Effects of calcination parameters on the silica phase of original and leached rice husk ash

This paper presents a contribution to the study of the effects of calcination parameters, including temperature and time, on the silica phase of original and leached rice husk ash. X-ray diffraction (XRD) analysis reveals the presence of totally crystalline silica in the original rice husk ash prepared at 800 °C. Fortunately, no indication of the presence in crystalline phase is found in the leached rice husk ash due to leaching. However, specific surface area analysis indicates that the high calcination temperature or the long calcination time renders the amorphous silica in the leached rice husk ash less activity. Therefore, the leaching procedure, the low calcination temperature and the short calcination time are proposed in order to prepare more active amorphous silica from the rice husk.     

基于敏感性分析的掘进施工进度影响因素综合评价

利用敏感性分析方法对国外某铜锌矿采选总包工程矿山井巷掘进施工各影响因素进行分析,以月掘进进尺作为分析指标,首先对影响因素进行不确定性遴选,排除确定性因素,其次分析各不确定因素工作参数的合理性,选定可优化的因素进行敏感性分析,再分析各敏感因素的变动极限,最后根据分析结果,对各因素进行综合评价。提出掘进施工优化方向。分析得出,卡车数量、断面超挖、单循环凿岩面数、通风时长等4个因素为该矿山可优化因素,按合理工作参数优化后,可将月掘进进尺提高12%左右。     

基于粗糙集特征级融合的肺结节检测算法

以肺结节的检测为研究目标,针对肺结节特征级融合检测算法中存在特征结构不合理和特征表达不紧致两个问题,提出了一种基于粗糙集特征级融合的肺结节检测算法,该算法首先分析肺部CT影像的医学征象,提出了六个新的三维特征,并综合其他二维和三维特征共42维特征分量共同量化ROI;然后基于粗糙集对提取的特征集合进行5次特征级融合实验;最后利用网格寻优算法优化核函数的SVM作为分类器进行肺结节识别.以70例肺结节患者的肺部CT影像为原始数据,通过4组对比实验验证算法的有效性和稳定性,实验结果表明,经过粗糙集特征级融合的肺结节检测算法识别肺结节的能力得到了有效提升.     

Analysis of excavation-induced responses of loaded pile foundations considering unloading effect

In urban areas, the excavation of tunnels and foundation pits will inevitably influence the working performance of adjacent pile foundations, and many failure cases have been reported in recent years. Thus, it is important to accurately evaluate the additional pile responses. Most existing methods tend to neglect the influence of working load on excavation-induced additional pile responses, and some of them cannot properly consider the nonlinear characteristics of pile-soil interaction. In this paper, governing differential equations, which take the coupling effect of longitudinal and lateral deformation into account, are established for both single piles and pile groups. A new theoretical method, in which the deflection curves of the enclosure structure calculated by the modified “m” method are taken as basic calculating data, is developed to estimate the free-field soil movements induced by foundation pit excavation. A two-stage analysis method is then proposed to study the behavior of pile foundations subjected to excavation-induced ground movements. This method can take the influence of working loads acting on pile heads into account, and overcome some deficiencies of existing methods. Then, the proposed method is verified by comparing the calculated results with boundary element solutions and centrifuge test data. Good agreements between these solutions are demonstrated. Thereafter, this method is employed to study the influence of the vertical working load on the excavation-induced pile responses. It can be found that the influence of the vertical working load on the vertical pile responses is significant, and under some special situations, the influence of axial force on lateral responses is not negligible and the coupling effect should be factually considered.     

Effects of hydrogen addition on the premixed laminar-flames of ethanol–air gaseous mixtures: An experimental study

The effects of hydrogen addition on the laminar premixed-flame characteristics of ethanol–air gaseous mixtures were investigated experimentally by using outwardly propagating spherical flames. The experiments were conducted in a constant-volume combustion vessel with a central ignition at an initial temperature of 383 K, a pressure of 0.1 MPa, a hydrogen fraction from 0% to 100%, and an equivalence ratio from 0.6 to 1.6, and the flame images were obtained by a high-speed schlieren camera system. The results show that the unstretched flame propagation speeds and burning velocities increase exponentially with the increase in hydrogen fraction for a constant equivalence ratio. When the hydrogen fraction is equal to or less than 60%, the burned gas Markstein length reduces with the increase of equivalence ratio, indicating a positive correlation between the flame instability and hydrogen fraction, while the opposite effect is observed when the hydrogen fraction is greater than 60%. At an equivalence ratio below 1.4, the Markstein length decreases with increased hydrogen fraction, indicating that the flame instability is exacerbated with hydrogen addition, while the reverse holds in the case of equivalence ratio above 1.4. Finally, an empirical formula is developed to estimate the laminar burning velocity of ethanol–hydrogen–air flames on the basis of present experimental data.     

Electropolymerization of high stable poly(3,4-ethylenedioxythiophene) in ionic liquids and its potential applications in electrochemical capacitor

Poly(3,4-ethylenedioxythiophene) (PEDOT) has been successfully electropolymerized using a purified 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]) as both the growth medium and the supporting electrolyte. The electrochemical performance of the PEDOT thin film was investigated in 1 mol L⁻¹ H₂SO₄ solution. It possesses nearly ideal capacitive property, and its specific capacitance is about 130 F g⁻¹. Compared with other conducting polymers, enhanced cycling lifetime (up to 70,000 cycles), which is close to that of active carbon materials, was observed on repetitive redox cycling.