• Corrosion Science and Technology
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• v.8 no.6
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• pp.223-226
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• 2009

Polymer coatings are commonly applied to metal substrates to prevent corrosion in aggressive environments such as high humidity and under salt water. Once the polymer coating has been breached, for example due to cracking or scratches, it loses its effectiveness, and corrosion can rapidly propagate across the substrate. The self-healing system we will describe prevents corrosion by healing the damage through a healing reaction triggered by the actual damage event. This self-healing coating solution can be easily applied to most substrate materials, and our dual-capsule healing system provides a general approach to be compatible with most common polymer matrices. Specifically, we expect an excellent anti-corrosion property of the self-healing coatings in damaged parts coated on galvanized metal substrates.

• Smart Structures and Systems
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• v.32 no.3
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• pp.167-177
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• 2023

A probabilistic micromechanical framework is proposed to quantify numerically the self-healing capabilities of polymers containing microcapsules. A two-step self-healing process is designed in this study: A probabilistic micromechanical framework based on the ensemble volume-averaging method is derived for the polymers, and a hitting probability model combined with a crack nucleation model is then utilized for encountering microcapsules and microcracks. Using this framework, a series of parametric investigations are performed to examine the influence of various model parameters (e.g., the volume fraction of microcapsules, microcapsule radius, radius ratio of microcracks to microcapsules, microcrack aspect ratio, and scale parameter) on the self-healing capabilities of the polymers. The proposed framework is also implemented into a finite element code to solve the self-healing behavior of tapered double cantilever beam specimens.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.2110-2112
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• 2000

This paper describes the self healing characteristics of a metalized polypropylene film(MPPF) used for energy storage capacitors. In the experiment, a d.c. voltage was applied to the MPPF, and the partial discharge inception voltages(PDIVs), the applied voltages at self healing, the burn out area and the current in the grounding conductor were measured and recorded. As a result, it was found that no PDs were found till the first pre-self healing occurred, and the applied voltage at self healing was increased with PPF thickness. Self healing was much more dependant on the shape of the air void than its diameter and the burn out area and the current in the grounding conductor at self healing was also increased with the applied voltage at self healing.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.983-986
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• 2006

Self-healing 키 분배 방법은 불안정한 채널에서 규모가 크고 동적인 그룹에 적합하다. 제한된 전력과 컴퓨팅 능력을 가진 다수의 노드들을 기반으로 하는 센서네트워크 환경에서 self-healing 키 분배 방법은 효율적인 키 분배를 제공할 수 있는 접근법이다. 더불어 local collaboration은 같은 그룹에 속한 노드들이 서로 협력하여 그룹 키를 보호하고 침입자에 의해 손상된 노드를 발견할 수 있는 유용한 방법이다. 본 논문에서는 기존의 self-healing 키 분배 방법을 보완하여 센서네트워크 환경에 적용하기 위하여 임의의 변수를 적용한 지역적 협력(local collaboration)을 사용한다. 결과적으로 그룹 단위로 키를 안전하게 분배 및 관리를 할 수 있으며 센서 노드들 간의 통신비용 및 메모리에 대한 효율성 향상을 가져올 수 있음을 실험을 통하여 검증한다.

• Electronics and Telecommunications Trends
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• v.35 no.5
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• pp.30-42
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• 2020

Unlike in previous generations of mobile technology, machine learning (ML)-based self-healing research trend are currently attracting attention to provide high-quality, effective, and low-cost 5G services that need to operate in the HetNets scenario where various wireless transmission technologies are added. Self-healing plays a vital role in detecting and mitigating the faults, and confirming that there is still room for improvement. We analyzed the research trend in self-healing framework and ML-based fault detection, fault diagnosis, and fault compensation. We propose that to ensure that self-healing is a proactive instead of being reactive, we have to design an ML-based self-healing framework and select a suitable ML algorithm for fault detection, diagnosis, and outage compensation.

• Macromolecular Research
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• v.12 no.5
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• pp.478-483
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• 2004

Two different diene monomers [dicyclopentadiene (DCPD) and 5-ethylidene-2-norbornene (ENB)] as self-healing agents for polymeric composites were microencapsuled by in situ polymerization of urea and formaldehyde. We obtained plots of the storage modulus (G') and tan $\delta$ as a function of cure time by using dynamic mechanical analysis to investigate the cure behavior of the unreacted self-healing agent mixture in the presence of a catalyst. Glass transition temperatures (T$\_$g/) and exothermic reactions of samples cured for 5 and 120 min in the presence of different amounts of the catalyst were analyzed by differential scanning calorimetry. Of the two dienes, ENB may have advantages as a self-healing agent because, when cured under same conditions as DCPD, it reacts much faster in the presence of a much lower amount of catalyst, has no melting point, and produces a resin that has a higher value of T$\_$g/. Microcapsules containing the healing agent were successfully formed from both of the diene monomers and were characterized by thermogravimetric analysis. Optical microscopy and a particle size analyzer were employed to observe the morphology and size distribution, respectively, of the microcapsules. The microcapsules exhibited similar thermal properties as well as particle shapes and sizes.

