Hydrogen evolution reaction(HER)has become a key factor affecting the cycling stability of aqueous Zn-ion batteries,while the corresponding fundamental issues involving HER are still unclear.Herein,the reaction mechan...Hydrogen evolution reaction(HER)has become a key factor affecting the cycling stability of aqueous Zn-ion batteries,while the corresponding fundamental issues involving HER are still unclear.Herein,the reaction mechanisms of HER on various crystalline surfaces have been investigated by first-principle calculations based on density functional theory.It is found that the Volmer step is the ratelimiting step of HER on the Zn(002)and(100)surfaces,while,the reaction rates of HER on the Zn(101),(102)and(103)surfaces are determined by the Tafel step.Moreover,the correlation between HER activity and the generalized coordination number(CN)of Zn at the surfaces has been revealed.The relatively weaker HER activity on Zn(002)surface can be attributed to the higher CN of surface Zn atom.The atomically uneven Zn(002)surface shows significantly higher HER activity than the flat Zn(002)surface as the CN of the surface Zn atom is lowered.The CN of surface Zn atom is proposed as a key descriptor of HER activity.Tuning the CN of surface Zn atom would be a vital strategy to inhibit HER on the Zn anode surface based on the presented theoretical studies.Furthermore,this work provides a theoretical basis for the in-depth understanding of HER on the Zn surface.展开更多
Molecular-frame photoelectron momentum distributions(MF-PMDs) of an H_(2)^(+) molecule ion in the presence of a pair of counter-rotating circularly polarized attosecond extreme ultraviolet laser pulses is studied by n...Molecular-frame photoelectron momentum distributions(MF-PMDs) of an H_(2)^(+) molecule ion in the presence of a pair of counter-rotating circularly polarized attosecond extreme ultraviolet laser pulses is studied by numerically solving the two-dimensional time-dependent Schrodinger equation within the frozen-nuclei approximation. At small time delay, our simulations show that the electron vortex structure is sensitive to the time delay and relative phase between the counterrotating pulses when they are partially overlapped. By adjusting time delay and relative phase, we have the ability to manipulate the MF-PMDs and the appearance of spiral arms. We further show that the internuclear distance can affect the spiral vortices due to its different transition cross sections in the parallel and perpendicular geometries. The lowest-order perturbation theory is employed to interpret these phenomena qualitatively. It is concluded that the internuclear distancedependent transition cross sections and the confinement effect in diatomic molecules are responsible for the variation of vortex structures in the MF-PMDs.展开更多
According to international standard plant quarantine measures and principle risk analysis(ISPM No.11),a risk assessment was carried out for Passalora sequoiae through geographical distribution,possibility of colonizat...According to international standard plant quarantine measures and principle risk analysis(ISPM No.11),a risk assessment was carried out for Passalora sequoiae through geographical distribution,possibility of colonization,probability of diffusion,economic importance and difficulty in risk management.Results show that P.sequoiae has a greater risk of introduction and diffusion,and it has distributed in parts of China.It is suggested that P.sequoiae should be added to the list of forest dangerous pests in China.Besides,porting departments should focus on the pathogen on imported host seedlings like Cryptomeria.展开更多
The mega-constellation network has gained significant attention recently due to its great potential in providing ubiquitous and high-capacity connectivity in sixth-generation(6G)wireless communication systems.However,...The mega-constellation network has gained significant attention recently due to its great potential in providing ubiquitous and high-capacity connectivity in sixth-generation(6G)wireless communication systems.However,the high dynamics of network topology and large scale of mega-constellation pose new challenges to the constellation simulation and performance evaluation.In this paper,we introduce UltraStar,a lightweight network simulator,which aims to facilitate the complicated simulation for the emerging mega-constellation of unprecedented scale.Particularly,a systematic and extensible architecture is proposed,where the joint requirement for network simulation,quantitative evaluation,data statistics and visualization is fully considered.For characterizing the network,we make lightweight abstractions of physical entities and models,which contain basic representatives of networking nodes,structures and protocol stacks.Then,to consider the high dynamics of Walker constellations,we give a two-stage topology maintenance method for constellation initialization and orbit prediction.Further,based on the discrete event simulation(DES)theory,a new set of discrete events is specifically designed for basic network processes,so as to maintain network state changes over time.Finally,taking the first-generation Starlink of 11927 low earth orbit(LEO)satellites as an example,we use UltraStar to fully evaluate its network performance for different deployment stages,such as characteristics of constellation topology,performance of end-to-end service and effects of network-wide traffic interaction.The simulation results not only demonstrate its superior performance,but also verify the effectiveness of UltraStar.展开更多
