• Journal of the Korean Society of Combustion
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• v.4 no.1
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• pp.95-103
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• 1999

Experimental study on combustion characteristics of a regenerative combustor has performed. High-temperature air combustion in the regenerative combustor is obtained through heat recovery from exhaust gas flow by porous ceramic materials and through alternation of air flow direction through the combustor. Temperature field, CO and NOx emission with respect to the frequency of alternation are measured. It is found that at initial stage of the alternation, temperature of inlet section of main combustion chamber is increased sharply since both high temperature air preheated by the ceramics and prompt fuel injection results in rapid combustion. Following this initial stage, combustion temperature is reduced as the preheated air temperature is reduced. However peak temperature in the chamber and exhaust gas temperature are decreased as the alternation period is reduced, increased temperature of ceramic is observed. CO and NOx emission with respect to the alternation period is also examined. It is found that there exists a range of optimum alternating period for CO and NOx emission characteristics.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.12
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• pp.1201-1208
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• 2009

Dome stretching tests and tension tests were performed to evaluate the formability of a copper alloy used for manufacturing the regenerative cooling chamber. The test specimens were prepared to investigate the effect of heat treatment and direction of specimens on the formability. The test results show that forming limit values are increased by the heat treatment of the material but the variation of the forming limit values by manufacturing direction is negligible compared to the heat treatment effect, and forming limit values are also different according to the test methods. These results indicate that the high temperature heat treatment of the material before bulging is a very important process to deform the inner cylindrical structure of the regenerative cooling chamber into a nozzle shape by the bulging process without necking or fracture and the test methods also have a great effect on a evaluation of the formability. The forming limit diagram obtained in this study would be utilized to the design of regenerative cooling chamber nozzles.

• BMB Reports
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• v.55 no.2
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• pp.65-71
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• 2022

Regenerative medicine is a research field that develops methods to restore damaged cell or tissue function by regeneration, repair or replacement. Stem cells are the raw material of the body that is ultimately used from the point of view of regenerative medicine, and stem cell therapy uses cells themselves or their derivatives to promote responses to diseases and dysfunctions, the ultimate goal of regenerative medicine. Stem cell-derived extracellular vesicles (EVs) are recognized as an attractive source because they can enrich exogenous microRNAs (miRNAs) by targeting pathological recipient cells for disease therapy and can overcome the obstacles faced by current cell therapy agents. However, there are some limitations that need to be addressed before using miRNA-enriched EVs derived from stem cells for multiplexed therapeutic targeting in many diseases. Here, we review various roles on miRNA-based stem cell EVs that can induce effective and stable functional improvement of stem cell-derived EVs. In addition, we introduce and review the implications of several miRNA-enriched EV therapies improved by multiplexed targeting in diseases involving the circulatory system and nervous system. This systemic review may offer potential roles for stem cell-derived therapeutics with multiplexed targeting.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.151-155
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• 2006

Elastic-viscoplastic structural analysis is performed for regenerative cooling chamber of liquid rocket thrust chamber using Bodner-Partom visco-plastic model. Strain rate test was also conducted for a copper alloy at various temperatures in order to get material constants of visco-plastic model used in the structural analysis. Material constants of visco-plastic model were obtained from strain rate test results and visco-plsstic model was incorporated into finite element program, Marc, by means of user subroutine. The structural analysis results indicate that the deformation of cooling channel is mostly caused by thermal loading rather than pressure loading and confirmed structural stability of the cooling channel under operating condition.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.4
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• pp.69-76
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• 2006

Elastic-viscoplastic structural analysis has been performed for regenerative cooling chamber of liquid rocket thrust chamber using Bodner-Partom visco-plastic model. Strain rate test was conducted for a copper alloy at various temperatures in order to get material constants of visco-plastic model used in the structural analysis. Material constants of visco-plastic model were obtained from strain rate test results and visco-plastic model was incorporated into finite element program, Marc, by means of a user subroutine. The structural analysis results indicated that the deformation of cooling channel is mostly caused by thermal loading rather than pressure loading and confirmed structural stability of the cooling channel under the operating condition.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.38 no.6
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• pp.321-325
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• 2012

