Clear Science Corporation (United States)

A physics-based, reduced-order, aeroservoelastic model of an F-18 aircraft has been developed using the method of proper orthogonal decomposition (POD), introduced to the field of fluid mechanics by Lumley. The model is constructed with data from high-dimensional, high-fidelity aeroservoelastic computational fluid dynamics (CFD-ASE) simulations that couple equations of motion of the flow to a modal model of the aircraft structure. Through POD modes, the reduced-order model (ROM) predicts both the structural dynamics and the coupled flow dynamics, offering much more information than typically employed, low-dimensional models based on system identification are capable of providing. ROM accuracy is evaluated through direct comparisons between predictions of the flow and structural dynamics with predictions from the parent, the CFD-ASE model. The computational overhead of the ROM is six orders of magnitude lower than that of the CFD-ASE model—accurately predicting the coupled dynamics from simulations of an F-18 fighter aircraft undergoing flutter testing over a wide range of transonic and supersonic flight speeds on a single processor in 1.073 s.

Physics-based reduced-order models have been developed that can accurately and efficiently simulate key aspects of aircraft flight operations including aerodynamics, aeroelasticity, and control-surface dynamics at subsonic, transonic, and supersonic flight speeds and rapidly changing, nonlinear post-stall conditions. The modeling technology enables flight simulations and virtual flight testing of agile (highly maneuverable) fighter aircraft. Order reduction is effected by transforming from physical space to modal space using the method of proper orthogonal decomposition. Modal models constructed with a relatively small set of data from high-fidelity, computationally intensive CFD simulations (where flow properties are computed in physical space) are capable of accurately predicting the flight dynamics for a wide range of aggressive aircraft maneuvers in simulations that are significantly faster than real time. Model accuracy is demonstrated through comparisons with data from CFD simulations of an open-source fighter aircraft with and without wing stores (modeled after an F-16) and an F-16 aircraft with articulating control surfaces. Model evaluations include both rigid and flexible versions of the aircraft.

Postcessation weight gain is common and a frequent cause of relapse. Although interventions to address weight gain and weight gain concerns exist, the experience of telephone cessation coun- sellors in addressing weight concerns is unknown. We surveyed 134 cessation counsellors providing quitlines for 30 states regarding their experiences and attitudes about how to address weight gain concerns among smokers trying to quit. Counsellors estimated they discuss weight in 40% of their calls, primarily discussing concerns about gaining weight. Counsellors estimated that smokers gain about 4.1 kg after quitting and about 48% gain more than 2.3 kg. Most counsellors believed that exercise, education about weight gain and preparing smokers for weight gain would help people quit, which is consistent with current science. A total of 51% of counsellors believed that dieting while quitting would reduce weight gain and only 35% correctly identified that dieting reduces a smokers' ability to quit. Some counsellors believed they needed more training in weight management and may need to be reassured that they are currently following treatment guidelines when confronted with smokers who have concerns about postcessation weight gain.

A closed-loop control system has been developed and tested for tracking prescribed values of aerodynamic force on a NACA 4412 airfoil. The system includes a measurementbased estimator that utilizes a low-dimensional model of the perturbation flow—based on the method of proper orthogonal decomposition—and a stochastic correlation between the measurement and the state estimate. The system also includes nonlinear and linear approximations of the performance output, defined as unsteady oscillations in the lift coefficient. The control objective is to reduce or eliminate the oscillations by tracking a prescribed, constant value of lift. Using a proportional-integral regulator, a series of control-in-the-loop CFD simulations demonstrates that lift oscillations are reduced by a factor of approximately six with the nonlinear controller in the loop. This reduction is maintained with and without measurement noise. With the linear output approximation in the loop, performance gradually deteriorates when there is no measurement noise and eventually fails entirely when noise is included in the measurement.

Few interpreters of Aristotle have denied that both empirical, inductive methods and some kind of systematic deduction played a role in the philosophy of the biologist who expounded the West's first formal logic. But it has usually been the fashion to focus on one side of this polarity. In recent decades the focus has been on the empirical Aristotle. But some of the latest studies emphasize that Aristotle varied his methods according to context. G. E. L. Owen, for example, although he feels that Aristotle took little care to separate inductive and deductive methods in the treatises, does allow that he uses deduction at times, and mentions book 6 of the Physics among them.

Article Resolving Parent-Daughter Mixtures of Radionuclides with Straight-Line Forms of Equations for Growth and Decay was published on May 1, 1965 in the journal Radiochimica Acta (volume 4, issue 1).