The evolution of a pure coherent state into a chaotic state is described very well by a master equation, as is validated via an examination of the coherent state＇s evolution during the diffusion process, fully utiliz...The evolution of a pure coherent state into a chaotic state is described very well by a master equation, as is validated via an examination of the coherent state＇s evolution during the diffusion process, fully utilizing the technique of integration within an ordered product （IWOP） of operators. The same equation also describes a limitation that maintains the coherence in a weak diffusion process, i.e., when the dissipation is very weak and the initial average photon number is large. This equation is dp/dt = -κ[a＋ap -a＋pa -apa＋ ＋ paa＋]. The physical difference between this diffusion equation and the better-known amplitude damping master equation is pointed out.展开更多
Spontaneous alpha oscillations are a ubiquitous phenomenon in the brain and play a key role in neural information processing and various cognitive functions.Jansen＇s neural mass model（NMM） was initially proposed to...Spontaneous alpha oscillations are a ubiquitous phenomenon in the brain and play a key role in neural information processing and various cognitive functions.Jansen＇s neural mass model（NMM） was initially proposed to study the origin of alpha oscillations.Most of previous studies of the spontaneous alpha oscillations in the NMM were conducted using numerical methods.In this study,we aim to propose an analytical approach using the describing function method to elucidate the spontaneous alpha oscillation mechanism in the NMM.First,the sigmoid nonlinear function in the NMM is approximated by its describing function,allowing us to reformulate the NMM and derive its standard form composed of one nonlinear part and one linear part.Second,by conducting a theoretical analysis,we can assess whether or not the spontaneous alpha oscillation would occur in the NMM and,furthermore,accurately determine its amplitude and frequency.The results reveal analytically that the interaction between linearity and nonlinearity of the NMM plays a key role in generating the spontaneous alpha oscillations.Furthermore,strong nonlinearity and large linear strength are required to generate the spontaneous alpha oscillations.展开更多
In this paper, we introduce the notion of a （2＋1）-dimenslonal differential equation describing three-dimensional hyperbolic spaces （3-h.s.）. The （2＋1）-dimensional coupled nonlinear Schrodinger equation and its...In this paper, we introduce the notion of a （2＋1）-dimenslonal differential equation describing three-dimensional hyperbolic spaces （3-h.s.）. The （2＋1）-dimensional coupled nonlinear Schrodinger equation and its sister equation, the （2＋1）-dimensional coupled derivative nonlinear Schrodinger equation, are shown to describe 3-h.s, The （2 ＋ 1 ）-dimensional generalized HF model：St=（1/2i[S,Sy]＋2iσS）x,σx=-1/4i tr（SSxSy）, in which S ∈ GLc（2）/GLc（1）×GLc（1）,provides another example of （2＋1）-dimensional differential equations describing 3-h.s. As a direct con-sequence, the geometric construction of an infinire number of conservation lairs of such equations is illustrated. Furthermore we display a new infinite number of conservation lairs of the （2＋1）-dimensional nonlinear Schrodinger equation and the （2＋1）-dimensional derivative nonlinear Schrodinger equation by a geometric way.展开更多
The present work deals with the behavior of fermions moving in a static magnetic induction and a time-harmonic electric field, both oriented along Oz. For the ultra-relativistic particles described by a Heun double co...The present work deals with the behavior of fermions moving in a static magnetic induction and a time-harmonic electric field, both oriented along Oz. For the ultra-relativistic particles described by a Heun double confluent equation, we derive the corresponding wave functions and the conserved current density components.展开更多
Instructions:Use the letters after the clues(information that helps you to find the answers)below to make words used to describe people.Then use the letters in the yellow boxes to make another word that describes some...Instructions:Use the letters after the clues(information that helps you to find the answers)below to make words used to describe people.Then use the letters in the yellow boxes to make another word that describes someone.展开更多
In this paper, the influence of sampling intervals on the chattering in sliding mode （SM） control systems is considered. The describing function （DF） approach is employed to analyze the chattering characteristics ...In this paper, the influence of sampling intervals on the chattering in sliding mode （SM） control systems is considered. The describing function （DF） approach is employed to analyze the chattering characteristics in the sampling SM control. By the DF calculations and limit cycle existence conditions, an unstable limit cycle and two stable limit cycles are found in the SM control system. The frequencies and amplitudes of the two limit cycles can also be estimated by graphical calculations. The estimation accuracy of chattering parameters is evaluated by the simulations. The results of simulations show that the system could converge to a large and a small limit cycle from different initial conditions.展开更多
