In order to study the work-ability and establish the optimum hot formation processing parameters for industrial 1060 pure aluminum, the compressive deformation behavior of pure aluminum was investigated at temperature...In order to study the work-ability and establish the optimum hot formation processing parameters for industrial 1060 pure aluminum, the compressive deformation behavior of pure aluminum was investigated at temperatures of 523?823 K and strain rates of 0.005?10 s?1 on a Gleeble?1500 thermo-simulation machine. The influence rule of processing parameters (strain, strain rate and temperature) on flow stress of pure aluminum was investigated. Nine analysis factors consisting of material parameters and according weights were optimized. Then, the constitutive equations of multilevel series rules, multilevel parallel rules and multilevel series ¶llel rules were established. The correlation coefficients (R) are 0.992, 0.988 and 0.990, respectively, and the average absolute relative errors (AAREs) are 6.77%, 8.70% and 7.63%, respectively, which proves that the constitutive equations of multilevel series rules can predict the flow stress of pure aluminum with good correlation and precision.展开更多
This paper presents a novel blind adaptive noncoherent decorrelative multiuser detector for nonlinearly modulated satellite mobile Code Division Multiple Access (CDMA) systems. By using the known signature waveforms o...This paper presents a novel blind adaptive noncoherent decorrelative multiuser detector for nonlinearly modulated satellite mobile Code Division Multiple Access (CDMA) systems. By using the known signature waveforms of the counterpart earth station in the blind adaptive multiuser detector, the system performance has been improved obviously. The computation results about the convergence properties of the new detector and the previous detectors demonstrate that the proposed multiuser detector has better performance than previous multiuser detectors for nonlinearly modulated CDMA systems.展开更多
Steady-state periodical response is investigated for an axially moving viscoelastic beam with hybrid supports via approximate analysis with numerical confirmation. It is assumed that the excitation is spatially unifor...Steady-state periodical response is investigated for an axially moving viscoelastic beam with hybrid supports via approximate analysis with numerical confirmation. It is assumed that the excitation is spatially uniform and temporally harmonic. The transverse motion of axially moving beams is governed by a nonlinear partial-differential equation and a nonlinear integro-partial-differential equation. The material time derivative is used in the viscoelastic constitutive relation. The method of multiple scales is applied to the governing equations to investigate primary resonances under general boundary conditions. It is demonstrated that the mode uninvolved in the resonance has no effect on the steady-state response. Numerical examples are presented to demonstrate the effects of the boundary constraint stiffness on the amplitude and the stability of the steady-state response. The results derived for two governing equations are qualitatively the same,but quantitatively different. The differential quadrature schemes are developed to verify those results via the method of multiple scales.展开更多
An approach of stochastically statistical mechanics and a unified molecular theory of nonlinear viscoelasticity with constraints of Nagai chain entanglement for polymer melts have been proposed. A multimode model stru...An approach of stochastically statistical mechanics and a unified molecular theory of nonlinear viscoelasticity with constraints of Nagai chain entanglement for polymer melts have been proposed. A multimode model structure for a single polymer chain with n tail segments and N reversible entanglement sites on the test polymer chain is developed. Based on the above model structure and the mechanism of molecular flow by the dynamical reorganization of entanglement sites, the probability distribution function of the end-to-end vectr for a single polymer chain at entangled state and the viscoelastic free energy of deformation for polymer melts are calculated by using the method of the stochastically statistical mechanics. The four types of stress-strain relation and the memory function are derived from this thery. The above theoretical relations are verified by the experimentaf data for various polymer melts. These relations are found to be in good agreement with the experimental results展开更多
In the paper, 3-D analysis method with unitive schemes is set up, which is used to resolve the uplift with multiple moving boundaries and multiple nonlinear coupling for anchored liquid storage tanks. hi it, an algori...In the paper, 3-D analysis method with unitive schemes is set up, which is used to resolve the uplift with multiple moving boundaries and multiple nonlinear coupling for anchored liquid storage tanks. hi it, an algorithm of quasi-harmonious finite elements for arbitrary quadrilateral of thin plates and shells is built up to analyze the multiple coupling problems of general thin plates and shells structures with three dimensions, the complementary equations for analyzing uplifting moving boundary problems are deduced. The axial symmetry and presumption of beam type mode are not used. In it, an algorithm is put forward for analyzing the Navier-Stokes problems of unsteady, three-dimensional, and viscous liquid with sloshing of moving boundary surfaces in large amplitude under ALE frame by scheme of time-split-steps to which linear potential theory is not applied. The algorithms can be used to analyze the solid-liquid multiple nonlinear coupling problems with 3-D moving boundary with friction in multiple places.展开更多
