• Journal of Korean Society on Water Environment
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• v.38 no.6
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• pp.316-326
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• 2022

This study aimed to investigate the causes of the increasing Total Phosphate(TP) in the mainstream of Mangyeong river over the past 10 years, and suggested a reduction plan of about 3 points. First, the high TP concentration was continuously released in the discharge outlet of the Haepo bridge stormwater pipeline. The average TP concentration was 5.066 mg/L and values as high as 29.470 mg/L were measured. The highest pollution contribution rate to the Mangyeong river was more than 70 %. The cause of the pollution was expected to take place somewhere in Wanju Industrial Complex. Second, the average TP concentration of wastewater-treated effluent in the H factory was 0.405 mg/L. If a TP reduction facility is additionally installed in the H factory, it will help reduce TP uptake by Lake Saemangeum. Third, the TP concentration of untreated non-point source point flowing into the Samrae stream was very high with an average of 2.828 mg/L. Also, the pollution contribution rate of Samraecheon 2 to Mangyeong river was 21.8 % on average and up to 58 %. The pollution contribution rate was also high during the agricultural season and the winter, during which the flow rate is decreased. Investigation of these three points may be continuously needed, and analysis results and policy proposals presented to Jeollabukdo and Wanjugun to manage pollution sources.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.727-730
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• 2023

The operation of electric automatic windows is used in harsh environments, and the energy density decreases as charging and discharging are repeated, and as soundness deteriorates due to damage to the internal separator, the vehicle's mileage decreases and the charging speed slows down, so about 5 to 10 Batteries that have been used for about a year are classified as waste batteries, and for this reason, as the risk of battery fire and explosion increases, it is essential to diagnose batteries and estimate SOH. Estimation of current battery SOH is a very important content, and it evaluates the state of the battery by measuring the time, temperature, and voltage required while repeatedly charging and discharging the battery. There are disadvantages. In this paper, measurement of discharge capacity (C-rate) using a waste battery of a Tesla car in order to predict SOH estimation of a lithium-ion battery. A Support Vector Machine (SVM), one of the machine models, was applied using the data measured from the waste battery.

• Journal of the Institute of Convergence Signal Processing
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• v.24 no.3
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• pp.153-159
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• 2023

As research results showed that ozonated olive oil has excellent therapeutic effects on skin diseases, attempts were made to develop cosmetics manufacturing technology using ozone. Ozone is harmful to the human body, so a separate facility must be prepared to manufacture ozonated olive oil as a cosmetic raw material. The manufacturing device developed in this study was designed as an optimized process for manufacturing cosmetics while ensuring the safety of workers involved in production. To verify the ozonated olive oil produced from the implemented device, a toxicity test was conducted on animals. After applying ozonated oil (high concentration) to the rabbit's back for 24 hours, mortality, general symptoms and symptoms were measured. A skin irritation evaluation was performed. As a result of the experiment, as a result of evaluating the test substance treatment area after a certain period of time, it was confirmed that no skin irritation was observed in all animals, confirming the safety of the ozonated oil production process and the safety of the product.

• Composites Research
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• v.36 no.6
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• pp.422-428
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• 2023

The electrical contact resistance between the bipolar plate (BP) and the carbon felt electrode (CFE), which are in contact by the stack clamping pressure, has a great impact on the stack efficiency because of the relatively low clamping pressure of the vanadium redox flow battery (VRFB) stack. In this study, a polyethylene (PE) composite-CFE hybrid bipolar plate structure is developed through a local heat welding process to reduce such contact resistance and improve cell performance. The PE matrix of the carbon fiber composite BP is locally melted to create a direct contact structure between the carbon fibers of CFE and the carbon fibers of BP, thereby reducing the electrical contact resistance. Area specific resistance (ASR) and gas permeability are measured to evaluate the performance of the PE composite-CFE hybrid bipolar plate. In addition, an acid aging test is performed to measure stack reliability. Finally, a VFRB unit cell charge/discharge test is performed to compare and analyze the performance of the developed PE composite-CFE hybrid BP and the conventional BP.

