• Journal of the Korean Society of Industry Convergence
• /
• v.27 no.2_2
• /
• pp.389-395
• /
• 2024

The purpose of this study was to evaluate the effect of different washing solvents and washing methods on the flexural strength of 3D printed temporary resin. A bar(25 × 2 × 2 mm) was produced with a layer thickness of 50 ㎛ using an LCD-type 3D printer and divided into 15 groups(n = 10, each) according to washing solution(IPA; 99% isopropyl alcohol, TPM; 93% Tripropylene glycol monomethylether, ETL; Ethanol, TWC; Twin 3D Cleaner, and DNC; DIO navi Cleaner) and washing method(Dip; Dip washing, Ultra; Ultrasonic washing, and Auto; Automated washing). All groups were washed for 5 minutes, and post-cured for 5 minutes using a UV LED light curing machine. The Flexural strength was measured using a three-point bending test using a universal testing machine. For statistical analysis, one-way ANOVA, Tukey HSD post hoc test, Kruskal-Wallis test and post-hoc by Bonferroni-Dunn test(𝛼=.05) were performed depending on whether the normality test was satisfied. In all washing solvents except TPM and DNC, the Dip group showed the lowest flexural strength values, while the Auto group showed the highest flexural strength values except for DNC. Additionally, the washing solution showed completely different flexural strength values depending on the washing method.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.8 no.1
• /
• pp.1-8
• /
• 2005

We estimated the loadings of nitrogen and phosphorus flowing into Gwangyang Bay front river for monthly interval from April to December of 2003. We analyzed the concentrations of nitrogen and phosphorus in water and estimated the flowing rates of fresh water in 34 rivers. The amounts of water flowing into the Gwdngyang Bay from Sum-Jin River was 51-76％ in the total inflow of the river. The river water over 96％ of discharge was from Sumjin River, Dong River, Ju-Kyo River, Seo River and Shinkyum River. The flowing patterns of nitrogen and phosphorus into Gwangyang Bay were similar to the flowing of river. The nitrogen and phosphorus loadings into the Bay were higher in July and August than in dry seasons. In particular, the concentrations of phosphorus were high in Namshu River, Deukyang River and Kilho River sewage during in dry seasons. The range of DIN and TN loadings from Sumjim River were 46-66％ and 36-64％, respectively. The loading of DIP and TP from Sumjim River were 2-55％ and 12-67％, respectively. These results show that the most efficient control of N. p flow into Gwangyang Bay is to restrain the inflows of N, p from Namshu River, Deukyang River and Kilho River and to restrain the flows of N, p from Dong River, Ju-Kyo River and industrial plant. The DIN/DIP atom ratio in river water was about 18 in July and August, while the ratio was more higher in dry seasons than July and August of rainy seasons. The TN/TP atom ratio in river water was about 7 in rainy seasons, while the ratios were higher than 100 in the other months of dry seasons.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.16 no.1
• /
• pp.27-38
• /
• 2011

The distributions of phytoplankton assemblages and environmental factors in Jinhae Bay and their relationships were investigated to estimate the potential limiting nutrient for phytoplankton growth and community structure. In situ algal bioassay experiments were also conducted to assess the species-specific characteristics in phytoplankton responses under different nutrient conditions (control, N(+) and P(+) treatment). During the study periods, bacillariophyceae and cryptophyceae occupied more than 90% of total phytoplankton assemblages. Phytoplankton standing crops in the inner part of Masan Bay were higher than that of Jinhae Bay. The DIN:DIP ratio, pH and transparency showed the significant positive correlation with phytoplankton biomass. According to cluster and multidimensiolnal scaling (MDS) analysis based on phytoplankton community data from each station, the bay was divided into three groups. The first group included stations from the south-western part of Jinhae bay where cryptophyta species were dominated. The second group was distinguished from inner stations in Masan Bay. These stations showed low transpancy and high DIN:DIP ratio. The other cluster included the stations from the eastern part and central part of Jinhae Bay, which was characterized by the high DSi:DIP ratio and dominant of diatom species. Phosphorous (P) was limited in Masan Bay due to significantly increases in the phytoplankton abundances. Based on stoichiometric limitation and algal bio-assay in Jinhae Bay, nitrogen (N) was a major limiting factor for phytoplankton production. However, silicate (Si) was not considered as limiting factor, since Si/DIN and Si/P ratio and absolute concentration of nutrient did not create any potential stoichiometric limitation in the bay. This implies that high Si availability in winter season contributes favorably to the maintenances of diatom species.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.37 no.1
• /
• pp.67-76
• /
• 2024

