• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.449-452
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• 2008

Flow difference between reacting and non-reacting case in a swirl stabilized annular combustor is investigated using 3D Large Eddy Simulation with flamelet turbulent combustion model. The combustor of concern is the LM6000, lean premixed dry low-NOx annular combustor, developed by GEAE. Boundary conditions are based on experimental data. Heat release as a result of combustion put the dilatation of density in primary combustion zone highly increased so that the main swirl stream behind of a swirl cup stretched further downstream than that of non-reacting case. The oval shape of core flow in cross-section to flow direction, which clearly observed in non-reacting case, tends to be circle, and small vorticities in wide range in non-reacting case disappears, but the size of iso-vorticity increase in reacting case.

• Journal of Powder Materials
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• v.26 no.4
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• pp.282-289
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• 2019

Ti has received considerable attention for aerospace, vehicle, and semiconductor industry applications because of its acid-resistant nature, low density, and high mechanical strength. A common precursor used for preparing Ti materials is $TiCl_4$. To prepare high-purity $TiCl_4$, a process based on the removal of $VOCl_3$ has been widely applied. However, $VOCl_3$ removal by distillation and condensation is difficult because of the similar physical properties of $TiCl_4$ and $VOCl_3$. To circumvent this problem, in this study, we have developed a process for $VOCl_3$ removal using Cu powder and mineral oil as purifying agents. The effects of reaction time and temperature, and ratio of purifying agents on the $VOCl_3$ removal efficiency are investigated by chemical and structural measurements. Clear $TiCl_4$ is obtained after the removal of $VOCl_3$. Notably, complete removal of $VOCl_3$ is achieved with 2.0 wt% of mineral oil. Moreover, the refined $TiCl_4$ is used as a precursor for the synthesis of Ti powder. Ti powder is fabricated by a thermal reduction process at $1,100^{\circ}C$ using an $H_2-Ar$ gas mixture. The average size of the Ti powder particles is in the range of $1-3{\mu}m$.

• Journal of Urban Science
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• v.7 no.2
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• pp.53-60
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• 2018

Digital Twin is a technology that creates a photocopy of real-world objects on a computer and analyzes the past and present operational status by fusing the structure, context, and operation of various physical systems with property information, and predicts the future society's countermeasures. In particular, 3D rendering technology (UAS, LiDAR, GNSS, etc.) is a core technology in digital twin. so, the research and application are actively performed in the industry in recent years. However, UAS (Unmanned Aerial System) and LiDAR (Light Detection And Ranging) have to be solved by compensating blind spot which is not reconstructed according to the object shape. In addition, the terrestrial LiDAR can acquire the point cloud of the object more precisely and quickly at a short distance, but a blind spot is generated at the upper part of the object, thereby imposing restrictions on the forward digital twin modeling. The UAS is capable of modeling a specific range of objects with high accuracy by using high resolution images at low altitudes, and has the advantage of generating a high density point group based on SfM (Structure-from-Motion) image analysis technology. However, It is relatively far from the target LiDAR than the terrestrial LiDAR, and it takes time to analyze the image. In particular, it is necessary to reduce the accuracy of the side part and compensate the blind spot. By re-optimizing it after fusion with UAS and Terrestrial LiDAR, the residual error of each modeling method was compensated and the mutual correction result was obtained. The accuracy of fusion-based 3D model is less than 1cm and it is expected to be useful for digital twin construction.

• Journal of The Korean Society of Agricultural Engineers
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• v.63 no.4
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• pp.23-32
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• 2021

For agricultural water management, it is essential to establish the digital infrastructure data such as agricultural watershed, irrigated area and canal network in rural areas. Approximately 70,000 irrigation facilities in agricultural watershed, including reservoirs, pumping and draining stations, weirs, and tube wells have been installed in South Korea to enable the efficient management of agricultural water. The total length of irrigation and drainage canal network, important components of agricultural water supply, is 184,000 km. Major problem faced by irrigation facilities management is that these facilities are spread over an irrigated area at a low density and are difficult to access. In addition, the management of irrigation facilities suffers from missing or errors of spatial information and acquisition of limited range of data through direct survey. Therefore, it is necessary to establish and redefine accurate identification of irrigated areas and canal network using up-to-date high resolution images. In this study, previous existing data such as RIMS (Rural Infrastructure Management System), smart farm map, and land cover map were used to redefine irrigated area and canal network based on appropriate image data using satellite imagery, aerial imagery, and drone imagery. The results of the building the digital infrastructure in rural areas are expected to be utilized for efficient water allocation and planning, such as identifying areas of water shortage and monitoring spatiotemporal distribution of water supply by irrigated areas and irrigation canal network.

