8,283 research outputs found
An Email Attachment is Worth a Thousand Words, or Is It?
There is an extensive body of research on Social Network Analysis (SNA) based
on the email archive. The network used in the analysis is generally extracted
either by capturing the email communication in From, To, Cc and Bcc email
header fields or by the entities contained in the email message. In the latter
case, the entities could be, for instance, the bag of words, url's, names,
phones, etc. It could also include the textual content of attachments, for
instance Microsoft Word documents, excel spreadsheets, or Adobe pdfs. The nodes
in this network represent users and entities. The edges represent communication
between users and relations to the entities. We suggest taking a different
approach to the network extraction and use attachments shared between users as
the edges. The motivation for this is two-fold. First, attachments represent
the "intimacy" manifestation of the relation's strength. Second, the
statistical analysis of private email archives that we collected and Enron
email corpus shows that the attachments contribute in average around 80-90% to
the archive's disk-space usage, which means that most of the data is presently
ignored in the SNA of email archives. Consequently, we hypothesize that this
approach might provide more insight into the social structure of the email
archive. We extract the communication and shared attachments networks from
Enron email corpus. We further analyze degree, betweenness, closeness, and
eigenvector centrality measures in both networks and review the differences and
what can be learned from them. We use nearest neighbor algorithm to generate
similarity groups for five Enron employees. The groups are consistent with
Enron's organizational chart, which validates our approach.Comment: 12 pages, 4 figures, 7 tables, IML'17, Liverpool, U
Degradation and reuse of radiative thermal protection system materials for the space shuttle
Three silicide coated columbium alloys and two cobalt alloys were subjected to identical simulated reentry profiling exposures in both static (controlled vacuum leak) and dynamic (hypersonic plasma shear) environments. Primary emphasis in the columbium alloy evaluation was on the Cb752 and C129Y alloys with a lesser amount on FS85. Commercial silicide coatings of the R512E and VH109 formulations were used. The coated specimens were intentionally defected to provide the types of coating flaws that are expected in service. Temperatures were profiled up to peak temperatures of either 2350 F or 2500 F for 15 minutes in each cycle
The WAY theorem and the quantum resource theory of asymmetry
The WAY theorem establishes an important constraint that conservation laws
impose on quantum mechanical measurements. We formulate the WAY theorem in the
broader context of resource theories, where one is constrained to a subset of
quantum mechanical operations described by a symmetry group. Establishing
connections with the theory of quantum state discrimination we obtain optimal
unitaries describing the measurement of arbitrary observables, explain how
prior information can permit perfect measurements that circumvent the WAY
constraint, and provide a framework that establishes a natural ordering on
measurement apparatuses through a decomposition into asymmetry and charge
subsystems.Comment: 11 pages, 3 figure
Methane flux from the Central Amazonian Floodplain
A total of 186 methane measurements from the three primary Amazon floodplain environments of open water lakes, flood forests, and floating grass mats were made over the period 18 July through 2 September 1985. These data indicate that emissions were lowest over open water lakes. Flux from flooded forests and grass mats was significantly higher. At least three transport processes contribute to tropospheric emissions: ebullition from sediments, diffusion along the concentration gradient from sediment to overlaying water to air, and transport through the roots and stems of aquatic plants. Measurements indicate that the first two of these processes are most significant. It was estimated that on the average bubbling makes up 49% of the flux from open water, 54% of that from flooded forests, and 64% of that from floating mats. If the measurements were applied to the entire Amazonian floodplain, it is calculated that the region could supply up to 12% of the estimated global natural sources of methane
A Review of Factors Affecting the Burning Behaviour of Wood for Application to Tall Timber Construction
Self-Consistent Measurement and State Tomography of an Exchange-Only Spin Qubit
We report initialization, complete electrical control, and single-shot
readout of an exchange-only spin qubit. Full control via the exchange
interaction is fast, yielding a demonstrated 75 qubit rotations in under 2 ns.
Measurement and state tomography are performed using a maximum-likelihood
estimator method, allowing decoherence, leakage out of the qubit state space,
and measurement fidelity to be quantified. The methods developed here are
generally applicable to systems with state leakage, noisy measurements, and
non-orthogonal control axes.Comment: contains Supplementary Informatio
Dynamical Arrest in Attractive Colloids: The Effect of Long-Range Repulsion
We study gelation in suspensions of model colloidal particles with
short-ranged attractive and long-ranged repulsive interactions by means of
three-dimensional fluorescence confocal microscopy. At low packing fractions,
particles form stable equilibrium clusters. Upon increasing the packing
fraction the clusters grow in size and become increasingly anisotropic until
finally associating into a fully connected network at gelation. We find a
surprising order in the gel structure. Analysis of spatial and orientational
correlations reveals that the gel is composed of dense chains of particles
constructed from face-sharing tetrahedral clusters. Our findings imply that
dynamical arrest occurs via cluster growth and association.Comment: Final version: Phys. Rev. Lett. 94, 208301 (2005
Universal continuous-variable quantum computation: Requirement of optical nonlinearity for photon counting
Although universal continuous-variable quantum computation cannot be achieved
via linear optics (including squeezing), homodyne detection and feed-forward,
inclusion of ideal photon counting measurements overcomes this obstacle. These
measurements are sometimes described by arrays of beam splitters to distribute
the photons across several modes. We show that such a scheme cannot be used to
implement ideal photon counting and that such measurements necessarily involve
nonlinear evolution. However, this requirement of nonlinearity can be moved
"off-line," thereby permitting universal continuous-variable quantum
computation with linear optics.Comment: 6 pages, no figures, replaced with published versio
Quantum gates on hybrid qudits
We introduce quantum hybrid gates that act on qudits of different dimensions.
In particular, we develop two representative two-qudit hybrid gates (SUM and
SWAP) and many-qudit hybrid Toffoli and Fredkin gates. We apply the hybrid SUM
gate to generating entanglement, and find that operator entanglement of the SUM
gate is equal to the entanglement generated by it for certain initial states.
We also show that the hybrid SUM gate acts as an automorphism on the Pauli
group for two qudits of different dimension under certain conditions. Finally,
we describe a physical realization of these hybrid gates for spin systems.Comment: 8 pages and 1 figur
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