Optical solitons,as self-sustaining waveforms in a nonlinear medium where dispersion and nonlinear effects are balanced,have key applications in ultrafast laser systems and optical communications.Physics-informed neur...Optical solitons,as self-sustaining waveforms in a nonlinear medium where dispersion and nonlinear effects are balanced,have key applications in ultrafast laser systems and optical communications.Physics-informed neural networks(PINN)provide a new way to solve the nonlinear Schrodinger equation describing the soliton evolution by fusing data-driven and physical constraints.However,the grid point sampling strategy of traditional PINN suffers from high computational complexity and unstable gradient flow,which makes it difficult to capture the physical details efficiently.In this paper,we propose a residual-based adaptive multi-distribution(RAMD)sampling method to optimize the PINN training process by dynamically constructing a multi-modal loss distribution.With a 50%reduction in the number of grid points,RAMD significantly reduces the relative error of PINN and,in particular,optimizes the solution error of the(2+1)Ginzburg–Landau equation from 4.55%to 1.98%.RAMD breaks through the lack of physical constraints in the purely data-driven model by the innovative combination of multi-modal distribution modeling and autonomous sampling control for the design of all-optical communication devices.RAMD provides a high-precision numerical simulation tool for the design of all-optical communication devices,optimization of nonlinear laser devices,and other studies.展开更多
The current journal is mainly focused in zoological systematics. According to Systematics Agenda 2000(1994), systematics is the science built on the following tasks: Taxonomy—the science of discovering, describing, a...The current journal is mainly focused in zoological systematics. According to Systematics Agenda 2000(1994), systematics is the science built on the following tasks: Taxonomy—the science of discovering, describing, and classifying species or groups of species(together termed taxa);Phylogenetic analysis—the discovery of the evolutionary relationships among a group of species;and Classification—the grouping of species, ultimately on the basis of evolutionary relationships.展开更多
INTRODUCTION.Crustal velocity model is crucial for describing the subsurface composition and structure,and has significant implications in offshore oil and gas exploration and marine geophysical engineering(Xie et al....INTRODUCTION.Crustal velocity model is crucial for describing the subsurface composition and structure,and has significant implications in offshore oil and gas exploration and marine geophysical engineering(Xie et al.,2024).Currently,travel time tomography is the most commonly used method for velocity modeling based on ocean bottom seismometer(OBS)data(Zhang et al.,2023;Sambolian et al.,2021).This method usually assumes that the sub-seafloor structure is layered,and therefore faces challenges in high-precision modeling with strong lateral discontinuities.展开更多
City designs and urban imaginaries often follow geocentric principles.Enault[1]describes that these principles reflect ethological and psychological theories of egocentrism and introduces how and where these are detec...City designs and urban imaginaries often follow geocentric principles.Enault[1]describes that these principles reflect ethological and psychological theories of egocentrism and introduces how and where these are detectable and made visible in the perceptions of urban citizens.A crucial element here is that distance is subjective.An equal distancemay,for example,be considered‘far’if onemust travel fromthe centre to the periphery,whereas the same distance is felt as‘nearby’if the direction is from the periphery to the centre.Based on this perception,most centric city(re-)designs use distance to the centre as a key indicator.An“x-minute city”design,with“x”being a variable such as 15,20,or 60,echoes this travel time and reflects the idea that a resident needs time-related proximity or accessibility to certain‘central’points of interest,such as stations,shops,medical services,government offices.On a larger scale,cities and countries are oftenmapped from the idea that a centre or central point of interest is also the most important location for all residents,which reflects an egocentric and centralistic territorial perspective.For this reason,many country maps and world maps also start from this central point of power and authority instead of reasoning from where the most relevant artefacts or activities take place.展开更多
The flutter characteristics of an actuator-fin system are investigated with structural nonlinearity and dynamic stiffness of the electric motor.The component mode substitution method is used to establish the nonlinear...The flutter characteristics of an actuator-fin system are investigated with structural nonlinearity and dynamic stiffness of the electric motor.The component mode substitution method is used to establish the nonlinear governing equations in time domain and frequency domain based on the fundamental dynamic equations of the electric motor and decelerator.The existing describing function method and a proposed iterative method are used to obtain the flutter characteristics containing preload freeplay nonlinearity when the control command is zero.A comparison between the results of frequency domain and those of time domain is studied.Simulations are carried out when the control command is not zero and further analysis is conducted when the freeplay angle is changed.The results show that structural nonlinearity and dynamic stiffness have a significant influence on the flutter characteristics.Limit cycle oscillations(LCOs)are observed within linear flutter boundary.The response of the actuator-fin system is related to the initial disturbance.In the nonlinear condition,the amplitude of the control command has an influence on the flutter characteristics.展开更多
