• Journal of Digital Convergence
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• v.2 no.2
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• pp.45-62
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• 2004

E-commerce is now a familiar form of commercial transaction, especially in the transactions between businesses. This online transaction poses a good deal of problems to the traditional tax system and administration. Realignment of tax system and tax administration in the e-commerce is one of the major topics on the International problem. In the area of consumption tax, they reaffirmed the destination principle. They agreed to decide the recipient's business presence and usual residence as the place of consumption. In the area of consumption tax, they reaffirmed the destination principle. They agreed to decide the recipient's business presence and usual residence as the place of consumption. Currently, the Korean VAT law does not have a basis for taxation on international transactions that are considered to be services. Considering the tax revenue loss and the inequality between domestic suppliers and foreign suppliers when international transactions are not taxed, the Korean Tax Authority needs to amend the current law.

• Bulletin of the Korean Mathematical Society
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• v.60 no.4
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• pp.1101-1129
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• 2023

In this study we propose a model of optimal retirement, consumption and portfolio choice of an individual agent, which encompasses a large class of the models in the literature, and provide a methodology to solve the model. Different from the traditional approach, we consider the problems before and after retirement simultaneously and identify the difference in the dual value functions as the utility value of lifetime labor. The utility value has an option nature, namely, it is the maximized value of choosing the retirement time optimally and we discover it by solving a variational inequality. Then, we discover the dual value functions by using the utility value. We discover the value function and optimal policies by establishing a duality between the value function and the dual value function. The model and approach offer a significant advantage for computation of optimal policies for a large class of problems.

• Journal of Korean Society of Rural Planning
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• v.22 no.2
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• pp.109-119
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• 2016

Most of countries are trying to increase the supply of renewable energy as the substitute of the fossil energy for reducing greenhouse gas emissions. However, renewable energy sources account for only about 3.86% of the total Korea primary energy supply. To increase the rate of renewable energy in Korea's energy consumption, various policies for expanding the use of renewable energy should be applied. Also these policies should be consider renewable energy resources distribution and regional inequality. In this study, the potentials of photovoltaic, wind power and bioenergy from rice straw, livestock waste and food waste are calculated and the distribution characteristic and regional inequalities are analyzed using Gini's coefficient and Gini decomposition method. As the results, technical potentials of photovoltaic and wind power of city region(Gu) has more potential rate than theoretical potentials. Livestock waste has the most unequal distribution (Gini's coefficient: 0.617) among renewable resources.

• Journal of the Korean Professional Engineers Association
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• v.44 no.5
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• pp.21-25
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• 2011

Food sovereignty is the right of peoples to healthy and culturally appropriate food produced through ecologically sound and sustainable methods, and their right to define their own food and agriculture systems. An increase in the price of food that occurs as a result of increased demand from human consumption and use as an alternative energy resource. Furthermore, agflation, a combination of the words "agriculture" and "inflation", will also affect non-vegetative foods as the price increases for grain will make livestock feed more expensive as well. Food sovereignty implies new social relations free of oppression and inequality between men and women, peoples, racial groups, social classes and generations.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.4
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• pp.427-432
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• 1998

There are many demands for ship control system and many studies have been proposed. For example, if a ship diesel engine is operated by consolidated control with Controllable Pitch Propeller(CPP), the minimum fuel consumption is achieved, satisfying the demanded ship speed. For this, it is necessary that the ship is operated on the ideal operating line which satisfies the minimum fuel consumption. In this context of view, this paper presents a controller design method for a ship propulsion system with CPP by Linear Matrix Inequality(LMI) which satisfies the given $H_{\infty}$ control performance and robust stability in the presence of physical parameter perturbations. The validity and applicability of this approach are illustrated through a simulation in the all operating ranges.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.9
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• pp.33-42
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• 1998

If a ship diesel engine is operated by consolidated control with Controllable Pitch Propeller(CPP), the minimum fuel consumption is achieved together with the demanded ship speed. For this, it is necessary that the ship is operated on the ideal operating line which satisfies the minimum fuel consumption and that the pitch angle of CPP and throtle valve angle are controlled simultaneously. In this point of view, this paper presents a controller design method for a ship propulsion system with CPP based on the decoupling control theory. To do this, Linear Matrix Inequality(LMI) approach is introduced for the control system to satisfy the given $H_\infty$ control performance and robust stability in the presence of physical parameter perturbations. The validity and applicability of this approach are illustrated by simulation in the all operating ranges.

