Finite Element Modeling of Ultrasonic Waves Produced by a Pulsed Laser

As part of an effort to apply laser ultrasonics to stress evaluation, sequential thermal and mechanical finite element analyses were used to simulate heating a region of an aluminum surface by a laser pulse and the stress waves that result. As residual or applied stresses can be related to changes in wave velocities, time-of-flight measurements may be used to determine the stresses. The goal of the effort is to improve time-of-flight measurements, and therefore resolution of the calculated stresses, using calculated waveform shapes in model-based signal processing techniques [1]. Detailed finite element simulations of laser ultrasonics may also be used to aid development of techniques that can generate narrow band ultrasound. Because penetration of Rayleigh waves is frequency dependent, they can be used to obtain information about gradients near a surface. If the frequency of the laser generated Rayleigh waves can be controlled, laser ultrasound becomes a more useful tool for examining gradients in material properties or stresses at the surface of a part

An Overview of the Role of Systems Analysis in NASA's Hypersonics Project

NASA's Aeronautics Research Mission Directorate recently restructured its Vehicle Systems Program, refocusing it towards understanding the fundamental physics that govern flight in all speed regimes. Now called the Fundamental Aeronautics Program, it is comprised of four new projects, Subsonic Fixed Wing, Subsonic Rotary Wing, Supersonics, and Hypersonics. The Aeronautics Research Mission Directorate has charged the Hypersonics Project with having a basic understanding of all systems that travel at hypersonic speeds within the Earth's and other planets atmospheres. This includes both powered and unpowered systems, such as re-entry vehicles and vehicles powered by rocket or airbreathing propulsion that cruise in and accelerate through the atmosphere. The primary objective of the Hypersonics Project is to develop physics-based predictive tools that enable the design, analysis and optimization of such systems. The Hypersonics Project charges the systems analysis discipline team with providing it the decision-making information it needs to properly guide research and technology development. Credible, rapid, and robust multi-disciplinary system analysis processes and design tools are required in order to generate this information. To this end, the principal challenges for the systems analysis team are the introduction of high fidelity physics into the analysis process and integration into a design environment, quantification of design uncertainty through the use of probabilistic methods, reduction in design cycle time, and the development and implementation of robust processes and tools enabling a wide design space and associated technology assessment capability. This paper will discuss the roles and responsibilities of the systems analysis discipline team within the Hypersonics Project as well as the tools, methods, processes, and approach that the team will undertake in order to perform its project designated functions

Co-Occurrence and Characteristics of Patients With Axial Spondyloarthritis Who Meet Criteria for Fibromyalgia Results From a UK National Register

Objective. To estimate the proportion of patients with axial spondyloarthritis (SpA) in a UK national biologics registry who met criteria for fibromyalgia (FM), and to delineate the characteristics of these patients. Methods. Two cohorts of patients are prospectively recruited from across 83 centers in the UK for the British Society for Rheumatology Biologics Register in Ankylosing Spondylitis (BSRBR-AS). All patients are required to meet Assessment of SpondyloArthritis international Society (ASAS) criteria for axial SpA. Patients are either newly starting biologic therapy (biologics cohort) or are naive to treatment with biologic agents (non-biologics cohort) at the time of recruitment, and all patients are followed up prospectively. At recruitment and follow-up, clinical information and measurements are recorded while patients complete the 2011 research criteria for FM and assessments of the level of disease activity and work impact. Results. Of the patients registered in the BSRBR-AS, 1,504 (68% male) were eligible for the current analysis, of whom 311 (20.7%) met the 2011 research criteria for FM. Prevalence of FM was similar between patients who fulfilled the modified New York criteria for AS (19.7%) and those who fulfilled ASAS imaging criteria but not the modified New York criteria (25.2%); however, among those who fulfilled only the ASAS clinical criteria, the prevalence of FM was lower (9.5%). Patients who met FM criteria reported significantly worse disease activity, function, global severity scores, and quality of life, and were more likely to have moderate or severe levels of mood disorder and clinically important fatigue. Patients who met FM criteria reported experiencing work impairment around half their working time. Meeting FM criteria was not related to elevated C-reactive protein levels or most extraspinal manifestations, but was associated with a higher likelihood of having received biologic therapy. Conclusion. Developing management approaches that would address the significant unmet clinical needs of the 1 in 5 patients with axial SpA who meet criteria for FM should be a research priority

