• Smart Structures and Systems
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• v.29 no.6
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• pp.799-805
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• 2022

Permanent magnet synchronous motors (PMSMs) are widely used in systems requiring high control precision, efficiency, and reliability. Predicting the remaining useful life (RUL) with health monitoring of PMSMs prevents catastrophic failure and ensures reliable operation of system. In this study, a model-based method for predicting the RUL of PMSMs using phase current and vibration signals is proposed. The proposed method includes feature selection and RUL prediction based on a particle filter with a degradation model. The Paris-Erdogan model describing micro fatigue crack propagation is used as the degradation model. An experimental set-up to conduct accelerated life test, capable of monitoring various signals was designed in this study. Phase current and vibration data obtained from an accelerated life test of the PMSMs were used to verify the proposed approach. Features extracted from the data were clustered based on monotonicity and correlation clustering, respectively. The results identify the effectiveness of using the current data in predicting the RUL of PMSMs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.3
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• pp.721-739
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• 2023

Rating prediction is an important issue in recommender systems, and its accuracy affects the experience of the user and the revenue of the company. Traditional recommender systems use Factorization Machinesfor rating predictions and each feature is selected with the same weight. Thus, there are problems with inaccurate ratings and limited data representation. This study proposes a deep recommendation model based on self-attention Factorization (SAFMR) to solve these problems. This model uses Convolutional Neural Networks to extract features from user and item reviews. The obtained features are fed into self-attention mechanism Factorization Machines, where the self-attention network automatically learns the dependencies of the features and distinguishes the weights of the different features, thereby reducing the prediction error. The model was experimentally evaluated using six classes of dataset. We compared MSE, NDCG and time for several real datasets. The experiment demonstrated that the SAFMR model achieved excellent rating prediction results and recommendation correlations, thereby verifying the effectiveness of the model.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.382-387
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• 2009

Requirement management is an important phase that has a significant influence on the project success. As a risk to a project fail is getting bigger, people adopt Systems Engineering method to the development of the effective requirement management. Accordingly, Railroad Safety Technology R&D Corps. is progressing the plan of the construction of Railway Safety Test Facilities as a part of the Railway Total Safety Project to enhance the railway safety, and carrying out researches on effective requirement management methods with Systems Engineering techniques. To support that, we introduce the Systems Engineering Requirement Management Process and propose the more effectual management method of constructing the Railway Safety Test Facilities applying the model-based systems engineering tool to the research.

• Journal of Information Processing Systems
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• v.14 no.6
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• pp.1301-1306
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• 2018

Artificial intelligence is one of the key technologies of the Fourth Industrial Revolution. This paper introduces the diverse kinds of approaches to subjects that tackle diverse kinds of research fields such as model-based MS approach, deep neural network model, image edge detection approach, cross-layer optimization model, LSSVM approach, screen design approach, CPU-GPU hybrid approach and so on. The research on Superintelligence and superconnection for IoT and big data is also described such as 'superintelligence-based systems and infrastructures', 'superconnection-based IoT and big data systems', 'analysis of IoT-based data and big data', 'infrastructure design for IoT and big data', 'artificial intelligence applications', and 'superconnection-based IoT devices'.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.8
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• pp.77-83
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• 2016

International standards for systems safety have been established in various areas of industry. Such standards recommend that safety design activities be carried out early on in the beginning of systems development. Hazard analysis should be done in close interaction with the conceptual design of the system. This paper focuses on how to verify whether the safety goals are met while considering system design issues. The architecture of the underlying system was first modeled using SysML, a systems modeling language, and then hazard analysis was performed based on architectural information to obtain a system failure model. Thereafter, an integrated model was developed by combining the SysML failure model and the architectural model, and then safety designs were added to prevent system failure. Finally, a simulation of the developed model was performed to see if a system functions even when some components are failing.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.3
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• pp.358-379
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• 2010

Multiple object association is an important capability in visual surveillance system with multiple cameras. In this paper, we introduce locally initiating line-based object association with the parallel projection camera model, which can be applicable to the situation without the common (ground) plane. The parallel projection camera model supports the camera movement (i.e. panning, tilting and zooming) by using the simple table based compensation for non-ideal camera parameters. We propose the threshold distance based homographic line generation algorithm. This takes account of uncertain parameters such as transformation error, height uncertainty of objects and synchronization issue between cameras. Thus, the proposed algorithm associates multiple objects on demand in the surveillance system where the camera movement dynamically changes. We verify the proposed method with actual image frames. Finally, we discuss the strategy to improve the association performance by using the temporal and spatial redundancy.

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.4
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• pp.308-315
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• 2016

This paper addresses a formation control problem for a phugoid model-based multi-agent system in discrete time by using a Takagi-Sugeno (T-S) fuzzy model-based controller design technique. The concerned discrete-time model is obtained by Euler's method. A T-S fuzzy model is constructed through a feedback linearization. A fuzzy controller is then designed to stabilize the T-S fuzzy model. Design condition is presented in the linear matrix inequality format.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.425-433
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• 2016

The construction of a light rail transit (LRT) system is a large and complex infrastructure project involving hundreds of billions of won in construction costs for a single route, and it is very important to carry out such a project from a life-cycle perspective because of its long-term operation. Systems engineering is a means and methodology to successfully implement customers' needs, and it is useful in large projects such as light rail transit. An application model called Systems Engineering for Light Rail Transit (SELRT) was developed to support systems engineering activities in light rail transit projects. In order to utilize SELRT, it is necessary to ensure that system requirements are met. As such, in this paper, we present a verification procedure and architecture based on a systems engineering-based methodology, thereby identifying the system requirements and deriving the verification requirements to confirm the SELRT model for the proposed method. The results show that the traceability of the system requirements and verification requirements, the verification method for each requirement, and the demonstration results for computerized tools are mutually connected, and that the initial requirements are clearly implemented in the SELRT. The proposed method is valid for verifying the SELRT, which can also be utilized in a LRT project.

• Journal of the Korean Society of Systems Engineering
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• v.15 no.2
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• pp.17-30
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• 2019

Due to difficulties in tracking design information of existing document-based configuration management, the research on the development of plant SysML model was started to apply the model-based system engineering methodology to comprehensively manage various design information. However, until now, in order to create the SysML model, the engineers are checking the design information and inputting it to the SysML model. This process requires a lot of time and manpower, it is required to minimize it. Therefore, this study has recognized the problem, a plug-in that extracts the plant design information in the design document and automatically converts the SysML plant model from it. Specifically, the development was performed in the following order. First, the extraction file was selected as the most commonly used Excel file as the plant design document. Next, the design information in the document was analyzed, and extracted information including tag number, name, and the capacity were selected. Finally, the plant SysML model conversion module was implemented. The developed plug-in is confirmed that the task load of the engineers by the SysML model conversion can be minimized and the model can be generated more quickly and accurately.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2304-2308
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• 2003

Ocean thermal energy conversion (OTEC) is an effective method of power generation, which has a small impact on the environment and can be utilized semi-permanently. This paper describes a dynamic model for a pilot OTEC plant built by the Institute of Ocean Energy, Saga University, Japan. This plant is based on Uehara cycle, in which binary mixtures of ammonia and water is used as the working fluid. Some simulation results attained by this model and the analysis of the results are presented. The developed computer simulation can be used to actual practice effectively, such as stable control in a steady operation, optimal determination of the plant specifications for a higher thermal efficiency and evaluation of the economic prospects and off-line training for the operators of OTEC plant.