Land Surface Albedo Variations in Sanjiang Plain from 1982 to 2015: Assessing with GLASS Data

As a key parameter for indicating the fraction of surface-reflected solar incident radiation, land surface albedo plays an important role in the Earth’s surface energy budget(SEB). Since the Sanjiang Plain has been severely affected by human activities(e.g., reclamation and shrinking of wetlands), it is important to assess the spatiotemporal variations of surface albedo in this region using a long-term remote sensing dataset. In order to investigate the surface albedo climatology, trends, and mechanisms of change, we evaluated the surface albedo variations in the Sanjiang Plain, China from 1982 to 2015 using the Global LAnd Surface Satellite(GLASS) broadband surface albedo product. The results showed that: 1) an increasing annual trend(+0.000 58/yr) of surface albedo was discovered in the Sanjiang Plain based on the GLASS albedo dataset, with a much stronger increasing trend(+0.001 26/yr) occurring during the winter. Most of the increasing trends occurred over the cultivated land, unused land, and land use conversion types located in the northeastern Sanjiang Plain. 2) The increasing trend of land surface albedo in Sanjiang Plain can be largely explained by the changes of both snow cover extent and land use. The surface albedo in winter is highly correlated with the snow cover extent in the Sanjiang Plain, and the increasing trend of surface albedo can be further enhanced by the land use changes.

Influence of Non-smooth Surface on Tribological Properties of Glass Fiber-epoxy Resin Composite Sliding against Stainless Steel under Natural Seawater Lubrication

With the development of bionics, the bionic non-smooth surfaces are introduced to the field of tribology. Although non-smooth surface has been studied widely, the studies of non-smooth surface under the natural seawater lubrication are still very fewer, especially experimental research. The influences of smooth and non-smooth surface on the frictional properties of the glass fiber-epoxy resin composite（GF/EPR） coupled with stainless steel 316 L are investigated under natural seawater lubrication in this paper. The tested non-smooth surfaces include the surfaces with semi-spherical pits, the conical pits, the cone-cylinder combined pits, the cylindrical pits and through holes. The friction and wear tests are performed using a ring-on-disc test rig under 60 N load and 1000 r/min rotational speed. The tests results show that GF/EPR with bionic non-smooth surface has quite lower friction coefficient and better wear resistance than GF/EPR with smooth surface without pits. The average friction coefficient of GF/EPR with semi-spherical pits is 0.088, which shows the largest reduction is approximately 63.18% of GF/EPR with smooth surface. In addition, the wear debris on the worn surfaces of GF/EPR are observed by a confocal scanning laser microscope. It is shown that the primary wear mechanism is the abrasive wear. The research results provide some design parameters for non-smooth surface, and the experiment results can serve as a beneficial supplement to non-smooth surface study.

Abnormal IR Spectra of CO Adsorbed on the Surface of Glass Carbon Electrode Modified with Polypyrrole Film with Platinum Microparticles

Abnormal IR spectra of CO adsorbed at the surface of glass carbon electrode modified with polypyrrole film with Pt microparticles are reported.

POLYMER CHAIN DIFFUSION AT A TEMPERATURE BELOW ITS BULK GLASS TRANSITION TEMPERATURE

In this study, it was examined whether the dynamics of polymer chains at a surface is different from that in thebulk, and if so, to what extent they differ in terms of surface glass transition temperature and diffusion coefficient. Obtainedresults clearly indicate that surface chains can travel for a relatively large distance in comparison with the characteristiclength scale of usual segmental motion even at a temperature below its bulk glass transition temperature, T_g^b. This isconsistent with our previous results that the surface glass transition temperature is much lower than the corresponding T_g^b.Also, it was experimentally revealed that there was a gradient of molecular motion in the surface region.

