29 research outputs found
Configuration management and automatic control of an augmentor wing aircraft with vectored thrust
An advanced structure for automatic flight control logic for powered-lift aircraft operating in terminal areas is under investigation at Ames Research Center. This structure is based on acceleration control; acceleration commands are constructed as the sum of acceleration on the reference trajectory and a corrective feedback acceleration to regulate path tracking errors. The central element of the structure, termed a Trimmap, uses a model of the aircraft aerodynamic and engine forces to calculate the control settings required to generate the acceleration commands. This report describes the design criteria for the Trimmap and derives a Trimmap for Ames experimental augmentor wing jet STOL research aircraft
Flight-Time Identification of a UH-60A Helicopter and Slung Load
This paper describes a flight test demonstration of a system for identification of the stability and handling qualities parameters of a helicopter-slung load configuration simultaneously with flight testing, and the results obtained.Tests were conducted with a UH-60A Black Hawk at speeds from hover to 80 kts. The principal test load was an instrumented 8 x 6 x 6 ft cargo container. The identification used frequency domain analysis in the frequency range to 2 Hz, and focussed on the longitudinal and lateral control axes since these are the axes most affected by the load pendulum modes in the frequency range of interest for handling qualities. Results were computed for stability margins, handling qualities parameters and load pendulum stability. The computations took an average of 4 minutes before clearing the aircraft to the next test point. Important reductions in handling qualities were computed in some cases, depending, on control axis and load-slung combination. A database, including load dynamics measurements, was accumulated for subsequent simulation development and validation
On the presence of the family Torrenticolidae Piersig (Acari, Hydrachnidia) in interstitial waters of Sicily (South Italy) : description of a new species
Eleven species of the water mite family Torrenticolidae Piersig are reported from interstitial waters of Sicily. The male, female and deutonymph of Torrenticola hyporheica n.sp. are described. The morphological traits of the new species suggest adaptation to life in groundwaters and indicate affinities with other hyporheobiont species of the genus such as T. ramigera Szalay and T. jeanneli Motas & Orghidan. The high number of Torrenticolid-species found in interstitial habitats may be related to the adaptive morphological features of members of this family and more directly to hydrogeological conditions on the island. Torrenticola lativalvata, Torrenticola hyporheica and Torrenticola trinacriae were the most abundant species collected. Marked differences between the distributions of species of the family in Sicily and Corsica are pointed out
Recherches faunistiques et Ă©cologiques sur les Hydracariens de l'Apennin (Italie). Le genre Torrenticola, Piersig (Acari, Actinedida, Torrenticolidae)
Ce travail concerne les données faunistiques et écologiques relatives aux espèces italiennes du genre Torrenticola recueillies dans l'Apennin. Treize espèces ont été signalées, cinq sont nouvelles pour la faune italienne (T. similis, T. lativalvata, T. brevirostris, T. ungeri et T. amplexa). L'étude des caractères dimensionels a permis d'individualiser quelques indices morphologiques de valeur discriminante à un niveau spécifique et a permis de mettre en synonymie quatre espèces. Une distribution différente des espèces entre les secteurs de l'Apennin abruzzin et calabrais a été aussi mise en évidence. L'importance du microhabitat, déterminée par la typologie du cours d'eau, a été soulignée afin d'expliquer la distribution géographique des espèces dans le bassin méditerranéen
La successione ecologica di Acari Macrochelidi nello sterco bovino e relazioni con gli Scarabaeoidea coprofagi.
