Designing a robust controller for a system with timevarying delays poses a major challenge. In this paper, we propose a method based on mixed sensitivity H∞ for the control of linear time invariant（LTI） systems wit...Designing a robust controller for a system with timevarying delays poses a major challenge. In this paper, we propose a method based on mixed sensitivity H∞ for the control of linear time invariant（LTI） systems with varying time delays. The time delay is assumed bounded and the upper bound is known. In the technique we propose, the delay affecting the plant to be controlled is treated as an unmodeled uncertainty（in form of multiplicative uncertainty）. That uncertainty is approximated and then an H∞based controller, for the plant represented by the multiplicative uncertainty and the nominal model, is calculated. The obtained H∞controller is used to control the LTI systems with varying time delays. Simulation examples are given to illustrate the effectiveness of the proposed method.展开更多
According to requirements of the bank-to-turn (BTT) control for a small diameter bomb (SDB), the robust design problem for the roll autopilot was studied by H∞-mixed sensitivity control method. A roll channel dynamic...According to requirements of the bank-to-turn (BTT) control for a small diameter bomb (SDB), the robust design problem for the roll autopilot was studied by H∞-mixed sensitivity control method. A roll channel dynamics model was established. Considering the couple between the yaw and roll channel as uncertain disturbance, the roll autopilot was designed using dual-loop scheme which takes a linear quadratic regulator (LQR) as inner-loop, to ensure the control effect of the certain part in model, and an H∞-mixed sensitivity control as outer-loop, to restrain coupling disturbance and strengthen the system's robust performance. The dynamic tracking performance and the robustness for the parameter disturbance of the roll controller were analyzed. The simulated results show that the roll control system functions better and robustly.展开更多
The tracking performance of motor current is an important factor that affects the assistance torque of electric power steering （EPS） system. Bad tracking performance will cause assistant torque delay, and make road ...The tracking performance of motor current is an important factor that affects the assistance torque of electric power steering （EPS） system. Bad tracking performance will cause assistant torque delay, and make road feeling bad, and is influenced by the input steering torque and system measuring noise. However the existing methods have some shortages on system＇s robust dynamic performance and robust stability. The mixed H2/H∞ strategy for recirculating ball-type EPS system in a pure electric bus is proposed, and vehicle dynamic model of the system is established. Due to the existence of system model uncertainty, disturbance signals, sensor noises and the demand of system dynamic performance, the indexes of robust performance and road feeling for drivers are defined as the appraisal control objectives. The H∞ method is introduced to design the H∞ controller, and the H2 method is applied to optimize the H∞ controller, thus the mixed H2/H∞ controller is designed. The response of EPS system to the motor current command with amplitude of 20 A, the road disturbance with amplitude of 500 N and the sensor random noise with the amplitude of 1 A is simulated. The simulation results show that the recirculating ball-type EPS system with the mixed H2/H∞ controller can attenuate the random noises and disturbances and track the boost curve well, so the mixed H2/H∞ controller can improve the system＇s robust performance and dynamic performance. For the purpose of verifying the performance of the designed control strategy, the motor current tracking performance ground tests are conducted with step response input of the steering wheel, double-lane steering test and lemniscate steering test, respectively. The tests show that the mixed H2/H∞ controller for the recirculating ball-type EPS system of pure electric bus is feasible. The designed controller can solve the robust performance and robust stability of the system, thus improve the tracking performance of the EPS system and provide satisfied road feeling for the drivers.展开更多
For the appearance of the additive perturbation of controller gain when the controller parameter has minute adjustment at the initial running stage of system,to avoid the adverse effects,this paper investigates the mi...For the appearance of the additive perturbation of controller gain when the controller parameter has minute adjustment at the initial running stage of system,to avoid the adverse effects,this paper investigates the mixed H_2/H_∞ state feedback attitude control problem of microsatellite based on extended LMI method.Firstly,the microsatellite attitude control system is established and transformed into corresponding state space form.Then,without the equivalence restriction of the two Lyapunov variables of H_2 and H∞performance,this paper introduces additional variables to design the mixed H_2/H_∞ control method based on LMI which can also reduce the conservatives.Finally,numerical simulations are analyzed to show that the proposed method can make the satellite stable within 20 s whether there is additive perturbation of the controller gain or not.The comparative analysis of the simulation results between extended LMI method and traditional LMI method also demonstrates the effectiveness and feasibility of the proposed method in this paper.展开更多
