Numerical Simulation Study of Vibration Characteristics of Cantilever Traffic Signal Support Structure under Wind Environment

Computational fluid dynamics(CFD)and the finite element method(FEM)are used to investigate the wind-driven dynamic response of cantilever traffic signal support structures as a whole.By building a finite element model with the same scale as the actual structure and performing modal analysis,a preliminary understanding of the dynamic properties of the structure is obtained.Based on the two-way fluid-structure coupling calculation method,the wind vibration response of the structure under different incoming flow conditions is calculated,and the vibration characteristics of the structure are analyzed through the displacement time course data of the structure in the crosswind direction and along-wind direction.The results show that the maximum response of the structure increases gradually with the increase of wind speed under 90°wind direction angle,showing a vibration dispersion state,and the vibration response characteristics are following the vibration phenomenon of galloping;under 270°wind direction angle,the maximum displacement response of the structure occurs at the lower wind speed of 5 and 6m/s,and the vibration generated by the structure is vortex vibration at this time;the displacement response of the structure in along-wind direction increaseswith the increase of wind speed.The along-wind displacement response of the structure will increase with increasing wind speed,and the effective wind area and shape characteristics of the structurewill also affect the vibration response of the structure.

拉盖尔–高斯光束在小尺度流场内的气动光学效应

为研究拉盖尔–高斯(LG)光束在经过由微小凸起造成的流场后的气动光学效应,采用二阶紧致差分对抛物型的复振幅微分方程进行求解,并使用四阶龙格库塔沿光束路径积分。比较了具有不同拓扑荷数的LG光束以及高斯光束在不同马赫数、不同攻角、不同海拔下的Strehl比(SR)以及成像偏移。仿真结果表明,在同样流场中,LG光束的拓扑荷数越大,相位稳定性越好且均优于高斯光束,但振幅稳定性越差,当且仅当径向指数为0,拓扑荷数为1时LG光束优于高斯光束。

Observational results of MUSER during 2014–2019

The solar radio signal that can be received by the ground-based telescopes covers a wide frequency range,allowing us to monitor the complex physical processes occurred from the solar surface to the vast interplanetary space.MingantU SpEctral Radioheliograph(MUSER),as the latest generation of solar dedicated radio spectral-imaging instrument in the centimeter-decimeter wavelengths,has accumulated a large number of observational data since its commissioning observation in 2014.This paper presents the main observational results identified by MUSER from 2014 to 2019,including the quiet Sun and 94 solar radio burst events.We find that there are 81 events accompanied with Geostationary Operational Environmental Satellites(GOES)soft X-ray(SXR)flares,among which the smallest flare class is B1.0.There are 13 events without accompanying any recorded flares,among which the smallest SXR intensity during the radio burst period is equivalent to level-A.The main characteristics of all radio burst events are presented,which shows the powerful ability of MUSER to capture the valuable information of the solar non-thermal processes and the importance for space weather.This work also provides a database for further in-depth research.

A New Position Calibration Method for MUSER Images

The Mingantu Spectral Radioheliograph(MUSER),a new generation of solar dedicated radio imagingspectroscopic telescope,has realized high-time,high-angular,and high-frequency resolution imaging of the Sun over an ultra-broadband frequency range.Each pair of MUSER antennas measures the complex visibility in the aperture plane for each integration time and frequency channel.The corresponding radio image for each integration time and frequency channel is then obtained by inverse Fourier transformation of the visibility data.However,the phase of the complex visibility is severely corrupted by instrumental and propagation effects.Therefore,robust calibration procedures are vital in order to obtain high-fidelity radio images.While there are many calibration techniques available—e.g.,using redundant baselines,observing standard cosmic sources,or fitting the solar disk—to correct the visibility data for the above-mentioned phase errors,MUSER is configured with non-redundant baselines and the solar disk structure cannot always be exploited.Therefore it is desirable to develop alternative calibration methods in addition to these available techniques whenever appropriate for MUSER to obtain reliable radio images.In the case where a point-like calibration source contains an unknown position error,we have for the first time derived a mathematical model to describe the problem and proposed an optimization method to calibrate this unknown error by studying the offset of the positions of radio images over a certain period of the time interval.Simulation experiments and actual observational data analyses indicate that this method is valid and feasible.For MUSER’s practical data the calibrated position errors are within the spatial angular resolution of the instrument.This calibration method can also be used in other situations for radio aperture synthesis observations.

Stability analysis of wireless network with improved fluid model

Wireless communication is easily disturbed by unfortunate factors which drive the wireless environment unstable and complicated. Therefore, it is essential to consider these factors in stability analysis of the wireless network. However, wireless channel characteristics and packets collisions are neglected in the classical fluid model. A wireless TCP fluid model （WTFM） for stability analysis of wireless network is proposed based on cross layers, which not only makes the congestion control based on random early detection （RED） available for wireless network, but also provides a more accurate model to analyze the stability of wireless system theoretically. In the proposed model, active queue management, abnormality of wireless channels and packets collisions are taken into consideration. The comparisons between evaluating results from the WTFM and the practical performance from NS2 simulations validate the accuracy of the proposed WTFM in the perspectives of delay, dropping probability, throughput, sliding window size and queue length. A set of comparisons among the proposed WTFM, the classical fluid model and the convex optimization model are conducted. The results demonstrate that the proposed WTFM model performs better than other schemes in comprehensive aspects on capturing the characteristic of the wireless network and computing complexity.

