4,327 research outputs found
The mechanical design of a vapor compressor for a heat pump to be used in space
A heat pump developed for use in Spacelab as a stand-alone refrigeration unit as well as within a fluid loop system is discussed. It will provide an active thermal control for payloads. Specifications for the heat pump were established: (1) heat removal rates at the source; (2) heat source temperatures from room temperature; (3) heat-sink fluid temperatures at condenser inlet; and (4) minimum power consumption. A reversed Carnot cycle heat pump using Freon 12 as working fluid incorporating a one-cylinder reciprocating compressor was selected. The maximum crankshaft speed was fixed relatively high at 100 rpm. The specified cooling rates then made it necessary to select a cylinder volume of 10 cu cm, which was obtained with a bore of 40 mm and a stroke of 8 mm
Approach to a rational rotation number in a piecewise isometric system
We study a parametric family of piecewise rotations of the torus, in the
limit in which the rotation number approaches the rational value 1/4. There is
a region of positive measure where the discontinuity set becomes dense in the
limit; we prove that in this region the area occupied by stable periodic orbits
remains positive. The main device is the construction of an induced map on a
domain with vanishing measure; this map is the product of two involutions, and
each involution preserves all its atoms. Dynamically, the composition of these
involutions represents linking together two sector maps; this dynamical system
features an orderly array of stable periodic orbits having a smooth parameter
dependence, plus irregular contributions which become negligible in the limit.Comment: LaTeX, 57 pages with 13 figure
Solidifying system of democracy in the Central and Eastern European new EU members
The paper examines the requirements of an effective and legitimized democratic political system in the process of transition. The analysis and the conclusions are based on the Hungarian experience, which can carefully be applied to all Central and Eastern European (CEE) countries. Special focus is given to the relationship of legal certainty and the efficiency of the democratic system, to the tension between legalism and managerialism and to the characteristics of civil society organizations. In the conclusion special features of the transitional countries are pointed out
Blip glitches in Advanced LIGO data
Blip glitches are short noise transients present in data from ground-based
gravitational-wave observatories. These glitches resemble the
gravitational-wave signature of massive binary black hole mergers. Hence, the
sensitivity of transient gravitational-wave searches to such high-mass systems
and other potential short duration sources is degraded by the presence of blip
glitches. The origin and rate of occurrence of this type of glitch have been
largely unknown. In this paper we explore the population of blip glitches in
Advanced LIGO during its first and second observing runs. On average, we find
that Advanced LIGO data contains approximately two blip glitches per hour of
data. We identify four subsets of blip glitches correlated with detector
auxiliary or environmental sensor channels, however the physical causes of the
majority of blips remain unclear
Discretized rotation has infinitely many periodic orbits
For a fixed k in (-2,2), the discretized rotation on Z^2 is defined by
(x,y)->(y,-[x+ky]). We prove that this dynamics has infinitely many periodic
orbits.Comment: Revised after referee reports, and added a quantitative statemen
Very Extended X-ray and H-alpha Emission in M82: Implications for the Superwind Phenomenon
We discuss the properties and implications of a 3.7x0.9 kpc region of
spatially-coincident X-ray and H-alpha emission about 11.6 kpc to the north of
the galaxy M82 previously discussed by Devine and Bally (1999). The PSPC X-ray
spectrum is fit by thermal plasma (kT=0.80+-0.17 keV) absorbed by only the
Galactic foreground column density. We evaluate the relationship of the
X-ray/H-alpha ridge to the M82 superwind. The main properties of the X-ray
emission can all be explained as being due to shock-heating driven as the
superwind encounters a massive ionized cloud in the halo of M82. This encounter
drives a slow shock into the cloud, which contributes to the excitation of the
observed H-alpha emission. At the same time, a fast bow-shock develops in the
superwind just upstream of the cloud, and this produces the observed X-ray
emission. This interpretation would imply that the superwind has an outflow
speed of roughly 800 km/s, consistent with indirect estimates based on its
general X-ray properties and the kinematics of the inner kpc-scale region of
H-alpha filaments. The gas in the M82 ridge is roughly two orders-of-magnitude
hotter than the minimum "escape temperature" at this radius, so this gas will
not be retained by M82.
