Thermoelastic vibration test techniques

The structural integrity of proposed high speed aircraft can be seriously affected by the extremely high surface temperatures and large temperature gradients throughout the vehicle's structure. Variations in the structure's elastic characteristics as a result of thermal effects can be observed by changes in vibration frequency, damping, and mode shape. Analysis codes that predict these changes must be correlated and verified with experimental data. The experimental modal test techniques and procedures used to conduct uniform, nonuniform, and transient thermoelastic vibration tests are presented. Experimental setup and elevated temperature instrumentation considerations are also discussed. Modal data for a 12 by 50 inch aluminum plate heated to a temperature of 475 F are presented. These data show the effect of heat on the plate's modal characteristics. The results indicated that frequency decreased, damping increased, and mode shape remained unchanged as the temperature of the plate was increased

Determination of the effects of heating on modal characteristics of an aluminum plate with application to hypersonic vehicles

The structural integrity of proposed high speed aircraft can be seriously affected by the extremely high surface temperatures and large temperature gradients throughout the vehicle's structure. Variations in the structure's elastic characteristics as a result of thermal effects can be seen by changes in vibration characteristics. Analysis codes that predict these changes must be correlated and verified with experimental data. Analytical and experimental modal test results are given from uniform, nonuniform, and transient thermoelastic vibration tests of a 12 x 50 x 0.19 aluminum plate. The data show the effect of heat on the modal characteristics of the plate. The results showed that frequencies decreased, damping increased, and mode shapes remained unchanged as the temperature of the plate increased. Analytical predictions provided good correlation with experimental results

Hydrologic Response of Alternative Valley Fill Reclamation Designs

Mountaintop mining (MTM) is a widely practiced surface mining technique in Central Appalachian Conventional reclamation (Approximate Original Contour), involves the construction of valley fills of headwater systems. Recent research suggests that current MTM reclamation techniques increase stormflow response of the affected watersheds when compared to the original, undisturbed conditions. One method that has shown success in reclaiming surface mine sites in semi-arid regions of the western U.S. is geomorphic landform design. Geomorphic reclamation is based upon creating landforms that resemble the mature surrounding watersheds in both topography and hydrologic response. The objective of this research was to predict the hydrologic response of a mine site reclaimed using geomorphic methods for a location in southern West Virginia. Three alternative geomorphic reclamation designs were modeled using Aquaveo\u27s Watershed Modeling System: i) a geomorphic reclamation of the valley fill; ii) a geomorphic reclamation of the valley fill with three detention ponds; and, iii) a geomorphic retrofit design. Results were compared to the response of both the original, undisturbed topography and a conventional valley fill. The peak flowrate, time to peak, and runoff volumes were evaluated at three stages of reclamation (during mining, post-mining ( 5 years)) for a range of storm events (1- through 500-year, 24-hour). The hydrologic response of the geomorphic landform design without detention ponds most closely resembled the values obtained for the original watershed. The geomorphic design with detention ponds lowered the peak flowrate, time of peak, and total runoff volume below the values generated by the original watershed. The runoff storage within the detention ponds provides the potential to allow stream flow in excess of ephemeral conditions. However, the ponds need to be properly sized to allow greater runoff storage if intermittent or perennial stream flow is desired. The effectiveness of the retrofit reclamation design was difficult to determine due to changes in watershed area and drainage pattern. These results indicate that geomorphic landform designs could be used to recreate the approximate hydrologic response of the original watershed for reclaimed mountaintop mine sites in southern West Virginia watersheds