With the overwhelming number of older reinforced concrete buildings that need to be assessed for seismic vulnerability in a city,local governments face the question of how to assess their building inventory.By leverag...With the overwhelming number of older reinforced concrete buildings that need to be assessed for seismic vulnerability in a city,local governments face the question of how to assess their building inventory.By leveraging engineering drawings that are stored in a digital format,a well-established method for classification reinforced concrete buildings with respect to seismic vulnerability,and machine learning techniques,we have developed a technique to automatically extract quantitative information from the drawings to classify vulnerability.Using this technique,stakeholders will be able to rapidly classify buildings according to their seismic vulnerability and have access to information they need to prioritize a large building inventory.The approach has the potential to have significant impact on our ability to rapidly make decisions related to retrofit and improvements in our communities.In the Los Angeles County alone it is estimated that several thousand buildings of this type exist.The Hassan index is adopted here as the method for automation due to its simple application during the classification of the vulnerable reinforced concrete buildings.This paper will present the technique used for automating information extraction to compute the Hassan index for a large building inventory.展开更多
A high-performance terahertz Schottky barrier diode(SBD)with an inverted trapezoidal epitaxial cross-sectional structure featuring high varactor characteristics and reverse breakdown characteristics is reported in thi...A high-performance terahertz Schottky barrier diode(SBD)with an inverted trapezoidal epitaxial cross-sectional structure featuring high varactor characteristics and reverse breakdown characteristics is reported in this paper.Inductively coupled plasma dry etching and dissolution wet etching are used to define the profile of the epitaxial layer,by which the voltage-dependent variation trend of the thickness of the metal-semiconductor contact depletion layer is modified.The simulation of the inverted trapezoidal epitaxial cross-section SBD is also conducted to explain the physical mechanism of the electric field and space charge region area.Compared with the normal structure,the grading coefficient M increases from 0.47 to 0.52,and the capacitance modulation ratio(C^(max)/C_(min))increases from 6.70 to 7.61.The inverted trapezoidal epitaxial cross-section structure is a promising approach to improve the variable-capacity ratio by eliminating the accumulation of charge at the Schottky electrode edge.A 190 GHz frequency doubler based on the inverted trapezoidal epitaxial cross-section SBD also shows a doubling efficiency of 35%compared to that 30%of a normal SBD.展开更多
Thin and flexible composite solid-state electrolyte(SSE) is considered to be a prospective candidate for lithium-oxygen(Li-O_(2)) batteries with the aim to address the problems of unsatisfied safety, terrible durabili...Thin and flexible composite solid-state electrolyte(SSE) is considered to be a prospective candidate for lithium-oxygen(Li-O_(2)) batteries with the aim to address the problems of unsatisfied safety, terrible durability as well as inferior electrochemical performance. Herein, in order to improve the safety and durability, a succinonitrile(SN) modified composite SSE is proposed. In this SSE, SN is introduced for eliminating the boundary between ceramic particles, increasing the amorphous region of polymer and ensuring fast ionic transport. Subsequently, the symmetric battery based on the proposed SSE achieves a long cycle life of 3000 h. Moreover, the elaborate cathode interface through the SN participation effectively reduces the barriers to the combination between lithium ions and electrons, facilitating the corresponding electrochemical reactions.As a result, the solid-state Li-O_(2)battery based on this SSE and tuned cathode interface achieves improved electrochemical performance including large specific capacity over 12,000 m Ah g^(-1), enhanced rate capacity as well as stable cycle life of 54 cycles at room temperature. This ingenious design provides a new orientation for the evolution of solid-state Li-O_(2)batteries.展开更多
Tunable magnetic phase transition in two-dimensional materials is a fascinating subject of research.We perform first-principle calculations based on density functional theory to clarify the magnetic property of CrSeTe...Tunable magnetic phase transition in two-dimensional materials is a fascinating subject of research.We perform first-principle calculations based on density functional theory to clarify the magnetic property of CrSeTe monolayer modulated by the biaxial compressive strain.Based on the stable structure confirmed by the phonon calculation,CrSeTe is determined to be a ferromagnetic metal that undergoes a phase transition from a ferromagnetic state to an antiferromagnetic state with nearly 2.75%compressive strain.We identify the stress-magnetism behavior originating from the changes in interactions between the nearest-neighboring Cr atoms(J_(1)) and the next-nearest-neighboring Cr atoms(J_(2)).Through Monte Carlo simulation,we find that the Curie temperature of the CrSeTe monolayer is 160 K.The CrSeTe monolayer could be an intriguing platform for the two-dimensional systems and potential spintronic material.展开更多
The solid oxide electrolytic cell(SOEC)is one of the most promising energy conversion and storage devices,which could convert CO_(2) to CO with high Faradaic efficiency and production rate.However,the lack of active a...The solid oxide electrolytic cell(SOEC)is one of the most promising energy conversion and storage devices,which could convert CO_(2) to CO with high Faradaic efficiency and production rate.However,the lack of active and stable cathode materials impedes their practical applications.Here we focus on the promising perovskite oxide cathode material Sr_(2)Fe_(1.5)Mo_(0.5)O_(6)-σ,with the aim of understanding how A-atom stoichiometry and catalytic performance are linked.We find that increasing the strontium content in the perovskite improves the chemisorption of CO_(2) on its surface,forming a SrCO_(3) phase.This hinders the charge transfer and oxygen exchange processes.Simulta-neously,strontoium segregation to the cathode surface facilitates coking of the surface during CO_(2) electrolysis,which poisons the electrode.Consequently,a small number of Sr deficiencies are optimal for both electrochemical performance and long-term stability.Our results provide new insights for designing high-performance CO_(2) electrolysis cathode materials.展开更多
