青云寺滑坡隐患体稳定性分析及防治措施

本文以安丘市青云寺滑坡为例,开展了滑坡隐患体稳定性分析及防治措施研究。根据滑坡基本特征,从地形地质、大气降水和人为因素三个方面分析了诱发滑坡的原因。综合分析认为,该滑坡破坏模式为前缘先滑动后牵引坡体及后缘滑动的小型土质滑坡。根据工程地质勘察数据,采用瑞典条分法开展滑坡体稳定性定量计算与评价,获得了三种荷载组合工况的坡体稳定性状态,并在此基础上提出了相应的防治对策。研究成果可为类似滑坡隐患体防治提供借鉴。     

Effectiveness of predicting tunneling-induced ground settlements using machine learning methods with small datasets

Prediction of tunneling-induced ground settlements is an essential task, particularly for tunneling in urban settings. Ground settlements should be limited within a tolerable threshold to avoid damages to aboveground structures. Machine learning (ML) methods are becoming popular in many fields, including tunneling and underground excavations, as a powerful learning and predicting technique. However, the available datasets collected from a tunneling project are usually small from the perspective of applying ML methods. Can ML algorithms effectively predict tunneling-induced ground settlements when the available datasets are small? In this study, seven ML methods are utilized to predict tunneling-induced ground settlement using 14 contributing factors measured before or during tunnel excavation. These methods include multiple linear regression (MLR), decision tree (DT), random forest (RF), gradient boosting (GB), support vector regression (SVR), back-propagation neural network (BPNN), and permutation importance-based BPNN (PI-BPNN) models. All methods except BPNN and PI-BPNN are shallow-structure ML methods. The effectiveness of these seven ML approaches on small datasets is evaluated using model accuracy and stability. The model accuracy is measured by the coefficient of determination (R²) of training and testing datasets, and the stability of a learning algorithm indicates robust predictive performance. Also, the quantile error (QE) criterion is introduced to assess model predictive performance considering underpredictions and overpredictions. Our study reveals that the RF algorithm outperforms all the other models with the highest model prediction accuracy (0.9) and stability (3.02 × 10^?27). Deep-structure ML models do not perform well for small datasets with relatively low model accuracy (0.59) and stability (5.76). The PI-BPNN architecture is proposed and designed for small datasets, showing better performance than typical BPNN. Six important contributing factors of ground settlements are identified, including tunnel depth, the distance between tunnel face and surface monitoring points (DTM), weighted average soil compressibility modulus (ACM), grouting pressure, penetrating rate and thrust force.     

Stability analysis of layered slopes in unsaturated soils

This study presents stability analyses of layered soil slopes in unsaturated conditions and uses a limit equilibrium method to determine the factor of safety involving suction stress of unsaturated soil. One-dimensional steady infiltration and evaporation conditions are considered in the stability analyses. An example of a two-layered slope in clay and silt is selected to verify the used method by comparing with the results of other methods. Parametric analyses are conducted to explore the influences of the matric suction on the stability of layered soil slopes. The obtained results show that larger suction stress provided in unsaturated clay dominates the stability of the layered slopes. Therefore, the location and thickness of the clay layer have significant influences on slope stability. As the water level decreases, the factor of safety reduces and then increases gradually in most cases. Infiltration/evaporation can obviously affect the stability of unsaturated layered slopes, but their influences depend on the soil property and thickness of the lower soil layer.     

Optimal capacitor placement for enhancing voltage stability in distribution systems using analytical algorithm and Fuzzy-Real Coded GA

Two algorithms for optimal capacitor placement, with a view to enhance voltage stability are introduced. In the analytical algorithm the nodes, whose voltage stability index values are lower than a threshold value, are ranked in ascending order as the candidate nodes for compensation. The additional reactive power compensation to be provided at a node is obtained by solving linearized VSI formula. The maximum compensation at each node is limited to the initial reactive power delivered by the respective node prior to compensation for avoiding over-dimensioning of the capacitor banks. However, capacitor placement based on voltage stability index has proven less than satisfactory and not always indicated the appropriate placement.As an alternative a fuzzy expert system is used for extracting suitability of capacitor location from power loss reduction index and improving the voltage profile within voltage constraints. A combination of fuzzy expert system for capacitor placement and real coded GA for capacitor sizing, with a view to enhance voltage stability is proposed for optimal capacitor placement. The result is enhancement of the overall system stability index and potential achievement of maximum net money savings due to power and energy loss reduction vs. expenditure in capacitors.The overall accuracy and reliability of the proposed Fuzzy-Real Coded GA algorithm has been validated and tested on 33-node radial distribution system. Comparison of obtained results with those in recent publications showed that the Fuzzy-Real Coded GA algorithm is capable of producing high-quality solutions with good performance of convergence, and demonstrated viability.     

