• Journal of Intelligence and Information Systems
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• v.29 no.2
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• pp.267-283
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• 2023

The COVID-19 pandemic, which began in December 2019 and continues to this day, has left the public needing information to help them cope with the pandemic. However, COVID-19-related fake news on social media seriously threatens the public's health. In particular, if fake news related to COVID-19 is massively spread with similar content, the time required for verification to determine whether it is genuine or fake will be prolonged, posing a severe threat to our society. In response, academics have been actively researching intelligent models that can quickly detect COVID-19-related fake news. Still, the data used in most of the existing studies are in English, and studies on Korean fake news detection are scarce. In this study, we collect data on COVID-19-related fake news written in Korean that is spread on social media and propose an intelligent fake news detection model using it. The proposed model utilizes the frequency information of parts of speech, one of the linguistic characteristics, to improve the prediction performance of the fake news detection model based on Doc2Vec, a document embedding technique mainly used in prior studies. The empirical analysis shows that the proposed model can more accurately identify Korean COVID-19-related fake news by increasing the recall and F1 score compared to the comparison model.

• Korean Chemical Engineering Research
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• v.61 no.3
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• pp.362-367
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• 2023

Recently, research and development of proton exchange membrane fuel cells (PEMFC) membranes are progressing in the direction of thinning to reduce prices and improve performance. Demand for hydrogen-powered vehicles for commercial vehicles is also increasing, and their durability should be five times greater than those for passenger vehicles. Despite the thinning of the membranes, the durability of the membranes must be increased five times, so the improvement of the durability of the membranes has become more important. Since the acceleration durability evaluation time also needs to be shortened, the protocol using oxygen instead of air in the existing protocol was applied to a 10 ㎛ thin membrane to evaluate durability. The accelerated durability test (Open circuit voltage holding) was terminated at 720 hours. If the air-based department of energy (DOE) protocol was used, a lifespan of 450,000 km of driving hours would be expected, with a durability of about 1,500 hours. During the chemical durability evaluation, the active area of the electrode decreased by 51%, suggesting that catalyst degradation had an effect on membrane durability. Reducing the catalyst degradation rate is expected to increase membrane durability.

• Journal of Microbiology and Biotechnology
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• v.33 no.6
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• pp.831-839
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• 2023

Tylosin is a potent veterinary macrolide antibiotic produced by the fermentation of Streptomyces fradiae; however, it is necessary to modify S. fradiae strains to improve tylosin production. In this study, we established a high-throughput, 24-well plate screening method for identifying S. fradiae strains that produce increased yields of tylosin. Additionally, we constructed mutant libraries of S. fradiae via ultraviolet (UV) irradiation and/or sodium nitrite mutagenesis. A primary screening of the libraries in 24-well plates and UV spectrophotometry identified S. fradiae mutants producing increased yields of tylosin. Mutants with tylosin yield 10% higher than the wild-type strain were inoculated into shake flasks, and the tylosin concentrations produced were determined by high-performance liquid chromatography (HPLC). Joint (UV irradiation and sodium nitrite) mutagenesis resulted in higher yields of mutants with enhanced tylosin production. Finally, 10 mutants showing higher tylosin yield were re-screened in shake flasks. The yield of tylosin A by strains UN-C183 (6767.64 ± 82.43 ㎍/ml) and UN-C137 (6889.72 ± 70.25 ㎍/ml) was significantly higher than that of the wild-type strain (6617.99 ± 22.67 ㎍/ml). These mutant strains will form the basis for further strain breeding in tylosin production.

• Nuclear Engineering and Technology
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• v.55 no.5
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• pp.1802-1813
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• 2023

