1,854 research outputs found
Turbulence in a gaseous hydrogen-liquid oxygen rocket combustion chamber
The intensity of turbulence and the Lagrangian correlation coefficient for a LOX-GH2 rocket combustion chamber was determined from experimental measurements of tracer gas diffusion. A combination of Taylor's turbulent diffusion theory and a numerical method for solving the conservation equations of fluid mechanics was used to calculate these quantities. Taylor's theory was extended to consider the inhomogeneity of the turbulence field in the axial direction of the combustion chamber, and an exponential function was used to represent the Lagrangian correlation coefficient. The results indicate that the value of the intensity of turbulence reaches a maximum of 14% at a location about 7" downstream from the injector. The Lagrangian correlation coefficient associated with this value is given by the above exponential expression where alpha = 10,000/sec
Experimental determination of turbulence in a GH2-GOX rocket combustion chamber
The intensity of turbulence and the Lagrangian correlation coefficient for a gaseous rocket combustion chamber have been determined from the experimental measurements of the tracer gas diffusion. A combination of Taylor's turbulent diffusion theory and Spalding's numerical method for solving the conservation equations of fluid mechanics was used to calculate these quantities. Taylor's theory was extended to consider the inhomogeneity of the turbulence field in the axial direction of the combustion chamber. An exponential function was used to represent the Lagrangian correlation coefficient. The results indicate that the maximum value of the intensity of turbulence is about 15% and the Lagrangian correlation coefficient drops to about 0.12 in one inch of the chamber length
Building a 3.5 m prototype interferometer for the Q & A vacuum birefringence experiment and high precision ellipsometry
We have built and tested a 3.5 m high-finesse Fabry-Perot prototype
inteferometer with a precision ellipsometer for the QED test and axion search
(Q & A) experiment. We use X-pendulum-double-pendulum suspension designs and
automatic control schemes developed by the gravitational-wave detection
community. Verdet constant and Cotton-Mouton constant of the air are measured
as a test. Double modulation with polarization modulation 100 Hz and
magnetic-field modulation 0.05 Hz gives 10^{-7} rad phase noise for a 44-minute
integration.Comment: This draft has been presented in the 5th Edoardo Amaldi Conference on
Gravitational Wave
Improved Simulation of the Mass Charging for ASTROD I
The electrostatic charging of the test mass in ASTROD I (Astrodynamical Space
Test of Relativity using Optical Devices I) mission can affect the quality of
the science data as a result of spurious Coulomb and Lorentz forces. To
estimate the size of the resultant disturbances, credible predictions of
charging rates and the charging noise are required. Using the GEANT4 software
toolkit, we present a detailed Monte Carlo simulation of the ASTROD I test mass
charging due to exposure of the spacecraft to galactic cosmic-ray (GCR) protons
and alpha particles (3He, 4He) in the space environment. A positive charging
rate of 33.3 e+/s at solar minimum is obtained. This figure reduces by 50% at
solar maximum. Based on this charging rate and factoring in the contribution of
minor cosmic-ray components, we calculate the acceleration noise and stiffness
associated with charging. We conclude that the acceleration noise arising from
Coulomb and Lorentz effects are well below the ASTROD I acceleration noise
limit at 0.1 mHz both at solar minimum and maximum. The coherent Fourier
components due to charging are investigated, it needs to be studied carefully
in order to ensure that these do not compromise the quality of science data in
the ASTROD I mission.Comment: 20 pages, 14 figures, submitted to International Journal of Modern
Physics
Identification of Non-unitary triplet pairing in a heavy Fermion superconductor UPt_3
A NMR experiment recently done by Tou et al. on a heavy Fermion
superconductor UPt is interpreted in terms of a non-unitary spin-triplet
pairing state which we have been advocating. The proposed state successfully
explains various aspects of the seemingly complicated Knight shift behaviors
probed for major orientations, including a remarkable d-vector rotation under
weak fields. This entitles UPt as the first example that a charged many
body system forms a spin-triplet odd-par ity pairing at low temperatures and
demonstrates unambiguously that the putative spin-orbit coupling in UPt is
weak.Comment: 4 pages, 2 eps figures, to be published in J. Phys. Soc. Jpn. 67
(1998) No.
