Cloud Physics Experimental Chamber (CPEC)와 에어로졸 및 구름 미세물리 관측 장비

엄준식,차주완,염성수,이경미,Belorid Miloslav,박성민,김정규,박민수 한국기상학회 2022 한국기상학회 학술대회 논문집 Vol.2022 No.4

Calculations of Mass Extinction Efficiency for Polydispersed Aerosol Using Harmonic Mean Approximation

엄준식,정창훈,장성현 한국환경과학회 2020 한국환경과학회 학술발표회 발표논문집 Vol.2020 No.11

강거더 교량의 신뢰성해석을 위한 저항모델 개발

엄준식 한국신뢰성학회 2013 신뢰성응용연구 Vol.13 No.4

Because of financial and safety concerns, there are needs for more accurate prediction of bridge behavior. Underestimation of the bridge load carrying capacity can have serious economic consequences, as deficient bridges must be repaired or rehabilitated. Therefore, the knowledge of the actual bridge behavior under live load may lead to a more realistic calculation of the load carrying capacity and eventually this may allow for more bridges to remain in service with or without minor repairs. The presented research is focused on the reliability evaluation of the actual load carrying capacity of existing bridges based on the field testing. Seventeen existing bridges were tested under truck load to confirm their adequacy of reliability. The actual response of existing bridge structures under live load is measured. Reliability analysis is performed on the selected representative bridges designed in accordance with AASHTO codes for bridge component (girder). Bridges are first evaluated based on the code specified values and design resistance. However, after the field testing program, it is possible to apply the experimental results into the bridge reliability evaluation procedures. Therefore, the actual response of bridge structures, including unintentional composite action, partial fixity of supports, and contribution of nonstructural members are considered in the bridge reliability evaluation. The girder distribution factors obtained from the tests are also applied in the reliability calculation. The results indicate that the reliability indices of selected bridges can be significantly increased by reducing uncertainties without sacrificing the safety of structures, by including the result of field measurement data into calculation.

처짐한계상태함수를 이용한 노후 강거더 교량의 신뢰성해석 모델 구축

엄준식 한국구조물진단유지관리공학회 2014 한국구조물진단유지관리공학회 논문집 Vol.18 No.2

이 연구에서는 중소지간 합성형 강거더교량에 대한 신뢰성 해석을 위해 강거더와 콘크리트슬래브의 강성을 토대로 처짐을 고려한 한계함수를 구축하여 신뢰성해석을 수행하였다. 확률적 하중과 저항모델을 통해 처짐을 예측하기 위해 계산에 필요한 변수들을 확률변수로 고려하였다. 강재의 부식에 의한 단면의 감소, 그리고 콘크리트의 크리프는 합성형교의 처짐에 많은 영향을 미친다. 따라서 이 연구에서는AASHTO LRFD 기준으로 설계된 교량에 대해 시간에 따른 변수를 고려하여 강재단면의 감소와 크리프의 영향을 통계적 모델에 반영하기 위해 몬테-카를로 시뮬레이션 기법을 이용하였으며, 처짐과 사용성을 고려하여 다양한 지간과 거더간격을 가진 교량에 신뢰성 해석을수행하였다. 그 결과, 장지간 교량의 경우, 단지간 교량과 비교해 보았을 때 상대적으로 크리프와 강재단면감소의 처짐에 대한 영향이 작았으며, 이에 반해 단지간 거더 교량의 경우 크리프의 진행에 따라 처짐에 많은 영향을 미친다는 것을 알 수 있었다. The paper investigates the limit state of deflection for short and medium span steel girder bridges. Deflection depends on stiffness of steel girders and integrity of the reinforced concrete slab (composite action). Load and resistance parameters are treated as random variables. A probabilistic model is developed for prediction of the deflection. The structural performance can be affected by deterioration of components, in particular corrosion of steel girders. In addition, the creep of concrete can greatly influence the deflection of composite structures. Therefore, the statistical models for creep and corrosion of structural steel are incorporated inthe model. Structures designed according to the AASHTO LRFD Code are considered. Load and resistance models are developedto account for time-variability of the parameters. Monte Carlo simulations are used to estimate the deflections and probabilities of serviceability failure. Different span lengths and girder spacing are considered for structures designed as moment-controlled and deflection-controlled. A summary of obtained results is presented.

