Relativistic collapse of stellar clusters after loss of stability

1988 ◽  
Vol 147 (1) ◽  
pp. 121-135 ◽  
Author(s):  
G. S. Bisnovatyi-Kogan ◽  
L. R. Yangurazova
Keyword(s):  
Loss Of Stability ◽  
Stellar Clusters ◽  
Relativistic Collapse

Stability of dense stellar clusters against relativistic collapse

1993 ◽  
Vol 414 ◽  
pp. 187 ◽  
Author(s):  
G. S. Bisnovatyj-Kogan ◽  
M. Merafina ◽  
R. Ruffini ◽  
E. Vesperini
Keyword(s):  
Stellar Clusters ◽  
Relativistic Collapse

scholarly journals Stability of Dense Stellar Clusters against Relativistic Collapse. II. Maxwellian Distribution Functions with Different Cutoff Parameters

1998 ◽  
Vol 500 (1) ◽  
pp. 217-232 ◽  
Author(s):  
G. S. Bisnovatyi‐Kogan ◽  
M. Merafina ◽  
R. Ruffini ◽  
E. Vesperini
Keyword(s):  
Distribution Functions ◽  
Maxwellian Distribution ◽  
Stellar Clusters ◽  
Relativistic Collapse

THE SUPPORT BONDS RIGIDITY INFLUENCES ON THE CARRYING CAPACITY REDUCTION OF THE SHALLOW SHELLS ON A RECTANGULAR PLAN

2020 ◽  
Vol 92 (6) ◽  
pp. 3-12
Author(s):  
A.G. KOLESNIKOV ◽  
Keyword(s):  
Variable Thickness ◽  
Carrying Capacity ◽  
Geometric Nonlinearity ◽  
Progressive Collapse ◽  
Geometrically Nonlinear ◽  
Loss Of Stability ◽  
Shallow Shells ◽  
Capacity Reduction ◽  
Internal Forces ◽  
Hinged Support

Geometric nonlinearity shallow shells on a square and rectangular plan with constant and variable thickness are considered. Loss of stability of a structure due to a decrease in the rigidity of one of the support (transition from fixed support to hinged support) is considered. The Bubnov-Galerkin method is used to solve differential equations of shallow geometrically nonlinear shells. The Vlasov's beam functions are used for approximating. The use of dimensionless quantities makes it possible to repeat the calculations and obtain similar dependences. The graphs are given that make it possible to assess the reduction in the critical load in the shell at each stage of reducing the rigidity of the support and to predict the further behavior of the structure. Regularities of changes in internal forces for various types of structure support are shown. Conclusions are made about the necessary design solutions to prevent the progressive collapse of the shell due to a decrease in the rigidity of one of the supports.

Evolution of a long-wave train in loss of stability of a phase interface in geothermal systems

2008 ◽  
Vol 43 (1) ◽  
pp. 97-104 ◽  
Author(s):  
A. T. Il’ichev ◽  
V. E. Odintsova
Keyword(s):  
Wave Train ◽  
Phase Interface ◽  
Loss Of Stability ◽  
Geothermal Systems ◽  
Long Wave

Feedback control to delay or advance linear loss of stability in planar Poiseuille flow

1994 ◽  
Vol 447 (1930) ◽  
pp. 299-312 ◽  
Keyword(s):  
Feedback Control ◽  
Poiseuille Flow ◽  
Control Strategies ◽  
Linear Stability Theory ◽  
Flow Instabilities ◽  
Loss Of Stability ◽  
Stress Sensors ◽  
Shear Stress Sensors ◽  
Linear Loss ◽  
Adjacent Wall

By using linear stability theory, we demonstrate theoretically that the critical Reynolds number for the loss of stability of planar Poiseuille flow can be significantly increased or decreased through the use of feedback control strategies which enhance or suppress disturbance dissipating mechanisms in the flow. The controller studied here consists of closely packed, wall mounted, shear stress sensors and thermoelectric actuators. The sensors detect flow instabilities and direct the actuators to alter the fluid’s viscosity by modulating the adjacent wall temperature in such a way as to suppress or enhance flow instabilities. Results are presented for water and air flows.

scholarly journals The ecology of the galactic centre: Nuclear stellar clusters and supermassive black holes

2019 ◽  
Vol 14 (S351) ◽  
pp. 80-83 ◽  
Author(s):  
Melvyn B. Davies ◽  
Abbas Askar ◽  
Ross P. Church
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Large Fraction ◽  
Galactic Nuclei ◽  
Supermassive Black Holes ◽  
Galactic Centre ◽  
Stellar Clusters ◽  
Stellar Cluster ◽  
Supermassive Black Hole ◽  
Multiple Clusters

