3,636 research outputs found
The FIR-absorption of short period quantum wires and the transition from one to two dimensions
We investigate the FIR-absorption of short period parallel quantum wires in a
perpendicular quantizing magnetic field. The external time-dependent electric
field is linearly polarized along the wire modulation. The mutual Coulomb
interaction of the electrons is treated self-consistently in the ground state
and in the absorption calculation within the Hartree approximation. We consider
the effects of a metal gate grating coupler, with the same or with a different
period as the wire modulation, on the absorption. The evolution of the
magnetoplasmon in the nonlocal region where it is split into several Bernstein
modes is discussed in the transition from: narrow to broad wires, and isolated
to overlapping wires. We show that in the case of narrow and not strongly
modulated wires the absorption can be directly correlated with the underlying
electronic bandstructure.Comment: 15 pages, 9 figures, Revtex, to appear in Phys. Rev.
Visualization of electrical machines
Π Π΄ΠΎΠΊΠ»Π°Π΄Π΅ "ΠΠΈΠ·ΡΠ°Π»ΠΈΠ·Π°ΡΠΈΡ ΠΏΡΠΎΡΠ΅ΡΡΠΎΠ² Π² ΡΠ»Π΅ΠΊΡΡΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΌΠ°ΡΠΈΠ½Π°Ρ
" ΡΠ°ΡΡΠΌΠΎΡΡΠ΅Π½Ρ Π²ΠΎΠΏΡΠΎΡΡ Π²ΠΈΠ·ΡΠ°Π»ΠΈΠ·Π°ΡΠΈΠΈ ΡΠ»Π΅ΠΊΡΡΠΎΠΌΠ°Π³Π½ΠΈΡΠ½ΡΡ
ΠΏΡΠΎΡΠ΅ΡΡΠΎΠ² Π² ΡΠ»Π΅ΠΊΡΡΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΌΠ°ΡΠΈΠ½Π°Ρ
Ρ ΠΏΠΎΠΌΠΎΡΡΡ ΠΊΠΎΠΌΠΏΡΡΡΠ΅ΡΠ½ΠΎΠΉ Π°Π½ΠΈΠΌΠ°ΡΠΈΠΈ Π½Π° ΠΎΡΠ½ΠΎΠ²Π΅ ΠΏΠ°ΠΊΠ΅ΡΠ° 3D STUDIO ΠΠΠ₯. Π Π°Π±ΠΎΡΠ° Π²ΡΠΏΠΎΠ»Π½Π΅Π½Π° Π£ΡΠ°Π»ΡΡΠΊΠΈΠΌ Π³ΠΎΡΡΠ΄Π°ΡΡΡΠ²Π΅Π½Π½ΡΠΌ ΡΠ΅Ρ
Π½ΠΈΡΠ΅ΡΠΊΠΈΠΌ ΡΠ½ΠΈΠ²Π΅ΡΡΠΈΡΠ΅ΡΠΎΠΌ (Π ΠΎΡΡΠΈΡ) ΡΠΎΠ²ΠΌΠ΅ΡΡΠ½ΠΎ Ρ ΠΠ΅Π½ΡΡΠΊΠΈΠΌ ΡΠ½ΠΈΠ²Π΅ΡΡΠΈΡΠ΅ΡΠΎΠΌ (ΠΠ΅Π»ΡΠ³ΠΈΡ) Π² ΡΠ°ΠΌΠΊΠ°Ρ
ΠΏΡΠΎΠ΅ΠΊΡΠ° URALELECTR
Pulse Propagation in Resonant Tunneling
We consider the analytically solvable model of a Gaussian pulse tunneling
through a transmission resonance with a Breit-Wigner characteristic. The
solution allows for the identification of two opposite pulse propagation
regimes: if the resonance is broad compared to the energetic width of the
incident Gaussian pulse a weakly deformed and slightly delayed transmitted
Gaussian pulse is found. In the opposite limit of a narrow resonance the dying
out of the transmitted pulse is dominated by the slow exponential decay
characteristic of a quasi-bound state with a long life time (decaying state).
