• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10A
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• pp.935-942
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• 2006

The performance of ROF systems can be severely degraded due to nonlinear effects in the channel. Also, Orthogonal Frequency Division Multiplex(OFDM), as a standard for broadband wireless and mobile internet networks, is being proposed for deployment with ROF systems to facilitate the total performance of a system. In this paper, at first, the performance of the OFDM-based RoF system with a Mach-Zehnder(MZ) modulator distortion effects has been analyzed at 5.8GHz. Evaluation of mean-squared error of the proposed OFDM-RoF system was carried out to compare with the conventional single carrier system based RoF link after the modulator distortion case and also for fixed signal to noise ratio(SNR) of 20dB using undistorted OFDM signal. Nominal and offset baising pre-distortion techniques are applied in proposed system to linearize the OFDM-RoF link. Finally, a comparison between the aforementioned pre-distortion techniques applied showed important observation in terms of distortion-free dynamic range and SNR to choose offset pre-distortion technique for our proposed system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.6
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• pp.517-524
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• 2017

The objective of this research is to improve the efficiency of data collection from many machine components on smart factory floors using IoT(Internet of things) techniques and cloud platform, and to make it easy to update outdated diagnostic schemes through online deployment methods from cloud resources. The short-term analysis is implemented by a micro-controller, and it includes machine-learning algorithms for inferring snapshot information of the machine components. For long-term analysis, time-series and high-dimension data are used for root cause analysis by combining a cloud platform and multivariate analysis techniques. The diagnostic results are visualized in a web-based display dashboard for an unconstrained user access. The implementation is demonstrated to identify its performance in data acquisition and analysis for rotating machinery.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2A
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• pp.174-185
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• 2010

A seamless handover between the 3G LTE and legacy 3G system is required for the smooth deployment of the 3G LTE system which is the next generation cellular network system. Especially on voice call handover, the service interruption time is very sensitive for user's satisfaction and therefore, a seamless voice call handover scheme is necessarily required. However, handover between the 3G LTE and the 3G CS system is hard to be achieved due to the lack of interface between two systems and the restriction of radio resource. In this paper, a new network entity called SCSE is proposed and inter-working between the 3G LTE and the 3G CS systems is enabled. Also contributed to the feature of the SCSE, the handover procedure is simplified and the service interruption time is minimized as a consequence. The evaluation result shows that the proposed SCSE scheme exclusively meets the service interruption time requirement which is smaller than 300 ms.

• Journal of Digital Convergence
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• v.13 no.3
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• pp.127-135
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• 2015

This study has become a construction company will help you establish a Management Accounting System target model to move forward. Research method was to present the basic concepts and techniques used in managing complex accounting convergence look at the whole construction industry. For the successful deployment of a construction company management accounting system Responsibility Accounting System, Target Profit, Target Cost, and requires a key technique of Performance Evaluation, which the CEO's firm determination and persistence for support, proactive communication in the field and headquarters staff, the goal organizations and institutions to support the model, the standardization is required. This study is based on case studies in the future through the Delphi Method and AHP are needed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.7
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• pp.100-111
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• 2003

The HAUSAT-1(Hankuk Aviation University SATellite-1) will orbit at the altitude of 650km-800 km with 65 or 98 degree inclination angle. The effects of magnetic field and Earth gravity are more predominant than other space disturbances because the HAUSAT-1 will be positioned in LEO(Low Earth Orbit). The HAUSAT-1 design implements a magnetic control system and gravity-stable system which implement the solar panel deployment system. The simulation using MATLAB was performed to make sure the attitude stability of HAUSAT-1, which is based on the 8th order magnetic field model and non-linear equations of disturbances and the HAUSAT-1 attitude. The stability is investigated for two different HAUSAT-1 configurations and attitude which are affected by disturbances through simulation. The results for gravity-gradient stable and non gravity-gradient stable system are compared. Methodology of attitude stabilization was explored to develop an effective attitude control system for the HAUSAT-1 using magnetic torquers.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.3
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• pp.255-266
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• 2009

