28,513 research outputs found
Evolvability signatures of generative encodings: beyond standard performance benchmarks
Evolutionary robotics is a promising approach to autonomously synthesize
machines with abilities that resemble those of animals, but the field suffers
from a lack of strong foundations. In particular, evolutionary systems are
currently assessed solely by the fitness score their evolved artifacts can
achieve for a specific task, whereas such fitness-based comparisons provide
limited insights about how the same system would evaluate on different tasks,
and its adaptive capabilities to respond to changes in fitness (e.g., from
damages to the machine, or in new situations). To counter these limitations, we
introduce the concept of "evolvability signatures", which picture the
post-mutation statistical distribution of both behavior diversity (how
different are the robot behaviors after a mutation?) and fitness values (how
different is the fitness after a mutation?). We tested the relevance of this
concept by evolving controllers for hexapod robot locomotion using five
different genotype-to-phenotype mappings (direct encoding, generative encoding
of open-loop and closed-loop central pattern generators, generative encoding of
neural networks, and single-unit pattern generators (SUPG)). We observed a
predictive relationship between the evolvability signature of each encoding and
the number of generations required by hexapods to adapt from incurred damages.
Our study also reveals that, across the five investigated encodings, the SUPG
scheme achieved the best evolvability signature, and was always foremost in
recovering an effective gait following robot damages. Overall, our evolvability
signatures neatly complement existing task-performance benchmarks, and pave the
way for stronger foundations for research in evolutionary robotics.Comment: 24 pages with 12 figures in the main text, and 4 supplementary
figures. Accepted at Information Sciences journal (in press). Supplemental
videos are available online at, see http://goo.gl/uyY1R
Ăner Tan Syndrome: Review and Emergence of Human Quadrupedalism in Self-Organization,\ud Attractors and Evolutionary Perspectives\ud
The first man reported in the world literature exhibiting habitual quadrupedal locomotion was discovered by a British traveler and writer on the famous Baghdat road near Havsa/Samsun on the middle Black-Sea coast of Turkey (Childs, 1917). Interestingly, no single case with human quadrupedalism was reported in the scientific literature after Child's first description in 1917 until the first report on the Uner Tan syndrome (UTS: quadrupedalism, mental retardation, and impaired speech or no speech)in 2005 (Tan, 2005, 2006). Between 2005 and 2010, 10 families exhibiting the syndrome were discovered in Turkey with 33 cases: 14 women (42.4%) and 19 men (57.6%). Including a few cases from other countries, there were 25 men (64.1%)and 14 women (35.9%). The number of men significantly exceeded the number of women (p < .05). Genetics alone did not seem to be informative for the origins of many syndromes, including the Uner Tan syndrome. From the viewpoint of dynamical systems theory, there may not be a single factor including the neural and/or genetic codes that predetermines the emergence of the human quadrupedalism.Rather, it may involve a self-organization process, consisting of many decentralized and local interactions among neuronal, genetic, and environmental subsystems. The most remarkable characteristic of the UTS, the diagonal-sequence quadrupedalism is well developed in primates. The evolutionarily advantage of this gait is not known. However, there seems to be an evolutionarily advantage of this type of locomotion for primate evolution, with regard to the emergence of complex neural circuits with related highly complex structures. Namely, only primates with diagonal-sequence quadrupedal locomotion followed an evolution favoring larger brains, highly developed cognitive abilities with hand skills, and language, with erect posture and bipedal locomotion, creating the unity of human being. It was suggested that UTS may be considered a further example for Darwinian diseases, which may be associated with an evolutionary understanding of the disorders using evolutionary principles, such as the natural selection. On the other hand, the human quadrupedalism was proposed to be a phenotypic example of evolution of reverse, i.e., the reacquisition by derived populations of the same character states as those of ancestor populations. It was also suggested that the emergence of the human quadrupedalism may be related to self-organizing processes occurring in complex systems, which select or attract one preferred behavioral state or locomotor trait out of many possible attractor states. Concerning the locomotor patterns, the dynamical systems in brain and body of the developing child may prefer some kind of locomotion, according to interactions of the internal components and the environmental conditions, without a direct role of any causative factor(s), such as genetic or neural codes, consistent with the concept of self-organization, suggesting no single element may have a causal priority
Development of titanium dioxide nanoparticles/nanosolution for photocatalytic activity
Biological and chemical contaminants by man-made activities have been serious
global issue. Exposure of these contaminants beyond the limits may result in serious
environmental and health problem. Therefore, it is important to develop an effective
solution that can be easily utilized by mankind. One of the effective ways to
