799 research outputs found
Desirability to characterize process capability
Over the past few years continuously new process capability indices have been developed, most of them with the aim to add some feature missed in former process capability indices. Thus, for nearly any thinkable situation now a special index exists which makes choosing a certain index as difficult as interpreting and comparing index values correctly. In this paper we propose the use of the expected value of a certain type of function, the so-called desirability function, to assess the capability of a process. The resulting index may be used analogously to the classical indices related to Cp, but can be adapted to nearly any process and any specification. It even allows a comparison between different processes regardless of their distribution and may be extended straightforwardly to multivariate scenarios. Furthermore, its properties compare favorably to the properties of the ?classical? indices. --
Parametric down-conversion in photonic crystal waveguides
Photonic crystals create dramatic new possibilities for nonlinear optics.
Line defects are shown to support modes suitable for the production of pairs of
photons by the material's second order nonlinearity even if the phase-matching
conditions cannot be satisfied in the bulk. These structures offer the
flexibility to achieve specific dispersion characteristics and potentially very
high brightness. In this work, two phase matching schemes are identified and
analyzed regarding their dispersive properties.Comment: Due to a miscommunication the unrevised version of this paper was
published instead of this one. v2 has quite some modifications and
corrections. 7 pages, 4 figure
Boxfishes (Teleostei: Ostraciidae) as a model system for fishes swimming with many fins: kinematics
Swimming movements in boxfishes were much more
complex and varied than classical descriptions indicated.
At low to moderate rectilinear swimming speeds
(<5 TL s^(-1), where TL is total body length), they were
entirely median- and paired-fin swimmers, apparently
using their caudal fins for steering. The pectoral and
median paired fins generate both the thrust needed for
forward motion and the continuously varied, interacting
forces required for the maintenance of rectilinearity. It
was only at higher swimming speeds (above 5 TL s^(-1)), when
burst-and-coast swimming was used, that they became
primarily body and caudal-fin swimmers. Despite their
unwieldy appearance and often asynchronous fin beats,
boxfish swam in a stable manner. Swimming boxfish used
three gaits. Fin-beat asymmetry and a relatively nonlinear
swimming trajectory characterized the first gait
(0–1 TL s^(-1)). The beginning of the second gait (1–3 TL s^(-1))
was characterized by varying fin-beat frequencies and
amplitudes as well as synchrony in pectoral fin motions.
The remainder of the second gait (3–5 TL s^(-1)) was
characterized by constant fin-beat amplitudes, varying finbeat
frequencies and increasing pectoral fin-beat
asynchrony. The third gait (>5 TL s^(-1)) was characterized
by the use of a caudal burst-and-coast variant. Adduction
was always faster than abduction in the pectoral fins.
There were no measurable refractory periods between
successive phases of the fin movement cycles. Dorsal and
anal fin movements were synchronized at speeds greater
than 2.5 TL s^(-1), but were often out of phase with pectoral
fin movements
A Fast and Compact Quantum Random Number Generator
We present the realization of a physical quantum random number generator
based on the process of splitting a beam of photons on a beam splitter, a
quantum mechanical source of true randomness. By utilizing either a beam
splitter or a polarizing beam splitter, single photon detectors and high speed
electronics the presented devices are capable of generating a binary random
signal with an autocorrelation time of 11.8 ns and a continuous stream of
random numbers at a rate of 1 Mbit/s. The randomness of the generated signals
and numbers is shown by running a series of tests upon data samples. The
devices described in this paper are built into compact housings and are simple
to operate.Comment: 23 pages, 6 Figs. To appear in Rev. Sci. Inst
Modally Resolved Fabry-Perot Experiment with Semiconductor Waveguides
Based on the interaction between different spatial modes, semiconductor
Bragg-reflection waveguides provide a highly functional platform for non-linear
optics. Therefore, the control and engineering of the properties of each
spatial mode is essential. Despite the multimodeness of our waveguide, the
well-established Fabry-Perot technique for recording fringes in the optical
transmission spectrum can successfully be employed for a detailed linear
optical characterization when combined with Fourier analysis. A prerequisite
for the modal sensitivity is a finely resolved transmission spectrum that is
recorded over a broad frequency band. Our results highlight how the features of
different spatial modes, such as their loss characteristics and dispersion
properties, can be separated from each other allowing their comparison. The
mode-resolved measurements are important for optimizing the performance of such
multimode waveguides by tailoring the properties of their spatial modes.Comment: 8 pages, 7 figure
Polarization entangled photons from quantum dots embedded in nanowires
We present a first measurement of photon polarization entanglement from the
biexciton to ground state cascade of a single InAsP quantum dot embedded in an
InP nanowire. We observe a fidelity of 0.76(2) to a reference maximally
entangled state as well as a concurrence of 0.57(6)
Superpositions of the Orbital Angular Momentum for Applications in Quantum Experiments
Two different experimental techniques for preparation and analyzing
superpositions of the Gaussian and Laguerre-Gassian modes are presented. This
is done exploiting an interferometric method on the one hand and using computer
generated holograms on the other hand. It is shown that by shifting the
hologram with respect to an incoming Gaussian beam different superpositions of
the Gaussian and the Laguerre-Gaussian beam can be produced. An analytical
expression between the relative phase and the amplitudes of the modes and the
displacement of the hologram is given. The application of such orbital angular
momenta superpositions in quantum experiments such as quantum cryptography is
discussed.Comment: 18 pages, 4 figures. to appear in Journal of Optics
Jet propulsion without inertia
A body immersed in a highly viscous fluid can locomote by drawing in and
expelling fluid through pores at its surface. We consider this mechanism of jet
propulsion without inertia in the case of spheroidal bodies, and derive both
the swimming velocity and the hydrodynamic efficiency. Elementary examples are
presented, and exact axisymmetric solutions for spherical, prolate spheroidal,
and oblate spheroidal body shapes are provided. In each case, entirely and
partially porous (i.e. jetting) surfaces are considered, and the optimal
jetting flow profiles at the surface for maximizing the hydrodynamic efficiency
are determined computationally. The maximal efficiency which may be achieved by
a sphere using such jet propulsion is 12.5%, a significant improvement upon
traditional flagella-based means of locomotion at zero Reynolds number. Unlike
other swimming mechanisms which rely on the presentation of a small cross
section in the direction of motion, the efficiency of a jetting body at low
Reynolds number increases as the body becomes more oblate, and limits to
approximately 162% in the case of a flat plate swimming along its axis of
symmetry. Our results are discussed in the light of slime extrusion mechanisms
occurring in many cyanobacteria
Solving the Einstein-Podolsky-Rosen puzzle: the origin of non-locality in Aspect-type experiments
So far no mechanism is known, which could connect the two measurements in an
Aspect-type experiment. Here, we suggest such a mechanism, based on the phase
of a photon's field during propagation. We show that two polarization
measurements are correlated, even if no signal passes from one point of
measurement to the other. The non-local connection of a photon pair is the
result of its origin at a common source, where the two fields acquire a well
defined phase difference. Therefore, it is not actually a non-local effect in
any conventional sense. We expect that the model and the detailed analysis it
allows will have a major impact on quantum cryptography and quantum
computation.Comment: 5 pages 1 figure. Added an analysis of quantum steering. The result
is that under certain conditions the experimental result at B can be
predicted if the polarization angle and the result at A are known. The paper
has been accepted for publication in Frontiers of Physics. arXiv admin note:
substantial text overlap with arXiv:1108.435
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