• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.1
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• pp.37-46
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• 2012

The ultimate goal of periodontal therapy is the regeneration of supporting tissues. It is recommended to avoid probing until 6~9 months following the regenerative therapy because the probing may jeopardize the newly formed tissues. We can measure tooth mobility objectively using Periotest. The purpose of this study is to investigate whether Periotest can be used to evaluate the treatment results alternatively, and whether there are the correlations between the changes of Periotest value (PTV) and other clinical parameters. Regenerative treatments have been performed on 29 teeth of twenty five patients, at Department of Periodontology, Pusan National University Hospital. We measured the tooth mobility by Periotest and other parameters at the baseline, 6 and 12 months after regenerative treatment. Compared to the baseline, there were the statistically significant improvements in all the parameters at 6 months and 12 months. There were statistically significant correlations among the probing depth, attachment level, gingival recession and PTV at baseline, 6 months, and 12 months. Also there was the correlation between changes in PTV and in the attachment level at each time of observation period. We may conclude that regenerative therapy would improve the clinical parameters and periodontal status and PTV would be an alternative index to evaluate the healing process after regenerative surgery.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.134.1-134.1
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• 2017

In this study, we propose a new scaffold fabrication method, "direct electro-hydrodynamic jet process," using the initial jet of an electrospinning process and ethanol media as a target. The fabricated threedimensional (3D) fibrous structure was configured with multilayered microsized struts consisting of randomly entangled micro/nanofibrous architecture, similar to that of native extracellular matrixes. The fabrication of the structure was highly dependent on various processing parameters, such as the surface tension of the target media, and the flow rate and weight fraction of the polymer solution. As a tissue regenerative material, the 3D fibrous scaffold was cultured with preosteoblasts to observe the initial cellular activities in comparison with a solid-freeform fabricated 3D scaffold sharing a similar structural geometry. The cell-culture results showed that the newly developed scaffold provided outstanding microcellular environmental conditions to the seeded cells (about 3.5-fold better initial cell attachment and 2.1-fold better cell proliferation).

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.134-138
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• 2005

The structural analysis and water pressure test of regenerative liquid rocket thrust chamber cooling channel specimens are performed at room temperature. material properties of copper alloy are obtained by uniaxial tension test at room temperature and used of elastic-plastic structural analysis. The plate type of cooling channel specimen are manufactured and performed water pressure test in order to confirm the analysis results. The differences between results of elastic-plastic analysis and that of water pressure test of cooling channel specimen are small and find that manufacturing process affect the structural stability of cooling channel very much because cooling channel thickness is small

• Korean Journal of Materials Research
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• v.24 no.12
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• pp.704-709
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• 2014

In this study, we fabricated a novel micro porous hybrid scaffold of biphasic calcium phosphate (BCP) and a polylectrolyte complex (PEC) of chitosan (CS) and hyaluronic acid (HA). The fabrication process included loading of CS-HA PEC in a bare BCP scaffold followed by lypophilization. SEM observation and porosimetry revealed that the scaffold was full of micro and macro pores with total porosity of more than 60 % and pore size in the range of $20{\sim}200{\mu}m$. The composite scaffold was mechanically stronger than the bare BCP scaffold and was significantly stronger than the CS-HA PEC polymer scaffold. Bone morphogenetic growth factor (BMP-2) was immobilized in CS-HA PEC in order to integrate the osteoinductive potentiality required for osteogenesis. The BCP frame, prepared by sponge replica, worked as a physical barrier that prolonged the BMP-2 release significantly. The preliminary biocompatibility data show improved biological performance of the BMP-2 immobilized hybrid scaffold in the presence of rabbit bone marrow stem cells (rBMSC).

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.3
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• pp.278-286
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• 2015

This paper presents the analytical results of the thermodynamic performance characteristics for a cogeneration system using regenerative organic Rankine cycle (ORC) driven by low-grade heat source. The combined heat and power cogeneration system consists of a regenerative superheated ORC and an additional process heater in a series circuit. Eight working fluids of R134a, R152a, propane, isobutane, butane, R245fa, R123, and isopentane are considered for the analysis. Special attention is paid to the effect of turbine inlet pressure on the system performance such as thermal input, net power and useful heat productions, electrical, thermal, and system efficiencies. The results show a significant effect of the turbine inlet pressure and selection of working fluid on the thermodynamic performance of the system.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.4
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• pp.36-42
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• 2004

