• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.4
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• pp.380-389
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• 1994

Larvae of the freshwater shrimp, Macrobrachium nipponense(De Haan) were reared in the laboratory under constant conditions ($25^{\circ}C,\;7\%0$ S), and their feeding rate, oxygen consumption, ammonia nitrogen excretion, and growth were measured at regular intervals during development from hatching to post larval stage. Growth was measured as dry weight, carbon, nitrogen, hydrogen, protein and lipid. All these physiological and biochemical traits revealed significant changes from instar to instar. Average feeding rate was high in intermolt stage of the molt cycle and it showed a bell-shaped pattern. Respiration(R) increased from hatching to post larval stage. Excretion(U) increased in intermolt phase of larvae and it showed a bell-shaped variation pattern, in all larval instars with a maximum near the middle of the molt cycle. Regression equations describing rates of feeding, growth, respiration and ammonia excretion as functions of time during individual larval molt cycles were inserted in a simulation model, in order to analyse time-dependent patterns of variation as well as in bioenergetic efficiencies. Carbon was initially increased and nitrogen showed a tendency to increase in premolt phase during individual molt cycles. Protein remained clearly the predominant biochemical constituent in larval biomass.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.306-311
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• 2017

This paper deals with the design optimization of the kinematic characteristics of an automotive suspension system. The kinematic characteristics of the suspension determine the attitude of the wheels, such as the toe and camber, which not only relates to tire wear during driving, but also greatly affects the control of the vehicle and its stability, which corresponds to the motion performance of the vehicle. Therefore, it is very important to determine the characteristics of the suspension mechanism at the initial stage of the design. In this study, a displacement analysis is performed to determine the kinematic properties of the suspension for the McPherson strut suspension. For this purpose, a set of constraint equations for the joints constituting the suspension mechanism was established and a program was developed to solve them. We also used ADS, a design optimization program, to obtain the desired kinematic characteristics of the suspension. As the design variables for optimization, we used the coordinates of the hard points, which are the points of attachment of the suspension to the vehicle body, and are defined as the summation of the toe-in for the up and down movement of the wheel as the objective function. As the constraint functions, the maximum camber angle and minimum roll center height, which are design requirements, are considered. As a result of this study, it was possible to determine the optimal locations of the hard points that satisfy both constraint functions and minimize the change of the toe-in.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.409-422
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• 2019

In this study, we carried out the 3D numerical simulation to investigate the hydraulic characteristics of Synchronous Edge wave known as the driving mechanism of beach cusp using the Tool Box called the ihFoam that has its roots on the OpenFoam. As a wave driver, RANS (Reynolds Averaged Navier-Stokes equation) and mass conservation equation are used. In doing so, we materialized short-crested waves known as the prerequisite for the formation of Synchronous Edge waves by generating two obliquely colliding Cnoidal waves. Numerical results show that as can be expected, flow velocity along the cross section where waves are focused are simulated to be much faster than the one along the cross section where waves are diverged. It is also shown that along the cross section where waves are focused, up-rush is moving much faster than its associated back-wash, but a duration period of up-rush is shortened, which complies the typical characteristics of nonlinear waves. On the other hand, due to the water-merging effect triggered by the redirected flow toward wave-diverging area at the pinacle of run-up, along the cross section where waves are diverged, offshore-ward velocity is larger than shore-ward velocity at the vicinity of shore-line, while at the very middle of shoaling process, the asymmetry of flow velocity leaned toward the shore is noticeably weakened. Considering that these flow characteristics can be found without exception in Synchronous Edge waves, the numerical simulation can be regarded to be successfully implemented. In doing so, new insight about how the boundary layer streaming occur are also developed.

• Journal of Digital Convergence
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• v.18 no.10
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• pp.41-50
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• 2020

This study is about entrepreneurial intention of baby boomers who started retirement, starting with the second phase of life. A research model was constructed focusing on factors that will affect the entrepreneurial intention of baby boomers. In order to test the study model, a questionnaire was surveyed on baby boomers, and among them, 204 people, which was valid, was used for analysis. The hypothesis test was a structural equation model using the AMOS 23 statistical package. As a result of the hypothesis test, self-efficacy and social capital had a positive (+) relationship with entrepreneurial intention. Economic preparation was found to have a significant negative (-) relationship with entrepreneurial intention. Social capital was found to have the most influence on baby boomers' entrepreneurial intention. On the other hand, achievement experience and role model learning experience were the antecedent variables affecting self-efficacy. As a result of testing their relationship, achievement experience and role model learning experience had a significant positive (+) influence on self-efficacy. Based on the research results, academic and practical implications were presented.

• Journal of Digital Convergence
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• v.18 no.3
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• pp.149-162
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• 2020

The purpose of this study was to suggest implications for improving training performance by studying how the capacity of IPP workers and the characteristics of training programs affect the training performance through social support of employees. The study was conducted by distributing the online questionnaire to 270 IPP learning worker(of 9 university). As a result, it was found that the characteristics of the learning worker and the characteristics of training programs were positively related to the social support of the employees, and their social support was positively related to the training performance. The results of this study can contribute to the training performance when used as reference materials for selection of trainees and participating companies and development and operation of training courses. However, the limitation of this study is that the objectivity of the result is rather low by deriving the response centered on the recognition of the learning workers. In future studies, it is necessary to increase the objectivity of the results through three-dimensional cross-checks with training participants.

