1,946 research outputs found
Active Optical Remote Sensing Sensors and Instrumentation for NASAs Future Earth and Space Science Measurements/Missions
AbstractActive optical (Laser/Lidar) measurement techniques are critical for the future National Aeronautics and Space Administration (NASA) Earth, Planetary Science, Exploration, and Aeronautics measurements. The latest science decadal surveys recommend a number of missions requiring active optical systems to meet the science measurement objectives and the aeronautics community continues to use Laser/Lidar technologies to meet the aeronautics measurement objectives. This presentation will provide an overview of NASA efforts in developing and maturing state-of-the-art advanced solid-state flight laser/lidar systems for airborne and space-borne remote sensing measurements. The presentation will also provide details of a strategic approach for active optical technologies and techniques to meet the NASAs future Earth and Space Science measurement ments for space-based applications
An integral fluctuation theorem for systems with unidirectional transitions
The fluctuations of a Markovian jump process with one or more unidirectional
transitions, where but , are studied. We find that such
systems satisfy an integral fluctuation theorem. The fluctuating quantity
satisfying the theorem is a sum of the entropy produced in the bidirectional
transitions and a dynamical contribution which depends on the residence times
in the states connected by the unidirectional transitions. The convergence of
the integral fluctuation theorem is studied numerically, and found to show the
same qualitative features as in systems exhibiting microreversibility.Comment: 14 pages, 3 figure
Current in nanojunctions : Effects of reservoir coupling
We study the effect of system reservoir coupling on currents flowing through
quantum junctions. We consider two simple double-quantum dot configurations
coupled to two external fermionic reservoirs and study the net current flowing
between the two reservoirs. The net current is partitioned into currents
carried by the eigenstates of the system and by the coherences between the
eigenstates induced due to coupling with the reservoirs. We find that current
carried by populations is always positive whereas current carried by coherences
are negative for large couplings. This results in a non-monotonic dependence of
the net current on the coupling strength. We find that in certain cases, the
net current can vanish at large couplings due to cancellation between currents
carried by the eigenstates and by the coherences. These results provide new
insights into the non-trivial role of system-reservoir couplings on electron
transport through quantum dot junctions. In the presence of weak coulomb
interactions, net current as a function of system reservoir coupling strength
shows similar trends as for the non-interacting case.Comment: 9 pages, 12 figure
Statistics of an adiabatic charge pump
We investigate the effect of time-dependent cyclic-adiabatic driving on the
charge transport in quantum junction. We propose a nonequilibrium Greens
function formalism to study statistics of the charge pumped (at zero bias)
through the junction. The formulation is used to demonstrate charge pumping in
a single electronic level coupled to two (electronic) reservoirs with time
dependent couplings. Analytical expression for the average pumped current for a
general cyclic driving is derived. It is found that for zero bias, for a
certain class of driving, the Berry phase contributes only to the odd
cumulants. To contrast, a quantum master equation formulation does not show
Berry-phase effect at all
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