Linear switch reluctance machine(LSRM)has been tried to act as an alternative generator for direct drive linear wave energy converter(WEC).Many researchers have proposed new topologies of LSRM to improve the power den...Linear switch reluctance machine(LSRM)has been tried to act as an alternative generator for direct drive linear wave energy converter(WEC).Many researchers have proposed new topologies of LSRM to improve the power density,efficiency and reliability.However,the control methods for LSRM applied in direct drive WEC have been paid little attention,especially control methods considering the wave energy generator operating characteristics.In this paper,according to the generator control requirements of the direct drive WEC,force control algorithm for LSRM operating in four quadrants without a speed closed loop is put forward.The force ripple of LSRM is suppressed using force sharing function method.The four-quadrant control is easy to realize requiring only phase currents information.Simulation results validate the proposed method and indicate that LSRM is able to be used as the generator for direct drive WEC.展开更多
Evaluation is widely acknowledged as a powerful means of improving the quality of education and it is a very important component of the education system. However, the current mainstream evaluation method is based on t...Evaluation is widely acknowledged as a powerful means of improving the quality of education and it is a very important component of the education system. However, the current mainstream evaluation method is based on the examination as the common way, which has very limited help to instructors' teaching. In this paper, based on an online learning platform named "educoder", we design an evaluation method by using "Four-quadrant law", which divides students' learning situations into four types. In addition, we provide some suggestions for instructors about how to give targeted teaching to different students in each type. We verify that our method is useful by setting up experiments. The experiment results show that our method can effectively improve the quality of instructors' teaching.展开更多
AIM To characterize esophageal endoluminal landmarks to permit radial and longitudinal esophageal orientation and accurate lesion location.METHODS Distance from the incisors and radial orientation were estimated for t...AIM To characterize esophageal endoluminal landmarks to permit radial and longitudinal esophageal orientation and accurate lesion location.METHODS Distance from the incisors and radial orientation were estimated for the main left bronchus and the left atrium landmarks in 207 consecutive patients using white light examination.A sub-study was also performed using white light followed by endoscopic ultrasound(EUS)in 25 consecutive patients to confirm the findings.The scope orientation throughout the exam was maintained at the natural axis,where the left esophageal quadrant corresponds to the area between 6 and 9 o'clock.When an anatomical landmark was identified,it was recorded with a photograph and its quadrant orientation and distance from the incisors were determined.The reference points to obtain the distances and radial orientation were as follows:the midpoint of the left main bronchus and the most intense pulsatile zone of the left atrium.With the video processor system set to moderate insufflation,measurements were obtained at the end of the patients'air expiration.RESULTS The left main bronchus and left atrium esophageal landmarks were identified using white light in 99%and 100%of subjects at a mean distance of 25.8 cm(SD2.3),and 31.4 cm(SD 2.4)from the incisors,respectively.The left main bronchus landmark was found to be a tubular,concave,non-pulsatile,esophageal external compression,occupying approximately 1/4 of the circumference.The left atrium landmark was identified as a round,convex,pulsatile,esophageal external compression,occupying approximately 1/4 of the circumference.Both landmarks were identified using white light on the anterior esophageal quadrant.In the substudy,the left main bronchus was identified in 24(92%)patients at 25.4 cm(SD2.1)and 26.7 cm(SD 1.9)from the incisors,by white light and EUS,respectively.The left atrium was recognized in all patients at 30.5 cm(SD 1.9),and 31.6 cm(SD2.3)from the incisors,by both white light and EUS,respectively.EUS confirmed that the landmarks corresponded to these two structures,respectively,and that they were located on the anterior esophageal wall.The Bland-Altman plot demonstrated high agreement between the white light and EUS measurements.CONCLUSION This study provides an endoscopic characterization of esophageal landmarks corresponding to the left main bronchus and left atrium,to permit radial and longitudinal orientation and accurate lesion location.展开更多
Frequency lock loops （FLL） discriminating algorithms for direct-sequence spread-spectrum are discussed. The existing algorithms can＇t solve the problem of data bit reversal during one pre-detection integral period....Frequency lock loops （FLL） discriminating algorithms for direct-sequence spread-spectrum are discussed. The existing algorithms can＇t solve the problem of data bit reversal during one pre-detection integral period. And when the initial frequency offset is large, the frequency discriminator can＇ t work normally. To solve these problems, a new FLL discriminating algorithm is introduced. The least-squares discriminator is used in this new algorithm. As the least-squares discriminator has a short process unit period, the correspond- ing frequency discriminating range is large. And the data bit reversal just influence one process unit period, so the least-squares discriminated result will not be affected. Compared with traditional frequency discriminator, the least-squares algorithm can effectively solve the problem of data bit reversal and can endure larger initial frequency offset.展开更多
