1.IntroductionSince the theory of spinodal decompo-sition in a supersaturated solid solution wasformulated by Hillert[1]and Cahn[2],thephenomena of spinodal decomposition havebeen found in many alloys.Tamura[3]haspoin...1.IntroductionSince the theory of spinodal decompo-sition in a supersaturated solid solution wasformulated by Hillert[1]and Cahn[2],thephenomena of spinodal decomposition havebeen found in many alloys.Tamura[3]haspointed out that spinodal decompositioncould also occur in maraging steels.A mod-ulated structure in 8Ni maraging steel was展开更多
A series of perovskite compounds of La1-x-yCaxKyMnO3 was prepared by hydrothermal disproportionation reaction of MnO2. The three oxidation states of manganese(Mn3+, Mn4+ and Mn5+) can stably exist in the compound...A series of perovskite compounds of La1-x-yCaxKyMnO3 was prepared by hydrothermal disproportionation reaction of MnO2. The three oxidation states of manganese(Mn3+, Mn4+ and Mn5+) can stably exist in the compounds. Under room temperature conditions, twice and three times modulated structure produced by the charge ordering can be observed by X-ray diffraction(XRD), select area electron diffraction(SAED) and high resolution transmission electron microscopy(HR-TEM). The splits of the diffraction peaks of the single crystals confirmed by synchrotron X-ray diffraction experiment are in accordance with those of the powder sample. The existence of the different oxidation states of Mn3+, Mn4+ and Mn5+ can be considered to be the dominating reason of the complicated room temperature modulated structure.展开更多
The laminated transition metal disulfides(TMDs),which are well known as typical two-dimensional(2D)semiconductive materials,possess a unique layered structure,leading to their wide-spread applications in various field...The laminated transition metal disulfides(TMDs),which are well known as typical two-dimensional(2D)semiconductive materials,possess a unique layered structure,leading to their wide-spread applications in various fields,such as catalysis,energy storage,sensing,etc.In recent years,a lot of research work on TMDs based functional materials in the fields of electromagnetic wave absorption(EMA)has been carried out.Therefore,it is of great significance to elaborate the influence of TMDs on EMA in time to speed up the application.In this review,recent advances in the development of electromagnetic wave(EMW)absorbers based on TMDs,ranging from the VIB group to the VB group are summarized.Their compositions,microstructures,electronic properties,and synthesis methods are presented in detail.Particularly,the modulation of structure engineering from the aspects of heterostructures,defects,morphologies and phases are systematically summarized,focusing on optimizing impedance matching and increasing dielectric and magnetic losses in the EMA materials with tunable EMW absorption performance.Milestones as well as the challenges are also identified to guide the design of new TMDs based dielectric EMA materials with high performance.展开更多
Metal Fe/Pd compositionally modulated films(CMFs) were prepared by vapour depo- sition from two sources onto glass substrate under vacuum.The modulation and crystal structures of the films were examined by X-ray diffr...Metal Fe/Pd compositionally modulated films(CMFs) were prepared by vapour depo- sition from two sources onto glass substrate under vacuum.The modulation and crystal structures of the films were examined by X-ray diffraction.The magnetic properties were determined by vibrating sample magnetometer.The Pd layers in the Fe/Pd CMFs are of fcc structure,and the Fe layer structure transits from bcc into amorphous,state with decreasing thickness of Fe layer.The dependence of specific saturation magnetization on thickness of Fe layers has also been discussed.展开更多
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 ima...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.展开更多
Oxygen evolution reaction(OER)as the foremost stumbling block to generate cost-effective clean fuels has received extensive attention in recent years.But,it still maintains the challenge to manipulate the geometric an...Oxygen evolution reaction(OER)as the foremost stumbling block to generate cost-effective clean fuels has received extensive attention in recent years.But,it still maintains the challenge to manipulate the geometric and electronic structure during single reaction process under the same conditions.Herein,we report a simple self-template strategy to generate honeycomb-like Ni_(2)P/N,P-C hybrids with preferred electronic architecture.Experiments coupled with theoretical results revealed that the synthesized catalyst has two characteristics:firstly,the unique honeycomb-like morphology not only enables the fully utilization of catalytic active sites but also optimizes the mass/electron transportation pathway,which favor the diffusion of electrolyte to accessible active sites.Secondly,N,P-C substrate,on the one hand,largely contributes the electronic distribution near Fermi level(E_(F))thus boosting its electrical conductivity.On the other hand,the support effect result in the upshift of d-band center and electropositivity of Ni sites,which attenuates the energy barrier for the adsorption of OH~àand the formation of*OOH.In consequence,the optimized Ni_(2)P/N,P-C catalysts feature high electrocatalytic activity towards OER(a low overpotential of 252 m V to achieve10 m A cm^(-2))and 10 h long-term stability,the outstanding performance is comparable to most of transition metal catalysts.This work gives a innovative tactics for contriving original OER electrocatalysts,inspirng deeper understanding of fabricating catalysts by combining theoretical simulation and experiment design.展开更多
