Wiener filtering with a seismic underground array at the Sanford Underground Research Facility

A seismic array has been deployed at the Sanford Underground Research Facility in the former Homestake mine, South Dakota, to study the underground seismic environment. This includes exploring the advantages of constructing a third-generation gravitational-wave detector underground. A major noise source for these detectors would be Newtonian noise, which is induced by fluctuations in the local gravitational field. The hope is that a combination of a low-noise seismic environment and coherent noise subtraction using seismometers in the vicinity of the detector could suppress the Newtonian noise to below the projected noise floor for future gravitational-wave detectors. In this paper, we use Wiener filtering techniques to subtract coherent noise in a seismic array in the frequency band 0.05 -- 1\,Hz. This achieves more than an order of magnitude noise cancellation over a majority of this band. We show how this subtraction would benefit proposed future low-frequency gravitational wave detectors. The variation in the Wiener filter coefficients over the course of the day, including how local activities impact the filter, is analyzed. We also study the variation in coefficients over the course of a month, showing the stability of the filter with time. How varying the filter order affects the subtraction performance is also explored. It is shown that optimizing filter order can significantly improve subtraction of seismic noise, which gives hope for future gravitational-wave detectors to address Newtonian noise

Airfoil aerodynamic performance enhancement by manipulation of trapped vorticity concentrations using active flow control

The mechanisms of aerodynamic flow control over lifting surfaces in which global, large-scale changes in aerodynamic characteristics are engendered by momentum injection across the flow boundary are investigated in wind tunnel experiments. Due to the interaction of spanwise arrays of surface-mounted fluidic actuators with the local cross flow, the global flow field can be altered fluidically. The utility of this approach for aerodynamic flow control in the absence of moving control surfaces is demonstrated in the limits of fully-attached and separated cross flows. In the present investigations, the actuation frequency is selected to be sufficiently high to be decoupled from global flow instabilities. The changes in the aerodynamic loads are attained by leveraging the generation and regulation of “trapped” vorticity concentrations near the surface to alter its aerodynamic shape. Diagnostics include measurements of the aerodynamic forces and moments and of distributions of static pressure on the airfoil surface, and particle image velocimetry (PIV) of the flow over the airfoil and in its near wake. The present investigations have demonstrated that when the base flow is fully attached (at low angle of attack) fluidic actuation alters the aerodynamic characteristics of an airfoil leading to controlled changes in lift and pitching moment along with a significant reduction in form drag. The effectiveness of actuation for mitigation of the adverse effects of separation is demonstrated on a high-lift flap system. It is anticipated that flow control augmentation of the performance of current and future flight platforms will ultimately enable significant mechanical simplification with savings in both weight and maintenance costs.Ph.D

A Comparison of Aquatic- vs. Land-Based Plyometrics on Various Performance Variables

International Journal of Exercise Science 8(2) : 134-144, 2015. The purpose of this study was to compare the effects of an aquatic- (W) and land-based (L) plyometric program on balance, vertical jump height, and isokinetic quadriceps and hamstring strength. Thirty-four participants were randomized into three groups, W (n = 12), L (n = 11), and control (n = 11). The W and L groups completed an eight-week plyometric program. A two-way repeated measures ANOVA revealed a significant main effect of condition (F = 346.95, p \u3c 0.001) and interaction between condition by time (F = 1.88, p = 0.01). Paired samples t-tests revealed statistically significant improvements from pre- to post-testing in the L group for isokinetic quadriceps strength at 60 degrees per second (p = 0.02) and hamstring strength at 120 degrees per second (p = 0.02). Statistically significant improvements were observed from pre- to post-testing in the W group for balance (p = 0.003), vertical jump height (p = 0.008), isokinetic quadriceps strength at 60 and 120 degrees per second (p \u3c 0.001), and hamstring strength at 120 degrees per second (p = 0.03). Results demonstrate that aquatic-based plyometric training can be a valid form of training by producing improvements in balance, force output, and isokinetic strength while concurrently decreasing ground impact forces

2000-2001 Master Class - Michael Sachs (Trumpet)

https://spiral.lynn.edu/conservatory_masterclasses/1187/thumbnail.jp