• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.50-53
• /
• 2003

Most companies use technologies such as stereolithography, selective laser sintering, and fused deposition modeling to make parts for such small consumer products as telephones, heads, and shoes. The largest part that the existing RP systems can make is only 600 mm in length. Because most RP systems build parts by depositing, solidifying, or sintering material point-by-point, making larger objects takes a long time. and in many cases, large objects won't fit the build size. A new effective thick-layered RP process. Transfer type Variable Lamination Manufacturing using expandable polystyrene foam (VLM-ST) has been developed with thick layers and sloped surfaces. In this paper, a scaledown model of F16 Fighter with the length of 800 mm is rapidly fabricated using the VLM-ST process. In order to build a CAD model of F16 larger than 600 mm in length, the approach in VLM-ST is to build larger parts in multiple sub-parts and then glue them together. The fabricated result shows that the VLM-ST process employing thick layers and sloped surfaces is adequate for creating the real-sized large objects in the diverse fields such as automobiles, electric home appliances, electronics. and etc.

• 한국해양학회지
• /
• v.29 no.3
• /
• pp.287-295
• /
• 1994

The relationship between temperature profile and backscattering strength(S/SUB y/) computed by the ADCP data is studied in warm eddy of the southwestern parts of the East Sea of Korea in April, 1993. The result shows that S/SUB y/ with depth in N-S direction shows a symmetric shape that is almost the same as the warm eddy. But the profile of S/SUB y/ with depth in N-S direction shows a symmetric shape that is almost the same as the warm eddy. But the profile of S/SUB y/ in E-W direction shows asymmetric shape where the S/SUB y/ of the eastern parts is smaller than that of western parts. The asymmetric distribution may be due to the migration of a large number of scatterer(mainly zooplankton) carried by EKWC(East Korea Warm Current). Profile of the S/SUB y/ is similar to the temperature with depth in the ADCP data of CREAMS 93(Circulation Research of the East Asian Marginal Seas).

• Advances in materials Research
• /
• v.8 no.4
• /
• pp.275-293
• /
• 2019

The engine parts material used in gas turbines (GTs) should be resistant to high-temperature variations. Thermal barrier coatings (TBCs) for gas turbine blades are found to have a significant effect on prolonging the life cycle of turbine blades by providing additional heat resistance. This work is to study the performance of TBCs on the high-temperature environment of the turbine blades. It is understood that this coating will increase the lifecycles of blade parts and decrease maintainence and repair costs. Experiments were performed on the gas turbine blade to see the effect of TBCs in different combinations of materials through the air plasma method. Three-layered coatings using materials INCONEL 718 as base coating, NiCoCrAIY as middle coating, and La₂Ce₂O₇ as the top coating was applied. Finite element analysis was performed using a two-dimensional method to optimize the suitable formulation of coatings on the blade. Temperature distributions for different combinations of coatings layers with different materials and thickness were studied. Additionally, three-dimensional thermal stress analysis was performed on the blade with a commercial code. Results on the effect of TBCs shows a significant improvement in thermal resistance compared to the uncoated gas turbine blade.

• Korean Journal of Medicinal Crop Science
• /
• v.27 no.1
• /
• pp.24-29
• /
• 2019

Background: Camellia sinensis L.(CS) is a perennial evergreen species of plant whose leaves are used to produce tea. In this plant species, the parts used are the leaves, sub-branch parts are thrown out. Methods and Results: Ethanol extract of sub-branch parts was used for isolation of major compounds by column chromatography. Structures were identified as caffeine (1), (-)-epicatechin (2) and (-)-epicatechin gallate (3) by interpretation of spectroscopic analysis, including $^1H$- and $^{13}C$-NMR. High-performance liquid chromatography (HPLC) method was used to compare the quantitative level of marker compounds in various extraction solvents of sub-branch parts of CS. The content of caffeine, (-)-epicatechin, and (-)-epicatechin gallate in 30% ethanol extract showed higher value with $3.28{\pm}0.57mg/g$, $5.53{\pm}0.88mg/g$, and $1.29{\pm}0.24mg/g$, respectively. Conclusions: These results indicated that not only leaves parts but also sub-branch, could be a good source for the functional material and pharmaceutical industry.

• Journal of the Korean Vacuum Society
• /
• v.17 no.3
• /
• pp.175-182
• /
• 2008

This study is concerned with the evaluation of the corrosion resistance of coated semiconductor equipment parts with various processes. To select the appropriate basis for evaluation, replacement parts were observed during the semiconductor manufacturing process. This study also ran a dry corrosion test using $Al_2O_3$, which is mostly used as a coating material. This test quantitatively measured the efficiency of coated parts. Surface morphology, leakage current and breakdown voltage were also evaluated. This study showed that a dry corrosion process led to the drop of electrical properties, for example, the leakage current increase and the dielectric strength decrease. The surface morphology test displayed that surface damage is largely dependent on the exposure time to corrosive environments. By using the values that changed during the corrosion process, it may be possible to contrive a method to evaluate the efficiency of coated parts with various processes.

