• The Journal of Asian Finance, Economics and Business
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• v.9 no.8
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• pp.1-6
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• 2022

This paper uses the gravity model estimated by the random effect method to analyze the factors affecting Vietnam's coffee export turnover for the period 2007-2020 major markets according to statistics from the General Statistics Office and the General Department of Customs. Coffee export turnover was collected from the General Statistics Office, General Department of Customs, and Vietnam Cacao Coffee Association. The authors calculated the price of coffee based on output and export value from data on coffee export turnover; the authors calculated the economic gap based on population and Gross Domestic Product data (reference: geographic distance metrics on the website: http://www.distancefromto.net/countries.php) and other data was collected based on the databases of the Food and Agriculture Organization of the United Nations, the International Monetary Fund, and World Bank organizations. The results of the study show that from 2007 to 2020, the factors of Vietnam's export price of coffee, geographical distance, Gross Domestic Product of the importing country and Gross Domestic Product of Vietnam, the population of Vietnam, the economic gap between Vietnam and the importing country, the openness of the economy, all have an impact on Vietnam's coffee export turnover. Finally, some conclusions about the policy's impact are made based on the empirical results of the paper.

• Journal of the Korean Mathematical Society
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• v.60 no.2
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• pp.327-339
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• 2023

Let R be a commutative ring with identity and S be a multiplicatively closed subset of R. In this article we introduce a new class of ring, called S-multiplication rings which are S-versions of multiplication rings. An R-module M is said to be S-multiplication if for each submodule N of M, sN ⊆ JM ⊆ N for some s ∈ S and ideal J of R (see for instance [4, Definition 1]). An ideal I of R is called S-multiplication if I is an S-multiplication R-module. A commutative ring R is called an S-multiplication ring if each ideal of R is S-multiplication. We characterize some special rings such as multiplication rings, almost multiplication rings, arithmetical ring, and S-P IR. Moreover, we generalize some properties of multiplication rings to S-multiplication rings and we study the transfer of this notion to various context of commutative ring extensions such as trivial ring extensions and amalgamated algebras along an ideal.

• Journal of the Korean School Mathematics Society
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• v.12 no.4
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• pp.545-562
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• 2009

Calculus is used in various parts of human life and the basis of social science such as economics and public administration. Yet that is still considered important in the field of science and technology only, and there have been a lot of disputes on that phenomenon. Fortunately, calculus is going to be taught as part of the academic high school second-year mathematics curriculum in and after 2010. Students who face calculus for the first time should be helped not to lose interest in differentiation learning, not to be apprehensive of it nor to avoid it. The purpose of this study was to examine the types of errors made by students in the course of solving differentiation problems in an effort to lay the foundation for differentiation education. A pilot test was conducted after generalized differentiation problems to which students were usually exposed were selected, and experts were asked to review the pilot test. And then a finalized test was implemented to make an error analysis according to an error type analysis framework to serve the purpose.

• Journal of the Korean earth science society
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• v.34 no.6
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• pp.536-549
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• 2013

This study investigates the damages of and analyzes the social and economic impacts of volcanic ash eruptions in the world in order to estimate the potential volcanic ash impacts in South Korea when Mt. Baekdusan volcano erupts in the future. First, we build a comparison chart called "the impact of volcanic ash" on each economic and social sector by using major volcanic eruptions and we compare the damage with respect to volcanic ash thickness/weights. Secondly, we analyze the social and economic impact from volcanic ash. The economic damage is not likely to occur in South Korea, unless Mt. Baekdusan erupts in winter. However, the potential damage should not be overlooked because the volcanic ash may have a global impact around the world. If Mt. Baekdusan volcano erupts when the wind blows from north or northeast, the volcanic ash may then significantly affect South Korea of which economy is highly dependent on exports. Particularly when the volcanic ash moves to the densely populated metropolitan areas or agricultural areas, the damage can be significant. In preparation for the potential volcanic disasters, the volcanic ash forecast table suitable for South Korea should be prepared. In addition, building a Korean volcanic ash hazard map in advance will have a strategic significance.

