• Journal of the Korean Society of Industry Convergence
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• v.26 no.1
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• pp.87-94
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• 2023

TMCP(Thermo Mechanical Control Process) steel was continuously cast (CC) by varying the argon gas flow rate and vacuum time in the Ruhrstahl Heraeus (RH) refining process. Using the CC specimens, the distribution of the inclusions and the mechanical properties were evaluated. A lot of oxides and Al-O type inclusions were observed. The average Vickers hardness did not show a constant, but showed dispersion in a certain range. The shape and scale parameters of the CC specimen with an argon gas flow rate of 160Nm³ and a vacuum time of 12 minutes was the best. Mechanical properties (tensile strength, yield strength and elongation) were consistent with the Weibull probability distribution analysis results. The impact resistance was the best for CC specimens with an argon flow rate of 140 Nm³ and a vacuum time of 12 minutes. Although the inclusions and mechanical properties of the CC specimens were evaluated according to the argon gas flow rate and vacuum time, these values were no significant difference.

• Journal of Korean Society on Water Environment
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• v.39 no.4
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• pp.302-315
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• 2023

Distribution characteristics and altitudinal gradient of four species (E. strigata, E. separigata, E. orientalis-sachalinensis group) of the mayfly genus Ephemera (Order Ephemeroptera) were analyzed with probability distribution models (exponential, normal, lognormal, logistic, Weibull, gamma, beta, Gumbel). Data was collected from 23,846 sampling units of 6,787 sites in Korea from 2010 to 2021. The beta distribution model showed the best fit for positively skewed E. orientalis-sachalinensis and little-skewed E. strigata along with altitudinal gradient. The reversed lognormal distribution model showed the best-fit for negatively skewed E. separigata. E. orientalis-sachalinensis distributed at the range of altitude 1~700 m (mean 251 m, median 226 m, mode 124 m, and standard deviation 161 m), E. strigata distributed at the range of altitude 5~871 m (mean 474 m, median 478 m, mode 492 m, and standard deviation 200 m), E. separigata distributed at the range of altitude 7~846 m (mean 620 m, median 659 m, mode 760 m, and standard deviation 181 m). Altitudinal habitat suitability ranges were estimated to be 42~257 m for E. orientalis-sachalinensis, 335~644 m for E. strigata, and 641~824 m for E. separigata. Based on the altitudinal spectrum of suitability and altitude-related temperature analysis results, E. orientalis-sachalinensis was estimated to be thermophilic, E. strigata to be mesophilic, and E. separigata to be thermophobic. This is the first national-scale evaluation of the altitudinal distribution of Ephemera in Korea. These results will be used in a further research study on altitudinal shift of the species of Ephemera under climate change.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.126-126
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• 2023

최근 대한민국에서는 기후변화로 전국 각지에서 돌발성 호우와 태풍의 강도 및 발생빈도가 높아지고 있다. 이에 따라 주요 국가시설이 위치한 해안 도시의 2차원 3차원 모형을 통해 극한 조건하 침수 분석을 수행하였다. 먼저 해양수산부 "2019년 전국 심해설계파 보고서"를 기반으로 극치분포 중 Weibull 분포를 이용하여 극한 조건, 1,000년부터 1,000,000년 빈도의 재현기간의 파도 높이와 풍속을 계산하였다. 계산 결과를 SWAN(Simulating WAves Nearshore)의 입력값으로 해상에서 100m 간격의 파고 높이를 계산하였다. 이때 100m 간격으로는 방파제 지형을 정확히 해석하지 못하였기에, 상세파고 계산을 위한 Nesting 기법을 이용하여 20m 간격의 파고 결과를 도출하였고, 해안 도시 인근 해상에서 10.916m의 파고를 예측하였다. 또한, 예측된 파고를 이용해 EurOtop(2018) 매뉴얼의 경험식을 기반으로 연구 유역으로 유입되는 월류량 계산에 사용하였다. 결과로 16방위 중 SSE 방향, 1,000,000년 빈도 재현기간 조건에서 0.0306cms/m의 월파량을 예측했다. 예측된 자료를 바탕으로 2차원 침수해석은 FLO-2D 모형, 3차원 침수해석은 FLOW-3D 모형을 이용하였다. 2차원 침수해석 결과 주요 지점에서 0.18~0.33m의 침수가 예상되었고 3차원 침수해석 결과 동일한 지점에서 0.240~0.333m의 침수가 예상되었다. 모의 결과 2차원과 3차원 모형 간 침수 예측 결과가 0.3cm에서 6.1cm의 차이를 나타내어 모형 구축이 합리적으로 이뤄졌다고 판단하였으며 연구 유역에서는 침수가 예상된다는 결과를 도출하였다. 본 연구를 통해 기후변화에 따른 해안에 위치한 주요 도시지역과 국가 주요 시설물에 대한 침수해석을 실시하였고 분석결과를 생명과 재산을 보호하기 위한 대피계획 등 재난예방대책 수립에 활용할 수 있음으로 예상된다.