The COVID-19 pandemic has posed a serious threat to global mental health.Multiple lines of evidence suggest that there is a varying yet considerable increase in mental health issues among the general population and vu...The COVID-19 pandemic has posed a serious threat to global mental health.Multiple lines of evidence suggest that there is a varying yet considerable increase in mental health issues among the general population and vulnerable groups.12 The aftermath is obscure and speculative from a social,economic,individual and public mental health perspective.Recently published studies support the existence of an emotional epidemic curve,describing a high probability of an increase in the burden of mental health issues in the post-pandemic era.34 Furthermore,previous major public health emergencies showed that more than half of the population devel-oped mental health problems and required mental health intervention.45 There is,therefore,an urgent need to reorganise existing mental health services to address the current unmet needs for mental health and to prepare for future challenges in the postpandemic era in terms of prevention and management.展开更多
Rough set theory has a very good effect in information processing and knowledge discovery.In an information table,the current scholars regard all objects as a universe,and then establish various rough set models.Howev...Rough set theory has a very good effect in information processing and knowledge discovery.In an information table,the current scholars regard all objects as a universe,and then establish various rough set models.However,in the analysis of many data problems,it is more reasonable to select parts of objects which are useful to us or can meet the actual needs as a universe.Therefore,in order to make up for the deficiency of traditional models,a new model is introduced from the perspective of variable universe.Then,some interesting properties of this model,such as approximation sets,reduct of attributes and maximum part of universe,are discussed.Through the study of this paper,it can be seen that the model developed in our paper is not only more accurate but also more effective in describing uncertain knowledge.展开更多
How nonlinear joints affect the response of large space structures is an important problem to investigate.In this paper,a multi-harmonic equivalent modeling method is presented to establish a frequency-domain model of...How nonlinear joints affect the response of large space structures is an important problem to investigate.In this paper,a multi-harmonic equivalent modeling method is presented to establish a frequency-domain model of planar repetitive structures with nonlinear joints.First,at the local level,the nonlinear joint is modeled by the multi-harmonic describing function matrix.The element of the hybrid beam is obtained by the dynamic condensation of the beam-joint element.Second,at the global level,the displacement-equivalence method is used to model the multi-harmonic Euler continuum beam equivalent to the planar repetitive structure.Then,the pseudo-arc-length continuation method is applied to track the multi-harmonic trajectory of response.Afterwards,an experiment is conducted to validate the correctness of the modeling method,considering the effect of hanging rope and air damping.In the numerical studies,several simulation results indicate the similarity of response between a single-degree-of-freedom system with a single nonlinear joint and the system of the planar repetitive structure with a large number of nonlinear joints.Finally,the component of higher-order harmonics is shown to be important for predicting the resonance frequencies and amplitudes.展开更多
A robust controller method for flexible joint robot considering the effect caused by nonlinear friction was presented.The nonlinear friction was denoted as inverse additive output uncertainty relative to the nominal m...A robust controller method for flexible joint robot considering the effect caused by nonlinear friction was presented.The nonlinear friction was denoted as inverse additive output uncertainty relative to the nominal model in our work,based on which the describing function was analyzed in frequency domain,and the weighting function of nonlinear friction was further calculated as well. By combining the friction uncertainty,the mixed sensitivity H∞optimization was proposed as the benchmark for controller design, which also leaded to good performance of robustness. Furthermore,unstructured perturbation to the system was analyzed so that the stability was guaranteed. Simulation results show that the proposed controller can provide excellent tracking and regulation performance.展开更多
The correlation analysis of sea clutter data in a complex domain is conducted in this study. Specific to X-band sea clutter, the statistical characteristics of the complex correlation, particularly the phase character...The correlation analysis of sea clutter data in a complex domain is conducted in this study. Specific to X-band sea clutter, the statistical characteristics of the complex correlation, particularly the phase characteristics which are closely related to the phase difference of the sea clutter and the Doppler properties, are analyzed in detail based on the experimental data, recorded by the Mc Master University IPIX radar in 1993. That the phase term of the complex correlation presents linear change means that there exists the linearity of phase differences between different time intervals in the X-band sea clutter. This investigation explores the regularities about the effect of wind on the complex correlation with similar patterns for different polarization modes. The regularities indicate that the wind direction can be inferred from the distribution pattern of the complex correlation. Moreover, a model describing the relationships between the statistics of the complex correlation and wind parameters is proposed. The application for target detection based on the differences of characteristics of complex correlations between the sea clutter and the target are also investigated and the proposed features have been confirmed. The principle of the method is fundamental for broader future applications.展开更多
