Based on the flow simulation in the condensing zone of compact spinning with lattice apron and a bead-elastic rod dynamic model of the flexible fiber,trajectories of fibers with different negative pressure are simulat...Based on the flow simulation in the condensing zone of compact spinning with lattice apron and a bead-elastic rod dynamic model of the flexible fiber,trajectories of fibers with different negative pressure are simulated by specially designed Matlab procedure.Then displacement components of fibers at YZ profile under different negative pressure conditions are extracted and compared.The results show that the fibers of different initial positions gradually converge,and are interlaced for position change in yarn cross-section,caused by the airflow in the condensing zone.Finally,compact-spun yarn with different negative pressure and conventional ring spun yarn are produced and their twists are tested.Both the results of simulation and experiments illustrate the existence of additional twists.Also the relationship between additional twists and negative pressure is verified.展开更多
Success of the revolution represents but only the first step in a long march. ---Mao Zedong Mao Zedong’s announcement in 1949 that "the Chinese people have stoodup," ended the dark decades of domestic fragm...Success of the revolution represents but only the first step in a long march. ---Mao Zedong Mao Zedong’s announcement in 1949 that "the Chinese people have stoodup," ended the dark decades of domestic fragmentation and foreign subjugation,展开更多
Compact spinning with pneumatic grooves is a spinning process to gather fibers by blended actions of airflow and mechanical forces.Modified from the ring spinning system,the lateral compact spinning with pneumatic gro...Compact spinning with pneumatic grooves is a spinning process to gather fibers by blended actions of airflow and mechanical forces.Modified from the ring spinning system,the lateral compact spinning with pneumatic grooves can improve yarn appearance and properties due to generated additional twists.In this study,we investigated additional twists of the lateral compact spinning with pneumatic grooves via a finite element(FE)method.An elastic thin rod was used to model a fiber to simulate its dynamic deformation in the three-dimensional space,and the space bar unit was used to simplify the fiber model for the dynamic analysis.The stiffness equation of the elastic rod element and the dynamic equation of the rigid body mass element were derived from the differential equation of the elastic thin rod.In the analysis of the nonlinear geometric displacement of the space elastic thin rod unit,the large deformation problem was solved with the stepwise loading successive approximation.The simulation results explained the mechanism of generating additional twists,and the experiment results proved the existence of additional twists.The study demonstrated that the FE model is effective for predicting additional twists of fiber bundles in the agglomeration zone,and for simulating the fiber motion in the compact spinning with pneumatic grooves.展开更多
As China's micro-drama industry booms,grueling schedules,lack of clear standards and weak protection of rights are putting those in the industry at serious risk.
Let S be a Riemann surface that contains one puncture x. Let be the collection of simple closed geodesics on S, and let denote the set of mapping classes on S isotopic to the identity on S U {x}. Denote by tc the ...Let S be a Riemann surface that contains one puncture x. Let be the collection of simple closed geodesics on S, and let denote the set of mapping classes on S isotopic to the identity on S U {x}. Denote by tc the positive Dehn twist about a curve c ∈ . In this paper, the author studies the products of forms （tb^-m o t^na） o f^k, where a, b ∈ and f ∈ . It is easy to see that if a = b or a, b are boundary components of an x-punctured cylinder on S, then one may find an element f ∈ such that the sequence （tb^-m o t^na） ofk contains infinitely many powers of Dehn twists. The author shows that the converse statement remains true, that is, if the sequence （tb^-m o t^na） o f^k contains infinitely many powers of Dehn twists, then a, b must be the boundary components of an x-punctured cylinder on S and f is a power of the spin map tb^-1 o ta.展开更多
In this paper, we establish a relationship between fractional Dehn twist coefficients of Riemann surface automorphisms and modular invariants of holomorphic families of algebraic curves. Specially, we give a character...In this paper, we establish a relationship between fractional Dehn twist coefficients of Riemann surface automorphisms and modular invariants of holomorphic families of algebraic curves. Specially, we give a characterization of pseudo-periodic maps with nontrivial fractional Dehn twist coefficients. We also obtain some uniform lower bounds of non-zero fractional Dehn twist coefficients.展开更多
