8,346 research outputs found
Nationwide forestry applications program. Analysis of forest classification accuracy
The development of LANDSAT classification accuracy assessment techniques, and of a computerized system for assessing wildlife habitat from land cover maps are considered. A literature review on accuracy assessment techniques and an explanation for the techniques development under both projects are included along with listings of the computer programs. The presentations and discussions at the National Working Conference on LANDSAT Classification Accuracy are summarized. Two symposium papers which were published on the results of this project are appended
Highly electronegative metallic contacts to semiconductors using polymeric sulfur nitride
The Schottky barriers formed on nāZnS and nāZnSe by polymeric sulfur nitride have been compared to barriers formed by Au. Barrier energies as determined by photoresponse, currentāvoltage, and capacitanceāvoltage methods show that (SN)_x is approximately 1.0 eV higher than Au on nāZnS and 0.3ā0.4 eV higher than Au on nāZnSe. We believe that this is the first report of any metallic contact more electronegative than Au
BRAVO economic study of LANDSAT follow-on
The LANDSAT Follow-On satellite consists of two major systems: the instrument module and the Multi-Mission Modular Spacecraft (MMS). The instrument module contains the thematic mapper and the five-band multispectral scanner instruments. The instrument module also includes the solar array, the tracking and data relay satellite (TDRS) antenna, and the wideband data module. The MMS contains the modularized and standardized power, propulsion, attitude control, and command and data handling subsystems. The Shuttle will be supporting the LANDSAT Follow-On system. The LANDSAT Follow-On Project plans two Delta 3910 launches. The first is scheduled for 1981; the second Delta launch will occur as needed to keep one satellite operational on orbit. The second satellite will be ready six months after the first. It could be launched any time after that. Shuttle support of the system could begin in early 1983 but would be scheduled to start after the second Delta launch
Optical Polarization of 52 Radio-Loud QSOs and BL Lac Objects
Polarization measurements are presented for 52 radio-loud QSOs and BL Lac
objects. For 9 highly polarized (p >3%) AGN, these are the first published
polarization measurements. Of these 9, 7 are highly-polarized QSOs (HPQs), one
is a BL Lac object and another is a likely BL Lac object. Polarization
variability is confirmed for some of these new and previously known
highly-polarized AGN. While 6 of the HPQs have flat radio spectra are almost
certainly blazars, PKS 1452-217 is probably a new member of the rare class of
radio-loud QSOs that show high polarization by scattering, and is therefore
important for testing orientation Unified Schemes. In competition for the
highest redshift HPQ are the well-observed QSO PKS 0438-43 at z = 2.85, with
maximum p = 4.7%, and PKS 0046-315 at z = 2.72, for which we find p = 13%.Comment: 6 pages. Astronomical Journal, in pres
The Presence of Deep Levels in Ion Implanted Junctions
It has been found that ion implantation doping results in the generation and diffusion of defect species, forming deep trapping levels. The effect of these levels on the electrical characteristics of zincāimplanted GaAs diodes has been observed for the case of 70ākV implantation at 400Ā°C into substrates with nātype concentrations ranging from 1 Ć 10^16 to 1.8 Ć 10^18 atoms/cm^3. Capacitanceāvoltage measurements have indicated the presence of a semiāinsulating layer in the diodes, varying in thickness from 0.18 Ī¼ for the most heavily doped substrate to 2.7 Ī¼ for the lightest. Frequency dependence of the junction capacitance and power law variation of forward current vs voltage have also been observed and are attributed to deep levels
Quantifying inherent predictability and spatial synchrony in the aphid vector Myzus persicae - field-scale patterns of abundance and regional forecasting error in the UK
BACKGROUND
Sugar beet is threatened by virus yellows, a disease complex vectored by aphids that reduces sugar content. We present an analysis of Myzus persicae population dynamics with and without neonicotinoid seed treatment. We use six yearsā yellow water trap and field-collected aphid data and two decades of 12.2 m suction-trap aphid migration data. We investigate both spatial synchrony and forecasting error to understand the structure and spatial scale of field counts and why forecasting aphid migrants lacks accuracy. Our aim is to derive statistical parameters to inform regionwide pest management strategies.
RESULTS
Spatial synchrony, indicating the coincident change in counts over time across the region, is rarely present and is best described as stochastic. Uniquely, early season field populations in 2019, did show spatial synchrony to 90 km compared to the overall average weekly correlation length of 23 km. However, 70% of the time series were spatially heterogenous, indicating patchy between-field dynamics. Field counts lacked the same seasonal trend and did not peak in the same week. Forecasts tended to under-predict mid-season log10 counts. A strongly negative correlation between forecasting error and the proportion of zeros was shown.
CONCLUSION
Field populations are unpredictable and stochastic, regardless of neonicotinoid seed treatment. This outcome presents a problem for decision-support that cannot usefully provide a single regionwide solution. Weighted permutation entropy inferred that M. persicae 12.2 m suction-trap time series had moderate to low intrinsic predictability. Early warning using a migration model tended to predict counts at lower levels than observed
Identifying Roadkill Hotspots Using a Running Average
The identification of roadkill hotspots is necessary prior to the consideration of wildlife road mortality mitigation measures. In a previous study, 178 roadkill specimens were tallied via a driving survey along 21.4 km (13.3 mi) on three connected roadways in Baldwin County, Georgia. Roadkill locations were recorded to the nearest 0.16 km (0.1 mi) using the vehicle odometer. In the current study, location data were used to generate three graphical displays of roadkill distribution: 1) a linear graph of roadkills per 0.16 km (0.1 mi) bin; 2) a linear graph of roadkills per 0.8 km (0.5 mi) bin; and 3) a linear graph with a continuous running average incorporating 0.48 km (0.3 mi). The number and position of the peaks on each graph were compared in relation to roadway features that may influence animal movement and mortality such as vegetative boundaries, stream crossings, hills, and curves. The running average plot provided the best visual illustration of roadkill hotspot locations in relation to roadside features. The running average is a good technique to quickly and accurately identify hotspot locations and could help resource managers plan mitigation strategies to decrease wildlife road mortality
The Born Oppenheimer wave function near level crossing
The standard Born Oppenheimer theory does not give an accurate description of
the wave function near points of level crossing. We give such a description
near an isotropic conic crossing, for energies close to the crossing energy.
This leads to the study of two coupled second order ordinary differential
equations whose solution is described in terms of the generalized
hypergeometric functions of the kind 0F3(;a,b,c;z). We find that, at low
angular momenta, the mixing due to crossing is surprisingly large, scaling like
\mu^(1/6), where \mu is the electron to nuclear mass ratio.Comment: 21 pages, 7 figure
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