In this note, we provide an effective proof of the fundamental structure theorem of finitely generated modules over a principal ideal domain, from which we find the minimality of decomposition for a finitely generated...In this note, we provide an effective proof of the fundamental structure theorem of finitely generated modules over a principal ideal domain, from which we find the minimality of decomposition for a finitely generated module over a principal ideal domain.展开更多
Let Fbe a locally defined formation consisting of locally soluble groups, G a hyper-(cyclic or finite) locally soluble group and A a noetherian ZG-module with all irreducible ZG-factors being finite, G∈F, f(∞)f(p), ...Let Fbe a locally defined formation consisting of locally soluble groups, G a hyper-(cyclic or finite) locally soluble group and A a noetherian ZG-module with all irreducible ZG-factors being finite, G∈F, f(∞)f(p), f(p)≠ for each p∈π. The following conclutions are obtained: (1) if there exists a maximal submodule B of A such that A/B is F-central in G and B has no nonzero F-central ZG-factors, then A has an F-decomposition; (2) if there exists an irreducible F-central submodule B of A such that all ZG-composition factors of A/B are F-ecentric, then A has an F-decomposition.展开更多
Let (?) be a formation locally defined by f(P), G ∈ (?) and A a ZG-module, where p ∈ π = { all primes and symbol ∞}. Then a p-main-factor U/V of G is said to be (?)-central in G if G/CG(U/V) ∈f(p). In this paper,...Let (?) be a formation locally defined by f(P), G ∈ (?) and A a ZG-module, where p ∈ π = { all primes and symbol ∞}. Then a p-main-factor U/V of G is said to be (?)-central in G if G/CG(U/V) ∈f(p). In this paper, we have proved that: let (?) be a locally defined formation consisting of locally soluble groups, G a hyper-(cyclic or finite) locally soluble group and A an artinian ZG-module with all irreducible ZG-factors of A being finite; if G ∈ (?), f(∞) ≡ f(p) . f(p)≠φ for each p ∈ π, A has an (?)-decomposition.展开更多
With the aid of commercial finite element analysis software package ANSYS,investigations are made on the contributions of main components to stiffness of the main module for parallel machine tools,and it is found that...With the aid of commercial finite element analysis software package ANSYS,investigations are made on the contributions of main components to stiffness of the main module for parallel machine tools,and it is found that the frame is the main contributor.Then,influences of constraints,strut length and working ways of the main module have also been investigated.It can be concluded that when one of the main planes of the frame without linear drive unit is constrained,the largest whole stiffness can be acquired.And,the stiffness is much better when the main module is used in a vertical machine tool instead of a horizontal one.Finally,the principle of stiffness variation is summarized when the mobile platform reaches various positions within its working space and when various loads are applied.These achievements have provided critical instructions for the design of the main module for parallel machine tools.展开更多
In this paper, we prove that the Toeplitz operator with finite Blaschke product symbol Sψ(z) on Nφ has at least m non-trivial minimal reducing subspaces, where m is the dimension of H^2(Гω)⊙φ(ω)H^2(Гω...In this paper, we prove that the Toeplitz operator with finite Blaschke product symbol Sψ(z) on Nφ has at least m non-trivial minimal reducing subspaces, where m is the dimension of H^2(Гω)⊙φ(ω)H^2(Гω). Moreover, the restriction of Sψ(z) on any of these minimal reducing subspaces is unitary equivalent to the Bergman shift Mz.展开更多
For a ring A, an extension ring B, a fixed right A-module M, the endomorphism ring D formed by M, the endomorphism ring E formed by , and the endomorphism ring F formed by HomA (B,M), we present equivalences and duali...For a ring A, an extension ring B, a fixed right A-module M, the endomorphism ring D formed by M, the endomorphism ring E formed by , and the endomorphism ring F formed by HomA (B,M), we present equivalences and dualities between subcategories of B-modules which are finitely cogenerated injective as A-modules and E-modules and F-modules which are finitely generated projective as D-modules.展开更多
