The effects of the built environment factors on urban vitality have attracted wide attention in the urban planning fields in recent years,but few studies have considered the variables’relative importance and their no...The effects of the built environment factors on urban vitality have attracted wide attention in the urban planning fields in recent years,but few studies have considered the variables’relative importance and their nonlinear effects on urban vitality.Taking a Chinese metropolis—Hangzhou as a case study,this study applied the gradient boosting decision tree(GBDT)model to explore the nonlinear effects of the 5D factors of the urban built environment on urban social vitality and economic vitality and the importance of variables.The results show that the GBDT model has better goodness of fit than the traditional ordinary least squares(OLS)regression in the urban vitality models.The urban built environment plays an important role in affecting urban vitality,while built environment designs witness the most important effect.Specifically,the density of shopping facilities,medical facilities,and road networks are the most important factors affecting urban social vitality,while road network density,destination accessibility,and population density play the most important roles in affecting urban economic vitality.Finally,the urban built environment factors have nonlinear threshold effects on both urban economic and social vitality in Hangzhou,with differing nonlinear response patterns observed between social and economic dimensions.展开更多
In semiconductor precision packaging and other applications involving alignment of automated equipment,the nonlinear motion caused by structural characteristics and friction effects on torque-type rotating motion stag...In semiconductor precision packaging and other applications involving alignment of automated equipment,the nonlinear motion caused by structural characteristics and friction effects on torque-type rotating motion stages seriously affects output accuracy and stability.To solve this problem,the motion characteristics of a rotating stage and the mechanism by which friction nonlinearity influences accuracy are analyzed in detail.In addition,a compound control strategy based on a kinematic model and the Stribeck friction model is designed.A friction disturbance observer based on output position feedback is improved for simple parameter tuning.Finally,an experimental system is constructed to carry out validation tests,including identification of nonlinear characteristics and performance comparisons.The experimental results show that the linear tracking error of the torque-type rotating stage is less than 1.47µm after adoption of the proposed model-based composite control strategy,and the corresponding rotary angle deviation is less than 0.0153°.The linearity of output motion is increased to 97.59%and the error compensation effect is improved by 51.6%compared with the PID control method.The experimental results confirm that the analysis method adopted here and the proposed compensation strategy can effectively reduce frictional nonlinearity and improve motion accuracy.The proposed method can also be applied to other precision electromechanical systems.展开更多
Nonlinear effect is of importance to waves propagating from deep water to shallow water. The non-linearity of waves is widely discussed due to its high precision in application. But there are still some problems in de...Nonlinear effect is of importance to waves propagating from deep water to shallow water. The non-linearity of waves is widely discussed due to its high precision in application. But there are still some problems in dealing with the nonlinear waves in practice. In this paper, a modified form of mild-slope equation with weakly nonlinear effect is derived by use of the nonlinear dispersion relation and the steady mild-slope equation containing energy dissipation. The modified form of mild-slope equation is convenient to solve nonlinear effect of waves. The model is tested against the laboratory measurement for the case of a submerged elliptical shoal on a slope beach given by Berkhoff et al. The present numerical results are also compared with those obtained through linear wave theory. Better agreement is obtained as the modified mild-slope equation is employed. And the modified mild-slope equation can reasonably simulate the weakly nonlinear effect of wave propagation from deep water to coast.展开更多
Digital structured light （SL） profilometry is increasingly used in three-dimensional （3D） measurement technology. However, the nonlinearity of the off-the-shelf projectors and cameras seriously reduces the measure...Digital structured light （SL） profilometry is increasingly used in three-dimensional （3D） measurement technology. However, the nonlinearity of the off-the-shelf projectors and cameras seriously reduces the measurement accuracy. In this paper, first, we review the nonlinear effects of the projector-camera system in the phase-shifting structured light depth measurement method. We show that high order harmonic wave components lead to phase error in the phase-shifting method. Then a practical method based on frequency domain filtering is proposed for nonlinear error reduction. By using this method, the nonlinear calibration of the SL system is not required. Moreover, both the nonlinear effects of the projector and the camera can be effectively reduced. The simulations and experiments have verified our nonlinear correction method.展开更多
