12,718 research outputs found
Modal analysis of multistage gear systems coupled with gearbox vibrations
An analytical procedure to simulate vibrations in gear transmission systems is presented. This procedure couples the dynamics of the rotor-bearing gear system with the vibration in the gear box structure. The model synthesis method is used in solving the overall dynamics of the system, and a variable time-stepping integration scheme is used in evaluating the global transient vibration of the system. Locally each gear stage is modeled as a multimass rotor-bearing system using a discrete model. The modal characteristics are calculated using the matrix-transfer technique. The gearbox structure is represented by a finite element models, and modal parameters are solved by using NASTRAN. The rotor-gear stages are coupled through nonlinear compliance in the gear mesh while the gearbox structure is coupled through the bearing supports of the rotor system. Transient and steady state vibrations of the coupled system are examined in both time and frequency domains. A typical three-geared system is used as an example for demonstration of the developed procedure
Vibration signature analysis of multistage gear transmission
An analysis is presented for multistage multimesh gear transmission systems. The analysis predicts the overall system dynamics and the transmissibility to the gear box or the enclosed structure. The modal synthesis approach of the analysis treats the uncoupled lateral/torsional model characteristics of each stage or component independently. The vibration signature analysis evaluates the global dynamics coupling in the system. The method synthesizes the interaction of each modal component or stage with the nonlinear gear mesh dynamics and the modal support geometry characteristics. The analysis simulates transient and steady state vibration events to determine the resulting torque variations, speeds, changes, rotor imbalances, and support gear box motion excitations. A vibration signature analysis examines the overall dynamic characteristics of the system, and the individual model component responses. The gear box vibration analysis also examines the spectral characteristics of the support system
Dynamics of Multistage Gear Transmission with Effects of Gearbox Vibrations
A comprehensive approach is presented in analyzing the dynamic behavior of multistage gear transmission systems with the effects of gearbox induced vibrations and mass imbalances of the rotor. The modal method, with undamped frequencies and planar mode shapes, is used to reduce the degrees of freedom of the gear system for time-transient dynamic analysis. Both the lateral and torsional vibration modes of each rotor-bearing-gear stage as well as the interstage vibrational characteristics are coupled together through localized gear mesh tooth interactions. In addition, gearbox vibrations are also coupled to the rotor-bearing-gear system dynamics through bearing support forces between the rotor and the gearbox. Transient and steady state dynamics of lateral and torsional vibrations of the geared system are examined in both time and frequency domains to develop interpretations of the overall modal dynamic characteristics under various operating conditions. A typical three-stage geared system is used as an example. Effects of mass imbalance and gearbox vibrations on the system dynamic behavior are presented in terms of modal excitation functions for both lateral and torsional vibrations. Operational characteristics and conclusions are drawn from the results presented
CFD Simulations on the Heating Capability in a Human Nasal Cavity
The air conditioning capability of the nose is dependent on the nasal mucosal temperature and the airflow dynamics caused by the airway geometry. A computational model of a human nasal cavity obtained through CT scans was produced and CFD techniques were applied to study the effects of morphological differences in the left and right nasal cavity on the airflow and heat transfer of inhaled air. A laminar steady flow of 10L/min was applied and two inhalation conditions were investigated: normal conditions, 25°C, 35% relative humidity and cold dry air conditions, 12°C, 13% relative humidity. It was found that the frontal regions of the nasal cavity exhibited greater secondary cross flows compared to the middle and back regions. The left cavity in the front region had a smaller cross-sectional area compared to the right which allowed greater heating as the heat source from the wall was closer to the bulk flow regions. Additionally it was found that the residence time of the inhaled air was important for the heating ability in laminar flows
Cosmological constraints from Type I radio-loud quasars
We obtain a new sample of 1192 Type I quasars with the UV-optical, radio and
X-ray wavebands coverage by combining \citet{Huang2022} and other matching data
of SDSS-DR16 with FIRST, XMM-Newton, and Chandra Source Catalog, and a sample
of 407 flat-spectrum radio-loud quasars (FSRLQs) of blazars from the
Roma-BZCAT, which can be used to investigate their multi-band luminosity
correlations and measure the luminosity distances of these Type I radio-loud
quasars (RLQs) samples. We check the correlation between X-ray, UV-optical, and
radio luminosity for various groupings of radio-quiet quasars (RQQs) and RLQs
by parameterizing X-ray luminosity as a sole function of UV-optical or radio
luminosity and as a joint function of UV-optical radio luminosity, which also
can be employed to determine these cosmological distances. By Bayesian
information criterion (BIC), the data suggest that the X-ray luminosity of RQQs
is indirectly correlative with radio luminosity because of the connection
between UV-optical and radio luminosity. But for RLQs, the X-Ray luminosity is
directly related to radio luminosity, and the correlations between X-ray,
optical/UV, and radio luminosity increase with the ratio of monochromatic
luminosities logR. Meanwhile, we compare the results from RLQs with different
UV-optical power law index , the goodness of fit for RLQs with
seems to be better. Finally, we apply a combination of
Type I RLQs and SN Ia Pantheon to verify the nature of dark energy concerning
whether or not its density deviates from the constant, and give the statistical
results.Comment: arXiv admin note: text overlap with arXiv:2207.0839
Entangling two superconducting LC coherent modes via a superconducting flux qubit
Based on a pure solid-state device consisting of two superconducting LC
circuits coupled to a superconducting flux qubit, we propose in this paper that
the maximally entangled coherent states of the two LC modes can be generated
for arbitrary coherent states through flux qubit controls.Comment: 5 pages, 2 figure
Front Stability in Mean Field Models of Diffusion Limited Growth
We present calculations of the stability of planar fronts in two mean field
models of diffusion limited growth. The steady state solution for the front can
exist for a continuous family of velocities, we show that the selected velocity
is given by marginal stability theory. We find that naive mean field theory has
no instability to transverse perturbations, while a threshold mean field theory
has such a Mullins-Sekerka instability. These results place on firm theoretical
ground the observed lack of the dendritic morphology in naive mean field theory
and its presence in threshold models. The existence of a Mullins-Sekerka
instability is related to the behavior of the mean field theories in the
zero-undercooling limit.Comment: 26 pp. revtex, 7 uuencoded ps figures. submitted to PR
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