In this paper, a new pre-alignment approach based on Four-Quadrant-Photo-Detector （FQPD） for IC mask is presented. The voltage outputs from FQPDs are the functions of alignment mark＇s position offsets with respect ...In this paper, a new pre-alignment approach based on Four-Quadrant-Photo-Detector （FQPD） for IC mask is presented. The voltage outputs from FQPDs are the functions of alignment mark＇s position offsets with respect to FQPDs. The functions are obtained with least squares error （LSE）-based polynomial fitting after the normalization of experimental data. As the acquired functions are not monotonic about their variables, the alignment mark＇s position offset cannot be given by direct inverse operation on the obtained functions. However, the piecewise polynomial fitting gives the inverse function, with which the alignment mark＇s position offset can be predicted according to the voltage outputs of FQPDs. On the basis of prediction, a pre-alignment control strategy is proposed. The feasibility and robustness of the pre-alignment approach is shown by experiments. Furthermore, the results demonstrate that the maximum error of mask＇s position offset in the X- and Y- directions is less than 15μm after coarse pre-alignment. Keywords： Four-Quadrant-Photo-Detector （FQPD）, pre-alignment, IC mask, polynomial fitting展开更多
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
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
This study establishes a framework to assess greenspace supply-demand disparities related to thermal discomfort from the perspective of population mobility across urban functional zones(UFZs).High-resolution greenspac...This study establishes a framework to assess greenspace supply-demand disparities related to thermal discomfort from the perspective of population mobility across urban functional zones(UFZs).High-resolution greenspace maps and location-based service(LBS)datasets for Nanjing,China,were combined with Spearman correlation analyses and a four-quadrant model to elucidate associations and matching patterns between greenspace exposure and thermal comfort.The findings indicate that population fluctuations affect the availability of actual greenspace,with correlations to thermal discomfort showing significant temporal variations among different UFZs.During morning workday hours,commercial zones have a significantly higher representation in Quadrant Ⅱ(82.26%)compared to non-workdays(70.86%),which is characterized by high population density,low greenspace exposure,and pronounced thermal discomfort.In contrast,residential and public service zones maintain consistently high and stable proportions in Quadrant Ⅰ across all periods.This spatial mismatch is primarily caused by differences in available greenspace quantities and population mobility.Planning adjustments should focus on ensuring sufficient greenspace provision in key areas during peak population mobility periods to mitigate thermal discomfort.Minimizing residents'staying time in thermally uncomfortable zones,implementing time-specific greenspace access,and strategically increasing greenspace coverage are essential for improving the mismatch between greenspace supply and demand.展开更多
基金This work was supported by National High Technology Research and Development Program of PRC (No. 2002AA420040)National 973 Program of PRC (No. 2002CB312200).
文摘In this paper, a new pre-alignment approach based on Four-Quadrant-Photo-Detector （FQPD） for IC mask is presented. The voltage outputs from FQPDs are the functions of alignment mark＇s position offsets with respect to FQPDs. The functions are obtained with least squares error （LSE）-based polynomial fitting after the normalization of experimental data. As the acquired functions are not monotonic about their variables, the alignment mark＇s position offset cannot be given by direct inverse operation on the obtained functions. However, the piecewise polynomial fitting gives the inverse function, with which the alignment mark＇s position offset can be predicted according to the voltage outputs of FQPDs. On the basis of prediction, a pre-alignment control strategy is proposed. The feasibility and robustness of the pre-alignment approach is shown by experiments. Furthermore, the results demonstrate that the maximum error of mask＇s position offset in the X- and Y- directions is less than 15μm after coarse pre-alignment. Keywords： Four-Quadrant-Photo-Detector （FQPD）, pre-alignment, IC mask, polynomial fitting
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National Natural Science Foundation of China,No.42371397The Key Laboratory of Lake and Watershed Science for Water Security,No.NKL2023-KP03。
文摘This study establishes a framework to assess greenspace supply-demand disparities related to thermal discomfort from the perspective of population mobility across urban functional zones(UFZs).High-resolution greenspace maps and location-based service(LBS)datasets for Nanjing,China,were combined with Spearman correlation analyses and a four-quadrant model to elucidate associations and matching patterns between greenspace exposure and thermal comfort.The findings indicate that population fluctuations affect the availability of actual greenspace,with correlations to thermal discomfort showing significant temporal variations among different UFZs.During morning workday hours,commercial zones have a significantly higher representation in Quadrant Ⅱ(82.26%)compared to non-workdays(70.86%),which is characterized by high population density,low greenspace exposure,and pronounced thermal discomfort.In contrast,residential and public service zones maintain consistently high and stable proportions in Quadrant Ⅰ across all periods.This spatial mismatch is primarily caused by differences in available greenspace quantities and population mobility.Planning adjustments should focus on ensuring sufficient greenspace provision in key areas during peak population mobility periods to mitigate thermal discomfort.Minimizing residents'staying time in thermally uncomfortable zones,implementing time-specific greenspace access,and strategically increasing greenspace coverage are essential for improving the mismatch between greenspace supply and demand.