The nonlinear effects of unsteady multi-scale shale gas percolation,such as desorption,slippage,diffusion,pressure-dependent viscosity,and compressibility,are investigated by numerical simulation.A new general mathema...The nonlinear effects of unsteady multi-scale shale gas percolation,such as desorption,slippage,diffusion,pressure-dependent viscosity,and compressibility,are investigated by numerical simulation.A new general mathematical model of the problem is built,in which the Gaussian distribution is used to describe the inhomogeneous intrinsic permeability.Based on the Boltzmann transformation,an efficient semi-analytical method is proposed.The problem is then converted into a nonlinear equation in an integral form for the pressure field,and a related explicit iteration scheme is constructed by numerical discretization.The validation examples show that the proposed method has good convergence,and the simulation results also agree well with the results obtained from both numerical and actual data of two vertical fractured test wells in the literature.Desorption,slippage,and diffusion have significant influence on shale gas flows.The accuracy of the usual technique that the product of viscosity and compressibility is approximated as its value at the average formation pressure is examined.展开更多
The calcium fluoride(CaF_(2))whispering gallery mode crystalline resonator is an excellent platform for nonlinear optical applications because of the decreasing in threshold caused by ultrahigh quality(Q)factor.In thi...The calcium fluoride(CaF_(2))whispering gallery mode crystalline resonator is an excellent platform for nonlinear optical applications because of the decreasing in threshold caused by ultrahigh quality(Q)factor.In this paper,we achieved the observation of Raman lasing,first-order Raman comb,and second-order Raman lasing in a CaF_(2)disk resonator with a diameter of 4.96 mm and an ultrahigh-Q of 8.43×10^(8)at 1550-nm wavelength.We also observed thermal effects in CaF_(2)disk resonator,and the threshold of thermo-optical oscillation is approximately coincident with Raman lasing,since the intracavity power increases rapidly when the power reaches the threshold,and higher input pump power results in longer thermal drift and higher Raman emission power.With a further increase in pump power,the optical frequency combs range is from 1520 nm to 1650 nm,with a wavelength interval of 4×FSR.It is a promising candidate for optical communication,biological environment monitoring,spectral analysis,and microwave signal sources.展开更多
In this work,a new structure is used to enhance the nonlinear effect in the cavity,which improvesthe performance of the 1.3μm broadband swept source.The swept source adopts a semiconductoroptical amplifier(SOA),a cir...In this work,a new structure is used to enhance the nonlinear effect in the cavity,which improvesthe performance of the 1.3μm broadband swept source.The swept source adopts a semiconductoroptical amplifier(SOA),a circulator,a coupler,and a tunable filter.In the structure,the lightpasses through the nonlinear medium(SOA)twice in two opposite directions,which excites thenonlinear ffect and increases the performance of the swept source.The tunable filter is based on apolygon rotating mirror and gratings.Traditionally,multiple SOAs are adopted to improve thesweep range and the optical power,which increases the cost and complexity of the swept source.The method proposed in this paper can improve the spectral range and optical power of the sweptsources without additional accessories.For the short-cavity swept source,the power increasesfrom 6 mW to 7.7 mW,and the sweep range increases from 98 nm to 120 nm.The broadband swept sources could have wide applications in biomedical imaging,sensor system,measurementand so on.展开更多
The response of subsoil strata subjected to seismic excitations plays an important role in governing the response of the overlying superstructures at any site. Ground response analysis(GRA) helps to assess the influen...The response of subsoil strata subjected to seismic excitations plays an important role in governing the response of the overlying superstructures at any site. Ground response analysis(GRA) helps to assess the influence of soil characteristics on the propagating seismic stress waves from the bedrock level to the ground surface during an earthquake. For the northeastern region of India, located in the highest seismic zone in the country, conducting an extensive GRA study is of prime importance. Conventionally, most of the GRA studies are carried out using the equivalent linear method, which, being a simplistic approach, cannot capture the nonlinear behavior of soil during seismic shaking. This paper presents the outcomes of a one-dimensional effective stress based nonlinear GRA conducted for Guwahati city(located in northeast India) incorporating the non-Masing load/unload/reload characteristics. The various ground response parameters evaluated from this study help in assessing the ground shaking, soil amplification, and site responses expected in this region. 2D contour maps, which are representative of the distribution of some of these parameters throughout Guwahati city, are also developed. The results presented herein can serve as guidelines for the design of foundations and superstructures in this region.展开更多