A new semi-active suspension control strategy through mixed H2/H∞ robust technique was developed due to its flexibility and robustness to model uncertainties.A full car model with seven degrees of freedom was establi...A new semi-active suspension control strategy through mixed H2/H∞ robust technique was developed due to its flexibility and robustness to model uncertainties.A full car model with seven degrees of freedom was established to demonstrate the effectiveness of the new control approach.Magneto-rheological(MR) dampers were designed,manufactured and characterized as available semi-active actuators in the developed semi-active suspension system.The four independent mixed H2/H∞ controllers were devised in order to perform a distributed semi-active control system in the vehicle by which the response velocity and reliability can be improved significantly.The performance of the proposed new approach was investigated in time and frequency domains.A good balance between vehicle's comfort and road holding was achieved.An effective and practical control strategy for semi-active suspension system was thus obtained.This new approach exhibits some advantages in implementation,performance flexibility and robustness compared to existing methods.展开更多
Objective To evaluate the effects of simvastatin combined with omega-3 fatty acids on high sensitive C-reactive protein(HsCRP), lipidemia, and fibrinolysis in coronary heart disease (CHD) and CHD risk equivalent patie...Objective To evaluate the effects of simvastatin combined with omega-3 fatty acids on high sensitive C-reactive protein(HsCRP), lipidemia, and fibrinolysis in coronary heart disease (CHD) and CHD risk equivalent patients with mixed dyslipi-demia. Methods A randomized, double-blind placebo controlled and parallel group trial was conducted. Patients with CHD and CHD risk equivalents with mixed dyslipidemia were treated with 10 or 20 mg simvastatin for 6-12 weeks. Following with the treatment of patients whose low-density lipoprotein cholesterol (LDL-ch) reaching goal level (< 100 mg/dL) or close to the goal (< 130 mg/dL), while triglyceride (TG) ≥200 mg/dL and < 500 mg/dL, was combined with omega-3 fatty acids (3 g/d) or a placebo for 2 months. The effects of the treatment on HsCRP, total cholesterol (TC), LDL-ch, high-density lipoprotein cholesterol (HDL-ch), TG, lipoprotein (a) [LP (a)], apolipoprotein A1 (apoA1), apolipoprotein B (apoB), plasminogen activator inhibitor-1 (PAI-1), and tissue plasminogen activator (tPA) were investigated. Forty patients finished the study with each group consisting of twenty patients. Results (1) There were significant reductions of HsCRP, TG, TC, and TC/HDL-ch, which decreased by 2.16 ±2.77 mg/L (38.5%), 94.0 ±65.4 mg/dL (31.1%), 13.3 ±22.3 mg/dL (6.3%), 0.78 ±1.60 respectively in the omega-3 fatty acids group (P< 0.01, < 0.001, < 0.05, < 0.05) compared to the baseline. HsCRP and triglyceride reduction were more significant in omega-3 fatty acids group compared to the placebo group (P=0.021 and 0.011 respectively). (2) In the omega-3 fatty acids group, the values and percentage of TG reduction had a significantly positive relation with HsCRP reduction (r=0.51 and 0.45, P=0.021 and 0.047 respectively). Conclusion In CHD and CHD risk equivalent patients with mixed dyslipidemia, dyslipidemia’s therapeutic effect using simvastatin and omega-3 fatty acids may result from not only the combination of lipid adjustment, but also enhancement of their own nonlipid influences.展开更多
In the presence of mixed micelle of a cationic and a nonionic surfactants,the reaction of scandium(Ⅲ) with phenylfluorone or its derivatives results in a very sensitive colouration:furthermore this chromophoric syste...In the presence of mixed micelle of a cationic and a nonionic surfactants,the reaction of scandium(Ⅲ) with phenylfluorone or its derivatives results in a very sensitive colouration:furthermore this chromophoric system tolerates the existence of a considerable amount of masking agents,so that many interfering ions can be masked and its selectivity would be further improved.After studying the optimum conditions and main charac- ters of some similar systems,the system of Sc(Ⅲ)—Orthonitrophenyuorone—Cetyltrimethylammonium Bromide(CTMAB)—Triton X-200 is chosen for the spectrophotometric determination of microamount of scandium.The proposed method shows not only high sensitivity(with a molar absorptivity of 2.12×1~sL mol^(-1)·cm^(-1))and selectivity,but also high tolerance of chromophoric conditions.Beer's law is obeyed over a range of 0～6.0 μg Sc/25ml.If the dual-wavelength method is applied,a much higher molar absorptivity o|' 3.04×10~5L·mol^(-1)·cm^(-1)than those of other systems ever reported in the literatures can be attained:more- over.its linear range is extended to 0～8.0 μg Sc/25ml and its reproducibility is also improved.展开更多
In order to study the effects of the process parameters on springback and section deformation, a sensitivity analysis model was established based on the combination use of the multi-parameter sensitivity analysis meth...In order to study the effects of the process parameters on springback and section deformation, a sensitivity analysis model was established based on the combination use of the multi-parameter sensitivity analysis method and the springback/section deformation prediction finite element model, and by using this model the sensitivities of the springback and the section deformation to process parameters were analyzed and compared. The results show that the most sensitive process conditions for springback angle are the boost speed and the pressure of pressure die, and the most sensitive process condition for section deformation is the number of cores. When the clamp force, the boost speed and the pressure of pressure die are utilized to control section deformation, the effect of these process parameters on springback should be considered. When the process parameters are mainly used to control springback, the effect of these process parameters on the section deformation should be always considered.展开更多
