In this paper,we consider symbolic(hybrid trigonometric)parametrizations defined as tuples of real rational expressions involving circular and hyperbolic trigonometric functions as well as monomials,with the restricti...In this paper,we consider symbolic(hybrid trigonometric)parametrizations defined as tuples of real rational expressions involving circular and hyperbolic trigonometric functions as well as monomials,with the restriction that variables in each block of functions are different.We prove that the varieties parametrizable in this way are exactly the class of real unirational varieties of any dimension.In addition,we provide symbolic algorithms to implicitize and to convert a hybrid trigonometric parametrization into a unirational one,and vice versa.We illustrate by some examples the applicability of having these different types of parametrizations,namely,hybrid trigonometric and unirational.展开更多
We conduct an investigation to explore late-time cosmic acceleration through various dark energy parametrizations(Wettrich,Efstathiou,and Ma-Zhang)within the Horava-Lifshitz gravity framework.As an alternative to gene...We conduct an investigation to explore late-time cosmic acceleration through various dark energy parametrizations(Wettrich,Efstathiou,and Ma-Zhang)within the Horava-Lifshitz gravity framework.As an alternative to general relativity,this theory introduces anisotropic scaling at ultraviolet scales.Our primary objective is to constrain the key cosmic parameters and baryon acoustic oscillation(BAO)scale,specifically the sound horizon(rd),by utilizing 24 uncorrelated measurements of BAOs derived from recent galaxy surveys spanning a redshift range from z=0.106 to z=2.33.Additionally,we integrate the most recent Hubble constant measurement by Riess in 2022(denoted as R22)as an extra prior.For the parametrizations of Wettrich,Efstathiou,and Ma-Zhang,our analysis of BAO data yields sound horizon results of r_(d)=148.1560±2.7688 Mpc,r_(d)=148.6168±10.2469 Mpc,and r_(d)=147.9737±10.6096 Mpc,respectively.Incorporating the R22 prior into the BAO dataset results in r_(d)=139.5806±3.8522 Mpc,r_(d)=139.728025±2.7858 Mpc,and r_(d)=139.6001±2.7441 Mpc.These outcomes highlight a distinct inconsistency between early and late observational measurements,analogous to the H_(0) tension.A notable observation is that,when we do not include the R22 prior,the outcomes for rd tend to be in agreement with Planck and SDSS results.Following this,we conducted a cosmography test and comparative study of each parametrization within the Lambda Cold Dark Matter paradigm.Our diagnostic analyses demonstrate that all models fit seamlessly within the phantom region.All dark energy parametrizations predict an equation of state parameter close ω=-1,indicating a behavior similar to that of a cosmological constant.The statistical analysis indicates that neither of the two models can be ruled out based on the latest observational measurements.展开更多
This paper shows that the multiplicity of the base point locus of a projective rational surface parametrization can be expressed as the degree of the content of a univariate resultant.As a consequence,we get a new pro...This paper shows that the multiplicity of the base point locus of a projective rational surface parametrization can be expressed as the degree of the content of a univariate resultant.As a consequence,we get a new proof of the degree formula relating the degree of the surface,the degree of the parametrization,the base point multiplicity and the degree of the rational map induced by the parametrization.In addition,we extend both formulas to the case of dominant rational maps of the projective plane and describe how the base point loci of a parametrization and its reparametrizations are related.As an application of these results,we explore how the degree of a surface reparametrization is affected by the presence of base points.展开更多
A high-temperature and high-pressure valve is the key equipment of a wind tunnel system;it controls the generation of high-temperature and high-pressure gas.To reduce the adverse impact of high-temperature and high-pr...A high-temperature and high-pressure valve is the key equipment of a wind tunnel system;it controls the generation of high-temperature and high-pressure gas.To reduce the adverse impact of high-temperature and high-pressure gas on the strength of the valve body,a cooling structure is set on the valve seat.This can significantly reduce the temperature of the valve body and valve seat.The effects of its structure on the cooling characteristics and stress of the valve seat are studied,and six main parameters that can completely describe the geometry of the cooling structure are proposed.The central composite design method is used to select sample points,and the multi-objective genetic algorithm(MOGA)method is used for optimal structural design.A modification method according to the main parameters for the valve seat is proposed.The results show that the cooling structure weakens the pressure-bearing capability of the valve seat.Among the six main parameters of the valve seat,the distance from the end face of the lower hole to the Z-axis and the distance from the axis of the lower hole to the origin of the coordinates have the most obvious effects on the average stress of the valve seat.An optimum design value is proposed.This work can provide a reference for the design of high-temperature and high-pressure valves.展开更多
In recent years,the concept of digital human has attracted widespread attention from all walks of life,and the modelling of high-fidelity human bodies,heads,and hands has been intensively studied.This paper focuses on...In recent years,the concept of digital human has attracted widespread attention from all walks of life,and the modelling of high-fidelity human bodies,heads,and hands has been intensively studied.This paper focuses on head modelling and proposes a generic head parametric model based on neural radiance fields.Specifically,we first use face recognition networks and 3D facial expression database FaceWarehouse to parameterize identity and expression semantics,respectively,and use both as conditional inputs to build a neural radiance field for the human head,thereby improving the head model’s representation ability while ensuring editing capabilities for the identity and expression of the rendered results;then,through a combination of volume rendering and neural rendering,the 3D representation of the head is rapidly rendered into the 2D plane,producing a high-fidelity image of the human head.Thanks to the well-designed loss functions and good implicit representation of the neural radiance field,our model can not only edit the identity and expression independently,but also freely modify the virtual camera position of the rendering results.It has excellent multi-view consistency,and has many applications in novel view synthesis,pose driving and more.展开更多
