Solar adaptive optics systems for the New Vacuum Solar Telescope at the Fuxian Lake Solar Observatory

Adaptive optics(AO)is essential for high-quality ground-based observations with large telescopes because it counters the impact of wavefront aberrations caused by atmospheric turbulence.The new vacuum solar telescope(NVST)is one of the most important high-resolution solar observation instruments in the world.Three sets of solar adaptive optics systems have been developed and installed on this telescope:conventional adaptive optics,ground layer adaptive optics,and multi-conjugate adaptive optics.These have been in operation from 2018 to 2023.This paper details the development and application of solar adaptive optics on the NVST and discusses the newest instrumentation.

Erasure-Correction-Enhanced Iterative Decoding for LDPC-RS Product Codes

Low-density parity-check(LDPC)codes are widely used due to their significant errorcorrection capability and linear decoding complexity.However,it is not sufficient for LDPC codes to satisfy the ultra low bit error rate(BER)requirement of next-generation ultra-high-speed communications due to the error floor phenomenon.According to the residual error characteristics of LDPC codes,we consider using the high rate Reed-Solomon(RS)codes as the outer codes to construct LDPC-RS product codes to eliminate the error floor and propose the hybrid error-erasure-correction decoding algorithm for the outer code to exploit erasure-correction capability effectively.Furthermore,the overall performance of product codes is improved using iteration between outer and inner codes.Simulation results validate that BER of the product code with the proposed hybrid algorithm is lower than that of the product code with no erasure correction.Compared with other product codes using LDPC codes,the proposed LDPC-RS product code with the same code rate has much better performance and smaller rate loss attributed to the maximum distance separable(MDS)property and significant erasure-correction capability of RS codes.

EAST-Educational Adaptive-optics Solar Telescope

For the public having a better understanding of solar activities,the Educational Adaptive-optics Solar Telescope(EAST)was built in July 2021 and is located at the Shanghai Astronomy Museum.The EAST consists of a 65 cm aperture solar telescope with a 177-element adaptive optics system and two-channel high resolution imaging system at the Hαand TiO bands,in addition to three full disk solar telescopes at CaK,Hαand TiO bands equipped on the tube of the main telescope.In this paper,the configuration of the EAST is described.Its performance and on-sky observational results are presented.The EAST,to our knowledge,is the most advanced solar telescope for the popularization of science in the world.Due to its excellent performance,the data acquired by the EAST can also be used for research on solar physics and space weather prediction.

Comparison of three flocculants for heavy cyanobacterial bloom mitigation and subsequent environmental impact

Cyanobacteria can accumulate as a heavy biomass on the leeward side of large eutrophic lakes,posing a potential threat to public health.The mitigating capacity of three flocculants and their potential impacts on the major environmental features of water and sediments was evaluated.Results indicate that polyaluminum chloride(PAC)and ferric chloride(FeCl)are efficient flocculants that can rapidly mitigate cyanobacterial blooms with chlorophyll-a concentrations higher tnan 1500 ug/L within 15 min.In comparison,cationic starch with chitosan could only treat cyanobacterial blooms in chlorophyll-a concentrations of less than 200μg/L.The addition of FeClcaused a decline in the pH value,while dissolved oxygen in the water column dropped to 2 mg/L during cationic starch with chitosan treatment for a high cyanobacterial biomass group.Thus,a combination of flocculants and oxygenators should be considered when treating high-concentration cyanobacterial blooms for emergency purposes.Additionally,the cell lysis of cyanobacteria caused by cationic starch with chitosan can result in an increase in total dissolved phosphorus and total dissolved nitrogen.Furthermore,the high accumlation of nutrients in sediments after the settling of cyanobacteria can cause high internal phosphorus pollution.The increase in the total organic carbon of the sediments can threaten lake restoration achieved by planting submerged macrophytes.