A dynamic model of DNA molecules which takes into account the interaction of the nearestbase pairs between the different strands is presented.The nonlinear effect and phase transition aresimulated by the nuclear trans...A dynamic model of DNA molecules which takes into account the interaction of the nearestbase pairs between the different strands is presented.The nonlinear effect and phase transition aresimulated by the nuclear transport theory and the method of fractorial moment in high energy physics,re-spectively.The results show that the nonlinear interaction of the nearest base pairs between the differentstrands may play a rule in DNA molecules.展开更多
Conventional methods for near-field characterization have typically relied on the nanoprobe to point-scan the field,rendering the measurements vulnerable to external environmental influences.Here,we study the direct f...Conventional methods for near-field characterization have typically relied on the nanoprobe to point-scan the field,rendering the measurements vulnerable to external environmental influences.Here,we study the direct far-field imaging of the near-field polarizations based on the four-wave mixing effect.We construct a simulation model to realize the instantaneous extraction of the near-field distributions of a wide range of structured light fields,such as cylindrical vector vortex beams,plasmonic Weber beams,and topological spin textures,including photonic skyrmions and merons.This method is valuable for the studies on manipulation of structured light fields and light-matter interaction at the micro/nano scales.展开更多
A drag-free satellite is an important platform for space-borne gravitational wave(GW)observation.To achieve the high-precision control of a drag-free satellite in practical engineering,an accurate dynamic model is ess...A drag-free satellite is an important platform for space-borne gravitational wave(GW)observation.To achieve the high-precision control of a drag-free satellite in practical engineering,an accurate dynamic model is essential.This paper presents a nonlinear model of the electrostatic effect between a satellite and a test mass(TM),and designs a model predictive controller based on the drag-free satellite model with the nonlinear electrostatic effect.To determine the analytical form of the electrostatic effect,a comprehensive theoretical analysis is performed for gravitational reference sensors(GRSs).An electrostatic force and a torque are simulated with the displacement as a varying parameter through a commercial software.Then,the results are fitted to derive the nonlinear expressions of the electrostatic effect.The model predictive controllers based on the models with the nonlinear and linear electrostatic effects are designed in the capture mode.Finally,the control results are given to show the advantages of the nonlinear electrostatic effect.展开更多
Under investigation is the n-component nonlinear Schrödinger equation with higher-order effects,which describes the ultrashort pulses in the birefringent fiber.Based on the Lax pair,the eigenfunction and generali...Under investigation is the n-component nonlinear Schrödinger equation with higher-order effects,which describes the ultrashort pulses in the birefringent fiber.Based on the Lax pair,the eigenfunction and generalized Darboux transformation are derived.Next,we construct several novel higher-order localized waves and classified them into three categories:(i)higher-order rogue waves interacting with bright/antidark breathers,(ii)higher-order breather fission/fusion,(iii)higherorder breather interacting with soliton.Moreover,we explore the effects of parameters on the structure,collision process and energy distribution of localized waves and these characteristics are significantly different from previous ones.Finally,the dynamical properties of these solutions are discussed in detail.展开更多
A unified mathematical model is established to simulate the nonlinear unsteady percolation of shale gas with the consideration of the nonlinear multi-scale effects such as slippage, diffusion, and desorption. The cont...A unified mathematical model is established to simulate the nonlinear unsteady percolation of shale gas with the consideration of the nonlinear multi-scale effects such as slippage, diffusion, and desorption. The continuous inhomogeneous models of equivalent porosity and permeability are proposed for the whole shale gas reservoir includ- ing the hydraulic fracture, the micro-fracture, and the matrix regions. The corresponding semi-analytical method is developed by transforming the nonlinear partial differential governing equation into the integral equation and the numerical discretization. The nonlinear multi-scale effects of slippage and diffusion and the pressure dependent effect of desorption on the shale gas production are investigated.展开更多
