
Becker, F., Montealegre, P., Rapaport, I., & Todinca, I. (2020). The Impact Of Locality In The Broadcast Congested Clique Model. SIAM Discret. Math., 34(1), 682–700.
Abstract: The broadcast congested clique model (BCLIQUE) is a messagepassing model of distributed computation where n nodes communicate with each other in synchronous rounds. First, in this paper we prove that there is a oneround, deterministic algorithm that reconstructs the input graph G if the graph is ddegenerate, and rejects otherwise, using bandwidth b = O(d . log n). Then, we introduce a new parameter to the model. We study the situation where the nodes, initially, instead of knowing their immediate neighbors, know their neighborhood up to a fixed radius r. In this new framework, denoted BCLIQuE[r], we study the problem of detecting, in G, an induced cycle of length at most k (CYCLE <= k) and the problem of detecting an induced cycle of length at least k +1 (CYCLE>k). We give upper and lower bounds. We show that if each node is allowed to see up to distance r = left perpendicular k/2 right perpendicular + 1, then a polylogarithmic bandwidth is sufficient for solving CYCLE>k with only two rounds. Nevertheless, if nodes were allowed to see up to distance r = left perpendicular k/3 right perpendicular, then any oneround algorithm that solves CYCLE>k needs the bandwidth b to be at least Omega(n/ log n). We also show the existence of a oneround, deterministic BCLIQUE algorithm that solves CYCLE <= k with bandwitdh b = O(n(1/left perpendicular k/2 right perpendicular). log n). On the negative side, we prove that, if epsilon <= 1/3 and 0 < r <= k/4, then any epsilonerror, Rround, bbandwidth algorithm in the BCLIQUE[r] model that solves problem CYCLE(<= k )satisfies R . b = Omega(n(1/left perpendicular k/2 right perpendicular)).



Calderon, F., Lozada, A., Morales, P., BorquezParedes, D., Jara, N., Olivares, R., et al. (2022). Multiband elastic optical networks are a promising alternative to meet the bandwidth demand of the evergrowing Internet traffic. In this letter, we propose a family of band allocation algorithms for multiband elastic optical networks. Employing simulation, we evaluate the blocking performance of 3 algorithms of such a family and compare their performance with the only heuristic proposed to date. Results show that the three new algorithms outperform the previous proposal, with up to one order of magnitude improvement. We expect these results to help advance the area of dynamic resource allocation in multiband elastic optical networks. IEEE Commun. Lett., 26(2), 379–383.
Abstract: Multiband elastic optical networks are a promising alternative to meet the bandwidth demand of the evergrowing Internet traffic. In this letter, we propose a family of band allocation algorithms for multiband elastic optical networks. Employing simulation, we evaluate the blocking performance of 3 algorithms of such a family and compare their performance with the only heuristic proposed to date. Results show that the three new algorithms outperform the previous proposal, with up to one order of magnitude improvement. We expect these results to help advance the area of dynamic resource allocation in multiband elastic optical networks.



Carbonnel, C., Romero, M., & Zivny, S. (2022). The Complexity of GeneralValued Constraint Satisfaction Problems Seen from the Other Side. SIAM J. Comput., 51(1), 19–69.
Abstract: The constraint satisfaction problem (CSP) is concerned with homomorphisms between two structures. For CSPs with restricted lefthandside structures, the results of Dalmau, Languages and Programming, Springer, New York, 2007, pp. 279290] establish the precise borderline of polynomialtime solvability (subject to complexitytheoretic assumptions) and of solvability by boundedconsistency algorithms (unconditionally) as bounded treewidth modulo homomorphic equivalence. The generalvalued constraint satisfaction problem (VCSP) is a generalization of the CSP concerned with homomorphisms between two valued structures. For VCSPs with restricted lefthandside valued structures, we establish the precise borderline of polynomialtime solvability (subject to complexitytheoretic assumptions) and of solvability by the kth level of the SheraliAdams LP hierarchy (unconditionally). We also obtain results on related problems concerned with finding a solution and recognizing the tractable cases; the latter has an application in database theory.



