• Journal of Life Science
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• v.33 no.7
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• pp.549-554
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• 2023

Korean ginseng has been used for centuries in traditional Chinese medicine as an overall wellness supplement. Red ginseng (Ginseng Radix Rubra) is produced by steaming the roots, followed by drying. Soft red ginseng is produced using a new processing technology. This study investigated whether soft red ginseng differs from raw and hard red ginseng in its physicochemical composition. Results showed that the total phenol content of raw ginseng was 2.96 mg/g at 80℃ and 3.47 mg/g at 160 ℃. Meanwhile, the total phenols of hard and soft red ginseng were 4.12 mg/g and 4.18 mg/g at 160℃, respectively. The total phenol contents of raw, hard red, and soft red ginseng revealed a statistically significant difference (p>0.05). The total flavonoid contents of raw, hard red, and soft red ginseng were 2.62 mg/g, 3.97 mg/g, and 3.83 mg/g at 160℃, respectively. Among the three samples, soft red ginseng had the highest total sugar content at 160℃. The acidic polysaccharide contents of both soft and hard red ginseng were much higher than that of raw ginseng (49%-58%). Significant differences were observed among raw, hard red, and soft red ginseng (p<0.001). Soft red ginseng exhibited higher phenol content (25%), total flavonoid content (49%), and total sugar content (45%) than raw ginseng.

• Analytical Science and Technology
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• v.19 no.4
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• pp.290-300
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• 2006

Disinfection by-products(DBPs), such as volatile trihalomethanes and the nonvolatile organochlorine acids, created by chlorination have been extensively studied. However MX which contributes 20-50% of the mutagenic activity in drinking water began to people's attention since 1990. Its chemical name is 3-chloro-4-dichloromethyl-5-hydroxy-2(5H)-furanone. According to WHO guidelines its concentration should be controlled, but its value has not been set up. Due to analytical difficulties in measuring this compound at such a low concentrations and lack of information on toxicity to human. Because concentration (ng/L) of MX in drinking water is low traditional testing methods are ineffective. Therefore this study compared LLE and SPE and have chosen SPE to improve preconcentration. MX has been identified in chlorinated drinking water samples in several countries but not in korea Therefore this study analyzed concentration of MX in different water sources and in spring water. This study examined the causes of changing MX content. Chlorine dosage, seasons, water temperature and distance from the source was all discoverd to be relavant. MX was analyzed in various treatment to find optimum disinfection methods. The outcome was that the concentration of MX was minimized when using biological activated carbon-O3 and granular activated carbon.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.587-592
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• 2023

Cobalt oxide (Co₃O₄·CoO) ultra fine particles were synthesized by liquid phase precursor method. cobalt(II) chloride hexahydrate (CoCl₂·6H₂O) was as a starting material. A plant-derived crystalline cellulose was used as impregnating materials. A impregnated precursor was calcined at a temperature of 350 to 900℃ to obtain cobalt oxide particles having a particle size of 1 to 10㎛. The crystallization process and morphology according to the calcination temperature were examined, and the properties of the synthesized powder were evaluated using SEM and XRD. It was confirmed that a crystal phase of Co₃O₄ began to form around 350℃ and crystal growth occurred up to 900℃. At a temperature above 500℃, the Co₃O₄ crystal was changed to another crystal phase CoO.

• The Journal of the Convergence on Culture Technology
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• v.8 no.3
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• pp.485-491
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• 2022

The traditional economic order quantity (EOQ) model is analyzed under the basic assumption that the purchase price is paid immediately upon receiving the product. However, product suppliers may allow a certain period of deferral of payment for product purchase costs in order to differentiate themselves from competitors. From the distributor's point of view, such a credit transaction can temporarily divert product purchase costs, resulting in a reduction in inventory investment costs, and ultimately, a factor that lowers the selling price for the purpose of increasing end-customer demand can be. In addition, in that credit transactions are provided for the purpose of increasing the demand of suppliers as a means of differentiation from competitors, it is more general to be allowed flexibly according to the transaction volume. In this regard, assuming that the end customer's demand is represented by a linear decreasing function of the distributor's selling price, this study analyzes a model for determining the distributor's pricing and ordering policies under order-size-dependent delay in payments. For the analysis, we also assume that the inventory is depleted not only by customer's demand but also by decaying.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6B
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• pp.661-667
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• 2006

In this study, an experiment of sewage sludge dewatering is carried by using electrokinetic method, and the electrokinetic dewatering efficiency of digested sludge is analyzed. Digested sludge without coagulants is selected and gravitational and pressing dewatering methods are applied in combination with electro-osmotic and electro-osmotic pulse technology. After the test of digested sludge, dewatering test of thickened sludge is carried to evaluate the electrokinetic dewatering feasibility of thickened sludge. Under the condition of constantly applied voltage, however, electrical resistance increases with decreasing of water content so that dewatering rate decreases with time. To reduce such a hindrance caused by constantly applied voltage, electro-osmotic pulse technology which is considered to reduce the difference of water content with height, is applied. For the application of electro-osmotic pulse, the dewatered flow rate and the dewatered volume became more increasing from the middle of the dewatering process than that of continuous voltage. Through the test of thickened sludge, electro-osmotic dewatering combined with gravitational and expression also showed high dewatering rate, which proved the possibility of using electrokinetic dewatering.

