• Title, Summary, Keyword: Self-healing

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The Characteristics and Growth Mechanisms of Demetallization due to Self Healing on MPPF for Capacitor Applications

  • Jung, Jong-Wook;Kwak, Hee-Ro
    • KIEE International Transactions on Electrophysics and Applications
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    • v.4C no.3
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    • pp.117-122
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    • 2004
  • In order to help understand the growth mechanisms of demetallization due to self healing on a metallized polypropylene film (MPPF), several types of defects affecting the breakdown of capacitor dielectrics were made. The breakdown voltages with dielectric thickness were measured at self healing and the demetallized area was evaluated for all of the self healing events. The shapes and growth processes of the demetallized spots on the dielectrics were investigated. As a result, self healing mainly occurred at pin tips, wrinkle sides, and junctions of the wrinkles, and the breakdown voltages strongly depended on the thickness of the dielectrics. In addition, the demetallized area due to self healing was governed by the breakdown voltage and it has been mainly grown by some factors; the applied voltage; the consequent self healing events taking place at the circumference of the original self healing spots; the conductive paths formed by two or more self healing spots and by the consequent self healing spots.

Self-Healing Property of Hardened Cement Paste (시멘트 페이스트 경화체의 self healing 특성)

  • Kim, Jae Young;Byun, Seung Ho
    • Journal of The Korean Society of Civil Engineers
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    • v.28 no.2A
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    • pp.297-304
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    • 2008
  • It is well known that cracks in concrete decrease permeability and durability of concrete because cracks enhance the penetration of water or corrosive chemicals like as chlorides, carbon dioxides, sulfates and some others. But some of cracks in hardened cements may be sealed in case of contacting water. This phenomenon is called "self healing" and it has a close relation to hydration products newly formed on surfaces of cracks. Many studies on self healing in concretes commonly showed that CSH gel has been observed on crack surfaces. And some studies have reported that calcium hydroxides and ettringite were observed as well as CSH gel on crack surfaces. This study was carried out to investigate hydration products formed by self healing process and also examine the influence of waterproof admixture for concretes on self healing of cement. As a result of XRD, DSC, SEM and EDX analysis of crack surfaces, it was found that self healing of cement was related to CSH gel, calcium hydroxides and ettringite. And waterproof admixture increased fibrous (needle-like) hydration products which were in network form. It is estimated that such fibrous products are effective for self healing process of cement system.

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A Study on Influences of Waterproofing Admixtures for Concrete on Self-Healing Properties of Hardened Cement Paste (시멘트페이스트 경화체의 Self-Healing 특성에 미치는 구체방수재의 영향)

  • Kim, Jae-Young;Byun, Seung-Ho;Ma, Sang-Jun
    • 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.

The Self Healing Characteristics of MPPF for Energy Storage Capacitors (에너지저장 커패시터용 MPPF의 셀프힐링 특성)

  • Jung, Jong-Wook;Kwak, Hee-Ro;Park, Ha-Yong;Park, Jung-Shin;Kim, Young-Chan
    • Proceedings of the KIEE Conference
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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.

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A 3D analytical model for the probabilistic characteristics of self-healing model for concrete using spherical microcapsule

  • Zhu, Hehua;Zhou, Shuai;Yan, Zhiguo;Ju, Woody;Chen, Qing
    • Computers and Concrete
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    • v.15 no.1
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    • pp.37-54
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    • 2015
  • In general, cracks significantly deteriorate the in-situ performance of concrete members and structures, especially in urban metro tunnels that have been embedded in saturated soft soils. The microcapsule self-healing method is a newly developed healing method for repairing cracked concrete. To investigate the optimal microcapsule parameters that will have the best healing effect in concrete, a 3D analytical probability healing model is proposed; it is based on the microcapsule self-healing method's healing mechanism, and its purpose is to predict the healing efficiency and healing probability of given cracks. The proposed model comprehensively considers the radius and the volume fraction of microcapsules, the expected healing efficiency, the parameters of cracks, the broken ratio and the healing probability. Furthermore, a simplified probability healing model is proposed to facilitate the calculation. Then, a Monte Carlo test is conducted to verify the proposed 3D analytical probability healing model. Finally, the influences of microcapsules' parameters on the healing efficiency and the healing probability of the microcapsule self-healing method are examined in light of the proposed probability model.

Evaluation of Self-Healing Performance for Mortar Beams Containing Self-Healing Materials (자기치유 재료 혼입 모르타르 보의 자기치유 성능 평가)

  • Shin, DongIk;Muhammad, Haroon;Min, Kyung Sung;Lee, Kwang-Myong;Lee, Jung-Yoon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.24 no.1
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    • pp.67-73
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    • 2020
  • In this study, the self-healing performance of mortar beams containing self-healing materials was evaluated through experiments. Normal mortar beams and self-healing mortar beams were used In the experiments. The self-healing performance was evaluated by comparing the mortar compressive strength, member strength, and self-healing effects of cracks. The experimental results showed that the compressive strength of mortar containing self-healing material was smaller than that of normal mortar, but the ratio of 118 days compressive strength to 28 days compressive strength was the same. The member strength tended to increase with increasing curing period. In normal mortar specimens, the member strength did not recover even if the curing period increased, but the strength of the self-healing mortar specimens tended to recover as reaction products were produced. The crack width tended to decrease after the healing periods in both specimens, but the reaction product was observed only in the self-healing mortar specimens.

Study on Damage Repair of Polymer Composites Using Self-Healing Technique (Self-healing Technique을 적용한 폴리머 복합재의 손상 보수 연구)

  • ;;M.R. Kessler;S.R. White
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.93-96
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    • 2001
  • Structural polymer composites are susceptible to damage in the form of cracks, which form deep within the structure where detection is difficult and repair is almost impossible. A recent methodology for the damage repair of polymer composites using the self-healing technique is reported. The polymerization of the healing agent is triggered by contact with an embedded catalyst, being necessary to damage repair of polymer composites. For this purpose, the self-healing concept is introduced and the manufacturing process of microcapsule with the healing agent is briefly described. The polymerization between the healing agent and the catalyst is verified by the use of ESEM and IR spectroscopy. Finally the efficiency of the self-healing technique is investigated by measuring the critical load of TDCB specimen.

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The Electrical Characteristics of MPPF for Capacitor Applications under AC condition (커패시터용 MPPF의 교류전압 인가시 전기적 특성)

  • 정종욱;곽희로;박중신
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • pp.155-159
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    • 2000
  • This paper describes the self healing characteristics of metalized polypropylene film(MPPF) under ac condition. PDs were generally observed at relatively low voltage, and the PDIVs were differently varied depending on the number of pre-self healing due to void defects. Several pre-self healing events took place at lower voltage than the critical breakdown voltage of PPF. Self healing mainly occurred at pin tips, wrinkle sides, and cross points of wrinkles. The applied voltage at self healing was increased with PPF thickness. The burn out area at self healing was also increased with the applied voltage and PPF thickness. The peak currents in a grounding conductor at self healing was also increased with the applied voltage.

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Research Status on Machine Learning for Self-Healing of Mobile Communication Network (이동통신망 자가 치유를 위한 기계학습 연구동향)

  • Kwon, D.S.;Na, J.H.
    • 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.

Self-healing Coatings for an Anti-corrosion Barrier in Damaged Parts

  • Cho, Soo Hyoun
    • 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.