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Research in Astronomy and Astrophysics 2024年第9期24卷 214-224页

作者： Xu-Qiao Wang Lan Du Zhong-Kai Zhang Ze-Jun Liu Hao Xiang College of Geospatial Information Information Engineering UniversityZhengzhou 450001China Henan Industrial Technology Academy of Spatio-Temporal Big Data Zhengzhou 450046China

High-precision polar motion prediction is of great significance for deep space exploration and satellite *** motion is affected by a variety of excitation factors,and nonlinear prediction methods are more suitable for polar motion *** order to explore the effect of deep learning in polar motion *** paper proposes a combined model based on empirical wavelet transform(EWT),Convolutional Neural Networks(CNN)and Long Short Term Memory(LSTM).By training and forecasting EOP 20C04 data,the effectiveness of the algorithm is verified,and the performance of two forecasting strategies in deep learning for polar motion prediction is *** results indicate that recursive multi-step prediction performs better than direct multi-step prediction for short-term forecasts within 15 days,while direct multi-step prediction is more suitable for medium and long-term *** the 365 days forecast,the mean absolute error of EWT-CNN-LSTM in the X direction and Y direction is 18.25 mas and 15.78 mas,respectively,which is 23.5% and 16.2% higher than the accuracy of Bulletin *** results show that the algorithm has a good effect in medium and long term polar motion prediction.

关键词： data analysis methods:miscellaneous astrometry reference systems Earth

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The Application of Permanent Magnet Synchronous Motor with Small Electrical Time Constant in Fiber Positioner

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Research in Astronomy and Astrophysics 2024年第1期24卷 212-222页

作者： Shaoxiong Guo Yan Yang Yanbin Yin Yihu Tang Yang Tian Chao Zhai Department of Precision Machinery and Precision Instrumentation University of Science and Technology of ChinaHefei 230026China School of Biomedical Engineering Division of Life Sciences and MedicineUniversity of Science and Technology of ChinaHefei 230026China Experiment Center of Engineering and Material Science University of Science and Technology of ChinaHefei 230026China

With the development of cutting-edge multi-object spectrographs,fiber positioners located in the focal plane are being scaled down in size,and miniature hollow-cup Permanent Magnet motors are now being considered as a suitable replacement for Faulhaber Precistep stepper ***,the small electrical time constant of such coreless motors poses a challenge,as the problem of severe commutation torque ripple in a fiber positioner running a position loop has been *** overcome this challenge,it is advised to increase the Pulse Width Modulation(PWM)frequency as much as possible to mitigate the effects of the current *** must be done while ensuring adequate resolution of the PWM *** employing a voltage open-loop field-oriented control based on a modulation frequency of 1 MHz,the drive current only costs 25 m A under a 3.3 V power *** sine degree of phase current is immaculate,and the repeat positioning accuracy can reach 2μ***,it is possible to further shrink the bill of devices and the layout area of the Printed Circuit Board,especially in sizesensitive *** device has been developed under the new generation of The Large Sky Area MultiObject Fiber Spectroscopic Telescope.

关键词： instrumentation:adaptive optics instrumentation:spectrographs proper motions reference systems

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CHOICE OF THE GAUGE FOR THE FIRST POST-NEWTONIAN GRAVITATIONAL POTENTIAL OF THE EARTH

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南京大学学报(自然科学) 1999年第1期 121-123页

作者： Tao Jinhe Huang Tianyi (Department of Astronomy, Nanjing University, 210093, Nanjing, PRC)

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关键词： relativity celestial mechanics reference systems

The Woodcock＇s head： Resolving a morphological oddity using geometric morphometrics

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Zoological Systematics 2017年第1期42卷 102-107页

作者： jesus marugán-lobón unidad de paleontología dpto.biologíauniversidad autonóma de madridSpain

The scope of shape analysis based on geometric morphometrics has evolved into underscoring complex patterns of multidimensional shape change with multivariate statistical modelling （e.g., allometry, morphological integration, etc.）. Such breakthrough was made possible because the method relies on a consistent comparative reference system to compare shapes, the latter which is computed using the Cartesian coordinates of homologous landmarks. It has been shown elsewhere that traditional comparative reference systems based on anatomy, and oriented in stereotyped postures, such as the Frankfurt plane at rest, the Lateral Semicircular Canal when the animal is in alert, or the cranial floor when the animal is flying, are all inconsistent for anatomical comparisons. They vary too much and unpredictably across species. An extraordinary example of the problems that can arise in descriptive and comparative anatomy when using such reference systems is the traditional interpretation of the head of the Woodcock. Anywhere in literature it is written that the eyes of this gamebird are oriented backwards to protect itself from predators. Here, using geometric morphometrics it is demonstrated that the woodcock＇s skull is highly transformed, yet following a normal trend among birds. In turn, using GM it is demonstrated that the collective wisdom about this oddity is simply the result of interpreting the anatomy of its skull using unreliable reference systems.

关键词： Geometric morphometrics reference systems craniofacial skull Woodcock.

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Black Sun: Ocular Invisibility of Relativistic Luminous Astrophysical Bodies

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Journal of High Energy Physics, Gravitation and Cosmology 2016年第4期2卷 562-570页

作者： Jeffrey S. Lee Gerald B. Cleaver Early Universe Cosmology and Strings Group Center for Astrophysics Space Physics and Engineering Research Waco TX USA Department of Physics Baylor University Waco TX USA

Considered as a gedanken experiment are the conditions under which the relativistic Doppler shifting of visible electromagnetic radiation to beyond the human ocular range could reduce the incident radiance of the source, and render a luminous astrophysical body (LAB) invisible to a naked eye. This paper determines the proper distance as a function of relativistic velocity at which a luminous object attains ocular invisibility.

关键词： Relativistic Processes Black Hole Physics reference systems Luminous Astrophysical Body Relativistic Blackbody Spectrum