• Journal of Trauma and Injury
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• v.30 no.4
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• pp.192-196
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• 2017

Purpose: Blunt injury accounts for 80-95% of renal injury trauma in the United States. The majority of blunt renal injuries are low grade and 80-85% of these injuries can be managed conservatively. However, there is a debate on the management of patients with high-grade renal injury. We reviewed our experience of renal trauma at our trauma center to assess management strategy for high-grade blunt renal injury. Methods: We reviewed blunt renal injury cases admitted at a single trauma center between August 2007 and December 2015. Computed tomography (CT) scan was used to diagnose renal injuries and high-grade (according to the American Association for the Surgery of Trauma [AAST] organ injury scale III-V) renal injury patients were included in the analysis. Results: During the eight-year study period, there were 62 AAST grade III-V patients. 5 cases underwent nephrectomy and 57 underwent non-operative management (NOM). There was no difference in outcome between the operative group and the NOM group. In the NOM group, 24 cases underwent angioembolization with a 91% success rate. The Incidence of urological complications correlated with increasing grade. Conclusions: Conservative management of high-grade blunt renal injury was considered preferable to operative management, with an increased renal salvage rate. However, high-grade injuries have higher complication rates, and therefore, close observation is recommended after conservative management.

• Korean Journal of Plant Resources
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• v.31 no.5
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• pp.575-589
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• 2018

The purpose of this study is to provide the baseline data for conservation and management of the ecosystem of Gyeongju National Park by surveying and analysing the vascular plants distributed in Mt. Manhongbong (522 m). The vascular plants were surveyed form May 2012 to August 2017. The vascular plants on this site was classified as follow. Based on voucher specimens, the vascular plants of this site consisted of 91 families, 292 genera, 397 species, 4 subspecies, 48 varieties and 8 forms. The 2 taxa of threatened species, 11 taxa of rare plants and 14 taxa of Korean endemic plants were investigated. The specific plants by floristic region were totally 39 taxa, which were 3 taxa of grade V, 5 taxa of grade IV, 2 taxa of grade III, 11 taxa of grade II and 18 taxa of grade I. The naturalized plants were identified as 33 taxa and the percentage of naturalized index (NI) was 7.2%, and urbanized index (UI) was 10.3%, respectively. The invasive alien plants were 2 taxa, such as Ambrosia artemisiifolia L. and Aster pilosus Willd.

• Nuclear Engineering and Technology
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• v.53 no.2
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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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• v.52 no.5
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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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• v.56 no.1
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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.

• Transactions of the KSME C: Technology and Education
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• v.4 no.2
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• pp.101-109
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• 2016

The material properties of heat resistant materials at power plants are affected by thermal aging as operating time is accumulated. In this study, the influence of thermal aging on yield strength, tensile strength and fracture behavior for Mod.9Cr-1Mo (ASME Grade 91) steel which is a material widely adopted for Generation IV nuclear energy system has been investigated and analyzed. Service exposed Gr.91 steel materials sampled from a piping system of an ultra-supercritical (USC) plant in Korea with accumulated operation time of 73,716 hours were used for material testing. The test results of the service exposed material specimens were compared with those of the virgin Gr.91 steel specimens. Those test data were compared with the material properties of ASME code and RCC-MRx code. Conservatisms of the material properties in the design codes have been quantified based on the comparisons of those from virgin and service exposed material specimens.

• Journal of Korean Elementary Science Education
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• v.24 no.3
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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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.103-110
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• 2010

In this study, an assessment method on creep-fatigue crack initiation and crack growth for a Mod.9Cr-1Mo steel (ASME Grade 91) structure has been developed with an extension of the French RCC-MR A16 procedure. The current A16 guide provides defect assessment procedure for a creep-fatigue crack initiation and crack growth for an austenitic stainless steel, but no guideline is available yet for a Mod.9Cr-1Mo steel which is now widely being adopted for structural materials of future nuclear reactor system as well as ultra super critical (USC) thermal plant. In the present study an assessment method on creep-fatigue crack initiation and crack growth is provided for the FMS (Ferritic-Martensitic Steel) and assessment on the creep-fatigue crack behavior for a structure has been carried out. The assessment results were compared with the observed images from a structural test.

• Nuclear Engineering and Technology
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• v.49 no.3
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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.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.1
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• pp.62-69
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• 2023

For the nuclear power concrete plant structures in the UAE, it is necessary to consider the deterioration from high sulfate ions in the atmosphere and high chloride ions from the coast. In this study, two strength grade concrete mixture (40 MPa and 27 MPa) and two curing/diffusion temperatures (20 ℃ and 50 ℃) were considered for evaluating the temperature effects on diffusion and strength due to high average temperature above 38 ℃ a year in UAE. When the initial curing temperature was high, the compressive strength increased in high-temperature curing to 7 days, but the strength slightly increased in the 20 ℃ curing condition at 28 days. Regarding diffusion test, unlike the compressive test results, reduced chloride diffusion coefficients were evaluated both in 40 MPa and 27 MPa grade at 28 days. In the case of 91 days of curing, an increase in diffusivity due to high temperature and a decrease in diffusivity due to age effect occur simultaneously. Compared to the results of the curing and diffusion tests at 20 ℃ and 28 days, when the curing and diffusion tests were conducted at 50 ℃ in 91 days, the diffusion coefficients decreased to 76.2 % in 40 MPa grade and 85.4 % in 37 MPa grade with increasing curing period, respectively.