• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2017.11a
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• pp.8-10
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• 2017

지상파 UHD 방송은 시청자에게 기존 HD 방송화면보다 4배 더 선명한 영상 서비스를 제공하며, 광대역 통신망과 결합한 홈포탈(Home Portal) 서비스를 통해서 다양한 부가서비스를 지상파 방송과 함께 제공할 수 있다. 본 논문에서는 지상파 UHD TV 방송과 연계된 360도 가상현실(VR; Virtual Reality) 부가서비스 시스템과 이를 효과적으로 시청하기 위한 사용자환경을 제안한다. 방송의 ESG(Electronic Service Guide)를 통해 시청자는 VR 부가서비스임을 확인하고 스마트 단말기 또는 HMD(Head Mount Display) 등을 이용하여 마치 현장에 있는 듯한 체험을 즐길 수 있다. 제안한 부가서비스는 앱 형태로 스마트 단말기에 설치하여 실행하며 지상파 UHD TV의 ESG 정보로부터 프로그램 편성과 VR 지원여부를 확인한다. 이를 통해, 실시간 방송 뿐 아니라 VOD 형태로 제공되는 다양한 비디오 및 오디오 콘텐츠를 극장에서 보는 것과 같은 빅스크린 모드, 360도 VR 모드, 오디오 청취모드 등 다양한 시청환경에서 감상할 수 있다. 제안한 사용자 환경은 게임엔진을 기반으로 개발되어 가상의 시청 공간에서 장소를 이동하며 영상, 음향 등 미디어 콘텐츠를 감상할 수 있다. 전용컨트롤러를 이용하면 다양한 인터액티브 콘텐츠를 효과적으로 운용하여 감상할 수 있으며, 일반적으로 통용되는 VR 기기 제어 모드도 지원하여 HMD나 일반 스마트 단말기 어느 것을 이용해서도 용이하게 사용자 메뉴를 선택할 수 있다. 제안된 시스템의 시제품은 IBC 2017 및 평창 ICT 체험관을 통해 발표되었다.

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.3
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• pp.38-44
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• 2003

In this study, a performance model of the smart UAV propulsion system with ducts, tip jets and variable main nozzle, which has flight capability of the rotary wing mode for the take-off/landing and low speed forward flight as well as the fixed wing mode for high speed forward flight, has been newly developed With the proposed model, steady-state performance analysis was performed at various flight modes such as rotary wing mode, fixed wing mode, compound ing mode and altitude as well as at flight speed conditions. In investigation of performance analysis. it was noted that the operational capability of the propulsion system was limited due to the duct losses depending on each flight mode, and the limitation with the altitude variation case had much greater than that with the flight speed variation case.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.177-182
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• 2003

In this study, a performance model of the Smart UAV propulsion system with ducts, tip jets and variable main nozzle, which has flight capability of the rotary wing mode for the take-off/landing and low speed forward flight as welt as the fixed wing mode for high speed forward flight, has been newly developed. With the proposed model, steady-state performance analysis was performed at various flight modes and conditions, such as rotary wing mode, fixed wing mode, compound wing, mode altitude and flight speed. In investigation of performance analysis, it was noted that the operational capability of the propulsion system was limited due to the duct losses depending on each flight mode, and the limitation with the altitude variation case has much greater than that with the flight speed variation case.

• Aerospace Engineering and Technology
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• v.7 no.1
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• pp.30-39
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• 2008

This paper presents the result of VDL Mode 2 system design and implementation with AOA (ACARS Over AVLC) protocol based on international VDL Mode 2 specifications for the bit-oriented ATS applications. The designed VDL Mode 2 system is composed of airborne and ground subsystem. Airborne subsystem consists of VDR, CMU and Ground system consists of Ground Station and DSP. For the test of whole system, simplified CPDLC, ADS and AFN applications are implemented in test equipments.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.1
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• pp.35-42
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• 2021

This paper presents an on-line finite element model updating method for in-service structures using measured data. Conventional updating methods, which are based on numerical optimization, are not efficient for on-line updating because they generally require repeated eigenvalue analyses until convergence criteria are met. The proposed method enables fully automated on-line finite element model updating, almost simultaneously with vibration measurement, without any user intervention or off-line procedures. The automated covariance-driven stochastic subspace identification (Cov-SSI) method is utilized to identify modal frequencies and vectors, and the identified modal data is fed to the neural network of the inverse eigenvalue function to produce the updated finite element model parameters. Numerical examples for a wind excited 20-story building structure shows that the proposed method can update the series of finite element model parameters automatically. It is also shown that sudden changes in the structural parameters can be detected and traced successfully.

