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ON THE SINGULAR PERTURBATION OF A NONLINEAR ORDINARY DIFFERENTIAL EQUATION WITH TWO PARAMETERS 被引量:3
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作者 张汉林 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 1989年第5期471-480,共10页
In this paper,the method of differential inequalities has been applied to study theboundary value problems of nonlinear ordinary differential equation with two parameters.The asymptotic solutions have been found and t... In this paper,the method of differential inequalities has been applied to study theboundary value problems of nonlinear ordinary differential equation with two parameters.The asymptotic solutions have been found and the remainders have been estimated. 展开更多
关键词 REAL ON THE SINGULAR PERTURBATION OF A NONLINEAR ORDINARY DIFFERENTIAL equation WITH TWO parameterS exp
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An Efficient Accurate Direct Solution of Poisson's Equation for Computation of Meteorological Parameters
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作者 D.R.Chakraborty P.S.Salvekar 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 1989年第4期501-508,共8页
Poisson's equation is solved numerically by two direct methods, viz. Block Cyclic Reduction (BCR) method and Fourier Method. Qualitative and quantitative comparison between the numerical solutions obtained by two ... Poisson's equation is solved numerically by two direct methods, viz. Block Cyclic Reduction (BCR) method and Fourier Method. Qualitative and quantitative comparison between the numerical solutions obtained by two methods indicates that BCR method is superior to Fourier method in terms of speed and accuracy. Therefore. BCR method is applied to solve (?)2(?)= ζ and (?)2X= D from observed vorticity and divergent values. Thereafter the rotational and divergent components of the horizontal monsoon wind in the lower troposphere are reconstructed and are com pared with the results obtained by Successive Over-Relaxation (SOR) method as this indirect method is generally in more use for obtaining the streamfunction ((?)) and velocity potential (X) fields in NWP models. It is found that the results of BCR method are more reliable than SOR method. 展开更多
关键词 An Efficient Accurate Direct Solution of Poisson’s equation for Computation of Meteorological parameters
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THE SOLVABILITY OF THE INITIAL-BOUNDARY PROBLEM FOR EQUATIONS IN COMBUSTION DYNAMICS WITH LARGY PARAMETER
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作者 林正国 《Acta Mathematica Scientia》 SCIE CSCD 1990年第3期281-292,共12页
In this paper, we study the initial-boundary value problem with rigid wall for the equations in combustion dynamics with largy parameter. Introducing variable scalar norms and two seminorms, making use of the vorticit... In this paper, we study the initial-boundary value problem with rigid wall for the equations in combustion dynamics with largy parameter. Introducing variable scalar norms and two seminorms, making use of the vorticity operator, overcome the difficulty from the large parameter. By energy estimation, the existence and unique theorems of local smooth solution is proved. 展开更多
关键词 THE SOLVABILITY OF THE INITIAL-BOUNDARY PROBLEM FOR equationS IN COMBUSTION DYNAMICS WITH LARGY parameter
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Integral Operator Solving Process of the Boundary Value Problem of Abstract Kinetic Equation with the First Kind of Critical Parameter and Generalized Periodic Boundary Conditions
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作者 YU De-jian 《Chinese Quarterly Journal of Mathematics》 CSCD 2010年第1期110-117,共8页
In this paper the concepts of the boundary value problem of abstract kinetic equation with the first kind of critical parameter γ 0 and generalized periodic boundary conditions are introduced in a Lebesgue space whic... In this paper the concepts of the boundary value problem of abstract kinetic equation with the first kind of critical parameter γ 0 and generalized periodic boundary conditions are introduced in a Lebesgue space which consists of functions with vector valued in a general Banach space, and then describe the solution of these abstract boundary value problem by the abstract linear integral operator of Volterra type. We call this process the integral operator solving process. 展开更多
关键词 abstract kinetic equation with the first kind of critical parameter boundary value problem of abstract kinetic equation generalized periodic boundary conditions abstract linear integral operator of Volterra type integral operator solving process
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Dynamics and adaptive control of a dual-arm space robot with closed-loop constraints and uncertain inertial parameters 被引量:20
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作者 Ying-Hong Jia Quan Hu Shi-Jie Xu 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2014年第1期112-124,共13页
