Search

Distributed generators are being widely integrated into China’s urban distribution network unevenly, which accounts for different load rates of distribution transformer cluster in spatial dimension and low net load simultaneity rate in temporal dimension. Therefore, it is necessary to carry out flexible dispatching for the distribution transformer cluster in active distribution network to effectively reduce the grid loss. Different from the existing research on dynamic reconfiguration of the network supplied by a single transformer or a single feeder, the grid loss of distribution transformer cluster is optimized in the paper. Firstly, a 0-1 integer optimization model is established. The model is characterized by calculating the total grid loss of distribution transformer cluster based on the connectivity of power supply path and considering the spatio-temporal constraints such as total change times of switches. Secondly, uncertainty of renewable energy output is considered with k-means clustering algorithm effectively. The reduced scenarios are used for flexible dispatching simulation. Then, the discrete monkey algorithm, characterized by the cross iteration of local optimization and global search, is improved for solving 0-1 integer programming problem. The improved method can deal with the temporal coupling constraints in the model. Finally, the effectiveness of the proposed method is identified by case study. Flexible dispatching of distribution transformer cluster can greatly reduce the grid loss of active distribution network, and the optimal dispatching scheme will change along with the change of distributed generator output.

Piezoelectric catalysis (piezocatalysis) is a physical/chemical process that utilizes piezoelectric potential for accelerating chemical reactions, in which ubiquitous mechanical energies in nature are used for various catalysis applications, e.g., treating organic water pollutants. Despite the high efficiency achieved by piezocatalytic powders, the particles used tend to diffuse in water systems and are hard to be separated, thus causing secondary pollution. Herein, a free‐standing piezocatalytic foam is designed and fabricated, which is composed of BaTiO3 nanoparticles embedded in the PVDF scaffold. The as‐prepared PVDF–BaTiO3 composite foam demonstrates outstanding piezocatalytic efficiency in removing aqueous organics among state‐of‐the‐art integral piezocatalytic platforms, which lie in the synergy of piezoelectric materials and abundant interconnected pores within the foam. Significantly, PVDF–BaTiO3 foam is further applied for purifying natural water samples, by which the permanganate index of the water sample reduces by nearly 30% after 2 h of treatment. In addition, as a monolithic platform, PVDF–BaTiO3 foam is easy to be collected, with high reuse stability and applicability for treating various pollutants, resulting in dominant advantages over powder‐based systems for practical high‐flux wastewater treatment. Herein, a piezocatalytic platform is provided for the effective degradation of organic pollutants in water, with minimal environmental side effects.

Advances in neural electrode technologies can have a significant impact on both fundamental and applied neuroscience. Here, we report the development of flexible and biocompatible neural electrode arrays based on a nanopaper substrate. Nanopaper has important advantages with respect to polymers such as hydrophilicity and water wettability, which result in significantly enhanced biocompatibility, as confirmed by both in vitro viability assays and in vivo histological analysis. In addition, nanopaper exhibits high flexibility and good shape stability. Hence, nanopaper-based neural electrode arrays can conform to the convoluted cortical surface of a rat brain and allow stable multisite recording of epileptiform activity in vivo. Our results show that nanopaper-based electrode arrays represent promising candidates for the flexible and biocompatible recording of the neural activity.

The outbreak of the Covid-19 pandemic has aroused tremendous attention toward personal protective equipment (PPE) in both scientific research and industrial manufacture. Despite decades of development in PPE design and fabrication, there's still much room for further optimization, in terms, of both protection performance and wear comfort. Interdisciplinary efforts have been devoted to this research field in recent years. Significantly, the innovation of materials, which brings about improved performance and versatile new functions for PPEs, has been widely adopted in PPE design. In this minireview, recent progress in the development of novel materials and structural designs for PPE application are presented in detail with the introduction of various material-based strategies for different PPE types, as well as the examples, which apply auxiliary components into face masks to enrich the functionalities and improve the personal feelings in the pandemic period., Graphical abstract Image 1

Integrating electronics in clothing is a significant milestone of wearable technology. The priority is to develop flexible interconnector with great washability, durability and comfort wearability. In this work, we reported an air-permeable and machine-washable Cu/Ni interconnector based on highly flexible fibrous polyimide (FPI) membrane. Benefiting from the porous merit of FPI membrane and robust parylene encapsulation, the novel interconnector presents excellent conductivity (14 mΩ/sq), decent air-permeability (11 KPa*s/m) and superior electromechanical stability after abrasion of 50,000 cycles, bending of 10,000 cycles, and machine washing of 50 times. Moreover, assemblies made from the FPI-based circuit board not only show desirable lifespan in harsh environments, including seawater, ice, boiled water, and heavy rain, but also can be woven into fabrics for broad wearable applications. The work presents a facile and effective method to fabricate highly flexible, comfortable and durable interconnector, guaranteeing the reliability for long-term wearable application and showing great possibility for high-throughput production.

