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Articles de revues sur le sujet « Charring ablator »

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Auteur : Grafiati
Publié le 14 mars 2023

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1

Hakkaki-Fard, A., et F. Kowsary. « Heat Flux Estimation in a Charring Ablator ». Numerical Heat Transfer, Part A : Applications 53, no 5 (6 novembre 2007) : 543–60. http://dx.doi.org/10.1080/10407780701678240.

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Guo, Jin, et Haiming Huang. « A novel method for analysing the thermal behaviour of charring ablator ». Thermal Science and Engineering Progress 7 (septembre 2018) : 107–14. http://dx.doi.org/10.1016/j.tsep.2018.05.006.

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Weng, Haoyue, Ümran Düzel, Rui Fu et Alexandre Martin. « Geometric Effects on Charring Ablator : Modeling the Full-Scale Stardust Heat Shield ». Journal of Spacecraft and Rockets 58, no 2 (mars 2021) : 302–15. http://dx.doi.org/10.2514/1.a34828.

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Chen, Yih-Kanq, et Frank S. Milos. « Effects of Nonequilibrium Chemistry and Darcy—Forchheimer Pyrolysis Flow for Charring Ablator ». Journal of Spacecraft and Rockets 50, no 2 (mars 2013) : 256–69. http://dx.doi.org/10.2514/1.a32289.

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Li, Weijie, Haiming Huang, Ye Tian et Zhe Zhao. « A nonlinear pyrolysis layer model for analyzing thermal behavior of charring ablator ». International Journal of Thermal Sciences 98 (décembre 2015) : 104–12. http://dx.doi.org/10.1016/j.ijthermalsci.2015.07.002.

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Wang, Yeqing, Timothy K. Risch et Joseph H. Koo. « Assessment of a one-dimensional finite element charring ablation material response model for phenolic-impregnated carbon ablator ». Aerospace Science and Technology 91 (août 2019) : 301–9. http://dx.doi.org/10.1016/j.ast.2019.05.039.

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SZASZ, Bianca, Kei-ichi OKUYAMA, Sumio KATO, Takayuki SHIMODA et Sean Lee TUTTLE. « S1910102 Study of the Heat Shield Characteristics of a Lightweight Charring CFRP-based Ablator ». Proceedings of Mechanical Engineering Congress, Japan 2015 (2015) : _S1910102a. http://dx.doi.org/10.1299/jsmemecj.2015._s1910102a.

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8

Xu, Yi Hua, Chun Bo Hu, Zhuo Xiong Zeng et Yu Xin Yang. « Research on Mechanical Model of EPDM Insulation Charring Layer ». Applied Mechanics and Materials 152-154 (janvier 2012) : 57–63. http://dx.doi.org/10.4028/www.scientific.net/amm.152-154.57.

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The coupling effect of physics, chemistry and mechanics is through charring layer in the process of ablation of the insulation material. Description of the structure and mechanical properties of charring layer is the critical factor to numerical computation for foretelling the ablation of insulation material. The characteristic of charring layer structure of EPDM insulation at sorts of ablating condition were analyzed, and based on characteristic of porous medium of charring layer, the mechanical model with porosity as parameter was modeled by using theory of solid porous medium. According to the intensity determination of charring layer, the coefficient of intensity model was determined, then, the failure criterion of charring layer was set up, which can provide the mechanical parameters of charring layer for numerical computation to foretell the ablation of insulation material.
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Xiao, Jie, Lin Jiang et Qiang Xu. « Insight into chemical reaction kinetics effects on thermal ablation of charring material ». Thermal Science, no 00 (2021) : 85. http://dx.doi.org/10.2298/tsci201010085x.

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Thermal ablation plays an important role in the aerospace field. In this paper, to study the chemical kinetics effects on heat transfer and surface ablation of the charring ablative material during aerodynamic heating, a charring ablation model was established using the finite element method. AVCOAT5026-39H/CG material, one typical thermal protection material used in thermal protection system, was employed as the ablative material and heated by aerodynamic heating condition experienced by Apollo 4. The finite element model considers the decomposition of the resin within the charring material and the removal of the surface material, and uses Darcy?s law to simulate the fluid flow in the porous char. Results showed that the model can be used for the ablation analysis of charring materials. Then effects of chemical kinetics on ablation were discussed in terms of four aspects, including temperature, surface recession, density distribution, and mass flux of pyrolysis gas. The pre-exponential factor and activation energy have different effects on ablation, while the effect of the reaction order is little. This paper is helpful to understand the heating and ablation process of charring ablative materials and to provide technical references for the selection and design of thermal protection materials.
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10

Fu, Rui, Haoyue Weng, Jonathan F. Wenk et Alexandre Martin. « Thermomechanical Coupling for Charring Ablators ». Journal of Thermophysics and Heat Transfer 32, no 2 (avril 2018) : 369–79. http://dx.doi.org/10.2514/1.t5194.