Two-dimensional(2D)metal organic frameworks(MOFs)are emerging as low-cost oxygen evolution reaction(OER)electrocatalysts,however,suffering aggregation and poor operation stability.Herein,ultrafine Fe_(3)O_(4) nanopart...Two-dimensional(2D)metal organic frameworks(MOFs)are emerging as low-cost oxygen evolution reaction(OER)electrocatalysts,however,suffering aggregation and poor operation stability.Herein,ultrafine Fe_(3)O_(4) nanoparticles(diameter:6±2 nm)are homogeneously immobilized on 2D Ni based MOFs(Ni-BDC,thickness:5±1 nm)to improve the OER stability.Electronic structure modulation for enhanced catalytic activity is studied via adjusting the amount of Fe_(3)O_(4) nanoparticles on Ni-BDC.The optimal Fe_(3)O_(4)/Ni-BDC achieves the best OER performance with an overpotential of 295 mV at 10 mA cm^(-2),a Tafel slope of 47.8 mV dec^(-1) and a considerable catalytic durability of more than 40 h(less than 5 h for Ni-BDC alone).DFT calculations confirm that the active sites for Fe_(3)O_(4)/Ni-BDC are mainly contributed by Fe species with a higher oxidation state,and the potential-determining step(PDS)is the formation of the adsorbed O*species,which are facilitated in the composite.展开更多
The importance of the zeros of multwariable linear systems is well-knoiun in terms of measure obstructions to the controllability and the. observability. In this paper, a recursive decarnposi Am oj interconnected syst...The importance of the zeros of multwariable linear systems is well-knoiun in terms of measure obstructions to the controllability and the. observability. In this paper, a recursive decarnposi Am oj interconnected systems is outlined by taking into account the sequential structure of the connnections. The paper extends the, coordinate, module-theoretic studies from the elementary algebraic systems theory to include the case oj such linear interconnected systems which need not to be controllable or observable. Also, the properties of controllability and observability, the decoupling zeros and the signal Making issues are characterized.展开更多
In this paper,a flexible modular“Tetris”microsatellite platform is studied to implement the rapid integration and assembly of microsatellites.The proposed microsatellite platform is fulfilled based on a sandwich ass...In this paper,a flexible modular“Tetris”microsatellite platform is studied to implement the rapid integration and assembly of microsatellites.The proposed microsatellite platform is fulfilled based on a sandwich assembly mode which consists of the isomorphic module structure and the standard mechanical-electric-data-thermal interfaces.The advantages of the sandwich assembly mode include flexible reconfiguration and efficient assembly.The prototype of the sandwich assembly mode is built for verifying the performance and the feasibility of the proposed mechanical-electric-data-thermal interfaces.Finally,an assembly case is accomplished to demonstrate the validity and advantages of the proposed“Tetris”microsatellite platform.展开更多
During the incubation period of isothermal treatment(or aging) within the bainitic transformation temperature range in a salt bath (or quenching in water) immediately after solution treatment, not only are the def...During the incubation period of isothermal treatment(or aging) within the bainitic transformation temperature range in a salt bath (or quenching in water) immediately after solution treatment, not only are the defects formed at high temperatures maintained, but new defects can also be generated in alloys, iron alloys and steels. Due to the segregation of the solute atoms near defects through diffusion, this leads to non-uniform distributions of solute atoms in the parent phase with distinct regions of both solute enrichment and solute depletion. It is proposed that when the Ms temperature at the solute depleted regions is equal to or higher than the isothermal (or aged) temperature,nucleation of bainite occurs within these solute depleted regions in the manner of martensitic shear. Therefore it is considered that, at least in steel, iron and copper alloy systems, bainite is formed through a shear mechanism within solute depleted regions, which is controlled and formed by the solute atoms diffusion in the parent phase.展开更多
Sodium ion batteries(SIBs)have been regarded as one of the alternatives to lithium ion batteries owing to their wide availability and significantly low cost of sodium sources.However,they face serious challenges of lo...Sodium ion batteries(SIBs)have been regarded as one of the alternatives to lithium ion batteries owing to their wide availability and significantly low cost of sodium sources.However,they face serious challenges of low energy&power density and short cycling lifespan owing to the heavy mass and large radius of Na^(+).Vanadium-based polyanionic compounds have advantageous characteristic of high operating voltage,high ionic conductivity and robust structural framework,which is conducive to their high energy&power density and long lifespan for SIBs.In this review,we will overview the latest V-based polyanionic compounds,along with the respective characteristic from the intrinsic crystal structure to performance presentation and improvement for SIBs.One of the most important aspect is to discover the essential problems existed in the present V-based polyanionic compounds for high-energy&power applications,and point out most suitable solutions from the crystal structure modulation,interface tailoring and electrode configuration design.Moreover,some scientific issues of V-based polyanionic compounds shall be also proposed and related future direction shall be provided.We believe that this review can serve as a motivation for further development of novel V-based polyanionic compounds and drive them toward high energy&power applications in the near future.展开更多