When two layers of graphene are stacked with a twist angle of approximately 1.1°,strong interlayer coupling gives rise to a pair of flat bands in twisted bilayer graphene(TBG),resulting in pronounced electron–el...When two layers of graphene are stacked with a twist angle of approximately 1.1°,strong interlayer coupling gives rise to a pair of flat bands in twisted bilayer graphene(TBG),resulting in pronounced electron–electron interactions.At half filling of the flat bands,TBG exhibits correlated insulating states.Here,we investigate the electrical transport properties of heterostructures composed of TBG and the antiferromagnetic insulator chromium oxychloride(CrOCl),and propose a strategy to modulate the correlated insulating states in TBG.During the transition from a conventional phase to a strong interfacial coupling phase,kink-like features are observed in the charge neutrality point(CNP),correlated insulating state,and band insulating state.Under a perpendicular magnetic field,the system exhibits broadened quantum Hall plateaus in the strong interfacial coupling regime.Electrons localized in the CrOCl layer screen the bottom gate,rendering the carrier density in TBG less sensitive to variations in the bottom gate voltage.These phenomena are well captured by a charge-transfer model between TBG and CrOCl.Our results provide insights into the control of electronic correlations and topological states in graphene moirésystems via interfacial charge coupling.展开更多
In this paper,we prove the extreme values of L-functions at the central point for almost prime quadratic twists of an elliptic curve.As an application,we get the extreme values for the Tate-Shafarevich groups in the q...In this paper,we prove the extreme values of L-functions at the central point for almost prime quadratic twists of an elliptic curve.As an application,we get the extreme values for the Tate-Shafarevich groups in the quadratic twist family of an elliptic curve under the Birch and Swinnerton-Dyer conjecture.展开更多
Let S be a Riemann surface of analytically finite type （p, n） with 3p-3＋n 〉 0. Let a ∈ S and S = S - {a}. In this article, the author studies those pseudo-Anosov maps on S that are isotopic to the identity on S a...Let S be a Riemann surface of analytically finite type （p, n） with 3p-3＋n 〉 0. Let a ∈ S and S = S - {a}. In this article, the author studies those pseudo-Anosov maps on S that are isotopic to the identity on S and can be represented by products of Dehn twists. It is also proved that for any pseudo-Anosov map f of S isotopic to the identity on S, there are infinitely many pseudo-Anosov maps F on S - {b} = S - {a, b}, where b is a point on S, such that F is isotopic to f on S as b is filled in.展开更多
文摘Based on the flow simulation in the condensing zone of compact spinning with lattice apron and a bead-elastic rod dynamic model of the flexible fiber,trajectories of fibers with different negative pressure are simulated by specially designed Matlab procedure.Then displacement components of fibers at YZ profile under different negative pressure conditions are extracted and compared.The results show that the fibers of different initial positions gradually converge,and are interlaced for position change in yarn cross-section,caused by the airflow in the condensing zone.Finally,compact-spun yarn with different negative pressure and conventional ring spun yarn are produced and their twists are tested.Both the results of simulation and experiments illustrate the existence of additional twists.Also the relationship between additional twists and negative pressure is verified.
文摘Success of the revolution represents but only the first step in a long march. ---Mao Zedong Mao Zedong’s announcement in 1949 that "the Chinese people have stoodup," ended the dark decades of domestic fragmentation and foreign subjugation,
基金This work is supported in part by China Scholarship Council and National Key R&D Program of China(Grant No.2017YFB0309100).
文摘Compact spinning with pneumatic grooves is a spinning process to gather fibers by blended actions of airflow and mechanical forces.Modified from the ring spinning system,the lateral compact spinning with pneumatic grooves can improve yarn appearance and properties due to generated additional twists.In this study,we investigated additional twists of the lateral compact spinning with pneumatic grooves via a finite element(FE)method.An elastic thin rod was used to model a fiber to simulate its dynamic deformation in the three-dimensional space,and the space bar unit was used to simplify the fiber model for the dynamic analysis.The stiffness equation of the elastic rod element and the dynamic equation of the rigid body mass element were derived from the differential equation of the elastic thin rod.In the analysis of the nonlinear geometric displacement of the space elastic thin rod unit,the large deformation problem was solved with the stepwise loading successive approximation.The simulation results explained the mechanism of generating additional twists,and the experiment results proved the existence of additional twists.The study demonstrated that the FE model is effective for predicting additional twists of fiber bundles in the agglomeration zone,and for simulating the fiber motion in the compact spinning with pneumatic grooves.