A dynamics-based adaptive control approach is proposed for a planar dual-arm space robot in the presence of closed-loop constraints and uncertain inertial parameters of the payload. The controller is capable of contro... A dynamics-based adaptive control approach is proposed for a planar dual-arm space robot in the presence of closed-loop constraints and uncertain inertial parameters of the payload. The controller is capable of controlling the po- sition and attitude of both the satellite base and the payload grasped by the manipulator end effectors. The equations of motion in reduced-order form for the constrained system are derived by incorporating the constraint equations in terms of accelerations into Kane's equations of the unconstrained system. Model analysis shows that the resulting equations perfectly meet the requirement of adaptive controller design. Consequently, by using an indirect approach, an adaptive control scheme is proposed to accomplish position/attitude trajectory tracking control with the uncertain parameters be- ing estimated on-line. The actuator redundancy due to the closed-loop constraints is utilized to minimize a weighted norm of the joint torques. Global asymptotic stability is proven by using Lyapunov's method, and simulation results are also presented to demonstrate the effectiveness of the proposed approach. 展开更多
关键词 Space robot Dynamics. Adaptive control Closed-loop constraint parameter uncertainty - Kane's equation
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CONSTITUTIVE EQUATION OF A NEW AVIATION LUBRICATING OIL 被引量:6
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作者 DENG Sier TENG Hongfei +2 位作者 WANG Yanshuang LI Yunfeng YANG Boyuan 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2007年第5期28-31,共4页
The traction of a new aviation lubricating oil was measured on a self-made test rig. The calculating formulae of the rheological parameters of the oil such as Erying stress, limiting shear stress and shear elastic mod... The traction of a new aviation lubricating oil was measured on a self-made test rig. The calculating formulae of the rheological parameters of the oil such as Erying stress, limiting shear stress and shear elastic modulus were obtained under the condition of the high shear strain rate in elastohydrodynamic lubrication(EHL). The constitutive equation of this oil was determined and verified by test. The results of experiments show that the behavior of the new aviation lubricating oil behaves as visco-elastic fluid and the theoretical value agrees fairly well with the measured data, which implies that the constitutive equation of this oil is correct and feasible. 展开更多
关键词 Lubricating oil Constitutive equation Rheological parameters Traction
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Artificial Sun synchronous frozen orbit control scheme design based on J_2 perturbation 被引量:2
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作者 Gong-Bo Wang Yun-He Meng Wei Zheng Guo-Jian Tang 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2011年第5期809-816,共8页
Sun synchronous orbit and frozen orbit formed due to J 2 perturbation have very strict constraints on orbital parameters,which have restricted the application a lot.In this paper,several control strategies were illust... Sun synchronous orbit and frozen orbit formed due to J 2 perturbation have very strict constraints on orbital parameters,which have restricted the application a lot.In this paper,several control strategies were illustrated to realize Sun synchronous frozen orbit with arbitrary orbital elements using continuous low-thrust.Firstly,according to mean element method,the averaged rate of change of the orbital elements,originating from disturbing constant accelerations over one orbital period,was derived from Gauss' variation of parameters equations.Then,we proposed that binormal acceleration could be used to realize Sun synchronous orbit,and radial or transverse acceleration could be adopted to eliminate the rotation of the argument of the perigee.Finally,amending methods on the control strategies mentioned above were presented to eliminate the residual secular growth.Simulation results showed that the control strategies illustrated in this paper could realize Sun synchronous frozen orbit with arbitrary orbital elements,and can save much more energy than the schemes presented in previous studies,and have no side effect on other orbital parameters' secular motion. 展开更多
关键词 Continuous low-thrust Artificial Sun synchronous orbit Artificial frozen orbit Gauss' variation of parameters equations Mean element method
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Atrazine Adsorption Behavior on a Fluvo-Aquic Soil as Influenced by Contact Periods 被引量:2
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作者 DENG Jian-Cai JIANG Xin +3 位作者 LU Xin YU Gui-Fen Wang Fang ZHANG Bin 《Pedosphere》 SCIE CAS CSCD 2007年第6期786-791,共6页
