Higher-order band topology not only enriches our understanding of topological phases but also unveils pioneering lower-dimensional boundary states,which harbors substantial potential for next-generation device applica...Higher-order band topology not only enriches our understanding of topological phases but also unveils pioneering lower-dimensional boundary states,which harbors substantial potential for next-generation device applications.The distinct electronic configurations and tunable attributes of two-dimensional materials position them as a quintessential platform for the realization of second-order topological insulators(SOTIs).This article provides an overview of the research progress in SOTIs within the field of two-dimensional electronic materials,focusing on the characterization of higher-order topological properties and the numerous candidate materials proposed in theoretical studies.These endeavors not only enhance our understanding of higher-order topological states but also highlight potential material systems that could be experimentally realized.展开更多
Silicon nitride photonics has emerged as a promising integrated optical platform due to its broad transparency window,low optical loss,and mature fabrication technology.However,the inherent centrosymmetric crystal str...Silicon nitride photonics has emerged as a promising integrated optical platform due to its broad transparency window,low optical loss,and mature fabrication technology.However,the inherent centrosymmetric crystal structure of silicon nitride fundamentally restricts its applications in second-order nonlinear optical processes.Monolayer transition metal dichalcogenides,particularly tungsten disulfide(WS_(2)),exhibit strong second-order nonlinear responses,making them ideal candidates for nonlinear photonic applications.Herein,we demonstrate a heterogeneously integrated platform combining silicon nitride waveguides with chemical vapor deposition(CVD)-grown monolayer WS_(2),enabling second harmonic generation.A specially designed silica cladding featuring gentle-slope profile on silicon nitride strip waveguides facilitates the integration of centimeter-scale WS_(2)film with photonic circuits.This approach provides a robust solution for incorporating second-order nonlinearity into silicon nitride photonic systems.The demonstrated platform holds significant potential for advancing quantum networks,visible-light lasers,and integrated optical modulation/detection systems.展开更多
根据美国Second Life Library 2.0虚拟社区的建设现状,分析图书馆虚拟社区的营销模式,认为虚拟社区改变了用户被动服务的地位,获得了主动权。对此,图书馆需采用聚众为媒的策略,为虚拟社区中的用户营造良好的使用体验,引导用户成为创建...根据美国Second Life Library 2.0虚拟社区的建设现状,分析图书馆虚拟社区的营销模式,认为虚拟社区改变了用户被动服务的地位,获得了主动权。对此,图书馆需采用聚众为媒的策略,为虚拟社区中的用户营造良好的使用体验,引导用户成为创建服务的合作者和品牌传播的中间人。展开更多
（R）-2-Chloro-l-（m-chlorophenyl）ethanol,a precursor of（R）-3-chlorostyrene oxide which is the key chiral intermediate for the preparation of severalβ3-adrenergic receptor agonists was prepared in 40%yield and 99%...（R）-2-Chloro-l-（m-chlorophenyl）ethanol,a precursor of（R）-3-chlorostyrene oxide which is the key chiral intermediate for the preparation of severalβ3-adrenergic receptor agonists was prepared in 40%yield and 99%ee by the Lipozyme TL IM-catalyzed second resolution of the corresponding racemate in the presence of vinyl acetate.展开更多
Silica glasses doped with Bi2S3 microcystallite was prepared by the sol-gel process. Photoinduced second harmonic generation (SHG) was observed in the glass when it was irradiated with intense 1.06 mum and frequency d...Silica glasses doped with Bi2S3 microcystallite was prepared by the sol-gel process. Photoinduced second harmonic generation (SHG) was observed in the glass when it was irradiated with intense 1.06 mum and frequency doubled laser beams from a mode-locked Nd: YAG laser. It was found that the signal intensity increased with the irradiating time and approached a saturation gradually. The effect may be explained reasonably by the DC field model.展开更多
