• 한국수자원학회논문집
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• 제48권12호
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• pp.969-979
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• 2015

본 연구에서는 가뭄의 특성분석에 유리하며, 확률론적 접근이 가능한 은닉 마코프 모델(HMM) 기반의 가뭄 분석 기법을 적용하였다. HMM 기반의 가뭄의 심도뿐만 아니라 지속시간을 동시에 평가할 수 있도록 코플라 함수 기반의 이변량 가뭄빈도해석 기법을 도입하여 우리나라의 2015년 가뭄 빈도를 평가하였다. 가뭄빈도분석 결과 최근 40년 자료를 기준으로 영동지방에 비해 영서지방이 전체적으로 가뭄이 발생할 경우 가뭄의 심도가 큰 것으로 평가되었다. 심한가뭄의 발생 비율의 경우에 철원의 경우 10%를 상회하는 등 임진강 유역에서 상대적으로 심한가뭄의 발생비율이 크다는 것을 확인할 수 있었다. 한강유역 일부지점에서는 2014/2015년의 가뭄 지속기간 및 심도의 결합재현기간이 1,000년이 넘는 가뭄이 발생하고 있는 것으로 평가되었다. 특히 북한강 및 임진강 유역에 심한 가뭄이 발생하고 있으며 전반적으로 100년 이상의 기왕최대가뭄을 나타내고 있는 것으로 판단되었다.

• 한국IT서비스학회지
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• 제16권3호
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• pp.147-165
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• 2017

Recently, there have been numerous issues about password breaches and it is becoming important for the users to manage their passwords. In practice, the online service provider are asking the online users to change their passwords periodically. However, majority of the users are not changing their passwords regularly, and this can increase the risk of password breach. The purpose of this study is to investigate whether 'fear appeals' and 'message framing' enhance the behavior of changing passwords by the online users. Furthermore, we identify the mechanism on how the behavior of changing passwords is enabled using protection motivation theory. The results of an online experiment show that the online users who are exposed to 'fear appeals' perceived a more vulnerability and severity of password breaches, which in turn, increased the intention of changing their password. In addition, we found that perceived severity of password breaches affect fear positively. Moreover, we found that fear has significant impact on the willingness of changing passwords. Finally, Message framing plays a moderating role between fear and change intentions. That is, in a situation where 'fear appeal' is presented, it means that 'gain framing' is more effective than 'loss framing' These findings suggest that the online service providers may need to use 'fear appeals' to the online users. Security managers can address issues related to the password breaches by carefully designing 'fear appeals'.

• 동력기계공학회지
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• 제22권1호
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• pp.79-86
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• 2018

Many countries have conducted extensive studies for biomass co-firing to enhance the durability of reactor on high-temperature corrosion. However, due to the complicated mechanisms of biomass co-firing, there have been limitations in accurately determining the current state of corrosion and predicting the potential risk of corrosion of power plant. In order to solve this issue, this study introduced Lab-scale corrosion system to analyze the corrosion characteristics of the A213 T91 material under the biomass co-firing conditions. The corrosion status of the samples was characterized using SEM/EDS analysis and mass loss measurement according to various biomass co-firing conditions such as corrosion temperature, $SO_2$ concentration, and corrosion time. As a result, the corrosion severity of A213 T91 material was gradually increased with the increase of $SO_2$ concentration in the reactor. When $SO_2$ concentration was changed from 0 ppm to 500 ppm, both corrosion severity and oxide layer thickness were proportionally increased by 15% and 130%, respectively. The minimum corrosion was observed when the corrosion temperature was $450^{\circ}C$. As the temperature was increased up to $650^{\circ}C$, the faster corrosion behavior of A213 T91 was observed. A213 T91 was observed to be more severely corroded by the effect of chlorine, resulting in faster corrosion rate and thicker oxide layer. Interestingly, corrosion resistance of A213 T91 tended to gradually decrease rather than increases as the oxide layer was formed. The results of this study is expected to provide necessary research data on boiler corrosion in biomass co-firing power plants.