An experimental investigation of the dynamics of the interface between two low-viscosity fluids with high density contrast oscillating in a fixed vertical slotted channel has been conducted.It has been found that as t...An experimental investigation of the dynamics of the interface between two low-viscosity fluids with high density contrast oscillating in a fixed vertical slotted channel has been conducted.It has been found that as the amplitude of the liquid column oscillations increases,parametric oscillations of the interface are excited in the form of a standing wave located in the channel plane.In particular,depending on the interfacial tension,the standing waves have a frequency equal to that of liquid piston oscillations(harmonic response),or half of the frequency of oscillations of the liquid column in the channel(subharmonic response).The detected type of instability has a gravitational-capillary nature and is analogous to Faraday waves.The analysis of the overcritical dynamics of wave oscillations indicates that interfacial tension plays a crucial role in determining the type of parametric instability.At high interfacial tension,only synchronous(harmonic)wave modes are observed,and the threshold of the wave excitation is determined by the amplitude of piston oscillations of the liquid column.In this case,the oscillation acceleration does not play a role and has a small value in the threshold of the synchronous mode response.In the case of weak surface tension,subharmonic oscillations are observed.The threshold for the development of these oscillations is determined by the dimensionless acceleration of the oscillating liquid column and remains almost constant with variations in the dimensionless frequency of oscillations.At moderate values of interfacial tension(in the region of moderate dimensionless frequencies),a synchronous wave mode emerges in the stability threshold of the oscillating interface.As the dimensionless acceleration is increased further,a subharmonic mode is excited.The growth of subharmonic oscillations occurs against the background of harmonic wave oscillations,with the oscillations of the interface representing a combination of two standing waves.展开更多
Tensegrity structures,embodying the principles of continuous tensioning and discrete compression,have emerged as fundamental frameworks in locomotive soft robotics for navigating uneven and unpredictable environments,...Tensegrity structures,embodying the principles of continuous tensioning and discrete compression,have emerged as fundamental frameworks in locomotive soft robotics for navigating uneven and unpredictable environments,owing to their flexible and resilient traits.By means of a straightforward and cost-effective method to achieve structure-driven,vibration-driven tensegrity shows great potential,particularly in tasks demanding random exploration.However,the design guidance for vibration-driven tensegrity and their performance evaluation in unstructured terrain remain unrevealed due to the complex dynamics of the structure.This paper presents a small six-bar tensegrity robot,driven by wireless vibration motors,designed for deployment in disaster rescue and search scenarios.Finite element simulation is used to investigate how structural characteristics,excitation parameters,and the arrangement of motors affect the kinematic performance of this tensegrity system.A prototype of the six-bar tensegrity robot with three motors located on the lower ends of the three lower struts is designed and manufactured after the numerical simulations.A simple control policy which adjusts the motion of the tensegrity robot by turning on or off the motors on different locations is proposed.The prototype with and without the control policy is tested in man-made environments of various complexity.It shows that the ability and efficiency of the tensegrity robot in exploring unstructured environments is significantly enhanced by the proposed control policy.It is believed that the potential of the vibration-driven tensegrity robot could be further exploited by integrating multi-source sensors and more intelligent control policies.展开更多
Accurately modeling heavy-tailed data is critical across applied sciences,particularly in finance,medicine,and actuarial analysis.This work presents the heavy-tailed power XLindley distribution(HTPXLD),a unique heavy-...Accurately modeling heavy-tailed data is critical across applied sciences,particularly in finance,medicine,and actuarial analysis.This work presents the heavy-tailed power XLindley distribution(HTPXLD),a unique heavy-tailed distribution.Adding one more parameter to the power XLindley distribution improves this new distribution,especially when modeling leptokurtic lifetime data.The suggested density provides greater flexibility with asymmetric forms and different degrees of peakedness.Its statistical features,like the quantile function,moments,extropy measures,incomplete moments,stochastic ordering,and stress-strength parameters,are explored.We further investigate its use in actuarial science through the computation of pertinent metrics,such as value-at-risk,tail value-at-risk,tail variance,and tail variance premium.To obtain the point and interval parameter estimates,we use the maximum likelihood estimation approach.We do many simulation tests to evaluate the performance of our proposed estimator.Metrics like bias,relative bias,mean squared error,root mean squared error,average interval length,and coverage probability will be used in these tests to assess the estimator’s performance.To illustrate the practical value of our proposed model,we apply it to analyze three real-world datasets.We then compare its performance to established competing models,highlighting its advantages.展开更多
Inflatable deployable structures inspired by origami have significant applications in space missions such as solar arrays and antennas.In this paper,a generalized Miura-ori tubular cell(GMTC)is presented as the basic ...Inflatable deployable structures inspired by origami have significant applications in space missions such as solar arrays and antennas.In this paper,a generalized Miura-ori tubular cell(GMTC)is presented as the basic cell to design a family of inflatable origami tubular structures with the targeted configuration.First,the classification of rigid foldable degree-4 vertices is studied thoroughly.Since the proposed GMTC is comprised of forming units(FU)and linking units(LU),types of FUs and LUs are investigated based on the classification of degree-4 vertices,respectively.The rigid foldability of the GMTC is presented by studying the kinematics of the FUs and LUs.Volume of the GMTC is analyzed to investigate multistable configurations of the basic cell.The variations in volume of the GMTC offer great potential for developing the inflatable tubular structure.Design method and parametric optimization of the tubular structure with targeted configuration are proposed.The feasibility of the approach is validated by the approximation of four different cases,namely parabolic,semicircular,trapezoidal,and straight-arc hybrid tubular structures.展开更多
We prove the boundedness of the parametric Lusin's S functionμ_(S)^(?)(f)and Littlewood-Paley's g_(λ)^(*)-funtionμ_(λ),^(*,?)(f)on grand Herz-Morrey spaces with variable exponents.Additionally,we establish...We prove the boundedness of the parametric Lusin's S functionμ_(S)^(?)(f)and Littlewood-Paley's g_(λ)^(*)-funtionμ_(λ),^(*,?)(f)on grand Herz-Morrey spaces with variable exponents.Additionally,we establish the boundedness of higher-order commutators ofμ_(S)^(?)andμ_(λ),^(*,?)with BMO functions applying some properties of variable exponents and generalized BMO norms.展开更多
We utilize conventional wave-vector-resolved Brillouin light scattering technology to investigate the spin wave response in YIG thin films under high-power microwave excitation. By varying the microwave frequency, ext...We utilize conventional wave-vector-resolved Brillouin light scattering technology to investigate the spin wave response in YIG thin films under high-power microwave excitation. By varying the microwave frequency, external bias magnetic field, and in-plane wave vector, in addition to observing the dipole-exchange spin waves excited by parallel parametric pumping, we further observe broadband spin wave excitation within the dipole-exchange spin wave spectrum. This broadband excitation results from the combined effects of parallel and perpendicular parametric pumping, induced by irregularities in the excitation geometry, as well as magnon–magnon scattering arising from the absence of certain spin wave modes. Our findings offer new insights into the mechanisms of energy dissipation and relaxation processes caused by spin wave excitation in magnetic devices operating at high power.展开更多
