• Advances in nano research
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• v.15 no.1
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• pp.49-57
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• 2023

As composite materials are used in many applications, the modern world looks forward to significant progress. An overview of the application of composite fiber materials in sports equipment is provided in this article, focusing primarily on the advantages of these materials when applied to sports equipment, as well as an Analysis of the influence of sports equipment of fiber-reinforced composite material on social sports development. The present study investigated surface morphology and physical and mechanical properties of S-glass fiber epoxy composites containing Al₂O₃ nanofillers (for example, 1 wt%, 2 wt%, 3 wt%, 4 wt%). A mechanical stirrer and ultrasonication combined the Al₂O₃ nanofiller with the matrix in varying amounts. A compression molding method was used to produce sheet composites. A first physical observation is well done, which confirms that nanoparticles are deposited on the fiber, and adhesive bonds are formed. Al₂O₃ nanofiller crystalline structure was investigated by X-ray diffraction, and its surface morphology was examined by scanning electron microscope (SEM). In the experimental test, nanofiller content was added at a rate of 1, 2, and 3% by weight, which caused a gradual decrease in void fraction by 2.851, 2.533, and 1.724%, respectively, an increase from 2.7%. The atomic bonding mechanism shows molecular bonding between nanoparticles and fibers. At temperatures between 60 ℃ and 380 ℃, Thermogravimetric Analysis (TGA) analysis shows that NPs deposition improves the thermal properties of the fibers and causes negligible weight reduction (percentage). Thermal stability of the composites was therefore presented up to 380 ℃. The Fourier Transform Infrared Spectrometer (FTIR) spectrum confirms that nanoparticles have been deposited successfully on the fiber.

• Journal of Soil and Groundwater Environment
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• v.28 no.5
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• pp.1-11
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• 2023

The phenomenon of sediment resuspension in rivers and lakes causes contaminants (heavy metals and nutrients) accumulated in the sediment to leach into the overlying water. As a result, it can lead to changes in toxic effects and eutrophication in the aquatic ecosystem. In this regard, it is important to quantitatively determine the amount of contaminants leached during sediment resuspension. In this study, methods for assessing the amount of released contaminants and the types of contaminants potentially released due to sediment resuspension were studied and summarized. Methods for assessing leaching can be divided into three groups based on the principle of causing resuspension: (i) the oscillating grid chamber method, (ii) the mechanical stirrer method, and (iii) the shaker method. It was confirmed that the types of contaminants that can potentially be released include heavy metals bound to sulfides, as well as exchangeable and labile forms of heavy metals and nutrients. To effectively manage stable aquatic ecosystems in the future, a simplified leaching test method is needed to assess in advance the risks (i.e., changes in toxic effects and eutrophication) that sediment resuspension may pose to aquatic ecosystems.

• Journal of Korean Society for Quality Management
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• v.52 no.2
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• pp.377-394
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• 2024

Purpose: To derive the optimal conditions for the Rubber based colloidal suspension manufacturing process, which made using a stirrer, to apply the mixture design method. Methods: We used two process component and one process variable Mixture design to derive the optimal conditions for the process. The response variables were selected for rotational viscometer measures which can represent Rubber based colloidal suspension quality. The input variables were selected as the values of rubber-organic solvent expressed in proportions as process components and stirring amount as a process variable which are controllable factors in the process. Results: Based on the results of the experiment, rubber and organic solvent and the interaction between stirring amount and rubber and the interaction between stirring amount and rubber and organic solvent were significant. Reproducibility of the regression model was confirmed by the observation that the values obtained from the reproducibility experiment fell within the confidence interval. Additionally, the model predictions were found to be in close agreement with the field measurements. Conclusion: In this study, a regression model was developed to predict the viscosity change of colloidal suspensions based on the proportion of rubber based colloidal suspension. The developed regression model can lead to improved product quality.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.1
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• pp.9-17
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• 2010

