224 research outputs found
The Motion of Particles Caused by a Bubble in Gas-solid Fluidised Bed
The motion of particles caused by a single bubble which is blown into a two-dimensional fluidised bed has been studied. A drift line which is shown when a bubble has passed through the bed is obtained as a generalized curve. The experimental results can be explained fairly well by the authors' model. The model is as follows. 1. The motion of particles is assumed as the motion of perfect fluid caused by the motion of a circular cylinder in the perfect fluid. 2. There is an imaginary wall at the distance of the diameter of bubble below from the center of the moving bubble and it moves upwards with the same velocity as the bubble
Very Long Baseline Array Imaging of Parsec-scale Radio Emissions in Nearby Radio-quiet Narrow-line Seyfert 1 Galaxies
We conducted Very Long Baseline Array (VLBA) observations of seven nearby
narrow-line Seyfert 1 (NLS1) galaxies at 1.7 GHz (18cm) with milli-arcsecond
resolution. This is the first systematic very long baseline interferometry
(VLBI) study focusing on the central parsec-scale regions of radio-quiet NLS1s.
Five of the seven were detected at a brightness temperature of >~5x10^6 K and
contain radio cores with high brightness temperatures of >6x10^7 K, indicating
a nonthermal process driven by jet-producing central engines as is observed in
radio-loud NLS1s and other active galactic nucleus (AGN) classes. VLBA images
of MRK 1239, MRK 705, and MRK 766 exhibit parsec-scale jets with clear linear
structures. A large portion of the radio power comes from diffuse emission
components that are distributed within the nuclear regions (<~300 pc), which is
a common characteristic throughout the observed NLS1s. Jet kinetic powers
limited by the Eddington limit may be insufficient to allow the jets escape to
kiloparsec scales for these radio-quiet NLS1s with low-mass black holes of
<~10^7 M_sun.Comment: 12 pages, 3 figures, 3 tables, accepted for publication in Ap
Subsynchronous Shaft Vibration in an Integrally Geared Expander-Compressor due to Vortex Flow in an Expander
LecturesSubsynchronous shaft vibration was observed in an integrally
geared expander-compressor when the machine was operated
with a partial load in the course of plant start up. The root
cause of the synchronous shaft vibration was identified, by
means of CFD analysis, as the vortex flow which was
generated in the downstream piping of the gas expander
wheel.
OEM installed an object, called “vortex breaker”, in the piping
in order to eliminate the excitation force of the vortex flow,
and as the result, the subsynchronous shaft vibration
disappeared.
This paper provides the detailed shaft vibration data, root
cause analysis, countermeasure and the result from the
countermeasure
Fundamental Studies on Electron Beam Welding of Heat-resistant Superalloys for Nuclear Plants (Report II) : Correlation between Susceptibility to Weld Cracking and Characteristics in Hot Ductility and Trans-Varestraint Test
Fundamental Studies on Electron Beam Welding of Heat-resistant Superalloys for Nuclear Plants (Report I) : Effect of Welding Conditions on Some Characteristics of Weld Bead
Behaviours of Bubbles in the Gas-Solid Fluidized-Beds
The size, shape and rising velocity of bubbles and also particle concentration in bubbles which appeared in the air-solid fluidized bed were investigated by photography, X-ray photograpy, X-ray cinematography and capacitance method. The results were that the bubbles had nearly the shape of spherical cap and there were few particles in the bubbles. Although the rising velocity of the bubble was affected largely by other bubbles, it was proportional to the square root of the vertical bubble length and the bubbles became large with the process of repetition of coalescence and redispersion
High-Sensitivity 86GHz (3.5mm) VLBI Observations of M87: Deep Imaging of the Jet Base at a 10 Schwarzschild-Radius Resolution
We report on results from new high-sensitivity, high-resolution 86GHz (3.5
millimeter) observations of the jet base in the nearby radio galaxy M87,
obtained by the Very Long Baseline Array in conjunction with the Green Bank
Telescope. The resulting image has a dynamic range exceeding 1500 to 1, the
highest ever achieved for this jet at this frequency, resolving and imaging a
detailed jet formation/collimation structure down to ~10 Schwarzschild radii
(Rs). The obtained 86GHz image clearly confirms some important jet features
known at lower frequencies, i.e., a wide-opening angle jet base, a
limb-brightened intensity profile, a parabola-shape collimation profile and a
counter jet. The limb-brightened structure is already well developed at <
0.2mas (< 28Rs, projected) from the core, where the corresponding apparent
opening angle becomes as wide as ~100 degrees. The subsequent jet collimation
near the black hole evolves in a complicated manner; there is a "constricted"
structure at tens Rs from the core, where the jet cross section is locally
shrinking. We suggest that an external pressure support from the inner part of
radiatively-inefficient accretion flow may be dynamically important in
shaping/confining the footprint of the magnetized jet. We also present the
first VLBI 86GHz polarimetric experiment for this source, where a highly
polarized (~20%) feature is detected near the jet base, indicating the presence
of a well-ordered magnetic field. As a by-product, we additionally report a
43/86 GHz polarimetric result for our calibrator 3C 273 suggesting an extreme
rotation measure near the core.Comment: Accepted for publication in ApJ. 39 pages, 11 figures, 3 table
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