Transmission electron microscopy (TEM) study of SrPt2As2 reveals two incommensurate modulations appearing in the charge-density-wave (CDW) state below TCDW ≈ 470 K. These two structural modulations can be well ex...Transmission electron microscopy (TEM) study of SrPt2As2 reveals two incommensurate modulations appearing in the charge-density-wave (CDW) state below TCDW ≈ 470 K. These two structural modulations can be well explained in terms of condensations of two-coupled phonon modes with wave vectors of q1=0.62a* on the a*-b* plane and q2 = 0.23a* on the a*-c* plane. The atomic displacements occur along the b-axis direction for q1 and along the c-axis direction for q2, respectively. Moreover, the correlation between ql and q2 can be generally written as q1 = (q2 + a*)/2 in the CDW state, suggesting the presence of essential coupling between q1 and q2. A small fraction of Ir doping on the Pt site in Sr(Pt1-xIrx)2As2 (x ≤ 0.06) could moderately change these CDW modulations and also affect their superconductivities.展开更多
As a promising cathode material for sodium ion batteries,honeycomb-ordered layered Na_(3)Ni_(2)Sb O_(6)still suffers from rapid capacity fading because of partially irreversible phase transition.Herein,a substitution ...As a promising cathode material for sodium ion batteries,honeycomb-ordered layered Na_(3)Ni_(2)Sb O_(6)still suffers from rapid capacity fading because of partially irreversible phase transition.Herein,a substitution of Na+by Rb+with a larger ionic radius in honeycomb layered Na_(3)-xRbxNi_(2)Sb O_(6)is proposed to modulate the interlayer structure.The results unveil that biphasic transition reversibility of the intermediate P′3phase is substantially enhanced,and the structure evolution behavior during the charge/discharge process changes due to the structural modulation,which contributes to a suppression of the unfavorable O_(1)phase and an alleviation of the lattice distortion.Moreover,Rb substituted samples exhibited an improved Na+(de)intercalation thermodynamics and kinetics.Attributed to the modifications,the sample with optimized Rb content delivers superior cycle stability and rate capacity,demonstrating a feasible strategy for suppressing irreversible phase transition and developing high-performance honeycomb layered materials for sodium ion batteries.展开更多
The photoluminescence (PL) property effect of Sc3+ on the Er3+/Y3+/Yb3+ doped Al2O3 powders prepared by sol-gel method has been investigated. The X-ray diffraction (XRD) and transmission electron microscopy (...The photoluminescence (PL) property effect of Sc3+ on the Er3+/Y3+/Yb3+ doped Al2O3 powders prepared by sol-gel method has been investigated. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) implied that the distribution of dopants (Er3+ , Y3+ , Yb3+ , Sc3+) was improved effectively with the rise of Sc3+ concentration. The Fourier transform infrared spectra (FTIR) results demonstrated that the ligand around the quenching center -OH and the population of -OH were altered by introducing different amounts of Sc3+ . The PL intensity centered at 1530 nm was increasingly improved with the rise of Sc3+ concentration, as well as the corresponding full widths at the half maximum (FWHM) and lifetime. The optimized PL intensity was 4.7 times higher than that non-Sc3+ doped sample for the Al2O3 powders codoped with 10mol% Sc3+ . This material can be promising candidates for optical fiber amplifier.展开更多
Recently,many lead-free metal halides with diverse structures and highly efficient emission have been reported.However,their poor stability and single-mode emission color severely limit their applications.Herein,three...Recently,many lead-free metal halides with diverse structures and highly efficient emission have been reported.However,their poor stability and single-mode emission color severely limit their applications.Herein,three homologous Sb^(3+)-doped zero-dimensional(0D)air-stable Sn(IV)-based metal halides with different crystal structures were developed by inserting a single organic ligand into SnCl_(4)lattice,which brings different optical properties.Under photoexcitation,(C_(25)H_(22)P)SnC_(l5)@Sb⋅CH_(4O)(Sb^(3+)−1)does not emit light,(C_(25)H_(22)P)_(2)SnC_(l6)@Sb-α(Sb^(3+)−2α)shines bright yellow emission with a photoluminescence quantum yield(PLQY)of 92%,and(C_(25)H_(22)P)_(2)SnC_(l6)@Sb-β(Sb^(3+)−2β)exhibits intense red emission with a PLQY of 78%.The above three compounds show quite different optical properties should be due to their different crystal structures and the lattice distortions.Particularly,Sb^(3+)−1 can be successfully converted into Sb^(3+)−2αunder the treatment of C_(25)H_(22)PCl solution,accompanied by a transition from nonemission to efficient yellow emission,serving as a“turn-on”photoluminescence(PL)switching.Parallelly,a reversible structure conversion between Sb^(3+)−2αand Sb^(3+)−2βwas witnessed after dichloromethane or volatilization treatment,accompanied by yellow and red emission switching.Thereby,a triple-mode tunable PL switching of off-onI-onII can be constructed in Sb^(3+)-doped Sn(IV)-based compounds.Finally,we demonstrated the as-synthesized compounds in fluorescent anticounterfeiting,information encryption,and optical logic gates.展开更多
