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X(1835): A Possible Baryonium?
We point out that (1) the large coupling and suppressed mesonic
coupling of X(1835) and (2) the suppression of the three-body strange final
states strongly indicate that X(1835) may be a baryonium. We also
point out that the branching ratio of should be bigger
than that of . If BES further confirms the
non-observation of X(1835) in the channel, that will be very
puzzling. Finally, X(1835) may be used a tetraquark generator if X(1835) is
really established as a baryonium state.Comment: Comments and suggestions welcom
Spherical Tiling by 12 Congruent Pentagons
The tilings of the 2-dimensional sphere by congruent triangles have been
extensively studied, and the edge-to-edge tilings have been completely
classified. However, not much is known about the tilings by other congruent
polygons. In this paper, we classify the simplest case, which is the
edge-to-edge tilings of the 2-dimensional sphere by 12 congruent pentagons. We
find one major class allowing two independent continuous parameters and four
classes of isolated examples. The classification is done by first separately
classifying the combinatorial, edge length, and angle aspects, and then
combining the respective classifications together.Comment: 53 pages, 40 figures, spherical geometr
Multi-Objective Robust H-infinity Control of Spacecraft Rendezvous
Based on the relative motion dynamic model illustrated by C-W equations, the problem of robust Hinfin control for a class of spacecraft rendezvous systems is investigated, which contains parametric uncertainties, external disturbances and input constraints. An Hinfin state-feedback controller is designed via a Lyapunov approach, which guarantees the closed-loop system to meet the multi-objective design requirements. The existence conditions for admissible controllers are formulated in the form of linear matrix inequalities (LMIs), and the controller design is cast into a convex optimization problem subject to LMI constraints. An illustrative example is provided to show the effectiveness of the proposed control design method
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