Ultrasonic 3-D Reconstruction of Inclusions in Solids Using the Inverse Born Algorithm

Considerable progress has been made in recent years in the development of signal processing algorithms for use in ultrasonic non-destructive evaluation which yield the size, shape, and orientation of a flaw. This kind of flaw information is necessary in order that failure predictions of materials and components can be made from non-destructive tests. The signal processing algorithms that have been developed for ultrasonics are based upon both direct and inverse approximate solutions to the elastic wave scattering problem, and cover various ranges of the parameter ka where k=2π/λ is the wave number of the ultrasound and a is a flaw size dimension. In order to use these algorithms effectively in the determination of flaw parameters, it has been found necessary to obtain measurements of the flaw at several viewing angles. At this time, there is no ultrasonic transducer available which permits this to be done efficiently and conveniently in the long and intermediate wavelength end of the spectrum. This region has been shown to be quite rich in flaw information and is appropriate to ultrasonic NDE in many practical applications (e.g., thick wall sections).</p

Application of Ultrasonic Pod Models

The ability to quantify the reliability of nondestructive evaluation (NDE) inspection techniques is required to integrate inspectability into the component design process. Inspectability is typically evaluated on the basis of the design engineer’s experience and knowledge of NDE. While this approach can yield adequate designs with regard to inspection reliability, the potential for uninspectability remains. There is also the possibility that the designer’s knowledge of the reliability of NDE techniques may be limited to “standard” approaches which may be be inadequate for new component geometries or materials. This could lead the design engineer to imagine that a given component is inadequately inspectable and to redesign the part when the correct solution is either to modify the inspection protocol or to select a different technique. Alternatively, models which predict inspection reliability could be used to weigh the trade-offs and risks associated with selection among candidate NDE techniques to be applied to inspection of a given component design and to identify NDE system configurations for optimal reliability. This approach is, in fact, a key feature of the Unified Life Cycle Engineering concept currently being developed by the Air Force[l]

Technique for Generation of Unipolar Ultrasonic Pulses

Substantial progress has been made in recent years in the development of inverse elastic wave scattering theories for use in ultrasonic nondestructive evaluation (NDE). These include theories that are applicable in different ultrasonic frequency ranges and include formulations in various approximations [1–15]. It is by application of these inverse scattering solutions to ultrasonic inspection results that quantitative measures of the size, shape, and orientation of a flaw can be determined

Changing trends in mastitis

<p>Abstract</p> <p>The global dairy industry, the predominant pathogens causing mastitis, our understanding of mastitis pathogens and the host response to intramammary infection are changing rapidly. This paper aims to discuss changes in each of these aspects. Globalisation, energy demands, human population growth and climate change all affect the dairy industry. In many western countries, control programs for contagious mastitis have been in place for decades, resulting in a decrease in occurrence of <it>Streptococcus agalactiae </it>and <it>Staphylococcus aureus </it>mastitis and an increase in the relative impact of <it>Streptococcus uberis </it>and <it>Escherichia coli </it>mastitis. In some countries, <it>Klebsiella </it>spp. or <it>Streptococcus dysgalactiae </it>are appearing as important causes of mastitis. Differences between countries in legislation, veterinary and laboratory services and farmers' management practices affect the distribution and impact of mastitis pathogens. For pathogens that have traditionally been categorised as contagious, strain adaptation to human and bovine hosts has been recognised. For pathogens that are often categorised as environmental, strains causing transient and chronic infections are distinguished. The genetic basis underlying host adaptation and mechanisms of infection is being unravelled. Genomic information on pathogens and their hosts and improved knowledge of the host's innate and acquired immune responses to intramammary infections provide opportunities to expand our understanding of bovine mastitis. These developments will undoubtedly contribute to novel approaches to mastitis diagnostics and control.</p

Use of Models to Predict Ultrasonic NDE Reliability

The need to quantify and predict the probability of detection (POD) of defects by ultrasonic nondestructive evaluation (NDE) techniques is driven by the growing importance of damage tolerant design and maintenance philosophies. Experimental demonstration programs, while costly, are useful in assessing NDE system reliability for existent inspection hardware and for “typical” test specimens. However, such an approach is not effective for prediction of optimal inspection protocols nor for improving the inspectability of components at the design stage. There is, thus, a need for computationally efficient analytical models for such applications.</p

