Search

• Simultaneous modulation of material structure and surface has been proposed. • Such a modulation has been realized through hydrogenation and fluorination. • The designed TiO 2- x F y exhibits robust Na+ storage at a high rate of 20 C. • Full cells of TiO 2- x F y //Na 3 V 2 (PO 4) 2 O 2 F offer a remarkable power of 3700 W kg−1. Modulating the atomic structure and surface property represents a pivotal and intriguing approach to tailoring the energy storage performance of battery materials, but their simultaneous modulation via simple processes remains a grand challenge. Taking TiO 2 as an example, here we report the structure and surface modulation through a simple two-step operation, hydrogenation and fluorination, which impart high electrical conductivity and robust surface activity to the material. Hydrogenation introduces Ti3+ species in the TiO 2 bulk to accelerate electron transport, while surface fluorination speeds up sodium-ion reaction dynamics. This modulated TiO 2 exhibits robust Na+ storage, affording 181 mAh g−1 over 2500 cycles at a high rate of 20 C. In addition, when paring with a commercial Na 3 V 2 (PO 4) 2 O 2 F cathode, the designated TiO 2 allows the full cell to deliver a remarkable power of 3700 W kg−1, outperforming most sodium-ion batteries. The correlation between the robust performance and the material property is understood through energy band analysis and density functional theory calculations. [Display omitted] [ABSTRACT FROM AUTHOR]

In order to study the effects of REs (Ce, Y and Gd) on the grain size and the grain refinement mechanism of AZ91 as-cast magnesium alloy at different cooling rates, the AZ91-xRE(Ce, Y, Gd, x= 0, 0.3, 0.6, 0.9) alloys with different cooling rates were prepared by die casting. The results show that the addition of REs to AZ91 magnesium alloy and the increase in cooling rate both can refine the grain size of the alloy, but the grain refinement effects of REs on AZ91 magnesium alloy will be weakened when the alloy is solidified at a faster cooling rate. The grain refinement effects of REs on AZ91 magnesium alloy are mainly due to the rare earth compounds of Al4Ce, Al2Y and Al2Gd which can act as heterogeneous nucleation particle to promote nucleation and the inhibitory effects of rare earth compounds distributed near grain boundaries on the grain growth. Increasing the cooling rate of the alloy will reduce the effective constitutional supercooling zone and increase the proportion of nucleation-free zone, which will weaken the heterogeneous nucleation particle effect of Al4Ce, Al2Y and Al2Gd, thereby weakening the grain refinement effects of REs on the AZ91 magnesium alloy at a faster cooling rate.

In this contribution, we report the synthesis of an imine-based soft 2D covalent organic framework (S-COF) with compacted honeycomb topology via inveterately selecting a helically folded ditopic flexible linker and a trigonal building block. In contrast to various topological structures of rigid monomer-based COFs (R-COFs) reported so far, owing to the presence of flexible skeleton S-COF can spontaneously form a compacted and nonporous topological structure via intramolecular π stacking of presupposed honeycomb-like topology. Such S-COFs with a compacted honeycomb topology have neither been proposed theoretically nor been achieved experimentally. The compacted topological structure of 2D S-COF was clearly characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), and circular dichroism (CD) measurements. This study opens a new window to the development of S-COFs and will significantly expand the scope of COF materials.

AZ91-xRE(Ce, Y, Gd, x = 0, 0.3, 0.6, 0.9) alloys with different cooling rates were prepared by die casting. Effects of cooling rate and rare earth elements (Ce, Y and Gd) on Mg17Al12compound in the alloy and the role of Mg17Al12compound in fracture process were studied. The results show that the Mg17(Al, Zn)12compound will be formed in AZ91 alloy, the cooling rate and rare earth elements (Ce, Y and Gd) both can regulate the size, distribution and content of Mg17Al12compound. The cooling rate can regulate the size and distribution of Mg17Al12compound in the alloy, but has less effect on the content of Mg17Al12compound. The addition of rare earth elements can significantly reduce the content of Mg17Al12compound and refine its size. The reduction effect of Ce on the content of Mg17Al12compound in alloy is the largest, and the size optimization effect is also the most significant. The effects of Y are the second, and the effects of Gd are relatively poor. The Mg17Al12compound in alloy is the main crack source and important crack propagation path because of its large size and low strength. Increasing the cooling rate and adding rare earth elements Ce, Y and Gd can make Mg17Al12compound play a better role in second phase strengthening by optimizing the size, distribution, and content of Mg17Al12compound.

