地铁深基坑开挖的施工仿真分析

本文运用ABAQUS软件对武汉地铁2号线小龟山车站基坑开挖分别进行了二维和三维模拟计算。计算得到二维模拟条件下围护结构内力、变形和土体位移的变化趋势与三维相近,但相应数值均大于三维的情况,充分说明了基坑具有明显的空间效应。     

J4不锈钢热轧板冷轧横裂原因分析

分析发现了J4不锈钢热轧板冷轧横裂形成的主要原因是:钢中有大量显微气泡破坏基体的连续性,降低材料的塑性,导致裂纹形成。加大脱氧、脱气力度,可减少显微气泡,预防裂纹形成。     

Experimental analysis of wet mill load based on vibration signals of laboratory-scale ball mill shell

Real-time measurement of the mill load is the key to improve the production capacity and energy efficiency for the grinding process. In this paper, experimental analysis of the wet mill load based on the vibration signals of the laboratory-scale ball mill shell is presented. A series of experiments are conducted to investigate the vibration characteristics corresponding to different grinding conditions such as dry grinding, wet grinding and water grinding. The power spectral density of the vibration signals is systematically interpreted.Experimental results show that the rheological properties of the pulp affect the amplitude and frequency of the vibration signal. The most important conclusion is that the frequency range of the shell vibration of the laboratory wet mill can be divided into three parts, namely natural frequency band, main impact frequency band and secondary impact frequency band. Finally, soft-sensor models between vibration signal and mill operating parameters of mill load are established using genetic algorithm-partial least square (GA-PLS) technology. After more work on industry scale ball mill is done, the soft-sensor modeling based on the mill shell vibration for operating parameters of mill load will improve the performance of the ball mill in the grinding process.     

The microstructure and tensile property degradation of a gamma-TiAl alloy during isothermal and cyclic high temperature exposures

The microstructure and tensile property changes of a γTiAl-based alloy, Ti-47Al-2Cr-2Nb-0.15B, during isothermal and cyclic high temperature exposures have been investigated. Microstructure coarsening, including the fracture, dissolution and spheroidization of α₂ lamellae, is considered to be the main cause of the evident tensile property decreases of the alloy after isothermal and cyclic high temperature exposures. Dislocation emission near the broken lamellae is also an important phenomenon in the microstructure degradation during cyclic high temperature exposure, which originated from the thermal mismatch between α₂ and γ phases.     

Pattern matching of alarm flood sequences by a modified Smith–Waterman algorithm

Alarm flooding is one of the main problems in alarm management. Alarm flood pattern analysis is helpful for root cause analysis of historical floods and for incoming flood prediction. This paper deals with a data driven method for alarm flood pattern matching. An alarm flood is represented by a time-stamped alarm sequence. A modified Smith–Waterman algorithm considering the time stamp information is proposed to calculate a similarity index of alarm floods. The effectiveness of the algorithm is validated by a case study on actual chemical process alarm data.     

Model interpretation of electrochemical impedance spectroscopy and polarization behavior of H2/CO mixture oxidation in polymer electrolyte fuel cells

A mathematical model is proposed based on electrode kinetics analysis for the oxidation of 2% CO+H₂ mixture in polymer electrolyte fuel cells. Successful simulation of the polarization curve and experimental impedance spectra for Pt/C electrode system confirm the validity of the model which shows that the impedance is strongly dependent on electrode potential. With the increase of potential, an inductive behavior will occur. It is believed that the appearance of this inductive pattern can be used as a criterion for the onset of CO oxidation by the coincidence of the potential at which inductive behavior occurs with the ignition potential for CO oxidation. The effects of change of CO oxidation rate constant and CO adsorption equilibrium constant on impedance pattern, as well as on CO surface coverage and Faradaic current are also delineated with the use of the proposed model.     

NAO-1: Lunar Highland Soil Simulant Developed in China

A new lunar highland soil simulant, NAO-1, has been created in National Astronomical Observatories (NAO), Chinese Academy of Sciences. This simulant was produced by gabbro, which includes large quantity of feldspar (An>90). The simulant’s chemical composition, mineralogy, particle-size distribution, density, angle of internal friction, and cohesion have been analyzed and results demonstrated that most characteristics of NAO-1 are similar with lunar highland soil samples. NAO-1 will benefit the scientific and engineering research of lunar soil.     

Synthesis of Co2SnO4@C core-shell nanostructures with reversible lithium storage

This paper reports the synthesis of Co₂SnO₄@C core-shell nanostructures through a simple glucose hydrothermal and subsequent carbonization approach. The as-synthesized Co₂SnO₄@C core-shell nanostructures have been applied as anode materials for lithium-ion batteries, which exhibit improved cyclic performance compared to pure Co₂SnO₄ nanocrystals. The carbon matrix has good volume buffering effect and high electronic conductivity, which may be responsible for the improved cyclic performance.     

FB3-F银钎剂去膜机理

研究了由H₃BO₃、K₂B₄O₇和KF（质量比为7:10:3）3种组分配制而成的银钎剂的去膜机理。结果表明：在700 ℃时,K₂B₄O₇或KF都不能单独去除Q235钢板表面的氧化膜,且KF会加快高温下钢表面的氧化速率;H₃BO₃能够去除Q235钢表面的氧化膜,然而其反应产物具有明显的非晶结构特征,并且流动性差。此外在700 ℃时,H₃BO₃与KF能够发生反应,其反应产物可以去除钢表面氧化膜。KF和K₂B₄O₇之间也能在700 ℃发生类似的反应,然而其反应产物非常坚硬。因此,在700 ℃时,H₃BO₃、K₂B₄O₇和KF混合钎剂能够与Q235钢板表面氧化膜反应,且反应产物具有明显的非晶特征。KF的加入将非反应性H₃BO₃-K₂B₄O₇二元体系转化为反应性KF-H₃BO₃-K₂B₄O₇三元体系。在这个三元体系中,KF不但对钢板没有腐蚀性,反而促进了氧化膜的去除。     

基于LASSO-WOA-LSSVM的海洋管线外腐蚀速率预测

目的 构建海洋管线外腐蚀速率预测模型,提高海底油气管线外腐蚀速率预测的准确性.方法 建立基于套索(LASSO)回归和鲸鱼优化算法(WOA)的最小二乘支持向量机(LSSVM)腐蚀速率预测模型,采用LASSO回归方法对指标进行筛选,提取海洋管线腐蚀的主要影响因素.应用最小二乘支持向量机算法建立海洋管线外腐蚀速率预测模型,并使用鲸鱼优化算法对模型参数进行优化,避免了参数取值对模型回归性能的影响.以海洋挂片实验为例,通过MATLAB进行模拟仿真,分析验证模型预测结果,并将预测结果与其他模型进行对比分析.结果 LASSO回归算法筛选得到影响腐蚀速率的主要因素为:温度、溶解氧含量、pH值.采用WOA-LSSVM模型所预测的结果与实际值较为吻合,其平均相对误差为2.23％,均方根误差(RMSE)为0.3248,决定系数R2达到0.9708,均优于其他两种模型.结论 基于LASSO回归和鲸鱼优化算法的最小二乘支持向量机预测模型具有更优的泛化能力和预测精度,为海底管道腐蚀研究工作提供了新思路,也为海洋油气输送系统的结构安全与风险防范提供了参考.