• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.2
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• pp.205-210
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• 2014

The micro grid considered in this paper consists of a diesel generator, a photovoltaic array, a wind turbine, a fuel cell, and a energy storage system. This paper explains and simulates the micro grid components in terms of accuracy and efficiency of having a system model based on the costs of fuel as well as operation and maintenance. For operational efficiency, the objective function in a diesel generator consists of the fuel cost function similar to the cost functions used for the conventional fossil-fuel generating plants. The wind turbine generator is modeled by the characteristics of variable output. The optimization is aimed at minimizing the cost function of the system while constraining it to meet the customer demand and safety of micro grid. The operating cost in fuel-cell system includes the fuel costs and the efficiency for fuel to generate electric power. To develop the overall system model gives a possibility to minimize of the total cost of micro grid. The application of optimal operation can save the interruption costs as well as the operating costs, and improve reliability index in micro grid.

• Korean Journal of Human Ecology
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• v.9 no.2
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• pp.189-203
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• 2000

This study was proposed preschooler consumer education curriculum to give effect at a preschooler education institute and was investigated into relations with practical degree, needful degree and demandable degree according to preschooler teacher's characteristics. The survey of this research was conducted by means of questionnaire with 548 teachers of nursery and kindergarten in Seoul. Also it was carried out two stages cluster sampling, personal interview. the statistics used for data analysis was frequency, mean, percentile, t-test, one way ANOVA, Pearson's r, and regression using the SPSS/PC+ program. The results and findings of this study were summarized as follows. 1) Practical degree on total preschooler consumer education was looked into being low, also needful degree on total preschooler consumer education examined being very high. 2) Demandable degree on preschooler consumer education differed significantly according to preschooler education institute, preschooler's age in charge. 3) Practical degree on preschooler consumer education correlated positively to needful degree on preschooler consumer education. And practical degree on preschooler consumer education correlated negatively to demandable degree on preschooler consumer education. 4) Preschooler teacher's age and career had affected to money management in practical degree by regression analysis used to dummy variable related with characteristics of preschooler teacher.

• 한국연소학회:학술대회논문집
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• 2005.10a
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• pp.58-63
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• 2005

As fuel cells approach commercialization, hydrogen production becomes a critical step in the overall energy conversion pathway. Reforming is a process that produces a hydrogen-rich gas from hydrocarbon fuels. Hydrogen production via autothermal reforming (ATR) is particularly attractive for applications that demand a quick start-up and response time in a compact size. However, further research is required to optimize the performance of autothermal reformers and accurate models of reactor performance must be developed and validated. The design includes the requirement of accommodating a wide range of experimental set ups. Factors considered in the design of the reformer are capability to use multiple fuels, ability to vary stoichiometry, precise temperature and pressure control, implementation of enhancement methods, capability to implement variable catalyst positions and catalyst arrangement, ability to monitor and change reactant mixing, and proper implementation of data acquisition. A model of the system was first developed in order to calculate flowrates, heating, space velocity, and other important parameters needed to select the hardware that comprises the reformer. Predicted performance will be compared to actual data once the reformer construction is completed. This comparison will quantify the accuracy of the model and should point to areas where further model development is required. The end result will be a research tool that allows engineers to optimize hydrogen production via autothermal reformation.

• Journal of the Korea Computer Industry Society
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• v.3 no.9
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• pp.1315-1328
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• 2002

Recently there has been increasing demand on developing methodologies and tools for measuring the information security level of organizations for the efficient security management, as the growth of security incidents. However, most methodologies from foreign countries are not realistic in constructing the checklists, moreover their tools provide neither the ease of use nor the inexpensiveness, and most domestic works are not properly considering the characteristics of the organizations. In this study, based on the recently developed standard for information security management, an information security levelling tool is designed and implemented which can be used before building an information security management system while considering the characteristics of organizations more efficiently. The efficiency comes from applying multiple variable weights for security levelling according to the characteristics of organizations.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.10
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• pp.28-37
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• 2011

Though Korea has introduced CBP(Cost Based pool) power trading system since 2001, long-term Generation system planning has been executed by government for Cost minimization every 2 years. Until currently the model which is used for Generation system planning and best-mix only considers cost minimization and total yearly or quarterly electricity demand every year. In a view point of one day power supply operation, technical characteristics, like the ramp up/down rate of total generation system, minimum up/down time and GFRQ(Governor Free Response Quantity), are very important. this paper analyzes Optimal Fuel-Mix for 2022 Korea generation system satisfying these constraints of each fuel type and considering pump storage plants, construction cost and $CO_2$ emission charge Using MILP(Mixed Integer Linear Programming) method. Also the sensitivity analysis which follows in future power industry environmental change accomplished.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.5
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• pp.1077-1083
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• 2000