To analyze the correlation between the input energy parameters(V_(E))and typical intensity measures(IMs)of offshore ground motions,based on 273 earthquake events recorded by the K-NET in Japan,892 offshore ground moti...To analyze the correlation between the input energy parameters(V_(E))and typical intensity measures(IMs)of offshore ground motions,based on 273 earthquake events recorded by the K-NET in Japan,892 offshore ground motion records with moment magnitudes from 4.0 to 7.0 were used in this study.Residuals obtained through a ground motion model were calculated and analyzed for the correlation between V_(E) and amplitude,duration,frequency content and cumulative IMs.The results indicate that PGV and PGD have strong correlation with the V_(E)(T>0.2 s and T>0.4 s),the duration IMs have weakly negative correlation with the V_(E),Sd_(1) has a strong correlation with the V_(E) in the periods of T>0.4 s,T_(g) has a weak correlation with V_(E) and the cumulative IMs have strong correlation with the V_(E).The parametric predictive equations between typical IMs and V_(E) was proposed,and the differences between the prediction equations from the onshore ground motion records were compared.The differences in parametric predicted equations between offshore and onshore ground motions were confirmed in this study.Proposed correlation equations can be applied to offshore probabilistic seismic hazard analysis and the selection of ground motion records by generalized conditional intensity measures.展开更多
To further enhance the recovery rate of low-temperature waste heat,the low-temperature flue gas in the sinter annular cooler was chosen as the heat source of an organic Rankine cycle(ORC)system,and the comprehensive e...To further enhance the recovery rate of low-temperature waste heat,the low-temperature flue gas in the sinter annular cooler was chosen as the heat source of an organic Rankine cycle(ORC)system,and the comprehensive evaluation of energy,exergy and economic performance of the ORC system was conducted deeply.The energy,exergy and economic performance models of the ORC system were established,and proper candidate organic working fluids(OWFs)were selected based on the thermo-physical properties of OWF and operating characteristics of ORC system.Then,the effects of ORC crucial parameters on the system energy,exergy and economic performances were evaluated in detail.Finally,the bi-objective optimization based on the genetic algorithm was conducted to analyze the optimal performance of the ORC system under the designed ORC crucial parameters,and the exergy efficiency and electricity production cost were set as the evaluation indexes of parametric optimization.The results indicate that the ORC system with the higher evaporation temperature and lower condensation temperature can obtain the larger system exergy efficiency and smaller electricity production cost.The smaller the superheat degree of OWF and pinch-point temperature difference in the evaporator are,the better the energy and exergy performances of the ORC system are.Under the optimization results,R245fa has the best comprehensive performance with the exergy efficiency of 46.34%and electricity production cost of 0.12123$/kWh among the selected candidate OWFs,which should be preferentially chosen as the OWF of the ORC system.展开更多
Photon pairs with large nondegeneracy have recently attracted increasing interest, which gives rise to an urgent demand for revealing their complete and accurate spectral distribution. By thoroughly analyzing parametr...Photon pairs with large nondegeneracy have recently attracted increasing interest, which gives rise to an urgent demand for revealing their complete and accurate spectral distribution. By thoroughly analyzing parametric down-conversion(PDC), we put forward a model to directly describe the spatial-spectral distribution of these photon pairs, which is experimentally demonstrated by a 532-nm pumped type-I PDC in a beta barium borate(BBO) crystal. The measured spectral curves show good agreement with the theoretical predictions over the entire spectral range. We further demonstrate that, as signal wavelength increases, the photon pairs are initially spectrally distinguishable, then partly indistinguishable, finally completely indistinguishable with a maximum bandwidth of approximately 500 nm. Utilizing photon-number-resolving single-photon detectors(SPD), we observe the average photon number decreases significantly more slowly than the spectral intensity as the wavelength deviates from the peak, and the photon numbers follow a quasi-Poisson distribution well for wavelengths around the peak, but a thermal distribution better describes the statistics near the spectral boundaries. Finally,we use the signal photons as the trigger to generate heralded Fock states up to 10 photons in near-infrared range, which are suitable for quantum simulation and quantum key distribution in optical fiber networks.展开更多
Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycle...Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycles.However,the effects of tooth geometry parameters could manifest as the meshing cycles increase.This study investigated the effects of tooth geometry parameters on the multi-cycle meshing temperature of polyoxymethylene(POM)worm gears,aiming to control the meshing temperature elevation by tuning the tooth geometry.Firstly,a finite element(FE)model capable of separately calculating the heat generation and simulating the heat propagation was established.Moreover,an adaptive iteration algorithm was proposed within the FE framework to capture the influence of the heat generation variation from cycle to cycle.This algorithm proved to be feasible and highly efficient compared with experimental results from the literature and simulated results via the full-iteration algorithm.Multi-cycle meshing temperature analyses were conducted on a series of POM worm gears with different tooth geometry parameters.The results reveal that,within the range of 14.5°to 25°,a pressure angle of 25°is favorable for reducing the peak surface temperature and overall body temperature of POM worm gears,which influence flank wear and load-carrying capability,respectively.However,addendum modification should be weighed because it helps with load bearing but increases the risk of severe flank wear.This paper proposes an efficient iteration algorithm for multi-cycle meshing temperature analysis of polymer gears and proves the feasibility of controlling the meshing temperature elevation during multiple cycles by tuning tooth geometry.展开更多