Let G be a hyper finite locally solvable group, A a minimax ZG-medule, a locally defined formation consisting of locally solvable groups, A has no nonzero infinite irreducible ZG-factors, and G ∈ . The following resu...Let G be a hyper finite locally solvable group, A a minimax ZG-medule, a locally defined formation consisting of locally solvable groups, A has no nonzero infinite irreducible ZG-factors, and G ∈ . The following results are proved: if A has a maximal submodule B such that A/B is , central in G and B has no nonzero central ZG-factors, then A has an decomposition; ifA has an irreducible central submodule B such that all ZG-composition factors of A/B are o^eccentric, then A has an decomposition.展开更多
In order to achieve a modulator with broad bandwidth and perfect impedance match,a novel electro-optical modulator based on GeO2-doped silica waveguides on silicon substrate is designed.The finite element model of the...In order to achieve a modulator with broad bandwidth and perfect impedance match,a novel electro-optical modulator based on GeO2-doped silica waveguides on silicon substrate is designed.The finite element model of the whole electro-optical modulator is established by means of ANSYS.With the finite element method analysis,the performance of the novel modulator is predicted.The simulation reveals that the designed modulator operates with a product of 3 dB optical bandwidth and modulating length of 226.59 GHz·cm,and a characteristic impedance of 51.6 Ω at 1 550 nm wavelength.Moreover,the calculated electrical reflected power of coplanar waveguide electrode is below-20 dB in the frequency ranging from 45 MHz to 65 GHz.Therefore,the designed modulator has wide modulation bandwidth and perfect impedance match.展开更多
A wideband dipole signal is required for dipole dispersion correction and nearborehole imaging. To obtain the broadband flexural wave dispersion, we use a nonlinear frequency modulation (NLFM) signal and propose a s...A wideband dipole signal is required for dipole dispersion correction and nearborehole imaging. To obtain the broadband flexural wave dispersion, we use a nonlinear frequency modulation (NLFM) signal and propose a segment linear frequency modulation (SLFM) signal as the dipole excitation signal to compensate for the excitation intensity. The signal-to-noise ratio (SNR) of the signal over the entire frequency band is increased. The finite-difference method is used to simulate the responses from a Ricker wavelet, a linear frequency modulation (LFM) signal, an NLFM signal, and an SLFM signal in two borehole models of a homogeneously hard formation and a radially stratified formation. The dispersion and radial tomography results at low SNR of the sound source signals are compared. Numerical modeling suggests that the energy of the flexural waves excited by the Ricker wavelet source is concentrated near the Airy phase. In this case, the dispersion is incomplete and information regarding the formation near or far from the borehole cannot be obtained. The LFM signal yields dispersion information near the Airy phase and the high-frequency range but not in the low-frequency range. Moreover, the information regarding the formation far from the borehole is not accurate. The NLFM signal extends the frequency range of the flexural waves by compensating for the excitation intensity and yields information regarding the formation information, but it is not easy to obtain. The SLFM signal yields the same results as the NLFM signal and is easier to implement. Consequently, the dipole detection range expands and the S-wave velocity calculation accuracy improves.展开更多
CO2 laser rapid ablation mitigation(RAM)of fused silica has been used in high-power laser systems owing to its advantages of high efficiency,and ease of implementing batch and automated repairing.In order to study the...CO2 laser rapid ablation mitigation(RAM)of fused silica has been used in high-power laser systems owing to its advantages of high efficiency,and ease of implementing batch and automated repairing.In order to study the effect of repaired morphology of RAM on laser modulation and to improve laser damage threshold of optics,an finite element method(FEM)mathematical model of 351 nm laser irradiating fused silica optics is developed based on Maxwell electromagnetic field equations,to explore the 3D near-field light intensity distribution inside optics with repaired site on its surface.The influences of the cone angle and the size of the repaired site on incident laser modulation are studied as well.The results have shown that for the repaired site with a cone angle of 73.3°,the light intensity distribution has obvious three-dimensional characteristics.The relative light intensity on z-section has a