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Full-Text Articles in Mechanical Engineering

Detection Of Voids In Prestressed Concrete Bridges Using Thermal Imaging And Ground-Penetrating Radar, David G. Pollock, Kenneth J. Dupuis, Benjamin Lacour, Karl R. Olsen Dec 2008

Detection Of Voids In Prestressed Concrete Bridges Using Thermal Imaging And Ground-Penetrating Radar, David G. Pollock, Kenneth J. Dupuis, Benjamin Lacour, Karl R. Olsen

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

Thermal imaging and ground-penetrating radar was conducted on concrete specimens with simulated air voids. For the thermal imaging inspections, six concrete specimens were constructed during the month of June 2007 to simulate the walls of post-tensioned box girder bridges. The objective was to detect simulated air voids within grouted post-tensioning ducts, thus locating areas where the post-tensioning steel strands are vulnerable to corrosion. The most important deduction taken from these inspections was that PT-ducts and simulated voids were more detectable in the 20 cm (8 in.) thick specimens than in the 30 cm (12 in.) thick specimens. While inspections of ...


Predictive Control Of A Munition Using Low-Speed Linear Theory, Nathan Slegers Jan 2008

Predictive Control Of A Munition Using Low-Speed Linear Theory, Nathan Slegers

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

"Modified linear theory provides reasonable impact predictions at high speeds. However, for typical small UAS mission speeds, less than 20-m/s impact errors were substantial due to large angles of attack and pitch rates. Low-speed linear theory was developed by including higher-order terms involving w and q that modified linear theory neglects. As a result, the angle of attack, pitch, and yaw predictions are significantly improved, leading to accurate impact predictions even at very low speeds. A predictive control scheme was developed to reduce dispersion using control surfaces near the tail. The predictive controller uses low-speed linear theory to rapidly ...


The Role Of Diffusive Transport On Low And Intermediate Temperature Hydrocarbon Oxidation: Closed Reactor Experiments Using Equimolar N-Butane + Oxygen Premixtures At Reduced-Gravity, Howard Pearlman, Michael R. Foster Jan 2008

The Role Of Diffusive Transport On Low And Intermediate Temperature Hydrocarbon Oxidation: Closed Reactor Experiments Using Equimolar N-Butane + Oxygen Premixtures At Reduced-Gravity, Howard Pearlman, Michael R. Foster

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

Experiments were conducted in a closed, spherical reactor aboard NASA's KC-135 reduced-gravity aircraft using an equimolar n-C4H10 + 0 2 premixture ( Le = 1.3) at subatmospheric ยท pressures to compliment model predictions and further explore the reactive-diffusive structure of cool flames and ignitions. The pressure and radial temperature histories were recorded and analyzed for different initial conditions. In addition, the visible light emission from excited formaldehyde was recorded using an intensified video camera and was observed to be radially symmetric in all cases. Unexpectedly, however, the measured temperature distributions during (and after the passage of) the cool flames and ignitions were ...


The Role Of Diffusive Transport On Low And Intermediate Temperature Hydrocarbon Oxidation: Numerical Simulations Using The Wang-Mou Mechanism, Howard Pearlman, Michael R. Foster Jan 2008

The Role Of Diffusive Transport On Low And Intermediate Temperature Hydrocarbon Oxidation: Numerical Simulations Using The Wang-Mou Mechanism, Howard Pearlman, Michael R. Foster

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

The spatio-temporal temperature and species concentration distributions associated with low and intermediate temperature hydrocarbon oxidation are computed using a global thermo kinetic scheme augmented with diffusive transport. The scheme used for the computations was proposed by Wang and Mou and is extended to include diffusion of species and heat. The conservation equations for species and energy are then derived and solved for a one-dimensional and an axisymmetric, spherical domain for temperatures ranging from 540 to 660 Kat subatmospheric pressures. The predictions are then used to develop ignition diagrams for different Lewis ( Le) numbers. Increasing Le is found to promote oscillatory ...


Use Of Variable Incidence Angle For Glide Slope Control Of Autonomous Parafoils, Nathan Slegers, Eric Beyer, Mark Costello Jan 2008

Use Of Variable Incidence Angle For Glide Slope Control Of Autonomous Parafoils, Nathan Slegers, Eric Beyer, Mark Costello

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

Strictly speaking, most autonomous parafoil and payload systems possess only lateral control, achieved by right and left parafoil brake deflection. An innovative technique to achieve direct longitudinal control through incidence angle changes is reported. Addition of this extra control channel requires simple rigging changes and an additional servoactuator. The ability of incidence angle to alter the glide slope of a parafoil and payload aircraft is demonstrated through a flight-test program with a microparafoil system. Results from the flight-test program are synthesized and integrated into a six degree-of-freedom simulation. The simulation model is subsequently used to assess the utility of glide ...