Software for the grouped optimal aggregation technique

The grouped optimal aggregation technique produces minimum variance, unbiased estimates of acreage and production for countries, zones (states), or any designated collection of acreage strata. It uses yield predictions, historical acreage information, and direct acreage estimate from satellite data. The acreage strata are grouped in such a way that the ratio model over historical acreage provides a smaller variance than if the model were applied to each individual stratum. An optimal weighting matrix based on historical acreages, provides the link between incomplete direct acreage estimates and the total, current acreage estimate

Optical enhancement of sensitivity in laser Doppler velocity systems

Utilization of optical enhancement techniques prevents loss of light by reflections at the photocathode of a photomultiplier and increases signal detection sensitivity

Throat stability-by pass systems to increase the stable airflow range of a Mach 2.5 inlet with 60-percent internal contraction

The results of an experimental investigation to increase the stable airflow range (without unstart) of a supersonic mixed-compression inlet are presented. Various stability bypass entrances were located on the cowl side of the inlet throat. The types of entrance were distributed porous (normal holes), forward-slanted slot, and distributed educated slots. A large stable airflow range was obtained for each entrance type if a constant pressure was maintained in the stability bypass plenum. The distributed porous entrance provided the largest stable airflow range. Inlet unstart angle of attack was unaffected by the entrances

Distributed porous throat stability bypass to increase the stable airflow range of a Mach 2.5 inlet with 60 percent internal contraction

The results of an experimental investigation to increase the stable airflow operating range of a supersonic, mixed-compression inlet with 60-percent internal contraction are presented. Various distributed-porous, throat stability-bypass entrance configurations were tested. In terms of diffuser-exit corrected airflow, a large inlet stable airflow range of about 25 percent was obtained with the optimum configuration if a constant pressure was maintained in the by-pass plenum. The location of the centerbody bleed region had a decided effect on the overall inlet performance. Limited unstart angle-of-attack data are presented

Distributed educated throat stability bypass to increase the stable airflow range of a Mach 2.5 inlet with 60-percent internal contraction

The results of an experimental investigation to increase the stable airflow operating range of a supersonic mixed-compression inlet are presented. A distributed educated throat stability-bypass entrance configuration was tested. In terms of diffuser-exit corrected airflow, a large inlet stable airflow range of about 16.1 percent was obtained if a constant pressure was maintained in the bypass plenum. Limited unstart angle of attack data are presented

Heat transfer distributions around nominal ice accretion shapes formed on a cylinder in the NASA Lewis icing research tunnel

Local heat transfer coefficients were obtained on irregular cylindrical shapes which typify the accretion of ice on circular cylinders in cross flow. The ice shapes were grown on a 5.1 cm (2.0 in.) diameter cylinder in the NASA Lewis Icing Research Tunnel. The shapes were 2, 5, and 15 min accumulations of glaze ice and 15 min accumulation of rime ice. Heat transfer coefficients were also measured around the cylinder with no ice accretion. These icing shapes were averaged axially to obtain a nominal shape of constant cross section for the heat transfer tests. Heat transfer coefficients around the perimeter of each shape were measured with electrically heated copper strips embedded in the surface of the model which was cast from polyurethane foam. Each strip contained a thermocouple to measure the local surface temperature. The models were run in a 15.2 x 68.6 cm (6 x 27 in.) wind tunnel at several velocities. Background turbulence in the wind tunnel was less than 0.5 percent. The models were also run with a turbulence producing grid which gave about 3.5 percent turbulence at the model location with the model removed. The effect of roughness was also simulated with sand grains glued to the surface. Results are presented as Nusselt number versus angle from the stagnation line for the smooth and rough models for both high and low levels of free stream turblence. Roughness of the surface in the region prior to flow separation plays a major role in determining the heat transfer distribution

Selenium Concentrations in Forages of a Northern Herbivore

The importance of adequate selenium in diets of native wild herbivores can only be inferred from data for beef cattle where minimum dietary concentrations range from 50 to 100 ppb. Concern about possible selenium deficiencies in wild herbivores is based on a few reports of symptoms in wildlife, a paucity of data on selenium in their forages, and the idea that excessive atmospheric sulfur may increase the incidence of selenium deficiencies in herbivores. Concentrations of selenium in sedges, Carex spp., and reedgrasses, Calamagrostis spp., the main food plants of bison, Bison bison, in northwestern Canada, varied from 9 to 800 ppb in samples collected at three lowlands locations. However, approximately three-quarters of all the samples of plant species consumed by bison were dietarily deficient by the beef cattle standard.Key words: Carex, Calamagrostis, bison, selenium concentrationMots clés: Carex, calamagrostis, bison, concentration de séléniu

