Dependence Of Mass Loss Research Articles

Angular Momentum Loss during Stable Mass Transfer onto a Compact Object: The Effect of Mass Loss via Accretion Disk Winds

We use an analytic framework to calculate the evolution of binary orbits under a physically motivated model that accounts for angular momentum loss associated with winds from an accretion disk around the compact-objected accretor. Our prescription considers wind mass ejection from the surface of an accretion disk, accounting for a radial mass-loss dependence across the disk surface. We compare this to the standard prescription of angular momentum loss associated with isotropic mass loss from the vicinity of the accretor. The angular momentum loss from a disk wind is always larger. For mass ratios, q, between 2 and 10, angular momentum loss via a disk wind can be ≃3–40 times greater than the standard prescription. For the majority of mass ratios and disk properties, accounting for the disk wind can result in considerably smaller orbital separations compared to the standard formalism, the differences being ≃60% depending on how long the effect is integrated for. We conclude that it is important to consider the effects of angular momentum loss from a disk wind when evolving binary orbits.

Validation of the extended COCOSYS cable fire model based on a generic FLASH-CAT approach

Fire simulations and analytical validation approaches have gained more and more relevance, in particular with respect to fire safety assessment of operating nuclear power plants (NPPs). For providing an added value to the regulatory authorities and the technical safety experts authorized by them suitability and applicability of the analytical tools applied such as fire simulation codes need be known and demonstrated.The COCOSYS (Containment Code System) code developed by Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) gGmbH contains i.e. models for simulating cable as well as liquid fuel fires. In NPPs, cables represent a non-negligible fire load as initial fire source or contributor to fire spreading.To overcome some generic deficiencies of the existing so-called simple cable fire model in COCOSYS the model has been improved based on a more generic FLASH-CAT approach. The extended model uses a time dependent mass loss rate (MLR) density profile, can consider composite materials to regard the increase of the heat of combustion during the fire development and is able to consider under-ventilated conditions.The model was validated on several experiments performed in open atmosphere and confined environment by the French Institut de Radioprotection et de Sûreté Nucléaire (IRSN) and conducted within the PRISME 2 and PRISME 3 Projects, launched by the Organisation for Economic Co-operation and Development (OECD) Nuclear Energy Agency (NEA). One main objective is to provide one single set of input parameters for each cable type, which can be used under different ventilation conditions. The paper presents capabilities and remaining limitations of the new model.

Tracing the colliding winds of η Carinae in He i

ABSTRACT η Carinae is an extremely luminous and energetic colliding-wind binary. The combination of its orbit and orientation, with respect to our line of sight, enables direct investigation of the conditions and geometry of the colliding winds. We analyse optical He i 5876 and 7065 Å line profiles from the Global Jet Watch observatories covering the last 1.3 orbital periods. The sustained coverage throughout apastron reveals the distinct dynamics of the emitting versus absorbing components: the emission lines follow orbital velocities, while one of the absorption lines is detected only around apastron (0.08 < ϕ < 0.95) and exhibits velocities that deviate substantially from the orbital motion. To interpret these deviations, we conjecture that this He i absorption component is formed in the post-shock primary wind, and is only detected when our line of sight intersects with the shock cone formed by the collision of the two winds. We formulate a geometrical model for the colliding winds in terms of a hyperboloid in which the opening angle and location of its apex are parametrized in terms of the ratio of the wind momentum of the primary star to that of companion. We fit this geometrical model to the absorption velocities, finding results that are concordant with the panchromatic observations and simulations of η Carinae. The model presented here is an extremely sensitive probe of the exact geometry of the wind momentum balance of binary stars, and can be extended to probe the latitudinal dependence of mass-loss.

