Identification of XV-15 aeroelastic modes using frequency-domain methods

The XV-15 Tilt-Rotor wing has six major aeroelastic modes that are close in frequency. To precisely excite individual modes during flight test, dual flaperon exciters with automatic frequency-sweep controls were installed. The resulting structural data were analyzed in the frequency domain (Fourier transformed) with cross spectral and transfer function methods. Modal frequencies and damping were determined by performing curve fits to transfer function magnitude and phase data and to cross spectral magnitude data. Results are given for the XV-15 with its original metal rotor blades. Frequency and damping values are also compared with earlier predictions

A high pass, mechanical velocity filter for fast neutral molecular beams

Design and transmission characteristics of high pass, mechanical velocity filter for fast neutral molecular or atomic beam

Applications of flight control system methods to an advanced combat rotorcraft

Advanced flight control system design, analysis, and testing methodologies developed at the Ames Research Center are applied in an analytical and flight test evaluation of the Advanced Digital Optical Control System (ADOCS) demonstrator. The primary objectives are to describe the knowledge gained about the implications of digital flight control system design for rotorcraft, and to illustrate the analysis of the resulting handling-qualities in the context of the proposed new handling-qualities specification for rotorcraft. Topics covered in-depth are digital flight control design and analysis methods, flight testing techniques, ADOCS handling-qualities evaluation results, and correlation of flight test results with analytical models and the proposed handling-qualities specification. The evaluation of the ADOCS demonstrator indicates desirable response characteristics based on equivalent damping and frequency, but undersirably large effective time-delays (exceeding 240 m sec in all axes). Piloted handling-qualities are found to be desirable or adequate for all low, medium, and high pilot gain tasks; but handling-qualities are inadequate for ultra-high gain tasks such as slope and running landings

Helicopter mathematical models and control law development for handling qualities research

Progress made in joint NASA/Army research concerning rotorcraft flight-dynamics modeling, design methodologies for rotorcraft flight-control laws, and rotorcraft parameter identification is reviewed. Research into these interactive disciplines is needed to develop the analytical tools necessary to conduct flying qualities investigations using both the ground-based and in-flight simulators, and to permit an efficient means of performing flight test evaluation of rotorcraft flying qualities for specification compliance. The need for the research is particularly acute for rotorcraft because of their mathematical complexity, high order dynamic characteristics, and demanding mission requirements. The research in rotorcraft flight-dynamics modeling is pursued along two general directions: generic nonlinear models and nonlinear models for specific rotorcraft. In addition, linear models are generated that extend their utilization from 1-g flight to high-g maneuvers and expand their frequency range of validity for the design analysis of high-gain flight control systems. A variety of methods ranging from classical frequency-domain approaches to modern time-domain control methodology that are used in the design of rotorcraft flight control laws is reviewed. Also reviewed is a study conducted to investigate the design details associated with high-gain, digital flight control systems for combat rotorcraft. Parameter identification techniques developed for rotorcraft applications are reviewed

Topological conjugacy of locally free Rn−1{\bf R}^{n-1} actions on nn-manifolds

La scolarisation obligatoire imposée par la Troisième République s’est appuyée sur l’école communale jusqu’au début des années 1960. Depuis, la massification de l’enseignement secondaire et l’amplification de l’accès au baccalauréat ont reposé en partie sur la carte scolaire et la sectorisation qu’elle impose. Les lois de décentralisation et le développement de politiques prioritaires, « éducation prioritaire » et « politique de la ville » auraient pu conduire à une territorialisation des politiques scolaires. À l’observation, on constate que les contraintes et les préconisations qu’elles apportent ne touchent qu’une proportion réduite de la population. Les stratégies de contournement, d’évitement développées par les familles font qu’elles ne sont véritablement opposées qu’aux groupes les moins favorisés de la population, que les mesures de territorialisation mises en œuvre sont élaborées à l’extérieur des espaces considérés et que les territoires ainsi délimités sortent du droit commun : les populations résidentes sont considérées à part, la discrimination positive en faveur des établissements scolaires ne réduit pas la différenciation sociale négative.The compulsory schooling imposed by the “Troisième République” has had its own basis on local primary schools till the beginning of the sixties. Since then, the massiveness of secondary school and the widening of the access to the “baccalauréat” degree were partly supported by the system of spatial sectorisation or repartition called “carte scolaire”. Decentralisation laws and the development of priority politics, “priority schooling’’ and local politics could have led to a territorialisation of schooling politics. On the ground, one can observe that constraints and preconisations made these politics effect only a small proportion of the population. By-pass and avoidance strategies developed by families reveal that their effectiveness is only a matter for the least favoured groups but also that territorialisation rules are elaborated outside the concerned areas. What is more, territories thus delimited are beyond common law - its population is left aside and the affirmation action in favour of education does not reduce the negative social effects

