• Proceedings of the KSME Conference
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• 2000.04b
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• pp.335-340
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• 2000

A 3 valve-type pulse tube refrigerator optains its cooling effect from pressure drop by releasing the part of the charged gas through hot end nozzle. The objective of this study is to analyze the performance and to find an optimal expansion pressure of the 3 valve-type pulse tube refrigerator. It is assumed that gas lumps are not mixed and periodically repeat the adiabatic compression and expansion processes. And the nodal model is applied for the analysis of the regenerator. As the result of analysis, the optimum pressure at the end of expansion process was about 80-90% of the maximum pressure.

• Transactions of Materials Processing
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• v.30 no.2
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• pp.74-82
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• 2021

Stretch-flangeability, which is the ability of sheet steels to be deformed into complex shapes, is a critical formability property in automobile body parts. In this study, the center-hole for hole expansion test, which is normally used to evaluate the stretch-flangeability of sheet steels, was prepared by both punching and electrical discharge machining (EDM) methods. Hole expansion ratio (HER) of punched hole was far lower than the HER of EDM drilled hole because of damage/crack in hole-edge due to punching process. The effect of hole-edge condition on HER was quantified by mechanical, fractographic and geometric factors. Based on these factors, the empirical equation used to determine HER for various sheet steels was derived using non-linear regression.

• Journal of the Korean Institute of Telematics and Electronics
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• v.17 no.1
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• pp.1-9
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• 1980

In this paper several basic techniques for signal processing and analysis are surveyed. Firstly by the intervention of the uncertainty principle, an equality sign may have different degree of precision if non commutable operators are applied. Seconds y maximum entropy estimate and randam process based viewpoint must be enhanced to get rid of the well established and reigning deterministic image of science. Thirdly techniques for the analysis of a signal namely detection. ess]motion and modulation are explained as well as the positive definiteness of a covariance function, Karhunen-Loeve expansion and SVD of an image.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.613-618
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• 2002

Steel slag produced in steel making process is divided with electric arc furnace slag and converter slag. Compared with the blast furnace slag, converter slag has the expansibility due to the reaction with water and free CaO. Therefore it is specified in Standard Specification for Concrete in Korea that steel slag aggregate must not be used in concrete. In this study, we treat electric arc furnace slag aggregate(EAFSA) for concrete before and after several aging process to reduce expansibility. The fundamental properties are measured, which are specific gravity, unit weight, abrasion value and immersion expansion ratio, as concrete aggregate. To understand the suitability of EAFSA for concrete, we made the concrete with EAFSA and then determined the strength and the volume change in EAFSA concrete. From the results EAFSA treated with steam aging process has potentiality for concrete aggregate.

• Journal of the Korean Mathematical Society
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• v.54 no.1
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• pp.193-213
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• 2017

We investigate an efficient approximation of solution to stochastic Burgers equation driven by an additive space-time noise. We discuss existence and uniqueness of a solution through the Orstein-Uhlenbeck (OU) process. To approximate the OU process, we introduce the Karhunen-$Lo{\grave{e}}ve$ expansion, and sparse grid stochastic collocation method. About spatial discretization of Burgers equation, two separate finite element approximations are presented: the conventional Galerkin method and Galerkin-conservation method. Numerical experiments are provided to demonstrate the efficacy of schemes mentioned above.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.116-119
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• 2007

The application of light weight materials, such as aluminum alloy, has been limited due of their poor formability. Especially, aluminum alloy tube has limited expansion capability at most 15% at room temperature. New manufacturing process, called hot air forming, is introduced to apply aluminum tube to the automotive suspension components which have complex shape and require high expansion ratio about 40%. The process is carried out at the elevated temperature above $500^{\circ}C$, so numerous material properties and process parameters related to the high temperature should be investigated and determined to get a sound product. In this study, the effect of thermal properties and forming parameters such as the temperature of tool, axial feeding and gas pressure are analyzed by using explicit finite element method.

