The effect of roll-processing orientation on stress corrosion cracking of warm-rolled 304L stainless steel in oxygenated and deoxygenated high temperature pure water

Stress corrosion crack growth rates of 304L stainless steel after one-directionally warm-rolled along the longitudinal (L) direction were measured in oxygenated and deoxygenated pure water at 288 °C. The fracture mode is mainly intergranular in the Transverse-longitudinal (T-L) orientation specimen, while it is occasionally intergranular in the Longitudinal-transverse (L-T) orientation specimen. The crack growth rates in the T-L orientation are higher than those in the L-T orientation in both oxygenated and deoxygenated environments, which is related to the effective cracking growth path as the result of microstructural anisotropy and applied loading direction.     

Lamb波与瞬时相位技术在损伤识别中的应用

采用主动Lamb监测技术与瞬时相位相结合的方法对复合材料板进行健康监测。首先通过仿真试验,模拟损伤信号在正常信号中的叠加,结果表明其会引起瞬时相位曲线相应的变化;然后再利用Lamb波主动监测技术,在复合材料板上进行试验采集信号,其瞬时相位能够发现板结构中的损伤,说明瞬时相位可应用于结构的损伤识别。     

住宅小区环境的规划设计

1引言 以保护环境、实现可持续发展为前提的经济增长及居民生活水平的提高给居住小区的规划设计提出了许多新的课题.因此,城市规划设计特别是城市居住小区的规划设计必须尊重环境、因地制宜.     

全套管薄壁灌注桩在山区某工程基坑支护中的应用

结合工程施工实例,介绍了全套管薄壁灌注桩的施工工艺流程、关键工序的主要事项,并与其它大直径灌注桩进行对比,说明该桩型作为基坑支护的围护桩具有较大的经济社会效益和广阔的市场前景,同时也对存在的问题做了总结。     

Synthesis of sulfated ZrO2/MWCNT composites as new supports of Pt catalysts for direct methanol fuel cell application

Sulfated zirconia supported on multi-walled carbon nanotubes as new supports of Pt catalyst (Pt–S-ZrO₂/MWCNT) was synthesized with aims to enhance electron and proton conductivity and also catalytic activity of Pt electrocatalyst in terms of larger concentrations of ionizable OH groups on surfaces. Fourier transform infrared spectroscopy analysis shows that the sample surfaces were modified with sulfate. Transmission electron microscopy results show that the Pt and sulfated ZrO₂ particles dispersed relatively uniformly on the surface of the multi-walled carbon nanotube. X-ray diffraction shows that S-ZrO₂ and Pt coexist in the Pt–S-ZrO₂/MWCNT composites and S-ZrO₂ has no effect on the crystalline lattice of Pt. Pt–S-ZrO₂/MWCNT catalyst was evaluated in terms of the electrochemical activity for methanol electro-oxidation using cyclic voltammetry, steady-state polarization experiments and electrochemical impedance spectroscopy technique at room temperature. Pt–S-ZrO₂/MWCNT catalyst show higher catalytic activity for methanol electro-oxidation compared with Pt catalyst on non-sulfated ZrO₂/MWCNT support and commercial Pt/C (E-TEK).     

ENIG焊点的失效机理及镀层重工方法研究

采用显微形貌、微观结构和元素成分分析等物理分析方法,以不同类型的化镍浸金(electroless nickel/immersion gold,ENIG)基板为对象,分析了其焊点在不同情形下的失效模式和失效机理,阐述了"黑盘"缺陷的主要失效特征,研究了具有黑盘缺陷的化镍浸金基板的重工工艺.研究结果显示,Ni层断裂表面单一的高P含量或轻微Ni层腐蚀不能作为黑盘缺陷的唯一依据,已形成良好金属间化合物(intermetallic compound,IMC)层的Ni层腐蚀位置的焊接界面仍具有良好的机械结合强度,采用喷锡工艺(hot air solder level,HASL)对具有黑盘缺陷的化镍浸金基板进行重新处理切实可行.     

Experimental research of unsupervised Cameron/maximum-likelihood classification method for fully polarimetric synthetic aperture radar data

In this study, experimental research on classification is applied to fully polarimetric data in X-band from China. Considering the amplitude and phase error between H and V channels in the system, the authors firstly correct the error in original data. The authors also deduce the formula of Cameron?s classification method for the real data in our study. Then Cameron?s method is used to initially classify the site image. Finally, the initial classification map defines training sets for the maximum-likelihood (ML) classifier. The advantages of this method are the automated classification and interpretation of each class based on the scattering mechanism. The experiment demonstrates the feasibility of the proposed approach, which dramatically improves the X-band data classification result compared with the Cameron method and H/α/ML method.     

Synthesis of polyaniline nanostructures via soft template of sucrose octaacetate

Highly crystallized polyaniline (PANI) nanostructures were polymerized by oxidative polymerization in the presence of sucrose octaacetate acting as an in situ seed and a soft template, and ammonium peroxydisulfate (APS) acting as an oxidizing agent. PANI nanofibers and nanorods were obtained using 2 and 3 g sucrose octaacetate, respectively. The nanostructures containing irregular-shaped agglomerates, such as particulate particles and scaffolds were observed with increasing the concentrations of sucrose octaacetate. The polymerized PANI was characterized using Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetry analysis (TGA). Results showed that the presence of sucrose octaacetate during polymerization could only induce a change in morphology, but could not influence the molecular structure of the resulting PANI. Compared with those derived with 1, 3, and 4 g sucrose octaacetate, the polymerized PANI from 2 g sucrose octaacetate possessed higher thermal stability and electrical conductivity due to its higher crystallinity and highly ordered structure. A mechanism for the formation of PANI nanostructures is also proposed.     

浅析北京郊区公路绿化的现状与发展

以城、郊为界将北京公路绿化状况分为两部分,并进行了分析比较,从而找出两者现状差异,并根据效区公路绿化中的不足,从提高认识、加大投入、合理设计、科学养护4个方面找到解决问题的方法。     

Mass diffusion coefficients of oxygenated fuel additives in air

In this work, an experimental system based on digital real-time holographic interferometry for measuring the mass diffusion coefficients of fluid is introduced. The method of processing interference fringe hologram is also introduced thoroughly. By uncertainties analysis and experimental verification, the accuracy of this system is validated. The experimental uncertainties in temperature and mass diffusion coefficient are estimated to be no greater than ± 0.16 K and ± 0.2%, respectively. On this basis, mass diffusion coefficients of two fuel additives: 1,2-dimethoxyethane (ethyleneglycol dimethyl ether, GDME) and 2-methoxyethyl ether (diethylene glycol dimethyl ether, DGM) in air were measured at T = (278.15–338.15) K under atmospheric pressure, and polynomial was fitted by the experimental data.