This paper studies the technics of reducing item exposure by utilizing automatic item generation methods. Known test item calibration method uses item parameter estimation with the statistical data, collected during e...This paper studies the technics of reducing item exposure by utilizing automatic item generation methods. Known test item calibration method uses item parameter estimation with the statistical data, collected during examinees prior testing. Disadvantage of the mentioned item calibration method is the item exposure; when test items become familiar to the examinees. To reduce the item exposure, automatic item generation method is used, where item models are being constructed based on already calibrated test items without losing already estimated item parameters. A technic of item model extraction method from the already calibrated and therefore exposed test items described, which can be used by the test item development specialists to integrate automatic item generation principles with the existing testing applications.展开更多
BACKGROUND The six-minute walk test(6MWT)allows to determine,in addition to the main parameters,the time of heart rate recovery(THRR),cardiac function,adaptation index(AI),which characterize the compensatory reserve o...BACKGROUND The six-minute walk test(6MWT)allows to determine,in addition to the main parameters,the time of heart rate recovery(THRR),cardiac function,adaptation index(AI),which characterize the compensatory reserve of patients with chronic heart failure(CHF).At the same time,the significance of these parameters in patients taking beta-blockers for CHF is insufficiently studied,taking into account the negative chronotropic effect of drugs.In this regard,it is relevant to identify factors that can characterize the compensatory capabilities of a patient with CHF during 6MWT,not related to the calculation of heart rate.AIM To identify hemodynamic indicators of the adaptive capabilities of patients with CHF during paired 6MWT depending on their intake of beta-blockers.METHODS Seventy-four patients with compensated CHF due to coronary heart disease and/or hypertension formed the main group,comprising 46 individuals who were taking beta-blockers,and a comparison group comprising 28 individuals who had not been taking beta-blockers for at least one month before 6MWT.All participants underwent Doppler echocardiography(DECG),paired 6MWT,with assessment of hemodynamic parameters before and after both the first and second test.AI,THRR,blood pressure variability(BPV)were calculated.Multivariate,correlation analyses,univariate analysis of variance were used.RESULTS There were no significant associations between adaptation characteristics and DECG parameters or functional class(FC)of CHF in patients of the main group.In the comparison group,the indicators of compensatory reserve were significantly and directly associated with left ventricular ejection fraction(LVEF),and inversely with FC CHF and cardiac cavity size.In both groups,a greater difference in systolic blood pressure between the end of the first and the beginning of the second 6MWT was significantly associated with a higher index of right ventricular systolic dysfunction(Tricuspid annular plane systolic excursion)and LVEF,as well as a smaller left ventricular size and mass,and a lower pulmonary artery systolic pressure in patients in the main group.CONCLUSION Systolic BPV,measured immediately after 6MWT and 20 minutes after its completion,can indirectly characterize the compensatory reserve in patients with CHF,regardless of their beta-blocker intake.展开更多
Aeropropulsion System Test Facility (ASTF) is required to accurately control the pressure and temperature of the airflow to test the performance of the aero-engine. However, the control accuracy of ASTF is significant...Aeropropulsion System Test Facility (ASTF) is required to accurately control the pressure and temperature of the airflow to test the performance of the aero-engine. However, the control accuracy of ASTF is significantly affected by the flow disturbance caused by aero-engine acceleration and deceleration. This would reduce the credibility of ASTF’s test results for the aero-engine. Therefore, first, this paper proposes a feedforward compensation-based L1 adaptive control method for ASTF to address this problem. The baseline controller is first designed based on ideal uncoupled closed-loop dynamics to achieve dynamic decoupling. Then, L1 adaptive control is adopted to deal with various uncertainties and ensure good control performance. To further enhance the anti-disturbance performance, a feedforward strategy based on disturbance prediction is designed in the L1 adaptive control framework to compensate for the unmatched flow disturbance, which cannot be measured directly. In addition, this strategy takes into account the effects of actuator dynamics. With this method, the feedforward term can be determined from the nominal model parameters despite uncertainties. Finally, to demonstrate the effectiveness of the proposed method, various comparative experiments are performed on a hardware-in-the-loop system of ASTF. The experimental results show that the proposed method possesses excellent tracking performance, anti-disturbance performance and robustness.展开更多
Adaptive truss structures are a new kind of structures with integrated active members,whose dynamic characteristies can be beneficially modified to meet mission requirements.Active members containing actuating and sen...Adaptive truss structures are a new kind of structures with integrated active members,whose dynamic characteristies can be beneficially modified to meet mission requirements.Active members containing actuating and sensing units are the major components of adaptive truss structures.Modeling of adaptive truss structures is a key step to analyze the structural dynamic characteristics.A new experimental modal analysis approach,in which active members are used as excitatiDn sources for modal test,has been proposed in this paper.The excitation forces generated by the active members, which are different from the excitation forces exerted on structures in the conventional modal test,are internal forces for the truss structures.The relation between internal excitation forces and external forces is revealed such that the traditional identification method can be adopted to obtain modal parameters of adaptive structures.Placement problem of the active member in adaptive truss structures is also discussed in this work. Modal test and analysis are conducted with a planar adaptive truss structure by using piezoelectric active members in order to verify the feasibility and effectiveness of the proposed method.展开更多
