1,274 research outputs found
Comparison of release torques of tightened bolts in vacuum and air
Various combinations of stainless steel, mild steel, and aluminum bolt-nut couples are tightened to 60 lb-ft in partial vacuum and in air. Results are given for tests with and without two lubricants /a fluorosilicone and a sodium silicate bonded dry-film/
Pulsar data analysis with PSRCHIVE
PSRCHIVE is an open-source, object-oriented, scientific data analysis
software library and application suite for pulsar astronomy. It implements an
extensive range of general-purpose algorithms for use in data calibration and
integration, statistical analysis and modeling, and visualisation. These are
utilised by a variety of applications specialised for tasks such as pulsar
timing, polarimetry, radio frequency interference mitigation, and pulse
variability studies. This paper presents a general overview of PSRCHIVE
functionality with some focus on the integrated interfaces developed for the
core applications.Comment: 21 pages, 5 figures; tutorial presented at IPTA 2010 meeting in
Leiden merged with talk presented at 2011 pulsar conference in Beijing;
includes further research and development on algorithms for RFI mitigation
and TOA bias correctio
Parameters affecting electrostatic cooling
A high voltage electrostatic field is discussed which enhances the rate of normal convective cooling. This cooling rate is a function of starting temperature and voltage applied, and an inverse function of atmospheric pressure or the heat capacity of the surrounding media. It appears that the cooling rate is also a function of current flow; however, additional work is needed to separate other variables from the effect of current flow. The maximum increase in heat loss over the normal convective cooling was approximately 0.167 C/sec (0.3 F/sec) at 316 C (600 F) and 20,000 V. From the data taken it is assumed that the addeded rate of cooling would be increased with higher temperatures and higher voltages. It appears that a high voltage field disrupts the molecular layer of air surrounding a hot body and increases the rate of convective cooling
Cyclic Spectral Analysis of Radio Pulsars
Cyclic spectral analysis is a signal processing technique designed to deal
with stochastic signals whose statistics vary periodically with time. Pulsar
radio emission is a textbook example of this signal class, known as
cyclostationary signals. In this paper, we discuss the application of cyclic
spectral analysis methods to pulsar data, and compare the results with the
traditional filterbank approaches used for almost all pulsar observations to
date. In contrast to standard methods, the cyclic spectrum preserves phase
information of the radio signal. This feature allows us to determine the
impulse response of the interstellar medium and the intrinsic, unscattered
pulse profile directly from a single observation. We illustrate these new
analysis techniques using real data from an observation of the millisecond
pulsar B1937+21.Comment: Accepted for publication in MNRA
Toward an understanding of short distance repulsions among baryons in QCD -- NBS wave functions and operator product expansion --
We report on our recent attempts to determine the short distance behaviors of
general 2-baryon and 3-baryon forces, which are defined from the
Nambu-Bethe-Salpeter(NBS) wave function, by using the operator product
expansion and a renormalization group analysis in QCD. We have found that the
repulsion at short distance increases as the number of valence quarks increases
or when the number of different flavors involved decreases. This global
tendency suggests a Pauli suppression principle among quark fields at work.Comment: 14 pages, add two exmples in sect.3.4, a version accepted for
Progress of Theoretical Physic
The Massive Pulsar PSR J1614-2230: Linking Quantum Chromodynamics, Gamma-ray Bursts, and Gravitational Wave Astronomy
The recent measurement of the Shapiro delay in the radio pulsar PSR
J1614-2230 yielded a mass of 1.97 +/- 0.04 M_sun, making it the most massive
pulsar known to date. Its mass is high enough that, even without an
accompanying measurement of the stellar radius, it has a strong impact on our
understanding of nuclear matter, gamma-ray bursts, and the generation of
gravitational waves from coalescing neutron stars. This single high mass value
indicates that a transition to quark matter in neutron-star cores can occur at
densities comparable to the nuclear saturation density only if the quarks are
strongly interacting and are color superconducting. We further show that a high
maximum neutron-star mass is required if short duration gamma-ray bursts are
powered by coalescing neutron stars and, therefore, this mechanism becomes
viable in the light of the recent measurement. Finally, we argue that the
low-frequency (<= 500 Hz) gravitational waves emitted during the final stages
of neutron-star coalescence encode the properties of the equation of state
because neutron stars consistent with this measurement cannot be centrally
condensed. This will facilitate the measurement of the neutron star equation of
state with Advanced LIGO/Virgo.Comment: Accepted for publication in ApJ
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