By using non-static atmosphere equations including basic current, heating force and friction, we discuss the balance amplitude of vertical motion in the conditions of constant heating force, linear and non-linear inte...By using non-static atmosphere equations including basic current, heating force and friction, we discuss the balance amplitude of vertical motion in the conditions of constant heating force, linear and non-linear interaction between large-scale ascending motion and diabatic heating force. In the non-linear condition, the multiple equilibrium feature of the tropical cyclone development is discussed and the reason of the sudden varying of tropical cyclone intensity is studied preliminarily.展开更多
I. Introduction In this paper we are looking for solutions of the following Hamiltonian system of second order: where x= （x1, x2） and V satisfies （V. 1） V: R×R2→R is a C1-function, 1-periodic In t, （V.2） V...I. Introduction In this paper we are looking for solutions of the following Hamiltonian system of second order: where x= （x1, x2） and V satisfies （V. 1） V: R×R2→R is a C1-function, 1-periodic In t, （V.2） V is periodic in x1 with the period T>0, （V. 3） V→O, Vx→O as |x2|→∞, uniformly in （t, x1）.展开更多
Estimation of support pressure is extremely important to the support system design and the construction safety of tunnels.At present,there are many methods for the estimation of support pressure based on different roc...Estimation of support pressure is extremely important to the support system design and the construction safety of tunnels.At present,there are many methods for the estimation of support pressure based on different rock mass classification systems,such as Q system,GSI system and RMR system.However,various rock mass classification systems are based on different tunnel geologic conditions in various regions.Therefore,each rock mass classification system has a certain regionality.In China,the BQ-Inex(BQ system)has been widely used in the field of rock engineering ever since its development.Unfortunately,there is still no estimation method of support pressure with BQ-index as parameters.Based on the field test data from 54 tunnels in China,a new empirical method considering BQ-Inex,tunnel span and rock weight is proposed to estimate the support pressure using multiple nonlinear regression analysis methods.And then the significance and necessity of support pressure estimation method for the safety of tunnel construction in China is explained through the comparison and analysis with the existing internationally widely used support pressure estimation methods of RMR system,Q system and GSI system.Finally,the empirical method of estimating the support pressure based on BQ-index was applied to designing the support system in the China’s high-speed railway tunnel—Zhengwan high-speed railway and the rationality of this method has been verified through the data of field test.展开更多
Understanding the strength characteristics and deformation behaviour of the tunnel surrounding rock in a fault zone is significant for tunnel stability evaluation.In this study,a series of unconfined compression tests...Understanding the strength characteristics and deformation behaviour of the tunnel surrounding rock in a fault zone is significant for tunnel stability evaluation.In this study,a series of unconfined compression tests were conducted to investigate the mechanical characteristics and failure behaviour of completely weathered granite(CWG)from a fault zone,considering with height-diameter(h/d)ratio,dry densities(ρd)and moisture contents(ω).Based on the experimental results,a regression mathematical model of unconfined compressive strength(UCS)for CWG was developed using the Multiple Nonlinear Regression method(MNLR).The research results indicated that the UCS of the specimen with a h/d ratio of 0.6 decreased with the increase ofω.When the h/d ratio increased to 1.0,the UCS increasedωwith up to 10.5%and then decreased.Increasingρd is conducive to the improvement of the UCS at anyω.The deformation and rupture process as well as final failure modes of the specimen are controlled by h/d ratio,ρd andω,and the h/d ratio is the dominant factor affecting the final failure mode,followed byωandρd.The specimens with different h/d ratio exhibited completely different fracture mode,i.e.,typical splitting failure(h/d=0.6)and shear failure(h/d=1.0).By comparing the experimental results,this regression model for predicting UCS is accurate and reliable,and the h/d ratio is the dominant factor affecting the UCS of CWG,followed byρd and thenω.These findings provide important references for maintenance of the tunnel crossing other fault fractured zones,especially at low confining pressure or unconfined condition.展开更多
