Use of voltammetric solid-state (micro)electrodes for studying biogeochemical processes: Laboratory measurements to real time measurements with an in situ electrochemical analyzer (ISEA)

Solid-state voltammetric (micro)electrodes have been used in a variety of environments to study biogeochemical processes. Here we show the wealth of information that has been obtained in the study of sediments, microbial mats, cultures and the water column including hydrothermal vents. Voltammetric analyzers have been developed to function with operator guidance and in unattended mode for temporal studies with an in situ electrochemical analyzer (ISEA). The electrodes can detect the presence (or absence) of a host of redox species and trace metals simultaneously. The multi-species capacity of the voltammetric electrode can be used to examine complex heterogeneous environments such as the root zone of salt marsh sediments. The data obtained with these systems clearly show that O₂ and Mn²⁺ profiles in marine sedimentary porewaters and in microbial biofilms on metal surfaces rarely overlap indicating that O₂ is not a direct oxidant for Mn²⁺. This lack of overlap was suggested originally by Joris Gieskes' group. In waters emanating from hydrothermal vents, Fe²⁺, H₂S and soluble molecular FeS clusters (FeS_aq) are detected indicating that the reactants for the pyrite formation reaction are H₂S and soluble molecular FeS clusters. Using the ISEA with electrodes at fixed positions, data collected continuously over three days near a Riftia pachyptila tubeworm field generally show that O₂ and H₂S anti-correlate and that H₂S and temperature generally correlate. Unlike sedimentary environments, the data clearly show that Riftia live in areas where both O₂ and H₂S co-exist so that its endosymbiont bacteria can perform chemosynthesis. However, physical mixing of diffuse flow vent waters with oceanic bottom waters above or to the side of the tubeworm field can dampen these correlations or even reverse them. Voltammetry is a powerful technique because it provides chemical speciation data (e.g.; oxidation state and different elemental compounds/ions) as well as quantitative data. Because (micro)organisms occupy environmental niches due to the system's chemistry, it is necessary to know chemical speciation. Voltammetric methods allow us to study how chemistry drives biology and how biology can affect chemistry for its own benefit.     

水动力因素对砷在河砂中迁移影响的柱试验与模拟

河岸带作为一种典型的地下水-地表水相互作用带,不同水动力学条件下砷在该作用带中的行为较少有研究报道。基于此,采集河岸带河砂开展室内柱试验,分析不同水动力因素（包括流速和粒径）对砷在河砂中迁移的影响并建立相关模型。结果表明：(1) 0.5 mL/min流速下,河砂对As(V)的吸附速度和达到平衡所需的时间均比As(III)快,且粒径越小,该现象越明显;1.0 mL/min流速下,不同粒径的河砂对As(V)的吸附速度随粒径的增大而增大,对As(III)的吸附则没有明显差异;(2) 相同粒径的填充柱中,河砂对As(III)和As(V)的吸附能力均随流速的增加而降低;(3)不同流速和粒径条件下,As(III)和As(V)在砂柱中的迁移过程均更符合Thomas模型,拟合R2高于相同条件下Yoon-Nelson和Adams-Bohart模型。其中,低流速下,Thomas模型对0.15～0.25 mm粒径中As(III)和As(V)迁移过程拟合的R2（≥0.94）显著优于1.00～2.00 mm的较大粒径;高流速下,该模型对不同粒径中砷迁移过程的拟合R2差异不大。研究有助于加深对地下水-地表水相互作用下水动力因素对砷迁移转化规律影响的认识,并丰富和完善高砷地下水形成的机制理论。     

淋溶条件下石英砂柱中铁锰氧化物的形成特点

用不同浓度铁锰离子混合溶液对石英砂柱进行40次淋溶实验,研究砂柱中铁锰氧化物的形成状况.结果表明,淋出液中铁锰离子浓度与其pH值随着淋溶次数的增加呈现先降低后升高的趋势;各处理所形成的铁锰氧化物含量之间存在极显著差异,淋溶液中铁锰离子浓度越大,形成的铁锰氧化物含量越高,当淋溶液中铁锰摩尔浓度比即c(Fe2+)/c(Mn2+)为2∶1时最有利于铁锰氧化物的形成;随着淋溶次数的增加,铁锰氧化物含量的增长逐渐减慢;不同层次铁锰氧化物含量差异显著,下层(20～30 cm)含量明显高于其它层次;各阶段(每淋溶10次为一阶段)不同形态(非晶形态、晶形态)铁锰氧化物含量间的相关性存在差异,铁锰氧化物尤其是非晶形态的相对比例(Fe/Mn)随着淋溶次数的增加逐渐增大.     

钢管混凝土边框内藏带斜肋钢板中高剪力墙抗震性能试验

提出了钢管混凝土边框内藏斜撑肋钢板组合中高剪力墙.为研究这种组合剪力墙的抗震性能,进行了5个不同构造的中高剪力墙模型低周反复荷载试验.分析了试件的损伤特征、承载力、耗能、滞回特性,提出了正截面抗弯承载力计算模型,计算结果与试验符合较好.研究表明:钢管混凝土边框内藏钢板组合剪力墙具有较高的承载力和良好的耗能性能;钢管混凝土边框内藏带斜撑肋钢板中高剪力墙,适于在墙体厚度小于钢管尺寸或内藏钢板厚度较薄的“强边框、弱墙体”情况下应用,可明显减轻钢管混凝土边框底部的损伤,延缓墙体性能退化,提高组合剪力墙的抗震能力.     