In order to advance the research on suppressing tearing modes and driving plasma rotation, a DC power supply （PS） system has been developed for dynamic resonant magnetic perturbation （DRMP） coils and applied in th...In order to advance the research on suppressing tearing modes and driving plasma rotation, a DC power supply （PS） system has been developed for dynamic resonant magnetic perturbation （DRMP） coils and applied in the J-TEXT experiment. To enrich experimental phe- nomena in the J-TEXT tokamak, applying the circulating current four-quadrant operation mode in the DRMP DC PS system is proposed. By using the circulating current four-quadrant oper- ation, DRMP coils can be smoothly controlled without the dead-time when the current polarity reverses. Essential circuit analysis, control optimization and simulation of desired scenarios have been performed for normal current. Relevant simulation and test results are also presented.展开更多
A precise two-degree-of-freedom measuring system (2DMS) is developed based on single-mode optical fiber, LD, cube corner retroreflector and four-quadrant photodetector (4-Q), and the simultaneous on-line measurement o...A precise two-degree-of-freedom measuring system (2DMS) is developed based on single-mode optical fiber, LD, cube corner retroreflector and four-quadrant photodetector (4-Q), and the simultaneous on-line measurement of lateral and vertical direction straightness errors of the linear stage is carried out. The moving part is wireless, which eliminates any errors introduced by pushing and pulling the wires. The sensitivity of the straightness error measurement can be improved by a factor of 2 with the cube corner retroreflector. This fiber-based optically aligned beam is used to establish a reference line for the straightness measurement of any mechanical system. 4-Q detector is used to receive the laser beam. A chip microcomputer is developed to conduct all data acquisition and signal processing. The beam drift influence can be removed in the greatest extent from the system. The experiments on the measurement system stability, repeatability and its comparison with the HP5528 double-frequency laser interferometer are carried out.展开更多
Real-time monitoring of wavelength is important for high-speed wavelength phase-shifting interferometry.In this paper,a wavelength sensor based on a polarization-maintaining fiber interferometer with four-quadrant dem...Real-time monitoring of wavelength is important for high-speed wavelength phase-shifting interferometry.In this paper,a wavelength sensor based on a polarization-maintaining fiber interferometer with four-quadrant demodulation was proposed.We built the wavelength sensing system with resolution better than 0.005 pm and 0.1 ms sampling interval and measured the response time of the tuned wavelength at 35 ms in the phase-shifting process of a commercial wavelength phase-shifting free-space interferometer,as well as the wavelength drift velocity of 0.01 pm per second in the hysteresis process.The optical fiber wavelength sensor with four-quadrant demodulation provides a real-time wavelength sensing scheme for high-speed wavelength phase-shifting interferometers.展开更多
The superior performance of active vibration control systems largely depends on the four-quadrant controllable execution capability in the available force-velocity diagram of active actuators.Although semi-active vibr...The superior performance of active vibration control systems largely depends on the four-quadrant controllable execution capability in the available force-velocity diagram of active actuators.Although semi-active vibration control systems have the advantages of low energy consumption,simple structure,and high reliability,the system performance is not comparable to active control systems,due to the partial capability in only the first and third quadrants.On the basis of the comprehensive advantages of active and semi-active actuators,to reform the design philosophy of semi-active actuators to realize pseudo-active actuators that have both mechanical properties of active actuators and energy consumption advantages of semi-active actuators,that is,new semi-active actuators with four-quadrant controllable execution capability,will very likely cause a revolution in the related fields of mechanical design and system control.The basic design principle of pseudo-active actuators that use semi-active controllable actuators to achieve active actuator performance in the way of conceptual analysis is proposed.The proposed pseudo-active actuators should consist of two half-four-quadrant actuators,that is,one is for the first and third quadrants and the other one for the second and fourth quadrants.This study employs two semi-active controllable damping actuators and one mechanical compensation mechanism.One of the actuators provides the damping force in the first and third quadrants,and the other one combining with the mechanical compensation mechanism is for the second and fourth quadrants.A global mathematical model of the proposed actuator is established to describe the four different operational modes of the proposed actuator.It is proved that the two operational modes of the proposed actuator can realize active vibration control,and a case study of realizing active control is presented.The other two operational modes are compared with the conventional two-degree-of-freedom model.More specifically,the application cases of the pseudo-active operational mode of the proposed actuator in the quarter-car/body-powertrain suspension system are given,a pseudo-active suspension named dual-hook automobile suspension is presented.Furthermore,an equivalent expression of the electrical network is given for the mechanical network under different operational modes of the proposed actuator.展开更多
基金This work was supported in part by the National Natural Science Foundation of China under Grant U1806224,61733010in part by the Guangdong Key Research and Development Program under Grant 2019B090917001.
