• Journal of the Korean Society for Precision Engineering
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• v.12 no.1
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• pp.22-28
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• 1995

Micro Drills have found ever wider application. However micro drilling is a machining to integrate the difficult machinablities such as tool stiffness, position control and revolution accuracy, and is known to cost and time consuming. So, this study aimed to practice ultraminiature drilling(0.05 .phi. ) wiht simple component, if possible. System is developed as the three modules : feed drives, spindle and monitoring part. The dynamics of measured current signals from the spindle of Micro Hole Drilling machine are investigated to establish the criteria of stepfeed mechanism. Cutting experiments identify the relationship of spindle rpm, feed rate and tool life. The smaller drill diameter is, the more suitable cutting condition have to be selected because of chip packing.

• Management & Information Systems Review
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• v.36 no.5
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• pp.99-120
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• 2017

Recent studies shows that international entrepreneurship orientation is recognized as a very important tool for improving corporate performance in international business activities. However, these relationships show various research results. Therefore, it can be a very interesting research topic to examine whether these relationships are linear or non-linear when selected as a target in developing country like China. The purpose of this study is to examine whether the effects of international entrepreneurship orientation on the export performance is non-liner type in China's manufacturing firms. And investigated the moderating role of degree of internationalization and market dynamism relative to the relationship between the international entrepreneurial-orientation and the export performance. A total of 478 questionnaires were used for the hypothesis test. The results of this study are summarized as follows: First, there is a J-shaped. relationship between international entrepreneurship orientation and export performance. Second, degree of Internationalization strengthened the reverse J-shaped relationship between international entrepreneurship orientation and export performance. Finally, degree of internationalization and market dynamics show that J-shaped relationship between international entrepreneurial orientation and export performance is strengthened. The results of the study's theoretical contribution and the managerial contribution is as followed. As a theoretical contribution, it is confirmed that international entrepreneurial orientation (J-shaped) and export performance form a non-linear relationship, and it is possible to make an empirical contribution that can newly approach the relationship between international entrepreneurial orientation and export performance. The managerial contribution suggests that China's exporting companies have a higher degree of Internationalization in their international business activities and that the higher the dynamics of the overseas markets, the more advanced the international entrepreneurial behavior should be required to improve the export performance.

• Korean Journal of Environmental Agriculture
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• v.32 no.4
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• pp.294-303
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• 2013

BACKGROUND: It is well known that rice-fields can provide excellent foraging places for birds including seasonal migrants, wintering, and breeding and hence the high biodiversity of rice-fields may be expected. However, how environmental change including climate-changes on life-history and population dynamics in birds on rice-fields has not been fully understood. In order to investigate how climate-change affects population migratory patterns and migration timing, I modeled a population dynamics of birds in rice-fields over a whole year. METHODS AND RESULTS: I applied the Lotka-Volterra equation to model the population dynamics of birds that have been foraging/visiting rice-fields in Korea. The simple model involves the number of interspecific individuals and temperature, and the model parameters are periodic in time as the biological activities related to the migration, wintering and reproduction are seasonal. As results, firstly there was a positive relationship between the variation of seasonal population sizes and temperature change. Secondly, the reduced lengths of season were negatively related to the population size. Overall, the effects of the difference of lengths of season on seasonal population dynamics were higher than the effects of seasonal temperature change. CONCLUSION(S): Climate change can alter population dynamics of birds in rice-fields and hence the variation may affect the fitness, such as reproduction, survival and migration. The unstable balances of population dynamics in birds using paddy rice field as affected by climate change can reduce the population growth and species diversity in rice fields. The results suggest that the agricultural production is partly affected by the unstable balance of population in birds using rice-fields.