Due to the maturing of Internet technology, the adaptive testing can be utilized in the web-based environment and the examinee can take the test anywhere and any time. The purpose of the research is to apply item resp...Due to the maturing of Internet technology, the adaptive testing can be utilized in the web-based environment and the examinee can take the test anywhere and any time. The purpose of the research is to apply item response theory （IRT）, adaptive testing theory and web-service technique to construct an XML format itembank and a system of web- based adaptive testing （WAT） by the framework of threetiered client server distance testing.展开更多
To eliminate the node traction coupling during wind turbine blade full-scale static testing,a model free adaptive control algorithm is presented based on fuzzy control performance function compensation. Based on the u...To eliminate the node traction coupling during wind turbine blade full-scale static testing,a model free adaptive control algorithm is presented based on fuzzy control performance function compensation. Based on the universal model theory,the fuzzy model free adaptive control( FMFAC) algorithm is designed by configuring the spot static testing experiences as compensation function F( ·). Then the algorithm implementation process is provided and its quick convergence is proved. Using software to establish static load coupling model of multi-nodes,simulate and verify the validity of FMFAC algorithm,which is applied to wind turbines blade full-scale static testing. The results show that the adaptive decoupling ability of FMFAC is better. The traction of four load points can stay steady and change coordinately. Process error is not over ± 6 k N. The error rate is lower than 1% in special phase.This algorithm effectively eliminates the traction coupling of the static testing process,and makes wind turbine blade testing steadily.展开更多
This paper proposes a compensation method for using the Harmonic Amplitude-Phase Adaptive Control(HAPAC)to increase the precision of sinusoidal motion simulators. It also expounds on the HAPAC principle and structural...This paper proposes a compensation method for using the Harmonic Amplitude-Phase Adaptive Control(HAPAC)to increase the precision of sinusoidal motion simulators. It also expounds on the HAPAC principle and structural disposition, develops the HAPAC control laws and analyzes the system stability in the HAPAC. A method for further improving the precision using online identification of the system’s frequency-response models is presented. The tested data and tracking errors of the simulator demonstrate that the HAPAC makes the sinusoidal motions achieve higher precision than the common classical controls. The HAPAC can also be used in other tracking systems of precision sinusoidal motions.展开更多
文摘This paper studies the technics of reducing item exposure by utilizing automatic item generation methods. Known test item calibration method uses item parameter estimation with the statistical data, collected during examinees prior testing. Disadvantage of the mentioned item calibration method is the item exposure; when test items become familiar to the examinees. To reduce the item exposure, automatic item generation method is used, where item models are being constructed based on already calibrated test items without losing already estimated item parameters. A technic of item model extraction method from the already calibrated and therefore exposed test items described, which can be used by the test item development specialists to integrate automatic item generation principles with the existing testing applications.
基金Supported by Ministry of Health of the Russian Federation titled Development of a Hardware-Software Complex for the Non-Invasive Monitoring and Prediction of Circulatory Decompensation in Patients with Chronic Heart Failure,No.125030703255-7.
文摘BACKGROUND The six-minute walk test(6MWT)allows to determine,in addition to the main parameters,the time of heart rate recovery(THRR),cardiac function,adaptation index(AI),which characterize the compensatory reserve of patients with chronic heart failure(CHF).At the same time,the significance of these parameters in patients taking beta-blockers for CHF is insufficiently studied,taking into account the negative chronotropic effect of drugs.In this regard,it is relevant to identify factors that can characterize the compensatory capabilities of a patient with CHF during 6MWT,not related to the calculation of heart rate.AIM To identify hemodynamic indicators of the adaptive capabilities of patients with CHF during paired 6MWT depending on their intake of beta-blockers.METHODS Seventy-four patients with compensated CHF due to coronary heart disease and/or hypertension formed the main group,comprising 46 individuals who were taking beta-blockers,and a comparison group comprising 28 individuals who had not been taking beta-blockers for at least one month before 6MWT.All participants underwent Doppler echocardiography(DECG),paired 6MWT,with assessment of hemodynamic parameters before and after both the first and second test.AI,THRR,blood pressure variability(BPV)were calculated.Multivariate,correlation analyses,univariate analysis of variance were used.RESULTS There were no significant associations between adaptation characteristics and DECG parameters or functional class(FC)of CHF in patients of the main group.In the comparison group,the indicators of compensatory reserve were significantly and directly associated with left ventricular ejection fraction(LVEF),and inversely with FC CHF and cardiac cavity size.In both groups,a greater difference in systolic blood pressure between the end of the first and the beginning of the second 6MWT was significantly associated with a higher index of right ventricular systolic dysfunction(Tricuspid annular plane systolic excursion)and LVEF,as well as a smaller left ventricular size and mass,and a lower pulmonary artery systolic pressure in patients in the main group.CONCLUSION Systolic BPV,measured immediately after 6MWT and 20 minutes after its completion,can indirectly characterize the compensatory reserve in patients with CHF,regardless of their beta-blocker intake.