Conjugate heat transfer between liquid metal and solid is a common phenomenon in a liquid-metal-cooled fast reactor's fuel assembly and heat exchanger, dramatically affecting the reactor's safety and economy. Therefore, comprehensively studying the sophisticated conjugate heat transfer in a liquid-metal-cooled fast reactor is profound. However, it has been evidenced that the traditional Simple Gradient Diffusion Hypothesis (SGDH), assuming a constant turbulent Prandtl number (Pr_t,, usually 0.85 - 1.0), is inappropriate in the Computational Fluid Dynamics (CFD) simulations of liquid metal. In recent decades, numerous studies have been performed on the four-equation model, which is expected to improve the precision of liquid metal's CFD simulations but has not been introduced into the conjugate heat transfer calculation between liquid metal and solid. Consequently, a four-equation model, consisting of the Abe k - ε turbulence model and the Manservisi k_𝜃 - ε_𝜃 heat transfer model, is applied to study the conjugate heat transfer concerning liquid metal in the present work. To verify the numerical validity of the four-equation model used in the conjugate heat transfer simulations, we reproduce Johnson's experiments of the liquid lead-bismuth-cooled turbulent pipe flow using the four-equation model and the traditional SGDH model. The simulation results obtained with different models are compared with the available experimental data, revealing that the relative errors of the local Nusselt number and mean heat transfer coefficient obtained with the four-equation model are considerably reduced compared with the SGDH model. Then, the thermal-hydraulic characteristics of liquid metal turbulent pipe flow obtained with the four-equation model are analyzed. Moreover, the impact of the turbulence model used in the four-equation model on overall simulation performance is investigated. At last, the effectiveness of the four-equation model in the CFD simulations of liquid sodium conjugate heat transfer is assessed. This paper mainly proves that it is feasible to use the four-equation model in the study of liquid metal conjugate heat transfer and provides a reference for the research of conjugate heat transfer in a liquid-metal-cooled fast reactor.

• Proceedings of the Korean Society of Computer Information Conference
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• 2020.07a
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• pp.575-576
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• 2020

본 논문은 근래에 식용곤충 식품에 대한 수요 및 국민적 관심이 증가하여 관련 산업이 급격히 성장하고 있는 가운데, 건강기능성 효과가 널리 알려진 흰점박이꽃무지 유충의 안정적인 생산량 확보를 위한 스마트 사육사를 제작하고 그 성능을 평가한 결과이다. 사육사는 L6m×W3m×H2.8m 크기로 제작하였으며, 안정적인 사육환경을 위하여 사육실과 공조실을 분리하여 설계하였다. 공시재료는 생후 15일이 경과된 흰점박이꽃 무지 유충 1령이며, 스마트 사육사 내 사육환경은 온도 25±2℃, 습도 65±5%로 제어하였다. 사육조사는 매주 1회, 유충의 체중, 길이, 두께를 측정하였으며, 스마트 사육사의 성능평가를 위해 일반 사육농가(전북 소재)와 비교·분석하였다. 사육 4주 후 조사 결과, 스마트 사육사에서 사육한 유충의 체중과 길이는 각각 평균 1.97g/마리와 3.75cm로, 일반농가의 1.58g/마리와 3.55cm에 비해 비교적 높은 것으로 나타났다. 하지만, 두께의 경우 2주 차까지 일반농가에서 대체로 높은 것으로 나타났으며, 이후 3~4주 차에서는 큰 차이를 보이지 않았다. 따라서 본 연구를 통해 개발한 흰점박이꽃무지 유충 스마트 사육사는 일반농가와 비교해 사육이 비교적 빠르고 생산량을 더 많이 확보할 수 있는 시스템으로 농가소득 증대에 유용할 것으로 판단되며, 장소 및 시간에 상관없이 생육환경 제어가 가능하여 개발된 시제품의 보급 확대가 필요하다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1D
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• pp.135-143
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• 2009

Integrating the Global Positioning System (GPS) and Inertial Navigation System (INS) sensor technologies using the precise GPS Carrier phase measurements is a methodology that has been widely applied in those application fields requiring accurate and reliable positioning and attitude determination; ranging from 'kinematic geodesy', to mobile mapping and imaging, to precise navigation. However, such integrated system may not fulfil the demanding performance requirements when the baseline length between reference and mobil user GPS receiver is grater than a few tens of kilometers. This is because their positioning/attitude determination is still very dependent on the errors of the GPS observations, so-called "baseline dependent errors". This limitation can be remedied by the integration of GPS and INS sensors, using multiple reference stations. Hence, in order to derive the GPS distance dependent errors, this research proposes measurement processing algorithms for multiple reference stations, such as a reference station ambiguity resolution procedure using linear combination techniques, a error estimation based on Kalman filter and a error interpolation. In addition, all the algorithms are evaluated by processing real observations and results are summarized in this paper.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2C
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• pp.71-79
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• 2009

This study is to develope the resilient modulus prediction model, which is the function of mean effective principal stress and axial strain, for three types of railroad trackbed materials such as crushed stone, weathered granite soil, and crushed-rock soil mixture. The model consists of the maximum Young's modulus and nonlinear values for higher strain, analogous to dynamic shear modulus. The maximum value is modeled by model parameters, $A_E$ and the power of mean effective principal stress, $n_E$. The nonlinear portion is represented by modified hyperbolic model, with the model parameters of reference strain, ${\varepsilon}_r$ and curvature coefficient, a. To assess the performance of the prediction models proposed herein, the elastic response of a test trackbed near PyeongTaek, Korea, was evaluated using a 3-D elastic multilayer computer program (GEOTRACK). The results were compared with measured elastic vertical displacement during the passages of freight and passenger trains at two locations, whose sub-ballasts were crushed stone and weathered granite soil, respectively. The calculated vertical displacements of the sub-ballasts are within the order of 0.6mm, and agree well with measured values. The prediction models are thus concluded to work properly in the preliminary investigation.

