Balanced realisations of all-pass systems using exact arithmetic with application to the approximation of delay systems

Numerically well-conditioned state-space realisations for all-pass systems, such as Padé approximations to exp(-s), are derived that can be computed using exact integer arithmetic. This is then applied to the a series of functions of exp(-s). It is also shown that the H-infinity norm of the transfer function from the input to the state of a balanced realisation of the Padé approximation of exp(-s) is unity. © 2012 IEEE.

Primary antibody deficiency and diagnostic delay.

AIMS: To assess the occurrence of diagnostic delay in primary antibody deficiency in the period 1989-2002, since a similar study in 1989, and to assess the impact of UK national guidelines communicated in 1995. METHODS: A retrospective case note review was performed of 89 consecutive patients with antibody deficiency referred to a regional referral centre for clinical immunology in north west England and north Wales. The delay in diagnosis and the estimated resulting morbidity in terms of infections were assessed. RESULTS: Fifty six of the 89 patients experienced delay in diagnosis. The overall median delay was 2 years (mean, 4.4), resulting in substantial morbidity (equivalent to two major infections and one minor infection). This shows a moderate improvement since the previous study in 1989 and since the introduction of UK national guidelines in 1995. Respiratory infections are the most frequent presenting infections, and respiratory physicians the most common source of referral. CONCLUSIONS: There is still considerable delay in the diagnosis of primary antibody deficiency, but the data suggest an improvement in practice since the previous study in 1989 and the distribution of national guidelines in 1995.

On the time delay in continuous in-cylinder sampling from IC engines

When gas sample is continuously drawn from the cylinder of an internal combustion engine, the sample that appears at the end of the sampling system corresponds to the in-cylinder content sometime ago because of the finite transit time which is a function of the cylinder pressure history. This variable delay causes a dispersion of the sample signal and makes the interpretation of the signal difficult An unsteady flow analysis of a typical sampling system was carried out for selected engine loads and speeds. For typical engine operation, a window in which the delay is approximately constant may be found. This window gets smaller with increase in engine speed, with decrease in load, and with the increase in exit pressure of the sampling system.

A perturbation approach to the stabilization of nonlinear cascade systems with time-delay

The effect of bounded input perturbations on the stability of nonlinear globally asymptotically stable delay differential equations is analyzed. We investigate under which conditions global stability is preserved and if not, whether semi-global stabilization is possible by controlling the size or shape of the perturbation. These results are used to study the stabilization of partially linear cascade systems with partial state feedback.