• 한국지진공학회논문집
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• 제2권1호
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• pp.1-10
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• 1998

동적 지반-구조물해석과정에는 수많은 불확실성 요소가 내재되어 있다. 이러한 요소는 입력운동의 정의, 지반-구조물시스템의 모델작성, 해석기법 등에 포함된다. 이 논문은 점탄성 층상지반상의 원자로건물의 지진응답에 대한 매개변수해석을 수행한 결과를 제시한 것이다. 많은 매개변수 중에 입력운동의 정의위치, 구조물의 묻힘정도, 상부토층의 두께와 지반의 강성을 선택하여 지진응답에 미치는 영향을 중점적으로 이 연구에서 다루었다. 해석방법은 진동수에 무관한 지반임피던스를 사용하는 부분구조법인 시간영역에서의 모드중첩법이다. 지반-구조물시스템의 모드감쇠값은 각 모드에 대해 변형에너지에 대한 소멸에너지의 비를 구하여 결정되었다. 이 연구결과로부터 부분구조법에 의한 지반-구조물상호작용해석법의 실용적 이용에 참고할 수 있는 지진응답에 미치는 각 파라메터의 민감도가 제시되었다.

• The Korean Journal of Pain
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• 제35권1호
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• pp.4-13
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• 2022

Changes in diagnostic criteria, for example, the various International Classification of Headache Disorders criteria, would lead to changes in the outcomes of epidemiological studies. International Classification of Headache Disorders-1 was based mainly on expert opinion, yet most of the diagnostic criteria were reliable and valid, but it did not include chronic migraine. In its second version, the classification introduced chronic migraine, but this diagnosis resembled more a high-frequency migraine rather than the actual migraine transformation process. It also introduced medication overuse headache, but it necessitated analgesic withdrawal and subsequent headache improvement to be diagnosed as such. Hence patients having medication overuse headache could only be diagnosed in retrospect, which was an awkward situation. Such restrictive criteria for chronic migraine and medication overuse headache omitted a high proportion of patients. International Classification of Headache Disorders-3 allows a diagnosis of medication overuse headache due to combination analgesics if taken for at least 10 days per month for more than three months. Hence the prevalence rate of medication overuse headache and chronic migraine can increase compared to the previous version of the headache classification. Different criteria have been used across studies to identify chronic migraine and medication overuse headache, and therefore the information acquired from previous studies using earlier criteria becomes uncertain. Hence much epidemiological research would need to be interpreted cautiously or repeated with the most updated criteria, since the subjects in studies that apply the latest criteria may be phenotypically different from those in older studies.

• 한국물환경학회지
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• 제40권3호
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• pp.121-129
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• 2024

Harmful cyanobacterial blooms (HCBs) are caused by the rapid proliferation of cyanobacteria and are believed to be exacerbated by climate change. However, the extent to which HCBs will be stimulated in the future due to increased temperature remains uncertain. This study aims to predict the future occurrence of cyanobacteria in the Nakdong River, which has the highest incidence of HCBs in South Korea, based on temperature rise scenarios. Representative Concentration Pathways (RCPs) were used as the basis for these scenarios. Data-driven model simulations were conducted, and out of the four machine learning techniques tested (multiple linear regression, support vector regressor, decision tree, and random forest), the random forest model was selected for its relatively high prediction accuracy. The random forest model was used to predict the occurrence of cyanobacteria. The results of boxplot and time-series analyses showed that under the worst-case scenario (RCP8.5 (2100)), where temperature increases significantly, cyanobacterial abundance across all study areas was greatly stimulated. The study also found that the frequencies of HCB occurrences exceeding certain thresholds (100,000 and 1,000,000 cells/mL) increased under both the best-case scenario (RCP2.6 (2050)) and worst-case scenario (RCP8.5 (2100)). These findings suggest that the frequency of HCB occurrences surpassing a certain threshold level can serve as a useful diagnostic indicator of vulnerability to temperature increases caused by climate change. Additionally, this study highlights that water bodies currently susceptible to HCBs are likely to become even more vulnerable with climate change compared to those that are currently less susceptible.

