly used but a maximum of 20 values was also used. The concrete thickness for primary structures including the ceiling, bottom, sidewalls, and door was sufficient for radiation shielding. The P and W factors affect the calculation of the structural shielding design, and several parameters, such as the absorbed dose, patients, QA dose, days and F factor can be varied according to the type of shielding structure. To ensure the safety of the radiation shielding, it is necessary to use the NCRP No. 151 report for the standard recommendation values.

• Nuclear Engineering and Technology
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• 제53권8호
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• pp.2661-2668
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• 2021

Gamma radiation shielding features for three series of binary alloys identified as (Pb-Sn), (Pb-Zn), and (Zn-Sn) have been investigated. The mass attenuation coefficients (µ/ρ) for the selected alloys were simulated using the MCNP-5 code in the energy range between 0.01 and 15 MeV. Moreover, the (µ/ρ) values were computed using WinXCOM database in the same energy range to validate the simulation results. Results reveal a good agreement between the simulated and computed values. The half value layer (HVL), mean free path (MFP), effective atomic number (Z_eff) and exposure buildup factor (EBF) were evaluated for the selected binary alloys. Results showed that the PS1, PZ1, and ZS2 alloys have the best shielding parameters and better than the commercially standard and available radiation shielding materials. Therefore, the investigated alloys can be used as effective radiation shielding materials against gamma ray with energies between 0.01 and 15 MeV.

• 한국위성정보통신학회논문지
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• 제3권1호
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• pp.35-40
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• 2008

본 논문에서는 위성용 전자 부품 또는 장비를 내장한 함체의 개구가 유전체로 막힌 경우 차폐효과를 계산하는 해석적 방법을 제안한다. 차폐효과는 주파수, 유전체의 유전율, 함체 내에서 차폐효과를 정의하는 위치에 영향을 받는다. 또한, 유전체 판의 일부가 도체로 막혀 있는 경우도 해석하였다. 계산 결과를 보면, 유전체에 의하여 함체 공진의 Q 값이 감소되었으며, 개구에서 멀어질수록 차폐효과 개선되는 것을 확인 할 수 있었다.

• Nuclear Engineering and Technology
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• 제55권2호
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• pp.749-755
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• 2023

A new approximation method was proposed for treating the non-resonant spatial self-shielding effects of double heterogeneous region such as the double heterogeneous effect of VHTR fuel compact in the thermal energy range and that of BP compact with BISO. The method was developed based on the effective homogenization method and a spherical unit cell model with explicit coated layers and a matrix layer. The self-shielding factor was derived from the relation between the collision probabilities for a double heterogeneous compact and the effective cross section for the homogenized compact. First, the collision probabilities and transmission probabilities for all layers of the spherical model were calculated using conventional collision probability solver. Then, the effective cross section for the homogenized sphere cell representing the homogenized compact was obtained from the transmission probability calculated using the probability density function of a chord length. The verification calculations revealed that the proposed method can predict the self-shielding factor with a maximum error of 2.3% and the double heterogeneous effect with a maximum error of 200 pcm in the typical VHTR problems with various packing fractions and BP compact sizes.

• 전기학회논문지
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• 제65권4호
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• pp.684-688
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• 2016

The magnetic resonance method requires high quality factor(Q-factor) of resonators. Superconductor coils were used in this study to increase the Q-factor of wireless power transfer(WPT) systems in the magnetic resonance method. The results showed better transfer efficiency compared to copper coils. However, as superconducting coils should be cooled below critical temperatures, they require cooling containers. In this viewpoint, shielding materials for the cooling containers were applied for the analysis of the WPT characteristics. The shielding materials were applied at both ends of the transmitter and receiver coils. Iron, aluminum, and plastic were used for shielding. The electric field distribution and S-parameters (S11, S21) of superconducting coils were compared and analyzed according to the shield materials. As a result, plastic shielding showed better transfer efficiency, while iron and aluminum had less efficiency. Also, the maximum magnetic field distribution of the coils according to the shielding materials was analyzed. It was found that plastic shielding had 5 times bigger power transfer rate than iron or aluminum. It is suggested that the reliability of superconducting WPT systems can be secured if plastic is used for the cooling containers of superconducting resonance coils.

• 한국의학물리학회지:의학물리
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• 제29권4호
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• pp.115-122
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• 2018

Although the current internationally recommended standard for the use factor (U) applied to CyberKnife is 0.05 (5%), the CyberKnife shielding standard is applied more stringently. This study, based on clinical data, was aimed at examining the appropriateness of existing shielding guidelines. Sixty patients treated with G4 CyberKnife were selected. The patients were divided into two groups, according to whether they underwent skull or spine tracking. Based on the results, the use factors for each wall ranged from 0.028 (2.8%) to 0.031 (3.1%) for the intracranial treatment and 0.020 (2.0%) to 0.022 (2.2%) for the body treatment. Excessive barrier thickness resulted in inefficient use of space and higher cost to the institutions. Furthermore, because the use factor is influenced by the position of the robot, the use factor determined based on the clinical data of this study would facilitate more reasonable treatment room design.