Research on Ultra-wide Bandwidth Low-frequency Signal Channelization for Xinjiang 110m Radio Telescope

Aiming at the subband division of ultra-wide bandwidth low-frequency(UWL)signal(frequency coverage range:704–4032 MHz)of the Xinjiang 110 m QiTai radio Telescope(QTT),a scheme of ultra-wide bandwidth signal is designed.First,we analyze the effect of different window functions such as the Hanning window,Hamming window,and Kaiser window on the performance of finite impulse response(FIR)digital filters,and implement a critical sampling polyphase filter bank(CS-PFB)based on the Hamming window FIR digital filter.Second,we generate 3328 MHz simulation data of ultra-wideband pulsar baseband in the frequency range of 704–4032 MHz using the ultra-wide bandwidth pulsar baseband data generation algorithm based on the 400 MHz bandwidth pulsar baseband data obtained from Parkes CASPSR observations.Third,we obtain 26 subbands of 128 MHz based on CS-PFB and the simulation data,and the pulse profile of each subband by coherent dispersion,integration,and folding.Finally,the phase of each subband pulse profile is aligned by non-coherent dedispersion,and to generate a broadband pulse profile,which is basically the same as the pulse profile obtained from the original data using DSPSR.The experimental results show that the scheme for the QTT UWL receiving system is feasible,and the proposed channel algorithm in this paper is effective.

河口海岸潮滩蟹类生物扰动行为过程研究进展

河口海岸潮滩是具有较高生物生产力和生物多样性的生态系统。蟹类作为一种典型的生态系统工程师,分布广泛、种类繁多,可影响整个潮滩生态系统的物质与能量循环。蟹类的分布与盐度、淹水时长、湿度、温度、底质等非生物因子有关,也与植被、捕食作用、种内种间竞争等生物因子和人类活动有关。蟹类挖掘洞穴,形成了优先排水通道,增加了土壤蒸发速率,改变了孔隙水循环以及土壤的物理化学性质,进而可影响潮滩泥沙稳定性以及微地貌形态,甚至会影响中长期潮滩地貌演变。目前,蟹类对于沉积物稳定性、泥沙输运规律、微地貌演变的影响依然有待深入研究,有必要开展中长期现场观测和试验、多因子驱动下系统演变数值模拟以及综合分析,推动相关研究从定性向定量层面迈进。

进鱼口水深不足时竖缝式鱼道水力特性及进出口允许最大水深差

为研究竖缝式鱼道进鱼口水深不足时鱼道进出口允许最大水深差,构建了鱼道整体数学模型,对鱼道流速、流态、水面线等进行了数值模拟分析。结果表明:当进鱼口水深不足时,上游段水深与出鱼口水深一致,流速稳定;中间段水深开始缓慢下降,流速逐渐变大;下游段水深急剧下降,流速迅速变大,在进鱼口处出现跌水,流速出现最大值。当鱼道坡度相同时,出鱼口水深与进出口允许最大水深差呈线性关系,出鱼口水深越大,进出口允许最大水深差越大;当出鱼口水深相同时,鱼道坡度与进出口允许最大水深差也呈线性关系,鱼道坡度越陡,进出口允许最大水深差越小。

进鱼口水深超高时竖缝式鱼道允许水位差

若鱼道设计不当,进鱼口水深超高会影响诱鱼效果,从而降低鱼类上溯率。依托某实例工程建立鱼道整体数学模型,对鱼道流速、流态、水面线等进行研究,探究进鱼口水深超高时鱼道上下游允许水位差。研究发现,壅水工况,上游段水深与出鱼口水深一致,流速稳定,下游段水深开始缓慢增加直至达到进鱼口水深,流速随之减小,出现极小值;坡度越陡,出鱼口水深对允许水位差的影响越大,坡度相同时允许水位差和出鱼口水深呈正线性相关,随出鱼口水深增加,允许水位差变大;出鱼口水深越大,坡度对允许水位差的影响越小,出鱼口水深相同时允许水位差和坡度也呈正线性相关,坡度越陡,允许水位差越大。通过多元线性回归法,将试算数据整理为以坡度和出鱼口水深为自变量的允许水位差求解公式。研究成果可为大幅提高鱼道适应水位变动的能力提供技术支持。

