Plane wave analysis of panel wedges

The aim of this study is to compare the physical wedge (PW) with enhanced dynamic wedge (EDW) to determine the difference in the dose distribution affecting the treated breast and the contralateral breast, lungs, heart, esophagus, spine, and surrounding skin in the radiotherapy of breast cancer. Computed tomography (CT) data sets of 30 breast cancer patients were selected from the database for the study. The treatment plans which were executed with PW were re-planned with EDW without changing the beam parameters. Keeping the wedge angles same, the analytic anisotropic algorithm (AAA) with heterogeneity correction was used for dose calculation in all plans. The prescription was 50 Gy in 25 fractions. The dose- volume histogram (DVH) of the planning target volume (PTV) and critical structures of both PW and EDW plans were analyzed. The analysis showed that the maximum dose within the target volume is higher in EDW plan compared to PW plan. However the PTV conformity index (CI) remained the same in both plans. For all the critical structures, the EDW technique offered less dose compared to PW technique. The effect of volume of the contralateral breast on the dose to contralateral breast and the effect of volume of PTV breast for patients with carcinoma left breast on the dose to heart were studied and analyzed for the two wedges. No correlation between volumes and dose parameters was found for the two techniques. The number of monitor units to deliver a particular dose with EDW field is less than that of PW field due to change in wedge factor. As EDW produces less scattered dose to structures outside the treatment field, the risk of a second malignancy can be reduced with this technique.

As assyriologists have to handle tremendous amounts of important documents of ancient history written in cuneiform script, like the epic of Gilgamesh, we are developing an efficent system to support their daily tasks. Previous projects demonstrated the application of holography and early close-range 3D scanners for this task. Based on experiences from our previous projects in archaeology, we are focusing on processing the vast amounts of data of high resolution 3D models from todays close-range 3D scanners like the Breuckmann smartSCAN-3D-HE. The presented method exploits the high-resolution of the 3D models to extract the impressed characters as well as other features like fingerprints. Previous work typically used rendering techniques from computer graphics to visualize the characters, which then had to be processed manually. More recent approaches use methods from differential geometry for detection and extraction of coarse contour lines. These methods are computationally fast, and well-established for industrial application, but cannot cover the variations of human handwriting in form of the – wedge shaped – cuneiform script. To overcome the variations in size of the wedges, we choose a multiscale approach using integrating geometry. A transformation invariant function is achieved by calculating the volumes of multiple concentric spheres intersecting the volume below the 3D model's surface at each point. Due to this multiscale approach, this function is represented by the so-called feature vector. By classifying these feature vectors using auto-correlation, our system – called GigaMesh – can automatically extract characters, requiring only one parameter: the approximated line (wedge) width in mm. Results are shown for cuneiform tablets from the collections of the Assyriologie Heidelberg as well as from the Uruk-Warka Sammlung. Finally an outlook regarding character (en)coding and integration into related projects like the Cuneiform Digital Library Initiative (CDLI) is given.

The lower Eocene Roda Sandstone (Figols Group, south-central Pyrenees) mainly consists of mouth bars and delta-front sandstone lobes deposited in a flood-dominated river-delta system. The deposition of these bodies was strongly controlled by an interaction between flood-dominated gravity flows entering seawater, topographic confinement and tidal currents. The Roda Sandstone is made up of six depositional sequences of different hierarchical order each of which is characterized by a basal deltaic sandstone wedge (R1 to R6) that passes upward into a siltstone and mudstone interval. Each basal deltaic sandstone wedge is composed of three types of facies association and respective facies tract ( sensu Mutti 1992) that, from proximal to distal zones, are indicated as T1, T2 and T3. These three facies tracts are created by the downcurrent evolution of different types of sediment-laden stream flows entering seawater and related hyperpycnal flows. Their deposits are constituted by three different types of coarse-grained mouth bars and corresponding fine-grained delta-front sandstone lobes. The tidal influence is present in facies tract T3 in the R5 and R6 sandstone units, where the passage between flood-dominated mouth bars and the delta-front sandstone lobes occurs through intermediate facies characterized by different types of sigmoidal-cross stratification whose meaning will be discussed. The basal deltaic sandstone wedges of Roda sandstone are characterized by a progressive forestepping culminating in the R6 unit that erodes the underlying R5 unit and by an overlying backstepping unit indicated as R7. The erosive surface at the base of R6 unit is interpreted as a sequence boundary that divides the Roda Sandstone into two parts: 1) an underlying highstand system tract (HST) and falling stage system tract (FSST) (units R1 to R5) and 2) an overlying low-stand delta (the R6 unit) that passes upward into highstand mudstone through a transgressive system tract represented by the R7 unit. Pdf