Soil surface roughness, denoted by the root mean square height(RMSH), and soil moisture(SM) are critical factors that affect the accuracy of quantitative remote sensing research due to their combined influence on spec...Soil surface roughness, denoted by the root mean square height(RMSH), and soil moisture(SM) are critical factors that affect the accuracy of quantitative remote sensing research due to their combined influence on spectral reflectance(SR). In regards to this issue, three SM levels and four RMSH levels were artificially designed in this study; a total of 12 plots was used, each plot had a size of 3 m × 3 m. Eight spectral observations were conducted from 14 to 30 October 2017 to investigate the correlation between RMSH, SM, and SR. On this basis, 6 commonly used bands of optical satellite sensors were selected in this study, which are red(675 nm), green(555 nm), blue(485 nm), near infrared(845 nm), shortwave infrared 1(1600 nm), and shortwave infrared 2(2200 nm). A negative correlation was found between SR and RMSH, and between SR and SM. The bands with higher coefficient of determination R^2 values were selected for stepwise multiple nonlinear regression analysis. Four characterized bands(i.e., blue, green, near infrared, and shortwave infrared 2) were chosen as the independent variables to estimate SM with R^2 and root mean square error(RMSE) values equal to 0.62 and 2.6%, respectively. Similarly, the four bands(green, red, near infrared, and shortwave infrared 1) were used to estimate RMSH with R^2 and RMSE values equal to 0.48 and 0.69 cm, respectively. These results indicate that the method used is not only suitable for estimating SM but can also be extended to the prediction of RMSH. Finally, the evaluation approach presented in this paper highly restores the real situation of the natural farmland surface on the one hand, and obtains high precision values of SM and RMSH on the other. The method can be further applied to the prediction of farmland SM and RMSH based on satellite and unmanned aerial vehicle(UAV) optical imagery.展开更多
Design for six sigma （DFSS） is a powerful approach of designing products, processes, and services with the objective of meeting the needs of customers in a cost-effective maimer. DFSS activities are classified into ...Design for six sigma （DFSS） is a powerful approach of designing products, processes, and services with the objective of meeting the needs of customers in a cost-effective maimer. DFSS activities are classified into four major phases viz. identify, design, optimize, and validate （IDOV）. And an adaptive design for six sigma （ADFSS） incorporating the traits of artifidai intelligence and statistical techniques is presented. In the identify phase of the ADFSS, fuzzy relation measures between customer attributes （CAs） and engineering characteristics （ECs） as well as fuzzy correlation measures among ECs are determined with the aid of two fuzzy logic controllers （FLCs）. These two measures are then used to establish the cumulative impact factor for ECs. In the next phase （ i. e. design phase）, a transfer function is developed with the aid of robust multiple nonlinear regression analysis. Furthermore, 1this transfer function is optimized with the simulated annealing （ SA ） algorithm in the optimize phase. In the validate phase, t-test is conducted for the validation of the design resulted in earlier phase. Finally, a case study of a hypothetical writing instrument is simulated to test the efficacy of the proposed ADFSS.展开更多
The application of a closed-loop specification oriented feedback control design method, which addresses the design of controllers to satisfy multiple simultaneous conflicting closed-loop performance specifications is ...The application of a closed-loop specification oriented feedback control design method, which addresses the design of controllers to satisfy multiple simultaneous conflicting closed-loop performance specifications is presented. The proposed approach is well suited to the design of controllers which must meet a set of conflicting performance specifications. Gain tuning is central to the design process, however, the tuning process is greatly simplified over that presented by the problem of tuning a PID controller for example. The proposed control method is applied to an AC induction motor, with an inner-loop flux vector controller applied to design a position control system. Experimental results verify the effectiveness of this method.展开更多
Total organic carbon(TOC)content is a crucial evaluation parameter in the process of shale gas exploration and development.Marine-continental transitional shale is characterized by strong heterogeneity and thin single...Total organic carbon(TOC)content is a crucial evaluation parameter in the process of shale gas exploration and development.Marine-continental transitional shale is characterized by strong heterogeneity and thin single-layer thickness.The discrete TOC data measured by experimental methods are unable to accurately reflect the reservoir characteristics of marine-continental transitional shale.In this paper,a multivariate nonlinear regression prediction model(R-MNR)was established,and the model was applied to predict the TOC content of shale for the first time.TheΔlgR model,multiple linear regression model(MLR),BP neural network model(BP model),and R-MNR model were built to predict the TOC of shale in Benxi Formation.The coefficient of determination(R2),mean-absolute-percentage-error(MAPE),root-mean-square-error(RMSE),and the number of input layer parameters(NILP)were employed to assess the efficacy of the model through the analytic hierarchy process(AHP)method.The total weight of R-MNR is 0.361,and that of BP model is 0.336.The weights of the two traditional models are 0.104 and 0.199,respectively.The results indicate that the R-MNR is comparable to the BP model in terms of prediction accuracy,and both models are significantly more accurate than the traditional prediction model.The R-MNR is capable of obtaining a clear TOC prediction formula,which is convenient for verification and promotion.During the training process of the R-MNR,the influence of each parameter and coupling relationship on the prediction results is elucidated,which enables researchers to gain a deeper understanding of the geophysical significance and geological process of the model.The result of this study suggests that the R-MNR can be employed to predict the TOC content of marine-continental transitional shale effectively in the future.展开更多