Metabolomics comparison of serum and urine in dairy cattle using proton nuclear magnetic resonance spectroscopy

엄준식,김언태,김현상,최유영,이신자,Lee Sang Suk,김선호,Lee Sung Sill 아세아·태평양축산학회 2021 Animal Bioscience Vol.34 No.12

Objective: The aim of the study was to conduct metabolic profiling of dairy cattle serum and urine using proton nuclear magnetic resonance (1H-NMR) spectroscopy and to compare the results obtained with those of other dairy cattle herds worldwide so as to provide a basic dataset to facilitate research on metabolites in serum and urine. Methods: Six dairy cattle were used in this study; all animals were fed the same diet, which was composed of total mixed ration; the fed amounts were based on voluntary intake. Blood from the jugular neck vein of each steer was collected at the same time using a separate serum tube. Urine samples were collected by hand sweeping the perineum. The metabolites were determined by 1H-NMR spectroscopy, and the obtained data were statistically analyzed by performing principal component analysis, partial least squares-discriminant analysis, variable importance in projection scores, and metabolic pathway data using Metaboanalyst 4.0. Results: The total number of metabolites in the serum and urine was measured to be 115 and 193, respectively, of which 47 and 81, respectively were quantified. Lactate (classified as an organic acid) and urea (classified as an aliphatic acylic compound) exhibited the highest concentrations in serum and urine, respectively. Some metabolites that have been associated with diseases such as ketosis, bovine respiratory disease, and metritis, and metabolites associated with heat stress were also found in the serum and urine samples. Conclusion: The metabolites measured in the serum and urine could potentially be used to detect diseases and heat stress in dairy cattle. The results could also be useful for metabolomic research on the serum and urine of ruminants in Korea. Objective: The aim of the study was to conduct metabolic profiling of dairy cattle serum and urine using proton nuclear magnetic resonance (¹H-NMR) spectroscopy and to compare the results obtained with those of other dairy cattle herds worldwide so as to provide a basic dataset to facilitate research on metabolites in serum and urine.Methods: Six dairy cattle were used in this study; all animals were fed the same diet, which was composed of total mixed ration; the fed amounts were based on voluntary intake. Blood from the jugular neck vein of each steer was collected at the same time using a separate serum tube. Urine samples were collected by hand sweeping the perineum. The metabolites were determined by ¹H-NMR spectroscopy, and the obtained data were statistically analyzed by performing principal component analysis, partial least squares-discriminant analysis, variable importance in projection scores, and metabolic pathway data using Metaboanalyst 4.0.Results: The total number of metabolites in the serum and urine was measured to be 115 and 193, respectively, of which 47 and 81, respectively were quantified. Lactate (classified as an organic acid) and urea (classified as an aliphatic acylic compound) exhibited the highest concentrations in serum and urine, respectively. Some metabolites that have been associated with diseases such as ketosis, bovine respiratory disease, and metritis, and metabolites associated with heat stress were also found in the serum and urine samples.Conclusion: The metabolites measured in the serum and urine could potentially be used to detect diseases and heat stress in dairy cattle. The results could also be useful for metabolomic research on the serum and urine of ruminants in Korea.