提高供热空调系统水力稳定性的技术途径

供热空调对我国居民的生活产生了十分重要的影响。本文在分析供热空调水力稳定性的基础上，分析了如何不断提升水利稳定性的措施。     

Improved phase stability and electrochemical performance of (Y,In,Ca)BaCo3ZnO7+δ cathodes for intermediate temperature solid oxide fuel cells

With an aim to combine the performance-enhancing properties of Ca with the stability-promoting properties of In in the swedenborgite YBaCo₄O_7+δ-based cathodes for solid oxide fuel cells (SOFC), cation-substituted Y_1−x−yIn_xCa_yBaCo₃ZnO_7+δ (0.2 ≤ (x + y) ≤ 0.5) oxides have been explored. All samples presented in this work are stable in air after 120 h exposure to 600, 700, and 800 °C. Increasing In content shows a negligible impact on polarization resistances (R_p), but causes an increase in the activation energies (E_a) of (Y,In,Ca)BaCo₃ZnO_7+δ + Gd_0.2Ce_0.8O_1.9 (GDC) composite cathodes on 8 mol% yttria-stabilized zirconia (8YSZ) electrolyte supported symmetric cells. Increasing Ca content shows a decrease in R_p and an increase in E_a on similar electrochemical cells. All (Y,In,Ca)BaCo₃ZnO_7+δ samples investigated here show superior performance compared to the unsubstituted YBaCo₃ZnO_7+δ + GDC cathode in the range of 400–800 °C. Especially, the Y_0.5In_0.1Ca_0.4BaCo₃ZnO_7+δ + GDC composite cathode exhibits good performance on GDC electrolytes in the range of 400–600 °C. With superior phase stability and electrochemical performance, the (Y,In,Ca)BaCo₃ZnO_7+δ series of oxides are attractive cathode candidates for intermediate temperature SOFCs.     

Electronic structure and ferromagnetism of Fe11NiSi4, Fe11CoSi4, Fe11CrSi4 and Fe3Si from first principles

Based on the density functional theory (DFT), the plane-wave pseudopotential method was used to calculate structural stabilities, electronic structures, and ferromagnetism of Fe₃Si, Fe₁₁NiSi₄, Fe₁₁CoSi₄ and Fe₁₁CrSi₄ intermetallic compound. This study showed that the Fe₁₁NiSi₄ and Fe₁₁CrSi₄ phase are more stable than Fe₃Si phase, especially Fe₁₁NiSi₄, but decreased with Fe₁₁CoSi₄ phase. Calculating the density of states and the Mulliken electronic populations showed that Fe₁₁NiSi₄ had the highest structural stability because of its Fermi level, which was close to the bottom of the pseudo-gap. Fe₁₁NiSi₄ also had the largest Mulliken population, which increased the metallic bonding of the alloying system. The total magnetic moments of Fe₁₁NiSi₄, Fe₁₁CoSi₄ and Fe₁₁CrSi₄ were 20.04μ_B, 19.98μ_B, and 18.81μ_B, respectively. These magnetic moments mainly originated from the 3d spin polarization of Fe and those of additional atoms.     

Microstructure and thermal stability of low-oxygen SiC fibers prepared by an economical chemical vapor curing method

Continuous SiC fibers (SiC-CVC fibers) with low oxygen content (~2 wt%) were prepared by pyrolysis of polycarbosilane (PCS) fibers cured with chemical vapor curing (CVC). PCS fibers were cured by cyclohexene vapor as curing agent. Their structure and properties were compared with those of SiC fibers obtained from electron beam irradiation curing (SiC-EB fibers). SiC-CVC fibers were similar to SiC-EB fibers, with distinctly better thermomechanical stability than that of fibers cured by thermal oxidation curing (commercial KD-I fibers). CVC is a more economical and practicable approach for preparing high-performance SiC fibers than other strategies.     

Synthesis and evaluation of some novel additives as antioxidants and corrosion inhibitors for petroleum fractions

Benzoxazinone 2 was prepared and reacted with formamide,acetamide,some primary aromatic amines and heterocyclic amines giving the corresponding quinazolone derivatives 3-15 respectively.The reaction of benzoxazinone 2 with hydrazine hydrate and phenyl hydrazine was also studied.Representative compounds of the synthesized products were evaluated as antioxidants and corrosion inhibitors for gasoline engine lubricating oil.The highest antioxidant activities were obtained with compounds 10-15.The optimum concentration recommended for these new additives was found to be 0.lg for 1L ofoil for compounds 13-15.In addition,some of the highly effective antioxidant additives,namely 10-15,were thermally analyzed by using thermogravimetric analysis （TGA） and differential thermal gravimetric analysis （DTGA） techniques and the results indicated that compounds are thermally stable and could be used under thermal conditions.Moreover,a comparison of the oxidation stability between the tested oil containing the prepared products and lubricating oil containing commercial additives was also studied.