Custom EMAT Instrumentation: Correlation Receiver and Flaw Detector

New, custom instrumentation is presented which is designed to complement and exploit the unique properties of EMAT\u27s. A two channel correlation receiver is described which allows simultaneous detection of the in-phase and quadrature components of an ultrasonic signal with the optimum noise figure and improved interference rejection. In addition, a prototype, fully self-contained EMAT flaw detector is presented. This is a surface wave device for handheld use and incorporates such features as battery operations, correlation detection, search and inspect modes, and digital readout of flaw position and reflected signal amplitude

New EMAT Applications: Ultrasonic Ellipsometer and Detection of Cracks under Fasteners

The ability to excite new wave types, such as the horizontally polarized shear (SH) waves, enables EMAT\u27s to perform functions not easily realized with conventional piezoelectric transducers. This paper describes two examples. An ultrasonic ellipsometer is presented which can excite, and detect, shear waves of arbitrary elliptical polarization. It therefore becomes possible to make precision measurements of elastic properties by making direct comparison of the propagation properties of the SH and SV (vertically polarized) components of the wave. The principles of operation are demonstrated by measuring fluid level, a surface property which .produces differential attenuation of the two components of the wave and thus a change in its elliptical polarization, and texture, a bulk property which produces differential velocity shifts. Preliminary data directed towards the measurement of adhesive bond strength is also included. A second technique presented is a new approach to the problem of detecting cracks under fasteners in wing lap joints. It has be.en found that SH waves, excited on the outer surface of the wing, can be injected into the lower surface of the joint by a wave guiding effect. The reflections of these waves from fastener holes contains information indicating the presence, and size, of flaws. Preliminary experimental results demonstrating this new technique are included

Robust multi-fidelity design of a micro re-entry unmanned space vehicle

This article addresses the preliminary robust design of a small-scale re-entry unmanned space vehicle by means of a hybrid optimization technique. The approach, developed in this article, closely couples an evolutionary multi-objective algorithm with a direct transcription method for optimal control problems. The evolutionary part handles the shape parameters of the vehicle and the uncertain objective functions, while the direct transcription method generates an optimal control profile for the re-entry trajectory. Uncertainties on the aerodynamic forces and characteristics of the thermal protection material are incorporated into the vehicle model, and a Monte-Carlo sampling procedure is used to compute relevant statistical characteristics of the maximum heat flux and internal temperature. Then, the hybrid algorithm searches for geometries that minimize the mean value of the maximum heat flux, the mean value of the maximum internal temperature, and the weighted sum of their variance: the evolutionary part handles the shape parameters of the vehicle and the uncertain functions, while the direct transcription method generates the optimal control profile for the re-entry trajectory of each individual of the population. During the optimization process, artificial neural networks are utilized to approximate the aerodynamic forces required by the optimal control solver. The artificial neural networks are trained and updated by means of a multi-fidelity approach: initially a low-fidelity analytical model, fitted on a waverider type of vehicle, is used to train the neural networks, and through the evolution a mix of analytical and computational fluid dynamic, high-fidelity computations are used to update it. The data obtained by the high-fidelity model progressively become the main source of updates for the neural networks till, near the end of the optimization process, the influence of the data obtained by the analytical model is practically nullified. On the basis of preliminary results, the adopted technique is able to predict achievable performance of the small spacecraft and the requirements in terms of thermal protection materials

Portable Instrument for Detection of Surface Flaws Using EMATs

The work reported here is the development of a first prototype portable ultrasonic inspection instrument based on EMAT (electromagnetic acoustic transducer) technology. The goal was to demonstrate EMAT inspection capabilities for small-size flaws in metal parts and to build a self-contained NDE unit that had a high degree of signal processing on-board so that human interpretation was minimized. The unit also served as a test bed, so that a number of new concepts could be evaluated. This instrument is viewed as an important step in the development of future NDE equipment

