• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.1
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• pp.1-7
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• 2007

In this study, the influence of compressive residual stress and corrosive condition for corrosion fatigue crack was investigated, after immersing in 3.5%NaCl, $10%HNO_3+3%HF,\;6%FeCl_3$. The immersion period was performed for 90days. The fatigue characterization of a spring steel with processed shot peening were performed by considering the several corrosion environments in the range of stress ratio of 0.05 by means of opening mode displacement. By using the methods mentioned above, the following conclusions have been drawn: The fatigue life shows more improvement in the shot peened material than that in the un peened material. And the fatigue life shows improvement in ambient than in corrosion conditions. Threshold stress intensity factor range of the shot peened materials has higher than of the un peened materials. And the threshold stress intensity factor range was decreased in corrosion environments over ambient.

• International Journal of Automotive Technology
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• v.4 no.3
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• pp.109-117
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• 2003

The analysis and evaluation of the transient performance by the transient response specifications under various acceleration speeds and types based on driver's typical acceleration habit are implemented by the experimental study to provide the appropriate direction for the transient control in a gasoline engine. The concept of the transient response specifications which consist of delay time, rising time, maximum overshoot and settling time, and the analysis method using them are introduced to evaluate the characteristics of the transient performance quantitatively. Furthermore four acceleration speeds and four acceleration types are set respectively to realize the various transient states which are similar to the real drive. Several performance parameters in terms of engine speed, manifold absolute pressure, fuel injection duration and air excess ratio are measured simultaneously during the various acceleration using a throttle actuator controlled by a PC. The transient response specifications characterized well the transient performance for the various acceleration speed and types quantitatively. Delay and rising time with increment of the acceleration speed became shorter, but settling time did longer. Intensified acceleration type appeared to be the most economical in view of fuel consumption, and linear acceleration type was found to have the least harmful emission concentration.

• Journal of the Korean Institute of Gas
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• v.7 no.4 s.21
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• pp.53-60
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• 2003

Accident occurred by gas explosion in house or building causes damage on lives and properties. To avoid secondary damage, this study drew area ratio of vent area with the experiment for pressure variation with vent area versus building volume by selection of model for different size and shapes of vent area generated by explosion. In addition, Appropriate model was chosen to predict the damage by minimum pressure with the experiment of opening are shapes. This model can prevent secondary damage with the selected vent area and shape to guarantee building safety.

• Macromolecular Research
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• v.17 no.3
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• pp.156-162
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• 2009

Supramolecular hydrogels were instantaneously fabricated by mixing aqueous solutions of $\alpha$-cyclodextrins ($\alpha$-CDs) and amphiphilic methoxy (polyethylene glycol) (MPEG)-$\varepsilon$-caprolactone (CL) oligomer, which was synthesized via the ring-opening polymerization of the CL monomer using low-molecular-weight MPEG ($M_n$ of MPEG=2,000 g/mol) as an initiator. The supramolecular structure of the hydrogels was revealed by X-ray diffraction (XRD) analyses. Rheological studies of the hydrogels revealed an elastic character when the number of CL units in the oligomer was more than 2, and the obtained hydrogels showed high storage modulus but relatively low shearing viscosity due to the low-molecular-weight character of the oligomer, which was more preferable for use as an injectable delivery system. The physical properties of the hydrogels could be modulated by controlling the chain morphology and concentration of the oligomers, as well as the feed molar ratio of the oligomer to $\alpha$-CD. The components of the supramolecular hydrogels are biocompatible and can readily be eliminated from the body. These features render the supramolecular hydro gels suitable as drug delivery systems and tissue engineering scaffolds.

• Journal of Technologic Dentistry
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• v.43 no.3
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• pp.106-116
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• 2021

Purpose: This is to provide fundamental resources for the improvement in the department of dental technology curriculum which will ensure effective preparation for the license examination for dental technicians as well as improvement in the students practical skills. Methods: Research analysis was conducted regarding the 2020 academic curriculum table of the department of dental technology established in 19 universities nationwide, from 5th of October 2020 to 30th of November 2020. Results: Research of the ratio of the establishment credit of the 3-year-course major in department of dental technology to the establishment credits of the license examination subjects showed, second semester of the first year (p<0.05), by academic discipline the whole first year (p<0.05) and second semester of first year, to be statistically significant. Conclusion: Hence, it can be concluded that there is a need for the management of a curriculum with distribution of adequate subjects according to academic year and semester, in order to satisfy not only the preparation for the license examination for dental technicians, but also students' academic desires.