Molybdenum disulfide (MoS2) has been recognized as one of the most promising candidates to replace precious Pt for hydrogen evolution reaction (HER) catalysis, due to the natural abundance, low cost, tunable electroni...Molybdenum disulfide (MoS2) has been recognized as one of the most promising candidates to replace precious Pt for hydrogen evolution reaction (HER) catalysis, due to the natural abundance, low cost, tunable electronic properties, and excellent chemical stability. Although notable processes have been achieved in the past decades, their performance is still far less than that of Pt. Searching effective strategies to boosting their HER performance is still the primary goal. In this review, the recent process of the electronic regulation of MoS2 for HER is summarized, including band structure engineering, electronic state modulation, orbital orientation regulation, interface engineering. Last, the key challenges and opportunities in the development of MoS2-based materials for electrochemical HER are also discussed.展开更多
Low-loss tungsten–bronze microwave dielectric ceramics are dielectric materials with potential application value for miniaturized dielectric filters and antennas in the fifth-generation(5G)communication technology.In...Low-loss tungsten–bronze microwave dielectric ceramics are dielectric materials with potential application value for miniaturized dielectric filters and antennas in the fifth-generation(5G)communication technology.In this work,a novel Al/Nd co-doping method of Ba_(4)Nd_(9.33)Ti_(18)O_(54)(BNT)ceramics with a chemical formula of Ba_(4)Nd_(9.33+z/3)Ti_(18−z)Al_(z)O_(54)(BNT–AN,0≤z≤2)was proposed to improve the dielectric properties through structural and defect modulation.Together with Al-doped ceramics(Ba_(4)Nd_(9.33)Ti_(18−z)Al_(4z/3)O_(54),BNT–A,0≤z≤2)for comparison,the ceramics were prepared by a solid state method.It is found that Al/Nd co-doping method has a significant effect on improving the dielectric properties compared with Al doping.As the doping amount z increased,the relative dielectric constant(εr)and the temperature coefficient of resonant frequency(τf)of the ceramics decreased,and the Q×f values of the ceramics obviously increased when z≤1.5.Excellent microwave dielectric properties ofεr=72.2,Q×f=16,480 GHz,andτf=+14.3 ppm/℃were achieved in BNT–AN ceramics with z=1.25.Raman spectroscopy and thermally stimulated depolarization current(TSDC)technique were firstly combined to analyze the structures and defects in microwave dielectric ceramics.It is shown that the improvement on Q×f values was originated from the decrease in the strength of the A-site cation vibration and the concentration of oxygen vacancies(VO××),demonstrating the effect and mechanism underlying for structural and defect modulation on the performance improvement of microwave dielectric ceramics.展开更多
Using finite element method, lots of calculating focusing on polymer electro-optic modulators with ultra-broadband were done, a few structures were analyzed. Coplanar waveguide electrode system was advanced, a few rea...Using finite element method, lots of calculating focusing on polymer electro-optic modulators with ultra-broadband were done, a few structures were analyzed. Coplanar waveguide electrode system was advanced, a few real examples was given.展开更多
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 op...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.展开更多
Red phosphor,with longer wavelength,is highly desirable for full-spectrum WLEDs.Targeted deep red phosphors(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)were designed from the initial model of SrLiAl_(3)N_(4):Eu^(2+)by structural ...Red phosphor,with longer wavelength,is highly desirable for full-spectrum WLEDs.Targeted deep red phosphors(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)were designed from the initial model of SrLiAl_(3)N_(4):Eu^(2+)by structural modification.The correlations among structural evolution,crystal-field environment,and luminescence properties were elucidated.Replacing Sr^(2+)with Gd^(3+)in(Sr,Gd)LiAl_(3)N_(4):Eu^(2+)leads to the enhanced crystal field splitting,larger Stokes shift,and increased structural polyhedron distortion differences,consequently resulting in spectral red-shift and broadening.For further spectral tuning,Mg,with lower electronegativity,was also introduced to modify the local crystal structure,consequently resulting in a further red-shift towards 675 nm and enhanced photoluminescence intensity in(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+).What’s more,w-LEDs were fabricated by using blue LED chip,blue,green,red and deep red((Sr,Gd)Li(Al,Mg)_(3)N_(4):Eu^(2+))phosphors whose color rendering index were Ra 96.0 and R997.7.All above results demonstrate that the partial replacements of Sr^(2+)by Gd^(3+)and Al^(3+)by Mg^(2+)are effective methods for spectral modulation and(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)phosphors are suitable for highquality full-spectrum WLEDs.展开更多
文摘1.IntroductionSince the theory of spinodal decompo-sition in a supersaturated solid solution wasformulated by Hillert[1]and Cahn[2],thephenomena of spinodal decomposition havebeen found in many alloys.Tamura[3]haspointed out that spinodal decompositioncould also occur in maraging steels.A mod-ulated structure in 8Ni maraging steel was
基金Supported by the National Natural Science Foundation of China(No.90922034)
文摘A series of perovskite compounds of La1-x-yCaxKyMnO3 was prepared by hydrothermal disproportionation reaction of MnO2. The three oxidation states of manganese(Mn3+, Mn4+ and Mn5+) can stably exist in the compounds. Under room temperature conditions, twice and three times modulated structure produced by the charge ordering can be observed by X-ray diffraction(XRD), select area electron diffraction(SAED) and high resolution transmission electron microscopy(HR-TEM). The splits of the diffraction peaks of the single crystals confirmed by synchrotron X-ray diffraction experiment are in accordance with those of the powder sample. The existence of the different oxidation states of Mn3+, Mn4+ and Mn5+ can be considered to be the dominating reason of the complicated room temperature modulated structure.
