Impact sound prediction of finite floor structures with the modal transfer matrix method

The transfer matrix method (TMM) is commonly employed for wave propagation analysis in layered media of fluid, elastic and porous nature. Up to now it has been used extensively to analyze airborne sound transmission and sound absorption. Its use for impact sound transmission has been investigated to a limited extent, i.e. for thick homogeneous elastic plates of infinite extent and for specific receiver points. This contribution aims to broaden the scope such that the global impact sound, radiated by finite floor structures containing elastic, fluid and/or porous layers, can be analyzed in a more robust way than previously available in literature. A disadvantage of the conventional TMM is that only floors of infinite extent can be implemented. It is possible to remove this drawback using a spatial windowing technique. Furthermore, the modal behavior of the floor is approximately taken into account by projecting the impact force onto the mode shapes and only allowing for the propagation of those waves, corresponding to modal wavenumbers, in the structure. Predictions of the radiated sound power are made for various bare floors and floating floor systems of both infinite and finite extent.

Development of a simple, portable, colorimetric arsenic sensor based on Molybdenum Blue Chemistry

Ultrasound imaging based on transmitting plane waves (PW) enables ultrafast imaging. Coherent PW compounding ultrasound imaging can reach the image quality of optimal multifocus image. In the image reconstruction, it was assumed that an infinite extent PWs was emitted. In this thesis, we propose a new image reconstruction algorithm – Synthetic-aperture plane-wave (SAPW) imaging – without using this assumption. The SAPW imaging was compared with the PWs imaging in numerical simulations and experimental measurements. The measured RF data in PW imaging was first decoded in the frequency domain using a pseudoinverse algorithm to estimate the RF data Then, SAPW RF data were used to reconstruct images through the standard synthetic transit aperture (STA) method. Main improvements in the image quality of the SAPW imaging in comparison with the PWs imaging are increases in the depth of penetration and the field of view when contrast-to-noise ratio (CNR) was used as a quantitative metric

Development of a simple, portable, colorimetric arsenic sensor based on Molybdenum Blue Chemistry

Ultrasound imaging based on transmitting plane waves (PW) enables ultrafast imaging. Coherent PW compounding ultrasound imaging can reach the image quality of optimal multifocus image. In the image reconstruction, it was assumed that an infinite extent PWs was emitted. In this thesis, we propose a new image reconstruction algorithm – Synthetic-aperture plane-wave (SAPW) imaging – without using this assumption. The SAPW imaging was compared with the PWs imaging in numerical simulations and experimental measurements. The measured RF data in PW imaging was first decoded in the frequency domain using a pseudoinverse algorithm to estimate the RF data Then, SAPW RF data were used to reconstruct images through the standard synthetic transit aperture (STA) method. Main improvements in the image quality of the SAPW imaging in comparison with the PWs imaging are increases in the depth of penetration and the field of view when contrast-to-noise ratio (CNR) was used as a quantitative metric

Multipolar Lattice Resonances in Plasmonic Finite-Size Metasurfaces

Collective lattice resonances in regular arrays of plasmonic nanoparticles have attracted much attention due to a large number of applications in optics and photonics. Most of the research in this field is concentrated on the electric dipolar lattice resonances, leaving higher-order multipolar lattice resonances in plasmonic nanostructures relatively unexplored. Just a few works report exceptionally high-Q multipolar lattice resonances in plasmonic arrays, but only with infinite extent (i.e., perfectly periodic). In this work, we comprehensively study multipolar collective lattice resonances both in finite and in infinite arrays of Au and Al plasmonic nanoparticles using a rigorous theoretical treatment. It is shown that multipolar lattice resonances in the relatively large (up to 6400 nanoparticles) finite arrays exhibit broader full width at half maximum (FWHM) compared to similar resonances in the infinite arrays. We argue that our results are of particular importance for the practical implementation of multipolar lattice resonances in different photonics applications.

Numerical study of flow across an ellipse and a circle placed in a uniform stream of infinite extent

As an example of an aerodynamics prototypical study, we examined a two-dimensional low Reynolds number flow over obstacles immersed in a stream of infinite extent. The Navier Stokes equation is being discretized by non conforming finite element method approach. The resulting discretized nonlinear algebraic system is being solved by using the fixpoint method and the Newton method and multigrid method for the linear sub-problem employed. The magnitude of the uniform upstream velocity under the study of the problem for Reynolds number in the range 1 < Re < 100 and the angle of attack of the upstream velocity at α = -5; 0; 5 degrees performed. Analysis of the resulting drag and lift forces acting on obstacles with respect to the angle of attack of the upstream velocity and the Reynolds number is made. Moreover, the influence of one obstacle on the resulting drag and lift coefficients of other obstacles determined. The results are being presented in a graphical and vector form.

INFLUENCE OF BEACH LENGTH ON THE DEVELOPMENT OF ESTUARINE DELTAS

Larson et al. (1987) proposed a closed-form solution to describe the development of river delta coastlines owing to sediment supply from the river. This solution is for a beach of infinite extent adjacent to the river mouth. However, in reality, the beach length is always finite due to the existence of man-made structures or headlands. It is, therefore, useful to derive a new analytical solution to gain a better understanding of beach behavior under the effect of boundaries.

An Efficient High-Frequency Method to Compute EM Scattering of a Target on Rough Surface

The physical optics and shooting and bouncing rays method are combined to rapidly compute the electromagnetic (EM) scattering from electrically large three- dimensional targets on a dielectric rough surface. To avoid modeling the rough surface of infinite extent, image theory is first used to account for the EM interactions between the target and the infinite planar surface. Next, the dielectric rough surface is accounted for by multiplying the Fresnel reflection coefficient with a roughness coefficient. In this way, only the target needs to be modeled. Thus, the proposed method can reduce significantly the computational costs and achieve a reasonable accuracy for the composite scattering problem, such as a ship-sea model.

Solitary interfacial hydroelastic waves

Solitary waves travelling along an elastic plate present between two fluids with different densities are computed in this paper. Different two-dimensional configurations are considered: the upper fluid can be of infinite extent, bounded by a rigid wall or under a second elastic plate. The dispersion relation is obtained for each case and numerical codes based on integro-differential formulations for the full nonlinear problem are derived. This article is part of the theme issue ‘Nonlinear water waves’.