Goles, E., Maldonado, D., & Montealegre, P. (2021). On the complexity of asynchronous freezing cellular automata. Inf. Comput., 281, 104764.
Abstract: In this paper we study the family of freezing cellular automata (FCA) in the context of asynchronous updating schemes. A cellular automaton is called freezing if there exists an order of its states, and the transitions are only allowed to go from a lower to a higher state. A cellular automaton is asynchronous if at each timestep only one cell is updated. We define the problem ASYNCUNSTABILITY, which consists in deciding there exists a sequential updating scheme that changes the state of a given cell.
We begin showing that ASYNCUNSTABILITY is in NL for any onedimensional FCA. Then we focus on the family of lifelike freezing CA (LFCA). We study the complexity of ASYNCUNSTABILITY for all LFCA in the triangular and square grids, showing that almost all of them can be solved in NC, except for one rule for which the problem is NPComplete. (C) 2021 Elsevier Inc. All rights reserved.



Goles, E., Medina, P., Montealegre, P., & Santivanez, J. (2022). Majority networks and consensus dynamics. Chaos Solitons Fractals, 164, 112697.
Abstract: Consensus is an emergent property of many complex systems, considering this as an absolute majority phenomenon. In this work we study consensus dynamics in grids (in silicon), where individuals (the vertices) with two possible opinions (binary states) interact with the eight nearest neighbors (Moore’s neighborhood). Dynamics emerge once the majority rule drives the evolution of the system. In this work, we fully characterize the subneighborhoods on which the consensus may be reached or not. Given this, we study the quality of the consensus proposing two new measures, namely effectiveness and efficiency. We characterize attraction basins through the energylike and magnetizationlike functions similar to the Ising spin model.



Grigioni, I., Polo, A., Dozzi, M. V., Stamplecoskie, K. G., Jara, D. H., Kamat, P. V., et al. (2022). Enhanced Charge Carrier Separation in WO3/BiVO4 Photoanodes Achieved via Light Absorption in the BiVO4 Layer. ACS Appl. Energy Mater., 5(11), 13142–13148.
Abstract: Photoelectrochemical (PEC) water splitting converts solar light and water into oxygen and energyrich hydrogen. WO3/BiVO4 heterojunction photoanodes perform much better than the separate oxide components, though internal charge recombination undermines their PEC performance when both oxides absorb light. Here we exploit the BiVO4 layer to sensitize WO3 to visible light and shield it from direct photoexcitation to overcome this efficiency loss. PEC experiments and ultrafast transient absorption spectroscopy performed by frontside (through BiVO4) or backside (through WO3) irradiating photoanodes with different BiVO4 layer thickness demonstrate that irradiation through BiVO4 is beneficial for charge separation. Optimized electrodes irradiated through BiVO4 show 40% higher photocurrent density compared to backside irradiation.



Montealegre, P., PerezSalazar, S., Rapaport, I., & Todinca, I. (2020). Graph reconstruction in the congested clique. J. Comput. Syst. Sci., 113, 1–17.
Abstract: In this paper we study the reconstruction problem in the congested clique model. Given a class of graphs g, the problem is defined as follows: if G is not an element of g, then every node must reject; if G is an element of g, then every node must end up knowing all the edges of G. The cost of an algorithm is the total number of bits received by any node through one link. It is not difficult to see that the cost of any algorithm that solves this problem is Omega(log vertical bar g(n)vertical bar/n), where g(n) is the subclass of all nnode labeled graphs in g. We prove that the lower bound is tight and that it is possible to achieve it with only 2 rounds. (C) 2020 Elsevier Inc. All rights reserved.



