• 천문학회지
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• 제52권4호
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• pp.133-144
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• 2019

We develop forecast models of daily probabilities of major flares (M- and X-class) based on empirical relationships between photospheric magnetic parameters and daily flaring rates from May 2010 to April 2018. In this study, we consider ten magnetic parameters characterizing size, distribution, and non-potentiality of vector magnetic fields from Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager (HMI) and Geostationary Operational Environmental Satellites (GOES) X-ray flare data. The magnetic parameters are classified into three types: the total unsigned parameters, the total signed parameters, and the mean parameters. We divide the data into two sets chronologically: 70% for training and 30% for testing. The empirical relationships between the parameters and flaring rates are used to predict flare occurrence probabilities for a given magnetic parameter value. Major results of this study are as follows. First, major flare occurrence rates are well correlated with ten parameters having correlation coefficients above 0.85. Second, logarithmic values of flaring rates are well approximated by linear equations. Third, using total unsigned and signed parameters achieved better performance for predicting flares than the mean parameters in terms of verification measures of probabilistic and converted binary forecasts. We conclude that the total quantity of non-potentiality of magnetic fields is crucial for flare forecasting among the magnetic parameters considered in this study. When this model is applied for operational use, it can be used using the data of 21:00 TAI with a slight underestimation of 2-6.3%.

• 한국수자원학회논문집
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• 제43권9호
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• pp.813-822
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• 2010

빈도해석에 있어서 중요한 문제는 특정 재현기간에 대한 수문량의 크기를 산정하는 것으로, 빈도해석에서는 일반적으로 관측기간보다 긴 재현기간에 해당하는 수문량의 크기를 산정하기 위해 가정된 확률분포형을 표본 자료에 적합시키게 된다. 따라서 적절한 확률분포형의 선정이 무엇보다 중요하며 이는 일반적으로 대상 자료로부터 얻어지는 경험적 빈도분포와 가정한 확률분포의 일치 정도를 판단하는 적합도 검정 방법을 이용하게 된다. 일반적으로 많이 사용되는 적합도검정 방법들은 모든 표본 자료들의 적합 정도를 동일하게 고려하기 때문에 극치사상의 크기 증가에 따른 영향은 반영하기 힘든 방법들이다. 따라서 본 연구에서는 모의실험을 통해 극치사상에 대하여 가중치를 주는 modified Anderson-Darling (AD) 검정 방법의 Gumbel 분포형에 대한 검정 통계량 한계값을 제시하였으며, 기존의 여러 적합도 검정 방법과의 기각력을 비교해 보고, 이를 실제 자료에 적용하여 그 결과를 살펴보았다. 그 결과 modified AD 검정 방법이 기존의 여러 가지 적합도 검정 방법보다도 기각력이 더 우수한 것으로 나타났으며, 기존의 적합도 검정 방법으로는 부족한 분포형 선정 기준의 부족한 부분을 어느 정도 보완해 줄 수 있을 것으로 판단되었다.

• 유통과학연구
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• 제14권4호
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• pp.117-125
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• 2016

Purpose - As consumers' needs for purchasing fresh and safe food have been bigger in Korea, their interest in local food is also growing recently. So, the number of local food stores has been increased from 3 in 2012 to 103 in 2015. Local food stores should operate a business responding consumers' needs in order that local food stores are not to be a one-time fad. Therefore, the purpose of this study is to analyze the characteristics of consumers who use a local food store and provide helpful implications to design a strategy for sustainable growth of local food store. Research design, data, and methodology - In this study, Probit model was used for empirical analysis in order to examine the effect of purchase choice attributes of agricultural products, consumer's satisfaction, and their demographic factors upon the intention to use a local food store. After estimating coefficients of the probit model, marginal effects were calculated as a standard normal, and cumulative distribution is differentiated with respect to explanatory variables. To collect the data, questionnaire survey was carried out with the consumers using the local food store (Youngjin Nonghyup near to Jeonju city located in Jeollabuk-do). Result - The data analysis found that the more consumers are satisfied with local food store, the higher intention they have to use the local food store. In addition, it was known that the factors related to quality of agricultural products and shopping convenience among the purchase choice attributes have a considerable impact on the purchase intention of a local food store. In demographic factors, income was turned out to be an important factor affecting purchase intention of local food. Such a result supports the hypothesis that high income consumers are likely to purchase local food, which is based on the inference that consumers who have a high income tend to pursue wellbeing life. Futhermore, information delivery, through a reputable media source among general factors, was known to play an important role in forming an intention to purchase local food. According to the analysis of marginal effects, probability of purchase intention of a local food store is increased by 11.4%, if a monthly average income of a household is above 4.5 million Won(Korean currency). If purchasing satisfaction with local food stores is high, the probability of purchase intention would be increased by 24.1%. Likewise, such a probability goes up by 8.7%, 5.8%, respectively as an increasing one unit of quality of agricultural products and shopping convenience of local food stores, respectively. Conclusion - For attaining sustainable growth in a local food store, it is considered necessarily to establish a proper store operation system to meet consumers' needs, especially for quality and shopping convenience of local food. Moreover, as it was found that appropriate communication through media source has a positive effect on the intention to use local food store, PR activity seems to be necessary to expand the consumers' demands for local foods.

