• Archives of Plastic Surgery
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• v.38 no.5
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• pp.567-575
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• 2011

Purpose: Acellular human dermis is very useful implant for use in plastic and reconstructive surgery. However, the volume of acellular human dermis graft is known to decrease for a long time. Basic fibroblast growth factor (bFGF) is a polypeptide that enhances the collagen synthesis and angiogenesis. In the current study we examined whether bFGF could improve the survival of acellular human dermis ($SureDerm^{(R)}$) by increasing angiogenesis of the graft. Methods: Forty rats were divided into two groups (control and bFGF). A 2-mm thick piece of $SureDerm^{(R)}$ was cut into smaller pieces that were $15{\times}5$ mm in size. Two subcutaneous pockets were made on the back of each rat. Grafts sprayed with bFGF were implanted in the bFGF group and injected with bFGF after transplantation every 3 days for 2 weeks. In the control group, the grafts were treated with phosphate-buffered saline (PBS) instead of bFGF. Four days, and 1, 4, and 12 weeks after the implantation, the grafts were harvested and gross and histologic examinations were performed. Inflammation grade, graft thickness, neocollagen density, and neocapillary count were measured. Results: The bFGF group displayed more rapid accumulation of inflammatory cells with a higher density of neocapillaries, and increased active collagen synthesis. After 12 weeks, the thickness of the grafts in the control and bFGF groups was $75.15{\pm}4.80%$ and $81.79{\pm}5.72%$, respectively, in comparison to the thickness before transplantation. There was a statistically significant difference between both groups ($p$ <0.05). Conclusion: bFGF was effective in reducing the absorption of acellular human dermal grafts by increasing angiogenesis and accelerating engraftment. In conclusion, bFGF may be a good tool for use in acellular human dermal graft transplantation for reconstructive surgery involving soft-tissue defects.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.835-841
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• 2013

Modern solid-state gyroscopes (HRG) with hemispherical resonators from high-purity quartz glass and special surface superfinishing and ultrathin gold coating become the best instruments for precise-grade inertial reference units (IRU) targeting long-term space missions. Designing of these sensors could be a notable contribution into development of Korea as a space nation. In participial, 40mm diameter thin-shell resonator from high-purity fused quartz, fabricated as a single-piece with its supporting stem has been designed, machined, etched, tuned, tested, and delivered by STM Co. (ATS of Ukraine) several years ago; an extremely-high Q-factor (upto 10~20 millions) has been shown. Understanding of the best way how to match such a unique sensor with inner glass assembly of the gyro means how to use the high potential in a maximal extent; and this has become the urgent task. Inner quartz glass assembly has a very thin indium (In) layer soldered the resonator and its silica base (case), but effects of internal resonances between operational modal pair of the shell-cup and its side (parasitic) modes can notable degrade the potential of the sensor as a whole, instead of so low level of resonator's intrinsic losses. Unfortunately, there are special combinations of dimensions of the parts (so-called, "resonant sizes"), when intensive losses of energy occurs. The authors proposed to use the length of stem's fixture as an additional design parameter to avoid such cases. So-called, a cyclic scheme of finite element method (FEM) and ANSYS software were employed to estimate different combinations of gyro assembly parameters. This variant has no mismatches of numerical origin due to FEM's discrete mesh. The optimum length and dangerous "resonant lengths" have been found. The special attention has been paid to analyses of 3D effects in a cup-stem transient zone, including determination of a difference between the positions of geometrical Pole of the resonant hemisphere and of its "dynamical Pole", i.e., its real zone of oscillation node. Boundary effects between the shell (cup) and 3D short "beams" (inner and outer stems) have been ranged. The results of the numerical experiments have been compared with the classic model of a quasi-hemispherical shell band with inextensional midsurface, and the solution using Rayleigh's functions of the $1^{st}$ and $2^{nd}$ kinds. To guarantee the truth of the recommended sizes to a designer of the real device, the analytical and FEM results have been compared with experimental data for a party of real resonators. The consistency of the results obtained by different means has been shown with errors less than 5%. The results notably differ from the data published earlier by different researchers.

• Composites Research
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• v.35 no.4
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• pp.269-276
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• 2022

In this paper, a composite stiffened panel was fabricated using a three-dimensional weaving method that can reduce the risk of delamination, and mechanical properties such as buckling load and natural frequency were investigated. The preform of the stringer and skin of the stiffened panel were fabricated in one piece using T800 grade carbon fiber and then, resin (EP2400) was injected into the preform. The compression test and natural frequency measurement were performed for the stiffened panel, and the results were compared with the finite element analyses. In order to compare the performance of 3D weaving structures, the stiffened panels with the same configuration were fabricated using UD and 2D plain weave (fabric) prepregs. Compared to the tested buckling load of the 3D woven panel, the buckling loads of the stiffened panels of UD prepreg and 2D plain weave exhibited +20% and -3% differences, respectively. From this study, it was confirmed that the buckling load of the stiffened panel manufactured by 3D weaving method was lower than that of the UD prepreg panel, but showed a slightly higher value than that of the 2D plain weave panel.