• Journal of Korean Neurosurgical Society
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• 제63권4호
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• pp.470-476
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• 2020

Objective : The objective of this study was to develop a score to predict patients with acute ischemic stroke (AIS) who will not benefit from endovascular treatment (EVT) using computed tomographic angiography (CTA) parameters. Methods : The CTA-ABC score was developed from 3 scales previously described in the literature: the Alberta Stroke Program Early CT Score (0-5 points, 3; 6-10 points, 0), the clot burden score (0-3 points, 1; 4-10 points, 0), and the leptomeningeal Collateral score (0-1 points, 2; 2-3 points, 0). We evaluated the predictive value of CTA parameters associated with symptomatic intracranial hemorrhage (sICH) or malignant middle cerebral artery infarction (MMCAI) after EVT and developed the score using logistic regression coefficients. The score was then validated. Performance of the score was tested with an area under the receiver operating characteristic curve (AUC-ROC). Results : The derivation cohort consisted of 115 and the validation cohort consisted of 40 AIS patients. The AUC-ROC was 0.97 (95% confidence interval [CI], 0.94-0.99; p<0.001) in the derivation cohort. The proportions of patients with sICH and/or MMCAI in the derivation cohort were 96%, 73%, 6%, and 0% for scores of 6, 5, 1, and 0 points, respectively. In the validation group, the proportions were similar (90%, 100%, 0%, and 0%, respectively) with an AUC-ROC of 0.96 (95% CI, 0.90-1.00; p<0.001). Conclusion : Our CTA-ABC score reliably assessed risk for sICH and/or MMCAI in patients with AIS who underwent EVT. It can support clinical decision-making, especially when the need for EVT is uncertain.

• 한국수정란이식학회지
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• 제28권1호
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• pp.1-6
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• 2013

A lot of works have been dedicated to clarify the reasons why the establishment of embryonic stem cells (ESCs) from pig is more difficult than that from mouse and human. Several concomitant factors such as culture condition including feeder layer, sensitivity of cell to cell contact, definitive markers of pluripotency for evaluation of the validity and optimal timing of derivation have been suggested as the disturbing factors in the establishment of porcine ESCs Traditionally, attempts to derive stem cells from porcine embryos have depend on protocols established for mouse ESCs using inner cell mass (ICM) for the isolation and culture. And more recently, protocols used for primate ESCs were also applied. However, there is no report for the establishment of porcine ESCs. Indeed, ungulate species including pigs have crucial developmental differences unlike rodents and primates. Here we will review recent studies about issues for establishment of porcine ESCs and discuss the promise and strategies focusing on the timing for derivation and pluripotent state of porcine ESCs.

• Molecules and Cells
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• 제19권1호
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• pp.46-53
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• 2005

Human embryonic stem (hES) cells, unlike most cells derived from adult or fetal human tissues, represent a potentially unlimited source of various cell types for basic clinical research. To meet the increased demand for characterized hES cell lines, we established and characterized nine new lines obtained from frozen-thawed pronucleus-stage embryos. In addition, we improved the derivation efficiency from inner cell masses (to 47.4%) and optimized culture conditions for undifferentiated hES cells. After these cell lines had been maintained for over a year in vitro, they were characterized comprehensively for expression of markers of undifferentiated hES cells, karyotype, and in vitro/in vivo differentiation capacity. All of the cell lines were pluripotent, and one cell line was trisomic for chromosome 3. Improved culture techniques for hES cells should make them a good source for diverse applications in regenerative medicine, but further investigation is needed of their basic biology.

• 통합자연과학논문집
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• 제3권4호
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• pp.226-230
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• 2010

Calculation of partial charge is important in chemistry. However, because there are many methods developed, it is of considerable interest to know how to calculate and apply properly to address various chemical problems. For basis set, usually double zeta quality is acceptable, and double zeta polarization function would be enough for most cases. To describe electronic state more accurately, Many electron configurations would be necessary to describe highly strained or anionic species. The NPA population introduced new concept about amide bonds, i.e., the planar geometry of nitrogen atom may not come from resonance, but from the lowering of p-orbital energy by electronegative carbonyl carbon atom. The issues for hypervalent atomic charges was also addressed by various charge derivation scheme. When the charge schemes were applied to organolithium compounds, the ionic nature of boding was revealed. This comes from the fact that previous Mulliken partial atomic charges overemphasized the covalent character, wihout much justification. The other partial charge derivation schemes such as NPA(natural population analysis), IPP (Integrated Projected Population) showed that much more ionic picture. ESP potential derived charges are generally believed to be suitable to describe intermolecular interactions, therefore they are used for molecular dynamics simulations and CoMFA (comparative molecular field analysis). The charge derivation schemes using multipole polarization was mainly applied to reproduce experimental infrared spectroscopy. In some reports these schemes are also suitable for intermecular electrostatic interactions. Charges derived from electron density gradient have shown the some bonds are not straight, but actually bent. The proper choice of charge-calculation method along with suitable level of theory and basis set are briefly discussed.

• 정보보호학회논문지
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• 제25권3호
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• pp.547-557
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• 2015

암호 알고리즘과 암호 프로토콜은 사용되는 키들의 기밀성이 유지된다는 가정 하에서 안전성을 보장받을 수 있다. 대부분의 암호시스템에는 전반적으로 사용되는 키들을 안전하게 관리하는 키관리 메커니즘이 필수 요소로 구현되어 있으며, 키관리 메커니즘의 내부에는 하나의 마스터키로부터 더 많은 종류의 키들을 생성하는 키유도함수(KDF)가 존재한다. NIST SP 800-108에서는 PRF-기반 KDF를 표준안으로 제안하고 있다. 본 논문에서는 KDF와 암호화 운영모드에 대한 증명가능 안전성 관점의 차이를 분석하고, PRF-기반 KDF 중 Counter 모드와 Feedback 모드에 대하여 핵심함수인 PRF의 입력값으로 카운터 값이 XOR과 연접 연산 형태로 입력되는 경우를 비교하여 안전성을 규명한다. 증명가능 안전성 관점에서 카운터 값이 XOR 형태로 입력되는 경우의 KDF는 안전하지 않은 반면, 연접 연산 형태로 삽입되는 경우의 KDF는 안전함을 증명한다.

