10,881 research outputs found
Conformal Symmetry on the Instanton Moduli Space
The conformal symmetry on the instanton moduli space is discussed using the
ADHM construction, where a viewpoint of "homogeneous coordinates" for both the
spacetime and the moduli space turns out to be useful. It is shown that the
conformal algebra closes only up to global gauge transformations, which
generalizes the earlier discussion by Jackiw et al. An interesting
5-dimensional interpretation of the SU(2) single-instanton is also mentioned.Comment: 7 pages, LaTeX, version to appear in J. Phys. A: Math. Ge
Nonleptonic two-body charmless B decays involving a tensor meson in the Perturbative QCD Approach
Two-body charmless hadronic B decays involving a light tensor meson in the
final states are studied in the perturbative QCD approach based on
factorization. From our calculations, we find that the decay branching ratios
for color allowed tree-dominated decays and modes are of order and , respectively.
While other color suppressed tree-dominated decays have very small branching
ratios. In general, the branching ratios of most decays are in the range of
to , which are bigger by one or two orders of magnitude than
those predictions obtained in Isgur-Scora-Grinstein-Wise II model and in the
covariant light-front approach, but consistent with the recent experimental
measurements and the QCD factorization calculations. Since the decays with a
tensor meson emitted from vacuum are prohibited in naive factorization, the
contributions of nonfactorizable and annihilation diagrams are very important
to these decays, which are calculable in our perturbative QCD approach. We also
give predictions to the direct CP asymmetries, some of which are large enough
for the future experiments to measure. Because we considered the mixing between
and , the decay rates are enhanced significantly for some
decays involving meson, even with a small mixing angle.Comment: 26 pages, 2 figure
A survey design for a sensitive binary variable correlated with another nonsensitive binary variable
published_or_final_versio
Modified Volterra model-based non-linear model predictive control of IC engines with real-time simulations
Modelling of non-linear dynamics of an air manifold and fuel injection in an internal combustion (IC) engine is investigated in this paper using the Volterra series model. Volterra model-based non-linear model predictive control (NMPC) is then developed to regulate the air–fuel ratio (AFR) at the stoichiometric value. Due to the significant difference between the time constants of the air manifold dynamics and fuel injection dynamics, the traditional Volterra model is unable to achieve a proper compromise between model accuracy and complexity. A novel method is therefore developed in this paper by using different sampling periods, to reduce the input terms significantly while maintaining the accuracy of the model. The developed NMPC system is applied to a widely used IC engine benchmark, the mean value engine model. The performance of the controlled engine under real-time simulation in the environment of dSPACE was evaluated. The simulation results show a significant improvement of the controlled performance compared with a feed-forward plus PI feedback control
A Note on the Generalization of the GEMS Approach
This paper is a supplement of our earlier work JHEP 0410 (2004)
011[gr-qc/0409107].We map the vector potential of charged black holes into GEMS
and find that its effect on the thermal spectrum is the same as that on the
black hole side, i.e., it will induce a chemical potential in the thermal
spectrum which is the same as that in the charged black holes.We also argue
that the generalization of GEMS approach to non-stationary motions is not
possible.Comment: Latex file, 10 pages, no figure; v2: minor corrections; v3: revised
with title changed, one new section added and references adde
A Boundary Meshless Method Using Chebyshev Interpolation and Trigonometric Basis Function for Solving Heat Conduction Problems
A boundary meshless method has been developed to solve the heat conduction equations through the use of a newly established two-stage approximation scheme and a trigonometric series expansion scheme to approximate the particular solution and fundamental solution, respectively. As a result, no fundamental solution is required and the closed form of approximate particular solution is easy to obtain. The effectiveness of the proposed computational scheme is demonstrated by several examples in 2D and 31). We also compare our proposed method with the finite-difference method and the other meshless method showed in Sarler and Vertnik (Comput. Math. Appl. 2006; 51:1269-1282). Excellent numerical results have been observed. Copyright (C) 2007 John Wiley & Sons, Ltd
Newton-Hooke Limit of Beltrami-de Sitter Spacetime, Principles of Galilei-Hooke's Relativity and Postulate on Newton-Hooke Universal Time
Based on the Beltrami-de Sitter spacetime, we present the Newton-Hooke model
under the Newton-Hooke contraction of the spacetime with respect to the
transformation group, algebra and geometry. It is shown that in Newton-Hooke
space-time, there are inertial-type coordinate systems and inertial-type
observers, which move along straight lines with uniform velocity. And they are
invariant under the Newton-Hooke group. In order to determine uniquely the
Newton-Hooke limit, we propose the Galilei-Hooke's relativity principle as well
as the postulate on Newton-Hooke universal time. All results are readily
extended to the Newton-Hooke model as a contraction of Beltrami-anti-de Sitter
spacetime with negative cosmological constant.Comment: 25 pages, 3 figures; some misprints correcte
Genetic diversity among natural populations of Ottelia acuminata (Gaghep.) Dandy revealed by ISSR
Ottelia acuminata (Gagnep.) Dandy, an aquatic species of the Hydrocharitaceae, is endemic to China. A performance comparison of genetic diversity of 4 natural populations was conducted to investigatewhether or not water pollution in their habitats has anything to do with this species being endangered. A total number of 120 O. acuminate accessions were analyzed, by amplification of their DNAs with 15 primers (ISSR). Thirteen primers were scored and 214 bands were detected, of which 170 werepolymorphic (79.44%). The results showed that the genetic indices in polluted Jian Lake group were always the smallest ones, when compared with those of the other groups. It indicated that the polluted water did affect the genetic diversity of O. acuminate populations. And ISSRs seemed to be effectivetools for detecting genetic variation among O. acuminate geographical groups
Sim-to-Real Transfer for Quadrupedal Locomotion via Terrain Transformer
Deep reinforcement learning has recently emerged as an appealing alternative for legged locomotion over multiple terrains by training a policy in physical simulation and then transferring it to the real world (i.e., sim-to-real transfer). Despite considerable progress, the capacity and scalability of traditional neural networks are still limited, which may hinder their applications in more complex environments. In contrast, the Transformer architecture has shown its superiority in a wide range of large-scale sequence modeling tasks, including natural language processing and decision-making problems. In this paper, we propose Terrain Transformer (TERT), a high-capacity Transformer model for quadrupedal locomotion control on various terrains. Furthermore, to better leverage Transformer in sim-to-real scenarios, we present a novel two-stage training framework consisting of an offline pretraining stage and an online correction stage, which can naturally integrate Transformer with privileged training. Extensive experiments in simulation demonstrate that TERT outperforms state-of-the-art baselines on different terrains in terms of return, energy consumption and control smoothness. In further real-world validation, TERT successfully traverses nine challenging terrains, including sand pit and stair down, which can not be accomplished by strong baselines
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