Background With an aggravated social ageing level, the number of patients with Alzheimer's disease (AD) is gradually increasing, and mild cognitive impairment (MCI) is considered to be an early form of Alzheimer&#...Background With an aggravated social ageing level, the number of patients with Alzheimer's disease (AD) is gradually increasing, and mild cognitive impairment (MCI) is considered to be an early form of Alzheimer's disease. How to distinguish diseases in the early stage for the purposes of early diagnosis and treatment is an important topic. Aims The purpose of our study was to investigate the differences in brain cortical thickness and surface area among elderly patients with AD, elderly patients with amnestic MCI (aMCI) and normal controls (NC). Methods 20 AD patients, 21 aMCIs and 25 NC were recruited in the study. FreeSurfer software was used to calculate cortical thickness and surface area among groups. Results The patients with AD had less cortical thickness both in the left and right hemisphere in 17 of the 36 brain regions examined than the patients with aMCI or NC. The patients with AD also had smaller cerebral surface area both in the left and right hemisphere in 3 of the 36 brain regions examined than the patients with aMCI or NC. Compared with the NC, the patients with aMCI only had slight atrophy in the inferior parietal lobe of the left hemisphere, and no significant difference was found. Conclusion AD, as well as aMCI (to a lesser extent), is associated with reduced cortical thickness and surface area in a few brain regions associated with cognitive impairment. These results suggest that cortical thickness and surface area could be used for early detection of AD.展开更多
With the rapid development of information technology,audit objects and audit itself are more and more inseparable from software.As an important means of software security audit,code security audit will become an impor...With the rapid development of information technology,audit objects and audit itself are more and more inseparable from software.As an important means of software security audit,code security audit will become an important aspect of future audit that cannot be ignored.However,the existing code security audit ismainly based on source code,which is difficult to meet the audit needs of more and more programming languages and binary commercial software.Based on the idea of normalized transformation,this paper constructs a cross language code security audit framework(CLCSA).CLCSA first uses compile/decompile technology to convert different highlevel programming languages and binary codes into normalized representation,and then usesmachine learning technology to build a cross language code security audit model based on normalized representation to evaluate code security and find out possible code security vulnerabilities.Finally,for the discovered vulnerabilities,the heuristic search strategy will be used to find the best repair scheme from the existing normalized representation sample library for automatic repair,which can improve the effectiveness of code security audit.CLCSA realizes the normalized code security audit of different types and levels of code,which provides a strong support for improving the breadth and depth of code security audit.展开更多
We investigate the chaotic and regular spatial structures of Bose–Einstein condensates(BECs)with a spatially modulated atom-atom interaction and without an external trapping potential.A BEC with a spatially modulated...We investigate the chaotic and regular spatial structures of Bose–Einstein condensates(BECs)with a spatially modulated atom-atom interaction and without an external trapping potential.A BEC with a spatially modulated atom-atom interaction is equivalent to being constrained by a nonlinear optical lattice.Theoretical analyses show the existence of a steady atomic current in the BEC with a spatially varying phase.Under perturbative conditions,the Melnikov chaos criteria of BECs with a spatially varying phase and a constant one are theoretically obtained,respectively.When the perturbative conditions cannot be satisfied,for a repulsive BEC with a spatially varying phase,numerical simulations demonstrate that changing the initial condition can eliminate the chaotic spatial structure and then the system transitions into a biperiodic spatial structure.Increasing the chemical potential can result in a transition from the biperiodic spatial structure to a single-periodic spatial structure.For an attractive BEC with a spatially varying phase,numerical simulations show that decreasing the chemical potential can lead to a high atomic density,but when the wave number of the laser inducing the optical Feshbach resonance exceeds a critical value,the atomic density falls back to a finite range.Regardless of whether the BEC has a spatially varying phase or a constant one,modulating the laser wave number can effectively suppress the chaotic spatial structure in the BEC and then force it into a regular spatial structure.展开更多
Single-atom catalysts(SACs)are promising for oxygen reduction reaction(ORR)on account of their excellent catalytic activity and maximum utilization of atoms.However,due to the complicated preparation processes and exp...Single-atom catalysts(SACs)are promising for oxygen reduction reaction(ORR)on account of their excellent catalytic activity and maximum utilization of atoms.However,due to the complicated preparation processes and expensive reagents used,the cost of SACs is usually too high to put into practical application.The development of cost-effective and sustainable SACs remains a great challenge.Herein,a low-cost method employing biomass is designed to prepare efficient single-atom Fe-N-C catalysts(SA-Fe-N-C).Benefiting from the confinement effect of porous carbon support and the coordination effect of glucose,SA-Fe-N-C is derived from cheap flour by the two-step pyrolysis.Atomically dispersed Fe atoms exist in the form of Fe-N_(x),which acts as active sites for ORR.The catalyst shows outstanding activity with a half-wave potential(E_(1/2))of 0.86 V,which is better than that of Pt/C(0.84 V).Additionally,the catalyst also exhibits superior stability.The ORR catalyzed by SA-Fe-N-C proceeds via an efficient 4e transfer pathway.The high performance of SA-Fe-N-C also benefits from its porous structure,extremely high specific surface area(1450.1 m^(2)/g),and abundant micropores,which are conducive to increasing the density of active sites and fully exposing them.This work provides a cost-effective strategy to synthesize SACs from cheap biomass,achieving a balance between performance and cost.展开更多
