258,229 research outputs found
A finite-strain hyperviscoplastic model and undrained triaxial tests of peat
This paper presents a finite-strain hyperviscoplastic constitutive model
within a thermodynamically consistent framework for peat which was categorised
as a material with both rate-dependent and thermodynamic equilibrium hysteresis
based on the data reported in the literature. The model was implemented
numerically using implicit time integration and verified against analytical
solutions under simplified conditions. Experimental studies on the undrained
relaxation and loading-unloading-reloading behaviour of an undisturbed fibrous
peat were carried out to define the thermodynamic equilibrium state during
deviatoric loading as a prerequisite for further modelling, to fit particularly
those model parameters related to solid matrix properties, and to validate the
proposed model under undrained conditions. This validation performed by
comparison to experimental results showed that the hyperviscoplastic model
could simulate undrained triaxial compression tests carried out at five
different strain rates with loading/unloading relaxation steps.Comment: 30 pages, 16 figures, 4 tables. This is a pre-peer reviewed version
of manuscript submitted to the International Journal of Numerical and
Analytical Methods in Geomechanic
Deterministic entanglement of two neutral atoms via Rydberg blockade
We demonstrate the first deterministic entanglement of two individually
addressed neutral atoms using a Rydberg blockade mediated controlled-NOT gate.
Parity oscillation measurements reveal an entanglement fidelity of
, which is above the entanglement threshold of , without
any correction for atom loss, and after correcting for
background collisional losses. The fidelity results are shown to be in good
agreement with a detailed error model.Comment: 4 figure
Control of beam propagation in optically written waveguides beyond the paraxial approximation
Beam propagation beyond the paraxial approximation is studied in an optically
written waveguide structure. The waveguide structure that leads to
diffractionless light propagation, is imprinted on a medium consisting of a
five-level atomic vapor driven by an incoherent pump and two coherent spatially
dependent control and plane-wave fields. We first study propagation in a single
optically written waveguide, and find that the paraxial approximation does not
provide an accurate description of the probe propagation. We then employ
coherent control fields such that two parallel and one tilted Gaussian beams
produce a branched waveguide structure. The tilted beam allows selective
steering of the probe beam into different branches of the waveguide structure.
The transmission of the probe beam for a particular branch can be improved by
changing the width of the titled Gaussian control beam as well as the intensity
of the spatially dependent incoherent pump field.Comment: 10 pages, 9 figure
A unary error correction code for the near-capacity joint source and channel coding of symbol values from an infinite set
A novel Joint Source and Channel Code (JSCC) is proposed, which we refer to as the Unary Error Correction (UEC) code. Unlike existing JSCCs, our UEC facilitates the practical encoding of symbol values that are selected from a set having an infinite cardinality. Conventionally, these symbols are conveyed using Separate Source and Channel Codes (SSCCs), but we demonstrate that the residual redundancy that is retained following source coding results in a capacity loss, which is found to have a value of 1.11 dB in a particular practical scenario. By contrast, the proposed UEC code can eliminate this capacity loss, or reduce it to an infinitesimally small value. Furthermore, the UEC code has only a moderate complexity, facilitating its employment in practical low-complexity applications
Profiling user activities with minimal traffic traces
Understanding user behavior is essential to personalize and enrich a user's
online experience. While there are significant benefits to be accrued from the
pursuit of personalized services based on a fine-grained behavioral analysis,
care must be taken to address user privacy concerns. In this paper, we consider
the use of web traces with truncated URLs - each URL is trimmed to only contain
the web domain - for this purpose. While such truncation removes the
fine-grained sensitive information, it also strips the data of many features
that are crucial to the profiling of user activity. We show how to overcome the
severe handicap of lack of crucial features for the purpose of filtering out
the URLs representing a user activity from the noisy network traffic trace
(including advertisement, spam, analytics, webscripts) with high accuracy. This
activity profiling with truncated URLs enables the network operators to provide
personalized services while mitigating privacy concerns by storing and sharing
only truncated traffic traces.
In order to offset the accuracy loss due to truncation, our statistical
methodology leverages specialized features extracted from a group of
consecutive URLs that represent a micro user action like web click, chat reply,
etc., which we call bursts. These bursts, in turn, are detected by a novel
algorithm which is based on our observed characteristics of the inter-arrival
time of HTTP records. We present an extensive experimental evaluation on a real
dataset of mobile web traces, consisting of more than 130 million records,
representing the browsing activities of 10,000 users over a period of 30 days.
Our results show that the proposed methodology achieves around 90% accuracy in
segregating URLs representing user activities from non-representative URLs
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