High-resolution visible imaging with piezoelectric deformable secondary mirror: experimental results at the 1.8-m adaptive telescope

Integrating deformable mirrors within the optical train of an adaptive telescope was one of the major innovations in astronomical observation technology,distinguished by its high optical throughput,reduced optical surfaces,and the incorporation of the deformable mirror.Typically,voice-coil actuators are used,which require additional position sensors,internal control electronics,and cooling systems,leading to a very complex structure.Piezoelectric deformable secondary mirror technologies were proposed to overcome these problems.Recently,a high-order piezoelectric deformable secondary mirror has been developed and installed on the 1.8-m telescope at Lijiang Observatory in China to make it an adaptive telescope.The system consists of a 241-actuator piezoelectric deformable secondary mirror,a 192-sub-aperture Shack-Hartmann wavefront sensor,and a multi-core-based real-time controller.The actuator spacing of the PDSM measures 19.3 mm,equivalent to approximately 12.6 cm when mapped onto the primary mirror,significantly less than the voicecoil-based adaptive telescopes such as LBT,Magellan and VLT.As a result,stellar images with Strehl ratios above 0.49 in the R band have been obtained.To our knowledge,these are the highest R band images captured by an adaptive telescope with deformable secondary mirrors.Here,we report the system description and on-sky performance of this adaptive telescope.

Bit-Level Composite Signal Design for Simultaneous Ranging and Communication

As the complexity of space exploration missions augments,how to enhance the overall performance of communication,ranging or other functions has become a challengeable problem.Considering the integration of communication and ranging,we present a bit-level composite signal for simultaneous ranging and communication.In this composite method,through a specially designed mapping scheme using low-weight codewords,the information sequence is converted to a sparse sequence which is then superimposed on the ranging code.For ranging,the correlation characteristics of the ranging code component can be maintained to calculate the transmitter-receiver distance.For communications,the sparse sequence can be extracted without interference by eliminating the ranging code component.Simulation results show that the proposed composite signal can support communication and ranging simultaneously with limited sacrifice of ranging performance,and the performance loss of ranging can be controlled and minimized by lowering the density of information sequences using different sparsification encoding methods.

Terminal-to-Terminal Calling for GEO Broadband Mobile Satellite Communication

Satellite and terrestrial components of IMT-Advanced need to be integrated so that the traditional strengths of each component can be fully exploited. LTE/LTE-A is now a recognized foundation of terrestrial 4G networks, and mobile satellite networks should be based on it. Long transmission delay is one of the main disadvantages of satellite communication, especially in a GEO system, and terminal-to-terminal （TtT） design reduces this delay. In this paper, we propose a protocol architecture based on LTE/LTE-A for GEO mobile satellite communication. We propose a detailed call procedure and four TtT modes for this architecture. We describe the division of tasks between the satellite gateway （SAT-GW） and satellite as well as TtT processing in the physical layer of the satellite in order to reduce delay and ensure compatibility with a terrestrial LTE/LTE-A system.

First light of the 1.8-m solar telescope–CLST

Large-aperture solar telescopes play an important role in solar observations and research,and require high temporal and spatial resolution[1].To solve some fundamental problems such as the solar dynamo,coronal heating,and the triggering of major solar eruptions,the spatial resolution for solar-atmosphere observation should reach at least 0.1 arcsec[2].

Effect of scraping therapy on weightlifting ability

OBJECTIVE:To verify the effects of scraping therapy on the weightlifting ability by measuring the subjective sensation,and changes of biomarkers.METHODS:Five students,who have been trained for 3 years in a sport school in China were participated in this study.A course of scraping therapy was applied to intervene during the normal 7-week of weightlifting training programme.The ability of weightlifting,the scale of rating perceived exertion and serum biochemical markers were measured before and after the intervention.RESULTS:Scraping therapy caused a significant increase in weightlifting ability(P<0.05).The level of rating perceived exertion remained stable with the increase in the training volume.Immuno-globulinA was significantly increased(P<0.05),and creatine kinase and blood urea nitrogen were significantly decreased(P<0.05).No significant changes were observed in white blood cell,neutrophil,and testosterone.CONCLUSION:Scraping therapy may facilitate weightlifting ability mainly by decreasing weight sensation and improving serum biochemical parameters.

