scholarly journals Orthogonal pulsars as a key test for pulsar evolution

2020 ◽  
Vol 494 (3) ◽  
pp. 3899-3911 ◽  
Author(s):  
E M Novoselov ◽  
V S Beskin ◽  
A K Galishnikova ◽  
M M Rashkovetskyi ◽  
A V Biryukov
Keyword(s):  
Inclination Angle ◽  
Theoretical Models ◽  
Radio Pulsars ◽  
Direct Information ◽  
Alignment Problem ◽  
Pulsar Evolution ◽  
Evolution Trajectory

ABSTRACT At present, there is no direct information about evolution of inclination angle χ between magnetic and rotational axes in radio pulsars. As to theoretical models of pulsar evolution, they predict both the alignment, i.e. evolution of inclination angle χ to 0°, and its counter-alignment, i.e. evolution to 90°. In this paper, we demonstrate that the statistics of interpulse pulsars can give us the key test to solve the alignment/counter-alignment problem as the number of orthogonal interpulse pulsars (χ ≈ 90°) drastically depends on the evolution trajectory.

Viscosity Effect on Thermocapillary Rupture of Falling Liquid Films

2010 ◽  
Author(s):  
Dmitry Zaitsev ◽  
Andrey Semenov ◽  
Oleg Kabov
Keyword(s):  
Heat Flux ◽  
Film Thickness ◽  
Inclination Angle ◽  
Theoretical Models ◽  
Liquid Films ◽  
Liquid Viscosity ◽  
Inclined Plate ◽  
Film Rupture ◽  
Generalize Data ◽  
Wide Range

Rupture of a subcooled liquid film flowing over an inclined plate with a 150×150 mm heater is studied for a wide range of liquid viscosity (dynamic viscosity μ = (0.91–17.2)x10−3 Pa·s) and plate inclination angle with respect to the horizon (Θ = 3–90 deg). The main governing parameters of the experiment and their respective values are: Reynolds number Re = 0.15–54, heat flux q = 0–224 W/cm2. The effect of the heat flux on the film flow leads to the formation of periodically flowing rivulets and thin film between them. As the heat flux grows the film thickness between rivulets gradually decreases, and, upon reaching a certain threshold heat flux, qidp, the film ruptures in the area between the rivulets. The threshold heat flux increases with the flow rate of liquid and with the liquid viscosity, while the plate inclination angle has little effect on qidp. Criterion Kp, which is traditionally used in the literature to predict thermocapillary film rupture, was found to poorly generalize data for high viscous liquids (ethylene glycol, and aqueous solutions of glycerol) and also data for Θ≤45 deg. The criterion Kp was modified by taking into account characteristic critical film thickness for film rupture under isothermal conditions (no heating), deduced from existing theoretical models. The modified criterion has allowed to successfully generalize data for whole ranges of μ, Re, Θ and q, studied.

scholarly journals X-ray and Gamma-ray Observations of Pulsars

1981 ◽  
Vol 95 ◽  
pp. 241-250 ◽  
Author(s):  
R. Buccheri
Keyword(s):  
Gamma Ray ◽  
Theoretical Models ◽  
Radio Pulsars ◽  
X Ray ◽  
Special Regard ◽  
Energy Domain ◽  
Similarities And Differences

Measurements of pulsars in the energy domain above ~ 1 keV have provided in the last few years new and interesting results. This paper presents a review of the observational features of PSR 0531+21 and PSR 0833–45 (the Crab and Vela pulsars). Searches for pulsed emission from old radio pulsars in the same energy domain are also reviewed and results assessed. The comparison of the observed features with each other and with the corresponding features observed at lower energies reveals similarities and differences capable to constrain theoretical models with special regard to the geometry of the emission mechanisms.

Thermal Characters of Mesh Structure in a Flat Heat Pipe

2003 ◽  
Author(s):  
Liang-Han Chien ◽  
Y.-C. Shih
Keyword(s):  
Heat Pipe ◽  
Inclination Angle ◽  
Mesh Size ◽  
Heat Pipes ◽  
Theoretical Models ◽  
Working Fluid ◽  
Internal Space ◽  
Mesh Structure ◽  
Horizontal Orientation ◽  
Plate Type

In this study plate type heat pipes having mesh capillaries were investigated experimentally and theoretically. A test apparatus was designed to test thermal performance of plate type copper-water heat pipe having one or two layers of #50 or #80 mesh capillary structures with 5-to-50 W heat input. The working fluid, water is charged with 25% or 33% volume of the heat pipe internal space. In addition to horizontal orientation, the heat pipes were tested with the evaporator section elevated up to 40 degree inclination angle. Temperature distribution of the heat pipe was measured, and the evaporator, adiabatic and condensation resistances of the heat pipe were calculated separated. The effects of mesh size, charge volume, and inclination angle on each thermal resistance were discussed. In general, the #80 mesh yields lower thermal resistances than the #50 mesh; inclination angle has more significant effect on condenser than evaporator. Theoretical models of evaporation and condensation in flat heat pipes were proposed to interpolate the experimental results. The present evaporation model predicts the experimental data of evaporation resistance between −20% and +30%, and the condensation model predicts most condensation resistance data within ±30%.

scholarly journals The Evolution of the Magnetic Fields of Neutron Stars

1992 ◽  
Vol 128 ◽  
pp. 26-34
Author(s):  
Dipankar Bhattacharya
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Theoretical Models ◽  
Radio Pulsars ◽  
Secular Evolution ◽  
History Of ◽  
Field Decay ◽  
The Magnetic Field