Graphical abstract:

Formation process of main compounds in AZ91-0.9Gd alloy was studied, and main crack sources and fracture mechanism were analyzed. Experimental results show that AZ91-0.9Gd alloy is mainly composed of α-Mg, Mg17Al12, bulk Al2Gd compound and a small amount of Al–Mn-Gd ternary compound. Formation sequence is α-Mg, Al2Gd, Mg17Al12and Al–Mn-Gd. During load process, Al2Gd and Mg17Al12compounds are main crack sources and important locations of crack propagation path. The main crack locations include grain boundary, phase boundary, Al2Gd and Mg17Al12compounds. The continuous network distribution along grain boundaries of Mg17Al12compound is an important reason for intergranular fracture and poor plasticity of alloy. Fracture mechanism is that with the increase of load, there are many micro cracks occur at Al2Gd and Mg17Al12in alloy, a micro crack grows rapidly to form main crack, and gradually connects with other micro cracks, so that the main crack becomes larger until alloy fracture failure.

Cirrus clouds often contain numerous hollow ice crystals, which are distinct in scattering properties from solid ice crystals, and will be challenging to microphysical retrieval and radiative forcing assessment. Currently, hollow ice crystals have not been observed by remote sensing methods, and the estimation of their hollowness is a complex task. To address this issue, the Mixed Modal Hollow Columns (MMHC) model for hollow ice crystals is introduced, and its backscattering properties are computed using the physical optics approximation method. Through comparison with spaceborne lidar observations, we identify a specific type of cirrus associated with the MMHC model for the first time. The visible optical depth of this cirrus is less than or equal to 0.1, and the temperature is between −60 and −40°C. The MMHC characteristic cirrus clouds are prevalent in middle and high latitudes but less comm+on in low latitudes. They exhibit distinct patterns in terms of sea and land distribution as well as seasonal variation. Cirrus clouds typically form at altitudes exceeding 6 km and consist of non‐spherical ice crystals, each with unique optical properties affecting the earth’s radiation balance through scattering and absorption. Notably, these crystals include hollow formations, which are distinct in scattering properties from their solid counterparts. The coexistence of hollow and solid ice crystals presents challenges in accurately inverting ice crystal morphology in remote sensing and evaluating radiation properties in climate models. To address these complexities, we propose a MMHC model. Through analysis of spaceborne lidar observational data, we identify characteristic cirrus clouds associated with such type of ice crystals and study the global distribution and seasonal distribution of this kind of cirrus clouds. A Mixed Modal Hollow Columns model is formulated to characterize the presence of hollow ice crystals in cirrus cloudsFor the first time, hollow characteristic cirrus clouds are observed using spaceborne lidarHollow characteristic cirrus clouds exhibit distinct global and seasonal distribution variations A Mixed Modal Hollow Columns model is formulated to characterize the presence of hollow ice crystals in cirrus clouds For the first time, hollow characteristic cirrus clouds are observed using spaceborne lidar Hollow characteristic cirrus clouds exhibit distinct global and seasonal distribution variations

Molecular weaving is a powerful approach to make molecularly woven materials that have showed unprecedented characteristics and properties intrinsically distinct to those of non-woven materials. We here report a facile and efficient approach for the synthesis of 2D woven supramolecular polymers by differentiated self-assembly through orthogonal noncovalent interactions. Importantly, the difference in binding strength of two orthogonal noncovalent interactions can be used to control the process of molecular weaving. Consequently, single-layered 2D woven supramolecular polymers were synthesized and fully characterized by various techniques. This study demonstrates a controllable method for molecular weaving, and will significantly hasten the development of molecularly woven materials.

The development of low-cost and high-energy aqueous battery technologies is of significance for renewable and stationary energy applications. However, this development has been bottlenecked by poor conductivity, low capacity, and limited cycling stability of existing electrode materials. In this work, we report on an energetic aqueous copper ion system based on CuS nanosheet arrays, taking profit of high conductivity of CuS and efficient charge carrier of copper ions. Electrochemical results reveal a high capacity of 510 mAh g–1, robust rate capability of 497 mAh g–1at a high rate of 7.5 A g–1, and ultrastable cycling by retaining 91% of the initial capacity over 2500 cycles. The charge-storage mechanism was systematically investigated by ex situand in situtechniques involving a reversible transition from CuS to Cu7S4and to Cu2S through the redox of Cu2+/Cu+. Moreover, we demonstrate a hybrid ion battery consisting of CuS positive electrode and Zn negative electrode, which affords an energy and power of 286 Wh kg–1and 900 W kg–1, respectively, on the basis of both electrodes, exceeding many aqueous battery systems.