This thesis deals with electromagnetic inspired acoustic metamaterials, enabling sound-matter interactions in different wave scenarios that include propagation, guided-waves, radiation, refraction, reflection and transmission. To this end, a particular emphasis is placed on introducing novel applications for acoustic metamaterials operating on each one of the aforementioned wave scenarios. A few years ago, metamaterials have been introduced as a new class of composite artificial materials, engineered to produce unusual effective material properties not readily available in nature. Electromagnetic metamaterials are probably the oldest class of metamaterials, being nowadays in the process of reaching maturity and being proposed for interesting commercial applications. On the other hand, as in most young but not yet mature emerging fields of science, acoustic metamaterials are still providing lots of fertile and unexplored ground for research and study. Despite many inherent physical differences, the propagation of electromagnetic and acoustic waves are both governed by a similar mathematical model, the so-called Helmholtz wave equation. The main purpose of this work is to leverage this amazing similarity by translating recent advances in electromagnetic metamaterials into their corresponding, previously unseen, applications in acoustics. The first contribution of this thesis is to adapt the classic electromagnetic transmission-line theory to allow the design of acoustic metamaterials. The proposed circuit-based theory finds a direct application in the design of composite right/left hand transmission-line metamaterials, which yield novel guided-wave applications for acoustic metamaterials. Then, the developed theory is leveraged to model and achieve optimal design of different acoustic metamaterial-based devices, such as leaky-wave antennas and reflector-type metasurfaces. The second part of the thesis spins around acoustic leaky-wave antennas and their different functionalities, showing that they are able to act as acoustic dispersive prisms in the refraction mode and as acoustic single sensor direction finder in the radiation mode. Studying reflection phenomena in sound-metasurface interactions constitutes the next part of this thesis, where a membrane-capped cavity is introduced performing as an ultra-thin unit-cell for reflective acoustic metasurfaces. This leads to exciting applications of the concept, like acoustic reflectarray antennas and acoustic metasurface skin-cloaks Finally, the last part of this thesis deals with transmission phenomena in acoustic metasurfaces and, especially, in orbital angular momentum metasurfaces. This concept results in the design of an innovative labyrinthine-type helicoidal unit-cell that is used for phase coding a surface and transforming impinging acoustic wavefronts into transmitted helical wavefronts.

The objective of this investigation is to examine the buoyancy-driven gravitational spreading currents, especially as applied to ocean disposal of wastewater and the accidental release of hazardous fluids, such as liquefied natural gas. A series of asymptotic solutions are used to describe the displacement of a gravitationally driven spreading front during an inertial phase of motion and the subsequent viscous phase. Solutions are derived by a force scale analysis and a self-similar technique for flows in stagnant, homogeneous, or linearly density-stratified environments. The self-similar solutions for inertial-buoyancy currents are found using an analogy to the well-known shallow-water wave propagation equations and also to those applicable to a blast wave in gasdynamics. For the viscous-buoyancy currents the analogy is to the viscous long wave approximation to a nonlinear diffusive wave, or thermal wave propagation. Other similarity solutions describing the initial stage of motion of the flow formed by the collapse of a finite volume fluid are developed by analogy to the expansion of a gas cloud into a vacuum. For the case of a continuous discharge there is initially a starting jet flow followed by the buoyancy-driven spreading flow. The jet mixing zone in such flows is described using Prandtl's mixing length theory. Dimensional analysis is used to derive the relevant scaling factors describing these flows.

Propagation and radiation of electromagnetic waves in a lossless, reciprocal, chiral medium is studied in this thesis. Such a medium is described electromagnetically by the constitutive relations D = eE + iγB and H = iγE + (1/µ)B. The constants e, µ, γ are real and have values that are fixed by the size, shape, and the spatial distribution of the elements that collectively compose the medium. The plane wave propagation in an unbounded chiral medium is considered. The propagation constants are obtained and the polarization properties of electromagnetic waves in such a medium are discussed in detail. The problem of reflection from, and transmission through a semi-infinite chiral medium is solved by obtaining the Fresnel equations. The conditions for the total internal reflection of the incident wave from the interface, and the existance of the Brewster angle are obtained. The effects of the chirality on the polarization and intensity of the reflected wave from the chiral half-space are discussed and illustrated by employing the Stokes parameters. The propagation of electromagnetic waves through an infinite slab of chiral medium is formulated for oblique incidence and solved analytically for the case of normal incidence. The radiation emitted by an oscillating dipole in an unbounded, lossless, chiral medium is calculated. From the constitutive relations and from the time-harmonic Maxwell equations ∇ x E = iωB and ∇ x H = J - iωD, it is seen that the wave equation for such a medium is given by ∇ x ∇ x E - ω2µeE - 2ωµγ∇ x E = iωµJ where the source term J is the current density of the oscillating dipole and where E is the electric vector of the radiated field. The desired solution of this wave equation is found by the dyadic Green's function method, that is, by first constructing the dyadic Green's function Γ and then evaluating the expression E = iωµ∫Γ(r,r')•J(r')dV'. The dyadic Green's function Γ and the components of the radiated electric field E are obtained in closed form. The components of the radiated B, D, and H fields can be derived from knowledge of E by using the Maxwell equation B = (1/iω)∇ x E and the constitutive relations. The wave impedance of the medium and the radiation resistance of the dipole are also obtained. The effects of the chiral medium on the polarization and intensity of the dipole radiation are discussed.

