• Title/Summary/Keyword: 거시 모델

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Giant Magnetoresistance Phenomenon under the Double Magnetic Fields (이중자장하에서 거대자기저항 현상)

  • 송용진;주승기
    • Journal of the Korean Magnetics Society
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    • v.4 no.4
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    • pp.340-346
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    • 1994
  • Change in the electrical resistance of artificial superlattice under two magnetic fields-the main and the secondary magnetic field-has been studied with respect to each magnetic field strength in (200) textured Co/Cu artificial superlattice. When the two magnetic fields were applied in the same direction, lateral shift of the magnetoresistance curve occurred, while splitting phenomenon of the maximum resistance appeared when the two magnetic fields were applied at the right angle. When the angle between the two magnetic fields became $45^{\circ}$ shifting as well as splitting occurred in the magnetoresistance curve. This magnetoresistance behavior with double magnetic fields in the artificial superlattices could be explained with the macroscopic spin alignment model newly suggested in this work.

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Non-linear Time History Analysis of Piloti-Type High-rise RC Buildings (필로티형 고층 RC건물의 비선형시간이력해석)

  • Ko, Dong-Woo;Lee, Han-Seon
    • Journal of the Earthquake Engineering Society of Korea
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    • v.13 no.1
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    • pp.35-43
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    • 2009
  • Two types of piloti-type high-rise RC building structures having irregularity in the lower two stories were selected as prototypes, and nonlinear time history analysis was performed using OpenSees to verify the analysis technique and to investigate the seismic capacity of those buildings. One of the buildings studied had a symmetrical moment-resisting frame (BF), while the other had an infilled shear wall in only one of the exterior frames (ESW). A fiber model, consisting of concrete and reinforcing bar represented from the stress-strain relationship, was adapted and used to simulate the nonlinearity of members, and MVLEM (Multi Vertical Linear Element Model) was used to simulate the behavior of the wall. The analytical results simulate the behavior of piloti-type high-rise RC building structures well, including the stiffness and yield force of piloti stories, the rocking behavior of the upper structure and the variation of the axial stiffness of the column due to variation in loading condition. However, MVLEM has a limitation in simulating the abrupt increasing lateral stiffness of a wall, due to the torsional mode behavior of the building. The design force obtained from a nonlinear time history analysis was shown to be about $20{\sim}30%$ smaller than that obtained in the experiment. For this reason, further research is required to match the analytical results with real structures, in order to use nonlinear time history analysis in designing a piloti-type high-rise RC building.

A Study on Forecasting Model of the Apartment Price Behavior in Seoul (서울시 아파트 가격 행태 예측 모델에 관한 연구)

  • Kwon, Hee-Chul;Yoo, Jung-Sang
    • Journal of Digital Convergence
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    • v.11 no.2
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    • pp.175-182
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    • 2013
  • In this paper, the simulation model of house price is presented on the basis of pricing mechanism between the demand and the supply of apartments in seoul. The algorithm of house price simulation model for calculating the rate of price over time includes feedback control theory. The feedback control theory consists of stock variable, flow variable, auxiliary variable and constant variable. We suggest that the future price of apartment is simulated using mutual interaction variables which are demand, supply, price and parameters among them. In this paper we considers three items which include the behavior of apartment price index, the size of demand and supply, and the forecasting of the apartment price in the future economic scenarios. The proposed price simulation model could be used in public needs for developing a house price regulation policy using financial and non-financial aids. And the quantitative simulation model is to be applied in practice with more specific real data and Powersim Software modeling tool.

Conversion Profit and Optimal Capacity of Cloud Computer for Integrating Legacy Campus Web Servers (캠퍼스내 레거시 웹서버 통합 운영을 위한 클라우드 컴퓨팅의 최적용량 및 전환이익 분석)

  • Lee, Goo Yeon;Choi, Chang Yeol;Choi, Hwang Kyu;Jang, Min;Yoon, Jae Ku
    • Journal of Digital Contents Society
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    • v.15 no.2
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    • pp.289-300
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    • 2014
  • Cloud computing helps users to save a significant amount of cost that is related to infrastructure investment, management, and maintenance. In this paper, we study the conversion planning from campus legacy web servers into an integrated cloud computing web server system. We also analyze the conversion profit when campus web servers are integrated into a cloud computer. We first investigate the cost of legacy system model of campus web servers operated by individual laboratories, departments, institutes and so on. Next, we set up a cloud computer model for the integrated web services meeting the same performance requirements. Then, we derive the conversion profit. From the result of the derivation, we see that the conversion can be effectively applied to and adopted by mid or large sized campuses and similar institutions that provide web services.

