An eco-epidemiological model with an epidemic in the predator and with a Holling type Ⅱ function is considered.A system with diffusion under the homogeneous Neumann boundary condition is studied.The existence for a p...An eco-epidemiological model with an epidemic in the predator and with a Holling type Ⅱ function is considered.A system with diffusion under the homogeneous Neumann boundary condition is studied.The existence for a positive solution of the corresponding steady state problem is mainly discussed.First,a prior estimates（positive upper and lower bounds） of the positive steady states of the reaction-diffusion system is given by the maximum principle and the Harnack inequation.Then,the non-existence of non-constant positive steady states by using the energy method is given.Finally,the existence of non-constant positive steady states is obtained by using the topological degree.展开更多
The multi-piped freezing method is usually applied in artificial ground freezing （AGF） projects to fulfill special construction requirements, such as two-, three-, or four-piped freezing. Based on potential superpos...The multi-piped freezing method is usually applied in artificial ground freezing （AGF） projects to fulfill special construction requirements, such as two-, three-, or four-piped freezing. Based on potential superposition theory, this paper gives analytical solutions to steady-state frozen temperature for two, three, and four freezing pipes with different temperatures and arranged at random. Specific solutions are derived for some particular arrangements, such as three freezing pipes in a linear arrangement with equal or unequal spacing, right and isosceles triangle arrangements, four freezing pipes in a linear arrangement with equal spacing, and rhombus and rectangle arrangements. A comparison between the analytical solutions and numerical thermal analysis shows that the analytical solutions are sufficiently precise. As a part of the theory of AGF, the analytical solutions of temperature fields for multi-piped freezing with arbitrary layouts and different temperatures of freezing pipes are approached for the first time.展开更多
An internal state variable(ISV)model was established according to the experimental results of hot plane strain compression(PSC)to predict the microstructure evolution during hot spinning of ZK61 alloy.The effects of t...An internal state variable(ISV)model was established according to the experimental results of hot plane strain compression(PSC)to predict the microstructure evolution during hot spinning of ZK61 alloy.The effects of the internal variables were considered in this ISV model,and the parameters were optimized by genetic algorithm.After validation,the ISV model was used to simulate the evolution of grain size(GS)and dynamic recrystallization(DRX)fraction during hot spinning via Abaqus and its subroutine Vumat.By comparing the simulated results with the experimental results,the application of the ISV model was proven to be reliable.Meanwhile,the strength of the thin-walled spun ZK61 tube increased from 303 to 334 MPa due to grain refinement by DRX and texture strengthening.Besides,some ultrafine grains(0.5μm)that played an important role in mechanical properties were formed due to the proliferation,movement,and entanglement of dislocations during the spinning process.展开更多
A one-dimensional stationary nonisentropic hydrodynamic model for semiconductor devices with non-constant lattice temperature is studied. This model consists of the equations for the electron density, the electron cur...A one-dimensional stationary nonisentropic hydrodynamic model for semiconductor devices with non-constant lattice temperature is studied. This model consists of the equations for the electron density, the electron current density and electron temperature, coupled with the Poisson equation of the electrostatic potential in a bounded interval supplemented with proper boundary conditions. The existence and uniqueness of a strong subsonic steady-state solution with positive particle density and positive temperature is established. The proof is based on the fixed-point arguments, the Stampacchia truncation methods, and the basic energy estimates.展开更多
In order to investigate the mechanism of the temperature oscillation in loop heat pipes,this paper investigated the movement of the phase interface as the changed input power by a mass-spring-damper model.The model wa...In order to investigate the mechanism of the temperature oscillation in loop heat pipes,this paper investigated the movement of the phase interface as the changed input power by a mass-spring-damper model.The model was solved with MATLAB and was used to explain the high-frequency and low-amplitude temperature oscillation.Temperature variation with the input power from 20 W to 75 W was investigated based on a LHP prototype in a literature.The model agreed well with the experimental data in the literature.The simulation results suggested that the movement of the liquid column was caused by the fluctuation of pressure difference applied on the liquid column and the stiffness coefficients of the vapor springs increasing with the input power.According to parameter analyses,the temperature oscillation at the outlet of the condenser can be weakened by increasing the mass of the liquid column and keeping the temperature at the outlet of the condenser steady.展开更多
A numerical model for the charge state distribution of plasmas in a collisional radiative steady state （CRSS） is established by averaging over the atomic process rate coefficients in universal kinetic equations. It ...A numerical model for the charge state distribution of plasmas in a collisional radiative steady state （CRSS） is established by averaging over the atomic process rate coefficients in universal kinetic equations. It is used to calculate the mean ion charge and ion population for a given temperature and density of the plasmas, ranging from low Z to high Z elements. The comparisons of the calculated results with those of other non-local thermodynamic equilibrium kinetics codes show that this model possesses acceptable precision. Furthermore, the NLTE effects are investigated by virtue of the model, and the differences between CRSS and LTE models for low density plasmas are quite evident.展开更多
