• Korean Journal of Materials Research
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• v.9 no.6
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• pp.589-594
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• 1999

The effect of $\beta$-heat treatment on th microstructure, mechanical properties and texture in the nuclear fuel cladding of Zircaloy-4 tubes was chosen at 1000, 1100 and 120$0^{\circ}C$, and the tubes were heat-treated by a high frequency vacuum induction furnace. Morphology of the second phase particles and $\alpha$-grain of as-received tubes were markedly changed by heat treatment. The average sizes of second phase particles of as-received and $\beta$-heat treated tubes were 0.1$\mu\textrm{m}$ and 0.076$\mu\textrm{m}$, respectively. However, the average sizes of second phase particles were not much changed in the $\beta$-heated temperatures. With increasing heat treatment temperatures, the 0.2% yield strength and the hoop strength were decreased because of changes in preferred orientation as will as $\alpha$-plate width. Heat treated Zircaloy-4 tubes exhibited texture changes but the preferred orientation of grains still remained.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.12
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• pp.3804-3821
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• 1996

The configuration optimization is a structural optimization method which includes the coordinates of a structure as well as the sectional properties in the design variable set. Effective reduction of the weight of discrete structures can be obrained by changing the geometry while satisfying stress, Ei;er bickling, displacement, and frequency constraints, etc. However, the nonlinearity due to the configuration variables may cause the difficulties of the convergence and expensive computational cost. An efficient approximation method for the configuration optimization has been developed to overcome the difficulties. The method approximates the constraint functions based onthe second-order Taylor series expansion with reciprocal design variables. The Hessian matrix is approzimated from the information on previous design points. The developed algotithms are coded and the examples are solved.

• Korean Journal of Metals and Materials
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• v.49 no.5
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• pp.367-373
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• 2011

This paper studies the experimental method that uses the homogeneous precipitation method to prepare mica flakes coated with anatase-type titania pearlescent pigment with urea as precipitant. The optimum technology parameters, the chemical composition, the microstructure, and the color property of resulting pigments are discussed. The coating principle of mica coated titania with various coating thickness is analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy(TEM) and tested by spectrophotometer analysis. The colored nanocrystalline pigments with different morphology and coating thickness 45-170 nm were prepared by homogeneous precipitation treatment of $TiOSO_4$(titanum oxysulfate) aqueous solutions. Characterizations on the pigments show that the pearlescent effects of the pigments depend mainly on mica size, thickness of the metal oxide deposit, its chemical composition, and crystal structure.

• Prospectives of Industrial Chemistry
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• v.14 no.3
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• pp.25-36
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• 2011

압축공기 중의 수분은 공압설비의 모든 요소에 중대한 해를 입히며 밸브의 고착, 계기의 막힘 또는 공압기기의 오작동을 일으키며 생산하는 제품의 질에 있어서도 많은 해를 입혀서 제품의 질을 떨어뜨리는 역할을 하게 된다. 따라서 수분을 제거하는 방법이 필요하며 기존의 냉동식 및 흡착식을 대신하여 분리막 법이 적용될 수 있다. 현재 제습용 기체분리막 모듈은 적용이 시작된 단계에 있다. 제습용 기체분리막은 의료기기, 분석기기, Instrument air 장비에 응용이 진행되고 있다. 최근 들어 선진각국 뿐만 아니라 국내에서도 막소재 개발, 복합막 개발, 모듈 개발, 시스템 설계 및 제작 기술 개발이 진행되고 있다. 현재로서는 제습막공정에 적합한 막소재의 개발이 시급하지만 이후 적용확대를 위해서는 제습용 기체분리막의 신뢰성 향상을 위한 다각도의 노력이 필요하다.

• Asia Marketing Journal
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• v.11 no.2
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• pp.173-192
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• 2009

As video games gain popularity and become a normal part of home entertainment, concern about youth access to inappropriate games continues to grow. Some people have claimed that violent video games influence children's aggressive behavior and that violent video games have some responsibility for violence in the school. In response to people's concerns, the video game industry created a video game rating system in 1995 to help parents decide which video games are appropriate for their children. This study investigated whether parents were aware of the video game rating system and how often they have used it when selecting video games for their children. This study attempted to find relationships among parents' attitudes toward video games, their guidance styles for their children's video game play, and their use of the video game rating system. This study found that most parents have used the video game ratings very frequently when they select video games for their children. But many parents still don't understand the video game rating system. This study showed that parents who had more negative attitudes or less positive attitudes toward video games were more likely to impose restrictions on their children's video game play and to use the video game rating system as a means to restrict their children's access to violent video games.