• International Commerce and Information Review
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• v.15 no.1
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• pp.161-183
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• 2013

The essential purpose of this study is to exemplify empirically some relations of between Korea image attributes and Korea image making in Uzbekistan. This study is for providing basically empirical analysis for intensifying Korea's economic capacity based on Korean image in Uzbekistan and for offering any kinds of implications for the entry and management activities of Korean enterprises in world-wide business. This study is organized in two stages. First, the study model is designed by reappraising relevant theories, previous studies and the current investment qualifications concerning the country image attributes and image making. Second, the survey of Uzbekistan people who are living in South Korea is accomplished by collecting questionnaires. SPSS 15.0 for windows is being activated for correlation, reliability, validity and finally the statistical method of structural equation modeling is utilized to testing the hypothesis by AMOS 7.0 for windows. In conclusion partially, Korea image attributes: economic capability, popular culture, national traits and enterprise competence are proved to influence positively to Korea image making: recognition, attractiveness and confidence which is considered generally by Uzbekistan people.

• Journal of Educational Research in Mathematics
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• v.14 no.2
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• pp.187-205
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• 2004

The purpose of this study is to examine the relationships among attitude towards mathematics, mathematics activity, and mathematics achievement, and compare the relationship between the United States and Korea using the Third International Mathematics and Science Study (TIMSS) database. Since Korea is one of the countries where performance was among the highest and the United States is one of countries where performance was among the middle in mathematics, and many previous researchers reported that attitude towards mathematics and class activities are factors that affect mathematics achievement. the comparison study between two countries would be very important to analyze how factors are affected by country difference. The major research questions are as follows: (1) What constitutes attitude towards mathematics and mathematics activities in the TIMSS database\ulcorner (2) How do these two variables, attitude towards mathematics and mathematics activities, affect mathematics achievement differently between the United States and Korea\ulcorner The result indicates that the relationship between the attitude towards mathematics and the mathematics achievement is stronger for Korea than for the United States; however no country difference is found between the mathematics activities and mathematics achievement. According to this study high mathematics achievement is expected when students' attitude towards mathematics is positively high.

• Journal of Navigation and Port Research
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• v.39 no.1
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• pp.69-75
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• 2015

The concrete purpose of this study is to suggest actually a debt ratio to optimize the capital structure providing a kind of approach to estimate the proper debt ratio with an analytical model and empirical data in Korean shipping industry. The mathematical and analytical model is started from the first equation about ROE, return of net operating income on equity, with an independent variable, debt ratio. It is constructed with several parameters, ROS(return of operating income on sales), TAT(total assets turnover), and NFCL(net finance cost to liabilities). There could not be a certain relationship between debt ratio and ROS or TAT, while some correlation or causality between debt ratio and NFCL. In other words, most of firms with high debt ratio is likely to burden higher finance cost than others with low one. In this case, there is a linearity relationship between debt ratio and NFCL, so then the second equation considering this relation could be included within the analytical approach of this paper. To be short, if the criteria of adequate debt ratio has to be defined as some level of debt ratio to optimize ROE, the ROE could be illustrated as a quadratic equation to debt ratio from two equations. Next, this research estimated those parameters' numbers through the single regression method with data over 12 years of Korean shipping industry, and identified empirically the fact that optimal debt ratio would be approximately 400%. To conclude, if that industry's sales and operating incomes are stable, the debt ratio could be accepted until twice of 200% had forced in order to guarantee its financial safety in past time.

• Environmental and Resource Economics Review
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• v.19 no.3
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• pp.597-632
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• 2010

There is general agreement that global warming is occurring and that the main contributor to this probably is the buildup of green house gasses, GHG, in the atmosphere. Two main contributors are the utilization of fossil fuels and the deforestation of many regions of the world. The burning of fossil fuels increases atmospheric carbon while the burning of fuel-wood reducing fossil fuel consumption along with its forest source maintain an atmospheric carbon level. The standing timber in the forests is a carbon sink, as are wood buildings and structures, and fossil fuel in the ground. This paper is designed to examine a number of current issues related to mitigating the global warming problem through forestry. For this purpose, we develop a modeling approach by integrating timber market, fossil fuel market and carbon cycling model. We use discrete time optimal control theory to identify optimal time paths, the laws of motion, and stationary stats solutions of endogenous variables in the model. On the basis of these results, we identify the optimal amounts of subsidies to be provided or taxes to be imposed by the regulatory agency to mitigate atmospheric carbon accumulation. We also present a numerical example to help illustrate the characteristics of variables in the model when the social cost for atmospheric carbon incrementally shifts upward. A surprising result is that the social cost function for atmospheric carbon has a very smaller impact on the optimal rotation period than previous literature suggested.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.317-325
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• 2020

Using a structural model, this study aims to verify the association between job stress, burnout, and self-efficacy levels of health teachers responsible for school health. Structured questionnaires were administered to 814 health teachers, and validated through Structural Equation Modeling (SEM). The study results show that job stress of the health teacher was 2.9±0.64 and burnout was 2.6±0.52, which was slightly lower than the median of the Likert 5-point scale, while self-efficacy was 4.1±0.51. Various sub-factors contributed to the scores: 'student and family' and 'peer teacher's perception' were high for job stress, while 'work in charge' was high for burnout. Job stress of health teachers resulted in increased burnout and decreased self-efficacy. Furthermore, increased burnout significantly decreased self-efficacy. Hence, job stress affected burnout, and burnout affected self-efficacy. Our data clearly demonstrates that job stress is very important to reduce burnout of health teachers and increase their self-efficacy. Therefore, various efforts are required to lower job stress. This study will help to establish new policies and practical improvement plans to reduce job stress and exhaustion of health teachers, and consequently increase their self-efficacy.