Background This work aims to provide an overview of the Mixed Reality(MR)technology’s use in maritime industry for training purposes.Current training procedures cover a broad range of procedural operations for Life-S...Background This work aims to provide an overview of the Mixed Reality(MR)technology’s use in maritime industry for training purposes.Current training procedures cover a broad range of procedural operations for Life-Saving Appliances(LSA)lifeboats;however,several gaps and limitations have been identified related to the practical training that can be addressed through the use of MR.Augmented,Virtual and Mixed Reality applications are already used in various fields in maritime industry,but their full potential have not been yet exploited.SafePASS project aims to exploit MR advantages in the maritime training by introducing a relevant application focusing on use and maintenance of LSA lifeboats.Methods An MR Training application is proposed supporting the training of crew members in equipment usage and operation,as well as in maintenance activities and procedures.The application consists of the training tool that trains crew members on handling lifeboats,the training evaluation tool that allows trainers to assess the performance of trainees,and the maintenance tool that supports crew members to perform maintenance activities and procedures on lifeboats.For each tool,an indicative session and scenario workflow are implemented,along with the main supported interactions of the trainee with the equipment.Results The application has been tested and validated both in lab environment and using a real LSA lifeboat,resulting to improved experience for the users that provided feedback and recommendations for further development.The application has also been demonstrated onboard a cruise ship,showcasing the supported functionalities to relevant stakeholders that recognized the added value of the application and suggested potential future exploitation areas.Conclusions The MR Training application has been evaluated as very promising in providing a user-friendly training environment that can support crew members in LSA lifeboat operation and maintenance,while it is still subject to improvement and further expansion.展开更多
Without applying any stable element techniques in the mixed methods, two simple generalized mixed element(GME) formulations were derived by combining the minimum potential energy principle and Hellinger–Reissner(H–R...Without applying any stable element techniques in the mixed methods, two simple generalized mixed element(GME) formulations were derived by combining the minimum potential energy principle and Hellinger–Reissner(H–R) variational principle. The main features of the GME formulations are that the common C0-continuous polynomial shape functions for displacement methods are used to express both displacement and stress variables, and the coefficient matrix of these formulations is not only automatically symmetric but also invertible. Hence, the numerical results of the generalized mixed methods based on the GME formulations are stable. Displacement as well as stress results can be obtained directly from the algebraic system for finite element analysis after introducing stress and displacement boundary conditions simultaneously. Numerical examples show that displacement and stress results retain the same accuracy. The results of the noncompatible generalized mixed method proposed herein are more accurate than those of the standard noncompatible displacement method. The noncompatible generalized mixed element is less sensitive to element geometric distortions.展开更多
Climate change will have important implications in water shore regions,such as Huang-Huai-Hai（3H） plain,where expected warmer and drier conditions might augment crop water demand.Sensitivity analysis is important in...Climate change will have important implications in water shore regions,such as Huang-Huai-Hai（3H） plain,where expected warmer and drier conditions might augment crop water demand.Sensitivity analysis is important in understanding the relative importance of climatic variables to the variation in reference evapotranspiration（ET 0）.In this study,the 51-yr ET 0 during winter wheat and summer maize growing season were calculated from a data set of daily climate variables in 40 meteorological stations.Sensitivity maps for key climate variables were estimated according to Kriging method and the spatial pattern of sensitivity coefficients for these key variables was plotted.In addition,the slopes of the linear regression lines for sensitivity coefficients were obtained.Results showed that ET 0 during winter wheat growing season accounted for the largest proportion of annual ET 0,due to its long phenological days,while ET 0 was detected to decrease significantly with the magnitude of 0.5 mm yr-1in summer maize growing season.Solar radiation is considered to be the most sensitive and primarily controlling variable for negative trend in ET 0 for summer maize season,and higher sensitive coefficient value of ET 0 to solar radiation and temperature were detected in east part and southwest part of 3H plain respectively.Relative humidity was demonstrated as the most sensitive factor for ET 0 in winter wheat growing season and declining relativity humidity also primarily controlled a negative trend in ET 0,furthermore the sensitivity coefficient to relative humidity increased from west to southeast.The eight sensitivity centrals were all found located in Shandong Province.These ET 0 along with its sensitivity maps under winter wheat-summer maize rotation system can be applied to predict the agricultural water demand and will assist water resources planning and management for this region.展开更多
