Collective behaviors of isotropic phoretic microswimmers: from crystalline solids to active turbulence

Chemically phoretic microswimmers including Janus colloids and isotropic active droplets have recently shown great potential for self-organizing into active materials. However, the fascinating self-organization of these swimmers remains enigmatic owing to an incomplete understanding of their collective dynamics. We investigate a paradigmatic suspension of phoretic swimmers represented by isotropic phoretic disks. By varying the activity and area fraction of disks, we observe their diverse collective phenomena: formation of crystalline solids resembling Wigner crystals, melting, gas-like dynamic chaining, active transition and turbulence. Notably, altering the activity alone leads to solid-fluid phase transition and subsequently the fluid's laminar-turbulent transition. Our observations are based on large-scale simulations explicitly resolving the many-body, long-range hydrochemical interactions among the phoretic agents. We reproduce independent experimental phenomena that have not been collectively captured by a single model, emphasizing the importance of incorporating full physicochemical hydrodynamics. We develop a predictive scaling delineating the solid-liquid transition and further dissect it as a defect-mediated two-step melting scenario via a hexatic phase. We demonstrate that the fluid phase exhibits oscillatory instability with waves, transition due to wave-breaking clusters, and active turbulence manifesting vortices. These progressive scenarios evidence a closer phenomenological resemblance between active and classical fluids in their laminar-turbulent transition than previously demonstrated. Our findings elucidate the collective dynamics of phoretic agents, potentially facilitating the design of active material systems by harnessing non-equilibrium phoretic collectives

BDTS: Blockchain-based Data Trading System

Trading data through blockchain platforms is hard to achieve \textit{fair exchange}. Reasons come from two folds: Firstly, guaranteeing fairness between sellers and consumers is a challenging task as the deception of any participating parties is risk-free. This leads to the second issue where judging the behavior of data executors (such as cloud service providers) among distrustful parties is impractical in the context of traditional trading protocols. To fill the gaps, in this paper, we present a \underline{b}lockchain-based \underline{d}ata \underline{t}rading \underline{s}ystem, named BDTS. BDTS implements a fair-exchange protocol in which benign behaviors can get rewarded while dishonest behaviors will be punished. Our scheme requires the seller to provide consumers with the correct encryption keys for proper execution and encourage a rational data executor to behave faithfully for maximum benefits from rewards. We analyze the strategies of consumers, sellers, and dealers in the trading game and point out that everyone should be honest about their interests so that the game will reach Nash equilibrium. Evaluations prove efficiency and practicability.Comment: ICICS 2023 (Best Paper Award

Interfacial nucleation in iPP/PB-1 blends promotes the formation of polybutene-1 trigonal crystals

The formation of trigonal Form I\ub4 crystals of polybutene-1 (PB-1) directly from melt has drawn much attention in past decades. In this study, we investigate the fractionated crystallization behavior of PB-1 within droplets formed by blending PB-1 with an excess of isotactic polypropylene (iPP) employing DSC, SEM, in situ synchrotron WAXD and FT-IR. When PB-1 is dispersed into a large number of small size droplets, the heterogeneous nucleation of Form II crystals can be inhibited because the number of droplets is larger than that of active nucleation sites for Form II (i.e., active heterogeneities originally present in bulk PB-1). The nucleation of the finely dispersed PB-1 droplets does not occur homogenously, but at the interface with the iPP matrix, which induces the crystallization of the droplets into Form I\ub4. The crystallization rate of Form I\ub4 at different temperatures was determined by Fourier transform infrared spectroscopy. It was found that trigonal Form I\ub4 crystallizes faster when the content of PB-1 in the blend is lower, and the specific interfacial surface area is larger. The opposite effect has been observed for the kinetics of the metastable Form II formation. It is therefore suggested that Form I\ub4 crystallization is driven by the nucleation of PB-1 at the crystalline iPP surface, which competes with the crystallization of Form II induced by nucleating heterogeneities present in PB-1 droplets

Decentralized Finance (DeFi): A Survey

Decentralized Finance (DeFi) is a new paradigm in the creation, distribution, and utilization of financial services via the integration of blockchain technology. Our research conducts a comprehensive introduction and meticulous classification of various DeFi applications. Beyond that, we thoroughly analyze these risks from both technical and economic perspectives, spanning multiple layers. Lastly, we point out research directions in DeFi, encompassing areas of technological advancements, innovative economics, and privacy optimization

Développement des capacités métalinguistiques chez des élèves apprenant une langue étrangère en utilisant la poésie

