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A series of novel red-emitting BaLiZn3(BO3)3:Eu3+ phosphors was synthesized through the high temperature solid state reaction method. The phase composition, crystal structure, morphology and photoluminescence property of the BaLiZn3(BO3)3:Eu3+ samples are systematically investigated. The phosphor can be efficiently excited by the near ultraviolet light (NUV) of 396 nm and blue light of 466 nm, and give out red light emission at 618 nm corresponding to the electric dipole transition (5D0→7F2). The optimal doping concentration of Eu3+ ions in BaLiZn3(BO3)3 is determined to be about 3 mol%, and the concentration-quenching phenomenon arise from the electric dipole–dipole interaction. The temperature dependent luminescence behavior of BaLiZn3(BO3)3:0.03Eu3+ phosphor exhibits its good thermal stability, and the activation energy for thermal quenching characteristics is calculated to be 0.1844 eV. The decay lifetime of the BaLiZn3(BO3)3:0.03Eu3+ is measured to be 1.88 ms. These results suggest that the BaLiZn3(BO3)3:Eu3+ phosphors have the potential application as a red component in white light emitting diodes (WLEDs) with NUV or blue chips.

Graphene is a competitive electrode material for supercapacitors due to its unique two-dimensional structure, large surface area, high conductivity, and good physicochemical stability. However, random agglomeration and restacking of graphene sheets result in a reduced surface area and a loose structure with low density, which severely restricts the application for high gravimetric/volumetric energy density devices. Rational design of the layered-stacking structure of graphene assemblies can effectively prevent the restacking of graphene sheets, construct efficient ion transport channels, and improve spatial utilization, demonstrating the huge potential for developing advanced electrode materials. Herein, from the aspect of improving the electrochemical kinetics through designing efficient electron and ion transport paths, we first highlight the advantages of layered-stacking graphene assemblies, describe some common routes for preparing graphene building units, and then summarize the novel methods to design layered-stacking structures. A comprehensive review of the typical structure including nanocarbon pillared graphene, porous graphene blocks, and graphene ribbon films is provided with a focus on the mechanisms behind the performance improvements. Finally, critical challenges and some general ideas for future development are proposed, which may open up new opportunities for material chemistry and device innovation.

Improving both surface and space utilization of active carbon is crucial for compact supercapacitors. Herein, two activated carbons are prepared through homogeneous activation (HAC) and traditional outside-in activation (OIAC). Compared with OIAC with deep and branched porous structure, HAC shows an interconnected porous structure, leading to higher density, better gravimetric and volumetric capacitances, and improved rate performance. The results demonstrate that interconnected porous structure by homogeneous activation promotes high surface and space utilization as well as robust ion transport kinetics of activated carbon for capacitive energy storage.

The powder samples of Ca9Sc(PO4)7:xDy3+ white emitting phosphors were prepared via a solid state reaction technique. The Ca9Sc(PO4)7:Dy3+ samples were researched by using the GSAS Rietveld refinement and X-ray diffraction (XRD) methods, and SEM images and elemental maps were recorded. Under 350 nm excitation, the emission spectra of Ca9Sc(PO4)7:xDy3+ samples have two obvious peaks and one weak peak at 484, 572 and 660 nm, corresponding to the characteristic electron transitions of (4F9/2 → 6H15/2, blue), (4F9/2 → 6H13/2, yellow) and (4F9/2 → 6H11/2, red), respectively. The concentration quenching effect, decay lifetime and thermal quenching of the as-synthesized Ca9Sc(PO4)7:Dy3+ samples were researched systematically. The Ca9Sc(PO4)7:0.02Dy3+ phosphor possesses a good thermal stability, of which the emission intensity at 423 K can maintain 79% of the initial value (273 K). In addition, through the study of the chromaticity coordinates of the Ca9Sc(PO4)7:0.02Dy3+ phosphor, it is found that it is located in the white region, and the Commission Internationalede L'Eclairage (CIE) chromaticity coordinates are (0.339, 0.389). The above results show that Ca9Sc(PO4)7:xDy3+ phosphors can be excellent candidate material for applications in NUV-excited white LEDs.

This article constructs a comprehensive evaluation index system from four aspects: economic vitality, innovation efficiency, green development, and people’s lives. Use the entropy method to comprehensively measure the urban competitiveness level of 25 counties and cities in the economic zone, clarify the differences in their high-quality development levels, and use spatial econometric analysis methods to study the spatial agglomeration and dispersion and spatial convergence of regional urban competitiveness. The results show that the following: (1) the overall high-quality development level of the Huaihe River Eco-Economic Zone is not high, and the overall time and space characteristics is “high in the east and low in the west”; (2) there is a positive spatial autonomy in urban competitiveness and the spatial distribution of the Huaihe River, and relevantly, the degree of closeness of spatial associations between cities is generally low; (3) the gap between the level of urban competitiveness in Jiangsu Province is shrinking, the development of other provinces has a time lag effect, and there are differences in the level of urban competitiveness. Finally, to promote the high-quality development of the Huaihe Economic Zone, we must follow the law of the basin and the characteristics of spatial distribution and implement targeted strategies.

In this study, experiments on the vented deflagration of hydrogen–methane–air mixtures were performed in a vertical rectangular duct with a vent at its top end. A nondimensional vent coefficient ( K v ) was employed to characterize the effects of vent area ( A v ) on flame evolution and pressure buildup within and outside the duct. The maximum internal overpressure was attained near the duct bottom for a certain K v . As K v was increased from 2.2 to 11.9, the maximum internal overpressure near the vent and at the center of the duct increased monotonically; however, a nonmonotonic trend was observed at the duct bottom. Helmholtz oscillations of the internal flame and overpressure were observed in the tests for low K v , and acoustic oscillations of the internal overpressure with a frequency of ~1200 Hz appeared in all tests. The maximum external overpressure first increased and then decreased with an increase in K v . The external explosion induced a pressure peak in the duct, and the effect of external explosion on the venting of the internal deflagrations was weakened as K v ≥ 7.8.