This paper investigates the problem of global disturbance rejection for a class of switched nonlinear systems where the solvability of the disturbance rejection problem for subsystems is not assumed. The disturbances ...This paper investigates the problem of global disturbance rejection for a class of switched nonlinear systems where the solvability of the disturbance rejection problem for subsystems is not assumed. The disturbances are assumed to be sinusoidal with completely unknown frequencies, phases and amplitudes. First, as an extension of the classic concept of internal model for non-switched systems, a switched internal model is proposed. Second, in order to solve the problem under study, an adaptive control method is established on the basis of the multiple Lyapunov functions method. Also,adaptive state-feedback controllers of subsystems are designed and incorporated with a switching law to asymptotically reject the unknown disturbances. Finally, an example is provided to demonstrate the effectiveness of the proposed design method.展开更多
The construction of urban metro systems in Southwest China is invariably challenged by adverse geological conditions characteristic of water-rich karst formations.This study investigates the damage evolution mechanism...The construction of urban metro systems in Southwest China is invariably challenged by adverse geological conditions characteristic of water-rich karst formations.This study investigates the damage evolution mechanisms in the cavern-containing stratum and the extent of stratum damage through a comprehensive analysis of the shield tunnel construction in the Shenzhen-Huizhou double-line project.Firstly,the ground surface settlement curve was calculated by numerical modeling and theoretical calculation,and the results were verified by on-site monitoring data.The analysis confirmed that the tunnel construction simulation employed a synchronized excavation method for both parallel tunnels.Subsequently,the stratum dissolution rate(δ)and fissure surface roughness(f)were introduced,and PFC^(2D)was utilized to study the damage evolution mechanisms in the cavern-containing stratum.The data were then compared with the actual monitoring data to ensure the accuracy of the numerical simulation.It was found that the cave-containing stratum under the tunnel was most prone to collapse.Finally,to study the extent of damage to the stratum under such conditions,four factors,namely,fissure width e,fissure surface roughness f,dynamic viscosity of water u,and karst water pressure P_(w),were introduced to study and predict the extension of single-cave fissures.Additionally,the degree of connectivity(L^(*))between multiple caves was introduced to obtain the law between the L^(*)and karst water pressure and caved location.The results of the study provided some guidance for the prevention and control of water inrush disasters in karst areas.展开更多
In recent years,there have been many studies on the recognition of strawberry maturity,but there are still problems such as low recognition accuracy and expensive experimental instruments.These factors make their meth...In recent years,there have been many studies on the recognition of strawberry maturity,but there are still problems such as low recognition accuracy and expensive experimental instruments.These factors make their methods difficult for farmers to use.To solve these problems,we developed a fast,non-destructive,accurate and convenient method for strawberry maturity identification using smartphones.In this paper,strawberry maturity is divided into three levels:mature,nearly-mature and immature.Considering the actual strawberry harvest process and postharvest handling,we focus on the differentiation between the mature and the nearly-mature ones to help farmers reduce possible damage in transit and improve profitability.We obtained the images of strawberries with different maturities at 535 nm and 670 nm wavelengths through a smartphone and got absorbance data by image processing based on the region of interest.The absorbance data were used to establish three maturity recognition models—i.e.,multivariate linear,multivariate nonlinear and SoftMax regression classifier.The results showed that the multivariate nonlinear model had the highest identification accuracy(which is over 94%)in the greenhouse.Therefore,this method has considerable potential as a means for rapid recognition of strawberry maturity.展开更多
To deal with train delays in large high-speed railway stations,a multi-objective mixedinteger nonlinear programming(MO-MINLP)optimization model was proposed.The model used the arrival time,departure time,track occupat...To deal with train delays in large high-speed railway stations,a multi-objective mixedinteger nonlinear programming(MO-MINLP)optimization model was proposed.The model used the arrival time,departure time,track occupation,and route selection as the decision variables,and fully considered the station infrastructure layout,train operational requirements,and time standards as limiting factors.The optimization objectives were to minimize train delays and reduce track and to route adjustments.To realize the large-scale and rapid solution of the MO-MINLP model,this study proposed a rolling horizon optimization algorithm that used half an hour as a time interval and solved the rescheduling and platforming problem of each time interval step-by-step.In numerical experiments,227 train movements under delay circumstances in Hangzhoudong station were optimized by using the proposed model and solution algorithm.The results show that the proposed MO-MINLP model could resolve route conflicts,compress unnecessary dwell times,and reduce train delays,and the solution algorithm could efficiently increase the computational speed.The maximum solution time for optimizing the 227 train movements is 15 min 24 s.展开更多