circularly distribution,and the radius of the annular intensification zone increases with the decrease of z.While the distribution of maximum relative light intensity on y-section is parabolical with the increase of y.As the cone angle of the repaired site decreases,the effect of the repaired surface on light modulation becomes stronger,leading to a weak resistance to laser damage.Moreover,the large size repaired site would also reduce the laser damage threshold.Therefore,a repaired site with a larger cone angle and smaller size is preferred in practical CO2 laser repairing of surface damage.This work will provide theoretical guidance for the design of repaired surface topography,as well as the improvement of RAM process.展开更多
This paper introduces a novel method for fast calculating the electromagnetic forces in interior permanent magnet synchronous machines(IPMSMs)under pulse width modulation(PWM)voltage source inverter(VSI)supply based o...This paper introduces a novel method for fast calculating the electromagnetic forces in interior permanent magnet synchronous machines(IPMSMs)under pulse width modulation(PWM)voltage source inverter(VSI)supply based on the small-signal time-harmonic finite element analysis(THFEA),which has been successfully utilized for fast calculating the PWMinduced losses in silicon steel sheets and permanent magnets.Based on the small-signal THFEA,the functional relationships between high-frequency harmonic voltages(HFHVs)and corresponding airgap flux densities are established,which are used for calculating the flux density spectra caused by each HFHV in the PWM voltage spectra.Then,the superposition principle is applied for calculating the flux density spectra caused by fundamental currents and all HFHVs,which are converted to the electromagnetic force spectra at last.The relative errors between the force density spectra calculated with the proposed method and those obtained from traditional time-stepping finite element analysis(TSFEA)using PWM voltages as input are within 3.1%,while the proposed method is 24 times faster than the traditional TSFEA.展开更多
In order to characterize the mechanics of jet breakup, the finite volume formulations were employed to solve the Navier-Stokes equations and continuity equation of jet. The volume of fluid(VOF) method was used to trac...In order to characterize the mechanics of jet breakup, the finite volume formulations were employed to solve the Navier-Stokes equations and continuity equation of jet. The volume of fluid(VOF) method was used to track the free surface of jet. The spray process of the molten Pb63Sn37 alloy was simulated based on the mathematical model by means of FLUENT code. The configuration of jets generated in different disturbance ratios and modulation ratios was obtained. The theoretical results show that the droplets merge together by the number of disturbance ratio N, which agrees with the corresponding picture captured in the experiment. In addition, the droplet streams broken at non-optimal frequency are also uniform according to simulation results, which proves that the A-M disturbance can increase the width of the uniform droplet generating frequency.展开更多
A compact electro-absorption modulator based on graphene photonic crystal fiber is proposed. To enhance the graphene–light interaction efficiency, the innermost six air-holes of photonic crystal fiber are replaced by...A compact electro-absorption modulator based on graphene photonic crystal fiber is proposed. To enhance the graphene–light interaction efficiency, the innermost six air-holes of photonic crystal fiber are replaced by two large semicircular holes, and monolayer graphene is deposited on the two large semicircular holes. By optimizing the structure parameters, a strong graphene–light interaction is obtained. Moreover, the switch on–off point of the modulator is unchangeable,which is only related to the frequency of the incident light. The influence factors of this composite structure have been analyzed. The proposed modulator is compared with other graphene-based modulators, and the results show that it is filled without dielectric spacer. There are some excellent performances, such as an extinction ratio 7 dB of y-polarization mode,3-dB modulation bandwidth of 70 GHz with small footprint of 205 μm, and a consumption of energy per bit 59 pJ/bit.展开更多
