• 대한교통학회지
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• 제36권2호
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• pp.141-154
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• 2018

지속적으로 증가하는 국제선 항공수요에 대웅하기 위해 지방 광역권에도 새로운 공항 건설 및 기존 공항 확장 계획이 이루어지고 있다. 그러나 기존 항공수요예측은 우리나라 전체 항공수요 또는 주요 도시 간의 항공수요에 대해서 수행되어 왔으며, 지방의 고유 특성을 고려한 지역별 항공수요예측은 많이 이루어지지 않았다. 본 연구에서는 영남권 국제선 항공수요를 대상으로 하였고, 현실적으로 관측하기 어려운 지방 광역권의 고유 특성을 반영할 수 있는 패널 자료를 활용한 fixed-effects model을 최적 모형으로 제안하였다. 모형 검증결과를 살펴보면 패널 자료 분석은 시계열 특성을 가지는 몇 개의 거시 사회경제지표만을 사용한 모형에서 다루기 어려운 허구적 회귀와 미관찰 이질성을 효과적으로 처리하고 있음을 알 수 있다. 다양한 통계적 검증과 적합성 평가를 통해서 본 연구에서 제안한 fixed-effects model이 다른 계량경제 모형들에 비해서 영남권 국제선 수요예측에 있어서 우수함을 증명하였다.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1998년도 Proceedings of UNESCO-internetwork Cooperative Regional Seminar and Workshop on Bioassay Guided Isolation of Bioactive Substances from Natural Products and Microbial Products
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• pp.185-185
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• 1998

As part of our continuing attempts to evaluate biologically active compounds from fruiting bodies of cultivated fungus of Paecilomyces japonicus Yasuda, we conducted series of experiments on various fractions and compounds isolated by systematic fractionations. Our main efforts were concentrated on searching for compounds showing antitumor activities, which were tested on mice carrying Sarcoma-180 ascitic tumor. The antitumor activity was assessed by the life spans after these mice were administered Lp. with test compounds for consecutive 20 days. One of two pure compounds, which we have isolated to date, demonstrated significant prolongation of life span. ( Mean Survival Time: 30.3 days compared to that of control: 23.6 days). Structural analysis showed that this compound corresponds to D-mannitol. On the other hand, Ergosterol, another isolated pure compound didn't show efficient antitumor activity. We also obtained water-soluble fractions containing protein-bound polysaccharides and n-butantol fractions, which showed strong antitumor activities, 35.4(150%) and 32.1(136.0%) days of MST, respectively. In SRB assay, however, the test materials didn't show any toxic effects, but the level of acid phosphatase increased significantly when they were applied in cultured macrophage in vitro. Therefore, we concluded that antitumour activities might be attributed to immunostimulating rather than cytotoxic effects. Further experiments are underway to purify and structurally characterize new antitumour compounds from the active fractions.

• 한국분말재료학회지
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• 제20권6호
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• pp.432-438
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• 2013

In this study, analysis on the oxidation behavior was conducted by a series of high-temperature oxidation tests at both $800^{\circ}C$, $900^{\circ}C$ and 1000 in the air with sintered STS 316L. The weight gain of each oxidized specimen was measured, the oxidized surface morphologies and composition of oxidation layer were analyzed with Scanning Electron Microscope-Energy Dispersive x-ray Spectroscopy (SEM-EDS), finally, the phase change and composition of the oxidized specimen were shown by X-Ray Diffraction (XRD). As a result, the weight gain increased sharply at $1000^{\circ}C$ when oxidation test was conducted for 210 hours. Also, a plentiful of pores were observed in the surface oxidation layers at $900^{\circ}C$ for 210 hours. In addition, the following conclusions on oxidation behavior of sintered STS 316L can be obtained: $Cr_2O_3$ can be formed on pores by influxing oxygen through open-pores, $(Fe_{0.6}Cr_{0.4})_2O_3$ can be generated on the inner oxidation layer, and $Fe_2O_3$ was on the outer oxidation layer. Also, $NiFe_2O_4$ could be precipitated if the oxidation time was kept longer.

