• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.286-304
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• 2017

In this study, we proposed a new-type of circular perforated caisson breakwater consisting of a bundle of latticed blocks that can be applied to a small port such as a fishing port, and numerically investigated the hydraulic characteristics of the breakwater. The numerical method used in this study is OLAFOAM which newly added wave generation module, porous media analysis module and reflected wave control module based on OpenFOAM that is open source CFD software published under the GPL license. To investigate the applicability of OLAFOAM, the variations of wave pressure acting on the three-dimensional slit caisson were compared to the previous experimental results under the regular wave conditions, and then the performance for irregular waves was examined from the reproducibility of the target irregular waves and frequency spectrum analysis. As a result, a series of numerical simulations for the new-type of circular perforated caisson breakwaters, which is similar to slit caisson breakwater, was carried out under the irregular wave actions. The hydraulic characteristics of the breakwater such as wave overtopping, reflection, and wave pressure distribution were carefully investigated respect to the significant wave height and period, the wave chamber width, and the interconnectivity between them. The numerical results revealed that the wave pressure acting on the new-type of circular perforated caisson breakwaters was considerably smaller than the result of the impermeable vertical wall computed by the Goda equation. Also, the reflection of the new-type caisson breakwater was similar to the variation range of the reflection coefficient of the existing slit caisson breakwater.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.180-186
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• 2020

ICT convergence using smart livestock is that in the first-generation dairy smart farm model, each device made by several manufacturers uses its own communication method, limiting the mutual operation of each device. This study uses a model based on open control technology to secure interoperability of existing ICT devices and to manage data efficiently. The open integrated control derived from this process is the software interface structure of Open API. It is an observer that serves as real-time data collection according to the communication method of ICT devices and sensors located at each end. It consists of a broker that connects and transmits to the upper integrated management server. As a result of the performance analysis through verification of two first-generation dairy smart farm model sites, the average daily milk production increased compared to the previous year (farm A 5.13%, farm B 1.33%, p<0.05). Cow days open (DO) was reduced by 17.5% on farm A and 13.3% for farm B(p<0.05). Cows require an adaptation period after the introduction of the ICT device, but if continuous effects are observed, the effect of production can be expected to increase gradually.

• Archives of design research
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• v.19 no.5 s.67
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• pp.55-64
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• 2006

As digital systems were introduced to automotive design in the mid 1980s, the design process has adopted many digital programs to save time compared to the conventional hand drafting. Digital technology was introduced not only to satisfy the reeds of the global environment, as the number of automobiles exported to many different parts of the world has increased, but also to save time and effort in developing several models of quality automobiles. Therefore, every automotive manufacturer in the world has expanded its virtual reality(VR) studio to establish visualization systems that visualize automobiles in the actual size and a co-operation system that enables simultaneous feedback from all of its design studios around the world. Unlike the existing design reviewing methos, the new improved feedback system is assessed as a reasonable method to evaluates and understand how the automobiles are actually manufactured in simulation. It is especially helpful when advanced products and concept cars require fast results. Other strengths of the new system include shorter development period, cost efficiency, no more manual labor, various designs within a short period of time, and realistic visualization of concepts. Large-scale products, including automobiles, need to be projected in the actual size and high clarity through the Power-wall System and are examined in a virtual space called a Cave. Therefore, it took much time to establish digital infrastructure. An infrastructure would constantly require system improvement and performance enhancement, but it is certain that now is the right time for the take-off to utilizing the strengths of digital design and improve the weaknesses. In this respect, this study provided an understanding of the importance of digital design based on digital reinforcements and examined an effective utilization of digital technology for an efficient development of automobiles in the future.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.817-825
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• 2017

The AC-common bus microgrid system can overcome several weaknesses of the DC microgrid system by interconnecting the DC/AC inverters used for renewable energy with an AC network. Nevertheless, the unbalanced loads inherent in the electric power systems of island and small communities can deteriorate the performance of the AC microgrid system. This is because of the limited voltage regulation capability and mixed power flow in the voltage source inverter. In order to overcome the unbalanced load condition, this paper proposes a voltage and current control algorithm for the 4-leg inverter based on the single phase d-q control method, as well as the modeling of the voltage controller using Matlab/Simulink S/W. From the S/W simulation and experiment of the 250KW proto-type inverter, it is confirmed that the proposed algorithm is a useful tool for the design and operation of the AC microgrid system.

• Transactions of the KSME C: Technology and Education
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• v.3 no.3
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• pp.165-173
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• 2015

This paper presents numerical results of static structural stability analysis in development of a vertical transfer device of a PRT(Personal Rapid Transit) vehicle. The vertical transfer of a fully occupied vehicle operating on a road network is the first attempt, which is expected to contribute to overcome the limitations of conventional 2-dimensional operation mode. In particular, the vertical transfer apparatus designed based on vertical circulating conveyors is capable of continuous transfer without time delay so that it enables to accommodate a high traffic density. This system has been frequently used in a logistics field; however, it is essential to assess a structural integrity because an external force by a vehicle weight is exerted on the conveyors in the form of a concentrated load unlike a conventional logistic transport. In this study, prior to the production process, the structural performance of the pilot design in an early stage is numerically evaluated using the commercial finite element method (FEM) solver (i.e., $Ansys^{(R)}$).