• Korean Journal of Radiology
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• 제24권9호
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• pp.890-902
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• 2023

Objective: The clinical impact of artificial intelligence-based computer-aided detection (AI-CAD) beyond diagnostic accuracy remains uncertain. We aimed to investigate the influence of the clinical implementation of AI-CAD for chest radiograph (CR) interpretation in daily practice on the rate of referral for chest computed tomography (CT). Materials and Methods: AI-CAD was implemented in clinical practice at the Seoul National University Hospital. CRs obtained from patients who visited the pulmonology outpatient clinics before (January-December 2019) and after (January-December 2020) implementation were included in this study. After implementation, the referring pulmonologist requested CRs with or without AI-CAD analysis. We conducted multivariable logistic regression analyses to evaluate the associations between using AI-CAD and the following study outcomes: the rate of chest CT referral, defined as request and actual acquisition of chest CT within 30 days after CR acquisition, and the CT referral rates separately for subsequent positive and negative CT results. Multivariable analyses included various covariates such as patient age and sex, time of CR acquisition (before versus after AI-CAD implementation), referring pulmonologist, nature of the CR examination (baseline versus follow-up examination), and radiology reports presence at the time of the pulmonology visit. Results: A total of 28546 CRs from 14565 patients (mean age: 67 years; 7130 males) and 25888 CRs from 12929 patients (mean age: 67 years; 6435 males) before and after AI-CAD implementation were included. The use of AI-CAD was independently associated with increased chest CT referrals (odds ratio [OR], 1.33; P = 0.008) and referrals with subsequent negative chest CT results (OR, 1.46; P = 0.005). Meanwhile, referrals with positive chest CT results were not significantly associated with AI-CAD use (OR, 1.08; P = 0.647). Conclusion: The use of AI-CAD for CR interpretation in pulmonology outpatients was independently associated with an increased frequency of overall referrals for chest CT scans and referrals with subsequent negative results.

• 한국강구조학회 논문집
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• 제26권3호
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• pp.177-189
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• 2014

최근 강재의 고강도화를 통한 부재 단면 사이즈의 절감은 종종 강성의 부족으로 이어져 과도한 처짐이나 진동문제를 야기한다. 따라서 적절한 설계나 예방을 통해 구조물의 바닥진동에 대한 보완이 필수적이다. 이러한 바닥진동 문제를 해결하기 위해 동조질량감쇠기가 종종 쓰이고 있다. 동조질량감쇠기는 바닥의 진동수에 대해 정확히 설계되었을 때에는 효율적으로 바닥진동을 제어할 수 있다. 하지만 바닥질량의 크기와 외부하중의 특성에 따라 바닥의 진동수가 수시로 변하는 경우에는 그 효율이 급격히 낮아질 가능성이 있다. 이러한 현상을 동조이탈이라고 한다. 본 연구는 실제 바닥에 가해지는 하중의 변화에 따라 바닥의 진동수가 달라지는 양상을 실험을 통해 고찰한다. 실험 바닥에 기존의 단일동조질량감쇠기를 적용하여 단일동조질량 감쇠기의 한계인 동조이탈현상을 확인한다. 또한, 바닥진동제어의 강건성을 확보하기 위해 진동수의 불확실성을 반영한 비대칭 동조질량감쇠기의 활용을 제안한다. TMD의 강건성이란 진동수가 변화하는 상황에서 바닥진동제어 성능이 얼마나 지속되느냐를 뜻한다. 제안된 비대칭 TMD는 두 개의 비대칭 강성을 가지고 있기 때문에 병진운동과 회전운동을 하면서 진동에너지를 소산한다. 제안된 비대칭TMD의 최적화 결과, 비대칭TMD는 기존 STMD에 비해 28%이상의 진동제어성능을 확보하였으며, 외부의 환경 변화에 대한 강건성은 약 1.4배 개선되었다.

• 한국치위생학회지
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• 제5권1호
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• pp.39-51
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• 2005

