12,012 research outputs found
A study of the durability of beryllium rocket engines
An experimental test program was performed to demonstrate the durability of a beryllium INTEREGEN rocket engine when operating under conditions simulating the space shuttle reaction control system. A vibration simulator was exposed to the equivalent of 100 missions of X, Y, and Z axes random vibration to demonstrate the integrity of the recently developed injector-to-chamber braze joint. An off-limits engine was hot fired under extreme conditions of mixture ratio, chamber pressure, and orifice plugging. A durability engine was exposed to six environmental cycles interspersed with hot-fire tests without intermediate cleaning, service, or maintenance. Results from this program indicate the ability of the beryllium INTEREGEN engine concept to meet the operational requirements of the space shuttle reaction control system
Studies of Autumn calving suckler cows, bulls at pasture and winter grazing
End of project reportMost beef and dairy cows are spring calving leading to distinct seasonality of supply. Calving
a proportion of the beef herd in the autumn would lead to a more uniform annual supply of
cattle for slaughter and potentially increase the proportion of grazed grass in the diet of the
suckler progeny. Autumn calving sucklers also facilitate the use of AI, which should enhance
the product quality.
This project aimed to address the technical aspects of autumn calving sucklers, which differ
from those of spring calvers. The currently available international energy models were
evaluated for autumn calving lactating suckler cows using the type of cow typically found in
Irish suckler herds (Experiment 1). The winter accommodation of the suckler cow and calf
unit and its impact on cow reproductive performance was evaluated (Experiment 2).
The final part of the project evolved into component studies to determine the effect of
supplementary feed on the performance of grazing bulls (Experiment 3), and the
consequences of weanling cattle grazing pasture in winter as an alternative to housing them in winter (Experiments 4 to 7)
Field Emission for resonance sensing in MEMS/NEMS
In the past decades, there is a considerable interest in the sensor community to move from micron to nano-devices, typically scaling of resonators such as cantilever beams
Salt-gradient Solar Ponds: Summary of US Department of Energy Sponsored Research
The solar pond research program conducted by the United States Department of Energy was discontinued after 1983. This document summarizes the results of the program, reviews the state of the art, and identifies the remaining outstanding issues. Solar ponds is a generic term but, in the context of this report, the term solar pond refers specifically to saltgradient solar pond. Several small research solar ponds have been built and successfully tested. Procedures for filling the pond, maintaining the gradient, adjusting the zone boundaries, and extracting heat were developed. Theories and models were developed and verified. The major remaining unknowns or issues involve the physical behavior of large ponds; i.e., wind mixing of the surface, lateral range or reach of horizontally injected fluids, ground thermal losses, and gradient zone boundary erosion caused by pumping fluid for heat extraction. These issues cannot be scaled and must be studied in a large outdoor solar pond
Single shot measurement of a silicon single electron transistor
We have fabricated a custom cryogenic Complementary Metal-Oxide-Semiconductor
(CMOS) integrated circuit that has a higher measurement bandwidth compared with
conventional room temperature electronics. This allowed implementing single
shot operations and observe the real-time evolution of the current of a
phosphorous-doped silicon single electron transistor that was irradiated with a
microwave pulse. Relaxation times up to 90 us are observed, suggesting the
presence of well isolated electron excitations within the device. It is
expected that these are associated with long decoherence time and the device
may be suitable for quantum information processing
Life history differences across a latitudinal gradient in side-blotched lizards (Uta stansburiana)
Latitudinal variation has long been known to affect life history. Bergmann and Allen made latitudinal “rules” for mammalian anatomy and Lack, Skutch, and Moreau described differences in life history in birds. Trade-offs occur between important life history processes, like self maintenance (immunity) and other expensive but necessary processes. It is likely that trade-offs occur mostly when resources are limited. Side-blotched lizards have a wide geographic range, and more northerly lizards have been observed to have longer lifespans than their southern conspecifics. We hypothesized that northern sideblotched lizards would invest more energy into self-maintenance compared to shorter-lived southern animals
An Experimental Investigation of the Scaling of Columnar Joints
Columnar jointing is a fracture pattern common in igneous rocks in which
cracks self-organize into a roughly hexagonal arrangement, leaving behind an
ordered colonnade. We report observations of columnar jointing in a laboratory
analog system, desiccated corn starch slurries. Using measurements of moisture
density, evaporation rates, and fracture advance rates as evidence, we suggest
an advective-diffusive system is responsible for the rough scaling behavior of
columnar joints. This theory explains the order of magnitude difference in
scales between jointing in lavas and in starches. We investigated the scaling
of average columnar cross-sectional areas due to the evaporation rate, the
analog of the cooling rate of igneous columnar joints. We measured column areas
in experiments where the evaporation rate depended on lamp height and time, in
experiments where the evaporation rate was fixed using feedback methods, and in
experiments where gelatin was added to vary the rheology of the starch. Our
results suggest that the column area at a particular depth is related to both
the current conditions, and hysteretically to the geometry of the pattern at
previous depths. We argue that there exists a range of stable column scales
allowed for any particular evaporation rate.Comment: 12 pages, 11 figures, for supporting online movies, go to
http://www.physics.utoronto.ca/nonlinear/movies/starch_movies.htm
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