The LCC (Liquid Cadmium Cathode) structure to be developed for inhibiting the formation and growth of the uranium dendrite has been known as a key part in the electrowinning process for the simultaneous recovering of uranium and TRU (TRans Uranium) elements from spent fuels. A zinc-gallium (Zn-Ga) experimental system which is able to be functional in aqueous condition and normal temperature has been set up to observe the formation and growth phenomena of the metal dendrites on liquid cathode. The growth of the zinc dendrites on the gallium cathode and the performance of the existing stirrer type and pounder type cathode structure were observed. Although the mechanical strength of the dendrites appeared to be weak in the electrolyte and easily crashed by the various cathode structures, it was difficult to effectively submerge the dendrite into the bottom of the liquid cathode. Based on the results of the aqueous phase experiments, a lab-scale electrowinning experimental apparatus which are applicable to the development of LCC srtucture for the electrowinning process was established and the performance tests of the different types of LCC structure were conducted to prohibit the uranium dendrite growth on LCC surface. The experimental results of the stirrer type LCC structures have shown that they could not effectively remove the uranium dendrites growing at the inner side of the LCC crucible and the performances of the paddle and harrow type LCC structure were similar. Therefore a mesh type LCC structure was developed to push down the uranium dendrites to the bottom of the LCC crucible growing on the LCC surface and at the inner side of the crucible. From the experimental results for the performance test of the mesh type LCC structure, the uranium was recovered over 5 wt% in cadmium without the growth of uranium dendrites. After completion of the experiments, solid precipitates of the bottom of the LCC crucible were identified as an intermetallic compound (UCd11) by the chemical analysis.

• Food Science and Preservation
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• v.22 no.2
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• pp.267-274
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• 2015

This study was conducted to evaluate the antioxidant activities and the quality characteristics of 70% ethanol extracts from onion peels with different extraction methods (autoclave extraction, AE; low temperature high pressure extraction, LTPE; reflux extraction, RE; and stirrer extraction, SE). The yields of AE, LTPE, RE and SE were 9.00%, 5.39%, 13.21% and 12.41%, respectively. The total polyphenol and flavonoid contents in the AE were significantly higher than in the other extracts. The DPPH radical scavenging abilities with a concentration of 100 mg% (w/v) were : AE, 28.9%; RE, 26.07%; LTPE, 24.35%; and SE, 19.53%. The ABTS radical scavenging ability and the nitrite scavenging activity showed the same tendency as that of the DPPH radical scavenging ability. The angiotensin-converting enzyme (ACE) inhibitory activities of the LTPE and AE were higher than those of the RE and SE. The ${\alpha}$-Glucosidase inhibitory activity of the RE was higher than that of the extracts with other extraction methods. The nitrite scavenging activities with a concentration of 10 mg/mL were: AE. 33.97%; RE, 35.47%; LTPE, 21.86%; and SE, 21.71%. The ferrous ion chelating activity of the LTPE (54.73%) was significantly higher than that of the other extracts. These results suggest that AE is the superior method for the enhancement of anti-oxidant activity, and onion peel can be used as a natural antioxidant material for health foods and can be a good ingredient of functional foods.

• Journal of Korea Foresty Energy
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• v.18 no.2
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• pp.47-54
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• 1999

This study was to analyze the chemical components of the pollens of Pinus densiflora S. et Z. and P. thunbergii Parl. and to investigate the optimal conditions for pollen pulverization. The results were as follow : (1) The contents of moisture, crude ash, crude protein, crude fat, crude filber and carbohydrate in the pollen of P. densiflora were 9.8%, 2.3%, 11.9%, 2.9%, 7.7%, and 65.4%, respectively, while those of P. thunbergii were 10.5%, 2.2%, 13.5%, 3.5%, 8.5% and 61.8%, respectively. All the contents of P. densiflora and P.thunbergii were much higher than those general crop grains. (2) The pollen of Pinus densiflora and P. thunbergii eighteen different amino acids were detected in. Among them, ten esssential amino acids were identified, which showed high nutrition values. (3) The contents of vitamins A, B1, B2, C and E in the pollen of P. densiflora were 7.9mg, 8.7mg, 19.2mg, 31.5mg and 2.0mg, respectively, while those in the pollen of P. thunbergii were 8.5mg, 9.4mg, 15.7mg, 35.3mg, and 1.8mg respectively. Vitamin C among them was abundant. (4) When the pollen grains of P. densiflora were pilverized for 40 minutes at 5,000rpm and P. thunbergii, for 50 minutes at 5,000rpm by overhead stirrer, the 100% of pollen pulverization was possible.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.11
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• pp.1701-1708
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• 2014

