46,563 research outputs found
De-ossifying the Internet Transport Layer : A Survey and Future Perspectives
ACKNOWLEDGMENT The authors would like to thank the anonymous reviewers for their useful suggestions and comments.Peer reviewedPublisher PD
Evolution of Swarm Robotics Systems with Novelty Search
Novelty search is a recent artificial evolution technique that challenges
traditional evolutionary approaches. In novelty search, solutions are rewarded
based on their novelty, rather than their quality with respect to a predefined
objective. The lack of a predefined objective precludes premature convergence
caused by a deceptive fitness function. In this paper, we apply novelty search
combined with NEAT to the evolution of neural controllers for homogeneous
swarms of robots. Our empirical study is conducted in simulation, and we use a
common swarm robotics task - aggregation, and a more challenging task - sharing
of an energy recharging station. Our results show that novelty search is
unaffected by deception, is notably effective in bootstrapping the evolution,
can find solutions with lower complexity than fitness-based evolution, and can
find a broad diversity of solutions for the same task. Even in non-deceptive
setups, novelty search achieves solution qualities similar to those obtained in
traditional fitness-based evolution. Our study also encompasses variants of
novelty search that work in concert with fitness-based evolution to combine the
exploratory character of novelty search with the exploitatory character of
objective-based evolution. We show that these variants can further improve the
performance of novelty search. Overall, our study shows that novelty search is
a promising alternative for the evolution of controllers for robotic swarms.Comment: To appear in Swarm Intelligence (2013), ANTS Special Issue. The final
publication will be available at link.springer.co
Paging and Registration in Cellular Networks: Jointly Optimal Policies and an Iterative Algorithm
This paper explores optimization of paging and registration policies in
cellular networks. Motion is modeled as a discrete-time Markov process, and
minimization of the discounted, infinite-horizon average cost is addressed. The
structure of jointly optimal paging and registration policies is investigated
through the use of dynamic programming for partially observed Markov processes.
It is shown that there exist policies with a certain simple form that are
jointly optimal, though the dynamic programming approach does not directly
provide an efficient method to find the policies.
An iterative algorithm for policies with the simple form is proposed and
investigated. The algorithm alternates between paging policy optimization and
registration policy optimization. It finds a pair of individually optimal
policies, but an example is given showing that the policies need not be jointly
optimal. Majorization theory and Riesz's rearrangement inequality are used to
show that jointly optimal paging and registration policies are given for
symmetric or Gaussian random walk models by the nearest-location-first paging
policy and distance threshold registration policies.Comment: 13 pages, submitted to IEEE Trans. Information Theor
NASA Center for Intelligent Robotic Systems for Space Exploration
NASA's program for the civilian exploration of space is a challenge to scientists and engineers to help maintain and further develop the United States' position of leadership in a focused sphere of space activity. Such an ambitious plan requires the contribution and further development of many scientific and technological fields. One research area essential for the success of these space exploration programs is Intelligent Robotic Systems. These systems represent a class of autonomous and semi-autonomous machines that can perform human-like functions with or without human interaction. They are fundamental for activities too hazardous for humans or too distant or complex for remote telemanipulation. To meet this challenge, Rensselaer Polytechnic Institute (RPI) has established an Engineering Research Center for Intelligent Robotic Systems for Space Exploration (CIRSSE). The Center was created with a five year $5.5 million grant from NASA submitted by a team of the Robotics and Automation Laboratories. The Robotics and Automation Laboratories of RPI are the result of the merger of the Robotics and Automation Laboratory of the Department of Electrical, Computer, and Systems Engineering (ECSE) and the Research Laboratory for Kinematics and Robotic Mechanisms of the Department of Mechanical Engineering, Aeronautical Engineering, and Mechanics (ME,AE,&M), in 1987. This report is an examination of the activities that are centered at CIRSSE
A Framework for M-Commerce Implementation in Nigeria
The Internet has brought about the concept of grobalilation, which has
revolutionized the way business is transacted all over the world. The E-comnterce
