A critical layer model for turbulent pipe flow

A model-based description of the scaling and radial location of turbulent fluctuations in turbulent pipe flow is presented and used to illuminate the scaling behaviour of the very large scale motions. The model is derived by treating the nonlinearity in the perturbation equation (involving the Reynolds stress) as an unknown forcing, yielding a linear relationship between the velocity field response and this nonlinearity. We do not assume small perturbations. We examine propagating modes, permitting comparison of our results to experimental data, and identify the steady component of the velocity field that varies only in the wall-normal direction as the turbulent mean profile. The "optimal" forcing shape, that gives the largest velocity response, is assumed to lead to modes that will be dominant and hence observed in turbulent pipe flow. An investigation of the most amplified velocity response at a given wavenumber-frequency combination reveals critical layer-like behaviour reminiscent of the neutrally stable solutions of the Orr-Sommerfeld equation in linearly unstable flow. Two distinct regions in the flow where the influence of viscosity becomes important can be identified, namely a wall layer that scales with $R^{+1/2}$ and a critical layer, where the propagation velocity is equal to the local mean velocity, that scales with $R^{+2/3}$ in pipe flow. This framework appears to be consistent with several scaling results in wall turbulence and reveals a mechanism by which the effects of viscosity can extend well beyond the immediate vicinity of the wall.Comment: Submitted to the Journal of Fluid Mechanics and currently under revie

Acoustically induced oscillation and rotation of a large drop in space

A 2.5 cm diameter water drop was successfully deployed and manipulated in a triaxial acoustic resonance chamber during a 240 sec low-gravity SPAR rocket flight. Oscillation and rotation were induced by modulating and phase shifting the signals to the speakers. Portions of the film record were digitized and analyzed. Spectral analysis brought out the n = 2, 3, 4 free oscillation modes of the drop, its very low-frequency center-of-mass motion in the acoustic potential well, and the forced oscillation frequency. The drop boundaries were least-square fitted to general ellipses, providing eccentricities of the distorted drop. The normalized equatorial area of the rotating drop was plotted vs a rotational parameter, and was in excellent agreement with values derived from the theory of equilibrium shapes of rotating liquid drops

Embodied consciousness in non-fiction illness narratives : a phenomenological-sociological approach.

This dissertation uses a phenomenological and sociological lens to explore how non-fiction illness narratives help us understand how perception of the self is disrupted because of serious illness or injury. Specifically, I use the French philosopher, M. Merleau-Ponty\u27s phenomenological thought concerning the body and the sociological perspective of medical sociologist, Arthur Frank and his types of narratives and how culture helps construct illness. I analyze the works of four different writers: Sarah Manguso, Oliver Sacks, Jean Dominique-Bauby, and Anatole Broyard. Chapter one serves as an introduction to the subject of illness writing and an overview of some of the material published during the past several decades. I discuss some of the functions of illness writing and summarize Frank\u27s narrative types as well as explain some of the theories of Merleau-Ponty which are relevant to this study. In chapter two I analyze Sarah Manguso\u27s The Two Kinds of Decay approaching her narrative as a poetic type of prose in which she addresses her illness from the perspective of someone who came through a particularly harrowing illness experience and emerged to cautiously recount the experience several years later. The third chapter\u27s focus is Jean Dominique-Bauby\u27s The Diving Bell and the Butterfly. I discuss Bauby\u27s sense of disassociation caused by locked-in syndrome as a result of his need to escape what he metaphorically names the diving bell. Bauby, like Anatole Broyard who is discussed in the last chapter, does not survive the illness. Chapter four\u27s focus is Oliver Sacks and his book, A Leg To Stand On. Like Manguso, Sacks tells the story looking back from the present into the past. He moves beyond his injury, but the self-objectification that occurs in his narrative is a testament to the nature of disembodiment as an almost necessary phenomenon for living through severe physical trauma. Chapter five is a discussion of Anatole Broyard and his book, Intoxicated By My Illness. Broyard\u27s book is a compilation of his writings - mainly journals created during the time from his diagnosis and his subsequent journey through prostate cancer, which eventually took his life. In the conclusion I speculate about the effect of these narratives on the reader and briefly explore several other texts written by professional writers who were ill

Jacobi multipliers, non-local symmetries and nonlinear oscillators

Constants of motion, Lagrangians and Hamiltonians admitted by a family of relevant nonlinear oscillators are derived using a geometric formalism. The theory of the Jacobi last multiplier allows us to find Lagrangian descriptions and constants of the motion. An application of the jet bundle formulation of symmetries of differential equations is presented in the second part of the paper. After a short review of the general formalism, the particular case of non-local symmetries is studied in detail by making use of an extended formalism. The theory is related to some results previously obtained by Krasil'shchi, Vinogradov and coworkers. Finally the existence of non-local symmetries for such two nonlinear oscillators is proved.Comment: 20 page

