Results 1 - 10 of 185
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[en] Highlights: • In situ hydrolysis of tetraethoxysilane within the confined galleries region of graphite oxide. • New porous sandwiched graphene/Si nanocomposites were prepared by magnesium thermal reduction. • The Si nanostructure was compactly sandwiched between two neighboring graphenes. • The Si/graphene anodes deliver large reversible capacity with excellent cycling stability. - Abstract: Porous sandwiched graphene/Si nanocomposites (PG-Si) are prepared by in situ hydrolysis of tetraethoxysilane within the confined gallery region of graphite oxide, and then magnesium thermal reduction of the intra-gallery SiO2 to Si nanocrystals. The Si nanostructures are in situ formed within the confined gallery region of graphite, and they are compactly sandwiched between two neighboring graphene sheets. This compactly sandwiched structure affords enhanced electron conductivity, and prevents Si nanoparticles from aggregation. Meanwhile, the free voids between neighboring Si nanocrystals alleviate the volume change of Si during cycling. As a consequence, the resulting PG-Si nanocomposites are high-performance anode materials for lithium-ion batteries which show long cycle life (>500 cycles) and high specific charge capacity (1464 mAh g−1 at a current density of 200 mA/g, 920 mAh g−1 at a current density of 1.68A/g after 500 cycles). The Li+ diffusion kinetics in PG-Si is also discussed.
[en] In this note, we consider the observational constraints on some cosmological models by using the 307 Union type Ia supernovae (SNIa), the 32 calibrated gamma-ray bursts (GRBs) at z>1.4, the updated shift parameter R from WMAP 5-year data (WMAP5), and the distance parameter A of the measurement of the baryon acoustic oscillation (BAO) peak in the distribution of SDSS luminous red galaxies with the updated scalar spectral index ns from WMAP5. The tighter constraints obtained here update the ones obtained previously in the literature. (orig.)
[en] Unparticle physics has been an active field since the seminal work of Georgi. Recently, many constraints on unparticles from various observations have been considered in the literature. In particular, the cosmological constraints on the unparticle dark component put it in a serious situation. In this work, we try to find a way out of this serious situation, by including the possible interaction between dark energy and the unparticle dark component. (orig.)
[en] Effective spatial-temporal analysis of the availability of agricultural biomass is crucial for cost-effective development of bioenergy. Using statistical data, simulation modeling, and a dynamic analysis framework, the authors assess the potential and distribution of regional agricultural biomass in Heilongjiang, China. The results indicate 32.48 × 106 t of agricultural biomass were available in 2003; this soared to 77.13 × 106 t in 2013. Gray correlation analysis demonstrated that precipitation, total population, mechanical power and agricultural planting structure largely influenced the availability of biomass resources. The support of corn oil storage plays an important role of agricultural planting structure. Statistical and Net Primary Production data were used to study the dynamic change in the availability of agricultural biomass. The growth rate of available biomass exceeded 2 t km−2 y−1 in most areas of the Sanjiang Plain, and ranged from − 1.5 to 2.0 t km−2 y−1 in the Songnen Plain. The establishment of a scientific resource management and scheduling platform is suggested to achieve the dynamic allocation and scheduling of agricultural biomass that will improve resource stability. The methods here can also be applied to other regions and provide baseline data for local authorities to further consider a strategy for bioenergy planning and development. - Highlights: • Dynamic analysis framework combined NPP modeling has been adopted. • Agricultural biomass is a reliable resource for bioenergy in Heilongjiang. • Precipitation, mechanical power effect biomass amounts. • Corn oil storage projects influence on planting structure & biomass amounts. • Biomass in Sanjiang Plain is robust and most reliable on bioenergy development.