Effect of Protective Coatings on Wooden Elements Exposed to a Small Ignition Initiator

This paper presents the results of monitoring the behaviour of selected wood species exposed to a small ignition initiator. We specifically aimed to investigate the effect of retardant coating on the combustion process of the wood species spruce (Picea abies), red spruce (Larix decidua), Scots pine (Pinus sylvestris), ash (Fraxinus excelsior L.), beech (Fagus sylvatica), and oak (Quercus robur) when exposed to a small initiator of ignition. At the same time, we studied the effect of different types of fungicidal agents (based on N-(3-aminopropyl)-N-dodecylpropane-1,3-diamine; alkyl (C12–16) dimethylbenzyl ammonium chloride or 3-iodo-prop-2-inylbutylcarbamate) on the effectiveness of a flame retardant (containing ferric phosphate) applied to the selected fungicide-treated wood samples. The experimentally obtained mass-loss and flame-spread results were statistically evaluated using the QtiPlot software program. A significant dependence of mass loss and surface flame spread on wood species was the primary focus. It was only confirmed for the surface-flame-spread variable. The dependence of the effect of fungicide treatment on the effectiveness of the selected retardant was confirmed. Fungicidal coatings with the active ingredient alkyl/benzyl (C12–16) dimethylbenzyl ammonium chloride indicated the lowest mass loss rate and flame spread for all wood samples.

New predictions for radiation-driven, steady-state mass-loss and wind-momentum from hot, massive stars

Context. Reliable predictions of mass-loss rates are important for massive-star evolution computations. Aims. We aim to provide predictions for mass-loss rates and wind-momentum rates of O-type stars, while carefully studying the behaviour of these winds as functions of stellar parameters, such as luminosity and metallicity. Methods. We used newly developed steady-state models of radiation-driven winds to compute the global properties of a grid of O-stars. The self-consistent models were calculated by means of an iterative solution to the equation of motion using full non-local thermodynamic equilibrium radiative transfer in the co-moving frame to compute the radiative acceleration. In order to study winds in different galactic environments, the grid covers main-sequence stars, giants, and supergiants in the Galaxy and both Magellanic Clouds. Results. We find a strong dependence of mass-loss on both luminosity and metallicity. Mean values across the grid are Ṁ~L*2.2 and Ṁ~L*0.95; however, we also find a somewhat stronger dependence on metallicity for lower luminosities. Similarly, the mass loss-luminosity relation is somewhat steeper for the Small Magellanic Cloud (SMC) than for the Galaxy. In addition, the computed rates are systematically lower (by a factor 2 and more) than those commonly used in stellar-evolution calculations. Overall, our results are in good agreement with observations in the Galaxy that properly account for wind-clumping, with empirical Ṁ versus Z* scaling relations and with observations of O-dwarfs in the SMC. Conclusions. Our results provide simple fit relations for mass-loss rates and wind momenta of massive O-stars stars as functions of luminosity and metallicity, which are valid in the range Teff = 28 000–45 000 K. Due to the systematically lower values for Ṁ, our new models suggest that new rates might be needed in evolution simulations of massive stars.

Erosion research of CX-2002U carbon composites under low-temperature high-flux hydrogen plasma

The net erosion yield of CX-2002U carbon fiber composites under high-flux low-temperature hydrogen plasma is investigated using a linear plasma device. It is found that the net erosion yield decreases rapidly first, and then tends to saturate with the increase of hydrogen–plasma flux. When the temperature of the sample eroded by hydrogen plasma is above 300 °C, the hybridization of electrons outside the carbon atom would change. Then the carbon atoms combine with hydrogen atoms to form massive spherical nanoparticles of hydrocarbon compounds and deposit on the surface at the flux condition of 1.77 × 1022 m−2·s−1. Under the irradiation of hydrogen plasma loaded with negative bias, the surface morphology of the matrix carbon is changed dramatically. Moreover, the energy dependence of mass loss does not increase in proportion to the increase of hydrogen–plasma energy, but reaches a peak around 20 V negative bias voltage. Based on the analysis of different samples, it can be concluded that the enhancement of energy could make a contribution to chemical erosion and enlarge the size of pores existing on the surface.

