scholarly journals Transparency and stability of low density stellar plasma related to Boltzmann statistics and to thermal bremsstrahlung

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Y. Ben-Aryeh
Keyword(s):  
Large Volume ◽  
Spherical Symmetry ◽  
Total Mass ◽  
Electron Gas ◽  
Low Density ◽  
Gravitational Forces ◽  
Magnetic Spectrum ◽  
Boltzmann Statistics ◽  
Electro Magnetic ◽  
The Stability

AbstractThe stability of low density stellar plasma is analyzed for a star with a spherical symmetry which is in equilibrium between the gravitational attractive forces and the repulsive pressure forces of an ideal electron gas where the analysis is developed by the use of Boltzmann statistics. Fundamental results are obtained for the radius and total mass of such star and its gravitational forces are large due to the extreme large volume. The absorption and emission of radiation for extremely low density star plasmas is very small over the entire electro-magnetic spectrum.

scholarly journals An unusually low density ultra-short period super-Earth and three mini-Neptunes around the old star TOI-561

2020 ◽  
Author(s):  
G Lacedelli ◽  
L Malavolta ◽  
L Borsato ◽  
G Piotto ◽  
D Nardiello ◽  
...  
Keyword(s):  
Transit Time ◽  
Time Variation ◽  
Planetary System ◽  
Radial Velocities ◽  
Low Density ◽  
Outer Planets ◽  
Short Period ◽  
The Stability

Abstract Based on HARPS-N radial velocities (RVs) and TESS photometry, we present a full characterisation of the planetary system orbiting the late G dwarf After the identification of three transiting candidates by TESS, we discovered two additional external planets from RV analysis. RVs cannot confirm the outer TESS transiting candidate, which would also make the system dynamically unstable. We demonstrate that the two transits initially associated with this candidate are instead due to single transits of the two planets discovered using RVs. The four planets orbiting TOI-561 include an ultra-short period (USP) super-Earth (TOI-561 b) with period Pb = 0.45 d, mass Mb = 1.59 ± 0.36 M⊕ and radius Rb = 1.42 ± 0.07 R⊕, and three mini-Neptunes: TOI-561 c, with Pc = 10.78 d, Mc = 5.40 ± 0.98 M⊕, Rc = 2.88 ± 0.09 R⊕; TOI-561 d, with Pd = 25.6 d, Md = 11.9 ± 1.3 M⊕, Rd = 2.53 ± 0.13 R⊕; and TOI-561 e, with Pe = 77.2 d, Me = 16.0 ± 2.3 M⊕, Re = 2.67 ± 0.11 R⊕. Having a density of 3.0 ± 0.8 g cm−3, TOI-561 b is the lowest density USP planet known to date. Our N-body simulations confirm the stability of the system and predict a strong, anti-correlated, long-term transit time variation signal between planets d and e. The unusual density of the inner super-Earth and the dynamical interactions between the outer planets make TOI-561 an interesting follow-up target.

Temperature Dependence of Degradation of Colored Oxo-Biodegradable Low-Density Polyethylene Films under Accelerated Thermal Aging

2017 ◽  
Vol 890 ◽  
pp. 82-85 ◽  
Author(s):  
Reymark D. Maalihan ◽  
Bryan B. Pajarito
Keyword(s):  
Thermal Aging ◽  
Degradation Products ◽  
Low Density Polyethylene ◽  
Effect Of Temperature ◽  
Low Density ◽  
Polyethylene Films ◽  
Hot Air ◽  
Taguchi Design Of Experiments ◽  
Oxidant Concentration ◽  
The Stability

This work reports the effect of temperature on degradation of colored low-density polyethylene (PE) films during thermal aging. Film samples were formulated according to Taguchi design of experiments where colorant, thickness, and pro-oxidant concentration were varied accordingly. Tensile properties of films were monitored with time during heat aging in a hot air oven at 50, 70, and 90 °C. Likewise, surfaces of aged films were analyzed to evaluate the degree of oxidation of PE during thermal aging. The Arrhenius equation was then used to predict the lifetime of PE at an in-use temperature of 30 °C. Results indicate that increasing the temperature reduces the tensile strength and modulus of films. Formation of carbonyl groups as degradation products is also observed at higher temperatures. Consequently, thermal aging at 90 °C offers the highest extent of degradation of exposed films. Regression analysis reveals that white films degrade at a higher rate than yellow and non-colored films. The presence of TiO2 in white films shortens the lifetime of PE while amine stabilizer in yellow films enhances the stability of PE during thermal aging.

scholarly journals Relaxation of spin-polarized low-density electron gas

2017 ◽  
pp. 1-23
Author(s):  
Igor Vadimovich Fomin ◽  
Pavel Vasilievich Sasorov
Keyword(s):  
Electron Gas ◽  
Low Density ◽  
Spin Polarized

System identification of a low-density jet via its noise-induced dynamics

2019 ◽  
Vol 862 ◽  
pp. 200-215 ◽  
Author(s):  
Minwoo Lee ◽  
Yuanhang Zhu ◽  
Larry K. B. Li ◽  
Vikrant Gupta
Keyword(s):  
System Identification ◽  
Limit Cycle ◽  
Landau Equation ◽  
Nonlinear Behaviour ◽  
Low Density ◽  
Limit Cycle Oscillations ◽  
Unconditionally Stable ◽  
Stable Regime ◽  
The Stability ◽  
Hydrodynamic Systems

Low-density jets are central to many natural and industrial processes. Under certain conditions, they can develop global oscillations at a limit cycle, behaving as a prototypical example of a self-excited hydrodynamic oscillator. In this study, we perform system identification of a low-density jet using measurements of its noise-induced dynamics in the unconditionally stable regime, prior to both the Hopf and saddle-node points. We show that this approach can enable prediction of (i) the order of nonlinearity, (ii) the locations and types of the bifurcation points (and hence the stability boundaries) and (iii) the resulting limit-cycle oscillations. The only assumption made about the system is that it obeys a Stuart–Landau equation in the vicinity of the Hopf point, thus making the method applicable to a variety of hydrodynamic systems. This study constitutes the first experimental demonstration of system identification using the noise-induced dynamics in only the unconditionally stable regime, i.e. away from the regimes where limit-cycle oscillations may occur. This opens up new possibilities for the prediction and analysis of the stability and nonlinear behaviour of hydrodynamic systems.

scholarly journals ‘Scraggy’ dark haloes around bulge-less spiral

2019 ◽  
Vol 486 (3) ◽  
pp. 3697-3701 ◽  
Author(s):  
I D Karachentsev ◽  
V E Karachentseva
Keyword(s):  
Total Mass ◽  
Spiral Galaxies ◽  
Stellar Mass ◽  
Low Density ◽  
Mean Square ◽  
Velocity Difference ◽  
Orbital Mass ◽  
Local Volume ◽  
The Mean ◽  
K Band

ABSTRACT We use a sample of 220 face-on bulge-less galaxies situated in the low-density environment to estimate their total mass via orbital motions of supposed rare satellites. Our inspection reveals 43 dwarf companions having the mean projected separation of 130 kpc and the mean-square velocity difference of 96 km s−1. For them, we obtain the mean orbital-mass-to-K-band luminosity ratio of 20 ± 3. Seven bulge-less spirals in the Local Volume are also characterized by the low mean ratio, Morb/LK = 22 ± 5. We conclude that bulge-less Sc–Scd–Sd galaxies have poor dark haloes, about two times lower than that of bulgy spiral galaxies of the same stellar mass.

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