Effects of Numerical Modeling on Concrete Heterogeneity (콘크리트 비균질성에 대한 수치모델의 영향)

  • Rhee, In-Kyu;Kim, Woo
    • Journal of the Korea Concrete Institute
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    • v.18 no.2 s.92
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    • pp.189-198
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    • 2006
  • The composition of most engineering materials is heterogeneous at some degree. It is simply a question of scale at which the level of heterogeneity becomes apparent. In the case of cementitious granular materials such as concrete the heterogeneity appears at the mesoscale where it is comprised of aggregate particles, a hardened cement paste and voids. Since it is difficult to consider each separate particle in the topological description explicitly, numerical models of the meso-structure are normally confined to two-phase matrix particle composites in which only the larger inclusions are accounted for. 2-D and 3-D concrete blocks(Representative Volume Element, RVE) are used to simulating heterogeneous concrete meso-structures in the form of aggregates in the hardened mortar with nearly zero-thickness linear or planar interfaces. The numerical sensitivity of these meso-structures are Investigated with respect to the different morphologies of heterogeneity and the different level of coupling constant among fracture mode I, II and III. In addition, a numerically homogenized concrete block in 3-D using Hashin-Shtrikman variational bounds provides an evidence of the effective cracking paths which are quite different with those of heterogenous concrete block. However, their average force-displacement relationship show a pretty close match each other.

Suggested Method for Determining a Complete Set of Micro-Parameters Quantitatively in PFC2D (PFC2D 활용을 위한 정량적 미시변수 결정법)

  • Jong, Yong-Hun;Lee, Chung-In
    • Tunnel and Underground Space
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    • v.16 no.4 s.63
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    • pp.334-346
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    • 2006
  • The discrete element code in 2-D, PFC2D, has been used as a tool to simulate various phenomena in rock mechanics and rock engineering. However, the code has an disadvantage that procedure to determine micro-parameters, namely properties of particles and contacts is repetitive and time-consuming. In this study, we analyzed the effect of micro-parameters(for generation of a contact-bonded model) on macro-properties(that were measured numerically by uniaxial compressive test). Based on the analysis, also, the time-saving and reliable method was suggested to determine a complete set of micro-parameters. In order to verify the suggested method, numerical specimens were generated in PFC2D for 10 different rock types at home and abroad. By the two trials for each specimen, in the result, the Young's modulus, Poisson's ratio and uniaxial compressive strength could be reproduced with being in relative error by about 5% to the values obtained by laboratory tests.

A Design of Model For Interoperability in Multi-Database based XMDR on Distributed Environments (분산환경에서 XMDR 기반의 멀티데이터 베이스 상호운영 모델 설계)

  • Jung, Kye-Dong;Hwang, Chi-Gon;Choi, Young-Keun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.11 no.9
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    • pp.1771-1780
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    • 2007
  • The necessity of Information integration has emphasized by advancement of internet and change of enterprise environment. In enterprises, it usually integrates the multi-database constructing by M&A. For this integration of information it must guarantee interpretation and integration which is stabilized with solving heterogeneous characteristic problem. In this paper, we propose the method that change the global XML query to local XML query for interpretation. It is based on XMDR(eXtended Meta-Data Registry) which expresses the connection between the standard and the local for solve the interoperability problem in heterogeneous environment. Thus, we propose the legacy model that can search and modify by one Query with creating global XML Query by XMDR. and for his, we use the 2PC technique which is the distributed transaction control technique of existing.

Beat control method of Korean bells using artificial dumshoi (인공 덤쇠를 이용한 한국종의 맥놀이 조절법)

  • Kim, Seockhyun;Lee, Jae Ho
    • The Journal of the Acoustical Society of Korea
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    • v.40 no.3
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    • pp.192-200
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    • 2021
  • Korean bell is a macroscopically axi-symmetrical structure, but has a slight asymmetry due to complex patterns and casting irregularity. Small asymmetry separates one vibration mode into a mode pair with slight frequency difference. The mode pair interferes and creates a beat. The vivid beat with an appropriate period makes the bell sound magnificent and lively feeling. In this study, we propose a method to make the vivid beat using artificial dumshoi. This method creates the vivid beat by designing artificial dumshoi that overwhelms the bell asymmetry. To this end, the asymmetry of Korean bell is quantified by analyzing the beat period data of a number of Korean bells cast in modern times. Based on the measured beat period data, the magnitude of asymmetry is quantified using an equivalent bell model and artificial dumshoi is applied. The movement of mode pair by dumshoi is predicted through finite element analysis. Finally, a design example of the artificial dumshoi for clear beat is introduced.