This paper analyzes the language employed in the representations of women in Doukhobor Russian ritual texts called ＂ncanMbf＇ （psalms） from the viewpoint of linguistic text analysis performed in the Russian traditi...This paper analyzes the language employed in the representations of women in Doukhobor Russian ritual texts called ＂ncanMbf＇ （psalms） from the viewpoint of linguistic text analysis performed in the Russian tradition of folklore stylistics. While addressing the representations of Biblical female characters, such as the Holy Virgin Mary Magdalene, the Heavenly Bride, and the Whore of Babylon, along with the portrayals of Doukhobor and other women, the paper identifies stylistic features in their textual descriptions. The study establishes connections between Doukhobor texts and Russian folklore and liturgical tradition. The paper strives to identify the place of Doukhobor psalms as an integral part of the Russian literary and folklore heritage展开更多
MicroRNAs（miRNAs）are small noncoding RNAs of 19-24 nt and play important roles in post-transcriptional regulation of gene expression（Baek et al.,2008;Zhou et al.,2011）and various biological processes including gro...MicroRNAs（miRNAs）are small noncoding RNAs of 19-24 nt and play important roles in post-transcriptional regulation of gene expression（Baek et al.,2008;Zhou et al.,2011）and various biological processes including growth,展开更多
At present, the myopia illness of the students (including the students of university, middle schools andprimary schools) is a serious problem. For preventing and curing it, we must search for the developing lowsof myo...At present, the myopia illness of the students (including the students of university, middle schools andprimary schools) is a serious problem. For preventing and curing it, we must search for the developing lowsof myopia illness to provide the theory foundation for researches on and preventions from myopia illness.We provide the mathematial model on describing the poor eyesight of the students after analysing thedeveloping lows of the poor eyesight of the students as follows:where p(r,t) is the student’s myopia falling ill rate function at time t and age r, u(r) denotes the initial stagemyopia falling ill rate function and v(t), the baby myopia falling ill rate function. It is a first order quasi-展开更多
基金Project supported by the National Basic Research Program of China(Grant No.2012CB922103)the National Natural Science Foundation of China(GrantNos.11175113 and 11274104)the Natural Science Foundation of Hubei Province of China(Grant No.2011CDA021)
文摘The evolution of a pure coherent state into a chaotic state is described very well by a master equation, as is validated via an examination of the coherent state＇s evolution during the diffusion process, fully utilizing the technique of integration within an ordered product （IWOP） of operators. The same equation also describes a limitation that maintains the coherence in a weak diffusion process, i.e., when the dissipation is very weak and the initial average photon number is large. This equation is dp/dt = -κ[a＋ap -a＋pa -apa＋ ＋ paa＋]. The physical difference between this diffusion equation and the better-known amplitude damping master equation is pointed out.
基金Project supported by the National Natural Science Foundation of China(Grant No.61473208)the Tianjin Research Program of Application Foundation and Advanced Technology,China(Grant No.15JCYBJC47700)+1 种基金the National Institutes of Health,USA(Grant Nos.R01DA040990 and R01EY027544)the Project of Humanities and Social Sciences from the Ministry of Education,China(Grant No.17YJAZH092)
文摘Spontaneous alpha oscillations are a ubiquitous phenomenon in the brain and play a key role in neural information processing and various cognitive functions.Jansen＇s neural mass model（NMM） was initially proposed to study the origin of alpha oscillations.Most of previous studies of the spontaneous alpha oscillations in the NMM were conducted using numerical methods.In this study,we aim to propose an analytical approach using the describing function method to elucidate the spontaneous alpha oscillation mechanism in the NMM.First,the sigmoid nonlinear function in the NMM is approximated by its describing function,allowing us to reformulate the NMM and derive its standard form composed of one nonlinear part and one linear part.Second,by conducting a theoretical analysis,we can assess whether or not the spontaneous alpha oscillation would occur in the NMM and,furthermore,accurately determine its amplitude and frequency.The results reveal analytically that the interaction between linearity and nonlinearity of the NMM plays a key role in generating the spontaneous alpha oscillations.Furthermore,strong nonlinearity and large linear strength are required to generate the spontaneous alpha oscillations.
