• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.11
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• pp.1225-1231
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• 2003

In this paper, we present the analysis of electromagnetic scattering from arbitrarily shaped three-dimensional conducting objects coated with dielectric materials. The integral equation treated here is the combined field integral equation(CFIE). The objectives of this paper is to illustrate that only the CFIE formulation is a valid methodology in removing the interior resonance problem, which occurs at a frequency corresponding to an internal resonance of the structure. Numerical results of radar cross section for coated conducting structures are presented and compared with other available solutions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.11
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• pp.1183-1189
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• 2014

The accuracy of the resistive-sheet technique in calculating the RCS(Radar Cross Section) of a deciduous leaf is examined in this paper for various thicknesses and dielectric constants, and a range of thicknesses for the resistive sheet technique is proposed. At first, a leaf was assumed to be a lossy dielectric disk, and the dielectric disk was again assumed to be a resistive sheet with an appropriate resistivity for a given thickness, a dielectric constant, and a frequency. Then, the RCS of the leaf was computed using the physical optics(PO) method, and was compared with the calculation results of a numerical analysis: i.e., a commercial tool based on the FEM (Finite Element Method) technique. It was shown that the error increases as the thickness increases. The error was 0.1 dB, for example, when the thickness is 1.2 mm and 3.7 dB when the thickness is 3 mm with a dielectric constant of(21.4, 9.7) at 9.6 GHz. It was also found that the error decreases as the dielectric constant increases. This study will be very useful for calculating the scattering characteristics of numerous leaves in a vegetation canopy for estimating its radar backscatter using scattering model.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.6 no.2
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• pp.54-60
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• 2010

Piping failures due to thermal fatigue have been widely reported in normally stagnant non-isolable reactor coolant branch lines. Since the thermal fatigue due to thermal stratification was not considered in the piping fatigue design in old NPPs, it is important to evaluate the effect of thermal stratification on the integrity of branch lines. In this study, geometrical screening criteria for Up-horizontal branch lines in MRP-132 were applied to SI(Safety Injection) lines of KSNP 2-loop and WH 3-loop. Some computational fluid dynamic(CFD) analyses on the Reactor Coolant System(RCS) branch lines were also performed to develop the regulatory guidelines for screening criteria. As a result of applying MRP-132 screening criteria, KSNP 2-loop and WH 3-loop SI lines are determined to need further detailed evaluation. Results of CFD analyses show that both valve isolation and amount of leakage through valve can be used as technical bases for the screening criteria on the thermal fatigue analysis.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.236-245
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• 2016

In a reactor coolant system of a nuclear power plant (NPP), an overpressure protection system keeps pressure in the loop within 110% of design pressure. However if the system does not work properly, pressure in the loop could elevate hugely in a short time. It would be seriously disastrous if a weak point in the pressure boundary component bursts and releases radioactive material within the containment; and it may lead to a leak outside the containment. In this study, a gross deformation that leads to a burst of pressure boundary components was investigated. Major components in the primary pressure boundary that is structurally important were selected based on structural mechanics, then, they were used to study the burst pressure of components by finite element method (FEM) analysis and by number of closed forms of theoretical relations. The burst pressure was also used as a metric of design optimization. It revealed which component was the weakest and which component had the highest margin to bursting failure. This information is valuable in severe accident progression prediction. The burst pressures of APR-1400, AP1000 and VVER-1000 reactor coolant systems were evaluated and compared to give relative margins of safety.

• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2477-2487
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• 2021

To improve safety analysis technology for a nuclear reactor containment considering an interaction between a reactor coolant system (RCS) and containment, this study aims at an experimental investigation on the integrated simulation of the RCS and containment, with an integral effect test facility, ATLAS-CUBE. For a realistic simulation of a pressure and temperature (P/T) transient, the containment simulation vessel was designed to preserve a volumetric scale equivalently to the RCS volume scale of ATLAS. Three test cases for a steam line break (SLB) transient were conducted with variation of the initial condition of the passive heat sink or the steam flow direction. The test results indicated a stratified behavior of the steam-gas mixture in the containment following a high-temperature steam injection in prior to the spray injection. The test case with a reduced heat transfer on the passive heat sink showed a faster increase of the P/T inside the containment. The effect of the steam flow direction was also investigated with respect to a multi-dimensional distribution of the local heat transfer on the passive heat sink. The integral effect test data obtained in this study will contribute to validating the evaluation methodology for mass and energy (M/E) and P/T transient of the containment.

• International Journal of Naval Architecture and Ocean Engineering
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• v.4 no.1
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• pp.20-32
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• 2012

A software system for a complex object scattering analysis, named SYSCOS, has been developed for a systematic radar cross section (RCS) analysis and reduction design. The system is based on the high frequency analysis methods of physical optics, geometrical optics, and physical theory of diffraction, which are suitable for RCS analysis of electromagnetically large and complex targets as like naval ships. In addition, a direct scattering center analysis function has been included, which gives relatively simple and intuitive way to discriminate problem areas in design stage when comparing with conventional image-based approaches. In this paper, the theoretical background and the organization of the SYSCOS system are presented. To verify its accuracy and to demonstrate its applicability, numerical analyses for a square plate, a sphere and a cylinder, a weapon system and a virtual naval ship have been carried out, of which results have been compared with analytic solutions and those obtained by the other existing software.

