17,726 research outputs found
A simplified flight-test method for determining aircraft takeoff performance that includes effects of pilot technique
A method for evaluating aircraft takeoff performance from brake release to air-phase height that requires fewer tests than conventionally required is evaluated with data for the XB-70 airplane. The method defines the effects of pilot technique on takeoff performance quantitatively, including the decrease in acceleration from drag due to lift. For a given takeoff weight and throttle setting, a single takeoff provides enough data to establish a standardizing relationship for the distance from brake release to any point where velocity is appropriate to rotation. The lower rotation rates penalized takeoff performance in terms of ground roll distance; the lowest observed rotation rate required a ground roll distance that was 19 percent longer than the highest. Rotations at the minimum rate also resulted in lift-off velocities that were approximately 5 knots lower than the highest rotation rate at any given lift-off distance
SPAR VI Technical Report for Experiment 76-22: Directional Solidification of Magnetic Composites
Samples of eutectic Bi/MnBi were directionally solidified during a low-g interval aboard the SPAR 6 flight and in a l-g environment under identical furnace velocity and thermal conditions. The Bi/MnBi eutectic is characterized by a regular rod eutectic whose morphology may be sensitive to thermo-solutal convection and by its components, MnBi, which is ferromagnetic. Morphological analyses on samples show statistically smaller interrod spacings and rod diameters with respect to samples grown under identical solidification furnace conditions in l-g. An adjustment between the interrod spacing, growth velocity, and total undercooling at the solidification interface is proposed. Morphological analyses on samples grown in l-g indicate little difference between results for different growth orientations with respect to the gravity vector. The magnetic properties are significantly affected, however, by the presence of a nonequilibrium magnetic phase and the nonequilibrium phase transforms to the equilibrium ferromagnetic phase during isothermal heat treatment
The growth of metastable peritectic compounds
The influence of gravitationally driven thermosolutal convection on the directional solidification of peritectic alloys is considered as well as the relationships between the solidification processing conditions, and the microstructure, chemistry, and magnetic properties of such alloys. Analysis of directionally solidified Pb-Bi peritectic samples indicates that appreciable macrosegregation occurs due to thermosolutal convection and/or Soret diffusion. A peritectic solidification model which accounts for partial mixing in the liquid ahead of the planar solidification interface and describes macrosegregation has been developed. Two-phase dendritic and banded microstructures were grown in the Pb-Bi peritectic system, refined two-phase microstructures have were observed, and candidate formation mechanisms proposed. Material handling, containment, casting, microstructural and magnetic characterization techniques were developed for the Sm-Co system. Alloys produced with these procedures are homogeneous
Remotely Engaged? A Framework for Monitoring the Success of Stakeholder Engagement in Remote Regions
The importance of stakeholder engagement for the success of natural resources management processes is widely acknowledged, yet evaluation frameworks employed by administrators of environmental programs continue to provide limited recognition of or insistence upon engagement processes. This paper presents a framework for monitoring and evaluation of engagement that aims to better incorporate community engagement into mainstream environmental programs, in particular in remote regions such as arid and desert regions of the world. We argue that successful monitoring of engagement should not only comprise a generic set of indicators but rather, in addition to the principles of good monitoring practice, should take into account a variety of the stakeholder interests as well as key regional drivers, addressing them at right geographic, institutional and time scale.engagement, evaluation, governance, natural resources, participation, stakeholders
Duality in Shearing Rheology Near the Athermal Jamming Transition
We consider the rheology of soft-core frictionless disks in two dimensions in
the neighborhood of the athermal jamming transition. From numerical simulations
of bidisperse, overdamped, particles, we argue that the divergence of the
viscosity below jamming is characteristic of the hard-core limit, independent
of the particular soft-core interaction. We develop a mapping from soft-core to
hard-core particles that recovers all the critical behavior found in earlier
scaling analyses. Using this mapping we derive a duality relation that gives
the exponent of the non-linear Herschel-Bulkley rheology above jamming in terms
of the exponent of the diverging viscosity below jamming.Comment: 5 pages, 4 figures. Manuscript revisions: new title, additional text
concerning connections to experiment, revised Fig. 4, other minor changes and
clarifications in text. Conclusions remain essentially unchanged. Accepted
for publication in Phys. Rev. Let
Thermal and hydrodynamic effects in the ordering of lamellar fluids
Phase separation in a complex fluid with lamellar order has been studied in
the case of cold thermal fronts propagating diffusively from external walls.
