• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.3-23
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• 2017

The achievement of tissue engineering can be highly depending on the capability to generate complicated, cell seeded three dimensional (3D) micro/nano-structures. So, various fabrication techniques that can be used to precisely design the architecture and topography of scaffolding materials will signify a key aspect of multi-functional tissue engineering. Previous methods for obtaining scaffolds based on top-down are often not satisfactory to produce complex micro/nano-structures due to the lack of control on scaffold architecture, porosity, and cellular interactions. However, a bioprinting method can be used to design sophisticated 3D tissue scaffolds that can be engineered to mimic the tissue architecture using computer aided approach. Also, in recent, the method has been modified and optimized to fabricate scaffolds using various natural biopolymers (collagen, alginate, and chitosan etc.). Variation of the topological structure and polymer concentration allowed tailoring the physical and biological properties of the scaffolds. In this presentation, the 3D bioprinting supplemented with a newly designed plasma treatment for attaining highly bioactive and functional scaffolds for tissue engineering applications will be introduced. Moreover, various in vivo and in vitro results will show that the fabricated scaffolds can carry out their structural and biological functionality.

• Bulletin of the Korean Chemical Society
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• v.30 no.11
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• pp.2647-2650
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• 2009

Cold shock proteins (Csps) are a subgroup of the cold-induced proteins on reduction of the growth temperature below the physiological temperature. They preferentially bind to single-stranded nucleic acids to translational regulation via RNA chaperoning. Csp plays important role in cold adaptations for the psychrophilic microorganism. Recently, Cold shock protein from psychrophilic bacteria, Colwellia psychrerythraea (CpCsp) has been identified. Three dimensional structures of a number of Csps from various microorganisms have been solved by NMR spectroscopy or X-ray crystallography, but structures of psychrophilic Csps were not studied yet. Therefore, cloning and purification protocols for further structural study of psychrophilic Csp have been optimized in this study. CpCsp was expressed in E. coli with pET-11a vector system and purified by ion exchange, size exclusion, and reverse phase chromatography. Expression and purification of CpCsp in M9 minimal media was carried out and $^{15}N$-labeled proteins with high purity over 90% was obtained. Further study will be carried out to investigate the tertiary structure and dynamics of CpCsp.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.38 no.5
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• pp.425-433
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• 2020

Three-dimensional data has been used for different applications such as robotics, building reconstruction, and so on. 3D data can be generated from an optical camera or a laser scanner. Especially, a wearable multi-sensor system including the above-mentioned sensors is an optimized structure that can overcome the drawbacks of each sensor. After finding the geometric relationships between sensors, georeferencing of the datasets acquired from the moving system, should be carried out. Especially, in an indoor environment, error propagation always causes problem in the georeferencing process. To improve the accuracy of this process, other sources of data were used to combine with LiDAR (Light Detection and Ranging) data, and various registration methods were also tested to find the most suitable way. More specifically, this paper proposed a new process of NDT (Normal Distribution Transform) to register the LiDAR point cloud, with additional information from other sensors. For real experiment, a wearable mapping system was used to acquire datasets in an indoor environment. The results showed that applying the new process of NDT and combining LiDAR data with IMU (Inertial Measurement Unit) information achieved the best result with the RMSE 0.063 m.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.8
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• pp.611-616
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• 2016

Computational fluid dynamic simulation based on the ABAQUS software was conducted to observe the inside flow of slot-die nozzle. The slot-die nozzle was modeled as 3-dimensional structure and three significant parameters were determined: inlet velocity of fluid, reservoir angles, number of strips none of which have been mentioned previously in the literature. The design of experiment, full factorial analysis was performed within determined design and process levels. The simulation result shows the inlet fluid velocity is most significant factor for the flows of inside nozzle. As an interaction effect, reservoir angle is closely related with number of strip that should address when the nozzle is designed. Moreover, the optimized values of each determined parameter were obtained as 35 mm/s of inlet velocity, 3 of strip numbers, and $22^{\circ}$ of reservoir angles. Based on these parameters, the outlet velocity was obtained as 0.53% of outlet uniformity which is improved from 8.67% of nominal results.

• Current Optics and Photonics
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• v.5 no.5
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• pp.500-505
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• 2021

We demonstrated a wide-fan-angle flat-top irradiance pattern with a very narrow linewidth by using an aspheric lens and a long-pitch reflective diffraction grating. First, we numerically designed a diffraction-based linear beam homogenizer. The structure of the Al diffraction grating with an isosceles triangular shape was optimized with 0.1-mm pitch, 35.5° slope angle, and 0.02-mm radius of the rounding top. According to the numerical results, the linear uniformity of the irradiance was more sensitive to the working distance than to the shape of the Al grating. The designed Al grating reflector was fabricated by using a conventional mold injection and an Al coating process. A uniform linear irradiance of 405-nm laser diode with a 100-mm flat-top length and 0.176-mm linewidth was experimentally demonstrated at 140-mm working distance. We believe that our proposed linear beam homogenizer can be used in various potential applications at a precise inspection system such as three-dimensional morphology scanner with line lasers.

