• 한국자원식물학회지
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• 제31권5호
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• pp.575-589
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• 2018

본 연구는 토함산지구 내 만호봉 일대에 분포하는 관속식물 상을 조사 및 분석함으로서 경주국립공원의 생태계를 관리 및 보전하기 위한 기초 자료 제공에 목적이 있다. 2012년 5월부터 2017년 8월까지 관속식물상을 조사한 결과는 다음과 같다. 증거표본을 기초로 관속식물상 목록을 작성한 결과, 91과 292속 397종 4아종 48변종 8품종 등 총 457분류군으로 나타났다. 멸종위기야생생물은 2분류군, 희귀식물은 11분류군, 한국특산식물은 14분류군이 조사되었다. 식물구계학적 특정식물은 총 39분류군으로, V등급은 3분류군, IV등급은 5분류군, III등급은 2분류군, II등급은 11분류군, I등급은 18분류군이다. 귀화식물은 33분류군이고 귀화율(NI)과 도시화지수(UI)는 각7.2%, 10.3%이다. 생태계교란식물은 돼지풀과 미국쑥부쟁이 2분류군이다.

• Nuclear Engineering and Technology
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• 제53권2호
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• pp.572-582
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• 2021

This study investigated the creep and creep crack growth (CCG) behavior of the base metal (BM), weld metal (WM), and heat affected zone (HAZ) in a Gr. 91 weldment, which was made by a shield metal arc weld process. A series of tensile, creep, and CCG tests were performed for the BM, WM, and HAZ at 550 ℃. Creep behavior of the BM, WM, and HAZ was analyzed in terms of various creep laws; Norton's power-law, Monkman-Grant relation and damage tolerance factor (λ), and their constants were determined. In addition, each CCGR law for the BM, WM, and HAZ was proposed and compared in terms of a C^*-fracture parameter. The WM and HAZ revealed faster creep rate, lower rupture ductility, and faster CCGRs than the BM, but they showed a similar behavior in the creep and CCG. The CCGRs obtained in the present study exhibited a marginal difference when compared with those of RCC-MRx of currently elevated design code in France. A creep crack path in the HAZ plane progressed towards a weak fine-grained HAZ adjacent to the BM.

• Journal of Korean Neurosurgical Society
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• 제52권5호
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• pp.459-465
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• 2012

Objective : To present the accuracy and safety of cervical pedicle screw insertion using the technique with direct exposure of the pedicle by laminoforaminotomy. Methods : We retrospectively reviewed 12 consecutive patients. A total of 104 subaxial cervical pedicle screws in 12 patients had been inserted. We also assessed the clinical and radiological outcomes and analyzed the direction and grade of pedicle perforation (grade 0: no perforation, 1: <25%, 2: 20% to 50%, 3: >50% of screw diameter) on the postoperative vascular-enhanced computed tomography scans. Grade 2 and 3 were considered as incorrect position. Results : The correct position was found in 95 screws (91.3%); grade 0-75 screws, grade 1-20 screws and the incorrect position in 9 screws (8.7%); grade 2-6 screws, grade 3-3 screws. There was no neurovascular complication related with cervical pedicle screw insertion. Conclusion : This technique (technique with direct exposure of the pedicle by laminoforaminotomy) could be considered relatively safe and easy method to insert cervical pedicle screw.

• Nuclear Engineering and Technology
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• 제56권1호
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• pp.1-8
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• 2024

In this study, the influence of thermal aging on structural integrity is investigated for Gr. 91 steel. A commercial grade Gr. 91 steel is used for the virgin material, and service-exposed Gr. 91 steel is sampled from a steam pipe of a super critical plant. Time versus creep strain curves are obtained through creep tests with various stress levels at 600 ℃ for the virgin and service-exposed Gr. 91 steels, respectively. Based on the creep test results, the improved Omega model is characterized for describing the total creep strain curve for both Gr. 91 steels. The proposed parameters for creep deformation model are used for predicting the steady-state creep strain rate, creep rupture curve, and stress relaxation. Creep-fatigue damage is evaluated for the intermediate heat exchanger (IHX) in a large-scale sodium test facility of STELLA-2 by using creep deformation model with proposed creep parameters and creep rupture curve for both Gr. 91 steels. Based on the comparison results of creep fatigue damage for the virgin and service-exposed Gr. 91 steels, the thermal aging effect has been shown to be significant.

