scholarly journals Some Aspects of Radio Pulsar Evolution

1992 ◽  
Vol 128 ◽  
pp. 39-41
Author(s):  
V. S. Beskin ◽  
A. V. Gurevich ◽  
Ya. N. Istomin
Keyword(s):  
Neutron Star ◽  
Dense Plasma ◽  
Radio Pulsar ◽  
Energy Losses ◽  
Complete Suppression ◽  
Plasma Energy ◽  
Longitudinal Current ◽  
Pulsar Evolution ◽  
Good Agreement

It is shown that pulsar statistics are in good agreement with the theory of current (plasma) energy losses of a neutron star. Up to now two theories of pulsar braking have been considered. The first well known model is connected with the radiation of vacuum magneto-dipole waves (Ostriker and Gunn 1969). However, according to the electrodynamical theory of pulsars, the presence of a rather dense plasma in the magnetosphere of a neutron star leads inevitably to a complete suppression of magneto-dipole losses—the dynamics of the stellar slow down is determined by the longitudinal current only (Beskin, Gurevich, and Istomin 1983).

scholarly journals A Method of Predicting the Energy Losses in Vaneless Diffusers of Centrifugal Compressors

1989 ◽  
Author(s):  
Huashu Dou
Keyword(s):  
Experimental Data ◽  
Energy Loss ◽  
Total Energy ◽  
Wall Friction ◽  
Energy Losses ◽  
Flow Conditions ◽  
Centrifugal Compressors ◽  
Flow Losses ◽  
Vaneless Diffusers ◽  
Good Agreement

The flow losses in the veneless diffusers of centrifugal compressors is investigated. It is found that the total energy loss in vaneless diffusers is a function of Bsin2 α0 when inlet flow conditions and radius ratio between inlet and outlet are given. A wall friction coefficient equation is derived and a method of predicting the total energy loss excepting mixing loss is presented. A comparison is made between results obtained from this method and experimental data generated by the author as well as data from the literature. Good agreement is obtained.

scholarly journals Binary pulsar evolution: unveiled links and new species

2012 ◽  
Vol 8 (S291) ◽  
pp. 121-126
Author(s):  
Andrea Possenti
Keyword(s):  
New Species ◽  
Neutron Star ◽  
Evolutionary Path ◽  
Binary Pulsar ◽  
Galactic Field ◽  
New Class ◽  
Binary Pulsars ◽  
Low Mass ◽  
Pulsar Searches ◽  
Pulsar Evolution

AbstractIn the last years a series of blind and/or targeted pulsar searches led to almost triple the number of known binary pulsars in the galactic field with respect to a decade ago. The focus will be on few outliers, which are emerging from the average properties of the enlarged binary pulsar population. Some of them may represent the long sought missing links between two kinds of neutron star binaries, while others could represent the stereotype of new groups of binaries, resulting from an evolutionary path which is more exotic than those considered until recently. In particular, a new class of binaries, which can be dubbed Ultra Low Mass Binary Pulsars (ULMBPs), is emerging from recent data.

scholarly journals Generation of hot and dense plasmas in laser accelerated colliding foil systems

1998 ◽  
Vol 16 (1) ◽  
pp. 21-30 ◽  
Author(s):  
P. Angelo ◽  
H. Derfoul ◽  
P. Gauthier ◽  
P. Sauvan ◽  
A. Poquerusse ◽  
...  
Keyword(s):  
Thermal Conduction ◽  
Focal Spot ◽  
Laser Intensity ◽  
Dense Plasma ◽  
Lateral Expansion ◽  
Dense Plasmas ◽  
Monochromatic Imaging ◽  
Thin Foils ◽  
Plasma Effects ◽  
Good Agreement