• 한국농공학회논문집
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• 제57권1호
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• pp.37-45
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• 2015

Recent droughts in South Korea have had large economic and environmental impacts across the country. Changes in rainfall and hydrologic patterns due to climate change can potentially increase the occurrence of extreme droughts and affect the future availability of water resources. Therefore, it is necessary to evaluate drought vulnerability for water resources planning and management, and identify the appropriate mitigation actions to conduct a drought risk analysis in the context of climate change. The objective of this study is changes in the temporal trends of drought characteristics in South Korea to examine drought impacts under climate change. First, the changes of drought occurrence were analyzed by applying the Standardized Precipitation Evapotranspiration Index (SPEI) for meteorological data on 54 meteorological stations, and were analyzed for the past 30 years (1981-2010), and Representative Concentration Pathways (RCP) climate change scenarios (2011-2100). Second, the changes on the temporal trends of drought characteristics were performed using run theory, which was used to compare drought duration, severity, and magnitude to allow for quantitative evaluations under past and future climate conditions. These results show the high influence of climate change on drought phenomenon, and will contribute to water resources management and drought countermeasures to climate change.

• 항공우주시스템공학회지
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• 제14권spc호
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• pp.13-21
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• 2020

RTCA DO-178C는 항공기 시스템의 감항성을 보장하기 위한 소프트웨어 개발 지침서이다. 하지만, DO-178C는 최대이륙중량 150kg 이상의 무인기 인증에 적용하는 것은 무인기로 인한 위험의 심각도(severity)가 보통의 항공기보다 낮기 때문에 과도한 규제라는 의견이 있다. 이러한 문제를 해결하기 위해, EASA와 FAA는 기존 항공기 인증 체계를 간소화 한 새로운 인증 체계 수립을 목표로 항공전자 인증표준 재편 및 간소화(RESSAC: Re-Engineering and Streamlining the Standards for Avionics Certification) 프로젝트를 2016년부터 수행하고 있다. 본 논문에서는 현재 적용되는 DO-178C 인증 프로세스를 분석하였고, DO-178C 인증 프로세스보다 과정 및 산출물을 간소화하면서도 비행 안전성을 확보 할 수 있는 새로운 RESSAC 인증 프로세스를 비교 분석하고 장점을 도출하여 제시하였다.

• 산업경영시스템학회지
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• 제34권4호
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• pp.179-188
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• 2011

재제조는 사용 후 제품을 체계적으로 회수하여 분해, 세척, 검사, 보수조정, 재조립 등의 공정을 거쳐 원래의 성능을 유지할 수 있도록 만드는 과정이다. 자동차 교류발전기를 재제조하기 위해서는 재제조품에 요구되는 품질 및 신뢰성을 확실히 달성하기 위하여 공정 별 복잡한 작업들에 대하여 세부적인 사항들을 결정하고 이를 설계하는 일이 중요하다. 본 연구의 목적은 재제조를 위한 최적의 공정설계를 위해 FMEA를 활용한 체계적인 가이드라인을 제시하여 재제조품의 품질 및 신뢰성을 확보하는데 있다. 코어 부품의 상태 수준에 따른 작업과정과 재정비여부를 결정하기 위해 위험성 지표에 의한 방법도 연구되었다. 특히, 재제조기업의 사례연구를 통하여 FMEA의 유용성과 가이드라인의 적절성을 보여준다.

• Tuberculosis and Respiratory Diseases
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• 제76권2호
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• pp.66-74
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• 2014

Background: The increasing number of outpatients with multidrug-resistant (MDR) pathogens has led to a new category of pneumonia, termed healthcare-associated pneumonia (HCAP). We determined the differences in etiology and outcomes between patients with HCAP and those with community-acquired pneumonia (CAP) to clarify the risk factors for HCAP mortality. Methods: A retrospective study comparing patients with HCAP and CAP at Jeju National University Hospital. The primary outcome was 30-day mortality. Results: A total of 483 patients (208 patients HCAP, 275 patients with CAP) were evaluated. Patients with HCAP were older than those with CAP (median, 74 years; interquartile range [IQR], 65-81 vs. median, 69 years; IQR, 52-78; p<0.0001). Streptococcus pneumoniae was the major pathogen in both groups, and MDR pathogens were isolated more frequently from patients with HCAP than with CAP (18.8% vs. 4.9%, p<0.0001). Initial pneumonia severity was greater in patients with HCAP than with CAP. The total 30-day mortality rate was 9.9% and was higher in patients with HCAP based on univariate analysis (16.3% vs. 5.1%; odds ratio (OR), 3.64; 95% confidence interval (CI), 1.90-6.99; p<0.0001). After adjusting for age, sex, comorbidities, and initial severity, the association between HCAP and 30-day mortality became non-significant (OR, 1.98; 95% CI, 0.94-4.18; p=0.167). Conclusion: HCAP was a common cause of hospital admissions and was associated with a high mortality rate. This increased mortality was related primarily to age and initial clinical vital signs, rather than combination antibiotic therapy or type of pneumonia.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2016년도 학술발표회
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• pp.197-197
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• 2016

