8,191 research outputs found
Multimegawatt dynamic NEP PMAD study
The National Aeronautics and Space Administration Lewis Research Center (NASA LeRC) is developing a FORTRAN-based model of a complete nuclear electric propulsion (NEP) vehicle to be used for piloted or cargo missions to the Moon or Mars. The proposed vehicle will use either a Brayton or K-Rankine power conversion cycle, and either ion or magnetoplasmadynamic (MPD) thrusters. In support of this effort, Rocketdyne evaluated various power management and distribution (PMAD) approaches and selected a low-frequency design that is based on the direct use of the alternator voltage and frequency for power transmission. This approach was compared with dc and high-frequency ac designs, and selected on the basis of mass, efficiency, and qualitative assessment of power quality, reliability and development costs. This low-frequency architecture will be used as the reference in future NEP PMAD studies and for the subsequent FORTRAN model development
Quantifying the effectiveness of silver ring splints to correct swan-neck deformity
Swan-neck deformity is a common symptom of rheumatoid arthritis affecting the fingers. It can be classified by hyperextension of the proximal interphalangeal (PIP) joint and flexion of the distal interphalangeal joint [1]. Methods to correct hyperextension of the PIP joint range from surgery to splinting techniques [2]. Silver ring splints (SRSs) were recently identified as a possible alternative to surgery and traditional thermoplastic splints because patient adherence was improved by their appearance [3]. The objective of this study was to investigate whether the SRSs restrict PIP joint hyperextension during a fine dexterity task
Enhanced energy relaxation process of quantum memory coupled with a superconducting qubit
For quantum information processing, each physical system has different
advantage for the implementation and so hybrid systems to benefit from several
systems would be able to provide a promising approach. One of the common hybrid
approach is to combine a superconducting qubit as a controllable qubit and the
other quantum system with a long coherence time as a memory qubit. The
superconducting qubit allows us to have an excellent controllability of the
quantum states and the memory qubit is capable of storing the information for a
long time. By tuning the energy splitting between the superconducting qubit and
the memory qubit, it is believed that one can realize a selective coupling
between them. However, we have shown that this approach has a fundamental
drawback concerning energy leakage from the memory qubit. The detuned
superconducting qubit is usually affected by severe decoherence, and this
causes an incoherent energy relaxation from the memory qubit to the
superconducting qubit via the imperfect decoupling. We have also found that
this energy transport can be interpreted as an appearance of anti quantum Zeno
effect induced by the fluctuation in the superconducting qubit. We also discuss
a possible solution to avoid such energy relaxation process, which is feasible
with existing technology
Coulomb crystallization in expanding laser-cooled neutral plasmas
We present long-time simulations of expanding ultracold neutral plasmas,
including a full treatment of the strongly coupled ion dynamics. Thereby, the
relaxation dynamics of the expanding laser-cooled plasma is studied, taking
into account elastic as well as inelastic collisions. It is demonstrated that,
depending on the initial conditions, the ionic component of the plasma may
exhibit short-range order or even a superimposed long-range order resulting in
concentric ion shells. In contrast to ionic plasmas confined in traps, the
shell structures are built up from the center of the plasma cloud rather than
from the periphery
Spatiotemporal dynamics of quantum jumps with Rydberg atoms
We study the nonequilibrium dynamics of quantum jumps in a one-dimensional
chain of atoms. Each atom is driven on a strong transition to a short-lived
state and on a weak transition to a metastable state. We choose the metastable
state to be a Rydberg state so that when an atom jumps to the Rydberg state, it
inhibits or enhances jumps in the neighboring atoms. This leads to rich
spatiotemporal dynamics that are visible in the fluorescence of the strong
transition.Comment: 10 page
Initializing a Quantum Register from Mott Insulator States in Optical Lattices
We propose and quantitatively develop two schemes to quickly and accurately
generate a stable initial configuration of neutral atoms in optical microtraps
by extraction from the Mott insulator state in optical lattices. We show that
thousands of atoms may be extracted and stored in the ground states of optical
microtrap arrays with one atom per trap in one operational process
demonstrating massive scalability. The failure probability during extraction in
the first scheme can be made sufficiently small (10^{-4}) to initialize a large
scale quantum register with high fidelity. A complementary faster scheme with
more extracted atoms but lower fidelity is also developed.Comment: 5 pages, 3 figure
Obscenity Prosecutions in Cyberspace: The Miller Test Cannot “Go Where No [Porn] Has Gone Before”
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