Dynamic characteristics of priority control system for high-speed on–off digital valve

Dynamic characteristics of the priority control system are of great influence to the control effect, response speed, and working stability of the high-speed on–off digital valve. The main focus of this study is on revealing the dynamic properties of the priority control system for a developed high-speed on–off digital valve. In this article, a detailed introduction to the high-speed on–off digital valve and its priority control system is performed first, which includes the system function, structural composition, and operation principle. Thereafter, a simulation model of the priority control system is established using the AMESim software and the dynamic characteristics are simulated. Simulation results including the variations in the pulse-width modulation signal, coil current, and the main spool displacement of the directional valve are presented and discussed. They indicate that the opening time of the main spool increases with the duty ratio of the voltage signal. Moreover, the main spool displacement is basically equal in one single pulse-width modulation signal cycle, and thus, it is proportional to the cycle number of the pulse-width modulation signal. As a consequence, the priority control system possesses a good dynamic characteristic for the high-speed on–off digital valve as a pilot valve to achieve proportional control of main spool displacement for the directional valve

A Novel Cellular Network Traffic Prediction Algorithm Based on Graph Convolution Neural Networks and Long Short-Term Memory through Extraction of Spatial-Temporal Characteristics

In recent years, cellular communication systems have continued to develop in the direction of intelligence. The demand for cellular networks is increasing as they meet the public’s pursuit of a better life. Accurate prediction of cellular network traffic can help operators avoid wasting resources and improve management efficiency. Traditional prediction methods can no longer perfectly cope with the highly complex spatiotemporal relationships of the current cellular networks, and prediction methods based on deep learning are constantly growing. In this paper, a spatial-temporal parallel prediction model based on graph convolution combined with long and short-term memory networks (STP-GLN) is proposed to effectively capture spatial-temporal characteristics and to obtain accurate prediction results. STP-GLN is mainly composed of a spatial module and temporal module. Among them, the spatial module designs dynamic graph data based on the principle of spatial distance and spatial correlation. It uses a graph convolutional neural network to learn the spatial characteristics of cellular network graph data. The temporal module uses three time series based on the principle of temporal proximity and temporal periodicity. It uses three long and short-term memory networks to learn the temporal characteristics of three time series of cellular network data. Finally, the results learned from the two modules are fused with different weights to obtain the final prediction results. The mean absolute error (MAE), root mean square error (RMSE), and R-squared (R2) are used as the performance evaluation metrics of the model in this paper. The experimental results show that STP-GLN can more effectively capture the spatiotemporal characteristics of cellular network data; compared with the most advanced model in the comparison model on the real cellular traffic dataset in one cell, the RMSE can be improved about 81.7%, the MAE is improved about 82.7%, and the R2 is improved about 2.2%

Matching the Optimal Operating Mode of Polydimethylsiloxane Check Valves by Tuning the Resonant Frequency of the Resonator in a Piezoelectric Pump for Improved Output Performance

This paper proposes to improve the output performance of a piezoelectric pump by matching the resonant frequency of the resonator to the optimal operating mode of bridge-type polydimethylsiloxane (PDMS) check valves. Simulation analyses reveal that the side-curling mode of the PDMS valve is conducive to liquid flow and exhibits a faster frequency response compared with the first bending mode. The first bending resonant frequency of a beam-type piezoelectric resonator was tuned close to the side-curling mode of the PDMS valve by adjusting the weight of two mass blocks installed on both ends of the resonator, so that both the resonator and the valve could work at their best conditions. Experiments were conducted on a detachable prototype piezoelectric pump using PDMS valves with three different lengths. The results confirm that the peak flowrate at the resonant point of the pump reaches its maximum when the resonant frequencies between the resonator and the valve are matched. Maximum peak flowrates of 88 mL/min, 72 mL/min and 70 mL/min were achieved at 722 Hz, 761 Hz and 789 Hz, respectively, for diaphragm pumps using five-, four- and three-inlet-hole PDMS valves, under a driving voltage of 300 Vpp

Optimization Design of Velocity Distribution in the Airways of the Fluidized Bed Based on CFD and Taguchi Algorithm