Phenolic compounds, physiological properties, and digestive enzyme inhibitory effect of 70% ethanol extracts from Aster scaber with different extraction methods (stirrer extraction, SE; reflux extraction, RE; autoclave extraction, AE; low temperature high pressure extraction, LTPE; ultrasonification extraction, USE) were investigated. Total polyphenols and flavonoids contents in LTPE were significantly higher than those of other extracts. The amount of substances related to cynarin (1,3-O-dicaffeoylquinic acid) was highest in USE (34.34 mg/g), followed by LTPE (33.83 mg/g), RE (32.27 mg/g), AE (25.40 mg/g), and SE (18.17 mg/g). Chlorogenic acid (5-O-caffeoylquinic acid) and astragalin (kaempferol-3-O-glucopyranoside) were highest in AE and LTPE, respectively. Xanthine oxidase, angiotensin- I converting enzyme, 3-hydroxy-3-methylglutaryl coenzyme A reductase and acetylcholin esterase inhibitory activities of LTPE and USE at a concentration of 50 mg% (w/v) were somewhat higher than those of other extracts. The ${\alpha}$-amylase, ${\alpha}$-glucosidase, trypsin and lipase activities showed the same tendency as physiological properties (concentration of 500 mg%, w/v). Additionally, there was significantly higher or slightly lower inhibitory activity compared to the control group. These results suggest that extracts from Aster scaber have potential to act as functional materials, and LTPE and USE are superior for the enhancement of biological activity.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.12
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• pp.1113-1122
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• 2009

In order to find the way to solve the problem of sewage sludge discharge into the ocean, the sludge solubilization by ultrasonic and the improvement methods of wastewater treatment process were studied. In the membrane bioreactor the sludge retention time was stepwise increased from 5.1 day to 442 days where the biomass average concentration has been increased from $c_B$=3.4 $gTSSL^{-1}$ to $c_B$=14.5 $gTSSL^{-1}$ respectively. At the same time, the biomass yield coefficients were reduced from 0.5-0.7 at SRT=5.1 day to 0.005-0.007 at SRT=442 days which means the reduction of sludge production. Oxygen mass transfer coefficients and ${\alpha}$-factor were investigated with changing stirrer speed to find the relation between the high biomass concentration and aeration efficiency in the propeller loop reactor. As a result of sludge solubilization, the solubilization of sludge by ultrasound was increased with increasing energy input and it led to improved anaerobic digestion rate with more biogas production than that of nonsolubilized sewage sludge.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.1
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• pp.144-151
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• 2005

Erosion is believed to be the predominant cause of teeth wear in children and young adults, although there will at ways be a contribution from attrition and abrasion. The pH of cola is known to be low and have, therefore, been implicated in the increasing incidence of erosion. The aim of present study was to evaluate the effect of cola on the progression of erosive demineralization in human enamel using demineralization model in vitro. Six groups of human enamel slap were immersed(5 min each bath) in fresh cola, with immersions taking place with or without agitation, and under 3 regimes of frequency intake(low intake, 1 immersion/day; medium, 5/day; high, 10/day). Quantitative assessments of surface erosion were done over an 8-day interval using surface microhardness testing. 1. The average pH of cola was 2.5, which was acidic enough to cause tooth erosion. 2. All the enamel specimen exposed to cola showed erosion like lesions and surface hardness decreased in proportion to the length of immersion (p<0.05). 3. The surface hardness of enamel decreased in proportion to the frequency of immersion (p<0.05). 4. Increased degassing from the drink by gitation accelerated the enamel softening compared with those without agitation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.9
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• pp.895-900
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• 2012

This paper aims to examine the effect of nanodroplets on pool-type absorption heat transfer enhancement and to find the relationship between the dispersion stability and the absorption performance. The concentrations of oil and surfactant are considered as the key parameters. $C_{12}E_4$ and Tween20 are used as the surfactants and N-decane oil is added to the $NH_3/H_2O$ solution to make the binary nanoemulsion fluids. Binary nanoemulsion fluids are dispersed by the ultrasonic vibrator and the stirrer under specific conditions. The dispersion stability of binary nanoemulsion fluids for each oil concentrations is evaluated from the droplet size and Tyndall effect analysis. The absorption performance of binary nanoemulsion fluids is compared with the result of dispersion stability. In addition, it is found that the binary nanoemulsion fluid is a strong candidate as a new working fluid for absorption applications.