In the vector network analyzer, the excitation source signal will produce nonlinear compression after being amplified for many times, resulting in the reduction of spurious rejection ratio. In power ...measurement, the spurious signal is detected as the main signal, while in narrowband reception, the spurious signal is filtered out and the amplitude decreases on the curve. This paper introduces a method to improve the spurious suppression of excitation signal. The spurious suppression is increased by 18dB.
Distributed machine learning (DML) technology makes it possible to train large neural networks in a reasonable amount of time. Meanwhile, as the computing power grows much faster than network ...capacity, network communication has gradually become the bottleneck of DML. Current multi-tenant GPU clusters face network contention caused by hash-collision problem which not only further increases the overhead of communication, but also creates unfairness and affects the user experience. In this paper, we firstly analyse how network contention affects the training time in a cluster with 32 NVIDIA V100 GPUs. Then we propose vClos to eliminate network contention by jointly optimizing network topology and communication pattern in distributed training. An OCS-vClos which introduces a layer of optical circuit switches (OCSs) in the leaf-spine network is also proposed to reduce potential network resource fragmentation caused by resource allocation strategy in vClos. Testbed experiments and real-trace-based large-scale simulations are conducted to demonstrate the superiority of vClos over existing network resource scheduling strategies.
Ultra-wideband frequency synthesis source is an important part of vector network analyzer. It mainly provides excitation source signal and local oscillator source signal for vector network analyzer. ...Its main technical indicators include: frequency range, frequency resolution, phase noise, spurious, harmonic suppression, output power, etc. According to the hardware scheme and technical specification requirements of the vector network analyzer, this paper studies the frequency synthesis technology, designs and implements an ultra-wideband frequency synthesis source based on DDS and PLL, DDS output frequency range: 10MHz~250MHz, PLL output Frequency range: 2000~4000MHz, the frequency resolution is better than 1Hz, and it has excellent spectral characteristics. After testing, the frequency synthesis source meets the design index requirements, and can be widely used in the excitation source and local oscillator source of the vector network analyzer(VNA).
For vector network analyzer, the output power of excitation source determines its measurement ability. For this reason, the output power is required to be as large as possible. However, it is ...difficult to improve the maximum output power in the design of excitation source. This paper introduces a method to improve the output power of excitation source of vector network analyzer with power synthesis technology. The design of power synthesis circuit based on microstrip power divider.
Ka-band Ultra-Wideband Microstrip Filter Design Sun, Shengkai; Cao, Zhiying; Zhang, Qinglong ...
2022 7th International Conference on Computer and Communication Systems (ICCCS),
2022-April-22
Conference Proceeding
In order to meet the development needs of miniaturization of measuring instruments, this paper designs a Ka-band ultra-wideband microstrip filter based on PCB board. Firstly, the advantages and ...disadvantages of various filter forms are analyzed according to the PCB process conditions and project plan requirements. The quarter-wave two parrallel short-circuit stub is selected as the form of the microstrip filter. In order to make the simulation results closer to the actual situation, HFSS three-dimensional electromagnetic field simulation software is used to simulate and optimize the designed filter and optimize the form of short-circuit grounding vias. Finally, through the processing and measure the designed filter has an insertion loss of less than 3dB when the operating frequency is 23GHz to 45GHz, and a suppression of more than 20dBc below 20GHz, which meets the design requirements.
In this paper, we propose a novel saliency detection model. We manage to balance the conflict between quality and efficiency by introducing Octave Convolution (OctConv). The proposed detection model ...is based on a typical encoder- decoder framework, and all encoded side-out features are de- composed into low and high frequency parts, respectively. The low frequency parts locate coarse salient regions, while the high frequency parts help capture edge details. And a two-stream attention module is proposed to emphasize important global and local context. A top-down attention transfers a global saliency prior to shallow layers and a bottom-up attention helps deep layers focus more on the edges. Compared to the state-of-the- art saliency methods, proposed model is of much lighter-weight (68.6 MB), runs faster (63.7 fps in real-time) and achieves competitive performances on six public benchmarks in terms of both quantitative and qualitative evaluation.
The detection of trace metals is of great significance for understanding and utilizing ocean resources. However, in-situ detection of trace metals with high detection accuracy remains an important ...problem because of the complexity of the marine environment. In this paper, we have successfully fabricated gel-integrated mercury-plated microelectrode array sensors and realized the detection of trace metals in standard metal solutions by anodic stripping voltammetry (ASV). We have coated 1.5% agarose gel film on the microelectrode array, which can prevent electrodes from being polluted and not affect the diffusion of metal ions. For the analysis of trace metals, mercury is deposited on the iridium-based microelectrode array. Cyclic voltammetry shows that mercury plating effectively expands the negative application range of working electrodes and can be used for simultaneous detection of Zn, Cd and Pb. The detection limits of Zn, Cd and Pb were 0.63, 0.60 and 0.59 μg/mL in standard metal solution at the deposition time of 2000 s. In summary, quantitative detection of three metal ions in standard metal solution is realized, which embodies the advantages of anodic stripping voltammetry in seawater metal detection.
Academic debate still exists as to whether and how multi-scale microstructure recovery is linked to creep properties rejuvenation of superalloys. We propose a rejuvenation heat treatment (RHT) for ...one single-crystal superalloy crept at 1100 °C/120 MPa, by which the degraded phase- and dislocation-microstructure can be recovered to standard heat treatment one. Despite experiencing different plastic deformation, such recovered microstructure leads to nearly a fixed 20% improvement in creep life. Through triple creep-RHT-creep cycle tests, the complete rejuvenation of creep life after special creep time has been validated, while the plastic deformation limit increases, where creep properties recoverability remains.
Special creep time and plastic deformation limit determined complete rejuvenation: the first relates to phase- and dislocation-recovery, and the latter is not fixed depending on plastic deformation accumulation mechanism.
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