A vital component that is frequently employed in the industrial powder conveying sector is the fluidized bed. In the light of powder unloading with a fluidized bed as the research object, an orthogonal experiment with two factors and four levels was established for the structural parameters of the fluidized bed. In the case of different noise factors, 16 schemes are designed and all schemes via computational fluid dynamics numerical simulation. The Taguchi method and regression analysis are used to analyze the response. Finally, the accuracy of the optimization results is tested. The results show that gas velocity decreases sharply at the airway’s entrance and, then, gas flows to the second half of the airway and velocity decreases steadily and uniformly. Airway arc length L exerts a greater effect on the signal-to-noise ratio (SNR) than airway height H. The parameter combination of 180 mm L and 17 mm H for obtaining the optimal velocity distribution uniformity is determined. The test results indicate that the overall fluidization effect of the fluidized bed with the optimal parameters is better. The linked research findings can be used as a guide when designing a fluidized bed system for transporting comparable powder

Design, synthesis, and antiviral activities of myricetin derivatives containing phenoxypyridine

A series of myricetin derivatives containing phenoxypyridine structure were designed and synthesized on the basis of the natural product myricitrin, which were structurally characterized on NMR and HRMS. The results of antiviral activity tests showed that some of the target compounds exhibited better inhibitory effects. Among them, B19 and B21 showed better curative activity with EC50 values of 195.67 and 173.64 μg/mL, respectively, which were superior to that of the control agent ningnanmycin(NNM) (238.30 μg/mL). B21 showed better protective activity with EC50 value of 236.37 μg/mL, which was better than that of the control agent NNM (269.89 μg/mL). The results of microcalorimetry showed that B1, B19 and B21 had good binding affinity with tobacco mosaic virus capsid protein (TMV-CP), and the Kd values were 0.059, 0.093 and 0.069 μM, which was higher than that of NNM (Kd = 2.78 μM). The molecular docking results showed that the hydrogen bond lengths between B1, B21 and the key amino acid residues of TMV-CP were shorter and with more tightly bound than those of NNM. In B21-treated tobacco leaves, chlorophyll content and superoxide dismutase (SOD) activity were significantly elevated, indicating that B21 can participate in regulating plant photosynthesis as well as defense enzymes and inducing plants to improve disease resistance

Healthier diet associated with reduced risk of excessive gestational weight gain: A Chinese prospective cohort study

Abstract Limited studies have examined the associations between diet quality and gestational weight gain (GWG) among Chinese pregnant women, adopting Chinese GWG guidelines. We prospectively investigate the associations of diet quality, using the Chinese Healthy Diet Index for Pregnancy (CHDI‐P), which assessed diet quality from ‘Diversity’, ‘Adequacy’ and ‘Limitation’ dimensions with overall 100 points, with GWG among participants enroled in Southwest China. Food consumption was collected by 24 h dietary recalls for three consecutive days and CHDI‐P scores were divided into tertiles. GWG was calculated according to the weight measured before delivery and classified into adequate weight gain (AWG), insufficient weight gain (IWG) and excessive weight gain(EWG) following Chinese GWG guidelines. Multinomial regression analyses and stratified analyses by pre‐pregnancy body mass index were performed to estimate the association between CHDI‐P and GWG. A total of 1416 participants were recruited in early pregnancy, and 971 and 997 participants were respectively followed up in middle and late pregnancy. The mean CHDI‐P score was 56.44 ± 6.74, 57.07 ± 7.44 and 57.38 ± 7.94 points in early, middle and late pregnancy, respectively. Women in the lowest CHDI‐P scores group had an increased risk of EWG in middle (OR = 1.53, 95% confidence interval [CI] = 1.08–2.17) and late pregnancy (OR = 1.71, 95% CI = 1.21–2.41) than women in the highest group, while overweight/obese women had a greater risk of EWG in late pregnancy (OR = 4.25, 95% CI = 1.30–13.90). No association was found between the CHDI‐P scores and IWG. Poor diet quality in middle and late pregnancy was associated with a higher risk of EWG