BACKGROUND Neck pain,a primary symptom of cervical spondylosis,affects patients'physical and mental health,reducing their quality of life.Pain and emotional state interact;however,their longitudinal interrelations...BACKGROUND Neck pain,a primary symptom of cervical spondylosis,affects patients'physical and mental health,reducing their quality of life.Pain and emotional state interact;however,their longitudinal interrelationship remains unclear.In this study,we applied a dual-trajectory model to assess how neck pain and emotional state evolve together over time and how clinical interventions,particularly acupuncture,influence these trajectories.AIM To investigate the longitudinal relationship between neck pain and emotional state in patients with cervical spondylosis.METHODS This prospective cohort study included 472 patients with cervical spondylosis from eight Chinese hospitals.Participants received acupuncture or medication and were followed up at baseline,and at 1,2,4,6,and 8 weeks.Neck pain and emotional distress were assessed using the Northwick Park Neck Pain Questionnaire(NPQ)and the affective subscale of the Short-Form McGill Pain Questionnaire(SF-MPQ),respectively.Group-based trajectory models and dual trajectory analysis were used to identify and correlate pain-emotion trajectories.Multivariate logistic regression identified predictors of group membership.RESULTS Three trajectory groups were identified for NPQ and SF-MPQ scores(low,medium,and high).Higher NPQ trajectory was associated with older age(OR=1.058,P<0.001)and was significantly reduced by acupuncture(OR=0.382,P<0.001).Similarly,acupuncture lowered the odds of high SF-MPQ trajectory membership(OR=0.336,P<0.001),while age increased it(OR=1.037,P<0.001).Dual-trajectory analysis revealed bidirectional associations:69.1%of patients with low NPQ had low SF-MPQ scores,and 42.6%of patients with high SF-MPQ also had high NPQ scores.Gender was a predictor for medium SF-MPQ trajectory(OR=1.629,P=0.094).Occupation and education levels differed significantly across the trajectory groups(P<0.05).CONCLUSION Over time,neck pain and emotional distress are closely associated in patients with cervical spondylosis.Acupuncture alleviates both outcomes significantly,while age is a risk factor.Integrated approaches to pain and emotional management are encouraged.展开更多
In this paper,a grey Kalman filter model is proposed for lithium battery charge state estimation.Firstly,this paper establishes a recursive relation equation between the front and back terms through the grey model(GM)...In this paper,a grey Kalman filter model is proposed for lithium battery charge state estimation.Firstly,this paper establishes a recursive relation equation between the front and back terms through the grey model(GM).Secondly,the state space expression is constructed based on the recursive relationship equation.Next,the Kalman filter algorithm is integrated to form a grey Kalman filter model.Finally,the charge state is estimated based on public lithium battery data.In this paper,the state of charge is estimated from three different aspects,including different driving cycles,randomly mixed driving cycles,and the estimation of the state of charge by different temperatures under the same driving cycle conditions.On this basis,the model is applied to a life scenario using the charge state of 20 electric vehicles.The results show that the proposed model has good accuracy.展开更多
This study investigates the volumetric behaviors of various soils during freeze-thaw(FT)cycles and subsequent one-dimensional(1D)compression from experimental and theoretical studies.Experimental studies were performe...This study investigates the volumetric behaviors of various soils during freeze-thaw(FT)cycles and subsequent one-dimensional(1D)compression from experimental and theoretical studies.Experimental studies were performed on saturated expansive soil specimens with varying compaction conditions and soil structures under different stress states.Experimental results demonstrate that the specimens expand during freezing and contract during thawing.All specimens converge to the same residual void ratio after seven FT cycles,irrespective of their different initial void ratio,stress state,and soil structure.The compression index of the expansive soil specimens increases with the initial void ratio,whereas their swelling index remains nearly constant.A model extending the disturbed state concept(DSC)is proposed to predict the 1D compression behaviors of FT-impacted soils.The model incorporates a parameter,b,to account for the impacts of FT cycles.Empirical equations have been developed to link the key model parameters(i.e.the normalized yield stress and parameter b)to the soil state parameter(i.e.the normalized void ratio)in order to simplify the prediction approach.The proposed model well predicts the results of the tested expansive soil.In addition,the model’s feasibility for other types of soils,including low-and high-plastic clays,and high-plastic organic soils,has been validated using published data from the literature.The proposed model is simple yet reliable for predicting the compression behaviors of soils subjected to FT cycles.展开更多
The deformation energy(Wd)of soil-like tectonic coal is crucial for investigating the mechanism of coal and gas outbursts.Tectonic coal has a significant nonlinear constitutive relationship,which makes traditional ela...The deformation energy(Wd)of soil-like tectonic coal is crucial for investigating the mechanism of coal and gas outbursts.Tectonic coal has a significant nonlinear constitutive relationship,which makes traditional elastic-based models for computing Wdunsuitable.Inspired by critical state soil mechanics,this study theoretically established a new calculation model of Wdsuitable for the coal with nonlinear deformation characteristics.In the new model,the relationship between energy and stress no longer follows the square law(observed in traditional linear elastic models)but exhibits a power function,with the theoretical value of the power exponent ranging between 1 and 2.Hydrostatic cyclic loading and unloading experiments were conducted on four groups of tectonic coal samples and one group of intact coal samples.The results indicated that the relationship between Wdand stress for both intact and tectonic coal follows a power law.The exponents for intact and tectonic coal are close to 2 and 1,respectively.The stress-strain curve of intact coal exhibits small deformation and linear characteristics,whereas the stress-strain curves of tectonic coal show large deformation and nonlinear characteristics.The study specifically investigates the role of coal viscosity in the cyclic loading/unloading process.The downward bending in the unloading curves can be attributed to the time-dependent characteristics of coal,particularly its viscoelastic behavior.Based on experimental statistics,the calculation model of Wdwas further simplified.The simplified model involves only one unknown parameter,which is the power exponent between Wdand stress.The measured Wdof the coal samples increases with the number of load cycles.This phenomenon is attributed to coal's viscoelastic deformation.Within the same stress,the Wdof tectonic coal is an order of magnitude greater than that of intact coal.The calculation model of Wdproposed in this paper provides a new tool for studying the energy principle of coal and gas outbursts.展开更多