Strong unitary and overlap uncertainty relations: theory and experiment

We derive and experimentally investigate a strong uncertainty relation valid for any $n$ unitary operators, which implies the standard uncertainty relation as a special case, and which can be written in terms of geometric phases. It is saturated by every pure state of any $n$-dimensional quantum system, generates a tight overlap uncertainty relation for the transition probabilities of any $n+1$ pure states, and gives an upper bound for the out-of-time-order correlation function. We test these uncertainty relations experimentally for photonic polarisation qubits, including the minimum uncertainty states of the overlap uncertainty relation, via interferometric measurements of generalised geometric phases.Comment: 5 pages of main text, 5 pages of Supplemental Material. Clarifications added in this updated versio

Analysis of fluorine addition to the vanguard first stage

The effect of adding fluorine to the Vanguard first-stage oxidant was anlyzed. An increase in specific impulse of 5.74 percent may be obtained with 30 percent fluorine. This increase, coupled with increased mass ratio due to greater oxidant density, gave up to 24.6-percent increase in first-stage burnout energy with 30 percent fluorine added. However, a change in tank configuration is required to accommodate the higher oxidant-fuel ratio necessary for peak specific impulse with fluorine addition

Structural basis for the membrane fusion step in Hantavirus entry

Hantaviruses are important emerging human pathogens and are the causative agents of serious diseases in humans with high mortality rates. Like other members in the Bunyaviridae family their M segment encodes two glycoproteins, GN and GC, which are responsible for the early events of the viral infection. Hantaviruses deliver their tripartite genome into the cytoplasm by fusion of the viral and endosomal membranes in response to the reduced pH of the endosome. Unlike phleboviruses (e.g. Rift valley fever virus), that have an icosahedral glycoprotein envelope, hantaviruses display a pleomorphic virion morphology as GN and GC assemble into spikes with apparent four- fold symmetry organized in a grid-like pattern on the viral membrane. We determined the crystal structure of glycoprotein C (GC) from Puumala virus (PUUV), a representative member of the Hantavirus genus. The crystal structure shows GC as the membrane fusion effector of PUUV and it presents a class II membrane fusion protein fold. Furthermore, GC was crystallized in its post-fusion trimeric conformation that until now had been observed only in Flavi- and Togaviridae family members. The PUUV G C structure together with our functional data provides new mechanistic insights into class II membrane fusion proteins and reveals new targets for membrane fusion inhibitors against these important pathogens. Both similarities and differences to other class II membrane fusion proteins implies a revise paradigm for the evolution of these unique proteins

Vanillyl alcohol oxidase from Diplodia corticola:Residues Ala420 and Glu466 allow for efficient catalysis of syringyl derivatives

Vanillyl alcohol oxidases belong to the 4-phenol oxidases family and are found predominantly in lignin-degrading ascomycetes. Systematical investigation of the enzyme family at the sequence level resulted in discovery and characterization of the second recombinantly produced VAO member, DcVAO, from Diplodia corticola. Remarkably high activities for 2,6-substituted substrates like 4-allyl-2,6-dimethoxy-phenol (3.5 ± 0.02 U mg -1) or 4-(hydroxymethyl)-2,6-dimethoxyphenol (6.3 ± 0.5 U mg -1) were observed which could be attributed to a Phe to Ala exchange in the catalytic center. In order to rationalize this rare substrate preference among VAOs, we resurrected and characterized three ancestral enzymes and performed mutagenesis analyses. The results indicate that a Cys/Glu exchange was required to retain activity for ɣ-hydroxylations and shifted the acceptance towards benzyl ethers (up to 4.0 ± 0.1 U mg -1). Our findings contribute to the understanding of the functionality of VAO enzyme group, and with DcVAO, we add a new enzyme to the repertoire of ether cleaving biocatalysts. </p