• Nuclear Engineering and Technology
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• 제49권1호
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• pp.254-266
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• 2017

Finite-element analysis based on elastic-perfectly plastic material was conducted to examine the influence of structural deformations on collapse loads of circumferential through-wall critically cracked $90^{\circ}$ pipe bends undergoing in-plane closing bending and internal pressure. The critical crack is defined for a through-wall circumferential crack at the extrados with a subtended angle below which there is no weakening effect on collapse moment of elbows subjected to in-plane closing bending. Elliptical and semioval cross sections were postulated at the bend regions and compared. Twice-elastic-slope method was utilized to obtain the collapse loads. Structural deformations, namely, ovality and thinning, were each varied from 0% to 20% in steps of 5% and the normalized internal pressure was varied from 0.2 to 0.6. Results indicate that elliptic cross sections were suitable for pipe ratios 5 and 10, whereas for pipe ratio 20, semioval cross sections gave satisfactory solutions. The effect of ovality on collapse loads is significant, although it cancelled out at a certain value of applied internal pressure. Thinning had a negligible effect on collapse loads of bends with crack geometries considered.

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.2788-2802
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• 2021

Multigroup cross section (MG XS) generation by the UNIST in-house Monte Carlo (MC) code MCS for fast reactor analysis using nodal diffusion codes is reported. The feasibility of the approach is quantified for two sodium fast reactors (SFRs) specified in the OECD/NEA SFR benchmark: a 1000 MW_th metal-fueled SFR (MET-1000) and a 3600 MW_th oxide-fueled SFR (MOX-3600). The accuracy of a few-group XSs generated by MCS is verified using another MC code, Serpent 2. The neutronic steady-state whole-core problem is analyzed using MCS/RAST-K with a 24-group XS set. Various core parameters of interest (core k_eff, power profiles, and reactivity feedback coefficients) are obtained using both MCS/RAST-K and MCS. A code-to-code comparison indicates excellent agreement between the nodal diffusion solution and stochastic solution; the error in the core k_eff is less than 110 pcm, the root-mean-square error of the power profiles is within 1.0%, and the error of the reactivity feedback coefficients is within three standard deviations. Furthermore, using the super-homogenization-corrected XSs improves the prediction accuracy of the control rod worth and power profiles with all rods in. Therefore, the results demonstrate that employing the MCS MG XSs for the nodal diffusion code is feasible for high-fidelity analyses of fast reactors.

• 한국환경보건학회지
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• 제41권5호
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• pp.358-367
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• 2015

Objectives: This study was performed to evaluate the analytical method for PAH metabolites in human urine using enzyme hydrolysis and solid-phase extraction coupled with LC-(ESI)-MS/MS technique. Methods: We employed HPLC tandem mass spectrometry techniques with appropriate pre-treatment for analysis of 16 OH-PAHs in human urine. Samples were hydrolysis by ${\beta}$-flucuronidase/Aryl sulfatase, and target compounds were extracted by solid-phase extraction with a strata-x cartridge. Cross-validation was performed between Eulji University and Green Cross laboratories with 200 human urine samples. Results: The accuracies were between 90.3% and 118.8%, and precisions (relative standard deviations) were lower than 10%. The linearity obtained was satisfying for the 16 OH-PAH compounds, with a coefficient of determination ($r^2$) higher than 0.99. The results of cross-validation at the two organizations were compared by ICC (interclass correlation coefficient) values. The cross-validation results were excellent or good for all compounds. Conclusion: An analytical method was validated for low nanogram levels of 16 OH-PAHs in human urine. Also, satisfying results were obtained for method validation such as accuracy, precision and ICC of cross-validation.

• The Journal of the Acoustical Society of Korea
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• 제20권3E호
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• pp.31-37
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• 2001

Finite element model of a cMUT is constructed using the commercial code ANSYS to analyze the cross talk mechanism. Calculation results of the complex load impedance seen by single capacitor cells are presented, and then followed by a calculation of the plane wave real load impedance seen by a parallel combination of many cells that are used to make a transducer. Cross talk between 1-D array elements is found to be due to two main sources: coupling through a Stoneley wave propagating at the transducer-water interface and coupling through Lamb waves propagating in the substrate. To reduce the cross talk level, the effect of various structural variations of the substrate are investigated, which include a change of its thickness and etched trenches or polymer walls between array elements.

• 제어로봇시스템학회논문지
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• 제20권4호
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• pp.437-442
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• 2014

Due to electrical cross-coupling between modulation voltage and photodetector output in a closed-loop fiber optic gyro, deadzone inevitably occurs. In this paper, deadzone error by cross-coupling effect was analyzed and the overcoming method was suggested. Simulation and measurement results show the main reason for deadzone is mainly related to electrical cross-coupling, and it can be effectively reduced by square-wave dithering method.

