• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.2
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• pp.253-260
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• 2009

This paper, mathematically analyzes the performance of newly proposed TR-UWB system which the frequency components of a UWB pulse were processed so that the system could be implemented with ADCs of a few MHz sampling rate, and presents the comparison with an existing frequency-domain based TR-UWB system. The comparison is mainly based on the SNR ratio which depends on the mean and the variance of the frequency components. We also shows that the simulation results to support the theoretical analysis where the comparison is made under the IEEE 802.15.3a channel model as well as AWGN channel.

• Journal of Convergence for Information Technology
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• v.7 no.2
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• pp.67-76
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• 2017

Along with shortening the life cycle of software utilization and supporting various types of user functions, the importance of software architecture development has been emphasized recently. If a software architecture is developed flexibly and reliably for expansion to support new functionality, it can quickly cope with new market demands. This paper proposes an architecture design method based on design recovery of open source software to reuse the software in the development of sustainable software system. When using open source software to develop a software system based on software architecture, we can develop a software system rapidly and also can improve the reliability of the system because we use the already proven open source software in the development.

• International Journal of Railway
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• v.4 no.2
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• pp.34-41
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• 2011

Using a test run data, the dynamics of the interface between the catenary and pantograph constituting the current collection system in high-speed trains are investigated. The test run signals are analyzed to determine the dynamic parameters critical to the current collection performance. There are found to be frequency components of the pantograph motion that are dependent on train speed as well as components that are stationary such as the resonant mode of the panhead suspension in the pantograph. From contact force measurement using load cell, the mean contact force was found to be stable while the fluctuating component was found to be dependent on the range of the frequency of the pantograph motion taken into account. The finding implies that numerical investigations reported in the literature that are based on lumped element models of the catenary and/or pantograph provide accurate predictions on the mean value but are of limited use in estimating fluctuation of the contact force. It is concluded that simulation studies based on lumped-element models which do not incorporate panhead structural vibration modes is inaccurate at high train speeds.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.6
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• pp.535-540
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• 2022

DC-link capacitors are reliability-critical components in a photovoltaic (PV) inverter. Typically, the lifetime of a DC-link capacitor is evaluated by considering the voltage and hot-spot temperature of the capacitor under the specific operating condition of the PV inverter. However, the output of the PV inverter is determined by solar irradiation and ambient temperature, which vary with the seasons; accordingly, the hot-spot temperature of the capacitor also changes. Therefore, the mission profile of the PV system should be considered to effectively evaluate the reliability of the DC-link capacitor. In this study, the reliability of the DC-link capacitor of a three-level NPC inverter is comparatively analyzed with and without considering the mission profiles of the PV system, where two mission profiles recorded in Arizona and Iza are considered. The accumulated damage of the DC-link capacitor is calculated based on the lifetime model by analyzing its thermal loading. Afterward, a reliability evaluation of the DC-link capacitor is performed at the component level and then at the system level by considering all capacitors by means of Monte Carlo analysis. Results reveal the importance of performing a mission-profile-based reliability evaluation during the design of high-reliability PV inverters to achieve the target reliability performance.

• Current Optics and Photonics
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• v.5 no.6
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• pp.686-698
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• 2021

A camouflaged encryption scheme based on Hadamard matrix and ghost imaging is proposed. In the process of the encryption, an orthogonal matrix is used as the projection pattern of ghost imaging to improve the definition of the reconstructed images. The ciphertext of the secret image is constrained to the camouflaged image. The key of the camouflaged image is obtained by the method of sparse decomposition by principal component orthogonal basis and the constrained ciphertext. The information of the secret image is hidden into the information of the camouflaged image which can improve the security of the system. In the decryption process, the authorized user needs to extract the key of the secret image according to the obtained random sequences. The real encrypted information can be obtained. Otherwise, the obtained image is the camouflaged image. In order to verify the feasibility, security and robustness of the encryption system, binary images and gray-scale images are selected for simulation and experiment. The results show that the proposed encryption system simplifies the calculation process, and also improves the definition of the reconstructed images and the security of the encryption system.

