• Journal of the Korean institute of surface engineering
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• v.40 no.4
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• pp.170-174
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• 2007

High Velocity Oxygen Fuel (HVOF) thermal spray coating of nano size WC-Co powder (nWC-Co) has been studied as one of the most promising candidate for the possible replacement of the traditional hard plating in some area which causes environmental and health problems. nWC-Co powder was coated on Inconel 718 substrates by HVOF technique. The optimal coating process obtained from the best surface properties such as hardness and porosity is the process of oxygen flow rate (FR) 38 FMR, hydrogen FR 57 FMR and feed rate 35 g/min at spray distance 6 inch for both surface temperature $25^{\circ}C\;and\;500^{\circ}C$. In coating process a small portion of hard WC decomposes to less hard $W_2C$, W and C at the temperature higher than its decomposition temperature $1,250^{\circ}C$ resulting in hardness decrease and porosity increase. Friction coefficient increases with increasing coating surface temperature from 0.55-0.64 at $25^{\circ}C$ to 0.65-0.76 at $500^{\circ}C$ due to the increase of adhesion between coating and counter sliding surface. Hardness of nWC-Co is higher or comparable to those of other hard coatings, such as $Al_2O_3,\;Cr,\;Cr_2O_3$ and HVOF Tribaloy 400 (T400). This shows that nWC-Co is recommendable for durability improvement coating on machine components such as high speed spindle.

• Environmental Engineering Research
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• v.24 no.2
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• pp.238-245
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• 2019

This study investigated the characteristic of aerobic granular sludge (AGS) process to treat the sewage having low carbon/nitrogen ratio (Biochemical oxygen demand ($BOD_5$):Total nitrogen (T-N), 4.5:1) in sequencing batch reactor (SBR). The removal efficiency of $BOD_5$, suspended solid (SS), T-N and phosphorus ($PO_4{^{3-}}$-P) were 92.6%, 64.3% and 90.1%. Concentration and size of AGS were changed in proportion to the organic matters and nitrogen concentration of the influent (Concentration and size of AGS: 1,700-3,000 mg/L, 0.5-1.0 mm). Mixed liquor suspended solid (MLSS) also changed with the concentration of AGS (MLSS: 2,000-3,500 mg/L). When the settling time was shortened from 15 min to 10 min, size and shape of AGS were maintained (Size of AGS: 1.0-1.5 mm). In addition, the concentration of AGS and MLSS increased (Concentration of AGS: 3,500 mg/L, MLSS: 4,000 mg/L). Concentration, size and shape of AGS were affected the settling time of the reactor more than the concentration of organic matter and nitrogen in the influent. In the results of removal efficiency and changes in AGS, we confirmed that the SBR process using AGS can be used to treat the sewage having low carbon/nitrogen ratio by applying short settling time.

• Journal of the Korea Institute of Building Construction
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• v.19 no.1
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• pp.39-46
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• 2019

A three-dimensional flow simulation model for high flow concrete was developed using Incompressible Smoothed Particle Hydrodynamics (ISPH), which can solved Navier-Stokes equation with the assumption of a fluid to be incompressible. For the simulation, a computer program code for ISPH was implemented with MATALB programming code. A piecewise cubic spline function was used for the kernel function of ISPH. Projetion method was used to calculate the velocity and pressure of particles as a function of time. Fixed ghost particle was used for wall boundary condition. Free surface boundaries were determined by using virtual density of particles. In order to validate the model and the code, the simulation results of slump flow test, $T_{500}$ test and L-box test were compared with experimental ones. The simulation results were well matched with the experimental results. The simulation described successfully the characteristics of the flow phenomenon according to the change of the viscosity and yield stress of high flow concrete.

• Clinics in Orthopedic Surgery
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• v.10 no.4
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• pp.500-507
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• 2018

Background: The sagittal alignment of the spine and pelvis is not only closely related to the overall posture of the body but also to the evaluation and treatment of spine disease. In the last few years, the EOS imaging system, a new low-dose radiation X-ray device, became available for sagittal alignment assessment. However, there has been little research on the reliability of EOS. The purpose of this study was to evaluate the intrarater and interrater reliability of EOS for the sagittal alignment assessment of the spine and pelvis. Methods: Records of 46 patients were selected from the EOS recording system between November 2016 and April 2017. The exclusion criteria were congenital spinal anomaly and deformity, and previous history of spine and pelvis operation. Sagittal parameters of the spine and pelvis were measured by three examiners three times each using both manual and EOS methods. Means comparison t-test, Pearson bivariate correlation analysis, and reliability analysis by intraclass correlation coefficients (ICCs) for intrarater and interrater reliability were performed using R package "irr." Results: We found excellent intrarater and interrater reliability of EOS measurements. For intrarater reliability, the ICC ranged from 0.898 to 0.982. For interrater reliability, the ICC ranged from 0.794 to 0.837. We used a paired t-test to compare the values measured by manual and EOS methods: there was no statistically significant difference between the two methods. Correlation analysis also showed a statistically significant positive correlation. Conclusions: EOS showed excellent reliability for assessment of the sagittal alignment of the spine and pelvis.

• Journal of IKEEE
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• v.22 no.4
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• pp.953-958
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• 2018

In this study, a portable detection system was developed that can detect harmful gas and signals simultaneously in an enclosed space of industrial sites and underground facilities. The developed system is a sensor module for gas detection, a patch type 1 channel small ECG sensor, a module for three-axial acceleration detection sensor, and a system for statistics. In order to verify the performance of the system modules, the digital resolution, signal frequency, output voltage, and ultra-small modules were evaluated. As a result of the performance of the developed system, the digital resolution was 300 (rps) and the signal amplification gain was 500 dB or more, and the ECG module was manufactured with $50mm{\times}10mm{\times}10mm$ to increase patch utilization. It is believed that the product of this research will be valuable if it is used as an IoT-based management system for real-time monitoring of industrial workers.

