• Bulletin of the Korean Chemical Society
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• 제32권1호
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• pp.213-218
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• 2011

The scope of homogeneous Lewis acid-catalyzed benzo[N,N]-heterocyclic condensation was expanded to include the use of various metal salts not reported in the literature and $SnCl_2{\cdot}2H_2O$ was finally selected. Among various solid supports activated with $SnCl_2$, heterogeneous $SnCl_2/SiO_2$ proved to be the most effective and significantly higher conversions were achieved compared to $SnCl_2{\cdot}2H_2O$ itself. The results of TG-DTA and BET indicated that dispersed $SnCl_2$ coordinates with surface hydroxyl groups of silica leading to formation of stable Lewis acid sites. Low catalyst loading, operational simplicity, practicability and applicability to various substrates render this eco-friendly approach as an interesting alternative to previously applied procedures.

• Journal of Korean Neurosurgical Society
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• 제59권4호
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• pp.357-362
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• 2016

Papillary and rhabdoid meningiomas are pathologically World Health Organization (WHO) grade III. Any correlation between clinical prognosis and pathologic component is not clear. We analyzed the prognoses of patients with meningiomas with a rhabdoid or papillary component compared to those of patients with anaplastic meningiomas. From 1994 to June 2013, 14 anaplastic meningiomas, 6 meningiomas with a rhabdoid component, and 5 meningiomas with papillary component were pathologically diagnosed. We analyzed magnetic resonance imaging (MRI) findings, extent of removal, adjuvant treatment, progression-free survival (PFS), overall survival (OS), and pathologic features of 14 anaplastic meningiomas (group A), 5 meningiomas with a predominant (${\geq}50%$) papillary or rhabdoid component (group B1), and 6 meningiomas without a predominant (<50%) rhabdoid or papillary component (group B2). Homogeneous enhancement on MRI was associated with improved PFS compared to heterogeneous enhancement (p=0.025). Depending on pathology, the mean PFS was $134.9{\pm}31.6\;months$ for group A, $46.6{\pm}13.4\;months$ for group B1, and $118.7{\pm}19.2\;months$ for group B2. The mean OS was $138.5{\pm}24.6\;months$ for group A and $59.7{\pm}16.8\;months$ for group B1. All recurrent tumors were of the previously diagnosed pathology, except for one tumor from group B1, which recurred as an atypical meningioma without a papillary component. Group B1 tumors showed a more aggressive behavior than group B2 tumors. In group B2 cases, the pathologic findings of non-rhabdoid/papillary portion could be considered for further adjuvant treatment.

• 대한화학회지
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• 제47권5호
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• pp.519-529
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• 2003

본 연구에서는 해결자${\cdot}$청취자 활동에서 사전 성취 수준이 다른 여러 소집단들의 언어적 상호작용의 특성을 조사하였다. 서울시에 소재한 고등학교 2개 학급을 선정하여 동질적 소집단의 해결자${\cdot}$청취자 활동 집단과 이질적 소집단의 해결자${\cdot}$청취자 활동 집단으로 배치한 후, 화학 수업을 실시하였다. 이 중 일부 동질적 소집단(상${\cdot}$상, 중${\cdot}$중)과 이질적 소집단(상${\cdot}$중, 상${\cdot}$하)을 선정하여 화학 반응식과 화학양론에 관한 정량적 문제 해결 과정을 녹화/녹음하였다. 동질적 소집단 가운데 상${\cdot}$상 조의 경우 해결자는 ''동의 요청''을, 청취자는 ''동의''를 많이 나타내었다. 이에 비해 중${\cdot}$중 조는 이질적 소집단인 상${\cdot}$중, 상${\cdot}$하 조와 유사하게 청취자의 ''지적''이나 해결자의 ''수정''이 많이 나타났다. 언어적 상호작용은 전반적으로 대칭형이 많았는데, 그 중에서도 상${\cdot}$상 소집단에서 ''동의 요청-동의''가 많이 나타났다. 해결자 주도형 상호작용으로는 상${\cdot}$상 소집단에서 ''풀이-동의'', 청취자 주도형 상호작용으로는 상${\cdot}$하 소집단에서 ''지적-수정''이 가장 많이 나타났다. 문제 해결 단계에서는 ''풀이'' 단계의 빈도가 크게 나타났고 ''검토'' 단계와 관련된 언어적 행동은 거의 나타나지 않았다.