Serrated plastic flow behavior and microstructure in a Zr-based bulk metallic glass processed by surface mechanical attrition treatment

The serrated plastic flow,microstructure and residual stress of a Zr_（55）Cu_（30）Ni_5Al_（10） bulk metallic glass（BMG）undergone surface mechanical attrition treatment（SMAT）have been investigated by a combination of compression tests with scanning electron microscopy（SEM）,high resolution transmission electron microscopy（HRTEM）and the incremental hole-drilling strain-gage method.It is found that SMAT leads to various microstructural modifications and residual stress distribution in the surface layers of the Zrbased BMG due to the mechanically-induced nanocrystallization and generation of shear bands.As a result,the BMG alloy exhibits a remarkable work-hardening like behavior and significant increase of plastic strain from less than 1%to 15%,and its plastic deformation dynamics yields a power-law distribution of shear avalanches.Based upon the analysis of the experimental results,it is indicated that this can be connected to the SMAT-induced microstructural modifications and the resulting residual compressive stress in the Zr-based BMG.

Unusually thick shear-softening surface of micrometer-size metallic glasses

The surface of glass is crucial for understanding many fundamental processes in glassy solids.A common notion is that a glass surface is a thin layer with liquid-like atomic dynamics and a thickness of a few tens of nanometers.Here,we measured the shear modulus at the surface of both millimeter-size and micrometer-size metallic glasses(MGs)through high-sensitivity torsion techniques.We found a pronounced shear-modulus softening at the surface of MGs.Compared with the bulk,the maximum decrease in the surface shear modulus(G)for the micro-scale MGs reaches~27%,which is close to the decrease in the G upon glass transition,yet it still behaves solid-like.Strikingly,the surface thickness estimated from the shear-modulus softening is at least 400 nm,which is approximately one order of magnitude larger than that revealed from the glass dynamics.The unusually thick surface is also confirmed by measurements using X-ray nano-computed tomography,and this may account for the brittle-to-ductile transition of the MGs with size reductions.The unique and unusual properties at the surface of the micrometer-size MGs are physically related to the negative pressure effect during the thermoplastic formation process,which can dramatically reduce the density of the proximate surface region in the supercooled liquid state.

Fibrinogen Structural Changes Caused by Glass Surface Adsorption Detected by Solid Surface Fluorescence Spectroscopy

Solid surface fluorescence (SSF) spectra of fibrinogen (FG) adsorbed on a glass surface were measured. For comparison, solution fluorescence (SF) spectra of native, thermally denatured, urea denatured FG solution with FG desorbed from a glass surface and the SSF spectra of native FG powder were recorded. To analyze the structural changes induced by the surface adsorption, all the aqueous samples mentioned above were analyzed by circular dichroism (CD) spectroscopy. The results demonstrated that the structural changes of FG induced by glass adsorption caused changes in the spectroscopic features of the SSF spectra, especially in the excitation (EX) spectra. It is suggested that SSF spectroscopy may be a useful tool for studying the structures of surface/interface biomolecules and for evaluating the biocompatibility of biomaterials.

Plasticityimprovement of a Zr-based bulk metallic glass by micro-arc oxidation

Mciro-arc oxidation（MAO）was used to coat porous films on the surface of a Zr-based bulk metallic glass sample.The compressive test results indicated that,compared with the as-cast sample,the MAO treated one exhibited higher deformation capacity,associated with multiple shear bands with higher density on the side surface and well-developed vein patterns with smaller size on the fractured surface.The pore in the MAOed film and the matrix/coating interface initiated the shear bands and impeded the rapid propagation of shear bands,thus favoring the enhanced plasticity of the MAO treated sample.The obtained results demonstrated that MAO can be considered as an effective method to finely tune the mechanical performance of monolithic bulk metallic glasses.

General synthesis of sponge-like ultrafine nanoporous metals by dealloying in citric acid

A general method is proposed to synthesize ultrafine nanoporous Cu, Ag, and Ni with novel sponge-like morphologies, high porosities, and large surface areas. The materials are produced by dealloying Mgc~/IzsY10 （M = Cu, Ag, and Ni） metallic glasses in citric acid. Citric acid played a key role due to its capping effect, which reduced the surface diffusion of metals. A structural model consistent with the sponge-like morphology was constructed to calculate the porosity and the surface area. The mechanism of the dealloying process in citric acid, involving ligament formation and coarsening, was illustrated. The mechanism was capable of explaining the experimental trends of dealloying, especially the morphology. A glucose sensor, which can be further developed into a high-precision real-time glucose monitor for medical use, was constructed using sponge-like nanoporous copper. Our findings are not only relevant to understanding the dealloying mechanism of metallic glasses, but also provide promising materials for multiple applications.