Because of the complexity of groundwater systems and human activities, fuzzy and random uncertainties are two kinds of uncertain factors that exist widely in groundwater systems. The fuzziness of the variables is usually described by membership functions. When the variables obey different membership functions, the fuzzy risk of adverse events may be different. To explore the influence of the membership function type on the reliability of the estimation results of allowable groundwater drawdown, taking groundwater exploitation in desert oasis areas that have great dependence on groundwater as an example, a fuzzy stochastic coupling model of the allowable groundwater drawdown is established. Using the theory of the cut level λ, fuzzy variables are transformed into random variables to obtain the fuzzy risk. The results show that unlike the random risk, the fuzzy random risk is an interval. The membership functions with a normal distribution and quasi-normal distribution have little effect on the fuzzy risk in the case study. When λ 0.8, it has the smallest risk interval of all the membership functions. If the skewness of the design parameters is taken into consideration, the lognormal membership function is a better choice, with a fuzzy random risk of 57.68% at λ = 0.5. The results of this paper can also provide references for groundwater exploitation risk assessment.

Dense carbon materials with fast sodium storage performance are strongly desired for developing high-energy and high-power devices, but remain challenging because of the sluggish Na+ transport kinetics. Herein, we report that the defect density and sp2 cluster size of dense graphene blocks (DGB) can be elaborately modulated by ball-milling to achieve both high gravimetric and volumetric capacities and outstanding rate performance for Na+ storage. The loose graphene flakes are cut into small platelets with enriched defects and simultaneously densified by mechanical forces, leading to abundant active sites for Na+ storage, controlled sp2 size as conductive networks, and large interlayer spacing for fast Na+ transport. The DGB performs a novel capacitive Na+ storage with high capacities of 507 mAh g−1 and 397 mAh cm−3 at 50 ​mA ​g−1, and an ultrahigh rate of 181 mAh g−1 at 10 ​A ​g−1. It also shows a remarkable cycle stability due to the strongly-coupled layer structure. The comprehensive performance is superior to most of the reported carbons. The Na-ion capacitor delivers an ultrahigh energy density of 45 ​Wh kg−1 even at 14,205 ​W ​kg−1. Our work broadens the avenue for preparing advanced carbon materials for compact Na+ storage.

In this study, experiments on the vented deflagration of stoichiometric hydrogen–methane–air mixtures were performed in a 300 mm (length) × 300 mm (width) × 1000 mm (height) duct with a 250 mm × 250 mm vent on the top surface, to investigate the effect of hydrogen fraction in fuel (χ) ranging from 0 to 1.0 on flame evolution and pressure buildup within and outside the duct. The results reveal that χ significantly affects flame propagation and pressure–time histories. The movement of the entire flame bubble toward and away from the vent and a spike-shaped structure, which had been observed in a vented methane–air mixture in a previous study, was observed for low χ in current tests. For a given χ, the maximum overpressure in the duct increased with the distance to the vent. Both the maximum internal and external overpressure increased slowly as χ increased from 0 to 0.7, and increased quickly with a further increase in χ. Violent external explosions occurred for χ = 0.8 and 1.0, and an extremely high internal overpressure appeared under the effect of the external explosion.

Conventional sparsity-driven synthetic aperture radar (SAR) imagery often encounters the sensitivity of nonsystematic errors and highly computational load. In this article, a cooperative multitask learning algorithm is proposed based on an autocalibrated alternating direction method of multipliers (AutoCal-ADMM) framework, by which the sparse feature of the scenes/targets-of-interests can be enhanced, and simultaneously the nonmodeled motion errors of either airborne platform or moving target can be autocalibrated in a synergistic manner. By leveraging the entropy and sparsity regularizers in the AutoCal-ADMM framework, the proposed algorithm is particularly tailored to obtain focused SAR images with enhanced sparsity. A reasonable surrogate function is designed for a convex objective function, so that an analytical proximal mapping of the entropy regularizer can be derived. Both nonsystematic range cell migration (NsRCM) and azimuthal phase errors (APEs) are concerned and coherently compensated. A linear and complex soft-thresholding operator is introduced for the sparse solution. The proposed algorithm is capable of greatly alleviating “error propagation” between multiple tasks, where an optima balance between the sparse and focusing features can be achieved. Superior performance in terms of convergence and efficiency can be guaranteed. Both raw SAR and canonical ground moving target imaging (GMTIm) data sets are processed and comparisons with conventions are performed, where the effectiveness and superiority of the proposed AutoCal-ADMM algorithm are validated.

This paper explores the inverse scattering problem that reconstructs the obstacle shape with far-field information in the acoustic environment. Taking the planar wave as the incident wave, the authors put forward a shape reconstruction method for an impenetrable obstacle with a sound-soft boundary. Firstly, the linear sampling method (LSM) was performed to acquire the prior information about the obstacle shape. Next, a shape parameter inversion model was constructed based on neural network and gating thought, and it was denoted as the SPIMNNG. The model parameters were updated through self-learning. After that, the shape parameters of obstacle boundary were inversed according to the far-field information and the prior information about obstacle shape. On this basis, the boundary shape of the obstacle was reconstructed. The computing complexity of the SPIMNNG model was also calculated. Finally, several numerical experiments were carried out to verify the proposed method. The results show that our method can effectively inverse the shape parameters of obstacles.

