Design and fabrication of the Mini-Brayton Recuperator (MBR)

Development of a recuperator for a 2.0 kW closed Brayton space power system is described. The plate-fin heat exchanger is fabricated entirely from Hastelloy X and is designed for 10 years continuous operation at 1000 K (1300 F) with a Xenon-helium working fluid. Special design provisions assure uniform flow distribution, crucial for meeting 0.975 temperature effectiveness. Low-cycle fatigue, resulting from repeated startup and shutdown cycles, was identified as the most critical structural design problem. It is predicted that the unit has a minimum fatigue life of 220 cycles. This is in excess of the BIPS requirement of 100 cycles. Heat transfer performance and thermal cycle testing with air, using a prototype unit, verified that all design objectives can be met

Third Arkansas record of Mountain Bluebird (Sialia currucoides), with notes on habitat and behavior

Mountain Bluebird (Sialia currucoides) breeds in western North America and winters east to the Great Plains from Nebraska to Texas (Johnson and Dawson 2020). Vagrants are occasionally reported in eastern North America, mostly from November through March, but relatively few wintering records have been documented in the lower Mississippi Valley east of 96° W longitude and south of 37° N latitude

Study of the technique of stellar occultation

The results are reported of a study of the stellar occultation technique for measuring the composition of the atmosphere. The intensity of starlight was monitored during the occultation using the Wisconsin stellar ultraviolet photometers aboard the Orbiting Astronomical Observatory (OAO-A2). A schematic diagram of an occultation is shown where the change in intensity at a given wavelength is illustrated. The vertical projection of the attenuation region is typically 60 km deep for molecular oxygen and 30 km deep for ozone. Intensity profiles obtained during various occultations were analyzed by first determining the tangential columm density of the absorbing gases, and then Abel inverting the column densities to obtain the number density profile. Errors are associated with each step in the inversion scheme and have been considered as an integral part of this study

Measuring Ages and Elemental Abundances from Unresolved Stellar Populations: Fe, Mg, C, N, and Ca

We present a method for determining mean light-weighted ages and abundances of Fe, Mg, C, N, and Ca, from medium resolution spectroscopy of unresolved stellar populations. The method, pioneered by Schiavon (2007), is implemented in a publicly available code called EZ_Ages. The method and error estimation are described, and the results tested for accuracy and consistency, by application to integrated spectra of well-known Galactic globular and open clusters. Ages and abundances from integrated light analysis agree with studies of resolved stars to within +/-0.1 dex for most clusters, and to within +/-0.2 dex for nearly all cases. The results are robust to the choice of Lick indices used in the fitting to within +/-0.1 dex, except for a few systematic deviations which are clearly categorized. The realism of our error estimates is checked through comparison with detailed Monte Carlo simulations. Finally, we apply EZ_Ages to the sample of galaxies presented in Thomas et al. (2005) and compare our derived values of age, [Fe/H], and [alpha/Fe] to their analysis. We find that [alpha/Fe] is very consistent between the two analyses, that ages are consistent for old (Age > 10 Gyr) populations, but show modest systematic differences at younger ages, and that [Fe/H] is fairly consistent, with small systematic differences related to the age systematics. Overall, EZ_Ages provides accurate estimates of fundamental parameters from medium resolution spectra of unresolved stellar populations in the old and intermediate-age regime, for the first time allowing quantitative estimates of the abundances of C, N, and Ca in these unresolved systems. The EZ_Ages code can be downloaded at http://www.ucolick.org/~graves/EZ_Ages.htmlComment: Accepted to ApJ

Shuttle payload bay thermal environments: Summary and conclusion report for STS Flights 1-5

The thermal data for the payload bay of the first five shuttle flights is summarized and the engineering evaluation of that data is presented. After a general discussion on mission profiles and vehicle configurations, the thermal design and flight instrumentation systems of the payload bay are described. The thermal flight data sources and a categorization of the data are then presented. A thermal flight data summarization section provides temperature data for the five phases of a typical mission profile. These are: prelaunch, ascent, on-orbit, entry and postlanding. The thermal flight data characterization section encompasses this flight data for flight to flight variations, payload effects, temperature ranges, and other variations. Discussion of the thermal environment prediction models in use by industry and various NASA Centers, and the results predicted by these models, is followed by an evaluation of the correlation between the actual flight data and the results predicted by the models. Finally, the available thermal data are evaluated from the viewpoint of the user concerned with establishing the thermal environment in the payload bay. The data deficiencies are discussed and recommendations for their elimination are presented

Evaluation of Road Weather Information System: Interim Report

The objectives of this study are to monitor and evaluate the Roadway Weather Information System (RWIS). Six RWIS sites have been installed at locations selected by the Kentucky Department of Highways. Each site includes sensors which measure temperature, precipitation, relative humidity, wind speed, pavement temperature, surface condition, and chemical concentration. The data can be accessed remotely using a Windows-based software program. The data are also stored in a central database for future use. A preliminary reliability study has been completed for five of the sites, and data are being collected for a more extensive reliability assessment. The accuracy of the atmospheric sensors will be determined through a comparison with National Weather Service records. Data are being collected to compare the pavement sensor readings with observed road conditions. The storm logs of chemical usage will be obtained from the Department of Highways to compare with National Weather Service records and the RWIS database. These data will be used to perform a cost-benefit analysis. The primary use of the RWIS data during the winter of 1997 - 1998 will be to evaluate the system. In the future, the RWIS will supplement existing sources of information used to make decisions about snow and ice control. The data are expected to increase the efficiency of the snow and ice control operations. Other uses for the weather data are also being considered

Evaluation of Road Weather Information System

The objectives of this study were to monitor and evaluate the Kentucky Transportation Cabinet\u27s Road Weather Information System (RWIS). Six systems were installed and all became operational in November 1997. Each site includes sensors which measure temperature, precipitation, relative humidity, wind speed, pavement temperature, surface condition, and chemical concentration. The data can be accessed remotely using a Windows-based software program. The data are also stored in a central database for future use. The accuracy of the system was evaluated through comparison of atmospheric data with airport data and through site observations of surface condition, pavement temperature, and air temperature. The reliability was evaluated by reviewing the history log files to locate gaps in the data. Problems with individual sensors were also documented. The accuracy of the system was found to be good for the sensors that could be directly evaluated. The reliability was satisfactory with the larger gaps in data being caused by delays in detecting minor problems. Maintenance. of the system was a problem during the evaluation period. Additional installations of RWIS are not recommended until a more formalized process is developed by the Kentucky Transportation Cabinet for use of the data in management of winter weather events