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Asghar, Muhammad, Nadeem Iqbal, Sadia Sagar Iqbal, Mohsin Farooq et Tahir Jamil. « Ablation and thermo-mechanical tailoring of EPDM rubber using carbon fibers ». Journal of Polymer Engineering 36, no 7 (1 septembre 2016) : 713–22. http://dx.doi.org/10.1515/polyeng-2015-0337.

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Abstract Carbon fibers (CFs) are incorporated into ethylene propylene diene monomer (EPDM) rubber to fabricate charring elastomeric ablative composites for ultrahigh temperature applications. Ablation characteristics of the ablative composites were evaluated using ASTM E285-08. Variant content incorporation of short CFs in the basic composite formulation reduced the backface temperature acclivity and the ablation rate rose up to 48% and 78%, correspondingly. Thermal stability and endothermic capability were improved with increasing short fiber contents in the rubber matrix. Experimental thermal conductivity measurement results elucidate that thermal conductivity reduces 60% at 473 K with 6 wt% addition of the fibers. A remarkable improvement was scrutinized in the tensile strength and rubber hardness with increasing fiber to matrix ratio. Scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS) analysis of the composite specimens revealed the uniform dispersion of CFs within the host matrix, formation of voids during ablation, char-reinforcement interaction and composition of the charred ablators and the impregnated fibers.
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12

Huang, Hai-Ming, Wei-Jie Li et Hai-Ling Yu. « Thermal analysis of charring materials based on pyrolysis interface model ». Thermal Science 18, no 5 (2014) : 1591–96. http://dx.doi.org/10.2298/tsci1405591h.

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Charring thermal protection systems have been used to protect hypersonic vehicles from high heat loads. The pyrolysis of charring materials is a complicated physical and chemical phenomenon. Based on the pyrolysis interface model, a simulating approach for charring ablation has been designed in order to obtain one dimensional transient thermal behavior of homogeneous charring materials in reentry capsules. As the numerical results indicate, the pyrolysis rate and the surface temperature under a given heat flux rise abruptly in the beginning, then reach a plateau, but the temperature at the bottom rises very slowly to prevent the structural materials from being heated seriously. Pyrolysis mechanism can play an important role in thermal protection systems subjected to serious aerodynamic heat.
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Molavi, Hosein, Iraj Pourshaban, Ali Hakkaki-Fard, Mehdi Molavi, Anahita Ayasoufi et Ramin K. Rahmani. « Inverse Identification of Thermal Properties of Charring Ablators ». Numerical Heat Transfer, Part B : Fundamentals 56, no 6 (29 janvier 2010) : 478–501. http://dx.doi.org/10.1080/10407790903508129.

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14

Chen, Yih-Kanq, et Tahir Gökçen. « Implicit Coupling Approach for Simulation of Charring Carbon Ablators ». Journal of Spacecraft and Rockets 51, no 3 (mai 2014) : 779–88. http://dx.doi.org/10.2514/1.a32753.

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Lin, J. L., et C. S. Yang. « Heat transfer analysis of charring ablators under aerodynamic heating ». Aircraft Engineering and Aerospace Technology 77, no 3 (juin 2005) : 214–21. http://dx.doi.org/10.1108/00022660510597232.

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Tallant, D. R., I. Auerbach et K. L. Higgins. « Evaluation and Mapping of Heat-Shield Flight Temperature and Composition with Raman Spectroscopic Techniques ». Applied Spectroscopy 49, no 5 (mai 1995) : 598–604. http://dx.doi.org/10.1366/0003702953963968.

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A Raman spectroscopic technique has been developed which can measure the maximum temperatures experienced by charring heat-shield materials and determine their post-test compositions (char, pyrolysis zone, and virgin resin). The technique has the capabilities of analyzing circular areas less than 0.1 mm in diameter or rectangles 0.1 mm in width and 2 mm in length. It can provide fine detailed surface and internal mappings and perform the analyses rapidly and conveniently in the laboratory following testing or flight recovery. Representative plots of temperature and composition profiles are provided. The data are compared with computations from the Charring Material Ablation (CMA) code.
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17

Leone, Scott A., Robert L. Potts et Anthony L. Laganelli. « Enhancements to integral solutions to ablation and charring ». Journal of Spacecraft and Rockets 32, no 2 (mars 1995) : 210–16. http://dx.doi.org/10.2514/3.26598.

