• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.386-386
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• 2021

대기 중 온실가스 농도는 인간의 인위적 활동에 의해 증가하고 있으며, 이로 인하여 발생하는 기후변화는 극한 수문 사상에 상당한 영향을 미치고 있다. 특히, 기후변화로 인한 강수 특성의 변화는 홍수, 가뭄, 태풍 등과 같은 극한사상의 변화로 이어지며, 급격한 도시화와 복잡한 사회기반시설물 등과 맞물려 더욱 취약한 홍수위험 문제로 대두된다. 기후변화에 따른 미래의 불확실한 변화에 적응하기 위하여 다양한 기후모델들이 개발되었고, 기후변화와 관련된 많은 응용 연구들이 기후모델에서 모의된 자료를 기반으로 미래를 전망하고 있다. IPCC (Intergovernmental Panel on Climate Change) 제6차 평가보고서(The 6th Assessment Report: AR6)에서는 사회경제 구조의 변화를 반영한 공통사회경제경로 시나리오(Shared Socioeconomic Pathways, SSP) 개념을 도입하였다. SSP 시나리오는 사회경제 변화를 기준으로 기후변화에 대한 완화와 노력에 따라 5개의 시나리오로 구별된다. 기상청 기후정보포털(http://www.climate.go.kr/)에서는 4개 조합의 시나리오(SSP1-RCP2.6, SSP2-RCP4.5, SSP3-RCP7.0, SSP5-RCP8.5) 결과가 제공된다. 자료는 동아시아 지역에 대해 생산한 자료로 25km의 공간해상도를 가지고 있으며, 현재모의기간(1979-2014, S_HIST)과 미래시나리오기간(2015-2020, S_SSP)으로 구분된다. 본 연구에서는 전술한 SSP-RCP 시나리오 조합 중 SSP1-RCP2.6, SSP5-RCP8.5 조합을 이용하여 광주지역 극한강우의 미래 변화를 분석하였다. 시나리오 기반 강우자료의 통계적 특성 분석을 위해 연최대 자료를 추출하여 경향성 및 변동성 분석을 수행하였고, 광주지역 강우 자료에 내재된 특성 변화를 정량적으로 분석하였다.

• Korean Journal of Agricultural and Forest Meteorology
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• v.21 no.1
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• pp.55-64
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• 2019

The flowering seasons can be advanced due to climate change that would cause an abnormally warm winter. Such warm winter would increase the frequency of crop damages resulted from sudden occurrences of low temperature before and after the vegetative growth stages, e.g., the period from germination to flowering. The degree and pattern of freezing damage would differ by the development stage of each individual fruit tree even in an orchard. A critical temperature, e.g., killing temperature, has been used to predict freeze damage by low-temperature conditions under the assumption that such damage would be associated with the development stage of a fruit flower bud. However, it would be challenging to apply the critical temperature to a region where spatial variation in temperature would be considerably high. In the present study, a phenological model was used to estimate major bud development stages, which would be useful for prediction of regional risks for the freeze damages. We also derived a linear function to calculate a probabilistic freeze risk in spring, which can quantitatively evaluate the risk level based solely on forecasted weather data. We calculated the dates of freeze damage occurrences and spatial risk distribution according to main production areas by applying the spring freeze risk function to apple, peach, and pear crops in 2018. It was predicted that the most extensive low-temperature associated freeze damage could have occurred on April 8. It was also found that the risk function was useful to identify the main production areas where the greatest damage to a given crop could occur. These results suggest that the freezing damage associated with the occurrence of low-temperature events could decrease providing early warning for growers to respond abnormal weather conditions for their farm.

• Journal of the Korean GEO-environmental Society
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• v.21 no.5
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• pp.23-33
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• 2020

As the scale of the economy expands, the number of cases of damage in enclosed spaces such as tunnels is increasing due to the accident of transportation vehicles of dangerous substances such as explosive flammable materials that have increased rapidly. In the case of road tunnels in particular, in the aspect of protection against the long-winding trend and the environment in the downtown area, the number of cases of passing through the downtown area increases, and securing the safety of structures against unexpected extreme disasters such as explosions during tunnel passage is very urgent. For this reason, developed countries are already conducting a review of internal bombardment, but there are almost no evaluation and countermeasures for explosion risk in Korea. Therefore, in this study, in order to evaluate the explosion safety of road tunnels, a boiling liquid explosive explosion (BLEVE), which is considered to have the greatest explosion load among vehicles driving on the road, is set as a reference explosion source, and the equivalent TNT explosion load is used for simulation of the explosion. A method of conversion was presented. In addition, by applying the derived explosion load, dynamic behavior simulation was performed by assuming various variables for the tunnel, and the explosion safety of the tunnel was analyzed.

