Uniform asymptotics for robust location estimates when the scale is unknown

Most asymptotic results for robust estimates rely on regularity conditions that are difficult to verify in practice. Moreover, these results apply to fixed distribution functions. In the robustness context the distribution of the data remains largely unspecified and hence results that hold uniformly over a set of possible distribution functions are of theoretical and practical interest. Also, it is desirable to be able to determine the size of the set of distribution functions where the uniform properties hold. In this paper we study the problem of obtaining verifiable regularity conditions that suffice to yield uniform consistency and uniform asymptotic normality for location robust estimates when the scale of the errors is unknown. We study M-location estimates calculated with an S-scale and we obtain uniform asymptotic results over contamination neighborhoods. Moreover, we show how to calculate the maximum size of the contamination neighborhoods where these uniform results hold. There is a trade-off between the size of these neighborhoods and the breakdown point of the scale estimate.Comment: Published by the Institute of Mathematical Statistics (http://www.imstat.org) in the Annals of Statistics (http://www.imstat.org/aos/) at http://dx.doi.org/10.1214/00905360400000054

Uniform asymptotics for robust location estimates when the scale is unknown

Most asymptotic results for robust estimates rely on regularity conditions that are difficult to verify and that real data sets rarely satisfy. Moreover, these results apply to fixed distribution functions. In the robustness context the distribution of the data remains largely unspecified and hence results that hold uniformly over a set of possible distribution functions are of theoretical and practical interest. In this paper we study the problem of obtaining verifiable and realistic conditions that suffice to obtain uniform consistency and uniform asymptotic normality for location robust estimates when the scale of the errors is unknown. We study M-location estimates calculated withan S-scale and we obtain uniform asymptotic results over contamination neighbourhoods. There is a trade-off between the size of these neighbourhoods and the breakdown point of the scale estimate. We also show how to calculate the maximum size of the contamination neighbourhoods where these uniform results hold.

Cambios en la velocidad de nado como indicador del efecto tóxico del cadmio en Astyanax fasciatus y Australoheros facetum

Numerous studies have shown that the swimming performance parameters of fish may be useful indicators of their environmental stress. The swimming speed was evaluated in two Pampean species and its alteration as a result of their exposure to sublethal Cadmium concentrations. The swimming speed was calculated from a daily registry of the distance and the time of displacement of fish by means of special software. Juveniles specimens of Astyanax fasciatus and Australoheros facetum were used in the assays; fish were acclimated during 7 days in aereated fresh-water (FW), at constant temperature (20 ± 1ºC) and photoperiod (12D:12N). The experimental design contemplated three successive periods: Control (4 days in FW), Exposure (4 days in FW + 0.3 and 0.5 mg Cd L-1) and Recovery (7 days in FW); simultaneously the speed of individuals maintained in FW during 15 days (CoP) was determined. The swimming speed in both species increased in the Exposure period. After transfer to clean media (Recovery period), the altered values in A. facetum, exhibited a slight tendency to recovery (but without reaching the basal values registered in the Control period). In A. fasciatus a clear cut recovery response was registered in fish exposed to 0.3 mg. L-1 while in animals exposed to the highest concentration of Cd no recovery was registered. These differences were interpreted as evidences of dissimilar uptake and depuration rates of the toxic.Instituto de Limnología "Raúl A. Ringuelet

Cambios en la velocidad de nado como indicador del efecto tóxico del cadmio en Astyanax fasciatus y Australoheros facetum

Numerous studies have shown that the swimming performance parameters of fish may be useful indicators of their environmental stress. The swimming speed was evaluated in two Pampean species and its alteration as a result of their exposure to sublethal Cadmium concentrations. The swimming speed was calculated from a daily registry of the distance and the time of displacement of fish by means of special software. Juveniles specimens of Astyanax fasciatus and Australoheros facetum were used in the assays; fish were acclimated during 7 days in aereated fresh-water (FW), at constant temperature (20 ± 1ºC) and photoperiod (12D:12N). The experimental design contemplated three successive periods: Control (4 days in FW), Exposure (4 days in FW + 0.3 and 0.5 mg Cd L-1) and Recovery (7 days in FW); simultaneously the speed of individuals maintained in FW during 15 days (CoP) was determined. The swimming speed in both species increased in the Exposure period. After transfer to clean media (Recovery period), the altered values in A. facetum, exhibited a slight tendency to recovery (but without reaching the basal values registered in the Control period). In A. fasciatus a clear cut recovery response was registered in fish exposed to 0.3 mg. L-1 while in animals exposed to the highest concentration of Cd no recovery was registered. These differences were interpreted as evidences of dissimilar uptake and depuration rates of the toxic.Instituto de Limnología "Raúl A. Ringuelet

Cambios en la velocidad de nado como indicador del efecto tóxico del cadmio en Astyanax fasciatus y Australoheros facetum

