Preparation and electrochemical characterization of Ti-based amorphous metallic glass with high strength

Ti-based amorphous metallic glasses have excellent mechanical, physical, and chemical properties, which is an important development direction and research hotspot of metal composite reinforcement. As a stable, simple, efficient, and large-scale preparation technology of metallic powders, the gas atomization process provides an effective way of preparing amorphous metallic glasses. In this study, the controllable fabrication of a Ti-based amorphous powder, with high efficiency, has been realized by using gas atomization. The scanning electron microscope, energy-dispersive spectrometer, and X-ray diffraction are used to analyze surface morphology, element distribution, and phase structure, respectively. A microhardness tester is used to measure the mechanical property. An electrochemical workstation is used to characterize corrosion behavior. The results show that as-prepared microparticles are more uniform and exhibit good amorphous characteristics. The mechanical test shows that the hardness of amorphous powder is significantly increased as compared with that before preparation, which has the prospect of being an important part of engineering reinforced materials. Further electrochemical measurement shows that the corrosion resistance of the as-prepared sample is also significantly improved. This study has laid a solid foundation for expanding applications of Ti-based metallic glasses, especially in heavy-duty and corrosive domains.     

Synthesis of N-methylglucamine modified macroporous poly(GMA-co-TRIM) and its performance as a boron sorbent

A chelating polymeric sorbent was developed by functionalizing poly(glycidyl methacrylate-co-trimethylolpropane trimethacrylate), poly(GMA-co-TRIM), with N-methylglucamine (MG) via a simple post-grafting route. The resulting well-defined millimeter-sized spheres of poly(GMA-co-TRIM)–MG had permanent macropore structures and low swelling degree, with accessible ligands of 1.84 mmol/g. The boron adsorption behavior of the sorbent was studied in batch mode by varying different parameters like the pH value, the initial concentration of boron and the adsorption time under noncompetitive conditions. It was found that the sorbent always maintained the high capacity between pH 2.6 and 8.6, in which the optimum pH was 7.5. The adsorption behavior of the sorbent obeyed the Langmuir isotherm well. The adsorption capacity of the sorbent for boron was in the same level as that of a commercially available N-methylglucamine-type polystyrene resin. However, it adsorbed boron more quickly. The sorbent also showed good durability and reusability through the fixed-bed adsorption tests. The study on the separation of boron from brine of salt lake showed a high selectivity of the sorbent, though the capacity for boron decreased due to the interference of diverse ions in brine.     

TrajStat: GIS-based software that uses various trajectory statistical analysis methods to identify potential sources from long-term air pollution measurement data

Statistical analysis of air mass back trajectories combined with long-term ambient air pollution measurements are useful tools for source identification. Using these methods, the geographic information system (GIS) based software, TrajStat, was developed to view, query, and cluster the trajectories and compute the potential source contribution function (PSCF) and concentration weighted trajectory (CWT) analyses when measurement data are included.     

Influence of boundary conditions on the cooling effect of crushed-rock embankment in permafrost regions of Qinghai–Tibetan Plateau

The crushed-rock layer is a highly porous medium that has been used to ensure the stability of embankment in permafrost regions. At present, depending on different boundary conditions (impermeable and permeable) of crushed-rock layer in embankment, the crushed-rock embankments are divided into two kinds of structures in the construction of Qinghai–Tibetan railway in China. One is a closed-boundary crushed-rock embankment; the other is an open-boundary crushed-rock embankment. In order to investigate the influence of boundary conditions (impermeable and permeable) on the cooling effect of a crushed-rock embankment, two numerical models of the unsteady two-dimensional hydrokinetic equations for incompressible fluid are presented to analyze the velocity and temperature characteristics of crushed-rock embankment with different embankment heights under impermeable and permeable boundary conditions for a period of 50 years. The results indicate: (1) the boundary conditions (impermeable and permeable) of crushed-rock embankment can have a very large impact on the heat transfer pattern within it in windy permafrost regions of Qinghai–Tibetan Plateau. The cooling effect of the closed crushed-rock embankment mainly relies on natural convection within crushed-rock layer, which is caused by the thermal boundary condition, but the cooling effect of the open crushed-rock embankment is due to the heat transfer enhancement because of internal forced convection induced by the external low temperature air flow (wind); (2) from the temperature distributions of crushed-rock embankments, it can be found that, under the assumption that the air temperature will be warmed up by 2.6 °C in a period of 50 years and in the areas where the mean annual air temperature is − 4.0 °C, when embankment is low, the cooling effects of crushed-rock embankment have no obvious difference under the two boundary conditions, and the cooling effect of closed crushed-rock embankment is only a little better than that of open one; however, when embankment is high, the boundary conditions cause a distinct influence on the temperature distribution of crushed-rock embankment, and the cooling effect under the permeable boundary condition is far better than that under the impermeable boundary condition. However, the asymmetric temperature distribution problem of the high crushed-rock embankment, caused by permeable boundary and external wind, must be considered when it is designed and constructed.     

