Theoretical Approach to Contrast Mechanism for U-AFM

When the Ultrasonic-Atomic Force Microscope (U-AFM) is used to form an image of a surface of a specimen having discontinuities, contrast of the specimen in the image is usually stronger than that of an image formed by a conventional Atomic Force Microscope (AFM). In this article, the mechanism of the contrast of the image obtained by the U-AFM was explained by theoretical analysis. A ceramic and metal jointed bar (Steel/Cu/Si3N4) was selected as a specimen for this study. The specimen was located on the surface of a disc transducer generating ultrasonic waves up to 500 KHz, and was vibrated, wherein its first resonant frequency was 133.43 kHz. Both stress and displacement of the specimen were analyzed by classical beam theory and the two-dimensional elasto-dynamic theory. Experimental U-AFM imaging analyses were also carried out to compare the results.

Development in High Frequency Ultrasonic Imaging and Transducers

There has been intense interest recently in ultrasonic imaging in the frequency range from 20 MHz and beyond in biomedicine. High frequency ultrasound has applications in dermatology, ophthalmology and intravascular imaging because of its superior resolution. The performance of ultrasonic imaging systems especially at high frequencies depends critically upon the transducers/arrays, the design of which in turn is determined to a large degree by the materials and fabrication methodology of the piezoelectric element and supporting structures. Recent developments in these areas are discussed in this paper.

In Vitro Imaging Technique of Cell Adhesion

It is the first object of this article to contribute a side-view imaging technique to investigate adhesion to a surface-immobilized ICAM-1 in shear flow, wherein T-leukemic Jurket cells have been used. A side view image has revealed that the cell adhesion on ICAM-1 under flow conditions in vitro is quasistratic. Changes in flow shear stress, cell deformability, or substrate ligand strength resulted in a significant change in the characteristic adhesion binding time and contact length. The elongation of cells in shear flow tempers hydrodynamic shear forces on the cell, which affects the transients in cell-surface adhesion. It is the second object to calculate a 3-D flow field with shear stress acting on an adherent cell based on the shape of the cell obtained from the image. The application of the side-view imaging technique and the image analysis may provide a practical assay to reveal fundamental behavior of a cell.

Phased Array UT Technology for Nuclear Pipe Inspection

Phased array UT technologles have been applied to improve pipe inspection speed and reliability. Recent results on similar and dissimilar metal welds show clear, accurate, and fast results. Phased array ultrasound has been developed and commercialized already for high-value, inspections such as turbines and boiling water reactor (BWR) core shrouds. This paper describes how the benefits of phased array technology are being extended for application to piping examinations, including the detection and length sizing of intergranular stress corrosion cracking (IGSCC) in austenitic and dissimilar metal welds. The costs associated with pipe inspections contain factors related to the duration and reliability of inspections. The phased array improvements in flaw detectability, sizing accuracy, and speed, will lower the cost and increase the reliability of piping examinations by reducing qualification costs, radiation exposure, re-scans, and repairs. EPRI is encouraging the deployment of phased array pipe inspection technology by coordinating the technique development with several vendors so that when the technique is qualified, the vendor(s) will be ready to deliver it. This approach has already worked well for other phased array applications. As more vendors develop phased array capabilities, the deployment task becomes easier. To encourage the use of this technology, EPRI has developed and qualified through the Performance Demonstration Initiative (PDI) an automated phased array procedure for piping weld inspection.

Characterization of Thin Biological Tissue With Scanning Acoustic Microscopy

The present article reports a technique to measure velocity of a biological specimen, wherein the thickness of the biological specimen and the diameter of the measurement area of the specimen are in the order of a few microns. The kidney was selected for the specimen as an example of the soft material. The kidney was thinly sliced by a microtome and located on a substrate. The thickness of the specimen was substantially 3 μm. For the substrate, fused quartz was used because its elastic properties are known and stable. The spherical acoustic lens was used to determine the position for the measurement. The frequencies of 400 and 600 MHz were used for the measurement and the visualization respectively. The generation of the Rayleigh waves in the above conditions was simulated by numerical calculations based on the wave propagation theory for layered media.