With rising demand of Internet Service, the existing communication for users (aced the restricted capability and speed, and also failed to satisfy consumer's desire for providing service-quality to them. It can be accomplished the broad-band on subscribe-line to offer various multimedia service to subscriber. But it takes a lot of times and costs. Consequently, it stands out the most economic subscribe-line for acheving a broadband scheme that new transmission technology can be realized the high-speed data communication as the present telephone-line and telephone by the general public of FTTH(Fiber To The Home). As using the pseudo line, this paper have the result that the mesured speed was improved by connecting a variable resistor on the line.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.2
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• pp.70-78
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• 2012

Due to the variable nature of renewable energy resources and power demand by consumers, it is difficult to operate a power system installed with only one type of renewable energy resource. Grid-based renewable generation may be the only solution to overcome this problem. The conventional approach based on a low-voltage converter with power frequency transformer is commonly employed for grid connection of offshore renewable energy systems. Because of the heavy weight and large size of the transformer, the system can be expensive and complex in terms of installation and maintenance. In this paper, an 11-kV series connected H-bridge (SCHB) multilevel voltage source converter (VSC) is proposed to achieve a compact and light direct grid connection of renewable energy systems. This paper presents the design, simulation and analysis of a five level (5L)-SCHB and an eleven level (11L)-SCHB VSC for 11-kV grid-based renewable energy systems. The performance, cost, modulation scheme and harmonic spectra of the converter are analyzed.

• Convergence Security Journal
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• v.2 no.2
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• pp.123-135
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• 2002

As the development of information technology and thus the growth of security incidents, there has been increasing demand on developing methodologies and tools for measuring the information security level of organizations for the efficient security management. However, most works from foreign countries are not realistic in constructing the checklists, moreover their tools provide neither the ease of use nor the inexpensiveness, and most domestic works are not properly considering the characteristics of the organizations when measuring the information security level. In this study, an efficient information security levelling tool is suggested, which applies the multiple variable weights for security levelling according to the characteristics of organizations and the fuzzy technique to reduce the user's subjectivity.

• 아동간호학회:학술대회논문집
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• 1997.11a
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• pp.35-47
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• 1997

Mothers with cerebral palsy children have much stress that is related to the care of children with cerebral palsy and to other household duties, and this state of the mother has an effect on the cerebral palsy child and on other household member. Mothers in such stressful situations use various coping patterns. The purpose of this study was as follows : to develop instruments that can be used for measuring the stress and coping patterns of mothers with cerebral palsy children, and to test a hypothetical model on the relationship between the mother's stress, her coping patterns and the variable affecting the stress and coping patterns. The results of this study can be summarized as follows : 1. The stress scale was composed of 44 items and Cronbach's ${\alpha}$ was .94, and the coping pattern scale was composed of 19 items and Cronbach's ${\alpha}$ was .80. The mean score of stress scale was 136.12 out of a total of 220, and the mean score of the coping scale was 72.87 in a total of 95. 2. In test of the hypothetical model, it was found that extra-care demand, the support of the husband, the degree of handicap, health status and self-esteem had statistically significant influence on the mother's stress(r=.285, -.262, -.133, -.126). And the support of the husband, formal support, informal support, and economic status were found to have statitically significant influence on the mother's coping patterns(r=.412, .178, .178, .138).

• Asia pacific journal of information systems
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• v.16 no.2
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• pp.47-67
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• 2006

This study takes a quantitative approach to the influence of TTF (Task-Technology Fit) on the individual's use and performance of GSS (Group Support Systems), while traditional studies on TTF have taken the experimental approach to explore the characteristic fit between diverse tasks and technologies. We have the following two research inquires: Are the IS use and performance maximized when information technologies are provided by the exact amount of demand?; and, Does TTF at the high level between task and IT produce better IS use (or performance) than at the low level? To investigate these issues, we use the polynomial regression analysis and response surface methodology of Edwards (1993) instead of traditional direct measure of TTF. This method measures the degree of desired and actual level of information technologies in conducting tasks, and traces the dynamic changes of dependent variables (IS use and performance) according to the variances of each independent variable. Our results conclude that user's IS use and performance are maximized when information technologies are actually provided by no more or less than the desired level. We also found that TTF at the high level promotes better IS use and performance than TTF at the low level.