• 대한기계학회논문집 C: 기술과 교육
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• 제4권2호
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• pp.101-109
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• 2016

발전소 내열강의 물성치는 고온 가동시간이 누적됨에 따라 열시효의 영향을 받는다. 본 연구에서는 제 4 세대 원자력시스템의 재료로 널리 채택되고 있는 Mod.9Cr-1Mo (ASME Grade 91)강을 대상으로 항복강도, 인장강도 및 파괴거동에 열시효가 미치는 영향에 대해 조사 및 분석하였다. 국내에서 가동 중인 초초임계(USC) 화력발전소의 배관계통에서 채취한, 73,716 시간의 가동 이력을 겪은 Gr.91 강 재료가 재료 실험을 위해 사용되었고, 동 시험결과와 가동 이력을 겪지 않은 신재의 시험결과를 비교 분석하였다. 또한 ASME 코드의 물성치와 RCC-MRx 의 물성치와 비교 분석하였고, 이들 설계기술기준 물성치의 보수성은 신재 및 가동 이력을 겪은 재료의 시험결과와 비교 분석을 통해 정량화하였다.

• 한국초등과학교육학회지:초등과학교육
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• 제24권3호
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• pp.236-241
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• 2005

The purpose of this study was to investigate the elementary and middle school students' understanding of observation, prediction, and hypothesis in everyday and science educational contexts. The questionnaires for testing understanding of three categories were developed, which obtained Cronbach alpha .91. It was consisted of 40 questions of 10 items related to observation, prediction, and hypothesis. Thy test was administrated to 868 subjects from grade 3 to grade 9. The results showed that the each level of their understanding of observation, prediction, and hypothesis ranged between $29{\~}58\%$, $43{\~}53\%$, and $10{\~}25\%$. The level of understanding of observation and prediction showed tendency to promote increasingly from grade 3 to grade 9, but the level of hypothesis did not.

• 대한기계학회논문집A
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• 제34권1호
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• pp.103-110
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• 2010

본 연구에서는 프랑스의 RCC-MR A16 절차에 기초하여 Mod.9Cr-1Mo 강(ASME Grade 91) 구조의 크리프-피로 균열 개시 및 성장 평가법을 확장 개발하였다. 현재의 A16 지침은 오스테나이트 스테인리스강에 대해서만 크리프-피로 균열 개시 및 성장 평가법을 제시하고 있지만, 현재 초초임계(USC) 화력발전소는 물론 미래형 원자로 시스템의 구조재료로서 폭넓게 채택되고 있는 Mod.9Cr-1Mo 강에 대한 지침은 제시하지 않고 있다. 본 연구에서는 FMS(페리틱-마르텐사이트강)에 대한 크리프-피로 균열 개시 및 성장 평가법을 제시하고 있고, 구조물에 대한 크리프-피로 균열 거동 평가를 수행하였다. 평가결과는 구조시험을 수행한 결과 얻은 관찰 이미지와 비교하였다.

