Finite element model of the drilling process of carbon fiber reinforced plastic (CFRP)

Department of Mechanical EngineeringCarbon fiber reinforced plastic (CFRP) is a composite, composed of reinforcing carbon fiber and matrix resin. CFRP is widely used in various fields, such as aerospace, automotive, robotics, and civil infrastructures, due to its excellent corrosion resistance and superior physical characteristics like strength-to-weight ratio, compared with traditional metals. Therefore, it has been constantly utilized and developed as the state-of-the-art material in numerous applications. Machining is indispensable when applying CFRP in these various industries, among which drilling process is indispensable for assembling different parts into products. However, unlike metals, CFRP holds heterogeneous properties. During the drilling process, delamination and uncut fibers are generated by the thrust force generated in the feed direction. While delamination at the outer surface can be detected by visual inspection, internal defect cannot be observed by the naked eye. These defects need to be predicted because of not only reducing the durability of the product but also causing deterioration in quality. This thesis presents the simplified FE model and method to predict the mechanical phenomena during the drilling process. To investigate these phenomena, a simulation model was developed with commercial FEM software, ABAQUS. Through the developed FE model, it was possible to predict the delamination through the stress distribution of each layer generated after the drilling process. In addition, it was possible to identify uncut fibers for each layer through this, and furthermore, the possibility of suggesting optimum processing conditions can be confirmed. Also, based on the analysis data obtained from the FE model, the change in the thrust force according to the drill entry position at the time of drilling was confirmed, and the accuracy of the developed analytical model was confirmed by comparing the experimental data with the analytical data. Therefore, FE model was developed to investigate defect prediction, and the results from FE analysis was compared this with experimental data to minimize errors in CFRP drilling process.ope

Time-worn pebbles or unpolished gemstones? (Un)usable pasts and possible futures of comparative education

This article draws on the contributions to this special issue to highlight the urgent need to restore checks and balances in our evaluation of ‘usable pasts’ in comparative education. Considering that our reading of the field’s history not only moulds our understanding of comparative education now but also shapes our imagination of its potential futures, reflecting our implicit biases and the way we construct and narrate its history becomes imperative. This article unveils the persistence of silences and exclusions concerning specific histories, countries, and topics, and highlights the possible influence of evolving geopolitical power dynamics on the future of comparative education. Consequently, it urges critical examination of the field’s positionality amid shifting geopolitical tensions and calls for a thorough scrutiny of entrenched silences and the reductionist use of sweeping policy signifiers such as globalisation, decolonisation, excellence, and the notion of ‘future’ as explanatory concepts

Happiness, politics and education reform in South Korea: building ‘happy human capital’ for the future

There has been a growing tendency to use humanistic and utopian goals in the naming and framing of education policies. The case of the Happiness Education Policy (HEP) in South Korea is illustrative and demonstrates the potential of such framing, combined with references to external authorities, to neutralise domestic opposition and generate support from diverse national stakeholders. The HEP focuses on nurturing ‘happy human capital’ for the future through education initiatives such as the Free Semester/Year Initiative, character education, STEAM-based curriculum, and software education. Through an analysis of a corpus of policy documents and press releases, this article demonstrates how happiness, as a floating signifier, has been redefined in ways that align and support the different sociotechnical imaginaries envisioned by political regimes over the past decade which depart from its humanistic focus. // 教育政策的命名及制定越来越倾向于使用人文主义和乌托邦的目标。韩国的幸福教育政策（HEP）就是一个例子，它显示了这种框架的潜力，结合对外部权威的引用，可以化解国内的反对意见，并获得国内不同利益相关者的支持。韩国幸福教育政策的重点是通过自由学期/学年倡议、品格教育、基于STEAM的课程和软件教育等教育举措，为未来培养“幸福的人力资本”。通过对一系列政策文件和新闻稿的分析，本文展示了幸福作为一个漂浮的能指，是如何被重新定义，以配合和支持过去十年中政权所设想的不同的社会技术愿景，而这些愿景却偏离了人文主义的主旨

Scripting solutions for the future: the OECD’s advocacy of happiness and well-being