Achieving high rate capability of porous carbon at high mass loading is important for developing advanced supercapacitors. But it still remains a big challenge because thick electrode causes severely reduced electric conductivity and blocked ion migration channels. Herein, we develop a micelle-induced assembly method to prepare conductive porous carbon through puzzling flexible graphene quantum dots (GQDs). The unique sp2 hybridized GQDs ensure the product with a two times higher electric conductivity than the commercial activated carbon. The interconnected mesoporous structure promotes robust ion transport kinetics especially at high mass loadings. As supercapacitor electrode, it shows high capacitances of 315 and 170 F g−1 at 1 and 100 A g−1, respectively. Importantly, at a very high mass loading of 20 mg cm−2, it shows a remarkably high areal capacitances of 2.8 F cm−2 at 10 A g−1, which is much better than other reported carbon materials. The symmetric supercapacitors show maximum energy densities of 9.21 and 6.45 Wh kg−1 at the mass loadings of 2 mg cm−2 and 20 mg cm−2, respectively, revealing the structural advantage of GQD-puzzled porous carbon for practical applications.

With the ever-increasing demands for miniaturization of high-power supercapacitors, carbon materials maintaining good rate capability at high mass loadings are urgently needed. Herein, we prepare mesopore-dominated hollow carbon nanoparticles with good capacitive performance from commercial carbon black through an extremely simple air oxidation method. Taking advantage of the crystallinity inhomogeneity of carbon black nanoparticles, the hollow carbon nanoparticles are prepared by selective removal of the amorphous cores while maintaining of the ordered skins. The hollow carbon nanoparticles show large inner cavities, perforated mesoporous structure, and increased surface area from 87.4 to 753.2 m2 g−1, providing abundant electrolyte reservoirs, ion migration channels, and active sites especially for thick electrodes. The sample shows a dramatically enhanced capacitance from 5 F g−1 of the carbon black to 175 F g−1. Importantly, the assembled symmetric device exhibits high areal capacitance of 2.31 F cm−2 at 1 A g−1 and remarkable rate performance of 1.59 F cm−2 at 10 A g−1 even with an ultrahigh mass loading of 15 mg cm−2. Our work helps the deep understanding of the structural transformation of carbon black, and provides a scalable preparation route for hollow carbon nanoparticles with great potential for supercapacitors application.

Coal has played a significant role in daily life. However, the highly effective combustion and reducing combustion-caused hazards of the coal still hold a great challenge. In this work, effect of particle size on combustion behaviors of two kinds of coals, i.e., Tashan weakly caking coal (TS) and Ningxia coking coal (NX), was studied by the cone calorimeter. The results obtained from cone calorimeter testing indicated that the time to ignition and the values of peak of heat release rate of TS and NX coal samples increased with increasing their particle size. TS coal samples showed an increased content of char residues with the increment in the particle size, whereas the char residues of NX were decreased with the increase in the particle size. The total smoke production values of the TS coal samples were increased as the particle size increased, whereas NX coal samples presented an opposite trend in the total smoke production. This phenomenon is caused by the difference in density of char residues during the combustion process of the coal samples. With regard to the volatile gaseous release, it was noted that the highest total carbon monoxide yield of TS was higher than that of NX. In addition, the total carbon dioxide yields of TS and NX coal samples were decreased with the increase in the particle size. This work paves a potential pathway to explore highly effective burning model of coal.

A series of mesophase pitch-based composite carbon fibers with various contents of chemically derived graphene nanosheets (CGNSs) were prepared through melt-spinning, stabilization, carbonization, and graphitization. By means of scanning electron microscopy, X-ray diffraction, single-filament testing, and resistivity testing, the effect of CGNSs content on the structures and properties of the composite carbon fibers were investigated. And the thermal conductivity of the composite carbon fibers was predicted by indirect measurement. The results show that the presence of CGNSs can effectively avoid the generation of unwanted radial transverse texture and wedge cleavages of the carbon fibers prepared from pure mesophase pitch. Although the crystalline structure of CGNSs/mesophase pitch-based composite carbon fibers is not apparently improved, appropriate CGNSs content can enhance the tensile strength as well as the conductivity of the composite carbon fibers. When the CGNSs content is 0.1 wt%, the tensile strength, breaking elongation, electrical resistivity and thermal conductivity of the composite carbon fibers can attain 2.12 GPa, 0.35%, 0.95 μΩ m, and 1322 W m−1 K−1, respectively. And the successful preparation of the composite carbon fibers provides a new solution for the cost reduction of mesophase pitch-based carbon fibers with high thermal conductivity.

Traditional positive electrode materials consisting of transition metal oxides, sulfides, hydroxides, and conductive polymers exhibit ultra-high capacitances for asymmetric supercapacitors. However, negative electrode materials are rather poor. Herein, we report a simple but efficient template carbonization method to covalently graft p-phenylenediamine molecules onto a hollow “bubble-like” carbon sphere (PPD–BC) surface as the negative electrode for high performance asymmetric supercapacitors. In this strategy, the “bubble-like” carbon spheres can not only act as “reservoirs” to physically store pseudocapacitance additive p-phenylenediamine (PPD) molecules through a spatially constrained behavior, but also chemically confine the PPD using CO–NH chemically covalent bonds. As a result, the specific capacitance of PPD–BC (451 F g−1) is about three times higher than that of hollow bubble carbon (166 F g−1) due to the extra addition of faradaic reactions. More importantly, the as-assembled PPD–BC//Ni(OH)2 asymmetric supercapacitor exhibits a remarkably high energy density of 94 W h kg−1 at a power density of 423 W kg−1, as well as outstanding cycling performance with 88% capacitance retention after 1000 cycles. Therefore, the design of organic molecule modified carbon materials holds great promise for ultrahigh energy density storage devices.

Chlorinated paraffins (CPs) are produced in large amounts and used worldwide. Dietary intake is the primary pathway for the exposure of pets to CPs, but limited information is available concerning the potential contamination of pet food by CPs. In the present study, the concentrations and congener group profiles of short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) were assessed in 35 imported commercial dry cat and dog foods collected in China, and the estimated daily intakes of SCCPs and MCCPs for cats and dogs through the consumption of such foods was calculated. The concentrations of SCCPs and MCCPs in the cat and dog foods were determined to be in the ranges of 108–45,300 ng/g (median: 1340 ng/g) and 3.8–52,700 ng/g (median: 11 ng/g), respectively. The predominant congener groups were C10Cl6 for SCCPs and C14Cl7-8 for MCCPs. The high levels of CPs found in certain pet foods suggest the potential for adverse health effects.

