Numerical simulation of steady supersonic flow

A noniterative, implicit, space-marching, finite-difference algorithm was developed for the steady thin-layer Navier-Stokes equations in conservation-law form. The numerical algorithm is applicable to steady supersonic viscous flow over bodies of arbitrary shape. In addition, the same code can be used to compute supersonic inviscid flow or three-dimensional boundary layers. Computed results from two-dimensional and three-dimensional versions of the numerical algorithm are in good agreement with those obtained from more costly time-marching techniques

Shock waves and drag in the numerical calculation of isentropic transonic flow

Properties of the shock relations for steady, irrotational, transonic flow are discussed and compared for the full and approximate governing potential in common use. Results from numerical experiments are presented to show that the use of proper finite difference schemes provide realistic solutions and do not introduce spurious shock waves. Analysis also shows that realistic drags can be computed from shock waves that occur in isentropic flow. In analogy to the Oswatitsch drag equation, which relates the drag to entropy production in shock waves, a formula is derived for isentropic flow that relates drag to the momentum gain through an isentropic shock. A more accurate formula for drag, based on entropy production, is also derived, and examples of wave drag evaluation based on these formulas are given and comparisons are made with experimental results

Classification of lower extremity movement patterns based on visual assessment: reliability and correlation with 2-dimensional video analysis

CONTEXT: Abnormal movement patterns have been implicated in lower extremity injury. Reliable, valid, and easily implemented assessment methods are needed to examine existing musculoskeletal disorders and investigate predictive factors for lower extremity injury. OBJECTIVE: To determine the reliability of experienced and novice testers in making visual assessments of lower extremity movement patterns and to characterize the construct validity of the visual assessments. DESIGN: Cross-sectional study. SETTING: University athletic department and research laboratory. PATIENTS OR OTHER PARTICIPANTS: Convenience sample of 30 undergraduate and graduate students who regularly participate in athletics (age = 19.3 ± 4.5 years). Testers were 2 experienced physical therapists and 1 novice postdoctoral fellow (nonclinician). MAIN OUTCOME MEASURE(S): We took videos of 30 athletes performing the single-legged squat. Three testers observed the videos on 2 occasions and classified the lower extremity movement as dynamic valgus, no change, or dynamic varus. The classification was based on the estimated change in frontal-plane projection angle (FPPA) of the knee from single-legged stance to maximum single-legged squat depth. The actual FPPA change was measured quantitatively. We used percentage agreement and weighted κ to examine tester reliability and to determine construct validity of the visual assessment. RESULTS: The κ values for intratester and intertester reliability ranged from 0.75 to 0.90, indicating substantial to excellent reliability. Percentage agreement between the visual assessment and the quantitative FPPA change category was 90%, with a κ value of 0.85. CONCLUSIONS: Visual assessments were made reliably by experienced and novice testers. Additionally, movement-pattern categories based on visual assessments were in excellent agreement with objective methods to measure FPPA change. Therefore, visual assessments can be used in the clinic to assess movement patterns associated with musculoskeletal disorders and in large epidemiologic studies to assess the association between lower extremity movement patterns and musculoskeletal injury

Inductive algebras and homogeneous shifts

Inductive algebras for the irreducible unitary representations of the universal cover of the group of unimodular two by two matrices are classified. The classification of homogeneous shift operators is obtained as a direct consequence. This gives a new approach to the results of Bagchi and Misra

Unsettling subjectivity across local, national, and global imaginaries : producing an unhappy consciousness

This article analyzes the complex and subtle dynamics involved in producing and representing the global-local nexus in everyday life. Its socio-historical context is the destabilization of the current globalization system – and its associated global imaginary – marked by the 2008 Global Financial Crisis, continuing with the populist explosion in the mid 2010s, and climaxing in the 2020 Global Coronavirus Pandemic. But rather than mischaracterizing the current context as “deglobalization”, we describe it as a contemporary intensification of what we have been calling the “Great Unsettling”. This era of intensifying objective instability is linked to foundational subjective processes. In particular, we examine the production of an “unhappy consciousness” torn between the enjoyment of global digital mobility and the visceral attachment to the familiar limits of local everyday life. In doing so, we rewrite the approach to the sources of ontological security and insecurity

Safari Science: assessing the reliability of citizen science data for wildlife surveys

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140025/1/jpe12921.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/140025/2/jpe12921_am.pd

Japanese historic “timescapes”: An anthropological approach

In this article, I propose a methodology to investigate “timescapes” in Japanese history from an anthropological perspective by analyzing historical sources on social activities, more specifically on sleeping and napping. It provides the methodological basis for a research project on premodern Japanese “timescapes” at the University of Cambridge. Rather than studying the social use of the clock to investigate the extent to which various time structures have penetrated people’s private lives, I approach these questions by paying attention to how sleep and other social activities have been organized on a socio-temporal level; in other words, how people have been “doing time.” I argue that this focus makes abstract notions of time tangible. Issues discussed are time-use priorities, time measurement, appropriateness of performing certain tasks at specific times, regulating time as a tool of power, disciplining bodies through scheduling and early rising, as well as monochronic and polychronic time use

Superlinear Increase of Photocurrent due to Stimulated Scattering into a Polariton Condensate

We show that when a monopolar current is passed through an n-i-n structure, superlinear photocurrent response occurs when there is a polariton condensate. This is in sharp contrast to the previously observed behavior for a standard semiconductor laser. Theoretical modeling shows that this is due to a stimulated exciton-exciton scattering process in which one exciton relaxes into the condensate, while another one dissociates into an electron-hole pair.Comment: 17 pages with 10 figure