• Journal of Korean Neurosurgical Society
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• v.52 no.1
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• pp.14-20
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• 2012

Objective : Intracranial meningiomas are primarily benign tumors with a good prognosis. Although WHO grade II meningiomas are rare (2-10%), WHO grade II meningiomas have higher recurrence and mortality rates than benign. We evaluated the patient recurrence rate and investigated the prognostic factors of WHO grade II meningiomas. Methods : Between 1993 and 2005, 55 patients were diagnosed with WHO grade II meningiomas in our hospital. WHO grade II meningiomas (n=55) were compared with other WHO grades meningiomas (I, n=373; and III, n=20). The patients had a median age of 48.4 years (range, 14-17 years), a male-to-female ratio of 26 : 29, and a mean follow-up time of 45 months (range, 3-175 months). Results : In WHO grade II meningiomas, only the extent of resection was a significant prognostic factor. Post-operative radiotherapy had no significant influence on tumor recurrence (p=0.053). The relative risk of recurrence was significantly higher in WHO grade II meningiomas with incomplete resection (10/27, RR=37%) than in WHO grade II meningiomas with complete resection (4/28, RR=14%) regardless of post-operative radiotherapy. In the incomplete resection group, Simpson grade III or IV had a significantly high risk of recurrence regardless of post-operative RT (n=3, RR=100%) However, if the degree of resection was Simpson grade II, the recurrence rate was similar to the complete resection group even though post-operative RT was not performed. Conclusion : Complete resection was the most powerful independent predictive factor of the recurrence rate in WHO grade II meningiomas. Post-operative adjuvant RT was not a significant factor in this study.

• The Korean Journal of Nuclear Medicine Technology
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• v.28 no.1
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• pp.41-47
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• 2024

Purpose: ¹⁸F-FET, a radiopharmaceutical based on a Tyrosine amino acid derivative using the Sodium-Potassium Pump-independent Transporter (System L) for non-invasive evaluation of primary, recurrent, and metastatic brain tumors, exhibits distinct characteristics. Unlike the widely absorbed ¹⁸F-FDG in both tumor and normal brain tissues, ¹⁸F-FET demonstrates specific uptake only in tumor tissue while almost negligible uptake in normal brain tissue. This study aims to compare and evaluate the usefulness of ¹⁸F-FDG and ¹⁸F-FET Brain PET/CT quantitative analysis in brain tumor diagnosis. Materials and Methods: In 46 patients diagnosed with brain gliomas (High Grade: 34, Low Grade: 12), Brain PET/CT scans were performed at 40 minutes after ¹⁸F-FDG injection and at 20 minutes (early) and 80 minutes (delay) after ¹⁸F-FET injection. SUV_max and SUV_peak of tumor areas corresponding to MRI images were measured in each scan, and the SUV_max-to-SUV_peak ratio, an indicator of tumor prognosis, was calculated. Differences in SUV_max, SUV_peak, and SUV_max-to-SUV_peak ratio between ¹⁸F-FDG and ¹⁸F-FET early/delay scans were statistically verified using SPSS (ver.28) package program. Results: SUV_max values were 3.72±1.36 for ¹⁸F-FDG, 4.59±1.55 for ¹⁸F-FET early, and 4.12±1.36 for ¹⁸F-FET delay scans. The highest SUV_max was observed in ¹⁸F-FET early scans, particularly in HG tumors (4.85±1.44), showing a slightly more significant difference (P<0.0001). SUV_peak values were 3.33±1.13 for ¹⁸F-FDG, 3.04±1.11 for ¹⁸F-FET early, and 2.80±0.96 for ¹⁸F-FET delay scans. The highest SUV_peak was in ¹⁸F-FDG scans, while the lowest was in ¹⁸F-FET delay scans, with a more significant difference in HG tumors (P<0.001). SUV_max-to-SUV_peak ratio values were 1.11±0.09 for ¹⁸F-FDG, 1.54±0.22 for ¹⁸F-FET early, and 1.48±0.17 for ¹⁸F-FET delay scans. This ratio was higher in ¹⁸F-FET scans for both HG and LG tumors (P<0.0001), but there was no statistically significant difference between ¹⁸F-FET early and delay scans. Conclusion: This study confirms the usefulness of early and delay scans in ¹⁸F-FET Brain PET/CT examinations, particularly demonstrating the changes in objective quantitative metrics such as SUV_max, SUV_peak, and introducing the SUV_max-to-SUV_peak ratio as a new evaluation metric based on the degree of tumor malignancy. This is expected to further contributions to the quantitative analysis of Brain PET/CT images.

