Radiometric absolute noise-temperature measurement system features improved accuracy and calibration ease

Radiometric receiver system, which measures noise temperatures in degrees Kelvin, does not require cryogenic noise sources for routine operation. It eliminates radiometer calibration errors associated with RF attenuation measurements. Calibrated noise source is required only for laboratory adjustment and calibration

Five-Year Response of Spontaneous Vegetation to Removal of Invasive Amur Bush Honeysuckle Along an Urban Creek

Non-native invasive species have major impacts on landscapes worldwide, but their effects in urban areas are not well documented. We quantified the response of naturally regenerating vegetation along an urban creek to removal of the invasive shrub Lonicera maackii (Amur Bush Honeysuckle). Over the 5-year study, species richness more than doubled. Most new plants were native, disturbance-adapted, early successional species. Trend analysis of function traits revealed annuals that rely on seed dispersal by wind or externally on animals were significantly overrepresented among new plants in comparison to their proportion in the countywide species pool. Increased species richness did not result in improved habitat quality, as indicated by Floristic Quality Assessment. Eight new invasive species appeared over the course of the study. Active management of this site may be needed in perpetuit

Shock associated noise reduction from inverted-velocity-profile coannular jets

Acoustic measurements show that the shock noise from the outer stream is virtually eliminated when the inner stream is operated at a Mach number just above unity, regardless of all the other jet operating conditions. At this optimum condition, the coannular jet provides the maximum noise reduction relative to the equivalent single jet. The shock noise reduction can be achieved at inverted-as well as normal-velocity-profile conditions, provided the coannular jet is operated with the inner stream just slightly supersonic. Analytical models for the shock structure and shock noise are developed indicate that a drastic change in the outer stream shock cell structure occurs when the inner stream increases its velocity from subsonic to supersonic. At this point, the almost periodic shock cell structure of the outer stream nearly completely disappears the noise radiated is minimum. Theoretically derive formulae for the peak frequencies and intensity scaling of shock associated noise are compared with the measured results, and good agreement is found for both subsonic and supersonic inner jet flows

DSN advanced receiver: Breadboard description and test results

A breadboard Advanced Receiver for use in the Deep Space Network was designed, built, and tested in the laboratory. Field testing was also performed during Voyager Uranus encounter at DSS-13. The development of the breadboard is intended to lead towards implementation of the new receiver throughout the network. The receiver is described on a functional level and then in terms of more specific hardware and software architecture. The results of performance tests in the laboratory and in the field are given. Finally, there is a discussion of suggested improvements for the next phase of development

A Preliminary Study of Airplane Performance

Flight tests were carried out at the Langley Field laboratory of the NACA, on several airplanes for the purpose of determining their relative performance with the same engine and the same propeller. The method used consisted in flying each airplane on a level course and measuring the airspeed for the whole range of engine revolutions. In general the results show that a small change in the wing section or the wing area has but a slight effect upon the performance, but changes in those parts which cause the structural resistance have a very important effect

USB flow characteristics related to noise generation

The effects of nozzle and flap geometry on upper surface blown flow field characteristics related to noise generation were examined experimentally using static models. Flow attachment and spreading characteristics were observed using flow visualization techniques. Velocity and turbulence profiles in the trailing edge wake were measured using hot-wire anemometry, and the effects of the geometric variables on peak velocity and turbulence intensity were determined. It is shown that peak trailing edge velocity is a function of the ratio of flow length to modified hydraulic diameter

Atomic clouds as distributed sources for the plasma torus

Implications of recent developments for the neutral particle environment of Jupiter are considered. The first detection is reported of very hot S+ ions with gyrospeeds comparable to the corotations speed, a phenomenon which results from a neutral sulfur cloud. Evidence supports the hypothesis that extensive neutral clouds of oxygen and sulfur exist and are important sources of ions and energy for the Io torus

Age discrimination among basalt flows using digitally enhanced LANDSAT imagery

Digitally enhanced LANDSAT MSS data were used to discriminate among basalt flows of historical to Tertiary age, at a test site in Northwestern Saudi Arabia. Spectral signatures compared favorably with a field-defined classification that permits discrimination among five groups of basalt flows on the basis of geomorphic criteria. Characteristics that contributed to age definition include: surface texture, weathering, color, drainage evolution, and khabrah development. The inherent gradation in the evolution of geomorphic parameters, however, makes visual extrapolation between areas subjective. Therefore, incorporation of spectrally-derived volcanic units into the mapping process should produce more quantitatively consistent age groupings