日前,瑞士高级珠宝商de GRISOGONO帝致稀世奇珍——e Art of de GRISOGONO Creation I项链在日内瓦佳士得＂瑰丽珠宝拍卖＂中,以33,500,000瑞士法郎（33701000美元）成交,创造了拍卖史上D色无瑕钻石的拍卖新纪录。在拍卖前,《芭莎珠宝...日前,瑞士高级珠宝商de GRISOGONO帝致稀世奇珍——e Art of de GRISOGONO Creation I项链在日内瓦佳士得＂瑰丽珠宝拍卖＂中,以33,500,000瑞士法郎（33701000美元）成交,创造了拍卖史上D色无瑕钻石的拍卖新纪录。在拍卖前,《芭莎珠宝》受邀亲临香港佳士得巡展现场,见到这件传说中的稀世珍宝。1993年,de GRISOGONO帝致品牌于瑞士日内瓦创立,严守卓越工艺、技术革新及前卫创意的宗旨。明年品牌即将迎来25周年,展开更多
In the process of shield tunneling through soft soil layers,the presence of confined water ahead poses a significant threat to the stability of the tunnel face.Therefore,it is crucial to consider the impact of confine...In the process of shield tunneling through soft soil layers,the presence of confined water ahead poses a significant threat to the stability of the tunnel face.Therefore,it is crucial to consider the impact of confined water on the limit support pressure of the tunnel face.This study employed the finite element method(FEM)to analyze the limit support pressure of shield tunnel face instability within a pressurized water-containing layer.Subsequently,a multiple linear regression approach was applied to derive a concise solution formula for the limit support pressure,incorporating various influencing factors.The analysis yields the following conclusions:1)The influence of confined water on the instability mode of the tunnel face in soft soil layers makes the displacement response of the strata not significant when the face is unstable;2)The limit support pressure increases approximately linearly with the pressure head,shield tunnel diameter,and tunnel burial depth.And inversely proportional to the thickness of the impermeable layer,soil cohesion and internal friction angle;3)Through an engineering case study analysis,the results align well with those obtained from traditional theoretical methods,thereby validating the rationality of the equations proposed in this paper.Furthermore,the proposed equations overcome the limitation of traditional theoretical approaches considering the influence of changes in impermeable layer thickness.It can accurately depict the dynamic variation in the required limit support pressure to maintain the stability of the tunnel face during shield tunneling,thus better reflecting engineering reality.展开更多
An electromagnetic field is generated through the accelerating movement of two equal but opposite charges of a single dipole. An electromagnetic field can also be generated by a time-varying infinitesimal point charge...An electromagnetic field is generated through the accelerating movement of two equal but opposite charges of a single dipole. An electromagnetic field can also be generated by a time-varying infinitesimal point charge. In this study, a comparison between the electromagnetic fields of an infinitesimal point charge and a dipole has been presented. First, the time-domain potential function of a point source in a 3D conductive medium is derived. Then the electric and magnetic fields in a 3D homogeneous lossless space are derived via the relation between the potential and field. The field differences between the infinitesimal point charge and the dipole in the step-off time, far-source, and near-source zones are analyzed, and the accuracy of the solutions from these sources is investigated. It is also shown that the field of the infinitesimal point charge in the near-source zone is different from that of the dipole, whereas the far-source zone fields of these two sources are identical. The comparison of real and simulated data shows that the infinitesimal point charge represents the real source better than the divole source.展开更多
Aim To analyze the transient speciality of nonlinear, anisotropic, AC+DC coupling electric field, and to compare the withstand voltage strength of different insulation structures. Methods The transient process o...Aim To analyze the transient speciality of nonlinear, anisotropic, AC+DC coupling electric field, and to compare the withstand voltage strength of different insulation structures. Methods The transient process of polarity reversal is analyzed, considering the anisotropic property of oil immersed press board, a new finite element model based on Galerkin method is presented and verified. The model developed is applied to calculate the electric field distribution in four typical winding end structures of the converter transformer. Results\ The whole ring structure possesses the best insulation characteristics. Conclusion\ By introducing reasonable insulation components, insulation strength with the same surrounding sizes can be improved more than 30%.展开更多
The influence of Ga and In on the electrochemical properties of Mg anode materials were investigated by the polarization and galvanostatic curve tests. The microstructure and the corroded surface of the Mg-In-Ga alloy...The influence of Ga and In on the electrochemical properties of Mg anode materials were investigated by the polarization and galvanostatic curve tests. The microstructure and the corroded surface of the Mg-In-Ga alloys were observed by scanning electron microscopy （SEM）. The corrosion product of the Mg-0.8%In （mass fraction） and Mg-0.8%Ga-0.3%In alloy were determined by X-ray diffraction. The results show that no second phase exists in the Mg-xIn （x=0-0.8%） allloys. Intergranular compounds containing Ga and In elements occur in the Mg-0.8%In-xGa （x=0-0.8%） alloys. The addition of In into Mg as well as the addition of 0.05%-0.5%Ga into Mg-In alloy promotes the corrosion resistance. The addition of Ga into Mg-In alloys also promotes the electrochemical activity. The Mg-0.8%In-0.8%Ga alloy has the most negative mean potential,-1.682 V, which is more negative than -1.406 V in AZ91D. The corrosion type of the Mg-In-Ga alloys is general corrosion and the corrosion product is Mg（OH）2.展开更多