• Current Applied Physics
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• v.18 no.12
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• pp.1513-1522
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• 2018

Bismuth telluride ($Bi_2Te_3$) thin films were prepared with various electrolyte temperatures ($10^{\circ}C-70^{\circ}C$) and concentrations [$Bi(NO_3)_3$ and $TeO_2:1.25-5.0mM$] in this study. The surface morphologies differed significantly between the experiments in which these two electrodeposition conditions were separately adjusted even though the applied current density was in the same range in both cases. At higher electrolyte temperatures, a dendrite crystal structure appeared on the film surface. However, the surface morphology did not change significantly as the electrolyte concentration increased. The dendrite crystal structure formation in the former case may have been caused by the diffusion lengths of the ions increasing with increasing electrolyte temperature. In such a state, the reactive points primarily occur at the tops of spiked areas, leading to dendrite crystal structure formation. In addition, the in-plane thermoelectric properties of $Bi_2Te_3$ thin films were measured at approximately 300 K. The power factor decreased drastically as the electrolyte temperature increased because of the decrease in electrical conductivity due to the dendrite crystal structure. However, the power factor did not strongly depend on the electrolyte concentration. The highest power factor [$1.08{\mu}W/(cm{\cdot}K^2$)] was obtained at 3.75 mM. Therefore, to produce electrodeposited $Bi_2Te_3$ films with improved thermoelectric performances and relatively high deposition rates, the electrolyte temperature should be relatively low ($30^{\circ}C$) and the electrolyte concentration should be set at 3.75 mM.

• Journal of Convergence for Information Technology
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• v.11 no.6
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• pp.219-225
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• 2021

As for the battery package method, a prismatic package method is preferred for stability reasons, but it is rapidly expanding due to the stability verification of a pouch type package. The pouch type using the lamination process has an advantage of high battery energy density because it can reduce space waste, but has a disadvantage of low productivity. Therefore, in this paper, by extracting edge detection algorithm precision, pattern algorithm precision, and motion controller recall rate by improving backlight lighting fixtures to minimize light diffusion, securing standards for stereo camera position relationship displacement monitoring, and securing standards for lens release monitoring. We propose to implement a system that ensures accuracy and reliability in positioning. As a result of the experiment, the proposed system shows an average error range of 0.032mm for edge detection, 0.02mm for pattern algorithm, and 0.014mm for motion controller, thus ensuring the accuracy and reliability of the positioning mechanism.

• Journal of the Korean institute of surface engineering
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• v.54 no.4
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• pp.178-183
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• 2021

The temperature and frequency dependence of the dielectric constant of the BaTiO₃ substituted with two types of donor dopants, Nb⁵⁺ and Ta⁵⁺, respectively, were compared and analyzed. Dielectric specimens of four specific compositions, Ba_0.95Nb_0.05TiO₃, Ba_0.90Nb_0.10TiO₃, Ba_0.95Ta_0.05TiO₃, and Ba_0.90Ta_0.010TiO₃ were prepared by calcining at 1100 ℃ and sintering at 1300 ℃ to have a perovskite structure to measure capacitance. XRD and SEM analysis were used to observe the structure, with particular focus on the integration into the Nb⁵⁺ and Ta⁵⁺ substituted BaTiO₃ crystal lattice. X-ray diffraction peaks in the (200) and (002) planes were observed between 45.10° and 45.45° of the BaTiO₃ solid solution substituted with different fractions of Nb⁵⁺ and Ta⁵⁺. The dielectric properties were analyzed and the relationship between the properties and structure of the substituted BaTiO₃ was established. The fine particles and high density of the substituted BaTiO₃ were maintained like pure BaTiO₃, and in particular, a shift toward the low temperature side of the phase transition temperature range was clearly found, unlike pure BaTiO₃. In addition, the phase transition at a temperature higher than the Curie temperature relatively satisfies the modified Curie-Weiss law.