is of particular interest, though widely used but still has some security challenges
in terms of transparency and confidentiality of transactiorts. This papei focuses
on M-contnrcrce as an extensiott to E-commerce hnplementatiott with the Bankiltg
industry proposed as core implementation consideration in ortler to guarantee
high level security. We have reviewed some cqses of onlilrc frauds and eliscussed
tlte emerging critical issues afficting software development of M-cornmerce
applicatiotts. Afranrcworkfor M-commerce implementationis therefore,proposed
for countries such as Nigeria, Romania and Indonesia where cases of online
scam are alanning
Coherent energy migration in solids: Determination of the average coherence length in one‐dimensional systems using tunable dye lasers
The coherent nature of energy propagation in solids at low temperatures was established from the time resolved response of the crystal to short optical pulses obtained from a dye laser (pumped by a nitrogen gas laser). The trapping and detrapping of the energy by shallow defects (x traps) was evident in the spectra and enabled us to extract the coherence length: l≳700 Å=186 molecules for the one‐dimensional triplet excitons of 1,2,4,5‐tetrachlorobenzene crystals at T<4.2° K. This length which clearly exceeds the stochastic random walk limit is related to the thermalization mechanisms in this coupled exciton–trap system, and its magnitude supports the notion that exciton–phonon coupling is responsible for the loss of coherence on very long molecular chains (trap concentration is 1/256 000)
Distributed SIR-Aware Opportunistic Access Control for D2D Underlaid Cellular Networks
In this paper, we propose a distributed interference and channel-aware
opportunistic access control technique for D2D underlaid cellular networks, in
which each potential D2D link is active whenever its estimated
signal-to-interference ratio (SIR) is above a predetermined threshold so as to
maximize the D2D area spectral efficiency. The objective of our SIR-aware
opportunistic access scheme is to provide sufficient coverage probability and
to increase the aggregate rate of D2D links by harnessing interference caused
by dense underlaid D2D users using an adaptive decision activation threshold.
We determine the optimum D2D activation probability and threshold, building on
analytical expressions for the coverage probabilities and area spectral
efficiency of D2D links derived using stochastic geometry. Specifically, we
provide two expressions for the optimal SIR threshold, which can be applied in
a decentralized way on each D2D link, so as to maximize the D2D area spectral
efficiency derived using the unconditional and conditional D2D success
probability respectively. Simulation results in different network settings show
the performance gains of both SIR-aware threshold scheduling methods in terms
of D2D link coverage probability, area spectral efficiency, and average sum
rate compared to existing channel-aware access schemes.Comment: 6 pages, 6 figures, to be presented at IEEE GLOBECOM 201
A systematic review of digital interventions for improving the diet and physical activity behaviors of adolescents
Many adolescents have poor diet and physical activity behaviors, which can lead to the development of noncommunicable diseases in later life. Digital platforms offer inexpensive means of delivering health interventions, but little is known about their effectiveness. This systematic review was conducted to synthesize evidence on the effectiveness of digital interventions to improve diet quality and increase physical activity in adolescents, to effective intervention components and to assess the cost-effectiveness of these interventions. Following a systematic search, abstracts were assessed against inclusion criteria, and data extraction and quality assessment were performed for included studies. Data were analyzed to identify key features that are associated with significant improvement in behavior. A total of 27 studies met inclusion criteria. Most (n = 15) were Web site interventions. Other delivery methods were text messages, games, multicomponent interventions, emails, and social media. Significant behavior change was often seen when interventions included education, goal setting, self-monitoring, and parental involvement. None of the publications reported cost-effectiveness. Due to heterogeneity of studies, meta-analysis was not feasible.It is possible to effect significant health behavior change in adolescents through digital interventions that incorporate education, goal setting, self-monitoring, and parental involvement. Most of the evidence relates to Web sites and further research into alternate media is needed, and longer term outcomes should be evaluated. There is a paucity of data on the cost-effectiveness of digital health interventions, and future trials should report these data
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