• Composites Research
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• v.36 no.1
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• pp.25-31
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• 2023

Composite structures have been designed by stacking the laminae with different stacking angles to meet the required mechanical performance. Although the induced stresses on the composite structures under the external loads usually differ depending on the location, we determined the stacking sequence based on the maximum stress, which leads to low efficiency and generally is not the optimum design. Recently, piecewise integrated composites (PICs) were suggested for solving this inefficiency. PICs assume the perfect bonding between adjacent pieces, but this is ideal and hard to accomplish. Therefore, the overlap at the boundary is essential to prevent separation from each other. In this study, we investigated the effect of the overlap design on the impact failure mode of PIC plates. We fabricated the sample composite plates with different overlap designs using the fast curing carbon prepreg and conducted the impact tests according to ASTM D 7136. We found that PICs had different failure modes according to the overlap design, which lead the changes of absorbed impact energies as well as impact load curves.

• Journal of Advanced Technology Convergence
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• v.2 no.3
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• pp.17-24
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• 2023

I am designing a research paper with the aim of studying hybrid vehicles. Hybrid vehicles, as the next-generation automobiles, feature a combination of internal combustion engines and battery engines, resulting in a revolutionary reduction in fuel consumption and harmful gas emissions compared to conventional vehicles. The electric motor in hybrid cars derives power from a high-voltage battery installed within the vehicle, which is recharged during vehicle motion. In contrast to traditional cars, which often experience energy losses due to idling caused by traffic congestion, hybrid systems optimize efficiency by skillfully managing the interplay between the internal combustion engine and the electric motor. This approach effectively addresses the inherent drawbacks of gasoline or diesel engines.Hybrid cars offer an array of benefits, including improved fuel efficiency, environmental friendliness, cost-effectiveness, and reduced noise emission. Consequently, they are progressively becoming a favored alternative among a growing number of individuals. This research endeavor has the potential to contribute towards curbing environmental pollution and dedicating efforts to future automotive research.

• Journal of the Korean Geotechnical Society
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• v.39 no.8
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• pp.17-28
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• 2023

Laboratory-scale hydraulic fracturing experiments were conducted on granite specimens at various viscosities and injection rates of the fracturing fluid. A series of cross-sectional computed tomography (CT) images of fractured specimens was obtained via a three-dimensional X-ray CT imaging method. Pixel-level fracture segmentation of the CT images was conducted using a convolutional neural network (CNN)-based Nested U-Net model structure. Compared with traditional image processing methods, the CNN-based model showed a better performance in the extraction of thin and complex fractures. These extracted fractures extracted were reconstructed in three dimensions and morphologically analyzed based on their fracture volume, aperture, tortuosity, and surface roughness. The fracture volume and aperture increased with the increase in viscosity of the fracturing fluid, while the tortuosity and roughness of the fracture surface decreased. The findings also confirmed the anisotropic tortuosity and roughness of the fracture surface. In this study, a CNN-based model was used to perform accurate fracture segmentation, and quantitative analysis of hydraulic stimulated fractures was conducted successfully.

• Journal of International Area Studies (JIAS)
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• v.13 no.2
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• pp.47-72
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• 2009

Since the Soviet Union collapsed, Russia has been aggressively seeking a role and place in the U.S.-led international order. Russia conditionally cooperated with the U.S. global policy, efforts to protect and expand the national interests in Post-soviet region. In this context, Post-soviet space is the arena of the struggle among the world powers. Especially in Ukraine as the Axis power of Post-soviet space, hegemony conflicts so called 'New Cold War' between Russia and western powers including U.S. have appeared. This paper examines what are Russian military security strategy and policy, how these come to fruition in Ukraine, what are important factors of complications and its aspect.

• Knowledge Management Research
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• v.24 no.1
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• pp.127-145
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• 2023

This paper analyzed a patent trend for technological domain of hydrogen fuel cell, can improve future energy and pollution problems. Patent analysis is used in establishing a technological roadmap which it can discover the current technology capability and future technological development direction. However, the previous patent analysis is qualitative analysis and simple statistical analysis. The reason why it incorrectly analysis patent does not reflect the current technology environment. The current technology environment is development through recombination of technologies. In addition to, the speed of technological development is rapidly growing. So, qualitative analysis does not satisfy the analysis requirements of the times. This paper utilized KP(Knowledge Persistence)-based main path analysis and text mining methods to reflect the current technological environment. As a result, we found core patents, main technology development, and promising technologies for technological domain of the hydrogen fuel cell.

