Size charge fractionation of metals in municipal solid waste landfill leachate

Municipal solid waste landfill leachates from 9 Norwegian sites were size charge fractionated in the field, to obtain three fractions: particulate and colloidal matter >0.45microm, free anions/non-labile complexes <0.45microm and free cations/labile complexes <0.45microm. The fractionation showed that Cd and Zn, and especially Cu and Pb, were present to a large degree (63-98%) as particulate and colloidal matter >0.45microm. Cr, Co and Ni were on the contrary present mostly as non-labile complexes (69-79%) <0.45microm. The major cations Ca, Mg, K, and Mn were present mainly as free cations/labile complexes <0.45microm, while As and Mo were present to a large degree (70-90%) as free anions/non-labile complexes <0.45microm. Aluminium was present mainly as particulate and colloidal matter >0.45microm. The particulate and colloidal matter >0.45microm was mainly inorganic; indicating that the metals present in this fraction were bound as inorganic compounds. The fractionation gives important information on the mobility and potential bioavailability of the metals investigated, in contrast to the total metal concentrations usually reported. To study possible changes in respective metal species in leachate in aerated sedimentation tanks, freshly sampled leachate was stored for 48h, and subsequently fractionated. This showed that the free heavy metals are partly immobilized during storage of leachate with oxygen available. The largest effects were found for Cd and Zn. The proportion of As and Cr present as particulate matter or colloids >0.45microm also increased.     

Non-monotonic salt concentration dependence of inverted electrokinetic flow

Modeling of electrokinetic flows is crucial to understand numerous phenomena associated with electrochemistry, biophysics, and colloidal science. Here, we incorporate the modified Gaussian renormalized fluctuation theory into transport equations for electrolyte solutions to study the ion-correlation-induced inversion of electrokinetic flows, also known as charge inversion. We are able to capture the non-monotonic dependence of inverted streaming current and reversed electrophoretic mobility on salt concentration. By analyzing the double-layer structure, we elucidate that this non-monotonicity is a consequence of the competition between spatially varying ion correlations and the translational entropy of the ions. We find that for practical values of surface charge densities, the excluded volume effect does not play any significant role. In a significant improvement over existing theories, our theoretical predictions are in quantitative agreement with experimental measurements for charge inversion in trivalent salts.     

聚合物熔体微分静电纺电场对射流的影响及其物理模型

为研究电场强度及接收装置材质对无针静电纺丝射流效率和射流分布均匀性的影响,在提出的熔体微分直线静电纺丝装置上,通过改变纺丝电压和接收装置材质,分析了喷头端最大电场强度和电离电荷对射流效率及均匀性的影响。结果表明:喷头端电场强度越大,射流效率越高,射流分布越均匀;当接收端的局部电压高于喷头端的电压时,电离离子宏观上表现出向喷头端运动,会抑制射流的形成;在高压收集端铺设电阻值为2.7×10⁵ Ω的纸,可以实现电离电荷的二次均匀分布,消除局部离子流引起的射流缺失现象;在接收装置上铺设电阻值大于1.0×10¹¹ Ω的聚对苯二甲酸乙二醇酯(PET)会增加纺丝回流的电阻,导致电荷在PET上聚集,反作用削弱喷头端的电场强度,引起射流效率的降低。     

基于LTC6804-2的锂电池SOC应用研究

分析了电池荷电状态(SOC)测量原理,设计了一种基于LTC6804-2的锂电池SOC应用系统,系统硬件包括锂电池电压测量电路、锂电池电芯表壳温度测量电路、锂电池充放电霍尔电流测量电路、LPC2478为嵌入式主控芯片的ARM7电路;系统软件包括LTC6804-2芯片的配置与电池电量数据读取、温度数据读取、充放电电流计算、LPC2478任务管理与通信。经过实际拷机测试,系统运行稳定,系统测量误差小于0.05%,测量精度高,可以推广到UPS在线式电源或矿用锂电池管理系统等工程实际中使用。     

乌努格吐山铜钼矿冻土层爆破设计方案

乌努格吐山铜钼矿冬季气温常在-30~-40℃左右,持续时间长达五个月。冬季开采爆破时,上部冻土层易产生大块,影响铲装效率,造成安全隐患;在矿石区块度过大,易造成选矿厂粗碎站堵仓,增加旋回破碎机的故障率,严重时甚至会造成停产。文章根据乌努格吐山冻土层特点,进行了爆破漏斗实验和冬季冻土层爆破参数方案设计,并对所取得的经济效益进行了简要分析。     

单根碳纳米管场致发射表面电荷分布研究

考虑碳纳米管尺寸及端帽形状,计算得到了比较精确的金属型纳米管表面电荷密度相对分布曲线。与先前的理论结果作比较,消除了曲线上的波动,曲线相对抬高,尖端附近电荷量所占比例减小。进一步研究了长度、半径和长径比对电荷密度相对分布曲线的影响,表明长度主要影响管身电荷密度相对分布,半径主要影响尖端电荷密度相对分布。在忽略其他条件影响下,长径比相同的碳纳米管,电荷密度相对分布曲线趋势完全相同。     

压制球形药包解决退模问题的技术措施

文中简要阐述了在制备球形药包过程中,为解决压装药件的退模问题所采取的技术措施,并提出了较佳的成型底座的设计方案。     

同轴介质阻挡放电功率和等效电容特性研究

以同轴—针放电结构为研究基础,采用Lissajous图像法,研究了介质阻挡放电管径、载气流速变化对放电功率和介质等效电容的影响关系;设计了正交实验,进一步研究载气流速和放电管径对周期传输电荷量显著性影响的大小.研究结果表明:随着载气速度的提升,放电功率和介质等效电容都呈减小趋势;随着放电管径的增大,介质等效电容减小.正交实验中,管径的F值为22.15,相比载气流速对传输电荷量的影响更加显著.     

一种多输出直流稳压电源的设计

本文提出了一种多输出线性直流稳压电源的设计.该直流供电电源设计以固定式和可调式集成稳压器件为核心,可以提供多个固定的直流电压输出,和一个电压连续可调的直流电压输出.该电源采用了双重过载保护电路和抗干扰技术.经对电源样机的实验测试,该电源性能好、工作可靠,可以满足用于压电传感器的电荷放大器对多种直流电的需要.