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18

Li, Wei, Jun Zhang, GuoDong Fang, WeiJie Li, Jun Liang et SongHe Meng. « Evaluation of numerical ablation model for charring composites ». Science China Technological Sciences 62, no 8 (18 juin 2019) : 1322–30. http://dx.doi.org/10.1007/s11431-018-9476-2.

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19

Lin, Wen-Shan. « Quasi-steady solutions for the ablation of charring materials ». International Journal of Heat and Mass Transfer 50, no 5-6 (mars 2007) : 1196–201. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2006.11.011.

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20

Pan, Yun Ping, Wen Juan Yang et Yi Min Mo. « Ablation Characteristic Analysis of Short Pulse Laser Processing Composite Materials ». Advanced Materials Research 189-193 (février 2011) : 3759–63. http://dx.doi.org/10.4028/www.scientific.net/amr.189-193.3759.

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Short pulse lasers, including picosecond laser and femtosecond laser are involved to investigate the ablation characteristics of processing carbon fiber reinforced plastics (CFRPs). The ablation threshold of the femtosecond laser, 0.453 J/cm2, is twice higher than that of the picosecond laser 0.867 J/cm2, since the former generates an intense and shorter pulse and the atoms excitation and multi-photon absorption may occur as short as 10 ps or less. The ablation test also describes the processing qualities, where the femtosecond laser has processing abilities without visible thermal defects or charring over the picosecond laser.
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21

Li, Weijie, Jingran Ge et Jun Liang. « Influence factors on the multi-field coupling performances of charring ablators on the basis of a mesoscopic ablation model ». Applied Thermal Engineering 161 (octobre 2019) : 114126. http://dx.doi.org/10.1016/j.applthermaleng.2019.114126.

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Kamar Affendi, Nur Hafizah, Rohana Ahmad, Farhad Vahidi, Mohd Zulkifli Hassan et Siti Nadia Rahimi. « The Integration of a Dual-Wavelength Super Pulsed Diode Laser for Consistent Tissue Ablation in the Esthetic Zone : A Case Series ». Case Reports in Dentistry 2020 (3 décembre 2020) : 1–6. http://dx.doi.org/10.1155/2020/8883156.

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Introduction. A diode laser is one of the universally compact accepted laser systems used fundamentally for soft tissue applications. Most diode laser devices have a single wavelength of either 810 nm for superior coagulation or 980 nm for tissue ablation. In these case series, the use of dual wavelengths (810 nm and 980 nm) in combination with super pulsing has provided a cleaner cut (no charring) with faster healing that eases the placement of the final restoration in the esthetic zone. Case Description. The present case series describe four cases in the esthetic zone that achieved hemostasis ablation without collateral damage to enhance gingival balance of definitive restoration. The gingivoplasty and gingivectomy modes are used to achieve efficient tissue ablation. Although there is no specific mode indicated in the FDA laser requirement for gingival depigmentation, the procedure could be safely performed with the dual-wavelength diode laser Result. All four patients revealed a good esthetic outcome and reported no pain postoperatively. Healing was uneventful, and definitive restoration was delivered within two to four weeks postoperatively. Conclusion. Within the limitation of these case series, the dual-wavelength super pulsed diode laser has the capacity to deliver peak powers resulting in efficient cutting and less tissue charring and also as an alternative tool for removal of gingival pigmentation. Prospective clinical research with larger sample size is needed for conclusive results.
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Li, Weijie, Haiming Huang et Xiaoliang Xu. « A coupled thermal/fluid/chemical/ablation method on surface ablation of charring composites ». International Journal of Heat and Mass Transfer 109 (juin 2017) : 725–36. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2017.02.052.

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Potts, Robert L. « Application of integral methods to ablation charring erosion - A review ». Journal of Spacecraft and Rockets 32, no 2 (mars 1995) : 200–209. http://dx.doi.org/10.2514/3.26597.

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Li, Weijie, Haiming Huang, Qing Wang et Zimao Zhang. « Protection of pyrolysis gases combustion against charring materials’ surface ablation ». International Journal of Heat and Mass Transfer 102 (novembre 2016) : 10–17. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2016.05.143.