The effect of a plane discontinuity on a plane wave propagated in a cylindrical tube is calculated by variational methods. In carrying out the calculations a transmission line analogy is used and the effect of the discontinuity at a distance is represented by a capacitance placed at the discontinuity. In section 1 the equations of motion for the propagation of a small disturbance in a cylindrical tube are established, culminating in the tyro-dimensional wave equation, while the solutions to the equations are discussed in section 2. These solutions constitute an infinite set of modes, in addition to the plane wave usually treated in the literature. In section 3 the analogy between propagation of sound and an electrical transmission line is established, and it is shown that each mode requires a separate transmission line. In section 4 it is shown that the effect of the higher modes excited by a plane discontinuity may be represented by a lumped capacitance, and this capacitance is given by a variational expression which gives a systematic method of calculation yielding an upper bound to the true answer. For the case of a window, a variational principle is produced inihich gives a lower bound to the true answer. In section B this method is applied to a window in a rectangular tube in some detail, in section 7 it is applied to a change of cross section in a rectangular tube, and in section 8 it is applied to windows and changes of cross section in circular tubes. In section 9 the reflection and transmission factors are calculated, and in section 10 the resonant frequency of certain types of resonators is calculated. To the authors's knowledge this is the first rigorous treatment of the above problems with the exception of an earlier paper calculating the reflection due to a change of cross section in a circular tube.

Ultrasonic guided waves have attracted increasing attention for non-destructive testing (NDT) and structural health monitoring (SHM) of bridge cables. They offer advantages like single measurement, wide coverage of acoustical field, and long-range propagation capability. To design defect detection systems, it is essential to understand how guided waves propagate in cables and how to select the optimal excitation frequency and mode. However, certain cable characteristics such as multiple wires, anchorage, and polyethylene (PE) sheath increase the complexity in analyzing the guided wave propagation. In this study, guided wave modes for multi-wire bridge cables are identified by using a semi-analytical finite element (SAFE) technique to obtain relevant dispersion curves. Numerical results indicated that the number of guided wave modes increases, the length of the flat region with a low frequency of L(0,1) mode becomes shorter, and the cutoff frequency for high order longitudinal wave modes becomes lower, as the number of steel wires in a cable increases. These findings were used in design of transducers for defect detection and selection of the optimal wave mode and frequency for subsequent experiments. A magnetostrictive transducer system was used to excite and detect the guided waves. The applicability of the proposed approach for detecting and locating wire breakages was demonstrated for a cable with 37 wires. The present ultrasonic guided wave method has been found to be very responsive to the number of broken wires and is thus capable of detecting defects with varying sizes.

Three-port tunable optical filter is a key device in the all-optic intelligent switching network and dense wavelength division multiplexing system. The characteristics of the reflecting spectrum, especially the reflectivity and the isolation degree are very important to the three-port filter. Angle-tuned thin film filter is widely used as a three-port tunable filter for its high rectangular degree and good temperature stability. The characteristics of the reflecting spectrum are greatly influenced not only by the incident angle, but also by the wedge angle parameter of the non-paralleled wedge thin film filter. In the present paper, the influences of the wedge angle parameter to the reflectivity and the half bandwidth are analyzed, and the reflecting spectrum characterstics are simulationed in different wedge angle parameter and polarity. The wedge angle-tuned thin film filter with 0.8° wedge angle parameter is fabricated. The experimental results show that keeping the wedge angle the same orientation to the incident angle will worsen the reflectivity and the rectangular degree of the reflecting spectrum. However, keeping the wedge angle orientation reverse to the incident angle will enhance the reflectivity and decrease the bandwidth, which will give higher reflectivity and isolation degree to the three-port filter than that of high parallel degree angle-tuned thin film filter.

In the present note, we study the conditions for propagation of interface waves when one of the solids is a thermo-elastic halfspace and the other an elastic halfspace. The propagation of plane waves along the interface is studied and the frequency equation is derived. In view of the complicated form of this equation, two limiting cases corresponding to very high or very low frequencies are studied. It is also shown that when the coupling constant in the thermo-elastic solid is put equal to zero, the frequency equation reduces to the equation derived by Stoneley. As another particular case, the frequency equations corresponding to very high or very low wave lengths are obtained.