• Journal of the Korean Society of School Health
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• v.21 no.2
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• pp.47-60
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• 2008

Objectives: The purpose of this study was to compare Fast foods and Soft drinks consumption of Korean adolescents in a large city, a medium city, and a rural area. Methods: This was a descriptive comparative survey using a convenience sample of 2,261 8th and 11th grade students. The data were analyzed by X2-test and ANOVA using SPSS 10.0 statistical program. Results: For fast food consumptions, the higher in a large city than in a medium city and a rural area(p=.000). For soft drinks in a school, cafeteria or vending machines was higher in a large city and a medium city then in a rural area(p=.000). For eating snacks including cookies and popcorns was higher among students in a rural area than those in a medium city and large city(p=.008). Conclusions: 1. Overall, the health information among rural students is lower than those among other areas, as well as taking a health education course among rural students is also lower. Thus, the health inequality by regional differences should be considered. To decrease health inequality among different regions, health professionals who can systematically teach a health education course for middle and high school students and undertake students' health are needed. 2. Soft drinks sold in schools are higher in a large city and medium city than in a rural area. Therefore, there is a need of strong regulations and policies about the restriction of soft drinks sold in vending machines or school cafeterias.

• Asia-Pacific Journal of Business
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• v.3 no.2
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• pp.34-41
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• 2012

The aim of this paper is to depict the social problems common to South Korea and Japan by comparing their consumption behaviors. For that purpose, we utilize the Survey of Household Economy of both countries and attempt to determine the similarities and differences between the two countries. Our empirical analysis revealed the following. First, although both countries are aging, the first quartile (the poorest in under the definition in this paper) in South Korea has aged more rapidly than in to Japan. As the wages in these two countries formerly increased with age, this substantial divergence in the age composition in the poorest quartile is a remarkable change and suggests that income inequality has been more widely spreading out in South Korea than in Japan. Furthermore, the education expenditure ratio in South Korea is statistically significant for higher income level, while this is not the case in Japan. If the opportunity for better education is dominated by wealthier households, the prompt implementation of a policy to break this vicious circle is necessary in South Korea.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.2
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• pp.123-133
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• 2014

Minimizing the cylinder wear and the consumption rate of cylinder oil in a large two-stroke diesel engine is of great economic importance. A motor-driven cylinder lubricator for Sulzer RT-flex large two-stroke diesel engines developed by authors is in need of improving the lubricating system to lubricate cylinder parts optimally by an electronically controlled quill device according to changes of engine load and revolution speed. In order to apply the developed accumulating distributor to an integrated cylinder lubricator by the electronically controlled system as the third research stage, the lubricating system is improved in the electronically controlled quill device with a solenoid valve. In this study, the effects of lubricator revolution speed, driving pressure(or plunger stroke) and cylinder back pressure on oil feed rate and lubrication inequality rate are investigated by using the integrated cylinder lubricator system with an accumulated distribution by the electronic control(I.C.S.), and the oil feed rate and lubrication inequality rate of I.C.S. are compared with those of the motor-driven cylinder lubricator by the electronically controlled quill system equipped with an accumulating distributor(E.D.S.). It is found that the oil feed rate of I.C.S. is smaller than that of E.D.S. due to the reduction of delivery velocity by the higher delivery pressure, and the variances of lubrication inequality rate for I.C.S. have become smaller than those of E.D.S. as the driving pressure in all experimental conditions increases, except for the driving pressure of 26 bar(plunger stroke 2 mm) at the cylinder lubricator speed of 120 rpm.

• Journal of Mechanical Science and Technology
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• v.20 no.5
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• pp.612-620
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• 2006

This paper proposes an optimal trajectory generation method for biped robots for walking up-and-down stairs using a Real-Coded Genetic Algorithm (RCGA). The RCGA is most effective in minimizing the total consumption energy of a multi-dof biped robot. Each joint angle trajectory is defined as a 4-th order polynomial of which the coefficients are chromosomes or design variables to approximate the walking gait. Constraints are divided into equalities and inequalities. First, equality constraints consist of initial conditions and repeatability conditions with respect to each joint angle and angular velocity at the start and end of a stride period. Next, inequality constraints include collision prevention conditions of a swing leg, singular prevention conditions, and stability conditions. The effectiveness of the proposed optimal trajectory is shown in computer simulations with a 6-dof biped robot model that consists of seven links in the sagittal plane. The optimal trajectory is more efficient than that generated by the Modified Gravity-Compensated Inverted Pendulum Mode (MGCIPM). And various trajectories generated by the proposed GA method are analyzed from the viewpoint of the consumption energy: walking on even ground, ascending stairs, and descending stairs.