• Industry Promotion Research
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• v.7 no.1
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• pp.1-8
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• 2022

We investigated various types of machine learning methods that can be applied to censored data. Exploratory data analysis reveals the distribution of each feature, relationships among features. Next, classification problem has been set up where the dependent variable is death_event while the rest of the features are independent variables. After applying various machine learning methods to the data, it has been found that just like many other reports from the artificial intelligence arena random forest performs better than logistic regression. But recently well performed artificial neural network and gradient boost do not perform as expected due to the lack of data. Finally Kaplan-Meier and Cox proportional hazard model have been employed to explore the relationship of the dependent variable (t_i, δ_i) with the independent variables. Also random forest which is used in machine learning has been applied to the survival analysis with censored data.

• Korean Journal of Construction Engineering and Management
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• v.8 no.1 s.35
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• pp.96-106
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• 2007

This study aims to evaluate the financial impact of construction firms' business diversification. Specifically, from the construction firms' perspective, this study attempted to present basic investment model by analyzing the effect of investment in residential facilities for retired seniors. Analyses results indicated that the financial impact, in terms of sales volume and gross profit, varies according to the size of firms. The results drawn from this study could be a valuable source when construction firms plan to invest and operate residential facility for retired seniors in order to diversify their business portfolio and stabilize financial structure.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.430-430
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• 2011

최근 지구온난화, 엘리뇨 및 라니냐 등 지구환경 변화에 따른 기후변화의 영향으로 짧은 시간에 매우 높은 강도를 가진 이상호우에 의해 많은 인명과 재산피해가 발생하고 있다. 우리나라의 경우에도 1990년대 후반부터 과거와 달리 국지적 집중호우가 빈번히 발생하고 있으며 집중호우에 의한 홍수는 우리나라의 가장 빈번한 자연재해 중 하나가 되었다. 이러한 성격의 홍수는 소유역 규모의 좁은 지역과 급경사지역에서 짧은 지속시간과 집중적인 강우강도에 의해 발생하고, 빠른 유속과 토사를 동반하는 빠른 수문반응으로 홍수에 대비할 시간이 부족한 것이 특징이기 때문에 기존의 홍수예보모형을 이용하여 발생홍수의 특성을 예측하기에는 많은 어려움이 있다. 유출수문곡선의 특성을 분석하여 홍수의 특성을 분석하는 연구는 Kyiamah (1996)가 유출수문곡선의 기초적인 상승곡선, 지체시간, 첨두홍수량을 이용하여 돌발홍수사상에 대한 크기를 산정하였으며, 이를 바탕으로 Bhaskar 등 (2000)은 유출수문곡선의 상승부 기울기, 첨두 홍수량비, 홍수 반응시간을 이용하여 돌발홍수지수(Flash Flood Index)를 산정하고 이 지수에 의해 돌발홍수를 설명하고자 하였다. 국내에서는 정재철 (2000)이 보청천을 대상으로 단 몇 개의 사상만을 대상으로 Bhaskar 등 (2000)이 제시한 돌발홍수지수를 적용한 바가 있다. 그러나, 이들 연구에서는 소수의 수문사상만을 이용하였기 때문에 상대심도를 산정하는데 있어 문제가 있으며 상대심도를 산정하는데 있어 각 심도계수들의 임의적인 도수분포를 이용하였기 때문에 매우 주관적이라고 할 수 있다. 김병식 등 (2008)은 한강유역의 과거 101개의 홍수사상에 대해 돌발홍수의 상대심도를 파악하기 위하여 돌발홍수지수를 산정하고 2006년 7월의 집중호우에 의해 발행한 홍수사상의 돌발홍수 심도를 시간 및 공간적으로 정량화하였다. 이러한 기존의 연구는 홍수심도 산정시에 필요한 유출수문곡선을 실측된 자료를 이용하여 산정하였으나 국내의 소유역의 경우 실측된 유출수문곡선 자료가 그다지 많지 않은 관계로 인해 홍수심도를 산정하는데 많은 어려움을 내포하고 있다. 따라서 본 연구에서는 미계측 소유역중 시범유역을 선정하고 30년 이상 장기간 실측 강우의 기왕최대 시강우량 자료에 대하여 강우-유출모형을 통한 홍수유출수문곡선을 모의한 후, 빈도별 확률강우량에 대한 수문곡선 특성인자들의 비를 무차원 지수화하여 극한홍수사상에 대한 설계강우의 취약성을 평가하기 위한 홍수위험지수 (Flood Hazard Index) 산정방법을 제시하였다.

