Gregory Ojakangas | Drury University (original) (raw)
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Papers by Gregory Ojakangas
An analytic description of debris cloud evolution starting from the equations of motion
Results are presented of computations for a versatile model of the debris cloud evolution. The ev... more Results are presented of computations for a versatile model of the debris cloud evolution. The evolution of a debris cloud is described using an approach in which the equations of motion of particles in a cloud are solved collectively. The resulting system of time-varying orbital elements is transformed into an analytical expression of spatial density as a function of time
Episodic Heatflow in Tidally Heated Satellites
Effect of Elastic Strain Energy on Polar Wander
Thickness and Polar Wander of an Ice Shell on Europa
Viscosity and Mass Transport in Keplerian Disks with Radial Gradients in Surface Density
The Viscosity Formula for a Uniform Planetary Ring Also Applies if Optical Thickness Varies Radially
Photometry of Jovian Cloud Features
Miranda
Observed geology, photometry, and geophysical data are used to examine various processes and prop... more Observed geology, photometry, and geophysical data are used to examine various processes and properties that may have contributed to Maranda's evolution. Global tectonics and surface flow features constrain the possible heating mechanisms and materials. Statistics on impact craters and comparisons with other satellites suggest that the impactor-source population evolved through time and that ejecta mantling has resurfaced significant portions of
Two examples of planetary bodies that may have coupled thermal and dynamical evolutions are inves... more Two examples of planetary bodies that may have coupled thermal and dynamical evolutions are investigated. The work is presented in three individual papers. The first example is that of a tidally heated satellite in an orbital resonance, for which the tidal dissipation rate is a strongly increasing function of the internal temperature. For such a satellite, a feedback mechanism exists
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2009
In [1], the first footnote should have included the following sentence. The first two authors con... more In [1], the first footnote should have included the following sentence. The first two authors contributed equally to this work.
Defining orbital debris environmental conditions for spacecraft vulnerability assessment
Journal of Spacecraft and Rockets, 1992
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2009
Although most brain-machine interface (BMI) studies have focused on decoding kinematic parameters... more Although most brain-machine interface (BMI) studies have focused on decoding kinematic parameters of motion such as hand position and velocity, it is known that motor cortical activity also correlates with kinetic signals, including active hand force and joint torque. Here, we attempted to reconstruct torque trajectories of the shoulder and elbow joints from the activity of simultaneously recorded units in
Solid-rocket-motor contribution to large-particle orbital debris population
Journal of Spacecraft and Rockets, 1996
An analytic description of debris cloud evolution starting from the equations of motion
Space Programs and Technologies Conference, 1990
ABSTRACT Results are presented of computations for a versatile model of the debris cloud evolutio... more ABSTRACT Results are presented of computations for a versatile model of the debris cloud evolution. The evolution of a debris cloud is described using an approach in which the equations of motion of particles in a cloud are solved collectively. The resulting system of time-varying orbital elements is transformed into an analytical expression of spatial density as a function of time and altitude.
Orbital debris environment
Space Programs and Technologies Conference, 1990
Specimens of siltstone beds from a roadcut in the lower member of the ~1.9 Ga Pokegama Formation ... more Specimens of siltstone beds from a roadcut in the lower member of the ~1.9 Ga Pokegama Formation at the village of Midway near Virginia, Minnesota contain laminae that record possible neap-spring cycles and a strong diurnal inequality. These laminae provide support for the tidal origin of the formation proposed by R. Ojakangas (1983) on the basis of other sedimentary structures. In order to enhance observed cyclicities in the presence of significant diagenetic alteration, a new algorithm was developed that transforms digital images of lamina sequences to horizontal uniformity, and then averages them horizontally to reduce noise and enhance lamina boundaries. Although too short and noisy to provide results of appreciable confidence, spectral analysis of a lamina sequence from the Pokegama Formation suggests minimum values for the lunar orbit radius (greater than 30 earth radii) and length of day (greater than 10 hours) at the time of deposition, consistent with theoretical expectatio...
