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Search Results: 1 - 10 of 49041 matches for " ZHAO Rong-Gen "
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Prepare and Formation Mechanism of the Zirconia Coating on Aluminium Alloy by Plasma Electrolytic Oxidation
XIN Shi-Gang,ZHAO Rong-Gen,DU Hui,SONG Li-Xin
无机材料学报 , 2009, DOI: 10.3724/sp.j.1077.2009.00107
Abstract: Zirconia coating was produced on aluminium alloy by plasma electrolytic oxidation (PEO). The alkaline electrolyte containing Zr(OH)a4 powders was used. The composition and structure of the coating were investigated by XRD, EPMA. The results show that the coating consists of a t-ZrO2, a m-ZrO2, a | /SUB>-Al2O3 and a ||/EM>-Al2O3. a t-ZrOa2 is the main phase and distributes in outer layer of the coating, however, a | /EM>-Al2O3 appears in inner layer of the coating. Many micro-particles appear on the coating surface with dimension of a 1£2| aa. In the process of plasma electrolytic oxidation, Zr(OH)a4 powders move and deposite on the mouth of plasma discharge channel under the effect of electric field force, then it is transformed to ZrOa2 by the high temperature of plasma discharge.
More on QCD Ghost Dark Energy
Rong-Gen Cai,Zhong-Liang Tuo,Ya-Bo Wu,Yue-Yue Zhao
Physics , 2012, DOI: 10.1103/PhysRevD.86.023511
Abstract: The difference between vacuum energy of quantum fields in Minkowski space and in Friedmann-Robterson-Walker universe might be related to the observed dark energy. The vacuum energy of the Veneziano ghost field introduced to solve the $U(1)_A$ problem in QCD is of the form, $ H+ {\cal O}(H^2)$. Based on this, we study the dynamical evolution of a phenomenological dark energy model whose energy density is of the form $\alpha H+\beta H^2$. In this model, the universe approaches to a de Sitter phase at late times. We fit the model with current observational data including SnIa, BAO, CMB, BBN, Hubble parameter and growth rate of matter perturbation. It shows that the universe begins to accelerate at redshift $z\sim 0.75$ and this model is consistent with current data. In particular, this model fits the data of growth factor well as the $\Lambda CDM$ model.
A Dark Energy Model Characterized by the Age of the Universe
Cai, Rong-Gen
High Energy Physics - Phenomenology , 2007, DOI: 10.1016/j.physletb.2007.09.061
Abstract: Quantum mechanics together with general relativity leads to the K\'arolyh\'azy relation and a corresponding energy density of quantum fluctuations of space-time. Based on the energy density we propose a dark energy model, in which the age of the universe is introduced as the length measure. This dark energy is consistent with astronomical data if the unique numerical parameter in the dark energy model is taken to be a number of order one. The dark energy behaves like a cosmological constant at early time and drives the universe to an eternally accelerated expansion with power-law form at late time. In addition, we point out a subtlety in this kind of dark energy model.
Critical behavior in black hole thermodynamics
Rong-Gen Cai
Physics , 1999,
Abstract: In this talk I introduce the critical behavior occurring at the extremal limit of black holes. The extremal limit of black holes is a critical point and a phase transition takes place from the extremal black holes to their nonextremal counterparts. Some critical exponents satisfying the scaling laws are obtained. From the scaling laws we introduce the concept of the effective dimension of black holes and discuss the relationship between the critical behavior and the statistical interpretation of black hole entropy.
Thermodynamics of Apparent Horizon in Brane World Scenarios
Rong-Gen Cai
Physics , 2007, DOI: 10.1143/PTPS.172.100
Abstract: Applying the Clausius relation, $\delta Q=TdS$, to the apparent horizon of FRW universe in brane world scenarios, we show that an explicit entropy expression associated with the apparent horizon can be obtained. On the apparent horizon, the relation, $dE=TdS +WdV$, also holds in the brane world scenarios. We show these results in the RSII model, warped DGP model and the more general case with a Gauss-Bonnet term in the bulk and an intrinsic curvature term on the brane.
Stability of degenerate Cauchy horizons in black hole spacetimes
Rong-Gen Cai
Physics , 1998, DOI: 10.1103/PhysRevD.59.104004
Abstract: In the multihorizon black hole spacetimes, it is possible that there are degenerate Cauchy horizons with vanishing surface gravities. We investigate the stability of the degenerate Cauchy horizon in black hole spacetimes. Despite the asymptotic behavior of spacetimes (flat, anti-de Sitter, or de Sitter), we find that the Cauchy horizon is stable against the classical perturbations, but unstable quantum mechanically.
A Note on Curvature Fluctuation of Noncommutative Inflation
Rong-Gen Cai
Physics , 2004, DOI: 10.1016/j.physletb.2004.04.078
Abstract: An elegant approach, which incorporates the effect of the stringy spacetime uncertainty relation, to calculate power spectra of fluctuations during inflation has been suggested by Brandenberger and Ho. In this approach, one of important features is the appearance of an upper bound on the comoving momentum $k$, at which the stringy spacetime uncertainty relation is saturated. As a result, the time-dependent upper bound leads us to choose naturally a set of initial vacua for each mode, in which the stringy uncertainty relation is saturated. In this note, with that set of vacua we calculate power spectrum of curvature fluctuation for a power law inflation, up to the leading order of a parameter describing the spacetime noncommutativity. It turns out that this choice of initial vacuum has a significant effect on the power spectrum of fluctuations.
Effective spatial dimension of extremal non-dilatonic black p-branes and the description of entropy on the world volume
Rong-Gen Cai
Physics , 1997, DOI: 10.1103/PhysRevLett.78.2531
Abstract: By investigating the critical behavior appearing at the extremal limit of the non-dilatonic, black p-branes in (d+p) dimensions, we find that some critical exponents related to the critical point obey the scaling laws. From the scaling laws we obtain that the effective spatial dimension of the non-dilatonic black holes and black strings is one, and is p for the non-dilatonic black p-branes. For the dilatonic black holes and black p-branes, the effective dimension will depend on the parameters in theories. Thus, we give an interpretation why the Bekenstein-Hawking entropy may be given a simple world volume interpretation only for the non-dilatonic black p-branes.
Constant Curvature Black Hole and Dual Field Theory
Rong-Gen Cai
Physics , 2002, DOI: 10.1016/S0370-2693(02)02498-X
Abstract: We consider a five-dimensional constant curvature black hole, which is constructed by identifying some points along a Killing vector in a five-dimensional AdS space. The black hole has the topology M_4 times S^1, its exterior is time-dependent and its boundary metric is of the form of a three-dimensional de Sitter space times a circle, which means that the dual conformal field theory resides on a dynamical spacetime. We calculate the quasilocal stress-energy tensor of the gravitational background and then the stress-energy tenor of the dual conformal field theory. It is found that the trace of the tensor does indeed vanish, as expected. Further we find that the constant curvature black hole spacetime is just the "bubble of nothing" resulting from Schwarzschild-AdS black holes when the mass parameter of the latter vanishes.
A Note on the Positive Constant Curvature Space
Rong-Gen Cai
Physics , 2002, DOI: 10.1016/S0370-2693(02)03096-4
Abstract: We construct a positive constant curvature space by identifying some points along a Killing vector in a de Sitter Space. This space is the counterpart of the three-dimensional Schwarzschild-de Sitter solution in higher dimensions. This space has a cosmological event horizon, and is of the topology ${\cal M}_{D-1}\times S^1$, where ${\cal M}_{D-1}$ denotes a $(D-1)$-dimensional conformal Minkowski spacetime.
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