• Journal of Computing Science and Engineering
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• 제6권1호
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• pp.26-38
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• 2012

Java has been increasingly used in programming for real-time systems. However, some of Java's features such as automatic memory management and dynamic compilation are harmful to time predictability. If these problems are not solved properly then it can fundamentally limit the usage of Java for real-time systems, especially for hard real-time systems that require very high time predictability. In this paper, we propose to exploit multicore computing in order to reduce the timing unpredictability that is caused by dynamic compilation and adaptive optimization. Our goal is to retain high performance comparable to that of traditional dynamic compilation, while at the same time, obtain better time predictability for Java virtual machine (JVM). We have studied pre-compilation techniques to utilize another core more efficiently, preoptimization on another core (PoAC) scheme to replace the adaptive optimization system (AOS) in Jikes JVM and the counter based optimization (CBO). Our evaluation reveals that the proposed approaches are able to attain high performance while greatly reducing the variation of the execution time for Java applications.

• 방송공학회논문지
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• 제8권2호
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• pp.126-135
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• 2003

디지털 본 방송 실시 이후 디지털 방송의 수신 환경 및 수신성능을 개선하기 위해 다양한 실제 전파 수신 채널 환경에 대한 분석을 수행할 필요성이 높아지고 있다. 본 논문에서는 디지털 신호처리 기법과 고속의 하드디스크 저장 기술을 이용하여 지상파DTV의 RF신호를 실시간으로 저장 및 재생하는 시스템을 설계, 제작하고 그 성능을 분석하였다. 개발된 시스템은 DTV RF 수신신호를 하드디스크에 실시간으로 저장 및 재생하기 때문에 특정지역의 실제 전파 수신환경을 매번 측정, 분석하는 번거로운 작업을 없앨 수 있을 뿐만 아니라 기존 수신기로 수신이 곤란한 지역들의 채널 환경을 저장하거나 특정 RF신호 패턴을 저장하고 이를 실험실에서 반복적으로 재생함으로 DTV 수신기의 성능을 측정하거나 각 지역의 채널 환경을 분석하는데 효율적으로 활용될 수 있을 것이다.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 1998년도 가을 학술발표논문집 Vol.25 No.2 (1)
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• pp.573-575
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• 1998

실시간 내장형 시스템(real-time embedded system)의 반응 동작(reactive behavior)을 정확하게 분석하기 위해서 상태차트(statechart)에 바탕을 둔 객체 지향 모델링 방법론들이 많이 사용되고 있다. 하지만 이들 방법론들은 경성 실시간 시스템(hard real-time system)이라면 반드시 고려해야할 스케줄링 가능성분석(scheduability analysis)에 필요한 시간에 대한 정보와 시간 제약을 정확히 나타내지 못하는 문제점이 있다. 본 논문에서는 최근 OMG(Object Management Group)에서 객체 지향개발의 기준으로 채택된 UML(Unifies Modeling Language) ver1.1을 사용하여 실시간 내장형 시스템의 반응 동작과 시스템의 시제 동작(temporal behavior)을 모델링하여, 모델링된 시스템이 스케줄링 가능성 분석이 효과적으로 이루어지는 방안을 제안한다.

• 반도체디스플레이기술학회지
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• 제19권3호
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• pp.55-60
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• 2020

The hard mask photo-resist strip inspection system for the semiconductor wafer manufacturing process inspects the position of the circuit pattern formed on the wafer by measuring the distance from the edge of the wafer to the strip processing area. After that, it is an inspection system that enables you to check the process status in real time. Process defects can be significantly reduced by applying a tester that has not been applied to the existing wafer strip process, edge etching process, and wafer ashing process. In addition, it is a technology for localizing semiconductor process inspection equipment that can analyze the outer diameter of the wafer and the state of pattern formation, which can secure process stability and improve wafer edge yield.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권5호
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• pp.203-211
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• 2002

In this paper, the implementation of a new AF(Automatic Focusing) system for a digital still camera is introduced. The proposed system operates in real-time while adjusting focus after the measurement of distance to an object using a passive sensor, which is different from a typical method. In audition, measurement errors were minimized by using the data acquired empirically, and the optimal measuring time was obtained using EV(Exposure Value) which is calculated from CCD luminance signal. Moreover, this system adopted an auxiliary light source for focusing in absolute dark conditions, which is very hard for CCD image Processing. Since this is an open-loop system adjusting focus immediately after the distance measurement, it guarantees real-time operation. The performance of this new AF system was verified by comparing the focusing value curve obtained from AF experiment with the one from the measurement by MF(Manual-Focusing). In both case, edge detector was used for various objects and backgrounds.