Chinese education is like a large competitive game in the past time,with a lot of over-step learning and pre-emptive education increasing the extra—curricular pressure on primary and secondary school students day by ...Chinese education is like a large competitive game in the past time,with a lot of over-step learning and pre-emptive education increasing the extra—curricular pressure on primary and secondary school students day by day.In 2021,the national"double reduction"policy was implemented,and in 2022,the"Family Education Promotion Law of the People's Republic of China"was introduced.With the combined effect of"one government,one law",the status and role of family education have become more prominent,so it is of great practical significance to understand the education investment behavior of Chinese families.Therefore,this study is a case study of three students and their families from different schools in Weifang,Shandong Province in China.Through semi-structured interviews,this paper discusses the educational investment of well-off families after the implementation of the double reduction policy.The results show that art-related learning content dominates the education expenditure of well-off families after the implementation of the double-reducing policy,while cultural tutoring decreases.Becasue of(a)parents mainly want to cultivate their children's interests and hobbies or provide guidance for weak subjects;(b)the lack of understanding of the double reduction policy,leading to parents and students blindly follow the trend,increasing the pressure of students and parents'anxiety.This study focuses on the feelings of students and parents after the implementation of the double reduction policy,and attaches importance to the problems arising after the implementation of the policy.The findings are helpful to provide reference for future research on the educational investment of wealthy families after the implementation of the double reduction policy.展开更多
<strong>Objectives:</strong> This study aims to present the characteristics of the undergraduate dental curriculum system using network modelling and visualisation analysis based on complex network theory,...<strong>Objectives:</strong> This study aims to present the characteristics of the undergraduate dental curriculum system using network modelling and visualisation analysis based on complex network theory, thus providing a theoretical foundation for the course development and curriculum reform. <strong>Methods:</strong> The correlation coefficient was used to quantify the intensity of the correlation between courses, and a visualisation complex network of the dental curriculum was built to explore the curriculum pattern from a dynamic perspective. Further, the statistical measurements of curriculum network were adopted to express the most relevant topological features. Subsequently, the minimum spanning tree and parallel coordinates plot were drawn to explore the curriculum community structure, quantify the key courses, and present different courses in time and space relationships. <strong>Results:</strong> The correlation analysis results show that the courses are closely related to each other. The main courses focus on pathology, pathophysiology, oral anatomy and physiology, closely connecting almost all medicine-related courses. The whole course network has an average degree value of 41.53, and a clustering coefficient of 0.78, indicating an obvious small-world characteristic. From the perspective of curriculum attributes, the number of public and theoretical courses was more than that of skills and practical courses. Moreover, the academic performance of skills and practical courses was lower than that of public and theoretical courses. <strong>Conclusion:</strong> The undergraduate dental courses have a progressive structure from basic professional knowledge to professional skills, which is reasonable for the dental education in China. However, some efforts towards curriculum reform based on this study are needed.展开更多
Continuum-based discrete element method(CDEM)is an explicit numerical method used for simulation of progressive failure of geological body.To improve the efficiency of contact detection and simplify the calculation st...Continuum-based discrete element method(CDEM)is an explicit numerical method used for simulation of progressive failure of geological body.To improve the efficiency of contact detection and simplify the calculation steps for contact forces,semi-spring and semi-edge are introduced in calculation.Semispring is derived from block vertex,and formed by indenting the block vertex into each face(24semisprings for a hexahedral element).The formation process of semi-edge is the same as that of semi-spring(24semi-edges for a hexahedral element).Based on the semi-springs and semi-edges,a new type of combined contact model is presented.According to this model,six contact types could be reduced to two,i.e.the semi-spring target face contact and semi-edge target edge contact.By the combined model,the contact force could be calculated directly(the information of contact type is not necessary),and the failure judgment could be executed in a straightforward way(each semi-spring and semi-edge own their characteristic areas).The algorithm has been successfully programmed in C++program.Some simple numerical cases are presented to show the validity and accuracy of this model.Finally,the failure mode,sliding distance and critical friction angle of Jiweishan landslide are studied with the combined model.展开更多
