2,984 research outputs found
Biology helps you to win a game
We present a game of interacting agents which mimics the complex dynamics
found in many natural and social systems. These agents modify their strategies
periodically, depending on their performances using genetic crossover
mechanisms, inspired by biology. We study the performances of the agents under
different conditions, and how they adapt themselves. In addition the dynamics
of the game is investigated.Comment: 4 pages including 6 figures. Uses REVTeX4. Submitted for Conference
Proceedings of the "Unconventional Applications of Statistical Physics",
Kolkat
Community detection in complex networks using Extremal Optimization
We propose a novel method to find the community structure in complex networks
based on an extremal optimization of the value of modularity. The method
outperforms the optimal modularity found by the existing algorithms in the
literature. We present the results of the algorithm for computer simulated and
real networks and compare them with other approaches. The efficiency and
accuracy of the method make it feasible to be used for the accurate
identification of community structure in large complex networks.Comment: 4 pages, 4 figure
An automata characterisation for multiple context-free languages
We introduce tree stack automata as a new class of automata with storage and
identify a restricted form of tree stack automata that recognises exactly the
multiple context-free languages.Comment: This is an extended version of a paper with the same title accepted
at the 20th International Conference on Developments in Language Theory (DLT
2016
Waveform Optimization and Beam Focusing for Near-field Wireless Power Transfer with Dynamic Metasurface Antennas and Non-linear Energy Harvesters
Radio frequency (RF) wireless power transfer (WPT) is a promising technology
for future wireless systems. However, the low power transfer efficiency (PTE)
is a critical challenge for practical implementations. One of the main
inefficiency sources is the power consumption and loss introduced by key
components such as high-power amplifier (HPA) and rectenna, thus they must be
carefully considered for PTE optimization. Herein, we consider a near-field
RF-WPT system with the emerging dynamic metasurface antenna (DMA) at the
transmitter and non-linear energy harvesters. We provide a mathematical
framework to calculate the power consumption and harvested power from
multi-tone signal transmissions. Then, we propose an approach relying on
alternating optimization and successive convex approximation for waveform
optimization and beam focusing to minimize power consumption while meeting
energy harvesting requirements. Numerical results show that increasing the
transmit tones reduces the power consumption by leveraging the rectifier's
non-linearity. Moreover, it is demonstrated that increasing the antenna length
improves the performance, while both DMA and fully-digital architectures may be
favorable depending on the setup. Finally, our results verify that the
transmitter generates accurate energy beams pointed to devices located in the
near-field, while energy beams are formed in devices' direction in the
far-field region.Comment: 13 pages, 12 figure
Isien identiteetti lapsen kuoleman jälkeen: Osatutkimus I & II
The purpose of the research was to describe the identity of fathers after the death of their child and to assess the effects of the support intervention on the fathers’ personal growth. The research consisted of two parts. In Part I, The sample consisted of eight fathers who had lost a child. The data were collected using an open-ended questionnaire and interviews. The data were analysed using inductive qualitative content analysis. In Part II, the study participants were grieving fathers (intervention group N = 62 and control group N = 41) whose child has died at the age of three years and younger (including perinatal deaths at 22 weeks gestation or fetuses over 500 g) and whose child has died in a university hospital (N = 5) in Finland. The data were collected from the fathers using a questionnaire which consisted of background variables and the variables of the personal growth dimension (12) of the Hogan Grief Reactions Checklist (HGRC). A statistical method was used to analyse the data. The fathers experienced negative and positive changes in their identity after the death of their child that focused on their self, spirituality, values, life, and social relations. The support intervention had a positive effect on the fathers’ personal growth in the intervention group. The personal growth of fathers in the intervention group was stronger compared to fathers in the control group who received routine support from the hospital after hospitalization, and the difference was statistically significant. In conclusion, the death of a child will change a father’s identity and social support can increase a father’s positive personal growth.
Parametric scaling of power exhaust in EU-DEMO alternative divertor simulations
Investigations of parametric scaling of power exhaust in the alternative
divertor configuration (ADC) SOLPS-ITER simulation database of the EU-DEMO are
conducted and compared to predictions based on the Lengyel model. The Lengyel
model overpredicts the necessary argon concentrations for LFS divertor
detachment by about a factor of 5-10 relative to the SOLPS-ITER simulations.
Therefore, while the Lengyel model predicts that plasmas with accetable
divertor heat loads in EU-DEMO would exceed the tolerable upstream impurity
concentrations by a large margin, there are several SOLPS-ITER solutions within
an acceptable operational space. The SOLPS-ITER simulations indicate that,
unlike assumed by the standard Lengyel model, there are significant heat
dissipation mechanisms other than argon radiation, such as cross-field
transport, that reduce the role of argon radiation by a factor of 2 to 3.
Furthermore, the Lengyel model assumes that the radiation front is powered by
parallel heat conduction only, which tends to lead to a narrow radiation front
as the radiative efficiency increases strongly with reducing thermal
conductivity. As a result, the radiative volume and total impurity radiation
are suppressed for a given impurity concentration. However, the SOLPS-ITER
simulations indicate that other mechanisms, such as cross-field transport, can
compete with parallel heat conduction within the radiative front and increase
the radiative volume. Due to these findings, usage of the standard Lengyel
model for analyzing scaling between divertor conditions and configurations for
devices such as EU-DEMO is strongly discouraged
Proving Safety with Trace Automata and Bounded Model Checking
Loop under-approximation is a technique that enriches C programs with
additional branches that represent the effect of a (limited) range of loop
iterations. While this technique can speed up the detection of bugs
significantly, it introduces redundant execution traces which may complicate
the verification of the program. This holds particularly true for verification
tools based on Bounded Model Checking, which incorporate simplistic heuristics
to determine whether all feasible iterations of a loop have been considered.
We present a technique that uses \emph{trace automata} to eliminate redundant
executions after performing loop acceleration. The method reduces the diameter
of the program under analysis, which is in certain cases sufficient to allow a
safety proof using Bounded Model Checking. Our transformation is precise---it
does not introduce false positives, nor does it mask any errors. We have
implemented the analysis as a source-to-source transformation, and present
experimental results showing the applicability of the technique
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