基金Project(51275414)supported by the National Natural Science Foundation of ChinaProject(2015JM5204)supported by the Natural Science Foundation of Shaanxi Province,China+1 种基金Project(Z2015064)supported by the Graduate Starting Seed Fund of the Northwestern Polytechnical University,ChinaProject(130-QP-2015)supported by the Research Fund of the State Key Laboratory of Solidification Processing(NWPU),China
文摘In order to study the work-ability and establish the optimum hot formation processing parameters for industrial 1060 pure aluminum, the compressive deformation behavior of pure aluminum was investigated at temperatures of 523?823 K and strain rates of 0.005?10 s?1 on a Gleeble?1500 thermo-simulation machine. The influence rule of processing parameters (strain, strain rate and temperature) on flow stress of pure aluminum was investigated. Nine analysis factors consisting of material parameters and according weights were optimized. Then, the constitutive equations of multilevel series rules, multilevel parallel rules and multilevel series ¶llel rules were established. The correlation coefficients (R) are 0.992, 0.988 and 0.990, respectively, and the average absolute relative errors (AAREs) are 6.77%, 8.70% and 7.63%, respectively, which proves that the constitutive equations of multilevel series rules can predict the flow stress of pure aluminum with good correlation and precision.
文摘This paper presents a novel blind adaptive noncoherent decorrelative multiuser detector for nonlinearly modulated satellite mobile Code Division Multiple Access (CDMA) systems. By using the known signature waveforms of the counterpart earth station in the blind adaptive multiuser detector, the system performance has been improved obviously. The computation results about the convergence properties of the new detector and the previous detectors demonstrate that the proposed multiuser detector has better performance than previous multiuser detectors for nonlinearly modulated CDMA systems.
基金supported by the National Natural Science Foundation of China (10902064 and 10932006)China National Funds for Distinguished Young Scientists (10725209)+2 种基金the Program of Shanghai Subject Chief Scientist (09XD1401700)Shanghai Leading Talent Program,Shanghai Leading Academic Discipline Project (S30106)the program for Cheung Kong Scholars Programme and Innovative Research Team in University (IRT0844)
文摘Steady-state periodical response is investigated for an axially moving viscoelastic beam with hybrid supports via approximate analysis with numerical confirmation. It is assumed that the excitation is spatially uniform and temporally harmonic. The transverse motion of axially moving beams is governed by a nonlinear partial-differential equation and a nonlinear integro-partial-differential equation. The material time derivative is used in the viscoelastic constitutive relation. The method of multiple scales is applied to the governing equations to investigate primary resonances under general boundary conditions. It is demonstrated that the mode uninvolved in the resonance has no effect on the steady-state response. Numerical examples are presented to demonstrate the effects of the boundary constraint stiffness on the amplitude and the stability of the steady-state response. The results derived for two governing equations are qualitatively the same,but quantitatively different. The differential quadrature schemes are developed to verify those results via the method of multiple scales.
文摘An approach of stochastically statistical mechanics and a unified molecular theory of nonlinear viscoelasticity with constraints of Nagai chain entanglement for polymer melts have been proposed. A multimode model structure for a single polymer chain with n tail segments and N reversible entanglement sites on the test polymer chain is developed. Based on the above model structure and the mechanism of molecular flow by the dynamical reorganization of entanglement sites, the probability distribution function of the end-to-end vectr for a single polymer chain at entangled state and the viscoelastic free energy of deformation for polymer melts are calculated by using the method of the stochastically statistical mechanics. The four types of stress-strain relation and the memory function are derived from this thery. The above theoretical relations are verified by the experimentaf data for various polymer melts. These relations are found to be in good agreement with the experimental results
文摘In the paper, 3-D analysis method with unitive schemes is set up, which is used to resolve the uplift with multiple moving boundaries and multiple nonlinear coupling for anchored liquid storage tanks. hi it, an algorithm of quasi-harmonious finite elements for arbitrary quadrilateral of thin plates and shells is built up to analyze the multiple coupling problems of general thin plates and shells structures with three dimensions, the complementary equations for analyzing uplifting moving boundary problems are deduced. The axial symmetry and presumption of beam type mode are not used. In it, an algorithm is put forward for analyzing the Navier-Stokes problems of unsteady, three-dimensional, and viscous liquid with sloshing of moving boundary surfaces in large amplitude under ALE frame by scheme of time-split-steps to which linear potential theory is not applied. The algorithms can be used to analyze the solid-liquid multiple nonlinear coupling problems with 3-D moving boundary with friction in multiple places.