Aqueous zinc ion batteries show prospects for next-generation renewable energy storage devices.However,the practical applications have been limited by the issues derived from Zn anode.As one of serious problems,Zn den...Aqueous zinc ion batteries show prospects for next-generation renewable energy storage devices.However,the practical applications have been limited by the issues derived from Zn anode.As one of serious problems,Zn dendrite growth caused from the uncontrollable Zn deposition is unfavorable.Herein,with the aim to regulate Zn deposition,an artificial solid–electrolyte interface is subtly engineered with a perovskite type material,BaTiO3,which can be polarized,and its polarization could be switched under the external electric field.Resulting from the aligned dipole in BaTiO3 layer,zinc ions could move in order during cycling process.Regulated Zn migration at the anode/electrolyte interface contributes to the even Zn stripping/plating and confined Zn dendrite growth.As a result,the reversible Zn plating/stripping processes for over 2000 h have been achieved at 1 mA cm^(−2) with capacity of 1 mAh cm−2.Furthermore,this anode endowing the electric dipoles shows enhanced cycling stability for aqueous Zn-MnO2 batteries.The battery can deliver nearly 100%Coulombic efficiency at 2 Ag^(−1) after 300 cycles.展开更多
A multi beam sonar survey is carried out in the continental slope of the Taixinan Basin to obtain submarine topographic and water column data. The data are processed to obtain water column images. Anomalous water colu...A multi beam sonar survey is carried out in the continental slope of the Taixinan Basin to obtain submarine topographic and water column data. The data are processed to obtain water column images. Anomalous water column images, displaying plume characteristics, are found in gas hydrate enriched areas in the Taixinan Basin.This indicates the presence of natural gas resources in the Taixinan Basin. The multibeam sonar system is shown to provide an accurate and effective approach for detecting sub-sea gas hydrate.展开更多
A hollow cathode is the electronic source and neutralizer of the Hall thruster and an ion thruster.When the orbit of an all-electric propulsion satellite changes from 100 km to 36 000 km, the backpressure changes by t...A hollow cathode is the electronic source and neutralizer of the Hall thruster and an ion thruster.When the orbit of an all-electric propulsion satellite changes from 100 km to 36 000 km, the backpressure changes by two to three orders of magnitude. In this paper, the influence of the backpressure on the discharge characteristics of the hollow cathode has been studied experimentally in the so-called diode configuration. With the increase in the backpressure, the anode voltage decreases gradually, and the amplitude of the current oscillation decreases significantly. Additionally, the plasma is relatively stable, the most probable ion energy and the width of the ion energy distribution reduces, and the electron distribution function inclines toward the Maxwell distribution under high backpressure. The analysis results show that the backpressure affects the gas ionization and the ionic acoustic turbulence, which also affects the discharge characteristics of the hollow cathode.展开更多
The hydrogen evolution reaction (HER) and dendrite growth associated with Zn anode have become the main bottlenecks for the further development of zinc ion batteries (ZIBs).In this work,the electrochemical activity of...The hydrogen evolution reaction (HER) and dendrite growth associated with Zn anode have become the main bottlenecks for the further development of zinc ion batteries (ZIBs).In this work,the electrochemical activity of H_(3)O^(+) is inhibited by the supramolecular host–guest complex composed of H_(3)O^(+) as guest and 18-crown-6 as host.The even Zn plating is induced by the host–guest complex electrostatic shielding layer on Zn anode,as detected by in-situ optical microscopy.The lamellar Zn is plated which profits from the improved Zn plating behavior.Density functional theory (DFT) calculation presents the stable structure of complex.The less produced H_(2) content is monitored online by a mass spectrometer during Zn plating/stripping,which indicates HER can be hampered by the host–guest behavior.Thus,the ZIBs with long life and high Coulombic efficiency are achieved via introducing 18-crown-6.The proposed host–guest supramolecular interaction is expected to facilitate the furthermore development of Zn batteries.展开更多
Skin ulceration syndrome(SUS)is the main diseases aff ected the development of sea cucumber(Apostichopus japonicus)culture industries.To better observe the changes in the sea cucumber A.japonicus with SUS and understa...Skin ulceration syndrome(SUS)is the main diseases aff ected the development of sea cucumber(Apostichopus japonicus)culture industries.To better observe the changes in the sea cucumber A.japonicus with SUS and understand the pathogenesis of the disease,activities of superoxide dismutase(SOD),catalase(CAT),and level of malondialdehyde(MDA)in coelomic fluid were detected using the Assay Kit and metabolites in the body wall were assessed using ultra-performance liquid chromatography and quadrupole-time of flight mass spectrometry.The results indicated that level of MDA was increased during SUS compared with healthy individuals(P<0.01),but activities of SOD and CAT were reduced(P<0.05).In metabolomics analysis,metabolites,such as adenosine,choline,betaine aldehyde,palmitic acid,and taurine,were found to be upregulated and 2-oxoadipic acid,anthranilic acid(vitamin L1),thioetheramide-PC,cholesterol-3-sulfate,and pentadecanoic acid were downregulated(VIP>1 and P<0.1).Pathway enrichment analysis indicated most enrichment of KEGG pathways were mainly related to energy metabolism,immunity,and osmoregulation such as ABC transporters,glycine,serine and threonine metabolism,tryptophan metabolism and neuroactive ligand-receptor interaction.Our study reflected the difference in enzyme activity and metabolites between A.japonicus with SUS and those without,which will provide reference data for investigating SUS.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(22075171)Natural Science Foundation of Shanghai(23ZR1423400)The firstprinciples calculations were supported by the High Performance Computing Center of Shanghai University.