• Wind and Structures
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• v.38 no.3
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• pp.161-170
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• 2024

In recent years, there have been an increasing number of experimental studies showing the need to include robustness criteria in the design process to develop complex active control designs for practical implementation. The paper investigates the crosswind aerodynamic parameters after the blocking phase of a two-dimensional square cross-section structure by measuring the response in wind tunnel tests under light wind flow conditions. To improve the accuracy of the results, the interpolation of the experimental curves in the time domain and the analytical responses were numerically optimized to finalize the results. Due to this combined effect, the three aerodynamic parameters decrease with increasing wind speed and asymptotically affect the upper branch constants. This means that the aerodynamic parameters along the density distribution are minimal. Taylor series are utilized to describe the fuzzy nonlinear plant and derive the stability analysis using polynomial function for analyzing the aerodynamic parameters and numerical simulations. Due to it will yield intricate terms to ensure stability criterion, therefore we aim to avoid kinds issues by proposing a polynomial homogeneous framework and utilizing Euler's functions for homogeneous systems. Finally, we solve the problem of stabilization under the consideration by SOS (sum of squares) and assign its fuzzy controller based on the feasibility of demonstration of a nonlinear system as an example.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.39 no.4
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• pp.329-335
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• 2013

Three-dimensional quantitative structure-activity relationships (3D-QSARs) models between the substituents with changing groups ($R_1$ & $R_2$) of 4-hydroxybenzyl alcohol (4-HBA) derivatives as substrate molecule and their inhibitory activities against tyrosinase were derived and discussed quantitatively. The optimized CoMSIA FF model showed the best predictability and fitness ($r^2$ = 0.858 & $q^2$ = 0.951). The contour maps of the optimized CoMSIA FF model showed that, the inhibitory activities of the analogues against tyrosinase were expected to increase when hydrophobic (Hy) favor, negative charge (E) favor, steric (S) disfavor and hydrogen bond donor (HD) disfavor groups were substituted at the $R_2$ position. When the hydrogen bond donor (HD) favor groups were substituted at the $R_1$ position, it is predicted that the substituents will be able to increase the inhibitory activity.

• Korean Journal of Veterinary Research
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• v.58 no.4
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• pp.211-217
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• 2018

Mesenchymal stem cells (MSCs) are useful candidates for tissue engineering and cell therapy. Physiological cell environment not only connects cells to each other, but also connects cells to the extracellular matrix that provide mechanical support, thus exposing the entire cell surface and activating signaling pathways. Hydrogel is a polymeric material that swells in water and maintains a distinct 3-dimensional (3D) network structure by cross linking. In this study, we investigated the optimized cellular function for canine adipose tissue-derived MSCs (cAD-MSCs) using hydrogel. We observed that the expression levels of Ki67 and proliferating cell nuclear antigen, which are involved in cell proliferation and stemness, were increased in transwell-hydrogel (3D-TN) compared to the transwell-normal (TN). Also, transforming growth factor-${\beta}1$ and SOX9, which are typical bone morphogenesis-inducing factors, were increased in 3D-TN compared to the TN. Collagen type II alpha 1, which is a chondrocyte-specific marker, was increased in 3D-TN compared to the TN. Osteocalcin, which is a osteocyte-specific marker, was increased in 3D-TN compared to the TN. Collectively, preconditioning cAD-MSCs via 3D culture systems can enhance inherent secretory properties that may improve the potency and efficacy of MSCs-based therapies for bone regeneration process.

• Journal of Korean Society of Steel Construction
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• v.25 no.3
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• pp.307-320
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• 2013

This paper proposes a new hybrid support structure by the driven piles which removes disadvantages of the existing type of support structure for offshore wind turbines. The hybrid type of support structure is combined with concrete cone and steel shaft, and is supported not only by gravity type foundations but also by driven piles. For three dimensional analysis of the huge and thick concrete structure, a solid-shell element that is capable of exact modeling and node interpolations of stresses is developed. By applying wave theory of stream function and solid-shell element in XSEA simulation software for fixed offshore wind turbines, a quasi-static analysis and natural frequency analysis of proposed support structure are performed with the environmental condition on Southwest Coast in Korea. In the result, lateral displacement is not exceed allowable displacement and a superiority of dynamic behavior of new hybrid support structure is validated by natural frequency analysis. Consequently, the hybrid support structure presented in this study has a structural stability enough to be applied on real-site condition in Korea. The optimized structures based on the preliminary design concept resulted in an efficient structure, which reasonably reduces fabrication costs.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.2
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• pp.259-267
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• 2004

Most steel frame structures are constructed to one side without considering the arrangement of major-minor axis of column and bracing. This research presents more safety and economic efficiency can be obtained by just rearrangement of major-minor axis. Because most of steel-frame structures are excessively designed with Allowable Stress Design, and it needs to be changed to other specifications. The arrangement of major-minor axis of column is partly referred in AISC-LRFD, but still insufficient. This study compared with the each result from rearrangement of major-minor axis of column, arrangement of bracing, the connecting method of bracing, and consequence with different specifications. Moreover it demonstrated the direction of more economically optimized design.