An H^1-Galerkin mixed finite element method is discussed for a class of second order SchrSdinger equation. Optimal error estimates of semidiscrete schemes are derived for problems in one space dimension. At the same t...An H^1-Galerkin mixed finite element method is discussed for a class of second order SchrSdinger equation. Optimal error estimates of semidiscrete schemes are derived for problems in one space dimension. At the same time, optimal error estimates are derived for fully discrete schemes. And it is showed that the H1-Galerkin mixed finite element approximations have the same rate of convergence as in the classical mixed finite element methods without requiring the LBB consistency condition.展开更多
A highly efficient H1-Galerkin mixed finite element method （MFEM） is presented with linear triangular element for the parabolic integro-differential equation. Firstly, some new results about the integral estimation ...A highly efficient H1-Galerkin mixed finite element method （MFEM） is presented with linear triangular element for the parabolic integro-differential equation. Firstly, some new results about the integral estimation and asymptotic expansions are studied. Then, the superconvergence of order O（h^2） for both the original variable u in H1 （Ω） norm and the flux p = u in H（div, Ω） norm is derived through the interpolation post processing technique. Furthermore, with the help of the asymptotic expansions and a suitable auxiliary problem, the extrapolation solutions with accuracy O（h^3） are obtained for the above two variables. Finally, some numerical results are provided to confirm validity of the theoretical analysis and excellent performance of the proposed method.展开更多
An H1-Galerkin expanded mixed finite element method is discussed for a class of second order semi-linear hyperbolic wave equations. By using the mixed formulation, we can get the optimal approximation for three variab...An H1-Galerkin expanded mixed finite element method is discussed for a class of second order semi-linear hyperbolic wave equations. By using the mixed formulation, we can get the optimal approximation for three variables: the scalar unknown, its gradient and its flux(coefficient times the gradient), simultaneously. We also prove the existence and uniqueness of semi-discrete solution. Finally, we obtain some numerical results to illustrate the efficiency of the method.展开更多
Background:We used mixed models with random components to develop height-diameter(h-d) functions for mixed,uneven-aged stands in northwestern Durango(Mexico),considering the breast height diameter(d) and stand variabl...Background:We used mixed models with random components to develop height-diameter(h-d) functions for mixed,uneven-aged stands in northwestern Durango(Mexico),considering the breast height diameter(d) and stand variables as predictors.Methods:The data were obtained from 44 permanent plots used to monitor stand growth under forest management in the study area.Results:The generalized Bertalanffy-Richards model performed better than the other generalized models in predicting the total height of the species under study.For the genera Pinus and Quercus,the models were successfully calibrated by measuring the height of a subsample of three randomly selected trees close to the mean d,whereas for species of the genera Cupressus,Arbutus and Alnus,three trees were also selected,but they are specifically the maximum,minimum and mean d trees.Conclusions:The presented equations represent a new tool for the evaluation and management of natural forest in the region.展开更多
A new mixed scheme which combines the variation of constants and the H1-Galerkin mixed finite element method is constructed for nonlinear Sobolev equation with nonlinear con- vection term. Optimal error estimates are ...A new mixed scheme which combines the variation of constants and the H1-Galerkin mixed finite element method is constructed for nonlinear Sobolev equation with nonlinear con- vection term. Optimal error estimates are derived for both semidiscrete and fully discrete schemes. Finally, some numerical results are given to confirm the theoretical analysis of the proposed method.展开更多
H1-Galerkin mixed methods are proposed for viscoelasticity wave equation.Depending on the physical quantities of interest,two methods are discussed.The optimal error estimates and the proof of the existence and unique...H1-Galerkin mixed methods are proposed for viscoelasticity wave equation.Depending on the physical quantities of interest,two methods are discussed.The optimal error estimates and the proof of the existence and uniqueness of semidiscrete solutions are derived for problems in one space dimension.And the methods don＇t require the LBB condition.展开更多
文摘Designing a robust controller for a system with timevarying delays poses a major challenge. In this paper, we propose a method based on mixed sensitivity H∞ for the control of linear time invariant（LTI） systems with varying time delays. The time delay is assumed bounded and the upper bound is known. In the technique we propose, the delay affecting the plant to be controlled is treated as an unmodeled uncertainty（in form of multiplicative uncertainty）. That uncertainty is approximated and then an H∞based controller, for the plant represented by the multiplicative uncertainty and the nominal model, is calculated. The obtained H∞controller is used to control the LTI systems with varying time delays. Simulation examples are given to illustrate the effectiveness of the proposed method.