• Nuclear Engineering and Technology
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• 제49권3호
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• pp.581-591
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• 2017

Influences of hold time and stress ratio on cyclic creep properties of Grade 91 steel were systemically investigated using a wide range of cyclic creep tests, which were performed with hold times (HTs) of 1 minute, 3 minutes, 5 minutes, 10 minutes, 20 minutes, and 30 minutes and stress ratios (R) of 0.5, 0.8, 0.85, 0.90, and 0.95 under tension loading cycles at $600^{\circ}C$. Under the influence of HT, the rupture time increased to HT = 5 minutes at R = 0.90 and R = 0.95, but there was no influence at R = 0.50, 0.80, and 0.85. The creep rate was constant regardless of an increase in the HT, except for the case of HT = 5 minutes at R = 0.90 and R = 0.95. Under the influence of stress ratio, the rupture time increased with an increase in the stress ratio, but the creep rate decreased. The cyclic creep led to a reduction in the rupture time and an acceleration in the creep rate compared with the case of monotonic creep. Cyclic creep was found to depend dominantly on the stress ratio rather than on the HT. Fracture surfaces displayed transgranular fractures resulting from microvoid coalescence, and the amount of microvoids increased with an increase in the stress ratio. Enhanced coarsening of the precipitates in the cyclic creep test specimens was found under all conditions.

• 한국건설순환자원학회논문집
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• 제11권1호
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• pp.62-69
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• 2023

UAE 지역에 시공되는 원전구조물의 노출환경에서 대기 중의 높은 황산염 이온 및 해안의 높은 염화물 이온에 의한 열화를 고려할 필요가 있다. 본 연구에서는 연평균 38 ℃ 이상의 높은 온도에 따른 확산성과 강도의 영향을 평가하기 위해 두가지 강도 등급(40 MPa 및 27 MPa) 및 두 가지 양생/확산 온도 조건(20 ℃ 및 50 ℃)을 고려하였다. 초기 양생 온도가 높은 경우, 7일 전 초기재령에서는 압축강도가 고온 양생에서 크게 발현하였으나, 28일 재령에서는 20 ℃ 양생 온도 조건에서 압축강도가 약간 증가하였다. 염화물 확산의 경우, 강도 평가결과와 다르게 28일 재령에서 초기 양생 온도가 높은 경우, 40 MPa 및 27 MPa 에서 모두 확산계수가 감소하였다. 91일 재령의 경우, 온도의 증가에 따른 확산성의 증가와 재령 효과에 의한 확산성의 감소가 동시에 발생하였다. 재령 28일에 20 ℃로 양생 및 확산 실험을 한 결과에 비하여, 재령 91일에 50 ℃로 양생 및 확산 실험을 한 경우, 재령의 증가에 따라 40 MPa에서는 76.2 % 수준으로, 27 MPa 에서는 85.4 % 수준으로 확산계수가 감소하였다.

• 대한족부족관절학회지
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• 제13권1호
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• pp.80-84
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• 2009

Purpose: The purpose of this article is to assess the efficacy of a bioabsorbable polylactide (PLA) plate and screw for treating injuries of ankle fractures. Materials and Methods: 24 patients who underwent an open reduction and internal fixation operation for ankle fractures from July 2005 to March 2007 were enrolled into the study. There were 15 men and 9 women. The average age of the patients was 44 years and the average follow-up period was 16 years and two months (16.2 months). All cases were divided into low grade fracture patient (11) who belongs in type A and B of Danis-Weber classification and high grade fracture patient (13) who belongs in type C1, C2 of Danis-Weber classification, and each groups were analyzed by clinical (Meyer score) and radiological finding at the time of their last follow-up evaluation. Results: The clinical results according to Meyer scoring system, showed that all patient with low grade fracture had good to excellent result, but only 54% of patient with high grade fracture had good to excellent result. According to Cedell's radiologic finding, there were 91% cases above fair in low grade fracture. But there were 62% of patient above fair result in high grade fracture, the reduction losses were seen in 38% of patient with high grade fracture. Conclusion: Bioabsorbable PLA plate and screw is good internal fixation device which doesn't have additional operation for removal of implant because of slow absorption within the human body. It showed sufficient strength for acquisition and maintenance of reduction in low grade fracture, but need attention to use because of many cases of reduction loss in high grade fracture. So, it seems to be safe and effective when used in heeling of low grade fracture under considering about type of fracture sufficiently.