• 수산해양기술연구
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• 제46권4호
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• pp.476-486
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• 2010

Fishing efficiency of a trawl vessel can be enhanced by increasing the swept area per unit time, which can be attained either by increasing the mouth size of the net, or by increasing the towing speed. To improve fishing and fuel efficiency of trawl vessels targeting fishes of greater mobility, in which the towing speed is more critical in determining fishing efficiency, we conducted a series of model tests to evaluate the performance of the newly-designed nozzle propeller before installing it in a trawl vessel to verify its towing speed and fuel efficiency in the sea. By conducting further model tests in the experimental basin, we redesigned the propeller of stern trawler to improve the resistance and propulsion performance. Through actual fishing operations, we evaluated the improvement in fuel and fishing efficiency by installing the new nozzle propeller. The trawling speed increased by 0.6kts at the same engine power (RPM), while the engine margin increased by more than 20%. The increased towing speed by installing the redesigned propeller is expected to enhance fishing performance through increasing the number of hauling- and casting operations per unit times, while shortening the towing duration. Analysis of the Catch-Per-Unit-Effort (CPUE) data indicated that the mean CPUE of trawl fishery increased from 3.04kg/m in year 2007 to 6.15kg/m in year 2008, confirming enhanced fishing efficiency by adopting the redesigned propeller.

• 보건행정학회지
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• 제30권2호
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• pp.178-184
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• 2020

Background: Korea set up a new diagnosis-related group as a demonstration project in 2009. The new diagnosis-related group was reformed in 2016. The main purpose of the study is to identify the effect of reform on coverage of national health insurance. Methods: This study collected inpatient data from a hospital that contains medical information and cost from 2015 July to 2016 June. The dependent variable was the coverage of national health insurance. The dependent variable was divided by total, internal medicine partition, surgical partition, and psychiatric partition. To analyze the effect of the reform, this study conducted an interrupted time series analysis. The final sample included 23,695. Results: The health insurance coverage of internal medicine has the highest, followed by surgery and psychiatry. The health insurance coverage of bundle payment is higher than that of unbundled payment. The proportion of bundled payment and non-benefit decreased and the proportion of unbundled payment increased. The coverage of national health insurance significantly increased after policy reform in internal medicine partition (p-value=0.0356). Conclusion: The results of the study imply that policy reform enhanced the coverage of national health insurance in internal medicine. The government needs to monitor side effects such as an increase of unbundled payment.

• 보건행정학회지
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• 제21권2호
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• pp.249-262
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• 2011

Since May 1st in 2008, the products of ginkgo biloba extract have had to be used with the patient's out-of-pocket payment due to reimbursement restriction guidelines. This study aims to analyze the policy effects of reimbursement restriction on pharmaceutical expenditures using interrupted time series(ITS) analysis. We retrieved monthly NHI claims data for the period between May, 2005 and December 2009. The ingredients identified as a substitute for ginkgo biloba have similar indications based on the similar pharmacological activities. The effects of changes in reimbursement scope were evaluated both for all relevant pharmaceuticals within the same therapeutic class and for 2 separate groups : ginkgo biloba's and its substitutes. According to the study results, restrictions on reimbursement scope resulted in savings of the drug expenditures in the targeted therapeutic class. Direct restriction on ginkgo biloba was associated with a decrease in expenditure level by 60.1% and changes in trend from an average increase rate of 1.4% to an average decrease rate of 1.5% for the therapeutic class, with a dramatic decrease in expenditure level(-191.5%) for ginkgo biloba itself, but with an increased expenditure level(+50.1%) and changes in trend from an average increase rate of 2.0% to an average decrease rate of 1.0% for the substitute group. Further policy to restrict nicergoline was associated with additional decrease in expenditure level for the therapeutic class. Additionally, we could identify the balloon effect - a new policy squeezing one part results in bulging out elsewhere. After the restriction of ginkgo biloba, the utilization of and expenditures on its substitutes increased significantly. In conclusion, we demonstrated that consecutively introduced policies effectively reduced overall expenditures on the therapeutic class of interest. Some ingredients played as a substitute while others did not. Further studies need to be conducted to identify which factors determine a substitute.

• 대한의용생체공학회:의공학회지
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• 제24권3호
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• pp.151-158
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• 2003

심장혈관 신호에 있어서 단기간의 beat-to-beat 변이(variability)에 대한 여러 연구에서 선형 분석기법들이 사용되었다. 그러나 단기간 beat-to-beat 변이에 대해 선형기법 사용의 타당성에 대한 연구나 선형과 비선형 특성을 비교한 연구는 수행되지 않았다. 본 논문의 목적은 단기간 beat-to-beat 변이의 비선형성 특성을 조사함으로써 선형기법 사용의 적절함을 증명하고자 한다. 이를 위해 선형 ARMA와 비선형 신경망(NN) 모델을 사용하여 예측을 수행하였는데, 과거의 순시 심박(HR)과 평균 혈압(BP)으로부터 현재의 심박과 혈압 예측을 상호 비교하였다. 이러한 예측모델을 평가하기 위해 MIMIC 데이터베이스로부터 HR와 BP 시계열을 사용하였다. 실험결과에 의하면 신경망에 의한 비선형성은 단기간 beat-to-beat 변이를 생성하는 시스템 동특성을 나타내는데 의미있는 역할을 하지 못하였으며, 이 사실은 ARMA 선형 분석기법이 이러한 시스템 동특성을 나타내는데 적절함을 보여주고 있다

