• 대한기계학회논문집B
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• 제22권12호
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• pp.1669-1680
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• 1998

A method is developed to include the effect of volume expansion in the description of the flame dynamics using G-equation. Line volume-source is used to represent the effect of the exothermic process of combustion with source strength assigned by the density difference between the burned and the unburned region. The present model provides good agreement with the experimental results. Including volume expansion, the flow field is adjusted to accommodate the increased volume flow rate which crossing the flame front and the result predicts the same behavior of measured velocity field qualitatively. The effect of increasing volume expansion does not change the initial growth rate of flame area but increase the residence time. Consequently this effect increases the maximum area of flame front. The flame propagation in varying flow field due to volume expansion provides a promising way to represent the wrinkled turbulent premixed flames in a numerically efficient manner.

• 센서학회지
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• 제26권5호
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• pp.338-341
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• 2017

We have investigated a temperature sensor on a thermal expansion effect of a fused optical fiber coupler. Both side of the fused tapered region of the coupler were fixed on a metal support to induce the high thermal expansion effect. The sensor showed that the peak coupling wavelengths were shifted to shorted wavelength region with increased of environmental temperature. The sensitivity of the sensor was $0.12nm/^{\circ}C$.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1998년도 제17회 KOSCI SYMPOSIUM 논문집
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• pp.139-154
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• 1998

Under certain circumstance, premixed turbulent flame can be treated as wrinkled thin laminar flame and its motion in a hydrodynamic flow field has been investigated by employing G-equation. Past studies on G-equation successfully described certain aspects of laminar flame propagation such as effects of stretch on flame speed. In those studies, flames were regarded as a passive interface that does not influence the flow field. The experimental evidences, however, indicate that flow field can be significantly modified by the propagation of flames through the volume expansion of burned gas. In the present study, a new method to be used with G -equation is described to include the effect of volume expansion in the flame dynamics. The effect of volume expansion on the flow field is approximated by Biot-Savart law. The newly developed model is validated by comparison with existing analytical solutions of G -equation to predict flames propagating in hydrodynamic flow field without volume expansion. To further investigate the influence of volume expansion, present method was applied to initially wrinkled or planar flame propagating in an imposed velocity field and the average flame speed was evaluated from the ratio of flame surface area and projected area of unburned stream channel. It was observed that the initial wrinkling of flame cannot sustain itself without velocity disturbance and wrinkled structure decays into planar flame as the flame propagates. The rate of decay of the structure increased with volume expansion. The asymptotic change in the average burning speed occurs only with disturbed velocity field. Because volume expansion acts directly on the velocity field, the average burning speed is affected at all time when its effect is included. With relatively small temperature ratio of 3, the average flame speed increased 10%. The combined effect of volume expansion and flame stretch is also considered and the result implied that the effect of stretch is independent of volume release.

• Computers and Concrete
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• 제18권5호
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• pp.937-950
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• 2016

This study applied autoclave expansion and heat curing to accelerate the hydration of concrete and investigated how these methods affect the expansion rate, crack pattern, aggregate size effect, and expansion of electric arc furnace oxidizing slag (EOS)-containing concrete. An expansion prediction model was simulated to estimate the expansion behavior over a long period and to establish usage guidelines for EOS aggregates. The results showed that the EOS content in concrete should range between 20% and 30% depending on the construction conditions, and that coarse aggregates with a diameter of ${\geq}4.75-mm$ are not applicable to construction engineering. By comparison, aggregates with a size of 1.18-0.03 mm resulted in higher expansion rates; these aggregates can be used depending on the construction conditions. On Day 21, the prediction model attained a coefficient of determination ($R^2$) of at least 0.9.

• 한국도로학회논문집
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• 제17권4호
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• pp.19-24
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• 2015

PURPOSES : The objective of this study is to evaluate the effect of the residual mortar of recycled concrete aggregate on the expansion behavior during alkali silica reaction (ASR). METHODS: In order to evaluate the net effect of residual mortar on ASR expansion behavior, two aggregate samples with the same original virgin aggregate source but different residual mortar volumes were used. ASTM C1260 test was used to evaluate the ASR expansion behavior of these two aggregates and the original virgin aggregate. RESULTS: The greater the amount of residual mortar in recycled concrete aggregates, the less is the induced ASR expansion. Depending on the amount of residual mortar in recycled concrete aggregate, the ASR expansion of recycled concrete aggregate may be less than half of that of the original virgin aggregate. CONCLUSIONS: The residual mortar of recycled concrete aggregate may lead to the under estimation of the ASR expansion behavior of the original virgin aggregate.

