• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.10
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• pp.728-737
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• 2019

In this study, the minimized on-board computer (OBC) module for integrated navigation is developed, which provides satellites' relative position information in formation flying and cluster operation situations. The scalability is considered to apply the user-selected wireless communication module and Global Positioning System (GPS) receiver for navigation, while considering to meet the structural design standard of nano-satellites. As a result of the product development and production, the processing speed of integrated navigation and real-time data synchronization is satisfied for cluster operation nano-satellites by using micro controller unit (MCU). From a heat/vacuum, vibration and radiation test, the OBC was confirmed to be operated in space environments. From these results, a mass production system of OBC was made which is a key part of development on satellite formation flying and cluster/constellation missions that the community demands are increasing.

• Journal of Digital Convergence
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• v.17 no.3
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• pp.161-168
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• 2019

The purpose of this study analyze consumer usage characteristics and product development guide of electronic pen based on TAM theory(Davies, 1989). Research methods apply contents analysis(qualitative research) and Activity/Inactivity analysis of main consumer participation. Research results are as follows. Active consumer indicated 30-49 age, male, office job and research fellow. And they suggested stable power supply system, App connected pen function extension, add the modified pen function, advanced data recognition of pen, advanced take note ability and stable grip feeling of pen, selected line width, synchronization improvement with other smart device and charging function. These result indicated the importance product improvement diffusion factor of early market to main market. The future research of electric pen focused on different product strategy between electric pen and smart device connected electric pen.

• The Journal of the Korea Contents Association
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• v.21 no.3
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• pp.454-462
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• 2021

The purpose of this paper is to compare and analyze the status of ship departures by major ports in Korea. To this end, we collected necessary data from the National Statistical Office (National Statistical Portal), "Transportation·Logistics ⇨ Ship Departure Status by Port". The analysis period is 141 months from January 2009 to September 2020. The increase rate was higher in the order of Yeosu, Pyeongtaek Dangjin, Gwangyang, Busan, Incheon and Ulsan. In the analysis of the rate of change, Yeosu showed an uptrend while other ports showed a modest downtrend. In the scatter analysis, the total ship departure shows a high degree of synchronization with other ports except Yeosu. As a result of the empirical analysis, the recent trend of ship departures is slowly falling below 0%, and the current movement is expected to continue for the time being. As the southern logistics of China and ASEAN and northern logistics of Eurasia become active, the role of major ports is expected to expand further. It is necessary to develop a differentiated logistics service for each port and find an efficient way to increase the volume of goods by deriving factors for improving logistics.

• Journal of Broadcast Engineering
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• v.26 no.4
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• pp.356-367
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• 2021

With the recent development of IoT and artificial intelligence technology, research and applications for optimization of real-world problems by collecting and analyzing data in real-time have increased in various fields such as manufacturing and smart city. Representatively, the digital twin platform that supports real-time synchronization in both directions with the virtual world digitized from the real world has been drawing attention. In this paper, we define a digital twin concept and propose a digital twin platform prototype that links real objects and predicted results from the virtual world in real-time by utilizing the oneM2M-based IoT platform. In addition, we implement an application that can predict accidents from object collisions in advance with the prototype. By performing predefined test cases, we present that the proposed digital twin platform could predict the crane's motion in advance, detect the collision risk, perform optimal controls, and that it can be applied in the real environment.

• Journal of Biomedical Engineering Research
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• v.43 no.6
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• pp.375-381
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• 2022

Brain-computer interface (BCI) is a technology that allows users with motor disturbance to control machines by brainwaves without a physical controller. Motor imagery (MI)-BCI is one of the popular BCI techniques, but it needs a long calibration time for users to perform a mental task that causes high fatigue to the users. MI is reported as showing a similar neural mechanism as motor execution (ME) and motor observation (MO). However, integrative investigations of these three tasks are rarely conducted. In this study, we propose a new paradigm that incorporates three tasks (MI, ME, and MO) and conducted a comparative analysis. For this study, we collected Electroencephalograms (EEG) of motor imagery/execution/observation from 28 healthy subjects and investigated alpha event-related (de)synchronization (ERD/ERS) and classification accuracy (left vs. right motor tasks). As result, we observed ERD and ERS in MI, MO and ME although the timing is different across tasks. In addition, the MI showed strong ERD on the contralateral hemisphere, while the MO showed strong ERD on the ipsilateral side. In the classification analysis using a Riemannian geometry-based classifier, we obtained classification accuracies as MO (66.34%), MI (60.06%) and ME (58.57%). We conclude that there are similarities and differences in fundamental neural mechanisms across the three motor tasks and that these results could be used to advance the current MI-BCI further by incorporating data from ME and MO.

• Tribology and Lubricants
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• v.37 no.6
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• pp.261-272
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• 2021

This study investigates the structural characteristics of oil-free, gas beam foil journal bearings (GBFJBs) for use in high speed motors. Mathematical modeling was carried out, and reaction force modeling for static load was performed to predict the structural characteristics of the GBFJB. Mathematical modeling and reaction force modeling for static load are performed to predict the structural characteristics of GBFJBs. The reaction force of the test bearing against static loads was measured during experiments and compared with the predicted results. The measured experimental data reveal the nonlinear stiffness characteristics of the GBFJB against varying displacement and agree well with the predictions. Dynamic load tests using an exciter allow to identify the vibration characteristics of the GBFJB. Test results show that the vibration displacement, dynamic force, and acceleration measured on the test bearing are most dominant at the applied dynamic load (synchronization) frequency. Futhermore, the test results show that the hysteresis area recorded during the dynamic tests increases with the excitation amplitude and frequency, and that the beam stick phenomena occurr at high excitation frequencies. The single degree of freedom (DOF) vibration model aids to identify the stiffness and damping coefficient of the GBFJB, which decrease as the excitation frequency increases.

