|
Zeldovich
Yakov Borisovich Zeldovich ( be, Я́каў Бары́савіч Зяльдо́віч, russian: Я́ков Бори́сович Зельдо́вич; 8 March 1914 – 2 December 1987), also known as YaB, was a leading Soviet physicist of Belarusian origin, who is known for his prolific contributions in physical cosmology, physics of thermonuclear reactions, combustion, and hydrodynamical phenomena. From 1943, Zeldovich, a self-taught physicist, started his career by playing a crucial role in the development of the former Soviet program of nuclear weapons. In 1963, he returned to academia to embark on pioneering contributions on the fundamental understanding of the thermodynamics of black holes and expanding the scope of physical cosmology. Biography Early life and education Yakov Zeldovich was born into a Belarusian Jewish family in his grandfather's house in Minsk. However, in mid-1914, the Zeldovich family moved to Saint Petersburg. They resided there until August 1941 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zeldovich Spontaneous Wave
A Zeldovich spontaneous wave, also referred to as Zeldovich gradient mechanism, is a reaction wave that propagates spontaneously in a reacting medium with a nonuniform initial temperature distribution when there is no interaction between different fluid elements. The concept was put forward by Yakov Zeldovich in 1980, based on his earlier work with his coworkers. The spontaneous wave is different from the other two conventional combustion waves, namely the subsonic deflagrations and supersonic detonations. The wave, although strictly speaking unrealistic because gasdynamic effects are neglected, is often cited to explain the yet-unsolved problem of deflagration to detonation transition (DDT). The mechanism behind the spontaneous wave is readily explained by considering a reaction medium at rest with a nonuniform temperature distribution such that the spatial temperature gradients are small or at least it is not sufficiently large (large temperature gradients will evidently lead ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zeldovich–Taylor Flow
Zeldovich–Taylor flow (also known as Zeldovich–Taylor expansion wave) is the fluid motion of gaseous detonation products behind Chapman–Jouguet detonation wave. The flow was described independently by Yakov Zeldovich in 1942 and G. I. Taylor in 1950, although G. I. Taylor carried out the work in 1941 that being circulated in the British Ministry of Home Security. Since naturally occurring detonation waves are in general a Chapman–Jouguet detonation wave, the solution becomes very useful in describing real-life detonation waves. Mathematical description Consider a spherically outgoing Chapman–Jouguet detonation wave propagating with a constant velocity D. By definition, immediately behind the detonation wave, the gas velocity is equal to the local sound speed c with respect to the wave. Let v(r,t) be the radial velocity of the gas behind the wave, in a fixed frame. The detonation is ignited at t=0 at r=0. For t>0, the gas velocity must be zero at the center r=0 and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rashid Sunyaev
Rashid Alievich Sunyaev ( tt-Cyrl, Рәшит Гали улы Сөнәев, russian: Раши́д Али́евич Сюня́ев; born 1 March 1943 in Tashkent, USSR) is a German, Soviet, and Russian astrophysicist of Tatar descent. He got his MS degree from the Moscow Institute of Physics and Technology (MIPT) in 1966. He became a professor at MIPT in 1974. Sunyaev was the head of the High Energy Astrophysics Department of the Russian Academy of Sciences, and has been chief scientist of the Academy's Space Research Institute since 1992. He has also been a director of the Max Planck Institute for Astrophysics in Garching, Germany since 1996, and Maureen and John Hendricks Distinguished Visiting Professor in the School of Natural Sciences at the Institute for Advanced Study in Princeton since 2010. Works Sunyaev and Yakov B. Zeldovich developed the theory for the evolution of density fluctuations in the early universe. They predicted the pattern of acoustic fluctuations that ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zeldovich–Liñán Model
In combustion, Zel'dovich–Liñán model is a two-step reaction model for the combustion processes, named after Yakov Borisovich Zel'dovich and Amable Liñán. The model includes a chain-branching and a chain-breaking (or radical recombination) reaction. The model was first introduced by Zel'dovich in 1948 and later analysed by Liñán using activation energy asymptotics in 1971. The mechanism reads as : \begin \rm + \rm &\rightarrow 2\rm \\ \rm + \rm + \rm &\rightarrow 2\rm +\rm \end where \rm is the fuel, \rm is an intermediate radical, \rm is the third body and \rm is the product. The first reaction is the chain-branching reaction, which is considered to be auto-catalytic (consumes no heat or releases no heat), with very large activation energy and the second reaction is the chain-breaking (or radical-recombination) reaction, where all of the heat in the combustion is released, with almost negligible activation energy.Dold, J., Daou, J., & Weber, R. (2004). Reactive-diffusive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Classical Nucleation Theory
Classical nucleation theory (CNT) is the most common theoretical model used to quantitatively study the kinetics of nucleation.H. R. Pruppacher and J. D. Klett, ''Microphysics of Clouds and Precipitation'', Kluwer (1997)P.G. Debenedetti, ''Metastable Liquids: Concepts and Principles'', Princeton University Press (1997) Nucleation is the first step in the spontaneous formation of a new thermodynamic phase or a new structure, starting from a state of metastability. The kinetics of formation of the new phase is frequently dominated by nucleation, such that the time to nucleate determines how long it will take for the new phase to appear. The time to nucleate can vary by orders of magnitude, from negligible to exceedingly large, far beyond reach of experimental timescales. One of the key achievements of classical nucleation theory is to explain and quantify this immense variation. Description The central result of classical nucleation theory is a prediction for the ''rate of nucleati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zeldovich Pancake