The Pfaffian property of graphs is of fundamental importance in graph theory,as it precisely characterizes those graphs for which the number of perfect matchings can be computed in polynomial time with respect to the ...The Pfaffian property of graphs is of fundamental importance in graph theory,as it precisely characterizes those graphs for which the number of perfect matchings can be computed in polynomial time with respect to the number of edges.The study of Pfaffian graphs originated from the enumeration of perfect matching in planar graphs.References[5,6,8]demonstrated that every planar graph is Pfaffian.Therefore,the Pfaffian property and planarity of graphs play a vital role in modern matching theory.This paper contributes a complete characterization of the Pfaffian property and planarity of connected Cayley graphs over the dicyclic group T_(4n) of order 4n(n≥3),shows that the Cayley graph Cay(T_(4n),S)is Pfaffian if and only if n is odd and S={a^(k_(1)),a^(2n−k_(1)),ba^(k_(2)),ba^(n+k_(2))},where 1≤k_(1)≤n−1,0≤k_(2)≤n−1 and(k_(1),n)=1,and furthermore,shows that Cay(T4n,S)is never planar.展开更多
Chemical short-range order(SRO),a phenomenon at the atomic scale resulting from inhomogeneities in the local chemical environment,is usually studied using machine learning force field-based molecular dynamics simulati...Chemical short-range order(SRO),a phenomenon at the atomic scale resulting from inhomogeneities in the local chemical environment,is usually studied using machine learning force field-based molecular dynamics simulations due to the limitations of experimental methods.To promote the reliable application of machine potentials in high-entropy alloy simulations,first,this work uses NEP models trained on two different datasets to predict the SRO coefficients of NbMoTaW.The results show that within the same machine learning framework,there are significant differences in the prediction of SRO coefficients for the Nb-Nb atomic pair.Subsequently,this work predicts the SRO coefficients of NbMoTaW using the NEP model and the SNAP model,both of which are trained on the same dataset.The results reveal significant discrepancies in SRO predictions for like-element pairs(e.g.,Nb-Nb and W-W)between the two potentials,despite the identical training data.The findings of this study indicate that discrepancies in the prediction results of SRO coefficients can arise from either the same machine learning framework trained on different datasets or different learning frameworks trained on the same dataset.This reflects possible incompleteness in the current training set's coverage of local chemical environments at the atomic scale.Future research should establish unified evaluation standards to assess the capability of training sets to accurately describe complex atomic-scale behaviors such as SRO.展开更多
The transverse-traceless gauge condition is an important concept in the theory of gravitational waves.It is well known that a vacuum is one of the key conditions to guarantee the existence of the transverse-traceless ...The transverse-traceless gauge condition is an important concept in the theory of gravitational waves.It is well known that a vacuum is one of the key conditions to guarantee the existence of the transverse-traceless gauge.Although it is thin,the interstellar medium is ubiquitous in the Universe.Therefore,it is important to understand the concept of gravitational waves when matter is presented.Bondi-Metzner-Sachs theory has solved the gauge problem related to gravitational waves.But it does not help with cases when the gravitational wave propagates in matter.This paper discusses possible extensions of the transverse-traceless gauge condition to Minkowski perturbation with matter presented.展开更多
High-energy continuous wave(CW)lasers are mostly used in laser damage applications,but efficient laser ablation of transparent materials is challenging due to low optical absorption.Considering the potential of femtos...High-energy continuous wave(CW)lasers are mostly used in laser damage applications,but efficient laser ablation of transparent materials is challenging due to low optical absorption.Considering the potential of femtosecond(fs)laser-induced air filament for high-peak laser transmission over long distances,femtosecond(fs)laser-induced air filaments are combined with a millisecond(ms)laser to form an fs-ms CPL,enhancing the efficiency of sapphire ablation through synchronized spatial-temporal focusing.Experimental results show that ablation efficiency increases with the ms peak power and duty ratio.Excessive thermal stress leads to fragmentation of the sapphire when the ms duty ratio is over 30%at the peak power of 800 W,or when the peak power is over 500 W at a duty ratio of 100%.Also,the mechanism of high-efficiency damage is revealed through in-situ high-speed imaging.According to it,the ablation process went through 4 stages within 1.5 ms:defect-creating,melting and ablation,spattering,and fragmentation.Finally,the equivalent ablation efficiency of the fs-ms CPL is as high as 1.73×10^(7)μm^(3)/J,about 28 times higher compared to the fs laser only.The CPL damage method explored in this paper can provide theoretical guidance for efficient laser damage of transparent materials.展开更多
A mathematical model of the particle heating process in the reaction shaft of flash smelting furnace was established and the calculation was performed.The results indicate that radiation plays a significant role in th...A mathematical model of the particle heating process in the reaction shaft of flash smelting furnace was established and the calculation was performed.The results indicate that radiation plays a significant role in the heat transfer process within the first 0.6 m in the upper part of the reaction shaft,whilst the convection is dominant in the area below 0.6 m for the particle heating.In order to accelerate the particle ignition,it is necessary to enhance the convection,thus to speed up the particle heating.A high-speed preheated oxygen jet technology was then suggested to replace the nature gas combustion in the flash furnace,aiming to create a lateral disturbance in the gaseous phase around the particles,so as to achieve a slip velocity between the two phases and a high convective heat transfer coefficient.Numerical simulation was carried out for the cases with the high-speed oxygen jet and the normal nature gas burners.The results show that with the high-speed jet technology,particles are heated up more rapidly and ignited much earlier,especially within the area of the radial range of R=0.3−0.6 m.As a result,a more efficient smelting process can be achieved under the same operational condition.展开更多