文摘By using non-static atmosphere equations including basic current, heating force and friction, we discuss the balance amplitude of vertical motion in the conditions of constant heating force, linear and non-linear interaction between large-scale ascending motion and diabatic heating force. In the non-linear condition, the multiple equilibrium feature of the tropical cyclone development is discussed and the reason of the sudden varying of tropical cyclone intensity is studied preliminarily.
文摘I. Introduction In this paper we are looking for solutions of the following Hamiltonian system of second order: where x= （x1, x2） and V satisfies （V. 1） V: R×R2→R is a C1-function, 1-periodic In t, （V.2） V is periodic in x1 with the period T>0, （V. 3） V→O, Vx→O as |x2|→∞, uniformly in （t, x1）.
基金Projects(51878567,51878568,51578458)supported by the National Natural Science Foundation of ChinaProjects(2017G007-F,2017G007-H)supported by China Railway Science and Technology Research and Development Plan。
文摘Estimation of support pressure is extremely important to the support system design and the construction safety of tunnels.At present,there are many methods for the estimation of support pressure based on different rock mass classification systems,such as Q system,GSI system and RMR system.However,various rock mass classification systems are based on different tunnel geologic conditions in various regions.Therefore,each rock mass classification system has a certain regionality.In China,the BQ-Inex(BQ system)has been widely used in the field of rock engineering ever since its development.Unfortunately,there is still no estimation method of support pressure with BQ-index as parameters.Based on the field test data from 54 tunnels in China,a new empirical method considering BQ-Inex,tunnel span and rock weight is proposed to estimate the support pressure using multiple nonlinear regression analysis methods.And then the significance and necessity of support pressure estimation method for the safety of tunnel construction in China is explained through the comparison and analysis with the existing internationally widely used support pressure estimation methods of RMR system,Q system and GSI system.Finally,the empirical method of estimating the support pressure based on BQ-index was applied to designing the support system in the China’s high-speed railway tunnel—Zhengwan high-speed railway and the rationality of this method has been verified through the data of field test.
基金supported by the National Natural Science Foundation of China,NSFC(No.42202318).
文摘Understanding the strength characteristics and deformation behaviour of the tunnel surrounding rock in a fault zone is significant for tunnel stability evaluation.In this study,a series of unconfined compression tests were conducted to investigate the mechanical characteristics and failure behaviour of completely weathered granite(CWG)from a fault zone,considering with height-diameter(h/d)ratio,dry densities(ρd)and moisture contents(ω).Based on the experimental results,a regression mathematical model of unconfined compressive strength(UCS)for CWG was developed using the Multiple Nonlinear Regression method(MNLR).The research results indicated that the UCS of the specimen with a h/d ratio of 0.6 decreased with the increase ofω.When the h/d ratio increased to 1.0,the UCS increasedωwith up to 10.5%and then decreased.Increasingρd is conducive to the improvement of the UCS at anyω.The deformation and rupture process as well as final failure modes of the specimen are controlled by h/d ratio,ρd andω,and the h/d ratio is the dominant factor affecting the final failure mode,followed byωandρd.The specimens with different h/d ratio exhibited completely different fracture mode,i.e.,typical splitting failure(h/d=0.6)and shear failure(h/d=1.0).By comparing the experimental results,this regression model for predicting UCS is accurate and reliable,and the h/d ratio is the dominant factor affecting the UCS of CWG,followed byρd and thenω.These findings provide important references for maintenance of the tunnel crossing other fault fractured zones,especially at low confining pressure or unconfined condition.