基金The project partially supported by National Natural Science Foundation of China
文摘In this paper, we introduce the notion of a （2＋1）-dimenslonal differential equation describing three-dimensional hyperbolic spaces （3-h.s.）. The （2＋1）-dimensional coupled nonlinear Schrodinger equation and its sister equation, the （2＋1）-dimensional coupled derivative nonlinear Schrodinger equation, are shown to describe 3-h.s, The （2 ＋ 1 ）-dimensional generalized HF model：St=（1/2i[S,Sy]＋2iσS）x,σx=-1/4i tr（SSxSy）, in which S ∈ GLc（2）/GLc（1）×GLc（1）,provides another example of （2＋1）-dimensional differential equations describing 3-h.s. As a direct con-sequence, the geometric construction of an infinire number of conservation lairs of such equations is illustrated. Furthermore we display a new infinite number of conservation lairs of the （2＋1）-dimensional nonlinear Schrodinger equation and the （2＋1）-dimensional derivative nonlinear Schrodinger equation by a geometric way.
文摘The present work deals with the behavior of fermions moving in a static magnetic induction and a time-harmonic electric field, both oriented along Oz. For the ultra-relativistic particles described by a Heun double confluent equation, we derive the corresponding wave functions and the conserved current density components.
文摘Instructions:Use the letters after the clues(information that helps you to find the answers)below to make words used to describe people.Then use the letters in the yellow boxes to make another word that describes someone.
基金supported by Industrial Research Projects in department of education of Shaanxi province(2014K05-29)Science Research Projects in department of education of Shaanxi province(14JK1669,14JF028)
文摘In this paper, the influence of sampling intervals on the chattering in sliding mode （SM） control systems is considered. The describing function （DF） approach is employed to analyze the chattering characteristics in the sampling SM control. By the DF calculations and limit cycle existence conditions, an unstable limit cycle and two stable limit cycles are found in the SM control system. The frequencies and amplitudes of the two limit cycles can also be estimated by graphical calculations. The estimation accuracy of chattering parameters is evaluated by the simulations. The results of simulations show that the system could converge to a large and a small limit cycle from different initial conditions.
基金supported by the National Key R&D Program of China(Grant No.2022YFA1604200)National Natural Science Foundation of China(Grant No.12261131495)+1 种基金Beijing Municipal Science and Technology Commission,Adminitrative Commission of Zhongguancun Science Park(Grant No.Z231100006623006)Institute of Systems Science,Beijing Wuzi University(Grant No.BWUISS21)。
文摘Optical solitons,as self-sustaining waveforms in a nonlinear medium where dispersion and nonlinear effects are balanced,have key applications in ultrafast laser systems and optical communications.Physics-informed neural networks(PINN)provide a new way to solve the nonlinear Schrodinger equation describing the soliton evolution by fusing data-driven and physical constraints.However,the grid point sampling strategy of traditional PINN suffers from high computational complexity and unstable gradient flow,which makes it difficult to capture the physical details efficiently.In this paper,we propose a residual-based adaptive multi-distribution(RAMD)sampling method to optimize the PINN training process by dynamically constructing a multi-modal loss distribution.With a 50%reduction in the number of grid points,RAMD significantly reduces the relative error of PINN and,in particular,optimizes the solution error of the(2+1)Ginzburg–Landau equation from 4.55%to 1.98%.RAMD breaks through the lack of physical constraints in the purely data-driven model by the innovative combination of multi-modal distribution modeling and autonomous sampling control for the design of all-optical communication devices.RAMD provides a high-precision numerical simulation tool for the design of all-optical communication devices,optimization of nonlinear laser devices,and other studies.
文摘The current journal is mainly focused in zoological systematics. According to Systematics Agenda 2000(1994), systematics is the science built on the following tasks: Taxonomy—the science of discovering, describing, and classifying species or groups of species(together termed taxa);Phylogenetic analysis—the discovery of the evolutionary relationships among a group of species;and Classification—the grouping of species, ultimately on the basis of evolutionary relationships.
