A robust active controller using spatially feedforward structure is proposed for broadband attenuation of noise in ducts. To meet the requirements of performance and robust stability in the presence of plant uncertainties, an H2 cost function and an H(infinity) constrain are employed in the synthesis of the controller. The design is then converted into a convex programming problem using Q-param...

Wireless underwater transmission is considered using electric field generated by a pair of electrodes with opposite current and detected by two receiving electrodes. Experiments were conducted at frequencies between 100 kHz and 6.35 MHz, using orthogonal frequency division multiplexing (OFDM). Our lab tests were performed in a plastic tank filled with salt water, and our sea test at the ocean s...

In this paper we describe and evaluate an image-based spectral CT method. Its central formula expresses measured CT data as a spectral integration of the spectral attenuation coefficient multiplied by a Local Weighting Function (LWF). The LWF represents the local energy weighting in the image domain, taking into account the system and reconstruction properties and the object self attenuation. A...

---------------------------ABSTRACT----------------------------The potential of employing ultrasonic waves to detect sealworms embedded deep in the fish musculature was demonstrated. Images were made of sealworm-infested cod by using both the scanning laser acoustic microscopic technique, as well as the pulse-echo technique at 10 MHz, Also, attenuation of ultrasound in the frequency range from ...

stress waves contain useful information about the properties of porous materials; they can be recovered through different non-destructive testing methods such as crosswell, vertical seismic profile, borehole logging as well as sonic tests. in all these methods, it is crucial to assess the effects of frequency on wave attributes including velocity and intrinsic attenuation. the dependency of per...

Sound attenuation and velocity in nickel single crystals have been studied as function of frequency (10 to 250 MHz), temperature, strength and direction of external magnetic field along , (110> and , for the three pure wave modes propagating along . The observed effects are found to be specific for each combination of sound mode and field direction, and especially interesting for...