• 한국해안·해양공학회논문집
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• 제31권5호
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• pp.241-252
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• 2019

폭풍으로 인한 연안재해 피해에 대한 적절한 대응책을 수립하기 위해서는 빈도 해일고 산정에 대한 연구가 필요하다. 과거에 관측된 태풍은 모집단 수가 적기 때문에 tropical cyclone risk model(TCRM)을 이용해 역사태풍의 이동경로와 중심기압을 확률밀도함수로 추정하여 확률적으로 발생하는 176,689개의 합성태풍을 생성하였다. 아울러 중국 남동부 연안으로 상륙한 후 재부상 하거나 소멸되는 태풍 특성을 합성태풍에 고려하기 위해 역사태풍의 이동각도를 확률밀도함수로 추정하고 감쇠 매개변수와 함께 적용하여 중국 남동부 연안에서 서남해안으로 이동하는 태풍의 통과율이 개선되었다. 태풍속성은 역사태풍으로부터 분석하였으며 중심기압과 최대풍속($V_{max}$), 최대풍속 반경($R_{max}$)의 상관관계식을 산정하여 합성태풍에 적용하였다. 해일고는 ADCIRC 모형을 이용해 조석과 합성태풍을 고려하여 산정하였으며 Perl script로 자동화하였다. 확률적으로 발생시킨 합성태풍에 의한 해일고는 실제 자연현상에서 발생하는 해일고와 유사하게 나타나기 때문에 빈도 해일고를 산정할 수 있다. 따라서 일반화된 극치분포(Generalized Extreme Value, GEV)의 모수를 추정하여 극치 해일고를 산정하였으며, 100년 빈도 해일고는 경험모의기법으로 산정한 빈도 해일고와 비교하여 만족스러운 결과가 도출되었다. 본 연구에서 제안한 방법은 일반 해역에서 빈도 해일고 산정시 활용될 수 있다.

• 한국지진공학회논문집
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• 제26권5호
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• pp.191-202
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• 2022

Markov envelope as a theoretical solution of the parabolic wave equation with Markov approximation for the von Kármán type random medium is studied and approximated with the convolution of two probability density functions (pdf) of normal and gamma distributions considering the previous studies on the applications of Radiative Transfer Theory (RTT) and the analysis results of earthquake records. Through the approximation with gamma pdf, the constant shape parameter of 2 was determined regardless of the source distance r_o. This finding means that the scattering process has the property of an inhomogeneous single-scattering Poisson process, unlike the previous studies, which resulted in a homogeneous multiple-scattering Poisson process. Approximated Markov envelope can be treated as the normalized mean square (MS) envelope for ground acceleration because of the flat source Fourier spectrum. Based on such characteristics, the path duration is estimated from the approximated MS envelope and compared to the empirical formula derived by Boore and Thompson. The results clearly show that the path duration increases proportionately to r_o^1/2-r_o², and the peak value of the RMS envelope is attenuated by exp (-0.0033r_o), excluding the geometrical attenuation. The attenuation slope for r_o≤100 km is quite similar to that of effective attenuation for shallow crustal earthquakes, and it may be difficult to distinguish the contribution of intrinsic attenuation from effective attenuation. Slowly varying dispersive delay, also called the medium effect, represented by regular pdf, governs the path duration for the source distance shorter than 100 km. Moreover, the diffraction term, also called the distance effect because of scattering, fully controls the path duration beyond the source distance of 300 km and has a steep gradient compared to the medium effect. Source distance 100-300 km is a transition range of the path duration governing effect from random medium to distance. This means that the scattering may not be the prime cause of peak attenuation and envelope broadening for the source distance of less than 200 km. Furthermore, it is also shown that normal distribution is appropriate for the probability distribution of phase difference, as asserted in the previous studies.