In this paper we introduced a definition for the primary radical of a submodule with some of its basic properties. We also define the P-radical submodule and review some results about it. We find a method to character...In this paper we introduced a definition for the primary radical of a submodule with some of its basic properties. We also define the P-radical submodule and review some results about it. We find a method to characterize the primary radical of a finitely generated submodule of a free module.展开更多
Let F be a locally defined formation consisting of locally solvable groups, G a hyper-( cyclic or finite) locally solvable group and A a noetherian ZG-module with all irreducible ZG-factors being finite. The followi...Let F be a locally defined formation consisting of locally solvable groups, G a hyper-( cyclic or finite) locally solvable group and A a noetherian ZG-module with all irreducible ZG-factors being finite. The following conclusion is obtained: if G∈F, f( ∞ ) include f(p), f(p) ≠φ for each p∈π, and A has no nonzero F central ZG- images, then any extension E of A by G splits conjugately over A, and A has no nonzero F central ZG-factors.展开更多
In this paper, the module coradical is introduced. From this, we show that any Hopf module coalgebra which is local finite can be uniquely decomposed into a direct sum of its indecomposable components. This result is ...In this paper, the module coradical is introduced. From this, we show that any Hopf module coalgebra which is local finite can be uniquely decomposed into a direct sum of its indecomposable components. This result is a generalization of the decompostion theorem of coalgebra.展开更多
KH2PO4 crystal is a crucial optical component of inertial confinement fusion. Modulation of an incident laser by surface micro-defects will induce the growth of surface damage, which largely restricts the enhancement ...KH2PO4 crystal is a crucial optical component of inertial confinement fusion. Modulation of an incident laser by surface micro-defects will induce the growth of surface damage, which largely restricts the enhancement of the laser induced damage threshold. The modulation of an incident laser by using different kinds of surface defects are simulated by employing the three-dimensional finite-difference time-domain method. The results indicate that after the modulation of surface defects, the light intensity distribution inside the crystal is badly distorted, with the light intensity enhanced symmetrically. The relations between modulation properties and defect geometries (e.g., width, morphology, and depth of defects) are quite different for different defects. The modulation action is most obvious when the width of surface defects reaches 1.064 p-m. For defects with smooth morphology, such as spherical pits, the degree of modulation is the smallest and the light intensity distribution seems relatively uniform. The degree of modulation increases rapidly with the increase of the depth of surface defects and becomes stable when the depth reaches a critical value. The critical depth is 1.064 μm for cuboid pits and radial cracks, while for ellipsoidal pits the value depends on both the width and the length of the defects.展开更多
The category consisting of finitely generated modules which are left orthogonal with a cotilting bimodule is shown to be functorially finite. The notion of left orthogonal dimension is introduced , and then a necessar...The category consisting of finitely generated modules which are left orthogonal with a cotilting bimodule is shown to be functorially finite. The notion of left orthogonal dimension is introduced , and then a necessary and sufficient condition of selforthogonal modules having finite injective dimension and a characterization of cotilting modules are given.展开更多
文摘In this note, we provide an effective proof of the fundamental structure theorem of finitely generated modules over a principal ideal domain, from which we find the minimality of decomposition for a finitely generated module over a principal ideal domain.
基金TheNationalNaturalScienceFoundationofChina (No .10 1710 74 )
文摘Let Fbe a locally defined formation consisting of locally soluble groups, G a hyper-(cyclic or finite) locally soluble group and A a noetherian ZG-module with all irreducible ZG-factors being finite, G∈F, f(∞)f(p), f(p)≠ for each p∈π. The following conclutions are obtained: (1) if there exists a maximal submodule B of A such that A/B is F-central in G and B has no nonzero F-central ZG-factors, then A has an F-decomposition; (2) if there exists an irreducible F-central submodule B of A such that all ZG-composition factors of A/B are F-ecentric, then A has an F-decomposition.