According to the analysis of the problems about the operation of marine propulsion shafting in steady state,the geometric and mechanical coupling relationships between marine propulsion shafting and oil film of bearin...According to the analysis of the problems about the operation of marine propulsion shafting in steady state,the geometric and mechanical coupling relationships between marine propulsion shafting and oil film of bearings in two-dimensional space are established,and a coupling mathematical model of the marine propulsion shafting in steady operating state is proposed.Then the simulation of a real ship is carried out,and the variation laws of some special parameters such as bearing load and deflection are obtained.Finally,the results of simulation are verified by experimental data of a real ship,which can provide the mathematical model and analysis method for the research on the characteristics of ship propulsion shafting condition in steady state.展开更多
Adsorptive reactors(AR),in which an adsorptive functionality is incorporated into the catalytic reactors,offer enhanced performance over their conventional counterparts due to the effective manipulation of concentrati...Adsorptive reactors(AR),in which an adsorptive functionality is incorporated into the catalytic reactors,offer enhanced performance over their conventional counterparts due to the effective manipulation of concentration and temperature profiles.The operation of these attractive reactors is,however,inherently unsteady state,complicating the design and operation of such sorption-enhanced processes.In order to capture,comprehend and capitalize upon the rich dynamic texture of adsorptive reactors,it is necessary to employ cyclic steady state algorithms describing the entire reaction-adsorption/desorption cycle.The stability of this cyclic steady state is of great importance for the design and operation of adsorptive reactors.In this paper,the cyclic steady state of previously proposed novel adsorptive reactor designs has been calculated and then optimized to give maximum space–time yields.The results obtained revealed unambiguously that an improvement potential of up to multifold level could be attained under the optimized cyclic steady state conditions.This additional improvement resulted from the reduction of the regeneration time well below the reaction-adsorption time,which means,in turn,more space–time yield.展开更多
In this paper,we consider the positive steady state solutions of a predator-prey model with Holling type Ⅱfunctional response and cross-diffusion,where two cross-diffusion rates represent the tendency of prey to keep...In this paper,we consider the positive steady state solutions of a predator-prey model with Holling type Ⅱfunctional response and cross-diffusion,where two cross-diffusion rates represent the tendency of prey to keep away from its predator and the tendency of the predator to chase its prey,respectively.Applying the fixed point index theory,some sufficient conditions for the existence of positive steady state solutions are established.Furthermore,the non-existence of positive steady state solutions is studied.展开更多
<span style="font-family:Verdana;">The increase of energy production is very important nowadays. It is necessary to improve the performance and efficiency of heat production facilities. The objective i...<span style="font-family:Verdana;">The increase of energy production is very important nowadays. It is necessary to improve the performance and efficiency of heat production facilities. The objective is to reduce pollutant emissions and regulate investment costs. One </span><span style="font-family:Verdana;">of the </span><span style="font-family:Verdana;">solution</span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;"> is to control fuel and electricity consumption. </span><span style="font-family:Verdana;">This article develops a new model of simulation heat diffusion on the recovery system of condensing boiler. The method is based on the first and second thermodynamic systems. The Numerical discrete Model (NDM) was applied using MATLAB to simulate different characteristics of heat transfer in the recovery system. The result shows that the recovery unit can absorb the following temperatures;the range from 88°C to 90.7°C when the length of the tube is between respectively 110 and 111 m. the energy efficiency was between 0.55 and 0.57 which allowed confirming the model. This new model has some advantages such as;the use of an instantaneous calculation time. The heat recovered by the water tank can also serve as preheating different systems. One part of the heat recovered will be accumulated to be used as domestic hot water.</span>展开更多
A parameter estimation algorithm of the continuous hidden Markov model isintroduced and the rigorous proof of its convergence is also included. The algorithm uses theViterbi algorithm instead of K-means clustering use...A parameter estimation algorithm of the continuous hidden Markov model isintroduced and the rigorous proof of its convergence is also included. The algorithm uses theViterbi algorithm instead of K-means clustering used in the segmental K-means algorithm to determineoptimal state and branch sequences. Based on the optimal sequence, parameters are estimated withmaximum-likelihood as objective functions. Comparisons with the traditional Baum-Welch and segmentalK-means algorithms on various aspects, such as optimal objectives and fundamentals, are made. Allthree algorithms are applied to face recognition. Results indicate that the proposed algorithm canreduce training time with comparable recognition rate and it is least sensitive to the training set.So its average performance exceeds the other two.展开更多