• Particle and aerosol research
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• v.15 no.4
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• pp.149-157
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• 2019

Infiltration characteristics of airborne particulate matter had been investigated in real-life for about 90 days over 2 years in a Korean apartment building where a 3-person household had lived and the exclusive private area was 84.9 ㎡. Airtightness was measured by fan depressurization, and the ACH₅₀ was 2.41 times per hour. In and outdoor particle concentrations were measured by optical particle counters. Infiltration factors and filtration efficiencies of the house, which reflect the removal of outdoor particles penetrating building envelope and the deposition inside a building, were obtained from data screened based on an empirical evaluation process. Infiltration factor of fine particles showed a range from about 42% at 0.4 m/s of wind speed to 72% at 4.2 m/s of wind speed with closed windows and doors. Filtration efficiency was like a MERV 13 grade filter with an open window outside at a balcony at low outdoor wind speed under 1 m/s. The grade decreased to MERV 11 by opening another outside window at the other balcony. Filtration efficiencies decreased as much as 29% in average at a range of 0.3~2.5 ㎛.

• The Journal of Korean Physical Therapy
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• v.27 no.4
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• pp.234-239
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• 2015

Purpose: This study is not a fragmentary study on characteristics of respiratory synergist when breathing, however it was intended to determine the effect of currently available respiratory exercise and to provide basic clinical information through investigation of oxygen demand and respiratory synergist that mobilizes for respiration during application of respiratory exercise. Methods: Experimental group I was selected from second grade of severity classification of GOLD, which has the highest percentage among patients with COPD, and experimental group II was selected from third grade of severity classification as a clinical sampling. After respiration pursing up lips and diaphragm respiration exercise were mediated together for six weeks, activity of respiratory muscles and oxygen saturation were measured and analyzed. Results: In comparison of change of respiratory synergist and oxygen saturation, activity of respiratory synergist in sternocleidomastoid muscle and scalene muscle showed a meaningful decrease in experimental group I. And, in comparison of change of respiratory synergist and oxygen saturation, activity of respiratory synergist in rectus abdominis muscle showed a meaningful increase in experimental group II. In comparison of change of respiratory synergist and oxygen saturation, activity of respiratory synergist in sternocleidomastoid muscle, scalene muscle, and rectus abdominis muscle showed a meaningful difference between experimental groups. Conclusion: Respiratory synergists work mainly as agonist of chest and upper limbs. Therefore it is very important to lower mobilization of respiratory synergist when breathing. It is considered that a multilateral approach and continued clinical research for improvement of respiratory function for patients with COPD will be needed in the future.

• The Korean Journal of Health Service Management
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• v.5 no.3
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• pp.89-100
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• 2011

The present study aims to determine the grade and factors of the effects that influence the stress related to job finding of the university students majoring public health administration. The data was collected for 4days from June 7, 2011. Among a total of 360 cases of the questionaries, only 324 cases were used. To data were analyzed by frequency, t-test, ANOVA, correlation and regression using PASW statistics 18.0. From the analyses, it was found that school environment and study-related stress were some of major causes for stress in job finding. There was statistically significant difference in the sub-areas of job finding-related stress by gender, age, type of school, school grade, whether or not the graduating class and satisfaction with the major selected. There was statistically significant difference among the sub-areas of job finding-related stress such as academic achievements, characters, and school and family environments and whether in graduating class of collegians and their satisfaction with the major they chose turned out to exercise statistically significant impact upon the stress of the students majoring public health administration.

• Journal of Engineering Education Research
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• v.22 no.6
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• pp.40-50
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• 2019

The purpose of this study is to explore characteristics of engineering students' everyday creativity compared with those of undergraduate students. For this, we investigated whether there were differences in undergraduates' everyday creativity according to majors, gender and grade. Everyday creativity can be defined as thinking and activities producing useful and suitable personal products, and to solve problems in a new and unique ways. Thus everyday creativity is reported to be universal ability creative people can express in their everyday life. Eight hundred and fifty seven students from three universities in three Korean regions responded to Everyday Creativity Scale. Our findings show that firstly, there were significant differences in undergraduates' everyday creativity by majors and gender. Whereas there were no differences in the same survey by grade. Engineering students obtained significantly lower score of everyday creativity as well as its sub-scales. Also, there were significant differences in everyday creativity's sub-factors by gender. Based on these findings, practical implications for creativity education are discussed with particular attention to learner's individual variables.

