The Foundations of Statistics By Prof. Leonard J. Savage. (Wiley Publications in Statistics.) Pp. xv + 294. (New York; John Wiley and Sons, Inc.; London: Chapman and Hall, Ltd., 1954.) 48s. net.

Probability and Statistical Inference

The Journal of the Acoustical Society of America

Ultrasonic testing of materials: Josef and Herbert Krautkramer Springer-Verlag Publishing Company, Berlin, Heidelberg, New York (1975) 669 pp, $63.00

Review of progress, QNDE

In this review, the use of x-ray computed tomography (XCT) is examined, identifying the requirement for volumetric dimensional measurements in industrial verification of additively manufactured (AM) parts. The XCT technology and AM processes are summarised, and their historical use is documented. The use of XCT and AM as tools for medical reverse engineering is discussed, and the transition of XCT from a tool used solely for imaging to a vital metrological instrument is documented. The current states of the combined technologies are then examined in detail, separated into porosity measurements and general dimensional measurements. In the conclusions of this review, the limitation of resolution on improvement of porosity measurements and the lack of research regarding the measurement of surface texture are identified as the primary barriers to ongoing adoption of XCT in AM. The limitations of both AM and XCT regarding slow speeds and high costs, when compared to other manufacturing and measurement techniques, are also noted as general barriers to continued adoption of XCT and AM.

/pdf/x-ray-computed-tomography-for-additive-manufacturing-a-1ouio0owzb.pdf

X-ray computed tomography for additive manufacturing: a review

Engineering of novel structures with high strength to weight ratio for applications in aerospace, renewable energy and naval industries has resulted in an increased popularity of sandwich structured composites. A sandwich-structured composite is fabricated by bonding a thick lightweight core between two stiff, thin skins such as Glass Fiber Reinforced Plastic (GFRP). Balsawood is a type of homogeneous core which is widely used for renewable energy structures, such as wind turbine blades. In this paper, a GFRP-balsawood sandwich structure is evaluated non-destructively for internal defects such as holes, using a CW Terahertz system in transmission mode. Internal defects will give rise to differential THz transmission and hence can be identified using THz imaging. The imaging studies are carried out with a central frequency of 0.35 THz and the sample is raster scanned using 2-D translational stages controlled by high precision stepper motors in x-y directions to obtain the THz image. The image acquired using CW THz system clearly identifies the defects in the GFRP-balsawood composite structure with good contrast demonstrating the potential of THz imaging for non-destructive testing of sandwich composite structures.

Non-destructive evaluation of GFRP-wood sandwich structure composite using terahertz imaging

Conventional ultrasonic imaging systems suffer from poor resolution imposed by the diffraction limit. The authors have recently demonstrated the use of holey-structured metamaterials (HSMs) to enable resolution beyond the diffraction limit in the ultrasonic regime. However, imaging with HSM requires acquisition of data at fine spatial intervals. Although the use of laser Doppler vibrometers (LDV) as a receiver can be a solution for this as reported in earlier experimental studies, they are highly sensitive to ambient disturbances, suffer from low signal-to-noise ratio and are also expensive, hampering a wider practical implementation. This Letter presents experimental results using hollow cone attachments coupled with conventional ultrasonic transducers for achieving subwavelength resolution imaging at a relatively higher speed and minimal cost. The proposed methodology can be implemented easily for practical inspections and has great potential for commercialisation.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/el.2020.1061

Ultrasonic imaging beyond diffraction limit using conventional transducers with conical baffles

This paper investigates the feasibility of using ultrasonic guided waves for assessing the cortical bone and hence detect conditions such as osteoporosis. Guided wave propagation in bone systems modeled as multi-layered tubular structures consisting of anisotropic bone filled with viscous marrow and surrounded by tissue is studied using the Semi Analytical Finite Element (SAFE) method. Effects of changes to cortical bone thickness and mechanical properties are investigated. An attempt is also made to consider bone anisotropy in the models.The results, validated by experiments with bone phantoms, show that material and geometric condition strongly impacts the velocity of guided waves supported in the bone system. Identification of optimal guided wave modes for practical assessment is also discussed.

Ultrasonic guided waves in bone system with degradation

This paper proposes a novel design for a hermetically sealable device, consisting of charged linear and nonlinear membranes driven in the gigahertz range in vacuum setting, as a source of antibunched single phonons. Constraints for effecting phonon antibunching are found using the stationary Liouville–von Neumann master equation. Using analytical calculations and material and geometry optimization, we show that sizes of the proposed system can be upscaled to the near-micrometer range in a trade-off with the system operating temperature. The results are significant to realize quantum phononics, which has much promise as a modality for sensing and computing applications.

Novel hermetically sealed device to realize unconventional phonon blockade at near-micron dimensions and milliKelvin temperatures

This paper considers the interaction of the fundamental shear horizontal (SH0) mode with through‐slits in an isotropic plate, in the context of higher resolution ultrasonic guided wave NDE. The background to this research and the case of normal incidence of the SH0 mode on through‐cracks were presented at QNDE, 2005. Here the results of the previous study are first validated with some preliminary experiments and further comparison with literature. Insights from these are then used to understand the more complex multi‐parameter case of scattering at an arbitrary angle of incidence. Finally the findings are used to draw implications for some key questions involving the development of array imaging procedures.

Prabhu Rajagopal

Papers

Non-destructive evaluation of GFRP-wood sandwich structure composite using terahertz imaging

Ultrasonic imaging beyond diffraction limit using conventional transducers with conical baffles

Ultrasonic guided waves in bone system with degradation

Novel hermetically sealed device to realize unconventional phonon blockade at near-micron dimensions and milliKelvin temperatures

Scattering of the Fundamental Shear Horizontal Guided Wave Mode Incident at an Arbitrary Angle on Finite Slits in an Isotropic Plate