• Polymer(Korea)
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• v.37 no.3
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• pp.356-361
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• 2013

Microcapsules of two different self-healing agents, 5-ethylidene-2-norbornene (ENB) and ENB with a crosslinker, surrounded by a melamine-urea-formaldehyde shell were manufactured. In this work, a red dye was incorporated into the self-healing agents as a tracer for better visual observations. It revealed that the incorporation of a red dye into self-healing agents did not disturb the formation of microcapsules from the examination of thermal resistance, particle size/size distribution and morphology of the resulting microcapsules. Releasing of self-healing liquid into the induced crack from ruptured microcapsules and filling between crack planes were observed using an optical microscope. Also observed was the reaction of filled healing agent with embedded Grubbs' catalyst in an epoxy coating layer.

• Composites Research
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• v.28 no.6
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• pp.395-401
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• 2015

This study investigated the thermal stability of Grubbs' catalyst and its reactivity with self-healing agents for self-healing damage repair. Four types of Grubbs' catalyst supplied by manufacturers were considered and each catalyst was tested in as-received and grinded conditions. Four types of self-healing agents were prepared by varying the mixing ratio of dicyclopentadiene (DCPD) and 5-ethylidene-2-norbonene (ENB). Heat flows as a function of temperature were measured through a differential scanning calorimetry (DSC) to determine the thermal stability of catalysts. Reaction heats of self-healing agents with the catalyst were measured to evaluate the reactivity of the catalyst. For this evaluation, Fluka Chemika Grubbs' catalyst was used based on the maximum temperature and the time to reach the maximum temperature. According to the results, catalysts had different shapes depending on the manufacturer and the results showed that the smaller the size of the catalyst the higher the reactivity with self-healing agents. As the ENB ratio in self-healing agents increased, the maximum temperature increased, and the time to reach the maximum temperature decreased. As the amount of the catalyst increased, the maximum temperature increased, and the time to reach the maximum temperature decreased. Considering the thermal stability of the catalyst and its reactivity with the self-healing agent, combination of 0.5 wt% catalyst and the D3E1 self-healing agent was optimal for self-healing damage repair. Finally, as the thermal decomposition may occur depending on the environmental temperature, the catalyst must not be exposed to temperature higher than that is necessary to maintain the thermal stability of the catalyst.

• Journal of the Korea Concrete Institute
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• v.20 no.1
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• pp.109-116
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• 2008

This study was performed to get information of self-healing mechanism in cement system and the influence of waterproofing admixtures for concrete on self-healing property. For testing, cement paste specimens cured for 7, 14 and 28 days were prepared and crushed into plate-shape pieces. Screened specimens with thickness not more than 1mm were covered with wet rags and cured in a plastic container for 7 and 28 days. After stopping hydration process of the specimens by treatment with acetone, the surfaces of specimens have been contacted with wet rags were analyzed by XRD, DSC, SEM and EDX. The analysis results showed that cement paste has self-healing property and this property is mainly affected by water. Self-healing in cement system is more effective and faster at an early stage of hydration as there is enough content of unreacted cement to make an additional hydration in this period. The results of this study also showed that waterproofing admixtures for concrete have a considerable effect on self-healing of cement pastes; i.e., they improved self-healing effect of cement and, especially, the specimen using admixture C has shown a lot of needle-like or fibrous hydration products which are estimated as ettringite. It is supposed that these ettringite products are effective to enhance self-healing in cement system.

• Journal of the Korea Institute of Building Construction
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• v.16 no.4
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• pp.289-296
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• 2016

In this study, the self-healing effect of a fiber-reinforced cement composite (FRCC) was examined using a drying-wetting test and an outdoor exposure test. The influence of various curing conditions on the self-healing effect of the FRCC was also investigated. The effect of self-healing was evaluated using a permeability coefficient and by investigating the cracks using a optical microscope. The results confirmed that the FRCC was capable of self-healing under a long wetting time and a low drying temperature. In addition, watertight performance by self-healing was shown to have a significant influence on wetting time. Meanwhile, this self-healing effect was enhanced by hydration as a result of rainfall when the FRCC was put under actual environmental conditions. Moreover, it was determined that cracking self-healing can be improved by using the appropriate admixture materials.