University of Science and Technology Beijing

About: University of Science and Technology Beijing is a education organization based out in Beijing, China. It is known for research contribution in the topics: Microstructure & Alloy. The organization has 41558 authors who have published 44473 publications receiving 623229 citations. The organization is also known as: Beijing Steel and Iron Institute.

Preparation of metallic coatings on polymer matrix composites by cold spray

Abstract: In the present work, an Al metallic coating and an Al/Cu bimetallic coating were prepared on the surface of a carbon fiber-reinforced polymer matrix composite (PMC) using a cold spray system with nitrogen as process and powder carrier gas. The microstructure, microhardness, and bond strength of the resultant coatings are analyzed. The bonding mechanism of the coatings, especially the deposition behavior of the Al particles on the PMC surface is discussed. Results had shown that cold spraying enables the deposition of the metallic and bimetallic coatings directly onto the PMC surface with precise process control and reasonable bonding of feedstock and substrate material. The surface metallization of PMC via cold spraying process presents promising application prospects.

Recent Developments in Graphene-Based Tactile Sensors and E-Skins

Abstract: DOI: 10.1002/admt.201700248 intelligence, healthcare monitoring, artificial prosthesis, and human–machine interaction electronics.[1–4] Human skin, served as the largest sensory organ in human body, can help us communicate with surroundings such as the contacted pressures, changed temperatures, shapes, and textures of touched objects, via the specialized sense receptors.[5,6] For an intact haptic system, the collected information will be sent to the central nervous systems for comprehending and processing the meaning of the received information, and then our body will be guided to respond to the physical contact successfully. To imitate the sophisticated perception of human skin, various kinds of functional electronic devices which can sense and distinguish external physical, chemical, and biological signals simultaneously are integrated in a flexible or elastic system likes human skin. The functional electronic devices including pressure sensor, temperature sensor, and humidity sensor[7–9] have the ability to transfer the generated information from physical signals into electrical signals that electronic devices can recognize.[10–12] However, there remains enormous challenges to construct E-skins with multimodal detection, fleet response, high sensitivity and resolution, even though much research has been reported on the imitation of human skin behaviors recently. The rise of E-skins in early years may be resulted from the inspiration of science fiction and movies, which builds a bridge between virtual imagination and scientific reality. Since a prosthetic hand with tactile feedback was demonstrated by Clippinger et al. in 1974,[13] several studies have been followed to explore the potential application of tactile bionics.[14–16] Especially, flexible electronics achieved significant progress which served as a foundation to construct E-skins, due to the particular importance of mechanical compliance and highly sensitive characteristics in mimicking human skin.[17–21] For examples, Rogers and co-workers developed flexible electronics technologies to transfer traditional Si electronic devices onto 100 nm ultrathin films connected by stretchable interconnects.[22,23] Someya and co-workers integrated a large-scale organic fieldeffect transistors (FETs) based on flexible pentacene which showed excellent pressure sensitivity.[24] Bao and coworkers developed novel self-healing and mechanical force sensing E-skins with microstructured elastomeric dielectrics.[25–27] In addition, piezoresistive, capacitive, and piezoelectric sensors are deemed as three major transduction mechanisms for the Human skin, the largest organ of human body, can perceive tactile sensations, temperature, humidity, and other complex environmental stimulations. To mimic the capabilities of human skin, graphene provides great potential in building wearable electronic skins (E-skins), which hold broad applications in advanced robotics, healthcare monitoring, artificial intelligence, human– machine interfaces, etc. Herein, the recent progress in flexible tactile sensors and E-skins based on graphene material is presented. A brief introduction of the main approaches to prepare graphene nanosheets is provided. The main developments on the functions and mechanisms of bionic functional devices in E-skins including tactile sensors, temperature sensors, and humidity sensors are then highlighted. The current and future applications for graphenebased E-skins, such as multifunctional biomimetic E-skins, healthcare monitoring, and interactive human–machine interface, are also described. Finally, the existing challenges and future development trends for graphenebased E-skins are discussed.

Fair Resource Allocation in an Intrusion-Detection System for Edge Computing: Ensuring the Security of Internet of Things Devices

Abstract: The recent trend of edge computing extends cloud computing and the Internet of Things (IoT) to the edge of the network. Similar to most systems, an intrusion-detection system (IDS) is commonly used to mitigate cybersecurity threats in edge computing. Due to the limitations in edge nodes (e.g., in terms of computational and storage capabilities), efficient and fair resource allocation within an IDS is challenging. This article studies IDS architecture and resource allocation in edge computing. Specifically, the proposed system is designed to facilitate multiple resources sharing and heterogeneous resource-demanding allocation. A general edge computing IDS architecture is presented, and we use this as the basis for our model for allocating resources. Then, a single-layer dominant and max-min fair (SDMMF) allocation is used, which has been theoretically proven to satisfy all hierarchical resource allocation properties, and a multilayer resource allocation scheme [in our system, the multilayer dominant and max-min fair (MDMMF) allocation] is used to cope with the multiple resources fair allocation in multiple layers.

The Role of Spontaneous Polarization in the Negative Thermal Expansion of Tetragonal PbTiO3-Based Compounds

Abstract: PbTiO(3)-based compounds are well-known ferroelectrics that exhibit a negative thermal expansion more or less in the tetragonal phase. The mechanism of negative thermal expansion has been studied by high-temperature neutron powder diffraction performed on two representative compounds, 0.7PbTiO(3)-0.3BiFeO(3) and 0.7PbTiO(3)-0.3Bi(Zn(1/2)Ti(1/2))O(3), whose negative thermal expansion is contrarily enhanced and weakened, respectively. With increasing temperature up to the Curie temperature, the spontaneous polarization displacement of Pb/Bi (δz(Pb/Bi)) is weakened in 0.7PbTiO(3)-0.3BiFeO(3) but well-maintained in 0.7PbTiO(3)-0.3Bi(Zn(1/2)Ti(1/2))O(3). There is an apparent correlation between tetragonality (c/a) and spontaneous polarization. Direct experimental evidence indicates that the spontaneous polarization originating from Pb/Bi-O hybridization is strongly associated with the negative thermal expansion. This mechanism can be used as a guide for the future design of negative thermal expansion of phase-transforming oxides.