Seismic response evaluation of the linked column frame system

The linked column frame (LCF) system is proposed as a seismic load resisting system that uses conventional components to limit seismic damage to relatively easily replaced elements. The LCF features a primary lateral system, denoted the linked column, which is made up of dual columns connected with replaceable links, and a secondary flexible moment frame system with beams having fully restrained connections at one end and simple connections at the other. The linked columns are designed to limit seismic forces and provide energy dissipation via link yielding, while preventing damage to the moment frame under certain earthquake hazard levels. A design procedure is proposed that ensures plastic hinges develop in the links of the linked columns at a significantly lower story drift than when plastic hinges develop in the moment frame beams. The large drift difference helps enable design of this system for two distinct performance states: rapid return to occupancy, where only link damage occurs and relatively simple link replacement is possible, and collapse prevention, where both the links and the beams of the moment frame may be damaged. A series of 3‐story, 6‐story, and 9‐story prototype LCF buildings were designed using the proposed design approach. Nonlinear models were developed for the designs with the link models validated using recent experimental results. The seismic response of these systems was investigated for ground motions representing various seismic hazard levels. Results show that the LCF system not only provides collapse prevention, but also has the capability of limiting economic loss by reducing structural damage and allowing for rapid return to occupancy following earthquakes with shorter return periods. Copyright © 2012 John Wiley & Sons, Ltd.     

Experimental evaluation of rectangular reinforced concrete column behaviour under biaxial cyclic loading

The cyclic behaviour of reinforced concrete columns has been the subject of many experimental studies in recent years. However, most of these studies have focused on the unidirectional loading of columns with square cross‐sections under constant axial loading conditions. In the present study, four types of full‐scale quadrangular building columns were tested under different types of loading, including uniaxial and biaxial loading conditions. The first two specimens of each column type were independently cyclically tested in the strong and weak directions. Bidirectional tests using different loading paths were performed on the other column specimens. All columns were tested under constant axial loading conditions. In this paper, the experimental results are presented, and the global behaviour of tested columns is discussed, particularly focusing on the stiffness and strength degradation because of the increasing cyclic demand. Finally, the deformation‐based performance limits proposed in Part 3 of Eurocode 8 were calculated and compared with the experimental results. Copyright © 2012 John Wiley & Sons, Ltd.     

Analysis and seismic tests of composite shear walls with CFST columns and steel plate deep beams

A composite shear wall concept based on concrete filled steel tube （CFST） columns and steel plate （SP） deep beams is proposed and examined in this study. The new wall is composed of three different energy dissipation elements： CFST columns; SP deep beams; and reinforced concrete （RC） strips. The RC strips are intended to allow the core structural elements - the CFST columns and SP deep beams - to work as a single structure to consume energy. Six specimens of different configurations were tested under cyclic loading. The resulting data are analyzed herein. In addition, numerical simulations of the stress and damage processes for each specimen were carried out, and simulations were completed for a range of location and span-height ratio variations for the SP beams. The simulations show good agreement with the test results. The core structure exhibits a ductile yielding mechanism characteristic of strong column-weak beam structures, hysteretic curves are plump and the composite shear wall exhibits several seismic defense lines. The deformation of the shear wall specimens with encased CFST column and SP deep beam design appears to be closer to that of entire shear walls. Establishing optimal design parameters for the configuration of SP deep beams is pivotal to the best seismic behavior of the wall. The new composite shear wall is therefore suitable for use in the seismic design of building structures.     

Natural frequencies of vertical cylindrical oscillating water column devices

This paper deals with the evaluation of the natural frequencies in heave motion of a single floating Oscillating Water Column device along with the natural frequencies of the water column inside the oscillating chamber. Two types of OWCs are examined, a simple-type device, consisting of a partially immersed toroidal body and a novel-type device, consisting also of a partially immersed toroidal body supplemented however by a coaxial interior truncated cylinder moving in phase with the outer chamber, thus forming a floating unit. Numerical results are given concerning the three boundary value problems, namely, the diffraction, the motion- and the pressure- dependent radiation problems, obtained through an analytical solution method using matched axisymmetric eigenfunction expansion formulations. The effect of the air pressure distribution inside the oscillating chamber on the natural frequencies in heave motion of the two examined types of OWCs and on the natural frequency of the water column motion inside the chamber, is presented and discussed thoroughly. It is demonstrated that the heave natural frequencies are strongly dependent on the type of the examined OWC and the device’s inner air pressure and should be taken into consideration when designing a floating OWC device.     

隐伏导水岩溶陷落柱的多源信息探查研究

开 滦 范各 庄 矿 是 一座 大 水 矿 井,主 要水 害 威 胁 来自 于 孤 立 发育 的 隐 伏 导水 岩 溶 陷 落柱 ,为 此,范 各庄 矿 使 用了 物探 、钻 探 、放水 试 验等 多种 勘 探方 法,取得 了 丰富 的地 质 资源 信息 。综合 利用 这 些多 源信 息 ,发 现范 各庄 矿 3-2皮带 巷原 设 计区 域存 在 着 13隐伏 导 水岩 溶陷 落 柱,具 有 强富 水 性及 导 水 性 。据 此 ,修改 3-2皮带 巷 设 计 ,避 免 再 次透 #水 灾害 的 发生 。