Search

Uncovering the community structure hidden in networks is crucial for understanding the function of networks. In this paper, an algorithm of biogeography-based optimization with consensus dynamics for community detection is proposed. The problems of seeking community structures in networks are exquisitely embedded into the framework of biogeography-based optimization. Hence the community structure unveiled in such an evolutionary and global manner is corresponding to the habitat with maximum modularity. We present a dynamical framework for generating initial distribution of solutions for the evolutionary process using consensus dynamics, which gives a reasonably good estimate of the community structure based on the topological information. Thereof, the proposed dynamical method of initialization promotes the efficiency of optimal solution search significantly, compared with the traditional random initialization. Then, the obtained partition is refined using biogeography-based optimization. In addition, a preferential selection strategy for generating the new solutions is developed based on local network topology. Furthermore, we also proposed an adaptive mutation operator that enhances the exploration ability of our evolutionary algorithm. The experimental results on both artificial random and real-world networks indicate the effectiveness and reliability of our algorithm. These findings shed new light on the role played by topological knowledge of networks extracted from consensus dynamics in the evolving optimization processes when finding complex mesoscale structures in networks such as community structure. • We unveil community structure via consensus and biogeography-based optimization. • We use consensus dynamics on networks to weave an estimate of solutions. • A preferential selection strategy via local network topology is developed. • An adaptive mutation operator promoting the exploration ability is proposed. • The developed algorithms operate on real-world and artificial random networks. [ABSTRACT FROM AUTHOR]

Control of convection plays an important role in heat transfer regulation, bio/chemical sensing, phase separation, etc. Current convection controlling systems generally depend on engineered energy sources to drive and manipulate the convection, which brings additional energy consumption into the system. Here the use of human hand as a natural and sustainable infrared (IR) radiation source for the manipulation of liquid convection is demonstrated. The fluid can sense the change of the relative position or the shape of the hand with the formation of different convection patterns. Besides the generation of static complex patterns, dynamic manipulation of convections can also be realized via moving of hand or finger. The use of such sustainable convections to control the movement of a floating "boat" is further achieved. The use of human hands as the natural energy sources provides a promising approach for the manipulation of liquid convection without the need of extra external energy, which may be further utilized for low‐cost and intelligent bio/chemical sensing and separation. [ABSTRACT FROM AUTHOR]

[Display omitted] Films with nanoengineered surfaces have found extensive utilization in versatile applications, such as freshwater harvesting, water purification, steam generation and thermal energy management. Herein, we develop a liquid metal (LM) nanoporous film on a copper substrate via a simple and scalable bubble-induced self-assembly method. The LM nanoporous film not only provides abundant nucleation sites of bubbles due to nanoscale pores, but also generates CuGa 2 intermetallic compound (IMC) as a thermal interface layer with low interfacial resistance due to in situ alloying with the copper substrate. When the film is used in ethanol-based boiling system, it shows a 172% enhanced heat transfer coefficient compared to the pristine copper. In addition, the metallic wetting force between the LM nanoporous film and CuGa 2 IMC results in a durable nanoporous film. When the LM nanoporous film is utilized for the phase-change thermal energy management of a high-power-density light emitting diode, it leads to a distinct decrease in temperature by 20.7 ℃ relative to the pristine copper. This work provides a strategy to combine nanoengineered surfaces with interface engineering to enhance phase-change heat transfer, which can result in efficient energy transport in various energy-related applications. [ABSTRACT FROM AUTHOR]

We investigate the explosive synchronization in networks with core-periphery structure. The effects of different patterns of core-periphery networks on explosive synchronization are studied by altering network structural parameters. With the variation of two core-periphery structural parameters, the relative connection strength between core and peripheral nodes, and the relative connection strength among peripheral nodes, we find distinct roles played by structural parameters in the path toward explosive synchronization. Our results show that the order parameter of periphery is closer to that of the core in the synchronization phase with the increment of connections between core and peripheral nodes. In addition, we find that sparser the connections among peripheral nodes are, the easier the whole dynamic network is to reach explosive synchronization. We also discover that if the number of connections between core and periphery scales vary sublinearly with the network size, there exists a novel two-jump behavior of the order parameter of the whole network. Moreover, as the level of the sublinearity increases, the order parameter starts to oscillate in a decaying manner, rather than being increasing monotonically and slowly as in the case of normal explosive synchronization when the coupling strength exceeds a critical threshold. Hence in this regime, it becomes increasingly difficult for the network to maintain stable explosive synchronization even though the underlying network topology is connected. [ABSTRACT FROM AUTHOR]

