• Polymer(Korea)
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• v.33 no.1
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• pp.79-83
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• 2009

Thin electric insulation layers were coated on aluminum plates and aluminum condenser cases by plasma polymerization of HMDSO+$O_2$. Electric resistances of the films were higher than 1.0 M$\Omega$ if they are thicker than 0.5 ${\mu}m$ independently of the type of films but their surface morphologies and adhesion strengths were dependent on the process conditions. Deposition rate and adhesion strength of the films were dependent on $O_2$/HMDSO flow ratio and discharge power. The best result was obtained at $O_2$/HMDSO flow ratio of 4 and discharge power of 60 W. Adhesion strength could also be highly improved if aluminum was pre-treated in boiling water for 30 min through the formation of Al-O-Si bonding between the film and the aluminum surface. The coated films showed excellent chemical and thermal resistances.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.736-741
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• 2017

This paper examines the design for improving the wiper system of rotorcraft. During rotorcraft operation, the wiping performance and excessive clearance can decrease. The wiper system consists of a wiper arm assembly, motor, convertor and flex drive. If there is a problem with the wiper system, the operation ability decreases because the operation is restricted in a rainy environment. There are two main causes of the problem of the wiper system: the lifting forces acting on the wiper arm in aircraft flight and the excessive gap of the components. To remedy these two problems, the wiper arm was improved. The improvements included increased contact pressure on the wiper arm (spring tension), improved gear clearance, and material and shape changes. Durability test, aircraft ground test and flight test were carried out to verify the improved shape, and it was confirmed that the wiping performance and clearance problems were solved. Currently, the rotorcraft is operated without problem by applying the improved shape, and this design improvement process will be a useful reference for future rotorcraft development.

• Journal of the Korea Society of Computer and Information
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• v.26 no.11
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• pp.1-9
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• 2021

3D-NAND flash memory provides high capacity per unit area by stacking 2D-NAND cells having a planar structure. However, due to the nature of the lamination process, there is a problem that the frequency of error occurrence may vary depending on each layer or physical cell location. This phenomenon becomes more pronounced as the number of write/erase(P/E) operations of the flash memory increases. Most flash-based storage devices such as SSDs use ECC for error correction. Since this method provides a fixed strength of data protection for all flash memory pages, it has limitations in 3D NAND flash memory, where the error rate varies depending on the physical location. Therefore, in this paper, pages and layers with different error rates are classified into clusters through the K-means machine learning algorithm, and differentiated data protection strength is applied to each cluster. We classify pages and layers based on the number of errors measured after endurance test, where the error rate varies significantly for each page and layer, and add parity data to stripes for areas vulnerable to errors to provides differentiate data protection strength. We show the possibility that this differentiated data protection policy can contribute to the improvement of reliability and lifespan of 3D NAND flash memory compared to the protection techniques using RAID-like or ECC alone.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.4
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• pp.359-365
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• 2019

This paper is a basic study for the performance evaluation, durability improvement and optimal design of tractor transmission. The engine torque of the 78 kW agricultural tractor during rotary tillage was measured using CAN communication. It was calculated with equivalent torque and then analyzed. In order to develop a reliable tractor, it is important to convert measured torque in various agricultural operations into equivalent torque and analyze it. The equivalent torque was calculated using Palmgren-Miner's rule, which is a representative cumulative damage law. The equivalent torque of rotary tillage period and steering period are 229.2 and 136.7 Nm, respectively. The maximum and average torque during rotary tillage period are 336.0 and 234.4 Nm, respectively. The maximum and average torque of the steering period are 288.0 and 134.6 Nm, respectively. The engine torque in rotary tillage period is higher than in the steering period because of cultivation of soil through PTO. The maximum and rated torque of engine are 387.0 and 323.0 Nm, respectively, which are 183% and 136% higher than the equivalent torque during rotary tillage and of steering section. Because transmission of agricultural tractor in Korea companies is generally designed by the rated torque of engine, there is a difference from measured torque during agricultural operations. Therefore, it is necessary to consider it for optimal design.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5A
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• pp.649-656
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• 2008

The enhancement of the service life of damaged or cracked structures is a major issue for researchers and engineers. The hierarchic void element based on the integrals of Legendre polynomials is used to characterize the fracture behaviour of unpatched crack as well as repaired crack with bonded composite patches by computing the stress intensity factors and stress contours at the crack tip. Since the equivalent single layer approach is adopted in this study, the proposed element is necessary to represent a discontinuous crack part as a continuum body with zero stiffness. Thus the aspect ratio of this element to represent the crack should be extremely slender. The sensitivity of numerical solution with respect to energy release rate, displacement and stress has been tested to show the robustness of zero stiffness element as the aspect ratio is increased up to 2000. The stiffness derivative method and displacement extrapolation method have been applied to calculate the stress intensity factors of Mode I problem. It is noted that the proposed hierarchical void element can be one of alternatives to analyze the patched crack problems.

