Stability Analysis of Subgrade under Dynamic Loading of Single and Double High-speed Railways in Karst Areas

Pengxiang Li,Mingzhou Bai,Zijun Wei,Xin Li,Hai Shi 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.8

With the increase in the use of high-speed trains, karst collapse disasters have become increasingly prominent during the construction and operation of railway projects. To study the propagation characteristics of vibration wave caused by single and double railways in karst area, as well as the influence of sinkholes on the stability of the roadbed, a coupling model of vehicle-track-subgrade (including underlying sinkhole) considering track irregularity was established based on the geological engineering characteristics of a karst site. The results show that the subgrade stability is controlled by multiple factors related to the upper load, the stability of the caves, and the soil state; increasing the upper load of the track further develops the sinkhole and has a negative effect on the subgrade stability. The amplitude of vertical dynamic displacement on the subgrade surface can reach 1.31 mm under the superimposed effect of the vibration of double railways, which is approximately 50% higher than that of a single railway. Under the long-term cumulative effect of train vibrations, the sinkholes grow faster in dynamic displacement amplitude than the roadbed surface, and will lead to abrupt displacement of subgrade surface.

Pilot Sequence Assignment for Spatially Correlated Massive MIMO Circumstances

( Pengxiang Li ),( Yuehong Gao ),( Zhidu Li ),( Dacheng Yang ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.1

For massive multiple-input multiple-output (MIMO) circumstances with time division duplex (TDD) protocol, pilot contamination becomes one of main system performance bottlenecks. This paper proposes an uplink pilot sequence assignment to alleviate this problem for spatially correlated massive MIMO circumstances. Firstly, a single-cell TDD massive MIMO model with multiple terminals in the cell is established. Then a spatial correlation between two channel response vectors is established by the large-scale fading variables and the angle of arrival (AOA) span with an infinite number of base station (BS) antennas. With this spatially correlated channel model, the expression for the achievable system capacity is derived. To optimize the achievable system capacity, a problem regarding uplink pilot assignment is proposed. In view of the exponential complexity of the exhaustive search approach, a pilot assignment algorithm corresponding to the distinct channel AOA intervals is proposed to approach the optimization solution. In addition, simulation results prove that the main pilot assignment algorithm in this paper can obtain a noticeable performance gain with limited BS antennas.

Adsorption of Anionic Surfactant on Silica

Pengxiang Li,Munehide Ishiguro 한국토양비료학회 2014 한국토양비료학회 학술발표회 초록집 Vol.2014 No.6

A Novel Interleaved Non-Isolated Switched-Capacitor Network High Step-Up DC/DC Converter

Xinying Li,Yan Zhang,Pengxiang Zeng,Jinshui Zhang,Jinjun Liu 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This paper introduces a novel interleaved non-isolated high step-up DC/DC converter with switchedcapacitor network. Due to interleaved structure and switched-capacitor network, the proposed converter has the advantage of low input current ripple, high step-up voltage conversion ratio and low voltage stress for all the switches and diodes which means lower voltage level semiconductors and high efficiency. After a detailed comparison with other recent existing topologies, it is clear that the proposed converter has a lower comprehensive cost, higher voltage conversion ratio, and lower output voltage ripple than other converters. The operation principle, steady-state analysis, parameter design for this converter are presented. Finally, experiment results are also presented to demonstrate the effectiveness of the proposed converter.

The characteristics of abnormal gas emission in tunneling through the small fault groups of Yizhong coal mine

Shu Ma,Qingsong Li,Zhenli Han,Pengxiang Zhang,Furu Kang 한국자원공학회 2016 Geosystem engineering Vol.19 No.5

In light of the complex tectonic structure, and large quantities of buried faults in Yizhong coal mine, the paper, on the basis of analyzing the characteristics of abnormal gas emission caused by production factors such as tunneling and blasting technologies, blasting strength, and tunneling rate, investigates the characteristics of abnormal gas emission in the context of diversified combinations of faults in tunneling through the fault groups in Yizhong coal mine. The study demonstrates the maximum absolute gas emission rate under the procedure of blasting in Yizhong coal mine is approximately 5 times higher than under other procedures, and generally returns to its normal level in 30–40 min; the tunneling rate and blasting strength are in direct proportion to absolute gas emission rate, and the mined coal surpassing 18 tons an hour for a time can cause the risk of gas concentration in return air exceeding limits; in tunneling through the small fault groups, the group largely embodies the influences of individual faults on gas emission, and it is easy to form a space sealed with gas between two sealing faults, where the gas emission intensity and its influence sphere are far greater than separate small faults.

Analysis of a Novel Double-Stator and Dual-PM Toroidal-Winding Linear Vernier Machine

Wang Mingjie,Ye Pengxiang,Li Yanyan,Liu Sheng 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.4

Aiming at the problem of low thrust density and large thrust ripple of conventional permanent magnet linear machine, this paper proposes a novel structure of double-stator and dual-PM toroidal-winding linear vernier machine (LVM) with high thrust density and low thrust ripple. The novelty of the proposed machine is adopted double-sided topology, toroidal-winding and permanent magnets (PMs) installed both on the stator side and the mover split teeth to improve thrust density. To emphasize the specificity of proposed dual-PM LVM in aspect of electromagnetic performance, three kinds of conventional LVMs with different topologies are compared with proposed machine by analyzing the air-gap flux density, inductance, no-load EMF, thrust, overload capability and power factor of the machines. The average thrust is increased by 11.5% under rated current, and the thrust ripple is decreased from 22.1 to 2.68% by optimizing the key parameters of the proposed structure. The harmonics contribution of EMF and thrust are discussed by semi-analytical method. The results of the semi-analytical method are in good agreement with the finite element method, which verifies the correctness of the semi-analytical method and proves that the proposed machine has good performance characteristics.

Performance and Applicability Analysis of Recognizing Microseismic Waveforms Using Neural Networks in Tunnel Engineering

Wei Zhang,Xin Bi,Lei Hu,Pengxiang Li,Zhibin Yao 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.2

The sudden and harmful nature of rockbursts in tunnels necessitates an accurate and applicable method for automatically recognizing rock fracture signals during rockburst microseismic (MS) monitoring. In this paper, the performance and applicability of recognizing MS waveforms using an artificial neural network (ANN) and a deep neural network (DNN) were studied in tunnels excavated by different methods. The results show that ANN performs very well in recognizing rock fracturing waveforms with a signal-to-noise ratio (SNR) ≥ 3 but has a low accuracy for those with an SNR < 3. The DNN also performs well for waveforms with SNR ≥3, and has a relatively high accuracy for waveforms with SNR < 3. The ANN model can be used in tunnels excavated by drilling and blasting (D&B) since there are fewer “small” rock fracturing events. The DNN model is applicable in tunnels excavated by the tunnel boring machine (TBM), recognizing more “small” events. In addition, the ANN model is a better choice, with fewer training samples at the initial stage of monitoring working. With continuous monitoring, the DNN model can be used to ensure and improve the accuracy. These results lay a foundation for automatic rockburst MS monitoring techniques in tunnel engineering.