Asteroseismology of luminous red giants with Kepler – II. Dependence of mass-loss on pulsations and radiation

ABSTRACT Mass-loss by red giants is an important process to understand the final stages of stellar evolution and the chemical enrichment of the interstellar medium. Mass-loss rates are thought to be controlled by pulsation-enhanced dust-driven outflows. Here, we investigate the relationships between mass-loss, pulsations, and radiation, using 3213 luminous Kepler red giants and 13 5000 ASAS–SN semiregulars and Miras. Mass-loss rates are traced by infrared colours using 2MASS and Wide-field Infrared Survey Explorer(WISE) and by observed-to-model WISE fluxes, and are also estimated using dust mass-loss rates from literature assuming a typical gas-to-dust mass ratio of 400. To specify the pulsations, we extract the period and height of the highest peak in the power spectrum of oscillation. Absolute magnitudes are obtained from the 2MASS Ks band and the Gaia DR2 parallaxes. Our results follow. (i) Substantial mass-loss sets in at pulsation periods above ∼60 and ∼100 d, corresponding to Asymptotic-Giant-Branch stars at the base of the period-luminosity sequences C′ and C. (ii) The mass-loss rate starts to rapidly increase in semiregulars for which the luminosity is just above the red-giant-branch tip and gradually plateaus to a level similar to that of Miras. (iii) The mass-loss rates in Miras do not depend on luminosity, consistent with pulsation-enhanced dust-driven winds. (iv) The accumulated mass-loss on the red giant branch consistent with asteroseismic predictions reduces the masses of red-clump stars by 6.3 per cent, less than the typical uncertainty on their asteroseismic masses. Thus mass-loss is currently not a limitation of stellar age estimates for galactic archaeology studies.

The Link between Hot and Cool Outflows

AbstractThe link between hot and cool stellar outflows is shown to be critical for correctly predicting the masses of the most massive black holes (BHs) below the so-called pair-instability supernova (PISN) mass gap. Gravitational Wave (GW) event 190521 allegedly hosted an “impossibly” heavy BH of 85 M⊙. Here we show how our increased knowledge of both metallicity Z and temperature dependent mass loss is critical for our evolutionary scenario of a low-Z blue supergiant (BSG) progenitor of an initially approx 100 M⊙ star to work. We show using MESA stellar evolution modelling experiments that as long as we can keep such stars above 8000 K such low-Z BSGs can avoid strong winds, and keep a very large envelope mass intact before core collapse. This naturally leads to the Cosmic Time dependent maximum BH function below the PISN gap.

Hydrodynamic Simulations of Pre-supernova Outbursts in Red Supergiants: Asphericity and Mass Loss

Abstract The activity of a massive star approaching core-collapse can strongly affect the appearance of the star and its subsequent supernova. Late-phase convective nuclear burning generates waves that propagate toward the stellar surface, heating the envelope and potentially triggering mass loss. In this work, we improve on previous one-dimensional models by performing two-dimensional simulations of the pre-supernova mass ejection phase due to deposition of wave energy. Beginning with stellar evolutionary models of a 15 M ⊙ red supergiant star during core O-burning, we treat the rate and duration of energy deposition as model parameters and examine the mass-loss dependence and the pre-explosion morphology accordingly. Unlike one-dimensional models, density inversions due to wave heating are smoothed by Rayleigh–Taylor instabilities, and the primary effect of wave heating is to radially expand the star’s hydrogen envelope. For low heating rates with long durations, the expansion is nearly homologous, whereas high but short-lived heating can generate a shock that drives envelope expansion and results in a qualitatively different density profile at the time of core-collapse. Asymmetries are fairly small, and large amounts of mass loss are unlikely unless the wave heating exceeds expectations. We discuss implications for pre-supernova stellar variability and supernovae light curves.

Mass loss and the Eddington parameter: a new mass-loss recipe for hot and massive stars

