24,123 research outputs found
Circuits on Cylinders
We consider the computational power of constant width polynomial size cylindrical circuits and nondeterministic branching programs. We show that every function computed by a Pi_2 o MOD o AC^0 circuit can also be computed by a constant width polynomial size cylindrical nondeterministic branching program (or cylindrical circuit) and that every function computed by a constant width polynomial size cylindrical circuit belongs to ACC^0
Meissner state in finite superconducting cylinders with uniform applied magnetic field
We study the magnetic response of superconductors in the presence of low
values of a uniform applied magnetic field. We report measurements of DC
magnetization and AC magnetic susceptibility performed on niobium cylinders of
different length-to-radius ratios, which show a dramatic enhance of the initial
magnetization for thin samples, due to the demagnetizing effects. The
experimental results are analyzed by applying a model that calculates the
magnetic response of the superconductor, taking into account the effects of the
demagnetizing fields. We use the results of magnetization and current and field
distributions of perfectly diamagnetic cylinders to discuss the physics of the
demagnetizing effects in the Meissner state of type-II superconductors.Comment: Accepted to be published in Phys. Rev. B; 15 pages, 7 ps figure
Full- and Reduced-order Model of Hydraulic Cylinder for Motion Control
This paper describes the full- and reduced-order models of an actuated
hydraulic cylinder suitable for system dynamics analysis and motion control
design. The full-order model incorporates the valve spool dynamics with
combined dead-zone and saturation nonlinearities - inherent for the orifice
flow. It includes the continuity equations of hydraulic circuits coupled with
the dynamics of mechanical part of cylinder drive. The resulted model is the
fifth-order and nonlinear in states. The reduced model neglects the fast valve
spool dynamics, simplifies both the orifice and continuity equations through an
aggregation, and considers the cylinder rod velocity as output of interest. The
reduced model is second-order that facilitates studying the system behavior and
allows for direct phase plane analysis. Dynamics properties are addressed in
details, for both models, with focus on the frequency response, system damping,
and state trajectories related to the load pressure and relative velocity.Comment: 6 pages, 6 figures, IEEE conferenc
Circuit elements at optical frequencies: nano-inductors, nano-capacitors and nano-resistors
We present some ideas for synthesizing nanocircuit elements in the optical
domain using plasmonic and non-plasmonic nanoparticles. Three basic circuit
elements, i.e., nano-inductors, nano-capacitors, and nano-resistors, are
discussed in terms of small nanostructures with different material properties.
Coupled nanocircuits and parallel and series combinations are also envisioned,
which may provide road maps for the synthesis of more complex nanocircuits in
the IR and visible bands. Ideas for the optical implementation of right-handed
and left-handed nano-transmission lines are also forecasted.Comment: 14 pages, 5 figures, submitted to Physical Review Letter
Topological code Autotune
Many quantum systems are being investigated in the hope of building a
large-scale quantum computer. All of these systems suffer from decoherence,
resulting in errors during the execution of quantum gates. Quantum error
correction enables reliable quantum computation given unreliable hardware.
Unoptimized topological quantum error correction (TQEC), while still effective,
performs very suboptimally, especially at low error rates. Hand optimizing the
classical processing associated with a TQEC scheme for a specific system to
achieve better error tolerance can be extremely laborious. We describe a tool
Autotune capable of performing this optimization automatically, and give two
highly distinct examples of its use and extreme outperformance of unoptimized
TQEC. Autotune is designed to facilitate the precise study of real hardware
running TQEC with every quantum gate having a realistic, physics-based error
model.Comment: 13 pages, 17 figures, version accepted for publicatio
Simulation model of the logistic distribution in a medical oxygen supply chain
Research activities on operations management in the last years are always more dedicated to supply chain and logistics optimization models. The study belongs to this branch and describes the problems related to a re-configuration of the distribution net in a company that produces medical oxygen cylinders for Italian market. The enterprise is particularly sensible to the optimization of supplying processes due to the characteristics of its product, as any delay in the delivery could create dangerous health situation for patients. The work has the objective to realize a software for supply chain management that could be a decision support system, analyzing strategic impacts that changes in distribution system create. In details, the model shows the differences in service level in case of closing one or more factories and the relative necessary changes in logistics net. The paper is articulated in the following parts: • analysis of company and construction of simulation model; • study of classic operation research techniques to solve dynamic vehicle routing problems; • description of possible scenes derived by strategic decision in closing factories; analysis of experiments and global conclusions and developments
Pump for delivering heated fluids
A thermomechanical pump particularly suited for use in pumping a warming fluid obtained from an RTG (Radioisotope Thermal Generator) through science and flight instrumentation aboard operative spacecraft is described. The invention is characterized by a pair of operatively related cylinders, each including a reciprocating piston head dividing the cylinder into a pressure chamber confining therein a vaporizable fluid, and a pumping chamber for propelling the warming fluid, and a fluid delivery circuit for alternately delivering the warming fluid from the RTG through the pressure chamber of one cylinder to the pumping chamber of the other cylinder, whereby the vaporizable fluid within the pair of pressure chambers alternately is vaporized and condensed for driving the associated pistons in pumping and intake strokes
Effective Dielectric Constants of Photonic Crystal of Aligned Anisotropic Cylinders: Application to the Optical Response of Periodic Array of Carbon Nanotubes
We calculate the static dielectric tensor of a periodic system of aligned
anisotropic dielectric cylinders. Exact analytical formulas for the effective
dielectric constants for the E- and H- eigenmodes are obtained for arbitrary 2D
Bravais lattice and arbitrary cross-section of anisotropic cylinders. It is
shown that depending on the symmetry of the unit cell photonic crystal of
anisotropic cylinders behaves in the low-frequency limit like uniaxial or
biaxial natural crystal. The developed theory of homogenization of anisotropic
cylinders is applied for calculations of the dielectric properties of photonic
crystals of carbon nanotubes
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