A prompt gamma-neutron activation analysis(PGNAA) system was developed to detect the iron content of iron ore concentrate. Because of the self-absorption effect of gamma-rays and neutrons, and the interference of chlo...A prompt gamma-neutron activation analysis(PGNAA) system was developed to detect the iron content of iron ore concentrate. Because of the self-absorption effect of gamma-rays and neutrons, and the interference of chlorine in the neutron field, the linear relationship between the iron analytical coefficient and total iron content was poor, increasing the error in the quantitative analysis. To solve this problem, gamma-ray self-absorption compensation and a neutron field correction algorithm were proposed, and the experimental results have been corrected using this algorithm. The results show that the linear relationship between the iron analytical coefficient and total iron content was considerably improved after the correction. The linear correlation coefficients reached 0.99 or more.展开更多
The nitrogen(N2)-to-ammonia(NH3)fixation driven by renewable energy has an attractive prospect to relieve the global warming and reduce the consumption of fossil fuels.Ideally,photocatalytic,electrochemical,and photoe...The nitrogen(N2)-to-ammonia(NH3)fixation driven by renewable energy has an attractive prospect to relieve the global warming and reduce the consumption of fossil fuels.Ideally,photocatalytic,electrochemical,and photoelectrochemical approaches are developed as the next-generation NH3 synthesis technologies to substitute the Haber–Bosch method.However,the NH3 yield rate of nitrogen reduction reaction(NRR)by green approaches is extremely low,resulting in the current dilemma of NRR and contamination issues.Thus,in this mini review,the past advances on the sustainable NRR are briefly summarized in the three aspects as follows:the selectivity and adjustment of various catalysts,the type of electrolyte/solvent system,and the investigation of reaction conditions.Subsequently,the recent critical activities in the area of sustainable NH3 synthesis are analyzed and discussed deeply,and a perspective for rational and healthy development of this area is provided positively。展开更多
We consider a branching random walk in an independent and identically distributed random environment ξ=(ξn) indexed by the time. Let W be the limit of the martingale Wn=∫e^-txZn(dx)/Eξ∫e^-txZn(dx), with Zn denoti...We consider a branching random walk in an independent and identically distributed random environment ξ=(ξn) indexed by the time. Let W be the limit of the martingale Wn=∫e^-txZn(dx)/Eξ∫e^-txZn(dx), with Zn denoting the counting measure of particles of generation n, and Eξ the conditional expectation given the environment ξ. We find necessary and sufficient conditions for the existence of quenched moments and weighted moments of W, when W is non-degenerate.展开更多
Hard carbons are promising anode materials for sodium-ion batteries.To meet practical requirements,searching for durable and conductive carbon with a stable interface is of great importance.Here,we prepare a series of...Hard carbons are promising anode materials for sodium-ion batteries.To meet practical requirements,searching for durable and conductive carbon with a stable interface is of great importance.Here,we prepare a series of vanadiummodified hard carbon submicrospheres by using hydrothermal carbonization followed by high-temperature pyrolysis.Significantly,the introduction of vanadium can facilitate the nucleation and uniform growth of carbon spheres and generate abundant V-O-C interface bonds,thus optimizing the reaction kinetic.Meanwhile,the optimized hard carbon spheres modified by vanadium carbide,with sufficient pseudographitic domains,provide more active sites for Na ion migration and storage.As a result,the HC/VC-1300 electrode exhibits excellent Na storage performance,including a high capacity of 420 mAh g^(-1)at 50mA g^(-1)and good rate capability at 1 A g^(-1).This study proposes a new strategy for the synthesis of hard carbon spheres with high tap density and emphasizes the key role of pseudographitic structure for Na storage and interface stabilization.展开更多
Waste carbon residue(WCR)was efficiently detoxicated and regenerated to high-purity graphite(PGC)used in lithium-ion batteries through the constant-pressure acid leaching technique.The leaching conditions were optimiz...Waste carbon residue(WCR)was efficiently detoxicated and regenerated to high-purity graphite(PGC)used in lithium-ion batteries through the constant-pressure acid leaching technique.The leaching conditions were optimized by the combination of orthogonal and single-factor experiments.Results show that PGC with 99.5%purity is regenerated at temperature of 60℃,initial acid concentration of 12%,leaching time of 180 min,and liquid-to-solid ratio of 25:1,satisfying the requirements of commercial graphite.Meanwhile,the sodium hydroxide precipitation process was designed to recover valuable components from leachate efficiently.Ni,Co,Mn,and Al recoveries reach 96.92%,87.5%,97.83%,and 92.17%,respectively,at pH=11.Moreover,the co-product NaF can be recovered with purity over 99%via evaporative crystallization.The loss rate of fluorine is less than 0.5%,thereby eliminating the pollution risk of fluorine to the environment.The proposed process shows considerable environmental and economic benefits.展开更多
Rainfall erosivity is an important climatic factor for predicting soil loss. Through the application of high-resolution pluviograph data at 5 stations in Huangshan City, Anhui Prov- ince, China, we analyzed the perfor...Rainfall erosivity is an important climatic factor for predicting soil loss. Through the application of high-resolution pluviograph data at 5 stations in Huangshan City, Anhui Prov- ince, China, we analyzed the performance of a modified Richardson model that incorporated the seasonal variations in parameters α andβ. The results showed that （1） moderate to high seasonality was presented in the distribution of erosive rainfall, and the seasonality of rainfall erosivity was even stronger; （2） seasonal variations were demonstrated in both parameters α and β of the Richardson model; and （3） incorporating and coordinating the seasonality of parameters αandβgreatly improved the predictions at the monthly scale. This newly modi- fied model is therefore highly recommended when monthly rainfall erosivity is required, such as, in planning soil and water conservation practices and calculating the cover-management factor in the Universal Soil Loss Equation （USLE） and Revised Universal Soil Loss Equation （RUSLE）.展开更多
To overcome the dimension limits of immiscible alloys produced by traditional techniques and enhance their mechanical properties,bulk Cu-Fe-based immiscible alloy with abundant nanotwins and stacking faults was succes...To overcome the dimension limits of immiscible alloys produced by traditional techniques and enhance their mechanical properties,bulk Cu-Fe-based immiscible alloy with abundant nanotwins and stacking faults was successfully produced by selective laser melting(SLM).The SLM-produced bulk immiscible alloy displays a heterogeneous microstructure characterized by micro-scaledγ-Fe particles dispersed in fineε-Cu matrix with a high fraction(~92%)of high-angle grain boundaries.Interestingly,abundant nanotwins and stacking faults are generated in the interior of nano-scaledγ-Fe particles embedded withinε-Cu matrix.The heterogeneous interface of soft domains(ε-Cu)and hard domains(γ-Fe)not only induces the geometrically necessary dislocations(GNDs)but also affects the dislocation propagation during plastic deformation.Therefore,the bimodal heterogeneous interface,and the resistance of nanotwins and stacking faults to the propagation of partial dislocation make the bulk immiscible alloy exhibit an enhanced strength of~590 MPa and a good ductility of~8.9%.展开更多
