• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.1-8
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• 2023

Marine and hydraulic structures are subject to durability damage not only due to the penetration of sea water but also due to the attachment of marine organisms. Therefore, in this study, we tried to develop an antifouling coating agent with self-cleaning function for marine concrete. It was confirmed that the antifouling coating agent mixed with AKD, cellulose nanofibers and BADGE had sufficient antifouling performance at a well hydrophobicity of around 140° in contact angle and an inclination angle of 15°. In the abrasion resistance test of the surface, only a maximum loss of 0.015 g occurred. In the durability test, as a result of the chloride ion permeation test, almost no chloride ion permeation occurred in the variable where the coating agent was applied, and carbonation and freeze-thaw damage also rarely occurred, so it was analyzed that it was effective in securing durability of concrete.

• Tribology and Lubricants
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• v.39 no.6
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• pp.256-261
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• 2023

This study is conducted to evaluate the durability of superhydrophobic surfaces, with a focus on two aspects: contact angle measurement and self-cleaning-performance analysis. Superhydrophobic copper and aluminum surfaces are fabricated using the immersion method and subjected to a rolling wear test, in which a 2 kg weight is placed on a rolling tester, under loaded conditions. To evaluate their durability, the contact angles of the specimens are measured for each cycle. In addition, the surface deformation of the specimens before and after the test is analyzed through SEM imaging and EDS mapping. The degradation of the self-cleaning performance is evaluated before and after the wear test. The results show that superhydrophobic aluminum is approximately 4.5 times more durable than superhydrophobic copper; the copper and aluminum specimens could endure 21,000 and 4,300 cycles of wear, respectively. The results of the self-cleaning test demonstrate that superhydrophobic aluminum is superior to superhydrophobic copper. After the wear test, the self-cleaning rates of the copper and aluminum specimens decrease to 72.7% and 83.4%, respectively. The relatively minor decrease in the self-cleaning rate of the aluminum specimen, despite the large number of wear cycles, confirms that the superhydrophobic aluminum specimen is more durable than its copper counterpart. This study is expected to aid in evaluating the durability of superhydrophobic surfaces in the future owing to the advantage of performing wear tests on superhydrophobic surfaces without damaging the surface coating.

• Tribology and Lubricants
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• v.40 no.3
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• pp.91-96
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• 2024

Recently, extensive studies have been carried out to enhance various performance aspects such as the durability, lifespan, and hardness by combining diverse materials or developing novel materials. The utilization of superhydrophobic surfaces, particularly in the automotive, textile, and medical device industries, has gained momentum to achieve improved performance and efficiency. Superhydrophobicity refers to a surface state where the contact angle when water droplets fall is above 150°, while the contact angle during sliding motion is smaller than 10°. Superhydrophobic surfaces offer the advantage of water droplets not easily sliding off, maintaining a cleaner state as the droplets leave the surface. Surface modification involves two fundamental steps to achieve superhydrophobicity: surface roughness increase and surface energy reduction. However, existing methods, such as time-consuming processes and toxic organic precursors, still face challenges. In this study, we propose a method for superhydrophobic surface modification using lasers, aiming to create roughness in micro/nanostructures, ensuring durability while improving the production time and ease of fabrication. The mechanical durability of superhydrophobic samples treated with lasers is comparatively evaluated against chemical etching samples. The experimental results demonstrate superior mechanical durability through the laser treatment. Therefore, this research provides an effective and practical approach to superhydrophobic surface modification, highlighting the utility of laser treatment.

• Journal of the Korean Operations Research and Management Science Society
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• v.16 no.2
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• pp.51-51
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• 1991

Recently financial institutions in Korea are experiencing an unfamiliar challenge in terms of their operational risk management due to the volatility of global financial market and the incessant development of new financial products. In this paper, we present an AHP(Analytic Hierarchy Process) model to evaluate the effectiveness of commercial softwares for risk management in banking. The AHP model considers software's performance. utility, serviceability and durability as major evaluation criteria. The weight of each criterion is generated by the questionnaire survey given to practitioners in risk management in domestic commercial banks.

• Korean Management Science Review
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• v.16 no.2
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• pp.51-59
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• 1999

Recently financial institutions in Korea are experiencing an unfamiliar challenge in terms of their operational risk management due to the volatility of global financial market and the incessant development of new financial products. In this paper, we present an AHP(Analytic Hierarchy Process) model to evaluate the effectiveness of commercial softwares for risk management in banking. The AHP model considers software's performance. utility, serviceability and durability as major evaluation criteria. The weight of each criterion is generated by the questionnaire survey given to practitioners in risk management in domestic commercial banks.

