• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.3722-3730
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• 2015

The performance improvement of a small centrifugal compressor for waste water treatment has been conducted by the design change of vaneless diffuser and volute casing. Existing two compressors use a common impeller, but the width and length of the vaneless diffuser and the cross-sectional shape of the volute casing are different, respectively. Based on the experiment of the existing two compressors and their CFD results, the design of the vaneless diffuser and the volute casing has been changed. It was found that the strength of the interaction among the volute tongues, the vaneless diffusers and the impellers of two existing/one improved compressors, was affected by the cross-sectional area and inlet radial length of the volute casing including system losses' change. The efficiency of the impeller with one existing design was increased as the decrease of the width of the vaneless diffuser, but losses at the diffuser were accumulated. In conclusion, approximately 2.88%p efficiency increase at the design point of the new compressor with the improved design has been confirmed by CFD analysis results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.1 no.1
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• pp.15-22
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• 2000

There are lots of industrial machines of which functions are achieved by operation of multi-phase fluids. Some of them take advantage of the characteristics of counter-current two-phase flow The maximum flow rates of gas and liquid phases which flow in opposite-directions (counter-current flow) are limited by a phenomenon known as a Counter-Current Flow Limitation (CCFL or Flooding) The mass and momentum conservation equations for each Phase were established to build a first-order hyperbolic partial derivative equations system. A new CCFL model is developed based on the characteristic equation of the hyperbolic PDE system. The present model has its applicationto the case in which a non-uniform flow is developed around a square or sharp-edged entrance of liquid phase. The model is able to he used to Predict the operating-limit of components in which mass and heat transfer are taking place between liquid and gas phases.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2246-2252
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• 2009

A new metamaterial antenna with dual resonant modes is presented using an asymmetrical periodic arrangement for orthogonal radiation patterns. The proposed antenna produces two orthogonal modes by the asymmetrical periodic unit-cell arrangement. The orthogonal resonant mode provides perpendicular radiation patterns without changing the antenna polarization at each resonant mode. The fabricated antenna shows good agreements with the theoretical analysis of the electric-field. The experimental results shows the orthogonal radiation patterns along x- and y-axises, and gains are 3.34 and 3.86 dBi at each radiating resonant mode, respectively. Additionally, slotted ground structures are embedded on the back side of the antenna in order to reduce the size and enhance the radiation efficiency of 12 % and 27 %, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.11
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• pp.4282-4290
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• 2010

Recently, business environment is spreading from singular business to supply-chain problem. SCM(Supply Chain Management) is changing from closed and static to opened and dynamic environment, so these environment changes of SCM require to enterprise different approach than past. As supply chain is becoming opened and dynamic, a claim is being naming that converse of real-time the get reaction from to recognizing the level of supply chain problem, grope of alternative plan to solving this problem and choosing optimum alternative plan raise the enterprise competitive. But until present, the research to deal with these changes of SCM is on insufficient situation. Thus in this paper proposes the agent system by a way of realizing dynamic supply chain. The agent is going to accomplish the management activities in real-time depends on environment and given condition and designed for solving problems development and maintenance. Also, algorithms performance of the agent is tested on TAC SCM environment. Agents in TAC SCM are simulations of small manufacturers, who must compete with each other for both supplies and customers, and manage inventories and production facilities.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.345-352
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• 2019

The 2015 revised information curriculum emphasizes the ability to solve problems in real life based on the basic concepts, principles and techniques of computer science. How the contents of textbooks are designed is an important issue in terms of achievement of educational goals and whether contents can be easily and clearly communicated. The purpose of this study is to analyze the concept presentation method presented in middle school informatics textbooks by three types of text- centered type, picture-centered type, and case-centered type- to analyze differences in understanding according to individual variables (sex, subject preference). Analysis results found the figure-centered type showed the highest degree of comprehension among students, and the preference of contents design type and the difference of understanding according to sex did not show significant differences. According to the preferred subjects, understanding of the content design types were found to be significantly different according to preferred subjects.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.734-739
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• 2016