In the present paper, we use the Markov-switching model to test the nonlinear effects of government expenditure and taxes on private consumption in China. The results show that fiscal policy in China has a significant...In the present paper, we use the Markov-switching model to test the nonlinear effects of government expenditure and taxes on private consumption in China. The results show that fiscal policy in China has a significantly nonlinear effect. In years 1978-1980 and 1984- 1997, the effect of government consumption on private consumption is non-Keynesian. During the same periods, the effect of taxes is also non-Keynesian, but the effect is not significant. The effect of government investment is linear but asymmetric. After retesting the reasons for the existence of nonlinear effects, we find that in China initial fiscal conditions and the magnitude of fiscal consolidations are not related to the nonlinear effects of fiscal policy. The government should pay close attention to the characteristics of commodity and labor markets to identify the conditions and regimes associated with nonlinear effects.展开更多
We study the effects of mechanical nonlinearity arising from large thickness-shear deformation on the transient process of an AT-cut quartz plate resonator. Mindlin＇s two-dimensional plate equation is used, from whic...We study the effects of mechanical nonlinearity arising from large thickness-shear deformation on the transient process of an AT-cut quartz plate resonator. Mindlin＇s two-dimensional plate equation is used, from which a system of first-order nonlinear differential equations governing the evolution of the vibration amplitude is obtained. Numerical solutions by the Runge-Kutta method show that in common operating conditions of quartz resonators the nonlinear effect varies from noticeable to significant. As resonators are to be made smaller and thinner in the future with about the same power requirement, nonlinear effects will become more important and need more understanding and consideration in resonator design.展开更多
The scattering matrix theory has been developed to calculate the third-order nonlinear effect in sphere-grapheneslab structures. By designing structural parameters, we have demonstrated that the incident electromagnet...The scattering matrix theory has been developed to calculate the third-order nonlinear effect in sphere-grapheneslab structures. By designing structural parameters, we have demonstrated that the incident electromagnetic wave can be well confined in the graphene in these structures due to the formation of a bound state in the continuum(BIC) of radiation modes. Based on such a bound state, third-harmonic(TH) generation and four-wave mixing(FWM) have been studied. It is found that the efficiency of TH generation in monolayer graphene can be enhanced about 7 orders of magnitude. It is interesting that we can design structure parameters to make all beams(the pump beam, probe beam, and generated FWM signal) be BICs at the same time. In such a case, the efficiency of FWM in monolayer graphene can be enhanced about 9 orders of magnitude. Both the TH and FWM signals are sensitive to the wavelength, and possess high Q factors, which exhibit very good monochromaticity. By taking suitable BICs, the selective generation of TH and FWM signals for S-and P-polarized waves can also be realized,which is beneficial for the design of optical devices.展开更多
Knowledge of asymmetric catalytic reaction mechanism is very important for rational design and synthesis of new chiral catalysts or catalytic systems with high catalytic activity and stereoselectivity.The studies of n...Knowledge of asymmetric catalytic reaction mechanism is very important for rational design and synthesis of new chiral catalysts or catalytic systems with high catalytic activity and stereoselectivity.The studies of nonlinear effect have attracted wide attentions as a simple and practical mechanistic tool to probe complex asymmetric catalytic reactions.展开更多
Materials,where charge carriers have a linear energy dispersion,usually exhibit a strong nonlinear optical response in the absence of disorder scattering.This nonlinear response is particularly interesting in the tera...Materials,where charge carriers have a linear energy dispersion,usually exhibit a strong nonlinear optical response in the absence of disorder scattering.This nonlinear response is particularly interesting in the terahertz frequency region.We present a theoretical and numerical investigation of charge transport and nonlinear effects,such as the high harmonic generation in topological materials including Weyl semimetals(WSMs)and α-T_(3)systems.The nonlinear optical conductivity is calculated both semi-classically using the velocity operator and quantum mechanically using the density matrix.We show that the nonlinear response is strongly dependent on temperature and topological parameters,such as the Weyl point(WP)separation b and Berry phase ФB.A finite spectral gap opening can further modify the nonlinear effects.Under certain parameters,universal behaviors of both the linear and nonlinear response can be observed.Coupled with experimentally accessible critical field values of 10^(4)-10^(5) V=m,our results provide useful information on developing nonlinear optoelectronic devices based on topological materials.展开更多