• 제어로봇시스템학회논문지
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• 제10권3호
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• pp.232-238
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• 2004

The brake system of a high-speed train has a crucial role for the safety of human mass transportation. However, it is hard to acquire design parameters of the brake system in the design step of the new high-speed train. In this paper, we build a HILS (Hardware In-the- Loop Simulation) system for the brake system of the Korea High-Speed Train (KHST) that is supposed to run up to 350 km/h, and analyze the characteristics of the brake system of the KHST (composed of 7 cars) via real-time simulations. In the HILS system that is built using a DSP board of dSPACE, the dynamics of the 7 car bodies and several bogies and characteristics of springs and dampers of connection devices between cars are considered separately. Simulation results show that the designed brake system of the KHST is valid and satisfies design specifications.

• 로봇학회논문지
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• 제19권2호
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• pp.188-195
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• 2024

This paper proposes a photorealistic real-time dense 3D mapping system that utilizes a neural network-based image enhancement method and mesh-based map representation. Due to the characteristics of the underwater environment, where problems such as hazing and low contrast occur, it is hard to apply conventional simultaneous localization and mapping (SLAM) methods. At the same time, the behavior of Autonomous Underwater Vehicle (AUV) is computationally constrained. In this paper, we utilize a neural network-based image enhancement method to improve pose estimation and mapping quality and apply a sliding window-based mesh expansion method to enable lightweight, fast, and photorealistic mapping. To validate our results, we utilize real-world and indoor synthetic datasets. We performed qualitative validation with the real-world dataset and quantitative validation by modeling images from the indoor synthetic dataset as underwater scenes.

• 한국컴퓨터정보학회논문지
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• 제12권3호
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• pp.147-153
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• 2007

태스크 스케줄링은 여러 개의 수행 가능한 태스크 중에서 하나의 태스크를 선정하여 프로세서에 할당하는 중요한 역할을 한다. 실시간 시스템에서 경성 실시간 태스크를 적시에 스케줄링하지 못하면 시스템이 다운되는 최악의 상태가 발생하므로 실시간 시스템은 효율성, 자원 및 속도 등의 문제 외에도 시간 제약도 진지하게 고려해야 한다. 본 논문에서는 L-RE 좌표를 이용하여 실시간 다중프로세서 시스템에서의 새로운 우선순위 기준 스케줄링 알고리즘을 제안한다. L-RE 좌표 알고리즘은 태스크의 스케줄링 효율을 높이기 위해 고안 되었으며 우선순위를 할당하는데 데드라인과 함께 유휴시간을 고려하고 있다. 시뮬레이션 결과는 LR-E 알고리즘이 EDF보다 스케줄의 원활성을 높이고 또 LLF보다는 문맥교환 수를 줄일 수 있음을 보여준다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(5)
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• pp.173-176
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• 2002

DAS(Data Acquisition System) as a ground support equipment has played a critical role in proving the status of ready-to-fire of a rocket system before launch. But it is hard to implement and place a real-time measuring system in a control room at a long distance from the vehicle. In this paper DAS is introduced by being located at the LEC(Launch Equipment Container)[1], 50 meters away from the rocket and connected to remote monitoring system via fiber optics with TCP/IP protocol by means of client/server algorithm. Therefore real-time data acquisition and storage are guaranteed and a convenient and useful MMI (Man-Machine Interface) can be developed.

• 한국소음진동공학회논문집
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• 제26권3호
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• pp.323-330
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• 2016

This paper describes real-time unbalance moment compensation method for line of sight(LOS) stabilization control systems. The factors of system inertia, frictions and unbalance moment affect the control accuracy of drive systems that are equipped to on the move(OTM) platforms requiring LOS stabilization function. In case of the unbalance moment among those factors is continuously changed as variation of relative angle between gravity vector and drive torque vector. Then, consideration of the effect in real-time is very complicate. Therefore, its effect should be designed to be minimized, however, designing it almost zero is impossible in real condition. In other words, it is hard to achieve target performance overcoming stability issue of highly unbalanced systems. To solve these problems, this paper proposes calculation method of unbalance moment by using measured sensor data for LOS stabilization control and its use for control compensation. Also, kinematical converting process and control structure for compensation are explained. The effectiveness of the proposed method as variation of unbalance moment is verified under simulation circumstance modeled by assuming LOS control system with 2-axis gimbal structure.