An EMAT System for Detecting Flaws in Steam Generator Tubes

The detection of flaws in steam generator tubing is often made difficult by environmental considerations. The small diameter, 7/8 inch (2.2 cm), long, 70 feet (21.3m), tubes occur in large bundles with access only being possible from the inside of the end of each tube. Furthermore, inspection must be fully automatic when the steam generator is part of a nuclear power plant because of radiation exposure limits. Consequently, a couplant free probe which can be operated remotely at the end of an automatic probe puller is needed. This paper SUillllarizes the development of an EMAT systan for this application. The device uses periodic permanent magnet probes to excite the fundamental torsional mode traveling along the axis of the tube. Included is a discussion of data obtained during a recently completed feasibility study and a description of a prototype system presently under construction

A combined fragment-based virtual screening and STD-NMR approach for the identification of E-cadherin ligands

Cadherins promote cell-cell adhesion by forming homophilic interactions via their N-terminal extracellular domains. Hence, they have broad-ranging physiological effects on tissue organization and homeostasis. When dysregulated, cadherins contribute to different aspects of cancer progression and metastasis; therefore, targeting the cadherin adhesive interface with small-molecule antagonists is expected to have potential therapeutic and diagnostic value. Here, we used molecular docking simulations to evaluate the propensity of three different libraries of commercially available drug-like fragments (nearly 18,000 compounds) to accommodate into the Trp2 binding pocket of E-cadherin, a crucial site for the orchestration of the protein's dimerization mechanism. Top-ranked fragments featuring five different aromatic chemotypes were expanded by means of a similarity search on the PubChem database (Tanimoto index >90%). Of this set, seven fragments containing an aromatic scaffold linked to an aliphatic chain bearing at least one amine group were finally selected for further analysis. Ligand-based NMR data (Saturation Transfer Difference, STD) and molecular dynamics simulations suggest that these fragments can bind E-cadherin mostly through their aromatic moiety, while their aliphatic portions may also diversely engage with the mobile regions of the binding site. A tetrahydro-β-carboline scaffold functionalized with an ethylamine emerged as the most promising fragment

Design, Fabrication, and Experimental Validation of Microfluidic Devices for the Investigation of Pore-Scale Phenomena in Underground Gas Storage Systems

The understanding of multiphase flow phenomena occurring in porous media at the pore scale is fundamental in a significant number of fields, from life science to geo and environmental engineering. However, because of the optical opacity and the geometrical complexity of natural porous media, detailed visual characterization is not possible or is limited and requires powerful and expensive imaging techniques. As a consequence, the understanding of micro-scale behavior is based on the interpretation of macro-scale parameters and indirect measurements. Microfluidic devices are transparent and synthetic tools that reproduce the porous network on a 2D plane, enabling the direct visualization of the fluid dynamics. Moreover, microfluidic patterns (also called micromodels) can be specifically designed according to research interests by tuning their geometrical features and surface properties. In this work we design, fabricate and test two different micromodels for the visualization and analysis of the gas-brine fluid flow, occurring during gas injection and withdrawal in underground storage systems. In particular, we compare two different designs: a regular grid and a real rock-like pattern reconstructed from a thin section of a sample of Hostun rock. We characterize the two media in terms of porosity, tortuosity and pore size distribution using the A* algorithm and CFD simulation. We fabricate PDMS-glass devices via soft lithography, and we perform preliminary air-water displacement tests at different capillary numbers to observe the impact of the design on the fluid dynamics. This preliminary work serves as a validation of design and fabrication procedures and opens the way to further investigations

The evaluation of liver fibrosis regression in chronic hepatitis C patients after the treatment with direct-acting antiviral agents – A review of the literature

The second-generation of direct-acting antiviral agents are the current treatment for chronic viral hepatitis C infection. To evaluate the regression of liver fibrosis in patients receiving this therapy, liver biopsy remains the most accurate method, but the invasiveness of this procedure is its major drawback. Different non-invasive tests have been used to study changes in the stage of liver fibrosis in patients with chronic viral hepatitis treated with the second-generation of direct-acting antiviral agents: liver stiffness measurements (with transient elastography or acoustic radiation force impulse elastography) or different scores that use serum markers to calculate a fibrosis score. We prepared a literature review of the available data regarding the long-term evolution of liver fibrosis after the treatment with direct-acting antiviral agents for chronic viral hepatitis C

p 159analysis of early tumor shrinkage and depth of response in metastatic pancreatic cancer patients treated with first line modified folfirinox or gemcitabine nab paclitaxel

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