Despite the prevalence and validity of the universal distinct element code(UDEC)in simulations in geotechnics domain,water-weakening process of rock models remains elusive.Prior research has made positive contribution...Despite the prevalence and validity of the universal distinct element code(UDEC)in simulations in geotechnics domain,water-weakening process of rock models remains elusive.Prior research has made positive contributions to a presupposed link between modelling parameters and saturation degree,Sr.Nevertheless,this effort presents inaccurate results and limited implications owing to the misleading interpretation,that is,devoid of the basic logic in UDEC that modelling parameters should be calibrated by tested macroscopic properties in contrast to a presupposed relation with Sr.To fill this gap,a new methodology is proposed by coupling a computationally efficient parametric study with the simulation of water-weakening mechanisms.More specifically,tested macroscopic properties with different Sr values are input into parametric relations to acquire initial modelling parameters that are sequentially calibrated and modulated until simulations are in line with geomechanical tests.Illustrative example reveals that numerical water-weakening effects on macroscopic properties,mechanical behaviours,and failure configurations are highly consistent with tested ones with noticeable computational expediency,implying the feasibility and simplicity of this methodology.Furthermore,with compatibility across various numerical models,the proposed methodology substantially extends the applicability of UDEC in simulating water-weakening geotechnical problems.展开更多
In this paper,the class of starlike functions of complex order γ(γ∈ℂ−{0})is extended from the case on unit disk U=(z∈C:|z|<1)to the case on the unit ball B in a complex Banach space or the unit polydisk U^(n) i...In this paper,the class of starlike functions of complex order γ(γ∈ℂ−{0})is extended from the case on unit disk U=(z∈C:|z|<1)to the case on the unit ball B in a complex Banach space or the unit polydisk U^(n) in C^(n).Let g be a convex function in U. We mainly establish the sharp bounds of all terms of homogeneous polynomial expansions for a subclass of g-parametric starlike mappings of complex order γ on B (resp.U^(n))when the mappings f are k-fold symmetric, k ∈ N. Our results partly solve the Bieberbach conjecture in several complex variables and generalize some prior works.展开更多
This paper aims to evaluate the stochastic response of steel columns subjected to blast loads using the modified single degree of freedom(MSDOF)method,which assessed towards the conventional single degree of freedom(S...This paper aims to evaluate the stochastic response of steel columns subjected to blast loads using the modified single degree of freedom(MSDOF)method,which assessed towards the conventional single degree of freedom(SDOF)and the experimentally validated Finite Element(FE)methods(LSDYNA).For this purpose,special atten-tion is given to calculating the response of H-shaped steel columns under blast.The damage amount is determined based on the support rotation criterion,which is expressed as a function of their maximum lateral mid-span dis-placement.To account for uncertainties in input parameters and obtain the failure probability,the Monte Carlo simulation(MCS)method is employed,complemented by the Latin Hypercube Sampling(LHS)method to reduce the number of simulations.A parametric analysis is hence performed to examine the effect of several input pa-rameters(including both deterministic and probabilistic parameters)on the probability of column damage as a function of support rotation.First,the MSDOF method confirms its higher accuracy in estimating the probability of column damage due to blast,compared to the conventional SDOF.The collected results also show that un-certainties of several input parameters have significant effects on the column behavior.In particular,geometric parameters(including cross-sectional characteristics,boundary conditions and column length)have major effect on the corresponding column response,in the same way of input blast load parameters and material properties.展开更多
To investigate the influence of the shear lag effect on the bending shear stress of single-box multicell box gird-ers(MCBG),the shear lag warping additional deflection is selected as the generalized displacement.The g...To investigate the influence of the shear lag effect on the bending shear stress of single-box multicell box gird-ers(MCBG),the shear lag warping additional deflection is selected as the generalized displacement.The governing dif-ferential equations and boundary conditions for the shear lag of the MCBG are derived using the energy variational method.Based on the shear lag warping deformation state of the MCBG and by employing the microelement equilib-rium differential equation and the coordination conditions for shear lag warping deformation,the calculation method for the bending-warping shear stress of the MCBG is de-rived,and the influence of the width-to-span and height-to span ratios on bending-warping shear stress is analyzed.Ex-ample analysis shows that the bending-warping shear stress of the MCBG calculated by the proposed calculation method coincides with the finite element solution,and the warping shear stress satisfies the self-balancing condition of shear warping,thus verifying the accuracy of the proposed method.The warping shear stress exhibits an antisymmetric distribution about the vertical axis of symmetry and has a weakening effect on the shear stress of the elementary beam(EB).The larger the width-to-span ratio is,the larger the proportion of the warping shear stress of the EB.The larger the height-to-span ratio is,the smaller the proportion of the warping shear stress and the more significant the influence of the width-to-span ratio.The more the number of cells is,the smaller the influence of the warping shear stress on the total bending shear stress.The influence of the shear lag ef-fect can be ignored in the calculation of the bending shear stress of three or more cells in the MCBG.展开更多
Accurate determination of rock mass parameters is essential for ensuring the accuracy of numericalsimulations. Displacement back-analysis is the most widely used method;however, the reliability of thecurrent approache...Accurate determination of rock mass parameters is essential for ensuring the accuracy of numericalsimulations. Displacement back-analysis is the most widely used method;however, the reliability of thecurrent approaches remains unsatisfactory. Therefore, in this paper, a multistage rock mass parameterback-analysis method, that considers the construction process and displacement losses is proposed andimplemented through the coupling of numerical simulation, auto-machine learning (AutoML), andmulti-objective optimization algorithms (MOOAs). First, a parametric modeling platform for mechanizedtwin tunnels is developed, generating a dataset through extensive numerical simulations. Next, theAutoML method is utilized to establish a surrogate model linking rock parameters and displacements.The tunnel construction process is divided into multiple stages, transforming the rock mass parameterback-analysis into a multi-objective optimization problem, for which multi-objective optimization algorithmsare introduced to obtain the rock mass parameters. The newly proposed rock mass parameterback-analysis method is validated in a mechanized twin tunnel project, and its accuracy and effectivenessare demonstrated. Compared with traditional single-stage back-analysis methods, the proposedmodel decreases the average absolute percentage error from 12.73% to 4.34%, significantly improving theaccuracy of the back-analysis. Moreover, although the accuracy of back analysis significantly increaseswith the number of construction stages considered, the back analysis time is acceptable. This studyprovides a new method for displacement back analysis that is efficient and accurate, thereby paving theway for precise parameter determination in numerical simulations.展开更多
基金the CRUE-CSIC agreement with Springer Nature.the project ID2019-105621GB-I00 of Ministerio de Ciencia e Innovación.+1 种基金the GrantPID2020-113192GB-100(Math-ematical Visualization:Foundations,Algorithms and Applications)from the Spanish MICINN.A.Lastra is member of the Research Group ASYNACS(Ref.CT-CE2019/683).