• Korean Journal of Materials Research
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• v.34 no.5
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• pp.254-260
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• 2024

This study is to manufacture a titanium dioxide (TiO₂) photocatalyst by recycling sludge generated using titanium tetrachloride (TiCl₄) as a coagulant. Compared to general sewage, a TiCl₄ coagulant was applied to dyeing wastewater containing a large amount of non-degradable organic compounds to evaluate its performance. Then the generated sludge was dried and fired to prepare a photocatalyst (TFS). Scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), and nitrogen oxide reduction experiments were conducted to analyze the surface properties and evaluate the photoactive ability of the prepared TFS. After using titanium tetrachloride (TiCl₄) as a coagulant in the dyeing wastewater, the water quality characteristics were measured at 84 mg/L of chemical oxygen demand (COD), 10 mg/L of T-N, and 0.9 mg/L of T-P to satisfy the discharge water quality standards. The surface properties of the TFS were investigated and the anatase crystal structure was observed. It was confirmed that the ratio of Ti and O, the main components of TiO₂, accounted for more than 90 %. As a result of the nitric oxide (NO) reduction experiment, 1.56 uMol of NO was reduced to confirm a removal rate of 20.60 %. This is judged to be a photocatalytic performance similar to that of the existing P-25. Therefore, by applying TiCl₄ to the dyeing wastewater, it is possible to solve the problems of the existing coagulant and to reduce the amount of carbon dioxide generated, using an eco-friendly sludge treatment method. In addition, it is believed that environmental and economic advantages can be obtained by manufacturing TiO₂ at an eco-friendly and lower cost than before.

• Journal of Korean Society for Quality Management
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• v.51 no.4
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• pp.551-571
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• 2023

Purpose: The purpose of this study is to propose useful suggestions by analyzing the causal effect relationship between the failure rate of quality and the process variables in the C5ISR domain of the defense industry. Methods: The collected data through the in house Systems were analyzed using Big data analysis. Data analysis between quality data and A/S history data was conducted using the CRISP-DM(Cross-Industry Standard Process for Data Mining) analysis process. Results: The results of this study are as follows: After evaluating the performance of candidate models for the influence of inspection data and A/S history data, logistic regression was selected as the final model because it performed relatively well compared to the decision tree with an accuracy of 82%/67% and an AUC of 0.66/0.57. Based on this model, we estimated the coefficients using 'R', a data analysis tool, and found that a specific variable(continuous maximum discharge current time) had a statistically significant effect on the A/S quality failure rate and it was analysed that 82% of the failure rate could be predicted. Conclusion: As the first case of applying big data analysis to quality issues in the defense industry, this study confirms that it is possible to improve the market failure rates of defense products by focusing on the measured values of the main causes of failures derived through the big data analysis process, and identifies improvements, such as the number of data samples and data collection limitations, to be addressed in subsequent studies for a more reliable analysis model.

• Journal of Cardiovascular Imaging
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• v.30 no.1
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• pp.50-58
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• 2022

BACKGROUND: Little is known regarding right ventricular (RV) remodeling immediately after Tetralogy of Fallot (TOF) repair. We sought to describe myocardial deformation by cardiac magnetic resonance imaging (CMR) after TOF repair and investigate associations between these parameters and early post-operative outcomes. METHODS: Fifteen infants underwent CMR without sedation as part of a prospective pilot study after undergoing complete TOF repair, prior to hospital discharge. RV deformation (strain) was measured using tissue tracking, in addition to RV ejection fraction (EF), volumes, and pulmonary regurgitant fraction. Pearson correlation coefficients were used to determine associations between both strain and CMR measures/clinical outcomes. RESULTS: Most patients were male (11/15, 73%), with median age at TOF repair 53 days (interquartile range, 13,131). Most patients had pulmonary stenosis (vs. atresia) (11/15, 73%) and 7 (47%) received a transannular patch as part of their repair. RV function was overall preserved with mean RV EF of 62% (standard deviation [SD], 9.8). Peak radial and longitudinal strain were overall diminished (mean ± SD, 33.80 ± 18.30% and -15.50 ± 6.40%, respectively). Longer hospital length of stay after TOF repair was associated with worse RV peak radial ventricular strain (correlation coefficient (r), -0.54; p = 0.04). Greater pulmonary regurgitant fraction was associated with shorter time to peak radial RV strain (r = -0.55, p = 0.03). CONCLUSIONS: In this small study, our findings suggest presence of early decrease in RV strain after TOF repair and its association with hospital stay when changes in EF and RV size are not yet apparent.

