The paper discusses the development of the advanced polymer composite material applications in the building and civil/structural infrastructure over the past three to four decades. It endeavours to ...identify and prioritise the important in-service research areas which are necessary to improve the understanding of the behaviour of FRP materials and FRP structural components. The paper demonstrates the types of structures which have been developed from the FRP composite material and the most advantageous way to employ composites in civil engineering. The material has extraordinary mechanical and important in-service properties which when combined with other materials are utilised to improve the stiffness/strength, durability, the whole-life cost benefit and the environmental impact. The paper concludes by summarising key successes of the advanced polymer composite in the civil infrastructure and suggests areas in which, if they are employed innovatively, FRP composites could be used with great advantage.
The propensity of Zn‐metal anodes to form non‐uniform or dendritic electrodeposits is bound up with the nature of the electrode surface. However, the effect of surface structure on the inherent ...nucleation and deposition of Zn is not yet well understood. Here, the surface structure of a Zn‐metal anode is reconstructed with Sn‐crystal textures via a facile chemical displacement reaction. Compared to the bare Zn, the high‐affinity Zn binding sites of Sn afford lower deposition energy barrier, which promotes deposition kinetics. What is more, a Sn‐textured surface with moderate Zn affinity but high average surface energy ensures a better wettability from the deposits, leading to the lateral growth of Zn crystals. The resultant Sn‐textured Zn‐metal anode exhibits an extremely low voltage hysteresis of 20 mV and achieves a prolonged cycling stability over 500 h cycles without dendrite formation. This work provides new insights into the crystal‐texture‐dependent Zn electrodeposition process and offers direction for direct surface texturing to better stabilize Zn‐metal anodes with improved reversibility.
The surface of a Zn‐metal anode is reconstructed with Sn‐crystal textures via a facile chemical displacement reaction. Such a Sn‐textured surface not only endows a reduced Zn deposition energy barrier but also regulates the lateral growth of Zn crystals, which promotes dendrite‐free electrodeposits and leads to the achievement of an extremely low voltage hysteresis of 20 mV and prolonged cycling performance over 500 h.
A numerical method based on nonlinear incremental dynamic analysis is proposed in this paper to develop seismic fragility curves for rectangular subway station buried in layered soil and subjected to ...transverse seismic excitations. The proposed method primarily consists of four parts, namely, model verification, damage quantification, ground motion processing, and seismic performance assessment. The main section of the Daikai subway station collapsed during the Kobe Earthquake is used as an example to demonstrate the detailed procedure of the proposed method in construction of seismic fragility curves for underground structures. Results from the nonlinear soil-structure interaction model in this paper is firstly verified against the results from existing literature. The threshold values of different damage states of the underground structure are quantified by interstory drift ratio obtained from the nonlinear static pushover analysis of the soil-structure interaction system. Based on the results of the incremental dynamic analysis, it is found that the peak acceleration at the ground surface is an efficient and appropriate intensity measure of the ground motions for shallowly buried underground structure. The proposed method is validated by comparing with the existing empirical and numerical seismic fragility curves of buried rectangular underground structures and can be used as an effective approach in the development of seismic fragility database for underground structures.
Graphene quantum dots (GQDs), which are edge-bound nanometer-size graphene pieces, have fascinating optical and electronic properties. These have been synthesized either by nanolithography or from ...starting materials such as graphene oxide (GO) by the chemical breakdown of their extended planar structure, both of which are multistep tedious processes. Here, we report that during the acid treatment and chemical exfoliation of traditional pitch-based carbon fibers, that are both cheap and commercially available, the stacked graphitic submicrometer domains of the fibers are easily broken down, leading to the creation of GQDs with different size distribution in scalable amounts. The as-produced GQDs, in the size range of 1-4 nm, show two-dimensional morphology, most of which present zigzag edge structure, and are 1-3 atomic layers thick. The photoluminescence of the GQDs can be tailored through varying the size of the GQDs by changing process parameters. Due to the luminescence stability, nanosecond lifetime, biocompatibility, low toxicity, and high water solubility, these GQDs are demonstrated to be excellent probes for high contrast bioimaging and biosensing applications.
An X‐ray crystal structure of Kelch‐like ECH‐associated protein (Keap1) co‐crystallised with ...(1S,2R)‐2‐(1S)‐1‐(1,3‐dioxo‐2,3‐dihydro‐1H‐isoindol‐2‐yl)methyl‐1,2,3,4‐tetrahydroisoquinolin‐2‐carbonylcyclohexane‐1‐carboxylic acid (compound (S,R,S)‐1 a) was obtained. This X‐ray crystal structure provides breakthrough experimental evidence for the true binding mode of the hit compound (S,R,S)‐1 a, as the ligand orientation was found to differ from that of the initial docking model, which was available at the start of the project. Crystallographic elucidation of this binding mode helped to focus and drive the drug design process more effectively and efficiently.