"Napsterizing" Pharmaceuticals: Access, Innovation, and Consumer Welfare

We analyze the effects on consumers of an extreme policy experiment -- Napsterizing' pharmaceuticals -- whereby all patent rights on branded prescription drugs are eliminated for both existing and future prescription drugs without compensation to the patent holders. The question of whether this policy maximizes consumer welfare cannot be resolved on an a priori basis due to an obvious tradeoff: While accelerating generic entry will yield substantial gains in consumer surplus associated with greater access to the current stock of pharmaceuticals, future consumers will be harmed by reducing the flow of new pharmaceuticals to the market. Our estimates of the consumer surpluses at stake are based on the stylized facts concerning how generic entry has affected prices, outputs, and market shares. We find that providing greater access to the current stock of prescription drugs yields large benefits to existing consumers. However, realizing those benefits has a substantially greater cost in terms of lost consumer benefits from reductions in the flow of new drugs. Specifically, the model yields the result that for every dollar in consumer benefit realized from providing greater access to the current stock, future consumers would be harmed at a rate of three dollars in present value terms from reduced future innovation. We obtain this result even accounting for the stylized fact that after generic entry branded drugs continue to earn significant price premia over generic products and hence recognizing that Napsterizing does not completely eliminate the incentives to innovate.

Algorithm Development for Intrafraction Radiotherapy Beam Edge Verification from Cherenkov Imaging.

Imaging of Cherenkov light emission from patient tissue during fractionated radiotherapy has been shown to be a possible way to visualize beam delivery in real time. If this tool is advanced as a delivery verification methodology, then a sequence of image processing steps must be established to maximize accurate recovery of beam edges. This was analyzed and developed here, focusing on the noise characteristics and representative images from both phantoms and patients undergoing whole breast radiotherapy. The processing included temporally integrating video data into a single, composite summary image at each control point. Each image stack was also median filtered for denoising and ultimately thresholded into a binary image, and morphologic small hole removal was used. These processed images were used for day-to-day comparison computation, and either the Dice coefficient or the mean distance to conformity values can be used to analyze them. Systematic position shifts of the phantom up to 5 mm approached the observed variation values of the patient data. This processing algorithm can be used to analyze the variations seen in patients being treated concurrently with daily Cherenkov imaging to quantify the day-to-day disparities in delivery as a quality audit system for position/beam verification

Contamination Control Assessment of the World's Largest Space Environment Simulation Chamber

The Space Power Facility s thermal vacuum test chamber is the largest chamber in the world capable of providing an environment for space simulation. To improve performance and meet stringent requirements of a wide customer base, significant modifications were made to the vacuum chamber. These include major changes to the vacuum system and numerous enhancements to the chamber s unique polar crane, with a goal of providing high cleanliness levels. The significance of these changes and modifications are discussed in this paper. In addition, the composition and arrangement of the pumping system and its impact on molecular back-streaming are discussed in detail. Molecular contamination measurements obtained with a TQCM and witness wafers during two recent integrated system tests of the chamber are presented and discussed. Finally, a concluding remarks section is presented

UAS Surveillance Criticality

The integration of unmanned aircraft systems (UAS) into the national airspace system (NAS) poses considerable challenges. Maintaining human safety is perhaps chief among these challenges as UAS remote pilots will need to interact with other UAS, piloted aircraft, and other conditions associated with flight. A research team of 6 leading UAS research universities was formed to respond to a set of surveillance criticality research questions. Five analysis tools were selected following a literature review to evaluate airborne surveillance technology performance. The analysis tools included: Fault Trees, Monte Carlo Simulations, Hazard Analysis, Design of Experiments (DOE), and Human-in-the-Loop Simulations. The Surveillance Criticality research team used results from these analyses to address three primary research questions and provide recommendations for UAS detect-and-avoid mitigation and areas for further research

The influence of self-citation corrections on Egghe's g index

The g index was introduced by Leo Egghe as an improvement of Hirsch's index h for measuring the overall citation record of a set of articles. It better takes into account the highly skewed frequency distribution of citations than the h index. I propose to sharpen this g index by excluding the self-citations. I have worked out nine practical cases in physics and compare the h and g values with and without self-citations. As expected, the g index characterizes the data set better than the h index. The influence of the self-citations appears to be more significant for the g index than for the h index.Comment: 9 pages, 2 figures, submitted to Scientometric