The ever-increasing demands for low-cost, miniaturized, light-weight supercapacitors significantly enhance the standards of electrode materials. High capacitance and good rate performance at high mass loadings (>10 mg cm−2) are crucial for increasing the energy density of supercapacitors under the premise of high-power characteristic. However, most electrode materials show good performance only at a rather low mass loading. Increasing the electrode mass loading or thickness causes severely blocked electron and ion transport channels, decreased accessible active sites, as well as rapid fading of the capacitance and rate performance. The gap between the materials' theoretical and practical electrochemical performances drastically hinders their application. In this review, we summarize the design and preparation of high mass-loading carbon electrodes from the aspects of the entire conductive network and ion transport channels, dense structural design, and freestanding electrode construction. The basic electrochemical processes and kinetics, structure–property relationships, and new energy storage sites are discussed towards filling the gap between the new materials and practical applications. Finally, the future prospects, challenges, and promising strategies to solve the current problems are concluded to shed light on the development of high-performance practical carbon electrode materials.

We present a feature-based image registration method, the stepwise image registration (SIR), with a closed-form solution. Our SIR creates an inlier pool and a candidate pool as the initialization, and then gradually enriches the inlier pool and refines the transformation. In each step, the enriched correspondence exclusively tunes the transformation coefficient within the confirmed inlier pairs, instead of updating the mapping using the complete putative set. In turn, the refined transformation prunes inconsistent mismatches to alleviate the incoming matching ambiguity. The context-aware locality measure (CALM) is designed for dissimilarity measure. The capability of the CALM can be enhanced by the progressive inlier pool enrichment. Finally, a retrieval process is performed based on the finest CALM and alignment, by which the inlier pool is maximized. Extensive experiments of enrichment evaluation, feature matching, image registration, and image retrieval demonstrate the favorable performance of our SIR against state-of-the-art methods. The code and datasets are available at https://github.com/sucv/SIR .

Experiments were conducted in an obstructed 3-m-long duct to investigate the effects of equivalence ratio, thickness of rupture membrane, and vent area on vented hydrogen–air deflagrations. Shockwave-induced pressure peaks were observed inside and outside the duct in some tests. In the tests with one end of the duct totally opened, the location at which the overall maximum internal overpressure is achieved depends on the thickness of the rupture membrane for a given equivalence ratio; however, it is independent of equivalence ratio for a given thickness of rupture membrane. The pressure peak resulting from an external explosion always dominates the pressure–time histories 1.5 m downstream of the duct exit. The maximum internal and external overpressures first increase and then decrease as the equivalence ratio increases from 0.26 to 3.57, unexpectedly; none of these increase monotonically with an increase in the thickness of the rupture membrane. Two explosion venting regimes, namely sonic and subsonic, are observed. During sonic venting, the maximum internal overpressure increases exponentially with a decrease in vent area; it is nearly independent of the vent area during subsonic venting when the vent area is larger than approximately 19% of the cross-sectional area of the duct.

In this work, a facile template-assisted method has been applied to prepare hierarchical porous carbon (HPC), using the aqua-mesophase pitch (AMP) as the carbon precursor obtained through liquid phase oxidation, zinc nitrate hexahydrate (ZNH) as template, porogen and nitrogen source. The as-obtained HPC exhibits a high specific capacitance of 235.5 F g−1 at a current density of 1 A g−1, excellent rate capability with a capacitance retention of 58.6% at 50 A g−1. This research may deliver a scalable avenue for the design of novel carbon-based nanoarchitecture materials and effective utilization of abundant petroleum pitch resources for energy storage.

Superhydrophobic materials have a wide range of applications in oil/water separation, controlled corrosion and self-cleaning. However, most superhydrophobic polymer materials are surface-modified with fluorides or silicides, these materials will lose their superhydrophobic properties when exposed to strong acid, strong base or high temperatures. Herein, superhydrophobic carbon fibers (SCFs) with a core-shell structure have been prepared by electrospinning technology combined with subsequent chemical vapor deposition (CVD). The addition of oxidized coal (OC) increases the diameter of the fibers, while the CVD process achieves a graphitic carbon layer with low surface energy, ultimately resulting in a water contact angle (CA) as high as 159.5°. The as-prepared SCFs can effectively separate a series of oil/water mixtures with large flux and high separation efficiency. The SCFs have the ability to repel contamination of sand, orange juice, coffee and plant chlorophyll extract. What's more, the SCFs could maintain superhydrophobicity at the temperature of 97 °C under the corrosive liquid. In addition, the SCFs still maintain excellent superhydrophobicity after impregnating in strong acid, strong alkali and organic solvents for 120 days. The SCFs can be used repeatedly under various harsh conditions for a long time and may have a wide application prospect in the future.

Operating with a conceptual workflow for the appropriate processing of high-spatial resolution small unmanned aircraft system (sUAS) data for hydrologic modelling of floodplains during floo...

Experiments on explosion venting of a stoichiometric hydrogen-air mixture ignited near the top vent of a 1-m3 rectangular vessel with a hinged aluminum vent panel were performed to investigate the effect of the panel area density on the pressure build-up and flame behavior. When using aluminum panels, three pressure peaks could be distinguished in the pressure-time histories. The first pressure peak, which increases with the panel area density, is the dominant one. However, the second and the third pressure peaks, with magnitudes ranging from 5 to 10 kPa, are independent of the panel area density. The use of aluminum panels weakens the external explosion because the gas mixtures were vented laterally shortly after the vent panel was opened. Panel inertia has a negligible effect on the final stage of the downward propagating flame. The maximum external flame length decreases with the increase in panel area density.

