Full scale investigation of GCL damage mechanisms in small earth dam retrofit applications under earthquake loading

This paper reports results of full scale testing to further explore potential GCL damage mechanisms in earth dam retrofit applications in seismically active areas; in particular, to a) investigate whether shear displacements could reduce the magnitude of GCL panel overlap during earthquake shaking; b) explore the influence of gravel particles on GCL thickness at localised point of contact; and c) observe the consequences of an accidental exposure of an uncovered GCL to short duration rainfall in terms of moisture content and effects during subsequent compaction. The results of these experiments indicate that even under severe shaking no movements were detected at the GCL panel overlap. Whereas gravel particles were observed to locally reduce the thickness of the GCL to 2.2 mm, no plowing of the particle into the GCL occurred due to a lack of shear displacement at the interface, resulting in no localised internal erosion through the barrier. Furthermore, hydration of GCL panels during construction due to surface wetting was observed to result in a state of hydration less than its post-construction state. These results indicate that although each of the three GCL damage mechanisms cannot be ruled out to ever be relevant in practice, the performance of the GCL retrofitted earth dam tested was satisfactory under even severe Level 2 earthquake shaking, and suggests that the retrofitting of small earth dams with GCLs is a promising strategy to improve their static and seismic resistance.     

Fabrication of 0.24Pb(In1/2Nb1/2)O3-0.42Pb(Mg1/3Nb2/3)O3-0.34PbTiO3 transparent ceramics by conventional sintering technique

0.24Pb(In_1/2Nb_1/2)O₃-0.42Pb(Mg_1/3Nb_2/3)O₃-0.34PbTiO₃ transparent ceramics were fabricated by a conventional sintering technique. Through optimization of sintering conditions of calcination and sintering temperatures and time, the obtained ceramics showed high optical transmittance of 53% and 71% at light wavelengths of 1300 and 2000 nm, respectively. The ceramics showed a rhombohedral to tetragonal phase transition at ~120°C and a tetragonal to cubic phase transition at 222°C. These transition temperatures were higher than those of 0.67Pb(Mg_1/3Nb_2/3)-0.33PbTiO₃ ceramics. In addition, the ceramics had a ferroelectric hysteresis loop, a large piezoelectric constant d₃₃ of 407 pC/N, and a planar electromechanical coupling factor k_p of 52%. These results suggest that the transparent ceramics may be used as a temperature-stable, linear electro-optic material.     

LaMgAl11O19 synthesis using non-hydrolytic sol-gel methods

Polycrystalline LaMgAl₁₁O₁₉ (LMA) was prepared by four different non-hydrolytic sol-gel methods. From stable solutions, four powder precursors containing an amorphous and nanocrystalline phase with specific reactivity were obtained. The particle size, morphology, thermal behaviour, and phase composition of the powder precursors were studied using DLS, TEM, DSC/TG and XRD. Bulk ceramic samples containing LMA were prepared at 1200?°C for 16?h and examined in terms of phase purity and microstructure using XRD, SEM, and TEM. Raman spectroscopy of pure LMA was used to study the structure in detail. A mechanism of LMA formation and a relation between powder precursor properties and final phase composition is proposed. These findings may be useful for designing modern technologies for fabrication of LMA for optical or protective coating applications.     

Porous polyurethane film fabricated via the breath figure approach for sustained drug release

The breath figure (BF) method is an effective process for fabricating porous polymeric films. In this study, we fabricated porous polymer films from thermoplastic polyurethane (PU) through static BF with CHCl₃ as a solvent under 55–80% relative humidity. The porous PU films were prepared within various pore structures and sizes, which were adjustable, depending on the fabrication conditions. The humidity and exposure time were examined as variable parameters affecting the surface morphology, wettability, and cytotoxicity. Atorvastatin calcium, a hyperlipidemic agent, was loaded into the porous films during the casting process, and the drug-loading and drug-releasing behaviors of the porous PU membranes were evaluated. Approximately 60–80% of the drug was released in 14 days. The films exhibited sustained drug-release performances because of the hydrophobicity and nonbiodegradable nature of PU for perivascular drug administration. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47658.     