• Journal of the Korean institute of surface engineering
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• v.12 no.3
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• pp.207-216
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• 1979

Environmental pollution or contaminations caused by various kinds of pollutants have become one of most serious problems of our time. Environ mental pollution is the unfavoralble alteration of our surroundings, through direct or indirect effects of changes in energy patterns, rediation levels, chemical and physical constitution and abundances of organisms. These changes may affect humans directly or through their supplies of water and of agicultural and other biological products, their physical objects or possessions, or their opportunities for recreation and appreciation of nature. Pollutants that meet the criteria of this definition of environmental pollution are numerous: gases (such as sulfur dioxide and nitrogen oxides) and paniculate matter (such as smoke particles, lead aerosols, and asbestos) in the atmosphere; pesticides and radioactive isotopes in the atmosphee and in waterways; sewage, organic. chemicals, and phosphates in water; solid wastes on land; excessive heating (thermal pollution) of rivers and lakes; and many others. Some of these pollutants are introduced into the environment naturally, others by human actions, and most in both ways. Our major concer is with environmental pollution resulting wholly or largely as a by-product of human activities, because these can be controlled most readily. Environmental pollution cannot be solved by science and technology alone. It should be handled by an interdisciplinary approach with combined methods of science and technology as wen as social science disciplines for the better solution of this critical problem. In this respect, introducing "Environmental Science," a new scientific approach for the solution of environmental problems, which is now widely accepted by most developed countries of the world will be very helpful for systematization of theoretical basis for a new scientific approach to environmental pollution. Environmental science is "the study of all systems of air, land, water, energy, and life that surround Man. It includes all sciences directed to the system-level of understanding of the environment, drawing especially upon such disciplines as meteorology, geophysics, oceanography, and ecology, and utilizing to the fullest knowledge and techniques developed in such fields as physics, chemistry, biology, mathematics and engineering as well as many social science disciplines, such as economics, such as economics, law, political science and public administration." The components of this discipline are not new, for they are drawn from existing areas of science within biology chemistry, physics, and geoscience. What is really new about environmental science, however, is it siewpoint - its orientation to global problems, its conception of the earth as a set of interlocking, interacting systems, and its interest in Man as a part of these systems.

• Journal of the Korean Data and Information Science Society
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• v.28 no.4
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• pp.853-862
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• 2017

In this study, we analyse the determinants of the youth employment rate of public agencies and local public enterprises. On the other hand the youth employment rate contains information of the youth employment rate and the size of the youth employment. We use pooled tobit model and panel tobit model since dependent variable is a censored form observed only in a certain area. The results of the analysis are summarized as follows. First, the panel tobit model is more statistically significant as compared to the combined tobit model. Second, the youth employment rate is more statistically significantly higher in 2014 and 2015 than in 2011. Third, the youth employment rate in public enterprises is more statistically significantly higher than that in local public agencies. Finally, the higher the average wage is, the lower the youth employment ratio is.

• Journal of the Korean earth science society
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• v.34 no.6
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• pp.524-535
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• 2013

Catastrophe risk models require the damage functions of each vulnerable item in inventory to estimate volcanic ash losses. The damage functions are used to represent the relation between damage factors and damage and also widely used in engineering and natural hazard studies to calculate the vulnerability. In most cases, damage functions are constructed as fragility or vulnerability curves, and researchers are confused by the similarities between them particularly when they perform interdisciplinary research. Thus, we aim to explain the similarities and differences between fragility and vulnerability curves and their relationship by providing case studies to construct them. In addition, we suggest a simple method to construct the damage functions between damage ratio and volcanic ash thickness using limited damage data. This study comes from the fact that damage functions are generally constructed using damage data. However, there is no available volcanic ash damage data in Korea, and not even enough volcanic disaster data to construct damage functions in the world, compared to other hazards. Using the method suggested in the study and the limited damage data from Japan and New Zealand, we construct Weibull-type functions or linear functions dependent of available data to calculate volcanic ash loss estimation, which we think need to be corrected to make it more suitable for inventory characteristics and environmental conditions in Korea.