This study was conducted to investigate the dental health and physical & psychological health status of the aged. The subjects were 61 old persons, women who were over 65, living at Sahagu in Pusan. The data for this study were collected by using direct interviewing method from October 22th, 2004. The data were analysed by using a computerized program named statistical package for social science including frequency, percentage, ANOVA. The results of the study were summarized as follows: 1. The dental status and the use of dental care institute 1) In status of denture use, it was found to be no denture(45.2%), full denture(35.5%), partial denture(19.4%). 2) In the questionaire of "when did you go to the dental care institute recently?", it was found to be uncertain(41.9%), less than one year(38.8%), 2~3years(16.1%), 1~2years(3.2%). 3) In the questionaire of "what type of the dental care institute did you use?", it was found to be in the dental clinic(80.6%), others(9.7%), dental hospital(6.5%), department of dentistry in general hospital(3.2%). 4) In the questionaire of "why did you select the dental care institute?", it was found to be in the nearly distance(80.6%), relative advice(16.1%), advertisement(3.2%). 5) In the questionaire of "how did you go to the dental care institute?", it was found to be walking(71.0%), bus & subway(22.6%), car(3.2%) and others(3.2%). 6) In the questionaire of "how long did it take to the dental care institute?", it was found to be 10~30min(48.4%), less than 10min(38.7%), 30min~1h(6.5%), 1~2h(3.2%), more than 2h(3.2%). 7) In the questionaire of "what kind of dental care did you take?", it was found to be denture making(45.2%), extraction of tooth, dental surgery, general exam(12.9%), caries(9.7%), denture repair(6.5%), others(3.2%). 8) In the questionaire of "how much did you pay for dental care recently?", it was found to be less than 5,000won(35.5%), 20,000~100,000won(19.4%), 1~3million won(16.1%), 5,000~20,000won, 100,000~300,000won, 500,000~1million won, more than 3million(6.5%), 300,000~500,000won(3.2%). 9) Average score of the subject's physical health status was 4.11 and psychological health status, 4.01 in a 5 point Likert scale. 10) The physical and psychological health status showed the significant differences according to the frequency of eating snack(pE0.05) and snack type(pE0.01). Above findings suggest that geriatric oral health program is necessary in improving the dental health & health status of the aged.

• 한국수자원학회논문집
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• 제57권3호
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• pp.225-236
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• 2024

기후위기에 선제적으로 대비하기 위해서는 기후변화에 따른 영향을 예측 및 분석하고, 이를 바탕으로 기후위기 적응과 관련한 정책과 전략을 수립할 필요가 있다. 이를 위해 기후변화를 고려해야 하나, 기존 연구 방법인 시나리오 리드 접근법에서 연구자들은 기후변화 대표 시나리오를 선택하여 활용하기 때문에, 예측된 결과의 불확실성이 크고 신뢰도가 낮다. 이러한 연구 결과는 기후변화 관련된 수자원 정책 및 설계기준에 반영되는 데 한계가 있다. 따라서 기후변화로 인해 발생가능한 변화 범위를 고려하는 시나리오 중립 접근법을 활용할 필요가 있다. 본 연구에서는 보령시를 대상으로 총 343개의 기후스트레스 시계열을 생성한 뒤 이변량 가뭄빈도분석을 통해 재현기간을 산정하고 가뭄에 대한 수문학적 위험도를 산정하였다. 분석결과, SSP1-2.6 18개 및 SSP5-8.5에 18개에 대해 최대 재현기간의 가뭄이 20년 내에 발생할 수문학적 위험도는 0.15±0.025, 50년 내에 발생할 수문학적 위험도는 0.3125±0.0625 사이로 나타났다. 따라서 보령시에서는 해당 범위의 수문학적 위험도를 고려하여 가뭄 정책 및 대책 수립이 필요하다.

• Tuberculosis and Respiratory Diseases
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• 제66권4호
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• pp.295-299
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• 2009

연구배경: 기관지확장증의 원인은 체액성 면역결핍증을 포함해 매우 다양하지만 원인이 불분명한 경우도 높은 비중을 차지하는 것으로 알려져있다. 그러나 면역글로불린 G 아강 결핍이 기관지확장증과 관련이 있는지는 불분명하며, 이에 대한 연구도 매우 드물다. 이에 저자들은 원인이 불분명한 기관지확장증 환자에서 면역글로불린 G아강 결핍증을 포함한 면역글로불린 결핍증의 빈도를 측정하고, 이들 중 면역글로불린 G 아강 결핍을 보이는 환자들의 임상적 특징을 살펴보고자 하였다. 방 법: 한 대학병원 호흡기내과 외래 방문객 중 흉부 CT에서 기관지확장증이 확인된 환자들에 대해 문진과 검사를 시행하여 기관지확장증의 원인이 불분명한 것으로 판단되는 환자 31명을 선정하였다. 결 과: 대상 환자 31명 중 총면역글로불린 결핍증 환자는 2명이었고, 면역글로불린 G 아강 결핍은 14명(45%)으로 매우 빈도가 높았으며, 면역글로불린 G3 결핍을 보인 환자군과 정상인 환자군을 나누어 비교하였을 때 성, 연령, 부비동염과 천식의 빈도, 폐기능 이상의 빈도에 있어 의미 있는 차이를 보이지 않았다. 결 론: 기관지확장증 환자에서 그 원인이 분명하지 않은 경우 면역글로불린 G 아강의 농도를 측정해 볼 필요가 있으며, 향후 병인과의 관련성에 대한 추가적인 연구를 진행할 가치가 있을 것으로 판단된다.

