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1.
Eber Jafet Ávila-Martínez Juan Gonzalo Barajas-Ramírez 《Journal of The Franklin Institute》2021,358(4):2346-2366
This paper addresses the flocking motion problem for swarms of agents with two restrictions: limited communication/detection ranges and different input constraints. In this problem, the distance between pairs of agents determines if a communication/detection link exists among them, while each agent has a different control action bound. We use the notion of proximity graph to model communication/detection between agents and provide distributed controllers designed for leaderless and leader-followers flocking motion scenarios. Our proposed designs preserve the connectivity of the proximity graph while the control effort satisfies the bound of each particular agent. Unlike previous results, our protocols take advantage of the group’s input heterogeneity to use agents with a greater capacity to compensate for neighbors that are less capable of meeting the group’s requirements. Additionally, our designs are based only on local state errors and are robust to non-modeled edge failures. To illustrate the effectiveness of our proposal, we use numerical simulations of different flocking scenarios. 相似文献
2.
Jyoti P. Gurung Moein Navvab Kashani Sanaz Agarwal Gonzalo Peralta Murat Gel Matthew A. B. Baker 《Biomicrofluidics》2021,15(3)
Many motile bacteria are propelled by the rotation of flagellar filaments. This rotation is driven by a membrane protein known as the stator-complex, which drives the rotor of the bacterial flagellar motor. Torque generation is powered in most cases by proton transit through membrane protein complexes known as stators, with the next most common ionic power source being sodium. Sodium-powered stators can be studied through the use of synthetic chimeric stators that combine parts of sodium- and proton-powered stator proteins. The most well studied example is the use of the sodium-powered PomA-PotB chimeric stator unit in the naturally proton-powered Escherichia coli. Here we designed a fluidics system at low cost for rapid prototyping to separate motile and non-motile populations of bacteria while varying the ionic composition of the media and thus the sodium-motive force available to drive this chimeric flagellar motor. We measured separation efficiencies at varying ionic concentrations and confirmed using fluorescence that our device delivered eightfold enrichment of the motile proportion of a mixed population. Furthermore, our results showed that we could select bacteria from reservoirs where sodium was not initially present. Overall, this technique can be used to implement the selection of highly motile fractions from mixed liquid cultures, with applications in directed evolution to investigate the adaptation of motility in bacterial ecosystems. 相似文献
3.
According to the temporal-coding hypothesis (TCH; Savastano & Miller, Behavioural Processes 44:147–162, 1998), acquired associations include temporal information concerning the interval between the associated elements. Moreover, the TCH posits that subjects can integrate two independently acquired associations that share a common element (e.g., S2–S1 and S1–US), which results in the creation of a third association with its own temporal relationship (S2–US). Some evidence has suggested that such temporal integration occurs at the time of testing (Molet, Miguez, Cham, & Miller, Journal of Experimental Psychology: Animal Behavior Processes 38:369–380, 2012). Here we report two fear-conditioning experiments with rats conducted to identify the associative structure of the integrated temporal relationship. The goal was to distinguish between two possible associative structures that could exist following an initial test on which temporal integration occurs: (1) Conditioned responding to S2 on subsequent tests could be the result of recurring successive activation of two independently learned temporal maps that remain independently stored in memory (i.e., S2–S1 plus S1–US). (2) Temporal integration at the moment of initial testing could result in the formation of a direct S2–US (or S2–response) temporal map. Integration was found to occur at test and to produce a new association that was independent of associations with the common element (S1). However, the associative status of S1 appeared to modulate whether or not the new association with S2 was US-specific (S2–US) or directly activated a fear response (S2–response). 相似文献
4.
Travis Gagie Aleksi Hartikainen Kalle Karhu Juha Kärkkäinen Gonzalo Navarro Simon J. Puglisi Jouni Sirén 《Information Retrieval》2017,20(3):253-291
Most of the fastest-growing string collections today are repetitive, that is, most of the constituent documents are similar to many others. As these collections keep growing, a key approach to handling them is to exploit their repetitiveness, which can reduce their space usage by orders of magnitude. We study the problem of indexing repetitive string collections in order to perform efficient document retrieval operations on them. Document retrieval problems are routinely solved by search engines on large natural language collections, but the techniques are less developed on generic string collections. The case of repetitive string collections is even less understood, and there are very few existing solutions. We develop two novel ideas, interleaved LCPs and precomputed document lists, that yield highly compressed indexes solving the problem of document listing (find all the documents where a string appears), top-k document retrieval (find the k documents where a string appears most often), and document counting (count the number of documents where a string appears). We also show that a classical data structure supporting the latter query becomes highly compressible on repetitive data. Finally, we show how the tools we developed can be combined to solve ranked conjunctive and disjunctive multi-term queries under the simple \({\textsf{tf}}{\textsf{-}}{\textsf{idf}}\) model of relevance. We thoroughly evaluate the resulting techniques in various real-life repetitiveness scenarios, and recommend the best choices for each case. 相似文献
5.