文摘Hydrogen evolution reaction(HER)has become a key factor affecting the cycling stability of aqueous Zn-ion batteries,while the corresponding fundamental issues involving HER are still unclear.Herein,the reaction mechanisms of HER on various crystalline surfaces have been investigated by first-principle calculations based on density functional theory.It is found that the Volmer step is the ratelimiting step of HER on the Zn(002)and(100)surfaces,while,the reaction rates of HER on the Zn(101),(102)and(103)surfaces are determined by the Tafel step.Moreover,the correlation between HER activity and the generalized coordination number(CN)of Zn at the surfaces has been revealed.The relatively weaker HER activity on Zn(002)surface can be attributed to the higher CN of surface Zn atom.The atomically uneven Zn(002)surface shows significantly higher HER activity than the flat Zn(002)surface as the CN of the surface Zn atom is lowered.The CN of surface Zn atom is proposed as a key descriptor of HER activity.Tuning the CN of surface Zn atom would be a vital strategy to inhibit HER on the Zn anode surface based on the presented theoretical studies.Furthermore,this work provides a theoretical basis for the in-depth understanding of HER on the Zn surface.
基金Project supported by the Natural Science Foundation of Jilin Province,China (Grant No.20220101016JC)the National Key Research and Development Program of China (Grant No.2022YFE0134200)+1 种基金the National Natural Science Foundation of China (Grant Nos.12174147,91850114,and 11774131)the Open Research Fund of State Key Laboratory of Transient Optics and Photonics。
文摘Molecular-frame photoelectron momentum distributions(MF-PMDs) of an H_(2)^(+) molecule ion in the presence of a pair of counter-rotating circularly polarized attosecond extreme ultraviolet laser pulses is studied by numerically solving the two-dimensional time-dependent Schrodinger equation within the frozen-nuclei approximation. At small time delay, our simulations show that the electron vortex structure is sensitive to the time delay and relative phase between the counterrotating pulses when they are partially overlapped. By adjusting time delay and relative phase, we have the ability to manipulate the MF-PMDs and the appearance of spiral arms. We further show that the internuclear distance can affect the spiral vortices due to its different transition cross sections in the parallel and perpendicular geometries. The lowest-order perturbation theory is employed to interpret these phenomena qualitatively. It is concluded that the internuclear distancedependent transition cross sections and the confinement effect in diatomic molecules are responsible for the variation of vortex structures in the MF-PMDs.
基金Supported by Projects of General Administration of Customs(2020HK159)Nanjing Customs Research Projects(2023KJ20).
文摘According to international standard plant quarantine measures and principle risk analysis(ISPM No.11),a risk assessment was carried out for Passalora sequoiae through geographical distribution,possibility of colonization,probability of diffusion,economic importance and difficulty in risk management.Results show that P.sequoiae has a greater risk of introduction and diffusion,and it has distributed in parts of China.It is suggested that P.sequoiae should be added to the list of forest dangerous pests in China.Besides,porting departments should focus on the pathogen on imported host seedlings like Cryptomeria.
基金supported in part by the National Key Research and Development Program of China(2020YFB1806104)the Natural Science Fund for Distinguished Young Scholars of Jiangsu Province(BK20220067)the Natural Sciences and Engineering Research Council of Canada(NSERC)。
文摘The mega-constellation network has gained significant attention recently due to its great potential in providing ubiquitous and high-capacity connectivity in sixth-generation(6G)wireless communication systems.However,the high dynamics of network topology and large scale of mega-constellation pose new challenges to the constellation simulation and performance evaluation.In this paper,we introduce UltraStar,a lightweight network simulator,which aims to facilitate the complicated simulation for the emerging mega-constellation of unprecedented scale.Particularly,a systematic and extensible architecture is proposed,where the joint requirement for network simulation,quantitative evaluation,data statistics and visualization is fully considered.For characterizing the network,we make lightweight abstractions of physical entities and models,which contain basic representatives of networking nodes,structures and protocol stacks.Then,to consider the high dynamics of Walker constellations,we give a two-stage topology maintenance method for constellation initialization and orbit prediction.Further,based on the discrete event simulation(DES)theory,a new set of discrete events is specifically designed for basic network processes,so as to maintain network state changes over time.Finally,taking the first-generation Starlink of 11927 low earth orbit(LEO)satellites as an example,we use UltraStar to fully evaluate its network performance for different deployment stages,such as characteristics of constellation topology,performance of end-to-end service and effects of network-wide traffic interaction.The simulation results not only demonstrate its superior performance,but also verify the effectiveness of UltraStar.