COVID-19 has changed the way of learning and life of college students.The purpose is to explore the relationship between perceived stress and anxiety,and the mediating effect of resilience and regulatory emotional sel...COVID-19 has changed the way of learning and life of college students.The purpose is to explore the relationship between perceived stress and anxiety,and the mediating effect of resilience and regulatory emotional self-efficacy in college students during COVID-19.309 students from three colleges were selected as research participants(average age 19.79±1.11 years).SPSS was used to measure the correlation between variables.Amos was used to test the path coefficient and mediating effect of the hypothetical model.The results show that:Firstly,perceived stress has a significantly and positively predictive effect on anxiety.Secondly,psychological resilience and regu-latory emotional self-efficacy independently played a significant and partially mediating effect between perceived stress and anxiety.Among them,perceived stress had a negative predictive effect on psychological resilience and regulatory emotional self-efficacy.Psychological resilience and regulatory emotional self-efficacy had a negative predictive effect on anxiety.Thirdly,psychological resilience and regulatory emotional self-efficacy play a chain mediation role between psychological stress and anxiety.Regulatory emotional self-efficacy cannot only directly predict the level of anxiety,but also indirectly predict the level of anxiety by regulating psychological resilience.This study reveals the relationship between college students’perceived stress and anxiety,and the mediating effect of psychological resilience and regulatory emotional self-efficacy in the new time of COVID-19.The chain mediation role of psychological resilience and regulatory emotional self-efficacy reminds college mental health educators that improving students’regulatory emotional self-efficacy is an important way to promote students’mental health.展开更多
This work reports an improved method for the wet desulfurization of high-sulfur petroleum coke(petcoke)powder based on the combination of pre-calcination,H_(2)O_(2),and ultrasound.The results demonstrated that over 45...This work reports an improved method for the wet desulfurization of high-sulfur petroleum coke(petcoke)powder based on the combination of pre-calcination,H_(2)O_(2),and ultrasound.The results demonstrated that over 45%of the sulfur atoms were efficiently removed from Tianjin coke and Qilu coke(particle size<0.1 mm)by pre-calcination at 800℃ for 6 h followed by desulfurization with HNO3(8 mol/L)and H_(2)O_(2)(2 mol/L)solution at a reaction temperature of 60℃,a reaction time of 6 h,a liquid-to-solid ratio of 10 mL/g,and a 40 kHz ultrasonic power of 400 W.In addition,the specific surface area of the petcoke particles increased from 0.7 to 301.49 m^(2)/g.After desulfurization,the pore size distribution of the petcoke particles was more concentrated on micropores compared with the samples prior to petcoke treatment.Reactive force field molecular dynamics simulation results indicated that HNO_(3) continuously oxidized the carbon atoms adjacent to sulfur atoms in the petcoke macromolecules and promoted sulfur removal from petcoke via the cleavage of C-S bonds.The sulfur transformation mechanism can be summarized as follows:thiophene sulfur→branched chain carbon sulfur→CO_(2)S→C_(2)O_(2)S→C_(2)O_(3)NS→C_(2)O_(4)S→CO_(2)S.展开更多
Object identification and three-dimensional reconstruction techniques are always attractive research interests in machine vision,virtual reality,augmented reality,and biomedical engineering.Optical computing metasurfa...Object identification and three-dimensional reconstruction techniques are always attractive research interests in machine vision,virtual reality,augmented reality,and biomedical engineering.Optical computing metasurface,as a two-dimensional artificial design component,has displayed the supernormal character of controlling phase,amplitude,polarization,and frequency distributions of the light beam,capable of performing mathematical operations on the input light field.Here,we propose and demonstrate an all-optical object identification technique based on optical computing metasurface,and apply it to 3D reconstruction.Unlike traditional mechanisms,this scheme reduces memory consumption in the processing of the contour surface extraction.The identification and reconstruction of experimental results from high-contrast and low-contrast objects agree well with the real objects.The exploration of the all-optical object identification and 3D reconstruction techniques provides potential applications of high efficiencies,low consumption,and compact systems.展开更多
This study aims to provide evidence regarding whether Qingufei paidu decoction(清肺排毒汤,QFPD)treatment in the acute phase shows long-term benefits for coronavirus disease 2019-associated sequelae.The 10 databases wi...This study aims to provide evidence regarding whether Qingufei paidu decoction(清肺排毒汤,QFPD)treatment in the acute phase shows long-term benefits for coronavirus disease 2019-associated sequelae.The 10 databases will be retrieved.Every reference list of related trials and gray literature will be searched as well.Study screening,data extraction,and risk of bias evaluation will be performed by two reviewers(CUI Hanjin and FAN Rong).Data analysis will be conducted by using STATA(version 14).Statistical heterogeneity will be explored by a standardχ2 test with a significance level of P<0.10.Funnel plots,Egger’s&Begg’s test,and Trim and Fill analysis will be used for publication bias assessment.The results of the present Meta-analysis and systematic review will be disseminated via peer-review journal publication.Ethical approval is not required,as this Meta-analysis will not contain any individual patient data.This systematic review has been registered on PROSPERO(registration number:CRD42021246937)on 15 April 2021.展开更多
基金Collaborative Innovation Center for Translational Medicine at Shanghai Jiao Tong University School of Medicine TM201728National Nature Science Foundation of China 81571298+2 种基金Shanghai health system excellent talent training program (excellent subject leader) project 2017BR054Shanghai Municipal Education Commission-Gaofeng Clinical Medicine Grant Support 20172029Shanghai Pujiang Program 17PJD038.
