Wyniki wyszukiwania - BazTech

1

Kinetic energy partitions in electron–ion PIC simulations of ABC fields

Chen Qiang

Nukleonika

|

2023

|

Vol. 68, No. 1

25--28

EN

We explore the kinetic energy partitions between electrons and ions in the 2-D magnetostatic equilibria called Arnold–Beltrami–Childress (ABC) fields, using particle-in-cell (PIC) numerical simulations. We cover a wider range of ion–electron temperature combinations and get different results compared to previous studies of the Harris-layer-type magnetic reconnection simulations. We find that the initial ion–electron enthalpy ratio is an important indicator. The particle species that dominates the total enthalpy will also dominate the kinetic energy gains and the momentum distribution peaks, but the other species have higher nonthermal energy fractions because both species show similar maximum energies.

2

Study on Tensile Properties and Microstructures of Different Sites in Al-Si Alloy Casting Component

Tao Jianquan, Xiang Lin, Chen Xidong, Sun Jipeng, Wang Yanbin, Du Chuanhang, Peng Feifei, Gao Shiqing, Chen Qiang

Archives of Metallurgy and Materials

|

2023

|

Vol. 68, iss. 2

585--589

EN

The tensile properties and microstructures of ZL114A alloy component with a complex shape are investigated at room temperature and 200°C, using the tensile tests, scanning electron microscopy and electron backscattering diffraction. Both thin wall and thick structure exhibit excellent properties, of which max ultimate tensile strength and elongation at break reach 314 MPa and 2.5% at room temperature, respectively. The ultimate tensile strengths of thin wall are 40 MPa and 25 MPa greater than those of thick structure at room temperature and 200°C, respectively. Moreover, the eutectic Si phases of thin wall exhibit a predominantly spherical morphology while of the morphology of thick structure are rod-like, resulting in the different mechanical properties between thin wall and thick structure. The fracture morphologies of thin wall and thick structure are studied to explain the difference in performance between thin wall and thick structure.

3

Influence of grouting pressure volatility on additional response of adjacent pile foundation in shield construction

Zhang Chuan-Chuan, Li Dan-Mei, Zhang Jun, Yu Tong-Sheng, Chen Qiang

Journal of Theoretical and Applied Mechanics

|

2022

|

Vol. 60 nr 1

33--47

EN

Soil parameters along the heading direction are subjected to spatial variability during shield construction, so grouting pressure requires constant adjustment to ensure ground stress sta- bility. This causes grouting pressure to fluctuate around the design pressure/curve. There- fore, the influence of the grouting pressure volatility on the adjacent loaded-pile foundation should be considered in shield tunneling. In this study, a refined numerical simulation of the shield construction process is conducted using the Fast Lagrangian Analysis of Continua in Three Dimensions (FLAC3D) software. A total of 300 groups of grouting pressure pa- rameters with a skewed normal distribution are input into the numerical model. Then, the influence of the construction parameter uncertainty on the adjacent loaded-pile foundation is analyzed. Finally, the back analysis method is conducted based on the monitored data to evaluate how the construction process affects the pile foundation. The calculation results are compared with those of the traditional finite element method. The results indicate that in the tunneling process, the grouting pressure fluctuation greatly affects the additional bend- ing moment of the adjacent pile foundation. Under the influence of the grouting pressure, the additional axial force and additional bending moment of the pile foundation also follow the skewed normal distribution. The back analysis results of the pile foundation are greater than those of the typical numerical method by about 60% 100%, that is using the back analysis calculation results to evaluate the pile foundation additional response can reduce the risk.

4

Integrated seismic–geological prediction of tectonic coal via main controlling factors

Liu Jing, Chang Suoliang, Zhang Sheng, Li Yanrong, Chen Qiang

Acta Geophysica

|

2022

|

Vol. 70, no 1

173--190

EN

Tectonic coal in coal seams not only seriously restricts the development of coalbed methane (CBM), but also easily forms coal and gas outburst risk areas. Therefore, it is of great significance to effectively predict the tectonic coal in coal seams under the development scale. Currently, the prediction methods of tectonic coal include geological prediction and geophysical prediction. Due to the large scale of geological analysis and the low identifiability of geophysical response of thin coal seam, these two methods are difficult to meet the prediction requirements of tectonic coal in the development process. Therefore, this paper proposes a new method for predicting tectonic coal based on seismic–geological integrated analysis of main controlling fac tors. Firstly, the control factors of tectonic coal and their quantitative characterization are determined by geological analysis. Then, the characterization parameters of control factors are obtained by various seismic technologies. Finally, the main control factors are screened by grey correlation analysis, and the prediction model of tectonic coal distribution is established by using the main control factors, and applied in the Qinshui Basin. The results show that the structure, surrounding rock lithology and coal thickness are three kinds of geological factors controlling the development of tectonic coal and the control weight of each factor is different. Structure plays the most important role in controlling the development of tectonic coal, followed by coal thickness and surrounding rock lithology. The prediction error of two verification wells is less than 2%, which indicates that the method can provide effective guidance for coal structure evaluation in the process of CBM development and coal mining.

5

Suppression of multiple refection–refraction waves in the shallow low velocity zone via vertical source combination

Chang Suoliang, Qu Zhen, Zhang Sheng, Fu Yanning, Chen Qiang

Acta Geophysica

|

2021

|

Vol. 69, no. 5

1799--1811

EN

In seismic data from areas with low-velocity structures, a special type of multiple reflected refraction often appears, which seriously affects the effective refection wave of adjacent target layers and causes distortion of the refection wave shape. Based on the kinematic characteristics of the seismic wave field in shallow low-velocity zones, we demonstrate the generation mechanism of multiple reflected refractions. Then, a method of suppressing multiple reflected refractions through vertically combined dual sources is proposed. First, according to the relative position relationship between multiple reflection refractions and the effective wave, prerequisites for the suppression of multiple reflected refractions are established. Second, the optional range of vertical combination parameters is calculated according to the source combination equation, which is used to adjust the relative position of the two sources set vertically in the low-velocity zone. Subsequently, model data verification and application of the Loess Plateau exploration area prove that the vertical source combination method can suppress multiple reflected refractions in shallow low-velocity zones and effectively improve the signal-to-noise ratio of seismic data.