Whitham Averaged Equations and Modulational Stability of Periodic Traveling Waves of a Hyperbolic-Parabolic Balance Law

In this note, we report on recent findings concerning the spectral and nonlinear stability of periodic traveling wave solutions of hyperbolic-parabolic systems of balance laws, as applied to the St. Venant equations of shallow water flow down an incline. We begin by introducing a natural set of spectral stability assumptions, motivated by considerations from the Whitham averaged equations, and outline the recent proof yielding nonlinear stability under these conditions. We then turn to an analytical and numerical investigation of the verification of these spectral stability assumptions. While spectral instability is shown analytically to hold in both the Hopf and homoclinic limits, our numerical studies indicates spectrally stable periodic solutions of intermediate period. A mechanism for this moderate-amplitude stabilization is proposed in terms of numerically observed "metastability" of the the limiting homoclinic orbits.Comment: 27 pages, 5 figures. Minor changes throughou

A Content Analysis Investigating Relationships Between Communication and Business Continuity Planning

This study provides an exploratory content analysis of business continuity planning (BCP) literature. The researchers systematically sampled multiple databases and codified artifacts using a set of variables developed by the research team. Based on the analysis, arguments are presented concerning the nature of BCP, the state of the BCP literature, and the nature of the conversations taking place in regard to BCP among academics, government/legal institutions, the media, and trade industries. Finally, the researchers demonstrate gaps in the current knowledge on BCP and suggest future directions for applied and theoretical research.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

Understanding the cost of mental health at work: an integrative framework

Book synopsis: The SAGE Handbook of Organizational Wellbeing is a comprehensive and cutting-edge work providing the latest insights into a range of perspectives on organizational wellbeing, as well as highlighting global wellbeing issues and exploring new contexts. Topics covered include: digital working and social media, LGBTQIA+ identifications and work, suicide at work, refugee workers, and mental health. A multi- and inter-disciplinary work, this handbook embraces ideas and empirical work from a range of fields including psychology, business and management, economics, and science. This handbook draws together current knowledge whilst also outlining emerging issues and directions, making this an invaluable resource for students and researchers spanning a wide array of disciplines

Atmospheric Flow Validation for Contaminant Transport

Presentation on atmospheric flow validation for contaminant transport.https://digitalcommons.usmalibrary.org/presentations/1015/thumbnail.jp

Gas emissions, minerals, and tars associated with three coal fires, Powder River Basin, USA.

Ground-based surveys of three coal fires and airborne surveys of two of the fires were conducted near Sheridan, Wyoming. The fires occur in natural outcrops and in abandoned mines, all containing Paleocene-age subbituminous coals. Diffuse (carbon dioxide (CO(2)) only) and vent (CO(2), carbon monoxide (CO), methane, hydrogen sulfide (H(2)S), and elemental mercury) emission estimates were made for each of the fires. Additionally, gas samples were collected for volatile organic compound (VOC) analysis and showed a large range in variation between vents. The fires produce locally dangerous levels of CO, CO(2), H(2)S, and benzene, among other gases. At one fire in an abandoned coal mine, trends in gas and tar composition followed a change in topography. Total CO(2) fluxes for the fires from airborne, ground-based, and rate of fire advancement estimates ranged from 0.9 to 780mg/s/m(2) and are comparable to other coal fires worldwide. Samples of tar and coal-fire minerals collected from the mouth of vents provided insight into the behavior and formation of the coal fires

Metastability of solitary roll wave solutions of the St. Venant equations with viscosity

We study by a combination of numerical and analytical Evans function techniques the stability of solitary wave solutions of the St. Venant equations for viscous shallow-water flow down an incline, and related models. Our main result is to exhibit examples of metastable solitary waves for the St. Venant equations, with stable point spectrum indicating coherence of the wave profile but unstable essential spectrum indicating oscillatory convective instabilities shed in its wake. We propose a mechanism based on ``dynamic spectrum'' of the wave profile, by which a wave train of solitary pulses can stabilize each other by de-amplification of convective instabilities as they pass through successive waves. We present numerical time evolution studies supporting these conclusions, which bear also on the possibility of stable periodic solutions close to the homoclinic. For the closely related viscous Jin-Xin model, by contrast, for which the essential spectrum is stable, we show using the stability index of Gardner--Zumbrun that solitary wave pulses are always exponentially unstable, possessing point spectra with positive real part.Comment: 42 pages, 9 figure

Interfacial characteristics and microstructural evolution of ceramics exposed to high temperature sand laden combustion environments

Sand laden combustion environments are a current challenge plaguing ceramic thermal barrier coatings (TBCs) and environmental barrier coatings (EBCs) on metallic and emerging ceramic matrix composite (CMC) turbomachinery components. Exposure of thermal and environmental barrier coatings on ceramic matrix composites to environmental particulate laden deteriorates the ceramic structure via chemical reactions and infiltration into pore structures. The challenge of environmental particulates, collectively referred to as calcium-magnesium-aluminosilicate (CMAS), is expected to be exacerbated in future components that utilize ceramic matric composites (CMCs), since the higher operating temperatures will accelerate particulate melting, infiltration, and diffusion kinetics. This study first presents efforts at ARL to develop sandphobic coatings resistant to CMAS infiltration and deposition. The results of a recent full scale sand ingestion engine test used to evaluate several ARL layered and blended coating compositions are presented. The study also includes the evaluation of interactions of CMAS plasma sprayed environmental barrier coatings and HfO2-Si bond coats on SiC/SiC CMCs in rig simulated engine test conditions. The focus is on the microstructural evolution of the coatings and the interfacial characteristics between the TBCs and EBCs and CMAS. Interfaces between coating constituents are also of interest in order to tailor coatings with superior thermal, structural, and chemical characteristics. Controlled studies on YSZ-based ceramic compacts are also performed in order to gain a more fundamental understanding of the effect of porosity on infiltration kinetics, as well as the nature of interfaces and interfacial products wrought by CMAS infiltration into YSZ ceramic grain boundaries. These model studies on YSZ are conducted by immersing the ceramic compacts into AFRL-02 sand and exposing the system to temperatures of up to 1300 °C. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, electron back scattered diffraction, and focused ion beam (milling and imaging) are utilized for microstructural and interfacial characterization of the CMAS reacted thermal and environmental barrier coating systems