Determination of lubricant selection based on elastohydrodynamic film thickness and traction measurement

The project was conducted to aid in the development of an elastohydrodynamic specification for military lubricants. Experiments were conducted with a rolling disk apparatus designed to simulate a bearing or gear type contact. Measurements included lubricant film thickness, lubricant breakdown and traction for a range of loads, speeds, temperatures, and surface roughnesses. Several lubricants were used in the investigations including a traction fluid, two synthetic paraffinic lubricants and several lubricants conforming to MIL-L 7808 and 23699 specifications. Recommendations regarding an EHD specification are included

Algebraic Methods for Finite Linear Cellular Automata

PhDCellular automata are a simple class of extended dynamical systems which have been much studied in recent years. Linear cellular automata are the class of cellular automata most amenable to algebraic analytic treatments, algebraic techniques are used to study finite linear cellular automata and also finite linear cellular automata with external inputs. General results are developed for state alphabet a finite commutative ring and a notion of qualitative dynamical similarity is introduced for those systems consisting of a fixed linear cellular automata rule but with distinct time independent inputs. Sufficient conditions for qualitative dynamical similarity are obtained in the general case. Exact results are obtained for the case of state alphabet a finite field, including new results for finite linear cellular automata without inputs and a complete description of the behaviour of the corresponding system with time independent inputs. Necessary and sufficient conditions for qualitative dynamical similarity in this case are given. Results for the hitherto untreated case of state alphabet the integers modulo pk, p prime and k>1, are obtained from those for the finite field case by the technique of idempotent lifting. These two cases suffice for the treatment of the general case of st, ),t e alphabet the integers modulo any positive integer m>1, in particular a necessary and sufficient condition for qualitatively similar dynamics in the presence of time independent inputs is given for this case. The extension of the results for time independent inputs to the case of periodic and eventually periodic inputs is treated and the generalisation of the techniques developed to higher dimensional linear cellular automata is discussed

Hearing in the Juvenile Green Sea Turtle (Chelonia mydas): A Comparison of Underwater and Aerial Hearing Using Auditory Evoked Potentials

Sea turtles spend much of their life in aquatic environments, but critical portions of their life cycle, such as nesting and hatching, occur in terrestrial environments, suggesting that it may be important for them to detect sounds in both air and water. In this study we compared underwater and aerial hearing sensitivities in five juvenile green sea turtles (Chelonia mydas) by measuring auditory evoked potential responses to tone pip stimuli. Green sea turtles detected acoustic stimuli in both media, responding to underwater stimuli between 50 and 1600 Hz and aerial stimuli between 50 and 800 Hz, with maximum sensitivity between 200 and 400 Hz underwater and 300 and 400 Hz in air. When underwater and aerial hearing sensitivities were compared in terms of pressure, green sea turtle aerial sound pressure thresholds were lower than underwater thresholds, however they detected a wider range of frequencies underwater. When thresholds were compared in terms of sound intensity, green sea turtle sound intensity level thresholds were 2–39 dB lower underwater particularly at frequencies below 400 Hz. Acoustic stimuli may provide important environmental cues for sea turtles. Further research is needed to determine how sea turtles behaviorally and physiologically respond to sounds in their environment