overcome this problem is by using titanium dioxide (TiO2). TiO2 is a well-known
photocatalyst that widely used for environmental clean-up due to its ability to
decompose organic pollutant and kill bacteria. Although it is proven TiO2 has an
advantage to solve this concern, its usefulness unfortunately is limited only under
UV light irradiation. Therefore, the aim of this work was to investigate the potential
of TiO2 that can be activated under visible light by the incorporation of metal ions
(Fe, Ag, Zr and Ag-Zr). In this study, sol-gel method was employed for the synthesis
of metal ions incorporated TiO2. XRD analysis revealed that all samples content
biphasic anatase-brookite TiO2 of size 3 nm to 5 nm. It was found that the
incorporation of these metal ions did not change the morphology of TiO2 but the
crystallinity and optical properties were affected. The crystallinity of anatase in the
biphasic TiO2 was found to be decreased and favored brookite formation. PL analysis
showed metal ions incorporation suppressed the recombination of electron-hole pairs
while the band gap energy of TiO2 (3.2 eV) was decreased by the incorporation of Fe
(2.46 eV) and Ag (2.86 eV). Among this incorporation, Ag-Zr incorporated TiO2
showed highest performance for methyl orange degradation (93%) under fluorescent
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light irradiation for 10 h. This follows by Zr-TiO2 (82%), Fe-TiO2 (75%) and AgïżœTiO2 (43%). Meanwhile, the highest antibacterial performance was exhibited by AgïżœTiO2. TEM images showed that E.coli bacterium was killed within 12 h after treated
with Ag-TiO2. The results obtained from the fieldwork study established that Ag-Zr
incorporation have excellent performances for VOC removal and antibacterial test.
The VOC content after treated with Ag-Zr-TiO2 fulfilled the Industry Code of
Practice on Indoor Air Quality 2010 which is lower than 3 ppm. In addition, the
percentage of microbes also found to be decrease around 45 % within 5 days of
monitoring
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Electrifying Integration: Electricity Production and the South-East Europe Regional Energy Market
Persistent Homology analysis of Phase Transitions
Persistent homology analysis, a recently developed computational method in
algebraic topology, is applied to the study of the phase transitions undergone
by the so-called XY-mean field model and by the phi^4 lattice model,
respectively. For both models the relationship between phase transitions and
the topological properties of certain submanifolds of configuration space are
exactly known. It turns out that these a-priori known facts are clearly
retrieved by persistent homology analysis of dynamically sampled submanifolds
of configuration space.Comment: 10 pages; 10 figure
A Fast Algorithm for Sparse Controller Design
We consider the task of designing sparse control laws for large-scale systems
by directly minimizing an infinite horizon quadratic cost with an
penalty on the feedback controller gains. Our focus is on an improved algorithm
that allows us to scale to large systems (i.e. those where sparsity is most
useful) with convergence times that are several orders of magnitude faster than
existing algorithms. In particular, we develop an efficient proximal Newton
method which minimizes per-iteration cost with a coordinate descent active set
approach and fast numerical solutions to the Lyapunov equations. Experimentally
we demonstrate the appeal of this approach on synthetic examples and real power
networks significantly larger than those previously considered in the
literature
Developing Predictive Molecular Maps of Human Disease through Community-based Modeling
The failure of biology to identify the molecular causes of disease has led to disappointment in the rate of development of new medicines. By combining the power of community-based modeling with broad access to large datasets on a platform that promotes reproducible analyses we can work towards more predictive molecular maps that can deliver better therapeutics
Origin of symbol-using systems: speech, but not sign, without the semantic urge
Natural languageâspoken and signedâis a multichannel phenomenon, involving facial and body expression, and voice and visual intonation that is often used in the service of a social urge to communicate meaning. Given that iconicity seems easier and less abstract than making arbitrary connections between sound and meaning, iconicity and gesture have often been invoked in the origin of language alongside the urge to convey meaning. To get a fresh perspective, we critically distinguish the origin of a system capable of evolution from the subsequent evolution that system becomes capable of. Human language arose on a substrate of a system already capable of Darwinian evolution; the genetically supported uniquely human ability to learn a language reflects a key contact point between Darwinian evolution and language. Though implemented in brains generated by DNA symbols coding for protein meaning, the second higher-level symbol-using system of language now operates in a world mostly decoupled from Darwinian evolutionary constraints. Examination of Darwinian evolution of vocal learning in other animals suggests that the initial fixation of a key prerequisite to language into the human genome may actually have required initially side-stepping not only iconicity, but the urge to mean itself. If sign languages came later, they would not have faced this constraint
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