The Adsorption of Atomic Nitrogen on Ru(0001): Geometry and Energetics

The local adsorption geometries of the (2x2)-N and the (sqrt(3)x sqrt(3))R30^o -N phases on the Ru(0001) surface are determined by analyzing low-energy electron diffraction (LEED) intensity data. For both phases, nitrogen occupies the threefold hcp site. The nitrogen sinks deeply into the top Ru layer resulting in a N-Ru interlayer distance of 1.05 AA and 1.10 AA in the (2x2) and the (sqrt(3)x sqrt(3))R30^o unit cell, respectively. This result is attributed to a strong N binding to the Ru surface (Ru--N bond length = 1.93 AA) in both phases as also evidenced by ab-initio calculations which revealed binding energies of 5.82 eV and 5.59 eV, respectively.Comment: 17 pages, 5 figures. Submitted to Chem. Phys. Lett. (October 10, 1996

How the Dissent Becomes the Majority: Using Federalism to Transform Coalitions in the U.S. Supreme Court

This Article proposes that dissenting Supreme Court Justices provide cues in their written opinions about how future litigants can reframe case facts and legal arguments in similar future cases to garner majority support. Questions of federal-state power cut across most other substantive legal issues, and this can provide a mechanism for splitting existing majorities in future cases. By signaling to future litigants when this potential exists, dissenting judges can transform a dissent into a majority in similar future cases. We undertake an empirical investigation of dissenting opinions in which the dissenting Justice suggests that future cases ought to be framed in terms of federal-state powers. We show that when dissenting opinions signal a preference for transforming an issue into an argument about federal-state power, more subsequent cases in that area are decided on that basis. Moreover, the previous minority coalition is in the majority significantly more often, showing that these signals are systematically successful. Not only can federalism-based dissents transform the rhetoric of cases, they can systematically and significantly shift the outcome of cases in the direction of the dissenting Justices’ views

Structural and electronic properties of Li intercalated graphene on SiC(0001)

We investigate the structural and electronic properties of Li-intercalated monolayer graphene on SiC(0001) using combined angle-resolved photoemission spectroscopy and first-principles density functional theory. Li intercalates at room temperature both at the interface between the buffer layer and SiC and between the two carbon layers. The graphene is strongly $n$-doped due to charge transfer from the Li atoms and two $\pi$-bands are visible at the $\bar{K}$-point. After heating the sample to 300$^\circ$C, these $\pi$-bands become sharp and have a distinctly different dispersion to that of Bernal-stacked bilayer graphene. We suggest that the Li atoms intercalate between the two carbon layers with an ordered structure, similar to that of bulk LiC$_6$. An AA-stacking of these two layers becomes energetically favourable. The $\pi$-bands around the $\bar{K}$-point closely resemble the calculated band structure of a C$_6$LiC$_6$ system, where the intercalated Li atoms impose a super-potential on the graphene electronic structure that opens pseudo-gaps at the Dirac points of the two $\pi$-cones.Comment: 9 pages, 7 figure

Environmental Response Management Application

The Coastal Response Research Center (CRRC), a partnership between the University of New Hampshire (UNH) and NOAA\u27s Office of Response and Restoration (ORR), is leading an effort to develop a data platform capable of interfacing both static and real-time data sets accessible simultaneously to a command post and assets in the field with an open source internet mapping server. The Environmental Response Management Application (ERMA™) is designed to give responders and decision makers ready access to geographically specific data useful during spill planning/drills, incident response, damage assessment and site restoration. In addition to oil spill and chemical release response, this website can be relevant to other environmental incidents and natural disasters, responses and regional planning efforts. The platform is easy to operate, without the assistance of Information Technology or Geographic Information Systems (GIS) specialists. It allows users to access individual data layer values, overlay relevant data sets, and zoom into segments of interest. The platform prototype is being developed specifically for Portsmouth Harbor and the Great Bay Estuary, NH. The prototype demonstrates the capabilities of an integrated data management platform and serves as the pilot for web-based GIS platforms in other regions

Gravity wave flux modulation by planetary waves in a circulation model

Mit Hilfe eines Zirkulationsmodells der mittleren Atmosphäre wird die Ausbreitung der Quasi-Zwei-Tage-Welle simuliert. Das Modell verfügt über eine aktuelle Schwerewellenparametrisierung und ermöglicht daher die detaillierte Beschreibung der Wechselwirkung planetarer Wellen mit Schwerewellen. Bei Anwesenheit der Quasi-Zwei-Tage-Welle wird der Schwerewellenfluss mit der Periode von zwei Tagen und der räumlichen Struktur der Quasi- Zwei-Tage-Welle moduliert. Modellergebnisse zeigen, dass sich die Quasi-Zwei-Tage-Welle nicht gut in die untere Thermosphäre ausbreitet. Phasenvergleiche zwischen Quasi-Zwei-Tage-Welle und Divergenz des Eliassen-Palm-Flusses der Schwerewellen zeigen, dass dies eine Folge sekundärer Anregung der Quasi-Zwei-Tage-Welle durch brechende Schwerewellen ist, die außer Phase mit der Originalwelle erfolgt