To dock or not to dock? Nrf2 has become an attractive neuroprotective target, as the Nrf2 pathway provides a natural cell defense mechanism against damage. Targeting its physiological negative modulator Keap1 with small molecules may allow Nrf2 to play its protective role. To this end, an X‐ray structure of Keap1 co‐crystallised with compound (S,R,S)‐1 a was obtained, elucidating its binding mode, which in turn helped to drive the drug design process.
The unique band structure of graphene allows reconfigurable electric-field control of carrier type and density, making graphene an ideal candidate for bipolar nanoelectronics. We report the ...realization of a single-layer graphene p-n junction in which carrier type and density in two adjacent regions are locally controlled by electrostatic gating. Transport measurements in the quantum Hall regime reveal new plateaus of two-terminal conductance across the junction at 1 and Formula: see text times the quantum of conductance, e²/h, consistent with recent theory. Beyond enabling investigations in condensed-matter physics, the demonstrated local-gating technique sets the foundation for a future graphene-based bipolar technology.
Smart helical structures inspired by the pellicle of euglenids Noselli, Giovanni; Arroyo, Marino; DeSimone, Antonio
Journal of the mechanics and physics of solids,
February 2019, 2019-02-00, 20190201, 2019-02, Letnik:
123
Journal Article, Publication
Recenzirano
Odprti dostop
This paper deals with a concept for a reconfigurable structure bio-inspired by the cell wall architecture of euglenids, a family of unicellular protists, and based on the relative sliding of adjacent ...strips. Uniform sliding turns a cylinder resulting from the assembly of straight and parallel strips into a cylinder of smaller height and larger radius, in which the strips are deformed into a family of parallel helices. We examine the mechanics of this cylindrical assembly, in which the interlocking strips are allowed to slide freely at their junctions, and compute the external forces (axial force and axial torque at the two ends, or pressure on the lateral surface) necessary to drive and control the shape changes of the composite structure. Despite the simplicity of the structure, we find a remarkably complex mechanical behaviour that can be tuned by the spontaneous curvature or twist of the strips.
Nature has evolved efficient strategies to synthesize complex mineralized structures that exhibit exceptional damage tolerance. One such example is found in the hypermineralized hammer-like dactyl ...clubs of the stomatopods, a group of highly aggressive marine crustaceans. The dactyl clubs from one species, Odontodactylus scyllarus, exhibit an impressive set of characteristics adapted for surviving high-velocity impacts on the heavily mineralized prey on which they feed. Consisting of a multiphase composite of oriented crystalline hydroxyapatite and amorphous calcium phosphate and carbonate, in conjunction with a highly expanded helicoidal organization of the fibrillar chitinous organic matrix, these structures display several effective lines of defense against catastrophic failure during repetitive high-energy loading events.
We demonstrate an innovative memory device made of a single crystalline ZnO nanowire/microwire that works with a different mechanism from the p-n junction based memristor. A nonsymmetric, ...Schottky-Ohmic contacted ZnO nano/microwire can serve as a memristor if the channel length is short and the applied frequency is high. The observed phenomena could be explained based on a screening model of the polar charges at the two ends of the wire owing to the crystal structure of ZnO. The polar charges are usually fully screened by free electrons coming from the metal sides. But when the magnitude of the externally applied field exceeds a threshold value, the free electrons that screen the polar surfaces can be pulled away from the interface region, leading to a transient change in the effective height of the local Schottky barrier height owing to the electrical field formed by the polar surfaces of ZnO nanowires, which acts as a resistor with its magnitude depending on the total charges being transported. Such a phenomenon could be used for high density and fast writing/erasing data storage.
Using scanning tunneling microscopy and spectroscopy, we probe the electronic structures of single layer MoS2 on graphite. The apparent quasiparticle energy gap of single layer MoS2 is measured to be ...2.15 ± 0.06 eV at 77 K, albeit a higher second conduction band threshold at 0.2 eV above the apparent conduction band minimum is also observed. Combining it with photoluminescence studies, we deduce an exciton binding energy of 0.22 ± 0.1 eV (or 0.42 eV if the second threshold is use), a value that is lower than current theoretical predictions. Consistent with theoretical predictions, we directly observe metallic edge states of single layer MoS2. In the bulk region of MoS2, the Fermi level is located at 1.8 eV above the valence band maximum, possibly due to the formation of a graphite/MoS2 heterojunction. At the edge, however, we observe an upward band bending of 0.6 eV within a short depletion length of about 5 nm, analogous to the phenomena of Fermi level pinning of a 3D semiconductor by metallic surface states.
PDF