基金Sponsored by National Ministries and Commissions Research Program in Advance (102080403)
文摘According to requirements of the bank-to-turn (BTT) control for a small diameter bomb (SDB), the robust design problem for the roll autopilot was studied by H∞-mixed sensitivity control method. A roll channel dynamics model was established. Considering the couple between the yaw and roll channel as uncertain disturbance, the roll autopilot was designed using dual-loop scheme which takes a linear quadratic regulator (LQR) as inner-loop, to ensure the control effect of the certain part in model, and an H∞-mixed sensitivity control as outer-loop, to restrain coupling disturbance and strengthen the system's robust performance. The dynamic tracking performance and the robustness for the parameter disturbance of the roll controller were analyzed. The simulated results show that the roll control system functions better and robustly.
基金supported by National Natural Science Foundation of China (Grant No. 51005115, No. 51005248)Science Fund of State Key Laboratory of Automotive Safety and Energy of China (Grant No. KF11201)
文摘The tracking performance of motor current is an important factor that affects the assistance torque of electric power steering （EPS） system. Bad tracking performance will cause assistant torque delay, and make road feeling bad, and is influenced by the input steering torque and system measuring noise. However the existing methods have some shortages on system＇s robust dynamic performance and robust stability. The mixed H2/H∞ strategy for recirculating ball-type EPS system in a pure electric bus is proposed, and vehicle dynamic model of the system is established. Due to the existence of system model uncertainty, disturbance signals, sensor noises and the demand of system dynamic performance, the indexes of robust performance and road feeling for drivers are defined as the appraisal control objectives. The H∞ method is introduced to design the H∞ controller, and the H2 method is applied to optimize the H∞ controller, thus the mixed H2/H∞ controller is designed. The response of EPS system to the motor current command with amplitude of 20 A, the road disturbance with amplitude of 500 N and the sensor random noise with the amplitude of 1 A is simulated. The simulation results show that the recirculating ball-type EPS system with the mixed H2/H∞ controller can attenuate the random noises and disturbances and track the boost curve well, so the mixed H2/H∞ controller can improve the system＇s robust performance and dynamic performance. For the purpose of verifying the performance of the designed control strategy, the motor current tracking performance ground tests are conducted with step response input of the steering wheel, double-lane steering test and lemniscate steering test, respectively. The tests show that the mixed H2/H∞ controller for the recirculating ball-type EPS system of pure electric bus is feasible. The designed controller can solve the robust performance and robust stability of the system, thus improve the tracking performance of the EPS system and provide satisfied road feeling for the drivers.
文摘For the appearance of the additive perturbation of controller gain when the controller parameter has minute adjustment at the initial running stage of system,to avoid the adverse effects,this paper investigates the mixed H_2/H_∞ state feedback attitude control problem of microsatellite based on extended LMI method.Firstly,the microsatellite attitude control system is established and transformed into corresponding state space form.Then,without the equivalence restriction of the two Lyapunov variables of H_2 and H∞performance,this paper introduces additional variables to design the mixed H_2/H_∞ control method based on LMI which can also reduce the conservatives.Finally,numerical simulations are analyzed to show that the proposed method can make the satellite stable within 20 s whether there is additive perturbation of the controller gain or not.The comparative analysis of the simulation results between extended LMI method and traditional LMI method also demonstrates the effectiveness and feasibility of the proposed method in this paper.