A batch experiment was performed to investigate nonequilibrium adsorption behavior of atrazine (2-chloro-4-ethylamino-6-isopropylamlno-1,3,5-triazlne) on a fluvo-aquic soil. The amount of atrazine sorbed increased w... A batch experiment was performed to investigate nonequilibrium adsorption behavior of atrazine (2-chloro-4-ethylamino-6-isopropylamlno-1,3,5-triazlne) on a fluvo-aquic soil. The amount of atrazine sorbed increased with increasing adsorption contact periods. For a range of initial atrazlne concentrations, the percentage of atrazine sorbed within 24 h ranged from 24% to 77% of the observed total amount sorbed for the longest contact period; when adsorption contact periods were more than 72 h, the deviations in curves fitted using a nonlinear Freundllch equation gradually became less. The opposite trend was observed for the atrazine concentrations in solution. The effect of adsorption contact periods on atrazine adsorption behavior was evaluated by interpreting the temporal variations in linear and nonlinear Freundlich equation parameters obtained from the phase-distribution relationships. As the adsorption contact period increased, the nonlinear Freundlich capacity coefficient kf showed a significant linear increase (r^2 = 0.9063, P 〈 0.001). However, a significant negative linear correlation was observed for the nonlinear coefficient n, a dimensionless parameter (r^2 = 0.5666, P 〈 0.05). Furthermore, the linear distribution coefficient kd ranged from 0.38 to 1.44 and exhibited a significant linear correlation to the adsorption contact period (r^2 = 0.72, P 〈 0.01). The parameters kf and n obtained from a time-dependent isotherm rather than the distribution coefficient kd estimated using the linear Freundlich equation were more appropriate to predict the herbicide residue in the field and thus more meaningful for environmental assessment. 展开更多
关键词 adsorption contact periods ATRAZINE fluvo-aquic soil Freundlich equation parameters
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THEORETICAL PREDICTION OF THE KINETICS CURVES OFPEARLITIC TRANSFORMATION IN HYPO-PROEUTECTOID STRUCTURAL STEELS 被引量:4
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作者 Z.G.Li H.B.Chang +2 位作者 T.Y.Hsu Z.Y.Xu X.Y.Ruan 《Acta Metallurgica Sinica(English Letters)》 SCIE EI CAS CSCD 1998年第3期215-224,共10页
Supposing carbon contents of ferrite phases in pearlite precipitating from austenite in multicomponent steel at temperature T and in Fe-C ystem at T' are the same the pearlite formation temperature diference, can ... Supposing carbon contents of ferrite phases in pearlite precipitating from austenite in multicomponent steel at temperature T and in Fe-C ystem at T' are the same the pearlite formation temperature diference, can be calculated from the FeX phase diagrams and the equilibrium temperature Al. Using Tp and Fe-C binary thermodynamic model, the driving forces for phase transformation from austenite to pearlite in multicomponent steels have been successfully calculated. Through the combination of simplified Zener and Hillert's model for pearlite growth with Johnson-Mehl equation, using data from known TTT diagrams, the interfacial energy parameter and activation energy for pearlite formation can be determined and expressed as functions of chemical composition in steels by regression analysis. The calculated starting curves of pearlitic transformation in some commercial steels agree well with the experimental data. 展开更多
关键词 pearlite formation temperature difference interfacial energy parameter activation enerpy for pearlite transformation Johnson-Mehl equation
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Robust Estimation of Parameters in Nonlinear Ordinary Differential Equation Models 被引量:1
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作者 QIU Yanping HU Tao +1 位作者 LIANG Baosheng CUI Hengjian 《Journal of Systems Science & Complexity》 SCIE EI CSCD 2016年第1期41-60,共20页
Ordinary differential equation(ODE) models are widely used to model dynamic processes in many scientific fields.Parameter estimation is usually a challenging problem,especially in nonlinear ODE models.The most popular... Ordinary differential equation(ODE) models are widely used to model dynamic processes in many scientific fields.Parameter estimation is usually a challenging problem,especially in nonlinear ODE models.The most popular method,nonlinear least square estimation,is shown to be strongly sensitive to outliers.In this paper,robust estimation of parameters using M-estimators is proposed,and their asymptotic properties are obtained under some regular conditions.The authors also provide a method to adjust Huber parameter automatically according to the observations.Moreover,a method is presented to estimate the initial values of parameters and state variables.The efficiency and robustness are well balanced in Huber estimators,which is demonstrated via numerical simulations and chlorides data analysis. 展开更多
关键词 Asymptotic properties Huber parameter ordinary differential equation robust estimation