In this paper, we present a DIP-MLS testing method that combines digital image processing with a rigid body-based MLS differencing approach to measure mechanical variables and analyze the impact of target location and image resolution. This method assesses the displacement of the target attached to the sample through digital image processing and allocates this displacement to the node displacement of the MLS differencing method, which solely employs nodes to calculate mechanical variables such as stress and strain of the studied object. We propose an effective method to measure the displacement of the target's center of gravity using digital image processing. The calculation of mechanical variables through the MLS differencing method, incorporating image-based target displacement, facilitates easy computation of mechanical variables at arbitrary positions without constraints from meshes or grids. This is achieved by acquiring the accurate displacement history of the test specimen and utilizing the displacement of tracking points with low rigidity. The developed testing method was validated by comparing the measurement results of the sensor with those of the DIP-MLS testing method in a three-point bending test of a rubber beam. Additionally, numerical analysis results simulated only by the MLS differencing method were compared, confirming that the developed method accurately reproduces the actual test and shows good agreement with numerical analysis results before significant deformation. Furthermore, we analyzed the effects of boundary points by applying 46 tracking points, including corner points, to the DIP-MLS testing method. This was compared with using only the internal points of the target, determining the optimal image resolution for this testing method. Through this, we demonstrated that the developed method efficiently addresses the limitations of direct experiments or existing mesh-based simulations. It also suggests that digitalization of the experimental-simulation process is achievable to a considerable extent.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.30 no.1
• /
• pp.7-11
• /
• 2020

Carbon solubility on the paste deposition methods in the carbon-doped TiZrN coating was investigated in terms of lattice distortion and atomic concentration. After depositing the carbon paste by the dip coating, spin coating and screen printing, the laser was ablated to form the carbon gradient layer. Thickness and the concentration of doped carbon depended on the paste deposition method. Crystal structure analysis indicated that more lattice distortion occurred when coating layers were doped with spin coating and screen printing than when coating layers were doped with dip coating. The XPS depth profile showed that the thickness of carbon gradient layer by dip coating was about 30 nm, spin coating and screen printing are approximately 100 nm, formed more gradient layer. The hardness before laser carburization was about 30 GPa, and the hardness of 31 GPa with dip coating and 37 GPa with spin coating and screen printing. It was indicated that paste deposition methods for laser carburization contributed to lattice distortion and gradient layer.

• Journal of the Korean Electrochemical Society
• /
• v.8 no.4
• /
• pp.162-167
• /
• 2005

Using Pechini method, we synthesized the $La_{0.6}Ca_{0.41}CrO_3$ (LCC41) and $La_{0.8}Sr_{0.05}Ca_{0.15}CrO_3$ (LSCC) powders for slurry dip coating, and $La_{0.75}Ca_{0.27}CrO_3$ (LCC27) powder for air plasma spray coating. The sintering property of the powders and their coating properties were investigated. The average particle sizes of the LCC41, LSCC, LCC27 were 0.6, 0.9, $1.5{\mu}m$, respectively. The relative density of LCC41 bulk was to be found about 98%. The LSCC coating on anode support prevented Ca migration of the coated LCC41 on the anode some or less, which was confirmed from EDS result. The air plasma spray-coated LCC27 with the dip-coated LCC41 were more dense and showed better electrical conductivity than those of the air plasma spray-coated LCC27 and the dip-coated LSCC and LSCC41. The LCC41 and LCC27 showed good electrical conductivities, but the LSCC had a poor electrical conductivity probably due to low sinterability

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.2 no.1
• /
• pp.74-89
• /
• 1999

Distributions and budgets of nitrogen and phosphorus in inner and central areas of Hiroshima bay were investigated for three years from January 1991 to December 1993. The mean loadings of nitrogen and phosphorus Stowed into the entire bay were 870 tonN/month and 129 tonP/month, respectively. About 79 % of nitrogen and 84 % of phosphorus loadings were flowed into the inner area. The TN:TP and DIN:DIP atomic ratios of the discharged freshwater were about 15 and 21, respectively. The PON:POP and DIN:DIP atomic ratios of seawater in the bay varied from 8 to 14 with a mean value of 11, and from 8 to 18 with a mean value of 12, respectively. Estimated fluxes of nitrogen and phosphorus based on the exchange of seawater were 585 tonN/month and 106 tonP/month, respectively, from the inner area to the central area, whereas those fluxes were 62 tonN/month and 107 tonP/month, respectively, from the central area to Akinada. When the remainders of nitrogen and phosphorus substracted outflows from inflows should be sunk, sink fluxes of nitrogen and phosphorus per surface area of the entire bay would be about 9.83 gN/m²ㆍyr and 0.27 gP/m²ㆍyr, respectively. In the central area, the remainders of nitrogen and phosphorus were greater than those in inner area. The residence times of nitrogen and phosphorus were estimated to be about 112 days, respectively, in the entire of Hiroshima Bay.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.15 no.2
• /
• pp.91-98
• /
• 2009