文摘In this paper,we consider symbolic(hybrid trigonometric)parametrizations defined as tuples of real rational expressions involving circular and hyperbolic trigonometric functions as well as monomials,with the restriction that variables in each block of functions are different.We prove that the varieties parametrizable in this way are exactly the class of real unirational varieties of any dimension.In addition,we provide symbolic algorithms to implicitize and to convert a hybrid trigonometric parametrization into a unirational one,and vice versa.We illustrate by some examples the applicability of having these different types of parametrizations,namely,hybrid trigonometric and unirational.
文摘We conduct an investigation to explore late-time cosmic acceleration through various dark energy parametrizations(Wettrich,Efstathiou,and Ma-Zhang)within the Horava-Lifshitz gravity framework.As an alternative to general relativity,this theory introduces anisotropic scaling at ultraviolet scales.Our primary objective is to constrain the key cosmic parameters and baryon acoustic oscillation(BAO)scale,specifically the sound horizon(rd),by utilizing 24 uncorrelated measurements of BAOs derived from recent galaxy surveys spanning a redshift range from z=0.106 to z=2.33.Additionally,we integrate the most recent Hubble constant measurement by Riess in 2022(denoted as R22)as an extra prior.For the parametrizations of Wettrich,Efstathiou,and Ma-Zhang,our analysis of BAO data yields sound horizon results of r_(d)=148.1560±2.7688 Mpc,r_(d)=148.6168±10.2469 Mpc,and r_(d)=147.9737±10.6096 Mpc,respectively.Incorporating the R22 prior into the BAO dataset results in r_(d)=139.5806±3.8522 Mpc,r_(d)=139.728025±2.7858 Mpc,and r_(d)=139.6001±2.7441 Mpc.These outcomes highlight a distinct inconsistency between early and late observational measurements,analogous to the H_(0) tension.A notable observation is that,when we do not include the R22 prior,the outcomes for rd tend to be in agreement with Planck and SDSS results.Following this,we conducted a cosmography test and comparative study of each parametrization within the Lambda Cold Dark Matter paradigm.Our diagnostic analyses demonstrate that all models fit seamlessly within the phantom region.All dark energy parametrizations predict an equation of state parameter close ω=-1,indicating a behavior similar to that of a cosmological constant.The statistical analysis indicates that neither of the two models can be ruled out based on the latest observational measurements.
基金partially supported by FEDER/Ministerio de Ciencia,Innovación y Universidades-Agencia Estatal de Investigación/MTM2017-88796-P(Symbolic Computation:new challenges in Algebra and Geometry together with its applications)。
文摘This paper shows that the multiplicity of the base point locus of a projective rational surface parametrization can be expressed as the degree of the content of a univariate resultant.As a consequence,we get a new proof of the degree formula relating the degree of the surface,the degree of the parametrization,the base point multiplicity and the degree of the rational map induced by the parametrization.In addition,we extend both formulas to the case of dominant rational maps of the projective plane and describe how the base point loci of a parametrization and its reparametrizations are related.As an application of these results,we explore how the degree of a surface reparametrization is affected by the presence of base points.
基金supported by the National Natural Science Foundation of China(No.52175067)the Zhejiang Key Research&Development Project(No.2021C01021)+1 种基金the Natural Science Foundation of Zhejiang Province(No.LY20E050016)the Postdoctoral Fellowship Program of China Postdoctoral Science Foundation(CPSF)(No.GZC20241478)。
文摘A high-temperature and high-pressure valve is the key equipment of a wind tunnel system;it controls the generation of high-temperature and high-pressure gas.To reduce the adverse impact of high-temperature and high-pressure gas on the strength of the valve body,a cooling structure is set on the valve seat.This can significantly reduce the temperature of the valve body and valve seat.The effects of its structure on the cooling characteristics and stress of the valve seat are studied,and six main parameters that can completely describe the geometry of the cooling structure are proposed.The central composite design method is used to select sample points,and the multi-objective genetic algorithm(MOGA)method is used for optimal structural design.A modification method according to the main parameters for the valve seat is proposed.The results show that the cooling structure weakens the pressure-bearing capability of the valve seat.Among the six main parameters of the valve seat,the distance from the end face of the lower hole to the Z-axis and the distance from the axis of the lower hole to the origin of the coordinates have the most obvious effects on the average stress of the valve seat.An optimum design value is proposed.This work can provide a reference for the design of high-temperature and high-pressure valves.
文摘In recent years,the concept of digital human has attracted widespread attention from all walks of life,and the modelling of high-fidelity human bodies,heads,and hands has been intensively studied.This paper focuses on head modelling and proposes a generic head parametric model based on neural radiance fields.Specifically,we first use face recognition networks and 3D facial expression database FaceWarehouse to parameterize identity and expression semantics,respectively,and use both as conditional inputs to build a neural radiance field for the human head,thereby improving the head model’s representation ability while ensuring editing capabilities for the identity and expression of the rendered results;then,through a combination of volume rendering and neural rendering,the 3D representation of the head is rapidly rendered into the 2D plane,producing a high-fidelity image of the human head.Thanks to the well-designed loss functions and good implicit representation of the neural radiance field,our model can not only edit the identity and expression independently,but also freely modify the virtual camera position of the rendering results.It has excellent multi-view consistency,and has many applications in novel view synthesis,pose driving and more.
基金supported by the Ministry of Education of the Russian Federation(Project No.1023032300071-6-2.3.1).