The 0.8CaWO4-0.2EuMO4 (M = Nb, Ta) solid solution and Eu3+, Ta5+ and Nb5+ single doped CaWO4 were prepared by a high-temperature solid state reaction technique. Experiments show that the addition of Nb5+ and Ta5+ can increase the red luminescence of Eu3+ in CaWO4. In this paper, the composition and structure of solid solution were analyzed by X ray diffraction (XRD), Fourier transform infrared spectrum and Raman spectrum analysis. The luminescence properties of the solid solution were studied by means of stable photoluminescent spectra, diffuse reflectance spectra (DRS), fluorescent decay curves and variable temperature spectra. By combining structural analysis, J-O theoretical calculation and experimental results, we believe that the significant improvement of the emission efficiency comes from the decrease of non-radiation relaxation rate.

Experiments were conducted in a 6-m-long duct with a cross section of 300 mm × 300 mm to investigate the effects of the ignition, obstacle, and side vent locations on the vented deflagration of 18 vol% hydrogen–air mixtures. Significant effects of all three parameters were found. For ignitions near the open end, explosion venting was accompanied by continuous pressure oscillations. When the ignition location was near the closed end, dominant pressure peaks appeared at the exit of the duct, which were due to the shockwave resulting from flame acceleration induced by the obstacle. The overall maximum internal and external overpressures increased when the ignition location was moved from near the open end to the closed end of the duct but did not vary monotonically with the location of the obstacle or side vent. In the tests with different obstacle locations, the maximum internal pressure occurred near the open end when the obstacle was located at the center of the duct. Compared to the cases without a side vent, the maximum internal overpressure was effectively reduced when a side vent was introduced near the ignition point but increased when the side vent was located near the open end of the duct.

Multi-source Weber problem (MSWP) is a classical nonconvex and NP-hard model in facility location. A well-known method for solving MSWP is the location–allocation algorithm which consists of a location phase to locate new facilities and an allocation phase to allocate customers at each iteration. This paper considers the more general and practical case of MSWP called the constrained multi-source Weber problem (CMSWP), i.e., locating multiple facilities with the consideration of the gauge for measuring distances and locational constraints on new facilities. According to the favorable structure of the involved location subproblems after reformulation, an alternating direction method of multipliers (ADMM) type method is contributed to solving these subproblems under different distance measures in a uniform framework. Then a new ADMM-based location–allocation algorithm is presented for CMSWP and its local convergence is theoretically proved. Some preliminary numerical results are reported to verify the effectiveness of proposed methods.

This paper presents a novel hybrid model predictive multilayer control (HMPMC) strategy for modular multilevel converters (M2LCs). The proposed hybrid strategy uses a modified model predictive direct slope control (MPDSC) concept to regulate the load current while concurrently minimizing the switching frequency, circulating current, and capacitor voltage variations through a new MPMC concept. The multilayer philosophy uses dedicated control layers to independently evaluate its control variables. As the main advantage, the hybrid strategy enables operation of M2LC at low switching frequencies. Moreover, this paper proposes a hierarchical screening algorithm, which estimates the minimum number of switching states required to be evaluated for each control variable, reducing the computational burden. An execution order for each control layer, in which the variables are assigned to control layers as appropriate, is also incorporated to further reduce the computational burden. Instead of using conventional weighting factors, this paper uses tuning factors for each layer, which is based on the number of switching states of the lowest cost to make the tuning process efficient and adaptable to any operating conditions. To demonstrate the validity, a prototype single-phase, five-level, 380-VA M2LC is designed, built, and controlled through the proposed strategies. The performance of prototype is investigated under both the steady-state and transient conditions, and the experimental results are presented in comparison with simulations and benchmarked against both the conventional finite control set model predictive control (FCS-MPC) and an improved MPC strategy. The results clearly indicate that the proposed strategy enables efficient operation of the converter at both significantly lower switching frequency and reduced computational burden, which is preferred for high-power applications.

A series of novel single-component color tunable phosphors KAlGeO4:Bi3+,Eu3+ were synthesized by high-temperature solid state reaction. The crystal structure and electronic structure were analyzed by Rietveld refinement method and density functional theory (DFT) calculations, from which the lattice parameters and bandgap energy were determined. Photoluminescence properties, fluorescence decay and the energy transfer process have been investigated systematically. Under 320 nm excitation, KAlGeO4:Bi3+,Eu3+ shows both blue emission of Bi3+ and red emission of Eu3+, originating from the allowed 3P1–1S0 transition of Bi3+ and the 5D0–7FJ transitions of Eu3+, respectively. By adjusting the mole ratio of Bi3+ to Eu3+, the color of KAGO:Bi3+,Eu3+ can be tuned from blue to orange-red. The energy transfer mechanism was determined, and the energy transfer efficiency from Bi3+ to Eu3+ increased linearly with the increasing of Eu3+ concentration. Moreover, KAGO:Bi3+,Eu3+ has good thermal quenching properties.

Long-persistent phosphors can be used in diverse fields, such as emergency instruction, information storage and in vivo bioimaging. Currently, progress in research and development of white long-persistent phosphors is slow, although there is growing demand for applications in certain conditions. In this work, a novel white long-persistent phosphor Ba2Ga2GeO7:Pr3+ was synthesized and systematically investigated through its structural information, photoluminescence and phosphorescence properties. Under ultraviolet light excitation, this phosphor gives white emission containing greenish-blue and red components stemming from 3P0 and 1D2 multiplet electron transitions in the 4f level of Pr3+. The luminescent color of the phosphors is relatively stable at different temperatures and Pr3+ concentrations. Bright white afterglow can be observed by the naked eye in the dark for 3 hours after removal of the excitation source. Finally, a feasible afterglow mechanism of Ba2Ga2GeO7:Pr3+ with a trap–detrap scenario was proposed to clarify the generation of the white afterglow.

