• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05b
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• pp.125-129
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• 2004

The mold transformers have been widely used in underground substations in large building and have some advantages in comparison to oil-transformer, that is low fire risk, excellent environmental compatibility, compact size and high reliability. In addition, the application of mold transformer for outdoor is possible due to development of epoxy resin. The mold transformer generally has cooling duct between low voltage coil and high voltage coil. A mold transformer made by one body molding method has been developed for small size and low loss, but it needs some cooling method because heat radiation between each winding is difficult. The life of transformer is significantly dependent on the thermal behavior in windings. Many transformer designers have calculated temperature distribution and hot spot point by FEM(finite element method) to analyze winding temperature rise. In this paper, the temperature distribution and thermal stress analysis of 100kVA pole cast resin transformer for power distribution are investigated by FEM program.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.12
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• pp.1021-1030
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• 2016

The runner system of the injection mould and the injection volume of the injection molding process greatly affect the quality of the produced part. The goal of this paper is the design of the runner system and the prediction of the injection volume for the injection moulding of a housing part of small-size air cleaner to improve the formability through the three-dimensional injection moulding analysis. The effects of the runner system of the mould on the injection moulding characteristics are investigated. From the results of the investigation, a proper design of the runner system with uniform filling characteristics and the minimized defect formation is obtained. In addition, the influence of the moving distance of the screw on filling characteristics, weldline formation and deformation characteristics is examined. From the results of the examination, an appropriate moving distance of the screw for the housing part of small-size air cleaner is estimated.

• Macromolecular Research
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• v.16 no.3
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• pp.253-260
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• 2008

Environmentally friendly biocomposites were made using plant-based natural fibers, such as henequen and kenaf. The natural fiber reinforced polypropylene (PP) and unsaturated polyester (UP) biocomposites were examined in terms of the reinforcing effect of natural fibers on thermoplastic and thermosetting polymers. Kenaf (KE) and henequen (HQ) fibers were treated with an electron beam (EB) of 10 and 200 kGy doses, respectively, or with a 5 wt% NaOH solution. Four types of biocomposites (KE/PP, HQ/PP, KE/UP and HQ/UP) were fabricated by compression molding and each biocomposite was characterized by dynamic mechanical analysis and thermogravimetric analysis. The kenaf fiber had the larger reinforcing effect on the dynamic mechanical properties of both PP and UP biocomposites than the henequen fiber. The highest storage modulus was obtained from the biocomposite with the combination of UP matrix and 200 kGy EB treated kenaf fibers.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.6
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• pp.98-104
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• 2018

Deflected 4-way panels of ceiling air conditioners produced by injection molding process have caused dew condensation at the edge of products. In order to prevent this drawback with reducing weight and deformation, this study proposed renovated process adopting microcellular foaming. According to results from 2-sample t-test and analysis of variance(ANOVA), the critical factors affecting weight were melt temperature and injection speed. In addition, the vital effects on deformation were structure at the edge, mold temperature and cooling time. Optimal conditions of these parameters were derived by regressive analysis with CAE and response surface method(RSM), and then applied to an actual design and process stage to analyze performance. As a results, it clearly showed that new process improved process capability as well as reduced both weight and deformation by 18.8% and 71.9% respectively compared to the conventional method.

• Journal of the Korea Safety Management & Science
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• v.20 no.4
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• pp.1-6
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• 2018

Recently, bicycle has means of effective healthy transportation, and riding the bicycles is considered as popular recreational and sporting activities. Also, the saddle, steering system, driving device and braking device are researched briskly because of consumer's need for driving performance and comfort. Especially, the importance of a cassette responsible for transmission function by transmitting power to the drive shaft through the chain is very focused. The writer conducted structural analysis for the sprocket of each level using the ANSYS widely used for the analysis. Speed shifting performance was enhanced by minimization / simplification of shifting point through a sort of tooth profile of the cassette. By partitioning a clear value type and other shifting point, it has been modified to enable smooth speed-shifting. In addition, as titanium precision forming process, this study studied the molding technique by blanking and dies forging for mass production of the cassette. so it could be expected that the entire drive train would utilize that in the future. The stamping process capability for thin materials for the mass production of the sprockets is applicable to producing automobile parts, so lightweight component production is likely to be possible through that, for the safety of driving.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.4
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• pp.100-106
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• 2022

Topology optimization is applied for the optimal design of various products to ensure weight reduction and productivity improvement. Reducing the weight of the mold while maintaining its rigidity can ensure shortening of the production cycle, stabilization of the mold temperature, and reduction of mold material costs. In this study, a topology optimization technique was applied to the optimal design of the injection mold, and a topology-optimized model of the mold was obtained. First, the injection mold for the square specimens was modeled. Subsequently, a structural analysis was performed by implementing a load condition generated during the injection molding process. Topology optimization was performed based on the structural analysis results, and the models of the initial and topology-optimized designs were manufactured at 1/4 magnification using a 3D printer. Consequently, compared with the existing model, the weight of the topology-optimized model decreased by 9.8%, and the manufacturing time decreased by 7.61%.