• Nanomaterials
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• v.12 no.4
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• pp.680-690
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• 2022

Phase-pure ZnMn₂O₄ nanopowders and their aggregated microsphere powders for use as anode material in lithium-ion batteries were obtained by a simple spray drying process using zinc and manganese salts as precursors, followed by citric acid post-annealing at different temperatures. X-ray diffraction (XRD) analysis indicated that phase-pure ZnMn₂O₄ powders were obtained even at a low post-annealing temperature of 400 ℃. The post-annealed powders were transformed into nanopowders by simple milling process, using agate mortar. The mean particle sizes of the ZnMn₂O₄ powders post-treated at 600 and 800 ℃ were found to be 43 and 85 nm, respectively, as determined by TEM observation. To provide practical utilization, the nanopowders were transformed into aggregated microspheres consisting of ZnMn₂O₄ nanoparticles by a second spray drying process. Based on the systematic analysis, the optimum post-annealing temperature required to obtain ZnMn₂O₄ nanopowders with high capacity and good cycle performance was found to be 800 ℃. Moreover, aggregated ZnMn₂O₄ microsphere showed improved cycle stability. The discharge capacities of the aggregated microsphere consisting of ZnMn₂O₄ nanoparticles post-treated at 800 ℃ were 1235, 821, and 687 mA h g^-1 for the 1st, 2nd, and 100th cycles at a high current density of 2.0 A g^-1, respectively. The capacity retention measured after the second cycle was 84%.

• The Korean Journal of Nuclear Medicine Technology
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• v.13 no.3
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• pp.48-55
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• 2009

Purpose: As Korean nuclear law doesn't have any clear guideline about the dose and the external dose rate(uSv/h) requiring hospitalization in radioactive iodine treated patients, the patients are discharged when they meet the guideline of IAEA Basic Safety Standards(BSS). We measured external dose rate(${\mu}Sv/h$) of inpatient underwent 3700MBq (100 mCi) $^{131}I$ radioiodine treatment and considering external dose rate(${\mu}Sv/h$), residual activity(mCi) and excretion rate(%) we found the time for RA to be lowered from 3700MBq (100 mCi) to 1110 MBq (30 mCi) to give reference to set a guideline for discharge. Materials and Methods: Forty-two patients underwent thyroidectomy and scheduled for radioiodine treatment, who received 3700MBq (100 mCi) of $^{131}I$ orally and had no renal disease were examined. After 1, 2, 4, 8, and 20, 24, 40 hours iodine uptake and before/after the urination, the external dose rate(${\mu}Sv/h$) measured using FH40G-L(Thermo Fisher Scientific Inc., MA) at a distance and a height of 1 m for 20 sec on the average. Results and Conclusions: At 20 hours, the external dose rate was decreased to $49{\pm}13\;{\mu}Sv$/h, namely, 78% of administrated radioactivity was excreted and 814 MBq (30 mCi) was residual, and it met the accepted limit for discharge of (IAEA, BSS) under 1110 MBq (30 mCi) (1 m at 66 uSv/h).

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.3
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• pp.65-73
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• 2013

Recently the exterior attaching reinforcement method is being often used by using FRP (Fiber Reinforced Polymer) as a method of strengthening concrete structure. this FRP exterior attaching reinforcement method has several advantages like high intensity, stiffness, good durability and easy installment comparing to its weight. but its structure is airtight covered by reinforcement material whose water permeability is low and water can't be discharged, thus it may provoke a damage to the structure after a long while. the main purposes of this study are to develop GFRP reinforcement material which can discharge the surface water properly and to measure its special functions. for this, we have changed the normal reinforcement material to water permeable structure and measured its water permeance modulus by an indoor test which shows the process of water permeance with the parameter of contained GFRP quantity. also tried to verify the measured value of the water permeance modulus in theory by analyzing the numbers on water permeance process. the test result showed that the biggest quantity of water, 0.5129 g/h $m^2$ was discharged when the fiber contained quantity reached at 75% and the tensile strength was also biggest by 476.6MPa at 75%, so it appeared that COSREM GP panel with 75% fiber contained quantity is the best in ventilation and structure.