文摘Let (?) be a formation locally defined by f(P), G ∈ (?) and A a ZG-module, where p ∈ π = { all primes and symbol ∞}. Then a p-main-factor U/V of G is said to be (?)-central in G if G/CG(U/V) ∈f(p). In this paper, we have proved that: let (?) be a locally defined formation consisting of locally soluble groups, G a hyper-(cyclic or finite) locally soluble group and A an artinian ZG-module with all irreducible ZG-factors of A being finite; if G ∈ (?), f(∞) ≡ f(p) . f(p)≠φ for each p ∈ π, A has an (?)-decomposition.
文摘With the aid of commercial finite element analysis software package ANSYS,investigations are made on the contributions of main components to stiffness of the main module for parallel machine tools,and it is found that the frame is the main contributor.Then,influences of constraints,strut length and working ways of the main module have also been investigated.It can be concluded that when one of the main planes of the frame without linear drive unit is constrained,the largest whole stiffness can be acquired.And,the stiffness is much better when the main module is used in a vertical machine tool instead of a horizontal one.Finally,the principle of stiffness variation is summarized when the mobile platform reaches various positions within its working space and when various loads are applied.These achievements have provided critical instructions for the design of the main module for parallel machine tools.
文摘In this paper, we prove that the Toeplitz operator with finite Blaschke product symbol Sψ(z) on Nφ has at least m non-trivial minimal reducing subspaces, where m is the dimension of H^2(Гω)⊙φ(ω)H^2(Гω). Moreover, the restriction of Sψ(z) on any of these minimal reducing subspaces is unitary equivalent to the Bergman shift Mz.
文摘For a ring A, an extension ring B, a fixed right A-module M, the endomorphism ring D formed by M, the endomorphism ring E formed by , and the endomorphism ring F formed by HomA (B,M), we present equivalences and dualities between subcategories of B-modules which are finitely cogenerated injective as A-modules and E-modules and F-modules which are finitely generated projective as D-modules.
文摘Let G be a hyper finite locally solvable group, A a minimax ZG-medule, a locally defined formation consisting of locally solvable groups, A has no nonzero infinite irreducible ZG-factors, and G ∈ . The following results are proved: if A has a maximal submodule B such that A/B is , central in G and B has no nonzero central ZG-factors, then A has an decomposition; ifA has an irreducible central submodule B such that all ZG-composition factors of A/B are o^eccentric, then A has an decomposition.
基金Supported by National Natural Science Foundation of China (No.60577023)Key Laboratory of Opto-Electronics Information and Technical Science of Ministry of Education,China
文摘In order to achieve a modulator with broad bandwidth and perfect impedance match,a novel electro-optical modulator based on GeO2-doped silica waveguides on silicon substrate is designed.The finite element model of the whole electro-optical modulator is established by means of ANSYS.With the finite element method analysis,the performance of the novel modulator is predicted.The simulation reveals that the designed modulator operates with a product of 3 dB optical bandwidth and modulating length of 226.59 GHz·cm,and a characteristic impedance of 51.6 Ω at 1 550 nm wavelength.Moreover,the calculated electrical reflected power of coplanar waveguide electrode is below-20 dB in the frequency ranging from 45 MHz to 65 GHz.Therefore,the designed modulator has wide modulation bandwidth and perfect impedance match.
基金This work was supported by the National Natural Science Foundation of China (Nos. 11574347, 11734017, 91630308, and 11374322), the Youth Talent Project of the Institute of Acoustics of Chinese Academy of Sciences (No. QNYC201619), and the PetroChina Innovation Foundation (No. 2016D-5007-0304).