Noninvasive Ultrasound Mediated Transdermal Transport of Insulin Across Ex Vivo Human Skin

The purpose of this research was to improve low frequency (20 kHz) ultrasound methods for enhancing the transport of insulin across ex vivo human skin. The feasibility of using ultrasound produced by small, lightweight novel transducers was explored for enhancing the transport of insulin across skin. Previous investigators have used ultrasound devices such as large, heavy sonicators or commercially obtained transducers for this type of research. These experiments used two low-profile novel ultrasound transducer arrays, the stack and standard array, for improved transport of insulin. The stack array was driven with a spatial peak temporal peak intensity (Isptp) of 15.5 ± 2.0 mW/cm2 while the standard array had an Isptp of 173.7 ± 9.1 mW/cm2. Spectrophotometeric absorption techniques were used for determining insulin transport across ex vivo human skin. Compared to passive transmission (6.3 ± 14.0 U/hr), the standard array facilitated a 6-fold increase in the noninvasive transdermal transport of Humulin® insulin (39.6 ± 11.7 U/hr). These promising results indicate that low frequency ultrasound can be used in a practical device for enhanced transport across the stratum corneum.

Digital Radiography vs Conventional Radiography: Is Digital Radiography in Compliance With the Code?

Savannah River Technology Center filmless radiographic imaging system specialists have been “champions” of filmless radiographic imaging at the Savannah River Site since 1993. Recently a study was done comparing the differences between conventional film radiography and lens-coupled, charge-coupled-device digital radiography. Characteristics of both imaging methods that were considered in the study included resolution, latitude (called dynamic range by digital radiography imaging specialists), and modulation transfer functions. The results of those comparative experiments will be presented. A description of the lens-coupled, digital radiography imaging system will be provided.

Quantitative NDT and Fitness for Purpose

The concepts of Fitness for Purpose (FFP), now popular in engineering, have placed greater demands on Non-Destructive Testing/Evaluation (NDT) to provide quantitative results. No NDT method seems better adapted to provide quantitative results than ultrasonic testing. However, acceptance criteria presented to the ultrasonic operator are sometimes difficult to comply with, as they seem not to consider the limitations and tolerances intrinsic in the techniques used. Overly optimistic expectations of sizing accuracy could result in under-sizing of flaws, but overly stringent acceptance criteria to “compensate” for sizing errors can result in more repairs than would be required by radiographic workmanship acceptance criteria in spite of much higher detection rates by ultrasonic methods. This paper considers some ultrasonic sizing techniques and their associated accuracies and application limitations. Examples from early work in Time-Of-Flight Diffraction (TOFD) and tip diffraction are considered as well as statistical studies from girth weld inspection techniques.

Thermal and Acoustical Insult to Cells as Studied by In-Vivo Acoustic Microscopy

A plurality of articles discussing combined effects of acoustic high-pressure and heat caused by acoustic vibration on biological tissues and cells has been published. Herein, we contribute the article describing the behavior of living human skin cells when separately applying the pressure and the heat to them. First, for finding the heat effect, we located a container including living human skin cells and a culturing medium on the X-Y stage equipped with the heating plate with temperature controller of the Scanning Acoustic Microscope (SAM). Then, we gradually increased temperature of the culturing medium, and carried out in-situ observation. Second, for finding the acoustic high-power effect, we provided the pressure using high power ultrasonic pulses generated by a laser induced ultrasonic shock wave system to the cells, wherein the pressures caused by the pulses were measured by a hydrophone, and wherein temperature was monitored by thermocouples. The cells were observed with the SAM just after giving the impact. The difference between phenomena indicating cellular insult and injury (e.g., shrinkage or lift-off) were clearly visualized by the SAM with frequency at 1.0 GHz.

Guided Wave Resonance Tuning for Pipe Inspection

Tremendous interest has surfaced recently on the use of guided waves in pipe inspection in the oil, chemical, and power generating industries. Relatively long lengths of piping can be inspected for corrosion and cracking from a single probe position. This saves a great deal of time and money compared to using more standard point-by-point normal beam inspection procedures. Pipes can be inspected without removing insulation or tar coatings by controlling the guided wave modes and frequencies used to carry out the study. This paper will review the history and state of the art of the guided wave techniques in piping. Benefits and limitations of the various methods will be pointed out along with a vision of future directions in the area of pipe and elbow inspection.