The globe valve is a linear motion valve that is designed primarily to stop, start, and regulate flow. The disk of a globe valve can be removed totally from the flow path or it can completely close the flow path. In this study, numerical analysis using ANSYS-CFX was initially performed to predict the flow coefficient and build a prototype model of a globe valve. The flow coefficient is the volume of water at $15.6^{\circ}C$ that will flow per minute through a valve with a pressure drop of 1 psi across the valve. In other words, it is an important factor for determining the size of the valve. From the analysis results, the fluid flux of water and flow coefficient of the valve were extracted. From the numerical results, a prototype of ultra-fine precision control valve, which can regulate the fluid flow of range 0 ~ 0.1 gal per min, was developed. The experimental results were compared with the numerical results using the flow coefficient ($C_v$) graph. From the comparative results, the flow coefficient ($C_v$) error percentage between the numerical and experimental results was very low, which is acceptable, proving that the proposed prototype model is convincing. In addition, it is possible to predict the flow coefficient using only numerical analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.12
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• pp.5420-5429
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• 2011

The study objectively examined the effects on education results from the educational programs developed by adopting competency units of NCS(National Competency Standards)' technology sectors. The objects of the study are divided to learners and instructors. The learners were set bounds to vocational college students to take a degree and incumbent company workers. Research materials had been collected from April of 2010 to June of 2011. We use test papers and structured questionnaire for studying. And we analyzed by SPSS/WIN 17.0. we examined that student's got 1.4 point out of 3 points in their self-test paper before taking classes, below average grades in understanding contents of learning. And as frequency analysis on the after taking classes performance evaluation 62.48% of them answered they can perform their duties in better ways. On average, the company workers got 1.4 point out 3 point before taking classes. And as frequency of analysis on the performance evaluation 85.45% of them answered the can perform their duties in better ways. After instructors took classes on NCS, they gave highly 5.58 out of 7 poins about learners' job competence. On the whole, the educational programs using NCS had positive effects on education results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.4895-4906
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• 2011

The purpose of this study was to find the effect of servant leadership of sports administrator on job satisfaction and organizational citizenship behavior to provide effectiveness management. To accomplish this research objective, as the subjects 333 employees were selected who working at 3 branches of Korea Sports Promotion Organization and Korea Olympic Committee. As for data processing, this research made a frequency analysis, exploratory factor analysis, correlation analysis confirmatory factor analysis, and structural equation model analysis were utilized. The results using structural equation model indicated that servant leadership had directly positive effect on job satisfaction. and servant leadership had directly positive effect on organizational citizenship behavior. In addition, job satisfaction had directly positive effect on organizational citizenship behavior. The implications of the study suggest that sports organization administrator should strengthen servant leadership to build up effectiveness management.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.5
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• pp.566-573
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• 2021

In this study, safety management procedures were developed based on domestic and foreign guidelines and related maritime law to ensure the safe development and implementation of smart autonomous ship technology and Samsung Heavy Industry. The safety management procedure was developed according to the guidelines for (MASS) sea trials (MSC.1/Circ.1604, Annex: Interim guidelines for MASS trials), proposed by International Maritime Organization (IMO) for the relevant authorities and stakeholders of MASS to properly conduct tests of systems and infrastructure related to safety and environmental protection. The developed safety management procedure applies to the maritime demonstration test of a system applying autonomous navigation element technology mounted as a navigation aid on a ship operating under a watch system, while complying with the environmental protection and navigation safety of the coast of Korea.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.7
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• pp.4494-4499
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• 2014

The margin of transient stability of a weak grid system is very low because of the small short-circuit ratio and large impedance. If the fault of the weak grid is cleared by the protection system, one of the major lines is disconnected after the fault is cleared. This further reduces the system strength. Therefore, it is necessary that a new generation system be added to the weak grid to enhance the transient stability margin. A conventional synchronous generator and wind turbine generator were added to a base grid system. The results of transient stability analysis with additional generators using PSSE were compared. The simulations showed that wind turbine generators provide good damping performance and enhance the transient stability margin based on CCT up to 5 times.