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.5
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• pp.554-563
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• 2016

Ships are capable of operating on residual fuel oil. Recently, various attempts have been made to meet environmental regulations and with ships operating on residual fuel oil. One way of fulfilling these requirements is by using fuel additives. Dispersants and fuel combustion improvers will have a positive effect on improving the combustion characteristics of the residual fuel oil. As such, this study examines fuel oils blended with additives by using fuel combustion analysis (FIA/FCA) and thermogravimetric analysis (TGA). The results of FIA/FCA focuse only on the amount of work done by the fuel oil. Therefore, it is recommended in this study that a new method to evaluate the combustion efficiency via FIA/FCA processes be developed. The analysis with ROHR curve gained by FIA/FCA brought similar results with pressure trace curve therefore it can be said that new analysis method can be reliable. The TGA, analysis process is very sensitive to the evaporation of fuel, for example, which could be addressed. In the performance-related findings of this study, blended samples with additives containing iron compounds showed a greater improvement in early combustion characteristics than samples without additives.

• Journal of Energy Engineering
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• v.26 no.3
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• pp.105-112
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• 2017

A lot of piping systems have been used from nuclear power systems to water supply systems. The maintenance of the piping systems is needed to ensure proper operation of the piping systems. Failure of the large pipe systems especially such as KDHC(Korea District Heating Corporation) can be a matter directly related to the enterprise productivity and profitability. It can also lead to very important issues in promoting public safety and convenience. Therefore a method of quick and safety repairs have been emerged as the most important problem. In this study, freezing seal isolation method using liquid nitrogen cryogenic refrigerant was developed for the maintenance of a pre insulated heat transport pipe of KDHC with a diameter of 300 mm. In this study, by employing computational analysis techniques we performed the flow and heat transfer analysis for the targeted pre insulated heat transfer pipe and freezing seal jacket(ice-Plug) and have selected for optimal system. The detailed design model based on the results of the computational analysis finally was produced. A laboratory-scale test apparatus were designed and the freezing seal isolation self-test carried out. Also the performance assessment tests in the test bed of KDHC were carried out for on-site application.

• Journal of the Korean Ceramic Society
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• v.51 no.4
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• pp.271-277
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• 2014

To overcome the limitations of the solid oxide fuel cells (SOFCs) due to the high temperature operation, there has been increasing interest in proton conducting fuel cells (PCFCs) for reduction of the operating temperature to the intermediate temperature range. In present work, the perovskite $BaCe_{0.85-x}Zr_xY_{0.15}O_{3-\delta}$ (BCZY, x = 0.1, 0.3, 0.5, and 0.7) were synthesized via solid state reaction (SSR) and adopted as an electrolyte materials for PCFCs. Powder characteristics were examined using X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Brunauer, Emmett and Teller (BET) surface area analysis. Single phase BCZY were obtained in all compositions, and chemical stability was improved with increasing Zr content. Anode-supported cell with $Ni-BaCe_{0.55}Z_{0.3}Y_{0.15}O_{3-\delta}$ (BCZY3) anode, BCZY3 electrolyte and BCZY3-$Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-\delta}$ (BSCF) composite cathode was fabricated and electrochemically characterized. Open-circuit voltage (OCV) was 1.05 V, and peak power density of 370 ($mW/cm^2$) was achieved at $650^{\circ}C$.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.7
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• pp.900-905
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• 2016

The field of power system harmonics has been receiving a great deal of attention recently. This is primarily due to the fact that non-linear (or harmonic-producing) loads comprise an ever-increasing portion of what is handled at a typical industrial plant. The incidence rate of harmonic-related problems is low, but awareness of harmonic issues can still help increase offshore power plant system reliability. On the rare occasion that harmonics become a problem, this is either due to the magnitude of harmonics produced or power system resonance. This harmonic study used an electrical configuration for the offloading scenario of a Floating LNG (FLNG) unit, considering power load. This electrical network configuration is visible in the electrical network load flow study part of the project. This study has been carried out to evaluate the performance of an electric power system, focusing on the harmonic efficiency of an electrically driven motor system to ensure offshore plant safety. In addition, the design part of this study analyzed the electric power system of an FLNG unit to improve the safety of operation and maintenance.

• Journal of Korean Home Economics Education Association
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• v.31 no.4
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• pp.19-39
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• 2019

The purpose of this study is to explore the main characteristics regarding of implicating competence-based curriculum in Finland's home economics curriculum by analyzing curriculum documents and related literature. The research findings are categorized into four main characteristics. First, home economics in Finland belongs to the 7-9 grades. The key content areas are composed of 'food knowledge & skills and food culture', 'housing & living together' and 'consumer & financial skills' at an integrated approach. Secondly, the subject competences of home economics are not presented; however, the general objectives of transversal competences are defined in Finland's curriculum document. Transversal competences describe the aspects of the objectives that are emphasized in grades 7-9 and strengthens the connectivity with each subject. Thirdly, the objectives of home economics included in the instructions in Finland consist of a content system that links learning skills, content areas, and transversal competences. Both learning skills as a role of subject competences and content areas as objectives support teachers who restructure an curriculum. Fourth, in terms of achieving subject objectives, the assessment criteria in Finland home economics is to evaluate the achievement of good knowledge and skills through actual performance. Based on the research findings, the main features of the revised curriculum in Finland include encouragement of flexibility in education systems and learner's uniqueness in schools. If the implementation of subject competences in home economics is to be strengthened, it is necessary to intergrate the knowledge and competence, require a curriculum system for implements' subject competence, carryout assessment as learning to learn, and facilitate school community and teacher community for deeper co-operation.