Preparation,characterization and application of iron (III)-loaded chitosan hollow fiber membranes as a new bio-based As (V) sorbent

Fe (III)-loaded chitosan (CS) hollow fibers (CS-Fe (III) HF) were successfully prepared according to the dry-wet spinning technique. The CS-Fe (III) HFs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and thermal gravimetric analysis (TGA). Removal of pentavalent arsenic was studied through biosorption on CS-Fe (III) HF adsorptive membranes. The response surface methodology (RSM) was applied to investigate the influence of the main operating parameters such as contact time, pH, initial As (V) concentration and HFs dosage on the adsorption capacity of As (V). From the Pareto analysis, pH, [As (V)]_o, [CS-Fe (III) HF membranes] and squared effect of [As(V)]_o were found to produce the largest effect on biosorption of As (V). Kinetic studies showed that the pseudo-second-order kinetic model provides the best correlation to the experimental results. Equilibrium data fitted well with the Langmuir model with maximum adsorption capacity of 3,703 μg g^?1. A laboratory scale glass membrane module consisting of three CS-Fe(III) HFs has also been prepared and tested for biosorption of As (V) at a real scale. Permeability of As (V) ions through the CS-Fe (III) HF membranes was 0.145 μmol m^?2 h^?1 bar ^?1.     

Central Artery/Tunnel Project Excavation Induced Ground Deformations

Estimate of deformations around urban excavations is a primary concern for designers, contractors, owners, and potentially affected third parties. Significant efforts have gone into the development of empirically based methods to estimate deformations relying on a large number of case histories. The construction of the deep excavations for the central artery/tunnel project provides valuable information on observed deformations due to the construction of these excavations. Lateral deformations and surface settlements for three construction contracts are collected and summarized in a form similar to published empirical charts. The stiff support system used in these braced excavation and the embedment of the wall into stiff strata control deformations to minimal levels. The data show that surface settlements, although small, extend farther away from the excavation than previously reported.     

Designing optimal tuned mass dampers for nonlinear frames by distributed genetic algorithms

In this paper, the capabilities of tuned mass dampers (TMDs) for the mitigation of response of nonlinear frame structures subjected to earthquakes have been studied. To determine the optimal parameters of a TMD, including its mass, stiffness and damping, we developed an optimization algorithm based on the minimization of a performance index, defined as a function of the response of the nonlinear structure to be controlled. Distributed genetic algorithm has been used to solve the optimization problem. For illustration, the method has been applied to the design of a linear TMD for an eight‐story nonlinear shear building with bilinear hysteretic material behavior subjected to earthquake. The results have shown that the method has been successful in determining the TMD parameters to reduce the structure response. The simplicity and desirable convergence behavior of the method have also been two important results of the method. Two performance indices have been defined: (a) the minimization of the maximum drift and (b) the accumulated hysteretic energy. It has also been shown that the efficiency of the TMD has been influenced by the mass ratio of the TMD, the maximum TMD stroke length and the TMD design earthquake. Copyright © 2011 John Wiley & Sons, Ltd.     

基于数字信号处理器和IRMCK201的电梯门机伺服系统

介绍了一种基于数字信号处理器(DSP)和IRMCK201的电梯门机伺服系统解决方案。该方案采用IRMCK201实现永磁同步电机电流环和速度环,采用DSP实现速度曲线的生成、与上位机的通信以及其他辅助处理功能。实验证明,该方案具有性能优越、设计简单、开发周期短等优点,具有较好的推广意义。