AbstractSupermassive black holes are found in most galactic nuclei. A large fraction of these nuclei also contain a nuclear stellar cluster surrounding the black hole. Here we consider the idea that the nuclear stellar cluster formed first and that the supermassive black hole grew later. In particular we consider the merger of three stellar clusters to form a nuclear stellar cluster, where some of these clusters contain a single intermediate-mass black hole (IMBH). In the cases where multiple clusters contain IMBHs, we discuss whether the black holes are likely to merge and whether such mergers are likely to result in the ejection of the merged black hole from the nuclear stellar cluster. In some cases, no supermassive black hole will form as any merger product is not retained. This is a natural pathway to explain those galactic nuclei that contain a nuclear stellar cluster but apparently lack a supermassive black hole; M33 being a nearby example. Alternatively, if an IMBH merger product is retained within the nuclear stellar cluster, it may subsequently grow, e.g. via the tidal disruption of stars, to form a supermassive black hole.

scholarly journals Escherichia coli dnaJ deletion mutation results in loss of stability of a positive regulator, CRP.

1992 ◽  
Vol 267 (19) ◽  
pp. 13180-13184
Author(s):  
R Ohki ◽  
T Kawamata ◽  
Y Katoh ◽  
F Hosoda ◽  
M Ohki
Keyword(s):  
Escherichia Coli ◽  
Deletion Mutation ◽  
Loss Of Stability ◽  
Positive Regulator

scholarly journals The effect of photoionizing feedback on the shaping of hierarchically-forming stellar clusters

2020 ◽  
Vol 499 (1) ◽  
pp. 668-680
Author(s):  
Alejandro González-Samaniego ◽  
Enrique Vazquez-Semadeni
Keyword(s):  
Star Formation ◽  
Early Stage ◽  
Stellar Clusters ◽  
Low Mass Stars ◽  
Transfer Scheme ◽  
Star Forming ◽  
Secondary Star ◽  
Low Mass ◽  
Hydrodynamical Simulations ◽  
Formation Efficiency

ABSTRACT We use two hydrodynamical simulations (with and without photoionizing feedback) of the self-consistent evolution of molecular clouds (MCs) undergoing global hierarchical collapse (GHC), to study the effect of the feedback on the structural and kinematic properties of the gas and the stellar clusters formed in the clouds. During this early stage, the evolution of the two simulations is very similar (implying that the feedback from low-mass stars does not affect the cloud-scale evolution significantly) and the star-forming region accretes faster than it can convert gas into stars, causing the instantaneous measured star formation efficiency (SFE) to remain low even in the absence of significant feedback. Afterwards, the ionizing feedback first destroys the filamentary supply to star-forming hubs and ultimately removes the gas from it, thus first reducing the star formation (SF) and finally halting it. The ionizing feedback also affects the initial kinematics and spatial distribution of the forming stars because the gas being dispersed continues to form stars, which inherit its motion. In the non-feedback simulation, the groups remain highly compact and do not mix, while in the run with feedback, the gas dispersal causes each group to expand, and the cluster expansion thus consists of the combined expansion of the groups. Most secondary star-forming sites around the main hub are also present in the non-feedback run, implying a primordial rather than triggered nature. We do find one example of a peripheral star-forming site that appears only in the feedback run, thus having a triggered origin. However, this appears to be the exception rather than the rule, although this may be an artefact of our simplified radiative transfer scheme.

Motion periodicity and bifurcation of a wave excited hopping ball

2019 ◽  
Vol 475 (2228) ◽  
pp. 20190137
Author(s):  
Gaurang Ruhela ◽  
Anirvan DasGupta
Keyword(s):  
Wave Amplitude ◽  
Harmonic Wave ◽  
Inelastic Collisions ◽  
Loss Of Stability ◽  
Elastic Surface ◽  
Minimum Frequency ◽  
Surface Motion ◽  
Return Map ◽  
Ball Problem ◽  
Subsequent Loss

We consider the problem of a hopping ball excited by a travelling harmonic wave on an elastic surface. The ball, considered as a particle, is assumed to interact with the surface through inelastic collisions. The surface motion due to the wave induces a horizontal drift in the ball. The problem is treated analytically under certain approximations. The phase space of the hopping motion is captured by constructing a phase-velocity return map. The fixed points of the return map and its compositions represent periodic hopping solutions. The linear stability of the obtained periodic solution is studied in detail. The minimum frequency for the onset of periodic hops, and the subsequent loss of stability at the bifurcation frequency, have been determined analytically. Interestingly, for small values of wave amplitude, the analytical solutions reveal striking similarities with the results of the classical bouncing ball problem.

scholarly journals Structure of the Milky Way and the distribution of young stellar clusters

2006 ◽  
Vol 2 (S241) ◽  
Author(s):  
Maria Messineo ◽  
Karl M. Menten ◽  
Harm J. Habing ◽  
Monika Petr-Gotzens ◽  
Frédéric Schuller
Keyword(s):  
Milky Way ◽  
Stellar Clusters
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