A novel neuMOS source follower circuit is presented.The cell can complete the s ource follower function even if the input voltage is lower than the threshold of the source follower,thus high-precision operation of th...A novel neuMOS source follower circuit is presented.The cell can complete the s ource follower function even if the input voltage is lower than the threshold of the source follower,thus high-precision operation of the circuit is achieved. The simulation and the measurement results show that its precision is higher tha n that of other neuMOS source follower circuits.展开更多
文摘日前,瑞士高级珠宝商de GRISOGONO帝致稀世奇珍——e Art of de GRISOGONO Creation I项链在日内瓦佳士得＂瑰丽珠宝拍卖＂中,以33,500,000瑞士法郎（33701000美元）成交,创造了拍卖史上D色无瑕钻石的拍卖新纪录。在拍卖前,《芭莎珠宝》受邀亲临香港佳士得巡展现场,见到这件传说中的稀世珍宝。1993年,de GRISOGONO帝致品牌于瑞士日内瓦创立,严守卓越工艺、技术革新及前卫创意的宗旨。明年品牌即将迎来25周年,
基金Project(ZDRW-ZS-2021-3)supported by the Key Deployment Projects of Chinese Academy of SciencesProjects(52179116,51991392)supported by the National Natural Science Foundation of China。
文摘In the process of shield tunneling through soft soil layers,the presence of confined water ahead poses a significant threat to the stability of the tunnel face.Therefore,it is crucial to consider the impact of confined water on the limit support pressure of the tunnel face.This study employed the finite element method(FEM)to analyze the limit support pressure of shield tunnel face instability within a pressurized water-containing layer.Subsequently,a multiple linear regression approach was applied to derive a concise solution formula for the limit support pressure,incorporating various influencing factors.The analysis yields the following conclusions:1)The influence of confined water on the instability mode of the tunnel face in soft soil layers makes the displacement response of the strata not significant when the face is unstable;2)The limit support pressure increases approximately linearly with the pressure head,shield tunnel diameter,and tunnel burial depth.And inversely proportional to the thickness of the impermeable layer,soil cohesion and internal friction angle;3)Through an engineering case study analysis,the results align well with those obtained from traditional theoretical methods,thereby validating the rationality of the equations proposed in this paper.Furthermore,the proposed equations overcome the limitation of traditional theoretical approaches considering the influence of changes in impermeable layer thickness.It can accurately depict the dynamic variation in the required limit support pressure to maintain the stability of the tunnel face during shield tunneling,thus better reflecting engineering reality.
基金supported by Chinese National Programs for Fundamental Research and Development(No.2012CB416605)the National Natural Science Foundation of China(No.41174090)Development Project of National Key Scientific Equipment(No.ZDYZ2012-1-05-04)
文摘An electromagnetic field is generated through the accelerating movement of two equal but opposite charges of a single dipole. An electromagnetic field can also be generated by a time-varying infinitesimal point charge. In this study, a comparison between the electromagnetic fields of an infinitesimal point charge and a dipole has been presented. First, the time-domain potential function of a point source in a 3D conductive medium is derived. Then the electric and magnetic fields in a 3D homogeneous lossless space are derived via the relation between the potential and field. The field differences between the infinitesimal point charge and the dipole in the step-off time, far-source, and near-source zones are analyzed, and the accuracy of the solutions from these sources is investigated. It is also shown that the field of the infinitesimal point charge in the near-source zone is different from that of the dipole, whereas the far-source zone fields of these two sources are identical. The comparison of real and simulated data shows that the infinitesimal point charge represents the real source better than the divole source.
文摘Aim To analyze the transient speciality of nonlinear, anisotropic, AC+DC coupling electric field, and to compare the withstand voltage strength of different insulation structures. Methods The transient process of polarity reversal is analyzed, considering the anisotropic property of oil immersed press board, a new finite element model based on Galerkin method is presented and verified. The model developed is applied to calculate the electric field distribution in four typical winding end structures of the converter transformer. Results\ The whole ring structure possesses the best insulation characteristics. Conclusion\ By introducing reasonable insulation components, insulation strength with the same surrounding sizes can be improved more than 30%.
基金Project(20110162120051)supported by Specialized Research Fund for the Doctor Program of Higher Education,ChinaProject(51101171)supported by the National Natural Science Foundation of China
文摘The influence of Ga and In on the electrochemical properties of Mg anode materials were investigated by the polarization and galvanostatic curve tests. The microstructure and the corroded surface of the Mg-In-Ga alloys were observed by scanning electron microscopy （SEM）. The corrosion product of the Mg-0.8%In （mass fraction） and Mg-0.8%Ga-0.3%In alloy were determined by X-ray diffraction. The results show that no second phase exists in the Mg-xIn （x=0-0.8%） allloys. Intergranular compounds containing Ga and In elements occur in the Mg-0.8%In-xGa （x=0-0.8%） alloys. The addition of In into Mg as well as the addition of 0.05%-0.5%Ga into Mg-In alloy promotes the corrosion resistance. The addition of Ga into Mg-In alloys also promotes the electrochemical activity. The Mg-0.8%In-0.8%Ga alloy has the most negative mean potential,-1.682 V, which is more negative than -1.406 V in AZ91D. The corrosion type of the Mg-In-Ga alloys is general corrosion and the corrosion product is Mg（OH）2.
文摘A novel neuMOS source follower circuit is presented.The cell can complete the s ource follower function even if the input voltage is lower than the threshold of the source follower,thus high-precision operation of the circuit is achieved. The simulation and the measurement results show that its precision is higher tha n that of other neuMOS source follower circuits.
