• 한국정보통신학회논문지
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• 제26권3호
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• pp.456-462
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• 2022

본 논문에서는 세계협정시(UTC)를 결정하기 위해 GPS 위성에서 전송된 코드 신호에서 추출한 측정 데이터를 기반으로 한 정밀시각비교 기법에 딥러닝 모델인 LSTM을 적용하여 시각 오프셋을 예측하는 방법을 소개한다. 이를 위해 우선, 하루 단위로 GPS 위성으로부터 수신된 코드 신호에서 시각 정보를 추출하고 하루 단위의 시각 오프셋을 하나의 시계열 데이터로 구축하는 과정을 소개한다. 구축된 시각 오프셋 시계열 데이터에 대해 딥러닝 모델을 적용하는데, 순환신경망 중 하나인 LSTM을 적용하여 GPS의 시각 오프셋 예측을 수행하였다. 본 연구를 통해 GNSS 기반 정밀 시각비교분야에서 딥러닝을 적용한 시각 오프셋 예측의 가능성을 확인하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.175-181
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• 2006

The prediction of time-dependent column shortening is essential for tall buildings considering both strength and serviceability aspects. The Column shortening of tall buildings with transfer floor should be calculated considering the long-term deflection of transfer girder. In this study, both the column shortening and the deflection of transfer girder of 45-story tall concrete building are predicted. The column shortening considering deflection of transfer girder are compared with the actual column shortening by field measurement.

• 한국전자거래학회지
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• 제3권1호
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• pp.155-173
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• 1998

In this paper we present the development of internet banking and its impact on financial market. The internet banking has been introduced since 1990s, from which customers could obtain most financial services over internet, and will replace with the traditional banks. According to a survey, most of bankers agree that internet will play an important role in banking industry. The internet banking has an enormous impact on the transfer system and banking industry. The transfer system is divided into two-large-value transfer system and small-value transfer system, depending on the size of its transfer amount. The internet banking will enhance the transfer system, especially small-value transfer system. It will reduce the time lag between transaction of service and its payment. However, a congestion or a blockage in a part of network might stop the financial service all over the network, which is called "computer risk". As internet banking develops, banks have incentives to reduce their branches and have to compete with information-business companies which can offer financial EDI.

• Journal of Positioning, Navigation, and Timing
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• 제6권4호
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• pp.167-179
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• 2017

In this paper, a simplified Cubature Kalman Filter (SCKF) is proposed to reduce the computation load of CKF, which is then used as a filter for transfer alignment of shipboard INS. CKF is an approximate Bayesian filter that can be applied to non-linear systems. When an initial estimation error is large, convergence characteristic of the CKF is more stable than that of the Extended Kalman Filter (EKF), and the reliability of the filter operation is more ensured than that of the Unscented Kalman Filter (UKF). However, when a system degree is large, the computation amount of CKF is also increased significantly, becoming a burden on real-time implementation in embedded systems. A simplified CKF is proposed to address this problem. This filter is applied to shipboard inertial navigation system (INS) transfer alignment. In the filter design for transfer alignment, measurement type and measurement update rate should be determined first, and if an application target is a ship, lever-arm problem, flexure of the hull, and asynchronous time problem between Master Inertial Navigation System (MINS) and Slave Inertial Navigation System (SINS) should be taken into consideration. In this paper, a transfer alignment filter based on SCKF is designed by considering these problems, and its performance is validated based on simulations.

• 설비공학논문집
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• 제2권1호
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• pp.37-48
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• 1990

The drag and heat transfer reduction phenomena and degradation effects of drag reducing polymer solutions which are known as the viscoelastic fluids are investigated experimentally for the turbulent circular tube flows. Two stainless steel tubes are used for the experimental flow loops. Aqueous solutions of Polyacrylamide Separan AP-273 with concentrations from 300 to 1000 wppm are used as working fluids. Flow loops are set up to measure the friction factors and heat transfer coefficients of test tubes in the once-through system and the recirculating flow system. Test tubes are heated by power supply directly to apply constant heat flux boundary conditions on the wall. Capillary tube viscometer and falling ball viscometer are used to measure the viscous characteristics of fluids and the characteristic relaxation time of a fluid is determined by the Powell-Eyring model. The order of magnidude of the thermal entrance length of a drag reducing polymer solution is close to the order of magnitude of the laminar entrance length of Newtonian fluids. Dimensionless heat transfer coefficients of the viscoelastic non-Newtonian fluids may be represented as a function of flow behavior index n and newly defined viscoelastic Graetz number. As degradation continues viscosity and the characteristic relaxation time of the testing fluids decrease and heat transfer coefficients increase. The characteristic relaxation time is used to define the Weissenberg number and variations of friction factors and heat transfer coefficients due to degradation are presented in terms of the Weissenberg number.