文摘An experimental investigation of the dynamics of the interface between two low-viscosity fluids with high density contrast oscillating in a fixed vertical slotted channel has been conducted.It has been found that as the amplitude of the liquid column oscillations increases,parametric oscillations of the interface are excited in the form of a standing wave located in the channel plane.In particular,depending on the interfacial tension,the standing waves have a frequency equal to that of liquid piston oscillations(harmonic response),or half of the frequency of oscillations of the liquid column in the channel(subharmonic response).The detected type of instability has a gravitational-capillary nature and is analogous to Faraday waves.The analysis of the overcritical dynamics of wave oscillations indicates that interfacial tension plays a crucial role in determining the type of parametric instability.At high interfacial tension,only synchronous(harmonic)wave modes are observed,and the threshold of the wave excitation is determined by the amplitude of piston oscillations of the liquid column.In this case,the oscillation acceleration does not play a role and has a small value in the threshold of the synchronous mode response.In the case of weak surface tension,subharmonic oscillations are observed.The threshold for the development of these oscillations is determined by the dimensionless acceleration of the oscillating liquid column and remains almost constant with variations in the dimensionless frequency of oscillations.At moderate values of interfacial tension(in the region of moderate dimensionless frequencies),a synchronous wave mode emerges in the stability threshold of the oscillating interface.As the dimensionless acceleration is increased further,a subharmonic mode is excited.The growth of subharmonic oscillations occurs against the background of harmonic wave oscillations,with the oscillations of the interface representing a combination of two standing waves.
基金supported by the National Natural Science Foundation of China(Grant Nos.52178175 and 52108182)the National Natural Science Foundation of Zhejiang Province(Grant No.LZ23E080003).
文摘Tensegrity structures,embodying the principles of continuous tensioning and discrete compression,have emerged as fundamental frameworks in locomotive soft robotics for navigating uneven and unpredictable environments,owing to their flexible and resilient traits.By means of a straightforward and cost-effective method to achieve structure-driven,vibration-driven tensegrity shows great potential,particularly in tasks demanding random exploration.However,the design guidance for vibration-driven tensegrity and their performance evaluation in unstructured terrain remain unrevealed due to the complex dynamics of the structure.This paper presents a small six-bar tensegrity robot,driven by wireless vibration motors,designed for deployment in disaster rescue and search scenarios.Finite element simulation is used to investigate how structural characteristics,excitation parameters,and the arrangement of motors affect the kinematic performance of this tensegrity system.A prototype of the six-bar tensegrity robot with three motors located on the lower ends of the three lower struts is designed and manufactured after the numerical simulations.A simple control policy which adjusts the motion of the tensegrity robot by turning on or off the motors on different locations is proposed.The prototype with and without the control policy is tested in man-made environments of various complexity.It shows that the ability and efficiency of the tensegrity robot in exploring unstructured environments is significantly enhanced by the proposed control policy.It is believed that the potential of the vibration-driven tensegrity robot could be further exploited by integrating multi-source sensors and more intelligent control policies.
基金supported by researchers Supporting Project Number(RSPD2025R548)King Saud University,Riyadh,Saudi Arabia.
文摘Accurately modeling heavy-tailed data is critical across applied sciences,particularly in finance,medicine,and actuarial analysis.This work presents the heavy-tailed power XLindley distribution(HTPXLD),a unique heavy-tailed distribution.Adding one more parameter to the power XLindley distribution improves this new distribution,especially when modeling leptokurtic lifetime data.The suggested density provides greater flexibility with asymmetric forms and different degrees of peakedness.Its statistical features,like the quantile function,moments,extropy measures,incomplete moments,stochastic ordering,and stress-strength parameters,are explored.We further investigate its use in actuarial science through the computation of pertinent metrics,such as value-at-risk,tail value-at-risk,tail variance,and tail variance premium.To obtain the point and interval parameter estimates,we use the maximum likelihood estimation approach.We do many simulation tests to evaluate the performance of our proposed estimator.Metrics like bias,relative bias,mean squared error,root mean squared error,average interval length,and coverage probability will be used in these tests to assess the estimator’s performance.To illustrate the practical value of our proposed model,we apply it to analyze three real-world datasets.We then compare its performance to established competing models,highlighting its advantages.
基金supported by the National Natural Science Foundation of China(No.52222501,52075016,52192632)the Fundamental Research Funds for the Central Universities(Grant No.YWF-23-L-904).
文摘Inflatable deployable structures inspired by origami have significant applications in space missions such as solar arrays and antennas.In this paper,a generalized Miura-ori tubular cell(GMTC)is presented as the basic cell to design a family of inflatable origami tubular structures with the targeted configuration.First,the classification of rigid foldable degree-4 vertices is studied thoroughly.Since the proposed GMTC is comprised of forming units(FU)and linking units(LU),types of FUs and LUs are investigated based on the classification of degree-4 vertices,respectively.The rigid foldability of the GMTC is presented by studying the kinematics of the FUs and LUs.Volume of the GMTC is analyzed to investigate multistable configurations of the basic cell.The variations in volume of the GMTC offer great potential for developing the inflatable tubular structure.Design method and parametric optimization of the tubular structure with targeted configuration are proposed.The feasibility of the approach is validated by the approximation of four different cases,namely parabolic,semicircular,trapezoidal,and straight-arc hybrid tubular structures.
基金Supported by the Natural Science Research Project of Anhui Educational Committee(Grant No.2024AH050129)。
文摘We prove the boundedness of the parametric Lusin's S functionμ_(S)^(?)(f)and Littlewood-Paley's g_(λ)^(*)-funtionμ_(λ),^(*,?)(f)on grand Herz-Morrey spaces with variable exponents.Additionally,we establish the boundedness of higher-order commutators ofμ_(S)^(?)andμ_(λ),^(*,?)with BMO functions applying some properties of variable exponents and generalized BMO norms.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 52471200, 12174165, and 52201219)。
文摘We utilize conventional wave-vector-resolved Brillouin light scattering technology to investigate the spin wave response in YIG thin films under high-power microwave excitation. By varying the microwave frequency, external bias magnetic field, and in-plane wave vector, in addition to observing the dipole-exchange spin waves excited by parallel parametric pumping, we further observe broadband spin wave excitation within the dipole-exchange spin wave spectrum. This broadband excitation results from the combined effects of parallel and perpendicular parametric pumping, induced by irregularities in the excitation geometry, as well as magnon–magnon scattering arising from the absence of certain spin wave modes. Our findings offer new insights into the mechanisms of energy dissipation and relaxation processes caused by spin wave excitation in magnetic devices operating at high power.
