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Your search keyword '"Fresconi, Frank E"' showing total 7 results
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7 results on '"Fresconi, Frank E"'

2. Secondary velocity fields in the conducting airways of the human lung

Author

Fresconi, Frank E. and Prasad, Ajay K.

Subjects
Airway (Medicine) -- Evaluation, Bifurcation theory -- Research, Drug delivery devices -- Design and construction, Lungs -- Properties, Engineering and manufacturing industries, Science and technology
Abstract

An understanding of flow and dispersion in the human respiratory airways is necessary to assess the toxicological impact of inhaled particulate matter as well as to optimize the design of inhalable pharmaceutical aerosols and their delivery systems. Secondary flows affect dispersion in the lung by mixing solute in the lumen cross section. The goal of this study is to measure and interpret these secondary velocity fields using in vitro lung models. Particle image velocimetry experiments were conducted in a three-generational, anatomically accurate model of the conducting region of the lung. Inspiration and expiration flows were examined under steady and oscillatory flow conditions. Results illustrate secondary flow fields as a function of flow direction, Reynolds number, axial location with respect to the bifurcation junction, generation, branch, phase in the oscillatory cycle, and Womersley number. Critical Dean number for the formation of secondary vortices in the airways, as well as the strength and development length of secondary flow, is characterized. The normalized secondary velocity magnitude was similar on inspiration and expiration and did not vary appreciably with generation or branch. Oscillatory flow fields were not significantly different from corresponding steady flow fields up to a Womersley number of 1 and no instabilities related to shear were detected on flow reversal. These observations were qualitatively interpreted with respect to the simple streaming, augmented dispersion, and steady streaming convective dispersion mechanisms. [DOI: 10.1115/1.2768374] Keywords: respiratory airway, bifurcation, lung flow, secondary velocity, aerosol transport, dispersion, drug delivery

Published
2007

4. Heuristic-Based Nuisance Parameter Estimation of Low-Cost Accelerometers for Guided Spin-Stabilized Projectiles

Author

ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE, Fairfax, Luisa D, Maley, James M, Fresconi, Frank E, ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE, Fairfax, Luisa D, Maley, James M, and Fresconi, Frank E

Abstract

Accelerometer measurement errors due to low-cost devices and minimal ground calibration significantly affect inertial navigation performance in a spin-stabilized projectile application. A method of compensating for these nuisance parameters is proposed that leverages the spin-stabilized projectile flight dynamics and sensor modeling in an extended Kalman filter. Nonlinear modeling and practical simplification of the in-flight measurements was undertaken. An estimator algorithm was designed and validated in simulation. Results illustrate the manner in which corrupted measurements are enhanced. Monte Carlo analysis suggests that the nuisance parameter estimation improves navigation accuracy by three orders of magnitude, and under certain conditions is sufficient to increase overall system precision over the ballistic performance for munitions in a global positioning system-denied environment., The original document contains color images.

Published
2013

5. Position Estimation for Projectiles Using Low-cost Sensors and Flight Dynamics

Author

ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE, Fairfax, Luisa D, Fresconi, Frank E, ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE, Fairfax, Luisa D, and Fresconi, Frank E

Abstract

Navigation of gun-launched precision munitions using affordable technologies is investigated. Estimation algorithms were developed to blend flight dynamic models with measurements from inertial sensors and, if available, global positioning system (GPS). The launch and flight characteristics of the unique, gun-launched environment were exploited both in the state estimator and for novel heuristic parameter identification. The algorithm included using low-cost inertial sensor arrays and general GPS availability. Experimental results from guided mortar flights indicate that the algorithm with only inertial sensor measurements yields position errors less than 40 m over a 30-s flight. Position errors from the experiments decrease slightly using loose coupling when GPS is available. Simulations were conducted to assess algorithm performance over a wider range of conditions. These results demonstrate that position errors are less than tens of meters for flight times of interest to munitions. Estimation is intolerant to inertial sensor errors due to the novel manner in which known flight dynamics are used to compensate measurements. Overall, this effort shows that navigation error resulting from a low throughput algorithm using affordable inertial sensors is sufficient to increase system accuracy for munitions, The original document contains color images.

Published
2012

7. Convective dispersion during steady flow in the conducting airways of the human lung

Author

Fresconi, Frank E. and Prasad, Ajay K.

Subjects
Air pollution -- Health aspects, Airway (Medicine) -- Properties, Lungs -- Properties, Gas flow -- Evaluation, Bifurcation theory -- Research, Drug delivery systems -- Design and construction, Drugs -- Vehicles, Drugs -- Design and construction, Engineering and manufacturing industries, Science and technology
Abstract

The adverse health effects of inhaled particulate matter from the environment depend on its dispersion, transport, and deposition in the human airways. Similarly, precise targeting of deposition sites by pulmonary drug delivery systems also relies on characterizing the dispersion and transport of therapeutic aerosols in the respiratory tract. A variety of mechanisms may contribute to convective dispersion in the lung; simple axial streaming, augmented dispersion, and steady streaming are investigated in this effort. Flow visualization of a bolus during inhalation and exhalation, and dispersion measurements were conducted during steady flow in a three-generational, anatomically accurate in vitro model of the conducting airways to support this goal. Control variables included Reynolds number, flow direction, generation, and branch. Experiments illustrate transport patterns in the lumen cross section and map their relation to dispersion metrics. These results indicate that simple axial streaming, rather than augmented dispersion, is the dominant steady convective dispersion mechanism in symmetric Weibel generations 7-13 during normal respiration. Experimental evidence supports the branching nature of the airways as a possible contributor to steady streaming in the lung. [DOI: 10.1115/1.2838042] Keywords: respiratory airway, bifurcation, secondary flow, aerosol transport, dispersion, drug delivery

Published
2008

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