• 대한전기학회논문지:전력기술부문A
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• 제53권4호
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• pp.214-220
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• 2004

This paper describes a busbar current differential relay in conjunction with a current transformer(CT) compensating algorithm irrespective of the level of the remanent flux. The compensating algorithm detects the start of first saturation if the third-difference function of the current exceeds the threshold; it estimates the core flux at the first saturation start by inserting the negative value of the third-difference function of the current into the magnetization curve; thereafter, it calculates the core flux during the fault and compensates the distorted current using the magnetization curve. The algorithm estimates the correct secondary current irrespective of the level of the remanent flux and needs no saturation point of the magnetization curve. The proposed relay can improve not only security of the relay on an external fault with CT saturation but sensitivity of the relay on an internal fault; the relay can improve the operating speed on n internal fault with CT saturation. This paper concludes by implementing the relay into a digital signal processor based prototype relay.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권4호
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• pp.214-214
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• 2004

This paper describes a busbar current differential relay in conjunction with a current transformer(CT) compensating algorithm irrespective of the level of the remanent flux. The compensating algorithm detects the start of first saturation if the third-difference function of the current exceeds the threshold; it estimates the core flux at the first saturation start by inserting the negative value of the third-difference function of the current into the magnetization curve; thereafter, it calculates the core flux during the fault and compensates the distorted current using the magnetization curve. The algorithm estimates the correct secondary current irrespective of the level of the remanent flux and needs no saturation point of the magnetization curve. The proposed relay can improve not only security of the relay on an external fault with CT saturation but sensitivity of the relay on an internal fault; the relay can improve the operating speed on n internal fault with CT saturation. This paper concludes by implementing the relay into a digital signal processor based prototype relay.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 A
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• pp.421-423
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• 1999

The function of the automatic train operation(ATO) system is to regulate the train ride comfort during start, acceleration and deceleration and execute operation of constant speed travelling and fixed point parking. The mathematical model for the train is presented by considering unknown disturbances which consist of start resistance, travelling resistance, slope resistance, curve resistance and so on. The speed control of ATO system is designed by considering the disturbances. The simulation is executed to verify the speed control performance and compare its performance with that of a PID-type ATO control system under the disturbances. Simulation results show that the control performance of gain scheduled control for ATO system is better than that of the conventional PID controller.

• KIEE International Transactions on Power Engineering
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• 제3A권2호
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• pp.85-92
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• 2003

When a current transformer (CT) is saturated, the wave-shape of the secondary current is distorted and contains points of inflection, which correspond to the start or end of each saturation period. Discontinuity in the first-difference function of the current arises at points of inflection, where the second and third differences convert into pulses that can be used to detect saturation. This paper describes the design and evaluation of a CT saturation detection technique using the third-difference function and includes the countermeasure for a spike signal. Test results clearly demonstrate that the algorithm successfully detects the start and end of each saturation period irrespective of the remanent flux and magnetization inductance in the saturated region. This paper concludes by describing the results of hardware implementation of the algorithm using a DSP.

• 한국정보과학회논문지:데이타베이스
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• 제30권4호
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• pp.372-380
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• 2003

시간에 따라 변화하는 사건들을 저장하는 시간지원 데이타베이스에서 기존의 집계 처리 기법에 시간을 고려하여 처리하도록 확장해야 한다. 기존의 시간지원 집계 처리 기법들은 매번 질의의 대상이 되는 사건들이 다를 때마다 시간 구간을 반복해서 구하고 그 구간마다의 결과를 계산해야 한다는 문제점이 있다. 본 논문에서는 시간지원 데이타베이스에 저장된 사건의 시작 시간과 종료 시간만을 미리 읽어 들여서 구성한 시점 시퀀스를 이용하여 시간지원 집계를 처리하는 방법을 제안하였다. 또한 데이타베이스에서 저장된 사건의 삭제나 새로운 사건의 삽입에 따른 시점 시퀀스 갱신의 용이성에 대해서도 언급하였다. 시점 시퀀스는 시간 구간에 대한 정보를 미리 저장하고 있기 때문에, 질의의 대상이 되는 사건들이 다른 시간지원 집계 질의가 계속해서 들어올 때 기존의 방법에 비해 효율적으로 처리할 수 있다.

• Journal of Welding and Joining
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• 제31권6호
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• pp.37-43
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• 2013

This study targets to make clear the connection between MS (Martensite start) point and welding shrinkage. We approved that a Martensite-transformed weldment may not yield state under low MS point, but also admitted the limitation of numerical calculation by inherent strain approach or thermal strain approach. Therefore, new thermal strain formulae during cooling stages were made. As a thermal strain is obtained by integrating thermal extension coefficient, a constant of integration should be decided. In our suggested formulae, the origin was based on totally remained austenite, and added strain from volume changes in Martensite transformation was based on totally transformed ferrite. Through the suggested methodology, It is verified that an MS point under a critical temperature can let weld shrinkage relax and the critical value can be obtained. For supporting this process, 15 weld-consumables were made, were tested by fillet type and were measured. As a result, a positive correlation between MS point and level of weld-distortion was obtained, but it was rather weak.