Molybdenum disulfide (MoS 2) is a promising electrode material for sodium-ion batteries as it offers a large capacity through a distinct conversion reaction. However, the electrochemical potential of MoS 2 is often restrained by the poor conductivity as the dominant 2H phase is a semiconductor while the metallic 1T phase is thermodynamically unstable. In this work, we report a hybrid design and material preparation of freestanding nanosheets of MoS 2 composed of both 1T and 2H phases based on mild hydrothermal reaction. The introduction of the metallic 1T-MoS 2 phase into 2H-MoS 2 and their intimate hybridization enable a significant improvement in electronic conductivity, while the freestanding architecture avoids possible electrochemical aggregation. When used as electrodes for sodium storage, such a hybrid MoS 2 affords a high capacity of ∼500 mA h g−1 at 0.5 A g−1 after 300 cycles, and retains capacity of ∼200 mA h g−1 at a high current rate of 4 A g−1, thus demonstrating their potential in high-performance battery applications. [ABSTRACT FROM AUTHOR]

We report a nature-inspired design of tree-like architecture of cuprous oxide (Cu 2 O) stem and cobalt oxides (CoO) branch serving as an efficient anode for sodium-ion batteries. The construction of stem-branch architectures involves the growth of Cu 2 O nanorods and the subsequent deposition of CoO nanowires. Due to abundant active sites and full exposure to electrolyte, such a Cu 2 O@CoO stem-branch architecture demonstrates a robust storage toward Na+ ions, affording a capacity retention of ∼100% over 300 continuous cycles and a remarkable rate capability of 296 mAh g−1 at 1 A g−1. This result clearly shows the potential of nature-inspired materials engineering may find extensive applications in the design of high-performance electrodes for rechargeable batteries. [ABSTRACT FROM AUTHOR]

In the era of information technology, the exponential growth of data volume has compelled users to entrust their data to database service providers for efficient management. While traditional methods such as user authentication, security auditing, and access control have been implemented to safeguard data security across databases, cloud servers may face security challenges due to excessive internal administrator permissions. The audio technology of the Internet of Things (IoT) offers numerous advantages, including high bandwidth, short data transmission time, long transmission distance, and cost-effectiveness. It has found widespread applications in military, technological, industrial, and everyday life settings. With the advancements in modern information technology and the development and enhancement of wireless radio frequency technology in the IoT sector, IoT-based wireless audio interaction systems utilizing Wi-Fi have gradually become integrated into people's lives. These systems have enriched people's daily experiences and are increasingly popular among consumers. This paper, based on the theory of functional applied linguistics, combs the basic theoretical framework and the practical application prospect of functional Applied Linguistics of systemic language, especially emphasizes the important influence and application enlightenment of systemic functional linguistics on language teaching, and combines the "Recent Development Zone" The basic concepts of contemporary language and literature education, such as scaffolding, are summarized and analyzed. The paper establishes a comprehensive theoretical research framework for college spoken English teaching, and through the comprehensive theoretical analysis of communicative teaching methods and practical exploration of some problems that students may appear, it puts forward more effective and targeted specific solutions.

The extinction matrix for cirrus clouds has been calculated for the visible and infrared regions using the physical optics approximation. The cirrus clouds are modeled as a statistical ensemble of the hexagonal ice plates, distributed over their size and orientations by the gamma and Gaussian laws, respectively. Then, the extinction matrixes as the functions of the incident wavelength, incident direction, crystal size, and crystal orientation are numerically calculated for the first time. It is shown that the off-diagonal elements of the matrix are negligible. Therefore, the extinction in cirrus clouds is described with good accuracy by the scalar exponential law.

The errors in retrieved aerosol backscattering coefficients due to different lidar ratios are analyzed quantitatively in this paper. The actual calculation shows that the inversion error of the aerosol backscattering coefficients using the Fernald backward-integration method increases with increasing inversion distance. The greater the error in the lidar ratio, the faster the error in the aerosol backscattering coefficient increases. For the same error in lidar ratio, the smaller actual aerosol backscattering coefficient will get the larger relative error of the retrieved aerosol backscattering coefficient. The errors in the lidar ratios for dust or the cirrus layer have great impact on the retrievals of backscattering coefficients. The interval between the retrieved height and the reference range is one of the important factors for the derived error in the aerosol backscattering coefficient, which is revealed quantitatively for the first time in this paper. The conclusions of this article can provide a basis for error estimation in retrieved backscattering coefficients of background aerosols, dust and cirrus layer. The errors in the lidar ratio of an aerosol layer influence the retrievals of backscattering coefficients for the aerosol layer below it.