• Journal of Institute of Convergence Technology
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• v.13 no.1
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• pp.19-22
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• 2023

The rise of electrification and the advancement of autonomous driving technologies are leading to new forms of mobility, such as serving and delivery robots. However, due to factors such as the small-scale production of various products and the high cost of autonomous driving sensors, product prices have risen, limiting accessibility to consumers. To improve this, we developed a multi-purpose mobility platform that is mass-producible, based on inexpensive, reliable sensors and a configurable human tracking system. As a result, the unit price is approximately 50% of the launch prices of other mobility products, and additional cost savings are possible through component optimization in the future. In addition, more added value will be created through the distribution of integrated mobility platforms that can be combined with various usable modules to meet a variety of user needs, such as cargo transportation, wheelchair power kits, and mobile monitors.

• The KIPS Transactions:PartA
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• v.18A no.6
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• pp.241-248
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• 2011

Many learning systems are applying Self-Directed Learning to improve learning efficiency. The degree of understanding of the same learning contents can be different even if the learner's level is same. Therefore, it is difficult to represent an effective learning experience because the learning is progressed by the determined difficulty of learning and the learning process even thought the provided content is difficult to understand. In this paper, we augmented SCORM to reconstruct the learning contents which are suitable for the changed level of each learner in real-time. Also, we designed and implemented this augmented SCORM based DCOS(Differential Contents Organization System). In order to provide the suitable contents for each learner, DCOS reorganizes learning contents based on the learner's level, the learner's achievement of learning objectives, and the correlation between learning objects, that is the component of the learning content. Each 30 Each 30 students studied e-learning contents, which are constructed based on the existing System and DCOS respectively. And the average score and system's satisfaction of the students who studied DCOS based e-learning contents was higher.

• Nuclear Engineering and Technology
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• v.41 no.4
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• pp.447-454
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• 2009

This paper is a technical review of the research and development results of the Korea Nuclear Instrumentation and Control System (KNICS) project and Nu-Tech 2012 program. In these projects man-machine interface system architecture, two digital platforms, and several control and protection systems were developed. One platform is a Programmable Logic Controller (PLC) for a digital safety system and another platform is a Distributed Control System (DCS) for a non-safety control system. With the safety-grade platform PLC, a reactor protection system, an engineered safety feature-component control system, and reactor core protection system were developed. A power control system was developed based on the DCS. A logic alarm cause tracking system was developed as a man-machine interface for APR1400. Also, Integrated Performance Validation Facility (IPVF) was developed for the evaluation of the function and performance of developed I&C systems. The safety-grade platform PLC and the digital safety system obtained approval for the topical report from the Korean regulatory body in February of 2009. A utility and vendor company will determine the suitability of the KNICS and Nu- Tech 2012 products to apply them to the planned nuclear power plants.

• The Journal of the Korea Contents Association
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• v.8 no.1
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• pp.16-26
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• 2008

Despite intensive therapy, a large proportion of stroke survivors are left with significant disabilities. To improve the disable condition, a major component of stroke management is aimed at facilitating functional independence and community reintegration. There are many evidences that community-based rehabilitation after stroke is most effective when provided by a well-organized multidisciplinary team. Key to the implementation of community-based rehabilitation(CBR) is that the disabled person, their family and their community decide on what the priorities of the service should be. The stroke patients in the community need a wide range of services, including the traditional rehabilitation services of physiotherapy, occupational therapy, speech therapy, social workers, orthotists, nurses and so on. The purpose of this research was to investigate necessity and methods of community-based rehabilitation system in Korea.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.32 no.3
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• pp.142-158
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• 2009

The supplier selection problem is perhaps the most important component of the purchasing function. Some of the common and influential criteria in the selection of a supplier include quality, price, delivery, and service. These evaluation criteria often conflict, however, and it is frequently impossible to find a supplier that excels in all areas. In addition, some of the criteria are quantitative and some are qualitative. Thus, a methodology is needed that can capture both subjective and objective evaluation measures. The Analytic Hierarchy Process(AHP) is a decision-making method for ranking alternative courses of action when multiple criteria must be considered. This paper proposes the AHP-based approach which can structure the supplier selection process and the achievements-based procedure which can allocate order quantities for the selected suppliers In automotive part manufacturers. Also, through the practical case of 'D' automotive part manufacturing company, we shows that the proposed AHP based supplier selection approach and the achievements-based allocation procedure of order quantity can be successfully applied for supplier selection and order quantity allocation problems.