The long-term water-quality change of Asan Bay by the influx of polluted disposal water was predicted through a simulation with an Eco-hydrodynamic model. Eco-hydrodynamic model is composed of a multi-level hydrodynamic model to simulate the water flow and an ecosystem model to simulate water quality. The water quality simulation revealed that the COD(Chemical Oxygen Demand), dissolved inorganic nitrogen(DIN) and dissolved inorganic phosphorus(DIP) are increased at 5 stations for the subsequent 6 months after the influx of the effluent. COD, DIN and DIP showed gradual decreases in concentration during the period of one to two years after the increase of last 6 months and reached steady state for next three to ten years. Concentration levels of COD, DIN, and DIP showed the increase by the ranges of $11{\sim}67%$, $10{\sim}67%$, and $0.5{\sim}7%$, respectively, which represents that the COD and DIN are the most prevalent pollutants among substances in the effluent through the sewage treatment plant. The current water quality of Asan Bay based on the observed COD, TN and TP concentrations ranks into the class II of the Korean standards for marine water quality but the water quality would deteriorate into class III in case that the disposal water by the sewage plant is discharged into the Bay.

• Korean Journal of Ecology and Environment
• /
• v.33 no.4 s.92
• /
• pp.380-386
• /
• 2000

Alkaline phosphatase ($AP_{ase}$) activity was studied for the pure cultures and natural communities of phytoplankton. The Michaelis-Menten constant ($K_m$) showed large variation with species. Some green algae showed large $K_m$ ($650\;{\mu}M$ for Selenastrum capriconutum). Chlorella sp. and Nitzschia palea showed smaller Km (respectively1.7, 2.0 HM) than those of other species examined. The extracellular free enzyme in the filtrate of Anabaena flos-aquae showed smaller Km ($52\;{\mu}M$) than that of cellbound form ($276\;{\mu}M$). The $K_m$ ($12.0\;{\mu}M$) of summer phytoplankton in Lake Soyang. when Anabaena sp. was dominant species, was larger than that (1.5 HM) of spring phytoplankton when Asterionella sp. was the dominant. Although maximum activity($V_{max}$) in Lake Soyang was affected by the concentration of DIP within the lake, but the $V_{max}$ always varied not with the DIP concentration of the lake. Induction of $AP_{ase}$ may be more affected by the phosphate content within the cell of phytoplankton than by the concentration of DIP within the lake, The extracellular free $AP_{ase}$ activity accounted for $36{\sim}97%$ of total activity from fall to spring turnover in Lake Soyang. The $K_m$ ($1.1{\mu}3.5\;M$) of extracelluar free enzyme were simillar to those ($0.7{\mu}3.5\;M$) of the total activity. This indicates that the extracelluar free enzyme was derived from phytoplankton.

• Tunnel and Underground Space
• /
• v.25 no.1
• /
• pp.97-106
• /
• 2015

We must precisely investigate the mechanical characters of rock to design rock slope safely and efficiently. But the method of clinometer has some disadvantages. So, we need a new measurement that can replace the method of clinometer. In this study, we analyze the reliability of joint orientation measurements in rock slope using the 3D laser scanner and program Split-FX that is a point cloud data analysis software. We could acquire the 495 pieces joint data through the automatic extraction of features. And we confirmed that there were some errors occurred with ${\pm}4^{\circ}$ of dip and ${\pm}5^{\circ}$ of dip direction. Generally, the method of clinometer has ${\pm}5^{\circ}$ and ${\pm}10^{\circ}$ error ranges of the joint orientation(dip/dip direction) that are the results of the advance research. Therefore, we analyzed the method of 3D laser scanner, and it is found to be efficient, reliable. This method is expected to mend the disadvantages of Clinometer method.