Localized orbital amyloidosis involving the lacrimal sac and nasolacrimal duct

Purpose: To report the case of a 70-year-old man who presented with tearing in his left eye and a firm palpable lump in the area overlying his left lacrimal sac. Design: Retrospective interventional case report. Methods: Noninvasive diagnostic evaluation followed by external dacryocystorhinostomy, histopathologic studies, and systemic evaluation. Results: The patient was found to have idiopathic localized amyloidosis limited to the lacrimal sac and nasolacrimal duct. Conclusion: The localized form of amyloidosis is rare, typically involves the head and neck without systemic manifestations, and carries an excellent prognosis. Previous reports of orbital amyloidosis have described involvement of the lacrimal gland, extraocular muscles, and the cranial nerves. To our knowledge, this is the first report of a patient with nasolacrimal duct obstruction secondary to amyloid deposition in the lacrimal sac and fossa. © 2006 by the American Academy of Ophthalmology.link_to_subscribed_fulltex

Thermal Wave Scattering

In recent years there has been a significant amount of work on developing thermal wave systems to nondestructively detect and image features in materials [1-4]. The ultimate goal is, of course, to have a system that is also quantitative, providing information about the shape, extent and composition of the features. In order to accomplish this goal it is first necessary to develop an understanding of how thermal waves interact with features, that is, how thermal waves are scattered. Some work has been done, for example, the Born approximation has been applied to scattering from isolated cracks [5], but as with all scattering problems one really needs to treat the problem in some fashion that can, at least numerically, be shown to be exact. In this talk, we describe a numerical method for thermal wave scattering and demonstrate its convergence properties for some simple scatterers

Finding Linear Motif Pair from Protein Interaction Networks: A Probabilistic Approach

To exploit theoretical advances in elastic wave inverse scattering, an automated multiviewing ultrasonic transducer system and the associated signal processing algorithms have been developed at the Ames Laboratory for the reconstruction of the size, shape, and orientation of volumetric flaws [1]. The flaw sizing algorithm is based on elastic wave inverse scattering theories in the long and intermediate wavelength, regime [2,3] and the three-dimensional reconstruction algorithm finds the equivalent ellipsoid that best fits the flaw sizes in the various viewing directions [4,5]. The original multiprobe system consists of six peripheral transducers equally spaced in a circle surrounding one transducer at the center. The peripheral transducers may be tilted at an angle toward the center to increase the aperture and can also be translated along their respective axes to allow an equilization of the acoustic propagation time. The axis of the aperture cone is normally placed perpendicular to the part surface. The flaw sizing procedure was a one-dimensional inverse Born algorithm to determine the flaw’s centroid-to-tangent plane distances for a number (normally 13 or 19) of pulse-echo or pitch-catch scattering directions within a finite aperture cone. The flaw sizes are then used as inputs to a nonlinear least squares regression program to yield a complete geometric reconstruction in the form of three semi-axes and three Euler angles of the best-fit ellipsoid. Using this system, successful reconstructions have been obtained for both oblate spheroidal (disk-like) and prolate spheroidal (rod-like) inclusions and voids. The readers are referred to a complete description of the system in Ref. 1

Effect of chlorhexidine concentration on the mechanical properties of dental adhesive resins

Ultrasonic flaw sizing is critical in nondestructive evaluation. However, the data available for sizing are often quite limited. For example, it is common to have a single pulse-echo (back scattered) wavetrain of limited bandwidth: i.e. it contains wavelengths that are comparable to and larger than the dimensions of the flaw. On the other hand a fair amount is often known about the nature of the expected range of flaws. It may be known that the flaw is a void, or a crack or an inclusion of a certain material type. In addition the expected shape for a flaw may be known (e.g. the flaw may be known to be a spherical flaw of unknown radius). The problem is then to determine the relevant unknown features of the flaw from the available data