The distribution, enrichment and source of potential harmful elements in surface sediments of Bohai Bay, North China

A geochemical study of Bohai Bay surface sediments was carried out to analyze the potential harmful element (PHE: Ge, Mo, In, Sn, Sb,Te, Tl, Bi and V) concentrations, transportation and deposition, enrichment factors and sources. Germanium, Mo, In, Sn, Sb, Te, Tl, Bi and V concentrations in the surface sediments were: 1.43-1.71, 0.52-1.43, 0.04-0.12, 2.77-4.14, 1.14-2.29, 0.027-0.085, 0.506-0.770, 0.27-0.63 and 70.35-115.90 mu g/g, respectively. The distributions of total PHE concentrations, together with sequential extraction analyses, showed that the PHEs were mainly due to natural inputs from the continental weathering delivered to the bay by rivers and atmospheric transportation and deposition. However, high Mo, Sb, Te, Bi and V occurred in non-residual fractions, suggesting some anthropogenic inputs in addition to the natural inputs. Besides sources, the distributions of PHEs were influenced by the coupling of physical, chemical and biological processes. Enrichment factor (EF) was computed for each site for each element in order to assess the polluting elements and the degree of pollution at each site. Results revealed that the EFs were generally lower than 1.0, particularly for Ge, Mo, In, Sn, Tl and V; however, the EFs were higher (>1.5), particularly for Sb, Te and Bi, revealing moderate contamination. (C) 2010 Elsevier B.V. All rights reserved.

Sorption and desorption of lead (II) from wastewater by green algae Cladophora fascicularis

Biosorption is an effective method to remove heavy metals from wastewater. In this work, adsorption features of Cladophora fascicularis were investigated as a function of time, initial pH, initial Pb(II) concentrations, temperature and co-existing ions. Kinetics and equilibria were obtained from batch experiments. The biosorption kinetics followed the pseudo-second order model. Adsorption equilibria were well described by the Langmuir and Freundlich isotherm models. The maximum adsorption capacity was 198.5 mg/g at 298 K and pH 5.0. The adsorption processes were endothermic and the biosorption heat was 29.6 kJ/mol. Desorption experiments indicated that 0.01 mol/L Na(2)EDTA was an efficient desorbent for the recovery of Pb(II) from biomass. IR spectrum analysis suggested amido or hydroxy, C=O and C-O could combine intensively with Pb(II). (C) 2006 Elsevier B.V. All rights reserved.

Recovery of silver (I) using a thiourea-modified chitosan resin

This work describes the preparation of a chelating resin from chemically modified chitosan. The resin was synthesized by using O-carboxymethylated chitosan to cross-link a polymeric Schiffs base of thiourea/glutaraldehyde and characterized by IR. Batch method was applied for testing the resin's adsorption behavior. Adsorption experiments showed the resin had good adsorption capacity and high selectivity for Ag(I) in aqueous solution. The maximum uptake of Ag(I) exhibited was 3.77 mmol/g, at pH 4.0. The results also indicated that the adsorption process was exothermic and fit well with the pseudosecond-order kinetic model. Ag(I) desorption could reach 99.23% using 0.5 M thiourea-2.0 M HCl solution. (C) 2010 Elsevier B.V. All rights reserved.

一种7DOF冗余手臂构形的运动学与动力学特性研究

冗余度机构具有高度的灵活性和避障能力,利用冗余自由度可以改善仿人机器人手臂的运动性能。以实现人体手臂的运动特性和操作灵活性为目标,研制了一种7DOF冗余仿人机器人手臂,根据冗余手臂的机构学特点,研究了手臂的运动学和动力学性能,并在工作空间、肘部关节的自运动能力以及手臂自重引起的关节重力矩等方面与其它两种典型的冗余手臂构形进行了比较分析。

危险作业机器人控制系统的研究

随着科学技术的发展，移动机器人被寄予越来越高的期望，要求其具有更高的机动性、更强的环境适应及感知能力和快速反应能力。因此，研究高效的移动机构和高性能控制系统成为排爆、消防等各种地面遥操作危险作业移动机器人的共同课题。 本论文以中国科学院沈阳自动化研究所自行研发的“灵豹”反恐防暴机器人和子母消防搜救机器人(在研)为平台，对危险作业机器人的控制系统进行了较为系统的研究。 “灵豹”机器人采用轮-腿-履带复合移动机构。其轮式移动采用三轮机构，两前主动轮单独驱动，差速完成转向，后轮为万向从动脚轮，配合前轮转向，车体转向半径可实现从零到无限大。其控制系统以嵌入式控制器为核心，采用模块化方法设计构建，保证了系统体积紧凑、实时性好和可靠性高等的应用要求。 作为智能控制技术的一种，模糊控制可以对那些数学模型难以求取或无法求取的对象进行有效控制。用基于PC的可编程控制器实现模糊控制，关键在于前期处理和软件编程，因为必须充分考虑执行速度。针对实际的非完整约束三轮式移动机器人运动方向可控性差，PID控制器参数难以实现全局整定的问题，利用模糊控制器实现运动轨迹控制。 单纯用电子罗盘测量航向角作为模糊控制器输入，环境适应性较差，本文提出一种结合脚轮偏转角和罗盘航向角计算机器人角速度和航向角的算法。试验结果表明，设计的控制器能对机器人进行有效航向跟踪，能迅速缩小航向偏差，机器人转向灵活可控，且没有大的航向偏转角速度，提高了系统适应性和运动稳定性。 子母消防搜救机器人主要用于火场侦查搜救，分为子机器人和母机器人，既可单独执行任务，又可协作搜救。机器人体积小，内部空间极其有限，要求控制系统有较高的集成度，还要能耐高温、通讯可靠。火场环境一般比较复杂，尤其是在地下建筑，通讯不畅将严重影响消防搜救机器人深入到火场深处侦查。为充分保障通讯链路畅通，设计了子母机控制系统，母机和子机可互为通讯中继，有效减少通讯死角，扩大搜索范围。系统采用基于多载波调制技术的影音传输系统作为图像及语音信号的主要通信链路，采用数字电台传输指令数据。设计的通讯系统实时性好，抗干扰能力和绕射能力强。

PXJ-Ⅱ排险机器人

介绍了一种可在危险环境下作业的遥控机器人──PXJ－Ⅱ排险机器人，分析了其功能指标及结构，简述了以武器系统和传感器为主的机器人辅助系统及其实用意义。