In this study, a robust aerospace system design process for the aerospace system is developed by considering the uncertainties of user requirements, manufacturing errors, and operational environment variation. User requirements are analyzed and quantified by decision making models and system engineering methods to select alternative concepts which satisfies the various requirements. Robust design and optimization method is applied to derive the robust solution of the selected system. First, a variance of objective function is calculated, and a mean value and a variance of target value are determined by the deterministic design optimization results of the system. A robust optimum design formulation is then needed to derive the robust solution that minimizes the variance of the response and moves the mean values to the target value. It is applied to Very Light Jet (VLJ) aircraft to which much attention is paid recently in civil aerospace market.

• Convergence Security Journal
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• v.18 no.5_1
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• pp.75-81
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• 2018

As industries converge in recent years, the impact of the use of convergence tools among industries on the security of the organization is increasing. However, organizational members lack the ability to adapt to introduction of new system because they are operating business around existing systems, and thus, security considerations are an environment that will inevitably emerge as a follow-up priority. In this study, we studied cost-effective options for factors that should be considered first in order to establish a security system for small and medium-sized healthcare institutions in the healthcare convergence industry. Specifically, the current legal system was considered and the security status was analyzed through prior research, and the necessary security solution/system was derived from small and medium-sized healthcare institutions. In addition, it analyzed relative priorities for cost-efficient deployment of security systems to those involved in small and medium-sized healthcare institutions in actual business environments and presented measures to establish a overall security.

• Convergence Security Journal
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• v.20 no.5
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• pp.11-17
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• 2020

With the increase in cases of using Bluetooth devices used in the electric vehicle charging systems, security issues are also raised. Although various technical efforts have beed made to enhance security of bluetooth technology, various attack methods exist. In this paper, we propose an intelligent Bluetooth intrusion detection system based on a well-known machine learning method, Hidden Markov Model, for the purpose of detecting intelligently representative Bluetooth attack methods. The proposed approach combines packet types of H4, which is bluetooth transport layer protocol, and the transport directions of the packet firstly to represent the behavior of current traffic, and uses the temporal deployment of these combined types as the final input features for detecting attacks in real time as well as accurate detection. We construct the experimental environment for the data acquisition and analysis the performance of the proposed system against obtained data set.

• Journal of Advanced Navigation Technology
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• v.26 no.5
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• pp.312-318
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• 2022

Currently, the Republic of Korea is facing the problem of a decrease in military service resources due to the demographic cliff, and is pursuing military restructuring and changes in the military force structure in order to respond to this. In this situation, the Army is pushing forward the deployment of a drone-bot combat system that will lead the future battlefield. The battlefield of the future will be changed into an integrated battlefield concept that combines command and control, surveillance and reconnaissance, and precision strike. According to these changes, unmanned combat system, including dronebots, will be widely applied to combat situations that are high risk and difficult for humans to perform in actual combat. In this paper, as one of the countermeasures to these changes, autonomous behavior software with a BDI architecture-based decision-making system was developed. The autonomous behavior software applied a framework structure to improve applicability to multiple models. Its function was verified in a PC-based environment by assuming that the target UAV is a battalion-level surveillance and reconnaissance UAV.

• Journal of the Korea Convergence Society
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• v.13 no.1
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• pp.387-398
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• 2022

This paper presents a system that remotely monitors lone seniors at home and promptly alarms caregivers to recommend appropriate medical care services upon detecting abnormal behavior and critical conditions such as collapsing, excessive coughing, degradation of sleep quality, fever, and unusual indoor moving lines. Our system offers contactless monitoring techniques based on heterogeneous IoT sensors and deep learning to minimize the disruption to lone senior's daily life. In addition to the design and implementation of the sensor data collection and analysis system, we share our experience in installation, deployment, configuration, maintenance of the system through the case study conducted on the actual lone seniors living in Seoul Metropolitan. Based on our research, we recommend further development directions to prepare for the nationwide expansion of our system.