基金Under the auspices of the Excellent Youth Talent Project of Jilin Science and Technology Development Program(No.20170520078JH)Science and Technology Basic Work of Science and Technology(No.2014FY210800–4)National Natural Science Foundation of China(No.41601382)
文摘Soil surface roughness, denoted by the root mean square height(RMSH), and soil moisture(SM) are critical factors that affect the accuracy of quantitative remote sensing research due to their combined influence on spectral reflectance(SR). In regards to this issue, three SM levels and four RMSH levels were artificially designed in this study; a total of 12 plots was used, each plot had a size of 3 m × 3 m. Eight spectral observations were conducted from 14 to 30 October 2017 to investigate the correlation between RMSH, SM, and SR. On this basis, 6 commonly used bands of optical satellite sensors were selected in this study, which are red(675 nm), green(555 nm), blue(485 nm), near infrared(845 nm), shortwave infrared 1(1600 nm), and shortwave infrared 2(2200 nm). A negative correlation was found between SR and RMSH, and between SR and SM. The bands with higher coefficient of determination R^2 values were selected for stepwise multiple nonlinear regression analysis. Four characterized bands(i.e., blue, green, near infrared, and shortwave infrared 2) were chosen as the independent variables to estimate SM with R^2 and root mean square error(RMSE) values equal to 0.62 and 2.6%, respectively. Similarly, the four bands(green, red, near infrared, and shortwave infrared 1) were used to estimate RMSH with R^2 and RMSE values equal to 0.48 and 0.69 cm, respectively. These results indicate that the method used is not only suitable for estimating SM but can also be extended to the prediction of RMSH. Finally, the evaluation approach presented in this paper highly restores the real situation of the natural farmland surface on the one hand, and obtains high precision values of SM and RMSH on the other. The method can be further applied to the prediction of farmland SM and RMSH based on satellite and unmanned aerial vehicle(UAV) optical imagery.
基金Shanghai Leading Academic Discipline Project,China(No.B602)
文摘Design for six sigma （DFSS） is a powerful approach of designing products, processes, and services with the objective of meeting the needs of customers in a cost-effective maimer. DFSS activities are classified into four major phases viz. identify, design, optimize, and validate （IDOV）. And an adaptive design for six sigma （ADFSS） incorporating the traits of artifidai intelligence and statistical techniques is presented. In the identify phase of the ADFSS, fuzzy relation measures between customer attributes （CAs） and engineering characteristics （ECs） as well as fuzzy correlation measures among ECs are determined with the aid of two fuzzy logic controllers （FLCs）. These two measures are then used to establish the cumulative impact factor for ECs. In the next phase （ i. e. design phase）, a transfer function is developed with the aid of robust multiple nonlinear regression analysis. Furthermore, 1this transfer function is optimized with the simulated annealing （ SA ） algorithm in the optimize phase. In the validate phase, t-test is conducted for the validation of the design resulted in earlier phase. Finally, a case study of a hypothetical writing instrument is simulated to test the efficacy of the proposed ADFSS.
文摘The application of a closed-loop specification oriented feedback control design method, which addresses the design of controllers to satisfy multiple simultaneous conflicting closed-loop performance specifications is presented. The proposed approach is well suited to the design of controllers which must meet a set of conflicting performance specifications. Gain tuning is central to the design process, however, the tuning process is greatly simplified over that presented by the problem of tuning a PID controller for example. The proposed control method is applied to an AC induction motor, with an inner-loop flux vector controller applied to design a position control system. Experimental results verify the effectiveness of this method.
基金funded by the National Natural Science Foundation of China(Grant No.42372194)the Natural Science Foundation of Shanxi Province,China(No.20210302123165),the Chinese Postdoctoral Science Foundation(No.2024T170634)the Open Fund Project of Provincial Center of Technology Innovation for Coal Measure Gas Co-production(ZZGSSASMCYJ2024-0306).
文摘Total organic carbon(TOC)content is a crucial evaluation parameter in the process of shale gas exploration and development.Marine-continental transitional shale is characterized by strong heterogeneity and thin single-layer thickness.The discrete TOC data measured by experimental methods are unable to accurately reflect the reservoir characteristics of marine-continental transitional shale.In this paper,a multivariate nonlinear regression prediction model(R-MNR)was established,and the model was applied to predict the TOC content of shale for the first time.TheΔlgR model,multiple linear regression model(MLR),BP neural network model(BP model),and R-MNR model were built to predict the TOC of shale in Benxi Formation.The coefficient of determination(R2),mean-absolute-percentage-error(MAPE),root-mean-square-error(RMSE),and the number of input layer parameters(NILP)were employed to assess the efficacy of the model through the analytic hierarchy process(AHP)method.The total weight of R-MNR is 0.361,and that of BP model is 0.336.The weights of the two traditional models are 0.104 and 0.199,respectively.The results indicate that the R-MNR is comparable to the BP model in terms of prediction accuracy,and both models are significantly more accurate than the traditional prediction model.The R-MNR is capable of obtaining a clear TOC prediction formula,which is convenient for verification and promotion.During the training process of the R-MNR,the influence of each parameter and coupling relationship on the prediction results is elucidated,which enables researchers to gain a deeper understanding of the geophysical significance and geological process of the model.The result of this study suggests that the R-MNR can be employed to predict the TOC content of marine-continental transitional shale effectively in the future.