基金US National Science Foundation under Grant No.NSF-OAC-1835473。
文摘With the overwhelming number of older reinforced concrete buildings that need to be assessed for seismic vulnerability in a city,local governments face the question of how to assess their building inventory.By leveraging engineering drawings that are stored in a digital format,a well-established method for classification reinforced concrete buildings with respect to seismic vulnerability,and machine learning techniques,we have developed a technique to automatically extract quantitative information from the drawings to classify vulnerability.Using this technique,stakeholders will be able to rapidly classify buildings according to their seismic vulnerability and have access to information they need to prioritize a large building inventory.The approach has the potential to have significant impact on our ability to rapidly make decisions related to retrofit and improvements in our communities.In the Los Angeles County alone it is estimated that several thousand buildings of this type exist.The Hassan index is adopted here as the method for automation due to its simple application during the classification of the vulnerable reinforced concrete buildings.This paper will present the technique used for automating information extraction to compute the Hassan index for a large building inventory.
基金Project supported by the National Natural Science Foundation of China (Grant No.61871072)。
文摘A high-performance terahertz Schottky barrier diode(SBD)with an inverted trapezoidal epitaxial cross-sectional structure featuring high varactor characteristics and reverse breakdown characteristics is reported in this paper.Inductively coupled plasma dry etching and dissolution wet etching are used to define the profile of the epitaxial layer,by which the voltage-dependent variation trend of the thickness of the metal-semiconductor contact depletion layer is modified.The simulation of the inverted trapezoidal epitaxial cross-section SBD is also conducted to explain the physical mechanism of the electric field and space charge region area.Compared with the normal structure,the grading coefficient M increases from 0.47 to 0.52,and the capacitance modulation ratio(C^(max)/C_(min))increases from 6.70 to 7.61.The inverted trapezoidal epitaxial cross-section structure is a promising approach to improve the variable-capacity ratio by eliminating the accumulation of charge at the Schottky electrode edge.A 190 GHz frequency doubler based on the inverted trapezoidal epitaxial cross-section SBD also shows a doubling efficiency of 35%compared to that 30%of a normal SBD.
基金the partial financial support from the National Natural Science Foundation of China (22075171,21805182 and 22179080)。
文摘Thin and flexible composite solid-state electrolyte(SSE) is considered to be a prospective candidate for lithium-oxygen(Li-O_(2)) batteries with the aim to address the problems of unsatisfied safety, terrible durability as well as inferior electrochemical performance. Herein, in order to improve the safety and durability, a succinonitrile(SN) modified composite SSE is proposed. In this SSE, SN is introduced for eliminating the boundary between ceramic particles, increasing the amorphous region of polymer and ensuring fast ionic transport. Subsequently, the symmetric battery based on the proposed SSE achieves a long cycle life of 3000 h. Moreover, the elaborate cathode interface through the SN participation effectively reduces the barriers to the combination between lithium ions and electrons, facilitating the corresponding electrochemical reactions.As a result, the solid-state Li-O_(2)battery based on this SSE and tuned cathode interface achieves improved electrochemical performance including large specific capacity over 12,000 m Ah g^(-1), enhanced rate capacity as well as stable cycle life of 54 cycles at room temperature. This ingenious design provides a new orientation for the evolution of solid-state Li-O_(2)batteries.
基金the National Natural Science Foundation of China(Grant Nos.61874060,U1932159,and 61911530220)the Natural Science Foundation of Jiangsu Province(Grant No.BK20181388)+3 种基金the Natural Science Research of Jiangsu Higher Education Institutions of China(Grant No.21KJD140005)the Foundation of Nanjing University of Posts and Telecommunications(NUPT)‘1311 Talent Program’supported by the Natural Science Foundation of Jiangsu Province(Grant No.20KJB430010)NUPTSF(Grant No.NY219164)。
文摘Tunable magnetic phase transition in two-dimensional materials is a fascinating subject of research.We perform first-principle calculations based on density functional theory to clarify the magnetic property of CrSeTe monolayer modulated by the biaxial compressive strain.Based on the stable structure confirmed by the phonon calculation,CrSeTe is determined to be a ferromagnetic metal that undergoes a phase transition from a ferromagnetic state to an antiferromagnetic state with nearly 2.75%compressive strain.We identify the stress-magnetism behavior originating from the changes in interactions between the nearest-neighboring Cr atoms(J_(1)) and the next-nearest-neighboring Cr atoms(J_(2)).Through Monte Carlo simulation,we find that the Curie temperature of the CrSeTe monolayer is 160 K.The CrSeTe monolayer could be an intriguing platform for the two-dimensional systems and potential spintronic material.
基金financially supported by the National Natural Science Foundation of China(No.21975163)Natural Science Foundation of Guangdong Province of China(2020A1515011165)Shenzhen Sci-ence and Technology Program(No.KQTD20190929173914967)and(No.JCYJ20220818100004009)。
文摘The solid oxide electrolytic cell(SOEC)is one of the most promising energy conversion and storage devices,which could convert CO_(2) to CO with high Faradaic efficiency and production rate.However,the lack of active and stable cathode materials impedes their practical applications.Here we focus on the promising perovskite oxide cathode material Sr_(2)Fe_(1.5)Mo_(0.5)O_(6)-σ,with the aim of understanding how A-atom stoichiometry and catalytic performance are linked.We find that increasing the strontium content in the perovskite improves the chemisorption of CO_(2) on its surface,forming a SrCO_(3) phase.This hinders the charge transfer and oxygen exchange processes.Simulta-neously,strontoium segregation to the cathode surface facilitates coking of the surface during CO_(2) electrolysis,which poisons the electrode.Consequently,a small number of Sr deficiencies are optimal for both electrochemical performance and long-term stability.Our results provide new insights for designing high-performance CO_(2) electrolysis cathode materials.