Ground-layer adaptive optics for the New Vacuum Solar Telescope:Instrument description and first results

Ground-layer adaptive optics(GLAO)has shown its potential for use in solar observation owing to its wide field-of-view(FOV)correction.A high-order GLAO system that consists of a multiple direction Shack-Hartmann wavefront sensor(WFS),a realtime controller with a multi-CPU processor,and a 151-element deformable mirror was developed for the 1-m New Vacuum Solar Telescope at Yunnan Observatories,Chinese Academy of Sciences.A hexagonal microlens with 9×8 subapertures is employed in the WFS.The detection FOV is 42′′×37′′,in which 9(3×3)guide regions are extracted for multiple direction wavefront sensing with a frame rate of up to 2200 Hz.To our knowledge,this is the first professional solar GLAO system used as a regularly operating instrument for scientific observations.Its installation and adjustment were performed in the summer of 2021.In this article,a detailed account of the GLAO system and its first light results and a comprehensive analysis of the performance of the GLAO system are provided.The results show that this system can effectively improve the imaging quality after compensating for the wavefront aberration due to ground-layer turbulence.

Curative effect of scraping therapies on lumbar muscle strain

OBJECTIVE:To explore factors influencing the curative effect of scraping therapies (at acupoints or along channels) and to determine the relationship of scraping site and strength to curative effect. METHODS: Two hundred and ten patients with lumbar muscle strain were divided into five groups with 42 patients each.The "scraping therapy at acupoint until appearance of skin eruptions" and "scraping therapy along channel until appearance of skin eruptions" groups were treated with a 4-daycourse. The "scraping therapy at acupoint without appearance of skin eruptions", "scraping therapy along channel without appearance of skin eruptions", and acupuncture groups were treated with a 2-day course.The five groups were treated with seven courses. The visual analog scale (VAS), oswestry disability index (ODI), and lumbago scores were recorded in the five groups before treatment, after each treatment, and in follow-up visits one month and three months after treatment. RESULTS: VAS, ODI, and lumbago scores after treatment improved in the five groups (P<0.01). There was a statistical difference (P<0.01) in the change of VAS scores by appearance of skin eruptions and scraping site. CONCLUSION: Scraping therapy can effectively alleviate lumbago symptoms. The appearance of skin eruptions and scraping therapy along channels can enhance the curative effect of scraping therapy.

Use of laser speckle contrast imaging to reveal changes in temperature and blood perfusion in the skin of healthy subjects after administration of heated moxa sticks and Daiwenjiu ointment

OBJECTIVE: To investigate the influence of heated moxa sticks( "moxibustion") and Daiwenjiu ointment(DO) on changes in temperature and blood perfusion volume on the skin of the backs of healthy subjects.METHODS: DO was spread on the left side of the body, and the right side of the body was treated with a heated moxa stick. Images denoting blood perfusion and body temperature were collected 7-8 cm lateral to the spinous process of the sixth thoracic vertebra using laser speckle contrast imaging(LSCI). Data obtained from eight-frame images were analyzed and used to calculate the mean blood perfusion volume. Simultaneously,blood-perfusion images were collected from the body surface and used to compare the change in blood flow on the body surface and the actual position of imaging.RESULTS: After moxibustion, a rapid increase in blood perfusion volume and body temperature was noted in the local skin surface. The maximum blood perfusion volume and body temperature was noted at 20 min(P<0.05). At 80-110 min after the spreading of DO, a gradual increase was noted in blood perfusion volume(P<0.05) and body temperature(P<0.05) compared with the baseline level. The maximum blood perfusion volume was at 110 min.CONCLUSION: Using LSCI, these data revealed a rapid and sharp increase in blood perfusion volume and body temperature after treatment with moxibustion, but the respective changes seen in the DO group were gradual and moderate.