Off-axis telescope misalignment correction based on defocus spot moment features.

Optical mirror misalignments, which are caused by assembly mistakes and changes in the surrounding environment (such as gravity, temperature, and atmosphere), degrade the system's imaging performance. Therefore, active misalignment correction is essential for ensuring the image quality of the off-axis telescope. In this paper, a novel misalignment correction method without wavefront sensors is proposed. The point spread functions (PSFs) of the system are analytically related to the optical mirror misalignments. On this basis, a fully connected neural network (FCNN) is used to establish the mapping relationship between the misalignments and the discrete orthogonal unbiased finite impulse response (UFIR) moment features, which can effectively characterize changes of intensity and geometric of the spot image. The simulation and experimental results in this paper justify the effectiveness and practicality of the proposed method. This approach offers a low-cost and straightforward technical method for achieving high imaging quality throughout the alignment and observation phases. This approach can prevent the accumulation of errors caused by wavefront detection and the high delay of multiple iterations.

Vibration rejection of phased array telescope systems via disturbance-propagation-characteristics-based feedforward control.

Vibration rejection is one of the key techniques to stabilize the line of sight (LOS) for phased array telescope systems. Conventionally, feedback control based on image sensors is mainly used to correct the tip/tilt errors caused by disturbances and to keep the LOS stable. However, it is restricted by the sampling rate and time delay of image sensors, leading to a limited closed-loop bandwidth. Disturbances in the middle and high frequencies are hard to suppress. In this paper, disturbance-propagation-characteristics-based feedforward control is proposed to overcome these problems. A theoretical imaging model of the phased array telescope is developed to analyze the LOS disruption caused by disturbance. In addition, to improve the disturbance suppression bandwidth and correction accuracy of the system, the disturbance propagation characteristics of the phased array telescope system are analyzed. Combined with the disturbance feedforward, targeted compensation is achieved for the sub-apertures. Finally, a comparative experiment is carried out based on the self-developed Fizeau phased array telescope system to verify the superiority of the proposed method.

Demonstration of a Fizeau Directly-Imaging Sparse-Aperture Telescope with Pointing and Tracking Capabilities.

At present, the majority of sparse-aperture telescopes (SATs) are unable to observe moving targets. In this paper, we describe the construction of and present the results obtained using a Fizeau directly-imaging sparse-aperture telescope (FDISAT) that permits pointing and the tracking of moving targets. The telescope comprises three sub-apertures, each of which is equipped with a Risley prism system that permits a maximum tracking range of 5° and has independent boresight adjustment capability. On targets in various positions, experiments with pointing and tracking are conducted. The maximum root-mean-square error (RMSE) of pointing in the sub-apertures was found to be 8.22 arcsec. When considering a target moving at 0.01°/s for approximately 320 s, the maximum RMSE of tracking in the sub-apertures was found to be 4.23 arcsec. The images obtained from the focal plane detector exhibit clear interference fringes while tracking. The experimental results demonstrate that the system can effectively track moving targets, providing a method for SAT observation of moving targets.

Robust Risley prism control based on disturbance observer for system line-of-sight stabilization.

In this paper, a robust control based on disturbance observer is proposed to improve the tracking accuracy of the Risley prism system (RPS). Applying the flexible thin-wall ring mechanism in the RPS causes a series of tracking and pointing challenges. Disturbances such as friction, shaft deformation, and model perturbation significantly deteriorate the tracking and pointing accuracy of the RPS. Two different observer-based control methods are proposed to guarantee the tracking precision of the RPS. Moreover, the disturbance observation and compensation (DOC) performance of the proposed methods is analyzed and compared. Finally, simulation and experiment results indicate that the proposed control methods, especially the DOC-expanded state observer control mode, obtain the best performance for disturbance rejection in the RPS.

[Effects of 37 centigrade volume resuscitation on coagulation function and blood lactic acid in neonates with septic shock].

OBJECTIVE: To investigate the effect of volume resuscitation with normal saline (NS) at 37 centigrade on the coagulation function and microcirculation of neonates with septic shock. METHODS: Children with septic shock admitted to neonatal intensive care unit (NICU) of the First Affiliated Hospital of Gannan Medical University were enrolled. Twenty-four newborns with septic shock were divided into two groups by random number table method (12 in each group), and were resuscitated with 10 mL/kg at 25 centigrade NS and 37 centigrade NS respectively on the basis of routine treatment. Factor II, V, VII, VIII, IX, X, and prothrombin time (PT), thrombin Time (TT), fibrinogen (FIB), activated partial thromboplastin time (APTT), D-Dimer (DD), lactic acid (Lac) were detected before treatment and 6 hours and 12 hours after treatment. RESULTS: The levels of coagulation factors II, V, VII, VIII, IX, X were not significantly changed before and after treatment in the two groups, and there was no significant difference between the two groups. After treatment, PT and APTT in both groups were gradually shortened, DD and Lac were gradually decreased, FIB were gradually increased, while TT had no significant change. Among them, PT, APTT, DD and Lac at 6 hours after treatment in 37 centigradeNS group were significantly lower than those before treatment [PT (s): 14.07±1.02 vs. 17.08±1.54, APTT (s): 54.83±12.39 vs. 69.17±16.36, DD (mg/L): 2.40±0.63 vs. 4.18±0.88, Lac (mmol/L): 2.84±0.82 vs. 5.98±1.17, all P < 0.05]; DD and Lac at 6 hours after treatment in 25 centigrade NS group were significantly lower than those before treatment [DD (mg/L): 3.13±0.84 vs. 4.16±1.04, Lac (mmol/L): 4.83±0.64 vs. 5.69±0.74, both P < 0.05], and PT at 12 hours after treatment was significantly shorter than that before treatment (s: 14.63±1.14 vs. 16.48±1.61, P < 0.01); FIB in both 25 centigrade NS group and 37 centigrade NS group at 12 hours after treatment were significantly higher than those before treatment (g/L: 2.83±0.83 vs. 1.58±0.43, 2.87±0.87 vs. 1.47±0.41, both P < 0.01), but TT had no significant change. The comparison between groups showed that PT, DD and Lac in the 37 centigrade NS group were significantly lower than those in the 25 centigrade NS group at 6 hours after treatment [PT (s): 14.07±1.02 vs. 15.69±1.21, DD (mg/L): 2.40±0.63 vs. 3.13±0.84, Lac (mmol/L): 2.84±0.82 vs. 4.83±0.64, all P < 0.05]; at 12 hours after treatment, PT, APTT and DD in the 37 centigrade NS group were significantly lower than those in the 25 centigrade NS group [PT (s): 13.26±0.91 vs. 14.63±1.14, APTT (s): 37.08±10.43 vs. 54.75±14.96, DD (mg/L): 1.20±0.59 vs. 2.06±0.69, all P < 0.01], and FIB was significantly higher than that in the 25 centigrade NS group (g/L: 2.87±0.87 vs. 2.83±0.83, P < 0.05). CONCLUSIONS: Volume resuscitation at 37 centigrade can improve the coagulation function and microcirculation of newborns with septic shock.