Identification of XV-15 aeroelastic modes using frequency-domain methods

The XV-15 Tilt-Rotor wing has six major aeroelastic modes that are close in frequency. To precisely excite individual modes during flight test, dual flaperon exciters with automatic frequency-sweep controls were installed. The resulting structural data were analyzed in the frequency domain (Fourier transformed) with cross spectral and transfer function methods. Modal frequencies and damping were determined by performing curve fits to transfer function magnitude and phase data and to cross spectral magnitude data. Results are given for the XV-15 with its original metal rotor blades. Frequency and damping values are also compared with earlier predictions

Ariel - Volume 3 Number 2

Editors Richard J. Bonanno Robin A. Edwards Associate Editors Steven Ager Stephen Flynn Tom Williams Lay-out Editor Eugenia Miller Contributing Editors Paul Bialas Milton Packer Robert Breckenridge Lynne Porter Mark Pearlman Terry Burt Mike Leo Editors Emeritus Delvyn C. Case, Jr. Paul M. Fernhof

The Efficacy of Motor Imagery Training on Range of Motion, Pain and Function of Patients After Total Knee Replacement

The present study examined the potential of motor imagery training and investigated the role of motor imagery instructions (audio) to improve knee range of motion after a total knee replacement. The participants were randomly assigned to either an experimental motor imagery group (n=4) or a control group (n=6). Both groups performed specific exercises to improve their knee range of motion and strengthen their muscles. Participants in the Motor Imagery group performed a motor imagery training exercise for a knee flexion stretch on the stairs prior to performing the actual exercise. The motor imagery group demonstrated a significantly greater increase in knee range of motion when compared to the control group

Sensitivity and Estimation of Flying-Wing Aerodynamic, Propulsion, and Inertial Parameters Using Simulation

This paper explores the difficulties of aircraft system identification, specifically parameter estimation, for a rudderless aircraft. A white box method is used in conjunction with a nonlinear six degree-of-freedom aerodynamic model for the equations of motion in order to estimate 33 parameters that govern the aerodynamic, inertial, and propulsion forces within the mathematical model. The analysis is conducted in the time-domain of system identification. Additionally, all the parameters are estimated using a single flight rather than a series of shorter flights dedicated to estimating specific sets of parameters as is typically done. A final flight plan is developed with a mixture of lateral maneuvers interspersed throughout the flight to accentuate the significance of the lateral parameters during estimation. Certain parameters were ill-conditioned for parameter estimation using the mathematical model and final flight plan derived in this paper. The gradient-based optimization technique used in the estimation algorithm struggled to accurately estimate all 33 in a single flight due to the abundance of local minima within the solution space. The results of this work may provide a few insights for parameter estimation. First, to understand why system identification is performed the way it is currently done through multiple different flight maneuvers. Second, to gain some visual insight to the behavior of the nonlinear six degree-of-freedom aerodynamic model that describes the motion of fixed wing aircraft. This work may also be helpful in determining which parameters might likely be estimated together and which may struggle due to coupled dynamic relations within the mathematical model

Design of a vehicle based system to prevent ozone loss

Reduced quantities of ozone in the atmosphere allow greater levels of ultraviolet light (UV) radiation to reach the earth's surface. This is known to cause skin cancer and mutations. Chlorine liberated from Chlorofluorocarbons (CFC's) and natural sources initiate the destruction of stratospheric ozone through a free radical chain reaction. The project goals are to understand the processes which contribute to stratospheric ozone loss, examine ways to prevent ozone loss, and design a vehicle-based system to carry out the prevention scheme. The 1992/1993 design objectives were to accomplish the first two goals and define the requirements for an implementation vehicle to be designed in detail starting next year. Many different ozone intervention schemes have been proposed though few have been researched and none have been tested. A scheme proposed by R.J. Cicerone, Scott Elliot and R.P.Turco late in 1991 was selected because of its research support and economic feasibility. This scheme uses hydrocarbon injected into the Antarctic ozone hole to form stable compounds with free chlorine, thus reducing ozone depletion. Because most polar ozone depletion takes place during a 3-4 week period each year, the hydrocarbon must be injected during this time window. A study of the hydrocarbon injection requirements determined that 100 aircraft traveling Mach 2.4 at a maximum altitude of 66,000 ft. would provide the most economic approach to preventing ozone loss. Each aircraft would require an 8,000 nm. range and be able to carry 35,000 lbs. of propane. The propane would be stored in a three-tank high pressure system. Missions would be based from airport regions located in South America and Australia. To best provide the requirements of mission analysis, an aircraft with L/D(sub cruise) = 10.5, SFC = 0.65 (the faculty advisor suggested that this number is too low) and a 250,000 lb TOGW was selected as a baseline. Modularity and multi-role functionality were selected to be key design features. Modularity provides ease of turnaround for the down-time critical mission. Multi-role functionality allows the aircraft to be used beyond its design mission, perhaps as an High Speed Civil Transport (HSCT) or for high altitude research

Transmission of Vibrio cholerae Is Antagonized by Lytic Phage and Entry into the Aquatic Environment

Cholera outbreaks are proposed to propagate in explosive cycles powered by hyperinfectious Vibrio cholerae and quenched by lytic vibriophage. However, studies to elucidate how these factors affect transmission are lacking because the field experiments are almost intractable. One reason for this is that V. cholerae loses the ability to culture upon transfer to pond water. This phenotype is called the active but non-culturable state (ABNC; an alternative term is viable but non-culturable) because these cells maintain the capacity for metabolic activity. ABNC bacteria may serve as the environmental reservoir for outbreaks but rigorous animal studies to test this hypothesis have not been conducted. In this project, we wanted to determine the relevance of ABNC cells to transmission as well as the impact lytic phage have on V. cholerae as the bacteria enter the ABNC state. Rice-water stool that naturally harbored lytic phage or in vitro derived V. cholerae were incubated in a pond microcosm, and the culturability, infectious dose, and transcriptome were assayed over 24 h. The data show that the major contributors to infection are culturable V. cholerae and not ABNC cells. Phage did not affect colonization immediately after shedding from the patients because the phage titer was too low. However, V. cholerae failed to colonize the small intestine after 24 h of incubation in pond water—the point when the phage and ABNC cell titers were highest. The transcriptional analysis traced the transformation into the non-infectious ABNC state and supports models for the adaptation to nutrient poor aquatic environments. Phage had an undetectable impact on this adaptation. Taken together, the rise of ABNC cells and lytic phage blocked transmission. Thus, there is a fitness advantage if V. cholerae can make a rapid transfer to the next host before these negative selective pressures compound in the aquatic environment

Perioperative risk stratification in non cardiac surgery: role of pharmacological stress echocardiography

Perioperative ischemia is a frequent event in patients undergoing major non-cardiac vascular or general surgery. This is in agreement with clinical, pathophysiological, and epidemiological evidence and constitutes an additional diagnostic therapeutic factor in the assessment of these patients. Form a clinical standpoint, it is well known that multidistrict disease, especially at the coronary level, is a severe aggravation of the operative risk. From a pathophysiological point of view, however, surgery creates conditions able to unmask coronary artery disease. Prolonged hypotension, hemorrhages, and haemodynamic stresses caused by aortic clamping and unclamping during major vascular surgery are the most relevant factors endangering the coronary circulation with critical stenoses. From the epidemiological standpoint, coronary disease is known to be the leading cause of perioperative mortality and morbidity following vascular and general surgery: The diagnostic therapeutic corollary of these considerations is that coronary artery disease – and therefore the perioperative risk – in these patients has to be identified in an effective way preoperatively