Crustal velocity structure of central Gansu Province from regional seismic waveform inversion using firework algorithm

The firework algorithm（FWA） is a novel swarm intelligence-based method recently proposed for the optimization of multi-parameter, nonlinear functions. Numerical waveform inversion experiments using a synthetic model show that the FWA performs well in both solution quality and efficiency. We apply the FWA in this study to crustal velocity structure inversion using regional seismic waveform data of central Gansu on the northeastern margin of the Qinghai-Tibet plateau. Seismograms recorded from the moment magnitude（MW） 5.4 Minxian earthquake enable obtaining an average crustal velocity model for this region. We initially carried out a series of FWA robustness tests in regional waveform inversion at the same earthquake and station positions across the study region,inverting two velocity structure models, with and without a low-velocity crustal layer; the accuracy of our average inversion results and their standard deviations reveal the advantages of the FWA for the inversion of regional seismic waveforms. We applied the FWA across our study area using three component waveform data recorded by nine broadband permanent seismic stations with epicentral distances ranging between 146 and 437 km. These inversion results show that the average thickness of the crust in this region is 46.75 km, while thicknesses of the sedimentary layer, and the upper, middle, and lower crust are 3.15,15.69, 13.08, and 14.83 km, respectively. Results also show that the P-wave velocities of these layers and the upper mantle are 4.47, 6.07, 6.12, 6.87, and 8.18 km/s,respectively.

Mapping crustal S-wave velocity structure with SV-component receiver function method

In this article, we analyze the characters of SV-component receiver function of teleseismic body waves and its advantages in mapping the S-wave velocity structure of crust in detail. Similar to radial receiver function, SV-component receiver function can be obtained by directly deconvolving the P-component from the SV-component of teleseismic recordings. Our analyses indicate that the change of amplitude of SV-component receiver function against the change of epicentral distance is less than that of radial receiver function. Moreover, the waveform of SV-component receiver function is simpler than the radial receiver function and gives prominence to the PS converted phases that are the most sensitive to the shear wave velocity structure in the inversion. The synthetic tests show that the convergence of SV-component receiver function inversion is faster than that of the radial receiver function inversion. As an example, we investigate the S-wave velocity structure beneath HIA sta-tion by using the SV-component receiver function inversion method.

Improved multi-scale inverse bottleneck residual network based on triplet parallel attention for apple leaf disease identification

Accurate diagnosis of apple leaf diseases is crucial for improving the quality of apple production and promoting the development of the apple industry. However, apple leaf diseases do not differ significantly from image texture and structural information. The difficulties in disease feature extraction in complex backgrounds slow the related research progress. To address the problems, this paper proposes an improved multi-scale inverse bottleneck residual network model based on a triplet parallel attention mechanism, which is built upon ResNet-50, while improving and combining the inception module and ResNext inverse bottleneck blocks, to recognize seven types of apple leaf(including six diseases of alternaria leaf spot, brown spot, grey spot, mosaic, rust, scab, and one healthy). First, the 3×3 convolutions in some of the residual modules are replaced by multi-scale residual convolutions, the convolution kernels of different sizes contained in each branch of the multi-scale convolution are applied to extract feature maps of different sizes, and the outputs of these branches are multi-scale fused by summing to enrich the output features of the images. Second, the global layer-wise dynamic coordinated inverse bottleneck structure is used to reduce the network feature loss. The inverse bottleneck structure makes the image information less lossy when transforming from different dimensional feature spaces. The fusion of multi-scale and layer-wise dynamic coordinated inverse bottlenecks makes the model effectively balances computational efficiency and feature representation capability, and more robust with a combination of horizontal and vertical features in the fine identification of apple leaf diseases. Finally, after each improved module, a triplet parallel attention module is integrated with cross-dimensional interactions among channels through rotations and residual transformations, which improves the parallel search efficiency of important features and the recognition rate of the network with relatively small computational costs while the dimensional dependencies are improved. To verify the validity of the model in this paper, we uniformly enhance apple leaf disease images screened from the public data sets of Plant Village, Baidu Flying Paddle, and the Internet. The final processed image count is 14,000. The ablation study, pre-processing comparison, and method comparison are conducted on the processed datasets. The experimental results demonstrate that the proposed method reaches 98.73% accuracy on the adopted datasets, which is 1.82% higher than the classical ResNet-50 model, and 0.29% better than the apple leaf disease datasets before preprocessing. It also achieves competitive results in apple leaf disease identification compared to some state-ofthe-art methods.