Export Prediction Using Separated Learning Method and Recommendation of Potential Export Countries (분리학습 모델을 이용한 수출액 예측 및 수출 유망국가 추천)

  • Jang, Yeongjin;Won, Jongkwan;Lee, Chaerok
    • Journal of Intelligence and Information Systems
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    • v.28 no.1
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    • pp.69-88
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    • 2022
  • One of the characteristics of South Korea's economic structure is that it is highly dependent on exports. Thus, many businesses are closely related to the global economy and diplomatic situation. In addition, small and medium-sized enterprises(SMEs) specialized in exporting are struggling due to the spread of COVID-19. Therefore, this study aimed to develop a model to forecast exports for next year to support SMEs' export strategy and decision making. Also, this study proposed a strategy to recommend promising export countries of each item based on the forecasting model. We analyzed important variables used in previous studies such as country-specific, item-specific, and macro-economic variables and collected those variables to train our prediction model. Next, through the exploratory data analysis(EDA) it was found that exports, which is a target variable, have a highly skewed distribution. To deal with this issue and improve predictive performance, we suggest a separated learning method. In a separated learning method, the whole dataset is divided into homogeneous subgroups and a prediction algorithm is applied to each group. Thus, characteristics of each group can be more precisely trained using different input variables and algorithms. In this study, we divided the dataset into five subgroups based on the exports to decrease skewness of the target variable. After the separation, we found that each group has different characteristics in countries and goods. For example, In Group 1, most of the exporting countries are developing countries and the majority of exporting goods are low value products such as glass and prints. On the other hand, major exporting countries of South Korea such as China, USA, and Vietnam are included in Group 4 and Group 5 and most exporting goods in these groups are high value products. Then we used LightGBM(LGBM) and Exponential Moving Average(EMA) for prediction. Considering the characteristics of each group, models were built using LGBM for Group 1 to 4 and EMA for Group 5. To evaluate the performance of the model, we compare different model structures and algorithms. As a result, it was found that the separated learning model had best performance compared to other models. After the model was built, we also provided variable importance of each group using SHAP-value to add explainability of our model. Based on the prediction model, we proposed a second-stage recommendation strategy for potential export countries. In the first phase, BCG matrix was used to find Star and Question Mark markets that are expected to grow rapidly. In the second phase, we calculated scores for each country and recommendations were made according to ranking. Using this recommendation framework, potential export countries were selected and information about those countries for each item was presented. There are several implications of this study. First of all, most of the preceding studies have conducted research on the specific situation or country. However, this study use various variables and develops a machine learning model for a wide range of countries and items. Second, as to our knowledge, it is the first attempt to adopt a separated learning method for exports prediction. By separating the dataset into 5 homogeneous subgroups, we could enhance the predictive performance of the model. Also, more detailed explanation of models by group is provided using SHAP values. Lastly, this study has several practical implications. There are some platforms which serve trade information including KOTRA, but most of them are based on past data. Therefore, it is not easy for companies to predict future trends. By utilizing the model and recommendation strategy in this research, trade related services in each platform can be improved so that companies including SMEs can fully utilize the service when making strategies and decisions for exports.

The Difference-in-Difference Model Analysis about the Effects of Long-Term Care Insurance on Family Relationships' Change (노인장기요양보험제도가 가족관계의 변화에 미치는 영향에 대한 이중차이모델 분석)

  • Min, Kichae
    • 한국노년학
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    • v.31 no.4
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    • pp.999-1014
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    • 2011
  • The purpose of this study is to examine the effects of long-term care insurance(macro-system) on family relationship(micro-system)s' change based on ecosystems theory. Data come from the second(2007) and the fourth(2009) Korean Welfare Panel Study(KWPS). Experimental group is the beneficiary using long-term care insurance and the member of household in their households, and control group is the non-beneficiary not using long-term care insurance and the member of household in their households. The main findings of difference-in-difference model analysis are as follows. First, the ecosystems theory is a theory examining the correlation between long-term care insurance and family relationship. Second, the effects of long-term care insurance is not income effect but independent effect. This result shows that the meaning of family has faded away and family relationship has been weaken and that long-term care insurance has not complete characteristics as a social insurance. Thus, system reforms of long-term care insurance is highly needed for system comprehensiveness, coverage, adequacy, and service accessibility and is changed into family-friendly social policy.