基金supported by the National Natural Science Foundation of China under Grant Nos.61773100 and 61773098IAPI Fundamental Research Funds under Grant No.2013ZCX03-02Fundamental Research Funds for the Central Universities under Grant No.N150404024
文摘This paper investigates the problem of global disturbance rejection for a class of switched nonlinear systems where the solvability of the disturbance rejection problem for subsystems is not assumed. The disturbances are assumed to be sinusoidal with completely unknown frequencies, phases and amplitudes. First, as an extension of the classic concept of internal model for non-switched systems, a switched internal model is proposed. Second, in order to solve the problem under study, an adaptive control method is established on the basis of the multiple Lyapunov functions method. Also,adaptive state-feedback controllers of subsystems are designed and incorporated with a switching law to asymptotically reject the unknown disturbances. Finally, an example is provided to demonstrate the effectiveness of the proposed design method.
基金supported by the National Natural Science Foundation of China(Grant No.52278387).
文摘The construction of urban metro systems in Southwest China is invariably challenged by adverse geological conditions characteristic of water-rich karst formations.This study investigates the damage evolution mechanisms in the cavern-containing stratum and the extent of stratum damage through a comprehensive analysis of the shield tunnel construction in the Shenzhen-Huizhou double-line project.Firstly,the ground surface settlement curve was calculated by numerical modeling and theoretical calculation,and the results were verified by on-site monitoring data.The analysis confirmed that the tunnel construction simulation employed a synchronized excavation method for both parallel tunnels.Subsequently,the stratum dissolution rate(δ)and fissure surface roughness(f)were introduced,and PFC^(2D)was utilized to study the damage evolution mechanisms in the cavern-containing stratum.The data were then compared with the actual monitoring data to ensure the accuracy of the numerical simulation.It was found that the cave-containing stratum under the tunnel was most prone to collapse.Finally,to study the extent of damage to the stratum under such conditions,four factors,namely,fissure width e,fissure surface roughness f,dynamic viscosity of water u,and karst water pressure P_(w),were introduced to study and predict the extension of single-cave fissures.Additionally,the degree of connectivity(L^(*))between multiple caves was introduced to obtain the law between the L^(*)and karst water pressure and caved location.The results of the study provided some guidance for the prevention and control of water inrush disasters in karst areas.
基金This research was supported by the National Training Program of Innovation and Entrepreneurship for Undergraduates(No.201710019174).
文摘In recent years,there have been many studies on the recognition of strawberry maturity,but there are still problems such as low recognition accuracy and expensive experimental instruments.These factors make their methods difficult for farmers to use.To solve these problems,we developed a fast,non-destructive,accurate and convenient method for strawberry maturity identification using smartphones.In this paper,strawberry maturity is divided into three levels:mature,nearly-mature and immature.Considering the actual strawberry harvest process and postharvest handling,we focus on the differentiation between the mature and the nearly-mature ones to help farmers reduce possible damage in transit and improve profitability.We obtained the images of strawberries with different maturities at 535 nm and 670 nm wavelengths through a smartphone and got absorbance data by image processing based on the region of interest.The absorbance data were used to establish three maturity recognition models—i.e.,multivariate linear,multivariate nonlinear and SoftMax regression classifier.The results showed that the multivariate nonlinear model had the highest identification accuracy(which is over 94%)in the greenhouse.Therefore,this method has considerable potential as a means for rapid recognition of strawberry maturity.
基金supported by the National Key R&D Program of China,(No.2021YFB1600100)the Natural Science Foundation of Shanghai(Nos.21YF1450200 and 23ZR1467400)+1 种基金the National Natural Science Foundation of China(No.72101184)the Fundamental Research Funds for the Central Universities.
文摘To deal with train delays in large high-speed railway stations,a multi-objective mixedinteger nonlinear programming(MO-MINLP)optimization model was proposed.The model used the arrival time,departure time,track occupation,and route selection as the decision variables,and fully considered the station infrastructure layout,train operational requirements,and time standards as limiting factors.The optimization objectives were to minimize train delays and reduce track and to route adjustments.To realize the large-scale and rapid solution of the MO-MINLP model,this study proposed a rolling horizon optimization algorithm that used half an hour as a time interval and solved the rescheduling and platforming problem of each time interval step-by-step.In numerical experiments,227 train movements under delay circumstances in Hangzhoudong station were optimized by using the proposed model and solution algorithm.The results show that the proposed MO-MINLP model could resolve route conflicts,compress unnecessary dwell times,and reduce train delays,and the solution algorithm could efficiently increase the computational speed.The maximum solution time for optimizing the 227 train movements is 15 min 24 s.
