A constitutive model with damage for high temperature superalloys

A unified constitutive model is searched for that is applicable for high temperature superalloys used in modern gas turbines. Two unified inelastic state variable constitutive models were evaluated for use with the damage parameter proposed by Kachanov. The first is a model (Bodner, Partom) in which hardening is modeled through the use of a single state variable that is similar to drag stress. The other (Ramaswamy) employs both a drag stress and back stress. The extension was successful for predicting the tensile, creep, fatigue, torsional and nonproportional response of Rene' 80 at several temperatures. In both formulations, a cumulative damage parameter is introduced to model the changes in material properties due to the formation of microcracks and microvoids that ultimately produce a macroscopic crack. A back stress/drag stress/damage model was evaluated for Rene' 95 at 1200 F and is shown to predict the tensile, creep, and cyclic loading responses reasonably well

Multiple-function multi-input/multi-output digital control and on-line analysis

The design and capabilities of two digital controller systems for aeroelastic wind-tunnel models are described. The first allowed control of flutter while performing roll maneuvers with wing load control as well as coordinating the acquisition, storage, and transfer of data for on-line analysis. This system, which employs several digital signal multi-processor (DSP) boards programmed in high-level software languages, is housed in a SUN Workstation environment. A second DCS provides a measure of wind-tunnel safety by functioning as a trip system during testing in the case of high model dynamic response or in case the first DCS fails. The second DCS uses National Instruments LabVIEW Software and Hardware within a Macintosh environment

Proton magnetic resonance imaging with a nitrogen-vacancy spin sensor

Nuclear magnetic resonance (NMR) imaging with nanometer resolution requires new detection techniques with sensitivity well beyond the capability of conventional inductive detection. Here, we demonstrate two dimensional imaging of $^1$H NMR from an organic test sample using a single nitrogen-vacancy center in diamond as the sensor. The NV center detects the oscillating magnetic field from precessing protons in the sample as the sample is scanned past the NV center. A spatial resolution of 12 nm is shown, limited primarily by the scan accuracy. With further development, NV-detected magnetic resonance imaging could lead to a new tool for three-dimensional imaging of complex nanostructures, including biomolecules.Comment: Main text: 19 pages including 5 figures Supplementary Information: 9 pages including 3 figure

Reggae to Rachmaninoff: How and Why People Participate in Arts and Culture

Provides the results of a telephone survey conducted to help inform those whose aim is to broaden and diversify cultural participation, and promote the role of arts and culture in strengthening American communities

Influence of the public transportation system on the air quality of a major urban center. A case study: Milan, Italy

A sampling campaign was conducted in the city of Milan, Italy before and during a transportation strike in January 2004. This strike provided a unique opportunity to investigate the influence of public transportation on the air quality in a major metropolitan area. Twenty-four air samples were collected each day around the city on January 2nd, 7th and 9th. The samples were analyzed for methane, carbon monoxide, non-methane hydrocarbons (NMHCs), halocarbons and alkyl nitrates. Significant differences in the mixing ratios were observed among the three days of sampling, with January 2nd showing the lowest concentrations as a result of decreased activity in the city during the holiday season. January 9th showed the highest NMHC concentrations because of increased vehicular activity in the city due to a public transportation strike. This paper investigates the correlation between the increased number of vehicles and decreased air quality because of a reduction in public transportation. Computer simulations were able to reproduce measurements of ozone production during the January 2004 strike and a July 2005 strike. The measurements and simulations suggest that reduced VOC emissions due to the existence of public transportation lowers peak ozone by 11-33% during the summer months. © 2008 Elsevier Ltd. All rights reserved

Dehydration in the tropical tropopause layer: Implications from the UARS Microwave Limb Sounder

Measurements of H2O from the Microwave Limb Sounder (MLS) on the Upper Atmosphere Research Satellite (UARS) are used to investigate the structure of H2O in the near tropopause region and dehydration mechanisms in the tropical tropopause layer (TTL). The new MLS data are consistent with convective input of H2O into the bottom of the TTL followed by slow ascent with a maximum relative amplitude in the seasonal cycle occurring near the tropopause nearly in phase with the tropopause temperature seasonal cycle. The relative amplitude of the seasonal cycle shows a minimum at 121 hPa in the upwelling moist phase. These features are reproduced with the “cold-trap” dehydration hypothesis. Seasonal maps show wettest tropical 100 hPa H2O colocated with continental convection

The West: slowing, but still strong

Federal Reserve District, 12th

On-line analysis capabilities developed to support the AFW wind-tunnel tests

A variety of on-line analysis tools were developed to support two active flexible wing (AFW) wind-tunnel tests. These tools were developed to verify control law execution, to satisfy analysis requirements of the control law designers, to provide measures of system stability in a real-time environment, and to provide project managers with a quantitative measure of controller performance. Descriptions and purposes of the developed capabilities are presented along with examples. Procedures for saving and transferring data for near real-time analysis, and descriptions of the corresponding data interface programs are also presented. The on-line analysis tools worked well before, during, and after the wind tunnel test and proved to be a vital and important part of the entire test effort