• 한국산학기술학회논문지
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• 제13권9호
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• pp.4090-4097
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• 2012

본 연구는 대학생을 대상으로 절주동아리 활동을 실시한 후 음주에 대한 지식, 음주문화에 대한 인식도, 음주 문제에 대하여 미치는 효과를 알아보기 위한 것으로 비동등성 대조군 전후 설계인 유사실험연구이다. 2011년 4월에서 11월까지 K시에 재학 중인 대학생 95명을 대상으로 실시하였다. 실험군은 47명, 대조군은 48명으로 절주 동아리 활동 전에 음주에 대한 지식, 음주 문화 인식도, 음주 문제에 대하여 두 집단을 대상으로 사전 검사를 실시하였고, 동아리 활동 후 사후 검사를 실시하였다. 자료 분석은 SPSS 17.0을 이용하여 ${\chi}^2$-test, t-test를 실시하였다. 실험군과 대조군의 동질성 검증을 위해 일반적 특성, 사전 음주에 대한 지식, 음주문화 인식도, 음주 문제에 대하여 검사를 알아 본 결과 두 집단 간 유의한 차이가 없었다. 연구 결과를 보면 음주에 대한 지식에서는 실험군이 점수가 높았고 유의한 차이가 있어서 가설이 지지되었다. 그러나 음주문화 인식도, 음주문제에 대해서는 두 집단 간 유의한 차이가 없어 가설이 기각되었다. 향후에도 대학생을 대상으로 절주동아리 활동이 필요하다. 또한 알코올과 관련된 보다 다양한 프로그램을 적용할 필요가 있을 것이다.

• 한국분말재료학회지
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• 제17권2호
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• pp.107-112
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• 2010

Carbon-nanotube-embedded bismuth telluride (CNT/$Bi_2Te_3$) matrix composites were fabricated by a powder metallurgy process. Composite powders, whereby 5 vol.% of functionalized CNTs were homogeneously mixed with $Bi_2Te_3$ alloying powders, were successfully synthesized by using high-energy ball milling process. The powders were consolidated into bulk CNT/$Bi_2Te_3$ composites by spark plasma sintering process at $350^{\circ}C$ for 10 min. The fabricated composites showed the uniform mixing and homogeneous dispersion of CNTs in the $Bi_2Te_3$ matrix. Seebeck coefficient of CNT/$Bi_2Te_3$ composites reveals that the composite has n-type semiconducting characteristics with values ranging $-55\;{\mu}V/K$ to $-95\;{\mu}V/K$ with increasing temperature. Furthermore, the significant reduction in thermal conductivity has been clearly observed in the composites. The results showed that CNT addition to thermoelectric materials could be useful method to obtain high thermoelectric performance.

• Nuclear Engineering and Technology
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• 제50권3호
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• pp.340-355
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• 2018