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A computational model of the human glucose-insulin regulatory system 被引量:2
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作者 Keh-Dong Shiang Fouad Kandeel 《The Journal of Biomedical Research》 CAS 2010年第5期347-364,共18页
Objective:A computational model of insulin secretion and glucose metabolism for assisting the diagnosis of diabetes mellitus in clinical research is introduced.The proposed method for the estimation of parameters for... Objective:A computational model of insulin secretion and glucose metabolism for assisting the diagnosis of diabetes mellitus in clinical research is introduced.The proposed method for the estimation of parameters for a system of ordinary differential equations(ODEs)that represent the time course of plasma glucose and insulin concentrations during glucose tolerance test(GTT)in physiological studies is presented.The aim of this study was to explore how to interpret those laboratory glucose and insulin data as well as enhance the Ackerman mathematical model.Methods:Parameters estimation for a system of ODEs was performed by minimizing the sum of squared residuals(SSR)function,which quantifies the difference between theoretical model predictions and GTT's experimental observations.Our proposed perturbation search and multiple-shooting methods were applied during the estimating process.Results:Based on the Ackerman's published data,we estimated the key parameters by applying R-based iterative computer programs.As a result,the theoretically simulated curves perfectly matched the experimental data points.Our model showed that the estimated parameters,computed frequency and period values,were proven a good indicator of diabetes.Conclusion:The present paper introduces a computational algorithm to biomedical problems,particularly to endocrinology and metabolism fields,which involves two coupled differential equations with four parameters describing the glucose-insulin regulatory system that Ackerman proposed earlier.The enhanced approach may provide clinicians in endocrinology and metabolism field insight into the transition nature of human metabolic mechanism from normal to impaired glucose tolerance. 展开更多
关键词 Coupled ordinary differential equations glucose tolerance test parameters estimation sum of squared residuals cost function multiple shooting method
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Exploring traffic safety climate with driving condition and driving behaviour:a random parameter structural equation model approach
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作者 Daiquan Xiao Xiaofei Jin +2 位作者 Xuecai Xu Changxi Ma Quan Yuan 《Transportation Safety and Environment》 EI 2021年第3期304-315,共12页
This study aimed to explore traffic safety climate by quantifying driving conditions and driving behaviour.To achieve the objective,the random parameter structural equation model was proposed so that driver action and... This study aimed to explore traffic safety climate by quantifying driving conditions and driving behaviour.To achieve the objective,the random parameter structural equation model was proposed so that driver action and driving condition can address the safety climate by integrating crash features,vehicle profiles,roadway conditions and environment conditions.The geo-localized crash open data of Las Vegas metropolitan area were collected from 2014 to 2016,including 27 arterials with 16827 injury samples.By quantifying the driving conditions and driving actions,the random parameter structural equation model was built up with measurement variables and latent variables.Results revealed that the random parameter structural equation model can address traffic safety climate quantitatively,while driving conditions and driving actions were quantified and reflected by vehicles,road environment and crash features correspondingly.The findings provide potential insights for practitioners and policy makers to improve the driving environment and traffic safety culture. 展开更多
关键词 traffic safety culture traffic safety climate random parameter structural equation model driving condition driving behaviour
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Viscous holographic f(Q)cosmology with some versions of holographic dark energy with generalized cut-offs
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作者 Gargee Chakraborty Surajit Chattopadhyay Ertan Güdekli 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2021年第12期519-530,共12页