1996—2020年长江口九段沙湿地植被覆盖对潮沟演变规律的影响

长江口九段沙湿地是国家级自然保护区,认识植被覆盖与潮沟网络间的关系对保护九段沙湿地意义重大。基于长时序Landsat和HJ-1A多光谱图像,提取并分析长江口九段沙湿地潮沟和植被覆盖度数据。结果表明:①1996—2020年间,潮沟总长度以每年11.71 km速度增加,植被覆盖面积以每年4.79 km^(2)速度增加,至2020年潮沟等级最高为四级;②历年潮沟分布特征变化与高植被覆盖度区域密切相关;③各级别潮沟中,一级潮沟对潮沟网络的平均归槽水流长度影响最大,而不同植被覆盖参数中,植被覆盖面积影响最大;④平均归槽水流长度与植被覆盖面积符合指数函数关系,随着植被覆盖面积的增大,平均归槽水流长度逐渐减小,即潮沟网络排水效率增大。

1959-2018年九段沙地貌演化特征及动力机制

基于近60年(1959-2018年)系列水下地形资料,研究九段沙成形以来的地貌演化特征和动力成因。结果表明:九段沙1959-1990年处于稳速淤涨、以低滩为主的自然演化状态;近30年(1990-2018年),0 m及以上高滩受植被生长和长江口深水航道治理工程作用快速淤涨,-1^-2 m滩面受干扰程度小、稳速淤涨;近20年(1998-2018年),-3 m及以下低滩受流域减沙和临近的大型涉水工程影响淤涨放缓并由淤积转冲刷,期间流域减沙使得九段沙淤积放缓滩地由低到高向上延伸。未来流域来沙可能进一步下降并维持在较低水平,九段沙将面临-3 m及以下低滩进一步冲蚀,-3 m以上滩地淤积放缓并由低到高逐渐转冲的风险。

Design of RFSoC-based Digital Phased Array Feed(PAF)and Hybrid Architecture Beamforming System

As the number of array elements and bandwidth increase,the design challenges of the Phased Array Feed(PAF)front-end and its signal processing system increase.Aiming at the ng-PAF of the 110 m radio telescope,this article introduces the concept of fully digital receivers and attempts to use Radio Frequency System-on-Chip(RFSo C)technology to digitize close to the feed array,reduce the complexity and analog components of the front-end,and improve the fidelity of the signals.The article discusses the digital beamforming topology and designs a PAF signal processing experimental system based on RFSo C+GPU hybrid architecture.The system adopts a ZCU111board to design RF-direct digitization and preprocessing front-end,which can sample eight signals up to 2.048GSPS,12 bit,channelize the signals into 1024 chunks,then reorder into four data streams and select one of the 256MHz frequency bands to output through four 10 Gb links.A GPU server is equipped with four RTX 3090 GPUs running four HRBF_HASHPIPE instances,each receiving a 64 MHz bandwidth signal for high-throughput realtime beamforming.The experimental system uses a signal generator to emulate Sa-like signals and propagates through rod antennas,which verifies the effectiveness of the beamforming algorithm.Performance tests show that after algorithm optimization,the average processing time for a given 4 ms data is less than 3 ms in the four-GPU parallel processing mode.The RFSo C integrated design shows significant advantages in power consumption and electromagnetic radiation compared with discrete circuits according to the measurement results.