We report on the development of a blue light-emitting-diode-based incoherent broad-band cavity-enhanced absorption spectroscopy (IBBCEAS) instrument for the measurement of the aerosol extinction coefficient at λ=461  nm. With an effective absorption path length of 2.8 km, an optimum detection limit of 0.05  Mm^−1 (5×10^−10  cm^−1) was achieved with an averaging time of 84 s. The baseline drift of the developed spectrometer was about ±0.3  Mm^−1 over 2.5 h (1σ standard deviation). The performance of the system was evaluated with laboratory-generated monodispersed polystyrene latex (PSL) spheres. The retrieved complex refractive index of PSL agreed well with previously reported values. The relative humidity (RH) dependence of the aerosol extinction coefficient was measured using IBBCEAS. The measured extinction enhancement factor values for 200 nm dry ammonium sulphate particles at different RH were in good agreement with the modeled values. Field performance of the aerosol extinction spectrometer was demonstrated at the Hefei Radiation Observatory site.

In theory, lidar overlap factor can be derived from the difference between the particle backscatter coefficient retrieved from lidar elastic signal without overlap correction and the actual particle backscatter coefficient, which can be obtained by other measured techniques. The side-scatter technique using a CCD camera is testified to be a powerful tool to detect the particle backscatter coefficient in near ground layer during night time. A new experiment approach to determine the overlap factor for vertically pointing lidar is presented in this study, which can be applied to Mie lidars. The effect of overlap factor on Mie lidar is corrected by an iteration algorithm combining the retrieved particle backscatter coefficient using CCD side-scatter method and Fernald method. This method has been successfully applied to Mie lidar measurements during a routine campaign, and the comparison of experimental results in different atmosphere conditions demonstrated that this method is available in practice.

Abstract: The Young Companion, an important representative of Republican Shanghai’s popular magazines, organized a Healthy Baby Contest from August 1926 to March 1927. Though its slogan, “Strong babies promise strong people, strong people guarantee a strong nation” expressed a nationalistic spirit, this contest was rather a commercial activity organized by a popular magazine and its commercial sponsor exploiting nationalistic discourse. Such an integration of nationalistic discourse and commercial interests profoundly influenced mass culture and ultimately promoted China’s modernization and its development as a nation. With this contest as an example, this paper sheds light on the relationship between popular journals and the making of a nation.

A new iterative algorithm is developed to estimate LIDAR ratio for a thin cirrus cloud over an aerosol layer. First, the thin cirrus cloud is screened out and replaced by a modeled LIDAR signal and the extinction coefficients of the aerosol layer are derived using the Fernald backward method. These aerosol coefficients are referred as the "actual values". Second, the original LIDAR signal which includes the thin cirrus cloud is also inverted by the Fernald backward method down to the aerosol layer but using different LIDAR ratio for the thin cirrus cloud. Depending on the different assumptions about the LIDAR ratio of the thin cirrus cloud, different sets of aerosol extinction can be derived. The "actual values" which are found in the first step can be used to constrain this iterative progress and the correct LIDAR ratio of the thin cirrus cloud can be found. The detailed description of this method and retrieval examples are given in the paper. The cases compared with other methods are presented and the statistical result is also shown and agrees well with other studies.

The traditional approach to inverting aerosol extinction makes use of the assumption of a constant LIDAR ratio in the entire Mie-LIDAR signal profile using the Fernald method. For the large uncertainty in the cloud optical depth caused by the assumed constant LIDAR ratio, an not negligible error of the retrieved aerosol extinction below the cloud will be caused in the backward integration of the Fernald method. A new algorithm to determine aerosol extinction below a cirrus cloud from Mie-LIDAR signals, based on a new cloud boundary detection method and a Mie-LIDAR signal modification method, combined with the backward integration of the Fernald method is developed. The result shows that the cloud boundary detection method is reliable, and the aerosol extinction below the cirrus cloud found by inverting from the modified signal is more efficacious than the one from the measured signal including the cloud-layer. The error due to modification is less than 10% taken in our present example.

A new polarization lidar has been developed for detecting depolarization characteristics of aerosol and cirrus over Hefei (31.9 degree N, 117.16 degree E), China. The fundamental principle of polarization lidar is briefly introduced. Overall structure and specifications of the polarization lidar, as well as measurement method, are described. The observational results of depolarization ratio for cirrus over Hefei from February to May in 2005-2007 are presented and discussed. The exploring temperatures by radiosonde during the spring of 2005 are also presented and analyzed. The results show that the cirrus generally presents in the altitude from 7 to 12 km, and the depolarization ratio varies from 0.2 to 0.5. At the meanwhile, depolarization ratio appears a climbing tendency with the increasing height and the decreasing temperature.