文摘Linear switch reluctance machine(LSRM)has been tried to act as an alternative generator for direct drive linear wave energy converter(WEC).Many researchers have proposed new topologies of LSRM to improve the power density,efficiency and reliability.However,the control methods for LSRM applied in direct drive WEC have been paid little attention,especially control methods considering the wave energy generator operating characteristics.In this paper,according to the generator control requirements of the direct drive WEC,force control algorithm for LSRM operating in four quadrants without a speed closed loop is put forward.The force ripple of LSRM is suppressed using force sharing function method.The four-quadrant control is easy to realize requiring only phase currents information.Simulation results validate the proposed method and indicate that LSRM is able to be used as the generator for direct drive WEC.
文摘Evaluation is widely acknowledged as a powerful means of improving the quality of education and it is a very important component of the education system. However, the current mainstream evaluation method is based on the examination as the common way, which has very limited help to instructors' teaching. In this paper, based on an online learning platform named "educoder", we design an evaluation method by using "Four-quadrant law", which divides students' learning situations into four types. In addition, we provide some suggestions for instructors about how to give targeted teaching to different students in each type. We verify that our method is useful by setting up experiments. The experiment results show that our method can effectively improve the quality of instructors' teaching.
基金(in part)a grant in aid from the Emura Foundation for the Promotion of Cancer Research,No.01221
文摘AIM To characterize esophageal endoluminal landmarks to permit radial and longitudinal esophageal orientation and accurate lesion location.METHODS Distance from the incisors and radial orientation were estimated for the main left bronchus and the left atrium landmarks in 207 consecutive patients using white light examination.A sub-study was also performed using white light followed by endoscopic ultrasound(EUS)in 25 consecutive patients to confirm the findings.The scope orientation throughout the exam was maintained at the natural axis,where the left esophageal quadrant corresponds to the area between 6 and 9 o'clock.When an anatomical landmark was identified,it was recorded with a photograph and its quadrant orientation and distance from the incisors were determined.The reference points to obtain the distances and radial orientation were as follows:the midpoint of the left main bronchus and the most intense pulsatile zone of the left atrium.With the video processor system set to moderate insufflation,measurements were obtained at the end of the patients'air expiration.RESULTS The left main bronchus and left atrium esophageal landmarks were identified using white light in 99%and 100%of subjects at a mean distance of 25.8 cm(SD2.3),and 31.4 cm(SD 2.4)from the incisors,respectively.The left main bronchus landmark was found to be a tubular,concave,non-pulsatile,esophageal external compression,occupying approximately 1/4 of the circumference.The left atrium landmark was identified as a round,convex,pulsatile,esophageal external compression,occupying approximately 1/4 of the circumference.Both landmarks were identified using white light on the anterior esophageal quadrant.In the substudy,the left main bronchus was identified in 24(92%)patients at 25.4 cm(SD2.1)and 26.7 cm(SD 1.9)from the incisors,by white light and EUS,respectively.The left atrium was recognized in all patients at 30.5 cm(SD 1.9),and 31.6 cm(SD2.3)from the incisors,by both white light and EUS,respectively.EUS confirmed that the landmarks corresponded to these two structures,respectively,and that they were located on the anterior esophageal wall.The Bland-Altman plot demonstrated high agreement between the white light and EUS measurements.CONCLUSION This study provides an endoscopic characterization of esophageal landmarks corresponding to the left main bronchus and left atrium,to permit radial and longitudinal orientation and accurate lesion location.
文摘Frequency lock loops （FLL） discriminating algorithms for direct-sequence spread-spectrum are discussed. The existing algorithms can＇t solve the problem of data bit reversal during one pre-detection integral period. And when the initial frequency offset is large, the frequency discriminator can＇ t work normally. To solve these problems, a new FLL discriminating algorithm is introduced. The least-squares discriminator is used in this new algorithm. As the least-squares discriminator has a short process unit period, the correspond- ing frequency discriminating range is large. And the data bit reversal just influence one process unit period, so the least-squares discriminated result will not be affected. Compared with traditional frequency discriminator, the least-squares algorithm can effectively solve the problem of data bit reversal and can endure larger initial frequency offset.