Reliability Analysis Modeling for LRFD Design of Bridge Abutments

엄준식 한국지반공학회 2014 한국지반공학회논문집 Vol.30 No.8

The objective of this paper is to develop a rational reliability analysis procedure for the LRFD design provisions of bridge substructures. A bridge abutments is considered in this study. The reliability analysis is applied to determine the relationship between the major design parameters for bridge abutment and reliability index. The considered load components include dead load, vertical and horizontal earth pressure, earth surcharge, and vehicle live load. Several limit states are considered: foundation bearing capacity, sliding, and overturning. The analysis results show that the most important parameter in the reliability analysis is the effective stress friction angle of the soil. The reliability indices are calculated using Monte Carlo simulations for a selected bridge abutment. The results of the sensitivity analysis indicate that reliability index is most sensitive with regard to resistance factor and horizontal earth pressure factor.

강거더 연속교에 대한 충격계수에 관한 실험적 연구

엄준식,최종대 한국구조물진단유지관리공학회 2013 한국구조물진단유지관리공학회 논문집 Vol.17 No.6

본 연구에서는 강거더 연속교에 대해 국내외 설계기준에 규정되어 있는 활하중으로 인한 충격계수를 실험을 통해 검증하였다. 대부분의 도로교의 설계기준에서는 도로교의 경우 충격계수를 약 0.3 정도의 값으로 규정하고 있으나, 연속교의 경우에는 명확한 규정 및 명시가 없는 상황이다. 그러므로 단순교에 적용되는 충격계수를 연속교에 동일하게 적용하는 것이 일반적이다. 이 연구에서는 현장실험을 통해 연속교의 충격계수가 단순교에 적용되는 경우와 같이 사용될 수 있는지를 검증하였다. 현장실험 결과 얻어진 충격계수는 2차선 교량에서 1대의 만재트럭이 통과했을 경우 가장 하중이 많이 작용한 거더에서 0.2 이내의 충격계수가 계측되었으며, 2개의 차선을 통시에 만재트럭이 통과한 경우 그 충격계수는 0.05 이내의 값을 얻었다. The objective of the paper is to present the results of analytical and experimental studies dealing with dynamic load for continuous steel girder bridges due to normal truck traffic. Various bridge design codes specify dynamic load factor (defined as a fraction of static portion of live load) for short span structures at the level of about 0.3. However, there are not definite values specified for continuous brigdes. Therefore, it is an usual practice to use the code specified dynamic load factors for simple span bridges to continuous bridges without clear background. The field measurement results indicate that the actual dynamic load factors are less than 0.2 for a single truck, and less than 0.05 for two trucks side-by-side, regardless of positive and negative moment region.

물리적으로 일관된 구름 미세물리와 복사를 향하여: 단일산란, 항공기 관측, 구름물리실험챔버

엄준식 한국기상학회 2023 한국기상학회 학술대회 논문집 Vol.2023 No.4

강거더 연속교의 횡방향 활하중분배계수 검증

엄준식 한국구조물진단유지관리공학회 2005 한국구조물진단유지관리공학회 논문집 Vol.9 No.3

19세기 이후 역사문화도시로써 프랑스 파리의 형태적 변화에 관한 연구 - 도시의 정책적 발전 전략을 중심으로 -

엄준식 대한건축학회지회연합회 2021 대한건축학회연합논문집 Vol.23 No.1

In order for a city to have international competitiveness, it needs to have an urban identity. The purpose of this study is to examine the urban policy development strategies of Paris, France after the 19th century, and to analyze the urban morphological evoltion accordingly to understand the factors that constitute the identity as a historical and cultural city. As a research method, first, the paradigm of today's historical and cultural city was examined, and the process of Paris formation before the 19th century was examined. Next, after the 19th century, urban policy development strategies for each period were divided into 3 stages, and the characteristics of urban morphological evolution were analyzed, focusing on the development of major axes. In addition, the strategic characteristics of the historical and cultural city of Paris are divided into ‘the subjective role’, ‘the change of the urban axes’, and ‘the sustainable development plan’, etc. and synthesized. In conclusion, this study synthesizes the process of morphological change according to the urban policy strategy that enabled Paris to have an identity as a historical and cultural city, and predicts the value of this study.