基金This work was supported by the National Natural Science Foundation of China(52372289,52102368,52072192 and 51977009)Regional Joint Fund for Basic Research and Applied Basic Research of Guangdong Province(No.2020SA001515110905).
文摘The laminated transition metal disulfides(TMDs),which are well known as typical two-dimensional(2D)semiconductive materials,possess a unique layered structure,leading to their wide-spread applications in various fields,such as catalysis,energy storage,sensing,etc.In recent years,a lot of research work on TMDs based functional materials in the fields of electromagnetic wave absorption(EMA)has been carried out.Therefore,it is of great significance to elaborate the influence of TMDs on EMA in time to speed up the application.In this review,recent advances in the development of electromagnetic wave(EMW)absorbers based on TMDs,ranging from the VIB group to the VB group are summarized.Their compositions,microstructures,electronic properties,and synthesis methods are presented in detail.Particularly,the modulation of structure engineering from the aspects of heterostructures,defects,morphologies and phases are systematically summarized,focusing on optimizing impedance matching and increasing dielectric and magnetic losses in the EMA materials with tunable EMW absorption performance.Milestones as well as the challenges are also identified to guide the design of new TMDs based dielectric EMA materials with high performance.
文摘Metal Fe/Pd compositionally modulated films(CMFs) were prepared by vapour depo- sition from two sources onto glass substrate under vacuum.The modulation and crystal structures of the films were examined by X-ray diffraction.The magnetic properties were determined by vibrating sample magnetometer.The Pd layers in the Fe/Pd CMFs are of fcc structure,and the Fe layer structure transits from bcc into amorphous,state with decreasing thickness of Fe layer.The dependence of specific saturation magnetization on thickness of Fe layers has also been discussed.
基金supported in part by the General Program Hunan Provincial Natural Science Foundation of 2022,China(2022JJ31022)the Undergraduate Education Reform Project of Hunan Province,China(HNJG-20210532)the National Natural Science Foundation of China(62276276)。
文摘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.
基金supported by the Major Science and Technology Program for Water Pollution Control and Treatment(2017ZX07402001)the Ministry of Science and Technology of China for their financial support and the associated project is the Key Program for International S&T Cooperation Projects(No.2018YFE0124600)。
文摘Oxygen evolution reaction(OER)as the foremost stumbling block to generate cost-effective clean fuels has received extensive attention in recent years.But,it still maintains the challenge to manipulate the geometric and electronic structure during single reaction process under the same conditions.Herein,we report a simple self-template strategy to generate honeycomb-like Ni_(2)P/N,P-C hybrids with preferred electronic architecture.Experiments coupled with theoretical results revealed that the synthesized catalyst has two characteristics:firstly,the unique honeycomb-like morphology not only enables the fully utilization of catalytic active sites but also optimizes the mass/electron transportation pathway,which favor the diffusion of electrolyte to accessible active sites.Secondly,N,P-C substrate,on the one hand,largely contributes the electronic distribution near Fermi level(E_(F))thus boosting its electrical conductivity.On the other hand,the support effect result in the upshift of d-band center and electropositivity of Ni sites,which attenuates the energy barrier for the adsorption of OH~àand the formation of*OOH.In consequence,the optimized Ni_(2)P/N,P-C catalysts feature high electrocatalytic activity towards OER(a low overpotential of 252 m V to achieve10 m A cm^(-2))and 10 h long-term stability,the outstanding performance is comparable to most of transition metal catalysts.This work gives a innovative tactics for contriving original OER electrocatalysts,inspirng deeper understanding of fabricating catalysts by combining theoretical simulation and experiment design.