Cells grouping scheme against pilot contamination in large scale antennas system

The influence of cells groupings factor to the performance of the cells groupings time-shift pilot scheme is researched for the multiple cells large scale antennas systems（LSAS）. The former researches have confirmed that the cells groupings time-shift pilots scheme is effective to reduce inter-cell interference, especially pilot contamination, which results from the pilot reuse in adjacent cells. However, they have not specified reasonable cells groupings factor, which plays a critical role in the general performance of the LSAS. Therefore, this problem is researched in details. The time for reverse-link data transmission will be compressed, when the groupings factor surpasses a certain range. Thus it is not always beneficial to increase the cells groupings factor without limitation. Furthermore,a reasonable cells groupings factor is deduced from the perspective of optimization to enhance the system performance. Simulations verify the proposed cell grouping factor.

Developing a fluorescence substrate for HRP-based diagnostic assays with superiorities over the commercial ADHP

The combination of horseradish peroxidase(HRP)and a fluorescence substrate has been attracting great interests in developing sensitive biochemical analysis and immunoassays.10-Acetyl-3,7-dihydroxyphenoxazine(ADHP or Amplex red)is the most sensitive fluorogenic substrate known for HRP in current market,however,it suffers from some drawbacks,such as non-specific reactivity to carboxylesterase and limited fluorescence stability.In the present study,a novel HRP substrate10-cyclopropylcarbonyl-dichloro-dihydroxyphenoxazine(AR-2),has been prepared,which exhibited improved sensitivity than ADHP in sensing HRP.Moreover,the fluorescence of AR-2/HRP demonstrated improved tolerance to physiological relevant p H fluctuation as compared to ADHP/HRP.Successful detection of uric acid/urate oxidase reaction indicated excellent application prospect of AR-2/HRP for monitoring H_(2)O_(2)-generating biochemical reactions.More interestingly,an enzyme-linked immunosorbent assay(ELISA)using AR-2 as the fluorescence reporter has been successfully used in detecting IgG against severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)from human serum samples.Overall,AR-2 exhibits improved performances over the commercial ADHP,which will be an ideal alternative to ADHP in HRP-based fluorescence biochemical analysis and immunoassays.

Diverse Asgard archaea including the novel phylum Gerdarchaeota participate in organic matter degradation

Asgard is an archaeal superphylum that might hold the key to understand the origin of eukaryotes, but its diversity and ecological roles remain poorly understood. Here, we reconstructed 15 metagenomic-assembled genomes from coastal sediments covering most known Asgard archaea and a novel group, which is proposed as a new Asgard phylum named as the "Gerdarchaeota".Genomic analyses predict that Gerdarchaeota are facultative anaerobes in utilizing both organic and inorganic carbon. Unlike their closest relatives Heimdallarchaeota, Gerdarchaeota have genes encoding for cellulase and enzymes involved in the tetrahydromethanopterin-based Wood–Ljungdahl pathway. Transcriptomics showed that most of our identified Asgard archaea are capable of degrading organic matter, including peptides, amino acids and fatty acids, occupying ecological niches in different depths of layers of the sediments. Overall, this study broadens the diversity of the mysterious Asgard archaea and provides evidence for their ecological roles in coastal sediments.

Evolution of Low-Angle Normal Faults in the Enping Sag,the Northern South China Sea: Lateral Growth and Vertical Rotation

Low-angle normal faults(dip<30°,LANFs)are widespread in the northern margin of the South China Sea where the maximum crust thickness is approximately 30.0 km.Based on 3 D seismic survey data and drilling wells in the Enping sag,evidences for LANFs that initially formed at high-angles are discussed.After a detailed investigation of extensional fault system and description of 3 D fault geometry,the initial fault dips under the model of distributed vertical simple shear are also calculated.The results indicate that the present-day dip angles of the LANFs are in the range of 12°to 29°,and the initial fault dip angles are in the range of 39°to 49°.Deep seismic imaging suggests that the upper crust in the footwall block of the LANFs was tilted at an angle of ~14°to 22°due to the isostatic rebound during rifting.Moreover,the temporal and spatial sequences of the lateral growth of the LANFs have been investigated by the seismic interpretation of four isochronous stratigraphic interfaces,which demonstrates that two individual fault segments propagated towards each other and subsequently,were hard-linked during the Early Eocene.

Metagenomics reveals contrasting energy utilization efficiencies of captive and wild camels(Camelus ferus)

Captive conditions can affect the symbiotic microbiome of animals.In this study,we compared the structural and functional differences of the gastrointestinal microbiomes of wild Bactrian camels(Camelus ferus)between wild and captive populations,as well as their different host energy utilization performances through metagenomics.The results showed that wild-living camels harbored more microbial taxa related to the production of volatile fatty acids,fewer methanogens,and fewer genes encoding enzymes involved in methanogenesis,leading to higher energy utilization efficiency compared to that of captive-living camels.These findings suggest that the wild-living camel fecal microbiome demonstrates a series of adaptive characteristics that enable the host to adjust to a relatively barren field environment.Our study provides novel insights into the mechanisms of wildlife adaptations to habitats from the perspective of the microbiome.

The expanding Asgard archaea invoke novel insights into Tree of Life and eukaryogenesis

The division of organisms on the Tree of Life into either a three-domain(3D)tree or a two-domain(2D)tree has been disputed for a long time.Ever since the discovery of Archaea by Carl Woese in 1977 using 16S ribosomal RNA sequence as the evolutionary marker,there has been a great advance in our knowledge of not only the growing diversity of Archaea but also the evolutionary relationships between different lineages of living organisms.Here,we present this perspective to summarize the progress of archaeal diversity and changing notion of the Tree of Life.Meanwhile,we provide the latest progress in genomics/physiology-based discovery of Asgard archaeal lineages as the closest relative of Eukaryotes.Furthermore,we propose three major directions for future research on exploring the“next one”closest Eukaryote relative,deciphering the function of archaeal eukaryotic signature proteins and eukaryogenesis from both genomic and physiological aspects,and understanding the roles of horizontal gene transfer,viruses,and mobile elements in eukaryogenesis.