Application of a system modification technique to dynamic tuning of a spinning rotor blade

An important consideration in the development of modern helicopters is the vibratory response of the main rotor blade. One way to minimize vibration levels is to ensure that natural frequencies of the spinning main rotor blade are well removed from integer multiples of the rotor speed. A technique for dynamically tuning a finite-element model of a rotor blade to accomplish that end is demonstrated. A brief overview is given of the general purpose finite element system known as Engineering Analysis Language (EAL) which was used in this work. A description of the EAL System Modification (SM) processor is then given along with an explanation of special algorithms developed to be used in conjunction with SM. Finally, this technique is demonstrated by dynamically tuning a model of an advanced composite rotor blade

A direct interaction between the Parkinson's disease protein leucine-rich repeat kinase 2 and specific β-tubulin isoforms regulates tubulin acetylation

Mutations in LRRK2 are a common cause of Parkinson’s disease (PD). LRRK2 encodes leucine-rich repeat kinase 2 (LRRK2), a ROCO protein. It has an enzymatic core consisting of a Ras of complex proteins (Roc) GTPase domain and kinase domain, surrounded by protein-protein interaction regions. Pathogenic LRRK2 mutations modify activity in these enzymatic domains, but how this leads to neurodegeneration is still to be elucidated. One of the few confirmed LRRK2 interactors is tubulin, the main constituent of microtubules (MTs) and part of the cytoskeletal network. Disease-causing mutations in LRRK2 alter this network, reducing neurite outgrowth and leading to accumulation of hyperphosphorylated MT-associated protein (MAP) tau. Meanwhile changes in post-translational modifications of tubulin and MAPs alter the dynamic instability of MTs, leading to aberrant axonal transport, synaptic dysfunction and axonal degeneration. I investigated the LRRK2-tubulin interaction. Using yeast two-hybrid I demonstrated that the interaction is conferred by the LRRK2 Roc domain and the C-terminus of the β-tubulin isoforms TUBB, TUBB4 and TUBB6. The interaction requires Lys362 and Ala364 and is blocked in isoforms expressing a serine at these positions. This site is on the luminal face of MT protofibrils, close to the paclitaxel binding site and α-tubulin Lys40 acetylation site, both of which are involved in MT stability. This location is poorly accessible within mature, stabilised MTs but exposed in dynamic MT populations. Consistent with this finding, endogenous LRRK2 located to dynamic growth cone MTs in SH-SY5Y cells. Overexpression and knock-out studies in HEK cells and mouse embryonic fibroblasts showed that LRRK2 is associated with reduced α-tubulin acetylation. These results demonstrate the specificity of the LRRK2-tubulin interaction, suggesting LRRK2 distribution at the cytoskeleton is determined by the tubulin composition and may vary between cell types. Changes in MT acetylation in the presence of disease-causing LRRK2 mutations could contribute to pathogenic mechanisms, with altered MT stability implicated in PD neurodegeneration. As mutations affecting the β-tubulin C-terminal residues could disrupt the LRRK2 interaction without compromising MT integration, a cohort of late-onset familial PD cases was also screened for mutations within the cytoskeleton

Geometrical and structural properties of an Aeroelastic Research Wing (ARW-2)

Transonic steady and unsteady pressure tests were conducted on a large elastic wing known as the DAST ARW-2 wing. The wing has a supercritical airfoil, an aspect ratio of 10.3, a leading edge sweepback angle of 28.8 deg and is equipped with two inboard and one outboard trailing edge control surfaces. The geometrical and structural characteristics are presented of this elastic wing, using a combination of measured and calculated data, to permit future analyst to compare the experimental surface pressure data with theoretical predictions

Experimental transonic flutter characteristics of two 72 deg-sweep delta-wing models

Transonic flutter boundaries are presented for two simple, 72 deg. sweep, low-aspect-ratio wing models. One model was an aspect-ratio 0.65 delta wing; the other model was an aspect-ratio 0.54 clipped-delta wing. Flutter boundaries for the delta wing are presented for the Mach number range of 0.56 to 1.22. Flutter boundaries for the clipped-delta wing are presented for the Mach number range of 0.72 to 0.95. Selected vibration characteristics of the models are also presented

Supersonic aeroelastic instability results for a NASP-like wing model

An experimental study and an analytical study have been conducted to examine static divergence for hypersonic-vehicle wing models at supersonic conditions. A supersonic test in the Langley Unitary Plan Wind Tunnel facility was conducted for two wind-tunnel models. These models were nearly identical with the exception of airfoil shape. One model had a four-percent maximum thickness airfoil and the other model had an eight-percent maximum thickness airfoil. The wing models had low-aspect ratios and highly swept leading edges. The all-movable wing models were supported by a single-pivot mechanism along the wing root. For both of the wind-tunnel models, configuration changes could be made in the wing-pivot location along the wing root and in the wing-pivot pitch stiffness. Three divergence conditions were measured for the four-percent thick airfoil model in the Mach number range of 2.6 to 3.6 and one divergence condition was measured for the eight-percent thick airfoil model at a Mach number of 2.9. Analytical divergence calculations were made for comparison with experimental results and to evaluate the parametric effects of wing-pivot stiffness, wing-pivot location, and airfoil thickness variations. These analyses showed that decreasing airfoil thickness, moving the wing-pivot location upstream, or increasing the pitch-pivot stiffness have the beneficial effect of increasing the divergence dynamic pressures. The calculations predicted the trend of experimental divergence dynamic pressure with Mach number accurately; however, the calculations were approximately 25 percent conservative with respect to dynamic pressure

The application of active controls technology to a generic hypersonic aircraft configuration

Analytical methods are described for the prediction of aerothermoelastic stability of hypersonic aircraft including active control systems. Thermal loads due to aerodynamic heating were applied to the finite element model of the aircraft structure and the thermal effects on flutter were determined. An iterative static aeroelastic trim analysis procedure was developed including thermal effects. And active control technology was assessed for flutter suppression, ride quality improvement, and gust load alleviation to overcome any potential adverse aeroelastic stability or response problems due to aerodynamic heating. A generic hypersonic aircraft configuration was selected which incorporates wing flaps, ailerons, and all moveable fins to be used for active control purposes. The active control system would use onboard sensors in a feedback loop through the aircraft flight control computers to move the surfaces for improved structural dynamic response as the aircraft encounters atmospheric turbulence

Early Predictors of Successful Military Careers Among West Point Cadets

The importance of leadership to organizational performance puts a premium on identifying future leaders. Early prediction of high-potential talent enables organizations to marshal scarce develop- mental resources and opportunities to those who are best positioned to show distinction in elevated roles. Much of the existing literature indicates that general mental ability remains the strongest predictor of future professional performance. Using data from 13 classes of West Point graduates who stayed in the Army to be considered for at least early promotion to the rank of major (N = 5,505), regression analyses indicate that cadet military grade point average surpasses both cognitive ability and academic performance by a considerable margin in the ability to predict future professional outcomes such as selection for early promotion or battalion command. Moreover, these differences in predicting managerial career outcomes endure over 16 years. Both practical and theoretical implications are discussed.https://digitalcommons.usmalibrary.org/books/1054/thumbnail.jp

Using a Case Study to Teach Leaders How to Enact Positive Organizational Change

https://digitalcommons.usmalibrary.org/books/1062/thumbnail.jp