Spectrophotometric determination of trace nitrite with a novel self-coupling diazotizing reagent: J-Acid

A simple and sensitive method for the spectrophotometric determination of nitrite was described and optimum reaction conditions along with other important analytical parameters were established. In the presence of potassium bromide at 25°C, nitrite reacted with J-acid in hydrochloric acid producing diazonium salt and then coupled with excess J-acid in the sodium carbonate solution yielding red colored azo compounds. At wavelength of 500 nm, Beer’s law was obeyed over the concentration range of 0.02–0.60 mg·L^–1. The molar absorptivity was 3.92 × 10⁴ L·mol^–1·cm^–1. This method was easily applied to the determination of trace nitrite in environmental water with recoveries of 98.7–101.2%.     

Wind field simulation and wind‐induced responses of large wind turbine tower‐blade coupled structure

Herein, by a case study on a 5‐MW wind turbine system developed by Nanjing University of Aeronautics and Astronautics, the wind field simulation and wind‐induced vibration characteristics of wind turbine tower‐blade coupled systems is analyzed. First, the blade‐nacelle‐tower‐basis integrated finite element model with centrifugal forces induced by rotational blades is established. Then, based on a harmony superposition method and the modified blade element‐momentum theory, the fluctuating wind field of tower‐blade coupled systems is simulated, which considers wind shear effect, tower shadow effect, rotational effect, blade‐tower dynamic and model interaction effects. Finally, the wind‐induced dynamic responses and wind vibration coefficients of the wind turbine tower‐blade coupled structure are discussed through the ‘consistent coupled method’ previously proposed by us. The results indicate that the wind‐induced responses of a large wind turbine tower‐blade coupled structure present complicated modal responses and multimode coupling effect. Additionally, the rotational effect would amplify aerodynamic loads on blades with high frequency, wind‐induced dynamic responses and wind vibration coefficients of wind turbine tower. The centrifugal force effect could also amplify natural vibration frequency of the tower‐blade coupled system and reduce the wind‐induced dynamic responses and wind vibration coefficients of wind turbine tower. The research could contribute to wind‐resistant design of structure for a large‐scale wind turbine tower‐blade system. Copyright © 2014 John Wiley & Sons, Ltd.     

以三角形稳固基础来处理深基坑边坡及控制流砂

以三角形稳固基础为原则,结合工程实际,对深基坑中流砂成因进行分析,采取了桩承台剪力墙与混凝土连系梁联合加强边坡支护和稳固流砂的具体措施,从而达到抵抗流砂的目的,且承台剪力墙可作为边坡支撑,起到稳固边坡的作用。施工结果表明:采用的技术处理方法得当,加固后效果显著,可供相关工程参考。     

基于排列熵的电磁声发射信号到达时间识别

排列熵算法简单高效,能够反映出信号的微小变化,是一种有效的信号突变检测工具。通过引入信号包络排列熵分析方法,对声发射信号到达时间识别问题进行求解。排列熵对信号幅值的大小不敏感,但对信号幅值的变化敏感,通过记录信号包络排列熵的变化,根据包络排列熵第一个极小值时刻来识别信号到达时间。根据裂纹电磁声发射实测信号识别结果可知,包络排列熵方法对声发射信号到达时间具有较高的识别精度。     

城市匝道桥抗震分析及加固研究

以绵竹市回澜立交桥为工程实例,结合匝道桥实际震害,采用有限元软件SAP2000对该桥在地震作用下的抗震性能进行了分析计算。研究了匝道桥采用增加截面法和减隔震法进行抗震加固设计后的抗震性能。研究表明:采用增加截面法和减隔震法均能有效满足匝道桥的抗震安全性要求。     

中美建筑能效标准比较

该文概述了建筑能耗在全球最终能源消费中的现状,分析了全球建筑能效标准发展现状及目标,分别介绍了中美两国建筑能效标准发展的历程。通过对各国标准的研究,总结了建筑能效标准所涉及的主要内容。着重以美国建筑能效标准ASHRAE90.1—2010和中国公共建筑节能标准GB50189—2005为例,比较中美建筑能效标准的构架、内容及参数的差别。提出了国内建筑能效标准发展的几点建议。     

Estimation of the appropriate sampling interval for rock joints roughness using laser scanning

Bulletin of Engineering Geology and the Environment - The rock joint roughness greatly affects the mechanical behaviors and permeability characteristics of rock mass. To accurately and effectively...     

Application of two-level design method on subway tunnel crossing active fault: a case study on Urumqi subway tunnel intersected by reverse fault dislocation

Bulletin of Engineering Geology and the Environment - The tunnel crossing active fault is severely damaged under the action of fault dislocation. Considering the “economic and safety”...     

Investigation of the strength recovery characteristics of a red-bed landslide soil by SHS and ultrasonic experiments

Bulletin of Engineering Geology and the Environment - The strength recovery (healing) of the shear zone soil of a landslide during the dormant phase after the sliding affects the reactivation of...