• Composites Research
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• v.36 no.4
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• pp.264-269
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• 2023

Spent coffee grounds (SCG) are a ubiquitous byproduct of coffee consumption, representing a significant waste management challenge, as well as an untapped resource for economic development and sustainability. Improper disposal of SCG can result in environmental problems such as methane emissions and leachate production. This study aims to investigate the physicochemical properties of SCG and their potential as a reinforcement material in polypropylene (PP) to fabricate an eco-friendly composite via extrusion and injection molding, with SCG filler ratios ranging from 5-20%. To evaluate the effect of SCG on the morphological and mechanical properties of the bio- composite, thermogravimetric analysis, SEM, tensile, flexural, and impact tests were conducted. The results demonstrated that the addition of SCG lead to a slight increase in brittleness of the composite but did not significantly affect its mechanical properties. Impressively, the presence of a significant organic component in SCG contributed to the enhanced thermal performance of PP/SCG composites. This improvement was evident in terms of increased thermal stability, delayed onset of degradation, and higher maximum degradation temperature as compared to pure PP. These findings suggest that SCG has potential as a filler material for PP composites, with the ability to enhance the material's properties without compromising overall performance.

• Journal of the Korea Convergence Society
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• v.6 no.4
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• pp.1-7
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• 2015

This study is a case study of the research study and education with high school students of natural sciences. Recent development of the Internet of Things (IoT) based on the subject of various studies exist. This study is one of the most portable communication devices of these infancy, yet students were easy to define the molding process of contacting a pager that can go along way in making research topics. We called a pager. Today, it is given a large and complex smart mobile communication devices that can be used for big data. Prior pagers are taught the meaning of the first mobile communication means in our lives were given device. The internal structure is relatively simple and is thought to function relatively simple, just suitable as a teaching practices of high school students with an interest in science and engineering universities. This study can see all of the mechanical, electronic information contents of the radio pager in a relatively simple analysis of the injection molding ONE CAVITY analysis. Furthermore, the students also rated good educational practices that give meaning to remind the convergence training on mass production and process automation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.107-114
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• 2017

A turbocharger is an engine supercharger that is driven by exhaust gas. It improves the output and fuel efficiency by increasing the charging efficiency of the mixture gas, which is achieved by changing the rotatory power of the turbine connected to the exhaust passage. It is important to control the supercharging for this purpose. A nozzle slide joint is one of the core parts. Austenitic stainless steel is currently used as the material for this part, and its excellent mechanical properties include high heat resistance and corrosion resistance. However, because of its poor machinability, there are many difficulties in producing products with complicated shapes. Machining is used in the production of nozzle slide joints for high dimensional accuracy after metal powder injection molding. As design variables in this study, we investigated the sintering temperature, product stress, deformation rate, radius of curvature of the punch, and angle of the chamfer punch, which are related to the strain and shapes. The goal is to suggest a forming process using Nitronic 60 that does not require machining to manufacture a nozzle slide joint for a turbocharger. Accordingly, we determined the best process environment using finite-element analysis, the signal-noise ratio, and the Taguchi method for experiment design. The relative density and hydrostatic pressure of the final product were in accordance with the results of the finite element analysis. Therefore, we conclude that the Taguchi method can be applied to the design process of metal powder injection molding.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.7 no.2
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• pp.196-208
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• 1997

This study was performed to estimate quartz contents in the both bulk and airborne dust samples and to determine particle size distribution of airborne dust from the selected foundry operations. Total dust samples were collected by a 37mm cassette and respirable by a 10 mm nylon cyclone. Particle size distributions were determined by a Marple's 8-stage cascade impactor at the melting, molding, shakeout and finishing operations. The presence of elements in the dust samples were confirmed by the scanning electron microscopy equipped with the energy dispersive x-ray spectrometry. The quartz contents were estimated using the intensity of the absorption peak of quartz at 799 cm-l by the Fourie Transformed Infrared Spectroscopy (FTIR). The results were as follows: 1. The analysis of data from cascade Impactor showed bimodal distributions of particle size at the melting, molding and shakeout operations. Mass median aerodynamic diameters for the distributions determined by histogram were $0.48-1.65{\mu}m$ for small and $13.43-19.58{\mu}m$ for large modes. In the dust samples collected at the finishing operations, however, only a large mode of $18.89{\mu}m$ was found. 2. The percentages of total to respirable dust concentration calculated from the impactor data ranged from 42 % to 66 %. The average concentrations of respirable dust by cyclone were $0.85-1.28mg/m^3$ collected from the workers, and were $0.23-0.56mg/m^3$ from the areas surveyed. Dust concentrations of personal samples were statistically significantly higher than those of area samples. The highest dust concentration was obtained from the personal samples of the finishing operation. 3. The mean percentages of silicon and oxygen estimated by SEM-EDXA in the bulk samples ranged from 35.83 % to 36.02 % and from 39.93 %-41.64 %, respectively. 4. The average quartz contents estimated by FTIR in the respirable dust from personal samples ranged from 4.32 % to 5.36 % and 4.54 % to 4.70 % in the bulk samples. No statistical difference of quartz content was found between foundry operations. In this study, quartz content was quantified by FTIR. Although no statistically significant difference in quartz content between airborne and bulk, samples and between different foundry operations was found, it is recommended that quartz content in the individual sample of respirable dust be analyzed and the results be used either to select an applicable quartz limits or to calculate the exposure limit. Further studies, however, are needed to compare the results by FTIR and XRD since it is reported that the quartz content determined by FTIR is different from that by XRD.