基金National Social Science Foundation of China,No.20FJLB025National Natural Science Foundation of China,No.42471207,No.42471203Zhejiang Province Philosophy and Social Science Planning,Zhijiang Youth Special Project,24ZJQN118Y。
文摘The effects of the built environment factors on urban vitality have attracted wide attention in the urban planning fields in recent years,but few studies have considered the variables’relative importance and their nonlinear effects on urban vitality.Taking a Chinese metropolis—Hangzhou as a case study,this study applied the gradient boosting decision tree(GBDT)model to explore the nonlinear effects of the 5D factors of the urban built environment on urban social vitality and economic vitality and the importance of variables.The results show that the GBDT model has better goodness of fit than the traditional ordinary least squares(OLS)regression in the urban vitality models.The urban built environment plays an important role in affecting urban vitality,while built environment designs witness the most important effect.Specifically,the density of shopping facilities,medical facilities,and road networks are the most important factors affecting urban social vitality,while road network density,destination accessibility,and population density play the most important roles in affecting urban economic vitality.Finally,the urban built environment factors have nonlinear threshold effects on both urban economic and social vitality in Hangzhou,with differing nonlinear response patterns observed between social and economic dimensions.
基金funded by the European Union’s Horizon 2020 Research and Innovation Program under the Marie Sklodowska-Curie Grant Agreement(Grant No.101026104)by the National Natural Science Foundation of China(Grant No.U20A6004)in part by the State Key Laboratory of Precision Electronics Manufacturing Technology and Equipment(Grant No.JMDZ202314).
文摘In semiconductor precision packaging and other applications involving alignment of automated equipment,the nonlinear motion caused by structural characteristics and friction effects on torque-type rotating motion stages seriously affects output accuracy and stability.To solve this problem,the motion characteristics of a rotating stage and the mechanism by which friction nonlinearity influences accuracy are analyzed in detail.In addition,a compound control strategy based on a kinematic model and the Stribeck friction model is designed.A friction disturbance observer based on output position feedback is improved for simple parameter tuning.Finally,an experimental system is constructed to carry out validation tests,including identification of nonlinear characteristics and performance comparisons.The experimental results show that the linear tracking error of the torque-type rotating stage is less than 1.47µm after adoption of the proposed model-based composite control strategy,and the corresponding rotary angle deviation is less than 0.0153°.The linearity of output motion is increased to 97.59%and the error compensation effect is improved by 51.6%compared with the PID control method.The experimental results confirm that the analysis method adopted here and the proposed compensation strategy can effectively reduce frictional nonlinearity and improve motion accuracy.The proposed method can also be applied to other precision electromechanical systems.
文摘Nonlinear effect is of importance to waves propagating from deep water to shallow water. The non-linearity of waves is widely discussed due to its high precision in application. But there are still some problems in dealing with the nonlinear waves in practice. In this paper, a modified form of mild-slope equation with weakly nonlinear effect is derived by use of the nonlinear dispersion relation and the steady mild-slope equation containing energy dissipation. The modified form of mild-slope equation is convenient to solve nonlinear effect of waves. The model is tested against the laboratory measurement for the case of a submerged elliptical shoal on a slope beach given by Berkhoff et al. The present numerical results are also compared with those obtained through linear wave theory. Better agreement is obtained as the modified mild-slope equation is employed. And the modified mild-slope equation can reasonably simulate the weakly nonlinear effect of wave propagation from deep water to coast.
基金Project supported by the Science and Technology Major Projects of Zhejiang Province,China(Grant No.2013C03043-5)
文摘Digital structured light （SL） profilometry is increasingly used in three-dimensional （3D） measurement technology. However, the nonlinearity of the off-the-shelf projectors and cameras seriously reduces the measurement accuracy. In this paper, first, we review the nonlinear effects of the projector-camera system in the phase-shifting structured light depth measurement method. We show that high order harmonic wave components lead to phase error in the phase-shifting method. Then a practical method based on frequency domain filtering is proposed for nonlinear error reduction. By using this method, the nonlinear calibration of the SL system is not required. Moreover, both the nonlinear effects of the projector and the camera can be effectively reduced. The simulations and experiments have verified our nonlinear correction method.
