14,990 research outputs found
Instabilities of geared couplings: Theory and practice
The use of couplings for high speed turbocompressors or pumps is essential to transmit power from the driver. Typical couplings are either of the lubricated gear or dry diaphragm type design. Gear couplings have been the standard design for many years and recent advances in power and speed requirements have pushed the standard design criteria to the limit. Recent test stand and field data on continuous lube gear type couplings have forced a closer examination of design tolerances and concepts to avoid operational instabilities. Two types of mechanical instabilities are reviewed in this paper: (1) entrapped fluid, and (2) gear mesh instability resulting in spacer throw-out onset. Test stand results of these types of instabilities and other directly related problems are presented together with criteria for proper coupling design to avoid these conditions. An additional test case discussed shows the importance of proper material selection and processing and what can happen to an otherwise good design
The effect of support flexibility and damping on the dynamic response of a single mass flexible rotor in elastic bearings
The dynamic unabalance response and transient motion of the single mass Jeffcott rotor in elastic bearings mounted on damped, flexible supports are discussed. A steady state analysis of the shaft and the bearing housing motion was made by assuming synchronous precession of the system. The conditions under which the support system would act as a dynamic vibration absorber at the rotor critical speed were studied. Plots of the rotor and support amplitudes, phase angles, and forces transmitted were evaluated by the computer and the performance curves were plotted by an automatic plotter unit. Curves are presented on the optimization of the support housing characteristics of attenuate the rotor synchronous unbalance response
Geological and geothermal investigations for HCMM-derived data
An attempt was made to match HCMM- and U2HCMR-derived temperature data over two test sites of very local size to similar data collected in the field at nearly the same times. Results indicate that HCMM investigations using resolutions cells of 500 m or so are best conducted with areally-extensive sites, rather than point observations. The excellent quality day-VIS imagery is particularly useful for lineament studies, as is the DELTA-T imagery. Attempts to register the ground observed temperatures (even for 0.5 sq mile targets) were unsuccessful due to excessive pixel-to-pixel noise on the HCMM data. Several computer models were explored and related to thermal parameter value changes with observed data. Unless quite complex models, with many parameters which can be observed (perhaps not even measured (perhaps not even measured) only under remote sensing conditions (e.g., roughness, wind shear, etc) are used, the model outputs do not match the observed data. Empirical relationship may be most readily studied
Rabies in Iowa and the Upper Midwest: What a Rural Practitioner Should Know
A thorough history of rabies in the United States has been written by Steele,1 who begins by writing that the first reference to rabies in the United States occurred, in dogs, in Virginia and North Carolina, in 1753 and 1762, respectively. An outbreak that occurred in Boston and other North American towns in 1768 is considered the first major epizootic in North America. Canine madness, as it was called, raged allover colonial North America throughout the late 1700\u27s. Rabies reappeared in the eastern US in 1810 and in Ohio assumed an epizootic character affecting dogs, foxes, and wolves. Steele goes on to report that, following the Civil War, rabies was widespread across most of the USA. Mad dogs were reported in many urban as well as rural areas. Sylvatic rabies was recognized in the eastern US in the 18th century, and in the 19th century the disease was seen in foxes throughout the eastern part of the country
Satellite data relay and platform locating in oceanography. Report of the In Situ Ocean Science Working Group
The present and future use of satellites to locate offshore platforms and relay data from in situ sensors to shore was examined. A system of the ARGOS type will satisfy the increasing demand for oceanographic information through data relay and platform location. The improved ship navigation provided by the Global Positioning System (GPS) will allow direct observation of currents from underway ships. Ocean systems are described and demand estimates on satellite systems are determined. The capabilities of the ARGOS system is assessed, including anticipated demand in the next decade
Direct observation of size scaling and elastic interaction between nano-scale defects in collision cascades
Using in-situ transmission electron microscopy, we have directly observed
nano-scale defects formed in ultra-high purity tungsten by low-dose high energy
self-ion irradiation at 30K. At cryogenic temperature lattice defects have
reduced mobility, so these microscope observations offer a window on the
initial, primary damage caused by individual collision cascade events. Electron
microscope images provide direct evidence for a power-law size distribution of
nano-scale defects formed in high-energy cascades, with an upper size limit
independent of the incident ion energy, as predicted by Sand et al. [Eur. Phys.
Lett., 103:46003, (2013)]. Furthermore, the analysis of pair distribution
functions of defects observed in the micrographs shows significant
intra-cascade spatial correlations consistent with strong elastic interaction
between the defects
Particle Acceleration at Relativistic Shocks
I review the current status of Fermi acceleration theory at relativistic
shocks. I first discuss the relativistic shock jump conditions, then describe
the non-relativistic Fermi mechanism and the differences introduced by
relativistic flows. I present numerical calculations of the accelerated
particle spectrum, and examine the maximum energy attainable by this process. I
briefly consider the minimum energy for Fermi acceleration, and a possible
electron pre-acceleration mechanism.Comment: 17 pages, 4 figures. To appear in "Relativistic Flows in
Astrophysics", A.W. Guthmann, M. Georganopoulos, A. Marcowith and K.
Manolokou, eds., Lecture Notes in Pysics, Springer Verla
Improving Language Model Prompting in Support of Semi-autonomous Task Learning
Language models (LLMs) offer potential as a source of knowledge for agents
that need to acquire new task competencies within a performance environment. We
describe efforts toward a novel agent capability that can construct cues (or
"prompts") that result in useful LLM responses for an agent learning a new
task. Importantly, responses must not only be "reasonable" (a measure used
commonly in research on knowledge extraction from LLMs) but also specific to
the agent's task context and in a form that the agent can interpret given its
native language capacities. We summarize a series of empirical investigations
of prompting strategies and evaluate responses against the goals of targeted
and actionable responses for task learning. Our results demonstrate that
actionable task knowledge can be obtained from LLMs in support of online agent
task learning.Comment: Submitted to ACS 202
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