This paper focuses on designing an adaptive radial basis function neural network(RBFNN) control method for a class of nonlinear systems with unknown parameters and bounded disturbances. The problems raised by the unkn...This paper focuses on designing an adaptive radial basis function neural network(RBFNN) control method for a class of nonlinear systems with unknown parameters and bounded disturbances. The problems raised by the unknown functions and external disturbances in the nonlinear system are overcome by RBFNN, combined with the single parameter direct adaptive control method. The novel adaptive control method is designed to reduce the amount of computations effectively.The uniform ultimate boundedness of the closed-loop system is guaranteed by the proposed controller. A coupled motor drives(CMD) system, which satisfies the structure of nonlinear system,is taken for simulation to confirm the effectiveness of the method.Simulations show that the developed adaptive controller has favorable performance on tracking desired signal and verify the stability of the closed-loop system.展开更多
Because of the randomness of many impact factors influencing the dynamic assembly relationship of complex machinery, the reliability analysis of dynamic assembly relationship needs to be accomplished considering the r...Because of the randomness of many impact factors influencing the dynamic assembly relationship of complex machinery, the reliability analysis of dynamic assembly relationship needs to be accomplished considering the randomness from a probabilistic perspective. To improve the accuracy and efficiency of dynamic assembly relationship reliability analysis, the mechanical dynamic assembly reliability（MDAR） theory and a distributed collaborative response surface method（DCRSM） are proposed. The mathematic model of DCRSM is established based on the quadratic response surface function, and verified by the assembly relationship reliability analysis of aeroengine high pressure turbine（HPT） blade-tip radial running clearance（BTRRC）. Through the comparison of the DCRSM, traditional response surface method（RSM） and Monte Carlo Method（MCM）, the results show that the DCRSM is not able to accomplish the computational task which is impossible for the other methods when the number of simulation is more than 100 000 times, but also the computational precision for the DCRSM is basically consistent with the MCM and improved by 0.40-4.63% to the RSM, furthermore, the computational efficiency of DCRSM is up to about 188 times of the MCM and 55 times of the RSM under 10000 times simulations. The DCRSM is demonstrated to be a feasible and effective approach for markedly improving the computational efficiency and accuracy of MDAR analysis. Thus, the proposed research provides the promising theory and method for the MDAR design and optimization, and opens a novel research direction of probabilistic analysis for developing the high-performance and high-reliability of aeroengine.展开更多
In order to simultaneously attack a target with impact angle constraint in threedimensional(3-D) space, a novel distributed cooperative guidance law for multiple missiles under directed communication topologies is pro...In order to simultaneously attack a target with impact angle constraint in threedimensional(3-D) space, a novel distributed cooperative guidance law for multiple missiles under directed communication topologies is proposed without radial velocity measurements. First, based on missiles-target 3-D relative motion equations, the multiple missiles cooperative guidance model with impact angle constraint is constructed. Then, in Line-of-Sight(LOS) direction, based on multiagent system cooperative control theory, one guidance law with directed topologies is designed with strict proof, which can guarantee finite time consensus of multiple missiles' impact times. Next, in elevation direction and azimuth direction of LOS, based on homogeneous system stability theory and integral sliding mode control theory, two guidance laws are proposed respectively with strict proof, which can guarantee LOS angles converge to desired values and LOS angular rates converge to zero in finite time. Finally, the effectiveness of the designed cooperative guidance law is demonstrated through simulation results.展开更多
Background Radial artery spasm （RAS） is the most common complication in transradial coronary angiography and intervention. In this study, we designed to investigate the incidence of RAS during transradial procedures...Background Radial artery spasm （RAS） is the most common complication in transradial coronary angiography and intervention. In this study, we designed to investigate the incidence of RAS during transradial procedures in Chinese, find out the independent predictors through multiple regression, and analyze the clinical effect of RAS during follow-up. Methods Patients arranged to receive transradial coronary angiography and intervention were consecutively enrolled. The incidence of RAS was recorded. Univariate analysis was performed to find out the influence factors of RAS, and logistic regression analysis was performed to find out the independent predictors of RAS. The patients were asked to return 1 month later for the assessment of the radial access.Results The incidence of RAS was 7.8% （112/1427） in all the patients received transradial procedure. Univariate analysis indicates that young （P=0.038）, female （P=0.026）, small diameter