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Halbfass, Philipp, Jean-Yves Wielandts, Sébastien Knecht, Jean-Benoît Le Polain de Waroux, René Tavernier, Vincent De Wilde, Kai Sonne et al. « Safety of very high-power short-duration radiofrequency ablation for pulmonary vein isolation : a two-centre report with emphasis on silent oesophageal injury ». EP Europace 24, no 3 (10 novembre 2021) : 400–405. http://dx.doi.org/10.1093/europace/euab261.

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Abstract Aims Very high-power short-duration (vHPSD) via temperature-controlled ablation (TCA) is a new modality to perform radiofrequency pulmonary vein isolation (PVI), conceivably at the cost of a narrower safety margin towards the oesophagus. In this two-centre trial, we aimed to determine the safety of vHPSD-based PVI with specific emphasis on silent oesophageal injury. Methods and results Ninety consecutive patients with atrial fibrillation (AF) underwent vHPSD-PVI (90 W, 3–4 s, TCA) using the QDOT MICRO catheter, in conjunction with the nGEN (Bad Neustadt, n = 45) or nMARQ generator (Bruges, n = 45). All patients underwent post-ablation oesophageal endoscopy. Procedural parameters and complications were recorded. A subgroup of 21 patients from Bad Neustadt underwent cerebral magnetic resonance imaging (cMRI) to detect silent cerebral events (SCEs). Mean age was 67 ± 9 years, 59% patients were male, and 66% patients had paroxysmal AF. Pulmonary vein isolation was obtained in all cases after 96 ± 29 min. No steam pop, cardiac tamponade, stroke, or fistula was reported. None of the 90 patients demonstrated oesophageal ulceration (0%). Charring was not observed in the nMARQ cohort (0% vs. 11% in the nGEN group). In 5 out of 21 patients (24%), cMRI demonstrated SCE (exclusively nGEN cohort). Conclusion Temperature-controlled vHPSD catheter ablation allows straightforward PVI without evidence of oesophageal ulcerations or symptomatic complications. Catheter tip charring and silent cerebral lesions when using the nGEN generator have led to further modification.
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Alanyalioğlu, Çetin Ozan, et Yusuf Özyörük. « Conjugate Analysis of Silica-Phenolic Charring Ablation Coupled with Interior Ballistics ». Journal of Propulsion and Power 37, no 4 (juillet 2021) : 528–43. http://dx.doi.org/10.2514/1.b37839.

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Liu, Yang, Xiao-Cong Li, Jiang Li, Guo-Qiang He et Zong-Yan Li. « Ablation Model Based on Porous Charring Layer Under Alumina Erosion Condition ». AIAA Journal 57, no 11 (novembre 2019) : 4792–803. http://dx.doi.org/10.2514/1.j058479.

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Chen, Y. K., et F. S. Milos. « Two-Dimensional Implicit Thermal Response and Ablation Program for Charring Materials ». Journal of Spacecraft and Rockets 38, no 4 (juillet 2001) : 473–81. http://dx.doi.org/10.2514/2.3724.

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Li, Weijie, Haiming Huang, Ye Tian et Zhe Zhao. « Nonlinear analysis on thermal behavior of charring materials with surface ablation ». International Journal of Heat and Mass Transfer 84 (mai 2015) : 245–52. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2015.01.004.

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Li, Wei, Guodong Fang, Weijie Li, Jun Liang et Songhe Meng. « Numerical investigation of mesoscopic volumetric ablation of 3D braided charring composites ». Applied Thermal Engineering 181 (novembre 2020) : 116016. http://dx.doi.org/10.1016/j.applthermaleng.2020.116016.

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Wang, Xiao-Min, Li-Song Zhang, Chi Yang, Na Liu et Wen-Long Cheng. « Estimation of temperature-dependent thermal conductivity and specific heat capacity for charring ablators ». International Journal of Heat and Mass Transfer 129 (février 2019) : 894–902. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2018.10.014.

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Iqbal, Sadia Sagar, Tasawer Shahzad Ahmad, Arshad Bashir, Ali Bahadar et Farzana Siddique. « Tuning the Ablation, Thermal and Mechanical Characteristics of Phenolic Resin Reinforced EPDM Ultra-High Temperature Insulation ». Key Engineering Materials 875 (février 2021) : 88–95. http://dx.doi.org/10.4028/www.scientific.net/kem.875.88.

