The design, analysis, and testing of a low-budget wind-tunnel flutter model with active aerodynamic controls

A low budget flutter model incorporating active aerodynamic controls for flutter suppression studies was designed as both an educational and research tool to study the interfering lifting surface flutter phenomenon in the form of a swept wing-tail configuration. A flutter suppression mechanism was demonstrated on a simple semirigid three-degree-of-freedom flutter model of this configuration employing an active stabilator control, and was then verified analytically using a doublet lattice lifting surface code and the model's measured mass, mode shapes, and frequencies in a flutter analysis. Preliminary studies were significantly encouraging to extend the analysis to the larger degree of freedom AFFDL wing-tail flutter model where additional analytical flutter suppression studies indicated significant gains in flutter margins could be achieved. The analytical and experimental design of a flutter suppression system for the AFFDL model is presented along with the results of a preliminary passive flutter test

Soil organic matter fractions of no-tilled and tilled soils and their reactivity with herbicides

Properties of soil humic fractions were determined on surface and 7.5-15.0 cm soil samples of continuously (7-year) no-tilled and tilled cotton, corn, and soybean plots in West Tennessee. Soil humic and fulvic acid were extracted by standard methods and the humic acid was characterized by 13C--NMR spectroscopy, titration of total acidity and carboxyl groups, and infrared and elemental analysis. Humic acid NMR spectra were divided into six regions (0-40, 40-62, 62-105, 105-150, 150-170, 170-190 ppm) and peak areas were compared. Humic acid composition differed by depth and crop. Small differences were observed between tillage systems. Humic acid aliphatic and aromatic carbons ranged from 48 to 65% and 25 to 40% of total peak area, respectively. The humic acids extracted from soils with larger amounts of carbon (surface no-tilled treatments) had larger aliphatic to aromatic ratios, indicating less decomposed organic matter. Carboxyl groups of the humic acids ranged from 9 to 13% and samples from tilled soil had slightly greater amounts of carboxyl and aromatic groups. Carboxyl group determinations by 13C--NMR, compared more closely with total acidity determinations by titration than with carboxyl determinations by titration. All infrared spectra were similar. Elemental composition of humic acid averaged C, 52.7%: H, 5.6%; N, 4.8%; and O, 36.9%. A greenhouse herbicide bioassay was conducted on a cotton-cropped tilled soil and three no-tilled soils, where cotton was cropped with vetch, rye, and crimson clover cover crops. Total C ranged from 9.9 g kg-1 in the tilled soil to 13.5, 16.6, and 23.5 g kg-1 in the no-tilled soil with rye, vetch, and crimson clover covers, respectively. The tilled soil had the largest fraction of extractable C and fulvic acid, relative to total soil C. Sorghum growth was measured to indicate soil effects on activity of herbicides, metribuzin and oxyfluorfen. Herbicide activity was inversely related to soil C, extractable C, carboxyl groups of humic acid, and fulvic acid C of soils. Fulvic acid C best predicted herbicide phytoxicity. Results indicated that C was more reactive in tilled than in no-tilled soils

Decision at Sea: Five Naval Battles That Shaped American History

What history buff could possibly resist the subtitle “Five Naval Battles That Shaped American History”? Those so enticed will not be disappointed in Craig Symond’s exceptionally well writ- ten and fascinating accounts of these American naval battles: Oliver Hazard Perry’s far-reaching victory over the British in the 10 September 1813 battle for Lake Erie; the 8–9 March 1862 bat- tle of Hampton Roads (which ended in a draw) between America’s first iron- clad ships, USS Monitor and CSS Vir- ginia; the 1 May 1898 battle of Manila Bay; the 4 June 1942 battle of Midway; and the 18 April 1988 Operation PRAY- ING MANTIS in the Persian Gulf

How can we effectively treat stress urinary incontinence without drugs or surgery?

Q. How can we effectively treat stress urinary incontinence without drugs or surgery? A. Pelvic floor muscle training (PFMT) and intravaginal electrical stimulation seem to be the best bets. PFMT increases urinary continence and improves symptoms of stress urinary incontinence (SUI) (strength of recommendation [SOR]: A, systematic review or randomized, controlled trials [RCTs]). PFMT also improves quality of life (QOL) (activity and psychological impact) (SOR: B, 1 RCT). Intravaginal electrical simulation increases urinary continence and improves SUI symptoms; percutaneous electrical simulation also improve SUI symptoms and likely improves QOL measures (SOR: a, systematic review). Magnetic simulation doesn't increase continence, has mixed effects on SUI symptoms, and produces no clinically meaningful improvement in QOL (SOR: B, heterogeneous RCTs with conflicting results). Vaginal cones don't increase continence or QOL (SOR: B, 2 RCTs with methodoligic flaws)

Measurement of roadway roughness and automobile ride acceleration spectra

See this work in the Center for Transportation Research Library catalog: https://library.ctr.utexas.edu/Presto/catalogid=31632The present study is designed to support an overall program for the evaluation and establishment of ride quality criteria in transportation systems. This report, which is restricted to the automobile, outlines the procedures and equipment employed to measure, record, and analyze automotive vibrations and highway or roadway roughness. Detailed automobile vibration responses and corresponding roadway roughness have been measured and recorded here for 20 different roadway sections which are typical of those found in the Austin - Travis County, Texas, area. Our highway roughness models are also compared to some of the roughness models found in the literature.Department of Transportation Office of University Research (Washington D.C.)Center for Transportation ResearchSee this work in the Center for Transportation Research Library catalog

Updated Status of Bayou Darter, a Narrowly Ranged Endemic In a Geomorphically Active Watershed

Comparison of historical and current data are critical in establishing population trends for imperiled taxa. In this paper we revisit the status of the Bayou darter Nothonotus rubrum, an endemic fish restricted to the Bayou Pierre river system, Mississippi, USA. The Bayou Pierre has experienced substantial geomorphic change in the past century, leading to questions about persistence of this imperiled species. We employed historical field notes and museum records to identify collection localities, and we resampled 32 of these localities using methodologies comparable to the original samples. We further sampled an additional 10 sites with similar methodologies to fill in spatial data gaps. Rates of capture and numbers of individuals were similar between historical and contemporary samples; however, collections with multiple individuals in contemporary samples were largely restricted to the upstream periphery of their historical distribution. Qualitative comparisons of numbers of individuals caught over several decades using variable methodology suggest that declines in abundances have happened since the species was first described. Bayou darter occupancy was positively related to stream link magnitude (beta estimate = 3.07), and N-mixture modeling estimated contemporary abundance at 7.36 ± 3.83 individuals per site. Bayou darter counts were negatively related to variance in kilometer-scale stream elevation (beta estimate = -0.60). Our results suggest that this species remains imperiled and is experiencing a declining range, and that continued efforts to study and monitor this species, and to reduce geomorphic change in the system, are merited

Comparison of leading parallel NAS file systems on commodity hardware

High performance computing has experienced tremendous gains in system performance over the past 20 years. Unfortunately other system capabilities, such as file I/O, have not grown commensurately. In this activity, we present the results of our tests of two leading file systems (GPFS and Lustre) on the same physical hardware. This hardware is the standard commodity storage solution in use at LLNL and, while much smaller in size, is intended to enable us to learn about differences between the two systems in terms of performance, ease of use and resilience. This work represents the first hardware consistent study of the two leading file systems that the authors are aware of