The work reported in this paper demonstrates the cosmology of f(Q)gravity and the reconstruction of various associated parameters with different versions of holographic dark energy with generalized cut-offs,where Q=6 ... The work reported in this paper demonstrates the cosmology of f(Q)gravity and the reconstruction of various associated parameters with different versions of holographic dark energy with generalized cut-offs,where Q=6 H^(2).The Universe is considered to be filled with viscous fluid characterized by a viscous pressureΠ=-3 Hξ,whereξ=ξ0+ξ1 H+ξ2(˙H+H^(2)and H is the Hubble parameter.Considering the power law form of expansion,we have derived the expression of f(Q)under a non-viscous holographic framework and it is then extended to viscous cosmological settings with extended generalized holographic Ricci dark energy.The forms of f(Q)for both the cases are found to be monotonically increasing functions of Q.In the viscous holographic framework,f(Q)is reconstructed as a function of cosmic time t and is found to stay at a positive level with Nojiri-Odintsov cut-off.In these cosmological settings,the slow roll parameters are computed and a scope of exit from inflation and quasiexponential expansion are found to be available.Finally,it is observed that warm inflationary expansion can be obtained from this model. 展开更多
关键词 Holographic dark energy Ricci dark energy f(Q)gravity bulk-viscosity equation of state parameter slow roll parameter
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The Role of Technology in the Process of Learning Mathematics
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作者 Costica Lupu 《American Journal of Operations Research》 2015年第2期89-94,共6页
The research was achieved by applying several questionnaires and evaluation tests that have shown the efficacy of using the computer in building active thought and skills in the graphical representation of functions ,... The research was achieved by applying several questionnaires and evaluation tests that have shown the efficacy of using the computer in building active thought and skills in the graphical representation of functions , within a Cartesian reference system xOy. Our research was based on the following hypothesis: if we systematically use, in lessons of algebra and mathematical analysis, the GeoGebra software for drawing the graph of a function, then we shall contribute to building attitudes and competences in using the computer for the graphical representation of functions , within a Cartesian reference system xOy. The purpose of our study is to present a practical computer use model for the students from the Pre- and In-Service Teacher Training Department, “Vasile Alecsandri” University of Bacau, during their pedagogical practice stage of continuous training, aimed at building practical skills in supporting the teaching-learning process with computers. To deal with these issues, we are trying to find the best teaching-learning strategies by using the calculus technique. The research was conducted at the “Stefan cel Mare” National Pedagogical College from Bacau, by assisting 20 lessons of mathematics and 20 lessons of Information and Communication Technology, involving a group of 104 students in the 11th grade. In order to verify the hypothesis, we have established several objectives that orient and guide our activity: knowing the initial level of mathematical training in terms of graphical representation of functions;identifying the frame and reference objectives of the curriculum for mathematical education regarding the graphical representation of functions;designing and conducting a teaching process focused on the use of the computer and the GeoGebra software in learning the graphical representation of functions;final evaluation of the students’ level of training regarding the graphical representation of functions in a plane. 展开更多
关键词 Ameliorative and Formative Research Teaching and Learning Graphical Representation equations with parameter
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Bianchi type V universe with bulk viscous matter and time varying gravitational and cosmological constants
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作者 Prashant Singh Baghel Jagdish Prasad Singh 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2012年第11期1457-1466,共10页
We consider spatially homogeneous and anisotropic Bianchi type V space- time with a bulk viscous fluid source, and time varying gravitational constant G and cosmological term A. The coefficient of bulk viscosity ζ is... We consider spatially homogeneous and anisotropic Bianchi type V space- time with a bulk viscous fluid source, and time varying gravitational constant G and cosmological term A. The coefficient of bulk viscosity ζ is assumed to be a simple linear function of the Hubble parameter H (i.e. ζ = ζ0 + ζ1H, where ζ0 and ζ1 are constants). The Einstein field equations are solved explicitly by using a law of varia- tion for the Hubble parameter, which yields a constant value of the deceleration pa- rameter. Physical and kinematical parameters of the models are discussed. The models are found to be compatible with the results of astronomical observations. 展开更多
关键词 bulk viscosity -- Bianchi V -- relativity: equation of state -- cosmology:cosmological parameters -- miscellaneous
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Observational Hubble parameter data constraints on the interactive model of f(T) gravity with particle creation