The remaining useful life(RUL) prediction of mechanical products has been widely studied for online system performance reliability, device remanufacturing, and product safety(safety awareness and safety improvement). ...The remaining useful life(RUL) prediction of mechanical products has been widely studied for online system performance reliability, device remanufacturing, and product safety(safety awareness and safety improvement). These studies incorporated many di erent models, algorithms, and techniques for modeling and assessment. In this paper, methods of RUL assessment are summarized and expounded upon using two major methods: physics model based and data driven based methods. The advantages and disadvantages of each of these methods are deliberated and compared as well. Due to the intricacy of failure mechanism in system, and di culty in physics degradation observation, RUL assessment based on observations of performance variables turns into a science in evaluating the degradation. A modeling method from control systems, the state space model(SSM), as a first order hidden Markov, is presented. In the context of non-linear and non-Gaussian systems, the SSM methodology is capable of performing remaining life assessment by using Bayesian estimation(sequential Monte Carlo). Being e ective for non-linear and non-Gaussian dynamics, the methodology can perform the assessment recursively online for applications in CBM(condition based maintenance), PHM(prognostics and health management), remanufacturing, and system performance reliability. Finally, the discussion raises concerns regarding online sensing data for SSM modeling and assessment of RUL.展开更多
Aiming at handling complicated maneuvers or other unpredicted emergencies for hypersonic glide vehicle tracking,three coupled dynamic models of state estimation based on the priori information between guidance variabl...Aiming at handling complicated maneuvers or other unpredicted emergencies for hypersonic glide vehicle tracking,three coupled dynamic models of state estimation based on the priori information between guidance variables and aerodynamics are presented. Firstly, the aerodynamic acceleration acting on the target is analyzed to reveal the essence of the target’s motion.Then three coupled structures for modeling aerodynamic parameters are developed by different ideas: the spiral model with a harmonic oscillator, the bank model with trigonometric functions of the bank angle and the guide model with the changing rule of guidance variables. Meanwhile, the comparison discussion is concluded to show the novelty and advantage of these models.Finally, a performance assessment in different simulation cases is presented and detailed analysis is revealed. The results show that the proposed models perform excellent properties. Moreover, the guide model produces the best tracking performance and the bank model shows the second; however, the spiral model does not outperform the maneuvering reentry vehicle(MaRV) model markedly.展开更多
Based on the pioneering work of Konishi et al., in consideration of the influence of drivers＇ steady desired speed ef/ect on the traffic flow, we develop a new coupled map car-following model in the real world. By us...Based on the pioneering work of Konishi et al., in consideration of the influence of drivers＇ steady desired speed ef/ect on the traffic flow, we develop a new coupled map car-following model in the real world. By use of the control theory, the stability condition of our model is derived. The validity of the present theoretical scheme is verified via numerical simulation, confirming the correctness of our theoretical analysis.展开更多
This paper presents a method of thermal state calculation of combustion chamber in small thrust liquid rocket engine. The goal is to predict the thermal state of chamber wall by using basic parameters of engine: thrus...This paper presents a method of thermal state calculation of combustion chamber in small thrust liquid rocket engine. The goal is to predict the thermal state of chamber wall by using basic parameters of engine: thrust level, propellants, chamber pressure, injection pattern, film cooling parameters, material of wall and their coating, etc. The difficulties in modeling the startup and shutdown processes of thrusters lie in the fact that there are the conjugated physical processes occurring at various parameters for non-design conditions. A mathematical model to predict the thermal state of the combustion chamber for different engine operation modes is developed. To simulate the startup and shutdown processes, a quasi-steady approach is applied by replacing the transient process with time-variant operating parameters of steady-state processes. The mathematical model is based on several principles and data commonly used for heat transfer modeling: geometry of flow part, gas dynamics of flow, thermodynamics of propellants and combustion spices, convective and radiation heat flows, conjugated heat transfer between hot gas and wall, and transient approach for calculation of thermal state of construction. Calculations of the thermal state of the combustion chamber in single-turn-on mode show good convergence with the experimental results. The results of pulsed modes indicate a large temperature gradient on the internal wall surface of the chamber between pulses and the thermal state of the wall strongly depends on the pulse duration and the interval.展开更多
基金The National Natural Science Foundation of China (No.10601011)
文摘An eco-epidemiological model with an epidemic in the predator and with a Holling type Ⅱ function is considered.A system with diffusion under the homogeneous Neumann boundary condition is studied.The existence for a positive solution of the corresponding steady state problem is mainly discussed.First,a prior estimates（positive upper and lower bounds） of the positive steady states of the reaction-diffusion system is given by the maximum principle and the Harnack inequation.Then,the non-existence of non-constant positive steady states by using the energy method is given.Finally,the existence of non-constant positive steady states is obtained by using the topological degree.
