Abstract
We have carried out a detailed study of polarimetric individual pulse emission from the pulsar J1701−3726 (B1658−37), observed at 1369 MHz using the Parkes 64 m radio telescope. The ...single-pulse sequences reveal the presence of the three major emission phenomena of pulse nulling, mode changing, and subpulse drifting. Trimodal distribution of the pulse energy is present, implying one population of nulls and two others of emission in the phase window. The mean flux density of the normal mode is almost two times that of the abnormal mode. Our data show that, for PSR J1701−3726, 64% of the time was spent in the normal mode and 12% was in the abnormal mode. The single pulses show the presence of two distinct periodic modulations using a fluctuation spectral analysis. About 24% of the nulls are found to create alternating bunches of nulls and bursts in a quasiperiodic manner with a longer periodicity of 48 ± 4 rotational periods. Additionally, the pulsar presents a steady even–odd modulated feature with a stationary longitude within the pulse window. The ramifications for constraining the viewing geometry and understanding the radio emission mechanisms are discussed.
Abstract
Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we have recorded over 1.2 × 10
4
single pulses from PSR B0823+26 (J0826+2637) at 1.25 GHz with 500 MHz bandwidth. ...These high-sensitivity observations detected with FAST are unprecedented. We investigated potentially interesting emission features by analyzing the polarimetric individual pulses during the bright state. The average pulse profile has a weak postcursor component and a wide interpulse along with a narrow main pulse. The pulse energy distribution of the main pulse shows the presence of triple emission modes. When the emission ceases in the main pulse component, low-level emission in the interpulse component is detected, whereas the absence of any emission in the postcursor component is shown. In the postcursor emission region, bright pulses are detected in 422 rotations with the relative pulse energy described by a power-law distribution with index of −2.52 ± 0.09, while the peak flux density ratio appears to follow a logarithmic normal distribution. The intervals between bright pulses can be described with a Poisson process with the occurrence rate estimated to be one bright pulse every 14 s. The fluctuation spectral analysis reveals the existence of a form of periodic amplitude modulation unrelated to subpulse drifting in both the main pulse and interpulse components. Furthermore, the modulation patterns in the main pulse and interpulse are found to be locked in pulse longitude, signifying some information transfer between the two magnetic polar regions.
We describe an ultra-wide-bandwidth, low-frequency receiver ("UWL") recently installed on the Parkes radio telescope. The receiver system provides continuous frequency coverage from 704 to 4032 MHz. ...For much of the band (~60%) the system temperature is approximately 22K and the receiver system remains in a linear regime even in the presence of strong mobile phone transmissions. We discuss the scientific and technical aspects of the new receiver including its astronomical objectives, as well as the feed, receiver, digitiser and signal-processor design. We describe the pipeline routines that form the archive-ready data products and how those data files can be accessed from the archives. The system performance is quantified including the system noise and linearity, beam shape, antenna efficiency, polarisation calibration and timing stability.
For the problem of classification and identification of defects in polyethylene (PE) gas pipelines, this paper firstly performs preliminary screening of the acquired images and acquisition efficiency ...of defective image acquisition was improved. Images of defective PE gas pipelines were pre-processed. Then, edge detection of the defective images was performed using the improved Sobel algorithm and an adaptive threshold segmentation method was applied to segment the defects in the pipeline images. Finally, the defect images were morphologically processed to obtain binary images. The obtained binary images were applied with VGG16 to complete the training of the defect classifier. The experimental findings show that in the TensorFlow API environment, the test set’s highest accuracy reached 97%, which can achieve the identification of defect types of underground PE gas transmission pipelines.
With the development of astronomical observation technology, astronomical devices produce more data than ever. Astronomical telescopes are usually far away from city, so the long-distance data ...transmission between telescope and data center faces great challenges. Visualization system of astronomical data transmission with four-layer structure was built to manage data transmission. This visualization system has a four-layer structure: hardware layer, system layer, middle layer, and visualization layer. System function includes automatic data transmission, log recording of transmission process, and display of the transmission status in dynamic web pages. Besides, the middle layer contains an alarm subsystem that can automatically send system exceptions to administrator. We also design corresponding mechanisms to ensure the high stability of the system and to control the data transmission when the network is unstable through adaptive algorithms. In test, this visualization system can run stably for a long time in unmanned manner. This system also provides a solution for the astronomical observation bases to automatically transmit data to the data center.
A GPU-based Multigroup Genetic Algorithm was proposed, which parallelized the traditional genetic algorithm with a coarse-grained architecture island model. The original population is divided into ...several subpopulations to simulate different living environments, thus increasing species richness. For each subpopulation, different mutation rates were adopted, and the crossover results were optimized by combining the crossover method based on distance. The adaptive mutation strategy based on the number of generations was adopted to prevent the algorithm from falling into the local optimal solution. An elite strategy was adopted for outstanding individuals to retain their superior genes. The algorithm was implemented with CUDA/C, combined with the powerful parallel computing capabilities of GPUs, which greatly improved the computing efficiency. It provided a new solution to the TSP problem.
Implementation of CASPAR Firmware Interface on PYNQ-Z2 Duan, Xuefeng; Li, Jian; Pei, Xin ...
2022 IEEE 9th International Symposium on Microwave, Antenna, Propagation and EMC Technologies for Wireless Communications (MAPE),
2022-Aug.-26
Conference Proceeding
We proposed a new efficient and flexible FPGA design method for the PYNQ-Z2 platform. The CASPER firmware interface is developed based on the PYNQ-Z2, and the FPGA firmware programs are designed ...using the CASPER toolflow. We used the PYNQ system to create a TCP service for communication with the CASPER library to enable remote real-time interaction, configuration, program loading and data reading from the hardware platform. The performance of the implemented CASPER platform is verified by designing firmware programs for GPIO, software registers, FIR digital filters and related experiments. The implemented approach provides rich development resources for FPGA development, shortens development cycle, improves development efficiency, and greatly simplifies the FPGA firmware design flow through platform-independent hardware and software.
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