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作者 S.Ganjizadeh Alireza Amani M.A.Ramzanpour 《Chinese Physics C》 SCIE CAS CSCD 2022年第12期288-297,共10页
In this study,we consider an open system from the thermodynamic perspective for an adiabatic FRW universe model in which particle creation occurs within the system.In this case,the modified continuity equation is obta... In this study,we consider an open system from the thermodynamic perspective for an adiabatic FRW universe model in which particle creation occurs within the system.In this case,the modified continuity equation is obtained,and then,we make it correspond to the continuity equation of f(T)gravity.Therefore,we take f(T)gravity with a viscous fluid in the flat-FRW metric,where T is the torsion scalar.We assume the contents of the universe to be dark matter and dark energy and consider an interaction term between them.An interesting point of this study is that we make the modified continuity equation resulting from particle creation equivalent to the matter continuity equation resulting from f(T)gravity.The result of this evaluation establishes a relationship between the number of particles and scale factor.In what follows,we write the corresponding cosmological parameters in terms of the number of particles and also reconstruct the number of particles in terms of the redshift parameter.We then parameterize the Hubble parameter derived from power-law cosmology with 51 data points from the Hubble observational parameter data.Next,we plot the corresponding cosmological parameters for dark energy in terms of the redshift to investigate the accelerated expansion of the universe.In addition,by using the sound speed parameter,we discuss the stability and instability analyses of the present model in different eras of the universe.Finally,we plot the density parameter values for dark energy and dark matter in terms of the redshift parameter. 展开更多
关键词 equation of state parameter f(T)gravity viscous fluid particle creation stability analysis
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NLS equation wronskians Peregrine breather rogue waves
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作者 Pierre Gaillard Mickaёl Gastineau 《Communications in Theoretical Physics》 SCIE CAS CSCD 2016年第2期136-144,共9页
The Peregrine breather of order eleven(P_(11) breather) solution to the focusing one-dimensional nonlinear Schrdinger equation(NLS) is explicitly constructed here. Deformations of the Peregrine breather of order... The Peregrine breather of order eleven(P_(11) breather) solution to the focusing one-dimensional nonlinear Schrdinger equation(NLS) is explicitly constructed here. Deformations of the Peregrine breather of order 11 with 20 real parameters solutions to the NLS equation are also given: when all parameters are equal to 0 we recover the famous P_(11) breather. We obtain new families of quasi-rational solutions to the NLS equation in terms of explicit quotients of polynomials of degree 132 in x and t by a product of an exponential depending on t. We study these solutions by giving patterns of their modulus in the(x; t) plane, in function of the different parameters. 展开更多
关键词 Twenty parameters Families of Solutions to the NLS equation and the Eleventh Peregrine Breather
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Cosmic acceleration with bulk viscosity in an anisotropic f(R, Lm) background
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作者 Raja Solanki Bina Patel +1 位作者 Lakhan V Jaybhaye P K Sahoo 《Communications in Theoretical Physics》 SCIE CAS CSCD 2023年第7期103-112,共10页
In this article,we investigate the observed cosmic acceleration in the framework of a cosmological f(R,Lm)model dominated by bulk viscous matter in an anisotropic background.We consider the locally rotationally symmet... In this article,we investigate the observed cosmic acceleration in the framework of a cosmological f(R,Lm)model dominated by bulk viscous matter in an anisotropic background.We consider the locally rotationally symmetric Bianchi type I metric and derive the Friedmann equations that drive the gravitational interactions in f((R,Lm)gravity.Further,we assume the functional form f(R,Lm)=R/2+Lαm,where a is a free model parameter,and then find the exact solutions of field equations corresponding to our viscous matter dominated model.We incorporate the updated H(z)data and the Pantheon data to acquire the best-fit values of parameters of our model by utilizing theχ2 minimization technique along with the Markov Chain Monte Carlo random sampling method.Further,we present the behavior of physical parameters that describe the Universe’s evolution phase,such as density,effective pressure and EoS parameters,skewness parameter,and the statefinder diagnostic parameters.We find that the energy density indicates expected positive behavior,whereas the negative behavior of bulk viscous pressure contributes to the Universe’s expansion.The