The use of finite difference schemes to compute the scattering of acoustic waves by surfaces made up of different materials with sharp surface discontinuities at the joints would, invariably, result in the generations of spurious reflected waves. The spurious waves are caused by the use of a discrete computational method. Spurious scattered waves are produced even if a high-order scheme capable...

Diesel exhaust particles are a complex mixture of thousands of gases and fine substances that contain more than 40 different environmental contaminants. Being exposed to these exhaust particles (called soot) can cause lung damage and respiratory problems. Diesel particulate filters are used in many countries for mobile sources as a legal obligation to decrease harmful effect of these fine pa...

We consider classical acoustic waves in a medium described by a position dependent mass density %(x). We assume that %(x) is a random perturbation of a periodic function % 0 (x) and that the periodic acoustic operator A 0 = ?r 1 % 0 (x) r has a gap in the spectrum. We prove the existence of localized waves, i.e., nite energy solutions of the acoustic equations with the property that almost all ...

Solitary acoustic pulses can propagate along the surface of a coated homogeneous and inhomogeneous medium. It is shown how these nonlinear surface acoustic waves evolve out of initial pulselike conditions generated by pulsed laser excitation and how they can be monitored by optical detection. The solitary pulse shapes at the surface are computed on the basis of an evolution equation with nonloc...

Shock waves are defined as types of acoustic pressure waves that develop during sudden releases of energy. The best-known natural phenomenon is thunder following lightning. Another example is the “bang” an aircraft produces when it breaks the sound barrier. Both focused shock waves and unfocused sound waves are produced in these examples. Additionally, almost all other forms of energy are relea...

An attempt has been made to study the influence of geomagnetic storm on the tropospheric acoustic gravity waves at equatorial station, Tirunelveli (8.7°N, 77.8°E), India. The daily average of the amplitude and phase of acoustic gravity waves has been studied for the period 2000-2004. Severe geomagnetic storms occurred during April and September 2000, April 2001, October and November 2003 and No...

The OSER project (Optical Scintillation by Extraterrestrial Refractors) is proposed to search for scintillation of extragalactic sources through the galactic – disk or halo – transparent H2 clouds, the last unknown baryonic structures. This project should allow one to detect column density stochastic variations in cool Galactic molecular clouds of order of ∼ 3 × 10 −5 g/cm 2 per ∼ 10 000 km tra...

Finite amplitude Alfvén-cyclotron waves are believed to play an important role in coronal heating and nonthermal properties of velocity distribution functions. These effects are thought to be due to parametrically unstable Alfvén-cyclotron waves and electrostatic bursts of ion-acoustic like waves. It is shown here that large amplitude Alfvéncyclotron waves propagating in multi-ion plasmas with ...