3,963 research outputs found
Concentric differential gearing arrangement
Two input members and two concentric rotatable output members are interconnected by a planetary gear arrangement. The first input drives directly the first output. The second input engages a carrier having the planetary gears affixed thereto. Rotation of the carriage causes rotation of the central sun gear of the planetary gear system. The sun gear is journaled to the carriage and is drivingly connected to the second output through a direction reversing set of bevel gears. The first input drive member includes a ring gear drivingly connected to the planetary gears for driving the second output member in the same direction and by the same amount as the first output member. Motion of the first input results in equal motion of the two outputs while input motion of the second input results in movement of the second output relative to the first output. This device is useful where non-interacting two-axis control of remote gimbaled systems is required
Formaldehyde Silhouettes Against the Cosmic Microwave Background: A Mass-Limited, Distance-Independent, Extinction-Free Tracer of Star Formation Across the Epoch of Galaxy Evolution
We examine the absorption of cosmic microwave background (CMB) photons by
formaldehyde (H2CO) over cosmic time. The K-doublet rotational transitions of
H2CO become "refrigerated" - their excitation temperatures are driven below the
CMB temperature - via collisional pumping by molecular hydrogen (H2).
"Anti-inverted" H2CO line ratios thus provide an accurate measurement of the H2
density in molecular clouds. Using a radiative transfer model, we demonstrate
that H2CO centimeter wavelength line excitation and detectability are nearly
independent of redshift or gas kinetic temperature. Since the H2CO K-doublet
lines absorb CMB light, and since the CMB lies behind every galaxy and provides
an exceptionally uniform extended illumination source, H2CO is a
distance-independent, extinction-free molecular gas mass-limited tracer of
dense gas in galaxies. A Formaldehyde Deep Field could map the history of
cosmic star formation in a uniquely unbiased fashion and may be possible with
large bandwidth wide-field radio interferometers whereby the silhouettes of
star-forming galaxies would be detected across the epoch of galaxy evolution.
We also examine the possibility that H2CO lines may provide a standardizable
galaxy ruler for cosmology similar to the Sunyaev-Zel'dovich effect in galaxy
clusters but applicable to much higher redshifts and larger samples. Finally,
we explore how anti-inverted meterwave H2CO lines in galaxies during the peak
of cosmic star formation may contaminate HI 21 cm tomography of the Epoch of
Reionization.Comment: Accepted by ApJ Letters. 5 pages, 5 figure
Mechanical planetary compensating drive system
Drive enables two concentric output shafts to be controlled independently or rotated as a unit. Possible uses are pointing and tracking devices, rotary camera shutters with variable light control, gimbal systems with yaw and pitch movement, spectrometer mirror scanning devices, etc
SgpDec : Cascade (de)compositions of finite transformation semigroups and permutation groups
We describe how the SgpDec computer algebra package can be used for composing and decomposing permutation groups and transformation semigroups hierarchically by directly constructing substructures of wreath products, the so called cascade products.Final Accepted Versio
Cascade synthesis of finite-state machines
One can construct any finite-state machine as a cascade interconnection of machines whose inputs either permute the states or reset them all to one state. Each permutation group needed in the construction is a homomorphic image of a group generated by the action of a set of input sequences on a state subset of the original machine. Proofs of these facts will be given and their application to the Krohn-Rhodes theory described
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