La thèse actuelle propose un modèle interactif de capacité métalinguistique, de poésie et d'apprentissage des langues étrangères. Elle vise à examiner l'influence du cours d'anglais langue étrangère basé sur la poésie sur la capacité métaphonologique des élèves, et à explorer des relations entre leur capacité métaphonologique et les facteurs d'apprentissage tels que la pédagogie des enseignants, les stratégies d'apprentissage des langues des apprenants, l'exposition linguistique à l’anglais en dehors de la classe et les commentaires des élèves sur le cours d’anglais auquel on a intégré de la poésie. Deux études de cas visent à enquêter sur le développement de la capacité métaphonologique des élèves dans le cours d’anglais avec poésie, ainsi que les relations mentionnées ci-dessus. Une combinaison de méthodes quantitatives et de méthodes qualitatives est utilisée dans cette thèse. Les résultats de la quasi-expérience indiquent que la classe d'anglais prenant appui sur la poésie facilite le développement de la capacité métaphonologique des élèves dans une certaine mesure. La théorie de Bialystok (2001, 2012), la « noticing hypothesis » de Schmidt (Schmidt, 2010) et la poétique cognitive de Tsur (2008) sont utilisées pour analyser et expliquer les résultats des tests de capacité métaphonologique.The present study proposes an interactive model of metalinguistic awareness, poetry and foreign language learning. It aims at examining the influence from poetry-embedded class of English as a foreign language on pupils’ phonological awareness, with considering the relations between their phonological awareness and the factors in ecological learning environment that includes teacher’s instruction, learners’ language learning strategies, linguistic exposure to English that learners receive outside of classroom, and pupils’ feedback on the poetry sequence. Two case studies are conducted to probe into the development of pupils’ phonological awareness in the context of poetry-embedment English class, as well as the relations mentioned above. A combination of quantitative methods and qualitative methods are employed in the current study. The results of quasi-experiment of phonological awareness indicate poetry-embedment English class globally facilitates the development of pupils’ phonological awareness to some extent. Bialystok’s theory (2001, 2012) Schmidt’s noticing hypothesis (Schmidt,2010), and Tsur’s cognitive poetics (2008) are employed to interpret the results of phonological awareness tests

Secure and efficient cloud data deduplication with randomized tag

Cross-client data deduplication has been widely used to eliminate redundant storage overhead in cloud storage system. Recently, Abadi et al. introduced the primitive of MLE2 with nice security properties for secure and efficient data de-duplication

Cooperative target searching and tracking via UCT with probability distribution model

International audienceAs Unmanned Aerial Vehicle's (UAV) battery life and stability develop, multiple UAVs are having more and more applications in the uninterrupted patrol and security. Thus UAV's searching, tracking and trajectory planning become important issues. This paper proposes an online distributed algorithm used in UAV's tracking and searching, with the consideration of UAV's practical need to recharge under limited power. We propose a Quantum Probability Model to describe the partially observable target positions, and we use Upper Confidence Tree (UCT) algorithm to find out the best searching and tracking route based on this model. We also introduce the Teammate Learning Model to handle the nonstationary problems in distributed reinforcement learning

Transesterification induced mechanical properties enhancement of PLLA/PHBV bio-alloy

In order to improve the miscibility and mechanical properties of poly(l-lactic acid) (PLLA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) bio-alloy, small amount of transesterification catalyst, zinc acetate was added in the melt blending process. We show that the PLLA-PHBV copolymer generated during the melt blending significantly improves the miscibility and therefore enhances the mechanical properties of the product. Dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), and tensile tests were performed to study the miscibility and mechanical properties of the blends. Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) were used to reveal the molecular structural, and molecular weight changes of PLLA and PHBV after melt mixing with zinc acetate. SEM and FTIR results have clearly shown that the PLLA-PHBV copolymer generated from transesterification reaction acted as a compatibilizer and therefore resulted in an improved interfacial miscibility and ductility of PLLA/PHBV blend. In our mechanistic study, a competition between the PLLA/PHBV transesterification reaction and the thermal decomposition of PHBV was identified for the first time. On the basis of these observations, a new mechanism of transesterification reaction was proposed

Geochronology, Whole-Rock Geochemistry, and Sr–Nd–Hf Isotopes of Granitoids in the Tongshanling Ore Field, South China: Insights into Cu and W Metallogenic Specificity

The Qin-Hang Metallogenic Belt (QHMB), an important metallogenic belt in South China, hosts Cu and W–Sn polymetallic deposits. The Tongshanling ore field in the QHMB is characterized by the coexistence of Cu- and W-bearing polymetallic deposits, which are related to granodiorite and granite porphyry. This study examined whole-rock geochemistry, geochronology, and Sr–Nd–Hf isotopes to determine the genetic relationship between diverse ore-related granitoids (i.e., granodiorite and granite porphyry) and Cu–W metallogeny in the Tongshanling ore field. Zircon LA-ICP-MS U–Pb dating shows that the granodiorite and granite porphyry in the Tongshanling ore field were emplaced at 163.7 ± 0.4 Ma to 154.7 ± 0.6 Ma and 161.1 ± 0.3 Ma, respectively. Geochemically, the granodiorites are classified as oxidized I-type, while the highly evolved granite porphyry is reduced A-type. The Lu–Hf isotopic composition of the granodiorites is characterized by εHf(t) values ranging from –10.49 to –4.99 (average = –7.17), with corresponding TDMC ages ranging from 1524 to 1877 Ma (average = 1682 Ma). In contrast, the granite porphyry has higher εHf(t) values (–3.60 to –1.58, average = –2.78) and younger TDMC (1310–1438 Ma, average = 1387 Ma). The εNd(t) values of granodiorite are −8.06 to −7.37 and the two-stage model ages (TDM2) are 1543–1598 Ma, while the granite porphyry has higher εNd(t) values (−3.0 to −3.4) and younger TDM2 ages (1195–1223 Ma). The results show that the granodiorite and granite porphyry were formed from partial melting of different Mesoproterozoic basement rocks under varying degrees of crust–mantle interaction. Granite porphyry underwent well-recorded fractional crystallization. Compared to the Cu-forming granodiorite, the W-forming granite porphyry has a higher differentiation index, higher crystallization temperatures of zircon (average = 708 °C versus 631 °C), and lower oxygen fugacity (median ΔFMQ = –2.21 versus –1.77)