基金Project supported by the National Program on Key Basic Research Project(973 Program)(No.2013CB228002)
文摘The nonlinear effects of unsteady multi-scale shale gas percolation,such as desorption,slippage,diffusion,pressure-dependent viscosity,and compressibility,are investigated by numerical simulation.A new general mathematical model of the problem is built,in which the Gaussian distribution is used to describe the inhomogeneous intrinsic permeability.Based on the Boltzmann transformation,an efficient semi-analytical method is proposed.The problem is then converted into a nonlinear equation in an integral form for the pressure field,and a related explicit iteration scheme is constructed by numerical discretization.The validation examples show that the proposed method has good convergence,and the simulation results also agree well with the results obtained from both numerical and actual data of two vertical fractured test wells in the literature.Desorption,slippage,and diffusion have significant influence on shale gas flows.The accuracy of the usual technique that the product of viscosity and compressibility is approximated as its value at the average formation pressure is examined.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51727808,51922009,52005457,and 62004179)the Fund from the Key Laboratory of Quantum Sensing and Precision Measurement of Shanxi Province,China(Grant No.201905D121001)。
文摘The calcium fluoride(CaF_(2))whispering gallery mode crystalline resonator is an excellent platform for nonlinear optical applications because of the decreasing in threshold caused by ultrahigh quality(Q)factor.In this paper,we achieved the observation of Raman lasing,first-order Raman comb,and second-order Raman lasing in a CaF_(2)disk resonator with a diameter of 4.96 mm and an ultrahigh-Q of 8.43×10^(8)at 1550-nm wavelength.We also observed thermal effects in CaF_(2)disk resonator,and the threshold of thermo-optical oscillation is approximately coincident with Raman lasing,since the intracavity power increases rapidly when the power reaches the threshold,and higher input pump power results in longer thermal drift and higher Raman emission power.With a further increase in pump power,the optical frequency combs range is from 1520 nm to 1650 nm,with a wavelength interval of 4×FSR.It is a promising candidate for optical communication,biological environment monitoring,spectral analysis,and microwave signal sources.
基金supported by the National Key R&D Program of China(2016YFF0102003 and 2016YFF0102000).
文摘In this work,a new structure is used to enhance the nonlinear effect in the cavity,which improvesthe performance of the 1.3μm broadband swept source.The swept source adopts a semiconductoroptical amplifier(SOA),a circulator,a coupler,and a tunable filter.In the structure,the lightpasses through the nonlinear medium(SOA)twice in two opposite directions,which excites thenonlinear ffect and increases the performance of the swept source.The tunable filter is based on apolygon rotating mirror and gratings.Traditionally,multiple SOAs are adopted to improve thesweep range and the optical power,which increases the cost and complexity of the swept source.The method proposed in this paper can improve the spectral range and optical power of the sweptsources without additional accessories.For the short-cavity swept source,the power increasesfrom 6 mW to 7.7 mW,and the sweep range increases from 98 nm to 120 nm.The broadband swept sources could have wide applications in biomedical imaging,sensor system,measurementand so on.
文摘The response of subsoil strata subjected to seismic excitations plays an important role in governing the response of the overlying superstructures at any site. Ground response analysis(GRA) helps to assess the influence of soil characteristics on the propagating seismic stress waves from the bedrock level to the ground surface during an earthquake. For the northeastern region of India, located in the highest seismic zone in the country, conducting an extensive GRA study is of prime importance. Conventionally, most of the GRA studies are carried out using the equivalent linear method, which, being a simplistic approach, cannot capture the nonlinear behavior of soil during seismic shaking. This paper presents the outcomes of a one-dimensional effective stress based nonlinear GRA conducted for Guwahati city(located in northeast India) incorporating the non-Masing load/unload/reload characteristics. The various ground response parameters evaluated from this study help in assessing the ground shaking, soil amplification, and site responses expected in this region. 2D contour maps, which are representative of the distribution of some of these parameters throughout Guwahati city, are also developed. The results presented herein can serve as guidelines for the design of foundations and superstructures in this region.
