• 응용통계연구
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• 제26권6호
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• pp.1019-1032
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• 2013

최근 급격한 기대수명의 증가에 따라 미래 복지정책 등에 커다란 영향을 주는 장래 사망력의 정확한 예측은 중요한 이슈가 되고 있다. 사망력의 정확한 예측을 위하여 최적의 추정모형의 선택도 중요하지만 사망력에 대한 시계열 적용기간도 매우 중요한 이슈다. 이는 우리나라의 사망률 시계열이 짧고, 특히 1982년 이전 자료가 다소 불완전해서 이에 대한 고려가 필수적이기 때문이다. 본 논문에서는 우리나라 사망력 시계열을 기간에 따라 2개의 그룹(1976~2005년, 1983~2005년)으로 나누어서, 남녀별로 LC모형과 LC 코호트효과 확장모형에 대한 모수 추정값, 사망력지수와 코호트지수의 모형화 및 예측, 장래 기대수명의 예측 적합력을 각각 분석한 후 향후에 장래 기대수명 추계시 고려할 시사점을 제시하고자 한다.

• 대한한의학방제학회지
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• 제21권1호
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• pp.36-50
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• 2013

Objectives : To clarify the possible effect of Lycium chinese Mill (LC)., Morus alba L (MA)., and Lycium chinese Mill. +Morus alba L. (LC+MA), we have examined their influence on the development of pulmonary eosinophilic inflammation in the asthmatic murine model. Methods : Female Balb/c mice (5weeks) were immunized on two different days (21 days and 7 days before inhalational exposure) by intraperitonial injections of 0.2ml alum-precipitated Ag containing $100{\mu}g$ of OVA bound to 4 mg of aluminum hydroxide in PBS. Seven days after the second sensitization, mice were exposed to aerosolized ovalbumin for 30 minutes/day on 3 days/week for 8 weeks (at a flow rate of 250 L/min, 2.5% ovalbumin in normal saline) and, LC, MA, and LC+MA (500 mg/kg) were orally administered 3 times per a week for 8 weeks. Results : The suppressive effect of LC, MA, and LC+MA were demonstrated by the accumulation of eosinophills into airways, with the reduction of eosinophil, total lung leukocytes numbers. These were correlated with the marked reduction of IL-5, IL-13 and IL-4 levels in the BALF and serum. OVA-specific IgE levels were also decreased in serum and BAL from these mice. LC, MA, and LC+MA decreased eosinophil CCR3 expression and CD11b expression in lung cells. Conclusions : These results indicate that LC, MA, and LC+MA have high inhibitory effects on airway inflammation and hyper-responsiveness in the asthmatic murine model. The suppression of IL-5, IgE, eosinophil CCR3 expression and CD11b expression, and the increase of IFN-${\gamma}$ production in BALF seem to contribute to this effect. Hence, the results indicated that LC, MA, and LC+MA could act as a immuno-modulator which possesses anti-inflammatory and anti-asthmatic property by modulating the imbalance between Th1 and Th2 cytokines.

• Journal of Electrical Engineering and Technology
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• 제11권4호
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• pp.951-960
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• 2016

Tower insulators in electric power transmission network play a crucial role in preserving the reliability of the system. Electrical utilities frequently face the problem of flashover of insulators due to pollution deposition on their surface. Several research works based on leakage current (LC) measurement has been already carried out in developing diagnostic techniques for these insulators. Since the LC signal is highly intermittent in nature, estimation of pollution severity based on LC signal measurement over a short period of time will not produce accurate results. Reports on the measurement and analysis of LC signals over a long period of time is scanty. This paper attempts to use Random Forest (RF) classifier, which produces accurate results on large data bases, to analyze the pollution severity of high voltage tower insulators. Leakage current characteristics over a long period of time were measured in the laboratory on porcelain insulator. Pollution experiments were conducted at 11 kV AC voltage. Time domain analysis and wavelet transform technique were used to extract both basic features and histogram features of the LC signal. RF model was trained and tested with a variety of LC signals measured over a lengthy period of time and it is noticed that the proposed RF model based pollution severity classifier is efficient and will be helpful to electrical utilities for real time implementation.

