Lester W. Schmerr

Bio: Lester W. Schmerr is an academic researcher from Iowa State University. The author has contributed to research in topics: Ultrasonic sensor & Transducer. The author has an hindex of 20, co-authored 170 publications receiving 1991 citations.

Hypersingular Boundary Integral Equations: Some Applications in Acoustic and Elastic Wave Scattering

Abstract: Interpretation in terms of Hadamard finite-part integrals, even for integrals in three dimensions, is given, and this concept is compared with the Cauchy Principal Value, which, by itself, is insufficient to render meaning to the hypersingular integrals. Motivation for this work is given in the context of scattering of time-harmonic waves by cracks. A numerical example is given for the problem of acoustic scattering by a rigid screen in three spatial dimensions

Ultrasonic Nondestructive Evaluation Systems: Models and Measurements

Abstract: Ultrasonic Nondestructive Evaluation Systems: Models and Measurements provides the latest information and techniques available for ultrasonic nondestructive evaluation (NDE) inspections. Using a systems level approach, this book employs aspects of Fourier analysis, linear system theory, and wave propagation and scattering theory to develop a comprehensive model of an entire ultrasonic measurement system. The book also describes in detail the measurements needed to obtain all the system model parameters. This integrated approach leads to a new model-based engineering technology for designing, using and optimizing ultrasonic nondestructive evaluation inspections. Practicing engineers, teachers, and students alike will learn about the latest developments in NDE technology, including a recently developed pulse-echo method for measuring the sensitivity of an ultrasonic transducer, and the use of Gaussian beam theory in simulating the wave fields generated by ultrasonic transducers. In addition, this unique book incorporates MATLAB examples and exercises which allow readers to conduct simulated inspections and implement the latest modeling technology. Written by recognized experts in NDE research, Ultrasonic Nondestructive Evaluation Systems: Models and Measurements is designed to combine well-developed techniques with the latest advances in technology.

Fundamentals of Ultrasonic Phased Arrays

Abstract: It is shown that the wave field of an ultrasonic linear array is closely related to that of an equivalent single element transducer. Using this relationship, it is demonstrated how one can construct a simple and efficient ultrasonic beam model for the wave field of a steered linear array.

Generation of the basis sets for multi-Gaussian ultrasonic beam models--an overview.

Abstract: By using a small number of Gaussian basis functions, one can synthesize the wave fields radiated from planar and focused piston transducers in the form of a superposition of Gaussian beams. Since Gaussian beams can be transmitted through complex geometries and media, such multi-Gaussian beam models have become powerful simulation tools. In previous studies the basis function expansion coefficients of multi-Gaussian beam models have been obtained by both spatial domain and k-space domain methods. Here, we will give an overview of these two methods and relate their expansion coefficients. We will demonstrate that the expansion coefficients that have been optimized for circular piston transducers can also be used to generate improved field simulations for rectangular probes. It will also be shown that because Gaussian beams are only approximate (paraxial) solutions to the wave equation, a multi-Gaussian beam model is ultimately limited in the accuracy it can obtain in the very near field.

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

A Survey on Gas Sensing Technology

Abstract: Sensing technology has been widely investigated and utilized for gas detection. Due to the different applicability and inherent limitations of different gas sensing technologies, researchers have been working on different scenarios with enhanced gas sensor calibration. This paper reviews the descriptions, evaluation, comparison and recent developments in existing gas sensing technologies. A classification of sensing technologies is given, based on the variation of electrical and other properties. Detailed introduction to sensing methods based on electrical variation is discussed through further classification according to sensing materials, including metal oxide semiconductors, polymers, carbon nanotubes, and moisture absorbing materials. Methods based on other kinds of variations such as optical, calorimetric, acoustic and gas-chromatographic, are presented in a general way. Several suggestions related to future development are also discussed. Furthermore, this paper focuses on sensitivity and selectivity for performance indicators to compare different sensing technologies, analyzes the factors that influence these two indicators, and lists several corresponding improved approaches.

Thin Plates And Shells: Theory Analysis And Applications

Abstract: Part 1 Thin plates: introduction the fundamentals of the small-deflection plate bending theory rectangular plates circular plates bending of plates of various shapes plate bending by approximate and numerical methods advanced topics buckling of plates vibration of plates. Part 2 Thin shells: introduction to the general linear shell theory geometry of the middle surface the general linear theory of thin shells the membrane theory of shells applications of the membrane theory to the analysis of shell structures moment theory of circular cylindrical shells the moment theory of shells of revolution approximate theories of shell analysis and their application advanced topics buckling of shells vibration of shells. Appendices: some reference data Fourier series expansion verification of relations of the theory of surfaces derivation of the strain-displacement relations verification of equilibrium equations.