An analytic description of debris cloud evolution starting from the equations of motion
Results are presented of computations for a versatile model of the debris cloud evolution. The ev... more Results are presented of computations for a versatile model of the debris cloud evolution. The evolution of a debris cloud is described using an approach in which the equations of motion of particles in a cloud are solved collectively. The resulting system of time-varying orbital elements is transformed into an analytical expression of spatial density as a function of time
Episodic Heatflow in Tidally Heated Satellites
Effect of Elastic Strain Energy on Polar Wander
Thickness and Polar Wander of an Ice Shell on Europa
Viscosity and Mass Transport in Keplerian Disks with Radial Gradients in Surface Density
The Viscosity Formula for a Uniform Planetary Ring Also Applies if Optical Thickness Varies Radially
Photometry of Jovian Cloud Features
Miranda
Observed geology, photometry, and geophysical data are used to examine various processes and prop... more Observed geology, photometry, and geophysical data are used to examine various processes and properties that may have contributed to Maranda's evolution. Global tectonics and surface flow features constrain the possible heating mechanisms and materials. Statistics on impact craters and comparisons with other satellites suggest that the impactor-source population evolved through time and that ejecta mantling has resurfaced significant portions of
Two examples of planetary bodies that may have coupled thermal and dynamical evolutions are inves... more Two examples of planetary bodies that may have coupled thermal and dynamical evolutions are investigated. The work is presented in three individual papers. The first example is that of a tidally heated satellite in an orbital resonance, for which the tidal dissipation rate is a strongly increasing function of the internal temperature. For such a satellite, a feedback mechanism exists
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2009
In [1], the first footnote should have included the following sentence. The first two authors con... more In [1], the first footnote should have included the following sentence. The first two authors contributed equally to this work.
Defining orbital debris environmental conditions for spacecraft vulnerability assessment
Journal of Spacecraft and Rockets, 1992
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2009
Although most brain-machine interface (BMI) studies have focused on decoding kinematic parameters... more Although most brain-machine interface (BMI) studies have focused on decoding kinematic parameters of motion such as hand position and velocity, it is known that motor cortical activity also correlates with kinetic signals, including active hand force and joint torque. Here, we attempted to reconstruct torque trajectories of the shoulder and elbow joints from the activity of simultaneously recorded units in
Solid-rocket-motor contribution to large-particle orbital debris population
Journal of Spacecraft and Rockets, 1996
An analytic description of debris cloud evolution starting from the equations of motion
Space Programs and Technologies Conference, 1990
ABSTRACT Results are presented of computations for a versatile model of the debris cloud evolutio... more ABSTRACT Results are presented of computations for a versatile model of the debris cloud evolution. The evolution of a debris cloud is described using an approach in which the equations of motion of particles in a cloud are solved collectively. The resulting system of time-varying orbital elements is transformed into an analytical expression of spatial density as a function of time and altitude.
Orbital debris environment
Space Programs and Technologies Conference, 1990
Specimens of siltstone beds from a roadcut in the lower member of the ~1.9 Ga Pokegama Formation ... more Specimens of siltstone beds from a roadcut in the lower member of the ~1.9 Ga Pokegama Formation at the village of Midway near Virginia, Minnesota contain laminae that record possible neap-spring cycles and a strong diurnal inequality. These laminae provide support for the tidal origin of the formation proposed by R. Ojakangas (1983) on the basis of other sedimentary structures. In order to enhance observed cyclicities in the presence of significant diagenetic alteration, a new algorithm was developed that transforms digital images of lamina sequences to horizontal uniformity, and then averages them horizontally to reduce noise and enhance lamina boundaries. Although too short and noisy to provide results of appreciable confidence, spectral analysis of a lamina sequence from the Pokegama Formation suggests minimum values for the lunar orbit radius (greater than 30 earth radii) and length of day (greater than 10 hours) at the time of deposition, consistent with theoretical expectatio...