• Journal of Engineering Education Research
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• v.22 no.3
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• pp.18-31
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• 2019

In addition to technical skills and competencies, communication competence has been identified to be important to engineering students who will be drivers of innovation in a rapidly changing society. Drawing on the previous studies, this research examines the results of an empirical exploration of engineering students' perception of speaking ability and their communicative competence. To date, there has been most of the research conducted on 'writing' (e.g., its educational process, class designs, ability, etc.) for engineering students. However, relatively little attention has been paid to engineering students' speaking ability perception and their competence diagnosis. This study relies on quantitative data obtained from one survey questionnaire and one test conducted respectively. The sample consists of 386 engineering students as well as 481 non-engineering students for the 1st survey. And to measure communicative competence, 150 engineering students as well as 136 non-engineering students participated in the test. Our findings show that firstly, there were significant differences in perception of speaking ability by majors and gender. Whereas there was no difference in the same survey by grade. Secondly, there was a close and significant relationship between sub-factors of speaking ability. Thirdly, there were significant differences in communicative competence by majors. Whereas there was no difference by gender and grade. Fourthly, there was a close and significant relationship between sub-factors of communicative competence. These findings are expected to provide an explanation for the improvement on engineering students' speaking ability and to encourage the participation in extra-curricular activities and programs in engineering school.

• Transactions of Materials Processing
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• v.31 no.4
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• pp.179-185
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• 2022

The influence of post-roll bonding heat treatment conditions such as temperature and time on the variation in the diffusion layer, generated at the bonding interface and the subsequent mechanical properties of the roll-bonded Ti grade 1/Al1050/Ti grade 1 sheets, was systematically investigated. The intermetallic compound (IMC) phase generated by post heat treatment conditions adopted in this study was obviously indexed as monolithic TiAl₃. Whereas the thickness of IMC layer generated by annealing at 500 ℃ was approximately 100 nm scale, it drastically increased above 1.5 ㎛ when annealed at 600 ℃. Uniaxial tensile and peel tests were then performed to compare mechanical properties. As a result, the bonding strength drastically increased above 7.9 N/mm by annealing at 600 ℃, which implies that proper annealing condition was a prerequisite, to improving interface bonding strength as well as global elongation properties for Ti/Al/Ti 3-ply sheet.

• Economic and Environmental Geology
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• v.53 no.3
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• pp.297-306
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• 2020

The red mud generated from bauxite during the Bayer alumina production process has been regarded as an industrial waste due to the high alkaline property and high content of Na. Despite of its environmental problem, various studies for recovery of the valuable resources from red mud has been also carried out because of high content (25.7 wt.% as Fe₂O₃ in this study) of iron in red mud. In order to recover the iron resource in the red mud, microwave heating experiments were performed with adding of activated carbon and elemental sulfur to the red mud. Through the microwave heating the powdered red mud mixtures converted to porous and vitrified solid aggregates. The vitrified aggregates produced by microwave heating are composed of goethite, zero valent iron (Fe⁰), pyrrhotite and pyrite. And then, the microwave heating samples were dissolved in the aqua regia solution, and Fe precipitates were obtained as a Fe-chlorides by adding of NaCl salt in the aqua regia solution. The Fe recovery rates in the Fe-chloride precipitates showed differences depending on the experimental mixture conditions, and Fe grades of the end products are 49.0 wt.%, 58.0 wt.% and 59.5 wt.% under mixture conditions of red mud, red mud + activated carbon, and red mud + activated carbon + elemental S, respectively. The Fe content of 56.0 wt.% is generally known as the grade value of Fe in a iron ore for iron production, and the Fe grades of microwave heating samples with adding activated carbon and elemental S in this study are higher than the grade value of 56.0 wt.%.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.597-608
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• 1994

A new process for the production of high purity ${\alpha}-Al_2O_3$ from ammonium aluminium sulfate solution abtained through the sulfation of low grade bauxite ore with $(NH_4)_2SO_4$, and leaching of the sulfated product was investigated. This process is consisted of solvent extraction for Fe component removal from ammonium aluminum sulfate solution and homogeneous precipitation of Al containing precipitate from the refined ammonium aluminium sulfate solution by using urea as precipitator. The optimum conditions of solvent extraction with Alamine 336 as extractant were shaking time of 4min, organic phase ratio to aqueous phase of 0.25. The types of precipitation products from this precipitation were amorphous alumina gel, pseudo-boehmite and crystalline boehmite in the lower temperature of $100^{\circ}C$, in the range from $125^{\circ}C$ to $150^{\circ}C$, and above $150^{\circ}C$, respectively. And also amorphous alumina gel hydrate in $1000^{\circ}C$ and crystalline boehmite in $1250^{\circ}C$ were tranfered to ${\alpha}-Al_2O_3$, respectively. This alumina was identified as ${\alpha}-Al_2O_3$ of purity 99.7%.