• Journal of the Korean Society for information Management
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• v.35 no.3
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• pp.77-100
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• 2018

The objectives of this study is to present a discovering process of interdisciplinary convergence technology using text mining of big data. For the convergence research of biotechnology(BT) and information communications technology (ICT), the following processes were performed. (1) Collecting sufficient meta data of research articles based on BT terminology list. (2) Generating intellectual structure of emerging technologies by using a Pathfinder network scaling algorithm. (3) Analyzing contents with topic modeling. Next three steps were also used to derive items of BT-ICT convergence technology. (4) Expanding BT terminology list into superior concepts of technology to obtain ICT-related information from BT. (5) Automatically collecting meta data of research articles of two fields by using OpenAPI service. (6) Analyzing contents of BT-ICT topic models. Our study proclaims the following findings. Firstly, terminology list can be an important knowledge base for discovering convergence technologies. Secondly, the analysis of a large quantity of literature requires text mining that facilitates the analysis by reducing the dimension of the data. The methodology we suggest here to process and analyze data is efficient to discover technologies with high possibility of interdisciplinary convergence.

• Journal of KIISE:Information Networking
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• v.37 no.4
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• pp.272-283
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• 2010

Wireless Mesh Networks (WMNs) have gained a lot of attention recently. Based on the characteristic of WMNs as a highly connected wireless infrastructure, many efforts from research organizations are made in order to improve the performance of the flow throughput in WMNs. Therefore, it is very critical issue to establish efficient routing paths for multiple concurrent ongoing flows. In this paper, we propose a general modeling methodology to analyze the end-to-end throughput of multiple concurrent flows by analytical calculation taking into account the carrier sensing behaviors, interference and the IEEE 802.11 Distributed Coordination Function mechanism. After the comparison of the average service time for each successful transmission at each node, we analyze the bottlenecks of flows, and hence obtain the maximum end-to-end throughput of them. By using our proposed model, it is possible to predicate the throughput of several candidate routing paths for multiple concurrent ongoing data flows, so we can select the most efficient route that can achieve the highest throughput. We carry out simulations with various traffic patterns of multiple flows in WMNs to validate our modeling and our efficient route selection mechanism.

• Tunnel and Underground Space
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• v.30 no.6
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• pp.573-590
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• 2020

This study presents the current status of DECOVALEX-2023 project Task G and our research results so far. Task G, named 'Safety ImplicAtions of Fluid Flow, Shear, Thermal and Reaction Processes within Crystalline Rock Fracture NETworks (SAFENET)' aims at developing a numerical method to simulate the fracture creation and propagation, and the coupled thermohydro-mechanical processes in fracture in crystalline rocks. The first research step of Task G is a benchmark simulation, which is designed for research teams to make their modelling codes more robust and verify whether the models can represent an analytical solution for displacements of a single rock fracture. We reproduced the mechanical behavior of rock and embedded single fracture using a three-dimensional grain-based distinct element model for the simulations. In this method, the structure of the rock was represented by an assembly of rigid tetrahedral grains moving independently of each other, and the mechanical interactions at the grains and their contacts were calculated using 3DEC. The simulation results revealed that the stresses induced along the embedded fracture in the model were relatively low compared to those calculated by stress analysis due to stress redistribution and constrained fracture displacements. The fracture normal and shear displacements of the numerical model showed good agreement with the analytical solutions. The numerical model will be enhanced by continuing collaboration and interaction with other research teams of DECOVALEX-2023 Task G and validated using various experiments in a further study.