OcampoMelgar, A., Barria, P., Chadwick, C., & DiazVasconcellos, R. (2022). Rural transformation and differential vulnerability: Exploring adaptation strategies to water scarcity in the Aculeo Lake basin. Front. Environ. Sci., 10, 955023.
Abstract: The way of life of agricultural rural territories and their longterm capacity to adapt to changes will be challenged not only by the impacts of climate change; but by increased vulnerability stemming from previous inadequate climate adaptations and development policies. Studies that deepen understanding of the differential causes and implications of vulnerabilities will improve adaptation or transformation of institutions for climate change. The Aculeo basin of Central Chile suffered an extreme 10years rainfall deficit that resulted in the disappearance of a 12 km(2) lake and the economic transformation of the territory. This paper presents a crossscale exploration of the political, cultural and historical interconnections behind this dramatic story, while critically discussing whether today's land use configuration reflects the territory's adaptive capacity. The story is reconstructed using landuse change analysis along with literature review and CausalLoop Analysis. Results show how previous policies and other human factors contributed to the agroecosystem transformation, creating different vulnerabilities in different economic sectors. Today, what is observed as disparate capacities to adapt to climatic drought is actually the result of historic exacerbations of the vulnerabilities that had significantly contributed to the water scarcity crisis.



Peters, A. A., Vargas, F. J., Garrido, C., Andrade, C., & Villenas, F. (2021). PLTOON: A LowCost Experimental Platform for Teaching and Research on Decentralized Cooperative Control. Sensors, 21(6), 2072.
Abstract: In this paper, we present the development of a lowcost multiagent system experimental platform for teaching, and research purposes. The platform consists of trainlike autonomous agents equipped with local speed estimation, distance sensing to their nearest predecessor, and wireless communications with other agents and a central coordinator. The individual agents can be used for simple PID experiments in a classroom or laboratory setting, while a collection of agents are capable of performing decentralized platooning with cooperative adaptive cruise control in a variety of settings, the latter being the main goal of the platform. The agents are built from low cost components and programmed with open source software, enabling teaching experiences and experimental work with a larger number of agents that would otherwise be possible with other existing solutions. Additionally, we illustrate with experimental results some of the teaching activities that the platform is capable of performing.



VelazquezGuerrero, R., Pissaloux, E., DelValleSoto, C., CarrascoZambrano, M. A., MendozaAndrade, A., & VaronaSalazar, J. (2021). Mobility of blind people using the smartphone's GPS and a wearable tactile display. Dyna, 96(1), 98–104.
Abstract: This paper presents a novel wearable system devoted to assist the mobility of blind and visually impaired people in urban environments with the simple use of a smartphone and tactile feedback. The system exploits the positioning data provided by the smartphone's GPS sensor to locate in realtime the user in the environment and to determine the directions to a destination. The resulting navigational directions are encoded as vibrations and conveyed to the user via an onshoe tactile display. To validate the pertinence of the proposed system, two experiments were conducted. The first one involved a group of 20 voluntary normally sighted subjects that were requested to recognize the navigational instructions displayed by the tactilefoot device. The results show high recognition rates for the task. The second experiment consisted of guiding two blind voluntary subjects along public urban spaces to target destinations. Results show that the task was successfully accomplished and suggest that the system enhances independent safe navigation of people with visually impairments. Moreover, results show the potentials of smartphones and tactilefoot devices in assistive technology.



Wu, Y. X., Huang, M. Y., He, C. N., Wang, K. T., Nhung, N. T. H., Lu, S. M., et al. (2022). The Influence of Air Nanobubbles on Controlling the Synthesis of Calcium Carbonate Crystals. Materials, 15(21), 7437.
Abstract: Numerous approaches have been developed to control the crystalline and morphology of calcium carbonate. In this paper, nanobubbles were studied as a novel aid for the structure transition from vaterite to calcite. The vaterite particles turned into calcite (100%) in deionized water containing nanobubbles generated by highspeed shearing after 4 h, in comparison to a mixture of vaterite (33.6%) and calcite (66.3%) by the reaction in the deionized water in the absence of nanobubbles. The nanobubbles can coagulate with calcite based on the potential energy calculated and confirmed by the extended DLVO (DerjaguinLandauVerweyOverbeek) theory. According to the nanobubble bridging capillary force, nanobubbles were identified as the binder in strengthening the coagulation between calcite and vaterite and accelerated the transformation from vaterite to calcite.