文摘Background With an aggravated social ageing level, the number of patients with Alzheimer's disease (AD) is gradually increasing, and mild cognitive impairment (MCI) is considered to be an early form of Alzheimer's disease. How to distinguish diseases in the early stage for the purposes of early diagnosis and treatment is an important topic. Aims The purpose of our study was to investigate the differences in brain cortical thickness and surface area among elderly patients with AD, elderly patients with amnestic MCI (aMCI) and normal controls (NC). Methods 20 AD patients, 21 aMCIs and 25 NC were recruited in the study. FreeSurfer software was used to calculate cortical thickness and surface area among groups. Results The patients with AD had less cortical thickness both in the left and right hemisphere in 17 of the 36 brain regions examined than the patients with aMCI or NC. The patients with AD also had smaller cerebral surface area both in the left and right hemisphere in 3 of the 36 brain regions examined than the patients with aMCI or NC. Compared with the NC, the patients with aMCI only had slight atrophy in the inferior parietal lobe of the left hemisphere, and no significant difference was found. Conclusion AD, as well as aMCI (to a lesser extent), is associated with reduced cortical thickness and surface area in a few brain regions associated with cognitive impairment. These results suggest that cortical thickness and surface area could be used for early detection of AD.
基金This work was supported by the Universities Natural Science Research Project of Jiangsu Province under Grant 20KJB520026the Natural Science Foundation of Jiangsu Province under Grant BK20180821.
文摘With the rapid development of information technology,audit objects and audit itself are more and more inseparable from software.As an important means of software security audit,code security audit will become an important aspect of future audit that cannot be ignored.However,the existing code security audit ismainly based on source code,which is difficult to meet the audit needs of more and more programming languages and binary commercial software.Based on the idea of normalized transformation,this paper constructs a cross language code security audit framework(CLCSA).CLCSA first uses compile/decompile technology to convert different highlevel programming languages and binary codes into normalized representation,and then usesmachine learning technology to build a cross language code security audit model based on normalized representation to evaluate code security and find out possible code security vulnerabilities.Finally,for the discovered vulnerabilities,the heuristic search strategy will be used to find the best repair scheme from the existing normalized representation sample library for automatic repair,which can improve the effectiveness of code security audit.CLCSA realizes the normalized code security audit of different types and levels of code,which provides a strong support for improving the breadth and depth of code security audit.
基金Projects supported by the Natural Science Foundation of Hunan Province(2016JJ6020)the Scientific Research Fund of Hunan Provincial Education Department(18A436)the Scientific Research Fund of Hunan First normal University(XYS13N16)。
文摘We investigate the chaotic and regular spatial structures of Bose–Einstein condensates(BECs)with a spatially modulated atom-atom interaction and without an external trapping potential.A BEC with a spatially modulated atom-atom interaction is equivalent to being constrained by a nonlinear optical lattice.Theoretical analyses show the existence of a steady atomic current in the BEC with a spatially varying phase.Under perturbative conditions,the Melnikov chaos criteria of BECs with a spatially varying phase and a constant one are theoretically obtained,respectively.When the perturbative conditions cannot be satisfied,for a repulsive BEC with a spatially varying phase,numerical simulations demonstrate that changing the initial condition can eliminate the chaotic spatial structure and then the system transitions into a biperiodic spatial structure.Increasing the chemical potential can result in a transition from the biperiodic spatial structure to a single-periodic spatial structure.For an attractive BEC with a spatially varying phase,numerical simulations show that decreasing the chemical potential can lead to a high atomic density,but when the wave number of the laser inducing the optical Feshbach resonance exceeds a critical value,the atomic density falls back to a finite range.Regardless of whether the BEC has a spatially varying phase or a constant one,modulating the laser wave number can effectively suppress the chaotic spatial structure in the BEC and then force it into a regular spatial structure.
基金Project(52174338)supported by the National Natural Science Foundation of ChinaProjects(2022JJ20086,2021JJ30796)supported by the Natural Science Foundation of Hunan Province,China+1 种基金Project(2023CXQD005)supported by the Central South University Innovation-Driven Research Programme,ChinaProject(23B0841)supported by the Education Department of Hunan Provincial Government,China。
文摘Single-atom catalysts(SACs)are promising for oxygen reduction reaction(ORR)on account of their excellent catalytic activity and maximum utilization of atoms.However,due to the complicated preparation processes and expensive reagents used,the cost of SACs is usually too high to put into practical application.The development of cost-effective and sustainable SACs remains a great challenge.Herein,a low-cost method employing biomass is designed to prepare efficient single-atom Fe-N-C catalysts(SA-Fe-N-C).Benefiting from the confinement effect of porous carbon support and the coordination effect of glucose,SA-Fe-N-C is derived from cheap flour by the two-step pyrolysis.Atomically dispersed Fe atoms exist in the form of Fe-N_(x),which acts as active sites for ORR.The catalyst shows outstanding activity with a half-wave potential(E_(1/2))of 0.86 V,which is better than that of Pt/C(0.84 V).Additionally,the catalyst also exhibits superior stability.The ORR catalyzed by SA-Fe-N-C proceeds via an efficient 4e transfer pathway.The high performance of SA-Fe-N-C also benefits from its porous structure,extremely high specific surface area(1450.1 m^(2)/g),and abundant micropores,which are conducive to increasing the density of active sites and fully exposing them.This work provides a cost-effective strategy to synthesize SACs from cheap biomass,achieving a balance between performance and cost.