Electron transport in electrically biased inverse parabolic double-barrier structure

A theoretical study of resonant tunneling is carried out for an inverse parabolic double-barrier structure subjected to an external electric field. Tunneling transmission coefficient and density of states are analyzed by using the non-equilibrium Green＇s function approach based on the finite difference method. It is found that the resonant peak of the transmission coefficient, being unity for a symmetrical case, reduces under the applied electric field and depends strongly on the variation of the structure parameters.

Synthesis,Structure and Properties of Inverse-Keggin Potassium Tetraniobooctatungstosilicate

Potassium tetraniobooccatungotosilicate, K8 [SiNb4 W8 O40] · 12H2 O was pre-pared by the reaction of white powdery tungstic acid, potassium niobate and potas -sium silicate in aqueous solution with pH value adjusted by potassium carbonate。The heteropolyniobotungstate crystallized in cubic space group Pm3m with unit cellparameters ;: a = 1.0640(1)nm,Z=1,V=1 .2045(5)nm3,R=0.055,Rw =0.062。The anion has inverse,Keggin structure,in which the central SiO4 tetrahedron isdistributed statistically in two orientations。The twelve outer metal positions arerandomly occupied by four niobium and eight tungsten atoms. Moreover, infraredspectrat electronic :spectra and thermogram were measured。

Intrinsic electrochemical activity of Ni in Ni_(3)Sn_(4) anode accommodating high capacity and mechanical stability for fast-charging lithium-ion batteries

Fast interfacial kinetics derived from bicontinuous three-dimensional(3D)architecture is a strategic feature for achieving fast-charging lithium-ion batteries(LIBs).One of the main reasons is its large active surface and short diffusion path.Yet,understanding of unusual electrochemical properties still remain great challenge due to its complexity.In this study,we proposed a nickel–tin compound(Ni_(3)Sn_(4))supported by 3D Nickel scaffolds as main frame because the Ni_(3)Sn_(4) clearly offers a higher reversible capacity and stable cycling performance than bare tin(Sn).In order to verify the role of Ni,atomic-scale simulation based on density functional theory systematically addressed to the reaction mechanism and structural evolution of Ni_(3)Sn_(4) during the lithiation process.Our findings are that Ni enables Ni_(3)Sn_(4) to possess higher mechanical stability in terms of reactive flow stress,subsequently lead to improve Li storage capability.This study elucidates an understanding of the lithiation mechanism of Ni_(3)Sn_(4) and provides a new perspective for the design of high-capacity and high-power 3D anodes for fast-charging LIBs.

A novel super-broadband travelling-wave modulator with nonperiodic domain inversions and ridge structure

In order to obtain large broadband, a novel travelling-wave modulator with nonperiodic domain inversions and ridge structure is proposed. The composite structure is designed to achieve velocity matching between the optical wave and the microwave, to get a 50 characteristic impedance and to reduce the loss of the microwave electrodes with finite element method (FEM). The calculation results show that the frequency response of the new device is flat up to 350 GHz with interaction length of 1 cm, characteristic impedance of 49 , and microwave refractive index of 2.5.