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The present research reports the influences of variant phenolic resin concentrations on the thermo-mechanical and ablation characteristics of ethylene propylene diene monomer (EPDM) elastomer. Backface temperature acclivity (BTA), charring rates, and insulation indexes were executed for the fabricated composite specimens. It was noticed that BTA was enhanced while linear/radial/mass ablation rates were significantly diminished with increasing concentration of phenolic resin (PR) in base matrix (elastomeric polymer). The composite (30wt%PR/EPDM) has 25% high thermal endurance compared to virgin EPDM composite. Thermal conductivity was increased with increasing PR to EPDM ratio. PR incorporation has remarkably enhanced the ultimate tensile strength of the EPDM elastomer. An efficient improvement in elastomeric hardness was also observed with increasing PR contents in EPDM matrix. Scanning Electron Microscopy (SEM) results showed the porosity generation and polymer melting during ablation.
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Kato, Sumio, Keiichi Okuyama, Seiji Nishio, Ryuuji Sakata, Kazumori Hama et Yoshifumi Inatani. « Numerical Analysis of Charring Ablation for Ablative Materials of Re-Entry Capsules. » JOURNAL OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES 50, no 582 (2002) : 255–63. http://dx.doi.org/10.2322/jjsass.50.255.

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Fulton, James E. « Skin Resurfacing and Lesion Ablation with the Ultrapulse® CO2 Laser ». American Journal of Cosmetic Surgery 13, no 4 (décembre 1996) : 323–37. http://dx.doi.org/10.1177/074880689601300405.

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Although CO2 lasers have been available to the cosmetic surgeon for more than 20 years, it is only recently that the ultrapulse mode has made the laser user-friendly. Now, tissue can be vaporized without significant charring. To shorten our learning curve with this treatment modality, various skin lesions were ablated with variable spot sizes and energy settings. Our results are presented as personal guidelines. Large and small areas may be resurfaced. If occlusive dressings are used, rapid reepithelization occurs across previous skin lesions or scars. This results in the appearance of rejuvenation. The only troublesome sequela has been persistent erythema similar to that seen after a phenol peel.
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Guan, Yi-Wen, Jiang Li, Yang Liu et Qi-Long Yan. « Reaction kinetics and a physical model of the charring layer by depositing Al2O3 at ultra-high temperatures ». Physical Chemistry Chemical Physics 20, no 37 (2018) : 24418–26. http://dx.doi.org/10.1039/c8cp04169e.

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Xiao, Jie, Oisik Das, Rhoda Afriyie Mensah, Lin Jiang, Qiang Xu et Filippo Berto. « Ablation behavior studies of charring materials with different thickness and heat flux intensity ». Case Studies in Thermal Engineering 23 (février 2021) : 100814. http://dx.doi.org/10.1016/j.csite.2020.100814.

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Qian, Wei-qi, Kai-feng He et Yu Zhou. « Estimation of surface heat flux for ablation and charring of thermal protection material ». Heat and Mass Transfer 52, no 7 (6 août 2015) : 1275–81. http://dx.doi.org/10.1007/s00231-015-1653-9.

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Saltman, Adam E., Narayan R. Raju et Jon E. Block. « Histopathological Evaluation of a Novel Radiofrequency Surgical Ablation System ». Innovations : Technology and Techniques in Cardiothoracic and Vascular Surgery 3, no 2 (mars 2008) : 47–51. http://dx.doi.org/10.1097/imi.0b013e31817677a4.

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Purpose Using a porcine model, this feasibility study was undertaken to evaluate the histopathological characteristics of lesions created in the proximity of the pulmonary veins after ablation with a new endoscopic-guided radiofrequency device. Methods Five adult female swine underwent endoscopic surgical ablation on the epicardial surface of the beating heart. Histologic sections taken from around the pulmonary vein pedicle, representing 10 separate anatomic sites, underwent independent qualitative histopathological evaluation as well as quantitative histomorphometric measurement of lesion depth and section thickness. Results Sections from all five animals had histologically identical lesions, with the majority of ablation foci having pronounced thermal injury characterized by deep and extensive zones of acute myocardial necrosis in the absence of tissue charring. Fifty-seven percent (13 of 23) of the lesions were completely transmural and 91% (21 of 23) of the sections demonstrated ≥70% transmurality. No collateral injuries were noted. Conclusions This irrigated, suction-stabilized unipolar radiofrequency device can produce histologically transmural lesions around the pulmonary veins and is amenable to endoscopic-guided application on the beating heart.
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Schramm, Wolfgang, Deshan Yang, Bradford J. Wood, Frank Rattay et Dieter Haemmerich. « Contribution of Direct Heating, Thermal Conduction and Perfusion During Radiofrequency and Microwave Ablation ». Open Biomedical Engineering Journal 1, no 1 (19 septembre 2007) : 47–52. http://dx.doi.org/10.2174/1874120700701010047.

