• Journal of the Korean Society for Precision Engineering
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• v.33 no.5
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• pp.419-425
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• 2016

A powder spreading phenomenon is one of disadvantageous characteristics of the powder bed fusion process using electron beams. The powder spreading phenomenon can be controlled using a pre-heating process of metallic powders. The aim of this paper was to investigate the preheating process of Stellite21 powder using electron beams. Powder spreading experiments were performed to examine the influence of process parameters on the spreading behaviors of Stellite21 powder. Powder heating experiments were carried to investigate the effects of the focusing current of the electron beam on the quality of the heated region. Using the results of the powder spreading and heating experiments, an appropriate combination of process parameters was obtained. The pre-heating experiment of Stellite21 was performed using the estimated combination of process parameters. The results of preheating experiments showed that the preheated Stelllite21 layer with desired characteristics can be created when the estimated combination of process parameters is applied.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.526-531
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• 2009

This paper suggests the dehydration and RDF(Refuse Derived Fuel) production of organic sludge, livestock manure and sewerage sludge causing environmental problems, with hydrothermal pre-treatment process. The renewable technology from the organic wastes must involve short treatment time required, reusable energy source, anti-odor and viruses, low cost for the treatment, and well-fertilization. The hydrothermal pre-treatment process promotes to evaporate moisture in the sludge after being shortly treated in a reactor, which is supplied steam and heat by an external boiler, due to the pressure with steam breaks the cell walls of the sludge, so this process removes the internal moisture of the cell. Then, the treated sludge(solid-state) is mixed with waste vinyls called RDF(6,706kcal/kg).

• Proceedings of the Korea Society of Design Studies Conference
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• 2005.10a
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• pp.14-15
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• 2005

• Textile Coloration and Finishing
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• v.23 no.2
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• pp.69-75
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• 2011

A pre-treatment process has been developed for natural dyeing of wool by which the dyed materials have been imparted antimicrobial efficacy against both gram-positive and gram-negative bacteria durable up to 20 washes. In this process, wool fabrics were treated with citric acid under oxidizing condition prior to dyeing. The treated fabrics were then dyed with four different types of natural dye powders obtained from leaves of silver oak, wattle, tanner's senna and flame of forest. All the natural dyes produced yellowish brown colour on wool fabrics. The washing and light fastness properties of the fabrics subjected to pre-treatment were one grade higher compared to those of the dyed fabrics without pre-treatment. The pre-treated wool fabrics showed antimicrobial efficacy against both gram-positive bacteria (Staphylococcus aureus) and gram-negative bacteria (Escherichia coli). The fabrics dyed without pre-treatment showed antimicrobial efficacy against gram-positive bacteria (Staphylococcus aureus) only. The durability of antimicrobial efficacy was higher in pre-treated and dyed wool fabrics compared to the dyed fabrics without pre-treatment.

• Journal of Korean Elementary Science Education
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• v.36 no.4
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• pp.331-345
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• 2017

The purpose of this study is to collect and analyze the student's pre-inquire and to obtain information on how to use the teaching-learning process. The specific research problem is to confirm the level of the student's pre-inquire, to identify the characteristics of each type, and to check what pre-inquire can be used in the teaching-learning process. The research was conducted on 149 children in the $3^{rd}$ and $4^{th}$ grade of elementary school, and collected a total of 2,034 inquires. As a result of analyzing three times, the students' pre-inquires accounted for 90% of Level 2 and Level 3, which are the inquires that give meaningful answers in the teaching-learning process. These results show that the pre-inquires presented before the students take up the new lesson are not low-level inquires and they can present meaningful inquires that can be used for teaching-learning. Next, as a result of analyzing the student's inquire by type, the factual question was the largest with 50%, followed by comprehension question, procedural question, application question, and prediction question. The factual and procedural questions showed that they could be used as learning activities during the teaching-learning process. Comprehension questions included in the wonderment question can be used as a learning question. And the application question is a question that can be applied to deepening activities, and the prediction question can be used in the inquiry and experiment process of learning activities.