Three-dimensional lithospheric density distribution of China and surrounding regions

In this paper, we analyze lithospheric density distribution of China and surrounding regions on the basis of 30＇ × 30＇ gravity data and 1°×1 °P-wave velodty data, Firstly, we used the empirical equation be- tween the density and the P-wave velocity difference as the base of the initial model of the Asian lithospheric density. Secondly, we calculated the gravity anomaly, caused by the Moho discontinuity and the sedimentary layer discontinuity, by the Parker formula. Thirdly, the gravity anomaly of the spherical harmonics with 2 40 order for the anomalous body below the lithosphere is calculated based on the model of EGM96. Finally, by using Algebra Reconstruction Techniques （ART）, the inversion of 30＇ ~ 30＇ residual lithospheric Bouguer gravity anomaly caused by the lithosphere yields a rather detailed struc- tural model. The results show that the lithospheric density distribution of China and surrounding regions has a certain connection with the tectonic structure. The density is relatively high in the Philippine Sea plate, Japan Sea, the Indian plate, the Kazakhstan shield and the Western Siberia plain, whereas the Tibetan Plateau has low-density characteristics. The minimum value of density lies in the north of Philippines, in the Taiwan province and in the Ryukyu island arc.

Population inversion study of GaAs/AlGaAs three-quantum-well quantum cascade structures

A population inversion study of GaAs/AlxGa1-xAs three-quantum-well quantum cascade structures is presented. We derive the population inversion condition （PIC） of the active region （AR） and discuss the PICs on different structures by changing structural parameters such as the widths of quantum wells or barriers in the AR. For some instances, the PIC can be simplified and is proportional to the spontaneous emission lifetime between the second and the first excited states, whereas some other instances imply that the PIC is proportional to the state lifetime of the second excited state.

In situ establishment of Co/MoS_(2) heterostructures onto inverse opal‐structured N,S‐doped carbon hollow nanospheres:Interfacial and architectural dual engineering for efficient hydrogen evolution reaction

Rational design of low‐cost and high‐efficiency non‐precious metal‐based catalysts toward the hydrogen evolution reaction(HER)is of paramount significance for the sustainable development of the hydrogen economy.Interfacial manipulationinduced electronic modulation represents a sophisticated strategy to enhance the intrinsic activity of a non‐precious electrocatalyst.Herein,we demonstrate the straightforward construction of Co/MoS_(2) hetero‐nanoparticles anchored on inverse opal‐structured N,S‐doped carbon hollow nanospheres with an ordered macroporous framework(denoted as Co/MoS_(2)@N,S-CHNSs hereafter)via a templateassisted method.Systematic experimental evidence and theoretical calculations reveal that the formation of Co/MoS_(2) heterojunctions can effectively modulate the electronic configuration of active sites and optimize the reaction pathways,remarkably boosting the intrinsic activity.Moreover,the inverse opal‐structured carbon substrate with an ordered porous framework is favorable to enlarge the accessible surface area and provide multidimensional mass transport channels,dramatically expediting the reaction kinetics.Thanks to the compositional synergy and structural superiority,the fabricated Co/MoS_(2)@N,S-CHNSs exhibit excellent HER activity with a low overpotential of 105mV to afford a current density of 10 mA/cm^(2).The rationale of interface manipulation and architectural design herein is anticipated to be inspirable for the future development of efficient and earth‐abundant electrocatalysts for a variety of energy conversion systems.

Enhanced strength-ductility of CoCrFeMnNi high-entropy alloy with inverse gradient-grained structure prepared by laser surface heat-treatment technique

The inverse gradient-grained CoCrFeMnNi high-entropy alloy with a desirable mechanical property that evades the strength-ductility trade-off is fabricated by the process of cold rolling and subsequent laser surface heat-treatment.Due to the gradually decayed thermal effect along with the thickness,the grain size increases from the hard core to the soft surface in terms of the inverse gradient-grained sample,which is in good consistent with the microhardness profiles.The hetero-deformation induced strengthening and strain hardening caused by the inverse gradient-grained structure improve the strength-ductility combination,as well as the high-order hierarchal nanotwins due to the enhanced interaction with dislocations.For the laser surface heat-treatment technique,the strength and ductility are significantly increased by enlarging the microhardness difference and decreasing the thermal stress.Considering the high volume fraction of gradient-grained layer and a great deal of high-order hierarchal nanotwins in the central region,the laser surface heat-treatment technique is a promising way to produce the gradientstructured materials without thickness limitation.