基金Project supported by the National Natural Science Foundation of China （Nos. 51178336 and 51478340）, the Natural Science Foundation of Zhejiang Province, China （No. LZ13E080002）, and the China Ministry of Communications Construction Science ＆ Technology Projects （No. 2013318R11300）
文摘The multi-piped freezing method is usually applied in artificial ground freezing （AGF） projects to fulfill special construction requirements, such as two-, three-, or four-piped freezing. Based on potential superposition theory, this paper gives analytical solutions to steady-state frozen temperature for two, three, and four freezing pipes with different temperatures and arranged at random. Specific solutions are derived for some particular arrangements, such as three freezing pipes in a linear arrangement with equal or unequal spacing, right and isosceles triangle arrangements, four freezing pipes in a linear arrangement with equal spacing, and rhombus and rectangle arrangements. A comparison between the analytical solutions and numerical thermal analysis shows that the analytical solutions are sufficiently precise. As a part of the theory of AGF, the analytical solutions of temperature fields for multi-piped freezing with arbitrary layouts and different temperatures of freezing pipes are approached for the first time.
基金supported by the National Natural Science Foundation of China(No.51905123)Major Scientific and Technological Innovation Program of Shandong Province,China(Nos.2020CXGC010303,2022ZLGX04)Key R&D Programme of Shandong Province,China(No.2022JMRH0308).
文摘An internal state variable(ISV)model was established according to the experimental results of hot plane strain compression(PSC)to predict the microstructure evolution during hot spinning of ZK61 alloy.The effects of the internal variables were considered in this ISV model,and the parameters were optimized by genetic algorithm.After validation,the ISV model was used to simulate the evolution of grain size(GS)and dynamic recrystallization(DRX)fraction during hot spinning via Abaqus and its subroutine Vumat.By comparing the simulated results with the experimental results,the application of the ISV model was proven to be reliable.Meanwhile,the strength of the thin-walled spun ZK61 tube increased from 303 to 334 MPa due to grain refinement by DRX and texture strengthening.Besides,some ultrafine grains(0.5μm)that played an important role in mechanical properties were formed due to the proliferation,movement,and entanglement of dislocations during the spinning process.
基金the Educational Department of Hubei province(Q200628002)the National Science Foundation of China(10701057)
文摘A one-dimensional stationary nonisentropic hydrodynamic model for semiconductor devices with non-constant lattice temperature is studied. This model consists of the equations for the electron density, the electron current density and electron temperature, coupled with the Poisson equation of the electrostatic potential in a bounded interval supplemented with proper boundary conditions. The existence and uniqueness of a strong subsonic steady-state solution with positive particle density and positive temperature is established. The proof is based on the fixed-point arguments, the Stampacchia truncation methods, and the basic energy estimates.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51276012)
文摘In order to investigate the mechanism of the temperature oscillation in loop heat pipes,this paper investigated the movement of the phase interface as the changed input power by a mass-spring-damper model.The model was solved with MATLAB and was used to explain the high-frequency and low-amplitude temperature oscillation.Temperature variation with the input power from 20 W to 75 W was investigated based on a LHP prototype in a literature.The model agreed well with the experimental data in the literature.The simulation results suggested that the movement of the liquid column was caused by the fluctuation of pressure difference applied on the liquid column and the stiffness coefficients of the vapor springs increasing with the input power.According to parameter analyses,the temperature oscillation at the outlet of the condenser can be weakened by increasing the mass of the liquid column and keeping the temperature at the outlet of the condenser steady.
基金supported by National Natural Science Foundation of China(No.10475065)
文摘A numerical model for the charge state distribution of plasmas in a collisional radiative steady state （CRSS） is established by averaging over the atomic process rate coefficients in universal kinetic equations. It is used to calculate the mean ion charge and ion population for a given temperature and density of the plasmas, ranging from low Z to high Z elements. The comparisons of the calculated results with those of other non-local thermodynamic equilibrium kinetics codes show that this model possesses acceptable precision. Furthermore, the NLTE effects are investigated by virtue of the model, and the differences between CRSS and LTE models for low density plasmas are quite evident.