ABSTRACT Mass loss through stellar winds plays a dominant role in the evolution of massive stars. In particular, the mass-loss rates of very massive stars ($\gt 100\, M_{\odot}$) are highly uncertain. Such stars display Wolf–Rayet spectral morphologies (WNh), whilst on the main sequence. Metal-poor very massive stars are progenitors of gamma-ray bursts and pair instability supernovae. In this study, we extended the widely used stellar wind theory by Castor, Abbott & Klein from the optically thin (O star) to the optically thick main-sequence (WNh) wind regime. In particular, we modify the mass-loss rate formula in a way that we are able to explain the empirical mass-loss dependence on the Eddington parameter (Γe). The new mass-loss recipe is suitable for incorporation into current stellar evolution models for massive and very massive stars. It makes verifiable predictions, namely how the mass-loss rate scales with metallicity and at which Eddington parameter the transition from optically thin O star to optically thick WNh star winds occurs. In the case of the star cluster R136 in the Large Magellanic Cloud we find in the optically thin wind regime $\dot{M} \propto \Gamma _{\rm e}^{3}$, while in the optically thick wind regime $\dot{M} \propto 1/ (1 - \Gamma _{\rm e})^{3.5}$. The transition from optically thin to optically thick winds occurs at Γe, trans ≈ 0.47. The transition mass-loss rate is $\log \dot{M}~(\mathrm{M}_{\odot } \, \mathrm{yr}^{-1}) \approx -4.76 \pm 0.18$, which is in line with the prediction by Vink & Gräfener assuming a volume filling factor of $f_{\rm V} = 0.23_{-0.15}^{+0.40}$.

Considerations in the study of trophies

Roe deer is Laurasiatherian mammal from the family of Cervidae. It is autochthonous and one of the most valued trophy game species in Croatia (Zorić 2014.). Antlers (left and right branch) with complete or part of the skull are regarded as trophy. Despite the fact that roe deer antlers are easily accessible trophies, formulas for their evaluations are still largely debated. It is a consequence of large number of elements that need to be evaluated, possible use of coefficient instead of measuring volume and mass, and potential differences in trophy preparation. Guidelines of the International Council for Game and Wildlife Conservation (CIC) instructs that skulls should be cut through the eye cavities leaving intact nasal bones on the trophy. If otherwise cut or left intact with maxillar teeth, deduction of 65 or 90g is foreseen. Considering the fact that weight and density of bones varies between populations, we hypothesize that above mentioned deductions do not represent real values. Therefore the aim of this research was to determine the deviations from actual mass. A total of 40 roe buck skulls originating from the area of Central Croatia were analysed. All skulls were weighed 3 times, initially when intact, after shallow cut and after proscribed cut. Obtained data were statistically analysed. Following the shallow cut, skull is lighter for 25 to 52 g, which is 11 g less than proscribed 65 g. In other words application of shallow cut will result in the loss in trophy value. In cases of intact skulls loss in weight is related to gross skull mass. In this case even 68 to 70% of variability are explained by gross skull mass (R<sup>2</sup>=0.680; p<0.0001 – linear function, or R<sup>2</sup>=0.699; p<0.01 – potency function). According to the intersection of the lines (obligate deduction of 90 g and dependence of mass loss due to the cutting) milestone in the mass is at 310 g gross. In other words trophies lighter than 310 g should be cut according to proscriptions as they will lose less than 90 g, while heavier skulls should be left intact as they will lose more than proscribed 90 g. Regardless of the skull preparation, all obtained masses show statistically significant relation to volume. With increase in volume density of trophies decreases (R<sup>2</sup>=0.813; p<0.001), with the fact that cutting of the skull results in removal of denser, heavier parts of the trophy. Application of the coefficient 0.23 depends on the density of the trophy, meaning that its application in the case of heavier antlers with lower volume will increase the trophy value. In the case of porous antlers the real coefficient should be higher, as application of 0.23 results in lower trophy values. In the case of intact skulls we do not advice application of 0.23 coefficient as this will decrease the trophy value.

Threshold of the chloride to hydroxide ions ratio in relation to steel reinforcement corrosion

A simple method for determining the corrosion dependence of steel reinforcement on the content of chloride and hydroxide ions is described. Steel test specimens were immersed for nine months in solutions with 0.03%, 0.3% and 3% NaCl with increasing concentrations of hydroxide ions, and pH of 8.5 to 13. The test specimens were cleaned of corrosion products and weighed at given time intervals of one month. The dependence of mass loss expressed as a percentage of the concentration of chloride and hydroxide ions was determined. The concentration threshold of the cCl−/cOH− ratio of 0.5 was evaluated from the results. Higher values of this ratio resulted in the formation of corrosion products on the surface of the test specimens.