基金financially supported by the National Key R&D Program of China(No.2023YFF0803404)the Zhejiang Provincial Natural Science Foundation(No.LY23D040001)+4 种基金the Open Research Fund of Key Laboratory of Engineering Geophysical Prospecting and Detection of Chinese Geophysical Society(No.CJ2021GB01)the Open Re-search Fund of Changjiang River Scientific Research Institute(No.CKWV20221011/KY)the ZhouShan Science and Technology Project(No.2023C81010)the National Natural Science Foundation of China(No.41904100)supported by Chinese Natural Science Foundation Open Research Cruise(Cruise No.NORC2019–08)。
文摘INTRODUCTION.Crustal velocity model is crucial for describing the subsurface composition and structure,and has significant implications in offshore oil and gas exploration and marine geophysical engineering(Xie et al.,2024).Currently,travel time tomography is the most commonly used method for velocity modeling based on ocean bottom seismometer(OBS)data(Zhang et al.,2023;Sambolian et al.,2021).This method usually assumes that the sub-seafloor structure is layered,and therefore faces challenges in high-precision modeling with strong lateral discontinuities.
文摘City designs and urban imaginaries often follow geocentric principles.Enault[1]describes that these principles reflect ethological and psychological theories of egocentrism and introduces how and where these are detectable and made visible in the perceptions of urban citizens.A crucial element here is that distance is subjective.An equal distancemay,for example,be considered‘far’if onemust travel fromthe centre to the periphery,whereas the same distance is felt as‘nearby’if the direction is from the periphery to the centre.Based on this perception,most centric city(re-)designs use distance to the centre as a key indicator.An“x-minute city”design,with“x”being a variable such as 15,20,or 60,echoes this travel time and reflects the idea that a resident needs time-related proximity or accessibility to certain‘central’points of interest,such as stations,shops,medical services,government offices.On a larger scale,cities and countries are oftenmapped from the idea that a centre or central point of interest is also the most important location for all residents,which reflects an egocentric and centralistic territorial perspective.For this reason,many country maps and world maps also start from this central point of power and authority instead of reasoning from where the most relevant artefacts or activities take place.
基金National Natural Science Foundation of China(90716006,10902006)Research Fund for the Doctoral Program of Higher Education of China(20091102110015)
文摘The flutter characteristics of an actuator-fin system are investigated with structural nonlinearity and dynamic stiffness of the electric motor.The component mode substitution method is used to establish the nonlinear governing equations in time domain and frequency domain based on the fundamental dynamic equations of the electric motor and decelerator.The existing describing function method and a proposed iterative method are used to obtain the flutter characteristics containing preload freeplay nonlinearity when the control command is zero.A comparison between the results of frequency domain and those of time domain is studied.Simulations are carried out when the control command is not zero and further analysis is conducted when the freeplay angle is changed.The results show that structural nonlinearity and dynamic stiffness have a significant influence on the flutter characteristics.Limit cycle oscillations(LCOs)are observed within linear flutter boundary.The response of the actuator-fin system is related to the initial disturbance.In the nonlinear condition,the amplitude of the control command has an influence on the flutter characteristics.
文摘The COVID-19 pandemic has posed a serious threat to global mental health.Multiple lines of evidence suggest that there is a varying yet considerable increase in mental health issues among the general population and vulnerable groups.12 The aftermath is obscure and speculative from a social,economic,individual and public mental health perspective.Recently published studies support the existence of an emotional epidemic curve,describing a high probability of an increase in the burden of mental health issues in the post-pandemic era.34 Furthermore,previous major public health emergencies showed that more than half of the population devel-oped mental health problems and required mental health intervention.45 There is,therefore,an urgent need to reorganise existing mental health services to address the current unmet needs for mental health and to prepare for future challenges in the postpandemic era in terms of prevention and management.
基金supported by the National Natural Science Foundation of China(Nos.61976254,61772002)the Natural Science Foundation of Fujian Province(No.2020J01707)National Fund Cultivation program of Jimei University(No.ZP2020056).
文摘Rough set theory has a very good effect in information processing and knowledge discovery.In an information table,the current scholars regard all objects as a universe,and then establish various rough set models.However,in the analysis of many data problems,it is more reasonable to select parts of objects which are useful to us or can meet the actual needs as a universe.Therefore,in order to make up for the deficiency of traditional models,a new model is introduced from the perspective of variable universe.Then,some interesting properties of this model,such as approximation sets,reduct of attributes and maximum part of universe,are discussed.Through the study of this paper,it can be seen that the model developed in our paper is not only more accurate but also more effective in describing uncertain knowledge.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.11827801,12172181 and 11732006).