基金Supported by 2022 Chinese Medicine Scientific Research Project of Hebei Administration of Traditional Chinese Medicine,No.20221572025 Annual Scientific Research Project of Higher Education Institutions in Hebei Province,No.QN2025654.
文摘BACKGROUND Neck pain,a primary symptom of cervical spondylosis,affects patients'physical and mental health,reducing their quality of life.Pain and emotional state interact;however,their longitudinal interrelationship remains unclear.In this study,we applied a dual-trajectory model to assess how neck pain and emotional state evolve together over time and how clinical interventions,particularly acupuncture,influence these trajectories.AIM To investigate the longitudinal relationship between neck pain and emotional state in patients with cervical spondylosis.METHODS This prospective cohort study included 472 patients with cervical spondylosis from eight Chinese hospitals.Participants received acupuncture or medication and were followed up at baseline,and at 1,2,4,6,and 8 weeks.Neck pain and emotional distress were assessed using the Northwick Park Neck Pain Questionnaire(NPQ)and the affective subscale of the Short-Form McGill Pain Questionnaire(SF-MPQ),respectively.Group-based trajectory models and dual trajectory analysis were used to identify and correlate pain-emotion trajectories.Multivariate logistic regression identified predictors of group membership.RESULTS Three trajectory groups were identified for NPQ and SF-MPQ scores(low,medium,and high).Higher NPQ trajectory was associated with older age(OR=1.058,P<0.001)and was significantly reduced by acupuncture(OR=0.382,P<0.001).Similarly,acupuncture lowered the odds of high SF-MPQ trajectory membership(OR=0.336,P<0.001),while age increased it(OR=1.037,P<0.001).Dual-trajectory analysis revealed bidirectional associations:69.1%of patients with low NPQ had low SF-MPQ scores,and 42.6%of patients with high SF-MPQ also had high NPQ scores.Gender was a predictor for medium SF-MPQ trajectory(OR=1.629,P=0.094).Occupation and education levels differed significantly across the trajectory groups(P<0.05).CONCLUSION Over time,neck pain and emotional distress are closely associated in patients with cervical spondylosis.Acupuncture alleviates both outcomes significantly,while age is a risk factor.Integrated approaches to pain and emotional management are encouraged.
基金supported by the National Natural Science Foundation of China(92367301,72171116)the Fundamental Research Funds for the Central Universities(NK2023001,NP2024203)the“333 talent”project in Jiangsu Province.
文摘In this paper,a grey Kalman filter model is proposed for lithium battery charge state estimation.Firstly,this paper establishes a recursive relation equation between the front and back terms through the grey model(GM).Secondly,the state space expression is constructed based on the recursive relationship equation.Next,the Kalman filter algorithm is integrated to form a grey Kalman filter model.Finally,the charge state is estimated based on public lithium battery data.In this paper,the state of charge is estimated from three different aspects,including different driving cycles,randomly mixed driving cycles,and the estimation of the state of charge by different temperatures under the same driving cycle conditions.On this basis,the model is applied to a life scenario using the charge state of 20 electric vehicles.The results show that the proposed model has good accuracy.
基金support from the Natural Sciences and Engineering Research Council of Canada(NSERC)through the Discovery Grant(Grant No.5808)received in 2019 for his research programsThe third author appreciates the funding from the National Natural Science Foundation of China(Grant No.52378365)Hubei Key Research&Development Program(Grant No.2023BCB112).
文摘This study investigates the volumetric behaviors of various soils during freeze-thaw(FT)cycles and subsequent one-dimensional(1D)compression from experimental and theoretical studies.Experimental studies were performed on saturated expansive soil specimens with varying compaction conditions and soil structures under different stress states.Experimental results demonstrate that the specimens expand during freezing and contract during thawing.All specimens converge to the same residual void ratio after seven FT cycles,irrespective of their different initial void ratio,stress state,and soil structure.The compression index of the expansive soil specimens increases with the initial void ratio,whereas their swelling index remains nearly constant.A model extending the disturbed state concept(DSC)is proposed to predict the 1D compression behaviors of FT-impacted soils.The model incorporates a parameter,b,to account for the impacts of FT cycles.Empirical equations have been developed to link the key model parameters(i.e.the normalized yield stress and parameter b)to the soil state parameter(i.e.the normalized void ratio)in order to simplify the prediction approach.The proposed model well predicts the results of the tested expansive soil.In addition,the model’s feasibility for other types of soils,including low-and high-plastic clays,and high-plastic organic soils,has been validated using published data from the literature.The proposed model is simple yet reliable for predicting the compression behaviors of soils subjected to FT cycles.
