19,883 research outputs found
Some data processing requirements for precision Nap-Of-the-Earth (NOE) guidance and control of rotorcraft
Nap-Of-the-Earth (NOE) flight in a conventional helicopter is extremely taxing for two pilots under visual conditions. Developing a single pilot all-weather NOE capability will require a fully automatic NOE navigation and flight control capability for which innovative guidance and control concepts were examined. Constrained time-optimality provides a validated criterion for automatically controlled NOE maneuvers if the pilot is to have confidence in the automated maneuvering technique. A second focus was to organize the storage and real-time updating of NOE terrain profiles and obstacles in course-oriented coordinates indexed to the mission flight plan. A method is presented for using pre-flight geodetic parameter identification to establish guidance commands for planned flight profiles and alternates. A method is then suggested for interpolating this guidance command information with the aid of forward and side looking sensors within the resolution of the stored data base, enriching the data content with real-time display, guidance, and control purposes. A third focus defined a class of automatic anticipative guidance algorithms and necessary data preview requirements to follow the vertical, lateral, and longitudinal guidance commands dictated by the updated flight profiles and to address the effects of processing delays in digital guidance and control system candidates. The results of this three-fold research effort offer promising alternatives designed to gain pilot acceptance for automatic guidance and control of rotorcraft in NOE operations
Substitutability of Livestock Manure for Chemical Fertilizer: A Contingent Valuation Analysis of Crop Producers
The impact of new manure management regulations depends on the willingness of crop producers to accept manure. A contingent valuation analysis of crop producers was used to estimate the willingness of crop producers to accept or pay for manure. Results indicate that producers will pay a positive price on average, but some would require a payment before accepting manure.Farm Management,
Switching of the magnetic order in CeRhInSn in the vicinity of its quantum critical point
We report neutron diffraction experiments performed in the tetragonal
antiferromagnetic heavy fermion system CeRhInSn in its (, )
phase diagram up to the vicinity of the critical concentration
0.40, where long range magnetic order is suppressed. The propagation vector of
the magnetic structure is found to be =(1/2, 1/2, ) with
increasing from =0.298 to =0.410 when increases from =0
to =0.26. Surprisingly, for =0.30, the order has changed drastically and
a commensurate antiferromagnetism with =(1/2, 1/2, 0) is found.
This concentration is located in the proximity of the quantum critical point
where superconductivity is expected.Comment: 5 pages, 5 figures, submitted to Phys. Rev.
The effect of rotation and tidal heating on the thermal lightcurves of Super Mercuries
Short period (<50 days) low-mass (<10Mearth) exoplanets are abundant and the
few of them whose radius and mass have been measured already reveal a diversity
in composition. Some of these exoplanets are found on eccentric orbits and are
subjected to strong tides affecting their rotation and resulting in significant
tidal heating. Within this population, some planets are likely to be depleted
in volatiles and have no atmosphere. We model the thermal emission of these
"Super Mercuries" to study the signatures of rotation and tidal dissipation on
their infrared light curve. We compute the time-dependent temperature map at
the surface and in the subsurface of the planet and the resulting
disk-integrated emission spectrum received by a distant observer for any
observation geometry. We calculate the illumination of the planetary surface
for any Keplerian orbit and rotation. We include the internal tidal heat flow,
vertical heat diffusion in the subsurface and generate synthetic light curves.
We show that the different rotation periods predicted by tidal models
(spin-orbit resonances, pseudo-synchronization) produce different photometric
signatures, which are observable provided that the thermal inertia of the
surface is high, like that of solid or melted rocks (but not regolith). Tidal
dissipation can also directly affect the light curves and make the inference of
the rotation more difficult or easier depending on the existence of hot spots
on the surface. Infrared light curve measurement with the James Webb Space
Telescope and EChO can be used to infer exoplanets' rotation periods and
dissipation rates and thus to test tidal models. This data will also constrain
the nature of the (sub)surface by constraining the thermal inertia.Comment: 15 pages, 13 figures, accepted for publication in Astronomy &
Astrophysic
Suppression of hidden order in URu2Si2 under pressure and restoration in magnetic field
We describe here recent inelastic neutron scattering experiments on the heavy
fermion compound URu2Si2 realized in order to clarify the nature of the hidden
order (HO) phase which occurs below T_0 = 17.5 K at ambient pressure. The
choice was to measure at a given pressure P where the system will go, by
lowering the temperature, successively from paramagnetic (PM) to HO and then to
antiferromagnetic phase (AF). Furthermore, in order to verify the selection of
the pressure, a macroscopic detection of the phase transitions was also
achieved in situ via its thermal expansion response detected by a strain gauge
glued on the crystal. Just above P_x = 0.5 GPa, where the ground state switches
from HO to AF, the Q_0 = (1, 0, 0) excitation disappears while the excitation
at the incommensurate wavevector Q_1 = (1.4, 0, 0) remains. Thus, the Q_0 = (1,
0, 0) excitation is intrinsic only in the HO phase. This result is reinforced
by studies where now pressure and magnetic field can be used as tuning
variable. Above P_x, the AF phase at low temperature is destroyed by a magnetic
field larger than H_AF (collapse of the AF Q_0 = (1, 0, 0) Bragg reflection).
