1,045 research outputs found
Individual decision making in task-oriented groups
The strategies adopted by individuals to select relevant information to pass
on are central to understanding problem solving by groups. Here we use
agent-based simulations to revisit a cooperative problem-solving scenario where
the task is to find the common card in decks distributed to the group members.
The agents can display only a sample of their cards and we explore different
strategies to select those samples based on the confidences assigned to the
cards. An agent's confidence that a particular card is the correct one is given
by the number of times it observed that card in the decks of the other agents.
We use a Gibbs distribution to select the card samples with the temperature
measuring the strength of a noise that prevents the agents to correctly rank
the cards. The group is guaranteed to find the common card in all runs solely
in the infinite temperature limit, where the cards are sampled regardless of
their confidences. In this case, we obtain the scaling form of the time
constant that characterizes the asymptotic exponential decay of the failure
probability. For finite time, however, a finite temperature yields a
probability of failure that is several orders of magnitude lower than in the
infinite temperature limit. The available experimental results are consistent
with the decision-making model for finite temperature only
Policies for allocation of information in task-oriented groups: elitism and egalitarianism outperform welfarism
Communication or influence networks are probably the most controllable of all
factors that are known to impact on the problem-solving capability of
task-forces. In the case connections are costly, it is necessary to implement a
policy to allocate them to the individuals. Here we use an agent-based model to
study how distinct allocation policies affect the performance of a group of
agents whose task is to find the global maxima of NK fitness landscapes. Agents
cooperate by broadcasting messages informing on their fitness and use this
information to imitate the fittest agent in their influence neighborhoods. The
larger the influence neighborhood of an agent, the more links, and hence
information, the agent receives. We find that the elitist policy in which
agents with above-average fitness have their influence neighborhoods amplified,
whereas agents with below-average fitness have theirs deflated, is optimal for
smooth landscapes, provided the group size is not too small. For rugged
landscapes, however, the elitist policy can perform very poorly for certain
group sizes. In addition, we find that the egalitarian policy, in which the
size of the influence neighborhood is the same for all agents, is optimal for
both smooth and rugged landscapes in the case of small groups. The welfarist
policy, in which the actions of the elitist policy are reversed, is always
suboptimal, i.e., depending on the group size it is outperformed by either the
elitist or the egalitarian policies
Unipolar resistive switching in metal oxide/organic semiconductor non-volatile memories as a critical phenomenon
Diodes incorporating a bilayer of an organic semiconductor and a wide bandgap metal oxide can show unipolar, non-volatile memory behavior after electroforming. The prolonged bias voltage stress induces defects in the metal oxide with an areal density exceeding 10(17) m(-2). We explain the electrical bistability by the coexistence of two thermodynamically stable phases at the interface between an organic semiconductor and metal oxide. One phase contains mainly ionized defects and has a low work function, while the other phase has mainly neutral defects and a high work function. In the diodes, domains of the phase with a low work function constitute current filaments. The phase composition and critical temperature are derived from a 2D Ising model as a function of chemical potential. The model predicts filamentary conduction exhibiting a negative differential resistance and nonvolatile memory behavior. The model is expected to be generally applicable to any bilayer system that shows unipolar resistive switching. (C) 2015 Author(s).Dutch Polymer Institute (DPI), BISTABLE [704]; Fundacao para Ciencia e Tecnologia (FCT) through the research Instituto de Telecommunicacoes (IT-Lx); project Memristor based Adaptive Neuronal Networks (MemBrAiNN) [PTDC/CTM-NAN/122868/2010]; European Community Seventh Framework Programme FP7', ONE-P [212311]; Dutch Ministry of Education, Culture and Science (Gravity Program) [024.001.035]info:eu-repo/semantics/publishedVersio
Populational analysis of Saccharomyces cerevisiae strains from different appellations of origin and grape varieties by microsatellite analysis.
The objective of the present study was to evaluate populational relationships among Saccharomyces cerevisiae strains isolated from some of the Portuguese most important grapevine varieties in different appellations of origin, using polymorphic microsatellites. 
One hundred ninety two grape samples were collected during the 2006 and 2007 harvest season in the Vinho Verde (grape varieties: Arinto, Alvarinho, Avesso, Loureiro, Touriga Nacional) Bairrada (grape varieties: Arinto, Baga, Castelão Francês, Maria Gomes, Touriga Nacional) Alentejo (grape varieties, Aragonês, Trincadeira, Touriga Nacional), Terras do Sado (grape variety Castelão) Bucelas (grape variety Arinto) and Estremadura (grape varieties: Arinto, Aragonês, Castelão, Trincadeira, Touriga Nacional) appellations of origin. From the final stage of spontaneous fermentations, 2820 yeast isolates were obtained, mainly belonging to the species S. cerevisiae. An initial genetic screen, based on mitochondrial DNA restriction fragment length polymorphism (mtDNA RFLP) and/or interdelta sequence analysis was followed by microsatellite analysis of strains with unique genetic profiles, using 10 highly polymorphic microsatellites. Our results showed that microsatellite analysis revealed a high resolution populational screen, showing that genetic differences and populational structures among S. cerevisiae populations derived from both “diagnostic” vineyard-, specific alleles and the accumulation of small allele-frequency differences across ten microsatellite loci. Heterozygosity was three to four times lower than the expected value, confirming the strong populational substructuring. The presented large-scale approach shows that each vineyard contains differentiated S. cerevisiae populations, showing the occurrence of specific native strains that can be associated with a terroir. 