Correlated emission and spin-down variability in radio pulsars

The recent revelation that there are correlated period derivative and pulse shape changes in pulsars has dramatically changed our understanding of timing noise as well as the relationship between the radio emission and the properties of the magnetosphere as a whole. Using Gaussian processes we are able to model timing and emission variability using a regression technique that imposes no functional form on the data. We revisit the pulsars first studied by Lyne et al. (2010). We not only confirm the emission and rotational transitions revealed therein, but reveal further transitions and periodicities in 8 years of extended monitoring. We also show that in many of these objects the pulse profile transitions between two well-defined shapes, coincident with changes to the period derivative. With a view to the SKA and other telescopes capable of higher cadence we also study the detection limitations of period derivative changes.Comment: 4 pages, 2 Figures, Proceedings of IAU Symposium 337 "Pulsar Astrophysics - The Next 50 Years" held at Jodrell Bank Observatory, UK Sept. 4-8 201

The glitch activity of neutron stars

We present a statistical study of the glitch population and the behaviour of the glitch activity across the known population of neutron stars. An unbiased glitch database was put together based on systematic searches of radio timing data of 898 rotation-powered pulsars obtained with the Jodrell Bank and Parkes observatories. Glitches identified in similar searches of 5 magnetars were also included. The database contains 384 glitches found in the rotation of 141 of these neutron stars. We confirm that the glitch size distribution is at least bimodal, with one sharp peak at approximately $20\, \rm{\mu\,Hz}$, which we call large glitches, and a broader distribution of smaller glitches. We also explored how the glitch activity $\dot{\nu}_{\rm{g}}$, defined as the mean frequency increment per unit of time due to glitches, correlates with the spin frequency $\nu$, spin-down rate $|\dot{\nu}|$, and various combinations of these, such as energy loss rate, magnetic field, and spin-down age. It is found that the activity is insensitive to the magnetic field and that it correlates strongly with the energy loss rate, though magnetars deviate from the trend defined by the rotation-powered pulsars. However, we find that a constant ratio $\dot\nu_{\rm{g}}/|\dot\nu| = 0.010 \pm 0.001$ is consistent with the behaviour of all rotation-powered pulsars and magnetars. This relation is dominated by large glitches, which occur at a rate directly proportional to $|\dot{\nu}|$. The only exception are the rotation-powered pulsars with the highest values of $|\dot{\nu}|$, such as the Crab pulsar and PSR B0540$-$69, which exhibit a much smaller glitch activity, intrinsically different from each other and from the rest of the population. The activity due to small glitches also shows an increasing trend with $|\dot\nu|$, but this relation is biased by selection effects.Comment: Accepted for publication in A&

Effects of Ponderosa Pine Ecological Restoration on Forest Soils and Understory Vegetation in Northern Arizona

The human exclusion of wildfire and overgrazing by livestock since settlement have caused dramatic changes in ponderosa pine (Pinus ponderosa Dougl ex Laws) forest ecosystems. These changes include increased numbers of tree stems, reduced understory cover and diversity, and the introduction of invasive, non-native understory species. This study evaluated the coverage and species composition of understory vegetation present in the “cool-season” (late spring and early summer) in a ponderosa pine forest on grazed and ungrazed plots that had undergone restoration treatments on three different soil/geologic parent material types near Flagstaff, Arizona, twelve years after tree thinning and grazing exclosure treatments were applied. Several measured soil properties, such as soil respiration and temperature, were also evaluated in this study. Species richness of “cool-season” vegetation was influenced more by grazing practices than restoration treatments. Differences could be less or greater when vegetation that is active later in the season is measured. Vegetative cover was significantly influenced by restoration treatments (9.3% cover under open canopies and 6.5% under dense canopies), probably due to differences in competition for light and other resources (i.e. soil moisture and nutrients). Unlike finding by Abella et al. (2015), who studied “warm-season” vegetation, “cool-season” understory cover was not influenced by soil parent material type in this study, which might suggest that differences in understory cover due to soil properties are only seen shortly after restoration treatments are applied, or the time of year vegetation is evaluated may play a role in the differences seen. Soil respiration was highest on limestone soil parent material type (3.3 g C-CO2 m-2 day-1), and soil temperature was lowest under closed canopy treatments (15°C)