• 한국통신학회논문지
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• 제40권10호
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• pp.2080-2089
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• 2015

본 논문에서는 3차원 비디오 압축을 위한 표준으로서 3D-AVC와 3D-HEVC에 채택된 주위 블록의 변위 벡터정보를 이용한 블록 기반의 변위 벡터 추정 기법 (Neighboring block-based disparity vector, NBDV)을 설명하고 성능을 평가하여 분석한다. NBDV에서는 시간적 공간적으로 인접한 주위 블록에서 부호화를 완료한 변위 움직임 벡터 (disparity motion vector)를 이용하여 변위 벡터로 변환한다. 변위 벡터는 인접 시점에서 현재 블록에 대응하는 블록을 지시하는 벡터로 시점간 통계적 연관성을 이용함으로써 3차원 동영상의 부호화 효율을 증대하는데 중요한 기능을 제공한다. 제안 기술은 저 복잡도와 동일 화질에서 약 20%의 부호화 효율 증가, 그리고 네트워크 내 미디어 게이트웨이의 효율적인 동작을 제공하는 텍스쳐 비디오 우선 부호화 방식을 지원하여 3차원 비디오 압축 표준 기술로 최종 채택되었다.

• 정보보호학회논문지
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• 제15권6호
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• pp.93-103
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• 2005

XML에 대한 사용의 증가와 함께, XML. 객체에 대한 보안의 필요성이 계속해서 증가하고 있다. 특히, 다양한 사용자가 서로 결합되어 있는 환경에서 공유되는 XML. 객체에 대한 접근제어 문제의 해결은 매우 중요하다. 본 논문에서는 XML 객체에 대한 접근제어를 위하여 RBAC의 역할 계층과 계층적 키 유도/할당 기법을 결합한 접근제어 모델을 제안한다. RBAC는 자체적으로 주체에 대한 키 할당 기법은 지원하지 않으므로 계층적 키 분배 기법을 도입하여 접근제어 메커니즘이 실현되도록 하였다. 본 논문에서 제안된 방식은 XML. 객체를 위한 접근제어에서 RBAC이 제공하는 관리상의 이점뿐만 아니라, 상위 계층의 사용자가 하위 계층의 키를 유도하여 사용할 수 있게 지원하므로 각 역할계층에서 관리하는 키의 수가 기존 방식에 비하여 줄어드는 특징을 제공한다.

• 한국지진공학회논문집
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• 제27권5호
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• pp.213-220
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• 2023

Seismic fragility curves play a crucial role in assessing potential seismic losses and predicting structural damage caused by earthquakes. This study compares non-sampling-based methods of seismic fragility curve derivation, particularly the probabilistic seismic demand model (PSDM) and finite element reliability analysis (FERA), both of which require employing sophisticated finite element analysis to evaluate and predict structural damage caused by earthquakes. In this study, a three-dimensional finite element model of API 5L X65, a buried gas pipeline widely used in Korea, is constructed to derive seismic fragility curves. Its seismic vulnerability is assessed using nonlinear time-history analysis. PSDM and a FERA are employed to derive seismic fragility curves for comparison purposes, and the results are verified through a comparison with those from the Monte Carlo Simulation (MCS). It is observed that the fragility curves obtained from PSDM are relatively conservative, which is attributed to the assumption introduced to consider the uncertainty factors. In addition, this study provides a comprehensive comparison of seismic fragility curve derivation methods based on sophisticated finite element analysis, which may contribute to developing more accurate and efficient seismic fragility analysis.

• 대한지구과학교육학회지
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• 제12권1호
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• pp.94-108
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• 2019

이 연구는 과학영재 학생의 탐구 사고력 향상을 위해 안내된 R & E 프로그램을 개발하여 그 효과를 확인하고자 하였다. 우선 교사중심에서 학생 중심으로 3단계의 과정을 거쳐 R & E를 수행할 수 있도록 하는 안내된 R & E 수업 모형을 개발하였고, 5단계 절차에 맞는 안내된 R & E 프로그램을 개발하여 중학교 과학 영재 학생 38명을 대상으로 수업을 진행하였다. 그 결과, '가설 설정 > 변인 추출 > 탐구문제 도출 > 결론 도출 > 실험 설계 > 일반화 > 평가 > 자료 해석 > 자료 변환' 순으로 높은 평균 점수를 나타냈다. 세부적으로는 9개 평가 요소 중 '탐구문제 도출, 변인 추출, 가설 설정, 결론 도출'은 높은 수준을, '실험 설계'는 평균 수준을, '자료 해석, 일반화, 평가'는 낮은 수준을, '자료 변환'은 매우 낮은 수준을 나타냈다. 이번 연구를 계기로 안내된 R & E 프로그램이 탐구 과정별 요소를 잘 반영하여 과학영재 학생의 종합적 사고력과 창의적 문제해결력 향상에 도움이 되길 기대한다.

• 대한수학회보
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• 제38권4호
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• pp.709-718
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• 2001

In this paper we show that if D and G are continuous linear Jordan derivations on a Banach algebra A satisfying [D(x), x]x - x[G(x),x] $\epsilon$ rad(A)for all $\epsilon$ A, then both D and G map A into rad(A).