基金support from the Chinese Scholarship Council(201706220080)for W.H.the Natural Science Foundation of Hunan Province(2019JJ50526)for C.P.+1 种基金The Danish Council for Independent Research for the YDUN project(DFF 4093-00297)to J.Z.Villum Experiment(grant No.35844)for X.X.
文摘Two-dimensional(2D)metal organic frameworks(MOFs)are emerging as low-cost oxygen evolution reaction(OER)electrocatalysts,however,suffering aggregation and poor operation stability.Herein,ultrafine Fe_(3)O_(4) nanoparticles(diameter:6±2 nm)are homogeneously immobilized on 2D Ni based MOFs(Ni-BDC,thickness:5±1 nm)to improve the OER stability.Electronic structure modulation for enhanced catalytic activity is studied via adjusting the amount of Fe_(3)O_(4) nanoparticles on Ni-BDC.The optimal Fe_(3)O_(4)/Ni-BDC achieves the best OER performance with an overpotential of 295 mV at 10 mA cm^(-2),a Tafel slope of 47.8 mV dec^(-1) and a considerable catalytic durability of more than 40 h(less than 5 h for Ni-BDC alone).DFT calculations confirm that the active sites for Fe_(3)O_(4)/Ni-BDC are mainly contributed by Fe species with a higher oxidation state,and the potential-determining step(PDS)is the formation of the adsorbed O*species,which are facilitated in the composite.
文摘The importance of the zeros of multwariable linear systems is well-knoiun in terms of measure obstructions to the controllability and the. observability. In this paper, a recursive decarnposi Am oj interconnected systems is outlined by taking into account the sequential structure of the connnections. The paper extends the, coordinate, module-theoretic studies from the elementary algebraic systems theory to include the case oj such linear interconnected systems which need not to be controllable or observable. Also, the properties of controllability and observability, the decoupling zeros and the signal Making issues are characterized.
基金supported by the National Natural Science Foundation of China(6210333962073261)+1 种基金Shaanxi Natural Science Basic Research Program(2023-JC-YB-569)the Fundamental Research Funds for the Central Universities。
文摘In this paper,a flexible modular“Tetris”microsatellite platform is studied to implement the rapid integration and assembly of microsatellites.The proposed microsatellite platform is fulfilled based on a sandwich assembly mode which consists of the isomorphic module structure and the standard mechanical-electric-data-thermal interfaces.The advantages of the sandwich assembly mode include flexible reconfiguration and efficient assembly.The prototype of the sandwich assembly mode is built for verifying the performance and the feasibility of the proposed mechanical-electric-data-thermal interfaces.Finally,an assembly case is accomplished to demonstrate the validity and advantages of the proposed“Tetris”microsatellite platform.
基金This work was supported by the National Natural Science Foundation of China(Grant No.59171031)
文摘During the incubation period of isothermal treatment(or aging) within the bainitic transformation temperature range in a salt bath (or quenching in water) immediately after solution treatment, not only are the defects formed at high temperatures maintained, but new defects can also be generated in alloys, iron alloys and steels. Due to the segregation of the solute atoms near defects through diffusion, this leads to non-uniform distributions of solute atoms in the parent phase with distinct regions of both solute enrichment and solute depletion. It is proposed that when the Ms temperature at the solute depleted regions is equal to or higher than the isothermal (or aged) temperature,nucleation of bainite occurs within these solute depleted regions in the manner of martensitic shear. Therefore it is considered that, at least in steel, iron and copper alloy systems, bainite is formed through a shear mechanism within solute depleted regions, which is controlled and formed by the solute atoms diffusion in the parent phase.
基金financial support from the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA21070500)the DNL Cooperation Fund,CAS(DNL201914)。
文摘Sodium ion batteries(SIBs)have been regarded as one of the alternatives to lithium ion batteries owing to their wide availability and significantly low cost of sodium sources.However,they face serious challenges of low energy&power density and short cycling lifespan owing to the heavy mass and large radius of Na^(+).Vanadium-based polyanionic compounds have advantageous characteristic of high operating voltage,high ionic conductivity and robust structural framework,which is conducive to their high energy&power density and long lifespan for SIBs.In this review,we will overview the latest V-based polyanionic compounds,along with the respective characteristic from the intrinsic crystal structure to performance presentation and improvement for SIBs.One of the most important aspect is to discover the essential problems existed in the present V-based polyanionic compounds for high-energy&power applications,and point out most suitable solutions from the crystal structure modulation,interface tailoring and electrode configuration design.Moreover,some scientific issues of V-based polyanionic compounds shall be also proposed and related future direction shall be provided.We believe that this review can serve as a motivation for further development of novel V-based polyanionic compounds and drive them toward high energy&power applications in the near future.