We introduce the higher-order type 2 Bernoulli numbers and polynomials of the second kind.In this paper,we investigate some identities and properties for them in connection with central factorial numbers of the second...We introduce the higher-order type 2 Bernoulli numbers and polynomials of the second kind.In this paper,we investigate some identities and properties for them in connection with central factorial numbers of the second kind and the higher-order type 2 Bernoulli polynomials.We give some relations between the higher-order type 2 Bernoulli numbers of the second kind and their conjugates.展开更多
Nitrogen-doped carbon loaded single-atom catalysts(SACs)are promising candidates for electrocatalytic conversion of CO_(2)into high-valuable chemicals,and the modification of catalysts by heteroatom-doping strategy is...Nitrogen-doped carbon loaded single-atom catalysts(SACs)are promising candidates for electrocatalytic conversion of CO_(2)into high-valuable chemicals,and the modification of catalysts by heteroatom-doping strategy is an effective approach to enhance the CO_(2)reduction performance.However,the large difference exists in atomic radius between nitrogen atoms and the doped heteroatoms may lead to the poor stability of active sites.In this study,we have synthesized a Ni single atom catalyst with S doping at the secondshell on the ultrathin carbon nanosheets support(Ni-N_(4)-SC)by solid-phase pyrolysis.The S atom in the second-shell contributes to the higher efficiency of CO_(2)conversion at lower potentials while the Ni-N_(4)-SC can be more stable.The experimental results and theoretical calculations indicate that the S atom in second-shell breaks the uniform charge distribution and reduces the free energy of hydrogenation,which can increase the adsorption of CO_(2),accelerate charge transfer,and reduce the reaction energy barrier.This work reveals the close relationship between the second-shell and the electrocatalytic activity of single atom sites,which also provides a new perspective to design efficient single atom catalysts.展开更多
A key issue of practical importance in the two-dimensional (2-D) discrete system is stability analysis. Linear state-space models describing 2-D discrete systems have been proposed by several researchers. A popular mo...A key issue of practical importance in the two-dimensional (2-D) discrete system is stability analysis. Linear state-space models describing 2-D discrete systems have been proposed by several researchers. A popular model, called Forna- sini-Marchesini (FM) second model was proposed by Fornasini and Marchesini in 1978. The aim of this paper is to present a survey of the existing literature on the stability of FM second model.展开更多
With the pulsed laser deposition （PLD） method, amorphous 80GeS2-15Ga2S3-5CdS chalcogenide film was deposited on glassy substrate. Obvious second harmonic generation （SHG） was observed in the ultraviolet （UV）-pol...With the pulsed laser deposition （PLD） method, amorphous 80GeS2-15Ga2S3-5CdS chalcogenide film was deposited on glassy substrate. Obvious second harmonic generation （SHG） was observed in the ultraviolet （UV）-polarized film and the SHG intensity increased with the increase in single pulse energy and irradiation time. Through Raman spectra and transmission spectra, the mechanism of SHG was studied. The experimental results demonstrated that effective electron traps and hole traps were generated in the UV- polarized film. The energy of electrons and holes was using up due to the collision with other particles and crystal fields during their movement and finally they were captured by the traps and fixed, which made the electric charge distribution nonuniform in the film and destroyed the spatial isotropy. In the meantime, the center of positive and negative charges separated and a built-in electric field was formed which generated the optical second-order nonlinearity of the film.展开更多
The 2nd International Symposium on Refrac-toties jointly organized by the Chinese Ceramic So-ciety and the Chinese Society for Metals was heldin Beijing, China, On October 30-Novemeber 2,1992. The Technical Associatio...The 2nd International Symposium on Refrac-toties jointly organized by the Chinese Ceramic So-ciety and the Chinese Society for Metals was heldin Beijing, China, On October 30-Novemeber 2,1992. The Technical Association of Refractories,Japan, the American Ceramic Society, the Refrac-tories Association of Great Britain, the GermanRefractories Association, the Australian Ceramic展开更多
