• Journal of the Korean GEO-environmental Society
• /
• v.8 no.4
• /
• pp.19-25
• /
• 2007

Process analysis with ASM3 (Activated Sludge Model3) was performed to offer basic data for the optimization of aerated biofilter (ABF) process design and operation. This study was focused on the simulation of the nitrification reaction in ABF which was a part of the advanced nutrient treatment process using bio-adsorption. The ABF process has been developed for the removal of suspended solids and nitrification reaction in sewage. A GPS-X (General Purpose Simualtor-X) was used for the sensitivity analysis and operation assessment. Sensitivity of ASM3 parameters on ABF was analysed and 4 major parameters ($Y_A$, $k_{sto}$, ${\mu}_A$, $K_{A,HN}$) were determined by dynamic simulation using 70 days data from pilot plant operation. The optimized values were 0.14 for $Y_A$, 3.5/d for $k_{sto}$, 2.7/d for ${\mu}_A$ and 1.1 mg/L for $K_{A,HN}$, respectively. Simulation with optimized parameter values were conducted and TN, $NH_4{^+}-N$ and $NO_3{^-}-N$ concentrations were estimated and compared with measured data at the range of 10 min to 4 hrs of hydraulic retention time (HRT). The simulated results showed that optimized parameter values could represent the characteristics of ABF process. Especially, the ABF showed relatively high nitrification rate (60%) under very short HRT of 10 min. As a consequence, the ABF was thought to be successfully used in the site which having high variation of influent loading rate.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.9
• /
• pp.4274-4282
• /
• 2011

In this study, Fenton reaction was studied for the possibility of applying as advanced treatment and its optimal condition for the removal of refractory organics from the dye wastewater. Fenton reaction was applied to remove refractory organics after the bio-treatment (secondary treatment) inside test laboratory and on-site pilot plant. Wastewater from the secondary treatment was used and its $COD_{Mn}$ was measured as 30~50mg/L. After the Fenton reaction, the optimal condition was found as pH 3~3.5, reaction time 2~2.5hr, chemical input ratio of ($FeCl_2$(33%)/$H_2O_2$(35%)) was 3 : 1. When chemical input ratio of ($FeCl_2$(33%)/$H_2O_2$(35%)) was at its optimal, amount of sludge volume ($SV_{2hr}$) was 21~28%. With pilot plant test, removal rate was heavily influenced by the hydraulic retention time(HRT), and optimum value of HRT was 2.0 hr. When pilot plant($2m^3/d$) was placed on-site and operated continuously, it showed steady and fairly good treatment of COD where COD removal rate was 60~70%, treated water showed below 20mg/L.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.5
• /
• pp.3336-3344
• /
• 2014

The purpose of this study is small scale coagulation module is developed and demonstrated through a lab-scale test. Recent as a sewage treatment rate increases, have heightened the interest in the necessity on the nonpoint source and developing a small processing unit has been increased. Coagulation sedimentation module in this study is additional growth of floc through swirling in the outside zone, reduction of microstructure floc number and the internal settling zone through vertical/level flow complex sedimentation method after the coagulation process precipitation method as an effective high separation efficiency can be divided was also assessed. Coagulation sedimentation module can increase the load factor was 4.4 times compared to conventional clarifier base on the same volume and surface area through vertical/level flow. In this study, this process was selected formation and maintenance of swirling and uniform flow distribution in the internal settling zone as an important design factor, to derive its FLUENT was used to characteristics of the flow model. Through the simulation of swirling, influent velocity, dimensions of external basin, hopper depth of bottom cone was determined and through analysis of velocity distribution, flow distribution detailed specifications are derived like as diameter and number of effluent hole. Lab-scale($120{\ell}/hr$) test results, influent of 300~800 NTU to less than 10 NTU without polymer feeding was able to operate in the 20minutes retention time(surface loading rate $37.3m^3/m^2$-day), and through analysis FLUENT the possibility of using design parameters were derived.