Indicator value of lotic water mites (Acari: Hydrachnidia) and their use in macroinvertebrate-based indices for water quality assessment purposes
The Water Framework Directive (WFD) of the European Union includes benthic macroinvertebrates for the ecological assessment of running waters. The invertebrate-based Star-ICMi index, adopted in 2010, does not include Hydrachnidia (water mites) in its complex formulation. However, Hydrachnidia are associated with many environmental variables and may be useful for stream ecological characterization. We have therefore assessed the bioindicator value of Hydrachnidia in streams of central Italy, and the ability of two mite-containing (the PTH and the newly formulated PTHfam indices) and four mite-excluding biotic indices (Star-ICMi, BMWP, ASPT, and IBE) to characterize 216 sites ranging from semipristine to impacted. Mite bioindicator value was high at family level. Index reliability was consistently low for the PTH and ASPT indices. Distribution of mite families across quality classes (QCs) was fully separated only for the PTHfam index. QC assignment remained reliable at high index values (i.e., at high ecological status) for the PTHfam and BMWP indices, while logarithmic correlations between the PTHfam and the other indices suggest that the latter may misrepresent sites in high, good, and moderate ecological status sensu WFD. Further studies on the PTHfam index are warranted in light of its simplicity, high reliability, and low sampling and taxonomic identification effort
Global diversity of water mites (Acari, Hydrachnidia; Arachnida) in freshwater
The Hydrachnidia (water mites) represent the most important group of the Arachnida in fresh water. Over 6,000 species have been described worldwide, representing 57 families, 81 subfamilies and more than 400 genera. The article analyzes extant water mite diversity and biogeography. Data on distribution and species richness of water mites are substantial but still far from complete. Many parts of the world are poorly investigated, Oriental and Afrotropical regions in particular. Moreover, information among different freshwater habitats is unbalanced with springs and interstitial waters disproportionately unrepresented. Therefore, more than 10,000 species could be reasonably expected to occur in inland waters worldwide. Based on available information, the Palaearctic region represents one of the better investigated areas with the highest number of species recorded (1,642 species). More than 1,000 species have been recorded in each of the Neotropical (1,305 species) and Nearctic regions (1,025 species). Known species richness is lower in Afrotropical (787 species) and Australasian (694 species) regions, and lowest in the Oriental region (554 species). The total number of genera is not correlated with species richness and is distinctly higher in the Neotropical (164 genera); genus richness is similar in the Palaearctic, Nearctic and Australasian regions (128-131 genera) and is lower in the Afrotropical and Oriental regions with 110 and 94 genera, respectively. A mean number of about three genera per family occur in the Palaeartic, Nearctic and Oriental while an average of more than four genera characterizes the families of Australasian and Afrotropical regions and more than five genera those of the Neotropical. Australasian fauna is also characterized by the highest percentage of endemic genera (62%), followed by Neotropical (50.6%) and Afrotropical (47.2%) regions. Lower values are recorded for the Palaearctic (26.9%), Oriental (24.4%) and Nearctic (21.4%). The Palaearctic and Nearctic have the highest faunistic similarity, some minor affinities are also evident for the generic diversification of Holarctic and Oriental families. The faunas of Southern Hemisphere bioregions are more distinct and characterized by the presence of ancient Gondwanan clades with a regional diversification particularly evident in the Neotropics and Australasia. This scenario of water mite diversity and distribution reflect the basic vicariance pattern, isolation, phylogenetic diversification, recent climatic vicissitudes and episodes of dispersal between adjacent land masses together with extant ecological factors can be evoked to explain distribution patterns at a global scale
Effetti top-down sulla biodiversitĂ di comunitĂ di invertebrati in ecosistemi sorgentizi: il ruolo degli acari acquatici
Struttura, organizzazione trofico-funzionale e tratti biologici della comunitĂ di macroinvertebrati nei pacchi fogliari e in campionamenti bentonici di un fiume appenninico di terzo ordine (Fiume Aterno, Abruzzo, Italia Centrale)
Le informazioni sulla struttura e sul funzionamento degli ecosistemi fluviali sono essenziali per valutarne l’integrità ecologica. Gli indicatori strutturali sono principalmente basati sull’analisi della ricchezza, diversità e composizione delle comunità biologiche mentre le caratteristiche funzionali dei sistemi lotici restano tuttora più difficili da misurare. Il processo di decomposizione del detrito è considerato un utile descrittore funzionale e la tecnica dei pacchi fogliari è stata spesso utilizzata per valutare tale processo ecosistemico. Tuttavia, gli studi mirati ad evidenziare l’importanza reciproca degli indicatori strutturali e funzionali per una corretta valutazione dello stato di salute dei corsi d’acqua, hanno dato risultati contrastanti. Gli indici funzionali sono stati messi in relazione con la struttura della comunità campionata nel benthos o nei pacchi di foglie, senza nessun confronto diretto tra le due diverse situazioni. Obiettivo principale della ricerca è quello di analizzare l’assetto strutturale e funzionale della comunità macrobentonica di un corso d’acqua appenninico di terzo ordine, campionata in parallelo con la rete di Surber e con la tecnica dei pacchi fogliari. I risultati dimostrano che le due diverse metodologie devono essere considerate complementari in quanto consentono una migliore caratterizzazione dell’intero pool di taxa presenti