نتایج جستجو برای: mass loss

تعداد نتایج: 894569  

2006
Jorick S. Vink

I present the results of radiation-driven mass-loss predictions for hot stars of all mass. Mass loss is an important aspect for the evolution of massive stars, the rotational properties of the progenitors of gamma-ray bursts, and is essential in assessing whether the most massive stars explode as pair-instability supernovae, or avoid them due to mass loss. As a result, the rate of mass loss is ...

Journal: :مهندسی بیوسیستم ایران 0
احمد پیری دانشجوی دکتری مکانیک بیوسیستم- دانشگاه ارومیه علی محمدنیکبخت دانشیار گروه مهندسی مکانیک بیوسیستم- دانشگاه ارومیه

the purposes of this article are studying the effects of oxygen presence on waste wood pyrolysis process in order to produce bio-char. to reach the goal, cubic samples of size 2.5 cm pyrolized at 300 and 400 °c. the surface and center temperatures of samples were measured and their mass losses were calculated from the ratio of pyrolized mass to initial mass of the sample. increase in temperatur...

1999
Noam Soker

Any model for the formation of elliptical planetary nebulae (PNs) should account for the positive correlation between the mass loss rate and the degree of departure from sphericity of the AGB progenitor's wind. I propose that this correlation results from dust formation above magnetic cool spots. The model deals with elliptical PNs, but not with bipolar PNs. The basic assumption is that a weak ...

2008
Raphael Hirschi Cristina Chiappini André Maeder

Mass loss plays a dominant role in the evolution of massive stars at solar metallicity. After discussing different mass loss mechanisms and their metallicity dependence, we present the possibility of strong mass loss at very low metallicity. Our models at Z = 10−8 show that stars more massive than about 60 M⊙ may lose a significant fraction of their initial mass in the red supergiant phase. Thi...

1998
Kathryn V. Johnston Steinn Sigurdsson Lars Hernquist

We present the results of a study that uses numerical simulations to interpret observations of tidally disturbed satellites around the Milky Way. When analysing the simulations from the viewpoint of an observer, we find a break in the slope of the star count and velocity dispersion profiles in our models at the location where unbound stars dominate. We conclude that ‘extra-tidal’ stars and enha...

2008
R. S. Kolevatov

Collisional parton energy loss is revisited within a simple model assuming incoherent elastic scattering of on-shell projectile partons on partonic constituents of the QGP with HTL screening. The thermal motion of plasma particles is carefully taken into account. Results on dE/dx are found to be consistent with other authors. There is a significant discrepancy in the energy loss pattern for the...

Introduction: peak torque and peak joint power are two important variables in the performance of weightlifters. The purpose of this study was to investigate the effect of acute weight loss on the power and torque of the knee joint of elite weightlifters at different angular speeds of knee flexion and extension. Methods: The statistical sample of the research was selected according to the avail...

Journal: :جنگل و فرآورده های چوب 0
رضا قمری دانشجوی کارشناسی ارشد صنایع چوب و کاغذ، پردیس کشاورزی و منابع طبیعی، دانشگاه تهران اصغر طارمیان دانشیار گروه علوم و صنایع چوب و کاغذ، پردیس کشاورزی و منابع طبیعی دانشگاه تهران

in this research, the bioinsising impact of two wood decay fungi (pysisporinus vitreus and xylaria longipes) on radial air permeability and moisture diffusion coefficient of spruce wood (picea abies) was investigated. fungal cultivation was performed in an incubator at 25 °c and 85% relative humidity for 15, 30 and 45 days. results showed that the permeability, moisture diffusion and mass loss ...

A. nouri S. Astaraki

In this paper, optimization of the sound transmission loss of finite rectangular anisotropic laminated composite plate with simply supported boundary conditions has been developed to maximize transmission loss. Appropriate constraints were imposed to prevent the occurrence of softening effect due to optimization. For this purpose, optimization process was incorporated into comprehensive finite ...

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