Numerical Verification of the Weak Turbulent Model for Swell Evolution

The purpose of this article is numerical verification of the theory of weak turbulence. We performed numerical simulation of an ensemble of nonlinearly interacting free gravity waves (swell) by two different methods: solution of primordial dynamical equations describing potential flow of the ideal fluid with a free surface and, solution of the kinetic Hasselmann equation, describing the wave ensemble in the framework of the theory of weak turbulence. In both cases we observed effects predicted by this theory: frequency downshift, angular spreading and formation of Zakharov-Filonenko spectrum $I_{\omega} \sim \omega^{-4}$. To achieve quantitative coincidence of the results obtained by different methods, one has to supply the Hasselmann kinetic equation by an empirical dissipation term $S_{diss}$ modeling the coherent effects of white-capping. Using of the standard dissipation terms from operational wave predicting model ({\it WAM}) leads to significant improvement on short times, but not resolve the discrepancy completely, leaving the question about optimal choice of $S_{diss}$ open. In a long run {\it WAM} dissipative terms overestimate dissipation essentially.Comment: 41 pages, 37 figures, 1 table. Submitted in European Journal of Mechanics B/Fluid

Wave modelling - the state of the art

This paper is the product of the wave modelling community and it tries to make a picture of the present situation in this branch of science, exploring the previous and the most recent results and looking ahead towards the solution of the problems we presently face. Both theory and applications are considered. The many faces of the subject imply separate discussions. This is reflected into the single sections, seven of them, each dealing with a specific topic, the whole providing a broad and solid overview of the present state of the art. After an introduction framing the problem and the approach we followed, we deal in sequence with the following subjects: (Section) 2, generation by wind; 3, nonlinear interactions in deep water; 4, white-capping dissipation; 5, nonlinear interactions in shallow water; 6, dissipation at the sea bottom; 7, wave propagation; 8, numerics. The two final sections, 9 and 10, summarize the present situation from a general point of view and try to look at the future developments

Focused Ion Beam as a Nanofabrication Tool for Rapid Prototyping of Nanomagnetic Devices

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 200

Mobile application for controlling multiple robots

Smartphones are becoming more and more high-performance devices every year, which allows to use them in new types of applications, including control and automation. This paper presents an Android OS based control tool that unifies a remote control of heterogeneous robotic systems. The current version of the tool controls the humanoid ROBOTIS OP2 robot, the wheeled differential drive TIAGo Base mobile robot, and the crawler Servosila Engineer mobile robot. Communication between a mobile device and the robots employs the RosJava library and the TCP/IP network protocol stack. The controls were implemented for compound kinematic systems with 3D robots' models displaying. Sensory data visualization and robots' movements controls were added to the application

Patterned Soft Underlayers for Perpendicular Magnetic Recording

This paper will present an unconventional way to answer the above questions. In contrast to the conventional flat geometry of SUL, it is proposed to use a patterned SUL. FEM-based simulations will be performed to illustrate many key benefits of the use of a patterned SUL

Magnetoresistive nanojunctions fabricated via focused ion beam implantation

Focused ion beam (FIB) is used to implant Ga+ ions into a 30-nm thick magnetoresistive element to effectively reduce the track width of the sensor from 1 mu m to similar to 80 nm. Through magnetic recording industry-standard spinstand measurements, it is confirmed that a dose of similar to 10(3) ions/cm(2) at a 1-pA FIB current is sufficient to fully "de-activate'' magnetism in the exposed side regions. To record tracks required for spinstand tests, a FIB-trimmed ring type write head is used