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Finite-size effects of β-deformed AdS<sub>5</sub>/CFT<sub>4</sub> at strong coupling
Ahn, C.,Bombardelli, D.,Kim, M. North-Holland Pub. Co 2012 Physics letters: B Vol.710 No.3
We compute both classical and quantum finite-size corrections at leading order in the strong coupling limit for the (dyonic) giant magnon in the Lunin-Maldacena background. Based on the exact S-matrix conjectured for the deformed theory, we generalize the Luscher formula to include twisted boundary conditions and show that the results match with those derived both by finite-size classical solutions of the giant magnon and by algebraic curve analysis.
Detached Eddy Simulation of the Nonaerated Skimming Flow over a Stepped Spillway
Toro, Juan Pablo,Bombardelli, Fabiá,n A.,Paik, Joongcheol American Society of Civil Engineers 2017 Journal of hydraulic engineering Vol.143 No.9
<P>The unsteady three-dimensional (3D), nonaerated, skimming flow over a stepped spillway is investigated by means of a detached eddy simulation (DES). Special emphasis is placed on the description of the instantaneous velocity and vorticity fields on the step cavities, as well as on the 3D, long-term, average flow structure at a Reynolds number of approximately 10(5). Mean-flow velocities obtained from simulations on both relatively-coarse and fine meshes at different locations in the spillway are in very good agreement with particle image velocimetry (PIV) data published elsewhere. Nondimensional profiles of turbulence intensity and Reynolds stresses are also close to data, although numerical values are larger than the experimental counterparts. Snapshots of velocity vectors reveal that the flow near the pseudo-bottom is continuously flapping, and that it intermittently interacts with ejections of positive vorticity emanating from the cavities. As a result of the interaction between the shear flow and the 3D cavity flow, patches of positive and negative vorticity are carried away downstream, eventually interacting with the free surface. It is also found that the ratios of redistribution among components (terms) of the turbulent kinetic energy (TKE) at the step edges are very similar to those universal values for the intermediate region of open-channel flows. It is additionally shown that large-scale structures extracted from isosurfaces of the Q-criterion correspond primarily to well-organized, randomly-distributed thin tubes of vorticity. The instantaneous flow field revealed in this paper is considered crucial for modeling the even more complex aerated region. (C) 2017 American Society of Civil Engineers.</P>
Finite-size effect for four-loop Konishi of the β-deformed N=4 SYM
Ahn, C.,Bajnok, Z.,Bombardelli, D.,Nepomechie, R.I. North-Holland Pub. Co 2010 Physics letters: B Vol.693 No.3
We propose that certain twists of the su(2|2)S-matrix elements describe the β-deformation of N=4 supersymmetric Yang-Mills theory. We compute the perturbative four-loop anomalous dimension of the Konishi operator of the deformed gauge theory from the Luscher formula based on these twisted S-matrix elements. The result agrees exactly with the perturbative gauge theory computations.
A distributed piezo-polymer scour net for bridge scour hole topography monitoring
Loh, Kenneth J.,Tom, Caroline,Benassini, Joseph L.,Bombardelli, Fabian A. Techno-Press 2014 Structural monitoring and maintenance Vol.1 No.2
Scour is one of the leading causes of overwater bridge failures worldwide. While monitoring systems have already been implemented or are still being developed, they suffer from limitations such as high costs, inaccuracies, and low reliability, among others. Also, most sensors only measure scour depth at one location and near the pier. Thus, the objective is to design a simple, low cost, scour hole topography monitoring system that could better characterize the entire depth, shape, and size of bridge scour holes. The design is based on burying a robust, waterproofed, piezoelectric sensor strip in the streambed. When scour erodes sediments to expose the sensor, flowing water excites it to cause the generation of time-varying voltage signals. An algorithm then takes the time-domain data and maps it to the frequency-domain for identifying the sensor's resonant frequency, which is used for calculating the exposed sensor length or scour depth. Here, three different sets of tests were conducted to validate this new technique. First, a single sensor was tested in ambient air, and its exposed length was varied. Upon verifying the sensing concept, a waterproofed prototype was buried in soil and tested in a tank filled with water. Sensor performance was characterized as soil was manually eroded away, which simulated various scour depths. The results confirmed that sensor resonant frequencies decreased with increasing scour depths. Finally, a network of 11 sensors was configured to form a distributed monitoring system in the lab. Their exposed lengths were adjusted to simulate scour hole formation and evolution. Results showed promise that the proposed sensing system could be scaled up and used for bridge scour topography monitoring.