Security Defense of Large Scale Networks Under False Data Injection Attacks: An Attack Detection Scheduling Approach

In large scale networks, communication links between nodes are easily injected with false data by adversaries, so this paper proposes a novel security defense strategy to ensure the security of the network from the perspective of attack detection scheduling. Compared with existing attack detection methods, the attack detection scheduling strategy in this paper only needs to detect half of the neighbor node information to ensure the security of the node local state estimation. We first formulate the problem of selecting the sensor to be detected as a combinatorial optimization problem, which is Nondeterminism Polynomial hard (NP-hard). To solve the above problem, we convert the objective function into a submodular function. Then, we propose an attack detection scheduling algorithm based on sequential submodular maximization, which incorporates expert problem to better cope with dynamic attack strategies. The proposed algorithm can run in polynomial time with a theoretical lower bound on the optimization rate. In addition, the proposed algorithm can guarantee the security of the whole network under two kinds of insecurity conditions from the perspective of the augmented estimation error. Finally, a numerical simulation of the industrial continuous stirred tank reactor verifies the effectiveness of the developed approach

Electrical and thermal transport properties of kagome metals AV3_3Sb5_5 (A=K, Rb, Cs)

The interplay between lattice geometry, band topology and electronic correlations in the newly discovered kagome compounds AV$_3$Sb$_5$ (A=K, Rb, Cs) makes this family a novel playground to investigate emergent quantum phenomena, such as unconventional superconductivity, chiral charge density wave and electronic nematicity. These exotic quantum phases naturally leave nontrivial fingerprints in transport properties of AV$_3$Sb$_5$, both in electrical and thermal channels, which are prominent probes to uncover the underlying mechanisms. In this brief review, we highlight the unusual electrical and thermal transport properties observed in the unconventional charge ordered state of AV3Sb5, including giant anomalous Hall, anomalous Nernst, ambipolar Nernst and anomalous thermal Hall effects. Connections of these anomalous transport properties to time-reversal symmetry breaking, topological and multiband fermiology, as well as electronic nematicity, are also discussed. Finally, a perspective together with challenges of this rapid growing field are given.Comment: 34 pages,9 figures,an review article published in Tungsten 5,300(2023

A van der Waals pn heterojunction with organic/inorganic semiconductors

van der Waals (vdW) heterojunctions formed by two-dimensional (2D) materials have attracted tremendous attention due to their excellent electrical/optical properties and device applications. However, current 2D heterojunctions are largely limited to atomic crystals, and hybrid organic/inorganic structures are rarely explored. Here, we fabricate hybrid 2D heterostructures with p-type dioctylbenzothienobenzothiophene (C8-BTBT) and n-type MoS2. We find that few-layer C8-BTBT molecular crystals can be grown on monolayer MoS2 by vdW epitaxy, with pristine interface and controllable thickness down to monolayer. The operation of the C8-BTBT/MoS2 vertical heterojunction devices is highly tunable by bias and gate voltages between three different regimes: interfacial recombination, tunneling and blocking. The pn junction shows diode-like behavior with rectifying ratio up to 105 at the room temperature. Our devices also exhibit photovoltaic responses with power conversion efficiency of 0.31% and photoresponsivity of 22mA/W. With wide material combinations, such hybrid 2D structures will offer possibilities for opto-electronic devices that are not possible from individual constituents.Comment: 16 pages, 4 figure

Multiband effects in thermoelectric and electrical transport properties of kagome superconductors AAV3_3Sb5_5 (AA = K, Rb, Cs)

We studied the effects of multiband electronic structure on the thermoelectric and electrical transport properties in the normal state of kagome superconductors $A$V$_3$Sb$_5$ ($A$ = K, Rb, Cs). In all three members, the multiband nature is manifested by sign changes in the temperature dependence of the Seebeck and Hall resistivity, together with sublinear response of the isothermal Nernst and Hall effects to external magnetic fields in the charge ordered state. Moreover, ambipolar transport effects appear ubiquitously in all three systems, giving rise to sizable Nernst signal. Finally, possible origins of the sign reversal in the temperature dependence of the Hall effect are discussed.Comment: 8 pages, 5 figures. To appear in New Journal of Physic

Charge fluctuations above TCDWT_\mathrm{CDW} revealed by glasslike thermal transport in kagome metals AAV3_3Sb5_5 (AA = K, Rb, Cs)

We present heat capacity, electrical and thermal transport measurements of kagome metals $A$V$_3$Sb$_5$ ($A$ = K, Rb, Cs). In all three compounds, development of short-range charge fluctuations above the charge density wave (CDW) transition temperature $T_\mathrm{CDW}$ strongly scatters phonons via electron-phonon coupling, leading to glasslike phonon heat transport, i.e., phonon thermal conductivity decreases weakly upon cooling. Once the long-range charge order sets in below $T_\mathrm{CDW}$, short-range charge fluctuations are quenched, and the typical Umklapp scattering dominated phonon heat transport is recovered. The charge-fluctuations-induced glasslike phonon thermal conductivity implies sizable electron-phonon coupling in $A$V$_3$Sb$_5$.Comment: 8 pages, 5 figure