Collagen is widely used for regenerative therapy and pharmaceutical applications as one of the most useful scaffolds. Collagen is the most abundant protein in vertebrates and the natural substrate of various types of animal cells. Bone and dentin are mineralized tissues and almost similar in chemical components. They consist of collagen (18%), non-collagenous proteins (2%), hydroxyapatite (70%) and body fluid (10%) in weight volume. Pepsin-digested, type I collagen (atelocollagen) and heat-denatured collagen (gelatin) are basic collagenous materials for medical use. Demineralized dentin matrix (DDM) and demineralized bone matrix (DBM) belong to acid-insoluble group, and vital tooth-derived DDM is a unique dentin material including cementum and growth factors. In this review, collagen-based materials will be introduced and discussed for bone regenerative surgery.

• Journal of Periodontal and Implant Science
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• v.38 no.4
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• pp.621-628
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• 2008

Purpose: Osteopontin is one of the major non-collagenous protein of hard tissue. Use of peptide domain of biologically active protein has some advantages. The objective of this experimental study is evaluation of periodontal regenerative potency of synthetic peptide gel which containing collagen binding domain of osteopontin in the degree III periodontal defect of beagle dogs. Material and Methods: Experimental degree III furcation defect was made in the mandibular third and fourth premolar of beagles. Regenerative material was applied during flap operation. 8 weeks after regenerative surgery, all animals were sacrificed and histomorphometric measurement was performed to calculate the linear percentage of the new cementum formation and the volume percentage of new bone formation. Result: The linear percent of new cementum formation was 41.6% at control group and 67.1% at test group and there was statistically significant difference. The volume percent of new bone formation was 52.1% at control group and 58.9% at test group. Conclusion: As the results of present experiment, synthetic peptide gel containing collagen binding domain of osteopontin significantly increase new bone and cementum formation in the degree III furcation defect of canine mandible.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.4
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• pp.39-47
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• 2005

The structural analysis and water pressure tests are performed for liquid rocket thrust chamber regenerative cooling channel specimens at room temperature condition. Material properties of copper alloy to be used in the elastic-plastic structural analysis are obtained by uniaxial tension test at room temperature. The plate-type cooling channel specimens are manufactured and performed water pressure test to verify the analysis results. The results of elastic-plastic structural analysis and water pressure test show resonable agreements though with minor differences and it is revealed that structural stability of regenerative cooling channel is highly affected by the manufacturing tolerances due to very thin cross-sectional thickness of the cooling channel.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.3
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• pp.271-278
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• 2008

A study has been conducted on the bulging process of liquid rocket engine nozzle which is essential to the manufacturing regenerative cooling combustion chamber. Mechanical properties of the material used for the bulging were experimentally obtained by tension tests. Deformation of the bulged nozzle was confirmed by a structural analysis. The developed bulging process and the deformation analysis result were confirmed by manufacturing of the bulged nozzle specimens and the bulging test. There has been a bulging failure among 7 bulged specimens due to the necking of the material. The cause of necking was investigated by comparing microstructure of the material. The investigation has revealed grain size of the material has considerable effect on the occurrence of the necking.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.3
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• pp.230-237
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• 2017

Regenerative therapy in an interproximal intrabony defect is a challenge due to unaesthetic appearance after surgery. In this article, we introduce a case series of additional use of autogenous periosteal barrier membrane combined with bovine bone mineral and enamel matrix derivative (EMD) in interproximal periodontal intrabony defects to overcome an aforementioned shortcoming. During the periodontal regenerative surgery, autogenous periosteal membrane was additionally adopted besides xenograft material and EMD. Clinical and radiographic examinations were performed before surgery and 6 months after surgical treatment. All clinical parameters were improved and the intrabony defects were resolved on the radiography 6 months after surgery. Moreover, soft tissue esthetics such as the contour of interdental papilla was better than that of conventional regenerative therapy. Periodontal regenerative therapy using several graft materials and bioactive materials was effective in the treatment of periodontal intrabony defect. Moreover, using of autogenous periosteal barrier membrane combined with xenograft and EMD has additional effect for the treatment of an interproximal intrabony defect in terms of augmentation of interdental soft tissue volume.