We report a novel orange-emitting phosphor BaGa2O4:0.02Bi3+ with ultra-broadband emission and a large Stokes shift (1.88 eV). Its crystal structure, photoluminescence (PL) spectra, thermoluminescence (TL) spectra and long persistent luminescence (LPL) were investigated. The Bi3+ emission centers located at different six-membered rings are responsible for the asymmetric broadband PL spectra peaking at 638 nm. The integrated PL intensity of the phosphor at 200 °C still maintains 93.6%, 88.1% and 174.0% of the one at room temperature upon 310, 325 and 365 nm excitation due to the compensating emission losses of the phosphor with increasing temperature. Also, commendable LPL can be observed by the naked eye for 7 days and detected using a spectrofluorometer for 25 days in the dark after the stoppage of the 254 nm excitation. Both the unusual resistance to thermal quenching and super long LPL properties rely on the capture and release processes of the charge carriers in the traps. Finally, a white light emitting diode (WLED) with high Ra(>90) was obtained by combining the BaGa2O4:0.02Bi3+ phosphor with a UV-LED chip. Our concept of exploiting phosphors may open a gateway for discovering new multifunctional phosphors with excellent PL and LPL properties.

A rapid, selective, and quantitative method to determine clenbuterol content in animal urine based on Surface-Enhanced Raman Spectroscopy (SERS) by aggregated re-oxidized graphene oxide/Au nanoparticle (roGO/AuNPs) hybrids and liquid-liquid extraction has been proposed in this study. To realize the quantitative calculation, melamine was optimized as the internal standard. The peak intensity of melamine observed at △v = 709 cm−1 was first set to 1000 as basis, and the peak at △v = 1474 cm−1 was selected as the characteristic peak of clenbuterol used for the quantitative calculation. Sufficient linearity was obtained in the range of 1–20 ng mL−1 (R2 = 0.997). The limit of detection and quantification in urine matrix were as low as 0.5 and 1 ng mL−1, respectively. The recovery rates were 78.6–89.4% with coefficients of variation less than 9.8%, and the storage time of the substrates is approximately 180 days under 4℃. The detection results of the developed SERS detection method agree well with those determined by LC–MS/MS, while the cost time significantly reduced to 8 min/sample. This new protocol could be easily developed for the routine monitoring of the illicit use of clenbuterol in animal farming.

Designing multi-shelled structures is an efficient way to improve the rate performance and cycle stability of transition metal oxides for lithium and sodium storage. However, the sluggish electron transport kinetics caused by the lack of overall conductive networks especially for the inner shells drastically restricts their high-power ability. Herein, a novel multi-shelled V2O3/C composite with an in-built overall carbon scaffold coupled on each of the porous V2O3 thin shells was developed through a simple solvothermal process followed by thermal treatment based on a sequential self-template mechanism. This novel structure simultaneously enables outstanding electrical conductivity, fast ion transport kinetics, and excellent structural stability. As expected, the composite shows a remarkably fast lithium storage ability of 427 mA h g−1 at 5000 mA g−1 and extraordinary cycle stability with 96% retention after 600 cycles, which is one of the best performances among the reported vanadium oxide/carbon composites. Moreover, it also exhibits an excellent sodium storage ability of 173 mA h g−1 after 2000 cycles at 1000 mA g−1. We believe that this work would broaden the avenue for designing advanced electrode materials for energy storage and conversion.

We propose two new double projection algorithms for solving the split feasibility problem (SFP). Different from the extragradient projection algorithms, the proposed algorithms do not require fixed stepsize and do not employ the same projection region at different projection steps. We adopt flexible rules for selecting the stepsize and the projection region. The proposed algorithms are shown to be convergent under certain assumptions. Numerical experiments show that the proposed methods appear to be more efficient than the relaxed- CQ algorithm.

Although high-surface-area activated carbons have been widely used for supercapacitors, they usually have limited capacitive and rate performances primarily because of the low conductivity and sluggish electrochemical kinetics caused by their amorphous microporous structure. Here, we report a simple strategy to boost the electrochemical performance of activated carbons by embedding highly crystallized graphene quantum dots. Benefiting from the formation of the overall conductive networks, the charge-transfer and ion migration kinetics of the activated carbon are significantly improved, facilitating electrolyte ion transport and storage in deep and branched micropores. As a result, the graphene quantum dot embedded activated carbon, possessing a microporous structure with a specific surface area of 2829 m2 g−1, achieves a remarkably high electric double-layer capacitance of 388 F g−1 at 1 A g−1 as well as excellent rate performance with 60% capacitance retention at 100 A g−1 in a two-electrode system. The capacitive and rate performances are much higher than not only those of the activated carbon without graphene quantum dots, but also those of most porous carbons reported in the literatures. This strategy provides a new route for designing advanced porous carbon materials for high performance energy storage.

Pavement surface distress conditions are critical inputs for quantifying roadway infrastructure serviceability. Numerous computer-aided automatic examination techniques have been deployed for pavement distress condition assessments, such as digital image processing methods. However, their effectiveness and applicability are impeded due to information losses in 2-D image combination processes or extremely high costs in 3-D geo-referenced data set. In this paper, a cost-effective Kinect-based approach is proposed for 3-D pavement surface reconstruction and cracking recognition. We propose a comprehensive computational solution for the detection and recognition of pavement distress feature identification. Various cracking measurements such as alligator cracking, traverse cracking, longitudinal cracking, and so on. are identified and recognized for their severity examinations based on associated geometrical features. The experimental results indicate that this method is effective in reducing data collection costs and extracting analytical information on pavement cracking measurements. The research findings confirm that the proposed approach provides a viable, applicable solution to an automatic pavement surface condition detection and evaluation. The proposed methodology is transferable for pavement surface reconstruction and distress condition detection based on the other 3-D cloud point data. It provides an alternative inexpensive complement to existing pavement examination methodologies.