Forecasting future drought events in a region plays a major role in water management and risk assessment of drought occurrences. The creeping characteristics of drought make it possible to mitigate drought's effects with accurate forecasting models. Drought forecasts are inevitably plagued by uncertainties, making it necessary to derive forecasts in a probabilistic framework. In this study, a new probabilistic scheme is proposed to forecast droughts, in which a discrete-time finite state-space hidden Markov model (HMM) is used aggregated with the Representative Concentration Pathway 8.5 (RCP) precipitation projection (HMM-RCP). The 3-month standardized precipitation index (SPI) is employed to assess the drought severity over the selected five stations in South Kore. A reversible jump Markov chain Monte Carlo algorithm is used for inference on the model parameters which includes several hidden states and the state specific parameters. We perform an RCP precipitation projection transformed SPI (RCP-SPI) weight-corrected post-processing for the HMM-based drought forecasting to derive a probabilistic forecast that considers uncertainties. Results showed that the HMM-RCP forecast mean values, as measured by forecasting skill scores, are much more accurate than those from conventional models and a climatology reference model at various lead times over the study sites. In addition, the probabilistic forecast verification technique, which includes the ranked probability skill score and the relative operating characteristic, is performed on the proposed model to check the performance. It is found that the HMM-RCP provides a probabilistic forecast with satisfactory evaluation for different drought severity categories, even with a long lead time. The overall results indicate that the proposed HMM-RCP shows a powerful skill for probabilistic drought forecasting.

• 대한임상독성학회지
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• 제17권2호
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• pp.94-101
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• 2019

Purpose: This study examined the clinical characteristics of severe elderly poisoning patients to determine the factors that can prevent them. Methods: Data were collected from patients over 65 years of age presenting to the emergency center with poisoning from 2013 to 2018. Their medical records were analyzed retrospectively, and patients with a poisoning severity score of three or more were defined as the severe poisoning group. The risk factors were evaluated by univariate and multivariate analysis. Results: This study analyzed 292 patients, of whom 37 (12.7%) belonged to the severe poisoning group. The severe poisoning group showed a significantly higher association with pesticide poisoning and intentional suicide attempts. Loneliness and somatization were the cause of the suicidal ideas. No significant differences in age, sex, drinking, ingestion time, poisonous materials other than pesticides, and neuropsychological consultation were observed between the two groups. Conclusion: The severe elderly poisoning patients were the result of intentional poisoning for suicide. Loneliness and somatization were the most influential causes of suicidal poisoning. Therefore, psychiatric screening and frequent medical treatment for elderly people are required to prevent severe poisoning in elderly patients.

• 보건행정학회지
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• 제31권4호
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• pp.472-478
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• 2021

Background: Early identification of patients who are highly likely to develop severe illness among confirmed cases of coronavirus disease 19 (COVID-19) can be expected to lead to effective treatment. This study therefore aimed to determine whether the presence of nonalcoholic fatty liver disease (NAFLD) has an impact on the exacerbation of COVID-19 symptoms. Methods: The study used the Korean National Health Insurance claim data for treatment of COVID-19 patients in 2020. NAFLD includes nonalcoholic fatty liver (NAFL) and nonalcoholic steatohepatitis (NASH). The outcome variables used were hospitalization and the use of medical devices. Hospitalization was defined by a length of stay exceeding one day and the use of medical devices was defined as one or more uses of a ventilator or extracorporeal membrane oxygenation. Multivariable logistic regression analysis was performed to determine if there was a difference in the hospitalization and use of medical devices of COVID-19 patients depending on the presence of NAFLD. Results: The odds ratio of hospitalization was 1.059, indicating slightly higher odds of hospitalization for patients with NAFL or NASH compared to those without the conditions, but it was not statistically significant (0.969-1.156). On the other hand, the odds ratio of use of medical devices was high at 1.667 and was statistically significant (1.111-2.501). Conclusion: The study results found NAFLD to be a risk factor that can exacerbate symptoms in COVID-19 patients. Accordingly, it is necessary to identify NAFLD patients through preemptive screening and provide them with appropriate treatments.