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Both radiofrequency (RF) and microwave (MW) ablation devices are clinically used for tumor ablation. Several studies report less dependence on vascular mediated cooling of MW compared to RF ablation. We created computer models of a cooled RF needle electrode, and a dipole MW antenna to determine differences in tissue heat transfer. We created Finite Element computer models of a RF electrode (Cooled needle, 17 gauge), and a MW antenna (Dipole, 13 gauge). We simulated RF ablation for 12 min with power controlled to keep maximum tissue temperature at 100 ºC, and MW ablation for 6 min with 75 W of power applied. For both models we considered change in electric and thermal tissue properties as well as perfusion depending on tissue temperature. We determined tissue temperature profile at the end of the ablation procedure and calculated effect of perfusion on both RF and MW ablation. Maximum tissue temperature was 100 ºC for RF ablation, and 177 ºC for MW ablation. Lesion shape was ellipsoid for RF, and tear-drop shaped for MW ablation. MW ablation is less affected by tissue perfusion mainly due to the shorter ablation time and higher tissue temperature, but not due to MW providing deeper heating than RF. Both MW and RF applicators only produce significant direct heating within mm of the applicator, with most of the ablation zone created by thermal conduction. Both RF and MW applicators only directly heat tissue in close proximity of the applicators. MW ablation allows for higher tissue temperatures than RF since MW propagation is not limited by tissue desiccation and charring. Higher temperatures coupled with lower treatment times result in reduced effects of perfusion on MW ablation.
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Li, Weijie, Haiming Huang, Xiaoliang Xu et Jin Guo. « A new mechanism of surface ablation of charring materials for a vehicle during reentry ». Applied Thermal Engineering 106 (août 2016) : 838–49. http://dx.doi.org/10.1016/j.applthermaleng.2016.06.055.

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Ligon, Samuel, Gurdial Blugan et Jakob Kuebler. « Pulsed UV Laser Processing of Carbosilane and Silazane Polymers ». Materials 12, no 3 (24 janvier 2019) : 372. http://dx.doi.org/10.3390/ma12030372.

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Freestanding SiCNO ceramic pieces with sub-mm features were produced by laser crosslinking of carbosilane and silazane polymer precursors followed by pyrolysis in inert atmosphere. Three different pulsed UV laser systems were investigated, and the influence of laser wavelength, operating power and scanning speed were all found to be important. Different photoinitiators were tested for the two lasers operating at 355 nm, while for the 266 nm laser, crosslinking occurred also without photoinitiator. Pre-treatment of glass substrates with fluorinated silanes was found to ease the release of green bodies during solvent development. Polymer crosslinking was observed with all three of the laser systems, as were bubbles, surface charring and in some cases ablation. By focusing the laser beam several millimeters above the surface of the resin, selective polymer crosslinking was observed exclusively.
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MacDonell, Jacquelyn, Niravkumar Patel, Gregory Fischer, E. Clif Burdette, Jiang Qian, Vaibhav Chumbalkar, Goutam Ghoshal et al. « Robotic Assisted MRI-Guided Interventional Interstitial MR-Guided Focused Ultrasound Ablation in a Swine Model ». Neurosurgery 84, no 5 (14 juin 2018) : 1138–48. http://dx.doi.org/10.1093/neuros/nyy266.