Development of Pulsar Digital Backend Based on RFSoC

Radio Frequency System on Chip(RFSo C)offers great potential for implementing a complete next generation signal processing system on a single board for radio astronomy.We designed a pulsar digital backend system based on the ZCU111 board.The system uses RFSo C technology to implement digitization,channelization,correlation and high-speed data transmission in the Xilinx ZU28 DR device.We have evaluated the performance of the eight 12-bit RF-ADCs,which are integrated in RFSo C,with the maximum sampling rate of 4.096 GSPS.The RF-ADC sampling frequency,channel bandwidth and time resolution can be configured dynamically in our designed system.To verify the system performance,we deployed the RFSo C board on the Nanshan 26 m radio telescope and observed the pulsar signal with a frequency resolution of 1 MHz and time resolution of 64μs.In the observation test,we obtained pulsar profiles with high signal-to-noise ratio and accurately searched the DM values.The experimental results show that the performance of RF-ADCs,FPGA and CPU cores in RFSo C is sufficient for radio astronomy signal processing applications.

Opportunities to search for extraterrestrial intelligence with the FAST

The discovery of ubiquitous habitable extrasolar planets,combined with revolutionary advances in instrumentation and observational capabilities,has ushered in a renaissance in the search for extraterrestrial intelligence(SETI).Large scale SETI activities are now underway at numerous international facilities.The Five-hundred-meter Aperture Spherical radio Telescope(FAST)is the largest single-aperture radio telescope in the world,and is well positioned to conduct sensitive searches for radio emission indicative of exo-intelligence.SETI is one of the five key science goals specified in the original FAST project plan.A collaboration with the Breakthrough Listen Initiative was initiated in 2016 with a joint statement signed both by Dr.Jun Yan,the then director of National Astronomical Observatories,Chinese Academy of Sciences(NAOC),and Dr.Peter Worden,Chairman of the Breakthrough Prize Foundation.In this paper,we highlight some of the unique features of FAST that will allow for novel SETI observations.We identify and describe three different signal types indicative of a technological source,namely,narrow band,wide-band artificially dispersed and modulated signals.Here,we propose observations with FAST to achieve sensitivities never before explored.For nearby exoplanets,such as TESS targets,FAST will be sensitive to an EIRP of 1.9×1011 W,well within the reach of current human technology.For the Andromeda Galaxy,FAST will be able to detect any Kardashev type II or more advanced civilization there.

Assessment of immunization procedures for foot-and-mouth disease in large-scale pig farms in China based on actual data and dynamics

Foot-and-mouth disease(FMD)is an acute,highly infectious and pathogenic animal disease.In recent years,with the rapid development of the swine breeding industry in China,pig farms have shown a trend of larger-scale development.Large-scale pig farms employ standardized management,a high level of automation,and a strict_system.However,these farms have a large trading volume,and increased transmission intensity of FMD is noted inside the farm.At present,the main control measure against FMD is pig vaccination.However,a standard for immunization procedures is not available,and currently adopted immunization procedures have not been effectively and systematically evaluated.Taking a typical large-scale pig farm in China as the research subject and considering the breeding pattern,piggery structure,age structure and immunization procedures,an individual-based state probability model is established to evaluate the effectiveness of the immune procedure.Based on numerical simulation,it is concluded that the optimal immunization program involves primary immunization at 40 days of age and secondary immunization at 80 days of age for commercial pigs.Breeding boars and breeding sows are immunized 4 times a year,and reserve pigs are immunized at 169 and 259 days of age.According to the theoretical analysis,the average control reproduction number of individuals under the optimal immunization procedure in the farm is 0.4927.In the absence of immunization,the average is 1.7498,indicating that the epidemic cannot be controlled without immunization procedures.