文摘How nonlinear joints affect the response of large space structures is an important problem to investigate.In this paper,a multi-harmonic equivalent modeling method is presented to establish a frequency-domain model of planar repetitive structures with nonlinear joints.First,at the local level,the nonlinear joint is modeled by the multi-harmonic describing function matrix.The element of the hybrid beam is obtained by the dynamic condensation of the beam-joint element.Second,at the global level,the displacement-equivalence method is used to model the multi-harmonic Euler continuum beam equivalent to the planar repetitive structure.Then,the pseudo-arc-length continuation method is applied to track the multi-harmonic trajectory of response.Afterwards,an experiment is conducted to validate the correctness of the modeling method,considering the effect of hanging rope and air damping.In the numerical studies,several simulation results indicate the similarity of response between a single-degree-of-freedom system with a single nonlinear joint and the system of the planar repetitive structure with a large number of nonlinear joints.Finally,the component of higher-order harmonics is shown to be important for predicting the resonance frequencies and amplitudes.
基金National Natural Science Foundation of China(No.61273339)
文摘A robust controller method for flexible joint robot considering the effect caused by nonlinear friction was presented.The nonlinear friction was denoted as inverse additive output uncertainty relative to the nominal model in our work,based on which the describing function was analyzed in frequency domain,and the weighting function of nonlinear friction was further calculated as well. By combining the friction uncertainty,the mixed sensitivity H∞optimization was proposed as the benchmark for controller design, which also leaded to good performance of robustness. Furthermore,unstructured perturbation to the system was analyzed so that the stability was guaranteed. Simulation results show that the proposed controller can provide excellent tracking and regulation performance.
基金supported by the National Natural Science Foundation of China (61271406)
文摘The correlation analysis of sea clutter data in a complex domain is conducted in this study. Specific to X-band sea clutter, the statistical characteristics of the complex correlation, particularly the phase characteristics which are closely related to the phase difference of the sea clutter and the Doppler properties, are analyzed in detail based on the experimental data, recorded by the Mc Master University IPIX radar in 1993. That the phase term of the complex correlation presents linear change means that there exists the linearity of phase differences between different time intervals in the X-band sea clutter. This investigation explores the regularities about the effect of wind on the complex correlation with similar patterns for different polarization modes. The regularities indicate that the wind direction can be inferred from the distribution pattern of the complex correlation. Moreover, a model describing the relationships between the statistics of the complex correlation and wind parameters is proposed. The application for target detection based on the differences of characteristics of complex correlations between the sea clutter and the target are also investigated and the proposed features have been confirmed. The principle of the method is fundamental for broader future applications.
文摘This paper analyzes the language employed in the representations of women in Doukhobor Russian ritual texts called ＂ncanMbf＇ （psalms） from the viewpoint of linguistic text analysis performed in the Russian tradition of folklore stylistics. While addressing the representations of Biblical female characters, such as the Holy Virgin Mary Magdalene, the Heavenly Bride, and the Whore of Babylon, along with the portrayals of Doukhobor and other women, the paper identifies stylistic features in their textual descriptions. The study establishes connections between Doukhobor texts and Russian folklore and liturgical tradition. The paper strives to identify the place of Doukhobor psalms as an integral part of the Russian literary and folklore heritage
基金partly supported by the National Natural Science Foundation of China(Nos.61572363,91530321 and 61602347)the Natural Science Foundation of Shanghai(No.17ZR1445600)City University of Hong Kong(No.7004707)
文摘MicroRNAs（miRNAs）are small noncoding RNAs of 19-24 nt and play important roles in post-transcriptional regulation of gene expression（Baek et al.,2008;Zhou et al.,2011）and various biological processes including growth,
文摘At present, the myopia illness of the students (including the students of university, middle schools andprimary schools) is a serious problem. For preventing and curing it, we must search for the developing lowsof myopia illness to provide the theory foundation for researches on and preventions from myopia illness.We provide the mathematial model on describing the poor eyesight of the students after analysing thedeveloping lows of the poor eyesight of the students as follows:where p(r,t) is the student’s myopia falling ill rate function at time t and age r, u(r) denotes the initial stagemyopia falling ill rate function and v(t), the baby myopia falling ill rate function. It is a first order quasi-