文摘A dynamic model of DNA molecules which takes into account the interaction of the nearestbase pairs between the different strands is presented.The nonlinear effect and phase transition aresimulated by the nuclear transport theory and the method of fractorial moment in high energy physics,re-spectively.The results show that the nonlinear interaction of the nearest base pairs between the differentstrands may play a rule in DNA molecules.
基金supported by the Guangdong Major Project of Basic Research(No.2020B0301030009)the National Natural Science Foundation of China(Nos.62075139,61935013,and 12004260)+4 种基金the Natural Science Foundation of Guangdong(No.2024A1515012503)the Innovation Team Project of Ordinary University of Guangdong Provincial Education Bureau(No.2024KCXTD014)the Shenzhen Science and Technology Program(Nos.RCJC20200714114435063 and JCYJ20241202124532024)the Research Team Cultivation Program of Shenzhen University(No.2023QNT012)the Shenzhen University 2035 Initiative(No.2023B004)。
文摘Conventional methods for near-field characterization have typically relied on the nanoprobe to point-scan the field,rendering the measurements vulnerable to external environmental influences.Here,we study the direct far-field imaging of the near-field polarizations based on the four-wave mixing effect.We construct a simulation model to realize the instantaneous extraction of the near-field distributions of a wide range of structured light fields,such as cylindrical vector vortex beams,plasmonic Weber beams,and topological spin textures,including photonic skyrmions and merons.This method is valuable for the studies on manipulation of structured light fields and light-matter interaction at the micro/nano scales.
基金supported by the National Key Research and Development Program of China(No.2022YFC2204800)the National Natural Science Foundation of China(No.W2433004)the Jiangsu Funding Program for Excellent Postdoctoral Talent of China(No.2024ZB114)。
文摘A drag-free satellite is an important platform for space-borne gravitational wave(GW)observation.To achieve the high-precision control of a drag-free satellite in practical engineering,an accurate dynamic model is essential.This paper presents a nonlinear model of the electrostatic effect between a satellite and a test mass(TM),and designs a model predictive controller based on the drag-free satellite model with the nonlinear electrostatic effect.To determine the analytical form of the electrostatic effect,a comprehensive theoretical analysis is performed for gravitational reference sensors(GRSs).An electrostatic force and a torque are simulated with the displacement as a varying parameter through a commercial software.Then,the results are fitted to derive the nonlinear expressions of the electrostatic effect.The model predictive controllers based on the models with the nonlinear and linear electrostatic effects are designed in the capture mode.Finally,the control results are given to show the advantages of the nonlinear electrostatic effect.
基金Project supported by the National Natural Science Foundation of China(Grant No.12271096)the Natural Science Foundation of Fujian Province(Grant No.2021J01302)。
文摘Under investigation is the n-component nonlinear Schrödinger equation with higher-order effects,which describes the ultrashort pulses in the birefringent fiber.Based on the Lax pair,the eigenfunction and generalized Darboux transformation are derived.Next,we construct several novel higher-order localized waves and classified them into three categories:(i)higher-order rogue waves interacting with bright/antidark breathers,(ii)higher-order breather fission/fusion,(iii)higherorder breather interacting with soliton.Moreover,we explore the effects of parameters on the structure,collision process and energy distribution of localized waves and these characteristics are significantly different from previous ones.Finally,the dynamical properties of these solutions are discussed in detail.
基金supported by the National Basic Research Program of China(973 Program)(No.2013CB228002)
文摘A unified mathematical model is established to simulate the nonlinear unsteady percolation of shale gas with the consideration of the nonlinear multi-scale effects such as slippage, diffusion, and desorption. The continuous inhomogeneous models of equivalent porosity and permeability are proposed for the whole shale gas reservoir includ- ing the hydraulic fracture, the micro-fracture, and the matrix regions. The corresponding semi-analytical method is developed by transforming the nonlinear partial differential governing equation into the integral equation and the numerical discretization. The nonlinear multi-scale effects of slippage and diffusion and the pressure dependent effect of desorption on the shale gas production are investigated.