• Journal of Welding and Joining
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• v.27 no.6
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• pp.36-42
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• 2009

In the present day, new performances are demanded for automobile body steel sheet for example, light weight, durability, resistance corrosion and environmental protection. For an improvement of resistance corrosion, European automobile companies developed pre-sealed steel in 1990's. Pre-sealed steel have organic coated layer upper zinc coated layer. Evaluating a resistance spot weldability of pre-sealed steel plate is important because resistance spot welding is used mainly in automobile body joining process. In this study, evaluating a weldability of pre-sealed steel plate was carried out using lobe diagram, dynamic resistance and high-speed image. Usually, Pre-sealed steel has poor weldability than GA steel's. To improve a weldability of pre-sealed steel sheet, pre-current was applied to welding process. Pre-current is applied prior to base-current. In conclusion, the weldability of pre-sealed steel has been improved than GA steel's by applying pre-current.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.5
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• pp.655-659
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• 2005

Pre-filter system that was consisted of wasted-tire, non-woven fabrics, and sponge was developed as a primary treatment process prior to rainwater reservation or a pre-treatment process of rainwater reuse system for reclamation. By using this system, SS concentration, TOC, COD, and turbidity could decreased by 86.7%, 62.6%, 69.1% and 66.5%, respectively. From the results of particle size distribution of treated water, the particles over than $30{\mu}m$ of diameter were completely removed by pre-filter system. But 90% of particles less than $20{\mu}m$ of diameter were passed through pre-filter. Optimal depth of wasted-tire and non-woven fabrics were 15cm and 2.4cm, respectively. Pre-filter system was considered as an effective alternative for pre-treatment of rainwater including non-point pollutants and it could be also applied for the treatment of combined sewer overflow (CSO).

• Korean Journal of Computational Design and Engineering
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• v.18 no.6
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• pp.407-416
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• 2013

Acting an important risk management tool for main contractors, pre-qualification has served a key marketing tool for subcontractors in various industries. Current industrial environment has required the time intensive pre-qualification ability to small and medium-size subcontractors as a matter of competitive business. In order to support the subcontractors, this paper proposes a database model for pre-qualification management system (PQMS) that automates the pre-qualification process by using information technologies. The modeling process consists of specifications for its requirements, functional modules, and a database model for the PQMS.

• Journal of Adhesion and Interface
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• v.12 no.3
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• pp.99-104
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• 2011

Currently, automotive pre-primed coatings has been developed to overcome environmental regulations and to reduce manufacturing cost in automotive industry. By these reasons, an automotive pre-primed system has been investigated to remove the wash and pre-treatment process using a roll coating application. It is required to develop non-weldable pre-primed system for automotive structural adhesives, because pre-primed sheet coated with organic compounds is hard to be assembled by welding process. Primer 1 (polyester type) and primer 2 (urethane type) were designed to satisfy flexibility and formability for non-weldable pre-primed system. According to the results of physical property test of the primers, adhesion test such as single-lap shear test and T-peel test, primer 1 (polyester type) had better physical properties such as pencil hardness, solvent resistance, flexibility and adhesion with automotive adhesive than that of primer 2 (polyurethane type). In addition, the possibility of the non-weldable pre-primed system was applicable to automotive assembly process in place of welding process.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1992.10a
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• pp.112-120
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• 1992

The use of Pre-processor for building structural analysis used to rely upon filling up fixed format data, which was ineffective and error-prone. This research attempts to integrate structural analysis system with DBMS and CAD system in order to make it easy to exchange data between pre-process, analysis, and post-process stages. Automatic generation of database from pre-process stage allows easy preparation of main input data for other structural analysis programs. CAD system with some sub-programs written in LISP and C works as a graphic user interface. This approach gives an easy, effective and error-free way of inputing data for structural analysis.