762 research outputs found
Mass and Mean Velocity Dispersion Relations for Supermassive Black Holes in Galactic Bulges
Growing evidence indicate supermassive black holes (SMBHs) in the mass range
of lurking in central bulges of many
galaxies. Extensive observations reveal fairly tight power laws of
versus the mean stellar velocity dispersion of the host bulge. The
dynamic evolution of a bulge and the formation of a central SMBH should be
physically linked by various observational clues. In this contribution, we
reproduce the empirical power laws based on a self-similar
general polytropic quasi-static bulge evolution and a sensible criterion of
forming a SMBH surrounding the central density singularity of a general
singular polytropic sphere (SPS) \cite{loujiang2008}. Other properties of host
bulges and central SMBHs are also examined. Based on our model, we discuss the
intrinsic scatter of the relation and a scenario for the
evolution of SMBHs in different host bulges.Comment: 8 pages, 2 figures, accepted for publication in the Proceedings of
Science for VII Microquasar Workshop: Microquasars and Beyon
RESEARCH ON THE PREDICTION AND ANALYSIS OF CONSUMER PSYCHOLOGY CHANGES IN MACROECONOMIC OPERATION
RESEARCH ON THE PREDICTION AND ANALYSIS OF CONSUMER PSYCHOLOGY CHANGES IN MACROECONOMIC OPERATION
Correlation effects for semiconducting single wall carbon nanotube: a density matrix renormalization group study
In this paper, we report the applicability of the density matrix
renormalization group(DMRG) approach to the cylindrical single wall carbon
nanotube (SWCN) for purpose of its correlation effect. By applying the DMRG
approach to the ++ model, with and being the hopping and
Coulomb energies between the nearest neighboring sites, respectively, and
the onsite Coulomb energy, we calculate the phase diagram for the SWCN with
chiral numbers (), which reflects the competition between the
correlation energy and . Within reasonable parameter ranges, we
investigate possible correlated groundstates, the lowest excitations and the
corresponding correlation functions in which the connection with the excitonic
insulator is particularly addressed.Comment: 1 source files, 5 figure
Research on bearing radiation noise and optimization design based on coupled vibro-acoustic method
For bearings, radiation noise was an important evaluation index for mechanical property, in particularly mute machinery. Environmental pollution caused by bearing noise has always been the focus in bearing industry. In this paper, slippage of the rolling bearing and its own variable stiffness excitation were considered to accomplish the vibration coupling between the bearing and bearing seat as well as the coupling between bearing vibration and noise by means of combination of dynamic model, FEA model and boundary element method. A perfect coupled vibro-acoustic model of the bearing was built, and its results were compared with the experimental results to verify the reliability of the proposed method. Based on the verified simulation model, the improved design was carried out for the low-noise rolling bearings. Finally, in order to further verify the superiority of the proposed method in this paper, the designed rolling bearing was compared with that of the traditional design method. The results showed that the proposed design method was reliable
A Framework for Integrated Component and System Analyses of Instabilities
Instabilities associated with fluid handling and operation in liquid rocket propulsion systems and test facilities usually manifest themselves as structural vibrations or some form of structural damage. While the source of the instability is directly related to the performance of a component such as a turbopump, valve or a flow control element, the associated pressure fluctuations as they propagate through the system have the potential to amplify and resonate with natural modes of the structural elements and components of the system. In this paper, the authors have developed an innovative multi-level approach that involves analysis at the component and systems level. The primary source of the unsteadiness is modeled with a high-fidelity hybrid RANS/LES based CFD methodology that has been previously used to study instabilities in feed systems. This high fidelity approach is used to quantify the instability and understand the physics associated with the instability. System response to the driving instability is determined through a transfer matrix approach wherein the incoming and outgoing pressure and velocity fluctuations are related through a transfer (or transmission) matrix. The coefficients of the transfer matrix for each component (i.e. valve, pipe, orifice etc.) are individually derived from the flow physics associated with the component. A demonstration case representing a test loop/test facility comprised of a network of elements is constructed with the transfer matrix approach and the amplification of modes analyzed as the instability propagates through the test loop
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