• Tuberculosis and Respiratory Diseases
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• v.60 no.2
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• pp.228-234
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• 2006

Background : Acinetobacter baumannii is an important pathogen associated with nosocomial infections in intensive care units, and is responsible for nosocomial pneumonia, UTI, bacteremia, etc. The main concern is that this pathogen is often resistant to many antimicrobial agents, particularly to carbapenem. This study compared the clinical those of ICU admitted patients with the carbapenem resistant A. baumannii isolated from the sputum with characteristics of patients with carbapenem sensitive A. baumannii. Methods : A total of 49 patients with A. baumannii from a sputum culture who were admitted to the ICU from January to December 2003 were enrolled in this study. This study evaluated the demographic variables, mortality, APACHE II score, comorbidity, antibiotics used, hospital and ICU stay, Clinical Pulmonary Infection Score, and mechanical ventilation. A retrospective analysis was made by a review of the patients' medical records. Results : Carbapenem sensitive and resistant A. baumannii was isolated from 23 patients and 26 patients respectively. Univariate analysis revealed renal disease, the use of carbapenem and aminoglycoside to be statistically significant factors for carbapenem resistance. Multivariate analysis revealed carbapenem use(p=0.024; OR, 8.17; CI 1.32 to 50.68) to be positively associated with carbapenem resistance, and aminoglycoside use(p=0.026; OR, 0.18; CI, 0.04 to 0.82) to be negatively associated with carbapenem resistance. There was no significant difference in mortality between the carbapenem sensitive and resistant group(30 vs 42%. P=0.39). Conclusion : The occurrence of carbapenem resistant A. baumannii is positively associated with carbapenem use and negatively associated with aminoglycoside use. Carbapenem resistance in the sputum culture did not affect the mortality rate.

• Tunnel and Underground Space
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• v.32 no.1
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• pp.20-29
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• 2022

The existence of underground cavity should be considered in the assessment of georisk such as ground subsidence. Even if the shear strength of the ground around the cavity is known, it is difficult to accurately analyze the safety around the cavity due to the uncertainties related to geometric conditions such as the cavity size. In this paper, stability chart representing dimensionless stability constants was proposed based on the ground strength and geometric conditions. Numerical analysis had been carried out accounting for the stability constants such as the ground strength, the adhesion and friction angles, and the size and depth of the underground cavity. The proposed charts can help estimating the stability of ground with underground circular cavity.

• The Korean Journal of Nuclear Medicine
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• v.33 no.2
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• pp.143-151
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• 1999

Purpose: Dermatolymphangioadenitis (DLA) is a common and serious complication of lymphedema which deteriorates lymphatic function. The purpose of this study was to assess the risk of DLA by lymphos-cintigraphy in patients with lower extremity lymphedema. Materials and Methods: The subjects were 59 edematous lower extremities of 50 patients without previous episode of DLA and 12 lower extremities of 6 controls. Whole body images were acquired 1 min and 2 hr after subcutaneous injection of 37 MBq of Tc-99m-antimony sulfide colloid into interdigital spaces of both feet before therapy for lymphedema. The lymphosintigraphic and clinical variables were compared between groups with or without occurrence of DLA during clinical follow up. Results: There were 20 episodes of DLA in 12 extremities during clinical follow-up (19 :6 months). On univariate analysis, there were significant differences in ilioinguinal lymph node uptake, uptake pattern of main lymphatic vessel, clinical stage and therapy compliance between the two groups. After multivariate analysis, only the uptake pattern of main lymphatic vessel and therapy compliance fore confirmed to be independent variables. In other words, non-visualized main lymphatic vessel and poor compliance to therapy were more frequent in extremities with subsequent occurrence of DLA. Conclusion: Lymphoscintigraphy can be used to predict the risk of DLA and may thus be helpful for determining the initial therapeutic plan in patients with lower extremity lymphedema.

• Journal of Chest Surgery
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• v.38 no.9 s.254
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• pp.622-626
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• 2005

Background: Non-invasive interventional therapy has been performed for main bronchial obstruction by endobronchial tuberculosis because of the risk of main bronchial reconstruction regardless of the pulmonary function. But, effects of the inteeventional therapy are attacked by arguments. This study was aimed at interpreting the risk and effectiveness of bronchoplasty for benign bronchial stenosis over the last ten years in our hospital by reviewing the results based on clinical progression. Material and Method: We retrospectively reviewed the clinical records and out-patient medical records including 2f consecutive patients who underwent main bronchial reconstruction for obstruction by endobronchial tuberculosis. All of them had past medical history of anti-tuberculosis medication. They were preoperatively evaluated by bronchoscopy and chest computed tomography. Result: There were no incidences of postoperative mortality and signifcant morbidity. There were 2 cases of retained secretions but these problems were resolved by therapeutic bronchoscopy or intubation. All of the patients are still alive without obstructive airway problem. Conclusion: Bronchoplasty should be considered as one of the primary treatment modalities, if it is anatomically feasible.