基金supported by NSFC(No.12201202)NSF of Hunan Province(No.2023JJ30180)NSFC(No.12471022)。
文摘The Pfaffian property of graphs is of fundamental importance in graph theory,as it precisely characterizes those graphs for which the number of perfect matchings can be computed in polynomial time with respect to the number of edges.The study of Pfaffian graphs originated from the enumeration of perfect matching in planar graphs.References[5,6,8]demonstrated that every planar graph is Pfaffian.Therefore,the Pfaffian property and planarity of graphs play a vital role in modern matching theory.This paper contributes a complete characterization of the Pfaffian property and planarity of connected Cayley graphs over the dicyclic group T_(4n) of order 4n(n≥3),shows that the Cayley graph Cay(T_(4n),S)is Pfaffian if and only if n is odd and S={a^(k_(1)),a^(2n−k_(1)),ba^(k_(2)),ba^(n+k_(2))},where 1≤k_(1)≤n−1,0≤k_(2)≤n−1 and(k_(1),n)=1,and furthermore,shows that Cay(T4n,S)is never planar.
基金Project supported by the Hunan Provincial Natural Science Foundation(Grant Nos.2024JJ6190 and 2024JK2007-1)。
文摘Chemical short-range order(SRO),a phenomenon at the atomic scale resulting from inhomogeneities in the local chemical environment,is usually studied using machine learning force field-based molecular dynamics simulations due to the limitations of experimental methods.To promote the reliable application of machine potentials in high-entropy alloy simulations,first,this work uses NEP models trained on two different datasets to predict the SRO coefficients of NbMoTaW.The results show that within the same machine learning framework,there are significant differences in the prediction of SRO coefficients for the Nb-Nb atomic pair.Subsequently,this work predicts the SRO coefficients of NbMoTaW using the NEP model and the SNAP model,both of which are trained on the same dataset.The results reveal significant discrepancies in SRO predictions for like-element pairs(e.g.,Nb-Nb and W-W)between the two potentials,despite the identical training data.The findings of this study indicate that discrepancies in the prediction results of SRO coefficients can arise from either the same machine learning framework trained on different datasets or different learning frameworks trained on the same dataset.This reflects possible incompleteness in the current training set's coverage of local chemical environments at the atomic scale.Future research should establish unified evaluation standards to assess the capability of training sets to accurately describe complex atomic-scale behaviors such as SRO.
基金supported in part by the National Key Research and Development Program of China Grant No.2021YFC2203001in part by the NSFC(Grant Nos.11920101003,12021003 and 12005016)+1 种基金supported by‘the Fundamental Research Funds for the Central Universities’of Beijing Normal Universitysupported by the NSF of Hunan province(Grant No.2023JJ30179)。
文摘The transverse-traceless gauge condition is an important concept in the theory of gravitational waves.It is well known that a vacuum is one of the key conditions to guarantee the existence of the transverse-traceless gauge.Although it is thin,the interstellar medium is ubiquitous in the Universe.Therefore,it is important to understand the concept of gravitational waves when matter is presented.Bondi-Metzner-Sachs theory has solved the gauge problem related to gravitational waves.But it does not help with cases when the gravitational wave propagates in matter.This paper discusses possible extensions of the transverse-traceless gauge condition to Minkowski perturbation with matter presented.
基金Project(52105498) supported by the National Natural Science Foundation of ChinaProject(2021RC3074) supported by the Science and Technology Innovation Program of Hunan Province,China+2 种基金Project(2023YFB4605500) supported by the National Key Research and Development Program of ChinaProject(AHL2022KF04) supported by the Advanced Laser Technology Laboratory of Anhui Province,ChinaProject(kq2402089) supported by the Changsha Natural Science Foundation,China。
文摘High-energy continuous wave(CW)lasers are mostly used in laser damage applications,but efficient laser ablation of transparent materials is challenging due to low optical absorption.Considering the potential of femtosecond(fs)laser-induced air filament for high-peak laser transmission over long distances,femtosecond(fs)laser-induced air filaments are combined with a millisecond(ms)laser to form an fs-ms CPL,enhancing the efficiency of sapphire ablation through synchronized spatial-temporal focusing.Experimental results show that ablation efficiency increases with the ms peak power and duty ratio.Excessive thermal stress leads to fragmentation of the sapphire when the ms duty ratio is over 30%at the peak power of 800 W,or when the peak power is over 500 W at a duty ratio of 100%.Also,the mechanism of high-efficiency damage is revealed through in-situ high-speed imaging.According to it,the ablation process went through 4 stages within 1.5 ms:defect-creating,melting and ablation,spattering,and fragmentation.Finally,the equivalent ablation efficiency of the fs-ms CPL is as high as 1.73×10^(7)μm^(3)/J,about 28 times higher compared to the fs laser only.The CPL damage method explored in this paper can provide theoretical guidance for efficient laser damage of transparent materials.
基金funded by Jinguan Copper of Tongling Non-ferrous Metals Group Co., Ltd.
文摘A mathematical model of the particle heating process in the reaction shaft of flash smelting furnace was established and the calculation was performed.The results indicate that radiation plays a significant role in the heat transfer process within the first 0.6 m in the upper part of the reaction shaft,whilst the convection is dominant in the area below 0.6 m for the particle heating.In order to accelerate the particle ignition,it is necessary to enhance the convection,thus to speed up the particle heating.A high-speed preheated oxygen jet technology was then suggested to replace the nature gas combustion in the flash furnace,aiming to create a lateral disturbance in the gaseous phase around the particles,so as to achieve a slip velocity between the two phases and a high convective heat transfer coefficient.Numerical simulation was carried out for the cases with the high-speed oxygen jet and the normal nature gas burners.The results show that with the high-speed jet technology,particles are heated up more rapidly and ignited much earlier,especially within the area of the radial range of R=0.3−0.6 m.As a result,a more efficient smelting process can be achieved under the same operational condition.