基金Project(50775225) supported by the National Natural Science Foundation of ChinaProjects(CSTC, 2008AC6097, 2008BA6025) supported by National Natural Science Foundation of Chongqing, China
文摘A new semi-active suspension control strategy through mixed H2/H∞ robust technique was developed due to its flexibility and robustness to model uncertainties.A full car model with seven degrees of freedom was established to demonstrate the effectiveness of the new control approach.Magneto-rheological(MR) dampers were designed,manufactured and characterized as available semi-active actuators in the developed semi-active suspension system.The four independent mixed H2/H∞ controllers were devised in order to perform a distributed semi-active control system in the vehicle by which the response velocity and reliability can be improved significantly.The performance of the proposed new approach was investigated in time and frequency domains.A good balance between vehicle's comfort and road holding was achieved.An effective and practical control strategy for semi-active suspension system was thus obtained.This new approach exhibits some advantages in implementation,performance flexibility and robustness compared to existing methods.
文摘Objective To evaluate the effects of simvastatin combined with omega-3 fatty acids on high sensitive C-reactive protein(HsCRP), lipidemia, and fibrinolysis in coronary heart disease (CHD) and CHD risk equivalent patients with mixed dyslipi-demia. Methods A randomized, double-blind placebo controlled and parallel group trial was conducted. Patients with CHD and CHD risk equivalents with mixed dyslipidemia were treated with 10 or 20 mg simvastatin for 6-12 weeks. Following with the treatment of patients whose low-density lipoprotein cholesterol (LDL-ch) reaching goal level (< 100 mg/dL) or close to the goal (< 130 mg/dL), while triglyceride (TG) ≥200 mg/dL and < 500 mg/dL, was combined with omega-3 fatty acids (3 g/d) or a placebo for 2 months. The effects of the treatment on HsCRP, total cholesterol (TC), LDL-ch, high-density lipoprotein cholesterol (HDL-ch), TG, lipoprotein (a) [LP (a)], apolipoprotein A1 (apoA1), apolipoprotein B (apoB), plasminogen activator inhibitor-1 (PAI-1), and tissue plasminogen activator (tPA) were investigated. Forty patients finished the study with each group consisting of twenty patients. Results (1) There were significant reductions of HsCRP, TG, TC, and TC/HDL-ch, which decreased by 2.16 ±2.77 mg/L (38.5%), 94.0 ±65.4 mg/dL (31.1%), 13.3 ±22.3 mg/dL (6.3%), 0.78 ±1.60 respectively in the omega-3 fatty acids group (P< 0.01, < 0.001, < 0.05, < 0.05) compared to the baseline. HsCRP and triglyceride reduction were more significant in omega-3 fatty acids group compared to the placebo group (P=0.021 and 0.011 respectively). (2) In the omega-3 fatty acids group, the values and percentage of TG reduction had a significantly positive relation with HsCRP reduction (r=0.51 and 0.45, P=0.021 and 0.047 respectively). Conclusion In CHD and CHD risk equivalent patients with mixed dyslipidemia, dyslipidemia’s therapeutic effect using simvastatin and omega-3 fatty acids may result from not only the combination of lipid adjustment, but also enhancement of their own nonlipid influences.
文摘In the presence of mixed micelle of a cationic and a nonionic surfactants,the reaction of scandium(Ⅲ) with phenylfluorone or its derivatives results in a very sensitive colouration:furthermore this chromophoric system tolerates the existence of a considerable amount of masking agents,so that many interfering ions can be masked and its selectivity would be further improved.After studying the optimum conditions and main charac- ters of some similar systems,the system of Sc(Ⅲ)—Orthonitrophenyuorone—Cetyltrimethylammonium Bromide(CTMAB)—Triton X-200 is chosen for the spectrophotometric determination of microamount of scandium.The proposed method shows not only high sensitivity(with a molar absorptivity of 2.12×1~sL mol^(-1)·cm^(-1))and selectivity,but also high tolerance of chromophoric conditions.Beer's law is obeyed over a range of 0～6.0 μg Sc/25ml.If the dual-wavelength method is applied,a much higher molar absorptivity o|' 3.04×10~5L·mol^(-1)·cm^(-1)than those of other systems ever reported in the literatures can be attained:more- over.its linear range is extended to 0～8.0 μg Sc/25ml and its reproducibility is also improved.
基金Project (50975235) supported by the National Natural Science Foundation of ChinaProject (B08040) supported by the 111 Project
文摘In order to study the effects of the process parameters on springback and section deformation, a sensitivity analysis model was established based on the combination use of the multi-parameter sensitivity analysis method and the springback/section deformation prediction finite element model, and by using this model the sensitivities of the springback and the section deformation to process parameters were analyzed and compared. The results show that the most sensitive process conditions for springback angle are the boost speed and the pressure of pressure die, and the most sensitive process condition for section deformation is the number of cores. When the clamp force, the boost speed and the pressure of pressure die are utilized to control section deformation, the effect of these process parameters on springback should be considered. When the process parameters are mainly used to control springback, the effect of these process parameters on the section deformation should be always considered.