文摘A wideband dipole signal is required for dipole dispersion correction and nearborehole imaging. To obtain the broadband flexural wave dispersion, we use a nonlinear frequency modulation (NLFM) signal and propose a segment linear frequency modulation (SLFM) signal as the dipole excitation signal to compensate for the excitation intensity. The signal-to-noise ratio (SNR) of the signal over the entire frequency band is increased. The finite-difference method is used to simulate the responses from a Ricker wavelet, a linear frequency modulation (LFM) signal, an NLFM signal, and an SLFM signal in two borehole models of a homogeneously hard formation and a radially stratified formation. The dispersion and radial tomography results at low SNR of the sound source signals are compared. Numerical modeling suggests that the energy of the flexural waves excited by the Ricker wavelet source is concentrated near the Airy phase. In this case, the dispersion is incomplete and information regarding the formation near or far from the borehole cannot be obtained. The LFM signal yields dispersion information near the Airy phase and the high-frequency range but not in the low-frequency range. Moreover, the information regarding the formation far from the borehole is not accurate. The NLFM signal extends the frequency range of the flexural waves by compensating for the excitation intensity and yields information regarding the formation information, but it is not easy to obtain. The SLFM signal yields the same results as the NLFM signal and is easier to implement. Consequently, the dipole detection range expands and the S-wave velocity calculation accuracy improves.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51775147 and 51705105)the Science Challenge Project of China(Grant No.TZ2016006-0503-01)+2 种基金the Young Elite Scientists Sponsorship Program by CAST(Grant No.2018QNRC001)the China Postdoctoral Science Foundation funded project(Grant Nos.2018T110288 and 2017M621260)the Self-Planned Task of State Key Laboratory of Robotics and System(HIT)(Grant Nos.SKLRS201718A and SKLRS201803B).
文摘CO2 laser rapid ablation mitigation(RAM)of fused silica has been used in high-power laser systems owing to its advantages of high efficiency,and ease of implementing batch and automated repairing.In order to study the effect of repaired morphology of RAM on laser modulation and to improve laser damage threshold of optics,an finite element method(FEM)mathematical model of 351 nm laser irradiating fused silica optics is developed based on Maxwell electromagnetic field equations,to explore the 3D near-field light intensity distribution inside optics with repaired site on its surface.The influences of the cone angle and the size of the repaired site on incident laser modulation are studied as well.The results have shown that for the repaired site with a cone angle of 73.3°,the light intensity distribution has obvious three-dimensional characteristics.The relative light intensity on z-section has a circularly distribution,and the radius of the annular intensification zone increases with the decrease of z.While the distribution of maximum relative light intensity on y-section is parabolical with the increase of y.As the cone angle of the repaired site decreases,the effect of the repaired surface on light modulation becomes stronger,leading to a weak resistance to laser damage.Moreover,the large size repaired site would also reduce the laser damage threshold.Therefore,a repaired site with a larger cone angle and smaller size is preferred in practical CO2 laser repairing of surface damage.This work will provide theoretical guidance for the design of repaired surface topography,as well as the improvement of RAM process.
基金supported in part by the National Natural Science Foundation of China under projects 51907053by Natural Science Foundation of Jiangsu Province of China under Project BK20190489+1 种基金by the Fundamental Research Funds for the Central Universities under grant B200202167by the China Postdoctoral Science Foundation under grant no.2019M661708。
文摘This paper introduces a novel method for fast calculating the electromagnetic forces in interior permanent magnet synchronous machines(IPMSMs)under pulse width modulation(PWM)voltage source inverter(VSI)supply based on the small-signal time-harmonic finite element analysis(THFEA),which has been successfully utilized for fast calculating the PWMinduced losses in silicon steel sheets and permanent magnets.Based on the small-signal THFEA,the functional relationships between high-frequency harmonic voltages(HFHVs)and corresponding airgap flux densities are established,which are used for calculating the flux density spectra caused by each HFHV in the PWM voltage spectra.Then,the superposition principle is applied for calculating the flux density spectra caused by fundamental currents and all HFHVs,which are converted to the electromagnetic force spectra at last.The relative errors between the force density spectra calculated with the proposed method and those obtained from traditional time-stepping finite element analysis(TSFEA)using PWM voltages as input are within 3.1%,while the proposed method is 24 times faster than the traditional TSFEA.