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Abstract BACKGROUND Ablative lesions are current treatments for epilepsy and brain tumors. Interstitial magnetic resonance (MR) guided focused ultrasound (iMRgFUS) may be an alternate ablation technique which limits thermal tissue charring as compared to laser therapy (LITT) and can produce larger ablation patterns nearer the surface than transcranial MR guided focused ultrasound (tcMRgFUS). OBJECTIVE To describe our experience with interstitial focused ultrasound (iFUS) ablations in swine, using MR-guided robotically assisted (MRgRA) delivery. METHODS In an initial 3 animals, we optimized the workflow of the robot in the MR suite and made modifications to the robotic arm to allow range of motion. Then, 6 farm pigs (4 acute, 2 survival) underwent 7 iMRgFUS ablations using MRgRA. We altered dosing to explore differences between thermal dosing in brain as compared to other tissues. Imaging was compared to gross examination. RESULTS Our work culminated in adjustments to the MRgRA, iMRgFUS probes, and dosing, culminating in 2 survival surgeries; swine had ablations with no neurological sequelae at 2 wk postprocedure. Immediately following iMRgFUS therapy, diffusion-weighted imaging, and T1 weighted MR were accurate reflections of the ablation volume. T2 and fluid-attenuated inversion-recovery (FLAIR) images were accurate reflections of ablation volume 1-wk postprocedure. CONCLUSION We successfully performed MRgRA iFUS ablation in swine and found intraoperative and postoperative imaging to correlate with histological examination. These data are useful to validate our system and to guide imaging follow-up for thermal ablation lesions in brain tissue from our therapy, tcMRgFUS, and LITT.
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Chen, Zhiheng, Shida Han, Yuan Ji, Hong Wu, Shaoyun Guo, Ning Yan et Hongyan Li. « Effects of MWCNTs on Char Layer Structure and Physicochemical Reaction in Ethylene Propylene Diene Monomer Insulators ». Polymers 14, no 15 (26 juillet 2022) : 3016. http://dx.doi.org/10.3390/polym14153016.

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As one of the most promising ablative fillers, multi-walled carbon nanotubes (MWCNTs) have been used to improve the ablative resistance of Ethylene–Propylene–Diene Monomer (EPDM) insulators by facilitating the carbothermal reduction reaction of silica. However, the contribution of MWCNTs to char layer structure of the insulators was unclear. In this work, the effects of MWCNTs on char layer structure and ablative resistance were investigated in different EPDM-based insulators with and without silica. The results showed that adding only 3 phr MWCNTs can reduce the linear ablation rate of EPDM-based insulators without silica by 31.7%, while 6 phr MWCNTs are required to obtain similar results in EPDM-based insulators with silica. The char layer morphology of the two insulators gradually evolved into a dense porous structure as MWCNTs content increased, but their formation mechanisms were different. The XRD and Raman spectrum showed that different physicochemical reactions occurred around MWCNTs under different charring components. The proposed ablation mechanism was further verified by designing alternating multilayer distribution of MWCNTs and silica. This work can guide the construction of desirable char layer structure for increasing the ablative resistance of EPDM-based insulators.
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Long, Lianchun, Yao Huang et Jinfeng Zhang. « Experimental investigation and numerical simulation on continuous wave laser ablation of multilayer carbon fiber composite ». Proceedings of the Institution of Mechanical Engineers, Part L : Journal of Materials : Design and Applications 231, no 8 (27 septembre 2015) : 674–82. http://dx.doi.org/10.1177/1464420715608656.

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Laser beam machining is one of the most widely used advanced processing techniques, which can be applied to compound materials. As a large number of photons are absorbed into the composite, the subsequent local heat storage, charring and potential delamination make the study for the effect of laser on complex materials become significant. In this paper, a carbon fiber epoxy composite laminated sheet is irradiated by continuous wave chemical oxygen iodine laser. The peak temperature of front surface, the temperature distribution of rear surface, and the appearance of ablation zone are presented. Further, based on the birth–death elements technique of finite element method, a three-dimensional model for simulating the transient temperature distribution and material removal has been developed under the same condition. The results reveal that the peak temperature of irradiated region ranges from 2800 K to 3100 K, and the center point shows a higher temperature rise rate than the surroundings in the irradiated zone. The measured data and predicted data are in a good consistency, which suggests that the numerical model is appropriate for simulating laser ablation of carbon fiber epoxy composites.
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Makimoto, Hisaki, Andreas Metzner, Roland Richard Tilz, Tina Lin, Christian-H. Heeger, Andreas Rillig, Shibu Mathew et al. « Higher contact force, energy setting, and impedance rise during radiofrequency ablation predicts charring : New insights from contact force-guided in vivo ablation ». Journal of Cardiovascular Electrophysiology 29, no 2 (29 novembre 2017) : 227–35. http://dx.doi.org/10.1111/jce.13383.

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Choi, Youn Gyu, Kyung-Ho Noh, Jin Yong Park et Young Hwan Jo. « Pyrolysis and Chemical Ablation Analysis of Hypersonic Missile for Thermal Protection Design Applying Charring Phenol Resin Composites ». Journal of the Korean Society for Precision Engineering 35, no 10 (1 octobre 2018) : 987–93. http://dx.doi.org/10.7736/kspe.2018.35.10.987.