• 무역학회지
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• 제45권5호
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• pp.303-324
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• 2020

The objective of this study is to verify the effect of the market orientation, CEO capacity, and environmental characteristics of overseas markets on the performance of overseas expansion among the success factors of domestic overseas expansion companies. For this purpose, employees of domestic overseas companies based in the Seoul metropolitan area were surveyed, and the hypothesis test was conducted. As a result of the verification, among the contributors to overseas advancement of domestic overseas companies, the factors of CEO capacity, overseas business_education ability, market environment and market size have a significant positive effect on the financial performance of overseas expansion. However, market-oriented factors were found to have no significant effect on the financial performance of overseas expansion. Among the contributors to overseas advancement of domestic overseas companies, the market-oriented factor, the customer-oriented factor, has a significant positive effect on the non-financial performance of overseas expansion. However, factors in CEO competency and environmental characteristics in overseas markets do not have a significant positive effect on the non-financial performance of overseas expansion.

• 한국전자통신학회논문지
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• 제16권2호
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• pp.347-354
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• 2021

화학공장과 같은 장치산업은 고온·고압·유독성 유체가 배관을 통하여 각종 설비들 사이를 이동한다. 온도변화, 진동, 지진, 지반침하와 같은 주변환경의 변화에 의한 배관의 위치 이동과 파손은 인명피해를 수반하는 큰 사고로 연결되는 경우가 많다. 이러한 사고를 방지하기 위하여 배관에 가해지는 각종 충격을 흡수하고, 보완하여 사고를 미연에 방지하기 위한 여러 가지 종류의 익스펜션 조인트(Expansion Joint)를 사용한다. 따라서 사용된 익스펜션 조인트의 변형을 측정하고, 수명을 예측하는 것은 대형사고를 방지하기 위하여 매우 중요하다. 본 논문에서는 익스펜션 조인트의 변형을 일종의 모션으로 이해하고, Hall Effect Sensor와 9-Axis Sensor를 사용하여 변화를 측정하였다. 그리고 범용의 마이컴보드 아두이노와 C언어를 사용하여 측정된 데이터를 모으고, 분석하여 익스펜션 조인트의 변형을 예측할 수 있는 시스템에 대하여 연구하였다.

• 한국의류산업학회지
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• 제25권6호
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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.

• Physical Therapy Rehabilitation Science
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• 제10권4호
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• pp.430-437
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• 2021

Objective: The purpose of this study was to investigate the effect of 3-dimensional posture correction(3DPC) exercise program incorporating PNF respiratory muscle strengthening(RMS) exercise on spinal alignment and trunk expansion in patients with idiopathic scoliosis and the difference in intervention effect by type of idiopathic scoliosis. Design: Comparative study using paired t-test and analysis of variance measures. Methods: The subjects of this study were 5 men and 24 women diagnosed with idiopathic scoliosis with a Cobb angle greater than 10 degrees and less than 45 degrees. A 3DPC exercise program incorporating PNF RMS exercise was conducted twice a week for 1 hour per session for 6 weeks, and Cobb angle, Angle of trunk rotation, and trunk expansion were measured before and after the intervention. Results: After the intervention, Cobb angle and trunk rotation angle showed a statistically significant decrease, and trunk expansion showed a statistically significant increase. In the effect difference by type, there was a statistically significant difference in the angle of trunk rotation of the thoracic in 3C and Single Lumbar. Conclusions: In conclusion, it is thought that a 3DPC exercise program incorporating PNF RMS exercise can be effectively used in clinical practice to improve spinal alignment and trunk expansion in patients with idiopathic scoliosis.

• 대한전기학회논문지
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• 제41권9호
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• pp.994-1002
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• 1992

With regard to price elasticity and cross elasticity of electricity, optimal generation expansion planning method including load management effect is suggested. In addition, optimal peak time price can be determined simultaneously, and we adopt peak time tariff as load management strategy. Instead of using hourly marginal demand curves where we can get customer surplus, we used chronological load curve with constraints to preserve social welfare. This method is proved useful in short-term generation expansion planning.