[en] A better understanding of anthropogenic impact can help assess the diffuse trace metal accumulation in the agricultural environment. In this study, both river sediments and background soils were collected from a case study area in Northeast China and analyzed for total concentrations of six trace metals, four major elements and three lead isotopes. Results showed that Pb, Cd, Cu, Zn, Cr and Ni have accumulated in the river sediments after about 40 years of agricultural development, with average concentrations 1.23–1.71 times higher than local soil background values. Among them Ni, Cr and Cu were of special concern and they may pose adverse biological effects. By calculating enrichment factor (EF), it was found that the trace metal accumulation was still mainly ascribed to natural weathering processes, but anthropogenic contribution could represent up to 40.09% of total sediment content. For Pb, geochemical and isotopic approaches gave very similar anthropogenic contributions. Principal component analysis (PCA) further suggested that the anthropogenic Pb, Cu, Cr and Ni inputs were mostly related to the regional atmospheric deposition of industrial emissions and gasoline combustion, which had a strong affinity for iron oxides in the sediments. Concerning Cd, however, it mainly originated from local fertilizer applications and was controlled by sediment carbonates. - Graphical abstract: The trace metal accumulation was mainly ascribed to natural weathering processes, but anthropogenic contribution could represent up to 40.09% of total sediment content. Anthropogenic Pb, Cu, Cr and Ni mostly came from atmospheric deposition, while fertilizer application was the main anthropogenic source of Cd. - Highlights: • Trace metals have accumulated in the Naolihe sediments. • Natural weathering was still a major contributor to metal accumulation. • Anthropogenic Pb, Cu, Cr and Ni mostly came from atmospheric deposition. • Local fertilizer application was the main anthropogenic source of Cd
[en] Textile is related on life, work environment closely. In recent years, with the development of national economy and people's living standards, application fields of various types of civil and industrial fibers and textiles were expanded. The request of light, beautiful decorations curtains, wall covering, carpet, and curtain was increasing. However, these textiles were mostly combustible. When they fired, they released a large number of smoke and affected people's lives and property seriously. Using chemical methods to blending and copolymerization to finish flame-retardant, they had their own advantages, but the use of electron accelerators for radiation grafting technology, which had energy efficient, environmentally friendly, was able to ensure the flame-retardant effect while reducing the amount of flame retardants. Compared flame-retardant material with non-irradiated to radioactive materials and flame-retardant, flame-retardant properties and mechanical properties were better than before. And compared with chemical methods, the process of radiation grafting was simple and had a single product, high productivity and a huge advantage. (authors)
[en] In the literature, it was proposed that the growth index γ is useful to distinguish the scenarios of dark energy and modified gravity. In the present work, we consider the constraints on the growth index γ by using the latest observational data. To be model-independent, we use cosmography to describe the cosmic expansion history, and also expand the general γ(z) as a Taylor series with respect to redshift z or y-shift, y=z/(1+z). We find that the present value γ=γ(z=0)≃0.42 (for most of viable f(R) theories) is inconsistent with the latest observational data at high confidence level (C.L.). On the other hand, γ0≃0.55 (for dark energy models in GR) can be consistent with the latest observational data at 1σ C.L. in five of the nine cases under consideration, but is inconsistent beyond 2σ C.L. in the other four cases (while it is still consistent within the 3σ region). Thus, we can say nothing firmly about γ0≃0.55. We also find that a varying γ(z) is favored.
[en] The cosmological principle assumes that the universe is homogeneous and isotropic on cosmic scales. There exist many works testing the cosmic homogeneity and/or the cosmic isotropy of the universe in the literature. In fact, some observational hints of the cosmic anisotropy have been claimed. However, we note that the paucity of the data considered in the literature might be responsible for the ''found'' cosmic anisotropy. So, it might disappear in a large enough sample. Very recently, the Pantheon sample consisting of 1048 type Ia supernovae (SNIa) has been released, which is the largest spectroscopically confirmed SNIa sample to date. In the present work, we test the cosmic anisotropy in the Pantheon SNIa sample by using three methods, and hence the results from different methods can be cross-checked. All the results obtained by using the hemisphere comparison (HC) method, the dipole fitting (DF) method and HEALPix suggest that no evidence for the cosmic anisotropy is found in the Pantheon SNIa sample. (orig.)