The velocity hydrodynamic modes are taken into account by coupling the
convection-diffusion equation for the order parameter to a generalised
Navier-Stokes equation. The dynamical equations are simulated by implementing a
hybrid method based on a lattice Boltzmann algorithm coupled to finite
difference schemes. Simulations show that the ordering process occurs with
morphologies depending on the speed of the thermal fronts or, equivalently, on
the value of the thermal conductivity {\xi}. At large value of {\xi}, as in
instantaneous quenching, the system is frozen in entangled configurations at
high viscosity while consists of grains with well ordered lamellae at low
viscosity. By decreasing the value of {\xi}, a regime with very ordered
lamellae parallel to the thermal fronts is found. At very low values of {\xi}
the preferred orientation is perpendicular to the walls in d = 2, while
perpendicular order is lost moving far from the walls in d = 3.Comment: 8 pages, 3 figures. Accepted for publication in Phil. Trans. of Royal
Soc, Ser
Dilute gas of ultracold two-level atoms inside a cavity; generalized Dicke model
We consider a gas of ultracold two-level atoms confined in a cavity, taking
into account for atomic center-of-mass motion and cavity mode variations. We
use the generalized Dicke model, and analyze separately the cases of a
Gaussian, and a standing wave mode shape. Owing to the interplay between
external motional energies of the atoms and internal atomic and field energies,
the phase-diagrams exhibit novel features not encountered in the standard Dicke
model, such as the existence of first and second order phase transitions
between normal and superradiant phases. Due to the quantum description of
atomic motion, internal and external atomic degrees of freedom are highly
correlated leading to modified normal and superradiant phases.Comment: 10 pages, 7 figure
Do potatoes respond to nitrogen and phosphorus placement?
Non-Peer ReviewedPotato requires large amounts of fertilizer. Proper fertility management is essential to
optimize potato yield and quality under the relatively cool and short growing conditions in
Saskatchewan. Important aspects of fertility management include rate, placement, and timing of
fertilizer. This study examined the effects of placement (broadcast, side-band) of nitrogen and
phosphorus fertilizer on productivity for contrasting potato cultivars (Atlantic, Norland, Ranger
Russet, Russet Burbank, Russet Norkotah, Shepody) grown under dryland and irrigated
conditions. Three pre-plant nitrogen rates (50, 100, 150 kg N/ha) and three pre-plant phosphorus
rates (40, 80, 120 kg P2O5/ha) were tested in separate trials. In the nitrogen study under dryland, the average ‘seed’ and ‘consumption’ grade yields were 25 and 19 t/ha respectively. Under irrigation, ‘seed’ and ‘consumption’ grade yields averaged 40 t/ha. Nitrogen application method or rate had no effect on ‘seed’ or ‘consumption’ grade yields under both dryland and irrigated production. In the phosphorus study, the average dryland yields for ‘seed’ and ‘consumption’ grade tubers were 24 and 19 t/ha respectively. Under irrigation, ‘seed’ and ‘consumption’ grade yields averaged 38 and 34 t/ha respectively. Under irrigation, the rate and method of phosphorus application had no effect on tuber yields. Under dryland, there was no significant effect of rate of phosphorus on tuber yield. Side-banding tended to produce higher ‘seed’ and ‘consumption’ grade yields than broadcast application. Cultivars responded differently under dryland and irrigated production. The various cultivars responded similarly to rates and methods of nitrogen and phosphorus application under both production conditions. Further work is necessary to verify the effects of rate and method of nitrogen and phosphorus application on yield and quality of potato cultivars grown commercially under dryland and under irrigation in Saskatchewan
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