Scanning Probe Lithography Patterning of Monolayer Semiconductors and Application in Quantifying Edge Recombination

Scanning probe lithography is used to directly pattern monolayer transition metal dichalcogenides (TMDs) without the use of a sacrificial resist. Using an atomic‐force microscope, a negatively biased tip is brought close to the TMD surface. By inducing a water bridge between the tip and the TMD surface, controllable oxidation is achieved at the sub‐100 nm resolution. The oxidized flake is then submerged into water for selective oxide removal which leads to controllable patterning. In addition, by changing the oxidation time, thickness tunable patterning of multilayer TMDs is demonstrated. This resist‐less process results in exposed edges, overcoming a barrier in traditional resist‐based lithography and dry etch where polymeric byproduct layers are often formed at the edges. By patterning monolayers into geometric patterns of different dimensions and measuring the effective carrier lifetime, the non‐radiative recombination velocity due to edge defects is extracted. Using this patterning technique, it is shown that selenide TMDs exhibit lower edge recombination velocity as compared to sulfide TMDs. The utility of scanning probe lithography towards understanding material‐dependent edge recombination losses without significantly normalizing edge behaviors due to heavy defect generation, while allowing for eventual exploration of edge passivation schemes is highlighted, which is of profound interest for nanoscale electronics and optoelectronics.     

Living Materials Herald a New Era in Soft Robotics

Living beings have an unsurpassed range of ways to manipulate objects and interact with them. They can make autonomous decisions and can heal themselves. So far, a conventional robot cannot mimic this complexity even remotely. Classical robots are often used to help with lifting and gripping and thus to alleviate the effects of menial tasks. Sensors can render robots responsive, and artificial intelligence aims at enabling autonomous responses. Inanimate soft robots are a step in this direction, but it will only be in combination with living systems that full complexity will be achievable. The field of biohybrid soft robotics provides entirely new concepts to address current challenges, for example the ability to self‐heal, enable a soft touch, or to show situational versatility. Therefore, “living materials” are at the heart of this review. Similarly to biological taxonomy, there is a recent effort for taxonomy of biohybrid soft robotics. Here, an expansion is proposed to take into account not only function and origin of biohybrid soft robotic components, but also the materials. This materials taxonomy key demonstrates visually that materials science will drive the development of the field of soft biohybrid robotics.     

共价有机框架材料及其在关键核素分离中的应用进展

共价有机框架材料（COFs）是一类由共价键连接的多孔晶态材料。因具有单体链接方式灵活、结构可调、活性位点丰富、比表面积大、理化性质相对稳定等特点，它们在气体储存与分离、能量储存、催化和光电学领域受到了广泛的关注。本文主要从结构设计、合成方法及功能化、材料的分析表征和晶形控制等方面概括地介绍了COFs材料。在此基础上，综述了COFs材料在关键核素分离方面的研究进展，并展望了其在核素分离领域的应用前景和今后的研究方向。     

Adsorption studies of Pb (II) by two different magnetic MnFe2O4 materials synthesized with sol-gel process

Abstract

The spherical nanomaterials of MnFe-Ac and MnFe-Na can be synthesized with sol-gel method. The adsorption test of Pb (II) was carried out with two kinds of synthesized nanomaterials, and discussed their adsorption effects of Pb (II). The characteristic was analyzed by SEM, XRD, XPS and magnetic measurements. As the results showeed, the particles size of the material became smaller, but the morphology did not change after adsorption. The change of Ms was from 42.7 and 62.0?emu/g to 25.6 and 89.4?emu/g, respectively. By Langmuir and Freundlich models, the maximum adsorption amounts of Pb (II) were 23.40 and 41.56?mg/g, respectively, and analysis demonstrated that the adsorption of Pb (II) on samples was monolayer adsorption. The kinetic analysis showed that the adsorption of Pb (II) on the two materials was more in accordance with the pseudo-second-order model, which indicated that adsorption process of the materials for Pb (II) were primarily limited by the chemical adsorption.     

Friction Behavior of Human Skin Rubbing against Different Textured Polymeric Materials Obtained by a 3D Printing Microfabrication Technique

Understanding friction behavior of human skin is indispensable in order to optimize surfaces and materials in contact with the skin. The coefficient of friction (COF) for different materials contacting against the skin is mainly influenced by the nature of the materials, mechanical contact parameters, and physiological skin conditions. The aim of the present research work was to study the grip effect of two different polymeric materials by producing different textured patterns using a 3D printing microfabrication technique and a replication technique. It was found that under the same contact conditions, a difference in the friction amplitude exists between the two different polymeric materials and that positive texturing, which consists of high relief or protrusions, showed higher COFs than negative texturing, consisting of low relief, holes, or dimples, which showed a decrease in friction as the textured pattern area density increased.