• Geomechanics and Engineering
• /
• v.18 no.6
• /
• pp.615-626
• /
• 2019

Lightweight concrete (LWC) provides an attractive alternative to conventional piles by improving the durability of deep foundations. In this paper, the drivability of cylindrical and tapered piles made of lightweight and common concrete (CC) under hammer impacts was investigated by performing field tests and numerical analysis. The different concrete mixtures were considered to compare the mechanical properties of light aggregate which replaced instead of the natural aggregate. Driving tests were also conducted on different piles to determine how the pile material and geometric configurations affect driving performance. The results indicated that the tapering shape has an appropriate effect on the drivability of piles and although lower driving stresses are induced in the LWC tapered pile, their final penetration rate was more than that of CC cylindrical pile under hammer impact. Also by analyzing wave propagation in the different rods, it was concluded that the LWC piles with greater velocity than others had better performance in pile driving phenomena. Furthermore, LWC piles can be driven more easily into the ground than cylindrical concrete piles sometimes up to 50% lower hammer impacts and results in important energy saving.

• Corrosion Science and Technology
• /
• v.19 no.6
• /
• pp.310-317
• /
• 2020

This study investigated the damage to the specimen due to liquid droplet impingement erosion corrosion, which improved the corrosion resistance and durability via hard anodization of 5083-H321 aluminum alloy, which is widely used for small ships and marine structures. The experiment combined liquid droplet impingement erosion and electrochemical equipment with the flow rates in natural seawater solution. Subsequently, Tafel extrapolation of polarization curves was performed to evaluate damage due to the liquid droplet impingement erosion corrosion. The damaged surface was observed using a 3D microscope and a scanning electron microscope. The degree of pitting damage was measured using the Image J program, and the surface hardness was measured using the micro-Vickers hardness tester. The corrosion current density, area, depth, and ratio of the damaged areas increased with the increase in flow rate. The grain size of the damaged area at a flow rate of 20 m s-1 showed fewer and minor differences in height, and a smooth curved shape. The hardness of the damaged surface tended to decrease with increase in flow rate.

• Corrosion Science and Technology
• /
• v.21 no.4
• /
• pp.282-289
• /
• 2022

Aluminum 1000 series alloy, a pure aluminum with excellent workability and weldability, is mainly used in the ship field. Aluminum alloy can combine with oxygen in the atmosphere and form a natural oxide film with high corrosion resistance. However, its corrosion resistance and durability are decreased when it is exposed to a harsh environment for a long period of time. For solving this problem, a porous oxide film can be formed on the surface using an anodizing treatment method, a typical surface technique among various methods. In this study, aluminum 1050 alloy was anodized for 2 minutes, 6 minutes, and 10 minutes. The structure and shape of the oxide film were then analyzed to determine the corrosion resistance according to the thickness of the oxide film that changed depending on working condition using 15 wt% NaCl. After it was immersed in NaCl solution for 1, 5, and 10 days, corrosion damage was observed. Results confirmed that the thickness of the oxide film increased as the anodization time became longer. The depth of surface damage due to corrosion became deeper when the film was immersed in the 15 wt% NaCl solution for a longer period of time.

• Corrosion Science and Technology
• /
• v.21 no.6
• /
• pp.514-524
• /
• 2022

Carbon emissions from fuel consumption have been pointed by scientists as the cause of global warming. In particular, fossil fuels are known to emit more carbon when burned than other types of fuels. In this regard, International Maritime Organization has announced a regulation plan to reduce carbon dioxide emissions. Therefore, recently, Liquefied Natural Gas propulsion ships are responding to such carbon reduction regulation. However, from a long-term perspective, it is necessary to use carbon-free fuels such as hydrogen and ammonia. Nitrogen oxides might be generated during ammonia combustion. There is a possibility that incompletely burned ammonia is discharged. Therefore, rather than being used as a direct fuel, Ammonia is only used to reduce NO_X such as urea solution in diesel vehicle Selective Catalyst Reduction. Currently, LPG vehicle fuel feed system studies have evaluated the durability of combustion injectors and fuel tanks in ammonia environment. However, few studies have been conducted to apply ammonia as a ship fuel. Therefore, this study aims to evaluate corrosion damage that might occur when ammonia is used as a propulsion fuel on ships.

• Science of Emotion and Sensibility
• /
• v.25 no.2
• /
• pp.55-70
• /
• 2022

In the 21^st century, the demand for eco-friendly leather, such as eco-leather and vegan leather, is steadily increasing. This study examines the influence of eco-friendliness on consumers' purchasing intentions and the possibility of eco-friendly changes in the fashion accessory market, which is dominated by leather material and leather substitutes. This study administered a questionnaire survey to 227 males and females between 20 and 60 years of age in Korea. With a 5-point Likert scale, data were collected on evaluation criteria when purchasing shoes and bags and purchasing intention of various leather substitute materials according to the democratic variables. The eco-friendliness attitude was divided into eco-consciousness and green behavior. As the eco-friendly attitude increased, most purchasing standards increased, but the purchasing criteria, such as trends, brands, and prices, did not correlate with the eco-friendly attitude. The eco-consciousness of a consumer had a high correlation with the design evaluation criteria, while the green behavior of the consumer aligned with durability and comfort criteria when purchasing a bag. There was a preference for recycled leather, vegetable leather, synthetic leather, and chemical leather, and the fabric type was ranked as natural fiber, biodegradable fiber, and synthetic fiber. Consumers with both green behavior and eco-consciousness are more likely to purchase biodegradable textiles and vegetable leather for the material of shoes and bags.