of radial artery （P 〈0.001）, diabetes （P=0.026）, smoking （P=0.019）, moderate or severe pain during radial artery cannulation （P〈0.001）, unsuccessful access at first attempt （P=0.002）, big sheath （P=0.004）, number of catheters （〉3） （P=0.048）, rapid baseline heart rate （P=0.032） and long operation time （P=0.021） were associated with RAS. Logistic regression showed that female （OR=1.745, 95% CI： 1.148-3.846, P=0.024）, small radial artery diameter （OR=4.028, 95%CI： 1.264-12.196, P=0.008）, diabetes （OR= 2.148, 95%CI： 1.579-7.458, P=0.019） and unsuccessful access at first attempt （OR=1.468, 95%CI： 1.212-2.591, P=0.032） were independent predictors of RAS. Follow-up at （28±7） days after the procedure showed that, compared with non-spasm patients, the RAS patients had higher portion of pain （11.8% vs. 6.2%, P=0.043）. The occurrences of hematoma （7.3% vs. 5.6%, P=0.518） and radial artery occlusion （3.6% vs. 2.6%, P=0.534） were similar. Conclusions The incidence of RAS during transradial coronary展开更多
This article presents an approach which employs a commercial Reynolds-Averaged Navier-Stokes（RANS）solver to predict the steady wake field and loading distributions for a rim driven thruster.Four different cases of p...This article presents an approach which employs a commercial Reynolds-Averaged Navier-Stokes（RANS）solver to predict the steady wake field and loading distributions for a rim driven thruster.Four different cases of propeller blades are chosen to be calculated with the presented method.The propeller blade radial circulation and chordwise circulation density distributions are analyzed.The maximum radial circulation is found at the blade tip,which is different from conventional shaft driven propeller.The numerical results indicate that there is no tip leakage vortex in rim driven propulors.But there exist the tip joint vortex and the root region vortex.Bollard characteristics are calculated by taking rim surface effect into account.From the predicted results the second case in this paper is selected as the final one to perform hydrodynamic experiment.The calculation results with empirical rim surface corrections are compared with the measurement.It shows that the developed numerical method can well predict hydrodynamic performances of the rim driven thruster.展开更多
Background Aspirin and clopidogrel can improve myocardial reperfusion and alleviate myocardial injury during percutaneous coronary intervention （PCI）. Whether the addition of intravenous tirofiban during this proced...Background Aspirin and clopidogrel can improve myocardial reperfusion and alleviate myocardial injury during percutaneous coronary intervention （PCI）. Whether the addition of intravenous tirofiban during this procedure produces further benefit has not been clarified in ST segment elevation myocardial infarction （STEMI） patients. We evaluated this on STEMI patients who underwent primary PCI （p-PCI） via transradial artery approach. Methods Consecutive patients were randomized into tirofiban group （n=-72） or placebo group （n=-78）. Angiographic analysis included initial and final thrombolysis in myocardial infarction （TIMI） flow grade （TFG）, corrected TIMI frame count （CTFC） and TIMI myocardial perfusion grade （TMPG） of the thrombotic vessel. Platelet aggregation rate （PAR）, creatine phosphokinase （CPK）, CPK isoenzyme MB （CPK-MB） and troponin I levels were measured and TIMI definitions were used to assess bleeding complications. Left ventricular performance parameters were investigated with equilibrium radionuclide ventriculography. Major adverse cardiac events （MACE） were followed up for 6 months. Results The cases of TFG 0 and 1 before PCI, TFG 0 when first crossing of guide wire were less, and the cases of TFG 3 after PCI was more in tirofiban group than those in placebo group. The final CTFC was fewer and the incidence of no reflow phenomenon was lower, as well the percentage of final TFG 3 was higher in tirofiban group than those in placebo group （all P 〈0.05）. Mean peak CPK-MB was significantly lower, while the left ventricular performance parameters 1 week after PCI were much more improved in tirofiban group than those in the placebo group. PAR was significantly decreased shortly after tirofiban infusion. The incidence of 6-month MACE in tirofiban group was obviously lower than that in the placebo group. No statistical difference was noted between the two groups with regard to bleeding complications. Conclusions Intravenous tirofiban infusion, in additi展开更多
The growth of transcendental meromorphic functions in terms of their orders is investigated in this paper when they and their derivatives have radially distributed values following the discussion of the author . A sim...The growth of transcendental meromorphic functions in terms of their orders is investigated in this paper when they and their derivatives have radially distributed values following the discussion of the author . A simple andelementary way to study such subjects is exhibited in this paper; that is,once an estimation of B(r,*) in terms of a few C(r,**) in the Nevanlinna theory on angular domains is established, we can produce one result that the order of a mermorphic function with radially distributed values related to C(r,**) can be estimated under the assumption of existence of suitable deficient value. The results obtained in this paper lead us to a new singular direction in terms of Nevanlinna characterstic instead of the order of meromorphic functions.展开更多
