In CT, the nonlinear attenuation characteristics of polychromatic X-rays cause beam hardening artifacts in the reconstructed images. Statistical algorithms can effectively correct beam hardening artifacts while providing the benefit of noise reduction. In practice, a big challenge for CT is the difficulty at acquiring accurate energy spectrum information, which hinders the efficiency of beam ha...

The point spread function (PSF) is an important property for predicting beam propagation and imaging system performance. Measurements of the PSF in three different locations (Pacific Ocean, Tongue of the Ocean, and Sargasso Sea) are presented. These measurements are used to validate extensive laboratory measurements [S. Q. Duntley, "Underwater Lighting by Submerged Lasers and Incandescent Sourc...

Algorithms for estimating precipitation rates from spaceborne radar observations of apparent radar reflectivity depend on attenuation correction procedures. The algorithm suite for the Ku-band precipitation radar aboard the Tropical Rainfall Measuring Mission satellite is one such example. The well-known problem of nonuniform beam filling is a source of error in the estimates, especially in reg...

Quantum-well excitons dressed by a terahertz field have multiple optical resonances. An optical beam tuned to any of the resonant frequencies excites the dressed-exciton state; therefore the optical beam experiences attenuation upon its transmission. For two coherent optical beams tuned to two different resonant frequencies, however, one can judiciously choose the amplitudes and phases in such ...

The speckle in ultrasound images has long been thought to contain information related to the tissue microstructure. Many different investigators have analyzed the frequency characteristics of the backscattered signals to estimate the scatterer acoustic concentration and size. Previous work has been mostly restricted to unfocused or weakly focused ultrasound sources, thus limiting its implementa...

In the estimation of additional shielding requirements for primary beam apart from that provided by patient and hardware in the x-ray beam, there is the need to distinguish between attenuation and hardening properties of materials in comparison. In this work, numerical comparison of attenuation and hardening properties of phantom (Lucite, soft tissue, water) and hardware (aluminum and steel) ma...

The sum of all attenuation data acquired in one view of parallel-beam projections is a view angle independent constant. This fact is known as a data consistency condition on the two-dimensional Radon transforms. It plays an important role in tomographic image reconstruction and artifact correction. In this paper, a novel fan-beam data consistency condition (FDCC) is derived and presented. Using...

A new transducer beam model is developed for the generation of Rayleigh surface wave and Lamb plate waves by an angle beam transducer, which is one of the configurations commonly used for the generation of these wave types. The beam model is a fully 3-D model that takes into account the fields generated by the transducer acting on the surface of a wedge. The model also accounts for the leaky wa...

Compared to conventional attenuation imaging, Talbot-Lau X-ray grating interferometry applied within a polychromatic setup suffers from additional artifacts. Among those are beam hardening and dispersion effects due to the complex coupling of different physical effects involved in the image formation process. In computed tomography these effects lead to image degradation, such as cupping and st...

This paper aims to explore the working mechanism of sandwich-like meta-plates by periodically attaching nonlinear mass-beam-spring resonators for low-frequency wave attenuation. The MBS resonator consists a mass, cantilever beam, and spring provide negative stiffness in transverse vibration resonator; this is tunable changing parameters spring. Considering resonator, energy method applied obtai...