• Journal of Intelligence and Information Systems
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• v.29 no.4
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• pp.325-345
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• 2023

In the rapidly evolving domain of e-commerce, our study presents a cohesive approach to enhance customer satisfaction prediction from online reviews, aligning methodological innovation with practical insights. We integrate the RFE-SHAP feature selection with LDA topic modeling to streamline predictive analytics in e-commerce. This integration facilitates the identification of key features-specifically, narrowing down from an initial set of 28 to an optimal subset of 14 features for the Random Forest algorithm. Our approach strategically mitigates the common issue of overfitting in models with an excess of features, leading to an improved accuracy rate of 84% in our Random Forest model. Central to our analysis is the understanding that certain aspects in review content, such as quality, fit, and durability, play a pivotal role in influencing customer satisfaction, especially in the clothing sector. We delve into explaining how each of these selected features impacts customer satisfaction, providing a comprehensive view of the elements most appreciated by customers. Our research makes significant contributions in two key areas. First, it enhances predictive modeling within the realm of e-commerce analytics by introducing a streamlined, feature-centric approach. This refinement in methodology not only bolsters the accuracy of customer satisfaction predictions but also sets a new standard for handling feature selection in predictive models. Second, the study provides actionable insights for e-commerce platforms, especially those in the clothing sector. By highlighting which aspects of customer reviews-like quality, fit, and durability-most influence satisfaction, we offer a strategic direction for businesses to tailor their products and services.

• Journal of Internet Computing and Services
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• v.25 no.3
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• pp.43-54
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• 2024

This study employs text mining techniques to compare user responses across various Over-The-Top (OTT) service platforms. The primary objective of the research is to understand user satisfaction with OTT service platforms and contribute to the formulation of more effective review strategies. The key questions addressed in this study involve identifying prominent topics and keywords in user reviews of different OTT services and comprehending platform-specific user reactions. TF-IDF is utilized to extract significant words from positive and negative reviews, while BERTopic, an advanced topic modeling technique, is employed for a more nuanced and comprehensive analysis of intricate user reviews. The results from TF-IDF analysis reveal that positive app reviews exhibit a high frequency of content-related words, whereas negative reviews display a high frequency of words associated with potential issues during app usage. Through the utilization of BERTopic, we were able to extract keywords related to content diversity, app performance components, payment, and compatibility, by associating them with content attributes. This enabled us to verify that the distinguishing attributes of the platforms vary among themselves. The findings of this study offer significant insights into user behavior and preferences, which OTT service providers can leverage to improve user experience and satisfaction. We also anticipate that researchers exploring deep learning models will find our study results valuable for conducting analyses on user review text data.

• Journal of Korean Home Economics Education Association
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• v.36 no.2
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• pp.33-50
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• 2024

This study examined the trends in home economics education research across different curriculum periods and journals. A total of 374 papers related to the 2009, 2015, and 2022 revised curricula were selected and analyzed using network analysis from four journals. First, research trends were analyzed by curriculum period. Keyword frequency analysis revealed that articles on the 2009 and 2015 revised curricula primarily focused on analyzing the curriculum to develop textbooks or programs. In contrast, papers on the 2022 revised curriculum explored broader directions. Topic modeling results highlighted the prominent topics for each period: 'environmental education' in the 2009 revised curriculum, 'safety and health education' in the 2015 revised curriculum, and 'ecological transition' in the 2022 revised curriculum. Second, research trends were analyzed by journal. Keyword frequency analysis by journal exposed specific research tendencies. For example, in the Journal of Home Economics Research, 'perceptions of practical classes' and 'analysis of safety textbooks' were major topics for the 2009 revised curriculum, while 'teaching and learning plans for competence development' dominated research on the 2015 revised curriculum. This study demonstrates that the concepts and goals emphasized in curriculum revisions are reflected in the corresponding research.