Multiferroic Magnon Spin-Torque Based Reconfigurable Logic-In-Memory

Magnons, bosonic quasiparticles carrying angular momentum, can flow through insulators for information transmission with minimal power dissipation. However, it remains challenging to develop a magnon-based logic due to the lack of efficient electrical manipulation of magnon transport. Here we present a magnon logic-in-memory device in a spin-source/multiferroic/ferromagnet structure, where multiferroic magnon modes can be electrically excited and controlled. In this device, magnon information is encoded to ferromagnetic bits by the magnon-mediated spin torque. We show that the ferroelectric polarization can electrically modulate the magnon spin-torque by controlling the non-collinear antiferromagnetic structure in multiferroic bismuth ferrite thin films with coupled antiferromagnetic and ferroelectric orders. By manipulating the two coupled non-volatile state variables (ferroelectric polarization and magnetization), we further demonstrate reconfigurable logic-in-memory operations in a single device. Our findings highlight the potential of multiferroics for controlling magnon information transport and offer a pathway towards room-temperature voltage-controlled, low-power, scalable magnonics for in-memory computing

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Automatic Concept Extraction Based on Semantic Graphs From Big Data in Smart City

With the rapid development of smart cities, various types of sensors can rapidly collect a large amount of data, and it becomes increasingly important to discover effective knowledge and process information from massive amounts of data. Currently, in the field of knowledge engineering, knowledge graphs, especially domain knowledge graphs, play important roles and become the infrastructure of Internet knowledge-driven intelligent applications. Domain concept extraction is critical to the construction of domain knowledge graphs. Although there have been some works that have extracted concepts, semantic information has not been fully used. However, the excellent concept extraction results can be obtained by making full use of semantic information. In this article, a novel concept extraction method, Semantic Graph-Based Concept Extraction (SGCCE), is proposed. First, the similarities between terms are calculated using the word co-occurrence, the LDA topic model and Word2Vec. Then, a semantic graph of terms is constructed based on the similarities between the terms. Finally, according to the semantic graph of the terms, community detection algorithms are used to divide the terms into different communities where each community acts as a concept. In the experiments, we compare the concept extraction results that are obtained by different community detection algorithms to analyze the different semantic graphs. The experimental results show the effectiveness of our proposed method. This method can effectively use semantic information, and the results of the concept extraction are better from domain big data in smart cities. IEEEThis work was supported in part by the National Key Research and Development Plan under Grant 2018YFB0803504 and Grant 2018YEB1004003, in part by the Guangdong Province Key Research and Development Plan under Grant 2019B010137004, in part by the National Natural Science Foundation of China under Grant 61871140, Grant 61872100, Grant 61572153, and Grant U1636215, and in part by the Peng Cheng Laboratory Project of Guangdong Province under Grant PCL2018KP004.Scopu

Patterns of diversity and community assembly change across local to regional scales: An evidence of deterministic assembly processes along resource availability gradient at temperate forest

Diversity and its maintaining mechanism (community assembly) shift along resource availability gradients at local and regional levels. It is necessary to identify key natural factors shaping community assembly or diversity patterns, so that understanding the patterns of diversity and assembly along these factors across local to regional scales. In this study, we investigated the six local sites of plant community in Qinling Mountains region. Based on the relative importance of environmental factors in shaping the phylogenetic diversity, a complex resource availability gradient was established to assess taxonomic and phylogenetic diversity and assembly patterns along it at local or regional scale separately. Phylogenetic analyses and the biodiversity index were estimated along environmental gradients as well, to assess the difference between change tendencies along natural environmental and resource availability gradients. We found that 1) elevation was the most important regional-scale environmental predictor of phylogeny of community; 2) taxonomic and phylogenetic diversity studies showed similar patterns along both resource and elevational gradients at regional scale, and that diversity at local scale may differ regardless of gradients; 3) at the regional level, phylogenetic structures revealed convergent tendencies along the elevational gradient across different species pools. Phylogenetic assembly patterns along the elevation gradient at the local scale differed from the patterns at the regional scale, with consistent clustering tending to overspread along the resource availability gradient. In conclusion, resource availability shaped community assembly at the regional level. Local patterns of diversity influenced regional patterns differently because of variation in the colonization history or assembly process. Owing to varying assembly patterns along simple environmental gradients, it is vital to establish a complex resource availability gradient to dissect the real assembly mechanism or biodiversity patterns operating in local to regional-scale processes. These findings may provide valuable reference about forest restoration and management

Tuning Stoichiometry for Enhanced Spin‐Charge Interconversion in Transition Metal Oxides

Abstract Interconversion of spin and charge current provides a key route for low‐power spin memory and logic devices. Recent advances have revealed efficient spin‐charge interconversion in 4d and 5d transition metal oxides. However, the strategies to tune the conversion efficiency, essential for the generation and detection of spin‐current, are limited to engineering the crystalline structure of oxides. Here, a simple and broadly applicable approach by tuning the cation stoichiometry is reported. In the model system of 5d perovskite SrIrO3, it is shown that a significant Ir cation deficiency is induced by controlling the oxygen partial pressure during deposition. This off‐stoichiometry leads to an enhancement of the spin‐to‐charge conversion efficiency by around three times, accompanied by an increase of electrical resistivity at room temperature. Furthermore, a significant increase of inverse spin Hall voltage is observed by implementing the Ir‐deficient SrIr1‐xO3, highlighting the promising role of atomic defects in developing oxides for sensitive spin‐current detection. This work opens a new pathway to engineer the spin‐charge interconversion efficiency in oxides and offers new opportunities to integrate complex oxides in energy‐efficient spintronic devices