38,744 research outputs found
Supercharged topping rocket propellant feed system
A rocket propellant feed system utilizing a bleed turbopump to supercharge a topping turbopump is presented. The bleed turbopump is of a low pressure type to meet the cavitation requirements imposed by the propellant storage tanks. The topping turbopump is of a high pressure type and develops 60 to 70 percent of the pressure rise in the propellant
Using Adobe Flash Lite on mobile phones for psychological research: reaction time measurement reliability and inter-device variability
Mobile telephones have significant potential for use in psychological research, possessing unique characteristics—not least their ubiquity—that may make them useful tools for psychologists. We examined whether it is possible to measure reaction times (RTs) accurately using Adobe Flash Lite on mobile phones. We ran simple and choice RT experiments on two widely available mobile phones, a Nokia 6110 Navigator and a Sony Ericsson W810i, using a wireless application protocol (WAP) connection to access the Internet from the devices. RTs were compared within subjects with those obtained using a Linux-based millisecond-accurate measurement system. Results show that measured RTs were significantly longer on mobile devices, and that overall RTs and distribution of RTs varied across device
Observation of a subgap density of states in superconductor-normal metal bilayers in the Cooper limit
We present transport and tunneling measurements of Pb-Ag bilayers with
thicknesses, and , that are much less than the superconducting
coherence length. The transition temperature, , and energy gap, ,
in the tunneling Density of States (DOS) decrease exponentially with
at fixed . Simultaneously, a DOS that increases linearly from the Fermi
energy grows and fills nearly 40% of the gap as is 1/10 of of bulk
Pb. This behavior suggests that a growing fraction of quasiparticles decouple
from the superconductor as goes to 0. The linear dependence is consistent
with the quasiparticles becoming trapped on integrable trajectories in the
metal layer.Comment: 5 pages and 4 figures. This version is just the same as the old
version except that we try to cut the unnecessary white space in the figures
and make the whole paper look more compac
The Measure Problem in Cosmology
The Hamiltonian structure of general relativity provides a natural canonical
measure on the space of all classical universes, i.e., the multiverse. We
review this construction and show how one can visualize the measure in terms of
a "magnetic flux" of solutions through phase space. Previous studies identified
a divergence in the measure, which we observe to be due to the dilatation
invariance of flat FRW universes. We show that the divergence is removed if we
identify universes which are so flat they cannot be observationally
distinguished. The resulting measure is independent of time and of the choice
of coordinates on the space of fields. We further show that, for some
quantities of interest, the measure is very insensitive to the details of how
the identification is made. One such quantity is the probability of inflation
in simple scalar field models. We find that, according to our implementation of
the canonical measure, the probability for N e-folds of inflation in
single-field, slow-roll models is suppressed by of order exp(-3N) and we
discuss the implications of this result.Comment: 22 pages, 6 figures. Revised version with clarifying remarks on
meaning of adopted measure, extra references and minor typographical
correction
Angular momentum of the electromagnetic field: the plane wave paradox resolved
The angular momentum of a classical electromagnetic plane wave of arbitrary
extent is predicted to be, on theoretical grounds, exactly zero. However,
finite sections of circularly polarized plane waves are found experimentally to
carry angular momentum and it is known that the contribution to the angular
momentum arises from the edges of the beam. A mathematical model is described
that gives a quantitative account of this effect and resolves the paradox.Comment: 12 pages, 1 figur
Human factors aspects of control room design: Guidelines and annotated bibliography
A human factors analysis of the workstation design for the Earth Radiation Budget Satellite mission operation room is discussed. The relevance of anthropometry, design rules, environmental design goals, and the social-psychological environment are discussed
A new capacitive sensor for displacement measurement in a surface force apparatus
We present a new capacitive sensor for displacement measurement in a Surface
Forces Apparatus (SFA) which allows dynamical measurements in the range of
0-100 Hz. This sensor measures the relative displacement between two
macroscopic opaque surfaces over periods of time ranging from milliseconds to
in principle an indefinite period, at a very low price and down to atomic
resolution. It consists of a plane capacitor, a high frequency oscillator, and
a high sensitivity frequency to voltage conversion. We use this sensor to study
the nanorheological properties of dodecane confined between glass surfaces.Comment: 7 pages, 8 figure
- …