Wear is a major factor of disc cutters’ failure. No current theory offers a standard for the prediction of disc cutter wear yet. In the field the wear prediction method commonly used is based on the excavation length...Wear is a major factor of disc cutters’ failure. No current theory offers a standard for the prediction of disc cutter wear yet. In the field the wear prediction method commonly used is based on the excavation length of tunnel boring machine（TBM） to predict the disc cutter wear and its wear law, considering the location number of each disc cutter on the cutterhead（radius for installation）; in theory, there is a prediction method of using arc wear coefficient. However, the preceding two methods have their own errors, with their accuracy being 40% or so and largely relying on the technicians’ experience. Therefore, radial wear coefficient, axial wear coefficient and trajectory wear coefficient are defined on the basis of the operating characteristics of TBM. With reference to the installation and characteristics of disc cutters, those coefficients are modified according to penetration, which gives rise to the presentation of comprehensive axial wear coefficient, comprehensive radial wear coefficient and comprehensive trajectory wear coefficient. Calculation and determination of wear coefficients are made with consideration of data from a segment of TBM project（excavation length 173 m）. The resulting wear coefficient values, after modification, are adopted to predict the disc cutter wear in the follow-up segment of the TBM project（excavation length of 5621 m）. The prediction results show that the disc cutter wear predicted with comprehensive radial wear coefficient and comprehensive trajectory wear coefficient are not only accurate（accuracy 16.12%） but also highly congruous, whereas there is a larger deviation in the prediction with comprehensive axial wear coefficient（accuracy 41%, which is in agreement with the prediction of disc cutters’ life in the field）. This paper puts forth a new method concerning prediction of life span and wear of TBM disc cutters as well as timing for replacing disc cutters.展开更多
基金supported by National Outstanding Youth Science Foundation(61125306)National Natural Science Foundation of Major Research Plan(91016004,61034002)+2 种基金Specialized Research Fund for the Doctoral Program of Higher Education of China(20110092110020)Open Fund of Key Laboratory of Measurement and Control of Complex Systems of Engineering(Southeast University)Ministry of Education(MCCSE2013B01)
基金partially supported by the National Natural Science Foundation of China(61703402,61374048)
文摘This paper focuses on designing an adaptive radial basis function neural network(RBFNN) control method for a class of nonlinear systems with unknown parameters and bounded disturbances. The problems raised by the unknown functions and external disturbances in the nonlinear system are overcome by RBFNN, combined with the single parameter direct adaptive control method. The novel adaptive control method is designed to reduce the amount of computations effectively.The uniform ultimate boundedness of the closed-loop system is guaranteed by the proposed controller. A coupled motor drives(CMD) system, which satisfies the structure of nonlinear system,is taken for simulation to confirm the effectiveness of the method.Simulations show that the developed adaptive controller has favorable performance on tracking desired signal and verify the stability of the closed-loop system.
基金supported by National Natural Science Foundation of China(Grant Nos.51175017,51245027)Innovation Foundation of Beihang University for PhD Graduates,China(Grant No.YWF-12-RBYJ008)Research Fund for the Doctoral Program of Higher Education of China(Grant No.20111102110011)
文摘Because of the randomness of many impact factors influencing the dynamic assembly relationship of complex machinery, the reliability analysis of dynamic assembly relationship needs to be accomplished considering the randomness from a probabilistic perspective. To improve the accuracy and efficiency of dynamic assembly relationship reliability analysis, the mechanical dynamic assembly reliability（MDAR） theory and a distributed collaborative response surface method（DCRSM） are proposed. The mathematic model of DCRSM is established based on the quadratic response surface function, and verified by the assembly relationship reliability analysis of aeroengine high pressure turbine（HPT） blade-tip radial running clearance（BTRRC）. Through the comparison of the DCRSM, traditional response surface method（RSM） and Monte Carlo Method（MCM）, the results show that the DCRSM is not able to accomplish the computational task which is impossible for the other methods when the number of simulation is more than 100 000 times, but also the computational precision for the DCRSM is basically consistent with the MCM and improved by 0.40-4.63% to the RSM, furthermore, the computational efficiency of DCRSM is up to about 188 times of the MCM and 55 times of the RSM under 10000 times simulations. The DCRSM is demonstrated to be a feasible and effective approach for markedly improving the computational efficiency and accuracy of MDAR analysis. Thus, the proposed research provides the promising theory and method for the MDAR design and optimization, and opens a novel research direction of probabilistic analysis for developing the high-performance and high-reliability of aeroengine.
