• Journal of Korean Society of Forest Science
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• v.101 no.1
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• pp.130-137
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• 2012

This study has conducted to develop new gabion wall systems with vegetation base materials for stream bank stability and rapid rehabilitation. Vegetation base materials are primarily compounded with fine soil, organic composts and peat moss as plant fibers, a water retainer and a soil improver. Normally gabion wall systems resist the lateral earth pressures or stream power by their own weight. Therefore, fill material must have suitable weight, compressive strength and durability to resist the loading, as well as the effects of water and weathering. In this project, 100 to 200-mm clean, hard stones are basically specified, and about 50-mm rubbles are also used. Test application of new gabion wall system carried out in the stream bank of a small stream in the Gwangreung experimental forest, belonging to Korea Forest Research Institute (KFRI) in December 16th, 2006. As a result of the analysis of hydraulic stability of new gabion wall system, gabion wall system has highest threshold shear stress when the gabion wall covered by vegetation. New gabion wall system is highly resistant to sliding and overturning because safety coefficients exceed 1.5. As a result of term of slope stability analysis of new gabion wall system by Bishop and Fellenius methods, stability of stream bank was highly increased after the construction of gabion wall. Therefore, new gabion wall system is effective to stabilize unstable stream bank.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.1
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• pp.89-97
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• 2018

The test results of a 7-tonf-class engine for the third-stage engine of KSLV-II are presented. Hot-firing tests performed with two engineering model engines are classified into ground tests and high-altitude tests according to the test conditions. The operability verification of the engines were carried out through short and long duration tests. The full duration test performed for the durability verification of the engines revealed a few of items to be improved. Synthetically, encouraging data of adding power to engine development were obtained from the test results. New engines based on these results will be manufactured and consistently verified through hot-firing tests.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.1
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• pp.75-84
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• 2021

In this study, to evaluate deterioration propagation life and deterioration curve of the shop painted and field re-painted steel bridges, accelerated corrosion tests were carried out on 4 types of heavy-duty painting systems with different surface treatments. The surface treatments prior to painting were examined by hand tool(SSPC SP-2), power tool(SP-3,) or blast cleaning(SP-10) considering shop painting and field re-painting. The paint deterioration curves for each painting system and surface treatment were evaluated based on corrosion propagation from the initial paint defects. From the test results, the paint deterioration life of shop painted and field re-painted system was evaluated and compared by using corrosivity categories and durability performance evaluation of structural steel. The deterioration propagation life of shop and field paint was estimated in 18 to 21 years and 5.3 to 8.0 years with atmospheric corrosion category C4.

• Journal of Aerospace System Engineering
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• v.15 no.3
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• pp.1-10
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• 2021

The electro-hydrostatic actuators (EHA) are widely used in various industrial fields since they can independently execute the function of the hydraulic power source and have high efficiency. Particularly, in the aviation field, the EHA is mainly designed as dual redundant asymmetric tandem actuator to mitigate failure and minimize installation space. However, aviation EHAs designed in the form of dual redundant asymmetric tandem actuator have the disadvantage of decreased durability performance due to the occurrence of force fighting. In this paper, the controller is designed based on backstepping technique to improve control performance and reduce force fighting for aviation EHA. The augmented state observer is proposed to estimate the states required for control. Through simulation, it was verified that the proposed controller had superior control performance and significantly reduces the force fighting compared to the general PI controller.

• Membrane Journal
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• v.32 no.5
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• pp.283-291
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• 2022

Hydrogen energy has received much attention as a solution to the supply of renewable energy and to respond to climate change. Hydrogen is the most suitable candidate of storing unused electric power in a large-capacity long cycle. Among the technologies for producing hydrogen, water electrolysis is known as an eco-friendly hydrogen production technology that produces hydrogen without carbon dioxide generation by water splitting reaction. Membranes in water electrolysis system physically separate the anode and the cathode, but also prevent mixing of generated hydrogen and oxygen gases and facilitate ion transfer to complete circuit. In particular, the key to next-generation anion exchange membrane that can compensate for the shortcomings of conventional water electrolysis technologies is to develop high performance anion exchange membrane. Many studies are conducted to have high ion conductivity and excellent durability in an alkaline environment simultaneously, and various materials are being searched. In this review, we will discuss the research trends and points to move forward by looking at the research on anion exchange membranes based on commercial polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) block copolymers.

• Journal of Powder Materials
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• v.31 no.1
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• pp.16-22
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• 2024

Composite-based piezoelectric devices are extensively studied to develop sustainable power supply and self-powered devices owing to their excellent mechanical durability and output performance. In this study, we design a lead-free piezoelectric nanocomposite utilizing (Ba_0.85 Ca_0.15)(Ti_0.9Zr_0.1)O₃ (BCTZ) nanomaterials for realizing highly flexible energy harvesters. To improve the output performance of the devices, we incorporate porous BCTZ nanowires (NWs) into the nanoparticle (NP)-based piezoelectric nanocomposite. BCTZ NPs and NWs are synthesized through the solid-state reaction and sol-gel-based electrospinning, respectively; subsequently, they are dispersed inside a polyimide matrix. The output performance of the energy harvesters is measured using an optimized measurement system during repetitive mechanical deformation by varying the composition of the NPs and NWs. A nanocomposite-based energy harvester with 4:1 weight ratio generates the maximum open-circuit voltage and short-circuit current of 0.83 V and 0.28 ㎂, respectively. In this study, self-powered devices are constructed with enhanced output performance by using piezoelectric energy harvesting for application in flexible and wearable devices.

• Journal of the Korean association of regional geographers
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• v.22 no.3
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• pp.529-552
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• 2016

The purpose of this study is to examine the matter as to how the meaning of the physical therapeutic landscape by water, which is associated with physical, cultural, spatial, and economical aspects, appears in the space centering on women and is to look into the feminine factors in term of a rest area, consideration, and imagery for women. From a perspective of a rest area for women, the meaning of a physical aspect is remarkable and is materialized in thermal waters and bathing, atmosphere, subsidiary facilities and safe nightlife. According to these phenomena, female visitors are able to feel freedom, power, which can return themselves to the best condition by thermal waters, therapeutic equipments provided in a watering place continuously, safe protection and exchange with strangers with an open mind. And the cultural aspect of the therapeutic landscape by water is discovered in consideration for women. It is the fact that joins the Japanese culture based on consideration towards others to the traditional culture of hot springs by itself. For example, women can feel various pleasure, experience the protection or the support by someone and pursuit not only physical beauty but also mental or spiritual one through welcome bus, service of Okami san and Nakai san, decorations, funny installments and secure of private space. Lastly, the imagery of women can be identified in cultural, spatial, and economical aspects extensively somewhat and is embodied by advertising mediums, signs of hot springs, shrines, objets and products variously. It is made into healthiness, relaxation, comfort, familiarity and image that are realized to love or are connected to a happy marriage life. To sum up the results, the healing or therapeutic elements for women appearing in hot springs are gathered to some abstraction such as freedom, safe, effect beyond the body, pleasure, durability of healing or therapy, beauty and hope; furthermore, if these abstraction are combined each other closely, the effect of healing or therapy, which transforms anxiety into a stable condition, can be exposed externally.