A Zel'dovich pancake is a theoretical condensation of gas out of a primordial density fluctuation following the Big Bang. In 1970, Yakov B. Zel'dovich showed that for an ellipsoid of gas on a supergalactic scale, an approximation can be used that will model the collapse as occurring most rapidly along the shortest axis, resulting in a pancake form. This approximation assumes that the ellipsoid of gas is sufficiently large that the effect of pressure is negligible and only gravitational attraction needs to be considered. That is, the gas will collapse without being significantly perturbed by outward pressure. This assumption is especially valid if the collapse occurs before the recombination era that resulted in the formation of hydrogen atoms. In 1989, Zel'dovich and S. F. Shandarin showed that initial overlapping density fluctuations of random Gaussian fields would result in "dense pancakes, filaments, and compact clumps of matter". This model became known as a top-down model of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antidynamo Theorem
In physics and in particular in the theory of magnetism, an antidynamo theorem is one of several results that restrict the type of magnetic fields that may be produced by dynamo action. One notable example is Thomas Cowling's antidynamo theorem which states that no axisymmetric magnetic field can be maintained through a self-sustaining dynamo action by an axially symmetric current. Similarly, the Zeldovich's antidynamo theorem states that a two-dimensional, planar flow cannot maintain the dynamo action.Zeldovich, Y. B. (1957). The magnetic field in the two-dimensional motion of a conducting turbulent fluid. Sov. Phys. JETP, 4, 460-462. Consequences Apart from the Earth's magnetic field, some other bodies such as Jupiter and Saturn, and the Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zeldovich Mechanism
Zel'dovich mechanism is a chemical mechanism that describes the oxidation of nitrogen and NO''x'' formation, first proposed by the Russian physicist Yakov Borisovich Zel'dovich in 1946. The reaction mechanisms read as : + O _1 + , : + O2 _2 + , where k_1 and k_2 are the reaction rate constants in Arrhenius law. The overall global reaction is given by : + 2NO. The overall reaction rate is mostly governed by the first reaction (i.e., rate-determining reaction), since the second reaction is much faster than the first reaction and occurs immediately following the first reaction. At fuel-rich conditions, due to lack of oxygen, reaction 2 becomes weak, hence, a third reaction is included in the mechanism, also known as extended Zel'dovich mechanism (with all three reactions), : + _3 + . The forward rate constants of the reactions are given by :\begin k_ &= 1.47\times 10^ \, T^ \mathrm e^,\\ k_ &= 6.40\times 10^9 \, T \mathrm e^, \\ k_ &= 3.80\times 10^, \end where the pre-e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alexei Starobinsky
Alexei Alexandrovich Starobinsky (russian: Алексе́й Алекса́ндрович Староби́нский; born 19 April 1948) is a Soviet and Russian astrophysicist and cosmologist. He received the Kavli Prize in Astrophysics "for pioneering the theory of cosmic inflation", together with Alan Guth and Andrei Linde in 2014. Early life Starobinsky is a former student of Yakov Zeldovich at Moscow State University from where he earned a bachelor's degree in 1972. In 1975, he earned a PhD degree from the Landau Institute for Theoretical Physics of the Russian Academy of Sciences and is now a senior scientist at the institute. From 1990 to 1997, he headed the department of gravitation and cosmology and, from 1999 to 2003, he was the institute's deputy director. In the 1970s, Starobinsky worked on the theory of particle creation in the early universe and particle generation and radiation from rotating black holes (1973/74), a precursor of the theory of Hawking radiation. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deborah Dultzin
Deborah Dultzin Kessler (also published as Deborah Dultzin-Hacyan) is a Mexican astrophysicist specializing in quasars, blazars, active galactic nuclei, and supermassive black holes. She is a professor and researcher in the National Autonomous University of Mexico (UNAM) Institute of Astronomy. Education and career Dultzin is the daughter of Arieh Dulzin, a Zionist activist from Minsk in the Russian Empire and Soviet Union (now Belarus) who emigrated to Mexico in 1928, and to Israel in 1956. Her mother was Fredzia Kessler, an oil painter from Warsaw, Poland, who had also emigrated to Mexico as a child in 1929. She was born in Monterrey in 1945, and grew up with her mother after her father left Mexico. As a high school student and later at UNAM, she loved mathematics but struggled with physics. Nevertheless, she completed a degree in physics in order to aim for a career in astronomy. Her anti-American political stance, and the influence of Guillermo Haro, persuaded her to conti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Varun Sahni
Varun Bhisham Sahni (born March 29, 1956) is an Indian theoretical physicist, astrophysicist and a Distinguished Professor at the Inter-University Centre for Astronomy and Astrophysics. Known for his research on cosmology, Sahni is an elected fellow of all the three major Indian science academies viz. Indian Academy of Sciences, Indian National Science Academy and National Academy of Sciences, India. The Council of Scientific and Industrial Research, the apex agency of the Government of India for scientific research, awarded him the Shanti Swarup Bhatnagar Prize for Science and Technology, one of the highest Indian science awards, for his contributions to physical sciences in 2000. Sahni is reported to have studied the universe, more specifically its large-scale structure, the early inflationary phase and cosmological constant. His achievements include the establishment of a cosmic no-hair theorem related to inflation, analysis of the universe structure using self-developed statis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