基金supported by the National Natural Science Foundation of China(Nos.61603114,61673135)
文摘In order to simultaneously attack a target with impact angle constraint in threedimensional(3-D) space, a novel distributed cooperative guidance law for multiple missiles under directed communication topologies is proposed without radial velocity measurements. First, based on missiles-target 3-D relative motion equations, the multiple missiles cooperative guidance model with impact angle constraint is constructed. Then, in Line-of-Sight(LOS) direction, based on multiagent system cooperative control theory, one guidance law with directed topologies is designed with strict proof, which can guarantee finite time consensus of multiple missiles' impact times. Next, in elevation direction and azimuth direction of LOS, based on homogeneous system stability theory and integral sliding mode control theory, two guidance laws are proposed respectively with strict proof, which can guarantee LOS angles converge to desired values and LOS angular rates converge to zero in finite time. Finally, the effectiveness of the designed cooperative guidance law is demonstrated through simulation results.
文摘Background Radial artery spasm （RAS） is the most common complication in transradial coronary angiography and intervention. In this study, we designed to investigate the incidence of RAS during transradial procedures in Chinese, find out the independent predictors through multiple regression, and analyze the clinical effect of RAS during follow-up. Methods Patients arranged to receive transradial coronary angiography and intervention were consecutively enrolled. The incidence of RAS was recorded. Univariate analysis was performed to find out the influence factors of RAS, and logistic regression analysis was performed to find out the independent predictors of RAS. The patients were asked to return 1 month later for the assessment of the radial access.Results The incidence of RAS was 7.8% （112/1427） in all the patients received transradial procedure. Univariate analysis indicates that young （P=0.038）, female （P=0.026）, small diameter of radial artery （P 〈0.001）, diabetes （P=0.026）, smoking （P=0.019）, moderate or severe pain during radial artery cannulation （P〈0.001）, unsuccessful access at first attempt （P=0.002）, big sheath （P=0.004）, number of catheters （〉3） （P=0.048）, rapid baseline heart rate （P=0.032） and long operation time （P=0.021） were associated with RAS. Logistic regression showed that female （OR=1.745, 95% CI： 1.148-3.846, P=0.024）, small radial artery diameter （OR=4.028, 95%CI： 1.264-12.196, P=0.008）, diabetes （OR= 2.148, 95%CI： 1.579-7.458, P=0.019） and unsuccessful access at first attempt （OR=1.468, 95%CI： 1.212-2.591, P=0.032） were independent predictors of RAS. Follow-up at （28±7） days after the procedure showed that, compared with non-spasm patients, the RAS patients had higher portion of pain （11.8% vs. 6.2%, P=0.043）. The occurrences of hematoma （7.3% vs. 5.6%, P=0.518） and radial artery occlusion （3.6% vs. 2.6%, P=0.534） were similar. Conclusions The incidence of RAS during transradial coronary
文摘This article presents an approach which employs a commercial Reynolds-Averaged Navier-Stokes（RANS）solver to predict the steady wake field and loading distributions for a rim driven thruster.Four different cases of propeller blades are chosen to be calculated with the presented method.The propeller blade radial circulation and chordwise circulation density distributions are analyzed.The maximum radial circulation is found at the blade tip,which is different from conventional shaft driven propeller.The numerical results indicate that there is no tip leakage vortex in rim driven propulors.But there exist the tip joint vortex and the root region vortex.Bollard characteristics are calculated by taking rim surface effect into account.From the predicted results the second case in this paper is selected as the final one to perform hydrodynamic experiment.The calculation results with empirical rim surface corrections are compared with the measurement.It shows that the developed numerical method can well predict hydrodynamic performances of the rim driven thruster.