• Korean Journal of Medicinal Crop Science
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• v.27 no.1
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• pp.38-44
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• 2019

Background: Taraxacum platycarpum has been used in traditional medicine in Korea to treat intoxication and edema and as a diuretic. According to previous reports, it has anti-cancer, anti-gastritis, and anti-inflammation effects. However, the improvement effect of T. platycarpum on rheumatoid arthritis has not been investigated. The anti-oxidative and anti-inflammation effects of the aerial parts of T. platycarpum are different from those of its subterranean parts. Thus, we evaluated the effect of the water extracts of Taraxaci radix (WTR) on type II collagen-induced rheumatoid arthritis (CIA) in animal models. Methods and Results: Rheumatoid arthritis was induced by type II collagen. WTR (100 mg/kg and 500 mg/kg) was administered to the animal models. Methotrexate was used as the positive control. The levels of interleukin-6, TNF-alpha, and type II collagen IgG in the animals were measured by using enzyme-linked immunosorbent assay. Treatment with 500 mg/kg WTR decreased the serum levels of interleukin-6, TNF-alpha, and collagen IgG in the CIA models. Moreover, treatment with WTR diminished the arthritisinduced swelling of the hind legs and monocyte infiltration in the bloodvessels of the animal models. Conclusions: These results indicate that WTR has the potential to improve rheumatoid arthritis by reducing the levels of inflammatory cytokines such as interleukin-6 and TNF-alpha. However, further experiments are required to elucidate the influence of WTR on signal transduction in vitro and in vivo.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.4
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• pp.321-328
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• 2021

This paper derives numerically new buckling Knockdown factors for the lightweight design of the composite propellant tanks for space launch vehicles. A nonlinear finite element analysis code, ABAQUS, is used for the present postbuckling analysis of composite cylinders under compressive loads. Various thickness ratios (R/t) and slenderness ratios (L/R) are considered and Single Perturbation Load Approach is applied to represent the geometric initial imperfection of the composite cylinder. For the composite cylinder with thickness ratio of 500 and slenderness ratio of 2.04, the buckling Knockdown factor derived in this work is higher by 84.38% than NASA's previous buckling design criteria. Therefore, it is investigated that a lightweight design is possible when the present Knockdown factors are used for the design of composite propellant tanks. In addition, it is shown that global buckling loads and buckling Knockdown factors decrease as the thickness ratio or slenderness ratio of composite cylinders increases.

• Journal of the Korean Applied Science and Technology
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• v.38 no.1
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• pp.29-36
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• 2021

Among natural products, the shells of black walnut(Juglans nigra), which are not used commercially and mostly discarded, were examined to investigate the physiological activity and the efficacy for the cosmetic application. DPPH radical scavenging activity of hot water extract of black walnut shells was 76.06% at 300 ㎍/mL. ABTS radical scavenging activity of the extract was 61% at 1000 ㎍/mL, showing excellent antioxidant activity. When the black walnut shell extract was applied to HaCaT cells, a skin keratinocyte, the viability of the cells was 92.6% at 250 ㎍/mL, showing a remarkably low effect on cell viability. At the concentration of 500 ㎍/mL, 67.35% of nitric oxide(NO) production was inhibited. It also showed an inhibitory effect on Hyaluronidase 31 times higher than that of Vitamin C at 100 ㎍/mL concentration. In conclusion, the black walnut shell extract showed high potentials for the cosmeceutical applications, suggesting the possibility of using it as a high value-added natural material in various industries such as food, fragrance, healthcare, and pharmaceuticals.

• The Journal of the Korea Contents Association
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• v.22 no.7
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• pp.384-394
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• 2022

This study aimed to examine how COVID-19 affected life and health of welfare recipients by comparing groups associated with sex, living with children, and household type and suggest directions for welfare policy and services. Researchers collected a random sample of 500 recipients from 𐩒𐩒gu, Seoul who are registered in Haengbok E-eum, the social security information system and conducted a survey on overall life domains and physical and mental health. For data analysis, t-test, Anova and chi-square test were used. The results showed that factors of sex, living with children, and household type made significant differences in difficulties of employment status, child care, leisure and cultural activities and overall social activities. In terms of health status, mental health status and life satisfaction have been decreased after COVID-19. There were statistical differences in COVID blue and thinking about death among different groups. Based on these findings, this study suggested directions for welfare services for the future New Normal society.

• Journal of Industrial Convergence
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• v.21 no.1
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• pp.87-93
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• 2023

Determining the timing of buying and selling in stock investment is one of the most important factors to increase the return on stock investment. Buying low and selling high makes a profit, but buying high and selling low makes a loss. The price is determined by the quantity of buying and selling, which determines the price of a stock, and buying and selling is also related to corporate performance and economic indicators. The fear and greed index provided by CNN uses seven factors, and by assigning weights to each element, the weighted average defined as greed and fear is calculated on a scale between 0 and 100 and published every day. When the index is close to 0, the stock market sentiment is fearful, and when the index is close to 100, it is greedy. Therefore, we analyze the trading criteria that generate the maximum return when buying and selling the US S&P 500 index according to CNN fear and greed index, suggesting the optimal buying and selling timing to suggest a way to increase the return on stock investment.