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- Herbert Kay
- 1994

The Space Shuttle Reaction Control System (RCS) is a component of the space shuttle propulsion system that provides motion control for the shuttle orbiter. As part of a model-based monitoring and diagnosis system for the RCS, a qualitative model of the system was developed using the QSIM modeling language. This report describes the RCS model, the… (More)

- Bradley L. Richards, Ina Kraan, Marcos Vescovi, Adam Farquhar, Evangeline Gazi, Herbert Kay +2 others
- 1996

Numerical interval simulation: Combined qualitative and quantitative simulation to bound behaviors of non-monotonic systems. A generic method for computing the response of a numerically-known dynamic system to qualitative inputs. 37 x i (t) < x i (t) in which case there must be some time t 1 < t such that x i (t 1) = x i (t 1), or x i (t) = x i (t). Assume… (More)

- Herbert Kay
- 1997

While model-based process monitoring and system identiication share the common goal of describing the behavior of a physical system based on a mathematical model, the assumptions made by system identiication are typically too strong to apply it directly to monitoring problems. This article describes SQUID, a new system identiication method that uses… (More)

System identification takes a space of possible models and a stream of observational data of a physical system, and attempts to identify the element of the model space that best describes the observed system. In traditional approaches, the model space is specified by a parameterized differential equation, and identification selects numerical parameter… (More)

Semiquantitative models combine both qualitative and quantitative knowledge within a single semiquantitative qualitative differential equation (SQDE) representation. With current simulation methods, the quantitative knowledge is not exploited as fully as possible. This paper describes dynamic envelopes — a method to exploit quantitative knowledge more fully… (More)

- Herbert Kay, Lyle H Ungar
- 1993

Much work in qualitative physics involves constructing models of physical systems using functional descriptions such as \\ow monotonically increases with pressure." Semiquantitative methods improve model precision by adding numerical envelopes to these monotonic functions. Ad hoc methods are normally used to determine these envelopes. This paper describes a… (More)

- M. Matranga, M. Mathioudakis, H. R. M. Kay, F. P. Keenan
- 2005

X-ray spectra of the late-type star AB Dor, obtained with the XMM-Newton satellite are analysed. AB Dor was particularly active during the observations. An emission measure reconstruction technique is employed to analyse flare and quiescent spectra, with emphasis on the Fe XVII 15 − 17Å wavelength region. The Fe XVII 16.78Å/15.01Å line ratio increases… (More)

System identiication takes a space of possible models and a stream of observational data of a physical system, and attempts to identify the element of the model space that best describes the observed system. In traditional approaches, the model space is speciied by a parameterized diierential equation, and identiication selects numerical parameter values so… (More)

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