Chun-Hyon Chang

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When a database system is used in a real-time application, the concurrency control protocol must satisfy not only the consistency of shared data but also the timing constraints of the application. In this paper, we examine a prioritydriven two-phase lock protocol called the reador write-priority ceiling protocol. We show that this protocol is free of(More)
Timeliness-guaranteed computing considering the worst case can hardly be accomplished at run time because of the uncertainty caused by resource sharing, asynchronous events and conflicting timing constraints between tasks. An easier way to reach it is to do some off-line analysis from design time with predictable characteristics of tasks. The TMO model(More)
In this paper, we introduce the target scenario of our HELISCOPE project with the emphasis on the four modes for flying-camera task. We also explain the control points that are considered as the interfaces where the on-flight embedded software and mechanical implementation of the unmanned helicopter are contacted for the autopilot necessarily used in(More)
In developing multi-UAV (Unmanned Aerial Vehicle) system, a simulation environment is essential to verify the functionalities of the whole system with higher productivity and reduced risks of accidents. Simulations of multi-UAV systems are usually accomplished by using distributed systems where multiple standalone simulators are connected via a network.(More)
Autonomous landing for fixed-wing aircraft is one of issues in smart Unmanned Aerial Vehicles (UAV). In this paper, we present a robust real-time line tracking algorithm for UAV using image processing. In the proposed algorithm, we first reduce computation region, and then transform to Hough space to detect lines in frame. Finally, the line tracking is(More)
Real-Time Simulation is a most important tool that allows for prediction of system behavior in response to operator actions and events via the use of real-time and archived data. Virtual testing of operator actions prior to implementation can reveal potential problems, hence reducing human errors and the risk of service power system interruptions.(More)