Helicopter Vibratory Loads Alleviation through Combined Action of Trailing-Edge Flap and Variable-Stiffness Devices

The aim of this paper is the assessment of the capability of controllers based on the combined actuation of flaps and variable-stiffness devices to alleviate helicopter main rotor vibratory hub loads. Trailing-edge flaps are positioned at the rotor blade tip region, whereas variable-stiffness devices are located at the pitch link and at the blade root. Control laws are derived by an optimal control procedure based on the best trade-off between control effectiveness and control effort, under the constraint of satisfaction of the equations governing rotor blade aeroelastic response. The numerical investigation concerns the analysis of performance and robustness of the control techniques developed, through application to a four-bladed helicopter rotor in level flight. The identification of the most efficient control configuration is also attempted

The Impact of Company Grade Officer Self-Sacrificial Behavior on Subordinate Assessments of Leader Charisma

Newly commissioned officers in the U.S. Army are taught to lead their soldiers from the front and to voluntarily make personal sacrifices in the service of the nation. Although this facet of military culture is seen as critical to the integrity of the force, there are few research studies describing the impact of leader self-sacrifice in the U.S. Army. Research evolving from the transformational leadership literature indicates that civilian leaders who engage in self-sacrificial behavior are viewed as more charismatic than their counterparts and that this perception is particularly pronounced in crisis situations. The current study extended this research to a military population utilizing a quantitative experimental research design. Respondents were randomly assigned to written vignettes that manipulated leader self-sacrifice and the combat environment and then provided assessments of the company grade officer\u27s attributed charisma. Currently serving enlisted and commissioned officers in the California Army National Guard (n = 218) took part in the research, and ANOVA test results indicated that both self-sacrifice and the experience of combat significantly increase perceptions of a company grade officer\u27s attributed charisma. No significant interaction was found between leader self-sacrifice and combat. This study indicated that the self-sacrificial leadership model may have broad applicability across organizations and provides strong support for the Army\u27s emphasis on selfless service. This research can spur positive social change by fostering a more aspirational form of leadership within the Army that builds the psychological resilience of soldiers and results in stronger teams

Parametric Analysis of the Acoustic Response of the VEGA Launcher Fairing in Critical Acoustic Phases”. Relazione finale per la Convenzione di ricerca tra Dipartimento e Avio S.p.A., Luglio 2004.

Parametric Analysis of the Acoustic Response of the VEGA Launcher Fairing in Critical Acoustic Phases”. Relazione finale per la Convenzione di ricerca tra Dipartimento e Avio S.p.A., Luglio 2004

A Boundary-Field Integral Equation for Analysis of Cavity Acoustic Spectrum

The acoustic spectrum of cavities can be identified using integral equation formulations. Because of the transcendental dependence on frequency of the Green function, difficulties arise in calculating acoustic frequencies and modes of vibration when the Kirchhoff–Helmholtz boundary-integral operator is applied. This trouble is circumvented by the present, nonstandard, integral formulation that, by using the fundamental solution of the Laplace operator, allows the identification of acoustic spectra of cavities through solution of a standard eigenvalue problem. This formulation is compared both with that based on the Kirchhoff–Helmholtz operator and with an alternative integral approach introduced in the past that, akin to the one used here, analyzes cavity acoustics in terms of an eigenvalue problem. The numerical investigation deals both with a simple box-shaped cavity and with cavities related to applications of aeronautical interest