AbstractThe evolution of the magnetic field strength plays a major role in the life history of a neutron star. In this article the observational evidence of field evolution, in particular that of field decay and magnetic alignment, are critically examined. It is concluded that the observed decay of the spindown torque on radio pulsars cannot be caused by a secular evolution of the “obliqueness” of the neutron star, as suggested by some authors. Recent observations provide a strong indication that the decay of the magnetic field strength of a neutron star may be closely related to its evolution in a binary system. Theoretical models for such an evolution are discussed.

scholarly journals Probing fundamental physics with pulsars

2009 ◽  
Vol 5 (H15) ◽  
pp. 131-136
Author(s):  
Duncan R. Lorimer ◽  
Maura A. McLaughlin
Keyword(s):  
Large Scale ◽  
Radio Pulsars ◽  
Fundamental Physics ◽  
Superdense Matter ◽  
Pulsar Timing ◽  
Binary Evolution ◽  
Radio Transients ◽  
Pulsar Timing Array ◽  
Review Current ◽  
Pulsar Evolution

AbstractPulsars provide a wealth of information about General Relativity, the equation of state of superdense matter, relativistic particle acceleration in high magnetic fields, the Galaxy's interstellar medium and magnetic field, stellar and binary evolution, celestial mechanics, planetary physics and even cosmology. The wide variety of physical applications currently being investigated through studies of radio pulsars rely on: (i) finding interesting objects to study via large-scale and targeted surveys; (ii) high-precision timing measurements which exploit their remarkable clock-like stability. We review current surveys and the principles of pulsar timing and highlight progress made in the rotating radio transients, intermittent pulsars, tests of relativity, understanding pulsar evolution, measuring neutron star masses and the pulsar timing array

scholarly journals Comparing Gamma-ray Loud and Gamma-ray Quiet Radio Pulsars – A Unification Scheme

2017 ◽  
Vol 13 (S337) ◽  
pp. 88-91
Author(s):  
Patrick Weltevrede
Keyword(s):  
Inclination Angle ◽  
Gamma Ray ◽  
Light Curves ◽  
Radio Pulsars ◽  
Rotation Axes ◽  
Polarization Study ◽  
Magnetic Inclination ◽  
Line Region ◽  
Open Field Line ◽  
The Magnetic Field

AbstractA radio polarization study of gamma-ray-detected pulsars reveals a surprising tendency for the magnetic and rotation axes to be relatively aligned. This provides tension with gamma-ray models, which disfavour such alignment. The lack of correlation between these findings and those derived from the gamma-ray light curves suggests problems in the models. To make the data consistent with a random orientation of the magnetic field the emission regions could be assumed to extend outside what is traditionally thought to be the open-field-line region in a magnetic inclination angle dependent way. Both acceptance and rejection of this hypothesis has important consequences. Finally, a unification scheme is proposed to explain the observational differences between gamma-ray loud and gamma-ray quiet radio pulsars. This unification scheme takes the orientation of the line of sight and the magnetic inclination angle to be key parameters affecting both the radio and gamma-ray light-curve morphology.

C. The Continuous Spectrum of Pulsating Variable Stars

1967 ◽  
Vol 28 ◽  
pp. 177-206
Author(s):  
J. B. Oke ◽  
C. A. Whitney
Keyword(s):  
Continuous Spectrum ◽  
Variable Stars ◽  
Velocity Fields ◽  
The Other ◽  
Line Spectrum ◽  
Direct Information ◽  
Thermodynamic Structure ◽  
Diagnostic Interpretation ◽  
Pulsating Variable Stars ◽  
The Continuum

Pecker:The topic to be considered today is the continuous spectrum of certain stars, whose variability we attribute to a pulsation of some part of their structure. Obviously, this continuous spectrum provides a test of the pulsation theory to the extent that the continuum is completely and accurately observed and that we can analyse it to infer the structure of the star producing it. The continuum is one of the two possible spectral observations; the other is the line spectrum. It is obvious that from studies of the continuum alone, we obtain no direct information on the velocity fields in the star. We obtain information only on the thermodynamic structure of the photospheric layers of these stars–the photospheric layers being defined as those from which the observed continuum directly arises. So the problems arising in a study of the continuum are of two general kinds: completeness of observation, and adequacy of diagnostic interpretation. I will make a few comments on these, then turn the meeting over to Oke and Whitney.

Analytical Electron Microscopy of Surface-Modified Ceramics

1985 ◽  
Vol 43 ◽  
pp. 276-279
Author(s):  
P. S. Sklad
Keyword(s):  
Electron Microscopy ◽  
Analytical Electron Microscopy ◽  
Theoretical Models ◽  
Ceramic Materials ◽  
Solute Concentration ◽  
Second Phase ◽  
Analytical Electron ◽  
Implantation Techniques ◽  
Lattice Damage ◽  
Surface Modified

Over the past several years, it has become increasingly evident that materials for proposed advanced energy systems will be required to operate at high temperatures and in aggressive environments. These constraints make structural ceramics attractive materials for these systems. However it is well known that the condition of the specimen surface of ceramic materials is often critical in controlling properties such as fracture toughness, oxidation resistance, and wear resistance. Ion implantation techniques offer the potential of overcoming some of the surface related limitations.While the effects of implantation on surface sensitive properties may be measured indpendently, it is important to understand the microstructural evolution leading to these changes. Analytical electron microscopy provides a useful tool for characterizing the microstructures produced in terms of solute concentration profiles, second phase formation, lattice damage, crystallinity of the implanted layer, and annealing behavior. Such analyses allow correlations to be made with theoretical models, property measurements, and results of complimentary techniques.

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