Design of a multi-function high-speed digital baseband data acquisition system

A multi-function digital baseband data acquisition system is designed for the sampling,distribution and recording of wide-band multi-channel astronomical signals.The system hires a SNAP2board as a digital baseband converter to digitize,channelize and packetize the received signal.It can be configured dynamically from a single channel to eight channels with a maximum bandwidth of 4096 MHz.Eight parallel HASHPIPE instances run on four servers,each carrying two NVMe SSD cards,achieving a total continuous write rate of 8 GB s^(-1).Data are recorded in the standard VDIF file format.The system is deployed on a 25-meter radio telescope to verify its functionality based on pulsar observations.Our results indicate that during the 30-minute observation period,the system achieved zero data loss at a data recording rate of 1 GB s^(-1) on a single server.The system will serve as a verification platform for testing the functions of the QTT(Qi Tai radio Telescope)digital backend system.In addition,it can be used as a baseband/VLBI(Very Long Baseline Interferometry)recorder or D-F-engine of correlator/beamformer as well.

Water as dispersion medium to fabricate homogeneous nanohectorite solid-state electrolyte for suppressing lithium dendrite

The rational design of green chemical,low-cost,and highly efficient solid-state electrolytes for Li-metal anode is a promising but still challenging strategy for preventing Li dendrite growth and developing safe and ultralong cycle life Li-metal batteries.Herein,a homogeneous composite solid polymer electrolyte(CSPE)is fabricated with water as the ideal dispersion medium,hectorite(Ht)as nanofiller,and poly(ethylene oxide)(PEO)as the matrix,to guide uniform Li plating/stripping.Benefiting from the merit of Ht can form uniformly dispersed nanosheets in water,the obtained CSPE inheres to a low melting point,robust mechanical property,and high Li^(+)transference number.Moreover,the fabricated Li symmetric battery using PEO-Ht-LiClO_(4)CSPE keeps cycling steadily for 4000 h.The well demonstrated water-based CSPE paves the way for developing low-cost,environmentally friendly,and safe solid-state electrolytes for Li-metal batteries.

Forecast of peak infection and estimate of excess deaths in COVID-19 transmission and prevalence in Taiyuan City,2022 to 2023

In this paper,with the method of epidemic dynamics,we assess the spread and prevalence of COVID-19 after the policy adjustment of prevention and control measure in December 2022 in Taiyuan City in China,and estimate the excess population deaths caused by COVID-19.Based on the transmission mechanism of COVID-19 among individuals,a dynamic model with heterogeneous contacts is established to describe the change of control measures and the population's social behavior in Taiyuan city.The model is verified and simulated by basing on reported case data from November 8th to December 5th,2022 in Taiyuan city and the statistical data of the questionnaire survey from December 1st to 23rd,2022 in Neijiang city.Combining with reported numbers of permanent residents and deaths from 2017 to 2021 in Taiyuan city,we apply the dynamic model to estimate theoretical population of 2022 under the assumption that there is no effect of COVID-19.In addition,we carry out sensitivity analysis to determine the propagation character of the Omicron strain and the effect of the control measures.As a result of the study,it is concluded that after adjusting the epidemic policy on December 6th,2022,three peaks of infection in Taiyuan are estimated to be from December 22nd to 31st,2022,from May 10th to June 1st,2023,and from September 5th to October 13th,2023,and the corresponding daily peaks of new cases can reach 400000,44000 and 22000,respectively.By the end of 2022,excess deaths can range from 887 to 4887,and excess mortality rate can range from 3.06%to 14.82%.The threshold of the infectivity of the COVID-19 variant is estimated 0.0353,that is if the strain infectivity is above it,the epidemic cannot be control with the previous normalization measures.