Over the past decade, the OECD has gradually shifted its governing mechanism from promoting ‘best practices’ based on comparative data on pupils’ cognitive skills to actively advocating for individual and collective well-being as an alternative and ideal future. This article focuses on the OECD’s use of ‘techno-scientific fictive scripts’ as a strategy to promote happiness and well-being as solutions to anticipated crises, despite their conceptual ambiguity and token usage. It analyses how the OECD’s recent ‘Future of Education’ projects have sought to steer its audience towards shared concerns and expectations of the future, while simultaneously asserting its technical expertise in future studies methodologies. It argues that by returning from endorsing data-driven policies to making futuristic claims using future studies methodologies, the OECD endeavours to redefine itself as both a pathfinder and a problem solver, simultaneously blending its human capital imperatives with technological inevitability in its vision of the future

PHYTOCHEMICAL AND ANTIOXIDANT CHARACTERIZATION OF THINNED IMMATURE CITRUS UNSHIU FRUITS

Objective: We aimed to evaluate the characterization of thinned immature Citrus unshiu fruits with regard to their phytochemical profile and antioxidant capacity.Methods: Determination of total phenolic, flavonoid, and carotenoid and ascorbic acid contents was done by UV-Visible spectrophotometry, whereas UPLC-mass detection was used for the analysis of individual flavanone (naringin, hesperidin, hesperetin, neohesperedine and narirutin) and flavonol (rutin). In addition, free radicals (DPPH, O2-, H2O2 and NO) scavenging assays were used to determine the antioxidant capacity.Results: Naringin, hesperidine, neohesperedine and narirutin were the main flavanones in all thinned immature Citrus unshiu fruits. The contents of total phenolic, flavonoid and carotenoid were more prevalent in immature fruits than the level found in mature fruits. All thinned immature Citrus unshiu fruits possess an evident antioxidant capacity. The immature Citrus extract concentrations providing 50% inhibition (IC50) for free radicals; 1.2-1.49 mg/ml for DPPH, 1.03-1.46 mg/ml for superoxide, 1.95-3.43 mg/ml for hydrogen peroxide and 1.64-3.45 mg/ml for nitric oxide was lower than those of mature Citrus extracts.Conclusion: Thinned immature Citrus unshiu fruits could be an economic and readily accessible source of natural antioxidants and as a possible food and pharmaceutical supplement

Apoptotic properties of Citrus sudachi Hort, ex Shirai (Rutaceae) extract on human A549 and HepG2 cancer cells

Purpose: To investigate whether Citrus sudachi harvested at two stages of maturity can induce toxicity in a cell-specific manner and to determine the possible  mechanisms of Citrus sudachi-induced cytotoxic responses in two types of cancer cells (human lung adenocarcinoma A549 and hepatocellular carcinoma HepG2 cells) and two normal cell lines (lung 16HBE140- and liver CHANG cells).Methods: 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and annexin V/propidium iodidle assay were used to test the antiproliferative activity and apoptosis of methanol extract of Citrus sudachi, respectively. Griess reaction and reverse transcriptase-polymerase chain reaction (RT-PCR) were carried out to evaluate nitric oxide (NO•) production and the mRNA levels of inhibitors of apoptosis (IAP).Results: Citrus sudachi exerted cytotoxicity in a time-dependent manner in cancer cells which increased with increase in maturity but did not affect normal cells. Citrus sudachi was found to induce accumulation of cells in the sub-G1 cell cycle phase, fragmentation of DNA and cell death with characteristics of apoptosis, in both types of cancer cells. Moreover, Citrus sudachi upregulated cellular NO• produced by activation of nitric oxide synthase (NOS), while it suppressed the levels of IAP mRNA in both types of cancer cells.Conclusion: The results obtained suggest that Citrus sudachi induces apoptosis in A549 and HepG2 cells, which may be mediated by NO•. There is need for further studies on the role of Citrus sudachi in cancer treatment.Keywords: Apoptosis, Citrus sudachi, Human lung and liver cancer cells, Inhibitors of apoptosis, Nitric oxid