• The Journal of Society for e-Business Studies
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• v.27 no.2
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• pp.193-204
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• 2022

Smart card data is representative mobility data and can be used for policy development by analyzing public transportation usage behavior. This paper deals with the problem of classifying metro stations using metro usage patterns as one of these studies. Since the previous papers dealing with clustering of metro stations only considered traffic among usage behaviors, this paper proposes clustering considering traffic time as one of the complementary methods. Passengers at each station were classified into passengers arriving at work time, arriving at quitting time, leaving at work time, and leaving at quitting time, and then the estimated shape parameter was defined as the characteristic value of the station by modeling each transit time to Weibull distribution. And the characteristic vectors were clustered using the K-means clustering technique. As a result of the experiment, it was observed that station clustering considering pass time is not only similar to the clustering results of previous studies, but also enables more granular clustering.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.14-14
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• 2020

일반적으로 수문빈도해석은 치수계획 수립에 이용되는 설계강수량, 계획홍수량 등을 산정하기 위해 연최대치계열 또는 연초과치계열 자료를 이용한 극치빈도해석을 수행하고, 확률분포의 우측꼬리(right tail) 부분을 이용하여 확장된 재현기간에 해당하는 확률수문량을 추정한다. 하지만 가뭄 관련 분석에서는 확률분포의 좌측꼬리(left tail) 부분은 이용해 확장된 재현기간별 확률수문량을 추정해야할 경우가 발생한다. 또한 물관리 실무에서 장 단기 운영계획 수립을 위해 이용하는 갈수빈도 유입량 산정 등에서도 평년보다 작은 수문량에 대한 빈도해석이 필요한 경우가 있다. 국가 가뭄정보분석센터에서는 기존에 K-water연구원에서 개발한 빈도해석 프로그램인 K-FAT의 분석모듈을 이용해 극소치계열 또는 갈수빈도 유입량 분석에 특화된 가뭄빈도해석 프로그램을 개발하였다. 본 프로그램은 GEV, Gumbel, Weibull 등 14개의 확률분포형을 포함하며, 모멘트법, 최우도법 및 L-모멘트법을 사용하여 매개변수를 추정한다. 적합도 검정의 경우 χ², K-S, CVM, PPCC 및 수정 Anderson-Darling test를 이용하여 다각적인 검정을 할 수 있도록 하였다. 분석을 위한 입력 자료의 경우 사용자가 전처리를 통해 준비한 연최소치계열 등 연도별 시계열자료를 이용할 수 있으며, 일단위 및 월단위의 강수량 또는 댐 유입량 자료를 이용해 사용자가 원하는 기간의 누적강수량, 평균 유입량으로 변환할 수 있는 자료변환 기능을 추가하여 실무 활용성을 높였다. 또한 최적 확률분포 선정을 위해 참고할 수 있도록 AIC(Akaike information criteria)와 BIC(Bayesian information criteria) 분석이 포함되어 있으며, Bootstrap 기법 등을 이용한 불확실성 산정을 통해 추정 값의 신뢰구간을 표시하도록 하였다. 개발된 프로그램은 베타버전 시험배포를 거쳐 가뭄정보포털을 통해 배포할 예정이다.