• Korean System Dynamics Review
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• v.1 no.2
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• pp.5-31
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• 2000

The summit meeting of the South North Korean leaders was a turning point in the relationships between the two countries. It was followed by the Red-Cross Meeting, Minister-Level Meeting, economic agreements, which have increased the relationship more colorful in both quantities and qualities. However, the half-century period for separation was too long to overcome all the problems by only one event. The two countries have quite different social systems; one politically strong person is governing the North, while many interest groups are involved in political decision making processes in the South. In short, it would take a long time to settle down all the problems residing between the two countries. A system dynamics model is developed to describe the long term dynamics of the relations between the South and North Koreas. As a first attempt, the model focuses only on the diplomatic meeting issues between the South and North. The model aggregates diplomatic issues into 5 categories; economic issues, security issues, infrastructure, cultural issues, and past problems. It assumes that there would not be any dramatic changes between the two countries. It is a conceptual model composed of around 200 variables, and should not be used as a forecast tool. However, it captures most of the logics discussed in the papers and conferences concerning the South and North Korea relations. Many sensitivity studies and Monte Carlo simulations have shown that the simulation results matches with mental models of experts; that is the model can be used as a learning tool or as a secondary opinion until the data required by the model is collected. In order to analyze the current situation, five scenarios are simulated and analyzed; the functional approach, the conditional approach, the balanced approach, the circumstantial approach, and the strategic approach. The functional approach represents that the South makes efforts in the area where the possibility of agreement is high for the next 10 years. The conditional approach is a scenario where the South impose all difficult issues as conditions for resolving other diplomatic issues. The balanced approach is resolving the five issues with the same priorities, while the circumstantial approach is resolving issues which seem to be resolved easily. Finally, another optimum approach has been seek using the system dynamics model developed. The optimum strategy (it is named as the strategic approach) was strikingly different from other four approaches. The optimum strategy is so complicated that no one could find it with mental model(or by just insights). Considering that the system dynamic model used to find the optimum is a simplifind (maybe over simplified) version of the reality, it is concluded that a well designed system dynamics model would be of great help to resolving the complicated diplomatic problems in any kind.

• Journal of Korea Port Economic Association
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• v.33 no.1
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• pp.75-87
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• 2017

The purpose of this study is to utilize the system dynamics to carry out a medium and long-term forecasting analysis of the bunker price. In order to secure accurate bunker price forecast, a quantitative analysis was established based on the casual loop diagram between various variables that affects bunker price. Based on various configuration variables such as crude oil price which affects crude oil consumption & production, GDP and exchange rate which influences economic changes and freight rate which is decided by supply and demand in shipping and logistic market were used in accordance with System Dynamics to forecast bunker price and then objectivity was verified through MAPEs. Based on the result of this study, bunker price is expected to rise until 2029 compared to 2016 but it will not be near the surge sighted in 2012. This study holds value in two ways. First, it supports shipping companies to efficiently manage its fleet, offering comprehensive bunker price risk management by presenting structural relationship between various variables affecting bunker price. Second, rational result derived from bunker price forecast by utilizing dynamic casual loop between various variables.

• International Journal of Automotive Technology
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• v.7 no.1
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• pp.25-34
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• 2006

For decades, simulation technique has been well validated in areas such as computer and communication systems. Recently, the technique has been much used in the area of transportation and traffic forecasting. Several methods have been proposed for investigating complex traffic flows. However, the dynamics of vehicles and diversities of driver characteristics have never been considered sufficiently in these methods, although they are considered important factors in traffic flow analysis. In this paper, we propose a traffic simulation tool called Multi-Agent for Traffic Simulation with Vehicle Dynamics Model (MATDYMO). Road transport consultants, traffic engineers and urban traffic control center managers are expected to use MATDYMO to efficiently simulate traffic flow. MATDYMO has four sub systems: the road management system, the vehicle motion control system, the driver management system, and the integration control system. The road management system simulates traffic flow for various traffic environments (e.g., multi-lane roads, nodes, virtual lanes, and signals); the vehicle motion control system constructs the vehicle agent by using various vehicle dynamic models; the driver management system constructs the driver agent capable of having different driving styles; and lastly, the integrated control system regulates the MATDYMO as a whole and observes the agents running in the system. The vehicle motion control system and driver management system are described in the companion paper. An interrupted and uninterrupted flow model were simulated, and the simulation results were verified by comparing them with the results from a commercial software, TRANSYT-7F. The simulation result of the uninterrupted flow model showed that the driver agent displayed human-like behavior ranging from slow and careful driving to fast and aggressive driving. The simulation of the interrupted flow model was implemented as two cases. The first case analyzed traffic flow as the traffic signals changed at different intervals and as the turning traffic volume changed. Second case analyzed the traffic flow as the traffic signals changed at different intervals and as the road length changed. The simulation results of the interrupted flow model showed that the close relationship between traffic state change and traffic signal interval.