基金supported by the National Key Scientific Instrument and Equipment Development Projects(No.2012YQ240121)Liaoning science and technology project(No.2017220010)Changchun Science and Technology Bureau Local Company and College(University,Institution)Cooperation Projects(No.17DY023)
文摘A prompt gamma-neutron activation analysis(PGNAA) system was developed to detect the iron content of iron ore concentrate. Because of the self-absorption effect of gamma-rays and neutrons, and the interference of chlorine in the neutron field, the linear relationship between the iron analytical coefficient and total iron content was poor, increasing the error in the quantitative analysis. To solve this problem, gamma-ray self-absorption compensation and a neutron field correction algorithm were proposed, and the experimental results have been corrected using this algorithm. The results show that the linear relationship between the iron analytical coefficient and total iron content was considerably improved after the correction. The linear correlation coefficients reached 0.99 or more.
基金The authors are grateful to the National Natural Science Foundation of China(51402100,21573066,21825201,22075075,21805080,and U19A2017)the Provincial Natural Science Foundation of Hunan(2016JJ1006,2020JJ5044,and 2016TP1009)Australian Research Council(DP180100568 and DP180100731)for financial support of this research.
文摘The nitrogen(N2)-to-ammonia(NH3)fixation driven by renewable energy has an attractive prospect to relieve the global warming and reduce the consumption of fossil fuels.Ideally,photocatalytic,electrochemical,and photoelectrochemical approaches are developed as the next-generation NH3 synthesis technologies to substitute the Haber–Bosch method.However,the NH3 yield rate of nitrogen reduction reaction(NRR)by green approaches is extremely low,resulting in the current dilemma of NRR and contamination issues.Thus,in this mini review,the past advances on the sustainable NRR are briefly summarized in the three aspects as follows:the selectivity and adjustment of various catalysts,the type of electrolyte/solvent system,and the investigation of reaction conditions.Subsequently,the recent critical activities in the area of sustainable NH3 synthesis are analyzed and discussed deeply,and a perspective for rational and healthy development of this area is provided positively。
基金benefited from the support of the French government Investissements d’Avenir program ANR-11-LABX-0020-01partially supported by the National Natural Science Foundation of China(11571052,11401590,11731012 and 11671404)by Hunan Natural Science Foundation(2017JJ2271)
文摘We consider a branching random walk in an independent and identically distributed random environment ξ=(ξn) indexed by the time. Let W be the limit of the martingale Wn=∫e^-txZn(dx)/Eξ∫e^-txZn(dx), with Zn denoting the counting measure of particles of generation n, and Eξ the conditional expectation given the environment ξ. We find necessary and sufficient conditions for the existence of quenched moments and weighted moments of W, when W is non-degenerate.
基金National Natural Science Foundation of China,Grant/Award Numbers:51874362,51932011,52002407Scientific Research Project of Hunan Provincial Department of Education,Grant/Award Number:21B0815。
文摘Hard carbons are promising anode materials for sodium-ion batteries.To meet practical requirements,searching for durable and conductive carbon with a stable interface is of great importance.Here,we prepare a series of vanadiummodified hard carbon submicrospheres by using hydrothermal carbonization followed by high-temperature pyrolysis.Significantly,the introduction of vanadium can facilitate the nucleation and uniform growth of carbon spheres and generate abundant V-O-C interface bonds,thus optimizing the reaction kinetic.Meanwhile,the optimized hard carbon spheres modified by vanadium carbide,with sufficient pseudographitic domains,provide more active sites for Na ion migration and storage.As a result,the HC/VC-1300 electrode exhibits excellent Na storage performance,including a high capacity of 420 mAh g^(-1)at 50mA g^(-1)and good rate capability at 1 A g^(-1).This study proposes a new strategy for the synthesis of hard carbon spheres with high tap density and emphasizes the key role of pseudographitic structure for Na storage and interface stabilization.
基金the financial supports from the National Natural Science Foundation of China(Nos.52174338,51904349)the Natural Science Foundation of Hunan Province,China(No.2021JJ30796)。
文摘Waste carbon residue(WCR)was efficiently detoxicated and regenerated to high-purity graphite(PGC)used in lithium-ion batteries through the constant-pressure acid leaching technique.The leaching conditions were optimized by the combination of orthogonal and single-factor experiments.Results show that PGC with 99.5%purity is regenerated at temperature of 60℃,initial acid concentration of 12%,leaching time of 180 min,and liquid-to-solid ratio of 25:1,satisfying the requirements of commercial graphite.Meanwhile,the sodium hydroxide precipitation process was designed to recover valuable components from leachate efficiently.Ni,Co,Mn,and Al recoveries reach 96.92%,87.5%,97.83%,and 92.17%,respectively,at pH=11.Moreover,the co-product NaF can be recovered with purity over 99%via evaporative crystallization.The loss rate of fluorine is less than 0.5%,thereby eliminating the pollution risk of fluorine to the environment.The proposed process shows considerable environmental and economic benefits.
基金Fund for Creative Research Groups of National Natural Science Foundation of China, No.41321001 the National Natural Science Foundation of China, No.51379008 the Open Research Fund of the State Key Lab of Simulation and Regulation of Water Cycle in River Basin, No.2014QN04.
文摘Rainfall erosivity is an important climatic factor for predicting soil loss. Through the application of high-resolution pluviograph data at 5 stations in Huangshan City, Anhui Prov- ince, China, we analyzed the performance of a modified Richardson model that incorporated the seasonal variations in parameters α andβ. The results showed that （1） moderate to high seasonality was presented in the distribution of erosive rainfall, and the seasonality of rainfall erosivity was even stronger; （2） seasonal variations were demonstrated in both parameters α and β of the Richardson model; and （3） incorporating and coordinating the seasonality of parameters αandβgreatly improved the predictions at the monthly scale. This newly modi- fied model is therefore highly recommended when monthly rainfall erosivity is required, such as, in planning soil and water conservation practices and calculating the cover-management factor in the Universal Soil Loss Equation （USLE） and Revised Universal Soil Loss Equation （RUSLE）.