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.371-378
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• 2006

Recently sewage facilities mainly consisted of concrete structures are being deteriorated seriously by biodeterioration originated from sulfur-oxidizing bacteria. In this study, to prevent biochemical corrosion of the sewer concrete, antibiotics which prevent growth of sulfur-oxidizing bacteria were developed and antimicrobial performance of it was investigated. After that, to consider applicability of antibiotics to concrete, physical properties of concrete covered with antibiotics were investigated. As a results of the study, it was proved that the antimicrobial performance of antibiotics was available. Also compressive strength and bond strength of concrete didn't closely connected with antibiotics, and resistance to abrasion, water absorption, air permeability, carbonation, salt damage and chemical attack of concrete was improved remarkably by covering with it.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.773-776
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• 2008

Restraining cracks on concrete structures can be the basic condition to improve the durability, so in this research, the resistibility on the drying shrinkage of concrete structures in the long period was being confirmed and as the reason of this shrinkage, the density of minute textures was being analyzed using a wooden prototype of a full scale produced with ready-mixed concrete and agents of glycol which can be used as a surfactant. As result of those tests, PFB technology can reduce the drying shrinkage by approximately $-100{\sim}200{\times}10^{-6}$ on a wooden prototype of a full scale and can also reduce the pore volume as the obstruction to the movement of gas or liquid by approximately $2.4{\sim}3.5$% so that PFB technology can be used to assure the resistibility on the drying shrinkage.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.137-140
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• 2008

Minimizing the girder number and appling the long span deck of plate girder bridge is the main factors in the practical and economic design of the Twin Steel Girder Bridge. Therefore, it is important to verify the ability of the long span concrete deck. In this paper, to improve the problem, the precast concrete full depth deck has been used instead of cast-in-place concrete deck. The precast concrete full depth deck having longitudinal and transverse prestress is efficient to design of the long span concrete slabs. This paper introduces the design concept of Twin Steel Bridge using the precast concrete full depth deck and applied design case.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.1
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• pp.48-55
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• 2022

This study uses the recovered water as mixing water and artificial lightweight aggregate pre-wetting water as part of a study to increase the recycling rate and reduce greenhouse gas of the ready-mixed concrete recovered during the concrete transport process, and cement fine powder of blast furnace slag(BFS) and fly ash(FA). The engineering characteristics of the three-component lightweight aggregate mortar used as a substitute were reviewed. For this purpose, the flow, dry unit mass, compressive strength, drying shrinkage, neutralization depth, and chloride ion penetration resistance of the three-component lightweight aggregate mortar were measured. When used together with the formulation, when 15 % of BFS and 5 % of FA were used, it was found to be positive in improving the compressive strength and durability of the mortar.

• Clean Technology
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• v.28 no.1
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• pp.24-31
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• 2022

Petroleum-based plastics are used for various purposes and pose a significant threat to the earth's environment and ecosystem. Many efforts have been taken globally in different areas to find alternatives. As part of these efforts, this study manufactured alginate-based polyvinyl alcohol (PVA) blended films by casting from an aqueous solution prepared by mixing 10 wt% petroleum-based PVA with biodegradable, marine biomass-derived alginate. Glutaraldehyde was used as a cross-linking agent, and cardanol, an alkyl phenol-based bio-oil extracted from cashew nut shell, was added in the range of 0.1 to 2.0 wt% to grant antibacterial activity to the films. FTIR and TGA were performed to characterize the manufactured blended films, and the tensile strength, degree of swelling, and antibacterial activity were measured. Results obtained from the FTIR, TGA, and tensile strength test showed that alginate, the main component, was well distributed in the PVA by forming a matrix phase. The brittleness of alginate, a known weakness as a single component, and the low thermal durability of PVA were improved by cross-linking and hydrogen bonding of the functional groups between alginate and PVA. Addition of cardanol to the alginate-based PVA blend significantly improved the antibacterial activity against S. aureus and E. coli. The antibacterial performance was excellent with a death rate of 98% or higher for S. aureus and about 70% for E. coli at a contact time of 60 minutes. The optimal antibacterial activity of the alginate-PVA blended films was found with a cardanol content range between 0.1 to 0.5 wt%. These results show that cardanol-containing alginate-PVA blended films are suitable for use as various antibacterial materials, including as food packaging.