• 디지털융복합연구
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• 제12권8호
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• pp.219-227
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• 2014

인터넷을 통한 정보 전달 방법은 Ethernet과 ATM, CAN과 같은 다양한 통신 전달 프로토콜 및 방법을 통해 이루어지고 있다. 현재 연구된 네트워크상의 시간 지연 현상에 대한 연구는 일부 네트워크 모델을 바탕으로 연구되고 있으나 다양한 통신 환경 하에서 발생하는 시간 지연 현상에 대해 최적의 모델링 방법을 제시해 주고 있지 못하고 있다. 따라서 다양한 네트워크 환경에 적합하도록 인터넷 기반 비동기 샘플치 시스템 모델에 대한 연구가 필요하다. 아울러 인터넷을 통해 구성된 폐루프 시스템은 기존 제어 시스템과 다른 동작 특성과 외란 특성을 가지므로 인터넷 환경에 적합하게 설계된 견실 제어 방법이 필요하다. 따라서 안정성이 극히 요구되는 각종 산업 기기 등에 대한 웹기반 정밀 원격 제어를 원활히 수행하기 위해서는 웹 환경에 최적화된 강인 제어 이론 개발이 필요하다. 따라서, 본 논문에서는 원격지 플랜트에 대한 실시간 원격 제어를 안정적 및 효율적으로 수행하도록 인터넷상의 데이터 전송시 시간 지연 현상 분석 및 인터넷 기반 제어시스템의 전달 특성 분석하였다.

• 한국광학회지
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• 제17권6호
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• pp.514-518
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• 2006

높은 안정도를 가지는 100 MHz의 RF 신호를 23 km의 광섬유망을 통하여 전송하였다. 진동과 온도 변화에 의하여 생기는 광섬유 전송과정에서의 위상 잡음을 측정하고 이를 보상하는 회로를 구성하였다. 광섬유 잡음이 제거되었을 때, RF 신호 전송의 상대주파수 불안정도는 1초 평균시간에서 $6{\times}10^{14}$, 10000초 평균시간에서 $2{\times}10^{-17}$으로서 기준 RF 신호의 안정도와 거의 같은 수준으로 광섬유를 통하여 RF를 전송할 수 있었다. 잡음 보상에 의하여 단측파대 위상잡음은 푸리에 주파수 1 kHz 이하에서 20 dB 이상 감소하였다.

• 한국태양에너지학회 논문집
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• 제30권3호
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• pp.25-32
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• 2010

A real-time monitoring system was developed for transfer, receive, backup and analysis of wind power data at three wind farm(Hang won, Hankyung and Sung san) in Jeju. For this monitoring system a communication system analysis, a collection of data and transmission module development, data base construction and data analysis and management module was developed, respectively. These modules deal with mechanical, electrical and environmental problem. Especially, time series graphic is supported by the data analysis and management module automatically. The time series graphic make easier to raw data analysis. Also, the real-time monitoring system is connected with wind power forecasting system through internet web for data transfer to wind power forecasting system's data base.

• 한국전자통신학회논문지
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• 제12권4호
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• pp.575-584
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• 2017

제어시스템의 시간응답을 해석하기 위해 전기회로망을 제안한다. 전달함수와 상태방정식을 이용해 시스템의 시간응답을 계산함으로써 고전제어와 현대제어의 연계성을 분석한다. 상태천이방정식의 복잡한 적분과정을 생략하고, 상태천이행렬과 전달함수의 조합만으로도 시간응답의 해석이 가능함을 제시한다. 단위계단함수와 정현파입력에 따른 전압­전류의 출력응답을 표현하기 위해 프로그램을 코딩하였다. 단위계단입력에서는 과도응답을 해석하였으며, 정현파입력에서는 전압과 전류의 위상차를 해석하였다. 제안된 내용을 과도응답이나 상태공간에 기술함으로써 제어공학의 이해도와 설계능력을 높인다.

• 설비공학논문집
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• 제6권2호
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• pp.155-165
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• 1994

In this study, the following factors are investigated from experiments for a vertical parallel plate heat exchanger under the frosting condition ; the growth of frost layer, the characteristics of heat and mass transfer, the change of mass flow rate of the air passing through the heat exchanger, and the pressure drop of the air in the heat exchanger. The amount of heat and mass flux of water vapor transferred from the air stream to the heat exchanger surface is large at the early stage of frosting and then decreases dramatically, and the extent of decreasing rate becomes moderate with time. The frost layer formed near the inlet of the heat exchanger is thicker and denser than that formed near the outlet. It is found that the gradient of the amount of frost along the flow direction increases with time. In the early period of frost formation, the thermal resistance between the air and the cooling plate increases dramatically and then the extent of change decreases with time. Initially the convective thermal resistance is dominant. Then, while the convective thermal resistance decreases with time, the conductive thermal resistance continues to increase with time and finally the conductive thermal resistance becomes dominant.