• Implantology
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• v.18 no.2
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• pp.120-138
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• 2014

Purpose: The purpose of this study was to review the outcomes of a series of studies on tissue regeneration conducted in multiple institutions including the Department of Periodontology, College of Dentistry, Yonsei University. Materials and Methods: Studies were performed divided into the following three subjects; 1) Development of three-dimensional nano-hydroxyapatite (n-HA) scaffold for facilitating drug release and cell adhesion. 2) Synergistic effects of bone marrow-derived mesenchymal stem cells (BMMSC) application simultaneously with platelet-rich plasma (PRP) on HA scaffolds. 3) The efficacy of silk scaffolds coated with n-HA. Also, all results were analyzed by subjects. Results: Hollow hydroxyapatite spherical granules were found to be a useful tool for the drug release and avidin-biotin binding system for cell attachment. Also, BMMSC simultaneously with PRP applied in an animal bone defect model was seen to be more synergistic than in the control group. But, the efficacy of periodontal ligament cells and dental pulp cells with silk scaffolds could not be confirmed in the initial phase of bone healing. Conclusion: The ideal combination of three elements of tissue engineering-scaffolds, cells and signaling molecules could be substantiated due to further investigations with the potentials and limitations of the suggested list of studies.

• The Journal of Engineering Geology
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• v.33 no.4
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• pp.701-716
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• 2023

Microplastics (<5 mm diameter) in aquatic environments adsorb heavy metals, potentially exposing humans to their toxic effects via food chains. We investigated factors influencing the adsorption of heavy metals on microplastics in aquatic environments, examining their adsorption processes and mechanisms. Adsorption characteristics vary with polymer type, crystallinity, particle size, and environmental conditions (pH, temperature, weathering), and the adsorption capacity for heavy metals increases with weathering and reduction in polymer particle size. However, correlations between environment temperature, polymer crystallinity, and adsorption capacity for heavy metals could not be confirmed. The adsorption behavior of heavy metals can be explained in terms of physicochemical adsorption processes and evaluated through adsorption kinetics and isothermal studies, with multiple mechanisms usually being involved. An understanding of the adsorption of heavy metals by microplastics should aid evaluation of the potential risks of microplastics in aquatic environments.

• Journal of Korean Society of Forest Science
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• v.112 no.4
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• pp.554-560
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• 2023

To prevent illegal timber distribution, DNA markers have been used to identify the species and origin. However, extracting high-quality DNA from timber is difficult because of its physical and chemical properties. In this study, we investigated whether the age of timber tissue influences the yield of DNA extraction and the success rate of polymerase chain reaction (PCR) to understand the relationship between the establishment time of the wood annual ring and the extracted DNA concentration (ng/μl), purity (A260/A280), and PCR success rate (%) from pinewood, a major Korean domestic species. According to the results, it was observed that as the distance from the cambium increased, indicating that the tissue was older, the concentration and purity of the extracted DNA decreased significantly. For the trnM-trnV (285 bp) and rpoC1 (298 bp) regions, the PCR success rate was 100%. However, for the rbcL (1.3 kb) region, the PCR success rate was 66.67%. Moreover, PCR amplification of the rbcL region failed at all points older than 30 years. Thus, it is deduced that as time passes, along with the decay of timber cells, DNA is degraded, leading to a decrease in DNA concentration, purity, and PCR success rate. The results of this study are expected to be beneficial for future applications, such as the species identification of timber, providing valuable insights and potential utilization in this field.

• Applied Chemistry for Engineering
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• v.34 no.6
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• pp.674-678
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• 2023

The effect of Pt was investigated to the catalytic methane decomposition of CH₄ to H₂ over Pt(1)-Fe(30)/MCM-41 and Fe(30)/MCM-41 using a fixed bed flow reactor under atmosphere. The Fe₂O₃ and Pt crystal phase behavior of fresh Pt(1)-Fe(30)/MCM-41 were obtained via XRD analysis. SEM, EDS analysis, and mapping were performed to show the uniformed distribution of nano particles such as Fe, Pt, Si, O on the catalyst surface. XPS results showed O^2-, O^- species and metal ions such as Pt⁰, Pt²⁺, Pt⁴⁺, Ft⁰, Fe²⁺, Fe³⁺ etc. When 1 wt% of Pt was added to Fe(30)/MCM-41, automic percentage of Fe2p increased from 13.39% to 16.14%, and Pt4f was 1.51%. The yield of hydrogen over Pt(1)-Fe(30)/MCM-41 was 3.2 times higher than Fe(30)/MCM-41. The spillover effect of H₂ from Pt to Fe increased the reduction of Fe particles and moderate interaction of Fe, Pt and MCM-41 increased the uniform dispersion of fine nanoparticles on the catalyst surface, and improved hydrogen yield.

• Journal of The Korean Association For Science Education
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• v.27 no.5
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• pp.394-403
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• 2007

In this study, the effects of reciprocal peer questioning (RPQ) strategy upon students' concept learning were investigated. Ninety-two seventh graders at a co-ed middle school were assigned to control, reciprocal peer tutoring (RPT), and RPQ groups. The students were taught about 'three states of matter' and 'motion of molecules' for 12 class hours. Regardless of students' prior science achievement level, the RPQ group showed the highest scores among the three groups in the test of conceptual understanding, and the RPT group performed better than the control group. For high-level students, the scores of the RPQ group were significantly higher than those of the other groups in the test of the concept application, and those of the RPT group were higher than those of the control group. For low-level students, the scores of the RPT and RPQ groups in the concept application test were significantly higher than those of the control group, while those of the RPT and RPQ groups were not significantly different. These results indicated that verbal interaction by reciprocal tutoring helped students to understand chemical concept learning, and that using self-generated questions was more effective. Therefore, RPQ strategy is suggested to become one of the useful instructional methods to facilitate verbal interaction and concept learning in middle school science instructions.