基金National Natural Science Foundation of China under Grant No.52478568National Key R&D Program of China under Grant Nos.2021YFC3100701 and 2022YFC3003503the Nature Science Foundation of Hubei Province under Grant No.2023AFA030。
文摘To analyze the correlation between the input energy parameters(V_(E))and typical intensity measures(IMs)of offshore ground motions,based on 273 earthquake events recorded by the K-NET in Japan,892 offshore ground motion records with moment magnitudes from 4.0 to 7.0 were used in this study.Residuals obtained through a ground motion model were calculated and analyzed for the correlation between V_(E) and amplitude,duration,frequency content and cumulative IMs.The results indicate that PGV and PGD have strong correlation with the V_(E)(T>0.2 s and T>0.4 s),the duration IMs have weakly negative correlation with the V_(E),Sd_(1) has a strong correlation with the V_(E) in the periods of T>0.4 s,T_(g) has a weak correlation with V_(E) and the cumulative IMs have strong correlation with the V_(E).The parametric predictive equations between typical IMs and V_(E) was proposed,and the differences between the prediction equations from the onshore ground motion records were compared.The differences in parametric predicted equations between offshore and onshore ground motions were confirmed in this study.Proposed correlation equations can be applied to offshore probabilistic seismic hazard analysis and the selection of ground motion records by generalized conditional intensity measures.
基金the financial support for this work provided by the National Natural Science Foundation of China(51974087)Anhui Provincial Natural Science Foundation(1908085QE203)+1 种基金University Natural Science Research Foundation of Anhui Province(2022AH050262)Science Research Foundation of Anhui Jianzhu University(2020QDZ02).
文摘To further enhance the recovery rate of low-temperature waste heat,the low-temperature flue gas in the sinter annular cooler was chosen as the heat source of an organic Rankine cycle(ORC)system,and the comprehensive evaluation of energy,exergy and economic performance of the ORC system was conducted deeply.The energy,exergy and economic performance models of the ORC system were established,and proper candidate organic working fluids(OWFs)were selected based on the thermo-physical properties of OWF and operating characteristics of ORC system.Then,the effects of ORC crucial parameters on the system energy,exergy and economic performances were evaluated in detail.Finally,the bi-objective optimization based on the genetic algorithm was conducted to analyze the optimal performance of the ORC system under the designed ORC crucial parameters,and the exergy efficiency and electricity production cost were set as the evaluation indexes of parametric optimization.The results indicate that the ORC system with the higher evaporation temperature and lower condensation temperature can obtain the larger system exergy efficiency and smaller electricity production cost.The smaller the superheat degree of OWF and pinch-point temperature difference in the evaporator are,the better the energy and exergy performances of the ORC system are.Under the optimization results,R245fa has the best comprehensive performance with the exergy efficiency of 46.34%and electricity production cost of 0.12123$/kWh among the selected candidate OWFs,which should be preferentially chosen as the OWF of the ORC system.
基金Project supported by the National Natural Science Foundation of China (Grant No. 62075010)。
文摘Photon pairs with large nondegeneracy have recently attracted increasing interest, which gives rise to an urgent demand for revealing their complete and accurate spectral distribution. By thoroughly analyzing parametric down-conversion(PDC), we put forward a model to directly describe the spatial-spectral distribution of these photon pairs, which is experimentally demonstrated by a 532-nm pumped type-I PDC in a beta barium borate(BBO) crystal. The measured spectral curves show good agreement with the theoretical predictions over the entire spectral range. We further demonstrate that, as signal wavelength increases, the photon pairs are initially spectrally distinguishable, then partly indistinguishable, finally completely indistinguishable with a maximum bandwidth of approximately 500 nm. Utilizing photon-number-resolving single-photon detectors(SPD), we observe the average photon number decreases significantly more slowly than the spectral intensity as the wavelength deviates from the peak, and the photon numbers follow a quasi-Poisson distribution well for wavelengths around the peak, but a thermal distribution better describes the statistics near the spectral boundaries. Finally,we use the signal photons as the trigger to generate heralded Fock states up to 10 photons in near-infrared range, which are suitable for quantum simulation and quantum key distribution in optical fiber networks.
基金Supported by National Key R&D Program of China(Grant No.2019YFE0121300)。
文摘Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycles.However,the effects of tooth geometry parameters could manifest as the meshing cycles increase.This study investigated the effects of tooth geometry parameters on the multi-cycle meshing temperature of polyoxymethylene(POM)worm gears,aiming to control the meshing temperature elevation by tuning the tooth geometry.Firstly,a finite element(FE)model capable of separately calculating the heat generation and simulating the heat propagation was established.Moreover,an adaptive iteration algorithm was proposed within the FE framework to capture the influence of the heat generation variation from cycle to cycle.This algorithm proved to be feasible and highly efficient compared with experimental results from the literature and simulated results via the full-iteration algorithm.Multi-cycle meshing temperature analyses were conducted on a series of POM worm gears with different tooth geometry parameters.The results reveal that,within the range of 14.5°to 25°,a pressure angle of 25°is favorable for reducing the peak surface temperature and overall body temperature of POM worm gears,which influence flank wear and load-carrying capability,respectively.However,addendum modification should be weighed because it helps with load bearing but increases the risk of severe flank wear.This paper proposes an efficient iteration algorithm for multi-cycle meshing temperature analysis of polymer gears and proves the feasibility of controlling the meshing temperature elevation during multiple cycles by tuning tooth geometry.
基金supported by the National Natural Science Foundation of China under Grant Nos.41977249 and 42090052the China Scholarship Council under file No.202204910040.
