• The Korean Journal of Applied Statistics
• /
• v.33 no.6
• /
• pp.763-776
• /
• 2020

Onions show severe volatility in production and price because crop conditions highly depend on the weather. The government has designated onions as a sensitive agricultural product, and prepared various measures to stabilize the supply and demand. First of all, preemptive and reliable information on predicting onion production is essential to implement appropriate and effective measures. This study aims to contribute to improving the accuracy of production forecasting by developing a model to estimate the final weight of onions bulb. For the analysis, multi-level model is used to reflect the hierarchical data characteristics consisting of above-ground growth data in individual units and meteorological data in parcel units. The result shows that as the number of leaf, stem diameter, and plant height in early May increase, the bulb weight increases. The amount of precipitation as well as the number of days beyond a certain temperature inhibiting carbon assimilation have negative effects on bulb weight, However, the daily range of temperature and more precipitation near the harvest season are statistically significant as positive effects. Also, it is confirmed that the fitness and explanatory power of the model is improved by considering the interaction terms between level-1 and level-2 variables.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.3 no.3
• /
• pp.3-13
• /
• 2001

The behavior of the masonry lining is studied to gain basic information on how to reinforce the masonry tunnels. Apart from the previous works on the masonry structures, the multi-course masonry structure, realistic in field condition, is considered and the constitutive relationship of the masonry is, therefore, established. The design charts of the orthotropic material properties are proposed according to the stiffness ratio and the crack initiation and subsequent propagation model is also considered to model the brittle nature of the masonry. A numerical analysis on the masonry panel is investigated to verify the proposed model and future works of the masonry lining are briefly explained.

• Science of Emotion and Sensibility
• /
• v.19 no.4
• /
• pp.95-110
• /
• 2016

The purpose of this study was to propose a proper method for the multilevel mediation analysis, for which the hierarchical method should be utilized, then MLM (multilevel modeling) approach as a hierarchical method has been popularly utilized until MSEM (multilevel structural equation modeling) approach was not proposed. This purpose was covered by three research questions about statistical methods, analytic procedure, and real example. First, MSEM statistical method was preferred to MLM method for its estimation accuracy and analytic flexibility. Second, the four-step procedures of model building, assumption examination, model comparison, and coefficient testing were proposed for the multilevel mediation analysis. Third, the real data of 2695 students of elementary and secondary schools and 89 teachers were analyzed in the multilevel directions of $2{\rightarrow}2{\rightarrow}1$ and $1{\rightarrow}1{\rightarrow}2$. Out of these directions of $2{\rightarrow}2{\rightarrow}1$, and $1{\rightarrow}1{\rightarrow}2$ model, only the coefficient of $2{\rightarrow}2{\rightarrow}1$ model was significant at the 95% CI. Mplus programs used for the real example are attached on the Appendix. Based on the results, significance and limitations of this study, were discussed in detail.

• The Journal of Korean Association of Computer Education
• /
• v.20 no.6
• /
• pp.83-94
• /
• 2017

The purpose of this study is to analyze factors affecting elementary school students' computational thinking and SW education attitude using a 3-level multi-level models. The results of this study are as follows: First, 'Computer at home', 'SW competition participation experience', 'SW education satisfaction', and 'SW awareness' have a statistically significant effect on the initial value of computational thinking while 'SW period of education' and 'SW education experience at after school' have a statistically effect on the change rate of computational thinking. Second, 'SW awareness', 'SW education satisfaction' and 'gender' have a positive effect on the initial values of SW education attitude whereas 'SW period of education' has a slight negative influence on the change rate of SW education attitude.

• The Journal of the Korea Contents Association
• /
• v.14 no.2
• /
• pp.294-307
• /
• 2014

The purpose of this study is to examine the trajectory of early adolescent aggression and to assess the effects of perceived family factors on it. This study investigated the changes in aggression over time and the effects of three family factors, parental attachment, parental monitoring, and family conflict, on the changes using multilevel modeling. The data from Korea Youth Panel Survey(KYPS) of fourth graders who were followed over five years were analyzed. The results indicated that there was a significant average increase followed by a slight decrease in aggression over time; that is, the data followed a quadratic trend. Parental attachment, parental monitoring, and family conflict had significant time-independent effects on aggression, while only family conflict had a significant time-dependent effect on aggression. These results imply that family factors need to be emphasized in planning prevention and intervention programs to reduce aggression during adolescence.

• Survey Research
• /
• v.8 no.2
• /
• pp.21-42
• /
• 2007

In the present study, we studied the change patterns of adolescents' overt aggression during the middle school 2nd to the high school 1st grades and the effects of ecological factors on the change. For the research goals, we applied multi-level models to the Korean Youth Panel data. Results showed that adolescents' overt aggression decreased significantly during the period. Gender(males recoded as 1) and self-control had negative effects on the initial status(middle school 2nd grade) while the number of delinquency peers had a positive effect. On the other hand, gender and self-control showed positive effects on the change rate. The major strengths of the research are the study of various ecological factors and the longitudinal design. Few studies of adolescents' aggression have incorporated these methodological and substantive characteristics.