• Asia-Pacific Journal of Business
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• v.11 no.4
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• pp.243-254
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• 2020

Purpose - This paper explores whether overnight returns measured from the last closing price to today's opening price explain the cross-section of stock returns. Design/methodology/approach - This study is conducted using the Korean stock market data from 1998 to 2018, obtained from DataGuide database. The analysis begins with portfolio-level tests, followed by firm-level cross-sectional regressions. Findings - First, when decile portfolios sorted on the daily average of overnight returns in the previous months, the highest decile portfolio exhibits a significant negative risk-adjusted return. This suggests that stocks with higher average overnight returns are temporarily overvalued due to buying pressure from investors. Second, at least 6 months of persistence exists in average overnight returns, which is in line with the results reported by Barber, Odean and Zhu (2009) that investor sentiment persists over several weeks. Finally, Fama-MacBeth cross-sectional regression of expected returns after controlling for a variety of firm characteristic variables such as firm size, book-to-market ratio, market beta, momentum, liquidity, short-term reversal, the slope coefficient for overnight returns remains negative and statistically significant. Research implications or Originality - Overall, the evidence consistently suggests that overnight return is considered as a new priced factor in the cross-section of expected returns. The findings of this paper not only adds to finance literature, but also could be useful to practitioners in making stock investment decision.

• Current Photovoltaic Research
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• v.8 no.4
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• pp.120-123
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• 2020

Transparent photovoltaics (PV) are used in various applications such as building-integrated photovoltaics (BIPV). However, crystalline silicon (c-Si) is not used for developing transparent PV due to its opaque nature. Here. we fabficate the three holes in 6-inch c-Si solar cells using laser scribing process with an opening area ratio of about 6.8% for transparent c-Si solar modules. Moreover, we make the shingled strings using the perforated cells. Our 7 interconnected shingled string PV cells with 21 holes show a solar to power conversion of 5.721 W. In next work, we will fabricate a transparent c-Si PV module with perforated strings.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.3
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• pp.731-740
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• 2021

This research aims to investigate the determinants of real effective exchange rate in emerging ASEAN countries, including Indonesia, Malaysia, Philippines, Thailand, and Vietnam. The research was conducted by using quarterly time series data set from 1980Q1 to 2020Q3. Cointegration and the error correction model (ECM) methods were applied to test the long run and short run relationship of the real effective exchange rate and its determinants. The results indicate that the ratio of foreign direct investment to GDP and the government spending have significantly positive impact on real effective exchange rate in the Emerging ASEAN countries. The trade opening had influencing real effective exchange rate in most the Emerging ASEAN countries, except Vietnam. In addition, the international reserve (INR) had significant long-run impacts variables on real effective exchange rate in Malaysia, Thailand and Vietnam. In the short run equilibrium, the error collection term suggest that Indonesia and Malaysia are the fastest speed adjustment to equilibrium. In addition, the term of trade influence the real effective exchange rate in Indonesia, Malaysia, and the Philippines but it is not in Thailand and Vietnam. However, FDI is a major factor of the real effective exchange rate in Vietnam, but not for other countries.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.3
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• pp.165-172
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• 2022

Pintle injector is the most suitable injector for thrust control because it can control the area of propellant injection. Accordingly, the combustion test of multiple hole pintle injector and continuous type pintle injector was carried out in this paper using liquid oxygen and gas methane. The combustion performance of the two pintles was verified with the characteristic speed efficiency, and the experimental results were compared according to the O/F and combustion chamber pressure and under similar conditions. The efficiency of the multi hole pintle was generally somewhat higher than continuous pintle when pintle opening distance(the area of dispensing oxidizer) was in a 100% thrust condition.

• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.357-373
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• 2022

The high-temperature gas-cooled reactor pebble-bed module project is the first commercial Generation-IV NPP(Nuclear Power Plant) in China. A new joint is used for the vertical support of RPV(Reactor Pressure Vessel). The steel corbel is integrally embedded into the reactor-cabin wall through eight asymmetrically arranged pre-stressed high-strength bolts, achieving the different path transmission of shear force and moment. The vertical monotonic loading test of two specimens is conducted. The results show that the failure mode of the joint is bolt fracture. There is no prominent yield stage in the whole loading process. The stress of bolts is linearly distributed along the height of corbel at initial loading. As the load increases, the height of neutral axis of bolts gradually decreases. The upper and lower edges of the wall opening contact the corbel plate to restrict the rotation of the corbel. During the loading, the pre-stress of some bolts decreases. The increase of the pre-stress strength ratio of bolts has no noticeable effect on the structure stiffness, but it reduces the ultimate bearing capacity of the joint. A simplified calculation model for the elastic stage of the joint is established, and the estimation results are in good agreement with the experimental results.