The Properties of material, C18200 which is used for development of high performance liquid rocket engine combustor chamber were obtained by tension tests. The specimen for regenerative combustor was designed by structural analysis using that Properties. After the designed specimen was manufactured by the same manufacturing process of regenerative combustor. the yielding stress and yielding strain were obtained by strength tests. The properties of C18200 was degraded very much after brazing. The estimation of yielding pressure by structural analysis was almost same as that of strength test. The collector Part was yielded and failed previously than that of cooling channel part during strength test.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.1067-1071
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• 2004

In this paper, the characteristic of the regenerative pump is reviewed by the measurement and the analysis. The dominant noise sources are harmonic components of the rotating impeller frequency. The acoustic characteristics and the noise source position at the dump are identified. In order to reduce the high-level peak noise, the interior flow of the pump chamber is analyzed by CFD (Computational Fluid Dynamics). Acoustic pressure is calculated with Ffowscs Williams and Hawkings equation. As the result of the analysis new design of the pump chamber is recommended. The recommended pump is compared with original pump by evaluating the RMS value of a interior static pressure and the sound pressure level. The new pump chamber recommended by analysis results is proved by a process of the measurement. The overall SPL of a recommended pump is reduced about 3 dBA.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.49-54
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• 1994

A dynamic model for the cutting process in the end milling process is developed. This model, which describes the dynamic response of the end mill, the chip load geometry including tool runout, the dependence of the cutting forces on the chip load, is used to predict the dynamic cutting force during the end milling process. In order to predict accurately cutting forces and tool vibration, the model, which uses instantaneous specific cutting force, includes both regenerative effect and penetration effect. The model is verified through comparisons of model predicted cutting force with measured cutting forces obtained from machining experiments.

• Molecules and Cells
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• v.43 no.8
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• pp.739-748
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• 2020

Stringent regulation of the chondrocyte cell cycle is required for endochondral bone formation. During the longitudinal growth of long bones, mesenchymal stem cells condense and differentiate into chondrocytes. Epiphyseal chondrocytes sequentially differentiate to form growth-plate cartilage, which is subsequently replaced with bone. Although the importance of nuclear factor 1C (Nfic) in hard tissue formation has been extensively studied, knowledge regarding its biological roles and molecular mechanisms in this process remains insufficient. Herein, we demonstrated that Nfic deficiency affects femoral growth-plate formation. Chondrocyte proliferation was downregulated and the number of apoptotic cell was increased in the growth plates of Nfic^-/- mice. Further, the expression of the cell cycle inhibitor p21 was upregulated in the primary chondrocytes of Nfic^-/- mice, whereas that of cyclin D1 was downregulated. Our findings suggest that Nfic may contribute to postnatal chondrocyte proliferation by inhibiting p21 expression and by increasing the stability of cyclin D1 protein.

• International Journal of Oral Biology
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• v.36 no.3
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• pp.117-122
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• 2011

Endothelial cells are a vital constituent of most mammalian organs and are required to maintain the integrity of these tissues. These cells also play a major role in angiogenesis, inflammatory reactions, and in the regulation of thrombosis. Angiogenesis facilitates pulp formation and produces the vessels which are essential for the maintenance of tooth homeostasis. These vessels can also be used in bone and tissue regeneration, and in surgical procedures to place implants or to remove cancerous tissue. Furthermore, endothelial cell regeneration is the most critical component of the tooth generation process. The aim of the present study was to stimulate endothelial regeneration at a site of acute cyclophosphamide (CP)-induced endothelial injury by treatment with human umbilical cord-derived endothelial/mesenchymal stem cells (hEPCs). We randomly assigned 16 to 20-week-old female NOD/SCID mice into three separate groups, a hEPC ($1{\times}10^5$ cells) transplanted, 300mg/kg CP treated and saline (control) group. The mice were sacrificed on days 5 and 10 and blood was collected via the abdominal aorta for analysis. The alanine transaminase (ALT), aspartate aminotransferase (AST), serum alkaline phosphatase (s-ALP), and albumin (ALB) levels were then evaluated. Tissue sections from the livers and kidneys were stained with hematoxylin and eosin (HE) for microscopic analysis and were subjected to immunohistochemistry to evaluate any changes in the endothelial layer. CP treatment caused a weight reduction after one day. The kidney/body weight ratio increased in the hEPC treated animals compared with the CP only group at 10 days. Moreover, hEPC treatment resulted in reduced s-ALP, AST, ALT levels compared with the CP only group at 10 days. The CP only animals further showed endothelial injuries at five days which were recovered by hEPC treatment at 10 days. The number of CD31-positive cells was increased by hEPC treatment at both 5 and 10 days. In conclusion, the CP-induced disruption of endothelial cells is recovered by hEPC treatment, indicating that hEPC transplantation has potential benefits in the treatment of endothelial damage.