• Advances in materials Research
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• v.11 no.1
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• pp.41-57
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• 2022

This paper is focused on delamination analysis of a multilayered inhomogeneous viscoelastic beam subjected to linear creep under constant applied stress. The viscoelastic model that is used to treat the creep consists of consecutively connected units. Each unit consists of one spring and two dashpots. The number of units in the model is arbitrary. The modulus of elasticity of the spring in each unit changes with time. Besides, the modulii of elasticity and the coefficients of viscosity change continuously along the thickness, width and length in each layer since the material is continuously inhomogeneous in each layer of the beam. A time-dependent solution to the strain energy release rate for the delamination is derived. A time-dependent solution to the J-integral is derived too. A parametric analysis of the strain energy release rate is carried-out by applying the solution derived. The influence of various factors such as creep, material inhomogeneity, the change of the modulii of elasticity with time and the number of units in the viscoelastic model on the strain energy release rate are clarified.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.6
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• pp.803-807
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• 2022

In this study, the battery performance change according to the change of electrolyte flow rate. With increase of electrolyte flow rate the energy efficiency showed tendency of decrease. The electrochemical impedance spectroscopy results showed the increased resistance.

• Korea Real Estate Review
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• v.28 no.4
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• pp.75-88
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• 2018

The purpose of this study is to analyze the effect of the spread on housing mortgage loans. In particular, this study analyzes how the spread has a decisive effect on housing mortgage loans when a structural change occurs in the spread. For the sake of empirical analysis, this study utilizes the housing mortgage loan, housing mortgage loan interest rate, COFIX interest rate, and spread. The period of analysis is from December 2010 to December 2017. Results of the analysis show that there is a statistically significant structural change in the spread and housing mortgage loans (May and June 2015, respectively). It is estimated that the structural change in the spread has an influence on the structural change in housing mortgage loans. In addition, the effect of the spread on housing mortgage loans is larger than the effect of the COFIX interest rate and the housing mortgage loan interest rate. This indicates that the adjustment of the spread is a significant burden on housing mortgage loans. As economic uncertainties both internally and externally are increasing, pressure on interest rate hikes is also increasing. Considering these circumstances, interest rate hikes will be inevitable in the future. If the base interest rate and the spread increase simultaneously at Korea's current economic level, it will obviously lead to an economic recession as the burden on the repayment of principal and interest of housing mortgage loans will increase. Therefore, it is imperative that financial authorities prepare institutional arrangements in order to protect financial consumers by preventing arbitrary calculation of the spread, which would not be objective and would not be transparent from the banks.

• Journal of the Korean Geosynthetics Society
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• v.22 no.3
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• pp.97-103
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• 2023

Recently, research on the lateral resistance of pile foundations has been actively conducted. In experimental studies on the lateral resistance of pile foundations, displacement control or load control methods are used. However, in the case of the displacement control method, the lateral resistance of the pile varies depending on the rate of the load applied to the pile. Therefore, this study seeks to determine the change in lateral resistance of pile foundations according to lateral loading rate through model experiments. The experimental results showed that the lateral resistance of the pile tended to decrease as the lateral loading rate applied to the pile head increased. In order to confirm this, a model experiment of the side change of the ground and pile according to the loading rate was additionally conducted. Through inverse analysis, the change in the depth of the rotation point according to the lateral loading rate was identified. Through the change in the lateral resistance of the pile foundation and the depth of the rotating point according to the lateral loading rate, it was proposed to test the loading rate within 1.5 mm/min during the lateral loading test of the pile.

• International Commerce and Information Review
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• v.7 no.3
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• pp.269-286
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• 2005

The exchange rate volatility has been increased since the time when the floating exchange rate system was introduced in Korea. As a result, the increase of the exchange rate volatility raised the risk in international trades in Korea. The purpose of this study in to study the feature of exchange rate volatility and the main sources of its increase and to confirm whether the exchange rate volatility influence export volume and price of Korea. In the first place, I measured exchange rate volatility with two methods. The one is descriptive statistic method such as the width of daily exchange rate fluctuation and the rate of exchange rate devaluation. The other is the time varying conditional variance of exchange rate. Then, I studied the sources of exchange rate volatility. In the second place, I defined the exchange rate volatility as the time varying conditional variance and estimated it by using elastic a approach model which shows exchange rate is affected by itself and its conditional variance, I estimated its effects on export volumes and prices of electric home appliances, information & communication equal and semi-conductor. The result of this study is as follows. With presumed result EU and Korea because is not the goods which is to substantial competition relationship, The effect where the relative value change of presumed result expression anger and the dollar of import and export function goes mad to the import and export of Korea the income compared to is to export and it is appearing a lot. The EU goods is sold more expensively the Korean goods than from about length being caused by American market of the dollar and the balance of trade of Korea is visible like being visible the improvement of single breadth. Because the relationship of competition is weak but substantially there is to a short term and expression - the effect where the dollar rate fluctuation is big in Korean trade there is a possibility of saying that widely known it is not.