Effects of addition of H2 gas in air DB discharge on its optical and electrical characteristics have been studied. Optical emission spectroscopy is used to investigate the effect of hydrogen admixing on the emission i...Effects of addition of H2 gas in air DB discharge on its optical and electrical characteristics have been studied. Optical emission spectroscopy is used to investigate the effect of hydrogen admixing on the emission intensity of the nitrogen second positive systems (300 - 420 nm) and the relative population density of states. An obvious decaying of the emission intensity of the nitrogen second positive bands with the introduction of H2 has been observed. It has been concluded that quenching of the nitrogen excited state is the responsible reason of this decaying. Mechanisms of excitation and ionization processes of nitrogen molecules in this mixture have been studied. Processes which are responsible for the decaying of the population density of have been reported. Addition of H2 to air improves the electrical characteristics of the DB discharge. An abrupt increasing in the electron density, reached about thirty fold at H2 flow rate of 3 L/min, as a result of increasing the ionization processes has been reported. The breakdown voltage of the discharge decreased from 1.87 kV to about 1.25 kV by the addition of H2 at flow rate of 3 L/min.展开更多
Sufficient conditions for the existence and uniqueness of second boundary value problems of two kinds of even order nonlinear differential equations are obtained. The proofs are based on the lemma on bilinear form, de...Sufficient conditions for the existence and uniqueness of second boundary value problems of two kinds of even order nonlinear differential equations are obtained. The proofs are based on the lemma on bilinear form, developed by A.C.Lazer, Schauder fixed point theorem and the Leray-Schauder degree theory, respectively.展开更多
In order to promote the activeness and initiative of learners and allow them to take theirlearning advantages,a teacher should be fully aware of the psychological process and models ofL2L．For no matter how well learn...In order to promote the activeness and initiative of learners and allow them to take theirlearning advantages,a teacher should be fully aware of the psychological process and models ofL2L．For no matter how well learners can command a language,their subjective incentives play adecisive role,that is the case particularly for non—Eniglish majors,who are always exposed tocrowded,serious and teacher—centred learning contexts.展开更多
目的:探讨自由体位结合“2+1”分娩陪伴对初产妇第二产程、分娩疼痛及母婴结局等分娩结局的影响。方法:回顾性分析2021年3月至2024年6月于我院分娩的150例初产妇一般资料,将采用自由体位完成分娩者纳入对照组(n=87),将自由体位结合“2+...目的:探讨自由体位结合“2+1”分娩陪伴对初产妇第二产程、分娩疼痛及母婴结局等分娩结局的影响。方法:回顾性分析2021年3月至2024年6月于我院分娩的150例初产妇一般资料,将采用自由体位完成分娩者纳入对照组(n=87),将自由体位结合“2+1”分娩陪伴完成分娩者纳入观察组(n=63),记录不同分娩方式对产妇第二产程、分娩疼痛及母婴结局的影响。结果:观察组第一、第二产程时间及产时出血量均低于对照组(P<0.05),两组第三产程比较,差异无统计学意义(P>0.05);观察组不同产程现时疼痛强度(PPI)、疼痛评级指数(PRI)、视觉模拟评分(VAS)较对照组更低(P<0.05);观察组软产道裂伤情况与对照组比较,差异无统计学意义(P>0.05);观察组1 min Apgar评分显著高于对照组,新生儿并发症发生率更低(P<0.05)。结论:自由体位结合“2+1”分娩陪伴显著缩短初产妇的产程时间,降低分娩疼痛,并有助于提高母婴结局的质量,显示出优于传统自由体位分娩的效果。展开更多
基金supported by the National Natu-ral Science Foundation of China(Grants No.12174220 and No.12074217)the Shandong Provincial Science Foundation for Excellent Young Scholars(Grant No.ZR2023YQ001)+1 种基金the Taishan Young Scholar Program of Shandong Provincethe Qilu Young Scholar Pro-gram of Shandong University.
文摘Higher-order band topology not only enriches our understanding of topological phases but also unveils pioneering lower-dimensional boundary states,which harbors substantial potential for next-generation device applications.The distinct electronic configurations and tunable attributes of two-dimensional materials position them as a quintessential platform for the realization of second-order topological insulators(SOTIs).This article provides an overview of the research progress in SOTIs within the field of two-dimensional electronic materials,focusing on the characterization of higher-order topological properties and the numerous candidate materials proposed in theoretical studies.These endeavors not only enhance our understanding of higher-order topological states but also highlight potential material systems that could be experimentally realized.