• Journal of Internet of Things and Convergence
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• v.8 no.3
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• pp.63-68
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• 2022

Due to COVID-19, many paradigm shifts in existing manufacturing facilities and the expansion of non-face-to-face services are accelerating worldwide. A representative technology is digital twin technology. Such digital twin technology, which existed only conceptually in the past, has recently become feasible with the construction of a 5G-based network. Accordingly, this paper designed and implemented a part of the USB process to enable digital twins based on OPC UA communication, which is a standard interlocking structure, between real object objects and virtual reality-based USB process in accordance with this paradigm change. By reflecting the physical characteristics of real objects together, it is possible to simulate real-time synchronization of these with real objects. In the future, this can be applied to various industrial fields, and it is expected that it will be possible to reduce costs for decision-making and prevent dangerous accidents.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.372-372
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• 2023

강우 유출 시 지표면 토양수분포화도는 직접유출량 및 지하수 저류에 영향을 미칠 수 있기 때문에 강우에 의한 유역 유출량 산정에서 토양수분포화도는 보다 실제와 유사한 모의 결과를 도출하는데 중요한 인자가 될 수 있다. 기존의 모형 기반의 유출량 산정 연구에서 토양수분포화도의경우 강수량, 하천수위, 유량, 지하수위 등 타 수문순환 요소에 비하여 관측 지점 및 관측 자료가 부족하기 때문에 유역 내 수문환경 특성에 따라 가정 된 값을 입력하여 유출량을 산정하였다. 최근 IoT, 5G 통신 등 정보 기술의 혁신과 이상 홍수에 의한 피해 저감을 위한 실시간 유출량 해석 모형 개발 등에 적용할 경우 모의 결과가 실제와 매우 다르게 나타나는 경우가 발생할 수 있다. 본 연구에서는 토양수분포화도의 지상 관측 자료와 위성 관측 자료를 동기화 하는 기법을 개발함으로써 중권역 단위의 유출량 산정 정확도를 향상시키고자 하였다. 기존의 지상 관측 자료는 토양수분포화도의 비교적 정확한 데이터를 제공하나 관측 자료를 유역의 대푯값으로 적용할 수 있는 지에 대한 추가 검증이 필요하다. 위성 관측자료는 유역 전반의 토양수분포화도 정보를 관측할 수 있으나 고해상도의 자료를 제공하지 못하기 때문에 유역 전체에 일관된 데이터를 적용할 수밖에 없는 한계가 발생한다. 지상 관측자료와 위성관측자료의 동기화 기법을 개발함으로써 본 연구진은 중권역 단위의 유역 내 비교적 정확한 토양수분포화도 데이터를 적용할 수 있도록 하였다. 본 연구의 결과물은 유출량 해석 결과의 정확도를 높임으로써 급격한 호우 사상 발생에 따른 이상홍수에 대응할 수 있는 유역 물 관리 대책의 기초 자료로 활용 할 수 있을 것으로 기대된다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5284-5291
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• 2012

This research is to develop the Web-Based Ventilator Management Education Program that reflects the needs of nursing site nursing which is intended to help nursing duties. ISD model-building process has been developed for the analysis, design, development, operation, and evaluation of methods. The education program was developed from April to July 2011, and SPSS 18.0 was used for data analysis. The analysis stage, document review and requirement analysis, content analysis, learner analysis, technology and environment analysis have been executed. Through the processes, higher education requirements for the practical ventilator, a large number of subjects under the age of 30, and the career of less than 3 years of ICU were searched. At the design stage, the education content that was presented by the content expert group was executed in information design, mutual interaction design, synchronization design through discussion with program experts. At the development stage, author made the story flow and gathered data and integrated it through the review of related document and data. At the operation and evaluation stage, author executed the developed program and revised and supplemented it on the basis of the evaluation results through the experts and subjects evaluation. The Web-Based Ventilator Management Education Program could contribute to the improvement of nursing because the program has been developed to reflect the diverse needs of nursing practice in the process of building program.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.41 no.1
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• pp.1-8
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• 2004

The INS(Inertial Navigation System) provides high rate position, velocity and attitude data with good short-term stability while the GPS(Global Position System) provides position and velocity data with long-term stability. By integrating the INS with GPS, a navigation system can be achieved to Provide highly accurate navigation Performance. For the best performance, time synchronization of GPS and INS data is very important in GPS/INS integrated system But, it is impossible to synchronize them exactly due to the communication and computation time-delay. In this paper, to reduce the error caused by the measurement time-delay in GPS/INS integrated systems, error compensation methods using separate bias Kalman filter are suggested for both the loosely-coupled and the tightly-coupled GPS/INS integration systems. Linearized error models for the position and velocity matching GPS/INS integrated systems are Int derived by linearizing with respect to its time-delay and augmenting the delay-state into the conventional state equations for each case. And then separate bias Kalman Inter is introduced to estimate the time-delay during only initial navigation stage. The simulation results show that the present method is effective enough resulting in considerably less position error.