Free wave propagation in two-dimensional periodic plates

This thesis is a contribution towards developing cost-effective ways for reducing outdoor traffic noise in outdoor environments by exploiting the interaction between sound travelling directly to a listener from the source and sound reflected by the intervening ground. Sound propagation over different kinds of porous, rough and mixed impedance ground surfaces have been studied experimentally and numerically. Measurements of short-range acoustic level difference spectra over outdoor ground surfaces and artificially-created surfaces outdoors and in the laboratory have been compared with predictions to establish suitable impedance models. Sound propagation over mixed impedance ground having single or multiple impedance discontinuities has also been studied. Acoustic transmission loss through vegetation, crops and hedges has been investigated. The phenomenon of sound diffraction and periodicity due to rough periodic ground surfaces has been explored through artificially created rough surfaces in the laboratory and outdoors. The phenomenon of surface wave propagation over rough hard surfaces and porous surfaces has been explored through laboratory experiments. Measured data indoors and outdoors have been used to validate numerical (BEM and FEM), empirical and analytical (MST) prediction techniques. The validated numerical methods have been used to make predictions at scales suitable for attenuating traffic noise by means of carefully designed ground treatments. The work has also been extended to railway and tramway noise. It has been found that replacing hard ground with porous ground, introducing single or multiple impedance discontinuities, growing vegetation and introducing low height roughness can all contribute between 3 and 15 dB additional attenuation of traffic noise. In respect of replacing hard ground by porous ground, it is concluded that the ground with lowest flow resistivity i.e. grassland left untouched and allowed to grow wild gives the best attenuation performance. However, dividing a single width of soft ground into alternating strips of hard and soft surfaces does not improve the insertion loss. The overall width of the soft surface is the main factor. Cultivating crops over porous ground can enhance the attenuation but the effect is not very significant for A-weighted levels as most of additional attenuation occurs at higher frequencies above 3 kHz. A 0.3 m high and at least 3 m wide lattice structure design is found to be very useful for traffic noise attenuation since it offers greater insertion loss than the same width and height of parallel low walls and the resulting attenuation is azimuthal angle independent. It has been shown also that the potentially negative effect on insertion loss due to propagation of roughness-induced surface waves over rough surfaces can be reduced by introducing sound absorbing material in between the walls.

Wave Propagation in Functionally GradedPiezoelectric-piezomagnetic Rectangular Rings

Experimental studies of air entrainment by breaking waves are essential for advancing the understanding of these flows and creating valid models. The present study used three-dimensional simulations of a bow wave to examine its air entrainment process. The simulated waves were created by a deflecting plate mounted at an angle in a super-critical free surface flow. Since the air entrainment process is closely coupled with breaking wave dynamics, the present study included both air entrainment and free surface measurements. Measurements of the free surface wave were obtained from the simulated bow waves at two scales, and also from the bow wave created a towed wedge model. Contact line and bow wave profile measurements for the different experiments were compared, demonstrating the similarity of the experimental simulations to the towed model experiments. The plunging wave jet shape was measured in the larger scale stationary model and towed model experiments and used to calculate the jet thickness, velocity, and impingement angle. The bow wave profile data from the towed model experiments were used to investigate the scaling on the plunging wave face, and their wavelength, frequency, and velocity were measured. The primary mechanisms for air entrainment were the impact of the plunging wave jet and individual droplets in the splash region on the free surface. The air entrainment process was observed in the larger scale stationary model experiments, and the air bubbles were entrained in spatially periodic bubble clouds. Due to the shallow depth in these experiments, measurements of only the larger bubbles in the initial stages of air entrainment were obtained. An impedance based void fraction meter, developed specifically for the purpose, was used to measure the void fractions and bubble size distributions beneath the wave. The bubble cloud size and void fraction increased with downstream distance. There were indications that the surface disturbances control the periodicity of the bubble clouds. Namely, the surface disturbances divide the plunging liquid jet sheet into a series of plunging wave jets, each entraining air into a separate bubble cloud beneath the free surface.

This paper investigated the acoustic pressure characteristics analysis in cavity of the two-dimensional phononic crystal. Present phononic crystal is composed of PMMA cylindrical with square array embedded in air background. In order to obtain the band structures and acoustic pressure characteristics of the phononic crystal system, the plane wave expansion method and supercell are adopted and utilized. In addition, the effects of sizes and filling fractions are also investigated. Finally, the acoustic wave propagation and pressure characteristics in the PCs with point defect are simulated by the COMSOL Multiphysics software.