A toolbox to find the best mechanistic model to predict the behavior of environmental systems

Reliable prediction of the long-term behavior of environmental systems such as Municipal Solid Waste (MSW) landfills is challenging. While many driving forces influence this behavior, characterization of them is limited by measurement techniques. Therefore, a model structure for reliable prediction needs to optimally combine all measured information with suitable mechanistic information from literature. How to get such an optimal model structure? This study presents a toolbox to find and build the model structure that describes an environmental system as close as possible. The toolbox combines environmental frameworks to include all suitable mechanistic information; it fully couples kinetic and equilibrium reactions and contains multiple resources to obtain biogeochemical parameters. Several possible optimal model structures are quickly built and evaluated with objective statistical performance criteria obtained via Bayesian inference. By applying the novel methodology, we select the best model structure for anaerobic digestion of MSW in full scale landfills.     

Effects of size and autoclavation of fruit and vegetable wastes on biohydrogen production by dark dry anaerobic fermentation under mesophilic condition

Fermentative hydrogen production from fruit and vegetable wastes (FVWs) through Dry Fermentation Technology (DFT) was studied through three independent experiments in order to find out the effect of particle size and autoclaving pretreatment on bio-hydrogen production from FVWs and as follows: (1) autoclaved FVWs with sizes < 5 cm (experiment I); (2) raw FVWs with sizes < 5 cm (experiment II) and (3) autoclaved FVWs with sizes > 5 cm (experiment III). The assay with autoclaved waste yielded a higher percentage of hydrogen in the headspace of the dry fermenter reaching a maximum value of 44% in experiment I. However, the maximum hydrogen production was obtained in experiment III with 14573 NmL at a yield of 23.53 NmL H₂/gVS. Profiling of the microbial communities by denaturing gradient gel electrophoresis (DGGE) indicated that the most prominent species were the genera Clostridium, Bifidobacterium, and Lactobacillus.     

Impact of experimental warming on soil temperature and moisture of the shallow active layer of wet meadows on the Qinghai-Tibet Plateau

Climate change is now increasingly evident on the Qinghai–Tibet Plateau and has a strong impact on both the abiotic and biotic components of ecosystems, particularly on permafrost, active layer thickness, vegetation, and soil properties. Permafrost ecosystems are recognized to be sensitive to the influences of the changing climate, which may disturb the permafrost soil carbon (C) pool and lead to huge C emissions. To facilitate the assessment of warming effects on the temperature and moisture patterns in the shallow soil of the active layer of the wet meadows on the Qinghai–Tibet Plateau, near-surface air temperature was passively increased by using open-top chambers (OTCs) with two different temperature increments. Soil temperature and moisture were continuously monitored at depths of 5, 20, and 40 cm at hourly intervals in a wet meadow in the Beiluhe region on the Qinghai–Tibet Plateau from October 1, 2007 to June 24, 2009. When near-surface air temperature increased by 5.29 °C and 1.84 °C in the OTC2 and OTC1 plots, respectively, relative to the control plots, soil temperatures at depths of 5, 20, and 40 cm were seen to increase by 3.84°C, 2.23°C, and 1.42 °C, respectively, in the OTC2 plots and by 0.94°C, 0.27°C, and 0.25 °C, respectively, in the OTC1 plots. Soil moisture content at depths of 5, 20, and 40 cm declined by 8.04%, 1.79%, and 1.52%, respectively, in the OTC2 plots and by 5.33%, 0.69%, and 0.09%, respectively, in the OTC1 plots. Near-surface warming was found to extend the continuous thawing time of the shallow soil, delay the occurrence of the autumnal freezing process, and shorten the duration of continuous freezing. It was also seen to increase both the temperature of the shallow soil and the accumulated temperatures at different depths. Near-surface warming could be one of the main factors leading to the degradation of vegetation, thus threatening the stability of the soil C pool and the ecological safety of the Qinghai–Tibet Plateau.     

Effects of ZrO2 on the photoluminescence of 0.5 at% Eu:(Y0.9La0.1)2O3 transparent ceramics

Zr-codoped 0.5 at% Eu: (Y_0.9La_0.1)₂O₃ ceramics sintered in H₂-reducing atomsphere, together with the ceramics with annealing treatment, were fabricated by solid-state reactions and the effects of Zr codoping on these materials’ photoluminescence examined. The obtained emission spectra showed that Zr codoping adjust the materials’ photoluminescence with UV excitation and a logical explanation was proposed. The results suggested that an Eu-doped, yttrium-lanthanum oxide transparent ceramic with Zr in low concentration appeared to have promising potential in modern lighting applications.     

Which Chinese cities are more inclusive and why?

China's household registration system allows local governments to control migration by limiting migrants' eligibility to local public services. Many cities exclude migrant residents from important social benefits, which reduces labor mobility and contributes to the socioeconomic gap between migrants and urban natives. This study measures the extent of China's local migration restriction from the perspective of inclusive provision of public services and explains cross-city disparities. We define urban inclusiveness as the extent to which migrants can access social benefits provided locally and construct an urban inclusiveness index using factor analysis. We find significant cross-city differences in urban inclusiveness toward migrants. Statistical analyses suggest that local fiscal capacity and labor demand, instead of cultural tradition, are the major determinants of urban inclusiveness. We further use the gap between the inclusiveness toward high- and low-skilled migrants to measure local skill-based migration selectivity. We find that more developed cities, i.e., cities with larger populations, higher levels of gross regional product per capita, and greater shares of industrial sector, are more selective based on migrants' skills, while cultural openness does not help bring down skill-based selectivity. Our research suggests an instrumental view of migrants in China's urban policy that contributes to social inequality and the lack of labor mobility, which can restrict China's development in the long term.