INVERSE REGRESSION METHOD IN DATA STRUCTURE ANALYSIS

In order to explore the nonlinear structure hidden in high-dimensional data, some dimen-sion reduction techniques have been developed, such as the Projection Pursuit technique (PP).However, PP will involve enormous computational load. To overcome this, an inverse regressionmethod is proposed. In this paper, we discuss and develop this method. To seek the interestingprojective direction, the minimization of the residual sum of squares is used as a criterion, andspline functions are applied to approximate the general nonlinear transform function. The algo-rithm is simple, and saves the computational load. Under certain proper conditions, consistencyof the estimators of the interesting direction is shown.

Delicate synthesis of quasi-inverse opal structural Na_(3)V_(2)(PO_(4))_(3)/N-C and Na4MnV(PO_(4))_(3)/N-C as cathode for high-rate sodium-ion batteries

Poor conductivity and sluggish Na^(+) diffusion kinetic are two major drawbacks for practical application of sodium super-ionic conductor(NASICON) in sodium-ion batteries. In this work, we report a simple approach to synthesize quasi-inverse opal structural NASICON/N-doped carbon for the first time by a delicate one-pot solution-freeze drying-calcination process, aiming at fostering the overall electrochemical performance. Especially, the quasi-inverse opal structural Na_(3)V_(2)(PO_(4))_(3)/N-C(Q-NVP/N-C) displayed continuous pores, which provides interconnected channels for electrolyte permeation and abundant contacting interfaces between electrolyte and materials, resulting in faster kinetics of redox reaction and higher proportion of capacitive behavior.As a cathode material for sodium-ion batteries, the Q-NVP/N-C exhibits high specific capacity of 115 mAh·g^(-1) at 1C, still 61 mAh·g^(-1) at ultra-high current density of 100C,and a specific capacity of 89.7mAh·g^(-1) after 2000 cycles at 20C.This work displays the general validity of preparation method for not only Q-NVP/N-C,but also Na_(3)V_(2)(PO_(4))_(3),which provides a prospect for delicate synthesis of NASICON materials with excellent electrochemical performance.

Fluorinated inverse opal carbon nitride combined with vanadium pentoxide as a Z-scheme photocatalyst with enhanced photocatalytic activity

In this work,Z-scheme V_(2)O_(5) loaded fluorinated inverse opal carbon nitride(IO F-CN/V_(2)O_(5)) was synthesized as a product of ternary collaborative modification with heterostructure construction,element doping and inverse opal structure.The catalyst presented the highest photocatalytic activity and rate constant for degradation of typical organic pollutants Rhodamine B(RhB)and was also used for the efficient removal of antibiotics,represented by norfloxacin(NOR),sulfadiazine(SD)and levofloxacin(LVX).Characterizations confirmed its increased specific surface area,narrowed bandgap,and enhanced visible light utilization capacity.Further mechanism study including band structure study and electron paramagnetic resonance(EPR)proved the successful construction of Z-scheme heterojunction,which improved photogenerated charge carrier migration and provide sufficient free radicals for the degradation process.The combination of different modifications contributed to the synergetic improvement of removal efficiency towards different organic pollutants.

Fluorescence Retention of Organosilane-polymerized Carbon Dots Inverse Opals in CuCl Suspension

A novel and fluorescence retention inverse opal has been achieved from organosilane-polymerized carbon dots（SiCDs）, which is prepared via infiltrating SiCD solution into the interstice of photonic crystal（PC） template, low temperature treatment, heating polymerization and removing the colloidal template. The as-prepared SiCD inverse opals demonstrate close-cell structure, which is completely different from conventional open-cell structure. Then the fluorescence signal of as-prepared sample keeps almost unchanged in CuCl suspension while the fluorescence of SiCD solution can be quenched by CuCl suspension through an effective electron transfer process. This phenomenon can be attributed to the combined effect of high hydrostatic pressure in the pore structure, stable crosslinking network and fluorescence enhancement by PC structure. The SiCD inverse opals have advantages of unique close-cell structure, easy preparation and good repeatability that give an important insight into the design and manufacture of novel and advanced optical devices.