• 응용통계연구
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• 제31권5호
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• pp.637-653
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• 2018

빠른 고령화로 고령층의 증가는 인구구조 변화와 인구고령화에 영향을 미친다. 예전부터 선진국은 인구고령화를 주요현안으로 간주하여 고령화로 인한 연금 재정건전성, 건강 및 노인 복지 시스템의 지속 가능성에 집중하고 있다. 이처럼 고령층의 증가로 인구구조 변화와 인구고령화에 미치는 사망률 예측은 어느 때보다도 중요하다. 본 논문은 통계청 1970-2016년 각세별 생명표 자료를 활용하여 사망률 모형 6가지를 비교하였다. 이들 모형은 Lee-Carter(LC) 모형 (Lee and Carter, Journal of the American Statistical Association, 87, 659-671, 1992)에 근원을 두고 있으며, LC 의 가정을 수정하고 개선한 것이다. 이들 개선과정과 가정검토를 모형별로 살펴보고 우리나라에 적합한 사망률 모형을 모색했다. 분석결과 빠른 고령화와 연령별 사망률의 개선 효과를 보이는 우리나라의 경우 기대수명에 큰 변화를 주지 않고 이들 현상을 반영하고 연령별 사망률 패턴을 수정하는 LC-ER 모형 (Li 등, Demography, 50, 2037-2051, 2013)과 Li-Lee 모형과 LC-ER모형을 조합한 LL&LC-ER 모형으로 사망률을 예측하는 것이 바람직하다.

• 한국의류학회지
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• 제18권4호
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• pp.524-535
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• 1994

The interaction and detergency between oily soil and surfactant solution were studied Samples used were tristearin, tripalmitin and their mixture as a triglyceride, myristic acid as a fatty acid and sodium dodecyl sulfate (SDS) as surfactant. The results were as follows: 1. The mixtures of model oily soils were formed of eutectic point and their melting point were lower than them of individual oily soils. 2. The formation of liquid crystalline (LC) phase was recognized in the triangle phase diagram for SDS~ water~model oily soil system. The areas of LC phase region were in the order of SHS~ water~myristir acid> SDS~ water~mixture of tristearin, tripalmitin and myristic acid (TS/TP/M)>SDS~water~mixture of tristearin and tripalmitin (TS/TP) 3. The LC phase region expanded to wide concentration range of SDS solution and high concentration range of model oily soil with increasing temperature. Particularity, the LC phase region expanded highly at $30~40^{\circ}C$ but when the temperature was elevated above $40^{\circ}C$, expanding tendency decreased. 4. In the system of myristic acid and TS/TP/M contacted with SDS solution, the LC phase was already formed at $28^{\circ}C$ and the region of the LC phase were expanded with increasing temperature. But in the system of TS/TP contacted with SDS solution, the LC phase was not formed in whole experiment temperature. 5. The detergency of myristic acid was very high ann it was recognized that the formation of the LC phase played an important role in the detergency. The detergency of TS/TP was very for low, but when TS/TF was mixed with myristic acid, the detergency of TS/TP increased. It is supposed that the LC phase was formed butween SDS solution and myristic acid promoted to penetration of SDS solution into the inner parts of TS/TP.

• 응용통계연구
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• 제31권1호
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• pp.77-96
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• 2018

주택연금은 계약기간이 확정되어 있지 않기 때문에 계약 종료 시점에 대한 확률분포 예측이 장수리스크 관리를 위하여 중요하다. 따라서 고령화의 주요인인 기대수명의 연장은 연금 재정건전성에 심각한 영향을 끼칠 수 있기 때문에 사망률의 개선 추세가 적절히 반영된 사망률 예측 연구가 선행될 필요가 있다. 본 연구에서는 Lee-Carter (LC) 모형과 연생모형을 이용하여 주택연금 계리모형에 사망률 개선 효과를 반영하였다. 전통적 LC 모형을 통한 사망률 예측 방식은 미래 사망률이 지나치게 개선되는 현상을 보이고 있기 때문에 사망률 개선효과를 조금 더 적절한 수준으로 보정하고자 본 연구에서는 사망확률 분포의 편중을 나타내는 왜도를 활용한 LC 모형을 적용하였다. 왜도 예측 방식을 LC 모형에 적용한 방법론을 사용하여 주택연금 월 지급금을 산출해본 결과 전통적 LC 모형의 사망률 예측보다 사망률 개선효과를 더 적게 반영하여 더 큰 월 지급금이 산출되었고, 왜도 활용 LC 모형에 의한 이러한 결과는 장수 리스크를 덜 왜곡한다는 데 의의가 있다고 볼 수 있다. 본 연구 결과는 사망률 감소 추세를 적절하게 반영한 위험률을 계산하여 주택연금의 발행기관 및 보증기관의 적정한 월 지급금 지급과 차후 월 지급금의 과대지급으로 인한 지급불능을 방지할 수 있는 리스크 관리 방법으로 이용될 수도 있다.