Термічний аналіз деревини та кори робінії несправжньоакації в деревостанах Північного степу України

За допомогою методів термогравіметрії – термогравіметричної кривої (ТГ), диференціальної термогравіметричної кривої (ДТГ), або кривої інтенсивності зміни маси досліджуваного зразка, досліджено термічну деструкцію деревини і кори головної лісотвірної породи штучних лісових насаджень Північного Степу України – робінії несправжньоакації (Robinia pseudoacacia L.). Термічний аналіз зразків деревини і кори здійснено в окиснювальній (повітря) атмосфері. Встановлено стадії термічного розкладання деревинної речовини і кори в умовах програмованого нагріву до 600 оС зі швидкістю 10 оС/хв (ТГ/ДТГ/ДТА), їх температурні інтервали, втрату маси, інтенсивність втрати маси та теплові ефекти. На основі аналізу величин енергії активації на окремих стадіях термічного розкладання, залежності енергії активації від ступеня конверсії деревини і кори, а також із порівняння втрати маси на відповідних стадіях термодеструкції, теплових ефектів, залишкової маси і інших параметрів ТГ/ДТГ, охарактеризовано деревину і кору робінії. Деревина робінії характеризується значнішою термостабільністю, ніж кора. Запропоновано математичні моделі для оцінювання залежності втрати маси від температури деструкції складників надземної фітомаси (кори, деревини) досліджуваного деревного виду.

Melting temperature and heat of fusion of cytosine revealed from fast scanning calorimetry

Thermophysical properties in the melting range of cytosine, one of the five nucleobases of DNA and RNA, are hard to determine because of the low thermal stability of the compound and the high vapor pressure. As for other biomolecules fast heating rates allow melting of cytosine without detectable decomposition. By applying fast scanning calorimetry with the heating rate at 6000Ks−1 we succeeded to avoid decomposition and determine the melting temperature of cytosine (extrapolated to zero heating rate), as Tfus=(606±4)K, the glass transition temperature of the supercooled liquid state as Tg=(388±3)K, cold-crystallization temperature as Tcryst=(448±8)K, and the liquid state molar heat capacity Cp,m°(l)=(272±2) J mol−1K−1 at 423K. Taking into account the temperature dependent mass loss of the nanogram sized sample (up to 25% during the melting scan) we obtained the molar enthalpy of fusion of cytosine as ΔcrlH(Tfus)=(35±4) kJmol−1 in good agreement with the adjusted molar enthalpy of crystallization ΔlcrH(Tfus)=(34±2) kJmol−1.

Generation of two-dimensional binary mixtures in complex plasmas

Towards the investigation of polydisperse complex plasmas, the generation of binary mixtures is a first and important step. In this paper, the requirements for the generation of two-dimensional binary mixtures are discussed and first experiments are presented. In particular, the material dependent mass loss of the particles is taken into account by monitoring the charge-to-mass ratio of both species using a resonance method. The charge ratio q1/q2 of the species is determined and the spacial properties of the two-component crystals are examined and compared to numerical simulations.

A numerical and experimental study on fast pyrolysis of single woody biomass particles

A one-dimensional unsteady-state heat transfer model coupled with time dependent mass loss equation of wood particles exposed to drying and pyrolysis conditions was developed. The kinetic parameters were determined experimentally and the regime and characteristics of the conversion were evaluated in terms of the particle size and reactor temperature. The order of mass loss exponent varied from n=1 at temperatures lower than 350°C to n=0.5 at temperatures higher that 350°C. The analysis of conversion time, the time when particles lost 90% of their mass, showed that thermal treatment of particles larger than 0.5mm were controlled by internal thermal resistances. The valid range of particle size to use the simplified lumped model depends on the fluid temperature around the particles. The critical particle size was 0.6–0.7mm for the fluid temperature of 500°C and 0.9–1.0mm for the fluid temperature of 100°C.