• Fashion & Textile Research Journal
• /
• v.24 no.6
• /
• pp.775-781
• /
• 2022

As part of research to develop a permanent wave-reducing agent for hair, in the current study, 0.1%-1.0% of Polyquaternium-10 was added to a permanent reagent containing Nicotinoyl Dipeptide-23 to prepare the agent, which was tested on damaged hair. The pH change was relatively stable even after a date, but due to the hair's natural composition, 0.1%-0.6% of the Polyquaternium-10 concentration according to pH was suitable. The temperature safety experiment demonstrated it to be stable at a high temperature and at room temperature, but when a Polyquaternium-10 concentration of 0.9% or higher was added at 0℃, coagulation occurred. In terms of the force efficiency of permanent wave formation, wave efficiency lowered as the concentration increased: the longer the wave lasts, the lower the Polyquaternium-10 concentration. The permanent moisture content was found to be higher as the concentration of Polyquaternium-10 increased. Therefore, when Polyquaternium-10 is applied to the permanent wave-reducing agent, considering stability, permanent formation, durability, and moisture rate, the most suitable concentration was found to be that of Polyquaternium-10 in the cysteine-reducing agent. A novel finding from this study is that as the concentration of Polyquaternium-10 increases, the consistency of the permanent wave-reducing agent changes, shifting from a liquid to a viscous liquid formulation.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2021.05a
• /
• pp.307-308
• /
• 2021

Corrosion of reinforced steel inside concrete is an important cause of performance degradation of reinforced concrete structures and has a profound influence on the durability of structures. In this study, three groups of different reinforced concrete structures exposed to the natural environment were subjected to chloride ion accelerated corrosion tests for up to 180 days. The corrosion velocity and ambient temperature of the samples were measured and recorded every day. Based on Faraday's law, the corrosion speed of steel bars could be measured, and the ambient temperature and humidity around the structure in corresponding time were compared. Through the measurement of up to 180 days, the influence of external ambient temperature and humidity on the corrosion speed of steel bars inside the concrete structure was found out. The results show that there is a good direct proportional relationship between temperature and corrosion speed. When the ambient temperature increases by 15℃, the corrosion rate increases by about one time.

• Journal of Korean Association for Spatial Structures
• /
• v.24 no.2
• /
• pp.53-63
• /
• 2024

The cultural heritage of fortresses is often exposed to external elements, leading to significant damage from stone weathering and natural disasters. However, due to the nature of cultural heritage, dismantling and restoration are often impractical. Therefore, the stability of fortress cultural heritage was evaluated through non-destructive testing. The durability of masonry cultural heritages is greatly influenced by the physical characteristics of the back-fille material. Dynamic characteristics were assessed, and endoscopy was used to inspect internal fillings. Additionally, a finite element analysis model was developed considering the surrounding ground through elastic wave exploration. The analysis showed that the loss of internal fillings in the target cultural heritage site could lead to further deformation in the future, emphasizing the need for careful observation.

• Journal of Life Science
• /
• v.19 no.7
• /
• pp.899-904
• /
• 2009

We purified crude urushiol from natural lacquer produced in Korea, China, and Japan and then isolated several urushiol congeners known to induce allergic reactions. The 3 major kinds of urushiol congeners that were isolated and purified were RV-l (C$_{21}$H$_{34}$O$_2$, M.W. 314.462), RV-2 ((C$_{21}$H$_{32}$O$_2$, M.W. 316.240) and RV-3 ((C$_{23}$H$_{34}$O$_2$, M.W. 342.515), occupying 80% of total crude urushiol. The content of RV-l was the highest in natural lacquer from China at 70.07%, and was the lowest in that from Japan at 62.38%. However, the content of RV-2 in natural lacquer from Japan was 9.25%, 2$\sim$3 times higher than those from Korea (4.28%) and China (3.09%). As an allergy inducing character, RV-l had strong inducing power and durability in the primary stage, showing slow recovery. RV-2 had weak power in the primary stage and also showed slow recovery. Although RV-3 had comparatively weak power at the primary stage, it induced the strongest allergy contact dermatitis after 48 hr. However, it recovered to nearly the same level as control group 72 hr after sensitization time. Accordingly, we found out that RV-1 is the most influential of urushiol congeners in inducing allergic reactions, natural lacquer from China having the most inducible strength and slowest recovery compared to those from Korea and Japan.

• Journal of the Korean Institute of Gas
• /
• v.20 no.6
• /
• pp.23-30
• /
• 2016

The conventional natural gas engine realized lean combustion for the improved efficiency. However, in order to cope with exhaust gas regulations enforced gradually, the interest has shifted at the stoichiometric mixture combustion system. The stoichiometric mixture combustion method has the advantage of a three-way catalyst utilization whose purification efficiency is high, but the problem of thermal durability and the fuel economy remains as a challenge. Hydrogen-natural gas blend fuel (HCNG) can increase the rate of exhaust gas recirculation (EGR) because the hydrogen increases burning speed and lean flammability limit. The increase in the EGR rate can have a positive impact on heat resistance of the engine due to the decreased combustion temperature, and further can increase the compression ratio for efficient combustion. In this study, to minimize the exhaust emission developed HCNG engine with stoichiometric combustion method, developed three-way catalyst was applied to evaluate the conversion characteristics. The tests were carried out during the steady state and transient operating conditions, and the results were compared for both the conventional and proto-three-way catalyst of HCNG engine for city buses.