Copyright (c) 2009 All rights reserved. http://works.bepress.com/wdurgin Recent documents in William W. Durgin en-us Mon, 05 Jan 2009 15:02:19 PST 3600 http://works.bepress.com/wdurgin/65 http://works.bepress.com/wdurgin/65 Fri, 19 Dec 2008 08:37:51 PST This paper concerns an experimental study of the effects of the grid-generated turbulence on the propagation of acoustical waves in a wind tunnel. Turbulence effects are investigated using ultrasound time-of-flight method, employing counter-propagating ultrasonic pulses. Turbulence effects are an important source of error in the active probing of the atmosphere using sound sources. The emphasis is on the propagation time fluctuations and their interpretation using theoretical analysis of Kolmogorov. Tatiana A. Andreeva Research http://works.bepress.com/wdurgin/64 http://works.bepress.com/wdurgin/64 Wed, 22 Oct 2008 12:47:56 PDT This paper describes the experimental proof of concept study for an ultrasonic method of wake vortex detection. This new acoustic method uses travel time of acoustic pulses around a closed path to measure the net circulation within the acoustic path. In this application the closed path encloses the vorticity shed from one side of a Piper PA-28 aircraft wing. Magnitude and sign of circulation detected is comparable to the expected circulation generated by the Piper PA-28 test aircraft. This study demonstrates the validity of the acoustic method in detecting aircraft wake vortices. Further investigations and applications using this technique are discussed. Rebecca J. Rodenhiser Research http://works.bepress.com/wdurgin/63 http://works.bepress.com/wdurgin/63 Wed, 22 Oct 2008 12:33:33 PDT WPI was one of four colleges and universities awarded NASA grants for student design and development of an improved glove for space suits. This paper traces the design, development and testing of the WPI prototype glove. Test results showed that the glove did not significantly limit hand and finger motion when pressurized at 8 psi, except in the spherical grip mode. This project demonstrated that problems originating from space technology provide excellent vehicles for student learning and can generate creative solutions. William W. Durgin Research http://works.bepress.com/wdurgin/62 http://works.bepress.com/wdurgin/62 Wed, 22 Oct 2008 12:32:54 PDT Lance Schachterle Engineering Education http://works.bepress.com/wdurgin/61 http://works.bepress.com/wdurgin/61 Wed, 22 Oct 2008 12:32:27 PDT In the present paper the eikonal equation is considered in the form of a second order, nonlinear ordinary differential equation with harmonic excitation due to internal wave. The harmonic excitation is taken imperfect, i.e. there is a random phase modulation due to Gaussian white noise. The amplitude and wavelength of the acoustic wave are used as the principle signal characteristics in bifurcation analysis. The regions of instability, identified using the bifurcation diagrams, examined through phase diagrams and Poincare maps. The effect of stochastic nature in addition to chaotic one of internal waves is demonstrated by means of comparison of the numerical data obtained for perfectly periodic excitation. Preliminary analysis shows very strong dependence on noise intensity at some values of amplitude and wave length of internal wave. Tatiana A. Andreeva Research http://works.bepress.com/wdurgin/60 http://works.bepress.com/wdurgin/60 Wed, 22 Oct 2008 12:32:07 PDT To develop a noninvasive method of detecting arterial occlusive disease, pulse waveforms were recorded at two locations on the lower extremities of young normal volunteers and patients with arteriographically confirmed arterial occlusive disease. Pulses were monitored using impedance plethysmography at the kneeˇ and the iliac regions. The frequency spectra of the abnormal iliac waveforms contained 4-5 harmonics as compared to the 2-3 harmonics present in normals'. It was hypothesized that the occurrence of high frequencies resulted from pulse wave interactions with diseased portions of the vessel. This paper will present the results of a theoretical and experimental model developed to test this hypothesis. Lauren I. Stratouly Research http://works.bepress.com/wdurgin/59 http://works.bepress.com/wdurgin/59 Wed, 22 Oct 2008 12:31:44 PDT A demonstration system for the ultrasonic gauging of fluids in low-gravity has been designed and tested. For purposes of simplification, it was assumed that vapor within a liquid container in low-gravity would form a spherical bubble which would float freely in the container. The project was designed to show that ultrasonic techniques could be used to determine the geometry of the resulting sphere given a worst-case transducer arrangement. The motivation was to simplify transducer mounting requirements so that propellant or other storage vessels could be fitted with ultrasonic gauging systems with a single or perhaps a few transducer penetrations. Data was collected from a planar array of transducers. The high error expected due to the low triangulation was reduced by maximizing the amount of data collected. This was accomplished using the transducers in both pulse/echo and pitch/catch operational modes. A. T. Patten Research http://works.bepress.com/wdurgin/58 http://works.bepress.com/wdurgin/58 Wed, 22 Oct 2008 12:31:25 PDT Flow past deep wall cavities exhibits strong interaction with the standing wave system in the cavity. The shear layer separating the exterior flow from the cavity flow supports instabilities which excite the normal cavity modes. In turn, the cavity wave system reinforces the instabilities. Experimental studies have shown that two distinct instability modes are encountered as the external velocity is increased. The pressure coefficient versus Strouha1 number behavior reveals two maxima which correspond to different instability modes of the shear layer. Flow visualization studies have shown that these modes correspond to distinct shear 1ayer vortex structures. At high velocities, single large-scale vortices are formed on the interface. At lower velocities, two vortices are present, simultaneously. D. D. Erickson Research http://works.bepress.com/wdurgin/57 http://works.bepress.com/wdurgin/57 Wed, 22 Oct 2008 12:31:05 PDT Elastic properties of major arteries were measured in vivo in ten normal volunteers, age 26 to 44 years (mean = 32 years). A B-mode ultrasound imager was used to noninvasively measure mean diameter and pulsatile diameter change at five locations along the main arteries in the abdomen and the lower extremities. Together with pulsatile pressure (measured by the auscultatory method), strain (ε), compliance (C) and the pressure-strain elastic modulus (Ep l/C) were calculated. Ep increased significantly along the arterial tree; mean values (x105 N/m-2 ) were: 0.99 aorta, 1.21 common iliac artery (CIA), 1.43 common femoral artery (CFA), 1.57 superficial femoral artery (SFA), and 1.56 popliteal (POP) artery. Lauren I. Stratouly Research http://works.bepress.com/wdurgin/56 http://works.bepress.com/wdurgin/56 Fri, 17 Oct 2008 16:28:45 PDT In some nuclear reactor containment isolation applications, butterfly valves with pneumatic actuators are used to close pipelines in the event of containment pressure transients resulting from postulated accidents. A model is developed which predicts the closure time history of such valve/actuator systems under prescribed transients. Examples are presented which show the importance of the valve and actuator characteristics. It was found that actuation delays of sufficient magnitude could allow the dynamic torque to exceed the available actuator torque, thus preventing valve closure. William W. Durgin Research