Conductivity of Strongly Coupled Striped Superconductor

We study the conductivity of a strongly coupled striped superconductor using gauge/gravity duality (holography). The study is done analytically, in the large modulation regime. We show that the optical conductivity is inhomogeneous but isotropic at low temperatures. Near but below the critical temperature, we calculate the conductivity analytically at small frequency \omega, and find it to be both inhomogeneous and anisotropic. The anisotropy is imaginary and scales like 1/\omega. We also calculate analytically the speed of the second sound and the thermodynamic susceptibility.Comment: 32 page

The non-Abelian gauge theory of matrix big bangs

We study at the classical and quantum mechanical level the time-dependent Yang-Mills theory that one obtains via the generalisation of discrete light-cone quantisation to singular homogeneous plane waves. The non-Abelian nature of this theory is known to be important for physics near the singularity, at least as far as the number of degrees of freedom is concerned. We will show that the quartic interaction is always subleading as one approaches the singularity and that close enough to t=0 the evolution is driven by the diverging tachyonic mass term. The evolution towards asymptotically flat space-time also reveals some surprising features.Comment: 29 pages, 8 eps figures, v2: minor changes, references added: v3 small typographical changes

Application of the PISA design model to monopiles embedded in layered soils

The PISA design model is a procedure for the analysis of monopile foundations for offshore wind turbine applications. This design model has been previously calibrated for homogeneous soils; this paper extends the modelling approach to the analysis of monopiles installed at sites where the soil profile is layered. The paper describes a computational study on monopiles embedded in layered soil configurations comprising selected combinations of soft and stiff clay and sand at a range of relative densities. The study comprises (a) analyses of monopile behaviour using detailed three-dimensional (3D) finite-element analysis, and (b) calculations employing the PISA design model. Results from the 3D analyses are used to explore the various influences that soil layering has on the performance of the monopile. The fidelity of the PISA design model is assessed by comparisons with data obtained from equivalent 3D finite-element analyses, demonstrating a good agreement in most cases. This comparative study demonstrates that the PISA design model can be applied successfully to layered soil configurations, except in certain cases involving combinations of very soft clay and very dense sand. </jats:p

Meaning in life in the Federal Republic of Germany: results of a representative survey with the Schedule for Meaning in Life Evaluation (SMiLE)

This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

PISA design methods for offshore wind turbine monopiles

Abstract This paper provides an overview of the PISA design model recently developed for laterally loaded offshore wind turbine monopiles through a major European joint-industry academic research project, the PISA Project. The focus was on large diameter, relatively rigid piles, with low length to diameter (L/D) ratios, embedded in clay soils of different strength characteristics, sand soils of different densities and in layered soils combining clays and sands. The resulting design model introduces new procedures for site specific calibration of soil reaction curves that can be applied within a one-dimensional (1D), Winkler-type, computational model. This paper summarises the results and key conclusions from PISA, including design methods for (a) stiff glacial clay till (Cowden till), (b) brittle stiff plastic clay (London clay), (c) soft clay (Bothkennar clay), (d) sand of varying densities (Dunkirk), and, (e) layered profiles (combining soils from (a) to (d)). The results indicate that the homogeneous soil reaction curves applied appropriately for layered profiles in the 1D PISA design model provide a very good fit to the three-dimensional finite element (3D FE) calculations, particularly for profiles relevant to current European offshore wind farm sites. Only a small number of cases, involving soft clay, very dense sand and L/D = 2 monopiles, would appear to require more detailed and bespoke analysis.</jats:p