The methods and performance of a fast reactor multigroup cross section (XS) generation code EXUS-F are described that is capable of directly processing Evaluated Nuclear Data File format nuclear data files. RECONR of NJOY is used to generate pointwise XS data, and Doppler broadening is incorporated by the Gauss-Hermite quadrature method. The self-shielding effect is incorporated in the ultrafine group XSs in the resolved and unresolved resonance ranges. Functions to generate scattering transfer matrices and fission spectrum matrices are realized. The extended transport approximation is used in zero-dimensional calculations, whereas the collision probability method and the method of characteristics are used for one-dimensional cylindrical geometry and two-dimensional hexagonal geometry problems, respectively. Verification calculations are performed first for various homogeneous mixtures and cylindrical problems. It is confirmed that the spectrum calculations and the corresponding multigroup XS generations are performed adequately in that the reactivity errors are less than 50 pcm with the McCARD Monte Carlo solutions. The nTRACER core calculations are performed with the EXUS-F-generated 47 group XSs for the two-dimensional Advanced Burner Reactor 1000 benchmark problem. The reactivity error of 160 pcm and the root mean square error of the pin powers of 0.7% indicate that EXUF-F generates properly the broad-group XSs.

• International Journal of Advanced Culture Technology
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• 제11권3호
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• pp.156-162
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• 2023

The purpose of this study was to examine the effects of peer scaffolding on the writing fluency of English language learners. This study was intended to confirm that peer scaffolding in English as a foreign language (EFL) writing classes can improve students' English proficiency. An analysis of 20 EFL learners studying at a university in Gyeonggi Province was conducted based on the English Proficiency Test. In this study, 20 intermediate learners with similar proficiency levels were included in the sample. Randomly, 10 students were designated as members of the control group, and 10 students were designated as members of the experimental group. In the experimental group, students practiced essay writing, while a skilled student provided scaffolding for a less skilled student. A variety of tools were used to gather data, including tests, questionnaires, and interviews Statistical analyses of quantitative data were conducted using t-tests for independent samples, whereas analyses of qualitative data were conducted based on themes. Pre-test results indicated a significant value of sig. =0.87, which was higher than α = 0.05. According to the results of this study, the writing performance of both experimental and control groups of students was equal and homogeneous prior to treatment. However, there were significant differences between the writing of students in the two groups after the completion of the program. Due to the post-test analysis of the writing test, the test resulted in a sig. =0 .043, a value lower than α = 0.05. As a result, the experimental group participants showed a marked improvement in their writing abilities after treatment.

• 호남수학학술지
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• 제38권2호
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• pp.359-366
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• 2016

Let H be the 3-dimensional Heisenberg group, ($G=H{\times}S^1$, g) a product Riemannian manifold of Riemannian manifolds H and S with arbitrarily given left invariant Riemannian metrics respectively, and ${\Gamma}$ the discrete subgroup of G with integer entries. Then, on the Riemannian manifold ($M:=G/{\Gamma}$, ${\Pi}^*g=\bar{g}$), ${\Pi}:G{\rightarrow}G/{\Gamma}$, we evaluate the scalar curvature and the Ricci curvature.

• 산업공학
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• 제15권2호
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• pp.182-188
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• 2002

Clustering is widely used in various fields in order to investigate structural characteristics of the given data. One of the main tasks of clustering is to partition a set of objects into homogeneous groups for the purpose of data reduction. In this paper a simple but computationally efficient clustering procedure is devised and some statistical techniques to validate its clustered results are discussed. In the given procedure, the proper number of clusters and the clustered groups can be determined simultaneously. The whole procedure is applied to a practical clustering problem for the classification of reusable fuels in nuclear power plants.

• International Journal of Automotive Technology
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• 제2권3호
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• pp.93-101
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• 2001

Distribution of fuel-air mixture has a strong influence on performance and emissions of a compressed natural gas (CNG) engine. In this paper, parametric study is performed by KIVA-3V to investigate fuel-air mixture with respect to injection timing, cycle equivalence ratio and engine speed. With open-valve injection intensive mixing during intake and compression stroke results in relatively homogeneous mixture in the cylinder. Sequential induction of fuel-air mixture and fresh air results in stratification in the cylinder among the test cases at closed-valve injection. There is close similarity in the calculated distributions of the mixture in the cylinder with different cycle equivalence ratios and engine speeds. The results are compared against pressure traces and flame images obtained in a single cylinder engine converted from a 11L six-cylinder heavy duty diesel engine.