We create hot (Te > 200 eV) and dense (Ne > 1023 cm−3) plasmas in the colliding zone of two thin foils accelerated by two laser beams of the LULI facilities. Three spectroscopic diagnostics (two 1D space-resolved spectrographs and a 2D monochromatic imaging) are used to drive the efficiency of the compression. We show that 2D effects are important. Realistic simulations of these experiments must be done, taking into account the inhomogeneity of the laser intensity in the focal spot, the foil distorsion, the plasma lateral expansion, and the lateral thermal conduction. Two-dimensional LASNEX code results are in good agreement with our experimental results. The optimized compressed plasmas generated are favorable for the exhibition of dense plasma effects due to molecular formations, and they reproduce in laboratory some astrophysical situations.

scholarly journals EARLY PHASES OF DIFFERENT TYPES OF ISOLATED NEUTRON STAR

2005 ◽  
Vol 14 (06) ◽  
pp. 1075-1082 ◽  
Author(s):  
AŞKIN ANKAY ◽  
SERKAN ŞAHIN ◽  
GÖKÇE KARANFIL ◽  
EFE YAZGAN
Keyword(s):  
Neutron Star ◽  
Thermal Neutron ◽  
Early Phase ◽  
Radio Pulsar ◽  
Radio Pulsars ◽  
X Ray ◽  
Soft Gamma Repeaters ◽  
Different Types ◽  
Early Phases

Two Galactic isolated strong X-ray pulsars seem to be in the densest environments compared to other types of Galactic pulsar. X-ray pulsar J1846-0258 can be in an early phase of anomalous X-ray pulsars and soft gamma repeaters if its average braking index is ~1.8–2.0. X-ray pulsar J1811-1925 must have a very large average braking index (~11) if this pulsar was formed by SN 386AD. This X-ray pulsar can be in an early phase of the evolution of the radio pulsars located in the region P ~ 50–150 ms and Ṗ ~ 10-14–10-16 ss -1 of the P–Ṗ diagram. X-ray/radio pulsar J0540-69 seems to be evolving in the direction to the dim isolated thermal neutron star region on the P–Ṗ diagram. Possible progenitors of different types of neutron star are also discussed.

Belt-Drive Mechanics: Energy Losses in the Presence of Detachment Waves

2019 ◽  
Author(s):  
Yingdan Wu ◽  
Michael J. Leamy ◽  
Michael Varenberg
Keyword(s):  
Rolling Friction ◽  
Drive System ◽  
Energy Losses ◽  
Belt Drive ◽  
Interface Shear ◽  
Shear Traction ◽  
Friction Moment ◽  
The Difference ◽  
Contact Arc ◽  
Good Agreement

Abstract The dissipative rolling friction moment in a simple belt-drive system is estimated both experimentally and computationally while taking into account the detachment events at the belt-pulley interface. Shear traction is estimated based on measurements of the shear strain along the contact arc. It is shown that the dissipative moment can be approximated by taking the difference between the shear traction and the load carried by the belt. A model is developed for analyzing the contributions of different components to this dissipative moment by considering both the volumetric and surface hysteresis losses. The computed rolling friction moment is found to be in good agreement with that estimated based on the experiments. It is also found that while the shear- and stretching-induced energy losses contribute the most to the dissipation in the belt drive system, the losses associated with the Schallamach waves of detachment make up a considerable portion of the dissipation in the driver case.

scholarly journals Constraints on Microscopic and Phenomenological Equations of State of Dense Matter from GW170817

Universe ◽  
2019 ◽  
Vol 5 (10) ◽  
pp. 204 ◽  
Author(s):  
Domenico Logoteta ◽  
Ignazio Bombaci
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Equations Of State ◽  
Mean Field ◽  
Dense Matter ◽  
Neutron Star Matter ◽  
Field Approach ◽  
Relativistic Mean Field ◽  
Three Body ◽  
Good Agreement

We discuss the constraints on the equation of state (EOS) of neutron star matter obtained by the data analysis of the neutron star-neutron star merger in the event GW170807. To this scope, we consider two recent microscopic EOS models computed starting from two-body and three-body nuclear interactions derived using chiral perturbation theory. For comparison, we also use three representative phenomenological EOS models derived within the relativistic mean field approach. For each model, we determine the β -stable EOS and then the corresponding neutron star structure by solving the equations of hydrostatic equilibrium in general relativity. In addition, we calculate the tidal deformability parameters for the two neutron stars and discuss the results of our calculations in connection with the constraints obtained from the gravitational wave signal in GW170817. We find that the tidal deformabilities and radii for the binary’s component neutron stars in GW170817, calculated using a recent microscopic EOS model proposed by the present authors, are in very good agreement with those derived by gravitational waves data.