基金supported by the“Shuimu Tsinghua Scholar”Project,China(No.2024SM223)the National Science and Technology Major Project,China(No.Y2022-V-0002-0028).
文摘Aeropropulsion System Test Facility (ASTF) is required to accurately control the pressure and temperature of the airflow to test the performance of the aero-engine. However, the control accuracy of ASTF is significantly affected by the flow disturbance caused by aero-engine acceleration and deceleration. This would reduce the credibility of ASTF’s test results for the aero-engine. Therefore, first, this paper proposes a feedforward compensation-based L1 adaptive control method for ASTF to address this problem. The baseline controller is first designed based on ideal uncoupled closed-loop dynamics to achieve dynamic decoupling. Then, L1 adaptive control is adopted to deal with various uncertainties and ensure good control performance. To further enhance the anti-disturbance performance, a feedforward strategy based on disturbance prediction is designed in the L1 adaptive control framework to compensate for the unmatched flow disturbance, which cannot be measured directly. In addition, this strategy takes into account the effects of actuator dynamics. With this method, the feedforward term can be determined from the nominal model parameters despite uncertainties. Finally, to demonstrate the effectiveness of the proposed method, various comparative experiments are performed on a hardware-in-the-loop system of ASTF. The experimental results show that the proposed method possesses excellent tracking performance, anti-disturbance performance and robustness.
文摘Adaptive truss structures are a new kind of structures with integrated active members,whose dynamic characteristies can be beneficially modified to meet mission requirements.Active members containing actuating and sensing units are the major components of adaptive truss structures.Modeling of adaptive truss structures is a key step to analyze the structural dynamic characteristics.A new experimental modal analysis approach,in which active members are used as excitatiDn sources for modal test,has been proposed in this paper.The excitation forces generated by the active members, which are different from the excitation forces exerted on structures in the conventional modal test,are internal forces for the truss structures.The relation between internal excitation forces and external forces is revealed such that the traditional identification method can be adopted to obtain modal parameters of adaptive structures.Placement problem of the active member in adaptive truss structures is also discussed in this work. Modal test and analysis are conducted with a planar adaptive truss structure by using piezoelectric active members in order to verify the feasibility and effectiveness of the proposed method.
文摘Due to the maturing of Internet technology, the adaptive testing can be utilized in the web-based environment and the examinee can take the test anywhere and any time. The purpose of the research is to apply item response theory （IRT）, adaptive testing theory and web-service technique to construct an XML format itembank and a system of web- based adaptive testing （WAT） by the framework of threetiered client server distance testing.
基金National Natural Science Foundation of China(No.51567018)
文摘To eliminate the node traction coupling during wind turbine blade full-scale static testing,a model free adaptive control algorithm is presented based on fuzzy control performance function compensation. Based on the universal model theory,the fuzzy model free adaptive control( FMFAC) algorithm is designed by configuring the spot static testing experiences as compensation function F( ·). Then the algorithm implementation process is provided and its quick convergence is proved. Using software to establish static load coupling model of multi-nodes,simulate and verify the validity of FMFAC algorithm,which is applied to wind turbines blade full-scale static testing. The results show that the adaptive decoupling ability of FMFAC is better. The traction of four load points can stay steady and change coordinately. Process error is not over ± 6 k N. The error rate is lower than 1% in special phase.This algorithm effectively eliminates the traction coupling of the static testing process,and makes wind turbine blade testing steadily.
文摘This paper proposes a compensation method for using the Harmonic Amplitude-Phase Adaptive Control(HAPAC)to increase the precision of sinusoidal motion simulators. It also expounds on the HAPAC principle and structural disposition, develops the HAPAC control laws and analyzes the system stability in the HAPAC. A method for further improving the precision using online identification of the system’s frequency-response models is presented. The tested data and tracking errors of the simulator demonstrate that the HAPAC makes the sinusoidal motions achieve higher precision than the common classical controls. The HAPAC can also be used in other tracking systems of precision sinusoidal motions.