• Wind and Structures
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• v.38 no.3
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• pp.215-229
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• 2024

Guyed mast structures exhibit characteristics such as high flexibility, low mass, small damping ratio, and large aspect ratio, leading to a complex wind-induced vibration response mechanism. This study analyzed the time- and frequency-domain characteristics of the wind-induced response of a guyed mast structure using measured acceleration response data obtained from the Shenzhen Meteorological Gradient Tower (SZMGT). Firstly, 734 sets of 1-hour acceleration samples measured from 0:00 October 1, 2021, to 0:00 November 1, 2021, were selected to study the vibration shapes of the mast and the characteristics of the generalized extreme value (GEV) distribution. Secondly, six sets of typical samples with different vibration intensities were further selected to explore the Gaussian property and modal parameter characteristics of the mast. Finally, the modal parameters of the SZMGT are identified and the identification results are verified by finite element analysis. The findings revealed that the guyed mast vibration shape exhibits remarkable diversity, which increases nonlinearly along the height in most cases and reaches a maximum at the top of the tower. Moreover, the GEV distribution characteristics of the 734 sets of samples are closer to the Weibull distribution. The probability distribution of the structural wind vibration response under strong wind is in good agreement with the Gaussian distribution. The structural response of the mast under wind loading exhibits multiple modes. As the structural response escalates, the first three orders of modal energy in the tower display a gradual increase in proportion.

• Journal of Food Hygiene and Safety
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• v.14 no.4
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• pp.319-326
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• 1999

Recently, it is continuously rising to concern about the health risk being induced by microorganisms in food such as Escherichia coli O157:H7 and Listeria monocytogenes. Various organizations and regulatory agencies including U.S.FPA, U.S.DA and FAO/WHO are preparing the methodology building to apply microbial quantitative risk assessment to risk-based food safety program. Microbial risks are primarily the result of single exposure and its health impacts are immediate and serious. Therefore, the methodology of risk assessment differs from that of chemical risk assessment. Microbial quantitative risk assessment consists of tow steps; hazard identification, exposure assessment, dose-response assessment and risk characterization. Hazard identification is accomplished by observing and defining the types of adverse health effects in humans associated with exposure to foodborne agents. Epidemiological evidence which links the various disease with the particular exposure route is an important component of this identification. Exposure assessment includes the quantification of microbial exposure regarding the dynamics of microbial growth in food processing, transport, packaging and specific time-temperature conditions at various points from animal production to consumption. Dose-response assessment is the process characterizing dose-response correlation between microbial exposure and disease incidence. Unlike chemical carcinogens, the dose-response assessment for microbial pathogens has not focused on animal models for extrapolation to humans. Risk characterization links the exposure assessment and dose-response assessment and involve uncertainty analysis. The methodology of microbial dose-response assessment is classified as nonthreshold and thresh-old approach. The nonthreshold model have assumption that one organism is capable of producing an infection if it arrives at an appropriate site and organism have independence. Recently, the Exponential, Beta-poission, Gompertz, and Gamma-weibull models are using as nonthreshold model. The Log-normal and Log-logistic models are using as threshold model. The threshold has the assumption that a toxicant is produce by interaction of organisms. In this study, it was reviewed detailed process including risk value using model parameter and microbial exposure dose. Also this study suggested model application methodology in field of exposure assessment using assumed food microbial data(NaCl, water activity, temperature, pH, etc.) and the commercially used Food MicroModel. We recognized that human volunteer data to the healthy man are preferred rather than epidemiological data fur obtaining exact dose-response data. But, the foreign agencies are studying the characterization of correlation between human and animal. For the comparison of differences to the population sensitivity: it must be executed domestic study such as the establishment of dose-response data to the Korean volunteer by each microbial and microbial exposure assessment in food.