The field reentrance of the HO phase is demonstrated by the reappearance of its
characteristic Q_0 = (1, 0, 0) excitation. The recovery of a PM phase will only
be achieved far above H_AF at H_M approx 35 T. To determine the P-H-T phase
diagram of URu2Si2, macroscopic measurements of the thermal expansion were
realized with a strain gauge. The reentrant magnetic field increases strongly
with pressure. Finally, to investigate the interplay between superconductivity
(SC) and spin dynamics, new inelastic neutron scattering experiments are
reported down to 0.4 K, far below the superconducting critical temperature T_SC
approx 1.3 K as measured on our crystal by diamagnetic shielding.Comment: 5 pages, 7 figures, ICN 2009 conference proceeding
KY-CTDS Kentucky Contract Time Determination System (KYSPR 99-195-lF)
This paper reports on the results of research that was funded by the Kentucky Transportation Cabinet (KyTC) to develop a new method for determining construction contract time for its highway construction contracts. The current and other DOT systems were analyzed to determine how a new system could provide better estimated duration. It was pre-determined that a PC computer based system was best suited. The development of the system input was developed from KyTC engineers with construction experience. The study advisory committee worked with Kentucky Transportation Center research engineers to develop the basis for the new contract time determination system, called KY-CTDS.
The KY-CTDS program provides a conceptual estimating tool for predicting construction contract time for the Kentucky Department of Highways. It uses the pre-determined project classifications with only the major activities that control the project duration. Production rates and activity relationships were determined and are included in the program. Final adjustments in the project can be easily made by KyTC engineers. This system utilizes Microsoft Project® 98 and Microsoft Excel® Version 7.0 software operating on a personal computer. System outputs include a graphical bar chart schedule for estimating the contract time for bidding purposes. System output may also help in resolving construction disputes. The program is not suitable for detailed scheduling of construction operations
The Paris to Lexington Road Reconstruction Project
This report summarizes the effort to provide the Kentucky Transportation Cabinet with an evaluation of the results obtained for the Paris to Lexington Road Reconstruction Project from 1997 to 2001. A unique pre-qualification process was used for the project to select a fixed pool of contractor to provide input to the design and to bid on the work. The research started in 1996 during the design process and continued following construction until September of 2001.
Input was received from the Cabinet personnel working on the project, from the design firms, from the contractors, from the property owners involved, and from the citizen\u27s advisory committee overseeing the project. This was an environmentally sensitive project requiring special design and construction practices to meet the project objectives.
An evaluation was done on 15 key project attributes and the project cost. Although more expensive than traditional highway projects the project was very successful. It is an example of how a highway department can successfully partner with the other stakeholders in a historic and environmentally sensitive project. Several observations and conclusions are included in the report
Sanctions mémorielles et fragments littéraires au 1er siècle av. J.-C.
L\u27auteur "s\u27interroge (...) sur les liens pouvant exister entre l\u27état fragmentaire de différentes oeuvres latines du 1er siècle avant notre ère et les sanctions mémorielles, pouvant prendre la forme d\u27une véritable damnatio memoriae, sanctions auxquelles leurs auteurs respectifs ont été condamnés: Sylla, Marc Antoine et Caius Cornelius Gallus. De l\u27ouvrage considérable et novateur de Sylla, oeuvre autobiographique politique comportant vingt-deux livres, outre la trame fournie par Plutarque, il ne demeure que d\u27infimes fragments détachés de leurs contextes pour satisfaire la curiosité lexicologique et grammaticale d\u27auteurs tardifs (Aulu Gelle et Priscien). Marc Antoine fut littéralement réduit au silence par Auguste, son rival victorieux. Aucun fragment, au sens strict du terme, de ses écrits ne nous est parvenu. On ne connaît qu\u27une allusion à son pamphlet, De ebrietate sua, dans un passage de Pline, qui constitue une "destruction" en règle de l\u27ouvrage. De l\u27oeuvre de Gallus, poète élégiaque unanimement loué, il ne subsiste que deux fragments, dont l\u27un est transmis par un papyrus très endommagé. Tout laisse à penser que la disparition de son oeuvre s\u27explique par une censure, consécutive à la disgrâce qu\u27il subit, après avoir froissé Auguste..." (Fragments. Entre brisure et création, p.14-15)
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