• Korean Chemical Engineering Research
• /
• v.57 no.6
• /
• pp.861-867
• /
• 2019

$Li_4Ti_5O_{12}$ is a promising next-generation anode material for lithium-ion batteries due to excellent cycle life, low irreversible capacity, and little volume expansion during charge-discharge process. However, it has poor charge capacity at high current density due to its low electrical conductivity. To improve this weakness, porous $Li_4Ti_5O_{12}$ was synthesized by sol-gel method with P123 as chelating agent. The physical characteristics of as-prepared sample was investigated by XRD, SEM, and BET analysis, and electrochemical properties were characterized by cycle performance test, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS). $Li_4Ti_5O_{12}$ synthesized by 0.01mol ratio of P123/Ti showed most unified particle size, high specific surface area, and relatively high porosity. EIS analysis showed that depressed semicircle size was remarkably reduced, which suggested resistance value in electrode was decreased. Capacity in rate performance showed 178 mAh/g at 0.2C, 170 mAh/g at 0.5C, 110 mA/h at 5C, and 90 mAh/g at 10C. Capacity retention also showed 99% after rate performance.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.29 no.1
• /
• pp.12-18
• /
• 2019

The spherical $SiO_2$ powders were synthesized by the scaled-up ultrasonic pyrolysis (USP). The aqueous $SiO_2$ sol, which contained 20~30 nm $SiO_2$ particles, was used as a precursor for the scaled-up USP. The effects of the USP operating conditions and precursor conditions were systematically investigated, including reaction temperature, gas flow rate, and the concentration of $SiO_2$ sol on the morphologies of synthesized $SiO_2$ particles. the synthesized $SiO_2$ particle showed a pseudo-crystal phase, spherical morphology, and a smooth surface. The size of the spherical $SiO_2$ particle decreased as both reaction temperature increased and precursor concentration decreased. In addition, the synthesized $SiO_2$ particle size was increased by increasing the gas flow rate. Lastly, the scaled-up USP was compared with the lab-scale USP based on the same process conditions. Due to a short retention time in the reaction tube during the USP process, the $SiO_2$ particle synthesized via the lab-scale USP showed a larger particle size.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.33 no.1
• /
• pp.22-30
• /
• 2023

Currently, almost all product development in the jewelry industry utilizes 3D CAD and 3D printing. In this situation, 3D CAD modeling and 3D printing ability units in colleges, Tomorrow Learning Card Education, and Course Evaluation-type jewelry design related education are conducted with developed curriculum based on the standards for training standards, training hours, training equipment, and practice materials presented by NCS. Accordingly, this study analyzes 3D CAD modeling and 3D printing training facilities, training hours, training equipment, etc into three categories of NCS precious metal processing and jewelry design, and studies the development of educational systems such as 3D CAD/3D printing curriculum and various environments that meet these standards. Education using this 3D CAD/3D printing education system will enable us to continuously supply professional talent with practical skills not only in the jewelry industry but also in the entire 3D CAD/3D printing manufacturing industry, which is called as one of the pillars of the 4th Industry. The quality of employment of trainees receiving education and the long-term retention rate after employed can also have a positive effect. In addition, excellent educational performance will help improve the recruitment rate of new students in jewelry jobs or manufacturing-related departments, which are difficult to recruit new students in recent years.

• The Journal of Advanced Prosthodontics
• /
• v.15 no.4
• /
• pp.202-213
• /
• 2023

PURPOSE. This prospective clinical study was conducted to evaluate the clinical usefulness of the freely detachable zirconia ball- and spring-retained implant prosthesis (BSRP) through a comparative analysis of screw- and cement-retained implant prosthesis (SCRP). MATERIALS AND METHODS. A multi-center, randomized, prospective clinical study evaluating the clinical usefulness of the detachable zirconia ball- and spring-retained implant prostheses was conducted. Sixty-four implant prostheses in 64 patients were examined. Periodic observational studies were conducted at 0, 3, 6, and 12 months after delivery of the implant prosthesis. Factors such as implant success rate, marginal bone resorption, periodontal pocket depth, plaque and bleeding index, and prosthetic complications were evaluated, respectively. RESULTS. During the 1-year observation period, all implants survived without functional problems and clinical mobility, showing a 100% implant success rate. Marginal bone resorption was significantly higher in the SCRP group than in the BSRP group only at the time of implant prosthesis delivery (P = .043). In all observation periods, periodontal pocket depth was slightly higher in the BSRP group than in the SCRP group, but there was no significant difference (P > .05). The modified plaque index (mPI) scores of both groups were moderate. Higher ratio of a score 2 in modified sulcus bleeding index (mBI) was observed in the BSRP group in the 6- and 12-months observation. CONCLUSION. Within the limitations of this study, the newly developed zirconia ball- and spring-retained implant prosthesis could be considered as an applicable and predictable treatment method along with the existing screw- and cement-retained prosthesis.