• Bulletin of the Korean Mathematical Society
• /
• v.61 no.3
• /
• pp.621-635
• /
• 2024

An 𝑙-regular overpartition of n is an overpartition of n with no parts divisible by 𝑙. Recently, the authors introduced a partition statistic called r_𝑙-crank of 𝑙-regular overpartitions. Let M_r𝑙(m, n) denote the number of 𝑙-regular overpartitions of n with r_𝑙-crank m. In this paper, we investigate the monotonicity property and the unimodality of M_r3(m, n). We prove that M_r3(m, n) ≥ M_r3(m, n - 1) for any integers m and n ≥ 6 and the sequence {M_r3(m, n)}_|m|≤n is unimodal for all n ≥ 14.

• The Korean Journal of Elementary Counseling
• /
• v.7 no.1
• /
• pp.67-90
• /
• 2008

The purpose of this study was to examine the effects of solution focused group counseling program on peer relationship and school life adaption of elementary school children. The subjects in this study were the 4th graders at S Elementary School in Ansan, Gyeonggi-do. 20 students were selected through the preliminary test of peer relationship and school life adaption, that is to say, each 10 students of experimental group and control group. A solution focused group counseling program was provided by researcher to the experimental group in six sessions once or twice a week, 60 minutes each. but control group was not conducted for any program. In verifying of the program effects in this study, KOREAN SPSS/WIN(version 12.0) is used for statistical analysis. The major findings of this study are as follows: First, solution focused group counseling program has a positive effect on all parts of sub-factors of peer relationship except to union life between friends. Second, solution focused group counseling program has a effect on the school life adaption of elementary and its all parts of sub-factors except to school rules. As noted above, it is proved that solution focused group counseling program has a positive effect to improve parts of sub-factors of peer relationship and school life adaption. Accordingly, it is necessary to feel satisfaction and Qualitative improvement in peer relationship and help school life adaptation of elementary school children through solution focused group counseling program.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.16 no.3
• /
• pp.38-43
• /
• 2008

The hydroforming technology has been spreaded dramatically in automotive industry last 10 years. Itmay cause many advantages to automotive applications in terms of better structural integrity of the parts, lower cost from fewer part count, material saving, weight reduction, lower springback, improved strength and durability and design flexibility. In this study, the whole process of rear sub-frame parts development by tube hydroforming using steel material having tensile strength of 440MPa grade is presented. At the part design stage, it requires feasibility study and process design aided by CAE (Computer Aided Design) to confirm hydroformability in details. Effects of parameters such as internal pressure, axial feeding and geometry shape in automotive rear sub-frame by hydroforming process were carefully investigated. Overall possibility of hydroformable sub-frame parts could be examined by cross sectional analyses. Moreover, it is essential to ensure the formability of tube material on every forming step such as pre-bending, preforming and hydroforming. In addition, all the components of prototyping tool are designed and interference with press is examined from the point of geometry and thinning.

• Journal of the Korean Society for Precision Engineering
• /
• v.23 no.5 s.182
• /
• pp.51-58
• /
• 2006

The necessities for heightening fuel efficiency as well as lightweight design, lead to an increase of the use of aluminum alloys in the automobile industry. Extruded aluminum profile channels are used widely for the design of frame parts as lightweight assemblies, especially if a high stiffness is needed. While many applications can be realized with forming of hollow square-sectioned extruded profiles such as a stretch bending and a hydro-forming, some applications demand the use of a press bending which can be hardly found in the previous study. In this study, by introducing the use of a press bending into car sub-frames, the demands for higher accuracy as well as higher flexible method than the conventional methods will be satisfied. With respect to the design of sub-frames, the process planning was performed from the shape of a sub-frame product. The designed processes were analyzed by the commercial FEM code, DEFORM-3D. Forming dies for the each process were designed and prototypes of sub-frames were manufactured by the verified farming process. In addition, some of the important features of design parameters in the press bending were reviewed.

• Journal of Powder Materials
• /
• v.10 no.6
• /
• pp.443-447
• /
• 2003

Nano-sized $TiB_2$ was in situ synthesized in copper matrix through self-propagating high temperature synthesis (SHS) with high-energy ball milled Ti-B-Cu elemental mixtures as powder precursors. The size of $TiB_2$ particles in the product of SHS reaction decreases with time of preliminary mechanical treatment ranging from 1 in untreated mixture to 0.1 in mixtures milled for 3 min. Subsequent mechanical treatment of the product of SHS reaction allowed the $TiB_2$ particles to be reduced down to 30-50 nm. Microstructural change of $TiB_2$-Cu nanocomposite during spark plasma sintering (SPS) was also investigated. Under simultaneous action of pressure, temperature and electric current, titanium diboride nanoparticles distributed in copper matrix move, agglomerate and form a interpenetrating phase composite with a fine-grained skeleton.