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Fire resistance of steel beam to square CFST column composite joints using RC slabs: Experiments and numerical studies
In this paper, experimental investigation and numerical simulation of steel beam to square concrete-filled steel tube (CFST) column composite joints that use reinforced concrete (RC) slabs subjected to localized and global fire conditions are presented. Eight joints were tested under the ISO 834 fire standard, and the effect of different parameters including the load ratio of beams, the beam-to-column ratio of linear stiffness, and different fire scenarios was studied during testing. The failure patterns and the thermal responses of the structural members including the temperature distribution, axial displacement of columns, vertical deflection of the beam ends, and fire resistance of the joints were recorded and discussed. The results show that tube buckling of the square CFST columns, flange buckling of the steel beams, and separation between the top flange of the steel beams and the RC slabs were the primary failure patterns of this type of joint. Moreover, the temperatures of structural members within the connection zone were lower than those in the other regions. Compared with other factors, the load ratio of the beams demonstrated a significant influence on the displacement of the structural members and the fire resistance of the joints. A three-dimensional finite element analysis (FEA) model was built to simulate the fire performance of this type of composite joint. The simulation results were compared to the test results in terms of failure patterns, temperature distributions, displacements, and fire resistances, and good agreement in general was achieved. Finally, the FEA model was adopted to examine the effect of parameters on the fire resistance of the composite joints with axial and flexural constraints applied at the ends of the beam
A nonperturbative parametrization and scenario for EFT renormalization
We present a universal form of the -matrices renormalized in
nonperturbative regime and the ensuing notions and properties that fail
conventional wisdoms. A universal scale is identified and shown to be
renormalization group invariant. The effective range parameters are derived in
a nonperturbative scenario with some new predictions within the realm of
contact potentials. Some controversies are shown to be due to the failure of
conventional wisdoms.Comment: 5 pages, no figure, to appear in Europhys. Let
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Robust filtering for uncertain linear systems with delayed states and outputs
Copyright [2002] IEEE. This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of Brunel University's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.Deals with the robust filtering problem for uncertain linear systems with delayed states and outputs. Both time-invariant and time-varying cases are considered. For the time-invariant case, an algebraic Riccati matrix inequality approach is proposed to design a robust H∞ filter such that the filtering process remains asymptotically stable for all admissible uncertainties, and the transfer function from the disturbance inputs to error state outputs satisfies the prespecified H∞ norm upper bound constraint. We establish the conditions under which the desired robust H ∞ filters exist, and derive the explicit expression of these filters. For the time-varying case, we develop a differential Riccati inequality method to design the robust filters. A numerical example is provided to demonstrate the validity of the proposed design approac
Guest editorial: Memetic computing in the presence of uncertainties
Copyright @ Springer-Verlag 2010.The Guest Editors acknowledge the research support by the Academy of Finland, Akatemiatutkija 130600, Algorithmic
Design Issues in Memetic Computing, and by the UK Engineering and Physical Sciences Research Council (EPSRC) Project: Evolutionary Algorithms for Dynamic Optimisation Problems, under Grant EP/E060722/1
Field-ionization threshold and its induced ionization-window phenomenon for Rydberg atoms in a short single-cycle pulse
We study the field-ionization threshold behavior when a Rydberg atom is
ionized by a short single-cycle pulse field. Both hydrogen and sodium atoms are
considered. The required threshold field amplitude is found to scale
\emph{inversely} with the binding energy when the pulse duration becomes
shorter than the classical Rydberg period, and, thus, more weakly bound
electrons require larger fields for ionization. This threshold scaling behavior
is confirmed by both 3D classical trajectory Monte Carlo simulations and
numerically solving the time-dependent Schr\"{o}dinger equation. More
surprisingly, the same scaling behavior in the short pulse limit is also
followed by the ionization thresholds for much lower bound states, including
the hydrogen ground state. An empirical formula is obtained from a simple
model, and the dominant ionization mechanism is identified as a nonzero spatial
displacement of the electron. This displacement ionization should be another
important mechanism beyond the tunneling ionization and the multiphoton
ionization. In addition, an "ionization window" is shown to exist for the
ionization of Rydberg states, which may have potential applications to
selectively modify and control the Rydberg-state population of atoms and
molecules
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