• Journal of Welding and Joining
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• v.18 no.4
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• pp.38-47
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• 2000

Characteristics of the interface between tube and tube sheet which were formed by explosive expansion and roll expansion, have been studied in the research. The results are as follows: Optimum amounts of explosives for the expansion of Alloy 600 (19.05mm and 15.88mm) were found to be RDX 3.5-8.5g/m. Because explosive expansion caused les strain hardening and increased bounding strength, characteristics of the explosively expanded were better than those of mechanically expanded. As the transition region of the explosive expansion is inactive, the resistance to the stress corrosion cracking increases by 30∼40% compared to the roll and hydraulic expansion.

• Asia-Pacific Journal of Business
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• v.9 no.1
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• pp.57-76
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• 2018

This paper studies the influence of the bilateral expansion of Korean and Chinese banks on performance. To conduct the empirical analysis, we select eleven Banks in South Korea and thirteen Banks in China over the 2000-2014 time frame. The main regression results are as followed. First, the sample bank's overseas subsidiaries have a significant effect on profitability and the profitability is somewhat deteriorates. Second, the sample bank's overseas branch and subsidiaries have a significant effect on the bank's risk. That is, the loan loss provision ratio is slightly increased but impaired loan ratio is highly decreased. Third, the sample banks' overseas branch and subsidiaries also have a significant effect on bank efficiency. The ratio of customer deposits per employee worsens somewhat but the gross loan per employee are increased. In conclusion, as time passes, bank profitability or efficiency from mutual expansion of Korean banks and Chinese banks seem to be improving somewhat, and this phenomenon is more prominent at Korean banks than at Chinese banks.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.205-206
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• 2022

This study intends to conduct tests on subsidence and drying shrinkage by mixing CaO-CSA expansion materials to ensure the stability of CLC, and to understand its properties. Based on CLC of 0.6, the replacement ratio of CaO-CSA expansion material was conducted at five levels compared to blast furnace slag, and the results are as follows. The replacement of CaO-CSA expansion material at an appropriate level produces ethringhite and potassium hydroxide, and it is believed that the internal voids of CLC and the Tobelmorite interlayer structure are charged to increase the structural stability, leading to an increase in compressive strength and a decrease in the drying shrinkage. However, it is judged that tissue relaxation due to excessive substances in the high replacement ratio affects the stability of CLC. In the future, we will conduct additional experiments on density, absorption rate, flow test, and settlement, and evaluate and analyze the stability of CLC by selecting the optimal replacement ratio of CaO-CSA expansion materials.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.275-276
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• 2010

In this study, using experimental results on the autogenous expansion of concrete containing MgO, autogenous expansion model which considers water-binder ratio, amount of MgO and curing temperature was suggested. The results predicted by autogenous expansion model agreed well with experiment results.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.337-340
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• 2008

The gate expansion was planed to increase discharge capacity of gate structure at sea dike in Asan Bay. So it was estimated for changing of hydraulic states in Pyeongteak Harbor Zone caused by gate expansion, by 2D and 3D CFD Module. In result, influence of gate expansion was less than tidal current and discharge ratio between old gate and new gate was 4:6.

• Journal of Energy Engineering
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• v.21 no.4
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• pp.411-418
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• 2012

The effect of built-in volume ratio of expander on the performance of a two-loop Rankine cycle system for engine waste heat recovery of vehicle has been investigated. In the case of positive displacement expander in the various operating condition of the vehicle, it can operate in both under-expansion and over-expansion conditions. Therefore, the analysis of off-design performance for the expander is very important. Furthermore, the volume and weight of the expander as well as the efficiency must be considered in the optimization of the expander. This study shows that the built-in volume ratio of expander causing under-expansion at a target condition is more desirable considering the off-design performance and size of the expander, based on the simple modeling of off-design operation of the expander.

• The Journal of Engineering Research
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• v.6 no.2
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• pp.141-151
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• 2004

The physical properties of gold investment materials are depending on it's thermal expansion coefficients, compressive strength, and particles size distributions. Normally the gold investment materials are consisted of cristobalite, quartz and plaster. Since the thermal expansion coefficient of cristobalite and quartz are $2.6\times10^{-6}/^\circC$, $2.32\times10^{-6}/^\circC$, respectively, the composition ratio of each components influence the thermal and clinical properties of gold investment materials. Recently are imported from overseas and the commercial market is expected to expand. Thus it is necessary to develop the optimum strength and compressive strength of gold investment materials which the an homogeneous size distribution and thermal expansion coefficients. Therefore two different experiments has been done. Firstly the homogeneous cristobalite and quartz are made by pulverizing milling. Secondly the compressive strength and thermal expansion coefficients are analysed by the composition ratio of cristobalite and quartz. As a results of experiments, homogeneous distribution of cristobalite and quartz are observed by pulverizing and milling. The optimum compressive strength was obtained at the ratio of 45:25 cristobalite, quartz respectively.

• 한국연소학회:학술대회논문집
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• 1998.10a
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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.

• Polymer(Korea)
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• v.31 no.3
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• pp.206-214
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• 2007

The theoretical study is developed for predicting the thermal expansion changes of composites which include complex inclusion, which is used three-dimensional ellipsoid model ($a_1>a_2>a_3$), which has two aspect ratios (the primary aspect ratio, $\rho_{\alpha}=a_1/a_3$ and the secondary aspect ratio, $\rho_{\beta}=a_1/a_2$). We can predict the feature of general thermal expansion factors by theoretical approach of matrix with aligned ellipsoidal inclusion using the Eshelby's equivalent tensor. The coefficients of longitudinal linear thermal expansion ${\alpha}_{11}$ decrease to those of inclusions, ${\alpha}_f$, as both aspect ratios increase. The coefficients of transverse linear thermal expansion of composites ${\alpha}_{33}$ initially increase and show the parabolic corves with maximum values, as the concentrations of filler increase. The coefficient of thermal expansion, ${\alpha}_{22}$ in the transverse direction decreases, as $\rho_{\alpha}$ increases, however, ${\alpha}_{22}$ increases as $\rho_{\beta}$ increases. The coefficient of linear thermal expansion of composites, ${\alpha}_{33}$ in the normal direction increases, as $\rho_{\alpha}$ increases, while ${\alpha}_{33}$ decreases as $\rho_{\beta}$ increases.

• Journal of Power System Engineering
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• v.18 no.1
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• pp.69-75
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• 2014

The pressure and temperature characteristics of mixed refrigerant gases in bulb for thermostatic expansion valve were studied using R22 refrigerant and $N_2$ gases. The characteristics of mixed refrigerant gases were investigated according to pressure variation and the variation of composition ratio of R22 refrigerant and $N_2$ gases in the temperature range of -$15^{\circ}C$~$15^{\circ}C$. The Maximum operating pressure(MOP) of mixed refrigerant gases were showed a tendency to decrease with decreasing the mixing ratio of $N_2$ gas. The characteristics in the case of the mixing ratio of 90:1 for R22 refrigerant and $N_2$ gases were the same result as Reference refrigerant. In addition, the characteristics of the mixed refrigerant gases in the mixing ratio of 90:1 for R22 refrigerant and $N_2$ gases were showed almost linear in the measurement range of pressure-temperature, and the physical properties also were showed similar results with Reference refrigerant. It was able to confirm that a MOP on the thermostatic expansion valve for sensing bulb can be maintained by adjusting the mixing ratio of R22 refrigerant and $N_2$ gases.