基金This paper is supported by the Macao Foundation's research project"An Empirical Study on the Training Standards for Innovative Talents in the Guangdong-Hong Kong-Macao Greater Bay Area"(MF2315)and the 2021 General Project of the 14th Five-Year Plan of Philosophy and Social Sciences of Guangdong Province of China(Number:GD21CJY08).
文摘Chinese education is like a large competitive game in the past time,with a lot of over-step learning and pre-emptive education increasing the extra—curricular pressure on primary and secondary school students day by day.In 2021,the national"double reduction"policy was implemented,and in 2022,the"Family Education Promotion Law of the People's Republic of China"was introduced.With the combined effect of"one government,one law",the status and role of family education have become more prominent,so it is of great practical significance to understand the education investment behavior of Chinese families.Therefore,this study is a case study of three students and their families from different schools in Weifang,Shandong Province in China.Through semi-structured interviews,this paper discusses the educational investment of well-off families after the implementation of the double reduction policy.The results show that art-related learning content dominates the education expenditure of well-off families after the implementation of the double-reducing policy,while cultural tutoring decreases.Becasue of(a)parents mainly want to cultivate their children's interests and hobbies or provide guidance for weak subjects;(b)the lack of understanding of the double reduction policy,leading to parents and students blindly follow the trend,increasing the pressure of students and parents'anxiety.This study focuses on the feelings of students and parents after the implementation of the double reduction policy,and attaches importance to the problems arising after the implementation of the policy.The findings are helpful to provide reference for future research on the educational investment of wealthy families after the implementation of the double reduction policy.
文摘<strong>Objectives:</strong> This study aims to present the characteristics of the undergraduate dental curriculum system using network modelling and visualisation analysis based on complex network theory, thus providing a theoretical foundation for the course development and curriculum reform. <strong>Methods:</strong> The correlation coefficient was used to quantify the intensity of the correlation between courses, and a visualisation complex network of the dental curriculum was built to explore the curriculum pattern from a dynamic perspective. Further, the statistical measurements of curriculum network were adopted to express the most relevant topological features. Subsequently, the minimum spanning tree and parallel coordinates plot were drawn to explore the curriculum community structure, quantify the key courses, and present different courses in time and space relationships. <strong>Results:</strong> The correlation analysis results show that the courses are closely related to each other. The main courses focus on pathology, pathophysiology, oral anatomy and physiology, closely connecting almost all medicine-related courses. The whole course network has an average degree value of 41.53, and a clustering coefficient of 0.78, indicating an obvious small-world characteristic. From the perspective of curriculum attributes, the number of public and theoretical courses was more than that of skills and practical courses. Moreover, the academic performance of skills and practical courses was lower than that of public and theoretical courses. <strong>Conclusion:</strong> The undergraduate dental courses have a progressive structure from basic professional knowledge to professional skills, which is reasonable for the dental education in China. However, some efforts towards curriculum reform based on this study are needed.
基金the National Basic Research Program of the Ministry of Science and Technology of China (Grant No. 2010CB731506)the National Key Technology Research and Development Program of the Ministry of Science and Technology of China (Grant No. 2012BAK10B01)the Youth Science Fund of National Natural Science Foundation of China (Grant No. 11302230)
文摘Continuum-based discrete element method(CDEM)is an explicit numerical method used for simulation of progressive failure of geological body.To improve the efficiency of contact detection and simplify the calculation steps for contact forces,semi-spring and semi-edge are introduced in calculation.Semispring is derived from block vertex,and formed by indenting the block vertex into each face(24semisprings for a hexahedral element).The formation process of semi-edge is the same as that of semi-spring(24semi-edges for a hexahedral element).Based on the semi-springs and semi-edges,a new type of combined contact model is presented.According to this model,six contact types could be reduced to two,i.e.the semi-spring target face contact and semi-edge target edge contact.By the combined model,the contact force could be calculated directly(the information of contact type is not necessary),and the failure judgment could be executed in a straightforward way(each semi-spring and semi-edge own their characteristic areas).The algorithm has been successfully programmed in C++program.Some simple numerical cases are presented to show the validity and accuracy of this model.Finally,the failure mode,sliding distance and critical friction angle of Jiweishan landslide are studied with the combined model.