Aquatic foods are important sources of chlorinated paraffins (CPs) to humans. Farmed crabs are bottom-dwelling aquatic animals, and can accumulate CPs through food and aquatic environment. However, limited information is available on CPs concentrations in and sources to farmed crabs. In this study, short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) concentrations in 59 samples from the farmed crab food web (crab, crab feed, and aquaculture environment) were determined. The samples were from 17 crab farms in Anhui Province, Jiangxi Province, and Shanghai, in China. The SCCPs and MCCPs concentrations in the crab samples were 82–1760 and not detected–680 ng/g lipid weight, respectively. The dominant SCCPs and MCCPs in the crab samples were C10Cl6−7 and C14Cl7−8, respectively. The SCCPs concentrations in the crab food web samples were higher than the MCCPs concentrations. SCCPs contamination of the crab food web samples was not directly related to CPs product use. The main factors affecting SCCPs concentrations in the crab samples were different for different crab farms. Crab feed and the aquaculture environment could be sources of SCCPs to farmed crabs. No marked health risks are posed to humans through consuming CPs in Chinese mitten crabs farmed in China.

High surface area, good conductivity, and high mechanical strength are important for carbon nanofiber fabrics (CNFs) as high-performance supercapacitor electrodes. However, it remains a big challenge because of the trade-off between the strong and continuous conductive network and a well-developed porous structure. Herein, we report a simple strategy to integrate these properties into the electrospun CNFs by adding graphene quantum dots (GQDs). The uniformly embedded GQDs play a crucial bifunctional role in constructing an entire reinforcing phase and conductive network. Compared with the pure CNF, the GQD-reinforced activated CNF exhibits a greatly enlarged surface area from 140 to 2032 m

Climate change has become one of the major threats to global security. On the impact of climate change on national vulnerability, the researchers firstly select relevant factors and data and analyze the principal components to determine the weight of climate change on vulnerability so as to analyze the impact of climate change on national vulnerability. Secondly, based on the influencing factors, we obtain the national vulnerability score through the fuzzy comprehensive evaluation method, delineate the impact scope according to the score, and predict climate change by means of regression analysis and time series analysis. Finally, according to the characteristics of cities and continents, the model is revised, a PSR model and a cluster analysis model are established, and the prediction accuracy is improved.

The well-known multi-facility Weber problem (MFWP) is one of fundamental models in facility location. With the aim of enhancing the practical applicability of MFWP, this paper considers a generalized multi-facility Weber problem (GMFWP), where the gauge is used to measure distances and the locational constraints are imposed to new facilities. This paper focuses on developing efficient numerical methods based on alternating direction method of multipliers (ADMM) to solve GMFWP. Specifically, GMFWP is equivalently reformulated into a minmax problem with special structure and then some ADMM-type methods are proposed for its primal problem. Global convergence of proposed methods for GMFWP is established under mild assumptions. Preliminary numerical results are reported to verify the effectiveness of proposed methods.

In view of the significant impact of color centers on the physical and chemical properties of materials, studies on the origin of such color centers are needed. In this article, detailed crystal structure analysis and compositional characterization of CeAlO3 was carried out by applying XRD, XPS, HRTEM, STEM-EDS and ICP-OES techniques. The results revealed that crystal defects may be the main cause of color centers. The existence of oxygen and aluminum vacancy was proved and confirmed by the application of XPS, ICP-OES and STEM-EDS characterization methods. Overall, it unlikely that a single crystal defect would generate the yellow-green color of CeAlO3 crystals.

In this article we synthesized a series of phosphors K2MgGeO4:Bi3+ with high brightness for white light-emitting diodes (WLEDs) conversion and investigated their crystal structures and luminescence properties using powder X-ray diffraction, diffuse reflectance spectra, X-ray photoelectron spectroscopy, photoluminescence spectra, and absolute quantum efficiency. K2MgGeO4:Bi3+ phosphor exhibits intense absorption in near-UV area and presents a broad asymmetric emission band with the main peak located at 614 nm, which was ascribed to the 3P1 → 1S0 transition of Bi3+. The absolute quantum efficiency of the K2MgGeO4:0.01Bi3+ phosphor was measured to be 66.6%. Also, this orange emission with color chromaticity coordinates of (0.4989, 0.4400) has an excellent resistance to thermal quenching: its integrated intensity at 393 K still maintained ∼85% of the one at room temperature. The WLEDs devices with Ra = 93.8 were fabricated by employing K2MgGeO4:0.01Bi3+ as an orange phosphor, which contains abundant red light...

This paper presents a 2-D semi-analytical model for the vibration analyses of a plate with a power-law-profiled thickness variation, referred to as an Acoustic Black Hole (ABH) plate. The proposed model, along with the associated wavelet-based solution procedure, is intended to overcome major technical difficulties which are specific to ABH structures: the non-uniform wavelength distribution and ABH-induced wave compressions at the high frequency range in a realistic structure of finite size. Under the general Rayleigh-Ritz framework, Daubechies wavelet (DW) scaling functions are chosen as the admissible functions to decompose the transverse displacement of the plate with ABH indentations featuring a thickness variation along one direction of the panel. Modal and forced vibration analyses are carried out with results compared with those obtained by the FEM. It is shown that the model allows an accurate prediction of various vibration parameters and a realistic description of the typical ABH phenomena. Meanwhile, the use of Daubechies wavelet functions allows enhancing the effectiveness of the Rayleigh-Ritz method to reach the high frequency range, where systematic Acoustic Black Hole (ABH) effects are expected. Numerical analyses also reveal the potential of using strip ABH indentations in a plate to achieve a light-weight design with appealing vibration reduction properties. Analyses on the ABH-induced damping enhancement demonstrate the dominant effect of the local structural modes within indented area, which exhibit lower-order deformations (containing typically half and one wave along the direction in which the thickness is tailored).

