Abstract In the research of UHV pillar equipment, the dynamic amplification factor of bracket is a key parameter. This paper mainly focuses on the relationship between the dynamic amplification factor of ceramic equipment under the condition of seismic acceleration response spectrum when the structural parameters of the bracket are the same. In this paper, the stiffness of the bracket is changed by altering the elastic modulus of the steel. The dynamic amplification factors of the speed, displacement, stress and acceleration of the bracket in the two kinds of overall structures are compared and analyzed by numerical simulation. At the same time, the relationship between the bracket frequency and the steel consumption is compared by calculating the steel consumption of different bracket structures. Based on the results of simulation analysis and considering the seismic design of porcelain electrical equipment in UHV substations and converter stations, it is suggested that the dynamic amplification factor, the envelope of displacement and stress amplification factor of 1.40 should be adopted, thus providing a theoretical basis for the design of UHV bracket equipment.
We have developed an all-solid-state tunable ultraviolet laser system employing recently developed Ce:LiCAF, a new degradation-free tunable ultraviolet laser medium pumped by the fourth harmonic of a conventional Q -switched Nd:YAG laser. The low- Q , short-cavity Ce:LiCAF laser produced satellite-free subnanosecond pulses in a tuning range of 281 nm to 297 nm under appropriate pumping-fluence control.
Abstract This article examines the stochastic response and seismic reliability of composite post-insulators under random seismic excitation. A random seismic motion model, tailored for power facility seismic research in China and compliant with the “Seismic Design Specification for Power Facilities” (GB50260-2013), is developed. This model accounts for both amplitude and frequency non-stationary. A nonlinear dynamic model for composite post insulators is then established, incorporating the nonlinearity at the multi-section insulator and flange connections. Numerical methods are employed for random seismic response analysis to address the non-stationary nature of seismic motion. The proposed model’s validity is confirmed by comparing it with the vibration table test results. Finally, the seismic reliability of composite post insulators, with root stress as the control criterion, is assessed using the probability density evolution method.
We have developed degradation-free tunable ultraviolet laser. A growth of 7-cm diameter Ce3+:LiCaAlF6 (Ce:LiCAF) boule succeeded in CF4 atmosphere by the Czochralski method. Chirped-pulse amplification (CPA) in the ultraviolet region is demonstrated by use of a large-sized, broadband Ce:LiCAF laser medium. A coaxially pumped, large-aperture ultraviolet power-amplifier is also demonstrated for a terawatt-class ultraviolet CPA laser system. Future scaling of this Ce:LiCAF laser system will make available a new category of high-peak-power lasers in the ultraviolet region.
The vibration isolation device based on geometric nonlinear theory is a hotspot in the field of dynamics in recent years. In order to deeply explore the application of this technology in the field of vibration isolation for power grid equipment, we establish a transformer-casing coupling nonlinear dynamic model considering seismic wave excitation, and use the classical fourth-order Runge-Kutta method to calculate and analyse the transient response behaviour and characteristics of the coupled system under different conditions. The analysis results reveal that the influence of the three parameters, including stiffness, length and damping of springs in shock absorber, on the anti-seismic performance of this coupling structure, which lays a theoretical foundation for the application of geometric nonlinear theory in the field of large-scale transformation equipment vibration isolation.
Coal mine roof accidents pose a significant threat to the safety of personnel and equipment. To mitigate these risks, this study presents an improved time-series prediction model, called Nadam-LSTM, for mining pressure data at the working face in coal mines. The Nadam-LSTM model combines long and short-term memory neural networks (LSTM) with the Nadam optimization algorithm to accurately forecast mining pressure and enhance safety measures. The model incorporates multiple parameters by utilizing factor analysis to identify the key variables influenced by pressure and correlation analysis to quantify their relationships. The Nadam-LSTM model takes into account various input factors, including mining height, coal thickness, burial depth, coal seam dip angle, working face length, roof lithology, and mining speed. The model provides predictions for important output variables, such as first pressure distance, first pressure intensity, periodic pressure distance, and periodic pressure intensity. To further enhance performance, the Nadam optimization algorithm and Dropout regularization are integrated into the model, enabling the construction of a control group prediction model and a mining pressure prediction optimization tool.The performance of the Nadam-LSTM model is evaluated using root mean square error (RMSE), mean absolute error (MAE), coefficient of determination (R), and R-squared (R^2). Furthermore, comparative analyses are conducted using Boxplot, Scatterplot, Violin plot, and Taylor diagram to assess and showcase the model's performance. These evaluations provide comprehensive insights into the model's accuracy, robustness, and predictive capabilities. Evaluation results demonstrate that the Nadam-LSTM model outperforms a single LSTM model, with significant changes observed in multiple indicators. Such as MAE and RMSE. Also, the inclusion of R and R^2 values provide a measure of the model's goodness-of-fit. Comparative visualizations, including Boxplot, Scatterplot, Violin plot, and Taylor diagram, further highlight the improved performance and effectiveness of the Nadam-LSTM model in accurately forecasting mining pressure.
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