[Display omitted] • A W-Cu vapor chamber (VC) improves thermal management systems at high temperature. • A Cu coating layer enhances bonding strength with wick and isolates working medium. • The lateral thermal conductivity of W-Cu VC is ~1700 W/(m∙K) under 1.6 kW/cm2. • The W-Cu VC reduces the thermal stress at the interface between the VC and chip. The electronic industry is facing pressing needs for cooling system with high-performance in heat transfer and matched coefficient of thermal expansion (CTE) with the chips. Metal composite materials (MCMs) with low CTE can be used in cooling chips to overcome the thermal expansion mismatch between the cooling substrate and chips. However, low thermal conductivity of MCMs limits their application in electronic cooling systems. Increasing the percentage of components with high thermal conductivity can enhance the thermal conductivity of MCMs, but it often leads to increase CTE as well. Here, we demonstrate that vapor–liquid phase change can improve the heat transfer performance of tungsten-copper (W-Cu) alloy-based MCMs while maintain their low CTEs. Such strategy reduces the maximum temperature and thermal resistance of MCMs, and also allows for heat spreading from concentrated heat source with high power density. The W-Cu alloy-based vapor chamber (VC) has low thermal resistance of 0.38 K/W at 100 W and high lateral thermal conductivity of ~1727 W/(m·K). The W-Cu alloy-based VC can be readily integrated with the chip and heat sink to serve as cooling substrates for dissipating the heat and simultaneously lowering the thermal expansion mismatch by using its high thermal conductivity and low CTE. [ABSTRACT FROM AUTHOR]

We consider the problem of seeking communities in directed networks. The common approach to this problem has been to simply ignore directions of edges and use algorithms developed for community detection in undirected networks, but this approach discards potentially indispensable information involved in the directions of edges. Here, we introduce an index for node dissimilarity in directed networks in the perspective of dynamics, which are driven by a novel parameter-free signal copying model, to incorporate information contained in the directions of edges. Our dissimilarity index gives a natural fusion between the local and global viewpoints of topological structure of directed networks. Thereby, we apply our index to uncover community structure in directed networks and conduct extensive experiments on synthetic and real-world ones. The results demonstrate that our method outperforms state-of-the-art methods. [ABSTRACT FROM AUTHOR]

• We generate a stably self-dispersed crumpled graphene/water nanofluid at 100 °C. • The nanofluid enhances the heat transfer coefficient by 89.1% over deionized water. • The enhancement is due to the porous structure generated by self-assembly. Boiling can induce the self-assembly of nanomaterials in nanofluids to generate reliable micro/nanostructures for enhancing boiling heat transfer. The practical applications of most nanofluids in boiling, however, are limited by the poor thermal stability at the boiling point, and improving the thermal stability of nanofluids at such high temperature is challenging. Here, we demonstrate that the crumpled graphene can remain uniformly and stably dispersed within deionized water at the boiling point of 100 °C due to its highly wrinkled structure, while self-assembling to generate a porous structure on the substrate during boiling. Such porous structure can vary the surface micromorphology, wettability and roughness, which increases the nucleation sites and departure frequency of bubbles, thus effectively enhancing the critical heat flux and the maximum heat transfer coefficient by 80.7 and 89.1% compared to the pristine copper substrate, respectively. This in situ boiling-induced self-assembly provides a facile and low-cost strategy to achieve high-performance boiling heat transfer for a wide variety of nanomaterials. The crumpled graphene/water nanofluid used can be directly utilized as a phase change working medium in boiling systems to harvest thermal energy and generate clean steam. [Display omitted] [ABSTRACT FROM AUTHOR]

