• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.18 no.7
• /
• pp.1986-2009
• /
• 2024

The integration of blockchain technology with the rapid growth of Internet of Things (IoT) devices has enabled secure and decentralised data exchange. However, security vulnerabilities and performance limitations remain significant challenges in IoT blockchain networks. This work proposes a novel approach that combines transaction representation and machine learning techniques to address these challenges. Various clustering techniques, including k-means, DBSCAN, Gaussian Mixture Models (GMM), and Hierarchical clustering, were employed to effectively group unlabelled transaction data based on their intrinsic characteristics. Anomaly transaction prediction models based on classifiers were then developed using the labelled data. Performance metrics such as accuracy, precision, recall, and F1-measure were used to identify the minority class representing specious transactions or security threats. The classifiers were also evaluated on their performance using balanced and unbalanced data. Compared to unbalanced data, balanced data resulted in an overall average improvement of approximately 15.85% in accuracy, 88.76% in precision, 60% in recall, and 74.36% in F1-score. This demonstrates the effectiveness of each classifier as a robust classifier with consistently better predictive performance across various evaluation metrics. Moreover, the k-means and GMM clustering techniques outperformed other techniques in identifying security threats, underscoring the importance of appropriate feature selection and clustering methods. The findings have practical implications for reinforcing security and efficiency in real-world IoT blockchain networks, paving the way for future investigations and advancements.

• Journal of Adhesion and Interface
• /
• v.22 no.2
• /
• pp.63-68
• /
• 2021

Unsaturated Polyester Resin (UPR) is in general used as a resin to prepare for composite materials with reinforcing materials such as glass fibers. UPR, a thermosetting resin, is used in industry to prepare for sheet molding compound (SMC) molding prepreg that has excellent productivity and is advantageous for mass production among various molding methods of composite materials. The fiber-reinforced composite material using UPR as a matrix material is light and has the advantage of excellent physical properties, but it is weak against impact and is fragile. Four types of polyurethane were synthesized and added to UPR resin to overcome the shortcomings.

• Korean Journal of Materials Research
• /
• v.27 no.1
• /
• pp.39-42
• /
• 2017

E-glass (electrical glass) fiber is the widely used as a reinforced composite material of PCBs (printed circuit boards). However, E-glass fiber is not stable because it has a dielectric constant of 6~7. On the other hand, D-glass (dielectric glass) fiber has a low dielectric constant of 3~4.5. Thus, it is adaptable for use as a reinforcing material of PCBs. In this study, we fabricated D-glass compositions with low dielectric constant, and measured the electrical and optical properties. In the glass composition, the boron content was changed from 9 to 31 wt%. To confirm the dependence of the dielectric constant on melting properties, D-glass with 22 wt% boron was melted at $1550^{\circ}C$ and $1650^{\circ}C$ for 2hrs. The glass melted at $1650^{\circ}C$ had a lower dielectric constant than the glass melted at $1550^{\circ}C$. Therefore, the D-glass with boron of 9~31 wt% was fabricated by melting at $1650^{\circ}C$ for 2hrs, and transparent clear glass was obtained. We identified the non-crystalline nature of the glass using an XRD (x-ray diffractometer) graph. The visible light transmittance values depending on the boron contents were measured and found to be 88.6 % ~ 82.5 %. Finally, the dielectric constant of the D-glass with 31 wt% boron was found to have decreased from 4.18 to 3.93.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.12
• /
• pp.118-125
• /
• 2017

In this study, we examined the bond performance of FRP Hybrid Bars. FRP Hybrid Bars are developed by wrapping glass fibers on the outside of deformed steel rebars to solve the corrosion problem. The surface of the FRP Hybrid Bars was coated with resin and silica sand to enhance its adhesion bonding performance with concrete. Various parameters, such as the resin type, viscosity, and size of the silica sand, were selected in order to find the optimal surface condition of the FRP Hybrid Bars. For the bonding test, FRP Hybrid Bars were embedded in a concrete block with a size of 200 mm3 and the maximum load and slip were measured at the interface between the FRP Hybrid Bar and concrete through the pull-out test. From the experimental results, the maximum load and bond strength were calculated as a function of each experimental variable and the resin type, viscosity and size of the silica sand giving rise to the optimal bond performance were evaluated. The maximum bond strength of the specimen using epoxy resin and No. 5 silica sand was about 35% higher than that of the deformed rebar.

• Journal of the Korean Electrochemical Society
• /
• v.4 no.1
• /
• pp.6-9
• /
• 2001

[ $SiO_2$ ] effect on the electrochemical properties of polymeric gel electrolytes(PGEs) reinforced with glass fiber cloth(GFC) was investigated . PGEs were composed of polyacrylronitrile(PAN), poly(vinylidenefluoride-co-hexafluoropropylene) (P(VdF-co-HFP)), $LiClO_4$ and three kind of plasticizer(ethylene carbonate, dietyl carbonate, propylene carbonate). $SiO_2$ was added to PGEs in the weight fraction of 10, 20, $30\%$ respectively. PGEs containing $SiO_2$ showed conductivity of over $10^{-3}S/cm\;at\;23^{\circ}C$ and electrochemical stability window to 4.8V. In the impedance spectra of the cells, which were constructed by lithium metals as electrodes, interfacial resistance increased due to growth of passivation layer during storage time and remarkable difference was not observed with content of $SiO_2$. In the impedance spectra of the lithium ion polymer batteries consisted of $LiClO_2$ and mesophase pitch-based carbon fiber(MCF), ohmic cell resistance of $SiO_2-free$ PGE was changed continuously with number of cycle, but those of $SiO_2-dispersed$ PGEs were not. Discharge capacity of the PGE containing $20wt\%\;SiO_2$ showed 132 mAh/g at 0.2C rate and $85\%$ of discharge capacity was retained at 2C rate.