基金Project supported by the National Innovative Training Program for College Students of China(Grant No.2023069)the University Research and Innovation Project of the National University of Defense Technology。
文摘Silicon nitride photonics has emerged as a promising integrated optical platform due to its broad transparency window,low optical loss,and mature fabrication technology.However,the inherent centrosymmetric crystal structure of silicon nitride fundamentally restricts its applications in second-order nonlinear optical processes.Monolayer transition metal dichalcogenides,particularly tungsten disulfide(WS_(2)),exhibit strong second-order nonlinear responses,making them ideal candidates for nonlinear photonic applications.Herein,we demonstrate a heterogeneously integrated platform combining silicon nitride waveguides with chemical vapor deposition(CVD)-grown monolayer WS_(2),enabling second harmonic generation.A specially designed silica cladding featuring gentle-slope profile on silicon nitride strip waveguides facilitates the integration of centimeter-scale WS_(2)film with photonic circuits.This approach provides a robust solution for incorporating second-order nonlinearity into silicon nitride photonic systems.The demonstrated platform holds significant potential for advancing quantum networks,visible-light lasers,and integrated optical modulation/detection systems.
基金support from the National Natural Science Foundation of China(No20672110)
文摘（R）-2-Chloro-l-（m-chlorophenyl）ethanol,a precursor of（R）-3-chlorostyrene oxide which is the key chiral intermediate for the preparation of severalβ3-adrenergic receptor agonists was prepared in 40%yield and 99%ee by the Lipozyme TL IM-catalyzed second resolution of the corresponding racemate in the presence of vinyl acetate.
文摘Silica glasses doped with Bi2S3 microcystallite was prepared by the sol-gel process. Photoinduced second harmonic generation (SHG) was observed in the glass when it was irradiated with intense 1.06 mum and frequency doubled laser beams from a mode-locked Nd: YAG laser. It was found that the signal intensity increased with the irradiating time and approached a saturation gradually. The effect may be explained reasonably by the DC field model.
基金This work was supported by the National Research Foundation of Korea(NRF)Grant Funded by the Korea Government(No.2020R1F1A1A01071564).
文摘We introduce the higher-order type 2 Bernoulli numbers and polynomials of the second kind.In this paper,we investigate some identities and properties for them in connection with central factorial numbers of the second kind and the higher-order type 2 Bernoulli polynomials.We give some relations between the higher-order type 2 Bernoulli numbers of the second kind and their conjugates.
基金financial support of the National Natural Science Foundation of China(Nos.52100186,52170082,51938007 and 52063024)the Jiangxi Provincial Natural Science Foundation(Nos.20225BCJ23003 and 20212ACB203008)。
文摘Nitrogen-doped carbon loaded single-atom catalysts(SACs)are promising candidates for electrocatalytic conversion of CO_(2)into high-valuable chemicals,and the modification of catalysts by heteroatom-doping strategy is an effective approach to enhance the CO_(2)reduction performance.However,the large difference exists in atomic radius between nitrogen atoms and the doped heteroatoms may lead to the poor stability of active sites.In this study,we have synthesized a Ni single atom catalyst with S doping at the secondshell on the ultrathin carbon nanosheets support(Ni-N_(4)-SC)by solid-phase pyrolysis.The S atom in the second-shell contributes to the higher efficiency of CO_(2)conversion at lower potentials while the Ni-N_(4)-SC can be more stable.The experimental results and theoretical calculations indicate that the S atom in second-shell breaks the uniform charge distribution and reduces the free energy of hydrogenation,which can increase the adsorption of CO_(2),accelerate charge transfer,and reduce the reaction energy barrier.This work reveals the close relationship between the second-shell and the electrocatalytic activity of single atom sites,which also provides a new perspective to design efficient single atom catalysts.
文摘A key issue of practical importance in the two-dimensional (2-D) discrete system is stability analysis. Linear state-space models describing 2-D discrete systems have been proposed by several researchers. A popular model, called Forna- sini-Marchesini (FM) second model was proposed by Fornasini and Marchesini in 1978. The aim of this paper is to present a survey of the existing literature on the stability of FM second model.