基金financially supported by the Projects of MOE Key Lab of Disaster Forecast and Control in Engineering in Jinan University(No.20200904006)the Guangdong Basic and Applied Basic Research Foundation(No.2020B1515420004)。
文摘To overcome the dimension limits of immiscible alloys produced by traditional techniques and enhance their mechanical properties,bulk Cu-Fe-based immiscible alloy with abundant nanotwins and stacking faults was successfully produced by selective laser melting(SLM).The SLM-produced bulk immiscible alloy displays a heterogeneous microstructure characterized by micro-scaledγ-Fe particles dispersed in fineε-Cu matrix with a high fraction(~92%)of high-angle grain boundaries.Interestingly,abundant nanotwins and stacking faults are generated in the interior of nano-scaledγ-Fe particles embedded withinε-Cu matrix.The heterogeneous interface of soft domains(ε-Cu)and hard domains(γ-Fe)not only induces the geometrically necessary dislocations(GNDs)but also affects the dislocation propagation during plastic deformation.Therefore,the bimodal heterogeneous interface,and the resistance of nanotwins and stacking faults to the propagation of partial dislocation make the bulk immiscible alloy exhibit an enhanced strength of~590 MPa and a good ductility of~8.9%.
文摘COVID-19 has changed the way of learning and life of college students.The purpose is to explore the relationship between perceived stress and anxiety,and the mediating effect of resilience and regulatory emotional self-efficacy in college students during COVID-19.309 students from three colleges were selected as research participants(average age 19.79±1.11 years).SPSS was used to measure the correlation between variables.Amos was used to test the path coefficient and mediating effect of the hypothetical model.The results show that:Firstly,perceived stress has a significantly and positively predictive effect on anxiety.Secondly,psychological resilience and regu-latory emotional self-efficacy independently played a significant and partially mediating effect between perceived stress and anxiety.Among them,perceived stress had a negative predictive effect on psychological resilience and regulatory emotional self-efficacy.Psychological resilience and regulatory emotional self-efficacy had a negative predictive effect on anxiety.Thirdly,psychological resilience and regulatory emotional self-efficacy play a chain mediation role between psychological stress and anxiety.Regulatory emotional self-efficacy cannot only directly predict the level of anxiety,but also indirectly predict the level of anxiety by regulating psychological resilience.This study reveals the relationship between college students’perceived stress and anxiety,and the mediating effect of psychological resilience and regulatory emotional self-efficacy in the new time of COVID-19.The chain mediation role of psychological resilience and regulatory emotional self-efficacy reminds college mental health educators that improving students’regulatory emotional self-efficacy is an important way to promote students’mental health.
基金This work was financially supported by the Scientific Research Project of Hunan Education Department(20C0410)the Fundamental Research Funds for the Central Universities of Central South University.
文摘This work reports an improved method for the wet desulfurization of high-sulfur petroleum coke(petcoke)powder based on the combination of pre-calcination,H_(2)O_(2),and ultrasound.The results demonstrated that over 45%of the sulfur atoms were efficiently removed from Tianjin coke and Qilu coke(particle size<0.1 mm)by pre-calcination at 800℃ for 6 h followed by desulfurization with HNO3(8 mol/L)and H_(2)O_(2)(2 mol/L)solution at a reaction temperature of 60℃,a reaction time of 6 h,a liquid-to-solid ratio of 10 mL/g,and a 40 kHz ultrasonic power of 400 W.In addition,the specific surface area of the petcoke particles increased from 0.7 to 301.49 m^(2)/g.After desulfurization,the pore size distribution of the petcoke particles was more concentrated on micropores compared with the samples prior to petcoke treatment.Reactive force field molecular dynamics simulation results indicated that HNO_(3) continuously oxidized the carbon atoms adjacent to sulfur atoms in the petcoke macromolecules and promoted sulfur removal from petcoke via the cleavage of C-S bonds.The sulfur transformation mechanism can be summarized as follows:thiophene sulfur→branched chain carbon sulfur→CO_(2)S→C_(2)O_(2)S→C_(2)O_(3)NS→C_(2)O_(4)S→CO_(2)S.
基金support from the National Natural Science Foundation of China(Grant Nos.12174097 and 12304321)the Natural Science Foundation of Hunan Province(Grant Nos.2021JJ10008 and 2023JJ40202)the Research Foundation of Education Bureau of Hunan Province(Grant No.22B0871).
文摘Object identification and three-dimensional reconstruction techniques are always attractive research interests in machine vision,virtual reality,augmented reality,and biomedical engineering.Optical computing metasurface,as a two-dimensional artificial design component,has displayed the supernormal character of controlling phase,amplitude,polarization,and frequency distributions of the light beam,capable of performing mathematical operations on the input light field.Here,we propose and demonstrate an all-optical object identification technique based on optical computing metasurface,and apply it to 3D reconstruction.Unlike traditional mechanisms,this scheme reduces memory consumption in the processing of the contour surface extraction.The identification and reconstruction of experimental results from high-contrast and low-contrast objects agree well with the real objects.The exploration of the all-optical object identification and 3D reconstruction techniques provides potential applications of high efficiencies,low consumption,and compact systems.
文摘This study aims to provide evidence regarding whether Qingufei paidu decoction(清肺排毒汤,QFPD)treatment in the acute phase shows long-term benefits for coronavirus disease 2019-associated sequelae.The 10 databases will be retrieved.Every reference list of related trials and gray literature will be searched as well.Study screening,data extraction,and risk of bias evaluation will be performed by two reviewers(CUI Hanjin and FAN Rong).Data analysis will be conducted by using STATA(version 14).Statistical heterogeneity will be explored by a standardχ2 test with a significance level of P<0.10.Funnel plots,Egger’s&Begg’s test,and Trim and Fill analysis will be used for publication bias assessment.The results of the present Meta-analysis and systematic review will be disseminated via peer-review journal publication.Ethical approval is not required,as this Meta-analysis will not contain any individual patient data.This systematic review has been registered on PROSPERO(registration number:CRD42021246937)on 15 April 2021.