Financially supported by the programs POCI 2010 (FEDER/FCT, POCTI/AGR/56102/2004) and AGRO (ENOSAFE, Nº 762).

A literacia ambiental dos alunos finalistas do ensino secundário : o caso da Escola Secundária da Moita
O presente trabalho pretendeu dar continuidade ao levantamento e monitorização da Literacia Ambiental (LA), dos alunos finalistas do Ensino Secundário, iniciada em várias outras Escolas Secundárias de Áreas Geográficas e realidades Socioeconómicas distintas da que foi alvo este estudo, a Escola Secundária da Moita. Para o seu desenvolvimento, recorreu-se a uma metodologia de inquérito por recurso ao questionário escrito, já devidamente testado e ajustado nas escolas onde foi anteriormente aplicado. Na situação em estudo, o questionário foi aplicado aos alunos do 12º ano do curso Cientifico Humanístico, de Ciências e Tecnologias, num total de 72 alunos. Demonstrou-se que estes alunos apresentam, globalmente, um nível Suficiente de Literacia Ambiental. O Conhecimento Informal apresenta desempenhos inferiores ao Conhecimento Escolástico, o que é reflexo do meio em que a escola se insere, dos modos de vida dos seus habitantes e da importância que estes atribuem à cultura e, particularmente, ao Ambiente. É ao nível das Atitudes pró-ambientais que o desempenho destes alunos apresenta melhores resultados, o que demonstra um bom nível de receptividade e envolvimento nas problemáticas ambientais
Mobility helps problem-solving systems to avoid Groupthink
Groupthink occurs when everyone in a group starts thinking alike, as when
people put unlimited faith in a leader. Avoiding this phenomenon is a
ubiquitous challenge to problem-solving enterprises and typical countermeasures
involve the mobility of group members. Here we use an agent-based model of
imitative learning to study the influence of the mobility of the agents on the
time they require to find the global maxima of NK-fitness landscapes. The
agents cooperate by exchanging information on their fitness and use this
information to copy the fittest agent in their influence neighborhoods, which
are determined by face-to-face interaction networks. The influence
neighborhoods are variable since the agents perform random walks in a
two-dimensional space. We find that mobility is slightly harmful for solving
easy problems, i.e. problems that do not exhibit suboptimal solutions or local
maxima. For difficult problems, however, mobility can prevent the imitative
search being trapped in suboptimal solutions and guarantees a better
performance than the independent search for any system size
Library for Simplified Timer Implementation using Standard C++
Temporization is a crucial aspects of control, automation and robotics systems. C++ is used in the
development of such systems, especially if they are more complex and powerful. Because, the language and
standard library do not support non-blocking timers with callbacks for event-driven programming,
developers resort to libraries and frameworks that offer such functionality. However, their timer
implementations are dependent on platform specificities and thus have more limited portability. C++11 has
introduced features that enable standard implementations of timers. We propose a library that implements
timers with simplified usage relatively to well-known libraries. The proposed library is contrasted with
timers of two well know libraries, through a series of usage scenarios. We describe the design and provide
performance measurements. The results show that it is faster and offers more accurate temporization.(undefined)info:eu-repo/semantics/publishedVersio
Prototype WSN platform for performing dynamic monitoring of civil engineering structures
Structural Health Monitoring represents the present and future of the civil engineering since, until few years ago, structural diagnosis works had been performed with few resources regarding to experimental techniques. Precisely in the field of monitoring sensors, the progress of new technologies based on wireless communications and Micro-Electro-Mechanical- Systems (MEMS) are of high interest for replacing the handle difficult wired sensors. However, three major limitations of the commercial off-the-shelf technology on WSN (combination of MEMS and wireless technology) for performing dynamic monitoring were identified by means of: (1) not enough sensitivity of the accelerometers; (2) low resolution of the ADC embedded; and (3) lack of synchronization algorithms implemented. This paper presents a new prototype system conceived for performing dynamic monitoring civil engineering structures. This system was jointly conceived by a team of civil, electrical and communication engineers and is a combination of the last technology on high resolution MEMS accelerometers and the state of the art of communication technologies. Despite the fact that the prototype system needs more improvements; the results of several rounds of validation experiences confirm the feasibility for its consideration as an alternative to the conventional wired based sensors.(undefined
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