An analysis of I/O efficient order-statistic-based techniques for noise power estimation in the HRMS sky survey's operational system

Noise power estimation in the High-Resolution Microwave Survey (HRMS) sky survey element is considered as an example of a constant false alarm rate (CFAR) signal detection problem. Order-statistic-based noise power estimators for CFAR detection are considered in terms of required estimator accuracy and estimator dynamic range. By limiting the dynamic range of the value to be estimated, the performance of an order-statistic estimator can be achieved by simpler techniques requiring only a single pass of the data. Simple threshold-and-count techniques are examined, and it is shown how several parallel threshold-and-count estimation devices can be used to expand the dynamic range to meet HRMS system requirements with minimal hardware complexity. An input/output (I/O) efficient limited-precision order-statistic estimator with wide but limited dynamic range is also examined

Hydrologic verification: A call for action and collaboration

Traditionally, little attention has been focused on the systematic verification of operational hydrologic forecasts. This paper summarizes the results of forecasts verification from 15 river basins in the United States. The verification scores for these forecast locations do not show improvement over the periods of record despite a number of forecast process improvements. In considering a root cause for these results, the authors note that the current paradigm for designing hydrologic forecast process improvements is driven by expert opinion and not by objective verification measures. The authors suggest that this paradigm should be modified and objective verification metrics should become the primary driver for hydrologic forecast process improvements. ©2007 American Meteorological Society

Analysis of aerothermal loads on spherical dome protuberances

Hypersonic flow over spherical dome protuberances was investigated to determine increased pressure and heating loads to the surface. The configuration was mathematically modeled in a time-dependent three-dimensional analysis of the conservation of mass, momentum (Navier-Stokes), and energy equations. A boundary mapping technique was used to obtain a rectangular parallelepiped computational domain, a MacCormack explicit time-split predictor-corrector finite difference algorithm was used to obtain solutions. Results show local pressures and heating rates for domes one-half, one, and two boundary layer thicknesses high were increased by factors on the order of 1.4, 2, and 6, respectively. Flow over the lower dome was everywhere attached while flow over the intermediate dome had small windward and leeside separations. The higher dome had an unsteady windward separation region and a large leeside separation region. Trailing vortices form on all domes with intensity increasing with dome height. Discussion of applying the results to a thermally bowed thermal protection system are presented

Effects of heat input rates on T-1 and T-1A steel welds

Technology of T-1 and T-1A steels is emphasized in investigation of their weld-fabrication. Welding heat input rate, production weldment circumstances, and standards of welding control are considered

Do Historically Black Colleges and Universities Enhance the College Attendance of African American Youths?

Recently, Historically Black Colleges and Universities (HBCUs) have become the center of intense policy debates. Do HBCUs enhance the college attendance of African American youths? Previous research has been inconclusive. Among other improvements, our study adjusts for the relative availability of HBCU enrollment opportunities in each state. We find that African Americans are more likely to choose HBCUs over other colleges if more HBCU openings are available. However, more HBCU openings don\u27t increase overall African American enrollment. As we have shown elsewhere, attendance at an HBCU does enhance African American students\u27 college graduation rates

Flight and ground tests of a very low density elastomeric ablative material

A very low density ablative material, a silicone-phenolic composite, was flight tested on a recoverable spacecraft launched by a Pacemaker vehicle system; and, in addition, it was tested in an arc heated wind tunnel at three conditions which encompassed most of the reentry heating conditions of the flight tests. The material was composed, by weight, of 71 percent phenolic spheres, 22.8 percent silicone resin, 2.2 percent catalyst, and 4 percent silica fibers. The tests were conducted to evaluate the ablator performance in both arc tunnel and flight tests and to determine the predictability of the albator performance by using computed results from an existing one-dimensional numerical analysis. The flight tested ablator experienced only moderate surface recession and retained a smooth surface except for isolated areas where the char was completely removed, probably following reentry and prior to or during recovery. Analytical results show good agreement between arc tunnel and flight test results. The thermophysical properties used in the analysis are tabulated

Climate data system supports FIRE

The NASA Climate Data System (NCDS) at Goddard Space Flight Center is serving as the FIRE Central Archive, providing a centralized data holding and data cataloging service for the FIRE project. NCDS members are carrying out their responsibilities by holding all reduced observations and data analysis products submitted by individual principal investigators in the agreed upon format, by holding all satellite data sets required for FIRE, by providing copies of any of these data sets to FIRE investigators, and by producing and updating a catalog with information about the FIRE holdings. FIRE researchers were requested to provide their reduced data sets in the Standard Data Format (SDF) to the FIRE Central Archive. This standard format is proving to be of value. An improved SDF document is now available. The document provides an example from an actual FIRE SDF data set and clearly states the guidelines for formatting data in SDF. NCDS has received SDF tapes from a number of investigators. These tapes were analyzed and comments provided to the producers. One product which is now available is William J. Syrett's sodar data product from the Stratocumulus Intensive Field Observation. Sample plots from all SDF tapes submitted to the archive will be available to FSET members. Related cloud products are also available through NCDS. Entries describing the FIRE data sets are being provided for the NCDS on-line catalog. Detailed information for the Extended Time Observations is available in the general FIRE catalog entry. Separate catalog entries are being written for the Cirrus Intensive Field Observation (IFO) and for the Marine Stratocumulus IFO. Short descriptions of each FIRE data set will be installed into the NCDS Summary Catalog

Improved self-gain in deep submicrometer strained silicon-germanium pMOSFETs with HfSiOx/TiSiN gate stacks

The self-gain of surface channel compressively strained SiGe pMOSFETs with HfSiOx/TiSiN gate stacks is investigated for a range of gate lengths down to 55 nm. There is 125% and 700% enhancement in the self-gain of SiGe pMOSFETs compared with the Si control at 100 nm and 55 nm lithographic gate lengths, respectively. This improvement in the self-gain of the SiGe devices is due to 80% hole mobility enhancement compared with the Si control and improved electrostatic integrity in the SiGe devices due to less boron diffusion into the channel. At 55 nm gate length, the SiGe pMOSFETs show 50% less drain induced barrier lowering compared with the Si control devices. Electrical measurements show that the SiGe devices have larger effective channel lengths. It is shown that the enhancement in the self-gain of the SiGe devices compared with the Si control increases as the gate length is reduced thereby making SiGe pMOSFETs with HfSiOx/TiSiN gate stacks an excellent candidate for analog/mixed-signal applications