Effect of Spin-Orbit Interaction in Spin-Triplet Superconductor: Structure of -vector and Anomalous O-NQR Relaxation in SrRuO
Supposing the spin-triplet superconducting state of SrRuO, the
spin-orbit (SO) coupling associated with relative motion in Cooper pairs is
calculated by extending the method for the dipole-dipole coupling given by
Leggett in the superfluid He. It is shown that the SO coupling works only
in the equal-spin pairing (ESP) state to make the pair angular momentum
and the pair spin angular momentum parallel with each other. The SO coupling gives rise to the internal
Josephson effect in a chiral ESP state as in superfluid A-phase of He with
a help of an additional anisotropy arising from SO coupling of atomic origin
which works to direct the {\bf d}-vector into -plane. This resolves the
problem of the anomalous relaxation of O-NQR and the structure of {\bf
d}-vector in SrRuO.Comment: Accepted for publication in J. Phys. Soc. Jpn. vol.79 (2010), No.2
(February issue); 18 pages, 2 figure
Thermal conductivity in B- and C- phase of UPt_3
Although the superconductivity in UPt_3 is one of the most well studied,
there are still lingering questions about the nodal directions in the B and C
phase in the presence of a magnetic field. Limiting ourselves to the low
temperature regime (T<<Delta(0)), we study the magnetothermal conductivity with
in semiclassical approximation using Volovik's approach. The angular dependence
of the magnetothermal conductivity for an arbitrary field direction should
clarify the nodal structure in UPt_3.Comment: 4 pages, 5 figure
ASTROD and ASTROD I -- Overview and Progress
In this paper, we present an overview of ASTROD (Astrodynamical Space Test of
Relativity using Optical Devices) and ASTROD I mission concepts and studies.
The missions employ deep-space laser ranging using drag-free spacecraft to map
the gravitational field in the solar-system. The solar-system gravitational
field is determined by three factors: the dynamic distribution of matter in the
solar system; the dynamic distribution of matter outside the solar system
(galactic, cosmological, etc.) and gravitational waves propagating through the
solar system. Different relativistic theories of gravity make different
predictions of the solar-system gravitational field. Hence, precise
measurements of the solar-system gravitational field test all these. The tests
and observations include: (i) a precise determination of the relativistic
parameters beta and gamma with 3-5 orders of magnitude improvement over
previous measurements; (ii) a 1-2 order of magnitude improvement in the
measurement of G-dot; (iii) a precise determination of any anomalous, constant
acceleration Aa directed towards the Sun; (iv) a measurement of solar angular
momentum via the Lense-Thirring effect; (v) the detection of solar g-mode
oscillations via their changing gravity field, thus, providing a new eye to see
inside the Sun; (vi) precise determination of the planetary orbit elements and
masses; (viii) better determination of the orbits and masses of major
asteroids; (ix) detection and observation of gravitational waves from massive
black holes and galactic binary stars in the frequency range 0.05 mHz to 5 mHz;
and (x) exploring background gravitational-waves.Comment: 17 pages, 6 figures, presented to The Third International ASTROD
Symposium on Laser Astrodynamics, Space Test of Relativity and
Gravitational-Wave Astronomy, Beijing, July 14-16, 2006; International
Journal of Modern Physics D, in press (2008
Josephson Current between Triplet and Singlet Superconductors
The Josephson effect between triplet and singlet superconductors is studied.
Josephson current can flow between triplet and singlet superconductors due to
the spin-orbit coupling in the spin-triplet superconductor but it is finite
only when triplet superconductor has , where and
are the perpendicular components of orbital angular momentum and spin angular
momentum of the triplet Cooper pairs, respectively. The recently observed
temperature and orientational dependence of the critical current through a
Josephson junction between UPt and Nb is investigated by considering a
non-unitary triplet state.Comment: 4 pages, no figure
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