Electron Beam Induced Mass Loss Dependence on Stained Thin Epon Resin Sections

Journal Article Electron Beam Induced Mass Loss Dependence on Stained Thin Epon Resin Sections Get access Radim Skoupy, Radim Skoupy Institute of Scientific Instrument, The Czech Academy of Sciences, Brno, Czech Republic Search for other works by this author on: Oxford Academic Google Scholar Jana Nebesarova, Jana Nebesarova Biology center, The Czech Academy of Sciences, Ceske Budejovice, Czech Republic Search for other works by this author on: Oxford Academic Google Scholar Vladislav Krzyzanek Vladislav Krzyzanek Institute of Scientific Instrument, The Czech Academy of Sciences, Brno, Czech Republic Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 22, Issue S3, 1 July 2016, Pages 926–927, https://doi.org/10.1017/S143192761600547X Published: 25 July 2016

Quantification of Mass Loss Dependence on Sample Orientation in 5xxx Series Aluminum Alloys

ASTM G67 is the standard test method for determining the susceptibility to intergranular corrosion (IGC) of 5xxx series aluminum alloys and requires measuring mass loss after exposure to nitric acid (the nitric acid mass loss test, NAMLT). This mass loss, and thus the IGC susceptibility, is dependent on orientation of the wrought product, but the quantitative degree of this dependence has not been well studied or documented. The orientation dependence of IGC susceptibility for AA5083 (UNS A95083) in H131 and H116 tempers is quantitatively presented herein. The underlying mechanism behind this dependence is also explored.

Simulations of micrometeoroid interactions with the Earth atmosphere

Micrometeoroids (cosmic dust with size between a few $\mu$m and $\sim$1 mm) dominate the annual extraterrestrial mass flux to the Earth. We investigate the range of physical processes occurring when micrometeoroids traverse the atmosphere. We compute the time (and altitude) dependent mass loss, energy balance, and dynamics to identify which processes determine their survival for a range of entry conditions. We develop a general numerical model for the micrometeoroid-atmosphere interaction. The equations of motion, energy, and mass balance are simultaneously solved for different entry conditions (e.g. initial radii, incident speeds and angles). Several different physical processes are taken into account in the equation of energy and in the mass balance, in order to understand their relative roles and evolution during the micrometeoroid-atmosphere interaction. In particular, to analyze the micrometeoroid thermal history we include in the energy balance: collisions with atmospheric particles, micrometeoroid radiation emission, evaporation, melting, sputtering and kinetic energy of the ablated mass. Low entry velocities and grazing incidence angles favor micrometeoroid survival. Among those that survive, our model distinguishes (1) micrometeoroids who reach the melting temperature and for which melting is the most effective mass loss mechanism, and (2) micrometeoroids for which ablation due to evaporation causes most of the the mass loss. Melting is the most effective cooling mechanism. Sputtering-induced mass loss is negligible.

VISCOUS ACCRETION OF A POLYTROPIC SELF-GRAVITATING DISK IN THE PRESENCE OF WIND

Self-similar and semi-analytical solutions are found for the height-averaged equations govern the dynamical behavior of a polytropic, self-gravitating disk under the effects of winds, around the nascent object. In order to describe time evolution of the system, we adopt a radius dependent mass loss rate, then highlight its importance on both the traditional $\alpha$ and innovative $\beta$ models of viscosity prescription. In agreement with some other studies, our solutions represent that Toomre parameter is less than one in most regions on the $\beta$-disk which indicate that in such disks gravitational instabilities can occur in various distances from the central accretor and so the $\beta$-disk model might provide a good explanation of how the planetary systems form. The purpose of the present work is twofold. First, examining the structure of disk with wind in comparison to no-wind solution; and second, to see if the adopted viscosity prescription affects significantly the dynamical behavior of the disk-wind system. We also considered the temperature distribution in our disk by a polytropic condition. The solutions imply that, under our boundary conditions, the radial velocity is larger for $\alpha$-disks and increases as wind becomes stronger in both viscosity models. Also, we noticed that the disk thickness increases by amplifying the wind or adopting larger values for polytropic exponent $\gamma$. It also may globally decrease if one prescribe $\beta$-model for the viscosity. Moreover, in both viscosity models, surface density and mass accretion rate reduce as wind gets stronger or $\gamma$ increases.