基金supported by the Fundamental Research Funds for the Central Universities(No.2024QN11072)National Natural Science Foundation of China(Nos.52404264 and 52174217)State Key Program of the National Natural Science Foundation of China(No.52034008)。
文摘The deformation energy(Wd)of soil-like tectonic coal is crucial for investigating the mechanism of coal and gas outbursts.Tectonic coal has a significant nonlinear constitutive relationship,which makes traditional elastic-based models for computing Wdunsuitable.Inspired by critical state soil mechanics,this study theoretically established a new calculation model of Wdsuitable for the coal with nonlinear deformation characteristics.In the new model,the relationship between energy and stress no longer follows the square law(observed in traditional linear elastic models)but exhibits a power function,with the theoretical value of the power exponent ranging between 1 and 2.Hydrostatic cyclic loading and unloading experiments were conducted on four groups of tectonic coal samples and one group of intact coal samples.The results indicated that the relationship between Wdand stress for both intact and tectonic coal follows a power law.The exponents for intact and tectonic coal are close to 2 and 1,respectively.The stress-strain curve of intact coal exhibits small deformation and linear characteristics,whereas the stress-strain curves of tectonic coal show large deformation and nonlinear characteristics.The study specifically investigates the role of coal viscosity in the cyclic loading/unloading process.The downward bending in the unloading curves can be attributed to the time-dependent characteristics of coal,particularly its viscoelastic behavior.Based on experimental statistics,the calculation model of Wdwas further simplified.The simplified model involves only one unknown parameter,which is the power exponent between Wdand stress.The measured Wdof the coal samples increases with the number of load cycles.This phenomenon is attributed to coal's viscoelastic deformation.Within the same stress,the Wdof tectonic coal is an order of magnitude greater than that of intact coal.The calculation model of Wdproposed in this paper provides a new tool for studying the energy principle of coal and gas outbursts.
基金the National Natural Science Founda-tion of China(No.51479154)。
文摘According to the analysis of the problems about the operation of marine propulsion shafting in steady state,the geometric and mechanical coupling relationships between marine propulsion shafting and oil film of bearings in two-dimensional space are established,and a coupling mathematical model of the marine propulsion shafting in steady operating state is proposed.Then the simulation of a real ship is carried out,and the variation laws of some special parameters such as bearing load and deflection are obtained.Finally,the results of simulation are verified by experimental data of a real ship,which can provide the mathematical model and analysis method for the research on the characteristics of ship propulsion shafting condition in steady state.
基金the German research council(Deutsche Forschungsgemeinschaft) for their financial support to the project:AG 26/18-1
文摘Adsorptive reactors(AR),in which an adsorptive functionality is incorporated into the catalytic reactors,offer enhanced performance over their conventional counterparts due to the effective manipulation of concentration and temperature profiles.The operation of these attractive reactors is,however,inherently unsteady state,complicating the design and operation of such sorption-enhanced processes.In order to capture,comprehend and capitalize upon the rich dynamic texture of adsorptive reactors,it is necessary to employ cyclic steady state algorithms describing the entire reaction-adsorption/desorption cycle.The stability of this cyclic steady state is of great importance for the design and operation of adsorptive reactors.In this paper,the cyclic steady state of previously proposed novel adsorptive reactor designs has been calculated and then optimized to give maximum space–time yields.The results obtained revealed unambiguously that an improvement potential of up to multifold level could be attained under the optimized cyclic steady state conditions.This additional improvement resulted from the reduction of the regeneration time well below the reaction-adsorption time,which means,in turn,more space–time yield.
基金Supported by the National Natural Science Foundation of China(Grant No.11761063).
文摘In this paper,we consider the positive steady state solutions of a predator-prey model with Holling type Ⅱfunctional response and cross-diffusion,where two cross-diffusion rates represent the tendency of prey to keep away from its predator and the tendency of the predator to chase its prey,respectively.Applying the fixed point index theory,some sufficient conditions for the existence of positive steady state solutions are established.Furthermore,the non-existence of positive steady state solutions is studied.
文摘<span style="font-family:Verdana;">The increase of energy production is very important nowadays. It is necessary to improve the performance and efficiency of heat production facilities. The objective is to reduce pollutant emissions and regulate investment costs. One </span><span style="font-family:Verdana;">of the </span><span style="font-family:Verdana;">solution</span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;"> is to control fuel and electricity consumption. </span><span style="font-family:Verdana;">This article develops a new model of simulation heat diffusion on the recovery system of condensing boiler. The method is based on the first and second thermodynamic systems. The Numerical discrete Model (NDM) was applied using MATLAB to simulate different characteristics of heat transfer in the recovery system. The result shows that the recovery unit can absorb the following temperatures;the range from 88°C to 90.7°C when the length of the tube is between respectively 110 and 111 m. the energy efficiency was between 0.55 and 0.57 which allowed confirming the model. This new model has some advantages such as;the use of an instantaneous calculation time. The heat recovered by the water tank can also serve as preheating different systems. One part of the heat recovered will be accumulated to be used as domestic hot water.</span>
文摘A parameter estimation algorithm of the continuous hidden Markov model isintroduced and the rigorous proof of its convergence is also included. The algorithm uses theViterbi algorithm instead of K-means clustering used in the segmental K-means algorithm to determineoptimal state and branch sequences. Based on the optimal sequence, parameters are estimated withmaximum-likelihood as objective functions. Comparisons with the traditional Baum-Welch and segmentalK-means algorithms on various aspects, such as optimal objectives and fundamentals, are made. Allthree algorithms are applied to face recognition. Results indicate that the proposed algorithm canreduce training time with comparable recognition rate and it is least sensitive to the training set.So its average performance exceeds the other two.
