• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.9
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• pp.1201-1212
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• 1999

A numerical analysis is performed to predict the thermal response and ablation rate for charring or non-charring material which is designed to be used as thermal protection system (TPS). The numerical program composed of in-depth energy balance equation and the aerotherm chemical equilibrium (ACE) program. The ACE program calculates various thermochemical state from ablation products. The developed numerical program is verified by comparing the reported results from literature. The sensitivity tests for input parameters are performed. The thermal behavior of ablating material is mainly affected by density of ablating material, convective heat transfer coefficient and recovery enthalpy of flow field.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.943-951
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• 1992

The objectives of this study are to analyse the thermal response behavior occurring in the charring ablative material more realistically by considering ablation and char phenomena occurring in several material layers, and to increase the reliability of thermal analysis by being able to get stable solutions through using the finite analytic method. A program has been developed to predict the temperature distribution, ablation thickness, char thickness, ablation velocity and char velocity by solving non-linear one-dimensional heat conduction equation. Results of calculation were compared with results of published papers. From this compariosn this program was proved to be a very good tool for thermal design and analysis of charring ablative materials used in the rocket propulsion system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.565-569
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• 2011

A two-dimensional thermal response and ablation analysis code for predicting charring material ablation and shape change on solid rocket nozzle is presented. For closing the problem of thermo-structural analysis, Arrhenius' equation and Zvyagin's ablation model are used. The moving boundary problem are solved by remeshing-rezoning method. For simulation of complicated thermal protection systems, this method is integrated with a three-dimensional finite-element thermal and structure analysis code.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.113-122
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• 2010

A two-dimensional thermal response and ablation analysis code for predicting charring material ablation and shape change on solid rocket nozzle is presented. For closing the problem of thermal analysis, Arrhenius' equation and Zvyagin's ablation model are used. The moving boundary problem are solved by remeshing-rezoning method. For simulation of complicated thermal protection systems, this method is integrated with a three-dimensional finite-element thermal and structure analysis code through continuity of temperature and heat flux.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.282-287
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• 2001

The CSCM Upwind method and Material Transport Analysis (MTA) have been used to predict the thermal response and ablation rate for non-charring material to be used as thermal protection material (TPM) in KSR-III test rocket nozzle. The thermal boundary conditions such as cold wall heat-transfer rate and recovery enthalpy for MTA code are obtained from the upwind Navier-Stokes solution procedure. The heat transfer rate and temperature variations at rocket nozzle wall were studied with shape change of the nozzle surface as time goes by. The surface recession was severely occurred at nozzle throat and this affected nozzle performance such as thrust coefficient substantially.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.311-314
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• 2009

A two-dimensional thermal response and ablation simulation code for predicting charring material ablation and shape change on solid rocket nozzle is presented. For closing the problem of thermal analysis, Arrhenius' equation and Zvyagin's ablation model are used. The moving boundary problem and endothermic reaction in thermal decomposition are solved by rezoning and effective specific heat method. For simulation of complicated thermal protection systems, this method is integrated with a three-dimensional finite-element thermal and structure analysis code through continuity of temperature and heat flux.

• Journal of Oral Medicine and Pain
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• v.22 no.1
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• pp.125-135
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• 1997

The Author examined the clinical and histological changes on the dorsal tongue mucosa of the adult rats after lasing by pulsed Nd:YAG laser and incising with scalpel. The dorsal tongue was lased through 320$\mu\textrm{m}$optic fiber moving 2.5mm/second to make linear incision 5mm. The five conditions of lasing were three application with 1.0W, 1.75W, 3.0W and 3.0W under saline cooling, and single application with 3.0W at 20Hz. With scalpel, linear incisions through the surface epithelium were performed to 5mm in length. After observing the clinical changes of the incised wounds, the animals were sacrified and the tissues were excised to make the tissue specimens. The stained microscopic tissue slide were observed histologically under the microscope. The following results were obtained : 1. While incision with scalpel causes severe bleeding, lasing does not cause bleeding. 2. In three applications with 1.75W and 20Hz, tissue ablation was limited to areas contacted with optic fiber. 3. In three applications with 3.0W and 20Hz, deep incised wound, extensive destruction of the adjacent epithelium and charring were observed. 4. In three applications with 3.0W and 20Hz under saline cooling, tissue ablation was limite to the superficial mucosa and charring was not observed. 5. In single application with 3.0W and 20Hz, the shape of the incised wound was similar to that of the scalpel incision.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.5
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• pp.32-44
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• 2010