effective EoS parameter favors the accelerating phase of the Universe’s expansion.Moreover,the skewness parameter shows the anisotropic nature of spacetime during the entire evolution phase of the Universe.Finally,from the statefinder diagnostic test,we found that our cosmological f(R,Lm)model lies in the quintessence region,and it behaves like a de-Sitter universe in the far future.We analyze different energy conditions in order to test the consistency of the obtained solution.We find that all energy conditions except strong energy condition(SEC)show positive behavior,while the violation of SEC favors the recently observed acceleration with the transition from decelerated to an accelerated epoch of the Universe’s expansion in the recent past. 展开更多
关键词 LRS Bianchi type I metric f(R Lm)gravity bulk viscosity skewness parameter equation of state parameter statefinder parameter
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Soil Wetting Patterns and Water Distribution as Affected by Irrigation for Uncropped Ridges and Furrows 被引量:1
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作者 ZHANG Yong-Yong ZHAO Xi-Ning WU Pu-Te 《Pedosphere》 SCIE CAS CSCD 2015年第3期468-477,共10页
The ridge-furrow tillage combined with furrow irrigation is being more widely applied and has been shown to be effective in the Loess Plateau of China. Accurate characterization of water infiltration behavior under ri... The ridge-furrow tillage combined with furrow irrigation is being more widely applied and has been shown to be effective in the Loess Plateau of China. Accurate characterization of water infiltration behavior under ridge-furrow irrigation could provide guidelines and criteria for future irrigation system design and operation. Our objective was to investigate soil water behavior during ponding infiltration in a cross-sectional ridge-furrow configuration. Soil water movement within three different soil textures was tested by tracking the spatial and temporal soil water content(SWC) variations in a soil chamber. The two-dimensional transient flow initially transferred rapidly, but gradually decreased with elapsed infiltration time, approaching a stable flow after 90 min. A technical parameter equation incorporating the Philip equation was developed using the water balance method to accurately predict total applied water volume(TAWV). The wetting patterns moved outward in an elliptical shape. The wetted lateral and downward distances fitted using equations accounted for capillary and gravitational driving forces in variably wetted soil media. Increasing initial SWC resulted in an increase in wetted soil volume, which can also be caused by decreasing bulk density in a homogeneous soil. Higher water level produced greater wetted lateral distance and more irrigation uniformity. The wetted lateral distance was almost identical to the wetted depth in silty clay loam soil; hence ridge-furrow irrigation should be implemented in such finer-textured soils. The wetted soil volume differed markedly among different soil textures(hydraulic properties), demonstrating that these properties can largely determine soil water spreading patterns and distribution. 展开更多
关键词 INFILTRATION ridge-furrow tillage soil texture soil water content technical parameter equation wetted soil volume
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Artificial frozen orbit control scheme based on J_2 perturbation 被引量:4
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作者 WANG GongBo MENG YunHe +1 位作者 ZHENG Wei TANG GuoJian 《Science China(Technological Sciences)》 SCIE EI CAS 2010年第11期3138-3144,共7页
Since the inclination of frozen orbit with non-rotation of the perigee that occurs due to J2 perturbation must be equal to the critical inclination, this regulation has restricted the application of frozen orbit a lot... Since the inclination of frozen orbit with non-rotation of the perigee that occurs due to J2 perturbation must be equal to the critical inclination, this regulation has restricted the application of frozen orbit a lot. In this paper, we propose two control strategies to eliminate the secular growth of the argument of the perigee for orbits that are not at the critical inclination. One control strategy is using transverse continuous low-thrust, and the other is using both the transverse and the radial continuous low-thrusts. Fuel optimization in the second control strategy is addressed to make sure that the fuel consumption is the minimum. Both strategies have no effect on other orbital parameters’ secular motion. It is proved that the strategy with transverse control could save more energy than the one with radial control. Simulations show that the second control strategy could save 54.6% and 86% of energy, respectively, compared with the two methods presented in the references. 展开更多
关键词 continuous low-thrust artificial frozen orbit Gauss’variation of parameters equations mean element method
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