Sensor failure detection for jet engines

Revisions to the advanced sensor failure detection, isolation, and accommodation (DIA) algorithm, developed under the sensor failure detection system program were studied to eliminate the steady state errors due to estimation filter biases. Three algorithm revisions were formulated and one revision for detailed evaluation was chosen. The selected version modifies the DIA algorithm to feedback the actual sensor outputs to the integral portion of the control for the nofailure case. In case of a failure, the estimates of the failed sensor output is fed back to the integral portion. The estimator outputs are fed back to the linear regulator portion of the control all the time. The revised algorithm is evaluated and compared to the baseline algorithm developed previously

Isolation of tributyltin-degrading bacteria citrobacter braakii and enterobacter cloacae from butyltin-polluted sediment

Tributyltin compound (TBT) released into the aquatic environment is generally degraded by bacteria in water and sediment. The isolation of TBT-degrading bacteria from TBT polluted sediment leads to the indication of specific potential TBT degraders. Two new strains of bacteria designated as B2 and B3 were successfully isolated using glycerol medium containing tributyltin chloride (TBTC) at 130 μM from contaminated sediment collected from Bowling Basin in Glasgow. The observed degradation after 14 days of the microcosm from the sediment and the isolated bacteria were investigated at an initial concentration of 1 μM TBTC. It was found that TBT was degraded by the bacterial strains B2 and B3 at 8.3 and 16.9 %, respectively. The results indicate that B2 and B3 are effective as TBT degraders. EC50 of B2 and B3 in water were 88.73 and 112.53 μM TBTC, which were significantly higher than the concentration of TBT measured at the basin, suggesting a low effect of TBT on the growth and activity of bacteria. After identification using API 20E and 16S sequencing, the bacterial isolate strain B2 is Citrobacter braakii and B3 is Enterobacter cloacae. Therefore, this study has discovered two species of high resistance TBT degrader which have never been previously studied or isolated based upon TBT degradation ability

And then there were four: a study of UK market concentration - causes, consequences and the scope for market adjustment

While concentration measures are a good indicator of market structure, the link with competitiveness is more complex than often assumed. In particular, the modern theory of industrial organisation makes no clear statement regarding the impact of concentration on competition - the focus of this paper is concentration and no inferences are made about competitive aspects of the market. The extent and nature of concentration within the UK listed company audit market as at April, 2002 and, pro forma, after the collapse of Andersen is documented and analysed in detail (by firm, market segment and industry sector). The largest four firms held 90 per cent of the market (based on audit fees) in 2002, rising to 96 per cent with the demise of Andersen. A single firm, Pricewaterhouse-Coopers, held 70 per cent or more of the share of six out of 38 industry sectors, with a share of 50 per cent up to 70 per cent in a further seven sectors. The provision of non-audit services (NAS) by incumbent auditors is also considered. As at April 2002, the average ratio of non-audit fees (paid to auditor) to audit fees was 208 per cent, and exceeded 300 per cent in seven sectors. It is likely, however, that disposals by firms of their management consultancy and outsource firms, combined with the impact of the Smith Report on audit committees will serve to reduce these ratios. Another finding is that audit firms with expertise in a particular sector appeared to earn significantly higher nonaudit fees from their audit clients in that sector. The paper thus provides a solid empirical basis for debate. The subsequent discussion considers the implications for companies and audit firms of the high level of concentration in the current regulatory climate, where no direct regulatory intervention is planned

Sensor failure detection system

Advanced concepts for detecting, isolating, and accommodating sensor failures were studied to determine their applicability to the gas turbine control problem. Five concepts were formulated based upon such techniques as Kalman filters and a screening process led to the selection of one advanced concept for further evaluation. The selected advanced concept uses a Kalman filter to generate residuals, a weighted sum square residuals technique to detect soft failures, likelihood ratio testing of a bank of Kalman filters for isolation, and reconfiguring of the normal mode Kalman filter by eliminating the failed input to accommodate the failure. The advanced concept was compared to a baseline parameter synthesis technique. The advanced concept was shown to be a viable concept for detecting, isolating, and accommodating sensor failures for the gas turbine applications

HYTESS: A hypothetical turbofan engine simplified simulation

A users manual for a hypothetical turbofan engine simplified simulation is presented. This digital simulation exists as FORTRAN source code. The program is self-contained and was developed to offer those interested in engine dynamics and controls research an efficient, realistic, and easily used engine simulation. The engine is modeled using a state space formulation. Matrix elements within the linear state space structure are nonlinear functions of various engine variables

Constructing Pointed Hopf Algebras by Ore Extensions

AbstractWe present a general construction producing pointed co-Frobenius Hopf algebras and give some classification results for the examples obtained

Interpolatory Weighted-H2 Model Reduction

This paper introduces an interpolation framework for the weighted-H2 model reduction problem. We obtain a new representation of the weighted-H2 norm of SISO systems that provides new interpolatory first order necessary conditions for an optimal reduced-order model. The H2 norm representation also provides an error expression that motivates a new weighted-H2 model reduction algorithm. Several numerical examples illustrate the effectiveness of the proposed approach