• 유통과학연구
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• 제18권5호
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• pp.83-88
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• 2020

Purpose of the research: In response to the increasing number of selling centers, this paper examines factors that influence the voluntary participation in selling centers. The goal of this study is to enable organizations to meet changing market conditions, which require interdisciplinary collaboration during sales projects. This paper also discusses potential problems which may occure during the implementation of these factors in practice. Research design and methodology: The research method consists of a qualitative cross-sectional study with N=12 interviewees. All interviewees are current or former selling center participants. During the interview sessions, semi-structured face-to-face interviews were used, which were evaluated using a qualitative content analysis. In addition, a frequency analysis was applied to evaluate the number of mentions per factor. Research results: In total, five factors were raised in order to improve the framework conditions of voluntary participation. These factors are performance incentives, transparency, availability of resources, goal orientation, as well as collegiality and affiliation. Major conclusions: The identified factors are also under discussion in the existing literature. Knowing about factors that generate voluntary participation in selling centers pays off particularly in improving the probability of completion of sales projects in which buying centers and selling centers are working together.

• International Journal of Concrete Structures and Materials
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• 제19권1E호
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• pp.11-16
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• 2007

Recently, probabilistic neural network (PNN) has been proposed to predict the compressive strength of concrete for the known effect of improvement on PNN by the iteration method. However, an empirical method has been incorporated in the PNN technique to specify its smoothing parameter, which causes significant uncertainty in predicting the compressive strength of concrete. In this study, a modified probabilistic neural network (MPNN) approach is hence proposed. The global probability density function (PDF) of variables is reflected by summing the heterogeneous local PDFs which are automatically determined by the individual standard deviation of each variable. The proposed MPNN is applied to predict the compressive strength of concrete using actual test data from a concrete company. The estimated results of MPNN are compared with those of the conventional PNN. MPNN showed better results than the conventional PNN in predicting the compressive strength of concrete and provided promising results for the probabilistic approach to predict the concrete strength by using the individual standard deviation of a variable.

• 대한기계학회논문집A
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• 제33권12호
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• pp.1464-1470
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• 2009

RBDO approach based on a sampling method with the Kriging metamodel and Constraint Boundary Sampling (CBS), which is sequential sampling method to generate metamodels is proposed. The major advantage of the proposed RBDO approach is that it does not require Most Probable failure Point (MPP) which is essential for First-Order Reliability Method (FORM)-based RBDO approach. The Monte Carlo Sampling (MCS), most well-known method of the sampling methods for the reliability analysis is used to assess the reliability of constraints. In addition, a Cumulative Distribution Function (CDF) of the constraints is approximated using Moving Least Square (MLS) method from empirical distribution function. It is possible to acquire a probability of failure and its analytic sensitivities by using an approximate function of the CDF for the constraints. Moreover, a concept of inactive design is adapted to improve a numerical efficiency of the proposed approach. Computational accuracy and efficiency of the proposed RBDO approach are demonstrated by numerical and engineering problems.

• Wind and Structures
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• 제27권3호
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• pp.149-161
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• 2018

A reliability analysis method is proposed in this paper based on the maximum entropy (MaxEnt) principle in which constraints are specified in terms of the fractional moments instead of integer moments. Then a multiplicative dimensional reduction method (M-DRM) is introduced to compute the fractional moments. The method is applicable for both explicit and implicit limit state functions of complex structures. After two examples illustrate the accuracy and efficiency of this method in comparison to the Monte Carlo simulation (MCS), the method is used to analyze the flutter reliability of suspension bridge. The results show that the empirical formula method in which the limit state function is explicitly represented as a function of variables is only a too conservative estimate for flutter reliability analysis but is not accurate adequately. So it is not suitable for reliability analysis of bridge flutter. The actual flutter reliability analysis should be conducted based on a finite element method in which limit state function is implicitly represented as a function of variables. The proposed M-DRM provide an alternate and efficient way to analyze a much more complicated flutter reliability of long span suspension bridge.

• Structural Engineering and Mechanics
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• 제46권5호
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• pp.629-644
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• 2013

This paper concerns about the raking damages on the ultimate residual hull girder strength of bulk carriers by applying the modified R-D diagram (advanced method). The limited raking damage scenarios, based on the IMO's probability density function of grounding accidents, were carried out by using sampling technique. Recently, innovative method for the evaluation of the structural condition assessment, which covers the residual strength and damage index diagram (R-D diagram), was proposed by Paik et al. (2012). This concept is applied in the present study and modified R-D diagram, which can be considered vessel size effect, is then proposed. Four different types of bulk carrier structures, i.e., Handysize (37K), Supramax (57K), Kamsarmax (82K) and Capesize (181K) by Common Structural Rule (CSR), were applied to draw the general tendency. The ALPS/HULL, intelligent supersize finite element method, was employed for the ultimate longitudinal strength analysis. The obtained empirical formulas will be useful for the condition assessment of bulk carrier structures. It can also cover different sizes of the bulk carriers in terms of ultimate longitudinal strength. Important insights and findings with useful guidelines developed in this study are summarized.