文摘Despite the prevalence and validity of the universal distinct element code(UDEC)in simulations in geotechnics domain,water-weakening process of rock models remains elusive.Prior research has made positive contributions to a presupposed link between modelling parameters and saturation degree,Sr.Nevertheless,this effort presents inaccurate results and limited implications owing to the misleading interpretation,that is,devoid of the basic logic in UDEC that modelling parameters should be calibrated by tested macroscopic properties in contrast to a presupposed relation with Sr.To fill this gap,a new methodology is proposed by coupling a computationally efficient parametric study with the simulation of water-weakening mechanisms.More specifically,tested macroscopic properties with different Sr values are input into parametric relations to acquire initial modelling parameters that are sequentially calibrated and modulated until simulations are in line with geomechanical tests.Illustrative example reveals that numerical water-weakening effects on macroscopic properties,mechanical behaviours,and failure configurations are highly consistent with tested ones with noticeable computational expediency,implying the feasibility and simplicity of this methodology.Furthermore,with compatibility across various numerical models,the proposed methodology substantially extends the applicability of UDEC in simulating water-weakening geotechnical problems.
基金supported by the National Natural Science Foundation of China(12061035)the Research Foundation of Jiangxi Science and Technology Normal University of China(2021QNBJRC003)supported by the Graduate Innovation Fund of Jiangxi Science and Technology Normal University(YC2024-X10).
文摘In this paper,the class of starlike functions of complex order γ(γ∈ℂ−{0})is extended from the case on unit disk U=(z∈C:|z|<1)to the case on the unit ball B in a complex Banach space or the unit polydisk U^(n) in C^(n).Let g be a convex function in U. We mainly establish the sharp bounds of all terms of homogeneous polynomial expansions for a subclass of g-parametric starlike mappings of complex order γ on B (resp.U^(n))when the mappings f are k-fold symmetric, k ∈ N. Our results partly solve the Bieberbach conjecture in several complex variables and generalize some prior works.
文摘This paper aims to evaluate the stochastic response of steel columns subjected to blast loads using the modified single degree of freedom(MSDOF)method,which assessed towards the conventional single degree of freedom(SDOF)and the experimentally validated Finite Element(FE)methods(LSDYNA).For this purpose,special atten-tion is given to calculating the response of H-shaped steel columns under blast.The damage amount is determined based on the support rotation criterion,which is expressed as a function of their maximum lateral mid-span dis-placement.To account for uncertainties in input parameters and obtain the failure probability,the Monte Carlo simulation(MCS)method is employed,complemented by the Latin Hypercube Sampling(LHS)method to reduce the number of simulations.A parametric analysis is hence performed to examine the effect of several input pa-rameters(including both deterministic and probabilistic parameters)on the probability of column damage as a function of support rotation.First,the MSDOF method confirms its higher accuracy in estimating the probability of column damage due to blast,compared to the conventional SDOF.The collected results also show that un-certainties of several input parameters have significant effects on the column behavior.In particular,geometric parameters(including cross-sectional characteristics,boundary conditions and column length)have major effect on the corresponding column response,in the same way of input blast load parameters and material properties.
基金The National Natural Science Foundation of China (No. 52368020)Gansu Provincial Universities Young Doctor Support Project (No. 2024QB-047)Gansu Province postdoctoral Fund (No. 386824)。
文摘To investigate the influence of the shear lag effect on the bending shear stress of single-box multicell box gird-ers(MCBG),the shear lag warping additional deflection is selected as the generalized displacement.The governing dif-ferential equations and boundary conditions for the shear lag of the MCBG are derived using the energy variational method.Based on the shear lag warping deformation state of the MCBG and by employing the microelement equilib-rium differential equation and the coordination conditions for shear lag warping deformation,the calculation method for the bending-warping shear stress of the MCBG is de-rived,and the influence of the width-to-span and height-to span ratios on bending-warping shear stress is analyzed.Ex-ample analysis shows that the bending-warping shear stress of the MCBG calculated by the proposed calculation method coincides with the finite element solution,and the warping shear stress satisfies the self-balancing condition of shear warping,thus verifying the accuracy of the proposed method.The warping shear stress exhibits an antisymmetric distribution about the vertical axis of symmetry and has a weakening effect on the shear stress of the elementary beam(EB).The larger the width-to-span ratio is,the larger the proportion of the warping shear stress of the EB.The larger the height-to-span ratio is,the smaller the proportion of the warping shear stress and the more significant the influence of the width-to-span ratio.The more the number of cells is,the smaller the influence of the warping shear stress on the total bending shear stress.The influence of the shear lag ef-fect can be ignored in the calculation of the bending shear stress of three or more cells in the MCBG.
基金supported by the National Natural Science Foundation of China(Grant Nos.52090081,52079068)the State Key Laboratory of Hydroscience and Hydraulic Engineering(Grant No.2021-KY-04).
文摘Accurate determination of rock mass parameters is essential for ensuring the accuracy of numericalsimulations. Displacement back-analysis is the most widely used method;however, the reliability of thecurrent approaches remains unsatisfactory. Therefore, in this paper, a multistage rock mass parameterback-analysis method, that considers the construction process and displacement losses is proposed andimplemented through the coupling of numerical simulation, auto-machine learning (AutoML), andmulti-objective optimization algorithms (MOOAs). First, a parametric modeling platform for mechanizedtwin tunnels is developed, generating a dataset through extensive numerical simulations. Next, theAutoML method is utilized to establish a surrogate model linking rock parameters and displacements.The tunnel construction process is divided into multiple stages, transforming the rock mass parameterback-analysis into a multi-objective optimization problem, for which multi-objective optimization algorithmsare introduced to obtain the rock mass parameters. The newly proposed rock mass parameterback-analysis method is validated in a mechanized twin tunnel project, and its accuracy and effectivenessare demonstrated. Compared with traditional single-stage back-analysis methods, the proposedmodel decreases the average absolute percentage error from 12.73% to 4.34%, significantly improving theaccuracy of the back-analysis. Moreover, although the accuracy of back analysis significantly increaseswith the number of construction stages considered, the back analysis time is acceptable. This studyprovides a new method for displacement back analysis that is efficient and accurate, thereby paving theway for precise parameter determination in numerical simulations.