Applying the Dark Target Aerosol Algorithm to MERSI-Ⅱ:Retrieval and Validation of Aerosol Optical Depth over the Ocean

The Medium-Resolution Spectral Imager-Ⅱ(MERSI-Ⅱ)instrument aboard China’s Fengyun-3D satellite shares similarities with NASA’s Moderate Resolution Imaging Spectroradiometer(MODIS)sensor,enabling the retrieval of global aerosol optical depth(AOD).However,no officially released operational MERSI-Ⅱ aerosol products currently exist over the ocean.This study focuses on adapting the MODIS dark target(DT)ocean algorithm to the MERSI-Ⅱ sensor.A retrieval test is conducted on the 2019 MERSI-Ⅱ data over the global ocean,and the retrieved AODs are validated against ground-based measurements from the automatic Aerosol Robotic Network(AERONET)and the shipborne Maritime Aerosol Network(MAN).The operational MODIS DT aerosol products are also used for comparison purposes.The results show that MERSI-Ⅱ AOD granule retrievals are in good agreement with MODIS products,boasting high correlation coefficients(R)of up to 0.96 and consistent spatial distribution trends.Furthermore,the MERSI-Ⅱ retrievals perform well in comparison to AERONET and MAN measurements,with high R-values(>0.86).However,the low-value retrievals from MERSI-Ⅱ tend to be slightly overestimated compared to MODIS,despite both AODs displaying a positive bias.Notably,the monthly gridded AODs over the high latitudes of the northern and southern hemispheres suggest that MERSI-Ⅱ exhibits greater stability in space and time,effectively reducing unrealistically high-value noise in the MODIS products.These results illustrate that the MERSI-Ⅱ retrievals meet specific accuracy requirements by maintaining the algorithmic framework and most of the algorithmic assumptions,providing a crucial data supplement for aerosol studies and climate change.

腹腔镜下获取带蒂大网膜瓣在乳腺癌术后乳房重建中的应用价值

大网膜具有较强的吸收功能和覆盖填充作用,因此可以应用于乳房切除后的乳房重建。但由于开腹获取大网膜对腹部有较大的创伤,且大网膜较小的体积难以填充较大的乳房,使其在临床上的应用受到了限制。笔者重点介绍通过腹腔镜技术获取大网膜从而减小供区创伤,以及乳房体积较大时采用大网膜联合假体置入完成乳房重建的方法。

腔镜带蒂大网膜获取技术在乳腺癌腔镜保乳肿瘤整形手术中的应用

目的研究腔镜带蒂大网膜获取技术在乳腺癌腔镜保乳肿瘤整形手术中的应用价值。方法回顾性分析2016年11月-2017年11月在首都医科大学附属北京友谊医院行腔镜保乳手术+腔镜带蒂大网膜肿瘤整形手术的11例乳腺癌患者的病例资料。记录并分析手术时间、术中出血量、拔除引流管时间、切口长度、手术并发症、术后美容效果、肿瘤复发情况。结果11例患者手术时间平均186min,术中出血量平均22ml,拔除引流管时间平均3.1d,切口总长度平均5.2cm。无严重并发症发生,1例患者出现术后嗳气增多。术后美容效果评分平均为14.7分(满分15分);其中“乳房外形”“切口瘢痕”2项,全部患者均为满分。元局部复发或远处转移病例。结论乳腺癌腔镜保乳手术与腔镜带蒂大网膜获取技术结合能安全而有效地恢复保乳手术后的乳房外形,达到较好的术后美容效果。

The Qitai radio telescope

This study presents a general outline of the Qitai radio telescope(QTT)project.Qitai,the site of the telescope,is a county of Xinjiang Uygur Autonomous Region of China,located in the east Tianshan Mountains at an elevation of about 1800 m.The QTT is a fully steerable,Gregorian-type telescope with a standard parabolic main reflector of 110 m diameter.The QTT has adopted an umbrella support,homology-symmetric lightweight design.The main reflector is active so that the deformation caused by gravity can be corrected.The structural design aims to ultimately allow high-sensitivity observations from 150 MHz up to115 GHz.To satisfy the requirements for early scientific goals,the QTTwill be equipped with ultra-wideband receivers and large field-of-view multi-beam receivers.A multi-function signal-processing system based on RFSo C and GPU processor chips will be developed.These will enable the QTT to operate in pulsar,spectral line,continuum and Very Long Baseline Interferometer(VLBI)observing modes.Electromagnetic compatibility(EMC)and radio frequency interference(RFI)control techniques are adopted throughout the system design.The QTT will form a world-class observational platform for the detection of lowfrequency(nano Hertz)gravitational waves through pulsar timing array(PTA)techniques,pulsar surveys,the discovery of binary black-hole systems,and exploring dark matter and the origin of life in the universe.The QTT will also play an important role in improving the Chinese and international VLBI networks,allowing high-sensitivity and high-resolution observations of the nuclei of distant galaxies and gravitational lensing systems.Deep astrometric observations will also contribute to improving the accuracy of the celestial reference frame.Potentially,the QTT will be able to support future space activities such as planetary exploration in the solar system and to contribute to the search for extraterrestrial intelligence.

