High frequency SAW devices based on third harmonic generation

We demonstrate the third harmonic generation in a ZnO/Si layered structure to obtain high frequency SAW devices. This configuration eliminates the need of high lithography resolution and allows easy integration of such devices and electronics on the same wafer. A theoretical study was carried out for the determination of the phase velocity and the electromechanical coupling coefficient (K²) dispersion curves of the surface acoustic waves. These results are also in agreement with those measured on a SAW filter designed for the third harmonic generation and the operating frequency is up to 2468 MHz.     

Inviscid and viscous stationary waves of gas flow through contracting-expanding nozzles

In this work we study steady states of one-dimensional viscous isentropic compressible flows through a contracting-expanding nozzle. Treating the viscosity coefficient as a singular parameter, the steady-state problem can be viewed as a singularly perturbed system. For a contracting-expanding nozzle, a complete classification of steady states is given and the existence of viscous profiles is established via the geometric singular perturbation theory. Particularly interesting is the existence of a maximal sub-to-super transonic wave and its role in the formation of other complicated transonic waves consisting of a sub-to-super portion.     

A hyperbolic model for the effects of urbanization on air pollution

A hyperbolic model to study effects of industrialization and urbanization on air pollution propagation is proposed.     

Far-Field Pattern of a Focal-Plane Array-Lens Antenna at Millimeter Wavelengths

In this paper an analysis of the far-field pattern of a focal-plane array in the case of two different lenses, a coma-free lens and a hyperbolic lens, and their comparison, are presented. Ray tracing and aperture integration are used. The calculated field pattern at W band is presented. The focal-plane elements are assumed to be corrugated horn. The f / D of the lens is 1.3. The coma-free lens is designed by step integration. The calculation results show that the coma-free lens is superior to the hyperbolic lens in the imaging performance. The coma-free lens can contain more pixels under the condition that the beam size and beam quality are almost constant over the range of angles scanned and the differences among beams gain less 1.8 dB. The aperture efficiency and directivity are also presented.     

Rogon-like solutions excited in the two-dimensional nonlocal nonlinear Schrödinger equation

We report the analytical one- and two-rogon-like solutions for the two-dimensional nonlocal nonlinear Schrödinger equation by means of the similarity transformation. These obtained solutions can be used to describe the possible physical mechanisms for rogue-like wave phenomenon. Moreover, the free function of space y involved in the obtained solutions excites the abundant structures of rogue-like wave propagations. The Hermite-Gaussian function of space y (normalized function) is, in particular, chosen to depict the dynamical behaviors for rogue-like wave phenomenon.     

Extreme Value Analysis of a Large Designed Experiment: A Case Study in Bulk Carrier Safety

The bulk carrier M.V. Derbyshire sank in 1980 when she encountered a typhoon near Japan. The most likely cause of her loss was finally explained in the report of the Re-opened Formal Investigation in 2000. The report also revealed inadequacies in safety standards for such vessels, particularly concerning regulations governing hatch cover strengths, and requested further work be undertaken to examine the sufficiency of aspects of the existing international standards for ship design. This paper describes the extreme value analysis of data from a large designed experiment intended to aid the revision of these safety standards. We highlight the importance of consistency of results over the different conditions examined, and how this can be achieved using various data pooling and regression techniques.     

Effect of a Localized Random Forcing Term on the Korteweg-De Vries Equation

In this work, we numerically investigate the influence of a white noise-type forcing on the phenomenon of forced generation of solitons by a localized moving disturbance. Our numerical method is based on finite elements and least-squares. We present numerical experiments for different values of noise amplitude and Froude number, which describe some damping effects on the emission of solitons.     

Shadow waves for pressureless gas balance laws

The pressureless gas dynamic model with body force as a source is considered. The problem is solved using the procedure used for finding delta shock type solutions to a special conservation laws known as Shadow Waves. If the body force is interpreted as the acceleration constant multiplied by the density, the solution obtained in this paper looks physically reasonable since the velocities of waves are changed accordingly with the acceleration.     

Hydrodynamics of natural oscillations of neutrally buoyant bodies in a layer of continuously stratified fluid

The flow patterns induced by floats of different shapes (sphere, short and long cylinders) freely sinking to the neutral-buoyancy horizon in a continuously stratified fluid are investigated using optical methods. General flow elements, both large-scale (waves, vortices, hydrodynamic wake) and fine-scale (boundary layers, extended autocumulative jets), are distinguished. For large times, the float oscillation frequencies are of the order of or greater than the buoyancy frequency of the medium. This indicates the significant effect of the induced flows on the motion of the float.