• Journal of the Korean Magnetic Resonance Society
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• v.25 no.4
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• pp.58-63
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• 2021

Apolipoprotein B-100 (apo B-100), the main protein component that makes up LDL (Low density lipoprotein), consists of 4,536 amino acids and serves to combine with the LDL receptor. The oxidized LDL peptides by malondialdehyde (MDA) or acetylation in vivo act as immunoglobulin (Ig) antigens and peptide groups were classified into 7 peptide groups with subsequent 20 amino acids (P1-P302). The biomimetic peptide P143 (IALDD AKINF NEKLS QLQTY) out of C-group peptides carrying the highest value of IgG antigens were selected for structural studies that may provide antigen specificity. Experimental results show that P143 has β-sheet in Ile[1]-Asn[9] and α-helice in Gln[16]-Tyr[20] structure. Homonuclear 2D-NMR (COSY, TOCSY, NOESY) experiments were carried out for NMR signal assignments and structure determination for P143. On the basis of these completely assigned NMR spectra and proton distance information, distance geometry (DG) and molecular dynamic (MD) were carried out to determine the structures of P143. The proposed structure was selected by comparisons between experimental NOE spectra and back-calculated 2D NOE results from determined structure showing acceptable agreement. The total Root-Mean-Square-Deviation (RMSD) value of P143 obtained upon superposition of all atoms were in the set range. The solution state P143 has a mixed structure of pseudo α-helix and β-turn(Phe[10] to Glu[12]). These results are well consistent with calculated structure from experimental data of NOE spectra. Structural studies based on NMR may contribute to the prevent oxidation studies of atherosclerosis and observed conformational characteristics of apo B-100 in LDL using monoclonal antibodies.

• Korean Journal of Materials Research
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• v.32 no.12
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• pp.560-564
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• 2022

In this study, lanthanum boron silicate glasses were prepared with a composition of x Li₂O-(60-x)B₂O₃-5CaO-5BaO-7ZnO-10SiO₂-10La₂O₃-3Y₂O₃ where x = 1,3,5,7, and 9 mol%. Each composition was melted in a platinum crucible under atmospheric conditions at 1,400 ℃ for 2 h. Clear glasses with a transmittance exceeding 85 % were fabricated. Their optical, thermal, and physical properties, such as refractive index, Abbe number, density, glass transition (T_g) and Knoop hardness were studied. The results demonstrated that refractive index was between 1.6859 and 1.6953 at 589.3 nm. The Abbe number was calculated using an equation for 589.3 nm (nd), 656.3 nm (nf) and 486.1 nm (nc) and was observed to be in the range from 57.5 to 62.6. As the Li₂O content increased, the glass transition temperature of the optical glass decreased from 608 ℃ to 564 ℃. If glass mold pressing is performed using a material with a low transition temperature and high mechanical strength, then the optical glasses developed in this study can be completely commercialized.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.1
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• pp.38-47
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• 2023

According to the government policy of environmental regulations, interest of ship, which made with High-Density Polyethylene (HDPE) as a low-carbon and eco-friendly material, is growing as a substitute for the existing fishery boat hull materials such as FRP, aluminum, steel etc. However, regulations related to the production of HDPE ship are still quite incomplete. Even there are no regulations related to structural analysis. Therefore, in this study, structural analysis is carried out by applying different design loads for each international classification for 38ft class HDPE power boats, and the results are compared and analyzed. According to this study, although there is a correlation between the based pressure value and the analysis result value of each class regulation, it is not necessarily proportional. Also, This analysis result shows a difference not only depending on the size of design load, but also application range of the load, the pressure adjustment factor and section shape. However, the occurrence point and trend of the maximum stress values were quite consistent. It is hoped that the results of this study will be used when establishing HDPE ship structure analysis procedures and standards in the future.