基金the partial financial support from the National Natural Science Foundation of China(21935003 and 21805182)National Key Research and Development Plan(2016YFB0901503)+1 种基金Shanghai Pujiang Program(18PJ1403800)the support from the Hundreds of Talents program of Sun Yat-sen University。
文摘Aqueous zinc ion batteries show prospects for next-generation renewable energy storage devices.However,the practical applications have been limited by the issues derived from Zn anode.As one of serious problems,Zn dendrite growth caused from the uncontrollable Zn deposition is unfavorable.Herein,with the aim to regulate Zn deposition,an artificial solid–electrolyte interface is subtly engineered with a perovskite type material,BaTiO3,which can be polarized,and its polarization could be switched under the external electric field.Resulting from the aligned dipole in BaTiO3 layer,zinc ions could move in order during cycling process.Regulated Zn migration at the anode/electrolyte interface contributes to the even Zn stripping/plating and confined Zn dendrite growth.As a result,the reversible Zn plating/stripping processes for over 2000 h have been achieved at 1 mA cm^(−2) with capacity of 1 mAh cm−2.Furthermore,this anode endowing the electric dipoles shows enhanced cycling stability for aqueous Zn-MnO2 batteries.The battery can deliver nearly 100%Coulombic efficiency at 2 Ag^(−1) after 300 cycles.
基金The National Key R&D Program of China under contract No.2017YFC0306003the National Natural Science Foundation of China under contract Nos 41506069,41876111 and 40706038
文摘A multi beam sonar survey is carried out in the continental slope of the Taixinan Basin to obtain submarine topographic and water column data. The data are processed to obtain water column images. Anomalous water column images, displaying plume characteristics, are found in gas hydrate enriched areas in the Taixinan Basin.This indicates the presence of natural gas resources in the Taixinan Basin. The multibeam sonar system is shown to provide an accurate and effective approach for detecting sub-sea gas hydrate.
基金supported by National Natural Science Foundation of China (Nos. 61571166, 11775063, and 51736003
文摘A hollow cathode is the electronic source and neutralizer of the Hall thruster and an ion thruster.When the orbit of an all-electric propulsion satellite changes from 100 km to 36 000 km, the backpressure changes by two to three orders of magnitude. In this paper, the influence of the backpressure on the discharge characteristics of the hollow cathode has been studied experimentally in the so-called diode configuration. With the increase in the backpressure, the anode voltage decreases gradually, and the amplitude of the current oscillation decreases significantly. Additionally, the plasma is relatively stable, the most probable ion energy and the width of the ion energy distribution reduces, and the electron distribution function inclines toward the Maxwell distribution under high backpressure. The analysis results show that the backpressure affects the gas ionization and the ionic acoustic turbulence, which also affects the discharge characteristics of the hollow cathode.
基金the partial financial support from the National Natural Science Foundation of China (22075171)。
文摘The hydrogen evolution reaction (HER) and dendrite growth associated with Zn anode have become the main bottlenecks for the further development of zinc ion batteries (ZIBs).In this work,the electrochemical activity of H_(3)O^(+) is inhibited by the supramolecular host–guest complex composed of H_(3)O^(+) as guest and 18-crown-6 as host.The even Zn plating is induced by the host–guest complex electrostatic shielding layer on Zn anode,as detected by in-situ optical microscopy.The lamellar Zn is plated which profits from the improved Zn plating behavior.Density functional theory (DFT) calculation presents the stable structure of complex.The less produced H_(2) content is monitored online by a mass spectrometer during Zn plating/stripping,which indicates HER can be hampered by the host–guest behavior.Thus,the ZIBs with long life and high Coulombic efficiency are achieved via introducing 18-crown-6.The proposed host–guest supramolecular interaction is expected to facilitate the furthermore development of Zn batteries.
基金Supported by the National Natural Science Foundation of China(No.31772849)the Scientific Research Funding Project of Liaoning Provincial Department of Education in 2019(No.DL201901)the Program for Liaoning Innovative Research Team in University(No.LT2019003)。
文摘Skin ulceration syndrome(SUS)is the main diseases aff ected the development of sea cucumber(Apostichopus japonicus)culture industries.To better observe the changes in the sea cucumber A.japonicus with SUS and understand the pathogenesis of the disease,activities of superoxide dismutase(SOD),catalase(CAT),and level of malondialdehyde(MDA)in coelomic fluid were detected using the Assay Kit and metabolites in the body wall were assessed using ultra-performance liquid chromatography and quadrupole-time of flight mass spectrometry.The results indicated that level of MDA was increased during SUS compared with healthy individuals(P<0.01),but activities of SOD and CAT were reduced(P<0.05).In metabolomics analysis,metabolites,such as adenosine,choline,betaine aldehyde,palmitic acid,and taurine,were found to be upregulated and 2-oxoadipic acid,anthranilic acid(vitamin L1),thioetheramide-PC,cholesterol-3-sulfate,and pentadecanoic acid were downregulated(VIP>1 and P<0.1).Pathway enrichment analysis indicated most enrichment of KEGG pathways were mainly related to energy metabolism,immunity,and osmoregulation such as ABC transporters,glycine,serine and threonine metabolism,tryptophan metabolism and neuroactive ligand-receptor interaction.Our study reflected the difference in enzyme activity and metabolites between A.japonicus with SUS and those without,which will provide reference data for investigating SUS.