Tarkista embargo, kun artikkeli julkaistu. Flexible electronics that can form tight interfaces with neural tissues hold great promise for improving the diagnosis and treatment of neurological disorders and advancing brain/machine interfaces. Here, the facile fabrication of a novel flexible micropillar electrode array (µPEA) is described based on a biotemplate method. The flexible and compliant µPEA can readily integrate with the soft surface of a rat cerebral cortex. Moreover, the recording sites of the µPEA consist of protruding micropillars with nanoscale surface roughness that ensure tight interfacing and efficient electrical coupling with the nervous system. As a result, the flexible µPEA allows for in vivo multichannel recordings of epileptiform activity with a high signal-to-noise ratio of 252 ± 35. The ease of preparation, high flexibility, and biocompatibility make the µPEA an attractive tool for in vivo spatiotemporal mapping of neural activity.

Subdural surface and penetrating depth probes are widely applied to record neural activities from the cortical surface and intracortical locations of the brain, respectively. Simultaneous surface and depth neural activity recording is essential to understand the linkage between the two modalities. Here, we develop flexible dual-modality neural probes based on graphene transistors. The neural probes exhibit stable electrical performance even under 90° bending because of the excellent mechanical properties of graphene, and thus allow multi-site recording from the subdural surface of rat cortex. In addition, finite element analysis was carried out to investigate the mechanical interactions between probe and cortex tissue during intracortical implantation. Based on the simulation results, a sharp tip angle of π/6 was chosen to facilitate tissue penetration of the neural probes. Accordingly, the graphene transistor-based dual-modality neural probes have been successfully applied for simultaneous surface and depth recording of epileptiform activity of rat brain in vivo. Our results show that graphene transistor-based dual-modality neural probes can serve as a facile and versatile tool to study tempo-spatial patterns of neural activities.

Controlled synthesis of hierarchically assembled titanium dioxide (TiO2) nanostructures is important for practical applications in environmental purification and solar energy conversion. We present here the fabrication of interconnected TiO2 nanotubes as a macroscopic bulk material by using a porous carbon nanotube (CNT) sponge as a template. The basic idea is to uniformly coat an amorphous titania layer onto the CNT surface by the infiltration of a TiO2 precursor into the sponge followed by a subsequent hydrolysis process. After calcination, the CNTs are completely removed and the titania is simultaneously crystallized, which results in a porous macrostructure composed of interconnected anatase TiO2 nanotubes. The TiO2 nanotube macrostructures show comparable photocatalytic activities to commercial products (AEROXIDE TiO2 P25) for the degradation of rhodamine B (RhB). Moreover, the TiO2 nanotube macrostructures can be settled and separated from water within 12 h after photocatalysis, whereas P25 remains suspended in solution after weeks. Thus the TiO2 nanotube macrostructures offer the advantage of easy catalyst separation and recycle and can be a promising candidate for wastewater treatment.

In this study, we report the polymer-based graphene foams through combination of bottom-up assembly and simple triaxially buckled structure design. The resulting polymer-based graphene foams not only effectively transfer the functional properties of graphene, but also exhibit novel negative Poisson’s ratio (NPR) behaviors due to the presence of buckled structure. Our results show that after the introduction of buckled structure, improvement in stretchability, toughness, flexibility, energy absorbing ability, hydrophobicity, conductivity, piezoresistive sensitivity and crack resistance could be achieved simultaneously. The combination of mechanical properties, multifunctional performance and unusual deformation behavior would lead to the use of our polymer-based graphene foams for a variety of novel applications in future such as stretchable capacitors or conductors, sensors and oil/water separators and so on.

Fault recovery of distribution network is realized by operating switches to change topological structure of the network. The final destination of fault recovery is power loss minimization, fault isolation and power load transfer. This article has built the mathematical model of fault recovery considering constraints of node voltage, line capacity and power flow balance. The objective function is power loss reduction. Further, the genetic algorithm is used to solve the proposed model. The optimal network structure and recovered power load could be derived through calculation. Finally, the author complied the program with Matlab and tested it on the IEEE33 bus system. The simulation and analysis results have verified the effectiveness of the proposed method. DOI : http://dx.doi.org/10.11591/telkomnika.v12i3.4567 Full Text: PDF

Smart distribution grid is the important part of smart grid which connects the main network with users. It is directly user oriented and the center of power distribution. This article has compared the smart distribution grid with regular traditional distribution network. Crucial techniques including automation technology, Informationization technology and interaction are the emphasis of discussion. The results have indicated that researches on advanced electric equipment, online monitoring, self healing, advanced metering infrastructure, integrated communication, micro gird and other technologies would be the principal directions of study on smart distribution grid, simultaneously providing reference for realization of practical application in future. KeywordsSmart distribution grid; Automation technology; Informationization technology; Interaction technology

This article has summarized the developing history of distribution automation technology and analyzed existing problems that hinder its practical application. Currently the automation level of the distribution network in our country is very low reflecting as insufficient and immature functions. The research results have shown that the development of distribution automation will be focused on diversification, integration and intellectualization. Considering the intimate connection with smart grid, the article has pointed out the further development trends of distribution automation. Keywordsdistribution automation; smart grid; development trend.