• Journal of Digital Convergence
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• v.19 no.1
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• pp.67-75
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• 2021

Despite the increase in sales of imported vehicles in Korea, research on the sales forecast of parts logistics centers is very limited. This study aims to perform a sales prediction on bestselling goods in the automobile part logistics center. System dynamics was adopted as a methodology for the prediction method, which considered causal relationship of variables that affected the dynamic characteristics and feedback loops. The analysis results showed that the consumable sales amount of oil increased over time. As a result of conducting the MAPE, the model was assessed to be a reasonable predictive model of 31.3%. In addition, the sales of battery products increased from every October in both of actual and predicted data followed by the peak sales in December and then decrease from next February. This study has academic implications that it secured actual data of specific imported automobile part logistics center, which has not done before in previous studies and quantitatively analyzed the prediction of the quantity of released goods of future sales through system dynamics.

• The Journal of the Korea Contents Association
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• v.20 no.12
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• pp.36-48
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• 2020

App market has continuously been growth since its launch. The market revenues will reach about 1,000 billion US dollars in 2019. App is a core service for smartphone. Currently, there are more than 1.5 million mobile apps in App platform calling out for attention. So, if you are looking at developing a successful app, you need to have a solid marketing and distribution strategy. Online word of mouth(eWOM) is one of the most effective, powerful App marketing method. eWOM affect potential consumers' decision making, and this effect can spread rapidly through online social network. Despite the increasing research on word of mouth, only few studies have focused on content analysis. Most of studies focused on the causes and acceptance of eWOM and eWOM performance measurement. This study aims to content analysis of mobile apps review In 2013, Google researchers announced Word2Vec. This method has overcome the weakness of previous studies. This is faster and more accurate than traditional methods. This study found out the relationship between mobile app reviews and checked for reactions by Word2vec.

• Journal of Families and Better Life
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• v.30 no.3
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• pp.69-82
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• 2012

The purpose of this study was to investigate the degree of sexual behavior. In particular, this study focused on the self-esteem, internet pornography addiction, and relationship satisfaction of freshmen as important predictors of sexual behavior and examined the dynamics of the relationships among the variables. The participants in this research were 1,806 university freshmen: 932 males and 828 females. All respondents submitted their answers on a self-report questionnaire. The data were analyzed with descriptive statistics and Pearson's correlations that used PASW 18.0, and AMOS 18.0, a statistical program for structural equation modeling(SEM), to estimate the hypothesized structural equation model. The major results of this study were as follows: (1) Relationship satisfactions mediated the relationships among self-esteem, internet pornography addiction, and sexual behavior. (2) Sexual behavior between male and female freshmen showed different influences on the test of the structural model invariance across the groups.

• Journal of the Korean Home Economics Association
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• v.30 no.3
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• pp.285-305
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• 1992

The purpose of this study was to describe the current status of dual-earner families in Seoul. The specific aims of this study were to examine the dynamics of marital relationship, parent-child relationship and old mother-daughter/daughter in law relationship in the same family. The sample consised of 265 dual-earner families was selected based on wives' jobs, primarily non-professional. The information was gathered from working couples and their school-aged children. The findings of this study were as follows: 1. Sex role attitude of husbands was more traditional than their wives. Therefore, housework sharing of husbands was very low and wives' perception of inequity was high. Wives' marital satisfaction was affected by the wives' perception of inequity, joint leisure activity, sexual satisfaction, and wives' job satisfaction. Husbands' marital satisfaction was affected by sexual satisfaction, perceived difficulties and problems of the husbands caused by wives' employment, and the degree of their housework participation. 2. The emotional uneasiness of children during mothers' absence was reported. The communication about mothers' job was helpful to gain children's understanding toward mothers' job. Mothers suffered from guilty feeling of neglecting their children in spite of their good performance of mothering role. 3. The employed daughters/daughters in law perceived high rewards and low cost in relationships with their mothers/mothers in law. The perceived quality of daughter-mother relationship was higher with low cost and high rewards than that of daughter in law/mother in law. Finally practical and policy implications were suggested.