秘鲁高等教育的发展进程可以划分为精英化、大众化、国际化三个阶段。20世纪60年代，秘鲁进
入高等教育大众化阶段，但自身经济发展模式和社会环境导致了科学教育基础薄弱、教育体制不健全、私人
教育投资不均衡等问题。面对新的教育国际化趋势，仍有许多问题亟待解决。回顾秘鲁高等教育近五百年
的发展历程，可以为中国的大学治理改革提供有益借鉴。 相似文献
6.
Marisa Raquel De Giusti Ariel Jorge Lira Gonzalo Luján Villarreal 《European Journal of Engineering Education》2008,33(5-6):587-596
Simulation is the process of executing a model that describes a system with enough detail; this model has its entities, an internal state, some input and output variables and a list of processes bound to these variables. Teaching a simulation language such as general purpose simulation system (GPSS) is always a challenge, because of the way it executes the models and the abstraction level it can achieve, very different compared with most well-known programming languages. This article presents an open source simulation framework that implements a subset of entities of GPSS, which could help students to improve the understanding of this language. This tool also stores all entities of simulations in every single simulation time, which is very useful for debugging simulations, but also for getting a detailed history of all entities in the simulations, knowing exactly how they have behaved in every simulation time. 相似文献
7.
Peñaloza Gonzalo El-Hani Charbel N. Mosquera-Suárez Carlos Javier 《Science & Education》2021,30(4):931-965
Science & Education - Despite the importance of evolution to understand living phenomena, evolution teaching confronts several tensions, especially with respect to teachers’ and... 相似文献
8.
Research in Science Education - The definition of biodiversity stated by the Convention on Biological Diversity (CBD) in 1992 was conceived as occurring on three different organizational levels:... 相似文献
9.
In the present experiments, we examined the role of within-compound associations in the interaction of the overshadowing procedure
with conditioned stimulus (CS) duration, using a conditioned suppression procedure with rats. In Experiment 1, we found that,
with elemental reinforced training, conditioned suppression to the target stimulus decreased as CS duration increased (i.e.,
the CS duration effect), whereas, with compound reinforced training (i.e., the overshadowing procedure), conditioned suppression to the target stimulus
increased as CS duration increased. In subsequent experiments, we replicated these findings with sensory preconditioning and
demonstrated that extinction of the overshadowing stimulus results in retrospective revaluation with short CSs and in mediated
extinction with long CSs. These results highlight the role of the duration of the stimulus in behavioral control. Moreover,
these results illuminate one cause (the CS duration) of whether retrospective revaluation or mediated extinction will be observed. 相似文献
10.
Studies of extinction in classical conditioning situations can reveal techniques that maximize the effectiveness of exposure-based
behavior therapies. In three experiments, we investigated the effect of varying the intertrial interval during an extinction
treatment in a fear-conditioning preparation with rats as subjects. In Experiment 1, we found less fear at test (i.e., more
effective extinction) when extinction trials were widely spaced, relative to intermediate or massed extinction trials. In
Experiment 2, we used an ABA renewal procedure and observed that spaced trials attenuated renewal of conditioned fear relative
to massed trials. In Experiment 3, we used a similar design, but instead of changing the physical context at the time of testing,
we interposed a retention interval after the extinction treatment to produce a change in the temporal context. The results
showed less spontaneous recovery of fear after spaced than after massed extinction trials. These results suggest that extinction
is more enduring when the extinction trials are spaced rather than massed. Although the benefits of spacing trials are small
when there is no contextual change from extinction to testing, a change in either physical or temporal context following massed
extinction trials leads to a recovery from extinction, which is reduced when the trials are spaced. 相似文献