基金supported by the Program for New Century Excellent Talents in University(NCET-10-0824)the Program of the Innovative Research Team of the Central University of Finance and Economics and the Program of Statistics Research in China(Grant number:2009LZ032)
文摘In the present paper, we use the Markov-switching model to test the nonlinear effects of government expenditure and taxes on private consumption in China. The results show that fiscal policy in China has a significantly nonlinear effect. In years 1978-1980 and 1984- 1997, the effect of government consumption on private consumption is non-Keynesian. During the same periods, the effect of taxes is also non-Keynesian, but the effect is not significant. The effect of government investment is linear but asymmetric. After retesting the reasons for the existence of nonlinear effects, we find that in China initial fiscal conditions and the magnitude of fiscal consolidations are not related to the nonlinear effects of fiscal policy. The government should pay close attention to the characteristics of commodity and labor markets to identify the conditions and regimes associated with nonlinear effects.
基金supported by the Program for New Century Excellent Talents in Universities(No.NCET-12-0625)the Natural Science Foundation for Distinguished Young Scholars of Jiangsu Province(No.SBK2014010134)+2 种基金the Fundamental Research Funds for Central Universities(No.NE2013101)the National Natural Science Foundation of China(No.11232007)a project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘We study the effects of mechanical nonlinearity arising from large thickness-shear deformation on the transient process of an AT-cut quartz plate resonator. Mindlin＇s two-dimensional plate equation is used, from which a system of first-order nonlinear differential equations governing the evolution of the vibration amplitude is obtained. Numerical solutions by the Runge-Kutta method show that in common operating conditions of quartz resonators the nonlinear effect varies from noticeable to significant. As resonators are to be made smaller and thinner in the future with about the same power requirement, nonlinear effects will become more important and need more understanding and consideration in resonator design.
基金National Key R&D Program of China(2017YFA0303800)National Natural Science Foundation of China(NSFC)(11574031,61421001)
文摘The scattering matrix theory has been developed to calculate the third-order nonlinear effect in sphere-grapheneslab structures. By designing structural parameters, we have demonstrated that the incident electromagnetic wave can be well confined in the graphene in these structures due to the formation of a bound state in the continuum(BIC) of radiation modes. Based on such a bound state, third-harmonic(TH) generation and four-wave mixing(FWM) have been studied. It is found that the efficiency of TH generation in monolayer graphene can be enhanced about 7 orders of magnitude. It is interesting that we can design structure parameters to make all beams(the pump beam, probe beam, and generated FWM signal) be BICs at the same time. In such a case, the efficiency of FWM in monolayer graphene can be enhanced about 9 orders of magnitude. Both the TH and FWM signals are sensitive to the wavelength, and possess high Q factors, which exhibit very good monochromaticity. By taking suitable BICs, the selective generation of TH and FWM signals for S-and P-polarized waves can also be realized,which is beneficial for the design of optical devices.
基金the National Key R&D Program of China(Grant No.2017YFA0700103)the NSFC(Grant Nos.22225107,21922112,21871258)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB20000000).
文摘Knowledge of asymmetric catalytic reaction mechanism is very important for rational design and synthesis of new chiral catalysts or catalytic systems with high catalytic activity and stereoselectivity.The studies of nonlinear effect have attracted wide attentions as a simple and practical mechanistic tool to probe complex asymmetric catalytic reactions.
文摘Materials,where charge carriers have a linear energy dispersion,usually exhibit a strong nonlinear optical response in the absence of disorder scattering.This nonlinear response is particularly interesting in the terahertz frequency region.We present a theoretical and numerical investigation of charge transport and nonlinear effects,such as the high harmonic generation in topological materials including Weyl semimetals(WSMs)and α-T_(3)systems.The nonlinear optical conductivity is calculated both semi-classically using the velocity operator and quantum mechanically using the density matrix.We show that the nonlinear response is strongly dependent on temperature and topological parameters,such as the Weyl point(WP)separation b and Berry phase ФB.A finite spectral gap opening can further modify the nonlinear effects.Under certain parameters,universal behaviors of both the linear and nonlinear response can be observed.Coupled with experimentally accessible critical field values of 10^(4)-10^(5) V=m,our results provide useful information on developing nonlinear optoelectronic devices based on topological materials.
