Concise stability conditions for systems with static nonlinear feedback expressed by a quadratic program

Copyright © 2008 Institution of Engineering and Technology (IET). This paper is a postprint of a paper submitted to and accepted for publication in IET Control Theory and Applications and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at IET Digital Library.The stability of the feedback connection of a strictly proper linear time-invariant stable system with a static nonlinearity expressed by a convex quadratic program (QP) is considered. From the Karush-Kuhn-Tucker conditions for the QP, quadratic constraints that may be used with a quadratic Lyapunov function to construct a stability criterion via the S-procedure are established. The approach is based on existing results in the literature, but gives a more parsimonious linear matrix inequality (LMI) criterion and is much easier to implement. This approach can be extended to model predictive control and gives equivalent results to those in the literature but with a much lower dimension LMI criterion

Face-gear drives: Design, analysis, and testing for helicopter transmission applications

The use of face-gears in helicopter transmissions was explored. A light-weight, split-torque transmission design utilizing face-gears is described. Face-gear design and geometry were investigated. Topics included tooth generation, limiting inner and outer radii, tooth contact analysis, contact ratio, gear eccentricity, grinding, and structural stiffness. Design charts were developed to determine minimum and maximum face-gear inner and outer radii. An analytical study showed that the face-gear drive is relatively insensitive to gear misalignment with respect to transmission errors, but the tooth contact is affected by misalignment. A method of localizing the bearing contact to permit operation with misalignment was explored. Two new methods for grinding of the face-gear tooth surfaces were also investigated. The proper choice of shaft stiffness enabled good load sharing in the split-torque transmission design. Face-gear experimental studies were also conducted. These tests demonstrated the feasibility of face-gears in high-speed, high-load applications such as helicopter transmissions

Application of Face-Gear Drives in Helicopter Transmissions

The use of face gears in helicopter transmissions was explored. A light-weight, split torque transmission design utilizing face gears was described. Face-gear design and geometry were investigated. Topics included tooth generation, limiting inner and outer radii, tooth contact analysis, contact ratio, gear eccentricity, and structural stiffness. Design charts were developed to determine minimum and maximum face-gear inner and outer radii. Analytical study of transmission error showed face-gear drives were relatively insensitive to gear misalignment, but tooth contact was affected by misalignment. A method of localizing bearing contact to compensate for misalignment was explored. The proper choice of shaft support stiffness enabled good load sharing in the split torque transmission design. Face-gear experimental studies were also included and the feasibility of face gears in high-speed, high-load applications such as helicopter transmissions was demonstrated

The relationship between objectification theory and muscle dysmorphia characteristics in men

Objectification theory has yielded mixed results when utilized to explain male’s body image concerns. This study investigated whether a revised model of objectification theory would represent the processes associated with male’s engagement in muscle dysmorphia characteristics. Specifically the mediating role of body shame, which has previously been used to explain the psychological consequences of self-objectification among women, was substituted for muscular dissatisfaction to capture the male experience. A sample of 257 male (Mage = 29.7, SD = 11.2), the majority from Australia, completed an online questionnaire assessing measures of internalization of the mesomorphic ideal, body surveillance, self-objectification, muscular dissatisfaction, and muscle dysmorphia characteristics. Path analyses were used to investigate the relationships among these variables. Results indicated that internalization of the mesomorphic ideal mediated body surveillance through self-objectification; consistent with previous research on objectification theory. Muscular dissatisfaction mediated the link of body surveillance with muscle dysmorphia characteristics. Additionally, muscular dissatisfaction mediated the link between internalization of the mesomorphic ideal and muscle dysmorphia characteristics. Taken together, these findings support the utility of objectification theory in understanding the processes under which muscle dysmorphia characteristics are likely to emerge

The Mass Power Spectrum in Quintessence Cosmological Models

We present simple analytic approximations for the linear and fully evolved nonlinear mass power spectrum for spatially flat cold dark matter (CDM) cosmological models with quintessence (Q). Quintessence is a time evolving, spatially inhomogeneous energy component with negative pressure and an equation of state w_Q < 0. It clusters gravitationally on large length scales but remains smooth like the cosmological constant on small length scales. We show that the clustering scale is determined by the Compton wavelength of the Q-field and derive a shape parameter, \Gamma_Q, to characterize the linear mass power spectrum. The growth of linear perturbations as functions of redshift, w_Q, and matter density \Omega_m is also quantified. Calibrating to N-body simulations, we construct a simple extension of the formula by Ma (1998) that closely approximates the nonlinear power spectrum for a range of plausible QCDM models.Comment: 5 pages with 3 inserted postscript figures, AAS LaTeX v4.0 emulateapj.sty. Astrophysical Journal Letters, in pres