• The Journal of the Korea Contents Association
• /
• v.21 no.10
• /
• pp.422-433
• /
• 2021

At this point in time when active participation in renewable energy projects is required, basic information on growth engines and substantial promotion strategies for participation in renewable energy projects is needed. According to the this study tried to provide basic information for vitalizing participation in the renewable energy business by analyzing the factors affecting the new energy business participation roadmap using the multi-layered model. As a result of this study, it can be seen that in order to achieve an effective new energy business participation roadmap, it is necessary to re-establish the new and renewable energy business participation factors by industry. Specifically, it is necessary to prepare appropriate countermeasures such as the leading organization of the project, profit distribution method, green industry financial support, project implementation method, power plant location, and comprehensive long-term strategy, and there is an institutional approach that can promote the development of related industries. found to be necessary. Above all, it suggested that in order to achieve an effective new energy project participation roadmap, an institutional approach is needed that can expand the supply of new and renewable energy while minimizing the burden on the national economy and promote the development of related industries.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 2005.05a
• /
• pp.746-752
• /
• 2005

본 논문에서는 다층 퍼셉트론 신경망 학습을 위한 새로운 두 단계 학습방법을 제안하고 이를 옵션 가격결정 모형에 응용하였다. 제안된 신경망 학습 알고리즘의 첫번째 단계는 Levenberg-Marquardt 알고리즘을 이용하여 빠르게 국소최적해를 찾는 것이고 두 번째 단계는 첫 번째 단계에서 찾은 국소최적해가 원하는 수준에 미치지 못할 경우 선형탐색 터널링을 이용해서 더 나은 해를 찾는 것이다. 이 두 단계를 반복적으로 수행함으로써 연결가중치 공간에서 구하고자 하는 해를 빠르고 안정적으로 찾을 수 있다. 현재 옵션가격결정 모형으로 많이 이용되고 있는 Black-Scholes 모형의 문제점을 극복하기 위해서 제안된 신경망 모형을 옵션가격결정 문제에 사용하였다. 이 모형을 KOSPI200 옵션 데이터로 실험한 결과 Black-Scholes 모형에 비해 검증오차를 60% 가량 줄일 수 있었다.

• Proceedings of the Korean Information Science Society Conference
• /
• 1999.10c
• /
• pp.244-246
• /
• 1999

본 논문에서는, multiple-buffered crossbar 스위치를 이용한 다층 연결 망의 성능 분석 모형을 제안하고, 스위치에 장착된 buffer의 개수 증가에 따른 성능 향상 추이를 분석하였다. Buffered 스위치 기법은 다층 연결 망 (Multistage Interconnection Network, MIN)의 내부의 데이터 충돌 문제를 효과적으로 해결할 수 있는 방법으로 알려져 있다. 제안된 성능 분석 모형은 먼저 네트웍 내부 임의 스위치 입력 단에 유입되는 데이터 패킷이 buffered 스위치 내부에서 전송되는 패턴을 확률적으로 분석하여 수립하였다. 분석 모형의 수학적 복잡도 절감을 위하여 확률식 유도 과정에 정상상태 확률 rosa(steady state probability)을 도입하였다. 제안한 모형은 스위치의 크기 및 스위치에 장착된 buffer의 수와 무관하게 확대 적용이 가능하다. 제안한 수학적 성능 분석 연구의 실효성 검증을 위하여 병행된 시뮬레이션 처리 결과는 상호 미세한 오차 범위 내에서 모형의 예측 데이터와 일치하는 결과를 보여 분석 모형의 타당성을 입증하였다. 2$\times$2 스위치로 구성된 8$\times$8 MIN을 대상으로 분석을 시행한 결과 스위치에 2~4개의 buffer를 장착했을 경우 unbuffer 스위치 경우와 비교하여 네트웍 정상상태 Throughout의 증가율이 높고 네트웍 Delay 또한 낮아져 효율적인 것으로 나타났다. 따라서 2~2 crossbar 스위치로 구성된 MIN의 경우 스위치에 장착된 buffer의 개수가 네 개 정도일 경우가 가격 대 성능비 면에서 가장 유리한 것으로 연구되었다.

• Journal of the Korean Geotechnical Society
• /
• v.25 no.9
• /
• pp.93-100
• /
• 2009

A core procedure of the direct search method used in this study is optimizing a difference between objective function and real displacement and correcting unknown variables. Because the research procedure comes from back-analyzing of the unknown variable of each layer, back-analyzing results need an additional optimization to minimize interferential effects of unknown variables. Therefore, the direct search method Is used to obtain optimized solutions without a partial differentiation of an objective function. The object of this research is developing the back analysis technique for multi-unknown variables by modeling the soil including underground structure Into upper and lower layer. In order to minimize interferent errors, repeated back analysis is performed and applicability on the real tunnel is examined. Consequently, the multi-layer analysis model is more precise in describing the real behavior of underground structure. It shows the validity of back analysis far multi-layer model which is the understructure placed on multi-layer boundaries.