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Zel'dovich
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 19 ... [...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 o ... [...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 In chemistry and physics, activation energy is the minimu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superradiance
In physics, superradiance is the radiation enhancement effects in several contexts including quantum mechanics, astrophysics and relativity. Quantum optics In quantum optics, superradiance is a phenomenon that occurs when a group of ''N'' emitters, such as excited atoms, interact with a common light field. If the wavelength of the light is much greater than the separation of the emitters, then the emitters interact with the light in a collective and coherent fashion. This causes the group to emit light as a high intensity pulse (with rate proportional to ''N''2). This is a surprising result, drastically different from the expected exponential decay (with rate proportional to ''N'') of a group of independent atoms (see spontaneous emission). Superradiance has since been demonstrated in a wide variety of physical and chemical systems, such as quantum dot arrays and J-aggregates. This effect has been used to produce a superradiant laser. Rotational superradiance Rotational supe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zeldovich Number
The Zel'dovich number is a dimensionless number which provides a quantitative measure for the activation energy of a chemical reaction which appears in the Arrhenius exponent, named after the Russian scientist Yakov Borisovich Zel'dovich, who along with David A. Frank-Kamenetskii, first introduced in their paper in 1938. In 1983 ICDERS meeting at Poitiers, it was decided to name after Zel'dovich.Clavin, P. (1985). Dynamic behavior of premixed flame fronts in laminar and turbulent flows. Progress in energy and combustion science, 11(1), 1-59. It is defined as :\beta = \frac \cdot \frac where *E_a is the activation energy of the reaction *R is the universal gas constant *T_b is the burnt gas temperature *T_u is the unburnt mixture temperature. In terms of heat release parameter \alpha, it is given by :\beta = \frac \alpha For typical combustion phenomena, the value for Zel'dovich number lies in the range \beta\approx 8-20. Activation energy asymptotics Activation energy asymp ... [...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-exp ... [...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 Germany, German, Soviet Union, Soviet, and Russia, 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 Moscow Institute of Physics and Technology, 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 bei München, 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 Zeldovich, Yakov B. Zeldovich developed the theory for the evol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Roman Juszkiewicz
Roman Juszkiewicz (9 August 1952 – 28 January 2012) was a Polish astrophysicist whose work concerned fundamental issues of cosmology. Juszkiewicz was born in Warsaw. He studied at Moscow State University (a student of Yakov Borisovich Zel'dovich), where he graduated in 1976. In 1981 he obtained a PhD at the University of Warsaw. During 1984–1986 he visited Cambridge and Sussex universities, he spent 1986–87 at Berkeley, 1987–1991 at Princeton, and from 1989 was a member of the Princeton Institute for Advanced Study. He also worked at the Institut d'Astrophysique de Paris and the University of Geneva. Juszkiewicz held a professor position at N. Copernicus Astronomical Center of the Polish Academy of Sciences, the University of Zielona Góra and the Multicultural Jacek Kuroń High School in Warsaw. Juszkiewicz obtained his professorial title on 20 August 2003. Juszkiewicz's scientific interests included the theory of gravitational instability, origins of the large-sca ... [...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] |
Sergei Kopeikin
Sergei Kopeikin (born April 10, 1956) is a USSR-born theoretical physicist and astronomer presently living and working in the United States, where he holds the position of Professor of Physics at the University of Missouri in Columbia, Missouri. He specializes in the theoretical and experimental study of gravity and general relativity. He is also an expert in the field of the astronomical reference frames and time metrology. His general relativistic theory of the Post-Newtonian reference frames which he had worked out along with Victor A. Brumberg, was adopted in 2000 by thresolutionsof the International Astronomical Union as a standard for reduction of ground-based astronomical observation. A computer program Tempo2 used to analyze radio observations of pulsars, includes several effects predicted by S. Kopeikin that are important for measuring parameters of the binary pulsars, for testing general relativity, and for detection of gravitational waves of ultra-low frequency. Serg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Minsk
Minsk ( be, Мінск ; russian: Минск) is the capital and the largest city of Belarus, located on the Svislach and the now subterranean Niamiha rivers. As the capital, Minsk has a special administrative status in Belarus and is the administrative centre of Minsk Region (voblast) and Minsk District (raion). As of January 2021, its population was 2 million, making Minsk the 11th most populous city in Europe. Minsk is one of the administrative capitals of the Commonwealth of Independent States (CIS) and the Eurasian Economic Union (EAEU). First documented in 1067, Minsk became the capital of the Principality of Minsk before being annexed by the Grand Duchy of Lithuania in 1242. It received town privileges in 1499. From 1569, it was the capital of the Minsk Voivodeship, an administrative division of the Polish–Lithuanian Commonwealth. It was part of a region annexed by the Russian Empire in 1793, as a consequence of the Second Partition of Poland. From 1919 to 1991, aft ... [...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] |