• Journal of Korean Society of Forest Science
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• v.104 no.3
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• pp.421-426
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• 2015

The objective of this paper is to look into the growth of Cryptomeria japonica stand in South Korea along with the evaluation on their yields, followed by their carbon stocks and removals. A total of 106 sample plots were selected from Jeonnam, Gyeongnam, and Jeju, where the groups of standard are grown. We only used 92 plots data except outlier. As part of the analysis, the Weibull diameter distribution was applied. In order to estimate the diameter distribution, the growth estimation equation for each of the growth factors including the height, the diameter at breast height, and the basal area was drafted out and the verification for each equation was examined. The site index for figuring out the forest productivity of Cryptomeria japonica stand for each district was also developed as a Schumacher model and 30yr was used as a reference age for the estimation of the site index. It was found that the site index for Cryptomeria japonica stand in South Korea ranges from 10 to 16 and this result was used as a standard for developing the stand yield table. According to the site 14 in the stand yield table, the mean annual increment (MAI) of the Cryptomeria japonica reaches $7.6m^3/ha$ on its 25yr and its growing stock is estimated to be at $190.1m^3/ha$. This volume is about $20m^3$ as high as that of the Chamaesyparis obtusa. Furthermore, the annual carbon absorptions for a Cryptomeria japonica stand reached the peak at 25yr, which is 2.14 tC/ha/yr, $7.83tCO_2/ha/yr$. When compared to the other conifers, this rate is slightly higher than that of a Chamaecyparis obtusa ($7.5tCO_2/ha/yr$) but lower than that of the Pinus koraiensis ($10.4tCO_2/ha/yr$) and Larix kaempferi ($11.2tCO_2/ha/yr$). With such research result as a base, it is necessary to come up with the ways to enhance the utilization of Cryptomeria japonica as timbers, besides making use of their growth data.

• Korean journal of applied entomology
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• v.57 no.4
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• pp.261-269
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• 2018

The cowpea aphid Aphis craccivora Koch (Hemiptera: Aphididae) is a polyphagous species with a worldwide distribution. We investigated the temperature effects on development periods of nymphs, and the longevity and fecundity of apterous female of A. craccivora. The study was conducted at six constant temperatures of 10.0, 15.0, 20.0, 25, 30.0, and $32.5^{\circ}C$. A. craccivora developed successfully from nymph to adult stage at all temperatures subjected. The developmental rate of A. craccivora increased as temperature increased. The lower developmental threshold (LT) and thermal constant (K) of A. craccivora nymph stage were estimated by linear regression as $5.3^{\circ}C$ and 128.4 degree-days (DD), respectively. Lower and higher threshold temperatures (TL, TH and TH-TL, respectively) were calculated by the Sharpe_Schoolfield_Ikemoto (SSI) model as $17.0^{\circ}C$, $34.6^{\circ}C$ and $17.5^{\circ}C$. Developmental completion of nymph stages was described using a three-parameter Weibull function. Life table parameters were estimated. The intrinsic rate of increase was highest at $25^{\circ}C$, while the net reproductive rate was highest at $20^{\circ}C$. Biological characteristics of A. craccivora populations from different geographic areas were discussed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.1
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• pp.69-83
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• 2006

A Level 3 reliability analysis has been performed for wave run-up and overtopping on a sloping seawall. A Monte-Carlo simulation was performed considering the uncertainties of various variables affecting the wave overtopping event. The wave overtopping probability was evaluated from the individual wave run-up by using the wave-by-wave method, while the mean overtopping rate was calculated directly from the significant wave height. Using the calculated overtopping probability and mean overtopping rate, the maximum overtopping volume was also calculated on the assumption of two-parameter Weibull distribution of individual wave overtopping volume. In addition, by changing wave directions, depths, and structure slopes, their effects on wave overtopping were analyzed. It was found that, when the variability of wave directions is considered or the water depth decreases toward shore, wave height become smaller due to wave refraction, which yields smaller mean overtopping rate, overtopping probability and maximum overtopping volume. For the same mean overtopping rate, the expected overtopping probability increases and the expected maximum overtopping volume decreases as approaching toward shore inside surfzone.