• Journal of Positioning, Navigation, and Timing
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• 제11권4호
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• pp.269-277
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• 2022

In this paper, we overview the system development status of the national maritime precise point positioning-real-time kinematic (PPP-RTK) service in Korea, also known as the Precise POsitioning and INTegrity monitoring (POINT) system. The development of the POINT service began in 2020, and the open service is scheduled to start in 2025. The architecture of the POINT system is composed of three provider-side facilities-a reference station, monitoring station, and central control station-and one user-side receiver platform. Here, we propose the detailed functionality of each component considering unidirectional broadcasting of augmentation data. To meet the centimeter-level user positioning accuracy in maritime coverage, new reference stations were installed. Each reference station operates with a dual receiver and dual antenna to reduce the risk of malfunctioning, which can deteriorate the availability of the POINT service. The initial experimental results of a testbed from corrections generated from the testbed network, including newly installed reference stations, are presented. The results show that the horizontal and vertical accuracies satisfy 2.63 cm and 5.77 cm, respectively. For the purpose of (near) real-time broadcasting of POINT correction data, we designed a correction message format including satellite orbit, satellite clock, satellite signal bias, ionospheric delay, tropospheric delay, and coordinate transformation parameters. The (near) real-time experimental setup utilizing (near) real-time processing of testbed network data and the designed message format are proposed for future testing and verification of the system.

• 전기전자학회논문지
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• 제18권1호
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• pp.152-158
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• 2014

본 연구에서는 저온유동성 성능검사 시스템 구현을 통해 디젤 차량용 통합형 연료히터의 성능을 평가한다. 저온 유동성 시험장치에서 $+20{\sim}-30^{\circ}C$ 온도범위에 따라 분리형과 통합형 연료히터 성능을 비교하고, 필터 전후에 따라 유압과 시동시간, 히터의 소모전력을 측정한다. 이때 다양한 종류의 필터면적을 사용함으로써 통합형 연료히터와 분리형을 비교한 결과 시동 시간이 23% 향상되었고, 저온시동성능은 19% 정도 향상된다.

• 정보학연구
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• 제6권1호
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• pp.71-84
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• 2003

본 논문에서는 제안한 2차원 이진 코드를 이용하는 효율적인 정보 인식 시스템을 제안한다. 먼저 전체 영상내에서 이진 영상의 위치를 검색하며 검색 방법은 블록 영역 분류 기법을 이용하여 각 블록의 경계선 영역을 검색하여 이진 부호 영상의 위치를 검색한다. 각 경계선 영역은 수직 영역과 수평영역으로 구분한다. 수평영역이 발견된 경우 6블록을 연속하여 수평영역인 경우 수평영역 검색을 시작한 처음 위치에서 수직영역을 검색하여 10블록 이상의 수직영역이 발견된 경우 부호 영역을 획득한다. 실제적인 부호영역은 평균값을 기준으로 이진화 과정을 수행한 후 이진화 영상으로부터 구한 전체 모서리의 비율을 검사함으로써 원하는 부호를 획득한다. 비율이 틀린 경우 다시 검색을 시작하여 전체 과정을 한번 더 수행하게 된다. 이때의 수행과정은 이미 영역분류가 이루어진 블록별 영상으로 수행하므로 수행 시간은 전체 영상에 적용한 것보다 빠르게 수행된다는 것을 알 수 있다. 이렇게 함으로써 본 논문에서 제안한 시스템은 이진 영상으로부터 다양한 정보들을 추출할 수 있다.

• 한국군사과학기술학회지
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• 제5권3호
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• pp.113-119
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• 2002

A target adaptive guidance(TAG) algorithm is proposed employing the near-zone signal that can be measured from an infrared seeker. The guidance order is composed of a conventional PNG command and an additional command to be calculable from an additional LOS rate between a hot point of target and a required intercept point. The characteristic of the near-zone signal is similar to that of LOS rate that is inversely proportional to the square of time-to-go. Hence the proposed scheme can be applied to real systems with no estimator for time-to-go. From analysis results on the miss distance with perfect missile and perfect seeker, it follows that the proposed TAG algorithm guarantees missile to be ideally guided to the required intercept point. And it is less affected by the TAG start time and a proportional navigation ratio than other TAG schemes using a LOS rate such as a step bias or a ramp bias.