基金Project(20070699076) supported by Specialized Research Fund of the Doctoral Program of Higher Education of ChinaProject supported by the Innovation Foundation by Northwestern Polytechnical University, China
文摘In order to characterize the mechanics of jet breakup, the finite volume formulations were employed to solve the Navier-Stokes equations and continuity equation of jet. The volume of fluid(VOF) method was used to track the free surface of jet. The spray process of the molten Pb63Sn37 alloy was simulated based on the mathematical model by means of FLUENT code. The configuration of jets generated in different disturbance ratios and modulation ratios was obtained. The theoretical results show that the droplets merge together by the number of disturbance ratio N, which agrees with the corresponding picture captured in the experiment. In addition, the droplet streams broken at non-optimal frequency are also uniform according to simulation results, which proves that the A-M disturbance can increase the width of the uniform droplet generating frequency.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61575170 and 61675176)the Key Basic Research Program of Hebei Province,China(Grant No.16961701D)the“Xin Rui Gong Cheng”Talent Project of Yanshan University。
文摘A compact electro-absorption modulator based on graphene photonic crystal fiber is proposed. To enhance the graphene–light interaction efficiency, the innermost six air-holes of photonic crystal fiber are replaced by two large semicircular holes, and monolayer graphene is deposited on the two large semicircular holes. By optimizing the structure parameters, a strong graphene–light interaction is obtained. Moreover, the switch on–off point of the modulator is unchangeable,which is only related to the frequency of the incident light. The influence factors of this composite structure have been analyzed. The proposed modulator is compared with other graphene-based modulators, and the results show that it is filled without dielectric spacer. There are some excellent performances, such as an extinction ratio 7 dB of y-polarization mode,3-dB modulation bandwidth of 70 GHz with small footprint of 205 μm, and a consumption of energy per bit 59 pJ/bit.
文摘In this paper we introduced a definition for the primary radical of a submodule with some of its basic properties. We also define the P-radical submodule and review some results about it. We find a method to characterize the primary radical of a finitely generated submodule of a free module.
文摘Let F be a locally defined formation consisting of locally solvable groups, G a hyper-( cyclic or finite) locally solvable group and A a noetherian ZG-module with all irreducible ZG-factors being finite. The following conclusion is obtained: if G∈F, f( ∞ ) include f(p), f(p) ≠φ for each p∈π, and A has no nonzero F central ZG- images, then any extension E of A by G splits conjugately over A, and A has no nonzero F central ZG-factors.
文摘In this paper, the module coradical is introduced. From this, we show that any Hopf module coalgebra which is local finite can be uniquely decomposed into a direct sum of its indecomposable components. This result is a generalization of the decompostion theorem of coalgebra.
基金Project supported by the National Natural Science Foundation of China (Grant No. 50875066)
文摘KH2PO4 crystal is a crucial optical component of inertial confinement fusion. Modulation of an incident laser by surface micro-defects will induce the growth of surface damage, which largely restricts the enhancement of the laser induced damage threshold. The modulation of an incident laser by using different kinds of surface defects are simulated by employing the three-dimensional finite-difference time-domain method. The results indicate that after the modulation of surface defects, the light intensity distribution inside the crystal is badly distorted, with the light intensity enhanced symmetrically. The relations between modulation properties and defect geometries (e.g., width, morphology, and depth of defects) are quite different for different defects. The modulation action is most obvious when the width of surface defects reaches 1.064 p-m. For defects with smooth morphology, such as spherical pits, the degree of modulation is the smallest and the light intensity distribution seems relatively uniform. The degree of modulation increases rapidly with the increase of the depth of surface defects and becomes stable when the depth reaches a critical value. The critical depth is 1.064 μm for cuboid pits and radial cracks, while for ellipsoidal pits the value depends on both the width and the length of the defects.
文摘The category consisting of finitely generated modules which are left orthogonal with a cotilting bimodule is shown to be functorially finite. The notion of left orthogonal dimension is introduced , and then a necessary and sufficient condition of selforthogonal modules having finite injective dimension and a characterization of cotilting modules are given.