• Maritime Security
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• v.6 no.1
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• pp.1-35
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• 2023

The purpose of this study is to present the direction of development of our navy's response strategy through analysis at the ends, ways, and means level of the Chinese navy's offensive strategy for the West Sea. As a result of the analysis, at the ends level, the Chinese Navy's offensive strategy for the West Sea strategy is being linked to a grand strategy to protect maritime rights and achieve maritime power between the U.S. and China competition, at the ways level, the Chinese Navy is expected to create a foundation for the international community to recognize the West Sea as China's inland sea through "routine entry" and "exercise authority", and in case of emergency, it will try to secure sea control in the West Sea in a short period of time by blocking Korea's maritime transportation route based on the overwhelming preemptive attack capability of aircraft carriers. At the means level, it is accelerating the construction of aircraft carrier warfare units and improving its ability to engage long-range missiles. As a direction of development of the Korean Navy's response strategy in response to this, first, Establishment and Development of National Maritime Security Strategy in conjunction with the Korean Indo-Pacific Strategy. Second, it proposes the development of the concept of effective security operations for the east sea area of the West Sea intermediate line, and third, the development of the concept of combat performance and capacity building to strengthen survival and lethality.

• Steel and Composite Structures
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• v.48 no.2
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• pp.207-233
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• 2023

Steel-concrete composite box girder bridges are widely used in the construction of highway and railway bridges both domestically and abroad due to their advantages of being light weight and having a large spanning ability and very large torsional rigidity. Composite box girder bridges exhibit the effects of shear lag, restrained torsion, distortion and interface bidirectional slip under various loads during operation. As one of the most commonly used calculation tools in bridge engineering analysis, one-dimensional models offer the advantages of high calculation efficiency and strong stability. Currently, research on the one-dimensional model of composite beams mainly focuses on simulating interface longitudinal slip and the shear lag effect. There are relatively few studies on the one-dimensional model which can consider the effects of restrained torsion, distortion and interface transverse slip. Additionally, there are few studies on vehicle-bridge integrated systems where a one-dimensional model is used as a tool that only considers the calculations of natural frequency, mode and moving load conditions to study the dynamic response of composite beams. Some scholars have established a dynamic analysis model of a coupled composite beam bridge-train system, but where the composite beam is only simulated using a Euler beam or Timoshenko beam. As a result, it is impossible to comprehensively consider multiple complex force effects, such as shear lag, restrained torsion, distortion and interface bidirectional slip of composite beams. In this paper, a 27 DOF vehicle rigid body model is used to simulate train operation. A two-node 26 DOF finite beam element with composed box beams considering the effects of shear lag, restrained torsion, distortion and interface bidirectional slip is proposed. The dynamic analysis model of the coupled composite box girder bridge-train system is constructed based on the wheel-rail contact relationship of vertical close-fitting and lateral linear creeping slip. Furthermore, the accuracy of the dynamic analysis model is verified via the measured dynamic response data of a practical composite box girder bridge. Finally, the dynamic analysis model is applied in order to study the influence of various mechanical effects on the dynamic performance of the vehicle-bridge system.

• The Journal of Bigdata
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• v.6 no.2
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• pp.71-84
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• 2021

Since small and medium-sized enterprises fell short of the securement of technological competitiveness in the field of big data and artificial intelligence (AI) field-core technologies of the Fourth Industrial Revolution, it is important to strengthen the competitiveness of the overall industry through technology commercialization. In this study, we aimed to propose a priority related to technology transfer and commercialization for practical use of public research results. We utilized public research performance information, improving missing values of 6T classification by deep learning model with an ensemble method. Then, we conducted topic modeling to derive the converging fields of big data and AI. We classified the technology fields into four different segments in the technology portfolio based on technology activity and technology efficiency, estimating the potential of technology commercialization for those fields. We proposed a priority of technology commercialization for 10 detailed technology fields that require long-term investment. Through systematic analysis, active utilization of technology, and efficient technology transfer and commercialization can be promoted.