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Mohammadiun, Hamid, et Mohammad Mohammadiun. « Numerical Modeling of Charring Material Ablation with Considering Chemical-Reaction Effects, Mass Transfer and Surface Heat Transfer ». Arabian Journal for Science and Engineering 38, no 9 (18 décembre 2012) : 2533–43. http://dx.doi.org/10.1007/s13369-012-0510-0.

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Steichen, John D., Robert B. Stewart, David N. Louis, Benjamin B. Choi, Robert Kung et Robert L. Martuza. « A new 1.9-µ wavelength laser for neurosurgery ». Journal of Neurosurgery 73, no 4 (octobre 1990) : 611–14. http://dx.doi.org/10.3171/jns.1990.73.4.0611.

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✓ The 1.9-µ wavelength component of a 1.9/1.06-µ two-wavelength laser with near-continuous wave properties was tested for its potential use in neurosurgery. The 1.9-µ wavelength has tissue-ablative capabilities, while the 1.06-µ wavelength (Nd:YAG) is suitable for achieving hemostasis. The advantages of the 1.9-µ wavelength over the CO2 laser include its ability to transmit through silica fiberoptic delivery systems and its deeper penetration in water (approximately 100 µ, a depth 10 times greater than for the CO2 laser), which is compatible with irrigation during ablation. To test the effectiveness of the laser, bilateral craniotomies were performed in anesthetized rats immobilized in a stereotactic frame. Under an operating microscope, lesions were made on the cortex by delivering the 1.9-µ laser beam through a 400-µ fiber at an average power of 1 W over a range of fluences. Subjective intraoperative observations were notable for minimal bleeding, absence of charring when the tissue was irrigated with a thin stream of saline, and uniform lesion formation. For comparison, lesions were generated with a commercially available continuous-wave CO2 laser at equivalent power and fluences. Histological specimens were divided into three groups based on the study after laser application: acute (30 minutes), subacute (48 hours), and chronic (14 days). The extent of thermal injury for the 1.9-µ laser in the acute lesions was quantitatively and histologically similar to that generated by the CO2 laser. Regions of injury extended approximately from the apex of the lesion, and crater depths generated by both lasers were similar (250 to 750 µ) in the range of fluences investigated (1.25 to 10 kJ/sq cm). Subacute and chronic histological specimens demonstrated inflammatory and repair responses that correlated with the acute injury regions in both the 1.9-µ and CO2 laser-treated specimens. This study demonstrates a neurosurgical potential for a new two-wavelength laser that ablates tissue effectively with limited thermal injury. The 1.9-µ laser is comparable to the widely used CO2 laser but offers several unique advantages, including the ability for delivery through a fiberoptic system and to irrigate tissue during use.
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Mueller, Dirk, David Clark, Joris VanNunen, Ed Rea et Hatim Haloui. « Laser-based Package Singulation and Trenching for SiP ». Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2016, DPC (1 janvier 2016) : 002182–202. http://dx.doi.org/10.4071/2016dpc-tha43.

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Pulsed lasers are solving some packaging challenges for SiP applications. SiP devices designed for mobile devices with communication capability often have a need for EMI shielding. Nanosecond UV and picosecond green lasers are finding use in cutting these multi-compound packages as well as trench for exposing board contacts used for grounding. Mechanical cutting may not be an option if the perimeter of the package is not a simple rectangle. Water jet cutting may bear the risk of the package to fail to to water seeping in between the package layers during cutting. We will demonstrate how laser-based SiP package cutting and trenching can ameliorate both of those concerns and point toward limitations of laser-based processes. Today's high power nanosecond UV lasers are capable of cutting 1mm thick packages at an effective cutting speed of more than 10mm/s. The resulting cut surface shows no charring or melting. The surface roughness allows for excellent adhesion of EMI shielding paint on the cut conformal compound. Since the laser beam can be controlled with a programmable scanner, arbitrary shapes can be cut just as easily as simple rectangles. Difference ablation rates between polymer and copper allow the laser to trench the conformal coating and stop automatically when a metal layer is exposed. This self-terminating process leads to a precise exposure even when the conformal coating thickness differs from part to part. For the utmost in surface quality picosecond lasers can be employed. Their shorter pulse duration allows for an even lower surface roughness and less thermal impact on the package. Using an ultrafast laser, such as a 10ps laser, has the additional advantage that the process scales in speed with increased laser power. The excellent edge quality and possibility to cut random shapes allow laser-based processes to complement mechanical processes in high-end applications. We will present a full cost of ownership model that allows the designer to predict the exact singulation and trenching cost for a given package size.
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