• 한국도로학회논문집
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• 제13권3호
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• pp.75-82
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• 2011

도로표지용 도료의 품질기준은 KS M 6080의 품질기준을 만족하는 제품들의 경우에도 시공 후 일정기간이 경과한 후에는 도료 자체의 부착력 문제로 교통량 증가에 따른 자동차 차륜에 의한 도료 자체의 마모 손실에 의하여 재귀반사 기능을 부여하는 유리알의 마모 및 탈리로 시인성이 급격히 저하되고 있다. 이에 따른 야간 교통 사고율 증가와 동시에 추가 교통 안전을 위한 부가 보완시공으로 안전시설 제비용이 직접비용으로 유발되고 있으며, 직접비용보다 추가공사로 인한 교통체증으로 사회간접 비용이 증가되고 있다. 특히, 차선의 품질 규격이 KS M 6080 제품에 만족한다 하더라도 빗물의 수막(水膜)에 의한 유리알의 굴절율 차로 재귀반사기능을 하는 차선 도료용 유리알의 기능을 발휘하지 못하여 운전자의 시인성은 열악함을 알 수 있다. 따라서, 국외에서 많이 사용되고 있는 마모성이 우수한 수용성 차선도료, 고성능 융착식 도료, 상온경화형 도료를 도입하여 성능을 비교 검토하였다. 본 연구에서는 차선재료의 내구성 향상을 위해 EN 1436규격에 의한 내마모성 시험을 수용성, 융착식, 상온경화형 도료에 실시하여, 재귀반사도 성능이 우수한 차선재료의 적용 가능성을 확인하였다.

• 대한치과기공학회지
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• 제37권4호
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• pp.271-284
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• 2015

Purpose: The purpose of this study was to examine the usage of CAD/CAM, which is one of dental technologist duties, in an effort to look for any possible changes in the usage of CAD/CAM. It's specifically meant to compare the results of this study with those of Lee Jong-do, Park Kwang-Sig(2011)'s study in March, 2011, to determine if there were any changes over the past four years. The selected variables that were investigated were the ownership of CAD/CAM, awareness of it, the route of acquiring the first information on it, the merits and demerits of its usage, usage experience and educational experience about it. Methods: An online survey was conducted on the dental technologists who worked in urban communities including metropolitan cities to find out the usage of CAD/CAM in 2015 from July 15 to 31, 2015, after existing questionnaire items were modified. The collected data were analyzed by IBM SPSS statistics 22.0, and statistical data on frequency, percentage, mean and standard deviation for each item were obtained. To figure out the characteristics of the subjects and the relationship between their occupational characteristics and the usage of CAD/CAM, crosstabs, independent-samples t-test and one-way ANOVA were utilized. As for the usage of CAD/CAM in 2011, the results of Lee Jong-do, Park Kwang-Sig(2011)'s study were selected, and then a comparative analysis was made. The level of significance was all set at .05. Total 250 questionnaires were distributed to them, and 190(76.0%) were returned. After excluding 23 whose answers were uncertain or seemed to lack reliability, total 167(66.8%) were used in final analysis. Results: As a result of analyzing the usage of CAD/CAM that was one of dental technologist duties, there was a great increase in the ownership of CAD/CAM in their workplaces from 2.4 percent in 2011 to 71.7 percent in 2015, and there was an improvement in awareness about it and the necessity of its usage as well. In 2011, the Internet and mass media were the most common route that they got to know about it. They had a strong tendency to acquire related knowledge through education in 2015, and there were some changes in the products that they used or preferred. In both years, the great merit of CAD/CAM was the simplified manufacturing process of restoration, and it had another great advantages in 2015 such as the improved quality of restoration or improved environments for dental technology. Concerning disadvantages, high price was a big problem in 2011. In 2015, not only price but the burden of material costs, frequent breakdown, poor demand among dental clinics and a lack of CAD/CAM professionals were pointed out a lot. In the future, this researcher intends to make research to seek ways of improving CAD/CAM professionals. Conclusion: There was more awareness of CAD/CAM in 2015 than in 2011 when the changes in awareness of it were analyzed, and the finding suggest the necessity of sustained education and concern.