A Simulation System and Speed Guidance Algorithms for Intersection Traffic Control Using Connected Vehicle Technology

In the connected vehicle environment, real-time vehicle-state data can be obtained through vehicle-toinfrastructure communication, and the prediction accuracy of urban traffic conditions can significantly increase.This study uses the C++/Qt programming language and framework to build a simulation platform. A two-way six-lane intersection is set up on the simulation platform. In addition, two speed guidance algorithms based on optimizing the travel time of a single vehicle or multiple vehicles are proposed. The goal of optimization is to minimize the travel time, with common indicators such as average delay of vehicles, average number of stops, and average stop time chosen as indexes of traffic efficiency. When the traffic flow is not saturated, compared with the case of no speed guidance, single-vehicle speed guidance can improve the traffic efficiency by 20%, whereas multi-vehicle speed guidance can improve the traffic efficiency by 50%. When the traffic flow is saturated, the speed guidance algorithms show outstanding performance. The effect of speed guidance gradually enhances with increasing penetration rate, and the most obvious gains are obtained when the penetration rate increases from 10% to 40%. Thus, this study has shown that speed guidance in the connected vehicle environment can significantly improve the traffic efficiency of intersections, and the multi-vehicle speed guidance strategy is more effective than the single-vehicle speed guidance strategy.

Spatial-Temporal ConvLSTM for Vehicle Driving Intention Prediction

Driving intention prediction from a bird’s-eye view has always been an active research area. However,existing research, on one hand, has only focused on predicting lane change intention in highway scenarios and, on the other hand, has not modeled the influence and spatiotemporal relationship of surrounding vehicles. This study extends the application scenarios to urban road scenarios. A spatial-temporal convolutional long short-term memory(ConvLSTM) model is proposed to predict the vehicle’s lateral and longitudinal driving intentions simultaneously. This network includes two modules: the first module mines the information of the target vehicle using the long short-term memory(LSTM) network and the second module uses ConvLSTM to capture the spatial interactions and temporal evolution of surrounding vehicles simultaneously when modeling the influence of surrounding vehicles. The model is trained and verified on a real road dataset, and the results show that the spatial-temporal ConvLSTM model is superior to the traditional LSTM in terms of accuracy, precision, and recall, which helps improve the prediction accuracy at different time horizons.

Advanced industrial informatics towards smart,safe and sustainable roads:A state of the art

The road is one of the most important civil infrastructures for serving society,where its service quality and life have direct impacts on the safety and comfort of users.Therefore,road construction,condition detection and monitoring,and timely maintenance are particularly important for engineers.Many engineering applications of industrial informatics approaches,like image processing technology,widely used computer-based algorithms,and advanced sensors,have been initially and gradually applied to roads.This state-of-the-art review first summarized the research on industrial applications of advanced information technologies in recent years,while analyzing and comparing the advantages and disadvantages of each technology.Especially,five topics were focused on road construction,road maintenance with decision strategy,road structure evaluation,smart sensing in the road,and cooperative vehicle infrastructure system.It is expected that advanced industrial informatics can help engineers promote the development of smart,safe,and sustainable roads.