• Nuclear Engineering and Technology
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• v.10 no.2
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• pp.73-78
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• 1978

The effect of temperature and strain rate on the deformation behavior of $\alpha$-uranium was investigated in the temperature ranged 300$^{\circ}$ to 55$0^{\circ}C$ by strain, rate change test. Strain rate sensitivity, activation volume, strain rate sensitivity exponent and dislocation velocity exponent were determined. The strain rate sensitivity exponent and dislocation velocity exponent were determined. The strain rate sensitivity exponent increases with strain below 40$0^{\circ}C$, while the exponent decreases with strain above 50$0^{\circ}C$. It is believed that the increase of strain rate sensitivity exponent with strain below 40$0^{\circ}C$ can be attributed to an increase in internal stress as a result of work hardening while decrease of the exponent with strain above 50$0^{\circ}C$ is due to predominance of thermal softening over work hardening because more slip, system are active in deformation above about 50$0^{\circ}C$.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.32 no.1
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• pp.11-19
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• 2009

A number of trend test methods, i.e., Military Handbook test and Laplace test etc., have been applied to investigate recurrent failures trend in repairable systems. Existing methods provide information about only existence of trend in the system. In this paper, we propose a new change-point test based on the Schwarz Information Criterion(SIC). The change-point approach is more informative than other trend test methods in that it provides the number of change-points and the location of change-points if it exists, as well as the existence of change-point for recurrent failures. The change-point test is applied to nine 300MW generating units operated in East China. We confirm that the change-point test has a potential for establishing optimal preventive maintenance policy by detecting change-point of failure rate.

• Journal of Power System Engineering
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• v.10 no.1
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• pp.90-95
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• 2006

Pneumatic control systems have been mainly used as a high speed operating system. Therefore, state change of air in a control volume was assumed to be adiabatic change and, pneumatic control systems have been analyzed by using this assumption. Especially, when absolute value of pressure change in the control volume is small, there is a tendency to neglect effect of temperature change on pneumatic control system because temperature change owing to pressure change is small. In this study, an effect of temperature change of air on the decompression control process was analyzed by considering change of mass flow rate, and heat transfer characteristics between air in the chamber and the chamber wall. As a result, this study could confirm that a slight temperature change of the air in the pneumatic pressure control system can influence on the dynamic characteristics of pressure response, and pressure control performance.

• The Korean Journal of Health Service Management
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• v.5 no.4
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• pp.127-136
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• 2011

The improving in physical activity of Disability elder is the most important and effective way of prevent and treatment. Especially, It improves ADL(Activities Daily of Living) by decreasing restrictive function and dependence. This study was researched on change by comparing before and after about ADL of Women elders who were instructed self rehabilitation exercise in bedside and have been take that. The whole subjects are 92 persons. Elders aged 65 to 69 are 32 persons. elders aged 70 to 74 are 22 persons 38 persons are over the age of 75. This study shows that the whole subjects have been improved ADL. especially, "Take a bath" in detail items of ADL comes to the most improvement rate. Next, "Sit to stand on the bed and transfer" comes to the second highest rate. According to findings upon the age group. "Take a bath" is also the highest improvement rate. Elders aged 60 to 65 show "Sit to stand on the bed and transfer" is the second highest rate of improvement" and elders aged 70 to 74 show that "control urine" is the second highest rate of improvement. and elders over the age of 75 shows that "sit to stand on the bed and transfer" is the second highest rate of improvement. This study have some problems on having possibilities of results because hospitalized persons have answered imperfect statement and being compare progressed for short term with rehabilitation exercise. so, There are some causes that is early to be generalized.

• Journal of Environmental Science International
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• v.25 no.6
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• pp.799-815
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• 2016

In this study, according to the reference setting based on the runoff video of 9:00 where the highest water level of 3.94 m has been recorded during the runoff of Cheon-mi Stream in Jeju Island by the attack of Typhoon no. 16 Sanba on September $17^{th}$, 2012, the error rate of long-distance and short-distance velocimetry and real-distance change rate by input error have been calculated and the input range value of reference point by stream has been suggested. In the reference setting process, if a long-distance reference point input error occurs, the real-distance change rate of 0.35 m in the x-axis direction and 1.35 m in y-axis direction is incurred by the subtle input error of 2~11 pixels, and if a short-distance reference point input error occurs, the real-distance change rate of 0.02 m in the x-axis direction and 0.81 m in y-axis direction is incurred by the subtle input error of 1~11 pixels. According to the long-distance reference point setting variable, the velocity error rate showed the range of fluctuation of at least 14.36% to at most 76.06%, and when calculating flux, it showed a great range of fluctuation of at least 20.48% to at most 78.81%.