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강윤수,정권수 順天大學校 師範大學 附屬 科學敎育硏究所 1996 科學과 敎育 Vol.4 No.-
Hanna stated that the stress on rigorous proofs does not improve the grasp of the mathematical facts. In this paper, we investigate the situation of Korean mathematical education in the perspective of Hanna's viewpoint. As a result, we make some suggestions through Fischbein's intuitive method of proofs, Leron's structural method of proofs and Hadar's method of generic - examples assisted proofs.
A Study of the Antioxidant and Anti-Inflammatory Effects of Dusokohwaeum
Seon Yun-Gwon,Jeong Jae Min,Yoon Jin-Sol,Noh Joonyong,Im Seung Kyu,Bang Sung-Pil,Shin Jeong Cheol,Kim Jae-Hong 대한침구의학회 2023 대한침구의학회지 Vol.40 No.4
Background: The aim of this study is to determine the antioxidant and anti-inflammatory effects of Dusokohwaeum (DOE). Methods: To measure the antioxidant and anti-inflammatory effects of DOE, the total flavonoid and polyphenol contents and radical scavenging activity were measured. Furthermore, reactive oxygen species (ROS), nitric oxide, and cytokine production were measured by treating lipopolysaccharide-induced RAW264.7 cells with DOE, and gene expression levels of inducible cyclooxygenase-2, nitric oxide synthase, and cytokines were evaluated. Results: Radical scavenging experiments revealed a significant concentration-dependent increase in scavenging capacity. The production of ROS, nitric oxide, and cytokines in the cells showed a significant concentration-dependent decrease when compared with the control group. The gene expression levels of inducible cyclooxygenase-2, nitric oxide synthase, and cytokines also showed a significant concentration-dependent decrease when compared with the control group. Conclusion: Interestingly, the antioxidant and anti-inflammatory effects of DOE were 23.42 ± 0.64 mg GAE/g and 20.83 ± 0.98 mg QE/g, respectively. The administration of DOE resulted in a concentration-dependent increase in scavenging ability in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azinobis-(3-ethylbenzothiazoline- 6-sulfonic acid) (ABTS) radical scavenging ability experiments. The production of intracellular ROS and nitric oxide was significantly reduced in the presence of DOE. The production of inflammatory cytokines (prostaglandin E2, tumor necrosis factor-alpha [TNF-α], interleukin-1 beta [IL-1β], and IL-6) was significantly reduced in the presence of DOE. Finally, the expression levels of inducible nitric oxide synthase, cyclooxygenase-2, TNF-α, IL-1β, and IL-6 were significantly decreased in the presence of DOE.
Yun Gu Gwon,Seul Gi Lee,Jeong Un Choi,A-Yeong Jang,Weerawan Rod-In,Woo Jung Park 한국식품영양과학회 2021 한국식품영양과학회 학술대회발표집 Vol.2021 No.10
Lysimachia capillipes, a traditional herbal medicine, has been used to treat cold and arthritis. The aim of this study was to investigate the anti-inflammatory activity of L. capillipes extract in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Treatments with L. capillipes extract at concentrations of 3.75,7.5,15, and 25 μg/mL had no cytotoxicity in LPS-stimulated RAW264.7 cells. L. capillipes extract dose-dependently suppressed the production of nitric oxide (NO) and the expression of pro-inflammatory cytokines including interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α in LPS-stimulated RAW264.7 cells. These were associated with the decrease of the mRNA expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) by L. capillipes extract (3.75-25 μg/mL). Moreover, L. capillipes extract also significantly inhibited the phosphorylation of MAPKs including p38, JNK and ERK1/2 as well as the expression of phosphorylated NF-κB-p65 in a dose-dependent manner. These results suggest that L. capillipes extract has anti-inflammatory properties, which activates through the inhibition of the NF-κB and MAPKs signaling pathway.
A Novel Method for Deriving Optimal Synchronism-Check Phase Angle in Transmission System
Yun-Sik Oh,Gi-Hyeon Gwon,Chul-Hwan Kim,Jeong-Jae Yang 대한전기학회 2016 Journal of Electrical Engineering & Technology Vol.11 No.5
Most of faults occurring in transmission system are transient. To cope with such faults, automatic reclosing is applied and it is economic and effective method to improve the reliability and transient stability of power system. Many countries applying 3-phase and leader-follower reclosing scheme use a synchronism-check relay to limit impacts associated with automatic reclosing under Live-Bus/Live-Line (LBLL) conditions. Most utilities generally use a standardized conservative setting that is in the range of 20° to 30°. However, it might be sometimes not a good idea because each transmission line in system has different system conditions such as system structure, line length and load flow that might result in undesirable system impacts. Therefore, it is necessary to derive the Optimal Synchronism-Check (OSC) phase angle which is appropriate for each transmission system. In this paper, a novel method composed of three steps is proposed to derive the OSC phase angle. The proposed method is applied to transmission system based on actual data from Korea. Computer simulations are performed using ElectroMagnetic Transient Program (EMTP) and simulation results show that proposed method is valid and effective.