• Korean Chemical Engineering Research
• /
• v.62 no.1
• /
• pp.19-26
• /
• 2024

In this study, the electrochemical properties of SiOx@C composite materials were prepared to alleviate volume expansion and cycle stability of silicon and to increase the capacity of anode material for LIBs. SiO₂ particles of 100, 200, and 500 nm were synthesized by the Stӧber method, and reduced to SiOx (0≤x≤2) through the magnesiothermic reduction method. Then, SiOx@C anode materials were synthesized by carbonization of PVC on SiOx. The physical properties of prepared SiOx and SiOx@C anode materials were analyzed by XRD, SEM, TGA, Raman spectroscopy, XPS and BET. The electrochemical properties were investigated by cycling performance, rate performance, CV and EIS test. As a result, the SiOx@C-7030 manufactured by coating carbon at SiOx : C = 70 : 30 on a 100 nm SiOx with the smallest particle size showed the best electrochemical properties with a discharge capacity of 1055 mAh/g and a capacity retention rate of 81.9% at 100 cycles. It was confirmed that cycle stability was impoved by reducing particle size and carbon coating.

• Journal of Korean Society of Forest Science
• /
• v.110 no.2
• /
• pp.129-140
• /
• 2021

The study investigates the correlation between the seasonal changes in the absorption of fine dusts and the fine structure of surface on each type of street tree, such as Quercus myrsinifolia, Quercus glauca, Quercus salicina, Camellia japonica, and Prunus × yedoensis in the southernareas of Korea. The absorption ranges of fine dust were 31.51~110.44 ㎍/cm² in January, 23.20~79.30 ㎍/cm² in November, 22.68~76.90 ㎍/cm² in May, and 9.88~49.91 ㎍/cm² in August. The absorption value was about 54.4% higher in January than in May. With the grooves and hairs on the leaf surface and lots of wax, Q. salicina seems related to the high absorption rate of fine dust for each fine dust particle size. The one with gloss and smooth leaf surface has a low amount of wax. C. japonica Prunus × yedoensisshowed a low absorption rate of fine dust in each season. Whereas the increase in porosity density, length, and leaf area size can be related to the reduced PM and increasedabsorption rate, the leaf surface roughness, total wax amount, and porosity width can be related to the increase in the PM absorption rate. There was also a high correlation between the total wax amount and absorption rate of the leaf surface at the size of PM_0.2 than PM₁₀ and PM_2.5. These results imply that the quantitative and qualitative trais of leaf, such as wax amounts and leaf surface,can increase the absorption of fine dusts, and the small-sized particles seem to be highly adsorbed with the high wax amounts.

• Journal of Bio-Environment Control
• /
• v.21 no.3
• /
• pp.213-219
• /
• 2012

Improving the physico-chemical properties of used media by mixing ratio of new plug media (NPM), used plug media (UPM) and perlite is necessary to improve seedling quality. In this study, five treatments were designed to investigate mixing ratio of UPM and NPM by ratio of volume 0 : 100, 25 : 75, 50 : 50, 75 : 25, 100 : 0, respectively. On the other hand, nine treatments were designed to investigate of perlite volumes were added to UPM and mixed media (UPM : NPM (50 : 50)) with 0, 5, 10, and 20% of ratio volume. The physicochemical properties of all mediums and their effect on growth response of tomato and cucumber seedlings were determined. The result indicates that physical properties was improved when NPM was mixed with UPM and at mixed ratio of volume 50 : 50 (v : v) has similar pore spare, bulk density and water retention to NPM. Seedling quality of tomato and cucumber in mixed media (50 : 50) are better than other mixed ratio and similar to NPM. Addition perlite to UPM and mixed media 50 : 50 (v : v) increased the pore space and water retention. Physical properties such as particle density, pore space and bulk density were increased when perlite volume increased. However, the best of seedling quality was observed by the addition at 10% volume of perlite. These results suggested that optimum of mixed ratio for recycled used media is new media and used media 1 : 1 mixed.