1,201 research outputs found
Face algebras and unitarity of SU(N)_L-TQFT
Using face algebras (i.e. algebras of L-operators of IRF models), we
construct modular tensor categories with positive definite inner product, whose
fusion rules and S-matrices are the same as (or slightly different from) those
obtained by at roots of unity. Also we obtain state-sums
of ABF models on framed links which give quantum SU(2)-invariants of
corresponding 3-manifolds.Comment: AMS-LaTeX, 36 pages, to appear in Commun. Math. Phy
Compressive Sampling for Remote Control Systems
In remote control, efficient compression or representation of control signals
is essential to send them through rate-limited channels. For this purpose, we
propose an approach of sparse control signal representation using the
compressive sampling technique. The problem of obtaining sparse representation
is formulated by cardinality-constrained L2 optimization of the control
performance, which is reducible to L1-L2 optimization. The low rate random
sampling employed in the proposed method based on the compressive sampling, in
addition to the fact that the L1-L2 optimization can be effectively solved by a
fast iteration method, enables us to generate the sparse control signal with
reduced computational complexity, which is preferable in remote control systems
where computation delays seriously degrade the performance. We give a
theoretical result for control performance analysis based on the notion of
restricted isometry property (RIP). An example is shown to illustrate the
effectiveness of the proposed approach via numerical experiments
Topological strings and 5d T_N partition functions
We evaluate the Nekrasov partition function of 5d gauge theories engineered
by webs of 5-branes, using the refined topological vertex on the dual
Calabi-Yau threefolds. The theories include certain non-Lagrangian theories
such as the T_N theory. The refined topological vertex computation generically
contains contributions from decoupled M2-branes which are not charged under the
5d gauge symmetry engineered. We argue that, after eliminating them, the
refined topological string partition function agrees with the 5d Nekrasov
partition function. We explicitly check this for the T_3 theory as well as
Sp(1) gauge theories with N_f = 2, 3, 4 flavors. In particular, our method
leads to a new expression of the Sp(1) Nekrasov partition functions without any
contour integrals. We also develop prescriptions to calculate the partition
functions of theories obtained by Higgsing the T_N theory. We compute the
partition function of the E_7 theory via this prescription, and find the E_7
global symmetry enhancement. We finally discuss a potential application of the
refined topological vertex to non-toric web diagrams.Comment: 79 pages, 27 figures; v2: minor improvements, references adde
Defect detection using quasi-scholte wave for plate loaded with water on single surface
Ultrasonic guided waves achieve non-destructive inspection of thin plates. However, issues such as large energy leakage and attenuation often plague guided wave inspection of storage tanks and pipes filled with fluid. This study experimentally investigated the non-destructive testing of a water-loaded flat aluminum alloy plate through the application of a quasi-Scholte (QS) wave that propagated along the fluid-plate interface without experiencing attenuation due to leakage. A QS wave was confirmed as having been generated and propagated in a plate loaded with water on the bottom surface using ultrasonic incidence and detection at the top water-free surface. Two-dimensional Fourier transform images of the waveforms revealed refiection of the QS wave from a defect as well as a forward incident QS wave. The visualization results experimentally confirmed-via measurements of waves in water using a laser Doppler vibrometer-that QS waves propagated along a plate surface, while scattered waves were generated by defects
Mode extraction technique for guided waves in a pipe
Guided waves propagating in a pipe consist of many modes with different velocities and dispersions. To analyze these complex guided waves through a normal mode expansion technique, that is the fundamental theory on guided waves, we must first extract guided wave modes from received signals. In this study, we develop a mode extraction technique in which many received signals at different circumferential positions can be processed based on the fact that guided wave modes have different displacement distributions in the circumferential direction. After discussing the relevant theory, we verify our mode extraction technique experimentally using eight signals at eight different circumferential positions. Moreover, we show that the circumferential position of an excitation transducer, as well as the distance between an excitation transducer and a receiver in a pitch-catch configuration can be identified using the mode extraction technique. © 2005 Taylor & Francis Ltd.This is an Accepted Manuscript of an article published by Taylor & Francis in Nondestructive Testing and Evaluation on 19 Aug 2006, available at http://wwww.tandfonline.com/10.1080/10589750500062771
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