• Design Convergence Study
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• v.15 no.2
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• pp.237-250
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• 2016

Along with rapid development, progress of the network technology and digital information technology, human are stepping into the intelligent society of internet. Thereby the quality of living environment and working environment are keep improving. Under the big background of internet era, the timeliness and convenience of smart home system has been improved greatly. While lots of smart products have gradually penetrated into people's daily life. The household appliances are among most popular ones. This paper is intended to compare smart features of household living products among most representative brands in China, Japan and South Korea. The smart features include self-learning, self-adapting, self-coordinating, self-diagnosing, self-inferring, self-organizing, and self adjusting. As result, most smart features of these products showed great similarity. While some features were dominated according to countries such as remote control feature in Korea, energy saving feature in Japan, and one button operation feature in China.

• The Journal of Bigdata
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• v.7 no.1
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• pp.139-171
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• 2022

Big Data and the fourth industrial revolution are the first revolution that has not spawned a new form of energy but has triggered a new technological phenomenon called digitization. Digital transformation has caused disruptive innovation, and each country and major corporations need to respond to it. Despite this importance, empirical studies at home and abroad are insufficient. Therefore, in this study, factors affecting the promotion of corporate digital transformation were discovered through literature review, and a research model was developed and empirically analyzed by modifying and supplementing it through a Delphi study. The research model was composed of the main standards such as technology, innovation, organization, and environment and 17 sub-standards by combining the IDT and TOE models. In order to empirically analyze this, the AHP decision-making technique was used for experts in domestic digital transformation promotion companies and business partners. Companies that promote digital transformation will be able to increase the chances of achieving successful digital transformation if they take into account the factors that influence the digital transformation promotion according to the characteristics of the type of industry and company size of the group to which the company belongs.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.727-730
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• 2023

The operation of electric automatic windows is used in harsh environments, and the energy density decreases as charging and discharging are repeated, and as soundness deteriorates due to damage to the internal separator, the vehicle's mileage decreases and the charging speed slows down, so about 5 to 10 Batteries that have been used for about a year are classified as waste batteries, and for this reason, as the risk of battery fire and explosion increases, it is essential to diagnose batteries and estimate SOH. Estimation of current battery SOH is a very important content, and it evaluates the state of the battery by measuring the time, temperature, and voltage required while repeatedly charging and discharging the battery. There are disadvantages. In this paper, measurement of discharge capacity (C-rate) using a waste battery of a Tesla car in order to predict SOH estimation of a lithium-ion battery. A Support Vector Machine (SVM), one of the machine models, was applied using the data measured from the waste battery.

• Journal of the Korean GEO-environmental Society
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• v.24 no.6
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• pp.5-11
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• 2023

The engineering industry heavily relies on fossil fuels such as coal and petroleum to generate energy through combustion. However, this process emits carbon dioxide into the atmosphere, leading to global warming. To mitigate this issue, researchers have explored various methods to reduce carbon dioxide emissions, one of which is carbon dioxide underground storage technology. This innovative technology involves capturing carbon dioxide from industrial plants and injecting it into the saturated ground layer beneath the earth's surface, storing it securely underground. Despite its potential benefits, carbon dioxide underground storage efficiency needs improvement to optimize storage in a limited space. To address this challenge, our research team has focused on improving storage efficiency by utilizing surfactants. Furthermore, we evaluated how different carbon dioxide states, including gaseous, liquid, and supercritical, impact storage efficiency based on their respective pressures and temperatures within the underground reservoir. Our findings indicate that using surfactants and optimizing the injection rate can effectively enhance storage efficiency across all carbon dioxide states. This research will pave the way for more efficient carbon dioxide underground storage, contributing to mitigating the environmental impact of fossil fuels on the planet.

• Journal of the Korean Society of Safety
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• v.10 no.3
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• pp.120-129
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• 1995

Since the rate and completeness of combustion in direct injection engines were controlled by the characteristics of gas flow fields and sprays, an understanding of those was essential to the design of the direct injection engines. In this study the numerical simulations of swirl effects on the characteristics of gas flow fields and sprays were performed using the spray model that could predict the interactions between gas fields and spray droplets. The governing equations were discretized by the finite volume method and the modified k- e model which included the compressibility effects due to the compression/expansion of piston was used. The results of numerical calculation of the spray characteristics in the quiescent environment were compared with the experimental data. There were good agreements between the results of calculation and the experimental data, except in the early stages of spray. In the motoring condition, the results showed that a substantial air entrainment into the spray volume was emerged and hence the squish motion was relatively unimportant during fuel injection periods. As the swirl ratio increased, the evaporation rate was increased due to the wide dispersion of the spray droplets and the strong interaction between spray droplets and gas fields.