Ruth Hardy

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This paper presents a Hoare-style logic for reasoning about the frequency response of control systems in the continuous-time domain. Two properties, the gain (amplitude) and phase shift, of a control system are considered. These properties are for a sinusoidal input of variable frequency. The logic operates over a simplified form of block diagram, including(More)
This paper introduces the Laconia Acropolis Virtual Archaeology project (LAVA), a cooperative archaeological learning environment that has been developed to address the need for students to be able to engage with realistic archaeological excavation scenarios. The practice of fieldwork lies at the heart of archaeology yet poses particular problems for the(More)
We introduce control engineering as a new domain of application for formal methods. We discuss design verification, drawing attention to the role played by diagrammatic evaluation criteria involving numeric plots of a design, such as Nichols and Bode plots. We show that symbolic computation and computational logic can be used to discharge these criteria and(More)
Real number theorem proving has many uses, particularly for verification of safety critical systems and systems for which design errors may be costly. We discuss a chain of developments building on real number theorem proving in PVS. This leads from the verification of aspects of an air traffic control system, through work on the integration of computer(More)
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Measurement and analysis of traffic traces are important for better understanding of network behaviour. In this research, we collected traffic traces from a hybrid satellite-terrestrial network operated by ChinaSat, a commercial satellite Internet service provider. We performed traffic analysis on packet, connection, protocol, and application layers. We(More)
This document discusses some of the basic concepts and methods used by control engineers in the development of control laws. It is not meant to act as an introduction as to how to use these techniques, but rather as a guide to some of the more important aspects and issues associated with this area. In Section 1 some of the different representations used to(More)