Numerous studies have shown that the swimming performance parameters of fish may be useful indicators of their environmental stress. The swimming speed was evaluated in two Pampean species and its alteration as a result of their exposure to sublethal Cadmium concentrations. The swimming speed was calculated from a daily registry of the distance and the time of displacement of fish by means of special software. Juveniles specimens of Astyanax fasciatus and Australoheros facetum were used in the assays; fish were acclimated during 7 days in aereated fresh-water (FW), at constant temperature (20 ± 1ºC) and photoperiod (12D:12N). The experimental design contemplated three successive periods: Control (4 days in FW), Exposure (4 days in FW + 0.3 and 0.5 mg Cd L-1) and Recovery (7 days in FW); simultaneously the speed of individuals maintained in FW during 15 days (CoP) was determined. The swimming speed in both species increased in the Exposure period. After transfer to clean media (Recovery period), the altered values in A. facetum, exhibited a slight tendency to recovery (but without reaching the basal values registered in the Control period). In A. fasciatus a clear cut recovery response was registered in fish exposed to 0.3 mg. L-1 while in animals exposed to the highest concentration of Cd no recovery was registered. These differences were interpreted as evidences of dissimilar uptake and depuration rates of the toxic.Instituto de Limnología "Raúl A. Ringuelet

Cambios en la velocidad de nado como indicador del efecto tóxico del cadmio en Astyanax fasciatus y Australoheros facetum

Numerous studies have shown that the swimming performance parameters of fish may be useful indicators of their environmental stress. The swimming speed was evaluated in two Pampean species and its alteration as a result of their exposure to sublethal Cadmium concentrations. The swimming speed was calculated from a daily registry of the distance and the time of displacement of fish by means of special software. Juveniles specimens of Astyanax fasciatus and Australoheros facetum were used in the assays; fish were acclimated during 7 days in aereated fresh-water (FW), at constant temperature (20 ± 1ºC) and photoperiod (12D:12N). The experimental design contemplated three successive periods: Control (4 days in FW), Exposure (4 days in FW + 0.3 and 0.5 mg Cd L-1) and Recovery (7 days in FW); simultaneously the speed of individuals maintained in FW during 15 days (CoP) was determined. The swimming speed in both species increased in the Exposure period. After transfer to clean media (Recovery period), the altered values in A. facetum, exhibited a slight tendency to recovery (but without reaching the basal values registered in the Control period). In A. fasciatus a clear cut recovery response was registered in fish exposed to 0.3 mg. L-1 while in animals exposed to the highest concentration of Cd no recovery was registered. These differences were interpreted as evidences of dissimilar uptake and depuration rates of the toxic.Numerous studies have shown that the swimming performance parameters of fish may be useful indicators of their environmental stress. The swimming speed was evaluated in two Pampean species and its alteration as a result of their exposure to sublethal Cadmium concentrations. The swimming speed was calculated from a daily registry of the distance and the time of displacement of fish by means of special software. Juveniles specimens of Astyanax fasciatus and Australoheros facetum were used in the assays; fish were acclimated during 7 days in aereated fresh-water (FW), at constant temperature (20 ± 1ºC) and photoperiod (12D:12N). The experimental design contemplated three successive periods: Control (4 days in FW), Exposure (4 days in FW + 0.3 and 0.5 mg Cd L-1) and Recovery (7 days in FW); simultaneously the speed of individuals maintained in FW during 15 days (CoP) was determined. The swimming speed in both species increased in the Exposure period. After transfer to clean media (Recovery period), the altered values in A. facetum, exhibited a slight tendency to recovery (but without reaching the basal values registered in the Control period). In A. fasciatus a clear cut recovery response was registered in fish exposed to 0.3 mg. L-1 while in animals exposed to the highest concentration of Cd no recovery was registered. These differences were interpreted as evidences of dissimilar uptake and depuration rates of the toxic

Robust Modal Filtering and Control of the X-56A Model with Simulated Fiber Optic Sensor Failures

The X-56A aircraft is a remotely-piloted aircraft with flutter modes intentionally designed into the flight envelope. The X-56A program must demonstrate flight control while suppressing all unstable modes. A previous X-56A model study demonstrated a distributed-sensing-based active shape and active flutter suppression controller. The controller relies on an estimator which is sensitive to bias. This estimator is improved herein, and a real-time robust estimator is derived and demonstrated on 1530 fiber optic sensors. It is shown in simulation that the estimator can simultaneously reject 230 worst-case fiber optic sensor failures automatically. These sensor failures include locations with high leverage (or importance). To reduce the impact of leverage outliers, concentration based on a Mahalanobis trim criterion is introduced. A redescending M-estimator with Tukey bisquare weights is used to improve location and dispersion estimates within each concentration step in the presence of asymmetry (or leverage). A dynamic simulation is used to compare the concentrated robust estimator to a state-of-the-art real-time robust multivariate estimator. The estimators support a previously-derived mu-optimal shape controller. It is found that during the failure scenario, the concentrated modal estimator keeps the system stable