• 한국산학기술학회논문지
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• 제21권4호
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• pp.218-225
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• 2020

현재 정부는 공익형 직불제를 통해 농업의 공익적 기능을 제고하기 위해 노력하고 있지만, 상호준수의무 세부항목에 대한 연구는 미흡한 실정이다. 이에 본 연구는 평가기준을 이용한 정량적 연구방법인 계층화 분석법과 퍼지 다기준 의사결정법을 이용하여 공익형 직불제 상호준수의무의 우선순위를 결정하고 정책적 시사점을 도출하고자 한다. 평가기준은 정책의 효율성, 농가수용성, 실행가능성이고, 평가 대상은 기본형 상호준수의무 후보와 부가형 상호준수의무 후보이다. 조사대상은 사회과학계(16명), 자연과학계(15명), 정책 및 언론단체(13명), 농업인 단체(6명)의 전문가 50명이며, 2019년 7월부터 약 한 달간 설문조사를 실시하였다. 분석결과 평가기준의 가중치는 농가수용성, 실행가능성, 정책의 효율성 순으로 높게 나타났다. 기본형 상호준수의무의 우선순위는 PLS 기준준수, 폐비닐 및 농약병 폐기준수, 토양검정실시, 유해물질 허용 기준 준수, 교육이수 항목 등이 높게 평가되었다. 부가형 상호준수의무는 미사용지하수 관정 폐공처리, 농업부산물 공동수거 및 처리, 공동공간 관리 및 청소, 빈집 및 불량시설 정비, 휴경기 녹비작불 재배 및 토양환원 항목 등이 높은 순위로 평가되었다. 본 연구는 공익형 직불제의 개편과 함께 논의되고 있는 상호준수의무의 우선순위를 정량적인 방법으로 결정하였다는 점에서 의의가 있으며, 향후 공익형 직불제의 상호준수의무 도입을 위한 기초자료로 활용될 것으로 기대된다.

• Journal of the Korean Wood Science and Technology
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• 제50권2호
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• pp.81-92
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• 2022

To analyze the relationship between climatic factors (mean monthly temperature and total precipitation) and tree-ring growths of Pinus densiflora S. et Z. from National Parks (according to region) of the Korea, 20 trees were sampled from 13 National Parks. Only trees that were successfully cross-dated were used for dendrochronological analysis, and at least 11 trees were included. The tree-ring chronology of Mt. Bukhan (covering the shortest period of 1917 - 2016 [100 years]) was assessed, as well as that of Mt. Seorak (covering the longest period of 1687 - 2017 [331 years]). After cross-dating, each ring width series was double-standardized by first fitting a logarithmic curve and then a 50-year cubic spline. The relationships between climate and tree-ring growth were calculated with response function analysis. The results show a significant positive correlation between a given year's February-March temperature, May precipitation levels, and tree-ring growth. It indicates that a higher temperature in early spring and precipitation before cambium activity are important for radial growths of Pinus densiflora in the Korea.

• 대한조선학회논문집
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• 제44권4호
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• pp.445-450
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• 2007

An optimum design process of the broad-band multi-layered radar absorbing material, using genetic algorithm, is established for the radar cross section reduction of a complex target, which consists of multiple reflection structures, such as surface warships. It follows the successive process of radar cross section analysis, scattering center analysis, radar absorbing material design, and reanalysis of radar cross section after applying the radar absorbing material. It is demonstrated that it is very effective even in the optimum design of the multi-layer radar absorbing material. This results from the fact that the three factors, i.e.. the incident angle range, broad-band frequencies, and maximum thickness can be simultaneously taken into account by adopting the genetic algorithm.

• 한국IT서비스학회지
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• 제3권1호
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• pp.63-77
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• 2004

The purpose of this research is to identify what factors influence a customer's purchasing intention and to identify if customer's attitudes are different between an Internet shopping mall in Singapore and Korea. To perform a cross-nation analysis between Singapore and Korea, this research reapplied the finding of Liao and Cheung(2001) in a Singapore Internet shopping mall, including transactions security, Internet usage, price, shopping experience, vendor quality, network speed. The empirical results of this research indicate that all hypotheses in our model are significant; therefore, Internet usage, price, vendor quality and network speed influence customer's purchasing intention positively and transactions security and shopping experience negatively. The results of a cross-nation analysis indicate that customer's attitudes in both Singapore and Korea are the same. Therefore, Asia's with similar cultures are the same factors In Internet shopping mall. In Conclusion, with the rapid growth of the Internet market in Asia, many cross-nations researches based on Asia culture must be published. Therefore, this research will be the foundation of these researches.

• Structural Engineering and Mechanics
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• 제62권1호
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• pp.33-42
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• 2017

We present in this paper a finite element formulation for nonlinear torsional analysis of 3D beams with arbitrary composite cross-sections. Since the proposed formulation employs a continuum mechanics based beam element with kinematics enriched by the extended St. Venant solutions, it can precisely account higher order warping effect and its 3D couplings. We propose a numerical procedure to calculate the extended St. Venant equation and the twisting center of an arbitrary composite cross-section simultaneously. The accuracy and efficiency of the proposed formulation are thoroughly investigated through representative numerical examples.