基金Project supported by the National Basic Research Program of China(Grant Nos.2011CBA00101,2010CB923002,2012CB821404,and 2011CB921703)the National Natural Science Foundation of China(Grant Nos.11190022,11274368,and 51272277)the Funds from the Chinese Academy of Sciences
文摘Transmission electron microscopy (TEM) study of SrPt2As2 reveals two incommensurate modulations appearing in the charge-density-wave (CDW) state below TCDW ≈ 470 K. These two structural modulations can be well explained in terms of condensations of two-coupled phonon modes with wave vectors of q1=0.62a* on the a*-b* plane and q2 = 0.23a* on the a*-c* plane. The atomic displacements occur along the b-axis direction for q1 and along the c-axis direction for q2, respectively. Moreover, the correlation between ql and q2 can be generally written as q1 = (q2 + a*)/2 in the CDW state, suggesting the presence of essential coupling between q1 and q2. A small fraction of Ir doping on the Pt site in Sr(Pt1-xIrx)2As2 (x ≤ 0.06) could moderately change these CDW modulations and also affect their superconductivities.
基金funded by the NSFC Grant(52177213)supported through NSFC Committee of Chinathe foundation(2020A1414010346 and 2019622163008)supported through the Science and Technology Bureau of Guangdong Governmentsponsored by the Student Research Program(X202110561688)supported through South China University of Technology。
文摘As a promising cathode material for sodium ion batteries,honeycomb-ordered layered Na_(3)Ni_(2)Sb O_(6)still suffers from rapid capacity fading because of partially irreversible phase transition.Herein,a substitution of Na+by Rb+with a larger ionic radius in honeycomb layered Na_(3)-xRbxNi_(2)Sb O_(6)is proposed to modulate the interlayer structure.The results unveil that biphasic transition reversibility of the intermediate P′3phase is substantially enhanced,and the structure evolution behavior during the charge/discharge process changes due to the structural modulation,which contributes to a suppression of the unfavorable O_(1)phase and an alleviation of the lattice distortion.Moreover,Rb substituted samples exhibited an improved Na+(de)intercalation thermodynamics and kinetics.Attributed to the modifications,the sample with optimized Rb content delivers superior cycle stability and rate capacity,demonstrating a feasible strategy for suppressing irreversible phase transition and developing high-performance honeycomb layered materials for sodium ion batteries.
基金supported by the Natural Science Foundation of Fujian Province (No. 2008J0146)
文摘The photoluminescence (PL) property effect of Sc3+ on the Er3+/Y3+/Yb3+ doped Al2O3 powders prepared by sol-gel method has been investigated. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) implied that the distribution of dopants (Er3+ , Y3+ , Yb3+ , Sc3+) was improved effectively with the rise of Sc3+ concentration. The Fourier transform infrared spectra (FTIR) results demonstrated that the ligand around the quenching center -OH and the population of -OH were altered by introducing different amounts of Sc3+ . The PL intensity centered at 1530 nm was increasingly improved with the rise of Sc3+ concentration, as well as the corresponding full widths at the half maximum (FWHM) and lifetime. The optimized PL intensity was 4.7 times higher than that non-Sc3+ doped sample for the Al2O3 powders codoped with 10mol% Sc3+ . This material can be promising candidates for optical fiber amplifier.
基金Guangxi Graduate Education,Grant/Award Number:YCSW2023026Scientific and Technological Bases and Talents of Guangxi,Grant/Award Numbers:AD23026119,AD21238027Guangxi NSF project,Grant/Award Number:2020GXNSFDA238004。
文摘Recently,many lead-free metal halides with diverse structures and highly efficient emission have been reported.However,their poor stability and single-mode emission color severely limit their applications.Herein,three homologous Sb^(3+)-doped zero-dimensional(0D)air-stable Sn(IV)-based metal halides with different crystal structures were developed by inserting a single organic ligand into SnCl_(4)lattice,which brings different optical properties.Under photoexcitation,(C_(25)H_(22)P)SnC_(l5)@Sb⋅CH_(4O)(Sb^(3+)−1)does not emit light,(C_(25)H_(22)P)_(2)SnC_(l6)@Sb-α(Sb^(3+)−2α)shines bright yellow emission with a photoluminescence quantum yield(PLQY)of 92%,and(C_(25)H_(22)P)_(2)SnC_(l6)@Sb-β(Sb^(3+)−2β)exhibits intense red emission with a PLQY of 78%.The above three compounds show quite different optical properties should be due to their different crystal structures and the lattice distortions.Particularly,Sb^(3+)−1 can be successfully converted into Sb^(3+)−2αunder the treatment of C_(25)H_(22)PCl solution,accompanied by a transition from nonemission to efficient yellow emission,serving as a“turn-on”photoluminescence(PL)switching.Parallelly,a reversible structure conversion between Sb^(3+)−2αand Sb^(3+)−2βwas witnessed after dichloromethane or volatilization treatment,accompanied by yellow and red emission switching.Thereby,a triple-mode tunable PL switching of off-onI-onII can be constructed in Sb^(3+)-doped Sn(IV)-based compounds.Finally,we demonstrated the as-synthesized compounds in fluorescent anticounterfeiting,information encryption,and optical logic gates.
