Reflection and transmission of line-source excited pulsed em fields at a thin, high-contrast layer with dielectric and conductive properties

A methodology is presented for analytically modeling the reflection and transmission of line-source excited pulsed electromagnetic fields fields at a thin, planar, high-contrast layer with dielectric and conductive properties. Closed-form time-domain expressions are derived for the field components in a two-dimensional setting via an extension of the Cagniard-DeHoop method. © 2011 IEEE.published_or_final_versionThe 2011 IEEE International Symposium on Antennas and Propagation (APSURSI), Spokane, WA., 3-8 July 2011. In IEEE APSURSI Digest, 2011, p. 2404-240

Time-domain field responses of the thin, high-contrast, finely layered structure in IC packagings

The thin, high-contrast, fine layers with dielectric and conductive properties, such as ground planes, are feature structures in IC packagings. Their responses to the pulsed electromagnetic field is important both theoretically and practically. In this paper, a new semi-analytical method is proposed to model the interaction of the layer with an incident electromagnetic field via a boundary condition that expresses the in-plane conduction and contrast electric polarization currents in terms of the exciting incident field by relating the jump in the tangential component of the magnetic field strength across the layer in terms of the (continuous) tangential component of the electric field strength in the layer. Expressions for pulse shapes of the reflected and transmitted fields are conveniently obtained based on this method. It provides a novel angle to investigate the ground plane effects inside IC packagings. ©2010 IEEE.published_or_final_versionThe 19th IEEE Conference on Electrical Performance of Electronic Packaging and Systems (EPEPS 2010), Austin, TX., 25-27 October 2010. In Proceedings of 19th EPEPS, 2010, p. 233-23

Transient Analysis of a Line-Focus Transducer Probing a Liquid/Solid Interface

The use of a line-focus ultrasonic transducer in a vertical scanning reflection acoustic microscope system is well known for quantitative materials characterization [1]. The technique relies on the measurement of the reflected radio frequency tone burst echo amplitude, V, as a fonction of amount of defocus, z, and analysis of the interference minima of the V(z) curve to obtain various interface wave speeds. The technique uses well developed theory [2,3,4] representing fixed frequency ultrasound generated and detected by a cylindrical lens in the frequency domain. We have developed a large aperture lensless line-focus transducer which is highly efficient and has a bandwidth wide enough to allow the generation and detection of narrow transient pulses [5]. From this transducer placed in water near a solid sample, the resulting echo waveforms have multiple features which can be interpreted as the arrival of a specularly reflected axial ray and leaky surface waves. Using this transducer, we have developed a time-resolved and polarization-sensitive testing technique for materials characterization [6]. The objective of this paper is to provide a theoretical basis for interpretation and analysis of these time domain waveforms

Theoretical Simulation of Experimental Observations of Surface Wave Propagation on a Fluid-Saturated Porous Material

Wave propagation in fluid-saturated porous materials presents very particular features like the appearance of a second compressional wave, the so-called slow compressional wave, in addition to the conventional P (or fast compressional) and the shear wave [1,2]. First experimental observation of the slow compressional wave was carried out by Plona in 1980 in water-saturated porous ceramics at ultrasonic frequencies [3]. In 1983 Feng and Johnson predicted the existence of a new surface mode along a fluid/fluid-saturated porous solid interface, in addition to the well-known leaky-Rayleigh and true Stoneley modes [4,5]. Feng and Johnson introduced the so-called surface stiffness, T, as a parameter which describes the boundary conditions at the interface. For a value of T=0 the pores at the surface are considered open, whereas for a value of T=∞ they are considered to be closed. However, according to the theory this new surface mode appears only when closed pores boundary conditions prevail at the interface. This last restriction renders the observation of the new mode problematic, because the extreme difficult in closing the surface pores without clogging all the pores close to the surface (e.g. by painting). In 1992 Nagy observed experimental evidence of the slow surface wave [6]. Nagy demonstrated that capillary forces can extend an ideally thin membrane over the surface pores at the interface between a porous solid saturated with a wetting fluid (e.g. water or alcohol) and a non-wetting fluid (e.g. air). Under this conditions, experimental evidence of a simple form of the new surface wave mode predicted by Feng and Johnson during alcohol saturation of a sintered glass beads specimen was obtained. However, due to problems inherent to the excitation of surface waves in fluid-saturated porous solids (e.g. extremely high attenuation, small propagation lengths, etc.) the results were not conclusive. In this work we will show that the experimental evidence of slow surface wave can be predicted by the analytical method of Feng and Johnson [5], if slight modifications are introduced into the calculation technique in order to account for some of the particular characteristics of the experiment

Mechanistic insight into point mutations in sedlin that result in spondyloepiphyseal dysplasia tarda

Understanding and predicting the effects of surface roughness on ultrasonic pulse-echo measurements is important in a variety of applications. In particular, it is of interest for cased well evaluation in the oilfield industry where the measurement is used to investigate the cement seal placed between the casing and the formation wall (see Fig. 1(a)) [1]. Here, the acoustic transducer signal arises from multiple reflections taking place at the various interfaces of the layered (borehole fluid)-(steel casing)-cement-(rocky formation) structure. Previous numerical models, developed to account for this measurement, have been limited to canonical configurations where, in particular, the various interfaces are smooth [2]. Typically, the cement-formation interface is rough with widely varying rms height and correlation length. In order to predict the effect of roughness of arbitrary sizeon the reflection echo attributed to this interface, a frequency-domain hybrid analytical/numerical simulation model has been developed. The model has been preliminary implemented for a two-dimensional (2D) configuration where an acoustic transducer with a Gaussian profile interacts with the aforementioned structure in a planar geometry (see Fig. 1(b)). In this configuration, the transducer aperture has a finite size in the (x, z) and is infinite in the y direction. The fluid, steel layer, cement layer, and halfspace formation are assumed to be isotropic and homogeneous. The cement-formation interface, denoted by S 0, is in general irregular or rough and parameterized by the function z = h(x) describing the height of a particle on S 0 measured from the (mean) plane z = 0. A time-harmonic variation e iωt is assumed throughout