A two-dimensional thermal response and ablation analysis code for predicting charring material ablation and shape change on solid rocket nozzle is presented. The thermogravimetric analysis (TGA) techniques have been used to characterize the thermal decomposition constants for Arrhenius parameters. Two heterogeneous reactions involving carbon and the oxidizing species of $H_2O$ and $CO_2$ are considered and determined by Zvyagin's ablation model and kinetic constants. The moving boundary problem and mesh moving are solved by remeshing-rezoning method in MSC-Marc-ATAS program. The difference between the calculated and experimental value of char and ablation thickness is up to 20%. For the performance prediction of thermal protection systems, this method will be integrated with a three-dimensional finite-element thermal and structure analysis code through the real time sensing of in-depth temperature and heat flux.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.4
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• pp.558-563
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• 2000

The lasers have been used in dentistry for more than 30 years and the application of lasers for drilling dental hard tissue has been investigated since the early developement of lasers. Recently, the Er:YAG laser was invented for hard tissue ablation. The Er:YAG laser, having a wavelength of 2.94um, is highly absorbed in both water and hydroxiapatite, leading to a very effective material for hard tissue removal by bursting off the solid tissue component that is, enamel and dentin are removed by the Er :YAG laser by water vaporization and microexplosion, without any melting of inorganic tissues. Therefore, the Er:YAG laser produced round craters with well defined margins and the surrounding tissues had no cracks and no charring. When used for cavity preparation, pulpal damage should not occur if hear buildup is minimized by careful selection of exposure parameters and by use of a water spray. The present study demonstrated that the Er:YAG laser cut the tooth substance adequately for composite resin restoration, without having undesirable side effects such as harmful effects on the pulp, discoloration or cracking etc. Also, the child patients were well cooperative during laser treatment mainly because of little noise, lesser vibration and minimal pain compared to conventional means of cavity preparation.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.2
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• pp.272-285
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• 2003

This study was conducted to observe the microscopic structures of cavities formed after ablation of primary teeth, permanent teeth, enamel and dentin in using a bur and cavities formed after ablation using laser and the following results were obtained after comparing the effects of ablation. Using a #330 bur and Er:YAG laser irradiated at 150 mJ, 200 mJ, 250 mJ and 300 mJ all at the frequency of 5 Hz, 1 mm enamel and dentin samples were ablated and the ablation time was measured. In order to measure the surfaces ablated, 5 each of primary teeth and permanent teeth were ablated using a #330 bur and Er:YAG laser at 150 mJ, 200 mJ, 250 mJ and 300 mJ for 1 sec and the cross section and vertical section were observed. The following results were obtained : 1. Cutting time of Er:YAG laser was longer than that of conventinal high-speed bur regardless of teeth type. 2. Cutting on enamel, Cutting time of conventional high-speed bur in deciduous teeth was longer than in permanent teeth(P<0.05). But Er:YAG laser was not showed any difference between the deciduous and permanent teeth(P>0.05). 3. Cutting on dentin, Cutting time of conventional high-speed bur in permanent teeth was longer than deciduous teeth. Er:YAG laser of 150 mJ, 5 Hz in permanent teeth was longer than in deciduous teeth(p<0.05). But laser of other power did not showed mean difference. 4. The cavity surface treated with the convetional high-speed bur revealed a relatively flat appearance, almost covered with a debris-like smear layer. Cavity wall showed striped appearance because of blade of bur. 5. The cavity surface treated by the Er:YAG laser system was irregular or rough surface with the absence charring, carbonization, or cracking of the dentin. In addition, there was an absence of a smear layer. Cavity floor was round and relatively smooth. According to these results, cutting time of Er:YAG laser was almostly same in permanent and deciduous teeth, but more effective in dentin than enamel. Cutting the sample, Er:YAG laser was needed more time than conventional bur. But SEM findings suggested that laser device produced favorable surface characteristic(i.e, no smear layer, irregular surface, cracking).