• Proceedings of the KIEE Conference
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• 2008.04a
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• pp.187-188
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• 2008

주기적으로 제어 성능을 평가하고, 평가 결과에 따라서 제어시스템의 제어기 상수를 최적화하거나 제어 밸브와 같은 제어기기의 문제점들을 사전에 개선하고자하는 노력이 있어왔다. 제어성능 평가방법은 제어목표 값에 대한 추종성을 평가하는 Set Point Analysis 방법을 주로 사용한다. 평가 지표는 Integral Absolute Error(IAE)와 같은 Error Integral 값과 Minimum Variance 방법이 실용적으로 사용된다. 본 논문에서는 평가 대상시스템으로 원자력발전소의 수위 제어시스템중 하나를 선정하고 Control Performance Assessment를 수행하였다. 이를 기반으로 대상 시스템의 제어모델링을 바탕으로 한 Minimum Integral Error를 만족하는 제어기 상수를 구하였으며 새로운 상수를 제어기에 설정한 후 다시 성능을 평가하였다. 평가 결과, 제어시스템의 제어 성능 평가 지표를 사용한 제어 루프의 평가와 예방 조치가 실제적으로 발전소의 안정적 운전에 유용하다는 것을 입증하였다.

• Journal of the Korean Society for Railway
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• v.17 no.3
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• pp.186-192
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• 2014

In this paper, a reliability analysis is performed where the pressure change inside a concrete tube is probabilistically estimated considering the uncertainties inherent in the material and the system discontinuity. A set of uncertain quantities related to the equivalent system air permeability and the atmospheric pressure, are defined as random variables with specific distribution. The pressure change inside a concrete tube is then probabilistically described using both analytical and simulation approaches. The reliability analysis confirms that the geometric configuration of a concrete tube needs to be changed from the initial configuration obtained from the deterministic analysis.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.2
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• pp.25-33
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• 2012

A genetic algorithm (GA) has been employed to optimize the major design variables of the liquid rocket engine. Pressure of the main combustion chamber, nozzle expansion ratio and O/F ratio have been selected as design variables. The target engine has the open gas generator cycle using the LO2/RP-1 propellant. The gas properties of the combustion chamber have been obtained from CEA2 and the mass has been estimated using reference data. The objective function has been set as multi-objective function with the specific impulse and thrust to weight ratio using the weight method. The result shows about 4% improvement of the specific impulse and 23% increase of the thrust to weight ratio. The Pareto frontier line has been also obtained for various thrust requirements.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.14-14
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• 2017

본 연구는 트랙터 주행노면의 토양 특성이 트랙터 승차진동에 미치는 영향을 분석하는 것을 목표로 하였다. 여러 토양조건에서 실제 트랙터 주행실험을 진행하는 것은 어렵기 때문에, 상용 CAE 프로그램을 이용하여 트랙터를 모델링하고 시뮬레이션을 진행하였다. 이를 통해 여러 토양조건에 따른 승차진동의 특성을 비교, 분석하였다. 모델의 유의성은 트랙터 아스팔트 주행실험을 통해 진동데이터를 획득하고 실측 진동 데이터와 시뮬레이션을 통해 얻어진 진동 데이터를 분석해 검토하였다. 이 때, 노면 토양의 특성에 따라서 트랙터가 장애물을 만났을 때 순간적인 진동 특성을 분석하기 위해서 트랙터 주행 노면을 사인범퍼(sine-bumper) 노면으로 설정하고 주행실험 및 시뮬레이션을 진행하였다. 본 연구에서는 강체 노면, Heavy clay, North Gower Clay Loam 토양, Grenvile Loam 토양의 네 가지 노면 조건을 분석하였다. 분석 결과 침하가 발생하지 않는 강체 노면보다 침하가 발생하는 세 가지 토양 조건에서 장애물에 따른 순간적인 진동이 더 크게 나타나는 것을 확인할 수 있었다. 다만 승차진동이 토양 파라미터와 단순히 선형적인 관계만을 보이는 것은 아니라는 것도 확인할 수 있었다. 이 후, North Gower Clay Loam 토양 조건에서 트랙터 속도에 따른 시뮬레이션 진행 결과를 분석하였을 때, 토양 침하가 발생하는 토양 조건에서도 속도가 증가함에 따라서 진동 크기가 증가하는 것을 확인할 수 있었다.