Gel electrolyte composite with high areal capacity cathode effectively improves battery energy density and safety. Still, the insufficient interface contact between electrolyte and electrode limits the capacity release inside the thick cathode. Here, we rationally design a self-supporting cathode and use the in-situ polymerization method to integrate the gel electrolyte with the cathode. This cathode can effectively reduce the content of inactive electrode components. Meanwhile, the design of the regularly-arranged pore structure of the cathode introduced by laser texturing facilitates the penetration of the prepolymer solution and enables outstanding lithium-ion transport. Notably, the quasi-solid LiFePO 4 /Li half-cell with active material loading of 8 mg cm−2 exhibits good electrochemical performance (118.5 mAh g−1 after 100 cycles at 0.2C at room temperature). Moreover, when the loading of active materials increases to 30 mg cm−2, the LiFePO 4 /Li 4 Ti 5 O 12 full-cell can still have a relatively high discharge capacity (105.9 mAh g−1 after 400 cycles at 0.2C at room temperature). It is worth noting that the quasi-solid pouch cell prepared by in-situ polymerization has a certain flexibility, indicating that this strategy has application potential in flexible electronic devices. [Display omitted] • Flexible quasi-solid batteries enabled by in-situ polymerization and laser drilling. • Full cell with high loading (30 mg cm−2) exhibits 105.9 mAh g−1 after 400 cycles. • Quasi-solid punch cell with a capacity of 3.27 mAh cm−2 exhibits good flexibility. • DRT analysis was used to analyze the internal impedance distribution of the battery. [ABSTRACT FROM AUTHOR]

[Display omitted] • A bottom-up strategy for producing isotropic liquid metal network in polymer. • Liquid metal composites can be applied for high-performance thermal management. • The approach is applicable for various liquid metal filler of different viscosity. • Thermal conductivity was controlled by volume fraction of filler and size of TPE. • A high intrinsic thermal conductivity (up to 32.71 W/mK) was obtained. This work presents a bottom-up approach to construct an isotropic network of liquid metal in polymer, and such generated isotropic liquid metal network brings large enhancement on the thermal and electrical conductivity of the composite for 3D thermal management. The building blocks are composed of polymer particles coated with liquid metal. The liquid metal starts to flow and fill the gaps between the polymer particles, and fuses with each other to assemble into a continuous liquid metal network in the polymer matrix under the mechanical load during heating. The continuous filler network provides effective paths for thermal and electrical conduction, and thus enhances the thermal and electrical conductivity of the composites. Using biphasic copper-eutectic gallium indium as the filler, we generated polymer composites with thermal conductivity as high as 32.71 W/m·K (90 vol%; under compression) and electrical conductivity up to 1.18 × 106 S/m. Moreover, the measurement of the in-plane and cross-plane thermal diffusivity reveals the isotropic enhancement of thermal conductivity in such composites, which may help expand the potential application of these composites in 3D thermal management, flexible electronics, energy conversion and soft robotics. [ABSTRACT FROM AUTHOR]

• Fabrication of thick low-tortuosity self-supporting cathodes by laser drilling. • Laser-drilled cathodes exhibit high areal capacity and good capacity retention. • The microchannels contribute to the capacity release of the cathodes. • The amorphous carbon layer on the channel walls constructs a stable CEI film. A thick electrode with high areal capacity is a promising way to improve the energy density of batteries, but the development of a thick electrode is limited by poor mechanical stability and sluggish ion and electron transport. Here, we design a self-supporting cathode that consists of cellulose nanofibers, multi-walled carbon nanotubes, and lithium iron phosphate (LFP), and introduce a uniform microchannel structure to the cathode by laser drilling technology. The cellulose nanofibers and multi-walled carbon nanotubes construct a conductive network. The microchannel structure enables outstanding ion and electron transport and significantly improves the rate capability of the electrode. Meanwhile, the local heat by the laser produces an amorphous carbon layer on the inner surface of the microchannel, which helps form a stable cathode-electrolyte interface and enhances the capacity retention of the thick electrode. Notably, the drilled thick cathode with an LFP load of 40 mg cm−2 and an areal capacity of 5.33 mAh cm−2 exhibits substantially improved cycling stability at 0.5C than the undrilled samples. This work demonstrates a promising design concept for thick electrodes to high-performance energy storage devices. [ABSTRACT FROM AUTHOR]