• Journal of Electrochemical Science and Technology
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• v.15 no.2
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• pp.253-260
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• 2024

Proton exchange membrane water electrolysis (PEMWE) is an efficient method for utilizing renewable energy sources such as wind and solar powers to produce green hydrogen. For PEMWE powered by renewable energy sources, its durability is a crucial factor in its performance since irregular and fluctuating characteristics of renewable energy sources, especially for wind power, can deteriorate the stability of PEMWE. Triangular voltage cycle is well able to simulate fluctuating wind power, but its effect on the durability has not been investigated extensively. In this study, the performance degradation of the PEMWE cell operated with the triangular voltage cycling was investigated at different ramping rates. The measured current responses during the cycling gradually decreased for both ramping rates, and I-V curve measurements before and after the cycling confirmed the degradation of the performances of PEMWE. For both measurements, the degradation rate was larger for 300 mV s^-1 than 30 mV s^-1, and they were determined as 0.36 and 1.26 mV h^-1 (at the current density of 2 A cm^-2) at the ramping rates of 30 and 300 mV s^-1, respectively. The comparison with other studies on triangular voltage cycling also indicate that an increase in the ramping rate accelerates the deterioration of the PEMWE performance. X-ray photoelectron spectroscopy and transmission electron microscopy results showed that the Ir catalyst was oxidized and did not dissolve during the voltage cycling. This study suggests that the ramping rate of the triangular voltage cycling is an important factor for the evaluation of the durability of PEMWE cells.

• Journal of the Korean Society of Safety
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• v.25 no.5
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• pp.39-43
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• 2010

The surfacing of bridge-decks are object to secure trafficability and to protect bridge face from impact load of traffic volume and other external conditions. But the deformation of pavements and cracks happen due to the damage of the bridge-decks surfacing from the increase of the traffic, short maintenance period and continuous vibration of bridge. This test is to make the 3-type high performance concrete that has different mixing ratio and is added the blast furnace slag, fly ash and silica respectively, and to compare 3-type high performance concrete of normal high strength concrete of $400kgf/cm^2$ strength through the static loading test and fatigue test. And test specimen is united floor slab and pavement for the durability of bridge.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.367-370
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• 2015

Building deterioration reflects the degradation of basic building performance including structural performance, energy performance, durability, and safety, and it also includes perceived deterioration, which considers a user-based perspective. More than 50% of the existing buildings in Korea are over 15 years old and public buildings compose 2.5% of all buildings domestically. Therefore, there are several different problems, such as poor energy efficiency, structural performance, and safety. To address the challenges of increasing stock in deteriorated buildings, it is necessary to make decisions about reconstruction or renovation. In this study, we propose a new method to evaluate public building value with a contingent valuation method (CVM). By estimating willing-to-pay (WTP) from users of private buildings in similar situation with the public building, it is possible to compare market prices and calculate a correction factor to adjust the WTP data. Finally, we apply the correction factor to the WTP of a public building and estimate market price, willingness to pay (WTP). Finally, we apply the correction factor to willing to pay (WTP) of public building and estimate market price.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.632-637
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• 1993

Rating systems of bevel gears(straight, spiral, and zerol bevel gears) which are commonly used as power transmission devices for non-parallel axes are developed on the personal computer, which analyze and/or evaluate the gear design and the service performance at the point of view of strength and durability. The typical considerations of the ratings are the bending strength the surface durability, and the scoring resistance. The ratings are carried out using the reliable standards of AGMA & Gleason Works. Therefore, the system is built so that the variables or factors considered differently in those standards and the strength, durability, and scoring partially in Gleason are appraised separatedly by each method, and a series of the estimation processes is integrated into the system so as to compare each result. The developed rating system can be used in the initial stage of gear design process, and also a better design can be performed by the evaluation of the initial design at the view point of gear strength and durability. Additionally, it is useful for the trouble-shooting of bevel gear systems and to the purpose of introducing the methods for maintaining design strength in service with appraising the gear strength after design or with appraising the influencing factors, as a whole. Therefore, this rating systems can help the aim of design automation of bevel gears.

• Nuclear Engineering and Technology
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• v.41 no.8
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• pp.1127-1134
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• 2009

Concrete has three major properties after a penetration-reinforcing agent is applied on its surface. First, the durability is improved by the sol-gel process of synthesized material from the polycondensation of TEOS (tetra-ethoxyorthosilicate) and acrylate monomer. Second, the capability to absorb impact energy is reinforced through the formation of a soft and flexible layer of organic monomers by Tea (Tetra Ethyl Amin). Third, the capability to prevent deterioration is enhanced by adding isobutyl-orthosilicate and alcohol. The performance and application of an agent developed through the synthesis of organic and inorganic material in an effort to prevent concrete from deterioration and improve the durability of concrete structures were verified in diverse experiments. The results of these experiments showed that the application of the proposed penetration-reinforcing agent has the effect of increasing the compressive strength by filling up the internal pores of concrete with physically and chemically stable compounds after penetrating the concrete. It also improves the durability against the deterioration factors such as salt water damage, carbonation, freezing and thawing, and compound deterioration. Therefore, it is confirmed that the penetration-reinforcing agent is a useful substance for the management and repair of concrete structures.