• Aerospace Engineering and Technology
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• v.9 no.2
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• pp.176-184
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• 2010

The power simulator for a LEO satellite is a useful tool to analyze mission validity and energy balance for various mission scenarios by estimating power generation, power consumption, depth of discharge, bus voltage, charging/discharging current, etc. In this paper, it is described the calculation algorithm of the solar array (SA) power, the satellite load power and the battery modeling method to develop a satellite power simulation. To simulate the SA power generation, three different operation modes (DET, MPPT, CV) of SAR (Solar Array Regulator) are considered with a SA model. The satellite load power is estimated using the satellite unit power database, the unit on/off configuration at some satellite operation modes. The bus voltage and battery charging/discharging current at the specific DoD (Depth of Discharge) are calculated based on the battery characteristics. By this satellite power simulator, it can be conveniently analyzed the energy balance and the validity of a planned mission of a LEO satellite.

• Aerospace Engineering and Technology
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• v.11 no.2
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• pp.33-38
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• 2012

A LEO Satellite performs automatic initial operations by FSW after separation from a launch vehicle. After initial operation by FSW is finished, preparation for normal operation is performed by ground during bus initial activation and checkout phase. First of all, we check state of health of the satellite including solar array deployment status. After then, each unit of spacecraft bus is activated and checked. After activation and checkout of every units used for normal operation, we check maneuver performance for imaging mission and orbit maintenance performance. Because the Bus IAC is performed during limited ground contact time, every detailed procedure must be designed considering ground contact. Therefore, the Bus IAC procedure is separated into several parts based on ground contact duration. In addition, the procedures for every possible operation including expected situation as results of IAC procedures and unexpected contingency situation must be prepared. The contingency operation is also designed based on ground contact duration. The LEO satellite was successfully launched and the Bus IAC was successfully performed. In this paper, we explain design concepts and execution results of Bus IAC.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.3
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• pp.186-194
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• 2017

In this paper, we analyze the main performance of satellite's Synthetic Aperture Radar system for high resolution and wide swath. We have used the radiation pattern of reflector antenna with array feed and comparison between the conventional ScanSAR mode and SweepSAR mode has been carried out. The SweepSAR mode is a high-resolution wide-swath mode that transmits beams over a wide range and receives echo signals through sequential beamforming based on SCORE(SCan On REceive). In this paper, we analyzed the operating principle and characteristics of satellite's SweepSAR mode and simulate system performances. In addition, in order to increase the utilization of image, performances analysis for multiple frequency bands(C-band, X-band) has been considered.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5A
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• pp.631-639
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• 2008

This paper reports the mode shapes of Seohae cable-stayed bridge extracted by TDD technique. In order to record total 72 acceleration points in the vertical direction of the bridge deck, a custom made data acquisition system with LAN communication has been especially developed and a set of ambient vibration tests has been conducted. For the measured acceleration responses, total twenty four mode shapes up to 2Hz has been extracted by TDD technique. The extracted mode shapes include many new modes that have not been identified in the current on-line health monitoring system installed in the bridge. It is confirmed that TDD technique is the most effective in extracting the high resolution mode shapes on a particularly long span bridge.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.5
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• pp.57-64
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• 2005

Modern versions of supersonic jet fighter aircraft using digital flight-by-wire flight control system receive aircraft flight condition such as altitude, airspeed and AoA(angle of attack) from IMFP(Integrated Multi-Function Probe). IMFP sensors data have triplex structure using three IMFP sensors. An air data reconfiguration mode is applied to a T-50 flight control law to guarantee the aircraft flight stability when 2 or 3 IMFP sensors data are invalided. In this study, linear analysis and HQS(Handling Quality Simulator) pilot simulation are performed to analyze flight stability when the air data reconfiguration mode is applied to the control law. And we propose an example that the air data reconfiguration mode is applied to the control law due to second failure of IMFP during T-50 flight. It is found that the aircraft flight stability is not affected when the T-50 flight control law is changed to the air data reconfiguration mode.