• Nutrition Research and Practice
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• v.10 no.2
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• pp.198-205
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• 2016

BACKGROUND/OBJECTIVES: A healthy diet has been reported to be associated with physical development, cognition and academic performance, and personality during adolescence. This study was performed to investigate the relationships among milk consumption and academic performance, learning motivation and strategies, and personality among Korean adolescents. SUBJECTS/METHODS: The study was divided into two parts. The first part was a survey on the relationship between milk consumption and academic performance, in which intakes of milk and milk products and academic scores were examined in percentiles among 630 middle and high school students residing in small and medium-sized cities in 2009. The second part was a survey on the relationships between milk consumption and learning motivation and strategy as well as personality, in which milk consumption habits were collected and Learning Motivation and Strategy Test (L-MOST) for adolescents and Total Personality Inventory for Adolescents (TPI-A) were conducted in 262 high school students in 2011. RESULTS: In the 2009 survey, milk and milk product intakes of subjects were divided into a low intake group (LM: ${\leq}60.2g/day$), medium intake group (MM: 60.3-150.9 g/day), and high intake group (HM: ${\geq}151.0g/day$). Academic performance of each group was expressed as a percentile, and performance in Korean, social science, and mathematics was significantly higher in the HM group (P < 0.05). In the 2011 survey, the group with a higher frequency of everyday milk consumption showed significantly higher "learning strategy total," "testing technique," and "resources management technique" scores (P < 0.05) in all subjects. However, when subjects were divided by gender, milk intake frequency, learning strategy total, class participation technique, and testing technique showed significantly positive correlations (P < 0.05) in boys, whereas no correlation was observed in girls. Correlations between milk intake frequency and each item of the personality test were only detected in boys, and milk intake frequency showed positive correlations with "total agreeability", "organization", "responsibility", "conscientiousness", and "intellectual curiosity" (P < 0.05). CONCLUSION: Intakes of milk and milk products were correlated with academic performance (Korean, social science, and mathematics) in Korean adolescents. In male high school students, particularly, higher milk intake frequency was positively correlated with learning motivation and strategy as well as some items of the personality inventory.

• Journal of the Korean School Mathematics Society
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• v.16 no.4
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• pp.771-796
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• 2013

The purpose of the study is to analyze the phenomenon of private education and to get the countermeasures of it. To do this, we approached the phenomenon of private education from the game theory, which is famous in economics. As result, we could make the mathematical model. One is a model consisted of two-person. This is a mathematical model simplifying the competition within the school. The problem of private education can be solved by the disconnection with private education and exam of school in this model. The other is a model consisted of three-person. This is a mathematical model simplifying the interscholastic competition. The problem of private education can not only be solved by the disconnection with private education and exam of school, but can be also solved by the specificity of school education in this model. We will hope that our study can give an aid in deciding an educational policy.

• Journal of Korea Water Resources Association
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• v.43 no.1
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• pp.95-104
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• 2010

The tap water supply in Korea mainly depends on the surface water. However, the advanced water purification process becomes a necessity due to the deterioration of surface water quality and the risk of accidental spill. High cost of water treatment and public concerns make the decision makers turn to riverbank filtration as an alternative to the surface water. Riverbank filtration has been employed for water supply in many developed countries for more than 150 years. In Korea, riverbank filtration has drawn attention since 1990s as a supply source having potential to stably meet the ever-increasing water demand. Some cities located in the Nakdong River Basin are currently supplying water through riverbank filtration. This work studies the site suitability analysis for riverbank filtration using game theory. Theory of games, which is a branch of applied mathematics used in social sciences (most notably economics), biology, engineering and computer science, was applied to candidate locations for the selection of riverbank filtration site. We proposed a policy game model as a new method adopting a probabilistic approach. The model developed turned out to be an effective tool for site selection.