The reasonable design of heterojunction nanostructures is a useful method for enhancing the properties of gas sensors based on metal oxide semiconductors. In this study, α-Fe2O3-In2O3 heterostructure nanocomposites were synthesized via a low-cost and simple hydrothermal route. The structure and morphology of α-Fe2O3-In2O3 heterostructure nanocomposites were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, the Brunauer–Emmett–Teller (BET) approach, and X-ray photoelectron spectroscopy. The results showed that the diameter of the α-Fe2O3-In2O3 heterostructure nanocomposites was about 2–3 μm, and the length and diameter of the Fe2O3 nanorods were about 1 μm and 10–15 nm, respectively. The BET surface area was calculated as 67.23 m2/g and the pore size was mainly distributed around 11 nm. Gas-sensing tests showed that the optimum operating temperature for the as-obtained α-Fe2O3-In2O3 heterostructure nanocomposite-based sensor was 300 °C. When the acetone concentration was 20 ppm, the response of the α-Fe2O3-In2O3 heterostructure nanocomposite-based sensor was about 37, which was about seven times higher than that of the pure material. Therefore, this α-Fe2O3-In2O3 heterostructure nanocomposite system merits further systematic investigation.

We present a dual-feature based point set registration method with global-local structural preservation. A finite mixture model which is able to deal with two features is first constructed. The mixture structure descriptor (MSD) is then obtained by smoothly combining the local structure descriptor (LSD) with the original coordinates through an annealing scheme. Substituting the MSD into the constructed model a fuzzy corresponding matrix is acquired. Next, the energy function which contains three main terms is formulated in the reproducing kernel Hilbert space. The first term is based on the L2 estimation (L2E) criterion, and the other two terms play a complementary role to improve the robustness and accuracy for transformation estimation at both global and local scales. The performances of our method in synthetic data, sequence data and real data against nine state-of-the-art methods are tested where our method shows favorable performance when compared with other methods.

The age of vegetation restoration has significant influences on near-surface hydrological function and soil quality in mining areas. This study analyzed the effects of restoration age and tree species on water conservation function (reflected by the water-holding characteristics of litter and soil) and soil fertility quality [reflected by soil bulk density (BD), soil organic carbon (SOC), total N (TN), available N (AN), available P (AP), and available K (AK)] of restored woodlands in phosphate mined-out areas. A primary forest (the control) and six woodlands restored for 4–25 years were selected as test sites. The results showed that total litter storage capacity, litter water-holding capacity, soil effective water-holding capacity, SOC, TN, AN, AP, and the comprehensive soil fertility index (SFI) increased with the restoration age, while small changes were also observed in soil total water-holding capacity, BD, and AK with restoration age. Compared to the control, the litter-modified interception amount, soil total water-holding capacity, and SFI in woodlands restored for 25 years were restored on average by 78%, 77%, and 92%, respectively. Furthermore, the litter water-holding capacities, soil capillary water-holding capacity, and AN in the Eucalyptus robusta woodlands restored for 10 years were significantly lower than those in woodlands of Alnus nepalensis restored for

Chlorinated paraffins (CPs) are used as plasticizers and flame retardants in plastics. Plastic packaging containing CPs is widely used for storage of animal feed, which can become contaminated by CPs that migrate into the feed. In the present study, 31 commercial animal feed packaging samples made of polypropylene (PP) or polyethylene (PE) were collected from animal feed manufacturers in China. The mean concentrations of short-chain chlorinated paraffins (SCCPs) in the PP and PE samples were 60.0 and 54.5 μg/g, respectively. The medium-chain chlorinated paraffin (MCCP) mean concentrations in the PP and PE samples were 62.7 and 9.23 μg/g, respectively. The carbon congener group profiles of SCCPs and MCCPs in the samples were different. The dominant SCCP and MCCP chlorine congener groups in all the samples were Cl6–7 and Cl6–8, respectively. Time and temperature influenced the migration of CPs from packaging into animal feed. As the time or temperature increased, the CP concentrations in the animal feed increased but the congener group profiles of the SCCPs and MCCPs in the animal feed did not change. To reduce contamination of animal feed by CPs, it is necessary to restrict the use of CPs in animal feed packaging.

Unmanned airborne systems (UAS), particularly the class of UAS referred to as small-unmanned airborne systems (S-UAS), have the potential to revolutionize the science, practice, and role of remote ...

A novel orange-red emitting Ba3Y4O9:Sm3+ phosphors were prepared by a high temperature solid-state reaction in air. X-ray diffraction (XRD), photoluminescence spectra, fluorescence decay and temperature-dependent emission spectra were utilized to characterize the structure and luminescence properties. The results show that the excitation spectrum includes a series of linear peaks at 350, 367, 382, 410, 424, 445, 470 and 495 nm, respectively. Under 410 nm excitation, the emission peaks were located at 574 nm (4G5/2—6H5/2), 608 nm (4G5/2—6H7/2), 659 nm (4G5/2—6H9/2) and 722 nm (4G5/2—6H11/2), respectively. The concentration quenching occurs when x equals 0.08 for Ba3Y4–xO9:xSm3+ phosphor and its mechanism is ascribed to the dipole–dipole interaction. The chromaticity coordinates of Ba3Y3.92O9:0.08Sm3+ phosphor are in the orange-red region. The temperature-dependent study shows that this phosphor has excellent luminescence thermal-stability. And the luminescence intensity of Ba3Y3.92O9:0.08Sm3+ phosphor at 473 K only declines by about 25.75% of its initial intensity. The experimental data indicate that Ba3Y4O9:Sm3+ phosphor may be promising as an orange-red emitting phosphor for white light emitting diodes.