• The Mathematical Education
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• v.54 no.4
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• pp.365-383
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• 2015

Factorization asks the recognition of the structure of polynomials, compared to polynomial expansion with process characteristic. Therefore it makes students experience a lot of difficulties. This study aims to figure out causes of the difficulties by identifying students' cognitive characteristics in factorizing in the perspective of 'structure sense'. To do this, we gave six factorizing problems of three types to middle school students and selected six participants as interviewees based on the test results. They were classified into two categories, structure sense and non-structure sense. Through this interview, we figured out the interviewee's cognitive characteristics and the causes of difficulty in the perspective of structure sense. Furthermore, we suggested some didactical implications for encouraging structure sense in factorizing by identifying assistances and obstacles for recognition of structures.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1626-1631
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• 2007

The purpose of the study is to simulate the displacement of the LCD glass during process of a large size imprint. During this process, a small temperature variation makes thermal stress, which causes the horizontal variation of mold and glass. During alignment process to fix the LCD glass on a alignment stage, the vertical displacement is made by the absorption pressure and the shear stress. This study simulates the horizontal displacement of mold and glass due to temperature variation, the vertical displacement depending on the shape of absorption surface fixing the LCD glass in the alignment process, and the horizontal and vertical displacement which occurs in the LCD glass at the alignment process. Algor which is a FEM code for a framework simulation was applied. Temperature variation above ${\pm}$ $0.1^{\circ}C$ on mold and glass causes the horizontal displacement of 150nm due to thermal expansion. The vertical displacement due to the circular is ten times of the case of rectangular absorption nozzle. The displacement of the LCD glass in the alignment process is about 49nm.

• Archives of Plastic Surgery
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• v.47 no.5
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• pp.419-427
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• 2020

Background This study evaluated the Blossom system, an innovative self-filling, rate-controlled, pressure-responsive saline tissue expander (TE) system. We investigated the feasibility of utilizing this technology to facilitate implant-based and combined flap with implant-based breast reconstruction in comparison to conventional tissue expansion. Methods In this prospective, single-center, single-surgeon pilot study, participants underwent either implant-based breast reconstruction or a combination of autologous flap and implantbased breast reconstruction. Outcome measures included time to full expansion, complications, total expansion volume, and pain scores. Results Fourteen patients (TEs; n=22), were included in this study. The mean time to full expansion was 13.4 days (standard error of the mean [SEM], 1.3 days) in the combination group and 11.7 days (SEM, 1.4 days) in the implant group (P=0.78). The overall major complication rate was 4.5% (n=1). No statistically significant differences were found in the complication rate between the combination group and the implant group. The maximum patient-reported pain scores during the expansion process were low, but were significantly higher in the combination group (mean, 2.00±0.09) than in the implant group (mean, 0.29±0.25; P=0.005). Conclusions The reported average duration for conventional subcutaneous TE expansion is 79.4 days, but this pilot study using the Blossom system achieved an average expansion duration of less than 14 days in both groups. The Blossom system may accommodate single-stage breast reconstruction. The overall complication rate of this study was 4.5%, which is promising compared to the reported complication rates of two-stage breast reconstruction with TEs (20%-45%).

• Fashion & Textile Research Journal
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• v.25 no.6
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• pp.704-714
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• 2023

This study explores how avatar customization influences the continuous intention to use the metaverse, mediated by self-expansion. The moderating effects of self-efficacy between avatar customization and self-expansion are also explored. Data were collected through an online survey using consumer panels. Participants were Zepeto users aged 18 or older who had used the platform within the previous six months. They were asked to recall a recent shopping experience of exploring the virtual fashion store via Zepeto. A total of 196 valid responses from participants were analyzed using SPSS 26.0 for descriptive statistics, reliability analysis, and PROCESS procedure, and AMOS 23.0 for confirmatory factor analysis. Results demonstrate that avatar customization increases continuous intention to use the metaverse; this effect is mediated by self-expansion. The moderated mediation effect of self-efficacy in the indirect path was significant and mediated by self-expansion. Specifically, the interplay effect of avatar customization and self-efficacy on self-expansion was statistically significant. For participants with high self-efficacy, avatar customization increases self-expansion, and it mediates the relationship between avatar customization and the continuous intention to use the metaverse. Findings contribute to expanding the literature on metaverse usage by testing the impact of avatar customization on self-expansion.