基金Supported by Fundamental Research Funds for the Central Universities of China(Grant No.DUT17GF214)
文摘The remaining useful life(RUL) prediction of mechanical products has been widely studied for online system performance reliability, device remanufacturing, and product safety(safety awareness and safety improvement). These studies incorporated many di erent models, algorithms, and techniques for modeling and assessment. In this paper, methods of RUL assessment are summarized and expounded upon using two major methods: physics model based and data driven based methods. The advantages and disadvantages of each of these methods are deliberated and compared as well. Due to the intricacy of failure mechanism in system, and di culty in physics degradation observation, RUL assessment based on observations of performance variables turns into a science in evaluating the degradation. A modeling method from control systems, the state space model(SSM), as a first order hidden Markov, is presented. In the context of non-linear and non-Gaussian systems, the SSM methodology is capable of performing remaining life assessment by using Bayesian estimation(sequential Monte Carlo). Being e ective for non-linear and non-Gaussian dynamics, the methodology can perform the assessment recursively online for applications in CBM(condition based maintenance), PHM(prognostics and health management), remanufacturing, and system performance reliability. Finally, the discussion raises concerns regarding online sensing data for SSM modeling and assessment of RUL.
基金supported by the National High-tech R&D Program of China(863 Program)(2015AA7326042 2015AA8321471)
文摘Aiming at handling complicated maneuvers or other unpredicted emergencies for hypersonic glide vehicle tracking,three coupled dynamic models of state estimation based on the priori information between guidance variables and aerodynamics are presented. Firstly, the aerodynamic acceleration acting on the target is analyzed to reveal the essence of the target’s motion.Then three coupled structures for modeling aerodynamic parameters are developed by different ideas: the spiral model with a harmonic oscillator, the bank model with trigonometric functions of the bank angle and the guide model with the changing rule of guidance variables. Meanwhile, the comparison discussion is concluded to show the novelty and advantage of these models.Finally, a performance assessment in different simulation cases is presented and detailed analysis is revealed. The results show that the proposed models perform excellent properties. Moreover, the guide model produces the best tracking performance and the bank model shows the second; however, the spiral model does not outperform the maneuvering reentry vehicle(MaRV) model markedly.
基金Project supported by the Major Consulting Project of Chinese Academy of Engineering(Grant No.2012-ZX-22)the National Natural Science Foundation of China(Grant No.71201178)+3 种基金the Natural Science Foundation of Chongqing City,China(Grant No.cstc2012jjB40002)the Research Fund for the Doctoral Program of Higher Education of China(Grant No.20120191110047)the Engineering Center Research Program of Chongqing City,China(Grant No.cstc2011pt-gc30005)the Key Technology R&D Project of Chongqing City,China(Grant Nos.cstc2011AB2052 and cstc2012gg-yyjsB30001)
文摘Based on the pioneering work of Konishi et al., in consideration of the influence of drivers＇ steady desired speed ef/ect on the traffic flow, we develop a new coupled map car-following model in the real world. By use of the control theory, the stability condition of our model is derived. The validity of the present theoretical scheme is verified via numerical simulation, confirming the correctness of our theoretical analysis.
文摘This paper presents a method of thermal state calculation of combustion chamber in small thrust liquid rocket engine. The goal is to predict the thermal state of chamber wall by using basic parameters of engine: thrust level, propellants, chamber pressure, injection pattern, film cooling parameters, material of wall and their coating, etc. The difficulties in modeling the startup and shutdown processes of thrusters lie in the fact that there are the conjugated physical processes occurring at various parameters for non-design conditions. A mathematical model to predict the thermal state of the combustion chamber for different engine operation modes is developed. To simulate the startup and shutdown processes, a quasi-steady approach is applied by replacing the transient process with time-variant operating parameters of steady-state processes. The mathematical model is based on several principles and data commonly used for heat transfer modeling: geometry of flow part, gas dynamics of flow, thermodynamics of propellants and combustion spices, convective and radiation heat flows, conjugated heat transfer between hot gas and wall, and transient approach for calculation of thermal state of construction. Calculations of the thermal state of the combustion chamber in single-turn-on mode show good convergence with the experimental results. The results of pulsed modes indicate a large temperature gradient on the internal wall surface of the chamber between pulses and the thermal state of the wall strongly depends on the pulse duration and the interval.
