Academic literature on the topic 'Stabilité longitudinale'

An assessment of the longitudinal motion of a hybrid configuration called the aerodynamically alleviated marine vehicle (AAMV) with the presence of waves, is demonstrated in the thesis. The development of this type of vehicle requires a mathematical framework to characterise its dynamics with the influence of external forces due to the waves’ motion. An overview of the effect of waves towards the models of dynamics developed for wing in ground effect (WIGE) craft and high-speed marine vehicles (planing craft) is carried out. However, the overview only leads to a finding that the longitudinal stability of a lifting surface over wavy ground effect is not entirely established. Taking this fact into account, the analysis of the model is proposed for a WIGE craft configuration. A simplification is adopted considering heave motion only in the modelling of oscillation. The simplification is made to thoroughly capture the effect of oscillation toward dynamic stability of the vehicle. To support the model verification, a numerical simulation followed by a semi-empirical design method was adopted to produce aerodynamic data, both in two-dimensional and three-dimensional domains, respectively. The results show that the combination of underpinning parameters, i.e. ride height, frequency and amplitude of oscillation, remarkably influence the aerodynamics. The characteristics in aerodynamics affect the production of stability derivatives and eventually stability behaviour of the chosen configuration. Some patterns in the results are identified but there also some data that show the peculiarity. Thus further investigation is needed.

Millions of people sustain a mild traumatic brain injury (concussion) each year. While most clinical signs and symptoms resolve within 7-10 days for the majority of typical concussions, some gait and balance tasks have shown abnormalities lasting beyond the resolution of clinical symptoms. These abnormalities can persist after athletes have been medically cleared for competition, yet the implications of such changes are unclear. Most prior research has examined straight gait and standard measures of balance, yet there is a lack of knowledge regarding potential persistent effects on non-straight maneuvers or on indicators of motor control variability or complexity. To expand the knowledge of post-concussion locomotor and postural changes, this investigation examined the recovery of recently concussed athletes longitudinally, over the course of one year, in three domains: 1) path selection and body kinematics during turning gait, 2) non-linear local dynamic stability during straight gait, and 3) postural control complexity during quiet standing. Compared to matched health controls, concussed athletes exhibited significant and persistent differences in turning kinematics, local dynamic stability, and postural complexity over the initial six weeks following injury. These motor differences may increase the risk of injury to concussed athletes who are cleared to return to play. Given the persistent nature of these effects, future clinical tests may benefit from incorporating gait assessments before returning athletes to competition. Future research should prospectively and longitudinally monitor locomotor and postural control in conjunction with structural and functional changes within the brain to better understand the pathophysiology of concussions and potential rehabilitation strategies.<br>Ph. D.

This work presents the open-loop stability analysis and an active control strategy for an airbreathing hypersonic vehicle. The 14-XB, a bidimensional flow airframe derived from the Brazilian 14-X Aerospace Hypersonic Vehicle, is adopted as study platform. In order to perform such analyses, a simulation mathematical model of the airframe longitudinal forces and moments is obtained using perfect gas equations, after considering the relevance of the real gas hypotheses for the expected Mach number range and verifying that the simpler formulation is sufficient. An all-moving horizontal tail is designed in order to enable the aircraft trimming. The horizontal tail design considered simple constraints based on static analysis, and the same gas equations as those used for the airframe study. In order to analyze the aircraft';s dynamic behavior, a Six-Degree-of-Freedom set of equations of motion considering a spherical, rotating Earth is presented in detail, and the necessary conditions to have adequate longitudinal trimming in this scenario are discussed. The open-loop stability of the 14-XB with the designed horizontal tail is assessed through eigenvalue analysis and numerical flight simulations with the horizontal tail fixed at a trim position. Having observed that the aircraft presents unstable long-term natural modes, an active control strategy is suggested in order to stabilize the vehicle and track a desired flight path angle, assuming that thrust is constant and the control surface is an all-moving horizontal tail. The suggested control structure presents pitch stability augmentation system and flight path angle compensator. Optimal gains are calculated using linear quadratic design, along with a gain-scheduling strategy based on simultaneous control design, and the resulting controller presents proper results.

Previous research has demonstrated mixed evidence on impaired memory functioning in autism spectrum disorder (ASD), with the only consensus that there appears to be much heterogeneity. In addition, no research to date has examined the stability of memory in ASD. This study examined the stability of memory function in ASD compared to typically developing age-matched controls. Participants were administered the Test of Memory and Learning (TOMAL) twice, three years apart, in an established longitudinal NIH-supported investigation of ASD. Based on available research contrasting memory development in healthy individuals versus those with ASD, it was hypothesized that memory performance in the control group would be stable across time and that, compared to the control group, the autism group would demonstrate less stable memory function as measured by the TOMAL. Repeated Measures ANOVA and Reliable Change Index calculations of TOMAL Index and Subtest scores largely supported these hypotheses. The control group remained stable across time on all TOMAL indices and the ASD group showed improvement on the Composite Memory Index, Verbal Memory Index, and Delayed Memory Index but not the Non Verbal Memory Index. Clinical and research implications are discussed.

ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California<br>One of the most important characteristics of an aircraft is its capability to return to its stable trimmed flight state after the occurrence of a disturbance or gust without the pilot intervention. The evaluation of such behavior, known as the aircraft stability, is divided into three sections: Lateral; Directional; and Longitudinal stabilities. The determination of the stability of an experimental aircraft requires the execution of a Flight Test Campaign (FTC). For the stability FTC the test bed should be equipped with a complete Flight Test Instrumentation (FTI) System which is typically composed by: a Pulse Code Modulation (PCM) Data Acquisition System (DAS); A sensor set; An airborne transmitter; and A data recorder. In the real-time operations, live data received over the Telemetry Link, that are processed, distributed and displayed at the Ground Telemetry System (GTS) enhances the FTC safety level and efficiency. The due to the lack of reliability, recorded data is retrieved in the post mission operations to allow the execution of data reduction analysis. This process is time consuming because recorded data has to be downloaded, converted to Engineering Units (EU), sliced, filtered and processed. The reason for the usage of this less efficient process relies in the fact that the real-time Telemetry data is less reliable as compared to recorded data (i.e. noisier). The upcoming iNET technology could provide a very reliable Telemetry Link. Therefore the data reduction analysis can be executed with live telemetry data in quasi-real time after the receipt of all valid tests points. In this sense the Brazilian Flight Test Group (GEEV) along with EMBRAER and with the support of Financiadora de Estudos e Projetos (FINEP) started the development of several applications. This paper presents the design of a tool used in the Longitudinal Static Stability Flight Tests Campaign. The application receives the Telemetry data over either a TCP/IP or a SCRAMnet Network, performs data analysis and test point validation in real time and when all points are gathered it performs the data reduction analysis and automatically creates Hyper Terminal Markup Language (HTML) formatted tests reports. The tool evaluation was executed with the instruction flights for the 2009 Brazilian Flight Test School (CEV). The result shows an efficiency gain for the overall FTC.