• Korean Journal of Materials Research
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• v.19 no.11
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• pp.588-595
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• 2009

The knowledge of grain growth of carbide particles is very important for manufacturing micrograined cemented carbides. In the present study, continuous and discontinuous grain growth in WC-Co and WC-VC-Co cemented carbides is investigated using the Monte Carlo computer simulation technique. The Ostwald ripening process (solution/re-precipitation) and the grain boundary migration process are assumed in the simulation as the grain growth mechanism. The effects of liquid phase fraction, grain boundary energy and implanted coarse grain are examined. At higher liquid phase content, mass transfer via solid/liquid interfaces plays a major role in grain growth. Growth rate of the implanted grain was higher than that of the matrix grains through solution/re-precipitation and coalescence with neighboring grains. The results of these simulations qualitatively agree with experimental ones and suggest that distribution of liquid phase and carbide particle/carbide grain boundary energy as well as contamination by coarse grain are important factors controlling discontinuous grain growth in WC-Co and WC-VC-Co cemented carbides. The contamination by coarse grains must by avoided in the manufacturing process of fine grain cemented carbides, especially with low Co.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.3
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• pp.7-15
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• 2018

Drilling processes require a cutting monitoring function that can be analyzed and gives feedback about strange conditions, tool collision and tool wear in real time. In this study, we proposed a drill monitor using the torque from the main spindle in CNC machine tools and a PROFIBUS network as a PLC-based interface. This paper studied drilling torque changes depending on drill size, the repetition cutting of the drilling and the drill's wear in the same cutting conditions. The material of the drills was high speed steel (HSS) and uncoated. The drills chosen were 2.7 mm, 6.7 mm, and 10.0 mm in diameter. These drills were selected because they had basic holes for their taps.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.3
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• pp.113-118
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• 2017

In this paper, a study on the performance evaluation of a cycloid reducer for remote weapons systems is presented. Reduction gears applied to remote weapons vehicles need to be compact and capable of large torque transmissions as well as require structural optimization, high load capacity, and high precision position control. To meet these requirements, a cycloid reducer with low backlash, high precision, high overload capability, high rigidity, and high efficiency is required. Thus, a cycloid reducer with a reduction ratio of 127:1, backlash of 1 arcmin (1/60 deg) or less, and reduction gear efficiency of 70% or more, which are the design requirements for a remote weapons system, was designed utilizing a design and analysis program (HEXAGON) for gear engineering. To confirm the performance of the cycloid reducer, the hardness of the main components of the manufactured cycloid reducer, reduction ratio, and efficiency were measured.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.3
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• pp.57-62
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• 2020

Concrete pump cars are a type of construction equipment that continuously supplies concrete using hydraulic pressure. When manually casting concrete, there may be a problem in the final quality of the concrete due to differences in the degree of cure between the pre-poured and subsequent concretes. Concrete pump cars are the most efficient machines to supply concrete in the shortest time; however, it is difficult to calculate their margin of safety during operation. In this paper, we verified the structural safety of the concrete pump car using a static/dynamic analysis at various position angles. Next, these results were compared with experimental results; strains using strain gages were compared with the strains measured using FEM software to verify the static analysis. In addition, the maximum displacement during the pumping was measured and it was used for fatigue analysis to evaluate the dynamic structural safety.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.6
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• pp.288-291
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• 2002

We developed a new RF indirect-heating LPE furnace. The thermal gradient of our newly developed furnace is less than that of direct heating, and is as gentle as that of the resistance-heating LPE furnace. With this new furnace, the heating and/or cooling is faster than that of the resistance-heating furnace. Impurity-doped YIG film was grown from a $PbO-B_{2}O_{3}$, based flux on a (111) GGG substrate. To study the effect of the impurities on the MSSW threshold power and the saturation response time, we used two microstrip lines to excite and propagate the MSSW at 1.9 GHz. The MSSW threshold power and saturation response time was found to be related to the $\Delta$H.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.982-986
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• 2005

Digital Manufacturing is a technology to facilitate effective product developments and agile productions by digital environments representing the physical and logical schema and the behavior of real manufacturing system including manufacturing resources, processes and products. A digital virtual factory as a well-designed and integrated environment is essential for successful applications of this technology. In this research, we constructed a sophisticated digital virtual factory by measuring and 3-D CAD modeling using parametric methods. Specific parameters of each objects were decided by object-oriented schema of the digital factory. It is expected that this method is very useful for constructions of a digital factory, and helps to manage diverse information and re-use 3D models.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.12
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• pp.89-96
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• 1998

LOM (Laminated Object Manufacturing) process is one of rapid prototyping processes, where shapes are formed by accumulating cross sections of laser-cut paper. The process expects wide popularity since it is simple and the material is familiar to conventional mockup makers. However the dimensional accuracy of LOM parts is not so good as that of traditional wooden mockups, since the stack of adhesive-spread papers causes significant dimensional error. Also it is unclear how the other unknown environmental effects cause the errors as well. In this work the dimensional errors of LOM parts are measured and analysed. Experiments with test parts were performed in order to see the effects of part shape, moist, and sealer on dimensional variations. The characteristic of the paper is also analysed. Re-heating LOM parts, which is shown to have the effect of recovering dimensional changes, is applied to an example part.

• Management Science and Financial Engineering
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• v.5 no.2
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• pp.1-23
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• 1999

We investigate a supply chain arrangement where a manufacturing company outsources it sassmbly operations to two contract manufacturers. Each contract manufacturer is different in improvement capability : e.g., one is more capable than the other. This improvement capability is supposed to in-duce supply cost reduction that ultimately benefits the manufacturing company. Over time, the manufacturer has to decide how much it should outsource to each contract manufacturer and how much processde/assembled the semi-finished units should be when they re shipped back to the manufacturing company from the contract manufacturers. We employ the optimal control theory to answer the questions, and suggest numerical examples focused on the relationship among the optimal outsourcing amounts, contract manufacturer's improvement capabilities, and their capacity con-straints.

• Proceedings of the CALSEC Conference
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• 2001.08a
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• pp.277-288
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• 2001

Nowadays, for the competitive power of an enterprise, there are many attempts to implement information system that could support business innovation by business process re-engineering. However, there is no effort to standardize the core business processes of enterprise based on standards of data, documents. These facts make it difficult to introduce and implement enterprise information system designed by business processes of the higher level. Therefore, standardization of business process by analyzing the functionality and relationships among them are important and necessary. The results of our research are summarized as process-driven standardization (standardization of core business processes) and development of a repository. In process-driven standardization, we proposed the reference model by analyzing the business processes of the leading enterprises for core business processes. The reference model focuses on core business processes, such as sales management, procurement management, production management, logistics management, and customer support in manufacturing industry. We developed a knowledge-based system as a repository for a integrated management system of business process. And this repository was built up web-based system for the purpose of both reference and management.

• Journal of Korean Institute of Industrial Engineers
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• v.42 no.2
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• pp.80-85
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• 2016

This study suggests a process design using cognitive processes. Job characteristic model for job design and recent cognitive engineering studies for process design are reviewed briefly. By using these concepts, the lean production system is re-interpreted in terms of cognitive engineering and the latent dimensions of the lean production system are revealed as the application of cognitive engineering principles. An integrated process design framework for cognitive manufacturing system using job characteristic model is suggested for the effective design of manufacturing system. Propositions for empirical analysis of this model are also analyzed through a questionnaire survey. Propositions are (1) experiential cognition and motivation potential affect the ability, role perception, and need for achievement of the operator in the manufacturing system, (2) the ability, role perception, and need for achievement of the operator affect the job performance. Both propositions are supported by correlation analysis and path analysis.