基金Supported by the Safe PASS project that has received funding from the European Union’s Horizon 2020 Research and Innovation programme (815146)。
文摘Background This work aims to provide an overview of the Mixed Reality(MR)technology’s use in maritime industry for training purposes.Current training procedures cover a broad range of procedural operations for Life-Saving Appliances(LSA)lifeboats;however,several gaps and limitations have been identified related to the practical training that can be addressed through the use of MR.Augmented,Virtual and Mixed Reality applications are already used in various fields in maritime industry,but their full potential have not been yet exploited.SafePASS project aims to exploit MR advantages in the maritime training by introducing a relevant application focusing on use and maintenance of LSA lifeboats.Methods An MR Training application is proposed supporting the training of crew members in equipment usage and operation,as well as in maintenance activities and procedures.The application consists of the training tool that trains crew members on handling lifeboats,the training evaluation tool that allows trainers to assess the performance of trainees,and the maintenance tool that supports crew members to perform maintenance activities and procedures on lifeboats.For each tool,an indicative session and scenario workflow are implemented,along with the main supported interactions of the trainee with the equipment.Results The application has been tested and validated both in lab environment and using a real LSA lifeboat,resulting to improved experience for the users that provided feedback and recommendations for further development.The application has also been demonstrated onboard a cruise ship,showcasing the supported functionalities to relevant stakeholders that recognized the added value of the application and suggested potential future exploitation areas.Conclusions The MR Training application has been evaluated as very promising in providing a user-friendly training environment that can support crew members in LSA lifeboat operation and maintenance,while it is still subject to improvement and further expansion.
基金supported by the National Natural Science Foundation of China (Grant 11502286)
文摘Without applying any stable element techniques in the mixed methods, two simple generalized mixed element(GME) formulations were derived by combining the minimum potential energy principle and Hellinger–Reissner(H–R) variational principle. The main features of the GME formulations are that the common C0-continuous polynomial shape functions for displacement methods are used to express both displacement and stress variables, and the coefficient matrix of these formulations is not only automatically symmetric but also invertible. Hence, the numerical results of the generalized mixed methods based on the GME formulations are stable. Displacement as well as stress results can be obtained directly from the algebraic system for finite element analysis after introducing stress and displacement boundary conditions simultaneously. Numerical examples show that displacement and stress results retain the same accuracy. The results of the noncompatible generalized mixed method proposed herein are more accurate than those of the standard noncompatible displacement method. The noncompatible generalized mixed element is less sensitive to element geometric distortions.
基金supported by the Key Technologies R&D Program of China during the 12th Five-Year Plan period(2012BAD09B01)the National 973 Program of China(2012CB955904)the Project of Food Security and Climate Change in the Asia-Pacific Region:Evaluating Mismatch between Crop Development and Water Availability and Project of National Non-profit Institute Fund,China-Australia(BSRF201206)
文摘Climate change will have important implications in water shore regions,such as Huang-Huai-Hai（3H） plain,where expected warmer and drier conditions might augment crop water demand.Sensitivity analysis is important in understanding the relative importance of climatic variables to the variation in reference evapotranspiration（ET 0）.In this study,the 51-yr ET 0 during winter wheat and summer maize growing season were calculated from a data set of daily climate variables in 40 meteorological stations.Sensitivity maps for key climate variables were estimated according to Kriging method and the spatial pattern of sensitivity coefficients for these key variables was plotted.In addition,the slopes of the linear regression lines for sensitivity coefficients were obtained.Results showed that ET 0 during winter wheat growing season accounted for the largest proportion of annual ET 0,due to its long phenological days,while ET 0 was detected to decrease significantly with the magnitude of 0.5 mm yr-1in summer maize growing season.Solar radiation is considered to be the most sensitive and primarily controlling variable for negative trend in ET 0 for summer maize season,and higher sensitive coefficient value of ET 0 to solar radiation and temperature were detected in east part and southwest part of 3H plain respectively.Relative humidity was demonstrated as the most sensitive factor for ET 0 in winter wheat growing season and declining relativity humidity also primarily controlled a negative trend in ET 0,furthermore the sensitivity coefficient to relative humidity increased from west to southeast.The eight sensitivity centrals were all found located in Shandong Province.These ET 0 along with its sensitivity maps under winter wheat-summer maize rotation system can be applied to predict the agricultural water demand and will assist water resources planning and management for this region.