基金the financial supports of the National Natural Science Foundation of China(Nos.21771169,51801075,and 11722543)the National Key Research and Development Program of China(No.2017YFA0206703)+1 种基金Anhui Provincial Natural Science Foundation(No.BJ2060190077)Re-cruitment Program of Global Expert,and the Fundamental Research Funds for the Central Universities(Nos.WK2060190074,WK2060190081,and WK2310000066).
文摘Molybdenum disulfide (MoS2) has been recognized as one of the most promising candidates to replace precious Pt for hydrogen evolution reaction (HER) catalysis, due to the natural abundance, low cost, tunable electronic properties, and excellent chemical stability. Although notable processes have been achieved in the past decades, their performance is still far less than that of Pt. Searching effective strategies to boosting their HER performance is still the primary goal. In this review, the recent process of the electronic regulation of MoS2 for HER is summarized, including band structure engineering, electronic state modulation, orbital orientation regulation, interface engineering. Last, the key challenges and opportunities in the development of MoS2-based materials for electrochemical HER are also discussed.
基金This work was supported by the National Key R&D Program of China(No.2017YFB0406301)the Key-Area Research and Development Program of Guangdong Province(No.2020B010176001)the National Natural Science Foundation of China(No.51872160).
文摘Low-loss tungsten–bronze microwave dielectric ceramics are dielectric materials with potential application value for miniaturized dielectric filters and antennas in the fifth-generation(5G)communication technology.In this work,a novel Al/Nd co-doping method of Ba_(4)Nd_(9.33)Ti_(18)O_(54)(BNT)ceramics with a chemical formula of Ba_(4)Nd_(9.33+z/3)Ti_(18−z)Al_(z)O_(54)(BNT–AN,0≤z≤2)was proposed to improve the dielectric properties through structural and defect modulation.Together with Al-doped ceramics(Ba_(4)Nd_(9.33)Ti_(18−z)Al_(4z/3)O_(54),BNT–A,0≤z≤2)for comparison,the ceramics were prepared by a solid state method.It is found that Al/Nd co-doping method has a significant effect on improving the dielectric properties compared with Al doping.As the doping amount z increased,the relative dielectric constant(εr)and the temperature coefficient of resonant frequency(τf)of the ceramics decreased,and the Q×f values of the ceramics obviously increased when z≤1.5.Excellent microwave dielectric properties ofεr=72.2,Q×f=16,480 GHz,andτf=+14.3 ppm/℃were achieved in BNT–AN ceramics with z=1.25.Raman spectroscopy and thermally stimulated depolarization current(TSDC)technique were firstly combined to analyze the structures and defects in microwave dielectric ceramics.It is shown that the improvement on Q×f values was originated from the decrease in the strength of the A-site cation vibration and the concentration of oxygen vacancies(VO××),demonstrating the effect and mechanism underlying for structural and defect modulation on the performance improvement of microwave dielectric ceramics.
基金The project is supported by Basic Research Foundation of Tsinghua University, No: JZ2000005.
文摘Using finite element method, lots of calculating focusing on polymer electro-optic modulators with ultra-broadband were done, a few structures were analyzed. Coplanar waveguide electrode system was advanced, a few real examples was given.
基金This work was supported by the National Natural Science Foundation of China(No.60077030)
文摘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.
基金supported by the National Key Research and Development Program of China(2021YFB3500402)。
文摘Red phosphor,with longer wavelength,is highly desirable for full-spectrum WLEDs.Targeted deep red phosphors(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)were designed from the initial model of SrLiAl_(3)N_(4):Eu^(2+)by structural modification.The correlations among structural evolution,crystal-field environment,and luminescence properties were elucidated.Replacing Sr^(2+)with Gd^(3+)in(Sr,Gd)LiAl_(3)N_(4):Eu^(2+)leads to the enhanced crystal field splitting,larger Stokes shift,and increased structural polyhedron distortion differences,consequently resulting in spectral red-shift and broadening.For further spectral tuning,Mg,with lower electronegativity,was also introduced to modify the local crystal structure,consequently resulting in a further red-shift towards 675 nm and enhanced photoluminescence intensity in(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+).What’s more,w-LEDs were fabricated by using blue LED chip,blue,green,red and deep red((Sr,Gd)Li(Al,Mg)_(3)N_(4):Eu^(2+))phosphors whose color rendering index were Ra 96.0 and R997.7.All above results demonstrate that the partial replacements of Sr^(2+)by Gd^(3+)and Al^(3+)by Mg^(2+)are effective methods for spectral modulation and(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)phosphors are suitable for highquality full-spectrum WLEDs.