(abridged)Comment: 24 pages (latex), 3 figures (2 gif files and one postscript),
accepted for publication in Part 1 of The Astrophysical Journa
Gravitational waves from Sco X-1: A comparison of search methods and prospects for detection with advanced detectors
The low-mass X-ray binary Scorpius X-1 (Sco X-1) is potentially the most
luminous source of continuous gravitational-wave radiation for interferometers
such as LIGO and Virgo. For low-mass X-ray binaries this radiation would be
sustained by active accretion of matter from its binary companion. With the
Advanced Detector Era fast approaching, work is underway to develop an array of
robust tools for maximizing the science and detection potential of Sco X-1. We
describe the plans and progress of a project designed to compare the numerous
independent search algorithms currently available. We employ a mock-data
challenge in which the search pipelines are tested for their relative
proficiencies in parameter estimation, computational efficiency, robust- ness,
and most importantly, search sensitivity. The mock-data challenge data contains
an ensemble of 50 Scorpius X-1 (Sco X-1) type signals, simulated within a
frequency band of 50-1500 Hz. Simulated detector noise was generated assuming
the expected best strain sensitivity of Advanced LIGO and Advanced VIRGO ( Hz). A distribution of signal amplitudes was then
chosen so as to allow a useful comparison of search methodologies. A factor of
2 in strain separates the quietest detected signal, at
strain, from the torque-balance limit at a spin frequency of 300 Hz, although
this limit could range from (25 Hz) to (750 Hz) depending on the unknown frequency of Sco X-1. With future
improvements to the search algorithms and using advanced detector data, our
expectations for probing below the theoretical torque-balance strain limit are
optimistic.Comment: 33 pages, 11 figure
Diet and Foraging Behaviors of Timber Rattlesnakes, Crotalus horridus, in Eastern Virginia
During a 17-yr telemetry study, we examined the diet and ambush behavior of a population of Crotalus horridus in southeastern Virginia. Forty dietary items were identified from 37 fecal samples. We documented 722 instances of snakes in an ambush posture, 61 of which were in a vertical-tree posture, as if hunting arboreal prey at the base of a tree. The most common prey items were Eastern Gray Squirrels (Sciurus carolinensis), which accounted for 45 of all dietary items and represented an estimated 78 of total biomass consumed by C. horridus. Prey was not consumed in proportion to availability, based on small mammal surveys. Our analysis provides indirect evidence that the vertical-tree foraging behavior is adopted to target arboreal Eastern Gray Squirrels. Further, we provide support for the hypothesis that C. horridus alters ambush behavior to forage selectively for specific prey types
On the Brightness and Waiting-time Distributions of a Type III Radio Storm observed by STEREO/WAVES
Type III solar radio storms, observed at frequencies below approximately 16
MHz by space borne radio experiments, correspond to the quasi-continuous,
bursty emission of electron beams onto open field lines above active regions.
The mechanisms by which a storm can persist in some cases for more than a solar
rotation whilst exhibiting considerable radio activity are poorly understood.
To address this issue, the statistical properties of a type III storm observed
by the STEREO/WAVES radio experiment are presented, examining both the
brightness distribution and (for the first time) the waiting-time distribution.
Single power law behavior is observed in the number distribution as a function
of brightness; the power law index is approximately 2.1 and is largely
independent of frequency. The waiting-time distribution is found to be
consistent with a piecewise-constant Poisson process. This indicates that
during the storm individual type III bursts occur independently and suggests
that the storm dynamics are consistent with avalanche type behavior in the
underlying active region.Comment: 14 pages, 4 figures, 1 table. Accepted for publication in
Astrophysical Journal Letter
Diet and Foraging Behaviors of Timber Rattlesnakes, \u3ci\u3eCrotalus Horridus\u3c/i\u3e, in Eastern Virginia
During a 17-yr telemetry study, we examined the diet and ambush behavior of a population of Crotalus horridus in southeastern Virginia. Forty dietary items were identified from 37 fecal samples. We documented 722 instances of snakes in an ambush posture, 61% of which were in a vertical-tree posture, as if hunting arboreal prey at the base of a tree. The most common prey items were Eastern Gray Squirrels (Sciurus carolinensis), which accounted for 45% of all dietary items and represented an estimated 78% of total biomass consumed by C. horridus. Prey was not consumed in proportion to availability, based on small mammal surveys. Our analysis provides indirect evidence that the vertical-tree foraging behavior is adopted to target arboreal Eastern Gray Squirrels. Further, we provide support for the hypothesis that C. horridus alters ambush behavior to forage selectively for specific prey types
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