基金Supported by the National Natural Science Foundation of China (10601022)Natural Science Foundation of Inner Mongolia Autonomous Region (200607010106)Youth Science Foundation of Inner Mongolia University(ND0702)
文摘An H^1-Galerkin mixed finite element method is discussed for a class of second order SchrSdinger equation. Optimal error estimates of semidiscrete schemes are derived for problems in one space dimension. At the same time, optimal error estimates are derived for fully discrete schemes. And it is showed that the H1-Galerkin mixed finite element approximations have the same rate of convergence as in the classical mixed finite element methods without requiring the LBB consistency condition.
基金Project supported by the National Natural Science Foundation of China(Nos.10971203,11271340,and 11101381)the Specialized Research Fund for the Doctoral Program of Higher Education(No.20094101110006)
文摘A highly efficient H1-Galerkin mixed finite element method （MFEM） is presented with linear triangular element for the parabolic integro-differential equation. Firstly, some new results about the integral estimation and asymptotic expansions are studied. Then, the superconvergence of order O（h^2） for both the original variable u in H1 （Ω） norm and the flux p = u in H（div, Ω） norm is derived through the interpolation post processing technique. Furthermore, with the help of the asymptotic expansions and a suitable auxiliary problem, the extrapolation solutions with accuracy O（h^3） are obtained for the above two variables. Finally, some numerical results are provided to confirm validity of the theoretical analysis and excellent performance of the proposed method.
基金Supported by the National Natural Science Fund(11061021)Supported by the Scientific Research Projection of Higher Schools of Inner Mongolia(NJZZ12011, NJ10006)+1 种基金Supported by the Program of Higher-level talents of Inner Mongolia University(125119)Supported by the Scientific Research Projection of Inner Mongolia University of Finance and Economics(KY1101)
文摘An H1-Galerkin expanded mixed finite element method is discussed for a class of second order semi-linear hyperbolic wave equations. By using the mixed formulation, we can get the optimal approximation for three variables: the scalar unknown, its gradient and its flux(coefficient times the gradient), simultaneously. We also prove the existence and uniqueness of semi-discrete solution. Finally, we obtain some numerical results to illustrate the efficiency of the method.
基金financially supported by the"Programa de Mejoramiento del Profesorado"(project:Seguimiento y Evaluacion de Sitios Permanentes de Investigación Forestal y el Impacto Socioeconómico delManejo Forestal en Norte de México)supported by"Programa Banco Santander-USC"(becas para estancias predoctorales destinadas a docentes e investigadores de America Latina)
文摘Background:We used mixed models with random components to develop height-diameter(h-d) functions for mixed,uneven-aged stands in northwestern Durango(Mexico),considering the breast height diameter(d) and stand variables as predictors.Methods:The data were obtained from 44 permanent plots used to monitor stand growth under forest management in the study area.Results:The generalized Bertalanffy-Richards model performed better than the other generalized models in predicting the total height of the species under study.For the genera Pinus and Quercus,the models were successfully calibrated by measuring the height of a subsample of three randomly selected trees close to the mean d,whereas for species of the genera Cupressus,Arbutus and Alnus,three trees were also selected,but they are specifically the maximum,minimum and mean d trees.Conclusions:The presented equations represent a new tool for the evaluation and management of natural forest in the region.
基金Supported by National Natural Science Fund of China (11061021)Key Project of Chinese Ministry of Education (12024)+2 种基金Natural Science Fund of Inner Mongolia Autonomous Region (2012MS0108,2012MS0106,2011BS0102)Scientific Research Projection of Higher Schools of Inner Mongolia (NJZZ12011,NJZY13199)Program of Higher-level talents of Inner Mongolia University (125119,Z200901004,30105-125132)
文摘A new mixed scheme which combines the variation of constants and the H1-Galerkin mixed finite element method is constructed for nonlinear Sobolev equation with nonlinear con- vection term. Optimal error estimates are derived for both semidiscrete and fully discrete schemes. Finally, some numerical results are given to confirm the theoretical analysis of the proposed method.
基金Supported by NNSF(10601022,11061021)Supported by NSF of Inner Mongolia Au-tonomous Region(200607010106)Supported by SRP of Higher Schools of Inner Mongolia(NJ10006)
文摘H1-Galerkin mixed methods are proposed for viscoelasticity wave equation.Depending on the physical quantities of interest,two methods are discussed.The optimal error estimates and the proof of the existence and uniqueness of semidiscrete solutions are derived for problems in one space dimension.And the methods don＇t require the LBB condition.