基金Funded by the National Natural Science Foundaition of China(Nos.51172169 and 61177084),NCET\(NCET-11-0687)the Fundamental Research Funds for the Central Universities(Wuhan University of Technology)
文摘With the pulsed laser deposition （PLD） method, amorphous 80GeS2-15Ga2S3-5CdS chalcogenide film was deposited on glassy substrate. Obvious second harmonic generation （SHG） was observed in the ultraviolet （UV）-polarized film and the SHG intensity increased with the increase in single pulse energy and irradiation time. Through Raman spectra and transmission spectra, the mechanism of SHG was studied. The experimental results demonstrated that effective electron traps and hole traps were generated in the UV- polarized film. The energy of electrons and holes was using up due to the collision with other particles and crystal fields during their movement and finally they were captured by the traps and fixed, which made the electric charge distribution nonuniform in the film and destroyed the spatial isotropy. In the meantime, the center of positive and negative charges separated and a built-in electric field was formed which generated the optical second-order nonlinearity of the film.
文摘The 2nd International Symposium on Refrac-toties jointly organized by the Chinese Ceramic So-ciety and the Chinese Society for Metals was heldin Beijing, China, On October 30-Novemeber 2,1992. The Technical Association of Refractories,Japan, the American Ceramic Society, the Refrac-tories Association of Great Britain, the GermanRefractories Association, the Australian Ceramic
文摘Effects of addition of H2 gas in air DB discharge on its optical and electrical characteristics have been studied. Optical emission spectroscopy is used to investigate the effect of hydrogen admixing on the emission intensity of the nitrogen second positive systems (300 - 420 nm) and the relative population density of states. An obvious decaying of the emission intensity of the nitrogen second positive bands with the introduction of H2 has been observed. It has been concluded that quenching of the nitrogen excited state is the responsible reason of this decaying. Mechanisms of excitation and ionization processes of nitrogen molecules in this mixture have been studied. Processes which are responsible for the decaying of the population density of have been reported. Addition of H2 to air improves the electrical characteristics of the DB discharge. An abrupt increasing in the electron density, reached about thirty fold at H2 flow rate of 3 L/min, as a result of increasing the ionization processes has been reported. The breakdown voltage of the discharge decreased from 1.87 kV to about 1.25 kV by the addition of H2 at flow rate of 3 L/min.
文摘Sufficient conditions for the existence and uniqueness of second boundary value problems of two kinds of even order nonlinear differential equations are obtained. The proofs are based on the lemma on bilinear form, developed by A.C.Lazer, Schauder fixed point theorem and the Leray-Schauder degree theory, respectively.
文摘In order to promote the activeness and initiative of learners and allow them to take theirlearning advantages,a teacher should be fully aware of the psychological process and models ofL2L．For no matter how well learners can command a language,their subjective incentives play adecisive role,that is the case particularly for non—Eniglish majors,who are always exposed tocrowded,serious and teacher—centred learning contexts.
文摘目的:探讨自由体位结合“2+1”分娩陪伴对初产妇第二产程、分娩疼痛及母婴结局等分娩结局的影响。方法:回顾性分析2021年3月至2024年6月于我院分娩的150例初产妇一般资料,将采用自由体位完成分娩者纳入对照组(n=87),将自由体位结合“2+1”分娩陪伴完成分娩者纳入观察组(n=63),记录不同分娩方式对产妇第二产程、分娩疼痛及母婴结局的影响。结果:观察组第一、第二产程时间及产时出血量均低于对照组(P<0.05),两组第三产程比较,差异无统计学意义(P>0.05);观察组不同产程现时疼痛强度(PPI)、疼痛评级指数(PRI)、视觉模拟评分(VAS)较对照组更低(P<0.05);观察组软产道裂伤情况与对照组比较,差异无统计学意义(P>0.05);观察组1 min Apgar评分显著高于对照组,新生儿并发症发生率更低(P<0.05)。结论:自由体位结合“2+1”分娩陪伴显著缩短初产妇的产程时间,降低分娩疼痛,并有助于提高母婴结局的质量,显示出优于传统自由体位分娩的效果。