• Information Systems Review
• /
• v.11 no.2
• /
• pp.183-207
• /
• 2009

In general, the introduction of information technology to domestic small and middle size firms is depending on the governmental supporting policy. However, even under this situation there is also a case that the building up of information technology is initiated by the management of small and middle size firms. An accumulated know-how for information technology and powerful leadership in such firms are considered as success factors. This study attempts to analyze a case for 'THEFACESHOP', in which MIS is successfully built. To achieve corporate goals, the CEO of THEFACESHOP based on the extensive knowledge of information technology drove to build up information system. Also, the board of directors supported him, and employees committed to their organization. Through the strong leadership of the CEO, the information system of THEFACESHOP became sufficient and efficient. And it led the organization and the information system to be competitive. In particular, the systematic approach of THEF ACESHOP reinforcing its competitiveness can be summarized as follows: First, it tried to construct basic information systems as like ERP etc. to increase work-efficiency. Second, it completed CRM related systems for analysis to maximize its customer orientation and marketing effect. Third, the last step can be stated as the building up of operation related CRM systems to improve the responsiveness of target marketing activities and the profitability of its agencies. Such endeavors of THEFACESHOP contributed to increase productivity and performance of the organization. As a result, THEFACESHOP has had its own 'Natural Story' and price competitiveness. For that reason THEFACESHOP became the best of brand-shop cosmetic firms. This success based on the strong leadership and the systematic investment on the information system.

• Journal of Korea Technology Innovation Society
• /
• v.15 no.4
• /
• pp.766-782
• /
• 2012

Science and technology(S&T) are not only advancing, but also the number of stakeholders in those fields are increasing, and so the demands of S&T strategy for a particular field are increasing. In Korea, especially, this tendency is remarkable, and is evidenced by the fact that more than one hundred of S&T strategies have been established and implemented. However, academic attempts to clarify scientific methodologies for establishing S&T strategy have so far been rare. In this paper, a methodology to establish S&T strategies in a particular field is proposed and examined through a case study to determine its usefulness. First, through an analysis of the literature, previous studies on the establishment of a national S&T strategy and its related concepts are reviewed. Also, a representative framework plans, in accordance with relevant legislation and regulations, are reviewed. Meanwhile, the methodology, PEST-SWOT-AHP, is proposed and the features and applications are identified. For the case study, the strategy establishment of a fusion research and development program is performed. In order to apply the PEST-SWOT-AHP tool, an environmental analysis based on the fusion R&D roadmap is conducted. To examine the usefulness of the proposed framework, a national fusion R&D strategy applying PEST-SWOT-AHP is derived. As a result of the case study, four strategies were derived. Those are be the first mover, promotion of basic research and cultivation of manpower, boost commercialization and public acceptance and reinforcing international cooperation.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.37 no.1
• /
• pp.121-127
• /
• 2013

With the continuing demand for lightweight bicycles, carbon fiber composite materials have been widely used in manufacturing bicycle frames and components. Unlike general isotropic materials, the structural characteristics of composite materials are strongly influenced by the staking directions and sequences of composite laminates. Thus, to verify the design process of bicycles manufactured using composites, structural analysis is considered essential. In this study, a carbon-fiber-reinforced plastic (CFRP) bicycle frame was designed and its structural behavior was investigated using finite element analysis (FEA). By measuring the failure indices of the fiber and matrix under various stacking sequences and loading conditions, the effect of the stacking condition of composite laminates on the strength of the bicycle structure was examined. In addition, the structural safety of the bicycle frame can be enhanced by reinforcing weak regions prone to failure using additional composite laminates.

• Journal of Korea Water Resources Association
• /
• v.54 no.11
• /
• pp.849-862
• /
• 2021

Laws, administrative rules, and task manuals have been revised to build a modern river maintenance system in Korea for the last decade. And various researches and technology developments have been carried out to resolve related issues. However, the recent enactment of the new Act and the catastrophe of flood damage in 2020 have accelerated more emphasis on the reorganization and reinforcement of the river maintenance system in terms of political and social aspects. In this study, we suggested promising directions for strengthening the technical and institutional competencies of river maintenance with respect to policy, R&D, planning, and technology. The open discussion was held with the participation of industry, academia, research institutes, and government officials, and all participants conducted the related survey to collect their opinions effectively. These results are expected to be used as a reference to secure the justification for integration of government organizations, planning of R&D, the introduction of new river maintenance, and related technology development when reestablishing and reinforcing the river management system in the future.

• Composites Research
• /
• v.30 no.5
• /
• pp.316-322
• /
• 2017

Carbon fiber is a material with excellent mechanical, electrical and thermal properties, which is widely used as a composite material made of a polymer matrix. However, this composite material has a weak point of interlaminar delamination due to weak interfacial bond with polymer matrix compared with high strength and elasticity of carbon fiber. In order to solve this problem, it is essential to use reinforcements. Due to excellent mechanical properties, graphene have been expected to have large improvement in physical properties as a reinforcing material. However, the aggregation of graphene and the weak interfacial bonding have resulted in failure to properly implement reinforcement effect. In order to solve this problems, dispersibility will be improved. In this study, functionalization of graphene nanoplatelet was proceeded with melamine and mixed with epoxy polymer matrix. The carbon fiber reinforced polymer composites were fabricated using the prepared graphene nanoplatelet/epoxy and flexural properties and interlaminar shear strength were measured. As a result, it was confirmed that the dispersibility of graphene nanoplatelet was improved and the mechanical properties of the composite material were increased.