scholarly journals Cosmic ray e± at high energy

2019 ◽  
Vol 208 ◽  
pp. 04001 ◽  
Author(s):  
Kfir Blum ◽  
Annika Reinert
Keyword(s):  
Secondary Production ◽  
Primary Source ◽  
Cosmic Ray ◽  
High Energy ◽  
Radiative Energy ◽  
Energy Losses ◽  
Propagation Time ◽  
Interstellar Matter ◽  
Independent Evidence ◽  
Good Agreement

There is a commonly expressed opinion in the literature, that cosmic-ray (CR) e+ come from a primary source, which could be dark matter or pulsars. In these proceedings we review some evidence to the contrary: namely, that e+ come from secondary production due to CR nuclei scattering on interstellar matter. We show that recent measurements of the total e± flux at E ≲ 3 TeV are in good agreement with the predicted flux of secondary e±, that would be obtained if radiative energy losses during CR propagation do not play an important role. If the agreement between data and secondary prediction is not accidental, then the requirement of negligible radiative energy losses implies a very short propagation time for high energy CRs: tesc ≲. 105 yr at rigidities R ≳ 3 TV. Such short propagation history may imply that a recent, near-by source dominates the CRs at these energies. We review independent evidence for a transition in CR propagation, based on the spectral hardening of primary and secondary nuclei around R ~ 100 GV. The transition rigidity of the nuclei matches the rigidity at which the e+ flux saturates its secondary upper bound.

Energy losses and scattering of fast electrons in a dense plasma

1993 ◽  
Vol 36 (9) ◽  
pp. 905-908
Author(s):  
V. I. Boiko ◽  
E. A. Gorbachev
Keyword(s):  
Dense Plasma ◽  
Energy Losses ◽  
Fast Electrons

Wave functions for the hydrogen atom in a dense plasma

2003 ◽  
Vol 81 (11) ◽  
pp. 1243-1248 ◽  
Author(s):  
Y P Varshni
Keyword(s):  
Hydrogen Atom ◽  
Dense Plasma ◽  
Wave Functions ◽  
Electron Interaction ◽  
Dipole Polarizability ◽  
Variational Wave Functions ◽  
Absorption Oscillator Strength ◽  
Variational Wave ◽  
Good Agreement ◽  
03.65 Ge

A hydrogen atom in a high-density plasma is simulated by a model in which the hydrogen atom is confined in an impenetrable spherical box, with the atom at the centre. For the proton–electron interaction the Debye–Huckel potential is used. Variational wave functions are proposed for the 1s and 2p states. Energies calculated from these for different values of the radius of box (r0) are shown to be in good agreement with the exact values. The variational wave functions are further employed to calculate the absorption oscillator strength for the 1s [Formula: see text] 2p transition and the dipole polarizability for different values of r0. PACS Nos.: 03.65.Ge, 32.70.Os, 31.70.Dk, 52.20.–j

An Explanation for the Asymmetry of the Modulation Sidebands about the Tooth Meshing Frequency in Epicyclic Gear Vibration

1985 ◽  
Vol 199 (1) ◽  
pp. 65-70 ◽  
Author(s):  
P D McFadden ◽  
J D Smith
Keyword(s):  
Complete Suppression ◽  
Vibration Spectra ◽  
Epicyclic Gear ◽  
The Asymmetry ◽  
The Relationship ◽  
Good Agreement

The vibration spectra of epicyclic gears commonly exhibit considerable asymmetry of the modulation sidebands and even complete suppression of the component at the tooth meshing frequency. A model is proposed which explains these observations in terms of the relationship between the vibrations generated by each of the planet gears as they move relative to the transducer location. Comparisons of the predictions of the model with measured vibration spectra for several epicyclic gearboxes show good agreement.

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