基金supported by the National ITER Project Foundation of China(No.2014GB118000)National Natural Science Foundation of China(No.11275080)
文摘In order to advance the research on suppressing tearing modes and driving plasma rotation, a DC power supply （PS） system has been developed for dynamic resonant magnetic perturbation （DRMP） coils and applied in the J-TEXT experiment. To enrich experimental phe- nomena in the J-TEXT tokamak, applying the circulating current four-quadrant operation mode in the DRMP DC PS system is proposed. By using the circulating current four-quadrant oper- ation, DRMP coils can be smoothly controlled without the dead-time when the current polarity reverses. Essential circuit analysis, control optimization and simulation of desired scenarios have been performed for normal current. Relevant simulation and test results are also presented.
文摘A precise two-degree-of-freedom measuring system (2DMS) is developed based on single-mode optical fiber, LD, cube corner retroreflector and four-quadrant photodetector (4-Q), and the simultaneous on-line measurement of lateral and vertical direction straightness errors of the linear stage is carried out. The moving part is wireless, which eliminates any errors introduced by pushing and pulling the wires. The sensitivity of the straightness error measurement can be improved by a factor of 2 with the cube corner retroreflector. This fiber-based optically aligned beam is used to establish a reference line for the straightness measurement of any mechanical system. 4-Q detector is used to receive the laser beam. A chip microcomputer is developed to conduct all data acquisition and signal processing. The beam drift influence can be removed in the greatest extent from the system. The experiments on the measurement system stability, repeatability and its comparison with the HP5528 double-frequency laser interferometer are carried out.
基金This work was supported by the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX21_0277)the National Natural Science Foundation of China(No.61875087).
文摘Real-time monitoring of wavelength is important for high-speed wavelength phase-shifting interferometry.In this paper,a wavelength sensor based on a polarization-maintaining fiber interferometer with four-quadrant demodulation was proposed.We built the wavelength sensing system with resolution better than 0.005 pm and 0.1 ms sampling interval and measured the response time of the tuned wavelength at 35 ms in the phase-shifting process of a commercial wavelength phase-shifting free-space interferometer,as well as the wavelength drift velocity of 0.01 pm per second in the hysteresis process.The optical fiber wavelength sensor with four-quadrant demodulation provides a real-time wavelength sensing scheme for high-speed wavelength phase-shifting interferometers.
基金The authors wish to acknowledge the Fundamental Research Funds for the Central Universities(No.JD2019JGPY0018)for the support of this study.
文摘The superior performance of active vibration control systems largely depends on the four-quadrant controllable execution capability in the available force-velocity diagram of active actuators.Although semi-active vibration control systems have the advantages of low energy consumption,simple structure,and high reliability,the system performance is not comparable to active control systems,due to the partial capability in only the first and third quadrants.On the basis of the comprehensive advantages of active and semi-active actuators,to reform the design philosophy of semi-active actuators to realize pseudo-active actuators that have both mechanical properties of active actuators and energy consumption advantages of semi-active actuators,that is,new semi-active actuators with four-quadrant controllable execution capability,will very likely cause a revolution in the related fields of mechanical design and system control.The basic design principle of pseudo-active actuators that use semi-active controllable actuators to achieve active actuator performance in the way of conceptual analysis is proposed.The proposed pseudo-active actuators should consist of two half-four-quadrant actuators,that is,one is for the first and third quadrants and the other one for the second and fourth quadrants.This study employs two semi-active controllable damping actuators and one mechanical compensation mechanism.One of the actuators provides the damping force in the first and third quadrants,and the other one combining with the mechanical compensation mechanism is for the second and fourth quadrants.A global mathematical model of the proposed actuator is established to describe the four different operational modes of the proposed actuator.It is proved that the two operational modes of the proposed actuator can realize active vibration control,and a case study of realizing active control is presented.The other two operational modes are compared with the conventional two-degree-of-freedom model.More specifically,the application cases of the pseudo-active operational mode of the proposed actuator in the quarter-car/body-powertrain suspension system are given,a pseudo-active suspension named dual-hook automobile suspension is presented.Furthermore,an equivalent expression of the electrical network is given for the mechanical network under different operational modes of the proposed actuator.
