epidemiological features of soil transmitted helminthes were studied in six villages in isfahan area. the mean overall prevalence of ascariasis and trichostrongyliasis were 91.5% and 70.9% respectively with higher infection rate among females. mean prevalence of trichuris and hymenolepis nana were 73.8% and 5.4% respectively. prevalences of ascaris and trichuris did not fluctuate very much in v...

© 2010 American Institute of Physics, S-0031-9228-1009-030-7 Recent developments in seismology, ultrasonics, and underwater acoustics have led to a radical change in the way scientists think about ambient noise—the diffuse waves generated by pressure fluctuations in the atmosphere, the scattering of water waves in the ocean, and any number of other sources that pervade our world. Because diffus...

A number of applications, for instance ultrasonic imaging and nondestructive testing, involve the transmission of acoustic energy across fluid–solid interfaces into dissipative solids. However, such transmission is generally hindered by the large impedance mismatch at the interface. In order to address this problem, inhomogeneous plane waves were investigated in this work for the purpose of imp...

S U M M A R Y The propagation of elastic waves is modelled in media with a random distribution of fluidfilled circular cavities, which display high physical impedance in contrast to background media. Theoretical attenuation expressions for media with circular cavities, which may be filled with any material (e.g. vacuum, fluid, elastic materials), are formulated using an ensemble treatment for f...

Abstract By using topology optimization, we consider the problem of designing a passive acoustic device that allows for one-way flow sound waves; such is often colloquially referred to as an diode. The Helmholtz equation used model time harmonic linear wave propagation together with Dirichlet-to-Neumann (DtN) type boundary condition, and finite element method discretization. objective this stud...

[1] It is well established that Extremely Low Frequency (ELF, 0.3–3 kHz) and Very Low Frequency (VLF, 3–30 kHz) radio waves can be generated via modulated High Frequency (HF, 3–10 MHz) heating of the lower ionosphere (60–100 km). The ionospheric absorption of HF power modifies the conductivity of the lower ionosphere, which in the presence of natural currents such as the auroral electrojet, cre...

We propose the design of wideband birefringent metamaterials based on spoof surface plasmon polaritons (SSPPs). Spatial k-dispersion design of SSPP modes in metamaterials is adopted to achieve high-efficiency transmission of electromagnetic waves through the metamaterial layer. By anisotropic design, the transmission phase accumulation in metamaterials can be independently modulated for x- and ...

List of Symbols ej Measured strain wave at the position of the gauge j (j = a, b) e; e Positive and negative strain waves, respectively epj ; e n j Positive and negative strain waves at the position of the gauge j (j = a, b), respectively ei; er; et Incident, reflected and transmitted strain waves, respectively e ; epþ Positive strain waves at the front and back sides of rock joints, respective...

In this paper, we study the transformation of surface envelope solitons traveling over a bottom step in water finite depth. Using coefficients earlier derived linear approximation, find parameters transmitted pulses and subsequent evolution course propagation. Relying on weakly nonlinear theory, analytic formulas are which describe maximum attainable wave amplitude neighborhood far zone. Solita...

In paper the problem of reflection and refraction a plane harmonic sound wave by homogeneous isotropic elastic plate with an continuously inhomogeneous anisotropic coating is considered. It assumed that adjoin to ideal fluids. The propagation small perturbations in fluid case steady state oscillations described Helmholtz’s equation. waves uniform scalar vector equations for longitudinal transve...