• Journal of the Korean Data and Information Science Society
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• 제26권2호
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• pp.289-299
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• 2015

본 연구는 PM10 농도에 대한 계량치 예측모형 개발을 목적으로 한다. 세 종류의 자료 (기상관측 자료, 세계기상통신망 중국 관측자료, 대기질 화학수치모델자료)를 예측인자로 사용하였으며, 일일 단기예보 시스템에 쉽게 적용할 수 있도록 시간자료를 일자료로 변환하였고 시차변환을 수행하였다. 상관분석과 다중공선성 진단을 통하여 예측인자를 선택하고 두 종류의 모형 (중회귀모형, 문턱치 회귀모형)을 각각 적합하였다. 모형 안정성 검사를 위하여 모형검증을 수행하였으며, 전체자료를 사용하여 모형을 재추정한 후 예측치와 관측치 사이의 산점도와 시계열그림, RMSE, 예측성 평가측도를 작성 및 산출하여 두 모형을 비교하였다. 문턱치 회귀모형의 예측력이 고농도 PM10예측에서 다소 우수한 결과를 보였다.

• 대한임상독성학회지
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• 제7권2호
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• pp.143-149
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• 2009

Purpose: Suicide attempts are known to be influenced by mass media reports. The purpose of this study was to evaluate the effects of mass media reporting celebrity suicides on an increase of intentional carbon monoxide (CO) poisoning and suicide attempts. Methods: We retrospectively reviewed the medical records of the consecutive patients who presented with suicide attempts to the Emergency Department of Ajou University Hospital during a 24 month period. We obtained the demographic data, any past history of suicide attempt and the methods of suicide attempts from the medical records of the suicide attempters. Time series analysis was conducted for evaluating the influence of mass media reporting of celebrity suicide on the suicide rates. Results: We finally enrolled 770 patients during the study period. The total number of suicide attempts by CO poisoning was 18 and the average number of suicide attempts by CO was $0.33{\pm}0.73$ per week. All of the suicide attempts by CO poisoning occurred after a celebrity committed suicide using CO from burning charcoal. Conclusion: This study showed that celebrity suicide by CO poisoning resulted in the Werther effect, which made the rate of intended CO poisoning increase, and the study provided further evidence for the need to actively restrain mass media reporting of suicide to decrease the Werther effect.

• STI Policy Review
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• 제8권1호
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• pp.113-156
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• 2017

Although technological progress is considered a key element for economic growth and development of a country, strong empirical evidence in this regard is not available yet. Therefore, to establish the empirical link between technology progress and economic development, it is advisable to carry out a time series analysis. In this regard, the Technology Achievement Index (TAI) of 100 top economies has been developed to examine the position of countries' technological progress for the 21 years spanning 1995 to 2015. Countries have been ranked on their TAI which is based on four pillars; technology creation, diffusion of older innovations, diffusion of recent innovations, and development of human skills. As well, this current study re-calculates the Humane Development Index (HDI) of 100 top economies for the 21 years from 1995 to 2015. Ranking of countries' HDI values reflects three dimensions: A long lifespan (life expectancy index), knowledge (Education Index) and a decent standard of living (Gross National Income Index, or GNI). The Standard Deviation (SD) technique has been used to investigate the technological gap between individual countries and groups of countries or regions. For a more meaningful assessment, technological gaps from the maximum achievement value (i.e., one of the countries under study) are presented as well. To investigate the impact of technological progress on economic development, this study introduces a model in which the HDI is used as the dependent variable and the TAI and Gross Capital Formation (GCF) are used as independent variables. The HDI, TAI and GCF are used in this model as proxy variables for economic development, technological progress and capital respectively. Econometric techniques have been used to show the impact of technological progress on economic development. The results show that long-term associations exist between technology progress and economic development; the impact of technology progress on economic development is 13.2% while the impact is 4.3% higher in eight selected East South Asian countries, at 13.5%, than in eight selected highly developed countries (9.2%).