We discuss the limitation of the achievable pulse transfer rate resulting from
the slow decay. Finally, it is demonstrated that for narrow resonances a small
second component is superimposed to the exponential decay which leads to
characteristic interference oscillations.Comment: 6 pages, 4 figure
Digital terrain modelling using triangulated irregular networks (poster)
Many marine scientists and users of the sea consider knowledge of the sea bottom as basic data, a mere context to carry out research or deploy activities. Some disciplines do need more accurate bathymetric data than others, depending on depth values being background information or crucial information for their research or activities. In bathymetry, the representation of the sea bottom surface is the main objective and hence, this discipline will try to render the sea bottom relief as accurate as possible. The latest bathymetric sounding equipment that is available nowadays, especially the multibeam echosounder, yield a very dense bottom sampling. When compared to the common singlebeam echosounder, an enormous amount of data is produced that needs to be processed in a correct and fast way. Grid-overlay (by local linear or more sophisticated interpolation and attributing values to individual grid cells) is not an option here as this method uses an interpolation of the measured values and hence will either cause accuracy loss or generate a still larger amount of data. A triangular irregular network (TIN for short), especially the Delaunay triangulation (Dt), does respect the actual measurements and will not generate new data. In literature, a number of algorithms have been developed that determine the Dt of a set of points (vertices) given in the plane.A performant divide-and-conquer algorithm for Delaunay triangulations was implemented to triangulate large quantities of data in minimum time. Comparison with other implemented algorithms demonstrates its excellent performance.In some cases, it will be necessary to adapt the terrain model. Theoretical terrain models (for instance design models for marine contractors) require manual interventions, while new surveys partially overlapping old data will have to replace the latter. Therefore, the incremental algorithm has been adapted to allow insertion of individual points. When eliminating individual vertices, the hole thus created has to be retriangulated. Vertices belonging to a triangulation that is (partially) covered by a new surveyed area can be eliminated and using a very keen adaptation of the divide-and-conquer principle, the overlapping triangulations can be stitched together. This is a novel technique with the big advantage of quickly and seamlessly joining two large triangulations, without the need for retriangulation of the entire area.Part of the immense amount of data generated by a multibeam echosounder will unavoidably be redundant. An important issue therefore will be: filtering these data, keeping those points that still assure an optimal accuracy. This accuracy can be expressed as a function of the topography or as a function of the volume. For the latter, not the height difference determines whether or not a vertex is allowed in the triangulation, the criterion is rather the change in volume caused by this one vertex. For marine contractors, it is mainly the latter that is important. A hybrid model would be most adequate
The amplifier effect: how Pin1 empowers mutant p53
Mutation of p53 occurs in 15 to 20% of all breast cancers, and with higher frequency in estrogen-receptor negative and high-grade tumors. Certain p53 mutations contribute to malignant transformation not only through loss of wild-type p53 but also through a gain of function of specific p53 mutations. How these hotspot mutations turn p53 from a tumor suppressor into an oncogene had until now remained incompletely understood. In an elegant paper published in the July 12 issue of Cancer Cell, Girardini and colleagues show how Pin1-mediated prolylisomerization, a regulatory mechanism intended by evolution to support p53's function as a guardian of the genome, can go haywire and accelerate malignant transformation when p53 carries a dominant-negative mutation
Qualitative Analysis of Partially-observable Markov Decision Processes
We study observation-based strategies for partially-observable Markov
decision processes (POMDPs) with omega-regular objectives. An observation-based
strategy relies on partial information about the history of a play, namely, on
the past sequence of observations. We consider the qualitative analysis
problem: given a POMDP with an omega-regular objective, whether there is an
observation-based strategy to achieve the objective with probability~1
(almost-sure winning), or with positive probability (positive winning). Our
main results are twofold. First, we present a complete picture of the
computational complexity of the qualitative analysis of POMDP s with parity
objectives (a canonical form to express omega-regular objectives) and its
subclasses. Our contribution consists in establishing several upper and lower
bounds that were not known in literature. Second, we present optimal bounds
(matching upper and lower bounds) on the memory required by pure and randomized
observation-based strategies for the qualitative analysis of POMDP s with
parity objectives and its subclasses
Exploring collaboration in challenging environments: from the car to the factory and beyond
We propose a daylong workshop at CSCW2012 on the topic collaboration in challenging and dicult environments, which are to our understanding all contexts, which go beyond traditional working/oce settings topic. Examples for these environments can be the automotive context or the context of a semiconductor factory, which show very specic contextual conditions and therefore oer special research challenges: How to address all passengers in the car, not only the driver? How to explore operator tasks in a cleanroom? How could the long-term (social) collaboration of robots and humans be investigated in privacy critical environments
Qualification Tests of the R11410-21 Photomultiplier Tubes for the XENON1T Detector
The Hamamatsu R11410-21 photomultiplier tube is the photodetector of choice
for the XENON1T dual-phase time projection chamber. The device has been
optimized for a very low intrinsic radioactivity, a high quantum efficiency and
a high sensitivity to single photon detection. A total of 248 tubes are
currently operated in XENON1T, selected out of 321 tested units. In this
article the procedures implemented to evaluate the large number of tubes prior
to their installation in XENON1T are described. The parameter distributions for
all tested tubes are shown, with an emphasis on those selected for XENON1T, of
which the impact on the detector performance is discussed. All photomultipliers
have been tested in a nitrogen atmosphere at cryogenic temperatures, with a
subset of the tubes being tested in gaseous and liquid xenon, simulating their
operating conditions in the dark matter detector. The performance and
evaluation of the tubes in the different environments is reported and the
criteria for rejection of PMTs are outlined and quantified.Comment: 24 pages, 16 figure
From LTL and Limit-Deterministic B\"uchi Automata to Deterministic Parity Automata
Controller synthesis for general linear temporal logic (LTL) objectives is a
challenging task. The standard approach involves translating the LTL objective
into a deterministic parity automaton (DPA) by means of the Safra-Piterman
construction. One of the challenges is the size of the DPA, which often grows
very fast in practice, and can reach double exponential size in the length of
the LTL formula. In this paper we describe a single exponential translation
from limit-deterministic B\"uchi automata (LDBA) to DPA, and show that it can
be concatenated with a recent efficient translation from LTL to LDBA to yield a
double exponential, \enquote{Safraless} LTL-to-DPA construction. We also report
on an implementation, a comparison with the SPOT library, and performance on
several sets of formulas, including instances from the 2016 SyntComp
competition
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