• Archives of Metallurgy and Materials
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• v.64 no.2
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• pp.613-616
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• 2019

The objective of the present research is to develop the novel multi-compaction technology to produce hybrid structure in powder metallurgy (P/M) components using dissimilar Fe-based alloys. Two distinct powder alloys with different compositions were are used in this study: Fe-Cr-Mo-C pre-alloyed powder for high strength and Fe-Cu-C mixed powder for enhanced machinability and lower material cost. Initially, Fe-Cu-C was pre-compacted using a bar-shaped die with lower compaction pressure. The green compact of Fe-Cu-C alloy was inserted into a die residing a half of the die, and another half of the die was filled with the Fe-Cr-Mo-C powder. Then they subsequently underwent re-compaction with higher pressure. The final compact was sintered at 1120℃ for 60 min. In order to determine the mechanical behavior, transverse rupture strength (TRS) and Vickers hardness of sintered materials were measured and correlated with density variations. The microstructure was characterized using optical microscope and scanning electron microscope to investigate the interfacial characteristics between dissimilar P/M alloys.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.5
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• pp.519-525
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• 2010

The finite element (FE) method is generally used to model and simulate the physical behavior of large structures, such as passenger vehicles or aircraft. However, FE analysis involves a very large computation time and cost for developing the analysis model. Therefore, the vibration characteristics of large structural systems are often analyzed using the component mode synthesis (CMS) method, which is one of the substructure synthesis methods. In this study, the vibration characteristics of passenger vehicles are analyzed by using the substructure synthesis method. A passenger vehicle model, which includes a vehicle body, suspension systems, and a sub-frame, is presented. The physical components of the vehicle system are modeled as equivalent substructures using the Craig-Bampton method of CMS. The vibration characteristics, such as the natural frequencies and mode shapes and frequency response, of the vehicle system are determined. The effects of variations in some design parameters on the vibration characteristics of the full vehicle model are also investigated.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.5
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• pp.503-512
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• 2014

People would like to be socially engaged not only with humans but also with robots. One of the most common ways in the robotic field to enhance human robot interaction is to use emotion and integrate emotional concepts into robots. Many researchers have been focusing on developing a robot's emotional expressions. However, it is first necessary to establish the psychological background of a robot's emotion generation model in order to implement the whole process of a robot's emotional behavior. Therefore, this article suggests a robot's motivational emotion model with value effectiveness from a Higgins' motivation definition, regulatory focus theory, and Circumplex model. For the test, a game with the best-two-out-of-three rule is introduced. Each step of the game was evaluated by the proposed model. As the results imply, the proposed model generated psychologically appropriate emotions for a robot in the given situation. The empirical survey remains for future work to prove that this research improves social human robot interaction.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.4
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• pp.26-31
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• 2006

An experimental investigation of an early injection strategy was conducted on a small single cylinder common-rail DI diesel engine to reduce the oxides of nitrogen($NO_x$) emission. The main objectives of this study were to investigate the emissions, performance and combustion characteristics in a diesel engine with early and two-stage injections. The two- stage injection was conducted to reduce the wall-wetting of early injected fuels on the cylinder wall or to promote the ignition of premixed charge. The engine test was performed at conditions of 1500rpm, injection timing ranging from TDC to BTDC $80^{\circ}$. The experimental results show that $NO_x$ emissions were decreased in both cases of early injection and two stage injection compared to the conventional diesel combustion by the near TDC injection. However, soot and products of incomplete products (i.e. HC and CO) are slightly increased. Also, the second injection near TDC promoted the ignition of premixed fuel, therefore, IMEP was increased.

• Journal of Welding and Joining
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• v.24 no.6
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• pp.21-27
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• 2006

This study was focused on the evaluation of the thermo-mechanical board-level reliability of Pb-bearing and Pb-free surface mount assemblies. The composition of Pb-bearing solder was a typical Sn-37Pb and that of Pb-free solder used in this study was a representative Sn-3.0Ag-0.5Cu in mass %. Thermal shock test was chosen for the reliability evaluation of the solder joints. Typical $Cu_6Sn_5$ intermetallic compound (IMC) layer was formed between both solders and Cu lead frame at the as-reflowed state, while a layer of $Cu_3Sn$ was additionally formed between the $Cu_6Sn_5$ and Cu lead frame during the thermal shock testing. Thickness of the IMC layers increased with increasing thermal shock cycles, and this is very similar result with that of isothermal aging study of solder joints. Shear test of the multi layer ceramic capacitor(MLCC) joints was also performed to investigate the degradation of mechanical bonding strength of solder joints during the thermal shock testing. Failure mode of the joints after shear testing revealed that the degradation was mainly due to the excessive growth of the IMC layers during the thermal shock testing.