94,400 research outputs found
Determination of elevated-temperature fatigue data on refractory alloys in ultra- high vacuum third quarterly report, 1 jan. - 1 apr. 1965
Fatigue data for refractory alloys at elevated temperatures in ultrahigh-vacuum environment
The packing chromatic number of the infinite square lattice is between 13 and 15
Using a SAT-solver on top of a partial previously-known solution we improve the upper bound of the packing chromatic number of the infinite square lattice from 17 to 15. We discuss the merits of SAT-solving for this kind of problem as well as compare the performance of different encodings. Further, we improve the lower bound from 12 to 13 again using a SAT-solver, demonstrating the versatility of this technology for our approach
Polarized heat current generated by quantum pumping in two-dimensional topological insulators
We consider transport properties of a two dimensional topological insulator
in a double quantum point contact geometry in presence of a time-dependent
external field. In the proposed setup an external gate is placed above a single
constriction and it couples only with electrons belonging to the top edge. This
asymmetric configuration and the presence of an ac signal allow for a quantum
pumping mechanism, which, in turn, can generate finite heat and charge currents
in an unbiased device configuration. A microscopic model for the coupling with
the external time-dependent gate potential is developed and the induced finite
heat and charge currents are investigated. We demonstrate that in the
non-interacting case, heat flow is associated with a single spin component, due
to the helical nature of the edge states, and therefore a finite and polarized
heat current is obtained in this configuration. The presence of e-e
interchannel interactions strongly affects the current signal, lowering the
degree of polarization of the system. Finally, we also show that separate heat
and charge flows can be achieved, varying the amplitude of the external gate.Comment: 13 pages, 5 figure
The non-linear transient behavior of second, third and fourth order phase-locked loops
Non-linear transient behavior of second, third, and fourth order phase-locked loop
Determination of the Rb ng-series quantum defect by electric-field-induced resonant energy transfer between cold Rydberg atoms
Resonant energy transfer between cold Rydberg atoms was used to determine
Rydberg atom energy levels, at precisions approaching those obtainable in
microwave spectroscopy. Laser cooled Rb atoms from a magneto-optical trap were
optically excited to 32d Rydberg states. The two-atom process 32d(j=5/2) +
32d(j=5/2) -> 34p(j=3/2) + 30g is resonant at an electric field of
approximately 0.3 V/cm. This process is driven by the electric dipole-dipole
interaction, which is allowed due to the partial f character that the g state
acquires in an electric field. The experimentally observed resonant field,
together with the Stark map calculation is used to make a determination of the
Rb ng-series quantum defect: delta_g (n=30) = 0.00405(6)
Facilitating the exploitation of ERTS-1 imagery using snow enhancement techniques
The author has identified the following significant results. The applications of ERTS-1 imagery for geological fracture mapping regardless of season has been repeatedly confirmed. The enhancement provided by a differential cover of snow increases the number and length of fracture-lineaments which can be detected with ERTS-1 data and accelerates the fracture mapping process for a variety of practical applications. The geological mapping benefits of the program will be realized in geographic areas where data are most needed - complex glaciated terrain and areas of deep residual soils. ERTS-1 derived fracture-lineament maps which provide detail well in excess of existing geological maps are not available in the Massachusetts-Connecticut area. The large quantity of new data provided by ERTS-1 may accelerate and improve field mapping now in progress in the area. Numerous other user groups have requested data on the techniques. This represents a major change in operating philosophy for groups who to data judged that snow obscured geological detail
Characterizing Planetary Orbits and the Trajectories of Light
Exact analytic expressions for planetary orbits and light trajectories in the
Schwarzschild geometry are presented. A new parameter space is used to
characterize all possible planetary orbits. Different regions in this parameter
space can be associated with different characteristics of the orbits. The
boundaries for these regions are clearly defined. Observational data can be
directly associated with points in the regions. A possible extension of these
considerations with an additional parameter for the case of Kerr geometry is
briefly discussed.Comment: 49 pages total with 11 tables and 10 figure
Extracting the Proton ubar content from pp->Direct Photon plus Jet Cross Sections
An analysis procedure is proposed to measure the antiquark distributions in
the proton over the region 0.01 < x < 0.1. The procedure involves the
measurement of high p_t asymmetric direct photon and jet final states in pp
interactions. This measurement can be made at the RHIC collider running in pp
mode at an energy of sqrt(s)=500 GeV/c. This analysis identifies a region of
phase space where the contribution from quark-antiquark annihilation
uncharacteristically approaches the magnitude of the contribution from the
leading process, quark-gluon Compton scattering. The forward-backward angular
asymmetry in the parton center of mass is sensitive to the antiquark content of
the proton and the ubar parton density function can be extracted.Comment: 21 pages, 7 figure
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