基金This project was supported by a grant from the Natural Science Foundation of Hebei Province （No. C2004000615）.
文摘Background Aspirin and clopidogrel can improve myocardial reperfusion and alleviate myocardial injury during percutaneous coronary intervention （PCI）. Whether the addition of intravenous tirofiban during this procedure produces further benefit has not been clarified in ST segment elevation myocardial infarction （STEMI） patients. We evaluated this on STEMI patients who underwent primary PCI （p-PCI） via transradial artery approach. Methods Consecutive patients were randomized into tirofiban group （n=-72） or placebo group （n=-78）. Angiographic analysis included initial and final thrombolysis in myocardial infarction （TIMI） flow grade （TFG）, corrected TIMI frame count （CTFC） and TIMI myocardial perfusion grade （TMPG） of the thrombotic vessel. Platelet aggregation rate （PAR）, creatine phosphokinase （CPK）, CPK isoenzyme MB （CPK-MB） and troponin I levels were measured and TIMI definitions were used to assess bleeding complications. Left ventricular performance parameters were investigated with equilibrium radionuclide ventriculography. Major adverse cardiac events （MACE） were followed up for 6 months. Results The cases of TFG 0 and 1 before PCI, TFG 0 when first crossing of guide wire were less, and the cases of TFG 3 after PCI was more in tirofiban group than those in placebo group. The final CTFC was fewer and the incidence of no reflow phenomenon was lower, as well the percentage of final TFG 3 was higher in tirofiban group than those in placebo group （all P 〈0.05）. Mean peak CPK-MB was significantly lower, while the left ventricular performance parameters 1 week after PCI were much more improved in tirofiban group than those in the placebo group. PAR was significantly decreased shortly after tirofiban infusion. The incidence of 6-month MACE in tirofiban group was obviously lower than that in the placebo group. No statistical difference was noted between the two groups with regard to bleeding complications. Conclusions Intravenous tirofiban infusion, in additi
基金This work was supported by the National Natural Science Foundation of China(Grant No.19971049)BRF of Tsinghua University.
文摘The growth of transcendental meromorphic functions in terms of their orders is investigated in this paper when they and their derivatives have radially distributed values following the discussion of the author . A simple andelementary way to study such subjects is exhibited in this paper; that is,once an estimation of B(r,*) in terms of a few C(r,**) in the Nevanlinna theory on angular domains is established, we can produce one result that the order of a mermorphic function with radially distributed values related to C(r,**) can be estimated under the assumption of existence of suitable deficient value. The results obtained in this paper lead us to a new singular direction in terms of Nevanlinna characterstic instead of the order of meromorphic functions.
基金Supported by National Natural Science Foundation of China (Grant No.51075147)National Hi-tech Research and Development Program of China (863 Program,Grant No.2012AA041803)
文摘Wear is a major factor of disc cutters’ failure. No current theory offers a standard for the prediction of disc cutter wear yet. In the field the wear prediction method commonly used is based on the excavation length of tunnel boring machine（TBM） to predict the disc cutter wear and its wear law, considering the location number of each disc cutter on the cutterhead（radius for installation）; in theory, there is a prediction method of using arc wear coefficient. However, the preceding two methods have their own errors, with their accuracy being 40% or so and largely relying on the technicians’ experience. Therefore, radial wear coefficient, axial wear coefficient and trajectory wear coefficient are defined on the basis of the operating characteristics of TBM. With reference to the installation and characteristics of disc cutters, those coefficients are modified according to penetration, which gives rise to the presentation of comprehensive axial wear coefficient, comprehensive radial wear coefficient and comprehensive trajectory wear coefficient. Calculation and determination of wear coefficients are made with consideration of data from a segment of TBM project（excavation length 173 m）. The resulting wear coefficient values, after modification, are adopted to predict the disc cutter wear in the follow-up segment of the TBM project（excavation length of 5621 m）. The prediction results show that the disc cutter wear predicted with comprehensive radial wear coefficient and comprehensive trajectory wear coefficient are not only accurate（accuracy 16.12%） but also highly congruous, whereas there is a larger deviation in the prediction with comprehensive axial wear coefficient（accuracy 41%, which is in agreement with the prediction of disc cutters’ life in the field）. This paper puts forth a new method concerning prediction of life span and wear of TBM disc cutters as well as timing for replacing disc cutters.