文摘As China's micro-drama industry booms,grueling schedules,lack of clear standards and weak protection of rights are putting those in the industry at serious risk.
文摘Let S be a Riemann surface that contains one puncture x. Let be the collection of simple closed geodesics on S, and let denote the set of mapping classes on S isotopic to the identity on S U {x}. Denote by tc the positive Dehn twist about a curve c ∈ . In this paper, the author studies the products of forms （tb^-m o t^na） o f^k, where a, b ∈ and f ∈ . It is easy to see that if a = b or a, b are boundary components of an x-punctured cylinder on S, then one may find an element f ∈ such that the sequence （tb^-m o t^na） ofk contains infinitely many powers of Dehn twists. The author shows that the converse statement remains true, that is, if the sequence （tb^-m o t^na） o f^k contains infinitely many powers of Dehn twists, then a, b must be the boundary components of an x-punctured cylinder on S and f is a power of the spin map tb^-1 o ta.
基金supported by National Natural Science Foundation of China (Grant No. 11601504)Fundamental Research Funds of the Central Universities (Grant No. DUT18RC(4)065)。
文摘In this paper, we establish a relationship between fractional Dehn twist coefficients of Riemann surface automorphisms and modular invariants of holomorphic families of algebraic curves. Specially, we give a characterization of pseudo-periodic maps with nontrivial fractional Dehn twist coefficients. We also obtain some uniform lower bounds of non-zero fractional Dehn twist coefficients.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52225207 and 52350001)the Shanghai Pilot Program for Basic Research–Fudan University 21TQ1400100(Grant No.21TQ006)the Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)。
文摘When two layers of graphene are stacked with a twist angle of approximately 1.1°,strong interlayer coupling gives rise to a pair of flat bands in twisted bilayer graphene(TBG),resulting in pronounced electron–electron interactions.At half filling of the flat bands,TBG exhibits correlated insulating states.Here,we investigate the electrical transport properties of heterostructures composed of TBG and the antiferromagnetic insulator chromium oxychloride(CrOCl),and propose a strategy to modulate the correlated insulating states in TBG.During the transition from a conventional phase to a strong interfacial coupling phase,kink-like features are observed in the charge neutrality point(CNP),correlated insulating state,and band insulating state.Under a perpendicular magnetic field,the system exhibits broadened quantum Hall plateaus in the strong interfacial coupling regime.Electrons localized in the CrOCl layer screen the bottom gate,rendering the carrier density in TBG less sensitive to variations in the bottom gate voltage.These phenomena are well captured by a charge-transfer model between TBG and CrOCl.Our results provide insights into the control of electronic correlations and topological states in graphene moirésystems via interfacial charge coupling.
基金supported by the National Key R&D Program of China (Grant No. 2021YFA1000700)National Natural Science Foundation of China (Grant Nos. 12001314 and 12031008)。
文摘In this paper,we prove the extreme values of L-functions at the central point for almost prime quadratic twists of an elliptic curve.As an application,we get the extreme values for the Tate-Shafarevich groups in the quadratic twist family of an elliptic curve under the Birch and Swinnerton-Dyer conjecture.
文摘Let S be a Riemann surface of analytically finite type （p, n） with 3p-3＋n 〉 0. Let a ∈ S and S = S - {a}. In this article, the author studies those pseudo-Anosov maps on S that are isotopic to the identity on S and can be represented by products of Dehn twists. It is also proved that for any pseudo-Anosov map f of S isotopic to the identity on S, there are infinitely many pseudo-Anosov maps F on S - {b} = S - {a, b}, where b is a point on S, such that F is isotopic to f on S as b is filled in.
