Engineering topics
Publications and source records attributed to Yen, A..
The conventional explanations for the formation of ferric oxides on Mars involve weathering under aqueous conditions. Mineralogical evidence, however, however, does not support extensive, global alteration by liquid water. An alternative method for producing the ferric oxides is based upon oxidation of meteoritic iron either soon after the impact event or over geologic timescales under present Martian conditions.
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The Viking Landers were unable to detect evidence of Life on Mars but, instead, found a chemically reactive soil capable of decomposing organic molecules.
Here we present work which shows that superoxide radicals form on mineral grain surfaces upon exposure to a simulated martian environment and suggest that these species actively decompose organic structures.
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The density and composition of the martian atmosphere allow solar ultraviolet photons with wavelengths as short as 190 nanometers to reach the surface. We investigate the hypothesis that this UV radiation is capable of inducing the realese of water from iron oxyhydroxide minerals resulting in the formation of oxide phases.
The Mars Microprobe Mission will be the second of the New Millennium Program's technology development missions to planetary bodies. The mission consists of two penetrators that weigh 2.4 kg each and are being carried as a piggy back payload on the Mars Polar Lander cruise ring.
The role of water in the development of the martian surface remains a fundamental scientific question.
Oriented superconducting YBa2Cu3O7 thin films were deposited on yttria stabilized zirconia and SrTiO3 substrates by ion-beam sputtering of a nonstoichiometric oxide target. The films exhibited zero-resistance critical temperatures as high as 83.5 K without post-deposition anneals. Both the deposition rate and the c-lattice parameter data displayed two distinct regimes of dependence on the beam power of the ion source. Low-power sputtering yielded films with large c-dimensions and low Tc. Higher-power sputtering produced a continuous decrease in the c-lattice parameter and increase in critical temperature. Films having the smaller c-lattice parameters were Cu rich. The Cu content of films deposited at beam voltages of 800 V and above increased with increasing beam power.
A continuous-vorticity panel method is developed and utilized to predict the steady aerodynamic loads on lifting surfaces having sharp-edge separation. Triangular panels with linearly varying vorticity are used. The velocity field generated by an individual element is obtained in closed form. An optimization scheme is constructed for finding the vorticity at the nodes of the elements. The method is not restricted by aspect ratios, angles of attack, planforms, or camber. Rectangular and delta wings are presented as numerical examples. The numerical results are in good agreement with the experimental data for incompressible flows.