• Communications for Statistical Applications and Methods
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• 제28권3호
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• pp.233-250
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• 2021

This paper studies if the accuracies of mortality models (LC model vs. 4-parametric model) are aggravated if a mortality structure changes due to the impact of COVID-19. LC model (LCM) uses dimension reduction for fitting to the log mortality matrix so that the performance of the dimension reduction method may not be good when the matrix structure changes. On the other hand, 4-parametric factor model (4-PFM) is designed to use factors for fitting to log mortality data by age groups so that it would be less affected by the change of the mortality structure. In fact, the forecast accuracies of LCM are better than those of 4-PFM when life-tables are used whereas those of 4-PFM are better when the mortality structure changes. Thus this result shows that 4-PFM is more reliable in performance to the structural changes of the mortality. To support the accuracy changes of LCM the functional aspect is explained by computing eigenvalues produced by singular vector decomposition

• Toxicological Research
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• 제31권4호
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• pp.331-337
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• 2015

Synthetic pyrethroids (SPs) are the most common pesticides which are recently used for indoor pest control. The widespread use of SPs has resulted in the increased exposure to wild animals and humans. Recently, some SPs are suspected as endocrine disrupting chemicals (EDCs) and have been assessed for their potential estrogenicity by adopting various analyzing assays. In this study, we examined the estrogenic effects of lambda-cyhalothrin (LC) and cypermethrin (CP), the most commonly used pesticides in Korea, using BG-1 ovarian cancer cells expressing estrogen receptors (ERs). To evaluate the estrogenic activities of two SPs, LC and CP, we employed MTT assay and reverse-transcription polymerase chain reaction (RT-PCR) in LC or CP treated BG-1 ovarian cancer cells. In MTT assay, LC ($10^{-6}M$) and CP ($10^{-5}M$) significantly induced the growth of BG-1 cancer cells. LC or CP-induced cell growth was antagonized by addition of ICI 182,720 ($10^{-8}M$), an ER antagonist, suggesting that this effect appears to be mediated by an ER-dependent manner. Moreover, RT-PCR results showed that transcriptional level of cyclin D1, a cell cycle-regulating gene, was significantly up-regulated by LC and CP, while these effects were reversed by co-treatment of ICI 182,780. However, p21, a cyclin D-ckd-4 inhibitor gene, was not altered by LC or CP. Moreover, $ER{\alpha}$ expression was not significantly changed by LC and CP, while down-regulated by E2. Finally, in xenografted mouse model transplanted with human BG-1 ovarian cancer cells, E2 significantly increased the tumor volume compare to a negative control, but LC did not. Taken together, these results suggest that LC and CP may possess estrogenic potentials by stimulating the growth of BG-1 ovarian cancer cells via partially ER signaling pathway associated with cell cycle as did E2, but this estrogenic effect was not found in in vivo mouse model.

• Computers and Concrete
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• 제32권6호
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• pp.577-594
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• 2023

Engineered cementitious composites with calcined clay limestone cement (LC³-ECC) as a kind of green, low-carbon and high toughness concrete, has recently received significant investigation. However, the complicated relationship between potential influential factors and LC³-ECC compressive strength makes the prediction of LC³-ECC compressive strength difficult. Regarding this, the machine learning-based prediction models for the compressive strength of LC³-ECC concrete is firstly proposed and developed. Models combine three novel meta-heuristic algorithms (golden jackal optimization algorithm, butterfly optimization algorithm and whale optimization algorithm) with support vector regression (SVR) to improve the accuracy of prediction. A new dataset about LC³-ECC compressive strength was integrated based on 156 data from previous studies and used to develop the SVR-based models. Thirteen potential factors affecting the compressive strength of LC³-ECC were comprehensively considered in the model. The results show all hybrid SVR prediction models can reach the Coefficient of determination (R²) above 0.95 for the testing set and 0.97 for the training set. Radar and Taylor plots also show better overall prediction performance of the hybrid SVR models than several traditional machine learning techniques, which confirms the superiority of the three proposed methods. The successful development of this predictive model can provide scientific guidance for LC³-ECC materials and further apply to such low-carbon, sustainable cement-based materials.

• 영어어문교육
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• 제15권4호
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• pp.345-364
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• 2009

This study attempts to provide a comprehensive framework for listening strategy use among university students in Korea in relation to TOEIC listening scores. In particular, this study tests whether motivation, based on the self-determination theory, mediates listening strategy use on listening comprehension (LC) process and whether reading comprehension ability moderates the use of listening strategy in LC achievement. One hundred seventy six freshmen students participated in the study during their first semester required English course. Self-report questionnaires were used to assess students' motivation and LC strategy use. The responses were statistically analyzed via the moderator and mediator model. The results indicate that internalized motivation mediates the use of listening strategy in LC achievement; however, reading comprehension skill doesn't affect students' use of listening strategies in relation to listening skill achievement. In other words, students who have internalized motivation were able to utilize listening strategies effectively in terms of achievement of the TOEIC listening skills. The findings of the current study offer in-depth understanding of the relationship among use of LC strategies, intrinsic motivation, and listening skill achievement shared by the mediator and moderator models.