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.2
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• pp.120-126
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• 2014

An accurate analysis of nutrient balance in different cropping systems is necessary for improving soil fertilities, causing higher crop yields and quality. This study was carried out to investigate the nutrient balance, changes in soil properties, and their effects on crop yield in long-term field cultivation under mono- and rotation-cropping systems (MCS and RCS, respectively). The analytical results of the soil properties showed that the application of mineral fertilizers alone in the MCS leads the reduction of soil CEC, exchangeable Ca, and microbial biomass C and N. Compared with the MCS of soybean, the RCS of soybean and barley significantly improved the soil properties, which increased crop yield. It might be due to the barley residue added to the RCS soil. Mean nutrient balances for 4 years were -55.9 kg N, +34.7 kg $P_2O_5$, and -0.3 kg $K_2O$ $ha^{-1}$ for the MCS and +19.7 kg N, +107.4 kg $P_2O_5$, and -48.6 kg $K_2O$ $ha^{-1}$ for the RCS, respectively. These nutrient imbalances mean that conventional fertilizer recommendations were inadequate for maintaining soil nutrient balance. From these results, we can conclude that the crop rotation may change comprehensive physical, chemical, and biological soil properties. These changes could affect the nutrient balance and then the crop yield.

• Safety and Health at Work
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• v.15 no.1
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• pp.96-101
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• 2024

Background: Silicosis among workers who fabricate engineered stone products in micro or small-sized enterprises (MSEs) was reported from several countries. Workplace exposure data of these workers at high risk of exposure to respirable crystalline silica (RCS) dust are limited. Methods: We surveyed workers performing cutting, shaping and polishing tasks at 6 engineered stone fabricating MSEs in Sydney, Australia prior to regulatory intervention. Personal exposure to airborne RCS dust in 34 workers was measured, work practices were observed using a checklist and worker demography recorded. Results: Personal respirable dust measurements showed exposures above the Australian workplace exposure standard (WES) of 0.1 mg/m³ TWA-8 hours for RCS in 85% of workers who performed dry tasks and amongst 71% using water-fed tools. Dust exposure controls were inadequate with ineffective ventilation and inappropriate respiratory protection. All 34 workers sampled were identified as overseas-born migrants, mostly from three linguistic groups. Conclusions: Workplace exposure data from this survey showed that workers in engineered stone fabricating MSEs were exposed to RCS dust levels which may be associated with a high risk of developing silicosis. The survey findings were useful to inform a comprehensive regulatory intervention program involving diverse hazard communication tools and enforcing improved exposure controls. We conclude that modest occupational hygiene surveys in MSEs, with attention to workers' demographic factors can influence the effectiveness of intervention programs. Occupational health practitioners should address these potential determinants of hazardous exposures in their workplace surveys to prevent illness such as silicosis in vulnerable workers.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.10a
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• pp.420.2-420
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• 2002

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.39 no.2
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• pp.29-38
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• 2021

According to the theory of concentration recovery(ART), experiencing landscapes with healing properties can heal human mental fatigue caused by intentional concentration. The ART illustrates four healing qualities of the landscape. ART admits that various landscapes can have healing properties, the four healing properties of the landscape explained that the greater the perceptual strength, the stronger the healing effect. Until now, research on healing landscapes has been mainly done on natural and urban landscapes. The purpose of this study is as follows. First, eIt is intended to evaluate the healing characteristics of the Yangdong village landscape using RCS and investigate the impact of the healing characteristics on the visiting preference of the target landscape. Second, Evaluating the landscape image of Yangdong Village landscape, Investigating the effect of landscape images on the healing properties of landscape. This study was conducted in Yangdong Village, Gyeongju, 127 college students participated in the survey. SD 16 items to analyze landscape images and RCS 22 items from Laumann(2001) to evaluate healing properties were used as measurement tools. The findings are summarized as follows. First, The landscape image of Yangdong Village was analyzed through SD method, the analysis of the factors of Yangdong Village landscape image results in two factors: place and singularity. Second, It demonstrates the reliability and validity of RCS, Three factors were extracted from the factor analysis results. Third, Landscape images have a positive effect on the three healing characteristics of RCS. Fourth, Three healing properties of RCS have been shown to have a positive effect on visiting preferences, The order of influence on the relative visiting preferences was analyzed as attractiveness, fit, sense of escape, and sense of space. The findings suggest that future work requires research to re-validate the reliability of RCS. It is also necessary to analyze landscape images for various landscape types to specifically understand the effects on healing characteristics.