25,724 research outputs found
The Meeting of Acquaintances: A Cost-efficient Authentication Scheme for Light-weight Objects with Transient Trust Level and Plurality Approach
Wireless sensor networks consist of a large number of distributed sensor
nodes so that potential risks are becoming more and more unpredictable. The new
entrants pose the potential risks when they move into the secure zone. To build
a door wall that provides safe and secured for the system, many recent research
works applied the initial authentication process. However, the majority of the
previous articles only focused on the Central Authority (CA) since this leads
to an increase in the computation cost and energy consumption for the specific
cases on the Internet of Things (IoT). Hence, in this article, we will lessen
the importance of these third parties through proposing an enhanced
authentication mechanism that includes key management and evaluation based on
the past interactions to assist the objects joining a secured area without any
nearby CA. We refer to a mobility dataset from CRAWDAD collected at the
University Politehnica of Bucharest and rebuild into a new random dataset
larger than the old one. The new one is an input for a simulated authenticating
algorithm to observe the communication cost and resource usage of devices. Our
proposal helps the authenticating flexible, being strict with unknown devices
into the secured zone. The threshold of maximum friends can modify based on the
optimization of the symmetric-key algorithm to diminish communication costs
(our experimental results compare to previous schemes less than 2000 bits) and
raise flexibility in resource-constrained environments.Comment: 27 page
Generation of a North/South Magnetic Field Component from Variations in the Photospheric Magnetic Field
We address the problem of calculating the transverse magnetic field in the
solar wind outside of the hypothetical sphere called the source surface where
the solar wind originates. This calculation must overcome a widely used
fundamental assumption about the source surface -- the field is normally
required to purely radial at the source surface. Our model rests on the fact
that a change in the radial field strength at the source surface is a change in
the field line density. Surrounding field lines must move laterally in order to
accommodate this field line density change. As the outward wind velocity drags
field lines past the source surface this lateral component of motion produces a
tilt implying there is a transverse component to the field.
An analytic method of calculating the lateral translation speed of the field
lines is developed. We apply the technique to an interval of approximately two
Carrington rotations at the beginning of 2011 using 2-h averages of data from
the Helioseismic Magnetic Imager instrument on the Solar Dynamics Observatory
spacecraft. We find that the value of the transverse magnetic field is
dominated on a global scale by the effects of high latitude concentrations of
field lines being buffetted by supergranular motions.Comment: 23 pages with 8 figures. Accepted by Solar Physics (LaTeX processing
with aastex6.cls instead of solarphysics.cls due to compatibility issues
A continuum-microscopic method based on IRBFs and control volume scheme for viscoelastic fluid flows
A numerical computation of continuum-microscopic model for visco-elastic flows based on the Integrated Radial Basis Function (IRBF) Control Volume and the Stochastic Simulation Techniques (SST) is reported in this paper. The macroscopic flow equations are closed by a stochastic equation for the extra stress at the microscopic level. The former are discretised by a 1D-IRBF-CV method while the latter is integrated with Euler explicit or Predictor-Corrector schemes. Modelling is very efficient as it is based on Cartesian grid, while the integrated RBF approach enhances both the stability of the procedure and the accuracy of the solution. The proposed method is demonstrated with the solution of the start-up Couette flow of the Hookean and FENE dumbbell model fluids
Parafoveal-foveal overlap can facilitate ongoing word identification during reading: evidence from eye movements.
Readers continuously receive parafoveal information about the upcoming word in addition to the foveal information about the currently fixated word. Previous research (Inhoff, Radach, Starr, & Greenberg, 2000) showed that the presence of a parafoveal word that was similar to the foveal word facilitated processing of the foveal word. We used the gaze-contingent boundary paradigm (Rayner, 1975) to manipulate the parafoveal information that subjects received before or while fixating a target word (e.g., news) within a sentence. Specifically, a reader's parafovea could contain a repetition of the target (news), a correct preview of the posttarget word (once), an unrelated word (warm), random letters (cxmr), a nonword neighbor of the target (niws), a semantically related word (tale), or a nonword neighbor of that word (tule). Target fixation times were significantly lower in the parafoveal repetition condition than in all other conditions, suggesting that foveal processing can be facilitated by parafoveal repetition. We present a simple model framework that can account for these effects
Solar Sources of Interplanetary Magnetic Clouds Leading to Helicity Prediction
This study identifies the solar origins of magnetic clouds that are observed
at 1 AU and predicts the helical handedness of these clouds from the solar
surface magnetic fields. We started with the magnetic clouds listed by the
Magnetic Field Investigation (MFI) team supporting NASA's WIND spacecraft in
what is known as the MFI table and worked backwards in time to identify solar
events that produced these clouds. Our methods utilize magnetograms from the
Helioseismic and Magnetic Imager (HMI) instrument on the Solar Dynamics
Observatory (SDO) spacecraft so that we could only analyze MFI entries after
the beginning of 2011. This start date and the end date of the MFI table gave
us 37 cases to study. Of these we were able to associate only eight surface
events with clouds detected by WIND at 1 AU. We developed a simple algorithm
for predicting the cloud helicity which gave the correct handedness in all
eight cases. The algorithm is based on the conceptual model that an ejected
flux tube has two magnetic origination points at the positions of the strongest
radial magnetic field regions of opposite polarity near the places where the
ejected arches end at the solar surface. We were unable to find events for the
remaining 29 cases: lack of a halo or partial halo CME in an appropriate time
window, lack of magnetic and/or filament activity in the proper part of the
solar disk, or the event was too far from disk center. The occurrence of a
flare was not a requirement for making the identification but in fact flares,
often weak, did occur for seven of the eight cases.Comment: 18 pages, 8 figures, 2 table
The F@ Framework of Designing Awareness Mechanisms in Instant Messaging
This paper presents our research on awareness support in Instant Messaging (IM). The paper starts with a brief overview of empirical study of IM, using an online survey and face-to-face interviews to identify user needs for awareness support. The study identified a need for supporting four aspects of awareness, awareness of multiple concurrent conversations, conversational awareness, presence awareness of a group conversation, and visibility of moment-to-moment listeners and viewers. Based on the empirical study and existing research on awareness, we have developed the F@ (read as fat) framework of awareness. F@ comprises of the abstract level and the concrete level. The former includes an in-depth description of various awareness aspects in IM, whilst the latter utilises temporal logic to formalise fundamental time-related awareness aspects. F@ helps developers gain a better understanding of awareness and thereby design usable mechanisms to support awareness. Applying F@, we have designed several mechanisms to support various aspect of awareness in IM
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